Innovation and challenges in materials design for flexible rechargeable batteries: from 1D to 3D

Due to the emergence of numerous flexible electronic devices, the design and fabrication of flexible power sources with high energy density have attracted great attention in the field. Among various energy storage technologies, flexible rechargeable batteries are the most promising, because of their unique features including high flexibility, high specific energy density, light weight properties, etc. To achieve the flexible battery concept, the flexibility of each component is considered a key property in addition to required electrochemical capacity and stability. In this review, recent advances in different kinds of flexible rechargeable batteries are discussed, including lithium-ion batteries (LIBs), lithium-sulfur (Li-S) batteries, lithium-air (Li-air) batteries, zinc-air batteries (ZABs), and sodium-ion batteries (SIBs). Based on the macro-shapes and micro-structures, flexible batteries are outlined into one-, two-, and three-dimensional. Further, sub-classification is performed within each type according to the role of materials in various batteries such as anodes, cathodes, electrolytes, and other components. It is important to note that the design for flexibility is also influenced by the assembly process of all of material components. Thus, this review focuses not only on the selection and preparation of battery materials, but also on the complete battery assembly process. Since some experimental data for flexible batteries are still limited by today's technology, performance simulations have also been included to predict and describe the battery performance. Finally, key challenges and perspectives for advanced flexible battery technologies are provided as general guidance for future research.