The sluggish kinetics of complicated multiphase conversions and the severe shuttling effect of lithium polysulfides (LiPSs) significantly hinder the applications of Li-S battery, which is one of the most promising candidates for the next-generation energy storage system. Herein, a bifunctional electrocatalyst, indium phthalocyanine self-assembled with carbon nanotubes (InPc@CNT) composite material, is proposed to promote the conversion kinetics of both reduction and oxidation processes, demonstrating a bidirectional catalytic effect on both nucleation and dissolution of Li2S species. The theoretical calculation shows that the unique electronic configuration of InPc@CNT is conducive to trapping soluble polysulfides in the reduction process, as well as the modulation of electron transfer dynamics also endows the dissolution of Li2S in the oxidation reaction, which will accelerate the effectiveness of catalytic conversion and facilitate sulfur utilization. Moreover, the InPc@CNT modified separator displays lower overpotential for polysulfide transformation, alleviating polarization of electrode during cycling. The integrated spectroscopy analysis, HRTEM, and electrochemical study reveal that the InPc@CNT acts as an efficient multifunctional catalytic center to satisfy the requirements of accelerating charging and discharging processes. Therefore, the Li-S battery with InPc@CNT-modified separator obtains a discharge-specific capacity of 1415 mAh g-1 at a high rate of 0.5 C. Additionally, the 2 Ah Li-S pouch cells deliver 315 Wh kg-1 and achieved 80% capacity retention after 50 cycles at 0.1 C with a high sulfur loading of 10 mg cm-2. Our study provides a practical method to introduce bifunctional electrocatalysts for boosting the electrochemical properties of Li-S batteries.
In this study, ZnO formation during the dissolution-passivation process of Zn anodes is observed via in situ Raman and optical characterization. The Zn passivation during galvanostatic anodization merely follows the dissolution-precipitation model, whereas that of potentiodynamic polarization exhibits different behaviors in different potential ranges. Initially, the Zn electrode is gradually covered by a ZnO precipitation film and then undergoes solid-state oxidation at ~255 mV. The starting point of solid-state oxidation is well indicated by the abrupt current drop and yellow coloration of the electrode surface. During the pseudo passivation, an intense current oscillation is observed. Further, blink-like color changes between yellow and dark blue are revealed for the first time, implying that the oscillation is caused by the dynamic adsorption and desorption of OH groups. The as-formed ZnOs then experience a dissolution-reformation evolution, during which the crystallinity of the primary ZnO film is improved but the solid-state-formed ZnO layer becomes rich in oxygen vacancies. Eventually, oxide densification is realized, contributing to the Zn passivation. This study provides new insights into the Zn dissolution-passivation behavior, which is critical for the future optimization of Zn batteries.
Si anode is of paramount importance for advanced energy-dense lithium-ion batteries (LIBs). However, the large volume change as well as stress generates during its lithiation-delithiation process poses a great challenge to the long-term cycling and hindering its application. Herein this work, a composite binder is prepared with a soft component, guar gum (GG), and a rigid linear polymer, anionic polyacrylamide (APAM). Rich hydroxy, carboxyl, and amide groups on the polymer chains not only enable intermolecular crosslinking to form a web-like binder, A2G1, but also realize strong chemical binding as well as physical encapsulating to Si particles. The resultant electrode shows limited thickness change of merely 9% on lithiation and almost recovers its original thickness on delithiation. It demonstrates high reversible capacity of 2104.3 mAh g-1 after 100 cycles at a current density of 1800 mA g-1, and in constant capacity (1000 mAh g-1) test, it also shows a long life of 392 cycles. Therefore, this soft-hard combining web-like binder illustrates its great potential in the future applications.
Metal-organic framework (MOF)-derived carbon composites have been considered as the promising materials for energy storage. However, the construction of MOF-based composites with highly controllable mode via the liquid-liquid synthesis method has a great challenge because of the simultaneous heterogeneous nucleation on substrates and the self-nucleation of individual MOF nanocrystals in the liquid phase. Herein, we report a bidirectional electrostatic generated self-assembly strategy to achieve the precisely controlled coatings of single-layer nanoscale MOFs on a range of substrates, including carbon nanotubes (CNTs), graphene oxide (GO), MXene, layered double hydroxides (LDHs), MOFs, and SiO2. The obtained MOF-based nanostructured carbon composite exhibits the hierarchical porosity (Vmeso/Vmicro: 2.4), ultrahigh N content of 12.4 at.% and “dual electrical conductive networks.” The assembled aqueous zinc-ion hybrid capacitor (ZIC) with the prepared nanocarbon composite as a cathode shows a high specific capacitance of 236 F g-1 at 0.5 A g-1, great rate performance of 98 F g-1 at 100 A g-1, and especially, an ultralong cycling stability up to 230 000 cycles with the capacitance retention of 90.1%. This work develops a repeatable and general method for the controlled construction of MOF coatings on various functional substrates and further fabricates carbon composites for ZICs with ultrastability.
Sodium-ion batteries (SIBs) have rapidly risen to the forefront of energy storage systems as a promising supplementary for Lithium-ion batteries (LIBs). Na3V2(PO4)2F3 (NVPF) as a common cathode of SIBs, features the merits of high operating voltage, small volume change and favorable specific energy density. However, it suffers from poor cycling stability and rate performance induced by its low intrinsic conductivity. Herein, we propose an ingenious strategy targeting superior SIBs through cross-linked NVPF with multi-dimensional nanocarbon frameworks composed of amorphous carbon and carbon nanotubes (NVPF@C@CNTs). This rational design ensures favorable particle size for shortened sodium ion transmission pathway as well as improved electronic transfer network, thus leading to enhanced charge transfer kinetics and superior cycling stability. Benefited from this unique structure, significantly improved electrochemical properties are obtained, including high specific capacity (126.9 mAh g-1 at 1 C, 1 C = 128 mA g-1) and remarkably improved long-term cycling stability with 93.9% capacity retention after 1000 cycles at 20 C. The energy density of 286.8 Wh kg-1 can be reached for full cells with hard carbon as anode (NVPF@C@CNTs//HC). Additionally, the electrochemical performance of the full cell at high temperature is also investigated (95.3 mAh g-1 after 100 cycles at 1 C at 50 ℃). Such nanoscale dual-carbon networks engineering and thorough discussion of ion diffusion kinetics might make contributions to accelerating the process of phosphate cathodes in SIBs for large-scale energy storages.
