Interfacial modification enabled room temperature solid-state lithium–metal batteries

Abstract

Lithium solid-state batteries (SSBs) with tantalum doped Li7La3Zr2O12 (LLZT) inorganic ceramic electrolytes have been attracting much interest for its extraordinary lithium ionic conductivity, non-flammability, and wide electrochemical window. However, poor solid–solid contact between the electrodes and electrolyte results in large interfacial resistance, which hinders its normal operation and practical application. Herein, triethylene glycol diacetate-2-propenoic acid butyl ester (TEGDA-BA) based gel polymer electrolytes (GPE) were fabricated and coated on both sides of spark plasma sintering (SPS)–derived LLZT pellet. GPE introduction not only provides intimate contact between solid electrolyte and electrodes but also avoids side reactions such as reduction of LLZT by lithium anode. Moreover, symmetric Li cell markedly reduced interfacial resistance and exhibited a critical current density up to 1.0 mA cm−2 at room temperature (25 °C), and it can also stably cycle at 0.5 mA cm−2 for over 277 h without Li dendrite formation. The assembled solid-state LiNi0.5Co0.2Mn0.3O2 (NCM523)/GPE–LLZT–GPE/Li battery exhibits high initial capacity (163.5 mAh g−1) at 0.2 C. This work provides a facile method to reduce the interfacial resistance and demonstrates durable high-energy solid-state lithium metal batteries suitable for practical application.