High-voltage-resistant electrolyte and lithium ion battery containing same

Abstract

The invention provides a high-voltage-resistant electrolyte and a lithium ion battery containing the same. The high-voltage-resistant electrolyte comprises electrolyte salt, an organic solvent and an additive, the additive comprises a thioester-containing compound, an aromatic amine compound, an organic boric acid ester and a silane group-containing compound. According to the invention, the stability of the electrolyte can be improved, a stable protective film is formed at the interface, and the occurrence of interface side reaction is inhibited.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more particularly to a high-voltage resistant electrolyte and a lithium-ion battery containing the same. Background Technology

[0002] The rapid development of new energy vehicles has led to power batteries gradually replacing gasoline as the power source for automobiles. Lithium-ion batteries have higher energy density and power density compared to other types of batteries; therefore, they are currently the most widely used battery type in new energy vehicles.

[0003] Currently used lithium-ion power battery cathode materials, such as lithium cobalt oxide, ternary lithium, lithium iron phosphate (manganese) phosphate, and lithium-rich manganese, when combined with silicon-carbon anode materials to form lithium-ion batteries, suffer from problems such as short lifespan or poor fast charge / discharge capabilities. Lithium cobalt oxide, ternary lithium, and lithium-rich manganese also have relatively high prices due to the presence of the scarce resource cobalt.

[0004] Spinel-type lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 Lithium manganese oxide (LiNiO4) is developed based on spinel-type lithium manganese oxide. Like lithium manganese oxide, it is a cathode material with three-dimensional lithium-ion channels. Lithium manganese oxide has a voltage plateau of around 3.7V, while lithium nickel manganese oxide (LiNiO4)... 0.5 Mn 1.5 The voltage plateau of O4 is around 4.7V, and its cycling stability at high temperatures is also significantly improved compared to lithium manganese oxide.

[0005] However, spinel nickel manganese oxide is prone to manganese dissolution during charging and discharging. The dissolved manganese can then electromigrate and damage the negative electrode, leading to a sharp decline in the electrochemical performance of the spinel nickel manganese oxide positive electrode battery. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high-voltage resistant electrolyte and a lithium-ion battery containing the electrolyte, which can improve the electrochemical performance and cycle stability of spinel-type lithium nickel manganese oxide cathode batteries under high-voltage conditions.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a high-voltage resistant electrolyte, the high-voltage resistant electrolyte comprising an electrolyte salt, an organic solvent, and additives. The additives include sulfur-containing esters, aromatic amine compounds, organoboroesters, and silane-containing compounds.

[0009] The high-voltage resistant electrolyte referred to in this invention is one that can withstand a voltage plateau of 4.7V or higher.

[0010] The aromatic amine compounds in the high-voltage electrolyte provided by this invention have a low oxidation potential, and under high voltage (>4.3V vs Li / Li) + The BO-Mn bond in the organic boron ester preferentially undergoes oxidation over other electrolyte components, forming a redox potential difference with lithium bis(fluorosulfonyl)imide (LiFSI). This creates a gradient of reaction products at the electrode interface, effectively preventing direct contact between the electrolyte and the highly active cathode material, thus significantly inhibiting the continuous oxidative decomposition of the electrolyte. The boron atoms in the organic boron ester have empty orbitals and are Lewis acids, forming stable complexes with Mn²⁺ to create a protective layer rich in BO-Mn bonds on the cathode surface. The BO bonds in the boron ester react to capture trace amounts of H₂O / HF in the electrolyte, protecting the entire battery system. Silicon-containing compounds have high reduction potentials and preferentially reduce on the anode surface, forming a flexible and mechanically strong SEI film to ensure the integrity of the anode during cycling. Sulfate-containing esters can provide both cathode and anode protection, participating in the formation of a stable SEI film and improving battery performance.

[0011] The high-voltage resistant electrolyte provided by this invention can effectively alleviate the problem of manganese leaching in spinel-type nickel-manganese lithium cathode batteries, and has broad application prospects.

