The founder and chairman of CATL, one of the world’s largest suppliers of batteries, says Elon Musk’s 4860 battery technology will never be successful. Robin Zeng made the comments in an interview with Reuters where he also discussed hopes of CATL opening a plant in the U.S. to manufacture batteries for the likes of Ford and Tesla.

CATL already supplies batteries to Tesla for vehicles produced at its Shanghai factory, and has a deal with the EV maker to license CATL’s technology for battery production in Nevada. But Tesla has for years proclaimed that an innovative, cylindrical battery designed in-house would be key to increasing range and bringing down the cost of its cars. Batteries make up around 30% of the cost of an EV, according to some estimates. Musk proclaimed in 2020 that Tesla’s 4860 battery would be 10-20% cheaper to produce and bring a fivefold increase in capacity.

Numerous reports have suggested Tesla has faced problems perfecting the 4860 battery, which is currently used in the Cybertruck and some other vehicles. Musk reportedly has pushed engineers in recent months to bring down costs further and fix a technical problem that causes the batteries to collapse on themselves while in use, according to The Information. Other challenges have included scaling the use of a dry-coating system for electrodes, which are applied to batteries using large rollers; moving the rollers at high speeds has reportedly resulted in issues with binding agents’ temperatures.

“We had a very big debate, and I showed him,” Zeng told Reuters about a recent meeting he had with Musk. “He was silent. He doesn’t know how to make a battery. It’s about electrochemistry. He’s good for the chips, the software, the hardware, the mechanical things.” Zeng was complimentary about Musk’s autonomous strategy that involves using cameras and AI instead of more expensive Lidar sensors, a controversial decision in the self-driving world.

CATL, which stands for Contemporary Amperex Technology Co, makes batteries for Tesla vehicles in China as well as for Ford vehicles in the U.S. The company uses a more traditional LFP battery technology, which doesn’t get as much range as the 4860 batteries from Tesla but can be produced in mass right now.

Reuters does not offer any elaboration on Zeng’s thinking, and whatever you think about Musk, he does prove naysayers wrong quite often. Zeng and his Chinese rival BYD have become dominant in the world of EV batteries, and BYD makes its own electric vehicles, quickly becoming one of the biggest electric carmakers in the world. That success might be making Zeng somewhat complacent.

Of course, Musk has suggested that he’s given up on making the elusive $25,000 car, instead focusing his efforts on making an autonomous robotaxi. Autonomy is Tesla’s new strategy to keep the stock ripping as sales growth will come in largely flat for 2024.