CN114824655B - Composite diaphragm, preparation method thereof and lithium ion battery - Google Patents

Composite diaphragm, preparation method thereof and lithium ion battery Download PDF

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CN114824655B
CN114824655B CN202210426143.3A CN202210426143A CN114824655B CN 114824655 B CN114824655 B CN 114824655B CN 202210426143 A CN202210426143 A CN 202210426143A CN 114824655 B CN114824655 B CN 114824655B
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layer
diaphragm
composite
membrane
base layer
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CN114824655A (en
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李峥
冯玉川
刘京亮
陈凯
何泓材
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Suzhou Qingtao New Energy S&T Co Ltd
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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
    • H01M50/44—Fibrous material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/426—Fluorocarbon polymers
    • 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
    • H01M50/454—Separators, membranes or diaphragms characterised by the material having a layered structure comprising a non-fibrous layer and a fibrous layer superimposed on one another
    • 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
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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
    • H01M50/491—Porosity

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Nanotechnology (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Cell Separators (AREA)

Abstract

The invention provides a composite diaphragm, a preparation method thereof and a lithium ion battery. The composite diaphragm comprises a base layer, a solid electrolyte layer coated on the surface of the base layer and a porous layer positioned on the surface of the solid electrolyte layer which are sequentially laminated; the porous layer is a PTFE nanofiber membrane or a PTFE microporous membrane layer. According to the invention, the PTFE nanofiber membrane or PTFE microporous membrane layer is directly used, instead of a mode of preparing polytetrafluoroethylene slurry and then coating in the prior art, the composite membrane can be obtained only by drying, a hot pressing technology is not needed, the damage of a pore structure is avoided, and the air permeability of the membrane is ensured. In addition, the prepared composite diaphragm is lighter and thinner, has small surface roughness, and is favorable for reducing the resistance between the diaphragm and the electrode material.

Description

Composite diaphragm, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of diaphragm materials, and particularly relates to a composite diaphragm, a preparation method thereof and a lithium ion battery.
Background
Compared with the traditional lead-acid battery, the lithium ion battery has received a great deal of attention due to the advantages of high voltage, high energy density, long service life, high safety and the like, and is also widely applied to the fields of portable electronic equipment, smart grids, electric automobiles and the like.
The main structure of the lithium battery is divided into four parts of positive electrode material, negative electrode material, electrolyte and diaphragm, and the diaphragm is used as an important part of the battery, plays a role in physically isolating the positive electrode material and the negative electrode material, avoids direct contact of the positive electrode material and the negative electrode material to generate short circuit, and has the effects of isolating electrons and allowing lithium ion transmission. The conventional lithium ion battery separator mostly adopts polyolefin separators, such as polypropylene or polyethylene, and with the improvement of the performance requirements of the battery, the requirements of the pure common separator are difficult to meet.
Currently, it is known to provide a solid electrolyte layer and a PTFE polymer layer on a separator substrate to improve the performance of the separator. However, the internal resistance of the battery is increased due to the difficulty in coating and the large thickness of the solid electrolyte layer, so that it is an important problem how to modify the preparation method to modify the structure of each layer of the composite separator so that the separator can meet the trend of light weight and light weight of the battery.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a composite diaphragm, a preparation method thereof and a lithium ion battery. According to the invention, the solid electrolyte layer is coated on the surface of the base layer and the porous layer is covered, so that the composite diaphragm can be obtained only by drying, a hot pressing technology is not needed, the damage of a pore structure is avoided, and the air permeability of the diaphragm is ensured.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a composite separator comprising a base layer, a solid electrolyte layer coated on the surface of the base layer, and a porous layer on the surface of the solid electrolyte layer, which are sequentially laminated;
the porous layer is a Polytetrafluoroethylene (PTFE) nanofiber membrane or a Polytetrafluoroethylene (PTFE) microporous membrane layer.
