CA1067571A - Rechargeable electric accumulator cell with at least one zinc electrode - Google Patents
Rechargeable electric accumulator cell with at least one zinc electrodeInfo
- Publication number
- CA1067571A CA1067571A CA256,943A CA256943A CA1067571A CA 1067571 A CA1067571 A CA 1067571A CA 256943 A CA256943 A CA 256943A CA 1067571 A CA1067571 A CA 1067571A
- Authority
- CA
- Canada
- Prior art keywords
- zinc
- electrolyte
- anode
- accumulator cell
- cathode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Hybrid Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
RECHARGEABLE ELECTRICAL ACCUMULATOR CELL WITH
AT LEAST ONE ZINC ELECTRODE
ABSTRACT OF THE DISCLOSURE
An improvement in accumulator batteries having a zinc anode and an oxide cathode (e.g., nickel oxide or silver oxide cathode) is disclosed. The zinc anode and/or separator part between the anode and cathode is vibrated at a frequency and amplitude sufficient to inhibit dendrite growth on the zinc anode. The electrolyte contains excess zinc such that solid zinc oxide is present in the fully charged condition. The separator may be provided with circulation enhancement means. The resulting batteries have long life with a large number of charging and dis-charging cycles.
AT LEAST ONE ZINC ELECTRODE
ABSTRACT OF THE DISCLOSURE
An improvement in accumulator batteries having a zinc anode and an oxide cathode (e.g., nickel oxide or silver oxide cathode) is disclosed. The zinc anode and/or separator part between the anode and cathode is vibrated at a frequency and amplitude sufficient to inhibit dendrite growth on the zinc anode. The electrolyte contains excess zinc such that solid zinc oxide is present in the fully charged condition. The separator may be provided with circulation enhancement means. The resulting batteries have long life with a large number of charging and dis-charging cycles.
Description
7S'71 The present invention deals with an electric accumulator cell with at least one cathode, at least one zinc anode, separator or spacer arranged between cathode and anode and an alkaline electrolyte. The anode and/or separator (or spacer) is arranged in such a way that it/
they vibrate in the plane of or parallel to the electrode.
Electric accumulator cells having zinc anodes in alkaline electrolyte are known in combination with various kinds of cathodes, for example, nickel oxide or silver oxide. The zinc anode-containing cell has several advantages such as, for example, high half cell potential, a high energy to weight ratio and, in comparison to alternative anode materials, a low price. Certain problems are, however, associated with the use of zinc anodes, particularly regarding the life of the cells and the need for large amounts of electrolyte. These problems stem from the special properties of zinc in an alkaline electrolyte.
The zinc anode is a so-called dissoluble electrode, , .
i.e., during the discharge reaction the zinc forms products soluble in the electrolyte. These products leave the anode. Zinc forms mainly zincate ions which then may react further in the electrolyte. The zincate ions then form zinc oxide which has a much lower solubility in the ~, electrolyte than the zincate ions. The zinc oxide precipitates as a solid. The main reactions during dis-charge of the zinc electrode and the precipitation of zinc oxide are the following:
they vibrate in the plane of or parallel to the electrode.
Electric accumulator cells having zinc anodes in alkaline electrolyte are known in combination with various kinds of cathodes, for example, nickel oxide or silver oxide. The zinc anode-containing cell has several advantages such as, for example, high half cell potential, a high energy to weight ratio and, in comparison to alternative anode materials, a low price. Certain problems are, however, associated with the use of zinc anodes, particularly regarding the life of the cells and the need for large amounts of electrolyte. These problems stem from the special properties of zinc in an alkaline electrolyte.
The zinc anode is a so-called dissoluble electrode, , .
i.e., during the discharge reaction the zinc forms products soluble in the electrolyte. These products leave the anode. Zinc forms mainly zincate ions which then may react further in the electrolyte. The zincate ions then form zinc oxide which has a much lower solubility in the ~, electrolyte than the zincate ions. The zinc oxide precipitates as a solid. The main reactions during dis-charge of the zinc electrode and the precipitation of zinc oxide are the following:
- 2-, Zn + 4 OH = Zn(OH)4 + 2e Zn(OH)4 = ZnO + H20 + 2 OH
'i, '' .
