electrodes for rechargeable alkaline batteries

Abstract

The present invention relates to an electrode for use in a rechargeable alkaline battery. The electrode comprises a current collector, an active material supported on the current collector, and an anion exchange membrane, wherein the active material comprises MnO2 or Zn, and the anion exchange membrane comprises a crosslinked benzimidazole polymer. The present invention further relates to a rechargeable alkaline battery comprising the electrode as a positive electrode when the active material comprises MnO2, or as a negative electrode when the active material comprises Zn.

Description

[Technical Field]

[0001] The present invention relates to an electrode for use in a rechargeable alkaline battery. The electrode comprises a current collector, an active material supported on the current collector, and an anion exchange membrane, wherein the active material comprises MnO2 or Zn, and the anion exchange membrane comprises a crosslinked benzimidazole polymer. The present invention further relates to a rechargeable alkaline battery comprising the electrode as a positive electrode when the active material comprises MnO2, or as a negative electrode when the active material comprises Zn. [Background technology]

[0002] Electrodes for electrochemical charge storage in Zn-MnO2 chemistry setups are limited to primary batteries. That is, there are currently no commercially available general-purpose Zn-MnO2 secondary batteries. One reason for this gap in the battery portfolio is that a reasonable degree of rechargeability has not yet been achieved with conventional electrode designs.

[0003] In fact, it has been observed that depth-of-discharge (DoD) levels exceeding 20% ​​of the initial electron capacity result in an irreversible phase transformation of manganese dioxide in Zn-MnO2 batteries. The cause of this irreversible phase transformation is likely a two-step reduction of MnO2. In the first reduction step, when Mn is reduced from the +4 oxidation state to the +3 oxidation state, manganese(III) oxyhydroxide (MnOOH) is formed. In the second reduction step, when Mn is reduced from the +3 oxidation state to the +2 oxidation state, Mn from MnOOH 3+Ions dissolve in the electrolyte, are reduced, and return as manganese(II) hydroxide (Mn(OH)2), which deposits on the electrode. However, this process simultaneously generates compounds such as hausmanite (Mn3O4) and hetaerolite (ZnMn2O4), which are electrochemically inert and insulating, resulting in permanent losses of capacitance and conductivity. Of the aforementioned compounds, hetaerolite is formed in the presence of zincate ions, which are originally generated at the negative electrode but can pass through known battery separator materials with little obstruction.

[0004] Various approaches have been proposed in conventional technology to improve the rechargeability of Zn-MnO2 batteries.

[0005] The first approach was proposed by Kordesch and his collaborators (Kordesch, K., Gsellmann, J., Peri, M., Tomantschger, K., Chemelli, R., Electrochim. Acta 26, 1495-1504, 1981). They found that the form of manganese dioxide used in the manufacture of the cathode should be carefully selected as it affects rechargeability. Furthermore, they recommended limiting the amount of zinc in the battery setup. Despite implementing these two measures, the DoD level achieved after 100-200 charge cycles was only in the range of 15-25% of the initial electron capacity. This is roughly equivalent to a DoD of 10% of the battery's total capacity.

[0006] More recently, Ingale and his collaborators (Ingale, ND, Gallaway, JW, Nyce, M., Couzis, A., Banerjee, S., J. Power Sources 276, 7-18, 2015) demonstrated stable reversible capacity of alkaline Zn-MnO2 batteries at DoD levels of 10% to 20% for 3000 and 500 cycles, respectively.

[0007] Another approach to improving the reversibility of batteries involved chemical or physical modification of manganese dioxide electrodes. For Bi-modified δ-MnO2 (barnesite) and β-MnO2 (pyrrolsite), near-perfect reversibility was demonstrated by Wroblowa et al. (Wroblowa, HS, Gupta, N., J. Electroanal. Chem. Interfacial Electrochem. 238, 1-2, 1987), but this was in the absence of Zn species. Similarly, Cu combined with Bi2O3 in an alkaline electrolyte without zincate (zinc salts)... 2+ Complete reversibility of intercalated δ-MnO2 has been demonstrated by Yadav and his collaborators (Yadav, GG, Gallaway, JW, Turney, DE, Nyce, M., Huang, J., Wei, X., Banerjee, S., Nat.Commun. 14424, 2017).

[0008] Further attempts to prevent irreversible structural changes in manganese dioxide electrodes and achieve rechargeability have been based on the use of additional layers positioned to block the diffusion of zincate ions toward the MnO2 electrode within the battery cell. Yadav and collaborators reported that up to 900 charge / discharge load cycles with >80% retention of DoD can be completed in a Zn-MnO2 battery (δ-MnO2 with Cu / Bi intercalated) when using a calcium hydroxide intermediate layer (Yadav, GG, Wei, X., Huang, J., Gallaway, JW, Turney, DE, Nyce, M., Secor, J., Banerjee, S., J. Mater. Chem. A5, 15845-15854, 2017). Duay and collaborators (Duay, J., Kelly, M., Lambert, TN, J. Power Sources 395, 430-438, 2018) have developed a ceramic Na3Zr2Si2PO 12Using a separator as an additional layer was found to increase battery life by 22% (at 5% DoD, C / 5 rate). Furthermore, films made from special polymers such as N-butylimidazolium-functionalized polysulfone (NBI-PSU) separators were found to extend the lifecycle of Zn-MnO2 batteries to 80 charge / discharge load cycles at high DoD levels (Kolesnichenko, IV, Arnot, DJ, Lim, MB, Yadav, GG, Nyce, M., Huang, J., Banerjee, S., Lambert, TN, ACS Appl. Mater. Interfaces 12, 50406-50417, 2020). In addition to all of the above, ion-selective films based on graphene and its oxides (GO PVA-III) have recently been found to selectively block zincate ions and discharge the MnO2 electrode for up to 150 charge / discharge load cycles (Huang, J., Yadav, GG, Turney, DE, Cho, J., Nyce, M., Wygant, BR, Lambert, TN, Banerjee, S., ACS Appl. Energy Mater. 5, 9952-9961, 2022).

[0009] Furthermore, approaches to facilitating rechargeability, which are already known from conventional technologies, are unsatisfactory for various reasons.

[0010] For most of the approaches summarized above, the desired MnO2 electrode reversibility is only possible at low DoD (or shallow discharge). This significantly reduces the energy density of the battery cell.

[0011] Furthermore, the use of additional layers arranged to block the diffusion of zincate ions has various drawbacks. When using a ceramic separator as the additional layer, for example, the resistivity of the battery cell becomes very high. In addition, the brittleness of the ceramic material is an obstacle to the fabrication of flexible electrodes. A film made of a special polymer is disadvantageous because its availability is limited. Also, such a polymer film has too short cycle life. In the case of a calcium hydroxide intermediate layer, the volumetric energy density of the Zn-MnO2 cell decreases and the resistivity increases. Also, zincate ions are trapped by the calcium hydroxide intermediate layer and can no longer participate in the recharge of the Zn electrode.

