Non-Uniform Separator Binding Layer for Li-Ion Battery Cycle Life
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Solution Overview
Problem
Commercial separators in lithium ion batteries face issues with adhesion between the separator and electrodes, leading to slow electrolyte transfer and premature capacity drop due to either overly strong or weak adhesion, which reduces cycle life.
Innovation Solution
A non-uniform separator binding layer with a first coating layer having higher adhesion to the electrodes than a second coating layer, optimized in terms of thickness, granularity, softening temperature, and degree of swelling, to balance adhesion and electrolyte transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a strong adhesion binding layer (oily PVDF) is used, then the interface adhesion between separator and electrode is improved, but the electrolyte transfer speed deteriorates
Solution Approach 1:
The binding layer is divided into multiple layers with different adhesion characteristics. The first binding layer (near electrode) provides strong adhesion, while the second binding layer (middle layer) provides weak adhesion to facilitate electrolyte transfer. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
Different regions of the binding layer have different adhesion properties tailored to their specific functions. The first binding layer has strong adhesion quality suitable for electrode interface, while the second binding layer has weak adhesion quality suitable for electrolyte flow channels. This local differentiation resolves the contradiction between adhesion strength and electrolyte transfer.
2Speed
If a weak adhesion binding layer (aqueous PVDF) is used, then the electrolyte transfer is improved, but the interface adhesion between separator and electrode deteriorates
Solution Approach 1:
The binding layer structure is segmented into multiple functional layers. The first binding layer (adjacent to electrode) uses strong adhesion material to ensure good interface contact, while the second binding layer (central region) uses weak adhesion material to maintain open electrolyte channels. This segmentation enables both strong adhesion and good electrolyte transfer simultaneously.
Solution Approach 2:
Different local regions of the binding layer possess different adhesion qualities optimized for their specific roles. The electrode-adjacent regions have strong adhesion quality for stable contact, while the central regions have weak adhesion quality for efficient electrolyte flow. This local quality differentiation resolves the contradiction between adhesion and electrolyte transfer.
3Ease of manufacture
If uniform adhesion is applied across the entire separator surface, then manufacturing simplicity is maintained, but cycle life deteriorates due to either excessive or insufficient adhesion in different regions
Solution Approach 1:
The binding layer is segmented into multiple zones with different adhesion properties. The first binding layer material and the second binding layer material are selected to have different adhesion strengths, allowing optimization of different regions for their specific functions. This segmentation improves cycle life by preventing both electrode detachment and lithium precipitation simultaneously.
Solution Approach 2:
Different regions of the separator are equipped with different adhesion qualities according to their functional requirements. Regions near electrodes have strong adhesion for stable contact during cycling, while central regions have weak adhesion for maintaining electrolyte flow paths. This local quality optimization resolves the contradiction between manufacturing simplicity and cycle life improvement.
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 enhances the cycle performance of lithium ion batteries by maintaining good adhesion while ensuring efficient electrolyte transfer, reducing lithium precipitation and extending battery life.
Implementation Method 1
the adhesive force between the first coating layer and the positive electrode or the negative electrode is greater than the adhesive force between the second coating layer and the positive electrode or the negative electrode
Implementation Method 2
the separator comprising a porous substrate
Data Source
AI summary
The present application provides an electrochemical device. The electrochemical device, comprising: a positive electrode; a negative electrode; and the separator, disposed between the positive electrode and the negative electrode, wherein the separator comprising a porous substrate, a first coating layer and a second coating layer, the first coating layer and the second coating layer are on a surface of the porous substrate, the first coating layer is disposed on at least one side of the second coating layer, the first coating layer includes a first binder, and the second coating layer includes a second binder, the adhesive force between the first coating layer and the positive electrode or the negative electrode is greater than the adhesive force between the second coating layer and the positive electrode or the negative electrode. The electrochemical device provided by the present application can further improve the cycle performance of the electrochemical device.