-2- ~t '` -', ' ' ' . - - .. , ,., . :
. i .: .: . . . , :
106757~
Other reactions and other types of ions are present, but the above are dominating and illustrate the main reactions in the cell.
The problems with zinc electrodes are caused by the redeposition of zinc on the electrodes during the charging process, during which the zinc to a large extent forms zinc dendrites which have a tendency to grow towards the counter electrode and cause a short circuit in the cell.
An additional cause of short circuits is the tendency of the zinc to collect at the edges of the electrodes, specially at the lower edge. Thus, there occurs a re-distribution of the zinc active material on the electrode during the charging-discharging cycling.
Different methods have been tried to solve these problems. The use of a semipermeable membrane between the zinc electrode and the counter electrode has become very common. The membranes are so dense that the growing of zinc dendrites is made difficult. A large number of additives of different kinds, organic as well as inorganic substances have been tried in the electrolyte, the membranes and the electrode. These endeavours have led to important improvements of cells with zinc electrodes, but the results are still not ~atisfactory. Attempts have been made to redistribute the active material on the surface of the electrode. One such attempt was to build the cell in such a way that fluid flow and diffusion in the electrolyte were obstructed as much as possible. Thus, the redeposition of zinc should take place on the same surface as from which the zinc had been dissolved during discharge. That, how-ever, circumscribes very much the availability of electrolyte ., .
.: . . . .. . .. . : . ~
i'75;~1 with consequences which shall be more closely considered below. Another way to solve the problem of the active material distribution is to pump the electrolyte around in the cells. This presupposes, however, cost increasing and space requiring auxiliary systems including pumps, tubings etc.
The zinc electrode has also shown a tendency for ~-passivation. The mechanism and reasons for such passi-vation are not fully known, but it is generally thought that one main reason for the passivation is the presence of zinc oxide particles in the active zinc material. These zinc oxide particles isolate portions of the zinc material from participating in the electrochemical process so that the load on the rest of the electrode increases. To avoid the passivation effect as far as possible, great importance ~ -has been put upon using such a large amount of electrolyte that the zinc dissolved from the electrodes should be present in a soluble form in the electrolyte. This requires comparatively large amounts of electrolytes in the cell, but even then, deposition of zinc oxide was not fully avoided. Zincate ions are slowly decomposed and form zinc oxide. The mechanism of the reaction is not fully known, but the consequence of this decomposition is that a formation of zinc oxide cannot be totally avoided. It is possible to oversaturate an electrolyte with respect to zincate ions and that has been used in accumulator cells, but the electrolyte volume still remains too large. To take away the zinc oxide which cannot be avoided in the electrolyte, it has also been proposed to pump the .. ~ .. . . .
.. . .
electrolyte through a filter on which the zinc oxide is filtered off.
The present invention relates to rechargeable electric accumulator cells containing at least one zinc anode, at least one cathode, a separator (or spacer) dispos~d between the zinc anode and cathode, the anode, cathode and separator being arranged in an alkaline electrolyte, in which aforementioned cell, the anode and/or separator between the anode and cathode are arranged to vibrate either in the plane of or parallel to the electrode and is characterized in that the zinc concentration in the electrolyte is so high that the electrolyte contains free solid zinc oxide in the fully charged accumulator cell.
The zinc anode and/or separator is vibrated in the direction of the plane of the anode or separator at a frequency and amplitude during the charging process sufficient to inhibit dendrite growth on the zinc anode e.g., at a frequency of between about 1 and 500 hz and an amplitude of between about 0.1 and 10 mm during the charging process. The vibrating part is mounted so that all portions thereof move substantially the same distance during each cycle o~
vibration and all portions of the vibrating part move in a reciprocating manner to have at the same moment the same rectilinear movement during all portions of the vibration cycle.
The difficulties involved with maintaining the electrolyte free from zinc oxide have been described above.
