A copper-infiltrated doped zinc metal negative electrode material for zinc ion batteries and a preparation method and application thereof

Abstract

The application discloses a copper-permeated doped zinc metal negative electrode material for a zinc ion battery and a preparation method and application thereof, and belongs to the field of battery materials. The preparation method of the negative electrode material comprises the following steps: stacking a copper foil and a zinc foil together, with the smooth surface of the copper foil being in contact with the zinc foil, then rolling into a cylindrical shape and fixing, and performing calcination under a protective gas, so that the copper-permeated doped zinc metal negative electrode material is obtained. The preparation method is simple, copper atoms are permeated into the zinc metal by heating, the surface of the zinc metal is changed from smooth to uniform granular, the structure makes it difficult for zinc ions to concentrate and deposit, the generation of a sharp tip effect and the phenomenon of uneven charge deposition are avoided, the problem of dendrite puncture of a diaphragm is effectively prevented, the polarization voltage of the battery is reduced, and the cycle stability of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a copper-doped zinc metal anode material for zinc-ion batteries, its preparation method, and its application. Background Technology

[0002] With rapid economic and technological development, the problem of dwindling fossil fuels is becoming increasingly prominent, necessitating the research, development, and utilization of efficient and clean renewable energy sources. Among numerous renewable energy sources, the technological development of lithium-ion batteries is limited by potential safety hazards and the depletion of lithium resources. Zinc (Zn) metal stands out among other alkali metals due to its high theoretical capacity (820 mAh / g), low plating / stripping potential (-0.76 V relative to the standard hydrogen electrode), and ease of processing. Zinc-ion batteries, in particular, exhibit excellent safety performance and are one of the effective ways to solve the energy crisis and environmental problems. However, the development of traditional zinc-ion batteries is limited by safety issues such as the flammability, corrosiveness, and poor thermal stability of organic electrolytes. In comparison, aqueous zinc-ion batteries (AZIB), with their high safety and high energy density, are considered the preferred direction for next-generation energy storage batteries, laying the foundation for zinc-ion batteries as a key research area in the future.

[0003] Zinc, as an amphoteric metal, is chemically reactive, reacting in both acidic and alkaline environments. Even in mild, neutral aqueous electrolytes, dendrite growth and "dead zinc" formation can occur. Zinc dendrite growth not only punctures the separator, causing short circuits, but also increases the specific surface area of ​​the negative electrode, accelerating corrosion and hydrogen evolution rates, resulting in low negative electrode utilization and coulombic efficiency. Furthermore, due to the poor adhesion between dendrites and the metal, they easily detach from the zinc negative electrode surface, forming "dead zinc," which reduces battery capacity.

[0004] Therefore, to improve battery reversibility, researchers have proposed many methods to suppress dendrite growth, hydrogen evolution, and corrosion, in order to obtain more stable and efficient zinc anodes. These methods mainly include interface modification, structural design, and electrolyte modification. However, these methods still suffer from relatively complex processes and difficulty in controlling process uniformity. Therefore, dendrite growth remains a problem that urgently needs to be solved in aqueous zinc-ion batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, one objective of this invention is to provide a method for preparing copper-doped zinc metal anode materials for zinc-ion batteries. The preparation method of this invention is simple, involving heating to allow copper atoms to penetrate into the zinc metal, transforming its surface from smooth to uniformly granular. This structure prevents zinc ions from concentrating and depositing, avoiding the formation of tip effects and uneven charge deposition. This effectively prevents dendrites from piercing the separator, while simultaneously reducing the battery's polarization voltage and improving cycle stability.

[0006] The objective of this invention is achieved through the following technical solutions.

[0007] A method for preparing a copper-doped zinc metal anode material for zinc-ion batteries includes the following steps:

[0008] Copper foil and zinc foil are stacked together, with the smooth surface of the copper foil in contact with the zinc foil. They are then rolled into a cylindrical shape and fixed, and calcined under a protective gas to obtain the copper-doped zinc metal anode material.

