Co~(2+)掺杂石墨烯/LiFePO_4锂离子电池复合正极材料的制备与表征

使用溶胶凝胶原位碳热还原制备了Co2+掺杂石墨烯/LiFePO4锂离子电池复合正极材料(石墨烯/LiCo0.03Fe0.97PO4),以期获得比容量高、充放电速率快和循环性能优良的锂离子电池正极材料。结构和形貌表征结果显示:石墨烯/LiCo0.03Fe0.97PO4复合材料具有三维导电网络结构,颗粒在石墨烯片层间生长均匀,粒径在200nm左右。电化学测试结果显示:石墨烯/LiCo0.03Fe0.97PO4复合材料具有高的可逆比容量和优异的循环倍率性能。2.0~4.0V充放电下0.1C时的首次放电比容量为159mA·h·g-1,在10.0C下首次放电比容量也有74mA·h·g-1;0.5C下循环100次,比容量保持率为99.7%。石墨烯/LiCo0.03Fe0.97PO4复合材料电化学性能提高的原因主要为Co2+掺杂和石墨烯包覆的协同作用。

Preparation and characterization of Co2+ doped graphene/LiFePO4composite cathode materials for lithium battery

In order to obtain lithium ion battery cathode materials with high specific capacity, fast charging and discharging rate and excellent cycle performance, Co²⁺ doped graphene/LiFePO₄ composite cathode materials for lithium battery (graphene/LiCo_0.03Fe_0.97PO₄) were synthesized by using a sol-gel in-situ carbothermal reduction treatment. The structure and morphology characterization results show that graphene/LiCo_0.03Fe_0.97PO₄ composites form 3D conducting network structure. The particles grow homogeneously in graphene sheets with the diameters of about 200 nm. The electrochemical test results show that graphene/LiCo_0.03Fe_0.97PO₄ composites exhibit high reversible specific capacity and superior cycle rate performance with the first discharge specific capacity of 159 mA·h·g^-1 at 0.1 C (2.0-4.0 V charge-discharge) and 74 mA·h·g^-1 at 10.0 C of the first discharge. The specific capacity retention is 99.7% after 100 cycles at 0.5 C. The enhanced electrochemical property of graphene/LiCo_0.03Fe_0.97PO₄ composites is attributed to the synergistic effect of Co²⁺ doping and graphene-modification.