Battery, electrolyte and compound for battery, and energy storage system

Abstract

The invention provides a battery, an electrolyte and a compound for the battery, and an energy storage system. The battery comprises a positive plate, a diaphragm, a negative plate and an electrolyte, the electrolyte comprises a flame retardant, the flame retardant comprises a compound shown in the formula (1), and the mass ratio of the compound shown in the formula (1) in the electrolyte is 0.1-4%; according to the flame retardant in the battery, under the condition that the addition amount of the flame retardant is not increased, the way of effectively blocking hydrogen generation can be realized, and the hydrogen production amount of the whole battery is reduced, so that the safety problems of combustion explosion and the like caused by excessive H2 are reduced.

Description

Technical Field

[0001] This application relates to the field of energy storage, specifically to a battery, an electrolyte and compound for the battery, and an energy storage system. Background Technology

[0002] Rechargeable batteries, such as lithium-ion batteries, are increasingly widely used in portable consumer electronics, new energy vehicles, and energy storage. However, the safety issues of lithium-ion batteries are also prominent, becoming a significant factor restricting their development. Sodium-ion batteries, due to their similar working mechanism to lithium-ion batteries, use similar solvents and additives in their electrolytes. Thermal runaway and other safety issues are also key risks for sodium-ion batteries. Currently, lithium-ion and sodium-ion batteries produce gases such as H2, CO, CO2, CH4, and C2H4 during cycling. Since H2 is one of the main gases released by batteries, and it is flammable and explosive, reducing H2 production has become a hot research topic. One current solution to address cell safety issues is to add flame retardants to the electrolyte to delay combustion or explosion by capturing combustion free radicals. However, current flame retardants are typically trimethyl phosphate or cyclophosphamide derivatives, and these flame retardants need to reach a certain concentration, such as greater than 5 wt%, to achieve a flame-retardant effect. However, the excessive addition of flame retardants can affect the conduction of ions in the electrolyte, reducing the battery's cycle life and rate performance. Therefore, there is currently a lack of flame retardants that can improve battery safety while maintaining normal battery electrical performance. Summary of the Invention

[0003] This application provides a battery, an electrolyte and compound for the battery, and an energy storage system to reduce the amount of H2 produced by the battery without reducing its electrical performance and to improve battery safety.

[0004] In a first aspect, this application provides a battery comprising a positive electrode, a separator, a negative electrode and an electrolyte, wherein the electrolyte comprises a flame retardant, the flame retardant comprising a compound of formula (1), wherein the compound of formula (1) comprises 0.1 to 4% by mass in the electrolyte;

[0005]

[0006] Wherein, R1 is selected from sulfone, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by sulfone.

[0007] R2 is selected from cyano, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; wherein at least one hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is replaced by a cyano group;

[0008] R3 is selected from trifluoromethyl, alkyl containing 1-10 carbon atoms, or aryl containing 6-20 carbon atoms; the hydrogen in the alkyl containing 1-10 carbon atoms or the aryl containing 6-20 carbon atoms may be replaced by a halogen.

[0009] The battery of this application includes a flame retardant in its electrolyte comprising a compound with the structure shown in formula (1), wherein the mass percentage of the compound shown in formula (1) in the electrolyte is 0.1-4%. In the compound shown in formula (1), the lone pair electrons of the P atom and the O atoms formed by the PO bond both contribute to the flame retardancy of the H atoms in the electrolyte. + Capture and reduce H in the battery cell + This reduces the hydrogen content, thereby decreasing the hydrogen production of the battery cell. Additionally, the cyano group in R2 can form a complex with transition metal ions in the positive electrode, inhibiting the dissolution of transition metal ions from the positive electrode and improving the structural stability of the positive electrode. This prevents transition metal ions from becoming catalytic reaction active centers at the positive or negative electrode, thus reducing the decomposition reaction of the electrolyte near the positive or negative electrode, and consequently reducing H2 production. + The formation of [something]. Therefore, the flame retardant added to the electrolyte in this application can, on the one hand, capture the H generated by the electrolyte. + On the other hand, it can reduce the decomposition reaction of the electrolyte and lower the H2O level. + The generation of hydrogen is reduced, thereby decreasing the amount of hydrogen produced by the electrolyte. Through the combined effect described above, the pathway for hydrogen generation can be effectively blocked without increasing the amount of flame retardant added, reducing the overall hydrogen production of the battery and thus reducing safety issues such as combustion and explosion caused by excessive H2. The battery of this application, due to the low content of flame retardant in the electrolyte, will not negatively affect the battery's capacity or cycle performance. Furthermore, the electrolyte of this application also has a high flame retardant effect. Therefore, the battery of this application, while possessing high safety, can maintain high electrical performance, such as high capacity and good cycle stability.

