Flame retardant and secondary battery containing the same

Abstract

The present application provides a flame retardant, comprising: a first monomer unit #imgabs0# a second monomer unit #imgabs1# a third monomer unit #imgabs2# wherein 10≤m≤10000, 1≤n≤1000, X1 and X2 are independently selected from one of ‑CH2‑, ‑CH2‑O‑, ‑C(=O)‑O‑, ‑NH‑, and ‑Si(‑O‑)3; R1 is C1‑C 10 Alkyl, C1-C 10 Aromatic, C1-C 10 One of the polyethers; Y is C1-C 10 Alkyl or C1-C 10 Aromatic group. The present application provides a novel flame retardant, which can be used on a battery separator to improve battery safety issues caused by flammable electrolyte, high-temperature oxygen release at the positive electrode, and heat generation from crosstalk between the positive and negative electrodes.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a flame retardant, an isolation film containing the flame retardant, and a secondary battery. Background Art

[0002] In recent years, the application scope of secondary batteries has become increasingly wide. They are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0003] The safety performance of secondary batteries has always been highly valued in the industry. Therefore, how to improve the safety performance of batteries remains an urgent problem to be solved. Summary of the invention

[0004] In order to achieve the above-mentioned purpose, the present application provides a flame retardant in the first aspect, comprising: a first monomer unit The second monomer unit The third monomer unit The first monomer unit and the third monomer unit are connected through the second monomer unit, 10≤m≤10000, 1≤n≤1000, X 1 , X 2 Each independently selected from -CH 2 -、-CH 2 -O-, -C(=O)-O-, -NH-, -Si(-O-) 3 One of the 1 C 1 -C 10 Alkyl, C 1 -C 10 Aromatic group, C 1 -C 10 One of the polyethers; Y is C 1 -C 10 Alkyl or C 1 -C 10 Aromatic group. Thus, the present application prepares a new type of flame retardant, which can be decomposed at high temperature to produce high-polymer polyphosphoric acid, forming a dense isolation layer on the surface of the combustible material to block oxygen and combustible gas and prevent combustion; at the same time, the small molecular phosphate side chain can capture the reactive intermediate H·, O· free radicals after high-temperature decomposition, interrupt the combustion chain reaction, and prevent the combustion reaction from continuing.

[0005] In any embodiment, in the first monomer unit, 200≤m≤2000.

[0006] In any embodiment, 1≤n≤100 in the third monomer unit.

[0007] By adjusting the different molecular weights of flame retardants, the thermal response temperature can be controlled within 150℃-400℃, thereby adapting to various positive electrode materials, capturing the released active oxygen in time, and preventing thermal runaway of the battery.

[0008] In any embodiment, the particle size Dv50 of the flame retardant is 50nm-10μm, and can be 200nm-2μm. The particle size of the flame retardant currently available on the market is large, which is difficult to be applied to the coating of battery materials. The particle size of the flame retardant prepared in this application is moderate, and can be well applied to the isolation membrane of the secondary battery.

[0009] In any embodiment, 1500≤m≤2000, 80≤n≤100.

[0010] In any embodiment, 600≤m<1000, 30≤n<50.

[0011] In any embodiment, 200≤m<600, 1≤n<30.

[0012] In any embodiment, 1000≤m<1500, 50≤n<80.

[0013] The second aspect of the present application also provides a method for preparing a flame retardant, comprising the following steps:

[0014] (1) Providing raw materials: a first raw material, a second raw material and a third raw material, wherein:

[0015] The structure of the first raw material is shown in Formula I,

[0016] Where 10≤m≤10000;

[0017] The second raw material structural formula is -R 1 -X 1 -R 2 -, where X 1 , X 2 Each independently selected from -CH 2 -、-CH 2 -O-, -C(=O)-O-, -NH-, -Si(-O-) 3 ; R 1 Selected from C 1 -C 10 Alkyl, C 1 -C 10 Aromatic group, C 1 -C 10 One of the polyethers;

[0018] The structure of the third raw material is shown in Formula II,

[0019] Among them, R 2 , R 3 are independently selected from C 1 -C 10 Alkyl, C 1 -C 10 Aromatic group, C 1 -C 10 Olefins, C 1 -C 10 Alkoxy, C 1 -C 10 Carboxyl, C 1 -C 10 At least one of alcohol, amino, -Cl, -Br, -OH;

[0020] (2) reacting the first raw material, the second raw material, and the third raw material at 20° C.-150° C.;

[0021] (3) Washing and drying to obtain the flame retardant.

