U.S. patent application number 10/266037 was filed with the patent office on 2003-02-27 for primary alkaline battery including nickel oxyhydroxide.
This patent application is currently assigned to The Gillette Company, a Delaware corporation. Invention is credited to Trainer, Philip, Wang, Enoch, Wang, Francis, Wei, Guang.
Application Number | 20030039888 10/266037 |
Document ID | / |
Family ID | 24538153 |
Filed Date | 2003-02-27 |
United States Patent
Application |
20030039888 |
Kind Code |
A1 |
Wang, Francis ; et
al. |
February 27, 2003 |
Primary alkaline battery including nickel oxyhydroxide
Abstract
An alkaline battery has a cathode including a nickel
oxyhydroxide.
Inventors: |
Wang, Francis; (Danbury,
CT) ; Wang, Enoch; (Mansfield, MA) ; Trainer,
Philip; (Sandy Hook, CT) ; Wei, Guang;
(Southboro, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
225 FRANKLIN ST
BOSTON
MA
02110
US
|
Assignee: |
The Gillette Company, a Delaware
corporation
|
Family ID: |
24538153 |
Appl. No.: |
10/266037 |
Filed: |
October 7, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10266037 |
Oct 7, 2002 |
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09633067 |
Aug 4, 2000 |
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6492062 |
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Current U.S.
Class: |
429/223 ;
252/182.1; 29/623.1 |
Current CPC
Class: |
H01M 4/364 20130101;
H01M 6/08 20130101; H01M 4/621 20130101; H01M 6/085 20130101; Y10T
29/49108 20150115; H01M 4/366 20130101; H01M 4/52 20130101 |
Class at
Publication: |
429/223 ;
29/623.1; 252/182.1 |
International
Class: |
H01M 004/52; H01M
004/32; H01M 006/04 |
Claims
What is claimed is:
1. A primary alkaline battery comprising: a cathode comprising
cobalt oxyhydroxide-modified nickel oxyhydroxide; an anode; a
separator; and an alkaline electrolyte.
2. The battery of claim 1, wherein the cobalt oxyhydroxide-modified
nickel oxyhydroxide has a coating of a cobalt oxyhydroxide on a
nickel oxyhydroxide.
3. The battery of claim 1, wherein the coating is substantially
uniform.
4. The battery of claim 1, wherein the nickel oxyhydroxide is
.gamma.-NiOOH.
5. The battery of claim 1, wherein the cobalt oxyhydroxide is a
sodium or potassium modified cobalt oxyhydroxide.
6. The battery of claim 5, wherein the cobalt oxyhydroxide is a
potassium modified cobalt oxyhydroxide.
7. The battery of claim 1, wherein the cobalt oxyhydroxide-modified
nickel oxyhydroxide is derived from nickel hydroxide coated with
between 2% and 15% cobalt hydroxide by weight.
8. The battery of claim 1, wherein the cobalt oxyhydroxide-modified
nickel oxyhydroxide is derived from nickel hydroxide coated with
between 3% and 10% cobalt hydroxide by weight.
9. The battery of claim 1, wherein the cobalt oxyhydroxide-modified
nickel oxyhydroxide is derived from nickel hydroxide coated with
between 4% and 8% cobalt hydroxide by weight.
10. The battery of claim 1, wherein the cobalt
oxyhydroxide-modified nickel oxyhydroxide is derived from nickel
hydroxide coated with 5% cobalt hydroxide by weight.
11. The battery of claim 1, wherein the cobalt
oxyhydroxide-modified nickel oxyhydroxide is derived from
.alpha.-Ni(OH).sub.2.
12. The battery of claim 1, wherein the anode comprises zinc.
13. The battery of claim 1, wherein the nickel oxyhydroxide is
substantially non-fractured.
14. The battery of claim 1, wherein the cathode further includes an
oxidizing additive.
15. The battery of claim 14, wherein the oxidizing additive
includes K.sub.2S.sub.2O.sub.8 or KMnO.sub.4.
16. A primary alkaline battery comprising: a cathode comprising a
nickel oxyhydroxide derived from .alpha.-Ni(OH).sub.2; an anode; a
separator; and an alkaline electrolyte.
17. The battery of claim 16, wherein the nickel oxyhydroxide is a
cobalt oxyhydroxide-modified nickel oxyhydroxide.
18. The battery of claim 16, wherein the cobalt
oxyhydroxide-modified nickel oxyhydroxide has a coating of a cobalt
oxyhydroxide on a nickel oxyhydroxide.
19. The battery of claim 18, wherein the coating is substantially
uniform.
