Electrolyte and battery or battery pack containing the electrolyte

Abstract

This invention provides an electrolyte and a battery or battery pack containing the electrolyte, relating to the field of lithium-ion batteries. The electrolyte contains a compound of formula I or formula II, and a compound of formula III. Formulas I and II do not contain a methylene group; R1, R2, R3, R1', R2', and R3' are selected from N or O, R1 or R3 is N, and R1' or R3' is N; R4 and R4' are selected from hydrogen, methyl, cyano, halogen, aryl, alkyl, phosphate ester, and phosphite ester groups; A and A', together with their respective connected semi-circular rings, form a cyclic structure; R5 and R6 are selected from hydrogen or phenyl. In formula III, R7, R9, and N form a ring, or R7 and R9 are selected from alkyl, alkenyl, alkoxy, and silane groups; R8 is selected from alkyl, aryl, alkoxy, alkenyl, ester, five-membered heterocycle, formula IV, formula V, and formula VI; at least one of R7, R8, and R9 contains silicon.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to an electrolyte and a battery or battery pack containing the electrolyte. Background Technology

[0002] As the adoption rate of lithium-ion batteries increases, the performance of existing lithium-ion batteries is gradually failing to meet user needs, especially in terms of energy density, cycle performance, and safety. In current technology, using high-voltage ternary materials can effectively improve battery energy density; however, these batteries suffer from poor high-temperature storage and cycle performance, severely limiting their widespread application. Specifically, after high-voltage charging, a hydrogenation reaction occurs on the surface of the battery's oxide positive electrode. During this process, hydrogen atoms in the electrolyte are converted into protons (H+). + Electrons are embedded in the surface of the cathode material lattice in a protonated form, causing the oxygen in the lattice to protonate. The electrons lost during the reaction reduce nearby high-valence transition metals, inducing lattice expansion and reducing the chemical and mechanical stability of the cathode material. Furthermore, lithium hexafluorophosphate (LiPF6) is a commonly used lithium salt in electrolytes, but high voltage and high temperature conditions promote its hydrolysis, producing hydrogen fluoride (HF). HF not only degrades the interface between the electrode material and the electrolyte but also causes transition metal leaching and damage to the electrode material interface, leading to reduced cycle stability and safety of the battery. Summary of the Invention

[0003] The main objective of this invention is to provide an electrolyte and a battery or battery pack containing the electrolyte, so as to solve the problem that lithium-ion batteries in the prior art are difficult to simultaneously have high energy density, good high-temperature storage performance and good high-temperature cycle performance.

[0004] To achieve the above objectives, according to one aspect of the present invention, an electrolyte is provided comprising a first additive and a second additive, wherein the first additive comprises a compound of formula I or a compound of formula II, and the second additive comprises a compound of formula III.

[0005] Formula I, Formula II, Formula III;

[0006] The first additive does not contain methylene (-CH2-) groups, and the first additive meets the following conditions:

[0007] (1) R1, R2, R3, R1', R2', and R3' are each independently selected from N and O, and at least one of R1 and R3 is selected from N, and at least one of R1' and R3' is selected from N; the degree of unsaturation of the five-membered ring containing R1, R2, and R3 is α, where 1≤α≤3; the degree of unsaturation of the five-membered ring containing R1', R2', and R3' is α', where 1≤α'≤3;

[0008] (2) R4 and R4' are each independently selected from hydrogen, methyl, cyano, halogen group, C6-C with or without halogen substituents. 10 One of the following: aryl, C1-C5 alkyl containing a halogen substituent, phosphate ester group containing a halogen substituent or without a substituent, and phosphite ester group containing a halogen substituent or without a substituent;

[0009] (3) A and its connected semi-circular ring together form the first ring structure, and A' and its connected semi-circular ring together form the second ring structure. The first ring structure and the second ring structure are each independently selected from one of the five-membered ring, six-membered ring, fused ring, and benzene fused heterocycle. The degree of unsaturation of the first ring structure is β, where 1≤β≤7. The first ring structure contains halogen substituents or does not contain substituents. The degree of unsaturation of the second ring structure is β', where 1≤β'≤7. The second ring structure contains halogen substituents or does not contain substituents.

[0010] (4) R5 and R6 are each independently selected from hydrogen, phenyl containing halogen substituents or without substituents;

[0011] The second additive must meet the following conditions:

[0012] (5) R7 and R9 are connected to form a ring, so that R7, R9 and N connected to R7 and R9 together constitute a five-membered silicon-nitrogen heterocycle, and the degree of unsaturation of the five-membered silicon-nitrogen heterocycle is 1;

[0013] Alternatively, R7 and R9 are each independently selected from one of the following: C1-C5 alkyl groups containing or without halogen substituents, C1-C5 alkenyl groups containing or without halogen substituents, C1-C5 alkoxy groups containing or without halogen substituents, and silane groups containing or without halogen substituents or C1-C3 alkyl substituents.

[0014] (6) R8 is selected from C1-C5 alkyl groups containing halogen substituents and / or containing oxo groups, C1-C5 alkyl groups without substituents, and C6-C5 alkyl groups containing halogen substituents or without substituents. 10One of the following: aryl, C1-C5 alkoxy group containing or without a silane substituent, C1-C5 alkenyl group containing or without a halogen substituent, C1-C5 ester group containing or without a silane substituent, five-membered heterocycle containing or without a silane substituent, group represented by Formula IV, or group represented by Formula V.

[0015] Formula IV, Formula V;

[0016] Among them, R 10 R 11 Each is independently selected from one of trimethylsilyl and C1-C5 alkyl groups, R 12 R 13 All are C1-C5 alkylene groups. This represents the position where R8 connects to N in Equation III;

[0017] (7) At least one of the groups R7, R8 and R9 contains silicon.

[0018] Furthermore, R1 is selected from N, R2 is selected from O, and R3 is selected from N.

[0019] Furthermore, R1' is selected from O, R2' is selected from O, and R3' is selected from N.

[0020] Furthermore, R4 and R4' are each independently selected from one of hydrogen, cyano, halogen group, unsubstituted phenyl, or halomethyl.

[0021] Furthermore, the first cyclic structure and the second cyclic structure are each independently selected from one of the following groups: furan group, phenyl group, naphthyl group, and indole group.

[0022] Furthermore, R5 and R6 are each independently selected from phenyl groups containing halogen substituents or without substituents.

[0023] Furthermore, R7 and R9 are linked to form a ring, such that R7, R9, and the N linked to R7 and R9 together constitute the group shown in formula VI.

[0024] Equation VI, where, The position where the group shown in formula VI is connected to R8;

[0025] Alternatively, in Formula III, R7 and R9 are each independently selected from trimethylsilyl groups.

[0026] Further, in Formula III, R8 is selected from one of the following: C1-C5 alkyl groups containing halogen substituents and / or containing oxo groups; C1-C5 alkyl groups without substituents; phenyl groups containing halogen substituents; C1-C5 alkoxy groups containing silane substituents or without substituents; C1-C5 alkenyl groups without substituents; C1-C5 ester groups containing silane substituents; five-membered heterocycles containing silane substituents; groups shown in Formula IV; and groups shown in Formula V.

