Electrochemical device and electronic device including the same

Abstract

The present invention relates to an electrochemical device and an electronic device including the same. The electrochemical device includes an electrolytic solution, the electrolytic solution includes a carboxylic acid ester compound and fluoroethylene carbonate (FEC), and based on the total weight of the electrolytic solution, the content of the carboxylic acid ester compound and the content of the fluoroethylene carbonate are w 1 and w 2 respectively. When they are set as 5% ≦ w 1 ≦ 60%, 2% ≦ w 2 ≦ 12%, and 2 ≦ w 1 / w 2 ≦ 20. The electrochemical device exhibits excellent rapid charging characteristics and high-temperature interval cycle characteristics.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technologies, and more specifically, to an electrochemical device and an electronic device including the same.

Background Art

[0002] Rechargeable electrochemical devices have advantages such as high energy density, relatively simple reaction mechanisms, high operating voltages, long lifetimes, and environmental friendliness, and thus are regarded as one of the most attractive energy storage systems. Currently, electrochemical devices such as lithium-ion batteries are widely used in electronic products such as notebook computers, smartphones, and wearable devices.

[0003] With the market's pursuit of rapid charging of electronic products, the requirements for the charging speed of electrochemical devices are becoming increasingly high, which requires that electrochemical devices have excellent electrochemical properties, especially excellent cycle properties, even at high-rate current densities. In addition, during rapid charging of electrochemical devices, heat generation often occurs, and the increase in temperature further deteriorates the cycle stability of electrochemical devices. For example, a notebook computer is first charged to a fully charged state during use, maintained in the fully charged state for several hours, and finally disconnected from the charger and discharged. The battery in the notebook computer generates heat and reaches a high-temperature state during this process. When the notebook computer is subjected to the intermittent operating conditions of the high-temperature storage and charge-discharge cycles, the attenuation of the battery capacity becomes serious, which imposes higher requirements on the high-temperature interval cycle (ITC) characteristics of electrochemical devices.

[0004] In view of this, in order to meet the above needs of people, it has become an urgent task to obtain an electrochemical device having excellent rapid charging characteristics and high-temperature interval cycle characteristics.

Summary of the Invention

[0005] In order to solve at least the above problems, the present invention improves the rapid charging characteristics and high-temperature interval cycle characteristics of the electrochemical device by improving the composition of the electrolytic solution and / or designing the size of the electrochemical device.

[0006] According to one aspect of the present invention, the present invention provides an electrolytic solution, wherein the electrolytic solution contains a carboxylic acid ester compound represented by formula (I) and fluoroethylene carbonate (FEC).

Chemical formula

[0007] According to an embodiment of the present invention, 4 ≤ w 1 / w 2 ≤ 10.

[0008] According to an embodiment of the present invention, the carboxylic acid ester compound represented by the formula (I) includes at least one of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, n-amyl propionate, isoamyl propionate, ethyl n-butyrate, n-propyl n-butyrate, propyl isobutyrate, n-amyl n-butyrate, isoamyl n-butyrate, n-butyl n-butyrate, isobutyl isobutyrate, and n-amyl n-valerate.

[0009] According to an embodiment of the present invention, the carboxylic acid ester compound represented by the formula (I) includes propyl propionate and ethyl acetate.

[0010] According to an embodiment of the present invention, the electrolytic solution further includes a nitrile compound. When the content of the nitrile compound is w based on the total weight of the electrolytic solution, 3 0.1% ≤ w 3 ≤ 12%.

[0011] According to an embodiment of the present invention, the nitrile compound includes at least one of the compounds represented by the formula (II) to the formula (V),

Chemical formula

[0012] According to an embodiment of the present invention, when the total molar amount of the cyano group (-CN) in the nitrile compound is x and the total molar amount of the nitrile compound is y, the cyano group content ratio x / y satisfies 2.16 ≦ x / y ≦ 2.71.

[0013] According to an embodiment of the present invention, the cyano group content ratio x / y, the content w of the carboxylic acid ester compound represented by the formula (I) 1 and the content w of the fluoroethylene carbonate 2 are 2w 1 2 -0.01w 1 +2.3 > x / y > 27w 2 2 -1.2w 2 +2.1 is satisfied.

[0014] According to an embodiment of the present invention, the electrolytic solution contains a lithium salt, and the lithium salt is LiPF 6 、LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 、LiSiF 6 、LiBOB, and at least one of LiDFOB.

[0015] According to another aspect of the present invention, the present invention further provides an electrochemical device including the electrolyte described in the above embodiments of the present invention.

[0016] According to an embodiment of the present invention, the electrochemical device further includes a positive electrode, a negative electrode, and a separator positioned between the positive electrode and the negative electrode, wherein the positive electrode, the negative electrode, and the separator are wound to form a cell, and the length L and width W of the cell satisfy 20 mm ≤ L ≤ 300 mm, 20 mm ≤ W ≤ 100 mm, and 1 ≤ L / W ≤ 4.

[0017] According to an embodiment of the present invention, the electrochemical device satisfies at least one of a) 1 ≤ L / W ≤ 3, b) 2 ≤ L / W ≤ 3, and c) 2 ≤ L / W ≤ 4.

[0018] According to an embodiment of the present invention, the electrochemical device further includes a positive electrode, a negative electrode, and a separator positioned between the positive electrode and the negative electrode, wherein the positive electrode, the negative electrode, and the separator are wound to form a cell, and the thickness T and width W of the cell satisfy 2 mm ≤ T ≤ 12 mm and W / T ≥ 5.

[0019] According to an embodiment of the present invention, the electrochemical device satisfies at least one of d) 5 ≤ W / T ≤ 25, e) 5 ≤ W / T ≤ 20, f) 5 ≤ W / T ≤ 15, and g) 10 ≤ W / T ≤ 25.

[0020] According to an embodiment of the present invention, the electrochemical device further includes a positive electrode, a negative electrode, and a separator positioned between the positive electrode and the negative electrode, wherein the positive electrode, the negative electrode, and the separator are wound to form a cell, and the length L and width W of the cell, and the content w of the carboxylic acid ester compound represented by the formula (I) 1 is such that w 1 × 100 / (L / W) ≥ 10.

[0021] According to an embodiment of the present invention, the electrochemical device satisfies h) 10 ≤ w 1 × 100 / (L / W) ≤ 40, i) 20 ≤ w1 ×100 / (L / W) ≤ 30, j) 20 ≤ w 1 ×100 / (L / W) ≤ 40, and k) 15 ≤ w 1 Satisfies at least one of ×100 / (L / W) ≤ 30.

[0022] According to another aspect of the present invention, the present invention further provides an electronic device including the electrochemical device described in the above embodiments of the present invention.

Brief Description of the Drawings

[0023] Hereinafter, for the purpose of describing the embodiments of the present invention, the drawings necessary for describing the embodiments of the present invention or the prior art will be briefly described. Obviously, the drawings in the following description are merely some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative labor.

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0024] Hereinafter, the embodiments of the present invention will be described in detail. The embodiments of the present invention should not be construed as limiting the present invention.

[0025] As used in this application, the terms "comprising", "containing", and "including" are intended to have an open and non-limiting meaning.

[0026] In addition, in this specification, amounts, ratios, and other numerical values may be presented in a range format. Such a range format is for the purpose of convenience and brevity and should be understood flexibly. This range format includes not only the numerical values clearly specified as range limitations but also each and every numerical value or sub-range included in the said range, which is equivalent to each numerical value or sub-range being clearly specified.

