Abstract:
An improved lithium iodine battery, depolarizer therefor and method of making same in which the depolarizer comprises a pelletized particulate mixture of iodine, an organic polymer of either poly-2-vinylpyridine or poly-2-vinylquinoline and a charge transfer complex consisting of the selected organic polymer and iodine wherein the mixture contains from 3 to 30 parts of iodine for each part of total organic.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an improved lithium halide primary cell, a depolarizer therefor and a method for making same. In particular, the invention is directed to lithium iodine cells in which the depolarizer or cathode material is a pelletized particulate mixture of an organic polymer consisting of poly-2-vinylpyridine (P2VP) or poly-2-vinylquinoline (P2VQ) iodine and a charge transfer complex of said organic polymer and iodine. The depolarizers are hereinafter collectively referred to as P2VP+P2VP.n 1  I 2  +n 2  I 2  were n 1  &gt;0 and n 1  +n 2  =3 to 30. 
     BACKGROUND OF THE INVENTION 
     The present invention provides a lithium halide primary cell having a shelf life extendable to more than ten years by utilizing a pelletized depolarizer consisting of P2VP+P2VP.n 1  +n 2  I 2  wherein n 1  &gt;0 and n 1  +n 2  is equal to 3 to 30 (parts of I 2  for each part of total organic). Preferably n 1  n 2  is equal to 15 to 26 parts of I 2  for each part of organic in the depolarizer. The cells of the present invention are particularly useful in electric watch, calculator and heart pacer applications. 
     U.S. Pat. Nos. 3,660,163 and 3,674,562 disclose batteries utilizing charge transfer complexes which are mixed with excess amounts of iodine. In particular, U.S. Pat. No. 3,674,562 teaches a novel cathode material which is &#34;plastic&#34; that is a pliable, putty-like solid. This material when used as a cathode in lithium primary cells has a low internal impedance and a relatively low self-discharge as measured by its heat of discharge. Cells manufactured in accordance with U.S. Pat. No. 3,674,562 are especially well suited for use in long-life, low current drains applications such as heart pacers. 
     What has been found is that 3-30 parts of iodine can be mixed with each part of the polymer P2VP or P2VQ having a weight average molecular weight* of above about 1×10 3  and pelletized without becoming plastic. Unlike the &#34;plastic&#34; depolarizer, P2VP.nI 2  and P2VQ.nI 2 , material of U.S. Pat. No. 3,674,562, the pelletized P2VP+P2VP.n 1  I 2  +n 2  I 2  (where n 1  +n 2  =3 to 30) depolarizer of the present invention has initially unacceptable electrical characteristics for battery applications. Typically, the initial impedance of a cell manufactured with the pelletized depolarizer of the present invention is quite high, for example, impedances from 2,000 ohms to 20,000 ohms are experienced. This compares with initial impedances of cells made with the material disclosed in U.S. Pat. No. 3,674,562 which have impedances in the range of about 30 to 300 ohms. 
    
