JP2024032969A - Electrochemical and electronic devices - Google Patents

Abstract

An object of the present invention is to provide an electrochemical device and an electronic device that achieve both high rate characteristics and good safety. In one aspect of the present invention, an electrochemical device includes a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector. , the negative electrode mixture layer contains a negative electrode active material, the yield point elongation of the negative electrode mixture layer is X%, the median diameter of the negative electrode active material is Yμm, and X and Y are 0.1≦X. /Y≦30, the electrolytic solution contains a compound having a cyano group, the compound having a cyano group contains a dinitrile compound and a trinitrile compound having an ether bond, and the content of the dinitrile compound is based on the weight of the electrolytic solution. An electrochemical device in which the amount is greater than the content of a trinitrile compound having an ether bond. [Selection diagram] None

Description

FIELD OF THE INVENTION The present invention relates to the field of energy storage, and specifically to electrochemical and electronic devices, particularly lithium ion batteries.

With the development of technology, electrochemical devices (eg, lithium ion batteries) have been widely applied in various fields of life and production. Lithium-ion batteries have advantages such as high energy density, long cycle life, and environmental friendliness. However, lithium-ion batteries also face many challenges during use, such as range, cost, charging performance, safety performance, and hill climbing performance. Improving the rate characteristics of a lithium ion battery usually results in an increase in the temperature of the lithium ion battery, reducing its safety.

In view of this, there is a need to provide electrochemical devices and electronic devices that have both high rate characteristics and good safety.

Embodiments of the present invention seek to solve, at least in part, at least one problem in the related art by providing electrochemical and electronic devices with improved rate characteristics and safety performance.

The present invention provides an electrochemical device including a positive electrode, a negative electrode, and an electrolytic solution, wherein the negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector; The mixture layer contains a negative electrode active material, and if the yield point elongation of the negative electrode mixture layer is X% and the median diameter of the negative electrode active material is Yμm, then X and Y are 0.1≦X/Y. ≦30, and the electrolytic solution contains a compound having a cyano group.

According to an embodiment of the invention, X is in the range 10-30 and Y is in the range 1-50.

According to an embodiment of the present invention, the content of the compound having a cyano group is Z% based on the weight of the electrolytic solution, and Z is in the range of 0.1 to 10.

According to an embodiment of the present invention, X and Z satisfy 2≦X/Z≦100.

According to an embodiment of the present invention, the negative electrode mixture layer includes rubber, and the rubber is at least one of styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluoro rubber, acrylonitrile-butadiene rubber, and styrene-propylene rubber. including.

According to an embodiment of the present invention, the rubber further includes at least one of an acrylic acid functional group, a chlorotrifluoroethylene functional group, and a hexafluoropropylene functional group.

According to an embodiment of the present invention, the negative electrode active material is:
(i): Contains at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, amorphous carbon, silicon-containing material, tin-containing material, and alloy material;
(ii): Contains a metal, the metal includes at least one of molybdenum, iron, or copper, and the content of the metal is 0.05% or less with respect to the weight of the negative electrode mixture layer.
satisfies at least one of the following.

According to an embodiment of the present invention, the compound having a cyano group includes succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, tetramethylsuccinonitrile, 2-methyl Glutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1, 4-dicyanobenzene, ethylene glycol bis(propionitrile) ether, 3,5-dioxa-pimeronitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2- cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl)ether, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethyl)ether ethoxy)pentane, ethylene glycol bis(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 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, 1,3,5-pentane tricarbonitrile, 1,2,3-propane tricarbonitrile, 1,3,6-hexane tricarbonitrile, 1,2,6-hexane tricarbonitrile Nitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1, 1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy) ) Hexane or 1,2,5-tris(cyanoethoxy)pentane.

According to an embodiment of the present invention, the compound having a cyano group contains a dinitrile compound containing no ether bond and a dinitrile compound containing an ether bond, and the content of the dinitrile compound containing no ether bond is greater than the ether bond. higher than the content of dinitrile compounds containing.

According to an embodiment of the present invention, the compound having a cyano group includes a dinitrile compound and a trinitrile compound, and the content of the dinitrile compound is greater than the content of the trinitrile compound.

According to an embodiment of the present invention, the compound having a cyano group includes a dinitrile compound and a trinitrile compound having an ether bond, and the content of the dinitrile compound is greater than the content of the trinitrile compound having an ether bond.

ここで、
Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５及びＲ^６は、それぞれ独立して、水素またはＣ_１～Ｃ_１０アルキル基であり、
Ｌ_１及びＬ_２は、それぞれ独立して、－（ＣＲ^７Ｒ^８）_ｎ－であり、
Ｒ^７及びＲ^８は、それぞれ独立して、水素またはＣ_１～Ｃ_１０アルキル基であり、及び、
ｎは、１、２または３である。 According to an embodiment of the invention, the electrolyte is:
a) fluoroethylene carbonate,
b) a compound containing a sulfur-oxygen double bond,
c) lithium difluorophosphate,
d) further comprises at least one compound represented by formula 1;

here,
R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently hydrogen or a C ₁ -C ₁₀ alkyl group,
L ₁ and L ₂ are each independently -(CR ⁷ R ⁸ ) _n -,
R ⁷ and R ⁸ are each independently hydrogen or a C ₁ -C ₁₀ alkyl group, and
n is 1, 2 or 3.

の少なくとも一種を含む。 According to an embodiment of the present invention, the compound represented by formula 1 is:

Contains at least one of the following.

According to an embodiment of the present invention, the content of the compound represented by Formula 1 is within the range of 0.01% to 5% based on the weight of the electrolytic solution.

According to an embodiment of the present invention, the content of the fluoroethylene carbonate is b% based on the weight of the electrolytic solution, and b is in the range of 0.1 to 10.

According to the embodiment of the present invention, Y and b satisfy 4≦Y×b≦200.

In a further aspect of the invention, the invention provides an electronic device comprising an electrochemical device as described in the invention.

Other aspects and advantages of embodiments of the invention are described, shown in part, below, or may be explained through practice of embodiments of the invention.

Examples of the present invention will be described in detail below. The examples of the invention should not be construed as limiting the invention.

As used herein, the terms listed below have the meanings indicated below, unless otherwise specified.

In the detailed description and claims, a list of terms connected by the term "at least one" can mean any combination of the listed terms. For example, if terms 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 other instances, if the terms A, B, and C are listed, the short phrase "at least one of A, B, and C" would mean A only, B only, C only, A and B(C ), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Term A may include a single element or multiple elements. Term B may include a single element or multiple elements. Term C may include a single element or multiple elements. The term "at least one" has the same meaning as the term "at least one."

As used herein, the term "alkyl group" contemplates a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "Alkyl group" is also contemplated as a branched or cyclic hydrocarbon structure having from 3 to 20 carbon atoms. When an alkyl group is specified having a specific number of carbon atoms, it is expected to include all geometric isomers having such number of carbon atoms. Thus, for example, "butyl" is meant to include n-butyl, s-butyl, isobutyl, t-butyl and cyclobutyl. "Propyl group" includes n-propyl group, isopropyl group, and cyclopropyl group. Examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, cyclopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, cyclobutyl group, n-pentyl group, Includes isopentyl group, neopentyl group, cyclopentyl group, methylcyclopentyl group, ethylcyclopentyl group, n-hexyl group, isohexyl group, cyclohexyl group, n-heptyl group, octyl group, cyclopropyl group, cyclobutyl group, norbornyl group, etc. Not limited to these.

As used herein, the term "halogenated" means that some or all of the hydrogen atoms in a group are replaced with halogen atoms (e.g., fluorine, chlorine, bromine or iodine). .

As electrochemical devices (eg, lithium ion batteries) become more widely used, demands on their performance, including rate characteristics and safety performance, are becoming higher. However, it is usually difficult to achieve both rate characteristics and safety performance. Measures such as selecting the active material for the positive or negative electrode, optimizing the composition of the electrolyte, and optimizing the battery design can contribute to improving the rate characteristics of lithium-ion batteries. This has a negative impact on the safety of lithium-ion batteries as they tend to generate heat.

In order to solve the above problems, the present invention combines an electrolytic solution containing a compound having a cyano group by adjusting the relationship between the yield point elongation of the negative electrode mixture layer and the median diameter (D50) of the negative electrode active material. By using it as It reduces the thickness expansion rate under thermal abuse and improves its safety performance.

In certain embodiments, the present invention provides an electrochemical device that includes a positive electrode, a negative electrode, and an electrolyte as described below.

I, negative electrode
The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on one or two surfaces of the negative electrode current collector, and the negative electrode mixture layer includes a negative electrode active material.

One feature of the electrochemical device of the present invention is that the yield point elongation X% of the negative electrode mixture layer and D50Yμm of the negative electrode active material satisfy 0.1≦X/Y≦30. In one embodiment, 0.5≦X/Y≦25 is satisfied. In some embodiments, 1≦X/Y≦20 is satisfied. In some embodiments, 3≦X/Y≦15 is satisfied. In some embodiments, X/Y is 0.1, 0.5, 1, 2, 5, 8, 10, 12, 15, 18, 20, 25, 30, or any two values listed above. It is within the range consisting of. When the yield point elongation X% of the negative electrode mixture layer and the D50Yμm of the negative electrode active material satisfy the above relationship, the rate characteristics and safety performance of the electrochemical device can be significantly improved.

When the negative electrode mixture layer is pulled, if the tensile force exceeds the limit of elastic deformation, the negative electrode mixture layer will be plastically deformed if the pulling continues, and the boundary point at which the negative electrode mixture layer switches from elastic deformation to plastic deformation is `` "Yield Point." The yield point elongation of the negative electrode mixture layer can be expressed as (length of extension of the negative electrode mixture layer to the yield point - original length of the negative electrode mixture layer)/original length of the negative electrode mixture layer x 100%. .

