Constructing ultrahigh capacitance (Co,Mn)(Co,Mn)₂O₄/Ni(OH)₂ electrode for boosted all-solid-state fiber asymmetric supercapacitors

To meet the practical demands of flexible fiber-shaped supercapacitors (FSSCs) for wearable electronics, it's crucial to develop electrodes with both high energy density and flexibility. In this work, an ultrahigh capacitance (Co,Mn)(Co,Mn)₂O₄/Ni(OH)₂ (CMO/Ni(OH)₂) fiber electrode is designed. The (Co,Mn)(Co,Mn)₂O₄ (CMO) nanosheets possessing large specific surface area and enriched active sites, which can be served as nano-substrate for the electrodeposition of Ni(OH)₂. This special structure facilitates the exposure of more electroactive sites and accelerate rapid electrons transfer, resulting in boosted electrochemical performance. Benefiting from these advantages, the area capacitance of the CMO/Ni(OH)₂ electrode is up to 4787.6 mF cm⁻² at 1 mA cm⁻², which is approximately 15 times higher than that of the CMO (311 mF cm⁻²), and 6.7 times higher than that of the Ni(OH)₂ (718 mF cm⁻²). Coupled with activated carbon (AC) electrode, the assembled all-solid-state CMO/Ni(OH)₂//AC FSSCs demonstrate a high energy density of 89.45 μW h cm⁻² at 1505 μW cm⁻², along with great flexibility and stability. Moreover, these devices can be integrated into clothes, and electronic watch, serving as an energy supply. This work offers a novel approach to designing high-performance fiber electrode for wearable flexible energy storage devices.