An electrolyte and a lithium-ion battery containing the same

Abstract

The present invention provides an electrolyte and a lithium ion battery containing the same. The electrolyte includes an organic solvent, a lithium salt, and an additive, and the additive includes a phosphate compound with a trialkoxysilane-containing side chain. In the electrolyte of the present invention, a phosphate compound with a trialkoxysilane-containing side chain is added. The silane in the compound can act as a stabilizer to adsorb free protons, reducing the contents of moisture and hydrofluoric acid in the electrolyte. The boron atom can complex with the transition metal of the ternary cathode material, reducing the reaction activity of the cathode material and reducing the side reactions between the cathode and the electrolyte. This electrolyte can improve the stability of the electrolyte, improve the high-temperature performance of the lithium ion secondary battery, and reduce the gas generation amount during storage.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and particularly to an electrolyte and a lithium-ion battery containing the same. Background Art

[0002] In recent years, the lithium-ion power battery industry for vehicles has developed rapidly. In order to meet the requirements of long driving range and wide temperature range environment for electric vehicles, it is necessary to develop lithium-ion secondary batteries with higher energy density, more excellent high-temperature cycle and storage performance to meet the life requirements of vehicle power batteries for more than 10 to 15 years. Lithium-ion secondary batteries with high energy density usually use high-nickel ternary positive electrodes with high energy density and high-voltage ternary positive electrodes. These materials are prone to interface deterioration, particle fragmentation, and oxidation of the electrolyte at high temperatures, resulting in a rapid decline in life at high temperatures.

[0003] Therefore, how to prepare an electrolyte that is stable at the interface with the positive electrode and can be applied under high-temperature conditions is an important research direction in this field. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an electrolyte that can stabilize the positive electrode interface and a lithium-ion battery containing the same.

[0005] To achieve this purpose, the present invention adopts the following technical solutions:

[0006] One of the purposes of the present invention is to provide an electrolyte, which includes an organic solvent, a lithium salt, and an additive, and the additive includes a phosphate compound with a trialkoxysilane-containing side chain.

[0007] The present invention adds a phosphate compound with a trialkoxysilane-containing side chain to the electrolyte. The silane in the compound can act as a stabilizer to adsorb free protons, reducing the content of water and hydrofluoric acid in the electrolyte. The boron atom can form a complex with the transition metal of the ternary positive electrode material, reducing the reaction activity of the positive electrode material and reducing the side reaction between the positive electrode and the electrolyte. This electrolyte can improve the stability of the electrolyte, improve the high-temperature performance of the lithium-ion secondary battery, and reduce the gas generation during storage.

[0008] As a preferred technical solution of the present invention, the phosphate compound includes any one or at least two combinations of Formula 1, Formula 2, or Formula 3. Typical but non-limiting examples of the combination include: the combination of Formula 1 and Formula 2, the combination of Formula 2 and Formula 3, or the combination of Formula 1 and Formula 3, etc.

[0009]

[0010] As a preferred technical solution of the present invention, based on the mass fraction of the electrolyte being 100%, the mass fraction of the phosphate compound is 0.01 - 5%, where the mass fraction can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable, preferably 0.1 - 2%.

[0011] As a preferred technical solution of the present invention, the additive further includes other additives.

[0012] Preferably, the other additives include any one or a combination of at least two of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, a sultone compound, a disulfonic acid compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic anhydride compound, a phosphite compound, a phosphate compound or a borate compound. Typical but non-limiting examples of the combination include: a combination of a cyclic carbonate compound containing an unsaturated bond and a halogen-substituted cyclic carbonate compound, a combination of a sulfate compound and a sulfite compound, a combination of a sultone compound, a nitrile compound and an aromatic compound, a combination of an isocyanate compound and a phosphazene compound, a combination of a cyclic anhydride compound and a phosphite compound, a combination of a phosphate compound and an aromatic compound, or a combination of a borate compound and a sulfate compound, etc.

[0013] Preferably, the cyclic carbonate compound containing an unsaturated bond includes vinylene carbonate and / or ethylene vinyl carbonate.

