A Manganese Positive Electrolyte and Its Application

Abstract

The present invention relates to the field of electrochemical energy storage technology, and in particular to a manganese positive electrode electrolyte and its application. The manganese positive electrode electrolyte comprises a divalent manganese salt, a solvent and a water-soluble organic small molecule redox reaction medium; the water-soluble organic small molecule redox reaction medium is at least one of hydroquinone, resorcinol and catechol. The manganese positive electrode electrolyte of the present invention uses a water-soluble organic small molecule catechol (hydroquinone, resorcinol or catechol) as a redox reaction medium, which has the advantages of simple structure and low cost. It not only has high self-reversibility, but also promotes its dissolution during the dissolution process of manganese dioxide. The catechol structure carries protons, which can react quickly with residual manganese dioxide, have a fast reaction speed, and react completely, which significantly improves the coulomb efficiency and cycle life of the manganese dioxide deposition / dissolution electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly to a manganese positive electrode electrolyte and its application. Background Art

[0002] Aqueous batteries are suitable for large-scale energy storage due to their high safety. Among them, the manganese positive electrode has the advantages of large reserves, high potential, no pollution, and low cost, and is very suitable as the positive electrode material for aqueous batteries. However, traditional manganese oxide positive electrode materials have an ion intercalation / deintercalation mechanism, and the valence change of manganese involves a single-electron Mn 4+ / Mn 3+ redox reaction, not only with a low theoretical capacity, but also the manganese oxide is affected by the Jahn-Teller effect during charge and discharge, resulting in an unstable structure and fast capacity decay. In recent years, the manganese dioxide deposition / dissolution reaction has gradually received attention, but there are problems such as low Coulomb efficiency and poor cycle life in the deposition / dissolution reaction. Although researchers have developed some redox mediators to promote the manganese dioxide deposition / dissolution reaction, such as Fe 2+ , Br - , I - etc., their reaction rate with residual manganese dioxide is slow and the reaction is incomplete, resulting in their inability to effectively solve the problem of low Coulomb efficiency in the manganese dioxide deposition / dissolution process. Therefore, it is necessary to develop a new type of redox reaction mediator to effectively dissolve residual manganese dioxide and improve the electrochemical performance of the manganese dioxide deposition / dissolution positive electrode electrolyte. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a manganese positive electrode electrolyte containing a water-soluble organic small molecule redox reaction mediator and its application.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One technical solution of the present invention is a manganese positive electrode electrolyte, comprising a divalent manganese salt, an acid, a solvent, and a water-soluble organic small molecule redox reaction mediator;

[0006] The water-soluble organic small molecule redox reaction mediator is at least one of hydroquinone, resorcinol, and catechol.

[0007] Another technical solution of the present invention is an aqueous battery, comprising a positive electrode current collector, a negative electrode current collector, a positive electrode electrolyte, a negative electrode electrolyte, and a separator;

[0008] The positive electrode electrolyte is the above-mentioned manganese positive electrode electrolyte.

[0009] The present invention discloses the following technical effects:

[0010] The manganese positive electrode electrolyte uses water-soluble organic small molecule benzenediol (hydroquinone, resorcinol or catechol) as the redox reaction medium, which has the advantages of simple structure and low cost, and its own high reversibility. At the same time, it promotes the dissolution of manganese dioxide during the dissolution process. The benzenediol structure has its own protons, which can quickly react with the residual manganese dioxide. The reaction speed is fast and the reaction is complete, significantly improving the Coulomb efficiency and cycle life of the manganese dioxide deposition / dissolution electrode. Brief Description of the Drawings

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0012] Figure 1 Charge-discharge curves and cycle performance of the manganese-tin stationary battery in Embodiment 1 of the present invention; where a is the charge-discharge curve after the battery is cycled 100 times, and b is the cycle stability of the battery.

[0013] Figure 2 SEM image of the positive electrode current collector of the manganese-tin stationary battery after 100 cycles in Embodiment 1 of the present invention.

[0014] Figure 3 Charge-discharge curves and cycle performance of the manganese-tin flow battery in Embodiment 2 of the present invention; where a is the charge-discharge curve after the battery is cycled 100 times, and b is the cycle stability of the battery.

[0015] Figure 4 Charge-discharge curves and cycle performance of the manganese-tin stationary battery in Comparative Example 1 of the present invention; a is the charge-discharge curve after the battery is cycled 70 times, and b is the cycle stability of the battery.

[0016] Figure 5 SEM image of the positive electrode current collector of the manganese-tin stationary battery after 70 cycles in Comparative Example 1 of the present invention.

