CN111613758B - Separator without polyolefin substrate, preparation method thereof and lithium battery containing separator - Google Patents
Separator without polyolefin substrate, preparation method thereof and lithium battery containing separator Download PDFInfo
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- CN111613758B CN111613758B CN202010318067.5A CN202010318067A CN111613758B CN 111613758 B CN111613758 B CN 111613758B CN 202010318067 A CN202010318067 A CN 202010318067A CN 111613758 B CN111613758 B CN 111613758B
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
- H01M10/0562—Solid materials
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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 relates to the field of lithium batteries, in particular to a diaphragm without a polyolefin substrate, a preparation method thereof and a lithium battery containing the diaphragm, wherein the diaphragm without the polyolefin substrate is prepared from solid electrolyte ceramic particles and an electrolyte soluble polymer binder, and the weight ratio of the solid electrolyte ceramic particles to the electrolyte soluble polymer binder is (90-80): (1-20), the particle diameter D50 of the solid electrolyte ceramic particles is 50nm-1 μm. The diaphragm does not contain a polyolefin substrate, so that the diaphragm has the characteristic of no plastic deformation, has excellent thermodynamic stability and shear deformation resistance, and increases the difficulty of large-area short circuit after shearing and needling of the battery. The diaphragm can be prepared by extruding and tabletting or coating and drying mixed slurry, and can also be prepared by direct melt extrusion, the two preparation methods are simple in process, the preparation of operators is convenient, and the mass production can be realized.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to a polyolefin-free separator, a preparation method thereof and a lithium battery containing the separator.
Background
The structure of the conventional lithium ion battery mainly comprises a positive plate and a negative plate, wherein any adjacent positive plate and negative plate are separated at intervals through a diaphragm. The diaphragm is an important component of the current lithium ion battery, is a high molecular functional material with a nano-scale microporous structure, and mainly has the functions of separating the anode and the cathode of the battery, absorbing electrolyte, and allowing only lithium ions to pass through but not allowing electrons to pass through. Currently, the material of the industrialized diaphragm is polyolefin.
Polyolefins (polyofefin) are based on Polyethylene (PE) or polypropylene (PP), however PE has a melting point of about 130 ℃ and PP has a melting point of about 160 ℃. When the internal temperature of the battery is higher than the melting point of the material, the isolating layer (film) will melt and contract to cause short circuit of the contact of the polar plate, and at the same time, a violent exothermic reaction between the polar layer and the electrolyte is initiated to cause explosion of the battery. Therefore, in recent years, development has been made toward multilayer separators and ceramic-coated separators.
For example, chinese patent No. 201580008710.1 discloses a polyolefin multilayer microporous battery separator having excellent mechanical strength and heat resistance. The separator has at least 3-layer structure of a first microporous layer (surface layer) composed of a polyethylene resin containing ultra-high-molecular-weight polyethylene and a second microporous layer (intermediate layer) composed of a polyolefin resin containing high-density polyethylene and polypropylene, and satisfies the following requirements (I) to (III): (I) the puncture strength is more than 25 g/mum; (II) the coefficient of static friction against the aluminum foil is 0.40 or more; and (III) a fusing temperature of 180 ℃ or higher.
The Chinese patent with the application number of 201721496312.1 discloses a diaphragm, which comprises a polyethylene porous diaphragm layer, wherein polyolefin fiber non-woven fabric diaphragm layers are respectively arranged on two sides of the polyethylene porous diaphragm layer, a ceramic particle layer is arranged on the outer side of the polyolefin fiber non-woven fabric diaphragm layer, and a plurality of micropores are formed in the polyethylene porous diaphragm layer. The diaphragm is provided with the cylindrical micropores on the polyethylene porous diaphragm layer, so that the electrolyte adsorption of the lithium battery diaphragm can be effectively increased, and ions can pass through the diaphragm; the outer ceramic particle layer further promotes the high temperature resistance of the lithium battery diaphragm, so that the lithium battery diaphragm is prevented from shrinking in size when being heated, and the safety performance of the lithium battery is improved.
