rate capability  . you can calculate this from  cyclic voltametry 

for example  you measured the capacitance at different scan rate

at 1 mv is 500 F/g , at 5 mv is 450F/g  and 50 mv is 400F/g ok 

to calculate rate capability  400/500*100 = 80%

while the cyclic stability  

you calculate the capcitance of first cycle  and from the  final cycle 

afterthat  the capacitance from final cycle is 80

and the capcitancefrom the first cycle is 90 

the stability is 80/90 *100 =88.8%

Thank you very much sir.

But Sir, The rate capability of electrode for different current density's by chronopotentiometery, how it is calculate.

Please explain me.

you calculate the capacitance from glvanostatic charge and discharge  at different current suchas   at 1 A/g , at 2A/g  and 3 A/g ok 

afterthat  the value of   specific capcitance  at 3A/g / the value of specific capcitance at 1A/g * 100

Thank you

 Thanks to Allaah