Electrolyte, lithium ion battery, battery pack, battery pack and electric equipment

Abstract

The invention discloses an electrolyte, a lithium ion battery, a battery pack, a battery pack and electric equipment, the electrolyte comprises a first additive, and the first additive comprises at least one of compounds shown in the following formula; a, b, c and d are respectively independent positive integers, 0 < = a < = 1, 0 < = b < = 1, 0 < = c < = 1, and 0 < = d < = 5. According to the electrolyte disclosed by the invention, further oxygenolysis of the electrolyte under high voltage is inhibited, the expansion risk of the lithium ion battery is reduced, the lithium ion battery prepared by adopting the electrolyte can work for a long time under high voltage, and excellent high-temperature performance, long-term storage performance and cycle performance are kept.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrolyte, a lithium-ion battery, a battery pack, a battery package and electrical equipment. Background Art

[0002] Lithium-ion batteries have the advantages of high specific energy, long cycle life, and no memory effect, and are widely used in the field of new energy vehicles. With the rapid development of the new energy vehicle industry, consumers have put forward higher requirements for driving range. In the related technology, in order to meet users' high requirements for driving range, that is, in order to improve the energy density of the battery, high-voltage positive electrode active materials are often used to improve the battery energy density. However, high-voltage positive electrode active materials have high oxidizability, and the interfacial side reactions between the electrolyte and the positive electrode active materials are aggravated, making the electrolyte easily oxidized and causing battery bloating. In addition, the transition metal ions in the positive electrode active material are easily dissolved and migrate to the negative electrode side through the electrolyte, which will destroy the solid electrolyte interface protective film (SEI) on the surface of the negative electrode, thereby causing the capacity of the lithium-ion battery to decay sharply. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first object of the present invention is to provide an electrolyte that inhibits the flatulence of lithium-ion batteries, thereby facilitating the lithium-ion batteries prepared using the electrolyte to work for a long time at high voltage and maintain excellent high temperature performance, long-term storage and cycle performance.

[0004] A second objective of the present invention is to provide a lithium-ion battery.

[0005] A third objective of the present invention is to provide a battery pack.

[0006] A fourth objective of the present invention is to provide a battery pack.

[0007] A fifth object of the present invention is to provide an electrical device.

[0008] The electrolyte according to the first aspect of the present invention includes: a first additive, wherein the first additive includes at least one of the compounds shown in the following formula;

[0009]

[0010] wherein a, b, c and d are all independent positive integers, and 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤5; R1 and R2 are each selected from any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an unsaturated hydrocarbon group having 2 to 5 carbon atoms, an aryl group having 6 to 10 carbon atoms or an alkylaryl group having 7 to 10 carbon atoms; the hydrogen atoms in the alkyl group having 1 to 5 carbon atoms, the unsaturated hydrocarbon group having 2 to 5 carbon atoms, the aryl group having 6 to 10 carbon atoms or the alkylaryl group having 7 to 10 carbon atoms may be partially or completely substituted by a substituent.

[0011] The electrolyte according to the embodiment of the present invention is conducive to forming a stable CEI film at the positive electrode and modifying the negative electrode SEI film through the above-mentioned first additive, thereby helping to reduce the contact between the electrolyte and the active material, inhibiting the dissolution of transition metal ions and their catalytic decomposition of the electrolyte, thereby effectively inhibiting further oxidative decomposition of the electrolyte under high voltage and inhibiting flatulence of the lithium-ion battery, which is conducive to the lithium-ion battery prepared using the electrolyte to work for a long time under high voltage and maintain excellent high temperature performance, long-term storage and cycle performance.

[0012] According to some embodiments of the present invention, the first additive includes at least one of the compounds shown in formula (a) to formula (f), wherein the compounds of formula (a) to formula (f) are:

[0013]

[0014]

[0015] According to some embodiments of the present invention, the content of the first additive is 0.1 wt % to 20 wt %.

