Biodegradable electrochemical devices

Abstract

A biodegradable solid aqueous electrolyte composition, an electrochemical device comprising the electrolyte composition, and a method for preparing the same are provided. The electrolyte composition may include a copolymer hydrogel and a salt dispersed in the hydrogel. The copolymer may include at least two polycaprolactone chains connected to a central polymer block. The electrochemical device may include an anode, a cathode, and the electrolyte composition disposed between the anode and the cathode. The electrolyte composition may include a crosslinked biodegradable polymer material that is radiation-curable prior to crosslinking.

Description

Technical Field

[0001] The embodiments or implementations disclosed in this invention relate to biodegradable electrochemical devices, their solid aqueous electrolytes, and methods for manufacturing or synthesizing them. Background Technology

[0002] The world's battery production is increasing due to the growing demand for portable and remote power sources. In particular, many new technologies require batteries to power embedded electronics. For example, embedded electronics such as portable and wearable electronics, Internet of Things (IoT) devices, patient healthcare monitoring, structural monitoring, environmental monitoring, and smart packaging all rely on battery power. While conventional batteries can be partially recycled, there are currently no commercially available environmentally friendly or biodegradable batteries. Therefore, the increased manufacture and use of conventional batteries leads to a corresponding increase in toxic and hazardous waste in the environment (if not properly disposed of or recycled). In light of the above, there is a need to develop biodegradable batteries, especially for applications requiring a limited time to use disposable batteries before they are discarded.

[0003] Furthermore, to meet the demand for flexible, low-cost, medium- or low-performance batteries, fully printed batteries have been developed and are commercially available as single-use disposable batteries. However, none of these fully printed batteries are biodegradable.

[0004] It is generally accepted that one of the biggest challenges in producing biodegradable batteries is the development of a biodegradable polymer electrolyte, which is the main polymer-based component of an all-printed battery. Furthermore, the development of this biodegradable polymer electrolyte—which can also be printed using existing printing techniques—is another challenge.

[0005] Conventional biodegradable polymeric electrolytes typically comprise a combination of a biodegradable polymer and a conductive salt. To obtain a biodegradable polymeric electrolyte, the biodegradable polymer and the conductive salt are dissolved in a solvent, followed by evaporation of the solvent at a relatively slow rate to produce a solid polymeric electrolyte membrane. Due to the low ionic mobility in the biodegradable polymer, these conventional biodegradable polymeric electrolytes typically exhibit low ionic conductivity at ambient temperatures (e.g., less than about 10⁻⁶ at RT). -5 (S / cm). However, sufficient conductivity can be achieved when the polymer electrolyte is heated to a temperature sufficient to allow polymer chain movement (i.e., the operating temperature), thus allowing ions to move more freely through the polymer electrolyte structure. Sufficient conductivity can also be achieved by incorporating additives that inhibit the crystallinity of the polymer electrolyte, thereby lowering its operating temperature. Therefore, the number of biodegradable polymer electrolytes that can operate with sufficient conductivity at room temperature is limited.

[0006] In addition to the drawbacks mentioned above, conventional biodegradable polymer electrolytes suffer from lengthy manufacturing processes due to the time required for solvent evaporation during production. For example, it typically takes several hours to evaporate the solvent under vacuum and / or temperature assistance to prepare a conventional biodegradable polymer electrolyte, thus limiting its compatibility with high-throughput printing processes—where consecutive layers must be printed on top of each other within minutes.

[0007] Therefore, there is a need for printable, biodegradable electrochemical devices, their solid aqueous electrolytes, and methods for their synthesis and manufacture. Summary of the Invention

[0008] The following is a simplified summary of the invention to provide a basic understanding of some aspects of one or more embodiments of this teaching. This summary is not a broad overview, nor is it intended to identify key or essential elements of this teaching, nor is it intended to depict the scope of this disclosure. Rather, its primary purpose is merely to present one or more concepts in a simplified form as a prelude to the specific embodiments presented later.

[0009] This disclosure provides an electrochemical device comprising an anode, a cathode, and an electrolyte composition. The electrolyte composition may be disposed between the anode and the cathode. The electrolyte composition may include a cross-linked, biodegradable polymer material, which may be radiation-curable prior to cross-linking.

[0010] In some embodiments, a plurality of electrochemical devices are provided. The plurality of electrochemical devices can be simultaneously printed in an array on a mesh in parallel processes. In one embodiment, the plurality of electrochemical devices can be printed independently or as interconnected elements.

[0011] In some embodiments, a plurality of electrochemical devices are provided. The biodegradable polymer material of the plurality of electrochemical devices can be radiation-cured within about 10 milliseconds (ms) to about 100 milliseconds.

[0012] In some embodiments, the biodegradable polymer material may contain radiation-curable functional groups prior to crosslinking. Radiation-curable functional groups may include one or more of acrylates, vinyl ethers, allyl ethers, olefins, alkynes, thiols, or combinations thereof.

[0013] In some embodiments, the electrolyte composition may be derived from a radiation-curable electrolyte precursor composition. The radiation-curable electrolyte precursor composition may include at least one photoinitiator.

[0014] In some embodiments, the at least one photoinitiator may include one or more of the following substances: lithium acylphosphinate (LAP), IRGACURE 2959, sodium 4-[2-(4-morpholino)benzoyl-2-dimethylamino]-butylbenzenesulfonate (MBS), monoacylphosphine oxide (MAPO) salts Na-TPO and Li-TPO, diacylphosphine oxide salts Na-BAPO, Li-BAPO, thioxanone derivatives, benzophenone derivatives, Irgacure 754, PEG-modified BAPO, or combinations thereof.

[0015] In some embodiments, the crosslinked biodegradable polymer material may have a Young's modulus of about 0.10 MPa to about 100 MPa. In some embodiments, the crosslinked biodegradable polymer material may have a yield strength of about 5 kPa or greater.

[0016] In some embodiments, the electrochemical device may include one or more biodegradable substrates. The one or more biodegradable substrates may be stable at approximately 120°C. The one or more biodegradable substrates may maintain structural integrity with a dimensional change of less than 10% after exposure to approximately 120°C. The one or more biodegradable substrates may include one or more of the following substances: polylactic acid (PLA), polylactic-co-glycolic acid (PLGA), fibroin, chitosan, polycaprolactone (PCL), polyhydroxybutyrate (PHB), rice paper, cellulose, or combinations or complexes thereof.

[0017] In some embodiments, the electrolyte composition may include a hydrogel. The hydrogel may include water and a cross-linked, biodegradable polymer material.

[0018] In some embodiments, the electrolyte composition may include a co-solvent. The co-solvent may include one or more of the following substances: ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, or a combination thereof.

[0019] In some embodiments, the anode may include one or more of the following substances: Zn, Li, C, Mg, Mg alloy, Zn alloy, or a combination thereof.

[0020] In some embodiments, the cathode may include one or more of the following substances: Fe, MnO2, C, Au, Mo, W, MoO3, Ag2O, Cu, or combinations thereof.

[0021] In some embodiments, the radiation-curable electrolyte precursor composition may include one or more of the following substances: ZnCl2, NH4Cl, NaCl, PBS, Na2SO4, ZnSO4, MnSO4, MgCl2, CaCl2, FeCl3, LiPF6, KOH, NaOH, or combinations thereof. In some embodiments, the concentration of the radiation-curable electrolyte precursor composition may be from about 3M to about 10M.

[0022] This disclosure may also provide an electrochemical device comprising an anode, a cathode, and an electrolyte composition disposed between the anode and the cathode. The anode may include a first biodegradable adhesive. The cathode may include a second biodegradable adhesive. The electrolyte composition may include a cross-linked biodegradable polymer material that is radiation-curable prior to cross-linking.

[0023] In some embodiments, the cathode and / or anode are arranged in a stacked geometry.

[0024] In some embodiments, the cathode and / or anode are disposed in a transverse XY plane geometry.

[0025] In some embodiments, each of the cathode and / or anode may include a biodegradable adhesive. The biodegradable adhesive may include one or more of the following substances: chitosan, polylactic-co-glycolic acid (PLGA), cellulose acetate butyrate (CAB), polyhydroxybutyrate (PHB), or combinations thereof.

[0026] In some embodiments, each of the cathode and / or anode may include both an active layer and a current collector layer.

[0027] In some embodiments, the cathode, anode, and electrolyte composition is printed.

[0028] In some embodiments, the electrochemical device may be flexible.

[0029] In some embodiments, the crosslinked biodegradable polymer material can be radiation-cured within about 10 milliseconds (ms) to about 100 milliseconds before being crosslinked.

[0030] This disclosure may also provide a process or method for manufacturing an electrochemical device. The process may include providing a biodegradable substrate. The process may further include depositing an electrode composition, and optionally, thermally drying the electrode composition. The process may also include depositing a biodegradable, radiation-curable electrolyte composition. The process may further include, optionally, thermally curing the biodegradable, radiation-curable electrolyte composition after thermally drying the electrode composition. The biodegradable substrate may be thermally compatible with the optional thermal drying process.

[0031] In some embodiments, depositing the electrode composition and depositing the biodegradable, radiation-curable electrolyte composition may include printing.

[0032] In some embodiments, radiation curing of a biodegradable radiation-curable electrolyte composition can be completed within about 10 milliseconds (ms) to about 100 milliseconds.

[0033] In some embodiments, radiation curing of a biodegradable radiation-curable electrolyte composition results in a crosslinked biodegradable electrolyte composition having a Young's modulus of about 0.10 MPa to about 100 MPa and a yield strength of about 5 kPa or greater.

[0034] In some embodiments, the method may further include depositing a biodegradable adhesive layer.

[0035] In some embodiments, the biodegradable substrate may be weldable / adhesive-compatible, eliminating the need for additional adhesives.

[0036] In some embodiments, the method may include depositing a biodegradable adhesive layer at the tabs.

[0037] In some embodiments, a biodegradable substrate may be provided in the form of a web-fed continuous roll.

[0038] In some embodiments, the electrode composition may be a metal foil composition.

[0039] In some embodiments, the method may include depositing a second electrode composition. The second electrode composition may be a different metal foil composition.

[0040] In some embodiments, the biodegradable substrate may be a continuous mesh or may be supported by a continuous mesh.

[0041] In some embodiments, multiple electrochemical devices can be printed simultaneously in an array as independent or connected elements on a mesh in a parallel process.

[0042] This disclosure may also provide biodegradable solid aqueous electrolytes comprising a copolymer hydrogel and a salt dispersed in the hydrogel. The copolymer may comprise at least two polycaprolactone chains attached to a central block of the polymer.

[0043] In some embodiments, the polymer central block may be derived from a naturally occurring biodegradable polymer having at least two free hydroxyl groups.

[0044] In some embodiments, the polymer central block may include hydroxyl-containing polysaccharides, biodegradable polyesters, or hydroxy fatty acids.

[0045] In some embodiments, the polymer central block may include polyvinyl alcohol, polybutylene succinate, or castor oil.

