CN114874465A - Organic-inorganic composite microsphere, battery diaphragm, preparation method of battery diaphragm and battery - Google Patents

Organic-inorganic composite microsphere, battery diaphragm, preparation method of battery diaphragm and battery Download PDF

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CN114874465A
CN114874465A CN202210659884.6A CN202210659884A CN114874465A CN 114874465 A CN114874465 A CN 114874465A CN 202210659884 A CN202210659884 A CN 202210659884A CN 114874465 A CN114874465 A CN 114874465A
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organic
inorganic composite
battery
microsphere
precursor
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肖政
邓豪
陈杰
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Huizhou Liwinon Energy Technology Co Ltd
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    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
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    • C—CHEMISTRY; METALLURGY
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    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M50/417—Polyolefins
    • 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
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
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    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/06—Polyethene
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    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2479/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2461/00 - C08J2477/00
    • C08J2479/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C08J2479/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
    • 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
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention discloses an organic-inorganic composite microsphere, a battery diaphragm, a preparation method thereof and a battery, wherein the preparation method of the organic-inorganic composite microsphere comprises the following steps: mixing polyamic acid and a silicon source to prepare a first precursor microsphere, putting the first precursor microsphere in first hydrolysate for hydrolysis, and then carrying out thermal imidization and dehydration treatment; or, preparing a second precursor microsphere by adopting a polyamic acid solution, and then mixing the second precursor microsphere with TiOSO 4 Mixing, complexing, hydrolyzing in the second hydrolysate, and thermal imidization and dewatering. The organic-inorganic composite microspheres prepared by the method have uniform core-shell structures and sizes, have excellent thermal stability and wettability, can be applied to surface modification of polyolefin diaphragms to enhance the thermal stability and the wettability of electrolyte of the diaphragms, can ensure the consistency of the thickness of a modified modification layer formed on the surfaces of the polyolefin diaphragms and the overall performance of the diaphragms, and can be further applied to batteries to improve the safety and the cycle performance of the batteries.

Description

Organic-inorganic composite microsphere, battery diaphragm, preparation method of battery diaphragm and battery
Technical Field
The invention relates to the technical field of lithium ion battery diaphragms, in particular to an organic-inorganic composite microsphere, a battery diaphragm, a preparation method of the battery diaphragm and a battery.
Background
Lithium ion batteries, as an efficient chemical energy storage and conversion device, are widely used in portable electronic devices due to their high energy density, good rate capability, environmental friendliness, and other characteristics; the lithium ion battery mainly comprises an anode, a cathode, a diaphragm, electrolyte, an aluminum plastic film and the like, wherein the diaphragm is one of important components of the battery, has the function of preventing the anode and the cathode from short circuit caused by direct contact, and can provide a channel for ion transmission.
Polyolefin materials such as polyethylene, polypropylene and the like are mostly adopted in lithium ion battery separators which are commercialized at present. The microporous membrane prepared from the polyethylene and polypropylene materials has the characteristics of stable chemical property, high mechanical strength, high thermal closing property, low cost and the like, so that the polyolefin material is used for preparing the diaphragm at the initial stage of the research and development of the lithium ion battery. Due to the influence of low melting point and non-polarity of polyolefin, the thermal stability and electrolyte wettability of the microporous polyolefin diaphragm are relatively poor, so that the uniform transmission of lithium ions in the battery is hindered, and the application of the microporous polyolefin diaphragm in a high-energy-density and high-rate lithium battery is limited. The polyolefin diaphragm is subjected to surface modification, so that the thermal stability and the surface polarity of the diaphragm can be effectively improved to a certain extent, and the thermal stability and the electrolyte wettability of the diaphragm are improved, so that the safety and the circulation stability of a battery are favorably improved, and therefore, the surface modification of the polyolefin diaphragm is a research hotspot at present. The common way of surface modification of polyolefin diaphragms is to arrange a modification layer on the surface of the diaphragm, but the improvement of the thermal stability and the wettability of electrolyte of the diaphragm by the existing surface coating modification method is limited, and the thickness consistency of the modification layers formed by some methods is poor.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides an organic-inorganic composite microsphere, a battery diaphragm, a preparation method of the organic-inorganic composite microsphere and the battery diaphragm, and a battery.
