"Irreversible damage to certain parts of the batteries will require repairs which will take several months," it said in a statement.
The team said last week that battery temperatures in the innovative craft had surged during a gruelling, five-day journey from Japan to Hawaii, and there was no way to cool the battery packs once the aircraft was in flight.
There had been hope that repairs could be completed by next month, but the statement said fixes will take until "early spring 2016."
"We don't know yet if we have to change everything or if we can repair (the existing material)", but any new parts would have to be produced by the project, she said.
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"It's not like you can order them," as the craft is unique, she added.
The aircraft has been flown by Swiss businessman and pilot Andre Borschberg, 62, who has already set a new record for the longest solo plane flight.
His partner, Swiss aviator Bertrand Piccard had been scheduled to pilot the next leg of the journey from Hawaii to Phoenix, Arizona.
The Solar Impulse 2 team said the battery overheating during the long flight across the Pacific Ocean was not caused by "a technical failure" or "a weakness in the technology."
Instead, the problem was a failure to fully anticipate the quick rate at which battery temperatures can rise in tropical climates.
"The Solar Impulse engineering team will be studying various options for better cooling and heating processes for very long flights," the project said.
Its wingspan is longer than a jumbo jet but its weight is roughly the same as a car thanks to its light construction.