Electrolyte, electrochemical apparatus, and electronic apparatus

Abstract

To provide an electrolyte that can clearly improve floating charge performance of electrochemical apparatuses at high voltage.SOLUTION: An electrolyte includes ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate, where, based on the total mass of the electrolyte, a mass percentage a% of ethyl propionate, a mass percentage b% of propyl propionate, a mass percentage c% of ethylene carbonate, and a mass percentage d% of propylene carbonate satisfy 20≤a+b≤50, 0<c / d<1, and 15≤c+d≤50.SELECTED DRAWING: None

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to a Chinese patent application filed with the China Patent Office on April 30, 2021, bearing application number 202110483270.2 and entitled "Electrolyte, Electrochemical Device and Electronic Device," and incorporates by reference all of the contents of the Chinese patent application.

[0002] Technical Field The present invention relates to electrolytes and to electrochemical and electronic devices containing the electrolytes. [Background technology]

[0003] With the rapid development of smartphones and household electrical appliances, the requirements for lithium-ion energy density are becoming increasingly stringent, and improving the voltage endurance of lithium-ion batteries is one of the important measures to improve the energy density. With the increase in voltage, more side reactions and safety issues arise, especially the impact on floating charge and cycle characteristics is more prominent. Reducing the side reactions caused by high voltage and improving the safety voltage window of lithium-ion batteries has become a major challenge for the industry. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides an electrolyte, and an electrochemical device and an electronic device containing the electrolyte. The electrolyte according to the present invention can obviously improve the floating charge characteristics of the electrochemical device 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 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.

[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 ratio 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 ratio 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 ratio 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, [Chemistry] The compound includes at least one of 1,3,6-hexanetrinitrile, 1,2,3-propanetricarbonitrile, 3,3'-[[2-[(2-cyanoethoxy)methyl]-2-ethyl-1,3-propanediyl]di(oxy)]di-propionitrile, 2,2,2-nitrilotriacetonitrile, ethylene-1,1,2-tricarbonitrile, 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 solution contains a boron-containing lithium salt, and the boron-containing lithium salt satisfies at least one of the following: (6) a mass content of the boron-containing lithium salt in the electrolyte solution is 0.01% to 1%; and (7) the boron-containing lithium salt contains at least one of lithium bis(oxalato)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 alkenyl sulfone compound is (8) The mass content of the alkenyl sulfone compound in the electrolyte solution is 0.001% to 5%; (9) the alkenyl sulfone compound comprises a compound of formula III; [ka] (where R 31 , R 32 , R 33 , R 34 are each independently selected from hydrogen, halogen, a hydroxy group, and a halogen-containing hydroxy group. (10) The alkenyl sulfone compound is [ka] and at least one of the following is satisfied:

[0014] In a second aspect, the present invention further provides an electrochemical device, said electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte according to the first aspect.

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

[0016] The electrolyte of the present invention contains ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate with a specific content range and ratio relationship, and thus can obviously improve the floating charge characteristics of electrochemical devices at high voltages. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below with reference to the embodiments. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of the embodiments. The relevant embodiments described in the present invention are for illustration and are used to fundamentally understand the present invention. The embodiments of the present invention should not be construed as limiting the present invention. Based on the technical solutions and embodiments provided by the present invention, all other embodiments obtained by those skilled in the art without creative labor also belong to the scope of the protection claims of the present invention.

[0018] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range. Also, each point or numerical value disclosed alone can be combined with any other point or numerical value as a lower limit or upper limit, or with any other lower limit or upper limit to form an unspecified range.

[0019] In the description of this specification, unless otherwise specified, "greater than or equal to" and "less than or equal to" include the numbers themselves.

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

[0021] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms means any combination of the listed items. For example, if items A and B are listed, the short phrase "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 phrase "at least one of A, B, and C" means A only, or B only, or C only, or A and B (excluding C), or A and C (excluding B), or B and C (excluding A), or all of A, B, and C. Item A may include one component or multiple components. Item B may include one component or multiple components. Item C may include one component or multiple components.

