Tesla is continuing its trade secrets fight with Rivian, alleging that the electric-truck hopeful poached employees and stole "highly proprietary" battery technology, according to a Bloomberg report.

The Silicon Valley firm filed a lawsuit against Rivian 14 months ago, but claims the company has continued poaching its staff, and using them to steal trade secrets. In a court filing last month, Tesla cited numerous alleged incidents of former employees stealing trade secrets on their way out the door to join Rivian.

Earlier reports suggested Tesla's lawsuit covered areas like charging, sales, and manufacturing. But next-generation battery tech is perhaps a much bigger accusation. It also comes as Rivian prepares for an initial public offering (IPO), with a reported $80 billion valuation. The company has also said it is ready to begin customer deliveries of its R1T electric pickup truck.

2022 Rivian R1T

2022 Rivian R1T

A California state court judge in San Jose allowed Tesla to add its new allegations to the pending case, and add three more of its former employees as defendants, according to the Bloomberg report. Rivian had reportedly objected, arguing the new allegations were unsupported by the facts and that expanding the scope of the litigation would delay resolving it. Rivian already lost its initial request for dismissal of the case in March, Bloomberg noted.

Rivian has boasted of some battery innovations, claiming 25% more energy density than other EVs—including Tesla.

The company has also planned ahead for second-life uses for the cells, and rolled out a battery warranty that tops that of Tesla. Its cell supplier, Samsung SDI, has reportedly considered an Illinois plant, potentially in the same town as Rivian's assembly plant.