Hydrogen-Storing Alloy Electrode for Nickel-Hydrogen Cells
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Solution Overview
Problem
Nickel-hydrogen secondary cells using rare-earth magnesium alloys face challenges with low alkaline resistance and short cell life due to corrosion reactions with alkaline electrolytes, leading to decreased discharge capacity and increased internal resistance, especially at higher volume energy densities.
Innovation Solution
A hydrogen-storing alloy electrode comprising a combination of rare-earth magnesium alloy and AB5-type hydrogen-storing alloy particles with specific compositions to enhance alkaline resistance and improve continuous-charging characteristics, including a first hydrogen-storing alloy with a composition expressed by (Laa1Ceb1Prc1Ndd1(A1)e1)1-xMgx(Ni1-y(T1)y)z and a second hydrogen-storing alloy with a composition expressed by Laa2Ceb2Prc2Ndd2(A2)e2(Ni1-f(T2)f)i, optimized to suppress corrosion reactions and maintain discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If rare-earth magnesium alloy is used to increase hydrogen storage capacity and volume energy density, then the cell can store more hydrogen, but the alkaline resistance decreases and cell life becomes short
Solution Approach 1:
The patent uses a composite hydrogen-storing alloy system combining rare-earth magnesium alloy (providing high hydrogen storage capacity) with AB5-type rare-earth alloy (providing high alkaline resistance). This composite approach allows the electrode to achieve both high hydrogen storage capacity and long cell life by leveraging the complementary strengths of different alloy types.
2Quantity of substance
If rare-earth magnesium alloy is used to improve volume energy density, then more hydrogen can be stored in smaller volume, but corrosion reaction with alkaline electrolyte increases
Solution Approach 1:
The AB5-type rare-earth alloy acts as a protective intermediary in the composite system. It forms a stable structure that reduces the direct exposure of magnesium to the alkaline electrolyte, thereby suppressing corrosion reactions while maintaining the high hydrogen storage capacity provided by the rare-earth magnesium alloy.
3Productivity
If continuous charging is performed to improve productivity, then charging speed increases, but discharge capacity in re-discharging decreases
Solution Approach 1:
The composite alloy structure provides a cushioning effect against the harmful impacts of continuous charging. The AB5-type alloy component stabilizes the electrode structure and prevents excessive oxidation during fast charging, thereby preserving discharge capacity for subsequent re-discharging cycles.
4Reliability
If alkaline electrolyte is consumed by corrosion reaction, then internal resistance increases, but the electrolyte is needed for cell reaction
Solution Approach 1:
The patent converts the potential harm of magnesium corrosion into a benefit by using a controlled composite alloy system. The AB5-type alloy component regulates the interaction between magnesium and alkaline electrolyte, converting what would be harmful unrestricted corrosion into a controlled process that maintains stable internal resistance while preserving cell life.
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 significantly improves alkaline resistance, extends cell life, and maintains high volume energy density and discharge capacity, ensuring longer operation with reduced internal resistance and oxygen production during overcharging.
Implementation Method 1
The hydrogen-storing alloy has been drawing attention as an energy conversion material and as an energy storage material, since it can store hydrogen safely and easily
Implementation Method 2
magnesium in the rare-earth magnesium alloy corrodes by reaction with an alkaline electrolyte, which decreases the negative-electrode capacity, and this corrosion reaction also consumes the alkaline electrolyte
Data Source
AI summary
A secondary cell has a hydrogen-storing alloy electrode as a negative-electrode plate 26, and the electrode contains first hydrogen-storing alloy particles 36 and second hydrogen-storing alloy particles 37. The first hydrogen-storing alloy particles 36 has composition expressed by general expression (I) (Laa1Ceb1Prc1Ndd1(Al)el)1−xMgx(Ni1−y(T1)y)z, where A1 represents at least one element selected from a group consisting of Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Sr, Sc, Y, Ti, Zr and Hf; T1 represents at least one element selected from a group consisting of V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Al, Ga, Zn, Sn, In, Cu, Si, P and B; a1, b1, c1, d1 and e1 are in the range of 0<a1≦0.25, 0≦b1, 0≦c1, 0≦d1 and 0≦e1 and satisfy the relation a1+b1+c1+d1+e1=1; and x, y and z are in the range of 0<x<1, 0≦y≦0.5 and 2.5≦z≦4.5.