[0022] 1. Electrolyte The present invention provides an electrolytic solution, which contains ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate. When the mass content of ethyl propionate is a%, the mass content of propyl propionate is b%, the mass content of ethylene carbonate is c%, and the mass content 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 of the present invention contains ethyl propionate and propyl propionate. Since ethyl propionate and propyl propionate have low viscosities, they can reduce the transmission impedance of lithium ions. During the charge and 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 ethyl propionate and propyl propionate have low oxidation resistance, for example, in 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 reaction, and the reaction products gather at the positive electrode, preventing the positive electrode material from reacting with other solvents, thereby achieving the improvement of the floating charge characteristics of the electrochemical device. 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. Although both ethylene carbonate and propylene carbonate can form a good solvent effect with lithium salts, ethylene carbonate has inferior stability compared to propylene carbonate in a high voltage state for a long time, and side reactions occur and gas is easily 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 salt 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, 0.9. Cyclic carbonates such as ethylene carbonate (abbreviated as EC) and propylene carbonate (abbreviated as PC) have a high interfacial constant and therefore good solubility for both lithium salts and additives. Here, the dielectric constant of ethylene carbonate is twice as high as 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 a low resistance to voltage and is prone to decomposition and gas generation. The content of ethylene carbonate is lower than that of propylene carbonate, which can improve the stability of the cyclic carbonate solvent at high voltage. Both ethylene carbonate and propylene carbonate can form a good solvent effect with lithium salts, but ethylene carbonate is less stable than propylene carbonate at high voltage for a long time, and side reactions occur and gas is easily generated. When the amount of ethylene carbonate used is lower than the amount of propylene carbonate used, the concentration of lithium salt increases around the ethylene carbonate, which improves the stability and improves the floating charge characteristics of the electrochemical device. In some embodiments of the present invention, c+d may be 15, 20, 25, 30, 35, 40, 45, 50, or a range consisting of any two of these values.

[0028] According to some embodiments of the present invention, the electrolyte further comprises a chain carbonate ester, the mass content of the chain carbonate ester being e%, where e satisfies 5≦e≦30. According to some embodiments of the present invention, e may be 5, 7, 13, 15, 17, 20, 21, 23, 25, 27, 29, or a range consisting of any two of these values. Due to the effect of solvation by lithium hexafluorophosphate, if the amount of the chain carbonate ester added is large, it is likely to decompose and generate gas, which in turn affects the electrical characteristics of the electrochemical device. In some examples, the chain 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. 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 device, the organic protective film is not cracked due to the contraction and expansion of the active material, so that the cycle characteristics of the electrochemical device are significantly improved. In some embodiments of the present invention, the mass content of the fluoroethylene carbonate is 0.01% to 15% with respect to the total mass of the electrolyte. According to some embodiments of the present invention, the mass content of the fluoroethylene carbonate may be 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or a range consisting of 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 solution contains a sultone compound, which can form a protective film containing a large amount of sulfonic acid groups on the surface of the active material, and the sulfonic acid groups have good resistance to high temperatures and can reduce the occurrence of side reactions at high temperatures, thereby improving the cycle characteristics and high temperature and high humidity characteristics of the electrochemical device.

[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 a range consisting of any two of these values. The sultone compound is prone to undergo a ring-opening reaction, and by forming a film on the positive and negative electrodes, the high temperature resistance properties of the interface protective film of the positive and negative electrodes are improved. As the amount of use increases, the film formation effect becomes stronger, and the formed film gradually impedes the transmission of lithium ions, thereby increasing the interface impedance of the electrochemical device and affecting the performance of the electrochemical device. In some embodiments of the present invention, the upper limit of the range of the mass content of the sultone compound of the present invention 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 invention, the sultone compound comprises a compound of formula I. [ka] Here, R 11 , R 12 , R 13 are each independently selected from hydrogen, a halogen, a hydroxy group, and a halogen-containing hydroxy group.

[0033] According to some embodiments of the present invention, R 11 , R 12 , R 13 are each 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 as used 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] including at least one of

[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 solution includes a polynitrile compound. The polynitrile compound can reduce the reactivity of transition metals in the positive electrode and improve the effect of floating charging at high voltage of the electrochemical device. In some examples of the present invention, the mass content of the polynitrile compound in the electrolyte solution is 0.001% to 10%, and may be, for example, 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of these values.

