CN111653717B - Preparation method of composite diaphragm, composite diaphragm and lithium ion battery - Google Patents
Preparation method of composite diaphragm, composite diaphragm and lithium ion battery Download PDFInfo
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- CN111653717B CN111653717B CN202010663136.6A CN202010663136A CN111653717B CN 111653717 B CN111653717 B CN 111653717B CN 202010663136 A CN202010663136 A CN 202010663136A CN 111653717 B CN111653717 B CN 111653717B
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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
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
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- 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 belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a composite diaphragm, which comprises the following operations: placing inorganic particles in a first solvent to obtain inorganic slurry, coating the inorganic slurry on at least one surface of a base film at intervals, and drying to obtain an inorganic thermal stable coating; placing organic particles in a second solvent to obtain organic slurry, and coating the organic slurry on the surface of the base film between the inorganic heat-stable coatings at intervals to obtain an organic bonding coating; and drying to obtain the composite diaphragm, wherein the thickness of the organic bonding coating is larger than that of the inorganic thermal stable coating. The invention solves the problems that inorganic particles and organic particles can not be regularly arranged, the organic particles can be buried by the inorganic particles, and the bonding effect of the organic particles, a base film and a pole piece is poor.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a composite diaphragm, the composite diaphragm and a lithium ion battery.
Background
Since the commercialization of lithium ion batteries in the 90 s, lithium ion batteries have been widely used in the fields of mobile phones, notebook computers, tablet computers, bluetooth headsets, MP3, digital cameras, and the like, due to their characteristics of high energy density, high operating voltage, light weight, and the like.
The lithium ion battery mainly comprises a positive pole piece, a negative pole piece and a diaphragm arranged between the positive pole piece and the negative pole piece, wherein the diaphragm is used for isolating the positive pole and the negative pole and preventing the positive pole and the negative pole from being in direct contact with each other to generate short circuit. At present, the diaphragm is mainly a porous medium composed of polyolefins such as polyethylene, polypropylene and the like, the polyolefin diaphragm has a melting point of 200 ℃ or lower, when the temperature of the battery is increased due to short circuit caused by internal or external factors, the contact short circuit of a positive electrode and a negative electrode caused by shrinkage is easy to occur, and even the thermal runaway of the battery is caused to cause fire accidents. In addition, the surface of the pole piece is uneven, or sharp foreign matters mixed in the battery assembly process are easy to damage the diaphragm to cause short circuit, and the battery is penetrated by a sharp object to cause short circuit.
In order to solve the above problems, an inorganic-organic hybrid coating layer is coated on the surface of the separator, wherein the inorganic-organic hybrid coating layer is prepared by dispersing inorganic ceramic particles and organic binder particles in a solvent to prepare a composite slurry, coating the composite slurry on the surface of the separator, and drying the composite slurry to prepare the composite separator. However, the composite separator prepared by this method has several problems: 1) because the inorganic ceramic particles and the organic bonding particles are randomly dispersed in the solvent and are not uniformly dispersed in the solvent, the problems that the bonding effect between the places with more organic bonding particles and the diaphragm is good and the bonding effect between the places with less organic bonding particles and the diaphragm is poor can be caused; 2) part of the organic bonding particles are buried among the inorganic ceramic particles, and the buried organic bonding particles cannot actually play a role of a bonding diaphragm; 3) the organic bonding particles can only bond the diaphragm, but do not bond the pole pieces; 4) the organic bonding particles can only bond the pole pieces, but do not bond the diaphragm.
In view of the above, it is necessary to provide a technical solution to the above technical problems.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the preparation method of the composite diaphragm is provided, the inorganic particles and the organic particles can be regularly arranged, the organic particles cannot be buried by the inorganic particles, and the bonding effect of the organic particles, the diaphragm and the pole piece is good.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a composite diaphragm comprises the following operations:
placing inorganic particles in a first solvent to obtain inorganic slurry, and coating the inorganic slurry on at least one surface of a base film at intervals to obtain an inorganic heat-stable coating;
placing organic particles in a second solvent to obtain organic slurry, and coating the organic slurry on the surface of the base film between the inorganic heat-stable coatings at intervals to obtain an organic bonding coating; and drying to obtain the composite diaphragm, wherein the thickness of the organic bonding coating is larger than that of the inorganic thermal stable coating.
