Battery cells with safety layers

Abstract

To provide a battery cell with a water responsiveness safety layer which can be protected from damages and / or electrolysis of tissue when the battery cell is exposed to an aqueous solution or a wet tissue.SOLUTION: A battery 50 comprises: a housing having a first electrode and a second electrode; and a composite water responsiveness safety layer that is a composite water responsiveness safety layer 64 having a polymer material and positioned so as to be adjacent to at least one of the first electrode and the second electrode, and short-circuits the battery at less than 1.5 V when the composite water responsiveness safety layer comes into contact with an aqueous solution, the composite water responsiveness safety layer containing at least one metal salt.SELECTED DRAWING: Figure 2B

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 16 / 016,466, filed June 22, 2018, which is a continuation-in-part of U.S. Patent Application No. 15 / 677,921, filed August 15, 2017, both of which are incorporated by reference in their entireties and made a part of this application.

[0002] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made under a CRADA (SC03 / 1672) between Procter & Gamble Company and Sandia National Laboratories, operated for the U.S. Department of Energy. Duracell Company and its subsidiary, Duracell US Operations, Inc., are successors in interest of Procter & Gamble Company under the CRADA (SC03 / 1672). The Government has certain rights in this invention.

[0003] The present disclosure relates to battery cells, and more particularly, to battery cells with water-responsive safety layers that can protect against tissue damage and / or electrolysis when the battery cells are exposed to aqueous solutions or moist tissue. [Background technology]

[0004] The background discussion provided herein is generally intended to provide a context for the present disclosure.

[0005] Electrochemical cells or batteries are commonly used as a source of electrical energy. Miniature batteries are particularly useful in powering consumer products. Miniature batteries come in a variety of cell types. Common miniature battery cell types are AAA, AA, B, C, D, 9V, CR2, and CR123A. Other types of miniature batteries known as button cells (including wider cells sometimes called coin cells) are frequently used to power a variety of products including, but not limited to, watches, cameras, calculators, keyless entry systems for vehicles, laser pointers, glucometers, and the like. FIG. 1 shows the structure of a typical button cell 10 with a cathode 12 disposed within a cathode can 14 and an anode 16 disposed within an anode cup 18. A separator 20 physically separates and electronically insulates the anode 16 from the cathode 12. An insulating gasket 22 helps seal the cell to prevent electrolyte loss and to insulate the cathode can 14 from the anode cup 18 to prevent ingress of ambient atmospheric components into the cell. Button cells typically have a long service life, e.g., typically well over a year in continuous use in a wristwatch. Furthermore, most button cells have low self-discharge and therefore retain their charge for a relatively long time when not under load.

[0006] Although button cell batteries are common in many portable consumer electronic devices, the size, shape, and appearance of these batteries, especially the 20 mm diameter coin cells such as the 2016 lithium cell and the 2032 lithium cell, can pose a swallowing hazard to infants, small children, and pets. These hazards can result in bodily harm, especially if the cells are swallowed without the knowledge of others around. Also, some of these button cell batteries can pose relatively greater hazards than other cells, which may not be fully understood by consumers. For example, coin cell batteries such as the 2016 3V lithium cell and the 2032 3V lithium cell, which are based on a chemical reaction between lithium and manganese dioxide, are sized such that they can easily get stuck in a person's throat, thus causing electrolysis of bodily fluids or, for example, burning of the esophagus / organ tissues if swallowed. Summary of the Invention [Problem to be solved by the invention]

[0007] In one aspect, the disclosure provides a battery comprising: a housing, the housing comprising first and second poles; and a composite water-responsive safety layer comprising a polymeric material and positioned adjacent to at least one of the first and second poles, the composite water-responsive safety layer configured to change from an electronically non-conductive state to an electronically conductive state upon contact with an aqueous solution, the composite water-responsive safety layer further comprising at least one metal salt.

[0008] In one refinement of the battery, the at least one metal salt of the composite water-responsive safety layer comprises at least a first metal salt and a second metal salt.

[0009] In another aspect, the disclosure provides a method including providing a battery housing comprising first and second poles; and forming a composite water-responsive safety layer between the first and second poles of the battery housing by depositing a composition between the poles such that the composition is adjacent to at least one of the first and second poles, the composition comprising a polymeric material and at least one metal salt, such that the composite water-responsive safety layer changes from an electronically non-conducting state to an electronically conducting state upon contact with an aqueous solution.

[0010] In one refinement of the method, the at least one metal salt of the composition comprises at least a first metal salt and a second metal salt.

[0011] While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the invention, the present invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which: The figures described below depict various embodiments of the battery cell disclosed herein, and it should be understood that each figure depicts an exemplary embodiment of the battery cell disclosed herein. [Brief description of the drawings]

[0012] [Figure 1] 1 shows a conventional button cell. [Figure 2A] An example of a battery in the form of a coin cell is shown having a composite water-responsive safety layer adapted to change from an electronically non-conductive state to an electronically conductive state upon contact with an aqueous solution. [Figure 2B] An example of a battery in the form of a coin cell is shown having a composite water-responsive safety layer adapted to change from an electronically non-conductive state to an electronically conductive state upon contact with an aqueous solution. [Diagram 3] FIG. 1 is a schematic diagram of a prototype battery configuration according to an example, in which a composite water-responsive safety layer comprises a polymer matrix comprising polyethylene glycol (PEG), a metal salt, and a metal powder. [Figure 4]4 is a plot of voltage change over time in different tests using the prototype battery configuration of FIG. 3 according to an example of a composite water-responsive safety layer exposed to an aqueous solution. [Diagram 5] 1 shows an example of a battery in the form of an example button cell having a composite water-responsive safety layer deposited at a specific location between the negative and positive electrodes of the battery. [Figure 6] 6 is a plot of voltage change over time for different tests of the battery configuration of FIG. 5 according to an example of a composite water-responsive safety layer exposed to an aqueous solution. [Figure 7] 1 shows a graph illustrating the time it takes an example battery cell with a composite water-responsive safety layer to short circuit when exposed to an aqueous solution. [Figure 8] 13 shows a graph illustrating the time it takes another example battery cell with a composite water-responsive safety layer to short circuit when exposed to an aqueous solution. [Figure 9] 13 shows a graph illustrating the time it takes for yet another exemplary battery cell with a composite water-responsive safety layer to short circuit when exposed to an aqueous solution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The electrochemical cells or batteries may be primary or secondary batteries. Primary batteries are intended to be discharged, for example, once to exhaustion and then discarded. Primary batteries are described, for example, in Handbook of Batteries by David Linden (McGraw-Hill, 4th ed., 2011). Secondary batteries are intended to be charged. Secondary batteries may be discharged and then recharged many times, for example, more than 50 times, more than 100 times, or more than 1000 times. Secondary batteries are described, for example, in Handbook of Batteries by David Linden (McGraw-Hill, 4th ed., 2011). Batteries may include aqueous or non-aqueous electrolytes. Thus, batteries may include various electrochemical combinations and electrolyte combinations. Consumer batteries may be either primary or secondary batteries. However, due to the charge stored in the battery and due to exposed poles, it is beneficial to protect consumer batteries, especially small batteries, from injury to the consumer when exposed to wet tissue. In particular, it is beneficial to protect the battery from exposing the consumer to electrolysis or burns, either of which may occur, for example, if the battery is swallowed. If the positive and negative electrodes of the battery are exposed to moist body fluids, electrolysis of water may occur resulting in the generation of hydroxide ions, which may cause tissue combustion, particularly of tissue adjacent to the negative electrode. This application describes techniques for short-circuiting the battery in such situations, thereby reducing the cell voltage and effectively preventing tissue damage.