[0009] This invention uses heat treatment to allow copper atoms to penetrate into the zinc metal, changing the morphology and structure of the zinc metal surface from smooth to uniform granular. This reduces the local current density, making the electric field distribution uniform and promoting uniform deposition of metal ions. This restricts the preferred orientation deposition of zinc ions, effectively inhibits dendrite growth, and thus improves the cycle stability of zinc-ion aqueous batteries, exhibiting excellent electrochemical performance.

[0010] Preferably, the copper foil is on the outside of the cylinder, and the zinc foil is on the inside of the cylinder.

[0011] Preferably, the calcination temperature is 200~400℃, and the calcination time is 3~5 hours. More preferably, the calcination temperature is 400℃, and the calcination time is 5 hours.

[0012] Preferably, the calcination conditions are as follows: heating to 200-400°C at a heating rate of 2-8°C / min, and then holding at that temperature for 3-5 hours.

[0013] Preferably, the protective gas is nitrogen, and the pressure of the protective gas introduced into the reactor is 0.3~0.5MPa.

[0014] Another object of the present invention is to provide a copper-doped zinc metal anode material prepared by the preparation method, wherein the surface of the material has a uniformly distributed granular structure.

[0015] Preferably, the particle size is 30~50nm.

[0016] Another object of the present invention is to provide the application of the copper-doped zinc metal anode material prepared by the above preparation method in zinc batteries.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The present invention uses heat treatment to allow copper atoms to penetrate into the zinc metal, making its surface change from smooth to uniform granular, promoting uniform deposition of metal ions, thereby limiting the preferred orientation deposition of zinc ions, effectively inhibiting dendrite growth, avoiding the generation of tip effect and the phenomenon of uneven charge deposition, thereby improving the cycle stability of zinc ion aqueous battery, while reducing the polarization voltage of the battery, which can effectively avoid the problem of dendrite piercing the separator.

[0019] (2) Compared with ordinary zinc anode materials, the anode materials prepared by the present invention have lower polarization voltage, higher coulombic efficiency and better cycle performance.

[0020] (3) At a current density of 5 A / g, the zinc-ion battery prepared using the copper-doped zinc metal anode material of the present invention has an initial capacity of more than 210 mAh / g, and after 200 cycles, the capacity can still reach more than 190 mAh / g, showing high capacity and excellent cycle stability. Attached Figure Description

[0021] Figure 1 This is a process flow diagram for preparing copper-doped zinc metal anode material according to the present invention;

[0022] Figure 2 This is a comparison image of the copper-doped zinc metal anode material of the present invention and ordinary zinc foil.

[0023] Figure 3 The XRD patterns of the permeation-doped zinc metal anode material prepared in Example 1, and ordinary zinc foil and ordinary copper foil are shown.

[0024] Figure 4 SEM images of the permeation-doped zinc metal anode materials prepared in Example 1, Comparative Examples 1 and 2, and ordinary zinc foil;

[0025] Figure 5 This is a graph showing the long-cycle performance of a symmetrical battery.

[0026] Figure 6 A comparison chart of the coulombic efficiency and single-cycle efficiency of a half-cell.

[0027] Figure 7 (NH4) x Discharge specific capacity diagrams of VO3 / / Cu-Zn full cells and ordinary Zn full cells, and single-cycle diagrams of the two samples in the same charge-discharge range;

[0028] Figure 8 (NH4) xCV cycle diagram of VO3 / / Cu-Zn full cell. Detailed Implementation

[0029] The applicant will now provide a detailed description of the method of the present invention with reference to specific embodiments, in order to enable those skilled in the art to clearly understand the present invention. However, the following embodiments should not be construed in any way as limiting the scope of protection claimed in the present invention.