[0017] Figure 6 Charge-discharge curves and cycle performance of the manganese-tin flow battery in Comparative Example 2 of the present invention; a is the charge-discharge curve after the battery is cycled 70 times, and b is the cycle stability of the battery. Detailed Description of the Invention

[0018] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0019] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0020] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0021] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0022] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0023] The first aspect of the present invention provides a manganese positive electrode electrolyte, comprising a divalent manganese salt, an acid, a solvent, and a water-soluble organic small molecule redox reaction medium;

[0024] The water-soluble organic small molecule redox reaction medium is at least one of hydroquinone, resorcinol, and catechol.

[0025] The water-soluble organic small molecule redox reaction medium has protons in its structure and can react rapidly with residual manganese dioxide. The reaction rate is fast and the reaction is complete, solving the problems of low Coulombic efficiency and poor cycle stability caused by the slow and incomplete reaction between the current redox medium and residual manganese dioxide.

[0026] The manganese positive electrode electrolyte of the present invention can improve the Coulombic efficiency and areal capacity of the manganese positive electrode (involving Mn 2+ / MnO 2 deposition / dissolution reaction). The water-soluble organic small molecule redox reaction medium has high reversibility and electrochemical reaction kinetics. At the same time, during the dissolution process of manganese dioxide, hydroquinone can rapidly and effectively reduce residual manganese dioxide particles, increasing the discharge capacity.

[0027] In some embodiments of the present invention, the concentration of the water-soluble organic small molecule redox reaction medium in the manganese positive electrode electrolyte is 0.01 - 0.5 M.

[0028] In some embodiments of the present invention, the divalent manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, manganese methanesulfonate, and manganese oxalate.

[0029] In some embodiments of the present invention, the concentration of the divalent manganese salt in the manganese positive electrode electrolyte is 0.1 - 3 M.

[0030] In some embodiments of the present invention, the solvent is water.

[0031] In some embodiments of the present invention, the concentration of the acid in the manganese positive electrode electrolyte is 0.5 - 5 M.

[0032] In some embodiments of the present invention, the acid can be at least one of sulfuric acid, hydrochloric acid, nitric acid, methanesulfonic acid, acetic acid, and oxalic acid.

[0033] The second aspect of the present invention provides an aqueous battery, comprising a positive electrode current collector, a negative electrode current collector, a positive electrode electrolyte, a negative electrode electrolyte, and a separator;

[0034] The positive electrode electrolyte is the above-mentioned manganese positive electrode electrolyte.

[0035] In some embodiments of the present invention, the positive electrode current collector is carbon felt, carbon cloth, carbon paper, activated carbon electrode, or reticulated vitreous carbon; the negative electrode current collector is carbon felt, carbon cloth, carbon paper, reticulated vitreous carbon, tin foil, tin mesh, tin-plated carbon felt, copper foil, copper mesh, copper foam, lead foil, lead mesh, or lead-based alloy;

[0036] In some embodiments of the present invention, when the aqueous battery is a manganese-tin battery, the negative electrode electrolyte is an electrolyte containing divalent tin ions; when the aqueous battery is a manganese-copper battery, the negative electrode electrolyte is an electrolyte containing divalent copper ions; when the aqueous battery is a manganese-lead battery, the negative electrode electrolyte is an electrolyte containing divalent lead ions.

[0037] When the aqueous battery is a manganese-tin battery, the positive electrode reaction of manganese is the Mn 2+ / MnO 2 deposition / dissolution reaction, and the negative electrode reaction of tin is the Sn 2+ / Sn deposition / dissolution reaction.

[0038] In some embodiments of the present invention, the aqueous battery is an electrolyte static battery (abbreviated as a static battery) or an electrolyte flow battery (i.e., a flow battery).

[0039] In some embodiments of the present invention, the aqueous battery can be a manganese-tin stationary battery, a manganese-tin flow battery, a manganese-copper stationary battery, a manganese-copper flow battery, a manganese-lead stationary battery or a manganese-lead flow battery.

[0040] In the present invention, the separator is an ion-selective membrane. Specifically, it can be a proton exchange membrane such as a perfluorosulfonic acid separator, a non-fluoropolymer membrane or a polybenzimidazole membrane.

[0041] The present invention does not make special limitations on the sources of the components in the positive electrode current collector, negative electrode current collector, separator and electrolyte, and commercially available products well-known to those skilled in the art can be used.