According to the invention, the PTFE nanofiber membrane or PTFE microporous membrane layer is directly used, instead of a mode of preparing polytetrafluoroethylene slurry and then coating in the prior art, the composite membrane can be obtained only by drying, a hot pressing technology is not needed, the damage of a pore structure is avoided, and the air permeability of the membrane is ensured. In addition, the prepared composite diaphragm is lighter and thinner, has small surface roughness, and is favorable for reducing the resistance between the diaphragm and the electrode material.
Preferably, the porous layer has a porosity of 50-80%, preferably 75-80%, for example 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, 72%, 73%, 75%, 78%, 80%.
In the invention, proper porosity can improve the air permeability of the diaphragm, improve the escape of air in the rolling process and ensure the performance maintenance of the battery in the use process, but the too high porosity is unfavorable for the stability of the film layer, and the polymer film layer is easy to damage under the condition of normal temperature rolling.
Preferably, the thickness of the porous layer is 0.1 to 3 μm, and may be, for example, 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 1 μm, 1.2 μm, 1.5 μm, 1.7 μm, 2 μm, 2.2 μm, 2.5 μm, 2.7 μm, 3 μm.
In the invention, the thickness of the porous layer is adjusted, so that the forming of the film layer is not facilitated when the thickness is too thin, and the internal resistance is increased when the thickness is too thick.
Preferably, the material of the base layer is PE, PP or PE/PP material. Wherein PE/PP material refers to a combination of PE and PP.
Preferably, the porosity of the material of the base layer is 20-80%, preferably 40-60%, further preferably 40-50%, for example 20%, 25%, 30%, 35%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 65%, 70%, 75%, 80%.
Preferably, the thickness of the base layer is 5-30 μm, preferably 8-12 μm, and may be, for example, 5 μm, 6 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 15 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm.
Preferably, the solid electrolyte layer is an inorganic solid electrolyte layer or a polymer solid electrolyte layer.
Preferably, the inorganic solid state electrolyte layer includes at least one of an oxide solid state electrolyte layer, a sulfide solid state electrolyte layer, or a halide solid state electrolyte layer.
In the present invention, the oxide solid electrolyte layer includes any one or more of garnet ceramics, LISICON-type oxides, NASICON-type oxides, or perovskite-type ceramics. For example, li 6.5 La 3 Zr 1.75 Te 0.25 O 12 、Li 7 La 3 Zr 2 O 12 、Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr 2 O 12 、 Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La 3 Zr 2 O 12 、Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 Or Li (lithium) 6.75 La 3 Zr 1.75 Nb 0.25 O 12 And combinations of at least two thereof.
In the present invention, the LISICON type oxide includes Li 14 Zn(GeO 4 ) 4 、Li 3+x (P 1-x Si x )O 4 (wherein 0<x<1)、Li 3+x Ge x V 1-x O 4 (wherein 0<x<1) And combinations of at least two thereof.
In the present invention, the NASICON type oxide has the chemical formula LiMM' (PO 4 ) 3 Wherein M and M' are independently selected from Al, ge, ti, sn, hf, zr or La. For example, li 1+x Al x Ge 2-x (PO 4 ) 3 (LAGP) (wherein 0.ltoreq.x.ltoreq.2), li 1+x Al x Ti 2-x (PO 4 ) 3 (LATP) (where 0.ltoreq.x.ltoreq.2), li 1+x Y x Zr 2-x (PO 4 ) 3 (LYZP) (wherein 0.ltoreq.x.ltoreq.2), li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、LiTi 2 (PO 4 ) 3 、LiGeTi(PO 4 ) 3 、 LiGe 2 (PO 4 ) 3 Or LiHf 2 (PO 4 ) 3 And combinations of at least two thereof.
