CA1098960A - Lead battery positive plate doped with manganese or chromium - Google Patents

Abstract

ABSTRACT
A manganese or chromium doped positive plate for a lead acid battery, and a method of manufacturing the same is disclosed. Also disclosed is a lead acid battery containing manganese or chromium in the electrolyte. The doped positive plate has increased cycle life, hardness, and resistance to shedding of the active material.

Description

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g BACKGROUND OF THE INVENTION
1~ The present invention relates to storage batteries 11 and more specifically to lead-acid type batteries incorpurating 12 small amounts of manganese or chromium* to increase cycle life, 1~ hardness, and resistance to shedding of the positive plate.
1~ . , The positive plates of secondary batteries usually are 1~ formed by one of two general methods, the Plante process and the pasted plate process. The Plante process involves charg-18 ing and discharging lead electrodes in an electrolytic solution, 19 usually consisting of dilute sulfuric acid, u~til anodes of lead dioxide (or peroxide) and cathodes of sponge lead are form-21 ed. Oftentimes, an oxidizing agent is included within the form-22 ing electrolyte to hasten the positive plate formation by at-

2~ tacking the lead and forming lead sulfate which is subsequently 24 converted to -the desired lead dioxide.
-; - * ~he terms "manganese" and "chromium" are used to designate - 2~ any and all of the soluble species thereof that may result when a soluble salt containing manganese or chromium atoms, X7 respectively, is introduced into the electrolyte. Such species may be any simple or comple~ ions of manganese or 28 chromium, respectively.

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1 The pasted plate process is the more commonly used 2 method for the commercial production of lead-acid battery positive plates since the forming time is shorter than for 4 other methods and plates of much greater electrical storage 5 capacity can be obtained. That process involves reacting a ~ paste uslly composed of a plurality of lead oxides includ-7 ing for example, red lead, litharge, and the like, with 8 dilute sulfuric acid to form a paste containing ledd sul-9 fate, basic lead sulfate and lead oxide, mechanically affix-10 ing the paste to a lead grid designed to secure the paste 11 from removal and;then electrolytically 02idi2ing the pasted 12 plate to form an active material comprised mainly of lead 13 dioxide with small amounts of lead oxide and lead s~llfate.
14 The lead sulfate is desirably present in minor quantities 15 as required to provide a paste having the desired final bulk, 1~ and also to serve a binding function.

18 In U.S. Patent 292,414 ~1883) and U.S. Patent 19 434,458 (1890), manganese compounds in relatively large 20 quantities were disclosed as oxidi~ing agents to reduce the 21 amount of time necessary to form the Plante electrodes and 22 increase their capacity. In U.S. Patent 566,231 ~1898) Z3 and U.S. Patent 911,141 (1909), man~anese compounds are 24 disclosed as binding agents for the active material. U.S.
2~ Patent 1,640,922 ~1927) claims an electrode paste contain- .' 28 ing 12 percent manganese peroxide to prevent discharge o~ t 27 the electrodes when open-circuited or dry-stored.

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1 Chromates have also been used as oxidizing agents*, and 2 it has been reported that ammonium chromate doubles the life of

3 the positive active material.*~ On the other hand, research

4 published in 19~2*** reported that manganese caused rapid self-discharge of lead-acid batteries and severe deterioration of the positive plates. Several years later, Vinal and Altrup~*~*
7 reported that manganese was particularly destructive to the 8 positive plates. Manganese further exhibits a strong and corrosive 9 oxidizing action on some organic materials that may be used in a battery, such as wood separators~ Therefore, storage battery 11 specifications si~ce the 1920's typically set ma~imum manganese 12 impurity levels in lead oxides for electrodes at 0.3 part*****
13 per million (ppm) and in sulfuric acid electrolytes at 0.2ppm.
14 Chromium has been considered to be detrimental in storage batteries in a manner similar to manganese.

1~ The present invention provides a manganese or chromium 19 treated positi~e plate for a lead acid bat-tery, and a method for producing the same. The treated positive plate consists 21 essentially of a lead or lead alloy grid, a composite of lead 22 dioxide, and from 0.1 to 0.4 percent of manganese or chromium, 23 calculated as the metal, based upon the weight of the plate.

* George W. Vinal, "Storage Battëries", 4th Edition, (Ne~
26 York, 1955), pp. 23 and 132.
** Morton Arendt, "Storage Batteries" (New York 1928), p.34.
2~ *** Helen C. Gillette, "A Study of Effect of Impurities on Storage Batteries", Trans. Am. Elect. Chem. Soc., XLI (1922).
27 **** G. W. Vinal and F. W. Altrup, "Effect of Certain Impurities in Storage Battery Electrolytes", Jour. Amer. Inst. Elec. Eng.
28 (1924)~
*~*~* The terms "parts" and "percent" are used herein, and in Z9 the appended claims, to refer to percent and parts ~y welght, unless otherwisé indicated.

