Lithium Battery Separator Coating for Thermal Shutdown and Adhesion
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Solution Overview
Problem
Existing separators for rechargeable lithium batteries lack high thermal and physical safety, mechanical strength, permeability, and heat resistance, which can lead to safety issues such as explosion or firing due to temperature increases and internal short circuits.
Innovation Solution
A separator for rechargeable lithium batteries is developed, comprising a porous substrate with a safety functional layer and an adhesive layer. The safety functional layer includes polymer particles with a melting point of 100° C. to 200° C., an aqueous crosslinked binder, and inorganic particles, while the adhesive layer enhances the electrode's adhesive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polyolefin micropore film is used as a separator, then chemical stability is improved, but thermal safety deteriorates due to low melting point causing deformation and short circuits
Solution Approach 1:
The patent applies composite materials by combining polyolefin micropore film with a heat-resistant porous inorganic layer and adhesive layer. The inorganic layer contains heat-resistant particles (such as alumina, silica) that maintain structural integrity at high temperatures, preventing the polyolefin from deforming and causing short circuits, thus resolving the thermal safety issue while preserving chemical stability
Solution Approach 2:
The patent uses porous materials in the form of a heat-resistant porous inorganic layer with controlled porosity (30-70%). This porous structure allows lithium ion transport while the inorganic nature provides heat resistance, preventing thermal runaway and maintaining separator function at elevated temperatures
2Productivity
If the separator thickness is reduced to improve current density and capacity, then productivity is improved, but mechanical strength deteriorates leading to safety issues
Solution Approach 1:
The patent employs a heat-resistant porous inorganic layer with optimized porosity (30-70%) that provides both mechanical reinforcement and ion transport pathways. The porous structure maintains mechanical strength even at reduced thickness while allowing sufficient lithium ion flux for high current density and capacity
Solution Approach 2:
The composite structure combines thin polyolefin micropore film with a heat-resistant porous inorganic layer, creating a multi-functional thin film separator that achieves both high current density (through optimized porosity) and adequate mechanical strength (through the inorganic reinforcement layer)
3Reliability
If the separator is made thinner to prevent battery explosion and improve safety, then reliability is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent creates a composite thin film separator where the heat-resistant porous inorganic layer provides mechanical reinforcement and thermal stability. This composite structure enables the separator to be made thinner for improved safety response (faster shutdown at lower temperatures) while the inorganic framework maintains adequate mechanical strength to prevent rupture and short circuits
4Reliability
If high mechanical strength is achieved to improve manufacturing safety, then reliability is improved, but permeability deteriorates reducing capacity and output
Solution Approach 1:
The patent optimizes the porosity of the heat-resistant porous inorganic layer to be between 30-70%, creating a balance where sufficient pore space allows high lithium ion permeability for improved capacity and output, while the inorganic framework provides the necessary mechanical strength for manufacturing and operational safety
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 proposed separator achieves excellent thermal and mechanical safety, high adhesive force to electrodes, and realizes high mechanical strength, permeability, and heat resistance, thereby ensuring the battery's cycle-life characteristics and preventing safety hazards.
Implementation Method 1
polymer particles having a melting point of 100° C. to 200° C.
Implementation Method 2
the aqueous crosslinked binder includes a crosslinked product of a poly(vinyl amide)-based copolymer
Implementation Method 3
inorganic particles
Data Source
AI summary
Disclosed are a separator for a rechargeable lithium battery, and a rechargeable lithium battery including the same, the separator for a rechargeable lithium battery including a porous substrate; a safety functional layer on at least one surface of the porous substrate; and an adhesive layer on the safety functional layer, wherein the safety functional layer includes polymer particles having a melting point of 100° C. to 200° C., an aqueous crosslinked binder, and inorganic particles, the aqueous crosslinked binder includes a crosslinked product of a poly(vinyl amide)-based copolymer, and the poly(vinyl amide)-based copolymer includes a unit derived from a vinyl amide monomer and a unit derived from a monomer including a crosslinkable group.