Hydrotalcite Polyolefin Separators for Heat Stability and Acid Scavenging
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Solution Overview
Problem
Existing lithium-ion and rechargeable Li metal battery separators lack both high temperature dimensional stability and acid-scavenging capabilities, which are crucial for improving safety and performance.
Innovation Solution
Incorporation of synthetic hydrotalcite particles within the polymer matrix or as a surface coating in microporous polyolefin membranes, providing both high temperature dimensional stability and acid-scavenging capabilities through an anion exchange mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene separator is used to achieve shutdown function at 130°C, then shutdown capability is improved, but high temperature dimensional stability deteriorates (separator shrinks above melting point)
Solution Approach 1:
The patent combines polyethylene with ceramic particles (alumina, boehmite, silica) to create a composite separator structure. The polyethylene matrix provides shutdown capability at 130°C, while the embedded ceramic particles maintain dimensional stability at temperatures above the polyethylene melting point, preventing excessive shrinkage and electrode shorting.
2Stability of the object's composition
If heat-resistant ceramic coating is applied to prevent oxidation and minimize shrinkage, then high temperature dimensional stability is improved, but acid-scavenging capability deteriorates (no acid-scavenging function)
Solution Approach 1:
The patent uses synthetic hydrotalcite particles that perform multiple functions simultaneously: (1) they provide high temperature dimensional stability through their heat-resistant ceramic structure, (2) they offer acid-scavenging capability through anion exchange mechanisms that neutralize HF and other acids, and (3) they maintain porosity for ion transport. This multi-functional particle replaces the need for separate heat-resistant coating and acid-scavenging additives.
3Stability of the object's composition
If inorganic particles are incorporated to provide high temperature stability, then dimensional stability is improved, but pore structure may collapse at high temperatures
Solution Approach 1:
The patent creates a microporous composite structure where ceramic particles are distributed within the polyethylene matrix while maintaining interconnected pores. The pores remain open at temperatures below the shutdown point, allowing efficient ion transport. At shutdown temperature, the polyethylene melts and pores close to stop ion flow, while the ceramic particles prevent excessive shrinkage and maintain 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 membranes exhibit low shrinkage at elevated temperatures and effectively scavenge acids, enhancing the safety and cycle life of energy storage devices like lithium-ion batteries.
Implementation Method 1
exhibit the ability to scavenge acids through an anion exchange mechanism
Implementation Method 2
in-plane high temperature dimensional stability (i.e., low shrinkage (e.g., less than 10% shrinkage)) at temperatures both above and below the melting point of the polymer matrix
Data Source
AI summary
The present disclosure relates to the formation of a freestanding. microporous polyolefin membrane that exhibits both high temperature dimensional stability and acid-scavenging capability. Such membranes can include hydrotalcite particles that can contribute to high temperature dimensional stability and acid scavenging. Such membranes can be used to improve the manufacturability, performance (e.g., cycle life), and safety of energy storage devices such as lithium-ion batteries.