Positive electrode electrolyte and titanium-cerium flow battery

Abstract

The invention belongs to the technical field of flow batteries, and relates to a positive electrode electrolyte and a titanium-cerium flow battery, the positive electrode electrolyte is formed by mixing an initial electrolyte and a hydrogen peroxide solution; wherein the initial electrolyte is an acidic aqueous solution containing supporting electrolyte and cerium ions. The hydrogen peroxide solution is mixed into the initial electrolyte to serve as the reducing additive, so that the efficiency and the cycle life of the titanium-cerium flow battery are effectively improved and prolonged.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and relates to a positive electrode electrolyte, and more particularly to a positive electrode electrolyte and a titanium-cerium flow battery. Background Technology

[0002] Titanium-cerium redox flow batteries are a novel type of flow battery that uses cerium ions in the positive electrode electrolyte and titanium ions in the negative electrode electrolyte as active materials. Due to their advantages such as high theoretical energy density, high battery voltage, low cost, safety, and environmental friendliness, they have broad application prospects in large-scale energy storage.

[0003] Titanium-cerium redox flow batteries with Ce 4+ / Ce 3+ Positive electrode and Ti 3+ / Ti 4+ As a redox pair, the negative electrode theoretically possesses advantages such as a high potential window, environmental friendliness, and low cost, leading to its increasing research in distributed energy storage in recent years. Research on optimizing the positive electrode electrolyte mainly focuses on the synergistic regulation of cerium ion concentration, acid medium type, and additives. Early work often used concentrations of 0.1–0.5 mol / L. Ce 3+ In the sulfuric acid system, Ce is inhibited by increasing the acidity to above 4 mol / L. 4+ Hydrolysis occurs, but the concentrated acid environment exacerbates the corrosion of the sealing material; additionally, organic acids such as methanesulfonic acid and aminosulfonic acid are introduced to enhance the solubility of cerium and reduce the hydrogen evolution side reaction through their weak coordination, resulting in a 50 mA / cm² solution. 2 The energy efficiency remained above 80% after 110 cycles. To further improve reaction kinetics, some studies have attempted to add complexing agents such as sulfosalicylic acid and EDTA to reduce Ce by adjusting the coordination environment. 4+ / Ce 3+ The charge transfer impedance is at 100 mA / cm. 2 It can still maintain a voltage efficiency of over 90%.

[0004] However, existing positive electrode electrolytes still face several bottlenecks: First, Ce... 4+ Under low acidity, it is easily hydrolyzed to form CeO2·xH2O colloid, which gradually clogs the electrode channels and pipes as the electrolyte circulates, leading to a rapid increase in polarization resistance and insufficient cycle life. Secondly, tetravalent cerium ions have a certain oxidative decomposition effect on organic components, and the complexing additives are continuously consumed during long-term operation, changing the electrolyte composition and causing capacity decay. Furthermore, during long-term operation, titanium-cerium redox flow batteries will experience the continuous accumulation of tetravalent cerium ions in the positive electrode electrolyte due to side reactions and ion migration, which means that there are insufficient trivalent titanium ions in the negative electrode electrolyte. This imbalance of the valence states of active ions in the electrolyte reduces the battery capacity and cycle life.

[0005] Therefore, how to reduce side reactions during the operation of titanium-cerium flow batteries, delay the reduction in battery capacity and the shortening of battery life caused by the accumulation of tetravalent cerium ions, has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a positive electrode electrolyte and a titanium-cerium flow battery to improve the efficiency and cycle life of the titanium-cerium flow battery.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a positive electrode electrolyte, which is formed by mixing an initial electrolyte with a hydrogen peroxide solution; wherein the initial electrolyte is an acidic aqueous solution containing a supporting electrolyte and cerium ions.

[0008] This invention involves mixing a hydrogen peroxide solution into the initial electrolyte. Because hydrogen peroxide has excellent reducing properties under acidic conditions, it acts as a reducing agent, reacting with the tetravalent cerium ions generated at the positive electrode during charging to reduce them to trivalent cerium ions. This prevents the continuous accumulation of tetravalent cerium ions in the positive electrode electrolyte during long-term cycling, thereby improving the efficiency and cycle life of the titanium-cerium redox flow battery. Even after cycle decay to a certain extent, an appropriate amount of hydrogen peroxide solution can still be added to the positive electrode electrolyte to reduce excess tetravalent cerium ions, thus achieving the goal of improving capacity and long-term cycle stability.

