A water-soluble lead-acid static storage battery

Abstract

This invention relates to a water-soluble lead-acid static storage battery. The invention includes a battery cell, which comprises electrode plates, a static electrolyte, and a container. The electrode plates are inserted into the electrolyte. The electrolyte composition includes water-soluble lead salts, acid, and water. It also includes a lead-dissolving agent or a structure extending the bottom of the negative electrode plate below the positive electrode plate. 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+ 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 effect of the lead dissolving agent. 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, and the composition remains stable over a long period.

Description

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 installed 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: (1)

[0022] negative electrode: (2)

[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:

[0026] (3)

[0027] (4)

[0028] (5)

[0029] Dissolving elemental lead:

[0030] (6)

[0031] (7)

[0032] (8)

[0033] Because oxygen evolution side reaction also occurs at the positive electrode during charging and discharging:

[0034] (9)

[0035] This reaction results in incomplete dissolution of lead. However, 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 equation:

[0036] (10)

[0037] (11)

[0038] (12)

[0039] 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.

[0040] 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.

[0041] Optionally, the lead dissolving agent is one or more of methanesulfonate and fluoroborate.

[0042] Optionally, the electrode plate is one or more of conductive plastic, graphite, graphite felt, copper, nickel, and stainless steel.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Optionally, the lead dendrite inhibitor is a methyl sulfate salt of alkyltrimethylammonium.

[0049] Optionally, the concentration of lead dendrite inhibitor in the electrolyte is 0-0.1 mol / L.

[0050] Optionally, the concentration of lead dendrite inhibitor in the electrolyte is 0-0.02 mol / L.

[0051] Compared with the prior art, this application has at least the following beneficial effects:

[0052] 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. It exhibits good cycle stability, maintains long-term component stability, and is cost-effective. Furthermore, the electrolyte does not contain harmful impurity ions.

[0053] 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.

[0054] 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

[0055] Figure 1 This is a schematic diagram of a traditional series-connected flow battery stack structure in existing technology;

[0056] Figure 2 This is a static storage battery structure in which electrode plates are arranged in parallel, wherein a is a single battery cell and b is a battery stack;

[0057] Figure 3 This 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;

[0058] Figure 4 This is the charge-discharge curve of Embodiment 4 of the present invention;

[0059] Figure 5 This is the charge-discharge curve of Embodiment 5 of the present invention;

[0060] Figure 6 This is the charge-discharge curve of Embodiment 6 of the present invention;

[0061] Figure 7 These are the battery state diagram (a) and charge / discharge curve (b) after charging and discharging of the battery in Embodiment 7 of the present invention.

[0062] 1. Isolation guide plate. Detailed Implementation

[0063] The present invention will now be described in further detail with reference to the accompanying drawings:

[0064] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0065] All reagents and materials used in this example can be purchased routinely.

[0066] In this invention, the electrode plates of the battery cell or the battery stack can be arranged in parallel, such as... Figure 2 As shown.

[0067] 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 of the negative electrode plate extends below the positive electrode plate (e.g., ...). Figure 3 a) Alternatively, the negative electrode can be used as a container to hold the electrolyte, with the positive electrode immersed in the electrolyte within the container (e.g., ...). Figure 3 b) 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 the isolation guide plate 1 (e.g.) Figure 3 c) 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, so that the lead dioxide that falls off the positive electrode plate can sink to the negative electrode plate under the action of gravity.

[0068] 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.

[0069] Comparative Example 1

[0070] A 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 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 ), spacing 2.5 cm, structure as follows Figure 2 As shown in Figure a, the mixture was stirred at 300 rpm using a magnetic stirrer; constant current charging and discharging was performed at 20 mA, with an upper voltage limit of 2.5 V and a lower voltage limit of 0 V. The charging time was 4 h, and the cycle was repeated 3 times, taking a total of 21.983 h. The average current efficiency was only 83.2%.

[0071] 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, for one cycle, taking 5.642 h, with a current efficiency of only 41.1%. This indicates that the current efficiency decreases significantly with increasing iron concentration.

