Electrolyte additive composition and use thereof

Abstract

The application discloses an electrolyte additive composition and application thereof, and the additive composition comprises: a first additive, the first additive at least comprises a pyrosulfate boron trifluoride complex metal salt with a structure shown in the following formula (I-1); and a second additive, the second additive is selected from sulfates with structures shown in the following formulas (II) and / or (III); in the formulas, M is Li or Na; and the mass ratio of the second additive and the first additive is (0.001-0.1):1. When the electrolyte additive composition is applied to a lithium ion battery electrolyte or a sodium ion battery electrolyte, a stable interface film can be constructed at an electrode / electrolyte interface, the high-temperature storage performance and the high-temperature cycle performance of the battery can be improved, the initial resistance of the battery can be reduced, the low-temperature performance can be improved, and the effects of taking into account the high-temperature and low-temperature performances of the battery are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion / sodium ion battery electrolyte, in particular to an additive composition containing pyrosulfate boron trifluoride complex metal salt and sulfate and its application in electrolyte formulation, and the application of the electrolyte obtained by formulation in lithium ion secondary battery or sodium ion secondary battery. BACKGROUND

[0002] As an indispensable part of lithium / sodium ion battery, electrolyte additives are mainly responsible for building electrode / electrolyte interface film to achieve electron insulation and facilitate lithium ion transmission. Under the influence of different functional groups of additives, the composition and structure of electrode / electrolyte interface film change, which ultimately affects the cycle life, high-temperature storage and low-temperature discharge performance of the battery.

[0003] Pyrosulfate boron trifluoride complex lithium salt is a new type of electrolyte additive developed by Zhejiang Chemical Research Institute Co., Ltd. Its patent CN202211583064.X discloses that the additive can improve the cycle performance, high-temperature storage performance and low-temperature performance of the battery. At the same time, patent CN202211583043.8 also discloses that pyrosulfate boron trifluoride complex lithium salt, vinyl sulfate and / or 1,3-propane sultone are used in combination, or further combined with vinylene carbonate, so that the lithium ion battery still has excellent cycle performance, high-temperature storage performance and gas inhibition effect in high energy density system and high voltage environment, and can inhibit the impedance growth during battery cycle, further improving the low temperature performance. However, although vinyl sulfate has excellent electrochemical performance, its poor stability can exacerbate the discoloration of electrolyte, and 1,3-propane sultone is also gradually controlled by European REACH regulations due to its carcinogenicity.

[0004] Therefore, it is an important research topic to continue to develop more stable, safe and environmentally friendly pyrosulfate boron trifluoride complex metal salt compositions and electrolyte formulations to meet the battery needs of different scenarios and different performances. SUMMARY

[0005] In order to solve the above technical problems, the present application further proposes an additive composition containing pyrosulfate boron trifluoride complex metal salt and sulfate and its application in electrolyte formulation and lithium ion battery or sodium ion battery. The additive composition can further improve the high-temperature storage performance and high-temperature cycle performance of the battery on the basis of maintaining the high and low temperature performance of pyrosulfate boron trifluoride complex metal salt, and will not increase the initial impedance of the battery.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] An electrolyte additive composition, the additive composition comprising:

[0008] A first additive, the first additive comprising at least a pyrosulfato boron trifluoride complex metal salt of the following formula (I-1):

[0009]

[0010] A second additive, the second additive selected from a sulfate salt of the following formula (II) and / or (III):

[0011]

[0012] wherein M is Li or Na; and the first additive and the second additive are both Li salts or both Na salts.

[0013] The mass ratio of the second additive to the first additive is (0.001-0.1):1, preferably the mass ratio is (0.01-0.1):1.

[0014] The first additive further comprises at least one of the following compounds of formula (I-2), (I-3), (I-4), (I-5), (I-6), and the first additive comprises at least 80wt% of the pyrosulfato boron trifluoride complex metal salt of the following formula (I-1):

[0015]

[0016]

[0017] In formula (I-2), (I-3), (I-4), (I-5), (I-6), M is Li or Na.

[0018] and the first additive comprises at least 80wt% of the pyrosulfato boron trifluoride complex metal salt of the following formula (I-1).

