A review on the development of electrolytes for lithium-based batteries for low temperature applications

Abstract

The aerospace industry relies heavily on lithium-ion batteries in instrumentation such as satellites and land rovers. This equipment is exposed to extremely low temperatures in space or on the Martian surface. The extremely low temperatures affect the discharge characteristics of the battery and decrease its available working capacity. Various solvents, cosolvents, additives, and salts have been researched to fine tune the conductivity, solvation, and solid-electrolyte interface forming properties of the electrolytes. Several different resistive phenomena have been investigated to precisely determine the most limiting steps during charge and discharge at low temperatures. Longer mission lifespans as well as self-reliance on the chemistry are now highly desirable to allow low temperature performance rather than rely on external heating components. As Martian rovers are equipped with greater instrumentation and demands for greater energy storage rise, new materials also need to be adopted involving next generation lithium-ion chemistry to increase available capacity. With these objectives in mind, tailoring of the electrolyte with higher-capacity materials such as lithium metal and silicon anodes at low temperatures is of high priority. This review paper highlights the progression of electrolyte research for low temperature performance of lithium-ion batteries over the previous several decades.

Graphical abstract

Keywords

electrolyte / lithium-ion / low temperature / aerospace / solid-electrolyte interface

1 Introduction

Lithium-ion batteries have permeated a considerable part of our daily lives, from digital cameras, cell phones, laptops, power tools, and recently to electric passenger vehicles and heavy-duty trucks [1]. These applications have pushed lithium-ion batteries toward higher operating voltage, energy, and power density, as well as increased lifespan and cheaper costs, qualities that already rendered them superior over commonly used alkaline cells [2,3]. Regardless of the use of lithium-ion batteries in diverse applications and environments, chemistry still limits their practical application in certain areas such as electric vehicles in colder climates and aerospace applications [4–7]. Lithium-ion batteries generally do not perform well at lower temperatures, requiring thermal management systems to maintain favorable operating temperatures [8].

The main problems encountered while applying lithium-ion batteries at lower temperatures include slower transport kinetics across the bulk electrolyte, unstable surface films on the electrode surfaces, increased impedance, and lithium plating on the anode [9–12]. Although rare under normal operating conditions, lithium plating is a major problem at low temperatures or under rapid current draws [13,14]. Electrochemical impedance spectroscopy (EIS) has demonstrated lithium intercalation into the electrode as an important rate limiting step [15]. Solid-electrolyte interphase (SEI) characteristics such as conductivity and thickness dictate the kinetics of lithium intercalation/deintercalation into a carbon anode, and SEI formation, in turn, is influenced by electrolyte composition [16,17]. Therefore, improving the electrolyte chemistry (for increased SEI stability) or modifying the cathode material has been the main research focus for improving the performance of lithium-ion batteries at low temperatures [18].

Electrolyte composition heavily influences the SEI structure, necessitating careful selection of components and additives [19]. At low temperatures, several bulk electrolyte characteristics have to be tuned to obtain favorable reaction kinetics, such as increased conductivity, decreased viscosity and melting point, and favorable solvation characteristics [20]. Organic carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) along with various additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) are the electrolytes of choice for lithium-ion cells operating at room temperature (considered as 23 °C throughout the paper) and low temperatures [21–24]. Low molecular weight esters such as methyl acetate (MA), ethyl acetate (EA), and ethyl propionate (EP) have been studied owing to their low viscosities and extremely low melting temperatures (−70 to −100 °C.) Because of their improved surface film stability, high molecular weight esters, such as methyl butyrate (MB), ethyl butyrate (EB), and methyl propionate (MP) have also been heavily investigated as electrolyte components to enable low temperature performance, with modest capacity retention being reported under operating temperatures as low as −60 °C (approximately 29% room temperature discharge capacity retention) [25,26]. As no single electrolyte has all the favorable characteristics required for developing a high performing cell, generally various organic carbonates and esters are mixed to obtain a combined electrolyte for achieving favorable kinetics and SEI formation [27].

Various metal oxides, such as LiCoO₂, LiNi_xCo_1–xO₂, LiFePO₄, LiMn₂O₄, LiNi_0.33Mn_0.33Co_0.33O₂, and LiNi_8.15Co_1.5Al_0.35O₂, have been used over the years [28–32]; the theoretical and practical specific capacities of a few of them are listed in Tab.1. Although mixed metal oxides offer synergistic benefits over single transition metals, other factors such as raw material costs, amount of cobalt, and environmental inertness also influence the choice of cathode material used [33,34]. Cathode treatments to improve low temperature performance include doping, surface coating, controlling component content, and reducing particle size [35–37]. These treatments have demonstrated success in cycle life performance (50–200 cycles and < 50% room temperature capacity retention) at temperatures as low as −20 °C [38].

This manuscript aims to share the knowledge gained over the previous two decades with regard to low temperature performance (−20 °C to −60 °C) and cell improvement of lithium-ion batteries. Low temperature performance of lithium-based batteries for aerospace applications requires not only favorable electrolyte characteristics but also functioning higher capacity electrodes. As load capacity increases on Mars Rover expeditions, the battery capacity must also follow. This review focuses on research spearheaded by the Jet Propulsion Laboratory (JPL) on low temperature electrolyte development specific to aerospace applications. This review also adopts a more historical and detailed approach to explain the evolution of electrolyte design over the last two decades and its application to JPL’s Mars Rover Missions and future mission goals. As electrolyte formulation is arguably the single most important factor in developing these cells for low temperature operations, most of this review focuses on electrolyte properties that improve low temperature performance. Electrolyte characteristics such as conductivity, viscosity, solvation, and SEI formation are discussed in detail. Organic esters that play an important role in lithium-ion battery performance at low-temperatures are also thoroughly discussed. The chemistry of cells selected for current JPL Mars missions that allow low temperature operation and high temperature cycling (−60 °C to 60 °C) is also reviewed because aerospace applications will gain the most from low temperature lithium-ion batteries. Both electrochemical analyses such as EIS and potentiodynamic polarization, as well as performance analysis of cycle life, capacity retention, and discharge characteristics are discussed in detail. One interesting point to note in low temperature lithium-ion battery research is that certain electrolyte formulations that might improve performance at −20 °C are not guaranteed to yield benefits at −40 °C. There is no “one size fits all” solution for all low temperature ranges, which is clarified throughout this review. A brief discussion on low temperature lithium metal batteries using liquid and solid electrolytes is also covered. Finally, improvements in cathode material and anode material are briefly considered. Cathode manipulation via component control, surface coating, doping, etc. is reviewed followed by a commentary on the potential outlook for advanced anode materials in addition to graphite for low temperature lithium-ion cells.

2 Electrolyte development for low temperature lithium-ion cells

Several processes occurring during a charge or discharge cycle can affect the rate performance and cycle life of a lithium-ion battery. Possible steps that can prove rate limiting factors include lithium deintercalation, diffusion through the SEI, ion transport across the bulk electrolyte, and intercalation into the cathode. Fig.1 illustrates the proposed 11 steps in the complete discharge cycle of a lithium-ion battery. According to Li et al. [39], lithium desolvation from electrolyte at the SEI layer is the main energy-consuming step at low temperatures. This observation supports the vast majority of research over the past decades devoted to improving electrolyte formulations, although early research reports proposed diffusion through the SEI layer of graphite as the most significant rate limiting factor [8]. Additionally, few studies have suggested freezing of electrolyte solvent as the predominant reason that hinders lithium-ion kinetics as opposed to behavior at the electrode/electrolyte interface [40]. Properties of mixed metal-oxide cathodes such as increased impedance across the interface and lattice contraction still play a vital role in low temperature performance [38], which we will discuss at the end.