It is, however, theoretically possible in known cells (and ohould also be praotioally po~sible in fully charged -~)67S71 relatively new cells) to keep the electrolyte free from zinc oxide. Such cells are not included in the invention according to which the zinc concentration shall be so high that the presence of solid zinc oxide theoretically or --practically cannot be avoided.
The electrolyte preferably consists of potassium hydroxide dissolved in water to a solution containing 20 to 45 percent by weight of the hydroxide. It has been found that it is possible with cells according to the present invention to use electrolytes containing such large quantities of zinc oxide that the electrolyte becomes viscous and slurrylike. Suitably, the electrolyte contains at least 200 grams of zinc oxide, preferably 250 to 400 grams zinc oxide, per liter of electrolyte when the cell is discharged. However, amounts of zinc oxide above 600 grams per liter have been used successfully.
Especially good results were obtained when the vibrating components were constructed so that the electrolyte was pumped between the electrodes. This pumping action ensures that the electrolyte not only ls moving back and forth and bac~ but also has a movement which results in an electrolyte circulation between the upper and lower parts of the electrode surfaces.
, . . . .
Figure 1 shows a cell according to the present invention and Figure 2 shows different possible constructions ~ of a separator ~or spacer) which i8 intended to vibrate `~ between the electrodes of the cell. In the cell shown in `' Figure 1 the anodes are arranged for vibration although it will be understood that the separator may also or alternatively be vibrated.
..
.
.~, .
5~1 As shown in Figure 1, the cell contains a plurality of dissoluble zinc electrodes 1 and counter electrodes 2 between which are disposed separators (or spacers) 3. The dissoluble zinc electrodes 1 are connected by connecting devices 4 to a common bridge 5. The zinc electrodes 1 are arranged to be vibrated by means of a shaft 6 journaled between bearings 8 in the cell wall 12. The shaft 6 is eccentrically formed. Circulatory motion may be imparted by shaft 6 by suitable means outside the cell (not shown) and vibratory movement is imparted to the zinc electrodes 1 by yoke 7 and suspension and connecting devices 18 and 19.
The shaft 6 is electrically insulated from the electrodes by using connecting devices formed of an insulating material. Through a flexible cord 17, the zinc electrodes may be connected to post 10 on the outside of the cell.
The electrodes 2 may similarly be connected to post 11 by conventional means not shown.
The separator shown in Figure 2 is provided with an outer edge 21, and attaehment 22 and distance ribs 23, 24, 25 and 26. These ribs are suitably but not necessarily formed likewise on the entire separator and may have, for example, one o the four different configurations shown in the Figure. These ribs 23, 24, 25 or 26 impart a circu-lation to the electrolyte in and up and down direction as ~, well as a back and forth movemept and thus enhance the 1 circulation or pumpting of the electrolyte.
The vibration frequency imparted to the zinc anode and/or separator is suitably 1 - 500 Hz and the amplitude is chosen in accordance herewith, in such a way that the linear velocity reaches about 20 mm/second or more, at .
::
~'`' , .
10ti;~7571 least at some instance during the up and down movement.
The amplitude may thus be on the order of from about G.l to 10 mm or more. Preferably, the amplitude is about 4 mm and the frequency about 50 Hz.
The principles, preferred embodiments and modes of operation of the present invention have been described in the ~oregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.
.' , .
,..
.
.
.j, .
' ~' '' .' .
'i, '' .
-2- ~t '` -', ' ' ' . - - .. , ,., . :
. i .: .: . . . , :
106757~
Other reactions and other types of ions are present, but the above are dominating and illustrate the main reactions in the cell.
The problems with zinc electrodes are caused by the redeposition of zinc on the electrodes during the charging process, during which the zinc to a large extent forms zinc dendrites which have a tendency to grow towards the counter electrode and cause a short circuit in the cell.
An additional cause of short circuits is the tendency of the zinc to collect at the edges of the electrodes, specially at the lower edge. Thus, there occurs a re-distribution of the zinc active material on the electrode during the charging-discharging cycling.
