Manganese positive electrode deposition / dissolution colloid electrolyte and application thereof

Abstract

The invention relates to the technical field of electrochemical energy storage, in particular to a manganese positive electrode deposition / dissolution colloid electrolyte and application thereof. The manganese positive electrode deposition / dissolution colloid electrolyte comprises a manganese salt, an acid, an additive and a solvent, the additive is lanthanum salt and / or cerium salt. At least one of lanthanum ions and cerium ions is added into the electrolyte, the rare earth metal ions and water molecules are strong in acting force and high in coordination number, the solvation structure of manganese ions can be influenced, the oxidation-reduction process of the manganese ions is further regulated and controlled, the particle size of manganese dioxide is remarkably reduced in the charging process, and a stable and non-settling colloidal solution is formed; the deposition / dissolution reaction reversibility of divalent manganese ions / manganese dioxide is improved, the coulombic efficiency of the flow battery is remarkably improved, and the cycle life of the flow battery is remarkably prolonged.

Description

Technical Field

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

[0002] Aqueous flow batteries use water as a solvent, are highly safe, and have no risk of fire or explosion. At the same time, flow batteries have unique advantages, such as the decoupling of energy and power. The two can be designed separately, making them suitable for large-scale energy storage applications. However, the widely studied all-vanadium flow batteries and zinc-bromine flow batteries both have their shortcomings. The high-priced 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 presents 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, have no environmental pollution risks, and are highly competitive positive electrode materials. The positive electrodes of the widely used alkaline primary batteries (i.e., AA, AAA dry batteries) all use manganese dioxide materials. In recent years, researchers have discovered that manganese dioxide can undergo a reversible deposition / dissolution reaction in an acidic environment. However, the manganese dioxide deposited during the charging process has poor conductivity and poor electrochemical activity. On the one hand, it hinders the subsequent oxidation of manganese ions, limits the area deposition capacity, and increases polarization. On the other hand, the manganese dioxide generated cannot be completely reduced to divalent manganese ions and dissolved in the electrolyte during the discharge process. These residual "dead manganese" accumulate rapidly during the charge and discharge process, eventually blocking the pores and flow channels of the carbon felt, causing the flow battery to fail. Researchers have developed a variety of additives to improve the performance of manganese dioxide deposition / dissolution reactions. Such as Fe 2+ ,Br - , I - , V 4+ However, 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 coulombic efficiency. In addition, the potential of the redox medium is lower than the manganese reaction potential, resulting in low energy efficiency. More importantly, these redox reaction media only act on the "dead manganese" remaining during the discharge process, 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 the reaction kinetics inevitably decrease rapidly, polarization increases, and eventually the reaction is forced to stop.

[0004] Therefore, developing a new manganese cathode deposition / dissolution colloidal electrolyte to improve deposition capacity, electrolyte utilization, current density and coulombic efficiency is of great significance in the field of electrochemical energy storage technology. Summary of the invention

[0005] In order to solve the problems that in the current manganese deposition / dissolution positive electrode electrolyte, the current collector is covered by the deposited manganese dioxide during the charging process, resulting in increased polarization; and in the discharge process, large pieces of manganese dioxide cannot be effectively reduced to divalent manganese ions, thereby forming large particles of "dead manganese", causing the accumulation of dead manganese in the electrolyte, blocking the pores of carbon felt and the flow pipes, and causing the capacity to decay rapidly, the present invention provides a manganese positive electrode deposition / dissolution colloidal electrolyte, which can significantly reduce the size of manganese dioxide particles generated during the charging process, improve its reaction activity, so as to 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: One of the technical solutions of the present invention is a manganese positive electrode deposition / dissolution colloidal electrolyte, comprising a manganese salt, an acid, an additive and a solvent; The additive is a lanthanum salt and / or a cerium salt.

[0007] A second technical solution of the present invention is a liquid flow battery, comprising 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 above-mentioned manganese positive electrode deposition / dissolution colloidal electrolyte.

