Critical interface between inorganic solid-state electrolyte and sodium metal

With widening applications in next-generation energy storage systems, rechargeable secondary batteries with enhanced safety and energy density are imperative for technological advancements. All-solid-state sodium batteries can be a promising low-cost and high-energy-density candidate, provided that stable cycling of the energy-dense Na metal anode can be achieved. However, the interface between Na metal and solid-state electrolyte remains a challenging problem. Here we comprehensively review various physical and chemical properties of different types of sodium-based solid-state electrolytes including sodium β-alumina, Na super ionic conductors (NASICON), chalcogenides, perovskites, complex hydrides and antiperovskites, and discuss some critical common factors that affect the Na/electrolyte interface stability. We also summarize the state-of-art strategies to engineer the interface for better electrochemical performances.     

A Single-Ion Conducting Borate Network Polymer as a Viable Quasi-Solid Electrolyte for Lithium Metal Batteries

Lithium-ion batteries have remained a state-of-the-art electrochemical energy storage technology for decades now, but their energy densities are limited by electrode materials and conventional liquid electrolytes can pose significant safety concerns. Lithium metal batteries featuring Li metal anodes, solid polymer electrolytes, and high-voltage cathodes represent promising candidates for next-generation devices exhibiting improved power and safety, but such solid polymer electrolytes generally do not exhibit the required excellent electrochemical properties and thermal stability in tandem. Here, an interpenetrating network polymer with weakly coordinating anion nodes that functions as a high-performing single-ion conducting electrolyte in the presence of minimal plasticizer, with a wide electrochemical stability window, a high room-temperature conductivity of 1.5 × 10⁻⁴ S cm⁻¹, and exceptional selectivity for Li-ion conduction (t_Li+ = 0.95) is reported. Importantly, this material is also flame retardant and highly stable in contact with lithium metal. Significantly, a lithium metal battery prototype containing this quasi-solid electrolyte is shown to outperform a conventional battery featuring a polymer electrolyte.     

Interfacial Interaction of Multifunctional GQDs Reinforcing Polymer Electrolytes For All-Solid-State Li Battery

Solid-state polymer electrolytes are highly anticipated for next generation lithium ion batteries with enhanced safety and energy density. However, a major disadvantage of polymer electrolytes is their low ionic conductivity at room temperature. In order to enhance the ionic conductivity, here, graphene quantum dots (GQDs) are employed to improve the poly (ethylene oxide) (PEO) based electrolyte. Owing to the increased amorphous areas of PEO and mobility of Li⁺, GQDs modified composite polymer electrolytes achieved high ionic conductivity and favorable lithium ion transference numbers. Significantly, the abundant hydroxyl groups and amino groups originated from GQDs can serve as Lewis base sites and interact with lithium ions, thus promoting the dissociation of lithium salts and providing more ion pathways. Moreover, lithium dendrite is suppressed, associated with high transference number, enhanced mechanical properties and steady interface stability. It is further observed that all solid-state lithium batteries assembled with GQDs modified composite polymer electrolytes display excellent rate performance and cycling stability.     

Lithium garnets: Synthesis,structure, Li+ conductivity,Li+ dynamics and applications

Inorganic solid fast Li⁺ conductors based batteries are expected to overcome the limitations over safety concerns of flammable organic polymer electrolytes based Li⁺ batteries. Hence, an all-solid-state Li⁺ battery using non-flammable solid electrolyte have attracted much attention as next-generation battery. Therefore, in the development of all-solid-state lithium rechargeable batteries, it is important to search for a solid electrolyte material that has high Li⁺ conductivity, low electronic conductivity, fast charge transfer at the electrode interface and wide electrochemical window stability against potential electrodes and lithium metal. Hence, significant research effort must be directed towards developing novel fast Li⁺ conductors as electrolytes in all-solid-state lithium batteries. Among the reported inorganic solid Li⁺ conductive oxides, garnet-like structural compounds received considerable attention in recent times for potential application as electrolytes in all-solid-state lithium batteries. The focus of this review is to provide comprehensive overview towards the importance of solid fast lithium ion conductors, advantages of lithium garnets over other ceramic lithium ion conductors and understanding different strategies on synthesis of lithium garnets. Attempts have also been made to understand relationship between the structure, Li⁺ conduction and Li⁺ dynamics of lithium garnets. The status of lithium garnets as solid electrolyte in electrochemical devices like all-solid state lithium battery, lithium-air battery and sensor are also discussed.     

