Boosting the capability of Li₂C₂O₄ as cathode pre-lithiation additive for lithium-ion batteries

Li₂C₂O₄, with a high theoretical capacity of 525 mAh·g⁻¹ and good air stability, is regarded as a more attractive cathode pre-lithiation additive in contrast to the reported typical inorganic pre-lithiation compounds which are quite air sensitive. However, its obtained capacity is much lower than the theoretical value and its delithiation potential (> 4.7 V) is too high to match with the most commercial cathode materials, which greatly impedes its practical application. Herein, we greatly improve the pre-lithiation performance of Li₂C₂O₄ as cathode additive with fulfilled capacity at a much-reduced delithiation voltage, enabling its wide applicability for typical commercial cathodes. We increase the capacity of Li₂C₂O₄ from 436 to 525 mAh·g⁻¹ by reducing its particle size. Through optimizing the types of conductive additives, introducing nano-morphological NiO, MnO₂, etc. as catalysts, and innovatively designing a bilayer electrode, the delithiation potential of Li₂C₂O₄ is successfully reduced from 4.778 to 4.288 V. We systematically study different particle size, conductive additives, and catalysts on the delithiation behavior of Li₂C₂O₄. Finally, it is applied to pre-lithiate the hard carbon anode, and it is found that Li₂C₂O₄ could effectively increase the capacity of the full cell from 79.0 to 140.0 mAh·g⁻¹ in the first cycle. In conclusion, our study proves that improving the reactivity is an effective strategy to boost the pre-lithiation of Li₂C₂O₄.