Hydrogen Storage Alloy Surface Composition for Alkaline Battery Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Alkaline storage batteries using rare earth-Mg—Ni-based hydrogen storage alloys with A5B19 type structure face challenges in maintaining output power stability due to variations in equilibrium pressure with state of charge (SOC), leading to reduced durability and lifetime discharge power, primarily because of the instability of the crystal structure and elution of aluminum into the electrolyte.
Innovation Solution
A hydrogen storage alloy composition of LaxReyMg1-x-yNin-m-vAlmTv with a main phase of A5B19 type crystal structure, where the aluminum to nickel ratio in the surface layer is lower than in the bulk layer, and controlled electrolyte retention amounts, to stabilize output characteristics and prevent aluminum elution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a rare earth-Mg—Ni-based hydrogen storage alloy with A5B19 type structure is used to improve high power characteristics, then output characteristics are improved, but crystal structure stability deteriorates leading to subphase generation and reduced output power stability
Solution Approach 1:
The patent applies local quality by creating a surface layer with different composition than the bulk material. The surface layer has lower aluminum content and modified stoichiometry compared to the interior, providing localized protection against subphase formation and crystal structure instability while maintaining the high power characteristics of the A5B19 type structure in the bulk.
Solution Approach 2:
The patent changes compositional parameters by controlling the stoichiometric ratio and aluminum content within specific ranges (0.03≤m≤0.22, 3.5≤n≤3.8). By adjusting these parameters and creating a surface layer with distinct composition, the patent stabilizes the crystal structure while preserving the high power output characteristics of the A5B19 type structure.
2Power
If aluminum content is increased to stabilize the A5B19 type structure, then high power characteristics are improved, but aluminum elution into electrolyte increases reducing durability
Solution Approach 1:
The patent creates a surface layer with reduced aluminum content compared to the bulk material. This localized compositional modification prevents aluminum elution into the electrolyte while maintaining sufficient aluminum content in the bulk to stabilize the A5B19 type structure and preserve high power characteristics.
Solution Approach 2:
The patent segments the alloy into two distinct regions: a surface layer with lower aluminum content that prevents elution, and a bulk region with higher aluminum content that stabilizes the crystal structure. This segmentation allows each region to fulfill its specific function without compromising the other.
3Productivity
If pulse charge and discharge cycles are repeated in partial charge-discharge control system, then high power application requirements are met, but output power stability varies with SOC variation
Solution Approach 1:
The patent changes the compositional parameters of the hydrogen storage alloy by controlling the stoichiometric ratio and creating a surface layer with modified composition. This parameter modification stabilizes the equilibrium pressure and prevents subphase formation, thereby maintaining output power stability during repeated pulse charge and discharge cycles across different SOC ranges.
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 enhances the stability of output characteristics and extends the lifetime discharge power by maintaining a stable surface condition and reducing aluminum elution, thereby improving the alkaline storage battery's durability and performance over 6000 hours of partial charge and discharge cycles.
Implementation Method 1
the equilibrium pressure of the hydrogen storage alloy does not largely vary associated with the SOC variation
Implementation Method 2
the equilibrium pressure of the hydrogen storage alloy does not largely vary associated with the SOC variation
Data Source
AI summary
To provide a hydrogen storage alloy for an alkaline storage battery that improves output power by pulverization of the alloy in the initial stage of partial charge and discharge cycles and that maintains its surface condition to improve the amount of lifetime work (Wh), and an alkaline storage battery and battery system. A hydrogen storage alloy for an alkaline storage battery includes a composition expressed by LaxReyMg1-x-yNin-m-vAlmTv (Re: rare earth element(s) including Y; T: Co, Mn, Zn; 0.17≦x≦0.64, 3.5≦n≦3.8, 0.06≦m≦0.22, v≧0), and a main phase of an A5B19 type crystal structure. A ratio of X/Y of the concentration ratio X of Al to Ni in a surface layer and the concentration ratio Y of Al to Ni in a bulk layer is 0.36≦X/Y≦0.85. An alkaline storage battery includes the hydrogen storage alloy in its negative electrode. An alkaline storage battery system performs partial charge and discharge control.