5~ -, 1 The plate is manufactured by immersing a lead or lead alloy grid 2 pasted with a typical battery plate paste composition in an electrolyte containing from 1.8 x 10 4 to 9.1 x 10-2 graD
4 atoms per liter of manganese, chromium, or both, and the~
applying an electric current thereto. Contrary to the under~
~ standing in the industry, such plates, treated with manganese~
7 chxomium, or both,in the above described narrow range of pro~
8 portions have increased cycle life, hardness, and resistance 9 to shedding of the active material as compared to non-treated positive plates. It will be understocd that batteries con-11 taining such plates must necessarily be made with separators 12 and other ancillary components that will not interfere with 13 the action of manganese or chromium. For example, separator 14 plates, battery cases and other components made of microporous polyethylene and polyvinyl chloride respectively have been 1~ found to be operable.

1~ The invention also provides a lead acid battery con-19 taining at least one positive plate as abcwe-described, as well as a battery containing at least one standard positive ~1 plate, comprised of a lead or lead alloy grid pasted with a 22 lead oxide composition and immersed in an electrolyte con-23 taining from 1.8 x 10-4 to 9.1 x 10 2 gram atom per liter of 24 manganese, chromium or bothO

2a EXAMPLE I
27 Two lead-calcium-tin (weight ratio 99.g2: o.oa:
28 1.00) grids, each 0.070 inch thick, were pasted ~ith a medium 29 density paste of lead oxide and air dried. The pasted grids were then soaked for seventeen hours in sulfuric acid having _5_ '~ :

6~3 -1 a specific gravity (Sp.Gr.) of 1.100, and charged for 96 2 hours at the rate of 2 amperes pex pound of dry paste. The S formed plates so produced were cycled in separate tanks con-taining 1.210 Sp.Gr. sulfuric acid and 9.1 x 10-3 gram a~om per liter of manganese, added as MnS04.H20. For purposes of comparison, but not in acrordance with the present in-

7 vention, two other plates were similarly formed and cycled,

8 but in a cycling bath which contained sulfuric acid only.

The plates were cycled by di~charging at 1.75 ampexeY
11 (approximately the 5-hour rate) and recharged for 17-18 12 hours at constant current to provide about 10% overcharge. The 13 initial capacity of the plates was about ten ampere hours. The 14 cycling of each pair of plates was continued until the capacity of one of the plates in the pair dropped to 2 ampere-hours. The 1~ number of cycles occuring before the capacity dropped to 2 17 ampere-hours is used herein as the cycle life of the plate, or 19 in this case the cycle life of the pair. The life in cycles 19 of the positive plates cycled in sulfuric acid containing Mn was 2.64 times that of the control (Control I~. Furthermore, 21 plates cycled in Mn provided 2.22 times more total energy over 22 the cycle life, measured in ampere-hours, than Control I.

The experiment described in Example I was duplicated 8~ as Examples II-V, except that the cycling tan~s contained 1. a x 27 10-4, 1.8 x 10-3, 1.8 x 10-2 and 9.1 x 10 2 gram atoms per liter 28 of manganese, respectively, added as MnS04.H20. The ratios of 29 cycle life and total energy out-put of each pair of experimental plates to those for the Control I plates, are shown in the 31 following Table:

, 1 TA~LE Y

OF MANGANESE
3(G~AM ATOMS CYCLE LIFE TOl'AL ENERGY OUTPU~
EXAMPLE PER LITER) (EXAMPLE/CONTROL I) (EXAMPLE/C T _L I) II 1.8 x 10 4 1.18 1.03 ~ III 1.8 x 10 3 1.55 1.41 7 IV 1.8 x 10 2 1.82 1.60 `' 8 V 9.1 x 10-~ 3.00 2.22 EXAMPLE VI
11 A lead-calcium-tin qrid 0.070 inch thick was pasted 1% with a medium density paste of lead oxide, as described in 1~ Example I, but the plate was subsequently cured at high humidity 1~ and a temperature of about 80-100C. rather than air dried.
16 The high temperature and humidity cure is known to develop dif-1~ ferent types of compounds in the paste than low temperature cures 17 (see e.g. B. P. Varma and C. W. ~leischmann, J. Electrochem.
lS i Soc., 124, 718 ~1977).) The plate was formed by soaking it for 19 16 hours in 1.100 Sp.Gr. sulfuric acid and was charged for 96 29 hours at the rate of 2 ampe,res per pound of dry paste. The 21 plate was cycled 25 described in Example I in 1.210 Sp.Gr. sul-22 furic acid containing 9.1 x 10-3 gram atom per liter of man- , 2~ ganese, added in the form of manganese sulfate monohydrate. For 24 p~lrposes of comparison, but not in accordance with the present invention, a control plate ~Control ~I) was similarly formed 2~ and cycled, except that the cycling bath contained s~llfuric 27 acid only. The cycle life of the manganese treated plate was 28 1.84 times that of the plate cycled in sulfuric acid only.

