High-Entropy Hydrogen Storage Alloy for Reversible Battery Electrodes
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Solution Overview
Problem
Current hydrogen storage alloys, such as AB5 type rare earth nickel-based alloys, have limited hydrogen storage capacity and high raw material costs, with ZrNi alloys exhibiting high chemical stability but poor desorption properties and high costs due to expensive components like Zr and Ni.
Innovation Solution
A high-entropy hydrogen storage alloy with a specific composition of Ti, Zr, Ni, Cr, and Mn, achieving a mixing entropy of 1.5 R or more and a C14 type crystal structure, allowing for efficient hydrogen absorption and desorption, reducing the usage and cost of expensive elements, and incorporating a subphase with a B2 type crystal structure for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AB5 type rare earth nickel-based hydrogen storage alloy is used, then the alloy has good electrochemical performance, but the hydrogen storage capacity is limited to about 1.2 mass % and raw material costs are high
Solution Approach 1:
The invention changes the compositional parameters by using a quinary alloy system (Ti-Zr-Ni-Cr-Mn) with specific atomic percentage ranges for each element, and achieves a high mixing entropy state (ΔSmix ≥ 1.5R) to form a C14 type main phase structure, thereby improving hydrogen storage capacity while maintaining electrochemical performance
Solution Approach 2:
The invention creates a composite alloy system combining five different elements (Ti, Zr, Ni, Cr, Mn) with specific phase composition (C14 type main phase and B2 type subphase), where the synergistic effect of multiple elements achieves both high hydrogen storage capacity and good electrochemical performance
2Reliability
If AB5 type rare earth nickel-based hydrogen storage alloy is used, then the alloy has good electrochemical performance, but the raw material costs are high due to expensive rare earth metals
Solution Approach 1:
The invention replaces expensive rare earth metals with more cost-effective elements (Ti, Zr, Ni, Cr, Mn) that are relatively abundant and have more stable prices, while maintaining the necessary electrochemical performance through optimized composition and phase structure
Solution Approach 2:
The invention changes the material composition parameters to eliminate rare earth elements and uses a high-entropy configuration (ΔSmix ≥ 1.5R) to achieve the desired performance at lower cost
3Quantity of substance
If ZrNi alloy is used, then the hydrogen storage capacity is higher, but the alloy easily produces chemically stable hydrides that are unlikely to desorb hydrogen
Solution Approach 1:
The invention introduces local compositional variations by incorporating multiple elements in specific ranges (5-35 atom % each) and creating a multi-phase structure (C14 type main phase and B2 type subphase), which locally modifies the hydride formation characteristics to enable reversible hydrogen absorption and desorption
Solution Approach 2:
The invention changes the compositional parameters from simple binary ZrNi to a quinary system with high mixing entropy, and controls the phase structure parameters to achieve appropriate hydride stability that allows both storage and release of hydrogen
4Quantity of substance
If ZrNi alloy is used, then the hydrogen storage capacity is higher, but the raw material costs are high due to expensive Zr and Ni
Solution Approach 1:
The invention changes the compositional parameters from binary ZrNi to a quinary alloy system with five elements in balanced proportions, optimizing the ratio of expensive to less expensive elements while achieving high hydrogen storage capacity through high mixing entropy configuration
Solution Approach 2:
The invention creates a composite alloy system combining five different elements where the synergistic effect reduces dependence on any single expensive element (Zr or Ni), achieving cost reduction while maintaining or improving hydrogen storage 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 high-entropy alloy achieves a higher hydrogen storage capacity, efficient desorption, and reduced raw material costs, making it suitable for alkaline storage batteries and hydrogen stations, with improved discharge capacity and cycle stability.
Implementation Method 1
The hydrogen storage alloy having such a chemical composition and such a crystal structure can repeatedly perform absorption and desorption of hydrogen
Implementation Method 2
the ZrNi alloy reacts with absorbed hydrogen to thereby easily produce a hydride having high chemical stability such as ZrNiH3 or ZrNiH. For this reason, there is a problem that the ZrNi alloy is unlikely to desorb the absorbed hydrogen to the outside
Data Source
AI summary
A high-entropy hydrogen storage alloy includes Ti: 5 atom % or more and 35 atom % or less, Zr: 5 atom % or more and 35 atom % or less, Ni: 5 atom % or more and 35 atom % or less, Cr: 5 atom % or more and 35 atom % or less, and Mn: 5 atom % or more and 35 atom % or less, in which a mixing entropy ΔSmix represented by the following formula (1) is 1.5 R or more. The crystal structure of a main phase is a C14 type.ΔSmix=−RΣxi ln(xi) (1)(wherein R in the formula (1) represents the gas constant, and xi represents a molar fraction of an individual element contained in the high-entropy hydrogen storage alloy.)