     It was found, however, that initial impedances greatly diminish with time so that the cell &#34;acquires&#34; the appropriate electrical characteristics for battery applications. In fact, cells made in accordance with the present invention result, after significant discharge, in impedances less than those made from the plastic depolarizer. In certain instances, the internal impedance in batteries of the present invention was less by a factor of five than those made with plastic depolarizers. 
     Generally, it has been well known to use various charge transfer materials, including P2VP and P2VQ, for complexing with halides, normally iodine, for use as depolarizers. Also, it has been equally well known that such materials could be pelletized for use in primary cells, U.S. Pat. Nos. 3,438,813 and 3,660,164. The depolarizer is each instance was in the form of a complex wherein the halogen comprises from 50 to 71% by weight of the complex. Cells produced in this manner had relatively short operating lives. Another proposed approach has been to utilize substantially pure iodine pellets having an additive of an electrically conductive material therein to which a coating of polyvinyl pyridine iodine is applied to the outer surface. U.S. Pat. No. 3,937,635. Typically, high portions of uncomplexed iodine increased the internal cell resistance. Pelletized cells having a charge transfer complex mixed with iodine in a ratio of 3 to 10 were found to have useful electrical properties. U.S. Pat. No. 3,660,163. The advantages of the greater iodine content, however, were achieved by forming the complex and iodine in the plastic state. See also U.S. Pat. No. 3,674,562. 
     It is, accordingly, an object of the present invention to provide a lithium halide battery in which the depolarizer is a pelletized particulate and comprises either P2VP+P2VP.n 1  I 2  +n 2  I 2  or P2VQ+P2VQ.n 1  I 2  +n 2  I 2  where n 1  &gt;0 and n 1  +n 2  =3 to 30. The batteries made in accordance with the present invention have significant advantages over prior art batteries. These advantages will become apparent from a perusual of the following description of the invention taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional elevation taken along line I--I of FIG. 2 of a battery utilizing the disc depolarizer of the present invention; and 
     FIG. 2 is a plan view of the battery shown in FIG. 1. 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, battery 10 of the present invention comprises an outer casement member 11, preferably made from stainless steel and shaped in the form of a cup to facilitate assembly. A pair of lithium anode discs 12 and 13 are positioned in member 11 with a disc 14 of pelletized depolarizer interposed between discs 12 and 13. Preferably, lithium discs 12 and 13 are of a configuration substantially conforming to the inner configuration of encasement member 11 to achieve a tight fit for electrical contact. Depolarizer disc 14 is dimension slightly smaller than the lithium anode discs to avoid electrical contact with encasement member 11. 
     Depolarizer disc 14 preferably includes a cathode current collector comprising a metal screen 16 made, for example, of nickel and having cathode lead 17 electrically connected thereto. Lead 17 is sheathed in an insulating material such as Halar® and is routed over lithium disc 13 to the center thereof. A top member 18 having opening 19 in its center is hermetically bonded to encasement 11. Lead 17 is positioned through opening 19 and sealed therethrough as the positive terminal. 
     It is clear that battery 10 may be otherwise embodied by using only one lithium disc or by isolating the lithium disc from case 11 and placing pellet 14 in contact therewith. In the latter case, electrical lead 17 would be connected to the lithium anode. Also, both the anode and depolarizer pellet 14 can be insulated from case 11 to form a bipolar battery requiring two electrical leads. 
     It has been discovered that pelletization of the organic polymer P2VP or P2VQ and I 2  results in a novel depolarizer that can be used in lithium halide primary cell 10. The material, P2VP+P2VP.n 1  I 1  +n 2  I 2 , greatly facilitates the manufacture of cells by permitting the use of automatic handling equipment. More importantly, the electrical characteristic of the depolarizer provide certain advantages over a depolarizer consisting of plastic P2VP.nI 2  or P2VQ.nI 2 . A battery utilizing pelletized particulate P2VP+P2VP.n 1  I 2  +n 2  I 2  will exhibit electrical characteristics quite different from batteries prepared in accordance with U.S. Pat. No. 3,674,562. Batteries prepared in accordance with the present invention have an open circuit voltage of about 2.8v (the same as conventional batteries), but the internal impedance of the batteries is quite high. Although the initial impedance of the pellet is unsuitably high, it was unexpectedly found that the initial impedance naturally decreases at a very fast rate. For example, decreases of between 50  to 60% during the first week are normal. Also, by gently warming the cells (&lt;100° C.), decreases in the impedance can be greatly accelerated. These decreases in internal impedance increase the voltage delivered by a battery under load. This increase typically continues until the decrease in internal impedance ends. 
     Another impedance factor associated with a battery using the pelletized depolarizer of the invention relates to the electrolyte. When such a battery is under load, the thickness of that component, lithium iodide, increases and consequently the impedance of that component of battery increases. Thus, as the battery is discharged, the total battery impedance will decrease as the pellet impedance decreases and will begin to increase as the increasing LiI 2  becomes the dominating factor. 
     It was originally thought that the noted characteristics were due to a transformation of the pellet into the &#34;plastic&#34; state in U.S. Pat. No. 3,674,562. However, it has been found that such is not the case; the pelletized depolarizer remains in substantially its initial form. It is presently believed these characteristics are associated with the formation of the electrolyte layer (LiI 2 ) in the pelletized P2VP+P2VP.n 1  I 2  +n 2  I 2  which has a large number of grain boundaries that promote ion migration. Also, mechanical defects are formed in the lithium halide electrolyte layer which provide channels for ion migration. In conventional cells, including those of the prior art which utilized pelletized cathode materials, impurities were added to create crystal defects in the lithium iodine layer. For example, it has been common practice to add impurities such as divalent ions (aluminum oxide and silicon dioxide are common examples) or waters of hydration. 
     In the present invention, no impurities are added. Defects are believed to form in the crystaline structure of the electrolyte which provide broader channels for ionic flow. The evidence indicates that the morphology of the depolarizer governs to a great extent the morphology of the lithium iodide layer. In prior P2VP.nI 2  or P2VQ.nI 2  cells the plastic state permitted a relatively perfect layer to form causing large regular crystals. The pelletized depolarizer, on the other hand, promotes a cracked layer in which crystal defects or disorders occur because of the mechanical arrangement of the physical structure of the depolarizer materials. Whatever the physical-mechanical reason, the pelletization of the P2VP+P2VP.n 1  I 2  +n 2  I 2  has resulted in cells having greater power density than those which utilized such material in the plastic state. 
     Additionally, the mechanical defects which promote ion migration also permit iodine vapor diffusion which results in self-discharge properties of the cells. For commercial purposes it is possible to trade higher self-discharge by reducing the internal impedance for reducing electrical data scatter. The preferred iodine ratio is from 18 to 26 parts of iodine for each part of organic (both complexed and uncomplexed). Higher iodine ratios reduce cracking (lower grain boundaries) and cause the formation of larger, more perfect crystals. The higher iodine ratios result in lower self-discharge, but never as low as that achieved by plastic depolarizer materials. The low iodine ratios e.g., 5:1 to 8:1, promote less perfect crystals and higher self-discharge. Cells constructed with these lower ratios have a high power density which makes them useful in short lived applications such as hearing aids. Accordingly, in the preferred range of iodine, the end of life characteristics can be extended. 
     In manufacturing depolarizer pellets, the iodine is ground in a ball mill into a particulate having a size of less than -70 mesh and the polymer is ground to a size of less than -100 mesh and preferably -150 to -200 mesh. It has been found that the particle size of the polymer and iodine as well as the molecular weight of the polymer and pellet density influence the initial cell impedance and the time necessary for the cell to reach full activation. The smaller the particle size, the lower the cell impedance with the size of the polymer having a greater effect than size of the iodine. 
     The particulate iodine and polymer are mixed together in the preferred ratio of 18 to 26 parts of iodine to one part of polymer. The mixture is placed in a die of the desired configuration and formed into a pellet with a pressure of from about 5,000 to 15,000 psi. Unlike prior pelletized depolarizers which used stoichemetric amounts of iodine, the pellets of P2VP+P2VP.n 1  I 2  +n 2  I 2  are not brittle. They retain their original shape, but have a slight tackiness for electrical contact. 
     By modifying the method set forth in U.S. Pat. No. 3,674,562, the same amount of polymerization initiator (n-butyl-lithium) is used, but it must be added much slower to allow the formation of longer polymer chains or by forming polymerization at a lower temperature. Otherwise a low molecular weight polymer is obtained which when mixed with iodine becomes plastic as disclosed in that patent. The precipitate is vacuum dried and ground as above. The increased polymer length permits mixing with the iodine without plasticity and subsequent pelletization of the mixture. Commercially pure grades of P2VP are useful in the present invention and do not result in a plastic depolarizer inasmuch as they normally have a molecular weight of from 6,000 to 13,000. 
     As mentioned above, the initial impedance (representative of depolarizer impedance) of a battery having the plastic depolarizer of U.S. Pat. No. 3,674,562 is much lower than batteries having the pelletized depolarizer of the present invention. However, the slope of the curve representative of impedance as a function of time (electrolyte layer) is less in the batteries of the present invention and intersect those curves of the batteries with plastic depolarizer within a relatively short time. Accordingly, batteries having the pelletized depolarizers of the present invention have significantly better end of life characteristics than prior plastic depolarizer cells having an equivalent amount of iodine. In batteries of the present invention, increasing the iodine ratio from 15:1 to 26:1 increases the end of life from 3 years to 10 or more years. 
     The following tables (A and B) compare a lithium anode enclosed battery made with the depolarizer of U.S. Pat. No. 3,674,562 (A) with similar battery made with the pelletized depolarizer of the present invention (B). Both batteries consisted of 15 to 1 by weight ratio of iodine to P2VP and both exhibited an open circuit voltage of 2.8 volts. The test were conducted at 37° C. 
     
