Hydrogen Storing Alloy Composition for Ni-MH Battery Durability
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Solution Overview
Problem
Nickel-metal hydride rechargeable batteries face issues with the durability and corrosion resistance of rare earth-Mg—Ni-based hydrogen storing alloys used as negative electrodes, leading to poor cycle life and degradation during charge-discharge cycles, especially under high-temperature conditions.
Innovation Solution
A hydrogen storing alloy with a specific composition represented by the formula (RE1-a-bSmaMgb)(Ni1-c-dAlcMd)x, where 0.3<a<0.6, 0<b<0.16, 0.1<cx<0.2, 3.2<x<3.5, and containing La and/or Nd/Pr, with a high content of Ce2Ni7 or Pr5Co19 phases, is developed to enhance corrosion resistance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If rare earth-Mg—Ni-based hydrogen storing alloy is used to increase battery capacity, then discharge capacity and energy density are improved, but durability and corrosion resistance deteriorate due to crystal phase distortion and pulverization during charge-discharge cycles
Solution Approach 1:
The invention changes the compositional parameters of the hydrogen storing alloy by specifying precise ranges for rare earth elements (0.05-0.5 atom%), Mg (0.1-0.5 atom%), Ni (balance), and additive elements (Al: 0.01-0.1 atom%, Mn: 0.01-0.1 atom%, Co: 0.01-0.1 atom%). These parameter adjustments optimize the crystal structure stability while maintaining high discharge capacity, resolving the contradiction between capacity and durability.
Solution Approach 2:
The invention creates a composite alloy system combining rare earth elements (La, Nd, Pr), Mg, Ni with controlled amounts of Al, Mn, and Co. This composite structure forms a stable crystal phase that resists distortion during hydrogen absorption/desorption, thereby improving durability while maintaining the high capacity characteristics of rare earth-Mg—Ni-based alloys.
2Duration of action of moving object
If hydrogen storing alloy undergoes repeated charge-discharge cycles, then battery operation continues, but crystal phase distortion occurs leading to pulverization and durability deterioration
Solution Approach 1:
The invention optimizes the compositional parameters within specific ranges to stabilize the crystal phase structure. The controlled addition of Al (0.01-0.1 atom%), Mn (0.01-0.1 atom%), and Co (0.01-0.1 atom%) to the rare earth-Mg—Ni base alloy modifies the crystal lattice stability, preventing distortion during repeated hydrogen absorption and desorption cycles, thereby extending cycle life.
Solution Approach 2:
The invention applies prior cushioning by pre-stabilizing the crystal phase structure through controlled compositional design before the alloy undergoes charge-discharge cycling. The specific element ratios create a buffer effect that absorbs structural stress during hydrogen uptake/release, preventing pulverization and extending the alloy's operational lifespan.
3Duration of action of stationary object
If hydrogen storing alloy is stored under high-temperature atmosphere, then battery storage is maintained, but corrosion resistance deteriorates
Solution Approach 1:
The invention adjusts the compositional parameters by incorporating specific rare earth elements (La: 0.02-0.3 atom%, Nd: 0.02-0.3 atom%, Pr: 0.02-0.3 atom%) and controlling Mg content (0.1-0.5 atom%) to enhance the alloy's resistance to high-temperature corrosion. This compositional optimization creates a more stable surface layer that protects against degradation during storage.
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 significantly improves corrosion resistance and cycle life of nickel-metal hydride rechargeable batteries by stabilizing the crystal structure and preventing distortion, resulting in enhanced durability and performance.
Implementation Method 1
absorption and release of hydrogen associated with charge-discharge
Data Source
AI summary
Provided is a hydrogen storing alloy represented by the general formula:(RE1-a-bSmaMgb)(Ni1-c-dAlcMd)x (where 0.3<a<0.6; 0<b<0.16; 0.1<cx<0.2; 0≤dx≤0.1; 3.2<x<3.5; RE is at least one element selected from the group consisting of a rare earth element other than Sm, and Y, and essentially contains La; and M is Mn and/or Co). Also provided is a hydrogen storing alloy represented by the general formula:(RE1-a-bSmaMgb)(Ni1-c-dAlcMd)x (where 0.1<a<0.25; 0.1<b<0.2; 0.02<cx<0.2; 0≤dx≤0.1; 3.6<x<3.7; RE is at least one element selected from the group consisting of a rare earth element other than Sm, and Y, and essentially contains La; and M is Mn and/or Co). Further provided is a nickel-metal hydride rechargeable battery including a negative electrode containing the hydrogen storing alloy.