A cadmium-bromine-manganese single-flow battery

Abstract

The application relates to a cadmium-bromine-manganese single liquid flow, wherein the positive electrolyte and the negative electrolyte are both 1-5M (preferably 1-4M, more preferably 2-3M) H2SO4 aqueous solution; the molar concentration of bromine ions in the electrolyte is 0.25-4mol / L; the molar concentration of cadmium ions in the electrolyte is 0.1-4mol / L; the molar concentration of divalent manganese ions in the electrolyte is 0.1-4mol / L; and the molar ratio of bromine ions to divalent manganese ions in the electrolyte is 0.25-4. The electrolyte is a mixed aqueous solution of cadmium salt, manganese salt and bromide, the cost is low, the solubility of the bromide and the manganese salt is very high, the energy density of the battery is high, the electrochemical activity of the electrolyte is better, the current density of the battery operation is very high, and the power density of the battery is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flow battery, in particular to the field of manganese-based flow battery. BACKGROUND

[0002] Renewable energy such as wind and solar energy is difficult to be directly utilized due to its discontinuity and instability, so energy storage technology is the key to realize the popularization and industrialization of renewable energy. Flow battery has the advantages of independent design of power and capacity, and no geographical environment restriction, and becomes one of the most promising large-scale energy storage devices.

[0003] At present, the developed flow batteries mainly include all-vanadium flow battery, zinc-bromine flow battery, etc., but the cost of all-vanadium flow battery is restricted by the price of vanadium resources; the negative electrode of zinc-bromine flow battery is affected by zinc dendrite, and is easy to pierce the separator to cause short circuit under high surface capacity, which limits the energy density thereof. The manganese-based flow battery can realize double electron transfer, and has the characteristics of high electrode potential, high active material solubility and low cost, and is expected to realize low cost and high energy density at the same time. SUMMARY

[0004] The technical problem to be solved by the present application (invention purpose)

[0005] At present, the manganese-based battery generally operates in an acidic or neutral electrolyte system. Under neutral conditions, the dense deposition of manganese dioxide on the electrode surface limits the surface capacity of the battery; and a ligand needs to be added to stabilize the positive electrode, which reduces the voltage of the battery. Under acidic conditions, divalent manganese ions are first oxidized to trivalent manganese ions, and then trivalent manganese ions are disproportionated into divalent manganese and manganese dioxide, causing irreversible capacity loss.

[0006] In order to solve the above problems, the specific technical scheme of the present application is as follows:

[0007] A cadmium-bromine-manganese single flow battery, comprising a single cell and a battery stack composed of multiple single cells, a negative electrolyte storage tank, and positive and negative electrolytes.

[0008] The positive electrolyte and the negative electrolyte are the same, and are a mixed aqueous solution of cadmium salt, manganese salt and bromide. The bromide is one or more than two of KBr, NaBr, CaBr2, MgBr2, HBr, CdBr2 and MnBr2, and the molar concentration of bromide in the electrolyte is 0.25-4 mol / L; the cadmium salt is one or more than two of CdCl2, CdBr2, CdSO4 and Cd(NO3)2, and the molar concentration of cadmium salt in the electrolyte is 0.1-4 mol / L; the manganese salt is one or more than two of MnCl2, MnBr2, MnSO4 and Mn(NO3)2, and the molar concentration of manganese salt in the electrolyte is 0.1-4 mol / L.

[0009] When the battery is charged, the active material of the negative electrode is pumped through the tank by pipeline to the negative electrode, and the active material of the positive electrode is reacted in the electrode cavity. On the positive electrode, Br- is oxidized to Br2 or polybromide, and Mn2+ is oxidized to MnO2, and Cd2+ on the negative electrode is reduced to Cd; when discharging, the positive electrode MnO2 is reduced to Mn 2+ , Br2 or polybromide is reduced to Br-, and Br- will continue to react with unconverted MnO2, and the Cd of the negative electrode is oxidized to Cd 2+ .

[0010] The structure of the single battery includes positive / negative electrode end plate, membrane, positive / negative electrode, current collector, and liquid flow frame.

[0011] The electrode material is one of carbon felt, graphite plate, metal plate or carbon cloth.

[0012] The cadmium-bromine-manganese single liquid flow battery uses a microporous membrane without ion exchange groups, including one or more than two of polyether sulfone (PES), polyethylene (PE), polypropylene (PP), polysulfone, polyetherimide (PEI), and polyvinylidene fluoride (PVDF), with a thickness of 100-1000 microns, preferably 500-1000 microns, a pore size of 10-100 nm, and a porosity of 30%-70%.