[0010] In one alternative implementation, when R1 is an alkyl group with 1 to 10 carbon atoms, at least one hydrogen atom in the alkyl group with 1 to 10 carbon atoms is replaced by a sulfone group; when R1 is an aryl group with 6 to 20 carbon atoms, at least one hydrogen atom in the aryl group with 6 to 20 carbon atoms is replaced by a sulfone group. In the electrolyte, the sulfone group can form an interfacial protective film containing sulfur oxides at the positive or negative electrode, improving interfacial thermal stability.

[0011] In one alternative implementation, the structure of R1 is as shown in equation (2):

[0012]

[0013] Wherein, * represents the connection site of O in equation (2) and equation (1); R 11Selected from alkyl groups with 1 to 10 carbon atoms or fluoroalkyl groups with 1 to 10 carbon atoms. R 11 Selecting from the above groups can help improve the overall structural stability of the compound.

[0014] In one alternative implementation, the structure of R2 is as shown in equation (3):

[0015] NC-R 21 -*,

[0016] Equation (3)

[0017] Wherein, * represents the connection site of O in equation (3) and equation (1); R 21 R2 is selected from alkyl groups with 1 to 10 carbon atoms or aryl groups with 6 to 20 carbon atoms. Selecting R2 from the above structures can help improve the overall structural stability of the compound.

[0018] In one alternative implementation, the structure of R3 is as shown in equation (4):

[0019] F3C-R 31 -*,

[0020] Equation (4)

[0021] Wherein, * represents the connection site of O in equation (4) and equation (1); R 31 The R3 is selected from alkyl groups with 1 to 10 carbon atoms or aryl groups with 6 to 20 carbon atoms. When R3 is selected from the above structures, the fluorinated group can participate in the film formation on the electrode surface of the battery cell, generating inorganic components rich in fluorides, stabilizing the electrode interface, and improving the cycle stability of the battery cell.

[0022] In one alternative implementation, R3 can be 1,1,2,2-tetrafluoroethyl, 2,2,3,3-tetrafluoropropyl, etc., in addition to the structure shown in formula (4). Using the above structural groups for R3 will result in a more stable structure and facilitate the synthesis of the compound shown in formula (1).

[0023] In one alternative implementation, the structure of the compound shown in equation (1) is as follows:

[0024]

[0025] When the compound shown in formula (1) satisfies the above structure, it can simultaneously possess sulfone, cyano and fluorinated groups. The sulfone group can improve the interfacial stability of the electrolyte in the battery, the cyano group can improve the structural stability of the positive electrode and reduce the decomposition reaction of the electrolyte, and the fluorinated group can improve the interfacial stability of the electrode. Thus, the battery can be improved in terms of both safety and cycle stability.

[0026] In one alternative implementation, the electrolyte comprises an organic solvent, which includes cyclic carbonates and chain carbonates, wherein the mass ratio of the cyclic carbonates to the chain carbonates is 0.5 to 1.0.

[0027] In one optional implementation, the electrolyte further includes additives, including fluoroethylene carbonate, sulfonate, sulfate, and sodium difluorooxalate borate. The fluoroethylene carbonate has a mass percentage (a) of 0.5-3% in the electrolyte, the total mass percentage (b) of the sulfonate and sulfate in the electrolyte is 0.3-3%, and the mass percentage (c) of the sodium difluorooxalate borate in the electrolyte is 0.2-2%.

[0028] In one alternative implementation, the mass percentage of the compound represented by formula (1) in the electrolyte is d, and the relationship between d, a, b and c satisfies that d / (a+b+c) is 0.02 to 1.54.

[0029] In a second aspect, this application provides an electrolyte comprising a flame retardant, the flame retardant comprising a compound of formula (1), wherein the compound of formula (1) accounts for 0.1-4% by mass in the electrolyte;

[0030]

[0031] Wherein, R1 is selected from sulfone, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by sulfone.

[0032] R2 is selected from cyano, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; at least one hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is substituted by a cyano group;

[0033] R3 is selected from trifluoromethyl, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by a halogen.

[0034] The electrolyte of this application contains a flame retardant comprising a compound with the structure shown in formula (1), wherein the mass percentage of the compound shown in formula (1) in the electrolyte is 0.1% to 4%. In the compound shown in formula (1), the lone pair electrons of the P atom and the O atoms formed by the PO bond both contribute to the flame retardancy of the H atoms in the electrolyte. + Capture and reduce H in the battery cell +This reduces the hydrogen content, thereby decreasing the hydrogen production of the battery cell. Additionally, the cyano group in R2 can form a complex with transition metal ions in the positive electrode, inhibiting the dissolution of transition metal ions from the positive electrode and improving the structural stability of the positive electrode. This prevents transition metal ions from becoming catalytic reaction active centers at the positive or negative electrode, thus reducing the decomposition reaction of the electrolyte near the positive or negative electrode, and consequently reducing H2 production. + The formation of [something]. Therefore, the flame retardant added to the electrolyte in this application can, on the one hand, capture the H generated by the electrolyte. + On the other hand, it can reduce the decomposition reaction of the electrolyte and lower the H2O level. + The generation of hydrogen is reduced, thereby decreasing the amount of hydrogen produced by the electrolyte. Through the combined effect described above, the pathway for hydrogen generation can be effectively blocked without increasing the amount of flame retardant added, reducing the overall hydrogen production of the battery and thus reducing safety issues such as combustion and explosion caused by excessive H2.