[0019] Preferably, the first additive comprises 80-95wt% of the pyrosulfato boron trifluoride complex salt of the following formula (I-1), and the rest is at least one of the compounds (I-2), (I-3), (I-4), (I-5) or (I-6).

[0020] The second additive of the present application specifically comprises the following sulfate salts of the following formula (II-1), (II-2), (III-1), (III-2):

[0021]

[0022] The additive composition of the present application can be prepared by reacting pyrosulfate with boron trifluoride, wherein the pyrosulfate can be prepared by first reacting inorganic lithium salt with dilute sulfuric acid to obtain bisulfate, and then preparing by thermal decomposition. In the thermal decomposition process of the above bisulfate, in addition to obtaining pyrosulfate, a small amount of sulfate will also be generated. Therefore, the additive composition prepared mainly contains the first additive and a small amount of the second additive. By adjusting the thermal decomposition temperature of the bisulfate or carrying out post-treatment, the content of the second additive in the additive composition can also be reduced until completely removed.

[0023] The first additive composition of the present application mainly contains compound I-1. By adjusting the preparation process, a mixture containing at least one of compounds (I-2), (I-3), (I-4), (I-5) or (I-6) and compound I-1 can also be obtained.

[0024] The first additive of the present application has a -B-O-S-O-S-O-B- structure which is easy to form a cross-linked network structure. Although it can provide a large number of ion transmission channels, the stability of such cross-linked network structure under high temperature and high voltage is poor. The SO4 2- The combination of the particles and boron atoms in the network structure can further improve the stability of the interface film, thereby further improving the performance of the battery under high temperature and high voltage on the basis of maintaining the impedance, room temperature and low temperature performance advantages.

[0025] The present application also provides a preparation method of an electrolyte, which comprises: adding a host salt to a non-aqueous solvent to obtain a molar concentration of the host salt of 0.1-4.0 mol / L, and then continuously adding the additive composition of any one of the above to obtain an electrolyte, and making the first additive account for 0.1-15.0 wt% of the total mass of the electrolyte, and the second additive account for 0.001-0.5 wt% of the total mass of the electrolyte.

[0026] Preferably, the first additive accounts for 0.1-10.0 wt% of the total mass of the electrolyte, and the second additive accounts for 0.01-0.5 wt% of the total mass of the electrolyte.

[0027] Since the additive is consumed in the construction of the interface film at the interface between the positive and negative electrodes of the battery during the formation and capacity distribution of the battery, there is a certain difference between the content of the additive detected in the actual battery product and the amount added during the preparation of the electrolyte. Therefore, the amount of the additive added in the preparation method of the present application is not necessarily equal to the content in the electrolyte of the battery.

[0028] The host salt is selected from a host lithium salt or a host sodium salt.

[0029] The main lithium salt is at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoro(oxalato)phosphate, lithium tris(oxalato)phosphate, lithium difluoro-bis(oxalato)phosphate; preferably, the main lithium salt is at least one selected from lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide, and the molar concentration in the non-aqueous solvent is 0.5-2.0 mol / L.

[0030] The main sodium salt is at least one selected from sodium hexafluorophosphate, sodium perchlorate, sodium difluorophosphate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium bis(trifluoromethylsulfonyl)imide or sodium bis(fluorosulfonyl)imide; preferably, the main sodium salt is at least one selected from sodium hexafluorophosphate and / or sodium bis(fluorosulfonyl)imide, and the molar concentration in the non-aqueous solvent is 0.5-2.0 mol / L.

[0031] The non-aqueous solvent is at least one selected from C3-C6 carbonate or fluorocarbonate compound, C3-C8 carboxylate or fluorocarboxylate compound, sulfone compound or ether compound.

[0032] Preferably, the C3-C6 carbonate or fluorocarbonate compound is at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate or ethyl propyl carbonate; the C3-C8 carboxylate or fluorocarboxylate compound is at least one selected from γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate; the sulfone compound is at least one selected from sulfolane, dimethyl sulfoxide, dimethyl sulfone or diethyl sulfone; and the ether compound is triethylene glycol dimethyl ether and / or tetraethylene glycol dimethyl ether.