In a first aspect of the present invention, a method for preparing organic-inorganic composite microspheres is provided, which comprises the following steps:
s1, preparing a first precursor microsphere by mixing polyamic acid and a silicon source;
s2, placing the first precursor microspheres in first hydrolysate for hydrolysis, and then performing thermal imidization and dehydration treatment to obtain the organic-inorganic composite microspheres.
The preparation method of the organic-inorganic composite microspheres provided by the embodiment of the invention has at least the following beneficial effects: the preparation method of the organic-inorganic composite microspheres adopts polyamide acid and a silicon source to prepare first precursor microspheres, and then the first precursor microspheres are placed in first hydrolysate to be hydrolyzed so as to generate Si (OH) on the surfaces of the first precursor microspheres in situ 4 Hydrolyzing the coating layer, imidizing PAA into Polyimide (PI) by thermal imidization and dehydration, and adding Si (OH) 4 Dehydrated into SiO 2 And obtaining the product organic-inorganic composite core-shell nano-microsphere. According to the method, after the first precursor microsphere is prepared, hydrolysis treatment is carried out, and then thermal imidization and dehydration treatment are carried out, so that the problem of excessive hydrolysis reaction caused by high temperature due to thermal treatment before hydrolysis can be avoided, and the core-shell structure of the prepared organic-inorganic composite microsphere is more uniform and the size is uniform; the composite microsphere has excellent thermal stability and wettability, can be applied to surface modification of polyolefin diaphragms, and can enhanceThermal stability and electrolyte wettability of the separator; and based on the uniformity of the structure and the size of the prepared composite microsphere, the thickness of a modified modification layer applied to the surface of the polyolefin diaphragm and the consistency of the overall performance of the diaphragm can be ensured.
In some embodiments of the invention, in step S1, the silicon source is selected from at least one of tetramethyl orthosilicate, tetraethyl orthosilicate (TEOS), ethyl orthosilicate, and tetrabutyl orthosilicate. The amount of silicon source may be selected according to the final SiO produced 2 Is SiO 2 And 10 to 40% (e.g., 10%, 15%, 20%, 30%, 40%) of the total mass of PI.
In step S1, the first precursor microsphere may be prepared by electrostatic spinning, specifically, a spinning solution may be prepared by mixing polyamic acid and a silicon source, and then electrostatic spinning is performed to prepare the first precursor microsphere. The electrospinning parameters can be controlled as follows: the positive pressure is plus 40KV to plus 60KV (preferably plus 50KV), the negative pressure is minus 8KV to minus 12KV (preferably minus 10KV), the spraying distance is 20cm to 25cm, and the liquid brushing speed is 5 cm/s to 20 cm/s.
In addition, in step S1, the polyamic acid may be prepared by polymerizing a dianhydride monomer and a diamine monomer in an aprotic polar organic solvent. The dianhydride monomer can be at least one selected from biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, diphenyl ether tetracarboxylic dianhydride, hexafluoro dianhydride and bisphenol A type diether dianhydride; the diamine monomer may be at least one selected from bis (4-aminophenyl) ether, p-phenylenediamine, 4 ' -diaminodiphenylmethane, and 4,4 ' -diamino-2, 2 ' -bistrifluoromethylbiphenyl. The polymerization reaction can be carried out in an ice-water bath; after the polymerization reaction is completed, aging treatment can be further performed to improve the uniformity of molecular weight distribution, and the aging treatment can be performed under the constant temperature condition of 45-55 ℃ (preferably 50 ℃). Preferably, the prepared polyamic acid (i.e., PAA solution) has a viscosity of 0.01 to 1 dl/g. Further preferably, the solid content of the PAA solution is 5-40%.
In some embodiments of the present invention, in step S2, the thermal imidization and dehydration treatment is a high temperature treatment at 250 to 350 ℃. The PAA is imidized into Polyimide (PI) and Si (OH) by high-temperature treatment at 250-350 DEG C 4 Dehydrated to SiO 2 . The specific temperature of the high-temperature treatment can be controlled to 250 ℃, 280 ℃, 300 ℃, 310 ℃, 350 ℃ and the like, and 300 ℃ is preferred; the high-temperature treatment time can be controlled within 1-3 h, preferably 2 h. Due to the interaction between PAA and silicon source, part of silicon source is remained in the polyamic acid nano-microsphere and can not migrate out, during the cyclization process of polyamic acid, the remained silicon source is reacted with water generated in the imidization process of PAA, and SiO can be formed in PI 2 Particles, finally obtaining the structure of SiO 2 @(PI/SiO 2 ) The core-shell nano-microsphere.
