Dell xps L502x battery manufactured with date 2014 will have same capacity in 2017 or does it loose some power holding capacity

I am going to buy  new battery for my Dell xps  L502x early 2011 15 inch laptop  which came with 6 cell battery.

I want to know if dell supports 9 cell battery in my laptop

And should I buy batteries manufactured in 2014

Does dell stoped  manufacturing the battery for this model.  I would prefer 2016  manufactured battery