[0014] The present disclosure provides battery cells with composite water-responsive safety layers and / or composite water- and pH-responsive safety layers that include polymers incorporating therein safe levels of benign materials that can result in an electrochemically generated short circuit when the composite water-responsive safety layer is wetted, such as when exposed to aqueous solutions in the form of saliva, gastric juices, or other fluids. The resulting short circuit can reduce the voltage of the battery cell below a desired threshold level, thereby reducing and / or effectively preventing the electrolysis of water and the associated formation of harmful electrochemically generated ions (e.g., hydroxide ions). The desired threshold level may vary, but in some examples detailed herein, the cell may be suitably shorted to less than 1.5 V, including less than 1.4 V, less than 1.3 V, less than 1.2 V, less than 1.1 V, less than 1.0 V, less than 0.9 V, less than 0.8 V, less than 0.7 V, less than 0.6 V, less than 0.5 V, less than 0.4 V, less than 0.3 V, less than 0.2 V, less than 0.1 V, or even to about 0 V. Preferably, the mere application of the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer does not affect the battery cell performance under normal use conditions, such that, for example, a battery has substantially the same voltage and capacity before and after the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer is provided to the battery. Although batteries incorporating the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer are illustrated and described herein using button cells, and more particularly coin cells, generally any battery type may be modified to include the composite water-responsive safety layer and / or the composite water- and pH-responsive safety layer according to the present disclosure, including but not limited to common consumer batteries such as AAAA, AAA, AA, B, C, D, 9V, CR2, CR123A, 1 / 3N, button cells, and coin cells. Generally, shorting the battery cell voltage below about 1.2V completely prevents water electrolysis, while reducing the voltage below 1.5V helps reduce the amount of electrolysis that would otherwise occur.Thus, in a preferred embodiment, the cell voltage is reduced to below 1.5V, more preferably below 1.2V within 2 hours (or 7200 seconds), since significant burning of esophageal tissue is not known to occur until after 2 hours.

[0015] The term "water-responsive" as used herein refers to a composite safety layer that does not transition from an electronically non-conductive state to an electronically conductive state when exposed to air. Instead, it is necessary for the composite safety layer to absorb a certain amount of moisture before transitioning from an electronically non-conductive state to an electronically conductive state. Thus, the composite water-responsive safety layer itself is hygroscopic. In particular, each component contained in the composite water-responsive safety layer is generally not hygroscopic, or in other words, the composite water-responsive safety layer generally includes a hygroscopic component and a non-hygroscopic component. As a result, air should not cause the composite water-responsive safety layer to transition from an electronically non-conductive state to an electronically conductive state, and therefore not short circuit. However, the composite water-responsive safety layer may short circuit if exposed to a high humidity environment for a long period of time. For example, a cell having a composite water-responsive safety layer described herein may be preferably stored for at least 2 hours, at least 12 hours, at least 10 days, at least 30 days, and / or at least 60 days in an environment having a relative humidity value of up to 90% (at a temperature between about 20° C. and about 50° C., e.g., at about 30° C. or at about 40° C.). In addition, a cell having a composite water-responsive safety layer described herein may be preferably stored for at least 2 days, at least 10 days, at least 60 days, and / or at least 90 days in an environment having a relative humidity value of up to 65% (at a temperature between about 20° C. and about 50° C., e.g., at about 30° C. or at about 40° C.).

[0016] As used herein, the term "water-responsive and pH-responsive" refers to a composite safety layer that does not necessarily transition from an electronically non-conductive state to an electronically conducting state when exposed to water alone. Specifically, a water-responsive and pH-responsive composite safety layer remains in a non-conductive state when in contact with an aqueous solution having a first predetermined pH range, and transitions from a non-conductive state to a conducting state in response to contact with an aqueous fluid having a second, different, predetermined pH range.

[0017] In one embodiment, a composite water-responsive and pH-responsive safety layer is provided that remains non-conductive in aqueous solutions having acidic or near-neutral pH values ​​and changes from a non-conductive state to a conductive state in response to contacting the composite water-responsive and pH-responsive safety layer with an aqueous fluid having a pH greater than 5.0, e.g., about 5.0 to about 12.0, about 5.5 to about 8.0, about 6.0 to about 7.8, about 6.2 to about 7.6, about 8.0 to about 10.0, about 10.0 to about 12.0, or greater than 12.0. Thus, the altered pH of saliva or the pH of bodily fluids as a result of the electrolysis of water may promote dendrite growth and associated shorting of the cell. As an example, the composite water-responsive and pH-responsive safety layer may comprise a polymer, e.g., polyvinyl acetate, a salt such as ammonium carbonate, and a metal powder, e.g., copper powder or zinc powder. When the composite water-responsive and pH-responsive safety layer is contacted with an alkaline medium such as saliva, the ammonium carbonate can form ammonia and carbonate anions, and the metal powder can oxidize to form metal cations that can be reduced at the negative electrode of the battery, such that dendritic metal structures can grow within the composite water-responsive safety layer to electronically connect the negative electrode to the positive electrode under safe conditions, such as when a person or infant swallows the battery cell.

[0018] In another embodiment, a composite water-responsive and pH-responsive safety layer is provided that remains non-conductive in an aqueous solution having a neutral or acidic pH, e.g., a pH less than 7.0, and changes from a non-conductive state to a conductive state in response to contacting the composite water-responsive layer with an aqueous fluid having an alkaline pH greater than 7.0, e.g., about 8.0 to about 12.0. As an example, the composite water-responsive and pH-responsive safety layer may comprise a polymer, e.g., polyvinyl acetate, a water-soluble salt, such as ammonium chloride, and a water-insoluble copper metal salt, such as copper carbonate. Upon contacting the composite water-responsive and pH-responsive safety layer with an alkaline medium, such as saliva, ammonium chloride (NH4Cl) may dissolve adjacent to and within the safety layer. Hydroxide ions generated at the negative electrode due to electrolysis of water deprotonate ammonium ions to form aqueous ammonia (NH3). Water-soluble / soluble ammonia reacts with the substantially insoluble metal salt copper carbonate to produce a soluble composite ion, Cu(NH3)4, which may be reduced at the negative electrode of the battery. 2+ whereby dendritic metal structures can grow within the composite water-responsive and pH-responsive layer to electronically connect the negative electrode to the positive electrode under safe conditions, such as when a person or infant swallows the battery cell.

