Polyurethane Sodium Salt Electrode Binder for SiO Swelling Control
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Solution Overview
Problem
Lithium secondary batteries face performance deterioration due to electrode swelling caused by charging and discharging, particularly when using SiO as a negative-electrode active material.
Innovation Solution
An electrode binder composition containing a polyurethane sodium salt, obtained by reacting an aliphatic or alicyclic polyisocyanate with a hydrogenated polybutadiene polyol, a carboxylic acid having active hydrogen groups, and a chain extender, is used to reduce electrode swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional polyurethane binders are used, then adhesion between electrode active material and current collector is achieved, but electrode swelling occurs during charging and discharging
Solution Approach 1:
The invention changes the chemical composition parameters of the polyurethane binder by using hydrogenated polybutadiene polyol instead of conventional polyols, and by incorporating carboxylic acid groups that form sodium salts. This chemical parameter change enables the binder to accommodate volume variations during charging/discharging while maintaining adhesion, thus resolving the contradiction between strength and stability.
Solution Approach 2:
The invention creates a composite binder system combining polyurethane with carboxylic acid groups and sodium salts. This composite material structure provides both the adhesion properties of polyurethane and the swelling-resistant properties of the carboxylic acid-sodium salt system, simultaneously achieving strong adhesion and reduced electrode swelling.
2Quantity of substance
If SiO is used as negative-electrode active material, then high energy density is achieved, but electrode swelling and gas generation occur during cycling
Solution Approach 1:
The invention converts the harmful gas generation by SiO during cycling into a beneficial effect by using the carboxylic acid-sodium salt system in the binder. This system appears to cause gas formation through neutralization reactions, but actually suppresses net gas generation and swelling by creating a flexible, adhesive matrix that accommodates SiO volume changes, thus converting potential harm into benefit.
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 electrode binder effectively reduces electrode swelling and suppresses gas generation during charging and discharging, thereby enhancing the cycling performance and stability of lithium secondary batteries.
Implementation Method 1
The binder is used in order to impart adhesion between the electrode active material and the current collector
Implementation Method 2
an electrode binder containing an aqueous dispersion of a polyurethane sodium salt obtained by causing a reaction of (A) at least one of an aliphatic polyisocyanate or an alicyclic polyisocyanate, (B) a hydrogenated polybutadiene polyol, (C) a carboxylic acid having one or more active hydrogen groups, and (D) a chain extender
Data Source
AI summary
To provide an electrode binder that is used for a lithium secondary battery and that can reduce swelling of an electrode caused by charging and discharging. An electrode binder for a lithium secondary battery according to an embodiment contains an aqueous dispersion of a polyurethane sodium salt obtained by causing a reaction of (A) at least one of an aliphatic polyisocyanate or an alicyclic polyisocyanate, (B) a hydrogenated polybutadiene polyol, (C) a carboxylic acid having one or more active hydrogen groups, and (D) a chain extender.