Capacity depends on molecular weight of your material and number of electrons it can hold .But, Structure will help  the best possible way of movement of your mobile cation(Li) that means if the mobile ion can pass freely in all the directions without making any damage to the system then those systems are called structurally stable .So,according to me their is no relation between capacity and structure.

  Doped materials generally makes structural stability so that ,way of mobile ion will be free  and it gives better capacity  than earlier and also i mentioned capacity depends on M.Wt ,if your dopent M.Wt is less than your metal obviously its capacity increase.and also dopent will decrease the negative points of your metal.

Dear Bosu Dasari thanks for your views on the question asked. 

1) Actually for my case the molecular weight is almost same Co, Ni, Mn all have consecutive molecular weight.

2) Also the weight has he effect on theoretical capacity, I am asking about practical capacity, 

3) Doping Mn in LiCoO2 is famously known to improve the structural stability, Ni is not good for structural stability, having more Ni in LiNixCo1-xO2 decreases the structural stability. (more Ni, high capacity but low structural stability). 

PS: The main point here is why can we extract more Li in  LiNixCo1-xO2 with more Ni or why the capacity is more in  LiNixCo1-xO2 with more Ni. 

Thanks