Battery cell with safety layer

Abstract

A battery cell is provided that includes a composite water-responsive safety layer and / or a composite water- and pH-responsive safety layer to prevent bodily tissue damage and / or electrolysis when the battery cell is exposed to an aqueous solution or bodily tissue.

Description

Technical Field

[0001] This disclosure relates to battery packs, and more specifically, to battery packs having a water-responsive safety layer that dissolves rapidly, thereby advantageously releasing an antagonist substantially immediately upon contact with an aqueous solution (e.g., when the battery pack is exposed to an aqueous solution or body tissue). Background Technology

[0002] Electrochemical batteries or battery packs are generally used as electrical energy sources. Small battery packs are particularly suitable for powering consumer products. Small battery packs come in various battery types. Common small battery pack battery types are AAAA, AAA, AA, B, C, D, 9V, CR2, and CR123A. Other types of small battery packs, known as button batteries (and also including wider batteries 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, blood glucose meters, etc.

[0003] Figure 1 The diagram illustrates the construction of a representative button cell battery 10 in the prior art. The button cell battery includes a cathode 12 and an anode 16, respectively disposed within a housing. The housing includes a cathode cup 14 corresponding to the positive terminal and an anode cap 18 corresponding to the negative terminal. A separator 20 physically separates and electrically insulates the anode 16 from the cathode 12. An insulating gasket 22 seals the battery to prevent electrolyte loss, prevents ambient atmospheric components from entering the battery, and electrically insulates the cathode cup 14 from the anode cap 18. Button cells typically have a long lifespan; for example, continuous use in a wristwatch usually exceeds one year. Furthermore, most button cells have low self-discharge, allowing them to retain charge for a relatively long time when not under load.

[0004] While button cell battery packs are common in many portable consumer electronics devices, the size, shape, and appearance of these packs, especially "coin batteries" such as the 2016, 2025, and 2032 lithium batteries characterized by a 20 mm diameter, can pose a swallowing hazard. These hazards can lead to bodily injury, particularly if the button cell battery pack is swallowed without the knowledge of others nearby. Furthermore, some of these button cell battery packs may pose a relatively greater risk than others. For example, coin battery packs based on lithium-manganese dioxide chemistry (such as the 2016 3V, 2025 3V, and 2032 3V lithium batteries) are designed to be sized so that they can become lodged in the throat, especially in the relatively small throats of young children, infants, or pets. Due to the charge stored in the battery pack and due to the exposed electrodes, such as in the case of swallowing, the battery pack can cause electrolysis of bodily fluids and / or burns to the esophagus and / or other body tissues.

[0005] Therefore, there is a desire to provide features that prevent infants, toddlers, and pets from swallowing consumer battery packs (especially relatively small battery packs designed to be sized so that, for example, they could get stuck in the throat if swallowed and cause electrolysis of bodily fluids and / or burns to the esophagus / body tissues). One innovation that helps maintain individual safety involves incorporating a bitter coating on coin battery packs (see, for example, "CR2032 Lithium Coin Battery with Bitter Coating," DURACELL USOperations Inc.). With commercialization, the bitter coating has been deposited as a water-soluble polymer ring on the cathode cup or anode cap and enhances child safety by preventing swallowing. While existing solutions involving a bitter coating as a water-soluble polymer ring on the cathode cup or anode cap of a coin cell battery pack are effective for delivering the irritant essentially immediately upon introduction of the battery pack into an aqueous fluid (such as saliva), these solutions can cause interference between the device contacts and the battery terminals corresponding to the cathode cup or anode cap, respectively (depending on the location of the bitter coating), thus hindering current flow and limiting the effectiveness of these solutions. Such interference is even more problematic in devices with cavities designed to accept two or more stacked lithium button cells (especially coin cells). Summary of the Invention

[0006] In one aspect, this disclosure provides a battery pack comprising a housing including a cathode cup corresponding to a positive battery terminal and an anode cap corresponding to a negative battery terminal; a cathode and an anode disposed within the housing; an insulating gasket disposed between the cathode cup and the anode cap, the insulating gasket sealing the housing and electrically insulating the cathode cup from the anode cap; and a water-responsive safety feature comprising a polymer blend and an antagonist, the polymer blend comprising a first polyvinylpyrrolidone and a polymer comprising an alkyl acrylate monomer, wherein the first polyvinylpyrrolidone has high water solubility.

[0007] In another aspect, this disclosure provides a battery pack comprising a housing including a cathode cup corresponding to a positive battery terminal and an anode cap corresponding to a negative battery terminal; a cathode and an anode disposed within the housing; an insulating gasket disposed between the cathode cup and the anode cap, the insulating gasket sealing the housing and electrically insulating the cathode cup from the anode cap; and a water-responsive safety feature comprising a polymer blend and an antagonist, the polymer blend comprising a first water-soluble polymer having high water solubility, a hydrolyzed stable polymer, and the antagonist. Attached Figure Description

[0008] Although this specification concludes by specifically pointing out and explicitly claiming protection for the claims that are regarded as forming the subject matter of the invention, the invention will be better understood from the following description taken in conjunction with the accompanying drawings.

[0009] Figure 1 The illustration depicts a conventional button cell battery in the prior art; and

[0010] Figure 2A and 2B An exemplary battery pack in the form of a coin cell according to the present disclosure is illustrated, which has a water-responsive safety feature comprising a polymer blend and an antagonist disposed in the gap between the positive and negative battery terminals. Detailed Implementation

[0011] This disclosure advantageously provides a battery pack with a water-responsive safety feature that dissolves rapidly enough to advantageously release an aversive agent substantially immediately upon contact with an aqueous solution (e.g., saliva or other fluid), thus preventing swallowing by quickly alerting an individual (e.g., an infant, toddler, or pet) to the presence of an unwanted object in their mouth and promoting spitting out the battery pack. Furthermore, this disclosure provides such a water-responsive safety feature in a specific location within the battery pack, which advantageously does not impede conductivity between any device contacts and any battery terminals, even when the battery pack consists of button cells arranged in a stacked configuration.