However, the present inventors found in the course of their research that the polyolefin modified separator of the prior art has the following disadvantages: due to the limitation of poor thermodynamic stability of the polymer, the diaphragm using polyolefin as the base material cannot endure thermal shock for a long time and at high temperature, such as above 300 ℃. The added multiple film layers and ceramic coating layers can treat the symptoms and not the root causes. In addition, when the battery is sheared or needled, due to the plastic deformation capability of the polymer material, the battery diaphragm at the blade after shearing can be stretched and thinned along the stress direction, so that the short circuit of the electrode is easy to occur.
Therefore, in recent years, ceramic barrier layers made of ceramic particles have attracted much attention as a substitute for known polyolefin barrier layers. As disclosed in U.S. patent application publication No. 2008/0138700, ceramic particles are first coated on a film such as PET, PEN, PI, or the like to form a ceramic barrier layer. Or the all-solid battery using the sulfide glass ceramic solid electrolyte as disclosed in the Chinese patent 201480045908.2, and realizes the internal series connection of the batteries.
However, the above-mentioned ceramic isolation layers have drawbacks that are difficult to overcome. For example, ceramic particles are first coated on a film such as PET, PEN, PI, etc. to form a ceramic separator, which has a problem that a polyolefin substrate is poor in thermodynamic stability and plastic deformation. The preparation process of the all-solid-state battery of the sulfide glass ceramic solid electrolyte is complicated, and the problem of difficult scale production exists.
Therefore, the diaphragm which is free of polyolefin base materials and convenient for large-scale battery production is developed to solve the problems that the existing diaphragm is poor in thermodynamic stability and easy to cause electrolyte decomposition due to plastic deformation, and is a technical problem which needs to be solved urgently by technical personnel in the field of lithium batteries at present.
Disclosure of Invention
In view of the defects in the prior art, a first object of the present invention is to provide a separator without a polyolefin substrate, which has the characteristics of no plastic deformation due to no polyolefin substrate, and has excellent thermodynamic stability and ionic conductivity, so as to increase the difficulty of large-area short circuit after shearing and needling of a battery, and facilitate the realization of large-scale lithium battery production.
A second object of the present invention is to provide a method for manufacturing a polyolefin-based separator, which is simple in operation process, convenient in operation, and capable of mass production.
The third purpose of the invention is to provide a lithium battery, which uses the separator without the polyolefin substrate to prepare a corresponding battery core, and the battery core can be compatible with the traditional lithium battery production equipment, so that the lithium battery can be produced in a large scale. The diaphragm plays a role in isolating the pole pieces in the lithium battery, can also transmit ions, and improves the electrical property of the lithium battery.
In order to achieve the first object, the invention provides the following technical scheme:
a separator without polyolefin substrate is prepared from solid electrolyte ceramic particles and electrolyte soluble polymer binder, wherein the weight ratio of the solid electrolyte ceramic particles to the electrolyte soluble polymer binder is (90-80): (1-20), the particle diameter D50 of the solid electrolyte ceramic particles is 50nm-1 μm.
Furthermore, the weight ratio of the solid electrolyte ceramic particles to the electrolyte soluble polymer binder is 9:1, and the particle size D50 of the solid electrolyte ceramic particles is 50nm-500nm.
Through adopting above-mentioned technical scheme, the diaphragm of this application is made by solid electrolyte ceramic particle and the soluble macromolecular binder of electrolyte, mainly is applicable to in the lithium cell that contains electrolyte.
In the lithium battery containing the electrolyte, a proper amount of electrolyte is filled around the diaphragm, the electrolyte soluble polymer binder is dissolved after the electrolyte is added, and then the electrolyte soluble polymer binder is diffused into the electrolyte, and only the ceramic layer formed by the solid electrolyte ceramic particles is left to block the positive plate and the negative plate, so that the electronic conduction between the positive plate and the negative plate is prevented. Meanwhile, pores are formed at the positions where the electrolyte soluble polymer binder is dissolved, and the pores are filled with the electrolyte, so that the ionic conductivity of the separator can be effectively improved.
Due to the dissolving effect of the electrolyte, the diaphragm finally existing in the lithium battery does not contain high molecular polymer materials, so that the diaphragm has the characteristic of no plastic deformation and has excellent thermodynamic stability and ionic conductivity, and the difficulty of large-area short circuit after the battery is sheared and needled is increased. In addition, the battery core made of the diaphragm is compatible with traditional lithium battery production equipment, a lithium battery with safety and high electrical property can be prepared by a mature and simple process, and the scale of battery production is convenient to realize.
