Lithium ion battery electrolyte, lithium ion battery and electric equipment

Abstract

The invention provides a lithium ion battery electrolyte, a lithium ion battery and electric equipment, and belongs to the technical field of lithium ion battery manufacturing. The lithium ion battery electrolyte comprises an organic solvent, a lithium salt and a first additive, the first additive comprises mannose trifluorosulfonate or / and 1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-trithione trisodium salt, and the second additive comprises mannose trifluorosulfonate or / and 1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-trithione trisodium salt. According to the lithium ion battery electrolyte, a corresponding battery has relatively excellent cycle performance and relatively low battery expansion rate when being applied under high-voltage and high-temperature conditions, and meanwhile, the corresponding battery also has relatively excellent discharge capacity retention rate when being applied under low-temperature conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery manufacturing, in particular to a lithium ion battery electrolyte, a lithium ion battery and an electric device. BACKGROUND

[0002] In the prior art, lithium ion batteries have the advantages of green environmental protection, high energy density and long cycle life, and have been widely used as power batteries in new energy vehicles. Due to the high energy and long endurance, high and low temperature use requirements of new energy vehicles, high energy manganese-based positive electrode materials have become one of the development hotspots of new power batteries, and the application conditions have high voltage (≥4.5V) and high temperature (≥45℃) characteristics. However, when the existing commercial electrolyte is charged and discharged under the application condition of high voltage and high temperature, the electrolyte is easily oxidized and decomposed at the positive electrode interface to generate a large amount of gas, causing the loss of lithium ions in the positive active material, resulting in a sharp decrease in the cycle life of the corresponding battery; at the same time, the manganese-based positive electrode material generally has the problem of dissolution of a large amount of Mn 2+ elements due to the Jahn-Teller effect (especially under the condition of high voltage and high temperature), and the deposition of the dissolved Mn 2+ elements on the surface of the negative electrode easily causes the loss of active lithium and the continuous growth of the internal resistance of the battery, which also affects the cycle performance of the battery.

[0003] On this basis, in order to solve the above technical problems, the technical personnel currently mainly adds 1,3-propylene sulfone (PST), maleic anhydride and other additives to the electrolyte, but these conventional additives have poor effect on the improvement of the performance of the battery, so that the battery still has the problems of serious gas production leading to high battery expansion rate and poor cycle performance under the application condition of high voltage and high temperature. In addition, these conventional additives also cause a large increase in the internal resistance of the battery during the application process, thereby affecting the low temperature performance of the battery. SUMMARY

[0004] The purpose of the present application is to provide a lithium ion battery electrolyte, a lithium ion battery and an electric device, which has excellent cycle performance and low battery expansion rate under the application condition of high voltage and high temperature, and also has excellent discharge capacity retention rate under the application condition of low temperature.

[0005] The embodiments of the present application are implemented as follows: In a first aspect, the embodiments of the present application provide a lithium ion battery electrolyte, which comprises an organic solvent, a lithium salt and a first additive, wherein the first additive comprises mannose triflate or / and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt.

[0006] In the above technical solution, in the first aspect, the mannose triflate can decompose on the surface of the positive and negative electrodes to form a stable interface film. Specifically, the C-O-C, COO- and other oligomer films formed by the ring-opening polymerization of the mannose six-membered ring in the mannose triflate have good lithium ion conductivity, which can effectively reduce the interface impedance of the corresponding battery to improve its low-temperature performance. At the same time, the inorganic salts such as lithium sulfite and lithium fluoride formed by the decomposition of the triflate group in the mannose triflate are beneficial to improve the thermal stability of the interface film, and can inhibit the decomposition of the electrolyte to produce gas at the positive electrode interface under high voltage and high temperature conditions; in the second aspect, the triazine ring in the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt structure has weak basicity, which can neutralize the hydrogen fluoride produced by the decomposition of the electrolyte under high voltage and high temperature conditions, thereby reducing the gas production of the battery. At the same time, the three sulfur atoms of the trithione can directly combine with the Mn 2+ form a stable complex, improve the Mn 2+ precipitation on the negative electrode (especially under high voltage and high temperature conditions). Because the mannose triflate and the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt have the above-mentioned properties, compared with the use of conventional 1,3-propylene sulfite (PST), maleic anhydride and other additives, the corresponding battery has excellent cycle performance and low battery expansion rate when applied under high voltage and high temperature conditions. At the same time, the corresponding battery also has excellent discharge capacity retention rate when applied under low temperature conditions.

