A high-voltage electrolyte additive composition, an electrolyte, and a lithium-ion battery

Abstract

The present invention discloses a high-voltage electrolyte additive composition, an electrolyte and a lithium-ion battery. The electrolyte additive composition includes: a first additive represented by the following formula (I); and a second additive selected from the structures represented by the following formula (II) and / or (III). The electrolyte additive composition is used in the electrolyte of a lithium-ion battery, and can simultaneously improve the high-temperature storage performance, high-temperature cycling performance and room-temperature cycling performance of the lithium-ion battery.

Description

Technical Field

[0001] The present invention relates to the field of batteries, in particular to lithium-ion batteries, and more particularly to an electrolyte additive composition for simultaneously improving the high-temperature storage performance, high-temperature cycling performance, and room-temperature cycling performance of high-voltage lithium-ion batteries and its application. Background Art

[0002] Lithium-ion batteries have the advantages of high working voltage, high energy density, no memory effect, no pollution, low self-discharge, etc., and are widely used in the fields of 3C, energy storage, power batteries, etc. The electrolyte is one of the key materials of lithium-ion batteries, and its role cannot be ignored. Additives are an important part of the electrolyte and are the most economical and effective method to improve battery performance.

[0003] During high-temperature storage, lithium-ion batteries are prone to gas generation, internal resistance increase, capacity attenuation, and even safety problems. These are the pain points of the new energy power system that are difficult to overcome in the industry at present. Especially in high-voltage batteries with a high energy density system, due to the instability of the cathode structure, metal ions dissolve and deposit on the anode, damaging the SEI film, thereby causing damage to the battery structure and attenuation of battery performance.

[0004] To solve the above problems, in existing research, the high-temperature storage performance of batteries is mainly improved by using two methods: film-forming additives and high-voltage solvents:

[0005] (1) Using film-forming additives: In the research of patents such as CN109860709B, CN109148951B, and CN107004901B, the film-forming additive ethylene carbonate (VC) is used to solve the interface problem, thereby improving the high-temperature storage performance of the battery. However, due to the poor high-voltage resistance of VC or its oxidation / reduction products, they are easily completely reacted to generate gases such as carbon dioxide in polycrystalline high-voltage materials with large polarization. The generated interfacial film structure is not stable, and in some specific high-voltage battery systems, it even deteriorates the high-temperature storage performance of the battery.

[0006] (2) Using high-voltage solvents: Patents JP2015195180A, CN103875116B, CN108780922A, and CN109155438A disclose a class of cyclic fluorinated ether compounds. Using such compounds as electrolyte solvents (usage amount > 10 wt%), the stability of the electrolyte and the cathode material at high voltages is improved. However, its disadvantage is that fluorine has a strong electron-withdrawing effect, which disperses the electron cloud density distribution of solvent molecules, making it difficult for solvent molecules to participate in the dissociation and solvation processes of lithium salts, thereby reducing the electrolyte conductivity and increasing the electrolyte viscosity at the same time.

[0007] That is, the prior art has not proposed a technical solution that can simultaneously solve the high-temperature storage performance, high-temperature cycling performance, and room-temperature cycling performance of high-voltage battery systems. This is because negative electrode film-forming additives generally require compounds with high reactivity, which leads to an increase in battery internal resistance. On the other hand, additives for improving room-temperature performance require compounds to reduce the battery internal resistance as much as possible during the film-forming process. It is difficult to achieve both simultaneously. On the other hand, fluorine-containing additives have problems such as high viscosity and poor salt solubility, which will have a certain negative impact on the room-temperature and high-temperature performance of the battery. There is also prior art that uses a combination of multiple additives to simultaneously solve various performance aspects of the battery. However, the additives themselves have strong reactivity, and different additives are prone to react with each other, thus affecting the battery performance. The use of such additive combinations is often limited to specific formulations and ratios, and has little significance in actual industrial applications. Summary of the Invention

[0008] To solve the above technical problems, the present invention proposes an electrolyte additive composition that can significantly improve the capacity retention and capacity recovery during high-temperature storage of high-voltage lithium-ion batteries, inhibit the growth of internal resistance and volume during high-temperature storage, and simultaneously improve the high-temperature cycling and room-temperature cycling of the battery. The electrolyte additive composition has a wide application range and does not react with each other.