[0027] Furthermore, the compound shown in Formula I includes at least one of the compounds shown in Formulas 1 to 2, and the compound shown in Formula II includes at least one of the compounds shown in Formulas 3 to 14.

[0028] Formula 1 Formula 2 Formula 3

[0029] Formula 4 Formula 5 Formula 6

[0030] Formula 7 Formula 8 Formula 9

[0031] Formula 10 Formula 11

[0032] Formula 12 Formula 13 Equation 14.

[0033] Furthermore, the compound shown in Formula III includes at least one of the compounds shown in Formulas 15 to 28:

[0034] Formula 15 Formula 16 Formula 17 Formula 18 Formula 19 Formula 20 Formula 21 Equation 22 Formula 23 Formula 24 Formula 25 Formula 26 Equation 27 Equation 28.

[0035] Furthermore, the mass percentage of the first additive in the electrolyte is a%, and 0.15≤a≤2.5.

[0036] Furthermore, the second additive accounts for b% of the mass of the electrolyte, and 0.2 ≤ b ≤ 3.

[0037] Furthermore, the electrolyte contains lithium salt, and the mass percentage of lithium salt in the electrolyte is c%, where 11.6 ≤ c ≤ 18.75.

[0038] Furthermore, the electrolyte contains a lithium salt selected from at least one of lithium hexafluorophosphate (LiPF6), lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)imide, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium bis(pentafluoroethylsulfonyl)imide, and lithium tri(trifluoromethylsulfonyl)methyl.

[0039] Furthermore, the electrolyte contains a solvent selected from at least one of cyclic carbonates, linear carbonates, cyclic carboxylic esters, linear carboxylic esters, sulfones, phosphates, and phosphites.

[0040] Furthermore, cyclic carbonates include at least one of ethylene carbonate and propylene carbonate; linear carbonates include at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and methyl ethyl carbonate; cyclic carboxylic acid esters include γ-butyrolactone, γ-valerolactone, and... - At least one of caprolactone; linear carboxylic acid esters including at least one of methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl acetate; sulfone compounds including at least one of dimethyl sulfoxide, sulfolane, and diphenyl sulfone; phosphate ester compounds including at least one of triethyl phosphate, trimethyl phosphate, and triphenyl phosphate; phosphite compounds including at least one of ethyl methyl phosphate, trimethyl phosphite, and tris(2,2,2-trifluoroethyl) phosphite.

[0041] Furthermore, the electrolyte contains a third additive selected from at least one of ethylene carbonate, vinylene carbonate, 1,3-propane sulpholactone, mannitol sulfate, 1,3-dioxane, 1,4-dioxane, lithium dioxaborate, lithium difluorooxaborate, lithium tetrafluoroborate, vinyl sulfate, 1,3-propane sulpholactone, propenyl-1,3-sulfonyl lactone, 2,4-butane sulpholactone, methanedisulfonate, 1,3-propanedisulfonic anhydride, ethylene sulfite, and propargyl phosphate.

[0042] According to another aspect of the present invention, a battery is provided, the battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte provided in the foregoing technical solutions; wherein the positive electrode contains a positive electrode material, and the positive electrode material comprises an active material.

[0043] Furthermore, the specific surface area of ​​the active material is X m. 2 / g, the mass percentage of the first additive in the electrolyte is a%, the mass percentage of the second additive in the electrolyte is b%, and the mass percentage of the lithium salt in the electrolyte is c.

[0044] Furthermore, 0.25 ≤ X ≤ 1.5.

[0045] Furthermore, 0.2 ≤ a / X ≤ 2.3.

[0046] Furthermore, 0.021 ≤ (b / c) / X ≤ 0.32.

[0047] Furthermore, the active material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium nickel cobalt manganese aluminum oxide, wherein in lithium nickel cobalt manganese oxide, the molar content of nickel element in the three metal elements nickel, cobalt, and manganese is 60% to 80%.

[0048] Furthermore, the active material contains a dopant element selected from at least one of Al, Mg, Ti, Nb, Cr, Y, Sr, S, F, and Zr.

[0049] Furthermore, the cathode material also includes a coating layer located on the surface of the active material, wherein the material of the coating layer is selected from at least one of oxides and phosphates.

[0050] Furthermore, the oxide is selected from at least one of aluminum oxide, titanium dioxide, and zirconium dioxide.

[0051] Furthermore, the phosphate is selected from at least one of lithium phosphate and lithium iron phosphate.

[0052] According to another aspect of the present invention, a battery pack is provided, which includes the battery provided in the foregoing technical solutions.

[0053] By applying the technical solution of this invention, the electrolyte contains a first additive and a second additive, which can effectively improve the high-temperature storage performance and high-temperature cycle performance of the battery. On one hand, the first additive does not contain methylene groups, thus avoiding the hydrogen atoms generated by the breaking of CH bonds under high voltage as proton hydrogen (H₂O). +The first and second additives are embedded in the surface of the cathode material lattice in a form that helps improve the chemical and mechanical stability of the cathode material. Simultaneously, both the first and second additives possess high HOMO energy levels. Their oxidation on the cathode side helps form a CEI film on the cathode material surface, composed of inorganic components such as Li3N, LiF, and Li2CO3, and cross-linked organic compounds. This CEI film helps improve the stability of the cathode particles, thereby suppressing crosstalk effects, reducing the risk of cell self-discharge under high-temperature fully charged conditions, and improving the battery's high-temperature storage performance and high-temperature cycle stability. On the other hand, the electrolyte contains a second additive, which reacts with H... + and fluoride ions (F - The lower Gibbs free energy required for binding helps to efficiently remove acidic substances generated in the electrolyte and inhibit the dissolution of transition metals, thereby improving the safety and cycle stability of the battery under high-temperature operating conditions. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0055] As described in the background section of this invention, existing technologies suffer from the problem that lithium-ion batteries cannot simultaneously possess high energy density, good high-temperature storage performance, and good high-temperature cycle performance. To address these issues, in a typical embodiment of this invention, an electrolyte is provided, comprising a first additive and a second additive. The first additive comprises a compound represented by Formula I or Formula II, and the second additive comprises a compound represented by Formula III.

[0056] Formula I, Formula II, Formula III;

[0057] The first additive does not contain methylene groups, and the first additive meets the following conditions:

[0058] (1) R1, R2, R3, R1', R2', and R3' are each independently selected from N and O, and at least one of R1 and R3 is selected from N, and at least one of R1' and R3' is selected from N; the degree of unsaturation of the five-membered ring containing R1, R2, and R3 is α, where 1≤α≤3; the degree of unsaturation of the five-membered ring containing R1', R2', and R3' is α', where 1≤α'≤3;

[0059] (2) R4 and R4' are each independently selected from hydrogen, methyl, cyano, halogen group, C6-C with or without halogen substituents. 10 One of the following: aryl, C1-C5 alkyl containing a halogen substituent, phosphate ester group containing a halogen substituent or without a substituent, and phosphite ester group containing a halogen substituent or without a substituent;

[0060] (3) A and its connected semi-circular ring together form the first ring structure, and A' and its connected semi-circular ring together form the second ring structure. The first ring structure and the second ring structure are each independently selected from one of the five-membered ring, six-membered ring, fused ring, and benzene fused heterocycle. The degree of unsaturation of the first ring structure is β, where 1≤β≤7. The first ring structure contains halogen substituents or does not contain substituents. The degree of unsaturation of the second ring structure is β', where 1≤β'≤7. The second ring structure contains halogen substituents or does not contain substituents.