[0030] Example 1

[0031] like Figure 1 As shown, the preparation method of the copper-doped zinc metal (named Cu-Zn) negative electrode material for zinc-ion batteries in this embodiment includes the following steps:

[0032] S1. First, cut both zinc foil and copper foil into squares with a side length of 9*9 cm. Then, stack the cut squares tightly together and roll them into a cylinder. After rolling, place the copper foil on the outside of the cylinder and the zinc foil on the inside of the cylinder. At the same time, the smooth side of the copper foil is in contact with the zinc foil, and the rough side is facing outward. After assembly, place it in a tube furnace.

[0033] S2. The sample was then calcined. Before calcination, the tube furnace program was set as follows: the starting temperature was room temperature, the heating rate was 8℃ / min, the heating time was 50 min, the maximum temperature was 400℃, the holding time was 300 min, the program was terminated after holding and the cooling began.

[0034] S3. After the program is set up, check the airtightness of the device. The initial nitrogen output rate is 100 mL / min. After a period of time, reduce the output rate to 50 mL / min and control the pressure at 0.50 MPa. Calcinate the sample. After the sample in the tube furnace has been calcined and cooled to room temperature, take out the sample.

[0035] Figure 2 The image shows a comparison between the Cu-Zn anode material prepared in Example 1 and ordinary zinc foil. It can be seen that the surface of the zinc foil changes from silvery-white to light yellow.

[0036] Figure 3 The XRD patterns of the Cu-Zn anode material prepared in Example 1, ordinary zinc foil, and ordinary copper foil are shown. As can be seen from the figure, Zn and Cu are consistent with the standard PDF card, indicating that the sample has high purity. The characteristic peaks of Cu-Zn material are consistent with those of Zn in the figure, indicating that it is based on Zn. The consistency with the characteristic peaks of Cu indicates that Cu atom doping was successful.

[0037] Example 2

[0038] The preparation method of Cu-Zn negative electrode material for zinc-ion batteries in this embodiment includes the following steps:

[0039] S1. First, cut both zinc foil and copper foil into squares with a side length of 8*8 cm. Then, stack the cut squares tightly together and roll them into a cylinder. After rolling, place the copper foil on the outside of the cylinder and the zinc foil on the inside of the cylinder. At the same time, the smooth side of the copper foil is in contact with the zinc foil, and the rough side is facing outward. After assembly, place it in a tube furnace.

[0040] S2. The sample was then calcined. Before calcination, the tube furnace program was set as follows: the starting temperature was room temperature, the heating rate was 5℃ / min, the heating time was 75 min, the maximum temperature was 375℃, and the holding time was 240 min. After holding, the program was terminated and the cooling process began.

[0041] S3. After the program is set up, check the airtightness of the device. The initial nitrogen output rate is 200 mL / min. After a period of time, reduce the output rate to 60 mL / min and control the pressure at 0.45 MPa. Calcinate the sample. After the sample in the tube furnace has been calcined and cooled to room temperature, take out the sample.

[0042] Example 3

[0043] The preparation method of Cu-Zn negative electrode material for zinc-ion batteries in this embodiment includes the following steps:

[0044] S1. First, cut both zinc foil and copper foil into squares with a side length of 7*7 cm. Then, stack the cut squares tightly together and roll them into a cylinder. After rolling, place the copper foil on the outside of the cylinder and the zinc foil on the inside of the cylinder. At the same time, the smooth side of the copper foil is in contact with the zinc foil, and the rough side is facing outward. After assembly, place it in a tube furnace.

[0045] S2. The sample was then calcined. Before calcination, the tube furnace program was set as follows: the starting temperature was room temperature, the heating rate was 4℃ / min, the heating time was 80 min, the maximum temperature was 320℃, and the holding time was 240 min. After holding, the program was terminated and the cooling process began.

[0046] S3. After the program is set up, check the airtightness of the device. The initial nitrogen output rate is 300 mL / min. After a period of time, reduce the output rate to 70 mL / min and control the pressure at 0.40 MPa. Calcinate the sample. After the sample in the tube furnace has been calcined and cooled to room temperature, take out the sample.