[0009] The object of the present invention is achieved by the following technical solutions:

[0010] A high-voltage electrolyte additive composition, the electrolyte additive composition comprising:

[0011] A first additive, the structure of the first additive being shown in the following formula (I):

[0012]

[0013] In the formula, R1 is selected from C1-C5 alkylene, C2-C6 alkenylene, C2-C6 alkynylene, C3-C6 isoalkylene, C3-C6 isoalkenylene, C3-C6 isoalkynylene, and the hydrogen in R1 can be substituted by fluorine, cyano, alkoxy, phenyl, phenoxy, fluorophenyl; R2 and R3 are independently selected from fluorine, cyano, C1-C5 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C3-C6 isoalkyl, C3-C6 isoalkenyl, C3-C6 isoalkynyl, and the hydrogen in R2 and R3 can be substituted by fluorine, cyano, alkoxy, phenyl, phenoxy, fluorophenyl; and at least three fluorine atoms are included in R1, R2, and R3;

[0014] A second additive, the second additive being selected from the structures shown in the following formula (II) and / or (III):

[0015]

[0016] In the formula, R4 and R5 are independently selected from hydrogen, C1-C3 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C3-C5 isoalkyl, C3-C5 isovinyl, C3-C5 isovinyl, and the hydrogen on R4 and R5 can be substituted by alkoxy or halogen; R6 and R7 are independently selected from hydrogen, fluorine, chlorine, C1-C3 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C3-C5 isoalkyl, C3-C5 isovinyl, C3-C5 isovinyl, and the hydrogen on R6 and R7 can be substituted by alkoxy or halogen.

[0017] Preferably, R1 is selected from C1-C3 alkylene, C2-C4 alkenylene, C2-C4 alkynylene, C3-C5 isoalkylene, C3-C5 isovinylene, C3-C5 isovinylene, and the hydrogen in R1 can be substituted by fluorine;

[0018] Preferably, R2 and R3 are independently selected from fluorine, C1-C3 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C3-C5 isoalkyl, C3-C5 isovinyl, C3-C5 isovinyl, and the hydrogen in R2 and R3 can be substituted by fluorine.

[0019] Preferably, R4 and R5 are independently selected from hydrogen, C1-C2 alkyl.

[0020] Preferably, R6 and R7 are independently selected from hydrogen, fluorine, C1-C2 alkyl, C2-C3 alkenyl, C3-C4 isoalkyl, C3-C4 isovinyl.

[0021] In order to improve the stability of the interfacial film formed after the reaction of the additive and reduce the flammability of the additive, in the first additive, R2 and R3 are the same, and the number of fluorine atoms does not exceed 12; the number of fluorine atoms in the second additive does not exceed 6.

[0022] Preferably, the first additive is selected from at least one of the following structures:

[0023]

[0024] The second additive is selected from at least one of the following structures:

[0025]

[0026]

[0027] In order to enable the above additive composition to better exert a synergistic effect and form a film together, while taking into account the high-temperature storage performance and cycle stability of the battery, the mass ratio of the first additive to the second additive is 1:5 to 5:1. Preferably, the mass ratio of the first additive to the second additive is 1:2 to 2:1.

[0028] When the electrolyte additive composition of the present invention is used in an electrolyte, the addition amount of the first additive in the electrolyte is 0.05 to 5.0%, and the addition amount of the second additive in the electrolyte is 0.05% to 10.0%. Preferably, the addition amount of the first additive in the electrolyte is 0.2 to 2.0%, and the addition amount of the second additive in the electrolyte is 0.2 to 5.0%.