[0008] The present invention discloses the following technical effects: The present invention adds at least one of lanthanum ions and / or cerium ions to the manganese deposition / dissolution positive electrode electrolyte. The rare earth metal ions have a strong interaction force with the water molecules in the electrolyte and a high coordination number, and can affect the solvation structure of the manganese ions in the electrolyte, thereby affecting the deposition / dissolution process of the manganese ions, significantly reducing the size of manganese dioxide particles, forming a stable non-sedimenting colloidal solution, reducing the generation and accumulation of dead manganese, and improving the reversibility of the deposition / dissolution reaction of divalent manganese ions / manganese dioxide.

[0009] The manganese deposition / dissolution positive electrode electrolyte provided by the present invention has high stability and high reversibility, the coulomb efficiency can reach 99.5%, and the number of cycles is greater than 3000. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1This is a charging state diagram of the manganese positive electrode electrolyte in Example 1 of the present invention after 1000 cycles; wherein a is the state just after charging; b is the state after standing for 12 hours after charging.

[0012] Figure 2 This is a discharge state diagram of the manganese positive electrode electrolyte in Example 1 of the present invention after 1000 cycles.

[0013] Figure 3 The manganese positive electrode electrolyte and the tin negative electrode electrolyte in Example 1 of the present invention are matched to form a charge and discharge curve diagram of a manganese-tin liquid flow battery after 1000 cycles.

[0014] Figure 4 The manganese positive electrode electrolyte and the tin negative electrode electrolyte in Example 1 of the present invention are matched to form a cycle performance diagram of a manganese-tin liquid flow battery.

[0015] Figure 5 This is a diagram of the charging state of the manganese positive electrode electrolyte in Comparative Example 1 of the present invention after 60 cycles; wherein a is the state just after charging; and b is the state after standing for 12 hours after charging.

[0016] Figure 6 This is a discharge state diagram of the manganese positive electrode electrolyte in Comparative Example 1 of the present invention after 60 cycles.

[0017] Figure 7 The manganese positive electrode electrolyte and the tin negative electrode electrolyte in Comparative Example 1 of the present invention are matched to form a charge and discharge curve diagram of a manganese-tin liquid flow battery after 60 cycles.

[0018] Figure 8 The manganese positive electrode electrolyte and the tin negative electrode electrolyte in Comparative Example 1 of the present invention are matched to form a cycle performance diagram of a manganese-tin liquid flow battery. DETAILED DESCRIPTION

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0021] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation 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 associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0022] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0023] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0024] The first aspect of the present invention provides a manganese positive electrode deposition / dissolution colloidal electrolyte, comprising a manganese salt, an acid, an additive and a solvent; The additive is a lanthanum salt and / or a cerium salt.

[0025] The reaction of the traditional manganese positive electrode electrolyte during the charging process 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 with the flowing electrolyte, making the electrolyte turbid; the reaction during the discharge process is the electroreduction process of manganese dioxide and trivalent manganese ions, generating divalent manganese ions, but because the generated manganese dioxide particles are large, poor in fluidity, and low in electrochemical activity, they will remain in the liquid storage tank and adhere to the inner wall of the circulation pipeline. Therefore, the electrolyte cannot be changed from a muddy state back to a clear and transparent state during the discharge process. With the repeated charging and discharging, these "dead manganese" accumulate more and more, eventually leading to a reduction in manganese active substances, pipeline blockage, and failure of the flow battery. The rare earth ion additive in the present invention can regulate the solvation structure of manganese ions through a strong effect with water molecules, significantly reduce the particle size of the generated manganese dioxide to the nanoscale, and form a stable and non-settling colloidal solution, thereby significantly increasing the electrochemical performance and fluidity of manganese dioxide, and achieving high coulomb efficiency and high stability.

[0026] In a preferred embodiment of the present invention, 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 Ce2(SO4)3, cerium sulfate Ce(SO4)2, cerium chloride, cerium nitrate, cerium methanesulfonate, and cerium acetate.

