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CN-122025996-A - Diatomite/nanocellulose composite diaphragm and preparation method and application thereof

CN122025996ACN 122025996 ACN122025996 ACN 122025996ACN-122025996-A

Abstract

The invention belongs to the technical field of electrochemical energy storage, and particularly relates to a diatomite/nanocellulose composite diaphragm, and a preparation method and application thereof. The composite diaphragm is prepared by blending nano cellulose slurry and natural diatomite powder which has unique disc-shaped morphology (the surface width is 10-50 mu m and the thickness is 3-10 mu m) and contains abundant porous structures and silicon hydroxyl groups in an aqueous phase, and then forming a film, exchanging a solvent and drying. The disc-shaped structure is favorable for horizontal directional stacking in the film forming process, and is self-assembled with a cellulose network through hydrogen bonds, so that a through and orderly multistage ion transmission channel is built in the diaphragm, and the mechanical strength of the film is greatly improved. The zinc ion coating agent is used for a water-based zinc ion battery, can effectively guide zinc ions to be uniformly deposited, inhibit dendrites, remarkably improve the cycle stability and the service life of the battery, and has wide industrialization prospect.

Inventors

  • WANG SUQING
  • FU CHEN

Assignees

  • 华南理工大学

Dates

Publication Date
20260512
Application Date
20260305

Claims (10)

  1. 1. The preparation method of the diatomite/nanocellulose composite membrane is characterized by comprising the following steps of: step one, mixing nano cellulose slurry, diatomite powder and deionized water to obtain diatomite/nano cellulose mixed dispersion; Step two, preparing the mixed dispersion liquid in the step one into a composite wet film; Step three, stripping the composite wet film obtained in the step two, and soaking in an alcohol solvent; And step four, drying the soaked composite wet film in the step three to obtain the diatomite/nanocellulose composite diaphragm.
  2. 2. The preparation method of the diatomite/nanocellulose composite membrane according to claim 1, wherein in the first step, the nanocellulose comprises at least one of bacterial cellulose and plant nanocellulose, the diameter of the nanocellulose is 40-120 nm, the length is not less than 20 μm, and the mass concentration of the nanocellulose slurry is 0.5-1.0 wt%.
  3. 3. The preparation method of the diatomite/nanocellulose composite membrane according to claim 2, wherein the use ratio of nanocellulose slurry, diatomite powder and deionized water in the first step is 0.005-0.025 g:2-4 mL:40-60 mL.
  4. 4. The preparation method of the diatomite/nanocellulose composite membrane according to claim 1, wherein the preparation of the composite wet membrane from the mixed dispersion liquid in the second step is a pouring method, wherein the mixed dispersion liquid is poured into a mold and is left to stand until a uniform wet membrane is formed, or the preparation of the composite wet membrane from the mixed dispersion liquid is a tape casting method, wherein the mixed dispersion liquid is uniformly cast on a substrate, and the substrate is any one of a polyethylene terephthalate plate, a glass plate and a polytetrafluoroethylene plate.
  5. 5. The preparation method of the diatomite/nanocellulose composite membrane according to claim 1, wherein in the third step, the alcohol solvent is at least one of methanol, ethanol, propanol and isopropanol or a mixed solution of the alcohol solvent and water, and the volume percentage of alcohol in the alcohol solvent is 50% -100%.
  6. 6. The method for preparing the diatomite/nanocellulose composite membrane as claimed in claim 1, wherein in the fourth step, the drying temperature is 50-80 ℃ and the drying time is 6-12 hours.
  7. 7. The method for preparing the diatomite/nanocellulose composite membrane as claimed in claim 1, wherein in the first step, the diatomite powder is subjected to a pre-purification treatment, and the purification treatment comprises dispersing diatomite raw material in water, standing, performing ultrasonic and centrifugal treatment, collecting precipitate, drying and sieving.
  8. 8. A diatomite/nanocellulose composite membrane, characterized in that it is prepared by the preparation method of the diatomite/nanocellulose composite membrane according to any one of claims 1-7.
  9. 9. The diatomite/nanocellulose composite membrane of claim 8, wherein said composite membrane is a composite structure formed by interweaving diatomite particles and a nanocellulose three-dimensional network, said diatomite particles are disc-shaped, the surface width is 10-50 μm, the thickness is 3-10 μm, multistage pore channels with the pore diameter of 200-600 nm are distributed on the surface of the disc, the porosity of said composite membrane is 60% -90%, the tensile strength is more than 30 MPa, and the ionic conductivity is more than 3 mS/cm.
  10. 10. The composite membrane obtained by the preparation method of the diatomite/nanocellulose composite membrane according to any one of claims 1-7 or the application of the diatomite/nanocellulose composite membrane according to any one of claims 8-9 is characterized by being used for an aqueous zinc ion battery.