[0027] In the embodiments for carrying out the invention and the claims, the terms "at least one of", "at least one of", "at least one kind of", or a list of items connected by other similar terms mean any combination of the listed items. For example, when items A and B are listed, the phrase "at least one of A and B" means only A, only B, or A and B. In other specific examples, when items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A, only B, only C, 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 include a single element or a plurality of elements. Item B may include a single element or a plurality of elements. Item C may include a single element or a plurality of elements.

[0028] The term "alkyl group" includes linear alkyl groups and branched-chain alkyl groups. For example, the alkyl group may be a C1-C50 alkyl group, a C1-C40 alkyl group, a C1-C30 alkyl group, a C1-C20 alkyl group, a C1-C12 alkyl group, a C1-C10 alkyl group, a C1-C6 alkyl group, a C2-C6 alkyl group, a C2-C5 alkyl group. In some embodiments, the alkyl group includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, heptyl, octyl, etc. Also, the alkyl group may be optionally substituted.

[0029] The term "alkenyl group" includes linear alkenyl groups and branched alkenyl groups. For example, the alkenyl group may be a C2-C50 alkenyl group, a C2-C40 alkenyl group, a C2-C30 alkenyl group, a C2-C20 alkenyl group, a C2-C12 alkenyl group, a C2-C10 alkenyl group, or a C2-C6 alkenyl group. Also, the alkenyl group may be optionally substituted.

[0030] The term "aryl group" includes monocyclic and polycyclic systems. The polycycle may be two or more rings in which two carbons are shared by two adjacent rings (the rings are "fused rings"), and at least one of the rings is an aromatic ring. For example, the other rings may be a cycloalkyl group, a cycloalkenyl group, an aryl group, a heterocyclyl group, and / or a heteroaryl group. For example, the aryl group may be a C6-C50 aryl group, a C6-C40 aryl group, a C6-C30 aryl group, a C6-C20 aryl group, or a C6-C10 aryl group. Also, the aryl group may be optionally substituted.

[0031] The term "alkoxy group" is an organic group having -O-R1, where R1 is the linear alkyl group or branched alkyl group described above.

[0032] The term "aryloxy group" is an organic group having -O-R2, where R2 is the aryl group described above.

[0033] The term "alkylene group" includes linear alkylene groups and branched alkylene groups. For example, the alkylene group may be a C1-C50 alkylene group, a C1-C40 alkylene group, a C1-C30 alkylene group, a C1-C20 alkylene group, a C1-C10 alkylene group, a C1-C6 alkylene group, a C2-C6 alkylene group, or a C2-C5 alkylene group. Also, the alkylene group may be optionally substituted.

[0034] The term "alkenylene group" may be a linear alkenylene group or a branched alkenylene group. For example, the alkenylene group may be a C2-C50 alkenylene group, a C2-C40 alkenylene group, a C2-C30 alkenylene group, a C2-C20 alkenylene group, a C2-C10 alkenylene group, a C1-C6 alkenylene group, or a C2-C6 alkenylene group. Further, the alkenylene group may be optionally substituted.

[0035] The term "heterocyclylene group" includes a closed-ring structure similar to a carbocyclic group in which one or more of the carbon atoms in the ring are elements other than carbon, such as nitrogen, sulfur, or oxygen, and includes, but is not limited to, an aziridine group, an oxirane group (epoxide, ethylene oxide), an ethylene sulfide group ( episulfide group), a dioxirane group, an azetidine group, an oxetane group, a thietane group, a dioxetane group, a dithietane group, a dithieto group, an azolidine group, a pyrrolidine group, a pyrroline group, an oxolane group, a dihydrofuran group, and a furan group.

[0036] When the group is substituted, the substituent can be independently selected from the group consisting of an alkyl group, an alkenyl group, an aryl group, an alkoxy group, an aryloxy group, a silane group, a siloxane group, an amino group, an ether group, an ester group, a carboxy group, a sulfonic acid group, a mercapto group, a cyano group, a halogen, and combinations thereof.

[0037] I. Electrolyte As an important component of an electrochemical device, the electrolyte is used to transport lithium ions between the positive electrode and the negative electrode so that lithium ions are continuously occluded and released in the positive and negative electrode materials, and plays a function of charge and discharge. Therefore, the electrolyte has a very important influence on the electrochemical characteristics of the electrochemical device.

[0038] In order to improve the rapid charging characteristics of an electrochemical device, the present invention improves the transport rate of lithium ions in the electrolyte by adding a carboxylic acid ester compound with a lower viscosity to the electrolyte. However, the present invention further found that the electrochemical window of the carboxylic acid ester compound is narrow and its high-temperature stability is poor. For example, under the intermittent operating conditions of high-temperature storage and charge-discharge cycles of an electronic device (e.g., a notebook computer), the carboxylic acid ester compound reacts at the negative electrode, consumes active lithium, destroys the solid electrolyte interface (SEI) film on the negative electrode surface, and causes rapid attenuation of the battery capacity.

[0039] In order to effectively alleviate the destruction of the carboxylic acid ester compound on the negative electrode SEI film and timely repair the negative electrode SEI film, the present invention further adds fluoroethylene carbonate (FEC) to the electrolyte. However, the present invention found that when the electrochemical device is under the intermittent operating conditions of high-temperature storage and charge-discharge cycles, the structure of the positive electrode is easily destroyed, an oxygen evolution reaction occurs, and at this time, FEC is easily oxidized and decomposed, and CO 2 is generated. As a result, it was further found that the electrochemical device generates swelling due to gas generation.

[0040] However, the present invention surprisingly found that by adjusting the content and ratio of the carboxylic acid ester compound and fluoroethylene carbonate in the electrolyte, the high-temperature interval cycle characteristics of the electrochemical device can be not deteriorated or only slightly deteriorated, and the rapid charging characteristics of the electrochemical device can be effectively improved. In some embodiments, based on the total weight of the electrolyte, when the contents of the carboxylic acid ester compound and fluoroethylene carbonate are w 1 and w 2 respectively, 5% ≤ w 1 ≤ 60%, 2% ≤ w 2 ≤ 12%, and 2 ≤ w 1 / w 2 ≤ 20.

[0041] In some embodiments, w 1may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%, or may be within the range consisting of any two of the above numerical values, but is not limited thereto. For example, 10% ≤ w 1 ≤ 50% or 15% ≤ w 1 ≤ 50%.

[0042] In some embodiments, w 2 may be 2%, 4%, 6%, 8%, 10% or 12%, or may be within the range consisting of any two of the above numerical values, but is not limited thereto. For example, 4% ≤ w 2 ≤ 12% or 4% ≤ w 2 ≤ 10%.

[0043] In some embodiments, w 1 / w 2 may be 2, 4, 6, 8, 10, 12, 14, 16, 18 or 20, or may be within the range consisting of any two of the above numerical values, but is not limited thereto. For example, 4 ≤ w 1 / w 2 ≤ 16 or 4 ≤ w 1 / w 2 ≤ 10.

[0044] In some embodiments, the carboxylic acid ester compound is a carboxylic acid ester compound represented by the following formula (I),

Chemical formula

[0045] In some embodiments, the carboxylic acid ester compound represented by formula (I) contains at least one of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, n-amyl propionate, isoamyl propionate, ethyl n-butyrate, n-propyl n-butyrate, propyl isobutyrate, n-amyl n-butyrate, isoamyl n-butyrate, n-butyl n-butyrate, isobutyl isobutyrate, and n-amyl n-valerate.

[0046] In some embodiments, the carboxylic acid ester compound represented by formula (I) contains at least propyl propionate. Compared with other carboxylic acid ester compounds, propyl propionate is advantageous for stabilizing the structure of the positive electrode, so it can improve the rapid charging characteristics of the electrochemical device, improve the high-temperature ITC characteristics, and suppress the generation of gas, thereby improving the overall characteristics of the electrochemical device.

