[Pete Comment: Li-SBs (aka Li-S or LSBs) if developed and safe, may replace LIBs in the late 2030s. See performance graph that allows some comparison of Lead-acid Batteries (currently used on subs) with LIBs and LSBs] The theoretical capacity and energy density of LSBs is 1672mgA/g and 2567 Watt Hours/kg, respectively. The latest laboratory [tested] value of energy density is around 1300Watt Hours/kg (which reduces to 1000Watt Hours/kg after 50 charge-discharge cycles). Practical but limited applications of small LSBs in the near future are expected.
Pete comment: Submarines are inherently high tech and it is essential that all the systems work together in a balanced, predictable, safe, way.
S and Pete