Enhanced rate performance and cycling stability of a CoCO3-polypyrrole composite for lithium ion battery anodes
Enhanced rate performance and cycling stability of a CoCO3-polypyrrole composite for lithium ion battery anodes
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DOI：
10.1039/c3ta12227a
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发表时间：
2013-01-01
影响因子：
11.9
通讯作者：
Zhang, Jianxin
中科院分区：
文献类型：
--
作者：
Ding, Zhaojun;Yao, Bin;Zhang, Jianxin
采用水热法合成海胆状CoCO 3微球（CC），并在其表面包覆聚吡咯（PPy），制备了CoCO 3-聚吡咯复合材料（CC-PPy）。与CC相比，所得CC-PPy表现出优异的循环稳定性、突出的倍率性能和大的恢复能力，在0.1、1、2、3、4和5 C下100次循环后分别提供1070.7、811.2、737.6、518.7、504.5和559 mA h g（-1）的可逆容量，在1 ~ 5 ℃下循环500次后，恢复容量高达1787 mAh g（-1）。一个更全面的锂存储机制的CoCO 3已被提出来支持实验数据，其中包括两步转换反应与7 Li/CoCO 3的总理论值。第一级反应包括CoCO 3还原成金属Co并形成Li 2 CO 3，第二级反应包括Li 2 CO 3进一步还原成Li x C 2（x = 0，1，2），沿着Li 2 O的形成。比较了CC和CC-PPy的锂化和脱锂过程，发现CC和CC-PPy的锂化和脱锂过程具有明显的二级动力学特征。根据奈奎斯特曲线分析了CC-PPy上级性能的动力学因素。此外，通过在CC-PPy的不同放电-充电状态下记录的非原位红外光谱，证实了CoCO 3到Li 2CO 3到Li 2 O的转变及其可逆性。
A CoCO3-polypyrrole composite (CC-PPy) for lithium ion battery anodes was prepared by first synthesizing urchin-like CoCO3 microspheres (CC) via a hydrothermal route and further modifying them with a PPy coating. The resulting CC-PPy exhibits excellent cycling stability, outstanding rate performance and a great recovery capability compared to CC, delivering a reversible capacity of 1070.7, 811.2, 737.6, 518.7, 504.5 and 559 mA h g(-1) after 100 cycles at 0.1, 1, 2, 3, 4 and 5 C, respectively, and a recovery capacity of up to 1787 mA h g(-1) after 500 cycles from 1 to 5 C. A more comprehensive lithium storage mechanism of CoCO3 has been proposed to support the experimental data, which includes two-step conversion reactions with a total theoretical value of 7 Li per CoCO3. The 'first-order' reaction involves reduction of CoCO3 to metallic Co and the formation of Li2CO3, and the second reaction involves the further reduction of Li2CO3 to LixC2 (x = 0, 1, 2), along with the formation of Li2O. The lithiation and delithiation processes of CC and CC-PPy have been compared based on their potential profiles and CV curves, which show clear two-order character. The kinetic factors for the superior performance of CC-PPy are analyzed based on the Nyquist plots. Furthermore, the transition from CoCO3 to Li2CO3 to Li2O and its reversibility is confirmed by ex situ IR spectra recorded at the different discharge-charge states of CC-PPy.