Electroconversion cell

Details Electroconversion cell Electroconversion cell

1997-06-27

2002-12-24

Maples, John S. (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Having magnetic field feature

C429S006000, C429S006000, C205S343000, C205S345000, C205S637000, C204S253000, C204S254000

Reexamination Certificate

active

06497973

ABSTRACT:

FIELD OF THE INVENTION
This invention is in the general field of electrochemical conversion, using, for example, electrochemical cells.
BACKGROUND OF THE INVENTION
Pressing requirements for clean transportation, load leveling of electric utilities, as well as many other electrochemical applications have promoted significant research for new electrochemical cells. Energy density, cost, cycle life, recharge efficacy, safety, environmental effects, and serviceability are among the factors to be considered in producing a battery suitable for practical use in many applications.
The ability to convert chemical to electrical energy and back again has been well known for almost two centuries. However, certain applications, such as electric vehicles, have requirements for energy density, low cost, and long cycle life which are difficult to meet when constructing commercially practical cells that are operable and safe. For example, a high theoretical energy density (see the discussion of this term below) may in some cases be associated with increased weight of the components, thereby undercutting the theoretical advantages.
SUMMARY OF THE INVENTION
I have discovered that the use of boron redox species can provide an electrochemical cell with a favorable balance of characteristics, such as available energy, energy density, capital and operating cost, recharge efficiency, safety, environmental impact, serviceability and longevity.
Accordingly one aspect of the invention generally features an electrochemical storage medium comprising a carrier mixed with a reduced boron-containing compound (preferably borohydride), the reduced compound being oxidizable to an oxidized boron-containing compound (preferably borate or polyborates; in non-aqueous systems using a halogen-containing reducing agent, borontrichloride may be produced) concurrent with the generation of an electric current when the storage medium is in electrical contact with an electrode that carries current generated during that oxidation. The carrier may be an aqueous or a non-aqueous solution, e.g., a liquid that dissolves the reduced compound and contacts the electrode so that the reduced boron-containing compound can provide electrons directly to the electrode, rather than indirectly through a stable intermediate such as hydrogen. Preferred non-aqueous liquids include anhydrous ammonia; dimethylformamide; dimethylsulfoxide, amines; non-amine organic bases; alcohols; alkene carbonates; and glycols; specific liquids include tripropylamine; pyridine; quinoline; triethanolamine; monoethanolamine; ethylene glycol; propylene glycol; methanol; ethanol; ethylene carbonate; and propylene carbonate. The non-aqueous solution may include a solubilizer or a conductivity enhancer, such as EDTA, crown ethers, cryptates, and quaternary ammonium salts.
A particularly interesting embodiment of this aspect of the invention includes a redox cycling pair that acts semi-catalytically to aid in the current generation. The redox cycling pair is chosen so that oxidized member of the redox cycling pair is reducible by borohydride to yield the reduced member of the redox cycling pair and borate, and the reduced member of the redox pair participates in a redox cycle which regenerates the oxidized member of the redox cycling pair while donating electrons. The storage medium is in electrical contact with an electrode for receiving those electrons in a current. Specific redox cycling pairs include: those having a metal hydride alloy as the reduced member; those having palladium or a palladium alloy (e.g., palladium/silver) as the reduced member; those having a metal as the reduced member; those having a metal hydride as the reduced member, as defined below in greater detail. Specific pairs are: gallium/gallate, sulfite/thiosulfate, Sn(OH)
6
/HSnO
2
, Mn/Mn
2+
, PO
3
−2
/HPO
3
−2
, Cr/CrO
2
, Te/Te
−2
