Bent Electrode Assembly Coating for Ion Migration Control
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Solution Overview
Problem
Secondary batteries face safety concerns due to the reduction of active ions to simple metals in bend regions during charging, leading to irreversible consumption and reduced cycle life, which compromises safety and performance.
Innovation Solution
An electrode assembly with a positive electrode plate featuring a polymer coating layer on bend portions, reducing ionic conductivity and obstructing active ion migration, thereby preventing the reduction of active ions to simple metals, while maintaining energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the positive electrode plate is bent during electrode assembly formation, then the electrode assembly can be formed into a compact structure, but active ions are reduced to simple metals in the bend region causing safety issues
Solution Approach 1:
The patent applies a polymer coating layer specifically to the positive active material in the bend region of the positive electrode plate, creating local quality differentiation. This coating layer has different properties (lower ionic conductivity) compared to the uncoated regions, allowing the bend area to have reduced ionic conductivity to prevent active ion reduction while other regions maintain normal ion transport for battery operation.
Solution Approach 2:
The polymer coating layer acts as an intermediary between the positive active material and the electrolyte/active ions. It mediates the ion transport process by selectively obstructing active ion migration in the bend region, preventing the harmful reduction reaction while allowing the electrode structure to maintain its compact bent shape.
2Reliability
If a polymer coating layer is applied to the positive active material in the bend region to reduce ionic conductivity, then safety performance is improved, but energy density is reduced
Solution Approach 1:
The polymer coating is applied locally only to the bend region rather than the entire positive electrode plate. This localized application ensures that the coating's ion-blocking effect is confined to where it is needed for safety (the bend region with high reduction probability), while the majority of the electrode area remains uncoated and maintains full energy storage capability.
Solution Approach 2:
The patent applies partial coating coverage rather than complete coverage of the positive active material. By coating only the bend region and leaving other regions uncoated, the solution achieves sufficient safety improvement without excessively reducing the overall energy density of the battery.
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 significantly enhances safety performance by reducing the probability of active ions being reduced to simple metals, thereby improving the overall safety and performance of the secondary battery without excessive weight increase.
Implementation Method 1
At least a part of the positive active material of the first bend portion includes a polymer coating layer capable of obstructing migration of active ions
Data Source
AI summary
An electrode assembly includes a positive electrode plate containing a positive active material and a negative electrode plate. The positive electrode plate includes a positive bend portion and a positive flat straight portion connected to the positive bend portion. At least a part of the positive active material of the positive bend portion includes a polymer coating layer capable of obstructing migration of active ions. A ratio of an ionic conductivity λ1 of the first bend portion to an ionic conductivity λ2 of the positive flat straight portion satisfies 0 ≤λ1/λ2< 1.