Coated Nickel Hydroxide Powder pH Control for Battery Electrode Packing
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Solution Overview
Problem
The existing nickel hydroxide powders for alkaline secondary battery positive electrodes are poor in conductivity and dispersibility, leading to low packing density and reduced battery performance, despite efforts to improve utilization ratio, lifetime, and output characteristics through cobalt compound coatings.
Innovation Solution
A coated nickel hydroxide powder with a cobalt compound layer is produced by controlling the pH of the suspension during the washing process to inhibit agglomeration, ensuring a pH of 10.2 or higher and reducing ammonium ion elution, which enhances dispersibility and packing density in three-dimensional metal porous bodies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel hydroxide particles are coated with cobalt compound to improve conductivity, then electrical conductivity is improved, but dispersibility in paste deteriorates
Solution Approach 1:
The invention changes the pH parameter of the suspension during washing from conventional low pH to specifically pH 10.2 or higher. This parameter change modifies the surface charge and electrostatic repulsion between particles, preventing agglomeration while maintaining the conductive cobalt compound coating. The controlled high pH environment preserves particle dispersion without compromising the coating's electrical conductivity function.
2Quantity of substance
If nickel hydroxide powder has high tap density for dense packing, then packing density improves, but dispersibility and anti-agglomeration properties deteriorate
Solution Approach 1:
The invention introduces a new parameter control - maintaining suspension pH at 10.2 or higher during washing - which creates electrostatic repulsion between particles. This allows particles to remain dispersed during handling and processing while achieving high packing density during electrode fabrication. The high pH condition prevents premature agglomeration that would otherwise limit packing efficiency.
3Ease of manufacture
If conventional washing is used to remove ammonium ions, then production cost is reduced, but pH control and dispersibility deteriorate
Solution Approach 1:
The invention inverts the conventional approach by specifying a high pH range (10.2 or higher) as the washing condition rather than using conventional neutral or acidic washing. This parameter specification simultaneously achieves ammonium ion removal, maintains particle dispersion, prevents agglomeration, and ensures proper pH control. The high pH condition creates electrostatic repulsion that keeps particles separated during washing and handling.
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 improved dispersibility and packing density of the coated nickel hydroxide powder result in higher discharge capacity and better battery characteristics, such as increased capacity and performance stability.
Implementation Method 1
The cobalt compound that coats the surface of the nickel hydroxide particles develops electrical conductivity and forms a conductive network between the nickel hydroxide particles
Implementation Method 2
controlling the pH of the suspension during the washing process to inhibit agglomeration, ensuring a pH of 10.2 or higher
Implementation Method 3
reducing ammonium ion elution
Data Source
AI summary
A coated nickel hydroxide powder that has improved dispersibility in a paste to inhibit agglomeration and can be densely packed in a three-dimensional metal porous body in the preparation of a positive electrode for alkaline secondary battery includes nickel hydroxide particles having a coating layer made of a cobalt compound formed on a surface of the nickel hydroxide particles, wherein when 10 mL of water is added to 10 g of the coated nickel hydroxide powder to prepare a suspension, the suspension has a pH of 10.2 or higher (as measured at 25° C.). The coated nickel hydroxide powder obtained through a crystallization step and a coating step is washed in a washing step until an amount of ammonium ions eluted into a suspension obtained by adding 10 mL of water to 10 g of the coated nickel hydroxide powder becomes 0.35 mmol/L or less.