[0022] The third aspect of the present application provides a secondary battery, comprising the flame retardant provided in the first aspect of the present application or the flame retardant prepared according to the preparation method provided in the second aspect of the present application.

[0023] In some embodiments, the secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator, and the flame retardant is applied to at least one of the positive electrode sheet, the negative electrode sheet, or the separator.

[0024] In some embodiments, a secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode collector and a positive electrode film layer formed on the surface of the positive electrode collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing phosphate, and the secondary battery includes a flame retardant with a molecular weight of 1500≤m≤2000, 80≤n≤100.

[0025] In some embodiments, the secondary battery includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes LiNi x Co y Mn 1-x-y O 2 Or lithium cobalt oxide, the secondary battery includes a flame retardant with 600≤m<1000, 30≤n<50, wherein 0.6≤x≤0.8 and x+y<1.

[0026] In some embodiments, the secondary battery includes a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes LiNi x Co y Mn1-x-y O 2 , the secondary battery includes a flame retardant with 200 ≤ m < 600 and 1 ≤ n < 30, where x ≥ 0.8 and x + y < 1.

[0027] In some embodiments, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes LiNi x Co y Mn 1-x-y O 2 , the secondary battery includes a flame retardant with 1000 ≤ m < 1500 and 50 ≤ n < 80, where 0 < x ≤ 0.6 and x + y < 1.

[0028] The fourth aspect of the present application provides a separator, including a porous substrate; and a coating disposed on at least one surface of the porous substrate, and the coating includes the flame retardant provided by the first aspect of the present application or the flame retardant prepared by the preparation method provided by the second aspect of the present application.

[0029] The fifth aspect of the present application provides an electrical device including the secondary battery of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of the action mechanism of the flame retardant according to an embodiment of the present application.

[0031] Figure 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0032] Figure 3 is Figure 2 an exploded view of the secondary battery according to an embodiment of the present application shown in

[0033] Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0034] Figure 5 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0035] Figure 6 is Figure 5 an exploded view of the battery pack according to an embodiment of the present application shown in

[0036] Figure 7 is a schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source.

[0037] Description of the reference numerals:

[0038] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly DETAILED DESCRIPTION

[0039] Below, the embodiments of the separator, positive electrode sheet, negative electrode sheet, electrolyte, secondary battery, battery module, battery pack and power device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0040] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0043] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0045] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0046] [Flame retardant]

[0047] One embodiment of the present application provides a flame retardant, including:

[0048] The first monomer unit The second monomer unit The third monomer unit The first monomer unit and the third monomer unit are connected through the second monomer unit, 10≤m≤10000, 1≤n≤1000, X 1 , X 2 Each independently selected from -CH 2 -、-CH 2 -O-, -C(=O)-O-, -NH-, -Si(-O-) 3 ; R 1 Selected from C 1 -C 10 Alkyl, C 1 -C 10 Aromatic group, C 1 -C 10 One of polyethers; Y is selected from C 1 -C 10 Alkyl or C 1 -C 10 Aromatic group.

[0049] Figure 1 This is a schematic diagram of the mechanism of action of the flame retardant of one embodiment of the present application. The structure adopts a polyphosphoric acid amine main chain and a phosphate ester side chain, which can form a dense oxide layer on the surface of the combustible material and generate meteoric free radicals at high temperature, thereby capturing active free radicals in the combustion chain reaction, interrupting the combustion chain reaction, and preventing the combustion from continuing.

[0050] In some embodiments, 200≤m≤2000 in the first monomer unit. The high molecular weight polyphosphoric acid amine main chain can be decomposed at high temperature to produce high molecular weight polyphosphoric acid, ammonia, and water. The high molecular weight polyphosphoric acid will form a dense isolation layer on the surface of the combustible material, blocking the transfer of oxygen, combustible gas, and heat, thereby breaking the three elements of combustion of the "fire triangle" and preventing combustion; in addition, the generated non-combustible gases such as ammonia and water can take away part of the heat and dilute the concentration of oxygen and combustible gas in the air.