[0042] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art. The reagents or raw materials used, unless otherwise specified, are all purchased from commercial channels or have been made public.

[0043] The solvent of the electrolyte used in the examples and comparative examples of the present invention is water.

[0044] The proton exchange membrane used in the examples and comparative examples of the present invention is a polybenzimidazole membrane.

[0045] The test methods involved in the present invention: for stationary batteries, the charge-discharge current is 10 mA, the charging capacity is 0.5 mAh, the electrolyte utilization rate is 18%, and the discharge cut-off voltage is 0 V. For flow batteries, the charge-discharge current is 200 mA, the charging capacity is 63 mAh, the electrolyte utilization rate is 60%, and the discharge cut-off voltage is 0.25 V.

[0046] The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be construed as limiting the protection scope of the present invention. Example 1

[0047] Stationary battery: The positive electrode current collector is carbon cloth, and the electrolyte is 1 M manganese sulfate + 1 M sulfuric acid + 0.2 M hydroquinone; the negative electrode current collector is tin foil, and the electrolyte is 2 M sulfuric acid + 0.2 M tin sulfate; the separator is a proton exchange membrane. The charge-discharge curve and cycle performance are as Figure 1 shown, where a is the charge-discharge curve of the full battery, and b is the cycle stability of the battery. As can be seen from Figure 1 a, the full battery has small polarization and high cycle reversibility. As can be seen from Figure 1 b, the Coulomb efficiency can reach 99.9%, the number of cycle turns is greater than 2000 turns, and the discharge capacity is stably maintained at ~0.5 mAh. After charge and discharge, the battery is disassembled, and the morphology of the carbon cloth is characterized. As Figure 2 shown, there is no residual manganese dioxide on the carbon cloth, indicating that hydroquinone significantly improves the reversibility and stability of the manganese dioxide deposition / dissolution reaction. Example 2

[0048] Flow battery: The positive current collector is carbon felt, and the electrolyte is 0.2 M manganese sulfate + 3 M sulfuric acid + 0.02 M hydroquinone; the negative current collector is carbon felt deposited with tin, and the electrolyte is 3 M sulfuric acid + 0.2 M tin sulfate; the separator is a proton exchange membrane. The charge-discharge curves and cycling performance are as Figure 3 shown, where a is the charge-discharge curve after 100 cycles of the battery, and b is the cycling stability of the battery. As can be seen from Figure 3 a, the polarization of the full battery is small, the charge-discharge curve is stable, and the cycling reversibility of the battery is very high. As can be seen from Figure 3 b, the Coulombic efficiency can reach 99%, the number of cycling turns is greater than 1000 turns, and the discharge capacity can be stably maintained at >62 mAh.

[0049] Comparative Example 1

[0050] Static battery: The positive current collector is carbon cloth, and the electrolyte is 1 M manganese sulfate + 1 M sulfuric acid; the negative current collector is tin foil, and the electrolyte is 2 M sulfuric acid + 0.2 M tin sulfate; the separator is a proton exchange membrane. (That is, the only difference from Example 1 is that the addition of 0.2 M hydroquinone in the manganese positive electrolyte is omitted.) The charge-discharge curves and cycling performance are as Figure 4 shown. The Coulombic efficiency is less than 95%, and it decays rapidly after 70 cycles. After charge and discharge, the battery is disassembled, and the morphology of the carbon cloth is characterized. Its SEM image is as Figure 5 shown, and a large amount of residual manganese dioxide is found.

[0051] Comparative Example 2

[0052] Flow battery: The positive current collector is carbon felt, and the electrolyte is 0.2 M manganese sulfate + 3 M sulfuric acid; the negative current collector is carbon felt deposited with tin, and the electrolyte is 3 M sulfuric acid + 0.2 M tin sulfate (that is, the only difference from Example 2 is that the addition of 0.02 M hydroquinone in the manganese positive electrolyte is omitted); the separator is a proton exchange membrane. The charge-discharge curves and cycling performance are as Figure 6 shown, where a is the charge-discharge curve after 70 cycles of the battery, and b is the cycling stability of the battery. As can be seen from Figure 6 a, due to the gradual increase of residual manganese dioxide with cycling, the polarization increases and the reversibility decreases. As can be seen from Figure 6 b, the Coulombic efficiency is lower than 97%, and it decays rapidly after 60 cycles. At 70 cycles, the discharge capacity < 40 mAh.

[0053] Comparative Example 3

[0054] The only difference from Example 2 is that 0.02 M hydroquinone in the manganese positive electrolyte is replaced by 0.02 M phenol.