[0016] According to some embodiments of the present invention, the content of the first additive is 0.5 wt % to 5 wt %.

[0017] According to some embodiments of the present invention, the electrolyte also includes a second additive, which includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), 1,3-propylene sultone (RPS), vinyl sulfate (DTD), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) phosphite (TMSPi), lithium difluorophosphate, lithium difluorobisoxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0018] According to some embodiments of the present invention, the electrolyte further includes a solvent, and the solvent includes carbonate and linear carboxylate.

[0019] According to some embodiments of the present invention, the carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, and γ-butyrolactone; and / or the linear carboxylic acid ester includes at least one of methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

[0020] According to some embodiments of the present invention, the linear carboxylic acid ester includes at least one of ethyl acetate, propyl acetate, butyl acetate and ethyl propionate.

[0021] According to some embodiments of the present invention, in parts by weight, 100 parts of the solvent include 10 parts to 60 parts of the linear carboxylic acid ester.

[0022] According to some embodiments of the present invention, in parts by weight, 100 parts of the solvent include 15 parts to 40 parts of the linear carboxylic acid ester.

[0023] According to some embodiments of the present invention, the electrolyte includes an electrolyte salt, and the concentration of the electrolyte salt is 0.5 mol / L to 2 mol / L.

[0024] According to some embodiments of the present invention, the concentration of the electrolyte salt is 0.9 mol / L to 1.3 mol / L.

[0025] According to some embodiments of the present invention, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalatoborate, lithium bisfluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium bisfluorosulfonylimide.

[0026] According to some embodiments of the present invention, the electrolyte salt includes the lithium hexafluorophosphate and the lithium bis(fluorosulfonyl)imide.

[0027] According to some embodiments of the present invention, the concentration of the lithium bis(fluorosulfonyl)imide is 0.1 mol / L to 0.4 mol / L.

[0028] The lithium-ion battery according to the second embodiment of the present invention comprises at least one electrolyte according to the first embodiment of the present invention.

[0029] A battery pack according to an embodiment of a third aspect of the present invention comprises at least one lithium-ion battery according to an embodiment of the second aspect of the present invention.

[0030] The battery pack according to the fourth aspect of the present invention comprises at least one lithium-ion battery according to the second aspect of the present invention, or comprises at least one battery pack according to the third aspect of the present invention.

[0031] The electrical equipment according to the fifth aspect of the present invention comprises at least one lithium-ion battery according to the second aspect of the present invention, or comprises at least one battery pack according to the third aspect of the present invention, or comprises at least one battery pack according to the fourth aspect of the present invention.

[0032] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0033] The following describes an electrolyte according to an embodiment of the first aspect of the present invention.

[0034] The electrolyte according to the first aspect of the present invention includes a first additive, and the first additive includes at least one of the compounds shown in the following formula:

[0035]

[0036] wherein a, b, c and d are all independent positive integers, and 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤5; R1 and R2 are each selected from any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an unsaturated hydrocarbon group having 2 to 5 carbon atoms, an aryl group having 6 to 10 carbon atoms or an alkylaryl group having 7 to 10 carbon atoms; the hydrogen atoms in the alkyl group having 1 to 5 carbon atoms, the unsaturated hydrocarbon group having 2 to 5 carbon atoms, the aryl group having 6 to 10 carbon atoms or the alkylaryl group having 7 to 10 carbon atoms may be partially or completely substituted by a substituent.

[0037] Wherein, the substituent of the hydrogen atom in the alkane group, unsaturated hydrocarbon group, aryl group or alkaryl group may be a halogen element (such as fluorine, chlorine, bromine and iodine). It is not specifically limited here. The number of carbon atoms in the substituents of R1 and R2 in the first additive is small, which is beneficial to reduce the steric hindrance at R1 and R2 of the first additive, thereby facilitating the first additive to play a role and facilitating film formation in the positive electrode to improve the stability of the positive electrode / electrolyte interface.