2.1 Electrolyte development: binary, ternary, and quaternary designs

To begin a discussion on useful electrolytes for low temperature lithium-ion batteries, a discussion on all the attributes that render an electrolyte favorable is imperative. They include high ionic conductivity, low viscosity, favorable coordination behavior, and perhaps most importantly, low freezing point. As mentioned previously, alkyl carbonates are currently the most widely used electrolytes for lithium-ion batteries; Fig.2 illustrates the properties of these carbonates. Early electrolyte formulations comprised 1 mol/L LiPF₆ in EC and DMC in a 30:70 ratio [9]. As observed from Fig.2, although EC may have a high dielectric constant, its melting point is well above the ambient temperature, with a higher viscosity than other alkyl carbonates. DEC has the lowest melting point, but also the lowest dielectric constant and intermediate viscosity. Clearly, no single electrolyte contains all the desired physical properties and combining various carbonates is the only way to obtain acceptable solvent qualities for low temperature performance.

After binary solutions, ternary and quaternary solutions have proved highly tunable and favorable for lower temperatures [9,20], Smart et al. [9,20] demonstrated in 1999 after research at the JPL that conductivity of the ternary system EC + DEC + DMC (1:1:1) remained higher than those of two binary solutions at −40 °C, as shown in Fig.3(a). This translated into an increased rate performance and lower cell impedance. The performance of the ternary system was compared in a full cell with LiCoO₂ and graphite as the cathode and anode, respectively. Either 1 mol/L LiPF₆ in EC + DEC (30:70), EC + DMC (30:70), or EC + DEC + DMC (1:1:1) were used as the electrolytes. The discharge curves at −20 °C, presented in Fig.3(b), illustrate the superior capacity and discharge voltages of the ternary system, resulting in 85% room temperature capacity retention. Cycle life performance was also demonstrated to have superior discharge voltages and capacity fade, as observed in Fig.3(c). The performance data suggest that the low temperature behavior of ternary electrolyte systems can be adequately utilized in lithium-ion batteries at temperatures as low as −20 °C.

While the ternary electrolyte system demonstrated superior ionic conductivity, kinetics, and performance to the binary electrolyte system, high EC content can still hinder ionic mobility owing to its high viscosity and melting point. An additional reason for considering a quaternary-based electrolyte system other than low EC content is the solvation effects of the multi-component system. Numerous solvent molecule types lead to a higher number of solvent arrangements, resulting in increased disorder, lower viscosity, and higher ionic conductivity [20]. As observed in Fig.2, EMC is one of the alkyl carbonates that have lower melting points, and has an intermediate dielectric constant and viscosity. As Smart et al. [20] demonstrated in 2003, choosing a quaternary electrolyte system with less than 25% EC by volume allows for great tunability of favorable qualities like better film forming characteristics (generated from EC and DMC) and lower melting points and high conductivity (generated from EMC and DEC). Although the ternary EC:DEC:DMC (1:1:1) electrolyte system worked satisfactorily, conductivity suffered at operating temperatures below −30 °C, conditions where the quaternary EC:DEC:DMC:EMC (1:1:1:3) electrolyte performed well, as illustrated in Fig.4(a) [20]. In full cells of Mesocarbon microbeads (MCMB)-LiCoNiO₂ (NCO) prepared for evaluating the discharge characteristics and cycle life performance, the quaternary electrolyte displayed superior capacity at −40 °C. These cells retained 50%–65% of their capacity from 23 °C. Fig.4(b) depicts the discharge curves for a full MCMB-NCO cell for different electrolyte combinations. The cells were charged and discharged at the same temperature (−40 °C).

While higher entropy solvent mixtures offer greater conductivity of lithium ions, the quantity of EC may be of higher importance than its ternary or quaternary nature alone. Okumura and Horiba reported that the effect of EC content on ionic conductivity greatly diminishes as the temperature decreases to −45 °C and tends toward insignificance below −50 °C [40]. One can observe this effect in Fig.4(a) and Fig.4(b), where the EC content in the ternary electrolyte in Fig.4(a) is approximately 33%, and below 20% in the quaternary electrolytes. Similarly in Fig.4(b), the best-performing quaternary electrolyte has approximately 17% EC content; however, a ternary electrolyte performs nearly as well with an EC content of 15%. The freezing point depression is more pronounced for the EC component when LiPF₆ is added than all other electrolyte components; a summary of this behavior is presented in Fig.4(c). The greater freezing point depression of EC is attributable to its higher dielectric constant and tighter coordinating behavior toward the lithium ions. A similar analysis could be useful for electrolyte formulations containing different lithium salts and formulations for low temperature lithium-ion batteries. An added challenge in developing functional lithium-ion batteries for low temperature use is the ability to not only discharge at sufficient rates and deliver adequate capacities, but also charge at lower temperature as well. Such batteries can eliminate the extra steps of charging at room temperature for the first few cycles and then transitioning to low temperature for the remainder of testing. This also demonstrates the robustness of SEI film-forming characteristics and ideal physical properties of the electrolyte.

The cumulative irreversible capacity after the first five cycles is commonly used to evaluate the SEI film forming characteristics [9]. The first few charge-discharge cycles of full cell testing are a little different than later cycles because a certain amount of lithium is attributed to forming the SEI layer, which cumulatively (generally considered after five cycles) is known as the irreversible capacity. The irreversible capacities of the ternary electrolyte EC:DEC:DMC (1:1:1) in a LiCoO₂-graphite cell compared with the binary systems EC:DEC (30:70) and EC:DMC (30:70) are listed in Tab.2. Ideally, a lower irreversible capacity is favored, implying less lithium is consumed for the SEI formation, and a greater amount is available for further charge/discharge cycles. As observed in Tab.2, the EC:DEC electrolyte exhibits the highest irreversible capacities whereas the EC:DMC electrolyte exhibits the lowest, which indicates the reactivity of DEC and stability of DMC when paired with a lithiated carbon electrode. The intermediary irreversible capacities of the ternary electrolyte are also evident from Tab.2, further supporting the combined effect of DEC and DMC. The irreversible capacity of the quaternary electrolyte EC:DEC:DMC:EMC (1:1:1:3) was reported to be 135 mAh/g, slightly higher than the EC:DEC mixture, indicating greater lithium uptake for forming the SEI than any of the binary or ternary electrolytes [26]. Although this indicates an electrolyte with greater reactivity, the cell can also be considered to have greater stability and kinetically favorable SEI layer after the first several cycles. Different types of analyses are required to understand this process better.

Along with performance analysis, basic electrochemical tests such as EIS and potentiodynamic polarization, and other techniques such as Fourier-Transform infrared spectroscopy (FTIR) and solid state ⁷Li NMR offer valuable information on SEI formation, stability, and lithium kinetics. The SEI protects against further reaction with electrolyte while simultaneously promoting lithium diffusion into and out of the anode material [9,11]. The characteristics of these films such as thickness, porosity, and impedance influence the ease of Li transport, thus requiring the basic electrochemical tests mentioned for thoroughly analyzing the migration kinetics. DC micropolarization, Tafel polarization, and AC impedance tests were conducted separately in three half-cells with graphite as the anode, at various temperatures down to −20 °C. DC micropolarization is a useful technique for determining the resistance or exchange current density of surface films. As expected, and presented in Tab.3, the exchange current density of all electrolyte samples reduces (resistance increases) as the temperature decreases to −20 °C. However, at lower temperatures (0 °C, −20 °C), it is evident that the ternary electrolyte exhibits higher exchange current densities than both binary solutions. Therefore, the higher reacting ternary electrolyte may still create an SEI layer additionally favorable toward facile Li transportation. Tafel polarization measurements provide valuable insight into the kinetics of lithium migration through the SEI layer, the transfer coefficient being an important calculated parameter. According to Tab.3, the ternary electrolyte mixture still displays the highest transfer coefficient at low temperatures compared with the binary electrolytes. The DMC-based electrolyte exhibits the lowest transfer coefficient, in line with the higher reactive and protective nature of the solvent.