[0072] Example 1

[0073] A 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 positive and negative electrodes are single-sided conductive plastic plates, inserted 1 cm into the electrolyte (i.e., with an effective area of ​​1 cm²). 2 ), spacing 2.5 cm, structure as follows Figure 2 As shown in a, the solution remained still; constant current charge and discharge was performed at 20 mA, with an upper voltage limit of 2.5 V and a lower voltage limit of 0 V. The charging time was 4 h, and the cycle was repeated 5 times, taking a total of 38.733 h. The average current efficiency was 93.7%.

[0074] Compared with Comparative Example 1, Example 1 showed higher current efficiency, indicating that keeping the solution static during the charging and discharging process can effectively prevent self-discharge caused by the convection and diffusion of the lead dissolving agent. After the charging and discharging was completed, 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 were completely dissolved, and there was no solid lead residue at the bottom of the container, indicating that the water-soluble lead-acid static battery can maintain good stability.

[0075] Continue adding ferrous methanesulfonate to 0.05 mol / L, and after stirring the electrolyte evenly, keep it still; constant current charge and discharge at 20 mA, upper voltage limit 2.5 V, lower voltage limit 0 V, charging time 4 h, 5 cycles, total time 36.455 h, current efficiency 82.3%, lower than the current density when iron content is 0.01 mol / L, indicating that increasing lead solvent content will accelerate self-discharge, but significantly higher than Comparative Example 1, indicating that in the absence of a separator and 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 solvent.

[0076] 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 indicates that increasing the content of the lead dissolving agent will accelerate the dissolution of lead dioxide, but it has no significant effect on the oxygen absorption dissolution of lead.

[0077] Example 2

[0078] A 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., with an effective area of ​​1 cm²). 2 The negative electrode is a nickel sheet, held in place by an L-shaped electrode clamp. The negative electrode is positioned horizontally and approximately 1 cm directly below the positive electrode, as shown in the diagram. Figure 3As shown in Figure a (the vertical direction here represents the insulating part of the electrode clamp), the solution remains stationary; constant current charging and discharging at 20 mA, upper voltage limit of 2.5 V, lower voltage limit of 0 V, charging time of 4 h, 5 cycles, total time of 35.701 h, current efficiency of 78.5%.

[0079] 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.

[0080] Example 3

[0081] A 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 into the electrolyte (i.e., with an effective area of ​​1 cm²). 2 The negative electrode is a nickel sheet, held in place by an L-shaped electrode clamp. The negative electrode is positioned horizontally and approximately 1 cm directly below the positive electrode, as shown in the diagram. Figure 3 As shown in Figure a (the vertical direction here represents the insulating part of the electrode clamp), the solution remained still; constant current charging and discharging at 20 mA, upper voltage limit 2.5 V, lower voltage limit 0 V, charging time 4 h, 5 cycles, total time 35.412 h, current efficiency 77.1%, no obvious dendrite growth or shedding was observed at the electrode edge (high current density region).

[0082] Example 4

[0083] 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., with an effective area of ​​1 cm²). 2 ), structure as Figure 3 As shown in b, the solution remained stationary; constant current charge-discharge was applied at 20 mA, with an upper voltage limit of 2.5 V and a lower voltage limit of 0 V. The charging time was 4 h, and the cycle was repeated 5 times, taking a total of 37.844 h. The current efficiency was 89.2%. The charge-discharge curves are shown in [Figure 1]. Figure 4 .

[0084] 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.

[0085] Example 5

[0086] 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., with an effective area of ​​1 cm²). 2 ), structure as Figure 3 As shown in b, the solution remained stationary; constant current charge-discharge was applied at 20 mA, with an upper voltage limit of 2.5 V and a lower voltage limit of 1 V. The charging time was 2 h, and the cycle was repeated 5 times. The current efficiency was 91.6%. The charge-discharge curves are shown in [Figure 1]. Figure 5 .

[0087] During the test, no lead dioxide solids were found at the bottom of the container.

