Electrolyte for inhibiting growth of zinc dendrites and application thereof

Abstract

The invention relates to the technical field of energy storage batteries, and particularly discloses an electrolyte for inhibiting zinc dendrite growth and application thereof. The electrolyte consists of electrolyte zinc salt, sodium lactate and water, and is beneficial to inhibiting Zn dendritic crystals and reducing the reaction rate of hydrogen precipitation. Besides, lactic acid anions (SC-) are more easily combined with water, so that a solvation shell structure of Zn < 2 + > is destroyed, deposition of Zn < 2 + > is more uniform, side reactions are reduced, and the zinc metal electrode can stably circulate for more than 500 hours under the condition of 5 mA cm <-2 >. Growth of zinc dendrites can be remarkably inhibited, the service life of the zinc metal negative electrode is prolonged, and the method has the advantages of being simple in preparation process, low in cost and good in application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage batteries, and particularly relates to an electrolyte for inhibiting zinc dendrite growth and its application. Background Art

[0002] Aqueous zinc-ion batteries (AZIBs) have emerged as promising next-generation energy storage devices due to their safety, abundance, high theoretical specific capacity (820 mAh g -1 ), and low redox potential (-0.76 V vs. SHE). Among them, zinc-manganese batteries with high redox potential, abundant resources, and low toxicity have been widely studied in academia and industry. However, manganese oxide cathodes often suffer from severe Jahn-Teller distortion, resulting in Mn loss, irreversible structural changes, and thus significantly deteriorating capacity decay. Specifically, Mn 3+ usually comes from manganese oxide electrodes. Subsequently, Mn 3+ will undergo Jahn-Teller distortion (2Mn 3+ →Mn 4+ +Mn 2+ ), leading to Mn loss during long cycling and irreversible structural changes in the positive electrode. To solve these problems, researchers usually use Mn 2+ additives to enhance the cycling stability of zinc-manganese batteries through Mn 2+ deposition. However, since Mn 2+ is prone to form dead manganese during battery cycling, ultimately resulting in a sharp decline in capacity, the improved cycling stability is ineffective. Therefore, there is an urgent need to develop a Mn-free electrolyte for zinc-manganese batteries to enhance the electrochemical performance of AZIBs. Additionally, for the zinc negative electrode, the tip effect leads to uneven electric field distribution, further causing the crazy growth of dendrites and increasing the risk of internal short circuit. Moreover, since the splitting of H2O at a lower potential leads to the hydrogen evolution reaction (HER), local pH increase, by-product (ZSH) formation, and surface passivation occur during zinc deposition. These challenges significantly affect the coulombic efficiency (CE) and long-term cycling performance of AZIBs, further affecting commercialization. Summary of the Invention

[0003] The purpose of the present invention is to provide an electrolyte for inhibiting zinc dendrite growth and its application, aiming to synergistically stabilize the positive and negative electrodes of zinc-manganese batteries, and providing an effective strategy for accelerating the scalable development of AZIBs.

[0004] To achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention is to provide an electrolyte for suppressing the growth of zinc dendrites, which is composed of an electrolyte zinc salt, sodium lactate, and water, and the chemical formula of the sodium lactate is C3H5NaO3 (SCNa).

[0005] Furthermore, the electrolyte zinc salt is any one of zinc sulfate, zinc trifluoromethanesulfonate, and zinc bis(trifluoromethylsulfonyl)imide.

[0006] Furthermore, the concentration of the electrolyte zinc salt is 2 - 3 M.

[0007] Furthermore, the concentration of the sodium lactate is 10 - 200 mM.

[0008] Furthermore, the electrolyte zinc salt is sodium sulfate.

[0009] Furthermore, the pH value of the electrolyte is 4 - 6.

[0010] The second object of the present invention is to provide the application of the above electrolyte in the preparation of an aqueous zinc-manganese ion battery, a symmetric button battery, or a half-cell.

[0011] Furthermore, in the aqueous zinc-manganese ion battery, a zinc sheet is used as the negative electrode material and manganese dioxide is used as the positive electrode material; in the symmetric button battery, a zinc sheet is used as both the positive electrode and the negative electrode; in the half-cell, a zinc sheet is used as the negative electrode and a copper foil is used as the positive electrode.

[0012] The third object of the present invention is to provide a preparation method for an aqueous zinc-manganese ion battery. The battery is composed of an electrolyte, a positive electrode, a negative electrode, and a separator, and is assembled into a sandwich structure in the order of positive electrode / separator / negative electrode, and then the electrolyte is added and sealed to obtain the battery. Among them, the electrolyte is the above electrolyte, the positive electrode material is manganese dioxide, the negative electrode material is metallic zinc, and the separator is a glass fiber membrane.