[0019] The composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer comprises a polymeric material. Any number of polymers may be used alone or in combination to form the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer. In a preferred embodiment, at least one of the polymers in the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer is a hygroscopic polymer, although the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer may also be rendered hygroscopic by a metal salt contained therein. In addition to polyethylene glycol (PEG), other polymers or combinations thereof may be used to form the layer matrix. Non-limiting examples include, but are not limited to, polyethylene oxide (PEO), polyacrylic acid (PAA), including but not limited to polymethyl methacrylic acid, polyamides (PA), polyacrylates, including but not limited to polymethacrylates such as polymethyl methacrylate, polyvinyl alcohol and modified polyvinyl alcohols, acrylate copolymers, polyvinyl acetate, poly(vinyl butyrate), poly(vinyl propionate), and poly(vinyl formate), polyvinylpyrrolidone, pullulan, gelatin, hydroxypropyl methylcellulose (HPMC), low viscosity grades of hydroxypropyl cellulose, polysaccharides, guar gum, xanthan gum, locust bean gum, carrageenan, and water soluble natural polymers, including but not limited to starch, modified starches, including but not limited to ethoxylated starch and hydroxypropylated starch, copolymers of the foregoing, including but not limited to polyvinyl ester copolymers such as poly(ethylene-vinyl acetate), and copolymers of any of the foregoing. The polymer is preferably a biologically inert material that is non-toxic or has little toxicity. The weight average molecular weight of the polymer is generally, but not limited to, at least 1 kD, for example, 1 kD to 1000 kD, 5 kD to 750 kD, 50 kD to 750 kD, for example, about 500 kD.

[0020] In an embodiment, the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer comprises a metal salt. The metal salt provides a reducible sacrificial material at the negative electrode of the battery so that dendritic metal structures can grow within the composite water-responsive film to electronically connect the negative electrode to the positive electrode under safe conditions, such as when a person or infant swallows the battery cell, thereby exposing the battery cell to aqueous solutions in the form of saliva, gastric juices, or other fluids, strategically shorting the cell without significant electrolysis of water and the associated production of hydroxide ions and burning of tissue. Copper(II) (Cu +2 ), iron(II)(Fe +2 ), mercury(II)(Hg +2 ), Nickel(II)(Ni +2 ), silver(I)(Ag + ) and the like, and zinc(II) (Zn +2 ), Bismuth(III)(Bi +3 ), Indium(III)(In +3 ), lead(II)(Pb +2 ), Tin(II)(Sn +2Suitable metal salts with cations may be used, including, but not limited to, other metal cations such as acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, butyrate, camphorate, camphorsulfonate, carbonate, chloride, citrate, cyclopentanepropionate, digluconate, dihydrochloride, diphosphate, dodecylsulfate, edetate, ethanesulfonate, fumarate, glucoheptonate, glucomate, glutamate, glycerophosphate, hemisulfate, heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, hydroxide, hydroxyethanesulfonate, hydroxynaphthoate, iodide, lactate, lactobionate, laurate, laurate Representative metal salts with anions including, but not limited to, maleate, malonate, mandelate, mesylate, methanesulfonate, methyl bromide, methyl nitrate, methyl sulfate, mucate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, polygalacturonate, propionate, salicylate, stearate, acetate, succinate, sulfate, tantate, tartrate, theophyllinate, thiocyanate, triethiodide, toluenesulfonate, undecanoate, valerate, and mixtures thereof may be used. Specific metal salts include, but are not limited to, bismuth carbonate, bismuth chloride, bismuth sulfate, bismuth nitrate, bismuth subsalicylate, bismuth oxide, copper carbonate, copper chloride, copper sulfate, copper oxalate, copper hydroxide, ferrous carbonate, ferrous chloride, ferrous sulfate, indium carbonate, indium chloride, indium sulfate, lead carbonate, lead chloride, lead sulfate, mercury carbonate, mercury chloride, mercury sulfate, nickel carbonate, nickel chloride, nickel sulfate, silver carbonate, silver chloride, silver sulfate, stannous carbonate, stannous chloride, stannous sulfate, zinc carbonate, zinc chloride, zinc sulfate, hydrates thereof, basic salts thereof (hydroxide salts, oxide salts), and combinations thereof.Non-metal salts such as ammonium carbonate ((NH4)2CO3) and ammonium chloride (NH4Cl) may also be used in combination with the metal salt. Additionally, other metal salts such as sodium chloride (NaCl) may be included that do not provide a reducible sacrificial material at the negative electrode of the battery but can support the transition from an electronically non-conducting state to an electronically conducting state, for example, by acting as a humectant and / or by increasing the conductivity of the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer.

[0021] As used herein, the term "copper carbonate" is used to refer to copper(II) carbonate (also known as cupric carbonate and neutral copper carbonate) and basic copper carbonate (also known as basic cupric carbonate, copper hydroxide, and malachite). Thus, the term copper carbonate (without further explanation) as used herein refers to both (neutral) copper(II) carbonate (CuCO3) and basic copper carbonate (CuCO3·Cu(OH)2). In general, the term is used herein to refer to basic copper carbonate, but it should be understood that both materials are intended unless further specified by the neutral or basic designation.

[0022] In one refinement, the at least one metal salt of the composite water-responsive safety layer comprises at least a first metal salt and a second metal salt. When a water-insoluble second metal salt, such as copper carbonate, is present in combination with a water-soluble salt, such as copper sulfate, the cell preferably does not exhibit a change in cell voltage, even after exposure to high relative humidity for an extended period of time. As used herein, "water-soluble" refers to a solute having a water solubility (at about 25° C., about pH 7) of greater than 100 mg / L, greater than 150 mg / L, greater than 200 mg / L, greater than 1000 mg / L, and / or greater than 100 g / L. As an example, copper sulfate has a water solubility (at about 25° C., about pH 7) of about 220 g / L. Meanwhile, "water-insoluble" refers to a solute having a water solubility (at about 25° C., about pH 7) of less than 10 mg / L, less than 7.5 mg / L, less than 5 mg / L, less than 2.5 mg / L, and / or less than 1 mg / L. As an example, copper(II) carbonate has a water solubility of about 1.46 mg / L (at about 25° C., about pH 7), and basic copper carbonate has a water solubility of about 4.68 mg / L (at about 25° C., about pH 7). When a combination of a water-insoluble salt and a water-soluble salt is used, there may be a difference in the magnitude of water solubility between the water-insoluble salt and the water-soluble salt of at least 10 times, at least 100 times, at least 1000 times, and / or at least 10,000 times. For example, copper sulfate is 10,000 times more soluble in water than basic copper carbonate. In other examples, the ratio of water solubility between the water-insoluble salt and the water-soluble salt may be at least about 1:10 (e.g., at least about 1:100, 1:1,000, 1:10,000, or more).

