Polyvinyl Acetal Binder for Lithium Battery Electrodes
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Solution Overview
Problem
Current binders for lithium secondary batteries face challenges such as poor thermal stability, low adhesiveness, and high irreversible capacity, leading to reduced battery performance and flexibility, especially at extreme temperatures and with electrolyte swelling.
Innovation Solution
A polyvinyl acetal resin with a specific meso/racemo ratio and hydroxy group content is used as a binder, providing thermal stability, improved adhesiveness, and resistance to electrolytes, allowing for high-capacity battery production with reduced irreversible capacity and low resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If N-methylpyrrolidone is used as a solvent to dissolve fluororesins, then the solubility of fluororesins is improved, but the thermal energy required for drying increases due to the high boiling point of the solvent
Solution Approach 1:
The patent changes the solvent parameter from high-boiling N-methylpyrrolidone to low-boiling alcohol solvents, thereby reducing the thermal energy required for drying while maintaining adequate solubility for binder formation
Solution Approach 2:
The patent uses readily available, low-cost alcohol solvents (methanol, ethanol, isopropanol) that can be easily evaporated, replacing expensive and energy-intensive high-boiling solvents
2Shape
If fluororesin is used as a binder to form a flexible negative electrode film, then the flexibility of the electrode is improved, but the binding properties between current collector and active material deteriorate, causing peeling
Solution Approach 1:
The patent uses a composite binder system combining fluororesin with carboxymethyl cellulose or styrene-butadiene copolymer, where each component contributes different properties: fluororesin provides flexibility and electrochemical stability, while the other polymer enhances adhesion and binding strength
Solution Approach 2:
The patent optimizes the local composition by controlling the weight ratio of fluororesin to other binders (specifically 70:30 to 90:10), ensuring that flexibility and adhesion are balanced in different regions of the electrode structure
3Strength
If an excessive amount of binder is added to improve binding properties, then the adhesion and flexibility are improved, but the amount of active material is reduced, lowering battery capacity
Solution Approach 1:
The patent changes the binder composition parameters to achieve superior binding performance with lower binder content (1-5 parts by weight per 100 parts active material). The modified binder has enhanced adhesion properties that allow reduced binder quantity while maintaining or improving binding strength and flexibility
4Strength
If carboxymethyl cellulose is used as an aqueous binder to improve adhesion, then the binding effect is improved, but the flexibility of the resin is insufficient, marking adhesion force to current collector
Solution Approach 1:
The patent creates a composite binder system where carboxymethyl cellulose (providing adhesion) is combined with fluororesin or styrene-butadiene copolymer (providing flexibility). This composite approach allows both adhesion force and flexibility to be simultaneously optimized
Solution Approach 2:
The patent optimizes the local properties by controlling the weight ratio of carboxymethyl cellulose to fluororesin (specifically 30:70 to 10:90), ensuring that adhesion and flexibility are balanced according to the electrode's specific requirements
Data Source
AI summary
The present invention aims to provide a binder for a power storage device electrode which exhibits thermal energy stability over a wide temperature range covering from a high-temperature condition to a low-temperature condition when used as a binder for a power storage device electrode, and which enables production of a high-capacity storage battery with a small irreversible capacity and low resistance to have excellent output characteristics. The present invention also aims to provide a binder for a power storage device electrode which is excellent in dispersibility of an active material and adhesiveness, which improves the flexibility of an electrode to be obtained, and which has high resistance against electrolytes to enable production of a high-capacity storage battery even when the added amount thereof is small. The present invention further aims to provide a composition for a power storage device electrode, a power storage device electrode, and a power storage device each prepared using the binder for a power storage device electrode. The present invention relates to a binder for a power storage device electrode used for an electrode of a power storage device, the binder including a polyvinyl acetal resin, the polyvinyl acetal resin having a meso/racemo ratio of an acetal ring structure of 10 or higher and a hydroxy group content of 30 to 60 mol %.