KR20000029983A - Coated paper separators for electrolytic cells - Google Patents

Abstract

PURPOSE: Present invention relates to electrochemical cells having coated paper separators for better storage property and performance. The separator coating comprises a starch and an additive. CONSTITUTION: A coated paper separator for an electrochemical cell is provided, whereby the coating comprises a starch and an additive. Cationic starch constitutes a majority of the starch component of the separator coating. The additive is a polyoxyalkylene, nitrogen containing compound and has a hydro-lipophilic balance of less than 17.

Description

Coated Paper Separator for Electrolytic Cells {COATED PAPER SEPARATORS FOR ELECTROLYTIC CELLS}

In order to improve the safety and performance characteristics of dry cell batteries (also referred to as zinc carbon, carbon zinc, or batteries), various components of the cell mixture, such as manganese oxide, have been investigated and are shown to reduce the amount of mercury used. To compensate, several additives were mixed. Not previously investigated in detail is a separator, ie a coating of the separator. This is because of the previously understood main purpose of preventing direct electrical contact between two electrodes, while the separator serve allows ion contact at the same time.

The present invention relates to a cell having a coated paper separator, wherein the separator coating comprises starch and additives for that separator.

What we have achieved is that, surprisingly, the separator and the coating of the separator can essentially affect the performance and safety characteristics of the cell so that the cell is improved in the Short Circuit Amperage (SCA) test where the cell is fresh.

In pending patent application PCT / GB96 / 01318, incorporated herein by reference,

Separation from high1y cross-linked starch, such as Vulca 90 (trademark of National), with ge1lant, such as CELACOL B1209 (trademark of Cortauld), which does not degrade when stored in zinc chloride solution. The advantages of making a coating of porcelain are described. In addition, in co-pending patent no. PCT / GB96 / 01319, incorporated herein by reference, we propose mixing a polyoxyalkylene nitrogen comprising a compound or additive such as Crodamet C20.

Crodamete C20 is a monoamine with two polyoxyethylene side-chanes and the number of units of oxyethylene is on average 20 moles per mole of Crodamet C20.

Separators with coatings containing these components will produce dry cell batteries that perform significantly better than those containing standard components in many standard battery tests. This is especially about abuse. There are many abuse tests, but we devise two tests to analyze leaks in abuse (HDCT and LDCT tests are described below). The HDCT test analyzes such conditions where the flashlight remains "on" via elapsed time after the battery has been "flat" to the user. The LDCT test simulates the state experienced by the battery, for example on a clock. The advantage of this test is that they can be performed relatively quickly, and you do not have to wait a year to see if the battery is working, for example, in a clock.

In co-pending patent no. PCT / GB96 / 02739, incorporated herein by reference, the properties of the paper used for the separator have a significant effect, and high density paper, which takes at least 4 minutes to absorb 50 μl of water droplets, It is found to work better than any paper currently used in standard batteries.

Despite the success of several modifications made to the so-called separators of carbon zinc cells in intrinsically reducing abuse leakage, the performance of cells containing such additives remains slightly degraded overall. Thus, the strains made on the separator are cells that rarely leak under abuse conditions, which are themselves a major goal which is extremely demanding in battery manufacturing. However, such cells tend to have surprisingly shorter service life when compared to cells of the prior art, and therefore it is necessary to balance the minimum leakage requirements against the trend of shorter service life.

Surprisingly what we found is that if the starch of the cation is used in the preparation of the separator coating for the cell, the storage properties of the cell comprising such separator are essentially improved, and the cell is stored after storage under very stringent environment. It still works well. In addition, it is possible to provide cells with equivalent or better performance than cells of the prior art, which provides a cell with a coated paper isolator containing an additive with cationic starch as well as a low hydro-lipophilic balance (HLB). It has been found that it can be obtained by.

In a first aspect, the present invention provides a coated paper separator for a cell, wherein the coating comprises starch, wherein the cationic starch is characterized by constituting the majority of starch elements of the separator coating.

In an optional subject matter, the present invention provides a coated paper separator for a cell, wherein the coating comprises starch and additives, characterized in that the starch is cationic starch and the additive has an HLB of less than 17.

In the past, it has been proposed that a particularly useful form of additive is a polyoxyalkylene nitrogen which is generally classifiable as a surfactant and in particular contains a compound. In addition, in the prior art, it is particularly required that the starch is a high cross-link, and that a very useful combination of the high cross-link starch and the additives is a starch like Vulca 90 and a polyoxyethylene amine like Crodamet C20. . Crodamet C20 has an average of 20 oxyethylene units per amine and has an alkyl group on the amine with an average of about 12 carbon atoms. Crodamet C20 has an HLB of 17.