[0013] Furthermore, the preparation process of the positive electrode is as follows: manganese dioxide powder is used as the positive electrode active material, carbon black is used as the conductive agent, and polyvinylidene fluoride is used as the binder, and they are mixed according to a certain mass ratio; then they are added to an n-methylpyrrolidone solvent, ground evenly with an agate mortar, coated on graphite paper, dried, and rolled into a sheet to obtain the positive electrode.

[0014] Compared with the prior art, the beneficial effects brought by the technical solution provided by the present invention are as follows: (1) An electrolyte for suppressing the growth of zinc dendrites provided by the present invention is composed of an electrolyte zinc salt, sodium lactate, and water, and the chemical formula of the sodium lactate is C3H5NaO3 (SCNa). The lactate anion (SC - ) in this electrolyte additive is more likely to combine with water, thereby changing Zn 2+Surrounding coordination forms a more stable solvation structure, regulates the pH of the electrolyte, and reduces the occurrence of side reactions. In addition, the SCNa molecule promotes uniform deposition on the Zn (002) plane through strong interactions between the carboxyl group and Zn. 2+ with Zn 2+ (002) plane.

[0015] (2) Compared with the basic electrolyte (2 M ZnSO4), the electrolyte containing carboxylate additive provided by the present invention has great advantages in the negative electrode performance compared with 2 M ZnSO4. The Zn / / Zn symmetric battery with carboxylate added can stably cycle for more than 500 h under the condition of 5 mA cm -2 .

[0016] (4) Compared with the 2 M ZnSO4 electrolyte, the electrolyte containing carboxylate additive has great advantages in the positive electrode performance compared with the 2 M ZnSO4 electrolyte, improving the charge-discharge capacity and charge-discharge rate of the zinc-manganese battery. Description of the Drawings

[0017] Figure 1 is the chemical structural formula of sodium lactate; Figure 2 is the X-ray absorption near-edge structure (XANES) test chart of the electrolytes prepared in Example 1 and Comparative Example 1; Figure 3 is the scanning electron microscope (SEM) test chart after cycling of the Zn / / Zn symmetric batteries in Example 2 and Comparative Example 2 at a current density of 5 mA cm -2 ; Figure 4 is the in-situ optical microscope cross-section test chart of the Zn / / Zn symmetric batteries in Example 2 and Comparative Example 2 at a current density of 5 mA cm -2 when cycling for 0 min, 20 min, 40 min, and 60 min respectively; Figure 5 is the cycling test chart of the Zn / / Zn symmetric batteries in Example 2 and Comparative Example 2 at a current density of 5 mA cm -2 ; Figure 6 is the transmission electron microscope (TEM) test chart of the zinc-manganese battery in Example 3 when discharging at a current density of 0.1 A g -1 ; Figure 7 is the zinc-manganese battery in Example 3 and Example 4 at current densities of 0.1 A g -1 , 0.3 A g -1 , 0.5 A g -1 , 0.8 A g -1 , 1 A g -1, 2Ag -1 Low magnification performance test chart; Figure 8 Test charts showing the power supply to a digital watch under the abuse conditions of bending, extrusion, cutting, and drilling for the zinc-manganese bag battery in Example 3, and the ability of three bag batteries to charge a mobile phone. Detailed implementation manners

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes in detail the specific implementation manners of the present invention with reference to specific embodiments and the accompanying drawings. For those not specified in the embodiments regarding the specific test methods, instrument equipment, or conditions, they shall be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0019] An embodiment of the present invention provides an electrolyte for suppressing the growth of zinc dendrites, which is composed of an electrolyte zinc salt, sodium lactate, and water. The chemical formula of sodium lactate is SCNa, and the chemical structural formula is as Figure 1 shown; the electrolyte zinc salt can be any one of zinc sulfate, zinc trifluoromethanesulfonate, and zinc bis(trifluoromethylsulfonyl)imide. The concentration of the electrolyte zinc salt is 2 - 3 M, the concentration of sodium lactate is 10 - 200 mM, and the pH value of the electrolyte is 4 - 6. Preferably, the electrolyte zinc salt is zinc sulfate, and the pH of the electrolyte is 4.3 - 4.5.

[0020] The lactate anions (SC - in the electrolyte additive are more likely to combine with water, thereby changing the coordination around Zn 2+ to form a more stable solvation structure, adjusting the pH of the electrolyte, and reducing the occurrence of side reactions. In addition, the SCNa molecule promotes the uniform deposition on the (002) plane of Zn 2+ through the strong interaction of the carboxyl group with Zn 2+ .