In some embodiments of the present invention, in step S2, the first hydrolysate is a mixed solution of alcohol and water, and the volume ratio of the alcohol to the water can be controlled to be 1 (3-5), preferably 1: 4. The alcohol may specifically be ethanol or isopropanol.
In a second aspect of the present invention, a method for preparing organic-inorganic composite microspheres is provided, which comprises the following steps:
s1, preparing a second precursor microsphere by adopting a polyamic acid solution;
s2, mixing the second precursor microsphere and TiOSO 4 Mixing, performing complex reaction, hydrolyzing in a second hydrolysate, performing thermal imidization and dehydration treatment, and obtaining the organic-inorganic composite microspheres.
According to the preparation method of the organic-inorganic composite microsphere provided by the embodiment of the invention, at least the following beneficial effects are achieved: the preparation method of the organic-inorganic composite microsphere adopts a polyamic acid solution to prepare a second precursor microsphere, and then the second precursor microsphere is mixed with TiOSO 4 Mixing to perform complex reaction, specifically, the-COOH and TiO on the surface of the second precursor microsphere 2+ Carrying out adsorption complex reaction; then placing the mixture in a second hydrolysate to allow the TiO to react with the first hydrolysate 2+ Hydrolysis takes place, in situ generation of TiO (OH) 2 Then, heat imidization and dehydration treatment are performed to imidize PAA into Polyimide (PI), and TiO (OH) 2 Dehydrated to TiO 2 And obtaining the organic-inorganic composite core-shell nano-microsphere. According to the method, after the first precursor microsphere is prepared, hydrolysis treatment is carried out, and then thermal imidization and dehydration treatment are carried out, so that high-temperature pairs caused by thermal treatment before hydrolysis can be avoidedThe surplus problem of hydrolysis reaction can lead the core-shell structure of the prepared organic-inorganic composite microsphere to be more uniform and the size to be uniform; the composite microsphere has excellent thermal stability and wettability, and can be applied to surface modification of a polyolefin diaphragm so as to enhance the thermal stability and electrolyte wettability of the diaphragm; and based on the uniformity of the structure and the size of the prepared composite microsphere, the thickness of a modified modification layer applied to the surface of the polyolefin diaphragm and the consistency of the overall performance of the diaphragm can be ensured.
In step S1, the second precursor microsphere may also be prepared by electrostatic spinning; the electrospinning parameters can be controlled as follows: the positive pressure is plus 40KV to plus 60KV (preferably plus 50KV), the negative pressure is minus 8KV to minus 12KV (preferably minus 10KV), the spraying distance is 20cm to 25cm, and the liquid brushing speed is 5 cm/s to 20 cm/s. The polyamic acid solution can also be prepared by polymerizing a dianhydride monomer and a diamine monomer in an aprotic polar organic solvent. The dianhydride monomer can be at least one selected from biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, diphenyl ether tetracarboxylic dianhydride, hexafluoro dianhydride and bisphenol A type diether dianhydride; the diamine monomer may be at least one selected from bis (4-aminophenyl) ether, p-phenylenediamine, 4 ' -diaminodiphenylmethane, and 4,4 ' -diamino-2, 2 ' -bistrifluoromethylbiphenyl. The polymerization reaction can be carried out in an ice-water bath; after the polymerization reaction is completed, aging treatment can be further performed to improve the uniformity of molecular weight distribution, and the aging treatment can be performed under the constant temperature condition of 45-55 ℃ (preferably 50 ℃). Preferably, the obtained polyamic acid (i.e., PAA solution) has an intrinsic viscosity of 0.01 to 1 dl/g. Further preferably, the solid content of the PAA solution is 5-40%.
In some embodiments of the present invention, in step S2, the thermal imidization and dehydration treatment is a high temperature treatment at 250 to 350 ℃. Namely, the imidization of PAA into Polyimide (PI) and TiO (OH) are realized by high-temperature treatment at 250-350 DEG C 2 Dehydrated to TiO 2 . The high-temperature treatment time can be controlled within 1-3 h, preferably 2 h. In addition, in step S2, deionized water is used as the second hydrolysate.