Further, the solid electrolyte ceramic particles are one or a mixture of more of lithium lanthanum zirconium oxide system oxide, lithium aluminum phosphate system oxide, lithium anti-perovskite system oxide, lithium lanthanum titanium oxide system oxide, lithium sulfide-phosphorus pentasulfide binary system sulfide, lithium sulfide-silicon disulfide binary system sulfide, lithium sulfide-phosphorus pentasulfide-germanium disulfide ternary system sulfide, lithium sulfide-germanium disulfide binary system sulfide, lithium sulfide-phosphorus pentasulfide-lithium chloride ternary system sulfide, lithium chloride-indium chloride binary system chloride, and lithium chloride-yttrium chloride binary system chloride.
Further, the solid electrolyte ceramic particles are lithium lanthanum zirconium oxide system oxide, lithium aluminum phosphate system oxide, lithium anti-perovskite system oxide and lithium lanthanum titanium oxide system oxide according to the weight ratio of (45-50): (15-20): (30-35): (5-10) are compounded.
By adopting the technical scheme, in the application, lithium lanthanum zirconium oxide system oxide, lithium aluminum phosphate lithium system oxide, lithium anti-perovskite system oxide, lithium lanthanum titanium oxide system oxide, lithium sulfide-phosphorus pentasulfide binary system sulfide, lithium sulfide-silicon disulfide binary system sulfide, lithium sulfide-phosphorus pentasulfide-germanium disulfide ternary system sulfide, lithium sulfide-germanium disulfide binary system sulfide, lithium sulfide-phosphorus pentasulfide-lithium chloride ternary system sulfide, lithium chloride-indium chloride binary system chloride and lithium chloride-yttrium chloride binary system chloride can be used as the solid electrolyte ceramic particles, so that the prepared solid electrolyte ceramic particles have excellent thermodynamic stability and ionic conductivity.
Wherein, when the solid electrolyte ceramic particles are lithium lanthanum zirconium oxide system oxide, lithium aluminum phosphate system oxide, lithium anti-perovskite system oxide and lithium lanthanum titanium oxide system oxide, the weight ratio is (45-50): (15-20): (30-35): (5-10) when compounded, the prepared diaphragm has obviously better thermodynamic stability and ionic conductivity than other solid electrolyte ceramic particles, so the solid electrolyte ceramic particles are preferred.
Further, the electrolyte soluble polymer binder is one or a mixture of more of polyvinylidene fluoride, trichloroethylene, polytetrafluoroethylene, acrylic acid adhesive, epoxy resin, polyethylene oxide, polyacrylonitrile, sodium carboxymethylcellulose, styrene butadiene rubber, polymethyl acrylate, polyacrylamide and polyvinylpyrrolidone.
Further, the electrolyte soluble polymer binder is prepared by compounding polymethyl acrylate, polyacrylamide and polyvinylpyrrolidone according to a weight ratio of 1.
By adopting the technical scheme, the polyvinylidene fluoride, the trichloroethylene, the polytetrafluoroethylene, the acrylic acid adhesive, the epoxy resin, the polyethylene oxide, the polyacrylonitrile, the sodium carboxymethylcellulose, the styrene butadiene rubber, the polymethyl acrylate, the polyacrylamide and the polyvinylpyrrolidone are common binders in the field, and the binder can be better applied to the diaphragm of the application and can firmly adhere to solid electrolyte ceramic particles.
Wherein, when the electrolyte soluble polymer binder is prepared by compounding polymethyl acrylate, polyacrylamide and polyvinylpyrrolidone according to the weight ratio of 1.
Further, the thickness of the separator is 1 to 50 μm.
By adopting the technical scheme, when the thickness of the diaphragm is 1-50 mu m, the diaphragm can better separate the positive plate and the negative plate and can ensure excellent thermodynamic stability and high ion conductivity.