20. The battery of claim 18, wherein the cobalt oxyhydroxide is a
sodium or potassium modified cobalt oxyhydroxide.
21. The battery of claim 18, wherein the cobalt oxyhydroxide is a
potassium modified cobalt oxyhydroxide.
22. The battery of claim 17, wherein the cobalt
oxyhydroxide-modified nickel oxyhydroxide is derived from nickel
hydroxide coated with between 2% and 15% cobalt hydroxide by
weight.
23. The battery of claim 16, wherein the anode comprises zinc.
24. The battery of claim 16, wherein the cathode further includes
an oxidizing additive.
25. The battery of claim 24, wherein the oxidizing additive
includes K.sub.2S.sub.2O.sub.8 or KMnO.sub.4.
26. A method of manufacturing a primary alkaline battery
comprising: forming a cobalt oxyhydroxide-modified nickel
oxyhydroxide; and assembling a cathode comprising the cobalt
oxyhydroxide-modified nickel oxyhydroxide, an anode, a separator,
and an alkaline electrolyte to form the alkaline battery.
27. The method of claim 26, wherein forming a cobalt
oxyhydroxide-modified nickel oxyhydroxide includes converting
.alpha.-Ni(OH).sub.2 to nickel oxyhydroxide.
28. The method of claim 26, wherein forming cobalt
oxyhydroxide-modified nickel oxyhydroxide includes converting
nickel hydroxide coated with between 3% and 15% cobalt hydroxide by
weight.
29. The method of claim 26, wherein the nickel oxyhydroxide is
substantially non-fractured.
30. The battery of claim 26, wherein the cathode further includes
an oxidizing additive.
31. The battery of claim 30, wherein the oxidizing additive
includes K.sub.2S.sub.2O.sub.8 or KMnO.sub.4.
32. A method of manufacturing a primary alkaline battery
comprising: forming substantially non-fractured nickel
oxyhydroxide; and assembling a cathode comprising the nickel
oxyhydroxide, an anode, a separator, and an alkaline electrolyte to
form the alkaline battery.
33. The method of claim 32, wherein forming nickel oxyhydroxide
includes converting .alpha.-Ni(OH).sub.2 to nickel
oxyhydroxide.
34. The method of claim 32, wherein the nickel oxyhydroxide is
modified with cobalt oxyhydroxide.
35. The method of claim 32, wherein the cathode further includes
K.sub.2S.sub.2O.sub.8 or KMnO.sub.4.
36. A method of decreasing capacity loss in a nickel oxyhydroxide
primary alkaline battery comprising: forming a cathode including a
nickel oxyhydroxide; and assembling the cathode, an anode, a
separator, and an alkaline electrolyte to form the alkaline
battery, wherein the battery has a capacity loss after storage for
2 weeks at 60.degree. C. of less than 40 percent.
37. The method of claim 36, further comprising converting
.alpha.-Ni(OH).sub.2 to the nickel oxyhydroxide.
38. The method of claim 36, further comprising converting cobalt
hydroxide-coated .alpha.-Ni(OH).sub.2 to the nickel
oxyhydroxide.
39. The method of claim 36, further comprising converting cobalt
hydroxide modified nickel hydroxide to the nickel oxyhydroxide.
40. A cathode for a battery comprising non-fractured nickel
oxyhydroxide or a cobalt oxyhydroxide-modified nickel oxyhydroxide.
Description
TECHNICAL FIELD
[0001] This invention relates to batteries
BACKGROUND
[0002] Batteries, such as primary alkaline batteries, are commonly
used as energy sources. Generally, alkaline batteries include a
cathode, an anode, a separator, and an electrolytic solution. The
cathode can include an active material, such as manganese dioxide
or nickel oxide, carbon particles that enhance the conductivity of
the cathode, and a binder. The anode may be, for example, a gel
including zinc particles as the active material. The separator is
disposed between the cathode and the anode. The electrolytic
solution can be, for example, a hydroxide solution that is
dispersed throughout the battery.
[0003] Desirable primary alkaline batteries have a high energy
density and low capacity loss upon storage. Capacity retention upon
storage can be important in primary battery systems where, unlike
secondary battery systems, capacity cannot be recovered thorough
recharging. Primary batteries having nickel oxide cathodes and
amalgamated zinc anodes have high energy densities, but can lose
significant amounts of capacity upon storage at 60.degree. C.
Self-discharge, either by hydrogen reduction or oxygen evolution
from the nickel oxide cathode can result in loss of discharge
capacity and formation of non-conductive regions.