In a third aspect of the present invention, there is provided an organic-inorganic composite microsphere, which is prepared by any one of the methods for preparing an organic-inorganic composite microsphere set forth in the first aspect of the present invention, or any one of the methods for preparing an organic-inorganic composite microsphere set forth in the second aspect of the present invention. The organic-inorganic composite microsphere has the advantages of uniform core-shell structure, uniform size, excellent thermal stability and wettability, can be applied to surface modification of a polyolefin diaphragm, and can enhance the thermal stability and electrolyte wettability of the diaphragm.
In a fourth aspect of the present invention, a battery separator is provided, which includes a polyolefin microporous base film and a modification layer disposed on a surface of the polyolefin microporous base film, wherein the modification layer is made of a material including an adhesive and the organic-inorganic composite microspheres provided in the third aspect of the present invention. The polyolefin microporous base membrane and the organic-inorganic composite microspheres on the modification layer of the polyolefin microporous base membrane in the battery diaphragm both have excellent electronic insulation property, can effectively prevent electronic migration, have excellent thermal stability and electrolyte wettability, are high in mechanical strength and good in thickness consistency, can be applied to preparation of a lithium ion battery, and can effectively improve the safety and cycle performance of the lithium ion battery.
Wherein, the thickness of the polyolefin microporous base membrane can be controlled to be 3-200 nm; in addition, the porosity can be 20-80%, and the air permeability can be 50-200 s/100 cc. The polyolefin microporous base film can specifically adopt any one of a polyethylene microporous base film, a polypropylene/polyethylene/polypropylene three-layer composite microporous base film, a polyvinylidene fluoride microporous base film and a polyvinylidene fluoride-hexafluoropropylene microporous base film.
In addition, the adhesive can adopt polymer adhesive, such as one or more of aqueous PVDF emulsion, polyvinyl alcohol, polyethylene oxide, acrylic acid water-soluble glue, styrene-butadiene rubber, sodium carboxymethyl cellulose and polyvinylpyrrolidone.
In a fifth aspect of the present invention, a method for preparing a battery separator according to the fourth aspect of the present invention is provided, comprising: mixing organic-inorganic composite microspheres, an adhesive and a solvent to prepare modified slurry; and then coating the modification slurry on the surface of the polyolefin microporous base membrane, and drying to obtain the battery diaphragm.
The slurry can be prepared by mixing the following components in parts by weight: 9-30 parts of organic-inorganic composite microspheres, 1-3 parts of adhesive and 67-90 parts of solvent. The solvent can be water or a mixed solution of water and alcohol.
In a sixth aspect of the present invention, a battery is provided, which includes the battery separator provided in the fourth aspect of the present invention or the battery separator obtained by the method for preparing the battery separator provided in the fifth aspect of the present invention. The battery is based on the battery diaphragm which has excellent thermal stability and electrolyte wettability, high mechanical strength and good thickness consistency, so that the battery has excellent safety performance and cycle performance.
Drawings
The invention is further described with reference to the following figures and examples, in which:
FIG. 1 is an SEM photograph of a battery separator prepared in example 3;
FIG. 2 is an SEM photograph of a battery separator prepared in example 4;
FIG. 3 is an SEM photograph of a battery separator prepared in comparative example 2;
FIG. 4 is a graph showing the results of the electrolyte wettability tests of the battery separators prepared in examples 3 to 4 and comparative example 2 and the polyethylene separator prepared in comparative example 3.
Detailed Description
The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.
Example 1
The embodiment prepares an organic-inorganic composite microsphere, and the preparation method specifically comprises the following steps:
s1, adopting dianhydride monomers of pyromellitic dianhydride and diamine monomer of bis (4-aminophenyl) ether, using aprotic polar N, N-dimethylformamide (DMF as a solvent, mixing the DMF in a mass ratio of 1: 1), putting the mixture in an ice water bath for polymerization reaction to synthesize a polyamide acid (PAA) solution with the solid content of 12 wt%, and then putting the solution in a constant temperature condition of 50 ℃ for aging treatment to obtain the polyamide acid (PAA) solution with uniform molecular weight distribution and the intrinsic viscosity of 0.3 dl/g;
s2, adding tetraethyl orthosilicate (TEOS) with the mass ratio of 10% into the polyamic acid (PAA) solution finally prepared in the step S1, sealing and stirring for 6 hours at room temperature, and preparing a clear, transparent and uniformly mixed PAA/TEOS mixed solution; then, adopting a PAA/TEOS mixed solution as a spinning solution to carry out electrostatic spinning, and controlling the spinning parameters to be positive pressure +50KV, negative pressure-10 KV, spraying distance of 20cm and brushing speed of 10cm/s to prepare a first precursor microsphere;
s3, placing the first precursor microspheres prepared in the step S2 in hydrolysate (ethanol and water with the volume ratio of 1: 4), hydrolyzing for 24h at room temperature, and generating Si (OH) on the surfaces of the first precursor microspheres in situ 4 Hydrolyzing the coating layer; then processing at 300 ℃ for 2h to imidize PAA into PI, Si (OH) 4 Dehydrated into SiO 2 In addition, due to the interaction between PAA and TEOS, part of TEOS remains in the polyamic acid nano-microspheres and cannot migrate out, during the cyclization process of the polyamic acid by high-temperature treatment, the residual TEOS in the interior reacts with water generated in the imidization process of PAA, and SiO can be formed in PI 2 Particles, finally obtaining the structure of SiO 2 @(PI/SiO 2 ) The core-shell nano-microspheres are organic-inorganic composite microspheres.
