Lithium or sodium ion battery electrolyte and applications thereof

Abstract

The application discloses an electrolyte applied to a lithium ion battery or a sodium ion battery, the electrolyte comprising a main salt, an organic solvent, and a first additive and a second additive, the first additive being a propargyl sulfonate compound with a structure shown in the following formula (A): the second additive being lithium difluorophosphate fluorophosphate with a structure shown in the following formula (B), lithium difluorophosphate fluorophosphate or sodium difluorophosphate fluorophosphate with a structure shown in the following formula (C); the definitions of the substituents in the formulas (A), (B) and (C) are shown in the specification; the first additive accounts for 0.1-3.0 wt% of the total mass of the electrolyte; and the second additive accounts for 0.1-5.0 wt% of the total mass of the electrolyte. The electrolyte disclosed by the application is beneficial to improving the high-temperature cycle stability and storage stability of the lithium ion battery or the sodium ion battery on the basis of taking into account the high-temperature and low-temperature performances.

Description

Technical Field

[0001] This invention relates to the field of electrolytes, and in particular to an electrolyte that improves the high-temperature cycling and high-temperature storage performance of lithium-ion or sodium-ion batteries and its applications. Background Technology

[0002] In recent years, the application of lithium-ion rechargeable batteries has expanded from traditional small electronic devices to large electronic devices, automobiles, and smart grids. Therefore, there are higher requirements for maintaining excellent performance in more complex external environments such as high and low temperatures. Some batteries used in pure electric vehicles (EVs) and hybrid electric vehicles (HEVs) may need to operate in high-temperature environments for extended periods due to geographical limitations. Meanwhile, in recent years, sodium-ion batteries have once again attracted widespread attention due to the relative scarcity of lithium resources and the abundant reserves of sodium resources (440 times that of lithium). Lithium and sodium both belong to Group IA alkali metals in the periodic table and share similar physical and chemical properties; theoretically, both can serve as metal ion carriers in rechargeable batteries.

[0003] Numerous studies have found that interfacial reactions occur between high-energy-density cathode materials and electrolytes, especially under high temperature and high voltage conditions. These side reactions intensify at the cathode interface and electrolyte. For example, taking the ternary layered cathode material NCM as an example, the dissolution of transition metal ions Ni and Mn is accelerated, and Li... + / Ni 2+ Cation mixing and loss of active lithium are reflected in battery electrochemical performance as phenomena such as battery gas generation and a continuous increase in DC impedance (DCIR), leading to battery capacity loss and power performance degradation, which seriously affects high-temperature storage and high-temperature cycling performance. Therefore, researching suitable high-temperature electrolytes and improving the interfacial stability between high-energy-density electrodes and electrolytes has always been a hot topic in electrolyte development. Patents JP2000195545A, CN100559648C, and CN110582883A disclose that propargyl methanesulfonate (CAS No.: 16156-58-4) has the function of adsorbing metal ions dissolved from the positive electrode under high voltage and forming a stable ion-conducting film on the electrode surface. In terms of electrochemical performance, it shows the ability to suppress gas generation during high-temperature storage of batteries and is a class of high-temperature additives with good effects.

[0004] However, the present invention found that although the additive can effectively suppress gas generation during high-temperature storage of pouch batteries, its film density is poor when used alone, which is not conducive to suppressing the DCIR growth of the battery during long-term dynamic cycling. Furthermore, as cycling and storage proceed, side reactions continue to occur at the interface, and the negative electrode interface impedance continues to increase, resulting in a significant degradation of cell performance and affecting the battery's lifespan.

[0005] Based on the technical requirements for long-cycle storage and cycling of batteries, as well as the requirements for overall battery performance, it is necessary to develop an electrolyte composition or electrolyte formulation that takes into account both high and low temperature performance of batteries and is conducive to improving the high-temperature cycling performance of lithium-ion or sodium-ion batteries. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a lithium-ion or sodium-ion battery electrolyte that improves the stability of the interfacial film between the positive and negative electrodes and the electrolyte, enhances the high-temperature cycle stability and storage stability of the battery, and also takes into account low-temperature discharge performance.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] An electrolyte for use in lithium-ion or sodium-ion batteries, comprising a main salt and an organic solvent, the electrolyte further comprising:

[0009] The first additive is a sulfonate propargyl ester compound with the structure shown in formula (A):

[0010]

[0011] In the formula, R is selected from C1-C6 alkyl or C2-C6 alkenyl, C1-C6 fluoroalkyl or C2-C6 fluoroalkenyl, C3-C8 cycloalkyl, C3-C8 fluorocycloalkyl or cycloalkenyl, phenyl, fluorobenzene or C1-C3 alkyl-substituted phenyl.

