Preparation method of fluorinated boron nitride coating of long-circulation stable battery negative electrode

Abstract

The invention discloses a preparation method of a fluorinated boron nitride coating of a long-circulation stable battery negative electrode, which comprises the following steps: mixing boron nitride and ammonium fluoride according to a certain proportion, uniformly grinding, adding a solvent according to a proportion, uniformly mixing, transferring into a reaction kettle for reaction, and washing, centrifugally drying a reaction product to obtain fluorinated boron nitride; mixing fluorinated boron nitride with a binder, dropwise adding an organic solvent, and fully stirring to obtain coating slurry; a passivation layer on the surface of the zinc foil is removed, unoxidized Zn is exposed, and the treated zinc foil is subjected to ultrasonic treatment and dried; and uniformly coating the surface of the treated zinc foil with the coating slurry, and carrying out vacuum drying to obtain the zinc foil containing the fluorinated boron nitride coating. The fluorinated boron nitride coating is adopted to protect the zinc negative electrode, hydrogen evolution reaction and growth of zinc dendrites are inhibited, zinc ion deposition is uniform, and the battery has better electrochemical long-term cyclicity.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and in particular relates to a method for preparing a boron fluoride coating for a long-cycle stable battery negative electrode. Background Technology

[0002] In order to cope with global climate change and energy crisis, China strives to build a new power system based on new energy sources. Therefore, the efficient conversion and storage of renewable energy is a key research direction at present. Due to its high energy density, high working voltage, rechargeability and mature commercial development, lithium-ion batteries play a very important role in the development of the modern era. However, the safety issues of lithium-ion batteries hinder their development and application. Compared with organic electrolyte system batteries, aqueous electrolyte system batteries have gradually become a popular research direction in the field of energy storage in recent years due to their good safety and high environmental friendliness. Among the many aqueous multivalent metal ions, zinc metal as the negative electrode material of aqueous batteries has the following advantages: (1) high theoretical capacity (820 mAh g-1), (2) suitable redox potential in aqueous electrolyte (-0.76 V vs. SHE), (3) abundant resources, (4) lower polarization compared with metal materials such as Mg and Al. Therefore, aqueous secondary zinc batteries are considered to be a strong contender for the next generation of electrochemical energy storage systems.

[0003] While aqueous zinc-ion batteries offer numerous advantages and hold promise as next-generation energy storage devices, several reactions in practical applications can impact the zinc deposition process. These reactions reduce zinc stripping efficiency and lead to incomplete zinc dissolution. Consequently, some zinc gradually accumulates unevenly on the zinc anode surface, forming needle-like zinc dendrites. The continuous formation and growth of these dendrites eventually puncture the separator, causing a short circuit. Furthermore, the mechanical rigidity and uneven structure of the formed dendrites cause them to detach from the zinc anode surface, creating "dead zinc," which reduces the amount of active material and capacity. At the electrode / electrolyte interface, phenomena such as hydrogen evolution reaction, metal corrosion, and passivation also occur. These phenomena are not independent but always interact, ultimately resulting in decreased coulombic efficiency, cycle stability, reversibility, and capacity of the zinc-ion battery. Therefore, it is necessary to regulate the stability of the zinc metal anode / electrolyte interface in aqueous zinc-ion batteries to suppress zinc dendrite formation, corrosion, and hydrogen evolution reaction, in order to achieve safe and stable aqueous energy storage devices. Summary of the Invention

[0004] The main technical problem solved by this invention is to improve the interfacial stability of zinc metal anode / electrolyte in aqueous zinc-ion batteries, thereby addressing the safety issues of lithium-ion batteries.

[0005] To address the above problems, this invention provides a method for preparing a boron fluoride coating for a long-cycle stable battery negative electrode, characterized by the following steps: Step S1, boron nitride and ammonium fluoride are mixed and ground evenly in a certain proportion, a solvent is added in a certain proportion, mixed evenly, transferred to a reaction vessel for reaction, and the reaction product is washed, centrifuged and dried to obtain boron fluoride.

[0006] Step S2: After mixing boron fluoride nitride with the binder, add organic solvent dropwise and stir thoroughly to obtain a coating slurry.

[0007] Step S3: Remove the passivation layer from the zinc foil surface to expose the unoxidized Zn. Ultrasonize and dry the treated zinc foil for later use.

[0008] Step S4: The coating slurry obtained in S2 is uniformly applied to the surface of the zinc foil treated in S3, and then dried under vacuum to obtain a zinc foil containing a boron fluoride coating.