Example 2
This example prepares an organic-inorganic composite microsphere, and the preparation method specifically includes:
s1, preparing polyamic acid (PAA) solution in the same operation as step S1 in example 1;
s2, taking the polyamic acid (PAA) solution finally prepared in the step S1 as spinning solution to carry out electrostatic spinning, and controlling spinning parameters to be positive pressure +50KV, negative pressure-10 KV, spraying distance to be 20cm, and brushing speed to be 10cm/S to prepare second precursor microspheres;
s3, placing the second precursor microsphere prepared in the step S2 in TiOSO with the concentration of 0.2mol/L 4 In the solution, a complex reaction is carried out at room temperature, specifically, -COOH on the surface of the second precursor microsphere and TiO will react 2+ Carrying out adsorption complex reaction; then placing the mixture in hydrolysate deionized water to ensure that the TiO is 2+ Hydrolysis takes place, in situ generation of TiO (OH) 2 (ii) a Further treating at 300 deg.C for 2h to imidize PAA into Polyimide (PI), and TiO (OH) 2 Dehydrated to TiO 2 The prepared structure is PI @ TiO 2 The core-shell nano-microsphere is an organic-inorganic composite microsphere.
Comparative example 1
The comparative example prepares an organic-inorganic composite microsphere, and the preparation method specifically comprises the following steps:
the operation of steps S1, S2 in this comparative example was the same as steps S1 and S2 in example 1, to prepare a first precursor microsphere; the preparation method of the organic-inorganic composite microspheres is different from that of the organic-inorganic composite microspheres in example 1 in that: s3, placing the first precursor microspheres in a 280 ℃ environment for heat treatment for 30min, then placing the first precursor microspheres into hydrolysate (ethanol and water with the volume ratio of 1: 4), and hydrolyzing for 24h at room temperature; and then placing the microspheres in a 300 ℃ blast oven for high-temperature treatment for 2 hours to obtain the organic-inorganic composite microspheres. Example 3
The embodiment prepares a battery separator, and the preparation method comprises the following steps:
s1, taking 9 parts of organic-inorganic composite microspheres prepared in example 1, 1 part of sodium carboxymethylcellulose (CMC) and 1 part of polyvinylpyrrolidone (PVP), placing the organic-inorganic composite microspheres and 98 parts of water and ethanol mixed solvent in a volume ratio of 1:1 into a homogenizer, homogenizing for 1h at a rotating speed of 8000rpm, uniformly mixing, and filtering by using a 300-mesh screen to obtain modified slurry;
s2, coating the modified slurry prepared in the step S1 on a polyethylene microporous base film by a flat plate blade coating machine at a coating gap of 100 microns, wherein the polyethylene microporous base film is purchased from the market, the thickness of the polyethylene microporous base film is 3-200 nm, the porosity of the polyethylene microporous base film is 20-80%, and the air permeability of the polyethylene microporous base film is 50-200S/100 cc; and after the coating is finished, placing the membrane on a super clean bench for natural drying, and then carrying out vacuum drying at 60 ℃ for 12h to obtain the product battery diaphragm. The battery diaphragm comprises a polyethylene microporous base film and a modification layer arranged on the surface of the polyethylene microporous base film, wherein the modification layer is prepared by mixing organic-inorganic composite microspheres prepared in the embodiment 1, an adhesive (CMC and PVP in a mass ratio of 1: 1) and a solvent.
