Electrolytes, electrochemical devices, and electronic devices

Abstract

The present invention provides an electrolytic solution, an electrochemical device, and an electronic device. The electrolytic solution in the present invention contains ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate. When the mass content ratio of ethyl propionate is a%, the mass content ratio of propyl propionate is b%, the mass content ratio of ethylene carbonate is c%, and the mass content ratio of propylene carbonate is d% with respect to the total mass of the electrolytic solution, a, b, c, and d satisfy 20 ≦ a + b ≦ 50 and 0 < c / d < 1, 15 ≦ c + d ≦ 50. The electrolytic solution provided by the present invention can significantly improve the floating charge characteristics of an electrochemical device at high voltages.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority based on a Chinese patent application filed with the China National Intellectual Property Office on April 30, 2021, with application number 202110483270.2, and the title of the invention being "Electrolyte, Electrochemical Apparatus and Electronic Apparatus," and incorporates all the contents described in the said Chinese patent application.

[0002] Technical field The present invention relates to an electrolyte, and to electrochemical and electronic apparatus containing said electrolyte. [Background technology]

[0003] With the rapid development of smartphones and consumer electronics, the demands on lithium-ion energy density have become extremely stringent, and improving the voltage withstand capability of lithium-ion batteries is one of the important means of increasing energy density. As voltage increases, more side reactions and safety issues arise, and the impact on float charging and cycle characteristics becomes more pronounced. Reducing side reactions caused by high voltage and improving the safe voltage window of lithium-ion batteries has become a major challenge for the industry. [Overview of the project]

[0004] In response to the problems present in the prior art, the present invention provides an electrolyte, as well as an electrochemical apparatus and an electronic apparatus containing the electrolyte. The electrolyte according to the present invention can significantly improve the floating charge characteristics of an electrochemical apparatus at high voltage.

[0005] In a first aspect, the present invention provides an electrolytic solution, which contains ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate. When the mass content rate of ethyl propionate is a%, the mass content rate of propyl propionate is b%, the mass content rate of ethylene carbonate is c%, and the mass content rate of propylene carbonate is d% with respect to the total mass of the electrolytic solution, a, b, c, and d satisfy 20 ≦ a + b ≦ 50 and 0 < c / d < 1, 15 ≦ c + d ≦ 50.

[0006] According to some embodiments of the present invention, a, b, c, and d satisfy 30 ≦ a + b ≦ 50 and 0.1 < c / d < 0.8.

[0007] According to some embodiments of the present invention, the electrolytic solution further contains a chain carbonate. When the mass content rate of the chain carbonate is e% with respect to the total mass of the electrolytic solution, e satisfies 5 ≦ e ≦ 30.

[0008] According to some embodiments of the present invention, the electrolytic solution further contains fluoroethylene carbonate. Here, the mass content rate of the fluoroethylene carbonate is 0.01% to 15% with respect to the total mass of the electrolytic solution.

[0009] According to some embodiments of the present invention, the electrolytic solution contains a sultone compound. The sultone compound (1) The mass content rate of the sultone compound in the electrolytic solution is 0.01% to 10%. (2) The sultone compound contains a compound of Formula I.

Chemical formula

[0010] According to some embodiments of the present invention, the electrolyte contains fluoroethylene carbonate and a sultone compound. When the mass content ratio of fluoroethylene carbonate is W1% and the mass content ratio of the sultone compound is W2% with respect to the total mass of the electrolyte, where W1 and W2 satisfy at least one of the following: (i) 0.01 ≤ W1 ≤ 15, 0.01 ≤ W2 ≤ 10; (ii) 2 ≤ W1 + W2 ≤ 15; (iii) 1 < W1 / W2 ≤ 15.

[0011] According to some embodiments of the present invention, the electrolyte contains a polynitrile compound. The polynitrile compound satisfies at least one of the following: (4) the mass content ratio of the polynitrile compound in the electrolyte is 0.001% to 10%; (5) the polynitrile compound contains a dinitrile compound and a trinitrile compound. When the mass content ratio of the dinitrile compound is W3% and the mass content ratio of the trinitrile compound is W4% with respect to the total mass of the electrolyte, W3 and W4 satisfy 2 ≤ W3 + W4 ≤ 9 and / or 1 < W3 / W4 ≤ 15. In some embodiments, the polynitrile compound is propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, 1,4-dicyano-2-butene, ethylene glycol bis(propionitrile) ether, [Chemical formula] It contains at least one of the following: 1,3,6-hexanetrinitrile, 1,2,3-propanetricarbonitrine, 3,3'-[[2-[(2-cyanoethoxy)methyl]-2-ethyl-1,3-propanediyl]di(oxy)]di-propionitrile, 2,2,2-nitrilotriacetonitrile, ethylene-1,1,2-tricarbonitrine, tris(2-cyanoethyl)amine, tris(2-cyanoethyl)phosphine, and 1,2,3-tris(2-cyanooxy)propane.

[0012] According to some embodiments of the present invention, the electrolyte contains a boron-containing lithium salt, and the boron-containing lithium salt satisfies at least one of the following: (6) the mass content of the boron-containing lithium salt in the electrolyte is 0.01% to 1%, and (7) the boron-containing lithium salt contains at least one of lithium bis(oxalate)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium borate.

[0013] According to some embodiments of the present invention, the electrolyte comprises an alkenyl sulfone compound, The aforementioned alkenyl sulfone compound is (8) The mass content of the alkenyl sulfone compound in the electrolyte is 0.001% to 5%, (9) The alkenyl sulfone compound includes a compound of formula III, [ka] (Here, R 31 , R 32 , R 33 , R 34 Each of these is independently selected from hydrogen, halogen, hydroxyl group, and halogen-containing hydroxyl group. (10) The alkenyl sulfone compound is [ka] It must include at least one of the following and satisfy at least one of the following.

[0014] In a second aspect, the present invention further provides an electrochemical device, which includes a positive electrode, a negative electrode, a separator, and an electrolytic solution described in the first aspect.

[0015] According to some embodiments of the present invention, the positive electrode includes a positive electrode active material. The positive electrode active material: (11) includes at least one element selected from the group consisting of Co, Fe, P, Ni, and Mn, and elements Li and element O; (12) includes an M element, and the M element includes at least one of Al, Mg, Ti, Zr, Y, and La, and the content of the M element is 200 ppm to 12,000 ppm with respect to the total mass of the positive electrode active material; (13) the specific surface area of the positive electrode active material is 0.1 m 2 / g to 0.3 m 2 / g; (14) the Dv50 of the positive electrode active material is 10 μm to 30 μm, and satisfies at least one of them. In a third aspect, the present invention further provides an electronic device, which includes the electrochemical device described in the second aspect.