Prior Art Documents

Non-Patent Documents

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Non-Patent Document 1

Non-Patent Document 2

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Non - Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0013] Therefore, the need for an alkaline battery with high rechargeability still remains. Thus, an object of the present invention is to provide an electrode that enables an alkaline battery to be recharged almost without limit, that is, to the same extent as, for example, a lead - acid battery, a nickel - metal hydride battery, or a nickel - cadmium battery.

Means for Solving the Problems

[0014] The above object is achieved by providing an electrode having the features of independent claim 1. Advantageous embodiments of this electrode may be derived from the dependent claims. Furthermore, a rechargeable alkaline battery having the features of claim 15 is provided.

[0015] The electrode according to the present invention comprises, in order from the inside out, a current collector, an active material supported on the current collector, and an anion exchange membrane, wherein the active material comprises MnO2 or Zn, and the anion exchange membrane (AEM) comprises a cross-linked benzimidazole polymer.

[0016] Because of this configuration, the electrodes are suitable for use in rechargeable alkaline batteries such as rechargeable Zn-MnO2 batteries.

[0017] In particular, and surprisingly, AEMs containing cross-linked benzimidazole polymers were found to be effective against processes that result in irreversible phase transformation of MnO2 active materials. In addition, AEMs have been shown to have a long lifetime in alkaline electrolytes. More specifically, AEMs containing cross-linked benzimidazole polymers are effective against hydroxide ions, i.e., OH - This enables the efficient transport of zincate ions, namely Zn(OH)4. 2- It blocks the diffusion and / or transport of [the substance]. Furthermore, its AEM has chemical stability and dimensional stability in alkaline electrolytes.

[0018] It is understood that the electrodes according to the present invention may have a symmetrical setup with respect to the current collector. In a symmetrical setup, the active material is supported (loaded) on each of the two opposing sides (faces) of the current collector, and the anion exchange membrane is also positioned on each of the two opposing sides of the current collector.

[0019] The underlying mechanism While we do not wish to be bound by theory, the transport of hydroxide ions in alkaline battery cells is thought to proceed through three basic mechanisms: diffusion, the Grotthuss mechanism, and surface site hopping. Surface site hopping, involving the movement of hydroxide ions by hopping along strongly interacting groups, is facilitated by the presence of tertiary ammonium groups in the backbone of the crosslinked benzimidazole polymer.

[0020] According to the current hypothesis, the transport of zincate ions is effectively hindered by the steric size exclusion principle. In this context, it should be noted that zincate ions have a relatively large solvodynamic radius. For example, in 4M NaOH, zincate ions have a solvodynamic radius of approximately 0.33 nm to 0.34 nm. Crosslinking in a benzimidazole polymer, which can be either ionic or covalent, preferably by a negative charge or covalent, results in the formation of channels within the AEM. These channels are appropriately sized and / or configured to block the passage of zincate ions. Furthermore, Zn 2+ ions are assumed to strengthen the benzimidazole polymer (PBI) network by coordination, creating continuous water channels, and exposing more polar groups. This process increases the accessible surface area of the water inside the membrane, leading to the development of sub-nanometer-sized molecular channels that enable rapid charge carrier transport. At the same time, Zn 2+ ions are trapped within the membrane by their coordination to the PBI network. 2+

[0021] In addition, the membrane may contain both positive charges, for example, derived from tertiary ammonium groups, and negative charges, such as those derived from sulfonic acid groups. These fixed charges establish an electrostatic environment within the polymer matrix and affect the distribution of mobile ions (such as hydroxide ions and zincate ions) in the surrounding medium. Due to the presence of both positive and negative charges within the membrane, certain ions may be selectively attracted or repelled by the fixed charges (Donnan exclusion principle). In a strong alkaline medium such as in an alkaline battery cell, the negative charges from sulfonic acid and imidazolide groups may preferentially interact with positively charged Zn 2+ ions, while the positive charges from alkylated / crosslinked tertiary ammonium groups may preferentially interact with negatively charged hydroxide ions (OH - ).

[0022] The balance of factors governing selective ion transport within AEMs is complex, and the challenge of designing a membrane that can maintain optimal anion conductivity while simultaneously exhibiting complete blocking of zincate ions has remained unresolved until now, requiring inventive skills to find a delicate equilibrium among all the phenomena described above.

[0023] In addition to all of the above, the stability of AEM may also be attributable to the presence of crosslinks. Crosslinks contribute to increased inertness and make it more difficult to access potential reaction sites.

[0024] definition Within the scope of this invention, the term “electrode” is not used only for a single electrical conduction phase. Rather, the term “electrode” is used for two or more electrical conduction phases connected in series, where charge carriers (ions or electrons) may be exchanged between them (see Bard, AJ, Inzelt, G., Scholz, F., Electrochem. Dict. (2nd Edition), Springer, Berlin, Heidelberg, 2012). These phases may be an electron conductor and an electrolyte, or an electron conductor and an ionic conductor, for example, an AEM.

[0025] An "electrochemical cell" is a system consisting of at least two electrodes in contact with an electrolyte and connected by an external electrical circuit. Therefore, the term "battery" can be understood as an electrochemical device consisting of one or more interconnected electrochemical cells configured in series or parallel to achieve desired voltage-current characteristics.

[0026] When the active material contains MnO2, the electrode may also be referred to as the “manganese oxide electrode” or “positive electrode.” In the context of this application, the term “manganese oxide” should be understood as a general term for MnO2 in any crystalline structure. When the active material contains Zn, the electrode may also be referred to as the “zinc electrode” or “negative electrode.”

[0027] The term "may be substituted" is intended to explicitly indicate that the identified group is either unsubstituted or substituted with one or more suitable substituents.

[0028] The term "benzimidazole polymer" refers to a polymer containing benzimidazole units. Benzimidazole polymers may be homopolymers or copolymers. In this invention, the term "copolymer" refers to a polymer prepared from at least two different monomers. In other words, the term "copolymer" also includes terpolymers and copolymers having four or more different monomer units. Therefore, a benzimidazole polymer may be a copolymer containing benzimidazole units and at least one further monomer unit different from the benzimidazole units.

[0029] The term "crosslinked" is a term used in polymer science. It describes a state in which polymer chains are bound together by covalent or ionic bonds, resulting in an interconnected network (Clemens, AL; Jayathilake, BS; Karnes, JJ; Schwartz, JJ; Baker, SE; Duoss, EB; Oakdale, JS; Tuning Alkaline Anion Exchange Membranes through Crosslinking: A Review of Synthetic Strategies and Property Relationships. Polymers, 2023;15(6), 1534). In other words, the term "crosslinked" refers to a state in which there is a permanent interaction between different sites in a polymer, for example, different sites in a benzimidazole copolymer. The crosslinked sites may be located on different polymer chains. Otherwise, the crosslinked sites may be separated by several repeating units, for example, at least five, preferably at least 50, repeating units. Furthermore, persistent interactions may be characterized by being stable under conditions that are dominant in alkaline battery cells, such as Zn-MnO2 battery cells. Similarly, persistent interactions may be covalent and / or ionic bonds. The presence of crosslinking results in the formation of an interconnected network structure. In the context of the present invention, crosslinking occurs during the casting process of anion exchange membranes, mainly due to the presence of various functional groups in the structure of the benzimidazole polymer that can promote ionic or covalent bonding within or between polymer chains.