Example 4
This example prepared a battery separator, which was prepared in substantially the same manner as in example 3, except that the organic-inorganic composite microspheres prepared in example 2 were used instead of the organic-inorganic composite microspheres prepared in example 1 used in example 3, and the other operations were the same as in example 3, except that the preparation method of the battery separator was changed as in example 3.
Comparative example 2
A battery separator according to the present comparative example was prepared in the same manner as in example 3, except that the organic-inorganic composite microspheres prepared in comparative example 1 were used instead of the organic-inorganic composite microspheres prepared in example 1 used in example 3, and the other operations were the same as in example 3. Performance testing
The battery separators obtained in examples 3 and 4 and comparative example 2 were observed by using a scanning electron microscope, and the results are shown in fig. 1 to 3, respectively. As can be seen from comparison of FIGS. 1 to 3, the separator prepared in examples 3 and 4 has better consistency than the battery separator prepared in comparative example 2.
In addition, the battery separators prepared in examples 3 and 4 and comparative example 2 and the polyethylene separator in comparative example 3 were tested with unmodified conventional polyethylene separator (i.e., microporous polyethylene base membrane used in example 3) as comparative example 3, and the specific performance parameters and methods for testing the performance of the polyethylene separator in comparative example 3 included:
(A1) thickness uniformity σ
The specific test method comprises the following steps: taking a section of each battery diaphragm, measuring the thickness once every 20cm, testing 30 values in total, and calculating the standard deviation sigma to represent the thickness consistency of the battery diaphragm.
(A2) Wettability
The specific test method comprises the following steps: and (3) vertically dropping 1 mu L of electrolyte on each battery diaphragm by using a liquid transfer gun, standing for one minute, and recording the size of the electrolyte diffused on the surface of the battery diaphragm. The electrolyte adopts LiPF6 with the molar concentration of 1M, and the solvent is a mixed solution of Ethylene Carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in the volume ratio of 1:1: 1.
(A3) Heat shrinkability
The specific test method comprises the following steps: and (3) putting the battery diaphragm into an oven to heat at the initial temperature of 25 +/-3 ℃, raising the temperature of the oven to 130 ℃ at the speed of 5 +/-2 ℃/min, keeping the temperature for 30min, and then stopping, and testing the shrinkage size ratio of the battery diaphragm before and after baking.
The battery separators manufactured in examples 3 and 4 and comparative example 2 and the polyethylene separator in comparative example 3 were tested for their respective properties by the above methods, and the results of the thickness uniformity and heat shrinkability tests are shown in table 1, the results of the electrolyte wettability tests are shown in fig. 4, and (a) to (d) of fig. 4 are graphs showing the results of the electrolyte wettability tests of the battery separator in example 3, the battery separator in example 4, the battery separator in comparative example 3 and the polyethylene separator in comparative example 3 in this order.
TABLE 1
Figure BDA0003690264030000071
Figure BDA0003690264030000081
As can be seen from the thickness uniformity test results shown in table 1, the thickness uniformity of the battery separators obtained in examples 3 and 4 was significantly superior to that of the battery separator obtained in comparative example 2. The difference between the comparative example 2 and the example 3 is that the organic-inorganic composite microsphere is adopted, and the organic-inorganic composite microsphere in the example 1 is adopted in the example 3, and the preparation process of the organic-inorganic composite microsphere is that after the first precursor microsphere is prepared, hydrolysis treatment is carried out, and high-temperature imidization and dehydration treatment are carried out; in comparison example 2, the organic-inorganic composite microspheres prepared in comparison example 1 are adopted, and in the preparation process, the first precursor microspheres are subjected to heat treatment, hydrolysis treatment and high-temperature treatment, so that in the preparation process of the organic-inorganic composite microspheres, the heat treatment is performed before the first precursor microspheres are hydrolyzed, the characteristics of the prepared organic-inorganic composite microspheres are influenced, and the thickness consistency of the modified battery diaphragm is further obviously influenced. The specific speculation is that the subsequent hydrolysis reaction is excessive due to the high temperature of the heat treatment before hydrolysis, so that the uniformity of the core-shell structure and the size consistency of the prepared composite microspheres are influenced, the thickness consistency of the surface modification layer of the battery diaphragm is further influenced, and the thickness consistency of the battery diaphragm is poor. Therefore, in the embodiments 1 and 2, after the first precursor microsphere is prepared, the organic-inorganic composite microsphere is subjected to hydrolysis treatment, and then is subjected to thermal imidization and dehydration treatment, so that the problem that excessive hydrolysis reaction is easily caused by high temperature due to heat treatment before hydrolysis can be avoided, the core-shell structure of the prepared organic-inorganic composite microsphere is more uniform, the size of the organic-inorganic composite microsphere is uniform, and the organic-inorganic composite microsphere is applied to surface modification of a battery diaphragm, so that the thickness consistency of a modified layer can be ensured, and the consistency of the overall performance of the diaphragm can be further ensured.
