An additive composition and an electrolyte containing the same

Abstract

The application discloses an additive composition and an electrolyte containing the same. The additive composition comprises a first additive and a second additive. The first additive is a glycerol carbonate-based compound as shown in the following formula (I): and the substituents are described in detail in the description. The additive composition can significantly reduce the internal resistance of a battery and the internal resistance growth of the battery during a cycle process, and effectively solves the problem that a conventional low-resistance additive has poor impedance reduction effect in a mature formula.

Description

Technical Field

[0001] This invention relates to the field of electrolytes, particularly lithium-ion battery electrolytes, and especially to an additive composition containing a glyceryl carbonate-based compound and a strong film-forming additive, an electrolyte containing the composition, and a lithium-ion battery containing the electrolyte. Background Technology

[0002] Impedance performance is of great importance for lithium-ion batteries. High battery impedance can easily lead to lithium plating on the negative electrode, cycle failure, and electrolyte side reactions, which in turn affect the battery's low-temperature performance, rate capability, and safety performance.

[0003] To reduce battery impedance, low-resistance additives are typically added to the electrolyte formulation. Commonly used low-resistance additives include LiDFP (lithium difluorophosphate), FEC (ethylene fluorocarbonate), and DTD (ethylene sulfate). Japanese Patent JP2010257616A discloses that LiDFP has a good effect on reducing impedance and improving battery cycle performance in simple electrolyte formulations. Japanese Patent JP5436657A discloses that FEC can improve negative electrode film formation, thereby suppressing electrolyte by-product decomposition and reducing battery internal resistance. Chinese Patent CN104766995A discloses that DTD has a significant advantage in reducing battery internal resistance, effectively suppressing capacity decay during battery cycling, and reducing battery expansion after high-temperature storage.

[0004] However, the aforementioned common low-resistance additives have some drawbacks. For example, LiDFP has low solubility, which causes inconvenience in production and application; FEC can lead to an increase in electrolyte acidity, reduce the battery's high-temperature storage stability, and cause gas generation and a significant increase in internal resistance during high-temperature storage; DTD can easily lead to excessive electrolyte acidity and color, which has a significant impact on battery performance and is not conducive to transportation and storage.

[0005] More importantly, although low-resistance additives such as LiDFP, FEC, and DTD have good impedance reduction effects in simple electrolyte formulations, their impedance reduction effect is very limited in mature formulations containing high-resistance additives (such as vinyl ethylene carbonate, 1,3-propane sulfonyl lactone, 1,3-propene sulfonate lactone, and lithium bis(oxalato)borate), which limits their application and promotion in electrolyte formulations.

[0006] For example, the paper "Effects of the LiPO2F2 additive on unwanted lithium plating inlithium-ion cells" [J]. Electrochimica acta, 2018, 263: 237-248 discloses that the use of lithium difluorophosphate in a formulation containing 2% 1,3-propenesulfonate lactone, 1% vinyl sulfate and 1% trimethylsilyl phosphite (PES211) not only fails to reduce the battery internal resistance, but also leads to a significant increase in the battery internal resistance and severe lithium plating on the graphite anode surface.

[0007] In fact, most existing commercially available electrolyte formulations contain high-resistance additives such as vinyl ethylene carbonate, 1,3-propane sulfonyl lactone, 1,3-propene sulfonate lactone, and lithium bis(oxalato)borate. Therefore, it is essential to develop an electrolyte that can reduce the battery's internal resistance in existing electrolyte formulations without producing negative effects. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes an additive composition that reduces internal resistance, particularly significantly reducing internal resistance and inhibiting its increase in the presence of a high-impedance additive, as well as an electrolyte containing the additive composition.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] An additive composition comprising:

[0011] The first additive is a glyceryl carbonate-based compound as shown in formula (I):

[0012]

[0013] Wherein, X is selected from carbon, sulfur, phosphorus, silicon or boron, and R1 and R2 are independently selected from hydrogen, fluorine, C1-C12 alkyl, C1-C12 alkoxy, C1-C12 fluoroalkyl, C1-C12 fluoroalkoxy, C2-C6 alkenyl or C2-C6 alkynyl.

