CN109970981B - Solid flame-retardant polymer, electrode plate, diaphragm and lithium secondary battery - Google Patents

Solid flame-retardant polymer, electrode plate, diaphragm and lithium secondary battery Download PDF

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CN109970981B
CN109970981B CN201711444931.0A CN201711444931A CN109970981B CN 109970981 B CN109970981 B CN 109970981B CN 201711444931 A CN201711444931 A CN 201711444931A CN 109970981 B CN109970981 B CN 109970981B
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halogenated
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alkenylene
lithium secondary
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CN109970981A (en
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马强
李阳兴
秦德君
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Huawei Technologies Co Ltd
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    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F130/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal
    • C08F130/02—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal containing phosphorus
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
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    • 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
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    • 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
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Abstract

The embodiment of the invention provides a solid flame-retardant polymer, which comprises a repeating unit containing a cyclotriphosphazene structure, is formed by graft polymerization of a monomer containing the cyclotriphosphazene structure through chemical bonds, and has a general formula shown as a formula (I) or a formula (II),
Figure DDA0001527313370000011
x is selected from the group consisting of alkylene, haloalkylene, alkyleneoxy, haloalkyleneoxy, alkenylene, haloalkenylene, alkenylene-oxy, haloalkenylene-oxy, arylene, haloarylene, aryloxylene, haloaryloxylene, substituted phospholene, substituted imide, or substituted sulfonylimide; y is selected from the group consisting of oxygen, sulfur, alkylene, haloalkylene, alkyleneoxy, haloalkyleneoxy, alkenylene, haloalkenylene, alkenylene-oxy, haloalkenylene-oxy, arylene, haloarylene, aryloxylene, haloaryloxylene, substituted phosphoethylene, substituted imide, and substituted sulfonylimide. The invention also provides an electrode plate of the lithium secondary battery, a diaphragm and the lithium secondary battery.

Description

Solid flame-retardant polymer, electrode plate, diaphragm and lithium secondary battery
Technical Field
The invention relates to the technical field of lithium secondary batteries, in particular to a solid flame-retardant polymer, an electrode plate, a diaphragm and a lithium secondary battery.
Background
The lithium secondary battery has been widely applied to portable electronic products (smart phones, digital cameras, notebook computers and the like) due to the advantages of high energy density, high working voltage, long service life, low self-discharge rate, environmental friendliness and the like, and has higher requirements on the energy density of the battery along with the rapid development of new energy industries such as electric vehicles, large-scale energy storage power grids and the like, wherein the development of high-specific-capacity positive and negative electrode materials and high-voltage positive electrode materials is a main technical means for improving the energy density of the lithium secondary battery at present. Focusing on the use of high specific capacity and high voltage materials, however, the safety problem of the liquid lithium secondary battery is bound to be brought about. The electrolyte of the lithium secondary battery is mainly non-aqueous organic electrolyte (carbonate electrolyte is generally used), and when the battery is in an abuse state (thermal shock, overcharge, acupuncture, external short circuit and the like), the electrolyte has hidden dangers of easy volatilization, easy combustion and the like, so that the safety problem caused by thermal runaway of the battery is easily caused.
At present, a commonly used method for improving the safety of a liquid lithium secondary battery is to directly add a flame retardant additive into a conventional electrolyte, although the flame retardant can improve the flame resistance of the electrolyte, the flame retardant can reduce the conductivity of the electrolyte and increase the viscosity of the electrolyte, and meanwhile, the flame retardant can generate side reactions in the battery circulation process, thereby causing certain negative effects on the electrochemical performance of the battery. Therefore, in order to solve the safety problem of the liquid lithium secondary battery and the negative effect caused by the direct addition of the flame retardant into the electrolyte, there is a real need to develop a novel flame retardant which can not only avoid the use in the electrolyte but also improve the safety of the lithium secondary battery, and at the same time, has good compatibility with the anode and cathode materials and does not affect the cycle performance of the lithium secondary battery.
Disclosure of Invention
In view of this, a first aspect of embodiments of the present invention provides a solid flame retardant polymer, which has excellent flame retardant properties, is insoluble in an electrolyte of a lithium secondary battery, has good compatibility with positive and negative electrode materials, can be directly doped into positive and negative electrodes or a separator, and does not affect the cycle performance of the battery while improving the safety of the battery, so as to solve the problem that in the prior art, the viscosity of the electrolyte is increased and the impedance is increased due to the direct addition of a flame retardant additive into the electrolyte, and the electrochemical performance of the lithium secondary battery is ultimately affected.
Specifically, the embodiment of the invention provides a solid flame-retardant polymer, which comprises a repeating unit containing a cyclotriphosphazene structure, and is formed by polymerizing a monomer containing the cyclotriphosphazene structure through chemical bond grafting, wherein the general formula of the solid flame-retardant polymer is shown as a formula (I) or a formula (II),
Figure GDA0003211266470000021
in the formula (I), X is selected from any one of alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkenylene oxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxy, halogenated arylene oxide, substituted phosphodiester group, substituted imide group and substituted sulfonylimide group; the R is1、R2、R3、R4Respectively selected from any one of fluorine, chlorine, bromine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy;
in the formula (II), Y is selected from any one of oxygen, sulfur, alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkyleneoxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxylene, halogenated aryloxylene, substituted phospholene, substituted imide and substituted sulfonylimide; the R is1’、R2’、R3’、R4’、R5' are respectively selected from any one of fluorine, chlorine, bromine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy.
In the first aspect of the present invention, in the X and the Y, the number of carbon atoms of the alkylene group, the halogenated alkylene group, the alkyleneoxy group, and the halogenated alkyleneoxy group is 1 to 20; the carbon atoms of the alkenylene, the halogenated alkenylene, the alkenylene oxide and the halogenated alkenylene oxide are 2-20; the carbon atoms of the arylene, the halogenated arylene, the aryloxy ene and the halogenated aryloxy ene are 6-20; the carbon atom number of the substituted group in the substituted phosphodiester group, the substituted imide group and the substituted sulfonyl imide group is 1-20.
In the first aspect of the present invention, in the X and the Y, the halogen in the haloalkylene group, haloalkyleneoxy group, haloalkenylene group, haloalkyleneoxy group, haloarylene group, and haloaryloxylene group includes fluorine, chlorine, bromine, and iodine, and the halogen is a perhalogenated or partially halogenated group.
In the first aspect of the invention, R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In the item' above, the alkyl group, haloalkyl group, alkoxy group, haloalkoxy group have 1 to 20 carbon atoms; the carbon atom number of the alkenyl, the halogenated alkenyl, the alkenyloxy and the halogenated alkenyloxy is 2-20; the number of carbon atoms of the aryl, halogenated aryl, aryloxy and halogenated aryloxy is 6-20.
