A bacterial cellulose@uiO-66 composite and preparation thereof, a bacterial cellulose@uiO-66 composite film and preparation and application thereof

Abstract

This invention relates to the field of battery materials technology, and more particularly to a bacterial cellulose@UiO-66 composite material and its preparation, a bacterial cellulose@UiO-66 composite membrane and its preparation and application. This invention provides a bacterial cellulose@UiO-66 composite material comprising bacterial cellulose and UiO-66 nanoparticles grafted onto the surface of the bacterial cellulose. The bacterial cellulose@UiO-66 composite membrane provided by this invention, as a separator for aqueous zinc-ion batteries, exhibits good mechanical strength, high ionic conductivity, and resistance to zinc dendrite penetration, significantly improving the long-cycle stability and safety of the battery. Furthermore, the preparation method of the bacterial cellulose@UiO-66 composite membrane is simple and does not require high temperature or special temperature control equipment.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a bacterial cellulose@UiO-66 composite material and its preparation, a bacterial cellulose@UiO-66 composite membrane and its preparation and application. Background Technology

[0002] Aqueous rechargeable batteries not only avoid the flammability issues of organic electrolyte systems, but also have a high ionic conductivity (approximately 1 S·cm). -1 The concentration is higher than that of organic electrolyte (approximately 1–10 mS·cm). -1 The difference is nearly two orders of magnitude, which is beneficial for rapid ion transfer and battery charging and discharging. Among them, aqueous zinc ion batteries (AZIBs) are particularly advantageous due to the high abundance of zinc, low redox potential (-0.76V vs. SHE), high tolerance to environmental humidity, high hydrogen evolution overpotential, and high volumetric energy density (5851 mAh·cm³). -3 Features such as ), and the two-electron redox mechanism can provide AZIBs anodes with a high theoretical capacity (820 mAh·g). -1 This has attracted significant attention from researchers. Therefore, AZIBs have broad application prospects in large-scale energy storage systems and smart wearable devices.

[0003] As a crucial component of batteries, the separator plays a vital role in regulating the transport of active ions between the positive and negative electrodes. Its properties, such as ionic conductivity, porosity, and electrolyte wettability, also significantly contribute to improving the electrochemical performance of aqueous zinc-ion batteries. However, research on separators for AZIBs (Aqueous Zinc-Ion Batteries) is currently limited. The most commonly used separator in AZIBs is the glass fiber (GF) separator, which possesses high hydrophilicity and resistance to zinc dendrites. However, the glass fiber thickness can reach hundreds of micrometers, which can reduce the weight and volumetric energy density of aqueous zinc-ion batteries to some extent. Furthermore, the mechanical strength of the glass fiber separator is insufficient to maintain its structural integrity during battery assembly and repeated charge-discharge cycles. Therefore, there is a need to develop a low-cost, high-mechanical-strength, and high-ionic-conductivity ultrathin aqueous zinc-ion battery separator that can resist zinc dendrite penetration without sacrificing battery energy density. Summary of the Invention

[0004] The purpose of this invention is to provide a bacterial cellulose@UiO-66 composite material and its preparation, a bacterial cellulose@UiO-66 composite membrane and its preparation and application. The bacterial cellulose@UiO-66 composite membrane provided by this invention, as a separator for aqueous zinc-ion batteries, has good mechanical strength, high ionic conductivity, and can resist the penetration of zinc dendrites, significantly improving the long-cycle stability and safety of the battery.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] The present invention provides a bacterial cellulose@UiO-66 composite material, comprising bacterial cellulose and UiO-66 nanoparticles grafted onto the surface of the bacterial cellulose.

[0007] This invention provides a method for preparing the bacterial cellulose@UiO-66 composite material described above, comprising the following steps:

[0008] A zirconium source, acetic acid, and dimethylformamide are mixed and subjected to a solvothermal reaction to obtain a suspension of zirconium-oxygen cluster nuclei; the temperature of the solvothermal reaction is 130–160 °C.

[0009] The suspension of the zirconium oxide cluster nuclei, bacterial cellulose, and dimethylformamide are mixed and a grafting reaction is carried out to graft the zirconium oxide cluster nuclei onto the surface of bacterial cellulose, resulting in a grafting solution; the temperature of the grafting reaction is 10–30°C.

