Best cell for this light: Samsung 30Q, in post #1 here: https://budgetlightforum.com/t/-/31589 for Banggood coupon code: M4D4BLF (Thanks Max). The 30Q is the best out there, combining top power and very good capacity. No need for protected cells with this light. Ignore that referral to protected cells in the Banggood listing - the light has low voltage protection (LVP) built in.
The SANYO GA is top capacity, but moderate max power - available here for example: MtnE-SANYO GA.