As an improvement of the preparation method of the composite separator of the present invention, the inorganic particles include at least one of boehmite, calcium oxide, zinc oxide, magnesium oxide, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, cerium dioxide, aluminum oxide, calcium carbonate, and barium titanate. The inorganic particles are not particularly limited as long as they are not oxidized or reduced in the lithium ion secondary battery and have excellent electronic insulation properties. Preferably, the inorganic particle is calcium carbonate. The calcium carbonate can adsorb acidic HF generated by the decomposition of the lithium hexafluorophosphate electrolyte, and can also improve the wettability of the composite diaphragm.
As an improvement of the preparation method of the composite separator of the present invention, the inorganic particles further include zeolite imidazole framework structure particles. The zeolite imidazole framework particles comprise methanol-modified ZIF-67 and/or ZIF-21. Because the electrolyte wettability of the base membrane is poor, however, the zeolite imidazole framework structure particles have developed pore channel structures, so that more electrolyte can be accommodated, the wettability of the inorganic thermal stable coating can be improved, the diffusion of lithium ions is facilitated, and the cycle performance of the lithium ion battery is improved. Furthermore, the methanol modified zeolite imidazole framework structure particles enable the composite diaphragm to have more excellent thermal stability.
As an improvement of the preparation method of the composite diaphragm, the organic particles include at least one of styrene-butadiene polymer, polyvinylidene fluoride-hexafluoropropylene, polyacrylic acid, polymethacrylic acid, polyacrylate, polymethyl acrylate, polyethylacrylate, polymethyl methacrylate, polyacrylonitrile, sodium carboxymethylcellulose, butadiene-acrylonitrile polymer, polyvinylpyrrolidone, and polyacrylic acid-styrene polymer.
As an improvement of the preparation method of the composite diaphragm, the organic particles facing the negative plate are water-based, and the organic particles facing the positive plate are oil-based. The binder of the negative electrode diaphragm is generally styrene-butadiene rubber, the styrene-butadiene rubber is aqueous binder, and the aqueous organic particles of the composite diaphragm have chemical properties similar to those of the styrene-butadiene rubber, so that the composite diaphragm has good binding property; the adhesive of the positive membrane is polyvinylidene fluoride generally, polyvinylidene fluoride is oily adhesive, and oily organic particles of the composite membrane have chemical properties similar to that of the polyvinylidene fluoride, so that the composite membrane has good adhesive property.
As an improvement of the preparation method of the composite diaphragm, the average particle size of the inorganic particles is 0.05-6 mu m. Further preferably, the particle size of the inorganic particles is 0.1 to 6 μm. Still more preferably, the inorganic particles have a particle size of 1 μm, 2 μm, 3 μm, 4 μm or 5 μm. Preferably, the thickness of the inorganic heat-stable coating is 0.5-50 μm. Preferably, the thickness of the inorganic heat-stable coating is 1-10 μm. Still further preferably, the thickness of the inorganic thermally stable coating is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm. The thickness of the organic bonding coating is larger than that of the inorganic heat-stable coating, but the thickness of the organic bonding coating cannot be too large, and the excessively thick organic bonding coating can reduce the bonding smoothness of the composite diaphragm and the pole piece.
As an improvement of the method for manufacturing the composite separator of the present invention, the inorganic particles are distributed in island or line shapes on the surface of the base film, and the organic particles are distributed among the inorganic particles. If the inorganic particles are distributed in the form of islands, the organic particles may be distributed around the island-shaped inorganic particles. If the inorganic particles are distributed in a linear form, the organic particles may be distributed on at least one side of the linear inorganic particles. The shape of the inorganic heat-stable coating can be preset, and the organic bond coating is coated in the interval of the inorganic heat-stable coating, so that the regular arrangement of the inorganic heat-stable coating and the organic bond coating is realized.