[0007] In some optional embodiments, the first additive includes mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt.

[0008] In the above technical solution, the first additive contains both mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt. Compared with the use of conventional 1,3-propylene sulfite (PST), maleic anhydride and other additives, the mannose triflate can more effectively improve the low-temperature cycle performance of the corresponding battery, and the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt can more effectively improve the cycle performance of the corresponding battery when applied under high voltage and high temperature conditions and effectively reduce the battery expansion rate. By using the two together, a synergistic effect can be achieved to make the corresponding battery have more excellent cycle performance and lower battery expansion rate when applied under high voltage and high temperature conditions. At the same time, the corresponding battery also has more excellent discharge capacity retention rate when applied under low temperature conditions.

[0009] In some optional embodiments, in the electrolyte, the mass percentage of the first additive is 0.2% to 5%.

[0010] In the technical solution, the mass percentage of the first additive in the electrolyte is limited in the range, so that the electrolyte has a suitable amount of the first additive, so that the corresponding battery has excellent cycle performance when applied under high-voltage high-temperature conditions, and the corresponding battery also has excellent discharge capacity retention rate when applied under low-temperature conditions.

[0011] In some optional embodiments, the mass ratio of the mannitol triflate to the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt in the electrolyte is (1-3):(1-3).

[0012] In the technical solution, the mass ratio of the mannitol triflate to the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt in the electrolyte is limited in the range, so that the two can better cooperate, so that the corresponding battery has more excellent cycle performance and lower battery expansion rate when applied under high-voltage high-temperature conditions, and the corresponding battery also has more excellent discharge capacity retention rate when applied under low-temperature conditions.

[0013] In some optional embodiments, the electrolyte further includes a second additive, and the second additive includes at least one of fluoroethylene carbonate, vinyl sulfate, vinyl ethylene carbonate, 1,3-propane sulfone lactone, methyl methylene disulfonate, 2-fluoropyridine, allyl isocyanate, triallyl isocyanurate, tris (trimethylsilyl) phosphite, and tripropylene phosphate.

[0014] In the technical solution, the specific type of second additive is added to the electrolyte, which can give the electrolyte more functions, so as to more comprehensively improve the comprehensive electrical performance (such as normal temperature cycle performance, high-low temperature cycle performance, etc.) of the corresponding battery.

[0015] In some optional embodiments, the mass percentage of the second additive in the electrolyte is 0.5% to 10%.

[0016] In the technical solution, the mass percentage of the second additive in the electrolyte is limited in the specific range, so that the electrolyte contains a suitable amount of the second additive, which can more comprehensively improve the comprehensive electrical performance of the corresponding battery while ensuring that various functional components in the electrolyte can effectively function.

[0017] In some optional embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bisfluorosulfonylimide, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl) imide, and lithium bisoxalate borate.

[0018] In the technical solution, the lithium salt provided by the embodiment of the application can be applied to a large number of types, and a large number of implementable schemes can be provided, thereby facilitating the popularization and application of the technical solution provided by the application.

[0019] In some optional embodiments, the mass percentage of the lithium salt in the electrolyte is 10% to 20%.

[0020] In the technical solution, the mass percentage of the lithium salt in the electrolyte is limited in the range, so that the electrolyte has a proper amount of lithium salt, and the corresponding battery has excellent cycle performance and low battery expansion rate when applied under high-voltage and high-temperature conditions, and the corresponding battery has excellent discharge capacity retention rate when applied under low-temperature conditions.

[0021] In some optional embodiments, the organic solvent includes at least one of ethylene carbonate, diethyl carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, 3,3,3-trifluoropropylene carbonate, methyl trifluoroethyl carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0022] In the technical solution, the organic solvent provided by the embodiment of the application can be applied to a large number of types, and a large number of implementable schemes can be provided, thereby facilitating the popularization and application of the technical solution provided by the application.

[0023] In a second aspect, the embodiment of the application provides a lithium ion battery, which includes a shell, an electrode assembly and a lithium ion battery electrolyte provided by the embodiment of the first aspect, the electrode assembly is contained in the shell, and the electrolyte is contained in the shell, wherein the positive active material in the positive electrode of the electrode assembly includes a manganese-based positive active material.

