Berlin Elon Musk says he's planning the world's largest battery factory at Grünheide near Berlin – next to the Tesla electric car plant already sprouting out of the ground – but the automaker has yet to apply for a building permit for the additional facility.

"The permitting authority has, at the current time, yet to receive the necessary application," Frauke Zelt, spokeswoman for the Brandenburg environment ministry, told Handelsblatt. However, the agency hasn't issued a final building permit for the car factory either.

Tesla is building its auto plant on the basis of provisional and partial permits. At a hearing held in September, critics of the project were given a chance to air their grieveances to Brandenburg state officials.

Zelt said statements made at the public hearing are currently being evaluated in the ministry: "Based on the submitted appeals [to the project], all arguments and submissions made at the time will be considered and will be taken into account as part of the decision-making process," she said.

While attending the European Battery Conference on Tuesday, Musk said he was planning on building a battery factory with a capacity of around 100 gigawatt hours at the Grünheide site.

Later, production could even be expanded to 250 gigawatt hours, Musk added. He said he was "quite confident that it would become the largest battery factory in the world."

The production of batteries for electric vehicles is currently dominated by Chinese, Japanese and South Korean companies, with Europe accounting for only a fraction of the market.

Tesla is currently swiftly building its car factory in Grünheide. It's scheduled to open by summer 2021 - even though the final permit is still pending.

The factory would be Tesla's first on European soil is initially supposed to produce 500,000 Model 3 saloons and Model Y SUVs per year.