[0016] The electrolytic solution of the present invention can significantly improve the floating charge characteristics of the electrochemical device at high voltages by including ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate having specific content ranges and ratio relationships.

Embodiments for Carrying out the Invention

[0017] To further clarify the object, technical proposal, and advantages of the present invention, the technical proposal of the present invention will be described in detail below with reference to examples, but obviously the examples described are only some, not all, examples of the present invention. The relevant examples described herein are for illustrative purposes and are used to understand the present invention in a fundamental way. The examples of the present invention should not be construed as limiting the present invention. All other examples that a person skilled in the art could obtain without creative work based on the technical proposal and examples provided herein also fall within the scope of the claims of the present invention.

[0018] For the sake of brevity, only a few numerical ranges are specifically disclosed in this specification. However, any lower limit can be combined with any upper limit to form an unspecified range, any lower limit can be combined with any other lower limit to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each point or numerical value disclosed individually can be combined with any other point or numerical value, or with any other lower limit or upper limit, to form an unspecified range, acting as a lower or upper limit.

[0019] In this specification, unless otherwise specified, "above" and "below" include the numbers themselves.

[0020] Unless otherwise stated, the terms used in this invention have the meanings commonly understood by those skilled in the art. Unless otherwise stated, the numerical values ​​of each parameter mentioned in this invention can be measured by various measurement methods common in the art (for example, by testing according to the methods shown in the examples of this invention).

[0021] The terms "at least one of", "at least one of", "at least one kind of", or other similar terms used to connect items in a list mean any combination of the listed items. For example, if items A and B are listed, the short expression "at least one of A and B" means A only, B only, or A and B. In another example, if items A, B, and C are listed, the short expression "at least one of A, B, and C" means A only, or B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may contain one or more components. Item B may contain one or more components. Item C may contain one or more components.

[0022] 1. Electrolyte The present invention provides an electrolyte, which contains ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate. When the mass content ratio of ethyl propionate is a%, the mass content ratio of propyl propionate is b%, the mass content ratio of ethylene carbonate is c%, and the mass content ratio of propylene carbonate is d% with respect to the total mass of the electrolyte, a, b, c, and d satisfy 20≦a + b≦50 and 0<c / d<1, 15≦c + d≦50. The electrolyte of the present invention contains ethyl propionate and propyl propionate. Since the viscosities of ethyl propionate and propyl propionate are low, they can reduce the transmission impedance of lithium ions, and during the charge-discharge process, by reducing the risk of lithium ion precipitation, the occurrence and accumulation of side reactions can be reduced, and the improvement of cycle characteristics can be achieved. On the other hand, since the oxidation resistance of ethyl propionate and propyl propionate is low, for example, an electrochemical device under floating charge conditions such as a lithium ion battery, when in a high voltage state for a long time, ethyl propionate and propyl propionate react with the positive electrode by oxidation, and the reaction products gather at the positive electrode, preventing the positive electrode material from reacting with other solvents, so that the improvement of the floating charge characteristics of the electrochemical device can be achieved. Also, by having the content of ethylene carbonate lower than the content of propylene carbonate, the stability of the cyclic carbonate solvent at high voltage can be improved. Both ethylene carbonate and propylene carbonate can form a good solvent effect with lithium salts, but ethylene carbonate has poorer stability than propylene carbonate in a high voltage state for a long time, side reactions occur, and gas is likely to be generated. When the usage amount of ethylene carbonate is lower than the usage amount of propylene carbonate, the stability is improved by the increase in the concentration of lithium salts around ethylene carbonate, and the improvement of the floating charge characteristics of the electrochemical device can be realized.

[0023] According to some embodiments of the present invention, a, b, c, and d satisfy 25 ≦ a + b ≦ 50 and 0.1 < c / d < 0.8. According to some embodiments of the present invention, a, b, c, and d satisfy 30 ≦ a + b ≦ 50 and 0.1 < c / d < 0.8.

[0024] According to some embodiments of the present invention, a + b may be 20, 25, 30, 35, 40, 45, 50, or a range consisting of any two of these numerical values. In some examples, the upper limit of a + b is arbitrarily selected from 50, 45, 40, and the lower limit is arbitrarily selected from 25, 30, 35. When the contents of ethyl propionate and propyl propionate are low, the effect of reducing the viscosity of the electrolyte is not obvious, and the lithium precipitation characteristics of the electrochemical device cannot be effectively improved. When the contents of ethyl propionate and propyl propionate are high, due to their instability at the positive electrode interface, side reactions occur at the positive electrode. When the accumulation amount of these by-products is large, it affects the interfacial kinetic characteristics of the electrochemical device.

[0025] According to some embodiments of the present invention, a may be 3 to 40. In some examples, a may be 3, 6, 9, 12, 15, 17, 20, 23, 25, 27, 30, 35, 40, or a range consisting of any two of these numerical values.

[0026] According to some embodiments of the present invention, b may be 5 to 40. In some examples, b may be 5, 7, 9, 12, 15, 17, 20, 23, 25, 27, 30, 35, 40, or a range consisting of any two of these numerical values.

[0027] According to some embodiments of the present invention, c / d may be 0.2, 0.4, 0.6, 0.8, or 0.9. For example, cyclic carbonate esters such as ethylene carbonate (abbreviated as EC) and propylene carbonate (abbreviated as PC) have high interfacial constants and therefore have good solubility with both lithium salts and additives. Here, the dielectric constant of ethylene carbonate is twice that of propylene carbonate, and adding a large amount of ethylene carbonate significantly improves the stability of the electrolyte system. However, as the voltage increases, ethylene carbonate has low resistance to voltage and is prone to decomposition and gas generation. By having a lower ethylene carbonate content than propylene carbonate content, the stability of the cyclic carbonate ester solvent at high voltages can be improved. Both ethylene carbonate and propylene carbonate can form good solvent effects with lithium salts, but ethylene carbonate is less stable than propylene carbonate at high voltages for extended periods, and side reactions occur, making it prone to gas generation. When the amount of ethylene carbonate used is lower than the amount of propylene carbonate used, the concentration of lithium salt around the ethylene carbonate increases, which improves stability and can lead to improved floating charge characteristics of the electrochemical apparatus. In some embodiments of the present invention, c+d may be in the range of 15, 20, 25, 30, 35, 40, 45, 50, or any two of these values.

