Battery Separator Coating for Heat Resistance and Ion Transport
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in achieving good safety performance while maintaining other performance aspects such as low impedance and electrolyte infiltration, leading to potential safety incidents due to separator damage.
Innovation Solution
A separator is designed with a coating comprising inorganic particles, first and second organic particles, and an organic-inorganic hybrid composite compound, where the organic particles form bulges and are embedded between inorganic and hybrid particles, bonded by a first binder with specific linear copolymers, enhancing adhesion and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a coating is applied on the separator substrate to improve safety, then heat resistance is improved, but impedance increases and ion transmission is hindered
Solution Approach 1:
The coating layer is constructed as a composite material system comprising inorganic particles (alumina, silica), organic particles (fluorinated polymer, polyacrylonitrile), and binder resin, creating a multi-phase structure that simultaneously provides thermal stability through inorganic components and ion conductivity through organic matrix and pore structures
Solution Approach 2:
The coating layer is designed with controlled porosity (30-70% void fraction) and interconnected pore structures with specific pore sizes (0.1-10 μm), allowing efficient ion transport pathways while maintaining thermal shutdown functionality and preventing complete pore blockage that would hinder ion transmission
2Strength
If the separator coating is made denser to improve adhesion, then bonding strength improves, but electrolyte infiltration is reduced
Solution Approach 1:
The coating structure exhibits spatial heterogeneity with different regions serving different functions: surface regions provide adhesion and mechanical strength, while internal porous regions facilitate electrolyte infiltration and ion transport, achieving both strong bonding and good electrolyte wettability simultaneously
Solution Approach 2:
Binder resins with specific functional groups (carboxyl, hydroxyl, amine) act as intermediaries that chemically bond to both the substrate and particle surfaces, creating strong interfacial adhesion while maintaining pore connectivity for electrolyte access
3Duration of action of stationary object
If organic particles are added to improve adhesion and ion conduction, then cycle performance improves, but thermal stability deteriorates
Solution Approach 1:
The coating combines thermally stable inorganic particles (alumina with Tg > 1000°C, silica) as the thermal backbone with organic particles and binder providing ion conductivity and adhesion, creating a composite where inorganic components prevent thermal runaway while organic components enable electrochemical functionality
Solution Approach 2:
The organic particles are selected with specific glass transition temperatures (Tg between -50°C to 50°C) and thermal decomposition temperatures (>200°C) to balance flexibility for ion transport during cycling with sufficient thermal stability to maintain structural integrity at battery operating temperatures
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 separator provides improved heat resistance, electrolyte infiltration, and ion transmission, resulting in enhanced safety and cycle performance of the battery.
Implementation Method 1
the coating has good affinity with an electrolytic solution, has good infiltration performance of the electrolytic solution
Implementation Method 2
the separator exhibits enhanced heat resistance
Data Source
AI summary
The present application provides a separator, which may include a substrate and a coating provided on at least one surface of the substrate, the coating including inorganic particles, first and second organic particles, organic-inorganic hybrid composite compound particles, and a first binder; where the first organic particles and the second organic particles may be embedded in the inorganic particles and the organic-inorganic hybrid composite compound particles and form bulges on a surface of the coating; the first organic particles and the second organic particles each may be independently one or more polymers containing one or more groups selected from: halogen, a phenyl group, an epoxy group, a cyano group, an ester group, an amide group, a hydroxyl group, a carboxyl group, a sulfonyl ester group, and a pyrrolidone group; and the first binder may include one or more linear copolymers containing a hydroxyl group and a carboxylate moiety.