Scintillation semiconductors play increasingly important medical diagnosis and industrial inspection roles. Recently, two-dimensional (2D) perovskites have been shown to be promising materials for medical X-ray imaging, but they are mostly used in low-energy (≤130 keV) regions. Direct detection of MeV X-rays, which ensure thorough penetration of the thick shell walls of containers, trucks, and aircraft, is also highly desired in practical industrial applications. Unfortunately, scintillation semiconductors for high-energy X-ray detection are currently scarce. Here, This paper reports a 2D (C4H9NH3)2PbBr4 single crystal with outstanding sensitivity and stability toward X-ray radiation that provides an ultra-wide detectable X-ray range of between 8.20 nGyair s-1 (50 keV) and 15.24 mGyair s-1 (9 MeV). The (C4H9NH3)2PbBr4 single-crystal detector with a vertical structure is used for high-performance X-ray imaging, delivering a good spatial resolution of 4.3 lp mm-1 in a plane-scan imaging system. Low ionic migration in the 2D perovskite enables the vertical device to be operated with hundreds of keV to MeV X-ray radiation at high bias voltages, leading to a sensitivity of 46.90 μC Gyair-1 cm-2 (-1.16 V μm-1) with 9 MeV X-ray radiation, demonstrating that 2D perovskites have enormous potential for high-energy industrial applications.
We present a method to fabricate handcrafted thermoelectric devices on standard office paper substrates. The devices are based on thin films of WS2, Te, and BP (P-type semiconductors) and TiS3 and TiS2 (N-type semiconductors), deposited by simply rubbing powder of these materials against paper. The thermoelectric properties of these semiconducting films revealed maximum Seebeck coefficients of (+1.32 ± 0.27) mV K-1 and (-0.82 ± 0.15) mV K-1 for WS2 and TiS3, respectively. Additionally, Peltier elements were fabricated by interconnecting the P- and N-type films with graphite electrodes. A thermopower value up to 6.11 mV K-1 was obtained when the Peltier element were constructed with three junctions. The findings of this work show proof-of-concept devices to illustrate the potential application of semiconducting van der Waals materials in future thermoelectric power generation as well as temperature sensing for low-cost disposable electronic devices.
In spite of the high potential economic feasibility of the tandem solar cells consisting of the halide perovskite and the kesterite Cu2ZnSn(S,Se)4 (CZTSSe), they have rarely been demonstrated due to the difficulty in implementing solution-processed perovskite top cell on the rough surface of the bottom cells. Here, we firstly demonstrate an efficient monolithic two-terminal perovskite/CZTSSe tandem solar cell by significantly reducing the surface roughness of the electrochemically deposited CZTSSe bottom cell. The surface roughness (Rrms) of the CZTSSe thin film could be reduced from 424 to 86 nm by using the potentiostatic mode rather than using the conventional galvanostatic mode, which can be further reduced to 22 nm after the subsequent ion-milling process. The perovskite top cell with a bandgap of 1.65 eV could be prepared using a solution process on the flattened CZTSSe bottom cell, resulting in the efficient perovskite/CZTSSe tandem solar cells. After the current matching between two subcells involving the thickness control of the perovskite layer, the best performing tandem device exhibited a high conversion efficiency of 17.5% without the hysteresis effect.
Here we introduce bismuth-based catalysts for the efficient electrochemical reduction of CO2 to formic acid (HCOOH), which are composed of petal-shaped Bi2O2CO3 (BOC) that spontaneously formed from Bi thin film in aqueous carbonate solution at room temperature. During the electrochemical reduction process, the BOC petals transform to reduced BOC (R-BOC) consisting of individual BOC and Bi domains. Lattice mismatch between both domains induces biaxial strain at the interfaces. Density functional theory calculations suggest that the tensile strain on the Bi domain stabilizes the *OCHO intermediate, reducing the thermodynamic barrier toward CO2 conversion to HCOOH. Together with the thermodynamic benefit and the unique nanoporous petal-shaped morphology, R-BOC petals have a superior Faradaic efficiency of 95.9% at -0.8 VRHE for the electrochemical conversion of CO2 to HCOOH. This work demonstrates that the spontaneously formed binary phases with desirable lattice strain can increase the activity of bismuth catalysts to the CO2 reduction reaction; such a strategy can be applicable in design of various electrocatalysts.
Flexible electronic sensors composed of flexible film and conductive materials play an increasingly important role in wearable and internet information transmission. It has received more and more attention and made some progress over the decades. However, it is still a great challenge to prepare biocompatible and highly transparent conductive films. Egg white is a pure natural protein-rich material. Hydroxypropylmethyl cellulose has a good compatibility and high transparency, which is an ideal material for flexible sensors. Here, we overcome the problem of poor mechanical flexibility and electrical conductivity of protein, and develop a high transparency and good flexibility hydroxypropylmethyl cellulose/egg white protein composite membrane-based triboelectric nanogenerator (‘X’-TENG). The experimental results show that the flexible pressure sensor based on ‘X’-TENG has a high sensitivity, fast response speed, and low detection limit. It can even be used as a touch/pressure sensing artificial electronic skin. It can also be made into an intelligent waffle keyboard for recording and tracking users of the keyboard. Our strategy may provide a new way to easily build flexible electronic sensors and move toward practical applications.