[0047] In some embodiments, the carboxylic acid ester compound represented by formula (I) contains ethyl propionate and ethyl acetate. In some embodiments, the carboxylic acid ester compound represented by formula (I) contains propyl propionate and ethyl acetate. In some embodiments, the carboxylic acid ester compound represented by formula (I) contains propyl propionate and ethyl propionate. In some embodiments, the carboxylic acid ester compound represented by formula (I) contains ethyl acetate, ethyl propionate, and propyl propionate.

[0048] In some embodiments, the electrolyte further contains a nitrile compound. The nitrile compound contains a cyano group (-CN) functional group. In some embodiments, based on the total weight of the electrolyte, the content of the nitrile compound is w 3 When it is set as, 0.1% ≤ w 3 ≤ 12%. In some embodiments, w 3It may be 0.1%, 1%, 2%, 4%, 6%, 8%, 10% or 12%, or may be within the range consisting of any two of the above numerical values, but is not limited thereto. When the content of the nitrile compound is within the above range, while considering the rapid charging characteristics of the electrochemical device, the high-temperature ITC characteristics of the electrochemical device can be improved, and the generation of gas can be suppressed. This is because the nitrile compound forms a nitrile protective film having excellent characteristics on the surface of the positive electrode, stabilizes the active metal in the positive electrode active material well, suppresses the elution of the active metal, and reduces the oxygen evolution reaction.

[0049] In some embodiments, the nitrile compound includes at least one of the compounds represented by Formula (II) to Formula (V),

Chemical formula

[0050] In some embodiments, the nitrile compound includes at least one of adiponitrile, succinonitrile, glutaronitrile, malononitrile, 2-methylglutaronitrile, pimelonitrile, sebaconitrile, azelaonitrile, 1,4-dicyano-2-butene, ethylene glycol bis(propionitrile) ether, 3,3'-oxydipropionitrile, thiodipropionitrile, 2-hexenedinitrile, butenedinitrile, 2-pentenedinitrile, ethyl succinonitrile, 3-hexenedinitrile, 2-methyleneglutaronitrile, 4-cyanopimelonitrile, 1,3,6-hexanetricarbonitrile, 1,3,5-hexanetricarbonitrile, 1,2,3-propanetricarbonitrile, and 1,2,3-tris(2-cyanoethoxy)propane.

[0051] The present invention evaluated the influence of the cyano group content ratio on the electrochemical properties. Here, the cyano group content ratio is the ratio of the total molar amount x of cyano groups (-CN) in the nitrile compound to the total molar amount y of the nitrile compound. The present invention found that, compared to adding a single nitrile compound, such as a dinitrile compound (i.e., x / y = 2) or a trinitrile compound (i.e., x / y = 3), to the electrolytic solution, when the cyano group content ratio x / y satisfies 2.16 ≤ x / y ≤ 2.71, the high-temperature ITC characteristics of the electrochemical device can be significantly improved, the generation of gas can be suppressed, and the adverse effect of the nitrile compound on the rapid charging characteristics of the electrochemical device can be greatly reduced, that is, the rapid charging characteristics and the high-temperature ITC characteristics can be improved simultaneously. It is speculated that this is because, compared to a thick SEI film composed of a polymer nitrile compound with a large number of cyano groups (e.g., a trinitrile compound) and an unstable SEI film composed of a small molecule nitrile compound with a small number of cyano groups (e.g., a dinitrile compound), by adding a plurality of nitrile compounds having different numbers of cyano groups to the electrolytic solution, a nitrile-containing SEI film in which a polymer and a small molecule are combined can be simultaneously formed on the surface of the positive electrode, thereby achieving a more excellent effect.

[0052] In addition, the present invention further examined the relationship between the content w of the carboxylic acid ester compound 1 , the content w of fluoroethylene carbonate 2 and the cyano group content ratio x / y. Specifically, the curve indicated by the solid dots in FIG. 1 is x / y = 2w 1 2 - 0.01w 1 + 2.3, while the curve indicated by the square dots in FIG. 2 is x / y = 27w 2 2 - 1.2w 2 + 2.1. Through research, it was found that when the cyano group content ratio x / y > 2w 1 2 - 0.01w 1 + 2.3, the concentration of the cyano group increases, which improves the viscosity of the electrolyte to a certain extent and inhibits the transport of lithium ions and the intercalation and deintercalation of lithium ions in the positive and negative electrode active materials. As a result, it was found that the probability of lithium ions depositing on the positive and negative electrodes to form lithium dendrites increases. And when the cyano group content ratio x / y < 27w 2 2 - 1.2w 2 + 2.1, the concentration of the cyano group decreases, so the structural stability of the SEI film formed on the positive electrode active surface is slightly inferior, and as a result, it was found that the probability of swelling due to gas generation increases.

[0053] Therefore, the relationship between the content w of the carboxylic acid ester compound 1 , the content w of fluoroethylene carbonate 2 and the cyano group content ratio x / y is 2w 1 2 - 0.01w 1 + 2.3 > x / y > 27w 2 2 - 1.2w 2When it satisfies +2.1, the viscosity of the electrolyte can be maintained within a more appropriate range, the transport of lithium ions in the electrolyte can be improved, and the rapid charging characteristics of the electrochemical device can be improved by significantly reducing the risk of lithium precipitation. Moreover, the complexation protection of the nitrile-based compound for the transition metal in the positive electrode active material can be strengthened, the oxygen evolution of the positive electrode under the operating conditions of high-temperature intermittent cycles can be reduced, and the high-temperature ITC characteristics of the electrochemical device can be improved by improving the structural stability of the positive electrode, and the generation of gas can be suppressed. That is, the electrochemical device is 2w 1 2 -0.01w 1 +2.3 > x / y > 27w 2 2 -1.2w 2 When it satisfies +2.1, the rapid charging characteristics and high-temperature ITC characteristics of the electrochemical device can be improved simultaneously, and the generation of gas can be suppressed.

[0054] In some embodiments, the electrolyte according to the present invention further contains a lithium salt. Examples of the lithium salt are LiPF 6 、LiBF 4 、LiClO 4 、LiAlF 4 、LiSbF 6 、LiWF 7 and other inorganic lithium salts such as LiWOF 5 ; lithium tungstate-based such as HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF2 CF 2 CO 2 Lithium carboxylate salts such as Li; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3 CF 2 CF 2 SO 3 Li, CF 3 CF 2 CF 2 CF 2 SO 3 Lithium sulfonate salts such as Li; LiN(FCO) 2 , LiN(FCO)(FSO 2 ), LiN(FSO 2 ) 2 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , Lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, imide lithium salts such as LiN(CF 3 SO 2 )(C 4 F 9 SO 2 ); LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3Lithium methylation salts such as; lithium (malonate) borate salts such as lithium bis(malonate) borate and lithium difluoro(malonate) borate; lithium (malonate) phosphate salts such as lithium tris(malonate) phosphate, lithium difluorobis(malonate) phosphate, and lithium tetrafluoro(malonate) phosphate; and LiPF 4 (CF 3 ) 2 、LiPF 4 (C 2 F 5 ) 2 、LiPF 4 (CF 3 SO 2 ) 2 、LiPF 4 (C 2 F 5 SO 2 ) 2 、LiBF 3 CF 3 、LiBF 3 C 2 F 5 、LiBF 3 C 3 F 7 、LiBF 2 (CF 3 ) 2 、LiBF 2 (C 2 F 5 ) 2 、LiBF 2 (CF 3 SO 2 ) 2 、LiBF 2 (C 2 F 5 SO 2 ) 2 Fluorine-containing organic lithium salt systems such as; lithium oxalate borate salt systems such as lithium difluoro(oxalate) borate and lithium bis(oxalate) borate; oxalate phosphate lithium salt systems such as lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, and lithium tris(oxalate) phosphate may be included, but are not limited thereto.

