Progress and challenges in metal oxide-based flexible Li-ion batteries for robust and wearable applications

Wearable devices have directly influenced our lives in recent years. Among portable electronic devices, flexible energy storage systems are crucial components. Lithium-ion batteries (LIBs) belong to the energy storage category, dominating the worldwide market. Conventional components of LIBs are not deformable enough, so they need to be replaced with flexible ones. This demands the designing of sustainable, cost-effective and innovative electrode structures. The discussion related to self-supported and free-standing electrodes is presented in this review. The need for flexible electronics and the most recent breakthroughs in the design concept, electrochemical and mechanical performance related to metal oxide-based electrodes for flexible LIBs are highlighted along with fabrication techniques. Moreover, crucial aspects related to challenges and prospects are summarized for the proper development of flexible LIBs from a practical perspective.