All-solid-state yarn supercapacitors based on hierarchically structured bacterial cellulose nanofiber-coated cotton yarns

Yarn supercapacitors (YSCs) have shown great application potential in wearable electronics or smart textiles due to their flexibility and weavability. The bottleneck of YSCs, however, is their low energy density. Here, we report an all-solid-state YSC based on hierarchically structured cotton yarns coated by bacterial cellulose (BC) nanofibers. Hierarchical structures facilitate the electrolyte to access the active materials and effectively reduce the diffusional limitation of electrolyte. This YSC shows a high capacitance of 76.6 mF cm(-2) at a discharge current density of 0.42 mA cm(-2) and an impressive energy density of 16.9 mu Wh cm(-2) at a power density of 10.9 mu W cm(-2). In addition, the YSC is highly flexible and durable in repeated bending tests.