Self-healable wire-shaped supercapacitors with two twisted NiCo_2O_4 coated polyvinyl alcohol hydrogel fibers

两根NiCo_2O_4涂覆的聚乙烯醇水凝胶纤维构建线状可自愈超级电容器（英文）

Wire-shaped supercapacitors（SCs） possessing light-weight, good flexibility and weavability have caught much attention, but it is still a challenge to extend the lifespan of the devices with gradual aging due to the rough usage or external factors. Herein, we report a new stretchable and selfhealable wire-shaped SC. In the typical process, two polyvinyl alcohol/potassium hydroxide（PVA/KOH） hydrogel wrapped with urchin-like NiCo2O4 nanomaterials were twisted together to form a complete SC devices. It is noted that the as-prepared PVA hydrogel can be easily stretched up to 300% with small tensile stress of 12.51 kPa, superior to nearly 350 kPa at 300%strain of the polyurethane. Moreover, the wire-like SCs exhibit excellent electrochemical performance with areal capacitance of 3.88 mF cm^-2 at the current density of 0.053 mA cm^-2, good cycling stability maintaining 88.23% after 1000 charge/discharge cycles, and 82.19% capacitance retention even after four damaging/healing cycles. These results indicate that wireshaped SCs with two twisted NiCo2O4 coated polyvinyl alcohol hydrogel fibers is a promising structure for achieving the goal of high stability and long-life time. This work may provide a new solution for new generation of self-healable and wearable electronic devices.

线状超级电容器因其轻量、柔性及可编织性的特点引起了广泛关注.如何延长超级电容器的使用寿命仍然是当前所面临的一个挑战.本文报道了一种新型的可拉伸和自愈的线状超级电容器.首先将两根由海胆状NiCo_2O_4纳米材料包裹的聚乙烯醇/氢氧化钾(PVA/KOH)水凝胶缠绕在一起,进而形成一个完整的超级电容器.值得注意的是,PVA水凝胶可以很容易地用一个比较小的拉力(12.51 kPa)实现300%的形变量.这一结果优于之前报道的以350 kPa的拉力拉伸到300%应变的聚氨酯.此外,该线状超级电容器表现出良好的电化学性能.在电流密度为0.053 mA cm^(-2)时面积比电容为3.88 mF cm^(-2),并且在1000次充放电后仍有88.23%的剩余面积比电容,显示了良好的循环稳定性.此外,在四次切断/自愈后电容保留量仍有82.19%.这项工作将会为下一代自愈和可穿戴设备提供一种新的设计方案.