CN115395174B - Composite diaphragm, secondary battery and electric equipment - Google Patents
Composite diaphragm, secondary battery and electric equipment Download PDFInfo
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- CN115395174B CN115395174B CN202211063955.2A CN202211063955A CN115395174B CN 115395174 B CN115395174 B CN 115395174B CN 202211063955 A CN202211063955 A CN 202211063955A CN 115395174 B CN115395174 B CN 115395174B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
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Abstract
The application discloses a composite diaphragm, a secondary battery and electric equipment. The composite diaphragm comprises a substrate and a coating arranged on at least one surface of the substrate; the coating comprises an NPS flame retardant, wherein the NPS flame retardant comprises N, P, S elements, and further comprises at least three of benzene rings, amino groups, nitrogen-containing heterocycle, phosphorus-oxygen double bonds and sulfur-oxygen double bonds. Compared with the traditional single-component phosphorus flame retardant and nitrogen flame retardant, the NPS flame retardant still has better flame retardant effect when the adding amount is lower, and meanwhile, the special functional group is introduced to ensure that the lithium battery diaphragm has better electrolyte wettability and ion conductivity, so that the performance of the diaphragm and the lithium ion battery is improved.
Description
Technical Field
The application belongs to the technical field of batteries, and particularly relates to a composite diaphragm, a secondary battery and electric equipment.
Background
As one of important components of a secondary battery, for example, a lithium ion battery, a separator has properties that directly affect the cycle performance, the internal resistance, the safety performance, and the like of the battery. The matrix material of the separator applied to the lithium ion battery at the present stage is mainly PE/PP material, when the battery is in thermal runaway, the internal temperature of the battery is up to 200-300 ℃, and the separator is molten at the moment, so that the separator is free of an isolation supporting layer to effectively block the risks of ignition, explosion and the like of the battery caused by contact of the anode and the cathode. It is therefore an urgent need to develop a separator material having high flame retardant properties.
Disclosure of Invention
The application provides a composite diaphragm, a secondary battery and electric equipment. Aims to solve the technical problems that the prior diaphragm has poor flame retardant effect and is easy to cause ignition or explosion of the battery when the battery is heated.
In a first aspect, the present application provides a composite separator.
The composite diaphragm provided by the application comprises a substrate and a coating arranged on at least one surface of the substrate;
the coating comprises an NPS flame retardant, wherein the NPS flame retardant comprises N, P, S elements; the NPS flame retardant comprises at least three of benzene ring, amino, nitrogen-containing heterocycle, phosphorus-oxygen double bond and sulfur-oxygen double bond.
Further, the nitrogen-containing heterocycle includes 1,3, 5-s-triazine, the phosphorus-oxygen double bond includes triphenyl phosphate, and the sulfur-oxygen double bond includes 2, 2-sulfur bis (5-aminobenzenesulfonic acid).
Further, in the infrared spectrum of the NPS flame retardant, 1150cm -1 ～1170cm -1 Has a peak of 1200cm -1 ～1250cm -1 Has a peak at 1400cm -1 ～1460cm -1 Has a peak at 1130cm -1 ～1150cm -1 Has a peak.
Further, the NPS flame retardant includes a structural formula shown in formula I:
further, the coating layer also comprises an inorganic ceramic material and an organic polymer;
the inorganic ceramic material comprises, by mass, 50-98 parts of an inorganic ceramic material, 1-30 parts of an organic polymer and 1-10 parts of an NPS flame retardant.
In the present application, the inorganic ceramic material may comprise boehmite, α -Al 2 O 3 、Si 3 N 4 、SiC、SiO 2 、TiO 2 、SnO 2 、ZrO 2 And Mg (OH) 2 One or more combinations of the above.
Further, the Mohs hardness of the inorganic ceramic material is more than 2, and the specific surface area of the inorganic ceramic material is 1-10 m 2 Per gram, the heat conductivity coefficient of the inorganic ceramic material is 0.01 to the whole90W/m·K。
Further, the organic polymer comprises an adhesive and/or a dispersing agent, wherein the adhesive comprises one or more of polyacrylate, polypropylene cyanide, polyphenyl and polyurethane; the dispersing agent comprises one or more of sodium carboxymethyl cellulose, polyacrylamide and sodium polyacrylate.
Further, the thickness of one side of the coating layer is 1-5 mu m.