[0014] Preferably, the halogen-substituted cyclic carbonate compound includes fluoroethylene carbonate.

[0015] Preferably, the sulfate compound includes ethylene sulfate.

[0016] Preferably, the sulfite compound includes ethylene sulfite.

[0017] Preferably, the sultone compound includes 1,3-propane sultone.

[0018] Preferably, the nitrile compound includes succinonitrile and / or adiponitrile.

[0019] Preferably, the aromatic compound includes biphenyl and / or cyclohexylbenzene.

[0020] Preferably, the isocyanate compound includes 1,4-butane diisocyanate.

[0021] Preferably, the phosphazene compound includes ethoxypentafluorocyclotriphosphazene.

[0022] Preferably, the cyclic anhydride compound includes succinic anhydride and / or maleic anhydride.

[0023] Preferably, the phosphite compound includes tris(trimethylsilyl) phosphite.

[0024] Preferably, the phosphate compound includes tris(trimethylsilyl) phosphate.

[0025] Preferably, the borate compound includes tris(trimethylsilyl) borate.

[0026] As a preferred technical solution of the present invention, the other additives include vinylene carbonate and ethylene sulfate.

[0027] Preferably, based on the mass fraction of the electrolyte being 100%, the mass fraction of vinylene carbonate in the electrolyte is 0 to 2%, where the mass fraction can be 0, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable, and preferably 0.2 to 0.8%.

[0028] Preferably, based on the mass fraction of the electrolyte being 100%, the mass fraction of ethylene sulfate in the electrolyte is 0 to 2%, where the mass fraction can be 0, 0.2%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable, and preferably 0.5 to 1.5%.

[0029] Preferably, based on the mass fraction of the electrolyte being 100%, the mass fraction of the other additives in the electrolyte is 0 to 2%, where the mass fraction can be 0, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 1.9% or 2%, etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0030] As a preferred technical solution of the present invention, the organic solvent includes cyclic carbonates and chain acid esters, and the chain acid esters include chain carbonates and chain carboxylates.

[0031] Preferably, the chain carbonate includes any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate or ethyl butyrate. Typical but non-limiting examples of the combination include: the combination of dimethyl carbonate and diethyl carbonate, the combination of methyl ethyl carbonate and methyl propyl carbonate, the combination of ethyl propyl carbonate and methyl formate, the combination of ethyl formate and propyl formate, the combination of methyl acetate and ethyl acetate, the combination of propyl acetate and methyl propionate, the combination of ethyl propionate and propyl propionate, the combination of methyl butyrate and diethyl carbonate, or the combination of ethyl butyrate and dimethyl carbonate, etc.

[0032] Preferably, the volume ratio of the cyclic carbonate to the chain acid ester is 5:95 to 50:50. The volume ratio can be 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55 or 50:50, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0033] Preferably, based on the mass fraction of the electrolyte being 100%, the mass fraction of the organic solvent in the electrolyte is 75 - 89%. The mass fraction can be 75%, 78%, 80%, 82%, 84%, 86%, 88% or 89%, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0034] As a preferred technical solution of the present invention, the lithium salt includes any one or a combination of at least two of LiPF6, Li(FSO2)2N (LiFSI), Li(CF3SO2)2N (LiTFSI), LiBF4, LiClO4, LiDFOB, LiBOB or LiPO2F2. Typical but non-limiting examples of the combination include: the combination of LiPF6 and Li(FSO2)2N (LiFSI), the combination of Li(FSO2)2N (LiFSI) and Li(CF3SO2)2N (LiTFSI), the combination of Li(CF3SO2)2N (LiTFSI) and LiBF4, the combination of LiBF4 and LiClO4, the combination of LiClO4 and LiDFOB, the combination of LiDFOB and LiBOB, or the combination of LiBOB and LiPO2F2, etc.

[0035] Preferably, the lithium salt includes lithium difluorophosphate and lithium hexafluorophosphate;

[0036] Preferably, based on the mass fraction of the electrolyte being 100%, the mass fraction of the lithium difluorophosphate in the electrolyte is 0.5-1.5%, wherein the mass fraction can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0037] Preferably, based on the mass fraction of the electrolyte being 100%, the mass fraction of the lithium salt in the electrolyte is 10-20%, wherein the mass fraction can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0038] A second object of the present invention is to provide a lithium-ion battery, wherein the lithium-ion battery comprises the electrolyte as described in the first object, and the lithium-ion battery further comprises a positive electrode sheet and a negative electrode sheet.

