Hydrogen Storage Alloy Composition for Alkaline Cell
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Solution Overview
Problem
Alkaline storage cells using rare earth-Mg—Ni hydrogen storage alloys for negative electrodes face challenges with hydrogen release, corrosion resistance, and cycle life due to limited discharge capacity and short cycle life.
Innovation Solution
A rare earth-Mg—Ni hydrogen storage alloy with a specific composition ((PrNd)αLn1-α)1-βMgβNiγ-δ-εAlδTε, where α > 0.7, 0.05 < β < 0.15, 3.0 ≤ γ ≤ 4.2, 0.15 ≤ δ ≤ 0.30, and 0 ≤ ε ≤ 0.20, is used to enhance hydrogen release, corrosion resistance, and cycle life by stabilizing the crystal structure and increasing hydrogen equilibrium pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If rare earth-Mg—Ni hydrogen storage alloy is used to enhance capacity, then hydrogen storage capacity is improved, but hydrogen release property deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional parameters of the hydrogen storage alloy. Specifically, it limits Mg content to 5-15 atom% and Al content to 15-30 atom%, while optimizing rare earth element ratios (Pr:Nd between 3:2 to 1:4). These parameter adjustments enable the alloy to achieve both high hydrogen storage capacity (700-800 mAh) and good hydrogen release properties, resolving the contradiction between capacity enhancement and release difficulty.
2Quantity of substance
If rare earth-Mg—Ni hydrogen storage alloy is used to enhance capacity, then hydrogen storage capacity is improved, but corrosion resistance to alkaline electrolyte deteriorates
Solution Approach 1:
The patent resolves the corrosion resistance issue through parameter changes in alloy composition. By limiting Mg content to 5-15 atom% and adding 15-30 atom% Al, the alloy forms a protective surface layer that significantly improves corrosion resistance to alkaline electrolyte. The optimized rare earth element composition (Pr and Nd in specific ratios) further enhances electrochemical stability, allowing the cell to maintain 70% of initial capacity after 300 charge-discharge cycles.
Solution Approach 2:
The patent employs composite material principles by creating a multi-element alloy system combining rare earth elements (Pr, Nd), Mg, Ni, and Al. This composite structure leverages the beneficial properties of each element: Pr and Nd provide high capacity, Mg enhances hydrogen storage, Ni ensures conductivity, and Al improves corrosion resistance. The synergistic combination resolves the contradiction between high capacity and corrosion resistance.
3Quantity of substance
If rare earth-Mg—Ni hydrogen storage alloy is used to enhance capacity, then hydrogen storage capacity is improved, but cycle life deteriorates
Solution Approach 1:
The patent extends cycle life through optimized compositional parameters. The controlled Mg content (5-15 atom%) prevents excessive alloy degradation during cycling, while Al (15-30 atom%) forms a stable protective layer. The specific Pr:Nd ratio (3:2 to 1:4) ensures structural stability during repeated charge-discharge cycles. These parameter optimizations enable the cell to maintain 70% of its initial 700-800 mAh capacity after 300 cycles, significantly improving cycle life.
4Quantity of substance
If AB5-type hydrogen storage alloy is used, then discharge capacity is achieved, but possibility of further enhancing capacity is limited
Solution Approach 1:
The patent overcomes the capacity limitation of conventional AB5-type alloys by developing a composite rare earth-Mg-Ni-Al alloy system. This composite structure incorporates Mg (5-15 atom%) for enhanced hydrogen storage capability and Al (15-30 atom%) for improved electrochemical performance. The optimized rare earth composition (Pr and Nd in 3:2 to 1:4 ratio) provides high theoretical capacity. This composite approach achieves discharge capacities of 700-800 mAh with significant room for further enhancement, unlike conventional AB5 alloys that already exceed 80% of theoretical capacity.
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 improved composition results in a high-capacity alkaline storage cell with enhanced discharge characteristics and extended cycle life by increasing the solid solubility of Al and preventing undesired phase precipitation, thus improving corrosion and oxidation resistance.
Implementation Method 1
it can store a large amount of hydrogen, but it has problems that it does not easily release the hydrogen stored
Implementation Method 2
it has problems that it does not easily release the hydrogen stored
Implementation Method 3
by setting Y indicating the proportion of Al to be greater than or equal to 0.02 in the general expression, the oxidation of the alloy is suppressed
Implementation Method 4
the corrosion resistance to the alkaline electrolyte is low
Data Source
AI summary
An alkaline storage cell has a positive electrode, a negative electrode containing a hydrogen storage alloy, and an alkaline electrolyte. The hydrogen storage alloy has a composition expressed by a general expression: ((PrNd)αLn1-α)1-&bgr;Mg&bgr;Niγ-δ-&egr;AlδT&egr;, where Ln represents at least one element chosen from a group consisting of La, Ce, etc., T represents at least one element chosen from a group consisting of V, Nb, etc., and subscripts α, &bgr;, γ, δ and &egr; represent numerical values which satisfy 0.7<α, 0.05<&bgr;<0.15, 3.0≦̸γ≦̸4.2, 0.15≦̸δ≦̸0.30 and 0≦̸&egr;≦̸0.20.