Boeing isn’t going into detail about the fix they proposed to the FAA, but Dominic Gates at the Seattle Times thinks it’s along the following lines:

• A stronger, sealed containment box enclosing the eight battery cells
• A system of venting tubes that in case of an incident would channel any flammable vapors or liquids directly out of the airplane
• Continuous monitoring of temperature and voltage of individual cells within the battery
• Better thermal separation of the cells, with some barrier such as high-temperature glass inserted between them

The article further explores the type of battery testing that may be required, moving forward, to satisfy the FAA and the Japan Transport Safety Board.