Different methods have been tried to solve these problems. The use of a semipermeable membrane between the zinc electrode and the counter electrode has become very common. The membranes are so dense that the growing of zinc dendrites is made difficult. A large number of additives of different kinds, organic as well as inorganic substances have been tried in the electrolyte, the membranes and the electrode. These endeavours have led to important improvements of cells with zinc electrodes, but the results are still not ~atisfactory. Attempts have been made to redistribute the active material on the surface of the electrode. One such attempt was to build the cell in such a way that fluid flow and diffusion in the electrolyte were obstructed as much as possible. Thus, the redeposition of zinc should take place on the same surface as from which the zinc had been dissolved during discharge. That, how-ever, circumscribes very much the availability of electrolyte ., .
.: . . . .. . .. . : . ~
i'75;~1 with consequences which shall be more closely considered below. Another way to solve the problem of the active material distribution is to pump the electrolyte around in the cells. This presupposes, however, cost increasing and space requiring auxiliary systems including pumps, tubings etc.
The zinc electrode has also shown a tendency for ~-passivation. The mechanism and reasons for such passi-vation are not fully known, but it is generally thought that one main reason for the passivation is the presence of zinc oxide particles in the active zinc material. These zinc oxide particles isolate portions of the zinc material from participating in the electrochemical process so that the load on the rest of the electrode increases. To avoid the passivation effect as far as possible, great importance ~ -has been put upon using such a large amount of electrolyte that the zinc dissolved from the electrodes should be present in a soluble form in the electrolyte. This requires comparatively large amounts of electrolytes in the cell, but even then, deposition of zinc oxide was not fully avoided. Zincate ions are slowly decomposed and form zinc oxide. The mechanism of the reaction is not fully known, but the consequence of this decomposition is that a formation of zinc oxide cannot be totally avoided. It is possible to oversaturate an electrolyte with respect to zincate ions and that has been used in accumulator cells, but the electrolyte volume still remains too large. To take away the zinc oxide which cannot be avoided in the electrolyte, it has also been proposed to pump the .. ~ .. . . .
.. . .
electrolyte through a filter on which the zinc oxide is filtered off.
The present invention relates to rechargeable electric accumulator cells containing at least one zinc anode, at least one cathode, a separator (or spacer) dispos~d between the zinc anode and cathode, the anode, cathode and separator being arranged in an alkaline electrolyte, in which aforementioned cell, the anode and/or separator between the anode and cathode are arranged to vibrate either in the plane of or parallel to the electrode and is characterized in that the zinc concentration in the electrolyte is so high that the electrolyte contains free solid zinc oxide in the fully charged accumulator cell.
The zinc anode and/or separator is vibrated in the direction of the plane of the anode or separator at a frequency and amplitude during the charging process sufficient to inhibit dendrite growth on the zinc anode e.g., at a frequency of between about 1 and 500 hz and an amplitude of between about 0.1 and 10 mm during the charging process. The vibrating part is mounted so that all portions thereof move substantially the same distance during each cycle o~
vibration and all portions of the vibrating part move in a reciprocating manner to have at the same moment the same rectilinear movement during all portions of the vibration cycle.
The difficulties involved with maintaining the electrolyte free from zinc oxide have been described above.
It is, however, theoretically possible in known cells (and ohould also be praotioally po~sible in fully charged -~)67S71 relatively new cells) to keep the electrolyte free from zinc oxide. Such cells are not included in the invention according to which the zinc concentration shall be so high that the presence of solid zinc oxide theoretically or --practically cannot be avoided.
The electrolyte preferably consists of potassium hydroxide dissolved in water to a solution containing 20 to 45 percent by weight of the hydroxide. It has been found that it is possible with cells according to the present invention to use electrolytes containing such large quantities of zinc oxide that the electrolyte becomes viscous and slurrylike. Suitably, the electrolyte contains at least 200 grams of zinc oxide, preferably 250 to 400 grams zinc oxide, per liter of electrolyte when the cell is discharged. However, amounts of zinc oxide above 600 grams per liter have been used successfully.