Silver-zinc (Ag-Zn) batteries are a promising battery system for flexible electronics owing to their high safety, high energy density, and stable output voltage. However, poor cycling performance, low areal capacity, and inferior flexibility limit the practical application of Ag-Zn batteries. Herein, we develop a flexible quasi-solid-state Ag-Zn battery system with superior performance by using mild electrolyte and binder-free electrodes. Copper foam current collector is introduced to impede the growth of Zn dendrite, and the structure of Ag cathode is engineered by electrodeposition and chloridization process to improve the areal capacity. This novel battery demonstrates a remarkable cycle retention of 90% for 200 cycles at 3 mA cm-2. More importantly, this binder-free battery can afford a high capacity of 3.5 mAh cm-2 at 3 mA cm-2, an outstanding power density of 2.42 mW cm-2, and a maximum energy density of 3.4 mWh cm-2. An energy management circuit is adopted to boost the output voltage of a single battery, which can power electronic ink display and Bluetooth temperature and humidity sensor. The developed battery can even operate under the extreme conditions, such as being bent and sealed in solid ice. This work offers a path for designing electrodes and electrolyte toward high-performance flexible Ag-Zn batteries.
We report the dielectric constant of 1 M LiPF6 in EC:EMC 3:7 w/w (ethylene carbonate/ethyl methyl carbonate) in addition to neat EC:EMC 3:7 w/w. Using three Debye relaxations, the static permittivity value, or dielectric constant, is extrapolated to 18.5, which is compared to 18.7 for the neat solvent mixture. The EC solvent is found to strongly coordinate with the Li+ cations of the salt, which results in a loss of dielectric contribution to the electrolyte. However, the small amplitude and large uncertainty in relaxation frequency for EMC cloud definitive identification of the Li+ solvation shell. Importantly, the loss of the free EC permittivity contribution due to Li+ solvation is almost completely balanced by the positive contribution of the associated LiPF6 salt, demonstrating that a significant quantity of dipolar ion pairs exists in 1 M LiPF6 in EC:EMC 3:7.
Oxygen vacancies enable modulating surface reconstruction of transition metal oxides containing metal-oxygen polyhedrons into metallic oxyhydroxide for oxygen evolution reaction (OER), while revealing reconstructing mechanism is stuck by the requirement to precisely control exact sites of these vacancies. Herein, oxygen vacancies are localized only within MoO4 tetrahedrons rather than CoO6 octahedrons in CoMoO4 catalyst, guaranteeing coherent reconstruction of CoO6 octahedrons into pure CoOOH with tunable activities for OER. Meanwhile, distorted tetrahedron accelerates the dissolution of Mo atoms into alkaline electrolyte, triggering spontaneous transition of partial CoMoO4 into Co(OH)2. CoO6 octahedrons in both CoMoO4 and Co(OH)2 can transform pure CoOOH completely at lower potential, resulting in excess intrinsic activity whose summit is identified by overpotential at 10 mA cm-2 with 22.9% reduction and Tafel slope with 65.3% reduction. Well-defined manipulation over the distorted polyhedrons offers one versatile knob to precisely modulate electronic structure of oxide catalysts with outstanding OER performance.
Urea synthesis through the simultaneous electrocatalytic reduction of N2 and CO2 molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production, in which the development of stable, highly efficient, and highly selective catalysts to boost the chemisorption, activation, and coupling of inert N2 and CO2 molecules remains rather challenging. Herein, by means of density functional theory computations, we proposed a new class of two-dimensional nanomaterials, namely, transition-metal phosphide monolayers (TM2P, TM = Ti, Fe, Zr, Mo, and W), as the potential electrocatalysts for urea production. Our results showed that these TM2P materials exhibit outstanding stability and excellent metallic properties. Interestingly, the Mo2P monolayer was screened out as the best catalyst for urea synthesis due to its small kinetic energy barrier (0.35 eV) for C-N coupling, low limiting potential (-0.39 V), and significant suppressing effects on the competing side reactions. The outstanding catalytic activity of the Mo2P monolayer can be ascribed to its optimal adsorption strength with the key *NCON species due to its moderate positive charges on the Mo active sites. Our findings not only propose a novel catalyst with high-efficiency and high-selectivity for urea production but also further widen the potential applications of metal phosphides in electrocatalysis.
Lithium metal batteries have been considered as one of the most promising next-generation power-support devices due to their high specific energy and output voltage. However, the uncontrollable side-reaction and lithium dendrite growth lead to the limited serving life and hinder the practical application of lithium metal batteries. Here, a tri-monomer copolymerized gel polymer electrolyte (TGPE) with a cross-linked reticulation structure was prepared by introducing a cross-linker (polyurethane group) into the acrylate-based in situ polymerization system. The soft segment of polyurethane in TGPE enables the far migration of lithium ions, and the -NH forms hydrogen bonds in the hard segment to build a stable cross-linked framework. This system hinders anion migration and leads to a high Li+ migration number (
Poly(ethylene oxide) (PEO) and Li6.75La3Zr1.75Ta0.25O12 (LLZTO)-based composite polymer electrolytes (CPEs) are considered one of the most promising solid electrolyte systems. However, agglomeration of LLZTO within PEO and lack of Li+ channels result in poor electrochemical properties. Herein, a functional supramolecular combination (CD-TFSI) consisting of active β-cyclodextrin (CD) supramolecular with self-assembled LiTFSI salt is selected as an interface modifier to coat LLZTO fillers. Benefiting from vast H-bonds formed between β-CD and PEO matrix and/or LLZTO, homogeneous dispersion and tight interface contact are obtained. Moreover, 6Li NMR spectra confirm a new Li+ transmission pathway from PEO matrix to LLZTO ceramic then to PEO matrix in the as-prepared PEO/LLZTO@CD-TFSI CPEs due to the typical cavity structure of β-CD. As a proof, the conductivity is increased from 5.3 × 10-4 S cm-1 to 8.7 × 10-4 S cm-1 at 60 ℃, the Li+ transference number is enhanced from 0.38 to 0.48, and the electrochemical stability window is extended to 5.1 V versus Li/Li+. Li‖LiFePO4 CR2032 coin full cells and pouch cells prove the practical application of the as-prepared PEO/LLZTO@CD-TFSI CPEs. This work offers a new strategy of interface modifying LLZTO fillers with functional supramolecular combination to optimize PEO/LLZTO CPEs for solid lithium batteries.
