A Manganese Cathode Deposition / Dissolution Colloidal Electrolyte and Its Application

Abstract

The present invention relates to the field of electrochemical energy storage technologies, and particularly to a manganese positive electrode deposition / dissolution colloidal electrolyte and its application. The manganese positive electrode deposition / dissolution colloidal electrolyte includes a manganese salt, an acid, an additive, and a solvent; the additive is a lanthanum salt and / or a cerium salt. In the present invention, at least one of lanthanum ions and cerium ions is added to the electrolyte. These rare earth metal ions have strong interactions with water molecules and a high coordination number, which can affect the solvation structure of manganese ions, thereby regulating the redox process of manganese ions, significantly reducing the particle size of manganese dioxide during the charging process, forming a stable colloidal solution that does not settle, improving the reversibility of the deposition / dissolution reaction of divalent manganese ions / manganese dioxide, and significantly improving the Coulombic efficiency and cycle life of the flow battery.

Description

Technical Field

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

[0002] Aqueous flow batteries use water as a solvent, have high safety, and have no risk of fire or explosion. At the same time, flow batteries have unique advantages, such as decoupling of energy and power, and the two can be designed separately, making them suitable for large-scale energy storage applications. However, the currently widely studied all-vanadium flow battery and zinc-bromine flow battery both have their deficiencies. The high-valent vanadium in the positive electrode of the all-vanadium flow battery is highly toxic and costly. The bromine positive electrode of the zinc-bromine flow battery is volatile, corrosive, and toxic, and there are serious self-discharge and safety hazards. Therefore, it is very necessary to develop a non-toxic, highly safe, and low-cost positive electrode for flow batteries.

[0003] Manganese-based electrode materials are low-cost and have no risk of environmental pollution, making them highly competitive positive electrode materials. The positive electrodes of currently widely used alkaline primary batteries (i.e., AA, AAA dry batteries) all use manganese dioxide materials. In recent years, researchers have found that manganese dioxide can undergo reversible deposition / dissolution reactions in an acidic environment. However, the manganese dioxide deposited during charging has poor conductivity and poor electrochemical activity. On the one hand, it hinders the continued oxidation of subsequent manganese ions, limits the area deposition capacity, and increases polarization. On the other hand, the generated manganese dioxide cannot be completely reduced to divalent manganese ions and dissolved in the electrolyte during discharge. These residual "dead manganese" rapidly accumulate during charge and discharge, ultimately clogging the pores of the carbon felt and the flow pipes, causing the flow battery to fail. Researchers have developed various additives to improve the performance of the manganese dioxide deposition / dissolution reaction. Such as Fe 2+ , Br - , I - , V 4+ and other redox reaction media, but their reaction ability with residual manganese dioxide is limited, and they cannot effectively solve the problems of low deposition capacity, low current density, and low Coulomb efficiency. Moreover, the potential of the redox reaction medium is lower than the manganese reaction potential, resulting in low energy efficiency. More importantly, these redox reaction media only act on the residual "dead manganese" during discharge and are powerless against the deposition process of manganese dioxide during charging. As the deposition amount continues to increase, the reaction sites of the current collector are covered, and inevitably the reaction kinetics rapidly decreases, polarization increases, and ultimately the reaction is forced to stop.

[0004] Therefore, developing a new manganese positive electrode deposition / dissolution colloidal electrolyte to improve deposition capacity, electrolyte utilization rate, current density, and Coulomb efficiency is of great significance for the technical field of electrochemical energy storage. Summary of the Invention

