An acidic lead-bromine flow battery

Abstract

This invention discloses an acidic lead-bromine flow battery, belonging to the field of energy storage battery technology. The negative electrode electrolyte of the battery is a hydrobromic acid solution containing dissolved lead-bromine complexes, and the positive electrode electrolyte is also a hydrobromic acid solution. Using hydrobromic acid as the supporting electrolyte, a solubility of up to 2M for the lead-bromine complexes is achieved, corresponding to a theoretical volumetric capacity of 64.3 Ah / L. ‑1 At 80mA cm ‑2 At the specified current density, after 160 cycles, the electrolyte utilization rate of the lead-bromine flow battery assembled with a negative electrode electrolyte containing 0.8 M lead-bromine complex still reaches 94.7%. After 160 cycles, the corresponding coulombic efficiency remains as high as 98.965%, and the energy efficiency is 89.5%. This indicates that the lead-bromine flow battery possesses high electrolyte utilization and excellent cycle performance. At 200 mA cm⁻¹ ‑2 At high current densities, the coulombic efficiency of the lead-bromine flow battery exceeds 99%, and the energy efficiency still exceeds 81%, indicating that the lead-bromine flow battery has good rate performance.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and specifically relates to an acidic lead-bromine flow battery. Background Technology

[0002] Energy storage systems are a crucial component in promoting the development of smart / microgrids and overcoming bottlenecks in the widespread application of renewable energy. Flow batteries, as an important energy storage system, store electrical energy by placing redox active materials at the positive and negative electrodes in dissolved or suspended form within an electrolyte tank. Based on the energy storage method and electrode reaction type, flow batteries can be broadly classified into two categories: liquid-liquid flow batteries and hybrid flow batteries. Currently, vanadium redox flow batteries (VFBs) among liquid-liquid flow batteries possess advantages such as high safety, good stability, high efficiency, and long lifespan, and are considered to have promising application prospects. However, the low energy density of VFBs and the highly toxic nature of pentavalent vanadium limit their large-scale application to some extent.

[0003] Zinc-bromine flow batteries, as a representative of hybrid flow batteries, have advantages such as high potential, high theoretical energy density, and low cost. However, zinc dendrites at the negative electrode lead to a low areal capacity and low electrolyte utilization. The activity of the bromine electrode is lower than that of the zinc electrode, which results in greater electrochemical polarization, lower operating current density, and lower actual power density in zinc-bromine flow batteries. The activity of the bromine electrode is higher under strong acid conditions than under neutral conditions, but zinc undergoes hydrogen evolution reaction under strong acid conditions.

[0004] As a representative of single-flow batteries, all-lead redox batteries have advantages such as high potential, high energy density, and no need for a separator. However, the poor kinetic properties of the redox couple at the positive electrode and incomplete discharge lead to low coulombic efficiency and poor cycle performance in all-lead redox batteries.

[0005] Overcoming the technical problems of the aforementioned flow battery system and developing a new flow battery system with better overall performance has always been a challenge that those skilled in the art have been striving to overcome. Summary of the Invention

[0006] To address the aforementioned technical problems, the purpose of this invention is to propose an acidic lead-bromine flow battery with high energy density, high utilization rate, and high performance. This invention replaces the original PbO2 / PbMSA positive electrode couple in an all-lead flow battery with a bromine couple, thereby improving the battery's operating current density and performance. Simultaneously, lead can exist stably in hydrobromic acid, avoiding the occurrence of the metal hydrogen evolution side reaction.

[0007] This invention uses hydrobromic acid as the supporting electrolyte and dissolves the active substance lead bromide in it to form a lead-bromine complex. The concentration of bromide ions in the electrolyte must be at least six times higher than the concentration of lead ions to ensure complete dissolution of lead bromide.

[0008] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0009] An acidic lead-bromine flow battery, the flow battery comprising a positive electrolyte and a negative electrolyte, wherein the negative electrolyte is a hydrobromic acid solution containing a lead-bromine complex, and the positive electrolyte is a hydrobromic acid solution.

[0010] Based on the above scheme, preferably, the preparation process of the negative electrode electrolyte is as follows: lead bromide is dissolved in hydrobromic acid solution to obtain hydrobromic acid solution containing lead bromide complex; the concentration of bromide ions in the negative electrode electrolyte is more than 6 times the concentration of lead ions.

[0011] Based on the above scheme, preferably, the concentration of hydrobromic acid in the negative electrode electrolyte is 1-5 mol / L, and the concentration of lead-bromine complex is 0.1-1 mol / L, more preferably 0.8-1 mol / L.

