Nonflammable pseudoconcentrated electrolytes for batteries

Electrolyte is essentially important for electrochemical and safety performance of batteries. The pseudoconcentrated electrolyte, with lean solvent but anion-involved solvation sheath and heterogeneous long-range structure, endows the electrolyte with superior interfacial properties and the bulk properties, enabling the high-voltage lithium-ion battery, lithium-metal battery, and sodium battery with outstanding electrochemical performances. Nonflammable solvents as diluent in the pseudoconcentrated electrolyte can reach 30–60% by volume share, making the electrolyte nonflammable and then showing great possibility in mitigating the thermal runaway of the battery. As a new family of liquid electrolyte, nonflammable pseudoconcentrated electrolyte is promising for high safety and high energy density secondary batteries.     

Recent progress in liquid electrolytes for lithium metal batteries

Li metal batteries are revived as the next-generation batteries beyond Li-ion batteries. The Li metal anode can be paired with intercalation-type cathodes LiMO₂ and conversion-type cathodes such as sulfur and oxygen. Then, energy densities of Li/LiMO₂ and Li/S,O₂ batteries can reach 400 Whkg^?1 and more than 500 Whkg^?1, respectively, which surpass that of the state-of-the-art LIB (280 Whkg^?1). However, replacing the intercalation-type graphite anode with the Li metal anode suffers from low coulombic efficiency during repeated Li plating/stripping processes, which leads to short cycle lifetime and potential safety problems. The key solution is to construct a stable and uniform solid electrolyte interphase with high Li⁺ transport and high elastic strength on the Li metal anode. This review summarizes recent progress in improving the solid electrolyte interphase by tailoring liquid electrolytes, a classical but the most convenient and cost-effective strategy.     

Recent progress in lithium-ion and lithium metal batteries

Moving towards carbon-free energy and global commercialization of electric vehicles stimulated extensive development in the field of lithium-ion batteries (LIBs), and to date, many scientific and technological advances have been achieved. The number of research works devoted to developing high-capacity and stable materials for lithium- ion and lithium metal batteries (LMBs) is constantly rising. This review covers the main progress in the development of LIBs and LMBs based on research works published in 2021. One of the main goals in the recent publications is to solve the problem of instability of layered nickel-rich lithium– nickel–cobalt–manganese oxides (Ni-rich NMC) cathodes, as well as silicon anodes. Improving the stability of NMC cathodes can be achieved by doping them with cations as well as by coating the oxides’ surfaces with protective layers (organic polymers and inorganic materials). The most effective strategies for dampening volumetric changes in silicon anodes include using porous silicon structures, obtaining composites with carbon, coating silicon-containing particles with inorganic or polymeric materials, and replacing standard binder materials. Much work has been devoted to suppressing dendrite formation in LMBs by forming stable coating layers on the surface of lithium metal, preparing composite anodes and alloys, and changing the composition of electrolytes. At the same time, in the field of electrolyte development, many research works have been devoted to the search for new hybrid polymer electrolytes containing lithium-conducting inorganic materials.     

Specific background electrolytes for nonaqueous capillary electrophoresis

The use of organic solvents or mixture of solvents in capillary electrophoresis is gaining wider attention. The electroosmotic flow mobility of eight organic solvents (acetonitrile, acetone, dimethylformamide, dimetylsulphoxide, propylene carbonate, methanol, ethanol, n-propanol) and of mixtures of several solvents (methanol-acetonitrile, methanol-propylene carbonate, acetonitrile-propylene carbonate) has been studied. The influence of 1,3-alkylimidazolium salts in different solvents on the separation of different analytes has been investigated. Some of these salts have shown usefulness for matrix-assisted laser desorption ionization matrices and off-line analysis of electrophoresis fractions. It also appears that nonaqueous capillary electrophoresis with 1,3-alkylimidazolium salts as background electrolytes is suitable for separation small inorganic ions.     