Rechargeable Zn-air batteries (ZAB) have drawn extensive attention due to their eco-friendliness and safety. However, the lack of high-performance and low-cost oxygen redox reactions (OER and ORR) catalysts has become one of the main stumbling blocks in their development. Herein, we successfully fabricate a CoFe nanobubble encapsulated in nitrogen-doped carbon nanocage on wood carbon support (CoFe@NC/WC) via pyrolysis of a novel Prussian blue analog (PBA)/spruce precursor. The hierarchical CoFe@NC/WC catalyst exhibits an excellent potential difference of 0.74 V between the OER potential at 10 mA cm-2 and half-wave potential of ORR in 0.1 M KOH, comparable to recently reported preeminent electrocatalysts. Further, CoFe@NC/WC shows outstanding electrochemical performance in liquid ZAB, with a peak power density of 138.9 mW cm-2 and a specific capacity of 763.5 mAh g-1. More importantly, a bacterial cellulose nanofiber reinforced polyacrylic acid (BC-PAA) hydrogel electrolyte shows ultrahigh tensile-breaking stress of 1.58 MPa. In conjunction with the as-prepared CoFe@NC/WC catalyst, BC-PAA-based wearable ZAB displays impressive rechargeability and foldability, and can power portable electronics, such as electronic timer and mobile phone, in bent states. This work provides a new approach toward high-activity and low-cost catalysts for ZAB.
Rhombohedral phase HfxZr1-xO2 (HZO, x from 0 to 1) films are promising for achieving robust ferroelectric polarization without the need for an initial wake-up pre-cycling, as is normally the case for the more commonly studied orthorhombic phase. However, a large spontaneous polarization observed in rhombohedral films is not fully understood, and there are also large discrepancies between experimental and theoretical predictions. In this work, in rhombohedral ZrO2 thin films, we show that oxygen vacancies are not only a key factor for stabilizing the phase, but they are also a source of ferroelectric polarization in the films. This is shown experimentally through the investigation of the structural properties, chemical composition and the ferroelectric properties of the films before and after an annealing at moderate temperature (400 °C) in an oxygen environment to reduce the VO concentration compared. The experimental work is supported by density functional theory (DFT) calculations which show that the rhombohedral phase is the most stable one in highly oxygen defective ZrO2 films. The DFT calculations also show that VO contribute to the ferroelectric polarization. Our findings reveal the importance of VO for stabilizing rhombohedral ZrO2 thin films with superior ferroelectric properties.
Slurry casting has been used to fabricate lithium-ion battery electrodes for decades, which involves toxic and expensive organic solvents followed by high-cost vacuum drying and electrode calendering. This work presents a new manufacturing method using a nonthermal plasma to create inter-particle binding without using any polymeric binding materials, enabling solvent-free manufacturing electrodes with any electrochemistry of choice. The cold-plasma-coating technique enables fabricating electrodes with thickness (>200 μm), high mass loading (>30 mg cm-2), high peel strength, and the ability to print lithium-ion batteries in an arbitrary geometry. This crosscutting, chemistry agnostic, platform technology would increase energy density, eliminate the use of solvents, vacuum drying, and calendering processes during production, and reduce manufacturing cost for current and future cell designs. Here, lithium iron phosphate and lithium cobalt oxide were used as examples to demonstrate the efficacy of the cold-plasma-coating technique. It is found that the mechanical peel strength of cold-plasma-coating-manufactured lithium iron phosphate is over an order of magnitude higher than that of slurry-casted lithium iron phosphate electrodes. Full cells assembled with a graphite anode and the cold-plasma-coating-lithium iron phosphate cathode offer highly reversible cycling performance with a capacity retention of 81.6% over 500 cycles. For the highly conductive cathode material lithium cobalt oxide, an areal capacity of 4.2 mAh cm-2 at 0.2 C is attained. We anticipate that this new, highly scalable manufacturing technique will redefine global lithium-ion battery manufacturing providing significantly reduced plant footprints and material costs.
The improvement in the efficiency of inverted perovskite solar cells (PSCs) is significantly limited by undesirable contact at the NiOX/perovskite interface. In this study, a novel microstructure-control technology is proposed for fabrication of porous NiOX films using Pluronic P123 as the structure-directing agent and acetylacetone (AcAc) as the coordination agent. The synthesized porous NiOX films enhanced the hole extraction efficiency and reduced recombination defects at the NiOX/perovskite interface. Consequently, without any modification, the power conversion efficiency (PCE) of the PSC with MAPbI3 as the absorber layer improved from 16.50% to 19.08%. Moreover, the PCE of the device composed of perovskite Cs0.05(MA0.15FA0.85)0.95Pb(I0.85Br0.15)3 improved from 17.49% to 21.42%. Furthermore, the application of the fabricated porous NiOX on fluorine-doped tin oxide (FTO) substrates enabled the fabrication of large-area PSCs (1.2 cm2) with a PCE of 19.63%. This study provides a novel strategy for improving the contact at the NiOX/perovskite interface for the fabrication of high-performance large-area perovskite solar cells.