[0012] Based on the above scheme, preferably, when the concentration of lead-bromine complex in the negative electrode electrolyte exceeds 1 mol / L, the electrolyte also includes sodium bromide or potassium bromide to provide excess bromide ions. The concentration of sodium bromide or potassium bromide is 1-5 mol / L, and the concentration of lead-bromine complex is 1-2 mol / L.

[0013] Based on the above scheme, preferably, the concentration of hydrobromic acid in the positive electrode electrolyte is 1-5 mol / L.

[0014] Based on the above scheme, preferably, the positive and negative current collectors of the flow battery are graphite plates or copper plates.

[0015] Based on the above scheme, preferably, the ion exchange membrane of the flow battery is a porous ion conduction membrane or an ion exchange membrane, and more preferably, a Nafion 115 membrane.

[0016] The assembly and testing method of the above-mentioned acidic lead-bromine flow battery mainly includes the following steps:

[0017] (1) Assemble the single cell in the following order: positive terminal plate, graphite current collector, positive electrode 6x8cm 2 Carbon felt, Nafion 115 membrane, negative electrode 6x8 cm 2 Carbon felt, graphite current collector, negative end plate.

[0018] (2) Preparation of negative electrode electrolyte: Dissolve 20g-190g of lead bromide in 100-500g of 40% hydrobromic acid, transfer to a 500mL volumetric flask and make up to volume to obtain negative electrode electrolytes of different concentrations; Dissolve 20-260g of sodium bromide in 100-500g of hydrobromic acid, then add 190-300g of lead bromide, transfer to a 500mL volumetric flask and make up to volume to obtain negative electrode electrolytes of different concentrations containing sodium bromide;

[0019] (3) Preparation of positive electrode electrolyte: Transfer 100-500g of 40% hydrobromic acid to a 500mL volumetric flask and make up to volume;

[0020] (4) Battery performance testing: The electrolyte flow rate in the battery is 60 mL / min. -1 The current density is 80-200 mA / cm². -2 It employs a voltage cutoff method, with a charging cutoff voltage of 1.5V and a discharging cutoff voltage of 0.1V, and uses a Nafion 115 membrane as the separator. At 80mA cm... -2 The following tests were conducted on acidic lead-bromine flow batteries assembled with lead-bromine complexes of different concentrations.

[0021] The advantages of this invention over the prior art are as follows:

[0022] (1) Compared with organic ligands, inorganic bromide ions, as ligands, exhibit higher solubility and lower viscosity. The addition of sodium bromide or potassium bromide can further increase the concentration of bromide ions, preventing the volatilization of high-concentration hydrobromic acid. Therefore, the solubility of the lead-bromine complex can reach up to 2M, corresponding to a theoretical volumetric capacity of 64.3 Ah L. -1 At 80mA cm -2 Below this, the discharge volumetric capacity of the lead-bromine flow battery is greater than 55 Ah / L. -1 The discharge energy density reaches 70Wh / L -1 above.

[0023] (2) At the 1.5V charging voltage cutoff and 80mA cm -2 At current densities, lead-bromine flow batteries assembled with 0.8-1.2M lead-bromine complex electrolytes showed little difference in performance, with coulombic efficiencies all exceeding 98% and energy efficiencies all exceeding 90%.

[0024] (3) At 80mA cm -2 After 160 cycles, the electrolyte utilization rate of the lead-bromine flow battery assembled with 0.8M lead-bromine complex electrolyte still reached 94.7%. The corresponding coulombic efficiency was still as high as 98%, and the energy efficiency was 89.5%. This indicates that the lead-bromine flow battery has high electrolyte utilization and excellent cycle performance.

[0025] (4) At 200mA cm -2 At high current densities, the coulombic efficiency of the lead-bromine flow battery exceeds 99%, and the energy efficiency still exceeds 81%, indicating that the lead-bromine flow battery has good rate performance. Attached Figure Description

[0026] To more clearly illustrate the embodiments of the present invention, the accompanying drawings related to the embodiments will be briefly described below.

[0027] Figure 1 This is a schematic diagram of the structure of the acidic lead-bromine redox flow battery provided by the present invention.

[0028] Figure 2 For 80mA cm -2 Comparison of the performance of acidic lead-bromine flow batteries at different lead-bromine complex concentrations in Example 1 at the given current density. Figure 2 a) and the corresponding discharge energy density variation diagram ( Figure 2 b).

[0029] Figure 3 At 80mA cm -2 At the current density, the long-cycle performance of the acidic lead-bromine flow battery at a concentration of 0.8 M lead-bromine complex in Example 2 is shown in the figure. Figure 3 a) and the corresponding charge / discharge volumetric capacity change diagram ( Figure 3 b).

