Coated Nickel Hydroxide Powder for Alkaline Battery Electrodes
Solution Overview
Problem
Nickel hydroxide powders for alkaline secondary battery positive electrodes are poor in conductivity and dispersibility, leading to low packing density and inadequate battery characteristics due to agglomeration issues during paste preparation.
Innovation Solution
A coated nickel hydroxide powder with a cobalt compound coating, produced using a method that controls ion elution by adjusting the atmosphere during drying and washing steps, to inhibit agglomeration and enhance dispersibility, resulting in improved packing density and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel hydroxide particles are coated with cobalt compound to improve conductivity, then electrical conductivity between particles is enhanced, but dispersibility in paste deteriorates leading to agglomeration
Solution Approach 1:
The invention changes the chemical composition parameters of the coating layer by controlling the molar ratio of cobalt to nickel (Co/Ni ratio) within 0.05-0.5, and controlling the thickness of the cobalt compound coating layer. These parameter changes optimize both conductivity and dispersibility, preventing agglomeration while maintaining electrical conductivity.
Solution Approach 2:
The invention creates a composite structure where nickel hydroxide particles are coated with a controlled layer of cobalt compound. This composite material combines the high conductivity of cobalt compound with the structural integrity of nickel hydroxide, achieving both improved electrical properties and maintained dispersibility through optimized coating composition.
2Reliability
If cobalt compound coating is applied to nickel hydroxide particles, then utilization ratio at high temperatures is improved, but packing density in positive electrode deteriorates
Solution Approach 1:
The invention optimizes the coating thickness and Co/Ni molar ratio parameters to control particle size and morphology. This ensures that the coated particles maintain appropriate dimensions for high utilization ratio while achieving sufficient packing density in the positive electrode structure.
3Reliability
If conventional coating method is used to produce coated nickel hydroxide powder, then conductivity is enhanced, but manufacturing complexity increases due to multiple processing steps
Solution Approach 1:
The invention merges the coating formation process with the existing nickel hydroxide particle production process. By controlling the precipitation conditions and adding cobalt salts during the nickel hydroxide formation, the coating is formed in-situ during the main manufacturing process, reducing the need for separate coating steps and simplifying the overall manufacturing流程.
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 coated nickel hydroxide powder achieves uniform packing in three-dimensional metal porous bodies, enhancing discharge capacity and overall battery characteristics by reducing ion elution and agglomeration, thereby improving the battery's performance.
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
immersing the nickel hydroxide particles in an aqueous solution of cobalt sulfate or cobalt nitrate, and neutralizing the aqueous solution with an aqueous alkali solution
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 and a coating layer made of a cobalt compound and 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, a total amount of eluted ions except for oxonium ions, hydroxide ions, and carbonate ions in the suspension is 6.5 mmol/L or less. The coated nickel hydroxide powder obtained through a crystallization step, a coating step, and a washing step is dried in a drying step in a decarbonated atmosphere whose partial pressure of a carbon-containing gas is 15 Pa or less.