Inspections of the All Nippon Airways Boeing 787 involved in an emergency landing on 16 January at Takumatsu airport have revealed damage to the aircraft's main battery.
ANA says the battery, located in the aircraft's forward electronic equipment bay, "was discoloured and the electrolysis solution had leaked".
The pilots were forced to make the emergency landing after cockpit warnings indicated a problem with the battery at 08:27 local while the aircraft was at 30,000ft (9,150m), it says.
Flightcrew also reported "an unusual smell in the cockpit as well as in the cabin", says ANA.
ANA has since cancelled all 787 flights on 16 and 17 January.
The aircraft in question (JA804A) began commercial service with ANA on 24 January 2012. It was operating flight NH692 on the Yamaguchi Ube to Tokyo Haneda route. All 129 passengers and eight crew were evacuated via inflatable slides at Takamatsu.
US regulators on 11 January launched a safety review of the 787 programme following a number of high-profile incidents since the type entered service.