Further, the substrate comprises a host material, a silane coupling agent and the NPS flame retardant; wherein the main material comprises at least one of polyolefin, polyimide and non-woven fabric, and the silane coupling agent comprises at least one of gamma-aminopropyl triethoxysilane, gamma- (2, 3-glycidoxy) propyl trimethoxysilane and vinyl triethoxysilane.
60-98 parts of main material, 1-10 parts of silane coupling agent and 1-30 parts of NPS flame retardant.
Further, the porosity of the base material is 10% -60%, the thickness is 2-30 mu m, the pore diameter is 20-100 nm, and the air permeability is less than 500s/100ml.
Further, the limiting oxygen index of the composite membrane is more than 40%.
In a second aspect, the present application provides a secondary battery.
The secondary battery lithium provided by the application comprises a positive electrode, a negative electrode, a diaphragm and electrolyte; the diaphragm is the composite diaphragm.
In a third aspect, the present application provides a powered device.
The electric equipment comprises the secondary battery, and the secondary battery is used as a power supply of the electric equipment.
Compared with the prior art, the application has the following beneficial effects:
when the NPS flame retardant is in thermal runaway, the phosphorus source in the flame retardant can form polyphosphoric acid, the polyphosphoric acid can generate dehydration reaction on the surface of the diaphragm to form a compact carbon layer structure, the thermal runaway caused by further contact of an anode and a cathode is isolated, and meanwhile, the nitrogen source burns to release ammonia gas to form a gas-phase flame retardant effect, so that an excellent flame retardant effect is shown. Meanwhile, the NPS flame retardant has benzene rings and amino functional groups, the amino functional groups are beneficial to improving the infiltration rate and infiltration effect of the composite diaphragm in the electrolyte, and the benzene rings are beneficial to improving the stability of the NPS flame retardant, so that the ionic conductivity and stability of the composite diaphragm in the electrolyte can be improved, and the electrochemical performance of the lithium ion battery can be further effectively improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:
FIG. 1 is a schematic structural view of a composite separator provided herein;
FIG. 2 is a synthetic route diagram of the NPS flame retardant provided herein;
FIG. 3 is an infrared spectrum of the NPS flame retardant prepared in example 1.
Detailed Description
The following further detailed description of the present application is provided in connection with the specific embodiments, and is not intended to limit the scope of the application. The examples provided below are intended as guidelines for further modifications by one of ordinary skill in the art and are not to be construed as limiting the application in any way.
The experimental methods in the following examples, unless otherwise specified, are conventional methods, and are carried out according to techniques or conditions described in the literature in the field or according to the product specifications. Materials, reagents and the like used in the examples described below are commercially available unless otherwise specified.
The application provides a composite separator.
The composite diaphragm comprises a substrate and a coating arranged on at least one surface of the substrate;
the coating comprises an NPS flame retardant, wherein the NPS flame retardant comprises N, P, S elements; the NPS flame retardant comprises at least three of benzene ring, amino, nitrogen-containing heterocycle, phosphorus-oxygen double bond and sulfur-oxygen double bond. In some embodiments, the nitrogen-containing heterocycle comprises 1,3, 5-s-triazine, the phosphorus-oxygen double bond comprises triphenyl phosphate, and the sulfur-oxygen double bond comprises 2, 2-sulfur bis (5-aminobenzenesulfonic acid).
Further, the NPS flame retardant includes a structural formula shown in formula I:
the NPS flame retardant contains P element, when the temperature is increased sharply due to abnormality in the battery, the phosphorus source in the NPS flame retardant can form polyphosphoric acid, dehydration reaction can be carried out on the surface of the diaphragm to form a compact carbon layer structure, and thermal runaway caused by further contact of the positive electrode and the negative electrode is isolated. Meanwhile, the flame retardant also contains N element, and the nitrogen source burns to release ammonia gas to form a gas-phase flame retardant effect, so that the flame retardant has excellent flame retardant effect. The NPS flame retardant also has benzene rings and amino functional groups, the amino functional groups are beneficial to improving the infiltration rate and infiltration effect of the diaphragm in the electrolyte, and the benzene rings are beneficial to improving the stability of the NPS flame retardant, so that the ion conductivity and stability of the diaphragm in the electrolyte can be improved, and the electrochemical performance of the lithium ion battery can be further effectively improved. The NPS flame retardant with the structural formula shown in the formula I is adopted, and the composite diaphragm has higher thermal stability due to the crosslinking action of the poly benzene ring, so that the swelling degree of the composite diaphragm in electrolyte is low, in addition, the composite diaphragm also has a poly amino functional group, the infiltration rate of the composite diaphragm in the electrolyte is further improved, and the ionic conductivity is further improved.