[0061] (4) R5 and R6 are each independently selected from hydrogen, phenyl containing halogen substituents or without substituents;

[0062] The second additive must meet the following conditions:

[0063] (5) R7 and R9 are connected to form a ring, so that R7, R9 and N connected to R7 and R9 together constitute a five-membered silicon-nitrogen heterocycle, and the degree of unsaturation of the five-membered silicon-nitrogen heterocycle is 1;

[0064] Alternatively, R7 and R9 are each independently selected from one of the following: C1-C5 alkyl groups containing or without halogen substituents, C1-C5 alkenyl groups containing or without halogen substituents, C1-C5 alkoxy groups containing or without halogen substituents, and silane groups containing or without halogen substituents or C1-C3 alkyl substituents.

[0065] (6) R8 is selected from C1-C5 alkyl groups containing halogen substituents and / or containing oxo groups, C1-C5 alkyl groups without substituents, and C6-C5 alkyl groups containing halogen substituents or without substituents. 10 One of the following: aryl, C1-C5 alkoxy group containing or without a silane substituent, C1-C5 alkenyl group containing or without a halogen substituent, C1-C5 ester group containing or without a silane substituent, five-membered heterocycle containing or without a silane substituent, group represented by Formula IV, or group represented by Formula V.

[0066] Formula IV, Formula V;

[0067] Among them, R 10 R 11 Each is independently selected from one of trimethylsilyl and C1-C5 alkyl groups, R12 and R 13 All are C1-C5 alkylene groups. This represents the position where R8 connects to N in Equation III;

[0068] (5) In formula III, at least one of the groups R7, R8 and R9 contains silicon.

[0069] In this invention, the electrolyte contains a first additive and a second additive, which can effectively improve the high-temperature storage performance and high-temperature cycle performance of the battery. On one hand, the first additive does not contain methylene groups, thus preventing hydrogen atoms generated by the breaking of CH bonds under high voltage from becoming proton hydrogen (H₂O). + The first and second additives are embedded in the surface of the cathode material lattice in a form that helps improve the chemical and mechanical stability of the cathode material. Simultaneously, both the first and second additives possess high HOMO energy levels. Their oxidation on the cathode side helps form a CEI film on the cathode material surface, composed of inorganic components such as Li3N, LiF, and Li2CO3, and cross-linked organic compounds. This CEI film helps improve the stability of the cathode particles, thereby suppressing crosstalk effects and reducing the risk of cell self-discharge under high-temperature fully charged conditions, thus improving the battery's high-temperature storage and cycling performance. On the other hand, the electrolyte contains a second additive, which reacts with H... + and fluoride ions (F - With a lower required Gibbs free energy, it can efficiently remove acidic substances generated in the electrolyte, inhibit transition metal dissolution, and improve the safety and cycle stability of the battery under high-temperature operating conditions.

[0070] Crosstalk refers to the phenomenon where, during charge-discharge cycles, transition metal ions in the positive electrode dissolve and enter the electrolyte. Subsequently, these transition metal ions migrate to the vicinity of the negative electrode and are deposited on the SEI film on the surface of the negative electrode particles, leading to a decrease in battery performance and a shortened lifespan.

[0071] In some implementations, R1 is selected from N, R2 is selected from O, and R3 is selected from N.

[0072] In the above embodiments of this application, the above structure helps to reduce the hydrogenation reaction that occurs on the surface of the cathode material under high voltage, improve the chemical and mechanical stability of the cathode material, and at the same time enable the first additive to have a higher HOMO energy level, which promotes the formation of a CEI film on the surface of the cathode material composed of inorganic components such as Li3N, LiF and Li2CO3 and cross-linked network organic compounds, effectively improving the high-temperature storage performance and high-temperature cycle performance of the battery.

[0073] In some implementations, R1' is selected from O, R2' is selected from O, and R3' is selected from N.

[0074] In the above embodiments of this application, the above structure helps to suppress H + Embedded into the surface of the cathode material lattice, it enhances the chemical and mechanical stability of the cathode material. At the same time, it gives the first additive a higher HOMO energy level, which helps to form a CEI film composed of inorganic components such as Li3N, LiF and Li2CO3 and cross-linked network organic compounds on the surface of the cathode material through oxidation, thereby improving the high-temperature storage performance and high-temperature cycle performance of the battery.

[0075] In some embodiments, R4 and R4' are each independently selected from hydrogen, cyano, halogen group, unsubstituted phenyl, and halomethyl.

[0076] In the above embodiments of this application, the above-mentioned groups help to reduce the hydrogen atoms generated in the electrolyte under high voltage conditions, improve the chemical and mechanical stability of the cathode material, and at the same time make the first additive have a higher HOMO energy level, which helps to improve the stability of the cathode material, thereby improving the high-temperature storage performance and high-temperature cycling performance of the battery.

[0077] In some embodiments, the first cyclic structure and the second cyclic structure are each independently selected from one of the following groups: furan group, phenyl group, naphthyl group, and indole group.

[0078] In the above embodiments of this application, the above structure helps to improve the stability of the first additive in a high temperature and high pressure environment, and at the same time makes the first additive have a higher HOMO energy level, thereby reducing the risk of cell self-discharge under high temperature and full charge state, and improving the high temperature storage performance and high temperature cycle performance of the battery.

[0079] In some embodiments, R5 and R6 are each independently selected from phenyl groups containing halogen substituents or without substituents.

[0080] In the above embodiments of this application, the aforementioned groups help to reduce the number of hydrogen atoms participating in the hydrogenation reaction on the surface of the cathode material, thereby improving the chemical and mechanical stability of the cathode material.

[0081] In some embodiments, R7 and R9 are linked to form a ring, such that R7, R9, and the N linked to R7 and R9 together constitute the group shown in Formula VI.

[0082] Equation VI, where, The position where the group shown in formula VI is connected to R8;

[0083] Alternatively, in Formula III, R7 and R9 are each independently selected from trimethylsilyl groups.

[0084] In the above embodiments of this application, on the one hand, the structure has silicon-containing groups, which helps to reduce the reaction between the second additive and H. + and / or F - By combining the required Gibbs free energy, HF generated in the electrolyte can be efficiently removed, improving the battery's safety and cycle stability under high-temperature operating conditions. Furthermore, the aforementioned structure contains nitrogen-containing heterocycles, giving the second additive a high HOMO energy level, which facilitates its participation in the formation of the CEI film, thereby suppressing crosstalk effects and improving the battery's high-temperature storage performance and high-temperature cycle stability.

