A cyclophosphazene compound containing a triphenylsilicon side group, and a preparation method and application thereof

Abstract

The application relates to the technical field of electrolyte flame retardants, in particular to a cyclophosphazene compound containing a triphenyl silicon side group and a preparation method and application thereof; at least one phenyl silicon side group is connected to a phosphorus atom in the cyclophosphazene compound, and the phosphorus atom and the phenyl silicon side group are connected through an oxygen atom; the structural formula of the cyclophosphazene compound is shown as formula 1; in formula 1, R1 is a halogen atom or a trifluoroethanol group; R2 is at least one of a halogen atom, a trifluoroethanol group and a phenyl silicon side group; the cyclophosphazene compound can organically combine the flame retardancy, film forming property, overcharge prevention ability and acid removal ability of electrolyte together; due to the excellent flame retardancy, the cyclophosphazene compound can be added into electrolyte in a low amount without affecting the performance of the electrolyte.

Description

Technical Field

[0001] This application relates to the field of electrolyte flame retardant technology, and in particular to a cyclophosphonitrile compound containing a triphenylsilane side group, its preparation method and application. Background Technology

[0002] Lithium-ion batteries are one of the most widely used chemical energy storage methods, and are already widely used in consumer digital electronic devices, new energy vehicles, energy storage base stations, aerospace and military equipment, and other fields. As one of the core materials of lithium-ion batteries, the electrolyte plays a crucial role. The electrolyte consists of three parts: lithium salt, solvent, and functional additives. Among these, functional additives play an important role in the energy density, cycle life, safety performance, and operating temperature range of lithium batteries. Based on their function, electrolyte additives can be divided into flame retardants, positive electrode protectants, lithium salt stabilizers, corrosion inhibitors, and SEI film-forming agents. The primary function of flame retardants is to improve the safety of the electrolyte without significantly reducing battery performance. Currently, most electrolytes use organophosphorus flame retardants, such as TMP (trimethyl phosphate), TBP (tributyl phosphate), and cyclophosphinitrogen compounds. Cyclophosphinitrogen compounds are considered ideal flame retardants because their cyclic structure allows for a higher phosphorus content, thus improving the flame retardant effect and reducing the amount of flame retardant needed.

[0003] Even with the aforementioned properties, cyclophosphonitrile compounds require an addition level of at least 10% in the electrolyte to achieve a good flame-retardant effect. However, at this level, various performance indicators of the lithium battery will decrease due to the additive's influence, such as increased impedance and reduced cycle life. Therefore, providing a cyclophosphonitrile compound containing triphenylsilane side groups to reduce the required addition amount is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application provides a cyclophosphonitrile compound containing a triphenylsilane side group, its preparation method, and its application, in order to solve the technical problem of excessive addition of cyclophosphonitrile compounds in functional additives of electrolytes in the prior art.

[0005] In a first aspect, this application provides a cyclophosphonitrile compound containing a triphenylsilane side group, wherein at least one phenylsilane side group is attached to the phosphorus atom in the cyclophosphonitrile compound, and the phosphorus atom and the phenylsilane side group are connected by an oxygen atom;

[0006] The structural formula of the cyclophosphonitrile compound is shown in Formula 1.

[0007]

[0008] In Equation 1,

[0009] R1 is a halogen atom or a trifluoroethanol group;

[0010] R2 is at least one of a halogen atom, a trifluoroethanol group, and a phenylsilane side group.

[0011] Optionally, the cyclophosphonitrile compound has a molecular structure as shown in Formula 2.

[0012]

[0013] Optionally, the cyclophosphonitrile compound has a molecular structure as shown in Formula 3.

[0014]

[0015] Secondly, this application provides a method for preparing the cyclophosphonitrile compound described in the first aspect, the method comprising:

[0016] Triphenylsilanol was added to a strong alkaline organic suspension and stirred for the first time to obtain a first mixed solution containing triphenylsilanol organic salt;

[0017] The first mixed solution was added to hexachlorocyclotriphosphazene, and the mixture was stirred a second time, followed by a third stirring and filtration to obtain the first filtrate.

