CN109980167B - Polyvinylidene fluoride film with bionic three-cycle minimum curved surface structure and preparation and application thereof - Google Patents

Polyvinylidene fluoride film with bionic three-cycle minimum curved surface structure and preparation and application thereof Download PDF

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CN109980167B
CN109980167B CN201910170558.7A CN201910170558A CN109980167B CN 109980167 B CN109980167 B CN 109980167B CN 201910170558 A CN201910170558 A CN 201910170558A CN 109980167 B CN109980167 B CN 109980167B
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sea urchin
pvdf
urchin shell
shell
shells
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CN109980167A (en
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刘育京
吴玉选
杨涛
袁华栋
郑建辉
胡华良
孙国元
卢功勋
张文魁
陶新永
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Zhejiang University of Technology ZJUT
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a polyvinylidene fluoride film with a bionic three-cycle extremely-small curved surface structure, and preparation and application thereof. The polyvinylidene fluoride membrane is obtained by taking a sea urchin shell with a three-cycle extremely-small curved surface structure as a template through the following method: preparing a sea urchin shell into a sea urchin shell slice with the thickness not more than 160 mu m, enabling PVDF to permeate into a framework of the sea urchin shell slice by means of a solvent and completely filling the framework, and removing a sea urchin shell template from the sea urchin shell slice filled with the PVDF by acid soaking to obtain the polyvinylidene fluoride film with the bionic three-cycle extremely-small curved surface structure. When the polyvinylidene fluoride film with the bionic three-cycle minimum curved surface structure is used as a lithium metal battery diaphragm, the cycle stability of the lithium metal battery can be obviously improved.

Description

Polyvinylidene fluoride film with bionic three-cycle minimum curved surface structure and preparation and application thereof
(I) technical field
The invention belongs to the field of lithium batteries, and relates to a polytetrafluoroethylene film with a bionic three-cycle minimum curved surface (TPMS) structure, preparation thereof and application thereof as a diaphragm in the field of lithium metal batteries.
(II) background of the invention
The separator material plays a very important role in the lithium battery, is positioned between the positive electrode and the negative electrode, prevents the positive electrode and the negative electrode from contacting, and can conduct ions freely while not conducting electrons. However, for the lithium metal battery, due to the activity of the metal lithium, the metal lithium continuously reacts with the organic electrolyte in the charging and discharging process to form SEI, and meanwhile, the metal lithium also can be accompanied with huge volume change in the charging and discharging process to cause continuous breakage of the SEI and continuous consumption of the electrolyte. Lithium dendrites are constantly generated due to non-uniformity of the metallic lithium during deposition, and piercing of the separator causes serious safety problems. In order to solve the problems of the lithium metal battery and obtain the lithium metal battery with higher coulombic efficiency and more excellent electrochemical performance, various solutions have been proposed, such as designing a current collector, using an electrolyte additive or designing a novel high-concentration electrolyte. Many people neglect the role of the separator in lithium metal batteries. PVDF has chemical resistance, processability, fatigue and creep resistance, and electrical insulation, and these excellent properties make PVDF particularly widely used in lithium battery applications, including adhesives, separators, and other fields. However, the traditional PVDF membrane material has complex preparation process and higher cost. To obtain porous PVDF separator materials, PVDF needs to be mixed with inorganic fillers, which limits its development to some extent, and it is more difficult to obtain separator materials with a three-cycle ordered network structure.
Sea urchins have existed in the earth for hundreds of millions of years, and are a low-grade ancient invertebrate in the ocean. Sea urchins are in various types, and more than 750 types exist in the world. The disc or spherical shell of sea urchin is hard shell and is generally regarded as solid waste in the sea urchin treatment process, but it is described that the sea urchin shell has no toxicity and can be used for treating asthma, stomachache and other symptoms in traditional Chinese medicine. Sea urchin shells are reported to have a three-cycle extremely small curved surface structure (TPMS). The invention aims to prepare a PVDF diaphragm with a sea urchin shell-shaped bionic three-cycle minimum curved surface structure by using a three-cycle minimum curved surface structure of a sea urchin shell as a template, and the PVDF diaphragm is used as a lithium metal battery diaphragm so as to obtain a lithium metal battery with excellent electrochemical performance.