[0055] In some embodiments, the lithium salt is LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiSiF 6 , and includes at least one of LiBOB and LiDFOB.

[0056] In some embodiments, based on the total weight of the electrolyte, the lithium salt content is 0.01 wt% - 20 wt%, 0.01 wt% - 10 wt%, 0.01 wt% - 5 wt%, 0.01 wt% - 3 wt%, 0.1 wt% - 20 wt%, 0.1 wt% - 10 wt%, 0.1 wt% - 5 wt%, 0.1 wt% - 3 wt%, 1 wt% - 20 wt%, 1 wt% - 10 wt%, 1 wt% - 5 wt%, or 1 wt% - 3 wt%.

[0057] In some embodiments, the electrolyte further includes any of the non-aqueous solvents used as solvents for electrolytes known in the prior art.

[0058] In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0059] In some embodiments, examples of the cyclic carbonate may include, but are not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonate has 3 to 6 carbon atoms.

[0060] In some embodiments, examples of the linear carbonate may include, but are not limited to, one or more of linear carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, etc. Examples of the linear carbonate substituted with fluorine may include, but are not limited to, one or more of bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, and 2,2,2-trifluoroethyl methyl carbonate.

[0061] In some embodiments, examples of the cyclic ether may include, but are not limited to, one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0062] In some embodiments, examples of the linear ether may include, but are not limited to, one or more of dimethoxyethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxyethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane.

[0063] In some embodiments, examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of trimethyl phosphate, triethyl phosphate, dimethylethyl phosphate, methyldiethyl phosphate, methylethylene phosphate, ethylethylene phosphate, triphenyl phosphate, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,3,3,3-pentafluoropropyl) phosphate.

[0064] In some embodiments, examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, and ethyl ethanesulfonate. In some embodiments, some of the hydrogen atoms in the sulfur-containing organic solvent may be substituted with fluorine.

[0065] In some embodiments, the aromatic fluorine-containing solvent includes, but is not limited to, one or more of fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0066] II. Positive Electrode The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material. The positive electrode active material layer may be a single layer or multiple layers. Each layer of the multiple layers of positive electrode active materials may contain the same or different positive electrode active materials. The positive electrode active material is any material that can reversibly occlude and release metal ions such as lithium ions.

[0067] The type of the positive electrode active material is not limited, and any material that can electrochemically occlude and release metal ions (e.g., lithium ions) may be used. In some embodiments, the positive electrode active material contains lithium and at least one transition metal. Examples of the positive electrode active material may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

[0068] In some embodiments, the transition metals in the lithium transition metal composite oxide include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some embodiments, the lithium transition metal composite oxide is 2 such as lithium cobalt composite oxide like LiCoO 2 such as lithium nickel composite oxide like LiNiO 2 , LiMnO 2 O 4 , Li 2 MnO 4 such as lithium manganese composite oxide like Li 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 such as lithium nickel manganese cobalt composite oxide, and a part of the transition metal atoms that are the main body of these lithium transition metal composite oxides are substituted with other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W. Examples of the lithium transition metal composite oxide are LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 etc. may be included, but are not limited thereto. Examples of combinations of lithium transition metal composite oxides are LiCoO 2 and LiMn 2 O 4 and combinations thereof, but are not limited thereto. A part of Mn in LiMn 2 O 4 may be substituted with a transition metal (for example, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), and a part of Co in LiCoO 2 may be substituted with a transition metal.

[0069] In some embodiments, the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some embodiments, the lithium-containing transition metal phosphate compound includes iron phosphate-based compounds such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 , etc., and cobalt phosphate-based compounds such as LiCoPO 4 . A part of the transition metal atoms that are the main body of these lithium transition metal phosphate compounds is substituted with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.

[0070] A substance different from the composition of the positive electrode active material may be adhered to the surface of the positive electrode active material. Examples of substances adhered to the surface include oxides such as aluminum oxide, silica, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, magnesium carbonate; carbon, etc., but are not limited thereto. By adhering a substance to the surface of the positive electrode active material, the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material can be suppressed, and the life of the electrochemical device can be improved. If the amount of the substance adhered to the surface is too small, the effect cannot be fully exerted. However, if the amount of the substance adhered to the surface is too large, the entry and exit of lithium ions may be inhibited, resulting in an increase in resistance. In the present invention, a positive electrode active material having a substance different from its composition adhered to the surface of the positive electrode active material is also referred to as a "positive electrode active material".

[0071] In some embodiments, it is preferable to use lithium cobaltate or lithium nickel cobalt manganese oxide as the "positive electrode active material".

[0072] In some embodiments, the shape of the positive electrode active material particles includes, but is not limited to, massive, polyhedral, spherical, ellipsoidal, plate-like, needle-like, columnar, etc. In some embodiments, the positive electrode active material particles include primary particles, secondary particles, or a combination thereof. In some embodiments, the primary particles may aggregate to form secondary particles.

[0073] The positive electrode further includes a positive electrode conductive material in order to improve the conductivity of the positive electrode. The type of the positive electrode conductive material is not limited, and any known conductive material may be used. Examples of the positive electrode conductive material include carbon materials such as graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; amorphous carbon such as needle coke; carbon nanotubes; graphene, etc., but are not limited thereto. The positive electrode conductive material may be used alone or in any combination.

[0074] The type of solvent for forming the positive electrode slurry is not limited, and any solvent that can dissolve or disperse the positive electrode active material, conductive material, positive electrode binder, and thickener used as required may be used. Examples of the solvent for forming the positive electrode slurry may include any one of aqueous solvents and organic solvents. Examples of aqueous solvents may include, but are not limited to, water and a mixed solvent of alcohol and water. Examples of organic solvents include aliphatic hydrocarbon-based such as hexane; aromatic hydrocarbon-based such as benzene, toluene, xylene, methylnaphthalene; heterocyclic compounds such as quinoline, pyridine; ketone-based such as acetone, methyl ethyl ketone, cyclohexanone; ester-based such as methyl acetate, methyl acrylate; amine-based such as diethylenetriamine, N,N-dimethylaminopropylamine; ether-based such as diethyl ether, propylene oxide, tetrahydrofuran (THF); amide-based such as N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide, dimethyl sulfoxide, etc., but are not limited thereto.

[0075] The thickener is generally used to adjust the viscosity of the slurry. When using an aqueous solvent, the slurry may be formed using a thickener and a styrene-butadiene rubber (SBR) emulsion. The type of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. The thickener may be used alone or in any combination.

[0076] The type of the positive electrode current collector is not particularly limited, and it may be any of the materials suitably used as known positive electrode current collectors. Examples of the positive electrode current collector may include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper, but are not limited thereto. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum.

[0077] In order to reduce the electrical contact resistance between the positive electrode current collector and the positive electrode active material layer, the surface of the positive electrode current collector may contain a conductive assistant. Examples of the conductive assistant may include carbon and noble metals such as gold, platinum, and silver, but are not limited thereto.

[0078] The positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be carried out by a conventional method. That is, the positive electrode active material, the binder, and, if necessary, a conductive material, a thickener, etc. are dry-mixed, formed into a sheet shape, and the obtained sheet-like material is pressure-bonded to the positive electrode current collector, or these materials are dissolved or dispersed in a liquid solvent to form a slurry, and this slurry is applied to the positive electrode current collector and dried to form a positive electrode active material layer on the current collector, thereby obtaining a positive electrode.

