Battery cell with safety layer

Abstract

To provide a water-responsive battery cell with a safety layer that can protect tissue from damage and / or electrolysis when the battery cell is exposed to aqueous solutions or moist tissue.SOLUTION: A battery 50 includes a housing having first and second poles, and a composite water-responsive safety layer 64 including a polymeric material and positioned adjacent to at least one of the first and second poles, the composite water-responsive safety layer is adapted 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 includes 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 Jun. 22, 2018, which is a continuation - in - part of U.S. Patent Application No. 15 / 677,921, filed Aug. 15, 2017, and these patent applications are hereby incorporated by reference in their entireties and form a part of this application.

[0002] Statement Regarding Federally Sponsored Research or Development This invention was made under CRADA (SC03 / 1672) between Procter & Gamble Company and Sandia National Laboratories and was operated for the U.S. Department of Energy. Duracell Company and its subsidiary Duracell U.S. Operations, Inc. are successors - in - interest to Procter & Gamble Company under 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 a water - responsive safety layer that can protect against tissue damage and / or electrolysis when the battery cell is exposed to an aqueous solution or wet tissue.

Background Art

[0004] The description of the background provided herein is generally intended to present the context of the present disclosure.

[0005] Electrochemical cells or batteries are generally used as electrical energy sources. Small batteries are particularly useful in powering consumer products. There are various cell types for small batteries. Common small battery cell types are AAA, AA, B, C, D, 9V, CR2, and CR123A. Another type of small battery known as a button cell (including a wide variety of cells sometimes called coin cells) is frequently used to power a variety of products including, but not limited to, wristwatches, cameras, calculators, keyless entry systems for vehicles, laser pointers, glucometers, etc. FIG. 1 shows the structure of a representative button cell 10 comprising a cathode 12 disposed within a cathode can 14 and an anode 16 disposed within an anode cup 18. A separator 20 physically separates the anode 16 from the cathode 12 and electrically insulates them. An insulating gasket 22 helps to seal the cell to prevent electrolyte loss and prevent the ingress of ambient air components into the cell, insulating the cathode can 14 from the anode cup 18. Button cells typically have a long service life, for example, generally far exceeding one year in continuous use in a wristwatch. Further, most button cells have low self-discharge and therefore hold their charge for a relatively long time when not under load.

[0006] Button cell batteries are common in many portable consumer electronics devices, but the size, shape, and appearance of these batteries, particularly coin cells with a diameter of 20 mm such as 2016 lithium cells and 2032 lithium cells, can pose a choking hazard to infants, young children, and pets. These hazards can cause physical harm, especially if the cell is swallowed without others around knowing. Also, some of these button cell batteries can pose a relatively greater risk than other cells, and consumers may not fully understand this risk. For example, coin cell batteries such as 2016 3V lithium cells and 2032 3V lithium cells based on the chemical reaction between lithium and manganese dioxide are sized such that they can easily clog a person's throat and thus may cause electrolysis of body fluids or combustion of esophageal / organ tissue if swallowed, for example.

Summary of the Invention

Problems to be Solved by the Invention

[0007] In one aspect, the present disclosure provides a battery comprising a housing having a first and a second pole, 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 being configured to change from an electronically non-conductive state to an electronically conductive state upon contact with an aqueous solution, and the composite water-responsive safety layer further comprising at least one metal salt.