                                           TABLE A__________________________________________________________________________ ELAPSEDDATE  TIME (Mos.)          VOLTS               Z    50K 1K   RDC  LOADYR DAY UNDER LOAD          (MV) (OHMS)                    (MV)                        (MV) (OHMS)                                  (OHMS)                                       MAHR COMMENTS__________________________________________________________________________76  317 0.0      2807.8               27  2803 2705 37   9999K                                       076  318 0.0      2807.4               28  2803 2702 38   1000K                                       076  321 0.1      2807.4               30  3803 2693 42   1000K                                       076  322 0.1      2807.0               31  2802 2686 44   1000K                                       076  323 0.2      2807.2               32  2802 2680 46   1000K                                       076  324 0.2      2807.2               34  2802 2673 49   1000K                                       076  325 0.2      2807.2               36  2801 2662 53   1000K                                       076  329 0.4      2806.9               42  2800 2634 64   1000K                                       176  336 0.6      2806.5               59  2797 2574 88   1000K                                       176  343 0.8      2806.2               85  2793 2494 123  1000K                                       276  348 1.0      2805.8               112 2789 2421 155  1000K                                       276  350 1.1      2805.7               129 2786 2371 179  1000K                                       276  357 1.3      2805.0               168 2780 2282 224  1000K                                       376  364 1.5      2804.2               208 2774 2197 270  1000K                                       377  5   1.7      2803.7               249 2768 2109 321  1000K                                       477  12  1.9      2803.2               282 2763 2041 364  1000K                                       477  19  2.2      2802.7               317 2757 1962 418  1000K                                       477  24  2.3      2802.4               339 2755 1923 446  1000K                                       577  24  2.3      2802.8               337 2757 1919 450  1000K                                       577  26  2.4      2802.3               353 2753 1887 473  1000K                                       577  33  2.6      2801.8               379 2749 1840 510  1000K                                       577  40  2.9      2801.4               410 2746 1788 553  1000K                                       677  47  3.1      2801.2               433 2743 1752 584  1000K                                       677  54  3.3      2800.8               448 2741 1716 617  1000K                                       777  61  3.6      2800.7               476 2738 1679 653  1000K                                       777  68  3.8      2800.3               512 2734 1629 702  1000K                                       877  73  4.0      2800.3               526 2732 1602 731  1000K                                       877  73  4.0      2800.3               527 2733 1602 731  1000K                                       877  82  4.2      2799.9               557 2729 1564 772  1000K                                       977  103 4.9      2795.7               568 2724 1509 836  1000K                                       1077  145 6.3      2797.8               738 2709 1354 1044 1000K                                       1377  257 10.0     2795.4               1152                   2673 1070 1579 1000K                                       2077  313 11.8     2794.9               1341                   2657 971  1841 1000K                                       2477  361 13.4     2794.2               1551                   2639 884  2118 1000K                                       2778  3   13.7     2793.9               1587                   2636 867  2180 1000K                                       2878  30  14.5     2793.5               1693                   2629 833  2305 1000K                                       3078  60  15.5     2793.3               1786                   2623 809  2405 1000K                                       32CHANGE/MONTH    -0.4               122   -9 -44  155            ON LAST 5                                            GOOD POINTS                                            AT 1000K__________________________________________________________________________                                            LOAD 
    
