Additive for zinc ion battery electrolyte, preparation method and application thereof

Abstract

The present disclosure relates to an additive for zinc ion battery electrolyte, and a preparation method and application thereof, the additive comprising a hydrophilic polyester with a specific structure, which can reduce the hydrogen absorption reaction of water and zinc metal, inhibit the generation of byproduct zinc dendrites, and improve the electrochemical stability and cycle life of the zinc ion battery.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of zinc ion battery preparation, in particular, to an additive for zinc ion battery electrolyte and a preparation method and application thereof. BACKGROUND

[0002] Aqueous zinc ion batteries have attracted extensive attention due to their low cost, high capacity, green friendliness and high safety, and are considered as one of the most promising lithium ion battery replacement systems and the most potential large-scale energy storage power systems. However, in the aqueous electrolyte, the zinc negative electrode will inevitably undergo corrosion and hydrogen absorption and other side reactions, resulting in low coulombic efficiency of the battery; and serious dendrite growth occurs during the charging and discharging process, resulting in poor cycle performance and rapid capacity decay of the battery. Therefore, the further large-scale application and promotion of aqueous secondary zinc ion batteries are greatly limited. In view of the above problems, the current research strategies focus on zinc anode modification, positive electrode material modification and electrolyte optimization, among which the optimization of electrolyte by using organic additives is a simple, effective and easy-to-implement method to inhibit dendrite formation and growth.

[0003] The electrolyte additive strategy is an effective modification method for protecting the zinc metal negative electrode and improving the electrochemical performance of the battery. It mainly regulates the combination state of zinc ions and water molecules by using electrolyte additives with specific functions, promotes the uniform distribution of zinc ions on the zinc negative electrode surface and the uniform dissolution / deposition of zinc metal during the cycle process, and inhibits dendrite growth to improve the cycle reversibility of the zinc negative electrode. So far, a large number of organic molecules have been reported to be effective in inhibiting dendrite growth, such as glucose, diethyl ether, polyacrylamide, polyethylene oxide (PEO) and the like. Although most of the zinc ion electrolyte additives currently improve the performance of zinc ion batteries to some extent, their functions are mostly single and have their own shortcomings. For example, metal ion additives cannot effectively promote the uniform deposition of zinc and inhibit the generation of dendrites by insufficient polarity induction to form a continuous protective layer on the zinc negative electrode surface; organic small molecule additives usually have a large amount of addition and have certain toxicity, which is not suitable for large-scale practical application. SUMMARY

[0004] The purpose of the present disclosure is to provide an additive for zinc ion battery electrolyte and a preparation method and application thereof. The additive of the present disclosure is green and environmentally friendly, can greatly improve the cycle performance and stability of zinc ion batteries, and the preparation method is simple in steps, low in cost and easy to mass produce.

[0005] To achieve the above purpose, the first aspect of the present disclosure provides an additive for zinc ion battery electrolyte, which comprises a polymer having a structure as shown in Formula 1:

[0006]

[0007] R1, R2, R3, R4, R5 and R6 are each independently H or comprise a repeating unit as shown in Formula 2, and R1, R2, R3, R4, R5 and R6 are not simultaneously H;

[0008]

[0009] each a is independently selected from any integer between 1 and 8;

[0010] each b is independently selected from any integer between 1 and 3.

[0011] Optionally, 1, 2, 3 or 4 of R1, R2, R3, R4, R5 and R6 are H.

[0012] Optionally, the polymer contains a structural unit as shown in Formula 3:

[0013]

[0014] Optionally, the additive has a number average molecular weight of 1 x 10 5 -1.6 x 10 5 .

[0015] The second aspect of the present disclosure provides a method for preparing an additive for zinc ion battery electrolyte, the method comprising:

[0016] reacting a first monomer having a structure as shown in Formula 4 with a second monomer having a structure as shown in Formula 5 in the presence of a catalyst;

[0017]

[0018] wherein X is selected from Cl;

[0019] a is selected from any integer between 1 and 8;

[0020] each b is independently selected from any integer between 1 and 3.

[0021] Optionally, the reaction conditions include a time of 6-12 h and a temperature of 40-55°C.