[0013] The cadmium-bromine-manganese single liquid flow battery solves the problem of manganese dioxide not being fully reduced in a manganese-based liquid flow battery under acidic conditions, has high energy density, low battery cost, high current density, and high power density.

[0014] The beneficial effects brought by the technical scheme of the present application are:

[0015] 1. The single liquid flow battery design is adopted, the active material of the negative electrode is pumped through the tank by pipeline to the negative electrode, and the active material of the positive electrode is only reacted in the electrode cavity. The positive and negative electrolytes are the same, effectively solving the problem of electrolyte migration from one electrode to another and battery efficiency decay caused by the inconsistent osmotic pressure of the positive and negative electrolytes in the operation process of the traditional zinc-iodine liquid flow battery, greatly reducing the mutual series of the positive and negative active materials in the battery operation process, improving the coulomb efficiency, effectively reducing the system maintenance cost caused by electrolyte migration, and the same positive and negative electrolytes enable the electrolyte to be recovered online, greatly saving the electrolyte replacement cost, and showing good application prospect.

[0016] 2. The electrolyte is a mixed aqueous solution of cadmium salt, manganese salt and bromide, the cost is low, the solubility of bromide and manganese salt is very high, the energy density of the battery is high, the electrochemical activity of the electrolyte is good, the current density of the battery is very high, and the power density of the battery is high.

[0017] 3. The active material of the positive electrode has two, one is Mn 2+ , the other is Br - , when the battery is charged, Br - on the positive electrode is oxidized to Br2or polybromide, Mn 2+ is oxidized to MnO2, Cd 2+ on the negative electrode is reduced to Cd; when the battery is discharged, MnO2on the positive electrode is reduced to Mn 2+ , Br2or polybromide is reduced to Br - , Br - will continue to react with unconverted MnO2, Cd on the negative electrode is oxidized to Cd 2+ . It can be ensured that MnO2can be completely converted to Mn 2+ during each discharge process, MnO2will not accumulate during the battery cycle, which will increase the polarization of the battery, reduce the efficiency and cycle stability of the battery.

[0018] Other halides (iodide or chloride) and manganese salts are used as the active material of the positive electrode, which reacts with manganese dioxide during discharge to improve the conversion rate of manganese dioxide. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the cadmium-bromine-manganese single flow battery, wherein 1 is the pump of the negative electrode; 2 is the negative electrode electrolyte storage tank; 3 is the positive and negative electrode end plate; 4 is the positive and negative electrode current collector plate; 5 is the positive and negative electrode liquid flow frame; 6 is the battery separator.

[0020] Figure 2 It is a charge-discharge curve diagram of the cadmium-bromine-manganese single flow battery single cell assembled in Example 1 and Comparative Example 1; the positive and negative electrode electrolytes of Example 1 are CdSO4: 0.5M, MnSO4: 1M, HBr: 1M, H2SO4: 2M; the positive and negative electrode electrolytes of Comparative Example 1 are CdSO4: 0.5M, MnSO4: 1M, H2SO4: 2M.

[0021] Figure 3 It is a cycle performance diagram of the cadmium-bromine-manganese single flow battery single cell assembled in Example 1; the positive and negative electrode electrolytes of Example 1 are CdSO4: 0.5M, MnSO4: 1M, HBr: 1M, H2SO4: 2M.

[0022] Figure 4 It is a cycle performance diagram of the cadmium-bromine-manganese single flow battery single cell assembled in Example 2; the positive and negative electrode electrolytes of Example 2 are CdSO4: 1M, MnSO4: 2M, HBr: 1M, H2SO4: 2M.

[0023] Figure 5Cadmium bromine manganese single flow battery cell rate capability plot assembled for Example 3; Example 3 positive and negative electrolytes are CdS04: 0.5M, MnS04: 1M, HBr: 1M, H2S04: 2M.

[0024] Figure 6 Cadmium bromine manganese single flow battery cell charge-discharge plot assembled for Example 4; Example 1 positive and negative electrolytes are CdS04: 1M, MnS04: 4M, HBr: 1M, H2S04: 2M.

[0025] Figure 7 Cadmium bromine manganese single flow battery cell efficiency plot assembled for Example 1, Example 5, Example 6; Example 1 positive and negative electrolytes are CdS04: 1M, MnS04: 4M, HBr: 1M, H2S04: 2M; Example 5 positive and negative electrolytes are CdS04: 1M, MnS04: 4M, HBr: 1M, H2S04: 1M; Example 1 positive and negative electrolytes are CdS04: 1M, MnS04: 4M, HBr: 1M, H2S04: 3M.

