Jelly-Roll Electrode Assembly With Auxiliary Separator Against Cracking
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Solution Overview
Problem
Secondary batteries with jelly-roll electrode assemblies experience cracks and disconnection due to contraction and expansion during charging/discharging cycles, leading to safety issues like short circuits and potential ignition.
Innovation Solution
An electrode assembly with a double-layer separation membrane structure, including a first separation membrane and an auxiliary separation membrane, is wound to prevent contact between the positive and negative electrodes, using ceramic particles in the coating layer and a base layer of polyethylene or its copolymers, with the auxiliary membrane extending to the center to buffer stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a jelly-roll type electrode assembly is formed by winding positive and negative electrodes with a separation membrane, then the battery can achieve high energy density and efficient space utilization, but contraction and expansion during charging/discharging cycles cause bending deformation and cracks at the electrode ends
Solution Approach 1:
The invention applies different structural characteristics to different regions of the electrode assembly. The first separation membrane has a length that extends beyond the electrode ends, creating a protective region at the vulnerable electrode terminals where bending deformation occurs during charging/discharging cycles. This local extension provides additional protection precisely where cracks are most likely to form.
Solution Approach 2:
The extended portion of the first separation membrane acts as a pre-positioned protective buffer that prevents direct contact between positive and negative electrodes before any harmful short circuit can occur. This beforehand cushioning compensates for the bending deformation and contraction/expansion movements that occur during normal battery operation, maintaining electrode separation even when the jelly-roll structure deforms.
2Device complexity
If the separation membrane is positioned only between the positive and negative electrodes, then the structure is simple and manufacturing is easy, but it cannot prevent contact between electrodes when bending deformation occurs at the electrode ends
Solution Approach 1:
The first separation membrane is preliminarily extended beyond the electrode ends during the winding process, creating a protective configuration before the battery undergoes any charging/discharging cycles. This preliminary action ensures that the separation membrane is already in position to prevent short circuits caused by subsequent bending deformation, without requiring additional components or complex assembly steps.
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 double-layer separation membrane structure effectively prevents cracks and short circuits, enhancing the safety of secondary batteries by reducing stress and maintaining structural integrity during repeated charge/discharge cycles.
Implementation Method 1
an auxiliary separation membrane disposed between the first electrode and the first separation membrane in a center of the jelly-roll structure
Implementation Method 2
the auxiliary separation membrane extending to the center to buffer stress and prevent cracking
Data Source
AI summary
An electrode assembly includes a first electrode; a second electrode; a separation membrane interposed between the first electrode and the second electrode, in which the first electrode, the second electrode, and the separation membrane are wound together to form a jelly-roll structure; and an auxiliary separation membrane disposed between the first electrode and the separation membrane in a center of the jelly-roll structure.