As an alternative to Li-ion batteries, aqueous Zn batteries have gained attention due to the abundance of Zn metal, low reduction potential (–0.76 V vs. standard hydrogen electrode), and high theoretical capacity (820 mAh g–1) of multivalent Zn2+ ion. However, the growth of Zn dendrites and the formation of irreversible surface reaction byproducts pose challenges for ensuring a long battery lifespan and commercialization. Herein, the Cu foil coated with a single-walled carbon nanotube (SWCNT) layer using a facile doctor blade casting method is utilized. The SWCNT-coated Cu foil demonstrates a significantly longer battery lifespan compared to the bare Cu in the half-cell tests. Through operando optical microscopy imaging, we are able to provide intuitive evidence that Zn deposition occurs between the carbon nanotube (CNT) coating and Cu substrate, in agreement with the computational results. Also, with various imaging techniques, the flat morphology and homogeneous distribution of Zn beneath the SWCNT layer are demonstrated. In addition, the full-cell using CNT-coated Cu exhibits a long cycle life compared to the control group, thereby demonstrating improved electrochemical performance with limited Zn for the cycling process.
The development of lithium–sulfur (Li–S) batteries is hindered by the disadvantages of shuttling of polysulfides and the sluggish redox kinetics of the conversion of sulfur species during discharge and charge. Herein, the crystallinities of a titanium nitride (TiN) film on copper-embedded carbon nanofibers (Cu-CNFs) are regulated and the nanofibers are used as interlayers to resolve the aforementioned crucial issues. A low-crystalline TiN-coated Cu-CNF (L-TiN-Cu-CNF) interlayer is compared with its highly crystalline counterpart (H-TiN-Cu-CNFs). It is demonstrated that the L-TiN coating not only strengthens the chemical adsorption toward polysulfides but also greatly accelerates the electrochemical conversion of polysulfides. Due to robust carbon frameworks and enhanced kinetics, impressive high-rate performance at 2 C (913 mAh g−1 based on sulfur) as well as remarkable cyclic stability up to 300 cycles (626 mAh g−1) with capacity retention of 46.5% is realized for L-TiN-Cu-CNF interlayer-configured Li–S batteries. Even under high loading (3.8 mg cm−2) of sulfur and relatively lean electrolyte (10 μL electrolyte per milligram sulfur) conditions, the Li–S battery equipped with L-TiN-Cu-CNF interlayers delivers a high capacity of 1144 mAh g−1 with cathodic capacity of 4.25 mAh cm−2 at 0.1 C, providing a potential pathway toward the design of multifunctional interlayers for highly efficient Li–S batteries.
Sodium-ion batteries (NIBs) have emerged as a promising alternative to commercial lithium-ion batteries (LIBs) due to the similar properties of the Li and Na elements as well as the abundance and accessibility of Na resources. Most of the current research has been focused on the half-cell system (using Na metal as the counter electrode) to evaluate the performance of the cathode/anode/electrolyte. The relationship between the performance achieved in half cells and that obtained in full cells, however, has been neglected in much of this research. Additionally, the trade-off in the relationship between electrochemical performance and cost needs to be given more consideration. Therefore, systematic and comprehensive insights into the research status and key issues for the full-cell system need to be gained to advance its commercialization. Consequently, this review evaluates the recent progress based on various cathodes and highlights the most significant challenges for full cells. Several strategies have also been proposed to enhance the electrochemical performance of NIBs, including designing electrode materials, optimizing electrolytes, sodium compensation, and so forth. Finally, perspectives and outlooks are provided to guide future research on sodium-ion full cells.
Ni–Fe-based oxides are among the most promising catalysts developed to date for the bottleneck oxygen evolution reaction (OER) in water electrolysis. However, understanding and mastering the synergy of Ni and Fe remain challenging. Herein, we report that the synergy between Ni and Fe can be tailored by crystal dimensionality of Ni, Fe-contained Ruddlesden–Popper (RP)-type perovskites (La0.125Sr0.875)n+1(Ni0.25Fe0.75)nO3n+1 (n = 1, 2, 3), where the material with n = 3 shows the best OER performance in alkaline media. Soft X-ray absorption spectroscopy spectra before and after OER reveal that the material with n = 3 shows enhanced Ni/Fe–O covalency to boost the electron transfer as compared to those with n = 1 and n = 2. Further experimental investigations demonstrate that the Fe ion is the active site and the Ni ion is the stable site in this system, where such unique synergy reaches the optimum at n = 3. Besides, as n increases, the proportion of unstable rock-salt layers accordingly decreases and the leaching of ions (especially Sr2+) into the electrolyte is suppressed, which induces a decrease in the leaching of active Fe ions, ultimately leading to enhanced stability. This work provides a new avenue for rational catalyst design through the dimensional strategy.
