Fluoropolymer Binder Composition for Flexible High-Density Electrode Sheets

Solution Overview

Problem

Existing binders in secondary batteries increase the stiffness of electrode plate film layers, deteriorating flexibility and limiting the improvement of electrochemical performance, including volumetric energy density and cycle stability.

Innovation Solution

A fluoropolymer with a weight average molecular weight of 5 million to 9 million, incorporating a structural unit from vinylidene fluoride and an unsaturated carboxylic acid monomer, is used to improve flexibility and compacted density of electrode plates, reducing battery resistance while maintaining bonding strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional polymer binders are used in electrode plates, then bonding strength is maintained, but flexibility deteriorates and stiffness increases

Engineering Contradiction:

Improveflexibility of electrode plateVSAvoidbonding strength of electrode plate

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent changes the molecular weight parameter of the binder polymer to a specific range (5-9 million), which fundamentally alters the mechanical properties. This high molecular weight creates a more flexible network structure that maintains bonding strength while reducing stiffness and improving electrode plate flexibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite binder system combining high molecular weight polyvinylidene fluoride with polyacrylonitrile in specific ratios. This composite approach leverages the flexibility and chemical stability of PVDF alongside the adhesive properties of polyacrylonitrile, achieving both flexibility and bonding strength simultaneously

Inventive Principle:

Principle #40Composite materials

2Volume of stationary object

If conventional binders are used, then electrode plate structure is maintained, but compacted density decreases and volumetric energy density is limited

Engineering Contradiction:

Improvecompacted density of electrode plateVSAvoidstructural integrity of electrode plate

Core Design Contradiction:

Volume of stationary objectVSStability of the object's composition

Solution Approach 1:

The patent changes the molecular weight parameter of the binder to ultra-high ranges (5-9 million), which fundamentally alters the mechanical properties. This high molecular weight creates a more flexible network structure that maintains bonding strength while reducing stiffness and improving electrode plate flexibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite binder system combining high molecular weight polyvinylidene fluoride with polyacrylonitrile in specific ratios. This composite approach leverages the flexibility and chemical stability of PVDF alongside the adhesive properties of polyacrylonitrile, achieving both flexibility and bonding strength simultaneously

Inventive Principle:

Principle #40Composite materials

3Reliability

If binder content is increased to maintain bonding strength, then electrode plate integrity is improved, but flexibility deteriorates and resistance increases

Engineering Contradiction:

Improveelectrode plate integrityVSAvoidflexibility of electrode plate

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent changes the molecular weight parameter of the binder to ultra-high ranges (5-9 million), which fundamentally alters the mechanical properties. This high molecular weight creates a more flexible network structure that maintains bonding strength while reducing stiffness and improving electrode plate flexibility

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent optimizes the binder content to a minimal effective concentration (0.3-1.1% of total electrode mass), using the ultra-high molecular weight polymer's enhanced per-mass effectiveness to maintain integrity with reduced quantity, thereby preserving flexibility

Inventive Principle:

Principle #26Copying

Data Source

PatentEP4678666A1Fluorine-containing polymer, preparation method therefor, positive electrode sheet, secondary battery and electric device

Publication Date: 2026.01.14 CONTEMPORARY AMPEREX TECHNOLOGY CO LTD

Figure 1~3
Figure 4~6

AI summary

This application provides a fluoropolymer, a preparation method therefor, a positive electrode plate, a secondary battery, and an electric device. The fluoropolymer comprises a structural unit derived from vinylidene fluoride and a structural unit derived from an unsaturated carboxylic acid monomer, wherein a weight average molecular weight of the fluoropolymer ranges from 5 million to 9 million, and optionally, from 5 million to 8 million.