Lithium Battery Cell Assembly: Winding vs Stacking — Which Is Better?

In battery mid-stage assembly there are two competing cell manufacturing approaches: winding and stacking. The competition focuses on cell space utilization, lifespan, production efficiency and capital investment.

Below we outline the main differences between the two processes.

Winding forms the electrode core by controlling foil speed, tension, size and tolerances, slitting matched electrode foils, separator and tapes, then winding them to the target dimensions.

Stacking alternately layers electrodes and separators to form a multi-layer stack.

From a cell format perspective, pouch and blade cells are designed around stacking, while prismatic cells can be produced by either stacking or winding. Currently Chinese battery makers favor winding—especially for cylindrical cells—but as stacking techniques improve many manufacturers are shifting toward stacking.

Advantages of stacking

Stacked cells typically achieve higher energy density, more stable internal structure, improved safety and longer cycle life.

1. Higher energy density

Wound cells have curved corners inside the roll, reducing usable space. Stacked cells more efficiently use internal volume, yielding higher energy density for the same cell size.

2. More stable internal structure

During cycling electrode expansion can cause uneven stresses in wound cells at the roll radius, producing wave-like deformation, worsening interfaces and causing uneven current distribution. Stacked cells experience more uniform stress and maintain better internal structure.

3. Improved safety

Because stacked cells deform less under electrode expansion and separator stretching, they are less prone to defects like delamination or tearing. Wound cells have bending stresses at tab areas that can cause flaking or burrs, while stacked cells exhibit smaller deformation and improved safety.

4. Longer cycle life

Stacked cells have multiple tabs and shorter electron paths, resulting in lower internal resistance and reduced heat generation, improving cycle performance. Wound cells are more prone to deformation that accelerates degradation.

Disadvantages of stacking

Stacking is not without drawbacks—lower throughput, higher equipment cost and somewhat lower yield compared with winding.

1. Lower production efficiency

Typical prismatic winding lines can reach about 12 ppm, while traditional Z-style stacking machines are often around 4 ppm—about three times slower. Stacking lines also occupy more floor space, further affecting throughput.

2. Higher capital investment

A winding production line investment depends on cell length; a single line may need ~10 winding machines with capital around ¥30 million, while a stacking line can require higher investment (~¥60 million) depending on stack count.

3. Slightly lower yield

Winding cells require fewer slit operations and typically easier handling, giving higher pass rates. Stacking requires many small pieces per cell; any misfeed or overlap during loading can create defects.

If stacking yield issues are solved, stacking could see wider adoption due to structural and performance advantages.

Atonm Metal Double-Sheet Detector MDSC-1000L is designed for stacking lines and detects ultra-thin, lightweight pieces (down to 0.01 mm) using non-contact sensing. It avoids contact damage and supports high-speed detection up to 600 pcs/min.

Why choose Atonm?

Atonm believes meeting specifications is just the entry requirement—stable detection is the true product value.

To improve reliability, Atonm optimized materials and design as shown in the comparison table below.

Robust materials and systemic design are required even in unseen components to ensure maximal production safety.

Patented metal housing — unlike common plastic or ordinary metal housings, Atonm engineers analyzed electromagnetic environments across workshops and selected a special 3mm-thick alloy for the detector housing, protected by patents.

Four-layer integrated PCB — PCB material choice and circuit design significantly improve anti-interference performance.

Many competitors still use discrete-component circuit designs which are cheaper but more vulnerable to interference and solder joint issues. Atonm solved zero-drift and sensitivity drift through integrated circuit design and manufacturing process improvements.

Higher reliability requires work in unseen areas.

Atonm also submitted its double-sheet detectors to accredited labs for EMC and environmental reliability testing: 28 test items over ~30 days, achieving near-zero false positives for single/double detection under strict conditions.

Test item overview:

“High reliability is both technical and ethical work.” Engineers emphasize using materials and designs that withstand harsh conditions and respecting customer trust.