Shell Material Choices and Market Leadership in the Full-Tab Era: CBAK Energy Explores the “Steel vs. Aluminum” Debate in Cylindrical Batteries

In April 2026, the 2026 (2nd) Start Point Lithium Cylindrical Battery Technology Forum, themed “Full-Tab Technology Leap and Large Cylindrical Market Leadership,” grandly opened in Shenzhen. At this annual event gathering over 500 industry elites, Suijun Shang, President of the Research Institute at CBAK Energy (NASDAQ: CBAT), delivered a keynote report titled “The Debate on the Shell Technology Pathway for Next-Generation Cylindrical Cells: Aluminum vs. Steel.”

The report provided an in-depth analysis of the decisive impact that shell material selection has on cell performance, manufacturing processes, and end-use applications, set against the backdrop of full-tab large cylindrical batteries accelerating their penetration into the motive power and energy storage sectors. It offered the industry a clear technology roadmap transitioning from “steel for small cylindrical cells” to “aluminum for large cylindrical cells,” becoming the focal topic of the day’s “Full-Tab Large Cylindrical Battery Technology Innovation Session.”

Electrochemical and Physical Properties Dictate Design

Regarding the debate over the advantages of steel versus aluminum shells, CBAK Energy compared their applications across four major dimensions: materials, design, manufacturing process, and end-use application. On the material front, steel shells ensure structural stability through their high-strength characteristics, while aluminum shells primarily offer lightweight advantages. However, the core dividing line determining the shell pathway lies in the electrochemical potential. The report emphasized that because aluminum’s potential is close to that of the anode, making it prone to forming a lithium-aluminum alloy, aluminum shells can only serve as the cathode. Conversely, due to potential oxidation issues, steel shells can only be designed as the anode. This fundamental electrochemical principle directly dictates the cell’s polarity design and the layout of its safety valves. On the design front, CBAK Energy used its star product, the 40135 large cylindrical cell, as an example to demonstrate these differences: the steel shell solution requires a cap CID/VENT combination, whereas the aluminum shell solution utilizes a cover-plate explosion-proof design.

The differences in shell materials further extend to the manufacturing process. Steel shell batteries mostly employ a grooving and liquid injection process through an injection port, and their pack assembly shows excellent compatibility with laser welding, resistance welding, and wire bonding. In contrast, aluminum shell batteries generally adopt a secondary sealing process for the injection hole, and their pack connection relies primarily on laser welding, which imposes distinct requirements on production line equipment configuration and process precision.

Scenario-Driven Segmentation: Clear Shell Trends for Small and Large Cylindrical Cells

During the forum’s roundtable discussion focusing on “emerging incremental application markets,” CBAK Energy presented a highly practical market segmentation conclusion: size determines the shell pathway. The report noted that because the 18 to 26 series small cylindrical cells are used in scenarios like power tools where durability is the top priority, steel shells maintain absolute dominance. Meanwhile, in the residential energy storage and portable power supply sectors—where there is an urgent demand for energy density and lightweight design—the penetration rate of aluminum shells in medium-to-large cylindrical cells of the 33 series and above has significantly increased. Particularly in the 40 to 46 series and the 50+ large cylindrical track, aluminum shell solutions are increasingly favored due to their weight advantages and high pack assembly efficiency.

This assessment coincides perfectly with the urgent demands for lightweight, high-power cylindrical batteries in emerging scenarios such as AI robots and drones, which were discussed with other peer enterprises at the forum. “The trend in shell pathways is now clear: steel for small cylindrical cells, aluminum for large cylindrical cells, and a mix of both for medium cylindrical cells,” the report concluded. The company’s leading advantage in the shipment volumes of various cylindrical cell models, such as the 32140 and 26700, precisely validates the success of its parallel multi-technology strategy. This strategy secures a solid foundation in the small cylindrical market with steel shell processes while strategically positioning aluminum shell solutions for the incremental large cylindrical market.

Accelerated Capacity Implementation, Leading the High-Power Track

As one of the focal enterprises at the forum, CBAK Energy disclosed its latest industrial progress at the end of the report. Currently, the company’s three major production bases in Dalian, Nanjing, and Shangqiu have an existing annual capacity of 8.3 GWh, achieving a daily output of 700,000 cylindrical cells.

The company primarily focuses on the 26, 32, and 40 series cylindrical battery products, with a product line spanning both small and large cylindrical cells. All relevant products have obtained the necessary certifications and boast substantial shipment volumes. Notably, driven by outstanding performance and strong market demand forecasts, the 32 and 40 series large cylindrical products are targeting a shipment goal of 100 million units in 2026.

According to forecasts by the Start Point Institute of Research, industry-wide shipments of large cylindrical batteries are expected to grow by over 40% in 2026. Driven by this high-growth industry trend, CBAK Energy leverages its precise assessment of shell pathways and strong market performance to drive continuous breakthroughs in cylindrical batteries across the dimensions of high safety, high performance, and low cost through material innovation and process iteration. This further consolidates the company’s leading position in the cylindrical battery track. Powered by the dual engines of robust technology and a globalized capacity layout, CBAK Energy is deeply unlocking the scalable value of cylindrical batteries across various new energy application scenarios, thereby leading the high-quality development of the industry.