In order to achieve the second object, the invention provides the following technical scheme:
a method for preparing a polyolefin substrate-free separator, comprising the steps of:
(1) preparation of glue solution
The weight ratio of (35-50): (65-50) adding 35-50 parts of electrolyte soluble polymer binder into 65-50 parts of electrolyte organic solvent to prepare binder glue solution;
(2) stirring the materials
Adding solid electrolyte ceramic particles into the binder glue solution according to a set ratio, and uniformly stirring to obtain mixed slurry;
(3) press forming of diaphragm
Adding the mixed slurry into an extruder, extruding into sheets under the pressure of 10-15Pa, and drying the electrolyte organic solvent at the temperature of 85-90 ℃ to obtain the final diaphragm;
or comprises the following steps:
(1) preparation of glue solution
The weight ratio of (35-50): (65-50) adding 35-50 parts of electrolyte soluble polymer binder into 65-50 parts of electrolyte organic solvent to prepare binder glue solution;
(2) stirring the materials
Adding solid electrolyte ceramic particles into the binder glue solution according to a set ratio, and uniformly stirring to obtain mixed slurry;
(3) coating and forming of the separator
And directly coating the mixed slurry on a positive plate or a negative plate to form a coating, and drying the electrolyte organic solvent at the temperature of 85-90 ℃ to obtain the final diaphragm layer.
A method for preparing a polyolefin substrate-free separator, comprising the steps of:
(1) stirring the materials
Uniformly mixing the solid electrolyte ceramic particles and the electrolyte soluble polymer binder according to a set ratio to obtain a mixture;
(2) melt extrusion
Putting the mixture into an extruder, extruding into sheets under the conditions of controlling the temperature to be 180-230 ℃ and the pressure to be 10-15Pa, and cooling to room temperature to obtain the final diaphragm.
By adopting the technical scheme, the diaphragm can be prepared by using a mode of firstly preparing mixed slurry and then extruding, tabletting or coating and drying, and can also be prepared by direct melt extrusion. The two preparation methods are simple in process, convenient for preparation of operators and capable of realizing mass production. The former can better ensure the effective active substance amount of each raw material, so that the prepared diaphragm has more excellent ion conductivity. The latter procedure reduces the addition and recovery of the organic solvent of the electrolyte, can reduce the preparation cost of the diaphragm to a certain extent, and is more environment-friendly.
In order to achieve the third object, the invention provides the following technical solutions:
a lithium battery comprises a battery core formed by sequentially stacking a positive plate, a diaphragm and a negative plate, wherein the diaphragm is the diaphragm without a polyolefin substrate.
Through adopting above-mentioned technical scheme, the lithium cell of this application uses this no polyolefin substrate's diaphragm to prepare corresponding electric core, and this electric core can compatible traditional lithium cell production facility to this can large-scale production. The diaphragm plays a role in isolating the pole pieces in the lithium battery, can also transmit ions, and improves the electrical property of the lithium battery, so that the diaphragm has a good market application prospect.
In conclusion, the invention has the following beneficial effects:
1. the diaphragm has the characteristic of no plastic deformation due to no polyolefin substrate, has excellent thermodynamic stability and ionic conductivity, thereby increasing the difficulty of large-area short circuit after the battery is cut and needled, and being convenient for realizing the scale production of the lithium battery; 2. the diaphragm of this application both can be made through extruding the preforming or the dry mode of coating by mixed thick liquids, also can directly melt and extrude and make, and two kinds of preparation methods processes are all comparatively simple, make things convenient for operating personnel's preparation, can realize the volume production, have good market perspective.
Drawings
FIG. 1 is a flow chart of a process for preparing a separator according to example 1 a;
FIG. 2 is a flow chart of a process for preparing a separator according to example 2 a;
fig. 3 is a process flow diagram for preparing a separator according to example 3 a.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
1. Examples of the embodiments
1.1, example 1a
A diaphragm without a polyolefin substrate is prepared from solid electrolyte ceramic particles and an electrolyte soluble polymer binder, wherein the weight ratio of the solid electrolyte ceramic particles to the electrolyte soluble polymer binder is 9:1, the grain diameter D50 of the solid electrolyte ceramic particles is within the range of 200nm-500 nm;
wherein the solid electrolyte ceramic particles are lithium lanthanum zirconium oxygen system oxide (Li) 7 La 3 Zr 2 O 12 ) Lithium aluminum phosphate system oxide (Li) 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 ) Lithium anti-perovskite system oxide (Li) 3 OCl), lithium lanthanum titanate series oxide (Li) 0.33 La 0.56 TiO 3 ) The adhesive is prepared by compounding the following components in parts by weight of 48;
the electrolyte soluble polymer binder is prepared by compounding polymethyl acrylate, polyacrylamide and polyvinylpyrrolidone according to the weight ratio of 1.