[0038] The cyano structure in the first additive can be complexed with transition metal ions, and the phosphonyl group can participate in the construction of the positive electrode electrolyte interphase (CEI). Therefore, the first additive can effectively inhibit the further oxidative decomposition of the electrolyte and inhibit the flatulence of the lithium-ion battery by inhibiting the dissolution of transition metal ions and their catalytic decomposition of the electrolyte. At the same time, the use of the first additive is conducive to the formation of a uniform and dense passivation film on the surface of the positive electrode, thereby effectively inhibiting the increase of the positive electrode interface impedance during the cycle and storage process, and improving the cycle life and storage performance of the lithium-ion battery.

[0039] The first additive has a low oxidation potential, which is conducive to the rapid formation of a complete, dense and uniform CEI film on the positive electrode surface, improving the stability of the positive electrode / electrolyte interface, thereby reducing the contact between the electrolyte and the active material using a stable interface protective film. According to DFT (Discrete Fourier Transform) calculation, compared with other components of the electrolyte, the first additive has a higher highest occupied molecular orbital (HOMO) energy level. The higher HOMO energy level means that the first additive is prone to lose electrons at the positive electrode and undergo oxidative decomposition, forming a CEI film on the positive electrode surface.

[0040] In addition, the first additive can also participate in the negative electrode film formation, wherein the sulfur-oxygen bond (sulfate ester) of the first additive can participate in the SEI film formation. The first additive decomposes a small amount in the first cycle to form sulfate compounds, which modify the negative electrode SEI film, effectively reduce the negative electrode impedance, and inhibit the generation of negative electrode surface gas in lithium-ion batteries under high temperature conditions.

[0041] In summary, the lithium-ion battery prepared using this electrolyte can operate for a long time at high voltage and maintain excellent high temperature performance, long-term storage and cycle performance.

[0042] The electrolyte according to the embodiment of the present invention is conducive to forming a stable CEI film at the positive electrode and modifying the negative electrode SEI film through the above-mentioned first additive, thereby helping to reduce the contact between the electrolyte and the active material, inhibiting the dissolution of transition metal ions and their catalytic decomposition of the electrolyte, thereby effectively inhibiting further oxidative decomposition of the electrolyte under high voltage and reducing the risk of flatulence of the lithium-ion battery, which is conducive to the lithium-ion battery prepared using the electrolyte to work for a long time at high voltage and maintain excellent high temperature performance, long-term storage and cycle performance.

[0043] According to some embodiments of the present invention, the first additive includes at least one of the compounds shown in formula (a) to formula (f), wherein the compounds of formula (a) to formula (f) are:

[0044]

[0045] The above compounds have a small molecular weight and short side chains. The first additive uses at least one of the above compounds, which is beneficial to increasing the formation rate of the interface film at the positive electrode and the negative electrode, thereby helping to inhibit the flatulence of the lithium-ion battery, and further helping to enable the lithium-ion battery to work for a long time at high voltage and maintain excellent high temperature performance, long-term storage and cycle performance.

[0046] According to some embodiments of the present invention, the content of the first additive is 0.1wt% to 20wt%. When the content of the first additive is less than 0.1wt%, the amount of the first additive is small and it is difficult to meet the needs of the lithium-ion battery, so that more gas will still be generated in the lithium-ion battery, which is easy to cause the lithium-ion battery to swell and reduce the performance of the lithium-ion battery; when the content of the first additive is greater than 20wt%, the amount of the first additive is large, thereby increasing the cost of the electrolyte. Therefore, by controlling the content of the first additive to 0.1wt% to 20wt%, it is beneficial to give full play to the role of the first additive, reduce the risk of bloating of the lithium-ion battery, and at the same time help control the cost of the electrolyte.