[0012] Preferably, the mass percentage of aromatic amine compounds in the high-voltage resistant electrolyte is 0.1~0.5wt%, for example, it can be 0.1wt%, 0.15wt%, 0.19wt%, 0.24wt%, 0.28wt%, 0.33wt%, 0.37wt%, 0.42wt%, 0.46wt%, or 0.5wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] Preferably, the mass percentage of organoboroate ester in the high-voltage resistant electrolyte is 0.1~0.5wt%, for example, it can be 0.1wt%, 0.15wt%, 0.19wt%, 0.24wt%, 0.28wt%, 0.33wt%, 0.37wt%, 0.42wt%, 0.46wt%, or 0.5wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Preferably, the mass ratio of aromatic amine compounds to organoboroate esters in the high-voltage electrolyte is (0.8~1):1, for example, it can be 0.8:1, 0.82:1, 0.83:1, 0.84:1, 0.85:1, 0.86:1, 0.89:1, 0.9:1, 0.92:1, 0.95:1, 0.98:1 or 1:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] The present invention preferably controls the mass ratio of aromatic amine compounds to organoboroesters within the above-mentioned range, which can better improve the interfacial stability of the electrolyte and effectively alleviate the problem of manganese leaching.

[0016] Preferably, the mass percentage of silane group compound in the high-voltage electrolyte is 0.5~1wt%, for example, it can be 0.5wt%, 0.56wt%, 0.62wt%, 0.67wt%, 0.73wt%, 0.78wt%, 0.84wt%, 0.89wt%, 0.95wt% or 1wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0017] The present invention preferably places the mass percentage of silane-containing compounds in the high-voltage electrolyte within the above-mentioned range, which can significantly improve the high-voltage cycle stability of the battery.

[0018] Preferably, the mass percentage of sulfur-containing esters in the high-voltage resistant electrolyte is 0.5~1wt%, for example, it can be 0.5wt%, 0.56wt%, 0.62wt%, 0.67wt%, 0.73wt%, 0.78wt%, 0.84wt%, 0.89wt%, 0.95wt%, or 1wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] Preferably, the aromatic amine compound includes any one or a combination of at least two of p-phenylenediamine, m-phenylenediamine, pyromellitic triamine, 3,5-diaminobenzoic acid, or 1,2,4-triaminobenzene, wherein typical but non-limiting combinations are the combination of p-phenylenediamine and m-phenylenediamine, the combination of pyromellitic triamine and m-phenylenediamine, the combination of p-phenylenediamine and 1,2,4-triaminobenzene, and the combination of 3,5-diaminobenzoic acid and m-phenylenediamine.

[0020] Preferably, the organoboroester comprises triethanolamine borate and / or nitrogen-containing heterocyclic organoboroester.

[0021] Preferably, the nitrogen-containing heterocyclic organic borate ester includes any one or a combination of at least two of pyridine-3-boronic acid pinacol ester, pyridine-4-boronic acid pinacol ester, indole-3-boronic acid pinacol ester, pyrrole-2-boronic acid pinacol ester, or imidazole-4-boronic acid pinacol ester, wherein typical but non-limiting combinations are combinations of pyridine-3-boronic acid pinacol ester and pyridine-4-boronic acid pinacol ester, combinations of pyrrole-2-boronic acid pinacol ester and pyridine-4-boronic acid pinacol ester, combinations of pyridine-3-boronic acid pinacol ester and pyrrole-2-boronic acid pinacol ester, combinations of imidazole-4-boronic acid pinacol ester and pyridine-4-boronic acid pinacol ester, and combinations of pyrrole-2-boronic acid pinacol ester and imidazole-4-boronic acid pinacol ester.

[0022] Preferably, the sulfur-containing esters include 1,3-propanesulfonyl lactone and / or vinyl sulfate.

[0023] In this invention, 1,3-propanesulfonyl lactone (PS) is primarily reduced at the negative electrode to form a Li₂SO₃-rich SEI film, effectively inhibiting the co-intercalation of solvent molecules on the negative electrode and improving initial coulombic efficiency and cycle life. Vinyl sulfate (DTD), an additive for high-voltage positive / silicon negative electrode batteries, provides both positive and negative electrode protection. Its vinyl groups readily polymerize under high voltage, forming a protective CEI film at the positive electrode, and can also be reduced at the negative electrode to participate in the formation of a stable SEI film, thus improving the performance of the positive / silicon-carbon battery. The synergy of these two components significantly enhances the performance of the electrolyte.