全固态锂离子电池中金属锂负极界面优化改性研究

以共聚物PEDOT-co-PEG作为锂金属阳极的表面改性层,采用磷酸铁锂复合阳极和“石榴石型”物质以及聚合氧乙烷聚合物组成的固体电解质制备了全固态锂离子电池。采用SEM分析了锂金属充电-放电反复操作后的形态学改变;采用电化学组抗谱试验研究了改性后的锂金属以及复合固体电解质接触面的稳定性并对全固态锂离子电池的充电-放电性能和界面稳定性进行了研究。结果表明,未改性的锂金属在固态电池充电-放电过程中会生成锂枝晶,从而导致全固态锂离子电池的高电流密度容量快速衰变;“石榴石型”物质以及聚合氧乙烷聚合物组成的固体电解质与改性后的金属锂具有良好的接触面,从而扼制锂枝晶的形成,提高全固态锂离子电池的机械性能;在PEDOT-co-PEG共聚物改性锂金属后,全固态锂离子电池的平稳性显著提高,且容量减弱放缓。     

固态电池中的正极/电解质界面性质研究进展EI北大核心CSCD

锂离子电池是便携式电子产品、电动汽车和智能电网的理想电源。目前使用有机液体电解质的锂离子电池仍然存在安全问题和寿命不足的问题,而使用不燃的固态电解质的固态电池有望解决这些问题。从原理上讲,不燃的固体电解质可以从根本上防止电池的燃烧和爆炸,并且只允许锂离子在固体电解质中传输,可以减少副反应的发生。近年来,随着几种高离子电导率的固态电解质的出现,锂离子在固态电解质中的传输不再是瓶颈。然而,固态电池中各种固态成分具有不同的化学/物理/力学性能,因此在固态电池中存在多种类型的界面,包括松散的物理接触、晶界、化学和电化学反应界面等,这些都可能增加界面离子传输阻力。而正极材料与电解质之间的界面反应尤其复杂,深入理解这些复杂的正极侧界面及其反应特点是实现实用高比能固态电池的必要条件。因此,本文主要回顾了近年来在探索和理解正极/电解质界面上的工作,总结了固态电池中典型的正极侧界面类型及其各自独特的反应特征。     

Regulating Li-Ion Transport through Ultrathin Molecular Membrane to Enable High-Performance All-Solid-State–Battery

Solid-state lithium metal batteries with garnet-type electrolyte provide several advantages over conventional lithium-ion batteries, especially for safety and energy density. However, a few grand challenges such as the propagation of Li dendrites, poor interfacial contact between the solid electrolyte and the electrodes, and formation of lithium carbonate during ambient exposure over the solid-state electrolyte prevent the viability of such batteries. Herein, an ultrathin sub-nanometer porous carbon nanomembrane (CNM) is employed on the surface of solid-state electrolyte (SSE) that increases the adhesion of SSE with electrodes, prevents lithium carbonate formation over the surface, regulates the flow of Li-ions, and blocks any electronic leakage. The sub-nanometer scale pores in CNM allow rapid permeation of Li-ions across the electrode–electrolyte interface without the presence of any liquid medium. Additionally, CNM suppresses the propagation of Li dendrites by over sevenfold up to a current density of 0.7 mA cm⁻² and enables the cycling of all-solid-state batteries at low stack pressure of 2 MPa using LiFePO₄ cathode and Li metal anode. The CNM provides chemical stability to the solid electrolyte for over 4 weeks of ambient exposure with less than a 4% increase in surface impurities.     