[0012] However, specific locations between the positive and negative terminals on a battery pack present significant, interrelated environmental, mechanical, and electrical stability challenges. More specifically, this disclosure provides a water-responsive safety feature comprising a polymer blend and an antagonist in a “gap” corresponding to the positive and negative terminals of a battery pack (e.g., between the cathode cup and anode cap of a coin cell (especially a coin cell) battery pack). In other battery pack forms (e.g., cylindrical alkaline battery packs), the water-responsive safety feature may be located in the gap between the positive terminal corresponding to the battery pack can and the negative terminal corresponding to the battery pack end cap (e.g., an insulating gasket separates the cap from the can when the cap is received by the can, similar to how the anode cap is received by the cathode cup in the coin cell construction shown in the figures). The gap between the positive and negative terminals of the battery pack can be a highly reactive space because it is affected by the battery potential of the battery pack (which may be greater than 3V for a conventional lithium coin cell). Therefore, placing a water-responsive safety feature in this location presents significant challenges, as the coating must be sufficiently environmentally, electrically, and mechanically stable, while also being sufficiently dissolvable to provide substantially immediate release of an antagonist upon contact with aqueous solutions (such as saliva or other aqueous fluids), as described above. Intentionally positioning the water-responsive safety feature according to this disclosure in this challenging reactive space between the positive and negative terminals of the battery pack advantageously avoids interference between the device contacts and the battery terminals. However, due to the high potential, the material placed in this reactive location is highly susceptible to corrosion and even short circuits in the battery pack, and these problems are exacerbated by the hygroscopic nature of the materials involved in providing the water-responsive safety feature, as these materials must be water-soluble.

[0013] To address these environmental, electrical, and mechanical challenges, the battery pack according to this disclosure advantageously includes a water-responsive safety feature comprising a polymer blend and an antagonist in the gap between the positive and negative terminals of the battery pack. The polymer blend comprises a first water-soluble polymer (also referred to as a highly water-soluble polymer) with high water solubility and a hydrolysis-stabilized polymer. For example, to address these environmental, electrical, and mechanical challenges, the battery pack according to this disclosure may advantageously include a water-responsive safety feature comprising a polymer blend and an antagonist in the gap between the positive and negative electrodes. The polymer blend comprises a first polyvinylpyrrolidone and a polymer comprising an alkyl acrylate monomer, wherein the first polyvinylpyrrolidone has high water solubility. Surprisingly, despite being made of water-soluble materials, the water-responsive safety feature comprising the polymer blend and the antagonist can exhibit enhanced corrosion resistance and short-circuit resistance while maintaining sufficient structural integrity (e.g., adhesion, edge sharpness, minimal delamination observed under accelerated aging conditions) and sufficient dissolution to allow it to advantageously release the antagonist substantially immediately upon contact with aqueous solutions (e.g., saliva or other fluids). Furthermore, as described in the examples, despite being made of water-soluble materials, the aforementioned water-responsive safety feature, which is incorporated as a substantially continuous concentric coating that essentially covers the insulating gasket and extends between the terminals, also unexpectedly and significantly increases the resistance to leakage (compared to batteries without the water-responsive safety feature).

[0014] As used herein, the term "water-responsive" refers to a safety feature that is sufficiently soluble to advantageously release the anatacritic contained therein substantially immediately upon contact with an aqueous solution (e.g., saliva or other fluid). In embodiments, upon immersion in an aqueous solution, the safety feature releases greater than about 20 wt.%, greater than about 25 wt.%, and / or greater than about 30 wt.% of the anatacritic contained therein within 5 seconds.

[0015] As used herein, “high water solubility” means that a given polymer, material, or other substance has a solubility in water at about 20°C greater than about 100 g / L, for example, greater than about 250 g / L, greater than about 500 g / L, and / or greater than about 1000 g / L. Generally, water solubility can be determined by accurately measuring 100 mL of water, adding the material in small, repeated additions until saturation (i.e., no more can be dissolved), filtering the mixture to remove any undissolved solids, and evaporating the water to determine the weight of the dissolved solute, and thus determining the solubility of the given material in 100 mL. Water solubility values ​​for polymers are sometimes found in the literature, but in this document, they can also be determined using the “flask method” or the “column elution method.” As described in the OECD Guideline for the Testing of Chemicals, "Test 105: Water Solubility" (page 7), adopted by the OECD on 27 July 1995 (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 high solubility (solubility greater than 10 mg / L).

[0016] In simple terms, water solubility can be determined in water at a relevant temperature. In the flask method, the test substance is first ground and weighed into a container, such that approximately five times the amount determined by preliminary testing is weighed into the container, and then an indicated amount of water (e.g., 1 L) is added to the container. 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 must be free of undissolved particles) can be determined by analysis using any useful method (e.g., 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 and an inert support (e.g., beads, silica, sand, etc.) is eluted with water, and the mass concentration of the substance in the eluent is determined when the concentration of the eluent is constant. This method is based on eluting the test substance from a column packed with a substance finely distributed on an inert support material using water at a constant temperature. The water flow rate should be adjusted so that the saturated solution exits the column. Saturation is achieved when the mass concentration, determined by a suitable method, remains constant in continuous eluent fractions at varying flow rates. This is indicated by a plateau period when the concentration is plotted against time or elution volume. As noted above, the mass concentration of the test substance dissolved in the aqueous solution can be determined by analysis using any useful method, such as gas or liquid chromatography, titration, photometry, and / or voltammetry. Gas chromatography is preferred.