[0039] As a preferred technical solution of the present invention, the active material of the positive electrode plate includes a transition metal oxide of lithium and / or a transition metal phosphate compound of lithium.

[0040] Preferably, the lithium transition metal oxide includes LiCoO2, LiNi x Co y Mn z O2、LiNi x Co y Al z O2、LiNi x Mn 1-x O2, LiMn2O4, LiMnO2, Li2MnO4, Li 1+a Mn 1-x M x O2、LiCo 1-x Mn x O2、LiNi 1-x Co x O4 or Li2Mn 1-x Any one or a combination of at least two of O4, wherein a typical but non-limiting example of the combination is: LiCoO2 and LiNi x Co y Mn z Combination of O2, LiNi x Co y Mn z O2 and LiNi x Co y Al zCombinations of O2, LiNi x Mn 1-x Combinations of O2 and LiMn2O4, LiMn2O4 and LiMnO2, LiMnO2 and Li2MnO4, Li2MnO4 and Li 1+a Mn 1-x M x Combinations of O2, LiCo 1- x Mn x Combinations of O2 and LiNi 1-x Co x Combinations with O4 or LiNi 1-x Co x Combinations with O4 and Li2Mn 1-x Combinations with O4, etc., where 0 ≤ a < 0.2, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1. The value of a can be 0, 0.05, 0.1, 0.15, or 0.2; the value of x can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc.; the value of y can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc.; the value of z can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc., but not limited to the listed values. Other unlisted values within the above numerical ranges are also applicable.

[0041] Preferably, the lithium transition metal phosphate compound is selected from any one or at least two combinations of LiFePO4, LiMnPO4, LiCoPO4, LiFe 1- x M x PO4, etc. Typical but non-limiting examples of the combinations are: combinations of LiFePO4 and LiMnPO4, LiMnPO4 and LiCoPO4, or LiCoPO4 and LiFe 1-x M x PO4, etc., where M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, 0 ≤ x ≤ 1. The value of x can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc., but not limited to the listed values. Other unlisted values within this numerical range are also applicable.

[0042] As a preferred technical solution of the present invention, the active material of the negative electrode sheet includes any one or a combination of at least two of soft carbon, hard carbon, artificial graphite, natural graphite, silicon oxide, silicon carbon or lithium metal. Typical but non-limiting examples of the combination are: the combination of soft carbon and hard carbon, the combination of hard carbon and artificial graphite, the combination of artificial graphite and natural graphite, the combination of natural graphite and silicon oxide, the combination of silicon oxide and silicon carbon, or the combination of silicon carbon and lithium metal, etc.

[0043] The numerical ranges described in the present invention include not only the point values exemplified above, but also any point values between the above numerical ranges not exemplified. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] In the electrolyte prepared by the present invention, a phosphate compound with a trialkoxysilane-containing side chain is added, which can improve the stability of the electrolyte, improve the high-temperature performance of the lithium-ion secondary battery, reduce the gas generation amount during storage, the storage capacity retention rate at 60 °C can reach more than 93%, the gas generation expansion rate after 30 days of storage can be as low as 13%, and the cycle capacity retention rate at 45 °C / 1C for 800 cycles can reach more than 93%. Detailed implementation manners

[0046] The technical solution of the present invention will be further described below through specific implementation manners.

[0047] Example 1

[0048] This example provides a lithium-ion battery electrolyte:

[0049] The electrolyte includes a lithium salt, an organic solvent and an additive;

[0050] Lithium salt: Based on the mass fraction of the electrolyte being 100%, lithium hexafluorophosphate accounting for 12.5% of the electrolyte mass and lithium difluorophosphate accounting for 1% of the electrolyte mass;

[0051] Organic solvent: Based on the mass fraction of the electrolyte being 100%, the organic solvent accounting for 84.5% of the electrolyte mass. The organic solvent includes ethylene carbonate, ethyl methyl carbonate and diethyl carbonate with a volume ratio of 30:50:20;

[0052] Additive: Based on the mass fraction of the electrolyte being 100%, vinylene carbonate accounting for 0.5% of the electrolyte mass, ethylene sulfate accounting for 1% of the electrolyte mass, and the phosphate compound as described in Formula 3 accounting for 0.5% of the electrolyte mass.