[0014] When X is carbon, m = 0 and n = 2, or m = 1 and n = 0;

[0015] When X is sulfur, m = 2 and n = 0, or m = 1 and n = 0;

[0016] When X is phosphorus, m = 1 and n = 1, or m = 0 and n = 1;

[0017] When X is silicon, m = 0 and n = 2;

[0018] When X is boron, m = 0 and n = 1;

[0019] Preferably, in formula (I), R1 and R2 are independently selected from hydrogen, fluorine, C1-C6 alkyl, C1-C6 alkoxy, C1-C6 fluoroalkyl, C1-C6 fluoroalkoxy, C2-C3 alkenyl, or C2-C3 alkynyl. More preferably, R1 and R2 are independently selected from hydrogen, methyl, trifluoromethyl, ethyl, ethoxy, pentafluoroethoxy, vinyl, or ethynyl.

[0020] The second additive is selected from at least one of the following structures: (II-1), (II-2), (II-3), (II-4), (II-5):

[0021]

[0022] In formula (II-1), A is selected from silicon, boron, or phosphorus; L is selected from oxygen or a straight bond; R3, R4, R5, and R6 are independently selected from C1-C5 alkyl, C1-C5 haloalkyl, C2-C5 unsaturated hydrocarbon, C2-C5 halounsaturated hydrocarbon, or C1-C5 cyanosubstituted hydrocarbon; a, b, c, and d are 0 or 1, and at least two of them are 1; formula (II-1) contains at least one unsaturated bond.

[0023] In formula (II-2), R7, R8, and R9 are independently selected from hydrogen, C1-C6 alkyl, C1-C6 alkoxy, C1-C6 fluoroalkyl, C1-C6 fluoroalkoxy, C2-C6 alkenyl, or C2-C6 alkynyl.

[0024] In equation (II-3), R 10 R 11 R 12 It is independently selected from C1-C6 alkyl, C1-C6 fluoroalkyl, C3-C6 alkenyl or C3-C6 alkynyl;

[0025] Equation (II-4) represents a multi-component heterocycle, where n represents the number of repeating units in the multi-component heterocycle, and n is selected from 2 to 5. 13 R 14 It is independently selected from C1-C6 alkyl, C1-C6 fluoroalkyl, C2-C6 alkenyl or C2-C6 alkynyl;

[0026] In equation (II-5), R 15 R 16 R 17 It is independently selected from C1-C6 alkyl, C1-C6 fluoroalkyl, C2-C6 alkenyl or C2-C6 alkynyl.

[0027] More preferably, in formula (II-1), R3, R4, R5, and R6 are independently selected from C1-C3 alkyl, C1-C3 haloalkyl, C2-C3 unsaturated hydrocarbon, C2-C3 halounsaturated hydrocarbon, or C1-C3 cyanosubstituted hydrocarbon; at least three of a, b, c, and d are 1;

[0028] In formula (II-2), R7, R8, and R9 are independently selected from hydrogen, C1-C3 alkyl, C1-C3 alkoxy, C1-C3 fluoroalkyl, C1-C3 fluoroalkoxy, C2-C3 alkenyl, or C2-C3 alkynyl.

[0029] In equation (II-3), R 10 R 11 R 12 It is independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl, C3-C4 alkenyl or C3-C4 alkynyl;

[0030] In equation (II-4), n is selected from 2 or 3, and R 13 R 14 It is independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl, C2-C3 alkenyl or C2-C3 alkynyl;

[0031] In equation (II-5), R 15 R 16 R 17 It is independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl, C2-C3 alkenyl or C2-C3 alkynyl.

[0032] Most preferably, the second additive is selected from at least one of the following formulas:

[0033]

[0034] Most preferably, the first additive is selected from at least one of the following formulas:

[0035]

[0036] The second additive is selected from at least one of the following structures:

[0037]

[0038] In order to achieve a better effect of reducing internal resistance in electrolyte formulations containing high-resistance additives, the mass ratio of the first additive to the second additive in this invention is 0.1 to 10.0:1, preferably 0.5 to 4.0:1.

[0039] Of course, the additive composition described in this invention can also reduce the internal resistance of the battery in electrolyte formulations that do not contain high-resistance additives. Because the battery impedance itself is not high in electrolyte formulations that do not contain high-resistance additives, the impedance reduction effect is not significant.