     
                                           TABLE B__________________________________________________________________________ ELAPSEDDATE  TIME (mos.)          VOLTS               Z     50K 1K   RDC  LOADYR DAY UNDER LOAD          (MV) (OHMS)                     (MV)                         (MV) (OHMS)                                   (OHMS)                                        MAHR COMMENTS__________________________________________________________________________76  335 0.0      2807.8               17860 1945                         136  18742                                   9999K                                        0    -170 Mesh P2VP, -20076  336 0.0      2742.7               12250 2109                         200  12242                                   1000K                                        0    Mesh I.sub.276  338 0.1      2748.2               8176  2261                         294  7968 1000K                                        0    Sieve Size76  339 0.1      2490.5               88030 1   1    1042 1000K                                        0    BAD DATA POINT76  341 0.2      2751.7               6364  2339                         371  6117 1000K                                        076  343 0.2      2754.3               5603  2373                         414  5368 1000K                                        076  348 0.4      2758.2               4344  2432                         518  4097 1000K                                        176  350 0.5      2757.5               4072  2444                         546  3830 1000K                                        176  357 0.7      2758.4               3187  2487                         665  2969 1000K                                        176  364 0.9      2761.2               2518  2525                         796  2326 1000K                                        277  5   1.1      2763.0               2167  2545                         885  1993 1000K                                        277  12  1.4      2766.3               1701  2570                         1006 1641 1000K                                        377  19  1.6      2767.7               1662  2578                         1059 1511 1000K                                        377  26  1.8      2769.4               1424  2596                         1167 1284 1000K                                        477  33  2.0      2770.0               1299  2603                         1225 1176 1000K                                        477  40  2.3      2771.7               1121  2616                         1328 1012 1000K                                        577  47  2.5      2772.7               992   2626                         1439 858  1000K                                        577  54  2.7      2773.8               854   2636                         1501 784  1000K                                        677  61  3.0      2774.5               756   2643                         1586 691  1000K                                        677  68  3.2      2775.5               658   2652                         1656 622  1000K                                        677  75  3.4      2776.3               506   2658                         1710 573  1000K                                        777  82  3.7      2777.2               525   2663                         1764 526  1000K                                        777  89  3.9      2778.0               466   2670                         1816 485  1000K                                        877  96  4.1      2778.8               422   2676                         1859 453  1000K                                        877  103 4.3      2779.5               335   2681                         1898 425  1000K                                        977  110 4.6      2780.2               355   2686                         1929 404  1000K                                        977  117 4.8      2780.8               327   2691                         1950 391  1000K                                        1077  145 5.7      2782.3               255   2707                         2031 342  1000K                                        1277  257 9.4      2785.2               220   2730                         2082 320  1000K                                        1977  313 11.2     2783.8               266   2729                         1988 383  1000K                                        23CHANGE         0.6  -12     6 10   -3             ON LAST 5/MONTH                                            GOOD POINTS                                             AT 1000K__________________________________________________________________________                                             LOAD 
    
     As can be seen from the table, prior art battery (A) was discharged on a 1000K ohm load an an initial impedance of 25-50 ohm which is typical. As the discharge proceeded, the internal impedance increased due to the build-up of the electrolyte layer. As a result of that increase, the voltage of the cell slowly decreased. After approximately 2.6 months the voltage decay rate was 2.1 milli-volts/month and the impedance had increased by 134 ohms/mon. 
     The battery (B) using the depolarizer pellet of the present invention had an initial impedance of 17,860 ohms. This impedance decreased by 50-60% the first week and continued to decrease thereafter, but at a much slower rate. As this decrease continued, the voltage under load delivered by the battery increased. In other tests impedances after 5 months at 37° C. were approximately 300 to 400 ohms. 
     Tables C, D (same batter as B), E and F show cells made in accordance with the present invention in which the impedance decreased when under 1000K ohm load. 
     
                                           TABLE C__________________________________________________________________________   ELAPSEDDATE    MOS.     VOLTS                 Z    50K 1K  RDC  LOADYR  DAY UNDER LOAD            (MV) (OHMS)                      (MV)                          (MV)                              (0HMS)                                   (OHMS)                                        MAHR COMMENTS__________________________________________________________________________76  335   0.0      2807.0                 30130                      1480                          73  12355                                   9999K                                        0    170 P2VP, -200 I.sub.276  336   0.0      2598.7                 20260                      1766                          129 17809                                   1000K                                        076  338   0.1      2640.5                 12660                      2014                          220 10077                                   1000K                                        076  339   0.1      2648.3                 60170                      2030                          213 10639                                   1000K                                        076  341   0.2      2657.7                 9984 2117                          282 7704 1000K                                        0    BAD Z DATA POINT76  343   0.2      2664.2                 8772 2159                          317 6763 1000K                                        076  348   0.4      2677.2                 7031 2240                          418 4905 1000K                                        176  350   0.5      2677.5                 6605 2252                          437 4647 1000K                                        176  357   0.7      2684.2                 5362 2305                          546 3527 1000K                                        176  364   0.9      2692.5                 4094 2349                          661 2759 1000K                                        277  5     1.1      2698.3                 3790 2376                          748 2331 1000K                                        277  12    1.4      2706.7                 3246 2407                          855 1926 1000K                                        377  19    1.6      2710.8                 2053 2427                          946 1654 1000K                                        377  26    1.8      2716.8                 2512 2448                          1041                              1421 1000K                                        477  33    2.0      2719.7                 2286 2461                          1108                              1279 1000K                                        477  40    2.3      2725.7                 1990 2480                          1216                              1085 1000K                                        477  47    2.5      2730.2                 1757 2497                          1311                              941  1000K                                        577  54    2.7      2735.2                 1530 2513                          1408                              815  1000K                                        577  61    3.0      2739.2                 1345 2526                          1490                              720  1000K                                        677  68    3.2      2744.2                 1160 2541                          1580                              629  1000K                                        677  75    3.4      2748.0                 1010 2554                          1649                              566  1000K                                        777  82    3.7      2752.4                 056  2566                          1717                              510  1000K                                        777  89    3.9      2756.3                 740  2578                          1784                              459  1000K                                        877  96    4.1      2759.7                 646  2589                          1835                              423  1000K                                        877  103   4.3      2762.5                 561  2600                          1882                              393  1000K                                        977  110   4.6      2765.3                 493  2610                          1922                              363  1000K                                        977  117   4.8      2767.8                 435  2620                          1958                              347  1000K                                        1077  145   5.7      2774.7                 273  2654                          2069                              290  1000K                                        1177  257   9.4      2781.5                 157  2705                          2164                              256  1000K                                        1977  313   11.2     2779.7                 177  2708                          2120                              284  1000K                                        23Change/Month       2.1                 -43   14  29 -11            On Last 5 Good Points                                             AT 1000K__________________________________________________________________________                                             LOAD 
    