[0017] A first water-soluble polymer with high water solubility effectively acts as the primary delivery medium for the anaerobic agent contained within the water-responsive safety feature. Generally, the highly water-soluble polymer is selected from one or more of the group consisting of polyethylene glycol, polyacrylic acid, polyamide, polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, hydroxypropyl cellulose, and copolymers comprising monomer units of one or more of the aforementioned polymers. More typically, the highly water-soluble polymer includes polyvinylpyrrolidone polymers. Therefore, the (first) polyvinylpyrrolidone polymer can be provided as a highly water-soluble polymer in polymer blends.

[0018] It has been found that the degree of polymerization of highly water-soluble polymers is an important characteristic regarding their substantially immediate dissolution upon contact with aqueous solutions (such as saliva or gastric juice). Highly water-soluble polymers with a degree of polymerization between about 60 and about 100, for example between about 70 and about 90, exhibit good solubility substantially immediately upon contact with saliva, gastric juice, or other aqueous fluids, and thus may help facilitate the substantially immediate release and delivery of aversive agents to, for example, an individual's mouth.

[0019] Highly water-soluble polymers typically have a number-average molecular weight between about 500 g / mol and about 65,000 g / mol, for example between about 1,000 g / mol and about 60,000 g / mol, between about 1,500 g / mol and about 55,000 g / mol, between about 2,000 g / mol and about 50,000 g / mol, between about 2,500 g / mol and about 45,000 g / mol, between about 3,000 g / mol and about 40,000 g / mol, between about 4,000 g / mol and about 35,000 g / mol, between about 5,000 g / mol and about 30,000 g / mol, and / or between about 5,500 g / mol and about 15,000 g / mol, for example, about 9,000 g / mol. Generally, in this article, molecular weight refers to the number-average molecular weight determined by gel permeation / size exclusion chromatography and a light scattering (LS) detector. As mentioned above, (first) polyvinylpyrrolidone polymers can be provided as highly water-soluble polymers in polymer blends. Therefore, the first polyvinylpyrrolidone may have a number-average molecular weight between about 500 g / mol and about 65,000 g / mol, for example between about 1,000 g / mol and about 60,000 g / mol, between about 1,500 g / mol and about 55,000 g / mol, between about 2,000 g / mol and about 50,000 g / mol, between about 2,500 g / mol and about 45,000 g / mol, between about 3,000 g / mol and about 40,000 g / mol, between about 4,000 g / mol and about 35,000 g / mol, between about 5,000 g / mol and about 30,000 g / mol, and / or between about 5,500 g / mol and about 15,000 g / mol, for example, about 9,000 g / mol. Providing highly water-soluble polymers with molecular weights within the aforementioned range is important for achieving adequate dissolution to provide substantially immediate release of the antagonist upon contact with aqueous solutions, thus ensuring water-responsive safety. Suitable highly water-soluble polymers include LUVITEC. ® Trademarks (e.g., LUVITEC) ® K 17 and LUVITEC ® K30 (BASF) sells polyvinylpyrrolidone polymers under the name SOKALAN. ® Trademark (specifically SOKALAN) ® K 17 P and SOKALAN ®Polyvinylpyrrolidone polymers sold by BASF (K 30 P), and those sold under the PLASDONE™ trademark (such as PLASDONE™ K-12 povidone, PLASDONE™ K-17 povidone, and PLASDONE™ K-25 povidone (Ashland Inc.)). Other highly water-soluble polymers containing other polyvinylpyrrolidone polymers may also be used.

[0020] Containing too much water-soluble polymer can make the water-responsive safety feature overly (mechanically) fragile. Additionally, too much water-soluble polymer can cause the water-responsive safety feature to be too hygroscopic, which can be particularly problematic in maintaining adequate electrical and mechanical stability, as excessive fragility can even corrode the battery pack and / or cause short circuits. On the other hand, containing too little water-soluble polymer can prevent the water-responsive safety feature from delivering the repellent substantially immediately upon contact with aqueous solutions (such as saliva or other fluids). Therefore, the amount of water-soluble polymer is important for providing the required environmental, electrical, and mechanical stability for the water-responsive safety feature. Generally, to provide the desired stability, the water-responsive safety feature includes a highly water-soluble polymer in an amount of at least about 1 wt.%, at least about 5 wt.%, at least about 7.5 wt.%, and / or at least about 10 wt.%, for example, between about 5 wt.% and about 25 wt.%, between about 5 wt.% and about 20 wt.%, or between about 7.5 wt.% and about 15 wt.%, based on total solids (which can also be described as the dry weight of the water-responsive safety feature).

[0021] As used herein, "hydrolysis-stabilized polymer" generally refers to a hydrolysis-resistant polymer, meaning that the polymer cannot depolymerize, soften, or otherwise degrade in the presence and / or reaction with water. Hydrolysis-stabilized polymers are typically included to provide the desired mechanical properties for water-responsive safety features. The hydrolytic stability of a polymer can also be tested using IPC-TM-650 method 2.6.11 as specified in Section 4.5.15 of IPC-SM-817. Test samples are prepared by coating a 0.25 ± 0.05 mm thick layer of polymer onto a template. When examined against light, the sample should be free of air bubbles or voids. The test sample can then be exposed to 94 ± 4% RH and 97 ± 2°C for 28 days, and visually inspected for signs of degradation (reversion) indicated by softening, powdering, blistering, cracking, loss of tackiness, adhesiveness, or liquefaction.

