Hydrogen Storage Alloy Phase Design for Capacity and Durability
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Solution Overview
Problem
AB3 to 3.8 type rare earth hydrogen storage alloys have high hydrogen storage capacities but are inferior in durability when used in secondary batteries compared to AB5 type alloys, limiting their discharge capacity retention over repeated charging and discharging.
Innovation Solution
A hydrogen storage alloy with a new phase defined by the chemical composition A5·xB1+xC24, where A is a rare earth element, B is Mg, Ca, or Ba, and C is Ni, Co, Mn, Al, etc., with a crystal structure belonging to the R-3m space group and a specific lattice constant ratio, enhancing durability and hydrogen storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If AB3 to 3.8 type rare earth hydrogen storage alloys are used, then hydrogen storage capacity is increased, but durability is deteriorated
Solution Approach 1:
The patent develops a composite alloy system with a new intermetallic phase combining rare earth elements (A), alkaline earth elements (B), and transition metals (C) in a specific stoichiometric ratio (A5·xB1+xC24). This composite structure integrates the high hydrogen storage capacity characteristics of AB3-type alloys with the improved durability of stabilized phase structures, resolving the contradiction between capacity and reliability.
Solution Approach 2:
The patent precisely controls the compositional parameters (x value ranging from -0.1 to 0.8) and structural parameters (c-axis to a-axis length ratio of 11.5 to 12.5) of the new phase to optimize both hydrogen storage capacity and durability. By adjusting these parameters, the alloy achieves high capacity while maintaining structural stability during charge-discharge cycles.
2Reliability
If AB5 type rare earth alloys are used, then durability is improved, but hydrogen storage capacity is limited
Solution Approach 1:
The patent creates a localized new intermetallic phase (A5BC24) with specific structural characteristics within the alloy system. This local phase possesses both the stability needed for durability and the compositional features enabling high hydrogen storage capacity, thereby overcoming the limitations of conventional AB5-type structures.
Solution Approach 2:
The patent transitions from conventional two-element ratio classifications (AB3, AB5) to a three-component phase system (A5BC24) with an additional compositional dimension. This new phase structure provides enhanced hydrogen storage capacity while maintaining durability through its unique crystallographic arrangement with specific c/a ratio.
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 new phase alloy exhibits high hydrogen storage capacity and excellent durability, maintaining a high discharge capacity retention ratio even after repeated charging and discharging, and is efficiently produced through a method involving rapid cooling and annealing in an inert gas atmosphere.
Implementation Method 1
a second step of producing a solidified body by solidifying the melt at a cooling speed of not less than 1000 K/second
Implementation Method 2
a third step of annealing the solidified body at 860 to 980° C. in an inert gas atmosphere in a pressurized state
Implementation Method 3
a third step of annealing the solidified body at 860 to 980° C. in an inert gas atmosphere in a pressurized state
Data Source
AI summary
A hydrogen storage alloy containing a phase of a chemical composition defined by a general formula A5·xB1+xC24: wherein in the general formula A5·xB1+xC24, A denotes one or more element(s) selected from rare earth elements; B denotes one or more element(s) selected from a group consisting of Mg, Ca, Sr, and Ba; C denotes one or more element(s) selected from a group consisting of Ni, Co, Mn, Al, Cr, Fe, Cu, Zn, Si, Sn, V, Nb, Ta, Ti, Zr, and Hf; and x denotes a numeral in a range from −0.1 to 0.8: and the phase has a crystal structure belonging to a space group of R-3m and having a length ratio of the c-axis to the a-axis of the lattice constant in a range of 11.5 to 12.5.