Water-soluble lead-acid static storage battery

Abstract

The present invention relates to a water-soluble lead-acid static storage battery. The present invention comprises a battery cell. The battery cell comprises electrode plates, a static electrolyte, and a container. The electrode plates are inserted in the electrolyte. The composition of the electrolyte comprises a water-soluble lead salt, an acid, and water, and further comprises a lead-dissolving agent, or a structure extends from a bottom end of a negative electrode plate to below a positive electrode plate. The lead-dissolving agent is capable of providing at least one water-soluble redox couple Rox / Rred, the electrode potential of the redox couple satisfying Eθ(Pb2+ / Pb)<Eθ(Rox / Rred)<Eθ(PbO2 / Pb2+). The present invention has no separator, and the electrolyte is in a static state, requiring no facilities such as a circulation pump, allowing lead ions to migrate under the action of a concentration gradient, while also greatly reducing self-discharge caused by convective shuttling of the lead-dissolving agent. During charging, lead and lead dioxide can be smoothly deposited on electrode surfaces, and can be completely dissolved during discharging, achieving good cycle stability and enabling components to remain stable over a prolonged period.

Description

A water-soluble lead-acid static storage battery Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and particularly relates to a water-soluble lead-acid static storage battery. Background Technology

[0002] Lead-acid batteries have been in use for over a century since their invention, and remain widely used due to their safety, economy, and reliability. However, the production and recycling processes of lead electrodes pose a problem of heavy metal pollution, and batteries typically have a cycle life of only a few hundred cycles. Pletcher et al. proposed a water-soluble lead-acid flow battery. This battery uses nickel sheets and carbon-plastic plates as electrodes, and lead methanesulfonate and methanesulfonic acid as active materials and supporting electrolytes. During charging, lead methanesulfonate is deposited as elemental lead and lead dioxide at the negative and positive electrodes, respectively, and is dissolved and regenerated during discharge. Compared to traditional lead-acid batteries, its production and recycling processes are simpler, produce less pollution, and have a higher lead utilization rate. Compared to conventional flow batteries, it does not require a separator and can adopt a single-flow structure, significantly reducing costs, thus showing great development potential. However, their disclosed water-soluble lead-acid flow battery suffers from problems such as oxygen evolution reaction at the positive electrode, pulverization and shedding of the positive electrode active material at the end of discharge, and incomplete dissolution of elemental lead at the negative electrode. After multiple cycles, the lead ion concentration in the electrolyte continuously decreases, leading to capacity decay.

[0003] Patent CN110190312B discloses an electrolyte for lead-acid flow batteries, using ferric nitrate, ferric hexafluorophosphate complex, or ferric chloride as catalysts to promote the redissolution of detached lead and lead dioxide into lead ions, thereby improving the cycle stability of the electrolyte. However, on the one hand, this solution does not mention whether a separator or other isolation device should be placed between the positive and negative electrodes. If there is no separator and the iron concentration in the electrolyte is sufficient to effectively dissolve solid lead (lead, lead dioxide), the iron / ferrous ions will shuttle back and forth between the positive and negative electrodes during the electrolyte flow, inevitably causing self-discharge and reducing current efficiency. If a separator is used, it will increase the cost of the flow battery and may also cause the problem of lead dendrites being difficult to dissolve after detachment. On the other hand, the electrolyte in this solution also contains fluoride ions, cobalt ions, nitrate ions, and chloride ions. The presence of impurity ions will have a negative impact on the charge and discharge process: fluoride ions easily generate free hydrofluoric acid molecules in strongly acidic solutions, and nitrate and chloride ions may participate in redox reactions and are detrimental to the electrodeposition of lead at the negative electrode. While this battery has solved the lead dioxide dissolution problem to some extent, it has caused problems such as self-discharge, and impurity ions can affect battery performance. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the present invention provides a water-soluble lead-acid static storage battery that can avoid the self-discharge problem caused by electrolyte flow.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, this application provides a water-soluble lead-acid static storage battery, comprising a battery cell, wherein the battery cell includes electrode plates, a static electrolyte, and a container for holding the electrolyte. The electrode plates are inserted into the electrolyte. The electrolyte comprises water-soluble lead salt, acid, a lead dissolving agent, and water. The lead dissolving agent provides at least one pair of water-soluble redox couples R. 氧化 With R 还原 The electrode potentials of the redox couple satisfy E θ (Pb 2+ / Pb) <E θ (R 氧化 / R 还原 ) <E θ (PbO2 / Pb 2+ ).