[0027] 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~0.2M.

[0028] 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; and the concentration of the manganese salt in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.1M~2M.

[0029] In a preferred embodiment of the present invention, the acid is an organic acid or an inorganic acid; and the concentration of the acid in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.5M~6M.

[0030] 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, aminosulfonic acid, benzenesulfonic acid and phenolsulfonic acid.

[0031] In a preferred embodiment of the present invention, the solvent is water.

[0032] A second aspect of the present invention provides a flow battery, comprising 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 above-mentioned manganese positive electrode deposition / dissolution colloidal electrolyte.

[0033] In a preferred embodiment of the present invention, the positive electrode current collector is carbon felt; the negative electrode current collector is carbon felt; and the separator is a proton exchange membrane.

[0034] In a preferred embodiment of the present invention, 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.

[0035] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0036] The solvent of the electrolyte used in the examples of the present invention and the comparative examples is water.

[0037] The proton exchange membrane used in the examples and comparative examples of the present invention is a polybenzimidazole proton exchange membrane.

[0038] The test method involved in the embodiment of the present invention is as follows: the charge and discharge current density is 60 mA cm -2, constant current charging to 43 mAh cut off, and discharge to 0V cut off.

[0039] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention. Example 1

[0040] This embodiment provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.05M cerium sulfate; the negative electrode current collector is carbon felt, the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; the separator is a proton exchange membrane. The voltage of the manganese-tin flow battery is about 1.6V, and the charging state of the manganese positive electrode electrolyte after 1000 cycles is as follows Figure 1 As shown, a is the state just after charging; b is the state after charging and standing for 12 hours. Figure 1 It can be seen that there is no stratification after standing for 12 hours; the discharge state of the manganese positive electrode electrolyte after 1000 cycles is as follows Figure 2 As shown by Figure 2 It can be seen that the manganese positive electrode electrolyte is a clear and transparent solution after discharge. The charge and discharge curve of the manganese-tin liquid flow battery after 1000 cycles is as follows Figure 3 As shown by Figure 3 It can be seen that the charge and discharge curve after 1000 cycles is very stable, there is no extra platform side reaction, and the polarization is small and the reversibility is good; the cycle performance of the manganese-tin liquid flow battery is as follows Figure 4 As shown by Figure 4 It can be seen that the initial discharge capacity is 40.2 mAh, and then the discharge capacity increases to 42.8 mAh and can remain stable. The coulomb efficiency can reach 99.5%, and the number of cycles is greater than 3000. Example 2

[0041] This embodiment provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.2M manganese sulfate + 4M sulfuric acid + 0.1M cerium sulfate + 0.05M cerium nitrate; the negative electrode current collector is carbon felt, the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; the diaphragm is a proton exchange membrane. The voltage of the manganese-tin flow battery is about 1.6V, the coulomb efficiency can reach 99%, and the number of cycles is greater than 3000. Example 3

[0042] This embodiment provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.5M manganese chloride + 3M hydrochloric acid + 0.1M cerium chloride; the negative electrode current collector is carbon felt, the electrolyte is 0.5M copper sulfate + 3M hydrochloric acid; and the diaphragm is a proton exchange membrane. The voltage of the manganese-copper flow battery is about 1V, the coulomb efficiency can reach 99%, and the number of cycles is greater than 3000. Example 4

[0043] This embodiment provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.2M manganese sulfate + 5M sulfuric acid + 0.2M cerium chloride; the negative electrode current collector is carbon felt, the electrolyte is 5M sulfuric acid + 0.3M silicotungstic acid; and the diaphragm is a proton exchange membrane. The voltage of the manganese-silicotungstic acid flow battery is about 1.2V, the coulomb efficiency can reach 99%, and the number of cycles is greater than 3000. Example 5