[0030] Within the scope of the present invention, the terms "membrane" or "anion exchange membrane" refer to a layer that has dimensional stability on its own, for example, a layer with a thickness of 1.0 μm or more, for example, 1.0 to 100 μm. In contrast, a "coating layer" is a layer that does not have dimensional stability on its own and needs to be placed on a substrate, for example, a layer with a thickness of less than 1.0 μm, such as 0.01 μm to less than 1.0 μm.

[0031] Benzimidazole polymer In preferred embodiments, the crosslinked benzimidazole polymer comprises repeating units represented by the following formula (I). [ka] In the formula, A is a bond or oxygen, particularly preferably a bond; B is a bond, phenylene, 4,4'-diphenylene ether or sulfonated 4,4'-diphenylene ether; R1 to R4 are independently selected from the group consisting of lone pairs, hydrogen, and C1 to C6 alkyl groups; and R5 is hydrogen or a sulfonic acid group, preferably hydrogen.

[0032] In the first preferred embodiment, the crosslinked benzimidazole polymer is a crosslinked benzimidazole polymer.

[0033] More preferably, the crosslinked benzimidazole polymer is a crosslinked benzimidazole polymer containing repeating units represented by the following formula (Ia). [ka]

[0034] The systematic name for the benzimidazole polymer consisting of the repeating units of formula (Ia) is poly-(1-(4,4'-diphenyl ether)-5-oxybenzimidazole)-benzimidazole (hereinafter also referred to as "PBI-OO").

[0035] In a particularly preferred embodiment, the crosslinked benzimidazole polymer is a crosslinked benzimidazole polymer containing repeating units represented by the following formula (Ia'). [ka]

[0036] The systematic name for the benzimidazole polymer consisting of repeating units of formula (Ia') is poly(4,4'-diphenyl ether-5,5'-bibenzimidazole) (hereinafter also referred to as "PBI-O").

[0037] A crosslinked benzimidazole polymer containing repeating units represented by the following formula (Ia) may be obtained by (i) reacting 4,4'-oxydibenzene-1,2-diamine and 4,4'-oxybis(benzoic acid) according to the following reaction formula (R1) to obtain a benzimidazole polymer consisting of repeating units of formula (Ia), and (ii) subjecting the benzimidazole polymer to crosslinking conditions. [ka] Both starting materials are commercially available. Compound 4,4'-oxydibenzene-1,2-diamine is commercially available, for example, from Alfa Chemistry (CAS 2676-59-7).

[0038] In another preferred embodiment, the crosslinked benzimidazole polymer is a crosslinked benzimidazole polymer comprising repeating units represented by the following formula (Ib) or (Ib'). [ka] In the formula, R1 to R4 are independently C1 to C6 alkyl groups. A benzimidazole polymer consisting of repeating units of formula (Ib) may be called "alkylated PBI-OO". A benzimidazole polymer consisting of repeating units of formula (Ib') may be called "alkylated PBI-O".

[0039] To obtain alkylated PBI-OO, a blend of lithium chloride and PBI-OO may be dissolved in anhydrous NMP under an inert argon environment. Subsequently, sodium hydride (as a 60% suspension in hexane) and a suitable alkylating agent (including, but not limited to, iodomethane or benzyl bromide) may be added to the solution. The reaction may be carried out according to the following reaction formula (R2). [ka]

[0040] In yet another preferred embodiment, the crosslinked benzimidazole polymer is a crosslinked benzimidazole polymer comprising repeating units represented by the following formula (Ic) or (Ic'). [ka] In the formula, R1 to R4 are independently C1 to C6 alkyl groups. A benzimidazole polymer consisting of repeating units of formula (Ic) may be called "sulfonated PBI-OO," and a benzimidazole polymer consisting of repeating units of formula (Ic') may be called "sulfonated PBI-O."

[0041] To obtain sulfonated PBI-OO, a direct sulfonation process may be carried out on alkylated PBI-OO using concentrated sulfuric acid, preferably under otherwise mild reaction conditions. The reaction temperature may be maintained in the range of 40 to 100°C, and the reaction time may be 1 to 24 hours. This reaction is reflected in the following reaction formula (R3). [ka]

[0042] The degree of sulfonation of sulfonated PBI-OO may be in the range of 1 to 5 mol%, preferably 2.5 to 5 mol%, as measured by the number of moles of sulfur atoms per repeating unit based on benzimidazole. The method for measuring the number of moles of sulfur atoms per repeating unit based on benzimidazole is, for example, by elemental analysis as described by Peron et al. (Peron, J., Ruiz, E., Jones, DJ, Roziere, J., J. Membr. Sci. 314, 1-2, 2008).

[0043] The crosslinked benzimidazole polymer may further contain other repeating units represented by the following formula (I'). [ka]

[0044] In formula (I'), E may be either CO or SO2, and Y may be a substituted or substituted phenylene. In this context, preferred substituents for diphenylene and phenylene are sulfonic acid groups.

[0045] Therefore, the second repeating unit may have the following formula (I'a). [ka]

[0046] In formula (I'a), each of X1 to X4 may independently be hydrogen or a sulfonic acid group, preferably one of X1 to X4 is a sulfonic acid group and the others are hydrogen.

[0047] The benzimidazole polymer has a number-average molecular weight M, preferably 20-100 kg / mol, preferably 50-60 kg / mol. n It has a number-average molecular weight M. n This is preferably measured by gel permeation chromatography (in DMF at 60°C with the addition of 0.5 g of LiCl).

[0048] The crosslinked benzimidazole polymer may further include ionic crosslinking and / or covalent crosslinking.

[0049] The covalent crosslinks are preferably selected from units having a structure represented by one of the following formulas (II) and (III). [ka] During the ceremony, * The symbol indicates the connection position.

[0050] Therefore, the bridged section may have a structure represented by one of the following formulas (IIa) or (IIIa). [ka]

[0051] Ionic crosslinking may also occur through interactions represented by the following formula (IIIb). [ka]

[0052] Anion exchange membrane (AEM) Anion exchange membranes containing crosslinked benzimidazole polymers may be cast membranes. In this case, the anion exchange membrane may be obtained by preparing a casting solution containing the benzimidazole polymer and casting the solution. Crosslinking may occur after or during the casting process. This membrane has inherent properties for effectively transporting hydroxide anions and is suitable for use as anion exchange membrane. The imidazolium groups present in the benzimidazole polymer are primarily involved in enhancing the anion exchange properties of the membrane.

[0053] Ionic crosslinks, for example, those represented by formula (IIIb), may be generated during the casting process by the self-assembly and alignment of polymer chains.