The yield point elongation of the negative electrode mixture layer can be measured by the following method. A polyethylene terephthalate (PET) film with a thickness of 50 μm is attached to one adhesive surface of the double-sided tape, and a negative electrode mixture layer is attached to the other adhesive surface of the double-sided tape. The negative electrode mixture layer and the PET film are peeled together from the negative electrode current collector to obtain a measurement sample. A sample for measurement with a length of 140 mm and a width of 15 mm is taken and fixed to a chuck (positioning grip) of a tensile tester, and the length of the tensile portion of the negative electrode mixture layer is set to 100 mm. In a room temperature environment (20° C.±5° C.), the measurement sample is pulled in a direction substantially perpendicular to the thickness direction of the negative electrode mixture layer (±10° in a direction perpendicular to the thickness direction). Every time the negative electrode mixture layer stretches by 1 mm (if it stretches by 1 mm, the stretch is 1%, if it stretches by 2 mm, the stretch is 2%, etc.), the tension is interrupted and the resistance is measured using a four-probe probe 300. The resistance of the negative electrode mixture layer is measured three times using a four-terminal method using a device, and the average value is taken. The above steps are repeated until the negative electrode mixture layer is broken. A rectangular coordinate system is created with the elongation of the negative electrode mixture layer as the horizontal axis and the resistance of the negative electrode mixture layer as the vertical axis, and the elongation is determined when the difference in resistance value between two adjacent measurement points exceeds 0.1Ω. The measurement point with a small value is recorded as the "yield point", and the yield point elongation of the negative electrode mixture layer is recorded. When there are multiple yield points, the yield point elongation with the smallest corresponding elongation is determined as the yield point elongation of the negative electrode mixture layer.

1. Negative electrode mixture layer
The negative electrode mixture layer may be a single layer or a multilayer. Each layer in a multilayer negative electrode active material may include the same or different negative electrode active materials. The negative electrode active material is a material that can reversibly insert and release arbitrary 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 to prevent unintentional deposition of lithium metal onto the negative electrode during charging. In some embodiments, the yield point elongation of the negative electrode mixture layer is in the range of 10% to 30%. In some embodiments, the yield point elongation of the negative electrode mixture layer is in the range of 15% to 25%. The yield point elongation of the negative electrode mixture layer is 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or is composed of any two values listed above. within the range. When the yield point elongation of the negative electrode mixture layer is within the above range, the rate characteristics and safety performance of the electrochemical device can be further improved.

In some embodiments, the median diameter (D50) of the negative electrode active material is in the range of 1 μm to 50 μm. In some embodiments, the median diameter (D50) of the negative electrode active material is in the range of 3 μm to 40 μm. In some embodiments, the median diameter (D50) of the negative electrode active material is in the range of 5 μm to 30 μm. In some embodiments, the median diameter (D50) of the negative electrode active material is in the range of 10 μm to 20 μm. In some embodiments, the median diameter of the negative electrode active material is 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or a range consisting of any two of the above values. It's within. When the median diameter (D50) of the negative electrode active material is within the above range, the rate characteristics and safety performance of the electrochemical device can be further improved.

The median diameter (D50) of the negative electrode active material can be measured by the following method. A carbon material is dispersed in a 0.2% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate and measured using a laser diffraction/scattering particle size distribution analyzer (LA-700 manufactured by Horiba Ltd.).

In one embodiment, the negative electrode mixture layer contains rubber. Rubber can effectively improve the interfacial stability of the negative electrode mixture layer, thereby significantly improving the rate characteristics and safety performance of the electrochemical device.

In some embodiments, the rubber includes at least one of styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluoro rubber, acrylonitrile-butadiene rubber, and styrene-propylene rubber.

In some embodiments, the rubber further includes at least one of an acrylic acid functional group, a chlorotrifluoroethylene functional group, and a hexafluoropropylene functional group.

In one embodiment, the content of the rubber is 10% or less based on the weight of the negative electrode mixture layer. In one embodiment, the content of the rubber is 8% or less based on the weight of the negative electrode mixture layer. In one embodiment, the content of the rubber is 5% or less based on the weight of the negative electrode mixture layer. In one embodiment, the content of the rubber is 3% or less based on the weight of the negative electrode mixture layer. In one embodiment, the content of the rubber is 2% or less based on the weight of the negative electrode mixture layer.

In one embodiment, the negative electrode active material satisfies at least one of the following (i) or (ii).

(i) Type of negative electrode active material
In one embodiment, the negative electrode active material includes at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, amorphous carbon, silicon-containing material, tin-containing material, and alloy material.

In some embodiments, the shape of the negative electrode active material includes, but is not limited to, fibrous, spherical, granular, and scaly shapes.

In one embodiment, the negative electrode active material includes a carbon material.

In some embodiments, the negative active material has a specific surface area of less than 5 m ² /g. In some embodiments, the negative active material has a specific surface area of less than 3 m ² /g. In some embodiments, the negative active material has a specific surface area of less than 1 m ² /g. In some embodiments, the negative active material has a specific surface area of greater than 0.1 m ² /g. In some embodiments, the negative active material has a specific surface area of greater than 0.7 m ² /g. In some embodiments, the negative active material has a specific surface area of more than 0.5 m ² /g. In one embodiment, the specific surface area of the negative electrode active material is within a range comprised of any two values described above. When the specific surface area of the negative electrode active material is within the above range, it is possible to suppress the precipitation of lithium on the surface of the electrode, and also to suppress the generation of gas due to the reaction between the negative electrode and the electrolyte. can.

The specific surface area (BET) of the negative electrode active material is measured using a surface area meter (fully automatic surface area measurement device manufactured by Okura Riken). After pre-drying the sample at 350°C for 15 minutes with nitrogen gas flowing, It can be measured by a nitrogen adsorption BET one-point method using a gas flow method using a nitrogen-helium mixed gas that has been accurately adjusted so that the relative pressure of nitrogen gas is 0.3.

In one embodiment, the interlayer distance of the lattice plane (002 plane) of the negative electrode active material is about 0.335 nm within a range of about 0.335 nm to about 0.360 nm, based on an X-ray diffraction pattern according to the Jakushin method. to about 0.350 nm or about 0.335 nm to about 0.345 nm.

In some embodiments, the negative electrode active material has a microcrystalline size (Lc) of greater than about 1.0 nm or greater than about 1.5 nm, based on an X-ray diffraction pattern according to the Jakushin method.

In certain embodiments, the negative active material has a Raman R value greater than about 0.01, greater than about 0.03, or greater than about 0.1. In certain embodiments, the negative active material has a Raman R value of less than about 1.5, less than about 1.2, less than about 1.0, or less than about 0.5. In one embodiment, the Raman R value of the negative electrode active material is within a range comprised of any two values described above.

The negative electrode active material is not particularly limited in its Raman peak half width around 1580 cm ⁻¹ . In certain embodiments, the Raman peak half width around 1580 cm ⁻¹ of the negative electrode active material is greater than about 10 cm ⁻¹ or greater than about 15 cm ⁻¹ . In some embodiments, the negative electrode active material has a Raman peak half width around 1580 cm ⁻¹ that is less than about 100 cm ⁻¹ , less than about 80 cm ⁻¹ , less than about 60 cm ⁻¹ , or less than about 40 cm ⁻¹ . In one embodiment, the half-value width of the Raman peak near 1580 cm ⁻¹ of the negative electrode active material is within a range consisting of any two values described above.

In certain embodiments, the length to thickness ratio of the negative active material is greater than about 1, greater than about 2, or greater than about 3. In certain embodiments, the length to thickness ratio of the negative active material is less than about 10, less than about 8, or less than about 5. In some embodiments, the length-to-thickness ratio of the negative electrode active material is within a range comprised of any two values described above. When the length-to-thickness ratio of the negative electrode active material is within the above range, more uniform coating can be achieved.

(ii) Trace elements
In one embodiment, the negative electrode active material includes a metal, and the metal includes at least one of molybdenum, iron, and copper. These metal elements can react with some organic substances having poor conductivity in the negative electrode active material, and can be made to be advantageous for forming a film on the surface of the negative electrode active material.

In some embodiments, the above-mentioned metal elements are present in the negative electrode mixture layer in trace amounts in order to prevent the formation of non-conductive by-products from adhering to the surface of the negative electrode. In one embodiment, the content of the metal is 0.05% or less based on the weight of the negative electrode mixture layer. In one embodiment, the content of the metal is 0.04% or less based on the weight of the negative electrode mixture layer. In one embodiment, the content of the metal is 0.03% or less based on the weight of the negative electrode mixture layer. In one embodiment, the content of the metal is 0.01% or less based on the weight of the negative electrode mixture layer. When the metal content in the negative electrode mixture layer is within the above range, the rate characteristics and safety performance of the electrochemical device can be further improved.

In one embodiment, the negative electrode mixture layer further includes at least one of a silicon-containing material, a tin-containing material, and an alloy material. In one embodiment, the negative electrode mixture layer further includes at least one of a silicon-containing material and a tin-containing material. In some embodiments, the negative electrode mixture layer further includes one or more of a silicon-containing material, a silicon-carbon composite material, a silicon-oxygen material, an alloy material, and a lithium-containing metal composite oxide material.

In some embodiments, the negative electrode mixture layer further includes one or more types of other negative electrode active materials, including, for example, metal elements and metalloid elements that can form an alloy with lithium. In some embodiments, examples of the metal and metalloid elements include Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd, and including, but not limited to, Pt. In some embodiments, the examples of metal and metalloid elements include Si, Sn, or combinations thereof. Si and Sn have excellent ability to release lithium ions and can provide high energy density to lithium ion batteries. In some embodiments, other types of negative electrode active materials may include one or more of metal oxides and polymeric compounds. In some embodiments, the metal oxides include, but are not limited to, iron oxide, ruthenium oxide, and molybdenum oxide. In certain embodiments, the polymeric compounds include, but are not limited to, polyacetylene, polyaniline, and polypyrrole.