[0018] The first filtrate was dried under vacuum to obtain a cyclophosphonitrile compound.

[0019] The strong base, the hexachlorocyclotriphosphazene, and the solvent of the first mixed solution are all low-boiling-point inert aprotic solvents.

[0020] Optionally, the molar ratio of the triphenylsilanol organic salt to the hexachlorocyclotriphosphazene is 1 to 6.

[0021] Thirdly, this application provides a method for preparing the cyclophosphonitrile compound described in the first aspect, the method comprising:

[0022] Triphenylsilanol was added to a strong alkaline organic suspension and stirred for the first time to obtain a first mixed solution containing triphenylsilanol organic salt;

[0023] Trifluoroethanol was added to a strongly alkaline organic suspension and stirred for the first time to obtain a second mixed solution containing trifluoroethanol organic salts.

[0024] The first mixed solution was added to hexachlorocyclotriphosphazene and stirred for the second time. Then the second mixed solution was added and stirred for the second time. Finally, the mixture was stirred for the third time and filtered to obtain the second filtrate.

[0025] The second filtrate was dried under vacuum to obtain a cyclophosphonitrile compound.

[0026] The solvents for the strong base, the first mixed solution, the second mixed solution, and the hexachlorocyclotriphosphazene are all low-boiling-point inert aprotic solvents.

[0027] Optionally, the second mixed solution, the first mixed solution, and the hexachlorocyclotriphosphazene satisfy the following:

[0028] M+N=6Q, and M:N=5~1 / 5;

[0029] Wherein, M is the amount of the trifluoroethanol organic salt, N is the amount of the triphenylsilanol organic salt, and Q is the amount of the hexachlorocyclotriphosphazene.

[0030] Optionally, the low-boiling-point inert aprotic solvent includes at least one of tetrahydrofuran, diethyl ether, acetone, dioxane, dioxane, toluene, and xylene.

[0031] Optionally, the first stirring time is 4 hours to 12 hours; and / or,

[0032] The second stirring time is 4h to 24h; and / or,

[0033] The third stirring time is 12h to 24h, and the temperature of the third stirring is 30℃ to 60℃.

[0034] Fourthly, this application provides an application of a cyclophosphonitrile compound containing a triphenylsilane side group, the application including the use of the cyclophosphonitrile compound described in the first aspect as a flame retardant in lithium battery electrolytes.

[0035] The technical solutions provided in this application have the following advantages compared with the prior art:

[0036] This application provides a cyclophosphonitrile compound containing triphenylsilane side groups. Compared to traditional cyclotriphosphonitrile flame retardants, it introduces phenylsilane side groups onto the phosphorus atoms and uses oxygen atoms to connect the silicon and phosphorus atoms linking the phenylsilane side groups. This increases the overall bond energy of the cyclophosphonitrile compound, thereby reducing the release of flammable gases, increasing the flash point of the cyclophosphonitrile compound, and consequently increasing the overall flash point of the electrolyte. Furthermore, the silicon-oxygen structure formed by the silicon and oxygen atoms also possesses excellent film-forming properties, enabling the flame retardant to rapidly form a film in the electrolyte, thus improving the film-forming performance of the electrolyte. Simultaneously, benzene... The triphenylsilane side group can effectively remove hydrogen fluoride and phosphorus pentafluoride generated during the operation of the electrolyte, improving the electrolyte's acid removal ability. Furthermore, the introduction of the benzene ring can also cooperate with the polymerization-promoting effect of oxygen atoms, giving the electrolyte containing the cyclophosphonitrile compound an overcharge prevention effect, which can further improve the electrolyte's flame retardancy. Therefore, the cyclophosphonitrile compound containing the above-mentioned triphenylsilane side group can organically combine the improvement of the electrolyte's flame retardancy, film-forming properties, overcharge prevention ability, and acid removal ability. Due to its excellent flame retardancy, it can be added to the electrolyte at a low dosage without affecting the electrolyte's performance. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic flowchart of a method for preparing cyclophosphonitrile compounds containing triphenylsilane side groups provided in the embodiments of this application;

[0040] Figure 2 This is a schematic diagram of another method for preparing cyclophosphonitrile compounds containing triphenylsilane side groups, provided in the embodiments of this application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0043] like Figure 1 As shown, this application provides a cyclophosphonitrile compound containing a triphenylsilane side group, wherein at least one phenylsilane side group is attached to the phosphorus atom in the cyclophosphonitrile compound, and the phosphorus atom and the phenylsilane side group are connected by an oxygen atom.

