Water-soluble lead-acid battery electrolyte, preparation method and battery

Abstract

The invention relates to a water-soluble lead-acid battery electrolyte, a preparation method and a battery. The water-soluble lead-acid battery electrolyte comprises water-soluble lead salt, acid, a lead dissolving agent and water, the lead dissolving agent can provide two or more pairs of water-soluble redox couple R oxidation and R reduction, and the electrode potentials of the two or more pairs of redox couple are different and meet E theta (Pb < 2 + > / Pb) lt; e [theta] (R oxidation / R reduction) [lt]; e theta (PbO2 / Pb2 +). The lead dissolving agent disclosed by the invention can still discharge and regenerate through an external circuit or diffusion by utilizing potential difference even if the diaphragm blocks shuttling or the electrolyte is kept static, so that the lead dissolving efficiency is greatly improved; the electrolyte is suitable for a water-soluble lead-acid static storage battery and a flow battery, has good cycle stability, and greatly prolongs the cycle life of the water-soluble lead-acid battery; and the condition of solid lead on the electrode can be judged according to the color of the electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and in particular relates to a water-soluble lead-acid battery electrolyte, a preparation method, and a battery. Background Art

[0002] Water-soluble lead-acid flow battery is a dual-deposition flow battery with water-soluble lead salt and corresponding acid as the main redox substances. Its characteristics of identical positive and negative electrolytes and no need for diaphragms have quickly attracted widespread attention and have broad application prospects. However, in actual applications, it is found that the lead dioxide deposited on the positive electrode during charging is easy to fall off during the discharge process, and there is an oxygen evolution side reaction, which makes the solid lead (lead, lead dioxide) unable to dissolve, causing the battery capacity to decay rapidly.

[0003] In order to solve the lead dissolution problem, patent CN110190312B discloses an electrolyte for lead flow battery, which uses iron nitrate or hexafluoroferric complex or iron chloride as catalyst. The principle is to use liquid flow stirring to promote Fe 3+ / Fe 2+ The discharge is shuttled between lead and lead dioxide, causing the solid lead to dissolve.

[0004] Fe 3+ / Fe 2+ Although the use of lead dissolving agent can promote the dissolution of solid lead, it also brings some problems. The first is the self-discharge caused by the lead dissolving agent. In an environment without a separator between the positive and negative electrodes, the lead dissolving agent shuttles back and forth between the positive and negative electrodes with the flow of the electrolyte, which will cause self-discharge during charging and discharging, greatly reducing the current efficiency. If a separator is used to prevent the lead dissolving agent from shuttling back and forth between the positive and negative electrodes, that is, the positive electrode electrolyte only contains the oxidized state of the lead dissolving agent (R 氧化 ), the negative electrode electrolyte contains only reduced state (R 还原 ), although it can reduce self-discharge and improve current efficiency, it cannot be dissolved after the negative lead dendrites dissolve and fall off. This is because the positive lead dioxide always falls off before the lead dendrites, and after the lead dioxide falls off, it can only be dissolved by the oxidation state R of the lead dissolving agent. 氧化 To dissolve the negative electrode, the lead on the negative electrode falls off again, and the negative electrode electrolyte contains only reduced R 还原 , cannot dissolve lead. It can be seen that the electrolyte has limited effect in dissolving lead in batteries with diaphragms. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a water-soluble lead-acid battery electrolyte, a preparation method, and a battery. The electrolyte has excellent lead dissolving effect in both static batteries and flow batteries, and the electrolyte has good cycle stability.

[0006] To achieve the above object, the technical solution provided by the present invention is as follows:

[0007] In a first aspect, the present application provides a water-soluble lead-acid battery electrolyte, comprising a water-soluble lead salt, an acid, a lead dissolving agent and water, wherein the lead dissolving agent can provide two or more pairs of water-soluble redox couples R 氧化 With R 还原 The electrode potentials of the two or more redox pairs are different and all satisfy E θ (Pb 2+ / Pb)< E θ (R 氧化 / R 还原 ) <E θ (PbO 2 / Pb 2+ ).

[0008] Optionally, the lead dissolving agent includes VO 2+ .

