Porous Separator Coating for Uniform Battery Packaging
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Solution Overview
Problem
Lithium-ion battery separators exhibit poor thickness consistency due to inadequate coating methods, leading to packaging performance issues, such as gelation phenomena and increased costs, particularly with the use of PVDF-HFP coatings which dissolve at high temperatures and affect lithium ion transport.
Innovation Solution
A separator with a porous substrate and a polymer coating having a specific thickness covariance value (COV) of 0.01 to 0.02, utilizing polymers like polyacrylamide or PVDF-HFP with controlled mass percentage and swelling degree to ensure adhesion and prevent gelation, while maintaining lithium ion transport efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If PVDF-HFP coating is used to enhance kinetic performance, then lithium ion transport is improved, but gelation phenomenon occurs at high temperatures affecting packaging performance
Solution Approach 1:
The patent changes the chemical composition parameters of the coating material by replacing PVDF-HFP with polyacrylonitrile (PAN) or its derivatives. PAN has different thermal stability characteristics that prevent gelation at high temperatures while maintaining lithium ion conductivity, thus resolving the contradiction between transport performance and thermal reliability
Solution Approach 2:
The patent uses composite coating structures where PAN-based coatings are applied on porous substrates. This composite approach combines the high ion conductivity of the polymer coating with the structural stability of the porous substrate, achieving both fast lithium ion transport and high-temperature stability without gelation
2Ease of manufacture
If spraying method is used for coating separator, then coating process is simple, but thickness consistency is poor affecting packaging performance
Solution Approach 1:
The patent replaces the mechanical spraying method with a dip-coating or slot-die coating method. These alternative coating techniques provide better control over coating thickness and uniformity while maintaining process simplicity, thus resolving the contradiction between ease of manufacture and manufacturing precision
Solution Approach 2:
The patent optimizes coating parameters such as coating speed, dip rate, and drying conditions to achieve uniform thickness. By carefully controlling these parameters, the coating process achieves both simplicity and high thickness consistency, eliminating the defect of poor uniformity associated with spraying
3Strength
If PVDF-HFP with high mass percentage is used to ensure adhesion, then coating adhesion is improved, but cost increases and gelation occurs
Solution Approach 1:
The patent replaces expensive PVDF-HFP material with more cost-effective PAN-based materials. PAN is generally less expensive than PVDF-HFP while providing adequate adhesion performance and superior thermal stability, thus reducing material cost without sacrificing adhesion
Solution Approach 2:
The patent optimizes the mass percentage of polymer in the coating to achieve adequate adhesion with minimal material usage. By finding the optimal concentration range, the patent reduces the amount of expensive polymer needed while maintaining sufficient adhesion strength, thereby lowering overall production cost
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 achieves improved thickness consistency and packaging performance of lithium-ion batteries, reducing gelation and lithium precipitation, and lowering production costs by using a polymer coating with optimized properties.
Implementation Method 1
a swelling degree of the polymer in a test electrolyte is 40% to 170%
Implementation Method 2
the porous substrate (pore size 10 nm to 80 nm) and the porous coating (polymer coating) both have a pore structure
Data Source
AI summary
A separator includes a porous substrate and a porous coating disposed on at least one surface of the porous substrate, where the porous coating includes a polymer and a thickness covariance value of the separator is 0.01 to 0.02. The separator provided has good thickness consistency, which is conducive to improving the packaging performance of the electrochemical device, and the resulting electronic device has a longer service life and good usage performance.