Ford Motor Co. has struck a deal with South Korean firm SK Innovation Co. to form a joint venture to build electric-car batteries in the US., the latest in the auto industry’s efforts to fortify supplies of this crucial part ahead of the rollout of more plug-in models.The No. 2 US automaker by sales stated on Thursday that it had entered into a memorandum of understanding with a battery-making company to establish the joint venture, which will be named BlueOvalSK. The partnership seeks to build batteries and related components in the US with the goal to produce roughly 60 gigawatt-hours annually by mid-decade, the two companies said. Ford executives stated the target output would likely lead the joint venture to build two new battery plants in North America, but details have yet to be finalized and are expected to arrive later this year. The venture and ownership structure are also still under discussion and will be subject to regulatory approvals.