Single-Ion Block Copoly(ionic liquid)s as Electrolytes for All-Solid State Lithium Batteries

Polymer electrolytes have been proposed as 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 lithium 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 polymerization technique is reported. These copolymers comprise poly(lithium 1-[3-(methacryloyloxy)-propylsulfonyl]-1-(trifluoromethylsulfonyl)imide) and poly(ethylene glycol) methyl ether methacrylate blocks. The obtained polyelectrolytes show low Tg values in the range of −61 to 0.6 °C, comparatively high ionic conductivity (up to 2.3 × 10−6 and 1.2 ×10−5 S cm−1 at 25 and 55 °C, respectively), wide electrochemical stability (up to 4.5 V versus Li+/Li), and a lithium-ion transference number close to unity (0.83). Owing to the combination of all mentioned properties, the prepared polymer materials were used as solid polyelectrolytes and as binders in the elaboration of lithium−metal battery prototypes with high charge/discharge efficiency and excellent specific capacity (up to 130 mAh g−1) at C/15 rate.