In the present invention, the perovskite ceramic includes Li 3.3 La 0.53 TiO 3 、LiSr 1.65 Zr 1.3 Ta 1.7 O 9 、 Li 2x-y Sr 1- x Ta y Zr 1-y O 3 (wherein x=0.75 y and 0.60<y<0.75)、Li 3/8 Sr 7/16 Nb 3/4 Zr 1/4 O 3 、 Li 3x La (2/3-x) TiO 3 (wherein 0<x<0.25 And combinations of at least two thereof.
In the present invention, the oxide solid state electrolyte has an ionic conductivity of greater than or equal to about 10 -5 S/cm to less than or equal to about 10 -1 S/cm。
In the present invention, the sulfide solid state electrolyte layer includes Li 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -MS x (wherein M is Si, ge and Sn and 0.ltoreq.x.ltoreq.2), li 3.4 Si 0.4 P 0.6 S 4 、Li 10 GeP 2 S 11.7 O 0.3 、Li 9.6 P 3 S 12 、Li 7 P 3 S 11 、 Li 9 P 3 S 9 O 3 、Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P 2 S 12 、 Li(Ge 0.5 Sn 0.5 )P 2 S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 、Li 10 GeP 2 S 12 (LGPS)、Li 6 PS 5 X (wherein X is Cl, br or I), li 7 P 2 S 8 I、Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S 4 、Li 10 SnP 2 S 12 、 Li 10 SiP 2 S 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 Or Li (lithium) (1-x) P 2 S 5-x Li 2 S (wherein 0.5.ltoreq.x.ltoreq.0.7) and combinations of at least two thereof.
In the present invention, the sulfide solid state electrolyte has an ionic conductivity of greater than or equal to about 10 -7 S/cm to less than or equal to about 1S/cm.
The halide solid electrolyte layer includes Li 2 CdC l4 、Li 2 MgC l4 、Li 2 Cd I4 、Li 2 ZnI 4 、Li 3 OCl、 LiI、Li 5 ZnI 4 Or Li (lithium) 3 OCl 1-x Br x (wherein 0<x<1) And combinations of at least two thereof.
In the present invention, the halide solid state electrolyte has an ionic conductivity of greater than or equal to about 10 -8 S/cm to less than or equal to about 10 -1 S/cm。
The polymer solid state electrolyte layer includes polyethylene glycol, polyethylene oxide (PEO), poly (p-phenylene oxide) (PPO), poly (methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP), or polyvinyl chloride (PVC), and combinations of at least two thereof.
In the present invention, the ionic conductivity of the polymer solid electrolyte is about 10 -4 S/cm。
Preferably, the thickness of the solid electrolyte layer is 1-2 μm, and may be, for example, 1 μm, 1.2 μm, 1.5 μm, 1.7 μm, 2 μm.
In the present invention, a thinner solid electrolyte layer is advantageous for improving the energy density of the battery and reducing the thickness of the battery by adjusting the thickness of the solid electrolyte, but an excessively thin solid electrolyte layer makes the molding process difficult and the solid electrolyte membrane difficult to complete.
In a second aspect, the present invention provides a method of preparing the composite separator of the first aspect, the method comprising the steps of:
and coating solid electrolyte slurry on the surface of the base layer, drying to obtain a diaphragm intermediate material, directly covering a porous layer on the surface of the diaphragm intermediate material, and rolling to obtain the composite diaphragm.
According to the invention, the PTFE nanofiber membrane or PTFE microporous membrane is covered on the surface of the base layer, and the composite membrane can be obtained only by drying, so that a hot pressing technology is not needed, the damage of a pore structure is avoided, and the air permeability of the diaphragm is ensured.
Preferably, the temperature of the rolling is 30-60 ℃, and the pressure of the rolling is 0.8-2kg.
In the present invention, the temperature of the rolling is 30 to 60℃and may be, for example, 30℃32℃35℃37℃40℃42℃45℃47℃50℃52℃55℃57℃60 ℃.
In the present invention, the rolling pressure is 0.8 to 2kg, and may be, for example, 0.8kg, 1kg, 1.2kg, 1.4kg, 1.6kg, 1.8kg, 2kg.