With the discovery that cationic starch significantly improved the storage properties of the cell, the problem remained that under the Light Industria 1 Flashlight (LIF) test, the performance was still about 10 percent less than conventional cells under any circumstances. In the past, experiments with additives with low HLB values improved the results obtained in the LIF test, but also resulted in severely worsening leaks. Surprisingly, additives with cationic starch and HLB less than 17 have not only improved performance in nature, but the problem of leakage is not severe even at low HLB such as 5.

In the attached test, it was shown that in the test environment, cationic starch bound to Crodamet C20 had only about 88 percent of the cells of the prior art under the LIF test. As stated, Crodamet C20 has an HLB of 17, which is more than required for the present invention.

Regardless of the theory, it is allowed that relative hydrophobic additives (or lipophilic) with HLB having a low relative hydrophilic cationic character of the starch used in the present invention can be used. It is believed.

In particular, if the discharge time is small and the current leakage is high, the zinc / isolator interface zones tend to dry out during long run tests such as LIF. LIF is a good example of a short discharge time with high current leakage. Drying under test increases the internal resistance of the cell in the zinc / isolator zone, resulting in too early failure of the cell. This condition is exacerbated by gas generation. This is why some tests are done with Araldite capped cells. Although many commercial cells are configured to allow the discharge of waste gas at a predetermined pressure, some cells have a tight seal to effectively prevent emissions, whereby aradite capping is such a cell. It is used to match. While aradite capping prevents gas leakage during discharge, it causes low discharge performance on the LIF. This is very noticeable in the following example where the LIF is given for "No Aradite" & "Aradite" capped cells.

Thus, an additive with an HLB of 14 acts like a prior art cell under the LIF test with a value of up to 96 percent of the prior art cell, and an additive with an HLB of 11 is effective under the LIF test (99 percent). And ideally works. In both cases, the tendency of leakage was greatly reduced compared to the prior art. However, very surprising, since the HLB of 9 was reached, the performance under the LIF test is better than 10 percent over the cells of the prior art. Thus, in either method, the cells of the present invention with additives with low HLB are superior to those of the prior art.

As above, adducts having less than 17 HLB are superior to a) cells of the prior art for reduced leak probability and b) cationic starch combined with Crodamet C20. Provide a cell.

Thus, any adduct having less than 17 HLB is useful for the separator of the present invention, but adducts having an HLB of less than 14 are preferred, and have substantially the same performance as conventional cells, but will not leak at all under misuse conditions. It will be appreciated that it allows the creation of unequal cells.

Particularly preferred are adducts having less than 11 HLB, which actually allows for improved performance compared to conventional cells. The presently preferred HLB is 9, and this value allows adducts with an HLB as low as 5 to have very similar LIF performance, but is not associated with increased leakage to the limit of adducts with such a low HLB. Nevertheless, the likelihood of leakage under misuse conditions of adducts with HLB as low as 5 is much less than in cells of the prior art. Thus, the preferred range of HLB is 5 to 11, most preferably 7 to 10, 8 or 9, especially 9.

HLB of the adduct is generated from the balance between hydrophobic constituents such as alkyl chains and oxyethylene units. For Chrodamet C20, the average alkyl chain length is effectively 12 and the average number of oxyethylene units is 20, corresponding to two decameron polyoxyethylene units replacing amines replaced with C12 alkyl side chains. However, it will be appreciated that the various mixtures consist of a unique product known as crodamet C20.

By reducing the HLB, the number of oxyethylene units can be reduced and the length of the alkyl side chains can be increased. Chrodamet C20 is based on coconut alkyl groups having an average chain length of 12, as described above. Chrodamet T5 comprising five oxyethylene groups has an HLB of 12. Therefore, it is desirable to increase the average alkyl chain so that the resin can find a useful alkyl chain having a plain group 18 carbon atoms. Ethylene TT203 is an amine having two oxyethylene substituents and an alkyl substituent having an average of 18 carbon atoms, which has five HLBs. For nine HLBs, chromadamet T5 (with five oxyethylene units) is preferred. However, it will be appreciated that the alkyl chain length and number of oxyethylene units can be varied in a manner suitable to obtain adducts with the desired HLB.

Moreover, for adducts with relatively low HLB, these adducts are preferably nonionics and nonionic adducts are preferred for the purposes of the present invention. The term "cartionic starch" as used herein relates to starch having at least one cation per starch molecule on average in molecular structure.

Cationic starch is well known in the art, for example, Starch, Chemistry and Technology (Academic Press, Inc., Eds. Whistler, R., Bemiller, J., and Paschalle, E., second edition, 1984). In general, cationic starch can be prepared as disclosed in GB-A-2063282 and US-A-4613407, where GB-A-2063282 and US-A-4613407 are incorporated for reference.

