Positive Electrode Coating for Battery Safety
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face safety issues due to uneven formation of porous inorganic particle layers on positive electrode active material surfaces, leading to potential short circuits and reduced battery safety.
Innovation Solution
A method for manufacturing a positive electrode involving the formation of a porous inorganic particle layer using an inorganic particle slurry with carboxymethyl cellulose (CMC) having an etherification degree of 0.8 or more and a viscosity of 800 mPa·s or more, coated using the gravure method to ensure evenness and prevent agglutination, with inorganic particles like titanium or aluminum oxide, and a binder content of 5% by mass or less to maintain insulating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous inorganic particle layer is formed on the positive electrode active material layer to improve battery safety, then insulating properties are enhanced, but the coating becomes uneven causing exposed portions that lead to short circuits
Solution Approach 1:
The invention changes the chemical composition parameters of the slurry by specifying CMC with an etherification degree of 0.7 or more and a viscosity of 500 mPa·s or more at a concentration of 0.5% by mass or more. These parameter changes prevent particle agglomeration and ensure uniform coating distribution, resolving the contradiction between safety improvement and coating evenness.
Solution Approach 2:
The invention uses CMC as an intermediary substance with specific properties (high etherification degree and high viscosity) to mediate between the inorganic particles and the electrode surface. This intermediary prevents particle aggregation and ensures uniform distribution during coating, achieving both safety enhancement and coating uniformity.
2Reliability
If submicron size inorganic particles are used to form the porous layer, then insulating effect is improved, but particles agglomerate causing uneven coating and reduced safety
Solution Approach 1:
The invention changes the slurry composition parameters by incorporating CMC with specific properties (etherification degree ≥0.7, viscosity ≥500 mPa·s at 0.5% concentration). These parameter changes create a stable slurry that prevents submicron particle agglomeration, maintaining both insulating effect and slurry stability.
Solution Approach 2:
The invention creates a composite slurry system combining submicron inorganic particles with specifically formulated CMC. This composite material approach allows the CMC to disperse and stabilize the submicron particles, preventing agglomeration while maintaining the desired insulating properties.
3Quantity of substance
If higher capacity materials like lithium nickel oxide are used to increase battery capacity, then energy density is improved, but battery safety is reduced
Solution Approach 1:
The invention applies local quality modification by forming a porous inorganic particle layer specifically on the surface of the positive electrode active material layer. This localized treatment enhances safety at the critical interface where short circuits occur, while allowing the bulk high-capacity materials to maintain their energy density benefits.
Solution Approach 2:
The porous inorganic particle layer acts as an intermediary between the high-capacity active material and the electrolyte. This intermediary layer provides the necessary insulation to prevent short circuits while allowing the underlying high-capacity materials to function, thus reconciling capacity and safety requirements.
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 method ensures a stable and evenly coated porous inorganic particle layer, enhancing the insulating properties of the positive electrode, thereby preventing internal short circuits and improving battery safety without significantly decreasing capacity.
Implementation Method 1
coating an inorganic particle slurry containing inorganic particles, CMC, and a binder on a surface of the positive electrode active material layer and thereafter drying the slurry to form a porous inorganic particle layer
Data Source
AI summary
A method for manufacturing a positive electrode for a nonaqueous electrolyte secondary battery includes forming an inorganic particle slurry layer formed on a surface of a positive electrode active material layer. The method includes forming a positive electrode active material layer on a surface of a positive electrode collector, and coating an inorganic particle slurry containing inorganic particles and carboxymethyl cellulose on a surface of the positive electrode active material layer and thereafter drying the slurry to form a porous inorganic particle layer. The inorganic particle slurry contains carboxymethyl cellulose having an etherification degree of 0.8 or more and a viscosity of 800 mPa·s or more in a 1% aqueous solution at a ratio of 0.2% by mass or more and 1.0% by mass or less with respect to the inorganic particles.