[0040] The present invention also provides a lithium-ion battery electrolyte, comprising: a main lithium salt, a non-aqueous solvent, and an additive composition for reducing internal resistance as described above.

[0041] In the electrolyte, the amount of the first additive is 0.1-10.0% of the total electrolyte, and the amount of the second additive is 0.1-5.0% of the total electrolyte. Preferably, the amount of the first additive is 0.2-3.0% of the total electrolyte, and the amount of the second additive is 0.2-3.0% of the total electrolyte.

[0042] The electrolyte further includes a high-resistance additive selected from at least one of vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sulpholactone, 1,4-butane sulpholactone, 1,3-propene sulpholactone, methanedisulfonate, succinic anhydride, maleic anhydride, citrate anhydride, lithium bis(oxalato)borate, fluorobenzene, p-fluorotoluene, biphenyl, or cyclohexylbenzene.

[0043] The main lithium salt can be any commonly used lithium salt in the electrolyte. Preferably, the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluoromethylsulfonyl)imide, and its molar concentration is 0.1–4.0 mol / L.

[0044] The non-aqueous solvent can be any solvent commonly used in electrolytes. Preferably, the non-aqueous solvent is selected from at least one of C3-C6 carbonate compounds, C3-C8 carboxylic acid ester compounds, sulfone compounds, and ether compounds.

[0045] Wherein: the C3 to C6 carbonate compounds are selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate, or difluoroethylene carbonate.

[0046] The C3-C8 carboxylic acid ester compounds 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, or ethyl fluoroacetate.

[0047] The sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone;

[0048] The ether compound is selected from at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0049] The present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and any of the lithium-ion battery electrolytes described above.

[0050] The active material of the positive electrode is selected from nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobalt oxide materials, or lithium iron phosphate materials; wherein, the nickel-cobalt-manganese ternary material is Li(Ni) x Co y Mn z O2, x≥0.5, y>0, z>0, x+y+z=1; the nickel-cobalt-aluminum ternary material is Li(Ni x Co y Al z) O2, x≥0.8, y>0, z>0, x+y+z=1.

[0051] The active material of the negative electrode is graphite, silicon carbide, silicon suboxide, silicon, tin, metallic lithium, or a composite material thereof.

[0052] The first additive of this invention has a unique structure, consisting of two parts: a carbonate group and functional groups centered on sulfur, phosphorus, silicon, boron, etc. The functional group participates in interfacial film formation and reduces battery internal resistance, while the carbonate group participates in the lithium-ion solvation process. During battery charging, it migrates to the graphite anode surface along with the functional group, preferentially participating in film formation. This results in an interfacial film rich in sulfur, phosphorus, silicon, boron, etc., exhibiting good ion conductivity, density, and stability. This unique compound structure allows the first additive to maintain excellent impedance reduction even in mature formulations containing high-impedance additives. Simultaneously, this invention uses a strong film-forming compound as the second additive, which easily forms a dense, robust, and stable interfacial film on the positive and negative electrode surfaces, reducing impedance growth during cycling. When used in conjunction with the first additive, it further improves the stability of the anode interfacial film formation and long-cycle cycling.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. This invention solves the problem of poor impedance reduction effect of conventional low impedance additives in mature formulations by using the combination of the first additive and the second additive, and at the same time improves the rate capability and high and low temperature performance of the battery.

[0055] 2. The electrolyte of the present invention can reduce the initial internal resistance of the battery and reduce the increase in internal resistance during battery cycling. Attached Figure Description

[0056] Figure 1 The LSV reduction curves after adding 1.0% of compound A1 to the base electrolyte of the examples are presented. Detailed Implementation

[0057] 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.

[0058] I. Preparation of Electrolyte

[0059] 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 at 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.

[0060] Example 1: 2.0% of 1,3-propenesulfonyl lactone, 1.0% of compound A1 and 0.5% of compound B1 were added to the basic electrolyte to obtain the electrolyte of this example.

[0061] Example 2: 2.0% of 1,3-propenesulfonate lactone, 1.0% of compound A1 and 1.0% of compound B1 were added to the basic electrolyte to obtain the electrolyte of this example.

[0062] Example 3: 2.0% of 1,3-propenesulfonate lactone, 2.0% of compound A1 and 0.5% of compound B1 were added to the basic electrolyte to obtain the electrolyte of this example.