[0009] In addition, the decomposition products of hydrogen peroxide are oxygen and water, and the reaction process does not introduce other impurities, so it has little impact on the chemical stability of the electrolyte. The water produced can also replenish the water consumed by the hydrogen evolution and oxygen evolution side reactions in the titanium-cerium flow battery, thereby reducing the change in water volume. Furthermore, hydrogen peroxide is inexpensive, widely available, green and pollution-free, making it suitable for industrial applications.

[0010] Preferably, the concentration of cerium ions in the positive electrode electrolyte is 0.1~2 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L or 2 mol / L, more preferably 0.2~1.5 mol / L, and the concentration of hydrogen ions is 0.5~8 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L or 8 mol / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0011] This invention limits the concentration of cerium ions in the positive electrode electrolyte within a reasonable range, balancing battery capacity and energy density. If the cerium ion concentration is too high, it is easy to precipitate due to exceeding the solubility of cerium ions, and it will also allow hydrogen peroxide to participate in the electrochemical reaction during the later charging process, causing a decrease in battery capacity; if the cerium ion concentration is too low, it will reduce the energy density.

[0012] Preferably, the amount of H2O2 in the hydrogen peroxide solution is 0.5 to 1.5 times m0, for example, it can be 0.5 times, 0.6 times, 0.7 times, 0.8 times, 0.9 times, 1.0 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times or 1.5 times, more preferably 1.0 to 1.2 times m0, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0013] Wherein, m0 is calculated by the following formula (1): In the above formula, m0 is the theoretical amount of H2O2 used, in grams; C v V represents the concentration of cerium ions in the initial electrolyte, in mol / L; V represents the volume of the initial electrolyte, in L; Q` represents the charge capacity of the titanium-cerium redox flow battery assembled using the initial electrolyte volume V` after the first charge-discharge cycle, in C; k is the ratio of V to V`, i.e., k = V / V`; M is the relative molecular mass of H2O2, with a value of 34.

[0014] This invention limits the amount of H2O2 in the hydrogen peroxide solution to within the range of 0.5 to 1.5 times m0, which is beneficial for further improving battery capacity. If the amount of H2O2 is too high, it will cause H2O2 to participate in the electrochemical reaction during the later charging process, resulting in a decrease in battery capacity; if the amount of H2O2 is too low, the excess tetravalent cerium ions cannot be completely consumed, resulting in insufficient improvement of battery capacity.

[0015] Preferably, the titanium-cerium redox flow battery assembled using the initial electrolyte includes at least the following components or parts: (a) Negative electrode electrolyte: an acidic aqueous solution containing supporting electrolytes and titanium ions; (b) Positive and / or negative electrode: carbon felt; (c) Ion exchange membrane: perfluorosulfonic acid membrane.

[0016] The supporting electrolyte includes at least one of methanesulfonic acid, sulfuric acid, or aminosulfonic acid, more preferably a combination of methanesulfonic acid and sulfuric acid, and the molar ratio of methanesulfonic acid to sulfuric acid is (0.1~10):1, for example, 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, preferably (1~5):1, but not limited to the listed values; other unlisted values ​​within this range are also applicable. More preferably, the concentrations of the supporting electrolyte in the negative electrode electrolyte and the positive electrode electrolyte are equal.

[0017] Preferably, the test conditions for the first charge-discharge cycle are: a charge-discharge current density of 50 mA / cm². 2 The charging and discharging voltage range is 0.8~1.8V.

[0018] In a second aspect, the present invention provides a method for preparing a positive electrode electrolyte as described in the first aspect, comprising at least the following steps: (1) Take a certain amount of initial electrolyte and negative electrode electrolyte to form a titanium-cerium flow battery, measure the charging capacity Q` of the battery in the first charge-discharge cycle, and calculate the amount of H2O2 in the hydrogen peroxide solution mentioned in step (2) according to the aforementioned formula; (2) Add a calculated proportion of hydrogen peroxide solution to the initial electrolyte to obtain the positive electrode electrolyte.

[0019] The positive electrode electrolyte preparation method provided by this invention is simple, requires no complex equipment or processes, has low production costs, and is safe and environmentally friendly.