[0044] The structural formula of the cyclophosphonitrile compound is shown in Formula 1.

[0045]

[0046] In Equation 1,

[0047] R1 is a halogen atom or a trifluoroethanol group;

[0048] R2 is at least one of a halogen atom, a trifluoroethanol group, and a phenylsilane side group.

[0049] In this embodiment, by grafting phenylsilane side groups onto the phosphorus atoms of the cyclotriphosphazene flame retardant, and then using oxygen atoms to connect the silicon atoms and phosphorus atoms in the phenylsilane side groups, the release of flammable gases can be effectively reduced, and the flash point of the flame retardant can be increased, thereby increasing the flash point of the electrolyte. Therefore, under the same flame retardant performance requirements, the amount of flame retardant added can be effectively reduced.

[0050] The phenylsilane side group is a type of active group with a silicon atom at the center, and the three side chains of the silicon atom are connected to phenyl groups to form phenylsilane groups.

[0051] In some alternative embodiments, the cyclophosphonitrile compound has a molecular structure as shown in Formula 2.

[0052]

[0053] In this embodiment of the application, by refining the R1 and R2 groups in Formula 1 to be both F, pentafluorotriphenylsiloxycyclotriphosphazene can be obtained. Since both R1 and R2 groups are halogen atoms, the pentafluorotriphenylsiloxycyclotriphosphazene has good flame retardancy and can effectively improve the flash point of the electrolyte. Therefore, under the same flame retardant performance requirements, the amount of flame retardant added can be effectively reduced.

[0054] Meanwhile, the phenylsilane side group can remove hydrogen fluoride and phosphorus pentafluoride from the electrolyte, which can improve the deacidification ability of the electrolyte. The silicon-oxygen structure has good film-forming properties, and the introduction of the benzene ring can also cooperate with the polymerization-promoting effect of oxygen atoms, so that the electrolyte containing cyclophosphonitrile compounds also has the effect of preventing overcharging.

[0055] In some alternative embodiments, the cyclophosphonitrile compound has a molecular structure as shown in Formula 3.

[0056]

[0057] In this embodiment of the application, by refining the R1 group in Formula 1 to be a trifluoroethanol group and the R2 group to be a trifluoroethanol group, a triphenylsilanol co-substituted phosphazene derivative can be obtained. Since the derivative contains multiple trifluoroethanol groups, it can greatly improve the bond energy of the flame retardant and improve the flame retardant performance of the flame retardant. It can also effectively improve the flash point of the electrolyte. Therefore, under the same flame retardant performance requirements, the amount of flame retardant added can be effectively reduced.

[0058] Meanwhile, the phenylsilane side group can remove hydrogen fluoride and phosphorus pentafluoride from the electrolyte, which can improve the deacidification ability of the electrolyte. The silicon-oxygen structure has good film-forming properties, and the introduction of the benzene ring can also cooperate with the polymerization-promoting effect of oxygen atoms, so that the electrolyte containing cyclophosphonitrile compounds also has the effect of preventing overcharging.

[0059] like Figure 1 As shown, based on a general inventive concept, this application provides a method for preparing the cyclophosphonitrile compound, the method comprising:

[0060] S1. Add triphenylsilanol to a strong base organic suspension and stir for the first time to obtain a first mixed solution containing triphenylsilanol organic salt;

[0061] S2. Add the first mixed solution to hexachlorocyclotriphosphazene, and stir for the second time, then stir and filter for the third time to obtain the first filtrate;

[0062] S3. Vacuum dry the first filtrate to obtain a cyclophosphonitrile compound;

[0063] The strong base, the hexachlorocyclotriphosphazene, and the solvent of the first mixed solution are all low-boiling-point inert aprotic solvents.