[0007] Secondly, this application provides a water-soluble lead-acid static storage battery, comprising a single battery cell. The single battery cell includes electrode plates, a static electrolyte, and a container holding the electrolyte. The electrode plates are inserted into the electrolyte. The electrolyte comprises water-soluble lead salts, acid, and water.

[0008] The battery is a stack of battery cells or at least two sets of battery cells connected in series; when the battery is a stack of battery cells connected in series, the electrolyte phases between different battery cells are isolated.

[0009] In a single battery cell, the electrode plates include a positive electrode plate and a negative electrode plate. The bottom end of the negative electrode plate extends below the positive electrode plate and / or the bottom end of the negative electrode plate is connected to the bottom end of the positive electrode plate through an isolation guide plate. The isolation guide plate is used to guide the active material that falls off the positive electrode plate to the negative electrode plate of the same battery cell under the action of gravity.

[0010] Optionally, the battery is a stack of battery cells or at least two sets of battery cells connected in series; when the battery is a stack of battery cells connected in series, the electrolyte phases between different battery cells are isolated.

[0011] Optionally, when the battery is a stack composed of battery cells connected in series, the electrode plates on both sides are used as the positive and negative electrodes respectively, and the electrode plate between the positive and negative electrodes is a bipolar plate, which is used to isolate the electrolyte phase between different battery cells.

[0012] Optionally, in a single battery cell, the electrode plates include a positive electrode plate and a negative electrode plate. The bottom end of the negative electrode plate extends below the positive electrode plate and / or the bottom end of the negative electrode plate is connected to the bottom end of the positive electrode plate via a separating guide plate. The separating guide plate is used to guide the active material detached from the positive electrode plate to the negative electrode plate of the same battery cell under the action of gravity. This design is also applicable to battery stacks obtained by connecting battery cells in series, where the electrode plate with the lower potential between adjacent plates in the stack is used as the negative electrode plate, and the electrode plate with the higher potential is used as the positive electrode plate.

[0013] The advantage of extending the bottom of the negative electrode plate to below the positive electrode plate and / or connecting the bottom of the negative electrode plate to the bottom of the positive electrode plate through an isolation guide plate is that the lead dioxide that falls off during the positive electrode discharge process can reach the negative electrode by gravity sedimentation, which is conducive to the reaction of active substances falling off the electrode into the electrolyte, eliminating the need for stirring or oscillation, simplifying the operation steps and the required additional equipment.

[0014] Optionally, when the battery is a stack composed of battery cells connected in series, the positive plate isolates the electrolyte between different battery cells, or the isolation guide plate and the positive plate work together to isolate the electrolyte between different battery cells.

[0015] Optionally, the isolation guide plate has an angle of ≥45° with the horizontal direction.

[0016] Optionally, the shortest distance between the positive and negative plates is 0.1-20 cm.

[0017] Optionally, the negative electrode can be used as a container for holding the electrolyte, and the positive electrode can be immersed in the electrolyte in the container.

[0018] Optionally, the electrolyte is in contact with air.

[0019] Optionally, the lead dissolving agent includes one or more of water-soluble iron salts, ferrous salts, vanadium(V) salts, vanadium(IV) salts, and vanadium(III) salts.

[0020] In the lead-acid static storage battery of this application, water-soluble lead salts participate in the main battery reaction, and acid acts as a supporting electrolyte and conductive agent. The reaction formula is as follows:

[0021] positive electrode:

[0022] negative electrode:

[0023] Equations (1) and (2) represent charging to the right and discharging to the left;

[0024] Because a small amount of lead dioxide will detach from the electrode during positive electrode discharge and cannot be dissolved, the lead dissolving agent can catalyze the discharge process. The reaction formula is as follows:

[0025] Dissolving lead dioxide: 2Fe 2++PbO2+4H + →2Fe 3+ +Pb 2+ +2H2O (3) 2V 3+ +PbO2→2VO 2+ +Pb 2+ (5)

[0026] Dissolving elemental lead: 2Fe 3+ +Pb→2Fe 2+ +Pb 2+ (6) 2VO 2+ +Pb+4H + →2V 3+ +Pb 2+ +2H2O (8)

