MELBOURNE, Australia — Japan has commissioned the first of a new class of diesel-electric submarines, bringing the planned expansion of its submarine fleet to 22 boats when it enters service.

The Taigei, meaning Big Whale, was commissioned Wednesday at the Mitsubishi Heavy Industries shipyard in the city of Kobe. It is the first of a successor class to Japan’s current Soryu-class boats.

Its home port will be the Japan Maritime Self-Defense Force’s base at Yokosuka, south of the capital Tokyo, where it will join Submarine Flotilla 2.

The Taigei is a 3,000-ton diesel-electric attack submarine measuring 84 meters (275 feet) long, slightly larger than the Soryu-class submarines. Seventy personnel will crew the vessel.

The class will be powered by lithium-ion batteries. The Taigei is the third submarine in the world to use such a power source after the last two Soryu-class subs.

Japan has conducted extensive research into the use of lithium-ion batteries on submarines since the early 2000s. The batteries, which are manufactured by GS Yuasa, are lithium nickel cobalt aluminum oxide batteries. The Japan Maritime Self-Defense Force previously said the new battery technology requires less maintenance and is capable of longer endurance at high speeds while submerged compared to lead-acid batteries.

The new submarine class is expected to be armed with Japan’s latest Type 18 heavyweight torpedo, which features improved propulsion as well as target-detection and -processing capabilities over the preceding Type 89 torpedo.

It can also launch the Boeing UGM-84L Harpoon Block II submarine-launched anti-ship missile, which can also be used against land targets.

A second Taigei-class sub, christened the Hakugei, or White Whale, is under construction and will join the Japanese maritime force in March 2023.

Japan has budgeted for four more of the class. Each will replace the older Oyashio-class submarines still in service.

Mike Yeo is the Asia correspondent for Defense News.

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