In addition, referring to the heat shrinkage performance test results shown in table 1 and the wettability test results shown in fig. 4, it can be seen that the battery separators with the surface modification layers prepared in examples 3 and 4 have heat shrinkage performance and electrolyte wettability significantly better than the unmodified conventional polyethylene separator in comparative example 3.
Application example
The prepared battery diaphragm can be further applied to the preparation of lithium ion batteries. In order to examine the influence of the battery diaphragm on the battery performance when the battery diaphragm is further applied to a lithium ion battery, the inventor carries out a specific application test, which comprises assembling the battery diaphragms of examples 3 and 4 and comparative examples 2 and 3 and a polyethylene diaphragm into a cell device, and further testing the safety performance and the cycle performance of the cell device.
Specifically, the assembled battery core comprises a positive pole piece, a negative pole piece, electrolyte and the battery diaphragm. The positive pole piece is prepared by mixing 80 wt% of active material lithium cobaltate, 10 wt% of Super P carbon and 10 wt% of polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to prepare slurry, casting the prepared slurry on a clean carbon coating aluminum foil, and drying at 80 ℃ for 12 hours; the negative pole piece is prepared by mixing 80 wt% of active material graphite, 10 wt% of SuperP carbon and 10 wt% of binder styrene butadiene rubber in water to prepare slurry, then casting the obtained slurry on fresh copper foil and drying at 60 ℃ for 12 hours; the electrolyte adopts LiPF6 with the molar concentration of 1M, and the solvent is a mixed solution of Ethylene Carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) with the volume ratio of 1:1: 1.
The battery diaphragms and the polyethylene diaphragms of the embodiments 3 and 4 and the comparative examples 2 and 3 are assembled according to the structures to correspondingly obtain the battery core samples 1-4. And then, respectively testing the safety performance and the cycle performance of each battery cell sample, wherein the test method specifically comprises the following steps:
(B1) cell safety performance
The specific test method comprises the following steps: and (3) putting the battery core into an oven (suspension test), heating the battery core by using circulating hot air at the initial temperature of 25 +/-3 ℃, raising the temperature of the oven to 132 +/-2 ℃ at the speed of 5 +/-2 ℃/min, keeping the temperature for 30min, and stopping the operation, wherein the surface temperature, the environmental temperature and the voltage of the battery core are monitored in the test process, and the battery core is not ignited and does not explode to be Pass.
In addition, the test was carried out by adjusting the maximum temperature rise of 132. + -. 2 ℃ to 135. + -. 2 ℃ in substantially the same manner as above.
The safety performance of the cell samples 1-4 was tested according to the above method, and the results are shown in table 2.
TABLE 2
Figure BDA0003690264030000091
As can be seen from the results shown in table 2, the heat box throughput of the battery separators of the battery cell samples 1 and 2, which are surface-modified and prepared in examples 3 and 4, is significantly better than that of the battery cell sample 4, which is prepared in comparative example 3 by using the unmodified polyethylene separator. Therefore, the organic-inorganic composite microspheres prepared in the embodiments 1 and 2 are applied to surface modification of the polyolefin diaphragm, and the safety performance of the battery using the polyolefin diaphragm can be improved.
(B2) Cell cycle performance
The specific test method comprises the following steps: and (3) charging the lithium battery core at normal temperature by adopting 1C multiplying power, discharging at 1C multiplying power, sequentially circulating for 600 times, and recording the battery capacity before and after each circulation. The capacity retention ratio after n cycles is (battery capacity after n cycles/battery capacity before cycles) × 100%.
The capacity retention rates of the cell samples 1 to 4 after 600 cycles were tested according to the above method, and the obtained results are shown in table 3.
