CN116706437A - Sodium ion battery coating diaphragm, preparation method thereof and sodium ion battery - Google Patents

Sodium ion battery coating diaphragm, preparation method thereof and sodium ion battery Download PDF

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Publication number
CN116706437A
CN116706437A CN202310638415.0A CN202310638415A CN116706437A CN 116706437 A CN116706437 A CN 116706437A CN 202310638415 A CN202310638415 A CN 202310638415A CN 116706437 A CN116706437 A CN 116706437A
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China
Prior art keywords
ion battery
sodium ion
coating
coated separator
sodium
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CN202310638415.0A
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Inventor
杨光辉
刘杲珺
张影
汤晓
吴奇阳
徐梦
白耀宗
杨浩
张绪杰
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Zhongcai Lithium Film Nanjing Co ltd
Sinoma Lithium Film Co Ltd
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Zhongcai Lithium Film Nanjing Co ltd
Sinoma Lithium Film Co Ltd
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Priority to CN202310638415.0A priority Critical patent/CN116706437A/en
Publication of CN116706437A publication Critical patent/CN116706437A/en
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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
    • 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
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • 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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/497—Ionic conductivity
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Cell Separators (AREA)

Abstract

The invention provides a sodium ion battery coating diaphragm, a preparation method thereof and a sodium ion battery. The sodium ion battery coating diaphragm comprises a base film and a mixed coating coated on one side of the base film; the mixed coating is obtained by coating mixed coating slurry, and the solid content of the mixed coating slurry is 20-40%; the material comprises the following raw materials in percentage by mass: boehmite (b): 72.0 to 97.7 percent; PAANa:1.0 to 20 percent; an adhesive: 1.0 to 5.0 percent; dispersing agent: 0.1 to 1.0 percent; wetting agent: 0.1 to 1.0 percent; and (3) a thickening agent: 0.1 to 1.0 percent. The sodium ion battery coating diaphragm has wettability and thermal stability, and has the functions of adhesion and sodium supplement. The preparation method of the sodium ion battery coated diaphragm provided by the invention has simple and efficient process, and the functions can be realized by one-time coating.

Description

Sodium ion battery coating diaphragm, preparation method thereof and sodium ion battery
Technical Field
The invention relates to a membrane technology and a material in the fields of new energy power and energy storage, in particular to a sodium ion battery coated membrane, a preparation method thereof and a sodium ion battery.
Background
Currently, separators for sodium ion batteries are mainly classified into three types, glass fiber separators, organic polymer non-woven fabrics and polyolefin composite separators. The glass fiber is a fibrous non-woven membrane prepared from inorganic materials, has high price, thicker thickness and lower tensile strength, is not suitable for high-energy-density batteries, can only be used as a sodium ion battery membrane in a laboratory at present, and is not suitable for large-scale use. The organic polymer non-woven fabric also has the problem of thicker thickness, and the energy density of the sodium ion battery can be further reduced.
The polyolefin composite membrane can be used in sodium ion batteries by compositing organic or inorganic materials with commercial polyolefin membranes, has a small thickness, and can be suitable for high-safety and high-power batteries if the problems of wettability and thermal stability can be solved.
Polyolefin is a separator material mature in the prior art and widely applied to lithium ion batteries. Sodium ion batteries are similar to lithium ion batteries in working principle and belong to the rocking chair type. The polyolefin separator used in the lithium ion battery can be used in the sodium ion battery. However, polyolefin separators have insufficient wettability in electrolytes such as esters and ethers, so that the contact surface between the separator and the electrolyte is limited, and the ion conductivity and the charge-discharge performance of the battery are limited.
