Ethylene Carbonate Separator Coating for Low-Temperature Battery Bonding
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Solution Overview
Problem
Existing lithium-ion battery separators face issues with high hot-pressing temperatures, low bonding strength, blocking of lithium ion transport, and side reactions due to polymer coatings, which reduce energy density and efficiency.
Innovation Solution
A separator using ethylene carbonate and an optional nucleating agent is coated onto a porous base film, allowing adhesion below 50°C and rapid bonding, with ethylene carbonate dissolving into the electrolyte, maintaining pore integrity and avoiding space occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polymer bonding material is used with high melting point and high melt viscosity, then bonding strength can be achieved, but hot-pressing temperature must be above 90°C and time exceeds 30 seconds, resulting in poor infiltration and low bonding force
Solution Approach 1:
The patent changes the melting point parameter of the bonding material from above 90°C to below 50°C by selecting specific polymers with low melting points. This allows hot-pressing to be performed at lower temperatures while maintaining adequate bonding force, resolving the contradiction between achieving bonding strength and avoiding excessive temperature requirements
Solution Approach 2:
The patent utilizes the phase transition of the polymer bonding material from solid to liquid at low temperature (below 50°C), enabling the material to infiltrate the separator and electrode sheet effectively during hot-pressing. The phase transition occurs rapidly at the specified temperature range, providing both infiltration capability and bonding strength without requiring high temperatures
2Strength
If polymer material is coated on separator surface to form bonding layer, then adhesion between separator and electrode sheet is improved, but pores of separator are blocked and transport of lithium ions is hindered, decreasing kinetic performance
Solution Approach 1:
The patent applies local quality by making the bonding layer semi-transparent to lithium ions. The polymer bonding material is applied locally on the separator surface where adhesion is needed, but its molecular structure allows lithium ion transport through the coating. This creates a localized bonding function that does not uniformly block ion transport pathways, maintaining kinetic performance while providing necessary adhesion
3Strength
If polymer film layer is added on separator surface, then bonding capability is improved, but internal space of battery is occupied, resulting in decrease in energy density
Solution Approach 1:
The patent employs a thin polymer bonding layer that serves its bonding function temporarily during battery assembly and then becomes part of the permanent structure. The bonding material is applied in minimal quantities sufficient to provide adhesion, and once bonding is achieved, the material effectively disappears as a separate functional layer, occupying negligible space in the final battery structure
Solution Approach 2:
The patent uses a thin film polymer bonding material that provides sufficient bonding capability while occupying minimal volume. The thin film nature of the coating ensures that it does not significantly reduce the internal space available for active materials, thereby maintaining high energy density while achieving the required bonding strength between components
4Strength
If various bonding agents, dispersants, wetting agents, and solvents are added to coating materials, then adhesion between separator and electrode sheet is improved, but complex design introduces uncontrollable factors and side reactions in electrochemical process, affecting overall battery performance
Solution Approach 1:
The patent extracts and removes the complex mixture of bonding agents, dispersants, wetting agents, and solvents from the coating formulation. Instead, it uses a single polymer bonding material that provides all necessary functions through its inherent properties. This simplification eliminates uncontrollable factors and side reactions associated with multiple additives while maintaining effective adhesion between separator and electrode sheet
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 approach enhances kinetic performance, prevents side reactions, and improves energy density by ensuring good adhesion and minimizing material occupation within the battery.
Implementation Method 1
ethylene carbonate dissolving into the electrolyte
Implementation Method 2
ethylene carbonate and an optional nucleating agent as a bonding agent... allowing adhesion below 50°C
Data Source
AI summary
The present application provides a separator, a secondary battery, a battery module, a battery pack, and a power consumption apparatus. The separator may include a porous base film and a bonding layer coated on one or both faces of the porous base film. The bonding layer may be composed of ethylene carbonate and an optional nucleating agent.