[0027] Because an oxygen evolution side reaction also occurs at the positive electrode during charging and discharging: 2H₂O → O₂ + 4H₂O + +4e - (9)

[0028] This reaction results in incomplete dissolution of lead. When the electrolyte is connected to the outside air or the air sealed inside the battery, the lead-dissolving agent reacts with oxygen in the air to generate a lead-dissolving agent in a higher oxidation state, as shown in the following reaction: 4Fe 2+ +O2+4H + →4Fe 3+ +2H2O (10) 4V 3+ +O2 + 2H2O → 4VO 2+ +4H + (11)

[0029] The high-valence lead dissolving agent produced participates in the reaction of dissolving elemental lead in the above formulas (6)-(8), which can accelerate the oxygen absorption and dissolution of residual elemental lead at the negative electrode.

[0030] In this application, no external force is required to be applied to the electrolyte. The electrolyte remains static and is exposed to an oxygen-containing environment. Lead ions migrate mainly due to the concentration gradient between the electrode and the electrolyte, while the lead dissolving agent diffuses slowly due to the static state of the electrolyte and the absence of a concentration gradient, reducing self-discharge. The residual lead at the negative electrode promotes Fe2+ diffusion through the participation of oxygen. 3+ The product can also react completely and dissolve.

[0031] Optionally, the lead dissolving agent is one or more of methanesulfonate and fluoroborate.

[0032] Optionally, the electrode plate is one or more of conductive plastic, graphite, graphite felt, copper, nickel, and stainless steel.

[0033] Optionally, the water-soluble lead salt is one or more of lead methanesulfonate and lead fluoroborate; the acid is one or more of methanesulfonic acid and fluoroborate.

[0034] Optionally, the electrolyte comprises the following components at the following concentrations: in mol / L, lead ions 0.05-3, hydrogen ions 0.001-8, iron ions 0-0.2, vanadium ions 0-0.2, methanesulfonate ions 0-8, and fluoroborate ions 0-8, wherein the concentrations of methanesulfonate and fluoroborate ions are 0 when they are different, and the concentrations of iron and vanadium ions are 0 when they are different.

[0035] Optionally, the electrolyte comprises the following components at the following concentrations: in mol / L, lead ions 1.5-2, hydrogen ions 0.5-1, iron ions 0-0.2, vanadium ions 0-0.2, methanesulfonate ions 0-4, and fluoroborate ions 0-4, wherein the concentrations of methanesulfonate and fluoroborate ions are 0 when they are different, and the concentrations of iron and vanadium ions are 0 when they are different.

[0036] Optionally, it also includes a lead dendrite inhibitor, wherein the lead dendrite inhibitor is one or more of methyl sulfate salt, methanesulfonate, and fluoroborate of alkyl trimethylammonium, wherein the alkyl group is a straight chain with 12-22 carbon atoms.

[0037] Lead dendrites are easily generated at the negative electrode during charging, especially in the methanesulfonic acid system. The rapid growth of dendrites can easily lead to contact with the positive electrode and cause a short circuit. They are also prone to falling off during discharge, so dendrite inhibitors are needed. Commonly used additives in lead electroplating, such as emulsifier OP-10, can effectively inhibit dendrite growth, but they are easily oxidized and decomposed by lead dioxide at the positive electrode. Alkyltrimethylammonium salts have good chemical stability, can withstand the strong oxidizing properties of lead dioxide in a strongly acidic environment without decomposition, and can also inhibit the growth of lead dendrites.

[0038] Optionally, the lead dendrite inhibitor is a methyl sulfate salt of alkyltrimethylammonium.

[0039] Optionally, the concentration of lead dendrite inhibitor in the electrolyte is 0-0.1 mol / L.

[0040] Optionally, the concentration of lead dendrite inhibitor in the electrolyte is 0-0.02 mol / L.

[0041] Compared with the prior art, this application has at least the following beneficial effects:

[0042] This invention eliminates the need for a diaphragm and maintains a static electrolyte, eliminating the need for circulation pumps and other facilities. This allows lead ions to migrate under the influence of a concentration gradient, while significantly reducing self-discharge caused by the convective shuttle of the lead solvent (oxidized / reduced state). During charging, lead and lead dioxide can be smoothly deposited on the electrode surface, and they can be completely dissolved during discharge. The invention exhibits good cycle stability, maintains long-term component stability, and is cost-effective. Furthermore, the electrolyte does not contain harmful impurity ions.