Inhibiting the agglomeration of molten aluminum particles packed in the binder network is a promising scheme to achieve efficient combustion of solid propellants. In this investigation, the hydroxyl-terminated structured fluorinated alcohol compound (PFD) was introduced to modify the traditional polyethylene glycol/polytetrahydrofuran block copolymerization (HTPE) binder; that is, a unique fluorinated polyether (FTPE) binder was synthesized by embedding fluorinated organic segments into the HTPE binder via crosslinking curing. The FTPE was applied in aluminum-based propellants for the first time. Due to the complete release of fluorinated organic active segments in the range of 300℃ to 400℃, the burning rate of FTPE-based propellant increased from 4.07 (0% PFD) to 6.36 mm/s (5% PFD), increased by 56.27% under 1 MPa. The reaction heat of FTPE propellants increased from 5.95 (0% PFD) to 7.18 MJ/kg (5% PFD) under 3.0 MPa, indicating that HTPE binder modified with PFD would be conducive to inhibiting the D90 of condensed combustion products (CCPs) dropped by 81.84% from 75.46 (0% PFD) to 13.71 μm (5% PFD) under 3.0 MPa, in consistent with the significant reduction of aluminum agglomerates observed on the quenched burning surface of the propellants. Those results demonstrated that a novel FTPE binder with PFD can release fluorinated organic active segments, which motivate preignition reaction with the alumina shell in the early stage of aluminum combustion, and then enhance the melting diffusion effect of aluminum to inhibit the agglomeration.
Suppressing nonradiative recombination and releasing residual strain are prerequisites to improving the efficiency and stability of perovskite solar cells (PSCs). Here, long-chain polyacrylic acid (PAA) is used to reinforce SnO2 film and passivate SnO2 defects, forming a structure similar to “reinforced concrete” with high tensile strength and fewer microcracks. Simultaneously, PAA is also introduced to the SnO2/perovskite interface as a “buffer spring” to release residual strain, which also acts as a “dual-side passivation interlayer” to passivate the oxygen vacancies of SnO2 and Pb dangling bonds in halide perovskites. As a result, the best inorganic CsPbBr3 PSC achieves a champion power conversion efficiency of 10.83% with an ultrahigh open-circuit voltage of 1.674 V. The unencapsulated PSC shows excellent stability under 80% relative humidity and 80℃ over 120 days.
Ingenious design and fabrication of advanced carbon-based sulfur cathodes are extremely important to the development of high-energy lithium-sulfur batteries, which hold promise as the next-generation power source. Herein, for the first time, we report a novel versatile hyphae-mediated biological assembly technology to achieve scale production of hyphae carbon fibers (HCFs) derivatives, in which different components including carbon, metal compounds, and semiconductors can be homogeneously assembled with HCFs to form composite networks. The mechanism of biological adsorption assembly is also proposed. As a representative, reduced graphene oxides (rGOs) decorated with hollow carbon spheres (HCSs) successfully co-assemble with HCFs to form HCSs@rGOs/HCFs hosts for sulfur cathodes. In this unique architecture, not only large accommodation space for sulfur but also restrained volume expansion and fast charge transport paths are realized. Meanwhile, multiscale physical barriers plus chemisorption sites are simultaneously established to anchor soluble lithium polysulfides. Accordingly, the designed HCSs@rGOs/HCFs-S cathodes deliver a high capacity (1189 mA h g−1 at 0.1 C) and good high-rate capability (686 mA h g−1 at 5 C). Our work provides a new approach for the preparation of high-performance carbon-based electrodes for energy storage devices.