US-A-4613407 describes a combination of grain and tuber cationic starch as a wet-end cationic additive for paper manufacture. Many uses are generally proposed for cationic starch in both references.

Cationic starch as described in GB-A-2063282 can be prepared by dissolving normal starch in water and exposing the starch to a suitable cationic agent in alkaline state. The agents described in GB-A-2063282 are low alkyl halohydrines and low alkyl haloepoxy compounds, which are measured in 1000 and 2000 Brabender units measured at a concentration of 5% v / v in water. It is suitable for producing cationic starch with higher viscosity than Brabender units.

As described in the prior art, general preferred levels of nitrogen elution are between 0.2 and 2% by dry weight of starch, although they can go up to 2.8%. Only the actual maximum is a practical limitation due to chemical and cost aspects.

In general, separator coating should be substantially as known in the art, but it is preferred to incorporate cationic starch in place of some or all of the components of the coating. Preferred paper and other components are generally as described herein.

Cationic starch should form most of the starch component of the coating for the separator and it is preferred to incorporate other components such as Vulca 90, but it is generally desirable to form the overall starch component.

In general, there is no limitation in the nature of the cationic starch of the present invention. However, it is generally preferred that cationic starch is not readily soluble in water, in which case it is preferred not to dissolve at all in water (at least cold water). In addition, cationic starch should not expand in water. However, cationic starch must be at least partially crosslinked. Although there is no significant difference in the action of highly crosslinked and moderately crosslinked starch, uncrosslinked cationic starch does not work satisfactorily.

Starch can be any suitable starch. Many suitable starches are known and include potato, corn and tapioca starch. Although the substance must be non-toxic for environmental reasons, the nature of the cation is not critical.

Suitable cations are sulfone, phosphorus and ammonia ions, of which the latter are preferred. It may be introduced into the starch using suitably alkalized molecules. Suitable alkyl amines will allow the starch to be replaced with trialkyl ammonia groups in the acidic state present in zinc carbon cells.

If the cationic starch used is present in the form of, for example, dialkylamino substituted starch, then this precursor can be converted to the cationic product by suitable treatment with an acid, which is either prior to incorporation of the separator into the cell or in situ. Can be done in

Particularly preferred cationic starch of the present invention is potato starch made by Roquette (Roqutte Freres, 4 rue Patou, F-59022 Lille Cedex, France) of LAB 2273, but other manufacturers also make suitable grades of cationic starch.

Separators generally require the use of a gelling agent in the preparation. It has been found that the natural rubbery and various dissolved starch gelling agents used to prepare the separators decompose during storage. However, etherified cellulose derivatives appear to be stable in aqueous solutions of zinc chloride, which is particularly advantageous for use in the present invention. Suitable examples of gelling agents for use in the present invention include Tylose MH20OK (Hoechst trademark), Tylose MH50, Culminal MHPC100 (Aqualon trademark) and Courtaulds DP 1209.

Particularly preferred etherified cellulose derivatives should ideally swell in water over a long period of time as described above in PCT / GB96 / 01318, substantially gel, and remain in a stable state, suitable etherified celluloses being methyl cellulose, Ethyl cellulose, hydroxymethyl cellulose, carboxymethyl cellulose (including salts such as sodium chloride), hydroxyethyl cellulose, ethylhydroxyethyl cellulose, methylhydroxyethyl cellulose, 2-hydroxypropyl cellulose, methylhydroxypropyl cellulose And 2-hydroxypropylmethyl cellulose.

In addition, in selecting the gelling agent, viscosity was set as an important factor. If the separator mixture is outside any viscous limits, typically in the range from 3000 to 70000 cp (3 to 7.0 Pa.s), undesirable results and poor cells can usually be obtained. Below 3000 cp (3 Pa.s), the mixture is often liquid and soaks directly into the paper, which can cause the paper to tear. Above 7000 cp (70 Pa.s) the mixture is usually very thick and cannot spread satisfactorily on paper.

Thus, it is desirable to provide a mixture that is within the aforementioned limits, which is generally possible by using etherified cellulose derivatives having a viscosity between 20 cps (0.02 Pa.s) and 300 cps (0.3 Pa.s). . The viscosity of the material used here (if not otherwise specified) is limited to 2% w / v aqueous solution of the material at 20 ° C. at neutral pH. The ideal viscosity is between 50 and 100 cps (0.05 and 0.1 Pa.s).

Useful adducts according to the invention are any form of nitrogen containing compound suitable for replacement by at least one polyoxyalkylene group. Amine and Ammonia Compounds Especially preferred are amine compounds, with other compounds having substitutable nitrogen bonds such as carbamoyl, diazo and axi-nitro compounds being suitable.