[0063] Example 4: 2.0% of 1,3-propenesulfonyl lactone, 0.5% of compound A1 and 1.0% of compound B1 were added to the basic electrolyte to obtain the electrolyte of this example.

[0064] Example 5: 2.0% of 1,3-propenesulfonate lactone, 1.0% of compound A2 and 0.5% of compound B1 were added to the basic electrolyte to obtain the electrolyte of this example.

[0065] Example 6: 2.0% of 1,3-propenesulfonyl lactone, 1.0% of compound A2 and 0.5% of compound B2 were added to the basic electrolyte to obtain the electrolyte of this example.

[0066] Example 7: 1.0% of 1,3-propenesulfonate lactone, 1.0% of compound A2 and 0.5% of compound B3 were added to the basic electrolyte to obtain the electrolyte of this example.

[0067] Example 8: 1.0% of 1,3-propenesulfonate lactone, 1.0% of compound A2 and 0.5% of compound B4 were added to the basic electrolyte to obtain the electrolyte of this example.

[0068] Example 9: 2.0% fluorobenzene, 1.0% compound A2 and 0.5% compound B5 were added to the basic electrolyte to obtain the electrolyte of this example.

[0069] Example 10: 2.0% cyclohexylbenzene, 1.0% compound A3 and 0.5% compound B6 were added to the basic electrolyte to obtain the electrolyte of this example.

[0070] Example 11: 2.0% succinic anhydride, 1.0% compound A3 and 0.5% compound B7 were added to the basic electrolyte to obtain the electrolyte of this example.

[0071] Example 12: 2.0% citrate anhydride, 1.0% compound A4 and 0.5% compound B8 were added to the basic electrolyte to obtain the electrolyte of this example.

[0072] Example 13: 2.0% vinyl ethylene carbonate, 1.0% compound A9 and 0.5% compound B9 were added to the basic electrolyte to obtain the electrolyte of this example.

[0073] Example 14: 2.0% vinyl ethylene carbonate, 1.0% compound A5 and 0.5% compound B10 were added to the basic electrolyte to obtain the electrolyte of this example.

[0074] Example 15: 1.0% vinyl ethylene carbonate, 1.0% compound A7 and 0.5% compound B13 were added to the basic electrolyte to obtain the electrolyte of this example.

[0075] Example 16: 2.0% lithium bis(oxalato)borate, 1.0% compound A8 and 0.5% compound B12 were added to the basic electrolyte to obtain the electrolyte of this example.

[0076] Example 17: 2.0% lithium bis(oxalato)borate, 1.0% compound A10 and 0.5% compound B14 were added to the basic electrolyte to obtain the electrolyte of this example.

[0077] Example 18: 2.0% lithium bis(oxalato)borate, 1.0% compound A11 and 0.5% compound B17 were added to the basic electrolyte to obtain the electrolyte of this example.

[0078] Example 19: 1.0% lithium bis(oxalato)borate, 1.0% compound A13 and 0.5% compound B18 were added to the basic electrolyte to obtain the electrolyte of this example.

[0079] Example 20: 1.0% of compound A1 and 0.5% of compound B1 were added to the base electrolyte to obtain the electrolyte of this example.

[0080] Example 21: 1.0% of compound A9 and 0.5% of compound B9 were added to the base electrolyte to obtain the electrolyte of this example.

[0081] Comparative Example 1: 2.0% of 1,3-propenesulfonate lactone and 1.5% of LiDFP were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0082] Comparative Example 2: 1.0% of 1,3-propenesulfonate lactone and 1.5% of LiDFP were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0083] Comparative Example 3: 2.0% vinyl ethylene carbonate and 1.5% LiDFP were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0084] Comparative Example 4: 2.0% of 1,3-propenesulfonate lactone and 1.0% of DTD were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0085] Comparative Example 5: 2.0% of 1,3-propenesulfonyl lactone and 1.5% of DTD were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0086] Comparative Example 6: 2.0% lithium bis(oxalato)borate and 1.5% DTD were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0087] Comparative Example 7: 2.0% vinyl ethylene carbonate and 1.5% DTD were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0088] Comparative Example 8: 2.0% cyclohexylbenzene and 1.5% FEC were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0089] Comparative Example 9: 2.0% 1,3-propenesulfonate lactone and 1.5% FEC were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0090] Comparative Example 10: 2.0% vinyl ethylene carbonate and 1.5% FEC were added to the base electrolyte to obtain the electrolyte of this comparative example.