, and Se/Se
−2
. Desirably, the hydrogen pressure of the reduced member of the redox pair is less than 760 mm, preferably less than 38 mm. The above described redox cycling pair can be used with the battery and other aspects of the invention described below.
In another aspect of the invention, the storage medium is positioned to be the anode of a battery, which includes an anode and a cathode in electrical communication. The reduced compound is oxidizable to an oxidized boron-containing compound concurrent with the discharge of the battery, e.g., when the reduced compound contacts the electrode and delivers electrons to it. Available air may be the oxidizing agent, or the battery may include an oxidizing agent, such as: O
2
; compounds comprising oxygen and a halogen; and X
2
, where X is a halogen. Preferred agents are: perchlorate (ClO
4
−
), chlorate (ClO
3
−
), chlorite (ClO
2
−
), hypochlorite (OCl
−
), chlorine (Cl
2
), bromine (Br
2
), bromate (BrO
3
−
) iodate (IO
3
−
) or other comparable halogen/oxygen compounds. Other preferred agents are those which contain elements that may easily change between two or more oxidation states, in general, starting in the higher state. These compounds may or may not be soluble in the carrier medium, and they may be used as a solution, slurry, paste, gel or any other desired form. Preferred agents include: a) [Mn(VII)O
4
]
−
(e.g., sodium permanganate); b) [Fe(VI)O
4
]
−2
(e.g., sodium ferrate); c) Ce (IV)OH(NO
3
)
3
(basic cerium nitrate); d) [Ce(IV)(NO
3
)
6
]
−2
(e.g., as ammonium cerium nitrate); e) [Fe(III)(CN)
4
]
−3
(ferricyanide); f) [Cr(VI)O
4
]
−2
(chromate); g) [Sn(IV)O
3
]
−2
(stannate); h) [Bi(V)O
3
]
−
(bismuthate); i) Mn(IV)O
2
; j) Ag(I)
2
O; k) Ag(II)O; l) Ce(IV)O
2
; m) Pb(IV)O
2
; n) Ni(III)O(OH); o) Ni(IV)O
2
; p) Co(III)O(OH); q) [N(V)O
3
]
−
(e.g., ammonium nitrate, sodium nitrate, lithium nitrate, calcium nitrate); r) [NO
2
]
−
(e.g., sodium nitrite); s) [S
2
O
8
]
−2
(e.g., ammonium or sodium peroxydisulfate); t) compounds containing Cu(III), Tl(III), Hg (II), Se (VI), or Te(VI); or u) R(NO
2
)
n
where R is an alkyl, aryl, or arylakyl organic group and n=1-6 (e.g., mono- or poly- or pernitro organic compounds). Note that valences are supplied simply to aid in understanding the nature of the oxidizing agents, but not necessarily as a claim limitation. Still other oxidizing agents are trinitrobenzoic acid, hexanitrobenzene, or trinitrobenzene.
The anolyte and catholyte of the battery may be separated by a permiselective membrane, such as an anionic membrane, a cationic membrane, or a bipolar membrane. The cathode may be an air breathing cathode, e.g., with a catholyte which can be oxidized by air (e.g., in basic solution) to produce an agent that then oxidizes borohydride to borate with the generation of electrical current, preferably in a cycle that includes regenerating the catholyte after it has generated electricity by oxidizing the borohydride, thus allowing its reuse. For example, the catholyte can contain iodate (IO
3
); ferricyanide and ferrocyanide; chromate and Cr+3; manganese at valence +2 and +3; tin at valence +2 and +4; Cobalt at valence +2 and +3; a catalyst to aid the reoxidation of the oxidation agent to the higher oxidation state by air. The battery may include a chamber separate from the cathode compartment in which reoxidation of the catholyte takes place. The battery may include two units, one that is the direct air breather, and another unit which comprises a catholyte which can be oxidized by air and can then oxidize borohydride to borate with the generation of electrical current using air indirectly. The battery may also include a bipolar electrode. It may have external storage tanks for storage of the anolyte, the catholyte, or both the anolyte and the catholyte. The cell to generate electricity by oxidation of borohydride may be physically separated from the cell to generate the borohydride from the

Affiliated with

Also associated with

Rating

Electroconversion cell does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Electroconversion cell, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electroconversion cell will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2961507