Solid polymer electrolyte (SPE) have been expected as high safety and reliable materials compared with conventional organic liquid electrolytes. In order to apply polymer electrolytes to all-solid-state Lithium Ion Battery (LIB), it is essential to improve their lithium ion conductivity and membrane stability. In this study, we focused on polymer nanofibers to overcome these issues on SPEs for LIB applications.

Polymer nanofibers have unique characteristics such as high surface area, good mechanical property, and great material transport property [1]. We have reported fabrication, characterizations, and applications of various functional polymer nanofibers prepared by an electrospinning method [2]. Recently, we developed proton or anion conductive polymer nanofibers and revealed their outstanding ion conductive properties [3]. The nanofiber framework (NfF) composite membranes consisting of the ion conductive nanofibers and polymer electrolyte matrix showed remarkable fuel cell properties due to their improved ion conductivity, gas barrier property, and membrane stability [4].

Here presents our recent work on lithium ion conductive polymer nanofibers and their application to all-solid-state LIBs. The electrospinning method was attempted to fabricate lithium ion conductive NfFs composed of lithium salt and polymers bearing ethylene oxide units in their main or side chains. The lithium ion conductive NfF composite membranes were prepared by filling polymer electrolyte matrices into the voids of the NfFs. Electrochemical, thermal, and mechanical properties of the NfFs and NfF composite membranes were evaluated to demonstrate improved electrolyte characteristics. Fabrication and evaluation of all-solid-state LIBs based on the NfF composite membranes will also be reported.

Acknowledgements

This work is partially supported by JSPS KAKENHI (26410225), and a grant (Platform for Technology and Industry) from Tokyo Metropolitan Government, Japan.

References

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[3] (a) Takemori, R.; Ito, G.; Tanaka, M.; Kawakami, H. RSC Advances 2014, 4, 20005-20009. (b) Watanabe, T.; Tanaka, M.; Kawakami, H. Nanoscale 2016, 8, 19614-19619. (c) (Focus Review) Tanaka, M. Polym. J. 2016, 48, 51-58.

[4] (a) Tanaka, M.; Takeda, Y.; Wakiya, T.; Wakamoto, Y.; Harigaya, K.; Ito, T.; Tarao, T.; Kawakami, H. J. Power Sources 2017, 342, 125-134. (b) Tanaka, M.; Makinouchi, T.; Kawakami, H. J. Memb. Sci. 2017, 530, 65-72. (c) Watanabe, T.; Tanaka, M.; Kawakami, H. Polym. Int. 2017 66, 382-387.