Functional Surface Modification of Ni-Rich Cathode for All-Solid-State Lithium-Ion Batteries Employing Sulfide Solid Electrolytes

Intensive research and development efforts have been directed towards lithium-ion battery (LIB) for electric vehicle applications. However, conventional LIBs utilize flammable organic liquid electrolytes, which pose inherent safety risks, including a propensity for fire-related incidents. These safety concerns have spurred heightened interests in all-solid-state batteries (ASSBs), which utilize inorganic solid electrolytes (SEs) instead. For ASSBs to meet the practical demands of high energy density, the use of Ni-rich layered oxide cathode active materials (CAMs), denoted as LiMO₂ (M = Ni, Co, Mn, and/or Al), which are prevalent in LIBs, is essential. However, a significant change arises with sulfide SEs, known for their high ionic conductivity but poor electrochemical stability. This instability necessitates the application of an insulating buffer layer on Ni-rich CAMs. Furthermore, Ni-rich CAMs are prone to structural instability, leading to internal cracking and significant degradation, notably an irreversible H2-H3 phase transition when in high states of charge. To address the structural stability issues inherent in Ni-rich CAMs, metal doping techniques have been commonly employed.<br/>In this presentation, we propose a comprehensive strategy that addresses not only the poor electrochemical stability of sulfide SEs but also the detrimental phase transition of Ni-rich CAMs. This approach involves the development of multi-component functional coatings. Along with significantly enhanced electrochemical performance, interfacial evolutions probed by complementary analyses are presented.