Some of the alkylenes in the polyoxyalkylene substituents may be the same or different, but will generally be the same due to the manufacturing methods used for such compounds. Useful alkylene groups tend to be limited to ethylene and propylene groups, but propylene groups are not as good as ethylene groups to inhibit gas, so polyoxyethylene nitrogen containing compounds, especially polyoxyethylene amines, are preferred. It will be appreciated that it is possible for some of the polyalkylenes to contain mixtures of lower alkylene groups such as methyl, ethyl and propyl. In such a case, the average alkylene length is preferably the length of two carbon atoms or the length approaching two carbon atoms.

It is particularly preferred that the nitrogen atom is substituted by at least one polyoxyalkylene group, and one saturated or unsaturated alkyl group. Preferably such group is an alkyl or alkenyl group. It is also anticipated but generally does not have an advantage for alkenyl groups. The group may be straight or branched and may be substituted by at least one substituent, such as a hydroxy group and a halogen atom, but generally it is preferred that the alkyl group is unsubstituted. The saturation level is ideally perfect, or there is only one or two carbon-carbon double bonds present. If the compound has an HLB of less than 17, the alkyl group must be a straight chain and contain 1 to 30 carbon atoms. It is preferable.

The compounds of the present invention may also contain one or more amine centers, in which case it is preferred that the individual amine groups are linked by alkylene groups, ie short chain alkylene groups such as trimethylene.

The nitrogen atom is substituted by an unsaturated group, in particular an alkenyl group, wherein the present invention provides a separator with such a compound according to the instructions of PCT / GB96 / 01319 which are incorporated herein by reference. In such a separator, an alkyl chain is disclosed in PCT / GB96 / 01319, wherein the alkyl chain can be substituted with an unsaturated chain if at least one alkyl is replaced by an unsaturated chain.

The chain length of the polyoxyalkylene group is not particularly important in the present invention, as long as the HLB is less than 17, but prefers that the chain length is 1 to 5, preferably the average length is 1 to 3, especially about 2 or 3 . Furthermore, compounds derived from animal oil amines are preferred, and animal oil alkyl groups contain about 18 carbon atoms.

Thus, the most preferred compounds of the present invention are mono- and di-amines, wherein the free alkyl group has about 18 carbon atoms and the side chains are polyoxyethylene substituents each having an average of 1 or 2 oxyethylene units, the compound Is diamine, so the link between the two amine centers is trimethylene.

Preferred compounds for use in the present invention are generally derived from animal oil, which has the following composition compared to coconut. Here, the chain length is the number of carbon atoms.

Any suitable paper can be used according to the present invention as long as it is suitable for use as a separator. However, most of the papers used in conventional separators come from a single source of pulp, which is relatively cheap to manufacture and tends to perform poorly in various tests. However, we have established that it is possible to produce papers that perform well in tests from a single source of pulp, and these papers have their ability to absorb 50 μl droplets in a period between 4 and 15 minutes at a temperature of 20 ° C. Is characterized. More preferably, this period is between 5 and 15 minutes, particularly preferably between 5 and 10 minutes.

If the paper absorbs drops of water in less than 4 minutes, the density of the paper tends to be too low and poor results can be obtained. If the paper absorbs water droplets in excess of 15 minutes, this causes practical problems during manufacture, where each cell needs to be at a voltage tested soon after assembly, and the delay in absorbing electrolyte from the mixture will cause the cells to be tested. This means that there is a storage period that cannot be allowed before.

The properties of the papers with the necessary absorption tend to be high beat and high density properties. Beating is performed on the pulp prior to paper formation, and the degree of beating can be measured by the use of a "Canadian standard freeness tester". The test is T 227m-58 of the Technical Association of the Paper and Pulp Industry, for example, "A Laboratory Handbook of Pulp and Paper Manufacture" (Auth. J. Grant, Pub. Edward Arnold, 2nd Ed. 1961, pp. 154 et seq.).

Conventional papers, such as Enso 8 O, typically have a density in the region of 0.5 g / cm ³ and even PBDElOO has a density of 62 g / cm ³ . However, although high density papers are preferred, both papers can be used according to the present invention.

Single pulp source papers preferred for the present invention typically have a density of at least 0.64 g / cm ³ . Although there is little room to choose a particular range of densities, preferred densities are from 0.65 to 1 g / cm ³ , more preferred densities are from 0.65 to 0.9 g / cm ³ . For example, one of the particularly preferred papers of the present invention is manufactured by Cordier (merchandise codes COK-70) and has a density of O. 64 g / cm ³ , the other of the particularly preferred papers of the present invention. Is prepared by Munksjo (product code 114440) and has a density of 0.76 g / cm ³ .

A list of some of the preferred papers useful in the present invention follows.