In some embodiments, referring to FIG. 3, the NPS flame retardant has an infrared spectrum of 1150cm -1 ～1170cm -1 Has a peak of 1200cm -1 ～1250cm -1 Has a peak at 1400cm -1 ～1460cm -1 Has a peak at 1130cm -1 ～1150cm -1 Has a peak. At 1150cm -1 ～1170cm -1 The peaks indicate that the NPS flame retardant has sulfate radical in the structure of 1200cm -1 ～1250cm -1 The peaks indicate that the NPS flame retardant has phosphate groups in the structure, and the structure is 1400cm -1 ～1460cm -1 The peak shows that the NPS flame retardant has triazine ring in the structure and is 1130cm in length -1 ～1150cm -1 The peaks indicate that the NPS flame retardant has benzene rings and amino groups in the structure.
In order to further improve the high temperature resistance, wear resistance, acid resistance and corrosion resistance of the coating, the coating also comprises an inorganic ceramic material.
In the present application, the inorganic ceramic material may comprise boehmite, α -Al 2 O 3 、Si 3 N 4 、SiC、SiO 2 、TiO 2 、SnO 2 、ZrO 2 And Mg (OH) 2 One or more combinations of the above. The inorganic ceramic material has excellent physical properties, can better promote the thermal stability of the composite diaphragm, and has wide sources and low cost.
Further, the Mohs hardness of the inorganic ceramic material is more than 2, and the specific surface area of the inorganic ceramic material is 1-10 m 2 And/g, wherein the heat conductivity coefficient of the inorganic ceramic material is 0.01-90W/m.K. The inorganic ceramic material with the specific surface area in the range can be better adhered to the surface of the base film, and meanwhile, the lithium ion transmission rate can be improved. The inorganic ceramic material with the heat conductivity coefficient can further improve the heat resistance of the composite diaphragm.
In order to improve the adhesive properties of the coating, as well as to improve the dispersibility, stability and uniformity of the slurry required for preparing the coating, the coating further comprises an organic polymer.
The organic polymer comprises an adhesive and/or a dispersing agent, and the adhesive comprises one or a combination of more of polyacrylate, polypropylene cyanide, polyphenyl polypropylene and polyurethane; the dispersing agent comprises one or more of sodium carboxymethyl cellulose, polyacrylamide and sodium polyacrylate.
In this embodiment, in order to balance the adhesion performance and dispersion performance of the coating, the mass ratio of the binder to the dispersant in the organic polymer may be 6: (0-2).
In another embodiment, the inorganic ceramic material is 50-98 parts by weight, the organic polymer is 1-30 parts by weight, and the NPS flame retardant is 1-10 parts by weight. For example, the inorganic ceramic material may be any one of 50 parts, 60 parts, 65 parts, 72 parts, 85 parts, 90 parts, 98 parts, or a range of values between any two of the values. The organic polymer may be any one of 1 part, 8 parts, 15 parts, 23 parts, 30 parts, or a range between any two. The NPS flame retardant may be any one of 1 part, 3 parts, 5 parts, 8 parts, 10 parts, or a range of values between any two. Within the above mass part range, the composite separator exhibits excellent flame retardant effect.
Further, the thickness of one side of the coating layer may be 1 to 5 μm. If the coating is too thin, the lithium ion transmission path can be reduced, the internal resistance of the battery is reduced, but the flame retardant effect is not ensured. If the coating diaphragm is arranged too thick, the lithium ion transmission path is increased, the battery polarization is increased, and the cost is increased. The thickness of the single side of the coating is set in the range, so that the excessive internal resistance of the battery can be avoided at the same time under the condition of ensuring the flame retardant effect, and the influence on the cycle performance of the battery is avoided.