[0047] Furthermore, the content of the first additive is 0.5wt% to 5wt%. In this way, the content of the first additive in the electrolyte is more reasonable, the effect of the first additive is more fully exerted, and the cost control of the first additive is more reasonable.

[0048] According to some embodiments of the present invention, the electrolyte further includes a second additive, and the second additive includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), 1,3-propylene sultone (RPS), vinyl sulfate (DTD), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) phosphite (TMSPi), lithium difluorophosphate, lithium difluorobisoxalate phosphate, and lithium tetrafluorooxalate phosphate. The above compounds are all conducive to forming a stable SEI film on the surface of the positive and negative electrodes of the lithium ion battery. The SEI film can reduce the continuous decomposition of the electrolyte, prevent the deposition of metallic lithium, and avoid the risk of internal short circuit of the lithium ion battery, thereby improving the cycle stability of the lithium ion battery and improving the overall safety of the lithium ion battery. The second additive includes at least one of the above compounds, which helps the electrolyte maintain good conductivity at different temperatures, so that the lithium ion battery can still work normally under extreme temperature conditions. In addition, vinylene carbonate can further promote the formation of SEI film under overcharge conditions, providing an additional protection mechanism to prevent lithium-ion batteries from being damaged by overcharge.

[0049] According to some embodiments of the present invention, the electrolyte further includes a solvent, and the solvent includes a carbonate and a linear carboxylate. The carbonate can be used as the main component of the solvent, thereby ensuring the solvent's dissolving effect on the electrolyte salt, etc. The linear carboxylate has good chemical stability and can remain stable within the operating voltage range of the lithium-ion battery to avoid the performance degradation of the lithium-ion battery. At the same time, the linear carboxylate has good electrical conductivity and good compatibility with other materials in the lithium-ion battery.

[0050] Further, the carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and γ-butyrolactone. The above carbonates all have high dielectric constants, good dissolution effects on electrolyte salts such as lithium salts, and good stability at high voltages. At the same time, the above carbonates have low viscosity, which helps to increase the migration speed of lithium ions.

[0051] The linear carboxylic acid ester includes at least one of methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate. The above-mentioned linear carboxylic acid ester has good chemical stability, conductivity and compatibility, so the use of the above-mentioned linear carboxylic acid ester is conducive to improving the reliability of the use of the solvent, and improving the safety and charge and discharge efficiency of the lithium-ion battery.

[0052] Furthermore, the linear carboxylic acid ester includes at least one of ethyl acetate, propyl acetate, butyl acetate and ethyl propionate. The linear carboxylic acid ester has good stability, low toxicity and high safety. The linear carboxylic acid ester as a component in the solvent is conducive to improving the reliability and safety of the electrolyte.

[0053] In addition, by weight, 100 parts of the solvent include 10 to 60 parts of linear carboxylic acid ester. The amount of linear carboxylic acid ester added to the solvent is relatively reasonable, which ensures that the solvent fully dissolves the electrolyte salt while avoiding the waste of linear carboxylic acid ester, which is beneficial to controlling the cost of the electrolyte and the lithium ion battery using the electrolyte.

[0054] Preferably, by weight, 100 parts of the solvent include 15 to 40 parts of the linear carboxylic acid ester.

[0055] The solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate. The above solvents have good solubility for lithium salts, which is beneficial to improving the electrochemical properties, thermal stability and safety of the electrolyte, thereby facilitating the optimization of lithium-ion batteries.

[0056] In addition, the electrolyte also includes electrolyte salt, and the concentration of the electrolyte salt is 0.5 mol / L to 2 mol / L. The concentration of the electrolyte salt is relatively reasonable, fully meeting the electrolyte requirements of the battery, improving the conductivity of the electrolyte, avoiding the waste of the electrolyte salt, and controlling the cost of the electrolyte.

[0057] Preferably, the concentration of the electrolyte salt is 0.9 mol / L to 1.3 mol / L.

