All-solid-state hybrid electrode configuration for high-performance all-solid-state batteries: Comparative study with composite electrode and diffusion-dependent electrode

To realize high-performance all-solid-state batteries, an efficient design for all-solid-state electrodes is vital. Composite electrode, which is comprised of well-mixed active material and solid electrolyte, is a typical structure to build well-percolated ionic pathways within the electrode. In contrast, diffusion-dependent electrode, which consists mostly of active material, is an emerging approach that utilizes interparticle diffusion between active material particles for charge/discharge. This design enables maximization of energy density and simplification of the fabrication process. Herein, we present a hybrid all-solid-state electrode that combines the merits of each electrode as a new electrode concept. This electrode consists of a bilayer structure of the composite electrode and the diffusion-dependent electrode, and its electrochemical features such as initial Coulombic efficiency, capacity retention, and energy density are systematically analyzed. Owing to the active utilization of lithium-ion transports via percolated solid electrolyte particles and interparticle diffusion of active material particles, the graphite-based hybrid electrode with a practically meaningful capacity (∼4 mA h cm⁻²) is demonstrated to deliver moderately high energy densities at various C-rates. In particular, silicon/graphite-based hybrid electrode can exhibit high normalized capacities of 5.83 mA h cm⁻² and 1300 mA h cm⁻³, which are among the highest values reported to date for all-solid-state batteries.