[0079] In some embodiments, when the weight fraction of the positive electrode active material is M% based on the total weight of the positive electrode active material layer, 90 ≦ M ≦ 99.5. In some embodiments, 95 ≦ M ≦ 99. In some embodiments, M may be 90, 92, 94, 95, 96, 97, 98, or 99, or may be within the range consisting of any two of the above numerical values. When the weight fraction of the positive electrode active material in the positive electrode active material layer satisfies the above relationship, the energy density of the electrochemical device can be significantly improved.

[0080] III. Negative Electrode The negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer may be a single layer or multiple layers. Each layer of the multiple layers of negative electrode active materials may contain the same or different negative electrode active materials. The negative electrode active material is any material that can reversibly occlude and release metal ions such as lithium ions. In some embodiments, the chargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material in order to prevent lithium metal from being deposited unintentionally on the negative electrode during charging.

[0081] As the current collector for holding the negative electrode active material, any known current collector may be arbitrarily used. Examples of the negative electrode current collector include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.

[0082] When the negative electrode current collector is a metal material, the form of the negative electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal strip coil, metal plate, metal film, expanded metal, punched metal, foamed metal, etc. In some embodiments, the negative electrode current collector is a metal film. In some embodiments, the negative electrode current collector is a copper foil. In some embodiments, the negative electrode current collector is a rolled copper foil by rolling method or an electrolytic copper foil by electrolysis method.

[0083] In some embodiments, the thickness of the negative electrode current collector is greater than 1 μm or greater than 5 μm. In some embodiments, the thickness of the negative electrode current collector is less than 100 μm or less than 50 μm. In some embodiments, the thickness of the negative electrode current collector is within the range consisting of any two of the above numerical values.

[0084] The anode active material is not limited, as long as it can reversibly occlude and release lithium ions. Examples of the anode active material may include carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn, etc., but are not limited thereto. The anode active material may be used alone or in any combination.

[0085] The anode active material layer may further contain an anode binder. The anode binder can improve the bonding between the anode active material particles and the bonding between the anode active material and the current collector. The type of the anode binder is not limited, as long as it is a material stable to the electrolyte or the solvent used during the manufacture of the electrode. In some embodiments, the anode binder includes a resin binder. Examples of the resin binder include, but are not limited to, fluororesin, polyacrylonitrile (PAN), polyimide resin, acrylic acid-based resin, polyolefin resin, etc. When preparing a slurry of the anode mixture using an aqueous solvent, the anode binder may include, but is not limited to, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salts, polyvinyl alcohol, etc.

[0086] The anode can be manufactured by the following method. After applying and drying a slurry of an anode mixture containing an anode active material, a resin binder, etc. on an anode current collector, and then rolling to form anode active material layers on both sides of the anode current collector, an anode can be obtained.

[0087] IV. Separator Generally, a separator is installed between the positive electrode and the negative electrode to prevent short circuit. In this case, the electrolyte of the present invention generally penetrates into this separator and is used.

[0088] The material and shape of the separator are not limited, as long as the effects of the present invention are not significantly impaired. The separator may be resin, glass fiber, an inorganic substance, etc. formed of a material stable to the electrolytic solution of the present invention. In some embodiments, the separator includes a porous sheet or a non-woven fabric form having excellent liquid retention properties. Examples of the material of the separator made of resin or glass fiber include, but are not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, etc. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above materials of the separator may be used alone or in any combination.

[0089] The separator may be a material formed by laminating the above materials, and examples thereof include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in this order.

[0090] Examples of the material of the inorganic substance may include, but are not limited to, oxides such as aluminum oxide and silica, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). The form of the inorganic substance may include, but is not limited to, particulate or fibrous forms.

[0091] The form of the separator may be a film form, and examples thereof include, but are not limited to, non-woven fabric, woven fabric, microporous membrane, etc. When the separator is in a film form, the pore diameter is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above independent film-like separator, a separator formed by forming a composite porous layer containing the above inorganic particles on the surface of the positive electrode and / or negative electrode using a resin-based binder may be used. For example, a separator formed by using a fluororesin as a binder and forming a porous layer on both sides of the positive electrode with aluminum oxide particles having a particle diameter of less than 1 μm accounting for 90% may be used.

[0092] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. In some embodiments, the thickness of the separator is within the range consisting of any two of the above values. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and the rate characteristics and energy density of the electrochemical device can be ensured.

[0093] When a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is arbitrary. In some embodiments, the porosity of the separator is greater than 10%, greater than 15%, or greater than 20%. In some embodiments, the porosity of the separator is less than 60%, less than 50%, or less than 45%. In some embodiments, the porosity of the separator is within the range consisting of any two of the above values. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, the sheet resistance can be suppressed, and the electrochemical device can be given good safety characteristics.

[0094] The average pore diameter of the separator is also arbitrary. In some embodiments, the average pore diameter of the separator is less than 0.5 μm or less than 0.2 μm. In some embodiments, the average pore diameter of the separator is greater than 0.05 μm. In some embodiments, the average pore diameter of the separator is within the range consisting of any two of the above values. When the average pore diameter of the separator exceeds the above range, short circuits are likely to occur. When the average pore diameter of the separator is within the above range, the electrochemical device can be given good safety characteristics.

[0095] V. Electrochemical device The electrochemical device according to the present invention includes any device in which an electrochemical reaction occurs, and specific examples thereof include a lithium metal secondary battery or a lithium ion secondary battery. The electrochemical device according to the present invention includes the electrolyte described in the above embodiments. In some embodiments, the electrochemical device according to the present invention further includes a positive electrode, a negative electrode, and a separator positioned between the positive electrode and the negative electrode.

[0096] Considering the design space secured for the electrochemical device in a notebook computer, the electrochemical device generally tends to have an elongated shape. In an elongated battery, due to the non-uniform distribution of current and the non-uniform formation of the SEI film, lithium precipitation is likely to occur at the upper and lower edge portions during charging at normal temperature or low temperature, leading to capacity decay. In addition, the precipitated lithium dendrites may break through the separator positioned between the positive and negative electrodes, short-circuiting the battery and causing safety problems.

[0097] In some embodiments, a cell is formed by winding the positive electrode, the negative electrode, and the separator. In some embodiments, a cell is formed by laminating the positive electrode, the negative electrode, and the separator.

[0098] The present invention has found that by adjusting the size of the cell, the charging rate window of the electrochemical device can be improved, lithium precipitation can be improved, and thereby the rapid charging characteristics of the electrochemical device can be improved.

[0099] In some embodiments, the length L and width W of the cell satisfy 20 mm ≤ L ≤ 300 mm, 20 mm ≤ W ≤ 100 mm, and 1 ≤ L / W ≤ 4. In some embodiments, the length L of the cell may be 20 mm, 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 175 mm, 200 mm, 225 mm, 250 mm, 275 mm, or 300 mm, or may be within a range consisting of any two of the above numerical values, but is not limited thereto. In some embodiments, the width W of the cell may be 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, or 100 mm, or may be within a range consisting of any two of the above numerical values, but is not limited thereto. In some embodiments, the aspect ratio L / W of the cell may be 1, 2, 3, or 4, or may be within a range consisting of any two of the above numerical values, but is not limited thereto.

