Aqueous electrolyte capable of buffering pH and stabilizing four-electron transfer of acidic indium-iodine secondary battery and preparation method thereof

Abstract

This invention belongs to the field of indium-ion battery technology, specifically relating to an aqueous electrolyte and its preparation method that can buffer pH and stabilize the four-electron transfer in acidic indium-iodine secondary batteries. The aqueous electrolyte of this invention consists of a soluble indium salt, a pH buffer additive, a halide salt, and deionized water. On one hand, the pH buffer additive maintains the pH stability of the electrolyte and inhibits the transfer of indium ions. 3+ Hydrolysis occurs, producing In(OH)3 precipitate; on the other hand, the NH4 in the additive... + Preferential adsorption forms a shielding layer on the surface of the indium anode, inhibiting indium dendrite growth, promoting uniform deposition of indium ions on the anode side, and improving the cycle stability of indium-ion batteries. In indium-iodine secondary batteries, the electrolyte activates the four-electron transfer of the iodine cathode through a high concentration of halide ions, improving the battery capacity and operating voltage. pH buffer additives maintain an acidic environment to inhibit I-. + The hydrolysis reaction stabilizes the four-electron transfer in indium iodine secondary batteries, thereby improving their electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of indium ion batteries, and particularly relates to a water-based electrolyte capable of buffering pH and stabilizing four-electron transfer of an acidic indium-iodine secondary battery and a preparation method thereof. BACKGROUND

[0002] At present, lithium ion batteries are widely used in large-scale energy storage, but their inherent defects seriously restrict further application. First, the organic electrolyte used in lithium batteries is flammable. When the battery overcharges or has internal short circuit, the positive electrode releases oxygen and reacts with the negative electrode lithium metal to trigger thermal runaway, thereby causing the battery to explode and cause serious harm to the life and property safety of the user. Second, the emission of volatile organic compounds in the organic electrolyte also causes air pollution, and the recovery process requires high-temperature cracking, which has high energy consumption and secondary pollution problems. Therefore, it is necessary to develop a high-safety and green secondary battery system under this background.

[0003] The indium metal negative electrode has a low redox potential (-0.34 V vs. SHE) and a high theoretical capacity (700 mAh g -1 ), so it can achieve a higher energy density; and the water-based electrolyte used in the indium ion battery eliminates the risk of spontaneous combustion from the thermodynamic point of view due to its non-flammable nature, and the waste electrolyte does not need high-temperature treatment, but can be recovered by precipitation and ion exchange, avoiding waste gas emission and heavy metal pollution, and meeting the green and environmental protection requirements. Therefore, the water-based indium secondary battery has great development potential and application prospect in the field of future electrochemical energy storage.

[0004] The water-based indium secondary battery uses indium metal as the negative electrode to obtain higher energy density, but during the charging and discharging process, the dendrite growth of the indium negative electrode limits the cycle life of the water-based indium ion battery. In order to solve these problems, researchers have developed a series of new strategies, such as substrate engineering, electrolyte optimization, etc. Among them, the use of new electrolyte optimization can inhibit the occurrence of side reactions such as dendrite growth, passivation, hydrogen evolution, corrosion and morphology change, and improve the working life of the water-based indium ion battery. Recently, the Huang Yunhui research group of Huazhong University of Science and Technology proposed an anion-regulated interface chemical strategy, which balances the In anode deposition kinetics by using anion-decoupled double electrolyte and optimizing the ratio of chloride ions to sulfate ions, thereby promoting the uniform deposition of indium ions. Therefore, by micro-regulating the electrolyte and electrochemical interface, the problem of uneven diffusion of indium ions in the surface compact layer of the indium negative electrode can be effectively solved.

[0005] From the above research results, it can be seen that electrolyte optimization is an effective strategy to improve the cycle stability of indium ion batteries, but the current strategy is only limited to promoting the balanced In anode deposition kinetics, thereby promoting the uniform deposition of indium ions, but ignoring the impact of the imbalance between the consumption and generation of H + and the resulting pH fluctuation on indium ion batteries.

