Study on the enhanced high power performance of lithium-ion battery

Abstract

After successful commercialization of small-sized lithium-ion batteries in portable electronics by Sony at 1991, new area of research and market which needs advanced performance of lithium-ion batteries is arising such as electric vehicle and hybrid electric vehicle. In the area, increased specific capacity of lithium-ion battery is very important, but enhanced high power performance is also significant and more complicated to be achieved. To improve the performance of lithium-ion batteries, when material is fixed, increasing electric conductivity or reducing ion diffusion length in solid phase is necessary. In this study, we focus on the reducing pathway of lithium ions in active materials. There have been a lot of researches to achieve it by synthesizing nanoparticle, nanorod, and nanowire and so on. However, in the purpose of mass production, only nanoparticle has an advantage in their preparation, because nanorod and nanowire need delicate and sensitive synthesis process which hinders large scale production of them. Even though nanoparticle has a merit in their production process, this form also has a problem of agglomeration when it is mixed with con-ducting agent and binder to cast on current collector. To solve all these problems, we used cellulose (cotton) as a template to synthesis nanoparticle but not to make them agglomerate by aligning them to form nanoparticle fiber structure. We believe that this form will enhance high power performance of lithium ion battery when this method is applied to synthesis of electrode active material. Therefore, we prepared LiCoO2 cathode active material by this cotton method and compared it with commercial LiCoO2 in SEM, XRD, BET and electrochemical tests especially for high rate performance. After comparison, excellent high power performance of LiCoO2 nanoparticle fibers was confirmed.