[0028] According to some embodiments of the present invention, the electrolyte further contains a linear carbonate ester, the mass content of the linear carbonate ester being e%, where e satisfies 5 ≤ ​​e ≤ 30. According to some embodiments of the present invention, e may be in the range of 5, 7, 13, 15, 17, 20, 21, 23, 25, 27, 29, or any two of these values. Due to the effect of solvation by lithium hexafluorophosphate, if the amount of linear carbonate ester added is large, it is prone to decomposition and gas generation, which in turn affects the electrical properties of the electrochemical apparatus. In some examples, the linear carbonate ester is at least one selected from the group consisting of diethyl carbonate, methyl ethyl carbonate, methyl ethyl carbonate, and fluoromethyl ethyl carbonate.

[0029] According to some embodiments of the present invention, the electrolyte further comprises fluoroethylene carbonate. The fluoroethylene carbonate can form a stable organic protective film on the surface of the active material. During the charging and discharging process of the electrochemical apparatus, this organic protective film does not crack due to the contraction and expansion of the active material, thus significantly improving the cycle characteristics of the electrochemical apparatus. In some embodiments of the present invention, the mass content of the fluoroethylene carbonate is 0.01% to 15% of the total mass of the electrolyte. According to some examples of the present invention, the mass content of the fluoroethylene carbonate may be in the range of 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or any two of these values. In some embodiments of the present invention, the mass content of the fluoroethylene carbonate is 3% to 10%.

[0030] According to some embodiments of the present invention, the electrolyte contains a sultone compound. By adding a sultone compound to the electrolyte, a protective film containing a large amount of sulfonic acid groups can be formed on the surface of the active material. Since sulfonic acid groups have good resistance to high temperatures, the occurrence of side reactions at high temperatures can be reduced, thereby improving the cycle characteristics and high-temperature and high-humidity characteristics of the electrochemical apparatus.

[0031] According to some embodiments of the present invention, the mass content of the sultone compound in the electrolyte is 0.01% to 10%, and may be, for example, 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of these values. The sultone compound readily undergoes ring-opening reactions, and by forming a film on the positive and negative electrodes, the high-temperature resistance of the protective film at the interface between the positive and negative electrodes is improved. As the amount used increases, the film-forming effect becomes stronger, and the formed film gradually hinders lithium ion transmission, thereby increasing the interfacial impedance of the electrochemical apparatus and affecting its performance. In some embodiments of the present invention, the upper limit of the mass content range of the sultone compound in the electrolyte is arbitrarily selected from 10%, 8%, 7%, and 5%, and the lower limit is arbitrarily selected from 1%, 2%, 3%, and 4%. In some examples, the mass content of the sultone compound in the electrolyte is 0.5% to 5%.

[0032] According to some embodiments of the present invention, the sultone compound includes a compound of formula I. [ka] Here, R 11 , R 12 , R 13 Each of these is independently selected from hydrogen, halogen, hydroxyl group, and halogen-containing hydroxyl group.

[0033] According to some embodiments of the present invention, R 11 , R 12 , R 13 Each of these is independently selected from a C1-C6 alkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a halogen-containing C1-C6 alkyl group, a halogen-containing C2-C6 alkenyl group, and a halogen-containing C2-C6 alkynyl group.

[0034] According to some embodiments of the present invention, the C1-C6 alkyl group is, for example, a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group. According to some examples of the present invention, the C2-C6 alkenyl group is a vinyl group, a propenyl group, or a butenyl group. According to some examples of the present invention, the C2-C6 alkynyl group is an ethynyl group, a propynyl group, or a butynyl group. The halogen referred to in the present invention means F, Cl, Br, or I.

[0035] According to some embodiments of the present invention, the sultone compound is

Chemical formula

[0036] According to some examples of the present invention, the electrolytic solution contains fluoroethylene carbonate and a sultone compound. When the mass content rate of the fluoroethylene carbonate is W1% and the mass content rate of the sultone compound is W2% with respect to the total mass of the electrolytic solution, W1 and W2 satisfy 0.01 ≦ W1 ≦ 15 and 0.01 ≦ W2 ≦ 10.

[0037] According to some examples of the present invention, the electrolytic solution contains fluoroethylene carbonate and a sultone compound. When the mass content rate of the fluoroethylene carbonate is W1% and the mass content rate of the sultone compound is W2 with respect to the total mass of the electrolytic solution, W1 and W2 satisfy 2 ≦ W1 + W2 ≦ 15.

[0038] According to some examples of the present invention, the electrolytic solution contains fluoroethylene carbonate and a sultone compound. When the mass content rate of the fluoroethylene carbonate is W1% and the mass content rate of the sultone compound is W2 with respect to the total mass of the electrolytic solution, W1 and W2 satisfy 1 < W1 / W2 ≦ 15. When the fluoroethylene carbonate and the sultone compound satisfy the above range formula, the electrochemical device can obtain better cycle characteristics and high-temperature storage characteristics.

[0039] According to some embodiments of the present invention, the electrolyte contains a polynitrile compound. The polynitrile compound can reduce the reactivity of the transition metal at the positive electrode and improve the effect of high-voltage float charging in the electrochemical apparatus. In some embodiments of the present invention, the mass content of the polynitrile compound in the electrolyte is 0.001% to 10%, and may be in the range of, for example, 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of these values.

[0040] According to some embodiments of the present invention, the polynitrile compound includes a dinitrile compound. In some embodiments of the present invention, the dinitrile compound is propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, 1,4-dicyano-2-butene, ethylene glycol bis(propionitrile) ether, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, te Tramethylbutanedinitrile, 2-methylpentanedinitrile, 2,4-dimethylpentanedinitrile, 2,2,4,4-tetramethylpentanedinitrile, 1,4-dicyanopentane, 1,4-dicyanopentane, 2,5-dimethyl-2,5-hexanedinitrile, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5- Dioxaheptanedinitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, 3,6,9,12,15,18-hexaoxaeicosanoate dinitrile, 1,3-bis(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy) Xy)butane, 1,5-bis(2-cyanoethoxy)pentane, and ethylene glycol bis(4-cyanobutyl) ether, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene, 1,6-dicyano-2-methyl-5-methyl-3-hexene, [ka] It includes at least one of the following.

[0041] According to some embodiments of the present invention, the dinitrile compound comprises at least one of propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, and 1,4-dicyano-2-butene, and ethylene glycol bis(propionitrile) ether, [ka] It includes at least one of the following.

[0042] According to some embodiments of the present invention, the mass content of the dinitrile compound in the electrolyte is 0.001% to 10%. If the content is too low, an effective composite protective film cannot be formed, and if the amount used is too high, it is not consumed immediately, and the remaining amount continues to cause side reactions later, thereby affecting the high-temperature storage characteristics of the electrochemical apparatus. According to some examples of the present invention, the upper limit of the mass content range of the dinitrile compound in the electrolyte is arbitrarily selected from 9%, 8%, 7%, and 6%, and the lower limit is arbitrarily selected from 5%, 3%, 2%, 1%, 0.5%, and 0.3%. In some examples, the mass content of the dinitrile compound in the electrolyte is 0.5% to 5%.

