An aqueous zinc-ion battery ferroelectric separator and a preparation method and application thereof

Abstract

This application provides a ferroelectric separator for an aqueous zinc-ion battery, its preparation method, and its application. The aqueous zinc-ion battery separator includes a core layer and surface layers on both sides of the core layer; the surface layers include ferroelectric ceramic materials and a first nanocellulose layer; the core layer includes a second nanocellulose layer. This application employs a composite structure of ferroelectric ceramic materials and nanocellulose, constructing a mesoporous composite layer separator through a unique surface-core-surface layer design. The polarization characteristics of the ferroelectric ceramic materials are utilized to actively regulate the distribution behavior of zinc ions at the electrode interface, thereby suppressing dendrite growth and hydrogen evolution side reactions, improving ion transport efficiency, and enabling the aqueous zinc-ion battery to exhibit long cycle life and cycle stability.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to an aqueous zinc-ion battery ferroelectric separator, its preparation method, and its application. Background Technology

[0002] In recent years, energy storage batteries have attracted widespread attention due to their excellent performance. Aqueous zinc-ion batteries, with their advantages of low cost and high safety, are gradually becoming one of the most promising electrochemical energy storage devices. Firstly, aqueous solutions have higher ionic conductivity than traditional organic solvent electrolytes, making them less prone to thermal runaway or explosions, thus offering greater reliability and safety for storing large-scale electrical energy. Secondly, zinc has a low redox potential, enabling efficient battery charge-discharge reactions as a negative electrode material. Furthermore, compared to lithium, zinc resources are relatively abundant and less expensive, helping to reduce battery manufacturing costs and promote the commercialization and widespread adoption of battery technology. Simultaneously, the use of zinc-ion batteries avoids the safety issues encountered in traditional lithium-ion batteries. Therefore, the significance of researching aqueous zinc-ion batteries lies in promoting the large-scale storage and utilization of renewable energy, facilitating energy transition, and realizing green energy.

[0003] Conventional aqueous zinc-ion batteries use metallic zinc as the anode, an aqueous solution containing zinc ions as the electrolyte, and materials such as glass fiber as the separator. However, due to side reactions, dendrite growth, passivation, and surface corrosion, the metal anode exhibits poor reversibility and stability, which is the main bottleneck limiting its application.

[0004] Therefore, developing a separator that can suppress dendrite growth and hydrogen evolution side reactions, improve ion transport efficiency, and thus enable aqueous zinc-ion batteries to have a long cycle life is of great significance for improving the performance of aqueous zinc-ion batteries and promoting their development. Summary of the Invention

[0005] This invention provides a ferroelectric separator for aqueous zinc-ion batteries, its preparation method, and its application. This ferroelectric separator can suppress dendrite growth and hydrogen evolution side reactions, improving ion transport efficiency, thereby enabling aqueous zinc-ion batteries using this separator to have long cycle life and cycle stability.

[0006] The present invention provides an aqueous zinc-ion battery separator, comprising a core layer and a surface layer existing on both sides of the core layer; the surface layer comprises a ferroelectric ceramic material and a first nanocellulose; the core layer comprises a second nanocellulose.

[0007] According to one embodiment of the present invention, the ferroelectric ceramic material includes one or more of barium titanate, lead zirconium titanate, lead titanate, lead niobate, bismuth titanate, and strontium niobate.

[0008] According to one embodiment of the present invention, the average particle size of the ferroelectric ceramic material is 30 nm to 200 nm.

[0009] According to one embodiment of the present invention, the mass ratio of the ferroelectric ceramic material and the first nanocellulose in the surface layer is 1:(0.15~3).

[0010] According to one embodiment of the present invention, the thickness of the core layer is 10 μm to 30 μm.

[0011] According to one embodiment of the present invention, the thickness of the surface layer is 15μm to 35μm.

[0012] According to one embodiment of the present invention, the thickness of the diaphragm is 40 μm to 100 μm.

[0013] According to one embodiment of the present invention, the pore size of the diaphragm is 1 nm to 40 nm.

[0014] The present invention also provides a method for preparing an aqueous zinc-ion battery separator, comprising the following steps: providing a mixture comprising ferroelectric ceramic material, a first nanocellulose and a first liquid dispersion medium; adding a portion of the mixture to a vacuum filter for filtration to remove the first liquid dispersion medium; adding a second dispersion comprising a second nanocellulose and a second liquid dispersion medium to the vacuum filter, and then filtration to remove the second liquid dispersion medium; adding another portion of the mixture to the vacuum filter for filtration to remove the first liquid dispersion medium, thereby obtaining a precursor; and drying the precursor to obtain a separator.

