An unblocked Li transport pathway for all-solid-state batteries enabled by boosting bulk diffusion kinetic and interfacial ion conduction

Abstract

The high interfacial resistance and dendrite growth associated with the high Li concentration gradient at the Li/solid-state electrolytes (SSEs) interface significantly hinder the cycle life of solid-state lithium metal batteries (SSLMBs). This limitation is primarily attributed to the slow diffusion of Li atoms in the bulk and the sluggish conduction of Li ions at the interface. Merely focusing on enhancing either aspect is typically not sufficient to fully address this challenge. Herein, we utilize AgNO3 molten salt to in-situ generate LixAg anode and nitrided interphase to simultaneously boost the bulk Li atom diffusion kinetics and the interfacial ion conduction, effectively constructing a fast-continuous ion/atom transport pathway and significantly reducing the concentration gradient of Li. The in-situ formed LixAg alloy, with a Li diffusion coefficient of approximately 10−8 cm2 s−1, demonstrates a diffusion rate three orders of magnitude higher than bulk Li (∼ 10−11 cm2 s−1), alleviating vacancy accumulation and contact loss at the anode/SSE interface. While the in-situ formed ionic conductive nitrided interphase promotes ion transport through the interface to reduce the Li concentration gradient and boost charge transfer kinetics. Benefiting from the high Li ion/atom transport rate in both bulk and interface, ultrahigh critical current density/areal capacity (1.2 mA cm−2;1.2 mAh cm−2) and cyclability (1.0 mA cm−2;0.5 mAh cm−2) are achieved for solid-state Li||Li symmetric cells. Impressively, an SSLMB assembled with a LiFePO4 electrode shows excellent cycling stability for as long as 1600 cycles at 0.5 C with a high capacity retention of 82.6 %.