As an improvement of the preparation method of the composite diaphragm, the base membrane is a polyolefin membrane grafted with at least one of glycidyl methacrylate, diethylene glycol dimethacrylate and polar acrylic monomers through ultraviolet irradiation. The base film of the conventional diaphragm is lack of polar groups, the surface performance of the base film is low, the base film can be well infiltrated in polar carbonate electrolyte, but the imbibition performance is poor, the ionic conductivity is low, and the imbibition rate can influence the imbibition time and the battery resistance during the assembly of the diaphragm and the battery, so that the battery has good imbibition performance and is extremely important for the battery performance. According to the invention, the polar group is grafted on the polyolefin base membrane, so that the liquid absorption rate and the liquid retention rate of the diaphragm can be improved, and the cycle performance of the battery is further improved. Wherein, the polyolefin film comprises any one of a polyethylene film, a polypropylene film and a polyethylene-polypropylene composite film.
As an improvement of the preparation method of the composite diaphragm, the base membrane is a polyimide-glass fiber composite membrane. After the glass fiber film is coated by polyimide, the size of the holes of the glass fiber is reduced, but the self-discharge of the battery is facilitated. The polyamic acid is in-situ crystallized after imidization to improve the mechanical strength of the glass fiber film. The glass fiber membrane coated by the polyimide has better flame retardant property and better liquid absorption property to electrolyte. The polyimide-glass fiber composite membrane is applied to a lithium ion battery, so that the battery can stably run at high temperature, and the cycle performance and the rate capability of the battery are improved.
As an improvement of the method for manufacturing the composite separator according to the present invention, the first solvent and the second solvent each independently include at least one of tetrahydrofuran, methyl ethyl ketone, dimethylformamide, dimethylacetamide, tetramethylurea, tetramethylphosphate, acetone, dichloromethane, chloroform, dimethylformamide, N-methylpyrrolidone, cyclohexane, and water.
The invention also provides a composite diaphragm prepared by the method in any one of the preceding specifications, which comprises a base film, and an inorganic thermal stable coating and an organic bonding coating which are coated on at least one surface of the base film, wherein the thickness of the organic bonding coating is larger than that of the inorganic thermal stable coating, the inorganic thermal stable coating comprises inorganic particles, the organic bonding coating comprises organic particles, the average particle size of the inorganic particles is smaller than that of the organic particles, the inorganic particles are distributed on the base film at intervals, and the organic particles are distributed among the inorganic particles at intervals.
The invention also provides a lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm arranged between the positive plate and the negative plate, and electrolyte, wherein the diaphragm is the composite diaphragm described in the specification. The organic bonding coating is bonded with the positive plate and/or the negative plate.
Compared with the prior art, the invention has the advantages that but not limited to:
1) according to the invention, the inorganic thermal stable coating is obtained by coating the inorganic slurry, and then the organic bonding coating is obtained by coating the inorganic slurry, so that regular arrangement of the inorganic particles and the organic particles is realized, and the coating shapes of the inorganic particles and the organic particles on the surface of the base film can be designed according to requirements.
2) According to the invention, the organic particles are directly coated on the surface of the base film, so that the organic particles are not buried by the inorganic particles, and the bonding effect of the organic particles and the base film is further improved.
3) According to the invention, the thickness of the organic bonding coating is larger than that of the inorganic thermal stable coating, so that the organic particles protrude out of the inorganic particles, and the organic particles can be tightly bonded with the base film and the pole piece.
Drawings
Fig. 1 is a cross-sectional view of a composite separator in example 1.
Fig. 2 is a top view of the composite separator of example 1.
Fig. 3 is a top view of the composite membrane of example 2.
Figure 4 is a cross-sectional view of a prior art septum.
In the figure: 1-base film, 2-inorganic particles, 3-organic particles.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.
A preparation method of a composite diaphragm comprises the following operations:
placing the inorganic particles 2 in a first solvent to obtain inorganic slurry, coating the inorganic slurry on at least one surface of the base film 1 at intervals, and drying to obtain an inorganic heat-stable coating;
dissolving the organic particles 3 in a second solvent to obtain organic slurry, and coating the organic slurry on the surface of the base film 1 between the inorganic heat-stable coatings at intervals to obtain an organic bonding coating; wherein, the thickness of the organic bonding coating is larger than that of the inorganic thermal stable coating, and the composite diaphragm is obtained after drying.