Negative conductive material
In one embodiment, the negative electrode mixture layer includes a negative electrode conductive material. The conductive material may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. including.

negative electrode adhesive
In one embodiment, the negative electrode mixture layer further includes a negative electrode adhesive. The negative electrode adhesive can improve the bond between particles of the negative electrode active material and the bond between the negative electrode active material and the current collector. The type of negative electrode adhesive is not particularly limited, and any material may be used as long as it is stable against the electrolytic solution or the solvent used during electrode manufacturing.

Examples of negative electrode adhesives include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; styrene-butadiene rubber (SBR), isoprene rubber, butadiene rubber, and fluorine rubber. , acrylonitrile-butadiene rubber (NBR), ethylene-propylene rubber, and other rubbery polymers; styrene-butadiene-styrene block copolymers or their hydrides; ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene - Thermoplastic elastomeric polymers such as butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers or their hydrides; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers , soft resinous polymers such as propylene-α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; alkali metal ions ( Examples include, but are not limited to, polymer compositions having ionic conductivity, particularly lithium ions. The negative electrode adhesives described above may be used alone or in any combination.

When the negative electrode mixture layer contains a fluorine-based polymer (e.g., polyvinylidene fluoride), in some embodiments, the content of the negative electrode adhesive is more than about 1%, based on the weight of the negative electrode mixture layer. More than 2%, or more than about 3%. In some embodiments, the content of the negative electrode adhesive is less than about 10%, less than about 8%, or less than about 5% based on the weight of the negative electrode mixture layer. The content of the negative electrode adhesive with respect to the weight of the negative electrode mixture layer is within a range comprised of the above two arbitrary values.

solvent
The type of solvent for forming the negative electrode slurry is not particularly limited, and any solvent may be used as long as it can dissolve or disperse the negative electrode active material, negative electrode adhesive, thickener and conductive material used as necessary. In some embodiments, the solvent for forming the negative electrode slurry may be either an aqueous solvent or an organic solvent. Examples of aqueous solvents include, but are not limited to, water, alcohol, and the like. Examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, ethylmethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), Including, but not limited to, toluene, acetone, diethyl ether, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like. The above-mentioned solvents may be used alone or in any combination.

thickener
Thickeners are typically used to adjust the viscosity of negative electrode slurry. The type of thickener is not particularly limited, and examples thereof include, but are not limited to, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. . The above-mentioned thickeners may be used alone or in any combination.

In some embodiments, the content of the thickener is greater than about 0.1%, greater than about 0.5%, or greater than about 0.6% based on the weight of the negative electrode mixture layer. In some embodiments, the content of the thickener is less than about 5%, less than about 3%, or less than about 2% based on the weight of the negative electrode mixture layer. When the content of the thickener is within the above range, it is possible to ensure that the negative electrode slurry has good coating properties while suppressing a decrease in capacity and an increase in resistance of the electrochemical device.

surface coating
In some embodiments, a substance having a composition different from that of the negative electrode mixture layer may be attached to the surface of the negative electrode mixture layer. Examples of substances attached to the surface of the negative electrode mixture layer include oxides such as aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; lithium sulfate, sodium sulfate, and sulfuric acid. Sulfates such as potassium, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and the like, but are not limited to these.

Content of negative electrode active material
In some embodiments, the content of the negative electrode active material is greater than about 80%, greater than about 82%, or greater than about 84% based on the weight of the negative electrode mixture layer. In some embodiments, the content of the negative electrode active material is less than about 99%, or less than about 98%, based on the weight of the negative electrode mixture layer. In one embodiment, the content of the negative electrode active material with respect to the weight of the negative electrode mixture layer is within a range comprised of any two values described above.

Density of negative electrode active material
In certain embodiments, the density of the negative active material in the negative mix layer is greater than about 1 g/cm ³ , greater than about 1.2 g/cm ³ , or greater than about 1.3 g/cm ³ . In some embodiments, the density of the negative active material in the negative mix layer is less than about 2.2 g/cm ³ , less than about 2.1 g/cm ³ , less than about 2.0 g/cm ³ , or about 1.9 g/cm 3 . less than ^cm3 . In one embodiment, the density of the negative electrode active material in the negative electrode mixture layer is within a range comprised of any two values described above.

When the density of the negative electrode active material is within the above range, damage to the negative electrode active material particles can be prevented, and the initial irreversible capacity of the electrochemical device can be increased or electrolysis near the negative electrode current collector/negative electrode active material interface can be prevented. Deterioration of high current density charge/discharge characteristics due to a decrease in liquid permeability can be suppressed, and furthermore, a decrease in capacity and an increase in resistance of an electrochemical device can be suppressed.

2. Negative electrode current collector
Any known current collector may be used as the current collector for maintaining the negative electrode active material. Examples of negative electrode current collectors include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, nickel plated steel, and the like. In some embodiments, the negative electrode current collector is copper.

When the negative electrode current collector is a metal material, the form of the negative electrode current collector includes metal foil, metal cylinder, metal coil, metal plate, metal foil, metal mesh sheet, punched metal, foamed metal, etc. Not limited. In some embodiments, the negative electrode current collector is a thin metal film. In some embodiments, the negative current collector is copper foil. In one embodiment, the negative electrode current collector is a rolled copper foil produced by a rolling method or an electrolytic copper foil produced by an electrolysis method.

In certain embodiments, the thickness of the negative electrode current collector is greater than about 1 μm, or greater than about 5 μm. In certain embodiments, the thickness of the negative electrode current collector is less than about 100 μm, or less than about 50 μm. In some embodiments, the thickness of the negative electrode current collector is within a range comprised of any two values described above.

The thickness ratio between the negative electrode mixture layer and the negative electrode current collector refers to the thickness of the negative electrode mixture layer on one side divided by the thickness of the negative electrode current collector, and its value is not particularly limited. In some embodiments, the thickness ratio is 50 or less. In some embodiments, the thickness ratio is 30 or less. In some embodiments, the thickness ratio is 20 or less. In some embodiments, the thickness ratio is 10 or less. In some embodiments, the thickness ratio is greater than or equal to 1. In some embodiments, the thickness ratio is within a range consisting of any two of the values listed above. When the thickness ratio is within the above range, the capacity of the electrochemical device can be ensured, and heat radiation of the negative electrode current collector during high current density charging and discharging can be suppressed.

II, electrolyte
The electrolytic solution used in the electrochemical device of the present invention includes an electrolyte and a solvent that dissolves the electrolyte. In some embodiments, the electrolyte used in the electrochemical device of the present invention further includes an additive.

Another feature of the electrochemical device of the present invention is that the electrolytic solution contains a compound having a cyano group.

In one embodiment, the compound having a cyano group is succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene , ethylene glycol bis(propionitrile) ether, 3,5-dioxa-pimeronitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, Tetraethylene glycol bis(2-cyanoethyl) ether, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethoxy)pentane, Ethylene glycol bis(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 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, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1, 2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris( cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane or 1 , 2,5-tris(cyanoethoxy)pentane.

In one embodiment, the compound having a cyano group includes a dinitrile compound that does not include an ether bond and a dinitrile compound that includes an ether bond, and the content of the dinitrile compound that does not include an ether bond is greater than the amount of the dinitrile compound that does not include an ether bond. More than the content.

In one embodiment, the compound having a cyano group includes a dinitrile compound and a trinitrile compound, and the content of the dinitrile compound is greater than the content of the trinitrile compound.

In one embodiment, the compound having a cyano group includes a dinitrile compound and a trinitrile compound having an ether bond, and the content of the dinitrile compound is greater than the content of the trinitrile compound having an ether bond.

In one embodiment, the content of the cyano group-containing compound is Z% based on the weight of the electrolytic solution, and Z is in the range of 0.1 to 10. In certain embodiments, Z is within the range of 0.5-8. In certain embodiments, Z is within the range of 1-5. In some embodiments, Z is 0.1, 0.5, 1, 2, 5, 8, 10, or within a range consisting of any two of the values listed above. When the content of the compound having a cyano group in the electrolytic solution is within the above range, the rate characteristics and safety performance of the electrochemical device can be further improved.

In a certain example, the content Z% of the compound having a cyano group in the electrolytic solution and the yield point elongation X% of the negative electrode mixture layer satisfy 2≦X/Z≦100. In some embodiments, 5≦X/Z≦80 is satisfied. In some embodiments, 10≦X/Z≦50 is satisfied. In some embodiments, 20≦X/Z≦30. In some embodiments, X/Z is 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or within a range consisting of any two values listed above. It is in. When the content Z% of the compound having a cyano group in the electrolytic solution and the yield point elongation X% of the negative electrode mixture layer satisfy the above relationship, the rate characteristics and safety performance of the electrochemical device can be further improved.

ここで、
Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５及びＲ^６は、それぞれ独立して、水素またはＣ_１～Ｃ_１０アルキル基であり、
Ｌ_１及びＬ_２は、それぞれ独立して、－（ＣＲ^７Ｒ^８）_ｎ－であり、
Ｒ^７及びＲ^８は、それぞれ独立して、水素またはＣ_１～Ｃ_１０アルキル基であり、及び、
ｎは、１、２または３である。 In some embodiments, the electrolyte is
a) fluoroethylene carbonate,
b) a compound containing a sulfur-oxygen double bond,
c) lithium difluorophosphate,
d) further comprises at least one compound represented by formula 1;

here,
R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently hydrogen or a C ₁ -C ₁₀ alkyl group,
L ₁ and L ₂ are each independently -(CR ⁷ R ⁸ ) _n -,
R ⁷ and R ⁸ are each independently hydrogen or a C ₁ -C ₁₀ alkyl group, and
n is 1, 2 or 3.

a) Fluoroethylene carbonate During charging/discharging of an electrochemical device, fluoroethylene carbonate and a compound having a cyano group work together to form a stable protective film on the surface of the negative electrode, causing a decomposition reaction of the electrolyte. suppress.

In certain embodiments, the fluorocarbonate has a structure of the formula C=O(OR _x )(OR _y ), where R _x and R _y each independently contain 1 to 6 carbon atoms. at least one of R _x and R _y is selected from fluoroalkyl groups having 1 to 6 carbon atoms, and R _x and R _y are optionally selected from fluoroalkyl groups having 1 to 6 carbon atoms; Together with the atoms to which they are connected, they form a 5- to 7-membered ring.

