Positive Electrode Binder Composition for High-Density Li-Ion Flexibility
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Solution Overview
Problem
Lithium-ion batteries with high compacted density positive electrode plates face brittle fracture issues due to lack of flexibility, leading to performance loss, necessitating an improvement in the flexibility of the positive electrode while maintaining high energy density.
Innovation Solution
Incorporating a fluorine-containing polymer binder with specific XRD diffraction peak ratios and molecular weight distribution in the positive electrode mixture layer, which enhances flexibility and adhesion, thereby improving the compacted density and cycling performance of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the compacted density of the positive electrode plate is increased to improve energy density, then the energy density of the lithium-ion battery is improved, but the positive electrode plate becomes brittle and prone to fracture during folding
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by introducing fluorine-containing polymers with specific molecular weight ranges (800,000-1,100,000) and controlling the ratio of vinylidene fluoride to hexafluoropropylene (95:5 to 90:10). This parameter optimization improves the binder's adhesion and flexibility, allowing the positive electrode to maintain structural integrity at high compacted densities (3.0-4.5 g/mm³) while resisting brittle fracture during folding and winding operations.
Solution Approach 2:
The patent creates a composite binder system by combining fluorine-containing polymers with specific copolymer compositions (vinylidene fluoride-hexafluoropropylene copolymer) and molecular weight distributions. This composite material approach provides both the adhesion strength needed for high compacted density and the flexibility required to prevent fracture, resolving the contradiction between energy density improvement and structural integrity.
2Quantity of substance
If the compacted density of the positive electrode plate is increased to improve energy density, then the energy density of the lithium-ion battery is improved, but the positive electrode plate suffers from performance loss due to fracture
Solution Approach 1:
The patent optimizes the binder's molecular weight (800,000-1,100,000) and copolymer composition ratio to achieve optimal adhesion strength. This parameter control ensures that the positive electrode maintains structural integrity during repeated folding and unwinding cycles, preventing fracture-induced performance loss while maintaining high compacted density (3.0-4.5 g/mm³) for improved energy density and reliable cycling performance.
3Quantity of substance
If the compacted density of the positive electrode plate is increased to improve energy density, then the energy density of the lithium-ion battery is improved, but the positive electrode plate exhibits swelling issues
Solution Approach 1:
The patent controls the binder's molecular weight (800,000-1,100,000) and copolymer composition to optimize adhesion strength and structural stability. This parameter optimization ensures that the positive electrode maintains dimensional stability during cycling at high compacted densities (3.0-4.5 g/mm³), preventing swelling while maintaining the high energy density required for improved battery 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
The use of the fluorine-containing polymer binder with controlled properties increases the flexibility and compacted density of the positive electrode, reducing the risk of brittle fracture and enhancing the anti-swelling and cycling performance of lithium-ion batteries.
Implementation Method 1
in an XRD diffraction pattern of the fluorine-containing polymer, a diffraction peak A appears at 25° to 27° and corresponds to a (111) crystal plane, and a diffraction peak B appears at 37° to 39° and corresponds to a (022) crystal plane
Implementation Method 2
the binder includes a fluorine-containing polymer... the positive electrode can have high flexibility, so that the positive electrode in this application has high flexibility and compacted density
Data Source
AI summary
An electrochemical apparatus includes a positive electrode, the positive electrode includes a current collector and a positive electrode mixture layer disposed on at least one surface of the current collector. The positive electrode mixture layer includes a positive electrode active substance and a binder. The binder includes a fluorine-containing polymer. In an XRD diffraction pattern of the fluorine-containing polymer, a diffraction peak A appears at 25° to 27° and corresponds to a (111) crystal plane, and a diffraction peak B appears at 37° to 39° and corresponds to a (022) crystal plane, where an area ratio of the diffraction peak A to the diffraction peak B satisfies 1≤A(111)/B(022)≤4.