U.S. patent number RE31,414 [Application Number 06/199,160] was granted by the patent office on 1983-10-11 for electrolyte salts for non aqueous electrochemical cells.
This patent grant is currently assigned to Duracell Inc.. Invention is credited to William L. Bowden, Arabinda N. Dey, John S. Miller.
United States Patent |
RE31,414 |
Dey , et al. |
October 11, 1983 |
Electrolyte salts for non aqueous electrochemical cells
Abstract
Novel electrolyte salts having high current carrying capability
for non-aqueous electrochemical cells particularly those containing
fluid depolarizer/electrolyte solvents. The salts have the general
formula M(ZX.sub.4).sub.n with "M" being an alkali or alkaline
earth metal, "Z" being gallium, .[.indium or thallium,.]. "X" being
a halogen and "n" being either 1 or 2.
Inventors: |
Dey; Arabinda N. (Needham,
MA), Miller; John S. (Charlestown, MA), Bowden; William
L. (Nashua, NH) |
Assignee: |
Duracell Inc. (Bethel,
CT)
|
Family
ID: |
26894522 |
Appl.
No.: |
06/199,160 |
Filed: |
October 21, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
956833 |
Nov 2, 1978 |
04177329 |
Dec 4, 1979 |
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Current U.S.
Class: |
429/101; 429/344;
429/345; 429/346 |
Current CPC
Class: |
H01M
6/14 (20130101); C01G 15/006 (20130101) |
Current International
Class: |
C01G
15/00 (20060101); H01M 6/14 (20060101); H01M
010/36 () |
Field of
Search: |
;429/101,194,195,196 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Walton; Donald L.
Attorney, Agent or Firm: Cornell; Ronald S. Nissenbaum;
Israel
Claims
What is claimed is:
1. A non-aqueous electrochemical cell comprising an anode,
comprised of one or more metals above hydrogen in the EMF series, a
cathode depolarizer and a dissolved electrolyte salt characterized
in that the electrolyte salt has the formula M(ZX.sub.4).sub.n
wherein "M" is selected from the group consisting of alkali and
alkaline earth metals, "Z" is .[.selected from the group consisting
of.]. gallium, .[.indium and thallium,.]. "X" is selected from the
group consisting of chlorine, bromine, iodine, fluorine and
mixtures thereof, and "n" is 1 when "M" is an alkali metal and "n"
is 2 when "M" is an alkaline earth metal.
2. The cell of claim 1 wherein said cathode depolarizer is a fluid
and functions as a solvent for said electrolyte salt.
3. The cell of claim 2 wherein said cathode depolarizer is selected
from the group consisting of fluid oxyhalides, non-metallic oxides,
non-metallic halides and mixtures thereof.
4. The cell of claim 3 wherein said cathode depolarizer is thionyl
chloride (SOCl.sub.2).
5. The cell of claim 1 wherein said metal is lithium.
6. The cell of claim 4 wherein said metal is lithium. .[.7. The
cell of claim 1 wherein said electrolyte salt is selected from the
group consisting of lithium tetrachlorogallate, lithium
tetrachloroindate and
lithium tetrachlorothallate..]. 8. The cell of claim 1 wherein
said
electrolyte salt is lithium tetrachlorogallate. 9. The cell of
claim 6 wherein said electrolyte salt is lithium
tetrachlorogallate. .Iadd. 10. A non-aqueous electrochemical cell
comprising a lithium anode, a fluid cathode depolarizer and an
electrolyte salt dissolved in said fluid cathode depolarizer
characterized in that said electrolyte salt consists of
LiGaCl.sub.4. .Iaddend.
Description
This invention relates to electrolyte salts for electrochemical
cells particularly non-aqueous high energy density cells and more
particularly inorganic cells having fluid depolarizers such as
thionyl chloride.
Recently much effort has been expended in the development of high
energy density cell systems which provide both higher voltages and
total capacity (volumetric and gravimetric) than those of the
Leclanche or alkaline cells having zinc anodes. The high energy
density cell systems are centered around the use of active metals
(metals above hydrogen in the EMF series which are unstable in
aqueous environments) as anodes in non-aqueous solution cells.
Lithium in particular has shown great promise as an anode material
because of its high potential and low weight.
Various cell systems have been developed utilizing lithium as the
anode electrode material. The ones showing the most promise in
terms of voltage stability and high discharge capability, are those
having fluid cathode depolarizers which serve the dual function of
electrolyte salt solvent and cathode depolarizer. When a cell of
this type is not being discharged, the fluid
depolarizer/electrolyte solvent reacts with the anode metal to a
limited extent with a protective coating being formed on the
surface of the anode. Full reaction between the anode and fluid
depolarizer with which it is in contact is thereby substantially
prevented. However, upon discharge the protective coating is
dissipated such that the cell can function.
