Multifunctional Lithium Compensation Agent Based on Carbon Edges Catalysis and its Application in Anode-Free Lithium Batteries

Abstract

Lithium batteries are subject to severe, and sometimes irreversible, capacity degradation over time. Lithium compensation agents, especially the self-sacrificing salts, can effectively compensate for the irreversible capacity loss, but most lithium compensation materials only have the function of lithium compensation and its mechanisms are still unknown. In this study, a method for preparing kilogram-scale multifunctional lithium compensation agent microspheres using spray drying method to extend the cycle life of anode-free batteries is proposed, and the catalytic effect of the carbon edges on Li2C4O4 decomposition has been figured out. The Li2C4O4 microspheres prepared have great electrochemical activity and water-oxygen stability. It can release additional specific 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. The catalytic effect of Zigzag and Armchair edges on the Li2C4O4 decomposition was discovered through experiments and density functional theory (DFT) calculations. When it was applied to LiFePO4 battery system, the capacity was increased from 60 mAh g-1 to 90 mAh g-1 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%.

Keywords: Li2C4O4, lithium compensation agent, carbon edges, LiFePO4, anode-free batteries