等离子体增强化学气相沉积法制备WO3-x/C复合材料及其储锂性能研究

三氧化钨(WO_3)凭借其在锂离子电池中较高的理论比容量(～700mAh·g~(-1))以及廉价易得的特性而引起了科研工作者广泛的研究兴趣,然而其相对较差的导电性以及在循环过程中所发生的较大体积变化导致其倍率性能和循环性能并不理想。为了增强其导电性,减缓体积变化所带来的负面影响,本文采用等离子体增强的化学气相沉积法成功地在所制备的WO_(3-x)纳米片上包覆含有氮元素掺杂的无定形碳。氮掺杂碳的包覆可以有效降低循环过程中发生的较大体积变化问题,而且可以提供更多的位点供锂离子进行嵌入/脱嵌。电化学测试表明,所制备的WO_(3-x)/C电极相比于WO_(3-x)电极和商业WO_3电极,展现出更好的倍率性能和循环性能。动力学模拟与计算表明,经过碳包覆的WO_(3-x)/C电极具有更小的电荷转移电阻和更快的锂离子扩散速率,从而有效提升其电化学性能。

Study on Preparation of WO3-x/C Nanocomposite by PECVD Method and Their Lithium-Ion Storage Properties

By virtue of the high theoretical capacity (~ 700 mAh?g -1) in lithium-ion battery and the comparatively low cost, tungsten trioxide (WO3) has attracted great interest of researchers. However, it still suffers from its low conductivity and the severe volume variation during the discharge/charge processes, which lead to the inferior rate performance and cycling performance. To enhance its conductivity and mitigate the adverse effects caused by the volume variation, a plasma-enhanced chemical vapor deposition (PECVD) method was successfully used to coat nitrogen-doped amorphous carbon on defective WO3-xnanosheets. N-doped amorphous carbon coating can effectively alleviate the unsatisfactory volume variation effects, and provide more sites for lithium-ions to insert and extract. The electrochemical evaluations demonstrated that the prepared WO3-x/C electrode exhibits superior rate and cycle performance than that of WO3-x electrode and commercial WO3 electrode. Dynamic simulation and analysis suggested that the WO3-x/C electrode has smaller charge transfer resistance and the faster lithium-ion diffusion coefficient, thereby effectively improving its electrochemical performance.