Secondary Battery Folding Grooves Rectangular Electrode Volume Efficiency
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Solution Overview
Problem
Existing secondary batteries face inefficiencies in volume utilization due to gaps between the battery case and the flat wound electrode body, which can be attributed to the lack of a base member for forming notches that could reduce the curvature radius and facilitate easier folding.
Innovation Solution
The proposed secondary battery incorporates folding grooves on the positive and negative electrode active material layers at corner positions, allowing the electrode sheets to be easily folded into a rectangular shape, thereby reducing the dead space when accommodated in a square battery case, enhancing volume efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the curvature radius of the R-parts is reduced to make the gap small, then the volume efficiency is improved, but the electrode body becomes difficult to fold and manufacture
Solution Approach 1:
The electrode body is divided into a flat surface part and corner parts by introducing folding grooves at the corner positions. This segmentation allows the corner parts to be folded independently along the grooves, enabling the formation of a rectangular shape with reduced gap while maintaining manufacturability through localized folding zones rather than requiring small curvature radii throughout the entire electrode body.
Solution Approach 2:
Folding grooves are formed in advance at the corner parts of the electrode body before winding. This preliminary action creates predetermined folding lines that guide the corner parts to fold easily along the grooves, enabling the electrode body to achieve a rectangular shape with minimal gap without requiring difficult small curvature radius folding during assembly.
2Ease of manufacture
If notches are formed on the base member to facilitate folding, then the ease of manufacture is improved, but the device complexity increases due to the need for a base member
Solution Approach 1:
The folding function is extracted from the base member structure and transferred to the electrode body itself by forming folding grooves directly on the electrode active material layers. This eliminates the need for a separate base member with notches, reducing device complexity while maintaining the ease of folding benefit through direct groove formation on the electrode sheets.
Solution Approach 2:
The electrode body is given multiple functions: it serves both as the electroactive component and as the structural element that provides folding capability through integrated folding grooves. This multi-functionality eliminates the need for a separate base member, reducing overall device complexity while maintaining ease of folding and winding.
Data Source
AI summary
The secondary battery includes: a square battery case; and a wound electrode body accommodated in the battery case. The wound electrode body has a positive electrode sheet and a negative electrode sheet overlapping with each other to be wound about a winding axis to have a rectangular shape when seen from a winding axis direction. The wound electrode body has corner parts positioned at four corners of the wound electrode body when seen from the winding axis direction. The positive electrode sheet has a positive electrode collector and a positive electrode active material layer. The negative electrode sheet has a negative electrode collector and a negative electrode active material layer. Folding grooves are formed along the winding axis direction at portions of the positive electrode active material layer or portions of the negative electrode active material layer that are positioned at the corner parts.