There are many kinds of carbon materials such as activated carbons, nanoporous carbons, carbon blacks, graphite, carbon nanotubes, carbon nanofibers, and graphene-like materials, and they have been used in a variety of batteries as active materials, conductive additives, and gas diffusion layers. Depending on the purpose of use, carbon materials are required to have appropriate porosity, electric conductivity, mechanical stability, and electrochemical stability. While the above mentioned carbon materials have individual advantages and disadvantages, it has been a challenging target to develop next-generation carbon materials to satisfy all the necessary requirements at the same time. In this talk, a new class of carbon material, “graphene mesosponge (GMS)”, is introduced as a feasible candidate [1]. GMS is synthesized by a hard-templating method using Al2O3 [1] or MgO [2] nanoparticles via precisely controlled chemical-vapor deposition in which the average stacking number of graphene sheets is adjusted to 1. After template removal, the resulting mesoporous carbon is annealed at 1800 °
C to form GMS. By such a high-temperature treatment, most of carbon edge sites which cause corrosion of batteries can be removed, and GMS exhibits ultra-high stability against chemical oxidation as well as electrochemical oxidation. Despite such durability, GMS possess a high surface area (ca. 2000 m2/g) and a large pore volume (> 3 cm3/g). Moreover, GMS has a high electric conductivity which is superior to carbon blacks. Furthermore, GMS is mechanically flexible and tough. GMS shows reversible deformation and recovery upon applying mechanical force and its removal [3]. Such unique properties of GMS enable its use as next-generation durable and high-performance carbon material to battery applications. As an electrode material for electric double-layer capacitors, GMS exhibits ultra-high voltage stability up to 4.4 V even in a conventional organic electrolyte (Et3MeN/BF4), which surpass single-walled carbon nanotubes [4]. Also, GMS is useful to a Pt support of polymer-electrolyte fuel cells [5] and to a cathode of Li-air batteries.
References
[1] H. Nishihara, T. Simura, S. Kobayashi, K. Nomura, R. Berenguer, M. Ito, M. Uchimura, H. Iden, K. Arihara, A. Ohma, Y. Hayasaka, T. Kyotani, Adv. Funct. Mater. 2016, 26, 6418-6427.
[2] S. Sunahiro, K. Nomura, S. Goto, K. Kanamaru, R. Tang, M. Yamamoto, T. Yoshii, J. N. Kondo, Q. Zhao, A. Ghulam Nabi, R. Crespo-Otero, D. Di Tommaso, T. Kyotani, H. Nishihara, J. Mater. Chem. A 2021, 9, 14296-14308.
[3] K. Nomura, H. Nishihara, M. Yamamoto, A. Gabe, M. Ito, M. Uchimura, Y. Nishina, H. Tanaka, M. T. Miyahara, T. Kyotani, Nat. Commun. 2019, 10, 2559.
[4] K. Nomura, H. Nishihara, N. Kobayashi, T. Asada, T. Kyotani, Energy Environ. Sci. 2019, 12, 1542-1549.
[5] A. Ohma, Y. Furuya, T. Mashio, M. Ito, K. Nomura, T. Nagao, H. Nishihara, H. Jinnai, T. Kyotani, Electrochim. Acta 2021, 370, 137705.