Sodium ion batteries can form a solid electrolyte membrane (SEI film) to consume sodium ions when being charged for the first time, and when sodium ions are embedded and released in pole piece active materials, part of the sodium ions are embedded in the pole piece materials and cannot be completely released, and sodium ions are consumed, so that movable sodium ions in the pole piece materials are lost, the capacity of the batteries is reduced, and the capacity retention rate is reduced. In addition, polyolefin materials have poor heat resistance, and may melt under overcharge and overdischarge, rapid charge and discharge, or high temperature, causing short-circuit fire or even explosion. Therefore, there is a need in the art to develop a separator for a sodium ion battery that has both wettability and thermal stability and can improve the electrical cycle performance of the battery when applied to a sodium ion battery.
In the prior art, a composite coating diaphragm is prepared by coating a sodium layer between a base film and an alumina coating, the liquid retaining capacity of the diaphragm is improved by using the sodium layer, meanwhile, the transmission of sodium ions is promoted, the cycle performance of a battery is improved, the generation of sodium dendrites is avoided, and the safety performance of the battery is improved. However, the scheme comprises a base film, a sodium layer and an aluminum oxide three-layer coating, the preparation process is complicated, the existence of the sodium layer leads to the risk of poor binding force between the aluminum oxide layer and the base film, and the coating can be caused to fall off when the battery is applied.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a sodium ion battery coating diaphragm, a preparation method thereof and a sodium ion battery.
The technical scheme of the invention is as follows:
one of the purposes of this patent is to the prior art not enough, provides a sodium ion battery coating diaphragm that has wettability and thermal stability, and has binding property and benefit sodium function concurrently.
A sodium ion battery coated separator comprising a base film and a hybrid coating coated on one side of the base film;
the base film is a composite diaphragm of polypropylene or polyethylene or both;
the mixed coating is obtained by coating mixed coating slurry, and the mixed coating slurry comprises boehmite and PAANa.
Further, the thickness of the mixed coating is 0.8-6 mu m; preferably, the thickness of the mixed coating is 2-4 μm.
Further, the base film is a polyethylene diaphragm with a thickness of 7-14 mu m and a needling strength of more than or equal to 400gf.
Further, the solid content of the mixed coating slurry is 20-40%; the solvent of the mixed coating slurry is deionized water, and the solid matters in the slurry consist of the following raw materials in percentage by mass:
boehmite (b): 72.0 to 97.7 percent
PAANa：1.0～20％
An adhesive: 1.0 to 5.0 percent
Dispersing agent: 0.1 to 1.0 percent
Wetting agent: 0.1 to 1.0 percent
And (3) a thickening agent: 0.1 to 1.0 percent.
Further, the boehmite has a particle size of 0.5 to 3.0. Mu.m, preferably 1.0. Mu.m.
Further, the PAANa has a molecular weight of 3000-5000 Da, preferably a molecular weight of 5000 Da.
Further, the adhesive is one or a combination of a plurality of Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA) and polyacrylate (ABR); preferably, the adhesive is polyacrylate (ABR).
Further, the dispersing agent is one or a combination of more of polyvinylpyrrolidone (PVP), polyacrylamide (PAM) and polyvinyl alcohol (PVA); preferably, the dispersant is Polyacrylamide (PAM).
Further, the wetting agent is one or a combination of more of anionic surfactant, polyethylene surfactant and polyol surfactant; preferably, the wetting agent is polyethylene glycol 200 (PEG 200).
Further, the thickener is one or a combination of more of methyl cellulose, sodium carboxymethylcellulose (CMC-Na) and Sodium Alginate (SA); preferably, the thickener is sodium carboxymethylcellulose (CMC-Na).
According to the invention, by adjusting the mass percentage of the components, the coating diaphragm has better thermal stability, liquid absorption and retention capacity and adhesiveness, is beneficial to preventing the diaphragm from deforming, improving the sodium ion transmission rate and improving the safety of the sodium ion battery and the infiltration capacity of the electrolyte.
According to the invention, the mechanical property of the coated membrane is better by adjusting the thickness and the needling strength of the base membrane, so that the sodium dendrite penetration resistance of the membrane is improved, and the safety of the sodium ion battery is further improved.