[0054] Covalent crosslinking may be obtained by (1) adding a crosslinking agent such as α,α0-dibromo-p-xylene to a casting solution, followed by casting and heating the cast film to, for example, about 80°C for 8 hours, or (2) exposing the cast film to a high temperature of 300-400°C, preferably about 350°C. Crosslinking such as that represented by formula (IIa) may preferably be obtained by means (1), while crosslinking such as that represented by formula (IIIa) may preferably be obtained by means (2). The specific type of crosslinking may be selected based on the intended application and the desired (mechanical) properties of the resulting film.

[0055] If the benzimidazole polymer contains covalent crosslinks, the crosslink content may be 1 to 20 mol%, preferably 5 to 15 mol%, per repeating unit based on benzimidazole. If the crosslink content exceeds 20 mol%, the transport of hydroxide ions may be inhibited. If the crosslink content is less than 1 mol% per repeating unit based on benzimidazole, the movement of zincate ions toward the active material of the positive electrode may not be effectively prevented.

[0056] Simultaneously or alternatively, the anion exchange membrane preferably has pores with an average diameter of less than 1.6 nm, and the pores are more preferably created by ionic crosslinking. In another preferred embodiment, the anion exchange membrane has pores with an average diameter preferably less than 0.8 nm, more preferably less than 0.34 nm, for example, 0.10 to any of the above upper limits. If the average diameter of the pores is greater than 0.8 nm, the passage of zincate ions through the AEM containing the crosslinked benzimidazole polymer may not be effectively prevented.

[0057] The AEM may be mounted within the frame or formed as a pouch.

[0058] When the AEM is mounted within a frame, the frame may be a polymer frame. It is advantageous if the frame is stable in alkaline and highly alkaline media. In one embodiment, the frame may essentially consist of an ABS composition or a PMMA composition. Sealing of the frame is possible by either mechanical sealing (e.g., by screwing) or by applying an adhesive. Furthermore, in a symmetrical electrode setup, it is understood that each of the two AEMs on each of the two opposing sides of the current collector may be mounted within a frame. In the latter case, the seal between the two frames is preferably formed by applying an adhesive.

[0059] When the AEM is formed as a pouch, the pouch surrounds at least the current collector and the active material. The pouch is preferably sealed with an adhesive or glue, particularly an epoxy adhesive or glue. The adhesive or glue may be a two-component adhesive or glue, which may include a binder component and a curing component. Particularly preferred adhesives or glues are bisphenol-F-(epichlorohydrin) epoxy resin or bisphenol-A-(epichlorohydrin) epoxy resin. Such adhesives or glues are commercially available from UHU GmbH in Buhl, Baden, under the trademark name "UHU plus endfest 300".

[0060] In another embodiment, the AEM has a thickness of 1.0 μm to 60 μm, preferably 5.0 μm to 50 μm, and more preferably 10.0 μm to 40 μm.

[0061] It is even more preferable that the weight of the cross-linked benzimidazole polymer is in the range of 70 to 99.9% by weight, preferably 90 to 99.9% by weight, relative to the weight of the AEM. In a particularly preferred embodiment, the AEM consists of a cross-linked benzimidazole polymer or substantially consists of a cross-linked benzimidazole polymer.

[0062] Furthermore, according to EDX elemental analysis (e.g., S9000G TESCAN FIB-SEM, TESCAN, measured in the Czech Republic) using an accelerating voltage of 30 kV and a probe current of 300 pA, the AEM preferably has a carbon content of 80-85 at%, more preferably 80-84.0 at%, an oxygen content of 4.0-6.0 at%, a nitrogen content of 10-15 at%, a sulfur content of 0.05-0.2 at%, and a bromine content of 0.05-1.0 at%, more preferably 0.1-0.2 at%.

[0063] coating layer In one embodiment of the present invention, the electrode further includes a coating layer between the active material and the anion exchange membrane. In an electrode with a symmetrical setup, the coating layer is positioned between the active material and the AEM on each of the two opposing sides of the current collector.

[0064] The coating layer may contain the same type of polymer as the anion exchange membrane. That is, the coating layer preferably contains a benzimidazole polymer, and more preferably contains a benzimidazole polymer containing repeating units represented by the following formula (I) as described above. The coating layer preferably has a thickness of less than 1.0 μm, for example, 0.01 to less than 1.0 μm or 0.1 to less than 1.0 μm.

[0065] Coating the electrode active material with the same polymer type used in anion exchange membranes (AEMs) significantly improves adhesion between the two and creates entanglement at their interface.

[0066] When the electrode according to the present invention is the positive electrode, the presence of a coating layer results in better electrochemical performance and increased retention of soluble Mn species such as MnOOH formed during battery discharge. The coating layer is effective in keeping these species close to the electrode surface and promoting their precipitation onto the electrode surface. Without the coating layer, the Mn species can diffuse away, and it becomes difficult to re-oxidize the Mn species to MnO2 due to their distance from the electrode surface.

[0067] When the electrode according to the present invention is the negative electrode, the presence of the coating layer improves electrochemical performance and further reduces the movement of zincate ions away from the electrode surface. During battery discharge, the coating layer keeps the zincate ions close to the Zn electrode and ensures their accessibility for reduction back to metallic zinc during the charging process. As a result, the coating layer can further improve the reversibility of the negative electrode and contribute to overall battery efficiency and lifespan.

[0068] active material If the active material in the electrode of the present invention contains MnO2, the active material may further contain carbon, Bi2O3, and an optional binder material.

[0069] If present, the binder material is preferably selected from the group consisting of benzimidazole polymers, preferably benzimidazole polymers comprising repeating units represented by the following formula (I); cellulose and fluoropolymers, such as polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene.

[0070] It is even more preferable if the active material contains 20 to 60% by weight of MnO2 relative to the total weight of the active material.

[0071] The active material may contain at least one compound selected from the group consisting of carbon, Bi2O3, a binder material, or a mixture thereof. Preferably, the carbon content is 30-45% by weight, the Bi2O3 content is 5-15% by weight, and the binder material content is 5-15% by weight, relative to the total weight of the active material.

[0072] If the active material contains MnO2, MnO2 is preferably α-MnO2 or electrolytic manganese dioxide (EMD). While the two preceding polymorphs are preferred, MnO2 may be a polymorph selected from the group consisting of β-MnO2, γ-MnO2, δ-MnO2, ε-MnO2, or λ-MnO2 and combinations thereof, as well as combinations of these with either or both α-MnO2 and EMD.

[0073] If the active material is α-MnO2, the α-MnO2 may be prepared by a microwave heating hydrothermal process. Furthermore, α-MnO2 can be Cu-exchanged α-MnO2(Cu 2+ It may also be / α-MnO2).

[0074] When the active material is EMD, the EMD may be produced electrolytically. In certain embodiments, the EMD corresponds to electrolytically produced γ-MnO2 and is a twin crystal of β-(pyrrolsite) and R-(ramsdelite) phases. The advantages of EMD are its shallow potential drop during discharge, its structure which facilitates proton transfer, and its low-cost availability.

