Electrolyte, lithium ion battery and electric device

Abstract

The application relates to the field of lithium ion batteries, and discloses a cyclotriphosphazene compound, a preparation method of the cyclotriphosphazene compound, an electrolyte, a lithium ion battery and an electric device. The cyclotriphosphazene compound comprises a structure shown in formula I, wherein R1-R6 are selected from chain hydrocarbon groups or cycloalkyl groups with 1-20 carbon atoms. The cyclotriphosphazene compound is connected with polymerizable acrylate on a phosphazene structure, can rapidly solidify liquid electrolyte under the action of a thermal initiator under battery overheating conditions, forms a highly crosslinked solid polymer, and if the solidification speed is not enough to cause combustion, the phosphazene and other flame-retardant components in the molecule can further retard the flame, so that the cyclotriphosphazene compound has both gas phase and condensed phase flame-retardant mechanisms, can avoid internal short circuit and thermal runaway of the lithium ion battery under overheating conditions, and simultaneously has the characteristics of low toxicity, high efficiency and good compatibility, and can be widely applied to the field of lithium battery flame retardation.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and more particularly to an electrolyte, a lithium-ion battery, and an electrical device. Background Technology

[0002] With the development of the electric vehicle industry, higher requirements have been placed on power batteries. New power batteries must have higher energy density, longer cycle life, and a wider electrochemical window. However, the increase in energy density can lead to some safety issues. In recent years, safety accidents caused by overheating of lithium-ion batteries have been frequent.

[0003] Currently, one solution to this problem is to add some flame-retardant additives to the electrolyte. However, traditional flame retardants do not significantly improve battery safety. Therefore, it is necessary to provide an electrolyte that can improve the above-mentioned problems. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a cyclotriphosphazene compound and a method for preparing the same, so that the cyclotriphosphazene compound can significantly improve the flame retardant effect.

[0005] Another objective of this application is to provide an electrolyte based on the cyclotriphosphazene compounds described in this application, which is non-ignitable or has a short ignition and extinguishing time when exposed to an open flame.

[0006] Another object of this application is to provide a lithium-ion battery and an electrical device based on the electrolyte.

[0007] To achieve the above objectives, as a first aspect of this application, a cyclotriphosphazene compound is provided, comprising the structure shown in Formula I:

[0008]

[0009] Among them, R1 to R6 are selected from chain hydrocarbon groups or cycloalkyl groups with 1 to 20 carbon atoms.

[0010] Optionally, at least one of R1 to R6 comprises at least one of the following groups:

[0011]

[0012] Optionally, the compound with the structure shown in Formula I includes one or two of the following compounds:

[0013]

[0014]

[0015] As a second aspect of this application, a method for preparing the aforementioned cyclotriphosphazene compound is provided, comprising:

[0016] Using trichlorophosphazene, HO-R-OH (R being at least one of R1 to R6) and acryloyl chloride as reactants, a cyclic triphosphazene compound with the structure of formula I is generated.

[0017] Optionally, the method for preparing the cyclotriphosphazene compound includes:

[0018] A substitution reaction was carried out using trichlorophosphazene and HO-R-OH (R being at least one of R1 to R6) as reactants to generate an intermediate product with the structure of formula II.

[0019] The intermediate of Formula II undergoes a substitution reaction with acryloyl chloride to generate a cyclotriphosphazene compound of Formula I.

[0020]

[0021] As a third aspect of this application, an electrolyte is provided, comprising a lithium salt, an organic solvent, and a first additive, wherein the first additive is a cyclotriphosphazene compound as described above.

[0022] Optionally, the electrolyte further includes a second additive, which includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl peroxide, and methyl ethyl ketone peroxide.

[0023] Optionally, the mass of the cyclotriphosphazene compound accounts for 0.5% to 10% of the total mass of the electrolyte.

[0024] Optionally, the mass ratio of the second additive to the cyclotriphosphazene compound is 1:(50-500);

[0025] As a fourth aspect of this application, a lithium-ion battery is provided, comprising the electrolyte described in this application.

[0026] As a fifth aspect of this application, an electrical device is also provided, including the lithium-ion battery described above.