[0064] In the embodiments of this application, strong base refers to alkaline oxides with a pH greater than that of sodium hydroxide, including alkaline earth metal hydrides such as sodium hydride or lithium hydride.

[0065] Low-boiling-point inert aprotic solvents refer to a class of inert solvents with extremely weak or no proton self-discharge reaction tendency. These solvents have low boiling points, so they can generate corresponding organic salt mixed solutions during the reaction stage, which facilitates the subsequent acquisition of pentafluorotriphenylsiloxycyclotriphosphazene products with molecular structures as shown in Formula 2.

[0066] The cations in triphenylsilanol organic salts correspond to the cations used in strong bases. For example, when sodium hydride is used as a strong base, the resulting first mixed solution contains sodium triphenylsilanol; when lithium hydride is used as a strong base, the resulting first mixed solution contains lithium triphenylsilanol.

[0067] This method is for the preparation of the above-mentioned cyclophosphonitrile compound. The specific structure of the cyclophosphonitrile compound can be referred to in the above embodiments. Since this method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0068] In some alternative embodiments, the molar ratio of the triphenylsilanol organic salt to the hexachlorocyclotriphosphazene is 1 to 6.

[0069] In the embodiments of this application, by controlling the specific molar ratio of triphenylsilanol organic salt and hexachlorocyclotriphosphazene, the reaction between triphenylsilanol organic salt and hexachlorocyclotriphosphazene can be completed in a low-boiling-point inert aprotic solution, thereby obtaining the pentafluorotriphenylsiloxycyclotriphosphazene product shown in Formula 2.

[0070] The ratio of the amounts of these substances can be 1, 2, 3, 4, 5, or 6.

[0071] like Figure 2 As shown, based on a general inventive concept, this application provides a method for preparing the cyclophosphonitrile compound, the method comprising:

[0072] S1. Add triphenylsilanol to a strong base organic suspension and stir for the first time to obtain a first mixed solution containing triphenylsilanol organic salt;

[0073] S2. Add trifluoroethanol to the strong base organic suspension and stir for the first time to obtain a second mixed solution containing trifluoroethanol organic salt;

[0074] S3. Add the first mixed solution to hexachlorocyclotriphosphazene and stir for the second time, then add the second mixed solution and stir for the second time, then stir for the third time and filter to obtain the second filtrate;

[0075] S4. Vacuum dry the second filtrate to obtain a cyclophosphonitrile compound;

[0076] The solvents for the strong alkali, the first mixed solution, the second mixed solution, and the hexachlorocyclotriphosphazene are all low-boiling-point inert aprotic solvents.

[0077] In the embodiments of this application, strong base refers to alkaline oxides with a pH greater than that of sodium hydroxide, including alkaline earth metal hydrides such as sodium hydride or lithium hydride.

[0078] Low-boiling-point inert aprotic solvents refer to a class of inert solvents with extremely weak or no proton self-discharge reaction tendency. These solvents have low boiling points, so they can generate corresponding organic salt mixed solutions during the reaction stage, which facilitates the subsequent acquisition of pentafluorotriphenylsiloxycyclotriphosphazene products with molecular structures as shown in Formula 2.

[0079] The cations in triphenylsilanol organic salts correspond to the cations used in strong bases. For example, when sodium hydride is used as a strong base, the resulting first mixed solution contains sodium triphenylsilanol; when lithium hydride is used as a strong base, the resulting first mixed solution contains lithium triphenylsilanol.

[0080] The cations in trifluoroethanol organic salts correspond to the cations used in strong bases. For example, when sodium hydride is used as a strong base, the resulting first mixed solution contains sodium trifluoroethanol; when lithium hydride is used as a strong base, the resulting first mixed solution contains lithium trifluoroethanol.

