A pretreatment method for negative electrode sheet of aqueous zinc ion battery

Abstract

The application discloses a pretreatment method for a negative electrode sheet of a water-based zinc ion secondary battery, which comprises the following steps: configuring a treatment solution composed of deionized water, alcohol organic matter and zinc tetrafluoroborate, immersing zinc foil into the treatment solution and standing for 1-3 days, and then washing and drying the zinc foil to obtain a surface-modified zinc negative electrode sheet. The application first proposes to use a functional electrolyte for the pretreatment process of the zinc negative electrode, realizes active and controllable modification of the zinc negative electrode interface, and avoids uncontrollability of the traditional self-formed interface in the first cycle. After the pretreatment, a uniform and dense interface layer is formed on the surface of the zinc negative electrode, which effectively inhibits zinc dendrite growth, hydrogen evolution, corrosion and other side reactions, and significantly improves the coulomb efficiency and cycle life. The application has the advantages of simple process, cheap raw materials, no need of complex equipment, easy integration with the existing battery production line, compatible treatment solution composition with the conventional water-based electrolyte, no influence on the subsequent normal operation of the battery, and good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials and electrolyte design, and in particular to a method for pretreating the negative electrode sheet of an aqueous zinc-ion secondary battery using an electrolyte. Background Technology

[0002] Currently, zinc is commonly used as the active material in the negative electrode of aqueous zinc-ion secondary batteries, with typical structures being zinc foil or coated zinc-based negative electrode sheets. In conventional battery assembly processes, the negative electrode sheet is usually directly assembled with the separator, positive electrode, and electrolyte without pretreatment or interface modification of the negative electrode surface using a specific functionalized electrolyte before assembly or during the initial cycling stage. This leads to poor cycle stability of the zinc negative electrode and dendrite growth. To improve the cycle stability of the zinc negative electrode and suppress dendrite growth, existing technologies mainly employ the following methods: electrolyte composition design, introducing Mn into basic electrolytes such as ZnSO4 and Zn(CF3SO3)2. 2+ Organic or inorganic additives such as ions and glucose are used to adjust the solvation structure of Zn²⁺ or induce uniform deposition; the negative electrode structure is designed to reduce local current density and alleviate zinc dendrite problems by constructing a three-dimensional porous zinc matrix, nanostructure coating or composite framework; the separator is modified or an interface protective layer is introduced, and an artificial electrolyte interface layer such as ZnF2 or CaCO3 is pre-coated on the negative electrode surface to physically block uneven deposition.

[0003] While existing technologies such as adjusting additives, designing the negative electrode structure, and constructing an interface protective layer have partially alleviated the problems of poor cycle stability and dendrite growth in zinc negative electrodes, the improvement and suppression effects are not ideal. Metallic zinc is prone to hydrogen evolution reaction (HER), corrosion, and passivation in aqueous electrolytes, especially under prolonged static conditions or high current densities. These side reactions not only consume active materials but also lead to changes in electrolyte pH and an increase in interfacial impedance, thus reducing the battery's coulombic efficiency and energy efficiency. Furthermore, existing technologies generally employ a "ready-to-use" assembly method, where the negative electrode sheet directly contacts the electrolyte without any surface treatment. The initial cycle of the battery relies on the spontaneously formed solid electrolyte interphase (SEI) layer during the first charge and discharge process. This process is uncontrollable and easily leads to an uneven and poorly compact interface layer, and the formation of Zn. 2+ Localized concentrated deposition induces dendritic growth. A significant amount of Zn is consumed during the initial cycle. 2+The formation of a non-ideal interface layer or the occurrence of irreversible side reactions can lead to high initial irreversible capacity loss, affecting the overall energy utilization rate of the battery. Furthermore, this reliance on "in-situ self-repair" or "dynamic regulation" mechanisms during battery operation lacks proactive, controllable, and scalable pretreatment of the negative electrode interface during battery manufacturing. This not only limits the consistency and repeatability of battery performance, hindering large-scale industrial production, but also misses the opportunity for proactive intervention and regulation at the source, such as soaking, electrochemical activation, or interface modification of the negative electrode sheet before battery packaging. Therefore, existing technologies struggle to fundamentally achieve long-term stable cycling (>1000 cycles), lack proactive intervention, and are prone to problems such as reduced coulombic efficiency and energy efficiency. To overcome these numerous shortcomings in existing technologies, a pretreatment method for the negative electrode sheet of aqueous zinc-ion secondary batteries is urgently needed. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery. This invention uses a composite electrolyte composed of water, organic alcohols, and zinc tetrafluoroborate as the treatment solution. The zinc negative electrode sheet is immersed in this solution before battery assembly to optimize the surface interface state of the zinc negative electrode, thereby inhibiting zinc dendrite growth, reducing side reactions, and improving the battery's cycle stability and coulombic efficiency. This pretreatment method requires only immersion, cleaning, and drying steps. The process is simple, requires no complex equipment, and the composition of the treatment solution is compatible with conventional aqueous electrolytes, not affecting the subsequent normal operation of the battery. It is easily integrated with existing battery production lines and has promising prospects for large-scale industrial application.

