Recent progress and prospects in the electrode materials of flexible sodium-ion battery

Flexible electrochemical energy systems (EES) have gained huge market value for powering flexible and wearable electronics from roll-up displays to implantable medical devices. Flexible EES should possess high flexibility under mechanical deformation (bending, folding, twisting and stretching), high energy and power density and simple design at low cost. Sodium-ion battery (NIB) is considered as a optimistic candidate to replace the flexible lithium-ion battery, due to low cost and large-scale availability. Here, we give a brief introduction to the electrode (anode and cathode) of flexible NIB. The article focused detailing on carbon-based (graphene, carbon nanofiber, and heteroatom doped material), metal composite-based material for the anode and layered transition metal oxide, polyanionic for the cathode. Among these categorized materials, anode with metal supported by carbon framework exhibits the highest charge capacity with 612.5 mAhg(-1) and cathode with polyanionic material on carbon substrate shows promising electrochemical activity. The electrical conductivity and the mechanical stability cum flexibility of carbon support plays a vital role in battery performance by overcoming the formation of a solid-electrolyte interface. Metal incorporated in such support will render high energy and power capacity to the battery. The review also covers, a general perspective on flexible NIB with regards to current and future industrial scope in continents like Asia, Europe and American are covered.