[0005] To solve the problems that during the charging process of the current manganese deposition / dissolution positive electrolyte, the current collector is covered by the deposited manganese dioxide, resulting in an increase in polarization; and during the discharging process, large chunks of manganese dioxide cannot be effectively reduced to divalent manganese ions, thus forming large particles of "dead manganese", causing the accumulation of dead manganese in the electrolyte, clogging the pores of the carbon felt and the flow channels, and leading to rapid capacity decay, the present invention provides a manganese positive deposition / dissolution colloidal electrolyte, which can significantly reduce the particle size of the manganese dioxide generated during the charging process, improve its reaction activity, effectively inhibit large particles of "dead manganese", and has good fluidity, will not cover the current collector, reduce polarization, increase the charge and discharge current, and improve the reversibility and cycle life of manganese deposition / dissolution.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a manganese positive deposition / dissolution colloidal electrolyte, which includes a manganese salt, an acid, an additive, and a solvent;

[0008] The additive is a lanthanum salt and / or a cerium salt.

[0009] Another technical solution of the present invention is a flow battery, which includes a positive current collector, a negative current collector, a positive electrolyte, a negative electrolyte, and a separator;

[0010] The positive electrolyte is the above-mentioned manganese positive deposition / dissolution colloidal electrolyte.

[0011] The present invention discloses the following technical effects:

[0012] The present invention adds at least one of lanthanum ions and / or cerium ions to the manganese deposition / dissolution positive electrolyte. The rare earth metal ions have a strong interaction with water molecules in the electrolyte and a high coordination number, which can affect the solvation structure of manganese ions in the electrolyte, and further affect the deposition / dissolution process of manganese ions, significantly reducing the particle size of manganese dioxide, forming a stable colloidal solution that does not settle, reducing the generation and accumulation of dead manganese, and improving the reversibility of the deposition / dissolution reaction of divalent manganese ions / manganese dioxide.

[0013] The manganese deposition / dissolution positive electrolyte provided by the present invention has high stability and high reversibility, the Coulomb efficiency can reach 99.5%, and the number of cycle turns is greater than 3000. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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 in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 It is the charging state diagram of the manganese positive electrode electrolyte in Example 1 of the present invention after 1000 cycles; among them, a is the state when just charged; b is the state after standing for 12 hours after charging.

[0016] Figure 2 It is the discharging state diagram of the manganese positive electrode electrolyte in Example 1 of the present invention after 1000 cycles.

[0017] Figure 3 It is the charge-discharge curve diagram of the manganese positive electrode electrolyte and the tin negative electrode electrolyte in Example 1 of the present invention, which are matched to form a manganese-tin flow battery after 1000 cycles.

[0018] Figure 4 It is the cycle performance diagram of the manganese positive electrode electrolyte and the tin negative electrode electrolyte in Example 1 of the present invention, which are matched to form a manganese-tin flow battery.

[0019] Figure 5 It is the charging state diagram of the manganese positive electrode electrolyte in Comparative Example 1 of the present invention after 60 cycles; among them, a is the state when just charged; b is the state after standing for 12 hours after charging.

[0020] Figure 6 It is the discharging state diagram of the manganese positive electrode electrolyte in Comparative Example 1 of the present invention after 60 cycles.

[0021] Figure 7 It is the charge-discharge curve diagram of the manganese positive electrode electrolyte and the tin negative electrode electrolyte in Comparative Example 1 of the present invention, which are matched to form a manganese-tin flow battery after 60 cycles.

[0022] Figure 8 It is the cycle performance diagram of the manganese positive electrode electrolyte and the tin negative electrode electrolyte in Comparative Example 1 of the present invention, which are matched to form a manganese-tin flow battery. Detailed Embodiments

[0023] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0024] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, 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. Any 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 can be independently included or excluded from the range.

[0025] 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 this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0026] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0027] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0028] The first aspect of this invention provides a manganese positive electrode deposition / dissolution colloidal electrolyte, comprising a manganese salt, an acid, an additive and a solvent;

[0029] The additive is a lanthanum salt and / or a cerium salt.