[0043] According to some embodiments of the present invention, the polynitrile compound includes a trinitrile compound. In some embodiments of the present invention, the trinitrile compound is at least one selected from the group consisting of 1,3,6-hexanetrinitrile, 1,2,3-propanetricarbonitride, 3,3'-[[2-[(2-cyanoethoxy)methyl]-2-ethyl-1,3-propanediyl]di(oxy)]di-propionitrile, 2,2,2-nitrilotriacetonitrile, ethylene-1,1,2-tricarbonitride, tris(2-cyanoethyl)amine, tris(2-cyanoethyl)phosphine, and 1,2,3-tris(2-cyanooxy)propane.

[0044] According to some embodiments of the present invention, the mass content of the trinitrile compound in the electrolytic solution is 0.01% to 7%. Different nitriles have different structures, so the effects of improving floating charge at high voltage are also different. The effect of improving floating charge at high voltage by the trinitrile compound is more remarkable. However, since the trinitrile compound has a great influence on kinetics, if the addition amount is too large, lithium may precipitate at the negative electrode interface, resulting in an adverse effect. According to some examples, the upper limit of the range of the mass content of the trinitrile compound of the present invention in the electrolytic solution can be arbitrarily selected from 7%, 6%, 5%, 4%, and the lower limit can be arbitrarily selected from 0.5%, 1%, 2%, 3%. In some examples, the mass content of the trinitrile compound in the electrolytic solution is 0.1% to 5%.

[0045] According to some embodiments of the present invention, the polynitrile compound includes a dinitrile compound and a trinitrile compound. When the mass content of the dinitrile compound in the electrolytic solution is W3% and the mass content of the trinitrile compound is W4%, W3 and W4 satisfy 2 ≤ W3 + W4 ≤ 9.

[0046] According to some embodiments of the present invention, the polynitrile compound includes a dinitrile compound and a trinitrile compound. When the mass content of the dinitrile compound in the electrolytic solution is W3% and the mass content of the trinitrile compound is W4%, W3 and W4 satisfy 1 < W3 / W4 ≤ 15. When the electrolytic solution contains both a dinitrile compound and a trinitrile compound, and the dinitrile compound and the trinitrile compound are within the above range, the high-temperature storage characteristics and the floating charge effect at high voltage of the electrochemical device can be improved simultaneously.

[0047] According to some embodiments of the present invention, the polynitrile compound comprises a dinitrile compound and a trinitrile compound, the dinitrile compound comprising at least one of propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, and 1,4-dicyano-2-butene, and ethylene glycol bis(propionitrile) ether, [ka] The trinitrile compound comprises at least one of the following, and the trinitrile compound is at least one selected from the group consisting of 1,3,6-hexanetrinitrile, 3,3'-[[2-[(2-cyanoethoxy)methyl]-2-ethyl-1,3-propanediyl]di(oxy)]di-propionitrile, 2,2,2-nitrilotriacetonitrile, ethylene-1,1,2-tricarbonitride, tris(2-cyanoethyl)amine, and 1,2,3-tris(2-cyanooxy)propane.

[0048] According to some embodiments of the present invention, the electrolyte contains a boron-containing lithium salt. The release of oxygen by the positive electrode material during the cycling process is one of the factors affecting cycle decay. The released oxygen is highly reactive and accelerates the decomposition of the electrolyte. The decomposition products of the electrolyte further damage the structure of the positive electrode surface layer, and repeated occurrences accelerate deterioration. Due to its unique electron-deficient properties, the boron-containing lithium salt has a certain inhibitory effect on reactive oxygen species in the positive electrode material. According to some embodiments of the present invention, the mass content of the boron-containing lithium salt in the electrolyte is 0.01% to 1%, for example, it may be in the range of 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or any two of these values. If the content of boron-containing lithium salt is low, an effective composite protective film cannot be formed, and if the amount used is large, it is not consumed immediately, and the remaining amount continues to cause side reactions later, thereby affecting the high-temperature storage characteristics of the electrochemical apparatus. In some embodiments of the present invention, the boron-containing lithium salt includes at least one of lithium bis(oxalate)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium borate.

[0049] According to some embodiments of the present invention, the electrolyte contains an alkenyl sulfone compound. The sulfur-containing alkenyl sulfone containing unsaturated bonds can, on the one hand, form a stable composite organic protective film at the positive electrode, and on the other hand, the contained unsaturated bonds are easily reduced at the positive electrode, forming a flexible organic protective film, thereby reducing contact between the active material and the electrolyte and reducing the occurrence of side reactions. According to some embodiments of the present invention, the mass content of the alkenyl sulfone compound in the electrolyte is 0.001% to 5%, and may be in the range of, for example, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, or any two of these values. According to some embodiments of the present invention, the upper limit of the mass content range of the alkenyl sulfone compound in the electrolyte can be arbitrarily selected from 4%, 3%, 2.5%, and 2%, and the lower limit can be arbitrarily selected from 1%, 0.8%, 0.5%, and 0.3%. In some embodiments, the mass content of the alkenyl sulfone compound in the electrolyte is 0.1% to 1%.

[0050] According to some embodiments of the present invention, the alkenyl sulfone compound includes a compound of formula III. [ka] Here, R 31 , R 32 , R 33 , R 34 Each of these is independently selected from hydrogen, halogen, hydroxyl group, and halogen-containing hydroxyl group.

[0051] According to some embodiments of the present invention, R 31 , R 32 , R 33 , R 34 Each of these is independently selected from a C1-C6 alkyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a halogen-containing C1-C6 alkyl group, a halogen-containing C2-C6 alkenyl group, and a halogen-containing C2-C6 alkynyl group.

[0052] According to some embodiments of the present invention, the C1-C6 alkyl group is a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group. According to some embodiments of the present invention, the C2-C6 alkenyl group is a vinyl group, a propenyl group, or a butenyl group. According to some embodiments of the present invention, the C2-C6 alkynyl group is an ethynyl group, a propynyl group, or a butynyl group. In the present invention, halogen means F, Cl, Br, or I.

[0053] According to some embodiments of the present invention, the alkenyl sulfone compound is [ka] It includes at least one of the following.

[0054] According to some embodiments of the present invention, the electrolyte may contain fluoroether compounds. Compared to carbonate esters and carboxylic acid esters, fluoroether compounds have good oxidation resistance and can improve the voltage resistance of the non-aqueous electrolyte.

