Beyond Graphene Anode Materials for Emerging Metal Ion Batteries and Supercapacitors

Abstract

Intensive research effort is currently focused on the development of efficient, reliable, and environmentally safe electrochemical energy storage systems due to the ever-increasing global energy storage demand. Li ion battery systems have been used as the primary energy storage device over the last three decades. However, low abundance and uneven distribution of lithium and cobalt in the earth crust and the associated cost of these materials, have resulted in a concerted effort to develop beyond lithium electrochemical storage systems. In the case of non-Li ion rechargeable systems, the development of electrode materials is a significant challenge, considering the larger ionic size of the metal-ions and slower kinetics. Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, MXenes and phosphorene, have garnered significant attention recently due to their multi-faceted advantageous properties: large surface areas, high electrical and thermal conductivity, mechanical strength, etc. Consequently, the study of 2D materials as negative electrodes is of notable importance as emerging non-Li battery systems continue to generate increasing attention. Among these interesting materials, graphene has already been extensively studied and reviewed, hence this report focuses on 2D materials beyond graphene for emerging non-Li systems. We provide a comparative analysis of 2D material chemistry, structure, and performance parameters as anode materials in rechargeable batteries and supercapacitors.

TMDs beyond MoS2 for Electrochemical Energy Storage

“…As a result of its layered structure, exfoliated TMDs exhibit very large surface areas which enable utilization of greater number of sites for electrochemical activity . Consequently, exfoliated sheets can store a much greater amount of charge than their bulk counterparts . Another important aspect of the exfoliated nanosheet structure is that it allows a greater degree of interaction at the electrode–electrolyte interface, thereby considerably reducing the path for charge transport and distribution …”

“…Moreover, it has also been shown that the TMDs store charge by a highly reversible and fast redox reaction process, which is facilitated by the atomic layers indicating their potential applications as pseudocapacitors . As a result of its layered structure, exfoliated TMDs exhibit very large surface areas which enable utilization of greater number of sites for electrochemical activity . Consequently, exfoliated sheets can store a much greater amount of charge than their bulk counterparts .…”

Mass Production of High‐Quality Transition Metal Dichalcogenides Nanosheets via a Molten Salt Method

“…As one of the most promising 2D materials, transition metal dichalcogenides (TMDs) have attracted significant attention due to their exceptional optical, electronic, chemical properties, and gained wide‐ranging applications such as field–effect transistors, energy storage, electrocatalysis, and so on. Current strategies for the synthesis of 2D TMDs primarily include chemical exfoliation, chemical vapor deposition (CVD), and liquid‐phase syntheses .…”

Emerging Applications of Elemental 2D Materials

“…Supercapacitors are composed of two electrodes that can collect and store charge through electrostatic ion adsorption (electrical double‐layer capacitors, or EDLCs) or through reversible redox reactions (pseudocapacitors). Owing to their form factor, layered 2D materials serve as ideal electrodes, offering high surface areas, high power densities, and high flexibility for EDLCs as well as pseudocapacitors . Among elemental 2D materials, phosphorene was one of the first materials studied for use in supercapacitors.…”

“…Owing to their form factor, layered 2D materials serve as ideal electrodes, offering high surface areas, high power densities, and high flexibility for EDLCs as well as pseudocapacitors. [245][246][247] Among elemental 2D materials, phosphorene was one of the first materials studied for use in supercapacitors. A flexible solid-state capacitor based on liquidphase exfoliated phosphorene nanosheets was reported to have a volumetric capacitance of 17.78 F cm −3 (59.3 F g −1 ) at 0.1 V s −1 and 1.43 F cm −3 (4.8 F g −1 ) at 10 V s −1 , exhibiting an excellent rate capacitance.…”