Synthesis and electrochemistry of polymer based electrolytes for lithium batteries

An overview is presented on the development of improved polymer based electrolytes during the past years. The emphasis lies on new approaches regarding chemical concepts that achieve a higher total conductivity and lithium transference number as well as an increased electrochemical, mechanical and thermal stability. With respect to the polymer chemistry, the focus is laid on siloxane and phosphazene derived systems. Topics are the chemical modification of the polymeric, cyclic and low molecular derivates of these systems, the formation of stable membranes from these by suitable cross-linking strategies and an extensive electrochemical characterization in corresponding lithium cells. Recent trends towards composite and hybrid materials are illustrated with examples and newly developed hybrid electrolytes. A particular chance for improvements comes from the design and use of stable small molecular additives in combination with optimized and electrochemically stable polymer networks. Special compounds are introduced which may act themselves as novel solvents with increased electrochemical stabilities. The relevance of chosen lithium salts for polymer electrolytes is discussed, too, and a new family of pyrazolide anions is introduced. In all cases, the electrochemical performance has been characterized by standard experimental techniques.     

Integrated lithium metal anode protected by composite solid electrolyte film enables stable quasi-solid-state lithium metal batteries

Lithium (Li) metal, possessing an extremely high theoretical specific capacity (3860 mAh/g) and the most negative electrode potential (−3.040 V vs. standard hydrogen electrode), is one the most favorable anode materials for future high-energy-density batteries. However, the poor cyclability and safety issues induced by extremely unstable interfaces of traditional liquid Li metal batteries have limited their practical applications. Herein, a quasi-solid battery is constructed to offer superior interfacial stability as well as excellent interfacial contact by the incorporation of Li@composite solid electrolyte integrated electrode and a limited amount of liquid electrolyte (7.5 μL/cm²). By combining the inorganic garnet Al-doped Li_6.75La₃Zr_1.75Ta_0.25O₁₂ (LLZO) with high mechanical strength and ionic conductivity and the organic ethylene-vinyl acetate copolymer (EVA) with good flexibility, the composite solid electrolyte film could provide sufficient ion channels, sustained interfacial contact and good mechanical stability at the anode side, which significantly alleviates the thermodynamic corrosion and safety problems induced by liquid electrolytes. This innovative and facile quasi-solid strategy is aimed to promote the intrinsic safety and stability of working Li metal anode, shedding light on the development of next-generation high-performance Li metal batteries.     

A novel ternary polymer electrolyte for LMP batteries based on thermal cross-linked poly(urethane acrylate) in presence of a lithium salt and an ionic liquid

A new ternary polymer electrolyte based on thermally cross-linked poly(urethane acrylate) (PUA), lithium bis(trifluoromethansulfonyl)imide (LiTFSI) and the ionic liquid N-butyl-N-methylpyrrolidinium TFSI (PYR₁₄TFSI) was developed and tested for application in LMP batteries. The polymer electrolyte was a transparent yellow self-standing material with quite good mechanical properties, i.e., comparable to that of a flexible rubber. The room temperature ionic conductivity of the dry polymer electrolyte was found to be as high as 0.1 mS cm⁻¹ for the compound containing 40 wt% of ionic liquid (PYR₁₄TFSI) and a O/Li ratio of 15/1 (Li⁺ from LiTFSI). The thermal analysis of the new cross-linked electrolyte showed that it was homogeneous, amorphous and stable over a wide temperature range extending from −40 °C to 100 °C. The homogeneity of the polymer electrolyte was also confirmed by SEM analysis.     

