Effective enhancement of electrochemical properties for LiFePO4/C cathode materials by Na and Ti co-doping
Effective enhancement of electrochemical properties for LiFePO4/C cathode materials by Na and Ti co-doping
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DOI：
10.1016/j.electacta.2012.11.081
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发表时间：
2013-02
影响因子：
6.6
通讯作者：
H. Shu;Xian-you Wang;Weicheng Wen;Qianqian Liang;Xiukang Yang;Qiliang Wei;Benan Hu;Li Liu;
中科院分区：
文献类型：
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作者：
H. Shu;Xian-you Wang;Weicheng Wen;Qianqian Liang;Xiukang Yang;Qiliang Wei;Benan Hu;Li Liu;
通过简单的高温固相方法合成了Na和Ti共掺杂Li1−xNaxFe1−xTixPO4/C（x=0.00、0.01、0.03和0.05）复合材料。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、充放电测试、电化学阻抗谱(EIS)和恒电流间歇滴定技术(GITT)对样品的结构、形貌和电化学性能进行表征。结果表明，Na和Ti共掺杂样品保留了LiFePO4的橄榄石结构，但Na和Ti共掺杂可以优化晶体微观结构，改变颗粒形貌，降低电荷转移电阻，提高交换电流密度、电导率和Li离子扩散速度，从而改善LiFePO4/C的电化学性能。在所有掺杂样品中，Li0.97Na0.03Fe0.97Ti0.03PO4/C表现出最好的倍率性能和循环稳定性。 Li0.97Na0.03Fe0.97Ti0.03PO4/C的首次放电容量为151.0mAhg−1，1C下循环100次后容量保持率为99.3%。特别是，即使在20C的高倍率下，它仍然表现出超过97.3mAhg−1的高放电容量。
Na and Ti co-doping Li1−xNaxFe1−xTixPO4/C (x=0.00, 0.01, 0.03 and 0.05) composites were synthesized by a simple high-temperature solid-state method. The structure, morphology and electrochemical performance of the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), charge/discharge tests, electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The results showed that the Na and Ti co-doped samples kept the olivine structure of LiFePO4, but Na and Ti co-doping can optimize the crystal microstructure, modify the particle morphology, decrease charge transfer resistance, enhance exchange current density, electrical conductivity and Li ion diffusion velocity, and thus improve the electrochemical performance of the LiFePO4/C. Among all the doped samples, Li0.97Na0.03Fe0.97Ti0.03PO4/C showed the best rate capability and cycling stability. The initial discharge capacity of Li0.97Na0.03Fe0.97Ti0.03PO4/C was 151.0mAhg−1with the capacity retention ratio of 99.3% after 100 cycles at 1C. Especially, it still showed a high discharge capacity of over 97.3mAhg−1even at a high rate of 20C.