SK On will switch to a sole CEO structure led by Yong-wook Lee (이용욱). Seok-hee Lee (이석희) said on May 28 he would resign as CEO, bringing to an end the co-CEO system launched in October last year after about seven months.

In a letter sent to employees that day, Lee said he wanted to conclude his duties as SK On's chief executive at the end of May. He said it was a great honour to be with SK On employees at the centre of the secondary battery industry.

The reason for his resignation is health and stamina issues. Lee, born in 1965, has been weighing whether to continue as CEO since the end of last year, it was reported.

The timing of his resignation was postponed until key management issues were wrapped up. SK On completed a restructuring on May 21 of BlueOval SK, a U.S. battery joint venture it operated with Ford. It also converted its Tennessee plant in the United States into a standalone entity. An assessment has emerged that this laid the groundwork to reduce the burden of borrowings and improve the financial structure.

Lee has been in charge of customer engagement and research and development technology innovation, mainly in North America. Despite health issues, it was reported that he was strongly determined to wrap up a key issue, the reshaping of the U.S. joint venture. In the letter, he said, "Since the end of last year, I have been deeply considering the issue of continuing to carry out the heavy role as CEO, but I delayed the timing of my resignation in order to properly wrap up key management matters, including the conclusion of the U.S. joint venture."

The co-CEO system began in October last year. At the time, SK On appointed Yong-wook Lee, then CEO of SK Siltron, as president and CEO, citing his strong expertise in materials and manufacturing. Roles were divided, with Seok-hee Lee tasked with strengthening global customer management and R&D competitiveness, while Yong-wook Lee was responsible for manufacturing competitiveness and profitability improvement.

As sole CEO, Yong-wook Lee now faces a growing list of tasks. With demand for electric vehicles slowing and a global battery industry downturn continuing, he is in a situation where he must push ahead with manufacturing efficiency, financial structure improvement and stabilising the North American business.