锂离子电池用Cr_2O_3/TiO_2复合材料的电化学性能

Electrochemical Performance of Cr_2O_3/TiO_2 Composite Material for Lithium Ion Batteries

采用高温固相反应法合成了Cr_2O_3/TiO_2复合材料,运用X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电测试、循环伏安(CV)、电化学阻抗谱(EIS)等对其结构、形貌和电化学性能进行了表征.研究结果表明:TiO_2掺杂能够显著改善Cr_2O_3的充放电循环性能,Cr_2O_3/TiO_2复合材料在充放电循环22周后仍有454mAh·g^(-1)的可逆循环容量,容量保持率达到了73.6%,主要归因于TiO_2掺杂能够显著提高Cr_2O_3的电导率.Cr_2O_3/TiO_2复合材料首次放电过程中由于电极体积膨胀导致的固体电解质相界面(SEI)膜迅速增厚和活性材料电导率的降低可能是其首次充放电过程中存在较大不可逆容量和循环容量衰减的重要原因.

The Cr2O3/TiO2 composite material was prepared by a high-temperature solid-state reaction and its structure, morphology, and electrochemical performance were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, charge-discharge test, cyclic voltammetry （CV）, and electrochemical impedance spectroscopy （EIS）. We found that TiO2 doping significantly improved the cyclic performance of Cr2O3 and the reversible capacity of the Cr2O3/TiO2 composite material was 454 mAh· g^-1 after 22 charge-discharge cycles, therefore, it has a capacity retention of 73.6% and this is mainly due to TiO2 doping that significantly increases the conductivity of Cr2O3. Our results revealed that the initial large irreversible capacity and the capacity fading could be attributed to an increase in the thickness of the solid electrolyte interface （SEI） film and a reduction in the conductivity of the materials. This was caused by a volume expansion of the Cr2O3/TiO2 electrode during the first discharge process.