[0043] The innovative design of this invention features a static lead-acid battery stack with electrolyte phase isolation between different battery cells. This avoids short circuits caused by some current moving along the electrolyte between the plates during charging and self-discharge caused by the potential difference of the active materials in the electrolyte connected on both sides of the bipolar plates after charging stops.

[0044] In this invention, the bottom end of the negative electrode plate is lower than the bottom end of the positive electrode plate, the bottom end of the negative electrode plate extends to the bottom of the positive electrode plate and / or the bottom end of the negative electrode plate is connected to the bottom end of the positive electrode plate through an isolation guide plate; the active material that falls off the positive electrode plate can directly settle under gravity or settle along the isolation guide plate to the surface of the negative electrode plate and be reduced; the electrolyte can be used for a long time under completely static conditions and maintain stable composition, and the battery efficiency is high. Attached Figure Description

[0045] Figure 1 is a schematic diagram of a conventional series-connected flow battery stack structure in the prior art;

[0046] Figure 2 shows the static battery structure with parallel electrode plates in this invention, where a is a single battery cell and b is a battery stack.

[0047] Figure 3 is a structural diagram of the improved electrode plate arrangement of the present invention, wherein a and b are individual battery cells, and c is a battery stack;

[0048] Figure 4 shows the charge-discharge curves of Embodiment 4 of the present invention;

[0049] Figure 5 shows the charge-discharge curves of Embodiment 5 of the present invention;

[0050] Figure 6 is the charge-discharge curve of Embodiment 6 of the present invention;

[0051] Figure 7 is a battery state diagram (a) and charge / discharge curve (b) after charging and discharging of the battery in Embodiment 7 of the present invention;

[0052] 1. Isolation guide plate. Detailed Implementation

[0053] The present invention will now be described in further detail with reference to the accompanying drawings:

[0054] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0055] All reagents and materials used in this example can be purchased routinely.

[0056] In this invention, the electrode plates of the battery cell or the battery stack can be arranged in parallel, as shown in Figure 2.

[0057] To facilitate the settling of the active material detached from the positive electrode plate to the negative electrode plate under gravity, the electrode plates in the battery cell can be configured such that the bottom end of the negative electrode plate extends below the positive electrode plate (as shown in Figure 3a), or the negative electrode is used as a container for holding the electrolyte, with the positive electrode immersed in the electrolyte in the container (as shown in Figure 3b), or the negative electrode plate extends towards the positive electrode plate and the bottom end of the negative electrode plate is connected to the bottom end of the positive electrode plate through an isolation guide plate 1 (as shown in Figure 3c). The side of the isolation guide plate 1 connected to the positive electrode plate is higher than the side connected to the negative electrode plate, thereby allowing the lead dioxide detached from the positive electrode plate to settle to the negative electrode plate under gravity.

[0058] In Examples 1-5 and Comparative Example 1, the width of the single-sided conductive plastic plate (the other side is insulated with tape) is 1 cm.

[0059] Comparative Example 1

[0060] The quartz beaker contains 40 mL of water-soluble lead-acid electrolyte, which contains 1.5 mol / L lead fluoroborate, 1 mol / L fluoroboric acid, and 0.01 mol / L ferrous methanesulfonate. Both the positive and negative electrodes are single-sided conductive plastic plates, inserted parallel to each other into the electrolyte to a depth of 1 cm (i.e., an effective area of ​​1 cm²). 2 The spacing is 2.5cm, and the structure is shown in Figure 2a. It is stirred with a magnetic stirrer at a speed of 300rpm; constant current charging and discharging at 20mA, upper voltage limit of 2.5V, lower voltage limit of 0V, charging time of 4h, 3 cycles, and a total time of 21.983h, with an average current efficiency of only 83.2%.

[0061] Continue adding ferrous methanesulfonate to 0.05 mol / L while stirring; perform constant current charge-discharge at 20 mA, with an upper voltage limit of 2.5 V and a lower voltage limit of 0 V, cycling for one cycle in 5.642 h, with a current efficiency of only 41.1%. This indicates that the current efficiency decreases significantly with increasing iron concentration.

