Li6.4La3Zr1.4Ta0.6O12 Reinforced Polystyrene-Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide)-Polystyrene pentablock copolymer-based composite solid electrolytes for solid-state lithium metal batteries

Abstract

The demand for lithium-ion batteries with high safety and high energy density is leading a research boom in solid electrolytes. Composite solid electrolytes (CSEs), which combine the advantages of inorganic solid electrolytes and polymer electrolytes, have recently been intensively investigated. Herein, a novel CSE is fabricated by incorporating Li6.4La3Zr1.4Ta0.6O12 (LLZTO) nanoparticles into a polystyrene-poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)-polystyrene (PS-PEO-PPO-PEO-PS) pentablock copolymer matrix. The addition of LLZTO not only improves the ionic conductivity of the CSE by reducing the degree of crystallinity of PS-PEO-PPO-PEO-PS, but also provides an additional transport channel for lithium-ions. As a result, the CSE with an optimal LLZTO content of 30 wt% shows an ionic conductivity of 3.10 × 10−4 S cm−1 (28 °C). In addition, the CSE exhibits an electrochemical stability window of 5.1 V and a lithium ion transfer number of 0.36 at 28 °C. The low interfacial impedance indicates the formation of a stable interface between the CSE and the electrodes. Thus, LiFePO4/Li cells prepared using the CSE deliver high discharge capacity of 151.2 mA h g−1 with capacity retention of 95.7% after 160 cycles at 0.1C. These results demonstrate the promise of the combination of block copolymer/lithium garnet composite electrolytes for practical applications in solid lithium-ion batteries.