[0024] In the technical solution, when the lithium ion battery contains the manganese-based positive active material and the lithium ion battery electrolyte provided by the embodiment of the first aspect, the electrolyte includes mannitol triflate or / and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, so that the battery has excellent cycle performance and low battery expansion rate when applied under high-voltage and high-temperature conditions, and the corresponding battery has excellent discharge capacity retention rate when applied under low-temperature conditions.

[0025] In some optional embodiments, the positive active material includes at least one of lithium manganese iron phosphate, lithium nickel cobalt manganese oxide and lithium nickel manganese oxide.

[0026] In the technical solution, the manganese-based positive active material applicable to the embodiments of the present application is more, and more implementable schemes can be provided, so that the technical solution provided by the present application is facilitated to be popularized and applied.

[0027] In some optional embodiments, in the electrode assembly, the negative active material includes at least one of graphite, soft carbon, hard carbon, silicon, silicon oxide compound and silicon-carbon composite.

[0028] In the technical solution, the negative active material applicable to the embodiments of the present application is more, and more implementable schemes can be provided, so that the technical solution provided by the present application is facilitated to be popularized and applied.

[0029] In a third aspect, the embodiments of the present application provide a power consumption device including the lithium ion battery provided in the second aspect. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0031] It should be noted that in the present application, "and / or", such as "feature 1 and / or feature 2", means that it can be "feature 1" alone, "feature 2" alone, or "feature 1" plus "feature 2". The three cases.

[0032] In addition, in the description of the present application, unless otherwise specified, "multiple" in "one or more" means two or more; the range of "value a~value b" includes both end values "a" and "b", and "unit of measurement" in "value a~value b+unit of measurement" represents the "unit of measurement" of both "value a" and "value b".

[0033] The lithium ion battery electrolyte, lithium ion battery and power consumption device of the embodiments of the present application are described in detail below.

[0034] In a first aspect, the embodiments of the present application provide a lithium ion battery electrolyte, including an organic solvent, a lithium salt and a first additive, wherein the first additive includes mannitol triflate or / and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt.

[0035] In the present application, in the first aspect, the mannose triflate can decompose on the surface of the positive and negative electrodes to form a stable interface film. Specifically, the C-O-C, COO- and other oligomer films formed by the ring-opening polymerization of the mannose six-membered ring in the mannose triflate have good lithium ion conductivity, which can effectively reduce the interface impedance of the corresponding battery to improve its low-temperature performance. At the same time, the inorganic salts such as lithium sulfite and lithium fluoride formed by the decomposition of the triflate group in the mannose triflate are beneficial to improve the thermal stability of the interface film, and can inhibit the decomposition of the electrolyte to produce gas at the interface of the positive and negative electrodes under high voltage and high temperature conditions; in the second aspect, the triazine ring in the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt structure has weak basicity, which can neutralize the hydrofluoric acid produced by the decomposition of the electrolyte under high voltage and high temperature conditions, thereby reducing the gas production of the battery. At the same time, the three sulfur atoms of the trithione can directly combine with the Mn 2+ combined to form a stable complex, improving the Mn 2+ dissolved in the negative electrode. Due to the above-mentioned properties of the mannose triflate and the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, compared with the use of conventional 1,3-propylene sulfite (PST), maleic anhydride and other additives, the corresponding battery has excellent cycle performance and low battery expansion rate under high voltage and high temperature conditions. At the same time, the corresponding battery also has excellent discharge capacity retention rate under low temperature conditions.

[0036] As an example, the first additive includes mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt.

[0037] In this embodiment, the first additive contains both mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt. Compared with the use of conventional 1,3-propylene sulfite (PST), maleic anhydride and other additives, the mannose triflate can more effectively improve the low-temperature cycle performance of the corresponding battery, and the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt can more effectively improve the cycle performance of the corresponding battery under high voltage and high temperature conditions and effectively reduce the battery expansion rate. By using the two together, a synergistic effect can be achieved to make the corresponding battery have more excellent cycle performance and lower battery expansion rate under high voltage and high temperature conditions. At the same time, the corresponding battery also has more excellent discharge capacity retention rate under low temperature conditions.

