Secondary Battery Mixture Sheet With Ultrafine Fibrillated Binder
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Solution Overview
Problem
Conventional secondary battery mixtures face challenges in achieving optimal performance due to insufficient fibrillation of binders, leading to subpar battery properties and efficiency, especially when using fibrillatable resins like polytetrafluoroethylene (PTFE) which require precise control of fibril diameter and content to maintain strength and flexibility.
Innovation Solution
A secondary battery mixture is developed using a fibrillatable resin with a fibrous structure and a fibril diameter of 100 nm or less, applied as a powdered binder to reduce solvent dependency and moisture content, allowing for improved ion conduction and battery performance by optimizing the binder content between 0.3% to 8% by mass, and employing specific production methods involving shear forces and calendering to achieve the desired fibril structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders with larger fibril diameters are used, then the mechanical strength is maintained, but the ion conduction and battery performance deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fibril diameter of the binder to 100 nm or less, transforming the binder from a conventional larger-fibril structure to an ultrafine fibrillar structure. This parameter change enables the binder to provide both mechanical strength and enhanced ion conduction pathways, resolving the contradiction between strength and performance.
Solution Approach 2:
The patent creates a composite structure where ultrafine binder fibrils (≤100 nm) are integrated with active material particles and conductive aids. This composite arrangement allows the fine fibrillar network to simultaneously provide mechanical binding and create continuous ion conduction channels throughout the electrode, achieving both strength and improved battery performance.
2Strength
If fibrillatable resin content is increased to improve binding, then the mechanical strength increases, but the ion conduction and active material content decrease
Solution Approach 1:
The patent changes the critical parameter of fibril diameter to 100 nm or less, which fundamentally alters the binder's functionality. This ultrafine dimension allows the binder to form a sparse yet effective network that provides adequate mechanical binding while leaving sufficient space for ion transport, eliminating the need for high binder content and preserving ion conduction.
Solution Approach 2:
The ultrafine fibrillar structure creates local quality variations where the binder forms concentrated binding zones at particle interfaces while maintaining open pathways in the interstitial spaces. This local differentiation enables the binder to fulfill both mechanical and conductive functions without requiring uniform high concentration throughout the electrode.
3Ease of manufacture
If solvent-based binders are used to achieve proper coating, then the ease of manufacture improves, but the moisture content increases affecting battery performance
Solution Approach 1:
The patent extracts and eliminates the solvent component from the binder system, transitioning from a solvent-based slurry to a solvent-free or low-solvent paste formulation. The ultrafine fibrillar binder structure provides sufficient lubricity and flow properties without requiring organic solvents, thereby removing the source of moisture and improving battery performance while maintaining manufacturability.
Solution Approach 2:
The patent changes the physical state parameter of the binder from a dissolved state in solvent to a dispersed ultrafine fibrillar state in paste form. This parameter change eliminates the need for solvent evaporation and drying steps, reducing moisture content and improving battery performance while simplifying the overall manufacturing process.
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 approach results in a secondary battery mixture with enhanced battery performance, including improved ion conduction, reduced moisture-related issues, and increased active material content, while maintaining mechanical strength and flexibility, thus overcoming the limitations of conventional binder-based mixtures.
Implementation Method 1
the binder is a fibrillatable resin having a fibrous structure with a fibril diameter (median value) of 100 nm or less
Implementation Method 2
employing specific production methods involving shear forces and calendering to achieve the desired fibril structure
Implementation Method 3
applied as a powdered binder to reduce solvent dependency and moisture content
Data Source
AI summary
The present disclosure provides a secondary battery mixture that has good properties, a secondary battery mixture sheet containing the mixture, and a secondary battery using the secondary battery mixture sheet. The secondary battery mixture contains a solid-state electrolyte and/or electrode active material, and a binder, wherein the binder is a fibrillatable resin having a fibrous structure with a fibril diameter (median value) of 100 nm or less, and is contained in the secondary battery mixture in an amount of 0.3% by mass or more and 8% by mass or less.