[0022] Optionally, the first monomer comprises one or more of malonyl chloride, succinyl chloride, glutaryl chloride and adipyl chloride;

[0023] the second monomer comprises one or more of tetramethylol glycoluril, tetrahydroxyethyl glycoluril and tetrahydroxypropyl glycoluril;

[0024] the catalyst comprises pyridine and / or triethylamine;

[0025] The molar ratio of the first monomer to the second monomer is (2-2.5):1;

[0026] The molar ratio of the second monomer to the catalyst is 1:(0.08-0.15).

[0027] Optionally, the method comprises: contacting a solution containing the second monomer and a first organic solvent, the catalyst, the first monomer and a second organic solvent to perform the reaction.

[0028] The first organic solvent comprises dimethyl sulfoxide and / or dimethyl formamide.

[0029] The second organic solvent comprises tetrahydrofuran and / or dichloromethane.

[0030] The third aspect of the present disclosure provides an additive prepared by the method of the second aspect of the present disclosure.

[0031] The fourth aspect of the present disclosure provides a zinc ion battery electrolyte, which comprises a zinc source, water and the additive of the first aspect or the third aspect of the present disclosure.

[0032] Optionally, the volume ratio of the additive to the water is (1-20):100.

[0033] Optionally, the zinc source comprises one or more of zinc sulfate, zinc acetate, zinc chloride and zinc trifluoromethane sulfonate.

[0034] Optionally, the method for preparing the zinc ion battery electrolyte comprises: mixing a solution containing the zinc source with the additive.

[0035] In the solution, the concentration of the zinc source in terms of zinc element is 0.5-2 mol / L.

[0036] The fifth aspect of the present disclosure provides a zinc ion battery, which comprises a positive electrode, a negative electrode and the electrolyte of the fourth aspect of the present disclosure.

[0037] By the above technical solution, the additive of the zinc ion battery electrolyte of the present disclosure has the following beneficial effects:

[0038] 1) The O and N heteroatoms in the hydrophilic polyester additive of the present disclosure have strong affinity with zinc negative electrode, which can effectively inhibit the formation and growth of zinc dendrites, and has multifunctionality for improving the stability of zinc electrode in aqueous electrolyte; can form a continuous protective layer on the surface of zinc negative electrode through chemical adsorption, effectively reducing the direct contact of zinc with electrolyte, and can compete for water molecules on the surface of zinc electrode through hydrogen bond interaction, reducing the activity of water and thus reducing the occurrence of zinc corrosion and hydrogen evolution and other side reactions; has a significant improvement on the cycle life of water-based zinc ions, especially under the condition of large current density, and can be widely used in water-based zinc ion batteries;

[0039] 2) The hydrophilic polyester high molecular additive of the present disclosure is prepared by low-cost monomer reaction, and the steps and operation are simple, economical and fast, which can realize large-scale production and application.

[0040] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0041] The accompanying drawings are used to provide further understanding of the present disclosure, and constitute a part of the specification, and are used to explain the present disclosure together with the following specific embodiments, but do not constitute a limitation on the present disclosure. In the drawings:

[0042] Figure 1 is the SEM image of (a) unused Zn negative electrode after sandpaper polishing; (b) SEM image of Zn negative electrode after soaking in B2 electrolyte for 7 days; (c) SEM image of Zn negative electrode after soaking in D1 electrolyte for 7 days;

[0043] Figure 2 is the XRD spectrum of zinc negative electrode after 50 cycles of Zn∥Zn symmetric battery in D1 and B2 electrolyte systems;

[0044] Figure 3 is the Tafel curve of zinc negative electrode in D1 and B2 electrolyte systems;

[0045] Figure 4 is the nuclear magnetic resonance hydrogen spectrum of the additive A1 prepared in the preparation example 1 of the present disclosure;

[0046] Figure 5 is the nuclear magnetic resonance carbon spectrum of the additive A1 prepared in the preparation example 1 of the present disclosure;

[0047] Figure 6 is the nuclear magnetic resonance hydrogen spectrum of the additive A2 prepared in the preparation example 2 of the present disclosure;