EIS is a highly useful non-destructive electrochemical test to determine cell impedance, and even elucidates separate distinct resistive processes from one another [15]. As expected, the impedance increases among all cells with decreasing temperature. Impedance results for half-cells of different electrolyte compositions with a graphite anode at temperatures of 0 °C and −20 °C are presented in Fig.5. It is clear from the figure that the ternary electrolyte composition exhibits less resistance at low temperatures than either of the binary electrolyte compositions, further confirming the superior SEI behavior of the ternary solvent regardless of its intermediary irreversible capacity. Interestingly, the EC:DEC and EC:DMC electrolytes exhibit the highest impedance at 0 °C and −20 °C, respectively, indicating that observed behaviors exhibit variance across below-ambient temperatures. These results are also quantified and illustrated in Tab.3. As mentioned previously, certain chemical features in a lithium-ion battery, such as electrolyte functionality or electrode behavior, do not remain constant throughout all low temperature conditions. One such example is the impedance behavior of cathode vs. anode at low temperatures.

Initial EIS studies demonstrated higher impedance across the cathodic surface films at temperatures between 23 °C and 0 °C [15]. However, Ratnakumar et al. [15] reported in 2002 that the anode SEI becomes the higher resistive film after sufficient lowering of the temperature (−40 °C and below). These impedance tests were performed in half-cells with a ternary EC:DEC:DMC (1:1:1) electrolyte and NCO/MCMB as the cathode and anode, respectively. There is a crossover in kinetic behavior between −20 °C and −40 °C where the resistance at the anode surface increases over that of the cathode surface. These results clearly suggest sufficiently drastic reduction in the kinetics at the anode, causing Li intercalation/deintercalation to become rate limiting at extreme cold temperatures [15]. This crossover behavior is not consistent in all electrolyte compositions, as observed in the quaternary EC:DEC:DMC:EMC (1:1:1:3) electrolyte with the same NCO/MCMB cathode and anode illustrated in Fig.6. Tafel polarization measurements conducted on these full cells revealed that the anode expresses considerably higher limiting current densities across nearly all temperatures than the cathode, apart from that at −40 °C. This strongly enforces the notion of the critical role played by the electrolyte composition in determining the electrochemical and performance behavior of lithium-ion batteries. Ternary and quaternary all-carbonate electrolyte compositions have been studied thoroughly and exhibited significant success in improving low temperature lithium-ion battery performance. Organic esters are another group of solvents studied extensively for their lower melting points and higher conductivities. Although these esters exhibit certain favorable qualities, they also display higher reactivity than all-carbonate-based electrolytes, necessitating their use in low proportions [25].

2.2 Electrolyte development: ester cosolvents

Although the advantages of an all-carbonate-based electrolyte have helped promote the use of lithium-ion batteries at low temperatures with sufficient discharge capacities and rates, offering a similar performance at temperatures below −30 °C has proved difficult [10]. An all-carbonate system has high melting points and suffers from decreased conductivity at extremely low temperatures (−40 °C and lower). While lowering the salt concentration could increase the solvent conductivity via lower viscosity, colligative properties dictate that this would also diminish the freezing point depression effect, resulting in higher melting points [10]. Herein, organic esters have emerged as the cosolvent of choice for exceptional lithium-ion battery performance at temperatures −40 °C and below. While selecting cosolvents, miscibility with carbonates and adequate solvation of the lithium salt should be considered [25].

As mentioned previously, organic esters exhibit lower melting points and higher ionic conductivities than organic carbonates (Tab.4). With the melting points of several esters well below −70 °C, cycling performance and kinetics should improve with the incorporation of these cosolvents. Previous studies by the JPL has revealed these esters to be extra reactive than carbonates; therefore, their proportions should be restricted under 30% to utilize their beneficial solvent qualities while mitigating the negative effects [25]. The study results of Smart et al. [25] at the JPL demonstrated their oxidative and reductive stability compared with a baseline ternary electrolyte via cyclic voltammetry. All ester-containing electrolytes exhibited greater reactivity than the baseline electrolyte, with low and high molecular weight esters displaying less reactivity at higher (cathode) potentials and low (anode) potentials, respectively, vs. Li⁺/Li [25]. The importance of high vs. low molecular weight esters will be discussed later. The results suggest that higher molecular weight ester cosolvents increase SEI stability and enhance the cycle life.

The conductivities of several initial ester electrolytes studied against a ternary all-carbonate-based electrolyte are presented in Fig.7(a). The ester cosolvents investigated include MA, EA, EP, and EB. As evident from the figure, the conductivity of the ternary carbonate electrolyte reduces drastically below −40 °C, while all ester cosolvent electrolytes retain significantly higher conductivity. These conductivity data further validate the exploration of organic esters as cosolvents toward low temperature lithium-ion battery performance. When full cells were tested using equiproportional electrolyte mixtures and MCMB-LiCoO₂ as the anode and cathode, respectively, the crossover behavior between temperatures −20 °C and −40 °C was again notable. As Fig.7(b) and Fig.7(c) illustrate, at −20 °C, full cells with ester cosolvents display poorer discharge capacities than the ternary EC:DEC:DMC electrolyte, with the exception of the EA-containing electrolyte. However, as temperature reduces to −40 °C, the capacity retention of the ternary electrolyte reduces drastically, whereas all ester cosolvent electrolytes retain significant percentages of their room temperature capacities. At temperatures of −40 °C and lower, the addition of ester cosolvents begin to provide substantial benefits in terms of electrolyte conductivity and discharge capabilities not present at warmer temperatures. An interesting trend among the ester cosolvents was reported by Smart et al. [25]. The electrochemical and consequently the performance traits are different for low molecular weight esters such as MA and EA, and high molecular weight esters such as EP and EB. A first look at irreversible capacities such as those listed in Tab.5 illustrates the different behavior among higher molecular weight ester cosolvents, with their higher cumulative irreversible capacities. This behavior is further demonstrated in the exchange current density results presented in Fig.8. The same ternary baseline electrolyte is compared with ester cosolvent-containing electrolytes at various temperatures. The figure illustrates that as the chain length (and therefore the molecular weight) increases, the exchange current density increases as the temperature is lowered (0, −20 °C). These results suggest a possible trend of higher molecular weight esters exhibiting greater favorable SEI formation characteristics [25]. With increasing performance requirements for rovers and satellites, lithium-ion batteries are required to not only include lower temperatures in their ideal operating temperature range but also deliver sufficient capacity at acceptable discharge rates over a wide temperature window as well (−60 °C to 60 °C) [26].