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~ EXAMPLE VI~
2 A lead-antimony grid (Pb-95.7 percent, Sb~.25 ~ percent Sn-0.4 percent, As-0,5 percent, Cd- 0.1 percent and 4 Cu-0.05 percent) 0.070 inch thick was pasted with a medium density paste of lead oxide and air dried. The plate was ~ formed by soaking it for 16 hours in 1.100 Sp.Gr. sulfuric 7 acid and then charging it for 96 hours at the rate of 2 8 amperes per pound of dry paste. The plate was cycled in

9 1.210 Sp.Gr. sulfuric acid containing 9.1 x 10-3 gram atoms per liter of manganese added i~ the form of manganese sul-11 fate monohydrate; in cycling, the di~charge was at a five 12 hour rate with a current of 1.75 amperes and the recharge 13 was at a constant current for 18 hours. For purposes of com-t4 parison, but not in accordance with the present invention, a control plate (Control VII) was similarly formed and cycled, 1~ except that the cycling bath contained sulfuric acid only;
17 the capacity of the manganese treated plate on the tenth 1~ cycle was 10 percent higher than that of the control. At the 19 end of the life of the control, the capacity of the treated plate was 2.72 times that of the control plate. The cycle 21 lie of the treatcd plate was substantially 20 percent 22 longer than that of the control.

A three-cell five~plate battery, constructed from 2a lead-calcium grids pasted with a medium density lead oxide 27 paste was asse~bled. The calcium content of the grids was 28 0.03 percent. The plates were soaked for six hours in 29 1.180 Sp.Gr. sulfuric acid and then formed in 1.180 Sp.Gr.
sulfuric acid by charging them for 96 hours at the rate of 2 31 amperes per pound of dry paste. E'ollowing the formation, the "

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1 cells were repeatedly discharged and charged in 1.210 Sp.Gr.
2 sulfuric acid until each of the cells gave comparable re-3 peated values for capacity. Manganese sulfate monohydrate in 1.210 Sp.Gr. sulfuric acid was then added to two of the cells to produce manganese concentrations ~f 3.6. x 10-3 and ~ 9.1 x 10-3 gram atoms per liter, respectively, in the electrolyte r therein; the manganese was mixed with the acid and the specific 8 gravity of the acid in each cell was adjusted to l.210. The 9 battery was then discharged and charged according to the follow-ing schedule until the first indication of shorting occurred:
11 Discharge - 4 minutes at 62.5 amperes ~ Rest - 2 minutes 13 . Charge 22 minutes at 14.4 amperes 14 Rest - 2 minutes The weight loss, or amount of shedding, of each positive 16 plate was determin~d. The positive plate in the cell containing 17 3.6 x 10-3 gram atoms per liter of manganese had 19 percent less 19 shedding than the control positive plate in the cell containing 19 pure sulfuric acid. The positive plate in the cell containing 9.1 x 10-3 gram atoms per liter of rnanganese had 37 percent less 21 shedding than the control plate.

2~ EXA~PLE IX
24 The steps in Example VIII were repeated, except that the battery grids were of the lead antimony type.
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27 The positive plate in the cell containing 3.6 x 10-3 gram atoms ~ per liter of manganese had 35 percent less shedding, and that 29 in the cell containing 9.1 x10-3 gram atoms per liter of man-ganese had 42 percent less shedding than the contxol plate.

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2 Two lead-calcium-tin grids of 0.070 inch thick-3 ness were pasted with a high density water paste of yellow 4 lead oxide. The paste was treated at high humidity a~d elevated temperature to effect conversion of the yellow oxide to the red oxide which forms electrochrmically more 7 readily. The plates were soaked for 17 hours and then 8 charged for 96 hours, at the rate of 2 amperes per pound of 9 dry paste in 1.100 Sp.Gr. sulfuric acid containing 9.1 x 10-3 gram atoms per liter of manganese, added in the form of man-~1 ganese sulfate monohydrate. One of the plates (Example XI) 12 was then taken out of the forming bath and cycled in another 13 tank containing sulfuric acid, specific gravity of 10210.
14 The other plate (Example X) was retained for chemical analysis.
In cycling, the discharge was at a five hour rate with a current 1~ of 1.75 amperes, and the recharge was at a constant current 17 for eighteen hours.

