Research And Application Of Flexible And Self-healable Zinc-ion Fiber Batteries

High-performance flexible energy storage devices must not only have the advantages of high energy density and high capacity,but also improve reliability and durability in practical applications.Research has found that fiber batteries can meet the above needs and are easily combined with textiles to provide power for wearable electronic products.However,fiber batteries tend to cause large capacity degradation and even safety problems under deformation.Therefore,effective measures need to be taken to solve this problem.And the fiber battery should be committed to achieving the requirements of excellent flexibility,self-healing,durability and superior electrochemical performance.Among the many types of fiber batteries,zinc-ion fiber batteries have attracted attention because of their high capacity,easy preparation,safety and environmental protection.In order to further improve its performance and reliability and meet people’s needs in the field of wearable energy storage,it is extremely urgent to develop flexible and self-healing high-performance zinc-ion fiber batteries.The exploration of suitable cathode materials and the development of electrolytes or materials with self-healing ability are crucial to its development.This paper makes a more in-depth study on the above two aspects:（1）The Multi-walled carbon nanotube-redox graphene（MWCNTs-RGO）composite fibers were prepared based on the spinning process.The MWCNTs-RGO composite fiber with a unique fold structure not only contributes to the electrodeposition of manganese dioxide（MnO₂）nanosheets,but also enhances the electrical conductivity of the composite fiber.For the first time,MnO₂-MWCNTs-RGO composite fiber was used as the cathode,Zn-MWCNTs-RGO composite fiber was used as the anode,2 M ZnSO₄,0.1 M MnSO₄ and polyacrylamide（PAM）composed of gel electrolyte and carboxylated polyurethane（CPU）substrate preparation self-healing Zn-MnO₂ fiber battery.The results show that the self-healing Zn-MnO₂ fiber battery has excellent electrochemical performance.The maximum discharge capacity is 190.9 m Ah g^-1(0.3 A g^-1),and the maximum energy density is 190.9 Wh kg^-1(or 234.9 m Wh cm^-3).When the current density is 2 A g^-1,the capacity retention rate is 64%after 300 charge-discharge cycles（150°bending）.What is impressive is that after 5 times of cutting and healing(0.3 A g^-1),the capacity of the fiber battery can reach 83%of the initial capacity.This work provides a new method for the development of flexible and self-healing high-performance zinc-ion fiber batteries.（2）The new device materials were studied for self-healing zinc ion fiber batteries.The fiber battery consists of electrodeposited cobalt manganese oxide（CoMn₂O₄）carbon fiber as the cathode,electrodeposited zinc carbon fiber as the anode,2 M ZnSO₄,0.1 M MnSO₄,0.1M CoSO₄ and PAM composed of gel polymer electrolyte and CPU substrate.As an energy storage device,the fiber battery provides a discharge capacity of 255.2 m Ah g^-1(0.26 A g^-1)in a gel electrolyte,and an energy density of 254.9 Wh kg^-1(266.7 W kg^-1).In addition,the flexible and self-healing zinc ion fiber battery still has a capacity of 77.8 m Ah g^-1(0.8 A g^-1)under a series of large-angle deformations,and the capacity remains at 71.9 m Ah g^-1 after the10th healing process(0.8 A g^-1).This work has opened up a new way to explore suitable cathode materials for flexible and self-healing zinc-ion fiber batteries.