Office Depot is offering the Duracell batteries with 100% Rewards Points. So not "technically" free, but they give you back the money in credits so you can use at Office Depot. Use their discounted gift cards to actually make money on this deal.
* Must be purchased by 12/19/2020 11:59pm EST
Step 1 - Buy discounted Office Depot gift cards
Go to CardBear to buy discounted Office Depot gift cards for a discount
* Limit of 5 Office Depot / Officemax gift cards can be used per purchase
Step 2 - Sign up for Office Depot rewards if you haven't yet
If you are not yet a Office Depot Rewards member, sign up here first