[0085] In some embodiments, R8 is selected from one of the following: C1-C5 alkyl groups containing halogen substituents and / or containing oxo-keto groups; unsubstituent C1-C5 alkyl groups; phenyl groups containing halogen substituents; C1-C5 alkoxy groups containing silane substituents or unsubstituent C1-C5 alkenyl groups; unsubstituent C1-C5 ester groups containing silane substituents; five-membered heterocycles containing silane substituents; groups represented by Formula IV; and groups represented by Formula V.

[0086] In the embodiments described above in this application, the aforementioned groups help to reduce the interaction between the second additive and H. + and / or fluoride ions (F - The required Gibbs free energy enables the second additive to rapidly combine with acidic substances in the electrolyte, reducing the corrosion of the positive electrode by acidic substances and inhibiting the dissolution of transition metals, thereby improving the safety and cycle stability of the battery under high-temperature operating conditions.

[0087] In some embodiments, the compound represented by Formula I includes at least one of the compounds represented by Formulas 1 to 2, and the compound represented by Formula II includes at least one of the compounds represented by Formulas 3 to 14.

[0088] Formula 1 Formula 2 Formula 3

[0089] Formula 4 Formula 5 Formula 6

[0090] Formula 7 Formula 8 Formula 9

[0091] Formula 10 Formula 11

[0092] Formula 12 Formula 13 Equation 14.

[0093] The CAS numbers corresponding to the compounds shown in Formulas 1 to 14 are shown in Table 1.

[0094] Table 1

[0095]

[0096] In the above embodiments of this application, the above structure helps to enable the first additive to have a higher HOMO energy level, thereby oxidizing and forming a CEI film composed of inorganic components such as Li3N, LiF and Li2CO3 and cross-linked network organic compounds on the positive electrode surface, improving the high-temperature storage performance and high-temperature cycle stability of the battery. At the same time, the above structure can effectively reduce the hydrogen atoms that migrate to the surface of the positive electrode material in a high-voltage environment, thereby improving the chemical stability and mechanical stability of the positive electrode material.

[0097] In some embodiments, the compound represented by Formula III includes at least one of the compounds represented by Formulas 15 to 28:

[0098] Formula 15 Formula 16 Formula 17 Formula 18 Formula 19 Formula 20 Formula 21 Equation 22 Formula 23 Formula 24 Formula 25 Formula 26 Equation 27 Equation 28.

[0099] The CAS numbers corresponding to the compounds shown in Formulas 15 to 28 are shown in Table 2.

[0100] Table 2

[0101]

[0102] In the above embodiments of this application, the above structure causes the second additive to react with H. + and fluoride ions (F -The lower Gibbs free energy required for binding helps to remove acidic substances generated in the electrolyte in a timely manner. At the same time, the second additive has a higher HOMO energy level, which helps to form a CEI film composed of inorganic components such as Li3N, LiF and Li2CO3 and cross-linked network organic compounds on the surface of the cathode material. This reduces the risk of cell self-discharge under high temperature and full charge conditions and improves the high temperature storage performance of the battery.

[0103] In some embodiments, the first additive has a mass percentage of a% in the electrolyte, and 0.15 ≤ a ≤ 2.5. Preferably, the first additive has a mass percentage of a% in the electrolyte, and 0.25 ≤ a ≤ 1.5.

[0104] In the above embodiments of this application, the mass ratio range of the first additive helps the first additive to form a CEI film composed of inorganic components such as Li3N, LiF and Li2CO3 and cross-linked network organic compounds on the surface of the positive electrode material during the oxidation of the positive electrode. At the same time, it can effectively reduce the hydrogen atoms migrating to the surface of the positive electrode, especially the hydrogen atoms in the first additive molecules, thereby improving the high-temperature storage performance and high-temperature cycle stability of the battery.

[0105] Typical, but not limiting, the mass percentage of the first additive in the electrolyte is 0.15%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.85%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, or any two of these values.

[0106] In some embodiments, the second additive accounts for b% of the electrolyte by mass, and 0.2 ≤ b ≤ 3. Preferably, the second additive accounts for b% of the electrolyte by mass, and 0.35 ≤ b ≤ 1.8.

[0107] In the above embodiments of this application, the mass ratio range of the second additive helps to efficiently remove acidic substances generated in the electrolyte, inhibit the dissolution of transition metals, and improve the safety and cycle stability of the battery under high-temperature operating conditions.

[0108] Typical, but not limiting, the mass percentage of the second additive in the electrolyte is 0.2%, 0.3%, 0.35%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any two of these values.

[0109] In some embodiments, the electrolyte contains a lithium salt, the lithium salt comprising c% of the electrolyte by mass, and 11.6 ≤ c ≤ 18.75.

[0110] In the above embodiments of this application, when the lithium salt content in the electrolyte is within the above range, on the one hand, the electrolyte can have good lithium-ion conductivity and promote the formation of CEI film on the positive electrode surface; on the other hand, the content of acidic substances in the electrolyte can be effectively controlled, thereby improving the safety and cycle stability of the battery under high-temperature operating conditions.

[0111] In some embodiments, the electrolyte comprises a lithium salt selected from at least one of LiPF6, lithium dioxolane borate, lithium difluorooxolane borate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium di(trifluoromethylsulfonyl)imide, lithium tetrafluorooxolane phosphate, lithium difluorobis(oxolane) phosphate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(pentafluoroethylsulfonyl)imide, and lithium tri(trifluoromethylsulfonyl)methyl.

[0112] In the embodiments described above, the electrolyte containing the aforementioned lithium salt exhibits high lithium-ion conductivity and low impedance. Simultaneously, the lithium salt promotes the formation of a CEI film on the positive electrode surface, thereby enhancing the battery's cycle stability. Furthermore, when the lithium salt and the second additive coexist, the second additive can rapidly combine with the acidic substances generated by the hydrolysis of the lithium salt under high voltage and high temperature conditions, thereby protecting the electrode materials and interface, and improving the battery's cycle stability and safety.

[0113] In some embodiments, the electrolyte comprises a solvent selected from at least one of cyclic carbonates, linear carbonates, cyclic carboxylic acid esters, linear carboxylic acid esters, sulfones, phosphate esters, and phosphites. Preferably, the cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate; the linear carbonate includes at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and methyl ethyl carbonate; and the cyclic carboxylic acid ester includes γ-butyrolactone, γ-valerolactone, etc. - At least one of caprolactone; linear carboxylic acid esters including at least one of methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl acetate; sulfone compounds including at least one of dimethyl sulfoxide, sulfolane, and diphenyl sulfone; phosphate ester compounds including at least one of triethyl phosphate, trimethyl phosphate, and triphenyl phosphate; phosphite compounds including at least one of ethyl methyl phosphate, trimethyl phosphite, and tris(2,2,2-trifluoroethyl) phosphite.