[0023] Water solubility values ​​for many salts can sometimes be found in the literature, but are determined here using either the "flask method" or the "column elution method." As described in EPA OPPTS 830.7840 (Water Solubility), which is incorporated herein by reference, column elution is used for substances with low solubility (solubility less than 10 mg / L) and flask method is used for substances with higher solubility (solubility greater than 10 mg / L).

[0024] Briefly, the water solubility is determined in water at the relevant pH (e.g., a pH of about 5.5 to about 8.5, such as 7.0) and at the relevant temperature (e.g., a temperature of about 20°C to 30°C, such as about 25°C). In the flask method, the test substance is first pulverized by grinding and weighed into a container, whereby about five times the amount determined by the preliminary test is weighed into the container, and then the indicated amount of water is added to the container (e.g., 1 L). Once saturation is achieved, the mixture is cooled to the test temperature and stirred until equilibrium is reached. The mass concentration of the test substance dissolved in the aqueous solution (which must not contain undissolved particles) can be analytically determined by any useful methodology (gas or liquid chromatography, titration, photometry, and / or voltammetry). Gas chromatography is preferred. In the column elution method, a microcolumn containing an excess of the test substance with an inert support (beads, silica, sand, etc.) is eluted with water, and the mass concentration of the substance in the eluate is determined when the concentration of the eluate is constant. The method is based on eluting the test substance with water at a constant temperature from a column packed with the substance finely distributed on an inert support material. The water flow rate should be adjusted so that a saturated solution leaves the column. Saturation is achieved when the mass concentration - determined by a suitable method - is constant in successive proportions of eluate at different flow rates. This is indicated by a plateau when concentration is plotted against time or elution volume. As mentioned before, the mass concentration of the test substance dissolved in the aqueous solution can be determined analytically by any useful methodology (e.g. gas or liquid chromatography, titration, photometry and / or voltammetry). Gas chromatography is preferred.

[0025] Further details on determining solubility can be found, for example, in the Organisation for Economic Co-operation and Development (OECD), "Test No. 105: Aqueous solubility", OECD Guidelines for Testing Chemicals, adopted on 27 July 1995 (7 pp.); OECD-Environment Directorate: Joint Meeting of the Committee on Chemicals and the Working Party on Chemicals, Pesticides and Biotechnology, "Guidance Document on the Transformation / Dissolution of Metals and Metal Compounds in Aqueous Media", OECD Test and Evaluation Series, No. 29, 23 July 2001 (19 pp.); "Determination of Test Methods Pursuant to Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) and Regulation (EC) No. 440 / 2008 of 30 May 2008" Official Journal of the European Union. L142, Part. A.6 (p. 57-66), May 31, 2008, (739 pp.); U.S. Environmental Protection Agency, "Product Characteristic Testing Guideline-OPPTS 830.7860 Aqueous Solubility (Generator Column Method)", EPA 712-C-96-042, August 1996 (19 pp.) and U.S. Environmental Protection Agency, "Product Characteristic Testing Guideline-OPPTS 830.7840, Aqueous Solubility: Column Elution Method, Shake Flask Method", EPA 712-C-98-041, March 1998 (14 pp.), each of which is incorporated herein by reference in its entirety.

[0026] In one embodiment, the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer comprises a polymer but is substantially free of (added) metal salts. In this regard, the metallic material of the negative electrode may be oxidized, thereby providing an ion source that can serve as a sacrificial material for dendrite growth. Thus, in another embodiment, the present disclosure provides a battery comprising a housing, the housing comprising first and second poles, the composite water-responsive safety layer comprising a polymer material and positioned adjacent to at least one of the first and second poles, the composite water-responsive safety layer adapted to change from an electronically non-conducting state to an electronically conducting state when contacted with an aqueous solution.

[0027] In embodiments, the composite water-responsive and pH-responsive safety layer comprises a non-metal salt. Specific non-metal salts include, but are not limited to, ammonium carbonate ((NH4)2CO3) and ammonium chloride (NH4Cl).

[0028] The composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer may optionally further comprise a reducing agent. The term "reducing agent" as used herein generally refers to an organic reducing agent, an inorganic reducing agent, or particles of elemental metal or metal alloy in its fully reduced state. The reducing agent can reduce soluble metal ions to conductive elemental metal (i.e., electroless deposition of metal occurs) even at a location far away from the negative electrode without application of a cell potential. Electroless deposition of metal may help provide bridging dendrite moieties as they grow in the composite water-responsive safety film to establish electronic connections between the battery poles, thereby facilitating shorting of the cell. Thus, in one embodiment, the composite water-responsive safety layer may include a polymeric material, a metal powder, such as zinc powder, and a powdered metal salt, such as copper sulfate, contained therein. In the dry state, the reaction between the zinc and copper sulfate is prevented and the safety layer is non-conductive. When exposed to an aqueous environment, such as in the case of accidental ingestion, copper can dissolve to produce copper ions, which can be reduced by zinc metal to produce copper dendrites that grow and connect to adjacent dendrites, thereby providing a conductive path across the gap between the battery poles, resulting in a short circuit in the cell. Reducing agents may be used, including, but not limited to, ascorbic acid or ascorbate, tocopherol, sodium borohydride, aluminum(0) (Al), calcium(0) (Ca), iron(0) (Fe), magnesium(0) (Mg), nickel(0) (Ni), tin(0) (Sn), titanium(0) (Ti), zinc(0) (Zn), and alloys and combinations thereof.

[0029] The composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer may optionally further comprise a metal powder. As used herein, the term "metal powder" generally refers to particles of elemental metal or metal alloy in its fully reduced state. The metal particles may have a particle size of about 0.1 μm to about 500 μm, such as about 0.50 μm to about 100 μm, and / or about 1 μm to about 50 μm. The metal powder may remain in a reduced form in the water-responsive safety layer and / or in the water-responsive and pH-responsive safety layer, where it aids in the bridging dendrite moieties as they grow, thereby establishing an electronic connection between the battery poles, thereby facilitating shorting of the cell. Elemental metals may be used, including but not limited to bismuth(0) (Bi), copper(0) (Cu), iron(0) (Fe), indium(0) (In), lead(0) (Pb), magnesium(0) (Mg), mercury(0) (Hg), nickel(0) (Ni), silver(0) (Ag), tin(0) (Sn), zinc(0) (Zn), and alloys and combinations thereof. Additionally, the metal powder provides an ion source that can be oxidized by the positive electrode, thereby serving as a sacrificial material for dendrite growth. The metal powder can also simultaneously serve as a bridge and a sacrificial material for dendrite growth. Thus, in yet another embodiment, the composite water-responsive safety layer may include a polymeric material and a metal powder as described above, substantially free of metal salts therein.

