Wound Li-Ion Cell Separator Bonding for Corner Lithium Control
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Solution Overview
Problem
Existing separators in lithium-ion batteries struggle to balance cycling performance and safety performance, particularly due to lithium precipitation and dendrite growth at the corners of the electrochemical apparatus.
Innovation Solution
The electrochemical apparatus is designed with a specific arrangement of separators and electrode plates, where the bonding forces between the active material layers and coating layers are regulated to alleviate compressive stresses at the corners, increasing interfacial gaps and enhancing electrolyte infiltration, thereby reducing lithium precipitation and dendrite growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing separators are used in lithium-ion batteries, then the battery structure is simple and easy to manufacture, but lithium precipitation and dendrite growth occur at the corners, reducing safety performance and cycling performance
Solution Approach 1:
The separator is divided into multiple coating layers (first coating layer, second coating layer, third coating layer, fourth coating layer) with different bonding forces applied at different locations. This segmentation allows different regions of the separator to have optimized properties for their specific functions, preventing lithium precipitation at corners while maintaining overall structural integrity.
Solution Approach 2:
Different coating layers are applied with specific bonding force characteristics at different locations of the separator. The first and second coating layers have different bonding forces than the third and fourth coating layers, creating local quality variations that address the specific problem of corner lithium precipitation while maintaining appropriate properties in other regions.
2Reliability
If uniform bonding force is applied between separator and electrode plate, then the separator structure is simple, but compressive stresses concentrate at the corners causing lithium precipitation
Solution Approach 1:
The bonding force distribution is made asymmetric with different bonding forces at different locations of the separator-electrode interface. The first coating layer has a first bonding force and the second coating layer has a second bonding force, creating an asymmetric stress distribution that prevents compressive stress concentration at the corners, thereby preventing lithium precipitation and improving cycling performance.
3Stability of the object's composition
If the bonding force between negative electrode plate and first separator is strong, then the interface stability is good, but compressive stresses at corners increase leading to fracturing bridge phenomenon
Solution Approach 1:
The bonding force parameter is changed at different locations of the separator. The first coating layer is designed with a specific bonding force parameter that is optimized to prevent lithium precipitation at corners, while the second coating layer has a different bonding force parameter. This parameter variation allows the interface to maintain stability in most regions while reducing compressive stresses at critical corner regions.
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
This design improves safety and cycling performance by reducing the risk of fracturing bridge phenomena and lithium precipitation, leading to enhanced mechanical stability and prolonged battery life.
Implementation Method 1
A bonding force between the first active material layer and the second coating layer is less than a bonding force between the second active material layer and the fourth coating layer
Implementation Method 2
interfacial gap at the corners are increased, which facilitates infiltration of more electrolyte at the corners
Data Source
AI summary
An electrochemical apparatus formed by stacking and then winding a first separator, a negative electrode plate, a second separator, and a positive electrode plate. The negative electrode plate includes a negative electrode current collector, a first active material layer and a second active material layer. In a winding direction, a length of the first active material layer is greater than a length of the second active material layer. The first separator comprises a first substrate layer, a first coating layer and a second coating layer. The second separator comprises a second substrate layer, a third coating layer and a fourth coating layer. A bonding force between a first active material layer and second coating layer is less than a bonding force between a second active material layer and a fourth coating layer.