Example 1
The embodiment provides a lithium ion battery, and a preparation method thereof comprises the following steps:
(1) preparing a composite diaphragm:
taking a polyethylene microporous film with the thickness of 16um as a base film;
preparation of inorganic thermally stable coatings: adding Al to deionized water 2 O 3 Particles (Al) 2 O 3 The average particle size of the particles is 1 μm) is stirred for 2 hours, then the particles are ground in a ball mill for 1 hour, sodium carboxymethylcellulose (CMC) is added into the ground slurry, and the inorganic slurry is prepared by continuously stirring for 1 hour. Coating inorganic slurry on two sides of the base film at intervals by adopting a gravure coating mode to ensure that Al 2 O 3 The particles are arranged on the surface of the base film at intervals in an island shape to obtain an inorganic heat-stable coating with the thickness of 5 mu m, and the inorganic heat-stable coating is dried for later use;
the preparation of the organic binding coating comprises the steps of adding polyvinylidene fluoride (PVDF) powder (the average grain diameter of the polyvinylidene fluoride powder is 1.5 mu m) into N-methyl pyrrolidone (NMP) solvent, and uniformly stirring for 2h to obtain organic slurry. Uniformly coating the organic slurry on Al by adopting a gravure coating mode 2 O 3 Obtaining an organic bonding coating with the thickness of 7 mu m on the base film among the particles;
and drying to obtain the composite diaphragm.
(2) Preparing a positive plate: lithium cobaltate, conductive carbon and a binder polyvinylidene fluoride according to a mass ratio of 96: 2.0: 2.0 mixing evenly in N-methyl pyrrolidone (NMP) solvent to prepare anode slurry, then coating on aluminum foil, drying at 110 ℃, cold pressing, splitting, cutting edges, and welding tabs to prepare the anode plate.
(3) Preparing the negative plate by mixing graphite, conductive carbon, thickener sodium carboxymethyl cellulose and binder styrene butadiene rubber according to a mass ratio of 95: 2.0: 1.0: 2.0 evenly mixing in deionized water to prepare cathode slurry, then coating the cathode slurry on a copper foil, drying at 85 ℃, cold pressing, splitting, cutting edges, and welding tabs to prepare a cathode sheet.
(4) The preparation of the battery comprises the steps of winding the positive plate, the composite diaphragm and the negative plate into a battery core, then placing the battery core into an aluminum-plastic packaging bag, injecting an electrolyte (ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate: 1:2:1, containing 1M lithium hexafluorophosphate), packaging, forming, capacity and the like to prepare the lithium ion battery.
Example 2
This example provides a lithium ion battery, which differs from example 1 in the preparation of a composite separator:
taking a glass fiber membrane with the thickness of 16 mu m, dissolving a synthetic polyamide acid solution in DMAc, then coating the mixed solution on the glass fiber membrane, firstly heating to 60 ℃, and keeping for 30 min; then heating to 120 ℃, and keeping for 30 min; heating to 200 ℃, keeping for 60min, drying to remove redundant solvent, and performing vacuum drying to complete imidization reaction to obtain a polyimide-glass fiber composite film as a base film;
preparation of inorganic thermally stable coatings: adding Al to deionized water 2 O 3 Particles (Al) 2 O 3 The average particle size of the particles is 1 μm), stirring for 2h, grinding in a ball mill for 1h, adding sodium carboxymethylcellulose (CMC) into the ground slurry, and continuously stirring for 1h to prepare the inorganic slurry. Coating inorganic slurry on two sides of the base film at intervals by adopting a gravure coating mode to ensure that Al 2 O 3 The particles are arranged on the surface of the base film at intervals in a linear manner to obtain an inorganic heat-stable coating with the thickness of 5 mu m, and the inorganic heat-stable coating is dried for later use;
the organic bond coat is prepared by adding polyvinylidene fluoride (PVDF) powder (polyvinylidene fluoride powder) to N-methylpyrrolidone (NMP) solventAverage particle diameter of 1.5 μm) was uniformly stirred for 2 hours to obtain an organic slurry. Uniformly coating the organic slurry on Al by adopting a gravure coating mode 2 O 3 Obtaining an organic bonding coating with the thickness of 7 mu m on the base film among the particles;
and drying to obtain the composite diaphragm.