Li−I2 batteries have attracted much interest due to their high capacity, exceptional rate performance, and low cost. Even so, the problems of unstable Li anode/electrolyte interface and severe polyiodide shuttle in Li−I2 batteries need to be tackled. Herein, the interfacial reactions on the Li anode and I2 cathode have been effectively optimized by employing a well-designed gel polymer electrolyte strengthened by cross-linked Ti–O/Si–O (GPETS). The interpenetrating network-reinforced GPETS with high ionic conductivity (1.88 × 10−3 S cm−1 at 25℃) and high mechanical strength endows uniform Li deposition/stripping over 1800 h (at 1.0 mA cm−2, with a plating capacity of 3.0 mAh cm−2). Moreover, the GPETS abundant in surface hydroxyls is capable of capturing soluble polyiodides at the interface and accelerating their conversion kinetics, thus synergistically mitigating the shuttle effect. Benefiting from these properties, the use of GPETS results in a high capacity of 207 mAh g−1 (1 C) and an ultra-low fading rate of 0.013% per cycle over 2000 cycles (5 C). The current study provides new insights into advanced electrolytes for Li−I2 batteries.
The commercialization of silicon-based anodes is affected by their low initial Coulombic efficiency (ICE) and capacity decay, which are attributed to the formation of an unstable solid electrolyte interface (SEI) layer. Herein, a feasible and cost-effective prelithiation method under a localized high-concentration electrolyte system (LHCE) for the silicon–silica/graphite (Si–SiO2/C@G) anode is designed for stabilizing the SEI layer and enhancing the ICE. The thin SiO2/C layers with –NH2 groups covered on nano-Si surfaces are demonstrated to be beneficial to the prelithiation process by density functional theory calculations and electrochemical performance. The SEI formed under LHCE is proven to be rich in ionic conductivity, inorganic substances, and flexible organic products. Thus, faster Li+ transportation across the SEI further enhances the prelithiation effect and the rate performance of Si–SiO2/C@G anodes. LHCE also leads to uniform decomposition and high stability of the SEI with abundant organic components. As a result, the prepared anode shows a high reversible specific capacity of 937.5 mAh g−1 after 400 cycles at a current density of 1 C. NCM 811‖Li-SSG-LHCE full cell achieves a high-capacity retention of 126.15 mAh g−1 at 1 C over 750 cycles with 84.82% ICE, indicating the great value of this strategy for Si-based anodes in large-scale applications.
Electrocatalytic water splitting seems to be an efficient strategy to deal with increasingly serious environmental problems and energy crises but still suffers from the lack of stable and efficient electrocatalysts. Designing practical electrocatalysts by introducing defect engineering, such as hybrid structure, surface vacancies, functional modification, and structural distortions, is proven to be a dependable solution for fabricating electrocatalysts with high catalytic activities, robust stability, and good practicability. This review is an overview of some relevant reports about the effects of defect engineering on the electrocatalytic water splitting performance of electrocatalysts. In detail, the types of defects, the preparation and characterization methods, and catalytic performances of electrocatalysts are presented, emphasizing the effects of the introduced defects on the electronic structures of electrocatalysts and the optimization of the intermediates' adsorption energy throughout the review. Finally, the existing challenges and personal perspectives of possible strategies for enhancing the catalytic performances of electrocatalysts are proposed. An in-depth understanding of the effects of defect engineering on the catalytic performance of electrocatalysts will light the way to design high-efficiency electrocatalysts for water splitting and other possible applications.
Lithium–sulfur batteries (LSBs) have drawn significant attention owing to their high theoretical discharge capacity and energy density. However, the dissolution of long-chain polysulfides into the electrolyte during the charge and discharge process (“shuttle effect”) results in fast capacity fading and inferior electrochemical performance. In this study, Mn2O3 with an ordered mesoporous structure (OM-Mn2O3) was designed as a cathode host for LSBs via KIT-6 hard templating, to effectively inhibit the polysulfide shuttle effect. OM-Mn2O3 offers numerous pores to confine sulfur and tightly anchor the dissolved polysulfides through the combined effects of strong polar–polar interactions, polysulfides, and sulfur chain catenation. The OM-Mn2O3/S composite electrode delivered a discharge capacity of 561 mA h g−1 after 250 cycles at 0.5 C owing to the excellent performance of OM-Mn2O3. Furthermore, it retained a discharge capacity of 628 mA h g−1 even at a rate of 2 C, which was significantly higher than that of a pristine sulfur electrode (206 mA h g−1). These findings provide a prospective strategy for designing cathode materials for high-performance LSBs.