[0051] In some embodiments, 1≤n≤100 in the third monomer unit. The small molecular phosphate side chain can generate gas-phase free radicals PO after high temperature decomposition. 2 ·、PO·、(PO 3 Y) n ·, etc., to capture the active intermediates H· and O· free radicals in the combustion chain reaction and generate chemically stable H 3 PO 4 , P 2 O 5 、H(PO 3 Y) n Thereby interrupting the combustion chain reaction and preventing the combustion reaction from continuing.

[0052] In some embodiments, the flame retardant has an average particle size Dv50 of 50 nm-10 μm, and can be optionally 200 nm-2 μm. Flame retardants with smaller particle sizes can be applied to the coating of battery materials. The cross-linking process opens the ammonium polyphosphate molecular chain, reduces the particle size, and obtains flame retardant particles with a suitable particle size. The preparation process is simple and the cost is low.

[0053] In some embodiments, 1500≤m≤2000, 80≤n≤100. When the molecular weight of the first monomer unit and the third monomer unit is controlled within this range, the thermal response temperature of the flame retardant is 350°C-450°C, which can be adapted to the lithium iron phosphate positive electrode material system. The thermal response temperature is when the flame retardant decomposes and produces PO 2 ·、PO·、(PO 3 Y) n The temperature of the free radicals.

[0054] In some embodiments, 600≤m≤1000, 30≤n≤50. When the molecular weights of the first monomer unit and the third monomer unit are controlled within this range, the thermal response temperature of the flame retardant obtained is 220°C-259°C, which can be adapted to LiNi x Co y Mn 1-x-y O 2 A positive electrode material system, wherein x is 0.6-0.8 and x+y<1.

[0055] In some embodiments, 200≤m≤600, 1≤n≤30. When the molecular weights of the first monomer unit and the third monomer unit are controlled within this range, the thermal response temperature of the flame retardant obtained is 180°C-219°C, which can be adapted to LiNi x Co y Mn 1-x-y O 2 A positive electrode material system, wherein x is 0.8-0.98 and x+y<1.

[0056] In some embodiments, 1000≤m≤1500, 50≤n≤80. When the molecular weights of the first monomer unit and the third monomer unit are controlled within this range, the thermal response temperature of the flame retardant obtained is 260°C-349°C, which can be adapted to LiNi x Co y Mn 1-x-y O 2 A positive electrode material system, wherein x is 0.3-0.6 and x+y<1.

[0057] [Preparation method of flame retardant]

[0058] One embodiment of the present application provides a method for preparing a flame retardant, characterized in that it comprises the following steps:

[0059] (1) Providing raw materials: a first raw material, a second raw material and a third raw material, wherein:

[0060] The structure of the first raw material is shown in Formula I,

[0061] Where 10≤m≤10000;

[0062] The second raw material structural formula is -R 1 -X 1 -R 2 -, where X 1 , X 2 Each independently selected from -CH 2 -、-CH 2 -O-, -C(=O)-O-, -NH-, -Si(-O-) 3 ; R1 Selected from C 1 -C 10 Alkyl, C 1 -C 10 Aromatic group, C 1 -C 10 One of the polyethers;

[0063] The structure of the third raw material is as shown in Formula II,

[0064] Among them, R 2 , R 3 are independently selected from C 1 -C 10 Alkyl, C 1 -C 10 Aromatic group, C 1 -C 10 Olefins, C 1 -C 10 Alkoxy, C 1 -C 10 Carboxyl, C 1 -C 10 At least one of alcohol, amino, -Cl, -Br, -OH;

[0065] (2) reacting the first raw material, the second raw material, and the third raw material at 20° C.-150° C.;

[0066] (3) washing and drying to obtain the flame retardant.

[0067] [Secondary battery]

[0068] Secondary batteries, also known as rechargeable batteries or storage batteries, refer to batteries that can be used continuously by activating active materials by charging after the battery is discharged. Usually, secondary batteries include positive electrode sheets, negative electrode sheets, separators and electrolytes. During the battery charging and discharging process, active ions (such as lithium ions) are embedded and released back and forth between the positive electrode sheets and the negative electrode sheets. The separator is arranged between the positive electrode sheets and the negative electrode sheets, and its main function is to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte is between the positive electrode sheets and the negative electrode sheets, and its main function is to conduct active ions.