In another embodiment, the substrate comprises a host material, a silane coupling agent, and an NPS flame retardant; wherein the main material comprises at least one of polyolefin, polyimide and non-woven fabric, and the silane coupling agent comprises at least one of gamma-aminopropyl triethoxysilane, gamma- (2, 3-glycidoxy) propyl trimethoxysilane and vinyl triethoxysilane. The NPS flame retardant is added into the main material to form the base material, so that the base material has flame retardant effect, and the silane coupling agent can improve the tensile property of the base material. The base material has flame retardant effect, so that the flame retardant property of the composite diaphragm can be further improved, and the safety performance of the battery is improved.
In some embodiments, the main material comprises 60-98 parts by weight, the silane coupling agent comprises 1-10 parts by weight, and the NPS flame retardant comprises 1-30 parts by weight. For example, the main material may be any one of 60 parts, 65 parts, 70 parts, 82 parts, 90 parts, 98 parts, or a range between any two of the values. The NPS flame retardant may be any one of 1 part, 8 parts, 15 parts, 23 parts, 30 parts, or a range between any two. The silane coupling agent may be any one of 1 part, 3 parts, 5 parts, 8 parts, 10 parts, or a range between any two of the values. Within the above mass part range, the composite separator exhibits a better and excellent flame retardant effect.
In another embodiment, the substrate has a porosity of 10% to 60%, a thickness of 2 to 30 μm, a pore size of 20 to 100nm, and a permeability of less than 500s/100ml. The base material with the characteristics can improve the liquid retention capacity of the composite diaphragm, improve the transmission rate of lithium ions and improve the cycle performance of the battery.
In another embodiment, the limiting oxygen index of the composite separator is > 40%. The limiting oxygen index refers to the volume fraction concentration of oxygen in a polymer in a mixture of oxygen and nitrogen as it just supports combustion, and is an index that characterizes the combustion behavior of the material. When the limiting oxygen index is more than 40%, the composite membrane is a non-inflammable substance, and has higher thermal stability compared with the existing PE/PP membrane.
The NPS flame retardant provided by the application can be prepared by the following preparation method: is prepared by the reaction of three monomers of triphenyl phosphate, melamine and 2, 2-thiobis (5-aminobenzene sulfonic acid) under certain conditions.
Further, the preparation method of the NPS flame retardant comprises the following steps:
s1: adding triphenyl phosphate into an acidic solvent for dissolution, and then adding a nitrifying agent for full reaction to obtain a solid product; reacting the solid product with stannous chloride dihydrate, absolute ethyl alcohol and concentrated hydrochloric acid, controlling the pH value of the solution by alkali liquor in the reaction process, carrying out suction filtration on the reaction system after the reaction is finished, and collecting filtrate, namely an S1 solution; wherein the acidic solvent may be concentrated sulfuric acid;
s2: dissolving melamine in acetone, then adding 2, 2-thiobis (5-aminobenzenesulfonic acid) for reaction to obtain a solid substance, and then dissolving the solid substance in an acetone solution, namely an S2 solution;
s3: and (3) dropwise adding the S2 solution into the S1 solution, magnetically stirring for reaction, and adjusting the pH value of the solution to 8-9 by using alkali liquor in the reaction process to obtain the final product NPS flame retardant.
In the step S1 of the method, the solvent is concentrated sulfuric acid with the mass fraction of 95-98%, the nitrating agent is mixed solution of concentrated sulfuric acid with the mass fraction of 95-98% and nitric acid, and the volume ratio of the two is 3:1, a step of; the mass fraction of the concentrated hydrochloric acid is 36-38%.
In the step S1 of the method, the dosage ratio of the triphenyl phosphate, the concentrated sulfuric acid and the nitrating agent is 1: (1-30): (1-20).
In the step S1 of the method, the ratio of the triphenyl phosphate, stannous chloride dihydrate, absolute ethyl alcohol and concentrated hydrochloric acid is 1: (1-3): (1-3): (1-2).
In the above method step S1, the reaction conditions of the reaction are: and reacting for 5-8 h at room temperature.
In the step S1 of the method, the pH value of the solution is controlled to be 8-9 by alkali liquor. The alkali liquor can be sodium hydroxide solution with the mass concentration of 5 percent.
In the above method step S2, the molar ratio of triphenyl phosphate, melamine and 2, 2-thiobis (5-aminobenzenesulfonic acid) is =6: 2:1, a step of;
in the above method step S2, the reaction conditions of the reaction are: reacting for 2-4 h at 45 ℃.
In the above method step S3, the S2 solution is slowly added dropwise to the S1 solution using a constant pressure funnel.
