Shares of firms under Korean steel giant Posco Group are skyrocketing, hitting new highs as the group is expected to excel amid high prospects for the battery industry,

Posco Holdings, the holding firm and leading stock of Posco Group, closed at 551,000 won ($428) Friday, more than double its closing price of 272,000 won on Jan. 2.

Posco Future M, the group's battery material maker, is also under the spotlight. Its shares closed at 495,000 won on the day, marking a significant increase from its closing at 191,500 won on Jan. 2.

With shares of Posco Holdings and its affiliate Posco Future M soaring high, shares of other subsidies under the group listed on the bourse are going up as well. Shares of Posco DX, Posco M-Tech, Posco International and Posco Steelion have hit a 52-week high last week.

The Posco Group’s rally stems from the high prospects in the battery industry and the steel conglomerate’s transition efforts to keep pace with the changes in the market.

"We will grow into a firm with a 100-year history that can strengthen competitiveness in low carbon emissions based on eco-friendly investments and add value in the world," Posco Group Chairman Choi Jeong-woo said through a report issued by Posco Holdings on Friday.

In July, the firm announced it plans to achieve 62 trillion won in sales of secondary cell materials by 2030 by expanding its production capacity. The figure is a 51.2 percent raise from the previous goal.

“Posco Holdings' goal for 2030 in the secondary cell industry shows an upgrade in the production capacity. The raised goal for cathode and lithium production were noticeable,” analyst Park Seong-bong from Hana Securities said.

“While the prospects for the cathode material are reflected on the company value of Posco Future M, the outlook for the lithium business is reflected on the value of Posco Holdings, as the main players are non-listed firms," Park assessed.

The group’s strong earnings are another factor leading the stock rally.

Posco Holdings estimated its second-quarter operating earnings at 1.3 trillion won through a regulatory filing made on Tuesday. Though it is down 38.1 percent from a year earlier, it shows the firm's improved performance, marking an 85.7 percent increase from the previous quarter.

The operating profit was 6.6 percent higher than the average estimate of the market. It is assumed the recovery of earnings stems from normalization of steel sales and a rise in product prices.

With the rosy expectations, Posco share prices are jumping, making the added market value of Posco Group affiliates surpass 90 trillion won, more than doubling from around 40 trillion won from earlier this year.

The market cap for Posco Holdings stood at 46.59 trillion won as of Friday, surpassing that of top automaker Hyundai Motors at 42.3 trillion won. It is the seventh largest on Kospi, excluding preferred stocks. The sixth on the list is battery maker Samsung SDI at 47.17 trillion won, just a step further away.

Retail investors, led by the frenzy in the battery industry -- best represented by the soaring stock prices of EcoPro and its affiliate EcoPro BM -- snapped up investments in Posco Holdings shares.

According to the Korea Exchange, the nation’s sole bourse operator, individual investors net bought shares worth 695 billion won in Posco Holdings from July 3 to 19, while foreign investors net sold 715 billion won in the same period.

Market experts are putting high expectations on the steel conglomerate for expanding its portfolio into the secondary cell industry.

"Shares of Posco Holdings are soaring high based on the expectation of higher earnings from cathode and anode materials, as well as raw materials such as lithium and nickel, as the group announced to beef up its investments in the area," analyst Jung Hye-jung from KB Securities said.

"The growth in earnings from the secondary cell industry are likely to show from the fourth quarter,” Jung said.