[0081] This method is for the preparation of the above-mentioned cyclophosphonitrile compound. The specific structure of the cyclophosphonitrile compound can be referred to in the above embodiments. Since this method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0082] In some alternative embodiments, the second mixed solution, the first mixed solution, and the hexachlorocyclotriphosphazene satisfy the following:

[0083] M+N=6Q, and M:N=5~1 / 5;

[0084] Wherein, M is the amount of the trifluoroethanol organic salt, N is the amount of the triphenylsilanol organic salt, and Q is the amount of the hexachlorocyclotriphosphazene.

[0085] In the embodiments of this application, by controlling the specific mass ratio of trifluoroethanol organic salt, triphenylsilanol organic salt and hexachlorocyclotriphosphazene, the reaction between trifluoroethanol organic salt, triphenylsilanol organic salt and hexachlorocyclotriphosphazene can be completed, thereby obtaining the triphenylsilanol co-substituted phosphazene derivative shown in Formula 3.

[0086] The ratio of the amounts of these substances can be 5:5, 4:5, 3:5, 2:5, or 1:5.

[0087] In some alternative embodiments, the low-boiling-point inert aprotic solvent includes at least one of tetrahydrofuran, diethyl ether, acetone, dioxane, dioxane, toluene, and xylene.

[0088] In the embodiments of this application, the specific type of low-boiling-point inert aprotic solvent is controlled so that the reaction between sodium triphenylsilanoate / lithium and hexachlorocyclotriphosphazene is complete, or the reaction between sodium trifluoroethanol / lithium, sodium triphenylsilanoate / lithium and hexachlorocyclotriphosphazene is complete, thereby obtaining a cyclophosphazene compound with the structure shown in Formula 2 or Formula 3.

[0089] In some optional embodiments, the first stirring time is 4h to 12h; and / or,

[0090] The second stirring time is 4h to 24h; and / or,

[0091] The third stirring time is 12h to 24h, and the temperature of the third stirring is 30℃ to 60℃.

[0092] In this embodiment, controlling the specific time of the first stirring allows for thorough mixing of the strong alkali and triphenylsilanol, resulting in a first mixed solution containing triphenylsilanol organic salt, which facilitates subsequent reactions.

[0093] The first stirring time can be 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours.

[0094] By controlling the specific time of the second stirring and the specific temperature and time of the third stirring, the triphenylsilyl alcohol organic salt and hexachlorocyclotriphosphazene can be fully mixed and reacted, or the trifluoroethanol organic salt can be further fully mixed with the triphenylsilyl alcohol organic salt and hexachlorocyclotriphosphazene, and then the subsequent reaction can be completed by the third stirring, thereby obtaining the pentafluorotriphenylsiloxycyclotriphosphazene product shown in Formula 2 or the triphenylsilyl alcohol co-substituted phosphazene derivative shown in Formula 3.

[0095] The second stirring time can be 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours.

[0096] The third stirring time can be 12h, 14h, 16h, 18h, 20h, 22h, or 24h.

[0097] The temperature of the third stirring can be 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, or 60℃.

[0098] Based on a general inventive concept, embodiments of this application provide an application of a cyclophosphonitrile compound containing a triphenylsilane side group, the application including the use of the cyclophosphonitrile compound as a flame retardant in lithium battery electrolytes.

[0099] In this embodiment, the lithium battery electrolyte is composed of lithium salt, organic solvent, phosphazene derivative flame retardant additives, and other functional additives.

[0100] The phosphazene derivative flame retardant additive is a triphenylsilanol co-substituted phosphazene derivative and / or pentafluorotriphenylsiloxycyclotriphosphazene.

[0101] The lithium salt includes at least one of LiPF6, LiClO4, LiAsF6, LiBF4, LiCH3SO3, LiCF3SO3, LiBOB, LiDFOB, LiN(FSO2)2 and LiN(CF3SO2)2.

[0102] The organic solvent includes at least one of carbonates, ethers, carboxylic acid esters, phosphate esters, and fluorinated organic solvents; wherein the carbonate organic solvent is a cyclic carbonate and / or a chain carbonate compound.

