Cross-linked poly(2,2,6,6-tetramethylpiperidinyl-N-oxyl-4-yl methacrylate) (PTMA) gel with higher ionic conductivity tends to show a higher diffusion coefficient. The gel swollen in ethylene carbonate (EC)/dimethyl carbonate (DMC) (4:6, v/v)-based electrolyte exhibits the highest diffusion coefficient among the gels swollen in EC-based electrolytes. The ORB with the electrolyte shows the best discharging rate characteristics in the ORBs with EC-based electrolyte, and the capacity at the 40C-rate is 83% of the 1C-rate capacity. The gel swollen in acetonitrile-based electrolyte, which has extremely high ionic conductivity, shows an approximately 5 times higher diffusion coefficient than that of the gel swollen in the EC/DMC-based electrolyte. In the ORB with acetonitrile-based electrolyte, 70% of the 1C-rate capacity remains at 200C-rate discharge. The higher diffusion coefficient in charge transportation of the cross-linked PTMA gel leads to better discharge rate characteristics for the ORBs. We clarify that charge transportation in the PTMA gel is an important determining factor of discharge rate properties.