Cylindrical Battery Can Geometry for Electrode Expansion Control

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Solution Overview

Problem

Cylindrical secondary batteries face challenges in maintaining battery capacity and cycle characteristics due to the expansion and contraction of the electrode assembly, which can lead to a mismatch between the outer diameter of the electrode assembly and the inner diameter of the exterior housing can, potentially causing deterioration in cycle characteristics and increased change in the outer circumferential shape of the exterior housing can.

Innovation Solution

The cylindrical secondary battery design includes an exterior housing can with a specific proportion of average outer diameters at the center relative to the bottom end, along with a standard deviation of outer diameters at the center, which helps in absorbing the expansion of the electrode assembly while preventing excessive binding pressure and maintaining the cylindrical shape of the exterior housing can.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the outer diameter of the electrode assembly is increased in advance to accommodate expansion, then battery capacity is improved, but the change in outer circumferential shape of the exterior housing can increases

Engineering Contradiction:

Improvebattery capacityVSAvoidouter circumferential shape of exterior housing can

Core Design Contradiction:

Quantity of substanceVSShape

Solution Approach 1:

The invention changes the geometric parameters of the exterior housing can, specifically setting the proportion of average outer diameters at the center relative to the bottom end within 100.10%-100.50% and controlling the standard deviation of outer diameters at the center within 0.020-0.050 mm. These parameter adjustments allow the housing to accommodate electrode assembly expansion while maintaining cylindrical shape integrity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the binding pressure of the exterior housing can is increased to suppress electrode assembly expansion, then cycle characteristics are improved, but the change in outer circumferential shape of the exterior housing can increases

Engineering Contradiction:

Improvecycle characteristicsVSAvoidouter circumferential shape of exterior housing can

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The invention optimizes the geometric parameters of the exterior housing can (proportion of average outer diameters and standard deviation of outer diameters) to create an optimal binding pressure distribution. This allows sufficient pressure to suppress electrode assembly expansion and improve cycle characteristics, while preventing excessive pressure that would cause housing deformation.

Inventive Principle:

Principle #35Parameter changes

3Shape

If the proportion of average outer diameters at the center relative to the bottom end is decreased, then the outer circumferential shape change is reduced, but the battery capacity decreases

Engineering Contradiction:

Improveouter circumferential shape of exterior housing canVSAvoidbattery capacity

Core Design Contradiction:

ShapeVSQuantity of substance

Solution Approach 1:

The invention identifies and implements optimal parameter ranges: the proportion of average outer diameters at the center relative to the bottom end should be 100.10%-100.50%, and the standard deviation of outer diameters at the center should be 0.020-0.050 mm. These parameter values balance shape maintenance with battery capacity optimization.

Inventive Principle:

Principle #35Parameter changes

4Shape

If the standard deviation of outer diameters at the center is increased, then the outer circumferential shape change is reduced, but the binding pressure distribution becomes uneven

Engineering Contradiction:

Improveouter circumferential shape of exterior housing canVSAvoidbinding pressure distribution

Core Design Contradiction:

ShapeVSStress or pressure

Solution Approach 1:

The invention determines the optimal standard deviation of outer diameters at the center should be within 0.020-0.050 mm. This parameter control ensures uniform binding pressure distribution across the electrode assembly, preventing localized stress concentrations that would cause housing deformation while maintaining overall shape integrity.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design effectively increases battery capacity and improves cycle characteristics by allowing for the expansion of the electrode assembly while maintaining the structural integrity of the exterior housing can, thus preventing excessive deformation and enhancing the battery's performance over repeated charge-discharge cycles.

Implementation Method 1

the expansion of the electrode assembly may be suppressed by the binding pressure of the exterior housing can

Methodology Applied

Scientific EffectBinding pressure: Compression

Data Source

PatentUS20250038274A1Cylindrical secondary battery

Publication Date: 2025.01.30 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A cylindrical secondary battery comprises an external can that has a cylindrical tube part and an electrode body that is provided inside the tube part. The electrode body is obtained by winding a positive electrode plate and a negative electrode plate with a separator therebetween. In the external can, the ratio of the average value of the outer diameter of the middle of the tube part in the axial direction of the external can to the average value of the outer diameter of the bottom-side end of the tube part is 100.10-100.50%, and the standard deviation of the outer diameter of the middle of the tube part is 0.020-0.050 mm.