Cordier COK-60

Cordier COK ~ 70

Sybil Dal1e 5806O (hereinafter referred to as "SDMF")

Munksjo 114440

Munksjo 114770

Tervakoski Oy Tertrans N75 0,75

Tervakoski Oy Terkab E70 10

The cordierian papers can be obtained from Papierfabrik Cordier GmbH, Pfalz, Germany; The Civildale papers can be obtained from Civildale, Vitry sur Seine, France; The Munksjo papers can be obtained from Munksjo Paper AB, Jongppong, Sweden (Munksjo Paper AB, Jonkpong, Sweden); And the Tervakoski papers can be obtained from cucumber, Tervakoski, Finland (oy, Tervakoski, Finland).

Papers with densities less than about 0.6 g / cm ³ tend to produce poor results in the tests, while papers with densities greater than about 1.0 g / cm ³ There is a tendency to absorb in more than 15 minutes in the droplet absorption test.

In general, cells incorporating the separator with cationic starch still retain their function under adverse storage conditions. In one test, the failure rate was 0% even after 26 weeks at 45 ° C. Without being bound by theory, this remarkably good result seems to be due to the interface between the separator and the water-bearing can. This is improved by the separator of the present invention. The total moisture content of the battery remains substantially the same, but other separators in the prior art tend to dry out. This is a problem previously recognized, but has frustrated all attempts to solve so far.

Another advantage of using cationic starch is that the quality of manganese dioxide is not as important as other cell configurations. This is a major advantage, because manganese dioxide is a major cost in the manufacture of batteries, and savings are greatly possible if, for example, relatively cheap sources of electrolytic manganese dioxide (EMD) can be used. At present, such low grade materials can only be used when it combines with high grade materials to avoid leakage, but this is no longer necessary if cationic starch is used in accordance with the present invention. The present invention now makes it possible to use cheaper materials, such as for example obtained from the People's Republic of China.

It will also be appreciated that the present invention provides an electrochemical cell comprising the separator of the present invention. Also provided is a coating mixture suitable for the preparation of the coated separator of the present invention and comprising cationic starch.

Typical cells in which the separator of the present invention can be used include first and second zinc carbon cells as well as alkaline cells as well as those known as Leclanche and zinc chloride cells. Electrolytes in zinc carbon cells are typically as follows: Leclanshe electrolyte—5-20% zinc chloride, 30-40% ammonium chloride, remaining water; Zinc chloride electrolyte-15-35% zinc chloride, 0-10% ammonium chloride, remaining water. Other suitable cells for use in the present invention are described in Chapter 5 of the Handbook of Batteries and Fuel Cells (edited by David Linden, published by McGraw Hill).

The cells may have any suitable form, such as round, square, or flat.

Two useful tests used here to confirm leakage under harsh conditions are the High Drain Continuous Test (HDCT) and the Low Drain Continuous Test (LDCT). The high drainage continuous test is intended to simulate harsh conditions such as allowing the battery to know whether the flashlight remains on for a period of time even after it has fallen to the user. The low multiple continuous test simulates the conditions experienced by the battery, for example, on a clock. HDCT results are evaluated in terms of the amount of leakage, while LDCT results are evaluated in terms of battery failure due to can bend or fragmentation. These tests yield very beneficial results in significantly less time than experienced differently under simulated conditions. For example, the amount of time required will be dependent on factors such as the cell being tested and the degree to which the cell is desired to be tested, but results can generally be obtained in about 4 to 10 weeks, respectively.

The low drainage continuous test for electrochemical cells is characterized by leaving the cans sealed but uncovered, high resistance between the cell plates to complete the current, and monitoring the cells at that condition. .

In this test, it will be understood that monitoring the cell is intended to confirm that the cell will fail during the test. Typical lifetimes for D-size zinc carbon cells are up to about 10 weeks when the resistance is about 300Ω. 300 Ω provides useful results, but other resistors may also be used as appropriate. Suitable resistance for C-size cells is about 500 ohms, while for AA-size cells is about 810 ohms. Omission of the lower cover and the upper tube exposes the can to the surrounding environment, thus increasing any failures that may occur, which is why this test can be performed in 10 weeks, for example, when it takes two years on a watch. to be.

A high drainage continuous test for an electrochemical cell preferably secures the cell to the bottom cover, attaches a low resistance between the top cover and a point on the can wall proximate to the top cover, and then practically without removing the resistance. Slid the top-tube onto the can to cover a large portion of one can, weigh the obtained assembly, store the cell at ambient temperature, preferably 20 ° C., and if necessary, weigh the cell during storage. Inventory is characterized by determining the amount of electrolyte lost during storage by weighing to confirm leakage. This last weighing can be accomplished by removing the top tube after storage and weighing the cell, or by weighing the cell without the top tube but with resistance or with both. The addition of the bottom cover during this test has particular advantages in preventing corrosion at the bottom of the can during the test.