[0048] Figure 7 is the nuclear magnetic resonance carbon spectrum of the additive A2 prepared in the preparation example 2 of the present disclosure. DETAILED DESCRIPTION

[0049] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0050] The first aspect of the present disclosure provides an additive for zinc ion battery electrolyte, the additive comprising a polymer having a structure as shown in Formula 1:

[0051]

[0052] R1, R2, R3, R4, R5 and R6 are each independently H, or contain a repeating unit as shown in Formula 2, and R1, R2, R3, R4, R5 and R6 are not simultaneously H;

[0053]

[0054] Each a is independently selected from any integer from 1 to 8;

[0055] Each b is independently selected from any integer from 1 to 3.

[0056] In the present disclosure, * represents a connection point between chemical bonds.

[0057] In order to further improve the performance of the additive, according to an embodiment of the present disclosure, each a is independently selected from any integer from 1 to 4, each a being the same or different, preferably the same; each b is the same or different, preferably the same.

[0058] According to an embodiment of the present disclosure, 1, 2, 3 or 4 of R1, R2, R3, R4, R5 and R6 are H.

[0059] According to an embodiment of the present disclosure, the polymer contains a structural unit as shown in Formula 3:

[0060]

[0061] According to a specific embodiment of the present disclosure, the polymer contains a structural unit as shown in Formula 3-1:

[0062]

[0063] According to an embodiment of the present disclosure, the number average molecular weight of the additive is 1x10 5 -1.6x10 5 , preferably 1.3x10 5 -1.5x10 5 .

[0064] The second aspect of the present disclosure provides a method for preparing an additive for zinc ion battery electrolyte, the method comprising:

[0065] reacting a first monomer having a structure shown in Formula 4 with a second monomer having a structure shown in Formula 5 in the presence of a catalyst;

[0066]

[0067] wherein X is selected from Cl;

[0068] a is selected from any integer from 1 to 8;

[0069] each b is independently selected from any integer from 1 to 3.

[0070] To facilitate the progress of the reaction, according to an embodiment of the present disclosure, the conditions of the reaction include: a time of 6h-12h, a temperature of 40℃-55℃; the reaction can be carried out in a water bath or an oil bath.

[0071] According to an embodiment of the present disclosure, the molar ratio of the first monomer to the second monomer is (2-2.5):1.

[0072] According to an embodiment of the present disclosure, the molar ratio of the second monomer to the catalyst is 1:(0.08-0.15).

[0073] According to an embodiment of the present disclosure, a is selected from any integer from 1 to 4; each b is the same or different, preferably the same.

[0074] According to an embodiment of the present disclosure, the first monomer comprises one or more of malonyl chloride, succinyl chloride, glutaryl chloride and adipyl chloride.

[0075] According to an embodiment of the present disclosure, the second monomer comprises one or more of tetramethylol glycoluril, tetrahydroxyethyl glycoluril and tetrahydroxypropyl glycoluril; the second monomer can be prepared by a conventional method, and tetramethylol glycoluril can also be commercially available.

[0076] According to an embodiment of the present disclosure, the catalyst comprises pyridine and / or triethylamine.

[0077] According to an embodiment of the present disclosure, the method for preparing the additive comprises: contacting a solution containing a second monomer and a first organic solvent, a catalyst, a first monomer and a second organic solvent, and reacting; wherein the first organic solvent comprises dimethyl sulfoxide and / or dimethyl formamide, the second monomer has good solubility in the first organic solvent, which is conducive to further promoting the reaction; the second organic solvent comprises tetrahydrofuran and / or dichloromethane; the amount of the first organic solvent and the second organic solvent is conventional, for example, the amount of the first organic solvent is 150 mL-280 mL and the amount of the second organic solvent is 1000 mL-1500 mL, relative to 1 mol of the second monomer, so as to fully dissolve the first monomer and the second monomer.

[0078] According to an embodiment of the present disclosure, the method for preparing the additive further comprises: performing solid-liquid separation on the mixture obtained by the reaction, and washing and drying the obtained solid; wherein the washing agent used for washing can be cyclohexane and diethyl ether; the drying method can be vacuum drying, and the conditions and steps are conventional in the art.