[0021] An embodiment of the present invention provides a preparation method for an aqueous zinc-manganese ion battery, which is composed of an electrolyte, a positive electrode, a negative electrode, and a separator. It is assembled into a sandwich structure in the order of positive electrode / separator / negative electrode, and then the electrolyte is added and encapsulated to obtain the battery. Among them, the electrolyte is the above-mentioned electrolyte, the positive electrode material is manganese dioxide, the negative electrode material is metallic zinc, and the separator is a glass fiber membrane. The preparation process of the positive electrode is as follows: using manganese dioxide powder as the positive electrode active material, carbon black as the conductive agent, and polyvinylidene fluoride as the binder, mixing them in a mass ratio of 7:2:1; then adding them to the n-methylpyrrolidone solvent in a mass ratio of 1:1, grinding them evenly with an agate mortar, coating them on graphite paper, drying them at 75 - 80 °C, and rolling them into sheets to obtain the positive electrode.

[0022] The assembly method of the aqueous zinc-manganese ion battery is as follows: Symmetric button battery: The assembly sequence is the positive electrode case, gasket, zinc sheet, separator, zinc sheet, gasket, spring sheet, negative electrode case. Each battery uses 150 μL of electrolyte containing SCNa. The Zn / / Zn symmetric battery is assembled for electrochemical testing. Assemble the zinc-manganese full battery for electrochemical testing. The assembly sequence is the positive electrode case, gasket, zinc sheet, separator, zinc sheet, gasket, spring sheet, negative electrode case. Each battery uses 150 μL of electrolyte containing SCNa.

[0023] The aqueous zinc-manganese ion battery provided by the present invention is a new energy storage technology that is safe and environmentally friendly, and can be widely used in fields such as portable electronic devices (such as remote controls, electronic toys), medical devices (such as blood glucose meters, sphygmomanometers), household appliances (such as electric toothbrushes), and emergency devices (such as emergency lights). It uses a water-based electrolyte, avoiding the flammability risk of organic electrolytes, and is particularly suitable for scenarios with high safety requirements. In addition, zinc-manganese batteries also show potential in military equipment (such as communication equipment) and energy storage systems. Due to their low cost and rich raw material reserves, they are suitable for large-scale applications.

[0024] The aqueous zinc-manganese ion battery is significantly superior to lithium batteries in terms of safety, cost, and environmental friendliness. First, its water-based electrolyte is non-flammable, which can solve the risk of high-temperature fire or explosion of lithium batteries, and can still supply power stably even under extreme conditions such as impact and cutting. Second, the zinc resource reserves far exceed those of lithium (the global zinc reserves are about 230 million tons, while lithium is only 14.47 million tons). The raw material cost is only 1 / 3 to 1 / 4 of that of lithium batteries, and no complex production process is required. In addition, zinc-manganese batteries are non-toxic and more environmentally friendly after being discarded, while the organic electrolyte and heavy metals of lithium batteries may cause pollution.

[0025] Some positive effects have been achieved during the research and development or use of the embodiments of the present invention, and it indeed has great advantages compared with the prior art. The following content will be described in combination with the data, charts, etc. of the test process.

[0026] Example 1 This example provides an electrolyte for inhibiting the growth of zinc dendrites.

[0027] Take 20 mL of 2M ZnSO4 and 200 mM SCNa electrolyte, stir for 30 min, and ultrasonicate for 30 min to obtain the electrolyte of the aqueous zinc-manganese battery.

[0028] Example 2 This example provides an electrolyte for inhibiting the growth of zinc dendrites.

[0029] Take 5 mL of 2M ZnSO4 and 50 mM SCNa electrolyte, stir for 30 min, and ultrasonicate for 30 min to obtain the electrolyte for the aqueous zinc-manganese battery.

[0030] Assemble a Zn / / Zn symmetric battery for electrochemical testing. The assembly sequence is the positive electrode case, gasket, zinc sheet, separator, zinc sheet, gasket, spring sheet, and negative electrode case. Each battery uses 150 μL of the electrolyte containing the SCNa additive.

[0031] Comparative Example 1 Take 20 mL of 2M ZnSO4 electrolyte, stir for 30 min, and ultrasonicate for 30 min to obtain the basic electrolyte for the aqueous zinc-manganese battery.

[0032] Comparative Example 2 (1) Take 5 mL of 2M ZnSO4 electrolyte, stir for 30 min, and ultrasonicate for 30 min to obtain the electrolyte for the aqueous zinc-manganese battery.

