Olefin Binder for Nonaqueous Battery Electrodes
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Solution Overview
Problem
Conventional binder materials for nonaqueous electrolyte secondary batteries, such as polyvinylidene fluoride (PVdF) and styrene butadiene latex, face issues with low binding force, oxidative degradation, and electrolyte solution instability, limiting their use in positive electrodes and affecting battery performance.
Innovation Solution
A binder comprising an olefin-based polymer and a fatty acid with a melting point of 25°C or less and a boiling point of 100°C or more is used, which provides improved binding strength, electrochemical stability, and resistance to oxidative degradation, eliminating the need for additional additives and enhancing battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVdF is used as binder material, then electrochemical stability is improved, but binding force is insufficient and capacity per unit volume is low
Solution Approach 1:
The patent uses a composite binder system combining PVdF with carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). This composite approach leverages the electrochemical stability of PVdF while adding the strong binding properties of CMC and SBR, thereby resolving the contradiction between electrochemical stability and binding force.
2Strength
If aqueous dispersion based SBR is used as binder material, then binding force is improved, but oxidative degradation occurs in positive electrode
Solution Approach 1:
The patent applies different binder materials to different electrodes based on their specific requirements: SBR is used in the negative electrode where strong binding is needed and oxidation is not an issue, while PVdF is used in the positive electrode where electrochemical stability is critical. This localized application resolves the contradiction between binding force and oxidative stability.
3Strength
If binder material with strong binding property is used, then binding force is improved, but capacity per unit volume decreases due to large amount required
Solution Approach 1:
The composite binder system allows for optimized formulation where each component contributes specific functions. CMC provides strong binding with low viscosity requirements, SBR enhances adhesion, and PVdF provides electrochemical stability. This synergistic combination achieves strong binding force while minimizing the total binder content, thereby maintaining high capacity per unit volume.
4Reliability
If PVdF is used as binder material, then electrochemical stability is improved, but dehydrofluorination reduction occurs and hydrogen fluoride is generated causing active material deterioration
Solution Approach 1:
The patent introduces CMC and SBR as intermediary materials that work synergistically with PVdF. These additives stabilize the PVdF structure and prevent dehydrofluorination reduction, thereby eliminating hydrogen fluoride generation while maintaining the electrochemical stability benefits of PVdF.
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 binder solution enhances the cycle characteristics of nonaqueous electrolyte secondary batteries by maintaining the stability of active materials, preventing electrolyte solution-induced deterioration, and improving conductivity, while reducing the need for viscosity-adjusting agents and dispersing agents, thus improving overall battery performance.
Implementation Method 1
a positive electrode and a negative electrode of a secondary battery such as a Ni—MH battery or a lithium ion battery are fabricated by binding each active material for the positive electrode and the negative electrode to a current collector with a binder material
Data Source
AI summary
An electrode for a nonaqueous electrolyte secondary battery of an embodiment includes: a current collector; and an active material layer including an active material and a binder, formed on the current collector, wherein the binder includes at least an olefin based polymer and a fatty acid, and the fatty acid has a melting point of 25° C. or less and a boiling point of 100° C. or more.