The preparation method of the separator without the polyolefin substrate, referring to fig. 1, comprises the following steps:
(1) preparation of glue solution
Adding 4kg of electrolyte soluble polymer binder into 6kg of electrolyte organic solvent (the electrolyte organic solvent can be adjusted according to solvent components in electrolyte during the production of a lithium battery, and dimethyl carbonate is taken as an example for the application) according to the weight ratio of 4:6 to prepare binder glue solution;
(2) stirring the materials
Adding 36kg of solid electrolyte ceramic particles into the binder glue solution according to a set ratio, and uniformly stirring to obtain mixed slurry; (3) press forming of diaphragm
And adding the mixed slurry into an extruder, extruding into a sheet under the pressure of 12Pa, and drying the electrolyte organic solvent at the temperature of 88 ℃ to obtain the final diaphragm with the thickness of 20 mu m.
1.2, examples 1b-1g
Examples 1b-1g the material parameters in the separator were adjusted based on the method of example 1, and the specific adjustment is shown in table one below.
TABLE raw Material parameter adjustment Table for separators of examples 1a to 1g
1.2, example 1h-1m
Examples 1h-1m the preparation parameters in the separator were adjusted based on the method of example 1, see table two below.
TABLE II preparation parameter adjustment Table for separator of example 1a, 1h-1m
1.3, example 2a
Example 2a the preparation method of the separator was modified based on the raw material of example 1 a.
A method for preparing a separator without a polyolefin substrate, see fig. 2, comprising the steps of:
(1) preparation of glue solution
Adding 4kg of electrolyte soluble polymer binder into 6kg of electrolyte organic solvent (dimethyl carbonate) according to the weight ratio of 4:6 to prepare binder glue solution;
(2) stirring the materials
Adding 36kg of solid electrolyte ceramic particles into the binder glue solution according to a set proportion, and uniformly stirring to obtain mixed slurry; (3) coating and forming of the separator
The mixed slurry is directly coated on a positive plate or a negative plate to form a coating, the coating is taken as an example, the positive plate is placed at the temperature of 88 ℃ to dry an electrolyte organic solvent, the drying temperature can be adjusted in a fluctuation mode within the range of 85-90 ℃, and a diaphragm layer bonded on the positive plate is obtained, and the thickness of the diaphragm is 20 microns.
1.4, example 3a
Example 3a the preparation of the separator was also modified on the basis of the starting material of example 1 a.
A method for preparing a separator without a polyolefin substrate, see fig. 3, comprising the steps of:
(1) stirring the materials
Uniformly mixing 36kg of solid electrolyte ceramic particles and 4kg of electrolyte soluble polymer binder according to a set ratio to obtain a mixture;
(2) melt extrusion
And putting the mixture into an extruder, extruding the mixture into sheets under the conditions that the temperature is controlled at 210 ℃ and the pressure is 13Pa, and cooling the sheets to room temperature to obtain the final diaphragm, wherein the thickness of the diaphragm is 20 microns.
1.5, examples 3b to 3c
Examples 3b-3c preparation parameters of the separator were adjusted based on the method of example 3a, see table three below.
TABLE III preparation parameter adjustment Table for separator of examples 1a, 1h-1m
| Melting temperature/. Degree.C | Extrusion pressure/Pa | |
| Example 3a | 210 | 13 |
| Example 3b | 230 | 10 |
| Example 3c | 180 | 15 |
2. Comparative example
2.1, comparative example 1
Comparative example 1 based on the raw materials and method of example 1a, the weight ratio of solid electrolyte ceramic particles to electrolyte soluble polymeric binder was controlled to be 1:1.