[0038] It should be noted that the effect of the additive is closely related to the amount thereof, and therefore, the amount of the additive can be limited in consideration of the final performance of the corresponding battery.

[0039] As an example, the mass percentage of the first additive in the electrolyte is 0.2% to 5%, such as but not limited to any one of the point values of 0.2%, 0.5%, 1%, 2%, 3%, 4%, and 5% or a range value between any two of them.

[0040] In this embodiment, the mass percentage of the first additive in the electrolyte is limited within the above range, so that the electrolyte has a suitable amount of the first additive, so that the corresponding battery has excellent cycle performance when applied under high-voltage high-temperature conditions, and at the same time, the corresponding battery has excellent discharge capacity retention rate when applied under low-temperature conditions.

[0041] It should be noted that when the first additive contains both mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, due to the difference between the effects of the two, the mass ratio of the two can be limited in consideration of the synergistic effect of the two.

[0042] As an example, the mass ratio of mannose triflate to 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt in the electrolyte is (1 to 3):(1 to 3), such as but not limited to any one of the point values of 1:1, 1:2, 1:3, 2:1, 2:3, 3:1, 3:2 or a range value between any two of them.

[0043] In this embodiment, the mass ratio of mannose triflate to 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt in the electrolyte is limited within the above range, so that the two can better synergize, and thus the corresponding battery has more excellent cycle performance and lower battery expansion rate when applied under high-voltage high-temperature conditions, and at the same time, the corresponding battery has more excellent discharge capacity retention rate when applied under low-temperature conditions.

[0044] As an example, the electrolyte further includes a second additive, and the second additive includes at least one of fluoroethylene carbonate, vinyl sulfate, vinyl ethylene carbonate, 1,3-propane sulfone lactone, methyl methylene disulfonate, 2-fluoropyridine, allyl isocyanate, triallyl isocyanurate, tris (trimethylsilyl) phosphite, and tripropylene phosphate.

[0045] In this embodiment, the addition of a specific type of second additive in the electrolyte can give the electrolyte more functions, so as to more comprehensively improve the overall electrical performance of the corresponding battery.

[0046] As an example, the second additive has a mass percentage of 0.5% to 10% in the electrolyte, for example but not limited to any one of the point values of 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%, or a range value between any two of them.

[0047] In this embodiment, the mass percentage of the second additive in the electrolyte is limited in the above specific range, so that the electrolyte contains a relatively appropriate amount of the second additive, which can comprehensively improve the overall electrical performance of the corresponding battery while ensuring that various functional components in the electrolyte can effectively function.

[0048] As an example, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bisfluorosulfonylimide, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bisoxalate borate.

[0049] In this embodiment, the technical solution provided by the embodiments of the present application can be applied to a large number of lithium salts, which can provide a large number of implementable solutions, thereby facilitating the popularization and application of the technical solution provided by the present application.

[0050] As an example, the lithium salt has a mass percentage of 10% to 20% in the electrolyte, for example but not limited to any one of the point values of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%, or a range value between any two of them.

[0051] In this embodiment, the mass percentage of the lithium salt in the electrolyte is limited in the above range, so that the electrolyte has a relatively appropriate amount of lithium salt, which can also enable the corresponding battery to have relatively excellent cycle performance and a relatively low battery expansion rate when applied under high-voltage high-temperature conditions, and can also enable the corresponding battery to have a relatively excellent discharge capacity retention rate when applied under low-temperature conditions.

[0052] As an example, the organic solvent includes at least one of ethylene carbonate, diethyl carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, 3,3,3-trifluoropropylene carbonate, methyl trifluoroethyl carbonate, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0053] In this embodiment, the technical solution provided by the embodiments of the present application can be applied to a large number of organic solvents, which can provide a large number of implementable solutions, thereby facilitating the popularization and application of the technical solution provided by the present application.

[0054] It should be noted that the components and the amount of the electrolyte not specially mentioned or limited in the electrolyte can be set according to the conventional selection in the field.

[0055] In a second aspect, the embodiments of the present application provide a lithium ion battery, comprising a shell, an electrode assembly and the lithium ion battery electrolyte provided in the first aspect, the electrode assembly is contained in the shell, and the electrolyte is contained in the shell, wherein the positive active material in the positive electrode of the electrode assembly comprises a manganese-based positive active material.