[0029] The electrolyte additive composition of the present invention can form a dense organic-inorganic composite interface film during the battery formation, formation capacity measurement, and initial use processes, thereby improving various performance aspects of the high-voltage battery system, especially improving the capacity retention and capacity recovery during high-temperature storage, and suppressing the increase in internal resistance and volume increase during high-temperature storage.

[0030] Specifically, when the electrolyte additive composition of the present invention is applied to a lithium-ion battery electrolyte, the first additive solves the problem of excessive increase in internal resistance of the second additive during the film formation process, thereby improving the high-temperature storage performance of the battery while ensuring cycle stability; the second additive solves the problem of insufficient stability of the first additive during the cycle process, thereby improving the long-cycle stability of the battery.

[0031] At the same time, the first additive and the second additive affect each other and have a synergistic effect during the film formation process. The first additive preferentially forms a film at a higher potential, forming an inorganic layer with a relatively high content of lithium fluoride and a relatively thin thickness. The second additive forms an outer interface film with a relatively high organic content at a lower potential. Compared with the sole use of the second additive, due to the formation of an inorganic layer that can isolate most electrons by the use of the first additive, the reaction activity of the second additive is inhibited, forming a thinner interface film and reducing the battery interface impedance. Compared with the sole use of the first additive, due to the formation of an organic layer that can isolate the electrolyte reaction on the periphery by the use of the second additive, the stability of the interface film is improved. In short, compared with the sole use of the first additive or the second additive, the electrolyte additive composition of the present invention can further improve the high-temperature storage performance of the battery without affecting the cycle stability of the battery.

[0032] The present invention also provides a lithium-ion battery electrolyte, which includes a main lithium salt and an organic solvent, and the lithium-ion battery electrolyte further includes the electrolyte additive composition described in any one of the above.

[0033] The main lithium salt of the present invention can be a commonly used lithium salt in the electrolyte. Preferably, the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorodioxalate phosphate, lithium tetrafluoroxalate phosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide, and the dosage accounts for 5 to 20% of the total mass of the electrolyte.

[0034] The organic solvents described in the present invention can be the commonly used organic solvents in electrolytes. Preferably, the organic solvents are selected from at least one of carbonate or fluorinated carbonate compounds with 3 to 6 carbon atoms, carboxylate or fluorinated carboxylate compounds with 3 to 8 carbon atoms, sulfone compounds, and ether compounds.

[0035] Preferably, the carbonate or fluorinated carbonate compounds with 3 to 6 carbon atoms are selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluorinated ethylene carbonate, and difluorinated ethylene carbonate;

[0036] Preferably, the carboxylate or fluorinated carboxylate compounds with 3 to 8 carbon atoms are selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate, and fluorinated ethyl acetate;

[0037] Preferably, the sulfone compounds are selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, and diethyl sulfone;

[0038] Preferably, the ether compounds are selected from at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0039] To further improve the battery performance, the lithium-ion battery electrolyte further includes basic additives, which are selected from at least one of carbonate compounds, sulfonate compounds, sulfate compounds, borate compounds, phosphate compounds, and fluorinated lithium salt compounds, and the dosage accounts for 0.1 to 5.0% of the total mass of the electrolyte.

[0040] Preferably, the carbonate compounds are selected from at least one of fluorinated ethyl methyl carbonate, fluorinated diethyl carbonate, and fluorinated dimethyl carbonate;

[0041] Preferably, the sulfate compounds are selected from at least one of ethylene sulfate, 4-methyl ethylene sulfate, and 4-ethyl ethylene sulfate;

[0042] Preferably, the sulfonate compounds are selected from at least one of 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, and methylene methanedisulfonate;

[0043] Preferably, the borate compounds are selected from at least one of tris(trimethylsilyl) borate, triethyl borate, tripropyl borate, tributyl borate, and triallyl borate;

[0044] Preferably, the phosphate compound is selected from at least one of tris(trimethylsilyl) phosphate, triallyl phosphate, tripropargyl phosphate, and tris(trimethylsilyl) phosphite;

[0045] Preferably, the fluorinated lithium salt compound is selected from at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium difluorooxalate borate, and lithium trioxalate phosphate, and the fluorinated lithium salt compound is different from the aforementioned main lithium salt.