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
This example provides a lithium ion battery, which differs from example 1 in the preparation of a composite separator:
taking a polyethylene microporous film with the thickness of 16um, and grafting glycidyl methacrylate through ultraviolet irradiation to serve as a base film;
preparation of inorganic thermally stable coating: adding Al to deionized water 2 O 3 Particles (Al) 2 O 3 The average particle size of the particles is 1 μm) is stirred for 2 hours, then the particles are ground in a ball mill for 1 hour, sodium carboxymethylcellulose (CMC) is added into the ground slurry, and the inorganic slurry is prepared by continuously stirring for 1 hour. Coating inorganic slurry on two sides of the base film at intervals by adopting a gravure coating mode to ensure that Al 2 O 3 The particles are arranged on the surface of the base film at intervals in an island shape to obtain an inorganic heat-stable coating with the thickness of 5 mu m, and the inorganic heat-stable coating is dried for later use;
the preparation of the organic binding coating comprises the steps of adding polyvinylidene fluoride (PVDF) powder (the average grain diameter of the polyvinylidene fluoride powder is 1.5 mu m) into N-methyl pyrrolidone (NMP) solvent, and uniformly stirring for 2h to obtain organic slurry. Uniformly coating the organic slurry on Al by adopting a gravure coating mode 2 O 3 Obtaining an organic bonding coating with the thickness of 7 mu m on the base film among the particles;
and drying to obtain the composite diaphragm.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
This example provides a lithium ion battery, which differs from example 1 in the preparation of a composite separator:
taking a polyethylene microporous film with the thickness of 16um as a base film;
preparation of inorganic thermally stable coatings: adding Al to deionized water 2 O 3 Particles (Al) 2 O 3 Average particle size of particles is 1 μm) and ZIF-67 zeolite imidazole framework structure particles (average particle size of ZIF-67 is 1 μm), stirring for 2h, grinding for 1h in a ball mill, adding sodium carboxymethylcellulose (CMC) into the ground slurry, and continuously stirring for 1h to prepare the inorganic slurry. Coating inorganic slurry on two sides of the base film at intervals by adopting a gravure coating mode to ensure that Al 2 O 3 The particles and ZIF-67 zeolite imidazole framework structure particles are arranged on the surface of the base membrane at intervals in an island shape to obtain an inorganic heat-stable coating with the thickness of 5 mu m, and the inorganic heat-stable coating is dried for later use;
the preparation of the organic binding coating comprises the steps of adding polyvinylidene fluoride (PVDF) powder (the average grain diameter of the polyvinylidene fluoride powder is 1.5 mu m) into N-methyl pyrrolidone (NMP) solvent, and uniformly stirring for 2h to obtain organic slurry. Uniformly coating the organic slurry on Al by adopting a gravure coating mode 2 O 3 Obtaining an organic bonding coating with the thickness of 7 mu m on the base film between the particles and the ZIF-67 zeolite imidazole framework structure particles;
and drying to obtain the composite diaphragm.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
The embodiment provides a lithium ion battery, and a preparation method thereof comprises the following steps:
(1) preparing a composite diaphragm:
taking a polyethylene microporous film with the thickness of 16um as a base film;
preparation of inorganic thermally stable coating: adding Al to deionized water 2 O 3 Particles (Al) 2 O 3 The average particle size of the particles is 1 μm), stirring for 2h, grinding in a ball mill for 1h, adding sodium carboxymethylcellulose (CMC) into the ground slurry, and continuously stirring for 1h to prepare the inorganic slurry. Coating inorganic slurry on two sides of the base film at intervals by adopting a gravure coating mode to ensure that Al 2 O 3 The particles are arranged on the surface of the base film at intervals in an island shape to obtain an inorganic heat-stable coating with the thickness of 5 mu m, and the inorganic heat-stable coating is dried for later use;
the preparation of the organic binding coating is that polyvinylidene fluoride (PVDF) powder (the average grain diameter of the polyvinylidene fluoride powder is 1.5 mu m) is added into N-methyl pyrrolidone (NMP) solvent and evenly stirred for 2h to obtain first organic slurry. Uniformly coating the first organic slurry on Al by adopting a gravure coating mode 2 O 3 On one side of the base film between the particles; adding polyacrylic acid powder (the average particle size of the polyacrylic acid powder is 1.5 mu m) into N-methylpyrrolidone (NMP) solvent, and uniformly stirring for 2h to obtain second organic slurry. Uniformly coating the second organic slurry on Al by adopting a gravure coating mode 2 O 3 And drying the other side of the base film among the particles to obtain the composite diaphragm.