The second purpose of this patent is to provide a preparation method of sodium ion battery coating membrane, which has simple and efficient process, aiming at the defects of the prior art.
A method of preparing a sodium ion battery coated separator, the method comprising the steps of:
(1) Dissolving boehmite, PAANa, an adhesive, a dispersing agent, a wetting agent and a thickening agent in a formula amount by using deionized water, and stirring to obtain uniformly dispersed mixed coating slurry for later use;
(2) And coating the mixed coating slurry on one side surface of the base film, and drying at 55-85 ℃ to obtain the sodium ion battery mixed coating diaphragm.
Further, the stirring speed in the step (1) is 200-1200rpm, and the stirring time is 0.1-12h.
Further, the unreeling tension of the coating in the step (2) is 0.5-40N, the reeling tension is 1-30N, the coating speed is 10-120m/min, and the contact pressure is 0.1-20N.
It is a third object of this patent to address the deficiencies of the prior art by providing a sodium ion battery comprising the sodium ion battery coated separator described above. The sodium ion battery has good cycle performance.
The sodium ion battery also comprises an anode, a cathode and electrolyte.
The coated diaphragm provided by the invention can improve the transmission rate of sodium ions of the coating, improve the electrical property reduction caused by sodium consumption, increase the bonding effect between a boehmite layer and an electrode, improve the interface resistance of a sodium ion battery and improve the capacity retention rate of the sodium ion battery.
The invention has the beneficial effects that:
according to the sodium ion battery coating diaphragm, the high-strength polyethylene diaphragm is used as a base film (the needling strength is more than or equal to 400 gf), so that the sodium dendrite penetration resistance of the diaphragm can be improved.
The boehmite in the coating layer of the coated diaphragm can improve the thermal stability and electrolyte wettability of the diaphragm, and reduce the 105 ℃/1h thermal shrinkage rate of the diaphragm: MD is less than or equal to 2.5 percent, TD is less than or equal to 0.8 percent, and the liquid absorption and retention rate of the diaphragm is improved: the liquid absorption rate is more than or equal to 83 percent, and the liquid retention rate is more than or equal to 72.5 percent.
Sodium polyacrylate PAA-Na in the coating membrane coating can improve the sodium ion transmission rate of the coating on one hand, can increase the bonding effect between a boehmite layer and an electrode on the other hand, improves the interface resistance of a sodium ion battery, improves the reduction of the battery capacity retention rate caused by sodium ion consumption, improves the electric cycle performance of the sodium ion battery, and has the capacity retention rate of more than 90% after 1000 cycles.
In addition, the preparation method of the sodium ion battery coated diaphragm provided by the invention has simple and efficient process, and the functions can be realized by one-time coating.
Drawings
Fig. 1 is a schematic structural view of a coated separator provided in example 1, wherein the 1-base film, 2-hybrid coating.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention in any way.
Example 1
This example provides a sodium ion battery coated separator comprising a polyethylene-based film having a film thickness of 9 μm and a needling strength of 520gf, and a hybrid coating layer coated on one side of the base film, as shown in fig. 1. The hybrid coating comprises boehmite (particle size 1.0 mu m), sodium polyacrylate PAANa (molecular weight 5000W Da) and an auxiliary agent, and the thickness of the coating is 3 mu m.
The preparation method comprises the following steps:
(1) Boehmite, PAANa, polyacrylate (ABR), polyacrylamide (PAM), polyethylene glycol 200, sodium carboxymethylcellulose (CMC-Na) and deionized water with the mass percentage of 85.5:8.5:4.5:0.5:0.2:0.8 are mixed. Sequentially stirring with 1200rpm paddles for 2h,1000rpm paddles for 30min at a temperature of less than or equal to 25deg.C, filtering with 150 mesh filter screen, grinding with grinder, and filtering with 200 mesh filter screen to obtain coating slurry with 30% solid content.