[0008] In one improvement of the battery, 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 present disclosure provides a method comprising: providing a battery housing having first and second electrodes; and forming a composite water-responsive safety layer between the first and second electrodes of the battery housing by depositing a composition between the electrodes such that the composition is adjacent to at least one of the first and second electrodes, the composition comprising a polymeric material and at least one metal salt, the composite water-responsive safety layer being configured to change from an electronically non-conductive state to an electronically conductive 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] This specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the invention. However, the invention is better understood from the following description when read in conjunction with the accompanying drawings. The figures described below depict various aspects of the battery cells disclosed herein. It should be understood that each figure depicts a typical aspect of the battery cells disclosed herein.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0013] The electrochemical cell or battery may be a primary battery or a secondary battery. A primary battery is, for example, designed to be discharged only once until it is consumed and then discarded. Primary batteries are described, for example, in David Linden's Handbook of Batteries (McGraw-Hill, 4th edition, 2011). A secondary battery is designed to be charged. The secondary battery is discharged and then may be 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 David Linden's Handbook of Batteries (McGraw-Hill, 4th edition, 2011). The battery may contain a water-soluble or water-insoluble electrolyte. Thus, the battery may include various electrochemical bonds and combinations of electrolytes. A consumer battery may be either a primary battery or a secondary battery. However, due to the charge stored in the battery and the exposed electrodes, it is beneficial to protect the consumer, especially when a small consumer battery is exposed to wet tissue, so that the consumer is not harmed. In particular, it is beneficial to protect the battery so that the consumer is not exposed to electrolysis or burns, both of which can occur, for example, if the battery is ingested. When the positive and negative electrodes of the battery are exposed to wet body fluids, electrolysis of water occurs, resulting in the generation of hydroxide ions, which can cause combustion of the tissue, especially the 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 a battery cell with a composite water-responsive safety layer and / or a composite water-responsive and pH-responsive safety layer that incorporates within it a polymer containing a benign material at a safe level that can result in a short circuit electrochemically generated when wet, such as when the composite water-responsive safety layer is exposed to an aqueous solution in the form of saliva, gastric juice, or other fluid. The resulting short circuit reduces the voltage of the battery cell below a desired threshold level, thereby reducing and / or effectively preventing the electrolysis of water and the formation of associated harmful electrochemically generated ions (e.g., hydroxide ions). The desired threshold level can vary, but in some examples detailed herein, the cell can preferably be shorted to less than 1.5V, further to about 0V, including less than 1.4V, less than 1.3V, less than 1.2V, less than 1.1V, less than 1.0V, less than 0.9V, less than 0.8V, less than 0.7V, less than 0.6V, less than 0.5V, less than 0.4V, less than 0.3V, less than 0.2V, less than 0.1V. 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 battery cell performance under normal use conditions, and thus, for example, the 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 are provided to the battery. Although a battery incorporating a composite water-responsive safety layer and / or a composite water-responsive and pH-responsive safety layer is illustrated and described herein using a button cell, more particularly a coin cell, generally any battery type including, but not limited to, general consumer batteries such as AAAA, AAA, AA, B, C, D, 9V, CR2, CR123A, 1 / 3N, button cells, and coin cells may be modified to include the composite water-responsive safety and / or the composite water and pH-responsive safety layer according to the present disclosure. Generally, shorting the voltage of the battery cell to less than about 1.2V completely prevents the electrolysis of water, while reducing the voltage to less than 1.5V helps to reduce the amount of electrolysis that would otherwise occur.Thus, in a preferred embodiment, since it is not known until 2 hours later that significant burning of the esophageal tissue occurs, the voltage of the cell is reduced to less than 1.5 V, more preferably less than 1.2 V, within 2 hours (or 7200 seconds).

[0015] As used herein, the term "water-responsive" refers to a composite safety layer that does not transition from an electron non-conductive state to an electron conductive state when exposed to air. Instead, it is necessary for the composite safety layer to absorb a specific amount of moisture before transitioning from an electron non-conductive state to an electron conductive state. Thus, the composite water-responsive safety layer itself is hygroscopic. In particular, each component included in the composite water-responsive safety layer is generally not hygroscopic. In other words, the composite water-responsive safety layer generally includes a hygroscopic component and a non-hygroscopic component. As a result, the atmosphere should not cause the composite water-responsive safety layer to transition from an electron non-conductive state to an electron conductive state and thus should not cause a short circuit. However, the composite water-responsive safety layer may short circuit when exposed to a high humidity environment for an extended period of time. For example, a cell having the composite water-responsive safety layer described herein can preferably be 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, for example at about 30°C or at about 40°C). In addition, a cell having the composite water-responsive safety layer described herein can preferably be 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, for example 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 electron non-conductive state to an electron conductive state when exposed only to water. Specifically, the water-responsive and pH-responsive composite safety layer remains non-conductive when in contact with an aqueous solution having a first predetermined pH range and transitions from a non-conductive state to a conductive state in response to contact with a water-soluble fluid having a second different predetermined pH range.

[0017] In one embodiment, it remains non-conductive in an aqueous solution having a pH value close to acidic or neutral, and the composite water-responsive and pH-responsive safety layer exceeds 5.0, for example, 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 a composite water-responsive and pH-responsive positive composite safety layer that changes from a non-conductive state to a conductive state in response to contact with a water-soluble fluid having a pH above 12.0 is provided. Thus, the pH of saliva or body fluids changed as a result of the electrolysis of water can promote dendrite growth and the accompanying short-circuiting of the cell. As an example, the composite water-responsive and pH-responsive safety layer may comprise a polymer, such as polyvinyl acetate, a salt such as ammonium carbonate, and a metal powder, such as copper powder or zinc powder. When the composite water-responsive and pH-responsive safety layer is contacted with an alkaline medium such as saliva, ammonium carbonate may form ammonia and carbonate anions, and the metal powder may oxidize to form metal cations that can be reduced at the negative electrode of the battery, whereby a dendritic metal structure grows within the composite water-responsive safety layer and, under safe conditions, for example, when a person or child ingests a battery cell, can electronically connect the negative electrode to the positive electrode.