[0088] Example 6

[0089] The plastic box is divided into compartments by three 5 cm × 10 cm 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 2 cm gap between adjacent plates, resulting in a static battery stack consisting of two cells connected in series. 50 mL of electrolyte is poured into each cell compartment, containing 1.5 mol / L lead fluoroborate, 1 mol / L fluoroboric acid, and 0.01 mol / L ferrous fluoroborate. The effective area of ​​each bipolar plate is approximately 14 cm². 2 The electrolyte in the compartment remained stagnant, and the electrodes at both ends and the middle bipolar plate were arranged in parallel. A constant current of 200 mA was applied for 3.1 hours, with a maximum voltage of 5 V, followed by discharge to 2 V. One cycle took 5.817 hours, with a current efficiency of 87.6%. The test results are shown below. Figure 6 .

[0090] Example 7

[0091] A quartz cup contains 50 mL of water-soluble lead-acid electrolyte, containing 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 to fit into the quartz cup and adhere 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, with one side covered with insulating tape. The single-sided conductive plastic plate is clamped using an L-shaped electrode clamp (clamping area 0.25 cm²). 2 The conductive side of the plastic plate is horizontal and facing downwards. It is immersed in the electrolyte and positioned 0.8 cm above the horizontal portion of the copper strip, serving as the positive electrode. The horizontal position of the conductive plastic plate is adjusted by rotating the electrode clamps so that its horizontal projection completely falls onto the horizontal portion of the copper strip. This ensures that all lead dioxide during the subsequent discharge process settles onto the negative electrode surface. After assembly... Figure 3 A structure shown in figure a.

[0092] To simulate high-rate charging scenarios in real-world applications (such as the need for batteries to have sufficient charging power during peak photovoltaic power generation periods to store as much energy as possible), the battery charging current in this embodiment is 320 mA (i.e., positive electrode current density of 80 mA / cm²). 2 The duration was 4 hours (i.e., the positive electrode surface capacity was 320 mAh / cm²). 2 The maximum voltage is 2.5 V, the discharge current is 80 mA, the maximum duration is 16 h, the minimum voltage is 0 V, and the cycle is 3 times.

[0093] 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 onto the surface of the negative electrode, but it was reduced during subsequent discharge or charging processes. No solid lead dioxide remained on the surface of the negative electrode after the next charging cycle. Figure 7 a. The charge / discharge curves are shown below. Figure 7 b. As can be seen from the figure, even when charging with high current density, the voltage remains at a low level, with an average charging voltage of 2.180 V over 3 cycles. The discharge voltage is also relatively high, with an average discharge voltage of 1.580 V 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%.

[0094] 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.

[0095] 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.

[0096] 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 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 flaws for water-soluble lead-acid flow batteries. To illustrate this issue more clearly... Figure 1 The structure of a traditional series-connected fuel cell stack (two cells connected in series) is presented, including stacks with and without a diaphragm. 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., the 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, there is a potential difference 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 costs. 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.

[0097] 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 cell includes an electrode plate, a static electrolyte, and a container for holding the electrolyte. The electrode plate is inserted into the electrolyte, and the electrolyte consists of water-soluble lead salt, 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. The bottom of the negative electrode plate extends to the bottom of the positive electrode plate, so that the lead dioxide that is detached from the positive electrode can reach the negative electrode by gravity sedimentation.

2. The water-soluble lead-acid static storage battery according to claim 1, characterized in that, The electrolyte composition also includes a lead-dissolving agent, which provides at least one water-soluble redox couple 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+ ).

3. The water-soluble lead-acid static storage battery according to claim 1, 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.

4. The water-soluble lead-acid static storage battery according to claim 1, 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.

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

6. The water-soluble lead-acid static storage battery according to claim 2, characterized in that, 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.

7. The water-soluble lead-acid static storage battery according to claim 2, characterized in that, The lead dissolving agent is one or more of methanesulfonate and fluoroborate.

8. The water-soluble lead-acid static storage battery according to claim 1 or 2, characterized in that, 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.

9. The water-soluble lead-acid static storage battery according to claim 2, 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.

10. 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.

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