[0046] In some embodiments, the hydrogel may include a copolymer loading of 20% or more by weight, preferably 30% or more by weight, or even more preferably 50% or more by weight, based on the total weight of the hydrogel.

[0047] In some embodiments, the hydrogel may include a copolymer loading of about 5% to about 50% by weight, based on the total weight of the hydrogel.

[0048] In some embodiments, the salt may include ammonium chloride (NH4Cl), zinc chloride (ZnCl2), or a mixture thereof.

[0049] In some embodiments, the salt may be present in the electrolyte at a concentration of at least 0.5 M.

[0050] In some embodiments, the salt may be present in the electrolyte at a concentration of at least 3M and at most 10M.

[0051] In some embodiments, the electrolyte may further include nanomaterial additives. In at least one embodiment, the nanomaterial additives may include cellulose nanocrystals, chitin nanocrystals, chitosan nanocrystals, starch nanocrystals, silica, alumina, layered silicates, lime, or any mixture thereof.

[0052] In some embodiments, the electrolyte may further comprise water and a co-solvent. The co-solvent may include one or more of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, or combinations thereof. In a preferred embodiment, the co-solvent may be selected from ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, or combinations thereof.

[0053] In some embodiments, the hydrogel may have or include a viscosity of about 1000 cP to about 1.0E+6 cP.

[0054] This disclosure may also provide an electrochemical device comprising an anode, a cathode, and a biodegradable solid aqueous electrolyte as described in any of paragraphs

[0042] -

[0053] . The biodegradable solid aqueous electrolyte may be disposed between the anode and the cathode.

[0055] In some embodiments, a biodegradable solid aqueous electrolyte can be printed on the cathode or anode.

[0056] This disclosure further provides a method for preparing a solid aqueous electrolyte. The method may include dissolving a salt and a functionalized copolymer in an aqueous solution. The copolymer may include at least two polycaprolactone chains linked to a central block of a polymer and functionalized with functional groups that promote hydrogel formation upon curing the aqueous solution with ultraviolet light. The method may also include forming an aqueous solution layer on a surface. The method may further include curing the aqueous solution with ultraviolet light to form a solid hydrogel comprising a copolymer in which the salt is dispersed.

[0057] In some embodiments, the polymer central block may be derived from a naturally occurring biodegradable polymer having at least two free hydroxyl groups.

[0058] In some embodiments, the polymer central block may include hydroxyl-containing polysaccharides, biodegradable polyesters, or hydroxy fatty acids.

[0059] In some embodiments, the polymer central block may include polyvinyl alcohol, polybutylene succinate, or castor oil.

[0060] In some embodiments, the aqueous solution may be formed directly on one or both electrodes of the battery before curing.

[0061] In some embodiments, the hydrogel may be formed with a copolymer loading of 20% by weight or greater, based on the total weight of the hydrogel.

[0062] In some embodiments, the salt may include ammonium chloride (NH4Cl), zinc chloride (ZnCl2), or a mixture thereof.

[0063] In some embodiments, the salt may be present in the electrolyte at a concentration of at least 0.5 M.

[0064] In some embodiments, the salt may be present in the electrolyte at a concentration of at least 3M and at most 10M.

[0065] Brief description of the attached figures

[0066] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings. These and / or other aspects and advantages of the embodiments of this disclosure will become apparent and more readily understood in conjunction with the accompanying drawings and the following description of various embodiments:

[0067] Figure 1 An exploded view of an exemplary biodegradable electrochemical device constructed side-by-side according to one or more of the disclosed embodiments is shown.

[0068] Figure 2 An exploded view of another exemplary biodegradable electrochemical device in a stacked configuration according to one or more of the disclosed embodiments is shown.

[0069] Figure 3 The following is shown: PCL-PEG-PCL macromonomer diol following step 1 of the synthetic scheme shown in Scheme 1. 1 H NMR spectrum.

[0070] Figure 4 The PCL-PEG-PCL macromonomer diacrylate following step 2 of the synthesis scheme shown in Scheme 1 is illustrated. 1 H NMR spectrum.

[0071] Figure 5A The stress-strain curves of a PCL-PEG-PCL-based solid aqueous electrolyte prepared from PCL-PEG-PCL macromonomers with block chain lengths of 239-20000-239 are shown.

[0072] Figure 5B It shows Figure 5A Young's modulus of a PCL-PEG-PCL-based solid aqueous electrolyte was measured in five different measurements at various concentrations of NH4Cl and ZnCl2.

[0073] Figure 6 This demonstrates a solid aqueous electrolyte containing PCL-PEG-PCL and exhibiting a discharge rate of 0.01 mA / cm² after standing for 10 hours prior to discharge. 2 Capacity of a fully discharged MnO2 / Zn electrochemical cell (mAh / cm³) 2 A graph of the battery voltage (V) versus the battery voltage.

[0074] Figure 7 A representative Nyquist plot of Re(Z) vs-Im(Z) for monitoring impedance changes during battery discharge in a MnO2 / Zn electrochemical cell containing a solid aqueous electrolyte based on PCL-PEG-PCL is shown.

[0075] Figure 8 A graph showing the open-circuit voltage (OCV) stability of a MnO2 / Zn electrochemical cell containing a solid aqueous electrolyte based on PCL-PEG-PCL versus a cell containing a liquid aqueous electrolyte is presented.

[0076] Figure 9 The discharge performance (mAh / cm³) of a MnO₂ / Zn electrochemical cell containing a PCL-PEG-PCL-based solid aqueous electrolyte is shown compared to that of a cell containing a liquid aqueous solution electrolyte. 2 A graph of the battery voltage (V) versus the battery voltage.

[0077] Figure 10The corresponding viscosities of the Zn anode slurry and MnO2 slurry prepared in Example 7 are shown. Detailed Implementation

[0078] The following description of various typical aspects is merely exemplary in nature and is in no way intended to limit this disclosure, its application, or its use.

[0079] As used throughout, "range" is used as a shorthand to describe each value within that range. Any value within the range can be chosen as the endpoint of the range. Furthermore, all references cited herein are incorporated herein by reference in their entirety. In the event of any conflict between definitions in this disclosure and definitions in cited references, this disclosure shall prevail.

[0080] Unless otherwise stated, all percentages and quantities expressed herein and elsewhere in this specification shall be understood as weight percentages. The quantities given are based on the effective weight of the material.

[0081] Furthermore, all numerical values ​​are “about” or “approximate” to indicated values, and take into account experimental errors and variations that a person skilled in the art would expect. It should be understood that all numerical values ​​and ranges disclosed herein are approximate values ​​and ranges, whether or not the word “about” is used in conjunction with them. It should also be understood that, as used herein, the term “about” in conjunction with a number means a value that can be ±0.01% (inclusive), ±0.1% (inclusive), ±0.5% (inclusive), ±1% (inclusive), ±2% (inclusive), ±3% (inclusive), ±5% (inclusive), ±10% (inclusive), or ±15% (inclusive). It should also be understood that when a numerical range is disclosed herein, any numerical value falling within that range is also specifically disclosed.

[0082] As used herein, unless the context clearly specifies otherwise, the term "or" is an inclusive operator and is equivalent to the term "and / or". Unless the context clearly specifies otherwise, the term "based on" is not exclusive and allows for basing on additional factors not described. In the specification, the statement "at least one of A, B, and C" includes embodiments containing A, B, or C, multiple instances of A, B, or C, or combinations of A / B, A / C, B / C, A / B / B, B / B / C, A / B / C, etc. Furthermore, throughout the specification, the meanings of "a", "an", and "described" include plural references. The meaning of "in" includes both "in" and "on".

[0083] Reference will now be made in detail to exemplary embodiments of this teaching, examples of which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same, similar, or analogous parts.

[0084] This document discloses a biodegradable electrochemical device. As used herein, the term "biodegradable" can refer to materials, components, substances, devices, etc., that can be or are configured to be decomposed by living organisms, particularly microorganisms in landfills, within a reasonable time. Materials, components, substances, devices, etc., can decompose into water, naturally occurring gases such as carbon dioxide and methane, biomass, or combinations thereof. As used herein, the expressions "biodegradable electrochemical device" or "biodegradable device" can refer to an electrochemical device or device, wherein at least one or more of its components are biodegradable. In some cases, a majority or a substantial number of the components of a biodegradable electrochemical device or a biodegradable device are biodegradable. In other cases, all polymer components of a biodegradable electrochemical device or a biodegradable device are biodegradable. For example, the polymer and / or other organic-based components of an electrochemical device are biodegradable, while the inorganic materials (including metals and / or metal oxides) of the electrochemical device disclosed herein may be non-biodegradable. It should be understood that if all polymeric and / or organic-based components of an electrochemical device are biodegradable, then the entire electrochemical device is generally considered biodegradable. As used herein, the term or expression “electrochemical device” can refer to a device that converts electricity into chemical reactions and / or vice versa. Illustrative electrochemical devices can be, or are not limited to, batteries, die-sensitized solar cells, electrochemical sensors, electrochromic glass, fuel cells, electrolyzers, etc.

[0085] As used herein, the terms or expressions “environmentally friendly electrochemical device” or “environmentally friendly device” may refer to an electrochemical device or apparatus that generally exhibits minimal, reduced, or no toxicity to an ecosystem or the environment. In at least one embodiment, the electrochemical device and / or its components disclosed herein are environmentally friendly.

[0086] In at least one embodiment, the biodegradable electrochemical device disclosed herein may include an anode, a cathode (i.e., a current collector and / or an active layer), and one or more electrolyte compositions (e.g., a biodegradable solid aqueous electrolyte composition). In another embodiment, the biodegradable electrochemical device may also include one or more substrates, one or more seals, or combinations thereof.

[0087] The biodegradable electrochemical devices disclosed herein can be flexible. As used herein, the term "flexible" can refer to a material, device, or component thereof that is capable of bending about a predetermined radius of curvature without breaking and / or cracking. The biodegradable electrochemical devices and / or components thereof disclosed herein can be bent about radii of curvature of about 30 cm or less, about 20 cm or less, about 10 cm or less, or about 5 cm or less without breaking or cracking.

[0088] Figure 1 An exploded view of an exemplary biodegradable electrochemical device 100 constructed side-by-side or coplanarly according to one or more embodiments is shown. Figure 1 As shown, the biodegradable electrochemical device 100 may include a first substrate 102, a first current collector 104 and a second current collector 106 disposed adjacent to or on top of the first substrate 102, an anode active layer 108 disposed adjacent to or on top of the first current collector 104, a cathode active layer 110 disposed adjacent to or on top of the second current collector 106, an electrolyte layer 112 disposed adjacent to or on top of the anode active layer 108 and the cathode active layer 110, and a second substrate 114 disposed adjacent to or on top of the electrolyte composition 112. It should be understood that the first current collector 104 and the anode active layer 108 may be collectively referred to herein as the anode 120 of the biodegradable electrochemical device 100. It should also be understood that the second current collector 106 and the cathode active layer 110 may be collectively referred to herein as the cathode 122 of the biodegradable electrochemical device 100. Figure 1 As shown, the anode 120 and cathode 122 of the biodegradable electrochemical device 100 may be coplanar, such that the anode 120 and cathode 122 are arranged along the same XY plane.