(2) Preparing a positive plate: mixing lithium cobaltate, conductive carbon and a binder polyvinylidene fluoride according to a mass ratio of 96: 2.0: 2.0 mixing evenly in N-methyl pyrrolidone (NMP) solvent to prepare anode slurry, then coating on aluminum foil, drying at 110 ℃, cold pressing, splitting, cutting edges, and welding tabs to prepare the anode plate.
(3) Preparing the negative plate by mixing graphite, conductive carbon, thickener sodium carboxymethyl cellulose and binder styrene butadiene rubber according to a mass ratio of 95: 2.0: 1.0: 2.0 evenly mixing in deionized water to prepare cathode slurry, then coating the cathode slurry on a copper foil, drying at 85 ℃, cold pressing, splitting, cutting edges, and welding tabs to prepare a cathode sheet.
(4) The preparation of the battery comprises the steps of coating polyvinylidene fluoride particles on the surface of a composite diaphragm, wherein the surface of the composite diaphragm is opposite to a positive plate, coating polyacrylic acid particles on the surface of the composite diaphragm is opposite to a negative plate, winding the positive plate, the composite diaphragm and the negative plate into a battery cell, placing the battery cell into an aluminum-plastic packaging bag, injecting electrolyte (ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate: 1:2:1, containing 1M lithium hexafluorophosphate), packaging, forming, capacity and the like to prepare the lithium ion battery.
Comparative example 1
This comparative example provides a lithium ion battery, which differs from example 1 in the preparation of a separator.
1) Taking a polyethylene microporous film with a diaphragm of which the thickness is 16um as a base film;
2) adding 13 wt% of polyacrylate emulsion (the content of the aqueous solution is 40%) into deionized water, stirring for 1h, and then adding 85 wt% of Al 2 O 3 After the particles are stirred for 2 hours, the particles are ground in a ball mill for 1 hour, 2 wt% of thickening agent sodium carboxymethyl cellulose (CMC) is added into the ground slurry, and the inorganic-organic mixed slurry is prepared after continuous stirring for 1 hour. And coating the inorganic-organic mixed slurry on two surfaces of the base film in a gravure coating mode, and drying to obtain the composite diaphragm with each surface compounded with the inorganic-organic composite coating.
The rest is the same as embodiment 1, and the description is omitted here.
The lithium ion batteries of the above comparative examples and examples were subjected to discharge rate test and cycle performance test, and the lithium ion batteries of the above comparative examples and examples were subjected to nail penetration safety test and separator liquid retention and retention rate test before and after cycle.
(1) Testing discharge rate, namely firstly charging the lithium ion battery at 25 ℃ by adopting a rate of 0.5C, discharging at a rate of 0.2C, and recording discharge capacity; then charging at 0.5C rate, discharging at 0.5C rate, and recording discharge capacity; then charging at 0.5C multiplying power, discharging at 1.0C multiplying power, and recording the discharge capacity; then charging at 0.5C multiplying power, discharging at 1.5C multiplying power, and recording the discharge capacity; and finally, charging at 0.5C multiplying power, discharging at 2.0C multiplying power, and recording the discharge capacity. Capacity retention rate at each different discharge rate (discharge capacity at each rate/discharge capacity at 0.2C rate) 100%. The results are shown in Table 1.
(2) And (3) cycle performance testing, namely charging the lithium ion battery at 25 ℃ by adopting a multiplying power of 0.5C, discharging at a multiplying power of 0.5C, sequentially performing 500 cycles, testing the battery capacity at the multiplying power of 0.5C in each cycle, comparing the battery capacity at 25 ℃ with the battery capacity before the cycle, and calculating the capacity retention rate after the cycle, wherein the capacity retention rate is 100 percent (the capacity at 0.5C multiplying power after the cycle/the capacity at 25 ℃ of the battery before the cycle). The thickness of the fully charged cell after 500 cycles was measured and compared with the thickness of the fully charged cell before cycle, and the thickness expansion rate of the cell was calculated as [ (thickness of the cell after full charge after cycle-thickness of the cell before cycle)/thickness of the fully charged cell before cycle ] × 100%. The results are shown in Table 2.
