Bipolar Electrode Current Distribution Relaxation Layer
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Solution Overview
Problem
Bipolar lithium-ion secondary batteries face issues with output power density and energy density due to electrical resistance in external connections, leading to electrode deterioration and reduced battery life.
Innovation Solution
A bipolar electrode with a current distribution relaxation layer having a lower volume resistivity than the active material layer is introduced, allowing for improved electric current flow and reducing variability in electric charge distribution, thereby suppressing electrode deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a resinous collector with added electrically conductive material is used, then the collector is lightweight and excellent in electrical conductivity, but the surface direction resistivity is high causing variability in electric current distribution
Solution Approach 1:
The invention applies a current distribution relaxation layer with different electrical properties specifically on the surface of the active material layer, creating local quality variation. This layer has higher electrical conductivity than the underlying active material layer,针对性地 addressing the surface resistivity issue without changing the bulk collector properties.
Solution Approach 2:
The invention uses a composite structure combining the resinous collector with a current distribution relaxation layer. The relaxation layer is formed by coating a slurry containing conductive particles (such as carbon black or metal particles) and binder onto the active material layer surface, creating a composite material system that addresses both lightweight requirements and current distribution uniformity.
2Device complexity
If batteries are connected through external electrical connection, then the connection is simple, but the output power is decreased due to electrical resistance
Solution Approach 1:
The invention merges the electrical connection function into the battery structure itself by using a bipolar electrode where the collector serves as both the current collector and the connection medium between positive and negative active material layers. This eliminates external electrical connections and reduces overall electrical resistance in the system.
3Weight of moving object
If a resinous collector is used, then the collector is lightweight, but the high surface resistivity accelerates electrode deterioration
Solution Approach 1:
The current distribution relaxation layer is applied locally on the surface of the active material layer to address the high surface resistivity issue. This layer has higher electrical conductivity that prevents current concentration and hot spot formation, thereby protecting the electrode from accelerated deterioration while maintaining the lightweight resinous collector structure.
Solution Approach 2:
The current distribution relaxation layer acts as a protective cushioning layer that prevents harmful current distribution patterns before they can cause electrode deterioration. By providing a low-resistance pathway on the surface, it preemptively protects the active material layer from overheating and localized overcharge/discharge conditions.
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 implementation of the current distribution relaxation layer enhances electrode durability, reduces local overcharge and discharge issues, and extends battery life by facilitating smoother electric current distribution.
Implementation Method 1
a current distribution relaxation layer having a volume resistivity lower than that of an active material layer is disposed on the side of the active material layer
Data Source
AI summary
A bipolar electrode includes a collector; a positive electrode active material layer disposed on one surface of the collector; and a negative electrode active material layer disposed on the other surface of the collector. The quotient of the volume resistance of the collector and that of the positive and negative electrode active material layers is between 10−3 and 104. The bipolar electrode further includes a current distribution relaxation layer having a volume resistivity lower than that of either the positive electrode active material layer or the negative electrode active material layer. At least one active material layer having a volume resistivity larger than that of the current distribution relaxation layer is disposed between the current distribution relaxation layer and the collector.