(2) Coating the coating slurry on one side of the base film in a coating mode, drying at 65 ℃ after coating, coating unreeling tension of 25N, reeling tension of 2N, coating speed of 60m/min, contact pressure of 12N, and drying to obtain the sodium ion coated membrane.
Example 2
The present example provides a sodium ion battery coated separator comprising a polyethylene-based film having a film thickness of 7 μm and a needling strength of 430gf, and a hybrid coating layer coated on one side of the base film. The hybrid coating comprises boehmite (particle size 1.0 mu m), sodium polyacrylate PAANa (molecular weight 5000W Da) and an auxiliary agent, and the thickness of the coating is 2 mu m.
The preparation method comprises the following steps:
(1) Boehmite, PAANa, polyacrylate (ABR), polyacrylamide (PAM), polyethylene glycol 200, sodium carboxymethylcellulose (CMC-Na) and deionized water with the mass percentage of 85.5:8.5:4.5:0.5:0.2:0.8 are mixed. Sequentially stirring with 1200rpm paddles for 2h,1000rpm paddles for 30min at a temperature of less than or equal to 25deg.C, filtering with 150 mesh filter screen, grinding with grinder, and filtering with 200 mesh filter screen to obtain coating slurry with 30% solid content.
(2) Coating the coating slurry on one side of the base film in a coating mode, drying at 60 ℃ after coating, coating unreeling tension of 25N, reeling tension of 2N, coating speed of 60m/min, contact pressure of 12N, and drying to obtain the sodium ion coated membrane.
Example 3
The present example provides a sodium ion battery coated separator comprising a polyethylene-based film having a film thickness of 12 μm and a needling strength of 580gf, and a hybrid coating layer coated on one side of the base film. The hybrid coating comprises boehmite (particle size 1.0 mu m), sodium polyacrylate PAANa (molecular weight 5000W Da) and an auxiliary agent, and the thickness of the coating is 4 mu m.
The preparation method comprises the following steps:
(1) Boehmite, PAANa, polyacrylate (ABR), polyacrylamide (PAM), polyethylene glycol 200, sodium carboxymethylcellulose (CMC-Na) and deionized water with the mass percentage of 85.5:8.5:4.5:0.5:0.2:0.8 are mixed. Sequentially stirring with 1200rpm paddles for 2h,1000rpm paddles for 30min at a temperature of less than or equal to 25deg.C, filtering with 150 mesh filter screen, grinding with grinder, and filtering with 200 mesh filter screen to obtain coating slurry with 30% solid content.
(2) Coating the coating slurry on one side of the base film in a coating mode, drying at 70 ℃ after coating, coating unreeling tension of 25N, reeling tension of 2N, coating speed of 60m/min, contact pressure of 12N, and drying to obtain the sodium ion coated membrane.
Example 4
The present example provides a sodium ion battery coated separator comprising a polyethylene-based film having a film thickness of 9 μm and a needling strength of 520gf, and a hybrid coating layer coated on one side of the base film. The hybrid coating comprises boehmite (particle size 1.0 mu m), sodium polyacrylate PAANa (molecular weight 5000W Da) and an auxiliary agent, and the thickness of the coating is 3 mu m.
The preparation method comprises the following steps:
(1) Boehmite, PAANa, polyacrylate (ABR), polyacrylamide (PAM), polyethylene glycol 200, sodium carboxymethylcellulose (CMC-Na) and deionized water with the mass percentage of 88.5:6.0:4.3:0.4:0.2:0.6 are mixed. Sequentially stirring with 1200rpm paddles for 2h,1000rpm paddles for 30min at a temperature of less than or equal to 25deg.C, filtering with 150 mesh filter screen, grinding with grinder, and filtering with 200 mesh filter screen to obtain coating slurry with 30% solid content.
(2) Coating the coating slurry on one side of the base film in a coating mode, drying at 65 ℃ after coating, coating unreeling tension of 25N, reeling tension of 2N, coating speed of 60m/min, contact pressure of 12N, and drying to obtain the sodium ion coated membrane.