(3) And (3) nail penetration testing: the battery was fully charged and then tested according to UL1642 with a nail diameter of 2.5mm and a nail penetration speed of 100 mm/s. And respectively carrying out nail penetration safety test on the battery before circulation and the battery after 500 circulations. The test results are shown in Table 3.
(4) And (3) testing the liquid retention amount and the liquid retention rate of the diaphragm: the test results are shown in Table 4.
TABLE 1 Capacity Retention ratio at different discharge rates for comparative example and example
TABLE 2 test results of the retention of cyclic capacity and the expansion of thickness for comparative and example
| Group of | Capacity retention rate | Rate of thickness expansion |
| Comparative example 1 | 82％ | 23％ |
| Example 1 | 92％ | 4％ |
| Example 2 | 95％ | 3％ |
| Example 3 | 96％ | 2％ |
| Example 4 | 94％ | 2％ |
| Example 5 | 95％ | 2％ |
Table 3 nail penetration test results of battery before and after cycle
TABLE 4 diaphragm liquid retention amount and rate test results
As can be seen from tables 1 to 3, compared with the comparative examples, the lithium ion batteries of examples 1 to 5 have higher passing rate in the nail penetration test and significantly lower thickness expansion rate, that is, the inorganic particles are uniformly distributed on the base film and the organic particles are distributed among the inorganic particles by coating twice, so that the deformation of the battery can be effectively improved and the safety performance of the battery can be improved without affecting the cycle performance of the battery. The organic particles are directly coated on the surface of the base film, so that the organic particles cannot be buried by the inorganic particles, and the bonding effect of the organic particles and the base film is good; and the thickness of the organic bonding coating is greater than that of the inorganic thermal stable coating, namely, the organic particles protrude out of the inorganic particles, so that the bonding effect of the organic particles and the pole piece is better, the bonding performance of the diaphragm and the pole piece is comprehensively improved, and the flatness and hardness of the battery are further improved.
From tables 3 to 4, it can be seen that the nail penetration rate of the lithium ion battery in example 2 is higher than that of example 1, because the mechanical strength of the glass fiber film is improved by in-situ crystallization after imidization of polyamic acid after the glass fiber film is coated with polyimide. The lithium ion battery of example 2 has a higher retention rate than that of example 1 because the polyimide-coated glass fiber membrane has better liquid absorption performance for the electrolyte.
As can be seen from tables 1 to 4, the liquid retention amount and the liquid retention rate are higher and the cycle performance is better in example 3 compared to example 1, because the electrolyte can be sufficiently absorbed after the polyolefin base film is grafted with the polar group, and the cycle performance of the battery is further improved.
As can be seen from tables 1 to 4, compared with example 1, example 4 has better liquid retention capacity and liquid retention rate and better cycle performance, because the zeolite imidazole framework structure particles ZIF-67 have a developed pore structure, and can accommodate more electrolyte, so that the wettability of the inorganic thermostable coating can be improved, the diffusion of lithium ions is facilitated, and the cycle performance of the lithium ion battery is improved.
As can be seen from tables 1 to 3, compared with example 1, the nail penetration rate of example 5 is better because the organic particles on the surface of the composite diaphragm facing the negative plate are polyacrylic acid, and the organic particles on the surface of the composite diaphragm facing the positive plate are polyvinylidene fluoride, because the binder of the negative plate is styrene butadiene rubber, the styrene butadiene rubber is an aqueous binder, and the polyacrylic acid organic particles on the surface of the composite diaphragm facing the negative plate also have hydrophilicity, so that the composite diaphragm and the pole piece have good cohesiveness; the adhesive of the positive pole membrane is generally polyvinylidene fluoride which is oily, and the organic particles on the surface of the composite membrane facing the positive pole membrane are also oleophilic, so that the composite membrane and the pole piece have good adhesive property.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. A method for preparing a composite membrane, characterized by comprising the following operations:
placing inorganic particles in a first solvent to obtain inorganic slurry, and coating the inorganic slurry on at least one surface of a base film at intervals to obtain an inorganic thermal stable coating;
placing organic particles in a second solvent to obtain organic slurry, and coating the organic slurry on the surface of the base film between the inorganic heat-stable coatings at intervals to obtain an organic bonding coating; the thickness of the organic bonding coating is larger than that of the inorganic thermal stable coating, the composite diaphragm is obtained after drying, the inorganic particles are distributed on the surface of the base film in an island shape or a linear shape, and the organic particles are distributed among the inorganic particles.