[0006] Therefore, it is necessary to solve the impact of the imbalance between the consumption and generation of H + and the resulting pH fluctuation on indium ion batteries, so as to improve the battery capacity and cycle stability of indium ion batteries. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the present application provides a water-based electrolyte capable of buffering pH and stabilizing the four-electron transfer of acidic indium-iodine secondary batteries and a preparation method. On the one hand, the electrolyte can promote the uniform deposition of indium ions, and NH4 + in the electrolyte is preferentially adsorbed on the surface of the indium negative electrode to form a shielding layer, effectively inhibiting the growth of indium dendrites and promoting the uniform deposition of indium ions on the negative electrode side; on the other hand, the electrolyte activates the four-electron transfer of indium-iodine secondary batteries through high-concentration halogen ions, and controls the proton concentration through its pH buffering effect, thereby effectively inhibiting the hydrolysis reaction of I + + + H2O →HIO + H + ), stabilizing the four-electron transfer of indium-iodine secondary batteries, and improving the electrochemical performance of indium-iodine secondary batteries.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0009] The first aspect of the present application provides a water-based electrolyte capable of buffering pH and stabilizing the four-electron transfer of acidic indium-iodine secondary batteries, which is composed of a soluble indium salt, a pH buffering additive, a halide salt and deionized water.

[0010] Further, the soluble indium salt is any one of indium chloride and indium sulfate.

[0011] Further, the pH buffering additive is any one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate and sodium dihydrogen phosphate.

[0012] Further, the pH buffering additive is ammonium dihydrogen phosphate.

[0013] Further, the halide salt is any one of lithium chloride, sodium chloride, lithium bromide and sodium bromide.

[0014] ​The second aspect of the present application provides a preparation method of the above-mentioned aqueous electrolyte capable of buffering pH and stabilizing the four-electron transfer of an acidic indium-iodine secondary battery, comprising the following steps:

[0015] (1) dissolving a soluble indium salt in deionized water to obtain a soluble indium salt base solution;

[0016] (2) adding a pH buffering additive to the soluble indium salt base solution and stirring until dissolved, and then adding a halide salt and stirring to obtain an electrolyte.

[0017] Further, in step (2), the stirring time of the halide salt is 24-25 h.

[0018] Further, in step (1), the mass ratio of the soluble indium salt to deionized water is 3.4-6.8:9.19-10.

[0019] Further, in step (2), the dosage ratio of the soluble indium salt base solution to the pH buffering additive is 10 mL:0.115-0.23 g.

[0020] Further, in step (2), the dosage ratio of the soluble indium salt base solution to the halide salt is 10 mL:8.05-8.48 g.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The pH buffering additive used in the present application dissociates into weak acid ions and weak base ions after dissolving in deionized water, which together maintain the pH stability of the electrolyte. After adding the pH buffering additive to the electrolyte of the symmetric indium ion battery, its role is to completely inhibit the In 3+ hydrolysis reaction caused by pH fluctuation, and prevent the generation of In(OH)3 precipitate to cause the loss of active material.

[0023] (2) After the pH buffering additive used in the present application is added to the electrolyte, NH4 + tends to preferentially adsorb on the surface of the indium negative electrode to form a shielding layer, effectively inhibiting the growth of indium dendrites, promoting the uniform deposition of indium ions on the negative electrode side, and effectively improving the cycle stability of the indium ion battery.

[0024] (3) The high-concentration halide salt used in the present application can form an interhalogen bond with the iodine species of the positive electrode, activate the four-electron transfer of the iodine positive electrode side of the indium-iodine secondary battery, and the pH buffering additive maintains the acidic environment of the electrolyte, effectively inhibiting the hydrolysis reaction of I + in the acidic indium-iodine secondary battery (I + + H2O → HIO + H + ); at the same time, in the acidic environment of the electrolyte, H+ can accelerate the transformation kinetics of I + to I 0 to I - , stabilize the four-electron transfer of indium-iodine secondary battery, and effectively improve the electrochemical performance of indium-iodine secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Schematic diagram of indium-iodine secondary battery assembled for Example 4.

[0026] Figure 2 Time-voltage curve of the symmetrical battery equipped with the electrolyte of Comparative Example 1, with a current density of 5 mA cm -2 and a deposition capacity of 1 mAh cm -2 .

[0027] Figure 3 Time-voltage curve of the symmetrical battery equipped with the electrolyte of Example 1, with a current density of 5 mA cm -2 and a deposition capacity of 1 mAh cm -2 .

[0028] Figure 4 Time-voltage curve of the symmetrical battery equipped with the electrolyte of Comparative Example 1, with a current density of 5 mA cm -2 and a deposition capacity of 5 mAh cm -2 .

[0029] Figure 5 Time-voltage curve of the symmetrical battery equipped with the electrolyte of Example 1, with a current density of 5 mA cm -2 and a deposition capacity of 5 mAh cm -2 .

[0030] Figure 6 Time-voltage curve of the symmetrical battery equipped with the electrolyte of Comparative Example 1, with a current density of 5 mA cm -2 and a deposition capacity of 1 mAh cm -2 Laser confocal microscope three-dimensional image of the zinc surface after 50 cycles.

