Metal hydride alloys with improved rate performance

Patent metadata

Field	Value
Publication number	US-2016344022-A1
Application number	US-201615046104-A
Country	US
Kind code	A1
Filing date	Feb 17, 2016
Priority date	Feb 17, 2015
Publication date	Nov 24, 2016
Grant date	—

Abstract

Methods of preparing improved metal hydride alloy materials are provided. The alloys include a mixture of at least four of vanadium, titanium, nickel, chromium, and iron. The alloy is processed by at least one of thermal and physical treatment to generate a refined microstructure exhibiting improved kinetics when used as electrodes in MH batteries (e.g., higher discharge current). The thermal treatment includes rapid cooling of the alloy at greater than 10 4 K/s. The physical treatment includes mechanical pulverization of the alloy after cooling. The microstructure is a single phase (body centered cubic) with a heterogeneous composition including a plurality of primary regions having a lattice parameter selected from the range of 3.02 Å to 3.22 Å and a plurality of secondary regions having a lattice parameter selected from the range of 3.00 Å to 3.22 Å and at least one physical dimension having a maximum average value less than 1 μm.

First claim

We claim:

1 . A method of fabricating a metal alloy, said method comprising the steps of:
providing an alloy precursor comprising at least four of titanium (Ti), chromium (Cr), vanadium (V), iron (Fe), and nickel (Ni); and processing the alloy precursor using at least one of a thermal or physical treatment to generate a heterogeneous microstructure having a body centered cubic (BCC) crystal structure, said heterogeneous microstructure comprising:
a plurality of primary regions characterized by a lattice parameter selected from the range of 3.02 Å to 3.22 Å; and
a plurality of secondary regions characterized by a lattice parameter selected from the range of 3.00 Å to 3.22 Å and having at least one physical dimension with a maximum average value less than 1 μm.

2 . The method of claim 1 , wherein the alloy is capable of sorbing at least 1.3 wt. % hydrogen at a pressure less than 2 atm.

3 . The method of claim 1 , wherein the maximum average value of the at least one physical dimension is less than 0.5 μm.

4 . The method of claim 1 , wherein a maximum average distance from a center of a primary region to a nearest secondary region is less than 1.5 μm.

5 . The method of claim 1 , wherein the secondary region is mixed within a matrix of the primary region.

6 . The method of claim 1 , wherein:
the plurality of primary regions are further characterized by an amount of vanadium greater than 54 at. % and an amount of nickel less than 9 at. %; and the plurality of secondary regions are further characterized by an amount of vanadium less than 40 at. % and an amount of nickel greater than 15 at %.

7 . The method of claim 1 , wherein:
the plurality of primary regions are further characterized by an amount of titanium less than 31 at. %; and the plurality of secondary regions are further characterized by an amount of titanium greater than 30 at. %.

8 . The method of claim 1 , wherein the heterogeneous microstructure further comprises a plurality of boundary regions extending between the plurality of primary regions and the plurality of secondary regions, said plurality of boundary regions characterized by a lattice parameter selected from the range of 3.00 Å to 3.22 Å.

9 . The method of claim 1 , wherein the composition of the primary region comprises at least four of:
18 at. % to 31 at. % Ti; 54 at. % to 72 at. % V; 6 at. % to 13 at. % Cr; 2 at. % to 12 at. % Fe; and 3 at. % to 9 at. % Ni.

10 . The method of claim 1 , wherein the composition of the secondary region comprises at least four of:
30 at. % to 50 at. % Ti; 8 at. % to 40 at. % V; 2 at. % to 5 at. % Cr; 5 at. % to 18 at. % Fe; and 15 at. % to 42 at. % Ni.

11 . The method of claim 1 , wherein said providing step comprises:
mixing at least four of titanium (Ti), chromium (Cr), vanadium (V), iron (Fe), and nickel (Ni); melting the mixture to generate a first melt; and cooling the first melt to generate an ingot of the alloy precursor comprising a mixture of the at least four of titanium (Ti), chromium (Cr), vanadium (V), iron (Fe), and nickel (Ni).