19 For purposes of comparison, but not in a~cordance with the present inventiQn, two control plates were similarly 21 formed except tha~ the forming bath contained pure sulfuric 22 acid only, and one tControl XI~ was si~lilarly cycled. The re-23 maining control plate (Control X) was retained for chemical 24 analysis. Althou~h the capacity per cycle for both cycled plates was similar in the initial cycles, the capacity of the 28 control plate subsequently began to drop relative to that of 27 the treated plate, such that, at the end of the life of the 28 control plate, the capacity of the manganese formed plate 29 was 3.3 times as great as that of the control. Chemical analysis of each of the plates for Mn is given on the following Table:

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Mn CONTENT
- tWEIG~lT PERCENT) 2 Ex~mp;~ X, not cycled0.2 3 Example XI a~ the end of the 0.2 ' llfc of the control g Control X, not cycled -6 Control XI, at the end of its o.o life EXAMPLE XII
~ Two lead-calcium-tin grids of 0.060 inch thickness 9 were pasted, soaked, formed and cycled as described in Example X, except that the forming bath contained 9.1 x 10 3 gram atoms

11 per liter of chromium, added as a chromate, rather than man-

12 ganese. ~or purposes of comparison; but not in accordance with

13 the present invention, two control plates (Control XII) were i4 similarly soaked, formed, and cycled except that the forming bath contained pure sulfuric acid only.
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17 Based upon the chromium concentration in the forming 1~ bath after formation, the formed plates were calculated to 19 contain 0.33 percent chromium. At the end of the life of the Z0 control plates, the chromium treated plates had an average 21 capacity 4.2 times greater than the average for the control plates.

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24 The procedure in Example XII was repeated, except that the forming bath contained 9.1 x l0 2 gram atoms per liter of 28 chromium. The formed plates were calculated to contain 3.3 per- c 2q cent chromium. The chromium treated plates, after the number o 2a cycles corresponding to end of life for the Control-XII platas, 29 had an average capacity per cycle 2.6 times greater than the average for Control XII, above.

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1 It will be apparent that variou~ chan~es and 2 modifications can be made from the specific details of 3 the invention as set forth in the foregoing discussion, 4 including the Examples~ without departing from the spi~it and scope of the invention, as defined in the appended claims.

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Claims (9)

WHAT I CLAIM IS:

1. A positive plate for a lead acid battery, said plate consisting essentially of a lead or lead alloy grid, a composition containing lead dioxide, and from 0.1 to 0.4 percent based upon the weight of said plate, of at least one element selected from the group consisting of manganese and chromium, said element hav-ing been introduced by electrolysis into said plate from solution in an electrolyte.

2. A positive plate for a lead acid battery, as defined in claim 1, said plate containing from 0.15 to 0.3 percent of said element.

3. A positive plate for a lead acid battery, as defined in claim 1, said plate containing 0.2 percent of manganese.

4. A positive plate for a lead acid battery, as defined in claim 1, said plate containing about 0.3 percent of chromium,

5. A lead acid storage battery including at least one negative plate, at least one positive plate, and an electrolyte, said positive plate consisting essentially of a lead or lead alloy grid, a composi-tion containing lead dioxide, and from 0.1 to 0.4 percent, based upon the weight of said positive plate, of at least one element selected from the group con-sisting of manganese and chromium, said element having been introduced by electrolysis into said plates from solution in an electrolyte.

6. A lead acid battery including at least one negative plate, at least one positive plate, and an electrolyte, said positive plate consisting essentially of a lead or lead alloy grid and a composition containing lead dioxide, and said electrolyte containing from 10 to 5000 parts per million of at least one element selected from the group consisting of manganese and chromium.

7. A lead acid storage battery as defined in claim 6 wherein the electrolyte is sulfuric acid.

8. A method of forming a positive plate for a lead acid battery, said method comprising the steps of immersing a lead or lead alloy grid pasted with a lead oxide composition in an electrolyte containing from 10 to 5000 parts per million of at least one element selected from the group consisting of manganese and chromium, and applying an electric current to said grid and said electrolyte.

9. A method as defined in claim 8 wherein said grid is immersed in an electrolyte containing 500 parts per million of said element.