[0005] In a first aspect, the present invention discloses a pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery, comprising the following steps:

[0006] S1. Prepare the treatment solution

[0007] Deionized water, alcoholic organic matter, and zinc tetrafluoroborate were mixed and stirred until completely dissolved to obtain a homogeneous and transparent treatment solution.

[0008] S2. Negative electrode pretreatment

[0009] Immerse the zinc negative electrode sheet in the treatment solution and let it stand for 1 to 3 days;

[0010] S3. Post-processing

[0011] After the pretreated negative electrode sheet is removed, it is rinsed and dried to obtain a surface-modified zinc negative electrode sheet.

[0012] Preferably, the volume ratio of deionized water to alcoholic organic matter in the treatment solution is 1:4 to 4:1, and the concentration of zinc tetrafluoroborate is 0.5 to 5.0 mol / L.

[0013] More preferably, the volume ratio of deionized water to alcoholic organic matter in the treatment solution is 1:1 to 3:1, and the concentration of zinc tetrafluoroborate is 1.0 to 2.0 mol / L.

[0014] Preferably, the zinc negative electrode sheet is a metallic zinc foil or a coated zinc-based negative electrode.

[0015] Preferably, the negative electrode pretreatment is a multi-step impregnation process:

[0016] S2-1. Immersion in low-concentration treatment solution

[0017] Immerse the zinc negative electrode sheet in a low-concentration treatment solution and let it stand for 12-36 hours;

[0018] S2-2. Immersion in high-concentration treatment solution

[0019] After removing the zinc negative electrode sheet, rinse and dry it, then immerse it in a high-concentration treatment solution and let it stand for 12-36 hours.

[0020] More preferably, the volume ratio of deionized water to alcoholic organic matter in the low-concentration treatment solution is 3:1 to 4:1, and the concentration of zinc tetrafluoroborate is 0.5 to 1.0 mol / L.

[0021] More preferably, the volume ratio of deionized water to alcoholic organic matter in the high-concentration treatment solution is 1:1 to 1:4, and the concentration of zinc tetrafluoroborate is 2.0 to 3.0 mol / L.

[0022] Preferably, the rinsing in step S3 involves rinsing with deionized water and anhydrous ethanol alternately 1 to 3 times.

[0023] Preferably, the settling process is performed at room temperature.

[0024] Secondly, the present invention also discloses an aqueous zinc-ion secondary battery, wherein the secondary battery is assembled from a zinc negative electrode sheet, a positive electrode, a separator, and a working electrolyte, and the zinc negative electrode sheet is pretreated according to a pretreatment method for a negative electrode sheet of an aqueous zinc-ion secondary battery disclosed in the first aspect of the present invention.

[0025] This invention provides a pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery. The method uses a composite electrolyte composed of water, organic alcohols, and zinc tetrafluoroborate as the treatment solution to impregnate the zinc negative electrode sheet before battery assembly. This optimizes the interface state of the negative electrode surface, thereby inhibiting zinc dendrite growth, reducing side reactions, and improving the cycle stability and coulombic efficiency of the battery. Compared with the prior art, this application has at least the following beneficial effects:

[0026] (1) This application proposes for the first time a pretreatment process for using functionalized electrolytes on negative electrode sheets, which realizes active and controllable modification of the zinc negative electrode interface and avoids the uncontrollability of the traditional interface that relies on the first cycle to "self-form".