The added challenge of formulating an electrolyte that provides adequate SEI-forming characteristics to allow discharge behavior at low temperatures (−60 °C) similar to that at room temperature and is sufficiently versatile to cycle between low and high temperatures places ester cosolvents at the focus of continued electrolyte research. While organic ester cosolvents enable lithium-ion battery performance at extremely low temperatures, their higher reactivity than organic carbonates should also be noted, rendering cycling to higher temperatures a particularly precarious endeavor. Research performed by Smart et al. [41] at the JPL in 2010 demonstrated the benefits of higher molecular weight esters over a wider temperature range (−60 to 60 °C); low temperatures are discussed here while the high temperature cycling will be discussed later. Formation characteristics presented in Tab.6 illustrate the benefits of higher molecular weight ester cosolvents compared with the binary EC:EMC (20:80) and ternary EC:DEC:DMC (1:1:1) electrolytes. The organic esters involved in the study are MP, EP, MB, EB, propyl butyrate (PB), and butyl butyrate (BB). As the table illustrates, the electrolytes containing ester cosolvents generally exhibit lower cumulative irreversible capacities and higher coulombic efficiencies. The most notable is the EC + EMC + MP (20:60:20) electrolyte that exhibits the lowest cumulative irreversible capacity and highest coulombic efficiency. MCMB carbon–NCO cells with the same ester cosolvents discharged to 2.0 V at C/16 and C/4 discharge rates at −40 °C and C/16 discharge rate at −50 °C, as presented in Fig.9. The discharge rate affects the capacity during low temperature operation, with faster discharge rates resulting in lower delivered capacities and hence a lower percentage of room temperature capacity. Fig.9(a) and 9(b) illustrate this effect at −40 °C for various ester cosolvent electrolytes and different discharge rates. As expected, a slower discharge rate (C/16) allows a higher percentage of room temperature capacity retention with most of the electrolytes displaying between 65% and 80% RT capacity. However, under a faster discharge rate (C/4), the capacity retention varies significantly, with the MP-containing electrolyte retaining the most RT capacity at 63%. When temperatures are lowered even further to −50 °C and discharge rate to C/16, the MP-containing electrolyte again displays excellent RT capacity percentage at 61% (Fig.9(c)). Electrochemical analyses such as EIS and Tafel polarization measurements can provide further insight into the reasons for these ester-containing electrolytes exhibiting such discharge profiles at low temperatures.

EIS data can illustrate the variances in series resistance of a full cell per electrolyte type based on different temperatures. Fig.10 depicts the series resistance of full cells as a function of temperature, illustrating the niche behavior of different electrolyte compositions. Between temperatures of 23 °C and −20 °C, the ternary all-carbonate-based mixture demonstrates the lowest series resistance. Crossover behavior is re-exhibited between electrolytes at temperatures of −30 °C and below, where the series resistance of the all-carbonate electrolyte increases dramatically. However, the MP-containing electrolyte maintains low resistance across all temperatures, and this ester cosolvent exhibits the lowest series resistance at −60 °C [41]. Tafel polarization measurements further illuminate the favorable reaction kinetics of the MP-containing electrolyte. Fig.11(a) presents the measurement results for NCO cathodes of various ester electrolytes at −60 °C, with MP-containing electrolyte exhibiting the highest exchange current densities among all solvent mixtures. When the same parameters were measured for the MCMB anode, the MP-containing electrolyte again demonstrated high exchange current densities, although lower than the PB-containing electrolyte (Fig.11(b)). These Tafel polarization measurements also demonstrate the difference in kinetic behavior for each electrode with regard to temperature. Although cathodic kinetics are generally less facile than anodic kinetics at warmer temperatures, higher crossover behavior is exhibited below −30 °C where anodic kinetics are less facile and become rate limiting [41]. Based on the previously discussed performance and electrochemical measurements, the MP-containing electrolyte is an extremely robust electrolyte combination for low temperature lithium-ion battery functions below −30 °C, evidence that propelled this ester cosolvent mixture as the electrolyte of choice for current and future JPL Mars missions.

2.3 Low temperature lithium-ion chemistry for JPL Mars missions

Most of the research related to electrolytes for low temperature lithium-ion batteries over the previous two decades has been conducted by the JPL in Pasadena, frequently in conjunction with the Department of Defense, Yardney Technical Products (Rhode Island, USA), US Airforce-Wright Patterson Air Force Base, and NASA-Glenn Research Center [7,18,42,43]. As satellites, landers, penetrators, and rovers all benefit from low temperature LIB use, the JPL naturally spearheaded the research in this direction. Mars rovers can benefit especially from this battery chemistry owing to the resultant high energy density, low self-discharge, and satisfactory low temperature performance. With changing specific energy requirements and low temperature operation demands, new battery chemistry was required to replace the old “heritage” chemistry where the ternary MP electrolyte is utilized.

The earliest use of lithium-ion batteries for JPL’s Mars missions was for the Mars Exploration Rover mission in 2003, which launched the Spirit and Opportunity rovers. These rovers were required to possess sufficient energy in their batteries to travel 600 m and remain viable for 90 Martian days with at least one rover active. The required battery was expected to operate over a range of temperatures (−20 °C to 30 °C) [7]. The chemical composition included an MCMB anode, LiNi_xCo_1–xO₂ cathode, and all-carbonate ternary electrolyte of EC:DEC:DMC (1:1:1, vol.%). The mission was a success, with the Spirit rover operating over seven years and the Opportunity rover remaining viable until 2018, and the success was largely attributed to the durability of the battery. The discharge capacity of the 8 Ah cell provided by Yardney Technical Products is illustrated in Fig.12(a) and exhibits 76% room temperature capacity retention at −20°C. The capacity delivered at −20 °C is sufficient for providing battery power for all instrumentation. The comparative cycle lives of this battery chemistry at −20 °C and 23 °C are demonstrated in Fig.12(b), and the lower temperature cells actually exhibit better capacity retention. However, the different charge rates (C/10 at −20 °C and C/5 at 23 °C) should be noted, and could explain the rapidly diminishing capacity of the room temperature cells. The low temperatures may also restrict any undesirable side reactions of the electrolyte with electrodes, explaining the better cycle life performance of the −20 °C cells. The great success of the all-carbonate ternary electrolyte prompted its further utilization in the 2005 Juno mission, 2007 Phoenix lander mission, 2011 Grail mission that mapped the interior of the moon, and 2011 Mars Science Laboratory mission, which launched the Curiosity rover functioning until recently [18].

While the Mars Science Laboratory (MSL) housed the Curiosity rover that operated on the same lithium-ion battery chemistry, a higher nameplate capacity (43 Ah) was used to compensate for the greater amount of instrumentation on board. Instead of solar panels, a multi-mission radio isotope generator was used to power the battery and maintain it within temperature limits. The performance of the lithium-ion battery on the Curiosity rover confirmed the robust chemistry of the all-carbonate ternary electrolyte. Fig.13(a) depicts the discharge capacity as a function of sols (Martian days), again demonstrating that with a higher capacity battery, satisfactory low temperature capacity at 20 °C is retained over 1200 sols. Similar to commercial appliances, where generally the battery is not completely discharged, the partial discharge of 43 Ah cells was investigated from 40% to 60% depth of discharge (DOD). According to Fig.13(b), only 8.6% capacity fade was observed at 50% DOD compared with that at 100% DOD at 18 °C. The lithium-ion chemistry containing MCMB anode, LiNi_xCo_1–xO₂ cathode, and ternary all-carbonate electrolyte was profoundly significant and facilitated the success of several JPL and NASA missions. Later missions, however, would require higher specific energy and the ability to operate over a wider temperature range.

