Polyimide-Coated Active Material Particles for Battery Electrodes
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Solution Overview
Problem
The use of polyimides as binders in negative electrodes for lithium secondary batteries is hindered by their insolubility in water, requiring organic solvents and leading to environmental concerns and reduced charge-discharge cycle characteristics due to the expansion and shrinkage of active material particles.
Innovation Solution
A polyimide-coated active material particle with a porous polyimide layer derived from a monomeric polyimide precursor is used, combined with an aqueous binder, reducing the need for organic solvents and improving the charge-discharge cycle characteristics by minimizing particle fracture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide resin is used as a binder in the active material layer, then charge-discharge cycle characteristics are improved, but organic solvents must be used which causes environmental concerns
Solution Approach 1:
The invention changes the fundamental parameter of binder solubility by using water-soluble polyimide resins instead of conventional water-insoluble polyimides. This allows the binder to be dissolved in water rather than organic solvents, eliminating the need for organic solvent processing while maintaining the protective function that improves charge-discharge cycle characteristics
Solution Approach 2:
The invention discards the harmful organic solvents from the processing system and replaces them with environmentally benign water. The water-soluble polyimide resin can be applied from aqueous solutions, and the water evaporates without leaving harmful residues, thus recovering from the environmental damage caused by organic solvent usage
2Reliability
If polyimide resin is used as a binder, then charge-discharge cycle characteristics are improved, but the complexity of the production process increases due to requiring polyimide precursor solutions
Solution Approach 1:
The invention simplifies the production process by changing the solubility parameter of the polyimide resin to be water-soluble. This eliminates the need for complex organic solvent handling, drying, and safety protocols, reducing production process complexity while maintaining the charge-discharge cycle improvement benefits
Solution Approach 2:
The water-soluble polyimide resin acts as an intermediary that provides the protective function of conventional polyimides while being compatible with simple aqueous processing. This intermediary material enables the use of straightforward water-based application methods rather than complex organic solvent-based processes
3Use of energy by moving object
If active material particles repeatedly expand and shrink during charging and discharging, then battery capacity is maintained, but the particles and binder are fractured causing deterioration of charge-discharge cycle characteristics
Solution Approach 1:
The water-soluble polyimide resin binder provides beforehand cushioning by forming a flexible, adhesive matrix that accommodates the expansion and shrinkage of active material particles during charge-discharge cycles. This protective matrix prevents particle fracture and binder detachment before they can occur, maintaining both battery capacity and cycle characteristics
Solution Approach 2:
The invention uses composite material structure where water-soluble polyimide resin forms a protective matrix surrounding and supporting the active material particles. This composite structure combines the high capacity of active materials with the protective, flexible properties of the polyimide binder, enabling repeated expansion-shrinkage cycles without fracture
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 solution effectively suppresses the deterioration of charge-discharge cycle characteristics and reduces environmental impact by using an aqueous binder system, maintaining performance comparable to polyimide-based systems while minimizing organic solvent usage.
Implementation Method 1
a polyimide layer derived from a monomeric polyimide precursor and coated on the active material particle
Implementation Method 2
the polyimide precursor solution is mixed with an active material to form a slurry, and the slurry is applied to a current collector and heated to form a negative electrode active material layer including a polyimide resin
Data Source
AI summary
A polyimide-coated active material particle (21) of the present invention includes an active material particle (23) and a polyimide layer (24) derived from a monomeric polyimide precursor and coated on the active material particle (23). A negative electrode (200) of the present invention includes a current collector (30) and an active material layer (20) including the negative electrode active material particle (21) coated with the polyimide layer (24) derived from a monomeric polyimide precursor, and an aqueous binder (22). With the polyimide-coated active material particle of the present invention, it is possible to suppress the amount of organic solvent used and improve the charge-discharge cycle of the electrode.