Lithium Battery Separator with Aromatic Polyamide Layer for Heat Suppression
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Solution Overview
Problem
Lithium secondary batteries face challenges in suppressing heat generation during abnormal conditions, particularly when lithium metal deposits on the negative electrode current collector, leading to increased temperature due to reactions with oxygen gas released from the positive electrode.
Innovation Solution
A lithium secondary battery design incorporating a separator with a substrate, a first layer containing lithium phosphate particles, and a second layer composed of aromatic polyamide, aromatic polyimide, or aromatic polyamide-imide polymers, which enhances heat suppression by reducing lithium reactivity and providing insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator with shutdown function is used, then ion conduction is blocked when abnormal heat occurs, but the separator cannot effectively suppress heat generation in lithium metal depositing batteries
Solution Approach 1:
The separator is constructed as a composite structure with a polyolefin substrate layer and an aromatic polyamide coating layer. The aromatic polyamide layer provides superior thermal stability and heat suppression capability compared to conventional single-material separators, effectively addressing the insufficient heat suppression in lithium metal batteries while maintaining the shutdown function of the polyolefin substrate.
Solution Approach 2:
The invention changes the thermal parameters of the separator by introducing aromatic polyamide material with higher decomposition temperature and thermal stability. This parameter change enables the separator to maintain structural integrity and continue blocking ion conduction at elevated temperatures, preventing thermal runaway in lithium metal depositing batteries.
2Quantity of substance
If lithium metal is used as negative electrode active material, then battery capacity is improved, but reactivity with oxygen gas increases leading to heat generation
Solution Approach 1:
The aromatic polyamide coating layer acts as an intermediary barrier between the lithium metal and oxygen gas. This intermediate layer reduces the direct reactivity between lithium metal and oxygen, suppressing the exothermic reactions that would otherwise generate excessive heat, while still allowing ion conduction during normal operation.
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 described separator structure effectively suppresses temperature increases during abnormal conditions by reducing lithium reactivity and thermal shrinkage, thereby improving the safety and performance of lithium secondary batteries.
Implementation Method 1
the first layer includes particles of phosphate containing lithium... reducing lithium reactivity
Implementation Method 2
the second layer includes a polymer and/or inorganic particles other than the particles of the phosphate, and the polymer is at least one selected from the group consisting of aromatic polyamide, aromatic polyimide, and aromatic polyamide-imide
Implementation Method 3
reducing lithium reactivity and thermal shrinkage
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The negative electrode is an electrode in which lithium metal deposits during charging and the lithium metal dissolves during discharging, the separator includes a substrate, a first layer disposed on a first side of the substrate, and a second layer disposed on a second side of the substrate, the first layer includes particles of phosphate containing lithium, the second layer includes a polymer and/or inorganic particles other than the particles of the phosphate, and the polymer is at least one selected from the group consisting of aromatic polyamide, aromatic polyimide, and aromatic polyamide-imide.