[0018] In other embodiments, it 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 contact with a water-soluble fluid having an alkaline pH greater than 7.0, e.g., from about 8.0 to about 12.0. A composite water-responsive and pH-responsive safety layer is provided. 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. When the composite water-responsive and pH-responsive safety layer is contacted with an alkaline medium such as saliva, ammonium chloride (NH4Cl) can dissolve in the vicinity of and within the safety layer. Hydroxide ions generated at the negative electrode due to the electrolysis of water deprotonate ammonium ions to form aqueous ammonia (NH3). The water-soluble / soluble ammonia reacts with the substantially insoluble metal salt copper carbonate to form soluble complex ions Cu(NH3)4 2+ that can be formed, whereby dendritic metal structures grow within the composite water-responsive and pH-responsive layer to electronically connect the negative electrode to the positive electrode under safe conditions, e.g., when a person or infant ingests 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 in 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 be made hygroscopic by metal salts 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 polyethylene oxide (PEO), polyacrylic acid (PAA) including but not limited to polymethylmethacrylic acid, polyamide (PA), polyacrylates including but not limited to polymethacrylates such as polymethylmethacrylate, polyvinyl alcohol and modified polyvinyl alcohol, acrylate copolymers, polyvinyl acetate, poly(vinyl butyrate), poly(vinyl propionate), and polyvinyl esters including but not limited to poly(vinyl formate), polyvinylpyrrolidone, pullulan, gelatin, hydroxypropylmethylcellulose (HPMC), low viscosity grade hydroxypropylcellulose, 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 poly(ethylene-vinyl acetate) and other polyvinyl ester copolymers, and copolymers of any of the foregoing including but not limited thereto. 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 not limited, but is generally 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. Since the metal salt provides a sacrificial material that is reducible at the negative electrode of the battery, a dendritic metal structure can grow within the composite water-responsive membrane and electronically connect the negative electrode to the positive electrode under safe conditions, for example when a person or child ingests the battery cell, whereby the battery cell is exposed to an aqueous solution in the form of saliva, gastric juice, or other fluids, and as a result, the cell shorts out strategically without significant electrolysis of water and the accompanying generation of hydroxide ions and combustion of tissue. Copper(II) (Cu +2 ), iron(II) (Fe +2 ), mercury(II) (Hg +2 ), nickel(II) (Ni +2 ), silver(I) (Ag + ), and transition metal cations such as the like, and zinc(II) (Zn +2 ), bismuth(III) (Bi +3 ), indium(III) (In +3 ), lead(II) (Pb +2 ), tin(II) (Sn +2) Suitable metal salts comprising cations including, but not limited to, other metal cations such as these and combinations thereof may also be used. Representative metal salts comprising anions including, but not limited to, acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, butyrate, camphorate, camphorsulfonate, carbonate, chloride, citrate, cyclopentanepropionate, digluconate, dihydrochloride, diphosphate, dodecyl sulfate, edetate, ethanesulfonate, fumarate, glucoheptonate, glucomate, glutamate, glycerophosphate, hemisulfate, heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, hydroxide, hydroxyethanesulfonate, hydroxynaphthoate, iodide, lactate, lactobionate, laurate, 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, subsalicylate, succinate, sulfate, tannate, tartrate, theophyllinate, thiocyanate, triethiodide, toluenesulfonate, undecanoate, valerate, and mixtures thereof may also 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, iron carbonate, iron chloride, iron 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, tin carbonate, tin chloride, tin sulfate, zinc carbonate, zinc chloride, zinc sulfate, their hydrates, their basic salts (hydroxide salts, oxide salts), and combinations thereof.In addition, non-metal salts such as ammonium carbonate ((NH4)2CO3) and ammonium chloride (NH4Cl) may be used in combination with metal salts. Further, other metal salts such as sodium chloride (NaCl) that do not provide a sacrificial substance reducible at the negative electrode of the battery but can support the transition from an electron non-conductive state to an electron conductive state by, for example, performing a function as a humectant and / or enhancing the conductivity of the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer may be included.

[0021] The term "copper carbonate" as used herein 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 qualification) as used herein refers to both (neutral) copper(II) carbonate (CuCO3) and basic copper carbonate (CuCO3·Cu(OH)2). Generally, this term is used herein to refer to basic copper carbonate, but it should be understood that both materials are intended when not further specified by indication of neutral or basic.

[0022] In one improvement, 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 the second metal salt, such as water-insoluble copper carbonate, is present in combination with a water-soluble salt such as copper sulfate, the cell preferably shows no change in cell voltage even after being exposed to a high relative humidity for a long period of time. As used herein, "water-soluble" refers to a solute having a solubility in water 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 (at about 25 °C and about pH 7). As an example, copper sulfate has a water solubility of about 220 g / L (at about 25 °C and about pH 7). On the other hand, "water-insoluble" refers to a solute having a solubility in water 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 (at about 25 °C and about pH 7). As an example, copper(II) carbonate has a solubility in water of about 1.46 mg / L (at about 25 °C and about pH 7), and basic copper carbonate has a solubility in water of about 4.68 mg / L (at about 25 °C and about pH 7). When a combination of a water-insoluble salt and a water-soluble salt is used, there may be a difference in water solubility of at least 10-fold, at least 100-fold, at least 1000-fold, and / or at least 10,000-fold between the water-insoluble salt and the water-soluble salt. For example, copper sulfate dissolves in water more than 10,000 times better than basic copper carbonate. In other examples, the ratio of water solubility between the water-insoluble salt and the water-soluble salt can be at least about 1:10 (e.g., at least about 1:100, 1:1000, 1:10000, or more).