[0058] The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalate borate, lithium bisfluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium bisfluorosulfonylimide. The above lithium salts all have good electrochemical stability and thermal stability, and good solubility in solvents, which is conducive to improving the consistency of the electrolyte, thereby improving the conductivity of the electrolyte.

[0059] Furthermore, the electrolyte salt includes lithium hexafluorophosphate and lithium bisfluorosulfonyl imide. The lithium salt combination of lithium hexafluorophosphate with a specific concentration and lithium bisfluorosulfonyl imide with a specific concentration can not only improve the conductivity and thermal decomposition temperature of the non-aqueous electrolyte, but also reduce the decomposition of lithium hexafluorophosphate, thereby further improving the service life of the battery.

[0060] Furthermore, the concentration of lithium bis(fluorosulfonyl)imide is 0.1 mol / L to 0.4 mol / L. Therefore, the concentration of lithium bis(fluorosulfonyl)imide is relatively reasonable, which improves the conductivity and thermal decomposition temperature of the electrolyte, effectively reduces the decomposition of lithium hexafluorophosphate, thereby optimizing the electrochemical performance of the battery and extending the service life of the battery.

[0061] The lithium-ion battery according to the second embodiment of the present invention comprises at least one electrolyte according to the first embodiment of the present invention.

[0062] The lithium-ion battery according to the embodiment of the present invention uses the above-mentioned electrolyte, which is beneficial to reducing the risk of flatulence of the lithium-ion battery, thereby improving the safety of the lithium-ion battery and extending the service life of the lithium-ion battery.

[0063] A battery pack according to an embodiment of a third aspect of the present invention comprises at least one lithium-ion battery according to an embodiment of the second aspect of the present invention.

[0064] The battery pack according to the embodiment of the present invention is beneficial to improving the safety of the battery pack and prolonging the service life of the battery pack in a high temperature environment.

[0065] The battery pack according to the fourth aspect of the present invention comprises at least one lithium-ion battery according to the second aspect of the present invention, or comprises at least one battery pack according to the third aspect of the present invention.

[0066] The battery pack according to the embodiment of the present invention is conducive to reducing the risk of battery pack bulging, improving the use stability of the battery pack, enriching the use conditions of the battery pack, and improving the market competitiveness of the battery pack.

[0067] The electrical equipment according to the fifth aspect of the present invention comprises at least one lithium-ion battery according to the second aspect of the present invention, or comprises at least one battery pack according to the third aspect of the present invention, or comprises at least one battery pack according to the fourth aspect of the present invention.

[0068] The electric device according to the embodiment of the present invention improves the power supply stability of the electric device and the use safety of the electric device, thereby facilitating the improvement of the market competitiveness of the electric device.

[0069] The embodiments of the present invention are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention. In addition, if not explicitly stated, all reagents used in the following embodiments are commercially available, or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0070] 1) Preparation of electrolyte

[0071] The electrolytes of Examples 1 to 16 and Comparative Examples 1 to 3 were prepared according to the following method:

[0072] Ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) are mixed in a mass ratio of EC:DMC:DEC=3:2:5, and then lithium hexafluorophosphate (LiPF6) is added to a molar concentration of 1.1 mol / L. The types of additives and their contents in the electrolytes of Examples 1 to 16 and Comparative Examples 1 to 3 are shown in Table 1, where the proportion of the additives is the proportion of the total weight of the electrolyte.

[0073] Table 1 Additives and their contents of Examples 1 to 16 and Comparative Examples 1 to 3

[0074]

[0075]

[0076] 2) Preparation of positive electrode

[0077] The positive electrode active materials NCM622 (LiNi 0.6 Co 0.2 Mn 0.2O2), conductive carbon black, carbon nanotubes (CNT) and polyvinylidene fluoride (PVDF), and then dispersed in N-methylpyrrolidone (NMP), stirred until stable and uniform under the action of a vacuum mixer to obtain a positive electrode slurry; the above positive electrode slurry was evenly coated on an aluminum foil with a thickness of 13 μm; the aluminum foil was dried at room temperature and then transferred to a 120°C blast oven for drying for 2 hours, and then cold pressed and slitting processes were performed to obtain a positive electrode sheet.

