Preparation And Properties Of Anode Materials For Flexible Fiber-shaped Sodium-ion Batteries

With the rapid development of flexible wearable electronic devices,the development of flexible sodium-ion batteries with excellent flexibility has become one of the research hotspots in the field of energy storage.In order to meet the power requirements of flexible wearable electronic devices,flexible energy storage devices must have high energy density and flexibility.In the work,a nanomaterial and an integrated self-supporting electrode structure are used to obtain a flexible sodium-ion anode with high energy density and excellent bending stability.The work mainly has the following two aspects:1.Flexible integrative sulfide-doped TiO₂?S-TiO₂?electrode:The TiO₂ nanotube array was prepared by anodizing on the surface of the titanium wire,and then subjected to sulfide doping to form a self-supported S-TiO₂ nanotube array anode.The S-TiO₂ nanotube electrode has good electrical conductivity,which can accelerate the electronic transmission.In addition,rich nanotube structure is beneficial to the diffusion of electrolyte.The electrode adopted integrated design have simple the preparation process.The flexible and self-supported S-TiO₂ nanotube electrode has excellent conductivity and the diffusion kinetics of sodium ions,thereby improving the sodium storage capacity of TiO₂.The flexible S-TiO₂ electrode has a specific capacity of 180 mAh g^-1,an energy density of 114 Wh kg^-1 at 40 mA g^-1.2.High energy density flexible Sn electrode:Due to the limited sodium storage capacity of TiO₂,it does not fully meet the demand for high energy density storage.On the basis of flexible S-TiO₂ nanotube array,a flexible fiber-shaped Sn@S-TiO₂ anode was prepared by pulse electrodeposition.The flexible Sn@S-TiO₂ electrode has a specific capacity of 855 mAh g^-1,an energy density of 500 Wh kg^-1.At the current density of 286 mA g^-1,the fiber-shaped sodium-ion battery assembled based on the Sn@S-TiO₂ electrode still has the reversible capacity of 310 mAh g^-1 after 700cycles,which shows that the fiber-shaped sodium-ion electrode has good cycling stability and a higher reversible capacity.In addition,the fiber-shaped battery is subjected to charge/discharge tests at different bending angles.The capacity of 560 mAh g^-1 is obtained at bending state of 180°.Further,the capacity of 550 mAh g^-1 still is observed after repeated bending?120°?for 500 times.