[0047] Example 4

[0048] The preparation method of Cu-Zn negative electrode material for zinc-ion batteries in this embodiment includes the following steps:

[0049] S1. First, cut both zinc foil and copper foil into squares with a side length of 6*6 cm. Then, stack the cut squares tightly together and roll them into a cylinder. After rolling, place the copper foil on the outside of the cylinder and the zinc foil on the inside of the cylinder. At the same time, the smooth side of the copper foil is in contact with the zinc foil, and the rough side is facing outward. After assembly, place it in a tube furnace.

[0050] S2. The sample was then calcined. Before calcination, the tube furnace program was set as follows: the starting temperature was room temperature, the heating rate was 3℃ / min, the heating time was 90 min, the maximum temperature was 270℃, the holding time was 210 min, the program was terminated after holding and the cooling began.

[0051] S3. After the program is set up, check the airtightness of the device. The initial nitrogen output rate is 400 mL / min. After a period of time, reduce the output rate to 80 mL / min and control the pressure at 0.50 MPa. Calcinate the sample. After the sample in the tube furnace has been calcined and cooled to room temperature, take out the sample.

[0052] Example 5

[0053] The preparation method of Cu-Zn negative electrode material for zinc-ion batteries in this embodiment includes the following steps:

[0054] S1. First, cut both zinc foil and copper foil into squares with a side length of 5*5 cm. Then, stack the cut squares tightly together and roll them into a cylinder. After rolling, place the copper foil on the outside of the cylinder and the zinc foil on the inside of the cylinder. At the same time, the smooth side of the copper foil is in contact with the zinc foil, and the rough side is facing outward. After assembly, place it in a tube furnace.

[0055] S2. The sample was then calcined. Before calcination, the tube furnace program was set as follows: the starting temperature was room temperature, the heating rate was 2℃ / min, the heating time was 100 min, the maximum temperature was 200℃, the holding time was 180 min, the program was terminated after holding and the cooling began.

[0056] S3. After the program is set up, check the airtightness of the device. The initial nitrogen output rate is 500 mL / min. After a period of time, reduce the output rate to 90 mL / min and control the pressure at 0.30 MPa. Calcinate the sample. After the sample in the tube furnace has been calcined and cooled to room temperature, take out the sample.

[0057] Comparative Example 1

[0058] The preparation method of the Cu-Zn anode material in this comparative example is basically the same as that in Example 1, except that step S1 is as follows: First, both zinc foil and copper foil are cut into squares with a side length of 9*9 cm. Then, the cut squares are stacked tightly together, with the smooth side of the copper foil in contact with the zinc foil, and then placed in a tube furnace.

[0059] The material obtained in this comparative example is named Cu-Zn (unrolled).

[0060] Comparative Example 2

[0061] The preparation method of the Cu-Zn anode material in this comparative example is basically the same as that in Example 1, except that the rough surface of the copper foil is brought into contact with the zinc foil in step S1.

[0062] The material obtained in this comparative example is named Cu-Zn (rough surface).

[0063] SEM images of Cu-Zn prepared in Example 1, Cu-Zn (unwound) prepared in Comparative Example 1, Cu-Zn (rough surface) prepared in Comparative Example 2, and ordinary zinc foil are shown below. Figure 4 As shown, (a) and (b) are SEM images of Cu-Zn prepared in Example 1, showing a distinct granular structure on the material surface; (c) and (d) are SEM images of Cu-Zn (unrolled) prepared in Comparative Example 1, showing numerous cracks on the material surface; (e) and (f) are SEM images of Cu-Zn (rough surface) prepared in Comparative Example 2, showing some small particles on the material surface, but without significant change compared to ordinary Zn foil; (g) and (h) are SEM images of ordinary zinc foil, showing a smooth material surface. In summary, heat treatment using the specific method of this invention can transform the smooth surface of zinc metal into an uneven surface with uniform granular structure, thus homogenizing the local charge distribution and inducing Zn... 2+ Uniform deposition effectively inhibits the growth of zinc dendrites and slows down the degradation rate of the electrode.