[0089] In at least one embodiment, the biodegradable electrochemical device 100 may include one or more seals (two shown as 116, 118) capable of or configured to seal or hermetically seal the current collectors 104, 106, the anode active layer 108, the cathode active layer 110, and the electrolyte composition 112 between the first and second substrates 102, 114 of the biodegradable electrochemical device 100. For example, as Figure 1As shown, the biodegradable electrical device 100 may include two seals 116, 118 inserted between first and second substrates 102, 114 and surrounding current collectors 104, 106, anode active layer 108, cathode active layer 110, and electrolyte composition 112 to seal or hermetically seal the biodegradable electrochemical device 100. In another embodiment, the biodegradable electrochemical device 100 may have no or substantially no seals 116, 118. For example, substrates 102, 114 may be fused or bonded together to seal the biodegradable electrochemical device 100.

[0090] Figure 2 An exploded view of another exemplary biodegradable electrochemical device 200 in a stacked configuration according to one or more embodiments is shown. Figure 2 As shown, the biodegradable electrochemical device 200 may include a first substrate 202, a first current collector 204 disposed adjacent to or on top of the first substrate 102, an anode active layer 208 disposed adjacent to or on top of the first current collector 204, an electrolyte layer 212 disposed adjacent to or on top of the anode 108, a cathode active layer 210 disposed adjacent to or on top of the electrolyte composition 212, a second current collector 206 disposed adjacent to or on top of the cathode active layer 210, and a second substrate 214 disposed adjacent to or on top of the second current collector 206. It should be understood that the first current collector 204 and the anode active layer 208 may be collectively referred to herein as the anode 220 of the biodegradable electrochemical device 200. It should also be understood that the second current collector 206 and the cathode active layer 210 may be collectively referred to herein as the cathode 222 of the biodegradable electrochemical device 200. Figure 2 As shown, the anode 220 and cathode 222 of the biodegradable electrochemical device 200 can be arranged in a stacked configuration or geometry such that the anode 220 and cathode 222 are positioned on top of or below each other.

[0091] In at least one embodiment, the biodegradable electrochemical device 200 may include one or more seals (two shown, 216, 218) capable of or configured to hermetically seal the current collectors 204, 206 between the first and second substrates 202, 214 of the biodegradable electrochemical device 200, the anode active layer 208, the cathode active layer 210, and the electrolyte composition 212. For example, as Figure 2As shown, the biodegradable electrical device 200 may include two seals 216, 218 inserted between the first and second substrates 202, 214 and surrounding the current collectors 204, 206, the anode active layer 208, the cathode active layer 210, and the electrolyte composition 212 to hermetically seal the biodegradable electrochemical device 200. In another embodiment, the biodegradable electrochemical device 200 may have no or substantially no seals 216, 218. For example, the substrates 202, 214 may be melted or bonded together to seal the biodegradable electrochemical device 200.

[0092] like Figure 1 and Figure 2 As shown, each of the current collectors 104, 106, 204, 206 may include a corresponding tab 124, 126, 224, 226, which may extend to the outside of the seals 116, 118, 216, 218 to provide a connection.

[0093] In at least one embodiment, any one or more of the substrates 102, 114, 202, 214 of the corresponding biodegradable electrochemical devices 100, 200 may be, or include, a biodegradable substrate. Exemplary biodegradable substrates may be, or include, one or more of polylactic acid (PLA), polylactic-co-glycolic acid (PLGA), fibroin, chitosan, polycaprolactone (PCL), polyhydroxybutyrate (PHB), rice paper, cellulose, or combinations or complexes thereof.

[0094] The biodegradable substrates of the corresponding biodegradable electrochemical devices 100, 200 are stable at temperatures ranging from about 50°C to about 150°C. As used herein, the term "stable" or "stable" can refer to the ability of a substrate to resist dimensional changes and maintain structural integrity when exposed to temperatures ranging from about 50°C to about 150°C. For example, a biodegradable substrate may be able to, or be configured to, maintain structural integrity after exposure to temperatures ranging from about 50°C to about 150°C with dimensional changes of less than about 20%, less than about 15%, or less than about 10%. In one embodiment, each biodegradable substrate is stable at temperatures ranging from about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, or about 110°C to about 120°C, about 130°C, about 140°C, or about 150°C (e.g., dimensional changes of less than 20%). In another embodiment, each biodegradable substrate can be stabilized at a temperature of at least 100°C, at least 105°C, at least 110°C, at least 115°C, at least 120°C, at least 125°C, at least 130°C, at least 135°C, at least 140°C, or at least 145°C. In at least one embodiment, the biodegradable substrate can be stabilized at a temperature of about 50°C to about 150°C for about 5 minutes to about 60 minutes or longer. For example, the biodegradable substrate can be stabilized at the above-mentioned temperatures for about 5 minutes, about 10 minutes, about 20 minutes, or about 30 minutes to about 40 minutes, about 45 minutes, about 50 minutes, about 60 minutes, or longer.

[0095] In at least one embodiment, the biodegradable substrate is weldable, adhesive, and / or permanently heat-sealed without the need for additional adhesives. For example, the biodegradable substrates of each of substrates 102, 114, 202, 214 may be weldable and / or adhesive to each other without the need for corresponding seals 116, 118, 216, 218. Exemplary biodegradable substrates that are weldable and / or adhesive to each other may be, or include, thermoplastics such as polylactic acid (PLA), polylactide modified with nucleating agents to enhance crystallinity, such as polylactide modified with nucleating agent D (PLA-D) and polylactide modified with nucleating agent E (PLA-E), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), blends of PLA and polyhydroxybutyrate (PHB), PHB-based blends, etc., or combinations thereof. As used herein, the terms or expressions “adhesive,” “weldable,” and / or “permanently heat-sealed” can refer to the ability of a material (e.g., a substrate) to heat-seal two surfaces together or to permanently bond two surfaces together by heating or melting.

[0096] The corresponding biodegradable electrochemical devices 100, 200 may have an anode active layer 108, 208 that can be, or includes, one or more of zinc (Zn), lithium (Li), carbon (C), cadmium (Cd), nickel (Ni), magnesium (Mg), magnesium alloys, zinc alloys, etc., or combinations thereof and / or alloys thereof. Exemplary anode active layers or their materials may be, or include, these, or combinations thereof. In at least one embodiment, the anode active layer may include a sufficient amount of zinc oxide (ZnO) to regulate or control H2 outgassing.

[0097] In at least one embodiment, the anolyte active layers 108, 208 of the corresponding biodegradable electrochemical devices 100, 200 can be prepared or manufactured from an anolyte slurry. For example, the anolyte active layer can be prepared from a zinc anolyte slurry. The anolyte slurry can be prepared in a grinding mill. In at least one embodiment, stainless steel shot can be placed in the grinding mill to facilitate the preparation of the anolyte slurry. The anolyte slurry may include one or more metals or metal alloys, one or more organic solvents, one or more styrene-butadiene rubber adhesives, or combinations thereof. In an exemplary embodiment, the anolyte slurry may include one or more of ethylene glycol, styrene-butadiene rubber adhesive, zinc oxide (ZnO), bismuth(III) oxide (Bi2O3), Zn powder, or combinations thereof. Exemplary organic solvents are known in the art and may be, but are not limited to, ethylene glycol, acetone, NMP, etc., or combinations thereof. In at least one embodiment, any one or more biodegradable adhesives may be used instead of or in combination with styrene-butadiene rubber adhesives.

[0098] The corresponding biodegradable electrochemical devices 100, 200 may have cathode active layers 110, 210 that can be, or include but are not limited to, one or more of the following: iron (Fe), iron oxide (VI), mercury oxide (HgO), manganese oxide (IV) (MnO2), carbon (C), carbon-containing cathodes, gold (Au), molybdenum (Mo), tungsten (W), molybdenum trioxide (MoO3), silver oxide (Ag2O), copper (Cu), vanadium oxide (V2O5), nickel oxide (NiO), cuprous iodide (Cu2I2), copper chloride (CuCl), etc., or combinations thereof and / or alloys thereof. In an exemplary embodiment, cathode active layers 110, 210 may include manganese oxide (IV). Carbon and / or carbon-containing cathode active layers can be used in aqueous metal-air batteries, such as zinc-air batteries.

[0099] In at least one embodiment, the cathode active layers 110, 210 may include one or more additives capable of or configured to at least partially enhance the electronic conductivity of the cathode active layers 110, 210. Exemplary additives may be, but are not limited to, carbon particles, such as graphite, carbon nanotubes, carbon black, or combinations thereof.

[0100] In at least one embodiment, the cathode active layers 110, 210 of the corresponding biodegradable electrochemical devices 100, 200 can be prepared or manufactured from cathode slurry. For example, the cathode active layers 110, 210 can be prepared from manganese oxide (IV) cathode slurry. The cathode slurry can be prepared in a grinding mill. In at least one embodiment, stainless steel pellets can be placed in the grinding mill to facilitate the preparation of the cathode slurry. The cathode slurry may contain one or more metals or metal alloys, one or more organic solvents (e.g., ethylene glycol), one or more styrene-butadiene rubber binders, or combinations thereof. In an exemplary embodiment, the cathode slurry may include one or more of ethylene glycol, styrene-butadiene rubber binders, manganese oxide (IV) (MnO2), graphite, or combinations thereof. Exemplary organic solvents are known in the art and may be, but are not limited to, ethylene glycol, acetone, NMP, etc., or combinations thereof. In at least one embodiment, the one or more organic solvents may be replaced with aqueous solvents or used in combination with aqueous solvents (e.g., water). For example, water may be used in combination with manganese oxide (IV).

[0101] The anode and / or cathode pastes may have a viscosity of about 100 cP to about 1E6 cP. For example, the anode and / or cathode pastes may have a viscosity greater than or equal to about 100 cP, greater than or equal to about 200 cP, greater than or equal to about 500 cP, greater than or equal to about 1000 cP, greater than or equal to about 1500 cP, greater than or equal to about 2000 cP, greater than or equal to about 10000 cP, greater than or equal to about 20000 cP, greater than or equal to about 50000 cP, greater than or equal to about 1E5 cP, greater than or equal to about 1.5E5 cP, greater than or equal to about 2E5 cP, greater than or equal to about 3E5 cP, greater than or equal to about 4E5 cP, greater than or equal to about 5E5 cP, greater than or equal to about 6E5 cP, greater than or equal to about 7E5 cP, greater than or equal to about 8E5 cP, or greater than or equal to about 9E5 cP. In another embodiment, the anode and / or cathode slurry may have a viscosity of less than or equal to about 200 cP, less than or equal to about 500 cP, less than or equal to about 1,000 cP, less than or equal to about 1,500 cP, less than or equal to about 2,000 cP, less than or equal to about 10,000 cP, less than or equal to about 20,000 cP, less than or equal to about 50,000 cP, less than or equal to about 1E5 cP, less than or equal to about 1.5E5 cP, less than or equal to about 2E5 cP, less than or equal to about 3E5 cP, less than or equal to about 4E5 cP, less than or equal to about 5E5 cP, less than or equal to about 6E5 cP, less than or equal to about 7E5 cP, less than or equal to about 8E5 cP, less than or equal to about 9E5 cP, or less than or equal to about 1E6 cP.

