Sulfur Vacancies Tune the Charge Distribution of NiCo 2 S 4 for Boosting the Energy Density of Stretchable Yarn-Based Zn Ion Batteries

Yarn-based batteries with the dual functions of wearable and energy storage have demonstrated promising potential in wearable energy textiles. However, it is still an urgent problem to construct efficient and flexible electrodes while optimize the configuration of yarn-based batteries to maintain excellent electrochemical performance under different mechanical deformations. Herein, NiCo 2 S 4− x nanotube arrays with tunable S-vacancies are constructed on carbon yarn (CY) (NiCo 2 S 4− x @CY) by a facile hydrothermal strategy. The aqueous zinc-ion batteries (ZIBs) with NiCo 2 S 4− x @CY as cathodes exhibit exceptional discharge capacity (271.7 mAh g −1 ) and outstanding rate performance (70.9% capacity retention at 5 A g −1 ), and reveal a maximum power density of 6,059.5 W kg −1 and a maximum energy density of 432.2 Wh kg −1 . It is worth noting that the tunable S-vacancies promote the surface reconfiguration and phase transitions of NiCo 2 S 4− x , thereby enhancing the conductivity and charge storage kinetics. The high reactivity and cycling stability of NiCo 2 S 4− x @CY can be related to the discharge products of S-doped NiO and CoO. Furthermore, flexible stretchable yarn-based ZIBs with wrapped yarn structures are constructed and exhibit excellent tensile stability and durability under a variety of mechanical deformations. As a proof of concept, the ZIBs integrated into the fabric show excellent electrochemical performance even in response to simultaneous stretching and bending mechanical deformations. The proposed strategy provides novel inspiration for the development of highly efficient and economical yarn-based ZIBs and wearable energy textiles. Graphical Abstract