Lithium Battery Separator with Destroyed Capsule Layer
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Solution Overview
Problem
Lithium secondary batteries face challenges in introducing a non-aqueous electrolyte solution without damaging the battery case and are prone to short circuits due to thermal shrinkage of porous polyolefin substrates, which can lead to overheating and explosion risks.
Innovation Solution
A lithium secondary battery design featuring a separator with a layer of destroyed capsules containing a binder polymer and inorganic particles, which are impregnated with a non-aqueous electrolyte solution, allowing for thermocompression to distribute the electrolyte uniformly and enhance mechanical strength, preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a non-aqueous electrolyte solution is introduced into the battery case using conventional methods, then the electrolyte can be provided to the battery, but the battery case must be cut and then closed, causing inconvenience and potential damage to the battery case materials
Solution Approach 1:
The non-aqueous electrolyte solution is pre-impregnated into the porous substrate before the electrode assembly is inserted into the battery case. This preliminary action eliminates the need for a separate electrolyte introduction step that would require cutting and closing the battery case, thereby preserving case integrity while ensuring electrolyte availability.
Solution Approach 2:
The electrolyte impregnation process is merged with the electrode assembly preparation process. The electrolyte solution is impregnated into the porous substrate during assembly formation, combining what were previously separate operations (electrode assembly preparation and electrolyte introduction) into one integrated process.
2Object-generated harmful factors
If porous polyolefin substrates are used as separators, then the separator can be manufactured with appropriate porosity, but the substrate undergoes severe thermal shrinkage at temperatures of 100°C or higher, causing short circuit between cathode and anode
Solution Approach 1:
The separator is constructed as a composite material consisting of a porous polyolefin substrate combined with a heat-resistant inorganic material layer. This composite structure maintains the porosity needed for ion transport while the inorganic component provides thermal stability and prevents shrinkage-induced short circuits at elevated temperatures.
Solution Approach 2:
The thermal properties of the separator are modified by incorporating heat-resistant inorganic materials. This parameter change transforms the separator from a material that shrinks severely above 100°C to one that maintains dimensional stability at higher temperatures, thereby preventing short circuits while retaining necessary porosity.
3Strength
If the separator is strengthened to prevent short circuits, then thermal runaway risk is reduced, but the mechanical property enhancement may affect the flexibility and ion transport capability of the separator
Solution Approach 1:
The separator uses a composite structure where heat-resistant inorganic materials are dispersed within or on the porous polyolefin substrate. This composite approach enhances mechanical strength and thermal stability while the porous architecture is preserved to maintain ion transport capability, balancing strength and functionality.
Solution Approach 2:
The heat-resistant inorganic materials are strategically positioned within the separator structure to provide localized reinforcement and thermal stability. This local quality enhancement strengthens the separator at critical regions without uniformly compromising the overall porosity and ion transport pathways.
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
This design simplifies the battery preparation process by eliminating the need for a separate electrolyte introduction step, improves electrolyte wetting, and strengthens the separator to prevent short circuits and thermal runaway.
Implementation Method 1
binder polymer from films of the destroyed capsules bonds the layer to the porous substrate
Implementation Method 2
the non-aqueous electrolyte solution may be impregnated in the electrode assembly... bringing the electrode assembly into thermocompression
Implementation Method 3
the inorganic particles are preferably selected from the group consisting of inorganic particles having a dielectric constant of 5 or higher, inorganic particles having the ability to transport lithium ions
Implementation Method 4
the layer further comprises pores and micropores, wherein the micropores comprise interstitial volumes present between inorganic particles, and wherein the pores comprise interstitial volumes present between destroyed capsules
Data Source
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AI summary
The present invention provides a lithium secondary battery and the preparation thereof, more specifically a lithium secondary battery comprising an electrode assembly having a cathode, an anode, and a separator interposed between the cathode and the anode; and a non-aqueous electrolyte solution impregnated in the electrode assembly, wherein the separator further comprises a layer having a plurality of destroyed capsules dispersed therein, the layer being formed on at least one surface of the separator coming into contact with the cathode and the anode, and the destroyed capsules has a film formed from a binder polymer and inorganic particles dispersed therebetween. The lithium secondary battery of the present invention can be prepared without the separate introducing process of a non-aqueous electrolyte solution, and has a separator exhibiting improved mechanical property and safety.