rate capacity is simply a variation of specific capacitance at difference current density. so measure specific capacitance at different current density from low to high and plot the data.

Thank you dibyajyoti 

can you please put some references....

I think you can apply the difference between the measurements of resistance using DC and AC voltages for rough estimation of capacity.

R=r / (1+r2 w2 C2 )2    where R is total resistance; r - resistance defined at DC, w - frequency; C - capacity. For estimation of specific C you have to use the current densities really. 

Rate capacity or rate capability are the same terms used for electrochemical storage devices. You can calculate capacitance at different current densities and plot them together