Cobalt-Oxyhydroxide Nickel Hydroxide Coating for Low Resistivity
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Solution Overview
Problem
Existing nickel-containing hydroxide coated with cobalt for positive electrode active material in secondary batteries experiences uneven coating, leading to increased battery resistance and volume resistivity, which hinders improved battery characteristics.
Innovation Solution
Control the average circularity of particles with diameters at a cumulative volume percentage of 50% (D50) within a predetermined range of 0.900 to 0.990, and adjust the molar ratios of nickel and cobalt or nickel, cobalt, and zinc to form a coating layer containing cobalt oxyhydroxide, optimizing the production process through controlled heating and oxidation steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating layer of cobalt compound is formed on nickel hydroxide particles to increase cobalt content, then battery characteristics are improved, but uneven coating occurs during production leading to increased battery resistance
Solution Approach 1:
The invention controls the average circularity of particles within a specific range (0.940-0.990) to ensure uniform coating. By adjusting particle shape parameters, the coating process achieves better uniformity and reduces battery resistance while maintaining improved battery characteristics from the cobalt coating.
Solution Approach 2:
The invention specifies that the coating layer should contain cobalt oxyhydroxide as the main component with cobalt content of 3-15 mass%, creating a localized high-cobalt region on the particle surface. This localized quality enhancement improves battery characteristics while the controlled particle circularity ensures this enhancement is achieved uniformly across all particles.
2Reliability
If cobalt content in nickel-containing hydroxide is increased to improve battery characteristics, then performance is enhanced, but volume resistivity increases
Solution Approach 1:
The invention optimizes the average circularity parameter to within 0.940-0.990, which enables the coating process to achieve uniform distribution of cobalt compounds. This uniform distribution prevents localized resistance buildup, allowing the material to maintain low volume resistivity (4.0 Ω·cm or less) even with increased cobalt content (3-15 mass%).
Solution Approach 2:
By controlling particle circularity to ensure uniform coating, the invention achieves homogeneous distribution of cobalt oxyhydroxide throughout the nickel-containing hydroxide structure. This homogeneity prevents the formation of high-resistivity regions, allowing high cobalt content to be maintained without increasing volume resistivity.
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
Reduces uneven coating and battery resistance, enhances electrical conductivity, and improves charge and discharge characteristics by maintaining volume resistivity at 4.0 Ω·cm or less, thereby achieving superior battery performance.
Implementation Method 1
a coating layer containing cobalt oxyhydroxide as a main component is formed on nickel-containing hydroxide particles
Implementation Method 2
an oxidation step of adding an alkaline solution to the nickel-containing hydroxide on which a coating layer containing cobalt is formed under heating conditions to chemically oxidize the cobalt(II) in the coating layer
Data Source
AI summary
Provided is a nickel-containing hydroxide coated with cobalt, having a coating layer containing cobalt oxyhydroxide formed on a nickel-containing hydroxide, in which an average circularity of particles having particle diameters equal to or more than a particle diameter at a cumulative volume percentage of 50% (D50) within a range of 0.900 or more and 0.990 or less.