[0022] Generally, hydrolysis-stabilized polymers are selected from one or more of the group consisting of acrylic resins, epoxy resins, acrylates, and polyurethanes. More typically, hydrolysis-stabilized polymers are polymers (or copolymers) comprising one or more alkyl acrylate monomers. Therefore, polymers comprising alkyl acrylate monomers can be provided as hydrolysis-stabilized polymers in polymer blends. Polymers comprising alkyl acrylate monomers can be selected from one or more of the group consisting of polymers comprising methyl methacrylate monomers, polymers comprising ethyl methacrylate monomers, polymers comprising propyl methacrylate monomers, and polymers comprising butyl methacrylate monomers. Polymers comprising alkyl acrylate monomers can be selected from one or more of the group consisting of copolymers comprising methyl methacrylate and ethyl methacrylate monomers, copolymers comprising methyl methacrylate and propyl methacrylate monomers, copolymers comprising methyl methacrylate and butyl methacrylate monomers, copolymers comprising ethyl methacrylate and propyl methacrylate monomers, copolymers comprising ethyl methacrylate and butyl methacrylate monomers, and copolymers comprising propyl methacrylate and butyl methacrylate monomers. Any of the aforementioned polymers and copolymers comprising one or more alkyl acrylate monomers may further comprise methacrylic monomers. In one embodiment, the polymer comprising alkyl acrylate monomers is poly(methyl methacrylate / ethyl acrylate / methacrylic acid).

[0023] Hydrolysis-stabilized polymers typically have a number-average molecular weight between about 10,000 g / mol and about 120,000 g / mol, for example between about 15,000 g / mol and about 110,000 g / mol, between about 20,000 g / mol and about 100,000 g / mol, between about 25,000 g / mol and about 90,000 g / mol, and / or between about 40,000 g / mol and about 80,000 g / mol, for example about 60,000 g / mol. Therefore, polymers (or copolymers) including alkyl acrylate monomers may have number average molecular weights between about 10,000 g / mol and about 120,000 g / mol, for example between about 15,000 g / mol and about 110,000 g / mol, between about 20,000 g / mol and about 100,000 g / mol, between about 25,000 g / mol and about 90,000 g / mol, and / or between about 40,000 g / mol and about 80,000 g / mol, for example about 60,000 g / mol. Suitable hydrolysis-stabilized polymers include, but are not limited to, those containing ELVACITE. ® Trademarks (e.g., ELVACITE) ® 4072, ELVACITE ® 2927 and ELVACITE ®2669 is an alkyl acrylate polymer sold by Mitsubishi Chemical America Inc. Of course, other alkyl acrylate polymers can also be used. For example, DORESCO polymers can also be used. ® Alkyl acrylate polymers sold by The Lubrizol Corporation and PARALOID™ (The Dow Chemical Company).

[0024] Containing too much hydrolyzable stabilized polymer can cause the repulsive agent to be encapsulated within the water-responsive safety feature by the hydrolyzable stabilized polymer, thus rendering the repulsive agent essentially unusable for delivery when the water-responsive safety feature comes into contact with aqueous solutions in the form of saliva, gastric juice, or other fluids. On the other hand, containing too little hydrolyzable stabilized polymer can lead to the water-responsive safety feature being prone to breakage and / or accidental detachment during transport or storage, as well as increased hygroscopicity of the water-responsive safety feature. Therefore, the amount of hydrolyzable stabilized polymer is important for providing the desired environmental, electrical, and mechanical stability to the water-responsive safety feature. Generally, to exhibit the desired environmental, electrical, and mechanical stability, the water-responsive safety feature includes at least 1 wt.% (wt.%), at least 5 wt.%, or at least 10 wt.%, based on total solids, for example, between about 5 wt.% and about 35 wt.%, or between about 10 wt.% and about 30 wt.%, for example, about 22 wt.%, of hydrolyzable stabilized polymer.

[0025] In addition to the aforementioned highly water-soluble polymers and hydrolyzed stable polymers, the polymer blends for water-responsive safety features may further include a second water-soluble polymer, typically a (second) polyvinylpyrrolidone, to provide the desired mechanical properties for the water-responsive safety features while promoting substantially immediate release and delivery of the antagonist upon contact with aqueous solutions (e.g., saliva or other fluids). The second water-soluble polymer typically has a lower water solubility than the highly water-soluble polymer or the first polyvinylpyrrolidone contained in the polymer blend.

[0026] Furthermore, the second water-soluble polymer or the second polyvinylpyrrolidone typically has a higher molecular weight than the highly water-soluble polymer or the first polyvinylpyrrolidone contained in the polymer blend. For example, the second polyvinylpyrrolidone typically has a number-average molecular weight between about 200,000 g / mol and about 2,000,000 g / mol, for example between about 400,000 g / mol and about 1,900,000 g / mol, between about 600,000 g / mol and about 1,800,000 g / mol, between about 800,000 g / mol and about 1,700,000 g / mol, and / or between about 1,000,000 g / mol and 1,600,000 g / mol, for example about 1,400,000 g / mol. Therefore, the second water-soluble polymer may have a number-average molecular weight that is at least about 50 times, at least about 75 times, at least about 100 times, and / or at least about 125 times higher than that of the first water-soluble polymer. Consequently, the solubility of the second water-soluble polymer in water is typically significantly lower than that of the first water-soluble polymer in water, for example, at least 10%, at least 20%, and / or at least 50% lower. Suitable second water-soluble polymers contain LUVITEC. ® Trademarks (e.g., LUVITEC) ® K 82, LUVITEC ® K 85 and LUVITEC ® Polyvinylpyrrolidone polymers sold by K 90 (BASF) under SOKALAN ® Trademark (specifically SOKALAN) ® Polyvinylpyrrolidone polymers sold under the PLASDONE™ trademark (PLASDONE™ K-90 polyvinylpyrrolidone (Ashland Corporation)). Other water-soluble polymers containing other polyvinylpyrrolidone polymers may also be used.

[0027] To provide sufficient mechanical stability while facilitating the delivery of the anaerobic agent, the water-responsive safety features include a second polyvinylpyrrolidone in an amount of at least about 10 wt.%, at least about 25 wt.%, at least about 35 wt.%, and / or at least about 40 wt.%, for example, in about 5 wt.% with about 65 wt.%, or in about 30 wt.% with about 60 wt.%, for example, about 50 wt.%.

