Size effect of tin oxide nanoparticles on high capacity lithium battery a node materials Yi-Chun Chen a, Jin-Ming Chen b, Yue-Hao Huang b, Yu-Run Lee b, Han C. Shih a,c,* a Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan b Materials and Chemical Engineering, Industrial Technology Research Institute, Chutung 310, Taiwan c Institute of Materials Science and Nanotechnology, Chinese Culture University, Taipei 111, Taiwan Available online 1 September 2007 Surface & Coatings Technology 202 (2007) 1313–1318 報告學生: 蔣昆璋 指導教授: 王聖璋 老師

目 錄 前言 實驗流程 結果與討論 結論 未來工作

前言 Lithium ion batteries have a high energy density and are widely used in electrical products, such as mobile phones and notebook computers. Graphite and other carbonaceous materials are the most used as commercial anodes for the lithium ion batteries. Nanotechnology has been applied in the anode materials as the nanocomposite materials. Carbonaceous materials are used as matrices to reduce the volume expansion effect and the nanotin composites are added to increase the capacity . The forms of nano-tin composites include Sn, SnO and SnO2. Tin is more applied as an anode material than the silicon because it has a low active voltage which is approximately 0.3 V and that of silicon exceeds 0.5 V. This work employs tin oxide nanoparticles as the active material, which was synthesized by the sol–gel method. Although the preparation of tin oxide nanoparticles by sol–gel method has been reported recently , this work develops another process for synthesizing the tin oxide nanoparticles (∼20 nm) which disperse uniformly on the graphite surface. Electrical measurements were used to analyze the nano-SnO2/graphite. Though tin is widely used as an active material in the anode, only few works are relevant to the study of the real utilization of tin as active materials. This work therefore discusses the utilization of tin as an anode material.

Electrochemical tests 實 驗 流 程 SnCl2·2H2O Ethanol 28 ml HCl 0.9 ml Stirring 24H >24H DI water 175 ml 2H Graphite powders X-rd SEM TGA Electrochemical tests Nano SnO2/graphite

Electrochemical tests graphite SnO2 powders Mixing 1:7 2H Electrochemical tests Micro-SnO2/graphie

結 果 與 討 論 Graphite JCPDS 41-1487 SnO2 JCPDS 41-1445 Fig. 1. X-ray diffraction pattern of the SnO2/graphite structure.

Fig. 2. SEM images of the SnO2/graphite at the magnification of (a) ×10,000, (b) ×50,000, and (c) ×150,000 and SEM images of the pure graphite at the magnification of (d) ×10,000 and (e) ×50,000

Fig. 3. TGA analysis of the nano-SnO2/graphite

Fig. 4. Charge/discharge curves of (a) graphite, (b) nano-SnO2/graphite, and (c) micro-SnO2/graphite

Fig. 5. The capacity varying with the cycle number of the graphite, nano-SnO2/ graphite and micro-SnO2/graphite.

結 論 The sol–gel method is effective in creating nano-sized SnO2 particles (~20 nm). (2) Adding SnO2 to pure graphite markedly improves the specific capacity, which nevertheless, fades and is related to the size and distribution of the particles. (3) Nano-sized SnO2 particles increase the utilization of Sn and clearly increase the cyclability over those of micro-SnO2. (4) Sn-based materials are therefore promising for use in anode and the sol–gel method is effective in reducing the particle size. (5) Further studies of the nanocompositions are required leading to the development of commercial anodes in the future.

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