Silicon Anode Binder Composition for Volume-Change Cycle Stability
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Solution Overview
Problem
Existing binders for secondary battery negative electrodes containing silicon-based active materials fail to adequately address the mechanical stress caused by volume changes during charging and discharging, leading to peeling and reduced cycle characteristics.
Innovation Solution
A binder composition comprising a carboxyl group-containing polymer and a hydroxyl group-containing polymer, with specific ratios and structural units, enhances the toughness and cycle characteristics of the electrode coating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a silicon-based active material is used to increase electric capacity, then the energy density is improved, but the electrode mixture layer peels and falls off due to large volume change during charging and discharging
Solution Approach 1:
The patent uses a composite binder system comprising both a carboxyl group-containing polymer and a hydroxyl group-containing polymer. This composite material approach allows the binder to form multiple types of interactions (hydrogen bonds, coordinate bonds) with the silicon-based active material, providing enhanced adhesion that accommodates the large volume changes during charging and discharging while maintaining electrode integrity.
Solution Approach 2:
The patent specifies particular parameter ranges for the binder components: the carboxyl group-containing polymer has a carboxyl group content of 1-50 mmol/g and the hydroxyl group-containing polymer has a hydroxyl group content of 1-10 mmol/g. These parameter optimizations ensure the binder has sufficient binding sites to accommodate the silicon material's volume expansion (2-4 times) during lithiation while maintaining structural integrity.
2Use of energy by moving object
If the ratio of silicon-based active material is increased to improve battery performance, then the electric capacity is enhanced, but the cycle characteristics deteriorate due to repeated volume changes
Solution Approach 1:
The binder acts as an intermediary between the silicon-based active material and the electrode structure. The carboxyl group-containing polymer and hydroxyl group-containing polymer work together to mediate the mechanical stress caused by volume changes, distributing the stress uniformly and preventing localized peeling that would lead to electrode failure during cycling.
Solution Approach 2:
The binder composition is designed to provide beforehand cushioning for the volume changes that occur during charging and discharging. The flexible polymer matrix accommodates the expansion and contraction of silicon particles in advance, preventing mechanical failure before it occurs during subsequent charge-discharge cycles.
3Ease of manufacture
If conventional binders are used for silicon-based active materials, then the manufacturing process is simple, but the binding property is insufficient leading to peeling
Solution Approach 1:
The carboxyl group-containing polymer and hydroxyl group-containing polymer exhibit self-service behavior by automatically forming strong bonds with the silicon-based active material through hydrogen bonding and coordinate bonding mechanisms. This self-bonding capability eliminates the need for complex crosslinking agents or multi-step processing, maintaining ease of manufacture while dramatically improving binding strength.
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 binder composition improves the mechanical properties and cycle life of secondary batteries by forming strong hydrogen bonds, resulting in a tougher coating film that withstands volume changes of the silicon-based active material.
Implementation Method 1
The binder includes a carboxyl group-containing polymer or a salt thereof and a hydroxyl group-containing polymer optionally having a carboxyl group or a salt thereof
Data Source
AI summary
The present invention provides an electrode binder capable of improving toughness of a binder coating film, and cycle characteristics of a secondary battery including a secondary battery negative electrode containing a silicon-based active material. The present invention also provides a composition for a secondary battery negative electrode mixture layer containing the binder, and a secondary battery negative electrode and a secondary battery obtained using the composition. An electrode binder for a secondary battery including a secondary battery negative electrode containing a silicon-based active material, the binder including a carboxyl group-containing polymer or a salt thereof (hereinafter, referred to as “polymer (A)”) and a hydroxyl group-containing polymer (different from the polymer (A), hereinafter, referred to as “polymer (B)”) optionally having a carboxyl group or a salt thereof.