[0010] Terephthalic acid is added to the grafting solution for secondary growth. The terephthalic acid reacts with zirconium oxide cluster nuclei to form UiO-66 nanoparticles, resulting in bacterial cellulose@UiO-66 composite material. The temperature of the secondary growth is 10–30°C.

[0011] Preferably, the zirconium source includes one or more of zirconium n-propoxide, zirconium tetrachloride, and zirconium oxychloride octahydrate; by weight, the zirconium source is 0.05 to 0.4 parts, the acetic acid is 6 to 25 parts, and the first dimethylformamide is 10 to 40 parts.

[0012] Preferably, the solvothermal reaction takes 2 to 5 hours.

[0013] Preferably, based on the unit weight parts of the zirconium source, the weight parts of the bacterial cellulose are 0.3 to 0.4 parts, and the weight parts of the second dimethylformamide are 90 to 400 parts; the grafting reaction time is 12 to 24 hours.

[0014] Preferably, based on the unit weight parts of the zirconium source, the weight parts of the terephthalic acid are 0.038 to 0.27 parts.

[0015] Preferably, the secondary growth time is 12 to 24 hours.

[0016] This invention provides a bacterial cellulose@UiO-66 composite membrane, which is composed of the bacterial cellulose@UiO-66 composite material described in the above scheme or the bacterial cellulose@UiO-66 composite material prepared by the preparation method described in the above scheme.

[0017] The present invention provides a method for preparing the bacterial cellulose@UiO-66 composite membrane described above, comprising the following steps: dispersing the bacterial cellulose@UiO-66 composite material in an organic alcohol and then drawing a membrane to obtain the bacterial cellulose@UiO-66 composite membrane.

[0018] This invention provides the application of the bacterial cellulose@UiO-66 composite membrane described in the above-described scheme or the bacterial cellulose@UiO-66 composite membrane prepared by the above-described preparation method as a battery separator in aqueous zinc-ion batteries.

[0019] This invention provides a bacterial cellulose@UiO-66 composite material, comprising bacterial cellulose and UiO-66 nanoparticles grafted onto the surface of the bacterial cellulose. Bacterial cellulose possesses high mechanical strength, while UiO-66 exhibits excellent water stability and variable pore size. UiO-66 significantly enhances ion sieving capacity, and its inherent three-dimensional through-holes provide additional high-speed channels for ion transport, effectively preventing the shuttle effect of electrode materials. This invention combines bacterial cellulose with UiO-66, resulting in a bacterial cellulose@UiO-66 composite membrane with high mechanical strength, effectively suppressing uneven growth of zinc dendrites and the occurrence of side reactions. It maintains high coulombic efficiency during long-term cycling, exhibiting excellent cycle stability. Furthermore, the overall electrochemical performance of the BC@UiO-66 battery separator is significantly improved compared to the GF separator, making it widely applicable.

[0020] This invention provides a method for preparing the bacterial cellulose@UiO-66 composite material described above, employing a room-temperature grafting and secondary growth method. Compared to electrospinning, which requires specialized equipment and increases experimental costs, and whose parameter control is more complex, including voltage, distance from the nozzle to the collector, and solution viscosity, this method, because the reaction is carried out at room temperature (10–30°C), avoids the need for high-temperature or specialized temperature control equipment, simplifies the experimental setup and operation, and reduces experimental complexity and cost.

[0021] Compared to the conventional direct blending method, which results in poor membrane uniformity and ultimately affects the electrochemical performance of the composite membrane, this invention uses a room-temperature grafting and secondary growth method to prepare a membrane in which UiO-66 particles are uniform in size, well dispersed, and do not agglomerate. This uniform particle distribution and good dispersion help improve the overall performance of the membrane.

