Polymer Binder Composition for Silicon Electrode Volume Stability
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Solution Overview
Problem
Existing electrode binders fail to provide sufficient binding capability for active materials with high lithium occlusion capacity, leading to deterioration and reduced charge-discharge durability in electrical storage devices, particularly when using silicon or olivine-type lithium-containing phosphoric acid compounds.
Innovation Solution
A binder composition comprising polymer particles with specific average particle size ratios and functional units, which improves binding capability and adhesion between the active material and collector, maintaining stability even with volume changes during charge and discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a known electrode binder is applied to a material having a high lithium occlusion capacity, then the binding capability is maintained, but the active material is removed due to deterioration in binding capability and capacity decreases significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating specific functional groups (carboxyl groups with pKa of 3.0-6.0 and hydroxyl groups) in controlled amounts. This parameter change enables the binder to maintain strong binding capability while accommodating the volume expansion and contraction of high-capacity active materials during charge-discharge cycles, thereby improving charge-discharge durability without sacrificing binding strength.
2Quantity of substance
If silicon material with theoretical lithium occlusion capacity of 4,200 mAh/g is used as the active material, then the energy density is increased, but the active material significantly changes in volume due to occlusion and release of lithium
Solution Approach 1:
The patent employs a flexible binder composition containing polymer particles with specific functional groups that can dynamically adjust to volume changes. The binder forms a flexible matrix that accommodates the expansion and contraction of silicon material during lithium occlusion and release, maintaining structural integrity and preventing active material removal while preserving high capacity.
3Strength
If techniques that control acid content on binder particles or use epoxy/hydroxyl group-containing binders are applied, then the binding capability is improved, but the binding capability is still insufficient for practical use with novel active materials
Solution Approach 1:
The patent creates a composite binder system combining polymer particles with specific functional groups (carboxyl and hydroxyl) in defined ratios. This composite approach synergistically enhances binding capability through multiple interaction mechanisms while ensuring practical durability with novel high-capacity active materials like silicon, overcoming the limitations of single-component binders.
Data Source
AI summary
An electrical storage device electrode binder composition exhibits an excellent binding capability, and makes it possible to produce an electrical storage device electrode that exhibits excellent charge-discharge durability characteristics. The electrical storage device electrode binder composition includes a polymer (A) and a liquid medium (B), wherein the polymer (A) is polymer particles, and the ratio (DA/DB) of the average particle size (DA) of the polymer particles measured by using a dynamic light scattering method to the average particle size (DB) of the polymer particles measured by TEM observation is 2 to 10.