[0053]

[0054] Among them, the synthesis method of the phosphate compound shown in Formula 3 is as follows:

[0055]

[0056] Example 2

[0057] This example provides a lithium-ion battery electrolyte:

[0058] The electrolyte includes a lithium salt, an organic solvent, and an additive;

[0059] Lithium salt: Based on the mass fraction of the electrolyte being 100%, lithium hexafluorophosphate accounting for 9.5% of the electrolyte mass fraction and lithium difluorophosphate accounting for 0.5% of the electrolyte mass fraction;

[0060] Organic solvent: Based on the mass fraction of the electrolyte being 100%, an organic solvent accounting for 89.7% of the electrolyte mass fraction, and the organic solvent includes butylene carbonate and propyl propionate with a volume ratio of 5:95;

[0061] Additive, based on the mass fraction of the electrolyte being 100%, vinylene carbonate accounting for 0.2% of the electrolyte mass fraction, ethylene sulfate accounting for 0.5% of the electrolyte mass fraction, and the phosphate compound as described in Formula 2 accounting for 0.1% of the electrolyte mass fraction,

[0062]

[0063] Among them, the synthesis method of the phosphate compound shown in Formula 2 is as follows:

[0064]

[0065] Example 3

[0066] This example provides a lithium-ion battery electrolyte:

[0067] The electrolyte includes a lithium salt, an organic solvent, and an additive;

[0068] Lithium salt: Based on the mass fraction of the electrolyte being 100%, lithium hexafluorophosphate accounting for 18.5% of the electrolyte mass fraction and lithium difluorophosphate accounting for 1.5% of the electrolyte mass fraction;

[0069] Organic solvent: Based on the mass fraction of the electrolyte being 100%, an organic solvent accounting for 75.5% of the electrolyte mass fraction, and the organic solvent includes butylene carbonate and ethyl butyrate with a volume ratio of 50:50;

[0070] Additives, based on the mass fraction of the electrolyte being 100%, include vinylene carbonate accounting for 0.8% of the mass fraction of the electrolyte, ethylene sulfate accounting for 1.5% of the mass fraction of the electrolyte, and a phosphate compound as shown in Formula 1 accounting for 2% of the mass fraction of the electrolyte.

[0071]

[0072] Among them, the synthesis method of the phosphate compound shown in Formula 1 is as follows:

[0073]

[0074] Example 4

[0075] In this example, except that the mass fraction of the phosphate compound as shown in Formula 3 in the electrolyte is replaced from 0.5% to 1%, other conditions are the same as those in Example 1.

[0076] Example 5

[0077] In this example, except that the mass fraction of the phosphate compound as shown in Formula 3 in the electrolyte is replaced from 0.5% to 2%, other conditions are the same as those in Example 1.

[0078] Example 6

[0079] In this example, except that the mass fraction of the phosphate compound as shown in Formula 3 in the electrolyte is replaced from 0.5% to 5%, other conditions are the same as those in Example 1.

[0080] Example 7

[0081] In this example, except that the mass fraction of the phosphate compound as shown in Formula 3 in the electrolyte is replaced from 0.5% to 0.01%, other conditions are the same as those in Example 1.

[0082] Example 8

[0083] In this example, except for not adding lithium difluorophosphate and replacing the mass fraction of the organic solvent with 85.5%, other conditions are the same as those in Example 1.

[0084] Example 9

[0085] In this example, except for not adding ethylene sulfate and replacing the mass fraction of the organic solvent with 85.5%, other conditions are the same as those in Example 1.

[0086] Comparative Example 1

[0087] In this comparative example, except for not adding the phosphate compound and replacing the mass fraction of the organic solvent with 85%, other conditions are the same as those in Example 1.