[0030] Figure 4 The rate performance diagram of the acidic lead-bromine flow battery at a lead-bromine complex concentration of 0.8 M in Example 3 ( Figure 4 a) and the corresponding charge-discharge curves ( Figure 4 b).

[0031] Figure 5 At 40mA cm -2 The cycling performance of the zinc-bromine flow battery in Comparative Example 1 is shown in the figure.

[0032] Figure 6 At 20mA cm -2 The cycle performance of the all-lead redox flow battery in Comparative Example 2 is shown in the figure at the current density. Detailed Implementation

[0033] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0034] The single cell in the embodiment is assembled in the following order: positive terminal plate, graphite current collector, and positive electrode 6x8cm. 2 Carbon felt, Nafion 115 membrane, negative electrode 6x8 cm 2 Carbon felt, graphite current collector, negative electrode plate. For example... Figure 1 As shown.

[0035] Battery performance testing: The electrolyte flow rate in the battery was 60 mL / min. -1 It employs voltage cutoff, with a current density of 80-200 mA / cm². -2 The charging cutoff voltage is 1.5V, the discharging cutoff voltage is 0.1V, and the film is Nafion 115.

[0036] The 40% hydrobromic acid mentioned in the following examples and comparative examples refers to a 40% hydrobromic acid solution by mass.

[0037] Example 1

[0038] 1) Preparation of negative electrode electrolyte: Dissolve 73.4g of lead bromide in 404.55g of 40% hydrobromic acid, transfer to a 500mL volumetric flask and make up to volume to obtain a negative electrode electrolyte with a lead-bromine complex concentration of 0.4M; Dissolve 146.8g of lead bromide in 404.55g of 40% hydrobromic acid, transfer to a 500mL volumetric flask and make up to volume to obtain a negative electrode electrolyte with a lead-bromine complex concentration of 0.8M; Dissolve 51.45g of sodium bromide in 404.55g of 40% hydrobromic acid, add 220.2g of lead bromide, transfer to a 500mL volumetric flask and make up to volume to obtain a negative electrode electrolyte with a lead-bromine complex concentration of 1.2M;

[0039] 2) Preparation of positive electrode electrolyte: Transfer 404.55g of 40% hydrobromic acid to a 500mL volumetric flask and make up to volume;

[0040] 3) At 80mA cm -2 Acidic lead-bromine flow batteries assembled with lead-bromine complexes of different concentrations were tested.

[0041] from Figure 2 As shown in Figure a, the performance of acidic lead-bromine flow batteries assembled with negative electrode electrolytes of different lead-bromine complex concentrations did not differ significantly, with coulombic efficiencies all exceeding 98% and energy efficiencies all exceeding 90%. This indicates good kinetic properties of the lead-bromine pair and excellent battery performance. The more dissolved lead bromide, i.e., the higher the concentration of the lead-bromine complex, the higher the battery energy density. From... Figure 2 As shown in b, with the increase of lead-bromine complex concentration (0.4M, 0.8M, 1.2M), the energy density of the acidic lead-bromine flow battery also increases, with the discharge energy density increasing from 24.72 W / L. -1 Up to 51.61 WL L -1 Then to 71.81WL L -1 .

[0042] Example 2

[0043] 1) Preparation of negative electrode electrolyte: Dissolve 146.8g of lead bromide in 404.55g of 40% hydrobromic acid, transfer to a 500mL volumetric flask and make up to volume to obtain a negative electrode electrolyte with a lead bromide complex concentration of 0.8M;

[0044] 2) Preparation of positive electrode electrolyte: Transfer 404.55g of 40% hydrobromic acid to a 500mL volumetric flask and make up to volume;

[0045] 3) At 80mA cm -2 The assembled acidic lead-bromine flow battery was subjected to long-cycle performance testing and capacity decay testing.

[0046] from Figure 3 As can be seen from a, at the 1.5V charging voltage cutoff and 80mA cm -2 At the specified current density, after 160 cycles, the lead-bromine flow battery assembled with a negative electrode electrolyte containing a 0.8 M lead-bromine complex still maintained a coulombic efficiency of 98.965% and an energy efficiency of 89.5%. Figure 3 As shown in b, the electrolyte utilization rate can still reach 94.7%. This indicates that the lead-bromine flow battery has excellent cycle performance and high electrolyte utilization rate.

