Improvement On Performance Of Co₃O₄Anode Materials For Lithium Ion Batteries And Optimizing Of Conductive Agent

Co3O4as a very important transition metal oxide is considered to be one of the most promising alternative anode materials due to its high theoretical capacity (890mAh g-1), as high as three times the capacity of graphite (372mAh g-1). However, it suffers from poor cycling stability and low initial coulombic efficiency. We synthesized net-structured Co3O4/C nanosheet array film to benefit from nanostructure and composite with carbon. Furthermore, we design the mixture formula for different electrode materials according to market demand in industrial application. We also optimized mixture ratio of a binary conductive agent. The main research contents can be devided into the following three parts:(1) Freestanding Co3O4nanosheet array growing directly on nickel foam substrate was synthesized using a hydrothermal approach. Comparing the electrochemistry performance with different ratio of Co(NO3)2·6H2O/HMT at different sintering temperature, the optimal ratio is1:3, and when sintering temperature was250℃, the Co3O4nanosheet array as synthesized shows the best electrochemistry performance.The Co3O4nanosheets are interconnected with each other, forming a highly open net-structure.(2) Co3O4/C nanosheet array composite film was synthesized, using direct current magnetron sputtering to form a thin carbon layer on the surface. The Co3O4/C nanosheet array delivers an initial discharge capacity of1340.4mAh g-1at0.1C, compared to1016.2mAh g-1of pure Co3O4, and it maintains a high specific capacity of859.5mAh g-1after100cycles at1C at room temperature. While at55℃, the Co3O4/C electrode can still remain85.5%of its initial discharge capacity (1214.9mAh g-1) after100cycles at1C. The enhanced electrochemical performances can be attributed to the introduction of thin carbon layer, which not only facilitate Li+and electron transportation in the electrode, but also improve its structure stability during cycling, resulting in improved capacity and cycle performance.(2) We design the mixture formula for LiFePO4. LiMn2O4and Li(NixCoyMn1-x-y)O2electrode materials according to market demand in industrial application. Meanwhile, we also optimized mixture ratio of a binary conductive agent consisting of two kinds of carbon particles with different sizes in a Li(NixCoyMn1-x-y)O2cathode. When ratio of Super-P/KS-6is3:1. it delivers the highest initial discharge capacity of146mAh g-at0.1C. with initial coulombic efficiency of79.3%. After100cycles at1C, it still remain86.9%of its initial discharge capacity, showing the best cycling stability.