Emerging flexible battery technology: Innovative structural design, material integration and wearable applications and beyond

A rapid growth in wearable technology has resulted in significant advances in flexible electronic devices. An ideal flexible battery should exhibit high electrochemical performance and excellent mechanical deformability. This review comprehensively examines the critical aspects of flexible batteries, including structural design, battery assembly, and performance comparison, beyond traditional LIBs, and practical applications. We explore various battery chemistry systems, including solid-state lithium-ion batteries, Na⁺/K⁺ ion batteries, LMBs, LSBs, MABs, and flexible ZIBs and their suitability for flexible applications. Additionally, we highlight recent efforts toward practical applications, current challenges, and future opportunities in developing flexible batteries. Special attention is given to structural design strategies, emphasizing the need for practical design to maintain stable electrochemical performance under strain. This paper highlights a new classification principle for flexible structures, which categorizes them as active material area deformation, partially active material area deformation, and inactive material area deformation.