[0022] The results of the examples show that, compared with cellulose membranes (BC membranes) and GF membranes, bacterial cellulose@UiO-66 composite membranes can maintain higher coulombic efficiency and have better long-term cycling stability and safety. Attached Figure Description

[0023] Figure 1 SEM images of the BC diaphragm and the BC@UiO-66 composite membrane of Example 5 at different magnifications;

[0024] Figure 2 A comparison chart of the half-cell coulombic efficiency performance of BC membrane, GF membrane and BC@UiO-66 composite membrane of Example 5;

[0025] Figure 3 Comparison of the cycle performance of zinc symmetric batteries using BC membrane, GF membrane, and BC@UiO-66 composite membrane from Example 5. Detailed Implementation

[0026] The present invention provides a bacterial cellulose@UiO-66 composite material, comprising bacterial cellulose and UiO-66 nanoparticles grafted onto the surface of the bacterial cellulose.

[0027] In this invention, the diameter of the bacterial cellulose is preferably 50-300 nm, more preferably 100-200 nm; the particle size of the UiO-66 nanoparticles is preferably 20-100 nm, more preferably 40-70 nm.

[0028] This invention provides a method for preparing the bacterial cellulose@UiO-66 composite material described above, comprising the following steps:

[0029] A zirconium source, acetic acid, and dimethylformamide (DMF) are mixed and subjected to a solvothermal reaction to obtain a suspension of zirconium-oxygen cluster nuclei; the temperature of the solvothermal reaction is 130–160 °C.

[0030] The suspension of the zirconium oxide cluster nuclei, bacterial cellulose, and dimethylformamide are mixed and a grafting reaction is carried out to graft the zirconium oxide cluster nuclei onto the surface of bacterial cellulose, resulting in a grafting solution; the temperature of the grafting reaction is 10–30°C.

[0031] Terephthalic acid is added to the grafting solution for secondary growth. The terephthalic acid reacts with zirconium oxide cluster nuclei to form UiO-66 nanoparticles, resulting in bacterial cellulose@UiO-66 composite material. The temperature of the secondary growth is 10–30°C.

[0032] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0033] This invention involves mixing a zirconium source, acetic acid, and dimethylformamide, and then performing a solvothermal reaction to obtain a suspension of zirconium-oxygen cluster nuclei.

[0034] In this invention, the zirconium source preferably includes one or more of zirconium n-propoxide, zirconium tetrachloride, and zirconium oxychloride octahydrate; by weight, the zirconium source is preferably 0.05-0.4 parts, the acetic acid is preferably 6-25 parts, and the first dimethylformamide is preferably 10-40 parts; in specific embodiments, the zirconium source can be 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, or 0.4 parts; the acetic acid can be 6 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts, 20 parts, or 25 parts by weight; and the first dimethylformamide can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, or 40 parts by weight. In this invention, the acetic acid acts as a modifier, and the first dimethylformamide acts as a synthesis solvent.

[0035] In this invention, the temperature of the solvothermal reaction is 130–160°C, and in specific embodiments, it can be 130°C, 140°C, 150°C, or 160°C; the time of the solvothermal reaction is preferably 2–5 hours, and in specific embodiments, it can be 2 hours, 3 hours, 4 hours, or 5 hours. During the solvothermal process, zirconium-oxygen cluster nuclei are formed.

[0036] After obtaining the suspension of zirconium oxide cluster nuclei, the present invention mixes the suspension of zirconium oxide cluster nuclei, bacterial cellulose, and dimethylformamide to carry out a grafting reaction, in which the zirconium oxide cluster nuclei are grafted onto the surface of bacterial cellulose to obtain a grafting solution.

[0037] In this invention, the purchased bacterial cellulose is typically an aqueous suspension of bacterial cellulose. To prevent the influence of water on the preparation, this invention preferably disperses the bacterial cellulose suspension in dimethylformamide (denoted as trimethylformamide), centrifuges, and obtains the bacterial cellulose. In this invention, the dispersion time is preferably 12–24 hours.

[0038] In this invention, based on the unit weight parts of the zirconium source, the weight parts of the bacterial cellulose are preferably 0.3 to 0.4 parts. In specific embodiments, they can be 0.3 parts, 0.32 parts, 0.35 parts, 0.38 parts, or 0.4 parts.

[0039] In this invention, based on the unit weight parts of the zirconium source, the weight parts of the second dimethylformamide are preferably 90 to 400 parts. In specific embodiments, it can be 90 parts, 150 parts, 200 parts, 250 parts, 300 parts, 350 parts, or 400 parts. The addition of the second dimethylformamide in this invention promotes uniform dispersion of cellulose. In order for the zirconium oxide cluster nuclei to be grafted onto the BC surface, the suspension must have good dispersibility.