[0046] The present invention also provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the lithium-ion battery electrolyte according to any one of the above.

[0047] The active material of the positive electrode is selected from nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobaltate materials, or lithium iron phosphate materials.

[0048] The active material of the negative electrode is selected from graphite, silicon-carbon, silicon monoxide, silicon, tin, metallic lithium, or their composite materials.

[0049] The charging cut-off voltage of the lithium-ion battery according to the present invention is higher than 4.2V. The high-voltage electrolyte of the present invention is particularly suitable for high-voltage and high-temperature battery systems.

[0050] The present invention aims to solve the problem that the electrode-electrolyte interface film formed during the battery formation, formation and initial use of the electrolyte is not dense and stable enough, or is easily decomposed during subsequent use, resulting in the attenuation of battery performance.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] 1. The electrolyte additive composition of the present invention can simultaneously improve the high-temperature storage performance, high-temperature cycling performance, and room-temperature cycling performance of the battery.

[0053] 2. The electrolyte additive composition of the present invention has good stability, good compatibility with common solvents and lithium salts, does not react or change color, and has a high mutual solubility ratio.

[0054] 3. The mass ratio range of the electrolyte additive composition of the present invention is wide, and it can be adjusted according to the actual use requirements and battery types within a certain ratio range. The controllability during the actual production process is strong, and the industrialization value is large. Detailed Embodiments

[0055] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternative, improved, and equivalent solutions that may be included within the scope of the claims.

[0056] I. Preparation of electrolyte solution

[0057] Preparation of basic electrolyte solution: In a glove box filled with argon (moisture < 5 ppm, oxygen content < 10 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed at a mass ratio of EC:EMC:DEC = 3:5:2. Lithium hexafluorophosphate (LiPF 6 ) was slowly added to the mixed solution until the mass concentration of LiPF 6 reached 12.5%, obtaining the basic electrolyte solution.

[0058] Example 1: In the basic electrolyte solution, 0.5 wt% of compound A1 and 0.5 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0059] Example 2: In the basic electrolyte solution, 0.2 wt% of compound A1 and 1.0 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0060] Example 3: In the basic electrolyte solution, 1.0 wt% of compound A1 and 0.2 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0061] Example 4: In the basic electrolyte solution, 0.5 wt% of compound A2 and 0.5 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0062] Example 5: In the basic electrolyte solution, 0.5 wt% of compound A3 and 0.5 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0063] Example 6: In the basic electrolyte solution, 0.25 wt% of compound A1 and 0.05 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0064] Example 7: In the basic electrolyte solution, 0.05 wt% of compound A1 and 0.25 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0065] Example 8: In the basic electrolyte solution, 5.0 wt% of compound A1 and 10.0 wt% of compound B2 were added to obtain the electrolyte solution of this example.

[0066] Example 9: In the basic electrolyte solution, 0.5 wt% of compound A6 and 0.5 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0067] Example 10: In the basic electrolyte solution, 0.5 wt% of compound A10 and 0.5 wt% of compound B1 were added to obtain the electrolyte solution of this example.

[0068] Comparative Example 1: This comparative example is the same as the base electrolyte.

[0069] Comparative Example 2: In the base electrolyte, 1.0 wt% of Compound A1 was added to obtain the electrolyte of this comparative example.

[0070] Comparative Example 3: In the base electrolyte, 1.0 wt% of Compound B1 was added to obtain the electrolyte of this comparative example.

