Microstructure and Electrochemical Properties of Various Carbon Materials in Li-ion Secondary Batteries

Abstract

Li-ion secondary batteries are currently the best electric energy storage device for portable electronic equipments. Recent development of the Li-ion secondary batteries has been achieved mainly by the use of selected carbon and graphite materials as an anode. The performances of Li-ion secondary batteries, such as the charge/discharge capacity, voltage profile and cyclic stability, depend strongly on the microstructure of the anode materials made by carbon or graphite. By the contribution of the carbon materials used in anode in last five years, the capacity of the typical Li-ion secondary battery has been improved by a factor of 1.7. However, it is still being studied actively to identify the key parameters for the preparation of carbons that can provide better anode properties. The reason for this is that carbon and graphite materials have large varieties in their microstructure, texture, crystallinity and morphology depending on their preparation processes and precursor materials, as well as various macroscopic forms such as powder, fibers and spherules. In the present article, we describe the correlation between the microstructural parameters and electrochemical properties of conventional and novel types of carbon materials for Li-ion secondary batteries. The carbon materials dealt in this article are: graphitizable carbons such as milled mesophase pitch-based carbon fibers (MPCF), vapor grown carbon fiber (VGCF), polyparaphenylene (PPP) polyvinylidene chloride (PVDC)-based carbon heat-treated at low temperatures and boron-doped graphitized materials, which were selected in connection with the market demand and trend of Li-ion secondary batteries. The basic scientific study on carbons can contribute to further developments of the Li-ion secondary batteries, such as polymer battery for consumer electronics, multimedia technology and even for future hybrid and electric vehicles.