锂离子电池在便携式电子产品和新能源汽车中发挥着重要的作用。相比传统的锂离子电池负极材料石墨，硅由于具有更高的理论比容量（4200 mAh/g）而得到了国内外学者的广泛关注。然而，硅负极在循环过程中的体积膨胀（400%）会导致电池容量的大幅衰减，这阻碍了硅材料成为一代锂离子电池负极材料。目前，如何解决硅的体积膨胀已成为研究人员所广泛关注的问题。硅纳米线由于良好的应力释放能力和一维方向的电子传导能力而被广泛应用于锂离子电池负极材料，金属辅助化学腐蚀法制备硅纳米线方法简单、产量较高，在锂离子电池领域具有极高的研究价值和应用前景。然而，传统的金属辅助化学腐蚀（MACE）法制备的硅纳米线直径大多在50 nm甚至100 nm以上，循环过程中容易体积膨胀而断裂，且硅纳米线作为一种半导体材料电子导电率较低，故MACE法制备的硅纳米线很难在锂离子电池的循环过程中具有较高的稳定性和比容量。在本文中，我们分别研究了超细硅纳米线的制备工艺，不同直径的硅纳米线负极材料的锂离子电池性能以及超细硅纳米线/还原氧化石墨烯复合材料负极的锂离子电池性能。

本文系统地探讨了双金属辅助化学腐蚀（BACE）法制备超细硅纳米线的工艺，探究了沉积电流、沉积时间以及靶材和基体距离对沉积所得双金属催化剂模板形貌以及后续腐蚀过程的影响，制备了平均直径为10 nm和30 nm的硅纳米线。用金属辅助化学腐蚀（BACE）法制备了平均直径为100 nm的硅纳米线。并对平均直径为10 nm的超细硅纳米线、30 nm的硅纳米线以及平均直径为100 nm的普通硅纳米线样品进行形貌和结构分析。

研究了100 nm普通硅纳米线、30 nm和10 nm硅纳米线三种不同直径的硅纳米线负极材料的储锂性能，并结合电化学测试手段分析了不同直径的硅纳米线的储锂机理。在三种硅纳米线材料中，30 nm的硅纳米线具有最优的锂离子电池性能，在300 mA/g的电流密度下的放电容量为1066.0 mAh/g，且50次循环容量保持率为89.5%。经分析，30 nm超细硅纳米线相对于100 nm硅纳米线和10 nm硅纳米线来说，在储锂性能上的优势主要归因于：(1) 30 nm的硅纳米线具有相对较小的直径，在循环过程中能够抵御较大的应力，因此不易粉化；(2) 30 nm的超细硅纳米线表面能够形成最优的SEI膜，使其具有最小的SEI膜阻抗和传荷阻抗，以及最高的锂离子扩散系数；(3) 30 nm的硅纳米线相较10 nm的硅纳米线比表面积较小，因此不会引入过多的副反应，导致容量的衰退。

探讨了超细硅纳米线/还原氧化石墨烯复合材料的制备方法。30 nm硅纳米线/还原氧化石墨烯复合材料在第2次放电时的比容量为2013.1 mAh/g, 第50次放电的比容量为1542.1 mAh/g，高于未被包覆的超细硅纳米线负极材料。同时，30 nm硅纳米线/还原氧化石墨烯复合材料负极的倍率性能相比未被包覆的超细硅纳米线负极也有所提升。30 nm硅纳米线/还原氧化石墨烯复合材料负极在1200 mA/g的电流密度下仍保持有1297.8 mAh/g的比容量，远高于未被包覆的硅纳米线负极材料。

Lithium-ion batteries (LIBs) have played an important role in portable electronic products and new energy vehicles (EVs). Compared with graphite, which is the traditional anode material, silicon has been widely concerned by researchers due to its higher theoretical specific capacity (4200 mAh/g). However, the volume expansion (400%) of silicon anodse in during cycling may cause significant reduction of its capacity, which prevents silicon from being used as the anode material of the next generation LIBs.Nowadays, how to solve the volume expansion of silicon has become a widespread concern. In this paper, we studied the preparation metod of ultra-thin silicon nanowires (UTSiNWs), the performance of lithium-ion batteries with different diameters of silicon nanowires (SiNWs) as negative materials, and the performance of lithium-ion batteries with UTSiNWs/ reduced graphene oxide (rGO) composite as anode materials.

In this paper, the technology of Bi-metal assisited chemical etching (BACE) method for the preparation of UTSiNWs is systematically discussed. The effects of deposition current, deposition time and distance between target and substrate on the morphology of Au/Pt catalyst template and subsequent etching process are investigated. The morphology and structure of UTSiNWs with an average diameter of 10 nm and 30 nm and SiNWs with an average diameter of 100 nm were analyzed. It was found that the silicon nanowires with a smaller average diameter have higher SiO_x content, which is mainly because the silicon nanowires with a smaller average diameter have a larger specific surface area, so they are easier to be oxidized.

In this paper, the lithium-ion battery performance of anode materials of SiNWs with different average diameters, i.e. 100 nm, 30 nm and 10 nm is discussed, and the lithium storage mechanism of SiNWs with different diameters is analyzed by means of electrochemical test. Among the three kinds of silicon nanowires, 30 nm silicon nanowires have the best performance for lithium-ion batteries. The discharge capacity is 1066.0 mAh/g at the current density of 300 mA/g, and the capacity retention rate of the 50th cycle is 89.5%. The performance advantages of 30 nm UTSiNWs are mainly attributed to the following three points: a) the diameter of 30 nm UTSiNWs is relatively small, which can resist large stress during cycling, so it is unlikely to be pulverized; b) The surface of the 30 nm UTSiNWs are coated with SiO_x of appropriate size, which can resist the volume expansion of the nanowires during cycling, making the 30 nm UTSiNWs anode have a more stable SEI film; c) The specific surface area of the 30 nm UTSiNWs is smaller than that of the 10 nm UTSiNWs, so less side reactions which may lead to capacity fading will be happened.

        In this paper, the preparation of UTSiNWs/rGO composite was studied. The specific discarage capacity of the composite is 2013.1 mAh/g in the 2nd cycle, and 1542.1 mAh/g in the 50th cycle, which is higher than that of the uncoated UTSiNWs. It can be seen that the specific capacity of UTSiNWs coated with rGO is significantly increased. This is because the coating of rGO improves the electronic conductivity of the electrode material, the interface resistance and the load transfer resistance are effectively reduced, so that the specific capacity of the electrode material is further improved. At the same time, the rate performance of the composite anode is also improved compared with the uncoated one. At the current density of 1200 mA/g, the specific capacity of UTSiNWs/rGO composite anode is still 1297.8 mAh/g. It can be seen that the coating of rGO makes the diffusion ability of lithium-ion in the electrode material stronger, so that the electrode material can still maintain a high capacity in the rapid charging and discharging process.