In the first aspect of the invention, R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In the' above, the halogen in the haloalkyl group, haloalkoxy group, haloalkenyl group, haloalkenyloxy group, haloaryl group or haloaryloxy group includes fluorine, chlorine, bromine or iodine, and the halogen is a perhalogenated or partially halogenated group.
In the first aspect of the present invention, in the formula (I), n is 2 to 1000.
In the first aspect of the present invention, in the formula (II), n is 2 to 1000.
In the first aspect of the present invention, said X and said Y are each selected from the group consisting of-CH2- (methylene), -CH2CH2- (ethylene), -CH2CH2CH2- (propylene), -C (CH)3)2- (isopropylidene), -CH2CH2CH2CH2- (butylene), -CH2CH2CH- (1-butenyl) and-CF2CF2CF2CF2- (perfluoro-substituted butylene) alkyl-, -OCH2CF2- (difluoro-substituted ethyleneoxy), methylphenylene, vinylphenylene, fluorophenylene, or-OP ═ O (OCH)3) O- (methylphosphonite group), -OP ═ O (OCH)2CF3) O- (trifluoroethyl phosphoric acid)Vinylene group), -NHC (═ O) CH2- (acetimidoyl) and-NHS (═ O)2CF2Any one of (difluoromethylenesulfonylimino).
The solid flame-retardant polymer provided by the first aspect of the embodiment of the invention is formed by polymerizing a monomer containing a cyclotriphosphazene structure through chemical bond grafting, has excellent flame-retardant performance, is insoluble in an electrolyte of a lithium secondary battery, has good compatibility with positive and negative electrode materials, can be directly doped into positive and negative electrode slurry to prepare positive and negative electrode plates, or is combined to the surface of a diaphragm through a binder, and is finally applied to the lithium secondary battery, so that the safety of the battery is improved, and the cycle performance of the battery is not influenced.
In a second aspect of the embodiments of the present invention, there is provided an electrode sheet for a lithium secondary battery, including a current collector, and an electrode active material layer disposed on the current collector, the electrode active material layer including the solid flame retardant polymer according to the first aspect of the present invention.
In the second aspect of the present invention, the solid flame retardant polymer accounts for 0.1% to 20% of the total mass of the electrode active material layer.
In the second aspect of the present invention, the solid flame retardant polymer is uniformly dispersed in the electrode active material layer.
In the second aspect of the present invention, the electrode sheet of the lithium secondary battery includes a positive electrode sheet of the lithium secondary battery or a negative electrode sheet of the lithium secondary battery.
The third aspect of the embodiments of the present invention provides a diaphragm, where the diaphragm includes a diaphragm body and flame retardant layers disposed on one or both sides of the diaphragm body, and the material of the flame retardant layers includes the solid flame retardant polymer according to the first aspect of the present invention and a binder.
In the third aspect of the present invention, in the flame-retardant layer, the mass ratio of the solid flame-retardant polymer to the binder is 1 to 100: 1.
In the third aspect of the present invention, the thickness of the flame retardant layer is 0.1 μm to 10 μm.
In a third aspect of the present invention, the binder includes one or more of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), Polyacrylonitrile (PAN), Polyimide (PI), polyethylene glycol (PEG), polyethylene oxide (PEO), Polydopamine (PDA), sodium carboxymethylcellulose/styrene butadiene rubber (CMC/SBR), polyvinyl alcohol (PVA), polyacrylic acid (PAA), lithium polyacrylate (lipa), polyvinylpyrrolidone (PVP), polylactic acid (PLA), Sodium Alginate (SA), poly (styrene sulfonic acid) (PSS), poly (styrene sulfonic acid) (LiPSS), and gelatin.
A fourth aspect of the embodiments of the present invention provides a lithium secondary battery including the electrode tab of the lithium secondary battery according to the second aspect of the present invention and/or the separator according to the third aspect of the present invention.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the background art of the present invention, the drawings required to be used in the embodiments or the background art of the present invention will be described below.
FIG. 1 is a front 100-cycle curve of a lithium secondary battery prepared in example 1 of the present invention;
FIG. 2 is a front 100-cycle curve of a lithium secondary battery prepared in example 9 of the present invention;
fig. 3 is a front 100-cycle curve of the lithium secondary battery prepared in comparative example 1;
fig. 4 is a cycle curve of the first 100 cycles of the lithium secondary battery prepared in comparative example 2.
Detailed Description
The embodiments of the present invention will be described below with reference to the drawings.
With the continuous development of high specific capacity and high voltage materials, the safety problem of the liquid lithium secondary battery is increasingly highlighted. The core components of the lithium secondary battery are mainly a positive electrode, a negative electrode, electrolyte and a diaphragm, wherein the electrolyte is a medium for transmitting lithium ions between the positive electrode and the negative electrode and plays an important role in the electrochemical performance and safety performance of the battery. The electrolyte mainly comprises conductive lithium salt, a non-aqueous organic solvent (conventionally a carbonate solvent) and an additive. At present, commercial electrolyte is mainly carbonate electrolyte, and when a battery is in an abuse state (thermal shock, overcharge, external short circuit and the like), the electrolyte has hidden dangers of easy volatilization, easy combustion and the like, so that the safety problem caused by thermal runaway of the battery is easily caused. Currently, most of the technologies mainly add flame retardant additives directly to the conventional electrolyte to improve the flame resistance of the electrolyte, but since the addition of the flame retardant additives can reduce the conductivity of the electrolyte and increase the viscosity of the electrolyte, the electrochemical performance of the battery will be negatively affected. Therefore, it is imperative to develop a novel flame retardant additive that can improve the safety of lithium secondary batteries while not affecting the electrochemical performance of lithium secondary batteries. In view of this, the embodiment of the present invention provides a solid flame retardant polymer, which has excellent flame retardant properties, is insoluble in an electrolyte of a lithium secondary battery, has good compatibility with positive and negative electrode materials, can be directly doped into positive and negative electrodes or a separator, and does not affect the cycle performance of the battery while improving the safety of the battery.
Specifically, the embodiment of the invention provides a solid flame-retardant polymer for a lithium secondary battery, the solid flame-retardant polymer comprises a repeating unit containing a cyclotriphosphazene structure, the repeating unit is formed by polymerizing a monomer containing the cyclotriphosphazene structure through chemical bond grafting, the general formula of the solid flame-retardant polymer is shown as a formula (I) or a formula (II),
Figure GDA0003211266470000041
in the formula (I), X is selected from any one of alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkenylene oxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxy, halogenated arylene oxide, substituted phosphodiester group, substituted imide group and substituted sulfonylimide group; the R is1、R2、R3、R4Respectively selected from any one of fluorine, chlorine, bromine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy;
in the formula (II), Y is selected from oxygen,Any one of sulfur, alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkenylene oxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxy, halogenated aryloxy, substituted phospholene group, substituted imide group and substituted sulfonylimide group; the R is1’、R2’、R3’、R4’、R5' are respectively selected from any one of fluorine, chlorine, bromine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy.
