China’s submarine fleet may soon be powered by lithium batteries
- Technical solutions have been found through extensive development and testing in booming electric car market, according to navy study
- Researchers say that replacing problematic lead-acid batteries with lithium could significantly boost subs’ survival and combat abilities
A lithium power source – instead of lead-acid batteries – could more than double the time a submarine can spend under water, give it Tesla-style acceleration and create more room for weapons, said researchers with the Naval Submarine Academy in Qingdao, Shandong province.
The changes could significantly boost a submarine’s survival and combat abilities, they said in a paper published in peer-reviewed Chinese journal Marine Electric and Electronic Engineering on October 15.
The navy had concerns about replacing batteries in the submarine fleet with lithium ones, in particular that they could catch fire or explode. But according to the study, technical solutions have been found through extensive development and testing in China’s electric car market – and lithium batteries have been shown to work safely in challenging situations.
“After solving these problems, the replacement of lead-acid batteries with lithium batteries in conventional submarines is just around the corner,” said the team led by Wang Feng, a submarine designer at the academy.
China has the world’s largest conventional submarine fleet, with an estimated 60 to 70 vessels.
Conventional submarines use diesel engines on the surface, but when submerged the propulsion system and other equipment draw power from a battery. In battery mode, they make less noise than a nuclear submarine that must use large, powerful pumps to cool the reactor. All US Navy submarines are nuclear-powered and there have reportedly been cases of modern conventional subs going undetected until they were dangerously close.
The main purpose of China’s conventional submarine fleet is to protect its coastal areas and strategic waters including the Taiwan Strait and the South China Sea.
But the lead-acid batteries on these subs, barely changed since World War II, have been problematic, according to the paper, which cited low energy storage capacity, being slow to charge, weak power output, a short lifespan and toxic gas leaks.
In theory, lithium can hold five times or more electricity than lead and has a much faster charge or discharge. But accidents – including exploding smartphone batteries – have raised concerns about the safety of the technology.
These accidents were in part caused by nickel and cobalt, elements that are added to boost the battery’s performance, and in recent years some Chinese battery makers have replaced them with iron and phosphate.
Low-cost and commonly available, iron and phosphate can form highly stable structures that significantly improve the safety of lithium batteries without causing a big drop in performance. In the Chinese market, the number of new electric cars using the iron phosphate technology has now surpassed those that use nickel and cobalt, according to industry data.
China depends heavily on other countries for supplies of nickel and cobalt, so lithium battery-powered submarines would most likely use the iron phosphate approach, according to Wang’s team, which could not be reached for comment.
They said other new and proven technologies – including hard carbon and a ceramic coating for battery cell packaging – would also be used for the submarines to improve safety.
China produces three-quarters of the world’s electric car batteries.
“Large-capacity lithium-ion batteries for electric cars have been successfully developed and their performance is world-leading,” the researchers said in the paper.
The booming electric car market has also brought changes in the defence industry.
“Lithium-ion batteries have been widely used in aerospace and defence including individual soldier systems, army combat vehicles, military communication equipment, the navy’s mini submarines and underwater vehicles and the air force’s unmanned reconnaissance aircraft,” Wang said in the paper.
China is not the only country seeking to equip its submarines with lithium batteries. Japan’s navy was the first to do so, in 2018, adding the metal manganese to the submarine’s lithium battery to improve safety but at the cost of performance.
South Korea launched its first lithium-powered submarine in 2021, using nickel and cobalt. The battery was technically the same as those used in smartphones, but the South Korean military said it had more protection measures built in to ensure its safe operation at sea.
Germany and France have also developed prototype lithium batteries for submarine use with plans for military service in the near future.