[0023] Water solubility values for many salts can sometimes be found in the literature, but here they are determined 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 the flask method is used for substances with higher solubility (solubility greater than 10 mg / L).

[0024] In short, water solubility is determined in water at a relevant pH (e.g., a pH of about 5.5 to about 8.5 such as 7.0) and a 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, placed in a container, and weighed, and then, after an amount about 5 times the amount determined by a preliminary test is placed in the container and weighed, the indicated amount of water is added to the container (e.g., 1 L). When 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 should not contain undissolved particles) can be analytically determined by any useful methodology (such as 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 carrier (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. This method is based on eluting the test substance with water at a constant temperature from a column filled with a substance finely distributed on an inert support material. The flow rate of water should be adjusted so that the saturated solution exits the column. Saturation is achieved when the mass concentration - determined in an appropriate manner - is constant in the eluate at successive ratios of different flow rates. This is indicated by a horizontal region when the concentration is plotted against time or the elution volume. As described above, the mass concentration of the test substance dissolved in the aqueous solution can be analytically determined by any useful methodology (e.g., gas or liquid chromatography, titration, photometry, and / or voltammetry). Gas chromatography is preferred.

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

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

[0027] In an embodiment, 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 the composite water-responsive and pH-responsive safety layer may optionally further comprise a reducing agent. As used herein, the term "reducing agent" generally refers to an organic reducing agent, an inorganic reducing agent, or particles of a metal element or metal alloy in its fully reduced state. The reducing agent can reduce soluble metal ions to conductive elemental metal without the application of a cell potential even at a location far from the negative electrode (i.e., electroless deposition of metal occurs). The electroless deposition of metal results in the growth of cross-linked dendrite portions as they grow in the composite water-responsive safety film, establishing an electronic connection between the battery electrodes and thereby helping to promote short-circuiting of the cell. Thus, in one embodiment, the composite water-responsive safety layer may comprise 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 zinc and copper sulfate is prevented and the safety layer is non-conductive. When exposed to a water-soluble environment, as in the case of accidental ingestion, copper can dissolve to form copper ions, which are reduced by zinc metal to yield copper dendrites that grow and connect to adjacent dendrites, thereby providing a conductive path spanning the gap between the battery electrodes and resulting in short-circuiting of 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 their alloys and combinations.

[0029] The composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer may optionally further comprise metal powder. As used herein, the term "metal powder" generally refers to particles of a metal element or metal alloy in its fully reduced state. The metal particles may have a particle size of from about 0.1 μm to about 500 μm, such as from about 0.50 μm to about 100 μm, and / or from about 1 μm to about 50 μm. The metal powder can remain in a reduced form in the water-responsive safety layer and / or in the water-responsive and pH-responsive safety layer, where it helps the cross-linked dendrite portion as they grow, thereby establishing an electronic connection between the battery electrodes, and as a result, promoting short-circuiting of the cell. Elemental metals 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 their alloys and combinations may be used. Further, the metal powder can be oxidized by the positive electrode, thereby providing an ion source that can function as a sacrificial material for dendrite growth. Also, the metal powder can simultaneously function as a bridge for dendrite growth and as a sacrificial material. Thus, in yet another embodiment, the composite water-responsive safety layer may comprise the polymer material and the metal powder as described above, without substantially containing a metal salt 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 the metal salt and the metal powder may be included in combination with one or more polymers to provide a composite water-responsive safety film. Any of the metal salt, the polymer, and the optional metal powder may be treated by various methods including, but not limited to, ball milling to reduce the particle size. The combination of the metal salt, the polymer, and the optional metal powder may be deposited to provide a safety polymer layer comprising the metal salt, the polymer, and the optional metal powder.

[0031] Generally, a combination of a polymer, one or more metal salts, and optional metal powder may include a solvent to facilitate processing. Generally, the solvent need not be limited. Suitable solvents include, but are not limited to, aliphatic solvents, aromatic solvents, and isoparaffin solvents. Specific examples include, but are not limited to, acetone, ethyl acetate, toluene, xylene, terpineol, n-methyl-2-pyrrolidone, hexane, pentane, and diglyme. By utilizing a solvent, a composite water-responsive safety layer can be provided using a solvent casting method such as spin casting. Additionally, by utilizing a solvent, a composite water-responsive safety layer can be deposited 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 flexographic printing, gravure printing, and pad printing. Further, a transfer printing technique where a composite water-responsive safety layer and / or a composite water-responsive and pH-responsive safety layer is deposited and dried on a substrate or backing so that the composite water-responsive safety layer can be removed and applied directly to the battery surface (similar to applying a sticker) may be used. The same solvent and method can be used to provide a 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 treatment or base treatment, etc. Such pre-deposition treatments may enhance the adhesion of the composite water-responsive safety layer and / or the composite water-responsive and pH-responsive safety layer to the battery surface. Adhesion promoters, particularly silane adhesion promoters, have been found to enhance the adhesion of the composite water-responsive safety layer and / or the 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; triethoxyvinylsilane; trimethoxymethylsilane; trimethoxymethylsilane; vinyltrimethoxysilane; and vinyltrimethoxysilane; trihalosilanes such as tert-butyltrichlorosilane; di-n-octyldichlorosilane; hexachlorodisilane; methyltrichlorosilane; methyltrichlorosilane; trichloro(dichloromethyl)silane; trichlorovinylsilane; 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, but are not limited thereto.