Rechargeable Lithium Metal Batteries with an In-Built Solid-State Polymer Electrolyte and a High Voltage/Loading Ni-Rich Layered Cathode

Solid-state batteries enabled by solid-state polymer electrolytes (SPEs) are under active consideration for their promise as cost-effective platforms that simultaneously support high-energy and safe electrochemical energy storage. The limited oxidative stability and poor interfacial charge transport in conventional polymer electrolytes are well known, but difficult challenges must be addressed if high-voltage intercalating cathodes are to be used in such batteries. Here, ether-based electrolytes are in situ polymerized by a ring-opening reaction in the presence of aluminum fluoride (AlF₃) to create SPEs inside LiNi_0.6Co_0.2 Mn_0.2O₂ (NCM) || Li batteries that are able to overcome both challenges. AlF₃ plays a dual role as a Lewis acid catalyst and for the building of fluoridized cathode–electrolyte interphases, protecting both the electrolyte and aluminum current collector from degradation reactions. The solid-state NCM || Li metal batteries exhibit enhanced specific capacity of 153 mAh g⁻¹ under high areal capacity of 3.0 mAh cm⁻². This work offers an important pathway toward solid-state polymer electrolytes for high-voltage solid-state batteries.     

Tuning the Anode–Electrolyte Interface Chemistry for Garnet-Based Solid-State Li Metal Batteries

Lithium (Li) metal is a promising candidate as the anode for high-energy-density solid-state batteries. However, interface issues, including large interfacial resistance and the generation of Li dendrites, have always frustrated the attempt to commercialize solid-state Li metal batteries (SSLBs). Here, it is reported that infusing garnet-type solid electrolytes (GSEs) with the air-stable electrolyte Li₃PO₄ (LPO) dramatically reduces the interfacial resistance to ≈1 Ω cm² and achieves a high critical current density of 2.2 mA cm⁻² under ambient conditions due to the enhanced interfacial stability to the Li metal anode. The coated and infused LPO electrolytes not only improve the mechanical strength and Li-ion conductivity of the grain boundaries, but also form a stable Li-ion conductive but electron-insulating LPO-derived solid-electrolyte interphase between the Li metal and the GSE. Consequently, the growth of Li dendrites is eliminated and the direct reduction of the GSE by Li metal over a long cycle life is prevented. This interface engineering approach together with grain-boundary modification on GSEs represents a promising strategy to revolutionize the anode–electrolyte interface chemistry for SSLBs and provides a new design strategy for other types of solid-state batteries.     

Protected Lithium‐Metal Anodes in Batteries: From Liquid to Solid

High‐energy lithium‐metal batteries are among the most promising candidates for next‐generation energy storage systems. With a high specific capacity and a low reduction potential, the Li‐metal anode has attracted extensive interest for decades. Dendritic Li formation, uncontrolled interfacial reactions, and huge volume effect are major hurdles to the commercial application of Li‐metal anodes. Recent studies have shown that the performance and safety of Li‐metal anodes can be significantly improved via organic electrolyte modification, Li‐metal interface protection, Li‐electrode framework design, separator coating, and so on. Superior to the liquid electrolytes, solid‐state electrolytes are considered able to inhibit problematic Li dendrites and build safe solid Li‐metal batteries. Inspired by the bright prospects of solid Li‐metal batteries, increasing efforts have been devoted to overcoming the obstacles of solid Li‐metal batteries, such as low ionic conductivity of the electrolyte and Li–electrolyte interfacial problems. Here, the approaches to protect Li‐metal anodes from liquid batteries to solid‐state batteries are outlined and analyzed in detail. Perspectives regarding the strategies for developing Li‐metal anodes are discussed to facilitate the practical application of Li‐metal batteries.     