[0015] According to one embodiment of the present invention, the second liquid dispersion medium comprises water.

[0016] According to one embodiment of the present invention, the concentration of the second nanocellulose in the second dispersion is 1 mg / mL to 5 mg / mL.

[0017] According to one embodiment of the present invention, the first liquid dispersion medium includes water.

[0018] According to one embodiment of the present invention, the process of providing a mixture comprising ferroelectric ceramic material, first nanocellulose and first liquid dispersion medium includes: mixing the ferroelectric ceramic material with a first dispersion containing the first nanocellulose and the first liquid dispersion medium, and then subjecting it to ultrasonic treatment to obtain the mixture.

[0019] According to one embodiment of the present invention, the concentration of the first nanocellulose in the first dispersion is 1 mg / mL to 5 mg / mL.

[0020] According to one embodiment of the present invention, the mass ratio of the ferroelectric ceramic material to the volume ratio of the first dispersion is (1~2) g: (300~600) ml.

[0021] According to one embodiment of the present invention, the frequency of the ultrasonic treatment is 20kHz to 60kHz, and the duration of the ultrasonic treatment is 3min to 20min.

[0022] According to one embodiment of the present invention, the drying temperature is 50°C to 100°C, and the drying time is 10h to 15h.

[0023] The present invention also provides an aqueous zinc-ion battery, comprising the above-described separator or a separator prepared according to the above-described method for preparing an aqueous zinc-ion battery separator.

[0024] The present invention provides an aqueous zinc-ion battery ferroelectric separator, its preparation method, and its application. It adopts a composite structure of ferroelectric ceramic materials and nanocellulose, and constructs a composite layer separator with a mesoporous structure through a unique surface-core-surface design. By utilizing the polarization characteristics of the ferroelectric ceramic materials, the distribution behavior of zinc ions at the electrode interface is actively regulated, thereby suppressing dendrite growth and hydrogen evolution side reactions, improving ion transport efficiency, and enabling the aqueous zinc-ion battery to have a long cycle life and cycle stability. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] Figure 1 The hysteresis loop curves of the ferroelectric ceramic material of Example 1 and the ferroelectric ceramic material of Example 2 of this application are shown.

[0027] Figure 2 This is a nitrogen adsorption curve of the membrane prepared in Example 1 of this application;

[0028] Figure 3 This is a nitrogen adsorption curve of the membrane prepared in Example 2 of this application;

[0029] Figure 4 This is a scanning electron microscope (SEM) image of the diaphragm prepared in Example 1 of this application;

[0030] Figure 5 This is a SEM image of the diaphragm prepared in Example 2 of this application;

[0031] Figure 6 The Zn-Zn symmetric cells of Examples 1, 2 and Comparative Example 1 of this application were tested at 1 mA cm⁻¹. -2 Cycle life curves at current densities;

[0032] Figure 7 The Zn-Zn symmetric cells of Examples 1, 2 and Comparative Example 1 of this application were tested at 5 mA cm⁻¹. -2 Cycle life curves at current densities;

[0033] Figure 8 The coulombic efficiency curves of the Zn-Cu asymmetric cells of Examples 1, 2 and Comparative Example 1 of this application are shown.

[0034] Figure 9 This is a SEM image of the zinc anode in the Zn-Zn symmetric battery prepared in Example 1 of this application;

[0035] Figure 10 This is a SEM image of the zinc anode in the Zn-Zn symmetric battery prepared in Example 2 of this application;

[0036] Figure 11 This is a SEM image of the zinc anode in the Zn-Zn symmetric battery prepared in Comparative Example 1 of this application.

[0037] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concepts of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, this application will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the invention and are not intended to limit its scope. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. When the following description relates to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0039] This application provides an aqueous zinc-ion battery separator, comprising a core layer and surface layers existing on both sides of the core layer; the surface layers comprise ferroelectric ceramic material and a first nanocellulose; the core layer comprises a second nanocellulose.

[0040] The aqueous zinc-ion battery separator provided in this application employs a composite structure of ferroelectric ceramic materials and nanocellulose. A unique surface-core-surface design constructs a mesoporous composite layer separator. The polarization characteristics of the ferroelectric ceramic material are utilized to actively regulate the distribution behavior of zinc ions at the electrode interface, thereby suppressing dendrite growth and hydrogen evolution side reactions, improving ion transport efficiency, and resulting in a long cycle life for the aqueous zinc-ion battery. Specifically, it has the following synergistic technical effects:

[0041] (1) Zinc dendrite suppression and electric field homogenization

[0042] The ferroelectric ceramic material in the surface layer exhibits spontaneous polarization characteristics. Its surface charge distribution can actively regulate the zinc ion flux, suppress the disordered growth of zinc dendrites, and prevent corrosion of the zinc anode and accumulation of dead zinc, thereby improving the cycle stability of the battery. The first nanocellulose in the surface layer, as a functional carrier, not only enhances the interfacial bonding of the ferroelectric ceramic material but also optimizes the ion transport path through its porous network structure, further homogenizing the electric field distribution and reducing the risk of dendrites piercing the separator.