The solid flame-retardant polymer provided by the embodiment of the invention has excellent flame-retardant property, is insoluble in electrolyte of a lithium secondary battery, has good compatibility with anode and cathode materials, can be directly doped into an anode, a cathode or a diaphragm, improves the safety of the battery, and does not influence the cycle performance of the battery. Specifically, because the cyclotriphosphazene structure contains P, N and other elements, under the condition of thermal runaway of the battery, P-series free radicals are generated and decomposed to capture H or OH free radicals generated by thermal decomposition of the electrolyte, and chain reaction is cut off; in addition, NH produced by decomposition3When gas substances dilute free radicals and oxygen generated by the thermal decomposition of the electrolyte, the concentration of combustion substances is reduced, so that the combustion of the electrolyte can be inhibited, the safety of the battery is improved, and the cyclotriphosphazene structure has good compatibility with positive and negative electrode materials; the flame retardant polymer is a solid polymer, is insoluble in the electrolyte of the lithium secondary battery, can be mixed with positive and negative electrode materials to prepare positive and negative electrode plates by stirring, or is coated on the surface of the diaphragm by a binder, so that the negative influence on the performance of the lithium secondary battery caused by directly adding a flame retardant into the electrolyte is avoided; therefore, the lithium secondary battery using the solid flame-retardant polymer composition can not only improve the safety of the battery, but also reduce negative factors affecting the performance of the battery.
In the embodiment of the invention, the polymer of the general formula (I) is formed by graft polymerization of a cyclotriphosphazene structure serving as a matrix through chemical bonds; the polymer of the general formula (II) is formed by graft polymerization of a cyclotriphosphazene structure serving as a branched chain through chemical bonds. The solid flame-retardant polymer provided by the embodiment of the invention has better stability and flame retardance than other small-molecule phosphazene flame retardants, and can obviously improve the safety performance of the lithium secondary battery.
In the embodiment of the present invention, in the general formula (I) and the general formula (II), in the X and the Y, the number of carbon atoms of the alkylene group, the halogenated alkylene group, the alkyleneoxy group, and the halogenated alkyleneoxy group is 1 to 20, and further 1 to 8; the carbon atom number of the alkenylene, the halogenated alkenylene, the alkenylene oxide and the halogenated alkenylene oxide is 2-20, and further, the carbon atom number is 2-8; the arylene group, the halogenated arylene group, the aryloxy group, and the halogenated aryloxy group have 6 to 20 carbon atoms, and further have 6 to 10 carbon atoms; the number of carbon atoms of the substituent group in the substituted phosphodiester group, the substituted imide group and the substituted sulfonylimide group is 1 to 20, and further, the number of carbon atoms is 1 to 8 or 6 to 14.
In an embodiment of the present invention, in the X and Y, the halogen in the haloalkylene group, haloalkyleneoxy group, haloalkenylene group, haloalkenyleneoxy group, haloarylene group, and haloalkryleneoxy group includes fluorine, chlorine, bromine, and iodine, and the halogen is a perhalogenated or partially halogenated group.
In an embodiment of the present invention, the substituted imide group may be represented by-NH-C (═ O) -Z1-, wherein the substituent group Z1Has 1 to 20 carbon atoms, further has 1 to 8 or 6 to 14 carbon atoms, and specifically Z1Can be selected from any one of alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkenylene oxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxy and halogenated aryloxy; the substituted sulfonylimino group may be represented by-NH-S (═ O)2-Z2-, wherein the substituent group Z2Has 1 to 20 carbon atoms, further has 1 to 8 or 6 to 14 carbon atoms, and specifically Z2The alkylene group may be any one selected from the group consisting of an alkylene group, a halogenated alkylene group, an alkyleneoxy group, a halogenated alkyleneoxy group, an alkenylene group, a halogenated alkenylene group, an arylene group, a halogenated arylene group, an aryloxy group, and a halogenated aryloxy group. The substituted imide group and the substituted sulfonyl groupThe halogen in the imino group can be fluorine, chlorine, bromine or iodine, and the halogen can be perhalogenated or partially halogenated. The alkylene group, the haloalkylene group, the alkyleneoxy group, the haloalkyleneoxy group, the alkenylene group, the haloalkenylene group, the alkenylene oxy group, and the haloalkenylene oxy group may be linear or branched.
In a particular embodiment of the invention, said X and said Y are each selected from-CH2- (methylene), -CH2CH2- (ethylene), -CH2CH2CH2- (propylene), -C (CH)3)2- (isopropylidene), -CH2CH2CH2CH2- (butylene), -CH2CH2CH- (1-butenyl) and-CF2CF2CF2CF2- (perfluoro-substituted butylene) alkyl-, -OCH2CF2- (difluoro-substituted ethyleneoxy), methylphenylene, vinylphenylene, fluorophenylene, or-OP ═ O (OCH)3) O- (methylphosphonite group), -OP ═ O (OCH)2CF3) O- (trifluoroethylidene phosphate), -NHC (═ O) CH2- (acetimidoyl) and-NHS (═ O)2CF2Any one of (difluoromethylenesulfonylimino).
In an embodiment of the invention, R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In the item (1), the alkyl group, the haloalkyl group, the alkoxy group, or the haloalkoxy group has 1 to 20 carbon atoms, and further has 1 to 8 carbon atoms; the number of carbon atoms of the alkenyl group, the haloalkenyl group, the alkenyloxy group and the haloalkenyloxy group is 2 to 20, and further the number of carbon atoms is 2 to 8; the aryl group, the halogenated aryl group, the aryloxy group, and the halogenated aryloxy group have 6 to 20 carbon atoms, and further have 6 to 10 carbon atoms.
In an embodiment of the invention, R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In' the halogen or halogen-containing group hasIs beneficial to enhancing the flame retardant property of the solid flame retardant polymer. Wherein, the halogen in the halogenated alkyl, halogenated alkoxy, halogenated alkenyl, halogenated alkenyloxy, halogenated aryl and halogenated aryloxy comprises fluorine, chlorine, bromine and iodine, and the halogen is perhalogenated or partially halogenated.
In a specific embodiment of the invention, R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5' may be selected from-OCH3(methoxy), -OCH2CH3(ethoxy), -OCH2CH2CH3(propoxy), -OCH (CH)3)2(isopropoxy), -OCH2CH2CH2CH3(butoxy), -OCH2CH2CH＝CH2(1-butenyloxy), -OCF2CF2CF2CF3(perfluoro-substituted butoxy), -OCH2CF3(trifluoro-substituted ethoxy), methylphenoxy, vinylphenoxy, fluorophenoxy.
