Role of Interfacial Defects on Electro-Chemo-Mechanical Failure of Solid-State Electrolyte

In-Situ Polymerized Solid/Quasi-Solid Polymer Electrolyte for Lithium-Metal Batteries: Recent Progress and Perspectives

In pursuit of high energy density, lithium metal batteries (LMBs) are undoubtedly the best choice. However, leakage and inevitable dendrite growth in liquid electrolytes seriously hinder its practical application. Solid/quasi-solid state electrolytes have emerged as an answer to solve the above issues. Especially, polymer electrolytes with excellent interface compatibility, high flexibility, and ease of machining have become a research hotspot for LMBs. Nevertheless, the interface contact between polymer electrolyte and inorganic electrode materials and the low ionic conductivity restrict its development. On account of these, in situ polymerized polymer electrolyte is proposed. Polymer solid electrolytes produced through in situ polymerization promote robust interface contact between the electrolyte and electrode while simplifying the preparation steps. This review summarized the latest research progress in in situ polymerized solid electrolytes for LMBs. These electrolytes were divided into three parts according to their polymerization methods: thermally induced polymerization, chemical initiator polymerization, ionizing radiation polymerization, and so on. Furthermore, we concluded the major challenges and future trends of in situ polymerized solid electrolytes for LMBs. It's hoped that this review will provide meaningful guidance on designing high-performance polymer solid electrolytes for LMBs.

Poly(ethylene oxide)-based composite solid electrolyte for long cycle life solid-state lithium metal batteries: Improvement of interface stability through a dual mechanism

Solid-state lithium metal batteries (SSLMBs) are promising candidates for safe and high-energy-density next-generation applications. However, harmful interfacial decomposition and uneven Li deposition lead to poor ion transport, a short cycle life, and battery failure. Herein, we propose a novel poly(ethylene oxide) (PEO)-based composite solid electrolyte (CSE) containing succinonitrile (SN) and zinc oxide (ZnO) nanoparticles (NPs), which improves interface stability through a dual mechanism. (1) By anchoring bis(trifluoromethanesulfonyl)imide (TFSI) anions to ZnO, a reliable solid electrolyte interface (SEI) later with abundant LiF can be obtained to inhibit interface decomposition. (2) The immobilization of escaping SN molecules in the SEI layer by ZnO NPs promotes the self-polymerization of SN and facilitates charge transfer through the interface. As a result, the ion conductivity of the stainless steel-symmetrical battery reaches 1.1 × 10-4 S cm-1 at room temperature, and a LiFePO4 (LFP) full battery exhibits ultrahigh stability (800 cycles) at 0.5 C. Thus, the present study provides valuable insights for the development of advanced PEO-based SSLMBs.

Designing Cooperative Ion Transport Pathway in Ultra-Thin Solid-State Electrolytes toward Practical Lithium Metal Batteries

Solid polymer electrolytes (SPEs) are promising for high-energy-density solid-state Li metal batteries due to their decent flexibility, safety, and interfacial stability. However, their development was seriously hindered by the interfacial instability and limited conductivity, leading to inferior electrochemical performance. Herein, we proposed to design ultra-thin solid-state electrolyte with long-range cooperative ion transport pathway to effectively increase the ionic conductivity and stability. The impregnation of PVDF-HFP inside pores of fluorinated covalent organic framework (CF3-COF) can disrupt its symmetry, rendering rapid ion transportation and inhibited anion immigration. The functional groups of CF3-COF can interact with PVDF-HFP to form fast Li+ transport channels, which enables the uniform and confined Li+ conduction within the electrolyte. The introduction of CF3-COF also enhances the mechanical strength and flexibility of SPEs, as well as ensures homogeneous Li deposition and inhibited dendrite growth. Hence, a remarkably high conductivity of 1.21×10-3 S cm-1 can be achieved. Finally, the ultra-thin SPEs with an extremely long cycle life exceed 9000 h can be obtained while the NCM523/Li pouch cell demonstrates a high capacity of 760 mAh and 96 % capacity retention after cycling, holding great promises to be utilized for practical solid-state Li metal batteries.

Achieving Stable Lithium Anodes through Leveraging Inevitable Stress Variations via Adaptive Piezoelectric Effect

Unleashing the potential of lithium-metal anodes in practical applications is hindered by the inherent stress-related challenges arising from their limitless volume expansion, leading to mechanical failures such as electrode cracking, solid electrolyte interphase damage, and dendritic growth. Despite the various protective strategies to "combat" stress in lithium-metal anodes, they fail to address the intrinsic issue fundamentally. Here, a unique strategy is proposed that leverages the stress generated during the battery cycling via the piezoelectric effect, transforming to the adaptive built-in electric field to accelerate lithium-ion migration, homogenize the lithium deposition, and alleviate the stress concentration. The mechanism of the piezoelectric effect in modulating electro-chemomechanical field evolution is further validated and decoupled through finite element method simulations. Inspired by this strategy, a high sensitivity, fast responsive, and strength adaptability polymer piezoelectric is used to demonstrate the feasibility and the corresponding protected lithium-metal anode shows cycling stability over 6000 h under a current density of 10 mA cm-2 and extending life in a variety of coin and pouch cell systems. This work effectively tackles the stress-related issues and decoupling the electro-chemomechanical field evolution also contributes to developing more stable lithium anodes for future research.