[0035] Thirdly, this application provides a compound with the structure shown in the following formula.

[0036]

[0037] Wherein, R1 is selected from sulfone, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by sulfone.

[0038] R2 is selected from cyano, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; wherein at least one hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is replaced by a cyano group;

[0039] R3 is selected from trifluoromethyl, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by a halogen.

[0040] The compound of this application can be used as a flame retardant in battery electrolytes. The P atom in its structure has a lone pair of electrons, and both this lone pair of electrons and the O in the PO bond contribute to the flame retardancy of H atoms in the electrolyte. + Capture and reduce H in the battery cell + The content of hydrogen produced by the battery cell is reduced. Additionally, the cyano group in R2 can form a complex with transition metal ions in the positive electrode, inhibiting the dissolution of these ions and improving the structural stability of the positive electrode. This prevents transition metal ions from becoming catalytic reaction active centers at the positive or negative electrode, thus reducing the decomposition reaction of the electrolyte near the positive or negative electrode and consequently reducing hydrogen production. +The formation of [something]. Therefore, the flame retardant added to the electrolyte in this application can, on the one hand, capture the H generated by the electrolyte. + On the other hand, it can reduce the decomposition reaction of the electrolyte and lower the H2O level. + The generation of hydrogen is reduced, thereby decreasing the amount of hydrogen produced by the electrolyte. Through the combined effect described above, the pathway for hydrogen generation can be effectively blocked without increasing the amount of flame retardant added, reducing the overall hydrogen production of the battery and thus reducing safety issues such as combustion and explosion caused by excessive H2.

[0041] Fourthly, this application provides an energy storage system, which includes a power converter and at least one battery of this application; the power converter is used to convert the voltage output by the battery into power and output it to the power grid or a load, and / or to convert the voltage output by an external power source into power and output it to the battery.

[0042] In this application, the data in each of the above possible implementations, such as the mass ratio of the flame retardant in the electrolyte of the compound shown in formula (1), the mass ratio of the flame retardant to the additive, etc., should all be understood as being within the range defined in this application when measured, provided that the values ​​are within the range of engineering measurement error. Attached Figure Description

[0043] Figure 1 For compound A1 31 P-NMR NMR spectrum;

[0044] Figure 2 For compound A1 19 F-NMR spectrum. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the application will now be described in further detail with reference to the accompanying drawings.

[0046] The terminology used in the following embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “an,” “the,” “the,” and “this” are intended to also be selected from expressions such as “one or more,” unless the context clearly indicates otherwise.

[0047] References to "one embodiment" or "some embodiments" as used in this specification mean a specific feature, structure, or characteristic selected from those described in connection with one or more embodiments of this application. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "selected from," "comprising," "having," and variations thereof mean "selected from, but not limited to," unless otherwise specifically emphasized.

[0048] For lithium-ion or sodium-ion batteries, the electrolyte contains a large amount of organic matter, which randomly generates gases such as H2, CO, CO2, CH4, and C2H4 during charge-discharge cycles at 45-55℃ or under high voltage. H2 constitutes a relatively high proportion of these gases and is flammable and explosive, easily causing thermal runaway problems such as combustion or explosion, thus reducing battery safety. Current methods to improve battery safety often involve adding a certain amount of flame retardant to the electrolyte, primarily phosphate ester compounds. These compounds mainly reduce the amount of gas generated during thermal runaway, thus mitigating the severity of the problem. However, they do not reduce the amount of hydrogen produced during operation, and therefore cannot fundamentally prevent hydrogen-induced thermal runaway.

[0049] To address the aforementioned problems, this application provides a battery. The battery includes a positive electrode, a separator, a negative electrode, and the electrolyte of this application. The positive electrode, the separator, and the negative electrode are alternately stacked, and the electrolyte wets the positive electrode, the separator, and the negative electrode. In the electrolyte of this application, the flame retardant can suppress hydrogen production during battery cycling, thereby improving battery safety.

[0050] The positive electrode sheet may include a positive current collector and a positive electrode material layer disposed on the surface of the current collector. The positive current collector may be a metal foil, such as copper foil or aluminum foil. The positive electrode material layer contains an active material capable of providing intercalation and deintercalation of active ions. Taking a lithium-ion battery as an example, the active material in the positive electrode material layer may be, for example, lithium phosphate, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium cobalt manganese oxide, lithium cobalt manganese nickel oxide, etc. When the battery is a sodium-ion battery, the active material in the positive electrode material layer may be a commonly used active material for sodium-ion batteries. Similarly, when the battery is another type of battery, it may be a conventional active material for the corresponding battery.