[0027] Compared with currently available commercial cyclotriphosphazene flame retardant additives, the cyclotriphosphazene compounds described in this application have polymerizable acrylates linked to the phosphazene structure. Under battery overheating conditions, the liquid electrolyte is rapidly solidified by a thermal initiator to form a highly cross-linked solid polymer. If the solidification speed is insufficient and combustion occurs, the flame retardant components such as phosphazenes in the molecule can further retard the flame. Therefore, the cyclotriphosphazene compounds of this application have both gas-phase and condensed-phase flame retardant mechanisms, which can prevent internal short circuits and thermal runaway of lithium-ion batteries under overheating conditions. At the same time, they have the characteristics of low toxicity, high efficiency and good compatibility, and can be widely used in the field of lithium battery flame retardancy. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application.

[0029] Figure 1 The figure shows the open-circuit voltage (OCV) of the conventional battery in Comparative Example 2 and the safety battery in Example 3 when the temperature rises. Detailed Implementation

[0030] This application discloses a cyclotriphosphazene compound, its preparation method, as well as an electrolyte, lithium-ion battery, and electrical device. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired results. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products and processes described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the products and processes described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0031] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0032] In a first aspect of this application, a cyclotriphosphazene compound having both a phosphazene structure and an acrylate structure is provided, comprising the structure shown in Formula I:

[0033]

[0034] Wherein, R1 to R6 are selected from chain hydrocarbon groups or cycloalkyl groups having 1 to 20 carbon atoms; in some embodiments of this application, the number of carbon atoms is 1 to 10; in other embodiments of this application, the number of carbon atoms is 1 to 6.

[0035] In some embodiments of this application, the hydrocarbon group is selected from one or more of alkyl, alkenyl, and ynyl groups; in other embodiments of this application, the alkyl, alkenyl, and ynyl groups are all straight-chain alkyl, alkenyl, and ynyl groups; in still other embodiments of this application, the hydrocarbon group is selected from one or more of straight-chain alkyl groups having 1 to 10 carbon atoms, more specifically from one or more of straight-chain alkyl groups having 1 to 6 carbon atoms, such as substituents with the following structures:

[0036]

[0037] In some embodiments of this application, the cycloalkane group is selected from one or more of monocyclic cycloalkyl, bicyclic cycloalkyl, and polycyclic cycloalkyl groups, wherein the bicyclic and polycyclic cycloalkyl groups include, but are not limited to, spirocyclic cycloalkyl, fused-ring cycloalkyl, or mixed combinations of cycloalkyl groups; in other embodiments of this application, the cycloalkane group is selected from one or more of monocyclic cycloalkane groups having 3 to 10 carbon atoms, more specifically from one or more of monocyclic cycloalkane groups having 3 to 6 carbon atoms, such as substituents with the following structures:

[0038]

[0039] In some embodiments of this application, the compound with the structure shown in Formula I includes one or more of the following compounds:

[0040]

[0041]

[0042] In a second aspect of this application, a method for preparing the aforementioned cyclotriphosphazene compound is provided, comprising:

[0043] Trichlorophosphazene, HO-R-OH (R being at least one of R1 to R6) and acryloyl chloride are used as reactants to generate cyclic triphosphazene compounds with the formula I. The reaction conditions, such as the amount of reactants and the reaction temperature, can be optimized through experiments to obtain the optimal reaction conditions.

[0044] In some embodiments of this application, the preparation method includes:

[0045] A substitution reaction was carried out using trichlorophosphazene and HO-R-OH (R being at least one of R1 to R6) as reactants to generate an intermediate product with the structure of formula II.

[0046] The intermediate product of Formula II undergoes a substitution reaction with acryloyl chloride to generate a cyclotriphosphazene compound of Formula I, as shown in the following reaction formula;

[0047]

[0048] In some embodiments of this application, organic solvents such as DMF and dichloromethane are used to provide the reaction environment during the preparation process; in other embodiments of this application, K2CO3, Na2CO3 or triethylamine is used as a base catalyst.

[0049] In certain embodiments of this application, the preparation method described herein is illustrated using compound A as the target compound:

[0050] Trichlorophosphazene, K2CO3 and organic solvent were placed in a reaction vessel, and then ethylene glycol was added dropwise. After the addition was complete, the system was placed at 80°C to react. After the reaction was completed, the mixture was cooled to room temperature, washed with water until neutral, and the organic phase was dried to obtain the intermediate product.