[0091] Comparative Example 11: 2.0% of 1,3-propenesulfonate lactone and 1.0% of compound A1 were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0092] Comparative Example 12: 2.0% vinyl ethylene carbonate and 1.0% compound A9 were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0093] Comparative Example 13: 2.0% 1,3-propenesulfonyl lactone and 0.5% compound B1 were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0094] Comparative Example 14: 2.0% vinyl ethylene carbonate and 0.5% compound B9 were added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0095] Comparative Example 15: Basic Electrolyte.

[0096] Comparative Example 16: 2.0% of 1,3-propenesulfonate lactone was added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0097] Comparative Example 17: 2.0% vinyl ethylene carbonate was added to the basic electrolyte to obtain the electrolyte of this comparative example.

[0098] The mass percentages of the high-resistivity additive, the first additive, the second additive, and other additives in the above embodiments and comparative examples are shown in Table 1 below.

[0099] Table 1. Additive dosage for each example / comparative example

[0100]

[0101]

[0102] II. Electrochemical Performance Testing

[0103] Figure 1 The LSV reduction curves after adding 1.0% compound A1 to the base electrolyte are presented, such as... Figure 1 As shown, a preferential reduction peak appears at around 1.1V, and the reduction peak of the electrolyte solvent disappears. This suggests that compound A1 has a modifying effect on the negative electrode interface and, when used in combination with the second additive, reduces internal resistance. Therefore, the electrochemical performance of the additive composition was tested, and the specific operation is as follows:

[0104] The electrolytes from the above embodiments and comparative examples were used to fabricate 1260mAh capacity 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, a lithium cobalt oxide material, or a lithium iron phosphate material. 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.

[0105] The performance of the prepared lithium-ion power battery (soft-pack cell) was tested, mainly including the following:

[0106] (1) Battery capacity test: After capacity division, the battery is charged at a constant current of 0.33C to 4.35V, and then charged at a constant voltage until the current of 0.05C is cut off; let it rest for 30 minutes; discharge it at a constant current of 1C to 2.8V to obtain the discharge capacity of the single cell.

[0107] (2) -20℃ battery discharge DCIR test: The battery was adjusted to 50% SOC state with a current of 0.33C and left to stand for 5 hours in a -20℃ environment to depolarize the battery. The open circuit voltage OCV1 was recorded after the stand was completed. The battery was discharged with a current of 3C for 10s and left to stand for 10min. The voltage OCV2 at the moment of termination of the high current discharge was tested. According to the formula DCIR=(OCV1-OCV2) / 3C, the low temperature discharge DCIR of the single cell was obtained.

[0108] (3) -20℃ battery discharge capacity test: The fully charged battery was left in a -20℃ environment for 5 hours and discharged to 2.8V with a current of 0.5C to obtain the low temperature discharge capacity of the single cell.

[0109] (4) 60℃ high temperature storage test: Charge the battery to 100% SOC and place it in an oven at 60±2℃ for 1 month. Test the volume change before and after storage to obtain the volume change rate of a single cell before and after storage at 60℃.

[0110] (5) 45℃ high temperature cycling test: The battery is cycled in an oven at 45±2℃ with a charge / discharge current of 1C / 1C. The charge capacity and discharge capacity are calculated every week. The DCIR change and volume change of the battery during the cycling process are monitored every 100 weeks. The capacity retention rate, DCIR growth rate and volume change rate of the single cell after 500 cycles at 45℃ are obtained.

[0111] Table 2 presents the test results of the basic performance (ACR internal resistance and initial capacity) and low-temperature performance of the pouch cells prepared with different electrolyte formulations in the embodiments and comparative examples of the present invention. Table 3 presents the test results of the high-temperature storage performance (volume change rate before and after storage, internal resistance growth rate before and after storage) and high-temperature cycling performance (volume change rate, DCIR internal resistance growth rate, capacity retention rate) of the pouch cells prepared with different electrolyte formulations in the embodiments and comparative examples of the present invention. Two identical pouch cells were prepared for parallel testing for each electrolyte formulation, and the specific results are shown in Tables 2 and 3 below.