     
                                           TABLE D__________________________________________________________________________ELAPSEDDATE MOS.     VOLTS              Z    50K 1K  RDC  LOADYR DAYUNDER LOAD         (MV) (OHMS)                   (MV)                       (MV)                           (OHMS)                                (OHMS)                                     MAHR COMMENTS__________________________________________________________________________76  3350.0      2807.8              17860                   1945                       136 18742                                9999K                                     0    -170 P2VP, -200 I.sub.2                                          (STANDARD MIX)76  3360.0      2742.7              12250                   2109                       200 12242                                1000K                                     076  3380.1      2748.2              8176 2261                       294 7968 1000K                                     076  3390.1      2490.5              88030                     1 1   1042 1000K                                     0    BAD Z DATA POINT76  3410.2      2751.7              6364 2339                       371 6117 1000K                                     076  3430.2      2754.4              5603 2373                       414 5368 1000K                                     076  3480.4      2758.2              4344 2432                       518 4097 1000K                                     176  3500.5      2757.5              4072 2444                       546 3830 1000K                                     176  3570.7      2758.4              3187 2487                       665 2969 1000K                                     176  3640.9      2761.2              2518 2525                       796 2326 1000K                                     277  3  1.1      2763.0              2167 2545                       885 1993 1000K                                     277  12 1.4      2766.3              1781 2570                       1006                           1641 1000K                                     377  19 1.6      2767.7              1662 2578                       1059                           1511 1000K                                     377  26 1.8      2769.4              1424 2596                       1167                           1284 1000K                                     477  33 2.0      2770.0              1299 2603                       1225                           1176 1000K                                     477  40 2.3      2771.7              1121 2616                       1328                           1012 1000K                                     577  47 2.5      2772.7              992  2626                       1439                           858  1000K                                     577  54 2.7      2773.8              854  2636                       1501                           784  1000K                                     677  61 3.0      2774.5              756  2643                       1586                           691  1000K                                     677  68 3.2      2775.5              658  2652                       1656                           622  1000K                                     677  75 3.4      2776.3              506  2658                       1710                           573  1000K                                     777  82 3.7      2777.2              525  2663                       1764                           526  1000K                                     777  89 3.9      2778.0              466  2670                       1816                           485  1000K                                     877  96 4.1      2778.8              422  2676                       1859                           453  1000K                                     877  1034.3      2779.5              335  2681                       1898                           425  1000K                                     977  1104.6      2780.2              355  2686                       1929                           404  1000K                                     977  1174.8      2780.8              329  2691                       1950                           391  1000K                                     1077  1455.7      2782.3              255  2707                       2031                           342  1000K                                     1277  2579.4      2785.2              220  2730                       2082                           320  1000K                                     1977  31311.2     2783.8              266  2729                       1988                           383  1000K                                     23CHANGE/MONTH    0.6              -12    6 10  -3              ON LAST 5 GOOD POINTS                                          AT 1000K__________________________________________________________________________                                          LOAD 
    
     
                                           TABLE E__________________________________________________________________________ELAPSEDDATE MOS.     VOLTS              Z    50K 1K  RDC  LOADYR DAYUNDER LOAD         (MV) (OHMS)                   (MV)                       (MV)                           (OHMS)                                (OHMS)                                     MAHR COMMENTS__________________________________________________________________________76  3350.0      2807.2              39720                   1170                       43  57700                                9999K                                     0    -100 +170 P2VP, -200                                          I.sub.276  3360.0      2545.2              35240                   1340                       60  39728                                1000K                                     076  3380.1      2593.2              23560                   1638                       99  23681                                1000K                                     076  3390.1      2604.3              21540                   1699                       110 21237                                1000K                                     076  3410.2      2622.0              17980                   1816                       137 16882                                1000K                                     076  3430.2      2634.7              15840                   1894                       161 14261                                1000K                                     076  3480.4      2658.2              11590                   2042                       225 9962 1000K                                     176  3500.5      2662.7              10610                   2073                       243 9177 1000K                                     176  3570.7      2677.4              8291 2165                       313 6919 1000K                                     176  3640.9      2690.2              6620 2237                       388 5419 1000K                                     277  5  1.1      2695.4              5660 2274                       440 4667 1000K                                     277  12 1.4      2701.9              4077 2312                       503 3974 1000K                                     377  19 1.6      2704.7              4384 2332                       544 3607 1000K                                     377  26 1.8      2708.3              3870 2358                       605 3152 1000K                                     477  33 2.0      2707.9              3644 2366                       634 2959 1000K                                     477  40 2.3      2712.4              3231 2388                       697 2611 1000K                                     477  47 2.5      2715.5              2940 2406                       755 2342 1000K                                     577  54 2719.2   2662 2422 812 2112                           1000K                                577  61 3.0      2722.2              2427 2436                       868 1918 1000K                                     677  68 3.2      2725.4              2218 2450                       928 1734 1000K                                     677  75 3.4      2727.9              2036 2461                       981 1591 1000K                                     777  82 3.7      2730.8              1866 2473                       1036                           1459 1000K                                     777  89 3.9      2734.3              1697 2486                       1105                           1311 1000K                                     877  96 2736.3   1566 2495 1157                       1209                           1000K                                877  1034.3      2738.5              1448 2504                       1213                           1111 1000K                                     977  1104.6      2740.7              1345 2512                       1262                           1033 1000K                                     977  1174.8      2742.7              1261 2519                       1307                           966  1000K                                     1077  1455.7      2751.8              928  2547                       1491                           734  1000K                                     1177  2579.4      2764.3              495  2589                       1759                           487  1000K                                     1977  31311.2     2764.9              433  2597                       1853                           414  1000K                                     22CHANGE/MONTH    3.7              -134  12 85  -87            ON LAST 5 GOOD                                          POINTS AT 1000K__________________________________________________________________________                                          LOAD 
    