The present application is not particularly limited to PTFE nanofiber membranes and PTFE microporous membranes, and any known PTFE nanofiber membranes or PTFE microporous membranes can be used in the present application without departing from the inventive concepts of the present application and with a porosity that meets the requirements of the present application.
In a third aspect, the invention provides a lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and an electrolyte, wherein the diaphragm is the composite diaphragm in the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a composite diaphragm, which is obtained by directly using a PTFE nanofiber membrane or a PTFE microporous membrane layer instead of a mode of preparing polytetrafluoroethylene slurry and then coating in the prior art, and the composite diaphragm can be obtained by drying without using a hot pressing technology, so that the damage of a pore structure is avoided, and the air permeability of the diaphragm is ensured. In addition, the prepared composite diaphragm is lighter and thinner, has small surface roughness, and is favorable for reducing the resistance between the diaphragm and the electrode material.
The preparation method of the invention is simple and easy to implement, has good repeated stability and is easy for industrialized application.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The invention provides a composite diaphragm, which comprises a PE base layer and Li coated on the surface of the base layer, wherein the PE base layer and the Li are sequentially laminated 7 La 3 Zr 2 O 12 Solid electrolyte layer and Li 7 La 3 Zr 2 O 12 And the PTFE nanofiber membrane on the surface of the solid electrolyte layer, wherein the porosity of the PTFE nanofiber membrane is 75%, and the porosity of the PE base layer is 50%.
The preparation method of the composite diaphragm comprises the following steps:
to solid electrolyte Li 7 La 3 Zr 2 O 12 (LLZO) dissolved in solvent N-methylpyrrolidone and coated onto PE substrate; after the coating is completed, drying is carried out to obtain an intermediate material with the coating thickness of 1.5 mu m;
and directly covering the surface of a diaphragm intermediate material with a PTFE nanofiber membrane, rolling at 45 ℃ under the pressure of 1.4kg, and obtaining the composite diaphragm.
Example 2
The invention provides a composite diaphragm, which comprises a PP base layer and Li coated on the surface of the base layer, wherein the PP base layer and the Li are sequentially laminated 10 GeP 2 S 12 Solid electrolyte layer and Li 10 GeP 2 S 12 The PTFE nanofiber membrane on the surface of the solid electrolyte layer, wherein the porosity of the PTFE nanofiber membrane is 78%, and the porosity of the PP base layer is 52%.
The preparation method of the composite diaphragm comprises the following steps:
to solid electrolyte Li 10 GeP 2 S 12 (LGPS) dissolved in a solvent N-methylpyrrolidone, coated on a PP substrate, and dried after the coating is completed to obtain an intermediate material having a coating thickness of 1 μm;
and directly covering the surface of a diaphragm intermediate material with a PTFE nanofiber membrane, rolling at 30 ℃ under the pressure of 0.8kg, and obtaining the composite diaphragm.
Example 3
The invention provides a composite diaphragm which comprises a PP base layer, a polymer solid electrolyte layer coated on the surface of the base layer and a PTFE microporous membrane positioned on the surface of the polymer solid electrolyte layer, wherein the porosity of the PTFE microporous membrane is 78%, and the porosity of the PP base layer is 58%.
The preparation method of the composite diaphragm comprises the following steps:
will be composed of PVDF and LiPF 6 Dissolving in a solvent N-methyl pyrrolidone to form polymer solid electrolyte slurry, coating the polymer solid electrolyte slurry on a PP base layer, and drying after coating to obtain an intermediate material with a coating thickness of 2 mu m;
and directly covering the PTFE microporous membrane on the surface of the intermediate material, rolling at 50 ℃ under the pressure of 1.2kg, and obtaining the composite membrane.
Example 4
This example differs from example 1 in that the porosity of the PTFE nanofiber membrane is 40%, and the other is the same as in example 1.