In certain embodiments, examples of the fluoroethylene carbonate include fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4 -Methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, and the like, but are not limited thereto.

In one embodiment, the content of the fluoroethylene carbonate is b% based on the weight of the electrolyte, and b is in the range of 0.1 to 10. In certain embodiments, b is within the range of 0.5-8. In certain embodiments, b is within the range of 1-5. In certain embodiments, b is within the range of 2-4. In some embodiments, b is 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or consists of any two values listed above. within range. When the content of fluoroethylene carbonate in the electrolytic solution is within the above range, the rate characteristics and safety performance of the electrochemical device can be further improved.

In one embodiment, the content b% of fluoroethylene carbonate in the electrolytic solution and the median diameter Y μm of the negative electrode active material satisfy 4≦Y×b≦200. In one embodiment, 5≦Y×b≦150 is satisfied. In one embodiment, 10≦Y×b≦100 is satisfied. In one embodiment, 20≦Y×b≦50 is satisfied. In some embodiments, Y x b is 4, 5, 10, 20, 50, 80, 100, 120, 150, 180, 200, or within a range consisting of any two values listed above. . When the content b% of fluoroethylene carbonate in the electrolytic solution and the median diameter Y μm of the negative electrode active material satisfy the above relationship, the rate characteristics and safety performance of the electrochemical device can be further improved.

b) Compounds containing sulfur-oxygen double bonds
In one embodiment, the sulfur-oxygen double bond-containing compound is at least one of a cyclic sulfate, a chain sulfate, a chain sulfonate, a cyclic sulfonate, a chain sulfite, or a cyclic sulfite. include.

In some embodiments, the cyclic sulfate ester is 1,2-ethylene glycol sulfate, 1,2-propylene glycol sulfate, 1,3-propylene glycol sulfate, 1,2-butylene glycol sulfate, 1,3 -Butylene glycol sulfate, 1,4-butylene glycol sulfate, 1,2-pentylene glycol sulfate, 1,3-pentylene glycol sulfate, 1,4-pentylene glycol sulfate, and 1,5-pentylene glycol sulfate including, but not limited to, one or more of lene glycol sulfate;

In one embodiment, the chain sulfate ester includes one or more of dimethyl sulfate, ethyl methyl sulfate, and diethyl sulfate, but is not limited thereto.

In some embodiments, the linear sulfonate esters include fluorosulfonate esters such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl dimethanesulfonate, 2-(methanesulfonyl including, but not limited to, one or more of methyl oxy)propionate and ethyl 2-(methanesulfonyloxy)propionate.

In certain embodiments, the cyclic sulfonic acid ester is 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane Sulton, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1-propylene-1,3-sultone, 2-propylene-1 ,3-sultone, 1-fluoro-1-propylene-1,3-sultone, 2-fluoro-1-propylene-1,3-sultone, 3-fluoro-1-propylene-1,3-sultone, 1-fluoro -2-propylene-1,3-sultone, 2-fluoro-2-propylene-1,3-sultone, 3-fluoro-2-propylene-1,3-sultone, 1-methyl-1-propylene-1,3 -Sultone, 2-methyl-1-propylene-1,3-sultone, 3-methyl-1-propylene-1,3-sultone, 1-methyl-2-propylene-1,3-sultone, 2-methyl-2 - One or more of propylene-1,3-sultone, 3-methyl-2-propylene-1,3-sultone, 1,4-butanesultone, 1,5-pentane sultone, methylenemethanedisulfonate, and ethylenemethanedisulfonate. including but not limited to.

In some embodiments, the linear sulfite ester includes one or more of dimethyl sulfite, ethyl methyl sulfite, and diethyl sulfite, but is not limited thereto.

In some embodiments, the cyclic sulfite is 1,2-ethylene glycol sulfite, 1,2-propylene glycol sulfite, 1,3-propylene glycol sulfite, 1,2-butylene glycol sulfite, 1,3 -Butylene glycol sulfite, 1,4-butylene glycol sulfite, 1,2-pentylene glycol sulfite, 1,3-pentylene glycol sulfite, 1,4-pentylene glycol sulfite and 1,5-pentylene glycol sulfite including, but not limited to, one or more of lene glycol sulfites;

ここで、
Ｗは、

から選択され、
Ｌは、それぞれ独立して、単結合またはメチレンから選択され、
ｍは、１、２、３または４であり、
ｎは、０、１または２であり、且つ
ｐは、０、１、２、３、４、５または６である。 In one embodiment, the compound containing a sulfur-oxygen double bond includes a compound represented by formula 2,

here,
W is

selected from
L is each independently selected from a single bond or methylene;
m is 1, 2, 3 or 4;
n is 0, 1 or 2, and p is 0, 1, 2, 3, 4, 5 or 6.

の少なくとも一種を含む。 In one embodiment, the compound represented by formula 2 is

Contains at least one of the following.

In one embodiment, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.01% to 10% based on the weight of the electrolyte. In one embodiment, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.05% to 8% based on the weight of the electrolyte. In one embodiment, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.1% to 5% based on the weight of the electrolyte. In one embodiment, the content of the sulfur-oxygen double bond-containing compound is in the range of 0.5% to 3% based on the weight of the electrolyte. In one embodiment, the content of the sulfur-oxygen double bond-containing compound is in the range of 1% to 2% based on the weight of the electrolyte. In one embodiment, the content of the sulfur-oxygen double bond-containing compound relative to the weight of the electrolytic solution is 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 2%, 5%, 8%, 10%, or within a range consisting of any two values listed above.

c) Lithium difluorophosphate (LiPO ₂ F ₂ )
In one embodiment, the content of the lithium difluorophosphate is 0.01% to 1.5% based on the weight of the electrolyte. In one embodiment, the content of the lithium difluorophosphate is 0.05% to 1.2% based on the weight of the electrolyte. In one embodiment, the content of the lithium difluorophosphate is 0.1% to 1.0% based on the weight of the electrolyte. In one embodiment, the content of the lithium difluorophosphate is 0.5% to 0.8% based on the weight of the electrolyte. In one embodiment, the content of the lithium difluorophosphate is 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0, based on the weight of the electrolyte. .25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.8%, 1%, 1.5%, or any two of the above. within a range consisting of two values.

の少なくとも一種を含む。 d) Compound represented by formula 1
In some embodiments, the compound represented by formula 1 is

Contains at least one of the following.

In one embodiment, the content of the compound represented by Formula 1 is in the range of 0.01% to 5% based on the weight of the electrolytic solution. In one embodiment, the content of the compound represented by Formula 1 is in the range of 0.05% to 4% based on the weight of the electrolytic solution. In one embodiment, the content of the compound represented by Formula 1 is in the range of 0.1% to 3% based on the weight of the electrolyte. In one embodiment, the content of the compound represented by Formula 1 is in the range of 0.5% to 2% based on the weight of the electrolyte. In one embodiment, the content of the compound represented by Formula 1 is in the range of 1% to 1.5% based on the weight of the electrolyte. In one embodiment, the content of the compound represented by formula 1 is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, based on the weight of the electrolytic solution. %, 3%, 4%, 5%, or within a range consisting of any two of the above values. When the content of the compound represented by Formula 1 in the electrolytic solution is within the above range, the rate characteristics and safety performance of the electrochemical device can be further improved.

solvent
In certain embodiments, the electrolyte further comprises any non-aqueous solvent used as a solvent for electrolytes known in the prior art.

In one embodiment, the non-aqueous solvent is a cyclic carbonate, a chain carbonate, a cyclic carboxylic ester, a chain carboxylic ester, a cyclic ether, a chain ether, a phosphorus-containing organic solvent, a sulfur-containing organic solvent, an aromatic fluorine-containing organic solvent, etc. Including, but not limited to, one or more solvents.

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

In some embodiments, examples of the linear carbonates include linear carbonates such as dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, etc. including, but not limited to, one or more carbonates; Examples of linear carbonates substituted with fluorine are bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoro One or more of ethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethylmethyl carbonate, 2,2-difluoroethylmethyl carbonate, and 2,2,2-trifluoroethylmethyl carbonate. including but not limited to.

In some embodiments, examples of the cyclic carboxylic esters include, but are not limited to, one or more of γ-butyrolactone and γ-valerolactone. In some embodiments, some of the hydrogen atoms of the cyclic carboxylic ester may be replaced with fluorine.

In certain embodiments, examples of the linear carboxylic esters include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate. , propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate. Not limited to these. In some embodiments, some of the hydrogen atoms of the chain carboxylic ester may be substituted with fluorine. In one embodiment, examples of fluorine-substituted linear carboxylic acid esters include methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluorotrifluoroacetate. Including, but not limited to, ethyl.

In certain embodiments, examples of the cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane. , 1,4-dioxane, and dimethoxypropane.

In some embodiments, examples of the linear ethers include dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, These include, but are not limited to, one or more of ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane.

In certain embodiments, examples of the phosphorus-containing organic solvents include trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, phosphorous acid. One or more of trimethyl, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,3,3,3-pentafluoropropyl) phosphate Including, but not limited to:

In certain embodiments, examples of the sulfur-containing organic solvents include sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethylsulfoxide, methyl methanesulfonate, methanesulfone. including, but not limited to, one or more of ethyl acid, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In certain embodiments, some of the hydrogen atoms of the sulfur-containing organic solvent may be replaced with fluorine.

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

In some embodiments, the solvent used in the electrolyte of the present invention includes a cyclic carbonate, a chain carbonate, a cyclic carboxylic acid ester, a chain carboxylic acid ester, and combinations thereof. In certain embodiments, the solvent used in the electrolyte of the present invention is selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, ethyl acetate, and combinations thereof. Contains organic solvents. In certain embodiments, the solvents used in the electrolytes of the present invention include ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, and combinations thereof.