[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 so that the composition does not settle rapidly. Typical stabilizers include dispersants such as polyurethane-based and polyacrylic-based dispersants available under the trade names Efka® PU and Efka® PA, respectively (BASF Corporation), fumed metal oxide rheology additives including, but not limited to, fumed silica and fumed alumina rheology 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 rheology additives may be used. Porogens may be used to promote wetting and adhesion. Typical porogens include, but are not limited to, ammonium chloride, ammonium carbonate, citric acid, water-soluble saccharides (e.g., glucose, sucrose, fructose, etc.), polyethylene glycol, sodium chloride, and sodium acetate. Pigments may be used to provide a desired aesthetic effect and may be selected from pigments, dyes, and combinations thereof.

[0034] The polymer material may be present in an amount of 5% to 90% by weight, such as 10% to 85% 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 metal salt may be present in an amount of 5% to 95% by weight, such as 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, such as 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, such as 10% to 90% 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 adhesion promoter, if present, may be present in an amount of 0.1% to 5% by weight, such as 0.25% to 2.0% 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 rheology 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 the composite water-responsive and pH-responsive safety layer is disposed over the gap between the positive electrode and the negative electrode and generally has a thickness of from 30 μm to 1000 μm, such as from 30 μm to 100 μm, from 50 μm to 200 μm, from 100 μm to 300 μm, from 50 μm to 500 μm, and / or from 100 μm to 1000 μm. Generally, the composite water-responsive safety layer and / or the 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 substantially 100% of the outer perimeter defined between the anode cup and the cathode can. Generally, the composite water-responsive layer and / or the composite water-responsive and pH-responsive safety layer contacts both a portion of the anode cup and a portion of the cathode can, but as will be described in more detail below, generally contact with only one of the battery electrodes is sufficient. In embodiments, the composite water-responsive layer and / or the composite water-responsive and pH-responsive safety layer has a width of from 200 μm to 2000 μm (corresponding to the gap between the positive and negative electrodes in a coin cell).

[0036] Figures 2A and 2B illustrate 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 surrounding the battery, the housing including a cathode can 54 and an anode cup 58, the cathode can 54 housing a cathode 52 within the housing, the anode cup 58 housing an anode 56 within the housing, and the cathode 52 and 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 the anode cup 58 are separated by a separator 60 that extends across the lateral extent of the cathode 52, e.g., substantially across the diameter of the battery 50. The can 54 and the cup 58 are electronically separated such that an insulating gasket 62 extends into the cathode can 54, thereby providing an insulating buffer that surrounds the anode cup 58 and 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 the composite water-responsive safety layer 64 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 electron short-circuit layer that changes from an electronically non-conductive state corresponding to the normal operating state of the battery cell 10 to an electronically conductive state that places the cell in a safe state, generally caused by exposure to saliva, gastric fluid, or other water-soluble fluids. For example, the safe state can be exposure of the battery cell 50 to an aqueous solution in the form of saliva, gastric fluid, or other water-soluble fluids when a person or child ingests the battery cell 50. As further described herein, the composite water-responsive safety layer 64 changes from an electronically non-conductive state to an electronically conductive state in response to contact with an aqueous solution, e.g., saliva or gastric fluid, water, or other water-soluble fluids.

[0039] In a representative example, the composite water-responsive safety layer 64 is formed by mixing polyethylene glycol (PEG), about 10 wt% zinc (Zn) particles (about 20 mesh size), and about 10 wt% copper sulfate (CuSO4) particles in a glass vial on a stirring 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 containing a metal oxide component, a reducible sacrificial material is advantageously provided at the negative electrode such that when a person or infant ingests the battery cell 50, a dendritic metal structure can grow and electrically connect the anode to the cathode under safe conditions, whereby the battery cell 50 is exposed to an aqueous solution in the form of saliva, gastric juice, or other fluid, and as a result, the button cell shorts out strategically without significant electrolysis of water and the accompanying production of hydroxide ions and combustion of tissue. The composite water-responsive layer is shown to contact both a portion of the anode cup 58 and a portion of the cathode can 54, but in general, contact with only one of the battery electrodes is sufficient since, for example, the device can include contact pads that help establish electrical 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 (about 200 μm apart) between two zinc wirings. The composition varies depending on the material to be tested. In the illustrated example, the composition comprised a polymer matrix containing polyethylene glycol (PEG), 10 wt% zinc particles (Zn powder), and 10 wt% copper sulfate, CuSO4 particles. To simulate a CR2032 button cell lithium battery rated at 3.0 volts, the voltage source to the two zinc wirings was set to 3 V and the current compliance was set to 30 mA (the maximum current of a CR2032 battery). A 200 μL aliquot of a 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 having a composite water-responsive safety layer, are shown in FIG. 4. Each test was run at a different start time, but each test showed that the anode and cathode short-circuited and reduced the effective battery voltage from 3V to less than 1V in just 90 seconds.

