And So It Came To Pass: The rise of the light metal battery submarine [Part I of 'Six Years On']

The recent US review of the AUKUS agreement underlines the glacial and uncertain route taken by Australia to secure nuclear powered submarines. Meanwhile, other nations are proceeding to more rapidly upgrade the capability of their submarine forces. Some six years ago we forecast that the adoption of light metal  battery (LMB) energy systems for conventional submarines would revolutionise their performance. Today, that is becoming reality.

Under the AUKUS agreement between Australia, the United Kingdom and the USA, the RAN is scheduled to receive three American nuclear powered submarines (SSN) between 2032 and later in the decade. Five British designed but locally built SSNs will follow from the early 2040s. This plan replaced a program to build 12 conventional Attack class SSKs in Australia, with the first in service around 2034. It is the first part of the agreement concerning the US-sourced SSNs that is now subject to a review by the US Department of Defence.

HMAS Attack was to have had a traditional heavy metal lead acid battery (LAB) energy system. Back in 2019 there was enough data to indicate that submarines with light metal batteries (LMB) would have greatly improved performance by the projected mid-2030s operational date for Attack. 30 to 40 days of zero indiscretion submerged patrol operation are likely possible by then, compared with four to five days for submarines restricted to LAB energy systems. This would likely have rendered Attack obsolescent before it began operations.

The then Coalition government circumvented this problem by opting for an SSN program. This was not their only option, nor do SSNs negate the effectiveness of conventional boats. China and India, both of which operate nuclear powered submarines, are further developing their conventional submarine fleets. At present most regional submarine operators are considering, planning for or building submarines to exploit the performance advantages of LMB energy systems.

In March 2020 the Japanese Maritime Self-Defense Force (JMSDF) commissioned the JS Oryu (SS-511), the world’s first operational naval attack submarine to be equipped with light metal lithium-ion (LIB) main batteries, replacing the lead acid (LAB) main batteries and air independent propulsion (AIP) systems fitted to earlier Soryu-class submarines. This provides immediate benefits in removing the complexity of AIP systems, reducing costs and enhancing operational flexibility.

The doubling of main battery capacity for JS Oryu and its sister JS Toryu was the most significant proportional increase in the main battery capacity of conventional naval submarines since Germany introduced the Type XXI Electroboat towards the end of WW2. By tripling the main battery capacity the Type XXI made the transition from submersible to submerged submarine, changing the nature of submarine operations. Yet, with no significant improvement in the capacity of LAB technology, conventional submarine performance and operations remained largely unchanged until the introduction of air independent propulsion (AIP) technology in the 1990s.

Japan now operates six LIB-equipped submarines (2 Soryu class, 4 Taigei class) and has a further four Taigei class boats under construction or planned. The sixth Taigei class submarine SS-518 JS Sogei was launched on 14 October and is expected to enter service in March 2027. During this transition there has been no interruption to the JMSDF’s standard schedule of commissioning a new boat every year. Both the modification of the last two Soryu acquisitions to LMB energy systems and the rollout of the Taigei class appears to have been trouble free.

A contract has been awarded to design the successor class for delivery in the early 2030s. It is likely that Japan will have an all-LMB submarine fleet by 2040.

By then it is reasonable to expect that LMB-equipped submarines will have main battery capacities 4-5 times larger than their LAB-equipped predecessors. This will bring significant advantages for zero-indiscretion submerged patrol endurance, faster transit speeds with reduced indiscretion, extended high speed submerged running, stealthy operation and advanced energy-intensive combat and sensor systems.

The navy of the Republic of Korea (ROKN) will begin operating LMB submarines next year. The latest of its Dosan Ahn Changho class (KSS-III Batch II) SS-087 Jang Yeong-sil was launched on 22 October and will be joined by a second vessel scheduled for 2028. These submarines are notable for the inclusion of 10 vertical tubes capable of launching cruise or ballistic missiles whilst submerged. At current levels of battery performance the use of LMB in the Batch II design is claimed to double underwater patrol-speed endurance and halve recharging times. Hanwha Ocean has offered the KSS III Batch II to Australia as an alternative to the life-of-type-extension (LOTE) Collins program.