[0055] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 97%, and it rapidly decayed after 90 cycles.

[0056] Comparative Example 4

[0057] The difference from Example 2 is only that 0.02 M hydroquinone in the manganese positive electrode electrolyte is replaced with 0.02 M 1,2,3-benzenetriol (pyrogallol).

[0058] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 96%, and it rapidly decayed after 70 cycles.

[0059] Comparative Example 5

[0060] The difference from Example 2 is only that 0.02 M hydroquinone in the manganese positive electrode electrolyte is replaced with 0.02 M 1,2,4-benzenetriol (hemimellitic acid).

[0061] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 97%, and it rapidly decayed after 70 cycles.

[0062] Comparative Example 6

[0063] The difference from Example 2 is only that 0.02 M hydroquinone in the manganese positive electrode electrolyte is replaced with 0.02 M 1,3,5-benzenetriol (phloroglucinol).

[0064] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 97%, and it rapidly decayed after 50 cycles.

[0065] Comparative Example 7

[0066] The difference from Example 2 is only that 0.02 M hydroquinone is replaced with 0.02 M 2,5-dihydroxybenzenesulfonic acid.

[0067] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 95%, and it rapidly decayed after 90 cycles. Example 3

[0068] The difference from Example 2 is only that the concentration of hydroquinone in the manganese positive electrode electrolyte is 0.5 M, and the concentration of sulfuric acid is 0.5 M.

[0069] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 98%, and the number of cycles was 800. Example 4

[0070] The difference from Example 2 is only that the concentration of hydroquinone in the manganese positive electrode electrolyte is 0.01 M.

[0071] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 99% and the number of cycles was 800 cycles. Example 5

[0072] The difference from Example 2 is only that the concentration of manganese sulfate in the manganese positive electrode electrolyte is 0.1 M, the concentration of hydroquinone is 0.1 M, and the concentration of sulfuric acid is 5 M.

[0073] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 98% and the number of cycles was 800 cycles. Example 6

[0074] The difference from Example 2 is only that 0.02 M of hydroquinone in the manganese positive electrode electrolyte is replaced by 0.02 M of resorcinol.

[0075] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 99% and the number of cycles was 900 cycles. Example 7

[0076] The difference from Example 2 is only that 0.02 M of hydroquinone in the manganese positive electrode electrolyte is replaced by 0.02 M of catechol.

[0077] The same effect verification as in Example 2 was carried out, and the results showed that the Coulombic efficiency was 99% and the number of cycles was 900 cycles.

[0078] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A manganese positive electrode electrolyte, characterized in that: It includes a divalent manganese salt, an acid, water and a water-soluble organic small molecule redox reaction medium; The water-soluble organic small molecule redox reaction medium is at least one of hydroquinone, resorcinol and catechol; The concentration of the water-soluble organic small molecule redox reaction medium in the manganese positive electrode electrolyte is 0.01-0.5M; The acid concentration in the manganese positive electrode electrolyte is 0.5-5M.

2. The manganese positive electrolyte according to claim 1, characterized in that The divalent manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate, manganese acetate, manganese methanesulfonate, and manganese oxalate.

3. The manganese positive electrode electrolyte according to claim 1, characterized in that The concentration of the divalent manganese salt in the manganese positive electrode electrolyte is 0.1-3M.

4. An aqueous battery, characterized in that: It includes a positive electrode current collector, a negative electrode current collector, a positive electrode electrolyte, a negative electrode electrolyte and a separator; The positive electrode electrolyte is the manganese positive electrode electrolyte according to any one of claims 1 to 3.

5. The aqueous battery according to claim 4, characterized in that: The positive electrode current collector is carbon felt, carbon cloth, carbon paper, activated carbon electrode or meshed glassy carbon; the negative electrode current collector is carbon felt, carbon cloth, carbon paper, meshed glassy carbon, tin foil, tin mesh, tin-plated carbon felt, copper foil, copper mesh, foam copper, lead foil, lead mesh or lead-based alloy.

6. The aqueous battery according to claim 4, characterized in that: When the aqueous battery is a manganese-tin battery, the negative electrode electrolyte is an electrolyte containing divalent tin ions; when the aqueous battery is a manganese-copper battery, the negative electrode electrolyte is an electrolyte containing divalent copper ions; when the aqueous battery is a manganese-lead battery, the negative electrode electrolyte is an electrolyte containing divalent lead ions.

7. The aqueous battery according to claim 4, characterized in that: The aqueous battery is an electrolyte static battery or an electrolyte flow battery.

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