[0051] The negative electrode sheet may include a negative electrode current collector and a negative electrode material layer, the negative electrode material layer being disposed on at least one surface of the negative electrode current collector. The negative electrode current collector may be a metal foil, such as copper foil, aluminum foil, etc. The active material in the negative electrode material layer may be a material capable of intercalating and deintercalating active ions. Taking a lithium-ion battery as an example, the active material in the negative electrode material layer includes, but is not limited to, carbon materials, silicon-based materials, alloy materials, or transition metal oxides.

[0052] The battery in this application embodiment can be a prismatic battery, a cylindrical battery, or a pouch battery. This application embodiment does not specifically limit the structural form of the battery. Furthermore, the battery in this application embodiment can be a single cell or a combination of multiple single cells connected in series and parallel.

[0053] In the battery of this application embodiment, the electrolyte includes organic solvent, metal salt, additives and flame retardant.

[0054] organic solvents

[0055] The organic solvent may be a carbonate organic solvent, for example, it may include at least one of cyclic carbonate organic solvents and chain carbonate organic solvents. Cyclic carbonate organic solvents may include one or a combination of at least two of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate (FEC). Chain carbonate organic solvents may include one or a combination of at least two of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, propyl propionate, and ethyl propionate.

[0056] When the organic solvent contains both cyclic carbonate organic solvents and chain carbonate organic solvents, the mass ratio of the cyclic carbonate organic solvents to the chain carbonate organic solvents can be 0.5 to 1.0. For example, the ratio can be any two values ​​between 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1.0, and the values ​​listed above can be used as upper or lower limits.

[0057] Metal salts

[0058] Metal salts in the electrolyte can ionize to form metal ions. These metal ions can be active ions that migrate back and forth during the charging and discharging process of the battery, and are consistent with the active ions in the positive electrode of the battery.

[0059] When the battery is a lithium-ion battery, the metal salt may be a lithium salt, which may be selected from at least one of inorganic or organic salts. For example, the lithium salt may be selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(oxalato)borate. When the battery is a sodium-ion battery, the metal salt is a sodium salt, which may be, for example, at least one of sodium hexafluorophosphate, sodium difluorophosphate, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, and sodium bis(oxalato)borate.

[0060] It is understood that the examples of metal salts above are merely illustrative. The type of metal salt varies depending on the active ions in the battery. When the battery is a magnesium-ion battery, the metal salt may be a magnesium salt. When the battery is a calcium-ion battery, the metal salt may be a calcium salt. When the battery is an aluminum-ion battery, the metal salt may be an aluminum salt. No specific limitation is made here regarding the type of metal salt.

[0061] In one embodiment, the concentration of the metal salt in the electrolyte can be the conventional salt molar concentration in the electrolyte, for example, 0.5 to 1.5 mol / L.

[0062] additive

[0063] This additive can be a conventional additive for the electrolyte in a battery. Taking lithium-ion batteries as an example, the additive may include at least one of fluoroethylene carbonate (FEC), sulfonates, sulfates, and sodium-difluoro(oxalato)borate (NaDFOB).

[0064] Among them, sulfonates include, but are not limited to, 1,3-propane sulfonate lactone (PS) and 1,3-propene sulfonate lactone.

[0065] Sulfate esters include, but are not limited to, vinyl sulfate (1,3,2-dioxathiolane 2,2-dioxide, DTD) and propylene sulfite (1,3-propylene sulfite, PST).

[0066] It should be noted that FEC can be used as both an organic solvent and an additive. When the amount of FEC added to the electrolyte is small, such as less than 5% of the electrolyte's mass, FEC can be used as an additive. When the amount of FEC added to the electrolyte is 20% or more, FEC can be used as an organic solvent.

[0067] In one embodiment, the additive may include FEC, sulfonates, sulfates, and NaDFOB. The mass percentage of FEC in the electrolyte may be 0.5% to 3%. Exemplarily, the mass percentage of FEC in the electrolyte may be any two values ​​between 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, or 3%, and the values ​​listed above may be considered as upper or lower limits. The total mass percentage of sulfonates and sulfates in the electrolyte may be 0.3% to 3%. For example, the total mass percentage of both in the electrolyte can be any two values ​​between 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, or 3% or more, and the values ​​listed above can be used as upper or lower limits. The mass percentage of NaDFOB in the electrolyte can be 0.2% to 2%. For example, the mass percentage of NaDFOB in the electrolyte can be any two values ​​between 0.2%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, or 2.0% or more, and the values ​​listed above can be used as upper or lower limits.

