正极组成对硫系全固态电池电化学性能的影响

Effect of Cathode Composition on Electrochemical Performance of All-Solid-State Battery with Sulfur-based Electrolyte

研究了LiCoO2/Li10GeP2S12(LGPS)/In全固态电池复合正极中不同含量LiCoO2对其电化学性能发挥的影响。在25℃、0.05 C倍率条件下,LiCoO2含量占比为35%(质量分数,下同)、50%、65%的复合正极具有134.1、137.7、131.3 mA?h/g的首圈放电容量,以及74.1%、88.2%、87.8%的首圈Coulomb效率,均在LiCoO2含量为50%时出现了最大值。功率特性和循环性能也出现了相似的趋势。这是因为正极中LiCoO2含量较低时,大量的导电碳和LGPS中的S诱发的副反应生成了界面非活性层,导致了电池阻抗上升,阻碍了LiCoO2电化学反应的正常进行。而当正极中LiCoO2含量较高时,导电碳和LGPS电解质含量不足,引发导电网路缺失,影响了LiCoO2电化学性能的有效发挥。

The effect of LiCoO2 content in a cathode on the overall electrochemical performance of all-solid-state battery with LiCoO2/Li10 GeP2 S12(LGPS)/In was investigated.The results show that the cells achieve 134.1,137.7,and 131.3 mA?h/g of discharge capacity and 74.1%,88.2%,and 87.8%of coulombic efficiency in first discharge process for the composite cathodes containing 35%(in mass,the same below),50%and 65%of LiCoO2 at 25℃and 0.05 C,respectively.The cells with the composite cathode containing 50%of LiCoO2 have the optimum discharge capacities,rate performance and cycle properties.For the cathode with deficient LiCoO2 contents,side reactions between LGPS and conductive carbon of excessive amount can generate an inactive layer at the interface,further increasing the battery impedance and hindering the normal electrochemical reaction of Li CoO2.Also,a greater content of LiCoO2 leads to the inefficiency in LGPS,and the resultant absence of conductive paths thus affects the electrochemical performance adversely.