[0030] The composite water-responsive safety layer may include one or more polymers, one or more metal salts, and optionally one or more metal powders. Any combination of metal salts and metal powders may be included in combination with one or more polymers to provide a composite water-responsive safety membrane. Any of the metal salts, polymers, and optional metal powders may be processed by various methods, including but not limited to ball milling, to reduce particle size. The combination of metal salts, polymers, and optional metal powders may be deposited to provide a safety polymer layer comprising metal salts, polymers, and optional metal powders.

[0031] In general, the combination of the polymer, one or more metal salts, and optional metal powder may include a solvent to facilitate processing. In general, the solvent need not be limited. Suitable solvents include, but are not limited to, aliphatic solvents, aromatic solvents, and isoparaffinic solvents. Specific examples include, but are not limited to, acetone, ethyl acetate, toluene, xylene, terpineol, n-methyl-2-pyrrolidone, hexane, pentane, and diglyme. Solvents can be used to provide the composite water-responsive safety layer using solvent casting methods such as spin casting. In addition, solvents can be used to deposit the composite water-responsive safety layer using inkjet printing deposition and various known jetting methods. Other deposition methods may be used, including, but not limited to, direct ink writing (where the composition is extruded from a nozzle and applied directly to the battery as described herein) and contact printing techniques such as flexography, gravure, and pad printing. Additionally, transfer printing, a technique may be used in which a composition for forming a composite water-responsive safety layer and / or a composite water-responsive and pH-responsive safety layer is deposited onto a substrate or backing and dried so that the composite water-responsive safety layer can be removed and applied directly to the battery surface (similar to applying a sticker). The same solvents and methods can be used to provide the composite water-responsive and pH-responsive safety layer.

[0032] The battery surface may be activated by any suitable surface activation technique, such as plasma treatment, including but not limited to argon or corona treatment, UV / ozone treatment, flame treatment, chemical treatment, including but not limited to acid or base treatment, etc. Such treatment prior to deposition may enhance adhesion of the composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer to the battery surface. Adhesion promoters, particularly silane adhesion promoters, have been found to enhance adhesion of the composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer to the battery surface, especially after the surface has been activated using UV / ozone treatment. Representative adhesion promoters include dialkoxysilanes such as diethoxydimethylsilane, diethoxy(methyl)vinylsilane; 1,3-diethoxy-1,1,3,3-tetramethyldisiloxane; dimethoxydimethylsilane; dimethoxydimethylsilane; dimethoxymethylvinylsilane; and methyldiethoxysilane; monoalkoxysilanes such as ethoxytrimethylsilane and methoxytrimethylsilane; trialkoxysilanes such as 3-aminopropyl)triethoxysilane ("APTES"); (chloromethyl)triethoxysilane; triethoxy(ethyl)silane; triethoxymethylsilane; triethoxymethylsilane; triethoxy Examples of silanes include, but are not limited to, vinyl silanes; trimethoxymethyl silane; trimethoxymethyl silane; vinyl trimethoxy silane; and vinyl trimethoxy silane; trihalosilanes such as tert-butyl trichlorosilane; di-n-octyl dichlorosilane; hexachlorodisilane; methyl trichlorosilane; methyl trichlorosilane; trichloro(dichloromethyl)silane; trichlorovinyl silane; bissilanes such as 1,2-bis(triethoxysilyl)ethane; 1,2-bis(trimethoxysilyl)ethane; 1,2-bis(trichlorosilyl)ethane; and bis(trichlorosilyl)methane; and combinations thereof.

[0033] The composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer may further comprise additives such as stabilizers, porogens, and / or pigments. Stabilizers may be used to maintain the rheology of the composition to prevent it from settling too quickly. Typical stabilizers include dispersants such as polyurethane-based and polyacrylic-based dispersants available under the trade names Efka® PU and Efka® PA (BASF Corporation), respectively, fumed metal oxide rheological additives including but not limited to fumed silica and fumed alumina rheological additives available under the trade names Aerosil® (Evonik) and CAB-O-SIL® (Cabot Corporation), and chelating agents such as sodium ethylenediaminetetraacetate. Of course, other metal oxide rheological additives may be used. Porogens may be used to promote wetting and promote adhesion. Exemplary porogens include, but are not limited to, ammonium chloride, ammonium carbonate, citric acid, water soluble sugars (e.g., glucose, sucrose, fructose, etc.), polyethylene glycol, sodium chloride, and sodium acetate. Pigments may be used to impart the desired aesthetic effect and may be selected from pigments, dyes, and combinations thereof.

[0034] The polymeric material may be present in an amount of 5% to 90% by weight, for example 10% to 85% by weight, based on the weight of the composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer. The metal salt may be present in an amount of 5% to 95% by weight, for example 10% to 90% by weight, based on the weight of the composite water-responsive safety layer. Similarly, the non-metal salt may be present in an amount of 5% to 95% by weight, for example 10% to 90% by weight, based on the weight of the composite water-responsive and pH-responsive safety layer. The metal powder, if present, may be present in an amount of 5% to 95% by weight, for example 10% to 90% by weight, based on the weight of the composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer. The adhesion promoter, if present, may be present in an amount of 0.1% to 5% by weight, for example 0.25% to 2.0% by weight, based on the weight of the composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer. The rheological additive, if present, may be present in an amount of 0.1% to 7.5% by weight, such as 0.25% to 5.0% by weight, based on the weight of the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer. The colorant, if present, may be present in an amount of 1% to 35% by weight, such as 2.5% to 30% by weight, based on the weight of the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer.

[0035] The composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer is disposed over the gap between the positive and negative electrodes and typically has a thickness of 30 μm to 1000 μm, e.g., 30 μm to 100 μm, 50 μm to 200 μm, 100 μm to 300 μm, 50 μm to 500 μm, and / or 100 μm to 1000 μm. Typically, the composite water-responsive safety layer and / or composite water-responsive and pH-responsive safety layer covers at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or nearly 100% of the circumference defined between the anode cup and the cathode can. Typically, the composite water-responsive layer and / or composite water-responsive and pH-responsive safety layer will contact both a portion of the anode cup and a portion of the cathode can, although contact with only one of the battery poles is generally sufficient, as described in more detail below. In embodiments, the composite water-responsive layer and / or composite water-responsive and pH-responsive safety layer has a width of 200 μm to 2000 μm (corresponding to the gap between the positive and negative electrodes in a coin cell).

[0036] 2A and 2B show a battery 50, which may be any type of primary or secondary battery, and in the illustrated example is a button cell type battery. The battery 50 includes a battery housing that encloses the battery, the housing including a cathode can 54 and an anode cup 58, the cathode can 54 containing the cathode 52 within the housing, the anode cup 58 containing the anode 56 within the housing, the cathode 52 and the anode 56 being electronically separated by a separator 60 within the cell 50. Each of the cathode can 54 and the anode cup 58 forms a different pole of the battery 50.

