Si-Based Lithium Battery Separator Coating for Thermal Stability
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Solution Overview
Problem
Rechargeable lithium batteries face issues with adherence between the separator and electrodes, leading to potential short circuits due to temperature increases from exothermic reactions and repeated charge-discharge cycles, which compromise stability and cycle-life characteristics.
Innovation Solution
A rechargeable lithium battery design incorporating a Si-based negative active material, a fluorine-based polymer coating layer, and an inorganic compound on a porous substrate separator, with a specific composition of non-aqueous organic solvents and additives to enhance adherence and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of heat-resistant inorganic particle is increased to improve thermal stability, then the amount of binder is decreased, but the adherence between separator and electrode deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the binder from conventional options to a specific copolymer containing carboxylic acid groups and hydroxyl groups in defined ratios. This parameter change allows the binder to maintain strong adherence to electrodes while simultaneously providing sufficient binding capacity for heat-resistant inorganic particles, thus resolving the contradiction between thermal stability and adherence strength
Solution Approach 2:
The patent uses a composite binder system comprising a copolymer of acrylic acid and vinyl alcohol in specific proportions, combined with heat-resistant inorganic particles. This composite material approach creates a synergistic effect where the copolymer's functional groups provide both strong electrode adhesion and effective particle binding, overcoming the trade-off between adherence and thermal stability
2Reliability
If a coating layer is applied to the separator to prevent short circuit at high temperature, then the separator structure becomes more complex, but the adherence between separator and electrode may be compromised
Solution Approach 1:
The patent employs a thin film coating layer composed of heat-resistant inorganic particles bound by the specialized copolymer. This thin film provides thermal stability and prevents short circuits while minimizing structural complexity and maintaining flexibility for good electrode contact
Solution Approach 2:
The copolymer binder acts as an intermediary substance between the inorganic particles and the electrode surface. Its dual functionality of adhering to both the particles and the electrode simplifies the overall separator structure while ensuring stable high-temperature performance
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
Improves adherence between the separator and electrodes, ensuring stability at high temperatures and extending cycle-life characteristics while preventing sharp contraction and deformation during charge and discharge.
Implementation Method 1
a coating layer positioned on at least one side of the porous substrate, wherein the coating layer includes a fluorine-based polymer, an inorganic compound, or a combination thereof
Implementation Method 2
coating the separator with a heat-resistant inorganic particle along with a binder on at least one side to secure stability of the battery
Data Source
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AI summary
Disclosed is a rechargeable lithium battery including a positive electrode including a positive active material; a negative electrode including a negative active material; an electrolyte solution including a lithium salt and a non-aqueous organic solvent; and a separator between the positive and the negative electrodes, the separator including a porous substrate and a coating layer positioned on at least one side of the porous substrate. The negative active material includes a Si-based material; the non-aqueous organic solvent includes cyclic carbonate including ethylene carbonate, propylene carbonate, or combinations thereof, the cyclic carbonate being included in an amount of about 20 volume% to about 60 volume% based on the total amount of the non-aqueous organic solvent; and the coating layer includes a fluorine-based polymer, an inorganic compound, or combinations thereof. The rechargeable lithium battery has improved cycle-life and high temperature storage characteristics.