[0040] In this invention, the mixing of the suspension of the zirconium oxide cluster nuclei, bacterial cellulose, and second dimethylformamide preferably includes: adding the suspension of the zirconium oxide cluster nuclei into a container containing bacterial cellulose, and then adding the second dimethylformamide.

[0041] In this invention, the grafting reaction temperature is preferably 10–30°C (i.e., room temperature), and the grafting reaction time is preferably 12–24 hours. In specific embodiments, the grafting reaction temperature can be 10°C, 15°C, 20°C, 25°C, or 30°C, and the grafting reaction time can be 12 hours, 15 hours, 17 hours, 20 hours, or 24 hours. During the grafting reaction process, zirconium oxide cluster nuclei are grafted onto the surface of bacterial cellulose.

[0042] After obtaining the grafting solution, the present invention adds terephthalic acid to the grafting solution for secondary growth. The terephthalic acid and zirconium oxide cluster nuclei form UiO-66 nanoparticles to obtain bacterial cellulose@UiO-66 composite material.

[0043] In this invention, based on the unit weight parts of the zirconium source, the weight parts of the terephthalic acid are preferably 0.038 to 0.27 parts. In specific embodiments, it can be 0.038 parts, 0.05 parts, 0.10 parts, 0.15 parts, 0.20 parts, 0.25 parts, or 0.27 parts. In this invention, the terephthalic acid serves as a ligand for the synthesis of UiO-66.

[0044] In this invention, the temperature of the secondary growth is preferably 10-30℃ (i.e., room temperature); the time of the secondary growth is preferably 12-24h. In specific embodiments, the temperature of the secondary growth can be 10℃, 15℃, 20℃, 25℃ or 30℃, and the time of the secondary growth can be 12h, 15h, 17h, 20h or 24h.

[0045] After the secondary growth is completed, the present invention preferably centrifuges and washes the obtained liquid to obtain bacterial cellulose@UiO-66 composite material.

[0046] This invention employs a room-temperature grafting and secondary growth method, which avoids the need for high-temperature or special temperature control equipment, simplifies the experimental setup and operation process, reduces the complexity and cost of the experiment, and ensures uniform dispersion of UiO-66.

[0047] This invention provides a bacterial cellulose@UiO-66 composite membrane, which is composed of the bacterial cellulose@UiO-66 composite material described in the above scheme or the bacterial cellulose@UiO-66 composite material prepared by the preparation method described in the above scheme.

[0048] Bacterial cellulose possesses high mechanical strength, while UiO-66 exhibits excellent water stability and variable pore size. UiO-66 significantly enhances ion sieving capacity, and its three-dimensionally penetrating inherent channels provide additional high-speed ion transport pathways, effectively preventing the shuttle effect of electrode materials. This invention combines bacterial cellulose with UiO-66 to obtain a bacterial cellulose@UiO-66 composite membrane with high mechanical strength. This membrane effectively inhibits the uneven growth of zinc dendrites and the occurrence of side reactions, maintains high coulombic efficiency during long cycles, and exhibits excellent cycle stability. Furthermore, the overall electrochemical performance of the BC@UiO-66 battery separator is significantly improved compared to the GF separator, making it widely applicable.

[0049] In this invention, the thickness of the bacterial cellulose@UiO-66 composite membrane is preferably 80-100 μm, more preferably 90 μm.

[0050] The present invention provides a method for preparing the bacterial cellulose@UiO-66 composite membrane described above, comprising the following steps: dispersing the bacterial cellulose@UiO-66 composite material in an organic alcohol and then drawing a membrane to obtain the bacterial cellulose@UiO-66 composite membrane.

[0051] In this invention, the organic alcohol is preferably ethanol. There are no special requirements for the amount of ethanol used; it is sufficient to uniformly disperse the bacterial cellulose@UiO-66 composite material.

[0052] The present invention does not have any special requirements for the film extraction process.

[0053] This invention provides the application of the bacterial cellulose@UiO-66 composite membrane described in the above-described scheme or the bacterial cellulose@UiO-66 composite membrane prepared by the above-described preparation method as a battery separator in aqueous zinc-ion batteries.