SUMMARY
[0004] The invention features a primary alkaline battery including
a nickel oxyhydroxide cathode. The battery preferably has a
capacity loss after storage for 2 weeks at 60.degree. C. of less
than 40 percent. The cathode can include a cobalt
oxyhydroxide-modified nickel oxyhydroxide or non-fractured nickel
oxyhydroxide, which can improve the capacity loss properties of the
battery.
[0005] Cobalt oxyhydroxide-modified nickel oxyhydroxide is a nickel
oxyhydroxide having cobalt oxyhydroxide on a portion of the surface
of the nickel oxyhydroxide. For example, the cobalt
oxyhydroxide-modified nickel oxyhydroxide can be nickel
oxyhydroxide having a coating of cobalt oxyhydroxide on a nickel
oxyhydroxide. The coating can be substantially uniform, meaning
that the coating covers at least 60% of the surface of the nickel
material.
[0006] The nickel oxyhydroxide can be substantially non-fractured.
Non-fractured nickel oxyhydroxide is nickel oxyhydroxide that is
formed from nickel hydroxide by oxidation and inter-layer spacing
contraction or no change in inter-layer spacing. For example, when
.alpha.-Ni(OH).sub.2 is used as the precursor the degree of
fracturing can be significantly reduced because
.alpha.-Ni(OH).sub.2 has an inter-layer spacing of about 8 .ANG.,
which contracts upon formation of .gamma.-NiOOH to about 7 .ANG..
Alpha nickel hydroxide, .alpha.-Ni(OH).sub.2, is a class of nickel
hydroxide materials that has the general formula:
(Ni.sub.1-nA.sub.n)(OH).sub.2X.sub.n/m.multidot.(H.sub.2O).sub.z
[0007] where A is Al, Co, Fe, Mn, or other trivalent metal ion, or
a mixture thereof,
[0008] X is an anion having charge of -m, m being 1 or 2,
[0009] n is between zero and 0.8, inclusive, and
[0010] z is between 0 and 0.3, inclusive. X can be a halide,
carbonate, carboxylate, sulfate, sulfite, phosphate, or phosphite.
Preferably, A is Al, Co, Fe, or Mn, or a mixture thereof, X is
CO.sub.3.sup.2-(m=2), NO.sub.3.sup.-(m=1), Cl.sup.-(m=1), or
SO.sub.4 .sup.2-(m=2) and n is between zero and 0.3.
[0011] In one aspect, the invention features a primary alkaline
battery including a cathode, an anode, a separator, and an alkaline
electrolyte. The cathode can include a cobalt oxyhydroxide-modified
nickel oxyhydroxide or a nickel oxyhydroxide derived from
.alpha.-Ni(OH).sub.2. The nickel oxyhydroxide can be .gamma.-NiOOH.
The nickel oxyhydroxide can be substantially non-fractured.
[0012] In another aspect, the invention features a method of
manufacturing an alkaline battery. The method includes assembling a
cathode, an anode, a separator, and an alkaline electrolyte to form
the alkaline battery. The method can include forming a cathode
including the nickel oxyhydroxide. The method can also include
forming a cobalt oxyhydroxide-modified nickel oxyhydroxide or
non-fractured nickel oxyhydroxide. Forming the nickel oxyhydroxide
can include converting .alpha.-Ni(OH).sub.2 to nickel oxyhydroxide,
for example, by exposing nickel hydroxide to ozone.
[0013] In yet another aspect, the invention features a method of
decreasing capacity loss in a nickel oxyhydroxide primary alkaline
battery. The method includes forming a cathode including a nickel
oxyhydroxide, and assembling the cathode, an anode, a separator,
and an alkaline electrolyte to form the alkaline battery. The
method can include converting .alpha.-Ni(OH).sub.2 to the nickel
oxyhydroxide or converting cobalt hydroxide-coated
.alpha.-Ni(OH).sub.2 to the nickel oxyhydroxide.
[0014] In another aspect, the invention features a cathode for a
primary battery including non-fractured nickel oxyhydroxide or a
cobalt oxyhydroxide-modified nickel oxyhydroxide.
[0015] The anode can include zinc.
[0016] In preferred embodiments, the cathode further includes an
oxidizing additive. Reduction reactions at the surface or in the
bulk of the nickel oxyhydroxide particles, which can lead to
decreased storage capacities, can be partially eliminated or
prevented by including oxidizing additives in the cathode.
Electrochemically active additives are preferred to reduce oxygen
evolution by raising the overpotential to avoid losses in capacity
that can result from the use of electrochemically inactive
additives.
[0017] Other features and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a cross-section view of a battery.
[0019] FIGS. 2a-c are electron micrographs of NiOOH particles.
