Battery Separator Structure for Lithium Metal Deposition Control
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Solution Overview
Problem
Current lithium secondary batteries face limitations in improving capacity and safety, with existing designs struggling to effectively manage lithium metal deposition and dissolution, leading to potential safety issues and capacity retention problems.
Innovation Solution
The lithium secondary battery design incorporates a separator with a heat-resistant layer and a spacer on the positive electrode side, where the spacer's average height is greater than the sum of the substrate and heat-resistant layer thicknesses, creating spaces for lithium metal deposition and dissolution while suppressing thermal contraction and maintaining high capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal is deposited on the negative electrode during charging to increase capacity, then the battery capacity increases, but the safety deteriorates due to potential short circuits and thermal runaway
Solution Approach 1:
A separator is introduced as an intermediary component between the positive and negative electrodes. This separator includes a substrate with a heat-resistant layer and a spacer that creates a physical barrier, preventing direct contact between electrodes while allowing lithium ion transport, thus ensuring safety during lithium metal deposition and dissolution
Solution Approach 2:
The heat-resistant layer and spacer are pre-configured on the separator to provide thermal and physical protection before thermal runaway or short circuit events occur. The heat-resistant layer prevents substrate deterioration at elevated temperatures, while the spacer maintains electrode separation, cushioning against potential safety failures
2Device complexity
If the separator structure is simplified to reduce manufacturing complexity, then the device complexity decreases, but the safety and capacity retention deteriorate due to insufficient lithium metal management
Solution Approach 1:
The separator is segmented into distinct functional layers: a substrate providing structural support, a heat-resistant layer for thermal protection, and a spacer for physical separation. This segmentation allows each layer to perform its specific function efficiently, achieving high safety and capacity retention without excessive manufacturing complexity
Solution Approach 2:
The separator is constructed as a composite structure combining different materials with complementary properties: the substrate material provides mechanical strength, the heat-resistant layer material provides thermal stability, and the spacer material provides physical separation. This composite approach achieves superior performance while maintaining manufacturing feasibility
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 configuration enhances the safety and capacity retention of lithium secondary batteries by managing lithium metal deposition and dissolution, reducing the risk of short circuits and maintaining high cell capacity, while also suppressing excessive temperature increases and substrate deterioration.
Implementation Method 1
suppressing thermal contraction
Implementation Method 2
a non-aqueous electrolyte having lithium ion conductivity
Data Source
AI summary
A disclosed lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte having lithium ion conductivity. The negative electrode is an electrode on which lithium metal is deposited during charging and from which the lithium metal dissolves during discharging. The separator includes a substrate, a heat-resistant layer, and a spacer. The heat-resistant layer is formed on at least one main surface selected from two main surfaces of the substrate. The spacer is disposed on the positive electrode side with respect to the substrate and the heat-resistant layer. An average height of the spacer is larger than a sum of an average thickness of the substrate and an average thickness of the heat-resistant layer.