[0051] The above intermediate product, organic solvent and K2CO3 were added sequentially to the reaction vessel. The system was placed in an ice bath and acryloyl chloride was added dropwise. After the addition was complete, the temperature was naturally raised to room temperature while monitoring the reaction until it was complete. The mixture was then washed with water, the organic phases were combined and dried to obtain the final product.

[0052] In certain embodiments of this application, the preparation method described herein is illustrated using compound B as the target compound:

[0053] Trichlorophosphazene, K2CO3 and organic solvent were placed in a reaction vessel, and then 1,4-cyclohexanediol was added dropwise. After the addition was complete, the system was placed at 80°C to react. After the reaction was completed, the mixture was cooled to room temperature, washed with water until neutral, and the organic phase was dried to obtain the intermediate product.

[0054] The above intermediate product, organic solvent and K2CO3 were added sequentially to the reaction vessel. The system was placed in an ice bath and acryloyl chloride was added dropwise. After the addition was complete, the temperature was naturally raised to room temperature while monitoring the reaction until it was complete. The mixture was then washed with water, the organic phases were combined and dried to obtain the final product.

[0055] In a third aspect of this application, an electrolyte is provided, comprising a lithium salt, an organic solvent, and a first additive. The first additive is a cyclotriphosphazene compound as described in this application. Compounds containing phosphazene structures possess both gas-phase and condensed-phase flame-retardant mechanisms in the electrolyte, providing excellent flame-retardant effects during battery thermal runaway combustion. Specifically, the phosphazene and other flame-retardant components in the cyclotriphosphazene compound of this application generate nitrogen-containing flammable gas (N2) and a heat-resistant glassy carbon layer during combustion, further enhancing the battery's safety performance.

[0056] In some embodiments of this application, the electrolyte further includes a second additive, which includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, tert-butyl peroxide, and methyl ethyl ketone peroxide.

[0057] Specifically, the second additive is a thermal initiator. Because the electrolyte provided in this application possesses a thermally triggered catalytic agent, it can rapidly decompose to generate free radicals under battery overheating conditions (approximately 100°C), thereby initiating the polymerization of the cyclotriphosphazene compounds of this application. This causes the liquid electrolyte in the battery to solidify, protectively shutting down the battery and preventing internal short circuits and thermal runaway, ensuring the battery's safety under overheating conditions. The solidification of the liquid electrolyte is based on the rapid polymerization of multifunctional monomers catalyzed by the thermal initiator. In this application, the reaction formula for the thermal initiator initiating the solidification of the cyclotriphosphazene compounds of this application is as follows:

[0058]

[0059] In some embodiments of this application, the safety performance of the battery is significantly improved by the synergistic effect of the first and second additives in the electrolyte.

[0060] In some embodiments of this application, the mass of the cyclotriphosphazene compound is 0.5% to 10% of the total mass of the electrolyte. Too little additive may slow down the polymerization reaction, while too much additive may increase the viscosity of the system and affect the battery performance. In other embodiments of this application, the mass of the cyclotriphosphazene compound is 1% to 5% of the total mass of the electrolyte. In still other embodiments of this application, the mass of the cyclotriphosphazene compound is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the total mass of the electrolyte, or any combination of two thereof.

[0061] In some embodiments of this application, the mass ratio of the second additive to the cyclotriphosphazene compound is 1:(50-500). Too little second additive will slow down the polymerization reaction rate, while too much second additive will not significantly help the flame retardant effect and will increase the cell impedance. In other embodiments of this application, the mass ratio of the second additive to the cyclotriphosphazene compound can be 1:50, 1:100, 1:150, 1:200, 1:250, 1:300, 1:350, 1:400, 1:450 or 1:500.

