Sodium alginate-based gel electrodes without binder for high-performance supercapacitors

Binder use results in an expansion of the dead volume of the active material and a decline in the active sites, which will lead to a decrease in the electrochemical activity of the electrode. Therefore, the construction of electrode materials without the binder has been the research focus. Here, a novel ternary composite gel electrode without the binder (reduced graphene oxide/sodium alginate/copper cobalt sulfide, rGSC)were designed using a convenient hydrothermal method. Benefiting from the dual-network structure of rGS via the hydrogen bonding between rGO and sodium alginate not only better encapsulates CuCo2S4 with high pseudo-capacitance, but also simplifies the electron transfer path, and reduces the electron transfer resistance, which leads to a remarkable enhanced electrochemical performance. The rGSC electrode exhibits a specific capacitance of up to 1600.25 F g-1 when the scan rate is 10 mV s-1. The asymmetric supercapacitor was constructed with rGSC and activated carbon as the positive and negative electrode in a 6 M KOH electrolyte. It has a large specific capacitance and high energy/power density (10.7 Wh kg-1/1329.1 W kg-1). This work proposes a promising strategy for designing gel electrodes for higher energy density and larger capacitance without the binder.