Suppressing shear strains in electrode calendering for enhanced high-voltage stability

Abstract Layered metal oxide cathodes suffer from pronounced structural degradation under high charging cut-off voltages, limiting their high-energy applications. While electrochemical degradation mechanisms have been extensively studied, the role of mechanical deformation introduced during electrode calendering remains largely unexplored. Here, using LiCoO₂ (LCO) as a model system, we demonstrate that industry-scale roll press calendering induces shear strain at the atomic scale, which triggers the O3-to-O1 phase transition during high-voltage ageing at 4.48 V. The propagation of shear strain during cycling leads to inhomogeneous layer gliding and structural deformation, contributing to the heterogeneous lithium distribution at the atomic scale. We establish a mechanistic link between calendering-induced shear strain and high-voltage structural failure. To mitigate this challenge, we have developed an isostatic calendering method that suppresses shear strain in LiCoO₂ while achieving an industry-level high tapped density (4.2 g/cm³), resulting in enhanced structural integrity and electrochemical stability. The findings position mechanically induced strain as a critical degradation driver in layered oxide cathodes, underscoring the importance of coupling material design and electrode engineering to advance battery technologies.