Ti掺杂改性LiNi0.6Co0.2Mn0.2O2正极材料及其电化学性能研究

The electrochemical performance of LiNi0.6Co0.2Mn0.2O2 material doped by Ti as cathode for lithium ion battery

高镍LiNi0.6Co0.2Mn0.2O2正极材料已商业应用于锂离子动力电池。进一步提升结构稳定性和电化学性能是高镍材料大规模应用的关键。采用Ti^4+掺杂来调变材料结构,研究Ti^4+掺杂对材料的晶体结构、形貌和电化学性能的影响及作用机制。实验结果表明Ti^4+掺杂对颗粒形貌无明显影响,但可有效抑制Li^+/Ni^2+离子混排,拓宽过渡金属层间距,提高锂离子扩散速率,从而改善材料循环和高倍率性能。由于Ti^4+为电化学惰性离子,低倍率下材料的放电比容量略有下降,1%Ti^4+掺杂的样品电化学性能最优。在3.0~4.3 V、5.0 C下的放电比容量为126.6 mA×h·g^−1,较原材料的91.0 mA×h·g^−1提升明显;1.0 C下放电比容量为144.2 mA×h×g^−1,循环100周后容量保持率高达95.0%。在3.0~4.6 V的电压区间内,1.0 C下循环100周的容量保持率仍有84.1%。

Ni-rich layered LiNi0.6Co0.2Mn0.2O2 material has been commercially used as cathode for lithium ion battery.The further improvement of structural stability and electrochemical performance is the key to the large-scale utilization of the material.Ti^4+doping was used to modify the structure of the material.The influence and mechanism of Ti^4+doping on the crystal structure,morphology and electrochemical property were investigated.The experimental results show that Ti^4+doping has no obvious effect on particle morphology,but can effectively inhibit cation Li^+/Ni^2+mixing and increase the diffusion rate of lithium ion due to wide space between transition metal layers,which improves the cycle and high rate performance of cathode material.However,the discharge specific capacity of the material is slightly reduced at low current density as Ti^4+is electrochemical inactive.At the voltage of 3.0~4.3 V,the discharge specific capacity of the 1%Ti^4+doped sample is 126.6 mA×h×g^−1 at 5.0 C,much higher than that of starting material 91.0 mA×h×g^−1,and is 144.2 mA×h×g^−1 at 1.0 C and the capacity retention is as high as 95.0%after 100 cycles.The capacity retention is as high as 84.1%after 100 cycles at the voltage of 3.0~4.6 V and 1.0 C.