[0031] Figure 7 Time-voltage curve of the symmetrical battery equipped with the electrolyte of Example 1, with a current density of 5 mA cm -2 and a deposition capacity of 1 mAh cm -2 Laser confocal microscope three-dimensional image of the zinc surface after 50 cycles.

[0032] Figure 8 Tafel curve spectrum of the symmetrical battery equipped with the electrolyte of Comparative Example 1.

[0033] Figure 9Tafel curve pattern of the symmetric cell assembled for the electrolyte of Example 1.

[0034] Figure 10 The indium-iodine secondary battery assembled for the electrolyte of Comparative Example 6 was charged and discharged at a working current density of 1 A g -1 Charge-discharge curve at the 100th cycle.

[0035] Figure 11 The indium-iodine secondary battery assembled for the electrolyte of Example 4 was charged and discharged at a working current density of 1 A g -1 Charge-discharge curve at the 100th cycle. DETAILED DESCRIPTION

[0036] The specific embodiments of the present application are described below. It should be noted that the description of these embodiments is intended to help understand the present application and is not intended to limit the present application. In addition, the technical features involved in each of the embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0037] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0038] Example 1

[0039] 3.4 g of indium sulfate nonahydrate was added to 9.19 mL of deionized water and stirred to dissolve. Then, 0.115 g of ammonium dihydrogen phosphate was added and stirred until completely dissolved to obtain an electrolyte.

[0040] Example 2

[0041] 5.1 g of indium sulfate nonahydrate was added to 9.5 mL of deionized water and stirred to dissolve. Then, 0.17 g of ammonium dihydrogen phosphate was added and stirred until completely dissolved to obtain an electrolyte.

[0042] Example 3

[0043] 6.8 g of indium sulfate nonahydrate was added to 10 mL of deionized water and stirred to dissolve. Then, 0.23 g of ammonium dihydrogen phosphate was added and stirred until completely dissolved to obtain an electrolyte.

[0044] Example 4

[0045] 3.4 g of indium sulfate nonahydrate was added to 9.19 mL of deionized water and stirred to dissolve. Then, 0.115 g of ammonium dihydrogen phosphate was added and stirred until completely dissolved. Finally, 8.05 g of lithium chloride was added and stirred for 24 h to obtain an electrolyte.

[0046] Example 5

[0047] Add 5.1g of indium sulfate nonahydrate to 9.5mL of deionized water and stir to dissolve. Then add 0.17g of ammonium dihydrogen phosphate and stir until fully dissolved. Finally, add 8.27g of lithium chloride and stir for 24.6h to obtain the electrolyte.

[0048] Example 6

[0049] Add 6.8g of indium sulfate nonahydrate to 10mL of deionized water and stir to dissolve. Then add 0.23g of ammonium dihydrogen phosphate and stir until fully dissolved. Finally, add 8.48g of lithium chloride and stir for 25h to obtain the electrolyte.

[0050] Comparative Example 1

[0051] Add 3.40g of indium sulfate nonahydrate to 9.19mL of deionized water and stir to dissolve, thus obtaining the electrolyte.

[0052] Comparative Example 2

[0053] 3.40 g of indium chloride was added to 9.19 mL of deionized water and stirred to dissolve, thus obtaining the electrolyte.

[0054] Comparative Example 3

[0055] Add 3.40g of indium sulfate nonahydrate to 9.19mL of deionized water and stir to dissolve. Then add 0.115g of diammonium hydrogen phosphate and stir until fully dissolved to obtain the electrolyte.

[0056] Comparative Example 4

[0057] Add 3.40g of indium chloride to 9.19mL of deionized water and stir to dissolve. Then add 0.115g of ammonium phosphate and stir until fully dissolved to obtain the electrolyte.

[0058] Comparative Example 5

[0059] Add 3.40g of indium sulfate nonahydrate to 9.19mL of deionized water and stir to dissolve. Then add 0.115g of sodium dihydrogen phosphate and stir until fully dissolved to obtain the electrolyte.

[0060] Comparative Example 6

[0061] 3.40 g of indium sulfate nonahydrate was added to 9.19 mL of deionized water and stirred to dissolve. Then, 8.05 g of sodium chloride was added and stirred for 24 h to obtain the electrolyte.

[0062] Comparative Example 7

[0063] 3.40 g of indium chloride was added to 9.19 mL of deionized water and stirred to dissolve. Then, 0.115 g of ammonium phosphate was added and stirred until fully dissolved. Finally, 8.27 g of lithium bromide was added and stirred for 24.6 h to obtain the electrolyte.

