以葡萄糖酸亚铁为碳源和部分铁源,采用固相法制备了LiFePO4/C复合正极材料。利用 XRD和SEM对所得样品进行了结构与形貌表征。以 LiFe-PO4/C作锂二次电池正极组装电池,用电化学工作站和充放电测试系统对样品进行电化学性能测试。当碳包覆量为4.75%,650℃烧结10h 时所制备的 LiFe-PO4/C复合材料在0.1、0.2和1C倍率下最高放电比容量分别为161.6、147.2和123.3mAh/g。1C 倍率下经50次循环材料的放电比容量无衰减。实验结果表明,由于葡萄糖酸根和铁离子之间较强的化学键,阻止了葡萄糖酸根热解过程中在材料内部的不均匀扩散,其热解后在材料颗粒表面形成均匀导电碳层,并在颗粒之间形成丝状无定形碳,有效抑制了晶粒的生长,提高了活性物质利用率,形成了完整的导电网络,增强了材料的综合电化学性能。
LiFePO4/C composite materials were prepared by solid-state reaction with ferrous gluconate as carbon source and partial iron source.The structure and morphology of sample materials were characterized by X-ray diffraction and scanning electromicro scopy.The electrochemical performances of composites were measured by electrochemical workstation and charge-discharge test system.The highest discharge capacity of LiFePO4/C composite with 4.75% carbon coating sintered at 650℃ for 10h was 161.6,147.2 and 123.3mAh/g at 0.1,0.2 and 1C rate,respectively.There was no fade of discharge capacity after being charge-discharge for 50 cycles at 1C rate.The results showed that due to the strong chemical bonds between gluconate and iron ions,a uniform layer of carbon film was formed on the surface of particles and some filamentous amorphous carbon was formed between the particles after sintering.The particle growth was inhibited during sintering and a complete conduc-tive network was formed due to the effective carbon coating,hence the utilization of active materials was im-proved and the electrochemical properties were enhanced.
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