[0102] In at least one embodiment, each of the anodes 120, 220 and cathodes 122, 222, or their active layers 108, 110, 208, 210, may independently include a biodegradable adhesive. The biodegradable adhesive functions to anchor the particles of the respective layers together and provide adhesion to the underlying substrate, said respective layers being anode current collectors 104, 204, cathode current collectors 106, 206, anode active layers 108, 208, cathode active layers 110, 210, or combinations thereof. Exemplary biodegradable adhesives may be, but are not limited to, one or more of chitosan, polylactic-co-glycolic acid (PLGA), gelatin, xanthan gum, cellulose acetate butyrate (CAB), polyhydroxybutyrate (PHB), or combinations thereof. In at least one embodiment, any one or more biodegradable polymers disclosed herein with respect to the electrolyte composition may also be used as biodegradable adhesives for anodes 120, 220, cathodes 122, 222, their components, or any combination thereof. As further described herein, said one or more biodegradable polymers may be crosslinked. Therefore, the biodegradable adhesives used for the anodes 120, 220, cathodes 122, 222 and / or components thereof may include the crosslinked biodegradable adhesives disclosed herein with respect to the electrolyte composition.

[0103] The electrolyte layers 112, 212 in the respective biodegradable electrochemical devices 100, 200 may be or include an electrolyte composition. The electrolyte composition may utilize a biodegradable polymer material. The electrolyte composition may be a solid aqueous electrolyte composition. The solid aqueous electrolyte composition may be or include a copolymer hydrogel and salts dispersed in and / or throughout the hydrogel. The copolymer may include at least two polycaprolactone (PCL) chains linked to a polymer central block (CB). For example, the copolymer may be a block copolymer or graft copolymer comprising at least two PCL chains coupled to a polymer central block, such as PCL-CB-PCL. In another embodiment, the copolymer may be a block copolymer or graft copolymer comprising at least one or more of polylactic acid (PLA), polyglycolic acid (PGA), polyethyleneimine (PEI), or combinations thereof coupled to a polymer central block.

[0104] The copolymer or solid may be present in the hydrogel in an amount of about 5% by weight or more to 90% by weight or less, based on the total weight of the hydrogel (e.g., the total weight of the solvent, polymer, and salt). For example, the copolymer may be present in an amount of about 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, or 35% by weight or more, based on the total weight of the hydrogel. In another embodiment, the copolymer may be present in an amount of 90% by weight or less, 80% by weight or less, 70% by weight or less, or 60% by weight or less, based on the total weight of the hydrogel. In a preferred embodiment, the copolymer or solid may be present in the hydrogel in an amount of about 5% by weight to about 60% by weight, about 5% by weight to about 50% by weight, about 20% by weight to about 40% by weight, or about 30% by weight, based on the total weight of the hydrogel. In another preferred embodiment, the copolymer or solid may be present in the hydrogel in an amount greater than 30% by weight to 60% by weight, based on the total weight of the hydrogel.

[0105] The copolymer may be present in the hydrogel in an amount sufficient to provide a continuous film or layer free of or substantially free of air bubbles. The copolymer may also be present in the hydrogel in an amount sufficient to provide a viscosity of about 1,000 cP to about 100,000 cP. For example, the copolymer may be present in the hydrogel in an amount sufficient to provide a viscosity of about 1,000 cP, about 5,000 cP, about 10,000 cP, or about 20,000 cP to about 30,000 cP, about 40,000 cP, about 50,000 cP, about 75,000 cP, about 90,000 cP, or about 100,000 cP.

[0106] The polymer central block of the copolymer can be a biodegradable polymer, thereby improving or increasing the biodegradability of the solid aqueous electrolyte composition. The biodegradable polymer of the polymer central block is preferably naturally occurring. The polymer central block can be, includes, or is derived from a polymer, such as a biodegradable polymer, comprising at least two free hydroxyl groups that can be reacted with ε-caprolactone. As further described herein, polymers comprising at least two free hydroxyl groups can react with ε-caprolactone to form copolymers. Exemplary polymers comprising at least two free hydroxyl groups that can be used to form the polymer central block (CB) can be, or include, one or more of polyvinyl alcohol (PVA), hydroxyl polysaccharides, biodegradable polyesters, hydroxy fatty acids (e.g., castor oil), etc., or combinations thereof. Exemplary hydroxyl polysaccharides can be, or include, starch, cellulose, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, chitin, guar gum, xanthan gum, agar, amylopectin, amylose, alginate, dextran, etc., or combinations thereof. Exemplary biodegradable polyesters may be, or include but are not limited to, polylactide, polyglycolic acid, polylactide-co-glycolic acid, polyitacrylic acid, polybutylene succinate, or combinations thereof. In a preferred embodiment, the polymer central block may be, or include, one or more of polyvinyl alcohol (PVA), hydroxyl-containing polysaccharides, biodegradable polyesters, or hydroxy fatty acids.

[0107] In at least one embodiment, the polymer central block of the copolymer may not be a biodegradable polymer. For example, the polymer central block of the copolymer may be, or includes but is not limited to, polyethylene glycol (PEG), hydroxyl-terminated polyester, hydroxyl-terminated polyolefin, such as hydroxyl-terminated polybutadiene, or combinations thereof.

[0108] A copolymer comprising at least two polycaprolactone (PCL) chains bonded to a polymer central block can be a graft copolymer or a block copolymer. Whether a copolymer is a graft copolymer or a block copolymer can be determined at least in part by the number and / or position of the at least two free hydroxyl groups in the polymer central block. For example, ε-caprolactone is reacted with polymer central blocks having hydroxyl groups on the monomer along the length of the polymer central block chain to form a graft copolymer. In another embodiment, ε-caprolactone is reacted with polymer central blocks where each hydroxyl group is located at the respective end of the polymer central block to form a block copolymer. Exemplary block copolymers can be or include triblock copolymers, tetrablock copolymers, star-shaped block copolymers, or combinations thereof.

[0109] As described above, the electrolyte composition can be a solid aqueous electrolyte composition comprising a copolymer hydrogel and a salt dispersed in the hydrogel. The salt in the hydrogel can be or includes any suitable ionic salt known in the art. Exemplary ionic salts can be, or include, one or more of organic-based salts, inorganic-based salts, room-temperature ionic liquids, deep eutectic solvent-based salts, and combinations thereof. In a preferred embodiment, the salt is or includes salts suitable for zinc / manganese (IV) (Zn / MnO2) electrochemistry. Exemplary salts can be, or include, zinc chloride (ZnCl2), ammonium chloride (NH4Cl), sodium chloride (NaCl), phosphate-buffered saline (PBS), sodium sulfate (Na2SO4), zinc sulfate (ZnSO4), manganese sulfate (MnSO4), magnesium chloride (MgCl2), calcium chloride (CaCl2), ferric chloride (FeCl3), lithium hexafluorophosphate (LiPF6), potassium hydroxide (KOH), sodium hydroxide (NaOH), and combinations thereof. In a preferred embodiment, the salt of the electrolyte composition may be or include ammonium chloride (NH4Cl), zinc chloride (ZnCl2), or combinations or mixtures thereof. In another embodiment, the salt may be or include alkali metal salts, such as sodium hydroxide (NaOH), ammonium hydroxide (NH4OH), potassium hydroxide (KOH), or combinations or mixtures thereof.

[0110] The salt may be present in an amount capable of, configured to, or sufficient to provide ionic conductivity. For example, the salt may be present in the hydrogel in an amount or concentration of at least 0.1 M, more preferably at least 0.5 M, even more preferably at least 2 M, even more preferably at least 4 M. The salt may be present in the hydrogel at a concentration of 10 M or less, more preferably 6 M or less. In another embodiment, the salt may be present in the hydrogel in an amount of about 3 M to about 10 M, about 4 M to about 10 M, about 5 M to about 9 M, or about 6 M to about 8 M. In an exemplary embodiment, the salt comprises ammonium chloride and zinc chloride, wherein the ammonium chloride is present in an amount of about 2.5 M to about 3 M, about 2.8 M to about 2.9 M, or about 2.89 M, and wherein the zinc chloride is present in an amount of about 0.5 M to 1.5 M, about 0.8 M to about 1.2 M, or about 0.9 M.

[0111] In at least one embodiment, the electrolyte composition may include one or more additives. These additives may be, but are not limited to, biodegradable or environmentally friendly nanomaterials. Biodegradable nanomaterials may be able to provide or be configured to provide and / or improve the structural strength of the electrolyte layer or the electrolyte composition thereof without sacrificing the flexibility of the electrolyte layer or the electrolyte composition thereof. Exemplary biodegradable nanomaterials for additives may be, but are not limited to, polysaccharide-based nanomaterials, inorganic nanomaterials, etc., or combinations thereof. Exemplary polysaccharide-based nanomaterials may be, but are not limited to, cellulose nanocrystals, chitin nanocrystals, chitosan nanocrystals, starch nanocrystals, etc., or combinations or mixtures thereof, one or more. Exemplary inorganic nanomaterials may be, but are not limited to, silicon dioxide (e.g., pyrolytic silica), alumina, layered silicates, or lime, or combinations or mixtures thereof, one or more. Exemplary layered silicates may be, or include but are not limited to, bentonite, kaolin, dickite, pearl clay, staplegite, illite, halloysite, montmorillonite, lithium montmorillonite, lithium fluoride montmorillonite, chlorodiazepite, bedeite, soapstone, volkonskoite, malachite, copper montmorillonite, hydrous malachite, zinc montmorillonite, muscovite, vermiculite, mica, hydromica, phegite, brammalite, chlorite, or one or more combinations or mixtures thereof.

[0112] One or more additives may be present in an amount of at least 0.1% by weight, based on the total weight of the hydrogel. For example, one or more additives may be present in an amount of at least 0.1%, at least 0.5%, or at least 1% by weight, based on the total weight of the hydrogel. One or more additives may also be present in an amount of 40% by weight or less, based on the total weight of the hydrogel. For example, one or more additives may be present in an amount of 40% by weight or less, 20% by weight or less, or 10% by weight or less, based on the total weight of the hydrogel.

[0113] In at least one embodiment, the electrolyte composition may include an aqueous solvent. For example, the electrolyte composition may include water. In at least one embodiment, the electrolyte composition may include a co-solvent. For example, the electrolyte composition may include water and another solvent. Exemplary co-solvents may be, but are not limited to, one or more of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, or combinations thereof. The co-solvent may include water in an amount greater than about 20%, greater than about 30%, greater than about 40%, greater than about 50% to greater than about 60%, greater than about 70%, greater than about 80%, greater than about 85%, or greater than about 90% by weight or volume of the aqueous solvents in the electrolyte composition.