[0020] Thirdly, the present invention provides a titanium-cerium flow battery, wherein the electrolyte system of the titanium-cerium flow battery is composed of a negative electrode electrolyte and a positive electrode electrolyte as described in the first aspect; wherein the negative electrode electrolyte is an acidic aqueous solution containing supporting electrolyte and titanium ions.

[0021] The titanium-cerium redox flow battery provided by this invention has both high charge and discharge capacity and long cycle life, improves electrolyte utilization, and has broad application prospects.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) In this invention, hydrogen peroxide solution is mixed into the initial electrolyte. Since hydrogen peroxide has good reducing properties under acidic conditions, it acts as a reducing agent to react with the excess tetravalent cerium ions accumulated in the positive electrode electrolyte during charging, reducing the tetravalent cerium ions to trivalent cerium ions. This avoids the continuous accumulation of tetravalent cerium ions in the positive electrode electrolyte during long-cycle processes, thereby improving the efficiency and cycle life of the titanium-cerium flow battery. When the cycle decay reaches a certain level, an appropriate amount of hydrogen peroxide solution can still be added to the positive electrode electrolyte to reduce the excess tetravalent cerium ions, thereby achieving the purpose of restoring capacity and long-cycle stability.

[0023] (2) The decomposition products of hydrogen peroxide are oxygen and water. The reaction process does not introduce other impurities and has little impact on the chemical stability of the electrolyte. The water produced can also replenish the water consumed by the hydrogen evolution and oxygen evolution side reactions in the titanium-cerium flow battery, thereby reducing the change in solution volume. Hydrogen peroxide is inexpensive, widely available, and environmentally friendly, making it suitable for industrial applications. Attached Figure Description

[0024] Figure 1 These are the capacity-voltage curves of the titanium-cerium redox flow batteries obtained in Application Example 1 and Comparative Application Example 1 after 30 cycles. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are merely simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be determined by the claims.

[0026] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0027] Example 1 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.5M Ce(CH3SO3)3+1M CH3SO3H+1M H2SO4, using deionized water as the solvent; (2) Using 0.02L of the initial electrolyte obtained in step (1), a titanium-cerium redox flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 871.2C. The theoretical amount of H2O2, m0, was calculated to be 0.033 g. In practice, 0.110 g of 40 wt% hydrogen peroxide solution was added to the initial 0.02 L electrolyte. That is, the amount of H2O2 in the hydrogen peroxide solution was 1.33 times m0. Finally, a positive electrode electrolyte with a cerium ion concentration of 0.5 mol / L and a hydrogen ion concentration of 2 mol / L was obtained.

[0028] In this embodiment, the assembly structure of the titanium-cerium flow battery in step (2) refers to CN118380619A, and includes the following components and parts: (a) Negative electrode electrolyte: 0.5M TiOSO4 + 1M CH3SO3H + 1M H2SO4; (b) Positive and negative electrodes: carbon felt; (c) Ion exchange membrane: perfluorosulfonic acid membrane.

[0029] Furthermore, the test conditions for the first charge-discharge cycle in step (2) are: a charge-discharge current density of 50 mA / cm². 2 The charge / discharge voltage range is 0.8~1.8V, and the electrolyte pump speed is 20mL / min.

[0030] Example 2 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.6M Ce(CH3SO3)3+2M CH3SO3H, using deionized water as the solvent; (2) Using 0.02L of the initial electrolyte obtained in step (1), a titanium-cerium redox flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 929.41C. The theoretical amount of H2O2, m0, was calculated to be 0.080 g. In practice, 0.220 g of 40 wt% hydrogen peroxide solution was added to the initial 0.02 L electrolyte. That is, the amount of H2O2 in the hydrogen peroxide solution was 1.10 times m0. Finally, a positive electrode electrolyte with a cerium ion concentration of 0.6 mol / L and a hydrogen ion concentration of 2 mol / L was obtained.

[0031] In this embodiment, the negative electrode electrolyte composition of the titanium-cerium flow battery in step (2) is 0.6M TiCl4+2MCH3SO3H. The rest of the assembly structure and the test conditions for the first charge-discharge cycle are the same as in Example 1, so they will not be described in detail here.