[0071] Comparative Example 4: In the base electrolyte, 1.0 wt% of Compound A2 was added to obtain the electrolyte of this comparative example.

[0072] Comparative Example 5: In the base electrolyte, 1.0 wt% of Compound A3 was added to obtain the electrolyte of this comparative example.

[0073] Comparative Example 6: In the base electrolyte, 0.01 wt% of Compound A1 and 0.01 wt% of Compound B1 were added to obtain the electrolyte of this comparative example.

[0074] Comparative Example 7: In the base electrolyte, 3.0 wt% of Compound A1 and 0.5 wt% of Compound B1 were added to obtain the electrolyte of this comparative example.

[0075] Comparative Example 8: In the base electrolyte, 0.5 wt% of Compound A1 and 3.0 wt% of Compound B1 were added to obtain the electrolyte of this comparative example.

[0076] Comparative Example 9: In the base electrolyte, 0.5 wt% of 1,3 - propanesultone (1,3 - PS) and 0.5 wt% of Compound B1 were added to obtain the electrolyte of this comparative example.

[0077] Comparative Example 10: In the base electrolyte, 0.5 wt% of Compound A1 and 0.5 wt% of lithium difluorophosphate (LiPO 2 F 2 ) were added to obtain the electrolyte of this comparative example.

[0078] Comparative Example 11: In the base electrolyte, 0.5 wt% of Compound A1 and 0.5 wt% of 1,3 - propanesultone (1,3 - PS) were added to obtain the electrolyte of this comparative example.

[0079] Comparative Example 12: In the base electrolyte, 15 wt% of Compound B2 was added to obtain the electrolyte of this comparative example.

[0080] Comparative Example 13: In the base electrolyte, 10 wt% of Compound A1 was added to obtain the electrolyte of this comparative example.

[0081] Comparative Example 14: In the basic electrolyte, 1.0 wt% of Compound A6 was added to obtain the electrolyte of this comparative example.

[0082] Comparative Example 15: In the basic electrolyte, 1.0 wt% of Compound A10 was added to obtain the electrolyte of this comparative example.

[0083] II. Battery Fabrication

[0084] The lithium-ion battery electrolytes of the above Examples 1-8 and Comparative Examples 1-13 were respectively made into soft-pack lithium-ion power batteries with a capacity of 1000 mAh. The lithium-ion power batteries include a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and battery accessories. The positive electrode active material is a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, a lithium cobaltate material, or a lithium iron phosphate material; the negative electrode active material is graphite, silicon-carbon, silicon monoxide, silicon, tin, metallic lithium, or a composite material thereof. The preparation process is as follows: The positive electrode sheet, the separator, and the negative electrode sheet are wound together into a core, sealed with an aluminum-plastic film, and then baked to make the electrode moisture meet the requirements. After baking, the electrolyte is injected into the battery cell, and the finished soft-pack battery cell is obtained through processes such as standing, formation, grading, and aging.

[0085] III. Battery Testing

[0086] The performance of the above lithium-ion batteries was tested, including:

[0087] 1. High-temperature storage performance test

[0088] Cycled for 1 week according to the cycle performance test method, record the discharge capacity, internal resistance, and volume in the first week, then charge at a constant current of 1C to the charge cut-off voltage and charge at a constant voltage until the current drops to 0.1C, and leave it standing in a constant-temperature oven at 60°C for 30 days. Then, according to the cycle performance test method, cycle for 2 weeks at room temperature, and record the discharge capacity in the first week after high-temperature standing, the discharge capacity in the second week, the internal resistance and volume after storage. Calculate the capacity retention rate, capacity recovery rate, internal resistance growth rate, and volume expansion rate of the battery after storage according to the following formulas:

[0089] Capacity retention rate = Discharge capacity in the first week after high-temperature standing / Discharge capacity in the first week * 100%.

[0090] Capacity recovery rate = Discharge capacity in the first week after high-temperature standing / Discharge capacity in the first week * 100%.

