Dendrite-free lithium metal solid battery with a novel polyester based triblock copolymer solid-state electrolyte

Solid-state polymer Li metal batteries have been regarded as a promising candidate for next-generation batteries due to their high-energy densities provided by the Li metal and the improved safety provided by the solid electrolyte. Polyester is one attractive polymer host, which could be an alternative to polyether-based solid electrolyte due to its excellent lithium ion transport ability and wide electrochemical stability window. Here, a BAB-type triblock copolymer is synthesized with poly (propylene carbonate) as A-block and poly (ε-caprolactone) as B-block. The triblock copolymer electrolyte exhibits a high ionic conductivity of 3 × 10−5 S cm−1 at 30 °C with a high lithium ion transference number (0.4) and an extremely wide electrochemical window (5 V). A highly stable interface against Li metal is maintained for more than 760 h at a current density of 0.1 mA cm−2. A LiFePO4 cathode based solid state battery delivers a high discharge capacity of 142 mA h g−1 at 0.05C, room temperature, and 161 mA h g−1 at 0.1C, 70 °C with a capacity retention of 90% after 200 cycles. To understand the excellent electrochemical performance, the morphology and chemical information at both anode and cathode interface are characterized and analyzed. The synthesis of this triblock copolymer demonstrates a new direction in developing high ionic conductivity solid polymer electrolyte for solid-state polymer batteries.