[0054] The following examples illustrate the bacterial cellulose@UiO-66 composite material and its preparation, as well as the bacterial cellulose@UiO-66 composite membrane and its preparation and application, but these should not be construed as limiting the scope of protection of this invention.

[0055] The raw material usage for Examples 1 to 5 is shown in Table 1.

[0056] The BC suspension used in the following examples and comparative examples was purchased from Guilin Qihong Technology Co., Ltd., with a mass concentration of 0.8%.

[0057] Example 1

[0058] S1. Add the bacterial cellulose (BC) suspension and the third DMF to a beaker in a certain proportion, stir and disperse for 24 hours to form a uniform BC dispersion, centrifuge and wash to remove excess water to obtain bacterial cellulose, and pack it into a beaker.

[0059] S2. Add zirconium propoxide, acetic acid, and DMF to a reaction vessel in a certain proportion and heat at 130°C for 3 hours to obtain a suspension of zirconium-oxygen cluster nuclei;

[0060] S3. Pour the suspension of zirconium oxide cluster nuclei from S2 into a beaker containing bacterial cellulose, add synthetic dispersant DMF and disperse for 24 hours to carry out the grafting reaction, and obtain the grafting solution.

[0061] S4. Add a second DMF to the grafting solution and add terephthalic acid to synthesize and grow UiO-66 at room temperature (10-30℃) for 24 hours;

[0062] S5. The synthesized BC@UiO-66 composite material was centrifuged and washed three times, and then dispersed with ethanol for 24 hours to form a uniform BC@UiO-66 suspension.

[0063] S6. The uniform BC@UiO-66 suspension is drawn into a film, and the film is placed in an oven and vacuum dried at 80℃ for 5h to obtain the BC@UiO-66 composite film.

[0064] Example 2

[0065] S1. Add bacterial cellulose (BC) suspension and DMF to a beaker in a certain proportion, stir and disperse for 24 hours to form a uniform BC dispersion, centrifuge and wash to remove excess water to obtain bacterial cellulose, and pack it into a beaker.

[0066] S2. Add zirconium propoxide, acetic acid, and synthetic solvent DMF to a reaction vessel in a certain proportion, and heat at 130°C for 3 hours to obtain a suspension of zirconium-oxygen cluster nuclei;

[0067] S3. Pour the suspension of zirconium oxide cluster nuclei from S2 into a beaker containing bacterial cellulose, add synthetic dispersant DMF and disperse for 24 hours to carry out the grafting reaction, and obtain the grafting solution.

[0068] S4. Add DMF and terephthalic acid to the grafting solution and perform 24h room temperature synthesis and secondary growth of UiO-66;

[0069] S5. The synthesized BC@UiO-66 composite material was centrifuged and washed three times, and then dispersed with ethanol for 24 hours to form a uniform BC@UiO-66 suspension.

[0070] S6. The uniform BC@UiO-66 suspension is drawn into a film, and the film is placed in an oven and vacuum dried at 80℃ for 5h to obtain the BC@UiO-66 composite film.

[0071] Example 3

[0072] S1. Add bacterial cellulose (BC) suspension and DMF to a beaker in a certain proportion, stir and disperse for 24 hours to form a uniform BC dispersion, centrifuge and wash to remove excess water to obtain bacterial cellulose, and pack it into a beaker.

[0073] S2. Add zirconium propoxide, acetic acid, and synthetic solvent DMF to a reaction vessel in a certain proportion, and heat at 130°C for 3 hours to obtain a suspension of zirconium-oxygen cluster nuclei;

[0074] S3. Pour the suspension of zirconium oxide cluster nuclei from S2 into a beaker containing bacterial cellulose, add synthetic dispersant DMF and disperse for 24 hours to carry out the grafting reaction, and obtain the grafting solution.

[0075] S4. Add DMF and terephthalic acid to the grafting solution and perform 24h room temperature synthesis and secondary growth of UiO-66;

[0076] S5. The synthesized BC@UiO-66 composite material was centrifuged and washed three times, and then dispersed with ethanol for 24 hours to form a uniform BC@UiO-66 suspension.