[0114] In the above embodiments of this application, the solvent has good solubility for lithium salts, and relatively good chemical and thermal stability, which helps to improve the high-temperature storage performance and high-temperature cycle stability of the battery.

[0115] In some embodiments, the electrolyte contains a third additive selected from at least one of ethylene carbonate, vinylene carbonate, 1,3-propane sulpholactone, mannitol sulfate, 1,3-dioxane, 1,4-dioxane, lithium dioxaborate, lithium difluorooxaborate, lithium tetrafluoroborate, vinyl sulfate, 1,3-propane sulpholactone, propenyl-1,3-sulfonyl lactone, 2,4-butane sulpholactone, methanedisulfonate, 1,3-propanedisulfonic anhydride, ethylene sulfite, and propargyl phosphate.

[0116] In the above embodiments of this application, the third additive helps to promote the formation of a thin and uniform dense SEI film on the surface of the negative electrode in the early stage of formation (when the battery voltage is low). The main components of the SEI film are LiF, Li2CO3, Li2O and sulfur-containing organic and inorganic components distributed in phase, thereby improving the stability of the negative electrode particles at high temperature, and / or, in the later stage of formation (when the battery voltage is high), promotes the formation of a dense CEI film on the surface of the positive electrode, thereby improving the stability of the positive electrode particles, and thus improving the high-temperature performance and cycle performance of the battery.

[0117] In another typical embodiment of the present invention, a battery is provided, which includes a positive electrode, a negative electrode, a separator, and an electrolyte provided in the foregoing embodiments; wherein the positive electrode contains a positive electrode material, and the positive electrode material includes an active material.

[0118] In some embodiments, the specific surface area of ​​the active material is X m 2 / g, 0.25≤X≤1.5. Preferably, the specific surface area of ​​the active material is X m². 2 / g, 0.5≤X≤1.3.

[0119] In the above embodiments of this application, when the specific surface area of ​​the active material is within the above range, it has more electrochemical reaction sites and a shorter lithium-ion diffusion path, thereby improving the rate performance of the battery, while ensuring that the active material has good structural stability, thereby improving the cycle performance of the battery.

[0120] Typical, but not limiting, active materials have a specific surface area of ​​0.25 m². 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g or a range of values ​​consisting of any two of its values.

[0121] In some embodiments, the specific surface area of ​​the active material is X m 2 / g, the mass percentage of the first additive in the electrolyte is a%, 0.2≤a / X≤2.3. Preferably, the specific surface area of ​​the active material is X m². 2 / g, the mass percentage of the first additive in the electrolyte is a%, 0.3≤a / X≤2.06.

[0122] In the above embodiments of this application, when a / X meets the above conditions, the content of the first additive is fully matched with the specific surface area of ​​the active material, which helps to form a uniform CEI film on the positive electrode surface that is rich in inorganic matter and encapsulates the positive electrode material. This effectively reduces interfacial side reactions, reduces positive electrode voltage drop, and thus improves the high-temperature storage performance and high-temperature cycle stability of the battery.

[0123] Typical, but not restrictive, values ​​of a / X are 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, 2.06, 2.1, 2.2, 2.3, or any two of these values.

[0124] In some embodiments, the specific surface area of ​​the active material is X m 2 / g, the mass percentage of the second additive in the electrolyte is b%, the mass percentage of the lithium salt in the electrolyte is c%, and 0.021≤(b / c) / X≤0.32. Preferably, the specific surface area of ​​the active material is X m². 2 / g, the mass percentage of the second additive in the electrolyte is b%, the mass percentage of the lithium salt in the electrolyte is c%, and 0.04≤(b / c) / X≤0.29.

[0125] In the above embodiments of this application, when (b / c) / X satisfies the above conditions, on the one hand, the content of the second additive matches the content of the lithium salt, which helps the second additive free in the electrolyte to fully remove the acidic substances generated by the hydrolysis of lithium salt; on the other hand, the content of the second additive matches the specific surface area of ​​the active material, which can minimize the amount of acidic substances migrating to the vicinity of the positive electrode, suppress crosstalk from the cathode to the anode, and improve the safety and cycle stability of the battery.

[0126] Typical, but not restrictive, values ​​of (b / c) / X are 0.021, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, or any two of these values.

[0127] In some embodiments, the active material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium nickel cobalt manganese aluminum oxide, wherein in lithium nickel cobalt manganese oxide, the molar content of nickel element in the three metal elements nickel, cobalt, and manganese is 60% to 80%.

[0128] In the above embodiments of this application, the active material can effectively improve the energy density of the battery. Using the electrolyte in combination with the active material can effectively improve the mechanical and chemical stability of the active material, so that the lithium-ion battery can simultaneously have high energy density, good high-temperature storage performance and good high-temperature cycling performance.

[0129] In some embodiments, the active material includes a dopant element selected from at least one of Al, Mg, Ti, Nb, Cr, Y, Sr, S, F, and Zr.

[0130] In the above embodiments of this application, the doping elements help to further improve the stability of the active material lattice and enhance the high-temperature storage performance and high-temperature cycling performance of lithium-ion batteries.

[0131] In some embodiments, the cathode material further includes a coating layer located on the surface of the active material, the coating layer being selected from at least one of oxides and phosphates. Preferably, the oxide is selected from at least one of aluminum oxide, titanium dioxide, and zirconium dioxide. Preferably, the phosphate is selected from at least one of lithium phosphate and lithium iron phosphate.

[0132] In the above embodiments of this application, the coating layer constructed on the surface of the active material can effectively block acidic substances and hydrogen atoms in the electrolyte, thereby improving the cycle stability and capacity retention of the battery under high voltage and high temperature conditions.

[0133] In another typical embodiment of the present invention, a battery pack is provided, which includes the battery provided in the foregoing embodiments.

[0134] In the above embodiments of this application, the battery pack has the battery provided in the aforementioned embodiments, and therefore has good cycle stability and safety under high temperature and high voltage conditions, and can be used in application scenarios with stringent requirements for energy density and thermal stability.

[0135] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0136] Some of the materials used in the examples and comparative examples are as follows:

[0137] Positive electrode active material-1: LiNi 0.6 Co 0.2 Mn 0.2 O2 has a specific surface area of ​​0.75 m². 2 / g (X=0.75), purchased from Gansu Jinchuan Ruixiang New Materials Co., Ltd.

[0138] Positive electrode active material-2: LiNi 0.6 Co 0.2 Mn 0.2 O2 has a specific surface area of ​​0.5 m². 2 / g (X=0.5), purchased from Gansu Jinchuan Ruixiang New Materials Co., Ltd.

[0139] Positive electrode active material-3: LiNi 0.6 Co 0.2 Mn 0.2 O2 has a specific surface area of ​​1.3 m². 2 / g (X=1.3), purchased from Gansu Jinchuan Ruixiang New Materials Co., Ltd.

[0140] Positive electrode active material-4: LiNi is selected 0.6 Co 0.2 Mn 0.2O2 has a specific surface area of ​​0.25 m². 2 / g (X=0.25), purchased from Gansu Jinchuan Ruixiang New Materials Co., Ltd.

