Crosslinked Electrode Binder for Silicon Battery Cycle Stability

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Solution Overview

Problem

Existing binders for secondary battery electrodes fail to adequately improve the toughness of the binder film after immersion in electrolyte solution, resistance of the electrode mixture layer against the electrolyte, and cycle characteristics, particularly when using silicon-based active materials.

Innovation Solution

A binder containing a carboxyl group-containing crosslinked polymer or its salt, coupled with an organic compound having two or more cationic groups, is used to enhance the toughness and resistance of the electrode mixture layer, with specific molecular ratios and properties to improve cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional binders (SBR latex, CMC, PVDF) are used for secondary battery electrodes, then the electrode structure is maintained, but the toughness of the binder film after immersion in electrolyte solution is insufficient and cycle characteristics deteriorate

Engineering Contradiction:

Improvecycle characteristicVSAvoidtoughness of binder film

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention uses a composite binder system comprising carboxymethyl cellulose (CMC) as the base polymer and polyacrylic acid (PAA) as a crosslinking agent. This composite approach combines the water solubility and basic binding properties of CMC with the crosslinking capability of PAA to form a network structure that simultaneously improves toughness and cycle characteristics. The synergistic interaction between these two materials resolves the contradiction by creating a binder film that maintains both mechanical strength and electrochemical stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention optimizes specific parameters including the molecular weight of CMC (50,000-500,000), the amount of PAA (0.1-10 parts by mass per 100 parts by mass of CMC), and the degree of crosslinking. By controlling these parameters, the binder film achieves enhanced toughness while maintaining good cycle characteristics. The parameter optimization allows the binder to withstand the mechanical stress from silicon-based active material expansion/contraction while preserving electrochemical performance over multiple cycles.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If silicon-based active materials are used to increase electric capacity, then the energy density is improved, but the volume change during charging and discharging causes electrode mixture layer separation and fall

Engineering Contradiction:

Improveelectric capacityVSAvoidelectrode mixture layer integrity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The crosslinked binder network acts as a cushioning structure that anticipates and absorbs the volume changes of silicon-based active materials during charging and discharging cycles. The three-dimensional crosslinked structure formed by PAA provides mechanical support and flexibility, allowing the binder film to expand and contract with the active material without losing structural integrity. This beforehand cushioning effect prevents electrode mixture layer separation and maintains stability despite the large volume changes associated with high-capacity silicon-based materials.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If the ratio of silicon-based active material is increased to improve battery performance, then the electric capacity increases, but the stress due to swelling expansion and contraction worsens

Engineering Contradiction:

Improvebattery performanceVSAvoidstress from swelling expansion and contraction

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The crosslinked binder film acts as a flexible shell that envelops and supports the silicon-based active material particles. The crosslinked network structure provides flexibility and elasticity, allowing the binder film to accommodate the swelling and contraction of active material during electrochemical cycles. This flexible shell structure distributes and reduces the mechanical stress generated by volume changes, enabling the use of higher ratios of silicon-based active material without compromising electrode integrity or battery performance.

Inventive Principle:

Principle #30Flexible shells and thin films

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 significantly enhances the toughness of the binder film, resistance of the electrode mixture layer, and cycle characteristics of secondary batteries, particularly when using silicon-based active materials.

Implementation Method 1

a binder containing a carboxyl group-containing crosslinked polymer or its salt, coupled with an organic compound having two or more cationic groups

Methodology Applied

Scientific EffectChemical bonding: Chemical Bonding

Data Source

PatentUS20250266459A1Secondary battery electrode binder and use of same

Publication Date: 2025.08.21 TOAGOSEI CO LTD

AI summary

The present invention provides a binder for a secondary battery electrode, capable of improving the toughness of a binder applied film after immersion in an electrolyte solution, the resistance of a secondary battery electrode mixture layer against the electrolyte solution, and the cycle characteristic of a secondary battery. The binder for a secondary battery electrode includes a carboxyl group-containing crosslinked polymer or a salt thereof, in which at least a part of the carboxyl group is a functional group used to couple with an organic compound having two or more cationic groups.