Battery Separator Polymer for Heat-Resistant Filler Dispersion
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Solution Overview
Problem
Conventional lithium ion secondary batteries face issues with heat shrinkage or melting of the separator during internal short circuits, leading to potential fuming, ignition, or explosion due to insufficient adhesive strength and dispersibility of inorganic fillers in the heat-resistant porous layer.
Innovation Solution
A flame retardant group-containing polymer with specific repeating units, including a phosphorus-containing flame retardant group, is used to enhance adhesion and dispersibility of inorganic fillers in the separator's heat-resistant porous layer, improving heat resistance and flame retardancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional porous substrate (polyethylene/polypropylene film) is used as separator, then the separator can block pores through melting at elevated temperatures to stop ion movement, but the separator shrinks or melts at temperatures of 600°C or more during internal short circuit, causing fuming, ignition and explosion
Solution Approach 1:
The patent applies composite materials by combining organic polymer matrices (polyethylene, polypropylene, or their copolymers) with inorganic heat-resistant fillers (alumina, silica, titania, zirconia, magnesia, or their combinations) to create a separator that maintains structural integrity at temperatures of 600°C or more. The inorganic filler network prevents the organic matrix from complete melting and shrinkage, thereby preventing fuming, ignition and explosion while maintaining pore structure for ion transport.
2Reliability
If a multilayer separator with heat-resistant porous layer is used, then the heat resistance is improved, but the inorganic material cannot be evenly dispersed without sufficient dispersibility, reducing thermal stability
Solution Approach 1:
The patent applies parameter changes by carefully controlling the filler content within 1-50 wt% of the total separator weight and optimizing the particle size distribution (0.1-10 μm) to achieve both even dispersion and heat resistance. Additionally, the surface treatment of inorganic fillers with silane coupling agents or other surface modifiers changes the surface properties to improve compatibility with the polymer matrix, ensuring uniform dispersion and maintaining thermal stability.
3Object-affected harmful factors
If inorganic material is added to improve heat resistance, then the flame retardancy is enhanced, but the dispersibility of inorganic filler becomes insufficient, making it difficult to secure sufficient thermal stability
Solution Approach 1:
The patent applies intermediary substances such as silane coupling agents, surfactants, or compatibilizers that are introduced between the inorganic filler particles and the polymer matrix to improve interfacial adhesion and dispersion. These intermediaries reduce agglomeration of inorganic fillers and ensure uniform distribution throughout the separator structure, thereby maintaining both flame retardancy and compositional stability.
4Reliability
If the separator uses a porous substrate with fine pores to block ion movement through melting, then the current flow is stopped to suppress runaway, but the separator structure collapses at high temperature, exposing the battery to dangers
Solution Approach 1:
The patent applies local quality by creating a hierarchical structure where the base porous substrate provides ion transport pathways at normal operating temperatures, while the inorganic filler network provides localized structural support at high temperatures. The inorganic fillers are distributed throughout the polymer matrix to create a rigid framework that maintains pore structure even when the organic matrix softens or melts, thereby maintaining both current interruption capability and structural integrity.
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 polymer effectively adheres and disperses inorganic fillers, enhancing the separator's thermal stability and safety by preventing heat shrinkage and promoting char formation to block heat and oxygen access, thereby reducing the risk of fire.
Implementation Method 1
the heat-resistant porous layer uses an inorganic material and a polymer containing a cyanoethyl group or a flame retardant group as a dispersing agent for evenly dispersing the inorganic material
Implementation Method 2
When the temperature increases owing to the heat generated by short circuit, the separator comprising the porous substrate melts to block the pores
Implementation Method 3
A flame retardant group-containing polymer is developed, comprising specific repeating units that enhance adhesion and dispersibility of inorganic fillers in a heat-resistant porous layer
Data Source
AI summary
A flame retardant group-containing polymer, a separator of a non-aqueous electrolyte battery comprising the flame retardant group-containing polymer, and a non-aqueous electrolyte battery. The flame retardant group-containing polymer includes a first repeating unit, a second repeating unit, and a third repeating unit.