DETAILED DESCRIPTION
[0020] Referring to the FIG. 1, battery 10 includes a cathode 12,
an anode 14, a separator 16 and a cylindrical housing 18. Battery
10 also includes current collector 20, seal 22, and a negative
metal top cap 24, which serves as the negative terminal for the
battery. The cathode is in contact with the housing, and the
positive terminal of the battery is at the opposite end of the
battery from the negative terminal. An electrolytic solution is
dispersed throughout battery 10. Battery 10 can be, for example, an
AA, AAA, AAAA, C, or D battery.
[0021] Cathode 12 includes a cathode material, carbon particles,
and a binder.
[0022] The cathode material can be nickel oxyhydroxide, silver
oxide, or silver permanganate. The nickel oxyhydroxide can be
.gamma.-NiOOH, which has a high running voltage and high specific
energy relative to manganese dioxide. The high valent .gamma. form
of NiOOH can be obtained by chemical oxidation, for example, by
treating a nickel hydroxide with sodium hypochlorite or ozone.
Alternatively, the high valent .gamma. form of NiOOH can be
prepared by electrochemical overcharging, for example, of
.beta.-NiOOH. Average nickel oxidation states as high as 3.67 can
be obtained. The Ni(OH).sub.2 oxidation reaction with ozone is
summarized in equation (1).
2Ni(OH).sub.2+O.sub.3.fwdarw.2NiOOH+O.sub.2+H.sub.2O (1)
[0023] In particular, the cathode material can be a non-fractured
nickel oxyhydroxide or a cobalt oxyhydroxide-modified nickel
oxyhydroxide. The non-fractured nickel oxyhydroxide can be derived
from .alpha.-Ni(OH).sub.2. Specifically, the .alpha.-Ni(OH).sub.2
can be oxidized by ozonation to form .gamma.-NiOOH. The
.gamma.-NiOOH formed in this manner is non-fractured. When
.gamma.-NiOOH is formed from .alpha.-Ni(OH).sub.2, the inter-layer
spacing expands from about 5 .ANG. in .beta.-Ni(OH).sub.2 to about
7 .ANG. in .gamma.-NiOOH. This relatively large crystallographic
expansion results in macroscopic fragmentation of .gamma.-NiOOH
particles. The fragmentation can increase interfacial area between
the NiOOH electrode and the electrolyte and result in significant
capacity loss upon storage. When .alpha.-Ni(OH).sub.2 is used as
the precursor, the degree of fracturing can be significantly
reduced. The .alpha.-Ni(OH).sub.2 has an inter-layer spacing of
about 8 .ANG., and after ozonation, the inter-layer spacing
contracts to about 7 .ANG. in .gamma.-NiOOH. The relatively small
change in inter-layer spacing, reduces the particle fragmentation.
The non-fractured nickel oxyhydroxide formed from the
.alpha..fwdarw..gamma. transformation maintains capacity upon
storage significantly better than the fractured nickel oxyhydroxide
formed from the .beta..fwdarw..gamma. transformation.
[0024] The cobalt oxyhydroxide-modified nickel oxyhydroxide can
include a coating of a cobalt oxyhydroxide on a nickel
oxyhydroxide. The cobalt oxyhydroxide can improve electrical
contact between particles in the cathode and can protect the
surface of the nickel oxyhydroxide from degradation. The coating
covers at least 60% of the surface of the nickel oxyhydroxide.
Preferably, the coating can cover at least 70%, preferably at least
80%, more preferably at least 90% of the surface. The cobalt
oxyhydroxide-modified nickel oxyhydroxide can be derived from
nickel hydroxide coated with between 2% and 15%, preferably between
3% and 10%, more preferably between 4% and 8%, and most preferably
5% cobalt hydroxide by weight.
[0025] The cobalt oxyhydroxide-modified nickel oxyhydroxide can be
prepared by chemical or electrochemical oxidation of cobalt
hydroxide and nickel hydroxide. The nickel hydroxide can be
pre-treated with the cobalt hydroxide, for example, by exposing
nickel hydroxide particles to a solution or suspension or cobalt
hydroxide in water and drying the exposed nickel. A solid phase-gas
phase technique can be used to produce the cobalt
oxyhydroxide-modified nickel oxyhydroxide. The CoOOH phase can be
formed by reaction of Co(OH).sub.2 with ozone. The NiOOH is also
formed by combining an alkali-metal hydroxide with Ni(OH).sub.2 and
exposing the mixture to ozone as described, for example, in U.S.
Pat. No. 3,911,094.
[0026] The solid-gas reaction of Co(OH).sub.2 and ozone produces
CoOOH and can be represented by equation (2).