[0100] In some embodiments, the thickness T of the cell satisfies 2 mm ≤ T ≤ 12 mm. In some embodiments, the thickness T of the cell may be 2, 4, 6, 8, 10, or 12, or may be within a range consisting of any two of the above numerical values, but is not limited thereto. In some embodiments, the ratio W / T of the width to the thickness of the cell satisfies W / T ≥ 5. In some embodiments, the ratio W / T of the width to the thickness of the cell satisfies W / T ≤ 25. In some embodiments, W / T may be 5, 10, 15, 20, or 25, or may be within a range consisting of any two of the above numerical values, but is not limited thereto.

[0101] In some embodiments, by designing the size of the battery and optimizing the content of the carboxylic acid ester compound in the electrolyte, the charging rate window of the electrochemical device can be further improved, lithium precipitation can be improved, and thereby the rapid charging characteristics of the electrochemical device can be further improved. In some embodiments, the length L and width W of the cell, and the content w of the carboxylic acid ester compound represented by formula (I) 1 is w 1It satisfies 100×(L / W) ≥ 10. In some embodiments, the length L and width W of the cell, and the content w of the carboxylic acid ester compound represented by formula (I) 1 is w 1 It satisfies 100×(L / W) ≤ 40. In some embodiments, w 1 100×(L / W) may be 10, 15, 20, 25, 30, 35 or 40, or may be within the range consisting of any two of the above numerical values, but is not limited thereto.

[0102] VI. Electronic device The present invention further provides an electronic device including the electrochemical device described in the present invention. The use of the electrochemical device of the present invention is not particularly limited, and it may be used in any of the electronic devices known in the prior art. In some embodiments, the electrochemical device according to the present invention is a notebook computer, a pen input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disk, a transceiver, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an auxiliary bicycle, a bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a flashlight, a camera, a large household storage battery, and a lithium ion capacitor, etc., but is not limited thereto. Examples

[0103] Hereinafter, taking a lithium ion battery as an example, the preparation of a lithium ion battery will be described with reference to specific examples. Those skilled in the art should understand that the preparation method described in the present invention is merely an example, and any other suitable preparation method is within the scope of the present invention.

[0104] (I) Preparation of lithium ion battery (1) Preparation of positive electrode Lithium cobaltate (LiCoO as the positive electrode active material 2) Super P, which is a conductive agent, and polyvinylidene fluoride, which is a binder, were mixed at a weight ratio of 97:1:2. N-methylpyrrolidone (NMP) was added and uniformly stirred by a vacuum stirrer to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on an aluminum foil, which is a positive electrode current collector. The aluminum foil was dried, and after cold rolling, cutting, and slitting, it was dried under vacuum conditions to obtain a positive electrode sheet.

[0105] (2) Preparation of negative electrode Artificial graphite, which is a negative electrode active material, sodium carboxymethyl cellulose (CMC), which is a thickener, and styrene-butadiene rubber (SBR), which is a binder, were mixed at a weight ratio of 97:1:2. Deionized water was added and a negative electrode slurry was obtained by vacuum stirring. The negative electrode slurry was uniformly coated on a copper foil, which is a negative electrode current collector. The copper foil was dried, and after cold rolling, cutting, and slitting, it was dried under vacuum conditions to obtain a negative electrode sheet.

[0106] (3) Preparation of electrolyte In a glove box with a dried argon gas atmosphere, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed at a weight ratio of 1:3:6, and LiPF 6 was added and uniformly mixed to form a base electrolyte. Here, the concentration of LiPF 6 was 1.2 mol / L. Additives were added to the base electrolyte as needed to obtain the electrolytes in the examples and comparative examples of the present invention. The specific types and contents of the additives are shown in Table 1-3 below.

[0107] (4) Preparation of separator Boehmite was mixed with polyacrylate and dissolved in deionized water to form a slurry of the coating layer. Then, the slurry of the coating layer was uniformly coated on both surfaces of a polyethylene porous substrate by a microgravure coating method, and after a drying treatment, a required separator was obtained.

[0108] (5) Preparation of lithium-ion battery The positive electrode, separator, and negative electrode were stacked in this order and wound to obtain a cell so that the separator was interposed between the positive and negative electrodes to play a role of isolation. After welding the tabs, the cell was placed in an aluminum plastic film which is an exterior foil, leaving a liquid injection port. The electrolyte prepared above was injected into the dried cell through the liquid injection port, and a lithium-ion battery was obtained through processes such as vacuum packaging, standing, formation, shaping, and capacity measurement.

[0109] (II), Measurement method 1. Measurement method for electrolyte components and contents The battery was discharged at a constant current of 0.1C to 2.8V, and the weight of the battery was weighed and designated as m. Then, the battery was disassembled, and the immediately obtained cell and the aluminum plastic film which is the exterior foil were put into high-purity acetonitrile (purity ≥ 99.9%) for extraction. The obtained clear liquid was measured by gas chromatography to obtain each component and its relative content p in the electrolyte. The cell and the aluminum plastic which is the exterior foil after extraction were dried in a vacuum oven, and the total weight was weighed and designated as m'. The weight n of the electrolyte was n = m - m'. The weight of each component in the battery was taken as the product of n and the relative content p of each component.

[0110] 2. Calculation method for the cyano group content ratio The cyano group content ratio was calculated using the following formula. [Number] Here, n1, n2, …… nx represent the mass (g) of different nitrile compounds, p1, p2, …… px represent the relative content (%) of different nitrile compounds, M1, M2, …… Mx represent the relative molar mass (g / mol) of different nitrile compounds, ε1, ε2, …… εx represent the number of cyano groups of different nitrile compounds.

[0111] 3. Measurement method for the size of the cell The outer aluminum plastic film was disassembled and removed to obtain the cell. As shown in Figure 4, the length L, width W, and thickness T of the cell were measured with a micrometer respectively.

[0112] 4. Measurement of the rapid charging characteristics of the lithium-ion battery The lithium-ion batteries were divided into 3 groups, and charge-discharge cycle tests were performed at currents of 0.7C, 1.5C, and 3C respectively. Here, there were 10 lithium-ion batteries per group. The lithium-ion batteries were left standing at 25 °C for 30 minutes, then charged to a voltage of 4.5V at 0.7C, 1.5C, and 3C respectively, charged at a constant voltage up to 0.05C, and then discharged at a constant current to 3.0V at 0.7C, 1.5C, and 3C respectively. According to the above process, charge-discharge was performed 250 cycles. The initial discharge capacity of each lithium-ion battery was recorded, and the average value was taken for the batteries within the group and designated as C1. The discharge capacity of each lithium-ion battery after 250 cycles was recorded, and the average value was taken for the batteries within the group and designated as C250. The cycle capacity retention rate of the lithium-ion battery at 0.7C, 1.5C, and 3C was calculated using the following formula. Cycle capacity retention rate = (C250 / C1)×100%

[0113] 5. Measurement of the high-temperature interval cycle (ITC) of the lithium-ion battery The lithium-ion battery was placed in an incubator at 45 °C and left standing for 30 minutes. Then, the lithium-ion battery was discharged to 3.0V at a current of 0.5C, and then charged to 4.5V at a current of 1C, and left standing for 24 hours. This was regarded as one cycle of charge-discharge cycle. According to the above process, charge-discharge was performed 50 cycles. The initial discharge capacity and the discharge capacity after 50 cycles were recorded, designated as C and C' respectively, and the cycle capacity retention rate of the lithium-ion battery was calculated using the following formula. Cycle capacity retention rate = (C' / C)×100% At the same time, the initial thickness η and the thickness η' after 50 cycles of the lithium-ion battery were measured with a micrometer. The thickness increase rate of the lithium-ion battery was calculated using the following formula. Thickness increase rate = (η' / η - 1) × 100%

[0114] (III) Measurement results Table 1 shows the effects of the contents of carboxylic acid ester compounds and FEC in the electrolyte and their ratios on the rapid charging characteristics and high-temperature ITC characteristics of lithium-ion batteries.

