Advanced flexible electrode materials and structural designs for sodium ion batteries

With the spectacular rise of wearable and portable electronics, flexible power supplying systems with robust mechanical flexibility and high energy storage performance under various mechanical deformation conditions are imperative to be needed. Sodium ion batteries (SIBs) with sustainable natural abundance, low cost and superb properties similar to equivalent lithium ion batteries (LIBs), which have shown significant potentials as energy source for flexible electronic devices. In this review, the recent advances in flexible electrode materials based on different types of conductive substrates are addressed and the strategies underlying rational design for flexible structures are highlighted, as well as their applications in flexible SIBs. The remaining key challenges in rational electrodes design are discussed, and perspectives for practical applications of flexible SIBs are proposed as general guidance for future research of high-performance flexible SIBs.