[0069] In some embodiments, a secondary battery includes the flame retardant provided in the first aspect of the present application or the flame retardant prepared according to the preparation method provided in the second aspect of the present application.

[0070] In some embodiments, the secondary battery includes a positive electrode sheet, a negative electrode sheet, and a separator, and the flame retardant is applied to at least one of the positive electrode sheet, the negative electrode sheet, or the separator.

[0071] In some embodiments, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing phosphate, and the secondary battery includes a flame retardant with 1500 ≤ m ≤ 2000 and 80 ≤ n ≤ 100.

[0072] In some embodiments, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes LiNi x Co y Mn 1-x-y O 2 or lithium cobaltate, and the secondary battery includes a flame retardant with 600 ≤ m < 1000 and 30 ≤ n < 50, where 0.6 ≤ x ≤ 0.8 and x + y < 1.

[0073] In some embodiments, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes LiNi x Co y Mn 1-x-y O 2 , and the secondary battery includes a flame retardant with 200 ≤ m < 600 and 1 ≤ n < 30, where x ≥ 0.8 and x + y < 1.

[0074] In some embodiments, the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes LiNi x Co y Mn 1-x-y O 2 , and the secondary battery includes a flame retardant with 1000 ≤ m < 1500 and 50 ≤ n < 80, where 0 < x ≤ 0.6 and x + y < 1.

[0075] [Separator membrane]

[0076] One embodiment of the present application provides an isolation membrane, comprising a porous substrate, which may be a polyolefin porous polymer; and at least one surface flame retardant coating disposed on the organic microporous substrate, wherein the flame retardant layer comprises a flame retardant and a binder. A flame-retardant diaphragm for a secondary battery comprises an organic microporous diaphragm substrate, at least one side of which is provided with a flame-retardant coating, the porous base film is made of at least one of a polyolefin porous polymer, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, polyacrylonitrile, polyimide, polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol or a blend or copolymer system derived from the above polymers; the flame-retardant coating comprises 60-99 parts by weight of a novel flame retardant and 1-40 parts by weight of a binder, the binder being an aqueous binder or an organic binder; the aqueous binder is at least one of sodium methyl cellulose and styrene-butadiene rubber, gelatin and polyvinyl alcohol, and a polyacrylate terpolymer latex; the organic binder is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polymethyl methacrylate. The thickness of the flame retardant layer is 0.5 μm-10 μm, preferably 2 μm-5 μm.

[0077] In some embodiments, the isolation film can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0078] The application scenarios of the flame retardant provided in the present application include but are not limited to the positive electrode, negative electrode or isolation membrane of the battery. Preferably, it is applied to the isolation membrane as a flame retardant coating to prepare a new isolation membrane with flame retardant effect.

[0079] [Positive electrode]

[0080] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0081] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0082] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0083] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds, etc. Examples of lithium phosphates containing olivine structures may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), at least one of a composite material of lithium manganese phosphate and carbon, a composite material of lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0084] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0085] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0086] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0087] [Negative electrode]

[0088] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0089] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0090] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0092] In some embodiments, the negative electrode film layer may further include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0093] In some embodiments, the negative electrode film layer may further include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0094] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0095] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0096] [Electrolytes]

[0097] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0098] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0099] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0100] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0101] In some embodiments, the electrolyte may further include additives. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0102] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0103] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0104] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0105] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 2 The secondary battery 5 is a square structure as an example.

[0106] In some embodiments, reference Figure 3, the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0107] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0108] Figure 4 4 is an example of a battery module. Figure 4 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0109] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0110] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0111] Figure 5 and Figure 6 1 is a battery pack 1 as an example. Figure 5 and Figure 6 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0112] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0113] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0114] Figure 7 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0115] [Example]

[0116] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0117] Example 1

[0118] Preparation of flame retardants

[0119] 50 parts by mass of ammonium polyphosphate, 8 parts by mass of γ-methacryloxypropyltrimethylsilane, and 500 parts by mass of N,N-dimethylformamide were mixed evenly and reacted at 70°C for 5 hours. Then, 25 parts by mass of phosphate acrylate, 2 parts by mass of azobisisobutyronitrile, and 1 part by mass of vanadium pentoxide were added, mixed evenly, reacted at 65°C for 8 hours, washed and dried, and a flame retardant was obtained.

