Positive electrode material and preparation method therefor, alkaline secondary battery
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Solution Overview
Problem
Existing methods for enhancing the electrical conductivity and stability of nickel hydroxide-based positive electrodes in alkaline secondary batteries face issues such as uneven distribution of cobalt compounds, insufficient oxidation to trivalent state, agglomeration, and instability at high temperatures, leading to reduced performance and capacity decay.
Innovation Solution
A positive electrode material with a core of nickel hydroxide and a coating layer containing at least 45 wt% tetravalent cobalt compound, prepared through a controlled coprecipitation and oxidation process using sodium hypochlorite, ensures uniform and stable conductivity and adhesiveness, preventing capacity decay and improving high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physical doping method is used to mix cobalt or cobalt compound with nickel hydroxide, then the electrical conductivity is improved, but the distribution of cobalt is uneven resulting in poor performance
Solution Approach 1:
The patent applies preliminary action by first forming a uniform cobalt compound coating layer on the nickel hydroxide particle surfaces through coprecipitation before battery assembly. This pre-established uniform distribution ensures consistent electrical conductivity throughout the electrode, eliminating the uneven distribution problem of physical doping while maintaining high reliability.
Solution Approach 2:
The patent creates a composite material structure where cobalt compounds (CoO, Co2O3, Co3O4, or Co(OH)2) are chemically integrated with nickel hydroxide particles through coprecipitation. This composite approach achieves uniform distribution at the particle level, combining the electrical conductivity benefits of cobalt with the structural integrity of nickel hydroxide.
2Manufacturing precision
If coprecipitation method is used to coat Co(OH)2 on nickel hydroxide particles, then the coating is uniform, but the bivalent cobalt compound is not conductive and requires electrochemical oxidation which cannot be completed fully
Solution Approach 1:
The patent applies parameter changes by controlling the coprecipitation process to directly form trivalent or tetravalent cobalt compounds instead of bivalent Co(OH)2. By adjusting the oxidation state parameter during coprecipitation (using appropriate pH conditions and oxidizing agents), the method achieves both uniform coating and inherent electrical conductivity without requiring incomplete electrochemical oxidation.
Solution Approach 2:
The patent converts the potential harm of requiring post-synthesis oxidation treatment into a benefit by directly forming conductive trivalent or tetravalent cobalt compounds during coprecipitation. This eliminates the harmful effect of incomplete oxidation and the associated conductivity limitations, turning a multi-step process with defects into a single-step process with superior performance.
3Reliability
If electroless plating is used to coat cobalt film on nickel hydroxide particles, then the coating provides conductivity, but the operating conditions are very rigorous and require noble metal catalysts
Solution Approach 1:
The patent replaces expensive noble metal catalysts required for electroless plating with inexpensive, readily available reagents for coprecipitation (such as sodium hydroxide, ammonium hydroxide, or carbonates). This substitution maintains the electrical conductivity benefit while dramatically simplifying the manufacturing process and reducing costs, making the method economically viable for large-scale production.
Solution Approach 2:
The patent substitutes the complex electrochemical system of electroless plating (requiring catalysts, controlled potentials, and specialized equipment) with a simple chemical precipitation system. The coprecipitation method uses basic solution chemistry to form cobalt compound coatings, replacing the sophisticated electrochemical machinery with straightforward chemical reactions that are easier to control and scale.
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 material achieves higher electrical conductivity, stability, and capacity retention, suitable for high-rate discharge and high-temperature applications, enhancing the performance of alkaline secondary batteries.
Implementation Method 1
cobalt is coprecipitated into nickel hydroxide
Implementation Method 2
Co(OH)2 precipitated on the surface of the nickel hydroxide particles
Implementation Method 3
it is oxidized to form cobalt oxyhydroxide coated on the surface of the nickel hydroxide particles
Data Source
AI summary
The present invention relates to a positive electrode material comprising a core material and a coating layer coated on the surface of the core material, the core material comprises nickel hydroxide, and the coating layer comprises a tetravalent cobalt compound; and based on the weight of the coating layer, the content of the tetravalent cobalt compound is no less than 45 wt %. The present invention also relates to a preparation method for the positive electrode material. The present invention further relates to an alkaline secondary battery containing the positive electrode material.