[0012] The second additive is lithium difluorophosphate-based fluoroborate or lithium difluorophosphate-based fluorophosphate with the structure shown in formula (B) for use in lithium-ion batteries, or sodium difluorophosphate-based fluoroborate or sodium difluorophosphate-based fluorophosphate with the structure shown in formula (C) for use in sodium-ion batteries.

[0013]

[0014] In the formula, M is selected as boron or phosphorus; when M is boron, x is selected as 1, 2, 3 or 4, y is selected as 0, 1, 2 or 3, and x + y = 4; when M is phosphorus, x is selected as 1, 2, 3, 4, 5 or 6, y is selected as 0, 1, 2, 3, 4 or 5, and x + y = 6;

[0015] The first additive accounts for 0.1 to 3.0 wt% of the total mass of the electrolyte;

[0016] The second additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.

[0017] Preferably, in formula (A), R is selected from C1-C3 alkyl or C2-C3 alkenyl, C1-C3 fluoroalkyl, C3-C6 cycloalkyl, C3-C6 fluorocycloalkyl or cycloalkenyl, phenyl, fluorophenyl or C1-C3 alkyl-substituted phenyl.

[0018] More preferably, the first additive is selected from at least one of the structures shown in the following formula:

[0019]

[0020] When the second additive is applied to a lithium-ion battery, it is selected from at least one of the following structures:

[0021]

[0022] When the second additive is applied to a sodium-ion battery, it is selected from at least one of the following structures:

[0023]

[0024] This invention reveals that when the first additive is used alone, the film density is poor, and continuous interfacial side reactions increase the battery's internal resistance, leading to a deterioration in high-temperature cycling performance. While the second additive, used alone, has a lower initial impedance, its DCIR increases rapidly during long-term high-temperature storage. When the first and second additives are used in combination, the first additive electrochemically decomposes to deposit sulfur-containing components (such as lithium alkyl sulfonates) on the electrode surface. The interfacial film formed under the modification of the second additive exhibits improved stability, effectively reducing interfacial side reactions and enhancing high-temperature cycling and storage stability. Simultaneously, the resulting SEI film has good lithium-ion permeability, improving the battery's low-temperature charge and discharge performance.

[0025] The different amounts of the first additive and the second additive in this invention will have different effects on the application effect. Preferably, the amount of the first additive is 0.2 to 1.0 wt% of the total mass of the electrolyte; and the amount of the second additive is 0.2 to 2.0 wt% of the total mass of the electrolyte.

[0026] The electrolyte also includes a basic additive, which is selected from at least one of sulfate ester compounds, carbonate compounds, cyclic ether compounds, polyene compounds, and fluorinated salt compounds;

[0027] The sulfate ester compound is selected from at least one of vinyl sulfate, methyl vinyl sulfate, monofluorovinyl sulfate, 4,4'-divinyl sulfate, or pentaerythritol bicyclic sulfate;

[0028] The carbonate compound is selected from at least one of fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl propylene carbonate, vinylene carbonate (abbreviated as VC), methylene carbonate, or vinyl ethylene carbonate, and the carbonate compound is different from the carbonate solvent used as a solvent.

[0029] The cyclic ether compounds are selected from at least one of 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane or 1,3,5-trioxane.

[0030] The polyene compounds are selected from at least one of tetravinylsilane (TVS), tetraallylsilane, 1,3,5-triallyl isocyanurate (TAIC), 2,4,6-tris(allyloxy)-1,3,5-triazine (TAC) or 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane.

[0031] When the fluorinated salt compound is used in a lithium-ion battery, it is selected from at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium fluorosulfonate, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, and lithium difluorooxalate borate, and the fluorinated lithium salt compound is different from the main salt.

[0032] When the fluorinated salt compound is used in a sodium-ion battery, it is selected from at least one of sodium difluorophosphate, sodium tetrafluoroborate, sodium difluorosulfonylimide, sodium bis(trifluoromethylsulfonyl)imide, sodium fluorosulfonate, sodium tetrafluorooxalate phosphate, sodium difluorobis(oxalate) phosphate, and sodium difluorooxalate borate, and the fluorinated sodium salt compound is different from the main salt.