Example 5
The present example provides a sodium ion battery coated separator comprising a polyethylene-based film having a film thickness of 7 μm and a needling strength of 430gf, and a hybrid coating layer coated on one side of the base film. The hybrid coating comprises boehmite (particle size 1.0 mu m), sodium polyacrylate PAANa (molecular weight 5000W Da) and an auxiliary agent, and the thickness of the coating is 2 mu m.
The preparation method comprises the following steps:
(1) Boehmite, PAANa, polyacrylate (ABR), polyacrylamide (PAM), polyethylene glycol 200, sodium carboxymethylcellulose (CMC-Na) and deionized water with the mass percentage of 88.5:6.0:4.3:0.4:0.2:0.6 are mixed. Sequentially stirring with 1200rpm paddles for 2h,1000rpm paddles for 30min at a temperature of less than or equal to 25deg.C, filtering with 150 mesh filter screen, grinding with grinder, and filtering with 200 mesh filter screen to obtain coating slurry with 30% solid content.
(2) Coating the coating slurry on one side of the base film in a coating mode, drying at 60 ℃ after coating, coating unreeling tension of 25N, reeling tension of 2N, coating speed of 60m/min, contact pressure of 12N, and drying to obtain the sodium ion coated membrane.
Example 6
The present example provides a sodium ion battery coated separator comprising a polyethylene-based film having a film thickness of 12 μm and a needling strength of 580gf, and a hybrid coating layer coated on one side of the base film. The hybrid coating comprises boehmite (particle size 1.0 mu m), sodium polyacrylate PAANa (molecular weight 5000W Da) and an auxiliary agent, and the thickness of the coating is 4 mu m.
The preparation method comprises the following steps:
(1) Boehmite, PAANa, polyacrylate (ABR), polyacrylamide (PAM), polyethylene glycol 200, sodium carboxymethylcellulose (CMC-Na) and deionized water with the mass percentage of 88.5:6.0:4.3:0.4:0.2:0.6 are mixed. Sequentially stirring with 1200rpm paddles for 2h,1000rpm paddles for 30min at a temperature of less than or equal to 25deg.C, filtering with 150 mesh filter screen, grinding with grinder, and filtering with 200 mesh filter screen to obtain coating slurry with 30% solid content.
(2) Coating the coating slurry on one side of the base film in a coating mode, drying at 70 ℃ after coating, coating unreeling tension of 25N, reeling tension of 2N, coating speed of 60m/min, contact pressure of 12N, and drying to obtain the sodium ion coated membrane.
Comparative example 1
This comparative example differs from example 1 in that only boehmite and an auxiliary agent are coated on the surface of the base film, and the same as in example 1 is applied except that the coating is a pure ceramic coating, which does not contain PAANa.
Comparative example 2
This comparative example differs from example 1 in that the PAANa in the coating was replaced by PVDF, all other things being equal to example 1.
Comparative example 3
This comparative example differs from example 1 in that only the same base film as in example 1 was provided, and the surface of the base film contained no coating layer.
Experimental example
The coated separators provided in examples 1 to 6 and comparative examples 1 to 3 were prepared to obtain sodium ion batteries, and the preparation method was as follows:
preparation of a positive plate: active material Na 2 MnFe(CN) 6 Binder PVDF and conductive carbon black according to 93:3:4, adding N-methyl pyrrolidone (NMP) after mixing in a mass ratio, stirring uniformly to prepare mixed slurry, uniformly coating the slurry on aluminum foil with the thickness of 15 mu m, drying in a constant temperature oven at 70 ℃ for 24 hours, and cutting to prepare the positive plate.
Preparing a negative plate: hard carbon, styrene Butadiene Rubber (SBR) and conductive carbon black were mixed according to 94:2: and 4, adding deionized water into the mixture after mixing according to the mass ratio, uniformly stirring the mixture to prepare mixed slurry, uniformly coating the slurry on aluminum foil with the thickness of 15 mu m, drying the aluminum foil in a constant-temperature oven at 70 ℃ for 24 hours, and cutting the aluminum foil to prepare the negative plate.