[0040] According to some embodiments of the present invention, the polynitrile compound comprises a dinitrile compound. In some embodiments of the present invention, the dinitrile compound is selected from the group consisting of 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, tetrahydrofuran ... tetramethylbutanedinitrile, 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- Dioxa-heptanedinitrile, 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-hexaoxaeicosanoic acid dinitrile, 1,3-bis(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)propane 1,5-bis(2-cyanoethoxy)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] The composition includes at least one of the following:

[0041] According to some embodiments of the present invention, the dinitrile compound includes at least one of propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, 1,4-dicyano-2-butene, and ethylene glycol bis(propionitrile) ether, [ka] The composition 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%-10%. If the content is low, an effective composite protective film cannot be formed, and if the amount used is large, the dinitrile compound is not consumed quickly, and the remaining dinitrile compound continues to cause side reactions in the later stage, thereby affecting the high-temperature storage characteristics of the electrochemical device. According to some embodiments of the present invention, the upper limit of the mass content range of the dinitrile compound in the electrolyte is optionally selected from 9%, 8%, 7%, 6%, and the lower limit is optionally selected from 5%, 3%, 2%, 1%, 0.5%, 0.3%. In some embodiments, the mass content of the dinitrile compound in the electrolyte is 0.5%-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-propanetricarbonitrile, 3,3'-[[2-[(2-cyanoethoxy)methyl]-2-ethyl-1,3-propanediyl]di(oxy)]di-propionitrile, 2,2,2-nitrilotriacetonitrile, ethylene-1,1,2-tricarbonitrile, 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 compounds include dinitrile compounds and trinitrile compounds, the dinitrile compounds include at least one of propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, 1,4-dicyano-2-butene, and ethylene glycol bis(propionitrile) ether, [ka] 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-tricarbonitrile, 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 oxygen released by the positive electrode material during the cycle process is one of the factors that affect the cycle decay. The released oxygen is highly active and accelerates the decomposition of the electrolyte, and the decomposition products of the electrolyte further destroy the structure of the positive electrode surface layer, and the deterioration is accelerated when this is repeated. Due to its unique electron deficiency, the boron-containing lithium salt has a certain inhibitory effect on the active oxygen of 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, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or a range consisting of any two of these values. If the content of the 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 quickly, and the remaining one continues to cause side reactions in the later stage, thereby affecting the high temperature storage characteristics of the electrochemical device. In some embodiments of the present invention, the boron-containing lithium salt comprises at least one of lithium bis(oxalato)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 an unsaturated bond can form a stable composite organic protective film at the positive electrode, and on the other hand, the unsaturated bond contained therein is easily reduced at the positive electrode to form a flexible organic protective film, thereby reducing the 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, 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 a range consisting of any two of these values. According to some embodiments of the present invention, the mass content of the alkenyl sulfone compound in the electrolyte is optionally selected from 4%, 3%, 2.5%, 2% and optionally selected from 1%, 0.8%, 0.5%, 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 invention, the alkenyl sulfone compound comprises a compound of formula III. [ka] Here, R 31 , R 32 , R 33 , R 34 are each independently selected from hydrogen, a halogen, a hydroxy group, and a halogen-containing hydroxy group.

[0051] According to some embodiments of the present invention, R 31 , R 32 , R 33 , R 34 are each 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, etc. 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] The composition includes at least one of the following:

[0054] According to some embodiments of the present invention, the electrolyte may include a fluoroether compound. Compared with carbonate esters and carboxylate esters, the fluoroether compound has 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 compound is specifically selected from the group consisting of desflurane, sevoflurane, fluroxene, 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-perfluoropropoxyperfluoropropyltrifluorovinyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 1H,1h,2H,3h-decafluorodipropyl ether, perfluorodiethylene glycol dimethyl ether, 2,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 not limited thereto.

