| 碳包覆对磷酸铁锂高温循环性能的影响机理 |
| Mechanism of the effect of carbon coating on high temperature cycle performance of LiFePO4 |
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| 摘要: 制备了碳包覆完整和不完整的2种磷酸铁锂，用以研究碳包覆对使用广泛的磷酸铁锂/石墨电池体系高温循环性能的影响机理。X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、粉末电阻率和扣式电池等测试表明2种物料的晶体结构、颗粒尺寸、克容量等性能相近，仅碳包覆完整度差异大。将2种物料组装成磷酸铁锂/石墨软包电芯并在60 ℃高温下进行1C充放电循环测试，结果表明完整的碳包覆可使其在1 250次循环后的容量保持率由80.4%提升至84.9%。在此基础上，我们成功定量极化容量和热力学容量的改善幅度，可知二者占比分别为76%和24%，这说明碳包覆的主要影响机制是为磷酸铁锂正极提供完整的导电网络，进而降低极化损失。铁溶出测试结果表明，碳包覆的直接抑制作用并不明显，其主要作用可能是通过降低电芯中的水含量从而间接抑制铁溶出，并减少部分热力学容量损失。 |
| 关键词: LiFePO4 石墨负极 锂离子电池 碳包覆 循环性能 机理分析 |
| 基金项目: |
| Abstract: To investigate mechanism of carbon coating on the high-temperature cycle performance of widely used LiFePO4/graphite batteries, two types of LiFePO4 cathode material with different carbon coating degrees were prepared. According to characterization results from X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), powder resistance, and coin cell, two types of LiFePO4 were almost identical with respect to the crystal structure, particle size, and specific capacity. Then LiFePO4/graphite pouch cells were prepared and cycled at 1C under 60 ℃. It turns out that carbon coating can improve capacity retention from 80.4% to 84.9% after 1 251 cycles. The capacity improvement for polarization capacity and thermodynamic capacity account for 76% and 24%, respectively. This demonstrates that the mechanism of carbon coating is to reduce the polarization capacity loss by forming integrated conducting networks. In contrast, carbon coating can not inhibit Fe dissolution directly. Instead, it may be an indirect interaction through the reduction of moisture. |
| Keywords: LiFePO4 graphite anode lithium-ion battery carbon coating cycle performance mechanism analysis |
| 投稿时间：2023-07-31 修订日期：2023-11-15 |
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| 柳娜.碳包覆对磷酸铁锂高温循环性能的影响机理[J].无机化学学报,2023,39(12):2287-2294. |
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