[0064] Comparative Example 8

[0065] The 3.40 g of indium sulfate nine hydrate was added into 9.19 mL of deionized water to be stirred and dissolved, 0.115 g of sodium dihydrogen phosphate was added to be stirred to be fully dissolved, and finally 8.48 g of sodium bromide was added to be stirred for 25 h to obtain the electrolyte.

[0066] Test Example 1

[0067] The indium metal symmetric battery was assembled by using the pure indium metal sheet as the negative electrode and the positive electrode, using the glass fiber membrane of Whatman as the separator, and using the electrolyte prepared in the above-mentioned Example 1-Example 3 and Comparative Example 1-Comparative Example 5, respectively. Then, the charge-discharge performance test was carried out under the condition that the current density was 5 mA cm -2 and the deposition capacity was 1 mAh cm -2 , and the test results are shown in Table 1.

[0068]

[0069] As can be seen from Table 1, the cycle length of the symmetric battery of Comparative Examples 1-3 and Comparative Examples 1-5, it can be seen that the life of the indium symmetric battery assembled by the electrolyte added with the pH buffer additive is obviously prolonged, which shows that the additive effectively maintains the pH stability of the electrolyte, inhibits the hydrolysis reaction of indium ions, and improves the cycle life of the indium ion battery. As can be seen from the comparison of Example 1 and Comparative Example 5, the additive of different cations also has an effect on the cycle life of the indium ion battery, and the electrolyte added with NH4 + has better cycle stability.

[0070] The pH of the indium metal symmetric battery assembled by the electrolyte prepared in Example 1 and Comparative Example 1, Comparative Example 3, and Comparative Example 4 was compared during the cycle process, and the results are shown in Table 2.

[0071]

[0072] As can be seen from Table 2, compared with other additives, ammonium dihydrogen phosphate can more effectively maintain the pH stability of the electrolyte, inhibit the hydrogen evolution and the hydrolysis reaction of In 3+ due to the pH fluctuation, prevent the corrosion of the indium metal, and effectively improve the electrochemical performance of the indium ion battery.

[0073] Figure 2 and Figure 3 are the time-voltage curve comparison diagrams of the symmetric button cells assembled by the electrolyte of Comparative Example 1 and Example 1 under the condition of 5 mA cm -2 and 1 mAh cm -2 , Figure 4 and Figure 5Symmetrical button cells assembled with electrolytes from Comparative Example 1 and Example 1, respectively, were tested at 5 mA cm⁻¹. -2 5mAh cm -2 A comparison of time-voltage curves under the given conditions, from Figure 2 and Figure 3 The comparison shows that at a current density of 5 mA cm⁻¹ -2 At a given current, the battery without ammonium dihydrogen phosphate exhibits a sudden increase in polarization after less than 500 cycles, while the battery assembled with an electrolyte containing ammonium dihydrogen phosphate can stably cycle for over 2000 cycles; from Figure 4 and Figure 5 The comparison shows that at a current density of 5 mA cm⁻¹ -2 The area capacity is 5mAh cm -2 Under the same conditions, the symmetric coin cell of Comparative Example 1, assembled using a blank electrolyte without added ammonium dihydrogen phosphate, only had a cycle time of 50 hours, after which the polarization suddenly and drastically increased. However, under the same test conditions, the In / / In symmetric cell assembled in Example 1 achieved a cycle time of 5 mAh cm⁻¹. -2 Under large capacity conditions, the cycle time can exceed 1000 hours, indicating that the aqueous electrolyte with added ammonium dihydrogen phosphate in Example 1 can greatly improve the cycle life of the battery.

[0074] Figure 6 This is a three-dimensional laser confocal microscope image of a symmetrical button cell assembled with the electrolyte of Comparative Example 1 after 50 cycles. It can be seen that the surface of the indium metal is uneven, and indium dendrites and indium corrosion are present. Figure 7 The image is a three-dimensional laser confocal microscope image of a symmetrical button cell assembled with the electrolyte of Example 1 after 50 cycles. It can be seen that the surface of the indium metal is smooth and flat, with uniform deposition and no corrosion or dendrites, indicating that the aqueous electrolyte with added ammonium dihydrogen phosphate can promote the uniform deposition of indium ions.

[0075] Test Example 2

[0076] Using pure indium metal sheet as the negative electrode, elemental iodine material as the positive electrode, and Whatman's glass fiber membrane as the separator, an indium-iodine full cell was assembled with the electrolytes prepared in Example 4 and Comparative Examples 1, 6-8. The cell was then operated at a current density of 1 A g. -1 Under the specified conditions, charge-discharge performance was tested, and the test results are shown in Table 3.

