SUZHOU, China—Batteries have emerged as a critical front in China’s campaign to be the global leader in electric vehicles, but foreign auto makers and experts say it is rigging the market to favor domestic suppliers.

Tianjin Lishen Battery Co. here in eastern China recently agreed to sell its battery packs to Kia Motors for the EVs the South Korean company makes in China and is now in talks to supply General Motors, Mercedes-Benz and Volkswagen, a supervisor for the Chinese company said.

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