Electro–Chemo–Mechanical Issues at the Interfaces in Solid‐State Lithium Metal Batteries

Abstract

Effective solid‐state interfacial contact of both the cathode and lithium metal anode with the solid electrolyte (SE) are required to improve the performance of solid‐state lithium metal batteries (SSBs). Electro–chemo–mechanical coupling (ECMC) strongly affects the interfacial stability of SSBs. On one hand, mechanical stress strongly influences interfacial contact and causes side reactions. On the other hand, electrochemical reactions such as lithium deposition cause mechanical deformation and stress at electrode/SE interfaces. To solve the degradation/failure problems of interfaces and provide guidelines to construct high‐performance SSBs, the ECMC at electrode/SE interfaces should be comprehensively investigated. In this review, the problems associated with ECMC at electrode/SE interfaces are summarized. The interfacial degradation/failure mechanisms, including the contact and electrochemical stability of interfaces, are introduced. Mechanical factors affecting interfacial contact and lithium deposition are highlighted. Experimental observation and computational analysis methods for electrode/SE interfaces are then summarized. Strategies to construct stable electrode/SE interfaces, such as assembling stress and wetting layers to improve interfacial contact, 3D SE structure, and plating stress relief to suppress lithium dendrite formation, are reviewed. The remaining challenges to better understanding ECMC and related solutions to aid SSB development are discussed.

Enabling Stable Cycling of 4.2 V High‐Voltage All‐Solid‐State Batteries with PEO‐Based Solid Electrolyte

“…[ 1 ] Among the prevalent ASSBs, poly(ethylene oxide) (PEO)‐based ASSB is one of the most practical battery system, [ 2 ] as the PEO‐based solid polymer electrolytes (SPEs) possess numerous merits in terms of high ionic conductivity, high processing ability, low cost, and acceptable stability against lithium metal. [ 3 ] Despite some early studies showing the stabilization of PEO‐SPEs to 4.2 V (versus Li/Li + ), [ 4 ] subsequent investigations have indicated that the reported “wide electrochemical window (EW)” is actually caused by kinetic polarization. [ 5 ] Xia et al firstly examined the EW of PEO‐SPEs by performing linear sweep voltammetry (LSV) measurements with carbon composite electrodes, and found that the oxidation of PEO‐SPEs started to occur at around 3.8 V. [ 5 ] Such restricted upper voltage limit was further confirmed by a sudden degradation of cycle life when the cut‐off charging voltage was increased to above 3.9 V. [ 6 ] Therefore, the widely reported PEO‐based ASSBs can only employ cathodes with low lithium storage potentials, for example V 2 O 5 [ 7 ] and LiFePO 4 , [ 8 ] as the capacity fades rapidly when PEO is paired with high voltage cathodes of above 3.9 V (e.g., LiCoO 2 , LiNi x Co y Mn 1‐ x ‐ y O 2 ).…”

Sulfide and Oxide Inorganic Solid Electrolytes for All-Solid-State Li Batteries: A Review

“…Furthermore, the fundamentals of ASSBs were reviewed by several authors [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. The number of reviews on various aspects of electrolytes, cathodes, mechanical properties, and interface engineering has grown exponentially since 2018 [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ...…”

Recent Advances in Polymer Electrolytes for Zinc Ion Batteries: Mechanisms, Properties, and Perspectives

“…Additionally, chemical/electrochemical stability is another important requirement for SEI. Strong chemical/electrochemical stability represents nearly no side reactions and dendrites free at SEI 82. Side reactions at the interface would lead to high internal resistance and serious zinc dendrites.…”