2Co(OH).sub.2+O.sub.3.fwdarw.2CoOOH+O.sub.2+H.sub.2O (2)
[0027] The solid phase-gas phase reaction can produce CoOOH
quantitatively. Ozonation can be carried out by exposing a powder
of starting material to ozone and agitating the reaction mixture.
The Co(OH).sub.2 changes color from light pink to dark brown as the
CoOOH forms. The temperature of the starting material is
maintained, for example, in a water bath. Moist ozone prepared from
air is the preferred oxidizing agent. Periodically the reaction can
be interrupted to grind the reactants to reduce agglomeration of
particles and increase the amount of oxidation of Co(OH).sub.2 that
occurs. Conductivity measurements for the CoOOH can be performed by
measuring the resistivity of polycrystalline samples as a function
of applied pressure. The conductivity of the CoOOH prepared by
ozonation was calculated to be 0.12 S/cm.sup.2 at a pressure of
2000 kg/cm.sup.2.
[0028] The electronic conductivity of the CoOOH can be modified in
a controlled manner by combining the Co(OH).sub.2 with various
metal hydroxides prior to treatment with ozone. Suitable metal
hydroxides include lithium hydroxide, sodium hydroxide, potassium
hydroxide, rubidium hydroxide, cesium hydroxide, beryllium
hydroxide, calcium hydroxide, magnesium hydroxide, or silver
hydroxide. For example, when treated with sodium or potassium
hydroxide, the cobalt oxyhydroxide can be a sodium- or
potassium-modified cobalt oxyhydroxide. The cobalt hydroxide can be
treated with a solid form of the metal hydroxide, such as a powder,
or a solution of metal hydroxide, for example, in water. The cobalt
hydroxide can be treated with up to 40% by weight, preferably 10%
to 25% by weight, metal hydroxide, which after oxidation produces
cobalt oxyhydroxide having favorable electronic conductivity and
electrochemical performance. For example, CoOOH formed by ozonation
after mixing 35 g of Co(OH).sub.2 with 6.3 g of solid KOH and 0.9 g
of solid NaOH had a general formula: Co.sub.0 69Na.sub.0 06K.sub.0
25OOH and a conductivity of 0.26S/cm.sup.2 at a pressure of 2000
kg/cm.sup.2.
[0029] Cobalt oxyhydroxide-coated nickel oxyhydroxide can be
prepared by a clean single-step process. In this process, the
electronic conductivity of the CoOOH can be effectively controlled
by the addition of a metal hydroxide. Ni(OH).sub.2 coated with 5%
by weight Co(OH).sub.2 can be treated with a mixture of sodium
hydroxide and potassium hydroxide which is then treated with ozone
to form conductive CoOOH coated NiOOH material.
[0030] The CoOOH coated NiOOH material produced by this method can
be used as a cathode material in a primary alkaline Ni/Zn cell.
Electrochemical characterization of alkaline Ni/Zn cells
constructed with the CoOOH coated NiOOH shows good electrochemical
performance and good storage characteristics. The coated cathode
material can retain 87% of fresh capacity after 1 week of storage
at 60.degree. C. under low rate, constant current discharge
conditions.
[0031] FIGS. 2a-c depict SEM electron micrographs showing elemental
mapping of three cross-sectioned particles. High concentrations of
cobalt are shown in the maps as bright spots. FIG. 2a is an
elemental map of the starting material, Co(OH).sub.2-coated
Ni(OH).sub.2. FIG. 2b is an elemental map of CoOOH-coated NiOOH.
FIG. 2c is an elemental map of NiOOH prepared from a mixture of
.beta.-Ni(OH).sub.2 and Co(OH).sub.2 according to the method
described in U.S. Pat. No. 3,911,094. The presence of cobalt in the
CoOOH coated NiOOH, shown in FIG. 2b is diffuse, covering the
surface of the particle, while the particle in FIG. 2c has a small
amount of cobalt associated with the surface of the particle.
[0032] Distributors of starting materials for making the cathode
material include HC Starck and JMC Tanaka Chemical Corp., Fukui,
Japan (spherical nickel hydroxide Tanaka Type Z; cobalt
hydroxide-coated spherical nickel hydroxide Tanaka Type CoZD).
Generally the cathode may include, for example, between 80% and
90%, and preferably between 86% and 88%, of cathode material by
weight.
[0033] The carbon particles can be graphite particles. The graphite
can be synthetic or non-synthetic, or a blend of synthetic and
non-synthetic. Suitable graphite particles can be obtained from,
for example, Brazilian Nacional de Grafite (Itapecerica, MG Brazil
(MP-0702X)) or Chuetsu Graphite Works, Ltd. (Chuetsu grades WH-20A
and WH-20AF) of Japan. The cathode may include for example, between
3% and 7%, preferably between 4% and 6.5% carbon particles by
weight.