[0103] The cyclic carbonate compounds include at least one of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate.

[0104] The chain carbonate compounds include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl ethyl carbonate (EMC), and carbonate derivatives synthesized from straight-chain or branched aliphatic monools with 3-8 carbon atoms and carbon dioxide.

[0105] The ether organic solvents include at least one of tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxolane, dimethoxymethane, 1,2-dimethoxyethylene, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0106] The carboxylic acid ester organic solvent includes at least one of methyl formate, ethyl formate, ethyl acetate (EA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), propyl butyrate (PB), and butyl butyrate (BB).

[0107] The phosphate ester organic solvent is selected from at least one of trimethyl phosphate (TMP), triethyl phosphate (TEP), and tributyl phosphate (TBP).

[0108] Other functional additives are additives well known to those skilled in the art, including at least one of vinylene carbonate (VC), ethylene ethylene carbonate (VEC), fluoroethylene carbonate (FEC), propane sulfonate lactone (PS), 1-propylene-1,3-sulfonate lactone (PST), butane sulfonate lactone (BS), vinyl sulfate (DTD), adiponitrile (ADN), and succinate (SN).

[0109] This application is based on the above-mentioned cyclophosphonitrile compound. The specific structure of the cyclophosphonitrile compound can be referred to in the above embodiments. Since this application adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0110] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0111] Example 1

[0112] like Figure 2 As shown, 50.2 g of trifluoroethanol was added dropwise to a tetrahydrofuran suspension containing 12 g of sodium hydride under ice bath conditions, and stirred for 10 h to obtain a tetrahydrofuran solution of sodium trifluoroethanol.

[0113] Under ice bath conditions, 27.6 g of a tetrahydrofuran solution of triphenylsilanol was added dropwise to a tetrahydrofuran suspension containing 12 g of sodium hydride, and stirred for 10 h to obtain a tetrahydrofuran solution of sodium triphenylsilanol.

[0114] The prepared sodium triphenylsilanoate tetrahydrofuran solution was added to a tetrahydrofuran solution containing 34.76 g of hexachlorocyclotriphosphazene under ice bath conditions, and stirred for 24 h. Then, sodium trifluoroethanol tetrahydrofuran solution was added dropwise, and stirred for 24 h. Finally, stirring was continued for 24 h at 60 °C.

[0115] The product was filtered and vacuum dried to obtain a triphenylsilanol co-substituted phosphazene derivative (as shown in Formula 3), with a yield of 83%.

[0116] Example 2

[0117] Comparing Example 2 with Example 1, the difference between Example 2 and Example 1 is as follows:

[0118] like Figure 2 As shown, 50.2 g of trifluoroethanol was added dropwise to a tetrahydrofuran suspension containing 12 g of sodium hydride under ice bath conditions, and stirred for 12 h to obtain a tetrahydrofuran solution of sodium trifluoroethanol.

[0119] A solution of 69.1 g of triphenylsilanol in tetrahydrofuran was added dropwise to a suspension of 6 g of sodium hydride in tetrahydrofuran under ice bath conditions, and stirred for 12 h to obtain a solution of sodium triphenylsilanol in tetrahydrofuran.

[0120] The prepared sodium triphenylsilanoate tetrahydrofuran solution was added to a tetrahydrofuran solution containing 43.45 g of hexachlorocyclotriphosphazene under ice bath conditions, and stirred for 20 h. Then, sodium trifluoroethanol tetrahydrofuran solution was added dropwise, and stirred for 20 h. Finally, stirring was continued for 20 h at 50 °C.

[0121] The product was filtered and vacuum dried to obtain a triphenylsilanol co-substituted phosphazene derivative (as shown in Formula 3), with a yield of 79%.

[0122] Example 3

[0123] Comparing Example 3 with Example 1, the difference between Example 3 and Example 1 is as follows:

[0124] like Figure 2 As shown, 50.2 g of trifluoroethanol was added dropwise to a dioxane suspension containing 12 g of lithium hydride under ice bath conditions, and stirred for 8 hours to obtain a dioxane solution of lithium trifluoroethanol.