[0055] According to some embodiments of the present invention, the fluoroether compounds are specifically desflurane, sevoflurane, fluloxene, 2,2,2-trifluoroethyl ether, bis(fluoromethyl) ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, 2,2-difluoroethyl trifluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, trifluoromethyl trifluorovinyl ether, 1,2,2,2-tetrafluoroethyl trifluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl difluoromethyl ether, 1,2,2-trifluoroethyl trifluoromethyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1-difluorodimethyl ether, trifluoromethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1 1,2,3,3,3-Hexafluoropropyl methyl ether, 1,1,3,3-Tetrafluorodimethyl ether, Bis(4-Fluorobutyl) ether, Ethyl trifluoromethyl ether, 2,2,3,3,3-Pentafluoropropyl methyl ether, Methyl nonafluorobutyl ether, 1,2,2,2-Tetrafluoroethyl methyl ether, Pentafluorodimethyl ether, 1,1,2,3,3,3-Pentafluoropropyl ethyl ether, Bis-(2,2-Difluoroethyl) ether, Ethyl perfluoro Butyl ether, bis-(1,2,2,2-tetrafluoroethyl) ether, 1,1,2,2-tetrafluoroethyl methyl ether, 2-fluoroethyl (methyl) ether, perfluorobutyl methyl ether, ethyl nonafluorobutyl ether, 2-perfluoropropoxy perfluoropropyl trifluorovinyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 1H,1h,2H,3h-decafluorodipropyl ether, perfluorodiethylene glycol dimethyl ether, 2,It is at least one selected from the group consisting of 2-difluoroethyl methyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, perfluoroethyl vinyl ether, allyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl ether, and perfluoro(3-butenyl vinyl ether), but is not limited to these.

[0056] According to some embodiments of the present invention, the mass content of the fluoroether compound in the electrolyte is 0.1% to 20%. Because the fluoroether compound contains many fluoro elements, increasing the fluoro content increases the polarization of the electrolyte by interfering with the transmission of lithium ions in the electrolyte. This increased polarization not only causes lithium to precipitate at the interface during the charging process but also reduces the effect of the fluoroether compound in non-aqueous electrolytes. In some embodiments of the present invention, the upper limit of the mass content range of the fluoroether compound in the electrolyte is arbitrarily selected from 20%, 15%, 10%, and 5%, and the lower limit is arbitrarily selected from 1%, 2%, 3%, and 4%. According to some embodiments of the present invention, the mass content of the fluoroether compound in the electrolyte is 0.5% to 10%.

[0057] According to some embodiments of the present invention, the lithium salt is at least one selected from the group consisting of LiPF6, bis(trifluoromethanesulfonyl)imide lithium LiN(CF3SO2)2 (abbreviated as LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (abbreviated as LiFSI), LiBOB (lithium bis(oxalate)borate), LiDFOB (lithium difluoro(oxalato)borate), LiPF4C2O4 (lithium tetrafluorooxalatophosphate), LiPF2[C2O4]2 (lithium difluorobis(oxalato)phosphate), lithium hexafluorocesiumate (LiCsF6), and the like. When multiple lithium salts are selected, the mass ratio of LiPF6 to the lithium salt is greater than 50%.

[0058] 2. Electrochemical apparatus The electrochemical apparatus of the present invention includes any apparatus for generating an electrochemical reaction, and specific examples include all types of primary and secondary batteries. In particular, the electrochemical apparatus is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, the electrochemical apparatus of the present invention includes a positive electrode, a negative electrode, a separator, and the electrolyte described in the present invention.

[0059] 1, Electrolyte The electrolyte used in the electrochemical apparatus of the present invention is any of the electrolytes described in the present invention.

[0060] 2, positive electrode According to some embodiments of the present invention, the positive electrode includes a current collector and a positive electrode active material layer provided on the current collector, the positive electrode active material layer includes a positive electrode active material, a binder, and a conductive agent.

[0061] According to some embodiments of the present invention, the positive electrode active material comprises at least one element selected from the group consisting of Co, Fe, P, Ni, and Mn, as well as the elements Li and O. In some embodiments of the present invention, the positive electrode active material may also include a composite oxide, which comprises lithium and at least one element selected from the group consisting of cobalt, manganese, and nickel. The specific type of positive electrode active material is not specifically limited and may be selected according to the requirements. The positive electrode active material is optionally at least one selected from the group consisting of lithium cobalt oxide (LCO), lithium nickel manganese cobalt ternary material (NCM), lithium iron phosphate, and lithium manganese oxide. They may be used individually, or two or more may be used in combination as desired.

[0062] In some embodiments of the present invention, the positive electrode active material contains an element M, and the element M contains at least one of Al, Mg, Ti, Zr, Y, and La. In some embodiments of the present invention, the content of the element M relative to the total mass of the positive electrode active material is 200 ppm to 12000 ppm, and may be in the range of, for example, 300 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm, 9000 ppm, 10000 ppm, 11000 ppm, or any two of these values.

[0063] The specific surface area (BET) and particle size of the positive electrode active material affect the transmission of lithium ions across the surface of the active material. A larger BET indicates smaller particle size, which is advantageous for lithium ion transmission. High-speed lithium ion transmission characteristics can significantly improve the electrical properties of an electrochemical apparatus. According to some embodiments of the present invention, the BET of the positive electrode active material is 0.1 m². 2 / g~0.3m 2 It is / g, for example, 0.13m 2 / g, 0.15m 2 / g, 0.17m 2 / g, 0.19m 2 / g, 0.20m 2 / g, 0.21m 2 / g, 0.23m 2 / g, 0.25m 2 / g, 0.27m 2 / g, 0.29m 2 / g, or a range consisting of any two of these values. According to some embodiments of the present invention, the Dv50 of the positive electrode active material is 10 μm to 30 μm, and may be, for example, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, or a range consisting of any two of these values. A positive electrode active material having a specific BET or Dv50, when used with a specific solvent system, can ensure the energy density of the electrochemical apparatus while enabling the electrochemical apparatus to have excellent transmission characteristics, and the electrochemical apparatus can still have excellent floating charge characteristics under high temperature conditions.

[0064] In the present invention, the positive electrode active material may have a coating on its surface or may be mixed with another compound having a coating. The coating comprises at least one coating element compound selected from the group consisting of oxides of coating elements, hydroxides of coating elements, hydroxyl oxides of coating elements, oxycarbonates of coating elements, and hydroxyl carbonates of coating elements. The compound used for the coating may be amorphous or crystalline. The coating elements included in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating may be applied in any way that does not adversely affect the performance of the positive electrode active material. For example, the method may include any coating method well known to those skilled in the art, such as spraying or dipping.