Organic redox compounds are attractive cathode materials in aqueous zinc-ion batteries owing to their low cost, environmental friendliness, multiple-electron-transfer reactions, and resource sustainability. However, the realized energy density is constrained by the limited capacity and low voltage. Herein, copper-tetracyanoquinodimethane (CuTCNQ), an organic charge-transfer complex is evaluated as a zinc-ion battery cathode owing to the good electron acceptation ability in the cyano groups that improves the voltage output. Through electrochemical activation, electrolyte optimization, and adoption of graphene-based separator, CuTCNQ-based aqueous zinc-ion batteries deliver much improved rate performance and cycling stability with anti-self-discharge properties. The structural evolution of CuTCNQ during discharge/charge are investigated by ex situ Fourier transform infra-red (FT-IR) spectra, ex situ X-ray photoelectron spectroscopy (XPS), and in situ ultraviolet visible spectroscopy (UV-vis), revealing reversible redox reactions in both cuprous cations (Cu+) and organic anions (TCNQx-1), thus delivering a high voltage output of 1.0 V and excellent discharge capacity of 158 mAh g-1. The remarkable electrochemical performance in Zn//CuTCNQ is ascribed to the strong inductive effect of cyano groups in CuTCNQ that elevated the voltage output and the graphene-modified separator that inhibited CuTCNQ dissolution and shuttle effect in aqueous electrolytes.
CO2 electrochemical reduction reaction (CO2RR) to formate is a hopeful pathway for reducing CO2 and producing high-value chemicals, which needs highly selective catalysts with ultra-broad potential windows to meet the industrial demands. Herein, the nanorod-like bimetallic In2O3/Bi2O3 catalysts were successfully synthesized by pyrolysis of bimetallic InBi-MOF precursors. The abundant oxygen vacancies generated from the lattice mismatch of Bi2O3 and In2O3 reduced the activation energy of CO2 to *CO2.- and improved the selectivity of *CO2.- to formate simultaneously. Meanwhile, the carbon skeleton derived from the pyrolysis of organic framework of InBi-MOF provided a conductive network to accelerate the electrons transmission. The catalyst exhibited an ultra-broad applied potential window of 1200 mV (from -0.4 to -1.6 V vs RHE), relativistic high Faradaic efficiency of formate (99.92%) and satisfactory stability after 30 h. The in situ FT-IR experiment and DFT calculation verified that the abundant oxygen vacancies on the surface of catalysts can easily absorb CO2 molecules, and oxygen vacancy path is dominant pathway. This work provides a convenient method to construct high-performance bimetallic catalysts for the industrial application of CO2RR.
The increasing demand for short charging time on electric vehicles has motivated realization of fast chargeable lithium-ion batteries (LIBs). However, shortening the charging time of LIBs is limited by Li+ intercalation process consisting of liquid-phase diffusion, de-solvation, SEI crossing, and solid-phase diffusion. Herein, we propose a new strategy to accelerate the de-solvation step through a control of interaction between polymeric binder and solvent-Li+ complexes. For this purpose, three alkali metal ions (Li+, Na+, and K+) substituted carboxymethyl cellulose (Li-, Na-, and K-CMC) are prepared to examine the effects of metal ions on their performances. The lowest activation energy of de-solvation and the highest chemical diffusion coefficient were observed for Li-CMC. Specifically, Li-CMC cell with a capacity of 3 mAh cm-2 could be charged to >95% in 10 min, while a value above >85% was observed after 150 cycles. Thus, the presented approach holds great promise for the realization of fast charging.
Piezoelectric ceramic and polymeric separators have been proposed to effectively regulate Li deposition and suppress dendrite growth, but such separators still fail to satisfactorily support durable operation of lithium metal batteries owing to the fragile ceramic layer or low-piezoelectricity polymer as employed. Herein, by combining PVDF-HFP and ferroelectric BaTiO3, we develop a homogeneous, single-layer composite separator with strong piezoelectric effects to inhibit dendrite growth while maintaining high mechanical strength. As squeezed by local protrusion, the polarized PVDF-HFP/BaTiO3 composite separator generates a local voltage to suppress the local-intensified electric field and further deconcentrate regional lithium-ion flux to retard lithium deposition on the protrusion, hence enabling a smoother and more compact lithium deposition morphology than the unpoled composite separator and the pure PVDF-HFP separator, especially at high rates. Remarkably, the homogeneous incorporation of BaTiO3 highly improves the piezoelectric performances of the separator with residual polarization of 0.086 μC cm-2 after polarization treatment, four times that of the pure PVDF-HFP separator, and simultaneously increases the transference number of lithium-ion from 0.45 to 0.57. Beneficial from the prominent piezoelectric mechanism, the polarized PVDF-HFP/BaTiO3 composite separator enables stable cyclic performances of Li||LiFePO4 cells for 400 cycles at 2 C (1 C = 170 mA g-1) with a capacity retention above 99%, and for 600 cycles at 5 C with a capacity retention over 85%.
Sodium dentrite formed by uneven plating/stripping can reduce the utilization of active sodium with poor cyclic stability and, more importantly, cause internal short circuit and lead to thermal runaway and fire. Therefore, sodium dendrites and their related problems seriously hinder the practical application of sodium metal batteries (SMBs). Herein, a design concept for the incorporation of metal-organic framework (MOF) in polymer matrix (polyvinylidene fluoride-hexafluoropropylene) is practiced to prepare a novel gel polymer electrolyte (PH@MOF polymer-based electrolyte [GPE]) and thus to achieve high-performance SMBs. The addition of the MOF particles can not only reduce the movement hindrance of polymer chains to promote the transfer of Na+ but also anchor anions by virtue of their negative charge to reduce polarization during electrochemical reaction. A stable cycling performance with tiny overpotential for over 800 h at a current density of 5 mA cm-2 with areal capacity of 5 mA h cm-2 is achieved by symmetric cells based on the resulted GPE while the Na3V2O2(PO4)2F@rGO (NVOPF)|PH@MOF|Na cell also displays impressive specific cycling capacity (113.3 mA h g-1 at 1 C) and rate capability with considerable capacity retention.
