Binder-free Co9S8/Ni7S6 heterostructure electrodes via one-step electrodeposition for high-performance coplanar micro-supercapacitors on paper

Coplanar micro-supercapacitors (CMSCs) are essential energy supply components for the development of wearable devices. However, inadequate energy density hinders their extensive utilization in flexible sensors and portable electronic gadgets. This study presents the design and preparation of a binder-free Co9S8/Ni7S6 electrode with a heterostructure, achieved by a one-step electrodeposition procedure to rectify existing deficiencies of CMSCs. Electrochemical evaluations are conducted to ascertain the appropriate amount of sulfur introduction, followed by the assembly of the optimized electrode and activated carbon into a hybrid supercapacitor. The resultant CMSC has an impressive energy density of 0.031 45 mW h cm−2 with 93.4% capacity retention after 8000 cycles. Notably, CMSC's capacity remains mostly unchanged even when folded, demonstrating its exceptional mechanical stability and usage. In addition, density functional theory simulations elucidate that the creation of heterostructures facilitates accelerated electron transportation in electrodes. This study provides a valuable viewpoint regarding fabrication techniques and electrode advancement of CMSCs.