Tesla is buying the battery-maker Maxwell Technologies

Tesla announced Monday that it plans to buy the battery maker Maxwell Technologies. 
Maxwell, based in San Diego, makes battery components including ultracapacitors and dry electrodes. 
Battery technology is key for Tesla as it ramps up production and expands its manufacturing presence into China. Tesla is buying Maxwell Technologies in a deal that values the battery-maker at $218 million, the two companies announced Monday.
The deal will be an all-stock transaction that values ea