[0077] S6. The uniform BC@UiO-66 suspension is drawn into a film, and the film is placed in an oven and vacuum dried at 80℃ for 5h to obtain the BC@UiO-66 composite film.

[0078] Example 4

[0079] S1. Add bacterial cellulose (BC) suspension and DMF to a beaker in a certain proportion, stir and disperse for 24 hours to form a uniform BC dispersion, centrifuge and wash to remove excess water to obtain bacterial cellulose, and pack it into a beaker.

[0080] S2. Add zirconium propoxide, acetic acid, and synthetic solvent DMF to a reaction vessel in a certain proportion, and heat at 130°C for 3 hours to obtain a suspension of zirconium-oxygen cluster nuclei;

[0081] S3. Pour the suspension of zirconium oxide cluster nuclei from S2 into a beaker containing bacterial cellulose, add synthetic dispersant DMF and disperse for 24 hours to carry out the grafting reaction, and obtain the grafting solution.

[0082] S4. Add DMF and terephthalic acid to the grafting solution and perform 24h room temperature synthesis and secondary growth of UiO-66;

[0083] S5. The synthesized BC@UiO-66 composite material was centrifuged and washed three times, and then dispersed with ethanol for 24 hours to form a uniform BC@UiO-66 suspension.

[0084] S6. The uniform BC@UiO-66 suspension is drawn into a film, and the film is placed in an oven and vacuum dried at 80℃ for 5h to obtain the BC@UiO-66 composite film.

[0085] Example 5

[0086] S1. Add bacterial cellulose (BC) suspension and DMF to a beaker in a certain proportion, stir and disperse for 24 hours to form a uniform BC dispersion, centrifuge and wash to remove excess water to obtain bacterial cellulose, and pack it into a beaker.

[0087] S2. Add zirconium propoxide, acetic acid, and synthetic solvent DMF to a reaction vessel in a certain proportion, and heat at 130°C for 3 hours to obtain a suspension of zirconium-oxygen cluster nuclei;

[0088] S3. Pour the suspension of zirconium oxide cluster nuclei from S2 into a beaker containing bacterial cellulose, add synthetic dispersant DMF and disperse for 24 hours to carry out the grafting reaction, and obtain the grafting solution.

[0089] S4. Add DMF and terephthalic acid to the grafting solution and perform 24h room temperature synthesis and secondary growth of UiO-66;

[0090] S5. The synthesized BC@UiO-66 composite material was centrifuged and washed three times, and then dispersed with ethanol for 24 hours to form a uniform BC@UiO-66 suspension.

[0091] S6. The uniform BC@UiO-66 suspension is drawn into a film, and the film is placed in an oven and vacuum dried at 80℃ for 5h to obtain the BC@UiO-66 composite film.

[0092] Example 6

[0093] S1. Add bacterial cellulose (BC) suspension and DMF to a beaker in a certain proportion, stir and disperse for 24 hours to form a uniform BC dispersion, centrifuge and wash to remove excess water to obtain bacterial cellulose, and pack it into a beaker.

[0094] S2. Add zirconium propoxide, acetic acid, and synthetic solvent DMF to a reaction vessel in a certain proportion, and heat at 130°C for 3 hours to obtain a suspension of zirconium-oxygen cluster nuclei;

[0095] S3. Pour the suspension of zirconium oxide cluster nuclei from S2 into a beaker containing bacterial cellulose, add synthetic dispersant DMF and disperse for 24 hours to carry out the grafting reaction, and obtain the grafting solution.

[0096] S4. Add DMF and terephthalic acid to the grafting solution and perform 24h room temperature synthesis and secondary growth of UiO-66;

[0097] S5. The synthesized BC@UiO-66 composite material was centrifuged and washed three times, and then dispersed with ethanol for 24 hours to form a uniform BC@UiO-66 suspension.

[0098] S6. The uniform BC@UiO-66 suspension is drawn into a film, and the film is placed in an oven and vacuum dried at 80℃ for 5h to obtain the BC@UiO-66 composite film.

[0099] Table 1. Raw material usage amounts for Examples 1-6

[0100]

[0101] Comparative Example 1

[0102] Preparation of BC membrane: First, DMF was added to the BC suspension and dispersed for 24 hours, then centrifuged, dispersed with ethanol for 24 hours, and finally filtered to form a membrane and dried in an oven.