[0024] Preferably, the mass ratio of 1,3-propanesulfonyl lactone to vinyl sulfate in the sulfur-containing ester is (0.8~1.2):1, for example, it can be 0.8:1, 0.82:1, 0.85:1, 0.88:1, 0.89:1, 0.9:1, 0.92:1, 0.95:1, 0.98:1, 1.0:1, 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1 or 1.2:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] Preferably, the silane-containing compound comprises any one or a combination of at least two of tri(trimethylsilane)borate, tri(trimethylsilane)phosphate, or tri(trimethylsilane)imidazole, wherein typical but non-limiting combinations are combinations of tri(trimethylsilane)borate and tri(trimethylsilane)phosphate, combinations of tri(trimethylsilane)imidazole and tri(trimethylsilane)phosphate, and combinations of tri(trimethylsilane)borate and tri(trimethylsilane)imidazole.

[0026] Preferably, the electrolyte salt comprises lithium bis(fluorosulfonyl)imide.

[0027] The preferred electrolyte salt of this invention includes lithium difluorosulfonylimide, which can form a redox potential difference with aromatic amine compounds to form a gradient reaction product, thereby improving the oxidative stability of the electrolyte.

[0028] Preferably, the molar concentration of the electrolyte salt in the high-voltage resistant electrolyte is 1~3 mol / L, for example, it can be 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.7 mol / L, 1.9 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the organic solvent includes fluorocarbonate and non-fluorocarbonate.

[0030] The present invention preferably uses fluorocarbonate as part of the organic solvent, which mainly plays a role through the fluorine (F) atoms in its molecules. Its core advantage lies in simultaneously improving the stability of the negative electrode interface and the high voltage tolerance of the electrolyte itself.

[0031] Preferably, the fluorocarbonate includes any one or a combination of at least two of dimethyl carbonate, ethylene carbonate, propylene carbonate, or diethyl carbonate, wherein typical but non-limiting combinations are combinations of dimethyl carbonate and ethylene carbonate, combinations of propylene carbonate and ethylene carbonate, combinations of dimethyl carbonate and propylene carbonate, and combinations of diethyl carbonate and ethylene carbonate.

[0032] Preferably, the mass ratio of non-fluorocarbonate to fluorocarbonate in the high-voltage electrolyte is (0.1~1):(1.5~8), wherein the number of parts of non-fluorocarbonate can be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable; the number of parts of fluorocarbonate can be, for example, 1.5, 2.3, 3, 3.7, 4.4, 5.2, 5.9, 6.6, 7.3 or 8, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] Preferably, the fluorocarbonate includes fluoroethylene carbonate and difluoroethylene carbonate.

[0034] Preferably, the mass ratio of fluoroethylene carbonate to difluoroethylene carbonate in the fluorocarbonate is (1~5):(0.5~3). The number of parts of fluoroethylene carbonate can be, for example, 1, 1.5, 1.9, 2.4, 2.8, 3.3, 3.7, 4.2, 4.6 or 5, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable; the number of parts of difluoroethylene carbonate can be, for example, 0.5, 0.8, 1.1, 1.4, 1.7, 1.9, 2.2, 2.5, 2.8 or 3, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0035] The present invention does not impose any special restrictions on the preparation method of the high-voltage electrolyte in the above process. Any device and method known to those skilled in the art can be used for preparation. The method can also be adjusted according to the actual process, such as uniform mixing.

[0036] In a second aspect, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the high-voltage resistant electrolyte described in the first aspect.

[0037] Preferably, the lithium-ion battery comprises a spinel-type lithium nickel manganese oxide cathode material.

[0038] The spinel-type lithium nickel manganese oxide cathode material described in this invention refers to LiNi 0.5 Mn 1.5 O4 material.

