Jelly-Roll Electrode Assembly With Overlapping Separators Against Shorts
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Solution Overview
Problem
Secondary battery electrode assemblies experience cracking and internal shorts due to bending deformation at the end portions during charging and discharging cycles, leading to safety and capacity issues.
Innovation Solution
A jelly-roll type electrode assembly with multiple layers of separators and an adhesive tape is designed to prevent damage by overlapping the separators and positioning them between the positive and negative electrodes, ensuring smooth lithium ion migration and preventing internal shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a jelly-roll type electrode assembly is used for high energy density, then energy density per weight is improved, but bending deformation occurs at the end portion during charging/discharging cycles
Solution Approach 1:
The separator overlapping portion is prepared in advance during assembly, creating a pre-positioned protective structure at the end portion of the electrode assembly. This preliminary structural arrangement prevents bending deformation before it occurs during charging/discharging cycles, addressing the technical contradiction by preparing the protective configuration beforehand.
Solution Approach 2:
The overlapping separator layers form a cushioning structure at the end portion that absorbs and distributes mechanical stress during electrode expansion and contraction. This beforehand cushioning prevents the bending deformation that would otherwise occur, allowing the jelly-roll structure to maintain high energy density while protecting against structural degradation.
2Duration of action of moving object
If the electrode assembly contracts and expands during charging/discharging cycles, then charge/discharge functionality is achieved, but bending deformation and cracking occur at the end portion
Solution Approach 1:
The separator overlapping portion is pre-configured at the end portion before the electrode assembly undergoes charging/discharging cycles. This preliminary structural preparation ensures that when contraction and expansion occur, the bending forces are distributed across multiple separator layers rather than concentrating at a single point, preventing cracking and maintaining reliability.
Solution Approach 2:
The overlapping separator layers create a cushioning effect that absorbs the mechanical stress generated during normal charge/discharge operations. This beforehand cushioning protects the end portion from bending deformation and cracking, ensuring the electrode assembly maintains its safety and functionality throughout its operational life.
3Device complexity
If a single layer of separator is used to simplify structure, then device complexity is reduced, but cracking and internal shorts occur during electrode deformation
Solution Approach 1:
The separator structure is segmented into multiple layers at the critical end portion where bending deformation occurs. This segmentation distributes the mechanical stress across multiple layers, preventing any single layer from cracking. The segmented multi-layer structure maintains reliability while keeping the overall design straightforward.
Solution Approach 2:
The separator structure applies local quality by using multiple layers specifically at the end portion where bending deformation and cracking risks are highest, while the rest of the separator structure can remain simpler. This localized multi-layer configuration provides enhanced protection exactly where needed without unnecessarily complicating the entire separator structure.
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
The solution effectively prevents cracking and internal shorts, enhancing the safety and lifespan of the secondary battery by maintaining separator integrity and facilitating lithium ion migration, thus improving cycle stability and capacity retention.
Implementation Method 1
an adhesive tape being located in at least one of a location between the outer surface the positive electrode and an inner surface of the first separator, and a location between an outer surface of the negative electrode and an inner surface of the first separator
Implementation Method 2
ensuring smooth lithium ion migration
Data Source
AI summary
A jelly-roll type electrode assembly includes a first separator, a second separator, a negative electrode, and a positive electrode. The first separator and second separator are positioned adjacent each other in a separator overlapping portion and extend with at least three layers in a first direction toward a core of the electrode assembly between an inner surface of the positive electrode and an outer surface of the negative electrode. An adhesive tape is located in at least one of a location between the outer surface of the positive electrode and an inner surface of the first separator, and a location between an outer surface of the negative electrode and the inner surface of the first separator.