(Invited) Production and Functionalization of Carbon Nanotubes for Electrochemical Energy Storage Devices

Abstract

Self-supporting, sponge-like paper of carbon nanotubes (CNTs) can be a new platform for high energy/power density batteries. Presently, battery electrodes are built on metallic foils having only two faces and large mass with the aid of polymeric binders and conductive fillers. CNT paper can replace all these components. Furthermore, it captures nanomaterials at high loading, activates insulative materials, and moderates volumetric change of active materials.We have developed semi-continuous fluidized bed chemical vapor deposition method [1], which yields submillimeter-long few-wall CNTs with carbon purity >99 wt% and metal impurity <0.1 wt% [2]. By capturing capacitive particles (99 wt%) with CNTs (1 wt%), a lithium ion full cell with graphite-CNT anode and LiCoO2-CNT cathode is demonstrated (Figure 1b) [3]. This platform is also effective to create electrodes of the emerging active materials such as Si anode [4] and S cathode [5] with practically high gravimetric, areal, and volumetric loadings, and realized Li x Si-S and Li-Li2S x full cells [6,7]. In addition, by combining with the insulative sponge of boron nitride nanotubes (BNNTs), the graphite-CNT|BNNT| LiCoO2-CNT full cell with high thermal stability was developed [8].[1] D.Y. Kim, et al., Carbon 49, 1972 (2011).[2] Z. Chen, et al., Carbon 80, 339 (2014).[3] K. Hasegawa and S. Noda, J. Power Sources 321, 155 (2016).[4] T. Kowase, et al., J. Power Sources 363, 450 (2017).[5] K. Hori, et al., J. Phys. Chem. C 123, 3951 (2019).[6] K. Hori, et al., Carbon 161, 612-621 (2020).[7] Y. Yoshie, et al., Carbon 182, 32-41 (2021).[8] K. Kaneko, et al., Carbon 167, 596-600 (2020).Figure 1. (a) Semi-continuous production of submillimeter-long few-wall CNTs by fluidized bed [1]. (b) Lithium ion full cell made of graphite-CNT anode and LiCoO2-CNT cathode [3]. Figure 1