[0112] Table 2. Results of Basic Performance and Low Temperature Performance Tests

[0113]

[0114]

[0115] Table 3. Test results of high-temperature storage at 60℃ and high-temperature cycling at 45℃

[0116]

[0117]

[0118] According to the test results in Tables 2 and 3:

[0119] 1. Comparing Examples 20, 21, and 15, it is evident that the combination of the first and second additives added to the base electrolyte can reduce the initial impedance, albeit by a small margin; it can significantly reduce the increase in internal resistance during battery cycling. Simultaneously, it significantly improves the battery's high-temperature storage and cycle stability, and suppresses the battery's volume expansion at high temperatures.

[0120] 2. Comparing Example 1 with Comparative Examples 1, 5, and 9, and Comparing Example 13 with Comparative Examples 3, 7, and 10, it can be seen that, in the presence of a high-resistivity additive, the combination of adding the first additive and the second additive to the electrolyte solves the problem of poor impedance reduction compared to using conventional low-resistivity additives (e.g., LiDFP, DTD, FEC), while improving the rate capability and high / low temperature performance of the battery.

[0121] 3. Comparing Example 1 and Comparative Example 16, and Comparing Example 13 and Comparative Example 17, it can be seen that in the presence of a high-resistivity additive, the combination of the first additive and the second additive can significantly reduce the initial internal resistance of the battery and improve the battery capacity performance.

[0122] 4. Comparing Example 1 with Comparative Examples 11 and 13, and Comparing Example 13 with Comparative Examples 12 and 14, it can be seen that, in the presence of a high-resistivity additive, the composition with the addition of the first additive and the second additive can reduce the initial internal resistance of the battery and reduce the increase in internal resistance during battery cycling compared to using the first additive alone or the second additive alone. Simultaneously, it can better suppress gas generation during high-temperature storage and high-temperature cycling, while also maintaining low-temperature performance.

[0123] In summary, the additive composition of the present invention has good compatibility with the positive and negative electrode interfaces, which not only significantly reduces the initial internal resistance of the battery, but also effectively reduces the increase of internal resistance during battery cycling, thereby improving the rate capability and high and low temperature performance of the battery.

Claims

1. A lithium-ion battery electrolyte, comprising: The electrolyte comprises a primary lithium salt and a non-aqueous solvent, characterized in that: the electrolyte further includes an additive composition for reducing internal resistance, the additive composition comprising: The first additive is selected from at least one of the following structures: The second additive is selected from at least one of the following structures: Furthermore, the mass ratio of the first additive to the second additive is 0.1 to 10.0:1; The electrolyte further includes a high-resistance additive selected from at least one of vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sulpholactone, 1,4-butane sulpholactone, 1,3-propene sulpholactone, methanedisulfonate, succinic anhydride, maleic anhydride, citrate anhydride, lithium bis(oxalato)borate, fluorobenzene, p-fluorotoluene, biphenyl, or cyclohexylbenzene.

2. The lithium-ion battery electrolyte according to claim 1, characterized in that: The second additive is selected from at least one of the following structures:

3. The lithium-ion battery electrolyte according to claim 1 or 2, characterized in that: The mass ratio of the first additive to the second additive is 0.5 to 4.0:

1.

4. The lithium-ion battery electrolyte according to claim 1, characterized in that: The first additive is added at a rate of 0.1% to 10.0% of the total electrolyte, and the second additive is added at a rate of 0.1% to 5.0% of the total electrolyte.

5. The lithium-ion battery electrolyte according to claim 1, characterized in that: The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluoromethylsulfonyl)imide, and its molar concentration is 0.1 to 4.0 mol / L.

6. The lithium-ion battery electrolyte according to claim 1, characterized in that: The non-aqueous solvent is selected from at least one of C3-C6 carbonate compounds, C3-C8 carboxylic acid ester compounds, sulfone compounds, and ether compounds.

7. The lithium-ion battery electrolyte according to claim 6, characterized in that: The C3 to C6 carbonate compounds are selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate, or difluoroethylene carbonate. The C3-C8 carboxylic acid ester compounds 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, or ethyl fluoroacetate. The sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone; The ether compound is selected from at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

8. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, characterized in that: The lithium-ion battery further includes the lithium-ion battery electrolyte according to any one of claims 1-7.

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