[0078] 3) Preparation of negative electrode

[0079] Stone artificial graphite, conductive carbon black, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 96.5:0.9:1.1:1.5, and then dispersed in deionized water to obtain a negative electrode slurry; the above negative electrode slurry is coated on a copper foil with a thickness of 6 μm; the copper foil is dried at room temperature and then transferred to a 120°C forced air oven for drying for 2 hours, and then subjected to cold pressing and slitting processes to obtain a negative electrode sheet.

[0080] 4) Preparation of lithium-ion batteries

[0081] The positive electrode sheet, negative electrode sheet and separator are made into a pole core through a lamination process. After the pole core is loaded into an aluminum-plastic film packaging shell, the electrolyte is injected and then sealed in sequence. After standing, hot and cold pressing, formation, capacity division and other processes, a lithium-ion battery is produced.

[0082] Performance Testing

[0083] (1) High temperature cycle test

[0084] In a 45°C constant temperature box, the lithium-ion battery is charged to 4.5V at a constant current of 0.5C, then charged to a cut-off current of 0.05C at a constant voltage, left to stand for 1h, and then discharged to 2.5V at a constant current of 0.5C, which is recorded as one charge and discharge cycle. Then, 500 cycles are performed under the above conditions; the discharge capacity of the first cycle is recorded as C0, and the discharge capacity of the 500th cycle is recorded as C1;

[0085] 45℃ cycle capacity retention rate (%) = (C1 / C0) × 100%;

[0086] (2) High temperature storage test

[0087] The lithium-ion battery was charged to 4.5V at 0.5C constant current and constant voltage at 25℃, cut off at 0.05C, and left to stand for 1h, then discharged to 2.5V at 0.5C constant current. This discharge capacity was counted as the initial capacity C0, and the volume of the lithium-ion battery before storage was measured as V0. The lithium-ion battery was transferred to a high-temperature test cabinet and stored at 60℃ for 28 days; after storage, the test lithium-ion battery was taken out and left at room temperature for 10h, and the volume of the lithium-ion battery after storage was measured as V1, and then discharged to 2.5V at 0.5C constant current, and the discharge capacity C1 was recorded. After leaving for 120min, it was charged to 4.5V at 0.5C constant current and constant voltage, cut off at 0.05C, and left to stand for 1h before discharging to 2.5V at 0.5C constant current, and the discharge capacity C2 was recorded. The parameters of the lithium-ion battery are calculated by the following formula:

[0088] Capacity remaining rate (%) = (C1 / C0)*100%;

[0089] Capacity recovery rate (%) = (C2 / C0)*100%;

[0090] Battery volume expansion rate (%) = [(V1-V0) / V0]*100%.

[0091] Table 2 Test results of Example 1-Example 16 and Comparative Example 1-Comparative Example 3

[0092]

[0093]

[0094] Test Results

[0095] In combination with Table 1 and Table 2, when the electrolyte of each lithium ion battery contains a high voltage functional additive (first additive) and a negative electrode film-forming additive (VC) (Example 1-Example 14), compared with the lithium ion batteries of Comparative Examples 1-3, the lithium ion batteries of the above embodiments have better improvement in high temperature cycle performance and high temperature storage performance.

[0096] From the data of Examples 15-16 and Comparative Examples 1-3, it can be seen that the effect of using only the first additive in the electrolyte is better than that of lithium-ion batteries with common additive combinations; it can be seen that using the first additive alone in the electrolyte can also optimize the electrochemical performance of lithium-ion batteries to a certain extent.