[0044] This embodiment provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.1M cerium sulfate; the negative electrode current collector is carbon felt, the electrolyte is 3M sulfuric acid + 0.2M titanium sulfate; and the diaphragm is a proton exchange membrane. The voltage of the manganese-titanium flow battery is about 1.2V, the coulomb efficiency can reach 99%, and the number of cycles is greater than 3000. Example 6

[0045] This embodiment provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.005M lanthanum sulfate; the negative electrode current collector is carbon felt, the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; and the diaphragm is a proton exchange membrane. The voltage of the manganese-tin flow battery is about 1.6V, the coulomb efficiency can reach 99%, and the number of cycles is greater than 2000. Example 7

[0046] This embodiment provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid + 0.05M cerium sulfate + 0.005M lanthanum sulfate; the negative electrode current collector is carbon felt, the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; the diaphragm is a proton exchange membrane. The voltage of the manganese-tin flow battery is about 1.6V, the coulomb efficiency can reach 99%, and the number of cycles is greater than 3000.

[0047] Comparative Example 1 This comparative example provides a flow battery, wherein the positive electrode current collector is carbon felt, the electrolyte is 0.2M manganese sulfate + 3M sulfuric acid; the negative electrode current collector is carbon felt, the electrolyte is 3M sulfuric acid + 0.2M tin sulfate; and the separator is a proton exchange membrane. The voltage of the manganese-tin flow battery is about 1.5V. The charging state of the manganese positive electrode electrolyte after 60 cycles is as follows: Figure 5 As shown in a, the state after standing for 12 hours after charging is as follows Figure 5 As shown in b; Figure 5 It can be seen that the charged electrolyte has obvious sedimentation and stratification after standing for 12 hours, indicating that the dead manganese has obvious sedimentation after standing. Figure 6 As shown by Figure 6 It can be seen that a large amount of manganese dioxide remains on the wall of the liquid storage tank, indicating that the manganese dioxide cannot be fully utilized. The charge and discharge curve of the manganese-tin liquid flow battery after 60 cycles is shown in the figure below. Figure 7 As shown by Figure 7 It can be seen that the charge and discharge curves are not stable, the polarization is large, and the reversibility is poor, indicating that a large amount of manganese dioxide has blocked the carbon felt and the flow pipes and cannot react reversibly. Figure 8 As shown by Figure 8 It can be seen that after 50 cycles, the discharge capacity and coulombic efficiency decay rapidly. At the 60th cycle, the coulombic efficiency is only 72%.

[0048] The above-described embodiments of the present invention mainly take manganese-tin, manganese-copper, manganese-silicotungstic acid, and manganese-titanium liquid flow batteries composed of tin, copper, silicotungstic acid, titanium negative electrodes and manganese positive electrodes as examples, and do not constitute a limitation on the protection scope of the present invention. Other liquid flow negative electrodes, such as vanadium negative electrodes, lead negative electrodes, etc. can be used to form corresponding liquid flow full batteries with the manganese positive electrode in the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in 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.

2. The manganese positive electrode deposition / dissolution colloidal electrolyte according to claim 1, characterized in that: 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.

3. The manganese positive electrode deposition / dissolution colloidal electrolyte according to claim 1, characterized in that: The concentration of the additive in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.005M~0.2M.

4. The manganese positive electrode deposition / dissolution colloidal electrolyte according to claim 1, characterized in that: The manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate, manganese methanesulfonate, manganese acetate, and manganese oxalate; and the concentration of the manganese salt in the manganese positive electrode deposition / dissolution colloidal electrolyte is 0.1M~2M.

5. The manganese positive electrode deposition / dissolution colloidal electrolyte according to claim 1, characterized in that: 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.

6. The manganese positive electrode deposition / dissolution colloidal electrolyte according to claim 5, characterized in that: 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.

7. The manganese positive electrode deposition / dissolution colloidal electrolyte according to claim 1, characterized in that: The solvent is water.

8. 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 any one of claims 1 to 7.

9. The flow battery according to claim 8, 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.

10. The flow battery according to claim 8, 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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