[0056] According to some embodiments of the present invention, the mass content of the fluoroether compound in the electrolyte is 0.1% to 20%. Since the fluoroether compound contains many fluoro elements, the increase in the fluoro content increases the polarization of the electrolyte by hindering the transmission of lithium ions in the electrolyte. The increase in polarization not only causes lithium to be precipitated at the interface during the charging process, but also reduces the effect of the fluoroether compound in the non-aqueous electrolyte. In some embodiments of the present invention, the upper limit of the mass content range of the fluoroether compound of the present invention 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, lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (abbreviated as LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (abbreviated as LiFSI), LiBOB (lithium bis(oxalato)borate), LiDFOB (lithium difluoro(oxalato)borate), LiPF4C2O4 (lithium tetrafluorooxalatophosphate), LiPF2[C2O4]2 (lithium difluorobis(oxalato)phosphate), lithium hexafluorocesium oxide (LiCsF6), etc. When multiple lithium salts are selected, the mass ratio of LiPF6 in the lithium salts is more than 50%.

[0058] 2. Electrochemical equipment The electrochemical device of the present invention includes any device that generates an electrochemical reaction, and specific examples thereof include all types of primary and secondary batteries. In particular, the electrochemical device 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 device of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte according to the present invention.

[0059] 1, Electrolyte The electrolyte used in the electrochemical device of the present invention may be any of the electrolytes described in this 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 disposed on the current collector, the positive electrode active material layer including 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 includes at least one element selected from the group consisting of Co, Fe, P, Ni, Mn, element Li, and element O. In some embodiments of the present invention, the positive electrode active material may include a complex oxide, and the complex oxide includes lithium and at least one element selected from the group consisting of cobalt, manganese, and nickel. The specific type of the positive electrode active material is not specifically limited and may be selected according to demand. 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 manganate. They may be used alone or in any combination of two or more.

[0062] In some embodiments of the present invention, the positive electrode active material includes an M element, and the M element includes at least one of Al, Mg, Ti, Zr, Y, and La. In some embodiments of the present invention, the content of the M element relative to the total mass of the positive electrode active material may be 200 ppm to 12000 ppm, and may be, 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 a range consisting of any two of these numerical values.

[0063] The specific surface area (abbreviated as BET) and particle size of the positive electrode active material affect the lithium ion transport on the surface of the active material. The larger the BET, the smaller the particle size, which is favorable for the lithium ion transport. The fast lithium ion transport property can significantly improve the electrical properties of the electrochemical device. According to some embodiments of the present invention, the BET of the positive electrode active material is less than 0.1 m 2 / g~0.3m 2 / 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 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, for example, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, or a range 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 device while allowing the electrochemical device to have excellent transmission characteristics, and the electrochemical device 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 the 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 the coating elements, hydroxides of the coating elements, hydroxyl oxides of the coating elements, oxycarbonates of the coating elements, and hydroxycarbonates of the coating elements. The compound used in 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 by any method as long as it does not adversely affect the performance of the positive electrode active material. For example, the method may include any coating method known to those skilled in the art, such as spraying, dipping, etc.

[0065] In some embodiments, the positive electrode active material layer further includes an adhesive, and may optionally further include a conductive material to impart electrical conductivity to the electrode. The adhesive improves adhesion between the positive electrode active material particles and also improves 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 (ester)-modified styrene butadiene rubber, epoxy resin, nylon, and the like. The conductive material may include any conductive material as long as it does not undergo a chemical change. 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.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

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

[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 the negative electrode active material is not specifically limited and may be selected according to needs. 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 lithiated TiO2-Li4Ti5O having a spinel structure. 12, Li-Al alloy. Examples of carbon materials include, but are not limited to, crystalline carbon, amorphous carbon, and mixtures thereof. Crystalline carbon may be amorphous or plate-like, small platelet-like, spherical, or fibrous natural graphite or artificial graphite. 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 include an adhesive, and may further include a conductive material to provide electrical conductivity to the electrode. The adhesive improves adhesion between the negative electrode active material particles and between the negative electrode active material and the current collector. Examples of adhesives include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethyleneoxy, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic acid (ester)-modified styrene butadiene rubber, epoxy resin, nylon, etc. The conductive material may include any conductive material as long as it does not undergo a chemical change. 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.), metal-based materials (e.g., metal powder, metal fiber, 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, conductive metal coated polymer substrate, and combinations thereof.

[0070] 4. Separator In some embodiments, the electrochemical device of the present application includes a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator used in the electrochemical device of the present application are not particularly limited and may be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or an inorganic material formed of a material stable against the electrolyte of the present application.

