A merger between SK Inc. and SK Materials has been completed to pave the way for a 5 trillion won ($4.2 billion) investment in key businesses including battery, chip and display materials, officials said Tuesday.

“By 2025, SK Inc. will invest a total of 5.1 trillion won into four key sectors -- battery materials, power and compound semiconductors, semiconductor materials and displays,” a company official said.

The core business SK Inc. will absorb from SK Materials is anodes, one of the four key components of electric vehicle batteries. Anodes are materials that go inside the minus sides of EV batteries. Anodes help stabilize EV batteries.

SK Materials this year formed a joint venture with a US-based startup Group14 Technologies. The two are building an 850-billion-won factory in Korea which will produce “silicon anodes” starting next year.

Anodes are typically made from 100 percent of graphite, a black carbon material that goes inside pencils. Graphite anodes are stable, but not powerful because it takes six graphite particles to absorb one lithium ion.

To overcome this limit, SK Materials and Group14 Technologies add silicon to graphite anodes. One silicon particle can take in four lithium ions. This enhances the performance of EV batteries but makes them less stable. When silicon particles absorb lithium ions, they expand, and sometimes don’t return to their original size after lithium ions are released.

Group14 Technologies solved this structural issue by developing a sponge-like carbon material that acts as a frame and contains silicon particles inside the pores.

According to Group14 Technologies, their silicon anodes can make EV batteries five times more powerful than those using graphite-based anodes.

SK Materials was formed in 2016 after SK Inc. acquired OCI Materials, a local manufacturer of a special gas called NF3, which is used during the manufacturing process of semiconductors, displays and solar panels. The gas removes residue left on the inner walls of the manufacturing chamber.