     
                                           TABLE F__________________________________________________________________________ELAPSEDDATE MOS.     VOLTS              Z    50K 1K  RDC  LOADUNDER LOAD         (MV) (OHMS)                   (MV)                       (MV)                           (OHMS)                                (OHMS)                                     MAHR COMMENTS__________________________________________________________________________76  3350.0      2810.5              36730                   1301                       54  44085                                9999K                                     0    -100 +170 P2VP, -200                                          I.sub.276  3360.0      2548.8              20590                   1503                       80  29130                                1000K                                     076  3380.1      2586.9              20260                   1728                       120 19273                                1000K                                     076  3390.1      2595.3              18750                   1774                       129 17826                                1000K                                     076  3410.2      2607.7              16410                   1855                       151 15154                                1000K                                     076  3430.2      2616.9              14870                   1910                       169 13526                                1000K                                     076  3480.4      2637.2              11670                   2029                       225 9891 1000K                                     176  3500.5      2640.8              10980                   2051                       235 9476 1000K                                     176  3570.7      2654.7              9014 2129                       289 7525 1000K                                     176  3640.9      2666.9              7468 2194                       347 6130 1000K                                     277  5  1.1      2672.3              6559 2228                       390 5356 1000K                                     277  12 1.4      2679.5              5748 2266                       443 4608 1000K                                     377  19 1.6      2683.5              5203 2290                       481 4170 1000K                                     377  26 1.8      2687.9              4678 2315                       529 3709 1000K                                     477  33 2.0      2689.2              4435 2325                       551 3528 1000K                                     477  40 2.3      2694.4              3788 2348                       602 3157 1000K                                     477  47 2.5      2698.7              3661 2367                       650 2854 1000K                                     577  54 2.7      2702.7              3353 2303                       697 2603 1000K                                     577  61 3.0      2706.2              3093 2398                       744 2381 1000K                                     677  68 3.2      2709.8              2853 2413                       795 2171 1000K                                     677  75 3.4      2712.7              2656 2424                       838 2012 1000K                                     777  82 3.7      2716.9              2427 2440                       898 1819 1000K                                     777  89 3.9      2720.7              2233 2452                       959 1644 1000K                                     877  96 4.1      2723.0              2089 2461                       995 1552 1000K                                     877  1034.3      2725.7              1949 2471                       1043                           1439 1000K                                     977  1104.6      2728.4              1823 2480                       1095                           1327 1000K                                     977  1174.8      2731.0              1713 2488                       1190                           1140 1000K                                     977  1455.7      2742.7              1266 2525                       1358                           893  1000K                                     1177  2579.4      2772.3              493  2621                       1826                           449  1000K                                     1977  31311.2     2776.8              402  2645                       1897                           406  1000K                                     22CHANGE/MONTH   7.5 -215   24                       119 -129           ON LAST 5 GOOD                                          POINTS AT 1000K__________________________________________________________________________                                          LOAD 
    
     Tables G, H, and I show decreases in the impedance under no load and when later subjected to a 50K ohm load show that nearly full capacity (250 mahr) was reached at approximately 5.7 months. 
     
                                           TABLE G__________________________________________________________________________ ELAPSEDDATE  MOS UN- VOLTS         Z    50K  1K  RDC LOADYR DAY DER LOAD         (MV) (OHMS)                   (MV)                       (MV)                           (OHMS)                                (OHMS)                                     MHR  COMMENTS__________________________________________________________________________77  13  0.0     2800.8              3639 2427                        544                           3802 9999K                                     0    STANDARD MIX, SCREEN 277  19  0.0     2800.7              2979 2462                        636                           3116 9999K                                     077  26  0.0     2792.8              1521 2552                       1012                           1604 9999K                                     077  33  0.0     2786.9              1109 2578                       1211                           1179 9999K                                     077  40  0.0     2780.5              830  2595                       1393                           897  9999K                                     077  47  0.0     2776.8              659  2607                       1528                           731  9999K                                     077  54  0.0     2775.7              556  2616                       1627                           628  9999K                                     077  61  0.0     2776.6              473  2625                       1716                           547  9999K                                     077  68  0.0     2777.7              411  2633                       1792                           404  9999K                                     077  75  0.0     2778.7              361  2640                       1856                           495  9999K                                     077  82  0.0     2779.3              326  2646                       1906                           400  9999K                                     077  84  0.0     2621.3              328  2660                       1898                           361  50K  07 87  0.1     2641.4              305  2581                       1937                           344  50K  477  89  0.2     2641.8              292  2582                       1954                           332  50K  6    71st DAY AFTER MFR.77  96  0.4     2641.3              270  2583                       1983                           313  50K  1577  103 0.6     2640.3              260  2582                       1994                           305  50K  2477  110 0.9     2638.7              263  2580                       1986                           309  50K  3377  117 1.1     2636.9              275  2578                       1965                           323  50K  4277  145 2.0     2624.4              370  2561                       1842                           405  50K  7777  257 5.7     2689.2              563  2619                       1596                           671  50K  220CHANGE/MONTH  -296.1              11207                   -290                       -243                           -114           ON LAST 5 GOOD                                          POINTS AT 50K__________________________________________________________________________                                          LOAD 
    