[0033] Generally, the non-aqueous solvent in the lithium ion battery electrolyte and the sodium ion battery electrolyte can be the same. Therefore, the above-mentioned non-aqueous solvent can be applied to the lithium ion battery electrolyte or the sodium ion battery electrolyte.

[0034] In a specific embodiment, the non-aqueous solvent is a mixed solvent of ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC), and the mass ratio of the three is EC: EMC: DEC = 4:4:2, which has relatively optimal comprehensive performance.

[0035] In another specific embodiment, the non-aqueous solvent is a mixed solvent of ethylene carbonate (EC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC) and dimethyl carbonate (DMC), and the mass ratio of the four is EC: EMC: DEC: DMC = 3:5:1:1, which can further improve the ionic conductivity of the electrolyte on the basis of having relatively optimal comprehensive performance.

[0036] In another specific embodiment, the non-aqueous solvent is a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and methyl acetate (EA), and the mass ratio of the four is EC: EMC: DEC: EA = 2:5:1:2, which has a lower freezing point on the basis of better comprehensive performance, and can further improve the low-temperature performance of the electrolyte.

[0037] To improve the comprehensive performance of the lithium ion battery, a base additive can also be added to the lithium ion battery electrolyte, the base additive is selected from at least one of fluoroethylene carbonate, vinylene carbonate, tris(trimethylsilyl) phosphate, 1,3-propane sultone, lithium difluorophosphate, lithium bisfluorosulfonylimide, succinic anhydride, adipodinitrile, cyclohexylbenzene, lithium difluorophosphate bisoxalate, or lithium difluoroboric acid oxalate, and any one of the base additives accounts for 0.1-5.0wt% of the total mass of the electrolyte.

[0038] In one specific embodiment, the base additive is vinylene carbonate and lithium difluorophosphate, each accounting for 0.1%-2% of the total mass of the electrolyte, which can further improve the room temperature cycle and high temperature cycle performance of the battery by being used in combination with the first additive and the second additive.

[0039] In another specific embodiment, the base additive is 1,3-propane sultone and tris(trimethylsilyl) phosphate, each accounting for 0.1%-2% of the total mass of the electrolyte, which can further inhibit gas generation of the lithium battery during high-temperature storage, reduce the initial impedance of the battery, and improve the low-temperature performance by being used in combination with the first additive and the second additive.

[0040] Generally, the base additive in the lithium ion battery electrolyte and the sodium ion battery electrolyte can be the same, and the only difference is that the anion in the salt additive contained in the base additive is different. Therefore, to improve the comprehensive performance of the sodium ion battery, a base additive can also be added to the sodium ion battery electrolyte, the base additive is selected from at least one of fluoroethylene carbonate, vinylene carbonate, tris(trimethylsilyl) phosphate, 1,3-propane sultone, sodium difluorophosphate, sodium bisfluorosulfonylimide, succinic anhydride, adipodinitrile, cyclohexylbenzene, sodium difluorophosphate bisoxalate, or sodium difluoroboric acid oxalate, and any one of the base additives accounts for 0.1-5.0wt% of the total mass of the electrolyte.

[0041] The application also provides a lithium ion secondary battery, which comprises a positive electrode sheet, a negative electrode sheet, and a separator, and is prepared by the following method:

[0042] The positive electrode sheet, separator, and negative electrode sheet are wound together into a core, sealed with an aluminum-plastic film, and then baked. After that, the electrolyte obtained by any of the above-mentioned preparation methods is injected into it, and a lithium-ion secondary battery is obtained after standing, formation, grading, and aging.

[0043] The active material of the positive electrode sheet of the lithium-ion battery is selected from nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobaltate materials, or lithium iron phosphate materials, and the active material of the negative electrode sheet is selected from graphite, silicon-carbon, silicon monoxide, silicon, tin, metallic lithium, or their composite materials.

[0044] The present invention also provides a sodium-ion secondary battery, including a positive electrode sheet, a negative electrode sheet, and a separator. The sodium-ion secondary battery is obtained by the following method:

[0045] The positive electrode sheet, separator, and negative electrode sheet are wound together into a core, sealed with an aluminum-plastic film, and then baked. After that, the electrolyte obtained by any of the above-mentioned preparation methods is injected into it, and a sodium-ion secondary battery is obtained after standing, formation, grading, and aging.

