Graphite–Silicon Diffusion‐Dependent Electrode with Short Effective Diffusion Length for High‐Performance All‐Solid‐State Batteries

Abstract Electrode design, which is closely related to electronic and ionic transport, is an essential factor that influences the performance of all‐solid‐state batteries. An in‐depth understanding of the movement of the charge carriers and its relationship to the electrode structure are urgently needed for the realization of advanced energy storage devices. Herein, a simple electrode configuration, which consists mostly of blended active materials of graphite and silicon, is presented to simultaneously satisfy the high power and high energy density of all‐solid‐state batteries. This electrode efficiently utilizes interdiffusion between the active material particles for charge/discharge. Mechanically compliant graphite accommodates the volume change of silicon and continuously provides abundant electrons to silicon, which enables a stable electrochemical reaction. Silicon with its higher volumetric capacity compared to graphite, shortens the effective diffusion pathway in the electrode. In particular, the use of the nanometer‐scale silicon leads to its uniform distribution throughout the electrode, which increases the contact area capable of interdiffusion between the graphite and silicon and reduces the diffusion in the agglomerated silicon with relatively low diffusivity. This morphology‐induced electrochemical change dramatically increases the achievable capacities at higher current densities (93.8% capacity retention (2.76 mAh cm −2 ) at 0.5 C‐rate (1.77 mA cm −2 ) relative to the capacity at 0.1 C‐rate).