[0043] (2) Optimized ion transport and low interfacial resistance

[0044] The core layer, primarily composed of second-layer cellulose nanofibers, forms a three-dimensional microporous network, providing rapid and uniform zinc ion transport channels. Compared to traditional glass fiber separators, this structure reduces ion diffusion resistance and improves battery rate performance. The high hydrophilicity of the first-layer cellulose nanofibers in the surface layer ensures good compatibility with aqueous electrolytes. Simultaneously, the hydrophobic surface layer of the ferroelectric ceramic material in the surface layer can moderately block electrolyte permeation, preventing localized overcharging or hydrogen evolution side reactions and maintaining electrolyte stability.

[0045] (3) Mechanical strength and interface stability

[0046] The composite of the ferroelectric ceramic material in the surface layer and the first nanocellulose enhances the tensile strength and flexibility of the separator, enabling it to withstand the volume changes of the zinc anode during charging and discharging, thus preventing separator rupture or deformation. The spontaneous polarization characteristics of the ferroelectric ceramic material in the surface layer remain stable during repeated charging and discharging, and combined with the chemical inertness of the first nanocellulose, significantly suppress interfacial side reactions (such as hydrogen evolution corrosion), extending the battery cycle life.

[0047] It should be noted that ferroelectric ceramic materials are a type of functional ceramic material with spontaneous polarization properties. Specifically, ferroelectric ceramic materials can be ferroelectric ceramic nanoparticles.

[0048] It should be noted that the specific choices of the first and second nanocellulose can be the same or different.

[0049] In some embodiments, the ferroelectric ceramic material includes one or more of barium titanate, lead zirconium titanate, lead titanate, lead niobate, bismuth titanate, and strontium niobate. By selecting different types of ferroelectric ceramic materials, different electrolyte systems and battery design requirements can be adapted. For example, the high dielectric constant of barium titanate can enhance the ability to regulate the polarization field, the wide polarization temperature range of lead zirconium titanate can improve the stability of the separator in low-temperature energy storage systems, and the high polarization intensity of lead titanate can enhance the ability to regulate the distribution of zinc ions, thereby extending battery life in a wider range of applications.

[0050] In some embodiments, the average particle size of the ferroelectric ceramic material is 30 nm to 200 nm. For example, it is a range of 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, or any combination thereof. The nanoscale particle size of the ferroelectric ceramic material significantly increases the specific surface area, resulting in a denser surface charge distribution, which can more effectively regulate the zinc ion flux and suppress dendrite growth.

[0051] In some embodiments, the mass ratio of the ferroelectric ceramic material to the first nanocellulose in the surface layer is 1:(0.15~3). For example, it is a range of 1:0.15, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or any combination thereof. By adjusting the ratio of the ferroelectric ceramic material to the first nanocellulose, a balance is achieved between electric field control capability, ion transport efficiency, mechanical strength, and interfacial stability.

[0052] In some embodiments, the thickness of the core layer is 10 μm to 30 μm. For example, it is a range of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any combination thereof.

[0053] In some embodiments, the thickness of the surface layer is 15 μm to 35 μm. For example, it is a range of 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or any combination thereof.

[0054] It should be noted that the thickness of the surface layer refers to the thickness of one side of the surface layer.

[0055] In some embodiments, the two surface layers on both sides of the core layer have the same thickness, that is, the surface layers are symmetrically arranged along the core layer.

[0056] In some embodiments, the thickness of the diaphragm is 40 μm to 100 μm. For example, it is a range of 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or any combination thereof.

[0057] By adjusting the thickness of the core layer, the thickness of the single-sided surface layer, and the overall thickness of the diaphragm, a reasonable thickness can ensure the integrity of the ion transport channel in the core layer and the effectiveness of surface polarization control, while avoiding excessive thickness that increases transport resistance and excessive thinness that reduces mechanical strength. This helps to synergistically optimize ion transport efficiency, zinc dendrite suppression, mechanical strength, and cost-effectiveness.

