3,4-乙烯二氧噻吩单体用作锂离子电池安全性改善添加剂的研究

Safety concern is a major obstacle hindering the wide applications of large-capacity lithium ion batteries (LIBs) in electric vehicles. In this paper, a polymerizable monomer of 3, 4-ethylenedioxythiophene (EDOT) was proposed and tested as an electrolyte additive for enhancing the safety of LIBs. The electro-oxidative polymerization behaviors and influence of PEDOT additive on the thermal behavior of LiCoO₂cathode, as well as the safety performance and electrochemical properties of LiCoO₂-based LIBs were investigated. The results from cyclic voltammetry (CY) and transmission electron microscope (TEM) characterizations indicated that the monomer additive can be electro-oxidatively polymerized to form a dense and uniform conductive polymer film (PEDOT) on the cathode surface during the first battery charging. The analysis results from differential scanning calorimetry (DSC) demonstrated that the heat released from the thermal decomposition of liquid electrolyte on the cathode surface was significantly reduced by 26% due to the PEDOT barrier layer, which prevents electrolyte from direct contact with highly oxidative cathode. The safety tests revealed that even with a monomer content of only 0.1% (by mass) in liquid electrolyte, the thermal runaway onset time of LiCoO₂-based pouch full cells could be delayed for 13.8 min under high temperature impact at 150 oC, representing a significantly enhanced safety. In addition, it is also found that the use of EDOT monomer as an electrolyte additive did not produce any negative influence on the normal charge-discharge performance of LIBs, showing a prospect for battery application.