2D Material-Based Flexible Lithium-Ion Batteries

The rapid evolution of wearable and portable electronics has driven an unprecedented demand for flexible, efficient, and durable energy storage solutions. Two-dimensional (2D) materials have captured significant interest due to their unique physical, chemical, and electrochemical characteristics and their ability to create heterostructures with other nanomaterials, enhancing both mechanical strength and electrochemical performance. This chapter delves into the current state-of-the-art knowledge surrounding these advanced flexible 2D material-based flexible lithium-ion batteries (LIBs), highlighting the unique properties of 2D materials that make them ideal for flexible energy storage systems. 2D materials, such as graphene, transition metal dichalcogenides (TMDs), MXenes, and black phosphorus (BP), exhibit exceptional electrical conductivity, large surface area, and mechanical flexibility, and are discussed here. These properties enable the fabrication of LIBs, which offer high energy and power densities and maintain performance under mechanical deformation. This chapter begins with an overview of 2D materials and then delves into recent advancements in 2D material-based flexible LIBs utilizing these materials. There is an emphasis on intricate relationships between the structure and properties of flexible electrodes, particularly focusing on their role in free-standing films. The chapter highlights the integration of these 2D materials into flexible architectures, such as fiber-based devices and wearable electronics, with the potential to revolutionize energy storage by enabling lightweight, flexible, and high-performance devices that conform to various shapes and applications. Fabrication techniques, including inkjet printing, chemical vapor deposition (CVD), and layer-by-layer assembly, facilitate the precise engineering of 2D material-based electrodes and flexible substrates. This chapter addresses the origins of quantum capacitance ( C Q ), its contribution to boosting overall capacitance, and various strategies to enhance C Q . It also reviews the current advancements in C Q for electrode materials, including carbon, 2D materials, and their composites. The concluding section addresses the existing challenges and the prospects for research on flexible LIB devices.