Additive
In some embodiments, examples of the additives include one or more of fluorocarbonates, ethylene carbonate containing carbon-carbon double bonds, compounds containing sulfur-oxygen double bonds, and acid anhydrides. but not limited to.

In some embodiments, the content of the additive is from 0.01% to 15%, from 0.1% to 10%, or from 1% to 5% based on the weight of the electrolyte.

According to an embodiment of the present invention, the content of the propionate is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 5 times that of the additive with respect to the weight of the electrolyte. It is 20 times more.

In certain embodiments, the additive includes one or more ethylene carbonates containing carbon-carbon double bonds. Examples of the ethylene carbonate containing the carbon-carbon double bond are vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, 1,2-dimethylvinylene carbonate, 1,2-diethylvinylene carbonate, fluorovinylene carbonate, trifluoromethyl Vinylene carbonate; vinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, 1-ethyl-2-vinyl ethylene carbonate, 1-n-propyl-2-vinyl ethylene carbonate, 1-methyl-2-vinyl A type of ethylene carbonate, 1,1-divinylethylene carbonate, 1,2-divinylethylene carbonate, 1,1-dimethyl-2-methyleneethylene carbonate, and 1,1-diethyl-2-methyleneethylene carbonate or many other types, including but not limited to. In one embodiment, the carbon-carbon double bond-containing ethylene carbonate includes vinylene carbonate, which is easily available and can achieve even better effects.

In some embodiments, the additive is a combination of fluorocarbonate and ethylene carbonate containing carbon-carbon double bonds. In some embodiments, the additive is a combination of a fluorocarbonate and a compound containing a sulfur-oxygen double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound having 2 to 4 cyano groups. In some embodiments, the additive is a combination of a fluorocarbonate and a cyclic carboxylic acid ester. In some embodiments, the additive is a combination of fluorocarbonate and cyclic phosphoric anhydride. In some embodiments, the additive is a combination of fluorocarbonate and carboxylic acid anhydride. In some embodiments, the additive is a combination of fluorocarbonate and sulfonic anhydride. In some embodiments, the additive is a combination of fluorocarbonate and carboxylic acid sulfonic anhydride.

Electrolytes
The electrolyte is not particularly limited, and any substance known as an electrolyte may be used. In the case of lithium secondary batteries, lithium salts are usually used. Examples of electrolytes are inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiWF ₇ ; lithium tungstates such as LiWOF ₅ ; 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 CF 2 CF 2 CO} Carboxylic acid lithium salts such as ₂ 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 Sulfonic acid lithium salts such as SO ₃ Li, CF ₃ CF ₂ CF ₂ CF ₂ SO ₃ 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-perfluoropropanedi Lithium imide salts such as sulfonylimide, 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 ) ₃ Lithium methylate salts such as lithium bis(malonato)borate, lithium difluoro(malonato)borate, lithium tris(malonato)phosphate, lithium difluorobis(malonato)phosphate, lithium tetrafluoro(malonato) Lithium ₍ malonato) phosphate salts such as phosphate; and _LiPF4 ( _CF3 ) ₂ , _{LiPF4 ( C2F5} ) _{2 , LiPF4} ( _{CF3SO2 ) 2} , _LiPF4 ( _C2F5SO2 ) 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 Fluorine-containing organic lithium salts such as (C ₂ F ₅ SO ₂ ) ₂ ; lithium oxalatoborates such as lithium difluoro(oxalato)borate and lithium bis(oxalato)borate; lithium tetrafluoro(oxalato)phosphate and lithium difluorobis (oxalato)phosphate, lithium (oxalato)phosphate salts such as lithium tris(oxalato)phosphate, and the like.

In some embodiments, _the electrolyte is _LiPF6 , LiSbF6, _FSO3Li , _CF3SO3Li , LiN( _FSO2 ) ₂ , LiN( _FSO2 )( _{CF3SO2 )} , LiN( _{CF3SO2 ) . 2} , LiN(C ₂ F ₅ SO ₂ ) ₂ , Lithium cyclic 1,2-perfluoroethanedisulfonylimide, Lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO ₂ ) ₃ , LiC(CF _{3 SO2 ) 3} , LiC( _{C2F5SO2 ) 3} , _{LiBF3CF3, LiBF3C2F5 , LiPF3} ( _{CF3 ) 3 , LiPF3} ( _C2F5 ) ₃ , Lithium _difluoro (oxalato) ) borate, lithium bis(oxalato)borate or lithium difluorobis(oxalato)phosphate. They contribute to improving the output characteristics, high rate charge/discharge characteristics, high temperature storage characteristics, cycle characteristics, etc. of the electrochemical device.

The content of the electrolyte is not particularly limited as long as it does not impair the effects of the present invention. In certain examples, the total molar concentration of lithium in the electrolyte is greater than or equal to 0.3 mol/L, greater than 0.4 mol/L, or greater than 0.5 mol/L. In certain examples, the total molar concentration of lithium in the electrolyte is less than 3 mol/L, less than 2.5 mol/L, or less than 2.0 mol/L. In some embodiments, the total molar concentration of lithium in the electrolyte is within a range consisting of any two of the values listed above. When the concentration of the electrolyte is within the above range, lithium, which is a charged particle, will be sufficient and the viscosity can be kept within an appropriate range, making it easy to ensure good electrical conductivity.

When two or more types of electrolytes are used together, the electrolyte contains at least one salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates. In certain embodiments, the electrolyte includes a salt selected from the group consisting of monofluorophosphates, oxalates, and fluorosulfonates. In some embodiments, the electrolyte includes a lithium salt. In some embodiments, the content of salts selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, based on the weight of the electrolyte, is greater than 0.01%, or 0. .1% or more. In some embodiments, the content of salts selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is less than 20%, or less than 10%, based on the weight of the electrolyte. It is. In certain embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is within a range consisting of any two of the above values. .

In some embodiments, the electrolyte includes one or more substances selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, and one or more other salts. Examples of other salts include the lithium salts exemplified above, and in some examples, LiPF ₆ , 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, LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiC( _They are _C2F5SO2 ) ₃ , _{LiBF3CF3 , LiBF3C2F5 , LiPF3} ( _{CF3 ) 3} , _{and LiPF3 ( C2F5} ) ₃ . In some embodiments, the other salt is _LiPF6 .

In certain embodiments, the content of other salts is greater than 0.01%, or greater than 0.1%, based on the weight of the electrolyte. In some embodiments, the content of other salts is less than 20%, less than 15%, or less than 10%, based on the weight of the electrolyte. In some embodiments, the content of other salts is within a range comprised of any two values listed above. Other salts having the above content contribute to balancing the electrical conductivity and viscosity of the electrolyte.

In addition to the above-mentioned solvent, additives, and electrolyte salt, the electrolytic solution may contain other additives such as a negative electrode film forming agent, a positive electrode protective agent, and an overcharge preventive agent, if necessary. As additives, additives normally used in non-aqueous electrolyte secondary batteries can be used, examples of which include vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluoroanisole, propane sultone. , propene sultone, and the like. These additives may be used alone or in any combination. Note that the content of these additives in the electrolytic solution is not particularly limited, and may be appropriately set depending on the type of the additive. In certain embodiments, the content of additives based on the weight of the electrolyte is less than 5%, in the range of 0.01% to 5%, or in the range of 0.2% to 5%.

III, positive electrode
The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on one or two surfaces of the positive electrode current collector.

1. Positive electrode active material layer
The positive electrode active material layer includes a positive electrode active material. The positive electrode active material layer may be a single layer or a multilayer. Each layer in a multilayer cathode active material may include the same or different cathode active materials. The positive electrode active material is a material that can reversibly insert and release metal ions such as arbitrary lithium ions.

The type of positive electrode active material is not particularly limited, as long as it can absorb and release metal ions (for example, lithium ions) in an electrochemical manner. In some embodiments, the positive active material is a material that includes lithium and at least one transition metal. Examples of positive electrode active materials include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

In one embodiment, the transition metal in the lithium transition metal composite oxide is V, Ti, Cr, Mn, Fe, Co, Ni, Cu, or the like. In some embodiments, the lithium _transition metal composite oxide is a lithium-cobalt composite oxide such as _LiCoO2 ; a lithium-nickel composite oxide such as _LiNiO2 ; a lithium transition metal composite oxide such as _LiMnO2 , _LiMn2O4 , _{Li2MnO4 ,} etc. - Manganese composite oxide; including lithium-nickel-manganese-cobalt composite oxides such as LiNi _1/3 Mn _1/3 Co _1/3 O ₂ and LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , Some of the transition metal atoms that form the main part of these lithium transition metal composite oxides are Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, and Zn. , Mg, Ga, Zr, Si, Nb, Mo, Sn, W, and other elements. Examples of lithium transition metal composite oxides 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 , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O ₄ and the like, but are not limited to these. Examples of combinations of lithium-transition metal composite oxides include, but are not limited to, combinations of LiCoO ₂ and LiMn ₂ O ₄ , and even if part of Mn in LiMn ₂ O ₄ is replaced with a transition metal. Often (eg, LiNi _0.33 Co _0.33 Mn _0.33 O ₂ ), some of the Co in LiCoO ₂ may be replaced with a transition metal.

In some embodiments, the transition metals in the lithium-containing transition metal phosphate compound include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like. In some embodiments, _the lithium-containing transition metal phosphate compounds include iron phosphates such as _{LiFePO4 , Li3Fe2} ( _PO4 ) ₃ , _LiFeP2O7 ; cobalt phosphates such as _LiCoPO4 ; Some of the transition metal atoms that are the main part of the lithium-containing transition metal phosphate compound are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb. , Si, and other elements.