[0079] The third aspect of the present disclosure provides an additive prepared by the method of the second aspect of the present disclosure.

[0080] The additive of the third aspect of the present disclosure has the same characteristics as the additive of the second aspect of the present disclosure, and will not be described here.

[0081] The fourth aspect of the present disclosure provides a zinc ion battery electrolyte, which comprises a zinc source, water and the additive of the first aspect or the third aspect of the present disclosure.

[0082] In order to make the electrolyte have a good effect of inhibiting zinc corrosion and hydrogen evolution reaction, while avoiding its impact on the performance of the battery, according to an embodiment of the present disclosure, the content of the zinc source in the zinc ion battery electrolyte is 0.5 mol / L-2 mol / L, for example, it can be 2 mol / L, calculated in terms of zinc element.

[0083] According to an embodiment of the present disclosure, the volume ratio of the additive to the water is (1-20):100, preferably (2-12):100, and further preferably (2-5):100.

[0084] In order to make the electrolyte have a good effect of inhibiting zinc corrosion and hydrogen evolution reaction, while avoiding its impact on the performance of the battery, according to an embodiment of the present disclosure, the method for preparing the zinc ion battery electrolyte comprises: mixing a solution containing the zinc source with the additive; the concentration of the zinc source in the solution is 0.5 mol / L-2 mol / L, for example, it can be 2 mol / L, calculated in terms of zinc element; and the mixing can be performed at room temperature.

[0085] According to one embodiment of the present disclosure, the volume ratio of the additive to the solution is (1-20): 100, preferably (2-12): 100, and more preferably (2-5): 100.

[0086] In the present disclosure, the type of zinc source is conventional in the art, for example, can include one or more of zinc sulfate, zinc acetate, zinc chloride and zinc trifluoromethane sulfonate. When the zinc source includes two or more, the present disclosure does not specifically limit the proportion thereof.

[0087] The fifth aspect of the present disclosure provides a zinc ion battery, which comprises a positive electrode, a negative electrode and the electrolyte of the fourth aspect of the present disclosure.

[0088] In the present disclosure, the zinc ion battery can be, for example, a zinc-manganese full battery, a zinc-zinc symmetric battery, etc.

[0089] In the present disclosure, the types of positive electrode and negative electrode are conventional in the art, the positive electrode can be zinc single element, manganese-based material, vanadium-based material, Prussian blue analogue, organic polymer, etc., for example, MnO2positive electrode, zinc sheet; the negative electrode can be zinc single element.

[0090] In the present disclosure, the zinc ion battery further comprises a separator, and the type of separator is conventional in the art, for example, can be glass fiber.

[0091] In the present disclosure, the assembly and preparation method of the positive electrode, the negative electrode and the zinc ion battery are conventional in the art.

[0092] The present disclosure will be described in detail below by way of examples, but is not limited to the following examples.

[0093] In the following examples and comparative examples, the reagents used are commercially available unless otherwise specified.

[0094] The test method of the number average molecular weight of the additive is gel permeation chromatography (GPC), and the mobile phase is DMSO, and the sample volume is 20 μL.

[0095] Preparation Example 1

[0096] The additive A1 is prepared by the following steps:

[0097]

[0098] A. Preparation of glycol: 0.1 mol of urea, 0.035 mol of glyoxal were added to 20 mL of distilled water to dissolve, then 1 mL of concentrated sulfuric acid was added, and the reaction was carried out by transferring to a water bath for 7 h at 50°C. The obtained white powdery solid was washed with sodium hydroxide solution and distilled water, respectively, and finally the solid was transferred to a constant temperature drying oven at 80.0°C for drying for standby;

[0099] B. Preparation of Tetrahydroxy Methyl Glycoluril (TA): After dissolving a solution containing 0.04 mol of glycoluril, 0.16 mol of formaldehyde and 15 mL of distilled water, NaOH solution was added to adjust the pH to 10, and then transferred to an oil bath for heating reaction, and continuous stirring, time 8 h, temperature 55°C. After the reaction was completed, the water was removed by vacuum drying, and the obtained light yellow liquid was added to a beaker containing methanol, stirred until the white solid was separated, and finally dried in a vacuum oven for storage;

