Solution-Treated Polyolefin Separator Wettability
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Solution Overview
Problem
Commercially available separators in lithium-ion batteries exhibit low wettability with electrolytes, leading to slow fill times and increased manufacturing overhead, which existing alternatives like ceramic coatings or alternative materials have not adequately addressed.
Innovation Solution
A solution-treated polyolefin separator is used, with a treatment solution of either acid or base having a pH of at most 2 or at least 12, applied for a specified duration at controlled temperatures, resulting in increased ionic functional groups and improved wettability, allowing the electrolyte to wet the separator effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional polyolefin separator is used, then the separator structure is simple and manufacturing is easy, but the wettability with electrolyte is low resulting in slow fill times
Solution Approach 1:
The patent applies parameter changes by treating the polyolefin separator with acid or base solutions to modify its surface chemical properties. This treatment introduces ionic functional groups that dramatically improve electrolyte wettability, reducing contact angle from typical high values to below 15 degrees, thereby accelerating electrolyte fill time without changing the fundamental separator structure
Solution Approach 2:
The patent uses acid or base solution as an intermediary substance to mediate between the polyolefin separator and the electrolyte. The treatment solution acts as a mediator that modifies the separator surface to enable better interaction with the electrolyte, improving wettability without requiring direct modification of the electrolyte composition
2Loss of time
If the separator wettability is improved through treatment, then electrolyte fill time is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by treating the separator with acid or base solution before battery assembly. This pre-treatment modifies the separator surface in advance to ensure optimal electrolyte wettability during battery manufacturing, reducing fill time and eliminating the need for complex in-line wettability control during assembly
Solution Approach 2:
The patent uses inexpensive acid or base solutions as disposable treatment media. These solutions can be applied in concentrated forms and discarded after use, providing a cost-effective method to improve separator wettability without requiring expensive equipment or complex process control systems
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-treated separator significantly enhances wettability, reducing ionic resistance and speeding up the electrolyte filling process, thereby improving battery cycle life and manufacturing efficiency.
Implementation Method 1
The solution-treated polyolefin separator has been treated with a treatment solution having a pH of either at most 2 or at least 12
Implementation Method 2
The contact angle of the electrolyte including the organic solvent upon the separator is 0 to 15 degrees. The surface of the solution-treated polyolefin layer may be substantially completely wetted when in contact with the electrolyte
Implementation Method 3
The separator prevents physical contact of the two electrodes (e.g., internal short circuits), while still allowing for rapid transportation of ionic charge carriers between the cathode and anode
Data Source
AI summary
In at least one embodiment, a rechargeable battery is provided comprising an electrolyte including an organic solvent and a solution-treated polyolefin separator. A contact angle of the electrolyte including the organic solvent upon the separator may be from 0 to 15 degrees. In one embodiment, the solution-treated polyolefin layer has an increased concentration of ionic functional groups at its surface compared to an untreated polyolefin layer. In another embodiment, the solution-treated polyolefin separator has been treated with a treatment solution having a pH of either at most 2 or at least 12. The separator may be treated with an acid or base solution for at least 30 seconds. The solution-treated separator may exhibit improved wetting with an electrolyte compared to an untreated separator.