Dual-coated single-crystal LiNi0.6Co0.2Mn0.2O2 as high-performance cathode materials for lithium-ion batteries

Abstract

Due to its superior high discharge capacity and cycling stability, single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials are rapidly gaining traction in the realm of electric vehicle power batteries. Nevertheless, the deterioration of surface structure in single-crystal LiNi_1−x−yCo_xMn_yO₂ cathode materials is further exacerbated when operating at higher cutoff voltages (exceeding 4.5 V). In this work, a unique single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ with ZnO and AlPO₄ dual-coating modification has been synthesized. The similar crystal structure of ZnO and NCM results in a more compact coating, while the incorporation of AlPO₄ enhances both the electronic conductivity (through the formation of conductive oxide Al-doped ZnO) and lithium-ion conductivity (via the formation of Li₃PO₄) within the coating. The coated SC-NCM cathode material exhibits excellent electrochemical performance even when operated at a higher cutoff voltage of 4.5 V. After 100 cycles (1 C, 2.75–4.5 V), the capacity retention for the ZnO and AlPO₄ coated SC-NCM sample reaches 91.2%, significantly surpassing that of the pristine samples (40.0%). Specifically, it exhibited an outstanding rate property, maintaining a discharge capacity of 150.8 mA h g⁻¹ at 8 C. The exceptional electrochemical properties can be attributed to the distinctive coating layer, which serves not only as a physical barrier to mitigate electrolyte side reactions but also facilitates rapid conduction of electrons and lithium ions.