[0058] In some embodiments, the pore size of the separator is 1 nm to 40 nm. For example, it is a range of 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, or any combination thereof. This range helps to optimize the zinc ion transport path, reduce diffusion resistance, and improve the battery ion transport efficiency, while also blocking dendrite penetration and further improving the battery cycle stability. It should be noted that this pore size refers to the average pore size of the separator, specifically obtained by fitting a nitrogen adsorption curve.

[0059] This application also provides a method for preparing an aqueous zinc-ion battery separator, comprising the following steps: providing a mixture containing ferroelectric ceramic material, first nanocellulose, and a first liquid dispersion medium; adding a portion of the mixture to a vacuum filter for filtration to remove the first liquid dispersion medium; adding a second dispersion containing second nanocellulose and a second liquid dispersion medium to the vacuum filter, and then filtration to remove the second liquid dispersion medium; adding another portion of the mixture to the vacuum filter for filtration to remove the first liquid dispersion medium, thus obtaining a precursor; and drying the precursor to obtain the separator. Through the mixture preparation-layer filtration-drying process, a three-layer composite structure is constructed, achieving the directional distribution of ferroelectric ceramic and nanocellulose, avoiding structural defects such as material agglomeration, and contributing to the batch stability of the separator preparation.

[0060] In some embodiments, the second liquid dispersion medium includes water, which is environmentally friendly, non-toxic, and inexpensive, and can uniformly disperse the second nanocellulose therein.

[0061] In some embodiments, the concentration of the second nanocellulose in the second dispersion is 1 mg / mL to 5 mg / mL. For example, a range of 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, or any combination thereof, helps to improve the film-forming uniformity of the core layer of the membrane and the stability of the microporous structure, avoiding film-forming defects caused by too low a concentration and pore blockage caused by too high a concentration.

[0062] In some embodiments, the first liquid dispersion medium includes water, which can uniformly disperse the ferroelectric ceramic material and the first nanocellulose therein.

[0063] In some embodiments, the process of providing a mixture comprising a ferroelectric ceramic material, a first nanocellulose and a first liquid dispersion medium includes: mixing the ferroelectric ceramic material with a first dispersion containing the first nanocellulose and the first liquid dispersion medium, and then subjecting it to ultrasonic treatment to obtain a mixture. The preparation of the mixture by ultrasonic treatment can utilize high-frequency vibration to avoid the agglomeration of the ferroelectric ceramic material and nanocellulose, achieve uniform dispersion of the two components, and help improve the consistency of the overall performance of the diaphragm.

[0064] In some embodiments, the concentration of the first nanocellulose in the first dispersion is 1 mg / mL to 5 mg / mL. For example, a range of 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, or any combination thereof, contributes to the film-forming uniformity and microporous structure stability of the membrane surface.

[0065] In some embodiments, the mass ratio of the ferroelectric ceramic material to the volume of the first dispersion is (1~2) g:(300~600) ml. For example, it is a range consisting of 1 g:300 ml, 1 g:400 ml, 1 g:500 ml, 1 g:600 ml, 2 g:300 ml, 2 g:400 ml, 2 g:500 ml, 2 g:600 ml, or any two of these ranges. This range ensures that the dispersion contains a sufficient effective loading of ferroelectric ceramic material per unit volume, which helps to provide the surface layer formed by subsequent filtration with sufficient polarization active sites. This avoids insufficient polarization field strength and weakened dendrite suppression effect due to excessively low material concentration, and helps to further improve the electrochemical performance of the membrane.

[0066] In some embodiments, the frequency of the ultrasonic treatment is 20 kHz to 60 kHz, for example, a range of 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz or any two thereof; the duration of the ultrasonic treatment is 3 min to 20 min, for example, a range of 3 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min or any two thereof.

[0067] Within the range of ultrasonic frequency and ultrasonic time mentioned above, it helps ferroelectric ceramic materials to be fully dispersed without agglomeration, while avoiding excessive ultrasonic damage to the material's crystal structure and loss of polarization performance; this combination of parameters can maximize the material dispersion uniformity and ensure the stability and performance consistency of diaphragm batch production.

[0068] In some embodiments, the drying temperature is 50°C to 100°C, for example, a range of 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or any two of these; the drying time is 10h to 15h, for example, a range of 10h, 11h, 12h, 13h, 14h, 15h, or any two of these.

[0069] Within the aforementioned drying time and temperature, residual moisture inside the diaphragm can be gently removed while preserving the three-dimensional network structure inside the diaphragm. The mechanical strength and flexibility of the dried diaphragm are simultaneously improved, which is beneficial for the long-term use of the diaphragm.

