Eliminate voltage decay of LiCoO2 at 4.6 V through a combined bulk and surface reconfiguration

Abstract

LiCoO₂ is an imperative cathode material for lithium-ion batteries due to its high discharge voltage and volumetric energy density. However, the practical application of LiCoO₂ at high voltage is greatly limited by the detrimental phase transition and interfacial side reactions. Herein, a combined bulk and surface reconfiguration via K⁺–Mg²⁺–Al³⁺–Ti⁴⁺ multi-ion doping and AlPO₄ coating is proposed to design high-voltage LiCoO₂ single crystals. This strategy can significantly change the morphology and microstructure of LiCoO₂, resulting in obviously increased Li⁺ diffusion kinetics and improved structural stability when charged to 4.6 V. In addition, the AlPO₄ coating layer can mitigate the cathode/electrolyte side reactions and contribute to form a robust LiF- and Li₃PO₄-rich cathode/electrolyte interphase during long-term cycling. As a result, voltage decay, particle cracks and the detrimental phase transition up to 4.6 V are effectively inhibited. The modified LiCoO₂ delivers a high discharge capacity of 136 mAh g^–1 at 10 C with outstanding capacity retention of 85.4% and negligible voltage decay after 1000 cycles. This work can be enlightening for designing stable high-voltage cathode materials for lithium-ion batteries with long lifespan.