Enhanced electrochemical performance of LiNaMnPOCO as a cathode material in "water-in-salt" electrolytes

A carbonophosphate compound of Li 2.72 Na 0.31 MnPO 4 CO 3 was synthesized via ion exchange. The initial discharge capacity of Li 2.72 Na 0.31 MnPO 4 CO 3 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 Li 2.72 Na 0.31 MnPO 4 CO 3 , the capacity retention degraded to 64% after 100 cycles. A full cell composed of ion-exchanged Li 2.72 Na 0.31 MnPO 4 CO 3 from Na 3 MnPO 4 CO 3 and LiTi 2 (PO 4 ) 3 with a water-in-salt electrolyte exhibites operation voltage of approximately 1 V.