Enhanced electrochemical performance of Li2.72Na0.31MnPO4CO3 as a cathode material in "water-in-salt" electrolytes.

A carbonophosphate compound of Li2.72Na0.31MnPO4CO3 was synthesized via ion exchange. The initial discharge capacity of Li2.72Na0.31MnPO4CO3 in 15 molal (or 15 m) LiTFSI was 110 mA h g−1 at 2 mA cm−2 (∼0.5C). Due to the decomposition of Li2.72Na0.31MnPO4CO3, the capacity retention degraded to 64% after 100 cycles.