Especially good results were obtained when the vibrating components were constructed so that the electrolyte was pumped between the electrodes. This pumping action ensures that the electrolyte not only ls moving back and forth and bac~ but also has a movement which results in an electrolyte circulation between the upper and lower parts of the electrode surfaces.
, . . . .
Figure 1 shows a cell according to the present invention and Figure 2 shows different possible constructions ~ of a separator ~or spacer) which i8 intended to vibrate `~ between the electrodes of the cell. In the cell shown in `' Figure 1 the anodes are arranged for vibration although it will be understood that the separator may also or alternatively be vibrated.
..
.
.~, .
5~1 As shown in Figure 1, the cell contains a plurality of dissoluble zinc electrodes 1 and counter electrodes 2 between which are disposed separators (or spacers) 3. The dissoluble zinc electrodes 1 are connected by connecting devices 4 to a common bridge 5. The zinc electrodes 1 are arranged to be vibrated by means of a shaft 6 journaled between bearings 8 in the cell wall 12. The shaft 6 is eccentrically formed. Circulatory motion may be imparted by shaft 6 by suitable means outside the cell (not shown) and vibratory movement is imparted to the zinc electrodes 1 by yoke 7 and suspension and connecting devices 18 and 19.
The shaft 6 is electrically insulated from the electrodes by using connecting devices formed of an insulating material. Through a flexible cord 17, the zinc electrodes may be connected to post 10 on the outside of the cell.
The electrodes 2 may similarly be connected to post 11 by conventional means not shown.
The separator shown in Figure 2 is provided with an outer edge 21, and attaehment 22 and distance ribs 23, 24, 25 and 26. These ribs are suitably but not necessarily formed likewise on the entire separator and may have, for example, one o the four different configurations shown in the Figure. These ribs 23, 24, 25 or 26 impart a circu-lation to the electrolyte in and up and down direction as ~, well as a back and forth movemept and thus enhance the 1 circulation or pumpting of the electrolyte.
The vibration frequency imparted to the zinc anode and/or separator is suitably 1 - 500 Hz and the amplitude is chosen in accordance herewith, in such a way that the linear velocity reaches about 20 mm/second or more, at .
::
~'`' , .
10ti;~7571 least at some instance during the up and down movement.
The amplitude may thus be on the order of from about G.l to 10 mm or more. Preferably, the amplitude is about 4 mm and the frequency about 50 Hz.
The principles, preferred embodiments and modes of operation of the present invention have been described in the ~oregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.
.' , .
,..
.
.
.j, .
' ~' '' .' .
Claims (4)
1. A rechargeable electric accumulator cell com-prising at least one cathode, at least one zinc anode part and a separator part disposed between each said cathode and zinc anode part arranged in a liquid alkaline electrolyte, vibratory means operatively connected with at least one said part to subject said part to a vibratory movement in the direction of the plane of the part, wherein the said electrolyte contains zinc in excess of that soluble in the electrolyte whereby solid zinc oxide is contained in the electrolyte of the fully charged cell.
2. The rechargeable electric accumulator cell of claim 1 wherein said zinc is present in an amount of at least 200 grams of zinc per liter of electrolyte.
3. The rechargeable electric accumulator cell of claim 2 wherein said zinc is present in an amount of from about 250 to 600 grams of zinc per liter of electrolyte.
4. The rechargeable electric accumulator cell of claim 1 wherein the separator part is provided with pumping enhancement means on the surface thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7508110A SE394842B (en) | 1975-07-16 | 1975-07-16 | RECHARGEABLE ELECTRIC ACCUMULATOR CELL |
| US05/636,603 US4015053A (en) | 1973-12-06 | 1975-12-01 | Rechargeable electric accumulator cell with at least one zinc electrode |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067571A true CA1067571A (en) | 1979-12-04 |
Family
ID=26656642
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA256,943A Expired CA1067571A (en) | 1975-07-16 | 1976-07-14 | Rechargeable electric accumulator cell with at least one zinc electrode |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1067571A (en) |
-
1976
- 1976-07-14 CA CA256,943A patent/CA1067571A/en not_active Expired
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