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

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

[0073] The inorganic layer includes 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, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0074] The polymer layer includes a polymer, and the polymer material is at least one selected from the group consisting of polyamide, polyacrylonitrile, acrylic 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 device comprising an electrochemical device according to the second aspect of the present invention.

[0076] The electronic device or apparatus of the present invention is not particularly limited. In some embodiments, the electronic device of the present invention includes, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, mobile phones, portable facsimiles, portable copy machines, portable printers, stereo headsets, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini disks, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power sources, motors, automobiles, motorcycles, assisted bicycles, bicycles, lighting equipment, toys, game machines, clocks, power tools, flashlights, cameras, large-scale 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 only used to illustrate the present invention and do not limit the scope of the present invention.

[0078] Preparation of electrolyte In a glove box with an argon atmosphere and a water content of <10 ppm, ethylene carbonate (abbreviated as EC), propylene carbonate (abbreviated as PC), ethyl propionate (abbreviated as EP), propyl propionate (abbreviated as PP), and chain carbonate ester (diethyl carbonate abbreviated as DEC, fluoromethylethyl carbonate abbreviated as FEMC) were mixed uniformly, and then LiPF6, which is a lithium salt that had been sufficiently dried, was dissolved in the above non-aqueous solvent, and the mass of LiPF6 added was 12% of the total mass of the electrolyte. Finally, the components shown in each of the examples and comparative examples in the table below were added and mixed uniformly to obtain an electrolyte. The contents of each substance in the electrolyte described below are all calculated based on the total mass of the electrolyte.

[0079] Examples including sultone compounds 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 B-containing lithium salts: lithium bis(oxalato)borate (abbreviated as LiBOB), lithium difluoro(oxalato)borate (abbreviated as LiDFOB)

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

[0084] Preparation of Li-ion batteries: 1) Preparation of positive electrode pieces: Lithium cobalt oxide (molecular formula is LiCoO2) as a positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride (abbreviated as PVDF) as a binder are thoroughly stirred and mixed in a weight ratio of 96:2:2 with an appropriate amount of N-methylpyrrolidone (abbreviated as NMP) as a solvent to obtain a uniform positive electrode slurry. This slurry is applied onto an Al foil as a positive electrode current collector, dried, and cold rolled to obtain a positive electrode piece, also called a positive electrode. 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: The negative electrode active materials graphite, styrene butadiene rubber (abbreviated as SBR), and sodium carboxymethyl cellulose (abbreviated as CMC) were thoroughly mixed in a weight ratio of 97:2:1 with an appropriate amount of deionized water solvent and stirred to obtain a uniform negative electrode slurry. This slurry was applied onto a Cu foil negative electrode current collector, dried, and cold rolled to obtain a negative electrode piece, also called a negative electrode.

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

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

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

[0089] Test 2: 45℃ cycle test procedure: At 45℃, the battery was discharged to 3.0V at 0.5C and left for 5min. It was then charged to 4.45V at 0.5C, charged to 4.45V at a constant voltage of 0.05C, and discharged to 3.0V at a current of 0.5C after charging was completed, which was counted as one cycle. This charge / discharge flow was cycled 300 times at a temperature of 45℃. The discharge capacity at the first cycle was C1, and the discharge capacity at the 300th cycle was C300, and the formula for calculating the capacity retention rate was: (C1 / C300)×100%.

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

[0091] [Table 1]

[0092] As can be seen from the comparison of Examples 1.1 to 1.12, increasing the amount of carboxylate ester used significantly improves the float charge of the battery at 45°C. On the one hand, the carboxylate ester has a low viscosity, which can improve the dynamic properties of the electrolyte and reduce lithium deposition on the negative electrode side of the battery. On the other hand, the carboxylate ester generates a side reaction at the positive electrode during the float charge process, which protects the interface of the positive electrode and reduces the reaction between the positive electrode interface and other components in the electrolyte. As can be seen from the comparison with Comparative Example 1.1, when the amount of carboxylate ester used exceeds 50%, the side reaction between the carboxylate ester and the surface of the active material is accelerated, which deteriorates the 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 chain carbonate ester used, it is possible to alleviate to some extent the side reaction between the carboxylate ester and the positive electrode interface, and to reduce gas generation and excessive float charging in the battery caused by the continued occurrence of side reactions at the interface. As can be seen from the comparison with Comparative Examples 1.1 and 1.2, by appropriately increasing the amount of chain carbonate ester, the float charging characteristics of the battery are improved to some extent.

