Use of LIBs may allow a submarine to stay submerged for a longer time than lead acid batterries as long as the submarine is not driven too quickly for too long as this runs the batteries flat.
Air independent propulsion (AIP)
Some confusion has been created that LIBs are some separate component replacing air independent propulsion (AIP). This is basically untrue. LIBs are replacing lead acid batteries in new submarines to be built from around 2015. LIBs cannot be retrofitted to replace lead acid batteries in individual submarines already operating. Any battery, LIB or lead acid, will almost always rely on regular recharging from a submarine's air dependent diesel engines. Some AIP technologies can charge batteries - but there are downsides-tradeoffs. The relatively few subs in the Asia-Pacific region that have AIP (none are Australian) might still use AIP even if they are in future built with LIBs. Those that use AIP might typically want their subs capable of a close to shore (closed shallow waters, littorals, straits and harbour mouths etc) near motionless, defensive missions of up to 3 weeks submerged.
AIP, unlike batteries, cannot be recharged during a mission.
AIP has been compared (by submarine sales teams and the mainstream media) to nuclear propulsion. This is not true. AIP might allow a submarine to move at 20+ knots for 5+ hours while a nuclear reactor can run at 30+ knots for 3 months or until a crew's food runs out.
Australia decided not to use AIP in the Collins class due to Australian submarine mission profiles which need much diesel for long range rapid transit. This is even though Australia bought its subs from Kockums who are AIP experts. I haven't heard of any Australian interest in AIP for the future submarine. It is unclear whether Singapore's two HDW 218SG's on order will use AIP (but likely) and LIBs (maybe). Some Chinese subs are believed to use AIP, most likely mainly in defensive mode, not far offshore.
AIP is basically a 200 ton plug in the submarine for inclusion of a small engine and storage of extra fuel, alcohol or hydrogen and an oxidiser. The first batch of 6 to 7 Soryus (up to SS-507?) do operate with Swedish designed Stirling engine AIP technology. The next 6 Soryu will most probably use LIBs.
The downsides of using AIP include: dangerous highly flamable oxidiser, heavy moving parts that need maintenance, less effective in warm seas, 3rd party contractual issues, technical advances including LIBs partly bypassing AIP, have persuaded the Japanese Navy that AIP is not worth including in their future Soryus. The 200 tons might be better used for more diesel or batteries. Australia, Malaysia and Indonesia have not used AIP in their submarines due to AIP's marginal worth.
More on LIBs
A second major difference is that aircraft LIBs have (or had) no dedicated fire suppressant systems while such systems should be built around submarine LIBs. Overall the experience of ironing out bugs on aircraft and car LIBs is valuable in the development of submarine LIBs.
One additional issue is that the Japanese Navy has been running its submarines with the assumption the service life is 15-20 years while Australia assumes submarines should be in service for at least 30 yours. This may or may not be a problem. After 15-20 years moving parts may or may not start to wear out. This may be most significant in the submarine's diesel engines and the very large electrical motor. Changing engines-motors is very heavy maintenance involving cutting into the submarine hull. This might only be possible in Japan for the Soryu? Maintenance realities may or may not be a problem.