[0037] The cathode can 54 and anode cup 58 are separated by a separator 60 that extends across the lateral extent of the cathode 52, e.g., substantially the diameter of the battery 50. Electronically isolating the can 54 and cup 58, an insulating gasket 62 extends into the cathode can 54 to provide an insulating buffer surrounding the anode cup 58 that also seals the cell to prevent electrolyte loss.

[0038] As shown, the battery 50 further includes a composite water-responsive safety layer 64 that surrounds at least a portion of the insulating gasket 62, and that contacts both a portion of the anode cup 58 and a portion of the cathode can 54. The composite water-responsive safety layer 64 is an electronically shorting layer that changes from an electronically non-conductive state, which corresponds to a normal operating condition of the battery cell 10, to an electronically conductive state that is caused by exposing the cell to a safe state, typically saliva, gastric fluids, or other aqueous fluids. For example, the safe state may be exposure of the battery cell 50 to an aqueous solution in the form of saliva, gastric fluids, or other aqueous fluids when a person or infant swallows the battery cell 50. As described further herein, the composite water-responsive safety layer 64 changes from an electronically non-conductive state to an electronically conductive state upon contact with an aqueous solution, such as saliva or gastric fluids, water, or other aqueous fluids.

[0039] In a representative example, the composite water-responsive safety layer 64 is formed by combining polyethylene glycol (PEG), about 10% by weight zinc (Zn) particles (about 20 mesh size), and about 10% by weight copper sulfate (CuSO4) particles in a glass vial on a stir plate maintained at about 50° C., and then depositing the composition on or around at least a portion of the insulating gasket 62. By covering at least a portion of the insulating gasket 62 with a composition including a metal oxide component, a reducible sacrificial material is advantageously provided at the negative electrode such that, under safe conditions, when the battery cell 50 is swallowed, for example by a person or an infant, a dendritic metal structure grows to electrically connect the anode to the cathode, thereby exposing the battery cell 50 to aqueous solutions in the form of saliva, gastric juices, or other fluids, strategically shorting the button cell without significant electrolysis of water and the associated generation of hydroxide ions and burning of tissue. Although the composite water-responsive layer is shown in contact with both a portion of anode cup 58 and a portion of cathode can 54, contact with only one of the battery electrodes is typically sufficient, for example, since the device may include contact pads that serve to establish electronic contact between the dendrites of the composite water-responsive layer and the other battery electrode.

[0040] To evaluate the polymer matrix for use in the composite water-responsive safety layer according to the present disclosure, a two-lead test was conducted, as shown in FIG. 3. A 50 μL sample of the sample material composition was deposited between two zinc wires (approximately 200 μm apart). The composition will vary depending on the material to be tested. In the illustrated example, the composition comprised a polymer matrix containing polyethylene glycol (PEG), 10% by weight zinc particles (Zn powder), and 10% by weight copper sulfate, CuSO4 particles. The voltage source to the two zinc wires was set at 3V to simulate a CR2032 button cell lithium battery rated at 3.0 volts, and the current compliance was set at 30 mA (the maximum current of a CR2032 battery). A 200 μL aliquot of saliva substitute solution (specifically, 25% Ringer's solution) was deposited on the polymer matrix. The potential was monitored for up to 1 hour.

[0041] The results of several repeated tests on different CR2032 batteries, each with a composite water-responsive safety layer, are shown in Figure 4. Although each test was performed at a different start time, each test shows that the anode and cathode shorted together, reducing the effective battery voltage from 3V to less than 1V in just 90 seconds.

[0042] 5 shows another example of a battery cell 100 with a cathode can 102, an anode cup 104, and a polymer layer 106. To help inhibit the occurrence of hydrogen bubbling during metal dendrite growth, which may prevent successful metal dendrite growth when the cell is exposed to aqueous solutions, as disclosed herein, the exposed anode cup 104 was first plated with a Zn layer 108, after which a composite water-responsive safety layer 106 was formed, for example, by plating dots of zinc metal onto the anode cup 104, and then depositing thereon a composition comprising one or more polymeric materials and one or more metal salts, optionally in further combination with one or more metal powders. The Zn layer 108 locally increases the hydrogen overpotential, thereby advantageously inhibiting hydrogen bubbling at the specific locations where the zinc layer was deposited. Alternatively, other metal layers having significantly higher overpotentials of hydrogen evolution (compared to the hydrogen overpotential of the material of the negative electrode, typically Ni or stainless steel), including tin (Sn), indium (In), bismuth (Bi), lead (Pb), zinc (Zn), and mercury (Hg), alone or in combination, can be used to suppress hydrogen bubbling and promote the formation of a metal dendritic short circuit connection between the cathode can 102 and the anode cup 104.

[0043] A composition comprising acetone, dissolved or suspended polyethylene glycol (having a weight average molecular weight of 4000 g / mol), copper sulfate powder (15% dissolved or suspended solids by weight in the slurry), and zinc metal dust (15% dissolved or suspended solids by weight in the slurry) was heated to about 50° C. on a hot plate and mixed thoroughly with a Teflon coated magnetic stir bar. A sample (15 μL) of this composition was pipetted into a position around the clip edge 112 of the half of the battery 100 having the Zn layer 108.

[0044] Thus, the composite water-responsive safety layer 106 may be formed as a substantially continuous layer around the battery surface of the anode cup 104, particularly such that the composite water-responsive safety layer is disposed along and preferably in contact with the periphery of the anode cup 104 and along and preferably in contact with the periphery of the cathode can 102, or, more generally, may be disposed between the first and second (e.g., positive and negative) battery poles as shown through the top end of the battery cell 100. In other examples shown through the bottom of the battery cell 100, the composite water-responsive safety layer 106 need not be continuous, but rather may be periodically positioned (e.g., deposited, layered, etc.), for example, deposited as discrete dots 110 as shown in FIG.

[0045] Direct measurements of the voltage across the battery 100 when the battery was immersed in a 25% Ringer's solution were used to confirm external battery cell shorting. The results showed that metal dendrites had grown to cause cell shorting and helped reduce the voltage of the battery cell 100 to a non-threatening value of less than 1 V, as shown in FIG.

[0046] In the example shown in FIG. 7, the composite water-responsive safety layer comprises about 12.5 wt. % polyvinyl acetate (PVAc), about 4.16 wt. % polyethylene oxide (PEO), about 8.33 wt. % copper sulfate particles (CuSO4), and about 75 wt. % basic copper carbonate particles (CuCO3·Cu(OH)2, also known as malachite). Advantageously, as shown in FIG. 7, the cell voltage drops very quickly and efficiently upon contact with the aqueous solution. Although the voltage drop is only exhibited for 20 minutes, the voltage becomes lower as time passes. In addition, the cell having the composite water-responsive safety layer comprising the aforementioned mixture showed no change in cell voltage even after being exposed to 90% relative humidity for at least 2 hours.