Disclosure of the invention
The invention aims to provide a polyvinylidene fluoride film with a bionic three-period minimum curved surface structure, a preparation method thereof and application thereof in a lithium metal battery.
The following specifically describes the technical means of the present invention.
In a first aspect, the invention provides a polyvinylidene fluoride film with a bionic three-cycle minimum curved surface structure, which is obtained by taking a sea urchin shell with a three-cycle minimum curved surface structure as a template through the following method: preparing a sea urchin shell into a sea urchin shell slice with the thickness not more than 160 mu m, enabling PVDF to permeate into a framework of the sea urchin shell slice by means of a solvent and completely filling the framework, and removing a sea urchin shell template from the sea urchin shell slice filled with the PVDF by acid soaking to obtain the polyvinylidene fluoride film with the bionic three-cycle extremely-small curved surface structure.
Preferably, the thickness of the thin sheet of sea urchin shells is 80 to 160 μm.
Preferably, the solvent is NMP, N N-Dimethylformamide (DMF) or dimethylacetamide (DMAc), more preferably NMP.
The acid used for soaking can be hydrochloric acid, acetic acid and the like which can react with calcium carbonate.
In a second aspect, the invention provides a preparation method of a polyvinylidene fluoride film with a bionic three-cycle minimum curved surface structure, which comprises the following steps:
(1) taking relatively flat waste white sea urchin shells, washing the waste white sea urchin shells with water, and removing residual organic components on the surfaces of the waste white sea urchin shells; then breaking the cleaned sea urchin shells, selecting a relatively flat part for standby, wherein the relatively flat part has the largest surface area as much as possible in the breaking process, so that a film with the largest area as much as possible can be prepared, and the preparation efficiency is improved;
(2) preparing the clean white sea urchin shells selected in the step (1) into sea urchin shell slices with the thickness not more than 160 mu m;
(3) flatly placing the sea urchin shell slices obtained in the step (2) in a container, dripping PVDF solution on the sea urchin shell slices until the sea urchin shell slices are completely covered by the PVDF solution, infiltrating the PVDF into the sea urchin shell slices by means of a solvent at the moment, completely filling the sea urchin shell frameworks with the PVDF, drying at 40-80 ℃ to remove the solvent, completely grinding a layer of dense PVDF covering the surfaces of the sea urchin shells to obtain the sea urchin shell slices filled with the PVDF;
(4) and (3) placing the sea urchin shell slices filled with the PVDF in acid to be fully soaked to remove the sea urchin shell templates, then sequentially washing the sea urchin shell slices with distilled water and ethanol to be neutral, and then placing the sea urchin shell slices in a drying oven at 40-80 ℃ for drying to obtain the polyvinylidene fluoride film with the bionic three-cycle minimum curved surface structure.
In the step (1), the white waste sea urchin shells are calcium carbonate materials taken from nature, and have a three-cycle minimum curved surface structure as a skeleton of sea urchins. Sea urchins in nature are various, and they are preferably white cake-shaped sea urchins having a larger flat area.
In step (2) of the present invention, the thickness of the thin sea urchin shell sheet is preferably 80 to 160 μm, since it is easily broken when the thickness is too thin. The sea urchin shell thin sheet can be obtained by cutting or grinding. The invention specifically recommends obtaining sea urchin shell flakes by grinding: grinding sea urchin shells to a required thickness by using sand paper, then ultrasonically washing in water and ethanol in sequence, and drying in an oven at 30-100 ℃ (preferably 60-80 ℃) to obtain the sea urchin shell slice. Preferably, the shells of the sea urchin are sequentially polished by sandpaper with different particle sizes in the order of the smaller particle size to the larger particle size (such as 400, 600, 800, 1000, 1200, etc.), the polishing efficiency can be improved by using the thicker sandpaper at the beginning, the later sandpaper with the thinner particle size is not easy to break, and a better appearance can be obtained. As a further preference, the grinding step is: firstly, grinding the sea urchin shells by using sand paper with the granularity of 400 until the two sides are smooth, then grinding by using sand paper with the granularity of 600 until the thickness is close to the required thickness, and finally grinding by using sand paper with the granularity of 1000 until the required thickness is reached.