[0103] Comparative Example 2

[0104] GF membrane: This is a commercial membrane, model GF / D, purchased from the Taobao website Cyber ​​Electrochemical Materials.

[0105] Structural characterization:

[0106] Scanning electron microscopy (SEM) was performed on the BC diaphragm of Comparative Example 1 and the BC@UiO-66 composite membrane of Example 5. The results are as follows: Figure 1 As shown, a is a low-magnification SEM image of the BC membrane, b is a high-magnification SEM image of the BC membrane, c is a low-magnification SEM image of the BC@UiO-66 composite membrane, and d is a high-magnification SEM image of the BC@UiO-66 composite membrane.

[0107] Depend on Figure 1As can be seen, the BC membrane fiber network is clear and uniformly distributed at low magnification. At high magnification, the fiber details are visible, with fiber diameters between 100 and 200 nm and smooth surfaces, indicating that the BC membrane possesses a good nanofiber structure. Compared to the pure BC membrane, the BC / UiO-66 composite membrane incorporates granular UiO-66; at high magnification, UiO-66 particles are observed to be uniformly distributed on and within the fiber surface, with a particle size of approximately 50 nm. This distribution contributes to improving the overall mechanical strength and functionality of the membrane. The UiO-66 particles in this membrane are uniform in size, well-dispersed, and show no aggregation. This uniform particle distribution and good dispersion contribute to improving the overall performance of the membrane. Furthermore, there is no entanglement between the fibers, significantly improving the structural uniformity and mechanical stability of the membrane. Its uniformly dispersed structure is beneficial for mass transfer and the regulation of zinc ion transport, enhancing the membrane's application potential in electrochemical devices. Good particle dispersion and uniform fiber structure not only enhance the mechanical strength of the separator, but may also improve its electrolyte absorption capacity and ionic conductivity, thus exhibiting superior performance in battery performance.

[0108] Performance testing:

[0109] GF membrane, BC membrane, and BC@UiO-66 membrane were respectively assembled into stainless steel symmetrical cells with two stainless steel electrode plates using 2M ZnSO4 solution as the electrolyte. A CHI760e electrochemical workstation was used in the frequency range of 10... 5 ~10 -2 Electrochemical impedance spectroscopy (EIS) was performed on batteries assembled from three different membrane samples at a frequency of Hz and an amplitude of 10 mV to obtain the impedance values ​​of the GF membrane, BC membrane, and BC@UiO-66 membrane. These values ​​were then substituted into formula (1-1) to derive the ionic conductivity (mS / m²) of the membranes. -1 The results are shown in Table 2.

[0110]

[0111] In the formula, L is the thickness of the diaphragm sample (m);

[0112] A—Area of ​​the stainless steel sheet (cm²) 2 );

[0113] R — the impedance value of the diaphragm (mΩ).

[0114] Using a zinc-copper battery (Zn||Cu) as the research object and Cu as the research electrode, the study investigated Zn. 2+ The deposition / dissolution behavior on its surface was investigated to study the effect of different membrane materials on Zn. 2+The impact on transport behavior and battery reversibility. Zn||Cu batteries assembled with different separator samples were tested on a blue battery testing system at 2mA cm⁻¹. -2 1mAh cm -2 Constant current charge-discharge tests were conducted under the specified test conditions to obtain battery coulombic efficiency and nucleation overpotential data. The results are shown in Table 2. The coulombic efficiencies of the batteries with BC separator, GF separator, and the BC / UiO-66 composite membrane from Example 5 are as follows: Figure 2 As shown.

[0115] Constant current charge-discharge tests were conducted on a Zn||Zn symmetric cell in a Blue Electric Battery testing system to investigate the influence of the separator material on the battery's cycle stability and zinc deposition / dissolution behavior. The Zn||Zn cell was kept at a constant current charge-discharge rate of 1 mA / cm². -2 1mAh cm -2 Constant current charge-discharge tests were conducted under the specified test conditions to test the cycle behavior. The results are shown in Table 2. The cycle performance of the BC membrane, GF membrane, and the BC / UiO-66 composite membrane from Example 5 are shown in Table 2. Figure 3 As shown.