[0070] This application utilizes the synergistic effect of ultrasonic dispersion and layered filtration to ensure uniform dispersion of ferroelectric ceramic materials within the first nanocellulose layer, while simultaneously constructing a composite layer structure of surface-core-surface. The polarization characteristics of the ferroelectric ceramic material in the surface layer, combined with the mesoporous distribution of the first nanocellulose layer, allow for dynamic regulation of zinc ion distribution in the electrolyte, thereby suppressing dendrite growth induced by excessively high local concentrations. Furthermore, the high porosity and hydrophilicity of the second nanocellulose layer in the core layer ensure rapid electrolyte permeation, while the introduction of the ferroelectric polarization field further suppresses the hydrogen evolution side reaction, ultimately achieving active regulation of zinc ion distribution and interfacial reactions by the membrane.

[0071] This application also provides an aqueous zinc-ion battery, including the above-described separator or a separator prepared according to the above-described method for preparing an aqueous zinc-ion battery separator.

[0072] Example 1

[0073] S1. Preparation of the diaphragm

[0074] 100 mg of nanocellulose (Cellulose Bio) was dispersed in 40 mL of deionized water to obtain a first dispersion with a concentration of 2.5 mg / mL. 200 mg of barium titanate (Shandong Yuxin New Materials) with an average particle size of 100 nm was added to the first dispersion and mixed. The mixture was then sonicated at a frequency of 40 kHz for 3 min to obtain 40 mL of the mixture. 50 mg of nanocellulose (Cellulose Bio) was dispersed in 20 mL of deionized water to obtain 20 mL of a second dispersion with a concentration of 2.5 mg / mL.

[0075] First, take 20 ml of the mixture and pour it into a vacuum filter (Qun'an Instruments, with a filter pore diameter of 80 mm) for vacuum filtration. Then, take 20 ml of the second dispersion and pour it into the vacuum filter for vacuum filtration. Finally, take the remaining 20 ml of the mixture and pour it into the vacuum filter for vacuum filtration to obtain the precursor. After drying in an oven at 60°C for 12 hours, cut it into 16 mm round pieces to obtain the diaphragm.

[0076] S2, Preparation of aqueous zinc-ion batteries

[0077] Preparation of positive electrode sheet: The positive electrode material LMO (lithium manganese oxide), conductive agent carbon nanotubes and binder nanocellulose are dispersed evenly in ethanol at a mass ratio of 8:1:1. After vacuum filtration to form a film, the film is dried in an oven at 60°C for 12 hours and then cut into circular positive electrode sheets with a diameter of 16 mm.

[0078] Preparation of electrolytes: (1) 2M zinc sulfate electrolyte: Take 5.75g of zinc sulfate heptahydrate and add it to 10ml of deionized water. Stir until completely dissolved to obtain 2M zinc sulfate electrolyte; (2) 2M ZnSO4 + 1M Li2SO4 mixed electrolyte: Take 5.75g of zinc sulfate heptahydrate and 1.10g of lithium sulfate and add it to 10ml of deionized water. Stir until completely dissolved to obtain 2M ZnSO4 + 1M Li2SO4 mixed electrolyte.

[0079] Preparation of the full cell: Zinc sheet is used as negative electrode, 80 μL of 2M ZnSO4 + 1M Li2SO4 mixed electrolyte is used as electrolyte, the separator prepared in this embodiment is used as separator material, and the above LMO electrode is used as positive electrode. The matching battery positive and negative electrode shells, gaskets and springs are taken and assembled to obtain a button aqueous zinc-ion battery.

[0080] Preparation of Zn-Cu asymmetric battery: Copper and zinc sheets are used as positive and negative electrodes, 80 μL of 2M zinc sulfate electrolyte is used as electrolyte, and the separator prepared in this embodiment is used as separator material. The matching battery positive and negative electrode shells, gaskets, and springs are taken and assembled to obtain Zn-Cu asymmetric battery.

[0081] Preparation of Zn-Zn symmetric battery: Zinc sheet is used as positive and negative electrode, 80 μL of 2M zinc sulfate electrolyte is used as electrolyte, and the separator prepared in this embodiment is used as separator material. The matching battery positive and negative electrode shell, gasket and spring are taken and assembled to obtain Zn-Zn symmetric battery.

[0082] Example 2: The difference from Example 1 is that the barium titanate with an average particle size of 100 nm was replaced with lead zirconate titanate (Shandong Yuxin New Materials) with an average particle size of 50 nm, and the ultrasonic treatment time was 10 min. The remaining conditions of Example 2 are the same as those of Example 1.