In an embodiment of the present invention, in the formula (I), R is1、R2、R3And R4May be the same or different groups. In the formula (II), the R1’、R2’、R3’、R4' and R5' may also be the same or different groups.
In the embodiment of the invention, the polymerization degree of the solid flame-retardant polymer can be set according to actual needs, and the proper polymerization degree can ensure that the polymer has higher stability, is not easy to dissolve in electrolyte and is easy to prepare. In the formula (I), n may be 2 to 1000, and further may be 5 to 1000, 20 to 200 or 10 to 100. The molecular weight range of the solid flame-retardant polymer can be 1000-1000000, and further can be 5000-50000 or 2000-30000.
In the embodiment of the present invention, in the formula (II), n may be 2 to 1000, further 5 to 1000, and 20 to 300. The molecular weight of the solid flame-retardant polymer can be 1000-1000000, and further can be 5000-100000.
In an embodiment of the present invention, the solid flame retardant polymer may be a chain or ring polymer.
Further, in a specific embodiment of the present invention, the molecular structural formula of the solid flame retardant polymer may be represented by formulas (a) to (C):
Figure GDA0003211266470000061
the solid flame-retardant polymer provided by the embodiment of the invention has excellent flame-retardant property, is insoluble in lithium secondary battery electrolyte, has good compatibility with positive and negative electrode materials, is prepared into positive and negative electrode plates by mixing with positive and negative electrode materials in a stirring way, or is coated on the surface of a diaphragm through a binder, so that not only can the safety of the battery be improved, but also the negative influence on the performance of the lithium secondary battery caused by directly adding a flame retardant into the electrolyte can be avoided.
The solid flame-retardant polymer shown in the formula (I) provided by the embodiment of the invention can be prepared by adopting the following synthesis steps:
respectively adding cyclotriphosphazene compound and solvent into a three-neck flask, slowly adding glycol (phenol) sodium compound into the three-neck flask at the temperature of-20 ℃, stirring and reacting for 6-48 hours at the temperature of 25-60 ℃, filtering, and drying under reduced pressure to obtain the solid flame-retardant polymer represented by the general formula (I).
Wherein the cyclotriphosphazene compound depends on the molecular structure of the solid flame retardant polymer to be prepared, and includes but is not limited to hexachlorocyclotriphosphazene, hexafluorocyclotriphosphazene, ethoxy (pentafluoro) cyclotriphosphazene, phenoxy (pentafluoro) cyclotriphosphazene, and the like. The solvent includes, but is not limited to, one or more of ethane, cyclohexane, dichloromethane, trichloromethane, diethyl ether, petroleum ether, benzene, toluene, chlorobenzene, fluorobenzene, acetone, acetonitrile, methanol, ethanol, tetrahydrofuran, nitromethane, dimethyl sulfoxide, N-dimethylformamide, ethyl acetate, and butyl acetate. Examples of the sodium (phenoxide) diol compounds include, but are not limited to, sodium ethylene glycol, sodium p-phenylene-diphenol, and the like.
The solid flame-retardant polymer shown in the formula (II) provided by the embodiment of the invention can be prepared by adopting the following synthesis steps:
respectively adding cyclotriphosphazene compound and solvent into a three-neck flask, slowly adding alkene alcohol (phenol) sodium compound into the three-neck flask at the temperature of-20 ℃, stirring and reacting for 6-48 hours at the temperature of 25-60 ℃, filtering, and drying under reduced pressure to obtain the corresponding monomer alkene compound. Then dissolving the corresponding monomer olefin compound in a solution containing an initiator, polymerizing at 50-120 ℃, and obtaining the solid flame-retardant polymer represented by the general formula (II) by a dissolution-precipitation technology.
Wherein the cyclotriphosphazene compound depends on the molecular structure of the solid flame retardant polymer to be prepared, and includes but is not limited to hexachlorocyclotriphosphazene, hexafluorocyclotriphosphazene, ethoxy (pentafluoro) cyclotriphosphazene, phenoxy (pentafluoro) cyclotriphosphazene, and the like. The solvent includes, but is not limited to, one or more of ethane, cyclohexane, dichloromethane, trichloromethane, diethyl ether, petroleum ether, benzene, toluene, chlorobenzene, fluorobenzene, acetone, acetonitrile, methanol, ethanol, tetrahydrofuran, nitromethane, dimethyl sulfoxide, N-dimethylformamide, ethyl acetate, and butyl acetate. Examples of the alkene sodium (phenoxide) compound include, but are not limited to, sodium vinyl alkoxide, sodium ethylene p-phenoxide, and the like. The initiator includes azo-type initiators, organic peroxy-type initiators, inorganic peroxy initiators, and oxidation-reduction initiators, and specifically, the initiators include, but are not limited to, Azobisisobutyronitrile (AIBN), dibenzoyl peroxide (BPO), potassium persulfate, hydrogen peroxide-ferrous chloride, and the like.
The embodiment of the invention also provides an electrode plate of a lithium secondary battery, which comprises a current collector and an electrode active material layer arranged on the current collector, wherein the electrode active material layer comprises the solid flame-retardant polymer.
In the embodiment of the present invention, the solid flame retardant polymer accounts for 0.1% to 20%, further 1% to 10%, and 2% to 8% of the total mass of the electrode active material layer.
In an embodiment of the present invention, the solid flame retardant polymer is in the form of particles or powder, and the particle size thereof is 0.01 μm to 10 μm; the solid flame retardant polymer is uniformly dispersed in the electrode active material layer.
In an embodiment of the present invention, the electrode plate of the lithium secondary battery includes a positive electrode plate of the lithium secondary battery or a negative electrode plate of the lithium secondary battery.
When the electrode sheet of the lithium secondary battery is a positive electrode sheet of the lithium secondary battery, the current collector may be an existing conventional positive current collector, such as an aluminum foil, the electrode active material layer includes a positive active material, a conductive agent and a binder, and the positive active material may be an existing conventional material, such as lithium cobaltate (LiCoO)2) (ii) a The conductive agent and the binder can be of the conventional types, the conductive agent can be super P, and the binder can be polyvinylidene fluoride (PVDF).
The positive pole piece of the lithium secondary battery can be prepared by adopting the following method: weighing a binder, a conductive agent, a solid flame-retardant polymer and a positive active material according to a certain mass ratio, sequentially adding the materials into an organic solvent, fully stirring and uniformly mixing, coating slurry on a positive current collector, and drying, cold-pressing and cutting to obtain the lithium secondary battery positive pole piece. Among them, the organic solvent may be, but is not limited to, N-methylpyrrolidone (NMP).
