Co3O4 Quantum Dot-Catalyzed Lithium Oxalate As a Capacity and Cycle-Life Enhancer in Lithium-Ion Full Cells

The demand for lithium compensation materials is becoming urgent as energy density requirements increase. As next-generation anodes, mixed silicon and carbon (Si-C) materials are limited by low efficiency in the first cycle owing to the formation of a solid electrolyte interphase film. However, most compensation materials are water- and oxygen-sensitive and exhibit low electrochemical activity and decomposition efficiency. In this study, water- and oxygen-stable lithium oxalate (Li2C2O4) was developed to enhance the capacity and cycle-life of the lithium-ion battery. Various metal oxides were screened to improve the electrochemical activity of Li2C2O4. Co3O4 exhibited the strongest catalytic performance, and the catalytic mechanism of Co3O4 on Li2C2O4 was studied by density functional theory. Ultrasonic atomization drying was used to combine Co3O4 quantum dots (Co3O4-QDs) with Li2C2O4 for improved efficiency. The electrochemical activity of the modified Li2C2O4 improved, and the decomposition voltage decreased from 4.65 to 4.0 V. The modified Li2C2O4 exhibits catalytic activity, and it can be used in LiFePO4, which has weak catalytic activity; the decomposition efficiency in the LiFePO4 system increased from 34.16 to 99.10%. In the Si-C//LiFePO4 full battery system, the first cycle discharge capacity increased from 80 to 160 mA h g(-1); the lost capacity of the first cycle was fully compensated for. Additionally, the CO2 produced by Li2C2O4 decomposition could inhibit the decomposition of the electrolyte, further improving the cycle performance of the battery.