[0046] The negative electrode of the sodium-ion battery is one or more of hard carbon, carbon black, amorphous carbon, graphite, SnS2, Na2Ti3O7, silicon-based materials, metal oxides, metal sulfides, or metallic sodium; the positive electrode material is NaMn (1-x-y) Ni y M x O2 (0 ≤ x, y ≤ 1, M is Cu, Fe, Co), sodium manganate, sodium vanadium phosphate, sodium fluorovanadium phosphate, sodium iron phosphate, sodium manganese phosphate, Na x MnFe(CN)6 (0 < x ≤ 2) or one or more of them.

[0047] Compared with the prior art, the beneficial effects of the present invention include:

[0048] The additive composition of the present invention has a synergistic effect in constructing a stable electrode / electrolyte interface. The pyrosulfate boron trifluoride composite metal salt as the first additive has a -B-O-S-O-S-O-B- structure, which can form a cross-linked network structure to provide a large number of ion transport channels, thereby increasing ion conductivity and reducing interfacial film impedance; at the same time, the O on the S=O bond in the structure of the first additive can also combine with the metal atoms on the surface of the battery positive electrode to improve the protection of the positive electrode. However, the interfacial film formed by the cross-linked network structure of the first additive has weakened stability at high temperature and high voltage. When used in combination with the sulfate as the second additive, an appropriate amount of SO4 in the second additive 2-The particles can be combined with the boron atoms in the cross-linked network structure to improve the stability of the interface film. Therefore, by the combination of the first additive and the second additive, the battery can be further improved in high-temperature performance under high-temperature and high-voltage environments while maintaining the advantages of impedance and low-temperature performance, so that the battery has better high and low temperature performance. DETAILED DESCRIPTION

[0049] The application will be further described in conjunction with specific examples, but the application is not limited to these specific examples. Those skilled in the art should recognize that the application encompasses all alternatives, improvements and equivalents within the scope of the claims.

[0050] In the examples and comparative examples of the application, the types of the first additive include the following:

[0051] The first additive A contains 95wt% of compound I-1 and 5wt% of compound I-2, and both are complex lithium salts;

[0052] The first additive B contains 90wt% of compound I-1, 6wt% of compound I-2 and 4wt% of compound I-3, and all are complex lithium salts;

[0053] The first additive C contains 85wt% of compound I-1, 7wt% of compound I-2, 5wt% of compound I-3 and 3wt% of compound I-4, and all are complex lithium salts.

[0054] The first additive D contains 95wt% of compound I-1 and 5wt% of compound I-2, and both are complex sodium salts.

[0055] I. Preparation of electrolyte

[0056] Preparation of base electrolyte 1: In an argon-filled glove box (moisture <5ppm, oxygen <10ppm), ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of EC: EMC: DEC = 3:5:2, and lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution until the molar concentration of LiPF6 was 1.2mol / L, to obtain the base electrolyte 1.

[0057] Preparation of base electrolyte 2: In an argon-filled glove box (moisture <5ppm, oxygen <10ppm), propylene carbonate (PC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of EC: EMC: DEC = 4:4:2, and sodium hexafluorophosphate (NaPF6) was slowly added to the mixed solution until the molar concentration of NaPF6 was 1.2mol / L, to obtain the base electrolyte 2.

[0058] Example 1

[0059] The base electrolyte 1 was added with 0.5wt% of the first additive A and 0.01wt% of the second additive II-1 to obtain the electrolyte of this example.

[0060] Example 2

[0061] The operation of this example was the same as that of Example 1, except that the addition amount of the first additive A was adjusted to 1wt% and the addition amount of the second additive II-1 was adjusted to 0.001wt% to obtain the electrolyte of this example.

[0062] Example 3

[0063] The operation of this example was the same as that of Example 1, except that the addition amount of the first additive A was adjusted to 1wt% and the addition amount of the second additive II-1 was adjusted to 0.1wt% to obtain the electrolyte of this example.

[0064] Example 4

[0065] The operation of this example was the same as that of Example 1, except that the addition amount of the first additive A was adjusted to 2wt% and the addition amount of the second additive II-1 was adjusted to 0.1wt% to obtain the electrolyte of this example.