[0141] Positive electrode active material-5: LiNi is selected 0.6 Co 0.2 Mn 0.2 O2 has a specific surface area of ​​1.5 m². 2 / g (X=1.5), purchased from Gansu Jinchuan Ruixiang New Materials Co., Ltd.

[0142] Example 1

[0143] This embodiment provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode contains a positive electrode material, which in turn contains an active material.

[0144] The battery manufacturing method includes the following steps:

[0145] Step S1, Preparation of the positive electrode sheet: Positive electrode active material-1, conductive carbon black Super P, and binder polyvinylidene fluoride (PVDF) are mixed at a mass ratio of 96:2:2 to obtain a first mixture. Then, N-methylpyrrolidone (NMP) is added to the mixture and stirred until homogeneous, resulting in a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry is uniformly coated on both sides of a 12 μm thick aluminum foil used as a positive electrode current collector. The foil is dried at 120°C, cold-pressed, and slit to obtain the positive electrode sheet. The compacted density of the positive electrode sheet is 3.55 g / cm³. 3 The surface density of both sides is 282 mg / cm³. 2 .

[0146] Step S2, Preparation of the negative electrode sheet: Graphite, sodium carboxymethyl cellulose, and styrene-butadiene rubber are mixed in a mass ratio of 96:2:2 to obtain a second mixture. Deionized water is then added to the second mixture and stirred until homogeneous, yielding a negative electrode slurry with a solid content of 45 wt%. The negative electrode slurry is uniformly coated on both sides of an 8 μm thick copper foil current collector, and then cold-pressed and slit to obtain the negative electrode sheet. The compacted density of the negative electrode sheet is 1.63 g / cm³. 3 The areal density of both sides is 190 mg / cm³. 2 .

[0147] Step S3, preparing the electrolyte: In an argon atmosphere glove box with a water content of <10ppm, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate are mixed uniformly at a mass ratio of 3:6:1 to obtain a solvent. Then, LiPF6 is added to the solvent and mixed uniformly to obtain a mixture. The first additive shown in Formula 9 and the second additive shown in Formula 21 are added to the mixture to obtain the electrolyte.

[0148] Formula 9 Equation 21.

[0149] The mass percentage of the first additive in the electrolyte is a% of 0.85%, the mass percentage of the second additive in the electrolyte is b% of 1.3%, the mass percentage of LiPF6 in the electrolyte is c% of 12.5%, a / X=1.133, (b / c) / X=0.139.

[0150] Step S4, assembling the battery: A 10μm thick polypropylene porous film is used as a separator. The components are stacked in the order of "positive electrode - separator - negative electrode". The stacked components are then wound and placed in an aluminum-plastic film. After baking at 80°C to remove moisture, the electrolyte is injected into the aluminum-plastic film. After vacuum sealing, standing for 48 hours, formation, and hot pressing, the battery is obtained.

[0151] Example 2

[0152] The difference between this embodiment and Embodiment 1 is that, in step S3, the first additive shown in Formula 9 is replaced with the first additive shown in Formula 1, and the mass percentage a% of the first additive in the electrolyte is 0.25%, a / X = 0.333, (b / c) / X = 0.139.

[0153] Formula 1.

[0154] Example 3

[0155] The difference between this embodiment and Embodiment 1 is that, in step S3, the first additive shown in Formula 9 is replaced with the first additive shown in Formula 5, and the mass percentage a% of the first additive in the electrolyte is 0.5%, a / X = 0.667, (b / c) / X = 0.139.

[0156] Formula 5.

[0157] Example 4

[0158] The difference between this embodiment and Embodiment 1 is that, in step S3, the first additive shown in Formula 9 is replaced with the first additive shown in Formula 13, and the mass percentage a% of the first additive in the electrolyte is 1.5%, a / X=2, (b / c) / X=0.139.

[0159] Formula 13.

[0160] Example 5

[0161] The difference between this embodiment and Embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-2. Simultaneously, in step S3, the first additive shown in Formula 9 is replaced with the first additive shown in Formula 10, where a / X = 1.7 and (b / c) / X = 0.208.

[0162] Formula 10.

[0163] Example 6

[0164] The difference between this embodiment and Embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-3. Simultaneously, in step S3, the first additive shown in Formula 9 is replaced with the first additive shown in Formula 10, where a / X = 0.654 and (b / c) / X = 0.08.

[0165] Formula 10.

[0166] Example 7

[0167] The difference between this embodiment and Embodiment 1 is that in step S3, the first additive shown in Formula 9 is replaced with the first additive shown in Formula 12, a / X=1.133, (b / c) / X=0.139.

[0168] Formula 10.

[0169] Example 8

[0170] The difference between this embodiment and Embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-3. At the same time, in step S3, the mass percentage a% of the first additive in the electrolyte is 0.39%, making a / X=0.3 and (b / c) / X=0.08.

[0171] Example 9

[0172] The difference between this embodiment and Embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-3. At the same time, in step S3, the mass percentage a% of the first additive in the electrolyte is 0.268%, making a / X=0.206 and (b / c) / X=0.08.

[0173] Example 10

[0174] The difference between this embodiment and Embodiment 1 is that, in step S1, positive electrode active material-1 is replaced with positive electrode active material-2, and in step S3, the mass percentage a% of the first additive in the electrolyte is 0.15%, a / X=0.3, and (b / c) / X=0.21.

[0175] Example 11

[0176] The difference between this embodiment and Embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-3. At the same time, in step S3, the mass percentage a% of the first additive in the electrolyte is 2.5%, a / X=1.923, and (b / c) / X=0.08.

[0177] Example 12

[0178] The difference between this embodiment and embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-3. At the same time, in step S3, the mass percentage a% of the first additive in the electrolyte is 0.26%, so that a / X=0.2 and (b / c) / X=0.08.

[0179] Example 13

[0180] The difference between this embodiment and Embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-2. At the same time, in step S3, the mass percentage a% of the first additive in the electrolyte is 1.15%, making a / X=2.3 and (b / c) / X=0.208.

[0181] Example 14

[0182] The difference between this embodiment and embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-4. At the same time, in step S3, the mass percentage a% of the first additive in the electrolyte is 0.283%, and the mass percentage b% of the second additive in the electrolyte is 0.434%, so that a / X=1.132 and (b / c) / X=0.139.

[0183] Example 15

[0184] The difference between this embodiment and Embodiment 1 is that in step S1, positive electrode active material-1 is replaced with positive electrode active material-5. At the same time, in step S3, the mass percentage a% of the first additive in the electrolyte is 1.7%, and the mass percentage b% of the second additive in the electrolyte is 2.61%, so that a / X=1.133 and (b / c) / X=0.139.

[0185] Example 16

[0186] The difference between this embodiment and embodiment 1 is that the second additive shown in formula 21 is replaced with the second additive shown in formula 16, and the mass percentage b% of the second additive in the electrolyte is 0.35%, the mass percentage c% of LiPF6 in the electrolyte is 11.6%, a / X=1.133, and (b / c) / X=0.04.