[0042] FIG. 5 shows another example of a battery cell 100 with a cathode can 102, an anode cup 104, and a polymer layer 106. As disclosed herein, to help suppress the generation of hydrogen bubbling during metal dendrite growth that can prevent good metal dendrite growth when the cell is exposed to an aqueous solution, the exposed anode cup 104 is first plated with a Zn layer 108 and then, for example, after plating dots of zinc metal on the anode cup 104, a composite water-responsive safety layer 106 is formed by optionally further combining and depositing one or more metal powders over a composition comprising one or more polymer materials and one or more metal salts thereover. The Zn layer 108 locally increases the hydrogen overvoltage, thereby advantageously suppressing hydrogen bubbling at the particular location where the zinc layer is deposited. Alternatively, other metal layers having a fairly high overvoltage for hydrogen evolution (compared to the hydrogen overvoltage of the negative electrode material, generally Ni or stainless steel) including tin (Sn), indium (In), bismuth (Bi), lead (Pb), zinc (Zn), and mercury (Hg) can be used alone or in combination to suppress hydrogen bubbling and promote the formation of a metal dendrite short-circuit connection between the cathode can 102 and the anode cup 104.

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

[0044] Accordingly, the composite water-responsive safety layer 106 may be formed as a substantially continuous layer around the battery surface of the anode cup 104 such that the composite water-responsive safety layer is preferably disposed in contact with and along the outer periphery of the anode cup 104 and preferably disposed in contact with and along the outer periphery of the cathode can 102, or more generally, may be disposed between the first and second (e.g., positive and negative) battery electrodes as shown through the upper end of the battery cell 100. In another example shown through the bottom of the battery cell 100, the composite water-responsive safety layer 106 need not be continuous, but rather may be positioned periodically (e.g., deposited, laminated, etc.), for example, deposited as discrete dots 110 as shown in FIG. 5.

[0045] Direct measurements of the voltage across the battery 100 when the battery was immersed in a 25% aqueous Ringer's solution were used to confirm a short circuit of the external battery cell. The results showed that, as shown in FIG. 6, metal dendrites grew such that a cell short circuit occurred and served to reduce the voltage of the battery cell 100 to a non-threatening value of less than 1 V.

[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). Preferably, as shown in FIG. 7, the voltage of the cell drops very rapidly and efficiently upon contact with an aqueous solution. The voltage drop is shown for only 20 minutes, but the voltage becomes even lower as time passes. In addition, a cell 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.

[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). Preferably, as shown in FIG. 8, the voltage of the cell drops very rapidly and efficiently upon contact with an aqueous solution. In FIG. 8, the voltage drop is shown for only 20 minutes, but the voltage becomes even lower as time passes. Consistent therewith, as seen in the table below, after 2 hours, the voltage of the cell with the aforementioned safety layer was well below 1.2 V, and the pH was relatively neutral and thus could not burn the tissue.

Table 1

[0048] In the example shown in FIG. 9, the composite water-responsive safety layer comprises about 16.67 wt% polyvinyl acetate (PVAc 500K, 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 is dissolved in about 1 mL of xylene, and thereto about 1 g of ball-milled CuSO4 and 1 g of ball-milled CuCO3·Cu(OH)2 are added. The composition is filled into a syringe, and after the composition is allowed to equilibrate at room temperature, it is deposited onto the cell in the gap between the first and second battery electrodes. After deposition, the composition is allowed to dry in air (about 24 hours). Preferably, as shown in FIG. 9, the voltage of the cell decreases very rapidly and efficiently when contacted with an aqueous solution. In fact, in these cells, the voltage drops below 1.2 V in less than 400 seconds.

[0049] In other specific examples, the composite water-responsive safety layer comprises about 22 wt% PEG 6K (polyethylene glycol having a weight average molecular weight of about 6,000), about 2 wt% PMMA 75K (polymethyl methacrylate having a weight average molecular weight of about 75,000), about 38 wt% zinc particles (Zn powder), and about 38 wt% copper sulfate CuSO4 particles. Generally, the polymer components are dissolved in acetone, and thereto zinc particles and ball-milled CuSO4 are added. The viscosity of the formulation is adjusted with terpineol. Using a nozzle tool, the formulation is deposited in contact with the outer periphery of the anode cup along the outer periphery of the anode cup and in contact with the outer periphery of the cathode can along the outer periphery of the cathode can, thereby forming a composite water-responsive safety layer in the gap between the first and second battery electrodes. Also, xylene is 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 wt% PVAc 100K (polyvinyl acetate having a weight average molecular weight of about 100,000), about 41.5 wt% zinc particles (Zn powder), and about 41.5 wt% copper sulfate CuSO4 particles. Generally, the polymer is dissolved in xylene at about 60 °C, and to it are added zinc particles and ball-milled CuSO4. The formulation was deposited by aerosol printing using an airbrush. Masking was used to facilitate deposition, and thus a composite water-responsive safety layer was formed in the gap between the first and second battery electrodes.