[0068] Flame retardant

[0069] In the electrolyte of this application embodiment, the flame retardant includes the compound shown in formula (1). The compound shown in formula (1) exists as a flame retardant in the electrolyte, and the mass percentage of the compound shown in formula (1) in the electrolyte is 0.1% to 4%. Exemplarily, the mass percentage of the compound shown in formula (1) in the electrolyte can be, for example, any two values ​​between 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, or 4%. The values ​​listed above can be used as the upper or lower limit of the mass percentage of the compound shown in formula (1).

[0070] The structure of the compound shown in formula (1) is as follows:

[0071]

[0072] R1 is selected from sulfone, alkyl groups containing 1 to 10 carbon atoms, or aryl groups containing 6 to 20 carbon atoms; the hydrogen in the alkyl group containing 1 to 10 carbon atoms or the aryl group containing 6 to 20 carbon atoms can be replaced by a sulfone group. When the hydrogen in the alkyl group containing 1 to 10 carbon atoms or the aryl group containing 6 to 20 carbon atoms is replaced by a sulfone group, the number of sulfone groups can be one, two, three, or more; no specific limitation is made on the number of sulfone groups. In one embodiment, the number of sulfone groups in R1 can be one. The sulfone group can be located in the main chain structure of the alkyl or aryl group, or at the end of the main chain or the end of a branch chain.

[0073] In one embodiment, the structure of R1 may be as shown in equation (2):

[0074]

[0075] Wherein, * represents the connection site of O in equation (2) and equation (1); R 11 Selected from alkyl groups with 1 to 10 carbon atoms or fluoroalkyl groups with 1 to 10 carbon atoms. When R 11 When the fluoroalkyl group is selected from 1 to 10 carbon atoms, the number of F substituents can be one, two, or three. In one embodiment, the fluoroalkyl group can be trifluoromethyl, trifluoroethyl, or other trifluoroalkyl groups, or 1,1,2,2-tetrafluoroethyl, or 2,2,3,3-tetrafluoropropyl. The fluoro group can participate in the film formation on the electrode surface, generating fluoride-rich inorganic components, stabilizing the electrode interface, and improving the cycle stability of the battery cell.

[0076] In formula (1) of this application embodiment, R2 is selected from cyano, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; at least one hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is replaced by a cyano. When the hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is replaced by a cyano, the number of cyano groups can be one, two, three, or more, and the specific number of cyano groups is not limited here. In one embodiment, the number of cyano groups in R2 can be one. The cyano group can be located in the main chain structure of the alkyl or aryl group, or at the end of the main chain or the end of the branch chain.

[0077] In one embodiment, the structure of R2 may be as shown in equation (3):

[0078] NC-R 21 -*,

[0079] Equation (3)

[0080] Wherein, * represents the connection site of O in equation (3) and equation (1); R 21 Selected from alkyl groups with 1 to 10 carbon atoms or aryl groups with 6 to 20 carbon atoms.

[0081] In formula (1) of this application embodiment, R3 is selected from trifluoromethyl, alkyl containing 1-10 carbon atoms, or aryl containing 6-20 carbon atoms; the hydrogen in the alkyl containing 1-10 carbon atoms or the aryl containing 6-20 carbon atoms can be replaced by a halogen. The halogen can be F, Cl, Br, or I. To improve the structural stability of the compound, the halogen can be F. The number of hydrogens in R3 replaced by F is not limited; it can be one, two, three, four, or more, depending on the structure and stability of the alkyl group.

[0082] In one embodiment, the structure of R3 may be as shown in equation (4):

[0083] F3C-R 31 -*,

[0084] Equation (4)

[0085] Wherein, * represents the connection site of O in equation (4) and equation (1); R 31 It is selected from alkyl groups with 1 to 10 carbon atoms or aryl groups with 6 to 20 carbon atoms. In addition to the above structures, R3 can also be a 1,1,2,2-tetrafluoroethyl or 2,2,3,3-tetrafluoropropyl group.

[0086] In one alternative implementation, the structure of the compound shown in equation (1) is as follows:

[0087]

[0088] In the general formula of the above embodiments of this application, the alkyl group with 1 to 10 carbon atoms can be a chain alkyl group, such as a straight-chain alkyl group or a branched alkyl group, or a cycloalkyl group, wherein the hydrogen on the ring of the cycloalkyl group can be replaced by the chain alkyl group. The lower limit of the number of carbon atoms in the alkyl group can be 1, 2, 3, 4, or 5, and the upper limit can be 4, 5, 6, 8, or 10. In some embodiments, the alkyl group can have 1 to 8 carbon atoms, or 1 to 6 carbon atoms, or 1 to 4 carbon atoms. For example, the alkyl group with 1 to 10 carbon atoms may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, 2-methylpentyl, 3-methylpentyl, 1,1,2-trimethyl-propyl, 3,3,-dimethyl-butyl, heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl, isoheptyl, octyl, nonyl, decyl.