Solid Interfaces for the Garnet Electrolytes

Solid-state electrolytes (SSEs) have attracted extensive interests due to the advantages in developing secondary batteries with high energy density and outstanding safety. Possessing high ionic conductivity and the lowest reduction potential among the state-of-the-art SSEs, the garnet type SSE is one of the most promising candidates to achieve high performance solid-state lithium batteries (SSLBs). However, the elastic modulus of the garnet electrolyte leads to deteriorated interfacial contacts, and the increasing in electronic conduction at either anode/garnet interface or grain boundary results in Li dendrite growth. Here, recent developments of the solid interfaces for the garnet electrolytes, including the strategies of Li dendrite suppression and interfacial chemical/electrochemical/mechanical stabilizations are presented. A new viewpoint of the double edges of interfacial lithiophobicity is proposed, and the rational design of the interphases, as well as effective stacking methods of the garnet-based SSLBs are summarized. Moreover, practical roles of the garnet electrolyte in SSLB industry are also discussed. This work delivers insights into the solid interfaces for the garnet electrolytes, which provides not only the promotion of the garnet-based SSLBs, but also a comprehensive understanding of the interfacial stabilization for the whole SSE family.

Computational approach inspired advancements of solid-state electrolytes for lithium secondary batteries: from first-principles to machine learning

The increasing demand for high-security, high-performance, and low-cost energy storage systems (EESs) driven by the adoption of renewable energy is gradually surpassing the capabilities of commercial lithium-ion batteries (LIBs). Solid-state electrolytes (SSEs), including inorganics, polymers, and composites, have emerged as promising candidates for next-generation all-solid-state batteries (ASSBs). ASSBs offer higher theoretical energy densities, improved safety, and extended cyclic stability, making them increasingly popular in academia and industry. However, the commercialization of ASSBs still faces significant challenges, such as unsatisfactory interfacial resistance and rapid dendrite growth. To overcome these problems, a thorough understanding of the complex chemical-electrochemical-mechanical interactions of SSE materials is essential. Recently, computational methods have played a vital role in revealing the fundamental mechanisms associated with SSEs and accelerating their development, ranging from atomistic first-principles calculations, molecular dynamic simulations, multiphysics modeling, to machine learning approaches. These methods enable the prediction of intrinsic properties and interfacial stability, investigation of material degradation, and exploration of topological design, among other factors. In this comprehensive review, we provide an overview of different numerical methods used in SSE research. We discuss the current state of knowledge in numerical auxiliary approaches, with a particular focus on machine learning-enabled methods, for the understanding of multiphysics-couplings of SSEs at various spatial and time scales. Additionally, we highlight insights and prospects for SSE advancements. This review serves as a valuable resource for researchers and industry professionals working with energy storage systems and computational modeling and offers perspectives on the future directions of SSE development.

Insight into Dendrites Issue in All Solid-State Batteries with Inorganic Electrolyte: Mechanism, Detection and Suppression Strategies

All solid-state batteries (ASSBs) are regarded as one of the promising next-generation energy storage devices due to their expected high energy density and capacity. However, failures due to unrestricted growth of lithium dendrites (LDs) have been a critical problem. Moreover, the understanding of dendrite growth inside solid-state electrolytes is limited. Since the dendrite process is a multi-physical field coupled process, including electrical, chemical, and mechanical factors, no definitive conclusion can summarize the root cause of LDs growth in ASSBs till now. Herein, the existing works on mechanism, identification, and solution strategies of LD in ASSBs with inorganic electrolyte are reviewed in detail. The primary triggers are thought to originate mainly at the interface and within the electrolyte, involving mechanical imperfections, inhomogeneous ion transport, inhomogeneous electronic structure, and poor interfacial contact. Finally, some of the representative works and present an outlook are comprehensively summarized, providing a basis and guidance for further research to realize efficient ASSBs for practical applications.

Correlating the Microstructure and Current Density of the Li/Garnet Interface

Solid-state lithium batteries hold great promise for next-generation energy storage systems. However, the formation of lithium filaments within the solid electrolyte remains a critical challenge. In this study, we investigate the crucial role of morphology in determining the resistance of garnet-type electrolytes to lithium filaments. By proposing a new test method, namely, cyclic linear sweep voltammetry, we can effectively evaluate the electrolyte resistance against lithium filaments. Our findings reveal a strong correlation between the microscopic morphology of the solid electrolyte and its resistance to lithium filaments. Samples with reduced pores and multiple grain boundaries demonstrate remarkable performance, achieving a critical current density of up to 3.2 mA cm-2 and excellent long-term cycling stability. Kelvin probe force microscopy and finite element method simulation results shed light on the impact of grain boundaries and electrolyte pores on lithium-ion transport and filament propagation. To inhibit lithium penetration, minimizing pores and achieving a uniform morphology with small grains and plenty of grain boundaries are essential.

Optimizing Li1.3Al0.3Ti1.7(PO4)3 Particle Sizes toward High Ionic Conductivity

NASICON-type Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) has attracted a lot of attention because of its high ionic conductivity and stability to air and moisture. However, the size effect of LATP primary particles on ionic conductivity is ignored. In this study, different sizes of LATP particles are prepared to investigate the morphology, relative density, and ionic conductivity of the LATP solid electrolyte. The influences of particle size and sintering temperature on the microstructure, phase composition, and electrical properties of LATP ceramics were systematically studied. The medium-sized LATP particle (2 μm) presents a great microstructure with a high relative density of over 97%, the highest ionic conductivity of 6.7 × 10^-4 S cm^-1, and an activation energy of 0.418 eV. The Li-Li symmetric cells and Li-LFP batteries delivering good electrochemical performance were fabricated with highly conductive LATP ceramics. These results make significant strides in elucidating the relationship between the particle sizes of LATP and its electrochemical performance.