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%.