[0039] This invention does not impose any special restrictions on other materials used in the positive electrode of the aforementioned lithium-ion battery. Any other materials known to those skilled in the art for use in the positive electrode can be employed, and adjustments can be made according to the actual process. For example, the conductive agent can be any one of acetylene black, carbon black, or Ketjen black, and the binder can be polyvinylidene fluoride.

[0040] This invention does not impose any special limitations on the negative electrode in the aforementioned lithium-ion battery. Any material well-known to those skilled in the art for use as a negative electrode can be used, and adjustments can be made according to the actual process. For example, it can be lithium metal, lithium titanate, graphite, silicon carbide, etc. The conductive agent in the negative electrode can be any one of acetylene black, carbon black, or Ketjen black, and the binder in the negative electrode can be polyvinylidene fluoride, sodium alginate, sodium carboxymethyl cellulose, styrene-butadiene rubber, lithium polyacrylate, acrylonitrile copolymers, etc.

[0041] The present invention does not impose any special restrictions on the separator in the above-mentioned lithium-ion battery. Any material known to those skilled in the art that can be used for the separator can be used, and adjustments can also be made according to the actual process. For example, it can be polypropylene, polyethylene, etc.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] The high-voltage resistant electrolyte provided by this invention can improve the oxidation stability of the electrolyte and form a stable interfacial film at the interface, thereby enhancing the high-voltage cycling stability of spinel-type lithium nickel manganese oxide cathode materials. Batteries prepared using the electrolyte provided by this invention retain more than 85% of their capacity after 1000 cycles at 2.5-4.95V and a high temperature of 55°C. Detailed Implementation

[0044] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0045] For ease of experimental comparison, the preparation method of the high-voltage resistant electrolyte in the following examples and comparative examples includes: mixing electrolyte salt, organic solvent and additives to obtain the high-voltage resistant electrolyte.

[0046] Example 1

[0047] This embodiment provides a high-voltage resistant electrolyte, which includes an electrolyte salt, an organic solvent, and additives; the additives include sulfur-containing esters, aromatic amine compounds, organoboroesters, and silane-containing compounds.

[0048] The high-voltage resistant electrolyte contains 0.2 wt% aromatic amine compounds; 0.2 wt% organoboronic esters; 0.8 wt% silane-containing compounds; and 0.7 wt% sulfur-containing esters.

[0049] The aromatic amine compound is 3,5-diaminobenzoic acid, the organoboroester is triethanolamine borate, and the silane-containing compound is tris(trimethylsilane) phosphate. The sulfur-containing esters include 1,3-propanesulfonyl lactone and vinyl sulfate; the mass ratio of 1,3-propanesulfonyl lactone to vinyl sulfate in the sulfur-containing esters is 1.0:1.

[0050] The electrolyte salt includes lithium bis(fluorosulfonyl)imide; the molar concentration of the electrolyte salt in the high-voltage electrolyte is 2.5 mol / L.

[0051] The organic solvent includes fluorocarbonate and non-fluorocarbonate; the mass ratio of non-fluorocarbonate to fluorocarbonate in the high-voltage electrolyte is 0.5:5.

[0052] The fluorocarbonate comprises fluoroethylene carbonate and difluoroethylene carbonate in a mass ratio of 2:3. The non-fluorocarbonate is ethylene carbonate.

[0053] Example 2

[0054] This embodiment provides a high-voltage resistant electrolyte, which includes an electrolyte salt, an organic solvent, and additives; the additives include sulfur-containing esters, aromatic amine compounds, organoboroesters, and silane-containing compounds.

[0055] The high-voltage resistant electrolyte contains 0.5 wt% aromatic amine compounds; 0.5 wt% organoboronic esters; 1 wt% silane-containing compounds; and 0.5 wt% sulfur-containing esters.

[0056] The aromatic amine compound is 1,2,4-triaminobenzene, the organoboroester is triethanolamine borate, and the silane-containing compound is tris(trimethylsilane) phosphate. The sulfur-containing esters include 1,3-propanesulfonyl lactone and vinyl sulfate; the mass ratio of 1,3-propanesulfonyl lactone to vinyl sulfate in the sulfur-containing esters is 0.8:1.

