During the last 60 years the infantry have received a lot more useful battery-powered equipment. These items include individual radios, night-vision equipment, flashlights, high-performance weapons sights and video/control units for lightweight UAVs like Raven and Switchblade. During that same period battery technology underwent a performance revolution because of lithium batteries. Compared to the previous generation of dry-cell batteries, lithium batteries carried up to three times more energy and had a longer shelf life. Those are qualities batteries for military equipment need the most, especially for equipment that operates continually or needs higher power levels to increase performance. An example of this is the Switchblade 300 munition. This lightweight (2.7 kg or about five pounds) tube launched aircraft carries a video camera and an explosive warhead. Its non-lithium battery kept it in the air for about 15 minutes and could broadcast video back to the operator over a distance of up to ten kilometers. The camera has night vision and is stabilized. The 300 can lock onto a target selected by the operator and track it. When the battery runs out, Switchblade self-destructs. With the new lithium batteries, Switchblade operates for 22 minutes. For a single-use system like Switchblade, that extended operating time is very useful.
Similar benefits are found in many other battery powered weapons and equipment. Recharging all these items is now possible using lightweight (under two kg/4.4 pound) methanol power cells that generate power as needed using liquid methanol capsules. More military trucks are equipped with charging stations for portable electronic equipment.
Lithium batteries have revolutionized the operation of major military systems, especially diesel-electric submarines. In 2022 Japan put Taigei, the first (of seven) Taigei class submarines, into service. This came 18 months after Taigei was launched (put into the water) so that installation of equipment could be completed and sea trials conducted. All seven subs of this class are supposed to be in service by 2026. Each one will cost about $700 million.
These are successors to twelve Soryu class subs. The last two Soryus made the Taigeis possible. These two Soryus were called “Super Soryu” because of their new lithium-ion battery tech and the higher cost that went with this new feature. The two Super Soryus entered service in 2020 and 2021 and their success confirmed the design of the Taigei was sound. The Super Soryu were different from the other Soryus because they had a number of improvements, especially the lithium-ion batteries. The Taigeis are basically similar to the Super Soryus with a few additional enhancements. The Taigeis are 3,000-ton subs with a crew of 70, six torpedo tubes and a top speed of 37 kilometers an hour (submerged) and 24 kilometers an hour on the surface.
Several nations, including South Korea, China, Germany and the United States have been working on making lithium-ion battery technology that will work in subs and those efforts became particularly intense after 2015. The main obstacle was the safety of lithium-ion batteries in a submarine. Lithium-ion batteries are known to be dangerous under certain conditions. Consumer products like cell phones and laptops have had problems. Not a lot but enough of the hundreds of millions of cellphones and laptops using lithium batteries have burst into flames or exploded to make the general public aware of the risk. These overheating problems had to be minimized to levels that made lithium-ion batteries safer than the current lead-acid batteries used for over a century in submarines. Several nations believe they have achieved the needed safety levels and Japan was the first to put a lithium-ion boat into service. This is encouraging for China, South Korea and Germany, who are planning on building subs with this new battery tech. Now there are three such subs in service and there will be at least nine by 2028.
South Korea has begun construction of a sub using lithium-ion batteries and it is supposed to enter service in 2026. This is the first of six Batch II subs of the Changho class. Only one of the three Batch I submarines is in service but the second one enters service this year and the third one by 2024. The Changhos are about 15 percent larger and more expensive than the Taigeis.
Germany has developed its own lithium-ion batteries for subs and plans to use them in new subs as well as replacing lead-acid batteries in current German built subs. China may already have one new sub equipped with lithium-ion batteries. China often tries to keep new developments like this secret for as long as it can.
The advantages of lithium-ion batteries are many. First, they store twice as much power as equivalent (in size and weight) lead-acid batteries. Lithium-ion batteries can release more power than lead-acid and take less time to recharge. Lithium-ion batteries do not degrade over time and have more recharging cycles. Lithium-ion batteries can enable subs to move faster under battery power. Putting out low levels (for low speed) of power, lithium-ion batteries can provide almost as much submerged time as current AIP (Air Independent Power) systems.
The last two Soryu class subs are dispensing with the AIP systems they were designed to use and rely only on lithium-ion batteries to provide the underwater endurance similar to that provided by AIP. This approach is also being watched closely by submarine builders because adding AIP is more expensive than installing lithium-ion batteries. The key factor is the safe operation of submarine lithium-ion batteries under all conditions, including accidents that damage the hull and internal equipment. This is something you can’t really test, only design for. The Japanese lithium-ion battery manufacturer insists they have all this covered. China was apparently convinced because they have built a few AIP subs but then said AIP was not worth the additional cost.