Longitudinal spatial charge transfer optimization in composite cathodes enables ultra-stable all-solid-state batteries

Abstract

All-solid-state batteries (ASSBs) promise high energy density and inherent safety but face critical challenges in the complex charge transfer process across the longitudinal cathode. Here, through the Multiphysics simulation, it is firstly revealed that charge transfer critically governs electrochemical reaction heterogeneity, dictating where reactions initiate preferentially along the length of cathodes. Building on this insight, a charge-transfer-optimized cathode (CTOC) is proposed to conceptually validate the effectiveness of charge-transfer regulation in homogenizing the longitudinal Li concentration. The CTOC features a double-layer architecture: a carbon-free layer with large-sized catholytes near the separator to enhance Li-ion transfer while reducing electron conduction and a carbon-containing layer near the current collector to ensure efficient electronic conductivity, thus tandemly modulating the spatial ion and electron transfer dynamics along the longitudnal axis. Through graded ionic and electronic conduction to achieve decoupled but synchronized ion and electron transport pathways, the CTOC enables longitudinally homogeneous Li distribution throughout the cathode. As a result, CTOC exhibits excellent cycling performance, retaining 82.7% capacity after 2000 cycles at 2C, a 27.4% durability improvement over conventional single-layer designs. This work establishes electrode-level charge transfer optimization as a design principle for heterogeneous reaction control, offering fundamental insights and practical strategies for high-performance ASSBs.