Slit Electrode Structure for Roll-Induced Warping Control
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Solution Overview
Problem
Secondary battery electrodes are prone to bending or warping during the rolling process due to uneven heat and pressure distribution, especially with increasing active material loading for high energy density cells.
Innovation Solution
Forming slits in the active material non-coating portion of the electrode and creating holes at the intersection of the slits with the coating portion to disperse stress and prevent warping and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the loading amount of electrode active material is increased to achieve high energy density, then the energy density is improved, but the electrode becomes more prone to bending and warping during rolling
Solution Approach 1:
The active material non-coating portion is divided into multiple segments by forming slits, which breaks the continuous structure into discrete segments. This segmentation allows each segment to independently accommodate stress during rolling, preventing the entire electrode from warping while maintaining high active material loading in the coating portions.
Solution Approach 2:
Different regions of the electrode are given different properties: the active material coating portions maintain high material loading for energy density, while the active material non-coating portions contain slits to provide stress relief. This local differentiation allows the electrode to simultaneously achieve high energy density and resistance to warping.
2Productivity
If the electrode sheet is compressed to reduce thickness for increased capacity density, then the capacity density is improved, but the electrode becomes more susceptible to warping due to uneven heat and pressure distribution
Solution Approach 1:
The slits divide the non-coating portion into segments that can independently deform during rolling compression. This segmentation prevents the accumulation of uneven stress that would otherwise cause warping, allowing the electrode to be compressed to reduced thickness while maintaining flatness.
Solution Approach 2:
The slits are formed in advance before the rolling process, creating predetermined stress relief paths. During subsequent rolling compression, these pre-formed slits cushion the uneven heat and pressure distribution, preventing warping from occurring in the first place.
3Stability of the object's composition
If slits are formed in the active material non-coating portion to prevent warping, then the electrode flatness is improved, but stress concentration may occur at the intersection with the coating portion
Solution Approach 1:
Holes are formed at the intersection points where slits meet the active material coating portion, extracting the stress concentration points from the continuous structure. This removal of material at critical locations eliminates the stress concentration that would otherwise lead to crack formation.
Solution Approach 2:
The electrode structure is made asymmetric by introducing slits and holes only in the active material non-coating portion, not in the coating portion. This asymmetric design strategically places stress relief features where they are needed without compromising the integrity of the active material regions.
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
Prevents electrode bending and warping post-rolling by distributing stress and reducing crack formation, maintaining electrode integrity and energy density.
Implementation Method 1
a process of allowing an electrode sheet to pass between two rolling rolls, which are heated at a high temperature, to compress the electrode sheet to a desired thickness and density
Implementation Method 2
compress the electrode sheet to a desired thickness and density
Implementation Method 3
the slit extends from one end of the active material non-coating portion to the other end, and a hole is formed at a position where the slit and the active material coating portion meet each other
Data Source
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AI summary
An electrode according to an embodiment of the present invention for solving the above problem comprises: an active material coating portion coated with an electrode active material on at least one surface of an electrode collector; and an active material non-coating portion which is formed at one side of the active material coating portion, is not coated with the electrode active material, and comprises at least one slit extending from one end to the other end thereof, wherein a hole is formed to pass through a point at which the slit and the active material coating portion meet each other.