Radio-photovoltaic cell is a micro nuclear battery for devices operating in extreme environments, which converts the decay energy of a radioisotope into electric energy by using a phosphor and a photovoltaic converter. Many phosphors with high light yield and good environmental stability have been developed, but the performance of radio-photovoltaic cells remains far behind expectations in terms of power density and power conversion efficiency, because of the poor photoelectric conversion efficiency of traditional photovoltaic converters under low-light conditions. This paper reports an radio-photovoltaic cell based on an intrinsically stable formamidinium-cesium perovskite photovoltaic converter exhibiting a wide light wavelength response from 300 to 800 nm, high open-circuit voltage (VOC), and remarkable efficiency at low-light intensity. When a He ions accelerator is adopted as a mimicked α radioisotope source with an equivalent activity of 0.83 mCi cm-2, the formamidinium-cesium perovskite radio-photovoltaic cell achieves a VOC of 0.498 V, a short-circuit current (JSC) of 423.94 nA cm-2, and a remarkable power conversion efficiency of 0.886%, which is 6.6 times that of the Si reference radio-photovoltaic cell, as well as the highest among all radio-photovoltaic cells reported so far. This work provides a theoretical basis for enhancing the performance of radio-photovoltaic cells.
Ionic-conductive solid-state polymer electrolytes are promising for the development of advanced lithium batteries yet a deeper understanding of their underlying ion-transfer mechanism is needed to improve performance. Here we demonstrate the low-enthalpy and high-entropy (LEHE) electrolytes can intrinsically generate remarkably free ions and high mobility, enabling them to efficiently drive lithium-ion storage. The LEHE electrolytes are constructed on the basis of introducing CsPbI3 perovskite quantum dots (PQDs) to strengthen PEO@LiTFSI complexes. An extremely stable cycling >1000 h at 0.3 mA cm-2 can be delivered by LEHE electrolytes. Also, the as-developed Li | LEHE | LiFePO4 cell retains 92.3% of the initial capacity (160.7 mAh g-1) after 200 cycles. This cycling stability is ascribed to the suppressed charge concentration gradient leading to free lithium dendrites. It is realized by a dramatic increment in lithium-ion transference number (0.57 vs 0.19) and a significant decline in ion-transfer activation energy (0.14 eV vs 0.22 eV) for LEHE electrolytes comparing with PEO@LiTFSI counterpart. The CsPbI3 PQDs promote highly structural disorder by inhibiting crystallization and hence endow polymer electrolytes with low melting enthalpy and high structural entropy, which in turn facilitate long-term cycling stability and excellent rate-capability of lithium-metal batteries.
Ultraviolet position-sensitive detectors (PSDs) are expected to undergo harsh environments, such as high temperatures, for a wide variety of applications in military, civilian, and aerospace. However, no report on relevant PSDs operating at high temperatures can be found up to now. Herein, we design a new 2D/3D graphitic carbon nitride (g-C3N4)/gallium nitride (GaN) hybrid heterojunction to construct the ultraviolet high-temperature-resistant PSD. The g-C3N4/GaN PSD exhibits a high position sensitivity of 355 mV mm-1, a rise/fall response time of 1.7/2.3 ms, and a nonlinearity of 0.5% at room temperature. The ultralow formation energy of -0.917 eV atom-1 has been obtained via the thermodynamic phase stability calculations, which endows g-C3N4 with robust stability against heat. By merits of the strong built-in electric field of the 2D/3D hybrid heterojunction and robust thermo-stability of g-C3N4, the g-C3N4/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm-1 and 1.4%, respectively, with high repeatability at a high temperature up to 700 K, outperforming most of the other counterparts and even commercial silicon-based devices. This work unveils the high-temperature PSD, and pioneers a new path to constructing g-C3N4-based harsh-environment-tolerant optoelectronic devices.
In situ surface-enhanced Raman scattering (SERS) is a widely used operando analytical technique, while facing numerous complex factors in applications under aqueous environment, such as low detection sensitivity, poor anti-interference capability, etc., resulting in unreliable detectability. To address these issues, herein a new hydrophobic SERS strategy has been attempted. By comprehensively designing and researching a SERS-active structure of superhydrophobic ZnO/Ag nanowires, we demonstrate that hydrophobicity can not only draw analytes from water onto substrate, but also adjust “hottest spot” from the bottom of the nanowires to the top. As a result, the structure can simultaneously concentrate the dispersed molecules in water and the enhanced electric field in structure into a same zone, while perfecting its own anti-interference ability. The underwater in situ analytical enhancement factor of this platform is as high as 1.67 × 1011, and the operando limited of detection for metronidazole (MNZ) reaches to 10-9 M. Most importantly, we also successfully generalized this structure to various real in situ detection scenarios, including on-site detection of MNZ in corrosive urine, real-time warning of wrong dose of MNZ during intravenous therapy, in situ monitoring of MNZ in flowing wastewater with particulate interference, etc., demonstrating the great application potential of this hydrophobic platform. This work realizes a synergistic promotion for in situ SERS performance under aqueous environment, and also provides a novel view for improving other in situ analytical techniques.
Zero-dimensional (0D) hybrid metal halides, which consist of organic cations and isolated inorganic metal halide anions, have emerged as phosphors with efficient broadband emissions. However, these materials generally have too wide bandgaps and thus cannot be excited by blue light, which hinders their applications for efficient white light-emitting diodes (WLEDs). The key to achieving a blue-light-excitable 0D hybrid metal halide phosphor is to reduce the fundamental bandgap by rational chemical design. In this work, we report two designed hybrid copper(I) iodides, (Ph3MeP)2Cu4I6 and (Cy3MeP)2Cu4I6, as blue-light-excitable yellow phosphors with ultrabroadband emission. In these compounds, the [Cu4I6]2- anion forms an I6 octahedron centered on a cationic Cu4 tetrahedron. The strong cation-cation bonding within the unique cationic Cu4 tetrahedra enables significantly lowered conduction band minimums and thus narrowed bandgaps, as compared to other reported hybrid copper(I) iodides. The ultrabroadband emission is attributed to the coexistence of free and self-trapped excitons. The WLED using the [Cu4I6]2- anion-based single phosphor shows warm white light emission, with a high luminous efficiency of 65 lm W-1 and a high color rendering index of 88. This work provides strategies to design narrow-bandgap 0D hybrid metal halides and presents two first examples of blue-light-excitable 0D hybrid metal halide phosphors for efficient WLEDs.