[0114] In at least one embodiment, the electrolyte composition comprises a copolymer hydrogel and a salt, a solvent (e.g., water or water and a cosolvent) dispersed in the hydrogel, one or more photoinitiators, optionally one or more additives, or combinations thereof. For example, the electrolyte composition comprises a copolymer hydrogel, a salt, a solvent, one or more additives, or combinations or mixtures thereof. In at least one embodiment, the electrolyte composition consists of or substantially consists of a copolymer hydrogel, a salt, and a solvent (e.g., water or water and a cosolvent) dispersed in the hydrogel. In another embodiment, the electrolyte composition consists of or substantially consists of a copolymer hydrogel, a salt, a solvent, and one or more additives dispersed in the hydrogel. The solvent, which may be water or a combination of water and a cosolvent, provides equilibrium for the hydrogel.

[0115] The solid aqueous electrolyte composition can be prepared according to scheme (1):

[0116] Step 1:

[0117]

[0118] Step 2:

[0119]

[0120] Step 3:

[0121]

[0122] Option 1

[0123] Step 1 of scheme (1) may include ε-caprolactone 1 and a polymer central block (CB(OH)) comprising at least two free hydroxyl groups. x 2. Ring-opening polymerization in the presence of a catalyst (i.e., a photoinitiator). ε-caprolactone 1 and the polymer central block (CB(OH)) x The ring-opening polymerization of 2 can produce (PCL). x -CB macromonomer 3, where x can be 2 or a larger integer. It should be understood that any suitable ring-opening polymerization catalyst can be used in step 1. In at least one embodiment, the catalyst can be or includes a tin catalyst, such as tin 2-ethylhexanoate.

[0124] The ring-opening polymerization in step 1 can typically be carried out at a high temperature or for a suitable period of time. In at least one embodiment, the ring-opening polymerization can be carried out at a temperature of about 50°C to about 200°C, more preferably at a temperature of about 100°C to about 150°C. The ring-opening polymerization can be carried out for about 5 hours to about 48 hours, more preferably about 24 hours.

[0125] PCL can be purified using commonly known methods. x-CB macromonomers 3. For example, they can be purified (PCL) by extraction, precipitation, and filtration. x -CB macromonomer 3. It can be purified once or multiple times to provide a product with relatively high purity. In at least one embodiment, the PCL chain of macromonomer 3 has or includes free hydroxyl groups. (PCL) x The free hydroxyl groups of the CB macromonomer 3 can be used for functionalization.

[0126] Step 2 of scheme (1) may include using functionalizing agent (FM)4 to make (PCL) x -CB macromonomers were functionalized to prepare functionalized macromonomers (FG-PCL). x -CB 5. Exemplary functionalizing agents (FM) may be, but are not limited to, acryloyl chloride, methacryl chloride, methacrylic anhydride, maleic anhydride, or combinations or mixtures thereof. Functionalizing agents (FM) may be capable of or configured to introduce, attach, or otherwise add functional groups (FG) to (PCL). x -CB macromonomer 3 to prepare functionalized macromonomers (FG-PCL) x -CB 5. Exemplary functional groups may be, but are not limited to, one or more of acrylates, vinyl ethers, allyl ethers, alkenes, alkynes, thiols, or combinations thereof. When functionalized macromonomers (FG-PCL) are subjected to radiant energy such as ultraviolet light... x When CB 5 is crosslinked in aqueous solution, (PCL) x Functionalization of CB macromonomer 3 – for the preparation of functionalized macromonomers (FG-PCL) x -CB 5——Promotes hydrogel formation.

[0127] Using functionalizing agent (FM)4 to make (PCL) x - CB macromonomers are 3-functionalized to prepare functionalized macromonomers (FG-PCL). x -CB 5 can be performed or carried out in a solvent in the presence of a base. The base can be or includes amines, such as trimethylamine or triethylamine. The solvent can be or includes polar aprotic solvents, such as dichloromethane. Functionalization can be carried out under an inert atmosphere. For example, functionalization can be carried out under inert gases such as nitrogen, argon, etc. Functionalization can be carried out under heating to promote the reaction. For example, the reaction can be carried out at temperatures up to about 60°C. The functionalized macromonomer (FG-PCL) can be purified by commonly known methods (e.g., extraction, precipitation, and filtration). x -CB 5.

[0128] Step 3 of scheme (1) may include functionalized macromonomer (FG-PCL) in an aqueous solvent or medium. x-CB 5, salt 6 and photoinitiator 7 are mixed, combined or otherwise contacted with each other to prepare an aqueous solution. Step 3 may also include irradiating the aqueous solution with radiation energy such as ultraviolet (UV) light to crosslink the aqueous solution and form a solid aqueous electrolyte in the form of a hydrogel 8.

[0129] An aqueous solution prepared by contacting the functionalized macromonomer (FG-PCL)x-CB5, salt 6, and photoinitiator 7 with each other can be placed on a substrate or its surface prior to irradiation with radiation energy. For example, the aqueous solution can be coated, cast, or printed (e.g., by a printing process) onto the substrate or its surface to prepare or form an aqueous layer on the substrate or its surface. In a preferred embodiment, the aqueous layer is printed onto the substrate by a printing process or method to form electrolyte layers 112, 212. As further described herein, the aqueous layer can be directly printed near one or both of the anolyte active layers 108, 208 and / or the cathode active layers 110, 210 of the respective biodegradable electrochemical devices 100, 200 to form the respective electrolyte layers 112, 212. In at least one embodiment, the aqueous solution may include one or more ink additives to facilitate or assist the printing process.

[0130] Photoinitiator 7 may be a UV crosslinking photoinitiator. Photoinitiator 7 may be water-soluble. Exemplary photoinitiators 7 may be, or include but are not limited to, acyl lithium phosphinate or phenyl (2,4,6-trimethylbenzoyl) lithium phosphinate (LAP), IRGACURE. TM 2959, DAROCUR TM 1173, Sodium 4-[2-(4-morpholino)benzoyl-2-dimethylamino]-butylbenzenesulfonate (MBS), monoacylphosphine oxide (MAPO) salts Na-TPO and Li-TPO, diacylphosphine oxide salts Na-BAPO, Li-BAPO, thioxanone derivatives, benzophenone derivatives, IRGACURE TM 754. PEG-modified BAPO or a combination thereof. In a preferred embodiment, the photoinitiator 7 used is or includes lithium acylphosphinate (LAP) because LAP is water-soluble, does not exhibit cytotoxicity, and does not require an inert atmosphere.

[0131] Crosslinking of aqueous solutions with radiation energy can be carried out at room temperature. Crosslinking of aqueous solutions with radiation energy can also be carried out without an inert atmosphere. Crosslinking of the aqueous solution may include exposing the aqueous solution to UV light of sufficient and / or appropriate wavelength and power output. It should be understood that the wavelength of the UV light may depend at least in part on the activation wavelength of the photoinitiator 7. In at least one embodiment, the activation wavelength of the photoinitiator 7 may be from about 250 nm to about 500 nm. It should also be understood that the power output of the UV light may at least in part determine the curing time of the aqueous solution. For example, increasing the power output of the UV light may reduce the curing time of the aqueous solution. It may be necessary to expose the aqueous solution to UV light for a duration of less than 60 minutes (min) to form a hydrogel. In a preferred embodiment, the aqueous solution is exposed to UV light for about 30 minutes or less, more preferably about 20 minutes or less, and even more preferably about 10 minutes or less. In some embodiments, the aqueous solution crosslinks over a time period of about 10 milliseconds (ms) to about 100 milliseconds (ms). Therefore, the power output of the UV light can be varied to provide sufficient, adequate, or complete crosslinking of the aqueous solution within a desired time period. Hydrogels prepared by crosslinking aqueous solutions can be used "as is". For example, hydrogels prepared by crosslinking aqueous solutions can be used as electrolyte layers 112, 212 of corresponding biodegradable electrochemical devices 100, 200.

[0132] As previously described, the electrolyte layers 112, 212 of the corresponding biodegradable electrochemical devices 100, 200 may be or include a solid aqueous electrolyte composition. The solid aqueous electrolyte composition may possess sufficient mechanical and electrochemical properties required for commercially printed batteries or commercially useful printed batteries. For example, the solid aqueous electrolyte composition may have a Young's modulus or storage modulus greater than about 0.10 MPa, greater than about 0.15 MPa, or greater than about 0.20 MPa, thereby providing sufficient strength to the solid aqueous electrolyte composition while maintaining sufficient flexibility to prevent breakage under stress. The solid aqueous electrolyte composition may have a Young's modulus less than or equal to about 100 MPa, less than or equal to about 80 MPa, less than or equal to about 60 MPa, or less.

[0133] As used herein, the term or expression “yield strength” refers to the maximum stress a material can experience or accept before it begins permanent deformation. Solid aqueous electrolyte compositions may have a yield strength of about 5 kPa or greater. For example, the solid aqueous electrolyte composition may have a yield strength of about 5 kPa or greater, about 8 kPa or greater, about 10 kPa or greater, about 12 kPa or greater, about 15 kPa or greater, or about 20 kPa or greater.

[0134] The solid aqueous electrolyte composition can be electrochemically stable for both the anode active layers 108, 208 and the cathode active layers 110, 210 of the corresponding biodegradable electrochemical devices 100, 200. For example, the solid aqueous electrolyte composition can maintain a stable open-circuit voltage over an extended period of time, thus exhibiting electrochemical stability for the anode active layers 108, 208 and the cathode active layers 110, 210 of the corresponding biodegradable electrochemical devices 100, 200. In at least one embodiment, the solid aqueous electrolyte composition can be electrochemically stable after being in contact with the electrode layers for at least one month, at least two months, at least three months, at least four months, at least five months, at least six months, at least one year, or longer.

[0135] The solid aqueous electrolyte compositions disclosed herein can be used in any electrochemical device, such as an electrochemical cell, a battery pack, and / or the biodegradable electrochemical devices 100, 200 disclosed herein. In a preferred embodiment, the solid aqueous electrolyte composition can be used in a battery comprising a Zn anode active layer and a MnO2 cathode active layer.

[0136] The current collectors 104, 106, 204, and 206 of the corresponding biodegradable electrochemical devices 100 and 200 can be capable of or configured to receive, conduct, and transport current. Exemplary current collectors 104, 106, 204, and 206 can be, or include but are not limited to, silver such as silver microparticles and silver nanoparticles, carbon such as carbon black, graphite, carbon fibers, carbon nanoparticles such as carbon nanotubes, graphene, reduced graphene oxide (RGO), etc., or any combination thereof.