[0089] The aryl group with 6 to 20 carbon atoms can be, for example, phenyl, biphenyl, naphthyl, binatyl, anthracene, phenanthryl, fluorenyl, benzo[a]fluorenyl, pyrene, fluoranyl, triphenylene, etc. In these aryl groups with 6 to 20 carbon atoms, the hydrogen atoms can be substituted, such as in 9,9-dialkyl-substituted fluorenyl groups.

[0090] Flame retardants using fluorophosphites with the above structure can suppress hydrogen production and improve battery cycle stability.

[0091] The mechanism by which the above-described fluorophosphite inhibits hydrogen production is as follows: It utilizes the lone pair electrons of the P atom in the fluorophosphite molecule and the O atoms after the formation of the PO bond to inhibit hydrogen production in the electrolyte. + Capture and reduce H in the battery + This reduces the hydrogen production associated with battery thermal runaway. The mechanism by which the above-described fluorophosphite structure enhances battery cycle stability is as follows: the fluorinated groups in the molecule participate in the surface film formation of the positive and negative electrodes, generating fluoride-rich inorganic components, stabilizing the electrode interface, and improving cell cycle stability. The sulfonate groups in the fluorophosphite molecule form a sulfur-containing interfacial protective film, improving interfacial thermal stability. The cyano groups in the fluorophosphite molecule form complexes with metal ions in the positive electrode, inhibiting the dissolution of transition metal ions, improving the structural stability of the positive electrode, and preventing transition metal ions from migrating to the negative electrode to become catalytic reaction active centers, thus reducing the occurrence of side reactions.

[0092] For example, the compound shown in formula (1) is selected from one of the following structures:

[0093]

[0094] The compounds described above are merely illustrative examples. The compounds defined in the embodiments of this application may also be combinations of other groups, which will not be listed here.

[0095] In one embodiment, the mass ratio of the compound shown in formula (1) to the additive can be 0.02 to 1.54, for example 0.2 to 1.5, or for example 0.5 to 1.2. If the amount of the compound with the structure shown in formula (1) added is too high, although it will suppress hydrogen production, it will reduce the cycle stability of the battery. By controlling the mass ratio of the compound with the structure shown in formula (1) to the additive, both reducing the amount of hydrogen produced by thermal runaway and the high cycle stability of the battery can be achieved. For example, the mass ratio of the compound shown in formula (1) to the additive is a value between any two points of 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.25, 0.3, 0.35, 0.4, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.20, 1.25, 1.30, 1.35, 1.4, 1.45, 1.50, or 1.54. All of the above values ​​can be the lower limit or upper limit of the mass ratio of the compound shown in formula (1) to the additive.

[0096] When the additive contains FEC, sulfonate, sulfate, and NaDFOB, the mass percentage of FEC in the electrolyte is denoted as a, the mass percentage of sulfonate and sulfate in the electrolyte is denoted as b, the mass percentage of NaDFOB in the electrolyte is denoted as c, and the mass percentage of the compound with the structure shown in formula (1) in the electrolyte is denoted as d. Then, the range of d / (a+b+c) is 0.02 to 1.54. When the additive also includes other substances, the ratio of d to a+b+c still satisfies 0.02 to 1.54.

[0097] The structure of the compound shown in formula (1) has been explained above. The preparation process of the compound shown in formula (1) will be explained below.

[0098] In the embodiments of this application, the raw materials for synthesizing the compound shown in formula (1) may include sulfonate compounds, trifluorool compounds, hydroxynitrile compounds, and phosphorus trichloride, the structures of which are shown below:

[0099]

[0100] Among them, R 11 R 21 and R 31 R in equations (1) to (3) above 11 R 21 and R 31 The selection range is the same. R is an alkyl group with 1-10 carbon atoms or an aryl group with 6-20 carbon atoms. The selection range of alkyl groups with 1-10 carbon atoms or aryl groups with 6-20 carbon atoms is the same as that of the alkyl groups with 1-10 carbon atoms or aryl groups with 6-20 carbon atoms mentioned above.

[0101] In one embodiment, the route of synthesizing the compound represented by the above compound formula (1) is as follows:

[0102]

[0103] For example, with For example, its synthetic raw materials are sulfonate, trifluoroethanol, hydroxypropionitrile, and phosphorus trichloride, and its molecular structure is shown below:

[0104]

[0105] The synthesis path is as follows:

[0106]

[0107] The battery in this application embodiment can be used in various application scenarios such as residential energy storage, site energy backup power, data center backup power, and smart photovoltaic backup power.

[0108] The electrolyte of this application will be further described in detail below with reference to specific embodiments.