[0009] Preferably, the boron nitride in step S1 is hexagonal boron nitride in powder form; the ammonium fluoride is a white crystalline powder.

[0010] Preferably, the reaction temperature in the reactor during step S1 is 150-300℃, and the reaction time is 12-36 hours.

[0011] Preferably, the reaction product washing in step S1 is performed by alternating washing with anhydrous ethanol and deionized water until the pH is neutral.

[0012] Preferably, the mass ratio of boron fluoride nitride to the binder in step S2 is 6:1-9:1.

[0013] Preferably, the stirring speed in step S2 is 300-600 rpm, and the stirring time is 2-8 hours.

[0014] Preferably, in step S3, the passivation layer on the zinc foil surface is removed using sandpaper, wherein the sandpaper has a mesh size of 400-4000.

[0015] Preferably, the coating thickness in step S4 is in the range of 5-30 micrometers.

[0016] Preferably, the vacuum drying temperature in step S4 is 40-80℃, and the drying time is 12h-24h.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention protects the zinc anode by using a boron fluoride-nitride coating, which can effectively suppress the generation of hydrogen evolution reaction, inhibit the growth of zinc dendrites, uniformly deposit zinc ions, improve the interfacial stability of zinc metal anode / electrolyte in aqueous zinc-ion batteries, improve the safety of lithium-ion batteries, and give the batteries better long-term electrochemical cycle performance. Attached Figure Description

[0018] Figure 1 A scanning electron microscope schematic diagram of a zinc sheet coated with boron fluoride nitride and an elemental analysis of the coating.

[0019] Figure 2 In Example 1, the current density was 1 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during the charging and discharging process of the lower Zn electrode.

[0020] Figure 3 In Example 1, the current density was 1 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during charge and discharge of a 10-micron coated BN@Zn electrode.

[0021] Figure 4 In Example 1, the current density was 1 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during charge and discharge of a PVDF@Zn electrode with a 10-micron coating thickness.

[0022] Figure 5 In Example 1, the current density is 1 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during charge and discharge of a 10-micron coated F-BN@Zn electrode.

[0023] Figure 6 In Example 2, the current density was 2 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during the charging and discharging process of the lower Zn electrode.

[0024] Figure 7 In Example 2, the current density was 2 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during charge and discharge of F-BN@Zn electrode with a 5-micron coating thickness.

[0025] Figure 8 Example 2 was performed at a current density of 2 mA cm⁻¹-2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during charge and discharge of a 10-micron coated F-BN@Zn electrode.

[0026] Figure 9 In Example 2, the current density was 2 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during charge and discharge of F-BN@Zn electrode with a 20-micron coating thickness.

[0027] Figure 10 In Example 2, the current density was 2 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during charge and discharge of F-BN@Zn electrode with a 30-micron coating thickness.

[0028] Figure 11 In Example 2, the current density was 0.5 mA cm⁻¹ -2 The surface current density is 0.5 mAh cm⁻¹. -2 The stability of coulombic efficiency during the charge and discharge process of the F-BN@Zn electrode.

[0029] Figure 12 In Example 2, the current density was 0.5 mA cm⁻¹ -2 The surface current density is 0.5 mAh cm⁻¹. -2 The stability of coulombic efficiency during the charging and discharging process of the Zn electrode.

[0030] Figure 13 In Example 3, the current density was 1 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during the charging and discharging process of the lower Zn electrode.

[0031] Figure 14 In Example 3, the current density was 1 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during the charging and discharging process of F-BN@Zn (F-BN:PVDF=8:1).

[0032] Figure 15 In Example 3, the current density was 1 mA cm⁻¹ -2 The surface current density is 1 mAh cm⁻¹ -2 Voltage stability during the charging and discharging process of F-BN@Zn (F-BN:PVDF=9:1). Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Example 1 0.2 g of hexagonal boron nitride (BN) powder was mixed evenly with 1 g of ammonium fluoride and further ground into a homogeneous state. Then, 20 ml of deionized water was added, mixed evenly, and transferred to a reaction vessel. The mixture was reacted at 180 °C for 24 h and then cooled to room temperature. The resulting reaction product was washed alternately with anhydrous ethanol and deionized water until the pH of the supernatant was close to neutral. After vacuum drying of the reactants, boron nitride fluoride (F-BN) was obtained. The obtained boron nitride fluoride was mixed with polyvinylidene fluoride (PVDF) binder at a mass ratio of 8:1, and N-methylpyrrolidone (NMP) organic solvent was added dropwise. The mixture was stirred at 600 rpm for 2 h to obtain a coating slurry. Take out a 10*10 zinc foil and remove the passivation layer with 4000-grit sandpaper to expose the unoxidized Zn. Sonicate the treated zinc foil in anhydrous ethanol and dry it for later use. Apply the coating slurry evenly to the surface of the treated zinc foil with a coating thickness of 10 micrometers. Dry the coated zinc foil at 40°C under vacuum for 24 hours to obtain fluorinated boron nitride coated zinc foil (F-BN@Zn).