[0137] method

[0138] Embodiments of this disclosure provide methods for manufacturing electrochemical devices such as the biodegradable electrochemical devices 100, 200 disclosed herein. The methods may include providing a biodegradable substrate. The methods may further include depositing electrodes and / or electrode compositions in proximity to or on the biodegradable substrate. The deposited electrodes may include depositing and drying a current collector for the electrode, and depositing and drying an active layer (i.e., anodic or cathode material) adjacent to or on the current collector. The methods may further include drying the electrodes and / or electrode compositions. The electrode compositions may be thermally dried (e.g., heated). The methods may further include depositing a biodegradable radiation-curable electrolyte composition on or near the electrode composition. The methods may further include radiation curing the biodegradable radiation-curable electrolyte composition. The biodegradable radiation-curable electrolyte composition may be radiation-cured before or after drying the electrode composition. The biodegradable substrate may be thermally compatible with optional thermal drying. For example, the biodegradable substrate may be dimensionally stable (e.g., without buckling and / or curling) during thermal drying. The methods may include depositing a second electrode and / or electrode composition on or near the biodegradable radiation-curable electrolyte composition. In at least one embodiment, each of the first electrode composition and the second electrode composition is a metal foil composition. The metal foil composition of the first electrode may be different from the metal foil composition of the second electrode.

[0139] In at least one embodiment, the electrochemical device, all or substantially all of its components, is manufactured by a printing process. Printing processes may include deposition, stamping, spraying, sputtering, jetting, coating, layering, etc. For example, one or more current collectors, one or more electrode compositions, a biodegradable, radiation-curable electrolyte composition, or combinations thereof may be deposited by a printing process. Exemplary printing processes may be, but are not limited to, one or more of screen printing, inkjet printing, flexographic printing (e.g., stamp printing), gravure printing, offset printing, air brush printing, aerosol printing, typesetting, roll-to-roll methods, etc., or combinations thereof. In a preferred embodiment, the components of the electrochemical device are printed by screen printing.

[0140] In at least one embodiment, radiation curing a biodegradable radiation-curable electrolyte composition includes exposing the electrolyte composition to radiation energy. The radiation energy may be ultraviolet light. Exposing the biodegradable radiation-curable electrolyte composition to radiation energy can at least partially crosslink the biodegradable radiation-curable electrolyte composition, thereby forming a hydrogel. The biodegradable radiation-curable electrolyte composition can be radiation-cured at room temperature. In at least one embodiment, the biodegradable radiation-curable electrolyte composition is cured under an inert atmosphere. For example, the biodegradable radiation-curable electrolyte composition can be cured under nitrogen, argon, or the like. In another embodiment, the biodegradable radiation-curable electrolyte composition can be cured in a non-inert atmosphere.

[0141] In at least one embodiment, the biodegradable radiation-curable electrolyte composition can be radiation-cured over a time period of about 5 ms to about 100 ms. For example, the biodegradable radiation-curable electrolyte composition can be radiation-cured over time periods of about 5 ms, about 10 ms, about 15 ms, about 20 ms, about 30 ms, about 40 ms, or about 50 ms to about 60 ms, about 70 ms, about 80 ms, about 85 ms, about 90 ms, about 95 ms, or about 100 ms. The time period sufficient for radiation curing of the biodegradable radiation-curable electrolyte composition can be determined at least in part by the power output of the UV light.

[0142] In at least one embodiment, the method may further include depositing an adhesive, such as a biodegradable adhesive, to provide seals 116, 118, 216, 218 of the respective biodegradable electrochemical devices 100, 200. For example, the method may include depositing adhesive layers to bond a substrate or a portion of the substrate of the electrochemical device (e.g., the area around tabs 124, 126, 224, 226) to each other. In some embodiments, the adhesive may be a hot-melt adhesive. In another embodiment, the electrochemical device may contain no or substantially no adhesive. For example, the biodegradable substrate may be weldable and / or heat-sealable without the use of additional adhesives.

[0143] In at least one embodiment, the biodegradable substrate may be a continuous mesh, or may be supported by a continuous mesh. As used herein, the term "mesh" may refer to a moving support surface, such as a conveyor belt. In at least one embodiment, multiple electrochemical devices are simultaneously printed on the continuous mesh as independent or connected elements or components. For example, multiple electrochemical devices may be simultaneously printed on the mesh in an array as independent or connected elements in a parallel process. As used herein, the terms or expressions "connected elements" or "connected components" may refer to elements or components of electrochemical devices that are physically in contact with, overlap, or otherwise in contact with each other. Exemplary connecting elements may be or include an active layer (e.g., a cathode active layer or anode active layer) disposed adjacent to or above the current collector layer, an electrolyte layer on top of the current collector layer and copper strip tabs or active cathode / anode layers.

[0144] Embodiments of this disclosure provide methods for manufacturing, preparing, or otherwise synthesizing solid aqueous electrolytes. The methods may include dissolving a salt and a functionalized copolymer in an aqueous solution to prepare an aqueous mixture. The functionalized copolymer may include at least two polycaprolactone (PCL) chains linked or coupled to a polymer central block. The functionalized copolymer may be functionalized with any suitable functional groups that promote or facilitate the formation of a hydrogel when the aqueous mixture is exposed to or cured with radiant energy (e.g., UV light). The methods may also include forming a layer of the aqueous mixture on a surface. The surface may be the anode and / or cathode of a battery. The methods may further include crosslinking the aqueous solution with radiant energy in the form of UV light to form a solid aqueous electrolyte, which may be a solid hydrogel comprising the functionalized copolymer and a salt dispersed in the functionalized copolymer.

[0145] Example

[0146] The embodiments and other implementations described herein are exemplary and are not intended to limit the full scope of the compositions and methods described herein. Equivalent changes, modifications, and variations can be made to the specific embodiments, materials, compositions, and methods within the scope of this disclosure, with substantially similar results.

[0147] Example 1

[0148] An exemplary solid aqueous electrolyte composition was prepared. In particular, the PCL-PEG-PCL-based solid aqueous electrolyte was prepared by the following method: synthesizing PCL-PEG-PCL macromonomer, synthesizing PCL-PEG-PCL acrylate, and subsequently using PCL-PEG-PCL acrylate to prepare the solid aqueous electrolyte.

[0149] For the synthesis of PCL-PEG-PCL macromonomers, the method or reaction shown in Scheme 2 is adapted from Xu et al. (Xu, C., Lee, W., Dai, G., and Hong, Y. ACS Appl. Mater. Interfaces 2018, 10, 12, 9969-9979), the contents of which are incorporated herein by reference to the extent consistent with this disclosure.

[0150]

[0151] Option 2

[0152] Specifically, approximately 5 g of ε-caprolactone, approximately 21.9 g of polyethylene glycol (PEG; MW = 20,000 Da), and approximately 34.8 mg of tin 2-ethylhexanoate catalyst were combined, mixed, or otherwise brought into contact with each other in a round-bottom flask and stirred with a magnetic stir bar. The round-bottom flask was purged with nitrogen and filled three times, then heated to approximately 120 °C for approximately 24 hours (h) with stirring to prepare the reaction mixture. The reaction mixture was cooled to room temperature, dissolved in dichloromethane (CH₂Cl₂), and the crude product was precipitated in cold anhydrous diethyl ether. The crude product... 1 H NMR shows Figure 3 In the middle. For example Figure 3 As shown, the initial precipitation of the macromonomer in diethyl ether results in the presence of unreacted ε-caprolactone in the crude product. To remove or separate the unreacted ε-caprolactone, the crude product is dissolved in about 50 mL of dichloromethane at room temperature. About 200 mL of diethyl ether is added dropwise over a short period of about 1 hour at room temperature to prepare a suspension. The suspension is stirred overnight at room temperature and filtered through a Buchner funnel. The resulting solid is dried overnight in a vacuum oven maintained at room temperature. The precipitation is repeated until... 1 The peaks attributed to ε-caprolactone were no longer observed in the 1H NMR spectrum, such as Figure 4 As shown in the image.

[0153] The above method was repeated using different amounts of polyethylene glycol to synthesize different macromonomers or macromonomer formulations with different polycaprolactone (PCL) to polyethylene glycol (PEG) ratios, as summarized in Table 1. 1 The block chain lengths of the corresponding PCL-PEG-PCL macromonomer formulations were determined by 1H NMR spectroscopy.

[0154] Table 1 – PCL-PEG-PCL macromonomer formulations

[0155]

[0156] For the synthesis of PCL-PEG-PCL acrylate, the method or reaction shown in Scheme 3 is adapted from Xu et al. (Xu, C., Lee, W., Dai, G., and Hong, Y. ACS Appl. Mater. Interfaces 2018, 10, 12, 9969-9979), the contents of which are incorporated herein by reference to the extent consistent with this disclosure.

[0157]

[0158] Option 3

[0159] Specifically, approximately 5 g of the PCL-PEG-PCL macromonomer was dissolved in approximately 15 mL of dichloromethane, and approximately 0.6 mL of triethylamine was added to the mixture with stirring, under nitrogen atmosphere in an ice bath for approximately 30 minutes. A solution comprising approximately 0.33 mL of acryloyl chloride and approximately 15 mL of dichloromethane was added dropwise to the reaction mixture and maintained for 30 minutes, resulting in a yellow color change of the solution. The solution was then heated under nitrogen atmosphere at approximately 40 °C for approximately 24 hours. After heating, the reaction mixture was subsequently cooled to room temperature, and the product was precipitated by dropwise addition of diethyl ether. 1 The presence of vinyl protons in the 1H NMR spectrum confirms the formation of PCL-PEG-PCL acrylate.

[0160] To prepare a solid aqueous electrolyte, namely a PCL-PEG-PCL hydrogel solid aqueous electrolyte, approximately 400 mg of PCL-PEG-PCL acrylate (Formulation C in Table 1) and approximately 2.5 mg of phenyl-2,4,6-trimethylbenzoyl lithium phosphine (LAP) were dissolved in 1 mL of 4 M ammonium chloride aqueous solution (NH4Cl / H2O). It should be understood that the molar concentration of ammonium chloride can be varied from approximately 0.5 M to approximately 6 M without any change or modification in the synthesis / method. The resulting solution was allowed to settle to remove air bubbles; however, nitrogen degassing was not performed. The pH of the solution was approximately 3 to 4. The resulting solution was uniformly placed on a 25 × 75 × 1 mm glass microscope slide that was taped to a glass plate. The solution was then subjected to DYMAX... TM Expose to Bluewave 200 (wavelength from approximately 300 to approximately 450 nm) for approximately 10 minutes at approximately 8 mW / cm². 2 The solution is irradiated with light, thus forming a hydrogel.

[0161] The hydrogel is yellow and contains ammonium chloride dispersed within it. It is also flexible and can be stretched without breaking. Analysis of the hydrogel shows that it can be dried and rehydrated, and the rehydrated hydrogel retains its flexibility. It was found that stable solid hydrogels cannot be produced when PCL-PEG-PCL acrylate is present at a concentration of about 10% by weight or less. In other words, surprisingly, it was discovered that a concentration of about 20% by weight or higher of PCL-PEG-PCL acrylate is required to prepare stable solid hydrogels.

