Preparation Of Silicon-based Thin Film Of Lithium Ion Battery Material And Electrochemical Properties

As the problems of the energy and environment become serious, how to develop low carbontechnology has become a big challenge. As a new energy which could possible to replace oil,Lithium ion battery plays a very important role. Among them, silicon alloy anode materials asthe lithium ion battery is widely attention because of its high capacity. In this article, differentkinds of Si thin films、Si/Al composite thin film and Si/C composite thin film are made bymagnetic puttering. After that, the modification of thin films has been studied. Andelectrochemical performance of thin films as Lithium battery anode material was tested, thecharge-discharge mechanism of thin films was researched, and characteristic of different thinfilms was contrast. The main conclusions are as below:(1) As lithium ion battery anode materials，the charge capacity and cycle performance ofpure silicon thin films are increased with the increase of the sputtering time. For example,sample Si50has the minimum irreversible capacity loss in the first cycle and the best cycleperformance with the first charge-discharge capacities are0.136mAh/cm~2,0.604mAh/cm~2. Inaddition, the impacts on electrochemical performance of crude copper foil substrates and smoothcopper foil substrate are compared. According to the results, the crude copper foil substrates donot make better performance which may because of magnetron sputtering time and structure andthickness of thin films.(2)The Si/Al composite thin films have a rough surface and obvious three layer structure.And the charge and discharge capacity, cycle performance, coulombic efficiency are increasedwith the increase of the sputtering time, and first cycle irreversible capacity reduced. SampleSi20-Al5-Si20has the best comprehensive performance：irreversible capacity loss in the firstcycle is only3.2%, capacity retention is0.028mAh/cm~2after20cycles. Compared with the pureSi thin film, Si/Al composite film has and a better electrochemical performance. Theintroduction of Al to Si improved the cycle performance of the Si film. In addition, the heattreatment did not improve the Si/Al composite thin films.(3) The surface of Si/C composite thin film is relatively smooth, and the structure is verydense. The results show that as the films with the cycle performance increase of graphitesputtering time in the rise. Si40-C60has the highest capacity retention and best electrochemicalperformance, and capacity retention of78.4%after20cycles. After heat treatment, the cycleperformance and the fist cycle coulomb efficiency are both reduced. The heat treatment did notimprove the Si/C composite thin films.