Composite Separator for Lithium Ion Battery
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Solution Overview
Problem
Lithium ion battery separators with thin thickness face issues such as static electricity, poor fit with electrodes, risk of short-circuit, and mechanical degradation due to high temperature, and poor adsorption of electrolyte, leading to performance degradation.
Innovation Solution
A composite separator composition comprising a blend of low and high melting point polymers, nanowires, and inorganic nanoparticle powder, coated on a base material using a phase inversion method, enhancing interface adhesion, heat resistance, and mechanical properties, and improving electrolyte adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator thickness is reduced to increase battery energy density, then the battery energy density is improved, but the mechanical strength and heat resistance of the separator deteriorate
Solution Approach 1:
The patent applies composite materials by combining polyolefin base material with ceramic particles (alumina, silica, boehmite) and binder resins to create a coating layer that enhances mechanical strength and heat resistance while maintaining thin thickness. The composite structure allows the separator to achieve improved energy density without sacrificing structural integrity.
Solution Approach 2:
The patent applies local quality by creating a coating layer with specific properties on the surface of the base material. The coating layer contains ceramic particles and binders in controlled ratios (0.1-10 parts ceramic to 1-5 parts binder) to provide localized enhancement of mechanical strength and thermal stability where needed, while the bulk remains thin for high energy density.
2Quantity of substance
If the separator thickness is reduced, then the battery energy density is improved, but the interface adhesion force between separator and electrode sheet deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the coating layer, specifically the ratio of ceramic particles to binder resins, and the molecular weight distribution of the polyolefin. These parameter adjustments optimize the balance between adhesion force and thickness, enabling thin separators to maintain strong electrode interface bonding.
3Reliability
If polyolefin microporous membrane is used, then the separator provides good electronic insulation, but the adsorption to electrolyte is poor
Solution Approach 1:
The patent applies composite materials by incorporating ceramic particles (alumina, silica, boehmite) into the polyolefin matrix. The ceramic particles provide polar surfaces that enhance electrolyte wettability and adsorption capacity, while the polyolefin base maintains electronic insulation properties. This composite approach resolves the contradiction between insulation and electrolyte affinity.
Solution Approach 2:
The patent maintains the microporous structure of the polyolefin base material while adding a coating layer with controlled porosity. The porous ceramic network in the coating layer provides additional pathways for electrolyte penetration and adsorption, enhancing ionic conductivity without compromising the electronic insulation of the base membrane.
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 composite separator improves the bonding force with electrodes, reduces the risk of short-circuit, enhances mechanical strength, and increases lithium ion conductivity, while maintaining high temperature stability and low swelling properties.
Implementation Method 1
the interface adhesion force provided by the low melting point polymer is higher than that of the high melting point polymer. The combined use of the high and low melting point polymers can improve the interface adhesion force between the composite separator and the electrode sheet
Implementation Method 2
coating and curing the slurry on the surface of the base material
Implementation Method 3
0-50 parts of an inorganic nanoparticle powder and 0-40 parts of a nanowire
Implementation Method 4
provides microporous channels for the migration of lithium ions
Implementation Method 5
the currently commonly used polyolefin microporous membrane has poor adsorption to the electrolyte, which is not conducive to the conduction of lithium ions during the charging and discharging process
Data Source
AI summary
Disclosed are a composition, a composite separator and a preparation method therefor, and a lithium ion battery. The composition includes 10-100 parts of a polymer resin, 0.5-10 parts of a polymer adhesive. 0-50 parts of an inorganic nanoparticle powder, and 0-40 parts of nanowires. The polymer resin includes a low melting point polymer and a high melting point polymer, wherein the low melting point polymer and the high melting point polymer are the same substance: the weight ratio of the low melting point polymer to the high melting point polymer is (5-90): (10-95), the melting point of the low melting point polymer is 145° C. or less, and the melting point of the high melting point polymer is in the range of 146-500° C.