In step (3) of the present invention, the solvent of the PVDF solution is preferably NMP, N N-Dimethylformamide (DMF) or dimethylacetamide (DMAc), more preferably NMP. The preparation method of the NMP solution of PVDF comprises the following steps: PVDF as PVDF: the NMP mass ratio is 1: 5-15 (preferably 1: 8-10) are dissolved in NMP and stirred continuously at 40-60 deg.C (preferably 50 deg.C) to completely dissolve PVDF in NMP without any bubbles or particles, resulting in a solution of PVDF in NMP.
In the step (3) of the present invention, it is preferable that a layer of dense PVDF covering the surface of the sea urchin shell is completely ground by sandpaper with different particle sizes in the order of the particle size from small to large (such as 400, 600, 800, 1000, 1200, etc.), the grinding efficiency can be improved by using relatively coarse sandpaper at the beginning, and the grinding efficiency is not easy to break by using relatively fine sandpaper at the later time, and a relatively good appearance can be obtained.
In step (4) of the present invention, the acid used for soaking may be hydrochloric acid, acetic acid, or other acid capable of reacting with calcium carbonate, preferably dilute hydrochloric acid with a concentration of 0.1-1mol/L, more preferably dilute hydrochloric acid with a concentration of 0.4-0.8 mol/L; the soaking time is preferably 12 to 48 hours, more preferably 12 to 24 hours.
In a third aspect, the invention provides an application of the polyvinylidene fluoride film with the sea urchin-shaped bionic three-cycle minimum curved surface structure as a diaphragm of a lithium metal battery.
Compared with the prior art, the invention has the following beneficial effects:
(1) due to the special bionic three-cycle minimum curved surface structure, compared with a compact PVDF film prepared by other methods, the polyvinylidene fluoride film prepared by the method has extremely high porosity and better mechanical properties (such as elastic modulus, yield stress and the like), and the polyvinylidene fluoride film used as a diaphragm of a lithium metal battery shows more excellent cycle stability than a conventional compact PVDF diaphragm and a commercial PP diaphragm.
(2) The polyvinylidene fluoride film is prepared by adopting a template method, and natural waste sea urchin shells are used as templates, so that the cost is saved to a great extent, and the polyvinylidene fluoride film has the characteristic of waste utilization; the preparation method is simple and efficient, and can reduce the cost of the lithium metal battery to a certain extent while solving the problem of the lithium metal battery, so that the requirements of sustainable development and commercialization of the new energy lithium metal battery in the future can be better met on the basis of meeting the performance of the lithium metal battery.
(IV) description of the drawings
Fig. 1-1 and 1-2 are optical images of the white sea urchin shell and the PVDF separator prepared in example 1.
FIG. 2-1, FIG. 2-2 and FIG. 2-3 are SEM plan views of sea urchin shells and SEM plan view of PVDF, respectively, in cross section.
FIGS. 3-1 and 3-2 show the current density of a lithium copper battery prepared using PVDF as a separator and a commercial separator in example 1, respectively2，5mA/cm2Comparative coulombic efficiency test cycle performance plots were performed.
FIGS. 4-1 and 4-2 are graphs showing the current density of 2mA/cm for a lithium copper battery prepared by using PVDF as a separator in example 1 and a conventional PVDF separator, respectively2，5mA/cm2Comparative coulombic efficiency test cycle performance plots were performed.
(V) detailed description of the preferred embodiment
The technical solution of the present invention is further described below by using specific examples, but the scope of the present invention is not limited thereto.