[0097] In particular, by comparing the data of Examples 1-7 and Examples 12-14, it can be seen that there is an optimal range for the dosage of the high-voltage functional additive (first additive) provided in the present application. When too much is added to the electrolyte (such as in Example 7), the viscosity of the electrolyte will be greatly increased, which can easily reduce the high-temperature storage effect of the lithium-ion battery. In addition, there are certain differences in the optimal ranges of dosage of different compounds. Screening out the optimal dosage range can maximize the performance of lithium-ion batteries.

[0098] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0099] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An electrolyte, characterized in that: include: A first additive, wherein the first additive comprises at least one of the compounds shown in the following formula; wherein a, b, c and d are all independent positive integers, and 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤5; R1 and R2 are each selected from any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an unsaturated hydrocarbon group having 2 to 5 carbon atoms, an aryl group having 6 to 10 carbon atoms or an alkylaryl group having 7 to 10 carbon atoms; the hydrogen atoms in the alkyl group having 1 to 5 carbon atoms, the unsaturated hydrocarbon group having 2 to 5 carbon atoms, the aryl group having 6 to 10 carbon atoms or the alkylaryl group having 7 to 10 carbon atoms may be partially or completely substituted by a substituent.

2. The electrolyte according to claim 1, characterized in that The first additive includes at least one of the compounds shown in formula (a) to formula (f), wherein the compounds of formula (a) to formula (f) are:

3. The electrolyte according to claim 1 or 2, characterized in that The content of the first additive is 0.1 wt% to 20 wt%.

4. The electrolyte according to claim 3, characterized in that The content of the first additive is 0.5wt% to 5wt%.

5. The electrolyte according to claim 1 or 2, characterized in that: It also includes a second additive, which includes at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), 1,3-propylene sultone (RPS), vinyl sulfate (DTD), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) phosphite (TMSPi), difluorolithium phosphate, difluorobis(oxalato) lithium phosphate and tetrafluorooxalato lithium phosphate.

6. The electrolyte according to claim 1 or 2, characterized in that Also included are solvents including carbonates and linear carboxylates.

7. The electrolyte according to claim 6, characterized in that The carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and γ-butyrolactone; and / or the linear carboxylic acid ester includes at least one of methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

8. The electrolyte according to claim 7, characterized in that The linear carboxylic acid ester includes at least one of ethyl acetate, propyl acetate, butyl acetate and ethyl propionate.

9. The electrolyte according to claim 8, characterized in that By weight, 100 parts of the solvent include 10 to 60 parts of the linear carboxylic acid ester.

10. The electrolyte according to claim 8, characterized in that By weight, 100 parts of the solvent include 15 parts to 40 parts of the linear carboxylic acid ester.

11. The electrolyte according to claim 1 or 2, characterized in that: The electrolyte salt is also included, and the concentration of the electrolyte salt is 0.5 mol / L to 2 mol / L.

12. The electrolyte according to claim 11, characterized in that The concentration of the electrolyte salt is 0.9 mol / L to 1.3 mol / L.

13. The electrolyte according to claim 11, characterized in that The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalatoborate, lithium bisfluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium bisfluorosulfonylimide.

14. The electrolyte according to claim 13, characterized in that The electrolyte salt includes the lithium hexafluorophosphate and the lithium bis(fluorosulfonyl)imide.

15. The electrolyte according to claim 14, characterized in that The concentration of the lithium bis(fluorosulfonyl)imide is 0.1 mol / L to 0.4 mol / L.

16. A lithium ion battery, characterized in that: Comprising at least one electrolyte according to any one of claims 1-15.

17. A battery pack, characterized in that: Comprising at least one lithium-ion battery according to claim 16.

18. A battery pack, characterized in that: Comprising at least one lithium-ion battery according to claim 16, or comprising at least one battery pack according to claim 17.

19. An electrical equipment, characterized in that: The invention comprises at least one lithium-ion battery according to claim 16, or comprises at least one battery pack according to claim 17, or comprises at least one battery package according to claim 18.

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