[0009] The water-soluble lead salt in the battery participates in the main battery reaction, and the acid acts as a supporting electrolyte and conductive agent. The reaction formula is as follows:

[0010] positive electrode: (1)

[0011] negative electrode: (2)

[0012] To the right is charging, to the left is discharging;

[0013] Active substances will fall off from the electrodes. To ensure the stability of the lead ion concentration in the electrolyte, the active substances (lead and lead dioxide) need to be redissolved into lead ions under the action of a lead dissolving agent. 2+ For example, the relevant reaction equation for lead dissolving as a lead dissolving agent is as follows:

[0014] Lead dioxide dissolution: (3)

[0015] Lead Dissolution: (4)

[0016] Lead dissolving agent regeneration: (5)

[0017] The lead dissolving agent provided by the present invention has the following principle: introducing two (or more) redox pairs of electrode potential as the lead dissolving agent; the two redox pairs R1 氧化 With R1 还原 , R2 氧化 With R2 还原 The electrode potential must satisfy E θ (Pb 2+ / Pb) <E θ (R1 氧化 / R1还原 ) <E θ (R2 氧化 / R2 还原 ) <E θ (PbO 2 / Pb 2+ ), and both have good solubility; when VO 2+ As a lead dissolving agent, it has both oxidizing and reducing properties, that is, R1 氧化 Also R2 还原 , VO 2 + As R2 氧化 , V 3+ As R1 还原 ; The electrode potential satisfies E θ (Pb 2+ / Pb) <E θ (VO 2+ / V 3+ ) <E θ (VO 2 + / VO 2+ ) <E θ (PbO 2 / Pb 2+ ). The initial electrolyte contains R1 氧化 and R2 还原 After charging, the electrolyte near the negative electrode contains R1 还原 , the electrolyte near the positive electrode contains R2 氧化 , R1 还原 and R2 氧化 There is a potential difference between them, which can be regenerated to R1 through an external circuit or direct mixed discharge 氧化 and R2 还原 , and then continue to dissolve the already detached lead and lead dioxide, achieving double-effect lead dissolution. The lead dissolving agent of the present invention can still utilize the potential difference to discharge and regenerate through an external circuit or diffusion even when the diaphragm blocks the shuttle or the electrolyte remains stationary, thereby greatly improving the lead dissolution efficiency.

[0018] Optionally, the lead salt concentration is 0.1-2.5 mol / L, and the vanadium element concentration is 0.001-0.2 mol / L.

[0019] Optionally, the lead salt concentration is 1.5-2 mol / L.

[0020] Optionally, one or more of iron salts and / or ferrous salts are also included, and the concentration of the iron element is 0-0.1 mol / L.

[0021] The electrolyte also contains VO 2 + with Fe3+ / Fe 2+ In addition to formula (3) and (4), the lead dissolving reaction of the compound also includes the following lead dissolving reaction:

[0022] Lead dioxide dissolution: (6)

[0023] Lead Dissolution: (7)

[0024] And lead dissolving agent regeneration:

[0025] (8)

[0026] (9)

[0027] The iron-containing dual-effect lead dissolving system is more inclined to undergo reactions (3), (6), (7), and (8), and has a higher lead dissolving efficiency.

[0028] Optionally, the electrolyte may be in communication with oxygen.

[0029] The positive electrode of the battery may have an oxygen evolution side reaction, and the negative electrode may still have lead residues after full discharge. If the electrolyte is exposed to an oxygen-containing environment, the lead dissolving agent can promote oxygen absorption and lead dissolution. The reaction formula is as follows:

[0030] (10)

[0031] (11)

[0032] The oxidation products produced by reactions (10) and (11) participate in (4) and (7), thereby accelerating the oxygen absorption and lead dissolution.

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

[0034] Optionally, the acid is methanesulfonic acid or fluoroboric acid, and the concentration is no more than 8 mol / L.

[0035] Optionally, V 3+ and / or VO 2 + .

[0036] Optionally, a lead dendrite inhibitor is also included, and the lead dendrite inhibitor is one or more of methyl sulfate, methyl sulfonate, and fluoroborate of alkyltrimethylammonium.

[0037] Optionally, the alkyl group in the lead dendrite inhibitor is a straight chain with 12-22 carbon atoms.

[0038] Optionally, the lead dendrite inhibitor concentration is 0-0.1 mol / L.

[0039] Optionally, the lead dendrite inhibitor is methyl sulfate of alkyltrimethylammonium.

