Porous polymer-carbon nanotube composites electrode for flexible lithium-ion batteries

Abstract

Strong interest has been aroused in the field of flexible energy devices for flexible or bendable electronic devices, recently. Among various types of energy devices, lithium-ion batteries are chosen as the great candiate since they show high energy density and portability. However, it is a great trial to develop flex-ible lithium ion batteies (FLIBs). This is due to the diffuculty to find out suitable materials that can satisfy electrochemical and mechanical properties. With a great interest in FLIBs, there have been many studies to develop FLIBs using suitable ma-terials such as a commercial paper, carbon nanotube (CNT), or graphene nanosheet. Even though they have shown good electrochemical property, it is difficult to satisfy other factors such as cost, mechanical property, or scaleability. In this study, polydimthylsiloxane (PDMS) and CNT are introduced to fabricate FLIBs. PDMS can present excellent mechanical support with outstanding flexibility and CNTs embedded in PDMS matrix play an role in both electrtical conductivity and lithium storage. Furthermore, pores are needed to enhance its specific capacity, since electrolyte can’t be pentrated into PDMS matrix due to the low surface energy of PDMS. To develop pores in PDMS-CNT nanocomposites, polymethylmethacrylate (PMMA) are introduced and phase separation occured between PDMS and PMMA is used. Also, block copolymer (PDMS-b PMMA) is added as a compatibilizer to control phase separation. As a result, porous PDMS-CNT nanocomposites with various pore sizes can be obtained depending on the fraction of PMMA, PDMS-b-PMMA, and drying temperature. Finally, electrochemical performance and mechanical properties of PDMS-CNT nanocomposites are measured. Since generated pores and residual PMMA in PDMS matrix simultaneously affect electrical conductivity, eletrolytes pentration, and mechanical properties, we can find the optimized pore size for FLIBs.