One of the most common of such fluid depolarizer/electrolyte
solvents is thionyl chloride (SOCl.sub.2) which, in combination
with lithium, provides a cell couple having an exceedingly high
voltage (.about.4 volts), discharge capability, energy density, and
stability of discharge. However, a limiting factor in the utility
especially with respect to high rate discharge) of cells containing
a Li/SOCl.sub.2 couple in the electrolyte salt used therein.
Generally an electrolyte salt must fulfill several criteria. It
should of course, have a high ionic or electrical conductivity for
material transport upon cell discharge. The electrolyte salt should
also be highly soluble in the fluid depolarizer/electrolyte whereby
such conductivity may be practically attained. Additionally, the
electrolyte salt should be stable with respect to both the fluid
depolarizer/electrolyte solvent and the anode metal. Electrolyte
salts or solutes used in thionyl chloride depolarized cells are,
for example, described at length in U.S. Pat. No. 3,926,699. Of the
enumerated salts in the aforesaid patent the most preferred and the
most widely used electrolyte salt or solute having the above
described requisite properties, is lithium tetrachloroaluminate
(LiAlCl.sub.4). However, under conditions of high rate discharge,
the energy density of cells containing lithium tetrachloroaluminate
has been found to be substantially reduced.
It is an object of the present invention to provide novel
electrolyte salts for non-aqueous electrochemical cells.
It is a further object of the present invention to provide novel
electrolyte salts for use in high energy density cells having fluid
depolarizer/electrolyte solvents such as thionyl chloride wherein
the high rate discharge capability of such cells is improved
without substantial loss of capacity.
These and other objects, features and advantages will be more
evident from the following discussion.
The present invention generally comprises the use of novel
electrolyte salts in high energy density, non-aqueous
electrochemical cells. The electrolyte salts have the general
formula M(ZX.sub.4).sub.n. "M" represents the alkali or alkaline
earth metals such as lithium, sodium, potassium, rubidium,
beryllium, magnesium, and calcium, and generally though not
necessarily corresponds to the metal used as the anode of the
electrochemical cell. "Z" represents .[.a member selected from the
group consisting of.]. gallium, .[.indium or thallium,.]. "X"
represents a halogen or mixture of halogens which halogens are
chlorine, bromine, iodine and fluorine and "n" represents either 1
or 2 with the value thereof being determined by whether "M" is an
alkali metal in which instance n=1 or whether "M" is an alkaline
earth metal in which instance n=2.
The preferred electrolyte salts are those in which "X" is chlorine
such as lithium tetrachlorogallate, .[.lithium tetrachloroindate
and lithium tetrachlorothallate.]. with the most preferred salt
being lithium tetrachlorogallate.
The anodes useful in high energy density cells containing the novel
electrolyte of the present invention include one or more of the
aforementioned lithium and other alkali or alkaline earth metals
such as sodium, potassium, rubidium, beryllium, magnesium, calcium
and other metals above hydrogen in the EMF series.
The novel electrolyte salts of the present invention have
particular utility in cells containing fluid
depolarizer/electrolyte solvents such as thionyl chloride which
cells are capable of being discharged at high rate. Examples of
other fluid depolarizer/electrolyte solvents include fluid
oxyhalides, non-metallic oxides and non-metallic halides and
mixtures thereof such as phosphorous oxychloride (POCl.sub.3),
selenium oxychloride (SeOCl.sub.2), sulfur dioxide (SO.sub.2),
sulfur trioxide (SO.sub.3), vanadium oxytri-chloride (VOCl.sub.3),
chromyl chloride (CrO.sub.2 Cl.sub.2), sulfuric oxychloride
(SO.sub.2 Cl.sub.2), Nitryl chloride (NO.sub.2 Cl), nitrosyl
chloride (NOCl), nitrogen dioxide (NO.sub.2), sulfur monochloride
(S.sub.2 Cl.sub.2) and sulfur monobromide (S.sub.2 Br.sub.2). Each
of the above can be used together with thionyl chloride
(SOCl.sub.2) as fluid depolarizer/electrolyte solvent or
separately.