Comparative example 1: preparation of conventional PVDF film
PVDF is prepared according to the mass ratio of 1: 10 was dissolved in NMP and stirred continuously at 50 ℃ to dissolve the PVDF completely in NMP without any air bubbles or particles present. The PVDF solution was poured onto a glass substrate, scraped with a 100 μm doctor blade to form a film, and then dried in an oven at 60 ℃ to give a PVDF film having a thickness of about 80 μm.
PVDF films of different thicknesses can be obtained by using doctor blades of different scales.
Example 1
Selecting relatively flat waste white sea urchin shells, washing the waste white sea urchin shells with a large amount of water, and removing residual protein and other organic components on the surfaces. Breaking the cleaned sea urchin shells to make the relatively flat part have the largest surface area; and (3) firstly polishing the obtained clean white sea urchin shells by using sand paper with the granularity of 400 until the two sides are smooth, then polishing the clean white sea urchin shells by using sand paper with the granularity of 600 until the size is close to 100 mu m, then continuously polishing the clean white sea urchin shells by using sand paper with the granularity of 1000 until the clean white sea urchin shells are in a semitransparent state (about 100 mu m), then ultrasonically washing the clean white sea urchin shells in water for 1h, then ultrasonically washing the clean white sea urchin shells in ethanol for 0.5h, and drying the clean white sea urchin shells in an oven at 80 ℃ to obtain almost transparent sea urchin shell slices with the thickness of about 100 mu m.
And flatly placing the dried sea urchin shell slice in a watch glass, and then, mixing PVDF according to a mass ratio of 1: 10 was dissolved in NMP and stirred continuously at 50 ℃ to dissolve the PVDF completely in NMP without any air bubbles or particles present. Then, dripping an NMP solution for dissolving PVDF on the sea urchin shell thin slices until the sea urchin shell thin slices are completely covered by the PVDF solution, and then placing the sea urchin shell thin slices in a drying oven at 60 ℃ to remove the NMP solution, so as to obtain the composite material of the sea urchin shell thin slices loaded with PVDF; grinding a PVDF sea urchin shell sheet composite material by sand paper with the granularity of 400, 600 and 1000 from small to large in sequence until the composite material is slightly thinner than the thickness of the sea urchin shell sheet, completely grinding a layer of dense PVDF covering the surface of the sea urchin shell, soaking in 0.8mol/L dilute hydrochloric acid for 24 hours to remove a sea urchin shell template, washing with distilled water and ethanol in sequence until the mixture is neutral, placing in a 60 ℃ oven for drying, and obtaining the polyvinylidene fluoride film with the three-cycle ordered network structure and the thickness of about 80 mu m.
The prepared polyvinylidene fluoride film with the three-cycle ordered network structure is used for a diaphragm of a lithium metal battery. The diaphragm is assembled into a lithium metal battery to carry out coulombic efficiency test. The specific assembly steps are as follows: for the Li/Cu half-cell coulombic efficiency test, firstly, the cut copper sheet is washed by dilute hydrochloric acid, then washed by a large amount of deionized water to be neutral, finally washed twice by alcohol, and dried at room temperature. The washed copper sheet was used as a current collector and a cut PVDF separator using 1M LiTFSI and 1 wt% LiNO3DOL/DME (1:1w/w) as an additive as an electrolyte in an argon glove box (H)2O＜0.01ppm,O2< 0.01ppm) was assembled. The control group was assembled by selecting a commercial PP separator and the 80 micron PVDF film prepared in comparative example 1.
And (2) testing the assembled half cell on a Xinwei cell frame, and for the coulomb efficiency test, firstly activating the half cell at 0.05mA in a voltage interval of 0.01-1V, then plating lithium with a certain capacity on a copper sheet at a certain current, namely discharging, and then pulling out the plated lithium at a certain voltage to calculate the coulomb efficiency of the half cell. As a result, as shown in FIGS. 3-1, 3-2, 4-1, and 4-2, it was found that lithium copper batteries prepared using the PVDF film having a three-cycle ordered network structure prepared in example 1 as a separator were each capable of measuring a current density of 2mA/cm2，5mA/cm2Under the condition of (1), circulating for 700 times and 400 times respectively, the coulombic efficiency can still be kept above 95%, and the performance of the composite membrane far exceeds that of a commercial PP membrane and a conventional PVDF membrane.
