Copolymer Binder for Carbon-Coated LiFePO4 Electrodes
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Solution Overview
Problem
Lithium iron phosphate electrodes face challenges due to low electrical conductivity, high material synthesis costs, and issues with existing binders such as PVDF, which cause lithium ion dissociation and corrosion of current collectors, limiting their commercialization.
Innovation Solution
A copolymer binder with a hard segment capable of hydrogen bonding and a soft segment with a polyol structure is used to form a polycarbonate-based electrode interface film, enhancing adhesion and electrochemical properties, and reducing the use of organic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF binder based on organic solvent is used, then adhesion to current collector is achieved, but lithium ion dissociation and corrosion of current collector occur
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by using a copolymer with specific hard segments (containing carboxyl, hydroxyl, or amine groups) and soft segments (polyol structure), replacing the conventional PVDF binder. This compositional change enables the binder to form a protective interface film that prevents corrosion while maintaining adhesion.
Solution Approach 2:
The patent employs a composite binder structure consisting of hard segments with functional groups (carboxyl, hydroxyl, or amine) and soft segments with polyol structure. This composite structure at the molecular level creates a binder that simultaneously provides adhesion, forms protective films, and prevents harmful reactions between electrolyte and current collector.
2Ease of manufacture
If aqueous binder is used, then environmental friendliness and processing cost are improved, but dissociation of lithium ions and corrosion of current collector occur
Solution Approach 1:
The patent changes the solvent system from aqueous to organic solvent-free by using a copolymer binder that can be processed without additional solvents. The copolymer's molecular structure (hard segments with functional groups and soft segments with polyol structure) enables direct application and forms a protective interface film that prevents corrosion, eliminating the harmful effects associated with aqueous binders.
3Strength
If high molecular weight PVDF binder is used, then adhesion is achieved, but aggregation of active material and low adhesivity occur
Solution Approach 1:
The patent segments the binder at the molecular level into distinct hard segments (containing functional groups like carboxyl, hydroxyl, or amine) and soft segments (with polyol structure). This segmentation allows different parts of the binder molecule to perform different functions: hard segments provide adhesion and form protective films, while soft segments ensure uniform dispersion and prevent aggregation of active material.
Solution Approach 2:
The patent applies local quality by giving different segments of the copolymer binder different functional properties. The hard segments are localized to provide adhesion and corrosion protection at the binder-current collector interface, while the soft segments are distributed to ensure uniform dispersion and prevent aggregation throughout the electrode structure.
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 copolymer binder improves mechanical properties, reduces interface resistance, and forms a strong polycarbonate-based interface layer with excellent ion conductivity, leading to enhanced electrochemical performance and extended service life of lithium secondary batteries.
Implementation Method 1
a binder for a lithium iron phosphate (c-LiFePO4) electrode exhibiting improved output and service life characteristics as compared to when an additive is absent by forming a polycarbonate-based electrode interface film via electrochemical reaction with the copolymer binder
Implementation Method 2
a copolymer binder containing a hard segment capable of hydrogen bonding with each electrode active material and a current collector
Data Source
AI summary
The present disclosure provides a polymer binder for a secondary battery electrode, which serves as a binder for a carbon-coated lithium iron phosphate (c-LiFePO4) electrode and is a copolymer containing a hard segment capable of hydrogen bonding in the electrode and a soft segment having a polyol structure.Also, the present disclosure provides a secondary battery electrode and a lithium secondary battery containing the same, wherein a nonaqueous electrolyte solution is applied to an electrode mixture containing the binder for an electrode.