[0028] For example, batteries having water-responsive safety features as described herein are preferably stored for at least 10 days, at least 30 days, at least 60 days, or at least 84 days in an environment with a relative humidity of up to 90% (at a temperature between about 20°C and about 50°C, for example, at about 30°C or about 40°C) without affecting the battery pack performance. Additionally, batteries having water-responsive safety features as described herein are preferably stored for at least 60 days, at least 90 days, and / or at least 1200 days in an environment with a relative humidity of up to 65% (at a temperature between about 20°C and about 50°C, for example, at about 30°C or about 40°C) without affecting the battery pack performance.

[0029] As described throughout, water-responsive safety features include aversive agents. A water-responsive safety layer may include aversive agents selected from one or more of the following groups: denatumene, ammonium benzoate, denatumose, denatum chloride, sucrose octaacetate, 2,3-dimethoxystrychnine, quassinolides, flavonoids, quercetin, wormwood, resin toxins, capsaicin, vanillin nonanoate, piperine, and allyl isothiocyanate. Generally, aversive agents include bittering agents, typically denatumene. Water-responsive safety features typically include aversive agents, typically denatumene, based on total solids greater than about 1 wt.%, greater than about 3 wt.%, greater than about 5 wt.%, for example, from about 1 wt.% to about 10 wt.%, or from about 3 wt.% to about 7.50 wt.%, for example, about 6.50 wt.%.

[0030] Additionally, the water-responsive safety feature may contain a colorant (e.g., dye, pigment, polymer dye, or a combination thereof). The colorant may be contained within the water-responsive feature and is capable of being delivered from the water-responsive feature during dissolution, thus eluting more water-soluble polymeric mediator (and / or any aversive agents dispersed therein) from the body of the water-responsive safety feature. Therefore, the colorant can facilitate the detection of ingestion of the battery pack by promoting the spitting out (or “coughing up”) of a colored fluid from an individual’s mouth (which signals to others that the battery pack has been accidentally swallowed), thus advantageously allowing adults or caregivers to more quickly identify potential ingestion of the battery pack by a child. Generally, the colorant should be present in the water-responsive safety feature in an amount sufficient to produce a visible color change substantially immediately upon contact with an aqueous fluid. For example, the colorant may comprise from about 0.1 wt.% to about 5 wt.%, from about 0.1 wt.% to about 2.0 wt.%, for example about 0.70 wt.% of the total solids, typically a dye.

[0031] The battery pack surface can be activated using any suitable surface activation technique, such as plasma treatment (including but not limited to argon or corona treatment), UV / ozone treatment, flame treatment, and chemical treatment (including but not limited to acid treatment, alkaline treatment, etc.). Such treatments prior to deposition can increase the adhesion of water-responsive safety features to the battery pack surface. Adhesion promoters (especially silane adhesion promoters) can enhance the adhesion of water-responsive safety features to the battery pack surface, particularly after surface activation using UV / ozone treatment. Representative adhesion promoters include, but are not limited to, 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; and triethoxy(ethyl)silane; Triethoxymethylsilane; triethoxymethylsilane; triethoxyvinylsilane; trimethoxymethylsilane; trimethoxymethylsilane; vinyltrimethoxysilane; and vinyltrimethoxysilane; trihalosilanes, such as tert-butyltrichlorosilane; di-n-octyldichlorosilane; hexachlorosilane; methyltrichlorosilane; methyltrichlorosilane; trichloro(dichloromethyl)silane; vinyltrichlorosilane; 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.

[0032] The water-responsive safety feature may further include additives, such as rheology modifiers or pore-forming agents. Rheology modifiers can be used to maintain the rheological properties of the water-responsive safety feature in liquid form during preparation, deposition, and / or drying to mitigate its rapid settling. Exemplary stabilizers contain dispersants, such as EKFA, etc. ® PU and EKFA ® PA trademark (BASF) available polyurethane and polyacrylate-based dispersants; gas-phase metal oxide rheology modifiers, including but not limited to AEROSIL. ® (Evonik) and CAB-O-SIL ® The trademark (Cabot Corporation) includes rheology modifiers for fumed silica and fumed alumina; and polysaccharides such as xanthan gum. ®NF-F, Vanderbilt Minerals, LLC. Pore-forming agents can be used to promote wetting and improve adhesion. Exemplary porogens include, but are not limited to, polyethylene glycol, sodium chloride, and sodium bicarbonate. When additives are included, the water-responsive safety characteristics typically include additives based on about 1 wt.% to about 10 wt.%, or about 2 wt.% to about 7.50 wt.%, for example, about 5.50 wt.% of total solids.

[0033] As is well known, and with Figure 1 The battery pack 10 shown is identical. Figure 2A and 2B A battery pack 50 is illustrated, which can be any type of primary or secondary battery pack, and in the illustrated example is a button cell type battery pack. The battery pack 50 includes a battery pack housing surrounding the battery pack, the housing including a cathode cup 54 and an anode cap 58, the cathode cup 54 and anode cap 58 enclosing a cathode 52 and an anode 56 within the housing, the cathode 52 and anode 56 being electrically separated by a separator 60 within the battery 50. Each of the cathode cup 54 and anode cap 58 forms a different electrode of the battery pack 50, wherein the cathode cup 54 corresponds to the positive battery terminal and the anode cap 58 corresponds to the negative battery terminal. Although the cathode cup 54 is in… Figure 2A and 2B The illustrated embodiment is shown in which an anode cap 58 is received, but an alternative configuration in which an anode cap 58 is received to receive a cathode cup 54 may be used.