[0033] (2) Assemble a Zn / / Zn symmetric battery for electrochemical testing. The assembly sequence is the positive electrode case, gasket, zinc sheet, separator, zinc sheet, gasket, spring sheet, and negative electrode case. Each battery uses 150 μL of the basic electrolyte.

[0034] Example 3 This example provides an aqueous zinc-manganese battery, and the specific preparation process is as follows: (1) Prepare the electrolyte: Take 5 mL of 2M ZnSO4 and 50 mM SCNa electrolyte, stir for 30 min, and ultrasonicate for 30 min to obtain the electrolyte for the aqueous zinc-manganese battery.

[0035] (2) Prepare the positive electrode: Use manganese dioxide (MnO2) powder as the positive electrode active material, carbon black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder, and mix them in a mass ratio of 7:2:1. Add them to the n-methylpyrrolidone solvent in a mass ratio of 1:1, use an agate mortar to grind them evenly, coat them on the graphite paper, dry them at 80 °C overnight, and then roll them to obtain the manganese dioxide electrode.

[0036] (3) Use the electrode in step (2) as the positive electrode, a 0.05 mm thick zinc foil as the negative electrode, and a glass fiber separator. Assemble them into a sandwich structure in the order of positive electrode / separator / negative electrode, add the electrolyte in step (1), and seal it to obtain the aqueous zinc-manganese battery.

[0037] Example 4 This example provides an aqueous zinc-manganese battery, and the specific preparation process is as follows: (1) Preparation of electrolyte: Take 5 mL of 2 M ZnSO4 electrolyte, stir for 30 min, and ultrasonicate for 30 min to obtain the aqueous zinc-manganese battery electrolyte.

[0038] (2) Preparation of the positive electrode: Use manganese dioxide (MnO2) powder as the positive electrode active material, carbon black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder, and mix them according to a mass ratio of 7:2:1. Add them to the n-methylpyrrolidone solvent according to a mass ratio of 1:1, grind them evenly using an agate mortar, coat them on graphite paper, take them out after drying overnight at 80 °C, and roll them to obtain the manganese dioxide electrode.

[0039] (3) Use the electrode in step (2) as the positive electrode, a 0.05 mm thick zinc foil as the negative electrode, and a glass fiber separator. Assemble them into a sandwich structure in the order of positive electrode / separator / negative electrode, add the electrolyte in step (1), and seal it to obtain the aqueous zinc-manganese battery.

[0040] As Figure 2 shown, it is the X-ray absorption near edge structure (XANES) test pattern of the electrolytes prepared in Example 1 and Comparative Example 1; as shown in a in the figure, compared with the electrolyte without the SCNa molecular additive, the energy of the ZnSO4+SCNa electrolyte is at a higher value, which indicates that the average charge polarization around Zn in the ZnSO4+SCNa electrolyte is higher. As shown in b in the figure, in the ZnSO4+SCNa electrolyte, the radial distance of Zn-O is 2.09 Å, and the coordination number (CN) is 5.74. In contrast, the radial distance of Zn-O in the electrolyte without the SCNa molecular additive is 2.08 Å, and the coordination number is 6.35. It shows that the SCNa molecule can effectively change the coordination structure of Zn in the ZnSO4 electrolyte and form a more stable solvation sheath. 2+ 2+

[0041] As Figure 3 shown, it is the scanning electron microscope (SEM) test pattern after cycling of the Zn / / Zn symmetric battery in Example 2 and Comparative Example 2 at a current density of 5 mA cm -2 ; The morphological characteristics of the Zn anode in the ZnSO4+SCNa and ZnSO4 electrolytes were observed using a scanning electron microscope (SEM). As shown in a in the figure, before cycling, the commercial Zn foil showed an exposed surface; as shown in b in the figure, after cycling in the electrolyte without the SCNa molecular additive, flaky and unevenly deposited zinc dendrites were observed; as shown in c in the figure, in the ZnSO4+SCNa electrolyte, the Zn deposition showed a uniform and flat morphology and had a dense deposition layer.

[0042] As Figure 4 shown, it is the Zn / / Zn symmetric battery in Example 2 and Comparative Example 2 at 5 mA cm​​-2 In-situ optical microscope cross-section test images at different current densities after cycling for 0 min, 20 min, 40 min, and 60 min respectively; in the ZnSO4 + SCNa electrolyte, the surface of the Zn electrode shows uniform and dense deposition without obvious corrosion. In the electrolyte without the SCNa molecular additive, severe HER will generate obvious bubbles on the Zn surface, while in the ZnSO4 + SCNa electrolyte, only a small amount of bubbles appear. The above results indicate that SCNa effectively inhibits the severe corrosion of Zn and HER, and promotes the 2+ uniform deposition of Zn on the surface.