[0187] Formula 16.

[0188] Example 17

[0189] The difference between this embodiment and embodiment 1 is that the second additive shown in formula 21 is replaced with the second additive shown in formula 17, and the mass percentage b% of the second additive in the electrolyte is 0.8%, the mass percentage c% of LiPF6 in the electrolyte is 18.75%, a / X=1.133, and (b / c) / X=0.057.

[0190] Formula 17.

[0191] Example 18

[0192] The difference between this embodiment and embodiment 1 is that the second additive shown in formula 21 is replaced with the second additive shown in formula 18, and the mass percentage b% of the second additive in the electrolyte is 0.8%, a / X=1.133, (b / c) / X=0.085.

[0193] Formula 18.

[0194] Example 19

[0195] The difference between this embodiment and embodiment 1 is that the second additive shown in formula 21 is replaced with the second additive shown in formula 19, and the mass percentage b% of the second additive in the electrolyte is 0.8%, the mass percentage c% of LiPF6 in the electrolyte is 10%, a / X=1.133, (b / c) / X=0.085.

[0196] Formula 19.

[0197] Example 20

[0198] The difference between this embodiment and embodiment 1 is that the second additive shown in formula 21 is replaced with the second additive shown in formula 28, and the mass percentage b% of the second additive in the electrolyte is 1.8%, a / X=1.133, (b / c) / X=0.192.

[0199] Equation 28.

[0200] Example 21

[0201] The difference between this embodiment and Embodiment 1 is that the mass percentage (b%) of the second additive in the electrolyte is 0.2%, a / X = 1.133, and (b / c) / X = 0.021.

[0202] Example 22

[0203] The difference between this embodiment and Embodiment 1 is that the mass percentage (b%) of the second additive in the electrolyte is 3%, a / X = 1.133, and (b / c) / X = 0.32.

[0204] Example 23

[0205] The difference between this embodiment and Embodiment 1 is that the electrolyte also contains a third additive, triargyl phosphate, and the mass percentage of the third additive in the electrolyte is 0.15%.

[0206] Comparative Example 1

[0207] The difference between this comparative example and Example 1 is that the first additive is not added in step S3.

[0208] Comparative Example 2

[0209] The difference between this comparative example and Example 1 is that no second additive is added in step S3.

[0210] Comparative Example 3

[0211] The difference between this comparative example and Example 1 is that the first additive and the second additive are not added in step S3.

[0212] The amounts of each component of the electrolyte used in the examples and comparative examples are shown in Table 3.

[0213] Table 3

[0214]

[0215] Performance testing

[0216] The battery provided in Examples 1 to 23 and Comparative Examples 1 to 3 was tested for its cycle capacity retention rate and storage capacity retention rate at 45°C.

[0217] Test method:

[0218] (1) Cycle capacity retention at 45°C: Under 45°C conditions, the lithium-ion battery was charged to 4.4V at a constant current of 1C, left to rest for 30 minutes, and then discharged to 2.8V at a constant current of 1C. The discharge capacity of this discharge was recorded as the initial discharge capacity. The aforementioned charge and discharge steps were repeated, and the discharge capacity at the 600th cycle was recorded. The cycle capacity retention at 45°C was calculated according to the following formula:

[0219] 45℃ cycle capacity retention rate (%) = Discharge capacity at 600th cycle / Initial discharge capacity × 100%.

[0220] (2) Storage capacity retention rate at 45℃: In a 25℃ environment, the lithium-ion battery was first charged to 4.4V at 1C, then charged to 0.05C via CV, left to stand for 30 minutes, and then discharged at a constant current of 1C to 2.8V. This cycle was repeated for 3 weeks, and the third discharge capacity was recorded as the first discharge capacity. Then, the battery was charged to 100% SOC and stored in a 45℃ environment. On the 30th day, the battery was removed and discharged at a constant current of 1C to 2.8V, and the discharge capacity on the 30th day of storage was recorded. The storage capacity retention rate at 45℃ was calculated according to the following formula:

[0221] Storage capacity retention rate at 45℃ = (discharge capacity on day 30 of storage / initial discharge capacity) × 100%.

[0222] Table 4 shows the cycle capacity retention rate and storage capacity retention rate at 45°C for the above embodiments and comparative examples.

[0223] Table 4

[0224]

[0225] As can be seen from the above, compared with Comparative Examples 1 to 3, the batteries of Examples 1 to 23 have significantly higher capacity retention under high temperature and high voltage charging conditions, and significantly higher storage capacity retention under high voltage charging and high temperature storage conditions. This indicates that the electrolyte containing both the first additive and the second additive can effectively improve the high temperature storage performance and high temperature cycling performance of the battery.

[0226] The electrolyte in Comparative Example 1 did not contain the first additive, which resulted in poor stability of the positive electrode particles in the battery prepared from it, leading to poor high-temperature storage performance and high-temperature cycle performance of the battery.

[0227] The electrolyte in Comparative Example 2 did not contain a second additive, resulting in poor stability of the positive electrode particles in the battery prepared from it. Furthermore, the acidic substances generated during the charging and discharging process of the electrolyte were difficult to remove, leading to poor cycle stability under high temperature and high pressure conditions and poor high temperature storage performance.

[0228] In Comparative Example 3, without the addition of the first and second additives, the battery prepared under high temperature and high pressure conditions exhibited the worst cycle stability and also had poor high temperature storage performance.

[0229] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte comprises a first additive and a second additive, wherein the first additive comprises a compound represented by Formula I or Formula II, and the second additive comprises a compound represented by Formula III. Formula I, Formula II, Formula III; The first additive does not contain methylene groups, and the first additive meets the following conditions: (1) R1, R2, R3, R1', R2', and R3' are each independently selected from N and O, and at least one of R1 and R3 is selected from N, and at least one of R1' and R3' is selected from N; the unsaturation degree of the five-membered ring containing R1, R2, and R3 is α, where 1≤α≤3; the unsaturation degree of the five-membered ring containing R1', R2', and R3' is α', where 1≤α'≤3; (2) R4 and R4' are each independently selected from hydrogen, methyl, cyano, halogen group, C6-C with or without halogen substituents. 10 One of the following: aryl, C1-C5 alkyl containing a halogen substituent, phosphate ester group containing a halogen substituent or without a substituent, and phosphite ester group containing a halogen substituent or without a substituent; (3) A and its connected semi-circular ring together form a first ring structure, and A' and its connected semi-circular ring together form a second ring structure. The first ring structure and the second ring structure are each independently selected from one of five-membered rings, six-membered rings, fused rings, and benzene fused heterocycles. The degree of unsaturation of the first ring structure is β, where 1≤β≤7. The first ring structure contains halogen substituents or does not contain substituents. The degree of unsaturation of the second ring structure is β', where 1≤β'≤7. The second ring structure contains halogen substituents or does not contain substituents. (4) R5 and R6 are each independently selected from hydrogen, phenyl containing halogen substituents or without substituents; The second additive meets the following conditions: (5) R7 and R9 are connected to form a ring, so that R7, R9 and N connected to R7 and R9 together constitute a five-membered silicon nitride heterocycle, and the degree of unsaturation of the five-membered silicon nitride heterocycle is 1; Alternatively, R7 and R9 are each independently selected from one of the following: C1-C5 alkyl groups containing or without halogen substituents, C1-C5 alkenyl groups containing or without halogen substituents, C1-C5 alkoxy groups containing or without halogen substituents, and silane groups containing or without halogen substituents or C1-C3 alkyl substituents. (6) R8 is selected from C1-C5 alkyl groups containing halogen substituents and / or containing oxo groups, C1-C5 alkyl groups without substituents, and C6-C5 alkyl groups containing halogen substituents or without substituents. 10 One of the following: aryl, C1-C5 alkoxy group containing or without a silane substituent, C1-C5 alkenyl group containing or without a halogen substituent, C1-C5 ester group containing or without a silane substituent, five-membered heterocycle containing or without a silane substituent, group represented by Formula IV, or group represented by Formula V. Formula IV, Formula V; Among them, R 10 R 11 Each is independently selected from trimethylsilyl, R 12 R 13 All are C1-C5 alkylene groups. This represents the position where R8 connects to N in Equation III; (7) At least one of the groups in R7, R8 and R9 contains silicon.