[0033] The amount of the basic additive is 0.1 to 5.0 wt% of the total mass of the electrolyte.

[0034] Preferably, the base additive is selected from carbonate compounds containing double bonds, such as VC, or polyolefin compounds, such as TAIC and TAC. When used in combination with the electrolyte, these additives can significantly improve the high-temperature cycle performance of the battery. It is speculated that the copolymer surface film formed by the electrochemical decomposition products of the triple-bonded compound and VC inhibits the continued decomposition of the additive at the electrode interface, thereby improving the high-temperature cycle performance of the battery.

[0035] The main salt described in this invention (the main lithium salt used in lithium batteries or the main sodium salt used in sodium batteries) can be any common lithium or sodium salt found in electrolytes. Preferably, the main lithium salt used in lithium batteries is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide, and its amount accounts for 5-30 wt% of the total electrolyte mass. Lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide are preferred, with an amount accounting for 8-16 wt% of the total electrolyte mass. The main sodium salt used in sodium-ion batteries is selected from at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide, and its amount accounts for 5-30 wt% of the total electrolyte mass. Sodium hexafluorophosphate and / or sodium bis(fluorosulfonyl)imide are preferred, with an amount accounting for 8-16 wt% of the total electrolyte mass.

[0036] The organic solvent used in this invention can be any solvent commonly used in electrolytes. Preferably, the non-aqueous organic solvent is selected from C3-C6 carbonate or C3-C6 carboxylic acid ester solvents, C3-C6 fluorocarbonate solvents, or C3-C6 fluorocarboxylic acid ester solvents.

[0037] The C3-C6 carbonate or C3-C6 carboxylic acid ester solvent is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, di-n-propyl carbonate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or propyl propionate.

[0038] The C3-C6 fluorocarbonate solvents are selected from at least one of fluoroethylene carbonate, difluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl difluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate or 3,3,3-trifluoropropylene carbonate.

[0039] The C3-C6 fluorocarboxylic acid ester solvents are selected from at least one of 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, 2,2-difluoroethyl propionate, or 2,2-difluoropropyl propionate.

[0040] The present invention also provides a lithium-ion battery or a sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, and any of the electrolytes described above.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. By combining the addition of a first additive and a second additive, the present invention can form a highly stable interface film on the electrode surface, which can effectively reduce the occurrence of interface side reactions and improve the high-temperature cycle stability and high-temperature storage stability of the 4.4V high-voltage lithium-ion battery. At the same time, the sulfur-containing components (such as lithium alkyl sulfonate) generated by the oxidation and decomposition of an appropriate amount of the first additive help to enhance the ion permeability of the electrode interface, reduce the interface impedance, and improve the low-temperature performance.

[0043] 2. This invention uses additives such as the first additive, the second additive, and the third additive (such as TAIC) that have both positive and negative electrode film-forming functions in combination, which can further improve the high-temperature cycle and storage performance of 4.4V high-voltage lithium-ion batteries.

[0044] 3. This invention, through the combined use of the first and second additives, helps to solve the problem of layered oxides (NaNi) in the O3 phase. 1 / 3 Fe 1 / 3 Mn 1 / 3 To address the technical problem of poor high-temperature cycle stability of sodium-ion batteries (O2), this paper discusses the use of film-forming additives such as fluoroethylene carbonate (FEC), TAIC, tris(trimethylsilyl) phosphate (TMSP), and / or sodium difluorophosphate (NaPO2F2) to further improve the high-temperature cycle and storage performance at a high voltage of 4.2V. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0046] I. Preparation of Lithium-ion Battery Electrolyte

[0047] Preparation of the basic electrolyte: In an argon-filled glove box (moisture < 5 ppm, oxygen < 10 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of EC:EMC:DEC = 3:5:2. Lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution until the molar concentration of LiPF6 reached 1.2 mol / L, thus obtaining the basic electrolyte.

[0048] Example 1

[0049] The electrolyte of this embodiment was obtained by adding 0.2 wt% of compound A1 and 1.0 wt% of compound B1 to the base electrolyte.

[0050] Example 2

[0051] The electrolyte of this embodiment was obtained by adding 0.5 wt% of compound A1 and 1.0 wt% of compound B1 to the base electrolyte.

