CVI法により作製したリチウムイオン電池用熱分解炭素負極

Abstract

Using pressure-pulsed chemical vapor infiltration (PCVI) method, novel preparation process of negative electrode for the lithium-ion rechargeable battery was investigated. This process consisted of two steps of the partial infiltration of TiN into highly porous carbon performs, and the infiltration of pyrolytic carbon as the active material. TiN was partially infiltrated into the highly porous carbon preforms at 850℃ from gas system of TiCl_4(1%)-N_2(20%)-H_2. The porous carbon preforms were prepared by the carbonization of commercial filter paper and wood at 1000℃ in Ar for 4 h. After 10000 pulses of PCVI, electro-conductive porous bodies were obtained, which had the porosity of 80% and more, the resistivity of 0.1 mΩ cm, and the average pore sizes of 10-40 μm. The geometric surface area per unite volume showed highest value with the sample obtained from carbonized wood preform. When the TiN/wood porous bodies were used as current collector, therefore, it was expected that contacting resistance between active materials and current collector became the lowest value. The plate-type negative electrodes were prepared by PCVI of pyrolytic carbon into the TiN-based porous bodies at 950℃ from C_3H_8 (30%)-H_2. Three-dimensional current paths were formed in the active material layers of the negative electrodes obtained by present process. The electrode showed the excellent rate performance, and capacity of pyrolytic carbon maintained 90% of initial value after the charge-discharge cycling of 50 times.