Example 2
Selecting relatively flat waste white sea urchin shells, washing the waste white sea urchin shells with a large amount of water, and removing residual protein and other organic components on the surfaces. Breaking the cleaned sea urchin shells to make the relatively flat part have the largest surface area; and (3) firstly polishing the obtained clean white sea urchin shells by using sand paper with the granularity of 600 until the two sides are smooth, then polishing the clean white sea urchin shells by using sand paper with the granularity of 800 until the size is close to 110 mu m, then continuously polishing the clean white sea urchin shells in a semitransparent state (110 mu m) by using sand paper with the granularity of 1200, then ultrasonically washing the clean white sea urchin shells in water for 2h, then ultrasonically washing the clean white sea urchin shells in ethanol for 1h, and drying the clean white sea urchin shells in an oven at 60 ℃ to obtain almost transparent sea urchin shell slices with the thickness of about 110 mu m.
And flatly placing the dried sea urchin shell slice in a watch glass, and then, mixing PVDF according to a mass ratio of 1: 15 was dissolved in NMP and stirred continuously at 55 c to dissolve the PVDF completely in NMP without any air bubbles or particles present. Then, dripping an NMP solution for dissolving PVDF on the sea urchin shell thin slices until the sea urchin shell thin slices are completely covered by the PVDF solution, and then placing the sea urchin shell thin slices in a drying oven at 60 ℃ to remove the NMP solution, so as to obtain the composite material of the sea urchin shell thin slices loaded with PVDF; grinding a PVDF sea urchin shell sheet composite material by sand paper with the granularity of 600, 800 and 1200 from small to large in sequence until the composite material is slightly thinner than the thickness of the sea urchin shell sheet, completely grinding a layer of dense PVDF covering the surface of the sea urchin shell, soaking in 0.5mol/L dilute hydrochloric acid for 24 hours to remove a sea urchin shell template, washing with distilled water and ethanol in sequence until the mixture is neutral, placing in a 60 ℃ oven for drying, and obtaining the 100 mu m thick polyvinylidene fluoride film with the three-cycle ordered network structure.
The prepared polyvinylidene fluoride film with the three-cycle ordered network structure is used for a diaphragm of a lithium metal battery. The diaphragm is assembled into a lithium metal battery to carry out coulombic efficiency test. The specific assembly steps are as follows: for the Li/Cu half-cell coulombic efficiency test, firstly, the cut copper sheet is washed by dilute hydrochloric acid, then washed by a large amount of deionized water to be neutral, finally washed twice by alcohol, and dried at room temperature. The washed copper sheet was used as a current collector and a cut PVDF separator using 1M LiTFSI and 1 wt% LiNO3DOL/DME (1:1w/w) as an additive as an electrolyte in an argon glove box (H)2O＜0.01ppm,O2< 0.01ppm) was assembled. The control group was assembled by selecting a commercial polypropylene PP separator and a 100 micron PVDF separator prepared in comparative example 1.
And (2) testing the assembled half cell on a Xinwei cell frame, and for the coulomb efficiency test, firstly activating the half cell at 0.05mA in a voltage interval of 0.01-1V, then plating lithium with a certain capacity on a copper sheet at a certain current, namely discharging, and then pulling out the plated lithium at a certain voltage to calculate the coulomb efficiency of the half cell. As a result, it was found that the lithium copper battery prepared by using the PVDF film having a three-cycle ordered network structure prepared in example 2 as a separator had higher coulombic efficiency and better cycle performance at a current density of 3mA/cm2Under the condition of (1), the respective circulation is carried out for 400 times, the coulombic efficiency can still be kept above 95%, and the performance of the composite membrane far exceeds that of a commercial PP membrane and a conventional PVDF membrane.