[0083] Example 3: The difference from Example 1 is that in step S1, 200 mg of nanocellulose was dispersed in 40 mL of water to obtain a first dispersion with a concentration of 5 mg / mL; 100 mg of nanocellulose was dispersed in 20 mL of deionized water to obtain a second dispersion with a concentration of 5 mg / mL; the ultrasonic treatment frequency was 60 kHz and the ultrasonic treatment time was 20 min. The remaining conditions of Example 3 were the same as those of Example 1.

[0084] Example 4: The difference from Example 1 is that in step S1, 40 mg of nanocellulose was dispersed in 40 mL of water to obtain a first dispersion with a concentration of 1 mg / mL; 20 mg of nanocellulose was dispersed in 20 mL of deionized water to obtain a second dispersion with a concentration of 1 mg / mL; and the frequency of ultrasonic treatment was 20 kHz. The remaining conditions of Example 3 were the same as those of Example 1.

[0085] Comparative Example 1

[0086] S1. Preparation of the diaphragm

[0087] Compared with Example 1, a commercial Olegeeino glass fiber diaphragm (GF / F2012, 200 μm thick, 1.20 μm average pore size; cut into 16 mm round pieces using a mold) was used instead of the diaphragm prepared in Example 1, and all other aspects were the same as in Example 1.

[0088] S2, Preparation of aqueous zinc-ion batteries

[0089] Compared with Example 1, the preparation of the aqueous zinc-ion battery uses the membrane of this comparative example instead of the membrane prepared in Example 1, and everything else is the same as in Example 1.

[0090] Test case

[0091] 1. Ferroelectric property testing of ferroelectric ceramic materials

[0092] The nonlinear closed-loop curve (hysteresis loop) of polarization intensity (P) versus electric field intensity (E) can characterize the ferroelectric properties of ferroelectric ceramic materials. Specifically, the ferroelectric ceramic materials used in each embodiment were taken as samples and measured using a ferroelectric testing system (Precision Multiferroic II) at a frequency of 1000 Hz, with polarization curve data recorded at a voltage range of -50V to 50V. The results show that the polarization intensity and cell strength of the ferroelectric ceramic materials used in each embodiment have a nonlinear closed-loop curve relationship, indicating that the ferroelectric ceramic materials used in each embodiment have typical ferroelectric properties.

[0093] Taking Examples 1 and 2 as examples, the hysteresis loop curves of the barium titanate ferroelectric ceramic material in Example 1 and the lead zirconate titanate ferroelectric ceramic material in Example 2 are shown in the figure below. Figure 1 As shown, from Figure 1 It can be seen that the polarization intensity and electric field intensity of the ferroelectric ceramic materials in Examples 1 and 2 have a nonlinear closed curve relationship, indicating that they all have typical ferroelectric properties.

[0094] 2. Structural morphology characterization test of the diaphragm

[0095] (1) The nitrogen adsorption curves of the membranes obtained in each embodiment were tested. Specifically, nitrogen adsorption-desorption tests were conducted using a fully automated specific surface area and pore size analyzer. High-purity nitrogen was used as the adsorbate, and adsorption-desorption isotherms were collected at a liquid nitrogen temperature of 77K with a relative pressure P / P0 range of 0.05 to 0.99. The specific surface area of ​​the material was calculated using the BET model, and the mesopore size distribution and total pore volume were analyzed using the BJH model. The results showed that the isotherms of the nitrogen adsorption curves of the membranes prepared in each embodiment were all type IV isotherms, and the peak values ​​of the pore size distribution curves were concentrated in the range of 1 to 40 nm, proving that the films prepared in each embodiment had a pore size distribution of 1 to 40 nm.

[0096] Taking Examples 1 and 2 as examples, the nitrogen adsorption curve of the membrane prepared in Example 1 is shown in the figure below. Figure 2 (The ordinate of the pore size distribution curve represents the differential pore volume distribution density (dV / dD)). The nitrogen adsorption curve of the membrane prepared in Example 2 is shown below. Figure 3 (The ordinate of the pore size distribution curve represents the differential pore volume distribution density (dV / dD)). As shown, from... Figure 2 and Figure 3 It can be seen that the nitrogen adsorption curves of the membranes prepared in Examples 1 and 2 are both type IV isotherms, and the pore size distribution is in the range of 1 nm to 40 nm.

[0097] (2) The diaphragms prepared in the examples were characterized using a scanning electron microscope. Specifically, the diaphragm samples prepared in the examples were firmly adhered to the sample stage using conductive adhesive, and then photographed. The results showed that the diaphragms prepared in each example had smooth surfaces, and the close arrangement of spherical ferroelectric ceramic materials could be observed.