Though the above electrolyte salts have been described for
particular utility in fluid cathode depolarizer/electrolyte solvent
cells they may be utilized in other cells requiring electrolyte
salts such as those containing solid cathodes such as metal
chromates and dichromates, vanadates, molybdates, halides, oxides,
permanganates, iodates and carbon monofluoride and organic
electrolyte solvents such as tetrahydrofuran, propylene carbonate,
dimethyl sulfite, dimethyl sulfoxide, N-nitrosodimethylamine,
gamma-butyrolactone, dimethyl carbonate, methyl formate, butyl
formate, dimethoxyethane, acetonitrile and N,N-dimethyl
formamide.
The salts of the present invention are utilized in the same manner
as prior art cells whereby they are simply dissolved in the
electrolyte salt solvent to the desired concentration. The
following examples, set forth, by way of illustration, the
preparation of a salt of the present invention, the testing of its
stability with respect to cell components and its performance in
electrochemical cells generally and as compared to cells containing
an electrolyte salt of the prior art. It is understood that the
following examples are for illustrative purposes only with the
invention not to be limited thereby.
EXAMPLE I
LiGaCl.sub.4 is prepared by mixing and melting equimolar amounts of
anhydrous GaCl.sub.3 and LiCl together. A one molar .[.LiGaCl.sub.4
-SoCl.sub.2.]. LiGaCl.sub.4 -.Iadd.SOCl.sub.2 .Iaddend. solution is
prepared (with the LiGaCl.sub.4 being readily soluble in
SOCl.sub.2) and the ionic conductivity is measured and is found to
be 1.13.times.10.sup.-2 ohm.sup.-1 cm.sup.-1 at room temperature.
This compares favorably with the conductivity of a similar solution
of 1 molar LiAlCl.sub.4 --SOCl.sub.2 which is 1.6.times.10.sup.-2
ohm.sup.-1 cm.sup.-1. The conductivity of LiGaCl.sub.4 is thus
suitable for a Li/SOCl.sub.2 cell with high discharge rate
capability.
EXAMPLE II
Shiny pieces of lithium foil are added to the LiGaCl.sub.4
--SOCl.sub.2 solution of Example I and refluxed for 8 days at about
85.degree. C. At the end of the refluxing period the lithium pieces
are found to be bright and shiny indicating that the LiGaCl.sub.4
--SOCl.sub.2 is chemically compatible with lithium and is therefore
useful as an electrolyte in a lithium anode cell. The absence of
discoloration and/or corrosion indicates that a protective coating
of sufficient but minimal thickness is formed on the surface of the
lithium with discoloration indicating a too thick coating and
corrosion indicating the absence of a coating.
EXAMPLE III
Several "D" size cells (OD 1.30", L 2.38") are constructed by
winding a lithium anode, having the dimensions of
21.25".times.2".times.0.015" with a carbon cathode on expanded
nickel metal, having the dimensions 20.times.1.75".times.0.025",
and two layers of glass fiber paper separators. The cells are each
filled with 45 grams of the 1 molar LiGaCl.sub.4 --SOCl.sub.2
solution of Examples I and II. The cells are discharged at various
currents with the results given in Table I.
TABLE I ______________________________________ Cell Discharge
Current Voltage amp hours to 2 volts
______________________________________ 1 0.13 amps 3.6 14 2 0.10
3.5 13.4 3 1.0 3.3 12.4 4 3.0 3.0 11
______________________________________
EXAMPLE IV
Several cells made in accordance with Example III are stored for
varying lengths of time at 25.degree. C. and discharged at a
current rate of 1 amp with the discharge characteristics as a
function of storage time given in Table II.
TABLE II ______________________________________ Storage duration
Capacity to 2.0 volts at Cell at 25.degree. C. (months) 1A (amp
hours) ______________________________________ 5 0 12.5 6 1 12.3 7 2
11.9 8 5 11.0 ______________________________________
EXAMPLE V (PRIOR ART)
A cell is constructed in accordance with the procedure of Example
III but with a 1 molar solution of LiAlCl.sub.4 --SOCl.sub.2
instead of LiGaCl.sub.4 --SOCl.sub.2. The cell is discharged at 3.0
A and delivers 9.0 amp hours with about a 3 volt constant
potential.
The 9.0 amp hours attained with a cell containing a LiAlCl.sub.4
electrolyte salt is nearly 20% less than that attained under
identical conditions with an identical cell containing the
electrolyte salt of the present invention.
The above examples are for illustrative purposes only. It is
understood that changes and variations with respect to cell
components utilized with the electrolyte salts of the present
invention may be made without departing from the scope of the
present invention as defined in the following claims.
* * * * *