The NASA InSight mission was launched in 2018 to place a lander on the Mars surface to study the deep interior of the planet. This lander required the ability to charge and discharge from −30 to 35 °C and survive for at least 709 sols [18]. The MP-containing electrolyte discussed earlier (EC:EMC:MP 20:60:20, vol.%), along with graphite-LiNiCoAlO₂ (NCA) anode-cathode represent the new generation chemistry that would allow such an operation. Fig.14(a) presents the comparative discharge energy values (Wh/kg) between the new NCA cathode/MP ternary electrolyte and the “heritage” NCO cathode/all-carbonate ternary electrolyte in 25 Ah capacity cells, with all cells charged and discharged at −25 °C. As visible from the figure, the NCA cell retains 31% higher capacity than the NCO cells, which clearly demonstrates its superior discharge characteristics even when charged at a lower temperature and rapid rate, both of which are considered to seriously hinder capacity retention. As stated previously, the new low temperature chemistry needed the added benefit of high-capacity retention not only at discharging from low temperatures, but also cycling between low and high temperatures. Fig.14(b) illustrates the comparative capacity retention values between new generation NCA cells and NCO cells after cycling between higher temperatures. Broken into three groups (NCO + heritage electrolyte, NCO + low temp electrolyte, and NCA + low temp electrolyte), the synergistic effects of the NCA cathode and low temperature electrolyte toward capacity retention at cycling extremes can be observed. The NCO + heritage, NCO + low temp, and NCA + low temperature electrolytes exhibit approximately 3.6%, 3.2%, and less than 1% capacity loss, respectively, after cycling to 35 °C. Use of the NCA cathode material also significantly raises the available capacity of the cell. Typically, for low temperature operations, lithium-ion cells are first charged at room temperature for a few cycles, acclimatized to low temperatures, and then operated continuously. Exhibiting minimal capacity fade upon discharge after charging for several cycles at low temperature is an impressive feat demonstrating the robustness of selected chemical composition. Fig.15 illustrates the results of 10th discharge curve at −30 °C after being cycled continuously after only one charge at 20 °C, with 92% retained capacity after the 10th cycle. Similar data were obtained after 234 cycles under variable temperature cycling mentioned previously, further illustrating the extreme durability and high performance of the graphite–NCA cell with EC + EMC + MP (20:60:20, vol.%) electrolyte developed at the JPL. This electrolyte will continue to be used in upcoming Mars rover applications.

2.4 Electrolyte additives for low temperature performance of lithium-ion batteries

Although organic carbonates and ester cosolvents have been the major components of electrolyte development for low temperature lithium-ion batteries, electrolyte additives have also played an important role in their development. Additives such as VC, FEC, and 2,2,2-trifluoroethyl butyrate (TFEB) have several advantages, such as increasing lithium solvation in the electrolyte, improving the film forming characteristics, decreasing the possibility of lithium plating, and even reducing the flammability of the organic electrolytes, in addition to improving low temperature performance. The most frequently used additives are fluorinated compounds, with fluorinated carbonates and esters among the most widely investigated [44]. A few partially fluorinated esters investigated by Smith et al. [44] at the JPL are presented in Fig.16. The electrochemical stability of these esters is illustrated in Fig.17(a) and Fig.17(b), where the fluorinated esters exhibit reduced stability at both anodic and cathodic potentials compared with that at the baseline (EC:EMC=20:80, vol.%). Ethyl trifluoroacetate (ETFA) exhibits the greatest deviation in stability among the partially fluorinated esters, in both oxidative and reductive aspects. When considering the effects of these additives on irreversible capacity, only TFEB exhibited comparable reversible capacity with all-carbonate solvents, implying either adequate electrochemical stability or favorable film forming characteristics. Performance of the 20% TFEB at low temperatures (−40 °C) demonstrates reasonable capacity retention of 74% room temperature capacity, when charged at room temperature and discharged at −40 °C at C/8 (50 mA) discharge rate. However, when charged and discharged at low temperature (−20 °C), over 90% room temperature capacity retention is demonstrated by the TFEB electrolyte-containing cell, proving its robust chemistry, as presented in Fig.18.

As mentioned in Section 2.3, a wide operating temperature range (ideally −60 to 60 °C) is now additionally critical than simply providing sufficient discharge capability at low temperatures. Several electrolyte additives have been investigated in recent years to help with high temperature resiliency. Smart et al. [22], in their study at the JPL in 2012, explored the effect of adding FEC, VC, lithium oxalate, and lithium bis(oxalato)borate (LiBOB) in small percentages (2%–4%) to electrolyte solutions of 1.2 mol/L LiPF₆ in EC:EMC:MB (20:20:60, vol.%) in MCMB-Li_xNi_yCo_1–yO₂ cells. As observed in Tab.7, irreversible capacity was low and coulombic efficiency is high in all additive-containing electrolytes within the first few cycles, with the FEC-containing electrolyte exhibiting the most favorable characteristics. Discharge curves at −40 °C (Fig.19) demonstrate the benefits of additives in the MB ternary electrolyte, with every additive-containing electrolyte significantly retaining higher room temperature capacity than the baseline. Electrolytes containing VC and LiBOB exhibited the highest capacity retention of the group, showing the positive effects on lithium solvation or SEI film-forming characteristics at such low temperatures. Finally, when cycled at high temperatures of 60 °C and 80 °C (Fig.20), it is noticeable that lithium oxalate and VC additives impart higher capacity retention behavior to the ternary electrolyte than the other additives. Thus far, the VC additive has displayed the highest improvement in electrolyte behavior from the baseline. To discern the effect of additives on processes, EIS tests were performed in experimental three electrode cells for both the cathode and anode.

Room temperature EIS results for both anode and cathode surfaces, respectively, after being cycled to high temperature (60 °C) are depicted in Fig.21(a) and Fig.21(b). The EIS results for the anode surface with various additives illustrate that the baseline electrolyte exhibits higher resistive processes than all the electrolytes with additives. This implies robust SEI formation with a possibly decreased size when compared with electrolytes with no additives. The EIS results for the cathode surface under similar conditions revealed significantly greater differentiation in behavior, with the lithium oxalate displaying the most favorable results. However, FEC and VC additives demonstrated high and medium resistivity, respectively, with the baseline being similar in behavior to lithium oxalate. The high resistivity of the FEC-containing electrolyte implies greater reactivity with the cathode electrolyte interphase (CEI) and formation of side products that hinder the intercalation processes. To understand the intercalation/deintercalation properties of the electrodes in greater detail, Tafel polarization measurements were also conducted for anode and cathode surfaces.

Potentiodynamic polarization results of various additives for both electrodes at −30 °C revealed different effects of each additive on the anode and cathode. As Fig.22(a) demonstrates, 4% FEC and lithium oxalate have an additionally significant effect on the anode than the cathode, exhibiting improved lithium deintercalation kinetics over the baseline. In contrast, according to Fig.22(b), the same additives exert a minimal effect on the cathode, with 2% VC and 0.10 mol/L LiBOB demonstrating improved kinetics over the baseline electrolyte. These results confirm not only the EIS data that indicate a greater influence of VC on the CEI than SEI, but also the discharge data that prove VC and lithium oxalate as excellent additive candidates for improving the discharge capacity in low and high temperature environments.

As mentioned previously, lithium plating can be a problem while charging and discharging at low temperatures, and various electrolyte additives help in mitigating such an effect. Jones et al. examined several structurally different additives at the JPL in 2020 to determine stability toward CEI and SEI, using an NCA cathode and graphite anode [23]. The considered additives included VC, LiBOB, lithium difluoro(oxalate)borate (LiDFOB), 1,3-propane sultone (PS), and lithium bis(fluorosulfonyl)imide (LiFSI) in 1 mol/L LiPF₆ EC + EMC + MP (20:20:60) electrolyte. An indirect sign of lithium plating is an appearance of a high voltage plateau during discharge, implying stripping of lithium metal from the anode surface [23]. As Fig.23 illustrates, a small plateau is observed on the second discharge of a cell containing LiBOB as an additive (charged and discharged at −30 °C), implying partial current contributing toward lithium stripping. After testing all the additives and comparing them with the baseline electrolyte at different temperatures, LiBOB, PS, and LiFSI are estimated to contribute less capacity toward lithium stripping at −40 °C while only LiFSI contributes less capacity toward lithium stripping at −30 °C, as observed in Fig.24. However, LiFSI contributes a greater portion of its capacity toward lithium stripping than any other electrolyte with or without additive at −50 °C. LiDFOB, a hybrid of LiBOB and lithium tetrafluoroborate (LiBF₄), displays higher ionic conductivity at lower temperatures as well, emerging as a potential candidate for improving low temperature cell performance [45]. As outlined in this Section, electrolyte additives offer numerous benefits, while simultaneously demonstrating that a small change in electrolyte composition can drastically alter behaviors such as low temperature performance, high temperature resilience, and lithium plating. These electrolyte additives will continue to shape research for use in low temperature lithium-ion batteries in the future.