12 . The method of claim 11 , further comprising processing the alloy precursor using a thermal treatment, said thermal treatment comprising:
melting the alloy precursor to generate a second melt; and cooling the second melt at a rate selected from the range of greater than 10 4 K/s to less than 10 8 K/s to generate the heterogeneous microstructure.

13 . The method of claim 12 , wherein said cooling is performed by at least one of suction casting, liquid quenching, air quenching, gas atomization and melt spinning.

14 . The method of claim 11 , further comprising processing the alloy precursor using a physical treatment, said physical treatment comprising pulverizing the alloy precursor to a powder having a particle size selected from the range of 0.1 μm to 75 μm.

15 . The method of claim 14 , wherein said pulverizing comprises at least one of mechanical crushing, grinding, and ball milling.

16 . The method of claim 1 , wherein:
the metal alloy composition is Ti a V b Ni c Cr d Fe e ; a is selected from the range of 0 to 97 at. %; b is selected from the range of 0 to 100 at. %; c is selected from the range of 3 to 20 at. %; d is selected from the range of 0 to 20 at. %; and e is selected from the range of 0 to 20 at. %.

17 . A method of forming a metal hydride electrode, comprising:
providing an active material comprising the alloy formed according to claim 1 ; mixing a powder of the active material with a binder; and compressing the mixture of powdered active material and the binder into a desired electrode shape.

18 . The method of claim 17 , wherein the active material is treated by a hydriding/dehydriding operation for 5 cycles under a pressure from the range between 8 bar to 50 bar prior to mixing with the binder.

19 . The method of claim 17 , wherein the binder is selected from at least one of nickel, copper, and carbon.

20 . The method of claim 17 , wherein the powdered active material and the binder are mixed in a ratio selected from the range of 95:5 and 25:75.

21 . The method of claim 17 , wherein the metal hydride electrode is capable of electrochemical discharge capacity of at least 350 mAh/g at currents of at least 10 mA/g.

22 . The method of claim 17 , wherein the metal hydride electrode is capable of discharging at least 65% of a total capacity of the electrode at 167 mA/g for at least 100 cycles.

23 . The method of claim 17 , wherein an exchange current density of the metal hydride electrode exhibits an improvement of at least 10% with respect to an electrode of the same composition in which the alloy precursor is not processed using at least one thermal or physical treatment.

24 . The method of claim 17 , wherein a limiting current density of the metal hydride electrode exhibits an improvement of at least 10% with respect to an electrode of the same composition in which the alloy precursor is not processed using at least one thermal or physical treatment.

25 . A metal alloy, comprising:
a composition comprising at least four of titanium (Ti), chromium (Cr), vanadium (V), iron (Fe), and nickel (Ni); the alloy further characterized by a heterogeneous, single phase microstructure having a body centered cubic (BCC) crystal structure, said heterogeneous microstructure comprising:
a plurality of primary regions characterized by a lattice parameter selected from the range of 3.02 Å to 3.22 Å; and
a plurality of secondary regions characterized by a lattice parameter selected from the range of 3.00 Å to 3.22 Å; and having at least one physical dimension with a maximum average value less than 1 μm.

26 . The metal alloy of claim 25 , wherein the metal alloy is capable of sorbing at least 1.3 wt. % hydrogen at a pressure less than 2 atm.

27 . The metal alloy of claim 25 , wherein the maximum average value of the at least one physical dimension is less than 0.5 μm.

28 . The metal alloy of claim 25 , wherein a maximum average distance from a center of a primary region to a nearest secondary region is less than 1.5 μm.

29 . The metal alloy of claim 25 , wherein the secondary region is mixed within a matrix of the primary region.

30 . The metal alloy of claim 25 , wherein:
the plurality of primary regions a

Assignees

• California Inst Of Techn

Inventors

• Weadock Nicholas J
• Tan Hongjin
• Fultz Brent T
• Yang Heng

Classifications

• H01M4/383 Primary

  Hydrogen absorbing alloys · CPC title

• H01M4/623

  fluorinated polymers · CPC title

• C22C1/02

  by melting {(C22C1/1036 takes precedence)} · CPC title

• C21D1/60

  Aqueous agents · CPC title

• B22D11/06

  into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars · CPC title