[0035] The scanning electron microscope schematic diagram of F-BN@Zn and the elemental analysis of the coating in this embodiment are as follows: Figure 1 As shown, boron nitride fluoride was successfully coated onto the zinc sheet surface. To evaluate the long-cycle stability of the boron nitride fluoride-coated zinc (F-BN@Zn) electrode, a current density of 1 mA cm⁻¹ was used. -2 The surface current density is 1 mAh cm⁻¹ -2 Under the given conditions, voltage stability tests were conducted on Zn electrodes, zinc electrodes coated with boron nitride (BN) with a 10-micron coating thickness (BN@Zn), zinc electrodes coated with polyvinylidene fluoride (PVDF) with a 10-micron coating thickness (PVDF@Zn), and F-BN@Zn electrodes with a 10-micron coating thickness during charge and discharge. From... Figure 2 , Figure 3 , Figure 4 , Figure 5 As can be seen, the F-BN@Zn electrode prepared in this embodiment, with a coating thickness of 10 micrometers, achieves a current density of 1 mA cm⁻¹. -2 The surface current density is 1 mAh cm⁻¹ -2 Under certain conditions, it exhibits long-term cycling stability.

[0036] Example 2 1.2 g of hexagonal boron nitride (BN) powder was mixed with 6 g of ammonium fluoride and further ground into a homogeneous form. Then, 120 ml of deionized water was added, mixed thoroughly, and transferred to a reaction vessel. The mixture was reacted at 180 °C for 24 h and then cooled to room temperature. The resulting reaction product was washed alternately with anhydrous ethanol and deionized water until the pH of the supernatant was close to 7. After vacuum drying, boron nitride fluoride (F-BN) was obtained. The obtained boron fluoride nitride was mixed with polyvinylidene fluoride (PVDF) binder at a mass ratio of 8:1, and then N-methylpyrrolidone (NMP) organic solvent was added dropwise. The mixture was stirred at 300 rpm for 8 hours to obtain a coating slurry. A 10*10 zinc foil was taken out and the passivation layer was removed with 400-4000 grit sandpaper to expose the unoxidized Zn. The treated zinc foil was ultrasonically dried in anhydrous ethanol and set aside. The coating slurry was uniformly applied to the surface of the treated zinc foil with coating thicknesses of 5 μm, 10 μm, 20 μm, and 30 μm. The coated zinc foil was dried under vacuum at 40-80℃ for 12-24 hours to obtain boron fluoride nitride coated zinc foil (F-BN@Zn).

[0037] To evaluate the voltage stability of the F-BN@Zn coated electrodes of different thicknesses during charge and discharge, a current density of 2 mA cm⁻¹ was used. -2 The surface current density is 1 mAh cm⁻¹ -2 Under certain conditions, the voltage stability during the charge-discharge process of uncoated Zn electrodes and F-BN@Zn electrodes coated with coatings of 5 μm, 10 μm, 20 μm, and 30 μm thicknesses was tested. Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 It can be seen that the F-BN@Zn electrode prepared in this embodiment has cycle stability under different coating thicknesses, with the cycle stability being more outstanding when the coating thickness is 10 micrometers.

[0038] To evaluate the stability of the coulombic efficiency of the prepared coated electrode during charge and discharge, a current density of 0.5 mA cm⁻¹ was used. -2 The surface current density is 0.5 mAh cm⁻¹. -2 Under certain conditions, the coulombic efficiency stability during charge-discharge processes of an uncoated Zn electrode and an F-BN@Zn electrode coated with a thickness of 10 micrometers was tested. Figure 11 and Figure 12 It can be seen that the 10-micrometer-thick F-BN@Zn electrode exhibits good coulombic efficiency stability during charge and discharge.

