Coated Nickel Hydroxide Powder for Alkaline Battery Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for coating nickel hydroxide powders with cobalt compounds to enhance conductivity and adhesion in alkaline secondary batteries face issues with non-uniformity and peeling of the cobalt hydroxide coating, leading to reduced utilization and output characteristics.
Innovation Solution
A method involving the controlled diffusion of aqueous cobalt salt and alkali solutions in a stirred suspension of nickel hydroxide powder, followed by oxidation to form a uniform cobalt oxyhydroxide coating, ensuring high adhesion and conductivity by maintaining specific pH and oxygen supply conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt compound powder is mixed with binder to form paste for coating nickel hydroxide powder, then conductivity between particles is improved, but uniform dispersion of cobalt compound on nickel hydroxide surface is poor leading to reduced utilization ratio
Solution Approach 1:
The cobalt compound is applied to the nickel hydroxide powder surface before binder addition, ensuring uniform dispersion on the particle surface prior to paste formation. This preliminary coating action prevents agglomeration and ensures consistent conductivity throughout the electrode structure.
Solution Approach 2:
The cobalt compound application step is separated from the binder mixing step. Instead of mixing cobalt compound with binder first, the cobalt compound is applied to nickel hydroxide powder separately, then the binder is added. This extraction of steps allows for better control of dispersion quality.
2Reliability
If cobalt hydroxide coating is formed on nickel hydroxide powder surface, then conductivity is enhanced, but coating uniformity and adhesion are poor causing peeling during paste preparation
Solution Approach 1:
A dispersant is introduced as an intermediary substance between the cobalt compound and nickel hydroxide powder. The dispersant facilitates uniform coating formation and enhances adhesion by mediating the interaction between cobalt hydroxide and nickel hydroxide surfaces, preventing peeling during subsequent processing.
Solution Approach 2:
The pH value of the coating solution is precisely controlled within the range of 8-11.5 to optimize cobalt hydroxide precipitation and adhesion to nickel hydroxide particles. This parameter control ensures uniform coating formation while maintaining strong bonding, preventing peeling during paste preparation.
3Quantity of substance
If nickel hydroxide powder is used as positive electrode active material, then high capacity is achieved, but electrical conductivity is poor reducing electrochemical availability
Solution Approach 1:
A composite structure is created where cobalt hydroxide coats the nickel hydroxide powder particles. This composite material combines the high capacity of nickel hydroxide with the excellent conductivity of cobalt compounds, achieving both high capacity and good electrical conductivity in the positive electrode active material.
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 achieves a stable, uniform cobalt oxyhydroxide coating on nickel hydroxide powders, preventing peeling and enhancing conductivity, thus improving the utilization ratio and output characteristics of alkaline secondary batteries, making them suitable for high-capacity and high-output applications.
Implementation Method 1
controlled diffusion of aqueous cobalt salt and alkali solutions in a stirred suspension of nickel hydroxide powder
Implementation Method 2
aqueous cobalt salt solution and an aqueous alkali solution are supplied to a stirred suspension obtained by dispersing a nickel hydroxide powder in water to form, on a surface of nickel hydroxide particles, a coating mainly containing cobalt hydroxide crystallized out by neutralization
Implementation Method 3
an oxidation step in which oxygen is supplied to a stirred slurry of the nickel hydroxide particles having the coating formed thereon to oxidize cobalt hydroxide in the coating
Data Source
AI summary
A method for producing coated nickel hydroxide powder for a positive electrode of an alkaline secondary battery wherein the pH of a suspension of a nickel hydroxide powder is kept at 8 to 11.5, and an aqueous cobalt salt solution and an aqueous alkali solution are supplied to the suspension to coat the surface of nickel hydroxide particles with cobalt hydroxide. Then, the pH of a slurry of the cobalt hydroxide-coated nickel hydroxide powder is adjusted to 12.5 to 13.0, and oxygen is supplied to the slurry so that the total amount of oxygen supplied per mole of cobalt in the coating is 30 l/mol or more to oxidize the cobalt hydroxide.