[0062] In some embodiments of this application, the lithium salt accounts for 8% to 20% of the total mass of the electrolyte. Too low a lithium salt concentration affects the conductivity of the electrolyte, while too high a concentration increases the viscosity. In other embodiments of this application, the lithium salt accounts for 12% to 13% of the total mass of the electrolyte, more specifically, it can be selected as 8%, 9%, 10%, 11%, 12%, 12.5%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%. In still other embodiments of this application, the lithium salt is one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorodioxalatophosphate (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0063] In some embodiments of this application, the organic solvent accounts for 80% to 90% of the total mass of the electrolyte, and more specifically, it can be selected as a range of 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, or any combination thereof. The organic solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), butenyl carbonate (BC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), diphenyl carbonate (DPhC), methyl formate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), γ-butyrolactone (γ-GBL), acetonitrile (AN), and sulfolane (TMS); in some other embodiments of this application, the organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 3:7.

[0064] In a fourth aspect of this application, a lithium-ion battery is provided, comprising the electrolyte described in this application. In some embodiments of this application, the lithium-ion battery includes the electrolyte described in this application, a positive electrode, a negative electrode, a separator, tabs, and outer packaging.

[0065] In some embodiments of this application, the positive electrode sheet includes a positive active material, a conductive agent, a binder, and a metal foil, and the negative electrode sheet includes a negative active material, a conductive agent, a binder, and a metal foil. In other embodiments of this application, the mass ratio of the positive / negative active material: conductive agent: binder is (90-95):(1-5):(1-5), and can be specifically selected as 94:3:3. In other embodiments of this application, the positive active material is Li(Ni) 0.8 Mn 0.1 Co 0.1 The anode material is graphite, the conductive agent is acetylene black (Super P), the binder is polyvinylidene fluoride (PVDF) or styrene-butadiene rubber (SBR), and the metal foil is copper foil or aluminum foil.

[0066] In some embodiments of this application, the lithium-ion battery is a pouch battery. The preparation process is as follows: the prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator in the middle of the positive and negative electrode sheets. After winding, hot pressing and shaping, and electrode tab welding, a bare cell is obtained. The bare cell is placed in an outer packaging aluminum-plastic film, baked, and then injected with the electrolyte described in this application. After standing, formation, and capacity testing, the preparation of the lithium-ion pouch battery is completed.

[0067] In a fifth aspect of this application, an electrical device is provided, including the lithium-ion battery described in this application, which can be a variety of devices powered by the lithium-ion battery, including but not limited to electric vehicles, electric cars, balance scooters, flatbed trucks, aircraft, lighting equipment, home appliances, etc.

[0068] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials remain consistent to ensure comparability. Furthermore, all materials used in this application are commercially available.

[0069] The following provides a further description of a cyclotriphosphazene compound, its preparation method, electrolyte, lithium-ion battery, and electrical device provided in this application.

[0070] Preparation of cyclotriphosphazene compound A

[0071] 3.44 g of trichlorophosphazene, 8.28 g of K2CO3 and 100 ml of DMF were placed in a 250 ml three-necked flask. 3.6 g of ethylene glycol was slowly added dropwise through a constant pressure dropping funnel. After the addition was complete, the system was placed in an 80 °C oil bath and reacted for 12 hours. The reaction was stopped and cooled to room temperature. The mixture was washed with water until neutral. The organic layer was dried with anhydrous sodium sulfate. Finally, the crude product was subjected to column chromatography (PE:EA = 1) to obtain the intermediate product.

[0072] The above intermediate product, 100 ml of dichloromethane, and 8.28 g of K₂CO₃ were added sequentially to a 250 ml round-bottom flask. The system was placed in an ice bath, and 6 g of acryloyl chloride was slowly injected dropwise using a syringe. After the addition was complete, the mixture was allowed to warm to room temperature, and the reaction was monitored by TLC until the reaction was complete. The mixture was then washed with water, and the organic phases were combined and dried over anhydrous sodium sulfate. Finally, the crude product was subjected to column chromatography (PE:EA = 3) to obtain 4.62 g of the product (overall yield of the two-step reaction was 56%).

[0073] The NMR results were as expected: 1 H NMR (CDCl3, 400MHZ) δ (ppm): 6.41 (dd, 6H), 6.21 (q, 6H), 5.83 (dd, 6H), 4.29 (t, 12H), 3.81 (t, 12H).

[0074] 13 CNMR(CDCl3,100MHZ)δ(ppm):166.5,131.3,128.2,65.9,54.5.