[0125] Under ice bath conditions, 138.2 g of triphenylsilanol dioxane solution was added dropwise to a dioxane suspension containing 12 g of lithium hydride, and stirred for 8 h to obtain a triphenylsilanol lithium dioxane solution.

[0126] The prepared triphenylsilane lithium dioxane solution was added to a dioxane solution containing 57.94 g of hexachlorocyclotriphosphazene under ice bath conditions, and stirred for 18 h. The dioxane solution of trifluoroethanol lithium was then added dropwise, and stirred for 18 h. Finally, stirring was continued for 18 h at 50 °C.

[0127] The product was filtered and vacuum dried to obtain a triphenylsilanol co-substituted phosphazene derivative (as shown in Formula 3), with a yield of 71%.

[0128] Example 4

[0129] Comparing Example 4 with Example 1, the difference between Example 4 and Example 1 is as follows:

[0130] like Figure 1As shown, a tetrahydrofuran solution containing 165.8 g of triphenylsilanol was added dropwise to a tetrahydrofuran suspension containing 14.39 g of sodium hydride under ice bath conditions, and the mixture was stirred for 12 h to obtain a tetrahydrofuran solution of sodium triphenylsilanol.

[0131] The prepared sodium triphenylsilanoate tetrahydrofuran solution was added to a tetrahydrofuran solution containing 149.32 g of hexafluorocyclotriphosphazene under ice bath conditions, and stirred for a second time for 24 h, and then stirred for a third time at 60 °C for 24 h.

[0132] The product was filtered and vacuum dried to obtain pentafluorotriphenylsiloxycyclotriphosphazene (as shown in Formula 2), with a yield of 94%.

[0133] Example 5

[0134] Comparing Example 5 with Example 1, the difference between Example 5 and Example 1 is as follows:

[0135] A solution of triphenylsilanol in tetrahydrofuran containing 165.8 g of triphenylsilanol was added dropwise to a suspension of lithium hydride containing 14.39 g of lithium dioxane under ice bath conditions, and stirred for 10 h to obtain a solution of lithium triphenylsilanol in dioxane.

[0136] The prepared triphenylsilane lithium dioxane solution was added to a dioxane solution containing 74.66 g of hexafluorocyclotriphosphazene under ice bath conditions, and stirred for 16 h for the second time. Then, stirring was continued for 16 h at 50 °C for the third time.

[0137] The product was filtered and vacuum dried to obtain pentafluorotriphenylsiloxycyclotriphosphazene (as shown in Formula 2), with a yield of 88%.

[0138] Example 6

[0139] Comparing Example 6 with Example 1, the difference between Example 6 and Example 1 is as follows:

[0140] A toluene solution containing 165.8 g of triphenylsilanol was added dropwise to a toluene suspension containing 14.39 g of lithium hydride under ice bath conditions, and the mixture was stirred for 8 hours to obtain a toluene solution of lithium triphenylsilanol.

[0141] The toluene solution of the prepared triphenylsilyl lithium was added to a toluene solution containing 24.88 g of hexafluorocyclotriphosphazene under ice bath conditions, and stirred for 13 h for the second time. Then, stirring was continued for 13 h at 40 °C for the third time.

[0142] The product was filtered and vacuum dried to obtain pentafluorotriphenylsiloxycyclotriphosphazene (as shown in Formula 2), with a yield of 62%.

[0143] Relevant experimental and effect data:

[0144] Experiments were conducted using two cyclotriphosphazene-based flame retardants obtained in Examples 1-6 to investigate the flame retardant effect, overcharge prevention effect, and battery cycle performance of the added electrolyte. The lithium salt purity was ≥99.9%, the organic solvent purity was ≥99.98%, and the additive purity was ≥99.9%. The abbreviations for each substance are as follows:

[0145] Lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalate borate) (LiBOB), ethylene carbonate (EC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), triethyl phosphate (TEP), tetraethylene glycol dimethyl ether (TEGDME), fluoroethylene carbonate (FEC), ethyl 2,2,2-trifluoroacetate (TFEA), diethyl fluorocarbonate (DFDEC), trifluoroethyl methyl carbonate (FEMC), vinylene carbonate (VC), propanesulfonate lactone (PS), 1-propene-1,3-sulfonate lactone (PST), ethylene sulfate (DTD), adiponitrile (ADN), pentafluorotriphenylsiloxycyclotriphosphazene (PFTPSiCPN) as shown in Formula 2, and triphenylsilanol co-substituted phosphazene (TPSiCPN) as shown in Formula 3.