Example 5
This example differs from example 1 in that the PTFE nanofiber membrane has a porosity of 85%, and the other is the same as in example 1.
Comparative example 1
This comparative example provides a composite separator comprising a PE-based layer, a solid electrolyte Li, laminated in this order 7 La 3 Zr 2 O 12 (LLZO) dissolved in solvent N-methylpyrrolidone and coated onto PE substrate; after the coating is completed, drying is carried out to obtain an intermediate material with the coating thickness of 1.5 mu m;
PTFE is dissolved in a solvent NMP, a PTFE polymer layer is coated on the surface of a diaphragm intermediate material, and then hot pressing is carried out, wherein the hot pressing temperature is 140 ℃, and the hot pressing pressure is 1.4kg, so that the composite diaphragm is obtained.
Comparative example 2
This comparative example provides a composite separator comprising a PE-based layer, a solid electrolyte Li, laminated in this order 10 GeP 2 S 12 (LGPS) dissolved in solvent N-methylpyrrolidone, coated onto PE substrate; after the coating is completed, drying is carried out to obtain an intermediate material with the coating thickness of 1 mu m;
PTFE is dissolved in a solvent NMP, a PTFE polymer layer is coated on the surface of a diaphragm intermediate material, and then hot pressing is carried out, wherein the hot pressing temperature is 150 ℃, and the hot pressing pressure is 0.8kg, so that the composite diaphragm is obtained.
The composite separators obtained in examples 1 to 5 and comparative examples 1 to 2 were prepared into lithium ion batteries by the following methods:
preparation of a positive plate: adding a positive electrode material NCM532, a conductive agent Super-P and a binder polyvinylidene fluoride into a solvent according to the mass ratio of 95:2:3, fully stirring to obtain mixed slurry, uniformly coating the mixed slurry onto an aluminum foil, and drying, rolling and cutting to obtain a required positive electrode sheet;
preparing a negative plate: adding graphite as a cathode material, super-P as a conductive agent, styrene-butadiene rubber as a binder and sodium carboxymethylcellulose into a solvent according to the mass ratio of 95:2:3, fully stirring to obtain mixed slurry, uniformly coating the mixed slurry onto copper foil, and drying, rolling and cutting to obtain a required anode sheet;
preparation of a lithium ion battery: and in a glove box filled with argon, laminating the prepared negative plate, the composite diaphragm and the positive plate, and sequentially injecting and forming to obtain the lithium ion battery.
Test conditions
The lithium ion batteries provided in application examples 1 to 5 and comparative application examples 1 to 2 were subjected to the test for heat shrinkage and electrochemical properties as follows:
(1) Heat shrinkage rate: the separator was left at 120 ℃ for 10min, and the area after shrinkage thereof was measured, and the heat shrinkage = (original area-area after shrinkage)/original area.
(2) And (3) testing the cycle performance: charging at 25deg.C+ -2deg.C with current density of 1C to a final voltage, cutting off current of 0.05C, and standing for 30min; then, discharge was performed at a current density of 1C to a discharge end pressure (2.75V), the discharge capacity was recorded, and the mixture was left to stand for 30 minutes, and the cycle was repeated, and the capacity retention after 1000 weeks of the test cycle was measured.
The results of the test are shown in table 1:
TABLE 1
As can be seen from examples 1-5 and comparative examples 1-2, the separator prepared by the preparation method of the present application has a flat appearance, and the existing PTFE nanofiber membrane and PTFE microporous membrane are utilized, so that the separator can also prepare an ultrathin solid electrolyte layer without hot rolling, and damage to the separator by hot rolling is avoided. Compared with the membrane substrate-solid electrolyte layer-PTFE layer prepared by the traditional coating method, the membrane substrate-solid electrolyte layer-PTFE layer has better cycle performance and membrane stability.
