碳包覆Li_3V_2(PO_4)_3正极材料在LiPF_6电解液中的表面/界面行为  

Surfacial/Interfacial Behavior of Carbon Coated Li_3V_2(PO_4)_3 Cathode Material in LiPF_6 Based Electrolyte

作　　者：边筱扉[1] 刘万强[1] 魏英进[2] 

机构地区：[1]长春理工大学材料科学与工程学院,长春130022 [2]吉林大学物理学院,长春130012

出　　处：《应用化学》2013年第5期602-607,共6页Chinese Journal of Applied Chemistry

基　　金：吉林省科技厅自然科学基金项目(201215141)

摘　　要：利用碳热还原法成功制备了碳包覆Li3V2(PO4)3正极材料。X射线衍射研究表明材料具有纯相单斜结构。高分辨透射电子显微镜观察到材料表面存在5～10 nm的包覆碳层。碳包覆Li3V2(PO4)3材料在3.0～4.3 V电压区间内可提供120 mA.h/g(C/4倍率)、115 mA.h/g(1C倍率)和110 mA.h/g(2C倍率)的可逆容量,并且在循环300次后容量保持率超过97%,显示出良好的应用前景。该材料在充放电循环初期经历了不可逆容量损失。高分辨透射电子显微镜研究表明,该不可逆容量损失来源于材料表面生成的固体电解质中间相(SEI膜),红外光谱分析表明,SEI膜的成份主要包括ROCO2Li和RCO2Li等有机物,以及Li2CO3、LixPFy和LixPOyFz等无机物。表面SEI膜经历初期电化学循环后趋于稳定,从而保证碳包覆Li3V2(PO4)3正极材料优良的电化学性能。Carbon coated monoclinic Li3V2（PO4）3 cathode material was prepared by the carbothermal reduction method. X-ray diffraction result showed that the material is phase pure monoclinic Li3 V2 （PO4 ）3 with space group of P21/n. HRTEM revealed a surfacial carbon layer with thickness about 5 ~ 10 nm. The material showed a reversible discharge capacity of 120 mA.h/g（C/4 rate）, 115 mA.h/g（1C rate） and 110 mA.h/g （2C rate） in the voltage window of 3.0 -4.3 V, which maintained excellent cycle stability after 300 cycles. The material suffered from a capacity loss in the initial charge-discharge cycles. The irreversible capacity loss was mainly due to the progressive formation of a solid electrolyte interface （SEI） that could be observed under HRTEM. FTIR analysis showed that the chemical species of the SEI film mainly contained some organic compounds such as ROCO2Li, RCO2Li, and aliphatic, as well as some inorganic compounds such as Li2CO3, LixPFy or LixPOyFx.

关 键 词：锂离子电池 正极材料 磷酸钒锂 表面 界面反应 

分 类 号：O646[理学—物理化学] TM911[理学—化学]