[0146] The electrolyte preparation process was carried out in an argon glove box, where the moisture and oxygen content were controlled below 0.5 ppm. 1 L of solvent was mixed with lithium salt in a certain proportion, and then a certain amount of additives were added and stirred thoroughly.

[0147] Tests showed that the electrolyte contained less than 20 ppm of water and less than 50 ppm of free acid.

[0148] The battery, with a capacity of 2Ah, was assembled in a glove box filled with high-purity argon (99.99%) gas, with a high-nickel electrode as the positive electrode, a silicon-carbon electrode as the negative electrode, a polyolefin separator, and a selected electrolyte. After pre-charging and formation, it was left to stand for 12 hours before the next test.

[0149] In the experimental example, the self-extinguishing time test was conducted as follows: 0.5g of electrolyte was placed in a glass dish with a diameter of 7cm, and then ignited using an igniter, exposing the electrolyte to the flame for 3 seconds. If ignition occurred, the time from when the igniter was removed (after 3 seconds) until the flame was completely extinguished was recorded, and converted into the combustion time per unit mass of electrolyte (in grams). -1 (Given). All measurements were performed 5 times, and the average value was taken as the self-extinguishing time.

[0150] In the experimental example, constant current and constant voltage charging / constant current discharging were used to conduct charge and discharge tests on the battery at a 1C rate.

[0151] The results are shown in Table 1.

[0152] Table 1. Composition, self-extinguishing time, overcharge protection, and room temperature cycling performance of various electrolytes.

[0153]

[0154]

[0155] As shown in Table 1, adding cyclophosphonitrile compounds containing triphenylsilane side groups to the electrolyte can significantly improve the flame retardant properties of the electrolyte. For example, the electrolytes in experimental groups 4 and 9, after adding 8% to 9% of cyclophosphonitrile compounds, can achieve a completely non-flammable effect (self-extinguishing time of 0s) and also exhibit excellent overcharge protection. However, in the prior art, the mass fraction of flame retardant additives in the electrolyte generally needs to reach 10% to 40% to achieve a good non-flammable effect. However, a higher mass fraction of flame retardant additives will increase the viscosity of the electrolyte, affecting the conductivity of the electrolyte and thus affecting the battery performance of the lithium battery.

[0156] As shown in Table 1, adding cyclophosphonitrile compounds containing triphenylsilane side groups to the electrolyte can improve the battery's electrical performance and maintain good cycle performance even without other additives, as seen in experimental groups 5 and 10.

[0157] In summary, traditional flame retardant additives can reduce the flammability of electrolytes, but the addition of most flame retardant additives has a significant negative impact on the performance of lithium batteries. Even a small amount of flame retardant additives can reduce the performance of lithium batteries.

[0158] In this application embodiment, the cyclophosphonitrile compound containing triphenylsilane side groups is provided as a flame retardant additive. When added to the electrolyte, only a small amount is needed to improve the cycle performance of the battery while ensuring excellent flame retardant effect and overcharge prevention effect. Therefore, the cyclophosphonitrile compound can reduce the amount of electrolyte additives added, thereby reducing the production cost of the electrolyte.

[0159] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0160] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0161] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A cyclophosphonitrile compound containing a triphenylsilane side group, characterized in that, The structural formula of the cyclophosphonitrile compound is selected from any of the following: 、 。 2. The application of a cyclophosphonitrile compound containing a triphenylsilane side group, characterized in that, The application is to use the cyclophosphonitrile compound as described in claim 1 as a flame retardant in lithium battery electrolytes.

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