[0027] (2) The pretreatment method of this application effectively suppresses zinc dendrite growth and side reactions such as hydrogen evolution and corrosion by constructing a uniform and dense interface layer on the surface of the zinc negative electrode sheet, which significantly improves the coulombic efficiency (>98%) and cycle life (>1000 times) of the battery.

[0028] (3) The pretreatment method of this application is simple, requiring only immersion, cleaning and drying steps, without the need for complex equipment, and is easy to integrate with existing battery production lines to achieve large-scale production, and has good industrial application prospects.

[0029] (4) The raw materials of the pretreatment solution used in this application are inexpensive and the composition of the pretreatment solution is compatible with conventional aqueous electrolytes. Even without rinsing and drying, it will not affect the normal operation of the battery, which provides greater convenience for large-scale production and further reduces battery costs.

[0030] (5) The alcohols in the pretreatment solution used in this application have a low freezing point, which can improve the fluidity of the pretreatment solution in low temperature environment and provide a research and development basis for low temperature battery design. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 An optical microscope photograph of the surface of the original zinc metal negative electrode sheet;

[0033] Figure 2 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Example 1 of the present invention;

[0034] Figure 3 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Embodiment 2 of the present invention;

[0035] Figure 4 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Example 3 of the present invention;

[0036] Figure 5 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Example 4 of the present invention;

[0037] Figure 6 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Example 5 of the present invention;

[0038] Figure 7 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Example 6 of the present invention;

[0039] Figure 8 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Comparative Example 2 of the present invention;

[0040] Figure 9 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Comparative Example 3 of the present invention.

[0041] Figure 10 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Comparative Example 4 of the present invention.

[0042] Figure 11 This is an optical microscope image of the surface of the zinc negative electrode sheet after electrolyte pretreatment in Comparative Example 5 of the present invention;

[0043] Figure 12 The diagram shows the cycle life of a zinc-ion battery assembled from the zinc negative electrode sheet pretreated according to Example 6 of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0045] Unless otherwise specified, all temperatures mentioned herein are in degrees Celsius, and the preferred embodiments can be freely combined as needed. Those skilled in the art will understand that the data and parameters described in the examples are merely exemplary and do not constitute a limitation of the invention. All components used in the following examples and comparative examples are compounds known in the art, and all equipment used is equipment publicly known in the art. All components and equipment used in this invention can be obtained commercially or prepared using known techniques.

[0046] This invention provides a pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery, comprising the following steps:

[0047] S1. Prepare the treatment solution

[0048] Deionized water, alcoholic organic matter, and zinc tetrafluoroborate were mixed and stirred until completely dissolved to obtain a homogeneous and transparent treatment solution.

[0049] S2. Negative electrode pretreatment

[0050] Immerse the zinc negative electrode sheet in the treatment solution and let it stand for 1 to 3 days;

[0051] S3. Post-processing

[0052] After the pretreated negative electrode sheet is removed, it is rinsed and dried to obtain a surface-modified zinc negative electrode sheet.

[0053] The alcohols in the treatment solution can adjust the polarity and dielectric constant of the solution, weakening the interaction between water molecules and Zn. 2+ The strong coordination effect of Zn. Simultaneously, alcohols also participate in the formation of an interfacial layer rich in organic-inorganic complex components, enhancing interfacial stability and thus inhibiting hydrogen evolution reaction and zinc corrosion. These side reactions not only consume active materials but also lead to changes in electrolyte pH and an increase in interfacial impedance, thereby reducing the battery's coulombic efficiency and energy efficiency. If a large amount of Zn... 2+ These substances are used to form an unstable, non-uniform, and undesirable interface layer or to cause irreversible side reactions, resulting in a high initial irreversible capacity loss and thus affecting the overall energy utilization rate of the battery.

[0054] The zinc tetrafluoroborate (Zn(BF4)2) in the treatment solution of this application can provide Zn 2+ and BF4 - Ion, BF4 - Ions preferentially decompose on the zinc surface, forming a stable interface phase rich in ZnF2, which is beneficial for constructing SEI-like structures. Zinc tetrafluoroborate can also synergistically regulate Zn content with alcohols and other organic compounds. 2+ The local coordination environment induces preferential deposition of the (002) crystal plane, thereby inhibiting zinc dendrite growth. If Zn 2+ Localized deposits of zinc tetrafluoroborate on the negative electrode surface can easily induce zinc dendrite growth, which in severe cases can penetrate the separator, causing internal short circuits, leading to battery failure and even safety risks. Furthermore, zinc tetrafluoroborate enhances the ionic conductivity of the treatment solution and promotes interfacial charge transfer.