2.5 Electrolyte design for lithium metal batteries at low temperatures

The discussion of electrolyte composition to date has focused on solvents and additives for traditional lithium-ion batteries using a lithium metal oxide and graphite electrodes. Other battery compositions with differing electrodes are also being heavily studied, with the lithium metal/ silicon cell, also known as the lithium metal battery (LMB), currently being the most popular owing to silicon’s and lithium metal’s extremely high theoretical capacities of 4200 mAh/g and 3800 mAh/g, respectively. As mentioned earlier in this review, dendrite growth is generally not a problem in traditional lithium-ion batteries unless under high discharge rates and under extremely low operating temperatures. Lithium metal batteries have that added challenge of formulating electrolyte mixtures to overcome dendrite growth. Similar to that in lithium-ion batteries, the desolvation behavior of lithium ion from bulk electrolyte into SEI is considered the most limiting step; therefore, electrolyte design needs to consider not only the ionic conductivities but also solvation characteristics [46]. The same carbonate-based electrolytes used in traditional lithium-ion batteries can and have been used in lithium metal batteries [47,48]. Similar electrolyte tailoring such as all fluorinated solvents used in traditional lithium-ion batteries have been used with lithium metal/nickel manganese cobalt (NMC) cells with improved performance at low temperatures [49]. Other electrolyte formulations utilize low-concentration dual-salt electrolytes to improve interfacial chemistry of the lithium metal [50]. Ether-based solvents are being considered as the base for electrolytes in lithium metal batteries owing to their drastically higher conductivities at extreme low temperatures, as illustrated in Fig.25 [51,52,53]. Holoubek et al. focused on two different solvent systems for lithium metal batteries, highlighting the specific coordination behavior and binding energy of each system in lithium-ion desolvation [54]. They reported that regardless of the higher ionic conductivity of LiFSI in 1,3-dioxolane/1,2-dimethoxyethane electrolyte, performance of cells containing LiFSI in diethyl ether were significantly better at ultra-low temperatures (−60 °C) because of the lower binding energy of solvent molecules toward lithium ion. These results are presented in Fig.26. Combining the two classes of solvents (carbonates and ethers) has also proven an effective strategy for low temperature performance as low as −60 °C with 50 cycles [55,56]. Thenuwara et al. [51] recognized that the nature of SEI formation drastically changes with reducing temperature, and devised electrolyte systems that probed the effect of combining these two solvent classes on the SEI morphology. Drastically different SEI layers for the same solvent are displayed in Fig.27 at different temperatures (−20 °C and −60 °C) and further classification is represented in the group’s published work. Although the continuous modification of liquid electrolytes for achieving lower melting temperatures, higher conductivities, and lower desolvation energies is pushing the boundaries of practical lithium-ion and lithium metal batteries, liquid organic solvents have their limitations. Solid state electrolytes, generally polymers, offer advantages of reduced reactivity with lithium metal but have difficulty retaining significant ionic conductivities, especially at lower temperatures [57,58]. Qian and coworkers [57] reported significant progress in this area using molecular simulations to experimentally test a lithium metal battery using poly(1,3-dioxolane) electrolyte, retaining 85% room temperature capacity for 200 cycles at −20 °C. The polymer electrolyte used in this work exhibited higher conductivity than traditional polymer electrolytes, yielding satisfactory lithium metal battery performance at low temperatures. Metal organic frameworks can also be used as a form of solid-state electrolyte, exhibiting sufficient ionic conductivities and acceptable low temperature performance (0 °C) in lithium metal batteries [59]. Different types of electrolytes as well as in situ regulated SEI formation are being explored to develop lithium metal batteries that perform well over a wide range of temperatures [60,61]. The timeline of electrolyte development for low-temperature lithium-based batteries is summarized in Fig.28.

3 Cathode and anode developments for low temperature lithium-ion batteries

Dictated by impedance measurements, considerable focus has been placed over the previous two decades on electrolyte development for low temperature lithium-ion battery use because it is the highest contributing factor toward impeded reaction kinetics. However, electrode development, primarily the metal oxide cathode, has also been researched to improve low temperature performance. Yao et al. [62] developed nano-sized LiFePO₄ spheres via a surface coating technique that enhanced electron conductivity and generated significantly greater capacity at −40 °C when compared with the pre-modified capacity. Similarly, development studies on the anode side have also been conducted. While Li₄Ti₅O₁₂ electrodes have been studied to improve performance at room temperature [63], Zaghib et al. [35] focused on a carbon–Li₄Ti₅O₁₂ anode with conventional and low temperature electrolyte at −10 °C in full cell 18650 configurations. Results revealed 49% room temperature capacity retention at −10 °C with a 0.1 C-rate discharge, displaying modest improvement. Gao et al. [64] focused in 2020 on a Li-LiCoO₂ cell utilizing self-assembled monolayers to stabilize the SEI on the lithium metal surface at low temperatures (−15 °C). With the lithium plating problem and dendrite formation during charging and discharging at low temperatures, this unique approach aimed to inhibit dendrite growth by controlling film formation and lithium nucleation. Results indicated successful dendrite-free lithium deposition and wide temperature cycling capability between −60 °C and 45 °C. Cells also exhibited high coulombic efficiency and durability (approximately 200–250 cycles). While these are successful developments in anode performance at low temperatures, high-capacity alternatives to graphite are yet to be studied and discussed. Research has been conducted over two decades on low temperature lithium-ion batteries and little focus has been placed on anode candidates such as silicon (4200 mAh/g), tin (994 mAh/g), or tin oxide (781 mAh/g) electrodes. There has been significant investigation on improving silicon performance at room temperature by improving conductivity or alleviating volume expansion [48,65,66], but almost no exploration of silicon electrodes at low temperatures [67,68]. These high-capacity anode materials will have to be investigated to continue improvement in low temperature (−60 °C) lithium-ion or lithium metal battery use toward aerospace applications as well as other industries.

4 Conclusions

Lithium-ion batteries generally do not perform well at colder temperatures. In summary, the state-of-the-art electrolyte composition varies with the overall cell design (choice of electrodes) and performance goals. When using traditional mixed metal oxides as the cathode and graphite as the anode, the electrolyte comprising 1 mol/L LiPF₆ EC:EMC:MP (20:60:20) is the best choice for high discharge capacity at temperatures as low as −60 °C. However, the goal is always to provide greater discharge capacity at ever decreasing operating temperatures, which cannot be achieved unless higher-capacity electrodes are used. When higher-capacity lithium metal is used as an electrode, ether-based electrolytes exhibit greater suitability over carbonate-based electrolytes. Considerable research is currently ongoing to obtain a state-of-the-art electrolyte for these cells and several electrolyte formulations are gaining reliability. The poor performance of a lithium-ion battery at lower temperatures has been attributed to several high-resistance processes during charging and discharging. Impedance results have demonstrated Li desolvation from the solvent and probable intercalation through the SEI as the rate limiting factors among all the processes. Accordingly, investigation into electrolytes, cosolvents, and additives has been the primary research focus regarding low temperature lithium-ion battery use. Insight on the interconnectedness between conductivity, lithium solvation characteristics, and film forming characteristics has guided research toward use of organic carbonates and esters in electrolytes. Similarly, several other carbonates and esters such as VC, FEC, and LiBOB have been investigated for use in small proportions as additives to enhance solvation or film forming characteristics. The exploration of several different electrolyte formulations has led to reasonable capacity retention at temperatures as low as −60 °C and resilient battery chemistry allowing for cycling between low and high temperatures right from −60 °C to 60 °C. Such robust chemistry has led to the selection of proper electrolyte formulations for application in lithium-ion batteries equipped on Mars rover missions that outlast their primary lifespan goals by several years. Liquid electrolytes based on ethers can be used in promising new lithium metal batteries at low temperatures with improvement over carbonate-based electrolytes. Solid-state polymer electrolytes are also being investigated for lithium metal batteries for their advantage of greater stability toward the reactive metal and better suited for mitigating lithium dendrite growth. Cathode and anode manipulation has resulted in positive effects on lithium-ion battery performance at low temperatures, although few studies have been conducted regarding operation below −20 °C via electrode manipulation alone. With extensive investigation of electrolytes and reasonably study of cathode material, higher capacity anode materials need to be investigated for low temperature lithium-ion battery use. As our exploration of space under extreme conditions continues to grow, the need for lithium-ion batteries at low temperatures is only going to grow.