When the electrode plate of the lithium secondary battery is a negative electrode plate of the lithium secondary battery, the current collector can be an existing conventional negative current collector, such as copper foil, the electrode active material layer comprises a negative active material, a conductive agent and a binder, and the negative active material can be an existing conventional material, such as graphite; the conductive agent and the binder can be the conventional common types, the conductive agent can be acetylene black, and the binder can be sodium carboxymethylcellulose (CMC) or Styrene Butadiene Rubber (SBR).
The negative pole piece of the lithium secondary battery can be prepared by adopting the following method: weighing the binder, the conductive agent, the solid flame-retardant polymer and the negative active material according to a certain mass ratio, sequentially adding the materials into the solvent, fully stirring and uniformly mixing, coating the slurry on a negative current collector, and drying, cold-pressing and cutting to obtain the lithium secondary battery negative pole piece. Wherein the solvent may be, but is not limited to, deionized water.
The electrode plate of the lithium secondary battery provided by the embodiment of the invention has excellent flame retardant property, can effectively improve the safety of the battery and ensure the exertion of the electrochemical property of the battery.
The embodiment of the invention also provides the diaphragm which comprises a diaphragm body and flame-retardant layers arranged on the surfaces of one side or two sides of the diaphragm body, wherein the flame-retardant layers comprise the solid flame-retardant polymer and the binder.
In an embodiment of the present invention, in the flame retardant layer, a mass ratio of the solid flame retardant polymer to the binder is 1 to 100:1, and further a mass ratio is 50 to 95:1 or 70 to 80: 1.
In an embodiment of the present invention, the thickness of the flame retardant layer is 0.1 μm to 10 μm, and further, the thickness is 1 μm to 8 μm, and 3 μm to 6 μm.
In an embodiment of the present invention, the binder includes one or more of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), Polyacrylonitrile (PAN), Polyimide (PI), polyethylene glycol (PEG), polyethylene oxide (PEO), Polydopamine (PDA), sodium carboxymethylcellulose/styrene butadiene rubber (CMC/SBR), polyvinyl alcohol (PVA), polyacrylic acid (PAA), lithium polyacrylate (lipa), polyvinyl pyrrolidone (PVP), polylactic acid (PLA), Sodium Alginate (SA), poly (styrene sulfonic acid) (PSS), poly (styrene sulfonic acid) (LiPSS), and gelatin.
In embodiments of the present invention, the separator body may be an existing conventional commercial separator, including but not limited to, a single layer PP (polypropylene), a single layer PE (polyethylene), a double layer PP/PE, a double layer PP/PP, and a triple layer PP/PE/PP separator.
The diaphragm provided by the embodiment of the invention can be prepared in the following way: the solid flame-retardant polymer and the binder are dissolved in an organic solvent according to a certain mass ratio, are stirred and mixed into a uniform solution, and are uniformly coated on a commercial diaphragm body by a scraper, so that the diaphragm provided by the invention is prepared. Among them, the organic solvent includes, but is not limited to, N-methylpyrrolidone (NMP).
The diaphragm provided by the embodiment of the invention has excellent flame retardant property, and can effectively improve the safety of the battery and ensure the exertion of the electrochemical property of the battery when being applied to the lithium secondary battery.
The embodiment of the invention also provides a lithium secondary battery, which comprises the electrode plate of the lithium secondary battery and/or the diaphragm of the lithium secondary battery. Namely, the lithium secondary battery can be doped with the solid flame-retardant polymer provided by the embodiment of the invention in at least one of the positive pole piece, the negative pole piece and the diaphragm. The lithium secondary battery of the embodiment of the invention has high safety due to the application of the solid flame-retardant polymer with excellent flame-retardant property, and the solid flame-retardant polymer exists in a solid form and has good compatibility with positive and negative electrode materials, so that the reduction of the conductivity of the electrolyte, the increase of the viscosity and the occurrence of side reactions can be effectively avoided, and the lithium secondary battery has good cycle performance.
The following examples are intended to illustrate the invention in more detail.
Example 1
A solid flame-retardant polymer, the molecular structural formula of which is shown in formula (A):
Figure GDA0003211266470000081
preparation of solid flame retardant polymer of this example (polyethoxy (pentafluoro) cyclotriphosphazene):
respectively adding 2.0mol of hexafluorocyclotriphosphazene and 300mL of acetonitrile into a 500mL three-neck flask, slowly dropwise adding 1.0mol of acetonitrile mixed solution of sodium glycol through a constant-pressure dropping funnel at 0 ℃, stirring and reacting for 24 hours at 40 ℃ after dropwise adding, filtering, and drying under reduced pressure to obtain the polyethoxy (pentafluoro) cyclotriphosphazene (A), wherein n is 36.
Preparing a positive pole piece of the lithium secondary battery:
weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P, 2% of solid flame-retardant polymer A and 94% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding N-methylpyrrolidone(s) (ii)NMP), stirring and mixing uniformly, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain the positive pole piece of the embodiment 1 of the invention.
Preparation of lithium secondary battery:
weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and cutting to obtain a negative pole piece;
preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a square battery cell, packaging by adopting a polymer, and filling 1.0mol/L LiPF6And (3) preparing the electrolyte (EC, EMC, DEC and PC in a weight ratio of 35:25:25:15) into the soft package lithium secondary battery of 3.6Ah by chemical synthesis and other processes.
Example 2
A solid flame-retardant polymer, the molecular structural formula of which is shown as formula (B):
Figure GDA0003211266470000091
the solid flame-retardant polymer (B) of this example was prepared in a similar manner to example 1.
Respectively adding 1.0mol of hexachlorocyclotriphosphazene and 200mL of acetonitrile into a 500mL three-neck flask, slowly dropwise adding 1.0mol of acetonitrile mixed solution of sodium p-phenylenediate through a constant-pressure dropping funnel at the temperature of 0 ℃, stirring and reacting for 48 hours at the temperature of 60 ℃ after dropwise adding, filtering, and drying under reduced pressure to obtain a solid flame-retardant polymer (B), specifically n1、n2、n3、n4Are all 12.
Preparing a positive pole piece of the lithium secondary battery:
weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P, 2% of solid flame-retardant polymer B and 94% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding the mixture into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain the anode of the embodiment 2 of the inventionAnd (6) pole pieces.
Preparation of lithium secondary battery:
weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and cutting to obtain a negative pole piece;
preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a square battery cell, packaging by adopting a polymer, and filling 1.0mol/L LiPF6And (3) preparing the electrolyte (EC, EMC, DEC and PC in a weight ratio of 35:25:25:15) into the soft package lithium secondary battery of 3.6Ah by chemical synthesis and other processes.