[0052] Example 3

[0053] The electrolyte of this embodiment was obtained by adding 1.0 wt% of compound A1 and 1.0 wt% of compound B1 to the base electrolyte.

[0054] Example 4

[0055] The electrolyte of this embodiment was obtained by adding 1.0 wt% of compound A1 and 2.0 wt% of compound B1 to the base electrolyte.

[0056] Example 5

[0057] The electrolyte of this embodiment was obtained by adding 1.0 wt% of compound A1 and 0.2 wt% of compound B1 to the base electrolyte.

[0058] Example 6

[0059] The electrolyte of this embodiment was obtained by adding 0.2 wt% of compound A2 and 1 wt% of compound B1 to the base electrolyte.

[0060] Example 7

[0061] The electrolyte of this embodiment was obtained by adding 0.2 wt% of compound A4 and 1 wt% of compound B1 to the base electrolyte.

[0062] Example 8

[0063] The electrolyte of this embodiment was obtained by adding 0.2 wt% of compound A1 and 1 wt% of compound B4 to the base electrolyte.

[0064] Example 9

[0065] The electrolyte of this embodiment was obtained by adding 0.2 wt% of compound A1, 1 wt% of compound B1 and 0.2 wt% of compound VC to the base electrolyte.

[0066] Example 10

[0067] The electrolyte of this embodiment was obtained by adding 0.2 wt% of compound A1, 1 wt% of compound B1 and 0.2 wt% of compound TAIC to the base electrolyte.

[0068] Example 11

[0069] The electrolyte of this embodiment was obtained by adding 0.2 wt% of compound A1, 1 wt% of compound B1 and 0.2 wt% of compound TAC to the base electrolyte.

[0070] Example 12

[0071] The electrolyte of this embodiment is obtained by adding 0.2 wt% of compound A1, 1 wt% of compound B1 and 0.5 wt% of vinyl sulfate (abbreviated DTD) to the base electrolyte.

[0072] Example 13

[0073] The electrolyte of this embodiment was obtained by replacing the EMC in the electrolyte of Example 1 with an equal amount of methyltrifluoroethyl carbonate (abbreviated as FEMC), and the rest was the same as in Example 1.

[0074] Example 14

[0075] The electrolyte of this embodiment was obtained by replacing the 1.2 mol / L LiPF6 in the electrolyte of Example 1 with 0.6 mol / L LiFSI and 0.6 mol / L LiPF6, and keeping the rest the same as in Example 1.

[0076] Comparative Example 1

[0077] The electrolyte of this comparative example was obtained by adding only 0.2 wt% of compound A1 to the base electrolyte.

[0078] Comparative Example 2

[0079] The electrolyte of this comparative example was obtained by adding only 1 wt% of compound A1 to the base electrolyte.

[0080] Comparative Example 3

[0081] The electrolyte of this comparative example was obtained by adding only 0.2 wt% of compound B1 to the base electrolyte.

[0082] Comparative Example 4

[0083] The electrolyte of this comparative example was obtained by adding only 1 wt% of compound B1 to the base electrolyte.

[0084] Comparative Example 5

[0085] The electrolyte of this comparative example was obtained by adding only 2 wt% of compound B1 to the base electrolyte.

[0086] Comparative Example 6

[0087] The electrolyte of this comparative example was obtained by adding 0.2 wt% of compound A1 and 0.2 wt% of compound TAIC to the base electrolyte.

[0088] Comparative Example 7

[0089] The electrolyte of this comparative example was obtained by adding 0.2 wt% of compound TAIC and 1 wt% of compound B1 to the base electrolyte.

[0090] Comparative Example 8

[0091] The electrolyte of this comparative example was obtained by adding 0.2 wt% of compound A1 and 1 wt% of lithium dioxaborate (LiDFOB) to the basic electrolyte.

[0092] II. Electrochemical Performance Testing of Lithium-ion Batteries

[0093] The electrolytes from the above embodiments and comparative examples were used to fabricate 1500mAh soft-pack lithium-ion batteries. Each lithium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, lithium cobalt oxide, or lithium iron phosphate. The negative electrode active material is graphite, silicon, or lithium metal. The positive electrode active material is a ternary positive electrode (LiNi). 0.6 Co 0.2 Mn 0.2 O2, the negative electrode active material is high-capacity graphite. The preparation process is as follows: the positive electrode sheet, separator and negative electrode sheet are wound together into a core, sealed with aluminum-plastic film and then baked to ensure that the electrode moisture meets the requirements. After baking, the cell is injected with electrolyte, and after standing, formation, capacity testing and aging processes, the finished soft-pack cell is obtained.

