Functionalities of the LiV3-xNbxO8 surface layer on a Li2NiO2 cathode additive for enhancing the moisture stability and cycling performance of lithium-ion batteries

Abstract

Incorporating an over-lithiated lithium nickel oxide (Li2NiO2) cathode additive is an effective way to compensate for the initial Li+ consumption, mainly caused by solid electrolyte interphase formation in high-capacity Si or SiOx anodes used in advanced lithium-ion batteries (LIBs). Li2NiO2 offers a large initial charge capacity (~320 mAh g−1) and high irreversibility (~70%), which is beneficial for providing surplus Li+ into the anodes. Then, the irreversible Li+ consumption can be compensated by the surplus Li+ in the first cycle, thereby increasing the practical energy density of LIBs. Unfortunately, the vulnerability of Li2NiO2 to moisture, owing to its high Li concentration, facilitates the formation of impurities such as LiOH and Li2CO3, leading to a significant increase in the interfacial resistance with a loss of cycling stability. In this study, we coat the surfaces of Li2NiO2 particles with a lithium trivanadate (LiV3O8) functional layer to enhance moisture stability and mechanical strength through surface stabilization. Furthermore, the structural engineering of LiV3O8 through the elemental substitution of Nb effectively reduces the interfacial resistance resulting from a strong enhancement in the ionic conductivity of LiV3-xNbxO8. In practice, a full-cell assembled with a cathode composed of LiNi0.8Co0.1Mn0.1O2 and LiV3-xNbxO8-coated Li2NiO2 exhibits enhanced energy density by compensating the capacity loss, maintaining a stable cycling performance over 200 cycles. In conclusion, this study offers a practical solution for enhancing lithium-ion battery performance by improving moisture stability, reducing interfacial resistance, and improving energy density and cycling longevity through advanced cathode surface engineering.