     
                                           TABLE H__________________________________________________________________________  ELAPSEDDATE   MOS.     VOLTS                Z    50K 1K  RDC  LOADYR DAY UNDER LOAD           (MV) (OHMS)                     (MV)                         (MV)                             (OHMS)                                  (OHMS)                                       MAHR   COMMENTS__________________________________________________________________________                                              STANDARD MIX,77 19  0.0      2802.5                8916 2352                         370 6130 9999K                                       0      SCREEN 277 26  0.0      2797.5                1963 2562                         873 2057 9999K                                       077 33  0.0      2794.3                1419 2600                         1073                             1495 9999K                                       077 40  0.0      2790.7                1099 2624                         1239                             1160 9999K                                       077 47  0.0      2733.2                88100                     4   3   651  9999K                                       077 54  0.0      2723.5                89740                     5   3   550  9999K                                       077 61  0.0      2724.9                89950                     5   3   468  9999K                                       0      BAD DATA POINTS77 68  0.0      2722.0                89950                     5   4   333  9999K                                       077 75  0.0      2784.5                527  2671                         1689                             601  9999K                                       077 82  0.0      2783.7                481  2676                         1745                             550  9999K                                       077 84  0.0      2648.2                481  2586                         1739                             507  50K  077 87  0.1      2678.2                444  2617                         1794                             478  50K  477 89  0.2      2681.8                423  2622                         1818                             460  50K  677 96  0.4      2685.5                339  2627                         1838                             430  50K  1577 103 0.6      2686.5                383  2628                         1857                             431  50K  2477 110 0.9      2685.7                416  2625                         1798                             479  50K  3377 117 1.1      2684.2                465  2621                         1724                             542  50K  4277 145 2.0      2679.2                572  2609                         1573                             691  50K  7977 257 5.7      2653.7                1267 2560                         1070                             1508 50K  222CHANGE                                             ON LAST 5 GOOD/MONTH          -225.0                4060 -251                         -233                             5236             POINTS at 50K                                              LOAD__________________________________________________________________________ 
    
     
                                           TABLE I__________________________________________________________________________ELAPSEDDATE MOS.     VOLTS              Z    50K 1K  RDC  LOADYR DAYUNDER LOAD         (MV) (OHMS)                   (MV)                       (MV)                           (OHMS)                                (OHMS)                                     MAHR COMMENTS__________________________________________________________________________77  13 0.0      2801.8              3281 2472                       587 3511 9999K                                     0    STANDARD MIX, SCREEN 277  19 0.0      2800.7              2773 2497                       665 2979 9999K                                     077  26 0.0      2791.9              1556 2571                       987 1693 9999K                                     077  33 0.0      2785.7              1186 2593                       1156                           1801 9999K                                     077  40 0.0      2779.2              929  2609                       1312                           1030 9999K                                     077  47 0.0      2777.3              764  2621                       1429                           866  9999K                                     077  54 0.0      2777.9              658  2632                       1518                           759  9999K                                     077  61 0.0      2778.2              571  2641                       1600                           673  9999K                                     077  68 0.0      2779.7              507  2648                       1668                           607  9999K                                     077  75 0.0      2780.3              452  2654                       1732                           550  9999K                                     077  82 0.0      2780.9              410  2660                       1784                           506  9999K                                     077  84 0.0      2632.0              413  2567                       1777                           462  50K  077  87 0.1      2660.7              380  2597                       1827                           438  50K  477  89 0.2      2661.9              364  2599                       1844                           424  50K  6    71st DAY AFTER MFR.77  96 0.4      2661.0              345  2598                       1866                           407  50K  1577  1030.6      2659.2              351  2595                       1854                           415  50K  2477  1100.9      2655.7              386  2589                       1798                           458  50K  3377  1171.1      2651.7              442  2582                       1719                           523  50K  4277  1452.0      2629.8              644  2549                       1506                           727  50K  7877  2575.7      2688.9              1025 2611                       1201                           1258 50K  221CHANGE/MONTH  -147.3              2394 -185                       -217                           3180           ON LAST 5 GOOD                                          POINTS AT 50K__________________________________________________________________________                                          LOAD 
    
     The foregoing cell are to be compared to the cells shown in Tables A, J and K which utilize a plastic depolarizer. At 220 Mahr cells utilizing the pelletized depolarizer of the present invention exhibited a Z of 500-2000 ohms. The prior cells (plastic depolarizer) typically showed a Z of greater than 2,000 ohms. The only difference in the cells was the depolarizer. 
     
