Composite Coated Battery Separator With Porous Microsphere Bonding
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Solution Overview
Problem
Current alumina-coated separators in lithium batteries exhibit poor bonding performance with cathode and anode sheets, leading to loose fitting and reduced lithium-ion transmission channels, affecting battery performance.
Innovation Solution
A composite coating separator is prepared by mixing inorganic powder, hollow latex microsphere emulsion, binder, and solvent to form a slurry with controlled viscosity and density, which is applied to a base film, allowing hollow microspheres to protrude and bond with electrode sheets under hot-press conditions, enhancing mechanical strength and forming stable pores for electrolyte accommodation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an adhesive coating is added to the alumina layer to improve bonding performance, then bonding performance between separator and electrode sheets is improved, but the coverage rate of PVDF increases and pores are blocked, reducing lithium-ion transmission channels
Solution Approach 1:
The patent uses hollow latex microspheres as a porous filling material in the adhesive coating layer. These microspheres create a three-dimensional porous structure that maintains high porosity (40-60%) while providing strong bonding. The hollow structure of the microspheres allows lithium ions to transmit through the coating without being blocked by solid PVDF material, thus resolving the contradiction between bonding performance and lithium-ion transmission.
Solution Approach 2:
The patent creates a composite adhesive coating by combining PVDF binder with hollow latex microspheres. This composite structure leverages the adhesive properties of PVDF while the hollow microspheres provide porosity and prevent pore blockage. The synergistic combination allows the coating to achieve both strong bonding performance and maintained lithium-ion transmission channels.
2Manufacturing precision
If multiple coating operations are performed to achieve complete coverage, then coating completeness is improved, but production efficiency is reduced
Solution Approach 1:
The patent optimizes the viscosity parameter of the slurry to 80-150 mPa·s, which is lower than conventional slurries. This viscosity adjustment, combined with the hollow microspheres' properties, enables the slurry to spread uniformly and form a complete coating in a single application. The controlled viscosity prevents dripping while ensuring full coverage, eliminating the need for multiple coating operations and thereby improving production efficiency.
3Strength
If the density of hollow microspheres is increased to improve bonding strength, then bonding performance is improved, but the ability of microspheres to protrude and form physical bonds under hot-press conditions is reduced
Solution Approach 1:
The patent precisely controls the density of hollow microspheres to be 0.8-0.9 g/cm³, which is slightly lower than the density of the slurry matrix. This density parameter optimization allows the microspheres to float to the surface during drying and form protrusions. Under hot-press conditions (80-120°C), these protruding microspheres can deform and form physical bonds with electrode sheets, achieving both bonding strength and hot-press capability.
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 method improves bonding uniformity and mechanical strength, increases electrolyte wetting, and provides a buffer space for anode expansion, thereby enhancing lithium battery performance and cycle stability.
Implementation Method 1
A porous coating layer is formed on the surface of the base film... the porous coating layer not only improves the wetting performance of the electrolyte on the separator but also provides a buffer space for the expansion of the anode sheet
Implementation Method 2
applying the mixed slurry to a surface of a base film and drying the mixed slurry on the base film
Data Source
AI summary
A method for preparing a composite coating separator is disclosed. The method includes: mixing raw materials including an inorganic powder, a hollow latex microsphere emulsion, a binder, and a solvent to obtain a mixed slurry; applying the mixed slurry to a surface of a base film, and drying the mixed slurry on the surface of the base film to obtain the composite coating separator. A mass ratio of the inorganic powder in the mixed slurry is 20%-35%, and a mass ratio of the hollow latex microsphere emulsion in the mixed slurry is 5%-10%. A viscosity of the mixed slurry is 100 mPa·s-120 mPa·s. The hollow latex microsphere emulsion includes hollow microspheres, and a density of the hollow microspheres is 0.8 g/cm3-0.9 g/cm3.