In the above method step S3, the reaction conditions of the reaction are: magnetically stirring the mixture at the temperature of 60 ℃ for reaction for 2 to 4 hours.
In the above method step S3, the base may be one or more of trimethylamine, triethylamine, sodium methoxide and sodium ethoxide.
The application also provides a preparation method of the composite diaphragm.
The preparation method of the composite diaphragm specifically comprises the following steps:
s1: preparing a base material: the main material, the NPS flame retardant and the silane coupling agent are mixed according to a certain mass ratio, and the base material is prepared through extrusion equipment. In some embodiments, the step of S1 may include: mixing a main material, an NPS flame retardant and a silane coupling agent according to a certain mass ratio, performing melt extrusion through an extruder, cooling and granulating an extrusion material to obtain modified master batch, adding the modified master batch into the extruder for secondary melt extrusion, and performing casting, annealing, stretching and heat treatment procedures to obtain a base material;
s2: preparing coating slurry: adding inorganic ceramic particles, an organic polymer, an NPS flame retardant and a solvent into a stirring tank according to a certain proportion, and fully stirring to obtain coating slurry; the organic polymer comprises an adhesive and/or a dispersing agent;
s3: preparing a flame-retardant modified diaphragm: and (3) coating the coating slurry in the step (S2) on at least one surface of the substrate, and drying to obtain the composite diaphragm.
In the step S2, the solvent is deionized water; the viscosity of the coating slurry is less than or equal to 600 mPa.s.
In the step S3, the coating method includes a micro gravure coating method; the drying conditions are as follows: baking in a baking oven at 60-70 ℃ for 5-30 s.
The present application also provides a secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte; the diaphragm is the composite diaphragm.
The application also provides electric equipment, which comprises the secondary battery.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
Example 1:
(1) Preparation of NPS flame retardant of formula I:
the structural formula of the NPS flame retardant is shown as follows:
s1: 1.956g (0.006 mol) triphenyl phosphate is added into a 500mL four-necked flask, and is added into 50mL of concentrated sulfuric acid solvent with mass concentration of 96% to be fully stirred for 2 hours, 5mL of nitrating agent is added after dissolution to react for 2 hours at normal temperature, ice water is slowly added to be stirred after full reaction, and a solid product is obtained through suction filtration, washing and drying; then reacting the solid product with 2g stannous chloride dihydrate, 10mL absolute ethyl alcohol and 10mL concentrated hydrochloric acid for 6 hours at normal temperature, titrating and controlling the pH value of a reaction solution to 8-9 by using a 5% concentration NaOH solution, carrying out suction filtration on the reacted solution, and recording the reserved solution as an S1 solution for later use;
s2: adding 0.252g (0.002 mol) melamine into a four-necked flask, adding 50mL of acetone solution, stirring for 2 hours at normal temperature, then adding 0.376g (0.001 mol) of 2, 2-thiobis (5-aminobenzenesulfonic acid), controlling the reaction temperature to be 45 ℃ for 3 hours, finally carrying out suction filtration, washing with acetone, filtering and drying to obtain a solid substance, and then dissolving the solid substance into 50mL of acetone solution for later use;
s3: slowly dripping the S2 solution into the S1 by using a constant pressure funnel, magnetically stirring and reacting for 3 hours at 60 ℃, adjusting the pH value of the solution to 8-9 by using triethylamine in the reaction process, and finally performing rotary evaporation, alkali washing and drying on the solution to obtain the NPS flame retardant with the final product of the structural formula. The infrared spectrum is shown in figure 3.
(2) Preparation of a composite diaphragm:
s1: preparing a base material: the weight average molecular weight is 100 ten thousand and the true density is 0.96g/m 3 Adding 90 parts by mass of the Polyethylene (PE), 9 parts by mass of the NPS flame retardant (9 parts by mass) prepared in the step (1) and 1 part by mass of the silane coupling agent (gamma-aminopropyl triethoxysilane) into an extruder, carrying out melt extrusion at a certain temperature, cooling and granulating an extruded material to obtain modified master batches, adding the modified master batches into the extruder for secondary melt extrusion, and then carrying out processes such as casting, annealing, stretching, heat treatment and the like to obtain the substrate with the porosity of 38%, the pore diameter of 20-100 nm and the thickness of 12 mu m.