[0098] Taking Examples 1 and 2 as examples for specific illustration, the SEM images of the membranes prepared in Examples 1 and 2 are shown below. Figure 4 and Figure 5 As shown, from Figure 4 and Figure 5 As can be seen, the diaphragm surfaces prepared in Examples 1 and 2 have closely arranged spherical ferroelectric ceramic materials.

[0099] In addition, the membrane thickness can be obtained by combining the specific dimensions observed in the field of view of a scanning electron microscope with a scale bar. The results show that the thickness of the membrane obtained in each embodiment is between 40μm and 100μm, the core layer thickness of the obtained membrane is between 10μm and 30μm, and the surface layer thickness is between 15μm and 35μm.

[0100] 3. Electrochemical performance characterization test

[0101] (1) The cycle life of the Zn-Zn symmetric cells prepared in the examples and comparative examples was tested in the BTS test software (Newway). There are two cycle test methods, specifically: (1) the current density is set to 1 mA cm⁻¹. -2 The surface capacity is 1mAh cm -2 (1) Set constant current charging and constant current discharging steps, with a charging cutoff voltage of 1.9V and a discharging cutoff voltage of 1.5V; (2) Set the current density to 5mA cm⁻¹ -2 The surface capacity is 1mAh cm -2 The constant current charging and discharging steps were set, with a charging cutoff voltage of 2.04V and a discharging cutoff voltage of 1.5V. The results showed that the Zn-Zn symmetric cells prepared in each embodiment had significantly higher cycle lives than the Zn-Zn symmetric cell in Comparative Example 1 under both test methods.

[0102] Taking Examples 1, 2, and Comparative Example 1 as examples, the Zn-Zn symmetric cells of Examples 1, 2, and Comparative Example 1 are specifically described at 1 mA cm⁻¹. -2 The cycle life curve at current density is shown in the figure. Figure 6 As shown, from Figure 6 As can be seen from the data, the cycle lives of the Zn-Zn symmetric cells of Example 1, Example 2, and Comparative Example 1 are 2000h, 3300h, and 200h, respectively; the cycle lives of the Zn-Zn symmetric cells of Example 1, Example 2, and Comparative Example 1 at 5mA cm⁻¹ -2 The cycle life curve at current density is shown in the figure. Figure 7 As shown, from Figure 7 As can be seen, the cycle lives of the Zn-Zn symmetric cells of Example 1, Example 2 and Comparative Example 1 are 1000h, 1700h and 200h, respectively; indicating that the separators prepared in Example 1 and Example 2 can significantly increase the cycle life of Zn-Zn symmetric cells.

[0103] (2) The coulombic efficiency of the Zn-Cu asymmetric cells prepared in each embodiment and comparative example was tested using the constant current deposition-constant current stripping mode of the electrochemical workstation. Specifically, the current density was set to 5 mA cm⁻¹. -2 Surface capacity 1mAh cm -2The number of cycles was set to 1000, and the voltage-time curve for each cycle was recorded. The coulombic efficiency (CE) after 1000 cycles was calculated using the following formula: Coulombic efficiency (CE) = (stripping capacity of the 1000th cycle / deposition capacity of the 1000th cycle) × 100%. The results showed that, compared with the comparative example, the Zn-Cu asymmetric cells prepared in each embodiment exhibited good cycle stability and still maintained high coulombic efficiency after 1000 cycles.

[0104] Taking Examples 1, 2, and Comparative Example 1 as examples, the coulombic efficiency curves of the Zn-Cu asymmetric cells prepared in Examples 1, 2, and Comparative Example 1 are shown in the figure below. Figure 8 As shown in the figure, after 1000 cycles, the coulombic efficiencies of the Zn-Cu asymmetric cells prepared in Example 1 and Example 2 were 96.8% and 98.7%, respectively, while the Zn-Cu asymmetric cell prepared in Comparative Example 1 failed after 160 cycles. This indicates that the separators prepared in Example 1 and Example 2 can significantly improve the cycle stability of Zn-Cu asymmetric cells.

[0105] (3) Characterization test of electrode surface morphology after cyclic testing

[0106] The Zn-Zn symmetric cells prepared in each embodiment and comparative example were subjected to cycle tests. Specifically, the current density was set to 5 mA cm⁻¹. -2 Surface capacity 1mAh cm -2 The cycle count was set to 150 cycles. After the test, the Zn-Zn symmetric battery was disassembled to obtain the zinc anode. The surface of the disassembled zinc anode was observed using a scanning electron microscope. Specifically, the anode sample was firmly adhered to the sample stage using conductive adhesive, and images were taken. The results showed that, compared with the comparative example, after 150 cycles, the surface of the zinc anode in each embodiment of the Zn-Zn symmetric battery did not show obvious dendrites. This indicates that the separator prepared in each embodiment of this application can effectively reduce the formation of dendrites during battery use and improve the cycle life and cycle stability of the battery.