[0066] Example 5

[0067] The operation of this example was the same as that of Example 1, except that the addition amount of the first additive A was adjusted to 2wt% and the addition amount of the second additive II-1 was adjusted to 0.3wt% to obtain the electrolyte of this example.

[0068] Example 6

[0069] The operation of this example was the same as that of Example 1, except that the addition amount of the first additive A was adjusted to 5wt% and the addition amount of the second additive II-1 was adjusted to 0.3wt% to obtain the electrolyte of this example.

[0070] Example 7

[0071] The operation of this example was the same as that of Example 1, except that the addition amount of the first additive A was adjusted to 10wt% and the addition amount of the second additive II-1 was adjusted to 0.5wt% to obtain the electrolyte of this example.

[0072] Example 8

[0073] The operation of this example was the same as that of Example 3, except that the second additive was changed from compound II-1 to compound III-1 to obtain the electrolyte of this example.

[0074] Example 9

[0075] The operation of this example is the same as that of Example 3, with the exception that the first additive A is replaced by the first additive B, the second additive is replaced by compound III-1 from compound II-1, and the rest is unchanged, to obtain the electrolyte of this example.

[0076] Example 10

[0077] The operation of this example is the same as that of Example 3, with the exception that the first additive A is replaced by the first additive C, the second additive is replaced by compound III-1 from compound II-1, and the rest is unchanged, to obtain the electrolyte of this example.

[0078] Example 11

[0079] The operation of this example is the same as that of Example 3, with the exception that 1% of vinylene carbonate (VC) is further added on the basis of Example 3, to obtain the electrolyte of this example.

[0080] Example 12

[0081] The operation of this example is the same as that of Example 3, with the exception that 1% of 1,3-propanesulfonic acid lactone (PS) is further added on the basis of Example 3, to obtain the electrolyte of this example.

[0082] Example 13

[0083] The operation of this example is the same as that of Example 8, with the exception that 1% of vinylene carbonate (VC) and 1% of lithium difluorophosphate (LiDFP) are further added on the basis of Example 8, to obtain the electrolyte of this example.

[0084] Example 14

[0085] 1.0wt% of the first additive D and 0.1wt% of the second additive II-2 are added to the base electrolyte 2 to obtain the electrolyte of this example.

[0086] Example 15

[0087] The operation of this example is the same as that of Example 14, with the exception that the second additive is replaced by compound III-2 from compound II-2, and the rest is unchanged, to obtain the electrolyte of this example.

[0088] Example 16

[0089] The operation of this example is the same as that of Example 15, with the exception that 1wt% of vinyl ethyl sulfate (DTD) is further added on the basis of Example 15, to obtain the electrolyte of this example.

[0090] Comparative Example 1

[0091] The operation of the present comparative example is the same as that of Example 2, except that no second additive is added to obtain the electrolyte of the present comparative example.

[0092] Comparative Example 2

[0093] The operation of the present comparative example is the same as that of Example 9, except that no second additive is added to obtain the electrolyte of the present comparative example.

[0094] Comparative Example 3

[0095] The operation of the present comparative example is the same as that of Example 5, except that no first additive is added to obtain the electrolyte of the present comparative example.

[0096] Comparative Example 4

[0097] The operation of the present comparative example is the same as that of Example 9, except that the amount of the second additive is adjusted to 1 wt% to obtain the electrolyte of the present comparative example.

[0098] Comparative Example 5

[0099] The operation of the present comparative example is the same as that of Example 9, except that the amount of the second additive is adjusted to 3 wt% to obtain the electrolyte of the present comparative example.

[0100] Comparative Example 6

[0101] The operation of the present comparative example is the same as that of Example 15, except that no second additive is added to obtain the electrolyte of the present comparative example.

[0102] Comparative Example 7

[0103] The operation of the present comparative example is the same as that of Example 15, except that no first additive is added to obtain the electrolyte of the present comparative example.

[0104] Comparative Example 8

[0105] The operation of the present comparative example is the same as that of Example 15, except that no first additive is added to obtain the electrolyte of the present comparative example.

[0106] Comparative Example 9

[0107] The operation of the present comparative example is the same as that of Example 15, except that no first additive is added to obtain the electrolyte of the present comparative example.