[0075] The active material may further contain nickel-based additives in an amount of preferably 0.5 to 10% by weight, more preferably 1.0 to 2.0% by weight, relative to the total weight of the active material.

[0076] Current collector The current collector may have various configurations. In particular, the current collector may be made of mesh, foil, or foam. For example, the current collector may be nickel foam for the positive electrode and copper foil for the negative electrode.

[0077] Furthermore, the current collector preferably includes a tab portion. The tab portion may be understood as a portion that extends beyond the periphery of other components of the electrode. The tab portion facilitates providing an electrical connection to the current collector that would otherwise be difficult to access when sandwiched by other components of the electrode.

[0078] Electrochemical cell Also disclosed is an electrochemical cell comprising an electrolyte and the above electrodes, which are configured as a positive electrode if the active material contains MnO2, or as a negative electrode if the active material contains Zn. This electrochemical cell further comprises a counter electrode connected to the above electrodes via an electrical circuit.

[0079] Rechargeable alkaline batteries The present invention further provides a rechargeable alkaline battery (rechargeable alkaline battery) comprising one or more of the above-described electrochemical cells. The battery comprises an electrolyte and at least one of the above-described electrodes, which is a positive electrode if the active material contains MnO2, or a negative electrode if the active material contains Zn.

[0080] If the rechargeable alkaline battery includes the above electrode as the positive electrode, the battery may further include a zinc negative electrode and an electrolyte, preferably an alkaline electrolyte. If the rechargeable alkaline battery includes the above electrode as the negative electrode, the battery may further include a manganese oxide-based positive electrode and an electrolyte, preferably an alkaline electrolyte.

[0081] The rechargeable alkaline battery may further include a housing and a separator. In one embodiment, the housing may be a molded box or container.

[0082] The rechargeable alkaline battery may have prismatic, cylindrical, or pouch-shaped battery cells. [Brief explanation of the drawing]

[0083] Embodiments of the present invention are shown as examples and are not limited to the drawings of the appended drawings. In the drawings, the same reference numerals represent similar elements.

[0084] [Figure 1] Figure 1 is a schematic diagram of an exemplary MnO2 electrode according to the present invention, shown as an exploded view. [Figure 2] Figure 2 shows a series of digital photographs illustrating the process of assembling and mounting electrodes within the frame. [Figure 3] Figure 3 shows the superior capacity retention of the MnO2 electrode of the present invention, in contrast to a simple MnO2 electrode. [Figure 4] Figure 4 shows the results of durability-performance tests of the MnO2 electrode of the present invention at 22%DoD and 44%DoD. [Figure 5] Figure 5 shows the results of the durability-performance test of the MnO2 electrode of the present invention at 100% DoD. [Figure 6] Figure 6 shows the charge / discharge profiles at 100% DoD for three MnO2 electrodes of the present invention with different area capacities. [Figure 7] Figures 7a and 7b show the measurement setup for the anode stripping voltammetry test. [Figure 8] Figures 8a–8i show the data used to establish calibration curves for anode stripping voltammetry, as well as the results of tests using anion exchange membranes containing crosslinked benzimidazole polymers and other anion exchange membranes. [Figure 9(1)] Figures 9a to 9e show the development of voltage-capacitance curves for several charge-discharge cycles for one MnO2 electrode and several reference electrodes according to the present invention, relative to an Hg / HgO reference electrode in 10M KOH + 0.25M ZnO. [Figure 9(2)] Figures 9a to 9e show the development of voltage-capacitance curves for several charge-discharge cycles for one MnO2 electrode and several reference electrodes according to the present invention, relative to an Hg / HgO reference electrode in 10M KOH + 0.25M ZnO. [Figure 9(3)] Figures 9a to 9e show the development of voltage-capacitance curves for several charge-discharge cycles for one MnO2 electrode and several reference electrodes according to the present invention, relative to an Hg / HgO reference electrode in 10M KOH + 0.25M ZnO. [Figure 10] Figures 10a and 10b show the voltage-capacitance curve development for a single cell containing both a positive MnO2 electrode and a negative Zn electrode over multiple charge-discharge cycles at various DoD levels. In addition, these figures show the relevant electrochemical setup and characteristics of the electrodes and electrolyte. [Figure 11(1)] Figures 11a-11c show the infrared spectra of exemplary anion exchange membranes, along with comparisons to literature data. Figure 11d shows digital images of the anion exchange membrane in DMAc taken before and after 8 hours at 80°C. [Figure 11(2)]Figures 11a-11c show the infrared spectra of exemplary anion exchange membranes, along with comparisons to literature data. Figure 11d shows digital images of the anion exchange membrane in DMAc taken before and after 8 hours at 80°C. [Modes for carrying out the invention]

[0085] Detailed description of drawings and embodiments Figure 1 is a schematic exploded view of an exemplary MnO2 electrode according to the present invention. The current collector 1 is configured as a mesh and has tab portions 1a that provide electrical connections. The current collector 1 is sandwiched between two layers of active material 2 and 2'. The active material layers 2 and 2' contain MnO2, carbon, and a PTFE binder material. Adjacent to each of the active material layers 2 and 2' are coating layers 3 and 3' made of substantially crosslinked benzimidazole polymer. On the outermost side are anion exchange membranes 4 and 4', respectively. The anion exchange membranes 4 and 4' are shown in Figure 1 as being mounted within polymer frames 5 and 5', but can also be molded into pouches and sealed in a pouch shape.

[0086] Figures 2a and 2b show the stepwise assembly process for both the MnO2 positive electrode (a) and the Zn negative electrode (b) encapsulated within a polymer frame.

[0087] The following steps are performed for the MnO2 cathode assembly (Figure 2a): Step 1: A first polymer (ABS, PMMA) frame (or "plastic frame") is coated with epoxy adhesive. Step 2: A first membrane (AEM) is placed on the epoxy adhesive-coated frame. Step 3: A current collector, supported on both sides by MnO2-based active material, is placed in the center of the first membrane, and a layer of epoxy adhesive is deposited on the edges of the membrane, avoiding contact with the surface of the current collector. Step 4: A second membrane layer is placed on top of the setup of the first membrane and current collector, and adhesive is applied to connect the two membranes. A third layer of adhesive is deposited on top of the membrane edges. Step 5: A second polymer frame (ABS, PMMA) is placed on top of the membrane, and the resulting electrode is gently pressed for 12 hours to allow the adhesive to cure and the assembly to be sealed.