[0094] As can be seen from the comparison of the examples, when the appropriate amount of carboxylate and the appropriate amount of chain carbonate are used, and the EC / PC ratio is less than 1, the float charge characteristics of the battery can be improved. This is mainly because, compared with propylene carbonate, ethylene carbonate has a low resistance to high pressure, and as the battery is used at high voltage for a long time, ethylene carbonate is more likely to undergo decomposition reactions, which leads to gas generation at high temperatures and ultimately causes the battery expansion rate to exceed the standard. As can be seen from the comparison of Comparative Examples 1.1 to 1.2, when the content of ethylene carbonate exceeds the content of propylene carbonate, the float charge of the battery is significantly deteriorated.

[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 the performance of a lithium-ion battery. Each example is a further improvement based on Example 1.8, that is, the only differences are the parameters in Table 2.

[0096] [Table 2]

[0097] As can be seen from the comparison between Example 1.8 and Examples 2.1 to 2.6, FEC greatly improves the cycle characteristics of the battery at 45°C. This is mainly because ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate with a certain content range and ratio relationship can be used together with FEC to achieve a good film formation effect, reduce the catalytic side reaction between the electrolyte and the active material, and thus reduce the consumption of the electrolyte. As can be seen from the comparison between Example 1.8 and Examples 2.7 to 2.13, the addition of sultone can further improve the cycle characteristics of the battery at 45°C, and can also improve the floating charge characteristics of the battery at 45°C. This is mainly because after the sultone is formed, the organic protective film contains a large amount of S element, and the organic protective film containing S has improved resistance to both high temperature and high voltage. Furthermore, as can be seen from Examples 2.14 to 2.17, the combined use of FEC and sultone can further improve the cycle characteristics of the battery.

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

[0099] [Table 3.1]

[0100] As can be seen from Example 1.8 and Example 3.1 to Example 3.7, after dinitrile is added, the cycle performance of the battery at 45°C is significantly improved. As can be seen from the comparison between Example 1.8 and Example 3.8 to Example 3.15, after trinitrile is added, the float charge performance of the battery is also significantly improved. As can be seen from Example 3.16 to Example 3.19, after dinitrile and trinitrile are added, the float charge performance of the battery is further improved. This is mainly because nitriles have electron-rich groups, which can alleviate the catalytic oxidation of the transition metal of the positive electrode to the electrolyte to a certain extent.

[0101] [Table 3.2]

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

[0103] Table 4 shows the effect of the type of boron-containing lithium salt and the mass content of boron-containing lithium salt in the electrolyte on the performance of lithium-ion battery. Each example is further improved based on Example 1.8, that is, 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, after adding boron-containing lithium salt, the cycle characteristics of the battery are significantly improved. This indicates that the boron-containing lithium salt can effectively reduce the side reaction at the interface during the cycle process. As can be seen from Examples 4.11 and 4.12, by adding boron-containing lithium salt after adding FEC, sultone, and nitriles, the cycle characteristics of the battery can be further improved.

[0107] Table 5 shows the effect of the type of alkenyl sulfone compound and the mass content of alkenyl sulfone compound in the electrolyte on the performance of lithium ion battery. Each example is further improved based on Example 1.8, that is, 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 floating 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, when the alkenyl sulfone is used in combination with other additives, good improvement effects can also be obtained.

[0111] Table 6 shows the BET and Dv50 of the positive electrode active material, and the effect of the doping element on the lithium ion battery performance. 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, the BET is 0.19 m 2 / g and Dv50 was 16 μm.

[0112] [Table 6]

[0113] [Table 7]

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

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

Claims

1. An electrolyte solution comprising ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate, An electrolyte, wherein a, b, c, and d satisfy 20≦a+b≦50, 0<c / d<1, and 15≦c+d≦50, where a mass content of ethyl propionate is a %, a mass content of propyl propionate is b %, a mass content of ethylene carbonate is c %, and a mass content of propylene carbonate is d %, relative to a total mass of the electrolyte.

