Dual-functional Li+ diffusion network in high-nickel cathodes for solid-state Li metal batteries

Abstract

The lithiation/deintercalation of cathode materials leads to poor contact between the cathode particles in solid-state batteries. This process leads to fast capacity attenuation as there is no continuous ion transport medium to fill up the voids caused by the volume change of active materials. Herein, we designed a dehydrofluorination polyvinylidene fluoride (PVDF) coating layer for LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) particles using residual Li₂CO₃ on the NCM surface to induce the dehydrofluorination reaction of PVDF. On the one hand, the in situ formed coating layer increased the contact area between the NCM particles and acted as a buffering barrier for the volume change of NCM, ensuring unobstructed Li⁺ transport during the lithiation/deintercalation process. On the other hand, the –CC– and LiF generated via the dehydrofluorination reaction was beneficial for Li⁺ diffusion. As a result, a sturdy and fast Li⁺ transport network was constructed, and the electrochemical performance of the solid-state battery was greatly improved. Thus, this dual-functional Li⁺ transport network simultaneously alleviates the poor particle contact and limited Li⁺ transport in cathodes, offering a novel approach for achieving high-performance solid-state batteries.