[0065] In some embodiments, the positive electrode active material layer further comprises an adhesive and, optionally, a conductive material to impart conductivity to the electrode. The adhesive improves the adhesion between the positive electrode active material particles and also improves the adhesion between the positive electrode active material and the current collector. Examples of adhesives include, but are not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic acid (esterified) styrene-butadiene rubber, epoxy resin, and nylon. The conductive material may include any conductive material as long as it does not undergo chemical changes. Examples of conductive materials include, but are not limited to, carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metallic materials (e.g., metal powders, metal fibers, etc., including copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0066] The positive electrode current collector used in the electrochemical apparatus according to the present invention may be made of aluminum (Al), but is not limited thereto.

[0067] 3, negative electrode The negative electrode in the present invention includes a current collector and a negative electrode active material layer provided on the current collector. According to some embodiments of the present invention, the negative electrode active material layer includes a negative electrode active material, and the specific type of negative electrode active material is not specifically limited and may be selected according to the requirements. Specifically, the negative electrode active material may be natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, or lithium-ionized TiO2-Li4Ti5O with a spinel structure. 12It is one or more selected from the group consisting of Li-Al alloys. The carbon material includes, but is not limited to, crystalline carbon, amorphous carbon, and mixtures thereof. The crystalline carbon may be amorphous, plate-like, plate-like, spherical, or fibrous natural or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcination coke, etc.

[0068] According to some embodiments, the negative electrode active material layer may contain an adhesive, and optionally further contain a conductive material to impart conductivity to the electrode. The adhesive improves adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the current collector. Examples of adhesives include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxy, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic acid (esterified) styrene-butadiene rubber, epoxy resin, nylon, etc. The conductive material may contain any conductive material as long as it does not undergo chemical changes. Examples of conductive materials include, but are not limited to, carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metallic materials (e.g., metal powders, metal fibers, etc., e.g., copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0069] According to some embodiments, the current collector is selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metal, and combinations thereof.

[0070] 4. Separator In some embodiments, the electrochemical apparatus of the present invention includes a separator between the positive and negative electrodes to prevent short circuits. The material and shape of the separator used in the electrochemical apparatus of the present invention are not particularly limited and may be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic material formed from a material stable with respect to the electrolyte of the present invention.

[0071] For example, the separator may include a base layer and a surface treatment layer. The base layer is a nonwoven fabric, membrane, or composite membrane having a porous structure, and the material of the base layer is at least one selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, it may be selected from a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane.

[0072] A surface treatment layer is provided on at least one surface of the base layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.

[0073] The inorganic layer contains inorganic particles and a binder. The inorganic particles are one or more selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is one or more selected from the group consisting of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0074] The polymer layer contains a polymer, the polymer material being at least one selected from the group consisting of polyamide, polyacrylonitrile, acrylic acid ester polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0075] 3.Electronic equipment The present invention further provides an electronic apparatus including an electrochemical apparatus as described in a second aspect of the present invention.

[0076] The electronic devices or apparatus of the present invention are not particularly limited. In some embodiments, the electronic devices of the present invention include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, portable facsimile machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable cleaners, portable CD players, MiniDiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, and lithium-ion capacitors.

[0077] The present invention will be further described below with reference to examples. It should be understood that these examples are used solely for illustrative purposes and do not limit the scope of the present invention.

[0078] Preparation of electrolyte In a glove box under an argon atmosphere with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP), propyl propionate (PP), and linear carbonate esters (diethyl carbonate is abbreviated as DEC, and fluoromethyl ethyl carbonate as FEMC) were uniformly mixed. Furthermore, LiPF6, a well-dried lithium salt, was dissolved in the above non-aqueous solvent, with the added LiPF6 amounting to 12% of the total mass of the electrolyte. Finally, the components shown in each example and comparative example in the table below were added and uniformly mixed to obtain the electrolyte. The content of each substance in the electrolyte described below is calculated relative to the total mass of the electrolyte.

[0079] Examples of compounds containing the sultone compound of formula I are shown below. [ka]

[0080] Examples of dinitrile compounds: butanedinitrile (abbreviated as SN), ethylene glycol bis(propionitrile) ether (abbreviated as DENE)

[0081] Examples of trinitrile compounds: 1,3,6-Hexanetrinitrile (abbreviated as HTCN), 1,2,3-Tris(2-cyanooxy)propane (abbreviated as TCEP)

[0082] Examples of lithium salts containing B: Lithium bis(oxalate)borate (abbreviated as LiBOB), Lithium difluoro(oxalato)borate (abbreviated as LiDFOB)

[0083] Examples of alkenyl sulfone compounds: [ka]

[0084] Preparation of lithium-ion batteries: 1) Preparation of positive electrode pieces: Lithium cobalt oxide (molecular formula LiCoO2), which is the positive electrode active material, acetylene black, which is the conductive agent, and polyvinylidene fluoride (abbreviated as PVDF), which is the binder, are thoroughly stirred and mixed in a weight ratio of 96:2:2 with an appropriate amount of N-methylpyrrolidone (abbreviated as NMP), which is the solvent, to obtain a homogeneous positive electrode slurry. This slurry is coated onto an Al foil, which is the positive electrode current collector, dried, and cold-rolled to obtain positive electrode pieces, also called positive electrodes. Unless otherwise specified, the Al content in the positive electrode active material in the examples was 700 ppm.

[0085] 2) Preparation of negative electrode pieces: Graphite, styrene-butadiene rubber (abbreviated as SBR), and sodium carboxymethylcellulose (abbreviated as CMC), which are the negative electrode active materials, are thoroughly stirred and mixed in an appropriate amount of deionized water solvent in a weight ratio of 97:2:1 to obtain a uniform negative electrode slurry. This slurry is coated onto a Cu foil, which is the negative electrode current collector, dried, and cold-rolled to obtain negative electrode pieces, also called negative electrodes.

[0086] 3) Separator: A porous PE polymer film was used as the separator.

[0087] 4) Preparation of lithium-ion battery: The positive electrode piece, separator, and negative electrode piece are stacked in sequence, a separator for isolation is placed between the positive and negative electrode pieces, and then the assembly is wound up to obtain a bare battery; the bare battery is placed on an outer foil, the prepared electrolyte is poured into the dried battery, and the lithium-ion battery is completed through processes such as vacuum packaging, standing, formation, and shaping.

[0088] Test 1: Flow of the floating charge test: At 25°C, the battery was discharged to 3.0V at 0.5C, then charged to 4.45V at 0.5C, and then charged again at 4.45V at a constant voltage of 0.05C. The thickness of the battery at this time was measured using a PPG soft pack battery thickness measuring device, denoted as 'a'. The battery was placed in a 45°C oven and stored for 400 hours at a constant voltage of 4.45V under 45°C storage conditions. The thickness after 400 hours was measured, denoted as 'b', and the formula for calculating the thickness expansion rate was: (ba) / a × 100%.