固态锂电池用MOF/聚氧化乙烯复合聚合物电解质

固态聚合物电解质具有柔韧性好和易于加工的优势, 可制备各种形状的固态锂电池, 杜绝漏液问题。但固态聚合物电解质存在离子电导率低以及对锂金属负极不稳定等问题。本研究以纳米金属-有机框架材料UiO-66为聚合物电解质的填料, 用于改善电解质的性能。UiO-66与聚氧化乙烯(poly(ethylene oxide), PEO)链上醚基的氧原子的配位作用以及与锂盐中阴离子的相互作用, 可显著提高聚合物电解质的离子电导率(25 ℃, 3.0×10 ^-5S/cm; 60 ℃, 5.8×10 ^-4 S/cm), 并将锂离子迁移数提高至0.36, 电化学窗口拓宽至4.9 V。此外, 制备的PEO基固态电解质对金属锂具有良好的稳定性, 对称电池在60 ℃、0.15 mA·cm ^-2电流密度下可稳定循环1000 h, 锂电池的电化学性能得到显著改善。     

Development of an Electrophoretic Deposition Method for the In Situ Fabrication of Ultra-Thin Composite-Polymer Electrolytes for Solid-State Lithium-Metal Batteries

All-solid-state lithium-metal batteries offer higher energy density and safety than lithium-ion batteries, but their practical applications have been pushed back by the sluggish Li⁺ transport, unstable electrolyte/electrode interface, and/or difficult processing of their solid-state electrolytes. Li⁺-conducting composite polymer electrolytes (CPEs) consisting of sub-micron particles of an oxide solid-state electrolyte (OSSE) dispersed in a solid, flexible polymer electrolyte (SPE) have shown promises to alleviate the low Li⁺ conductivity of SPE, and the high rigidity and large interfacial impedance of OSSEs. Solution casting has been by far the most widely used procedure for the preparation of CPEs in research laboratories; however, this method imposes several drawbacks including particle aggregation and settlement during a long-term solvent evaporation step, excessive use of organic solvents, slow production time, and mechanical issues associated with handling of ultra-thin films of CPEs (<50 µm). To address these challenges, an electrophoretic deposition (EPD) method is developed to in situ deposit ultra-thin CPEs on lithium-iron-phosphate (LFP) cathodes within just a few minutes. EPD-prepared CPEs have shown better electrochemical performance in the lithium-metal battery than those CPEs prepared by solution casting due to a better dispersion of OSSE within the SPE matrix and improved CPE contact with LFP cathodes.     

新型硅-硫锂电池研究进展

高比能量、高安全性是未来储能系统的重要发展方向,在电子产品、航天设备、高续航电动汽车等诸多领域均有迫切需求。硅具有很高的理论比容量,电压平台接近金属锂,采用硅替代锂金属作为负极可以得到新型硅-硫锂电池。本文阐述了新型硅-硫锂电池的特征及存在的关键问题,介绍了全电池中锂源的引入方式,综述了新型硅-硫锂电池正、负极的制备技术及研究进展,总结了不同制备方法存在的优缺点,并详述了目前液态电解质的常见组成、研究进展以及存在的问题。最后结合硅-硫锂电池的发展趋势提出未来重点研究的几个方向,如优化电极/电解质界面、开发固态电解质等。     

Simultaneous High Ionic Conductivity and Lithium-Ion Transference Number in Single-Ion Conductor Network Polymer Enabling Fast-Charging Solid-State Lithium Battery

Developing solid-state electrolyte with sufficient ionic conduction and flexible-intimate interface is vital to advance fast-charging solid-state lithium batteries. Solid polymer electrolyte yields the promise of interfacial compatibility, yet its critical bottleneck is how to simultaneously achieve high ionic conductivity and lithium-ion transference number. Herein, single-ion conducting network polymer electrolyte (SICNP) enabling fast charging is proposed to positively realize fast lithium-ion locomotion with both high ionic conductivity of 1.1 × 10⁻³ S cm⁻¹ and lithium-ion transference number of 0.92 at room temperature. Experimental characterization and theoretical simulations demonstrate that the construction of polymer network structure for single-ion conductor not only facilitates fast hopping of lithium ions for boosting ionic kinetics, but also enables a high dissociation level of the negative charge for lithium-ion transference number close to unity. As a result, the solid-state lithium batteries constructed by coupling SICNP with lithium anodes and various cathodes (e.g., LiFePO₄, sulfur, and LiCoO₂) display impressive high-rate cycling performance (e.g., 95% capacity retention at 5 C for 1000 cycles in LiFePO₄|SICNP|lithium cell) and fast-charging capability (e.g., being charged within 6 min and discharged over than 180 min in LiCoO₂|SICNP|lithium cell). Our study provides a prospective direction for solid-state electrolyte that meets the lithium-ion dynamics for practical fast-charging solid-state lithium batteries.     