2. The method according to claim 1, wherein the inorganic particles include at least one of boehmite, calcium oxide, zinc oxide, magnesium oxide, titanium dioxide, silicon dioxide, zirconium dioxide, tin dioxide, cerium dioxide, aluminum oxide, calcium carbonate, and barium titanate.
3. The method of manufacturing a composite separator according to claim 2, wherein the inorganic particles further include zeolite imidazole framework particles.
4. The method of manufacturing a composite separator according to claim 1, wherein the organic particles include at least one of styrene-butadiene polymer, polyvinylidene fluoride-hexafluoropropylene, polyacrylic acid, polymethacrylic acid, polyacrylate, polymethyl acrylate, polyethylacrylate, polymethyl methacrylate, polyacrylonitrile, sodium carboxymethylcellulose, butadiene-acrylonitrile polymer, polyvinylpyrrolidone, and polyacrylic acid-styrene polymer.
5. The method for producing a composite separator according to claim 1, wherein the organic particles on the side facing the negative electrode sheet are aqueous and the organic particles on the side facing the positive electrode sheet are oily.
6. The method of manufacturing a composite separator according to claim 1, wherein the base film is a polyolefin film grafted with at least one of glycidyl methacrylate, diethylene glycol dimethacrylate, and a polar acrylic monomer by ultraviolet irradiation.
7. The method for preparing the composite separator according to claim 1, wherein the base film is a polyimide-glass fiber composite film.
8. The method of manufacturing a composite separator according to claim 1, wherein the first solvent and the second solvent each independently include at least one of tetrahydrofuran, methyl ethyl ketone, dimethylformamide, dimethylacetamide, tetramethylurea, tetramethylphosphate, acetone, dichloromethane, chloroform, dimethylformamide, N-methylpyrrolidone, cyclohexane, and water.
9. A composite separator produced by the production method according to any one of claims 1 to 8.
10. A lithium ion battery, characterized by comprising a positive plate, a negative plate, a diaphragm arranged between the positive plate and the negative plate, and electrolyte, wherein the diaphragm is the composite diaphragm of claim 9.
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| KR102582604B1 (en) * | 2020-11-30 | 2023-09-22 | 컨템포러리 엠퍼렉스 테크놀로지 씨오., 리미티드 | Separator, its manufacturing method, and secondary batteries, battery modules, battery packs and devices related thereto |
| CN113244787B (en) * | 2021-04-22 | 2022-01-07 | 山东省科学院新材料研究所 | Preparation method of efficient high-temperature-resistant polyimide/ZIF-8 composite nanofiber air filter membrane |
| CN113363666B (en) * | 2021-05-06 | 2022-09-09 | 惠州锂威新能源科技有限公司 | Preparation method of diaphragm, diaphragm and electrochemical device applying diaphragm |
| CN113764818A (en) * | 2021-08-04 | 2021-12-07 | 河北金力新能源科技股份有限公司 | Strong-adhesion diaphragm slurry, preparation method thereof, diaphragm and lithium battery |
| CN113652211A (en) * | 2021-08-11 | 2021-11-16 | 远景动力技术(江苏)有限公司 | Phase-change heat-conducting slurry, heat-conducting diaphragm and lithium ion battery |
| CN113964373A (en) * | 2021-09-29 | 2022-01-21 | 惠州锂威新能源科技有限公司 | Diaphragm, preparation method thereof and lithium ion battery |
| CN114243208A (en) * | 2021-11-30 | 2022-03-25 | 惠州锂威新能源科技有限公司 | Composite diaphragm, preparation method thereof and secondary battery |
| CN117397109A (en) * | 2022-03-25 | 2024-01-12 | 宁德时代新能源科技股份有限公司 | Separator, preparation method thereof, battery and power utilization device |
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