Block copolymer electrolytes for rechargeable lithium batteries

Ion‐conducting block copolymers (BCPs) have attracted significant interest as conducting materials in solid‐state lithium batteries. BCP self‐assembly offers promise for designing ordered materials with nanoscale domains. Such nanostructures provide a facile method for introducing sufficient mechanical stability into polymer electrolyte membranes, while maintaining the ionic conductivity at levels similar to corresponding solvent‐free homopolymer electrolytes. This ability to simultaneously control conductivity and mechanical integrity provides opportunities for the fabrication of sturdy, yet easily processable, solid‐state lithium batteries. In this review, we first introduce several fundamental studies of ion conduction in homopolymers for the understanding of ion transport in the conducting domain of BCP systems. Then, we summarize recent experimental studies of BCP electrolytes with respect to the effects of salt‐doping and morphology on ionic conductivity. Finally, we present some remaining challenges for BCP electrolytes and highlight several important areas for future research. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1–16     

EC modified PEO/PVDF-LLZO composite electrolytes for solid state lithium metal batteries

The polymer-ceramic composite electrolytes have great application potential for next-generation solid state lithium batteries, as they have the merits to eliminate the problem of liquid organic electrolytes and enhancing chemical/electrochemical stability. However, polymer-ceramic composite electrolytes show poor ionic conductivity, which greatly hinders their practical applications. In this work, the addition of plasticizer ethylene carbonate (EC) into polymer-ceramic composite electrolyte for lithium batteries effectively promotes the ionic conductivity. A high ionic conductivity can be attained by adding 40 wt% EC to the polyethylene oxide (PEO)/polyvinylidene fluoride (PVDF)-Li₇La₃Zr₂O₁₂ (LLZO) based polymer-ceramic composite electrolytes, which is 2.64 × 10⁻⁴ S cm⁻¹ (tested at room temperature). Furthermore, the cell assembled with lithium metal anode, this composite electrolyte, and LiFePO₄ cathode can work more than 80 cycles at room temperature (tested at 0.2 C). The battery delivers a high reversible specific capacity after 89 cycles, which is 119 mAh g⁻¹.     

Soft matter lithium salt electrolytes: ion conduction and application to rechargeable batteries

Abstract  Soft matter provides diverse opportunities for the development of electrolytes for all solid state lithium batteries. Here we review soft matter solid electrolytes for lithium batteriesthat are primarily obtained starting from liquid electrolytic systems. This concept of solid electrolyte synthesis from liquid is significantly different from prevalent approaches. The novelty of our approach is discussed in the light of various fundamental issues and in relation to its application to rechargeable lithium batteries. Graphical abstract   M. Patel and S. K. Das have contributed equally to the work.     

Intercalation materials for lithium rechargeable batteries

An overview is given of intercalation materials for both the negative and the positive electrodes of lithium batteries, including the results of our own research. As well as lithium metal as a negative electrode, we consider insertion materials based on aluminium alloys. In the case of the positive electrode metal-oxides based on manganese, nickel and cobalt are discussed. Received: 27 May 1997 / Accepted: 30 July 1997     

Asymmetric double-layer composite electrolyte with enhanced ionic conductivity and interface stability for all-solid-state lithium metal batteries

All-solid-state Li metal battery has been regarded as a promising battery technology due to its high energy density based on the high capacity of lithium metal anode and high safety based on the all solid state electrolyte without inflammable solvent.However,challenges still exist mainly in the poor contact and unstable interface between electrolyte and electrodes.Herein,we demonstrate an asymmetric design of the composite polymer electrolyte with two different layers to overcome the interface issues at both the cathode and the anode side simultaneously.At the cathode side,the polypropylene carbonate layer has enough viscosity and flexibility to reduce the inter-facial resistance,while at the Li anode side,the polyethylene oxide layer modified with hexagonal boron nitride has high mechanical strength to suppress the Li dendrite growth.Owing to the synergetic effect between different components,the asprepared double layer composite polymer electrolyte demonstrates a large electrochemical window of5.17 V,a high ionic conductivity of 6.1×10~(-4) S/cm,and a transfe rence number of 0.56,featuring excellent ion transport kinetics and good chemical stability.All-solid-state Li metal battery assembled with LiFePO_4 cathode and Li anode delivers a high capacity of 150.9 mAh/g at 25℃ and 0.1 C-rate,showing great potential for practical applications.     