[0030] The reaction of traditional manganese positive electrode electrolytes during charging is the oxidation process of divalent manganese ions, generating manganese dioxide and trivalent manganese ions. A part of the generated manganese dioxide is deposited on the carbon felt, and a part enters the liquid flow pipeline along with the flowing electrolyte, making the electrolyte turbid; the reaction during discharging is the electroreduction process of manganese dioxide and trivalent manganese ions, generating divalent manganese ions. However, due to the large particle size, poor fluidity and low electrochemical activity of the generated manganese dioxide, it will remain in the storage tank and adhere to the inner wall of the flow pipeline. Therefore, the electrolyte cannot change back from the muddy state to the clear and transparent state during discharging. With the repeated charge and discharge, more and more of these "dead manganese" accumulates, ultimately resulting in the reduction of manganese active substances and the blockage of the pipeline, causing the flow battery to fail. The rare earth ion additive in this invention can regulate the manganese ion solvation structure through the strong interaction with water molecules, significantly reducing the particle size of the generated manganese dioxide to the nanoscale, forming a stable colloidal solution that does not settle, thereby significantly increasing the electrochemical performance and fluidity of manganese dioxide, and achieving high Coulomb efficiency and high stability.

[0031] In a preferred embodiment of this invention, the lanthanum salt is at least one of lanthanum sulfate, lanthanum chloride, lanthanum nitrate, lanthanum methanesulfonate, lanthanum acetate; the cerium salt is at least one of cerium sulfate Ce2(SO4)3, cerium(IV) sulfate Ce(SO4)2, cerium chloride, cerium nitrate, cerium methanesulfonate, cerium acetate.

[0032] In a preferred embodiment of the present invention, the concentration of the additive in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.005M to 0.2M.

[0033] In a preferred embodiment of the present invention, the manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate, manganese methanesulfonate, manganese acetate, and manganese oxalate; the concentration of the manganese salt in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.1M to 2M.

[0034] In a preferred embodiment of the present invention, the acid is an organic acid or an inorganic acid; the concentration of the acid in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.5M to 6M.

[0035] In a preferred embodiment of the present invention, the inorganic acid is at least one of sulfuric acid, hydrochloric acid, and nitric acid; the organic acid is at least one of methanesulfonic acid, sulfamic acid, benzenesulfonic acid, and phenolsulfonic acid.

[0036] In a preferred embodiment of the present invention, the solvent is water.

[0037] The second aspect of the present invention provides a flow battery, including a positive electrode current collector, a negative electrode current collector, a positive electrode electrolyte, a negative electrode electrolyte, and a separator;

[0038] The positive electrode electrolyte is the above-mentioned manganese positive electrode deposition / dissolution colloidal electrolyte.

[0039] In a preferred embodiment of the present invention, the positive electrode current collector is carbon felt; the negative electrode current collector is carbon felt; the separator is a proton exchange membrane.

[0040] In a preferred embodiment of the present invention, when the flow battery is a manganese-tin flow battery, the negative electrode electrolyte is an electrolyte containing divalent tin ions; when the flow battery is a manganese-copper flow battery, the negative electrode electrolyte is an electrolyte containing divalent copper ions; when the flow battery is a manganese-silicotungstic acid flow battery, the negative electrode electrolyte is an electrolyte containing silicotungstic acid; when the flow battery is a manganese-titanium flow battery, the negative electrode electrolyte is an electrolyte containing tetravalent titanium ions.

[0041] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are all purchased from commercial channels or are publicly available.

[0042] The solvent of the electrolytes used in the examples and comparative examples of the present invention is water.

[0043] The proton exchange membrane used in the examples and comparative examples of the present invention is a polybenzimidazole proton exchange membrane.

[0044] The testing method involved in the embodiments of the present invention is as follows: the charge-discharge current density is 60 mA cm -2 , constant current charging is carried out until 43 mAh is reached, and discharging is carried out until 0V is reached.

