For lithium ion batteries, the cathode materials that can be used should meet the characteristics of large reversible capacity, high potential and stability, non-toxic and low production cost. At present, lithium iron phosphate is the most common cathode material for lithium ion batteries. However, LiFePO4 has poor electrical conductivity and low lithium ion mobility. If LiFePO4 material is combined with graphene, its conductivity and multiplier performance can be improved theoretically.
Due to the particularity of graphene materials, relatively little research has been done on the cathode graphene materials. Studies have shown that when graphene is directly coated on the surface of LiFePO4 by hydrothermal method, the multiplier performance of composite materials is not very good. The reason may be the stacking or destruction of graphene material structure.
It was found that the material formed by wrapping LiFePO4 in graphene can improve the electrical conductivity of LiFePO4 material. However, ion transport efficiency decreases when it is fully wrapped, and it is speculated that lithium ions cannot pass through graphene's six-membered ring structure. LiFePO4 nanoparticles were sonically mixed with graphite oxide. LiFePO4/ graphene composites with more compact microstructure were prepared. After further conventional carbon coating, the specific capacity of lithium embedded in the material is greatly improved, which can still maintain around 70mAh/g under the condition of 60C high rate.
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