[0032] Example 3 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.5M Ce(CH3SO3)3+0.5M H2SO4, using deionized water as the solvent; (2) Using 0.02L of the initial electrolyte obtained in step (1), a titanium-cerium redox flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 828.68C. The theoretical amount of H2O2, m0, was calculated to be 0.048 g. In practice, a total of 0.160 g of 30 wt% hydrogen peroxide solution was added to the initial 0.02 L electrolyte. That is, the amount of H2O2 in the hydrogen peroxide solution was 1.0 times m0. Finally, a positive electrode electrolyte with a cerium ion concentration of 0.5 mol / L and a hydrogen ion concentration of 0.5 mol / L was obtained.

[0033] In this embodiment, the negative electrode electrolyte composition of the titanium-cerium flow battery in step (2) is 0.5M TiOSO4+0.5M H2SO4. The rest of the assembly structure and the test conditions for the first charge-discharge cycle are the same as in Example 1, so they will not be described in detail here.

[0034] Example 4 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.8M Ce(CH3SO3)3+1M CH3SO3H+0.5M H2SO4, using deionized water as the solvent; (2) Using the initial electrolyte obtained in step (1), a titanium-cerium redox flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 1279.51C. The theoretical amount of H2O2, m0, was calculated to be 0.093 g. In practice, 0.250 g of 40 wt% hydrogen peroxide solution was added to the initial 0.02 L electrolyte. That is, the amount of H2O2 in the hydrogen peroxide solution was 1.08 times m0. Finally, a positive electrode electrolyte with a cerium ion concentration of 0.8 mol / L and a hydrogen ion concentration of 1.5 mol / L was obtained.

[0035] In this embodiment, the negative electrode electrolyte composition of the titanium-cerium flow battery in step (2) is 0.8M TiCl4+1MCH3SO3H+0.5M H2SO4. The rest of the assembly structure and the test conditions for the first charge-discharge cycle are the same as in Example 1, so they will not be described in detail here.

[0036] Example 5 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.4M Ce(CH3SO3)3+0.1M Ce2(SO4)3+0.5M CH3SO3H+0.5M H2SO4, using deionized water as the solvent; (2) Using 0.02L of the initial electrolyte obtained in step (1), a titanium-cerium redox flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 893.77C. The theoretical amount of H2O2, m0, was calculated to be 0.093 g. In practice, 0.300 g of 40 wt% hydrogen peroxide solution was added to the initial 0.02 L electrolyte. That is, the amount of H2O2 in the hydrogen peroxide solution was 1.29 times m0. Finally, a positive electrode electrolyte with a cerium ion concentration of 0.6 mol / L and a hydrogen ion concentration of 1 mol / L was obtained.

[0037] In this embodiment, the negative electrode electrolyte composition of the titanium-cerium redox flow battery in step (2) is 0.3M TiOSO4+0.3M TiCl4+0.5M CH3SO3H+0.5M H2SO4. The rest of the assembly structure and the test conditions for the first charge-discharge cycle are the same as in Example 1, so they will not be described again here.

[0038] Example 6 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.2M Ce(CH3SO3)3+0.1M Ce2(SO4)3+1M NH2SO3H+1M H2SO4, using deionized water as the solvent; (2) Using the 0.02L initial electrolyte obtained in step (1), a titanium-cerium flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 613.08C. The theoretical amount of H2O2, m0, was calculated to be 0.056 g. In practice, 0.150 g of 40 wt% hydrogen peroxide solution was added to the initial 0.02 L electrolyte. That is, the amount of H2O2 in the hydrogen peroxide solution was 1.07 times m0. Finally, a positive electrode electrolyte with a cerium ion concentration of 0.4 mol / L and a hydrogen ion concentration of 2 mol / L was obtained.

[0039] In this embodiment, the negative electrode electrolyte composition of the titanium-cerium flow battery in step (2) is 0.2M TiOSO4+0.2M TiCl4+1M NH2SO3H+1M H2SO4. The rest of the assembly structure and the test conditions for the first charge-discharge cycle are the same as in Example 1, so they will not be described in detail here.

[0040] Example 7 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.5M Ce(CH3SO3)3+1M CH3SO3H+1M H2SO4, using deionized water as the solvent; (2) Using 0.02L of the initial electrolyte obtained in step (1), a titanium-cerium redox flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 860.74C. The theoretical amount of H2O2, m0, was calculated to be 0.037 g. In practice, after 25 cycles, 0.100 g of 40 wt% hydrogen peroxide solution was added to the initial 0.02 L electrolyte. That is, the amount of H2O2 in the hydrogen peroxide solution was 1.08 times m0. Finally, a positive electrode electrolyte with a cerium ion concentration of 0.5 mol / L and a hydrogen ion concentration of 2 mol / L was obtained.

