Bipolar Electrode Warping Control via Density Adjusting Additive
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Solution Overview
Problem
Bipolar secondary batteries face warping issues due to differential stresses between active material layers during the manufacturing process, which can lead to reduced capacity retention and durability, especially in high-energy density applications like electric vehicles.
Innovation Solution
Incorporating a density adjusting additive with higher compressive strength than the negative electrode active material layer helps to mitigate stress differences between the positive and negative electrode layers, ensuring optimal thickness and reducing warping during the pressing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different active material layers are arranged at the front and back of a collector and pressed simultaneously, then the bipolar electrode can be manufactured efficiently, but differential stresses occur causing the bipolar electrode to warp
Solution Approach 1:
The patent applies local quality by adding a density adjusting additive specifically to the second active material layer (negative electrode) that has lower compressive strength. This creates a localized modification in that specific layer to balance the compressive strength between the front and back sides of the collector, thereby preventing differential stress and warping while maintaining simultaneous pressing efficiency.
2Quantity of substance
If the negative electrode active material layer is pressed to high density, then filling density is improved, but the layer becomes too thin and warping occurs
Solution Approach 1:
The patent uses composite materials by incorporating a density adjusting additive into the second active material layer. This additive has higher compressive strength than the active material itself, creating a composite structure that maintains layer thickness and prevents warping while allowing high filling density to be achieved through pressing.
Data Source
AI summary
A bipolar electrode is composed of a first active material layer which is, for example, a positive electrode active material layer formed to include a first active material on one side of a collector, and a second active material layer which is, for example, a negative electrode active material layer formed to include a second active material with less compressive strength than that of the first active material on the other side of the collector. Then, a density adjusting additive which is an additive material with larger compressive strength than that of the second active material is included in the second active material layer.