[0088] The following steps are performed for the Zn negative electrode assembly (Figure 2b): Step 1: A first polymer (ABS, PMMA) frame (or "plastic frame") is coated with epoxy adhesive. Step 2: A first membrane (AEM) with a slit on the upper side is placed on the epoxy adhesive-coated frame. The slit allows gases generated during cycling to be released (vents, etc.) and prevents pressure buildup within the electrode. Step 3: A current collector, supported on both sides of the Zn-based active material, is placed in the center of the first membrane, and a layer of epoxy adhesive is applied to the edges and upper side (slit) of the membrane, avoiding contact with the surface of the current collector. Step 4: A second membrane is placed on top of the setup of the first membrane and current collector. Adhesive is applied to connect the two membranes, and a third layer of adhesive is deposited on top of the edges of the membranes. Step 5: The second polymer frame (ABS, PMMA) is placed on top of the film, and the electrodes are gently pressed for 12 hours to allow the adhesive to cure and the assembly to be sealed.

[0089] electrode Electrodes 20, 30, and 40 were prepared according to the process shown in Table 1 below.

[0090] [Table 1]

[0091] Process steps A.1 Synthesis of MnO2 α-MnO2 was prepared as a MnO2 polymorph. For this purpose, a microwave-heated hydrothermal process was used, following a protocol adapted from a scientific paper (Huang, H., Sithambaram, S., Chen, CH, King'ondu Kithongo, C., Xu, L., Iyer, A., Garces, HF, Suib, SL, Chemistry of Materials, 22(12), 3664-3669, 2010). First, 15.7 g of K2SO4 (0.09 mol) (Merck, Emsure®, ACS, ISO, European Pharmacopoeia reagent (Reag.Ph.Eur.)), 24.3 g of K2S2O8 (0.09 mol) (Fluka, special analytical grade (puriss.Pa)), and 10.15 g of MnSO4·H2O (0.06 mol) (Merck, ACS, European Pharmacopoeia reagent) were mixed with 0.5 L of deionized water (Milli-Q® water, TKA, water electrical conductivity 0.055 μS / cm). The mixture was transferred to a microwave reactor (Masterwave BTR, Anton Paar GmbH), held under stirring for 10 minutes, and then subjected to hot water treatment by heating at 200°C for 10 minutes. The synthesized product was washed with deionized water and recovered using a pressurized filtration system (Sartorius Stedim 16249 316 stainless steel). Finally, the material was dried overnight under vacuum at 60°C.

[0092] A.2 Preparation of Active Material The active material was prepared as a mixture of 40 wt% of the above α-MnO2, 25 wt% of commercially available carbon black (C-NERGY SUPER C65, Imerys Graphite & Carbon), 20 wt% of Ni powder (APS 3-7 microns, 99.9%, Alfa Acer), 5 wt% of Bi2O3 powder (99.999% trace metal base, Sigma-Aldrich), and 10 wt% of commercially available PTFE suspension (3M® Dyneon® PTFE TF 5060GZ). First, the above materials were mixed with ultrapure water to prepare a slurry. The volume of water was selected to obtain a slurry with a solid content of approximately 3 wt%. Next, the mixture was stirred for 10 minutes, sonicated for another 10 minutes, and dried using a rotary evaporator system (Rotavapor® R-300, BUECHI), in which the solvent was evaporated by rotating the mixture at 70°C under a pressure of 100 mbar. After complete removal of the solvent, the resulting powder was maintained overnight under vacuum at 60°C.

[0093] A.3 Assembly of the positive MnO2 electrode A porous nickel foam was used as the current collector. Before applying the active material, the current collector was cleaned in an ultrasonic bath containing acetone for 10 minutes, 2-propanol for 10 minutes, and ultrapure water for 10 minutes. The current collector was then immersed in a 6M HCl solution for another 10 minutes, rinsed multiple times with ultrapure water, and finally dried. Equal amounts of the dried active material (dough / paste) were applied to both sides of the current collector, with a load of 1.5 kN / cm². 2 (150kg / cm 2 A plain electrode was obtained by pressing it at 15 MPa for 1 minute. This plain electrode has a total thickness of 1.5 mm.

[0094] A.3' Assembly of the negative Zn electrode The current collector used was a 200 μm thick copper foil. Before applying the active material (Zn), the current collector underwent a thorough cleaning process including ultrasonic treatment in acetone, 2-propanol, and ultrapure water at 10-minute intervals, followed by a drying process. Then, two 400 μm thick Zn plates were spot-welded to the edges on both sides of the copper current collector. The resulting configuration was a simple electrode consisting of copper foil sandwiched between two Zn plates, with a total thickness of 1.0 mm.

[0095] A.4 Coating Simple electrodes were immersion-coated with a commercially available benzimidazole polymer / DMAc solution (FUMION® AMLD, 5-7 wt%) and dried using a heat gun. The immersion-coating / drying procedure was repeated three times. The coated electrodes were obtained after being stored / dried in an 80°C oven for at least 2 hours.

[0096] A.5 Preparation of electrode-membrane-ABS frame assembly To manufacture the electrodes of the present invention mounted on a polymer frame, coated electrodes were sealed in pouches made of a commercially available cross-linked benzimidazole polymer-based film (FUMASEP® FAAM-40), and the pouches were placed between ABS polymer frames as shown in Figure 2. After the adhesive cured, the assemblies were immersed in a 6M KOH solution for at least 24 hours.

[0097] Electrode testing The electrodes prepared as described above were tested using a VMP3 (Bio-logic) instrument as a current source / sink in constant current mode. All measurements were performed in ambient atmosphere and at controlled room temperature (T=21°C). The results are shown in Figures 3-5.

[0098] Figure 3 shows the exceptional capacity retention of the electrode 30 of the present invention, both of which have a coating layer and an AEM containing a cross-linked benzimidazole polymer. In contrast, the simple electrode 20 has neither a coating layer nor an AEM. The electrode 30 of the present invention has a current density j = 1 mA / cm².2 It maintains 100% capacity even after more than 80 charge / discharge cycles, but the capacity retention of electrode 20 is 1 mA / cm². 2 The capacity decreases to 50% after approximately 30 cycles. This decrease in capacity suggests that the discharge process leads to the irreversible formation of inert hetaerolite. On the other hand, electrode 30 can prevent the formation of the inert phase by blocking the crossing (crossing) of zincate ions to the MnO2 active material. Zincate ion Zn(OH)4 2- It should be noted that the presence of this substance is due to the dissolution of ZnO in concentrated alkaline electrolytes.

[0099] Figure 4 shows the results of durability-performance testing of electrode 30 of the present invention. Constant current charge-discharge cycles were performed using electrode 30 in a 6M KOH + 0.25M ZnO electrolyte prepared from ultrapure water (18 MΩ·cm) and an appropriate amount of KOH pellets (analytical grade, ≥85.0%, Merck) and ZnO powder (ReagentPlus®, 99.9%, Sigma-Aldrich). The three-electrode cell design used in this study is described in J. Power Sources 482 (2021) 22890. A Ni plate functioned as the counter electrode, and a custom-made Hg / HgO electrode was used as the reference electrode. The geometric area exposed to the electrolyte was 1 cm². 2 The MnO2 cathode used in this experiment was placed between polymer frames according to the example shown in Figure 2, with a capacity of 45 mAh / cm². 2 This resulted in an area capacity.