In Situ Construction of a LiF-Enriched Interface for Stable All-Solid-State Batteries and its Origin Revealed by Cryo-TEM

The application of solid polymer electrolytes (SPEs) is still inherently limited by the unstable lithium (Li)/electrolyte interface, despite the advantages of security, flexibility, and workability of SPEs. Herein, the Li/electrolyte interface is modified by introducing Li₂S additive to harvest stable all-solid-state lithium metal batteries (LMBs). Cryo-transmission electron microscopy (cryo-TEM) results demonstrate a mosaic interface between poly(ethylene oxide) (PEO) electrolytes and Li metal anodes, in which abundant crystalline grains of Li, Li₂O, LiOH, and Li₂CO₃ are randomly distributed. Besides, cryo-TEM visualization, combined with molecular dynamics simulations, reveals that the introduction of Li₂S accelerates the decomposition of N(CF₃SO₂)₂⁻ and consequently promotes the formation of abundant LiF nanocrystals in the Li/PEO interface. The generated LiF is further verified to inhibit the breakage of C O bonds in the polymer chains and prevents the continuous interface reaction between Li and PEO. Therefore, the all-solid-state LMBs with the LiF-enriched interface exhibit improved cycling capability and stability in a cell configuration with an ultralong lifespan over 1800 h. This work is believed to open up a new avenue for rational design of high-performance all-solid-state LMBs.     

聚合物复合固体电解质材料研究进展

固体电解质是发展高安全、高能量密度全固态锂电池的重要材料基础。由聚合物相与无机相复合形成的聚合物复合固体电解质,兼具聚合物轻质、柔性,以及无机材料高强度、高稳定性等优势,是最具应用潜力的固体电解质材料。目前,制约聚合物复合固体电解质实际应用的主要瓶颈问题为其室温离子电导率较低。综述了目前关于聚合物复合固体电解质离子传导机制的科学认识以及提升其离子电导率的方法,分析了先进表征工具在揭示聚合物复合固体电解质离子传导机制方面的应用潜力,并展望了聚合物复合固体电解质未来的发展方向和工作重点。     

Improving Room-Temperature Li-Metal Battery Performance by In Situ Creation of Fast Li+ Transport Pathways in a Polymer-Ceramic Electrolyte

Composite polymer-ceramic electrolytes have shown considerable potential for high-energy-density Li-metal batteries as they combine the benefits of both polymers and ceramics. However, low ionic conductivity and poor contact with electrodes limit their practical usage. In this study, a highly conductive and stable composite electrolyte with a high ceramic loading is developed for high-energy-density Li-metal batteries. The electrolyte, produced through in situ polymerization and composed of a polymer called poly-1,3-dioxolane in a poly(vinylidene fluoride)/ceramic matrix, exhibits excellent room-temperature ionic conductivity of 1.2 mS cm⁻¹ and high stability with Li metal over 1500 h. When tested in a Li|electrolyte|LiFePO₄ battery, the electrolyte delivers excellent cycling performance and rate capability at room temperature, with a discharge capacity of 137 mAh g⁻¹ over 500 cycles at 1 C. Furthermore, the electrolyte not only exhibits a high Li⁺ transference number of 0.76 but also significantly lowers contact resistance (from 157.8 to 2.1 Ω) relative to electrodes. When used in a battery with a high-voltage LiNi_0.8Mn_0.1Co_0.1O₂ cathode, a discharge capacity of 140 mAh g⁻¹ is achieved. These results show the potential of composite polymer-ceramic electrolytes in room-temperature solid-state Li-metal batteries and provide a strategy for designing highly conductive polymer-in-ceramic electrolytes with electrode-compatible interfaces.     