[0100] C. Synthesis of polyester macromolecular additive: After 0.038 mol of TA was completely dissolved in 8 mL of solvent dimethyl sulfoxide (DMSO), 0.084 mol of succinyl chloride, 40 mL of tetrahydrofuran (THF) and 0.004 mol of pyridine were added and mixed uniformly, then transferred to an oil bath for heating reaction, and continuous stirring, time 8 h, temperature 40°C. After the reaction was completed, the obtained precipitate was filtered, then washed with cyclohexane and diethyl ether respectively, and then vacuum dried to obtain the additive A1.

[0101] The nuclear magnetic test was carried out on the additive A1, and the results are shown in Figure 4 and 5 , and the specific data are as follows:

[0102] 1 H-NMR (400 MHz, D2O-d6) δ (ppm): 6.18 (s, N-CH-N), 5.73-5.59 (m, N-CH2-O), 2.72 (s, -CH2-).

[0103] 13 C-NMR (125 MHz, D2O-d6) δ (ppm): 178.22, 147.91, 71.74, 68.62, 67.97, 29.95.

[0104] The infrared spectrum test was carried out on the additive A1, and the specific data are as follows:

[0105] FT-IR (cm -1 ): 3363.9, 2197.7, 1709.4, 1632.9, 1540.9, 1485.2, 1389.4, 1332.3, 1238.7, 1022.2, 794.4, 753.1, 677.4.

[0106] Preparation Example 2

[0107] The additive A2 was prepared by a method similar to that of Preparation Example 1, except that:

[0108] C. Synthesis of the polyester macromolecular additive: 0.038 mol of TA was completely dissolved in 6 mL of solvent dimethyl sulfoxide (DMSO), then 0.092 mol of adipoyl chloride, 50 mL of tetrahydrofuran (THF) and 0.005 mol of pyridine were added and mixed uniformly, then transferred to an oil bath pot for heating reaction, and continuous stirring, time 12 h, temperature 55 °C. After the reaction was completed, the obtained precipitate was filtered, then washed with cyclohexane and diethyl ether respectively, and vacuum dried to obtain the additive A2.

[0109] The nuclear magnetic test was carried out on the additive A2, and the results are shown in Figure 6 and 7 , and the specific data are as follows:

[0110] 1 H-NMR (400 MHz, D2O-d6) δ (ppm): 6.36 (s, N-CH-N), 5.70-5.60 (m, N-CH2-O), 2.36 (s, -CH2-), 1.88 (s, -CH2-).

[0111] 13 C-NMR (125 MHz, D2O-d6) δ (ppm): 175.32, 156.24, 73.84, 70.72, 36.62, 27.05.

[0112] The infrared spectrum test was carried out on the additive A2, and the specific data are as follows:

[0113] FT-IR (cm -1 ): 3281.86, 1715.24, 1609.11, 1467.5, 1119.03, 1016.79, 772.61, 600.85, 517.84, 435.86.

[0114] In Preparation Examples 1 and 2, the product structure is exemplary, and the value of n makes the additive have a molecular weight shown in Table 1.

[0115] Test Example

[0116] The sample preparation and battery assembly method are as follows:

[0117] A. Preparation of electrolyte:

[0118] 1) 2M ZnSO4 solution was prepared with ZnSO4·H2O and deionized water;

[0119] 2) The solution was mixed with the additive to obtain the electrolyte, and the formula is listed in Table 1;

[0120] D1 electrolyte does not contain an additive, i.e. the D1 electrolyte is a 2M ZnSO4 solution; the additive DB-1 in the D2 electrolyte is tetramethylol glycoluril, the additive DB-2 in the D3 electrolyte is ethylene glycol (EG), and the additive DB-3 in the D4 electrolyte is KPF6.

[0121] The concentration of the additive KPF6 in the D4 electrolyte is 10 mM.