2. The electrolyte according to claim 1, characterized in that, At least one of the following conditions must be met: (1) R1 is selected from N, R2 is selected from O, and R3 is selected from N; (2) R1' is selected from O, R2' is selected from O, and R3' is selected from N; (3) R4 and R4' are each independently selected from one of hydrogen, cyano, halogen group, phenyl without substituent, and halomethyl; (4) The first cyclic structure and the second cyclic structure are each independently selected from one of the following groups: furan group, phenyl group, naphthyl group, and indole group; (5) R5 and R6 are each independently selected from phenyl groups containing halogen substituents or without substituents; (6) R7 and R9 are connected to form a ring, such that R7, R9, and the N connected to R7 and R9 together constitute the group shown in formula VI. Equation VI, where, This represents the position where the group shown in Formula VI is connected to R8; Alternatively, R7 and R9 may each be independently selected from trimethylsilyl groups; (7) The R8 is selected from one of the following: C1-C5 alkyl containing halogen substituents and / or containing oxo groups, C1-C5 alkyl without substituents, phenyl containing halogen substituents, C1-C5 alkoxy containing silane substituents or without substituents, C1-C5 alkenyl without substituents, C1-C5 ester containing silane substituents, five-membered heterocycle containing silane substituents, the group shown in Formula IV, and the group shown in Formula V.

3. The electrolyte according to claim 2, characterized in that, The compound represented by Formula I includes at least one of the compounds represented by Formulas 1 to 2, and the compound represented by Formula II includes at least one of the compounds represented by Formulas 3 to 14. Formula 1 Formula 2 Formula 3 Formula 4 Formula 5 Formula 6 Formula 7 Formula 8 Formula 9 Formula 10 Formula 11 Formula 12 Formula 13 Equation 14.

4. The electrolyte according to claim 2, characterized in that, The compound represented by Formula III includes at least one of the compounds represented by Formulas 15 to 28: Formula 15 Formula 16 Formula 17 Formula 18 Formula 19 Formula 20 Formula 21 Equation 22 Formula 23 Formula 24 Formula 25 Formula 26 Equation 27 Equation 28.

5. The electrolyte according to any one of claims 1 to 4, characterized in that, The first additive accounts for a% of the electrolyte by mass, and 0.15 ≤ a ≤ 2.5; and / or, The second additive accounts for b% of the mass of the electrolyte, and 0.2 ≤ b ≤ 3; and / or, The electrolyte contains a lithium salt, wherein the lithium salt constitutes c% of the electrolyte by mass, and 11.6 ≤ c ≤ 18.75; and / or, The electrolyte contains a lithium salt selected from at least one of lithium hexafluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium bis(pentafluoroethylsulfonyl)imide, and lithium tri(trifluoromethylsulfonyl)methyl.

6. The electrolyte according to any one of claims 1 to 4, characterized in that, The electrolyte satisfies at least one of the following conditions: (1) The electrolyte contains a solvent, which is selected from at least one of cyclic carbonates, linear carbonates, cyclic carboxylic acid esters, linear carboxylic acid esters, sulfones, phosphates, and phosphites; Preferably, the cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate; the linear carbonate includes at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and methyl ethyl carbonate; the cyclic carboxylic acid ester includes γ-butyrolactone, γ-valerate, and... At least one of caprolactone; the linear carboxylic acid ester includes at least one of methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl acetate; the sulfone compound includes at least one of dimethyl sulfoxide, sulfolane, and diphenyl sulfone; the phosphate ester compound includes at least one of triethyl phosphate, trimethyl phosphate, and triphenyl phosphate; the phosphite compound includes at least one of ethyl methyl phosphate, trimethyl phosphite, and tris(2,2,2-trifluoroethyl) phosphite; (2) The electrolyte contains a third additive, which is selected from at least one of ethylene carbonate, vinylene carbonate, 1,3-propane sulpholactone, mannitol sulfate, 1,3-dioxane, 1,4-dioxane, lithium dioxaborate, lithium difluorooxaborate, lithium tetrafluoroborate, vinyl sulfate, 1,3-propane sulpholactone, propenyl-1,3-sulfonyl lactone, 2,4-butane sulpholactone, methanedisulfonate, 1,3-propanedisulfonic anhydride, ethylene sulfite, and propargyl phosphate.

7. A battery, characterized in that, The battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte according to any one of claims 1 to 6; wherein the positive electrode contains a positive electrode material, and the positive electrode material comprises an active material.

8. The battery according to claim 7, characterized in that, The specific surface area of ​​the active material is Xm 2 / g, wherein the mass percentage of the first additive in the electrolyte is a%, the mass percentage of the second additive in the electrolyte is b%, and the mass percentage of the lithium salt in the electrolyte is c%, and at least one of the following conditions is met: （1）0.25≤X≤1.5； (2) 0.2 ≤ a / X ≤ 2.3; (3)0.021≤(b / c) / X≤0.

32.

9. The battery according to claim 7 or 8, characterized in that, At least one of the following conditions must be met: (1) The active material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium nickel cobalt manganese aluminum oxide, wherein the molar content of nickel in the three metal elements nickel, cobalt, and manganese in the lithium nickel cobalt manganese oxide is 60% to 80%; (2) The active material contains a doping element, which is selected from at least one of Al, Mg, Ti, Nb, Cr, Y, Sr, S, F, and Zr; (3) The positive electrode material further includes a coating layer located on the surface of the active material, wherein the material of the coating layer is selected from at least one of oxides and phosphates; Preferably, the oxide is selected from at least one of aluminum oxide, titanium dioxide, and zirconium dioxide; Preferably, the phosphate is selected from at least one of lithium phosphate and lithium iron phosphate.

10. A battery pack, characterized in that, The battery pack comprises the battery according to any one of claims 7 to 9.

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