Pathways of Developing High‐Energy‐Density Flexible Lithium Batteries

Flexible lithium-based batteries (FLBs) enable the seamless implementation of power supply to flexible and wearable electronics. They not only enhance the energy capacity by fully utilizing the available space but also revolutionize the form factors of future device design. To date, how to simultaneously acquire high energy density and excellent mechanical flexibility is the major challenge of FLBs. Here, a critical discussion for guiding the future development of FLBs toward high energy density and high flexibility is presented. First, the industrial criteria of FLBs for several desirable applications of flexible and wearable electronics are summarized. Then, strategies to achieve flexibility of FLBs are discussed, with highlights of representative examples. The performance of FLBs is benchmarked with a flexible battery plot. New materials and cell design principles are analyzed to realize high-energy-density and high-flexibility FLBs. Other important aspects of FLBs including materials to improve the cycling stability and safety are also discussed.