[0115]

Table 1

[0116] From the electrochemical measurement results in Table 1, it can be seen that by adding carboxylic acid ester compounds and FEC to the electrolyte and adjusting them so that their contents and the ratio of the two satisfy 5% ≤ w 1 ≤ 60%, 2% ≤ w 2 ≤ 12%, and 2 ≤ w 1 / w 2 ≤ 20, it is possible to improve the rapid charging characteristics of the electrochemical device without deteriorating or only slightly deteriorating the high-temperature ITC characteristics of the electrochemical device.

[0117] From Comparative Examples 1-1 to 1-3, it can be seen that by adding FEC alone to the electrolyte and setting its content within an appropriate range, the rapid charging characteristics of the electrochemical device can be improved to a certain extent. However, if the content of FEC is too high (for example, more than 12%), the generation of gas deteriorates, and the thickness of the battery during the high-temperature interval cycle clearly increases. Also, when the content of FEC is too high, the rapid charging characteristics of the electrochemical device at high currents (for example, 1.5C and 3C) deteriorate rather than improve. This is because an appropriate amount of FEC can effectively alleviate the destruction of the negative electrode SEI film during charge and discharge of the battery and can repair it in a timely manner, thereby improving the overcharge characteristics. However, when the content of FEC is too high, it is easy to form an overly thick SEI film, and the progress of the film-forming reaction also leads to lithium precipitation in the cell. As a result, it causes a rapid attenuation of the battery capacity. Also, when the content of FEC is too high, under the intermittent cycle operating conditions of ITC, the structure of the positive electrode is destroyed, an oxygen evolution reaction occurs, and FEC is oxidized to CO 2 is generated, and as a result, swelling due to gas generation in the battery occurs.

[0118] Comparative Examples 1-4 to 1-6 further added a chain carboxylic acid ester compound to the electrolyte compared to Comparative Example 1-1, so the rapid charging characteristics of the electrochemical device were improved, especially the rapid charging characteristics at high currents (for example, 1.5C and 3C) were clearly improved. Ethyl propionate and propyl propionate improve the rapid charging characteristics compared to ethyl acetate and do not substantially deteriorate the high-temperature ITC characteristics, and may even improve the high-temperature ITC characteristics.

[0119] Comparing Examples 1-1 to 1-4 with Comparative Examples 1-5, 1-7 to 1-9, the content of the carboxylic acid ester compound and FEC and the ratio of the two are 5% ≤ w 1 ≤ 60%, 2% ≤ w 2 ≤ 12%, and 2 ≤ w 1 / w 2When ≤20 is satisfied, it can be seen that the high-temperature ITC characteristics of the electrochemical device are not deteriorated or only slightly deteriorated, and the rapid charging characteristics of the electrochemical device can be improved. Comparing Examples 1-5 and 1-6 with Comparative Example 1-5, furthermore, w 1 / w 2 is adjusted so that it is in the range of 4 ≤ w 1 / w 2 ≤ 10, it can be seen that not only the rapid charging characteristics of the electrochemical device can be improved, but also the high-temperature ITC characteristics can be improved. Comparing Examples 1-7 and 1-8 with Comparative Examples 1-4 and 1-10, or comparing Examples 1-9 to 1-11 with Comparative Example 1-6, it can be seen that the same conclusion can be obtained.

[0120] Examples 1-12 to 1-15 use a combination of a plurality of carboxylic acid ester compounds. When 5% ≤ w 1 ≤ 60%, 2% ≤ w 2 ≤ 12%, and 2 ≤ w 1 / w 2 ≤ 20 are satisfied, the rapid charging characteristics and the high-temperature ITC characteristics can be improved simultaneously. For example, by adding propyl propionate and ethyl propionate to the electrolyte at the same time, excellent high-temperature ITC characteristics can be maintained, and the rapid charging characteristics can be improved more efficiently.

[0121] Table 2 shows the influence of the cyano group content, as well as the content of carboxylic acid ester and FEC in the electrolyte, on the rapid charging characteristics and high-temperature ITC characteristics of the lithium-ion battery. The examples in Table 2 are improved based on Example 1-14, and their difference is specifically that a nitrile-based compound is added to the electrolyte.

[0122] From the results of the characteristic measurements in Table 2, it can be seen that by further adding an appropriate amount of nitrile-based compound to the electrolyte, the high-temperature ITC characteristics can be improved on the premise that the rapid charging characteristics of the electrochemical device are not deteriorated or only slightly deteriorated.

[0123] Examples 2-1 to 2-8, compared with Example 1-14, added a single nitrile-based compound to the electrolytic solution, thereby slightly deteriorating the rapid charging characteristics of the electrochemical device, but significantly improving the high-temperature ITC characteristics. However, when a single nitrile-based compound is added in excess, the viscosity of the electrolytic solution increases to a certain extent. As a result, lithium ions cannot be released in a timely manner, and lithium precipitates, which has a certain adverse effect on the high-temperature ITC characteristics.

[0124] Examples 2-9 to 2-29 added a plurality of nitrile-based compounds to the electrolytic solution compared with Example 1-14. As shown in Examples 2-9 to 2-17, when the addition amount of the nitrile-based compound is constant, when the cyano group content ratio x / y satisfies 2.16 ≤ x / y ≤ 2.71, the rapid charging characteristics of the electrochemical device can be effectively improved without substantially deteriorating, and the high-temperature ITC characteristics can be effectively improved.

[0125] Furthermore, from the data in Table 2, when the cyano group content ratio x / y satisfies 2.16 ≤ x / y ≤ 2.71 and the content w of the nitrile-based compound 3 is controlled within the range of 0.1% ≤ w 3 ≤ 12%, it can be seen that the improvement effect of the high-temperature ITC characteristics by the addition of a single nitrile-based compound can be exceeded, and the adverse effect of the single nitrile-based compound on the rapid charging characteristics can be effectively alleviated.

[0126] At the same time, Examples 2-26 to 2-29 show that on the premise that the cyano group content ratio satisfies the above range, the total amount of the nitrile-based compound should not be too much or too little. However, from the comparison with Examples 2-19 and 2-25, it can be seen that when the cyano group content ratio x / y satisfies 2.16 ≤ x / y ≤ 2.71, the upper limit of the usage amount of a single nitrile-based compound can be exceeded, and the high-temperature ITC characteristics can be improved to the maximum extent.

[0127]

Table 2(1)

Table 2(2)

Table 2(3)

[0128] Table 3 shows the influence of the cell size and the content of carboxylic acid ester compound in the electrolyte on the high-temperature ITC characteristics of the lithium-ion battery. The examples in Table 3 are improved based on Examples 2-23, and their differences are specifically that the cell size and / or the content of carboxylic acid ester compound in the electrolyte are different.

[0129]

Table 3

[0130] From the measurement results in Table 3, by making the cell size and the content of carboxylic acid ester compound in the electrolyte conform to a certain relational expression, the charging rate window of the battery can be widened, lithium precipitation can be improved, and thereby, it can be understood that the rapid charging characteristics of the electrochemical device can be improved.

[0131] From Examples 3-1 to 3-12, when the electrolyte is not changed, by having the aspect ratio L / W in the range of 1 ≦ L / W ≦ 4 or the width-to-thickness ratio W / T in the range of W / T ≧ 5, the rapid charging characteristics of the electrochemical device can be improved. In particular, it can be understood that the rapid charging characteristics at a high-rate current of 1.5C or more can be significantly improved. This is mainly because when the cell is within the above range, the improvement in the current density and the temperature during charging in the upper and lower edge regions and the pole piece regions of the wound outer periphery is not much different from that in the main body region, so the lithium precipitation in the edge regions and the pole piece regions of the outer periphery is reduced, thereby improving the rapid charging characteristics.

