Calendering is the step where electrode quality is either locked in or lost. Press too lightly and the coating stays porous, with poor particle-to-particle contact. Press too hard and you destroy the capacity you just finished coating on - the patent states the mechanism plainly: excessive compaction density forces active material particles into contact too tightly, polarisation rises, working voltage drops, and the cell delivers less capacity than the coating weight promised.

Between those two failure modes there is a narrow window, and a press that applies one fixed pressure through one fixed nip cannot reliably stay inside it. CN215430810U, filed on 1 September 2021, splits compaction into two independently controlled stages, adds heat before the final nip, and - unusually - cleans itself while running.

Patent Information

The Production Problem This Patent Solves

The specification identifies three distinct failures in roller presses then in use.

Over-compaction destroys capacity. When compaction density is pushed too high, active material particles are pressed into excessive mutual contact. Polarisation increases, working voltage under load falls, and usable capacity drops below what the coating weight should deliver. The defect is invisible at the press and only appears at capacity grading - by which point an entire roll has been processed.

Tension variation produces thickness variation. The patent states that the tension performance and the hot rolling effect of the electrode are "one of two important influence factors." Different web tensions change the plasticity of the electrode material, and that change propagates directly into the thickness leaving the nip. A single fixed-pressure press has no mechanism to compensate.

Cleaning requires stopping the machine. Metal fragments and coating dust accumulate on the roll faces during production. In a conventional press the only remedy is to halt the line. On a production floor that stoppage - not the cleaning itself - is the real cost.

The Core Approach: Separate the Two Jobs Calendering Has to Do

A single nip is asked to do two incompatible things at once: consolidate loose coating into a dense layer, and hold a precise final thickness. Those two jobs want different pressures.

CN215430810U separates them. The web passes a light pressing stage first, then a heavy pressing stage, each on its own lifting cylinder. Consolidation happens in the first pass; final dimension is set in the second. Because the two cylinders are independent, the operator sets two separate gaps rather than one compromise value - the patent states that "because the light-pressure lifting cylinder and the heavy-pressure lifting cylinder are arranged, different extrusion thicknesses can be realized."

Heat is added between the stages for the same reason. Warming the electrode raises material plasticity, so the target density is reached at lower mechanical pressure - which is precisely the mechanism that avoids the over-compaction damage described above. The press reaches density through temperature rather than through force.

Structural Specification

Roller train, in web order

Independent lifting mechanisms

The light-pressing lower roller is welded to a light-pressing lifting frame, driven by the extension rod of a light-pressing lifting cylinder. The heavy-pressing lower roller has its own heavy-pressing lifting frame and heavy-pressing lifting cylinder. Two separate actuators mean the two gaps are set and held independently. Neither stage constrains the other.

Guided roller travel

Left and right guide grooves in the intermediate structure engage pulleys mounted on both sides of each pressing roller. The grooves constrain vertical travel to a single axis while the pulleys reduce sliding friction, so a commanded gap change produces the same actual gap change every time rather than binding and overshooting.

Inline heating roller

A heating cavity inside the metal heating roller carries an embedded heating pipe connected to an external supply. Heat is applied to the web itself in the roller train, not in a separate oven stage.

Continuous magnetic debris capture

An electromagnet is mounted on a transverse frame above the heavy upper pressing roller. It adsorbs residual metal fragments and dust continuously during production.

This placement is deliberate. The heavy upper roller sits at the last nip the electrode passes, so any ferrous particle not removed before that point gets pressed into the finished electrode - where it becomes a potential internal short circuit in the assembled cell, not a cosmetic mark.

Drive

The motor frame carries four motors, driving the roller train.

Claimed Benefits

How It Compares with Single-Pressure Roller Presses

The specification identifies three failures in the roller presses then in use: density could not be adjusted in production, metal debris built up on the rolls, and tension-driven variation disturbed the finished thickness. This patent answers each one inside a single machine.

Where This Technology Is Used Today

This patent covers the mechanical architecture of TOB's production roller presses. The two-stage principle it protects - consolidate first, dimension second, with heat between - is how our calendering equipment holds electrode thickness across a full production roll.

• High Precision Electrode Rolling Press Machine for 4680 Tabless Battery - the two-stage compaction principle applied to tabless cell production
• Continuous Hydraulic Roller Heat Press Machine for Lithium Battery - inline heat ahead of the final nip on a continuous line
• Hydraulic Heating Calendering Machine for Battery Electrode - hydraulic pressing with heated rolls for electrode calendering
• Electrode Preparation - the mixing, coating and calendering line this press sits in

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Patent Drawings

Frequently Asked Questions

Full specification and drawings: CN215430810U on Google Patents