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Coating width, web width and roller face: compare the right dimensions

Three width figures describe three different parts of an electrode coater. Keep them apart and the comparison stays honest.

By BatteryEquip Editorial Team · 2026-11-04

An electrode coater brochure can quote three widths: the roller face, the web and the coating. Each describes a different part of the machine. A buyer who compares only the largest number can shortlist a line that cannot produce the intended electrode, or pay for width the project never uses.

What each width measures

The roller face width is the physical length of the roll surface. It sets the outer mechanical limit, and it is always larger than anything the line actually processes.

The web width is the foil, or other substrate, that the unwind, guiding and rewind can carry. Aluminium foil for cathodes and copper foil for anodes arrive as rolls of a set width, so this number tells you which foil rolls fit.

The usable coating width is the band across the web where slurry is applied to the agreed thickness. It is narrower than the web, because each edge needs uncoated foil for tabs and for handling. In slot-die coating, the usual method in large-scale electrode production, the die lips and shims define this band.

Only the coating width tells you how much electrode the line produces per metre. The other two describe what the machine can hold.

A worked example from two catalogues

The Yinghe 1600 series lists a 1,600 mm roller face and a maximum coating width of 1,350 mm. Reading the roller figure as coating width would overstate the capability by 250 mm. The Lyric double-layer wide coater lists a 1,800 mm web width; that is a substrate limit and should not be relabelled as coating width until the supplier confirms the applied band. The HONBRO single-layer page gives a width figure without a unit, so ask HONBRO what it measures.

That gives three cases: a known coating width, a known web width and a width still to be clarified. They cannot be merged into one ranked column. None of them says which machine is better for a particular slurry.

Edges are where width is lost

Slurry tends to build up at the edges of a slot-die stripe, a heavy edge that later causes uneven calendering and wrinkles. Suppliers manage it with die design, shims and edge control, and some trim the edge off after drying. Either way, part of the nominal coating width may not become saleable electrode. Ask how much of the coated band meets the thickness tolerance and how that is measured across the width.

Double-sided electrodes add registration: the coating on the back must line up with the front, especially on intermittent (patterned) coating where each stripe ends at a tab gap. Ask for the front-to-back alignment figure and its method.

Speed and width only mean something with the process

A maximum web speed is one part of the specification. The drying oven decides the speed you can really run, because a wet layer has to leave the oven dry enough for the next step. State the foil material and thickness, the slurry formulation you can disclose, the target coat weight on a wet or dry basis, the coating pattern and whether it is single-sided or double-sided. Then ask which oven length, zones and air handling are included in the quotation, and under what conditions the quoted speed applies.

The same reasoning carries into the next steps of the line. The width that leaves the coater has to suit the electrode calendering rolls and the electrode slitting plan for the final cell format.

A comparison sheet that keeps the meanings

Use separate rows for incoming web width, usable coating width, roller face, edge allowance, pattern and coat weight. Leave a cell empty when its unit or meaning is unclear, and record the supplier's own label next to each value. A blank cell with a precise question is more useful than an assumed number that makes two different specifications look equal.

Ask for a trial with representative foil and slurry. Agree the sampling positions across the coated band and along the run, the measurement method for coat weight and thickness, and the acceptance limits before the trial starts. The examples here compare published specifications.