[0034] Examples of binders include polyethylene powders,
polyacrylamides, and fluorocarbon resins, such as PVDF and PTFE. An
example of polyethylene binder is sold under the trade name
Coathylene HA-1681 (available from Hoescht). The cathode may
include, for example, between 0.1 percent to about 1 percent of
binder by weight.
[0035] Cathode 12 can include other additives. Examples of these
additives are disclosed, for example, in U.S. Pat. No. 5,342,712,
which is hereby incorporated by reference. Cathode 12 may include,
for example, from about 0.2 weight percent to about 2 weight
percent TiO.sub.2.
[0036] The cathode can also include an oxidizing additive. The
cathode can include 1 to 10 weight percent oxidizing additive. The
oxidizing additive can be physically mixed with the other cathode
components, or one or more of the cathode components can be treated
with a solution containing the oxidizing additive. Treatment with
the solution can result in penetration of the additive into pores
of the cathode component, which may result in longer, more
sustained performance from the oxidizing additive.
[0037] The oxidizing additive is a material that is more readily
reduced than the cathode material. For example, the oxidizing
additive can be a material that is more oxidizing than nickel
oxyhydroxide, such as NaOCl, K.sub.2S.sub.2O.sub.8, KMnO.sub.4,
H.sub.2O.sub.2, AgMnO.sub.4, or AgO. In particular, an alkaline
cell using .gamma.-NiOOH as the cathode material can be stabilized
by the addition of small amounts (e.g., 1-10 wt %) of
K.sub.2S.sub.2O.sub.8 or KMnO.sub.4 into the cathode mixture by
physically mixing the oxidizing additive with the .gamma.-NiOOH and
graphite.
[0038] The electrolyte solution also is dispersed through cathode
12, and the weight percentages provided above and below are
determined after the electrolyte solution has been dispersed.
[0039] Anode 14 can be formed of any of the standard zinc materials
used in battery anodes. For example, anode 14 can be a zinc slurry
that includes zinc metal particles, a gelling agent, and minor
amounts of additives, such as gassing inhibitor. In addition, a
portion of the electrolyte solution is dispersed throughout the
anode.
[0040] The zinc particles can be any of the zinc particles
conventionally used in slurry anodes. Examples of zinc particles
include those described in U.S. Ser. No. 08/905,254, U.S. Ser. No.
09/115,867, and U.S. Ser. No. 09/156,915, which are assigned to the
assignee in the present application and are hereby incorporated by
reference. The anode may include, for example, between 67% and 71%
of zinc particles by weight.
[0041] The electrolyte can be an aqueous solution of KOH or NaOH.
The electrolyte can contain 20%-50% by weight alkali hydroxide
dissolved in H.sub.2O. The electrolyte can contain 0% to 4% by
weight zinc oxide.
[0042] Examples of gelling agents include polyacrylic acids,
grafted starch materials, salts of polyacrylic acids,
polyacrylates, carboxymethylcellulose, sodium
carboxymethylcellulose or combinations thereof. Examples of such
polyacrylic acids are Carbopol 940 and 934 (available from B.F.
Goodrich) and Polygel 4P (available from 3V), and an example of a
grafted starch material is Waterlock A221 or A220 (available from
Grain Processing Corporation, Muscatine, Iowa). An example of a
salt of a polyacrylic acid is Alcosorb G1 (available from Ciba
Specialties). The anode may include, for example, from 0.1 percent
to about 2 percent gelling agent by weight.
[0043] Gassing inhibitors can be inorganic materials, such as
bismuth, tin, and indium. Alternatively, gassing inhibitors can be
organic compounds, such as phosphate esters, ionic surfactants or
nonionic surfactants. Examples of ionic surfactants are disclosed
in, for example, U.S. Pat. No. 4,777,100, which is hereby
incorporated by reference.
[0044] Separator 16 can have any of the conventional designs for
battery separators. In some embodiments, separator 16 can be formed
of two layers of non-woven, non-membrane material with one layer
being disposed along a surface of the other. To minimize the volume
of separator 16 while providing an efficient battery, each layer of
non-woven, non-membrane material an have a basic weight of about 54
grams per square meter, a thickness of about 5.4 mils when dry and
a thickness of about 10 mils when wet. In these embodiments, the
separator preferably does not include a layer of membrane material
or a layer of adhesive between the non-woven, non-membrane layers.
Generally, the layers can be substantially devoid of fillers, such
as inorganic particles.
