An advanced 3D gel cathode with continuous ion and electron transport pathway for solid-state lithium batteries

Abstract

Ta-doped Li7La3Zr2O12 (LLZTO) is known as a garnet-type solid-state electrolyte with high ionic conductivity and good stability against lithium metal anode, which is regarded as one of the most promising electrolytes for the commercialization of solid-state batteries (SSBs). However, the poor electron and ion transport among cathode active material particles, as well as the large interfacial impedance between LLZTO ceramic pellet and cathode, remain major issues for SSBs. In this work, we proposed a novel 3D gel cathode based on the “cation-π” interaction between the organic cations in ionic liquid (IL) and the large electron-rich π-system in single-walled carbon nanotubes (SWNTs). The designed gel cathode, which is composed of SWNTs, IL and LiFePO4 (LFP) without binder, possesses a good wettability with the LLZTO ceramic pellet and affords highly efficient conductive pathways for electrons and ions through the interface and entire cathode. As a consequence, the assembled SSBs with the gel cathode exhibit excellent long-term cycling stability with a high capacity retention of 91.74% after 700 cycles at 0.5C, and a high coulombic efficiency close to 100% can be achieved over the course of cycling at 25 °C.