[0034] like Figure 2B As illustrated, the cathode cup 54 and the anode cap 58 are spaced apart by a separator 60 that extends laterally across the cathode 52, for example, substantially across the diameter of the battery pack 50, thus electrically insulating the cathode 52 from the anode 56 while simultaneously making it ionically conductive, as is well known. An insulating gasket 62 typically extends into the cathode cup 54 to provide insulation material substantially surrounding the anode cap 58, thus electrically isolating the cathode cup 54 from the anode cap 58, i.e., electrically isolating the positive terminal from the negative terminal. The insulating gasket also seals the battery pack 50 to prevent electrolyte loss. Therefore, the insulating gasket 62 seals the housing and electrically insulates the battery terminals from each other.

[0035] like Figure 2BAs best illustrated, the battery pack 50 further includes a water-responsive safety feature 64, typically disposed above and in direct contact with the insulating gasket 62 as illustrated. The water-responsive safety feature 64 comprises a polymer blend containing an antagonist dispersed therein. In the illustrated embodiment, the composite water-responsive safety feature 64 contacts a portion of the cathode cup 54 and a portion of the anode cap 58, and extends therebetween, such that the water-responsive safety feature provides a substantially continuous coating on the insulating gasket 62 (and in direct contact with the insulating gasket as illustrated) from the cathode cup 54 to the anode cap 58. Therefore, the water-responsive safety feature 64 is typically provided as a coating, specifically, a coating comprising a combination of polymers that work synergistically to deliver an antidote substantially immediately upon exposure to an aqueous fluid (e.g., saliva, gastric juice, or other aqueous fluid) while maintaining each of the following: (i) sufficient mechanical integrity to remain in place during storage and transport (e.g., demonstrated by adhesion and retention of discrete structures), (ii) sufficient electrical stability to resist corrosion and short circuits (e.g., demonstrated by the low opacity of the water-responsive safety feature and electrical short circuits in batteries), and (iii) sufficient environmental stability to avoid significant water adsorption during storage and transport, particularly when exposed to high humidity (e.g., demonstrated by a significant increase in weight after accelerated aging tests), as water adsorption can contribute to the degradation of mechanical and electrical stability. Therefore, the water-safe feature 64 must be able to dissolve without being too hygroscopic, too conductive, or too brittle.

[0036] When a water safety feature is too hygroscopic, the adsorbed water can promote the migration of any electronically or ionicly conductive material contained therein (or introduced into its vicinity, for example, due to battery leakage), and thus increase battery corrosion and / or short circuits. Therefore, in an optimized form, the water safety feature composition is substantially free of electronically or ionicly conductive material, which includes, but is not limited to, metal salts, acids, metals, and carbon. For example, as used herein, “substantially free of electronically or ionicly conductive material” means that the composition used to provide the water safety feature according to this disclosure contains trace amounts of one or more electronically or ionicly conductive materials (in terms of solids percentage by mass %). For example, the composition used to provide the water safety feature according to this disclosure may contain one or more electronically or ionicly conductive materials based on less than 2.0 wt.%, less than 1.0 wt.%, or less than 0.5 wt.% of total solids.

[0037] The electrochemical cells or battery packs used according to this disclosure may be primary or secondary. A primary battery pack means that it is discharged only once, for example until it is depleted, and then discarded. Primary battery packs are described, for example, in David Linden's *Handbook of Batteries* (McGraw-Hill, 4th edition, 2011). A secondary battery pack is designed to be recharged. A secondary battery pack can be discharged and subsequently recharged multiple times, for example, more than fifty times, more than one hundred times, or more than one thousand times. Secondary battery packs are described, for example, in David Linden's *Handbook of Batteries* (McGraw-Hill, 4th edition, 2011). The battery pack may contain aqueous or non-aqueous electrolytes. Therefore, the battery packs according to this disclosure may contain various electrochemical pairs and electrolyte combinations. While this article uses button cells, and more specifically coin cells, as examples to illustrate and describe battery packs incorporating composite water-responsive safety features, any type of battery pack (including, but not limited to, common consumer battery packs such as AAAA, AAA, AA, B, C, D, 9V, CR2, CR123A, 1 / 3N, button cells, and coin cells (e.g., 2016, 2025, and 2032 lithium batteries)) can generally be modified to include water-responsive safety features positioned between the positive and negative terminals as described herein.

[0038] Advantageously, the application of the water-responsive safety feature as disclosed herein does not affect the battery pack performance; therefore, for example, the battery pack has substantially the same voltage and capacitance before and after the composite water-responsive safety feature is placed in the gap between the positive and negative terminals of the battery pack.

[0039] In a representative example, the water-responsive safety feature 64 is formed by mixing an aqueous solution containing a polymer blend comprising a first water-soluble polymer with high water solubility and a hydrolyzed stable polymer with water containing an aversive agent and optionally a colorant (e.g., a dye) in a container maintained on a heating plate at about 50°C to about 60°C, and then preferably depositing the composition onto or around at least a portion of an insulating gasket 62 using a direct-write dispenser. By covering at least a portion of the insulating gasket 62 with the composition comprising the polymer blend and the aversive agent, when an individual swallows the battery pack 50, exposing the battery pack 50 to an aqueous solution in the form of saliva, gastric juice, or other fluid, at least one polymer in the polymer blend of the water-responsive safety feature dissolves substantially immediately, thus releasing the aversive agent and delivering it, for example, to the individual's mouth. Preferably, the water-responsive safety feature itself does not substantially dissolve or detach completely or partially from the battery pack. The components of the water safety feature are generally described herein as a percentage by weight of solids (%). Therefore, for this purpose, any solvents (including water) used to dissolve components and evaporate during deposition / casting are excluded. Although the composite water-responsive layer is shown as part of the contact anode cap 58 and the cathode cup 54, it does not need to contact the battery pack electrodes.

[0040] Throughout this specification, multiple instances can be implemented as components or structures of a single instance. Structures and functions that appear as independent components in an instance configuration can be implemented as composite structures or components. Similarly, structures and functions that appear as single features can be implemented as independent components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.