[0075]

[0076] Preparation of cyclotriphosphazene compound B

[0077] 3.44 g of trichlorophosphazene, 8.28 g of K2CO3 and 100 ml of DMF were placed in a 250 ml three-necked flask. 7.2 g of 1,4-cyclohexanediol was slowly added dropwise through a constant pressure dropping funnel. After the addition was complete, the system was placed in an 80 °C oil bath and reacted for 12 hours. The reaction was stopped and cooled to room temperature. The mixture was washed with water until neutral. The organic layer was dried with anhydrous sodium sulfate. Finally, the crude product was subjected to column chromatography (PE:EA = 1) to obtain the intermediate product.

[0078] The above intermediate product, 100 ml of dichloromethane, and 8.28 g of K₂CO₃ were added sequentially to a 250 ml round-bottom flask. The system was placed in an ice bath, and 6 g of acryloyl chloride was slowly injected dropwise using a syringe. After the addition was complete, the mixture was allowed to warm to room temperature, and the reaction was monitored by TLC until the reaction was complete. The mixture was then washed with water, and the organic phases were combined and dried over anhydrous sodium sulfate. Finally, the crude product was subjected to column chromatography (PE:EA = 3) to obtain 4.95 g of the product (overall yield of the two-step reaction was 45%).

[0079] The NMR results were as expected: 1 H NMR (CDCl3, 400MHZ) δ (ppm): 6.41 (dd, 6H), 6.12 (q, 6H), 5.83 (dd, 6H), 4.61 (m, 6H), 3.54 (m, 6H), 1.8-1.5 (m, 48H).

[0080] 13 CNMR(CDCl3,100MHZ)δ(ppm):165.2,131.3,128.2,75.9,67.2,29.4,27.4.

[0081]

[0082] The examples and comparative examples respectively provide an electrolyte and a lithium-ion battery containing the electrolyte. The composition of the electrolyte and the performance of the battery are shown in Table 1.

[0083] Preparation of electrolyte

[0084] At room temperature, in a glove box filled with argon (H2O < 1 ppm, O2 < 1 ppm), organic solvents are mixed evenly in proportion to obtain a mixed solvent. Then, lithium salt, a compound with the structure shown in Formula I, and a thermal initiator are added and stirred evenly to obtain an electrolyte.

[0085] Lithium-ion battery manufacturing

[0086] Positive electrode: The positive electrode active material Li(Ni) 0.8 Mn 0.1 Co 0.1 O2 (NMC811), conductive agent acetylene black (SuperP), and binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of NMC811:Super P:PVDF = 94:3:3, and then evenly dispersed in 1-methyl-2-pyrrolidone (NMP) to form a uniform black slurry. The mixed black slurry is coated on both sides of aluminum foil, and then baked, rolled, and cut into sheets to obtain the positive electrode sheet.

[0087] Negative electrode sheet: The negative electrode active material graphite, the conductive agent acetylene black (Super P) and the binder styrene-butadiene rubber (SBR) are mixed evenly in a mass ratio of graphite:Super P:SBR = 94:3:3, and then evenly dispersed in deionized water to form a uniform black slurry. The mixed slurry is coated on both sides of a copper foil, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet.

[0088] Soft-pack battery: The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator in the middle of the positive and negative electrode sheets. After winding, hot pressing and shaping, and welding of the tabs, a bare cell is obtained. The bare cell is placed in an outer packaging aluminum-plastic film and baked in an oven at 85±10℃ for 24 hours. The electrolyte is injected into the dried battery, and the battery is allowed to stand, form, and be capacity tested to complete the preparation of the lithium-ion soft-pack battery.

[0089] Self-extinguishing time test

[0090] Take the electrolyte out of the glove box, immerse a glass cotton ball weighing 0.01g and 3mm in diameter in the electrolyte, take it out and roll it on filter paper to remove the electrolyte on the surface, control the weight of the cotton ball to 0.1g, ignite it with an open flame and test the extinguishing time of the glass cotton ball.

[0091] The self-extinguishing time was tested using the electrolytes of the examples and comparative examples according to the above method, and the results are shown in Table 1;

[0092] Table 1

[0093]

[0094]

[0095] Note: The amounts mentioned in Table 1 are all percentages of the total mass of the electrolyte, and the proportions in the solvent are by mass.

