NiMH Negative Electrode Composition for Low-Temperature Cycle Life
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Solution Overview
Problem
Conventional nickel-metal hydride secondary batteries face challenges in achieving both improved cycle life and low-temperature discharge characteristics, as adding Co to the alloy or alkali treatment to suppress pulverization and corrosion often deteriorates reactivity.
Innovation Solution
Incorporating a negative electrode mixture layer with yttrium fluoride particles of specific size (1 μm to 7 μm) on a hydrogen storage alloy core body enhances reactivity and suppresses corrosion, ensuring adequate dispersion and reactivity during low-temperature discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Co is added to hydrogen storage alloy or alkali treatment is applied to suppress pulverization and corrosion, then cycle life is improved, but reactivity deteriorates and low-temperature discharge characteristic deteriorates
Solution Approach 1:
Yttrium fluoride particles are introduced as an intermediary substance between the hydrogen storage alloy and the alkaline electrolytic solution. These particles form a protective interface that prevents direct corrosive interaction while allowing beneficial electrochemical reactions to proceed, thus improving cycle life without sacrificing low-temperature discharge characteristics
Solution Approach 2:
The invention changes the chemical composition parameters of the negative electrode by incorporating yttrium fluoride at specific concentrations (0.1-10 wt%). This parameter modification alters the surface properties and electrochemical behavior of the alloy, achieving both improved durability and maintained reactivity under various temperature conditions
2Stability of the object's composition
If yttrium fluoride particle size is too small, then dispersion is improved, but corrosion suppression effectiveness decreases
Solution Approach 1:
The invention applies a specific range of yttrium fluoride particle sizes (1-7 μm) that provides optimal balance between dispersion and corrosion protection. This partial action approach uses neither ultra-fine particles (which would disperse well but protect poorly) nor coarse particles (which would protect well but disperse poorly), but rather an intermediate size range that achieves both objectives effectively
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 a negative electrode that improves both cycle life and low-temperature discharge characteristics by maintaining reactivity and reducing corrosion of the hydrogen storage alloy.
Implementation Method 1
a predetermined electrochemical reaction induced between the positive electrode plate and the negative electrode plate which face each other via the separator, whereby charging and discharging are performed
Implementation Method 2
the characteristics of fluorine suppress the corrosion of the hydrogen storage alloy by the alkaline electrolytic solution
Data Source
AI summary
A negative electrode for an alkaline storage battery that achieves both an improvement in cycle life and an improvement in low temperature discharge characteristics, and an alkaline storage battery including the negative electrode are disclosed. The negative electrode for an alkaline storage battery includes a negative electrode core body formed of metal, and a negative electrode mixture layer which contains at least a hydrogen storage alloy and yttrium fluoride, and is carried on the negative electrode core body. Particles of the yttrium fluoride are formed so that the average particle size thereof is equal to 1 μm or more and 7 μm or less.