Electrochemical properties of nanoporous carbon electrodes in various nonaqueous electrolytes

Electrical double layer and electrochemical characteristics at the nanoporous carbon|acetonitrile interface with additions of Et₄NBF₄, Et₃MeNBF₄, EtMe₃NBF₄, LiClO₄, and LiBF₄ have been studied by cyclic voltammetry and impedance spectroscopy methods. A value of zero charge potential, dependent on the structure of the cations as well as on the composition of the anions, the region of ideal polarizability, and other characteristics has been established. Analysis of the complex plane plots shows that the nanoporous carbon|acetonitrile+0.1 M electrolyte (Et₄NBF₄, Et₃MeNBF₄, or EtMe₃NBF₄) interface can be simulated by the equivalent circuit, in which the two parallel conduction parts in the solid and liquid phases are interconnected by the double layer capacitance in parallel with the complex admittance of the hindered reaction of the charge transfer process or of the partial charge transfer (i.e. adsorption stage limited) process. The values of the characteristic frequency depend on the electrolyte composition and on the electrode potential, i.e. on the nature of the ions adsorbed at the surface of the nanoporous carbon electrode. In the region of moderate a.c. frequencies, the modified Randles-like equivalent circuit has been used for simulation of the complex plane plots. In the region of negative surface charge densities, the intercalation process of Li⁺ ions from LiClO₄ and LiBF₄ solutions into the surface film is possible and these data can be simulated using the modified Ho et al. model or Meyer et al. model. Electronic Publication     

Recent progress of composite solid polymer electrolytes for all-solid-state lithium metal batteries

In comparison with lithium-ion batteries (LIBs) with liquid electrolytes, all-solid-state lithium batteries (ASSLBs) have been considered as promising systems for future energy storage due to their safety and high energy density. As the pivotal component used in ASSLBs, composite solid polymer electrolytes (CSPEs), derived from the incorporation of inorganic fillers into solid polymer electrolytes (SPEs), exhibit higher ionic conductivity, better mechanical strength, and superior thermal/electrochemical stability compared to the single-component SPEs, which can significantly promote the electrochemical performance of ASSLBs. Herein, the recent advances of CSPEs applied in ASSLBs are presented. The effects of the category, morphology and concentration of inorganic fillers on the ionic conductivity, mechanical strength, electrochemical window, interfacial stability and possible Li⁺ transfer mechanism of CSPEs will be systematically discussed. Finally, the challenges and perspectives are proposed for the future development of high-performance CSPEs and ASSLBs.     

All solid polymer electrolytes based on polar side group rotation for rechargeable lithium batteries

A novel polymer matrix with a polar carbonyl group was designed and used to prepare an all‐solid polymer electrolyte in lithium rechargeable batteries. The ionic conductivity of this type of polymer electrolyte was examined. The relationship between the lithium salt concentration and ionic conductivity was investigated by Fourier transform infrared (FTIR) spectroscopy. The carbonyl groups in the polymer matrix effectively interacted with the lithium salt, which improved the ionic conductivity at a large range of temperatures. The ionic conductivity of this type of polymer electrolyte was approximately 10^?4 S cm^?1 at room temperature. The stability of the interface between electrode and electrolyte was evaluated by measuring the alternating current (AC) impedance. Copyright © 2009 John Wiley & Sons, Ltd.     

基于表界面反应及优化的锂金属电池研究进展

金属锂具有高理论比容量和低还原电位, 是锂电池阳极的理想材料之一. 但在长期循环充放电过程中, 金属锂因锂枝晶生长会导致出现界面恶化及能量损失严重等问题, 对锂金属电极与电解质表界面反应的优化是一个重要研究方向. 本文介绍了锂枝晶产生的危害, 从分析及抑制锂枝晶沉积两方面综合评述了为解决这一问题所采取的方法, 包括固态电解质界面形成机制和保护机理、 表面改性、 三维锂阳极和液态/固态电解质等方法, 总结了各种方法的优劣势, 并展望锂金属电池在能源领域的研究前景.     