[0094] The prepared lithium-ion power battery (soft-pack cell) was subjected to performance testing. The specific test items and methods are as follows:

[0095] (1) 60℃ High-Temperature Storage Test: Cycle at 0.5C / 0.5C room temperature for one week, recording the discharge capacity, internal resistance, and volume in the first week. Then, charge at a constant current of 0.5C to 4.40V, and then charge at a constant voltage until the current drops to 0.05C. Place the battery in a 60℃ constant-temperature oven for 30 days, then cycle at 0.5C / 0.5C room temperature for two weeks. Record the discharge capacity in the first week after high-temperature storage, the discharge capacity in the second week, and the internal resistance and volume after storage. Calculate the capacity retention rate, capacity recovery rate, internal resistance growth rate, and volume expansion rate after battery storage using the following formula:

[0096] Capacity recovery rate = discharge capacity in the first week after high temperature settling / discharge capacity in the first week * 100%.

[0097] Volume expansion rate = (volume after storage - volume in week 1) / volume in week 1 * 100%.

[0098] (2) 45℃ high temperature cycling test: The battery is cycled in an oven at 45±1℃ with a charge / discharge current of 1C / 1C. The discharge capacity is calculated every week. The cycle is stopped when the cycle reaches 1000 cycles or the capacity retention rate is less than 80%. The DCR value after the cycle is tested and the capacity retention rate and DCR growth rate are calculated.

[0099] (3) Low-temperature performance test: Cycle at 0.5C / 0.5C room temperature for 1 week, record the discharge capacity in the first week, then charge at a constant current of 0.5C to 4.40V, and charge at a constant voltage until the current drops to 0.05C. Place in a -20℃ constant temperature oven for 5 hours, and discharge to 2.20V, record the low-temperature discharge capacity, and calculate the low-temperature discharge capacity retention rate according to the following formula:

[0100] Capacity retention rate = Discharge capacity after low-temperature storage / Discharge capacity in week 1 * 100%.

[0101] The test results are shown in Table 1 below:

[0102] Table 1. Electrochemical performance test results of lithium-ion batteries

[0103]

[0104]

[0105] According to the test results in Table 1 above:

[0106] Comparing Example 1 with Comparative Examples 1 and 4, it can be seen that the electrolyte composition using sulfonyl propargyl ester additives and boron-containing lithium salt additives of structural formula B1, compared with electrolytes using sulfonyl propargyl ester additives alone or using boron-containing lithium salt additives of structural formula B1 alone, can simultaneously ensure a higher capacity retention rate and a lower volume expansion rate during high-temperature storage, and has better high-temperature cycle capacity retention rate and low-temperature discharge capacity retention rate.

[0107] Comparing Examples 1 and 2 with Comparative Example 8, the electrolyte composition using sulfonyl propargyl ester additives and boron-containing lithium salt additives of structural formula B1 exhibits superior high-temperature storage performance while maintaining high-temperature cycling performance, especially in suppressing gas generation during storage at high temperatures and high voltages and maintaining low-temperature discharge capacity retention, compared to sulfonyl propargyl ester additives and commercially available boron-containing lithium salt additive LiDFOB.

[0108] Comparing Examples 10, 11 and Example 1, the three-component composition of sulfonate propargyl ester additive, boron-containing lithium salt additive of structural formula B1 and the third high-temperature film-forming additive has better high-temperature cycling performance and high-temperature storage performance than the two-component composition of sulfonate propargyl ester additive and boron-containing lithium salt additive of structural formula B1, while also taking into account low-temperature discharge performance.

[0109] III. Preparation of Sodium-ion Battery Electrolyte

[0110] Example 15

[0111] In an argon-filled glove box (moisture < 5 ppm, oxygen < 10 ppm), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of PC:EMC:DEC = 3:5:2. Sodium hexafluorophosphate (NaPF6) was slowly added to the mixed solution until the molar concentration of NaPF6 reached 1.2 mol / L. Subsequently, 0.2 wt% of compound A1 and 1.0 wt% of compound B7 were added to obtain the electrolyte of this embodiment.