[0056] In the present application, when the lithium ion battery contains the manganese-based positive active material and the lithium ion battery electrolyte provided in the first aspect, the electrolyte comprises mannitol triflate and / or 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, so that the battery has excellent cycle performance and low battery expansion rate when used under high voltage and high temperature conditions, and the corresponding battery also has excellent discharge capacity retention rate when used under low temperature conditions.

[0057] As an example, the positive active material comprises at least one of lithium manganese iron phosphate, lithium nickel cobalt manganese oxide and lithium nickel manganese oxide.

[0058] In this embodiment, the manganese-based positive active material applicable to the embodiments of the present application is more, and more implementable schemes can be provided, thereby facilitating the popularization and application of the technical solutions provided by the present application.

[0059] As an example, in the electrode assembly, the negative active material comprises at least one of graphite, soft carbon, hard carbon, silicon, silicon oxide compound and silicon-carbon composite.

[0060] In this embodiment, the negative active material applicable to the embodiments of the present application is more, and more implementable schemes can be provided, thereby facilitating the popularization and application of the technical solutions provided by the present application.

[0061] In a third aspect, the embodiments of the present application provide a power consumption device, comprising the lithium ion battery provided in the second aspect.

[0062] It should be noted that the type of the power consumption device is not limited, for example, a mobile phone, a portable device, a notebook computer, an electric vehicle, an electric automobile, a ship, an electric aircraft, a spacecraft, an electric toy, an energy storage device and an electric tool.

[0063] The features and performances of the present application are further described in detail in combination with the embodiments.

[0064] Embodiment 1 The embodiments of the present application provide a preparation method of a lithium ion battery electrolyte, comprising the following steps: Vinyl carbonate (EC), diethyl carbonate (DEC) and methyl trifluoroethyl carbonate (FEMC) are mixed in a mass ratio of 3:4:3 to obtain a mixed organic solvent; then, lithium hexafluorophosphate (LiPF6) and mannitol triflate (referred to as compound 1) are added to the mixed organic solvent and mixed uniformly to obtain a lithium ion battery electrolyte; wherein, according to the mass percentage, the mixed organic solvent: lithium hexafluorophosphate: mannitol triflate = 84: 15: 1.

[0065] Example 2 The embodiment of the present application provides a preparation method of a lithium ion battery electrolyte, comprising the following steps: Vinyl carbonate (EC), diethyl carbonate (DEC) and methyl trifluoroethyl carbonate (FEMC) are mixed in a mass ratio of 3:4:3 to obtain a mixed organic solvent; then, lithium hexafluorophosphate (LiPF6) and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt (referred to as compound 2) are added to the mixed organic solvent and mixed uniformly to obtain a lithium ion battery electrolyte; wherein, according to the mass percentage, the mixed organic solvent: lithium hexafluorophosphate: 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt = 84: 15: 1.

[0066] Example 3 The embodiment of the present application provides a preparation method of a lithium ion battery electrolyte, comprising the following steps: Vinyl carbonate (EC), diethyl carbonate (DEC) and methyl trifluoroethyl carbonate (FEMC) are mixed in a mass ratio of 3:4:3 to obtain a mixed organic solvent; then, lithium hexafluorophosphate (LiPF6), mannitol triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt are added to the mixed organic solvent and mixed uniformly to obtain a lithium ion battery electrolyte; wherein, according to the mass percentage, the mixed organic solvent: lithium hexafluorophosphate: mannitol triflate: 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt = 84: 15: 0.5: 0.5.

[0067] At the same time, in order to better understand the differences between the subsequent various embodiments, comparative examples and examples 1-3, the composition of the additives is summarized in the form of a table as follows, which can be seen in Table 1.

[0068]

[0069] Wherein, “-” represents that the component is not contained.

[0070] Test example Electrical performance test Test method: The lithium ion battery electrolyte prepared from Examples 1-13 and Comparative Example 1 was assembled into a battery and numbered accordingly, and then the capacity retention rate of the battery after 100 cycles at 25°C, the capacity retention rate after 100 cycles at 45°C, and the swelling rate after 15 days of storage at 45°C, and the discharge capacity retention rate at -20°C were tested, and then the test results were statistically recorded in Table 2.