[0107] Taking Example 1, Example 2, and Comparative Example 1 as examples, the SEM image of the zinc anode in the Zn-Zn symmetric battery prepared in Example 1 is shown below. Figure 9 As shown, the SEM image of the zinc anode in the Zn-Zn symmetric battery prepared in Example 2 is as follows. Figure 10 As shown, the SEM image of the zinc anode in the Zn-Zn symmetric cell prepared in Comparative Example 1 is as follows. Figure 11 As shown, from Figure 9 , Figure 10 , Figure 11 It can be seen that at 5 mA cm -2After 150 cycles at the current density, the surface of the zinc anode in the Zn-Zn symmetric battery of Comparative Example 1 showed obvious dendrites, while the surface of the zinc anode in the Zn-Zn symmetric batteries of Examples 1 and 2 was spherical and did not show obvious dendrites. This indicates that the separators prepared in Examples 1 and 2 can suppress the generation of dendrites during battery use.

[0108] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A water-based zinc-ion battery separator, characterized in that, It includes a core layer and surface layers existing on both sides of the core layer; the surface layers include ferroelectric ceramic material and a first nanocellulose; the core layer includes a second nanocellulose.

2. The aqueous zinc-ion battery separator according to claim 1, characterized in that, The ferroelectric ceramic material includes one or more of barium titanate, lead zirconium titanate, lead titanate, lead niobate, and strontium niobate. And / or, the average particle size of the ferroelectric ceramic material is 30nm~200nm.

3. The aqueous zinc-ion battery separator according to claim 1, characterized in that, The mass ratio of the ferroelectric ceramic material to the first nanocellulose in the surface layer is 1:(0.15~3).

4. The aqueous zinc-ion battery separator according to claim 1, characterized in that, The thickness of the core layer is 10μm~30μm; And / or, the thickness of the surface layer is 15μm~35μm; And / or, the thickness of the diaphragm is 40μm~100μm.

5. The aqueous zinc-ion battery separator according to claim 1, characterized in that, The pore size of the diaphragm is 1 nm to 40 nm.

6. A method for preparing an aqueous zinc-ion battery separator according to any one of claims 1 to 5, characterized in that, Includes the following steps: Provide a mixture comprising ferroelectric ceramic material, first nanocellulose and first liquid dispersion medium; A portion of the mixture is added to a vacuum filter for filtration to remove the first liquid dispersion medium therein. Then, a second dispersion containing the second nanocellulose and the second liquid dispersion medium is added to the filter, and then the filter is subjected to suction filtration to filter out the second liquid dispersion medium therein. Then another portion of the mixture is added to the filter and filtered to remove the first liquid dispersion medium, thus obtaining the precursor. The precursor is dried to obtain a diaphragm.

7. The method for preparing the aqueous zinc-ion battery separator according to claim 6, characterized in that, The second liquid dispersion medium includes water; And / or, the concentration of the second nanocellulose in the second dispersion is 1 mg / mL to 5 mg / mL; And / or, the first liquid dispersion medium includes water; And / or, the process of providing a mixture comprising ferroelectric ceramic material, first nanocellulose and first liquid dispersion medium includes: mixing the ferroelectric ceramic material with a first dispersion containing the first nanocellulose and the first liquid dispersion medium, and then subjecting it to ultrasonic treatment to obtain the mixture.

8. The method for preparing the aqueous zinc-ion battery separator according to claim 7, characterized in that, The concentration of the first nanocellulose in the first dispersion is 1 mg / mL to 5 mg / mL; And / or, the mass ratio of the ferroelectric ceramic material to the volume of the first dispersion is (1~2) g : (300~600) ml; And / or, the frequency of the ultrasonic treatment is 20kHz to 60kHz, and the duration of the ultrasonic treatment is 3min to 20min.

9. The method for preparing an aqueous zinc-ion battery separator according to any one of claims 6 to 8, characterized in that, The drying temperature is 50℃~100℃, and the drying time is 10h~15h.

10. An aqueous zinc-ion battery, characterized in that, This includes the separator as described in any one of claims 1 to 5, or the separator prepared according to the method for preparing an aqueous zinc-ion battery separator as described in any one of claims 6 to 9.

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