A123 Systems, a lithium-ion battery maker for electric cars and other business sectors, is suing Apple Inc. for what it alleges is an “aggressive campaign to poach employees.”

The complaint, filed in Massachusetts earlier this week, names five employees that have either defected to Apple or appear to be in the process recruiting others to join Apple AAPL, -3.17% . A123 believes Apple aims to build a competing battery business, partially relying on expertise from former A123 employees to help it succeed.