[0045] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention. Embodiment 1

[0046] This embodiment provides a flow battery. The positive current collector is carbon felt, and the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.05M cerium sulfate; the negative current collector is carbon felt, and the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; the separator is a proton exchange membrane. The voltage of the composed manganese-tin flow battery is about 1.6V. The charging state of the manganese positive electrolyte after 1000 cycles is as Figure 1 shown, where a is the state just after charging; b is the state after standing for 12 hours after charging. It can be seen from Figure 1 that there is no stratification after standing for 12 hours; the discharging state of the manganese positive electrolyte after 1000 cycles is as Figure 2 shown. It can be seen from Figure 2 that the manganese positive electrolyte is a clear and transparent solution after discharging. The charge-discharge curve of the manganese-tin flow battery after 1000 cycles is as Figure 3 shown. It can be seen from Figure 3 that the charge-discharge curve after 1000 cycles is very stable, without extra platform side reactions, with small polarization and good reversibility; the cycling performance of the manganese-tin flow battery is as Figure 4 shown. It can be seen from Figure 4 that the initial discharge capacity is 40.2 mAh, and then the discharge capacity increases to 42.8 mAh and can be continuously maintained stably. The Coulomb efficiency can reach 99.5%, and the number of cycling times is greater than 3000 cycles. Embodiment 2

[0047] This embodiment provides a flow battery. The positive current collector is carbon felt, and the electrolyte is 0.2M manganese sulfate + 4M sulfuric acid + 0.1M cerium sulfate + 0.05M cerium nitrate; the negative current collector is carbon felt, and the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; the separator is a proton exchange membrane. The voltage of the composed manganese-tin flow battery is about 1.6V, and the Coulomb efficiency can reach 99%, and the number of cycling times is greater than 3000 cycles. Embodiment 3

[0048] This embodiment provides a flow battery. The positive current collector is carbon felt, and the electrolyte is 0.5M manganese chloride + 3M hydrochloric acid + 0.1M cerium chloride; the negative current collector is carbon felt, and the electrolyte is 0.5M copper sulfate + 3M hydrochloric acid; the separator is a proton exchange membrane. The voltage of the composed manganese-copper flow battery is about 1V, the Coulomb efficiency can reach 99%, and the number of cycling times is greater than 3000 cycles. Example 4

[0049] This embodiment provides a flow battery. The positive current collector is carbon felt, and the electrolyte is 0.2M manganese sulfate + 5M sulfuric acid + 0.2M cerium chloride; the negative current collector is carbon felt, and the electrolyte is 5M sulfuric acid + 0.3M silicotungstic acid; the separator is a proton exchange membrane. The voltage of the composed manganese-silicotungstic acid flow battery is about 1.2V, the Coulomb efficiency can reach 99%, and the number of cycling times is greater than 3000 cycles. Example 5

[0050] This embodiment provides a flow battery. The positive current collector is carbon felt, and the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.1M cerium sulfate; the negative current collector is carbon felt, and the electrolyte is 3M sulfuric acid + 0.2M titanium sulfate; the separator is a proton exchange membrane. The voltage of the composed manganese-titanium flow battery is about 1.2V, the Coulomb efficiency can reach 99%, and the number of cycling times is greater than 3000 cycles. Example 6

[0051] This embodiment provides a flow battery. The positive current collector is carbon felt, and the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.005M lanthanum sulfate; the negative current collector is carbon felt, and the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; the separator is a proton exchange membrane. The voltage of the composed manganese-tin flow battery is about 1.6V, the Coulomb efficiency can reach 99%, and the number of cycling times is greater than 2000 cycles. Example 7

[0052] This embodiment provides a flow battery. The positive current collector is carbon felt, and the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.05M cerium sulfate + 0.005M lanthanum sulfate; the negative current collector is carbon felt, and the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; the separator is a proton exchange membrane. The voltage of the composed manganese-tin flow battery is about 1.6V, the Coulomb efficiency can reach 99%, and the number of cycling times is greater than 3000 cycles.