And (3) battery assembly: and sequentially laminating and assembling the positive plate, the coated diaphragm and the negative plate into an aluminum plastic film, injecting sodium hexafluorophosphate ion electrolyte into the electrode to completely infiltrate the electrode plate, and sealing and forming to prepare the soft-package sodium ion battery.
The coated separators provided in examples 1-6 and comparative examples 1-3 were subjected to performance testing as follows:
(1) Heat shrinkage: cutting the coated diaphragm into standard samples with the thickness of more than 10cm and the thickness of 10cm, marking TD and MD respectively in the transverse direction and the longitudinal direction of the diaphragm by adopting a ruler, measuring a cross line with the thickness of 10cm and the thickness of 10cm, flattening the samples at the middle position of A4 paper, and sealing the two sides of the A4 paper. Confirming that the oven reaches the set required temperature, placing A4 paper with a diaphragm on the middle position of the upper layer and the middle layer of the oven, closing a door, starting up to calculate time, and keeping at 105 ℃ for 1h.
(2) Liquid absorption and retention rate: cutting the coating diaphragm into standard samples of 25mm multiplied by 100mm, weighing on an electronic balance, marking the weighed weight as W1, then placing the standard samples in a 100ml beaker containing 30ml of electrolyte, completely immersing the standard samples in the electrolyte, sealing the beaker by using a preservative film, and reducing the evaporation of the electrolyte, wherein the soaking time is 60 minutes. The soaked sample was taken out, the electrolyte solution on both surfaces of the sample was gently sucked with folded filter paper so that the surface thereof had no obvious small beads and the surface of the sample was not whitened (excessively adsorbed), and rapidly placed in a weighing bottle, and weighed as W2. The weighed sample was allowed to stand in a fume hood for 60min, and weighed and designated as W3. Liquid absorption= (W2-W1)/w1×100%; retention = (W3-W1)/w1×100%.
(3) Adhesive strength: cutting an A4 paper size sample, placing the sample according to the sequence of A4 paper/diaphragm/A4 paper, and passing through a plastic packaging machine along the MD direction to obtain a semi-finished product. Cutting a test sample with the width of 25mm and the length of 30cm from the semi-finished product along the MD direction, firstly stripping the test sample by about 8-10cm, fixing the upper end and the lower end of the test sample on a tensile testing machine for testing, and taking the average value of the three sections of values as a test result.
(4) Ion conductivity: and (3) carrying out EIS test by adopting an electrochemical workstation, wherein the frequency range is 1-200KHz, the amplitude is 5mV, the ionic conductivity of the diaphragm is calculated by using a formula sigma=L/(R×A), L is the thickness of the diaphragm, A is the effective area of the diaphragm, R is the body resistance of the diaphragm, and the resistance at the intersection point of an EIS graph curve and a real axis is taken.
The sodium ion batteries provided in application examples 1 to 6 and comparative application examples 1 to 3 were subjected to the electrochemical performance test as follows:
capacity retention rate: and (3) carrying out an electric cycle performance test on the battery test system of the electrochemical workstation at 25 ℃, wherein the tested current density is 1C, the charge-discharge voltage window is 2.5-4.2V, and the cycle is 1000 circles.
The results of the test are shown in tables 1-2:
TABLE 1
TABLE 2
As can be seen from the data of tables 1 and 2, the sodium ion battery coated separator provided in examples 1 to 6 of the present invention has superior liquid absorption, retention, adhesive strength and ionic conductivity to the coated separator provided in comparative examples 1 to 2. The invention improves the wettability and the adhesiveness of the diaphragm by utilizing the mixed coating, improves the internal resistance of the battery interface and improves the ion conductivity.
