LiFePO4的软化学合成及锂快离子导体修饰

Soft Chemistry Synthesis and Lithium Fast Ionic Conductor Modification for LiFePO_4 Cathode Material of Li-Ion Battery

采用溶剂热法制备正极材料LiFePO_4,采用溶胶凝胶法制备Li_(0.5)La_(0.5)TiO_3(LLTO)粉体,并通过酒精悬浮法对LiFePO_4进行修饰,修饰量为LiFePO_4质量的1%~4%,获得了薄壁蜂窝状自组装结构的LiFePO_4上修饰有球状LLTO纳米颗粒的复合正极材料。通过进行充放电测试、交流阻抗测试及循环伏安测试,研究了不同修饰量对电池的充放电比容量、循环性能及可逆性的影响,发现当LLTO含量为3%(w/w)时,以2C和5C倍率放电相对于没有修饰LLTO的LiFePO_4的比容量分别提高29.7%和31.6%,30次循环之后,容量损失率较未改性前减小4.13%,循环伏安曲线上氧化还原峰之间的电位差仅为0.117 V,以3%的LLTO修饰改性的LiFePO_4显著提高了电池的倍率性能、循环性能和低温性能。

Soft chemistry synthesis and electrochemical properties via Li（0.5）La（0.5）TiO3（LLTO） fast ionic conductor modification for LiFePO4 cathode material of Li-ion battery were investigated. LiFePO4 was synthesized via solvothermal method, LLTO powder was synthesized via sol-gel method, LiFePO4 was modified by LLTO with the proportion of 1%~4%（w/w） via alcohol suspension mixing method, and the composite cathode materials of thin-wall cellular characteristic self-assembly LiFePO4 modified by spherical LLTO nano-particles were acquired. The effects of LLTO modified proportion on charge and discharge specific capacity, cycle performance and reversibility were studied by charge/discharge test, AC impedance test and cyclic voltammetry test. The results indicate when LLTO modified proportion is 3%（w/w）, the discharge specific capacity increases by 29.7% in the current rate of 2 C and increases by 31.6% in the current rate of 5 C, the capacity loss rate after 30 charge/discharge cycles decreas-es by 4.13% compared to unmodified condition, and the potential difference between redox peaks in cyclic voltammetry curve is only 0.117 V. LiFePO4 modified by LLTO with proportion of 3% significantly improves the current rate capability and cycle performance of Li-ion battery, and also improves the low temperature performance.