[0040] In a second aspect, the present application also provides a method for preparing a water-soluble lead-acid battery electrolyte, comprising: reducing pentavalent vanadium to obtain a VO 2+ The lead dissolving agent solution is prepared; a water-soluble lead salt is mixed with an acid to obtain a basic electrolyte, and then the basic electrolyte is mixed with the lead dissolving agent solution to obtain the water-soluble lead-acid battery electrolyte.

[0041] Optionally, the lead salt concentration is 0.1-2.5 mol / L, and the vanadium element concentration is 0.001-0.2 mol / L

[0042] Optionally, the pentavalent vanadium is vanadium pentoxide or one or more of ammonium metavanadate, sodium metavanadate, potassium metavanadate, calcium vanadate, and magnesium vanadate, and the reducing agent used for the reduction of the pentavalent vanadium is one or more of metallic lead, metallic iron, ferrous methanesulfonate, and ferrous fluoroborate.

[0043] Optionally, the equivalent ratio of pentavalent vanadium to reducing agent is 1:1.

[0044] Optionally, Fe is added during the preparation of the electrolyte. 2+ and / or Fe 3+ , the concentration of iron is 0-0.1 mol / L.

[0045] Optionally, a lead dendrite inhibitor is added during the preparation of the electrolyte.

[0046] In a third aspect, the present application further provides a water-soluble lead-acid battery, comprising the electrolyte described in the first aspect, wherein the water-soluble lead-acid battery is a static battery or a flow battery.

[0047] Compared with the prior art, this application has at least the following beneficial effects:

[0048] Compared with the iron-based single-effect lead dissolving agent in the prior art, the present invention provides a VO 2+ The lead dissolving agent can dissolve lead in a dual-effect manner, and the lead dissolving efficiency of the system is greatly improved. The electrolyte of the present invention is applicable to both water-soluble lead-acid static batteries and liquid flow batteries, and the electrolyte has good cycle stability, which greatly improves the cycle life of the water-soluble lead-acid battery electrolyte.

[0049] The different valence states of vanadium in the electrolyte of the present invention present different colors, and the valence from vanadium (V) to vanadium (III) is as follows: VO 2 + (Yellow)——VO 2 + / VO 2+ (yellow and blue mixed color)——VO2+ (Blue)——VO 2+ / V 3+ (Blue-green mixed color)——V 3+ (Green), green indicates excess lead, yellow indicates excess lead dioxide, and blue indicates a balance between the two. The color of the electrolyte can be used to determine the state of solid lead on the electrode without disassembling the battery for observation;

[0050] In the present invention, VO 2+ The lead dissolving agent can be directly prepared from relatively low-priced pentavalent vanadium compounds through a simple process. It is simple and efficient and does not introduce impurities that are harmful to negative electrode lead deposition or other processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is the charge and discharge process curve of comparative example 1;

[0052] Figure 2 It is the charge and discharge process curve of Example 1;

[0053] Figure 3 It is the charge and discharge process curve of Example 2;

[0054] Figure 4 This is the charge and discharge process curve of Example 3. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0056] The experimental methods used in the embodiments of the present invention are conventional methods unless otherwise specified.

[0057] The reagents and materials used in this example can all be purchased conventionally.

[0058] Comparative Example 1: The electrolyte of Example 1-2 is used in a liquid flow battery, wherein the liquid flow battery is configured as follows: a 3 mm thick graphite felt is used as the positive electrode, in conjunction with a 1 mm thick conductive plastic plate and a 1 mm thick titanium sheet current collector, a cation exchange membrane is used as a diaphragm, and a 0.1 mm thick copper foil is used as the negative electrode and current collector, with a distance of 3 mm from the diaphragm; from left to right, it is titanium sheet current collector-conductive plastic plate-graphite felt-diaphragm-(3 mm)-copper foil, with an effective area of ​​3 cm × 3 cm; the positive electrode electrolyte and the negative electrode electrolyte are the same, the dosage is 40 ml, and the flow rate through the liquid flow battery is 6 ml / min; the charge and discharge current is 100 mA, the upper limit of the charge voltage is 2.5 V, the upper limit of the charge time is 1 h, and the discharge cut-off voltage is 0 V.