[0071] Among them, the assembly of the battery is carried out according to the following method: S1 Mix LiNi 0.5 Mn 1.5 O4 (manganese-based positive active material), conductive carbon black (conductive agent) and polyvinylidene fluoride (binder) in N-methyl-2-pyrrolidone to obtain a positive electrode slurry; then, the positive electrode slurry is uniformly coated on both sides of an aluminum foil; then, it is sequentially dried, calendered and vacuum dried, and then an aluminum lead wire is welded on using an ultrasonic welding machine to obtain a positive electrode sheet with a thickness of 125 μm.

[0072] S2 Mix graphite (negative active material), conductive carbon black (conductive agent), butadiene rubber and carboxymethyl cellulose (binder) in a mass ratio of 95:1.5:1.5:2 in deionized water to obtain a negative electrode slurry; then, the negative electrode slurry is coated on both sides of a copper foil; then, it is sequentially dried, calendered and vacuum dried, and then a nickel lead wire is welded on using an ultrasonic welding machine to obtain a negative electrode sheet with a thickness of 125 μm.

[0073] S3 The prepared positive electrode sheet, negative electrode sheet and ion separator (PP / PE / PP three-layer composite separator) are wound to prepare a bare cell, and then the bare cell, shell and high-voltage electrolyte prepared from Examples 1-19 and Comparative Example 1 are injected into a dried battery, and then packaged, placed, formed, shaped and capacity tested to complete the battery assembly.

[0074] The test of the corresponding electrical parameters of the battery and the corresponding calculation formula are as follows: (1) Test of the capacity retention rate of the battery after 100 cycles at 25°C: Place the battery at 25°C, and use a 0.5 C current to charge and discharge the battery in the charge and discharge voltage range of 3.5-4.85 V, and record the discharge capacity retention at the 100th cycle.

[0075] (2) Test of the capacity retention rate of the battery after 100 cycles at 45°C: Place the battery at 45°C, and use a 0.5 C current to charge and discharge the battery in the charge and discharge voltage range of 3.5-4.85 V, and record the discharge capacity retention at the 100th cycle.

[0076] (3) Swelling rate test of battery at 45 °C high temperature storage for 15 days: The battery was subjected to 3 times of charge-discharge cycles at room temperature (25 °C) with 0.33 C current in the charge-discharge voltage range of 3.5-4.85 V, then fully charged with 0.33 C, and the thickness of the battery before high temperature storage was tested at room temperature (25 °C) environment, then the battery was placed at high temperature (45 °C) for 15 days, and then taken out and placed at room temperature (25 °C) for 2 h, and then the thickness of the battery after high temperature storage was tested.

[0077] (4) Discharge capacity retention rate test of battery at -20 °C low temperature: The battery was subjected to 3 times of charge-discharge cycles at room temperature (25 °C) with 0.33 C current in the charge-discharge voltage range of 3.5-4.85 V, then fully charged with 0.33 C, and the 0.33 C discharge capacity at room temperature 25 °C was recorded; then the battery was cooled in a low temperature box at -20 °C for 24 hours, and then started to discharge at 0.33 C constant current to 3.5 V cut-off, and the 0.33 C discharge capacity at -20 °C was recorded.

[0078] The calculation formula is as follows: 100 times cycle capacity retention rate (%) = (100th discharge retention capacity / 1st cycle discharge capacity) x 100%.

[0079] 45 °C storage for 15 days swelling rate (%) = (thickness of battery after high temperature storage-thickness of battery before high temperature storage) / thickness of battery before high temperature storage x 100%.

[0080] -20 °C discharge capacity retention rate (%) = (-20 °C 0.33 C discharge capacity at low temperature / 25 °C 0.33 C discharge capacity at room temperature) x 100%.

[0081] Table 2

[0082] Referring to Table 2, according to the test results of Examples 1-13 and Comparative Example 1, when the electrolyte contains mannose triflate or / and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, compared with the conventional maleic anhydride additive, the lithium ion battery corresponding to the former has excellent cycle performance and lower battery swelling rate under high voltage and high temperature conditions, and at the same time, the corresponding battery has excellent discharge capacity retention rate under low temperature conditions.