[0047] Example 3

[0048] 1) Preparation of negative electrode electrolyte: Dissolve 146.8g of lead bromide in 404.55g of 40% hydrobromic acid, transfer to a 500mL volumetric flask and make up to volume to obtain a negative electrode electrolyte with a lead bromide complex concentration of 0.8M;

[0049] 2) Preparation of positive electrode electrolyte: Transfer 404.55g of 40% hydrobromic acid to a 500mL volumetric flask and make up to volume;

[0050] 3) At 80-200mA cm -2 The performance and capacity change of the assembled acidic lead-bromine flow battery were tested at a current density of [value missing].

[0051] from Figure 4 It can be seen from this that at 200mA cm -2 At high current densities, the coulombic efficiency of the lead-bromine flow battery exceeds 99%, and the energy efficiency still exceeds 81%, indicating that the lead-bromine flow battery has good rate performance.

[0052] Comparative Example 1

[0053] 1) Preparation of positive and negative electrode electrolytes: Dissolve 111.75g ​​potassium chloride, 225.2g zinc bromide and 38.82g 40% MEP in ultrapure water, and transfer to a 500mL volumetric flask and make up to volume.

[0054] 2) At 40mA cm -2 Performance tests were conducted on the zinc-bromine flow battery assembled with Nafion 212 membrane at the current density.

[0055] from Figure 5 It can be seen from this that at 40mA cm -2 At the given current density, the energy efficiency of the zinc-bromine flow battery was only 74.23%, and it slowly decreased to 66.53%, indicating that the activity of the bromine couple was poor in the neutral system.

[0056] Comparative Example 2

[0057] 1) Preparation of positive and negative electrode electrolytes: Dissolve 397.4g of 50% lead methanesulfonate and 96.11g of methanesulfonic acid in ultrapure water, and transfer to a 500mL volumetric flask and make up to volume.

[0058] 2) At 20mA cm -2 Performance tests were conducted on an acidic all-lead redox flow battery assembled with a Nafion 212 membrane at a current density of [value missing].

[0059] from Figure 6 It can be seen from this that at 20mA cm -2 At the given current density, the coulombic efficiency of the all-lead redox flow battery is only 90.56%, and after 32 cycles, the coulombic efficiency is only 48.68%, and the energy efficiency is only 68.39%. This is mainly because the positive electrode couple of the all-lead redox flow battery has poor kinetic properties and incomplete discharge.

[0060] Comparative Example 3

[0061] 1) Preparation of negative electrode electrolyte: Dissolving 220.51g of lead bromide in 404.55g of 40% hydrobromic acid will result in a small amount of undissolved lead bromide. This will prevent the battery from charging and discharging normally. Therefore, the concentration of bromide ions in the electrolyte must be at least six times higher than the concentration of lead ions to ensure normal battery operation.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An acidic lead-bromine flow battery, the flow battery comprising a positive electrode electrolyte and a negative electrode electrolyte, characterized in that: The negative electrode electrolyte is a hydrobromic acid solution containing lead bromine complex, and the positive electrode electrolyte is a hydrobromic acid solution. The preparation process of the negative electrode electrolyte is as follows: lead bromide is dissolved in hydrobromic acid solution to obtain hydrobromic acid solution containing lead bromide complex; the concentration of bromide ions in the negative electrode electrolyte is more than 6 times the concentration of lead ions; When the concentration of lead-bromine complex in the negative electrode electrolyte exceeds 1 mol / L, sodium bromide or potassium bromide is also included in the negative electrode electrolyte to provide excess bromide ions.

2. The acidic lead-bromine flow battery according to claim 1, characterized in that, In the negative electrode electrolyte, the concentration of hydrobromic acid is 1-5 mol / L, and the concentration of lead-bromine complex is 0.1-1 mol / L.

3. The acidic lead-bromine flow battery according to claim 2, characterized in that, The concentration of lead-bromine complex in the negative electrode electrolyte is 0.8-1 mol / L.

4. The acidic lead-bromine flow battery according to claim 1, characterized in that, The concentration of sodium bromide or potassium bromide is 1-5 mol / L, and the concentration of the lead bromide complex is 1-2 mol / L.

5. The acidic lead-bromine flow battery according to claim 1, characterized in that, The concentration of hydrobromic acid in the positive electrode electrolyte is 1-5 mol / L.

6. The acidic lead-bromine flow battery according to claim 1, characterized in that, The positive and negative current collectors of the flow battery are graphite plates or copper plates.

7. The acidic lead-bromine flow battery according to claim 1, characterized in that, The ion-conducting membrane of the flow battery is a porous ion-conducting membrane or an ion-exchange membrane.

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