[0120] Preparation of isolation membrane

[0121] 80 parts by mass of the flame retardant and 20 parts by mass of polyvinylidene fluoride were dissolved in N-methylpyrrolidone, mixed evenly, coated on the surface of a single layer of a porous polyethylene separator, and dried to remove the solvent to obtain a separator.

[0122] Preparation of positive electrode

[0123] The positive electrode active material NCM523, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 96.5:1.5:2, and the positive electrode slurry is obtained after being fully stirred and mixed; then the positive electrode slurry is evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain the positive electrode sheet.

[0124] Preparation of negative electrode

[0125] The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water at a weight ratio of 95:2:2:1 and evenly mixed with the solvent deionized water to prepare a negative electrode slurry; then the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and the negative electrode film is obtained after drying, and then the negative electrode sheet is obtained by cold pressing and slitting.

[0126] Preparation of electrolyte

[0127] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte. In the electrolyte, LiPF 6 The concentration is 1 mol / L.

[0128] Preparation of secondary batteries

[0129] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is added. After packaging, standing, forming, aging and other processes, a secondary battery is obtained.

[0130] The preparation methods of Examples 2-4 are similar to those of Example 1, except that the preparation methods of the flame retardant and the isolation film are different.

[0131] Example 2

[0132] Preparation of flame retardants

[0133] 60 parts by mass of ammonium polyphosphate, 5 parts by mass of γ-aminotriethoxysilane, and 2000 parts by mass of a mixed solution of water: ethanol = 1:10 were mixed evenly and reacted at 60°C for 3 hours. Then 20 parts by mass of dimethyl phosphate and 2 parts by mass of aluminum oxide were added, mixed evenly, reacted at 70°C for 5 hours, washed and dried to obtain a new flame retardant.

[0134] Preparation of isolation membrane

[0135] 85 parts by weight of the novel flame retardant and 15 parts by weight of sodium carboxymethyl cellulose were dissolved in a 1:1 mixed solution of water and ethanol, mixed evenly, coated on both sides of a porous polypropylene diaphragm, dried to remove the solvent, and a flame retardant diaphragm for a lithium-ion battery was obtained.

[0136] Example 3

[0137] Preparation of flame retardants

[0138] 70 parts by mass of ammonium polyphosphate, 2 parts by mass of adipic acid, and 1000 parts by mass of N-methylpyrrolidone solution were mixed evenly and reacted at 50°C for 2 hours. Then 40 parts by mass of phenylphosphoric acid and 5 parts by mass of sulfuric acid were added, mixed evenly, reacted at 100°C for 6 hours, washed and dried to obtain a new flame retardant.

[0139] Preparation of isolation membrane

[0140] 70 parts by weight of the novel flame retardant and 30 parts by weight of styrene-butadiene rubber are dissolved in an acetone solution, mixed evenly, coated on both sides of a porous polyimide diaphragm, and dried to remove the solvent, thereby obtaining a flame retardant diaphragm for a lithium-ion battery.

[0141] Example 4

[0142] Preparation of flame retardants

[0143] 30 parts by mass of ammonium polyphosphate, 10 parts by mass of butadiene, 50 parts by mass of triallyl phosphate, 5 parts by mass of copper oxide, 5 parts by mass of benzoyl peroxide, and 6000 parts by mass of chloroform were mixed evenly, reacted at 80° C. for 12 hours, washed and dried, and a new flame retardant was obtained.

[0144] Preparation of isolation membrane

[0145] 75 parts by mass of the novel flame retardant and 25 parts by mass of polymethyl methacrylate were dissolved in N,N-dimethylformamide solution, mixed evenly, coated on one side of a porous polyethylene diaphragm, dried to remove the solvent, and thus a flame retardant diaphragm for lithium-ion batteries was prepared.

[0146] Comparative Example 1

[0147] Except that the separator was replaced with a separator prepared by coating polyphosphate amine on the surface of a commercial polyethylene separator, the rest of the battery was the same as that of Example 1-4.

[0148] Comparative Example 2

[0149] Except that the separator was replaced with a separator prepared by coating phosphoric acid acrylate on the surface of a commercial polyethylene separator, the rest of the battery was the same as that of Example 1-4.

