In situ polyaniline modified cathode material Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with high rate capacity for lithium ion batteries
In situ polyaniline modified cathode material Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with high rate capacity for lithium ion batteries
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DOI：
10.1039/c4ta04024d
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发表时间：
2014-10
影响因子：
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通讯作者：
Qingrui Xue;Jianling Li;Guofeng Xu;Hongwei Zhou;Xindong Wang;F. Kang
中科院分区：
文献类型：
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作者：
Qingrui Xue;Jianling Li;Guofeng Xu;Hongwei Zhou;Xindong Wang;F. Kang
采用快速共沉淀法制备了富锂层状Li[Li0.2Mn0.54Ni0.13Co0.13]O2，并采用原位化学氧化聚合法对导电聚苯胺（PANI，理论含量为5wt%、10wt%、15wt%、20wt%、30wt%）进行表面改性，以优化其电化学性能。通过场发射扫描电子显微镜（FESEM）和高分辨透射电子显微镜（HRTEM）观察，在Li[Li0.2Mn0.54Ni0.13Co0.13]O2颗粒表面成功地包覆了一层厚度为5 nm（10wt%）的均匀聚苯胺层。X射线粉末衍射（XRD）结果表明，所制备的样品均具有典型的层状六方α-NaFeO 2结构。PANI层通过保护电极在连续充电-放电循环期间免受外部侵蚀来保持Li[Li0.2Mn0.54Ni0.13Co0.13]O2颗粒的表面材料晶体结构的完整性。聚苯胺包覆的Li[Li0.2Mn0.54Ni0.13Co0.13]O2电极在室温下具有优异的电化学性能。初始放电容量为313.5 mA h g−1（0.05 C），库仑效率为89.01%（PANI，10重量%），相比之下，原始Li[Li0.2Mn0.54Ni0.13Co0.13]O2的库仑效率为291.9 mA h g−1（0.05 C），在2.0-4.8 V（vs. Li/Li+）的电势范围内为81.31%。在0.1C下80次循环后，放电容量保持在282.1mA h g-1。此外，PANI包覆的Li[Li0.2Mn0.54Ni0.13Co0.13]O2在10 C下表现出198.6 mA h g-1的优异高倍率容量。电化学阻抗谱（EIS）测试结果表明，PANI薄膜的存在显著降低了界面电荷转移电阻，优化了界面电化学反应活性。此外，质子酸掺杂过程中特殊的H+/Li+交换反应也促进了电化学性能的提高。
Lithium-rich layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is prepared by a fast co-precipitation method and surface modified with conducting polyaniline (PANI, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% theoretically) via in situ chemical oxidation polymerization to optimize the electrochemical properties. The uniform PANI layer with a thickness of 5 nm (10 wt%) has been successfully coated on the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles, as observed by field-emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The X-ray powder diffraction (XRD) results show that all the prepared samples have a typical layered hexagonal α-NaFeO2 structure. The PANI layer maintains the integrity of the surface material crystal structure of the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles by protecting the electrodes from external erosion during continuous charge–discharge cycles. PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 electrodes present excellent electrochemical properties at room temperature. The initial discharge capacity is 313.5 mA h g−1 (0.05 C) with a coulombic efficiency of 89.01% (PANI, 10 wt%), compared with 291.9 mA h g−1 (0.05 C) for the pristine Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with a coulombic efficiency of 81.31% in the potential range 2.0–4.8 V (vs. Li/Li+). The discharge capacity is retained at 282.1 mA h g−1 after 80 cycles at 0.1 C. Moreover, the PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 exhibits an excellent high rate capacity of 198.6 mA h g−1 at 10 C. The electrochemical impedance spectra (EIS) measurements reveal that the thin PANI coating layer significantly optimizes the interfacial electrochemical reaction activity by reducing the charge transfer resistance. Moreover, the special H+/Li+ exchange reaction during the proton acid doping procedure also promotes the improvement of the electrochemical performance.