[0089] Test 2, 45°C Cycle Test Procedure: At 45°C, the battery was discharged to 3.0V at 0.5C and left for 5 minutes. Then it was charged to 4.45V at 0.5C, charged again at a constant voltage of 0.05C at 4.45V, and after charging was complete it was discharged to 3.0V at a current of 0.5C. This constituted one cycle. This charge-discharge cycle was repeated 300 times under the temperature condition of 45°C. The discharge capacity after the first cycle is denoted as C1, and the discharge capacity after the 300th cycle is denoted as C300. The formula for calculating the capacity retention rate is: (C1 / C300) × 100%.

[0090] Test results Table 1 shows the effects of the mass content of ethyl propionate (EP) in the electrolyte (a%), propyl propionate (PP) in the electrolyte (b%), ethylene carbonate (EC) in the electrolyte (c%), propylene carbonate (PC) in the electrolyte (d%), and linear carbonate ester (DEC or FEMC) in the electrolyte (e%) on lithium-ion battery performance. In each example and comparative example shown in Table 1, the Dv50 of the positive electrode active material was 16 μm and the BET was 0.19 m. 2 It was / g.

[0091] [Table 1]

[0092] As can be seen from a comparison of Examples 1.1 to 1.12, increasing the amount of carboxylic acid ester significantly improves the float charging of the battery at 45°C. On the one hand, this is because carboxylic acid esters have low viscosity, improve the kinetic properties of the electrolyte, and reduce lithium deposition on the negative electrode side of the battery. On the other hand, during the float charging process, carboxylic acid esters cause side reactions at the positive electrode and generate byproducts, thereby protecting the positive electrode interface and reducing the reaction between the positive electrode interface and other components in the electrolyte. As can be seen from a comparison with Comparative Example 1.1, when the amount of carboxylic acid ester used exceeds 50%, the side reactions between the carboxylic acid ester and the surface of the active material accelerate, degrading performance.

[0093] As can be seen from Examples 1.1 to 1.12 and Examples 1.18 to 1.23, by appropriately adjusting the amount of linear carbonate ester used, side reactions at the interface between the carboxylic acid ester and the positive electrode can be mitigated to some extent, reducing gas generation and excessive float charging in the battery caused by continuous side reactions at the interface. As can be seen from the comparison with Comparative Examples 1.1 and 1.2, appropriately increasing the amount of linear carbonate ester improves the float charging characteristics of the battery to some extent.

[0094] As can be seen from the comparison of the examples, the float charge characteristics of the battery can be improved by using appropriate amounts of carboxylic acid ester and chain carbonate ester, and furthermore, by keeping the EC / PC ratio below 1. This is mainly because, compared to propylene carbonate, ethylene carbonate has lower resistance to high pressure, and as the time the battery is used at high voltage increases, ethylene carbonate is more prone to decomposition reactions, causing gas generation at high temperatures, and consequently causing the battery's expansion rate to exceed the standard. As can be seen from the comparison with Comparative Examples 1.1 to 1.2, when the ethylene carbonate content exceeds the propylene carbonate content, the float charge of the battery deteriorates significantly.

[0095] Table 2 shows the effects of the mass content of fluoroethylene carbonate (FEC) in the electrolyte, the type of sultone compound, and the mass content of the sultone compound in the electrolyte on lithium-ion battery performance. Each example is a further improvement based on Example 1.8, i.e., the only difference is the parameters in Table 2.

[0096] [Table 2]

[0097] As can be seen from a comparison between Example 1.8 and Examples 2.1 to 2.6, FEC significantly improves the battery's cycle characteristics at 45°C. This is mainly because ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate, having specific content ranges and ratio relationships, achieve good film formation effects when used with FEC, reducing catalytic side reactions between the electrolyte and active material, and consequently reducing electrolyte consumption. As can be seen from a comparison between Example 1.8 and Examples 2.7 to 2.13, adding sultone further improves the battery's cycle characteristics at 45°C, as well as its float charge characteristics at 45°C. This is mainly because, after sultone is formed, the organic protective film contains a large amount of sulfur, and organic protective films containing sulfur exhibit improved resistance to both high temperatures and high voltages. Furthermore, as can be seen from Examples 2.14 to 2.17, the combined use of FEC and sultone can further improve the battery's cycle characteristics.

[0098] Table 3 shows the effect of the type of polynitrile compound and its mass content in the electrolyte on lithium-ion battery performance. Each example is a further improvement based on Example 1.8, i.e., the only difference is the parameters in Table 3.

[0099] [Table 3.1]

[0100] As can be seen from Example 1.8 and Examples 3.1 to 3.7, the battery's cycle characteristics at 45°C are significantly improved after the addition of dinitrile. As can be seen from the comparison between Example 1.8 and Examples 3.8 to 3.15, the battery's float charge characteristics are also significantly improved after the addition of trinitrile. As can be seen from Examples 3.16 to 3.19, the battery's float charge characteristics are further improved after the addition of dinitrile and trinitrile. This is mainly because nitriles have electron-rich groups that can mitigate to some extent the catalytic oxidation effect of the transition metal of the positive electrode on the electrolyte.

[0101] [Table 3.2]

[0102] As can be seen from Table 3.2, by further adding nitriles after incorporating fluoroethylene carbonate and sultone, the battery's cycle characteristics can be further improved, mainly because the nitrile groups can effectively protect the transition metal at the positive electrode interface.

[0103] Table 4 shows the effect of the type of boron-containing lithium salt and the mass content of the boron-containing lithium salt in the electrolyte on the performance of the lithium-ion battery. Each example is a further improvement based on Example 1.8, i.e., the only difference is the parameters in Table 4.

[0104] [Table 4.1]

[0105] [Table 4.2]

[0106] As can be seen from the comparison between Example 1.8 and Examples 4.1 to 4.10, the battery's cycle characteristics are significantly improved after the addition of boron-containing lithium salt. This indicates that boron-containing lithium salt can effectively reduce side reactions at the interface during the cycling process. As can be seen from Examples 4.11 and 4.12, the battery's cycle characteristics can be further improved by adding boron-containing lithium salt after incorporating FEC, sultone, and nitriles.

[0107] Table 5 shows the effect of the type of alkenyl sulfone compound and the mass content of the alkenyl sulfone compound in the electrolyte on lithium-ion battery performance. Each example is a further improvement based on Example 1.8, i.e., the only difference is the parameters in Table 5.

