Separator Coating Composition for Low-Temperature Li-Ion Cycling
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Solution Overview
Problem
Lithium-ion batteries exhibit subpar charge and discharge performance under low-temperature conditions, limiting their application due to inadequate kinetic and cycle performance.
Innovation Solution
A separator with a specific first coating layer composition, including a polymer with a controlled mass percentage and softening point, and a second coating layer, optimized to enhance interfacial bonding and ion conductivity, is used to improve the bonding performance and infiltration of the electrolyte solution, thereby enhancing the battery's kinetic and low-temperature cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the content of the first polymer in the first coating layer is increased to improve interfacial bonding performance, then the bonding force between the coating layer and electrode plate is improved, but the interstices between polymer particles are reduced, impeding electrolyte solution transmission
Solution Approach 1:
The patent applies parameter changes by precisely controlling the mass percentage of the first polymer in the first coating layer to be between 60-90 wt%, and the softening point to be between 90-150°C. This optimization balances the bonding force and electrolyte transmission by adjusting the polymer content and thermal properties, ensuring sufficient interstices for electrolyte penetration while maintaining adequate adhesion to the electrode plate.
2Stability of the object's composition
If the softening point of the first polymer is increased to improve thermal stability, then the structural stability is improved, but the bonding force between the coating layer and electrode plate decreases due to reduced softening capability
Solution Approach 1:
The patent optimizes the softening point parameter of the first polymer to fall within 90-150°C. This parameter optimization ensures the polymer can soften at moderate temperatures to form strong bonds with the electrode plate during manufacturing, while maintaining sufficient thermal stability for battery operation. The balanced softening point allows adequate bonding capability without excessive thermal resistance.
3Strength
If the softening point of the first polymer is decreased to improve bonding capability, then the bonding force is improved, but the polymer blocks pores after softening, deteriorating kinetic performance
Solution Approach 1:
The patent controls the softening point of the first polymer within 90-150°C to prevent pore blocking while maintaining bonding capability. This optimized softening point range ensures the polymer softens sufficiently during manufacturing to adhere to the electrode plate, but does not soften excessively during battery operation to block the pores. The balanced softening point maintains both bonding force and kinetic performance.
4Strength
If the thickness of the first coating layer is increased to improve bonding performance, then the bonding force is improved, but the ion transmission distance is increased, deteriorating kinetic performance
Solution Approach 1:
The patent optimizes the thickness of the first coating layer to balance bonding performance and ion transmission. By controlling the coating layer thickness within an appropriate range and optimizing the polymer content and softening point, the patent achieves sufficient bonding force while minimizing the ion transmission path length. This parameter optimization ensures both adequate adhesion and efficient lithium ion transport.
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 optimized separator design significantly improves the bonding force between the coating layer and electrode plates, reduces self-discharge, and enhances the energy density and low-temperature cycle performance of lithium-ion batteries.
Implementation Method 1
a softening point of the first polymer is 90° C. to 150° C.... When the softening point of the first polymer is overly high (for example, higher than 150° C.), the first polymer can hardly be softened when heated, and the formed bonding area is relatively small, thereby impairing the bonding force between the first coating layer and the electrode plate.
Implementation Method 2
The separator includes a substrate and a first coating layer disposed on at least one surface of the substrate... By controlling the content and softening point of the first polymer in the first coating layer to fall within the above ranges, this application obtains the first coating layer with excellent interfacial bonding performance and a moderate interstice between polymer particles
Data Source
AI summary
A separator includes a substrate and a first coating layer disposed on at least one surface of the substrate. The first coating layer includes a first polymer. Based on a total mass of the first coating layer, a mass percent x of the first polymer is 60 wt % to 90 wt %. A softening point of the first polymer is 90° C. to 150° C. The separator of this application possesses excellent interfacial bonding strength, and improves kinetic performance of a lithium-ion battery, and especially cycle performance of the battery under a low-temperature condition.