Direct recycling is a novel approach to overcoming the drawbacks of conventional lithium-ion battery (LIB) recycling processes and has gained considerable attention from the academic and industrial sectors in recent years. The primary objective of directly recycling LIBs is to efficiently recover and restore the active electrode materials and other components in the solid phase while retaining electrochemical performance. This technology's advantages over traditional pyrometallurgy and hydrometallurgy are cost-effectiveness, energy efficiency, and sustainability, and it preserves the material structure and morphology and can shorten the overall recycling path. This review extensively discusses the advancements in the direct recycling of LIBs, including battery sorting, pretreatment processes, separation of cathode and anode materials, and regeneration and quality enhancement of electrode materials. It encompasses various approaches to successfully regenerate high-value electrode materials and streamlining the recovery process without compromising their electrochemical properties. Furthermore, we highlight key challenges in direct recycling when scaled from lab to industries in four perspectives: (1) battery design, (2) disassembling, (3) electrode delamination, and (4) commercialization and sustainability. Based on these challenges and changing market trends, a few strategies are discussed to aid direct recycling efforts, such as binders, electrolyte selection, and alternative battery designs; and recent transitions and technological advancements in the battery industry are presented.
For the performance optimization strategies of hard carbon, heteroatom doping is an effective way to enhance the intrinsic transfer properties of sodium ions and electrons for accelerating the reaction kinetics. However, the previous work focuses mainly on the intrinsic physicochemical property changes of the material, but little attention has been paid to the resulting interfacial regulation of the electrode surface, namely the formation of solid electrolyte interphase (SEI) film. In this work, element F, which has the highest electronegativity, was chosen as the doping source to, more effectively, tune the electronic structure of the hard carbon. The effect of F-doping on the physicochemical properties of hard carbon was not only systematically analyzed but also investigated with spectroscopy, optics, and in situ characterization techniques to further verify that appropriate F-doping plays a positive role in constructing a homogenous and inorganic-rich SEI film. The experimentally demonstrated link between the electronic structure of the electrode and the SEI film properties can reframe the doping optimization strategy as well as provide a new idea for the design of electrode materials with low reduction kinetics to the electrolyte. As a result, the optimized sample with the appropriate F-doping content exhibits the best electrochemical performance with high capacity (434.53 mA h g−1 at 20 mA g−1) and excellent rate capability (141 mA h g−1 at 400 mA g−1).
Solid-state supercapacitors (SSCs) are emerging as one of the promising energy storage devices due to their high safety, superior power density, and excellent cycling life. However, performance degradation and safety issues under extreme conditions are the main challenges for the practical application. With the expansion of human activities, such as space missions, polar exploration, and so on, the investigation of SSC with wide temperature tolerance, high energy density, power density, and sustainability is highly desired. In this review, the effects of temperature on SSC are systematically illustrated and clarified, including the properties of the electrolyte, ion diffusion, and reaction dynamics of the supercapacitor. Subsequently, we summarize the recent advances in wide-temperature-range SSCs from the aspect of electrolyte modification, electrode design, and interface adjustment between electrode and electrolyte, especially with critical concerns on ionic conductivity and cycling stability. In the end, a perspective is presented, expecting to promote the practical application of the SSC in harsh conditions.
Herein, we have designed a highly active and robust trifunctional electrocatalyst derived from Prussian blue analogs, where Co4N nanoparticles are encapsulated by Fe embedded in N-doped carbon nanocubes to synthesize hierarchically structured Co4N@Fe/N–C for rechargeable zinc–air batteries and overall water-splitting electrolyzers. As confirmed by theoretical and experimental results, the high intrinsic oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction activities of Co4N@Fe/N–C were attributed to the formation of the heterointerface and the modulated local electronic structure. Moreover, Co4N@Fe/N–C induced improvement in these trifunctional electrocatalytic activities owing to the hierarchical hollow nanocube structure, uniform distribution of Co4N, and conductive encapsulation by Fe/N–C. Thus, the rechargeable zinc–air battery with Co4N@Fe/N–C delivers a high specific capacity of 789.9 mAh g−1 and stable voltage profiles over 500 cycles. Furthermore, the overall water electrolyzer with Co4N@Fe/N–C achieved better durability and rate performance than that with the Pt/C and IrO2 catalysts, delivering a high Faradaic efficiency of 96.4%. Along with the great potential of the integrated water electrolyzer powered by a zinc–air battery for practical applications, therefore, the mechanistic understanding and active site identification provide valuable insights into the rational design of advanced multifunctional electrocatalysts for energy storage and conversion.