[0026] Figure 8 Cadmium bromine manganese single flow battery cell efficiency plot assembled for Example 7; Example 7 positive and negative electrolytes are CdS04: 1M, MnS04: 4M, HBr: 1M, H2S04: 2M.

[0027] Figure 9 Cadmium bromine manganese single flow battery cell efficiency plot assembled for Example 8; Example 8 positive and negative electrolytes are CdS04: 1M, MnS04: 4M, HBr: 1M, H2S04: 2M.

[0028] Figure 10 Cadmium bromine single flow battery cell cycle performance plot assembled for Comparative Example 2; Comparative Example 2 positive and negative electrolytes are CdS04: 1M, HBr: 1M, H2S04: 2M.

[0029] Figure 11 Cadmium bromine manganese single flow battery cell cycle performance plot assembled for Comparative Example 3; Comparative Example 3 differs from Example 1 in that a dual flow battery structure is used, the positive electrode structure is the same as the negative electrode, and the active material is pumped through a tank and delivered to the electrode cavity through a pipeline.

[0030] Figure 12 Zinc manganese single flow battery cell cycle performance plot assembled for Comparative Example 4; positive and negative electrolytes are ZnS04: 0.5M, MnS04: 1M, HBr: 1M, H2S04: 2M.

[0031] Figure 13The SEM morphology of the positive electrode of the cadmium-manganese single flow battery cell assembled for Comparative Example 5 after cycling, the positive and negative electrolytes being CdSO4: 0.5M, MnSO4: 1M. DETAILED DESCRIPTION

[0032] The following examples are further illustrations of the application and are not intended to limit the scope of the application.

[0033] The test of the battery performance: the assembly of the single cell is as follows: positive electrode end plate, current collector, positive electrode with liquid flow frame, diaphragm, negative electrode with liquid flow frame, negative electrode end plate. The flow rate of the electrolyte in the battery is 10 mL / min.

[0034] The single cell comprises a positive electrode, a membrane, a negative electrode; a positive electrode cavity and a negative electrode cavity separated by the membrane, the positive electrode being placed in the positive electrode cavity and the negative electrode being placed in the negative electrode cavity;

[0035] The negative electrolyte is circulated between the negative electrode cavity and the storage tank by a pump, and the positive electrolyte is filled in the positive electrode cavity;

[0036] When the battery is charged, Br- on the positive electrode is oxidized into Br2 or polybromide, and Mn2+ is oxidized into MnO2, and Cd2+ on the negative electrode is reduced into Cd;

[0037] When discharged, the positive electrode first undergoes a reduction reaction of MnO2 into Mn 2+ , and then Br2 or polybromide is reduced into Br-, which continues to react with unconverted MnO2 to generate Mn 2+ , and the Cd of the negative electrode is oxidized into Cd 2+ .

[0038] Example 1

[0039] The supporting electrolyte is 2M H2SO4 aqueous solution, and the electrolytes of the positive and negative electrodes are respectively prepared into electrolyte with a final concentration of 0.5M CdSO4, 1M MnSO4 and 1M HBr. A 900-micron polyolefin porous membrane (9 cm 2 in length, 5 cm in width, and 60% in porosity) is used as a diaphragm, and carbon felt is used as the positive and negative electrode materials to assemble a cadmium-bromine-manganese single flow battery cell. The battery is operated at a current density of 40 mA / cm 2 , and the control conditions are capacity and voltage double cut-off: the charge cut-off capacity is 60 Ah / L, the charge cut-off voltage is 2.3V, and the discharge cut-off voltage is 0.1V.

[0040] Example 2

[0041] The conditions and procedures are the same as in Example 1, except that: 2M H2SO4 is used as the supporting electrolyte, and the positive electrode active material is prepared using 1M CdSO4, 2M MnSO4, and 1M HBr. A 900-micron polyolefin porous membrane (9cm) is used as the separator. 2 A single-cell cadmium-bromine-manganese single-liquid-flow battery was assembled using a 60% porosity anode. The battery operates at 40 mA / cm². 2 It operates at a current density of 60Ah / L, with control conditions of capacity and dual voltage cutoff: charging cutoff capacity is 60Ah / L, charging cutoff voltage is 2.3V, and discharging cutoff voltage is 0.1V.