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

[0052] In a further additional specific example, the 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 is dissolved at about 70 °C in about 5 mL of xylene and about 50 or about 100 mg of fumed silica rheology additive CAB-O-SIL-EH-5, and then ball-milled CuSO4 and CuCO3·Cu(OH)2 are added to form the ink formulation. The formulation was deposited in the gap between the first and second battery electrodes by direct writing printing using a nozzle having a tip diameter of about 0.41 mm. Formulations with higher concentrations of fumed silica rheology additive showed higher resolution.

[0053] Additional 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 for 2 hours (Retsch Mixer Mill MM200, Retsch GmbH) to reduce the particle size to about 1 - 30 μm. After filtering the resulting slurry, the solid was 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 (in each of Examples A, B, D, 200 mg carbon black, 100 mg super copper, 400 mg titanium black, Example C contains no 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 mixture showed stability for at least 1 week. If precipitation occurred, vigorous stirring / mixing was sufficient to redisperse the solid components in the mixture.

[0056] The surface was cleaned and activated to enhance adhesion. As-received cells were cleaned and activated using UV / ozone treatment for several minutes. Sufficient activation was confirmed when a drop of deionized water readily wetted the activated surface and had a contact angle of less than 10 degrees. The activated surface was coated (for 5 - 10 minutes) with the formulated mixture re-suspended with all components as soon as possible after activation (within 1 hour for best results). APTES was added to the formulated mixture shortly before deposition (otherwise complete). The formulated mixture was further stirred for 5 minutes. Typical deposition amounts were 10 - 15 μL and were 20 μL or less. The formulated mixture was deposited manually or by extrusion using a nozzle tool in the gap between the first and second battery electrodes.

[0057] Measurements made using a rheometer showed that the coating was a gel at low shear (shear rate of 0.001 s -1 −1>1,000,000 Pa·s) and a viscous liquid at high shear (shear rate of 100 s -1 −1>1,000 Pa·s).

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

[0059] Throughout this specification, multiple instances may implement components or structures described as a single instance. In some example configurations, structures and functions provided as separate components may be implemented as a combined structure or component. Similarly, structures and functions 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] Any reference in this specification to "one embodiment" or "an embodiment" means that a particular element, feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Appearances of the phrase "in one embodiment" in various places in this specification are not necessarily all referring to the same embodiment.

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

[0062] Furthermore, the use of "a" or "an" is employed 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 following claims should be read to include one or at least one, and the singular also includes the plural unless it is obvious that it means something else.

[0063] Although it is not impossible to describe all possible embodiments, it is not practical, so the detailed description should be construed as an example and is not intended to describe all possible embodiments. Using either the current technology or technology developed after the filing date of this application, a number of alternative embodiments can be implemented.

Claims

1. A battery, comprising: A housing having a first electrode and a second electrode; A composite water-responsive safety layer comprising a polymeric material and positioned adjacent to at least one of the first electrode and the second electrode, wherein the composite water-responsive safety layer changes from an electronically non-conductive state to an electronically conductive state upon contact with an aqueous solution, and the composite water-responsive safety layer further comprises at least one metal salt; Comprising The battery, wherein the composite water-responsive safety layer is arranged to be exposed to the aqueous solution upon contact with the aqueous solution.

2. The battery according to claim 1, wherein the polymeric material comprises polyethylene glycol, polyethylene oxide, polyacrylic acid, polyacrylate, polyvinyl alcohol and modified polyvinyl alcohol, water-soluble acrylate copolymer, polyvinyl ester, polyvinyl pyrrolidone, pullulan, gelatin, hydroxypropyl methylcellulose (HPMC), low-viscosity grade hydroxypropyl cellulose, polysaccharides, water-soluble natural polymers, modified starch, copolymers of the foregoing, or combinations of the foregoing.

3. The battery according to claim 1, wherein the polymeric material is a biologically inert material.

4. The battery according to claim 1, wherein the composite water-responsive safety layer further comprises unoxidized metal powder.

5. The battery according to 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. The battery according to claim 1, further having a metal layer in contact with an outer surface of at least one of the electrodes.

7. A battery according to claim 1, wherein a metal layer contacts the negative electrode (corresponding to the anode of the battery) and contains 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 contains a polymer selected from polyethylene glycol (PEG), polyvinyl acetate (PVAc), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), and any combination thereof, and the metal salt contains copper sulfate (CuSO ４ ), the battery according to claim 1.

