The Preparation And Properties Of Tin Coated Polypyrrole Anode Materials For Lithium-ion Batteries

Lithium-ion battery is high voltage, high energy density, long cycle life andenvironmentally friendly. However, the capacity of traditional graphite anode materialfor lithium ion battery is only372mAhg-1, has been unable to meet the currentrequirements of the market. The theoretical capacity of metal tin (Sn) is about990mAh g-1, much higher than the theoretical capacity of graphite and this anodematerials have high safety performance, low cost. However, when tin is used as theanode materials of lithium ion batteries, there is a large volume expansion (300%) inthe lithium-ion intercalation and deintercalation process, resulting in powdering o f theelectrode active material, and fall off, the capacity rapidly declines, cycle performanceis poor.This paper prepared Sn nanoparticles of different sizes by chemical reduction,prepared Sn-Cu hollow nanoparticles by galvanic replacement reaction, preparedpolypyrrole-coated Sn nanoparticles and polypyrrole-coated Sn-Cu hollownanoparticles by oxidative chemical polymerization method. The size distribution ofSn nanoparticles is narrow, the particle size is uniformity, the hollow structure ofSn-Cu hollow nanoparticles is significant, the core-shell structure of Sn/PPy isobvious by scanning electron microscopy (SEM) and transmission electronmicroscopy (TEM) characterization.The cycle performance of the Sn-Cu hollow nanoparticles is much better than theSn nanoparticles by electrochemical characterization, the discharge capacity is381.35mAhg-1after50cycles, much higher than58.64mAhg-1of the pure Snnanoparticles. Its cycle performance can be further improved after being coated withpolypyrrole, the discharge capacity is453.63mAhg-1.