Example 3
Selecting relatively flat waste white sea urchin shells, washing the waste white sea urchin shells with a large amount of water, and removing residual protein and other organic components on the surfaces. Breaking the cleaned sea urchin shells to make the relatively flat part have the largest surface area; and (3) polishing the obtained clean sea urchin shells by using sand paper with the granularity of 400 until the two sides are smooth, then polishing the sea urchin shells by using sand paper with the granularity of 600 until the two sides are close to 160 mu m, then continuously polishing the sea urchin shells by using sand paper with the granularity of 1000 until the sea urchin shells are in a semitransparent state (about 160 mu m), then ultrasonically washing the sea urchin shells in water for 1h, then ultrasonically washing the sea urchin shells in ethanol for 0.5h, and drying the sea urchin shells in an oven at 80 ℃ to obtain almost transparent sea urchin shell slices with the thickness of about 160 mu m.
And flatly placing the dried sea urchin shell slice in a watch glass, and then, mixing PVDF according to a mass ratio of 1: 5 was dissolved in NMP and stirred continuously at 50 ℃ to dissolve PVDF completely in NMP without any air bubbles or particles. Then, dripping an NMP solution for dissolving PVDF on the sea urchin shell thin slices until the sea urchin shell thin slices are completely covered by the PVDF solution, and then placing the sea urchin shell thin slices in a drying oven at 60 ℃ to remove the NMP solution, so as to obtain the composite material of the sea urchin shell thin slices loaded with PVDF; grinding a PVDF sea urchin shell sheet composite material by sand paper with the granularity of 400, 600 and 1000 from small to large in sequence until the composite material is slightly thinner than the thickness of the sea urchin shell sheet, completely grinding a layer of dense PVDF covering the surface of the sea urchin shell, then soaking the composite material in dilute hydrochloric acid with the concentration of 1mol/L for 24 hours to remove a sea urchin shell template, then washing the sea urchin shell template to neutrality by distilled water and ethanol in sequence, and then drying the sea urchin shell template in a 60-DEG C drying oven to obtain a 150 mu m thick polyvinylidene fluoride film with a three-cycle ordered network structure.
The prepared polyvinylidene fluoride film with the three-cycle ordered network structure is used for a diaphragm of a lithium metal battery. The diaphragm is assembled into a lithium metal battery to carry out coulombic efficiency test. The specific assembly steps are as follows: for the Li/Cu half-cell coulombic efficiency test, firstly, the cut copper sheet is washed by dilute hydrochloric acid, then washed by a large amount of deionized water to be neutral, finally washed twice by alcohol, and dried at room temperature. The washed copper sheet was used as a current collector and a cut PVDF separator using 1M LiTFSI and 1 wt% LiNO3DOL/DME (1:1w/w) as an additive as an electrolyte in an argon glove box (H)2O＜0.01ppm,O2< 0.01ppm) was assembled. The control group was assembled using a commercial polypropylene PP separator and the 150 micron PVDF separator prepared in comparative example 1.
The assembled half cell is put into a Xinwei cellAnd (3) carrying out a test on a rack, and for the coulomb efficiency test, firstly activating by 0.05mA in a voltage interval of 0.01-1V, then plating lithium with a certain capacity on a copper sheet by a certain current, namely discharging, and then pulling out the plated lithium by a certain voltage to calculate the coulomb efficiency of the half cell. As a result, it was found that the lithium copper battery prepared by using the PVDF film having a three-cycle ordered network structure prepared in example 3 as a separator also had higher coulombic efficiency and better cycle performance at a current density of 2mA/cm2Under the condition of (1), the respective circulation is carried out for 400 times, the coulombic efficiency can still be kept above 95%, and the performance of the composite membrane far exceeds that of a commercial PP membrane and a conventional PVDF membrane.