In some embodiments, the positive electrode active material includes lithium phosphate, which can improve the continuous charging characteristics of the electrochemical device. There are no restrictions on the use of lithium phosphate. In some embodiments, the positive electrode active material and lithium phosphate are used in combination. In some embodiments, the content of lithium phosphate based on the weight of the positive electrode active material and lithium phosphate is more than 0.1%, more than 0.3%, or more than 0.5%. In some embodiments, the content of lithium phosphate based on the weight of the positive electrode active material and lithium phosphate is less than 10%, less than 8%, or less than 5%. In some embodiments, the content of lithium phosphate is within a range comprised of any two values listed above.

surface coating
A substance having a composition different from that of the positive electrode active material may be attached to the surface of the positive electrode active material described above. Examples of surface-attached substances include oxides such as aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, Sulfates such as calcium sulfate and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; carbon, and the like, but are not limited to these.

These surface-adhering substances can be prepared by dissolving or suspending the surface-adhering substances in a solvent, impregnating the positive electrode active material, adding it, and drying; It can be attached to the surface of the positive electrode active material by adding it to a precursor of the positive electrode active material and reacting it by heating or the like; or by adding it to a precursor of the positive electrode active material and baking it at the same time. When attaching carbon, a method of mechanically attaching a carbon material (for example, activated carbon, etc.) can also be used.

In some embodiments, the content of the surface-attached material is greater than 0.1 ppm, greater than 1 ppm, or greater than 10 ppm, based on the weight of the positive electrode active material layer. In some embodiments, the content of the surface-attached material is less than 10%, less than 8%, or less than 5% based on the weight of the positive electrode active material layer. In one embodiment, the content of the surface-attached substance relative to the weight of the positive electrode active material layer is within a range comprised of any two values described above.

By attaching a substance to the surface of the positive electrode active material, the oxidation reaction of the electrolyte 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 attached to the surface is too small, the effect will not be fully expressed, and if the amount of the substance attached to the surface is too large, the resistance may increase because occlusion and release of lithium ions are inhibited.

In the present invention, a positive electrode active material in which a substance having a composition different from that of the positive electrode active material is attached to the surface thereof is also referred to as a "positive electrode active material."

shape
In some embodiments, the shape of the particles of the positive electrode active material includes, but is not limited to, a block, a polyhedron, a sphere, an ellipsoid, a plate, a needle, a column, and the like. In some embodiments, the particles of positive electrode active material include primary particles, secondary particles, or a combination thereof. In some embodiments, primary particles may aggregate to form secondary particles.

tap density
In certain examples, the tap density of the cathode active material is greater than 0.5 g/cm ³ , greater than 0.8 g/cm ³ , or greater than 1.0 g/cm ³ . When the tap density of the positive electrode active material is within the above range, the amount of dispersion medium, conductive material, and positive adhesive required for forming the positive electrode active material layer can be suppressed, so that the filling rate of the positive electrode active material and The capacity of the electrochemical device can be secured. By using composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. In general, the higher the tap density, the better, and there is no particular upper limit. In certain examples, the tap density of the cathode active material is less than 4.0 g/cm ³ , less than 3.7 g/cm ³ , or less than 3.5 g/cm ³ . When the tap density of the positive electrode active material has the above upper limit, deterioration in load characteristics can be suppressed.

The positive electrode active material tapped density is determined as the powder packing density (tap density) when 5 g to 10 g of positive electrode active material powder is placed in a 10 mL glass graduated cylinder and tapped 200 times with a stroke of 20 mm.

Median diameter (D50)
When the positive electrode active material particles are primary particles, the median diameter (D50) of the positive electrode active material particles refers to the primary particle diameter of the positive electrode active material particles. When the primary particles of the positive electrode active material particles aggregate to form secondary particles, the median diameter (D50) of the positive electrode active material particles refers to the secondary particle diameter of the positive electrode active material particles.

In certain examples, the median diameter (D50) of the particles of the positive electrode active material is greater than 0.3 μm, greater than 0.5 μm, greater than 0.8 μm, or greater than 1.0 μm. In certain examples, the median diameter (D50) of the particles of the positive electrode active material is less than 30 μm, less than 27 μm, less than 25 μm, or less than 22 μm. In one embodiment, the median diameter (D50) of the particles of the positive electrode active material is within a range comprised of any two values described above. When the median diameter (D50) of the particles of the positive electrode active material is within the above range, a positive electrode active material with a high tap density can be obtained, and deterioration of the characteristics of the electrochemical device can be suppressed. On the other hand, it is possible to prevent problems such as the formation of streaks during the preparation process of the positive electrode of an electrochemical device (i.e., when the positive electrode active material, conductive material, adhesive, etc. are made into a slurry with a solvent and applied in the form of a thin film). can. Here, by mixing two or more types of positive electrode active materials having different median diameters, it is possible to further improve the filling property during the preparation of the positive electrode.

The particle median diameter (D50) of the positive electrode active material may be measured using a laser diffraction/scattering particle size distribution analyzer. When using HORIBA's LA-920 as a particle size distribution meter, a 0.1% sodium hexametaphosphate aqueous solution is used as the dispersion medium during measurement, and the measured refractive index is set to 1.24 after 5 minutes of ultrasonic dispersion. It is measured by

Average primary particle size
When the primary particles of the positive electrode active material particles aggregate to form secondary particles, in some embodiments, the average primary particle size of the positive electrode active material is greater than 0.05 μm, greater than 0.1 μm, or greater than 0.5 μm. It is. In certain examples, the average primary particle size of the positive electrode active material is less than 5 μm, less than 4 μm, less than 3 μm, or less than 2 μm. In one embodiment, the average primary particle diameter of the positive electrode active material is within a range comprised of any two values described above. When the average primary particle diameter of the positive electrode active material is within the above range, it is possible to ensure powder filling performance and specific surface area, suppress deterioration of battery characteristics, and obtain appropriate crystallinity. The reversibility of discharge can be ensured.

The average primary particle diameter of the positive electrode active material is obtained by observing an image using a scanning electron microscope (SEM). In a SEM image with a magnification of 10,000 times, for any 50 primary particles, find the longest value of the intercept by the left and right boundaries of the primary particles with respect to the horizontal line, and take the average value to determine the average primary particle diameter. is obtained.

Specific surface area (BET)
In certain examples, the specific surface area (BET) of the cathode active material is greater than 0.1 m ² /g, greater than 0.2 m ² /g, or greater than 0.3 m ² /g. In certain examples, the specific surface area (BET) of the cathode active material is less than 50 m ² /g, less than 40 m ² /g, or less than 30 m ² /g. In certain embodiments, the specific surface area (BET) of the cathode active material is within a range consisting of any two values described above. When the specific surface area (BET) of the positive electrode active material is within the above range, the positive electrode active material can have good coating properties while ensuring the characteristics of the electrochemical device.

The specific surface area (BET) of the positive electrode active material is measured using a surface area meter (e.g., fully automatic surface area measuring device manufactured by Okura Riken). After pre-drying the sample at 150°C for 30 minutes with nitrogen gas flowing It can be measured by a nitrogen adsorption BET one-point method using a gas flow method using a nitrogen-helium mixed gas that has been accurately adjusted so that the value of the relative pressure of nitrogen to atmospheric pressure is 0.3.

Positive conductive material
The type of positive electrode conductive material is not limited, and any known conductive material can be used. Examples of positive conductive materials include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; carbon nanotubes; graphene, and the like. The positive electrode conductive materials described above may be used alone or in any combination.

In some embodiments, the content of the cathode conductive material is more than 0.01%, more than 0.1%, or more than 1% based on the weight of the cathode active material layer. In some embodiments, the content of the cathode conductive material is less than 10%, less than 8%, or less than 5% based on the weight of the cathode active material layer. When the content of the positive electrode conductive material is within the above range, sufficient conductivity and capacity of the electrochemical device can be ensured.

positive electrode adhesive
The type of positive electrode adhesive used in manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material may be used as long as it is soluble or dispersible in the liquid medium used during electrode manufacturing. Examples of positive electrode adhesives include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; styrene-butadiene rubber (SBR), isoprene rubber, polybutadiene rubber, and fluororubber. , acrylonitrile-butadiene rubber (NBR), ethylene-propylene rubber, and other rubbery polymers; styrene-butadiene-styrene block copolymers or their hydrides; ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene - Thermoplastic elastomeric polymers such as butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers or their hydrides; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers , soft resinous polymers such as propylene-α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene-ethylene copolymers; alkalis It includes, but is not limited to, one or more polymer compositions having ionic conductivity for metal ions (particularly lithium ions). The positive electrode adhesives described above may be used alone or in any combination.

In some embodiments, the content of the positive electrode adhesive is more than 0.1%, more than 1%, or more than 1.5% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode adhesive is less than 10%, less than 8%, less than 4%, or less than 3% based on the weight of the positive electrode active material layer. When the content of the positive electrode adhesive is within the above range, the capacity of the electrochemical device can be ensured while giving the positive electrode good conductivity and sufficient mechanical strength.

solvent
The type of solvent for forming the positive electrode slurry is not limited, and any solvent may be used as long as it can dissolve or disperse the positive electrode active material, the conductive material, the positive electrode adhesive, and the thickener used as necessary. Examples of the solvent for forming the positive electrode slurry may include either an aqueous solvent or an organic solvent. Examples of aqueous solvents include, but are not limited to, water and mixtures of alcohol and water. Examples of organic solvents include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; and acetone, ethyl methyl ketone, and cyclohexanone. Ketones; Esters such as methyl acetate and methyl acrylate; Amines such as diethylenetriamine and N,N-dimethylaminopropylamine; Ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) ), dimethylformamide, dimethylacetamide, and other amides; aprotic polar solvents such as hexamethylphosphalamide, dimethylsulfoxide, and the like, but are not limited thereto.

thickener
Thickeners are commonly used to adjust the viscosity of the slurry. When using an aqueous solvent, a thickener and styrene-butadiene rubber (SBR) latex may be used to form a slurry. The type of thickener is not particularly limited, and examples thereof include, but are not limited to, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. . The above-mentioned thickeners may be used alone or in any combination.