Description

Diatomite/nanocellulose composite diaphragm and preparation method and application thereof Technical Field The invention relates to the technical field of electrochemical energy storage, in particular to a preparation method of a diatomite/nanocellulose composite membrane and application of the diatomite/nanocellulose composite membrane in a water system zinc ion battery. Background The water-based zinc ion battery has the advantages of abundant zinc cathode resources, high theoretical capacity (820 mAh g-1), intrinsically safe water-based electrolyte, low cost and the like, and has wide application prospect in the fields of power grid energy storage and the like. However, the problems of uneven ion transmission at the interface of the zinc anode, water-related side reactions such as hydrogen evolution and the like severely restrict the industrialization of the zinc anode. The diaphragm is a key component of the water-based zinc ion battery, and has the functions of physical insulation, regulation and control of ion transmission and inhibition of zinc dendrite growth, and is critical to the battery performance. The widely used glass fiber (such as WHATMAN GF/D type) diaphragm has chemical stability, but the structural characteristics are difficult to meet the long-acting application requirement, and the diaphragm is characterized by larger pore diameter (about 5 μm) and uneven distribution, cannot effectively inhibit zinc dendrite penetration, has large thickness (about 675 μm), reduces the volume energy density of the battery, has low mechanical strength (about 0.85 MPa) and is easy to damage under dendrite growth or battery assembly stress. These drawbacks result in a generally short battery cycle life (typically less than 100 times), coupled with their high cost (about 2000 yuan per square meter for commercial use), further pushing the overall cost of the energy storage system. Therefore, development of a novel separator which has excellent mechanical properties, a suitable pore structure, low cost and long service life is a key to promoting industrialization of water-based zinc ion batteries. The membrane is prepared by taking cellulose with wide sources and low cost as a raw material, and is a potential path. In the prior art, although specific schemes are provided in patent applications CN121238162a (bamboo fiber), CN119361965A (bacterial cellulose), CN120389199a (defatted cotton) and the like, the pure cellulose substrate has limited regulation and control capability on ion migration, and the fibers are easily aggregated due to capillary force in the drying process, so that the porosity is low, the ion conductivity is poor, and the battery performance is not improved enough. Therefore, effective functional modification of the cellulose-based separator is still needed to comprehensively improve the electrochemical performance and practicality. The existing improvement strategies mainly spread around two types, namely, compounding other high-performance fibers in a cellulose network, such as an aramid nanofiber and nanocellulose compounding scheme proposed in application number CN117855747A, but the preparation flow of the method is generally complex. Secondly, functional filler is introduced into the cellulose substrate to optimize ion transmission behavior, for example, application number CN119447690A proposes to compound modified cellulose with UiO series MOF, zeolite or ZIF microporous materials, and application number CN121440034A adopts Ti0.87O2 nano-sheets to compound bacterial cellulose. However, the method relies on complex synthesis process of fillers such as MOF, zeolite and the like and often involves an organic solvent, or the adopted Ti0.87O2 nanosheets and other materials have the problem of high cost, so that the process simplicity and economy are sacrificed while the performance is improved, and the large-scale application prospect is restricted. In summary, the existing diaphragm technology generally has the problems of complex process, non-adaptive aperture, insufficient mechanical strength, dependence on high-cost materials or toxic solvents, and the like. Therefore, development of a cellulose-based separator with a precise pore diameter adapted to zn2+ transport, high mechanical strength and excellent ion conductivity, and green process at low cost is needed. Disclosure of Invention In order to overcome the defects in the prior art, the invention aims to provide a diatomite/nanocellulose composite membrane, and a preparation method and application thereof. According to the method, natural diatomite with environmental friendliness and low cost is used as a functional filler, and the core problems of low porosity, insufficient ionic conductivity and the like of a pure nano cellulose diaphragm due to compact fiber accumulation are effectively solved by introducing the porous structure and the surface characteristics of the natural diatomite. The invention realizes the controllable pre