[0122] Table 1

[0123]

[0124] B. Preparation of MnO2

[0125] 1) KMnO4 was dissolved in ultrapure water for use, and MnSO4·2H2O was dissolved in ultrapure water and then sulfuric acid was added; the two solutions were mixed and stirred in the dark;

[0126] 2) The stirred solution was placed in a Teflon reactor (in the dark) for heating reaction;

[0127] 3) Filtration and vacuum drying for standby use.

[0128] C. Preparation of electrode and battery assembly

[0129] 1) Preparation of MnO2 positive electrode: PVDF, conductive carbon black and MnO2 were added to N-methyl pyrrolidone in a mass ratio of 7:2:1, respectively, and the prepared slurry was evenly coated on the surface of carbon paper after room temperature reaction, and then dried for standby use. The loading capacity of the active material was 2.0 mg cm -2 , and cut into a round piece with a diameter of 1.2 cm for standby use;

[0130] 2) Preparation of zinc electrode: zinc foil (99%) was cut into a round piece with a diameter of 1.2 cm by a slicing machine, and the metal zinc was polished with 800, 1200, 2000 and 3000 mesh SiC sandpaper in turn until a completely smooth and bright zinc surface was obtained. The polished zinc piece was immersed in an ethanol solution and ultrasonicated for 3 min, and then dried for standby use;

[0131] 3) Assembly of the battery: the aqueous zinc ion battery was assembled in air, the zinc electrode was used as the negative electrode, the MnO2 or zinc electrode was used as the positive electrode, 100 μL of the electrolyte prepared in the above examples and comparative examples was used as the electrolyte, the glass fiber filter paper was used as the separator, and the battery was assembled in the order of positive electrode shell, positive electrode piece, separator, electrolyte, negative electrode piece, gasket, spring, and negative electrode shell. After the assembly was completed, the battery was compacted by a tablet press, and then was left to stand at room temperature for 5 h before subsequent testing.

[0132] Example 1

[0133] In the above manner, the MnO2 positive electrode sheet was used as the positive electrode to assemble a Zn‖MnO2 full battery (model CR2032) for long cycle stability test of the battery.

[0134] (1) The button cell was tested by using a new battery test system, the voltage of charging was 0.8V-2V, and the current density was 0.2A g -1 , the cycle number was set to 100, and the results are shown in Table 2.

[0135] Table 2

[0136]

[0137]

[0138] According to the data in Table 2, compared with the electrolyte system without using the additive and using other types of additives, the cycle performance of the zinc ion battery prepared by using the electrolyte containing the hydrophilic polyester high molecular additive with the specific structure according to the present disclosure is greatly improved, which indicates that the use of the additive can effectively inhibit the corrosion reaction and hydrogen evolution reaction of zinc and reduce the growth of zinc dendrites; further, according to the comparison of B1-B3, when the volume ratio of the additive to the solution is in the range of preferably (2-5):100, the cycle capacity retention rate can be further improved.

[0139] (2) The button cell was tested by using a new battery test system, the voltage of charging was 0.8V-2.0V, and the current density was 1.0A g -1 , the cycle number was set to 2000, and the results are shown in Table 3.

[0140] Table 3

[0141]

[0142] According to the data in Table 3, the zinc ion battery prepared by using the electrolyte containing the hydrophilic polyester high molecular additive with the specific structure according to the present disclosure still has a high capacity retention rate under a high current density and a long cycle number.

[0143] Example 2

[0144] In the above manner, the zinc electrode sheet was used as the positive electrode to assemble a Zn‖Zn symmetric battery (model CR2032) for the following tests:

[0145] (1) The cycle stability was tested at a current density of 1mA cm -2 and 10mA cm -2 , and the charge-discharge capacity was 1mAh cm -2 , and the results are shown in Tables 4 and 5;

[0146] wherein, the "stable cycle time" refers to the time when the polarization voltage does not have a significant large fluctuation, and the "significant large fluctuation" refers to that the charge-discharge end voltage is 1.5 times or more than the charge-discharge end voltage of the last cycle, or the voltage drop after charge-discharge is 0.