S2: preparing coating slurry: the heat conductivity coefficient is 0.05W/m.K, the specific surface area is 5m 2 Inorganic ceramic particle boehmite (80 parts by mass), organicAdding 14 parts by mass of a polymer (comprising 2 parts by mass of dispersant sodium carboxymethyl cellulose and 12 parts by mass of adhesive polyacrylate), 6 parts by mass of the NPS flame retardant prepared in the step (1) and 100 parts by mass of a solvent (deionized water) into a stirring tank, and fully stirring to obtain a coating slurry;
s3: preparing a composite diaphragm: coating the coating slurry in the step S2 on two surfaces of a substrate in a micro-gravure mode, and baking the substrate in an oven at 60-70 ℃ for 30S to obtain the composite diaphragm with the double-sided coating, wherein the thickness of the coating on one side of the substrate is 3 mu m.
(3) Preparation of a lithium ion battery:
adding lithium iron phosphate, a conductive agent (conductive carbon black) and an adhesive PVDF dry powder into an NMP solvent according to the mass ratio of 97:1:2, fully stirring to form positive electrode slurry with solid content of 58% and viscosity of 6000-8000 mPa.s, coating the positive electrode slurry on an aluminum foil, drying, rolling and cutting for later use to obtain a positive electrode plate; adding graphite, conductive carbon black, a thickening agent CMC and a binder SBR into deionized water solvent according to the mass ratio of 96:1:1:2, fully stirring to form negative electrode slurry with the solid content of 53% and the viscosity of 2000-4000 mPa.s, and then coating the negative electrode slurry on copper foil, drying, rolling and cutting for later use to obtain a negative electrode plate; and then winding the positive electrode plate, the composite diaphragm and the negative electrode plate into a battery core, wherein the flame-retardant modified diaphragm is positioned between the adjacent positive electrode plate and the adjacent negative electrode plate, putting the battery core into an aluminum plastic film package, injecting electrolyte into the battery core for packaging, forming, capacity division and self-discharge testing procedures, and preparing the lithium ion battery with the capacity of 2.0Ah for rate performance testing.
Examples 2 to 6 are the same as example 1 except that the mass parts of the inorganic ceramic particles, the organic polymer and the NPS flame retardant are adjusted during the preparation of the coating paste to obtain coating pastes having different content ratios of the inorganic ceramic particles, the organic polymer and the NPS flame retardant.
Examples 7 to 11 are the same as example 1 except that the mass parts of the host material, the NPS flame retardant and the silane coupling agent were adjusted during the preparation of the substrate to obtain substrates having different content ratios of the host material, the NPS flame retardant and the silane coupling agent.
Examples 12 to 16, which are similar to example 1, except that inorganic ceramic particles having different thermal conductivities were used in the preparation of the coating paste, specifically, silica having a thermal conductivity of 1.4W/mK, zirconia having a thermal conductivity of 2.09W/mK, silicon nitride having a thermal conductivity of 12.6W/mK, and α -Al having a thermal conductivity of 20W/mK were used, respectively 2 O 3 83.6W/mK silicon carbide.
Examples 17 to 20 are the same as example 1 except that the coating thickness of the coating layer is adjusted during the preparation of the composite separator.
Examples 21 to 25 were identical to example 1, except that the stretching parameters were adjusted during the substrate preparation to obtain substrates of different thicknesses.
Examples 26 to 28 are the same as example 1, except that the stretching and heat treatment parameters are adjusted during the substrate preparation process to obtain substrates of different porosities.
Comparative example 1 was identical to example 1, except that no NPS flame retardant was contained in the coating, nor was other flame retardants contained.
Example 2 the same as example 1, except that a conventional flame retardant, which is a melamine polyphosphate flame retardant, purchased from synfat Anhui New Material technology Co., ltd, was used in the coating.
Comparative example 3 was identical to example 1, except that neither the coating nor the substrate contained NPS flame retardant nor other flame retardants.
The corresponding parameters of the composite separator prepared above are recorded in table 1.
TABLE 1
The resulting composite separators and the resulting lithium ion batteries prepared in examples 1 to 28 and comparative examples 1 to 3 above were subjected to performance tests, and the test results were recorded in table 2, with the following test methods:
1) Test method of limiting oxygen index: limiting oxygen index test the test was performed using astm d2863 standard.
2) The preparation method of the ventilation value of the composite diaphragm comprises the following steps: the test was performed using a Gurley tester.
