Preparation And Electrochemical Performances Of3D Structure-baesd Si Film Anode In Lithium-ion Batteries

Si is one of the most potential anode materials, due to the high theoretical specific capacity, low voltage platform, low cost and abundant in nature. However, severe volume change during Li insertion and extraction processes and poor electrical conductivity of Si anodes lead to poor cycle performance and rate performance. In the thesis, different3D structured collectors and a novel binder are applied to improve the electrochemical performance of Si based anode.First, the3D net structure Si film anode is prepared by magnetron sputtering method on a foam Ni collector. When the thickness of the Si film is200nm, the3D net structure Si film anode can cycle300cycles with a capacity of1472mAh/g at4.2A/g. We also prepared different3D porous structured collectors and high-performance Si films by magnetron sputtering method:(1) The3D leaf-like porous structure is prepared on panel Cu by chemical etching and electrochemical reduction method, following magnetron sputtering method to obtain Si films with thickness of0.2,0.4,0.6and1μm, respectively. The Si film with thickness of0.2μm shows excellent cycle performance and rate performance with a capacity of1461mAh/g after200cycles at0.8A/g. Even when the thickness of Si film increases to1μm (two Al films with thickness of10nm are added in the middle of the Si film), the Si film also exhibits wonderful cycle performance in the first120cycles with integrated structure.(2) Another3D needle-like porous structure based Si film is prepared on foam Cu by the same methods with thickness of0.6and1μm, respectively. The electrochemical performance of the3D needle-like porous structure based Si film with the thickness of0.6μm is excellent with a capacity of1132mAh/g after500cycles at0.8A/g. The Si film anode could also cycle100cycles with a capacity of1208mAh/g even when the thickness of the Si film increases to1μm.A new binder (guar gum) for Si-based anodes is also studied in the thesis. The electrochemical performances of Si-based electrode with guar gum binder are much better than that of CMC binder and Na alginate binder. When the guar gum is applied as a binder, the Si/C anode could cycle100cycles with a capacity as high as1283mAh/g, witch is much higher than that of Na alginate binder (991mAh/g).In brief, forming a3D structure is an effective way to improve the electrochemical performance of Si-based anode. And the guar gum is applied as a binder for Si-based anode for the first time to improve the electrochemical performances.