[0057] The electrolyte salt includes lithium bis(fluorosulfonyl)imide; the molar concentration of the electrolyte salt in the high-voltage electrolyte is 3 mol / L.

[0058] The organic solvent includes fluorocarbonate and non-fluorocarbonate; the mass ratio of non-fluorocarbonate to fluorocarbonate in the high-voltage electrolyte is 0.1:1.5.

[0059] The fluorocarbonate comprises fluoroethylene carbonate and difluoroethylene carbonate in a mass ratio of 1:0.5. The non-fluorocarbonate is dimethyl carbonate.

[0060] Example 3

[0061] This embodiment provides a high-voltage resistant electrolyte, which includes an electrolyte salt, an organic solvent, and additives; the additives include sulfur-containing esters, aromatic amine compounds, organoboroesters, and silane-containing compounds.

[0062] The high-voltage resistant electrolyte contains 0.1 wt% aromatic amine compounds; 0.1 wt% organoboronic esters; and 0.5 wt% silane-containing compounds. The high-voltage resistant electrolyte contains 1 wt% sulfur-containing esters. These sulfur-containing esters include 1,3-propanesulfonyl lactone and vinyl sulfate; the mass ratio of 1,3-propanesulfonyl lactone to vinyl sulfate in the sulfur-containing esters is 1.2:1.

[0063] The aromatic amine compound is 1,2,4-triaminobenzene, the organoboroester is indole-3-borate pinacol ester, and the silane-containing compound is tris(trimethylsilane)imidazole.

[0064] The electrolyte salt includes lithium bis(fluorosulfonyl)imide; the molar concentration of the electrolyte salt in the high-voltage electrolyte is 1 mol / L.

[0065] The organic solvent includes fluorocarbonate and non-fluorocarbonate; the mass ratio of non-fluorocarbonate to fluorocarbonate in the high-voltage electrolyte is 1:8.

[0066] The fluorocarbonate comprises fluoroethylene carbonate and difluoroethylene carbonate in a mass ratio of 5:3. The non-fluorocarbonate is diethyl carbonate.

[0067] Example 4

[0068] This embodiment provides a high-voltage resistant electrolyte. Except that the mass percentage of aromatic amine compounds in the high-voltage resistant electrolyte is 0.5 wt%, that is, the mass ratio of aromatic amine compounds to organoborolate is 2.5:1, the rest of the high-voltage resistant electrolyte is the same as that in Example 1, and will not be repeated here.

[0069] Example 5

[0070] This embodiment provides a high-voltage resistant electrolyte. Except that the mass percentage of aromatic amine compounds in the high-voltage resistant electrolyte is 0.1 wt%, that is, the mass ratio of aromatic amine compounds to organoborolate is 0.5:1, the rest of the high-voltage resistant electrolyte is the same as that in Example 1, and will not be repeated here.

[0071] Example 6

[0072] This embodiment provides a high-voltage resistant electrolyte. Except for the fact that the mass percentage of silane group compound in the high-voltage resistant electrolyte is 0.1 wt%, the rest of the high-voltage resistant electrolyte is the same as that in Example 1, and will not be repeated here.

[0073] Example 7

[0074] This embodiment provides a high-voltage resistant electrolyte. Except for the fact that the mass percentage of silane group compound in the high-voltage resistant electrolyte is 1.5 wt%, the rest of the high-voltage resistant electrolyte is the same as that in Example 1, and will not be repeated here.

[0075] Example 8

[0076] This embodiment provides a high-voltage resistant electrolyte. Except for replacing lithium difluorosulfonylimide with LiPF6, the high-voltage resistant electrolyte is the same as that in Example 1, and will not be described again here.

[0077] Example 9

[0078] This embodiment provides a high-voltage resistant electrolyte. Except for the organic solvent containing only ethylene carbonate, the high-voltage resistant electrolyte is the same as that in Example 1, and will not be described again here.

[0079] Example 10

[0080] This embodiment provides a high-voltage resistant electrolyte. Except for the organic solvent, which contains only fluoroethylene carbonate and difluoroethylene carbonate in a mass ratio of 2:3, the high-voltage resistant electrolyte is the same as that in Example 1, and will not be described again here.

