Solid State Li Metal/LMO Batteries based on Ternary Triblock Copolymers and Ionic Binders

Abstract

Triblock copolymers containing an ionophilic polymerized ionic liquid block, sandwiched between two ionophobic polystyrene blocks, were investigated as solid polymer electrolytes (SPE) to simultaneously provide mechanically robust, free-standing membranes with high lithium conductivity and an optimized electrolyte composition. The conductivity reached 8 × 10–5 S cm–1 and 6.5 × 10–4 S cm–1 at 30 and 80 °C, respectively, with an anodic stability above 4.5 V. Highly stable Li metal symmetric cycling was demonstrated, with an overpotential of 130 mV for over 300 h at 50 °C at a current density of 0.5 mA cm–2/0.5 mAh cm–2. Attempts were also made to incorporate the SPE as the binder in an LMO cathode formulation. The best cell performance, however, was obtained when substituting the SPE in the LMO cathode formulation with a PMA solid-state gel electrolyte, resulting in a high-performance solid-state Li|polymer eletrolyte|LMO device with stable cycling at C/5, and an impressive capacity retention (i.e., 105 mAh g–1 after 150 cycles at 0.1 mA cm–2) with a Coulombic efficiency around 99.4%.