[0112] Example 16

[0113] In an argon-filled glove box (moisture content < 5 ppm, oxygen content < 10 ppm), PC, EMC, and DEC were uniformly mixed at a mass ratio of PC:EMC:DEC = 3:5:2. NaPF6 was added until the molar concentration of NaPF6 reached 1.2 mol / L. Subsequently, 3 wt% fluoroethylene carbonate (FEC), 0.2 wt% compound A1, and 1.0 wt% compound B7 were added to obtain the electrolyte of this embodiment.

[0114] Example 17

[0115] The operation of this embodiment is the same as that of Example 15, except that 0.5 wt% of vinylene carbonate (VC) is added on the basis of Example 15 to obtain the electrolyte of this embodiment.

[0116] Example 18

[0117] The operation of this embodiment is the same as that of Example 15, except that 0.3 wt% TAIC is added on the basis of Example 15 to obtain the electrolyte of this embodiment.

[0118] Example 19

[0119] The operation of this embodiment is the same as that of Example 15, except that 0.3 wt% TMSP is added on the basis of Example 15 to obtain the electrolyte of this embodiment.

[0120] Example 20

[0121] The operation of this embodiment is the same as that of Example 15, except that 0.2 wt% NaPO2F2 is added on the basis of Example 15 to obtain the electrolyte of this embodiment.

[0122] Comparative Example 9

[0123] In an argon-filled glove box (moisture content < 5 ppm, oxygen content < 10 ppm), PC, EMC, and DEC were uniformly mixed in a mass ratio of PC:EMC:DEC = 3:5:2. NaPF6 was slowly added to the mixed solution until the molar concentration of NaPF6 reached 1.2 mol / L, thus obtaining the electrolyte of this comparative example.

[0124] Comparative Example 10

[0125] In an argon-filled glove box (moisture content < 5 ppm, oxygen content < 10 ppm), PC, EMC, and DEC were uniformly mixed in a mass ratio of PC:EMC:DEC = 3:5:2. NaPF6 was slowly added to the mixed solution until the molar concentration of NaPF6 reached 1.2 mol / L. Then, 0.2 wt% of compound A1 was added to obtain the electrolyte of this comparative example.

[0126] Comparative Example 11

[0127] In an argon-filled glove box (moisture content < 5 ppm, oxygen content < 10 ppm), PC, EMC, and DEC were uniformly mixed in a mass ratio of PC:EMC:DEC = 3:5:2. NaPF6 was slowly added to the mixed solution until the molar concentration of NaPF6 reached 1.2 mol / L. Then, 1 wt% of compound B7 was added to obtain the electrolyte of this comparative example.

[0128] Comparative Example 12

[0129] In an argon-filled glove box (moisture content < 5 ppm, oxygen content < 10 ppm), PC, EMC, and DEC were uniformly mixed in a mass ratio of PC:EMC:DEC = 3:5:2. NaPF6 was slowly added to the mixed solution until the molar concentration of NaPF6 reached 1.2 mol / L. Then, 3 wt% of compound FEC was added to obtain the electrolyte of this comparative example.

[0130] IV. Sodium-ion battery testing

[0131] The electrolytes from the above embodiments and comparative examples were used to fabricate 1000mAh capacity soft-pack sodium-ion batteries. Each sodium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is an O3-phase layered oxide (NaNi). 1 / 3 Fe 1 / 3 Mn 1 / 3 The negative electrode active material is hard carbon, the positive and negative electrode current collectors are aluminum foil, and the separator is a polyethylene film to form a soft-pack battery.

[0132] The prepared sodium-ion battery was subjected to performance testing. The specific test items and methods are as follows:

[0133] (1) 60℃ High-Temperature Storage Test: Cycle at 0.5C / 0.5C room temperature for 1 week, record the discharge capacity, internal resistance, and volume in the first week. Then charge at a constant current of 0.5C to 4.20V, and charge at a constant voltage until the current drops to 0.05C. Place in a 60℃ constant temperature oven for 30 days, then cycle at 0.5C / 0.5C room temperature for 2 weeks, record the discharge capacity in the first week after high-temperature storage, the discharge capacity in the second week, and 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 using the following formula:

[0134] Capacity recovery rate = discharge capacity in the first week after high temperature settling / discharge capacity in the first week * 100%.