[0081] Example 11

[0082] This embodiment provides a high-voltage resistant electrolyte. Except for the fact that the fluorocarbonate contains only fluoroethylene carbonate, the high-voltage resistant electrolyte is the same as that in Example 1, and will not be described again here.

[0083] Example 12

[0084] This embodiment provides a high-voltage resistant electrolyte. Except for the fact that the fluorocarbonate contains only difluoroethylene carbonate, the high-voltage resistant electrolyte is the same as that in Example 1, and will not be described again here.

[0085] Example 13

[0086] This embodiment provides a high-voltage resistant electrolyte. Except for the fact that the sulfur-containing ester contains only 1,3-propanesulfonyl lactone, the high-voltage resistant electrolyte is the same as that in Example 1, and will not be described again here.

[0087] Example 14

[0088] This embodiment provides a high-voltage resistant electrolyte. Except for the fact that the sulfur-containing esters contain only vinyl sulfate, the high-voltage resistant electrolyte is the same as that in Example 1, and will not be described again here.

[0089] Comparative Example 1

[0090] This comparative example provides an electrolyte that is identical to that in Example 1, except that all aromatic amine compounds are replaced with organoboroesters, and will not be described again here.

[0091] Comparative Example 2

[0092] This comparative example provides an electrolyte. The high-voltage resistant electrolyte is the same as that in Example 1, except that all organic borate esters are replaced with aromatic amine compounds. Therefore, it will not be described again here.

[0093] Comparative Example 3

[0094] This comparative example provides an electrolyte. The high-voltage resistant electrolyte is the same as that in Example 1, except that all silane-containing compounds are replaced with organoboroesters. It will not be described again here.

[0095] Comparative Example 4

[0096] This comparative example provides an electrolyte. The high-voltage resistant electrolyte is the same as that in Example 1, except that all sulfur-containing esters are replaced with organic borate esters. It will not be described again here.

[0097] Battery manufacturing:

[0098] 1. Preparation of positive electrode sheet

[0099] Spinel-type lithium nickel manganese oxide positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 94:3:3 and then added to the solvent N-methylpyrrolidone (NMP). After mixing evenly, a positive electrode slurry with a solid content of 45% was obtained. The positive electrode slurry was coated on both surfaces of the positive electrode current collector aluminum foil to form a positive electrode active coating. After vacuum drying, the positive electrode sheet was obtained.

[0100] 2. Preparation of negative electrode sheet

[0101] Silicon-carbon (SiC) anode active material, conductive carbon nanotubes, and binder lithium polyacrylate (PAALi) were mixed in a mass ratio of 8:1:1 and then added to deionized water as a solvent. After mixing evenly, an anode slurry with a solid content of 40% was obtained. The anode slurry was coated on both surfaces of the copper foil of the anode current collector to form an anode active coating. After vacuum drying, the anode sheet was obtained.

[0102] 3. The diaphragm was prepared using Celgard 2400 diaphragm from Celgard Diaphragm Company, USA.

[0103] 4. Preparation of electrolyte: The electrolytes of the above examples and comparative examples were used.

[0104] 5. Assembly of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain bare cells. The bare cells are placed in an outer packaging shell, dried, and then injected with the electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0105] Test method:

[0106] (1) Initial Coulomb efficiency

[0107] At 55℃, the lithium-ion battery was charged at a constant current and constant voltage rate of 0.33C to 4.95V, allowed to rest for 5 minutes, and then discharged at a constant current rate of 0.33C to 2.5V, allowed to rest for 5 minutes. The initial coulombic efficiency of the lithium-ion battery was calculated. Initial coulombic efficiency (%) = (Total capacity of lithium-ion battery during initial discharge at 0.33C) / (Total capacity of lithium-ion battery during initial charge at 0.33C) × 100%.