From the comparison of examples 1-2 and examples 4-5 of the present application, the use of the PTFE nanofiber membrane and the PTFE porous membrane of the specific porosity of the present application can simultaneously compromise both separator and battery performance, and if the porosity is too low, although advantageous for the separator, the cycle performance of the battery is affected due to insufficient air permeability; if the porosity is too high, the preparation of the ultrathin solid electrolyte layer is not facilitated, so that the internal of the diaphragm is collapsed, and the battery performance is greatly influenced.
The applicant states that the process of the invention is illustrated by the above examples, but the invention is not limited to, i.e. does not mean that the invention must be carried out in dependence on the above process steps. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of selected raw materials, addition of auxiliary components, selection of specific modes, etc. fall within the scope of the present invention and the scope of disclosure.

Claims (13)

1. The composite diaphragm is characterized by comprising a base layer, a solid electrolyte layer coated on the surface of the base layer and a porous layer covered on the surface of the solid electrolyte layer by rolling, wherein the base layer, the solid electrolyte layer and the porous layer are sequentially laminated;
the porous layer is a PTFE nanofiber membrane or PTFE microporous membrane layer;
the porosity of the porous layer is 75-80%;
the thickness of the solid electrolyte layer is 1-2 μm.
2. The composite separator of claim 1, wherein the porous layer has a thickness of 0.1-3 μm.
3. The composite separator of claim 1, wherein the base layer is a PE, PP or PE/PP material.
4. The composite separator of claim 1, wherein the porosity of the material of the base layer is 20-80%.
5. The composite separator of claim 4, wherein the porosity of the material of the base layer is 40-60%.
6. The composite separator of claim 5, wherein the porosity of the material of the base layer is 40-50%.
7. The composite membrane of claim 1 wherein the base layer has a thickness of 5-30 μm.
8. The composite membrane of claim 7 wherein the base layer has a thickness of 8-12 μm.
9. The composite separator of claim 1, wherein the solid state electrolyte layer is an inorganic solid state electrolyte layer or a polymer solid state electrolyte layer.
10. The composite separator of claim 9, wherein the inorganic solid state electrolyte layer comprises at least one of an oxide solid state electrolyte layer, a sulfide solid state electrolyte layer, or a halide solid state electrolyte layer.
11. A method of making the composite separator of any of claims 1-10, comprising the steps of:
and coating solid electrolyte slurry on the surface of the base layer, drying to obtain a diaphragm intermediate material, directly covering a porous layer on the surface of the diaphragm intermediate material, and rolling to obtain the composite diaphragm.
12. The method according to claim 11, wherein the temperature of the rolling is 30-60 ℃ and the pressure of the rolling is 0.8-2kg.
13. A lithium ion battery, characterized in that the lithium ion battery comprises a positive plate, a negative plate, a diaphragm and an electrolyte, wherein the diaphragm is the composite diaphragm according to any one of claims 1 to 10.
CN202210426143.3A 2022-04-21 2022-04-21 Composite diaphragm, preparation method thereof and lithium ion battery Active CN114824655B (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108682776A (en) * 2018-05-10 2018-10-19 北京工业大学 A kind of high performance lithium ion battery composite diaphragm and preparation method thereof
CN112838266A (en) * 2021-03-23 2021-05-25 上海电气集团股份有限公司 Composite electrolyte membrane, preparation method and application thereof, and solid-state lithium battery
CN113394514A (en) * 2021-06-11 2021-09-14 苏州清陶新能源科技有限公司 Composite diaphragm and preparation method and application thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108682776A (en) * 2018-05-10 2018-10-19 北京工业大学 A kind of high performance lithium ion battery composite diaphragm and preparation method thereof
CN112838266A (en) * 2021-03-23 2021-05-25 上海电气集团股份有限公司 Composite electrolyte membrane, preparation method and application thereof, and solid-state lithium battery
CN113394514A (en) * 2021-06-11 2021-09-14 苏州清陶新能源科技有限公司 Composite diaphragm and preparation method and application thereof

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