[0041] As used herein, any reference to "one embodiment" or "an embodiment" means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The phrase "in one embodiment" appearing in various places in this specification does not necessarily refer to the same embodiment.

[0042] As used herein, the terms “comprises / comprising,” “includes / including,” “has / having,” or any other variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, article of manufacture, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article of manufacture, or apparatus. Furthermore, unless expressly stated to the contrary, “or” means inclusive or not exclusive or. For example, element A or B is satisfied by any of the following: A exists and B does not exist, A does not exist and B exists, and both A and B exist.

[0043] Additionally, the use of "a / an" is for describing elements and components of the embodiments herein. This is done solely for convenience and to give a general meaning to the description. This specification and the appended claims should be understood to include one or at least one, and the singular also includes the plural, unless explicitly stated otherwise.

[0044] This detailed description is to be interpreted as merely illustrative and not as a description of every possible embodiment, as describing every possible embodiment would be impractical, if not impossible. Various alternative embodiments may be implemented using current technology or technology developed after the date of this application.

[0045] The following examples further illustrate the advantages of battery packs that incorporate water-responsive safety features as disclosed herein.

[0046] Example 1

[0047] In this example, the performance of the water-responsive safety features according to this disclosure, including polymer blends and antagonists, is compared with that of a contrasting prior art formulation used in a CR2032 lithium coin cell battery pack (DURACELL US Operations) with a bitter coating, wherein each of these formulations is disposed in a “gap” corresponding to a position between the positive and negative terminals of the battery pack (e.g., between the cathode cup and anode cap of the coin cell battery pack).

[0048] The existing formulations in comparison are unstable when placed between the positive and negative terminals of a coin cell and cause corrosion and / or short circuits when exposed to elevated temperatures and humidity during accelerated aging and safety / abuse tests.

[0049] The compositions shown in Table I below are prepared according to the water response characteristics of this disclosure:

[0050]

[0051] Prepare the formulations in Table 1 on a heated plate, with the water bath maintained at 50°C to 60°C. Place the mixing container in this bath and mount the mixing blade 1 inch from the bottom. Add diacetone alcohol solvent (DAA) and methyl methacrylate copolymer (ELVACITE) to this container. ® 2669). Continue mixing and heating until the solution is clear and colorless, for a maximum of 2 hours. The next step is to gradually add more solvent and two PVP resins (LUVITEC). ® K 17 and LUVITEC ®K30). Increase the mixing speed and continue heating until all polymers dissolve and the solution is clear and colorless (up to 4 hours). Then slowly add water and xanthan gum, followed by benzyl denatum. Continue heating and mixing until the solution is clear, colorless, and free of lumps. Finally, add the blue dye. Increase the mixing speed and reheat the solution for 2 hours. Remove the mixture from the heat source and allow it to cool, then transfer it to an HDPE bottle. Deposit the formulation in the gap corresponding to the position between the positive and negative terminals of the coin cell using a direct-write n. In accelerated aging and safety / abuse tests, no corrosion, short circuits, or leaks were detected after the battery was exposed to elevated temperature and humidity.

[0052] Furthermore, analytical tests determined that when the membrane manufactured from the aforementioned formulation was immersed in Ringer's solution and / or an aqueous solution comprising 60 wt.% methanol, a substantial portion (i.e., 45 wt.% to 59 wt.%) of denaphalonamine was delivered substantially immediately from the membrane within five seconds. Therefore, the combination of polymers in the aforementioned formulation advantageously provides good delivery of the anaerobic agent while enhancing resistance to corrosion, short circuits, and leaks.

[0053] Example 2

[0054] In this example, the performance of a water-responsive safety feature, comprising a polymer blend and an anti-repellent agent, placed in a "gap" between the positive and negative terminals of a battery pack (e.g., between the cathode cup and anode cap of a coin cell battery pack), is compared to that of a "naked" coin cell without any water-responsive safety feature.

[0055] The batteries underwent a temperature and humidity test (THT), during which both the battery pack and bare battery pack according to this disclosure were subjected to a relatively constant temperature of 40°C and a relative humidity of 90%. Leakage was typically confirmed by visual inspection. In this regard, the presence of white and / or green crystals on or around the insulating gasket separating the positive and negative terminals confirmed leakage. Although 30% of the bare batteries showed signs of leakage, the batteries incorporating the water-responsive safety feature surprisingly and unexpectedly showed no signs consistent with leakage. This result was particularly unexpected under conditions where the water-responsive safety feature was generated using water-soluble materials.

[0056] Additionally, the adhesion of the water-responsive safety feature to the battery is tested according to ASTM D3359. Specifically, an X-shaped cut is made in the water-responsive safety feature to the substrate (e.g., an insulating gasket), pressure-sensitive adhesive tape is applied to the cut and subsequently removed, and the adhesion is qualitatively evaluated based on a scale of 0 to 5, where a score of 0 corresponds to the removal of 100% of the film, a score of 1 corresponds to the removal of most of the area under the tape, a score of 2 corresponds to the removal of up to 30% of the water-responsive safety feature (or the applied "ring"), a score of 3 corresponds to the removal of up to 10% of the water-responsive safety feature (or the applied "ring"), a score of 4 corresponds to trace removal, and a score of 5 corresponds to no peeling or removal.

Claims

1. A battery pack comprising: The housing includes a cathode cup corresponding to the positive terminal of the battery and an anode cover corresponding to the negative terminal of the battery; The cathode and anode are housed within the casing; An insulating gasket is disposed between the cathode cup and the anode cover, the insulating gasket sealing the housing and electrically insulating the cathode cup from the anode cover; and The water-responsive safety features include a polymer blend and an antagonist, the polymer blend comprising a first polyvinylpyrrolidone and a polymer comprising an alkyl acrylate monomer, wherein the first polyvinylpyrrolidone has high water solubility.