[0059] Comparative Example 1

[0060] Basic lead carbonate is dissolved in a methanesulfonic acid solution to obtain a basic electrolyte containing 2 mol / L of lead methanesulfonate; iron powder and methanesulfonic acid are fully reacted to obtain a lead dissolving agent solution containing 1 mol / L of ferrous methanesulfonate and 1 mol / L of methanesulfonic acid; the basic electrolyte, the lead dissolving agent solution, water, methanesulfonic acid and hexadecyltrimethylammonium methylsulfate are mixed in proportion to obtain a water-soluble lead-acid battery electrolyte containing 1.5 mol / L of lead methanesulfonate, 1 mol / L of methanesulfonic acid, 0.05 mol / L of ferrous methanesulfonate and 0.005 mol / L of hexadecyltrimethylammonium methylsulfate, which is used for a liquid flow battery.

[0061] After 9 charge and discharge cycles, the current efficiency is 87.7%. Figure 1 After the experiment, a small amount of lead dendrites fell off at the bottom of the negative electrolyte container, and the color difference between the positive and negative solutions was not significant. The circuit was disconnected and the circulation pump continued to run for 24 hours, and the lead dendrites did not dissolve.

[0062] Example 1

[0063] Basic lead carbonate was dissolved in methanesulfonic acid solution to obtain a basic electrolyte containing 2 mol / L lead methanesulfonate; ammonium metavanadate and lead were mixed in a 2:1 molar ratio, 4 mol / L methanesulfonic acid solution was added, and stirred for 12 h to obtain a basic electrolyte containing VO 2+ 0.5 mol / L lead dissolving agent solution; mixing the basic electrolyte, the lead dissolving agent solution, water, methanesulfonic acid and hexadecyltrimethylammonium methyl sulfate in proportion to obtain a water-soluble lead-acid battery electrolyte containing 1.5 mol / L lead methanesulfonate, 1 mol / L methanesulfonic acid, 0.1 mol / L vanadium (IV) and 0.005 mol / L hexadecyltrimethylammonium methyl sulfate, which is used for liquid flow batteries.

[0064] After 10 charge and discharge cycles, the current efficiency is 77.0%. Figure 2 After the experiment, no lead dendrites were found at the bottom of the negative electrode electrolyte container, and both the positive and negative electrode solutions were close to blue. After the circuit was disconnected and the circulating pump continued to run for 24 hours, the color of the negative electrode electrolyte was greenish, and the color of the positive electrode electrolyte was close to yellow. The reason for the low current efficiency may be that the lead dioxide shed from the positive electrode did not oxidize vanadium (IV) to vanadium (V) in time, affecting the battery discharge.

[0065] Example 2

[0066] Basic lead carbonate is dissolved in methanesulfonic acid solution to obtain a basic electrolyte containing 2 mol / L lead methanesulfonate; the iron powder reacts fully with the methanesulfonic acid solution, and then an ammonium metavanadate solid equal to the ferrous ion is added and stirred to obtain a VO 2+The invention discloses a lead dissolving agent solution containing 0.5 mol / L lead ions and 0.5 mol / L iron ions; the basic electrolyte, the lead dissolving agent solution, water and methanesulfonic acid are mixed in proportion to obtain a water-soluble lead-acid battery electrolyte containing 1.5 mol / L lead methanesulfonate, 1 mol / L methanesulfonic acid, 0.05 mol / L vanadium (IV) and 0.05 mol / L iron ions, which is used for liquid flow batteries.

[0067] After 5 charge and discharge cycles, the current efficiency is 85.3%. The experimental results are shown in Figure 3 During and after the experiment, no lead dendrites were seen falling off at the bottom of the negative electrode electrolyte container, the positive electrode solution showed the yellow color of vanadium (V), and the negative electrode solution showed the blue color of vanadium (IV); this means that even if lead dendrites fall off at the negative electrode, the vanadium (V) in the positive electrode electrolyte can oxidize the ferrous ions in the negative electrode electrolyte into ferric ions, thereby quickly dissolving the fallen lead dendrites.

[0068] Example 3

[0069] Basic lead carbonate was dissolved in fluoroboric acid solution to obtain a basic electrolyte containing 2 mol / L lead fluoroborate; ammonium metavanadate and lead were mixed in a 2:1 molar ratio, 4 mol / L fluoroboric acid solution was added, and stirred for 12 h to obtain a VO-containing electrolyte. 2+ 0.5 mol / L lead dissolving agent solution; mixing the basic electrolyte, the lead dissolving agent solution, water and 50% by mass fluoroboric acid solution in proportion to obtain a water-soluble lead-acid battery electrolyte containing 1.5 mol / L lead fluoroborate, 1 mol / L fluoroboric acid and 0.01 mol / L vanadium (IV).