[0150] Experimental Example 1

[0151] (1) Particle size test

[0152] In this application, the Dv50 of a flame retardant is a well-known meaning in the art and can be tested by methods known in the art. For example, it can be directly tested by a laser diffraction particle size distribution meter (such as Malvern Mastersizer 3000 laser particle size analyzer) with reference to the standard GB / T 19077.1-2016. Dv50 refers to the particle size corresponding to the cumulative volume percentage of material particles or powders reaching 50%.

[0153] Table 1 Particle size test

[0154] sample Particle size Dv50 Example 1 500nm Example 2 60nm Example 3 9μm Example 4 1.8μm Comparative Example 1 10μm Comparative Example 2 8μm

[0155] The flame retardants currently available on the market have a relatively large particle size, usually around 10 μm. The large particle size makes it difficult to use in the coating of battery materials. The flame retardant prepared in this application has a moderate particle size, and some of the prepared flame retardants can reach the nanometer level, which is more suitable for the isolation membrane of secondary batteries.

[0156] (2) Acupuncture experiment

[0157] The lithium ion batteries prepared in Examples 1-4 and Comparative Examples 1-2 were charged at a current of 0.5C to an upper voltage limit of 4.35V, and then charged at a constant voltage at a corresponding cut-off voltage, with a cut-off current of 0.2C. A steel needle with a diameter of 3mm was completely inserted into the center of the battery at a speed of 50mm / s, and the insertion state was maintained for 1 hour or the battery surface temperature dropped to 50°C after thermal runaway occurred, and the test was terminated.

[0158] (3) Hot box test

[0159] The lithium ion batteries prepared in Examples 1-4 and Comparative Examples 1-2 were placed in a drying oven and heated to 160° C. at a heating rate of 5° C. / min and maintained for 30 minutes.

[0160] (4) Overcharge test

[0161] The lithium ion batteries prepared in Examples 1-4 and Comparative Examples 1-2 were charged to 120% SOC at 0.5C and observed for 1 hour.

[0162] Table 2 Battery safety performance test comparison

[0163] sample Acupuncture experiment Hot box experiment Overcharge test Example 1 No fire or explosion No fire or explosion No fire or explosion Example 2 No fire or explosion No fire or explosion No fire or explosion Example 3 No fire or explosion No fire or explosion No fire or explosion Example 4 No fire or explosion No fire or explosion No fire or explosion Comparative Example 1 Fire and explosion Fire and explosion Fire and explosion Comparative Example 2 Fire and explosion Fire and explosion Fire and explosion

[0164] Table 2 is a comparison of battery safety performance tests. The batteries of Comparative Examples 1 and 2 caught fire and exploded in all safety tests, while the batteries equipped with the new flame retardant modified diaphragm passed all safety tests without catching fire or exploding. This is because the new flame retardant proposed in this application can not only generate free radicals in the gas phase, capture the hydroxyl free radicals generated by the combustion chain reaction, and interrupt the combustion chain reaction; it can also form a dense heat-insulating and oxygen-isolating layer in the condensed phase, inhibit the diffusion of heat, combustible gas, and oxygen, and break the three combustion elements of the "fire triangle", thereby having an excellent flame retardant effect and ensuring battery safety in multiple dimensions.

[0165] Experimental Example 2

[0166] The lithium ion batteries prepared in Examples 5-8 and Comparative Examples 1-2 were placed in a battery performance test cabinet for testing.

[0167] Capacity retention test

[0168] Use a battery tester to perform charge and discharge tests on the battery cells to evaluate the electrochemical performance of the battery cells. The charge and discharge voltage is set to 3.0V-4.2V, the charge and discharge current is set to 512A (1C), and the battery cell capacity corresponding to the first charge and discharge and the discharge from 3.65V to 2.5V after 500 charge and discharge cycles is read. Take the average value of the three battery cell capacities as the battery cell capacity value of each embodiment. The capacity retention rate of the battery cell after 500 cycles is calculated by the following formula: 500 cycle capacity retention rate = (500th cycle battery cell discharge capacity / first battery cell discharge capacity) × 100%.