[0135] Volume expansion rate = (volume after storage - volume in week 1) / volume in week 1 * 100%.

[0136] (2) 45℃ high temperature cycle test: The battery is cycled in an oven at 45±1℃ with a charge / discharge current of 1C / 1C. The discharge capacity is calculated every week. The cycle is stopped after 1000 cycles or when the capacity retention rate is less than 80%. The capacity retention rate after the cycle is calculated.

[0137] (3) Low-temperature performance test: Cycle at 0.5C / 0.5C room temperature for 1 week, record the discharge capacity in the first week, then charge at a constant current of 0.5C to 4.20V, and charge at a constant voltage until the current drops to 0.05C. Place in a -20℃ constant temperature oven for 5 hours, and discharge to 2.20V, record the low-temperature discharge capacity, and calculate the low-temperature discharge capacity retention rate according to the following formula:

[0138] Capacity retention rate = Discharge capacity after low-temperature storage / Discharge capacity in week 1 * 100%.

[0139] The test results are shown in Table 2 below:

[0140] Table 2 Electrochemical performance test results of sodium-ion batteries

[0141]

[0142] As shown in Table 2, compared with Comparative Examples 10 and 11, the use of the 0.2% A1 and 1% B7 additive composition significantly improved the high-temperature cycle performance of sodium-ion batteries compared with the use of A1 and B7 alone. Comparing Comparative Examples 9 and 12, it can be seen that the use of FEC additives helps improve the cycle stability of sodium-ion batteries, while the HF generated by FEC significantly degrades the high-temperature storage performance of sodium-ion batteries. Furthermore, compared with Comparative Example 16 and 12, the use of the A1 and B7 composition significantly improved the high-temperature storage performance of sodium-ion batteries containing FEC electrolyte. Furthermore, compared with Comparative Examples 16 and 18, 19, and 20, the use of TAIC, TMSP, or NaPO2F2, which have positive and negative electrode film-forming effects, further improved the high and low temperature performance of the batteries.

Claims

1. An electrolyte for use in lithium-ion batteries or sodium-ion batteries, comprising a main salt and an organic solvent, characterized in that: The electrolyte further includes: The first additive is a sulfonate propargyl ester compound with the structure shown in formula (A): In the formula, R is selected from C1-C6 alkyl or C2-C6 alkenyl, C1-C6 fluoroalkyl or C2-C6 fluoroalkenyl, C3-C8 cycloalkyl, C3-C8 fluorocycloalkyl or cycloalkenyl, phenyl, fluorobenzene or C1-C3 alkyl-substituted phenyl. The second additive is lithium difluorophosphate-based fluoroborate or lithium difluorophosphate-based fluorophosphate with the structure shown in formula (B) for use in lithium-ion batteries, or sodium difluorophosphate-based fluoroborate or sodium difluorophosphate-based fluorophosphate with the structure shown in formula (C) for use in sodium-ion batteries. In the formula, M is selected as boron or phosphorus; when M is boron, x is selected as 1, 2, 3 or 4, y is selected as 0, 1, 2 or 3, and x+y=4; when M is phosphorus, x is selected as 1, 2, 3, 4, 5 or 6, y is selected as 0, 1, 2, 3, 4 or 5, and x+y=6. The first additive accounts for 0.1 to 3.0 wt% of the total mass of the electrolyte; The second additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.

2. The electrolyte for use in lithium-ion batteries or sodium-ion batteries according to claim 1, characterized in that: In formula (A), R is selected from C1-C3 alkyl or C2-C3 alkenyl, C1-C3 fluoroalkyl, C3-C6 cycloalkyl, C3-C6 fluorocycloalkyl or cycloalkenyl, phenyl, fluorophenyl or C1-C3 alkyl-substituted phenyl.

3. The electrolyte for use in lithium-ion or sodium-ion batteries according to claim 2, characterized in that: The first additive is selected from at least one of the following structures: When the second additive is applied to a lithium-ion battery, it is selected from at least one of the following structures: When the second additive is applied to a sodium-ion battery, it is selected from at least one of the following structures: 。 4. The electrolyte for use in lithium-ion batteries or sodium-ion batteries according to claim 1, characterized in that: The first additive accounts for 0.2 to 1.0 wt% of the total mass of the electrolyte; The second additive accounts for 0.2 to 2.0 wt% of the total mass of the electrolyte.