[0070] The above-mentioned dual-effect lead-dissolving water-soluble lead-acid battery electrolyte is applied to water-soluble lead-acid static batteries. The battery uses a 20 ml nickel container as the electrolyte container and the battery negative electrode, pours 15 ml of the above-mentioned electrolyte, and inserts a 1 cm wide single-sided conductive plastic plate (the other side is insulated with tape) into the electrolyte, with a depth of 1 cm, as the battery positive electrode. 20 mA constant current charge and discharge, charging time 2 hours, voltage upper limit 2.5 V, discharge voltage lower limit 1 V, 5 cycles. Test results are shown in Figure 4 During the charge and discharge process, the lead on the surface of the negative electrode was deposited evenly, and no lead dioxide was seen falling off the bottom of the positive electrode; after the charge and discharge were completed, the average current efficiency of 5 cycles reached 91.6%. The positive electrode was tapped to make the loose lead dioxide fall to the bottom of the container. After standing for 2 hours, the lead dioxide was completely dissolved, indicating that the vanadium-based lead dissolving agent has a good lead dissolving performance under the test conditions of this embodiment.

[0071] Taking into account the current efficiency and the shedding of lead dendrites, Comparative Example 1 and Examples 1-2 show that, in a liquid flow battery, a lead dissolving agent compounded with vanadium and iron can play a better lead dissolving role than using only a vanadium-based or iron-based lead dissolving agent. Example 3 shows that in a static battery, a good lead dissolving effect can be obtained by using only a vanadium-based lead dissolving agent.

Claims

1. A water-soluble lead-acid battery electrolyte, characterized in that: The invention comprises a water-soluble lead salt, an acid, a lead dissolving agent and water, wherein the lead dissolving agent can provide two or more pairs of water-soluble redox couples R 氧化 With R 还原 The electrode potentials of the two or more redox pairs are different and all satisfy E θ (Pb 2+ / Pb)< E θ (R 氧化 / R 还原 ) <E θ (PbO2 / Pb 2+ ).

2. The water-soluble lead-acid battery electrolyte according to claim 1, characterized in that: The lead dissolving agent includes VO 2+ .

3. The water-soluble lead-acid battery electrolyte according to claim 1, characterized in that: It also includes one or more of iron salts and / or ferrous salts, and the concentration of the iron element is 0-0.1 mol / L.

4. The water-soluble lead-acid battery electrolyte according to claim 1, characterized in that: The lead salt concentration is 0.1-2.5 mol / L, and the vanadium element concentration is 0.001-0.2 mol / L.

5. The water-soluble lead-acid battery electrolyte according to claim 1, characterized in that: The water-soluble lead salt is lead methanesulfonate or lead fluoroborate; and the acid is methanesulfonic acid or fluoroboric acid.

6. The water-soluble lead-acid battery electrolyte according to claim 1, characterized in that: It also includes a lead dendrite inhibitor, which is one or more of methyl sulfate, methyl sulfonate, and fluoroborate of alkyl trimethylammonium.

7. A method for preparing a water-soluble lead-acid battery electrolyte, characterized in that: include: The pentavalent vanadium is reduced to obtain VO 2 + Lead dissolving solution; The water-soluble lead salt is mixed with an acid to obtain a basic electrolyte, and then the basic electrolyte is mixed with a lead dissolving agent solution to obtain the water-soluble lead-acid battery electrolyte.

8. The method for preparing a water-soluble lead-acid battery electrolyte according to claim 7, characterized in that: The pentavalent vanadium is vanadium pentoxide or one or more of ammonium metavanadate, sodium metavanadate, potassium metavanadate, calcium vanadate, and magnesium vanadate. The reducing agent used for the reduction of the pentavalent vanadium is one or more of metallic lead, metallic iron, ferrous methanesulfonate, and ferrous fluoroborate.

9. The method for preparing a water-soluble lead-acid battery electrolyte according to claim 7, characterized in that: During the preparation of the electrolyte, Fe 2+ and / or Fe 3+ , the concentration of iron is 0-0.1 mol / L.

10. A water-soluble lead-acid battery, characterized in that: Comprising the electrolyte described in claims 1-6, the water-soluble lead-acid battery is a static battery or a flow battery.

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