Negative Electrode Variable Cutouts for Jelly-Roll Crack Prevention
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Solution Overview
Problem
Secondary batteries with jelly-roll-type electrode assemblies face issues due to the expansion of active materials, which causes tension and cracking in the non-coated portions of the negative electrode.
Innovation Solution
An electrode assembly design that includes a negative electrode with a variable unit at the outermost peripheral non-coated portion, featuring cutout portions of non-straight shape to adjust length or width, allowing for volume change accommodation during active material expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a jelly-roll-type electrode assembly is used, then the battery can be recharged with high capacity, but the active material expansion causes tension and cracking in the non-coated portion of the negative electrode
Solution Approach 1:
The negative electrode is divided into a coated portion with active material and a non-coated portion without active material. The non-coated portion is further segmented into a body part and an extension part that protrudes outward, allowing differential movement to accommodate expansion forces while maintaining overall structural integrity.
Solution Approach 2:
The extension part of the non-coated portion is designed to be movable relative to the battery casing, enabling it to dynamically adjust its position outward during charging when active material expands, and return during discharging, thereby preventing crack formation through controlled movement.
2Strength
If the non-coated portion is made rigid to maintain structural integrity, then strength is improved, but volume change accommodation during active material expansion is reduced
Solution Approach 1:
The negative electrode structure is segmented into rigid coated portions and a flexible non-coated portion with an extension part. This segmentation allows the coated portions to maintain structural strength while the non-coated extension part provides flexibility for volume accommodation during charge-discharge cycles.
Solution Approach 2:
Different parts of the negative electrode are given different properties: the coated portions maintain rigid structural integrity for strength, while the non-coated extension part is designed with movable characteristics to locally accommodate volume changes, achieving both strength and adaptability through localized property differentiation.
Data Source
AI summary
An electrode assembly is made by winding a positive electrode, a separator, and a negative electrode, in which the negative electrode includes a negative electrode active material portion made by applying a negative electrode active material onto a negative electrode current collector, a central negative electrode non-coated portion positioned at a winding center portion and having no negative electrode active material, and a negative electrode non-coated portion including an outermost peripheral negative electrode non-coated portion positioned at an outermost winding periphery, in which a variable unit is provided on the outermost peripheral negative electrode non-coated portion and configured to adjust a length or width thereof, and in which the variable unit includes one or more cutout portions having a non-straight shape, and a variable portion configured to adjust a length or width thereof.