1 Million 684Ah Stacking Cells Manufactured, Marking Mass Production Breakthrough

On December 23, the one‑millionth 684Ah stacking cell rolled off the production line at Sunwoda’s manufacturing base, signaling the start of large‑scale production for stacking‑type energy storage cells.

According to industry insights, it took only three months for the production line to achieve this delivery milestone. This demonstrates that stacking technology has overcome previous mass‑production yield constraints such as particle contamination, burrs, and alignment issues—paving the way for major battery makers to accelerate development of 600Ah+ stacking cells.

Three Months, One Million Cells Industry’s First Large‑Scale Dedicated Line

Earlier, there were doubts within the sector about mass‑producing large‑format stacking cells for energy storage, mainly due to concerns over particles, burrs, alignment, and wrinkling during manufacturing.

Since starting mass production in September, this first‑of‑its‑kind line dedicated to 684Ah stacking cells has reached the one‑million mark in just three months. The achievement confirms stable process control and full‑flow quality assurance, laying a solid foundation for reliable volume delivery by 2026.

Production processes for the 684Ah stacking cell are now mature, with defect rates controlled at the PPB level.

Behind this high‑quality output lies comprehensive optimization across production and inspection. On the manufacturing side, Sunwoda implemented multiple technologies—including four‑stage particle protection, Hi‑pot insulation testing, CIL ceramic edge sealing, a three‑axis alignment platform, and a three‑step anti‑wrinkle process—to systematically remove particles, eliminate burrs, align electrodes precisely, and ensure flatness. As a result, production yield now matches that of conventional winding processes.

For quality inspection, the stacking line features industry‑leading detection precision, incorporating micron‑level defect recognition, more than 230 inspection checkpoints, over 1,510 inspection instruments, 2.5D imaging, and AI‑based visual detection—forming a closed‑loop AI vision system. In‑line CT inspection is also used to achieve 100% testing of stacking OH, enabling PPB‑level defect control per cell and ensuring high‑quality delivery.

Stacking Process Emerges as Key Route for Energy Storage Cells

Driven by the global energy transition and carbon‑reduction goals, energy storage projects are scaling up, pushing cell technology toward higher capacity and energy density. The stacking cell, which balances economy and safety, has become a critical pathway to reduce system complexity and optimize lifecycle costs.

Below 500Ah, winding—a mature and proven process—still ensures safety and efficiency. However, for cells above 500Ah, increased thickness and width lead to stress concentration at winding corners during electrode and separator stacking, raising risks of lithium plating, internal short circuits, and even thermal runaway.

In contrast, the stacking approach chosen for the 684Ah cell offers higher performance, longer lifespan, and improved safety, representing an advanced direction for large‑format cells. By layering electrodes and separators without wasteful R‑angle space, stacking provides more uniform layout and higher energy density. It also reduces internal stress and swelling, lowering safety risks during cycling. Each electrode layer is independently connected to a tab, resulting in lower internal resistance and more even heat distribution compared with winding’s half‑tab design—leading to better charge‑discharge efficiency and extended service life.

Stacking Cell Adoption Accelerates, Capacity Set to Grow Through 2026

Mass production of the 684Ah stacking cell is shifting industry focus from size competition to technological advancement. Major cell manufacturers now view stacking as the next‑generation technology for large‑format cells. Besides Sunwoda, about 70% of leading cell makers—including CALB, REPT, Eve Energy, and SVOLT—have already embarked on stacking cell development. Capacity for 684Ah stacking cells is expected to continue rising through 2026.

As energy storage systems trend toward larger capacities, demand for 600Ah+ cells is growing. Several top system integrators have introduced specialized system‑level designs tailored for 600Ah+ stacking cells, upgrading overall system operation logic from cell selection to management—enabling high‑quality market deployment. The adoption of even larger cells, driven by technological progress and market needs, will further promote high‑quality, sustainable growth across the energy storage industry.

Edit by paco

Last Update:2025-12-27 09:17:12