超高镍正极材料具有高比能、高电压和低成本等特点, 在新一代锂离子电池中备受关注, 但在电池的长循环过程中会出现微裂纹、机械粉化和不可逆相变, 导致差的循环性能。本研究采用简便的湿化学法制备了一系列Ca₃(PO₄)₂包覆的超高镍LiNi_0.91Co_0.06Al_0.03O₂材料(NCA@nCP)。其中, NCA@1CP在1C (1C=200 mA/g)、2.7~4.3 V下可获得204.8 mAh/g的放电比容量, 100圈循环后容量保持率为91.5%, 甚至在2C的倍率下循环300圈后仍保留153.4 mAh/g的放电比容量。表征结果证实该包覆层可抑制材料的Li/Ni混排、不可逆相变和机械粉化, 从而大幅提升了循环稳定性。本研究表明Ca₃(PO₄)₂包覆策略在提升超高镍正极材料储锂稳定性方面具有较大的应用潜力。

Ultra-high nickel material as a new lithium-ion battery cathode has attracted much attention due to its high specific capacity, high voltage and low cost. However, the generated microcracks, mechanical pulverization and irreversible phase transformation during cycling, result in poor cycling stability. Herein, a series of Ca₃(PO₄)₂- coated ultra-high nickel LiNi_0.91Co_0.06Al_0.03O₂ materials with different thicknesses (NCA@nCP) were prepared through a facile wet-chemistry strategy. Among them, NCA@1CP manifested specific discharge capacity of 204.8 mAh/g under 2.7-4.3 V at 1C (1C=200 mA/g), with a capacity retention rate of 91.5% after 100 cycles. Even after 300 cycles at 2C, the specific discharge capacity retained 153.4 mAh/g. Material characterization results further confirm that the coating shell inhibits the Li/Ni mixing, irreversible phase transformation and mechanical pulverization of the NCA@1CP, greatly improving the cycling stability. This work shows that the Ca₃(PO₄)₂ coating strategy has great application potential in improving the lithium storage stability of ultra-high nickel cathode materials.