[0162] Example 2

[0163] The mechanical properties of the PCL-PEG-PCL hydrogel solid aqueous electrolyte prepared from formulation C in Example 1 were evaluated. This was done using INSTRON... TM The standard compression test of the 5548 micrometer provides stress-strain curves for each sample from five different measurements. Young's modulus represents the sample's ability to maintain deformation, also known as robustness. The Young's modulus from five different measurements at different concentrations of ammonium chloride and zinc chloride is summarized in... Figure 5A and 5B In the middle. For example Figure 5A and 5B As shown, the hydrogel exhibits a Young's modulus greater than 0.3 MPa, which is sufficient for use as a solid gel polymer electrolyte in batteries. It should be understood that the hydrogel exhibits sufficient mechanical properties to be used as or applied to a separator between battery electrodes. The results further indicate that salt concentrations from approximately 0.5 M to approximately 6 M have no effect on the mechanical properties of the hydrogel, as no significant differences in the measured Young's modulus were observed when the salt molar concentration was changed. Figure 5B As shown in the image.

[0164] Example 3

[0165] The electrochemical properties of the PCL-PEG-PCL hydrogel solid aqueous electrolyte prepared from Formulation C in Example 1 were evaluated. Specifically, the electrolyte stability on the zinc surface was assessed. Typically, zinc surfaces corrode over time upon contact with aqueous solutions, producing zinc oxide and zinc hydroxide. These zinc oxides and hydroxides migrate into the electrolyte and alkalize the pH. It should be understood that the migration of oxides and hydroxides into the electrolyte and alkalization can cause or lead to the precipitation of diamine chlorides or zinc chlorides from ammonium chloride or zinc chloride. These precipitates may saturate the electrolyte and result in a decrease or loss of conductivity in the solid aqueous electrolyte.

[0166] To evaluate electrolyte stability, the PCL-PEG-PCL hydrogel solid aqueous electrolyte prepared from formulation C in Example 1 was placed in direct contact with a zinc surface and kept there for one week. After one week, zinc surface corrosion into zinc oxide was observed. However, the formation of zinc oxide was minimal. Furthermore, surprisingly, no salt precipitates were found in the bulk of the hydrogel, indicating that zinc surface passivation occurred and the interface between the zinc surface and the solid electrolyte reached a stable state in which no further corrosion occurred. Therefore, the PCL-PEG-PCL hydrogel solid aqueous electrolyte demonstrates sufficient corrosion resistance for use as a polymer electrolyte in zinc-based batteries or systems.

[0167] Example 4

[0168] Various batteries were fabricated and evaluated using the PCL-PEG-PCL hydrogel solid aqueous electrolyte prepared from formulation C in Example 1. Zinc was used as the anode, and manganese oxide / carbon was used as the cathode. To fabricate the batteries, the PCL-PEG-PCL hydrogel solid aqueous electrolyte was placed between the anode and cathode. The PCL-PEG-PCL hydrogel solid aqueous electrolyte was used as both the separator and the electrolyte. After a 10-hour settling period, the corresponding batteries were tested by applying 0.01 mA / cm². 2 The battery's electrochemical performance is evaluated by continuously discharging the battery, monitoring the battery voltage during discharge, and measuring the battery capacity at the end of discharge. Figure 6 The paper depicts representative discharge curves of the battery. The changes in the battery's resistance at different stages of discharge are shown in... Figure 7 As shown in the figure, Figure 7 The Nyquist plot was obtained from electrochemical impedance spectroscopy measurements.

[0169] like Figure 6 As shown, when 0.01 mA / cm is applied 2 At current, the battery exhibits a relatively small overpotential of approximately 100 mV and further displays the typical tilted discharge curve of a water-containing MnO2 / Zn battery. For example... Figure 7 As shown, the frequency response plotted as Re(Z) vs-Im(Z) indicates only slight changes in solution resistance over time and very small changes related to charge transfer resistance, thus demonstrating the stability of the PCL-PEG-PCL hydrogel solid aqueous electrolyte during discharge. Therefore, the foregoing demonstrates the stability of the electrolyte both within and within the electrolyte itself during battery discharge, as well as the stability of the Zn and MnO2 electrodes.

[0170] Example 5

[0171] The open-circuit voltage (OCV) stability of the battery prepared in Example 4 was evaluated and compared with that of a battery containing a liquid aqueous electrolyte. The solid-state aqueous battery was manufactured in the same manner as in Example 1. For comparison of the liquid aqueous electrolyte, the same salt concentration was dissolved in Milli-Q low resistivity water (>18 MΩ·cm). A glass fiber separator was soaked in this newly prepared electrolyte and placed between the anode and cathode. Both the solid- and liquid-based batteries were placed at room temperature, and the OCV of the batteries was continuously monitored using a potentiostat / galvanometer for specified time periods. Figure 8 The diagram shows the OCV stability of a battery pack and a battery using a liquid aqueous electrolyte.

[0172] like Figure 8 As shown, the battery pack prepared in Example 4 exhibited voltage stability over a period of approximately 120 hours. Figure 8 As further shown, the voltage stability of the battery pack prepared in Example 4 is at least as good as that of the battery using a liquid aqueous electrolyte.

[0173] Example 6

[0174] The discharge performance of the battery prepared in Example 4 was evaluated and compared with that of a battery containing a liquid aqueous electrolyte. Specifically, the capacity (mAh / cm³) was measured relative to voltage (V). 2 To compare discharge performance, after resting at OCV for 24 hours, the battery was discharged at 0.06 mA / cm. 2 Discharge. The battery is considered fully discharged when the voltage reaches 0.5V. The cathode used consists of a MnO2 active layer deposited on a carbon-based current collector, and the anode is a Zn active layer deposited on a silver-based current collector. Voltage reference is given to the Zn anode. Discharge performance is summarized in... Figure 9 middle.

[0175] like Figure 9 As shown, the discharge performance of a MnO2 / Zn electrochemical cell containing a PCL-PEG-PCL-based solid aqueous electrolyte with 4M NH4Cl is at least as good as that of a cell containing a liquid aqueous electrolyte with the same concentration of the same salt.

[0176] Example 7

[0177] Exemplary biodegradable electrochemical devices, particularly biodegradable electrochemical cells, have been prepared. To prepare the biodegradable electrochemical device, an anode slurry is prepared, a cathode slurry is prepared, electrodes for the biodegradable electrochemical device are printed, electrolyte macromolecular monomers are prepared, a curable electrolyte ink is prepared and printed, and the biodegradable electrochemical device is assembled.

[0178] To prepare the anode paste, specifically the zinc (Zn) anode paste, approximately 150 g of approximately 3 mm stainless steel pellets, approximately 16.1 g of ethylene glycol, approximately 5.0 g of styrene-butadiene rubber (SBR) binder (available commercially from MTI Corporation of Richmond, CA), approximately 8.3 g of zinc oxide (ZnO), approximately 12.2 g of bismuth(III) oxide (Bi₂O₃), and approximately 78.3 g of Zn powder were loaded into a grinder equipped with a 75 mL stainless steel grinding mill. The grinder was run until the Zn anode paste reached an emulsion consistency. The Zn anode paste was then separated from the pellets and transferred to a sealed container to prevent ethylene glycol evaporation.

[0179] To prepare the cathode paste, specifically manganese dioxide (MnO2) cathode paste, approximately 150 g of approximately 3 mm stainless steel pellets, approximately 21 g of ethylene glycol, approximately 1 g of styrene-butadiene rubber (SBR) binder, approximately 30 g of manganese oxide (IV) (MnO2), and approximately 7.6 g of graphite were packed into a grinder equipped with a 75 mL stainless steel grinding apparatus. The grinder was run until the MnO2 cathode paste reached a creamy consistency. The MnO2 cathode paste was then separated from the pellets and transferred to a sealed container to prevent ethylene glycol evaporation.

[0180] The viscosity of Zn anode slurry and MnO2 cathode slurry was evaluated using a shear sweep method to determine their rheological properties. The viscosity of Zn anode slurry and MnO2 cathode slurry is summarized in... Figure 10 Both the anode and cathode pastes exhibited non-Newtonian shear thinning behavior consistent with screen-printable inks. Particle size was observed to have no significant effect on ink viscosity.

[0181] Electrodes for biodegradable electrochemical devices are prepared by printing. Specifically, a 180-mesh nylon sieve and an 80-hardness scraper are used to apply silver paste-like ink (…). A screen-printed current collector was prepared onto a PLA-D substrate using either 5025 or a paste ink (CI-2042; NAGASE AMERICA, LLC.). The screen-printed current collector was then dried in a forced-ventilation oven maintained at approximately 120°C for about 9 minutes to remove or evaporate the solvent contained in the paste ink and to dry the paste ink. The dried current collector had a thickness of approximately 6 μm.

[0182] Zn electrodes were prepared by depositing a Zn anode layer near the corresponding current collector using a previously prepared Zn anode paste. Specifically, the Zn anode paste was screen-printed onto the current collector using an 80-mesh nylon screen and a scraper with an 80-degree hardness, and then dried in a forced-air oven at approximately 120°C for about 9 minutes to remove or evaporate the solvent contained in the paste and prepare the Zn electrode. The dried Zn electrode had a thickness of approximately 40 μm.

[0183] MnO2 electrodes were prepared by depositing a cathode active layer near the corresponding current collector using a previously prepared MnO2 cathode paste. Specifically, the MnO2 cathode paste was screen-printed onto the current collector using an 80-mesh nylon screen and a scraper with an 80 hardness, and then dried in a forced-ventilation oven at approximately 120°C for about 9 minutes to remove or evaporate the solvent contained in the paste and prepare the MnO2 electrode. The dried MnO2 electrode had a thickness of approximately 40 μm.

[0184] Screen printing of MnO2 and Zn slurry to prepare electrodes showed effective wetting on the substrate with no signs of pinholes.

[0185] To prepare electrolyte macromonomers, PCL-PEG-PCL diol and PCL-PEG20-PCL-diacrylate were prepared.

[0186] To prepare a curable electrolyte ink, approximately 39.4 g of ZnCl2, approximately 4.87 g of NH4Cl, approximately 80 g of water, and approximately 20 g of ethylene glycol were combined to produce an electrolyte solution containing approximately 2.9 M ZnCl2, approximately 0.9 M NH4Cl, and approximately 20% by weight of ethylene glycol. Then, approximately 6 g of the electrolyte solution was combined with approximately 2 g of a macromonomer and allowed to soak overnight without mixing to promote dissolution. Approximately 0.5 g of a stock solution of lithium phenyl (2,4,6-trimethylbenzoyl)phosphinate (LAP) was combined with approximately 10 g of the electrolyte solution and approximately 20 drops of BYK-24 silicone defoamer additive (commercially available from BYK-CHEMIS GMBH of Wesel, Germany) to prepare the curable electrolyte ink.

