Electrolyte-free graphite electrode with enhanced interfacial conduction using Li⁺-conductive binder for high-performance all-solid-state batteries

Electrodes supported by conductive binders are expected to outperform ones with inert binders that potentially disturb electronic/ionic contacts at interfaces. Unlike electron-conductive binders, the employment of Li⁺-conductive binders has attracted relatively little attention due to the liquid electrolyte (LE)-impregnated electrode configuration in the conventional lithium-ion batteries (LIBs). Herein, an all-solid-state electrolyte-free electrode where electrolyte components are completely excluded is introduced as a new tactical electrode construction to evaluate the effectiveness of the Li⁺-conductive binder on enhancing the interfacial conduction, ultimately leading to high-performance all-solid-state batteries (ASSBs). Conductive lithium carboxymethyl cellulose (Li-CMC) is prepared through an optimized two-step cation-exchange reaction without physical degradation. The electrolyte-free graphite electrode employing Li-CMC as the binder shows strikingly improved areal and volumetric capacity of 1.46 mAh cm⁻² and 490 mAh cm⁻³ at a high current rate (1.91 mA cm⁻²) and 60 °C which are far superior to those (1.07 mAh cm⁻² and 356.7 mAh cm⁻³) using Na-CMC. Moreover, systematic monitoring of the lithiation dynamics inside the electrolyte-free electrode clarifies that the interfacial Li⁺ conduction is greatly promoted in the Li-CMC electrode. Complementary analysis from in-depth electrochemical measurements and multiscale simulations verifies that serious internal resistance from impeded interparticle diffusion by inert binders can be substantially mitigated using Li-CMC.