[0062] Example 1

[0063] The quartz beaker contains 40 mL of water-soluble lead-acid electrolyte, which contains 1.5 mol / L lead fluoroborate, 1 mol / L fluoroboric acid, and 0.01 mol / L ferrous methanesulfonate. Both the positive and negative electrodes are single-sided conductive plastic plates, inserted 1 cm into the electrolyte (i.e., an effective area of ​​1 cm²). 2 The spacing is 2.5 cm, and the structure is shown in Figure 2a. The solution is kept still. The constant current is 20 mA for charging and discharging, the upper limit of voltage is 2.5 V, the lower limit is 0 V, the charging time is 4 h, the cycle is 5 times, the total time is 38.733 h, and the average current efficiency is 93.7%.

[0064] Compared to Comparative Example 1, Example 1 exhibits higher current efficiency, indicating that keeping the solution static during the charging and discharging process effectively prevents self-discharge caused by the convection and diffusion of the lead dissolving agent. After charging and discharging, a small amount of solid lead dioxide remained at the bottom of the positive electrode. After stirring with a magnetic stirrer at 300 rpm for 8 hours, the lead and lead dioxide on the electrode completely dissolved, and no solid lead residue remained at the bottom of the container, demonstrating that the water-soluble lead-acid static battery can maintain good stability.

[0065] Continue adding ferrous methanesulfonate to 0.05 mol / L, and keep the electrolyte still after stirring. Charge and discharge at a constant current of 20 mA, with an upper voltage limit of 2.5 V and a lower voltage limit of 0 V. Charge for 4 hours, cycle 5 times, and take 36.455 hours. The current efficiency is 82.3%, which is lower than the current density when the iron content is 0.01 mol / L, indicating that increasing the lead solvent content will accelerate self-discharge. However, it is significantly higher than that of Comparative Example 1, indicating that in the absence of a separator and with electrolyte flow, ferric ions / ferrous ions shuttle back and forth between the positive and negative electrodes, resulting in severe self-discharge. Therefore, traditional separatorless water-soluble lead-acid flow batteries are not suitable for electrolytes containing lead solvents.

[0066] After the charge and discharge were completed, there was a small amount of lead dioxide at the bottom of the positive electrode. The lead dioxide at the bottom of the container was completely dissolved after stirring with a magnetic stirrer at 300 rpm for 10 minutes. After stirring for another 8 hours, most of the lead dissolved. This shows that increasing the content of lead dissolving agent will accelerate the dissolution of lead dioxide, but has no significant effect on the oxygen absorption dissolution of lead.

[0067] Example 2

[0068] The quartz beaker contains 40 mL of water-soluble lead-acid electrolyte, which contains 1.5 mol / L lead fluoroborate, 1 mol / L fluoroboric acid, and 0.05 mol / L ferrous methanesulfonate. The positive electrode is a single-sided conductive plastic plate, inserted 1 cm into the electrolyte (i.e., an effective area of ​​1 cm²). 2The negative electrode is a nickel sheet, held by an L-shaped electrode clamp. The negative electrode is set horizontally and located about 1 cm directly below the positive electrode, as shown in Figure 3a (the vertical direction is the insulating part of the electrode clamp). The solution is kept still. The constant current charge and discharge is 20mA, with an upper voltage limit of 2.5V and a lower voltage limit of 0V. The charging time is 4 hours, and the cycle is repeated 5 times, taking 35.701 hours in total. The current efficiency is 78.5%.

[0069] After charging and discharging, no lead dioxide residue was found on the surface of the negative electrode below the positive electrode, indicating that the lead dioxide was quickly dissolved upon settling onto the surface of the negative electrode. After being left to stand in an open container for 24 hours, most of the lead on the surface of the negative electrode dissolved by absorbing oxygen, indicating that a static battery, especially one with a structure where the negative electrode extends below the positive electrode, can allow the electrolyte to remain stable for a long time under completely static conditions.

[0070] Example 3

[0071] The quartz beaker contains 40 mL of water-soluble lead-acid electrolyte, which contains 1.5 mol / L lead methanesulfonate, 1 mol / L methanesulfonic acid, 0.05 mol / L ferrous methanesulfonate, and 0.01 mol / L ammonium hexadecyltrimethylammonium sulfate. The positive electrode is a single-sided conductive plastic plate, inserted 1 cm deep into the electrolyte (i.e., an effective area of ​​1 cm²). 2 The negative electrode is a nickel sheet, held by an L-shaped electrode clamp. The negative electrode is set horizontally and located about 1 cm directly below the positive electrode, as shown in Figure 3a (the vertical direction is the insulating part of the electrode clamp). The solution is kept still. The constant current charge and discharge is 20 mA, with an upper voltage limit of 2.5 V and a lower voltage limit of 0 V. The charging time is 4 h, and the cycle is 5 times, taking 35.412 h in total. The current efficiency is 77.1%. No obvious dendrite growth or shedding was observed at the electrode edge (high current density area).