[0108] II. Electrochemical performance test

[0109] The electrolytes of Examples 1-13 and Comparative Examples 1-6 above are respectively prepared into soft package capacity 1260 mAh lithium ion batteries, which include positive electrode sheet, negative electrode sheet, separator, electrolyte and battery auxiliary materials, and the positive electrode active material is ternary positive electrode LiNi 0.6 Co 0.2 Mn 0.2O2, and the negative active material is high-capacity graphite. The preparation process is as follows: the positive electrode sheet, the separator, and the negative electrode sheet are wound together into a roll core, and the roll core is sealed with an aluminum plastic film and then baked to make the water content of the electrode meet the requirements. After baking, the battery core is subjected to electrolyte injection, standing, formation, capacity grading, and aging processes to obtain a finished lithium ion battery soft package battery core.

[0110] The electrolyte of the above examples 14-16 and comparative examples 7-9 is made into a soft package sodium ion battery with a capacity of 1000 mAh, which comprises a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and battery accessories. The positive active material is a ternary positive electrode NaNi 0.33 Fe 0.33 Mn 0.33 O2, and the negative active material is hard carbon. The preparation process is as follows: the positive electrode sheet, the separator, and the negative electrode sheet are wound together into a roll core, and the roll core is sealed with an aluminum plastic film and then baked to make the water content of the electrode meet the requirements. After baking, the battery core is subjected to electrolyte injection, standing, formation, capacity grading, and aging processes to obtain a finished lithium ion battery soft package battery core.

[0111] The lithium ion battery and the sodium ion battery prepared above are subjected to performance tests (2.8-4.4V), mainly including:

[0112] (1) 60°C high-temperature storage test: the battery is charged to 100% SOC and stored in a 60±2°C oven for 28 days. The volume before and after storage is tested to obtain the volume expansion rate of the single battery before and after 60°C storage.

[0113] (2) 45°C high-temperature cycle test: the battery is cycled in a 45±1°C oven at a charge-discharge current of 1C / 1C. The discharge capacity per week is calculated, and the cycle is stopped after 500 cycles. The capacity retention rate after cycling is calculated.

[0114] (3) -20°C low-temperature discharge: the battery is discharged to 80% of the lower limit voltage at a discharge current of 1C in a -20±1°C oven, as the low-temperature discharge capacity, and the percentage of the low-temperature discharge capacity to the 1C discharge capacity at 25°C is calculated, which is recorded as the low-temperature discharge capacity retention rate.

[0115] The test results are shown in Table 1 below:

[0116] Table 1: Test results of battery electrochemical performance

[0117]

[0118]

[0119] The results of the electrochemical performance tests of the additive compositions applied to lithium ion batteries in Table 1 show that, by adding appropriate amounts of the first additive and the second additive in the electrolyte, the high-temperature cycle performance and the high-temperature storage performance can be improved, the initial impedance of the battery can be reduced, the low-temperature performance of the battery can be improved, and the effects of high- and low-temperature performances of the battery can be considered, especially when the amount of the first additive is 0.01% to 5%, the impedance can be obviously reduced and the low-temperature discharge can be obviously improved. When the amount of the first additive is 5% to 10%, more first additives can cause the interface film of the battery to be thicker, so that the effect of reducing the impedance of the battery by the additive composition is weakened, and at the same time, the high-temperature performance is gradually deteriorated, but the high-temperature performance is still improved compared with the base electrolyte.

[0120] Comparing Examples 1 to 10 in the above Table 1 with Comparative Examples 1 to 3 and Comparative Example 6 shows that, by adding appropriate amounts of the second additive to the electrolyte containing the first additive, the high-temperature performance of the battery can be further improved without increasing the initial DCR of the battery and without deteriorating the low-temperature discharge performance of the battery, which is mainly because the crosslinked network structure formed by the first additive, and the SO4 2- The particles in the second additive combine with the boron atoms in the crosslinked network structure to further improve the high-temperature stability of the interface film.

[0121] Comparing Example 9 in the above Table 1 with Comparative Examples 4 to 5 shows that, as the amount of the second additive increases, excessive sulfate may block the ion transmission channel, intensify the side reaction between the electrolyte and the electrode, and significantly increase the initial DCR of the battery and deteriorate the performance of the battery.