TABLE 3
Figure BDA0003690264030000101
As can be seen from the results shown in table 3, the cycle performance of the battery separators of the battery cell samples 1 and 2, which are surface-modified and prepared in examples 3 and 4, is significantly better than that of the battery cell sample 4, which is prepared in comparative example 3 by using the unmodified polyethylene separator. Therefore, the organic-inorganic composite microspheres prepared in the embodiments 1 and 2 are applied to surface modification of the polyolefin diaphragm, and the cycle performance of the battery using the polyolefin diaphragm can be improved.
According to the method, after the first precursor microsphere is prepared, the organic-inorganic composite microsphere is subjected to hydrolysis treatment, and then is subjected to thermal imidization and dehydration treatment, so that the problem of excessive hydrolysis reaction caused by high temperature due to heat treatment before hydrolysis can be avoided, and the prepared organic-inorganic composite microsphere has a more uniform core-shell structure and uniform size; the composite microsphere has excellent thermal stability and wettability, can be applied to surface modification of a polyolefin diaphragm, and can enhance the thermal stability and electrolyte wettability of the diaphragm; and based on the uniformity of the structure and the size of the prepared composite microsphere, the thickness of a modified modification layer formed on the surface of the polyolefin diaphragm and the uniformity of the overall performance of the diaphragm can be ensured, and the safety and the cycle performance of the battery can be improved when the modified modification layer is applied to the battery.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims (10)

1. A preparation method of organic-inorganic composite microspheres is characterized by comprising the following steps:
s1, preparing a first precursor microsphere by mixing polyamic acid and a silicon source;
s2, placing the first precursor microspheres in first hydrolysate for hydrolysis, and then performing thermal imidization and dehydration treatment to obtain the organic-inorganic composite microspheres.
2. The method for preparing organic-inorganic composite microspheres according to claim 1, wherein in step S1, the silicon source is at least one selected from the group consisting of tetramethyl orthosilicate, tetraethyl orthosilicate, ethyl orthosilicate, and tetrabutyl orthosilicate.
3. The method for preparing organic-inorganic composite microspheres according to claim 1, wherein the thermal imidization and dehydration treatment is a high temperature treatment at 250 to 350 ℃ in step S2.
4. The method for preparing organic-inorganic composite microspheres according to claim 1, wherein in step S2, the first hydrolysate is a mixture of alcohol and water.
5. A preparation method of organic-inorganic composite microspheres is characterized by comprising the following steps:
s1, preparing a second precursor microsphere by adopting a polyamic acid solution;
s2, mixing the second precursor microsphere with TiOSO 4 Mixing, performing complex reaction, hydrolyzing in a second hydrolysate, performing thermal imidization and dehydration treatment, and obtaining the organic-inorganic composite microspheres.
6. The method for preparing organic-inorganic composite microspheres according to claim 5, wherein in step S2, the thermal imidization and dehydration treatment is a high temperature treatment at 250-350 ℃.
7. An organic-inorganic composite microsphere obtained by the method for producing an organic-inorganic composite microsphere according to any one of claims 1 to 4 or the method for producing an organic-inorganic composite microsphere according to any one of claims 5 to 6.
8. A battery separator comprising a polyolefin microporous base film and a modification layer provided on the surface of the polyolefin microporous base film, wherein the modification layer is made of a material comprising an adhesive and the organic-inorganic composite microspheres according to claim 7.
9. The method of making a battery separator of claim 8, comprising: mixing organic-inorganic composite microspheres, an adhesive and a solvent to prepare modified slurry; and then coating the modification slurry on the surface of the polyolefin microporous base membrane, and drying to obtain the battery diaphragm.
10. A battery comprising the battery separator according to claim 8 or the battery separator obtained by the method for producing the battery separator according to claim 9.
CN202210659884.6A 2022-06-13 2022-06-13 Organic-inorganic composite microsphere, battery diaphragm, preparation method of battery diaphragm and battery Pending CN114874465A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116854952A (en) * 2023-08-07 2023-10-10 深圳中兴新材技术股份有限公司 Polar polyolefin microsphere and preparation method and application thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116854952A (en) * 2023-08-07 2023-10-10 深圳中兴新材技术股份有限公司 Polar polyolefin microsphere and preparation method and application thereof
CN116854952B (en) * 2023-08-07 2024-05-07 深圳中兴新材技术股份有限公司 Polar polyolefin microsphere and preparation method and application thereof

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