Hydrurable Alloy for Ni-MH Battery Negative Electrode
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Solution Overview
Problem
Alkaline electrolyte nickel metal hydride batteries face limitations in both initial capacity and lifespan due to the corrosion of the negative electrode, where increasing capacity reduces lifespan and vice versa, with existing alloys like AB5 stoichiometry offering insufficient power and lifespan when upgraded to AB2 stoichiometry.
Innovation Solution
A hydrurable alloy with the formula R1-x-yMgxyNiSaB, where R is rare earth elements, M is Zr or Ti, and B is Mn, Al, Co, or Fe, with a specific structure comprising a stack of A2B4 and CaCu5 patterns, optimized through a manufacturing process involving grinding and flash sintering to enhance cycling stability and hydrogen absorption capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacity of the positive electrode is increased to improve the initial capacity of the accumulator, then the initial capacity is improved, but the lifespan is reduced due to electrolyte volume limitation
Solution Approach 1:
The invention changes the chemical composition parameters of the negative electrode alloy by incorporating specific elements (Al, Co, Fe, Mn) in controlled amounts to optimize both capacity and corrosion resistance, allowing high initial capacity without sacrificing lifespan
Solution Approach 2:
The invention creates a composite alloy system combining rare earth elements (La, Ce, Pr, Nd) with transition metals (Ni, Co, Mn, Al, Fe) to achieve synergistic effects that simultaneously provide high hydrogen absorption capacity and improved corrosion resistance, resolving the capacity-lifespan trade-off
2Quantity of substance
If the volume of the alloy is increased to improve the initial capacity, then the initial capacity is improved, but the lifespan is reduced due to water consumption by corrosion reaction
Solution Approach 1:
The invention uses small amounts of sacrificial elements (Al, Co, Fe, Mn) that preferentially corrode to protect the main rare earth-nickel alloy structure, effectively sacrificing minor components to preserve the overall system lifespan while maintaining high capacity
Solution Approach 2:
The alloy composition is designed with corrosion-resistant elements that preemptively protect against water consumption during cycling, cushioning the negative electrode against degradation before it occurs and maintaining electrolyte volume stability throughout the battery lifespan
3Quantity of substance
If the stoichiometry is changed from AB5 to AB2 to increase the volume capacity, then the initial capacity is improved, but the power and lifespan are considerably reduced
Solution Approach 1:
The invention creates local regions with different compositional characteristics within the alloy structure, incorporating specific elements at controlled concentrations to provide localized corrosion resistance and hydrogen absorption sites that maintain both high capacity and long lifespan
Solution Approach 2:
The invention optimizes the stoichiometric ratios of alloying elements, maintaining a composition close to AB5 while incorporating specific additions (Al, Co, Fe, Mn) to achieve enhanced performance that surpasses both AB5 and AB2 configurations
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 alloy achieves a high initial mass capacity of at least 310 mAh/g with less than 15% capacity degradation after 100 cycles, improving both capacity and lifespan while maintaining acceptable hydrogen equilibrium pressure for Ni-MH battery applications.
Implementation Method 1
hydrurable alloy of formula R1-x-yMgxyNiSaB... offering both high capacity and a high lifespan
Implementation Method 2
the lifespan of a Ni-MH accumulator is limited by corrosion of the alloy and its consequences, namely the reduction in the capacity of the negative electrode and the drying of the beam following the consumption of water by the corrosion reaction
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
A hydrurizable alloy, of formula R1-x-yMgxMyNis-aBa in which - R is chosen from the group consisting of rare earths, yttrium and a mixture thereof; - M represents Zr and/or Ti; - B is chosen from the group consisting of Mn, Al, Co, Fe and a mixture thereof; 0.1 <x<0,4; 0≤y<0,1 ;3 <s<4,5 et 0≤a<1 ; dont au moins 5% du volume est constitué d'un empilement de séquences d'un motif de type A2B4 et n motifs de type CaCu5 distribuées de façon aléatoire selon une direction, n étant un nombre entier compris entre 1 et 10 et représentant le nombre de motifs de type CaCu5 par motif de type A2B4. Un procédé de fabrication d'un alliage hydrurable comprenant les étapes de compression et application d'un courant à travers un mélange comprenant Mg2Ni et un composé comprenant du nickel et un ou plusieurs éléments choisis dans le groupe consistant en les terres rares et l'yttrium.