[0100] The DoD was chosen to achieve an expected nominal voltage of approximately 1V, which is the minimum threshold voltage for conventional electronic devices. The nominal voltage value was determined by integrating the voltage-capacitance profile and dividing it by the total discharge capacity per cycle. (Asterisk on y label) * This value was calculated assuming there is no polarization from the Zn electrode (i.e., the electrode potential of Hg / HgO is Zn / Zn(OH)4, which has a potential of +1.35V relative to Hg / HgO). 2-It is important to note that this indicates that it has been converted to [a specific form of]. This test includes charge-discharge cycles under the conditions shown in Table 2 below.

[0101] [Table 2]

[0102] The results show that electrode 30 exhibits excellent capacity retention of 100% even at higher current densities throughout the entire experimental period of over 3360 hours (approximately 140 days).

[0103] Furthermore, the result was j = 10 mA / cm 2 This shows that even after cycle testing, the electrodes can recover to their initial discharge termination voltage. After approximately 100 cycles, the nominal voltage decreases slightly with increasing cycle count. Since the voltage recovered to its previous value once the electrolyte was refilled, this phenomenon is thought to be due to a change in electrolyte composition rather than electrode degradation.

[0104] Figure 5 shows the results of the durability-performance test of the electrode 30 of the present invention at 100% DoD. The durability-performance test was performed by charge-discharge cycles in a 10M KOH + 0.25M ZnO electrolyte, with an area capacity of 27 mAh / cm². 2 The procedure was carried out in a similar manner to that described in the context of Figure 4 above, with the difference being that the current density was 1-5 mA / cm². 2 The DoD reached (2e-):100%. The detailed conditions under which the test was conducted are shown in Table 3 below.

[0105] [Table 3]

[0106] Figure 6 shows the discharge and charge profiles at 100% DoD for electrodes 30 of the present invention having different area capacities as specified in Table 4 below.

[0107] [Table 4]

[0108] Figures 7a and 7b show the measurement setup for an anode stripping voltammetry test. Figure 7a shows an electrochemical cell with a separator between two cell halves. One of the two cell halves contains a solution of 6M KOH and zincate ions (referred to as the "feed solution"), and the other contains a 6M KOH solution without zincate (referred to as the "draw solution"). A glassy carbon (GC) rotating disk electrode (RDE) is used as the working electrode (WE). In addition, an Au rod is used as the counter electrode (CE), and an Hg / HgO electrode is used as the reference electrode (RE). As can be seen from the schematic detail in Figure 7b, an anion exchange membrane (AEM) is placed in a sealed state between the glass flanges of the cell halves.

[0109] Figure 8a shows the data obtained by square wave voltammetry to establish the calibration curve. The area under the peak is assumed to be proportional to the zincate concentration in the calibration solution.

[0110] Figures 8b to 8i show the results of anodic stripping voltammetry tests using different anion exchange membranes. Figures 8g to 8i show the results of anodic stripping voltammetry tests using AEMs containing cross-linked benzimidazole polymers (FAAM40, FAAM5, and Fumion AM). Figures 8b to 8f show the results of anodic stripping voltammetry tests using other AEMs.

[0111] The specifications of the AEM tested are listed in Table 5 below.

[0112] [Table 5(1)] [Table 5(2)]

[0113] For anode stripping voltammetry tests using each of the above AEMs, a washing step was performed at 0.3V versus Hg / HgO for 30 seconds with stirring. Next, since 1.75V versus Hg / HgO was found to be the potential with the highest integrated charge for the Zn peak, a 5-minute accumulation step was similarly performed at 1.75V versus Hg / HgO with stirring. Stirring was then stopped. After 15 seconds, a stripping voltammetry step was performed between -1.5V and 0.0V using a square wave voltammetry profile with an amplitude of 5mV, a pulse of 25mV, and a duration of 0.05 seconds, resulting in a formal scanning speed of 100mV / s.

[0114] The effectiveness of various membranes in blocking the diffusion of zincate ions has been investigated. A test at Celgard (Figure 8b) revealed that the draw solution reached a zinc concentration of 5 ppm after just 3 hours. In contrast, Pention (Figure 8c) required 8 hours, Tokuyama (Figure 8d) 20 hours, Celazole (Figure 8e) 48 hours, and Ionomr (Figure 8f) 50 hours to reach the same concentration. In contrast, membranes based on cross-linked benzimidazole polymers from FuMA-Tech, FAAM40 (Figure 8g), FAAM5 (Figure 8h), and Fumion AM (Figure 8i), showed no detectable levels of zinc in the draw solution throughout the experiment. In particular, the experiment with membrane FAAM40 was conducted over a long period of 46 days. Surprisingly, even the 5 μm thick membrane FAAM5 exhibited excellent zincate blocking properties, thus indicating that such properties are independent of membrane thickness. Furthermore, Fumion AM membranes that are ionically crosslinked instead of covalently crosslinked (as in the case of FAAM40 and FAAM5) showed a similar ability to block the diffusion of zincate ions. This indicates that the membrane's ability to block zincate ions is independent of the type of crosslinking agent used.

[0115] Figures 9a to 9e show the development of voltage-capacitance curves for several charge and discharge cycles with respect to an Hg / HgO reference electrode in an alkaline electrolyte, for one electrode according to the present invention (Figure 9a) and several reference electrodes (Figures 9b to 9e). The electrode potential relative to Hg / HgO is Zn / Zn(OH)4 with a potential of +1.35V relative to Hg / HgO. 2- It has been converted to [this]. The electrode according to the present invention contained FAAM40 as an AEM based on a crosslinked benzimidazole polymer. The reference electrode contained other AEMs. The characteristic elemental composition of each AEM, as measured by EDX, is shown in Table 6 below.

[0116] [Table 6]

[0117] The test protocol used to obtain the voltage-capacitance curves in Figures 9a-e began with electrode activation in 6M KOH for at least 24 hours. Subsequently, the electrodes were cycled in an alkaline electrolyte containing 10M KOH and 0.25M ZnO at the current densities listed in Table 7 below. The capacitance fading observed for each electrode after each cycle can also be extracted from Table 7.

[0118] [Table 7]

[0119] Figures 10a and 10b relate to a full-cell battery configuration including the electrodes of the present invention. More specifically, Figure 10a shows an example in which the electrode 30 (MnO2 positive electrode) and the electrode 40 (Zn negative electrode) of the present invention are combined to form a full-cell battery configuration (corresponding to a Zn-MnO2 battery) with respect to a Hg / HgO reference electrode RE, as shown in Figure 10a. The specifications of the electrodes are as follows.

[0120] MnO2 electrode 30 ·Geometric area: 12cm 2 ·Area capacity: 10mAh / m 2 Zn electrode 40 ·Geometric area: 12cm 2 ·Area capacity: approx. 400mAh / cm 2

[0121] To obtain the voltage-capacitance curve shown in Figure 10b, the electrodes were first activated in 6M KOH for at least 24 hours, and then subjected to a voltage-to-capacitance (1 mA / cm²) in an alkaline electrolyte consisting of 6M KOH, as listed in Table 8 below. 2 And it was cyclically processed at various DoD levels.