[0053] Comparative Example 1

[0054] This comparative example provides a 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, and the electrolyte is 3 M sulfuric acid + 0.2 M tin sulfate; the separator is a proton exchange membrane. The voltage of the composed manganese-tin flow battery is about 1.5 V. The charging state of the manganese positive electrolyte after 60 cycles is as shown in Figure 5 a in Figure 5 , and the state after standing for 12 hours after charging is as shown in Figure 5 b in Figure 6 . It can be seen from Figure 6 that there is obvious sedimentation and stratification in the charging electrolyte after standing for 12 hours, indicating that there is obvious sedimentation of dead manganese after standing. The discharging state of the manganese positive electrolyte after 60 cycles is as shown in Figure 7 . It can be seen from Figure 7 that a large amount of adhered manganese dioxide remains on the wall of the liquid storage tank, indicating that manganese dioxide cannot be fully utilized. The charge-discharge curve of this manganese-tin flow battery after 60 cycles is as shown in Figure 8 . It can be seen from Figure 8 that the charge-discharge curve is not stable, with large polarization and poor reversibility, indicating that a large amount of manganese dioxide blocks the carbon felt and the flow pipeline and cannot react reversibly. The cycling performance of this manganese-tin flow battery is as shown in

[0055] . It can be seen from Figure 8 that the discharge capacity and Coulomb efficiency decay rapidly after 50 cycles. At the 60th cycle, the Coulomb efficiency is only 72%.

[0055] The above-described embodiments of the present invention mainly take manganese-tin, manganese-copper, manganese-silicotungstic acid, and manganese-titanium flow batteries composed of tin, copper, silicotungstic acid, titanium negative electrodes and manganese positive electrodes as examples, which do not constitute a limitation on the protection scope of the present invention. Other flow battery negative electrodes, such as vanadium negative electrodes and lead negative electrodes, can be used to form corresponding flow full batteries with the manganese positive electrode in the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A manganese positive electrode deposition / dissolution colloidal electrolyte, characterized in that: Includes manganese salts, acids, additives and solvents; The additive is a lanthanum salt and / or a cerium salt; The lanthanum salt is at least one of lanthanum sulfate, lanthanum chloride, lanthanum nitrate, lanthanum methanesulfonate, and lanthanum acetate; the cerium salt is at least one of cerium sulfate, cerium sulfate, cerium chloride, cerium nitrate, cerium methanesulfonate, and cerium acetate; The concentration of the additive in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.005M~0.2M; The manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate, manganese methanesulfonate, manganese acetate, and manganese oxalate; the concentration of the manganese salt in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.1M~2M; The acid is an organic acid or an inorganic acid; the concentration of the acid in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.5M~6M; The inorganic acid is at least one of sulfuric acid, hydrochloric acid and nitric acid; the organic acid is at least one of methanesulfonic acid, aminosulfonic acid, benzenesulfonic acid and phenolsulfonic acid; The solvent is water; The colloidal electrolyte refers to an electrolyte in which divalent manganese ions are oxidized to generate manganese dioxide during charging, and the particle size of manganese dioxide is reduced to nanometer level under the action of additives to form a stable colloidal solution that does not settle.

2. A liquid flow 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 deposition / dissolution colloidal electrolyte according to claim 1.

3. The flow battery according to claim 2, characterized in that: The positive electrode current collector is carbon felt; the negative electrode current collector is carbon felt; and the separator is a proton exchange membrane.

4. The flow battery according to claim 2, characterized in that: When the liquid flow battery is a manganese-tin liquid flow battery, the negative electrode electrolyte is an electrolyte containing divalent tin ions; when the liquid flow battery is a manganese-copper liquid flow battery, the negative electrode electrolyte is an electrolyte containing divalent copper ions; when the liquid flow battery is a manganese-silicotungstic acid liquid flow battery, the negative electrode electrolyte is an electrolyte containing silicotungstic acid; when the liquid flow battery is a manganese-titanium liquid flow battery, the negative electrode electrolyte is an electrolyte containing tetravalent titanium ions.

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