Abstract

In recent years, the requirement for flexible and high-performance energy storage devices has increased substantially because of the rapidly increasing use of wearable electronic devices. In this context, many attempts have been made to boost the use of advanced 2D electrode materials, namely graphene, MXene, etc. The nanocomposites with novel 2D materials such as MXene and graphene using polymers are useful in making flexible device applications such as flexible supercapacitors, batteries, and nanogenerators. Novel 2D materials such as titanium carbide and nitrides and their composite forms with carbon nanostructures, such as graphene oxides and carbon nanotubes, using polymers with high volumetric capacitance and energy densities, could meet the current need for flexible energy storage devices such as lithium-ion batteries (LIBs) and supercapacitors. Flexible devices using 2D materials with high capacity and energy density are vital in flexible electronics because of their high strength, flexibility, bendability, low density, light weight, and ultra-thin properties. These 2D material composite flexible ultra-thin papers can be prepared using the cost-effective spray coating, solvent casting, and vacuum filtration methods. The 2D material MXenes/graphene in nanocomposites not only serve as an electronic conduction pathway for fast electron transport, which results in high charge storage, but also provides high strength free-standing papers that do not need the extra support of current collectors in energy storage devices. Further, these 2D material flexible electrodes can lead to cost effective flexible electronics such as wearable devices and implantable medical devices. This chapter focuses on the use of 2D materials for flexible electrode fabrication and the energy storage performance enhancement of flexible LIBs. It gives a brief overview of the various fabrication methods for flexible materials and the methods to improve the capacity and density of flexible storage devices, and discusses the mechanisms for understanding energy storage. Finally, we summarize the recent advances in this field and describe future opportunities for improving energy storage performance and flexible devices in the increasingly common wearable technology.