Electrode Assembly Fixing Structure for Uniform End-Pressure
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Solution Overview
Problem
Lithium secondary batteries experience issues with non-uniform pressure distribution and adhesion at the end portions of the electrode assembly, leading to lithium plating, swelling, and reduced performance due to decreased electrolyte impregnability, especially in long-cell structures used for electric vehicles.
Innovation Solution
The electrode assembly incorporates a thicker fixing member overlapping the positive electrode sliding portion to maintain adhesion with the separator and compensate for thickness decreases, ensuring uniform pressure transmission and minimizing lithium plating and swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a long-cell structure is used to achieve higher capacity and space efficiency, then battery capacity and space efficiency are improved, but pressure at the end portion of the electrode assembly decreases leading to reduced adhesion and intensified lithium plating
Solution Approach 1:
The patent applies local quality by positioning a thicker fixing member specifically at the end portion of the electrode assembly where the sliding portion is located. This localized thickness increase compensates for the reduced cell thickness at the end portion, maintaining uniform pressure distribution and adhesion between the separator and electrode throughout the long-cell structure, thereby preventing lithium plating while preserving the high capacity benefits.
2Productivity
If electrode assembly is prepared by coating with electrode slurry, then manufacturing efficiency is improved, but a sliding portion is formed at the end portion where thickness of active material layer decreases, reducing adhesion to separator
Solution Approach 1:
The patent applies preliminary action by pre-positioning the thicker fixing member at the end portion of the electrode assembly before the electrode is inserted into the module. This anticipatory measure compensates in advance for the thickness reduction and adhesion loss that will occur at the sliding portion, ensuring uniform pressure and adhesion are maintained from the outset, thereby preventing lithium plating without sacrificing the manufacturing efficiency of the coating process.
3Duration of action of moving object
If electrolyte amount decreases due to repeated charge and discharge, then battery cycling is enabled, but electrolyte may not reach electrode end portion reducing impregnability and causing lithium plating
Solution Approach 1:
The thicker fixing member at the end portion creates a localized structural support that maintains uniform pressure distribution throughout the electrode assembly during cycling. This compensates for the reduced cell thickness at the end portion, ensuring electrolyte can consistently reach and impregnate the electrode end portion even as electrolyte volume decreases over repeated charge and discharge cycles, thereby maintaining reliability throughout the battery's operational life.
Data Source
AI summary
An electrode assembly including an electrode stack, which includes a positive electrode including a positive electrode active material layer; a negative electrode including a negative electrode active material layer; and a separator disposed between the positive electrode and the negative electrode, and at least one fixing member which fixes the electrode stack by winding the electrode stack in an overall width direction, wherein the positive electrode includes a positive electrode sliding portion in which a thickness of the positive electrode active material layer decreases, the fixing member includes a first fixing member overlapping the positive electrode sliding portion and a second fixing member not overlapping the positive electrode sliding portion, and a thickness of the first fixing member is greater than a thickness of the second fixing member.