[0055] Therefore, the preferred volume ratio of deionized water to alcoholic organic matter in the treatment solution of the present invention is 1:4 to 4:1, and the preferred concentration of zinc tetrafluoroborate is 0.5 mol / L to 5.0 mol / L. More preferably, the volume ratio of deionized water to alcoholic organic matter is 1:1 to 3:1, and the concentration of zinc tetrafluoroborate is 1.0 mol / L to 2.0 mol / L.

[0056] The zinc anode sheet described in this invention can be any form of zinc-based anode, more commonly a metallic zinc foil or a coated zinc-based anode.

[0057] To optimize the density of the interface layer and achieve a gradient distribution of its components, the negative electrode pretreatment in step S2 of this invention can also be a multi-step impregnation process, including:

[0058] S2-1. Immersion in low-concentration treatment solution

[0059] Immerse the zinc negative electrode sheet in a low-concentration treatment solution and let it stand for 12-36 hours;

[0060] S2-2. Immersion in high-concentration treatment solution

[0061] After removing the zinc negative electrode sheet, rinse and dry it, then immerse it in a high-concentration treatment solution and let it stand for 12-36 hours.

[0062] In the low-concentration treatment solution, the volume ratio of deionized water to alcoholic organic matter is 3:1 to 4:1, and the concentration of zinc tetrafluoroborate is 0.5 to 1.0 mol / L; in the high-concentration treatment solution, the volume ratio of deionized water to alcoholic organic matter is 1:1 to 1:4, and the concentration of zinc tetrafluoroborate is 2.0 to 3.0 mol / L.

[0063] The alcohols used in this invention can be common alcohol solvents in the art, such as ethylene glycol, glycerol, etc.

[0064] By pretreating the zinc negative electrode sheet through a multi-step impregnation process, a gradient interface structure of "loose inside and dense outside" can be formed on the electrode sheet surface, which not only ensures smooth ion transport but also effectively inhibits zinc dendrite penetration.

[0065] The settling process described in step S2 of this invention can be completed at room temperature, and there are no special requirements for the settling temperature. The settling time can be selected as 36 hours to balance time cost and treatment effect. Moreover, the settling process in step S2 of this invention does not require the application of any potential; static immersion is sufficient.

[0066] The rinsing in step S3 of this invention can be performed using deionized water or anhydrous ethanol. Preferably, deionized water and anhydrous ethanol are used for multiple alternating rinses, optionally 1 to 3 times. The drying process in step S3 can be carried out under vacuum or an inert atmosphere, and then naturally air-dried at room temperature. To accelerate the drying process, a hair dryer can also be used for rapid drying.

[0067] On the other hand, the present invention also provides an aqueous zinc-ion secondary battery, which is assembled from a zinc negative electrode, a positive electrode, a separator, and a working electrolyte. The zinc negative electrode has undergone the pretreatment method described above for the pretreatment of negative electrode sheets of aqueous zinc-ion secondary batteries.

[0068] The present invention will now be described in more detail with reference to exemplary embodiments. The following embodiments or experimental data are intended to illustrate the present invention by way of example, and those skilled in the art should understand that the present invention is not limited to these embodiments or experimental data.

[0069] Treatment fluid raw materials

[0070] In the following examples and comparative examples, commercially available zinc foil with a thickness of 200 μm was used as the zinc negative electrode sheet, and deionized water, ethylene glycol, glycerol and zinc tetrafluoroborate were also commercially available. Figure 1 The image shown is an optical microscope photograph of the original surface of the zinc foil.

[0071] Example 1

[0072] A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery includes the following steps:

[0073] S1. Prepare the treatment solution

[0074] Deionized water and ethylene glycol were mixed at a volume ratio of 1:4, and then zinc tetrafluoroborate was added to a final concentration of 1.0 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, precipitate-free treatment solution.

[0075] S2. Negative electrode pretreatment

[0076] The zinc foil was completely immersed in the above treatment solution and left to stand at room temperature for 36 hours; no potential was applied, and the treatment was carried out solely by static immersion.