In some embodiments, the content of the thickener is greater than 0.1%, greater than 0.2%, or greater than 0.3%, based on the weight of the positive electrode active material layer. In some embodiments, the content of thickener is less than 5%, less than 3%, or less than 2%, based on the weight of the positive electrode active material layer. In one embodiment, the content of the thickener relative to the weight of the positive electrode active material layer is within a range comprised of any two values described above. When the content of the thickener is within the above range, it is possible to provide the positive electrode slurry with good coating properties while suppressing a decrease in capacity and an increase in resistance of the electrochemical device.

Content of cathode active material
In some embodiments, the content of the cathode active material is greater than 80%, greater than 82%, or greater than 84%, based on the weight of the cathode active material layer. In some embodiments, the content of the cathode active material is less than 99%, or less than 98%, based on the weight of the cathode active material layer. In one embodiment, the content of the positive electrode active material relative to the weight of the positive electrode active material layer is within a range comprised of any two values described above. When the content of the positive electrode active material is within the above range, the strength of the positive electrode can be maintained while ensuring the electric capacity of the positive electrode active material in the positive electrode active material layer.

Density of positive electrode active material layer
The positive electrode active material layer obtained by coating and drying may be subjected to a consolidation treatment using a hand press, a roller press, etc. in order to increase the packing density of the positive electrode active material. In certain examples, the density of the positive electrode active material layer is greater than 1.5 g/cm ³ , greater than 2 g/cm ³ , or greater than 2.2 g/cm ³ . In certain examples, the density of the positive electrode active material layer is less than 5 g/cm ³ , less than 4.5 g/cm ³ , or less than 4 g/cm ³ . In some embodiments, the density of the positive electrode active material layer is within a range comprised of any two values described above. When the density of the positive electrode active material layer is within the above range, an increase in resistance can be suppressed while giving the electrochemical device good charge and discharge characteristics.

Thickness of positive electrode active material layer
The thickness of the positive electrode active material layer refers to the thickness of the positive electrode active material layer on any one side of the positive electrode current collector. In certain embodiments, the thickness of the positive electrode active material layer is greater than 10 μm, or greater than 20 μm. In certain embodiments, the thickness of the positive electrode active material layer is less than 500 μm, or less than 450 μm.

Manufacturing method of positive electrode active material
The positive electrode active material may be manufactured by a common method for manufacturing inorganic compounds. In order to create a spherical or ellipsoidal positive electrode active material, the following manufacturing method may be employed. A transition metal raw material is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to create and collect a spherical precursor. After drying this as necessary, LiOH, A Li source such as Li ₂ CO ₃ or LiNO ₃ is added and fired at a high temperature to obtain a positive electrode active material.

2. Positive electrode current collector
The type of positive electrode current collector is not particularly limited, and may be any material applicable to any known positive electrode current collector. Examples of positive electrode current collectors include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, etc.; carbon materials such as carbon cloth, carbon paper, etc. In some embodiments, the positive electrode current collector is a metallic material. In some embodiments, the positive current collector is aluminum.

The form of the positive electrode current collector is not particularly limited. When the positive electrode current collector is a metal material, the form of the positive electrode current collector includes metal foil, metal cylinder, metal coil, metal plate, metal foil, metal mesh sheet, punched metal, foamed metal, etc. Not limited. When the positive electrode current collector is made of a carbon material, the form of the positive electrode current collector includes, but is not limited to, a carbon plate, a carbon thin film, a carbon cylinder, and the like. In some embodiments, the positive current collector is a metal foil. In one embodiment, the metal foil is mesh-like. The thickness of the metal foil is not particularly limited. In certain embodiments, the thickness of the metal foil is greater than 1 μm, greater than 3 μm, or greater than 5 μm. In certain embodiments, the thickness of the metal foil is less than 1 mm, less than 100 μm, or less than 50 μm. In some embodiments, the thickness of the metal foil is within a range consisting of any two values listed above.

In order to reduce the electronic contact resistance of the positive electrode current collector and the positive electrode active material layer, a conductive additive may be included on the surface of the positive electrode current collector. Examples of conductive aids include, but are not limited to, carbon and noble metals such as gold, platinum, silver, and the like.

The thickness ratio between the positive electrode active material layer and the positive electrode current collector refers to the thickness of the positive electrode active material layer on one side divided by the thickness of the positive electrode current collector, and its value is not particularly limited. In certain examples, the thickness ratio is less than 50, less than 30, or less than 20. In certain embodiments, the thickness ratio is greater than 0.5, greater than 0.8, or greater than 1. In some embodiments, the thickness ratio is within a range consisting of any two of the values listed above. When the thickness ratio is within the above range, heat radiation of the positive electrode current collector during high current density charging and discharging can be suppressed, and the capacity of the electrochemical device can be ensured.

3. Method for producing positive electrode
The positive electrode is produced by forming a positive electrode active material layer containing a positive electrode active material and an adhesive on a current collector. A positive electrode using a positive electrode active material can be produced by a conventional method. That is, a positive electrode active material, an adhesive, and if necessary a conductive material, a thickener, etc. are mixed together in a dry manner and formed into a sheet, which is then pressed onto a positive electrode current collector; or these materials are mixed into a liquid medium. A positive electrode can be obtained by dissolving or dispersing the slurry, applying it to a positive electrode current collector, and drying it to form a positive electrode active material layer on the current collector.

IV, separator
A separator is usually provided between the positive electrode and the negative electrode to prevent short circuits. In this case, the electrolytic solution of the present invention is usually used by impregnating the separator.

The material and shape of the separator are not particularly limited as long as they do not significantly impair the effects of the present invention. The separator may be made of a resin, glass fiber, an inorganic material, etc. made of a material that is stable to the electrolytic solution of the present invention. In one embodiment, the separator includes a porous sheet or non-woven material with excellent liquid retention properties. Examples of resin or fiberglass separator materials include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and the like. In certain embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The separator materials described above may be used alone or in any combination.

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

Examples of inorganic materials include, but are not limited to, oxides such as aluminum oxide, silicon dioxide; nitrides such as aluminum nitride, silicon nitride; sulfates (eg, barium sulfate, calcium sulfate, etc.). The form of the inorganic substance includes, but is not limited to, particulate or fibrous form.

The form of the separator is a thin film form, examples of which include, but are not limited to, nonwoven fabrics, woven fabrics, microporous films, and the like. In the form of a thin film, the separator has a pore diameter of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm. In addition to the above-mentioned independent thin film separators, separators in which a composite porous layer containing the above-mentioned inorganic particles is formed on the surface of the positive electrode and/or negative electrode using a resin adhesive, such as a pressure-sensitive adhesive. It is also possible to use a separator in which a porous layer of aluminum oxide having a 90% particle size of less than 1 μm is formed on both sides of the positive electrode using a fluororesin.

The thickness of the separator is arbitrary. In certain embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In certain 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 a range consisting of any two values listed above. When the thickness of the separator is within the above range, it is possible to ensure the rate characteristics and energy density of the electrochemical device while ensuring insulation and mechanical strength.

When using a porous material such as a porous sheet or a nonwoven fabric as a separator, the porosity of the separator is arbitrary. In certain embodiments, the porosity of the separator is greater than 10%, greater than 15%, or greater than 20%. In certain embodiments, the porosity of the separator is less than 60%, less than 45%, or less than 40%. In some embodiments, the porosity of the separator is within a range consisting of any two values listed above. When the porosity of the separator is within the above range, the resistance of the membrane can be suppressed while ensuring insulation and mechanical strength, and the electrochemical device can have good rate characteristics.

The average pore diameter of the separator is also arbitrary. In certain embodiments, the average pore size of the separator is less than 0.5 μm, or less than 0.2 μm. In certain embodiments, the average pore size of the separator is greater than 0.05 μm. In some embodiments, the average pore size of the separator is within a range comprised of any two values described above. If 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, short circuits can be prevented while suppressing membrane resistance, and the electrochemical device can have good rate characteristics.

V. Parts of electrochemical equipment
The parts of the electrochemical device include an electrode assembly, a current collection structure, an outer case, and a protection element.

electrode assembly
The electrode assembly has a laminated structure formed by laminating the above-described positive electrode and negative electrode with the above-mentioned separator interposed therebetween, and a structure in which the above-described positive electrode and negative electrode are spirally wound with the above-mentioned separator interposed therebetween. Either one of these may be provided. In some embodiments, the ratio of the mass of the electrode assembly to the internal battery volume (electrode assembly occupancy) is greater than 40%, or greater than 50%. In certain embodiments, the electrode assembly occupancy is less than 90%, or less than 80%. In some embodiments, the electrode assembly occupancy is within a range consisting of any two of the values listed above. When the electrode assembly occupancy is within the above range, it is possible to ensure the capacity of the electrochemical device while suppressing deterioration of characteristics such as repeated charging/discharging characteristics and high-temperature storage due to increases in internal pressure.

Current collection structure
The current collecting structure is not particularly limited. In some embodiments, the current collecting structure is a structure that reduces the resistance of the wiring portion and the bonding portion. When the electrode assembly has the above-described laminated structure, a structure in which the metal core portions of each electrode layer are bundled and welded to a terminal is preferably used. As the area of one electrode increases, the internal resistance increases, so it is also suitable to provide two or more terminals within the electrode to reduce the resistance. When the electrode assembly has the above-described wound structure, internal resistance can be lowered by providing two or more lead structures for each of the positive and negative electrodes and bundling them into a terminal.

exterior case
The material of the outer case is not particularly limited as long as it is stable with respect to the electrolyte used. For the exterior case, metals such as nickel-plated steel plates, stainless steel, aluminum or aluminum alloys, magnesium alloys, or laminated films of resin and aluminum foil are used, but are not limited thereto. In some embodiments, the outer case is aluminum or aluminum alloy metal, or a laminated film.