2. The battery pack of claim 1, wherein the polymer comprising alkyl acrylate monomers is selected from one or more of the group consisting of: polymers comprising methyl methacrylate monomers, polymers comprising ethyl methacrylate monomers, polymers comprising propyl methacrylate monomers, and polymers comprising butyl methacrylate monomers.

3. The battery pack according to claim 1 or 2, wherein the polymer comprising alkyl acrylate monomers is selected from one or more of the group consisting of: copolymers comprising methyl methacrylate and ethyl methacrylate monomers, copolymers comprising methyl methacrylate and propyl methacrylate monomers, copolymers comprising methyl methacrylate and butyl methacrylate monomers, copolymers comprising ethyl methacrylate and propyl methacrylate monomers, copolymers comprising ethyl methacrylate and butyl methacrylate monomers, and copolymers comprising propyl methacrylate and butyl methacrylate monomers.

4. The battery pack according to any of the preceding claims, wherein the polymer comprising alkyl acrylate monomers further comprises methacrylic acid monomers.

5. The battery pack according to any of the preceding claims, wherein the polymer comprising the alkyl acrylate monomer has a number-average molecular weight between about 10,000 g / mol and about 120,000 g / mol, for example between about 15,000 g / mol and about 110,000 g / mol, between about 20,000 g / mol and about 100,000 g / mol, between about 25,000 g / mol and about 90,000 g / mol, and / or between about 40,000 g / mol and about 80,000 g / mol, for example about 60,000 g / mol.

6. The battery pack according to any of the preceding claims, wherein the first polyvinylpyrrolidone has a number-average molecular weight between about 500 g / mol and about 65,000 g / mol, between about 1,000 g / mol and about 60,000 g / mol, between about 1,500 g / mol and about 55,000 g / mol, between about 2,000 g / mol and about 50,000 g / mol, between about 2,500 g / mol and about 45,000 g / mol, between about 3,000 g / mol and about 40,000 g / mol, between about 4,000 g / mol and about 35,000 g / mol, between about 5,000 g / mol and about 30,000 g / mol, and / or between about 5,500 g / mol and about 15,000 g / mol, for example, about 9,000 g / mol.

7. The battery pack according to any of the preceding claims, further comprising a second polyvinylpyrrolidone, wherein the second polyvinylpyrrolidone has a lower solubility in water than the first polyvinylpyrrolidone has in water.

8. The battery pack of claim 7, wherein the second polyvinylpyrrolidone has a molecular weight between about 200,000 g / mol and about 2,000,000 g / mol, for example between about 400,000 g / mol and about 1,900,000 g / mol, between about 600,000 g / mol and about 1,800,000 g / mol, between about 800,000 g / mol and about 1,700,000 g / mol, and / or between about 1,000,000 g / mol and 1,600,000 g / mol, for example about 1,400,000 g / mol.

9. The battery pack according to any of the preceding claims, wherein the aversive agent comprises a bittering agent.

10. The battery pack according to claim 9, wherein the aversive agent comprises ammonium benzoate, denatammonium benzoate, denatammonium sugar, denatammonium chloride, sucrose octaacetate, 2,3-dimethoxystrychnine, quassinolide, flavonoids, quercetin, wormwood, resin toxins, capsaicin, vanillin nonanoate, piperine, allyl isothiocyanate, or a combination thereof.

11. The battery pack according to any of the preceding claims, wherein the first polyvinylpyrrolidone is present in an amount of at least about 1 wt.%, at least about 5 wt.%, at least about 7.5 wt.%, and / or at least about 10 wt.% based on total solids.

12. The battery pack according to any of the preceding claims, wherein the polymer comprising alkyl acrylate monomers is present in an amount of at least 1 wt.% or at least 5 wt.% based on total solids.

13. The battery pack according to any of the preceding claims, wherein the second polyvinylpyrrolidone is present in an amount of at least about 10 wt.%, at least about 25 wt.%, at least about 35 wt.%, and / or at least about 40 wt.% based on total solids.

14. The battery pack according to any of the preceding claims, wherein the water-responsive safety feature further comprises a colorant.

15. The battery pack according to any of the preceding claims, wherein the battery pack is selected from AAAA battery packs, AAA battery packs, AA battery packs, B battery packs, C battery packs, D battery packs, 9V battery packs, CR2 battery packs, CR123A battery packs, 1 / 3N battery packs, button batteries and coin batteries.

16. A battery pack comprising: The housing includes a cathode cup corresponding to the positive terminal of the battery and an anode cover corresponding to the negative terminal of the battery; The cathode and anode are housed within the casing; An insulating gasket is disposed between the cathode cup and the anode cover, the insulating gasket sealing the housing and electrically insulating the cathode cup from the anode cover; and The water-responsive safety features include a polymer blend and an antagonist, the polymer blend comprising a first water-soluble polymer with high water solubility, a hydrolytically stable polymer, and an antagonist.

17. The battery pack of claim 16, wherein the water-soluble polymer has a degree of polymerization between about 60 and about 100.

18. The battery pack according to claim 16 or 17, wherein the highly water-soluble polymer is selected from one or more of the group consisting of: polyethylene glycol, polyacrylic acid, polyamide, polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl methylcellulose, hydroxypropyl cellulose, and copolymers comprising monomer units of one or more of the aforementioned polymers.

19. The battery pack according to any one of claims 16 to 18, wherein the hydrolysis-stabilized polymer is selected from one or more of the group consisting of acrylic resins, epoxy resins, acrylates, and polyurethanes.

20. The battery pack according to any one of claims 16 to 18, wherein the polymer blend further comprises a second water-soluble polymer having a number-average molecular weight that is at least about 50 times, at least about 75 times, at least about 100 times, and / or at least about 125 times higher than the number-average molecular weight of the first water-soluble polymer.

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