[0077] S3. Post-processing

[0078] The pretreated zinc foil was removed from the treatment solution, rinsed once with deionized water, then rinsed once with anhydrous ethanol, and then air-dried at room temperature under an inert atmosphere to obtain the surface-modified zinc negative electrode sheet. Figure 2 The image shown is an optical microscope photograph of the zinc negative electrode sheet surface after electrolyte pretreatment in this embodiment. It can be seen that the interface layer on the zinc foil surface is uniform and dense, and there is no zinc dendrite growth.

[0079] Example 2

[0080] A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery includes the following steps:

[0081] S1. Prepare the treatment solution

[0082] Deionized water and ethylene glycol were mixed at a volume ratio of 1:2, and then zinc tetrafluoroborate was added to a final concentration of 0.5 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, precipitate-free treatment solution.

[0083] S2. Negative electrode pretreatment

[0084] The zinc foil was completely immersed in the above treatment solution and left to stand at room temperature for 72 hours; no potential was applied, and the treatment was carried out solely by static immersion.

[0085] S3. Post-processing

[0086] The pretreated zinc foil is removed from the treatment solution, rinsed once with deionized water, and then air-dried at room temperature under an inert atmosphere to obtain a surface-modified zinc negative electrode sheet. Figure 3 The image shown is an optical microscope photograph of the zinc negative electrode sheet surface after electrolyte pretreatment in this embodiment. It can be seen that the interface layer on the zinc foil surface is uniform and dense, and there is no zinc dendrite growth.

[0087] Example 3

[0088] A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery includes the following steps:

[0089] S1. Prepare the treatment solution

[0090] Deionized water and glycerol were mixed at a volume ratio of 2:1, and then zinc tetrafluoroborate was added to a final concentration of 5.0 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, precipitate-free treatment solution.

[0091] S2. Negative electrode pretreatment

[0092] The zinc foil was completely immersed in the above treatment solution and left to stand at room temperature for 24 hours; no potential was applied, and the treatment was carried out solely by static immersion.

[0093] S3. Post-processing

[0094] The pretreated zinc foil was removed from the treatment solution, rinsed once with anhydrous ethanol, and then air-dried naturally under vacuum at room temperature to obtain a surface-modified zinc negative electrode sheet. Figure 4 The image shown is an optical microscope photograph of the zinc negative electrode sheet surface after electrolyte pretreatment in this embodiment. It can be seen that the interface layer on the zinc foil surface is uniform and dense, and there is no zinc dendrite growth.

[0095] Example 4

[0096] A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery includes the following steps:

[0097] S1. Prepare the treatment solution

[0098] Deionized water and ethylene glycol were mixed at a volume ratio of 4:1, and then zinc tetrafluoroborate was added to a final concentration of 4.0 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, precipitate-free treatment solution.

[0099] S2. Negative electrode pretreatment

[0100] The zinc foil was completely immersed in the above treatment solution and left to stand at room temperature for 48 hours; no potential was applied, and the treatment was carried out solely by static immersion.

[0101] S3. Post-processing

[0102] The pretreated zinc foil was removed from the treatment solution and rinsed once each with deionized water, anhydrous ethanol, and deionized water, and then dried quickly at room temperature using a hair dryer under an inert atmosphere to obtain a surface-modified zinc negative electrode sheet. Figure 5 The image shown is an optical microscope photograph of the zinc negative electrode sheet surface after electrolyte pretreatment in this embodiment. It can be seen that the interface layer on the zinc foil surface is uniform and dense, and there is no zinc dendrite growth.

[0103] Example 5

[0104] A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery includes the following steps:

[0105] S1. Prepare the treatment solution

[0106] Deionized water and ethylene glycol were mixed at a volume ratio of 3:1, and then zinc tetrafluoroborate was added to a final concentration of 0.5 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, precipitate-free, low-concentration treatment solution.

[0107] Deionized water and ethylene glycol were mixed at a volume ratio of 1:1, and then zinc tetrafluoroborate was added to a final concentration of 2.0 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, high-concentration treatment solution without precipitate.