                                           TABLE J__________________________________________________________________________ELASPSEDDATE MOS.     VOLTS              Z    50K 1K  RDC  LOADYR DAYUNDER LOAD         (MV) (OHMS)                   (MV)                       (MV)                           (OHMS)                                (OHMS)                                     MAHR__________________________________________________________________________76  3170.0      2800.5              27   2801                       2685                           44   9999K                                     076  3180.0      2802.4              36   2796                       2647                           57   50K  076  3210.1      2797.5              98   2785                       2470                           131  50K  476  3220.1      2795.4              125  2781                       2401                           162  50K  576  3230.2      2793.9              144  2778                       2357                           104  50K  776  3240.2      2792.2              163  2775                       2312                           206  50K  876  3250.2      2790.0              185  2771                       2262                           231  50K  976  3290.4      2783.9              248  2759                       2137                           301  50K  1576  3360.6      2772.2              362  2737                       1932                           432  50K  2476  3430.8      2762.2              467  2718                       1764                           564  50K  3376  3481.0      2755.7              549  2706                       1662                           658  50K  4076  3501.1      2752.0              593  2699                       1607                           713  50K  4376  3571.3      2744.7              689  2605                       1501                           831  50K  5276  3641.5      2736.5              800  2670                       1401                           960  50K  6177  5  1.7      2728.5              912  2655                       1303                           1105 50K  6977  12 1.9      2722.7              1001 2644                       1238                           1215 50K  7877  19 2.2      2715.0              1118 2629                       1160                           1362 50K  8877  24 2.3      2712.8              1164 2626                       1138                           1408 50K  9477  24 2.3      2713.2              1159 2626                       1137                           1412 50K  9477  26 2.4      2711.0              1189 2622                       1120                           1448 50K  9777  33 2.6      2706.5              1270 2613                       1076                           1547 50K  10677  40 2.9      2700.2              1344 2602                       1031                           1658 50K  11577  47 3.1      2696.8              1416 2595                       1003                           1733 50K  12477  54 3.3      2692.2              1488 2587                       970 1825 50K  13377  61 3.6      2687.2              1561 2578                       937 1923 50K  14277  68 3.8      2681.2              1652 2567                       904 2031 50K  15177  73 4.0      2677.8              1708 2560                       882 2107 50K  15777  73 4.0      2677.9              1712 2561                       884 2097 50K  16077  82 4.2      2672.3              1792 2551                       855 2201 50K  16977  1034.89     2656.3              2019 2524                       786 2479 50K  19677  1456.3      2460.3              4282 2224                       405 5602 50K  247CHANGE/MONTH  -365.2              2779 -340  -89                           -567 ON LAST 5 GOOD POINTS AT 50K__________________________________________________________________________                                LOAD 
    
     
                                           TABLE K__________________________________________________________________________ELAPSEDDATE MOS.     VOLTS              Z    50K 1K  RDC  LOADYR DAYUNDER LOAD         (MV) (OHMS)                   (MV)                       (MV)                           (OHMS)                                (OHMS)                                     MAHR__________________________________________________________________________ 76  3170.0      2808.2              26   2803                       2695                           41   9999K                                     076  3180.0      2802.7              37   2797                       2639                           61   50K  076  3210.1      2797.5              99   2787                       2479                           127  50K  476  3220.1      2795.5              121  2783                       2421                           154  50K  576  3230.2      2793.9              137  2780                       2383                           171  50K  776  3240.2      2792.5              153  2777                       2342                           191  50K  876  3250.2      2790.7              172  2774                       2297                           214  50K  976  3290.4      2785.8              227  2765                       2178                           278  50K  1576  3360.6      2778.2              324  2750                       1992                           395  50K  2476  3430.8      2769.0              384  2737                       1877                           476  50K  3376  3481.0      2762.7              414  2729                       1821                           520  50K  4076  3501.1      2760.2              440  2725                       1775                           559  50K  4376  3571.3      2759.2              519  2720                       1681                           647  50K  5276  3641.5      2755.7              604  2712                       1594                           737  50K  6177  5  1.7      2751.5              687  2703                       1512                           831  50K  7077  12 1.9      2748.0              758  2676                       1450                           908  50K  7977  19 2.2      2743.2              848  2687                       1379                           1006 50K  8877  24 2.3      2740.9              891  2683                       1352                           1047 50K  9577  24 2.3      2740.8              882  2683                       1355                           1042 50K  9577  26 2.4      2739.3              912  2680                       1336                           1070 50K  9777  33 2.6      2735.4              985  2672                       1285                           1152 50K  10677  40 2.9      2730.0              1080 2662                       1233                           1242 50K  11677  47 3.1      2725.5              1159 2654                       1192                           1317 50K  12577  54 3.3      2719.5              1241 2644                       1144                           1413 50K  13477  61 3.6      2713.2              1341 2632                       1089                           1533 50K  14377  68 3.8      2704.8              1471 2617                       1029                           1681 50K  15277  73 4.0      2697.7              1576 2604                       979 1818 50K  15977  75 4.0      2696.3              1595 2602                       973 1833 50K  16177  82 4.2      2684.7              1741 2582                       913 2017 50K  17077  1034.9      2587.5              2943 2421                       595 3584 50K  19777  1456.3      2284.2              7259 1975                       261 9172 50K  246CHANGE/MONTH   -3.2              2601  -2 0   -7471                                ON LAST 5 GOOD POINTS AT 50K__________________________________________________________________________                                LOAD 
    
     The ratio of iodine to P2VP or P2VQ may range widely from 3-30 to 1; however, a 3:1 ratio while having a desirable electrical properties is at the lowest practical capacity. A ratio of 30:1, on the other hand, approaches the upper limit with respect to internal impedance. A ratio of 15:1 is satisfactory, except that where such cells have been heated they have increased self-discharge which renders them useful for high current drain applications which require less than 10 year shelf lives. Where shelf lives are important as well as mild heating, higher ratios of iodine are preferred, for example, 18:1 to 22:1. 
     In such cells for use in electric watch applications, a self-discharge in terms of heat output of 10 μwatts has been established. A ratio of 20:1 decayed to 10 μwatts in 29 days, whereas it took a cell having a 15:1 ratio approximately 2,000 days. (Both cells were heated for 15 hrs. at 80° C.). A cell having 26:1 depolarizer had an initial self-discharge of 14 μwatts, but the impedance provided was sufficiently high to render a cell of only average electrical properties. Interestingly, cells with a plastic depolarizer and a ratio of 15:1 have low heat output, for example 5 μwatts at 60 days. The low heat output of the cells made with plastic depolarizers continues throughout the life of the cell since the internal impedance increases. 
     Accordingly, for long life pelletized cells, it is preferred to utilize a ratio of about 20:1 iodine to polymer. The pelletized depolarizer of the present invention provides multiyear batteries suitable for use in watches. While presently preferred embodiments of the invention have been described in particularity, the invention may be otherwise embodied within the scope of the appended claims.