As can be seen from the data of table 2, the sodium ion batteries provided in examples 1 to 6 of the present invention have a capacity retention rate of not less than 90% after 1000 cycles at 1C. The coated separator provided in comparative examples 1 to 2, which has a much lower capacity retention at 1C than the sodium ion battery provided in examples 1 to 6, further highlights the advantages of the coated separator provided in the present invention.
The foregoing description of the preferred embodiment of the invention is provided for the purpose of illustration only, and is not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims (14)

1. A sodium ion battery coated separator, characterized in that the sodium ion battery coated separator comprises a base film and a mixed coating coated on one side of the base film;
the base film is a composite diaphragm of polypropylene or polyethylene or both;
the mixed coating is obtained by coating mixed coating slurry, and the mixed coating slurry comprises boehmite and PAANa.
2. The sodium ion battery coated separator of claim 1, wherein the hybrid coating thickness is 0.8-6 μιη; preferably, the thickness of the mixed coating is 2-4 μm.
3. The coated membrane of sodium ion battery according to claim 1, wherein the base membrane is a polyethylene membrane with a thickness of 7-14 μm and a needling strength of not less than 400gf.
4. The sodium ion battery coated separator of claim 1 wherein the mixed coating slurry has a solids content of 20-40%; the solvent of the mixed coating slurry is deionized water, and the solid matters in the slurry comprise the following raw materials in percentage by mass: boehmite (b): 72.0 to 97.7 percent
PAANa：1.0～20％
An adhesive: 1.0 to 5.0 percent
Dispersing agent: 0.1 to 1.0 percent
Wetting agent: 0.1 to 1.0 percent
And (3) a thickening agent: 0.1 to 1.0 percent.
5. The sodium ion battery coated separator according to claim 1, wherein the boehmite has a particle size of 0.5-3.0 μm, preferably a particle size of 1.0 μm.
6. The sodium ion battery coated separator according to claim 1, wherein the PAANa has a molecular weight of 3000-5000 Da, preferably a molecular weight of 5000 Da.
7. The sodium ion battery coated separator of claim 1, wherein the binder is one or a combination of more of styrene-butadiene rubber, polyacrylic acid, polyacrylate; preferably, the adhesive is polyacrylate.
8. The sodium ion battery coated separator of claim 1, wherein the dispersant is one or a combination of more of polyvinylpyrrolidone, polyacrylamide, polyvinyl alcohol; preferably, the dispersing agent is polyacrylamide.
9. The sodium ion battery coated separator of claim 1, wherein the wetting agent is one or a combination of more of an anionic surfactant, a polyethylene surfactant, a polyol surfactant; preferably, the wetting agent is polyethylene glycol 200.
10. The sodium ion battery coated separator of claim 1, wherein the thickener is one or a combination of more of methylcellulose, sodium carboxymethylcellulose, sodium alginate; preferably, the thickener is sodium carboxymethyl cellulose.
11. A method for preparing a sodium ion battery coated separator, the method comprising the steps of:
(1) Dissolving boehmite, PAANa, an adhesive, a dispersing agent, a wetting agent and a thickening agent in a formula amount by using deionized water, and stirring to obtain uniformly dispersed mixed coating slurry for later use;
(2) And coating the mixed coating slurry on one side surface of the base film, and drying at 55-85 ℃ to obtain the sodium ion battery mixed coating diaphragm.
12. The method for preparing a coated separator for sodium ion battery according to claim 10, wherein the stirring speed in the step (1) is 200-1200rpm and the stirring time is 0.1-12h.
13. The method for preparing a coated separator for a sodium ion battery according to claim 10, wherein the unwinding tension of the coating in the step (2) is 0.5-40N, the winding tension is 1-30N, the coating speed is 10-120m/min, and the contact pressure is 0.1-20N.
14. A sodium ion battery comprising the sodium ion battery coated separator of claim 1.
CN202310638415.0A 2023-06-01 2023-06-01 Sodium ion battery coating diaphragm, preparation method thereof and sodium ion battery Pending CN116706437A (en)

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