[0042] Example 3

[0043] The conditions and procedures are the same as in Example 1, except that: 2M H2SO4 is used as the supporting electrolyte, and the positive electrode active material is prepared using 1M CdSO4, 1M MnSO4, and 1M HBr. A 900-micron polyolefin porous membrane (9cm) is used as the separator. 2 A single-cell cadmium-bromine-manganese single-liquid-flow battery was assembled using a 60% porosity anode. The battery operates at 40 mA / cm². 2 It operates at a current density of 60Ah / L, with control conditions of capacity and voltage dual cutoff: charging cutoff capacity is 60Ah / L, charging cutoff voltage is 2.3V, and discharging cutoff voltage is 0.1V.

[0044] Example 4

[0045] The conditions and procedures are the same as in Example 1, except that: 2M H2SO4 is used as the supporting electrolyte, and the positive electrode active material is prepared with 1M CdSO4, 4M MnSO4, and 1M HBr. A 900-micron polyolefin porous membrane (9cm) is used as the separator. 2 A single-cell cadmium-bromine-manganese single-liquid-flow battery was assembled using a 60% porosity anode. The battery operates at 40 mA / cm². 2 It operates at a current density of 60Ah / L, with control conditions of capacity and dual voltage cutoff: charging cutoff capacity is 60Ah / L, charging cutoff voltage is 2.3V, and discharging cutoff voltage is 0.1V.

[0046] Example 5

[0047] The conditions and procedures are the same as in Example 1, except that: 1M H2SO4 is used as the supporting electrolyte, and the positive electrode active material is prepared using 0.5M CdSO4, 1M MnSO4, and 1M HBr. A 900-micron polyolefin porous membrane (9cm) is used as the separator. 2 A single-cell cadmium-bromine-manganese single-liquid-flow battery was assembled using a 60% porosity anode. The battery operates at 40 mA / cm². 2The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V.

[0048] Example 6

[0049] The conditions and procedures were the same as Example 1, except that the electrolyte was prepared with 3 M H2SO4as the supporting electrolyte, 0.5 M CdSO4, 1 M MnSO4, 1 M HBr as the positive active material. The 900-micron polyolefin porous membrane was used as the separator (9 cm2, porosity 60%) to assemble the Cd-BM single flow battery cell. The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V. 2 2 The conditions and procedures were the same as Example 1, except that the electrolyte was prepared with 3 M H2SO4as the supporting electrolyte, 0.5 M CdSO4, 1 M MnSO4, 1 M HBr as the positive active material. The 900-micron polyolefin porous membrane was used as the separator (9 cm2, porosity 60%) to assemble the Cd-BM single flow battery cell. The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V.

[0050] Example 7

[0051] The conditions and procedures were the same as Example 1, except that the electrolyte was prepared with 2 M H2SO4as the supporting electrolyte, 0.5 M CdSO4, 1 M MnSO4, 1 M HBr as the positive active material. The 900-micron polyolefin porous membrane was used as the separator (9 cm2, porosity 60%) to assemble the Cd-BM single flow battery cell. The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V. 2 2 The conditions and procedures were the same as Example 1, except that the electrolyte was prepared with 2 M H2SO4as the supporting electrolyte, 0.5 M CdSO4, 1 M MnSO4, 1 M HBr as the positive active material. The 900-micron polyolefin porous membrane was used as the separator (9 cm2, porosity 60%) to assemble the Cd-BM single flow battery cell. The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V.

[0052] Example 8

[0053] The conditions and procedures were the same as Example 1, except that the electrolyte was prepared with 2 M H2SO4as the supporting electrolyte, 0.5 M CdSO4, 1 M MnSO4, 1 M HBr as the positive active material. The 900-micron polyolefin porous membrane was used as the separator (9 cm2, porosity 60%) to assemble the Cd-BM single flow battery cell. The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V. 2 2 The conditions and procedures were the same as Example 1, except that the electrolyte was prepared with 2 M H2SO4as the supporting electrolyte, 0.5 M CdSO4, 1 M MnSO4, 1 M HBr as the positive active material. The 900-micron polyolefin porous membrane was used as the separator (9 cm2, porosity 60%) to assemble the Cd-BM single flow battery cell. The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V.