Aliphatic Polycarbonate‐Based Solid‐State Polymer Electrolytes for Advanced Lithium Batteries: Advances and Perspective

Conventional liquid electrolytes based lithium‐ion batteries (LIBs) might suffer from serious safety hazards. Solid‐state polymer electrolytes (SPEs) are very promising candidate with high security for advanced LIBs. However, the quintessential frailties of pristine polyethylene oxide/lithium salts SPEs are poor ionic conductivity (≈10⁻⁸ S cm⁻¹) at 25 °C and narrow electrochemical window (<4 V). Many innovative researches are carried out to enhance their lithium‐ion conductivity (10⁻⁴ S cm⁻¹ at 25 °C), which is still far from meeting the needs of high‐performance power LIBs at ambient temperature. Therefore, it is a pressing urgency of exploring novel polymer host materials for advanced SPEs aimed to develop high‐performance solid lithium batteries. Aliphatic polycarbonate, an emerging and promising solid polymer electrolyte, has attracted much attention of academia and industry. The amorphous structure, flexible chain segments, and high dielectric constant endow this class of polymer electrolyte excellent comprehensive performance especially in ionic conductivity, electrochemical stability, and thermally dimensional stability. To date, many types of aliphatic polycarbonate solid polymer electrolyte are discovered. Herein, the latest developments on aliphatic polycarbonate SPEs for solid‐state lithium batteries are summarized. Finally, main challenges and perspective of aliphatic polycarbonate solid polymer electrolytes are illustrated at the end of this review.     

A Self-Healing Amalgam Interface in Metal Batteries

Poor cyclability and safety concerns caused by the uncontrollable dendrite growth and large interfacial resistance severely restrict the practical applications of metal batteries. Herein, a facile, universal strategy to fabricate ceramic and glass phase compatible, and self-healing metal anodes is proposed. Various amalgam-metal anodes (Li, Na, Zn, Al, and Mg) show a long cycle life in symmetric cells. It has been found that liquid Li amalgam shows a complete wetting with the surface of lanthanum lithium titanate electrolyte and a glass-phase solid-state electrolyte. The interfacial compatibility between the lithium metal anode and solid-state electrolyte is dramatically improved by using an in situ regenerated amalgam interface with high electron/ion dual-conductivity, obviously decreasing the anode/electrolyte interfacial impedance. The lithium-amalgam interface between the metal anode and electrolyte undergoes a reversible isothermal phase transition between solid and liquid during the cycling process at room temperature, resulting in a self-healing surface of metal anodes.     

Perovskite‐type Li‐ion solid electrolytes: a review

All-solid-state lithium batteries with inorganic solid electrolytes are recognized as the next-generation battery systems due to their high safety and energy density. To realize the practical applications of all-solid-state lithium battery, it is essential to develop solid electrolytes which exhibit high Li-ion conductivity, low electron conductivity, wide electrochemical window, and low interface resistance between the electrode and the solid electrolyte. Among many solid electrolytes, the perovskite-type lithium-ion solid electrolytes are promising candidates that can be applied to all-solid-state lithium batteries. However, the perovskite-type solid electrolytes still suffer from several significant problems, such as poor stability against lithium metal, high interface resistance, etc. In this review, we have analyzed and summarized the properties of perovskite-type solid electrolytes with two different systems, namely three-component oxide system Li_3xLa_2/3?xTiO₃ (LLTO) and four-component oxide system (Li, Sr)(B, B’)O₃ (B?=?Zr, Hf, Ti, Sn, Ga, etc., B’ = Nb, Ta, etc.). LLTO and (Li, Sr)(B, Ta)O₃ compounds exhibit high Li-ion conductivity of up to >?10^??4 S·cm^??1 at room temperature. Based on the review of academic literature, the ion transportation mechanism, composition design, electrical properties, stability, doping, and application of these solid electrolytes are discussed, which would be helpful for the further development of all-solid-state lithium batteries.