[0077]

[0078] From Table 3, the discharge specific capacity of the indium-iodine full cell of Comparative Example 4 and Comparative Examples 1, 6-8 can be seen. The addition of high-concentration halide salt to the electrolyte can activate the four-electron transfer of the iodine positive electrode, thereby improving the specific capacity of the indium-iodine cell. The comparison between Experimental Example 4 and Comparative Example 1 shows that the capacity of the cell is improved after the addition of the pH buffer additive, indicating that the additive maintains the pH stability of the electrolyte, inhibits the hydrolysis of I + ions, and reduces the capacity loss of the cell caused by the hydrolysis of I + ions. Compared with other halide salts, the indium-iodine cell with lithium chloride has better electrochemical performance. The schematic diagram of the indium-iodine secondary cell assembled in Experimental Example 4 is shown in Figure 1 .

[0079] Figure 10 and Figure 11 are the charge-discharge curves and cycle capacity comparison diagrams of the indium-iodine cells assembled with the electrolytes of Comparative Example 6 and Experimental Example 4, respectively. From the comparison between Figure 10 and Figure 11 , it can be seen that compared with the indium-iodine cell with the electrolyte of Comparative Example 6, the indium-iodine cell with the electrolyte of Experimental Example 4 can provide more capacity at the platform where the iodine element is converted into iodine ions at 1.3 V. This indicates that the addition of ammonium dihydrogen phosphate in Experimental Example 4 can effectively inhibit the hydrolysis of I + ions, recover the capacity loss caused by the hydrolysis of I + ions, and effectively improve the electrochemical performance of the cell.

[0080] Test Example 3

[0081] The electrolytes prepared in Experimental Example 1 and Comparative Example 1 were used to assemble three-electrode cells, with an indium foil as the working electrode, a platinum sheet electrode as the counter electrode, and a silver chloride electrode as the reference electrode. Tafel tests were performed at a potential range of -0.85 V to -0.25 V and a scan rate of 1 mV / s. From the comparison between Figure 8 and Figure 9 , it can be seen that the electrolyte prepared in Experimental Example 1 enables the indium negative electrode to have a more positive corrosion potential and a higher corrosion resistance.

[0082] The above describes the embodiments of the present application in detail, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements, and variations can be made to these embodiments without departing from the principles and spirits of the present application, and still fall within the protection scope of the present application.

Claims

1. A kind of water-based electrolyte capable of buffering pH and stabilizing four-electron transfer of acidic indium iodine secondary battery, characterized by, The electrolyte is composed of soluble indium salt, pH buffer additive, halide salt and deionized water; The pH buffer additive is any one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium phosphate; The mass ratio of the soluble indium salt and deionized water is 3.4-6.8:9.19-10, the soluble indium salt is dissolved in the deionized water to obtain a soluble indium salt base solution, and the dosage ratio of the soluble indium salt base solution and halide salt is 10 mL:8.05-8.48 g.

2. The aqueous electrolyte for buffering pH and stabilizing four-electron transfer in an acidic indium iodine secondary battery according to claim 1, characterized in that, The soluble indium salt is any one of indium chloride and indium sulfate.

3. The aqueous electrolyte for buffering pH and stabilizing four-electron transfer in an acidic indium-iodine secondary battery according to claim 1, characterized in that, The pH buffer additive is ammonium dihydrogen phosphate.

4. The aqueous electrolyte for buffering pH and stabilizing four-electron transfer in an acidic indium iodine secondary battery according to claim 1, characterized in that, The halide salt is any one of lithium chloride, sodium chloride, lithium bromide and sodium bromide.

5. A method for preparing a pH-buffering and stable acidic aqueous electrolyte for a four-electron transfer of an indium-iodine secondary battery according to any one of claims 1 to 4, characterized by, The method comprises the following steps: (1) dissolving the soluble indium salt in deionized water to obtain a soluble indium salt base solution; (2) adding the pH buffer additive into the soluble indium salt base solution and stirring until dissolved, and then adding the halide salt and stirring to obtain the electrolyte.

6. The method for preparing the pH-bufferable and stable acidic indium-iodine secondary battery four-electron transfer aqueous electrolyte according to claim 5, characterized in that, In step (2), the stirring time for adding the halide salt is 24-25 h.

7. The method for preparing a pH-bufferable and stable acidic indium-iodine secondary battery four-electron transfer aqueous electrolyte according to claim 5, characterized in that, In step (2), the dosage ratio of the soluble indium salt base solution and pH buffer additive is 10 mL:0.115-0.23 g.

Images