[0108] (2) Capacity retention rate after 1000 cycles at 55℃ high temperature 1C / 1C

[0109] At 55°C, the lithium-ion battery was charged at a constant current and constant voltage rate of 1C to 4.95V, with the constant voltage cutoff rate at 0.05C. After resting for 3 minutes, the lithium-ion battery was discharged at a constant current rate of 1C to 2.5V and then rested for 3 minutes. This constitutes one charge-discharge cycle. The lithium-ion battery was charged and discharged for 1000 cycles using the above method. The capacity retention rate of the lithium-ion battery after 1000 charge-discharge cycles at 1C / 1C was calculated.

[0110] The capacity retention rate (%) of a lithium-ion battery after N cycles = (discharge capacity of the Nth cycle / initial discharge capacity) × 100%, where N is the number of cycles of the lithium-ion battery.

[0111] The test results of the above embodiments and comparative examples are shown in Table 1.

[0112] Table 1

[0113]

[0114] The following points can be observed from Table 1:

[0115] (1) As can be seen from Examples 1 to 3, the batteries prepared using the high-voltage electrolyte provided by the present invention have high discharge specific capacity and good high-temperature long cycle performance. The initial coulombic efficiency is above 83.8%, the 1C discharge specific capacity at 55℃ is above 127.9 mAh / g, and the capacity retention rate at 55℃ for 1000 cycles of 1C / 1C is above 87.6%.

[0116] (2) The mass ratio of aromatic amine compounds to organoboroesters in Examples 4 and 5 is too high and too low, respectively, which makes it impossible to form a robust and stable CEI film. As a result, the electrolyte decomposes violently under high voltage and manganese dissolves severely, leading to poor long-cycle performance of the battery.

[0117] (3) In Example 6, the low mass percentage of silane compounds resulted in very poor high-temperature performance, cycle stability, and storage life of the battery. The high bond energy of Si-O or Si-N in the silicon compounds allowed them to preferentially react with trace amounts of water and hydrofluoric acid in the electrolyte, removing harmful substances. In Example 7, the high mass percentage of silane compounds resulted in low coulombic efficiency and cycle deviation of the battery. This is because excessive silane compounds would exacerbate irreversible decomposition reactions, consume more active lithium, and disrupt the chemical balance of the electrolyte and the stability of the electrode interface, affecting the dissolution and distribution of other additives and interfering with their normal function.

[0118] (3) In Example 8, lithium difluorosulfonylimide was replaced with LiPF6, which severely deteriorated the high-temperature performance. LiPF6 has poor thermal stability and will decompose to produce PF5 at high temperature. It reacts with water to generate HF, which corrodes the positive electrode, causing severe dissolution of transition metal ions. These ions will then migrate to the negative electrode to destroy the SEI film, resulting in continuous loss of active lithium and increased impedance, and the performance is very poor.

[0119] (4) The organic solvent in Example 9 does not contain fluorinated carbonate, resulting in poorer oxidation resistance of the electrolyte under 5V high voltage. Fluorinated carbonate has a higher oxidation decomposition potential, is more stable under high voltage, and is not easily oxidized. It can effectively participate in the formation of a high-quality CEI film and protect the positive electrode material under high voltage. After replacing it with ordinary carbonate, it is easier to oxidize and generate gas under high voltage, and the CEI film formed has poor protective properties. The organic solvent in Example 10 does not contain non-fluorinated carbonate, resulting in a higher electrolyte viscosity, relatively lower ionic conductivity, and poor wettability with electrode materials, leading to difficulties in interfacial ion transport and very poor rate performance.

[0120] (5) In Examples 11 and 12, the fluorocarbonate contained only fluoroethylene carbonate or difluoroethylene carbonate, resulting in excessive organic components (such as polycarbonate) in the CEI film, poor mechanical and chemical stability, high and unstable CEI impedance. Under repeated impacts of high voltage, the CEI film will continuously break, reconstruct and thicken, resulting in a continuous and rapid increase in interface impedance, manifested as increased charging voltage, decreased discharging voltage, intensified polarization and worsened cycle.

[0121] (6) Examples 13 and 14 contain only one of 1,3-propane sulfonyl lactone or vinyl sulfate, which makes it impossible to form a stable and dense SEI film rich in lithium sulfonate salt, Li2SO4 and other components at the negative electrode. This results in the electrolyte continuously decomposing and producing gas at the negative electrode, and the battery cycle performance is poor.