[0108] S2. Negative electrode pretreatment (multi-step impregnation process)

[0109] S2-1. Immersion in low-concentration treatment solution

[0110] Immerse the zinc negative electrode sheet in a low-concentration treatment solution and let it stand for 36 hours;

[0111] S2-2. Immersion in high-concentration treatment solution

[0112] After removing the zinc negative electrode sheet, rinse it with deionized water at room temperature and dry it, then immerse it in a high-concentration treatment solution and let it stand for 12 hours; no potential is applied during the above immersion process, only static soaking treatment is performed;

[0113] S3. Post-processing

[0114] The pretreated zinc foil was removed from the treatment solution, rinsed once with anhydrous ethanol, and then air-dried naturally under vacuum at room temperature to obtain a surface-modified zinc anode sheet with a gradient interface structure. Figure 6 The image shown is an optical microscope photograph of the surface of the zinc negative electrode sheet after electrolyte pretreatment in this embodiment. It can be seen that a gradient interface structure of "loose inside and dense outside" is formed on the surface of the zinc foil, and there is no zinc dendrite growth.

[0115] Example 6

[0116] A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery includes the following steps:

[0117] S1. Prepare the treatment solution

[0118] Deionized water and glycerol were mixed at a volume ratio of 4:1, and then zinc tetrafluoroborate was added to a final concentration of 1.0 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, precipitate-free, low-concentration treatment solution.

[0119] Deionized water and glycerol were mixed at a volume ratio of 1:4, and then zinc tetrafluoroborate was added to a final concentration of 3.0 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, high-concentration treatment solution without precipitate.

[0120] S2. Negative electrode pretreatment (multi-step impregnation process)

[0121] S2-1. Immersion in low-concentration treatment solution

[0122] Immerse the zinc negative electrode sheet in a low-concentration treatment solution and let it stand for 24 hours;

[0123] S2-2. Immersion in high-concentration treatment solution

[0124] After removing the zinc negative electrode sheet, rinse it with deionized water at room temperature and dry it, then immerse it in a high-concentration treatment solution and let it stand for 24 hours; no potential is applied during the above immersion process, only static soaking treatment is performed;

[0125] S3. Post-processing

[0126] The pretreated zinc foil was removed from the treatment solution, rinsed once with deionized water and once with anhydrous ethanol, and then air-dried at room temperature under an inert atmosphere to obtain a surface-modified zinc anode sheet with a gradient interface structure. Figure 7 The image shown is an optical microscope photograph of the surface of the zinc negative electrode sheet after electrolyte pretreatment in this embodiment. It can be seen that a gradient interface structure of "loose inside and dense outside" is formed on the surface of the zinc foil, and there is no zinc dendrite growth.

[0127] Comparative Example 1

[0128] Untreated zinc foil was used as the negative electrode of an aqueous zinc-ion secondary battery.

[0129] Comparative Example 2

[0130] This comparative example uses the same pretreatment method as the negative electrode sheet of an aqueous zinc-ion secondary battery in Example 1, except that zinc tetrafluoroborate is replaced with zinc hexafluorophosphate. Figure 8 The image shown is an optical microscope image of the zinc negative electrode surface after electrolyte pretreatment in this comparison. It can be seen that there are pores in the interface layer on the zinc foil surface and obvious zinc dendrite growth.

[0131] Comparative Example 3

[0132] This comparative example is exactly the same as the pretreatment method for the negative electrode sheet of the aqueous zinc-ion secondary battery in Example 1. The only difference is that the treatment solution uses only deionized water as a solvent. That is, in step S1, zinc tetrafluoroborate is added to deionized water to prepare a treatment solution with a final concentration of 1.0 mol / L. Figure 9 The image shown is an optical microscope image of the zinc negative electrode surface after electrolyte pretreatment in this comparison. It can be seen that the interface layer structure on the zinc foil surface is loose and zinc dendrite growth is obvious.

[0133] Comparative Example 4

[0134] This comparative example uses the same pretreatment method as the negative electrode sheet of an aqueous zinc-ion secondary battery in Example 1, the only difference being that ethylene glycol is replaced with ethylene glycol dimethyl ether. Figure 10 The image shown is an optical microscope photograph of the surface of the zinc negative electrode sheet after electrolyte pretreatment in this comparison. It can be seen that there are a large number of zinc dendrites on the surface of the zinc foil.

