The Japan Maritime Self-Defense Force (Kaijō Jieitai) on March 5 welcomed into service its first attack submarine using lithium-ion batteries with the commissioning of the 11th Soryu-class boat. In a ceremony held at the Mitsubishi Heavy Industries Mitsubishi (Jūkōgyō Kabushiki-kaisha, informally MHI) shipyard in the city of Kobe, officials welcomed the submarine Ouryu into service. The lithium-ion batteries attack submarine will be assigned to the 1st Submarine Flotilla in the nearby port of Kure. The Ouryu is the sixth Soryu-class boat to be built by MHI, with Kawasaki Heavy Industries having built five more and building the 12th and last such submarine ordered by Japan. The Ouryu was launched in October 2018.
Both Ouryu and the last boat in its class, which will be christened the Toryu, will be slightly different from the earlier boats in the class, as they’ll use lithium-ion batteries manufactured by GS Yuasa in lieu of Stirling-cycle engines that recharge traditional lead-acid batteries for submerged operations. The batteries used in the Ouryu and Toryu are lithium nickel cobalt aluminum oxide, or NCA, batteries. He said the technology requires less maintenance and is capable of longer endurance at high speeds while submerged compared to lead-acid batteries. Other advantages include shorter charging time and longer life spans. The latter factor would mean that fewer battery changes are required over the life of the submarine.
The Sōryū-class submarines (16SS) are diesel-electric attack submarines. The first boat in the class entered service with the Japan Maritime Self-Defense Force in 2009. The design is an evolution of the Oyashio-class submarine, from which it can most easily be distinguished by its X-shaped stern combination diving planes and rudders. It is Japan’s first air-independent propulsion submarine. The Soryu class displaces 2,900 tons surfaced and 4,200 tons submerged, measuring just less than 275 feet in length. Its top speed is 13 knots on the surface and 20 knots submerged. Each boat has a crew of 65, is equipped with six torpedo tubes, and can carry up to 30 21-inch heavyweight torpedoes, Harpoon anti-ship missiles or mines.