[0054] Comparative Example 1

[0055] The conditions and procedures were the same as Example 1, except that the electrolyte was prepared with 2 M H2SO4as the supporting electrolyte, 0.5 M CdSO4, 1 M MnSO4, 1 M HBr as the positive active material. The 900-micron polyolefin porous membrane was used as the separator (9 cm2, porosity 60%) to assemble the Cd-BM single flow battery cell. The cell was operated at a current density of 40 mA / cm2, controlled at capacity, voltage double cut-off: charge cut-off capacity of 60 Ah / L, charge cut-off voltage of 2.3 V, discharge cut-off voltage of 0.1 V. ​​​

[0056] Comparative Example 2

[0057] The conditions and processes are the same as in Example 1, except that the electrolyte of the positive electrode and the negative electrode does not contain manganese ions;

[0058] Comparative Example 3

[0059] The conditions and processes are the same as in Example 1, except that a double liquid flow battery structure is used, the positive electrode structure is the same as the negative electrode, and the active substances are respectively delivered to the electrode cavities by the pump through the pipeline.

[0060] Comparative Example 4

[0061] The conditions and processes are the same as in Example 1, except that the electrolyte of the positive electrode and the negative electrode does not contain manganese ions, and the negative electrode active substance is zinc sulfate.

[0062] Comparative Example 5

[0063] The conditions and processes are the same as in Example 1, except that the electrolyte of the positive electrode and the negative electrode does not contain sulfuric acid and hydrogen bromide, and the electrolyte is neutral.

[0064] As shown in Figure 1 , the application adopts a single liquid flow battery design in the battery structure, the active substance of the negative electrode is delivered to the negative electrode by the pump through the pipeline, and the active substance of the positive electrode only reacts in the electrode cavity. Effectively solve the problem of electrolyte migration from one electrode to another and the efficiency decay of the battery due to the inconsistent osmotic pressure of the positive and negative electrode electrolyte in the running process of the traditional zinc-iodine liquid flow battery. The positive electrode electrolyte is sealed in the electrode cavity, which also effectively reduces the risk of Br2 leakage and volatilization.

[0065] As shown in Figure 2 , Figure 3As shown, both of the two redox couples in the positive electrode of the cadmium-bromine-manganese single flow battery (Example 1) can undergo reversible reactions, in which the potential of the Mn redox couple can reach 2.1 V and the potential of the Br redox couple can reach 1.6 V (vs. Cd). The cadmium-bromine-manganese single flow battery has a stable coulombic efficiency of more than 97%, an energy efficiency of more than 75%, and a charge-discharge capacity of 60 Ah / L at 70% SOC. Compared with the cadmium-manganese flow battery system (Comparative Example 1), the cadmium-bromine-manganese single flow battery (Example 1) has higher capacity, smaller polarization, higher coulombic efficiency, and higher voltage efficiency. Moreover, the cadmium-bromine-manganese single flow battery has good cycle stability and does not have capacity decay after 350 cycles. The advantage of the above system is that during discharge, MnO2 in the positive electrode is reduced to Mn2+, and Br2 or polybromide is reduced to Br-. The Br-continuously reacts with unconverted MnO2, and Cd in the negative electrode is oxidized to Cd2+. This ensures that MnO2 can be completely converted to Mn2+ during each discharge process, and MnO2 does not accumulate during the cycle of the battery, thereby increasing the polarization of the battery and reducing the efficiency and cycle stability of the battery.

[0066] As shown in Figure 4 , Figure 6 , after increasing the concentration of the manganese salt, the cadmium-bromine-manganese single flow battery still has high energy efficiency and coulombic efficiency. When the concentration of the manganese salt reaches 4 M, the highest capacity density can reach 264 Wh / L, which is the highest energy density of the manganese-based battery at present.

[0067] As shown in Figure 5 , because Br- can act as a redox medium, it can promote the conversion of manganese dioxide and improve the kinetics of the reaction. The cadmium-bromine-manganese single flow battery has good rate performance. As the charge-discharge current density increases, the charge time shortens, the coulombic efficiency increases, the polarization increases, and the voltage efficiency decreases. At a current density of 120 mA / cm2, the energy efficiency is still more than 70%.

[0068] As shown in Figure 7 , increasing the proton concentration helps the conversion of manganese dioxide. As the concentration of sulfuric acid increases, the activity of the bromine redox couple increases and the polarization of the dissolution of manganese dioxide decreases, and the voltage efficiency of the battery increases. When the concentration of sulfuric acid is too high, the platform of the bromine redox couple shortens and the charge capacity decreases.

[0069] As shown in Figure 8 , the efficiency of the cadmium-bromine-manganese single flow battery does not decrease significantly at 50-80% SOC.