[0064] Application examples

[0065] ① Conduct long-cycle testing at 25℃

[0066] The materials prepared in Examples 1 and 1-2, along with ordinary zinc foil, were assembled into symmetrical cells. The assembled symmetrical cells were tested on a blue electrochemical testing system. The testing conditions were: the electrolyte was 2 mol / L ZnSO4•7H2O. Two pieces of the materials prepared in Examples 1 and 1-2, along with ordinary zinc foil, were cut into 12 mm diameter discs and used as the positive and negative electrodes, respectively, to assemble symmetrical cells. The test was conducted at 5 mA cm⁻¹. -2The battery was charged and discharged under constant current density, with a charge / discharge step time of 0.2 h. After each step, the battery was left to rest for 30 s to test its cycle stability.

[0067] Test results are as follows Figure 5 As shown, from Figure 5 (a) It can be seen that the Cu-Zn / / Cu-Zn symmetric cell prepared from the material of Example 1 has a performance of 5 mA cm⁻¹ -2 At lower current densities, it exhibits more stable cycling performance and lower polarization voltage. Furthermore, it improves upon local cycling... Figure 5 As can be seen from (b) and (c), compared to the other three types, the Cu-Zn / / Cu-Zn symmetric cell exhibits a more stable and smaller polarization voltage, and maintains a stable overpotential of 40 mV throughout, demonstrating stable long-cycle performance. This indicates that it can promote Zn... 2+ Uniform deposition inhibits the growth of zinc dendrites, resulting in a significant improvement in cycle stability.

[0068] ② Conduct coulombic efficiency test at 25℃

[0069] The Cu-Zn prepared in Example 1 was cut into 12 mm diameter discs and used as negative electrodes, with a 12 mm Cu foil as the positive electrode, to assemble a Cu-Zn / / Cu half-cell. The Cu-Zn (unrolled) prepared in Comparative Example 1 was cut into 12 mm diameter discs and used as negative electrodes, with a 12 mm Cu foil as the positive electrode, to assemble a Cu-Zn / / Cu half-cell (unrolled). The Cu-Zn (rough-surfaced) prepared in Comparative Example 2 was cut into 12 mm diameter discs and used as negative electrodes, with a 12 mm Cu foil as the positive electrode, to assemble a Cu-Zn / / Cu half-cell (rough-surfaced). Ordinary Zn foil was cut into 12 mm diameter discs and used as negative electrodes, with a 12 mm Cu foil as the positive electrode, to assemble an ordinary Zn / / Cu half-cell. The assembled half-cells were tested on a blue electric shock testing system. The half-cell test conditions were as follows: the electrolyte was 2 mol / L ZnSO4•7H2O, and the flow rate was 5 mA cm⁻¹. -2 Constant current discharge was performed at current density, with a discharge step time of 0.2 h and a charging cutoff voltage of 1 V. After each step, the battery was allowed to rest for 30 s. The coulombic efficiency of the battery was then tested.

[0070] Test results are as follows Figure 6 As shown, from Figure 6 (a) It can be seen that the battery assembled using Cu-Zn in Example 1 exhibits a more stable coulombic efficiency after 250 cycles compared to the other three batteries, and the coulombic efficiency consistently remains above 95%. Figure 6 As shown in (b), (c), (d), and (e), Cu-Zn has a smaller polarization voltage of only 57 mV when comparing single cycles at the 3rd, 50th, and 100th cycles, and its cycle stability is significantly improved.