[0088] Comparative Example 2

[0089] In this comparative example, except for not adding phosphate ester compounds, vinylene carbonate, and ethylene sulfate and replacing the mass fraction of the organic solvent with 86.5%, other conditions are the same as those in Example 1.

[0090] The electrolytes in Examples 1-9 and Comparative Examples 1-2 were assembled into lithium-ion batteries for testing storage performance and cycling performance. Among them, the assembly method of the lithium-ion battery includes:

[0091] Dissolve the cathode active material lithium nickel manganate (LiNi 0.75 Mn 0.25 O2), conductive agent Super-P, and binder PVDF in a mass ratio of 94:3.0:3.0 in the solvent N-methylpyrrolidone, mix them evenly to make the cathode slurry. Then, evenly coat the cathode slurry on the current collector aluminum foil, and the coating amount is 18 mg / cm 2 . Subsequently, after drying at 85 °C, perform cold pressing, trimming, slicing, and slitting, and then dry in a vacuum at 85 °C for 4 h, weld the electrode tabs to make the cathode plate of the lithium-ion secondary battery that meets the requirements;

[0092] Dissolve the anode active material hard carbon, conductive agent Super-P, thickening agent CMC, and binder SBR in a mass ratio of 96.5:1.0:1.0:1.5 in the solvent deionized water, mix them evenly to make the anode slurry. Then, evenly coat the anode slurry on the current collector copper foil, and the coating amount is 8.9 mg / cm 2 . Subsequently, after drying at 85 °C, perform cold pressing, trimming, slicing, and slitting, and then dry in a vacuum at 110 °C for 4 h, weld the electrode tabs to make the anode plate of the lithium-ion secondary battery that meets the requirements;

[0093] The electrolytes, cathode plates, anode plates, and separator membranes (PE membranes) obtained in Examples 1-9 and Comparative Examples 1-2 were made into batteries with a thickness of 8 mm, a width of 60 mm, and a length of 130 mm through the stacking process, vacuum baked at 85 °C for 10 h, injected with electrolyte, and left standing for 24 h. Then, charge at a constant current of 0.1C (200 mA) to 4.35 V, then charge at a constant voltage of 4.35 V until the current drops to 0.05C (100 mA), and then discharge at a constant current of 0.1C (200 mA) to 2.8 V. Repeat the charge and discharge 2 times, and finally charge at a constant current of 0.1C (200 mA) to 3.8 V to obtain the lithium-ion batteries corresponding to Examples 1-9 and Comparative Examples 1-2.

[0094] Test the capacity retention rate, battery volume expansion rate, and cycling performance of the lithium-ion batteries corresponding to Examples 1-9 and Comparative Examples 1-2. The test results are shown in Table 1.

[0095] Among them, the test method for the capacity retention rate after high-temperature storage is as follows: At 25°C, first charge the lithium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-2 at a constant current of 1C to 4.35V, and further charge at a constant voltage of 4.35V until the current is 0.05C. Then discharge the lithium-ion battery at a constant current of 1C to 2.8V. The discharge capacity this time is the discharge capacity of the lithium-ion battery before high-temperature storage. Then charge the lithium-ion battery at a constant current of 1C to 4.35V, place the lithium-ion battery at 60°C for 30 days of storage. After the storage ends, place the lithium-ion battery in a 25°C environment, and then discharge the lithium-ion battery at a constant current of 0.5C to 2.8V. After that, charge the lithium-ion battery at a constant current of 1C to 4.35V, further charge at a constant voltage of 4.35V until the current is 1C, and then discharge the lithium-ion battery at a constant current of 1C to 2.8V. The discharge capacity of the last time is the discharge capacity of the lithium-ion battery after high-temperature storage. The capacity retention rate (%) of the lithium-ion battery after high-temperature storage = [discharge capacity of the lithium-ion battery after high-temperature storage / discharge capacity of the lithium-ion battery before high-temperature storage] × 100%;

