The lithium battery winding machine is used to wind lithium battery cells. It is a machine that assembles the positive electrode sheet, negative electrode sheet and battery separator into a core pack (JR: JellyRoll) in a continuous rotating manner.

Winding machine principle

The lithium battery winding machine has a positive and negative electrode feeding unit, and the mechanism that winds the positive electrode, negative electrode and separator together is called a winding needle.According to the shape of the battery core, it is mainly divided into square and cylindrical battery cell winding machines. Generally, the winding equipment adopts the structure of two or more winding needles and single-side needle pulling.

The main mechanisms of the winding machine are: positive and negative pole pieces and diaphragm active unwinding, pole piece and diaphragm rewinding, automatic deviation correction, automatic tension detection and control.

The pole piece is introduced into the winding needle part by the pinch roller driving mechanism, and is wound together with the diaphragm according to the process requirements. After the winding is completed, the station is automatically changed, the diaphragm is cut off, and the termination tape is attached. After the finished bare cells are automatically unloaded, after pre-pressing and code scanning, the good-quality finished bare cells are automatically transferred to the tray and then transferred to the subsequent process. The defective bare cells are automatically unloaded to the collection place for defective bare cells.

Winding Mechanism Description

①Pre-winding: The initial feeding process of the positive and negative pole pieces.It is necessary to control the rotation angle and speed of the winding needle to match the pole piece feeding mechanism.this process involves two synchronizations: the unwinding speed of the diaphragm is synchronized with the needle winding speed, and the pole piece feeding speed is synchronized with the needle winding speed.

②Winding process: After the initial feeding process of the positive and negative electrodes is completed, the positive and negative electrodes are tightly wrapped by the separator and wound around the winding needle, and the continuous winding can be realized by turning the winding needle subsequently. In this process, the unwinding speed of the pole piece unwinding motor is adjusted by detecting the tension of the material roll to ensure the constant tension of the material roll during the winding process.

The control problem in pre-winding is an open-loop control problem. Whether the real synchronization between the winding needle, diaphragm and pole piece cannot be accurately measured, which requires us to establish an accurate winding control model.

Especially for the winding requirements of larger batteries. The tension of the material tape in winding can be controlled by closed-loop feedback control technology.

③Dynamic control model of the winding process: Since the pre-winding process belongs to open-loop control, an accurate mathematical model is the key to the success of the winding control system. Especially when the linear speed of the pole piece is greater than 1m/s, the accurate winding model is the key to control the stability of the winding tension and the quality control of the winding.

④ High-quality winding of the battery core: The core issue of high-quality winding of the battery core is that the battery separator and electrode sheets of the wound battery core are evenly bonded,

It is shown that there is no gap, and the contact stress between the separator and the pole piece is kept uniform in all directions during the use of the battery.

One is: after the winding core is pulled out, the bonding stress is still consistent, which is very important for the design of the contour shape of the needle.especially for square winding batteries, to ensure that the bonding stress between the pole piece and the separator is uniform after winding and pulling out the needle, the winding contour curve must be a closed curve with continuous first-order derivatives. The judging principle is that the curve is continuous, smooth and without sharp corners.

The second is: when the diaphragm and the pole piece enter the winding needle, the tension is consistent in the direction of the generatrix of the winding needle tangent.this requires that the deviation correction range of the diaphragm pole piece should not be too large, and a limit value within the elastic range of the diaphragm and pole piece should be guaranteed.