[0041] In this embodiment, the negative electrode electrolyte composition of the titanium-cerium redox flow battery in step (2) is 0.5M TiOSO4+1M CH3SO3H+1M H2SO4. The rest of the assembly structure and the test conditions for the first charge-discharge cycle are the same as in Example 1, so they will not be described in detail here.

[0042] Example 8 This embodiment provides a positive electrode electrolyte and its preparation method, specifically including the following steps: (1) Prepare the initial electrolyte according to 0.5M Ce(CH3SO3)3+2M CH3SO3H, using deionized water as the solvent; (2) Using 0.02L of the initial electrolyte obtained in step (1), a titanium-cerium redox flow battery was assembled. The charge capacity Q` of the battery after the first charge-discharge cycle was measured to be 604.08C. The theoretical amount of H2O2 required, m0, was calculated to be 0.381 g, and 0.06 L of initial electrolyte was used for testing. In practice, after 25 cycles, 0.990 g of 40 wt% hydrogen peroxide solution was added to the 0.06 L initial electrolyte. This means the amount of H2O2 used in the hydrogen peroxide solution was 1.04 times m0, ultimately yielding a positive electrode electrolyte with a cerium ion concentration of 0.5 mol / L and a hydrogen ion concentration of 2 mol / L.

[0043] In this embodiment, the negative electrode electrolyte composition of the titanium-cerium redox flow battery in step (2) is 0.5M TiOSO4+2M CH3SO3H. The rest of the assembly structure and the test conditions for the first charge-discharge cycle are the same as in Example 1, so they will not be described in detail here.

[0044] Example 9 This embodiment provides a positive electrode electrolyte and its preparation method. Except that the actual mass of 40wt% hydrogen peroxide solution added to 0.02L initial electrolyte in step (2) is changed to 0.0165g, that is, the amount of H2O2 in the hydrogen peroxide solution is 0.20 times m0, the other steps and conditions are the same as in Example 1, so they will not be repeated here.

[0045] Comparative Example 1 This comparative example provides a positive electrode electrolyte and its preparation method. Except for step (2), which is to directly use the initial electrolyte without adding hydrogen peroxide solution as the final positive electrode electrolyte, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0046] Application Examples 1-9 This set of application examples provides a titanium-cerium flow battery, which is assembled using the positive electrode electrolyte obtained in Examples 1 to 9 respectively. The specific assembly structure is the same as the assembly structure of the titanium-cerium flow battery obtained in step (2) of the corresponding example, so it will not be described in detail here.

[0047] Comparative Application Example 1 The comparative application examples in this group provide a titanium-cerium flow battery respectively. The titanium-cerium flow battery is assembled using the positive electrode electrolyte obtained from Comparative Examples 1 to 2 respectively. The specific assembly structure is the same as the assembly structure of the titanium-cerium flow battery obtained in step (2) of the corresponding examples, so it will not be described in detail here.

[0048] Performance testing The titanium-cerium redox flow batteries obtained in Application Examples 1-9 and Comparative Application Example 1 were subjected to cycle performance tests. The specific test conditions were: charge / discharge current density of 50 mA / cm². 2 The charge / discharge voltage range is 0.8~1.8V, and the electrolyte pump speed is 20mL / min.

[0049] For example, the capacity-voltage curves of the titanium-cerium redox flow batteries obtained in Application Example 1 and Comparative Application Example 1 after 30 cycles are shown in the figure. Figure 1 It can be seen that, at the 30th cycle, the discharge capacity of the battery with added hydrogen peroxide is significantly higher than that of the battery without added hydrogen peroxide, indicating that adding hydrogen peroxide helps to improve the battery capacity of the titanium cerium redox flow battery during cycling.

[0050] Specifically, the first-cycle charging capacity of the titanium-cerium flow batteries obtained in Application Examples 1-6, Application Example 9, and Comparative Application Example 1, as well as the charging capacity of Application Examples 7-8 in the 26th cycle, are shown in Table 1 below.