Claims (10)

1. The polyvinylidene fluoride film with the bionic three-cycle minimum curved surface structure is characterized in that a sea urchin shell with the three-cycle minimum curved surface structure is used as a template, the sea urchin shell is made into a sea urchin shell slice with the thickness not exceeding 160 mu m, PVDF is made to permeate into a framework of the sea urchin shell slice by means of a solvent and completely fill the framework, the sea urchin shell slice filled with PVDF is subjected to acid soaking to remove the sea urchin shell template, and the polyvinylidene fluoride film with the bionic three-cycle minimum curved surface structure is obtained.
2. The polyvinylidene fluoride film of claim 1, wherein: the thickness of the sea urchin shell sheet is 80-160 μm.
3. The polyvinylidene fluoride film of claim 1, wherein: the solvent is NMP, N N-dimethylformamide or dimethylacetamide.
4. A method for preparing a polyvinylidene fluoride film with a bionic three-cycle minimum curved surface structure as in any one of claims 1 to 3, comprising the following steps:
(1) taking relatively flat waste white sea urchin shells, washing the waste white sea urchin shells with water, and removing residual organic components on the surfaces of the waste white sea urchin shells; breaking the cleaned sea urchin shells, selecting a relatively flat part for later use, wherein the relatively flat part has the largest possible surface area in the breaking process;
(2) preparing the clean white sea urchin shells selected in the step (1) into sea urchin shell slices with the thickness not more than 160 mu m;
(3) flatly placing the sea urchin shell slices obtained in the step (2) in a container, dripping PVDF solution on the sea urchin shell slices until the sea urchin shell slices are completely covered by the PVDF solution, infiltrating the PVDF into the sea urchin shell slices by means of a solvent at the moment, completely filling the sea urchin shell frameworks with the PVDF, drying at 40-80 ℃ to remove the solvent, completely grinding a layer of dense PVDF covering the surfaces of the sea urchin shells to obtain the sea urchin shell slices filled with the PVDF;
(4) and (3) placing the sea urchin shell slices filled with the PVDF in acid to be fully soaked to remove the sea urchin shell templates, then sequentially washing the sea urchin shell slices with distilled water and ethanol to be neutral, and then placing the sea urchin shell slices in a drying oven at 40-80 ℃ for drying to obtain the polyvinylidene fluoride film with the bionic three-cycle minimum curved surface structure.
5. The method of claim 4, wherein: in the step (1), the shell of the white sea urchin is a white cake-shaped sea urchin with a large flat area.
6. The method of claim 4, wherein: in the step (2), obtaining a sea urchin shell slice by polishing: grinding the sea urchin shells to a required thickness by using sand paper, then ultrasonically washing the sea urchin shells in water and ethanol in sequence, and drying the sea urchin shells in an oven at the temperature of 30-100 ℃ to obtain the sea urchin shell slices.
7. The method of claim 5, wherein: in the step (2), the shells of the sea urchins are sequentially polished by using sand papers with different particle sizes according to the sequence of the particle sizes from small to large.
8. The method of claim 4, wherein: in the step (3), a layer of dense PVDF covering the surface of the sea urchin shell is completely ground by using sand papers with different particle sizes according to the sequence of the particle sizes from small to large.
9. The method of claim 4, wherein: in the step (4), the acid used for soaking is dilute hydrochloric acid with the concentration of 0.1-1mol/L, and the soaking time is 12-48 hours.
10. The use of the polyvinylidene fluoride film having a biomimetic three-cycle minimal surface structure according to claim 1 as a separator of a lithium metal battery.
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CN103880003A (en) * 2014-04-10 2014-06-25 苏州宇豪纳米材料有限公司 Graphene material prepared from biological calcium carbonate source and application thereof
CN109244318A (en) * 2018-09-03 2019-01-18 中国科学技术大学 The preparation method of porous aragonite structure micron chip, ceramic diaphragm and preparation method thereof

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CN103880003A (en) * 2014-04-10 2014-06-25 苏州宇豪纳米材料有限公司 Graphene material prepared from biological calcium carbonate source and application thereof
CN109244318A (en) * 2018-09-03 2019-01-18 中国科学技术大学 The preparation method of porous aragonite structure micron chip, ceramic diaphragm and preparation method thereof

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