Study on Electrochemical Stability and Safety of Double-Coated Ni-rich Cathode Materials

• Main Authors: Dao-Yi Wang, 王道一
• Other Authors: Bing-Joe Hwang
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/68rsrs

碩士 === 國立臺灣科技大學 === 化學工程系 === 107 === Nickel rich cathode materials are highly researching for recent decade due to its high capacity ~220 mAhg-1. However, owing to the many drawbacks, like poor thermal stability, side reaction with electrolyte and capacity fading. In this study, double-layered coating is mainly carried out. First part is to coat a metal oxide on the nickel-rich material powder with a dry coating method, Mechanofusion, to form an artificial solid electrolyte interface The nickel rich materials are isolated from the electrolyte to reduce the generation of side reactions and the dissolution of the transition metal ions to improve the stability of interphase and charge/discharge stability of the powder. Second layered, to use the heat-resistant polymer, bismaleimide and tripolythiocyanate, to coat on the nickel rich cathode material powder so that the battery can be polymerized to form an close circuit in the case of thermal runaway, increasing the safety of the battery. This study will compare the structure and electrochemical performance of a single process coated sample, a double coated sample and a non-modified powder. In the results and discussion, the mechanofusion is first applied to coat the surface of the secondary particles with different ratio and different time of LiNbO3, and the best stability was obtained with the least impedance increase, and in the case of double-layeredcoating. Perform high-temperature impedance analysis to see if the double-coated battery will increase the impedance due to polymer polymerization, which will increase the safety. The study found that the powder coated by LiNbO3 and double coated by heat resistant polymer has good stability at high C rate (0.5C) and the capacity can be maintained 49.4% after 100 cycles, it’s better than pristine sample. The impedence is also greatly increased at the high temperature due to the polymerization of the polymer so that the safety also improved.