核壳结构Ni/Si纳米墙阵列的制备、表面修饰及锂离子电池性能研究

To improve the electrochemical properties such as specific capacity, initial coulombic efficiency, cycling performance and rate properties of Si anode materials of lithium ion batteries, a core-shell Ni/Si nanowall array is prepared on nickel substrate and then surface-modified by high-dispersed Ni nanoparticles less than 10 nm. The core-shell nanowall structure has the ability of enhancing the conductivity and the structural stability of Si materials. The high-dispersed Ni nanoparticles have the ability of facilitating the decomposition of SEI layer due to their high catalytic activity. The effect of core-shell nanowall array structure on the specific capacity, cycling performance and rate properties is studied. The influence of high-dispersed Ni nanoparticles on the initial coulombic efficiency is also investigated. The volt-ampere feature and the impedance characteristics are systematically analyzed. Further, the evolution of the microsturcture, morphology and components during the charge-discharge process are studied. Finally the mechanism of performance improvement is proposed.

为了提高锂离子电池硅负极材料的电化学性能，本项目基于Ni核Si壳的纳米墙阵列结构具有增强Si材料导电性和结构稳定性的功能，以及高分散10 nm以下Ni颗粒具有催化Si材料表面SEI膜分解的作用，对电极进行结构设计，在Ni片集流体上制备了一种核壳结构的Ni/Si纳米墙阵列，并对其进行表面高分散纳米Ni修饰。研究Ni核Si壳的纳米墙阵列结构对Si负极材料容量、循环稳定性和高倍率充放电性能的改善，研究高分散10 nm以下Ni颗粒对Si材料首次库仑效率的提升，从而全面解决锂离子电池Si负极材料实际容量不高、首次库仑效率低、循环稳定性差、高倍率充放电性能差等问题。再系统地研究材料在充放电过程中电压、电流和阻抗的变化，以及材料结构、形貌和组成的演变，得出Si负极材料电化学性能得以改善的机理。

本项目采用化学水浴沉积法、氢气还原法和磁控溅射法制得了具有核壳结构的Ni/Si纳米墙阵列材料。通过调控化学水浴沉积的工艺参数来调控Ni纳米墙阵列的尺寸，通过调控磁控溅射的工艺参数来调控Si的负载量。将核壳Ni/Si纳米墙阵列应用于锂离子电池中，表现出优于块体材料和纯Si薄膜材料的电化学性能。进一步地，对薄膜材料进行Ni纳米颗粒修饰改性，进一步提升了材料的储锂性能。这样的电极结构设计，可以在增大Si材料负载量的同时不牺牲其电化学性能，从而较好地解决了硅材料可逆容量低、首次库仑效率低、高倍率性能和循环性能差等问题。通过研究核壳Ni/Si纳米墙阵列负极材料的充放电行为和充放电之后的微观组织结构，揭示了它们改善Si材料储锂性能的物理与化学机制。本项目共发表论文8篇，在投3篇。