Suitable resistance for this test for D-size cells is 3.9 Ω and 5 Ω for AA-size cells, and the test is typically performed for four weeks, testing at weekly intervals. Typical discharge life for D cells is about 6 hours in this test until the cells become unusable. For example, a four-week test confirms how the cell can withstand harsh conditions.

The invention will now be described in detail with reference to the accompanying examples which are not intended to be limiting of the invention. Unless stated otherwise, percentages herein are weight percentages. Experimental protocols suitable for this example preceded that example. Unless stated otherwise, the zinc cans used in the examples of the present invention typically contain 0.43% lead 0.03% manganese and have a wall thickness of 0.46 ± 0.03mm. Typically, the mixing for the cathode ray tube comprises 52% manganese dioxide, 0.4% zinc oxide, 6% acetylene black and 41.6% zinc chloride solution (26.5% zinc chloride w / v). In addition, the cells are manufactured according to conventional EP-A-303737.

Test protocol

Preparing the Separator

The first step in preparing the separator is to prepare a paste for the coating of the paper. The components used in the examples of the present invention are as follows.

64.3% of water

Adhesive 0.5%

Gelant (specially designated) 3.1%

Starch (usually Vulca 90 or Roquette 2273, unless otherwise noted) 32.1%

As provided in the "Industrial Surfactants Electronic Handbook" (co-author of Gower, Michael and Irene Ash), materials suitable as conventional adhesives are available as surfactants.

The following method is used to construct the pool.

The dried ingredients are mixed to add water and an organic adhesive, placed in a paddle mixer such as a Hobart mixer and mixed until a soft paste is obtained.

Separator paste is coated onto selected paper. In order to meet the weight required for drying, the technique used in the embodiments of the present invention involves turning coated paper between two rollers spaced a predetermined distance apart. The two rollers are suitably set such that the two rollers rotate in opposite directions due to the fast moving forward roller. A suitable coating machine is Dixon (Dixon Pilot Coating Machine Model 160, UK)

Suitable coating weights will be apparent to those of ordinary skill in the art. However, preferred embodiments of the present invention use a dry coating weight of about 40gm- ² .

The coated paper is dried by oven drying at 100-140 ° C. and / or drum drying at 100-150 ° C.

The defective cell in the embodiment of the present invention is a cell having the following configuration, and ES denotes a cell according to the prior art.

Unless otherwise noted, all other cells are prepared with a dry mixture of 40 gsm gel component. Final drying takes place by steam drum drying. Through the present invention, it has been found that the use of an adhesive such as polyvinyl pyrrolidone (PVP) with steam drum drying aids in the coating adhesion of the paper. The present invention also confirmed that when the starch is potato starch, the advantageous gsm is about 40 which corresponds substantially to a single grain layer on paper. When wheat or corn starch is a finder, it needs to be coated at about 20 gsm, although the amount is less important than for potatoes.

High Drain Continuous Test (HDCT)

1. The cell is prepared as above. The bottom cover is added but no over-tube is added.

2. A resistance of 3.9Ω is coupled in close proximity to the cover between the top and the top of the can. The weight of the cell is w1.

3. The overtube weighs w2.

4. The overtube is pushed on the cell but does not rotate inside. The weight of the cell is w3.

5. HDCT cells are stored at 20 ° C. for 4 weeks. In the 3.9Ω test, the D-cell's normal discharge life is about 6 hours. The four-week test is an excessive test to simulate the consumer leaving the equipment on.

6. At major intervals (1w, 2w, 3w and 4w), one quarter of the original cell is removed and measured. The weight of the fully discharged cell is w4.

7. The overtube is removed and weighs w5.

8. The weight of the final resultant cell with the combined resistance still intact is w6.

9. HDCT leakage is w1-w6.

Low Drain Continuous Test (LDCT)

1. The cell is prepared as above. For LDCT, no bottom cover is attached and no over-tube is added.

2. A resistance of 300 Ω is coupled in close proximity to the cover between the cover and the top of the can.

3. Cells are examined for up to 10 weeks at weekly intervals. This will be the normal life of the D cell in the 300Ω test. This test is a simulation of the cell being used in a long test such as a clock.

4. Cell breakage occurs when the can's perforation or splitting is observed. This allows for cell penetration of O ₂ , which leads to premature destruction on long tests.

In the following examples, various industry reference tests are used. Unless otherwise noted, the cells to be tested are D size. Undefined test is as follows.

SCA-The cell is short-circuited and the current passing through is measured with a zero (very low) impedance meter. The final measurement is the cell's short circuit amperage (SCA).