[0135] Comparative Example 5

[0136] A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery includes the following steps:

[0137] S1. Prepare the treatment solution

[0138] Deionized water and ethylene glycol were mixed at a volume ratio of 5:1, and then zinc tetrafluoroborate was added to a final concentration of 0.4 mol / L. The mixture was stirred thoroughly until completely dissolved to obtain a transparent, precipitate-free treatment solution.

[0139] S2. Negative electrode pretreatment

[0140] The zinc foil was completely immersed in the above treatment solution and left to stand at room temperature for 72 hours; no potential was applied, and the treatment was carried out solely by static immersion.

[0141] S3. Post-processing

[0142] The pretreated zinc foil was removed from the treatment solution, rinsed once with deionized water, then rinsed once with anhydrous ethanol, and then air-dried at room temperature under an inert atmosphere to obtain the surface-modified zinc negative electrode sheet. Figure 11 The image shown is an optical microscope photograph of the zinc negative electrode sheet surface after electrolyte pretreatment in this embodiment. It can be seen that the interface layer on the zinc foil surface is rough and contains a small amount of zinc dendrites. The interface layer structure is significantly worse than that in the previous embodiment.

[0143] Battery assembly and testing

[0144] The zinc negative electrode sheets prepared in Examples 1-6 and Comparative Examples 1-5 of this invention were used to assemble aqueous zinc-ion secondary batteries with a positive electrode, a separator, and a standard working electrolyte (2M ZnSO4 aqueous solution). Charge-discharge cycle tests were conducted at a 0.5C rate, and the capacity retention and coulombic efficiency were tested after 300 cycles. The test results are shown in Table 1.

[0145] Table 1. Test results of electrical performance of aqueous zinc-ion batteries

[0146]

[0147] Performance test results analysis

[0148] As shown in Table 1, the aqueous zinc-ion batteries assembled from the zinc anodes obtained in Examples 1-6 of this invention exhibit excellent capacity retention, coulombic efficiency, and cycle life exceeding 1000 cycles. Figure 12 As can be seen, the zinc-ion battery composed of the zinc negative electrode of Example 6 still maintains a stable specific capacity after 1500 cycles.

[0149] Comparative Example 1 of this invention is a zinc-ion battery assembled using an untreated zinc anode. All performance indicators are the worst, with a capacity retention rate of only 71.7%, a coulombic efficiency of only 76.5%, and a cycle life of only 300 cycles. Compared with Examples 1-6, this highlights the improvement of the zinc anode pretreatment process of this invention on the electrochemical performance of zinc-ion batteries.

[0150] In Comparative Example 2 of this invention, zinc tetrafluoroborate in Example 1 was replaced with zinc hexafluorophosphate. As can be seen from Table 1, the zinc anode was pretreated with zinc hexafluorophosphate, but the expected effect was not achieved. The zinc-ion battery composed of zinc anode from Comparative Example 2 still had poor capacity retention, coulombic efficiency, and cycle life, which shows the key role of zinc tetrafluoroborate in the pretreatment solution.

[0151] In Comparative Example 3 of this invention, the treatment solution used only deionized water as a solvent, and did not contain alcoholic organic solvents such as ethylene glycol and glycerol. As shown in Table 1, the electrical performance of the zinc-ion battery assembled using the zinc anode of Comparative Example 3 was still unsatisfactory. Using alcoholic organic compounds as solvents in the pretreatment solution can significantly improve the treatment effect of zinc tetrafluoroborate on the zinc anode sheet. In Comparative Example 4 of this invention, the ethylene glycol in Example 1 was replaced with ethylene glycol dimethyl ether as a solvent component. The treatment effect of the pretreatment solution in Comparative Example 4 was still unsatisfactory. After electrolyte pretreatment, a large number of zinc dendrites were present on the surface of the zinc anode sheet, resulting in poor performance of the zinc-ion battery assembled using this zinc anode.

[0152] Comparative Example 5 is essentially the same as the Examples of the present invention, except that the concentration of zinc tetrafluoroborate in the pretreatment solution is lower, at only 0.4 mol / L. Although the concentration of zinc tetrafluoroborate in Comparative Example 5 is lower than the preferred concentration of the present invention, it can be seen that after immersion pretreatment with the pretreatment solution of Comparative Example 5, the surface microstructure of the zinc anode is significantly improved, with only a small amount of dendrite growth. Moreover, the electrical performance of the zinc-ion battery obtained thereby is significantly improved compared with Comparative Examples 1-4, but it is still lower than the electrical performance of the zinc-ion batteries in Experimental Examples 1-6. This indicates that the concentration of zinc tetrafluoroborate as the core effective component in the pretreatment solution has a significant impact on the pretreatment effect.