9. A battery according to claim 8, wherein the composite water-responsive safety layer further has zinc (Zn) particles.

10. A battery according to 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. A battery according to claim 1, wherein the positive electrode is electronically separated from the negative electrode 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 the positive electrode (corresponding to the cathode of the battery) and the negative electrode (corresponding to the anode of the battery) and contacts both the positive electrode and the negative electrode.

12. A battery according to claim 11, wherein the composite water-responsive safety layer continuously extends across at least one outer periphery of the positive electrode and the negative electrode between the positive electrode and the negative electrode.

13. A battery according to claim 11, wherein the safety layer extends across a part of at least one outer periphery of the positive electrode and the negative electrode between the positive electrode and the negative electrode.

14. A battery according to claim 1, selected from AAA, AAA battery, AA battery, B battery, C battery, D battery, 9V battery, CR2 battery, CR123A battery, 1 / 3N battery, button cell, and coin cell.

15. The metal salt is Cu +2 , Fe +2 , Hg +2 , Ni +2 , Ag + , Zn +2 , Bi +3 , In +3 , Pb +2 , and Sn +2 The battery according to claim 1, comprising one or more cations selected from the group of

16. The metal salt is selected from the group consisting of acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, butyrate, camphorate, camphorsulfonate, carbonate, chloride, citrate, cyclopentanepropionate, digluconate, dihydrochloride, diphosphate, dodecyl sulfate, edetate, ethanesulfonate, fumarate, glucoheptonate, glucamate, glutamate, glycerophosphate, hemisulfate, heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, hydroxide, hydroxyethanesulfonate, hydroxynaphthoate, iodide, lactate, lactobionate, laurate, 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, subsalicylate, succinate, sulfate, tannate, tartrate, theophyllinate, thiocyanate, triethiodide, toluenesulfonate, undecanoate, and valerate, and the battery according to claim 1 containing one or more anions selected from the group.

17. The metal salt is selected from the group consisting of bismuth carbonate, bismuth chloride, bismuth sulfate, bismuth nitrate, bismuth subsalicylate, bismuth oxide, copper carbonate, copper chloride, copper sulfate, copper oxalate, copper hydroxide, iron carbonate, iron chloride, iron 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, tin carbonate, tin chloride, tin sulfate, zinc carbonate, zinc chloride, zinc sulfate, their hydrates, and their basic salts, and the battery according to claim 1 containing one or more metal salts selected from the group.

18. A method comprising: preparing a battery housing having a first electrode and a second electrode; A step of forming a composite water-responsive safety layer between the first electrode and the second electrode of the battery housing by depositing a composition between the electrodes such that the composition is located adjacent to at least one of the first electrode and the second electrode, wherein the composition comprises a polymer material and at least one metal salt, and the composite water-responsive safety layer is configured to change from an electronically non-conductive state to an electronically conductive state upon contact with an aqueous solution, and the composite water-responsive safety layer is arranged to be exposed to the aqueous solution upon contact with the aqueous solution. A method comprising the above. **Claim 19** The method according to claim 18, wherein the polymer material comprises polyethylene glycol, polyethylene oxide, polyacrylic acid, polyacrylate, polyvinyl alcohol and modified polyvinyl alcohol, water-soluble acrylate copolymer, polyvinylpyrrolidone, polyvinyl ester, pullulan, gelatin, hydroxypropylmethylcellulose (HPMC), low-viscosity grade hydroxypropylcellulose, polysaccharide, water-soluble natural polymer, modified starch, copolymer of the foregoing, or a combination of the foregoing. **Claim 20** The metal salt is Cu +2 , Fe +2 , Hg +2 , Ni +2 , Ag + , Zn +2 , Bi +3 , In +3 , Pb +2 , and Sn +2 The method according to claim 18, comprising one or more cations selected from the group of **Claim 21** The metal salt includes one or more anions selected from the group consisting of acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, butyrate, camphorate, camphorsulfonate, carbonate, chloride, citrate, cyclopentanepropionate, digluconate, dihydrochloride, diphosphate, dodecyl sulfate, edetate, ethanesulfonate, fumarate, glucoheptonate, glucomate, glutamate, glycerophosphate, hemisulfate, heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, hydroxide, hydroxyethanesulfonate, hydroxynaphthoate, iodide, lactate, lactobionate, laurate, 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, subsalicylate, succinate, sulfate, tannate, tartrate, theophyllinate, thiocyanate, triethiodide, toluenesulfonate, undecanoate, and valerate, according to the method described in claim 18.

22. The metal salt includes one or more metal salts selected from the group consisting of bismuth carbonate, bismuth chloride, bismuth sulfate, bismuth nitrate, bismuth subsalicylate, bismuth oxide, copper carbonate, copper chloride, copper sulfate, copper oxalate, copper hydroxide, iron carbonate, iron chloride, iron 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, tin carbonate, tin chloride, tin sulfate, zinc carbonate, zinc chloride, zinc sulfate, their hydrates, and their basic salts, according to the method described in claim 18.

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