Stress Analysis of Cylindrical Lithium Ion Power Battery during Winding Process

Abstract

In the manufacturing process of lithium-ion power battery, winding is a very critical process. In order to ensure the safety and stability of the battery, no buckling, wrinkling, and even fracture is allowed in the process of winding. Different battery models lead to different winding methods for the jellyroll. The most suitable winding method is determined by the external radius of the jellyroll. First, the winding layer is treated as a thin-film material, the constitutive equation of jellyroll is established by considering the constraint of winding tension to obtain hoop stress and radial stress distribution function at the place of r under plane strain state. The hoop stress and the radial stress at any place of r inside the jellyroll are obtained at the end of n coils. Moreover, the hoop stresses of the jellyrolls with different external radius are analyzed by calculating examples according to the type of winding tension, and the suitable winding methods for different external radius are suggested. With the increase of the external radius of jellyroll, the constant winding tension and taper winding tension are gradually no longer suitable, and the parabolic winding tension and compound winding tension are proposed. After the winding of the power battery is completed, the stress generated by the winding tension of jellyroll is equivalent to the prestress applied to the battery, which will affect the use of the power battery.

Keywords

• lithium-ion power battery
• plane strain state
• stress distribution
• winding tension
• hoop stress