[0072] Example 4

[0073] A nickel-plated container holds 15 mL of water-soluble lead-acid electrolyte containing 1.5 mol / L lead fluoroborate, 1 mol / L fluoroboric acid, and 0.02 mol / L ferrous fluoroborate. The positive electrode is a single-sided conductive plastic plate, inserted 1 cm into the electrolyte (i.e., an effective area of ​​1 cm²). 2 The structure is shown in Figure 3b. The solution is kept still. The constant current is 20mA for charging and discharging, the upper limit of voltage is 2.5V and the lower limit is 0V. The charging time is 4h, the cycle is 5 times, the total time is 37.844h, the current efficiency is 89.2%, and the charge and discharge curve is shown in Figure 4.

[0074] During the test, there was no lead dioxide solid at the bottom of the container, and the charging and discharging voltage tended to stabilize from the 5th cycle onwards; the container was in an open state, and there was almost no lead residue.

[0075] Example 5

[0076] A nickel-plated container holds 15 mL of water-soluble lead-acid electrolyte containing 1.5 mol / L lead fluoroborate, 1 mol / L fluoroboric acid, and 0.01 mol / L VO(BF4)2. The positive electrode is a single-sided conductive plastic plate, inserted 1 cm into the electrolyte (i.e., an effective area of ​​1 cm²). 2 The structure is shown in Figure 3b. The solution is kept still. The constant current charge and discharge is 20mA, the upper limit of voltage is 2.5V, the lower limit is 1V, the charging time is 2h, the cycle is 5 times, the current efficiency is 91.6%, and the charge and discharge curve is shown in Figure 5.

[0077] During the test, no lead dioxide solids were found at the bottom of the container.

[0078] Example 6

[0079] The plastic box is divided into compartments by three 5cm × 10cm conductive plastic bipolar plates (the electrolyte in different compartments cannot flow to each other). The conductive plastic bipolar plates are placed parallel to each other, with a 2cm gap between adjacent plates, resulting in a static battery stack consisting of two cells connected in series. 50mL of electrolyte is poured into each cell compartment, containing 1.5mol / L lead fluoroborate, 1mol / L fluoroboric acid, and 0.01mol / L ferrous fluoroborate. The effective area of ​​each bipolar plate is approximately 14cm². 2 The electrolyte in the compartment was kept still, and the electrodes at both ends and the bipolar plate in the middle were arranged in parallel. The constant current of 200mA was used for charging for 3.1 hours, with a voltage limit of 5V. Then it was discharged to 2V. One cycle took 5.817 hours, and the current efficiency was 87.6%. The test results are shown in Figure 6.

[0080] Example 7

[0081] 50 mL of water-soluble lead-acid electrolyte is placed in a quartz cup. The electrolyte contains 1.5 mol / L lead fluoroborate and 1 mol / L fluoroborate. A 4.5 cm wide copper strip is folded into an L-shape, and the horizontal portion is trimmed so that it fits into the quartz cup and adheres to the bottom. The upper vertical portion of the L-shaped copper strip is clamped, serving as the negative electrode. A 2 cm × 2 cm conductive plastic plate is taken, and one side is covered with insulating tape. The single-sided conductive plastic plate is clamped with an L-shaped electrode clamp (the clamping area is 0.25 cm²). 2 The conductive side of the plastic plate is horizontal and facing down. It is immersed in the electrolyte and positioned 0.8 cm above the horizontal part of the copper strip as the positive electrode of the battery. The horizontal position of the conductive plastic plate is adjusted by rotating the electrode clamp so that its horizontal projection completely falls into the horizontal part of the copper strip, ensuring that all lead dioxide in the subsequent discharge process settles to the surface of the negative electrode. The assembled structure is shown in Figure 3a.