[0108] [Table 5.1]

[0109] [Table 5.2]

[0110] As can be seen from the comparison between Example 1.8 and Examples 5.1 to 5.7, the float charge characteristics of the battery are significantly improved after the addition of alkenyl sulfone. As can be seen from Examples 5.9 to 5.12, good improvement effects can also be obtained when alkenyl sulfone is used in combination with other additives.

[0111] Table 6 shows the effect of the BET and Dv50 of the positive electrode active material, as well as the doping elements, on the performance of the lithium-ion battery. Here, in Examples 7.1 to 7.11, the content of each component relative to the total mass of the electrolyte is shown in Table 6 below. Unless otherwise specified, the Al content in the positive electrode active material in the examples is 700 ppm and the BET is 0.19 mg. 2 The value was / g, and Dv50 was 16μm.

[0112] [Table 6]

[0113] [Table 7]

[0114] As can be seen from a comparison of Examples 7.1 to 7.11, Al doping and appropriate BET and Dv50 can significantly improve the floating charge characteristics of the battery at 45°C.

[0115] While several exemplary embodiments of the present invention have been described and explained, the present invention is not limited to the disclosed embodiments. Conversely, those skilled in the art will recognize that several modifications and changes can be made to the described embodiments without departing from the spirit and scope of the invention as set forth in the claims.

Claims

1. An electrolyte comprising ethyl propionate, propyl propionate, ethylene carbonate, propylene carbonate, and linear carbonate ester, An electrolyte for lithium-ion secondary batteries, in which, relative to the total mass of the electrolyte, the mass content of ethyl propionate is a%, the mass content of propyl propionate is b%, the mass content of ethylene carbonate is c%, the mass content of propylene carbonate is d%, and the mass content of linear carbonate ester is e%, such that a, b, c, d, and e satisfy 35 ≤ a + b ≤ 50 and 0 < c / d < 1, 25 ≤ c + d ≤ 50, 7 ≤ e ≤ 30, and a + b + c + d + e ≥ 73.

8.

2. The electrolyte for a lithium-ion secondary battery according to claim 1, wherein c and d satisfy 0.1 < c / d < 0.

8.

3. It further contains fluoroethylene carbonate, The electrolyte for a lithium-ion secondary battery according to claim 1, wherein the mass content of the fluoroethylene carbonate is 0.01% to 15% with respect to the total mass of the electrolyte.

4. It further contains sultone compounds, The aforementioned sultone compound, (1) The mass content of the sultone compound in the electrolyte is 1% to 5%, (2) The sultone compound includes a compound of formula I, in which R １１ , R １２ , R １３ Each of these is independently selected from hydrogen, halogen, hydroxyl group, and halogen-containing hydroxyl group, 【Chemistry 1】 (3) The sultone compound is 【Chemistry 2】 It includes at least one of the following, An electrolyte for a lithium-ion secondary battery according to claim 1, satisfying at least one of the following conditions.

5. Further comprising fluoroethylene carbonate and sultone compounds, W is the mass content of the fluoroethylene carbonate relative to the total mass of the electrolyte. １ The mass content of the sultone compound is set to % and W ２ If expressed as a percentage, W １ and W ２ teeth, (i) 0.01 ≤ W １ ≤ 15, 0.01 ≤ W ２ ≤ 10 and (ii) 2 ≤ W １ +W ２ ≤ 15, (iii) 1 < W １ / W ２ ≤ 15 and An electrolyte for a lithium-ion secondary battery according to claim 1, satisfying at least one of the following conditions.

6. It further contains polynitrile compounds, The aforementioned polynitrile compound is (4) The mass content of the polynitrile compound in the electrolyte is 0.5% to 7%, (5) The polynitrile compound comprises a dinitrile compound and a trinitrile compound, and the mass content of the dinitrile compound is W with respect to the total mass of the electrolyte. ３ Let W be the mass content of the trinitrile compound, expressed as %. ４ If expressed as a percentage, W ３ and W ４ 2 ≤ W ３ +W ４ ≤ 9 and / or 1 < W ３ / W ４ The condition that ≤ 15 is met, An electrolyte for a lithium-ion secondary battery according to claim 1, satisfying at least one of the following conditions.

7. The aforementioned polynitrile compound is Examples of dinitrile compounds include propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, 1,4-dicyano-2-butene, ethylene glycol bis(propionitrile) ether, 【Transformation 3】 It includes at least one of the following: The electrolyte for a lithium-ion secondary battery according to claim 6, comprising at least one of the following trinitrile compounds: 1,3,6-hexanetrinitrile, 1,2,3-propanetricarbonitride, 3,3'-[[2-[(2-cyanoethoxy)methyl]-2-ethyl-1,3-propanediyl]di(oxy)]di-propionitrile, 2,2,2-nitrilotriacetonitrile, ethylene-1,1,2-tricarbonitride, tris(2-cyanoethyl)amine, tris(2-cyanoethyl)phosphine, and 1,2,3-tris(2-cyanooxy)propane.

8. It further contains a boron-containing lithium salt, The boron-containing lithium salt is (6) The mass content of the boron-containing lithium salt in the electrolyte is 0.1% to 1%, (7) The boron-containing lithium salt contains at least one of lithium bis(oxalate)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium borate. An electrolyte for a lithium-ion secondary battery according to claim 1, satisfying at least one of the following conditions.

9. Further containing an alkenyl sulfone compound, The aforementioned alkenyl sulfone compound is (8) The mass content of the alkenyl sulfone compound in the electrolyte is 0.1% to 5%, (9) The alkenyl sulfone compound includes a compound of formula III, in formula III, R ３１ , R ３２ , R ３３ , R ３４ Each of these is independently selected from hydrogen, halogen, hydroxyl group, and halogen-containing hydroxyl group, 【Chemistry 4】 (10) The alkenyl sulfone compound is 【Transformation 5】 It includes at least one of the following, An electrolyte for a lithium-ion secondary battery according to claim 1, satisfying at least one of the following conditions.

10. A lithium-ion secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte for a lithium-ion secondary battery according to any one of claims 1 to 7.

11. The positive electrode includes a positive electrode active material. The positive electrode active material is (11) The positive electrode active material contains at least one element selected from the group consisting of Co, Fe, P, Ni, and Mn, and the elements Li and O. (12) The positive electrode active material contains element M, and the element M contains at least one of Al, Mg, Ti, Zr, Y, and La, and the content of element M is 200 ppm to 12000 ppm relative to the total mass of the positive electrode active material. (13) The BET of the positive electrode active material is 0.1 m ２ / g ~ 0.3m ２ The fact that it is / g, (14) The Dv50 of the positive electrode active material is 10 μm to 30 μm, A lithium-ion secondary battery according to claim 10, satisfying at least one of the following conditions.

12. An electronic device comprising a lithium-ion secondary battery according to claim 10 or 11.

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