This article originally appeared on ABACUS What do smartphones, electric cars and NASA’s Curiosity Mars rover have in common? They all run on lithium-ion batteries. Since Sony managed to use one in a camcorder in 1991, the rechargeable cells have grown in popularity and are now used to power virtually all portable consumer gadgets, from game consoles and e-cigarettes to scooters and hoverboards. They’re also increasingly used on hybrid and electric vehicles. The world’s biggest supplier of lithium-ion batteries is China. The country is behind two-thirds of the world’s production . And occupying a place at the very end of this manufacturing line is Cao Ji and his team. Zhejiang Hangke Technology, the company he founded 35 years ago, builds testing equipment and other products for battery makers. “If you want to turn wheat into bread, you’ll have to ground it into flour. This is the first step,” Cao explained to Zhejiang News . “After it becomes flour, you’ll have to make dough. That’s the middle step. After it becomes dough, you’ll have to bake it. That’s the final step. What Hangke Technology does is the final step.” The challenge to “baking” a lithium-ion battery into completion is that lithium-ion batteries are essentially dormant dynamite. Lithium is an ideal battery component because it’s light and jam-packed with energy. But it can also be unstable, resulting in those rare but disastrous incidents of battery explosions famously seen in the Samsung Galaxy Note 7 and Tesla vehicles . The last step of building a lithium-ion battery involves making sure that it’s safe enough for use. But another important part is differentiating batteries of various capacities. “Batteries coming from the same ‘mother’ are actually different,” said Cao. “The difference stems from the raw materials used, the charging and discharging process, internal resistance and other factors.” Hangke’s customers include China’s largest manufacturer of electric vehicle batteries, CATL , and Warren Buffet-backed Chinese automaker BYD. The company’s overseas customers include Samsung, LG and Japan’s Murata (which bought Sony’s lithium-ion battery business ). The company is hoping that as automakers place more attention on battery-powered cars , demand for its products will also rise. By 2040, electric cars are forecast to make up more than half of the world’s passenger car sales, according to a recent report from research firm BloombergNEF . China, it says, will take a global lead, accounting for nearly half of all passenger electric cars sales by 2025. China’s electric vehicle industry is facing tough times , though, as the government begins to pull back on subsidies for consumers. Reports of layoffs and self-combusting cars are troubling some of the country’s leading industry startups. The future of Hangke could well rest in the hands of Cao’s son, Cao Zheng . A master’s graduate of Singapore’s Nanyang Technological University, the 36-year-old has been groomed through various roles in the company since 2008. The junior Cao believes there’s one thing that sets his father’s company apart. “The key to lithium batteries is safety,” he said at an industry conference earlier this year. “Hangke has more than 20 years of experience in the lithium battery production process. We have our own unique insights into safety.” For more insights into China tech, sign up for our tech newsletters , subscribe to our Inside China Tech podcast , and download the comprehensive 2019 China Internet Report . Also roam China Tech City , an award-winning interactive digital map at our sister site Abacus .