The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting challenge. Although Na4MnCr(PO4)3 has emerged as one of the most promising high-energy-density cathode materials owing to its three-electron reactions, it still suffers from serious structural distortion upon repetitive charge/discharge processes caused by the Jahn-Teller active Mn3+. Herein, the selective substitution of Cr by Zr in Na4MnCr(PO4)3 was explored to enhance the structural stability, due to the pinning effect of Zr ions and the ≈2.9-electron reactions, as-prepared Na3.9MnCr0.9Zr0.1(PO4)3/C delivers a high capacity retention of 85.94% over 500 cycles at 5 C and an ultrahigh capacity of 156.4 mAh g–1 at 0.1 C, enabling the stable energy output as high as 555.2 Wh kg–1. Moreover, during the whole charge/discharge process, a small volume change of only 6.7% was verified by in situ X-ray diffraction, and the reversible reactions of Cr3+/Cr4+, Mn3+/Mn4+, and Mn2+/Mn3+ redox couples were identified via ex situ X-ray photoelectron spectroscopy analyses. Galvanostatic intermittent titration technique tests and density functional theory calculations further demonstrated the fast reaction kinetics of the Na3.9MnCr0.9Zr0.1(PO4)3/C electrode. This work offers new opportunities for designing high-energy and high-stability NASICON cathodes by ion doping.
The redox couple of I0/I- in aqueous rechargeable iodine-zinc (I2-Zn) batteries is a promising energy storage resource since it is safe and cost-effective, and provides steady output voltage. However, the cycle life and efficiency of these batteries remain unsatisfactory due to the uncontrolled shuttling of polyiodide (I3- and I5-) and side reactions on the Zn anode. Starch is a very low-cost and widely sourced food used daily around the world. “Starch turns blue when it encounters iodine” is a classic chemical reaction, which results from the unique structure of the helix starch molecule-iodine complex. Inspired by this, we employ starch to confine the shuttling of polyiodide, and thus, the I0/I- conversion efficiency of an I2-Zn battery is clearly enhanced. According to the detailed characterizations and theoretical DFT calculation results, the enhancement of I0/I- conversion efficiency is mainly originated from the strong bonding between the charged products of I3- and I5- and the rich hydroxyl groups in starch. This work provides inspiration for the rational design of high-performance and low-cost I2-Zn in AZIBs.
Low-temperature, ambient processing of high-quality CsPbBr3 films is demanded for scalable production of efficient, low-cost carbon-electrode perovskite solar cells (PSCs). Herein, we demonstrate a crystal orientation engineering strategy of PbBr2 precursor film to accelerate its reaction with CsBr precursor during two-step sequential deposition of CsPbBr3 films. Such a novel strategy is proceeded by adding CsBr species into PbBr2 precursor, which can tailor the preferred crystal orientation of PbBr2 film from [020] into [031], with CsBr additive staying in the film as CsPb2Br5 phase. Theoretical calculations show that the reaction energy barrier of (031) planes of PbBr2 with CsBr is lower about 2.28 eV than that of (020) planes. Therefore, CsPbBr3 films with full coverage, high purity, high crystallinity, micro-sized grains can be obtained at a low temperature of 150 °C. Carbon-electrode PSCs with these desired CsPbBr3 films yield the record-high efficiency of 10.27% coupled with excellent operation stability. Meanwhile, the 1 cm2 area one with the superior efficiency of 8.00% as well as the flexible one with the champion efficiency of 8.27% and excellent mechanical bending characteristics are also achieved.
Searching for novel solid electrolytes is of great importance and challenge for all-solid-state Mg batteries. In this work, we develop an amorphous Mg borohydride ammoniate, Mg(BH4)2·2NH3, as a solid Mg electrolyte that prepared by a NH3 redistribution between 3D framework-γ-Mg(BH4)2 and Mg(BH4)2·6NH3. Amorphous Mg(BH4)2·2NH3 exhibits a high Mg-ion conductivity of 5 × 10-4 S cm-1 at 75 °C, which is attributed to the fast migration of abundant Mg vacancies according to the theoretical calculations. Moreover, amorphous Mg(BH4)2·2NH3 shows an apparent electrochemical stability window of 0-1.4 V with the help of in-situ formed interphases, which can prevent further side reactions without hindering the Mg-ion transfer. Based on the above superiorities, amorphous Mg(BH4)2·2NH3 enables the stable cycling of all-solid-state Mg cells, as the critical current density reaches 3.2 mA cm-2 for Mg symmetrical cells and the reversible specific capacity reaches 141 mAh g-1 with a coulombic efficiency of 91.7% (first cycle) for Mg||TiS2 cells.
Herein, we demonstrate the synthesis of bifunctional nickel cobalt selenide@nickel telluride (NixCo12–xSe@NiTe) core-shell heterostructures via an electrodeposition approach for overall urea electrolysis and supercapacitors. The 3D vertically orientated NiTe dendritic frameworks induce the homogeneous nucleation of 2D NixCo12–xSe nanosheet arrays along similar crystal directions and bring a strong interfacial binding between the integrated active components. In particular, the optimized Ni6Co6Se@NiTe with an interface coupling effect works in concert to tune the intrinsic activity. It only needs a low overpotential of 1.33 V to yield a current density of 10 mA cm-2 for alkaline urea electrolysis. Meanwhile, the full urea catalysis driven only by Ni6Co6Se@NiTe achieves 10 mA cm–2 at a potential of 1.38 V and can approach a constant level of the current response for 40 h. Besides, the integrated Ni6Co6Se@NiTe electrode delivers an enhanced specific capacity (223 mA h g–1 at 1 A g–1) with a high cycling stability. Consequently, a hybrid asymmetric supercapacitor (HASC) device based on Ni6Co6Se@NiTe exhibits a favorable rate capability and reaches a high energy density of 67.7 Wh kg–1 and a power density of 724.8 W kg–1 with an exceptional capacity retention of 92.4% after sequential 12 000 cycles at 5 A g–1.
