The Exploration Of Lithium-ion Battery Anodes Based On Thinning Si-MCP And Conductive Polypyrrole

With the rapid development of the microelectronics technology, the capacity of Lithium-ion (Li-ion) batteries require a further increment. Finding high-performance alternative to traditional carbon anode materials is the key to solving this problem. Silicon-based materials with a ultra-high specific capacity of 4200mAh.g-1 is one of the promising anode materials, but their severe capacity recession caused by the huge volume changes during the cycles, restricting their practical applications. To solve this problem, a series of explorations and researches on Li-ion batteries anode were made in this paper.1. The loss of Ni layer is the main reason for the capacity recession of Ni/Si-MCP anode during the charge and discharge process. To improve this situation, a conductive polypyrrole coated Ni/Si-MCP anode was prepared by electrochemical oxidation polymerization, and the galvanostatic C-D cycle tests was carried out under different conditions.In the non-limiting tests, the PPy/Ni/Si-MCP electrode exhibited a better performance than the rare Ni/Si-MCP electrode. During the 19th cycle, the PPy/Ni/Si-MCP electrode has a reversible discharge capacity of 1500mAh.g-1, while this corresponding value of the Ni/Si-MCP electrode is less than 1000 mAh.g-1.When the tests were carried out under designated capacities of 1000 mAh.g-1, the PPy/Ni/Si-MCP electrode can maintain the cycle more than 120 times. But for the Ni/Si-MCP electode, the cycles is only 80 times.2. To improve the cycling stability of the Si-MCP anode, a simple and easy chemical etching process was employed. Si-MCPs with thinning and rough sidewall can be obtained after this thinning treatment. Based on this thinning Si-MCP, an uniform continuous metal current collector layer were then deposited by a novel method, which is based on the principle of pressure difference.Compared to the original Ni/Si-MCP, the modified Ni/Si-MCP exhibits more excellent cycle performance in the galvanostatic tests. In the first 30cycles, the reversible capacity remains above 1500 mAh.g-1, and for the original Ni/Si-MCP anode, which has a value lower than 500 mAh.g-1.As an substitute for the Ni collector layer, the copper layer was deposited on the thinning Si-MCP structure. After testing, we found that the cycle performance of the Si-MCP based electrode has a further improvement. After 29 cycles, its reversible capacity is still up to 2000mAh.g-1.