Some Studies Including Multi-layered Cathodes for Safety Tolerance of Lithium-ion Batteries

摘要

With the increase in power consumption of portable electronic devices and the emergence of high power applications like hybrid electric vehicles, Li-ion batteries with high capacity and high power performance are in high demand. Accordingly, reliability becomes one of the most important issues in these Li-ion batteries. We have previously reported the use of LiCoO_2/LiMn_2O_4 composite cathode that gives better safety performance and is less susceptible to thermal runaway than commercial LiCoO_2 cathodes because of the thermal stability of LiMn_2O_4. However, the overall capacity is compromised with this system. In order to improve the safety performance of Li-ion batteries using LiCoO_2 cathodes without sacrificing the battery capacity, a new electrode concept with the use of a multi-layered cathode instead of a mixture of two materials, and new electrolyte candidates are introduced. A double-layered cathode consists of a LiCoO_2 main layer and a LiFePO_4 sub layer on top of an aluminum current collector was prepared. The effect of the LiFePO_4 layer on the tolerance of the batteries against overcharging is presented in this study. Some flame-retardant electrolyte candidates and a modified separator are also reported.