[0147] Table 4

[0148]

[0149] According to the data in Table 4, compared with the electrolyte system without using the additive and using other kinds of additives, the zinc ion battery prepared by the electrolyte containing the hydrophilic polyester high molecular additive with a specific structure has good cycle stability, which indicates that the use of the additive can effectively inhibit the growth of zinc dendrites, avoid the short circuit caused by the zinc dendrites piercing the separator and the direct contact between the positive electrode and the negative electrode; further, according to the comparison of B1-B3, when the volume ratio of the additive to the solution is in the preferred range of (2-5): 100, the cycle stability can be further improved.

[0150] Table 5

[0151]

[0152] According to the data in Table 5, the zinc ion battery prepared by the electrolyte containing the hydrophilic polyester high molecular additive with a specific structure has a long stable cycle time under a high current density, that is, has good cycle stability.

[0153] (2) Two pieces of zinc sheets with the same size were immersed in electrolytes D1 and B2 respectively for 7 days, and then the surface morphology of the zinc sheets was observed by scanning electron microscopy, and the results are shown in Figure 1 ;

[0154] wherein, (a) the SEM image of the unused Zn negative electrode after sandpaper polishing; (b) the SEM image of the Zn negative electrode immersed in the B2 electrolyte for 7 days; (c) the SEM image of the Zn negative electrode immersed in the D1 electrolyte for 7 days.

[0155] According to Figure 1 , compared with the unused Zn electrode sheet, the Zn negative electrode immersed in the D1 electrolyte has a darker color, no metal luster, a rough surface and obvious corrosion traces; the Zn negative electrode immersed in the B2 electrolyte has a smooth surface and only covers a small amount of nanoparticles. According to the above, the electrolyte containing the hydrophilic polyester high molecular additive with a specific structure can inhibit the corrosion reaction on the surface of the zinc negative electrode and effectively protect the zinc negative electrode.

[0156] (3) After the Zn‖Zn symmetric battery was cycled for 50 times in the D1 and B2 electrolytes respectively, the zinc negative electrode was disassembled, soaked in an ethanol solution, and subjected to XRD scanning test after the surface glass fiber separator was removed, and the results are shown in Figure 2 ; the test conditions are: the current density is 1 mA cm -2 , and the deposition capacity is 1 mAh cm -2 ;

[0157] According to Figure 2 , after the zinc negative electrode is cycled for 50 times, in the D1 electrolyte without the additive, the characteristic peaks at 2θ = 8.3°, 16.5° and 24.8° appear obviously, which are the characteristic peaks of the by-product zinc dendrite ZHS (Zn4SO4(OH)6·xH2O), which means that the zinc negative electrode has a serious side reaction in the D1 electrolyte. However, the characteristic peaks of the by-product ZHS do not appear in the B2 electrolyte containing the additive, which indicates that the addition of the additive significantly inhibits the occurrence of the hydrogen evolution reaction of the zinc negative electrode, thereby significantly reducing the generation of zinc dendrites.

[0158] (4) The Tafel curves of the zinc negative electrode in the D1 and B2 electrolyte systems were determined by using the potentiostatic polarization curve, and the details are as follows:

[0159] A three-electrode system was used: the zinc foil polished bright was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the platinum electrode was used as the counter electrode;

[0160] The test device was a CHI660E electrochemical workstation;

[0161] The specific test method was the traditional three-step method, first, the prepared electrolyte was placed for 30 min, and then the Tafel curve was determined under the conditions that the frequency range was 0.1 Hz to 10 5 HZ, the specific voltage interval was -0.8 V to -1.1 V, and the scanning speed was 1 mV / s -1 , and the results are shown in Figure 3 .

[0162] According to Figure 3 , compared with the ZnSO4 electrolyte D1, after the additive is added, the corrosion potential value changes from -0.899 V to -0.892 V, which increases by 7 mV, which indicates that the addition of the additive of the present disclosure reduces the possibility of corrosion of the zinc negative electrode. At the same time, the corrosion current is also reduced, which means that the rate of the corrosion reaction is also reduced. Therefore, the addition of the additive effectively reduces the possibility and intensity of the corrosion reaction of the zinc negative electrode in the ZnSO4 electrolyte. In addition, the inhibition of the corrosion reaction can make the surface of the zinc negative electrode more flat and smooth, which to some extent inhibits the formation of the surface zinc dendrites, which is helpful to improve the 2+The deposition / dissolution reversibility of zinc is of great significance.

