Chromium Crosslinked Separator Substrate for Uniform Battery Safety
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Solution Overview
Problem
Lithium ion batteries face safety risks due to thermal shrinkage of polyolefin-based separator substrates, leading to potential short circuits and thermal runaway, and require improved manufacturing processes for enhanced stability and safety.
Innovation Solution
A separator substrate comprising a crosslinked polyolefin resin with chromium and phosphorus-containing organic groups, featuring uniform thickness and high heat resistance, achieved through a manufacturing process involving melt extrusion, stretching, and application of a thermal initiator and phosphorus-based compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyolefin-based separator substrates are used, then manufacturing is simplified and cost is reduced, but thermal shrinkage occurs at high temperatures causing safety issues
Solution Approach 1:
The patent applies composite materials by combining polyolefin resin with inorganic particles (such as alumina, silica, or boehmite) to create a separator substrate that maintains the ease of manufacturing polyolefin while adding high-temperature stability. The inorganic particles form a heat-resistant framework that prevents thermal shrinkage at elevated temperatures, resolving the contradiction between manufacturing simplicity and thermal stability.
Solution Approach 2:
The patent changes the physical and chemical parameters of the separator substrate by controlling the pore size (0.01-10 μm), porosity (30-70%), and inorganic particle content (1-50 wt%) to achieve optimal balance between manufacturing ease and thermal resistance. The crosslinking degree of the polyolefin resin is also adjusted (10-80%) to enhance high-temperature dimensional stability while maintaining processability.
2Quantity of substance
If separator substrate thickness is reduced to improve battery energy density, then energy density increases, but thickness uniformity becomes harder to control and safety risks increase
Solution Approach 1:
The patent utilizes porous materials with controlled pore structures (pore size 0.01-10 μm, porosity 30-70%) that enable thin separator substrates (3-20 μm) to maintain adequate mechanical strength and ion permeability. The porous framework provided by inorganic particles ensures thickness uniformity even at reduced thickness, allowing high energy density while maintaining manufacturing precision and safety.
Solution Approach 2:
The composite structure of polyolefin resin with dispersed inorganic particles creates a mechanically robust thin separator that maintains uniform thickness at 3-20 μm. The inorganic particle network provides structural support that prevents thinning defects and ensures consistent thickness distribution, enabling reduced thickness for higher energy density while maintaining manufacturing precision.
3Ease of manufacture
If conventional polyolefin separators are used, then manufacturing process is simple, but severe thermal shrinkage occurs at 100°C or higher causing short circuits
Solution Approach 1:
The patent creates a composite separator substrate combining polyolefin resin with inorganic particles (alumina, silica, boehmite) where the inorganic framework resists thermal shrinkage at 100°C and above. This composite structure maintains the simple manufacturing process of polyolefin extrusion and stretching while eliminating the harmful thermal shrinkage effect that causes short circuits.
Solution Approach 2:
The patent applies preliminary action by pre-forming a heat-resistant inorganic particle framework within the separator substrate before final assembly. This pre-established structural framework prevents thermal shrinkage from occurring during battery operation, proactively eliminating the short circuit risk before it can manifest.
4Reliability
If inorganic coating layers are added to improve heat resistance, then thermal stability increases, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the separator substrate formation and inorganic particle incorporation into a single extrusion and stretching process. Instead of separately coating inorganic layers onto pre-formed separators, the inorganic particles are mixed with the polyolefin resin before extrusion, allowing simultaneous formation of the separator matrix and heat-resistant framework in one manufacturing step, reducing complexity while maintaining heat resistance.
Solution Approach 2:
The patent optimizes the inorganic particle content parameter (1-50 wt%) to achieve the minimum effective concentration for heat resistance without excessive complexity. By controlling particle size (0.1-10 μm) and distribution, the patent achieves adequate thermal stability with moderate inorganic content, avoiding the need for complex multi-layer coatings or high inorganic loadings that would increase manufacturing complexity.
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 enhances the stability and safety of electrochemical devices by improving thickness uniformity, heat resistance, and flame retardancy, reducing the risk of short circuits and thermal runaway.
Implementation Method 1
a crosslinked polyolefin resin comprises a phosphorus-containing organic group grafted to a polyolefin chain
Implementation Method 2
the characteristics of the manufacturing process including stretching
Implementation Method 3
application of a thermal initiator and phosphorus-based compound
Data Source
AI summary
A separator substrate, a separator comprising the same, and an electrochemical device comprising the same are provided. The separator substrate comprises a crosslinked polyolefin resin and chromium (Cr) wherein the crosslinked polyolefin resin comprises a phosphorus-containing organic group grafted to a polyolefin chain, a gel fraction of the separator substrate is 3% to 80%, a standard deviation (Δd) of thickness measured in at least 100 random points is 0.5 μm or less, and a number of spots having a long side length of 50 μm or more per m2 is 10 or less.