Light Weight Free Standing Carbon Nanotube Film for Flexible Lithium Ion Battery Anode

摘要

Lithium ion batteries (LIBs) have been widely used in portable IT devices such as smart phone, tablet PC and etc. Since these devices are getting smaller and lighter, LIBs should be smaller and lighter. However, metallic current collector such as Cu foil and Al foil is an obstacle to realize lightweight LIBs. Nanocarbon materials such as carbon nanotubes (CNTs) and graphene are considered as potential candidate for replacing metallic current collector due to their high electrical conductivity with low density. In addition, CNT and graphene can perform as LIB's anode due to their lithium storage ability. However, huge irreversible capacity and low coulombic efficiency at initial cycle owing to the formation of solid electrolyte interface (SEI) hinder the advantages of nanocarbon materials. In this study, in order to improve the initial irreversible capacity and coulombic efficiency of CNT film, stable SEI was preformed by directly contacting CNT film with Li metal in electrolyte (1M LiPF6 solution in ethyl carbonate (EC) and diethyl carbonate (DEC) (1:1 v/v) before cell assembly. The initial irreversible capacity and low coulombic efficiency of CNT film was remedied by direct prelithiation method and its capacity increased up to 1300 mAh/g at 300th cycle. Also, flexible pouch cell, which was assembled with the prelithiated CNT film, worked normally under mechanical deformation.