Alkaline Storage Cell Zinc Additive Voltage Stability
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Solution Overview
Problem
Alkaline storage cells using rare-earth magnesium alloys for negative electrodes face a decrease in operating voltage due to repeated charge/discharge cycles, limiting their capacity and performance.
Innovation Solution
Incorporating metal zinc or zinc compounds into the negative electrode of the alkaline storage cell, specifically using a hydrogen-storing alloy powder composition of Ln1-xMgx(Ni1-yTy)z, where Ln represents rare earth elements and T represents various transition metals, with x, y, and z within specific ranges, to suppress the decrease in operating voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If rare earth-Mg-Ni hydrogen-storing alloy is used to enhance capacity, then the hydrogen storage capacity increases, but the operating voltage decreases due to magnesium dissolution during charge/discharge cycles
Solution Approach 1:
Zinc powder is introduced as an intermediary substance that mediates between the magnesium-containing hydrogen-storing alloy and the electrolyte. The zinc reacts preferentially with the electrolyte to form a protective layer, preventing direct contact between the electrolyte and magnesium, thereby suppressing magnesium dissolution while maintaining hydrogen storage capacity
Solution Approach 2:
The harmful effect of zinc reacting with the electrolyte is converted into a beneficial protective mechanism. The zinc sacrificially reacts to form a stable protective layer that prevents the more detrimental magnesium dissolution, thus converting zinc's reactivity from a potential harm into a protective benefit
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 addition of zinc or zinc compounds enhances the capacity and stability of the alkaline storage cell by reducing the dissolution of magnesium into the electrolyte, thereby maintaining higher operating voltages over multiple charge/discharge cycles.
Implementation Method 1
the decrease in operating voltage due to repetition of the charge/discharge cycle can be suppressed by adding metal zinc or zinc compound for the negative electrode
Implementation Method 2
the rare earth-Mg—Ni hydrogen-storing alloy obtained by replacing the rare-earth element in the AB5-type rare-earth alloy partly with Mg has a characteristic that it can store a larger amount of hydrogen gas
Data Source
AI summary
An alkaline storage cell has a negative electrode containing hydrogen-storing alloy powder, additive powder containing metal zinc or zinc compound, and a binding agent for binding particles of the powders. The hydrogen-storing alloy powder has a composition expressed by a general expression: Ln1-xMgx(Ni1-yTy)z, where Ln represents at least one element chosen from a group consisting of the lanthanoids, Ca, Sr, Sc, Y, Ti, Zr and Hf, T represents at least one element chosen from a group consisting of V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Al, Ga, Zn, Sn, In, Cu, Si, P and B, and x, y and z represent numerical values which meet 0<x<1, 0≦y≦0.5 and 2.5≦z≦4.5.