2D materials for 1D electrochemical energy storage devices

One-dimensional (1D) electrochemical energy storage devices, such as fiber supercapacitors and cable-shaped batteries, are promising energy storage solutions for emerging wearable electronics due to their advantages in flexibility, weavability, and wearability. Two-dimensional (2D) materials with unique structures and properties can be used to create novel 1D electrochemical energy storage devices. Here, we reviewed recent research efforts in using various 2D materials, such as graphene, transitional metal dichalcogenides, transition metal oxides, transition metal hydroxides, and transitional metal carbides and carbonitrides, to construct fiber supercapacitors and cable-shaped batteries. For every 2D material, we first examined its intrinsic properties and their impacts on its energy storage performance. Next, we reviewed several universal approaches which have been used to enhance its performance, including creating nanostructures, controlling the stacking/alignment, modulating chemical properties via doping or phase engineering, forming nanocomposites to increase electrical conductivity or stability, and designing fiber/cable electrode architectures. Further, we also compared the key characteristics and energy storage performance of recently reported 1D electrochemical energy storage devices containing 2D materials. Last, we offer our perspectives on the challenges and potential future research directions in this area. We hope this review can stimulate more research to realize the applications of 2D materials in practical 1D electrochemical energy storage devices.