Enabling high-voltage stability and interface compatibility via Ta/Nb co-occupation in fluorinated Li-halide catholytes

Abstract

Solid electrolytes (SEs) possessing high voltage stability, good compatibility with oxide active materials, and fast ion transport are essential to act as a catholyte in developing all-solid-state Li batteries (ASSLBs) with high energy density. Nonetheless, many of the reported SEs are hard to reach these targets simultaneously. In this work, we report a type of fluorinated Li-halides by adopting LiF instead of LiCl as raw material, with a ratio of LiF:Li₂O:Ta(Nb)Cl₅ fixing to 1:1:1 and variant Ta/Nb ratios. The co-occupation of Ta/Nb enables the fluorinated Li-halides to simultaneously reach the targets aforementioned. Moreover, a soft feature with small Young's modulus is observed. The ASSLBs assembled using the cathode with the optimized SE and bare single-crystal LiNi_0.88Co_0.09Mn_0.03O₂ (SC-NCM88) demonstrate a high specific capacity and long-term cycling stability even at a cut-off voltage of 4.6 V. The intimate contact and superior interface stability inside the cathode are the origins for the superior electrochemical performance of the batteries. We also show the components we designed need only a short synthesis time (only 6 h).