[0091] Internal resistance growth rate = (Internal resistance after storage - Internal resistance in the first week) / Internal resistance in the first week * 100%.

[0092] Volume expansion rate = (Volume after storage - Volume in the first week) / Volume in the first week * 100%.

[0093] 2. Room-temperature cycle performance test

[0094] At 25°C, charge at a constant current of 1C to the charge cut-off voltage, then charge at a constant voltage until the current drops to 0.1C, then discharge at a constant current of 1C to 2.8V. Repeat this cycle for 1000 weeks, record the discharge capacity of the first week and the discharge capacity of the 1000th week, and calculate the capacity retention rate of the battery cycle as follows:

[0095] Capacity retention rate = discharge capacity at the 1000th cycle / discharge capacity at the 1st cycle*100%.

[0096] 3. High temperature cycle performance test

[0097] At 45°C, charge at a constant current of 1C to the charge cut-off voltage, then charge at a constant voltage until the current drops to 0.1C, then discharge at a constant current of 1C to 2.8V. Repeat this cycle for a specific number of weeks, record the discharge capacity of the first week and the discharge capacity of the last week, and calculate the capacity retention rate of the battery cycle as follows:

[0098] Capacity retention rate = discharge capacity in the last week / discharge capacity in the first week*100%.

[0099] The specific test results are shown in Tables 1 to 4 below:

[0100] Table 1 NCM622-4.4V test results

[0101]

[0102]

[0103] Table 1 Test battery, positive electrode active material is LiNi 0.6 Co 0.2 Mn 0.2 O 2 The negative electrode active material is high-capacity artificial graphite, and the charging cut-off voltage is 4.4V.

[0104] According to the test results in Table 1:

[0105] (1) By comparing Example 1 with Comparative Examples 2 and 3, or Example 4 with Comparative Examples 3 and 4, or Example 5 with Comparative Examples 3 and 5, or Example 9 with Comparative Examples 3 and 14, or Example 10 with Comparative Examples 3 and 15, it can be seen that the electrolyte additive composition used in the present invention can improve the capacity retention and recovery during high-temperature storage, inhibit the internal resistance and volume growth, and take into account both normal temperature and high temperature cycle performance compared to using the first additive or the second additive alone;

[0106] (2) By comparing Examples 2, 3, 6, 7 and Comparative Examples 6, 7, 8, it can be seen that the electrolyte additive composition used in the present invention can only meet the requirements of both high-temperature storage performance and cycle performance when the usage amount and ratio of the first additive to the second additive are within a specific range. Once the ratio exceeds the range, the performance of both cannot be excellent at the same time.

[0107] (3) By comparing Example 1 with Comparative Examples 9, 10, and 11, it can be seen that only by using the first additive of the present invention in combination with the second additive can both high-temperature storage performance and cycle performance be taken into account. Other additives having similar functions or effects to the first additive or the second additive cannot simultaneously make the performance of both additives excellent.

[0108] Table 2 NCM811-4.25V test results

[0109]

[0110] Table 2 Test battery, positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 The negative electrode active material is silicon carbon, and the charging cut-off voltage is 4.25V.

[0111] Table 3 LCO-4.5V test results

[0112]

[0113]

[0114] Table 3 Test battery, the positive electrode active material is lithium cobalt oxide, the negative electrode active material is silicon carbon, and the charging cut-off voltage is 4.5V.

[0115] Table 4 LNMO-4.8V test results

[0116]

[0117] Table 4 Test battery, the positive electrode active material is lithium nickel manganese oxide, the negative electrode active material is silicon carbon, and the charging cut-off voltage is 4.8V.

