2D Materials: Applications for Electrochemical Energy Storage Devices

Abstract

The intriguing properties of 2D crystals in atomically thin structures such as graphene and MoS₂ and their hybrids/composites with other 1D structures (such as nanowires and nanotubes) in recent years have witnessed numerous scientific explorations and technological advancements. The rich physics has demonstrated their potential applications in numerous fields, in particular, in energy storage devices (supercapacitors and batteries) and energy harvesting devices (solar cells). While atomic layers of MoX₂, WX₂ (with X = S, Se), and number of other 2D materials recently discovered are in very infancy in the post-graphene era, they have shown promising properties along the energy storage and conversion directions. Graphene, however, continues to be the major candidate due to its abundance, economic considerations, and robustness in electronic, thermal, mechanical, chemical, and even biocompatible characteristics. In this review, we present a comprehensive report on the present status and future perspective of two classic candidates of 2D materials family—Graphene and MoS₂. Although they share the same van der Waal inter-planar interaction, the atomic symmetry in intrinsic layer makes them very different in nature. We start with fundamentals of energy storage in supercapacitor applications and discuss practical achievements using these novel materials. Edge planes vs. basal plane reactivity and its impact are discussed. Defect incorporation and chemical functionalization with various elemental and functional groups with their impact on energy storage is discussed. The state-of-the-art results in the field are discussed, and finally our perspectives and challenges and opportunities in the field are discussed.