[0082] To simulate high-rate charging scenarios in real-world applications (e.g., during peak photovoltaic power generation periods, the battery needs sufficient charging power to store as much energy as possible), the battery charging current in this embodiment is 320mA (i.e., positive electrode current density of 80mA / cm²). 2 ), duration 4 hours (i.e., positive electrode surface capacity 320mAh / cm²) 2 The upper limit of voltage is 2.5V, the discharge current is 80mA, the maximum duration is 16h, the lower limit of voltage is 0V, and the cycle is 3 times.

[0083] During charging, no obvious lead dendrites appeared on the negative electrode. During discharging, a small amount of lead dioxide detached from the positive electrode and settled on the surface of the negative electrode, but it was reduced in subsequent discharge or charging processes. After the next charging cycle, no solid lead dioxide remained on the surface of the negative electrode, as shown in Figure 7a. The charge-discharge curves are shown in Figure 7b. It can be seen from the figure that even when charging at a high current density, the voltage remains at a low level, with an average charging voltage of 2.180V over 3 cycles. The discharge voltage is relatively high, with an average discharge voltage of 1.580V over 3 cycles, resulting in a voltage efficiency of 72.5%. The average current efficiency over 3 cycles is 92.1%, and the energy efficiency is 66.8%.

[0084] Examples 2-5 and 7 fully demonstrate that, regardless of whether the electrolyte contains a lead-dissolving agent, battery structures with the bottom of the negative electrode plate extending to the bottom of the positive electrode plate and / or the bottom of the negative electrode plate being connected to the bottom of the positive electrode plate via an isolation guide plate can allow the active material detached from the positive electrode to re-participate in the charge-discharge cycle, thus maintaining the stability of the electrolyte composition. Furthermore, there is no significant growth of lead dendrites on the negative electrode. This indicates that batteries with this structural feature have good lead-dissolving effect, require no stirring facilities, simplify auxiliary equipment, and reduce self-discharge.

[0085] In Examples 1 and 6, the battery structures do not have a negative electrode extending below the positive electrode. In batteries containing the lead-dissolving agent of this application, the active material detached from the positive electrode directly settles at the bottom of the container after discharge. Stirring after discharge also dissolves the lead oxide. Experiments showed that when the lead-dissolving agent in Example 1 is 0%, even stirring cannot completely dissolve the lead oxide. The active material detached from the positive electrode cannot participate in charge-discharge cycles, leading to battery capacity decay.

[0086] In terms of battery structure, traditional flow battery stacks typically employ a series assembly of individual cells. This method is simple and convenient, fully utilizing the bipolar plates and having low requirements for bipolar plate conductivity. However, in traditional series-connected stacks, the electrolyte is interconnected between the individual cells. The inventors discovered that conventional stack designs have serious technical defects for water-soluble lead-acid flow batteries. To illustrate this problem more clearly, Figure 1 shows the structure of a traditional series-connected stack (two cells connected in series), including stacks with and without separators. During charging, most of the current starts from the left end plate, passes through the middle bipolar plate, and reaches the right end plate (i.e., effective current I1). A considerable portion of the current also starts from the left end plate, flows along the electrolyte pipeline to the right end plate (i.e., I2), causing a short circuit. After charging stops, a potential difference exists between the active materials on both sides of the middle bipolar plate, and the electrolytes on both sides are connected through the pipeline, forming a closed loop (I3), causing self-discharge. For all-liquid flow batteries, such as vanadium redox flow batteries and iron-chromium flow batteries, the impact of currents I2 and I3 is limited (usually only reducing current efficiency and energy efficiency) because there is no active material deposition and the amount of active material stored in the stack is small, making it difficult to detect. However, for water-soluble lead-acid flow batteries, all the positive and negative electrode active materials are deposited on the bipolar plates. Short circuits during charging cause differences in the areal capacity of different bipolar plates. After charging stops, all bipolar plates except the left and right end plates experience severe self-discharge, resulting in a significant decrease in areal capacity and energy loss. Although this problem can be solved by equipping each battery cell with an independent flow pump, this would significantly increase the size and complexity of the stack, and substantially increase the cost. In addition, facilities such as electrolyte pipelines and storage tanks greatly increase the complexity of the energy storage system, reducing the energy density of flow batteries, increasing costs, and compromising portability. Therefore, this application isolates the electrolyte phase between different battery cells, avoiding short circuits caused by some current moving along the electrolyte between the plates during charging and self-discharge caused by the potential difference of the active materials between the connected electrolytes on both sides of the bipolar plates after charging stops.