References

[1] Wang X, Tang S, Guo W. . Advances in multimetallic alloy-based anodes for alkali-ion and alkali-metal batteries. Materials Today, 2021, 50(11): 259–275

[2] Yoshino A. The birth of the lithium-ion battery. Angewandte Chemie International Edition, 2012, 51(24): 5798–5800

[3] Manthiram A. An outlook on lithium ion battery technology. ACS Central Science, 2017, 3(10): 1063–1069

[4] Wittman R M, Perry M L, Lambert T N. . Perspective—on the need for reliability and safety studies of grid-scale aqueous batteries. Journal of the Electrochemical Society, 2020, 167(9): 090545

[5] Jaguemont J, Boulon L, Dubé Y. A comprehensive review of lithium-ion batteries used in hybrid and electric vehicles at cold temperatures. Applied Energy, 2016, 164: 99–114

[6] Ratnakumar B V, Smart M C, Huang C K. . Lithium ion batteries for Mars exploration missions. Electrochimica Acta, 2000, 45(8–9): 1513–1517

[7] Ratnakumar B V, Smart M C, Kindler A. . Lithium batteries for aerospace applications: 2003 Mars Exploration Rover. Journal of Power Sources, 2003, 119–121: 906–910

[8] Huang C K, Sakamoto J S, Wolfenstine J. . The limits of low-temperature performance of Li-ion cells. Journal of the Electrochemical Society, 2000, 147(8): 2893–2896

[9] Smart M C, Ratnakumar B V, Surampudi S. Electrolytes for low-temperaturelithium batteries based on ternary mixtures of aliphatic carbonates. Journal of the Electrochemical Society, 1999, 146(2): 486–492

[10] SmartM CRatnakumarB VSurampudiS. Electrolytes for Li-ion cells in low temperature applications. In: 14th Annual Battery Conference on Applications and Advances, Long Beach, USA, 1999

[11] SmartM CRatnakumarB VGreenbaumS, . The role of electrolyte upon the SEI formation characteristics and low temperature performance of lithium-ion cells with graphite anodes. Proceedings—Electrochemical Society, 1999, 98–16: 441–447

[12] SmartM CRatnakumarB VWhitcanackL, . Performance characteristics of lithium ion cells at low temperatures. In: Proceedings of the Annual Battery Conference on Applications and Advances, Long Beach, USA, 2002

[13] Smart M C, Ratnakumar B V. Effects of electrolyte composition on lithium plating in lithium-ion cells. Journal of the Electrochemical Society, 2011, 158(4): A379–A389

[14] Arai J, Nakahigashi R. Study of Li metal deposition in lithium ion battery during low-temperature cycle using in situ solid-state 7 Li nuclear magnetic resonance. Journal of the Electrochemical Society, 2017, 164(13): A3403–A3409

[15] Ratnakumar B V, Smart M C, Surampudi S. Electrochemical impedance spectroscopy and its applications. In: Annual Battery Conference on Applications and Advances, 2002, 273–277

[16] Ratnakumar B V, Smart M C, Surampudi S. Effects of SEI on the kinetics of lithium intercalation. Journal of Power Sources, 2001, 97–98: 137–139

[17] Smart M C, Ratnakumar B V, Surampudi S. . Irreversible capacities of graphite in low-temperature electrolytes for lithium-ion batteries. Journal of the Electrochemical Society, 1999, 146(11): 3963–3969

[18] Smart M C, Ratnakumar B V, Ewell R C. . The use of lithium-ion batteries for JPL’s Mars missions. Electrochimica Acta, 2018, 268: 27–40

[19] Kulova T L, Skundin A M. A critical review of electrode materials and electrolytes for low-temperature lithium-ion batteries. International Journal of Electrochemical Science, 2020, 15(9): 8638–8661

[20] Smart M C, Ratnakumar B V, Whitcanack L D. . Improved low-temperature performance of lithium-ion cells with quaternary carbonate-based electrolytes. Journal of Power Sources, 2003, 119–121: 349–358

[21] Smart M C, Ratnakumar B V, Behar A. . Gel polymer electrolyte lithium-ion cells with improved low temperature performance. Journal of Power Sources, 2007, 165(2): 535–543

[22] Smart M C, Lucht B L, Dalavi S. . The effect of additives upon the performance of MCMB/LiNi_xCo_1−xO₂ Li-ion cells containing methyl butyrate-based wide operating temperature range electrolytes. Journal of the Electrochemical Society, 2012, 159(6): A739–A751

[23] Jones J P, Smart M C, Krause F C. . The effect of electrolyte additives upon lithium plating during low temperature charging of graphite-LiNiCoAlO₂ lithium-ion three electrode cells. Journal of the Electrochemical Society, 2020, 167(2): 020536

[24] Etacheri V, Haik O, Goffer Y. . Effect of fluoroethylene carbonate (FEC) on the performance and surface chemistry of Si-nanowire Li-ion battery anodes. Langmuir, 2012, 28(1): 965–976

[25] Smart M C, Ratnakumar B V, Surampudi S. Use of organic esters as cosolvents in electrolytes for lithium-ion batteries with improved low temperature performance. Journal of the Electrochemical Society, 2002, 149(4): A361–A370

[26] Smart M C, Ratnakumar B V, Whitcanack L D. . Li-ion electrolytes containing ester Co-solvents for wide operating temperature range. ECS Transactions, 2008, 11(29): 99–108

[27] Zheng J, Yan P, Cao R. . Effects of propylene carbonate content in CsPF₆-containing electrolytes on the enhanced performances of graphite electrode for lithium-ion batteries. ACS Applied Materials & Interfaces, 2016, 8(8): 5715–5722

[28] Kim T, Song W, Son D Y. . Lithium-ion batteries: outlook on present, future, and hybridized technologies. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2019, 7(7): 2942–2964

[29] Purwanto A, Yudha C S, Ubaidillah U. . NCA cathode material: synthesis methods and performance enhancement efforts. Materials Research Express, 2018, 5(12): 122001

[30] Bruce P G, Armstrong A R, Gitzendanner R L. New intercalation compounds for lithium batteries: layered LiMnO₂. Journal of Materials Chemistry, 1999, 9(1): 193–198

[31] Liu C, Massé R, Nan X. . A promising cathode for Li-ion batteries: Li₃V₂(PO₄)₃. Energy Storage Materials, 2016, 4: 15–58

[32] Ni Q, Zheng L, Bai Y. . An extremely fast charging Li₃V₂(PO₄)₃ cathode at a 4.8 V cutoff voltage for Li-ion batteries. ACS Energy Letters, 2020, 5(6): 1763–1770

[33] Vadivel S, Phattharasupakun N, Wutthiprom J. . High-performance Li-ion batteries using nickel-rich lithium nickel cobalt aluminium oxide−nanocarbon core−shell cathode: in operando X–ray diffraction. ACS Applied Materials & Interfaces, 2019, 11(34): 30719–30727