[0045] In other embodiments, separator 16 includes a layer of
cellophane combined with a layer of non-woven material. The
separator also includes an additional layer of non-woven material.
The cellophane layer can be adjacent cathode 12 or the anode.
Preferably, the non-woven material contains from about 78 weight
percent to about 82 weight percent PVA and from about 18 weight
percent to about 22 weight percent rayon with a trace of
surfactant. Such non-woven materials are available from PDM under
the trade name PA25.
[0046] The electrolytic solution dispersed throughout battery 10
can be any of the conventional electrolytic solutions used in
batteries. Typically, the electrolytic solution is an aqueous
hydroxide solution. Such aqueous hydroxide solutions include
potassium hydroxide solutions including, for example, between 33%
and 38% by weight percent potassium hydroxide, and sodium hydroxide
solutions.
[0047] Housing 18 can be any conventional housing commonly used in
primary alkaline batteries. The housing typically includes an inner
metal wall and an outer electrically non-conductive material such
as heat shrinkable plastic. Optionally, a layer of conductive
material can be disposed between the inner wall and the cathode 12.
This layer may be disposed along the inner surface of wall, along
the circumference of cathode 12 or both. This conductive layer can
be formed, for example, of a carbonaceous material. Such materials
include LB1000 (Timcal), Eccocoat 257 (W. R. Grace & Co.),
Electrodag 109 (Acheson Colloids Company), Electrodag 112 (Acheson)
and EB0005 (Acheson). Methods of applying the conductive layer are
disclosed in, for example, Canadian Patent No. 1,263,697, which is
hereby incorporated by reference.
[0048] Current collector 28 is made from a suitable metal, such as
brass. Seal 30 can be made, for example, of nylon.
[0049] Button cells were prepared containing different nickel
oxyhydroxide cathode materials. The capacity losses of the
batteries were tested as described.
[0050] Reagent grade KOH (4.5 g) was dissolved in 100 mL of
de-ionized water. Non-coated alpha nickel hydroxide (20 g)
(Ni.sub.0 62Al.sub.0 18Co.sub.0 03,(OH).sub.2(CO.sub.3).sub.0
13(H.sub.2O).sub.0 17) (HC Starck) was added to the KOH solution.
The solution was heated on a hot-plate with stirring under a flow
of argon to evaporate the water. The system was kept free of carbon
dioxide to avoid carbonation of KOH. A paste was formed. The paste
was dried in an oven at 80.degree. C. under flowing argon to form a
dry powder.
[0051] The KOH-coated .alpha.-Ni(OH).sub.2(20 g) was placed in a
modified Erlenmeyer flask that was modified to have internal flaps
that help to disperse the powder. The flask was clamped to a holder
which was attached to a motor. Ozone was generated by an ozone
generator (Griffin Technics Inc., Model GTC-05). About 20 g/hr of
ozone was produced with oxygen as the feed gas at a flow rate of 7
L/min at 12 psi and 120V. The ozone was passed over the
Ni(OH).sub.2 powder inside the rotating flask inside a fume hood.
The flask was rotated in a water-cooling bath at room temperature
to maintain a constant temperature. Upon introduction of ozone, the
green .alpha.-Ni(OH).sub.2 turned immediately to black and
eventually to gray, signifying the end of the oxidation reaction
and the formation of .gamma.-NiOOH. The time for complete oxidation
was about 45 hours. After ozonation, the powder was removed from
the flask and stored in a Nalgene bottle.
[0052] The same process was used to prepare .gamma.-NiOOH from
.beta.-Ni(OH).sub.2, CoOOH-coated .gamma.-NiOOH from
Co(OH).sub.2-coated .alpha.-Ni(OH).sub.2, and CoOOH-coated
.gamma.-NiOOH from Co(OH).sub.2-coated .beta.-Ni(OH).sub.2.
[0053] Button cells were formed from four different cathode
materials: (1) the .gamma.-NiOOH produced from .beta.-Ni(OH).sub.2
(control); (2) the .gamma.-NiOOH produced from
.alpha.-Ni(OH).sub.2; (3) the CoOOH-coated .gamma.-NiOOH produced
from Co(OH).sub.2-coated .alpha.-Ni(OH).sub.2; and (4) and the
CoOOH-coated .gamma.-NiOOH produced from Co(OH).sub.2-coated
.beta.-Ni(OH).sub.2. The cathode of each cell was prepared by
combining 2.75 g of a .gamma.-NiOOH active material, 1.75 g of
graphite and 0.25 g of a 40 wt % KOH solution. These three
components are then thoroughly mixed with a pestle and mortar. 0.5
g of the cathode mixture was pressed into a 635 button cell. The
635 button cells were then assembled by the addition of a porous
polypropylene and 0.4 g of a Zn slurry containing 69 wt % Zn and 31
wt % aqueous KOH.