[0070] As shown in Figure 9 , as the temperature increases, the coulombic efficiency decreases and the voltage efficiency increases. This is because the bromine cross-bridging intensifies at high temperatures. The cadmium-bromine-manganese single flow battery has good temperature variation performance.

[0071] As shown in Figure 10As shown, compared with the cadmium-bromine flow battery system (Comparative Example 2), the cadmium-bromine-manganese single flow battery (Example 1) has higher capacity and better cycle stability. This is mainly because the introduction of the manganese electric pair improves the theoretical capacity of the battery, and is more stable than the bromine electric pair.

[0072] As shown, Figure 11 compared with the traditional double flow battery structure (Comparative Example 3), the cadmium-bromine-manganese single flow battery (Example 1) has higher efficiency and cycle stability, because in the single flow battery structure, the mutual stringing and volatilization of bromine are inhibited, and the use of single flow battery structure not only improves the battery performance, but also effectively reduces the safety risk of Br2 leakage and volatilization.

[0073] As shown, Figure 12 compared with the use of zinc sulfate as the negative active material (Comparative Example 4), the use of cadmium sulfate as the active material (Example 1) has higher efficiency and cycle stability, because the cadmium negative electrode has high hydrogen evolution overpotential in acidic conditions and can be operated stably.

[0074] As shown, Figure 13 under the condition of neutral electrolyte (Comparative Example 5), the manganese dioxide deposited is difficult to be completely reduced and will continuously accumulate on the electrode surface, resulting in irreversible capacity loss and efficiency reduction.

Claims

1. A cadmium-bromine-manganese single-flow battery, characterized in that: Both the positive and negative electrolytes are 1-5M H₂SO₄ aqueous solutions; the negative electrolyte is circulated between the negative electrode cavity and the storage tank by a pump, and the positive electrolyte is filled into the positive electrode cavity; The electrolyte contains bromide ions at a molar concentration of 0.25–4 mol / L; cadmium ions at a molar concentration of 0.1–4 mol / L; and divalent manganese ions at a molar concentration of 0.1–4 mol / L. The molar ratio of bromide ions to divalent manganese ions in the electrolyte is 0.25~4; The bromide used to provide bromide ions in the electrolyte is one or more of the following: KBr, NaBr, CaBr2, MgBr2, HBr, CdBr2, and MnBr2. The cadmium salts used to provide cadmium ions in the electrolyte are one or more of CdCl2, CdBr2, CdSO4, and Cd(NO3)2. The manganese salts used to provide manganese ions in the electrolyte are one or more of MnCl2, MnBr2, MnSO4, and Mn(NO3)2.

2. The flow battery according to claim 1, characterized in that: Both the positive and negative electrode electrolytes are 1-4M H2SO4 aqueous solutions; The electrolyte contains bromide ions at a molar concentration of 1-3 mol / L; cadmium ions at a molar concentration of 0.5-2 mol / L; and divalent manganese ions at a molar concentration of 1-3 mol / L. The molar ratio of bromide ions to divalent manganese ions in the electrolyte is 1-2.

3. The flow battery according to claim 1, characterized in that: The positive electrode electrolyte and the negative electrode electrolyte are the same.

4. The flow battery according to claim 1, characterized in that: When the battery is charging, Br- is oxidized to Br2 or polybrominated at the positive electrode, Mn2+ is oxidized to MnO2, and Cd2+ is reduced to Cd at the negative electrode. During discharge, MnO2 at the positive electrode first undergoes a reduction reaction to become Mn. 2+ Then Br2 or polybrominates are reduced to Br-, which then reacts with unconverted MnO2 to produce Mn. 2+ The Cd at the negative electrode is oxidized to Cd. 2+ .

5. The flow battery according to claim 1, 2, 3, or 4, characterized in that: A single cell includes a positive electrode, a membrane, and a negative electrode; a positive electrode cavity and a negative electrode cavity are separated by the membrane, with the positive electrode placed in the positive electrode cavity and the negative electrode placed in the negative electrode cavity; The electrode materials for the positive and negative electrodes are one or more of the following: carbon felt, graphite plate, metal plate, or carbon cloth. The cadmium-bromine-manganese single-flow battery uses a microporous membrane without ion exchange groups, including one or more of polyethersulfone (PES), polyethylene (PE), polypropylene (PP), polysulfone, polyetherimide (PEI), and polyvinylidene fluoride (PVDF), with a membrane thickness of 100~1000µm, a pore size of 10~100 nm, and a porosity of 30%~70%.

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