[0153] Correspondingly, the zinc-ion batteries in Experiments 5 and 6 of this invention exhibited the best electrical performance among all experimental examples. This indicates that increasing the zinc tetrafluoroborate concentration enhances the pretreatment effect, but when the zinc tetrafluoroborate concentration increases to 3.0 mol / L, the improvement effect on the zinc anode almost reaches its limit. On the other hand, the multi-step impregnation process also significantly enhances the pretreatment effect. The "poor inside, dense outside" gradient interface structure formed on the zinc anode surface significantly improves the capacity retention, coulombic efficiency, and cycle life of the zinc-ion battery.

[0154] In summary, this invention is the first to propose a pretreatment process for zinc anode sheets using functionalized electrolytes, achieving active and controllable modification of the zinc anode interface and avoiding the uncontrollability of the traditional method that relies on the "self-formation" of the interface during the first cycle. The zinc anode surface treated by this invention forms a uniform and dense interface layer, and even a surface density gradient interface structure, effectively suppressing zinc dendrite growth and side reactions such as hydrogen evolution and corrosion. Zinc secondary batteries assembled from anodes pretreated by this invention exhibit significantly improved coulombic efficiency (>98%) and cycle life (>1000 cycles). This pretreatment method is simple, uses inexpensive raw materials, requires no complex equipment, and is easily integrated with existing battery production lines. The treatment solution is compatible with conventional aqueous electrolytes and does not affect the normal operation of subsequent batteries, demonstrating promising industrial application prospects. This process is applicable to electrochemical energy storage units in large-scale energy storage systems, stationary energy storage devices, and portable electronic devices, especially suitable for applications with high requirements for cycle life and operational safety, and possesses good industrial scalability and system compatibility.

[0155] All materials used in this invention are commercially available and can be purchased from retail sources.

[0156] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pretreatment method for the negative electrode sheet of an aqueous zinc-ion secondary battery, characterized in that, Includes the following steps: S1. Prepare the treatment solution Deionized water, alcoholic organic matter, and zinc tetrafluoroborate were mixed and stirred until completely dissolved to obtain a homogeneous and transparent treatment solution. S2. Negative electrode pretreatment Immerse the zinc negative electrode sheet in the treatment solution and let it stand for 1 to 3 days; S3. Post-processing After the pretreated negative electrode sheet is taken out, it is rinsed and dried to obtain a surface-modified zinc negative electrode sheet. The negative electrode sheet pretreatment is a multi-step impregnation process: S2-1. Immersion in low-concentration treatment solution The zinc negative electrode sheet is immersed in a low-concentration treatment solution and left to stand for 12 to 36 hours; the volume ratio of deionized water to alcohol organic matter in the low-concentration treatment solution is 3:1 to 4:1, and the concentration of zinc tetrafluoroborate is 0.5 to 1.0 mol / L. S2-2. Immersion in high-concentration treatment solution After removing the zinc negative electrode sheet, rinse and dry it, then immerse it in a high-concentration treatment solution and let it stand for 12 to 36 hours; the volume ratio of deionized water to alcohol organic matter in the high-concentration treatment solution is 1:1 to 1:4, and the concentration of zinc tetrafluoroborate is 2.0 to 3.0 mol / L.

2. The pretreatment method according to claim 1, characterized in that, The zinc negative electrode sheet is a metallic zinc foil or a coated zinc-based negative electrode.

3. The pretreatment method according to claim 1, characterized in that, The rinsing described in step S3 involves rinsing 1 to 3 times alternately with deionized water and anhydrous ethanol.

4. The pretreatment method according to claim 1, characterized in that, The settling process is completed at room temperature.

5. An aqueous zinc-ion secondary battery, characterized in that, The secondary battery is assembled from a zinc negative electrode sheet, a positive electrode, a separator, and a working electrolyte. The zinc negative electrode sheet is pretreated according to any one of claims 1-4 using a pretreatment method for negative electrode sheets of aqueous zinc-ion secondary batteries.

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