[0096] Test of cycle performance: Test the high-temperature cycle performance of the lithium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-2 respectively. The specific method is as follows: At 45°C, first charge the lithium-ion batteries at a constant current of 1C to 4.35V, then charge at a constant voltage of 4.35V until the current is 0.05C, and then discharge the lithium-ion battery at a constant current of 1C to 2.8V. This is a charge-discharge cycle process, and the discharge capacity this time is the discharge capacity of the first cycle. Perform cycle charge-discharge tests on the lithium-ion batteries in the above manner, and take the discharge capacity of the 800th cycle;

[0097] Test method for battery volume expansion rate: Place the lithium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-2 at 60°C for 30 days of storage. After the storage ends, place the lithium-ion batteries in a 25°C environment, and use the drainage method to measure the volume of the batteries and use a micrometer to measure the thickness of the batteries. Then discharge the lithium-ion batteries at a constant current of 0.5C to 2.8V. After that, charge the lithium-ion batteries at a constant current of 1C to 4.35V, further charge at a constant voltage of 4.35V until the current is 1C, and then discharge the lithium-ion batteries at a constant current of 1C to 2.8V. The discharge capacity of the last time is the discharge capacity of the lithium-ion batteries after high-temperature storage. The battery volume expansion rate = (volume after storage / volume before storage - 1)%.

[0098] Table 1

[0099]

[0100] As can be seen from the above table, by comparing Comparative Examples 1-2 with Examples 1-3, it can be known that after adding the phosphate compound, the high-temperature performance of the battery is significantly improved and the gas generation of the battery is reduced. In the present invention, when the phosphate compound is combined with lithium difluorophosphate and vinylene sulfate, better high-temperature performance can be obtained.

[0101] By comparing Example 1 with Examples 4-7, it can be known that as the content of the phosphate compound of Structural Formula 3 increases, the high-temperature performance of the battery is improved. However, when the content is increased to more than 2%, the further improvement effect is not obvious, because the high content of the phosphate compound causes the viscosity of the electrolyte to become high.

[0102] By comparing Example 1 with Examples 8-9, it can be known that when the phosphate compound is combined with lithium difluorophosphate and vinylene sulfate, better high-temperature performance can be obtained.

[0103] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte includes an organic solvent, a lithium salt, and an additive, and the additive includes a phosphate compound; The phosphate compound includes any one or a combination of at least two of Formula 1, Formula 2, or Formula 3, 2. The electrolyte according to claim 1, characterized in that, Based on the mass fraction of the electrolyte being 100%, the mass fraction of the phosphate compound is 0.01 - 5%.

3. The electrolyte according to claim 1, wherein, Based on the mass fraction of the electrolyte being 100%, the mass fraction of the phosphate compound is 0.1 - 2%.

4. The electrolyte according to claim 1, wherein The additive further includes other additives.

5. The electrolyte according to claim 4, wherein The other additives include any one or a combination of at least two of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, a sultone compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic anhydride compound, a phosphite compound, a phosphate compound, or a borate compound.

6. The electrolyte according to claim 5, wherein, The cyclic carbonate compound containing an unsaturated bond includes vinylene carbonate and / or ethylene vinyl carbonate.

7. The electrolyte according to claim 5, characterized in that, The halogen-substituted cyclic carbonate compound includes fluoroethylene carbonate.

8. The electrolyte according to claim 5, wherein The sulfate compound includes ethylene sulfate.

9. The electrolyte according to claim 5, characterized in that, The sulfite compound includes ethylene sulfite.

10. The electrolyte according to claim 5, characterized in that The sultone compound includes 1,3-propane sultone.

11. The electrolyte according to claim 5, characterized in that, The nitrile compound includes succinonitrile and / or adiponitrile.

12. The electrolyte according to claim 5, characterized in that, The aromatic compound includes biphenyl and / or cyclohexylbenzene.

13. The electrolyte according to claim 5, characterized in that, The isocyanate compound includes 1,4-butane diisocyanate.

14. The electrolyte according to claim 5, characterized in that, The phosphazene compound includes ethoxy pentafluorocyclotriphosphazene.

15. The electrolyte according to claim 5, characterized in that, The cyclic anhydride compound includes succinic anhydride and / or maleic anhydride.

