|학술대회||2010년 봄 (05/13 ~ 05/14, 삼척 팰리스 호텔)|
|발표분야||C. Energy and the Environment(에너지 및 환경재료)|
|제목||Enhanced electrochemical performance of germanium based anode material by adding inactive material using RF/DC magnetron sputtering for lithium ion batteries|
|초록||The lithium ion battery is a promosing technology for reversible strorage in potable devices and electricity storage. Graphite or other carbonaceous materials was used for active mass in the negative electrode has the theoretical capacity (372mAh/g) of the LiC6-compound. A group-IV materials are ideal candidates as anode with respect to storage capacty. Among these, Si and Ge are the most interesting and popular materias. Si and Ge showed specific capacity of 4200mAh/g and 1600 mAh/g, respectively, when materials exhibied Li21M5 alloy. Despite this capacity merit, a large volume expansion is associated with the lithiation. This leads to mechanical stress and structural damages, which causes a huge capacity loss after a few cycles.
Germanium and Ge-based composite are promising candidates for use as negative electrode materials in lithium ion batteries because of their large specific capacities of up to ten times that of graphite. It also form a series of defined compounds, the advantage of this system is the diffusivity of lithium in germanium which is 400 times higher than the diffusivity of lithium in silicon at room temperature. A thinner native oxide layer in its surface leads to lower irreversible capacity during the first cycle. So germanium may be an attractive electrode material for the use in lithium ion batteries. Unfortunately, most lithium alloys are brittle, and hence, easily pulverized by the large volume change in charge and discharge reactions. To solve this problem, several research efforts have been carried out. An element (such as Co, Cr, Fe, Mn, Ni, V, Zr or Mo) that does not alloy with Li is assumed to effectively suppress volume change. The Mo elements in the film make Ge–Mo bonding and the inactive matrix incomplete. These inactive sites reduce mechanical stress during cycles. We have confirmed that the Ge-Mo composite electrode prepared by sputtering shows better cycle retention than only active material Ge as the anode of Li-ion batteries.
In order to identify the influence of the active material of anodes, cell tests were carried out on both half cell (Ge-Mo/Li metal) and full cell (Ge-Mo/LiCoO2). It may be successful to find materials as an anode with high capacity and improving capacity retention.
|키워드||Ge-Mo; anode; film; lithium ion batteries|