[0071] ③ Perform cyclic stability testing at 25℃

[0072] The positive electrode was prepared as follows: ammonium vanadate (positive active material), acetylene black (conductive agent), and polyvinylidene fluoride (binder) were mixed in a weight ratio of 7:2:1. N-methylpyrrolidone (N-methylpyrrolidone) was added as a solvent, and the mixture was thoroughly stirred to form a uniform positive electrode slurry. This slurry was coated onto a carbon paper substrate and then dried to obtain the positive electrode. The carbon paper thickness was 20 μm, and the active material layer on the substrate had a thickness of 30 μm. Cu-Zn from Example 1 and ordinary Zn foil were used as negative electrodes in the assembly of a full cell. The assembled battery was tested on a Blue Electric testing system. The full cell test conditions were: 2 mol / L ZnSO4•7H2O as the electrolyte; 15 mm Cu-Zn and ordinary Zn foil discs were used as negative electrodes; and a 12 mm positive electrode was used as the positive electrode. Constant current charging / discharging was performed at a current density of 5 A / g, with the charge / discharge range set to 0.4–1.8 V, to test the battery's cycle stability.

[0073] Test results are as follows Figure 7 As shown, from Figure 7 (a) It can be seen that at a current density of 5 A / g, (NH4) x The VO3 / / Cu-Zn full cell achieves an initial capacity of over 210 mAh / g, and after 200 cycles, its capacity still exceeds 190 mAh / g, demonstrating high capacity and excellent cycle stability. Figure 7 As shown in (b) and (c), the capacity curves indicate that (where the positive slope curve is the charging curve, which shows the trend of charging capacity with voltage change, indicating the charging platform; and the negative slope curve is the discharging curve, which shows the trend of discharging capacity decreasing with voltage change, reflecting the discharging platform), in the battery system with Cu-Zn as the negative electrode, the polarization voltage is smaller and the capacity platform is flatter, the curve fit is higher, and the stable voltage curve platform as a whole reflects the good compatibility of the positive and negative electrodes and the separator. On the obvious charging and discharging platforms of both, the specific capacity of Cu-Zn full cells with the same number of cycles is better than that of ordinary Zn full cells. This shows that Cu-Zn as the negative electrode of the present invention can significantly improve the long-cycle stability of zinc-ion batteries.

[0074] ④ Cyclic voltammetry (CV) performance was tested under constant temperature conditions of 25℃.

[0075] Cyclic CV tests were performed on the full cell assembled using Cu-Zn as the negative electrode in Application Example 1. The test conditions were: ChI660E electrochemical workstation, voltage range of 0.4~1.4V and scan rate of 1 mV / s, electrolyte of 2 mol / L ZnSO4•7H2O, with 15 mm Cu-Zn and ordinary Zn foil cut into discs as negative electrodes and 12 mm positive electrode as positive electrodes.

[0076] Test results are as follows Figure 8 As shown, by Figure 8 It can be seen that the potential of the oxidation peak is approximately 1.18 V, which corresponds to VO3. - The oxidation process; the reduction peak potential is approximately 0.872 V, corresponding to VO3. - The reduction process; the measured results show that the peak shape is symmetrical and sharp, indicating that the electrode has good reversibility.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a copper-doped zinc metal anode material for zinc-ion batteries, characterized in that, Includes the following steps: Copper foil and zinc foil are stacked together, with the smooth surface of the copper foil in contact with the zinc foil. The copper foil is on the outside of the cylinder, and the zinc foil is on the inside of the cylinder. Then, it is rolled into a cylindrical shape and fixed, and calcined under a protective gas to obtain the copper-doped zinc metal anode material. The protective gas is nitrogen or argon, and the pressure inside the reactor is 0.3~0.5MPa. The calcination conditions are: heating to 200~400℃ at a heating rate of 2~8℃ / min, and then holding at that temperature for 3~5h. The surface of the copper-doped zinc metal anode material has a uniformly distributed granular structure.

2. The preparation method according to claim 1, characterized in that, The calcination temperature is 400℃, and the calcination time is 5 hours.

3. The copper-doped zinc metal anode material prepared by the preparation method according to claim 1 or 2.

4. The copper-doped zinc metal anode material according to claim 3, characterized in that, The size of the granular structure is 30~50nm.

5. The application of the copper-doped zinc metal anode material as described in claim 3 or 4 in zinc batteries.

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