Alkaline Battery Positive Electrode with Cerium Dioxide Coating
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Solution Overview
Problem
Alkaline secondary batteries face challenges with reduced discharge capacity and performance degradation due to the reduction of cobalt oxyhydroxide during overdischarge, and the swelling of γ-type nickel oxyhydroxide, which increases internal resistance and shortens cycle life.
Innovation Solution
A positive active material for alkaline secondary batteries is developed, featuring a core layer of nickel hydroxide with a conductive auxiliary layer containing cobalt oxyhydroxide and cerium dioxide, and subjected to lithium impregnation, which inhibits the reduction of cobalt oxyhydroxide and enhances discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt oxyhydroxide is used as an electroconductive additive, then electric conductivity is improved, but reduction occurs during overdischarge leading to decreased conductivity and performance degradation
Solution Approach 1:
A coating layer comprising a compound of at least one metallic element selected from Ca, Sr, Ba, Cu, Ag, Cd, Y, Yb, Ce, Sm, Gd, and Er is applied to the surface of nickel hydroxide particles. This coating layer acts as an intermediary that prevents direct contact between cobalt oxyhydroxide and the electrolyte solution, thereby preventing reduction of cobalt oxyhydroxide during overdischarge while maintaining its electroconductive function.
Solution Approach 2:
The positive electrode active material is constructed as a composite structure with a core layer of nickel hydroxide and a coating layer containing metallic element compounds. This composite structure combines the high capacity of nickel hydroxide with the protective function of the coating layer, creating a material that maintains cobalt oxyhydroxide stability while enabling high performance.
2Quantity of substance
If γ type nickel oxyhydroxide is utilized to increase battery capacity, then discharge capacity is improved, but swelling phenomenon occurs causing increased internal resistance and shortened cycle life
Solution Approach 1:
The coating layer comprising compounds of metallic elements (Ca, Sr, Ba, Cu, Ag, Cd, Y, Yb, Ce, Sm, Gd, or Er) serves as a protective intermediary that restrains the swelling phenomenon of γ type nickel oxyhydroxide. This coating layer prevents direct interaction between the active material and electrolyte, thereby maintaining structural stability while preserving the high capacity characteristics of γ type nickel oxyhydroxide.
Solution Approach 2:
The invention changes the physical and chemical parameters of the nickel hydroxide surface by applying a coating layer with specific metallic element compounds. This modification allows the material to maintain the high capacity properties of γ type nickel oxyhydroxide while suppressing the harmful swelling effect through altered surface characteristics and restricted ion transport.
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 solution results in an alkaline secondary battery with increased discharge capacity and reduced performance degradation during overdischarge, maintaining high electric conductivity and cycle life.
Implementation Method 1
lithium impregnation, which inhibits the reduction of cobalt oxyhydroxide
Implementation Method 2
Cobalt oxide and cobalt hydroxide are oxidized into cobalt oxyhydroxide at the time of initial charge
Implementation Method 3
γ type nickel oxyhydroxide has a crystal structure in which alkali metal ions or water molecules are incorporated into a space between layers thereof, and has a larger volume than β type nickel oxyhydroxide, a swelling phenomenon of a positive electrode occurs
Data Source
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AI summary
The present invention aims to provide an alkaline secondary battery having a large discharge capacity, and little performance degradation during overdischarge. The object of the present invention can be achieved by a positive active material for an alkaline secondary battery having a core layer containing nickel hydroxide and a conductive auxiliary layer which coats the surface of the core layer, wherein the conductive auxiliary layer contains a cobalt oxyhydroxide phase and a cerium dioxide phase, and the active material contains lithium. The inclusion of the cerium dioxide phase in the conductive auxiliary layer enables the inhibition of reduction of cobalt oxyhydroxide even in conditions such as overdischarge. The inclusion of lithium in the active material and the inclusion of the cerium dioxide phase in the conductive auxiliary layer enable the increase of the battery discharge capacity.