[0047] In the example shown in FIG. 8, the composite water-responsive safety layer comprises about 16.75 wt.% polyvinyl acetate (PVAc), about 6.25 wt.% polyethylene oxide (PEO), about 12.5 wt.% copper sulfate particles (CuSO4), and about 62.5 wt.% basic copper carbonate particles (CuCO3·Cu(OH)2). Advantageously, as shown in FIG. 8, the voltage of the cell drops very quickly and efficiently upon contact with the aqueous solution. Although FIG. 8 only shows a voltage drop for 20 minutes, the voltage gets lower as time goes on. Consistently, as seen in the table below, after 2 hours, the voltage of the cell with the aforementioned safety layer was well below 1.2V, and the pH was relatively neutral, and therefore unable to burn tissue. [Table 1] In addition, cells having a composite water-responsive safety layer comprising the aforementioned mixture showed no change in cell voltage even after being exposed to 90% relative humidity for at least 2 hours.

[0048] In the example shown in FIG. 9, the composite water-responsive safety layer comprises about 16.67 wt. % polyvinyl acetate (PVAc 500K, a polyvinyl acetate having a weight average molecular weight of about 500,000), about 41.67 wt. % copper sulfate particles (CuSO4), and about 41.67 wt. % basic copper carbonate particles (CuCO3·Cu(OH)2). Generally, about 400 mg of polyvinyl acetate was dissolved in about 1 mL of xylene, to which about 1 g of ball-milled CuSO4 and 1 g of ball-milled CuCO3·Cu(OH)2 were added. The composition was loaded into a syringe, and the composition was allowed to equilibrate at room temperature before being deposited on the cell in the gap between the first and second battery poles. After deposition, the composition was allowed to dry in air (about 24 hours). Advantageously, as shown in FIG. 9, the voltage of the cell is very quickly and efficiently reduced upon contact with the aqueous solution. In fact, for these cells the voltage drops below 1.2V in less than 400 seconds.

[0049] In another embodiment, the composite water-responsive safety layer comprises about 22% by weight of PEG 6K (polyethylene glycol having a weight average molecular weight of about 6000), about 2% by weight of PMMA 75K (polymethyl methacrylate having a weight average molecular weight of about 75,000), about 38% by weight of zinc particles (Zn powder), and about 38% by weight of copper sulfate CuSO4 particles. Generally, the polymer components are dissolved in acetone, and the zinc particles and ball-milled CuSO4 are added thereto. The viscosity of the formulation is adjusted with terpineol. Using a nozzle tool, the formulation is deposited along and in contact with the periphery of the anode cup and along and in contact with the periphery of the cathode can, thereby forming a composite water-responsive safety layer in the gap between the first and second battery poles. Xylene is also used instead of acetone, and xylene is preferred for aerosol and microdispensing (such as inkjet printing) deposition.

[0050] In a further specific example, the composite water-responsive safety layer comprises about 17% by weight of PVAc 100K (polyvinyl acetate having a weight average molecular weight of about 100,000), about 41.5% by weight of zinc particles (Zn powder), and about 41.5% by weight of copper sulfate CuSO4 particles. Generally, the polymer is dissolved in xylene at about 60° C., and the zinc particles and ball-milled CuSO4 are added thereto. The formulation is deposited by aerosol printing using an airbrush. Masking is used to facilitate the deposition, thus forming a composite water-responsive safety layer in the gap between the first and second battery poles.

[0051] In a further specific example, the composite water-responsive safety layer comprises about 29% by weight of PVAc 100K (polyvinyl acetate having a weight average molecular weight of about 100,000) and about 71% by weight of copper sulfate CuSO4 particles. Generally, the polymer was dissolved in xylene at about 50° C., and ball-milled CuSO4 and a colorant, specifically phthalocyanine blue BN pigment, were added thereto. The formulation was deposited in the gap between the first and second battery poles by direct writing / extrusion using a nozzle tool.

[0052] In a further additional specific example, a composite water-responsive safety layer was prepared from an ink composition comprising about 1 g of PVAc 500K (polyvinyl acetate having a weight average molecular weight of about 500,000), about 2.5 g of copper sulfate CuSO4, particles, and about 2.5 g of basic copper carbonate particles (CuCO3·Cu(OH)2). Generally, polyvinyl acetate was dissolved in about 5 mL of xylene at about 70° C. and about 50 or about 100 mg of fumed silica rheological additive CAB-O-SIL-EH-5, after which ball-milled CuSO4 and CuCO3·Cu(OH)2 were added to form an ink formulation. The formulation was deposited in the gap between first and second battery poles by direct-write printing using a nozzle having a tip diameter of about 0.41 mm. The formulation with a higher concentration of fumed silica rheological additive showed higher resolution.

[0053] Further examples A-D were prepared according to Table 2. [Table 2]

[0054] All reagents can be used as received without further treatment or purification. However, to impart desirable rheological and anti-settling properties to the formulation, basic copper carbonate was first dispersed in a solvent (acetone) and then wet ball milled (Retsch Mixer Mill MM200, Retsch GmbH) for 2 hours to reduce the particle size to about 1-30 μm. After filtering the resulting slurry, the solids were placed in a container and dried (air or vacuum). Copper sulfate was dry ball milled for 30 minutes. Copper sulfate and (3-aminopropyl)triethoxysilane were stored in a desiccator until use.

[0055] In a 20 mL glass vial with a Teflon-coated magnetic micro-stir bar, 200 mg of PVAc (500 kD) was dissolved in 2 mL of toluene with continuous stirring on a magnetic stir plate for each of Examples A-D. When the PVAc was completely dissolved (up to 1 hour), basic copper carbonate (500 mg), copper sulfate (500 mg), colorants (200 mg carbon black, 100 mg super copper, 400 mg titan black in Examples A, B, and D, respectively; Example C did not contain any additional pigments), and Aerosil-200 (30 mg) were added and mixed for 5-10 minutes, thereby producing a uniformly dispersed slurry. When stored in a desiccator or other moisture-free environment, the mixtures were stable for at least one week. If precipitation occurs, vigorous stirring / mixing is sufficient to redisperse the solid components in the mixture.

[0056] The surfaces were cleaned and activated to enhance adhesion. The as-received cells were cleaned and activated using UV / ozone treatment for several minutes. Sufficient activation was confirmed when a drop of deionized water easily wets the activated surface with a contact angle of less than 10 degrees. The activated surface was coated (5-10 min) with the formulation mixed to resuspend all components as soon as possible after activation (within 1 hour for best results). APTES was added to the (otherwise complete) formulation shortly before deposition and the formulation was stirred for an additional 5 min. Typical deposition volumes were 10-15 μL, but not more than 20 μL. The formulation was deposited by extrusion using a nozzle tool or manually in the gap between the first and second battery poles.