[0109] Example 1

[0110] This embodiment describes an electrolyte for a sodium-ion battery, comprising an organic solvent, a sodium salt, additives, and a flame retardant. The organic solvent is a combination of cyclic and linear carbonates. The cyclic carbonate is ethylene carbonate, and the linear carbonate is dimethyl carbonate. The mass ratio of the cyclic to linear carbonates is 4:6. The sodium salt is sodium hexafluorophosphate at a concentration of 1.0 mol / L. The additives include FEC, sulfonates, sulfates, and NaDFOB. The mass percentage of FEC in the electrolyte is 'a', the mass percentage of sulfonates and sulfates in the electrolyte is 'b', and the mass percentage of NaDFOB in the electrolyte is 'c'. The flame retardant is compound A1, and the mass percentage of compound A1 in the electrolyte is 'd'.

[0111]

[0112] Figure 1 For compound A1 31 P-NMR NMR spectrum. For example... Figure 1 As shown, the peak position of P in the compound of this application is 139.3 ppm. Figure 2 For compound A1 19 F-NMR nuclear magnetic resonance spectrum. For example... Figure 2 As shown, the peak position of F in the compound of this application is -82.3 ppm.

[0113] Examples 2-14 and Comparative Examples 1-2

[0114] Examples 2-14 and Comparative Examples 1-2 are electrolytes with similar compositions to those in Example 1. The differences are listed in Table 1.

[0115] Sodium-ion batteries were assembled using the electrolytes from Examples 1-14 and Comparative Examples 1-2, respectively. The positive electrode material was polyanionic sodium iron pyrophosphate, and the negative electrode material was hard carbon. The separator was a PE membrane.

[0116] Example 15

[0117] This is a lithium-ion battery, and the metal salt in the electrolyte is a lithium salt. The other components are the same as in Example 1.

[0118] The cycle capacity retention and hydrogen content under 500W heating thermal runaway of the sodium-ion batteries corresponding to each embodiment and comparative example were tested respectively. The test results are listed in Table 1.

[0119] The test procedure for cycle capacity retention is as follows:

[0120] 1) Charge the battery at 45℃ with a constant current and constant voltage of 1C until it reaches 3.95V / 0.05C cutoff, and let it stand for 30 minutes;

[0121] 2) Discharge the battery at a constant current of 1C to 2.0V at 45℃, and let it stand for 30 minutes;

[0122] 3) Repeat steps 1-2 for 200 cycles.

[0123] The process for testing hydrogen content during thermal runaway under 500W heating is as follows:

[0124] 1. Pretreatment: The battery is charged at a constant current of 0.2C to 3.95V / 0.05C.

[0125] 2. Test environment preparation: Use a flat or rod-shaped heating device, and the heating device should be in direct contact with the battery.

[0126] 3. Charge with a constant current of 1It, start heating, power 500W, and continuously heat the test object at its maximum power.

[0127] 4. When the conditions for triggering thermal runaway are met, or when the temperature reaches 300℃ or the test time reaches 4 hours, charging and heating shall be stopped.

[0128] The following are the conditions for determining whether thermal runaway has occurred:

[0129] 1) Voltage ≤ 1V and three consecutive temperature rise rates ≥ 3℃ / s;

[0130] 2) Fire or explosion;

[0131] 5. Collect the gas generated during the thermal runaway process and analyze the H2 content using a gas chromatography-mass spectrometry (GC-MS) analyzer.

[0132] Table 1

[0133]

[0134] Based on the test data in Table 1, compared to Example 6, when the mass ratio of flame retardant to additive is controlled within the range of 0.02 to 1.54, the hydrogen content during thermal runaway can be effectively reduced. Compared to Example 6, when the mass ratio of flame retardant to additive is 2.0, exceeding 1.54, although the hydrogen content during thermal runaway decreases, the cycle capacity retention rate decreases significantly, affecting the cycle stability of the battery. Therefore, when preparing the electrolyte, it is necessary to control both the amount of flame retardant added within a certain range and the mass ratio of flame retardant to FEC, sulfonate esters, sulfate esters, and NaDFOB in the additives, to avoid excessive deviations in the addition amounts of flame retardant, FEC, sulfonate esters, sulfate esters, and NaDFOB, which could affect the performance of the flame retardant.

[0135] The test data from Examples 1, 7 and 8 show that when the ratio of cyclic carbonates to chain carbonates in the additives changes, it will have a certain impact on the cycle performance and hydrogen production of the battery, but all of them have good cycle stability and low hydrogen production.

[0136] Comparative data from Examples 1, 9, and 10 show that changes in the concentration of sodium salt in the additive can have a certain impact on the cycle performance and hydrogen production of the battery, but all examples exhibit good cycle stability and low hydrogen production.

[0137] In Examples 11-14, the flame retardants were compounds A2, A4, A7, and A10, respectively. The test data from Examples 11-14 show that when flame retardants A2, A4, A7, and A10 were used, hydrogen production was reduced compared to Comparative Example 1, while also exhibiting good cycle performance.