5. The electrolyte for use in lithium-ion or sodium-ion batteries according to any one of claims 1-4, characterized in that: The electrolyte also includes a basic additive, which is selected from at least one of sulfate ester compounds, carbonate compounds, cyclic ether compounds, polyene compounds, and fluorinated salt compounds; The sulfate ester compound is selected from at least one of vinyl sulfate, methyl vinyl sulfate, monofluorovinyl sulfate, 4,4'-divinyl sulfate, or pentaerythritol bicyclic sulfate; The carbonate compound is selected from at least one of fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl propylene carbonate, vinylene carbonate, ethylene methylene carbonate, or vinyl ethylene carbonate, and the carbonate compound is different from the carbonate solvent used as a solvent. The cyclic ether compounds are selected from at least one of 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane or 1,3,5-trioxane. The polyene compounds are selected from at least one of tetravinylsilane, tetraallylsilane, 1,3,5-triallyl isocyanurate, 2,4,6-tris(allyloxy)-1,3,5-triazine or 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane. When the fluorinated salt compound is used in a lithium-ion battery, it is selected from at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium fluorosulfonate, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, and lithium difluorooxalate borate, and the fluorinated lithium salt compound is different from the main lithium salt. When the fluorinated salt compound is used in a sodium-ion battery, it is selected from at least one of sodium difluorophosphate, sodium tetrafluoroborate, sodium difluorosulfonylimide, sodium bis(trifluoromethylsulfonyl)imide, sodium fluorosulfonate, sodium tetrafluorooxalate phosphate, sodium difluorobis(oxalate) phosphate, and sodium difluorooxalate borate, and the fluorinated sodium salt compound is different from the main sodium salt. The amount of the basic additive is 0.1 to 5.0 wt% of the total mass of the electrolyte.

6. The electrolyte for use in lithium-ion batteries or sodium-ion batteries according to claim 1, characterized in that: When the electrolyte is used in lithium-ion batteries, the main salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluoromethanesulfonyl)imide, and its amount accounts for 5 to 30 wt% of the total mass of the electrolyte. When the electrolyte is used in a sodium-ion battery, the main salt is selected from at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, or sodium bis(trifluoromethanesulfonyl)imide, and the amount used accounts for 5 to 30 wt% of the total mass of the electrolyte.

7. The electrolyte for use in lithium-ion or sodium-ion batteries according to claim 6, characterized in that: When the electrolyte is used in lithium-ion batteries, the main salt is selected from lithium hexafluorophosphate and / or lithium bisfluorosulfonyl imide, and its amount accounts for 8 to 16 wt% of the total mass of the electrolyte; When the electrolyte is used in a sodium-ion battery, the main salt is selected from sodium hexafluorophosphate and / or sodium difluorosulfonamide, and the amount used accounts for 8 to 16 wt% of the total mass of the electrolyte.

8. The electrolyte for use in lithium-ion or sodium-ion batteries according to claim 1, characterized in that: The organic solvent is selected from C3-C6 carbonate or C3-C6 carboxylic acid ester solvents, C3-C6 fluorocarbonate solvents, or C3-C6 fluorocarboxylic acid ester solvents; The C3-C6 carbonate or C3-C6 carboxylic acid ester solvent is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl acetate, methyl propionate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or propyl propionate. The C3-C6 fluorocarbonate solvents are selected from at least one of fluoroethylene carbonate, difluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl difluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate or 3,3,3-trifluoropropylene carbonate. The C3-C6 fluorocarboxylic acid ester solvents are selected from at least one of 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, 2,2-difluoroethyl propionate, or 2,2-difluoropropyl propionate.

9. The electrolyte for use in lithium-ion batteries or sodium-ion batteries according to claim 1, characterized in that: The negative electrode of the lithium-ion battery is one or more of graphite, silicon-based materials, hard carbon, amorphous carbon, lithium titanate, and metallic lithium, while the positive electrode is lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, or LiNi. (1-x-y) Co x Mn y One or more of the following: O2 (0≤x, y≤1), lithium manganese oxide, lithium iron manganese phosphate, and lithium titanate.

10. The electrolyte for use in lithium-ion batteries or sodium-ion batteries according to claim 1, characterized in that: 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 vanadium fluorophosphate, sodium iron phosphate, sodium manganese phosphate, Na x ₓMnFe(CN)₆ (0<x≤2), which is one or more of the above.

Images