3) The testing method of the impedance of the composite diaphragm comprises the following steps: the impedance of the diaphragm was obtained using electrochemical workstation testing.
4) The method for testing the ionic conductivity of the composite diaphragm comprises the following steps: the ion conductivity was obtained by the following calculation formula, i.e. separator ion conductivity = separator thickness/(separator impedance x effective area x 10).
5) The method for testing the direct current internal resistance of the battery comprises the following steps: discharging the lithium ion battery for 10s at 5C under the 50% SOC state, and calculating the internal resistance of the lithium ion battery during discharging, wherein the calculation formula is as follows: r=u/I, U is the voltage difference before and after discharge, I is the discharge current.
6) The testing method of the battery multiplying power performance comprises the following steps: based on the charge and discharge capacity of the lithium ion battery at 1C, the percentage of the charge and discharge capacity of 2C and the discharge capacity of 4C to the charge and discharge capacity of 1C is calculated.
TABLE 2
From the test results of examples 1 to 28 and comparative examples 1 to 3, it can be seen that the use of the NPS flame retardant of the present application in the coating layer and the substrate of the separator can significantly improve the limiting oxygen content of the separator, while also significantly improving the ionic conductivity and the internal resistance of the battery. Compared with the diaphragm prepared by the conventional flame retardant, the composite diaphragm provided by the application has a more obvious flame retardant effect.
The foregoing is merely a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and variations may be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims (12)
1. A composite diaphragm is characterized by comprising a base material and a coating layer arranged on at least one surface of the base material;
the coating comprises an NPS flame retardant, wherein the NPS flame retardant comprises N, P, S elements;
the NPS flame retardant comprises a structural formula shown in a formula I:
(formula I)
The thickness of one side of the coating is 1-5 mu m.
2. The composite membrane of claim 1 wherein 1150cm in the infrared spectrum of NPS flame retardant -1 ~1170cm -1 Has a peak of 1200cm -1 ~1250 cm -1 Has a peak at 1400cm -1 ~1460 cm -1 Has a peak at 1130cm -1 ~1150 cm -1 Has a peak.
3. The composite separator of claim 1, wherein the coating further comprises an inorganic ceramic material and an organic polymer;
the inorganic ceramic material comprises, by mass, 50-98 parts of an inorganic ceramic material, 1-30 parts of an organic polymer and 1-10 parts of an NPS flame retardant.
4. A composite separator as claimed in claim 3, wherein said inorganic ceramic material comprises bomStone, alpha-Al 2 O 3 、Si 3 N 4 、SiC、SiO 2 、TiO 2 、SnO 2 、ZrO 2 And Mg (OH) 2 One or more combinations of the above.
5. The composite membrane of claim 4 wherein the inorganic ceramic materials each have a mohs hardness of greater than 2 and a specific surface area of from 1 to 10m 2 And/g, wherein the heat conductivity coefficient of the inorganic ceramic material is 0.01-90W/m.K.
6. A composite separator according to claim 3, wherein the organic polymer comprises a binder and/or a dispersant, the binder comprising one or more combinations of polyacrylates, polyacrylcyanides, polyphenylprops, polyurethanes; the dispersing agent comprises one or more of sodium carboxymethyl cellulose, polyacrylamide and sodium polyacrylate.
7. The composite separator of claim 1, wherein the substrate comprises a host material, a silane coupling agent, and the NPS flame retardant; wherein the main material comprises at least one of polyolefin, polyimide and non-woven fabric, and the silane coupling agent comprises at least one of gamma-aminopropyl triethoxysilane, gamma- (2, 3-glycidoxy) propyl trimethoxysilane and vinyl triethoxysilane.
8. The composite membrane of claim 7, wherein the main material comprises 60-98 parts by weight, the silane coupling agent comprises 1-10 parts by weight, and the NPS flame retardant comprises 1-30 parts by weight.
9. The composite membrane of claim 8 wherein the substrate has a porosity of 10% to 40%, a thickness of 2 to 30 μm, a pore size of 20 to 100nm, and a permeability of less than 500s/100ml.
10. The composite membrane of any one of claims 1-9, wherein the composite membrane has a limiting oxygen index of > 40%.
11. A secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and the composite separator according to any one of claims 1 to 10.
12. An electric device, characterized in that the electric device comprises the secondary battery as claimed in claim 11 as a power supply source of the electric device.
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