[0138] Example 15 is an electrolyte for lithium-ion batteries. The difference from Example 1 is that lithium hexafluorophosphate is used instead of sodium hexafluorophosphate in the electrolyte. Everything else is the same as in Example 1. Data from Example 15 shows that the electrolyte of this application, when used in lithium-ion batteries, can achieve similar effects to sodium-ion batteries.

[0139] Furthermore, the test data from Examples 1-15 and Comparative Example 1 show that the cycle performance and hydrogen production of the batteries corresponding to Examples 1-15 are superior to those of Comparative Example 1. This indicates that by adding a compound conforming to formula (1) of this application to the electrolyte, the hydrogen production of the battery can be significantly reduced, and the cycle performance of the battery can be improved. The test data from Examples 1-15 and Comparative Example 2 show that when the mass percentage of the flame retardant in the electrolyte exceeds 2%, such as when the mass percentage in the comparative example is 3%, although the hydrogen production is reduced, the cycle performance of the battery is also significantly reduced.

[0140] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A battery, characterized in that, It includes a positive electrode, a separator, a negative electrode and an electrolyte, wherein the electrolyte includes a flame retardant, wherein the flame retardant includes a compound of formula (1), wherein the compound of formula (1) accounts for 0.1-4% of the mass of the electrolyte; Wherein, R1 is selected from sulfone, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by sulfone. R2 is selected from cyano, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; at least one hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is substituted by a cyano group; R3 is selected from trifluoromethyl, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by a halogen.

2. The battery according to claim 1, characterized in that, When R1 is an alkyl group with 1 to 10 carbon atoms, at least one hydrogen atom in the alkyl group with 1 to 10 carbon atoms is replaced by a sulfone group; when R1 is an aryl group with 6 to 20 carbon atoms, at least one hydrogen atom in the aryl group with 6 to 20 carbon atoms is replaced by a sulfone group.

3. The battery according to claim 1 or 2, characterized in that, The structure of R1 is shown in equation (2): Wherein, * represents the connection site of O in equation (2) and equation (1); R 11 It is selected from alkyl groups with 1 to 10 carbon atoms or fluoroalkyl groups with 1 to 10 carbon atoms.

4. The battery according to any one of claims 1-3, characterized in that, The structure of R2 is shown in equation (3): NC-R 21 -*, Equation (3) Wherein, * represents the connection site of O in equation (3) and equation (1); R 21 Selected from alkyl groups with 1 to 10 carbon atoms or aryl groups with 6 to 20 carbon atoms.

5. The battery according to any one of claims 1-4, characterized in that, The structure of R3 is shown in equation (4): F3C-R 31 -*, Equation (4) Wherein, * represents the connection site of O in equation (4) and equation (1); R 31 It is selected from alkyl groups with 1 to 10 carbon atoms or aryl groups with 6 to 20 carbon atoms.

6. The battery according to any one of claims 1-5, characterized in that, The structure of the compound represented by formula (1) is shown below:

7. The battery according to any one of claims 1-6, characterized in that, The electrolyte includes an organic solvent, which includes cyclic carbonates and chain carbonates, and the mass ratio of the cyclic carbonates to the chain carbonates is 0.5 to 1.

0.

8. The battery according to claim 7, characterized in that, The electrolyte further includes additives, including fluoroethylene carbonate, sulfonate, sulfate, and sodium difluorooxalate borate. The mass percentage (a) of the fluoroethylene carbonate in the electrolyte is 0.5-3%, the total mass percentage (b) of the sulfonate and sulfate in the electrolyte is 0.3-3%, and the mass percentage (c) of the sodium difluorooxalate borate in the electrolyte is 0.2-2%.

9. The battery according to claim 8, characterized in that, The mass percentage of the compound shown in formula (1) in the electrolyte is d, and the relationship between d, a, b and c satisfies that d / (a+b+c) is 0.02 to 1.

54.

10. An electrolyte, characterized in that, The electrolyte includes a flame retardant, which includes a compound of formula (1), wherein the compound of formula (1) accounts for 0.1 to 4% of the mass of the electrolyte. Wherein, R1 is selected from sulfone, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by sulfone. R2 is selected from cyano, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; at least one hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is substituted by a cyano group; R3 is selected from trifluoromethyl, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by a halogen.

11. A compound, characterized in that, The compound is shown in the following formula. Wherein, R1 is selected from sulfone, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by sulfone. R2 is selected from cyano, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; wherein at least one hydrogen atom in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms is replaced by a cyano group; R3 is selected from trifluoromethyl, alkyl containing 1 to 10 carbon atoms, or aryl containing 6 to 20 carbon atoms; the hydrogen in the alkyl containing 1 to 10 carbon atoms or the aryl containing 6 to 20 carbon atoms may be replaced by a halogen.

12. An energy storage system, characterized in that, The energy storage system includes a power converter and at least one battery as described in any one of claims 1-9; the power converter is used to convert the voltage output by the battery into power and output it to the power grid or a load, and / or to convert the voltage output by an external power source into power and output it to the battery.

Images