[0096] As shown in Table 1, the addition of the cyclotriphosphazene compound and the second additive in Examples 1-8 effectively improved the flame retardant performance after curing. With increasing content, the extinguishing time significantly decreased, all below 12 seconds. When the content reached 3% or more, it essentially did not ignite. Although adding excessive amounts of the cyclotriphosphazene compound effectively improved its flame retardant performance, it significantly increased the viscosity of the electrolyte, affecting battery performance. Therefore, the preferred content of the cyclotriphosphazene compound is 0.5%-10%, and a further preferred content can be determined according to specific requirements.

[0097] The second additive and the proportion of cyclotriphosphazene compounds being too small or the amount of cyclotriphosphazene compounds in the electrolyte being relatively small (Examples 9 and 10) both lead to a prolonged quenching time; when using ethoxy(pentafluoro)cyclotriphosphazene, which also belongs to the cyclotriphosphazene class, the quenching time is as high as 43s; the quenching time of Comparative Example 2, which did not use any flame retardant additives, is as high as 122s.

[0098] Furthermore, a comparison between Examples 1-3 and Examples 6-8 shows that the flame-retardant effects of compounds A and B are essentially equivalent. This indicates that the main flame-retardant groups in the cyclotriphosphazene compounds of this application are the acrylate structure for curing and the cyclotriphosphazene structure for flame retardancy. The former provides a protective mechanism (battery shut-off, preventing short circuits, and the flame-retardant performance of the cured battery is also enhanced), while the latter is used to retard open flames. Simultaneously, this application also compares the open-circuit voltage (OCV) of the conventional battery in Comparative Example 2 and the safety battery in Example 3 when the temperature rises. Figure 1 The results showed that the PE separator in conventional batteries melts at around 160℃, shrinks rapidly in size, and loses its barrier function to the positive and negative electrodes, causing a short circuit between them. In contrast, the safety battery, due to the second additive solidifying the liquid electrolyte under overheating conditions to form a highly cross-linked thermosetting material (with no melting point, maintaining dimensional stability at high temperatures), maintains a stable open-circuit voltage even at high temperatures, without experiencing internal short circuits between the positive and negative electrodes.

[0099] 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 cyclic triphosphazene compound, characterized by, comprising a structure represented by Formula I: Formula I wherein R1 to R6 are selected from one or more of monocyclic cycloalkane groups having 3 to 10 carbon atoms.

2. The cyclic phosphazene compound according to claim 1, wherein at least one of R1 to R6 has at least one of the following groups: 、 、 、 、 、 、 、 。 3. The cyclotriphosphazene compound according to claim 1, wherein the compound represented by Formula I includes any one or more of the following compounds: B、 C、 D。 4. The method for preparing the cyclotriphosphazene compound according to claim 1, characterized in that, comprising: a cyclotriphosphazene compound represented by Formula I is produced using trimeric phosphorus chloride, HO-R-OH, and acryloyl chloride as raw materials; R is at least one of R1 to R6.

5. The preparation method according to claim 4, characterized in that, an intermediate product represented by Formula II is produced by substitution reaction using trimeric phosphorus chloride and HO-R-OH as raw materials; R is at least one of R1 to R6; the intermediate product represented by Formula II is subjected to substitution reaction with acryloyl chloride to produce a cyclotriphosphazene compound represented by Formula I; Formula II.

6. An electrolyte, characterized by lithium salt, organic solvent, first additive, the first additive comprising a cyclotriphosphazene compound as claimed in any one of claims 1 to 3.

7. The electrolyte of claim 6, wherein the electrolyte solution comprises a second additive selected from one or more of azobis isobutyronitrile, azobis isoheptyl nitrile, benzoyl peroxide, t-butyl peroxy benzoate, and methyl ethyl ketone peroxide.

8. The electrolyte of claim 6, wherein the mass of the cyclotriphosphazene compound accounts for 0.5% to 10% of the total mass of the electrolyte solution.

9. The electrolyte of claim 6, wherein the mass ratio of the second additive to the cyclotriphosphazene compound is 1: (50 to 500).

10. A lithium-ion battery, characterized by, containing the electrolyte solution as claimed in any one of claims 6 to 9.

11. An electric device comprising the lithium ion battery as claimed in claim 10.

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