[0116] Table 2 Performance data for each embodiment

[0117]

[0118] Note: The coulomb efficiency of 98.6 (126 cycles) in Table 2 refers to the coulomb efficiency of 98.6% after 126 cycles of constant current charge and discharge, and so on.

[0119] From Table 2 and Figure 2 The results show that the BC / UiO-66 separator maintains a high coulombic efficiency during long cycles. The GF separator fails at 127 cycles, the BC separator at 189 cycles, while the BC / UiO-66 separator only fails at 633 cycles. Furthermore, the figure shows that the GF separator cannot regulate zinc ion deposition, resulting in a scattered coulombic efficiency and short circuits caused by dendrite penetration within a short cycle. This is mainly attributed to the presence of UiO-66, whose porous structure provides a uniform zinc ion distribution, reduces dendrite formation, and thus improves the reversibility and stability of the battery.

[0120] From Table 2 and Figure 3 The results show that at 1 mA·cm -2 and 1mAh·cm -2 Under these conditions, the BC / UiO-66 separator remained stable during a 2000-hour test without exhibiting any short circuits. The presence of UiO-66 improved the mechanical strength and electrochemical stability of the separator, preventing zinc dendrites from piercing it, thereby significantly enhancing the long-cycle stability and safety of the battery.

[0121] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bacterial cellulose@UiO-66 composite material, characterized in that, It includes bacterial cellulose and UiO-66 nanoparticles grafted onto the surface of the bacterial cellulose.

2. The method for preparing the bacterial cellulose@UiO-66 composite material according to claim 1, characterized in that, Includes the following steps: A zirconium source, acetic acid, and dimethylformamide are mixed and subjected to a solvothermal reaction to obtain a suspension of zirconium-oxygen cluster nuclei; the temperature of the solvothermal reaction is 130–160 °C. The suspension of the zirconium oxide cluster nuclei, bacterial cellulose, and dimethylformamide are mixed and a grafting reaction is carried out to graft the zirconium oxide cluster nuclei onto the surface of bacterial cellulose, resulting in a grafting solution; the temperature of the grafting reaction is 10–30°C. Terephthalic acid is added to the grafting solution for secondary growth. The terephthalic acid reacts with zirconium oxide cluster nuclei to form UiO-66 nanoparticles, resulting in bacterial cellulose@UiO-66 composite material. The temperature of the secondary growth is 10–30°C.

3. The preparation method according to claim 2, characterized in that, The zirconium source includes one or more of zirconium n-propoxide, zirconium tetrachloride, and zirconium oxychloride octahydrate; by weight, the zirconium source is 0.05 to 0.4 parts, the acetic acid is 6 to 25 parts, and the first dimethylformamide is 10 to 40 parts.

4. The preparation method according to claim 2 or 3, characterized in that, The solvothermal reaction takes 2 to 5 hours.

5. The preparation method according to claim 2, characterized in that, Based on the unit weight parts of the zirconium source, the weight parts of the bacterial cellulose are 0.3 to 0.4 parts, and the weight parts of the second dimethylformamide are 90 to 400 parts; the grafting reaction time is 12 to 24 hours.

6. The preparation method according to claim 2, characterized in that, Based on the unit weight parts of the zirconium source, the weight parts of the terephthalic acid are 0.038 to 0.27 parts.

7. The preparation method according to claim 2 or 6, characterized in that, The secondary growth period is 12–24 hours.

8. A bacterial cellulose@UiO-66 composite membrane, comprising the bacterial cellulose@UiO-66 composite material of claim 1 or the bacterial cellulose@UiO-66 composite material prepared by any one of claims 2 to 7.

9. The method for preparing the bacterial cellulose@UiO-66 composite membrane according to claim 8, characterized in that, Includes the following steps: The bacterial cellulose@UiO-66 composite material was dispersed in an organic alcohol and then drawn into a membrane to obtain the bacterial cellulose@UiO-66 composite membrane.

10. The application of the bacterial cellulose@UiO-66 composite membrane of claim 8 or the bacterial cellulose@UiO-66 composite membrane prepared by the preparation method of claim 9 as a battery separator in an aqueous zinc-ion battery.

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