[0169] Table 3 Comparison of battery cycle performance tests

[0170] sample 500 cycles capacity retention rate (%) Example 1 86.8 Example 2 87.4 Example 3 87.1 Example 4 87.5 Comparative Example 1 77.5 Comparative Example 2 30.5

[0171] Table 3 is a comparison of the cycle performance of the battery at a charge and discharge rate of 1C at room temperature. Due to the poor interface uniformity, the 500-cycle capacity retention rate of Comparative Example 1 is only 77.5%. The phosphate flame retardant of Comparative Example 2 is incompatible with the electrode material and will cause side reactions in the battery, so the 500-cycle capacity retention rate is only 30.5%. The battery assembled with the modified diaphragm of Examples 1-4 showed excellent cycle performance, with a 500-cycle capacity retention rate of more than 85%. This is because the macromolecular ammonium polyphosphate skeleton rivets the phosphate to prevent it from dissolving in the electrolyte and causing side reactions; in addition, the cross-linking process refines the ammonium polyphosphate particles and improves the interface performance between it and the electrode material, thus showing good cycle performance.

[0172] Experimental Example 3

[0173] Thermal response temperature test

[0174] Using a thermogravimetric-mass spectrometer at a heating rate of 5°C / min, the decomposition products were measured by mass spectrometry and PO·, PO 2 ·、(PO 3 Y) n The temperature of the free radical is the thermal response temperature.

[0175] Table 4 Thermal response temperature test results

[0176] sample Thermal response temperature (℃) Adapting the cathode material system Example 1 390 Lithium Iron Phosphate Example 2 220 <![CDATA[LiNi x Co y Mn 1-x-y O 2 (0.6≤x≤0.8), lithium cobalt oxide]]> Example 3 180 <![CDATA[LiNi x What y Mn 1-x-y ABOUT 2 (x≥0.8)]]> Example 4 260 <![CDATA[LiNi x What y Mn 1-x-y ABOUT 2 (0<x≤0.6)]]> Comparative Example 1 305 Lithium iron phosphate, lithium manganese oxide

[0177] Table 4 is a comparison of the thermal response temperatures of flame retardants. Too high or too low thermal response temperatures are not conducive to the effectiveness of flame retardants. Compared with ammonium polyphosphate, the thermal response temperatures of Examples 1-4 have changed, indicating that the thermal response temperature of flame retardants can be adjusted by designing reaction conditions and molecular structures to adapt them to various positive electrode materials.

[0178] Experimental Example 4

[0179] Flame retardant grade test

[0180] The test is carried out in a combustion box using the vertical combustion method. Cut the sample into a length of 130±3mm and a width of 13±0.3mm, fix it vertically on the fixture, light a Bunsen burner at the bottom of the sample, adjust the flame height to 20±2mm, and present a blue flame. Place the center of the Bunsen burner 10mm below the sample and align it with the center of the lower end of the sample. Start timing, remove the fire source after applying the flame to the sample for 10s, and record the flame burning time of the sample. After the flame of the sample is extinguished, apply the flame again for 10s according to the above method, and record the flame burning time of the sample. Evaluate the flame retardancy of the sample according to the flame burning situation:

[0181] V-0: The vertical sample stops burning within 10 seconds, and no droplets are allowed;

[0182] V-1: The vertical sample stops burning within 30 seconds, and no droplets are allowed;

[0183] V-2: The vertical sample stops burning within 30 seconds, and droplets are allowed;

[0184] HB: The vertical sample stops burning after 30 seconds, and dripping is allowed.

[0185] Table 5 Flame retardant grade comparison

[0186]

[0187]

[0188] Table 5 is a comparison of flame retardant grades. Since free radicals can be generated in the gas phase to capture the hydroxyl radicals of the combustion chain reaction and break the combustion chain reaction, and a dense heat-insulating and oxygen-isolating layer can be formed in the condensed phase to inhibit the diffusion of heat, combustible gas, and oxygen, breaking the three elements of the "fire triangle", the new flame retardants of Examples 1-4 show excellent flame retardant properties with a flame retardant grade of V-0. However, the flame retardant grades of ammonium polyphosphate and dimethyl phosphate are only HB.

[0189] According to the above results, the flame retardants of Examples 1-4 and the batteries of Examples 5-8, when containing the new flame retardant prepared in the present application, have good flame retardant effects, high capacity retention rates, and can be adapted to different positive electrode material systems, thereby improving battery safety performance while expanding usage scenarios.

