(Invited) Advanced Energy Storages Based on Carbon Nanomaterials and 2D Materials

Abstract

In this paper, I will present our team's recent advance in nanomaterials for high efficiency energy storages. Next-generation energy storage devices, such as Li-ion batteries (LIBs), supercapacitors and Li-sulfur batteries (LiS), demand high energy, power and better safety. Conventional graphite anode in Li-ion batteries falls short of fulfilling all these necessities. Carbon nanostructural materials (graphene and carbon nanotubes) have gained the spotlight as promising active materials for energy storage; they exhibit unique physico-chemical properties such as large surface area, short Li+ ion diffusion length, and high electrical conductivity, in addition to their long-term stability. Among all published literatures in Li-ion battery, nanostructured carbon materials occupy ~ 70%. Such an impressive figure signifies high interest and promising future of this class of materials in energy storage devices and compels us to look into the involved issues deeply. Carbon-nanostructured materials have issues with low areal and volumetric densities for the practical applications in electric vehicles, portable electronics, and power grid systems, which demand higher energy and power densities. One approach to overcoming these issues is to design and apply a three-dimensional (3D) electrode accommodating a larger loading amount of active materials (e.g., sulfur) while facilitating Li+ ion intercalation. Furthermore, 3D nanocarbon frameworks can impart a conducting pathway and structural buffer to high-capacity non-carbon nanomaterials, which results in enhanced Li+ ion storage capacity. Recent advance of two-dimensional (2D) materials enables us to design/fabricate atomic layer deposition on electrode materials for high-efficiency active electrode materials: (1) MoS2 - coated Li metal anode demonstrates a stable Li electrodeposition with the suppression of nucleation sites for dendrite growth. The MoS2 coated Li anodes assembled with 3D carbon nanotube-sulfur cathodes provide superior electrochemical performance ever reported to date. (2) 3D CNTs-MoS2 anode shows vertically-oriented MoS2 nanoflakes strongly bonded onto CNTs surface. The 3D CNTs-MoS2 shows high capacity, outstanding cycling stability, and good rate capability in Li-ion battery performance. The superior performance of 3D carbon nanotube structure and 2D materials in energy storages will be presented along with their mechanistic analysis.