[0083] As can be seen from the test results of Examples 1-3, when the mass percentage of the additive in the electrolyte is constant, compared with containing only one of the two additives, when the electrolyte contains both mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, the former electrolyte can exert the synergistic effect of mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, thereby making the lithium ion battery corresponding to the former have more excellent cycle performance and lower battery expansion rate when applied under high-voltage high-temperature conditions, and at the same time, the corresponding battery can also have more excellent discharge capacity retention rate when applied under low-temperature conditions.

[0084] As can be seen from the test results of Examples 3-5, when the mass percentage of the additive in the electrolyte is constant, compared with using one of the two additives with another additive other than the embodiments of the present application, when mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt are used together, due to the good synergistic effect of mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt, the lithium ion battery corresponding to the former has more excellent cycle performance and lower battery expansion rate when applied under high-voltage high-temperature conditions, and at the same time, the corresponding battery can also have more excellent discharge capacity retention rate when applied under low-temperature conditions.

[0085] As can be seen from the test results of Examples 3 and 6-11, when mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt are used together, limiting the mass percentage of the additive to the appropriate range of 0.2%-5% can make the lithium ion battery corresponding to the former have more excellent cycle performance when applied under high-voltage high-temperature conditions, and at the same time, the corresponding battery can also have more excellent discharge capacity retention rate when applied under low-temperature conditions, compared with not being in this range.

[0086] As can be seen from the test results of Examples 8 and Examples 12-13, when mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt are used together, further adding additional additives can further improve the high and low temperature cycle performance of the corresponding battery.

[0087] The above-described embodiments are part of the embodiments of the present application, not all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

Claims

1. A lithium-ion battery electrolyte, characterized in that, The electrolyte comprises an organic solvent, a lithium salt, and a first additive, wherein the first additive comprises mannose triflate and / or 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt.

2. The electrolyte for lithium ion batteries according to claim 1, characterized in that, The first additive comprises mannose triflate and 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt.

3. The electrolyte for lithium-ion batteries according to claim 2, characterized in that, The mass percentage of the first additive in the electrolyte is 0.2% to 5%.

4. The electrolyte for lithium-ion batteries according to claim 3, characterized in that, The mass ratio of the mannose triflate to the 1,3,5-triazine-2,4,6(1H,3H,5H)-trithione trisodium salt in the electrolyte is (1 to 3):(1 to 3).

5. The electrolyte for lithium-ion batteries according to any one of claims 1 to 4, characterized in that, The electrolyte further comprises a second additive, the second additive comprising at least one of fluoroethylene carbonate, vinyl sulfate, vinyl ethylene carbonate, 1,3-propane sulfone lactone, methyl methylene disulfonate, 2-fluoropyridine, allyl isocyanate, triallyl isocyanurate, tris(trimethylsilyl) phosphite, and tripropylene phosphate.

6. The electrolyte for lithium-ion batteries according to claim 5, characterized in that, The mass percentage of the second additive in the electrolyte is 0.5% to 10%.

7. The electrolyte for a lithium-ion battery according to any one of claims 1 to 4, characterized in that, The lithium salt comprises at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bisfluorosulfonylimide, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bisoxalate borate.

8. The lithium-ion battery electrolyte of claim 7, wherein, The mass percentage of the lithium salt in the electrolyte is 10% to 20%.

9. The electrolyte for lithium-ion batteries according to any one of claims 1 to 4, characterized in that, The organic solvent comprises at least one of vinyl carbonate, diethyl carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, 3,3,3-trifluoropropylene carbonate, methyl trifluoroethyl carbonate, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

10. A lithium-ion battery, characterized by, The lithium ion battery comprises a housing, an electrode assembly accommodated in the housing, and an electrolyte as claimed in any one of claims 1 to 9, the electrolyte being accommodated in the housing, wherein a positive active material in a positive electrode of the electrode assembly comprises a manganese-based positive active material.

11. The lithium-ion battery of claim 10, wherein, The positive active material comprises at least one of lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel manganese oxide.

12. The lithium-ion battery of claim 10, wherein, The negative active material in the electrode assembly comprises at least one of graphite, soft carbon, hard carbon, silicon, silicon oxide compound, and silicon-carbon composite.

13. An electrical device, characterized by The lithium ion battery comprises the lithium ion battery as claimed in any one of claims 10 to 12.

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