[0187] An electrolyte layer was prepared by screen printing a curable electrolyte ink onto the vicinity of the Zn electrode. The curable electrolyte ink was screen printed onto the vicinity of the Zn electrode using a 60-mesh sieve and an 80-hardness squeegee. The curable electrolyte layer was then cured for approximately 500 ms under a 14W, 395nm LED lamp to form a gelled electrolyte layer with a thickness of approximately 15 μm.

[0188] Similarly, another electrolyte layer was prepared by screen printing curable electrolyte ink onto the vicinity of the MnO2 cathode. The curable electrolyte ink was screen printed onto the vicinity of the MnO2 cathode using a 60-mesh sieve and an 80-hardness scraper. The curable electrolyte layer was then cured for approximately 500 ms under a 14W, 395nm LED lamp to form a gelled electrolyte layer with a thickness of approximately 15 μm.

[0189] To fabricate or assemble a biodegradable electrochemical device, a Zn electrode comprising a gel electrolyte layer, a Zn layer, and a current collector layer is stacked and placed on an MnO2 electrode comprising a gel electrolyte layer, an MnO2 layer, and a current collector layer. The Zn and MnO2 electrodes are oriented such that the corresponding electrolyte layers of each electrode face each other. A slight pressure is applied using rollers to promote close contact between the corresponding electrolyte layers of each Zn and MnO2 electrode, resulting in an unsealed biodegradable electrochemical device.

[0190] The unsealed, biodegradable electrochemical device was then placed on an 80 μm polyimide film (commercially available from DuPont of Wilmington, DE). The sheets are placed between the substrate to protect it from destructive melting during the subsequent sealing step. The edges of the stacked electrodes of the biodegradable electrochemical device are heat-sealed using a heat-sealing apparatus with a mold maintained at approximately 170°C. The sealed biodegradable electrochemical device is then removed from the polyimide film and allowed to cool.

[0191] Example 8

[0192] The open-circuit voltage across the exposed tab of the biodegradable electrochemical device prepared in Example 7 was measured to be 1.46 volts using a digital multimeter.

[0193] Example 9

[0194] Exemplary solid aqueous electrolyte compositions comprising a biodegradable central block are prepared. In particular, PVA-PCL-based solid aqueous electrolytes are prepared by synthesizing PVA-PCL macromonomers.

[0195] To synthesize the PVA-PCL macromonomer, the method or reaction shown in Example 3 is performed.

[0196] Step 1:

[0197]

[0198] Step 2:

[0199]

[0200] Option 3

[0201] Specifically, approximately 10 g of poly(vinyl alcohol) (average MW = 3000 g / mol) was placed in a round-bottom flash evaporator equipped with a magnetic stirrer and a condenser. The solid was dried under vacuum for approximately 2 hours. Approximately 20 mL of dimethyl sulfoxide was added, and the resulting mixture was heated at approximately 80 °C with stirring until completely dissolved. Once dissolved, the temperature was cooled to approximately 40 °C, and approximately 186 μL of ε-caprolactone and approximately 175 μL of 2-tin(II) (2-ethylhexanoic acid) were added. The reaction mixture was heated at approximately 100 °C for approximately 24 hours. After heating, the reaction mixture was cooled to approximately 40 °C. Approximately 30 mL of water was added, and the resulting free-flowing solution was poured into approximately 500 mL of acetone while stirring to prepare a suspension. The resulting suspension was centrifuged for approximately 10 minutes, and the resulting pellets were redispersed in acetone and centrifuged twice under the same conditions. The resulting solid was dried under vacuum overnight; approximately 6.7 g of PVA-PCL blocks were obtained as a yellow solid.

[0202] Approximately 6.7 g of PVA-PCL blocks were combined with approximately 200 mL of N,N-dimethylformamide (DMF) in a round-bottom flask equipped with a magnetic stirrer and a condenser, and heated at approximately 60 °C until completely dissolved. An additional aliquot of DMF was added to promote dissolution. The dissolved reaction mixture was then cooled to approximately 10 °C, and approximately 1.94 mL of trimethylamine was added. Approximately 1.94 mL of acryloyl chloride was added dropwise to the reaction mixture, followed by heating at approximately 40 °C for approximately 24 hours. The reaction mixture was then poured into acetone to form large particles of product. The particles were dried under vacuum overnight to yield approximately 1.6 g of PVA-PCL acrylate.

[0203] Example 10

[0204] Different biodegradable substrates were evaluated. Specifically, the biodegradable biopolyester substrates from Table 2 were extruded into sheets using an extruder equipped with a 20 cm wide flat die. The sheets were then calendered between two rolls. Release films based on polylactide blends were also 3D printed to obtain different surface qualities. Some sheets were annealed to enhance crystallinity and improve temperature resistance.

[0205] The temperature resistance of each sheet was evaluated by placing them in an oven on a flat metal plate at approximately 120°C or 150°C. Specifically, each sheet was placed on a flat surface in an oven maintained at the specified temperature for approximately 10 minutes. After heating, dimensional stability (e.g., flatness and uniformity) was evaluated. To pass the dimensional stability test, the corresponding sheet must not exhibit deformation. The results of the oven tests are summarized in Table 2.

[0206] In addition to assessing the dimensional stability of each biodegradable substrate, compatibility and adhesion with the inks were also evaluated. To assess the compatibility and adhesion of the inks to each substrate, previously prepared carbon-based and silver-based inks were screen-printed onto the respective biodegradable substrates, and adhesion was evaluated. Dimensional stability was also assessed after drying at approximately 120°C. To pass the ink adhesion assessment, the ink must maintain adhesion to the substrate (1) while being bent at an angle of approximately 45 degrees; and (2) the surface must be wiped with a cotton swab simultaneously. To pass the dimensional stability assessment after drying at approximately 120°C, each sheet must not exhibit deformation (e.g., maintain flatness and uniformity) after drying the ink at 120°C for 10 minutes. The results are summarized in Table 2.

[0207] Table 2. Size stability of different biodegradable substrates

[0208]

[0209] ＊ 3D printing

[0210] As shown in Table 2, all evaluated substrates, except for molten PBAT, passed the 120°C oven test. Further, as shown in Table 2, all substrates, except for PBAT and PBS, passed the 150°C oven test. Also as shown in Table 2, most substrates exhibited thermal instability during ink drying.

[0211] This disclosure has been described with reference to exemplary embodiments. Although a limited number of embodiments have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the foregoing detailed description. This disclosure is intended to be construed as including all such modifications and changes, provided they fall within the scope of the appended claims or their equivalents.

Claims

1. A biodegradable solid aqueous electrolyte comprising a copolymer hydrogel and a salt dispersed in the hydrogel, wherein the copolymer comprises at least two polycaprolactone chains connected to a central block of the polymer, and wherein the salt is present in the electrolyte at a concentration of at least 0.5 M.

2. The electrolyte of claim 1, wherein the polymer central block is derived from a naturally occurring biodegradable polymer having at least two free hydroxyl groups.

3. The electrolyte according to claim 1, wherein the polymer central block comprises a hydroxyl-containing polysaccharide, a biodegradable polyester, or a hydroxy fatty acid.

4. The electrolyte according to claim 1, wherein the polymer central block comprises polyvinyl alcohol, polybutylene succinate, or castor oil.

5. The electrolyte according to any one of claims 1 to 4, wherein the hydrogel comprises 20% by weight or more of a copolymer loading, based on the total weight of the hydrogel.

6. The electrolyte of claim 5, wherein the hydrogel comprises 30% by weight or more of a copolymer loading, based on the total weight of the hydrogel.

7. The electrolyte of claim 6, wherein the hydrogel comprises 50% by weight or more of a copolymer loading, based on the total weight of the hydrogel.

8. The electrolyte according to any one of claims 1 to 4, wherein the hydrogel comprises about 5% by weight to about 50% by weight of copolymer loading, based on the total weight of the hydrogel, wherein "about" in conjunction with a number means ±10% of that number including the end value.

9. The electrolyte according to any one of claims 1 to 4, wherein the salt comprises ammonium chloride (NH4Cl), zinc chloride (ZnCl2), or a mixture thereof.

10. The electrolyte according to any one of claims 1 to 4, wherein the salt is present in the electrolyte at a concentration of at least 3M and at most 10M.

11. The electrolyte according to any one of claims 1 to 4 further comprises nanomaterial additives.

12. The electrolyte according to claim 11, wherein the nanomaterial additives include cellulose nanocrystals, chitin nanocrystals, chitosan nanocrystals, starch nanocrystals, silica, alumina, layered silicates, lime, or any mixture thereof.

13. The electrolyte according to any one of claims 1 to 4, further comprising water and a co-solvent.

14. The electrolyte of claim 13, wherein the cosolvent comprises one or more of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, or combinations thereof.

15. The electrolyte according to claim 14, wherein the co-solvent is selected from ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and combinations thereof.

16. The electrolyte according to any one of claims 1 to 4, wherein the hydrogel has a viscosity of about 1000 cP to about 1.0E+6 cP, wherein "about" in conjunction with a number means ±10% of that number including the end value.

17. The electrolyte according to any one of claims 1 to 4, characterized in that... The solid aqueous electrolyte has a Young's modulus of about 0.10 MPa to about 100 MPa and a yield strength of about 5 kPa or greater, wherein "about" in conjunction with the number means ±10% of the number including the end value.

18. An electrochemical device, comprising: anode; cathode; and The biodegradable solid aqueous electrolyte of any one of claims 1 to 17, wherein the biodegradable solid aqueous electrolyte is disposed between the anode and the cathode.

19. The electrochemical device of claim 18, wherein a biodegradable solid aqueous electrolyte is printed on the cathode or anode.

20. A method for preparing a solid aqueous electrolyte according to any one of claims 1 to 17, the method comprising: Salt and functionalized copolymer are dissolved in an aqueous solution, wherein the copolymer comprises at least two polycaprolactone chains connected to a central block of a polymer, and is functionalized with functional groups that promote hydrogel formation when the aqueous solution is cured with ultraviolet light. An aqueous solution layer is formed on the surface; and An aqueous solution is cured with ultraviolet light to form a solid hydrogel, the solid hydrogel comprising a copolymer in which salts are dispersed.

21. The method of claim 20, wherein the polymer central block is derived from a naturally occurring biodegradable polymer having at least two free hydroxyl groups.

22. The method of claim 20, wherein the polymer central block comprises a hydroxyl-containing polysaccharide, a biodegradable polyester, or a hydroxy fatty acid.

23. The method of claim 20, wherein the polymer central block comprises polyvinyl alcohol, polybutylene succinate, or castor oil.

24. The method according to any one of claims 20 to 23, wherein the aqueous solution is formed directly on one or both electrodes of the battery prior to curing.

25. The method according to any one of claims 20 to 23, wherein the hydrogel is formed with a copolymer loading of 20% by weight or more, based on the total weight of the hydrogel.

26. The method according to any one of claims 20 to 23, wherein the salt comprises ammonium chloride (NH4Cl), zinc chloride (ZnCl2), or a mixture thereof.

27. The method according to any one of claims 20 to 23, wherein the salt is present in the electrolyte at a concentration of at least 3M and at most 10M.

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