Secondary Battery Insulating Tape Gradient Coating
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Solution Overview
Problem
In secondary batteries, the precipitation of metallic lithium on the negative electrode active material layer occurs due to the attachment of insulating tape on the positive electrode sheet, leading to uneven coating formation and increased resistance, which results in the elution of positive electrode material and subsequent metallic lithium precipitation.
Innovation Solution
A configuration where an insulating tape is attached to at least one end portion of the positive electrode sheet, with a coating provided along the edge of the tape that is inactive to battery reactions, and the coating's thickness decreases gradually as it moves away from the tape's edge, effectively suppressing metallic lithium precipitation by maintaining an optimal interelectrode distance and preventing excessive coating formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating tape is attached to the end portion of the positive electrode sheet, then the positive electrode material elution is suppressed, but the coating formation becomes uneven and resistance increases leading to metallic lithium precipitation
Solution Approach 1:
The patent applies local quality by providing a coating only at specific locations (along the edge of the insulating tape) rather than uniformly across the entire electrode. The coating thickness varies locally, being thicker near the insulating tape edge and gradually thinner toward the center, creating different functional zones that address both elution suppression and lithium precipitation prevention
Solution Approach 2:
The patent changes the parameter of coating thickness from a uniform value to a gradient distribution. The coating thickness decreases gradually from the edge toward the center of the positive electrode sheet, optimizing both the suppression of material elution near the tape and the prevention of lithium precipitation in other regions
2Reliability
If a coating is provided along the insulating tape edge, then the interelectrode distance is maintained, but excessive coating formation increases resistance
Solution Approach 1:
The coating is applied with locally varying thickness rather than uniform thickness throughout. The thickness is greatest where needed most (near the insulating tape edge for maintaining interelectrode distance) and gradually reduces in other areas, preventing excessive coating formation and associated resistance increases
Solution Approach 2:
The coating thickness is designed to vary dynamically across the electrode surface, creating a gradient structure that adapts to different functional requirements at different locations - thicker where structural support is needed, thinner where conductivity is prioritized
Data Source
AI summary
Provided is a technique capable of suppressing the precipitation of metallic lithium on a negative electrode active material layer. A secondary battery that is disclosed herein includes a wound electrode body in which a long sheet-shaped positive electrode sheet and a long sheet-shaped negative electrode sheet are wound in a longitudinal direction, with a separator being interposed therebetween and a non-aqueous electrolytic solution. At least one end portion of the positive electrode sheet in the longitudinal direction is provided with an insulating tape that covers the end portion and is attached onto a positive electrode active material layer and a coating that is provided on the positive electrode active material layer along the edge of the insulating tape and is inactive to a battery reaction. Here, a thickness of the coating decreases gradually as a distance between the coating and the edge of the insulating tape increases gradually.