Long Ye,Xinyou He,Yao Shi,Zhiming Xiao,Wei Wang,Lei Cheng,Xinming Fan,Bao Zhang,Xing Ou
The instability in the structural integrity caused by interfacial issues is commonly regarded as the primary drawback of Ni-rich layered cathode materials (LiNi x Co y Mn 1-x-y O 2 , where x ≥ 0.8), which must be addressed before their commercial application. Herein, a novel multiple-function surface modification strategy is proposed based on the single crystal structure to in-situ achieve the construction of a coating layer and surface doping with Ce element to enhance the structural stability of the LiNi 0.88 Co 0.09 Mn 0.03 O 2 (NCM). Notably, the introduction of Ce-O bonding adjusts the local oxygen coordination to achieve a more stabilized structure of the oxygen framework, which inhibits the evolution of lattice oxygen and enhances conductivity. Additionally, by benefiting from the in-situ synthesized coating layer of Li x CeO 2 , the occurrence of side reactions on the surface is effectively alleviated, resulting in a reduction in electrode polarization. Combined with comprehensive electrochemical tests, it is confirmed that the improved electrochemical performance originates from the reduction of the detrimental H2-H3 phase transition and enhanced conductivity. As expected, the modified material with 1 wt% content of Ce (NCM@Ce) exhibits a high initial discharge capacity of 196.3 mAh g −1 with a capacity retention of 79.7 % after 200 cycles, and its energy density reaches 574.3 Wh kg −1 after 200 cycles.
Ou Xing,Liu Tongchao,Zhong Wentao,Fan Xinming,Guo Xueyi,Huang Xiaojing,Cao Liang,Hu Junhua,Zhang Bao,Chu Yong S.,Hu Guorong,Lin Zhang,Dahbi Mouad,Alami Jones,Amine Khalil,Yang Chenghao,Lu Jun
High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi 0.88 Co 0.09 Mn 0.03 O 2 (SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 μm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg −1 at 0.1 C and 25 °C.
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