2.2 comparative example 2
Comparative example 2 based on the raw material and method of example 2a, all the solid electrolyte ceramic particles were used, and no electrolyte-soluble polymer binder was used. In this case, after the organic solution of the electrolyte is dried, the prepared diaphragm is too brittle to be used normally, and thus the following performance measurement is not performed.
2.3, comparative example 3
Comparative example 3 based on the raw materials and method of example 1a, solid electrolyte ceramic particles having a particle diameter D50 of 2 to 40nm were used.
2.4, comparative example 4
Comparative example 4 based on the raw materials and method of example 1a, the solid electrolyte ceramic particles used had a particle diameter D50 of 1.5 to 2 μm.
3. Membrane performance testing
The separators prepared in the above examples 1a to 1m, 2a, 3a to 3c and comparative examples 1 to 4 were respectively tested for thermodynamic stability, electron conductivity and ionic conductivity as follows, and the test results are shown in the following table four.
4. Lithium battery performance detection
The separators prepared in examples 1a to 1m, 2a, 3a to 3c and comparative examples 1 to 4 were used to prepare lithium batteries containing an electrolyte according to a conventional battery preparation method, and the lithium batteries were tested for cycle performance and safety. The safety test mainly comprises the steps of using a steel needle with the diameter of 5mm to puncture a fully charged lithium battery, shearing the fully charged lithium battery, and recording an open-circuit voltage-time change curve of the battery.The anode material is lithium cobaltate, the cathode material is metal lithium foil, and the electrolyte is LiPF with the concentration of 1mol/L 6 Solution in EC: DEC: DMC = 1. The charging and discharging voltage range is 3-4.3V, the current multiplying power is 0.5C, and the testing temperature is 25 ℃. The test results are shown in the following table four.
5. Test standards and results
5.1, measuring the thermodynamic stability of the diaphragm (testing the weight loss condition of the diaphragm heated to 600 ℃ in the air);
5.2, diaphragm electronic conductivity (after electrolyte with the mass ratio of 20wt% of the diaphragm is dripped, a steel/diaphragm/steel symmetrical battery is assembled, and the electronic conductivity of the battery is tested by using a direct current resistance tester);
5.3, diaphragm ionic conductivity (after electrolyte with the mass ratio of 20wt% of the diaphragm is dripped, a steel/diaphragm/steel symmetrical battery is assembled, and the ionic conductivity of the battery is tested by using an alternating current impedance tester);
5.4, the cycle performance of the battery (the anode material is lithium cobaltate, the cathode material is metal lithium foil, and the electrolyte is LiPF with 1mol/L 6 Solution in EC: DEC: DMC = 1;
5.5, the open circuit voltage of the battery changes after the needle punching (the diameter of the steel needle is 5 mm);
5.6, the open circuit voltage of the battery after shearing changes (ceramic scissors).
TABLE four test results of examples 1a to 1m, 2a, 3a to 3c, comparative examples 1 to 4
Referring to table four, comparing the results of examples 1a and 2a with those of comparative examples 1 to 4, it can be seen that the separator of the present application, which is made of solid electrolyte ceramic particles and an electrolyte-soluble polymer binder, is suitable for use in a lithium battery containing an electrolyte, has no plastic deformation characteristic, and has excellent thermodynamic stability and ionic conductivity. The battery core made of the diaphragm is compatible with traditional lithium battery production equipment, a lithium battery with safety and high electric performance can be prepared by using a mature and simple process, and the scale of battery production is convenient to realize.
In addition, the addition amount of the electrolyte soluble polymer binder in the diaphragm is extremely low, and the electrolyte soluble polymer binder is dissolved in electrolyte added later, so that the diaphragm has the characteristic of almost no plastic deformation and has better thermodynamic stability.
Comparing the results of examples 1a to 1c with those of examples 1D to 1e, it can be seen that when the weight ratio of the solid electrolyte ceramic particles to the electrolyte soluble polymer binder is 9:1 and the particle size D50 of the solid electrolyte ceramic particles is 50nm to 200nm, the prepared separator has more excellent thermodynamic stability, ionic conductivity and short circuit prevention effect (reflected in the voltage open circuit recovery after needling and shearing), and the lithium battery prepared from the separator has more excellent cycle performance.