[0122] Comparing Example 3 in the above Table 1 with Examples 11 to 12 shows that, by further adding VC to the electrolyte containing the first additive and the second additive, the cycle performance and the high-temperature storage performance of the battery can be further improved; by further adding PS to the electrolyte containing the first additive and the second additive, the high-temperature storage performance of the battery can be further improved. Comparing Example 8 with Example 13 shows that, by simultaneously adding VC and LiDFP to the electrolyte containing the first additive and the second additive, the comprehensive performance of the battery can be further improved.

[0123] The results of the electrochemical performance tests of the additive compositions applied to sodium ion batteries in Table 1 show that, in addition to the initial DCR of the sodium ion battery being slightly larger than that of the corresponding lithium ion battery due to the material itself, the regularity of the electrochemical performance test results of the additive compositions applied to lithium ion batteries and sodium ion batteries is basically the same, that is, appropriate amounts of the first additive and the second additive are combined, and the high- and low-temperature comprehensive performance of the sodium ion battery can be improved.

Claims

1. An electrolyte additive composition characterized in that: The additive composition comprises: a first additive comprising at least a pyrosulfate boron trifluoride complex metal salt of the following formula (I-1): The first additive further comprises at least one of the following compounds of formula (I-2), (I-3), (I-4), (I-5), (I-6): In formula (I-2), (I-3), (I-4), (I-5), (I-6), M is Li or Na; and the first additive contains at least 80wt% of the pyrosulfate boron trifluoride complex metal salt of the formula (I-1); a second additive selected from a sulfate salt of the following formula (II) and / or (III): In the formula, M is Li or Na; The mass ratio of the second additive to the first additive is (0.001-0.1):

1.

2. The electrolyte additive composition of claim 1, wherein: The mass ratio of the second additive to the first additive is (0.01-0.1):

1.

3. The electrolyte additive composition of claim 1, wherein: The first additive contains 80-95wt% of the pyrosulfate boron trifluoride complex metal salt of the formula (I-1), and the rest is at least one of the compounds (I-2), (I-3), (I-4), (I-5) or (I-6).

4. A method of formulating a lithium-ion battery electrolyte, characterized by: The preparation method comprises: adding a main lithium salt in a non-aqueous solvent to a molar concentration of 0.1-4.0 mol / L, and then continuously adding the additive composition of any one of claims 1-3 to obtain an electrolyte, so that the first additive accounts for 0.01-15.0wt% of the total mass of the electrolyte, and the second additive accounts for 0.001-0.5wt% of the total mass of the electrolyte; The non-aqueous solvent is selected from at least one of C3-C6 carbonate or fluorinated carbonate compounds, C3-C8 carboxylate or fluorinated carboxylate compounds, sulfone compounds or ether compounds; The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium bisfluorosulfonimide, lithium bis-trifluoromethylsulfonimide, lithium tetrafluorooxalate phosphate, lithium trioxalate phosphate, lithium difluorobisoxalate phosphate.

5. The method of formulating an electrolyte solution of claim 4, wherein: The first additive accounts for 0.1-10.0wt% of the total mass of the electrolyte, and the second additive accounts for 0.01-0.5wt% of the total mass of the electrolyte.

6. The method of formulating an electrolyte solution of claim 4, wherein: The C3-C6 carbonate or fluorinated carbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate or ethyl propyl carbonate; the C3-C8 carboxylate or fluorinated carboxylate compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone or diethyl sulfone; and the ether compound is selected from triethylene glycol dimethyl ether and / or tetraethylene glycol dimethyl ether.

7. The method of formulating an electrolyte solution according to any one of claims 4-6, characterized in that: The base additive is added in the electrolyte, and the base additive is at least one of fluoroethylene carbonate, vinyl ethylene carbonate, tris(trimethylsilyl)phosphate, 1,3-propylene sultone, lithium difluorophosphate, lithium bisfluorosulfonylimide, succinic anhydride, adiponitrile, cyclohexylbenzene, lithium difluorophosphate bisoxalate, or lithium difluoroboric acid oxalate, and any one of the base additives accounts for 0.1-5.0 wt% of the total mass of the electrolyte.