Light Industrial Flashlight (LIF)-The discharged cell traverses a 2.2Ω resistor in four eighth periods, with each cycle separated by about two minutes. This is repeated every day, and the end result is given in terms of time, which is the total cumulative total of eight minutes of discharge cycles to reach 0.9 V causing cell breakdown.

Motor (also referred to as DM)-The cell is discharged across a resistance of 3.9 ohms per hour for one hour until it reaches 0.9V causing cell breakdown. The end result is the total cumulative total of discharge time before the cell is destroyed.

Toy (also called DT)-Similar to a motor, except that the cell is discharged across a resistance of 2.2Ω for an hour a day until reaching 0.8V, which causes cell breakdown. The final result is the total cumulative total of the discharge time before breaking into the cell.

Continuous Toy (also called DY)-The cell continues to discharge across a 2.2Ω resistor until cell breakdown occurs at 0.75V. The end result is the total cumulative total of discharge time before the cell is destroyed.

DP-The cell is discharged across a resistance of 2.2Ω for eight quarters of an hour, with each period approximately two minutes apart. This is repeated every day, and the end result is given in terms of time, which is the total cumulative total of the four minute discharge cycles experienced until reaching 0.9V, which causes cell breakage.

The mixture used in the following examples, unless stated otherwise,

2.35 g H ₂ O / Ah, 0.34% (w / w) ZnCl ₂ / H ₂ O with 50% PRC MnO ₂ and 50% N56 Mn) 2.

Also in the following examples, potato starch is as follows.

Performance of Cells with Various Polyoxyethylene Additives

The cell is composed of the following separators and tested in the SCA and HDCT test v.ES cells. PI represents the cell's relative performance to the ES cell. Section EO refers to the oxyethylene content of the additive.

Table 1

# Crodament T15, Ethylan TT15

Crodament T5, Ethylan TT05, Proxonic MT05

From the above, it can be seen that the combination of cationic starch LAB2273 and tallow 5 gives a low possibility of leakage (HDCT) and a large fresh short circuit current amount.

Selective potato cationic starch obtained from Roquette Freres produced the following results as shown in Table 2.

TABLE 2

Although the above example was performed using tallow 8 (HLB 11) rather than tallow 5 (HLB 9), the properties of cationic starch are not important as long as they have at least related properties.

In Table 3, the effect of the additives during the run is confirmed when compared to the ES.

TABLE 3

Additive not used

Use of additive

In Table 4, the effect of the additive in the HDCT experiment is described. The results are g / battery leakage.

Table 4

It is clear that all the additives tested yield excellent results for prior art cells and that even additives with an HLB of about 5 have advantages.

Coating gsm

Potato starch is relatively coarse, whereas wheat (Ping bacteria particle size 0.006-0.015 nm) or corn wheat (average particle size 0.006-0.017 nm) sms is relatively fine.

This has the following effect on AA size cells.

Table 5

This test compares 20 and 40 gsm potato starch using Crodamet C20 and Sibille Dalle MF60 paper.

AW Plus-0.9V cell breakdown discharges for 15 seconds every minute across 1.8Ω.

A cell breakdown of AW-0.75V is continuously discharged across 3.9Ω.

40 gsm potatoes are clearly superior to 20 gsm potatoes. This is because potato starch is so coarse that it does not give full coverage of the paper at 20 gsm.

Table 6

This test compares 40 and 50 gsm potato starch without using tallow 8 Amine (Crodamet T8) and Munksj 11440 paper.

This shows that HDCT starts to increase when over 40 gsm potato starch is coated.

The optimum coating weight for potato rust that maximizes performance and minimizes HDCT leakage is clearly 40 gsm.

In the following Table 7, various papers are tested according to the present invention. This test is run with tallow 8, but even so, the paper coated according to the present invention provides the excellent properties of the cells containing them. Starch is Roquette 2273, Corrant is 1209, Adhesive is ISP PNP K120, and additive is Tallow 8 amine.

TABLE 7

In the following example, standard highly cross-linked cone starch was compared with various cationic starches. The form of the starch is shown in Table 8.

Tests as described in Table 9 were used.

Table 9

3R9 / 1h / 0V8 has a discharge of 3.9Ω for 1 hour per day until it fails at 0.8V. Similarly, 15 s / m represents 15 seconds every minute. In the LIF test, the cell is discharged for 4 cycles of 8 minutes per hour. AA represents AA size batteries and D represents tests for D size batteries.

In Table 10, the effects of starch thickness on variable starch and AA size cells are presented. It can be appreciated that for AA size cells cross-linked cationic potato starch should be used for thicker thicknesses, but does not perform the same performance as highly cross-link corn starch. As in the other tables, in the table, the coconut 20 amine is typically Chrodamet C20. In the following table, Resin 5 and Resin 8 amines are typically Chromatic, respectively T5 and T8. PRC EMD is an electrolytic manganese dioxide obtained from the People's Republic of China, and N65 NMD is a natural manganese dioxide obtained from Mexico.