[0122] (7) Comparative Example 1 does not contain aromatic amine compounds, Comparative Example 2 does not contain organoboroesters, Comparative Example 3 does not contain silane compounds, and Comparative Example 4 does not contain thioesters. These will all lead to the inability to form a complete solid electrolyte membrane on the positive and negative electrodes, resulting in very poor long-cycle performance of the battery.

[0123] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A high-voltage resistant electrolyte, characterized in that, The high-voltage resistant electrolyte includes electrolyte salts, organic solvents, and additives; The additives include sulfur-containing esters, aromatic amine compounds, organoboroesters, and silane-containing compounds.

2. The high-voltage resistant electrolyte according to claim 1, characterized in that, The mass percentage of aromatic amine compounds in the high-voltage resistant electrolyte is 0.1~0.5 wt%. Preferably, the organoboroate ester content in the high-voltage resistant electrolyte is 0.1~0.5 wt%; Preferably, the mass ratio of aromatic amine compounds to organoborolate esters in the high-voltage resistant electrolyte is (0.8~1):1; Preferably, the silane group compound in the high-voltage resistant electrolyte has a mass percentage of 0.5~1wt%; Preferably, the mass percentage of sulfur-containing esters in the high-voltage resistant electrolyte is 0.5~1wt%.

3. The high-voltage resistant electrolyte according to claim 1 or 2, characterized in that, The aromatic amine compounds include any one or a combination of at least two of p-phenylenediamine, m-phenylenediamine, pyromellitic triamine, 3,5-diaminobenzoic acid, or 1,2,4-triaminobenzene.

4. The high-voltage resistant electrolyte according to any one of claims 1 to 3, characterized in that, The organoboroesters include triethanolamine borate and / or nitrogen-containing heterocyclic organoboroesters; Preferably, the nitrogen-containing heterocyclic organic borate ester includes any one or a combination of at least two of the following: pyridine-3-boronic acid pinacol ester, pyridine-4-boronic acid pinacol ester, indole-3-boronic acid pinacol ester, pyrrole-2-boronic acid pinacol ester, or imidazole-4-boronic acid pinacol ester. Preferably, the sulfur-containing esters include 1,3-propanesulfonyl lactone and / or vinyl sulfate; Preferably, the mass ratio of 1,3-propanesulfonyl lactone to vinyl sulfate in the sulfur-containing ester is (0.8~1.2):

1.

5. The high-voltage resistant electrolyte according to any one of claims 1 to 4, characterized in that, The silane-containing compound includes any one or a combination of at least two of tri(trimethylsilane)borate, tri(trimethylsilane)phosphate, or tri(trimethylsilane)imidazole.

6. The high-voltage resistant electrolyte according to any one of claims 1 to 5, characterized in that, The electrolyte salt includes lithium difluorosulfonylimide; Preferably, the molar concentration of the electrolyte salt in the high-voltage resistant electrolyte is 1~3 mol / L.

7. The high-voltage resistant electrolyte according to any one of claims 1 to 6, characterized in that, The organic solvents include fluorocarbonates and non-fluorocarbonates; Preferably, the fluorocarbonate includes any one or a combination of at least two of dimethyl carbonate, ethylene carbonate, propylene carbonate, or diethyl carbonate; Preferably, the mass ratio of non-fluorocarbonate to fluorocarbonate in the high-voltage electrolyte is (0.1~1):(1.5~8).

8. The high-voltage resistant electrolyte according to claim 7, characterized in that, The fluorocarbonate includes fluoroethylene carbonate and difluoroethylene carbonate; Preferably, the mass ratio of fluoroethylene carbonate to difluoroethylene carbonate in the fluorocarbonate is (1~5):(0.5~3).

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the high-voltage resistant electrolyte as described in any one of claims 1 to 8.

10. The lithium-ion battery according to claim 9, characterized in that, The lithium-ion battery includes a spinel-type lithium nickel manganese oxide cathode material.

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