Comparing the results of examples 1a to 1c with those of examples 1f to 1g, it can be obtained that, in the separator raw material of the present application, when the solid electrolyte ceramic particles are a lithium lanthanum zirconium oxide system oxide, an aluminum lithium phosphate system oxide, a lithium inverse perovskite system oxide, a lithium lanthanum titanium oxide system oxide in a weight ratio of (45 to 50): (15-20): (30-35): (5-10), when the electrolyte soluble polymer binder is prepared by compounding polymethyl acrylate, polyacrylamide and polyvinylpyrrolidone according to a weight ratio of 1.
Comparing the results of examples 1a, 1h, 1i, 2a, and 3a-3c, it can be seen that the separator of the present application can be prepared from the mixed slurry by extrusion tableting or coating drying, or by direct melt extrusion, and both preparation methods are simple in procedure, convenient for the operator to prepare, and can realize mass production. Wherein, the former can better ensure the effective active material quantity of each component, so that the prepared diaphragm has more excellent ion conductivity. The latter procedure reduces the addition and recovery of the organic solvent of the electrolyte, can reduce the preparation cost of the diaphragm to a certain extent, and is more environment-friendly.
Comparing the results of examples 1a and 1j to 1m, it can be obtained that the separator can better block the positive electrode sheet and the negative electrode sheet and ensure excellent thermodynamic stability and high ionic conductivity when the thickness of the separator is 1 to 50 μm.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (4)
1. The diaphragm without the polyolefin substrate is characterized by being prepared from solid electrolyte ceramic particles and an electrolyte soluble polymer binder, wherein the weight ratio of the solid electrolyte ceramic particles to the electrolyte soluble polymer binder is 9:1, and the particle size D50 of the solid electrolyte ceramic particles is 50nm-200nm; the solid electrolyte ceramic particles are lithium lanthanum zirconium oxide system oxide, aluminum lithium phosphate system oxide, lithium anti-perovskite system oxide and lithium lanthanum titanium oxide system oxide according to the weight ratio of (45-50): (15-20): (30-35): (5-10) compounding; the electrolyte soluble polymer binder is prepared by compounding polymethyl acrylate, polyacrylamide and polyvinylpyrrolidone according to a weight ratio of 1; the thickness of the separator was 20 μm.
2. A method of making the polyolefin substrate-free separator of claim 1, comprising the steps of:
(1) preparation of glue solution
The weight ratio of (35-50): (65-50) adding 35-50 parts of electrolyte soluble polymer binder into 65-50 parts of electrolyte organic solvent to prepare binder glue solution;
(2) stirring the materials
Adding solid electrolyte ceramic particles into the binder glue solution according to a set ratio, and uniformly stirring to obtain mixed slurry;
(3) and press forming of the diaphragm
Adding the mixed slurry into an extruder, extruding into sheets under the pressure of 10-15Pa, and drying the electrolyte organic solvent at the temperature of 85-90 ℃ to obtain the final diaphragm;
or comprises the following steps:
(1) preparation of glue solution
The weight ratio of (35-50): (65-50) adding 35-50 parts of electrolyte soluble polymer binder into 65-50 parts of electrolyte organic solvent to prepare binder glue solution;
(2) stirring the materials
Adding solid electrolyte ceramic particles into the binder glue solution according to a set ratio, and uniformly stirring to obtain mixed slurry;
(3) coating and forming of the separator
And directly coating the mixed slurry on a positive plate or a negative plate to form a coating, and drying the electrolyte organic solvent at the temperature of 85-90 ℃ to obtain the final diaphragm layer.
3. The method for producing a polyolefin substrate-free separator according to claim 2, comprising the steps of:
(1) stirring the materials
Uniformly mixing the solid electrolyte ceramic particles and the electrolyte soluble polymer binder according to a set ratio to obtain a mixture;
(2) melt extrusion
Putting the mixture into an extruder, extruding into sheets under the conditions of controlling the temperature to be 180-230 ℃ and the pressure to be 10-15Pa, and cooling to room temperature to obtain the final diaphragm.
4. A lithium battery comprising a battery cell formed by sequentially stacking a positive electrode sheet, a separator and a negative electrode sheet, wherein the separator is the separator without a polyolefin substrate according to claim 1, and the separator is prepared by the preparation method according to any one of claims 2 or 3.
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