16. The electrolyte according to claim 5, characterized in that, The phosphite compound includes tris(trimethylsilyl) phosphite.

17. The electrolyte according to claim 5, wherein The phosphate compound includes tris(trimethylsilyl) phosphate.

18. The electrolyte according to claim 5, wherein The borate compound includes tris(trimethylsilyl) borate.

19. The electrolyte according to claim 4, characterized in that, The other additives include vinylene carbonate and ethylene sulfate.

20. The electrolyte according to claim 19, characterized in that, Based on the mass fraction of the electrolyte being 100%, the mass fraction of vinylene carbonate in the electrolyte is 0 - 2%.

21. The electrolyte according to claim 20, characterized in that, Based on the mass fraction of the electrolyte being 100%, the mass fraction of vinylene carbonate in the electrolyte is 0.2 - 0.8%.

22. The electrolyte according to claim 19, wherein, Based on the mass fraction of the electrolyte being 100%, the mass fraction of ethylene sulfate in the electrolyte is 0 - 2%.

23. The electrolyte according to claim 22, wherein, Based on the mass fraction of the electrolyte being 100%, the mass fraction of ethylene sulfate in the electrolyte is 0.5 - 1.5%.

24. The electrolyte according to claim 4, wherein Based on the mass fraction of the electrolyte being 100%, the mass fraction of the other additives in the electrolyte is 0 - 2%.

25. The electrolyte according to claim 1, characterized in that, The organic solvent includes cyclic carbonates and chain acid esters, and the chain acid esters include chain carbonates and chain carboxylates.

26. The electrolyte according to claim 25, characterized in that, The chain carbonate includes any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, or ethyl butyrate.

27. The electrolyte according to claim 25, characterized in that, The volume ratio of the cyclic carbonate to the chain acid ester is 5:95 - 50:

50.

28. The electrolyte according to claim 1, wherein Based on the mass fraction of the electrolyte being 100%, the mass fraction of the organic solvent in the electrolyte is 75 - 89%.

29. The electrolyte according to claim 1, characterized in that, The lithium salt includes any one or a combination of at least two of LiPF6, Li(FSO2)2N (LiFSI), Li(CF3SO2)2N (LiTFSI), LiBF4, LiClO4, LiDFOB, LiBOB, or LiPO2F2.

30. The electrolyte according to claim 1, characterized in that, The lithium salt includes lithium difluorophosphate and lithium hexafluorophosphate.

31. The electrolyte according to claim 30, wherein Based on the mass fraction of the electrolyte being 100%, the mass fraction of lithium difluorophosphate in the electrolyte is 0.5 - 1.5%.

32. The electrolyte according to claim 1, characterized in that, Based on the mass fraction of the electrolyte being 100%, the mass fraction of the lithium salt in the electrolyte is 10 - 20%.

33. A lithium-ion battery, characterized in that, The lithium ion battery includes the electrolyte according to any one of claims 1 - 32, and the lithium ion battery further includes a positive electrode sheet and a negative electrode sheet.

34. The lithium-ion battery according to claim 33, wherein, The active material of the positive electrode sheet includes lithium transition metal oxides and / or lithium transition metal phosphate compounds.

35. The lithium ion battery according to claim 34, wherein The transition metal oxides of lithium include LiCoO2, LiNi x Co y Mn z O2, LiNi x Co y Al z O2, LiNi x Mn 1-x O2, LiMn2O4, LiMnO2, Li2MnO4, Li 1+a Mn 1-x M x O2, LiCo 1-x Mn x O2, LiNi 1-x Co x O4 or Li2Mn 1-x O4, where 0 ≤ a < 0.2, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1.

36. The lithium ion battery according to claim 34, characterized in that, The transition metal phosphate compound of lithium is selected from any one or a combination of at least two of LiFePO4, LiMnPO4, LiCoPO4, LiFe 1-x M x PO4, where M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, and 0 ≤ x ≤ 1.

37. The lithium ion battery according to claim 33, characterized in that, The active material of the negative electrode sheet includes any one or a combination of at least two of soft carbon, hard carbon, artificial graphite, natural graphite, silicon oxide, silicon carbon, or lithium metal.

Images