[0087] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and optimizations can be made based on the content of this specification. The embodiments selected and specifically described in this specification are intended to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and apply the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A water-soluble lead-acid static storage battery, characterized in that, The battery includes a single cell, which comprises electrode plates, a static electrolyte, and a container for holding the electrolyte. The electrode plates are inserted into the electrolyte. The electrolyte comprises water-soluble lead salt, acid, lead dissolving agent, and water. The lead dissolving agent provides at least one pair of water-soluble redox couples R. 氧化 With R 还原 The electrode potentials of the redox couple satisfy E θ (Pb 2+ / Pb) <E θ (R 氧化 / R 还原 ) <E θ (PbO2 / Pb 2+ ).

2. A water-soluble lead-acid static storage battery, characterized in that, The battery includes a single battery cell, which comprises electrode plates, a static electrolyte solution, and a container for holding the electrolyte solution. The electrode plates are inserted into the electrolyte solution, which comprises water-soluble lead salts, acid, and water. The battery is a stack of battery cells or at least two sets of battery cells connected in series; when the battery is a stack of battery cells connected in series, the electrolyte phases between different battery cells are isolated. In a single battery cell, the electrode plates include a positive electrode plate and a negative electrode plate. The bottom end of the negative electrode plate extends below the positive electrode plate and / or the bottom end of the negative electrode plate is connected to the bottom end of the positive electrode plate through an isolation guide plate. The isolation guide plate is used to guide the active material that falls off the positive electrode plate to the negative electrode plate of the same battery cell under the action of gravity.

3. The water-soluble lead-acid static storage battery according to claim 1, characterized in that, The battery is a stack of battery cells or at least two sets of battery cells connected in series; when the battery is a stack of battery cells connected in series, the electrolyte phases between different battery cells are isolated.

4. The water-soluble lead-acid static storage battery according to claim 2 or 3, characterized in that, When the battery is a stack composed of battery cells connected in series, the electrode plates on both sides are used as the positive and negative electrodes respectively, and the electrode plate between the positive and negative electrodes is a bipolar plate, which is used to isolate the electrolyte phase between different battery cells.

5. The water-soluble lead-acid static storage battery according to claim 3, characterized in that, In a single battery cell, the electrode plates include a positive electrode plate and a negative electrode plate. The bottom end of the negative electrode plate extends below the positive electrode plate and / or the bottom end of the negative electrode plate is connected to the bottom end of the positive electrode plate through an isolation guide plate. The isolation guide plate is used to guide the active material that falls off the positive electrode plate to the negative electrode plate of the same battery cell under the action of gravity.

6. The water-soluble lead-acid static storage battery according to claim 2 or 5, characterized in that, The negative electrode is used as a container to hold the electrolyte, while the positive electrode is immersed in the electrolyte in the container.

7. The water-soluble lead-acid static storage battery according to claim 1 or 2, characterized in that, The electrolyte is in contact with air.

8. The water-soluble lead-acid static storage battery according to claim 1, characterized in that, The lead dissolving agent includes one or more of water-soluble ferrous salts, ferrous salts, vanadium(V) salts, vanadium(IV) salts, and vanadium(III) salts.

9. The water-soluble lead-acid static storage battery according to claim 1, characterized in that, The lead dissolving agent is one or more of methanesulfonate and fluoroborate.

10. The water-soluble lead-acid static storage battery according to claim 1 or 2, characterized in that, The electrolyte comprises the following components at the following concentrations: the water-soluble lead salt is one or more of lead methanesulfonate and lead fluoroborate; the acid is one or more of methanesulfonic acid and fluoroborate.

11. The water-soluble lead-acid static storage battery according to claim 1, characterized in that, The electrolyte comprises the following components at the following concentrations (mol / L): lead ions 0.05-3, hydrogen ions 0.001-8, iron ions 0-0.2, vanadium ions 0-0.2, methanesulfonate ions 0-8, and fluoroborate ions 0-8. The concentrations of methanesulfonate and fluoroborate ions are both 0 when they differ, and the concentrations of iron and vanadium ions are both 0 when they differ.

12. The water-soluble lead-acid static storage battery according to claim 1, characterized in that, It also includes lead dendrite inhibitors, wherein the lead dendrite inhibitors are one or more of methyl sulfate salts, methanesulfonates, and fluoroborates of alkyl trimethylammonium, wherein the alkyl group is a straight chain with 12-22 carbon atoms.

Images