Example 3
A solid flame-retardant polymer, the molecular structural formula of which is shown as formula (C):
Figure GDA0003211266470000101
preparation of solid flame retardant polymer (polyethylene-p-phenoxy (pentafluoro) cyclotriphosphazene) of this example:
respectively adding 1.0mol of hexafluorocyclotriphosphazene and 200mL of acetonitrile into a 500mL three-neck flask, slowly dropwise adding 1.0mol of acetonitrile mixed solution of ethylene-p-phenolate sodium through a constant-pressure dropping funnel at the temperature of 0 ℃, stirring and reacting for 12 hours at the temperature of 30 ℃ after dropwise adding is finished, filtering, and drying under reduced pressure to obtain the corresponding monomer ethylene-p-phenoxy (pentafluoro) cyclotriphosphazene. Then dissolving the corresponding monomer ethylene-p-phenoxy (pentafluoro) cyclotriphosphazene in acetonitrile solution containing initiator (AIBN), polymerizing at 60 ℃, and obtaining polyethylene-p-phenoxy (pentafluoro) cyclotriphosphazene (C) by dissolution-precipitation technology, wherein n is about 108.
Preparing a positive pole piece of the lithium secondary battery:
weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P, 2% of solid flame-retardant polymer C and 94% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing, and coating the slurry on an aluminum foil current collectorAnd drying, cold pressing and slitting to obtain the positive pole piece in the embodiment 3 of the invention.
Preparation of lithium secondary battery:
weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and cutting to obtain a negative pole piece;
preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a square battery cell, packaging by adopting a polymer, and filling 1.0mol/L LiPF6And (3) preparing the electrolyte (EC, EMC, DEC and PC in a weight ratio of 35:25:25:15) into the soft package lithium secondary battery of 3.6Ah by chemical synthesis and other processes.
Example 4
Preparing a negative pole piece of the lithium secondary battery:
weighing 1% of CMC, 2% of SBR, 1% of acetylene black, 2% of solid flame-retardant polymer A and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain the negative pole piece of the embodiment 4 of the invention.
Preparation of lithium secondary battery:
weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding the mixture into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain a positive pole piece;
preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a square battery cell, packaging by adopting a polymer, and filling 1.0mol/L LiPF6And (3) preparing the electrolyte (EC, EMC, DEC and PC in a weight ratio of 35:25:25:15) into the soft package lithium secondary battery of 3.6Ah by chemical synthesis and other processes.
Example 5
Preparing a negative pole piece of the lithium secondary battery:
weighing 1% of CMC, 2% of SBR, 1% of acetylene black, 2% of solid flame-retardant polymer B and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain the negative pole piece of the embodiment 5 of the invention.
Preparation of lithium secondary battery: the same as in example 4.
Example 6
Preparing a negative pole piece of the lithium secondary battery:
weighing 1% of CMC, 2% of SBR, 1% of acetylene black, 2% of solid flame-retardant polymer C and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain the negative pole piece of the embodiment 6 of the invention.
Preparation of lithium secondary battery: the same as in example 4.
Example 7
Preparing a diaphragm:
weighing 90 mass percent of solid flame-retardant polymer A and 10 mass percent of PVDF, dissolving the solid flame-retardant polymer A and the PVDF in NMP, stirring and mixing the mixture to form a uniform solution, and uniformly coating the uniform solution on two surfaces of a PP diaphragm by using a 1-micron scraper to obtain the diaphragm of the embodiment 7 of the invention.
Preparation of lithium secondary battery:
weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding the mixture into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain a positive pole piece;
weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and cutting to obtain a negative pole piece;
the positive pole piece, the negative pole piece and the diaphragm of the embodiment are prepared into a square battery cell, and the square battery cell is packaged by adopting a polymer and is filled with 1.0mol/L LiPF6And (3) preparing the electrolyte (EC, EMC, DEC and PC in a weight ratio of 35:25:25:15) into the soft package lithium secondary battery of 3.6Ah by chemical synthesis and other processes.
Example 8
Preparing a diaphragm:
weighing 90% by mass of solid flame-retardant polymer B and 10% by mass of PVDF, dissolving the solid flame-retardant polymer B and the PVDF in NMP, stirring and mixing the mixture to form a uniform solution, and uniformly coating the uniform solution on two surfaces of a PP diaphragm by using a 1-micron scraper to obtain the diaphragm of the embodiment 8 of the invention.
Preparation of lithium secondary battery: the same as in example 7.
Example 9
Preparing a diaphragm:
weighing 90 mass percent of solid flame-retardant polymer C and 10 mass percent of PVDF, dissolving the solid flame-retardant polymer C and the PVDF in NMP, stirring and mixing the mixture to form a uniform solution, and uniformly coating the uniform solution on two sides of a PP diaphragm by using a 1-micron scraper to obtain the diaphragm of the embodiment 9 of the invention.
Preparation of lithium secondary battery: the same as in example 7.
Comparative example 1
Preparation of lithium secondary battery: weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding the mixture into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain a positive pole piece;
weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and cutting to obtain a negative pole piece;
preparing the prepared positive pole piece, negative pole piece and commercial PP/PE/PP three-layer diaphragm into a square battery cell, packaging by adopting a polymer, and filling 1.0mol/L LiPF6And (3) preparing the electrolyte (EC, EMC, DEC and PC in a weight ratio of 35:25:25:15) into the soft package lithium secondary battery of 3.6Ah by chemical synthesis and other processes.
Comparative example 2
Preparation of lithium secondary battery: weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding into N-methyl pyrrolidone (NMP), stirring and mixing, and coating the slurry on aluminumDrying, cold pressing and cutting the foil current collector to obtain a positive pole piece;
weighing 2% of CMC, 3% of SBR, 1% of acetylene black and 94% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and cutting to obtain a negative pole piece;
PVDF which is equal to that in example 7 is weighed and dissolved in NMP, the mixture is stirred and mixed into uniform solution, and a scraper with the diameter of 1 mu m is used for uniformly coating the solution on two sides of a PP diaphragm to prepare the diaphragm of the comparative example 2;
preparing the prepared positive pole piece, negative pole piece and diaphragm into a square battery cell, packaging with polymer, and pouring 1.0mol/LLIPF6And (3) preparing the electrolyte (EC, EMC, DEC and PC in a weight ratio of 35:25:25:15) into the soft package lithium secondary battery of 3.6Ah by chemical synthesis and other processes.
Effects of the embodiment
In order to strongly support the beneficial effects brought by the technical scheme of the embodiment of the invention, the following tests are provided:
(1) safety performance test of lithium secondary battery
The lithium secondary batteries prepared in examples 1 to 9 of the present invention and comparative examples 1 to 2 were subjected to a needle punching experiment using a high temperature resistant steel needle having a diameter of 3 to 8mm at a speed of 10 to 40mm/s, and whether the battery cells were ignited and exploded was recorded, with the results shown in table 1.