[0122] [Table 8]

[0123] By utilizing an Hg / HgO reference electrode, the potentials of both the positive and negative electrodes could be monitored independently. The cell voltage was determined by the following equation: Cell voltage = E(positive electrode) - E(negative electrode). The charging and discharging behavior of both the MnO2 and Zn electrodes (indicated by arrows) is a reversible event at 100% DoD level. The superior performance of the electrode assembly of the present invention may be due not only to its ability to inhibit the formation of inert species by preventing zincate ions from approaching the MnO2 active material, but also to the reduced migration of zincate ions from the Zn electrode surface. This is because, during battery discharge, zincate ions are maintained near the Zn electrode surface, and metallic Zn 0 This is to facilitate their easy availability during charging for reduction and return. As a result, this promotes the reversibility of the negative electrode.

[0124] Figures 11a–11d show the results of characterization of the exemplary AEM used above. Figures 11a–11c show the FTIR spectra of anion exchange membranes derived from Fumion AM, exhibiting chemical-physical properties similar to those of the crosslinked benzimidazole polymer described in this patent application. As demonstrated in the reference (Peron, J., Ruiz, E., Jones, DJ, Roziere, J., J. Membr. Sci. 314, 247–256, 2008), Fumion AM exhibits characteristic bands of both PBI-OO (indicated by gray shaded vertical lines) and sulfonated sPBI-OO polymer (indicated by gray asterisks) in Figure 11a. The FTIR spectrum of Fumion AM shares similarities with that of a Celazole membrane (Figure 11b), at 1560 cm⁻¹. -1 and 1300cm -1 Two bands are shown, indicated by a white star symbol centered around the symbol. 1560cm -1 The absorption band at 1300 cm can be related to the conjugated ring vibration characteristics between the benzene ring and the imidazole ring, as well as the C=C and C=N stretching present in the benzene ring of the polybenzimidazole structure. -1The band may represent the breathing mode of the imidazole ring structure of the polybenzimidazole polymer (Asensio, JA, Borros, S., Gomez-Romero, P., J. Polym. Sci. A: Polym. Chem. 40, 3703-3710, 2002). In addition, the presence of alkyl groups may lead to CH bending vibrations of the alkyl chain, which may also contribute to the absorption band in this region. Figure 11c compares Fumion AM before covalent crosslinking with Fumion AM after covalent crosslinking (referred to as FAAM40). In particular, the two spectra show remarkable similarity, making it difficult to distinguish between the two types of crosslinking based solely on IR analysis. However, when the membranes were immersed in DMAc at 80°C for 8 hours, Fumion AM dissolved completely, while the covalently crosslinked membrane FAAM40 showed no signs of dissolution in the solvent (Figure 11d). This observation supports the hypothesis that the ability to block zincate ion transport is independent of the properties of the crosslinking agent, and rather depends on strong interactions between adjacent polymer chains, which may be ionic or covalent, resulting in a robust network that effectively captures zincate ions.

Claims

1. An electrode for use in a rechargeable alkaline battery, comprising, in order from the inside out, a current collector, an active material supported on the current collector, and an anion exchange membrane. The active material is MnO ２ or containing Zn, An electrode characterized in that the anion exchange membrane contains a crosslinked benzimidazole polymer.

2. The crosslinked benzimidazole polymer contains repeating units represented by the following formula (I): 【Chemistry 1】 In the formula, A is a bond or oxygen, preferably a bond. B is a bond, phenylene, 4,4'-diphenylene ether, or sulfonated 4,4'-diphenylene ether. R1 to R4 are independent of each other: lone pairs of electrons, hydrogen, and C. １ ~C ６ Selected from the group consisting of alkyl groups, R5 is hydrogen or a sulfonic acid group, preferably hydrogen. The electrode according to claim 1.

3. The crosslinked benzimidazole polymer comprises ionic crosslinks and / or covalent crosslinks, wherein the covalent crosslinks are preferably selected from units having a structure represented by one of the following formulas (II) and (III). 【Chemistry 2】 During the ceremony, ＊ This indicates the joining position. The electrode according to claim 1 or claim 2.

4. The benzimidazole polymer has a number-average molecular weight of 20 to 100 kg / mol, preferably 50 to 60 kg / mol M ｎ An electrode according to any one of claims 1 to 3, having the following characteristics.

5. The electrode according to any one of claims 1 to 4, wherein the benzimidazole polymer includes covalent crosslinks, the crosslink content is 1 to 20 mol%, preferably 5 to 15 mol%, per repeating unit based on benzimidazole, and / or the anion exchange membrane has pores having an average diameter of less than 1.6 nm, more preferably less than 0.8 nm, even more preferably less than 0.34 nm, and particularly 0.10 to 0.32 nm.

6. The electrode according to any one of claims 1 to 5, wherein the anion exchange membrane is formed as a pouch surrounding at least the current collector and the active material.

7. The electrode according to any one of claims 1 to 6, wherein the anion exchange membrane has a thickness of 1.0 μm to 60 μm, preferably 5.0 μm to 50 μm, and more preferably 10.0 μm to 40 μm.

8. The electrode according to any one of claims 1 to 7, further comprising a coating layer between the active material and the anion exchange membrane, wherein the coating layer comprises a benzimidazole polymer.

9. The active material is MnO ２ Contains carbon, Bi ２ O ３ The electrode according to any one of claims 1 to 8, further comprising a binder material, wherein the binder material is preferably selected from the group consisting of benzimidazole polymers, cellulose, and fluoropolymers, such as polytetrafluoroethylene and fluorinated ethylene propylene.

10. The active material contains 20 to 60% by weight of MnO ２ The electrode according to any one of claims 1 to 9, comprising the same.

11. The active material is carbon, Bi ２ O ３ It further comprises at least one compound selected from the group consisting of binder materials or mixtures thereof, preferably having a carbon content of 30 to 45% by weight, and Bi ２ O ３ The electrode according to claim 10, wherein the content of is 5 to 15% by weight, and the content of the binder material is 5 to 15% by weight.

12. The active material is MnO ２ If it includes the above MnO ２ is α-MnO ２ The electrode according to any one of claims 1 to 11, or electrolytic manganese dioxide (EMD).

13. The active material is MnO ２ The electrode according to any one of claims 1 to 12, further comprising a nickel-based additive in an amount preferably 0.5 to 10% by weight, more preferably 1.0 to 2.0% by weight, relative to the total weight of the active material.

14. The electrode according to any one of claims 1 to 13, wherein the current collector is a mesh, foil, or foam.

15. The electrolyte and the active material is MnO ２ A rechargeable alkaline battery comprising an electrode according to any one of claims 1 to 14, which is used as a positive electrode if it contains Zn, or as a negative electrode if the active material contains Zn.

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