[0057] Measurements performed using a rheometer showed that the coatings were able to withstand low shear (0.001s -1 It is a gel at a shear rate of >1,000,000 Pa s and at high shear (100 s -1 It was shown that it is a viscous liquid at a shear rate of 1,000 Pa·s.

[0058] The battery with the composite safety membrane according to Example A was evaluated for passivation performance and moisture resistance at 70% relative humidity (40°C). The composite water-responsive safety membrane preferably demonstrated no change in cell voltage even after exposure to 70% relative humidity for more than 16 days. Furthermore, the cell voltage decreased upon contact with aqueous solution, such that after 2 hours, the voltage of the cell with the aforementioned safety layer was well below 1.2V, in fact below 0.1V, and was pH neutral, thus unable to burn tissue.

[0059] Throughout this specification, multiple instances may implement components or structures that are described as a single instance. Structures and functionality provided as separate components in some configurations may be implemented as a combined structure or component. Similarly, structures and functionality provided as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements are within the scope of the subject matter herein.

[0060] As used herein, any reference to "one embodiment" or "one embodiment" means that a particular element, feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

[0061] As used herein, the terms "comprises," "comprising," "including," "including," "having," "having," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, element A or B may be satisfied by any one of the following: A is present and B is not present, A is not present and B is present, and both A and B are present.

[0062] Furthermore, the use of "a" or "an" is used to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the description. This description and the claims that follow should be read to include one or at least one, and the singular also includes the plural unless it is clear that it is meant otherwise.

[0063] The detailed description should be construed as an example and not as describing every possible embodiment, as it would be impractical, if not impossible, to describe every possible embodiment. Numerous alternative embodiments can be implemented using either current technology or technology developed after the filing date of this application.

Claims

1. A battery, a housing having a first pole and a second pole; a composite water-responsive safety layer comprising a polymeric material and positioned adjacent at least one of the first pole and the second pole, the composite water-responsive safety layer configured to short the battery to less than 1.5 V upon contact with an aqueous solution, the composite water-responsive safety layer further comprising at least one metal salt; Equipped with a battery.

2. 10. The battery of claim 1, wherein the polymeric material comprises one or more polymeric materials selected from one or more of the group: polyethylene glycol, polyethylene oxide, polyacrylic acid, polyacrylates, polyvinyl alcohol and modified polyvinyl alcohols, water soluble acrylate copolymers, polyvinyl esters, polyvinylpyrrolidone, pullulan, gelatin, hydroxypropyl methylcellulose (HPMC), low viscosity grades of hydroxypropyl cellulose, polysaccharides, water soluble natural polymers, modified starches, and copolymers of the foregoing.

3. 10. The battery of claim 1, wherein the polymeric material is a biologically inert material.

4. 10. The battery of claim 1, wherein the composite water-responsive safety layer further comprises a metal powder in an unoxidized state.

5. 5. The battery of claim 4, wherein the metal powder comprises one or more metal powders selected from the group consisting of bismuth(0) (Bi), copper(0) (Cu), iron(0) (Fe), indium(0) (In), lead(0) (Pb), nickel(0) (Ni), magnesium(0) (Mg), mercury(0) (Hg), silver(0) (Ag), tin(0) (Sn), zinc(0) (Zn), alloys thereof, and any combination thereof.

6. 10. The battery of claim 1, further comprising a metal layer in contact with an exterior surface of at least one of the poles.

7. 10. The battery of claim 1, wherein a metal layer contacts the second pole (corresponding to the battery's anode) and comprises a metal selected from the group consisting of bismuth(0) (Bi), indium(0) (In), lead(0) (Pb), mercury(0) (Hg), tin(0) (Sn), zinc(0) (Zn), alloys thereof, and any combination thereof.

8. The composite water-responsive safety layer includes one or more polymers selected from polyethylene glycol (PEG), polyvinyl acetate (PVAc), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), and any combination thereof, and the metal salt is copper sulfate (CuSO ４ 10. The battery of claim 1 comprising:

9. 10. The battery of claim 8, wherein the composite water-responsive safety layer further comprises zinc (Zn) particles.

10. 9. The battery of claim 8, wherein the copper sulfate is present in an amount of at least 5% by weight, based on the total weight of the composite water-responsive safety layer.

11. 10. The battery of claim 1, wherein the composite water-responsive safety layer further comprises an additive selected from one or more of the group: stabilizers and porogens.

12. 2. The battery of claim 1, wherein the first pole is electronically isolated from the second pole by an insulating gasket, the composite water-responsive safety layer is positioned adjacent to the insulating gasket, and the composite water-responsive safety layer extends between and contacts both the first pole (corresponding to a cathode of the battery) and the second pole (corresponding to an anode of the battery).

13. 13. The battery of claim 12, wherein the composite water-responsive safety layer extends continuously between the first pole and the second pole around a periphery of at least one of the first pole and the second pole.

14. The battery of claim 12, wherein the composite water-responsive safety layer extends between the first pole and the second pole and over a portion of the outer periphery of at least one of the first pole and the second pole.

15. 2. The battery of claim 1, wherein the battery is selected from an AAAA, an AAA battery, an AA battery, a B battery, a C battery, a D battery, a 9V battery, a CR2 battery, a CR123A battery, a 1 / 3N battery, a button cell, and a coin cell.

16. The battery of claim 1, wherein the at least one metal salt further comprises a first metal salt and a second metal salt.

17. 17. The battery of claim 16, wherein the second metal salt is water-insoluble and the first metal salt is water-soluble.

18. 1. A method comprising: Providing a battery housing having a first pole and a second pole; forming a composite water-responsive safety layer between the first pole and the second pole of the battery housing by depositing a composition between the poles such that the composition is located adjacent to at least one of the first pole and the second pole, the composition comprising a polymeric material and at least one metal salt, the composite water-responsive safety layer configured to short the battery to less than 1.5 V upon contact with an aqueous solution, the composite water-responsive safety layer being disposed on an exterior surface of the battery; A method comprising:

19. 20. The method of claim 18, wherein the polymeric material is selected from one or more of the group consisting of polyethylene glycol, polyethylene oxide, polyacrylic acid, polyacrylates, polyvinyl alcohol and modified polyvinyl alcohols, water soluble acrylate copolymers, polyvinyl esters, polyvinylpyrrolidone, pullulan, gelatin, hydroxypropyl methylcellulose (HPMC), low viscosity grades of hydroxypropyl cellulose, polysaccharides, water soluble natural polymers, modified starches, and copolymers of the foregoing.

20. 20. The method of claim 18, further comprising depositing at least one dot of zinc metal on the second pole prior to depositing the composition.

Images