Tin-based perovskite solar cells (TPSCs) have received great attention due to their eco-friendly properties and high theoretical efficiencies. However, the fast crystallization feature of tin-based perovskites leads to poor film quality and limits the corresponding device performance. Herein, a chlorofullerene, C60Cl6, with six chlorine attached to the C60 cage, is applied to modulate the crystallization process and passivate grain boundary defects of the perovskite film. The chemical interactions between C60Cl6 and perovskite components retard the transforming process of precursors to perovskite crystals and obtain a high-quality tin-based perovskite film. It is also revealed that the C60Cl6 located at the surfaces and grain boundaries can not only passivate the defects but also offer a role in suturing grain boundaries to suppress the detrimental effects of water and oxygen on perovskite films, especially the oxidation of Sn2+ to Sn4+. As a result, the C60Cl6-based device yields a remarkably improved device efficiency from 10.03% to 13.30% with enhanced stability. This work provides a new strategy to regulate the film quality and stability of TPSCs using functional fullerene materials.
The growing demand for substitutes of lithium chemistries in battery leads to a surge in budding novel anion-based electrochemical energy storage, where the chloride ion batteries (CIBs) take over the role. The application of CIBs is limited by the dissolution and side reaction of chloride-based electrode materials in a liquid electrolyte. On the flipside, its solid-state electrolytes are scarcely reported due to the challenge in realizing fast Cl— conductivity. The present study reports [Al(DMSO)6]Cl3, a solid-state metal-organic material, allows chloride ion transfer. The strong Al-Cl bonds in AlCl3 are broken down after coordinating of Al3+ by ligand DMSO, and Cl— in the resulting compound is weakly bound to complexions [Al(DMSO)6]3+, which may facilitate Cl— migration. By partial replacement of Cl— with
In recent years, the interest in the development of highly concentrated electrolyte solutions for battery applications has increased enormously. Such electrolyte solutions are typically characterized by a low flammability, a high thermal and electrochemical stability and by the formation of a stable solid electrolyte interphase (SEI) in contact to electrode materials. However, the classification of concentrated electrolyte solutions in terms of the classical scheme “strong” or “weak” has been controversially discussed in the literature. In this paper, a comprehensive theoretical framework is presented for a more general classification, which is based on a comparison of charge transport and mass transport. By combining the Onsager transport formalism with linear response theory, center-of-mass fluctuations and collective translational dipole fluctuations of the ions in equilibrium are related to transport properties in a lithium-ion battery cell, namely mass transport, charge transport and Li+ transport under anion-blocking conditions. The relevance of the classification approach is substantiated by showing that i) it is straightforward to classify highly concentrated electrolytes and that ii) both fast charge transport and fast mass transport are indispensable for achieving fast Li+ transport under anion-blocking conditions.
Designing flexible free-standing air-electrode with efficient OER/ORR performance is of vital importance for the application of Zinc-air batteries in flexible electronics. Herein, a flexible free-standing electrode (Ni/Fe-NC/NCF/CC) is synthesized by in-situ coupling of binary Ni/Fe-NC nanocubes and N-doped carbon nanofibers (NCF) rooted on carbon cloth. The highly dispersed binary Ni/Fe-NC sites ensure excellent ORR activity and create efficient OER active sites relative to Ni-NC and Fe-NC. The in-situ coupling of Ni/Fe-NC and NCF constructs a 3D interconnected network structure that not only provides abundant and stabilized reactive sites but also guarantees fast electron transfer and gas transportation, thus achieving efficient and fast operation of ORR/OER. Therefore, Ni/Fe-NC/NCF/CC displays a much positive potential (0.952 V) at 4.0 mA cm–2 for ORR and a low OER overpotential (310 mV) at 50 mA cm–2. The Zinc-air battery with Ni/Fe-NC/NCF/CC air-electrode exhibits excellent battery performance with outstanding discharge/charge durability for 2150 cycles. The flexible Zn-air batteries with foldable mechanical properties display a high power density of 105.0 mW cm–2. This work widened the way to prepare flexible bifunctional air-electrode by designing composition/structure and in-situ coupling.
In this work, we open an avenue toward rational design of potential efficient catalysts for sustainable ammonia synthesis through composition engineering strategy by exploiting the synergistic effects among the active sites as exemplified by diatomic metals anchored graphdiyne via the combination of hierarchical high-throughput screening, first-principles calculations, and molecular dynamics simulations. Totally 43 highly efficient catalysts feature ultralow onset potentials (|Uonset| ≤ 0.40 V) with Rh-Hf and Rh-Ta showing negligible onset potentials of 0 and -0.04 V, respectively. Extremely high catalytic activities of Rh-Hf and Rh-Ta can be ascribed to the synergistic effects. When forming heteronuclears, the combinations of relatively weak (such as Rh) and relatively strong (such as Hf or Ta) components usually lead to the optimal strengths of adsorption Gibbs free energies of reaction intermediates. The origin can be ascribed to the mediate d-band centers of Rh-Hf and Rh-Ta, which lead to the optimal adsorption strengths of intermediates, thereby bringing the high catalytic activities. Our work provides a new and general strategy toward the architecture of highly efficient catalysts not only for electrocatalytic nitrogen reduction reaction (eNRR) but also for other important reactions. We expect that our work will boost both experimental and theoretical efforts in this direction.