German submarine builder TKMS has been evaluating LMB technology since 2015, and is now proceeding with the partial refit of an existing German Navy Type 212A submarine with a lithium-ion battery, to demonstrate the technological advantages and performance of the LIB system under real operating conditions. TKMS is developing the Type 212CD successor class, which will be equipped with lithium-ion batteries and fuel cells. The Type 212CD is significantly larger than the Type 212A (~ 2500t vs 1500t) and features a stealthy diamond cross-sectional hull shape. Currently 8 Type 212CD submarines are on order for the German Navy (6) and Norwegian Navy (2).

TKMS has supplied 2 Type 218SG Invincible class submarines equipped with lithium-ion batteries and fuel cell AIP to the Republic of Singapore Navy. An additional 2 Type 218SGs are on order.

India has been evaluating LMB technology for both new and existing submarines. TKMS (Germany) has won the contract to supply six new conventional submarines (evolved Type 214) under the Project-75I program, and it is expected that they will be equipped with both AIP and LMB. India is also contracting with Naval Group to acquire another 3 Scorpene submarines to expand its Kalvari-class fleet, and it is likely that these will also be equipped with AIP and LMB. Retrofitting of the existing 6 Kalvari-class submarines with LMB is under evaluation.

The Italian Navy is developing a LMB system using lithium ferro phosphate (LFP) technology for its U212 Near Future Submarine program and intends to retrofit this into their earlier U212A class.

Indonesia has been modernising its submarine forces, with three conventional South Korean submarines in service by 2021. Earlier this year it selected Naval Group to provide two Scorpene Evolved vessels with a full Li-ion energy system. Naval Group claims this has “the highest security and safety standards and allows higher range of useful energy and a reduced charging time”. Indonesia intends to use this program to begin construction of its own submarines.

The Philippines is seeking to acquire submarines for the first time, and offers from South Korea, France, Spain, Italy and Germany are under consideration. South Korea is offering an LIB-only version of the KSS-III Batch II, while France is offering the Scorpene Evolved LIB submarine, similar to these being acquired by Indonesia. Spain is offering the Navantia S80, while the Italian/German consortium of Fincantieri and TKMS is offering the U212NFS.

Canada is in the process of replacing its Victoria-class submarines with up to 12 conventionally-powered submarines. Germany’s TKMS (Type 212CD) and South Korea’s Hanwha Ocean (KSS-III Batch II) have been shortlisted as potential suppliers, with both offering LMB energy systems.

Naval Group has won the contract to supply Holland with four submarines of the Orka class, beginning in 2034. These Blacksword Barracuda boats are larger than the Indonesian Scorpene Evolved and are essentially a version of the Shortfin Barracuda platform that was developed for the Australian Attack program, but equipped with a full Li-ion energy system instead of LAB. They will have oceanic endurance, meeting the Orka class requirement for trans-Atlantic deployment.

This situation looks very like the argument we put forward six years ago. Naval Group, the designer of Australia’s proposed Attack class, is aiming to deliver the design with an LMB energy system at about the same time Attack would have entered service. It is now very clear that, contrary to the repeated claims at the time that HMAS Attack would be a “regionally superior” submarine, a LAB-equipped HMAS Attack would have been “regionally inferior” on delivery in the mid-1930s.

Yet none of these developments is as significant as the announcement in October 2022, that the People’s Liberation Army Navy (PLA-N) is likely to adopt LMB energy systems for future versions of its Yuan Type 039 conventional submarine. The Yuan is numerically the largest class of conventional attack submarine in the world and China is capable of building them at a rate of two to three per year.

It seems likely that China will also apply LMB technology to its Olympic class small submarines, providing fleet submarine performance to an easily constructed 500 tonne vessel and further complicating any adversary’s response to a Chinese attack on Taiwan.

It is now evident that most conventional submarines entering service from 2030 onwards will be equipped with LMB energy systems. We estimate that by 2040 around 60 high performance LMB-equipped submarines will be operating in the Indo Asia Pacific region. This will severely complicate the RAN’s subsurface warfare environment, whatever option should be available for its future acquisition of submarines.

Part II of this series will discuss the implications of future performance in submarine LMB applications.

Derek Woolner and David Glynne Jones

25 October 2025