Table 10

In Table 11, the effect of variable paper thickness in the AA cell is shown, and it can be seen that thinner paper is useful, and is provided with the required structural increase.

Table 11

In Table 12, the effects on the discharge performance of different starch and manganese dioxide compositions in AA cells are shown. A mixture and all compositions performed satisfactorily are presented.

Table 12

The effects of various starches and additives on two leak tests on AA size cells are shown in Table 13. The JIS test for AA batteries relates to a continuous discharge across 5 ohms for 48 hours while observing leakage. For the D cell, discharge occurs across 2 ohms for 48 hours. Before measuring leakage, the discharge abuse test (DAT) relates to discharge across 15 Ω for 4 weeks for AA size and 5 Ω for 4 weeks for D cell. It can be seen that the associated cationic corn starch gives the best results.

Table 13

Table 14 describes how the results of the JIS test are scored. The total for 20 batches forms a leak index.

Table 14

In Table 15, the results of JIS and DAT on the D cell are shown. Once again, it can be seen that the associated cationic corn starch gives the best results. It is also shown that the wall thickness is important.

Table 15

Table 16 shows the effects of the various green films of the present invention on the D cell. Once again, it can be seen that the associated cationic corn starch gives the best results. It is also shown that the wall thickness is important.

Table 16

The present invention relates to a battery having a coated paper separator, the battery of the present invention is excellent in performance and safety characteristics.

Claims (26)

A coated paper separator for an electrochemical cell, wherein the coating comprises starch and additives, and the cationic starch constitutes the majority of the starch component of the separator coating. The method of claim 1, The additive is a polyoxyalkylene, nitrogen containing compound Coated paper separator. The method according to claim 1 or 2, The additive has a hydro-lipophilic balance of less than 17. Coated paper separator The method of claim 1, wherein The additive has a hydrophilic-hydrophobic balance of less than 14 Coated paper separator. The method of claim 1, wherein The additive has a hydrophilic-hydrophobic balance of less than 11 Coated paper separator. The method of claim 1, wherein The additive has a hydrophilic-hydrophobic balance of 9 or less Coated paper separator. The method of claim 1, wherein The additive has a hydrophilic-hydrophobic balance of greater than 5 Coated paper separator. The method of claim 1, wherein The additive has a hydrophilic-hydrophobic balance of 5 to 11 Coated paper separator. The method of claim 1, wherein The additive has a hydrophilic hydrophobic balance of 7 to 10 Coated paper separator. The method of claim 1, wherein The additive has a hydrophilic-hydrophobic balance of 8 to 9 Coated paper separator. The method of claim 1, wherein The additive has a hydrophilic-hydrophobic balance of 9 Coated paper separator. The method of claim 1, wherein The additive is non-ionic Coated paper separator. The method of claim 1, wherein The cationic element of the starch is nitrogen-based, the degree of nitrogen is 0.2 to 2% by weight relative to the dry weight of the starch Coated paper separator. The method of claim 1, wherein Cationic starch forms substantially all of the starch components Coated paper separator. The method of claim 1, wherein The starch is cross-linked Coated paper separator. The method of claim 1, wherein The starch is highly cross-linked Coated paper separator. The method of claim 1, wherein The starch is substantially insoluble in water at room temperature Coated paper separator. The method of claim 1, wherein The starch may be potato, corn or wheat starch. Coated paper separator. The method of claim 1, wherein The starch is wheat starch Coated paper separator. The method of claim 1, wherein The coating further comprises etherified cellulose as a gelant. Coated paper separator. The method of claim 20, The gelling agent can swell and gel substantially and instantly in water at room temperature and can remain stable there for a long time. Coated paper separator. The method of claim 20 or 21, The gelling agent has a viscosity of 20 cP (0.02 Pa.s) to 300 cP (0.3 Pa.s), preferably, 50 to 100 cP (0.05 to 0.1 Pa.s) Coated paper separator. The method of claim 1, wherein The additive is a mono- and di-amine polyoxyalkylene compound, wherein the free alkyl group is 18 carbon atoms, the side chain is a polyoxyethylene substituent having an average of 1 or 2 oxyethylene units each, and the compound is a diamine The link between the two amine centers is then a trimethylene link Coated paper separator. The method of claim 1, wherein The paper is capable of absorbing 50 μl of water droplets at a temperature of 20 ° C. for 4 to 15 minutes, preferably for 5 to 15 minutes, particularly preferably for 5 to 10 minutes. Coated paper separator. An electrochemical cell comprising the separator according to any one of the preceding claims. A coating mixture comprising cationic starch, which is suitable for the preparation of the separator according to any one of claims 1 to 24.