Positive Electrode Coating Composition for Uniform Wetting
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Solution Overview
Problem
The existing method for forming a coating film on positive electrode active materials using a slurry and coating solution suffers from poor wettability, leading to difficulties in achieving uniform coverage and high processing speed.
Innovation Solution
A coating solution comprising water as a solvent, a solute containing phosphorus or boron, with specific mass content ranges, low lithium content, and optional surfactant, optimized for surface energy and absorbance to enhance wettability and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional coating solution is used to form a coating film on positive electrode active material, then the processing speed can be improved, but the wettability between the positive electrode active material and the coating solution is poor, making it difficult to increase the coverage of the coating film
Solution Approach 1:
The patent changes the chemical composition parameters of the coating solution by specifying precise ranges for lithium content (less than 0.1% by mass), M element content (0.05-3.0% by mass), and absorbance (0.1 or less at 660 nm). These parameter adjustments optimize the coating solution's properties to achieve both high processing speed and excellent coverage, directly resolving the technical contradiction between productivity and manufacturing precision.
2Stability of the object's composition
If the surface energy of the coating solution is high, then the coating solution may have better stability, but the wettability between the coating solution and the positive electrode active material is poor, resulting in non-uniform spreading and reduced coverage
Solution Approach 1:
The patent optimizes the surface energy parameter of the coating solution by controlling the surface energy to be 50 mN/m or less. This parameter change improves the wettability between the coating solution and positive electrode active material, enabling uniform spreading and formation of a uniform coating film while maintaining solution stability through controlled composition.
3Quantity of substance
If the concentration of fine particles in the coating solution is high, then the coating solution may have higher solute content, but the coating film formed has more unevenness and greater non-uniformity in thickness
Solution Approach 1:
The patent controls the absorbance of the coating solution to be 0.1 or less at a wavelength of 660 nm, which directly limits the concentration of fine particles in the solution. This parameter control ensures that the coating film formed has minimal unevenness and uniform thickness, while still achieving adequate solute content for effective coating through optimized lithium and M element concentrations.
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 improves the coating ability and coverage by ensuring good wettability and uniform spreading of the coating film on the positive electrode active material, reducing non-uniformity and increasing the coverage ratio.
Implementation Method 1
the wettability between the positive electrode active material and the coating solution is poor, and therefore it tends to be difficult to increase the coverage of the coating film
Implementation Method 2
slurry containing a positive electrode active material and a coating solution is dropletized and such slurry droplets are flash-dried
Data Source
AI summary
A coating solution used for forming a coating film on a surface of a positive electrode active material, wherein the coating solution includes a solvent and a solute, the solvent includes water, the solute includes M element, the M element includes at least one selected from the group consisting of phosphorus and boron, a content of the M element in the coating solution is 0.05% by mass or more and 3.0% by mass or less, a content of lithium in the coating solution is less than 0.1% by mass, an absorbance in a wavelength 660 nm of the coating solution is 0.1 or less, and a surface energy of the coating solution is 50 mN/m or less.