[0118] According to the test results in Table 4:

[0119] Comparing Example 8 with Comparative Examples 12 and 13, it can be seen that for the electrolyte additive composition used in the present invention, when the usage amounts and ratios of the first additive and the second additive are within the ranges described in the present application, compared with using only the first additive or the second additive alone, both can improve the capacity retention and recovery during high-temperature storage, inhibit the increase of internal resistance and volume, and at the same time take into account the cycle performance at normal temperature and high temperature. It should be noted that as the charging cut-off voltage continues to increase, the side reactions generated by the electrolyte during the battery electrochemical reaction will intensify, thus increasing the demand for additives. Therefore, in a battery system where the charging cut-off voltage reaches 4.5 V or above, the usage amounts of the first additive and the second additive may reach the upper limit of the addition amounts described in the present application. In a battery system below 4.5 V, the usage amounts of the first additive and the second additive generally only need to be selected as the preferred addition amounts described in the specification of the present application.

[0120] According to the test results in Tables 1 to 4, it can be seen that:

[0121] The electrolyte additive composition used in the present invention is applicable to the positive and negative electrodes of different types of lithium-ion batteries.

Claims

1. A high-voltage electrolyte additive composition, characterized in that: the electrolyte additive composition includes: a first additive, and the first additive is selected from at least one of the following structures: a second additive, and the second additive is selected from at least one of the following structures: the mass ratio of the first additive to the second additive is 1:5 to 5:1; the addition amount of the first additive in the electrolyte is 0.05 to 5.0%, and the addition amount of the second additive in the electrolyte is 0.05% to 10.0%.

2. The high-voltage electrolyte additive composition according to claim 1, characterized in that: the mass ratio of the first additive to the second additive is 1:2 to 2:

1.

3. The high-voltage electrolyte additive composition according to claim 1, characterized in that: the addition amount of the first additive in the electrolyte is 0.2 to 2.0%, and the addition amount of the second additive in the electrolyte is 0.2 to 5.0%.

4. A lithium-ion battery electrolyte, comprising a main lithium salt and an organic solvent, characterized in that: the electrolyte further includes the electrolyte additive composition according to any one of claims 1-3.

5. The lithium-ion battery electrolyte according to claim 4, characterized in that: the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorodioxalate phosphate, lithium tetrafluoroxalate phosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide, and the dosage accounts for 5 to 20% of the total mass of the electrolyte; the organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate, fluoroethyl acetate, sulfolane, dimethyl sulfoxide, dimethyl sulfone, diethyl sulfone, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

6. The lithium-ion battery electrolyte according to claim 4 or 5, characterized in that: the electrolyte further includes a basic additive, and the basic additive is selected from at least one of fluoromethyl ethyl carbonate, fluorodiethyl carbonate, fluorodimethyl carbonate, sulfonate compounds, sulfate compounds, borate compounds, phosphate compounds, and fluorinated lithium salt compounds, and the dosage accounts for 0.1 to 5.0% of the total mass of the electrolyte.

7. The lithium-ion battery electrolyte according to claim 6, characterized in that: the sulfate compounds are selected from at least one of ethylene sulfate, 4-methyl ethylene sulfate, and 4-ethyl ethylene sulfate; the sulfonate compounds are selected from at least one of 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, and methylene methanedisulfonate; The borate compound is selected from at least one of tris(trimethylsilyl) borate, triethyl borate, tripropyl borate, tributyl borate, and triallyl borate; The phosphate compound is selected from at least one of tris(trimethylsilyl) phosphate, triallyl phosphate, tripropargyl phosphate, and tris(trimethylsilyl) phosphite; The fluorine-containing lithium salt compound is selected from at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium difluorooxalate borate, and lithium trioxalate phosphate, and the fluorine-containing lithium salt compound is different from the main lithium salt.

8. A lithium ion battery, comprising a positive electrode, a negative electrode, and a separator, characterized in that: The lithium ion battery further comprises the lithium ion battery electrolyte according to any one of claims 4-7.

9. The lithium ion battery according to claim 8, characterized in that: The charging cut-off voltage of the lithium ion battery is higher than 4.2V.

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