(2) Lithium secondary battery cycle performance test
The lithium secondary batteries prepared in examples 1 to 9 of the present invention and comparative examples 1 to 2 were subjected to charge and discharge cycle tests at a charge and discharge rate of 1.0/1.0C, graphite/LiCoO2The voltage range of the battery was 3.0-4.4V, and the capacity retention after 500 weeks was recorded, and the test results are shown in Table 1. In addition, fig. 1, 2, 3, and 4 are first 100-cycle curves of the lithium secondary batteries according to example 1, 9, comparative example 1, and comparative example 2 of the present invention, respectively.
TABLE 1 safety and cycling Performance test results for examples 1-9 and comparative examples 1-2
Figure GDA0003211266470000121
Figure GDA0003211266470000131
As can be seen from the test results in Table 1, the batteries of examples 1-9 according to the present invention did not suffer from ignition and explosion upon being subjected to the needling test, whereas the batteries of comparative examples 1-2 suffered from ignition upon being subjected to the needling test, indicating that the batteries comprising the solid flame retardant polymers of the examples according to the present invention had higher flame resistance and improved safety of lithium secondary batteries. In addition, as can be seen from the test results in table 1 and the cycle curve diagrams in fig. 1 to 4, compared with comparative examples 1 to 2, the batteries in examples 1 to 9 of the present invention have higher capacity retention rate and more excellent cycle performance, which is mainly because the solid flame retardant polymer in the examples of the present invention is insoluble in the electrolyte of the lithium secondary battery, and can be mixed with positive and negative electrode materials to prepare positive and negative electrode plates, or coated on the surface of the separator through an adhesive, so that the negative effect on the battery performance caused by directly adding a flame retardant to the electrolyte in the conventional method can be overcome. The solid flame-retardant polymer provided by the embodiment of the invention has the advantages that the performance of the electrolyte is not deteriorated, the solid flame-retardant polymer has good compatibility with positive and negative electrode materials, the electrochemical performance of the battery is improved, and the solid flame-retardant polymer has a wide application market.

Claims (25)

1. A solid flame-retardant polymer used for a lithium secondary battery is characterized in that the solid flame-retardant polymer comprises a repeating unit containing a cyclotriphosphazene structure, and is formed by polymerizing a monomer containing the cyclotriphosphazene structure through chemical bond grafting, the general formula of the solid flame-retardant polymer is shown as a formula (I),
Figure FDA0003423789690000011
in the formula (I), X is selected from alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkenyloxy and halogenated alkenyloxyAny one of arylene, halogenated arylene, aryloxy, halogenated aryloxy, substituted phosphodiester group, substituted imide group and substituted sulfonimide group; the R is1、R2、R3、R4Respectively selected from any one of fluorine, bromine, halogenated alkyl, halogenated alkoxy, halogenated alkenyl, halogenated alkenyloxy and halogenated aryl; in the formula (I), n is 5-1000.
2. The solid flame retardant polymer of claim 1 wherein in said X, the number of carbon atoms of said alkylene group, haloalkylene group, alkyleneoxy group, haloalkyleneoxy group is 1 to 20; the carbon atoms of the alkenylene, the halogenated alkenylene, the alkenylene oxide and the halogenated alkenylene oxide are 2-20; the carbon atoms of the arylene, the halogenated arylene, the aryloxy ene and the halogenated aryloxy ene are 6-20; the carbon atom number of the substituted group in the substituted phosphodiester group, the substituted imide group and the substituted sulfonyl imide group is 1-20.
3. The solid flame retardant polymer of claim 1 wherein the halogen in said haloalkylene, haloalkyleneoxy, haloalkenylene, haloalkenyleneoxy, haloarylene, haloaryloxylene of X comprises fluorine, chlorine, bromine, iodine, said halogen being perhalogenated or partially halogenated.
4. The solid flame retardant polymer of claim 1, wherein R is1、R2、R3、R4Wherein the carbon atom number of the halogenated alkyl group or the halogenated alkoxy group is 1 to 20; the carbon atom number of the halogenated alkenyl and the halogenated alkenyloxy is 2-20; the halogenated aryl group has 6 to 20 carbon atoms.
5. The solid flame retardant polymer of claim 1, wherein R is1、R2、R3、R4Wherein the halogen in the haloalkyl, haloalkoxy, haloalkenyl, haloalkenyloxy and haloaryl comprises fluorine, chlorine, or chlorine, or chlorine,bromine, iodine, the halogen is perhalogenated or partially halogenated.
6. The solid flame retardant polymer of claim 1 wherein X is selected from any one of methylene, ethylene, propylene, isopropylene, butylene, 1-butylene, perfluoro substituted butylene, difluoro substituted ethyleneoxy, methylphenyl, vinylphenylene, fluorophenylene, methylphosphonite, trifluoroethylenephosphonate, acetyieneimine and difluoromethylenesulphonimidone.
7. A lithium secondary battery electrode plate is characterized by comprising a current collector and an electrode active material layer arranged on the current collector, wherein the electrode active material layer comprises a solid flame-retardant polymer, the solid flame-retardant polymer comprises a repeating unit containing a cyclotriphosphazene structure, the repeating unit is formed by polymerizing a monomer containing the cyclotriphosphazene structure through chemical bond grafting, the general formula of the solid flame-retardant polymer is shown as a formula (I) or a formula (II),
Figure FDA0003423789690000021
in the formula (I), X is selected from any one of alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkenylene oxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxy, halogenated arylene oxide, substituted phosphodiester group, substituted imide group and substituted sulfonylimide group; the R is1、R2、R3、R4Respectively selected from any one of fluorine, bromine, halogenated alkyl, halogenated alkoxy, halogenated alkenyl, halogenated alkenyloxy and halogenated aryl; in the formula (I), n is 5-1000;
in the formula (II), Y is selected from the group consisting of oxygen, sulfur, alkylene, haloalkylene, alkyleneoxy, haloalkyleneoxy, alkenylene, haloalkenylene-oxy, arylene, haloarylene, aryloxylene, alkoxylene, or combinations thereof,Any one of halogenated arylene group, substituted phosphate ester group, substituted imide group and substituted sulfonyl imide group; the R is1’、R2’、R3’、R4’、R5' is selected from any one of fluorine, chlorine, bromine, halogenated alkyl, halogenated alkoxy, halogenated alkenyl, halogenated alkenyloxy and halogenated aryl; in the formula (II), n is 5-1000.
