(A) study on new binder materials for Lithium Ion secondary batteries

Abstract

one is Na-alginate and the other is spandex. Na-alginate binder was tested for both anode and cathode to confirm the possibility of commercialization. Through the tests of applying Na-alginate, we found that this binder could improve the cell performance partially but was not perfect for commercialization at this time. Spandex binder was tested for $LiFePO_4$ cathode. Despite of using same organic solvent, spandex binder showed good cell performance compared to conventional PVDF binder.

Since 1990s, Li ion battery has been used for cell phone, note PC and various mobile devices. Recently this battery technology was also adopted for xEVs (hybrid electric vehicle, plug-in hybrid electric vehicle, battery electric vehicles) which were the hot trends in automotive industry. For the vehicle applications, Li ion battery must have the various characteristics as follows: - high energy & power density at room & low temperature - good cycle life and high temperature calendar life - good abuse tolerance - low cost For these targets, Battery makers have been focused on new cathode and anode materials, but the material developments of anode and cathode are progressing very slowly. $LiCoO_2$ and graphite which were developed in the early stage of Li ion battery are still main cathode and anode materials. $LiMn_2O_4$ and $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ cathodes which are main cathodes for xEVs are not new materials in the battery industry. Many researchers have developed Si-based anode and Li-rich cathode materials over several years. But for commercial adoption for electric vehicles, these materials have many barriers to overcome. Actually energy density is not the only one requirement for xEVs. Low temperature performance, cycle life and calendar life are also inevitable requirements for xEVs. To overcome the problems of present active materials, we performed researches about electrode binders instead of active materials in this thesis. The amount of binder is very small in electrode, but binder can play an important role for increasing physical properties and cell performances. But up to now, most binder researches targeted the silicon anode and binder researches on conventional electrodes are progressing slowly. In this thesis, we will review two binders