Thermal study of organic electrolytes with fully charged cathodic materials of lithium-ion batteries

We systematically investigated thermal effects of organic electrolytes/organic solvents with fully charged cathodic materials (Li_0.5CoO₂) of Li-ion battery under rupture conditions by using oxygen bomb calorimeter. In the six studied systems, both the amount of combustion heat and heat release rates showed a pronounced increase with the increase in mass ratios of cathodic materials to electrolytes/solvents. More importantly, synergistic effects not simply physical mixtures have firstly been observed between cathodic materials and electrolytes/solvents in the complete combustion reactions. The results have been further analyzed by X-ray diffraction spectra, which revealed that Co₃O₄, CoO, and LiCoO₂ were the main solid products for the combustion reactions of studied systems. And there are more CoO and less LiCoO₂ products for the higher ratio of cathodic materials system and more amount of heat generated. It means that the combustion reaction, which produced CoO, generated more amount of heat than LiCoO₂. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Electrolyte using blend salts of LiTFSI and LLZO for long-term high-safety lithium ion battery

It is crucial to obtain a reliable electrolyte system that is used for replacing thermally unstable and the moisture sensitive LiPF₆ salt in liquid electrolytes for developing excellent cycle stability lithium ion batteries with high safety. In this work, a kind of hybrid electrolytes, adding Ga–Bi co-doped Li₇La₃Zr₂O₁₂ (LLZO) into LiTFSI based commercial electrolyte, was successfully prepared. The results shows that adding Ga–Bi co-doped LLZO ceramic particles is benefit for enhancing conductivity of LiTFSI based commercial electrolyte, which is 3.14 mS cm⁻¹ from 3.02 mS cm⁻¹. Furthermore, the LiFePO₄| |Li cell assembling with LiTFSI based electrolyte with Ga–Bi co-doped LLZO ceramic particles shows good cycle performance and coulomb efficiency (100% except for the initial cycle value of 88%) due to a passivation multi-element film formed for preventing severe corrosion to the Al foil. The battery delivered a high first cycle discharge capacity of 144.2 mAh g⁻¹ (85% of theoretical LiFePO₄.) and a maximum value of 152.6 mAh g⁻¹ after the 69th cycle. After the 300 stable cycle, the capacity of 130.8 mAh g⁻¹ (85.7% of the maximum data) remained.     

A tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte for advanced lithium ion batteries

Tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte is here studied. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that the electrolyte has conductivity higher than 10^− 3 S cm^− 1 at room temperature and about 10^− 2 S cm^− 1 at 60 °C, while thermogravimetry indicates a stability extending up to 180 °C. Sweep voltammetry of the electrolyte shows anodic stability extending over 4.6 V vs. Li and cathodic peak at about 1.5 V vs. Li/Li⁺, caused by a decomposition of LiBOB salt, and following prevented by using a pre-treated Sn-C anode. Furthermore, LiFePO₄ electrode is successfully used as cathode in a lithium cell using the TEGDME-LiBOB electrolyte. The promising electrochemical results, the low cost and the very high safety level candidate the electrolyte here reported as a valid alternative to the conventional electrolyte based on fluorinated salts presently used in the lithium ion battery field.     

The recent advances in constructing designed electrode in lithium metal batteries

In this review, we focus on the design of lithium electrode and its recent advancements, which suppress the growth of lithium dendrites and improve the performance of the rechargeable batteries. To suppress the growth of lithium dendrites, the general design rules of the system require a uniform lithium ion flux, a low current density, a homogeneous nucleation process and a stable SEI layer. Improvements of the battery performance have been achieved through the delicate design of lithium electrode and here they are summarized into three groups:i) optimizing the 3D porous nanostructure of the current collector, ii) constructing rational host for lithium metal and prelithiating the 3D host matrix with molten lithium, iii) protecting the surface of lithium metal by functional layers. An outlook of the challenges and the potentials of lithium metal battery is also provided, which will facilitate the future development of lithium metal battery.