[0039] Example 3 1.2 g of hexagonal boron nitride (BN) powder was mixed with 6 g of ammonium fluoride and further ground into a homogeneous form. Then, 120 ml of deionized water was added, mixed thoroughly, and transferred to a reaction vessel. The mixture was reacted at 180 °C for 24 h and then cooled to room temperature. The resulting reaction product was washed alternately with anhydrous ethanol and deionized water until the pH of the supernatant was close to 7. After vacuum drying, boron nitride fluoride (F-BN) was obtained. The obtained boron fluoride nitride and polyvinylidene fluoride (PVDF) binder were mixed at a mass ratio of 9:1, and then N-methylpyrrolidone (NMP) organic solvent was added dropwise. The mixture was stirred at 300 rpm for 8 hours to obtain the coating slurry.

[0040] Take out a 10*10 zinc foil and remove the passivation layer with 400-4000 grit sandpaper to expose the unoxidized Zn. Ultrasonize the treated zinc foil in anhydrous ethanol and dry it for later use. The coating slurry was uniformly applied to the surface of the treated zinc foil with a coating thickness of 10 micrometers. The coated zinc foil was then dried under vacuum at 40-80℃ for 12-24 hours to obtain fluorinated boron nitride coated zinc foil (F-BN@Zn).

[0041] To evaluate the voltage stability of the fabricated coated electrode F-BN@Zn during charge and discharge, a current density of 1 mA cm⁻¹ was used. -2 The surface current density is 1 mAh cm⁻¹ -2 Under certain conditions, the voltage stability during the charge-discharge process of an uncoated Zn electrode and an F-BN@Zn electrode coated with a 10-micron coating was tested. Figure 13 , Figure 14 It can be seen that the F-BN@Zn electrode prepared in this embodiment has cycle stability.

[0042] To evaluate the voltage stability changes of coatings prepared from boron fluoride nitride and polyvinylidene fluoride (PVDF) binders mixed in different mass ratios during charge and discharge, a current density of 1 mA cm⁻¹ was used. -2 The surface current density is 1 mAh / cm³. -2 Under the specified conditions, the voltage stability of F-BN@Zn electrodes with F-BN:PVDF=8:1 and F-BN:PVDF=9:1 coatings with a coating thickness of 10 micrometers during the charge and discharge process was tested. Figure 14 , Figure 15 It can be seen that the coatings prepared with mass ratios of F-BN:PVDF=8:1 and F-BN:PVDF=9:1 exhibit good voltage stability during charge and discharge processes.

[0043] In summary, the fluorinated boron nitride coated battery anode prepared by this invention has a good protective effect on the Zn electrode, can improve the interfacial stability of zinc metal anode / electrolyte in aqueous zinc-ion batteries, and effectively solve the safety problems of lithium-ion batteries. Among them, the F-BN@Zn electrode with a coating thickness of 10 micrometers shows the best performance during charge and discharge.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a boron fluoride coating for a negative electrode of a long-cycle stable battery, characterized in that, Includes the following steps: Step S1: Mix and grind boron nitride and ammonium fluoride in a certain proportion, then add solvent, mix evenly, transfer to a reaction vessel for reaction, and obtain boron nitride fluoride after washing, centrifugation and drying of the reaction product. Step S2: After mixing boron fluoride nitride with the binder, add organic solvent dropwise, stir thoroughly to obtain a coating slurry, and set aside. Step S3: Remove the passivation layer on the surface of the zinc foil, and then sonicate and dry the treated zinc foil. Step S4: The coating slurry obtained in step S2 is uniformly coated onto the surface of the zinc foil treated in step S3, and then vacuum dried to obtain a zinc foil containing a boron fluoride coating.

2. The method according to claim 1, characterized in that, In step S1, the boron nitride is hexagonal boron nitride and is in the form of powder; the ammonium fluoride is in the form of white crystalline powder.

3. The method according to claim 1, characterized in that, In step S1, the reaction temperature in the reactor is 150-300℃, and the reaction time is 12-36h.

4. The method according to claim 1, characterized in that, The reaction product in step S1 is washed with anhydrous ethanol and deionized water alternately until neutral.

5. The method according to claim 1, characterized in that, In step S2, the mass ratio of boron fluoride nitride to the binder is 6:1 to 9:

1.

6. The method according to claim 1, characterized in that, In step S2, the stirring speed is 300-600 rpm and the stirring time is 2-8 hours.

7. The method according to claim 1, characterized in that, In step S3, the passivation layer on the zinc foil surface is removed using sandpaper with a mesh size of 400-4000.

8. The method according to claim 1, characterized in that, In step S4, the thickness of the boron fluoride nitride ranges from 5 to 30 micrometers.

9. The method according to claim 1, characterized in that, In step S4, the vacuum drying temperature is 40-80℃ and the drying time is 12h-24h.

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