TiO2包覆对LiNi0.5Mn1.5O4正极材料电化学性能的影响

Effects of TiO2 coating on electrochemical performance of LiNi0.5Mn1.5O4 cathode materials

采用 TiO2对 LiNi0.5Mn1.5O4 (LNMO)正极材料进行表面包覆,以达到改善 LNMO 电化学性能的目的。利用 X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X 射线光电子能谱(XPS)、恒流充放电、循环伏安(CV)和交流阻抗(EIS)测试手段对制备的材料进行结构表征和电化学性能评价。结果表明,TiO2 能够在 LNMO 表面形成包覆层,且 LNMO-T-2 样品(TiO2包覆量为 w = 1.0%)表现出最为优异的倍率性能及循环稳定性。LNMO-T-2 样品在5 和 7 C (1 C = 140 mAh g 1)倍率下的放电比容量为 102.3 和 72.1 mAh g 1,比未包覆改性的 LNMO 分别提高 14.3%和33.5%。另外, LNMO-T-2 样品在 2 C 倍率下进行 200 次循环后放电比容量保持率达到 87.9%,高于未包覆改性的 LNMO的放电比容量保持率(82.7%)。LNMO-T-2 样品电化学性能的改善归因于 TiO2表面包覆可以有效减小电极极化,同时降低电荷转移阻抗(Rct)。

LiNi0.5Mn1.5O4 (LNMO) cathode materials were coated by TiO2 to enhance electrochemical performance. Structural characterization and electrochemical performance evaluation of the prepared materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy system (XPS), galvanostatic charge-discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests. The results indicate that there is a TiO2 layer on the surface of LNMO, and the LNMO-T-2 sample coated with w = 1.0% TiO2 exhibits the best rate capability and cycling stability. The corresponding discharge capacities of LNMO-T-2 were 102.3 and 72.1 mAh g 1, respectively, which showed an improvement of 14.3% and 33.5% at 5 and 7 C (1 C = 140 mAh g 1) compared with raw LNMO. Moreover, LNMO-T-2 kept 87.9% discharge capacity after 200 cycle charge-discharged tests at 2 C, which was higher than raw LMNO (82.7%). The improvement was due to TiO2 can reduce electrode polarization and charge-transfer resistance (Rct).