Synthesis and Properties of Sn₃₀Co₃₀C₄₀Ternary Alloy Anode Material for Lithium Ion Battery

Abstract

With the development of advanced lithium ion batteries, electrode materials with higher capacity are urgently in demand. With respect to the anode materials, Sn-based alloy materials with high theoretical capacity (990 mAh/g) have the potential to replace the traditional, low capacity carbon-based materials. However, the practical application of Sn-based anode materials is severely retarded due to the poor cycling stability of electrode, which is believed to be caused by the pulverization of active particles resulting from the large volume of Sn during lithiation/delithiation process. The Sn-Co-C ternary alloy with amorphous or nano microstructure can overcome this problem and therefore display attractive electrochemical performance, including high capacity and good cycle stability. In the present work, amorphous Sn 30 Co 30 C 40 alloy material was synthesized through a simple and scalable two-step method (carbothermal reduction-high energy ball milling method). CoSn 2 alloy was firstly prepared by the carbothermal reduction route from low cost metal oxide and activated carbon. Then the prepared CoSn 2 were mixed with metal cobalt and graphite in a molar ratio of 3∶3∶8 via a high energy ball milling process to synthesize the final Sn 30 Co 30 C 40 material. The preferential synthesis of CoSn 2 alloy was important to get Sn 30 Co 30 C 40 material with much smaller CoSn grain dispersed in carbon matrix and thus critical to the better electrochemical performance. XRD, SEM, TEM, HR-TEM, S-TEM and electrochemical tests were used to evaluate the structure and electrochemical performance of the CoSn 2 and Sn 30 Co 30 C 40 materials. The synthesized Sn 30 Co 30 C 40 material displayed micro-sized particle morphology, which in fact was composed of 10 nm CoSn grains distributed well in amorphous carbon matrix. The Sn 30 Co 30 C 40 material showed high specific capacity of 550 mAh/g with an initial coulombic efficiency of 80%, good cycling stability and excellent rate-capability. The specific capacity of 430, 380, 280 mAh/g could be achieved at the rate of 1 C, 2 C and 5 C, respectively.

Synthesis and Properties of FeSn₂-C Composites as Anode Materials for Lithium-Ion Batteries

“…2,3 但 Sn 在嵌脱锂过程中存在巨大的体积变化(高达 300%), 该变化易导致材料粉化、 脱落及电极导电网络的破 坏, 从而造成循环性能的急剧衰退. 4,5 为了提升 Sn 材 料的循环性能, 通常对其进行纳米化, 与第二相复 合等技术处理. 纳米化可以使其应力变化更加均 匀, 而与第二相复合可以减小材料在嵌脱锂过程中 整体的体积变化.…”