[0051] Table 1 As shown in Table 1: (1) As can be seen from Application Examples 1-8, by adding hydrogen peroxide solution to the positive electrode electrolyte, hydrogen peroxide has good reducing properties under acidic conditions. During charging, hydrogen peroxide acts as a reducing agent to react with the excess tetravalent cerium ions accumulated in the positive electrode electrolyte, reducing the tetravalent cerium ions to trivalent cerium ions. This avoids the continuous accumulation of tetravalent cerium ions in the positive electrode electrolyte during long-cycle processes, thereby preventing a decrease in the battery's energy storage efficiency and cycle life. In addition, after the cycle decay reaches a certain level, an appropriate amount of hydrogen peroxide can still be added to the positive electrode electrolyte to reduce some of the excess tetravalent cerium ions, thereby achieving the purpose of restoring capacity and long-cycle stability.

[0052] (2) Combining Application Example 1 and Application Example 9, it can be seen that controlling the amount of H2O2 in the positive electrode electrolyte within the range of 0.5 to 1.5 times m0 is beneficial to further improve the battery capacity. If the amount of H2O2 is too low (see Application Example 9), the excess tetravalent cerium ions cannot be completely consumed, resulting in insufficient improvement of battery capacity. Combining Application Example 1 and Comparative Application Example 1, it can be seen that if hydrogen peroxide is not added, the battery capacity is not improved. It is evident that adding hydrogen peroxide solution to the initial electrolyte improves the battery capacity and long-cycle stability.

[0053] In summary, this invention involves mixing a hydrogen peroxide solution into the initial electrolyte. Because hydrogen peroxide has excellent reducing properties under acidic conditions, it acts as a reducing agent to react with excess tetravalent cerium ions accumulated in the positive electrode electrolyte during charging, reducing them to trivalent cerium ions. This prevents the continuous accumulation of tetravalent cerium ions in the positive electrode electrolyte during long-cycle operation, thereby improving the efficiency and cycle life of the titanium-cerium redox flow battery. Even after cycle degradation to a certain extent, an appropriate amount of hydrogen peroxide solution can still be added to the positive electrode electrolyte to reduce excess tetravalent cerium ions, thus restoring capacity and long-cycle stability.

[0054] Furthermore, the decomposition products of hydrogen peroxide are oxygen and water, and the reaction process does not introduce other impurities, thus having minimal impact on the chemical stability of the electrolyte. The water produced can also replenish the water consumed in the hydrogen and oxygen evolution side reactions of the titanium-cerium flow battery, reducing the change in solution volume. Hydrogen peroxide is inexpensive, widely available, and environmentally friendly, making it suitable for industrial applications.

[0055] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A positive electrode electrolyte, characterized in that, The positive electrode electrolyte is formed by mixing an initial electrolyte with a hydrogen peroxide solution; wherein the initial electrolyte is an acidic aqueous solution containing supporting electrolytes and cerium ions.

2. The positive electrode electrolyte according to claim 1, characterized in that, The concentration of cerium ions in the positive electrode electrolyte is 0.1~2 mol / L, and the concentration of hydrogen ions is 0.5~8 mol / L.

3. The positive electrode electrolyte according to claim 1 or 2, characterized in that, The amount of H2O2 used in the hydrogen peroxide solution is 0.5 to 1.5 times m0, preferably 1.0 to 1.2 times m0; Wherein, m0 is calculated by the following formula (1): In the above formula, m0 is the theoretical amount of H2O2 used, in grams; C v V represents the concentration of cerium ions in the initial electrolyte, in mol / L; V represents the volume of the initial electrolyte, in L; Q` represents the charge capacity of the titanium-cerium redox flow battery assembled using the initial electrolyte volume V` after the first charge-discharge cycle, in C; k is the ratio of V to V`, i.e., k = V / V`; M is the relative molecular mass of H2O2, with a value of 34.

4. The positive electrode electrolyte according to any one of claims 1 to 3, characterized in that, The supporting electrolyte includes at least one of methanesulfonic acid, sulfuric acid, or aminosulfonic acid.

5. The positive electrode electrolyte according to claim 4, characterized in that, The supporting electrolyte is a combination of methanesulfonic acid and sulfuric acid, and the molar concentration ratio of methanesulfonic acid to sulfuric acid is (0.1~10):1, preferably (1~5):

1.

6. A titanium-cerium redox flow battery, characterized in that, The electrolyte system of the titanium-cerium flow battery consists of a negative electrode electrolyte and a positive electrode electrolyte as described in any one of claims 1 to 5; wherein the negative electrode electrolyte is an acidic aqueous solution containing supporting electrolyte and titanium ions.

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