[0054] The batteries were then tested according to the following
procedure. Cells were tested when freshly made or after storage at
60.degree. C. for 1, 2, or 4 weeks. Materials were discharged at 3
("low rate") and 43 mA ("high rate") in 635 button-cells. Specific
capacity values were measured at a cut-off value of 0.8V for both
fresh ("Initial Capacity") and stored ("Storage Capacity")
discharges. Percent capacity loss was calculated for each test by
the following equation:
(1-(Storage Capacity)/(Initial Capacity))*100.
[0055] Table 1 summarizes the storage properties of cells
containing .gamma.-NiOOH derived from .beta.-Ni(OH).sub.2 (control)
or .alpha.-Ni(OH).sub.2. The .gamma.-NiOOH derived from
.alpha.-Ni(OH).sub.2 has much less capacity loss than that of
.alpha.-NiOOH derived from .beta.-Ni(OH).sub.2 Table 2 summarizes
the storage properties of cells containing CoOOH-coated
.gamma.-NiOOH derived from Co(OH).sub.2-coated .beta.-Ni(OH).sub.2
(control) or Co(OH).sub.2-coated .alpha.-Ni(OH).sub.2. From Table
2, it is apparent that CoOOH-coated .gamma.-NiOOH derived from
.beta.-Ni(OH).sub.2 has much less capacity loss than that of
CoOOH-coated .gamma.-NiOOH derived from .alpha.-Ni(OH).sub.2. A
comparison of the results in Table 1 and Table 2 indicate that the
cobalt-modified nickel oxyhydroxide had better storage
characteristics than uncoated oxyhydroxide originating from the
same nickel source. The batteries did not exhibit leakage
attributable to gas evolution.
1TABLE 1 % loss after % loss after % loss after 1 week at 2 weeks
at 4 weeks at Cathode Material 60.degree. C. 60.degree. C.
60.degree. C. NiOOH from .beta.-Ni(OH).sub.2 at a 90 90+ 90+ high
rate NiOOH from .alpha.-Ni(OH).sub.2 at a N/A 24 33 high rate NiOOH
from .beta.-Ni(OH).sub.2 at a 70 70+ 70+ low rate NiOOH from
.alpha.-Ni(OH).sub.2 at a N/A 30 39 low rate
[0056]
2TABLE 2 % loss after % loss after % loss after 1 week at 2 weeks
at 4 weeks at Cathode Material 60.degree. C. 60.degree. C.
60.degree. C. CoOOH coated NiOOH from 20 29 38 .beta.-Ni(OH).sub.2
at a high rate CoOOH coated NiOOH from 12 17 23
.alpha.-Ni(OH).sub.2 at a high rate CoOOH coated NiOOH from 23 27
44 .beta.-Ni(OH).sub.2 at a low rate CoOOH coated NiOOH from 16 21
29 .alpha.-Ni(OH).sub.2 at a low rate
[0057] Button cells containing NiOOH prepared as described in U.S.
Pat. No. 3,911,094 had a capacity loss upon storage at 60.degree.
C. for 1 week of 53%.
[0058] In another example, NiOOH was prepared by coating ground KOH
pellets on alpha nickel hydroxide. The solid powders were
mechanically ground to a fine homogeneous mixture before oxidation.
Oxidation was carried out in ozone as described above. The
resulting material had charge storage characteristics similar to
the NiOOH prepared by exposure to a solution of KOH.
[0059] Another cell was prepared in which the cathode contained 5
wt % K.sub.2S.sub.2O.sub.8. 5 g of a cathode mix was prepared by
mixing together 2.75 g of .gamma.-NiOOH active material derived
from .beta.-Ni(OH).sub.2, 0.25 g of K.sub.2S.sub.2O.sub.8, 1.75 g
of graphite and 0.25 g of 40% KOH solution. These four components
were then thoroughly mixed with a pestle and mortar. 0.5 g of the
5% K.sub.2S.sub.2O.sub.8/NiOOH mixture was pressed into a 635
button cell. The 635 button cells are then assembled by the
addition of a porous separator and 0.4 g of a Zn slurry. The
batteries were stored at 60.degree. C. for 1, 2 and 4 weeks in 635
button-cells. The cells containing 5% K.sub.2S.sub.2O.sub.8/NiOOH
mixture, before and after storage, were discharged at 3 mA. The
capacity loss after storage at 60.degree. C. for 2 weeks was
32%.
[0060] Other embodiments are within the claims.
* * * * *