[0043] As Figure 5 shown, the cycling test diagrams of the Zn / / Zn symmetric cells in Example 2 and Comparative Example 2 at a current density of 5 mA cm -2 ; Figure 5 It shows the long-term cycling performance of the Zn / / Zn symmetric cell at 5 mA cm -2 to evaluate the stability in ZnSO4 + SCNa and ZnSO4 electrolytes. In the electrolyte without added SCNa, the zinc deposition / stripping process short-circuited within the first 100 hours. While in the ZnSO4 + SCNa electrolyte, the lifespan was extended to 500 h, and the voltage-time curve showed obvious smoothness.

[0044] As Figure 6 shown, the transmission electron microscope (TEM) test images of the zinc-manganese battery in Example 3 during discharge at a current density of 0.1 A g -1 ; Figure 6 It shows the scanning transmission electron microscope (STEM) and EDS analyses of a single KMO nanowire after the first discharge process. After being fully discharged to 0.8 V, the nanowire maintained its complete nanoscale morphology, and its surface was unevenly covered by flaky structures. The corresponding STEM-EDS analysis revealed the uniform distribution of Mn and O in the nanowire, indicating that the KMO structure remained intact after discharge.

[0045] As Figure 7 shown, the rate performance test diagrams of the zinc-manganese batteries in Example 3 and Example 4 at current densities of 0.1 A g -1 , 0.3 A g -1 , 0.5 A g -1 , 0.8 A g -1 , 1 A g -1 , 2 A g -1 respectively; for the zinc-manganese battery with SCNa molecular addition, at current densities of 0.1, 0.3, 0.5, 0.8, 1.0, and 2.0 A g −1The discharge specific capacities under [conditions] are 213.7, 209.7, 190.5, 176.1, 164.5, and 131.1 mAh g respectively −1 . It is much higher than the rate of zinc-manganese batteries without using additives. Therefore, adding the SCNa additive can enhance the zinc storage performance and effectively improve the capacity of the electrode.

[0046] As Figure 8 shown, the test diagrams are for the zinc-manganese bagged batteries in Example 3 to supply power to a digital meter under the abuse conditions of bending, squeezing, cutting, and drilling, and for three bagged batteries to charge a mobile phone.

[0047] Without conflict, the above embodiments and the features in the embodiments in this article may be combined with each other.

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electrolyte for inhibiting the growth of zinc dendrites, characterized in that, The electrolyte is composed of an electrolyte zinc salt, sodium lactate, and water, and the chemical formula of the sodium lactate is C3H5NaO3.

2. The electrolyte according to claim 1, characterized in that, The electrolyte zinc salt is any one of zinc sulfate, zinc trifluoromethanesulfonate, and zinc bis(trifluoromethylsulfonyl)imide.

3. The electrolyte according to claim 1, characterized in that, The concentration of the electrolyte zinc salt is 2 - 3 M.

4. The electrolytic salt according to claim 1, wherein The concentration of the sodium lactate is 10 - 200 mM.

5. The electrolyte according to claim 4, characterized in that, The electrolyte zinc salt is zinc sulfate.

6. The electrolyte according to claim 1, characterized in that, The pH value of the electrolyte is 4 - 6.

7. Use of the electrolyte according to any one of claims 1 - 6 in the preparation of an aqueous zinc-manganese ion battery, a symmetric button battery, or a half-cell.

8. The application according to claim 7, wherein The aqueous zinc-manganese ion battery uses a zinc sheet as the negative electrode material and manganese dioxide as the positive electrode material; the symmetric button battery uses a zinc sheet as both the positive electrode and the negative electrode; the half-cell uses a zinc sheet as the negative electrode and a copper foil as the positive electrode.

9. A preparation method of an aqueous zinc-manganese ion battery, characterized in that, The battery is composed of an electrolyte, a positive electrode, a negative electrode, and a separator, and is assembled into a sandwich structure in the order of positive electrode / separator / negative electrode, and then the electrolyte is added and sealed to obtain the battery. Among them, the electrolyte is the electrolyte according to any one of claims 1 - 6, the positive electrode material is manganese dioxide, the negative electrode material is metallic zinc, and the separator is a glass fiber membrane.

10. The preparation method according to claim 9, characterized in that, The preparation process of the positive electrode is as follows: Using manganese dioxide powder as the positive electrode active material, carbon black as the conductive agent, and polyvinylidene fluoride as the binder, they are mixed according to a certain mass ratio; then added to an n-methylpyrrolidone solvent, ground evenly with an agate mortar, coated on graphite paper, dried, and rolled into sheets to obtain the positive electrode.

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