[34] Yan P, Zheng J, Lv D. . Atomic-resolution visualization of distinctive chemical mixing behavior of Ni, Co, and Mn with Li in layered lithium transition-metal oxide cathode materials. Chemistry of Materials, 2015, 27(15): 5393–5401

[35] Zaghib K, Dontigny M, Perret P. . Electrochemical and thermal characterization of lithium titanate spinel anode in C–LiFePO₄//C-Li₄Ti₅O₁₂ cells at sub-zero temperatures. Journal of Power Sources, 2014, 248: 1050–1057

[36] Qin R, Wei Y, Zhai T. . LISICON structured Li₃V₂(PO₄)₃ with high rate and ultralong life for low-temperature lithium-ion batteries. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2018, 6(20): 9737–9746

[37] Ho C K, Li C Y V, Deng Z. . Hierarchical macropore-mesoporous shell carbon dispersed with Li₄Ti₅O₁₂ for excellent high rate sub-freezing Li-ion battery performance. Carbon, 2019, 145: 614–621

[38] Na Y, Sun X, Fan A. . Methods for enhancing the capacity of electrode materials in low-temperature lithium-ion batteries. Chinese Chemical Letters, 2020, 32(3): 973–982

[39] Li Q, Lu D, Zheng J. . Li⁺-desolvation dictating lithium-ion battery’s low-temperature performances. ACS Applied Materials & Interfaces, 2017, 9(49): 42761–42768

[40] Okumura T, Horiba T. Phase transition of carbonate solvent mixture solutions at low temperatures. Journal of Power Sources, 2016, 301: 138–142

[41] Smart M C, Ratnakumar B V, Chin K B. . Lithium-ion electrolytes containing ester cosolvents for improved low temperature performance. Journal of the Electrochemical Society, 2010, 157(12): A1361–A1374

[42] Smart M C, Ratnakumar B, Whitcanack L. . Performance demonstration of MCMB-LiNiCoO₂ cells containing electrolytes designed for wide operating temperature range. ECS Transactions, 2010, 25(36): 273–282

[43] Smart M C, Ratnakumar B V, Whitcanack L D. . Life verification of large capacity Yardney Li-ion cells and batteries in support of NASA missions. International Journal of Energy Research, 2010, 34(2): 116–132

[44] Smith K A, Smart M C, Prakash G K S. . Electrolytes containing fluorinated ester Co-solvents for low-temperature Li-ion cells. ECS Transactions, 2008, 11(29): 91–98

[45] Zhang S S. Lithium oxalyldifluoroborate as a salt for the improved electrolytes of Li-ion batteries. ECS Meeting Abstracts, 2006, MA2006-02(5): 267–267

[46] Li Q, Liu G, Cheng H. . Low-temperature electrolyte design for lithium-ion batteries: prospect and challenges. Chemistry (Weinheim an der Bergstrasse, Germany), 2021, 27(64): 15842–15865

[47] Jin Y, Kneusels N J H, Marbella L E. . Understanding fluoroethylene carbonate and binylene carbonate based electrolytes for Si anodes in lithium ion batteries with NMR spectroscopy. Journal of the American Chemical Society, 2018, 140(31): 9854–9867

[48] BachandG. Using copper nanoparticle additive to improve the performance of silicon anodes in lithium-ion batteries. Dissertation for the Master’s Degree. Reno: University of Nevada, 2017

[49] Holoubek J, Yu M, Yu S. . An all-fluorinated ester electrolyte for stable high-voltage Li metal batteries capable of ultra-low-temperature operation. ACS Energy Letters, 2020, 5(5): 1438–1447

[50] Zheng H, Xiang H, Jiang F. . Lithium difluorophosphate-based dual-salt low concentration electrolytes for lithium metal batteries. Advanced Energy Materials, 2020, 10(30): 2001440

[51] Thenuwara A C, Shetty P P, McDowell M T. Distinct nanoscale interphases and morphology of lithium metal electrodes operating at low temperatures. Nano Letters, 2019, 19(12): 8664–8672

[52] Zhang N, Deng T, Zhang S. . Critical review on low-temperature Li-ion/metal batteries. Advanced Materials, 2022, 34(15): 1–31

[53] Dong X, Wang Y G, Xia Y. Promoting rechargeable batteries operated at low temperature. Accounts of Chemical Research, 2021, 54(20): 3883–3894

[54] Holoubek J, Liu H, Wu Z. . Tailoring electrolyte solvation for Li metal batteries cycled at ultra-low temperature. Nature Energy, 2021, 6(3): 303–313

[55] Thenuwara A C, Shetty P P, Kondekar N. . Efficient low-temperature cycling of lithium metal anodes by tailoring the solid-electrolyte interphase. ACS Energy Letters, 2020, 5(7): 2411–2420

[56] Gupta A, Manthiram A. Designing advanced lithium-based batteries for low-temperature conditions. Advanced Energy Materials, 2020, 10(38): 2001972

[57] Zhou J, Ji H, Qian Y. . Molecular simulations guided polymer electrolyte towards superior low-temperature solid lithium-metal batteries. ACS Applied Materials & Interfaces, 2021, 13(41): 48810–48817

[58] Song S, Wu Y, Tang W. . Composite solid polymer electrolyte with garnet nanosheets in poly(ethylene oxide). ACS Sustainable Chemistry & Engineering, 2019, 7(7): 7163–7170

[59] Zhu F, Bao H, Wu X. . High-performance metal-organic framework-based single ion conducting solid-state electrolytes for low-temperature lithium metal batteries. ACS Applied Materials & Interfaces, 2019, 11(46): 43206–43213

[60] Fu C, Homann G, Grissa R. . A polymerized-ionic-liquid-based polymer electrolyte with high oxidative stability for 4 and 5 V class solid-state lithium metal batteries. Advanced Energy Materials, 2022, 12(27): 2200412

[61] Liu J, Xu R, Yan C. . In situ regulated solid electrolyte interphase via reactive separators for highly efficient lithium metal batteries. Energy Storage Materials, 2020, 30(5): 27–33

[62] Yao B, Ding Z, Zhang J. . Encapsulation of LiFePO₄ by in-situ graphitized carbon cage towards enhanced low temperature performance as cathode materials for lithium-ion batteries. Journal of Solid State Chemistry, 2014, 216: 9–12

[63] Fu C, Shen S, Wu R. . Facile controlled synthesis of hierarchically structured mesoporous Li₄Ti₅O₁₂/C/RGO composites as high-performance anode of lithium-ion batteries. Frontiers in Energy, 2022, 16(4): 607–612

[64] Gao Y, Rojas T, Wang K. . Low-temperature and high-rate-charging lithium metal batteries enabled by an electrochemically active monolayer-regulated interface. Nature Energy, 2020, 5(7): 534–542

[65] Bian Z, Tang Z, Xie J. . Preparation and lithium storage performances of G-C₃N₄/Si nanocomposites as anode materials for lithium-ion battery. Frontiers in Energy, 2020, 14(4): 759–766

[66] Wu H, Chan G, Choi J W. . Stable cycling of double-walled silicon nanotube battery anodes through solid-electrolyte interphase control. Nature Nanotechnology, 2012, 7(5): 310–315

[67] Hubble D, Brown D E, Zhao Y. . Liquid electrolyte development for low-temperature lithium-ion batteries. Energy & Environmental Science, 2022, 15(2): 550–578

[68] Domi Y, Usui H, Hirosawa T. . Impact of low temperatures on the lithiation and delithiation properties of Si-based electrodes in ionic liquid electrolytes. ACS Omega, 2022, 7(18): 15846–15853

RIGHTS & PERMISSIONS

Higher Education Press 2022