[0190] In contrast, in Comparative Examples 1-2, the isolation membrane has poor puncture strength and low flame retardancy, and the capacity cycle retention rate is low, and no effective improvement has been achieved in safety performance and versatility in application scenarios.

[0191] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A flame retardant, comprising: First monomer unit: Second monomer unit: The third monomer unit: wherein the first monomer unit and the third monomer unit are connected through the second monomer unit, 10≤m≤10000, 1≤n≤1000, X1 and X2 are independently selected from -CH2-, -CH2-O-, -C(=O)-O-, -NH-, -Si(-O-)3; R1 is selected from C1-C 10 Alkyl, C1-C 10 Aromatic, C1-C 10 One of the polyethers; Y is selected from C1-C 10 Alkyl or C1-C 10 Aromatic group.

2. The flame retardant according to claim 1, characterized in that In the first monomer unit, 200≤m≤2000.

3. The flame retardant according to claim 1 or 2, characterized in that In the third monomer unit, 1≤n≤100.

4. The flame retardant according to claim 1, characterized in that The particle size Dv50 of the flame retardant is 50nm-10μm.

5. The flame retardant according to claim 4, characterized in that The particle size Dv50 of the flame retardant is 200nm-2μm.

6. The flame retardant according to claim 4, characterized in that 1500≤m≤2000,80≤n≤100.

7. The flame retardant according to claim 4, characterized in that 600≤m<1000,30≤n<50.

8. The flame retardant according to claim 4, characterized in that 200≤m<600,1≤n<30.

9. The flame retardant according to claim 4, characterized in that 1000≤m<1500,50≤n<80.

10. A method for preparing a flame retardant, characterized in that: The following steps are involved: (1) Providing raw materials: a first raw material, a second raw material and a third raw material, wherein the structure of the first raw material is as shown in Formula I, Where 10≤m≤10000; The second raw material has a structural formula of -R1-X1-R2-, wherein X1 and X2 are independently selected from -CH2-, -CH2-O-, -C(=O)-O-, -NH-, and -Si(-O-)3; R1 is selected from C1-C 10 Alkyl, C1-C 10 Aromatic, C1-C 10 One of the polyethers; The structure of the third raw material is shown in Formula II, Wherein, R2 and R3 are independently selected from C1-C 10 Alkyl, C1-C 10 Aromatic, C1-C 10 Olefins, C1-C 10 Alkoxy, C1-C 10 Carboxyl, C1-C 10 At least one of alcohol, amino, -Cl, -Br, -OH; (2) reacting the first raw material, the second raw material, and the third raw material at 20° C.-150° C.; (3) washing and drying to obtain the flame retardant.

11. A secondary battery, comprising the flame retardant according to any one of claims 1 to 9 or the flame retardant prepared according to the method provided in claim 10.

12. The secondary battery according to claim 11, characterized in that: The secondary battery comprises a positive electrode sheet, a negative electrode sheet and a separator, and the flame retardant is applied to at least one of the positive electrode sheet, the negative electrode sheet or the separator.

13. The secondary battery according to claim 11 or 12, characterized in that: The secondary battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode collector and a positive electrode film layer formed on the surface of the positive electrode collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing phosphate, and the secondary battery comprises the flame retardant according to claim 6.

14. The secondary battery according to claim 11 or 12, characterized in that: The secondary battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises LiNi x Co y Mn 1-x-y O2 or lithium cobalt oxide, the secondary battery comprises the flame retardant according to claim 7, wherein 0.6≤x≤0.8 and x+y<1.

15. The secondary battery according to claim 11 or 12, characterized in that: The secondary battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises LiNi x Co y Mn 1-x-y O2, the secondary battery comprises the flame retardant according to claim 8, wherein x≥0.8 and x+y<1.

16. The secondary battery according to claim 11 or 12, characterized in that: The secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer formed on the surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes LiNi x Co y Mn 1-x-y O2. The secondary battery includes the flame retardant according to claim 9, wherein 0 < x ≤ 0.6 and x + y < 1.

17. A separation film, characterized in that: It comprises a porous substrate; and a coating, wherein the coating is disposed on at least one surface of the porous substrate, and the coating comprises the flame retardant according to any one of claims 1 to 9 or comprises a flame retardant prepared according to the method of claim 10.

Images