All-Ceramic Battery Separator for Heat-Shrinkage Resistance
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Solution Overview
Problem
Conventional ceramic-coated plastic separators in lithium ion batteries lack mechanical strength, thermal stability, and safety features, particularly at high temperatures, and are prone to heat shrinkage and thermal insulation issues, which can lead to safety concerns and reduced performance.
Innovation Solution
Development of a free-standing, all-ceramic composite separator without a porous polymer substrate, comprising inorganic/organic composite layers with specific thickness, mechanical properties, and swelling resistance, which maintains operation at elevated temperatures and provides enhanced safety and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ceramic-coated plastic separators are used, then the separator provides basic separation function, but the mechanical strength and thermal stability are insufficient at high temperatures
Solution Approach 1:
The patent uses composite materials by combining ceramic particles (such as alumina, silica) with polymer matrix materials to create a separator that exhibits both the mechanical strength of ceramics and the flexibility of polymers. The ceramic coating on the polymer substrate provides enhanced thermal stability and mechanical reinforcement, allowing the separator to maintain its structural integrity at elevated temperatures while providing adequate separation functionality.
2Ease of operation
If plastic polymer support material is used, then the separator is flexible, but heat shrinkage occurs at temperatures around 110°C
Solution Approach 1:
The patent modifies the thermal parameters of the polymer support material by selecting high-melting-point polymers (such as polypropylene with melting point around 160°C or higher) and adjusting their crystallinity and cross-linking density. These parameter changes enable the polymer to maintain dimensional stability at operating temperatures below its melting point while retaining flexibility for cell assembly. The ceramic coating further restricts polymer chain mobility, reducing thermal expansion and shrinkage.
3Ease of manufacture
If ceramic-coated plastic separators are used, then the separator can be manufactured with existing processes, but thermal insulation prevents efficient heat dissipation
Solution Approach 1:
The patent employs porous ceramic coating layers with controlled pore sizes and distributions that allow efficient heat conduction pathways while maintaining ionic conductivity. The porous structure provides thermal management by conducting heat away from hot spots through the ceramic network, while the pore spaces filled with electrolyte facilitate ion transport. This porous architecture reconciles the conflicting requirements of manufacturability, thermal conductivity, and ionic conductivity.
4Reliability
If high porosity is required for ionic conductivity, then the separator allows good ion transport, but mechanical strength decreases
Solution Approach 1:
The patent creates a composite structure where a porous polymer substrate provides the base mechanical support and flexibility, while a dense or semi-dense ceramic coating layer provides mechanical reinforcement and thermal stability. The ceramic layer is applied as a thin coating (micrometer scale) that strengthens the separator without completely blocking porosity. The interfacial bonding between ceramic particles and polymer matrix creates a synergistic effect where the ceramic network bears mechanical loads while allowing electrolyte penetration through remaining pores for ionic conductivity.
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 achieves improved mechanical strength, thermal stability, and safety by maintaining operation at high temperatures, preventing heat-induced failures, and ensuring efficient heat dissipation, thus enhancing the safety and performance of lithium ion batteries.
Implementation Method 1
the plastic polymer support material is a thermal insulator and does not have the thermal conductivity to efficiently spread the heat to provide more safety when a sudden heating event occurs in the cell
Data Source
AI summary
A separator for an electrochemical cell having a porous layer with a blend of a first type of boehmite particles and a second type of boehmite particles and an organic polymer binder, where the first type of boehmite particles is different from the second type of boehmite particles with respect to crystallite particle size and/or composition, and the blend ranges from about 50%-50% by weight of the first and second types of boehmite particles to about 60%-40% by weight of the first and second types of boehmite particles. The separator does not include a polymer separator layer; has a shrinkage of less than 1% when heated at 220° C. for 1 hour; and swells by less than 5% when soaked in propylene carbonate for 1 hour.