8. The electrode tab for lithium secondary batteries according to claim 7, wherein the alkylene group, the haloalkylene group, the alkyleneoxy group, and the haloalkyleneoxy group have 1 to 20 carbon atoms in the X and Y groups; the carbon atoms of the alkenylene, the halogenated alkenylene, the alkenylene oxide and the halogenated alkenylene oxide are 2-20; the carbon atoms of the arylene, the halogenated arylene, the aryloxy ene and the halogenated aryloxy ene are 6-20; the carbon atom number of the substituted group in the substituted phosphodiester group, the substituted imide group and the substituted sulfonyl imide group is 1-20.
9. The electrode sheet for lithium secondary batteries according to claim 7, wherein the halogen in said haloalkylene, haloalkyleneoxy, haloalkenylene, haloalkenyleneoxy, haloarylene, haloaryloxylene in said X and said Y comprises fluorine, chlorine, bromine, iodine, and said halogen is perhalogenated or partially halogenated.
10. The electrode tab of lithium secondary battery according to claim 7, wherein R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In the item's publication, the number of carbon atoms of the haloalkyl group or the haloalkoxy group is 1 to 20; the carbon atom number of the halogenated alkenyl and the halogenated alkenyloxy is 2-20; the halogenated aryl group has 6 to 20 carbon atoms.
11. The electrode tab of lithium secondary battery according to claim 7, wherein R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In the' above, the halogen in the haloalkyl group, haloalkoxy group, haloalkenyl group, haloalkenyloxy group or haloaryl group includes fluorine, chlorine, bromine or iodine, and the halogen is a perhalogenated or partially halogenated group.
12. The electrode sheet for lithium secondary batteries according to claim 7, wherein X and Y are each independently selected from the group consisting of methylene, ethylene, propylene, isopropylene, butylene, 1-butylene, perfluoro-substituted butylene, difluoro-substituted ethyleneoxy, methylphenyl, vinylphenylene, fluorophenylene, methylphosphonite, trifluoroethylenephosphocalcine, acetyimideimide and difluoromethylenesulfonylimido.
13. The electrode sheet for lithium secondary batteries according to claim 7, wherein the solid flame-retardant polymer accounts for 0.1 to 20% by mass of the total mass of the electrode active material layer.
14. The electrode tab for lithium secondary batteries according to claim 7, wherein the solid flame retardant polymer is uniformly dispersed in the electrode active material layer.
15. The lithium secondary battery electrode tab according to claim 7, wherein the lithium secondary battery electrode tab comprises a lithium secondary battery positive electrode tab or a lithium secondary battery negative electrode tab.
16. A diaphragm is characterized by comprising a diaphragm body and flame retardant layers arranged on the surfaces of one side or two sides of the diaphragm body, wherein the flame retardant layers are made of solid flame retardant polymers and binders, the solid flame retardant polymers comprise repeating units containing cyclotriphosphazene structures and are formed by polymerizing monomers containing the cyclotriphosphazene structures through chemical bond grafting, and the general formula of the solid flame retardant polymers is shown as a formula (I) or a formula (II),
Figure FDA0003423789690000031
in the formula (I), X is selected from any one of alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkenylene oxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxy, halogenated arylene oxide, substituted phosphodiester group, substituted imide group and substituted sulfonylimide group; the R is1、R2、R3、R4Respectively selected from any one of fluorine, bromine, halogenated alkyl, halogenated alkoxy, halogenated alkenyl, halogenated alkenyloxy and halogenated aryl; in the formula (I), n is 5-1000;
in the formula (II), Y is selected from any one of oxygen, sulfur, alkylene, halogenated alkylene, alkyleneoxy, halogenated alkyleneoxy, alkenylene, halogenated alkenylene, alkyleneoxy, halogenated alkenylene oxy, arylene, halogenated arylene, aryloxylene, halogenated aryloxylene, substituted phospholene, substituted imide and substituted sulfonylimide; the R is1’、R2’、R3’、R4’、R5' is selected from any one of fluorine, chlorine, bromine, halogenated alkyl, halogenated alkoxy, halogenated alkenyl, halogenated alkenyloxy and halogenated aryl; in the formula (II), n is 5-1000.
17. The membrane according to claim 16, wherein in X and Y, the number of carbon atoms of the alkylene group, the halogenated alkylene group, the alkyleneoxy group, and the halogenated alkyleneoxy group is 1 to 20; the carbon atoms of the alkenylene, the halogenated alkenylene, the alkenylene oxide and the halogenated alkenylene oxide are 2-20; the carbon atoms of the arylene, the halogenated arylene, the aryloxy ene and the halogenated aryloxy ene are 6-20; the carbon atom number of the substituted group in the substituted phosphodiester group, the substituted imide group and the substituted sulfonyl imide group is 1-20.
18. The membrane of claim 16, wherein the halogen of said haloalkylene, haloalkyleneoxy, haloalkenylene, haloalkenyleneoxy, haloarylene, haloaryloxylene in said X and said Y comprises fluorine, chlorine, bromine, iodine, and said halogen is perhalogenated or partially halogenated.
19. The membrane of claim 16, wherein R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In the item's publication, the number of carbon atoms of the haloalkyl group or the haloalkoxy group is 1 to 20; the carbon atom number of the halogenated alkenyl and the halogenated alkenyloxy is 2-20; the halogenated aryl group has 6 to 20 carbon atoms.
20. The membrane of claim 16, wherein R is1、R2、R3、R4、R1’、R2’、R3’、R4' and R5In the' above, the halogen in the haloalkyl group, haloalkoxy group, haloalkenyl group, haloalkenyloxy group or haloaryl group includes fluorine, chlorine, bromine or iodine, and the halogen is a perhalogenated or partially halogenated group.
21. The separator according to claim 16, wherein X and Y are each independently selected from the group consisting of methylene, ethylene, propylene, isopropylene, butylene, 1-butylene, perfluoro-substituted butylene, difluoro-substituted ethyleneoxy, methylphenyl, vinylphenylene, fluorophenylene, methylphosphonite, trifluoroethylenephosphocalcine, acetylimide and difluoromethylenesulfonylimide.
22. The separator of claim 16, wherein the mass ratio of the solid flame retardant polymer to the binder in the flame retardant layer is 1-100: 1.
23. The separator of claim 16, wherein the flame retardant layer has a thickness of 0.1 μ ι η to 10 μ ι η.
24. The separator of claim 16, wherein said binder comprises one or more of polyvinylidene fluoride, polymethyl methacrylate, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyimide, polyethylene glycol, polyethylene oxide, polydopamine, sodium carboxymethylcellulose/styrene butadiene rubber, polyvinyl alcohol, polyacrylic acid, lithium polyacrylate, polyvinylpyrrolidone, polylactic acid, sodium alginate, poly (styrene-co-sulfonic acid), lithium poly (styrene-co-sulfonic acid), and gelatin.
25. A lithium secondary battery comprising the lithium secondary battery electrode tab according to any one of claims 7 to 15 and/or the separator according to any one of claims 16 to 24.
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