[0132] From Examples 3-13 to 3-17, when the cell size does not change, the content of carboxylic acid ester compound in the electrolyte is w1 By adjusting to satisfy ×100 / (L / W)≥10, the rapid charging characteristics of the electrochemical device can be improved. In particular, it can be seen that the rapid charging characteristics at a high-rate current of 1.5C or more can be significantly improved. Although adding a carboxylic acid ester compound can improve the rapid charging characteristics of the electrochemical device, it has an adverse effect on the high-temperature ITC characteristics. Also, considering the size limitations of the electrochemical device applied to a notebook computer, designing the cell size and adjusting the carboxylic acid ester are regarded as effective measures to balance the dynamic characteristics and battery safety.

[0133] Throughout the specification, a reference by "Example", "Part of an example", "One example", "Another example", "Example", "Specific example", or "Part of an example" means that at least one example or instance of the present invention includes the specific features, structures, materials, or characteristics described in that example or instance. Thus, references throughout the specification, such as "In some examples", "In an example", "In one example", "In another example", "In one instance", "In a specific instance", or "Example" do not necessarily refer to the same example or instance in the present invention. Also, the specific features, structures, materials, or characteristics in this specification can be combined in any suitable manner in one or more examples or instances.

[0134] Exemplary examples have been disclosed and described, but those skilled in the art should understand that the above examples cannot be construed as limiting the present invention, and that the examples can be modified, substituted, and changed without departing from the technical idea, principle, and scope of the present invention.

Claims

1. An electrolytic solution, wherein the electrolytic solution contains a carboxylic acid ester compound represented by formula (I) and fluoroethylene carbonate (FEC), 【Chemical 1】 R １１ contains at least one of hydrogen, a hydroxyl group, a C1-C20 alkyl group, a C1-C20 alkoxy group, a C2-C20 chain alkenyl group, a C6-C30 aryl group, and a C6-C30 aryloxy group, R １２ includes at least one of a C1-C20 alkyl group, a C2-C20 chain alkenyl group, and a C6-C30 aryl group, Based on the total weight of the electrolytic solution, the content of the carboxylic acid ester compound represented by the formula (I) and the content of the fluoroethylene carbonate are w １ and w ２ respectively. When they are set as 5% ≤ w １ ≤ 60%, 2% ≤ w ２ ≤ 12%, and 2 ≤ w １ / w ２ ≤ 20, it is an electrolytic solution.

2. 4 ≤ w １ / w ２ ≤ 10, the electrolytic solution according to claim 1.

3. The electrolytic solution according to claim 1, wherein the carboxylic acid ester compound represented by formula (I) contains at least one of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, n-amyl propionate, isoamyl propionate, ethyl n-butyrate, n-propyl n-butyrate, propyl isobutyrate, n-amyl n-butyrate, isoamyl n-butyrate, n-butyl n-butyrate, isobutyl isobutyrate, and n-amyl n-valerate.

4. The electrolytic solution according to claim 1, wherein the carboxylic acid ester compound represented by formula (I) contains propyl propionate and ethyl acetate.

5. The electrolytic solution further contains a nitrile compound, Based on the total weight of the electrolytic solution, the content of the nitrile-based compound is w ３ When it is set as, 0.1% ≤ w ３ ≤ 12%, the electrolytic solution according to claim 1.

6. The nitrile compound contains at least one of the compounds represented by formula (II) to formula (V), [Chemical Formula 2] R ２１ contains at least one of a substituted or unsubstituted C1-C12 alkylene group and a substituted or unsubstituted C1-C12 alkyleneoxy group, R ３１ and R ３２ each independently contains hydrogen and at least one of substituted or unsubstituted C1-C12 alkylene groups R ４１ 、 R ４２ 、 R ４３ each independently contains at least one of hydrogen, a substituted or unsubstituted C1-C12 alkylene group, and a substituted or unsubstituted C1-C12 alkyleneoxy group, R ５１ contains at least one of a substituted or unsubstituted C1-C12 alkylene group, a substituted or unsubstituted C2-C12 alkenylene group, a substituted or unsubstituted C6-C26 arylene group, and a substituted or unsubstituted C2-C12 heterocyclylene group, and the heteroatom is at least one of N, S, and O. In the case of substitution, the substituent is halogen. The electrolytic solution according to claim 5.

7. When the total molar amount of the cyano group (—CN) in the nitrile compound is x and the total molar amount of the nitrile compound is y, the cyano group content ratio x / y satisfies 2.16 ≦ x / y ≦ 2.

71. The electrolytic solution according to claim 5.

8. The cyano group content ratio x / y, the content w of the carboxylic acid ester compound represented by the formula (I) １ and the content w of the fluoroethylene carbonate ２ is 2w １ ２ -0.01w １ +2.3 > x / y > 27w ２ ２ -1.2w ２ +2.1, and the electrolytic solution according to claim 7

9. The electrolytic solution contains a lithium salt, The lithium salt is LiPF ６ 、LiBF ４ 、LiAsF ６ 、LiClO ４ 、LiB(C ６ H ５ ) ４ 、LiCH ３ SO ３ 、LiCF ３ SO ３ 、LiN(SO ２ CF ３ ) ２ 、LiC(SO ２ CF ３ ) ３ 、LiSiF ６ 、The electrolytic solution according to claim 1, comprising at least one of LiBOB and LiDFOB.

10. An electrochemical device including the electrolytic solution according to any one of claims 1 to 9.

11. The electrochemical device further includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, The positive electrode, the negative electrode, and the separator are wound to form a cell, and the length L and width W of the cell satisfy 20 mm ≦ L ≦ 300 mm, 20 mm ≦ W ≦ 100 mm, and 1 ≦ L / W ≦ 4. The electrochemical device according to claim 10.

12. The electrochemical device, a) 1 ≦ L / W ≦ 3, b) 2 ≦ L / W ≦ 3, and c) 2 ≦ L / W ≦ 4 The electrochemical device according to claim 11, satisfying at least one of the above.

13. The electrochemical device further includes a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, The positive electrode, the negative electrode, and the separator are wound to form a cell, and the thickness T and width W of the cell satisfy 2 mm ≤ T ≤ 12 mm and W / T ≥ 5. The electrochemical device according to claim 10.

14. The electrochemical device is d) 5 ≤ W / T ≤ 25, e) 5 ≤ W / T ≤ 20, f) 5 ≤ W / T ≤ 15, and g) 10 ≤ W / T ≤ 25 The electrochemical device according to claim 13, satisfying at least one of the above.

15. The electrochemical device further includes a positive electrode, a negative electrode, and a separator positioned between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator are wound to form a cell, and the length L and width W of the cell, and the content w of the carboxylic acid ester compound represented by the formula (I) １ is such that w １ ×100 / (L / W) ≥ 10, and the electrochemical device according to claim 10

16. The electrochemical device is h) 10 ≤ w １ × 100 / (L / W) ≤ 40、 i) 20 ≤ w １ × 100 / (L / W) ≤ 30、 j) 20 ≤ w １ × 100 / (L / W) ≤ 40, and k) 15 ≤ w １ × 100 / (L / W) ≤ 30 The electrochemical device according to claim 15, satisfying at least one of the above.

17. An electronic device including the electrochemical device according to any one of claims 10 to 16.

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