LONDON—Tesla is turning to Mozambique for a key component in its electric car batteries in what analysts believe is a first-of-its-kind deal designed to reduce its dependence on China for graphite. Elon Musk’s company signed an agreement last month with Australia’s Syrah Resources, which operates one of the world’s largest graphite mines in the southern African country. It’s a unique partnership between an electric vehicle manufacturer and a producer of the mineral that is critical for lithium-ion batteries. The value of the deal hasn’t been released. Tesla will buy the material from the company’s processing plant in Vidalia, Louisiana, which sources graphite from its mine in Balama, Mozambique. The Austin, Texas-based electric automaker plans to buy up 80 percent of what the plant produces—8,000 tons of graphite per year—starting in 2025, according to the agreement. Syrah must prove the material meets Tesla’s standards. The deal is part of Tesla’s plan …