8. A lithium-ion secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a separator, characterized by: The lithium ion secondary battery is prepared by the following method: The positive electrode sheet, the separator, and the negative electrode sheet are wound together into a roll core, sealed with an aluminum plastic film, and baked, and then the electrolyte prepared by the preparation method of any one of claims 4-7 is injected into the roll core, the first additive and the second additive in the electrolyte are both lithium salts, and the lithium ion secondary battery is obtained after standing, formation, capacity distribution, and aging.

9. The lithium-ion secondary battery according to claim 8, characterized by: The active material of the positive electrode sheet is selected from nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium cobaltate material, or lithium iron phosphate material, and the active material of the negative electrode sheet is selected from graphite, silicon-carbon, silicon monoxide, silicon, tin, metallic lithium, or a composite material thereof.

10. A method of formulating a sodium-ion battery electrolyte, characterized by: The preparation method comprises: adding a main sodium salt in a non-aqueous solvent to a molar concentration of 0.1-4.0 mol / L of the main sodium salt, and then continuously adding the additive composition of any one of claims 1-3 to obtain an electrolyte, and the first additive accounts for 0.01-15.0 wt% of the total mass of the electrolyte, and the second additive accounts for 0.001-0.5 wt% of the total mass of the electrolyte; The non-aqueous solvent is at least one of C3-C6 carbonate or fluoro-carbonate compound, C3-C8 carboxylate or fluoro-carboxylate compound, sulfone compound, or ether compound; The main sodium salt is at least one of sodium hexafluorophosphate, sodium perchlorate, sodium difluorophosphate, sodium bisoxalate borate, sodium difluoroboric acid oxalate, sodium bis(trifluoromethylsulfonyl)imide, or sodium bisfluorosulfonylimide.

11. The method of formulating an electrolyte solution of claim 10, wherein: The first additive accounts for 0.1-10.0 wt% of the total mass of the electrolyte, and the second additive accounts for 0.01-0.5 wt% of the total mass of the electrolyte.

12. The method of formulating an electrolyte solution of claim 10, wherein: The C3-C6 carbonate or fluoro-carbonate compound is at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or ethyl propyl carbonate; the C3-C8 carboxylate or fluoro-carboxylate compound is at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or propyl propionate; the sulfone compound is at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone; and the ether compound is triethylene glycol dimethyl ether and / or tetraethylene glycol dimethyl ether.

13. The method of formulating an electrolyte solution according to any one of claims 10-12, wherein: A base additive is added to the electrolyte, the base additive being at least one selected from fluoroethylene carbonate, vinyl ethylene carbonate, tris(trimethylsilyl)phosphate, 1,3-propene sultone, sodium difluorophosphate, sodium bisfluorosulfonylimide, succinic anhydride, suberoylanilide hydroxamic acid, cyclohexylbenzene, sodium bis(oxalato) difluorophosphate, or sodium difluoro(oxalato)borate, and any one of the base additives accounts for 0.1-5.0 wt% of the total mass of the electrolyte.

14. A sodium-ion secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a separator, characterized by: The sodium-ion secondary battery is prepared by the following method: The positive electrode sheet, the separator, and the negative electrode sheet are wound together into a roll core, sealed with an aluminum plastic film, and baked, after which the electrolyte prepared by the preparation method of any one of claims 10-13 is injected into the roll core, the first additive and the second additive in the electrolyte are both sodium salts, and the sodium-ion secondary battery is obtained after standing, formation, capacity distribution, and aging; The negative electrode of the sodium ion battery is one or more of hard carbon, carbon black, amorphous carbon, graphite, SnS2, Na2Ti3O7, silicon-based material, metal oxide, metal sulfide or metallic sodium; the positive electrode material is NaMn (1-x-y) Ni y M x O2, sodium manganate, sodium aluminophosphate, sodium fluor aluminophosphate, sodium iron phosphate, sodium manganese phosphate, Na x MnFe(CN)6, or one or more of the formulae NaMn (1-x-y) Ni y M x O2, 0<=x, y<=1, M is Cu, Fe, Co, the formula Na x MnFe(CN)6, 0<x<=2.

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