Multifunctional lithium compensation agent based on carbon edges catalysis and its application in anode-free lithium batteries

Lithium compensation agents, especially the self-sacrificing salts, can effectively compensate for the irreversible capacity loss of lithium-ion battery, but most lithium compensation materials only have the function of lithium compensation and their mechanisms are still unknown. In this study, a method for preparing multifunctional lithium compensation agent Li2C4O4 (lithium squarate) microspheres using spray drying to extend the cycle life of anode-free batteries is proposed, and the catalytic effect of the carbon edges on Li2C4O4 decomposition was evaluated. The Li2C4O4 microspheres can release additional capacity via decomposition and produce CO2 to improve the stability of the battery, as well as generate carbon bridges at the carbon edges to improve the rate performance of the battery. When it was applied to LiFePO4 battery system, the capacity increased from 60 mAh/g to 90 mAh/g at a current density of 10C. When applied to a Cu||LiFePO4 anode-free battery, an active lithium reserve layer formed on the surface of copper foil through Li2C4O4 decomposition, thus prolonging the cycling performance of the battery without any surface modification. After 40 turns at a current density of 0.1C, the cycling capacity retention was higher than 96%.