2. The electrolyte according to claim 1 , wherein a, b, c, and d satisfy 30≦a+b≦50 and 0.1<c / d<0.

8.

3. Further comprising a chain carbonate ester, The electrolyte solution according to claim 1 , wherein e satisfies 5≦e≦30, where e is a mass content of the chain carbonate ester relative to a total mass of the electrolyte solution.

4. Further comprising fluoroethylene carbonate, 2. The electrolyte according to claim 1, wherein the mass content of the fluoroethylene carbonate is 0.01% to 15% based on the total mass of the electrolyte.

5. Further comprising a sultone compound, The sultone compound is (1) the mass content of the sultone compound in the electrolyte is 0.01% to 10%; (2) The sultone compound includes a compound of formula I, wherein R １１ , R １２ , R １３ are each independently selected from hydrogen, halogen, a hydroxy group, and a halogen-containing hydroxy group; 【Chemistry 1】 (3) The sultone compound is 【Chemistry 2】 and The electrolyte solution according to claim 1 , which satisfies at least one of the above.

6. Further comprising fluoroethylene carbonate and a sultone compound, The mass content of the fluoroethylene carbonate with respect to the total mass of the electrolyte solution is W １ %, and the mass content of the sultone compound is W ２ In the case of %, W １ and W ２ teeth, (i) 0.01≦W １ ≦15, 0.01≦W ２ ≦10, (ii) 2≦W １ +W ２ ≦15, (iii) 1<W １ / W ２ ≦15 and The electrolyte according to claim 1 , which satisfies at least one of the above.

7. Further comprising a polynitrile compound, The polynitrile compound is (4) the mass content of the polynitrile compound in the electrolyte is 0.001% to 10%; (5) The polynitrile compound includes a dinitrile compound and a trinitrile compound, and the mass content of the dinitrile compound with respect to the total mass of the electrolyte is W ３ %, and the mass content of the trinitrile compound is W ４ In the case of %, W ３ and W. ４ 2≦W ３ +W ４ ≦9 and / or 1<W ３ / W ４ ≦15 and The electrolyte according to claim 1 , which satisfies at least one of the above.

8. The polynitrile compound includes propanedinitrile, butanedinitrile, pentanedinitrile, hexanedinitrile, heptanedinitrile, 1,4-dicyano-2-butene, ethylene glycol bis(propionitrile) ether, 【Chemistry 3】 1,3,6-hexanetrinitrile, 1,2,3-propanetricarbonitrile, 3,3'-[[2-[(2-cyanoethoxy)methyl]-2-ethyl-1,3-propanediyl]di(oxy)]di-propionitrile, 2,2,2-nitrilotriacetonitrile, ethylene-1,1,2-tricarbonitrile, tris(2-cyanoethyl)amine, tris(2-cyanoethyl)phosphine, 1,2,3-tris(2-cyanooxy)propane, the electrolyte solution according to claim 7, containing at least one of these.

9. further comprising 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 0.01% to 1%; (7) The boron-containing lithium salt includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium borate; The electrolyte according to claim 1 , which satisfies at least one of the above.

10. Further comprising an alkenyl sulfone compound, The alkenyl sulfone compound is (8) The mass content of the alkenyl sulfone compound in the electrolyte solution is 0.001% to 5%; (9) The alkenyl sulfone compound comprises a compound of formula III, wherein R ３１ , R ３２ , R ３３ , R ３４ are each independently selected from hydrogen, halogen, a hydroxy group, and a halogen-containing hydroxy group; 【Chemistry 4】 (10) The alkenyl sulfone compound is 【Chemistry 5】 and The electrolyte solution according to claim 1 , which satisfies at least one of the above.

11. An electrochemical device comprising a positive electrode, a negative electrode, a separator, and the electrolyte solution according to any one of claims 1 to 8.

12. 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, as well as the element Li and the element O; (12) The positive electrode active material includes an M element, the M element including 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 BET of the positive electrode active material is 0.1 m ２ / g to 0.3 m ２ / g, (14) The positive electrode active material has a Dv50 of 10 μm to 30 μm; The electrochemical device according to claim 11 , wherein at least one of the above is satisfied.

13. An electronic device comprising an electrochemical device according to claim 11 or 12.

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