[0163] In summary, the cycle performance of the zinc ion battery prepared by the electrolyte containing the hydrophilic polyester polymer additive with the specific structure of the present disclosure has a large degree of improvement, which indicates that the use of the additive can effectively inhibit the corrosion reaction and hydrogen evolution reaction of zinc, reduce the growth of zinc dendrites, and further improve the cycle stability and electrochemical performance of the zinc ion battery.

[0164] The preferred embodiments of the present disclosure are described in detail above in combination with the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Within the technical concept range of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection range of the present disclosure.

[0165] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again in the present disclosure.

[0166] In addition, various different embodiments of the present disclosure can also be combined in any manner, as long as they do not deviate from the idea of the present disclosure, and they should also be considered as disclosed by the present disclosure.

Claims

1. A zinc ion battery electrolyte, characterized in that The electrolyte includes an additive, wherein the additive includes a polymer having a structure as shown in Formula 1: Formula 1; R1, R2, R3, R4, R5 and R6 are each independently H, or contain a repeating unit as shown in Formula 2, and R1, R2, R3, R4, R5 and R6 are not H at the same time; Formula 2; Each a is independently selected from any integer from 1 to 8; Each b is independently selected from any integer from 1-3.

2. The zinc ion battery electrolyte according to claim 1, wherein One, two, three or four of R1, R2, R3, R4, R5 and R6 are H.

3. The zinc ion battery electrolyte according to claim 1, wherein The polymer contains a structural unit as shown in Formula 3: Formula 3.

4. The zinc ion battery electrolyte according to claim 1, wherein The number average molecular weight of the additive is 1×10 5 -1.6×10 5 .

5. The zinc ion battery electrolyte according to claim 1, wherein The zinc ion battery electrolyte further comprises water and a zinc source.

6. The zinc ion battery electrolyte according to claim 5, wherein The volume ratio of the additive to the water is (1-20):

100.

7. The zinc ion battery electrolyte according to claim 5, wherein The zinc source includes one or more of zinc sulfate, zinc acetate, zinc chloride and zinc trifluoromethanesulfonate.

8. The zinc ion battery electrolyte according to claim 5, wherein The method for preparing the zinc ion battery electrolyte comprises: mixing a solution containing the zinc source with the additive; In the solution, the concentration of the zinc source calculated as zinc element is 0.5 mol / L-2 mol / L.

9. A method for preparing an additive for a zinc ion battery electrolyte, characterized in that: The method includes: In the presence of a catalyst, reacting a first monomer having a structure shown in Formula 4 with a second monomer having a structure shown in Formula 5; Formula 4; Formula 5; wherein X is selected from Cl; a is any integer selected from 1 to 8; Each b is independently selected from any integer from 1-3.

10. The method according to claim 9, wherein: The reaction conditions include: time of 6 h-12 h, temperature of 40° C.-55° C.

11. The method according to claim 9, wherein The first monomer includes one or more of malonyl chloride, succinyl chloride, glutaryl chloride and adipoyl chloride; The second monomer includes one or more of tetramethylol glycoluril, tetrahydroxyethyl glycoluril and tetrahydroxypropyl glycoluril; The catalyst includes pyridine and / or triethylamine; The molar ratio of the first monomer to the second monomer is (2-2.5):1; The molar ratio of the second monomer to the catalyst is 1:(0.08-0.15).

12. The method according to claim 9, wherein The method comprises: contacting a solution containing the second monomer and a first organic solvent, the catalyst, the first monomer, and the second organic solvent to carry out the reaction; The first organic solvent includes dimethyl sulfoxide and / or dimethylformamide; The second organic solvent includes tetrahydrofuran and / or dichloromethane.

13. An additive prepared by the method according to any one of claims 9 to 12.

14. A zinc ion battery, characterized in that The zinc ion battery comprises a positive electrode, a negative electrode and the electrolyte according to any one of claims 1 to 8.

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