Single-Ion Conducting Block Copolymer Electrolytes For Solid State Lithium Batteries

Polymer electrolytes have been proposed as a replacement for conventional liquid electrolytes in lithium-ion batteries (LIBs) due to their intrinsic enhanced safety. Nevertheless, the power delivery of these materials is limited by the concentration gradient of the Li salt. Single-ion conducting polyelectrolytes represent the ideal solution since their nature prevents polarization phenomena. Herein, the preparation of a new family of single-ion conducting block copolymer polyelectrolytes via reversible addition-fragmentation chain transfer (RAFT) polymerization technique is reported. The new anionic monomer, namely lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethyl-sulfonyl)imide (LiMTFSI) was designed, prepared and further used for the synthesis of well-defined anionic di- and tri-block copolymers via RAFT. Ionic block copolymers comprise poly(LiMTFSI) and poly(ethylene glycol) blocks. We introduce a novel approach for the creation of solid-state batteries by using the new family of single-ion conducting block copolymers as both the solid separator and the binder for electrode material. These single-ion conducting polymer electrolytes showed low Tg (−61 °C), high σ (~10-5 S cm-1 at 55 °C), lithium transference number ~1, and wide 4.5 V electrochemical stability. Owing to the combination of all mentioned properties, the resulting LiFePO4/Li cell prototypes deliver large capacities (> 130 mAh g−1), with impressive charge/discharge efficiency and capability to reversibly operate at high rates.