The metal exterior case includes a hermetically sealed structure in which metals are welded together by laser welding, resistance welding, or ultrasonic welding; or a rivet structure in which the above metals are used through a resin gasket. Not limited to these. Exterior cases using the above-described laminated film include, but are not limited to, a hermetically sealed structure formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminated film may be interposed between the resin layers described above. When creating a sealed structure by heat-sealing a resin layer through a current collector terminal, the metal and resin are bonded, so a resin with a polar group or a modified resin with a polar group introduced is used as the intervening resin. used. Moreover, the shape of the exterior case is also arbitrary, and may be any one of a cylindrical shape, a square shape, a laminate shape, a button shape, a large size, etc., for example.

protection element
As a protection element, positive temperature coefficient (PTC), which increases resistance when abnormal heat generation or excessive current flows, thermal fuse, thermistor, interrupts the current flowing to the circuit due to a sudden rise in battery internal pressure or internal temperature when abnormal heat generation occurs. A valve (current cutoff valve), etc. is used. The protection element described above may be an element that does not operate under normal use of high current, or may be designed to prevent abnormal heat generation or thermal runaway even without the protection element.

VI, Application
The electrochemical device of the present invention includes any device in which an electrochemical reaction occurs, specific examples of which include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery or a lithium ion secondary battery.

The invention further provides an electronic device comprising an electrochemical device according to the invention.

The application of the electrochemical device of the present invention is not particularly limited, and it can be used in any electronic device known in the existing technology. In certain embodiments, the electrochemical device of the present invention can be used in notebook computers, pen input computers, mobile computers, e-book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, headphone stereos, video movies, LCD televisions, and handy cleaners. , portable CDs, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting equipment, toys, game equipment, watches, power tools. , strobes, cameras, household large storage batteries, lithium ion capacitors, etc., but are not limited to these.

In the following, the preparation of lithium ion batteries will be explained with reference to specific examples, taking lithium ion batteries as an example, and those skilled in the art will understand that the preparation method described in the present invention is only an example and that other It should be understood that any suitable method of preparation is within the scope of the present invention.

EXAMPLES Hereinafter, examples and comparative examples of lithium ion batteries according to the present invention will be explained and performance evaluations will be performed.

1. Preparation of lithium ion battery 1. Preparation of negative electrode Artificial graphite, rubber, and sodium carboxymethyl cellulose were mixed with deionized water at a mass ratio of 96%:2%:2% and stirred uniformly to obtain a negative electrode slurry. . The negative electrode slurry was applied onto a 12 μm current collector, dried, cold pressed, punched, and tabs were welded to obtain a negative electrode.

2. Preparation of positive electrode Lithium cobalt oxide (LiCoO ₂ ), a conductive material (Super-P) and polyvinylidene fluoride (PVDF) are mixed with N-methylpyrrolidone (NMP) at a mass ratio of 95%:2%:3%, A positive electrode slurry was obtained by uniformly stirring. This positive electrode slurry was applied onto a 12 μm aluminum foil, dried, cold pressed, punched, and a tab was welded to obtain a positive electrode.

3. Preparation of electrolyte In a dry argon gas atmosphere, mix EC, PC and DEC (weight ratio 1:1:1), add LiPF ₆ so that the concentration of LiPF ₆ is 1.15 mol/L. Stir uniformly to form a base electrolyte. Different contents of additives were added to the basic electrolyte to obtain electrolytes of different examples and comparative examples.

The abbreviations and names of the components in the electrolyte are shown in Table 2 below.

4. Preparation of separator A polyethylene (PE) porous polymer thin film was used as a separator.

5. Preparation of lithium ion battery The obtained positive electrode, separator and negative electrode are wound in order and placed in an exterior foil, leaving a liquid injection port. A lithium-ion battery was obtained by injecting electrolyte through the injection port, sealing, chemical formation, and capacity measurement.

2.Measurement method 1.Measurement method of rate characteristics of lithium ion battery At 25℃, discharge the lithium ion battery to 3.0V at 0.2C, let it stand for 5 minutes, and charge it to 4.4V at 0.5C. After charging at a constant voltage to 0.05C, let it stand for 5 minutes, adjust the discharge rate, measure the discharge at 0.2C and 5.0C, obtain the discharge capacity, and calculate the rate of 5.0C. The capacity obtained at 0.2C was compared with the capacity obtained at 0.2C, the ratio was obtained, and the rate characteristics of the lithium ion battery were evaluated.

2. Method for measuring the thickness expansion rate of lithium ion batteries After leaving the lithium ion battery at 25°C for 30 minutes and measuring its thickness T1, the temperature was increased at a rate of 5°C/min. When the temperature reached 130°C, the temperature was held for 30 minutes and the thickness T2 of the lithium ion battery was measured. The thickness expansion rate of the lithium ion battery was calculated using the following formula.
Thickness expansion rate = [(T2-T1)/T1] x 100%

3. Measurement Results Table 3 shows the influence of the yield point elongation X% of the negative electrode mixture layer, the median diameter Y μm of the negative electrode active material, and their relationship on the rate characteristics and thickness expansion rate of the lithium ion battery.

From the results, when the yield point elongation X% of the negative electrode mixture layer and the median diameter Yμm of the negative electrode active material satisfy 0.1≦X/Y≦30, and the electrolyte contains a compound having a cyano group, charging and discharging are possible. It suppresses the expansion/contraction of the negative electrode caused by the process, stabilizes the interface between the negative electrode mixture layer and the electrolyte, and significantly improves the rate characteristics of lithium ion batteries, reduces its thickness expansion rate, and improves its safety. It can be seen that performance can be improved.

Table 4 shows the effect of rubber on the rate characteristics and thickness expansion of lithium ion batteries. The only difference between Examples 2-1 to 2-9 and Example 1-1 is the parameters listed in Table 4.

The results show that the yield point elongation of the negative electrode mixture layer can be adjusted by using different rubbers. When the yield point elongation of the negative electrode mixture layer is within the range of 10% to 30% and Y is within the range of 1 to 50, the rate characteristics of the lithium ion battery can be further improved and its thickness expansion rate can be increased. can be reduced.

Table 5 shows the influence of trace metals in the negative electrode active material on the rate characteristics and thickness expansion rate of lithium ion batteries. The only difference between Examples 3-1 to 3-8 and Example 1-1 is the parameters listed in Table 5.

The results show that the presence of trace metal elements (i.e. less than 0.05% iron, molybdenum and/or copper) in the negative electrode active material can further improve the rate characteristics of lithium-ion batteries and reduce their thickness expansion rate. It can be seen that the safety performance can be improved.

Table 6 shows the effects of compounds having cyano groups on the rate characteristics improvement and thickness expansion rate of lithium ion batteries. The only difference between Examples 4-1 to 4-6 and Example 1-1 is the parameters listed in Table 6.

As can be seen from Examples 4-1, 4-4 and 4-5, a dinitrile compound (ADN or SN) that does not contain a high content of ether bonds and a dinitrile compound (EDN) that contains a low content of ether bonds. When used in combination, it is possible to further improve the rate characteristics of the lithium ion battery, reduce its thickness expansion rate, and improve its safety performance.

As can be seen from Examples 4-2, 4-3 and 4-6, by combining a high content of a dinitrile compound not containing an ether bond (ADN or SN) and a low content of a trinitrile compound (HTCN or TCEP), By using it, it is possible to further improve the rate characteristics of the lithium ion battery, reduce its thickness expansion rate, and improve its safety performance.

Table 7 shows the influence of electrolyte components on the rate characteristics and thickness expansion rate of lithium ion batteries. The only difference between Examples 5-1 to 5-31 and Example 1-1 is the parameters listed in Table 7.

From the results, the yield point elongation X% of the negative electrode mixture layer and the median diameter Y μm of the negative electrode active material satisfy 0.1≦X/Y≦30, and the electrolyte solution contains a compound having a cyano group. In addition, when the electrolyte further contains fluoroethylene carbonate, a compound containing a sulfur-oxygen double bond, lithium difluorophosphate, and/or a compound represented by formula 1, the rate characteristics of the lithium ion battery are further improved, It can be seen that its thickness expansion rate can be reduced and its safety performance can be improved.

Table 8 shows the influence of the relationship between the median diameter Y μm of the negative electrode active material and the content b% of fluoroethylene carbonate in the electrolyte on the rate characteristics and thickness expansion rate of the lithium ion battery. The only difference between Examples 6-1 to 6-9 and Example 5-1 is the parameters listed in Table 8.

The results show that when the content of fluoroethylene carbonate in the electrolyte is between 0.1% and 10%, it can further improve the rate characteristics of lithium-ion batteries, reduce its thickness expansion rate, and improve its safety performance. I know that I can do it. When the median diameter Yμm of the negative electrode active material and the content b% of fluoroethylene carbonate in the electrolytic solution satisfy 4≦Y×b≦200, the rate characteristics of the lithium ion battery are further improved and its thickness expansion rate is reduced. and improve its safety performance.

Table 9 shows the influence of the relationship between the yield point elongation X% of the negative electrode mixture layer and the content Z% of the compound having a cyano group in the electrolyte on the rate characteristics and thickness expansion rate of the lithium ion battery. . The only difference between Examples 7-1 to 7-6 and Example 1-1 is the parameters listed in Table 9.

From the results, when the yield point elongation X% of the negative electrode mixture layer and the content Z% of the compound having a cyano group in the electrolytic solution satisfy 2≦X/Z≦100, the rate characteristics of the lithium ion battery can be further improved. , its thickness expansion rate can be reduced and its safety performance improved.

Throughout the specification, references to "embodiment", "subembodiment", "an embodiment", "another embodiment", "example", "specific embodiment" or "subexample" refer to the present invention. Reference to at least one embodiment or example of is meant to include the particular feature, structure, material or property described in that embodiment or example. Thus, in various places throughout the specification, for example, "in one embodiment," "in an embodiment," "in one embodiment," "in another instance," "in one example," " References to "in a particular example" or "example" are not necessarily referring to the same embodiment or example of the present invention. Additionally, the particular features, structures, materials, or characteristics described herein may be combined in any suitable manner in one or more embodiments or examples.

Although illustrative embodiments have been described and illustrated, those skilled in the art will understand that the above-described embodiments are not to be construed as limiting the invention and do not depart from the spirit, principle, and scope of the invention. It should be understood that modifications, substitutions and changes to the embodiments are possible.

Claims (16)

An electrochemical device comprising a positive electrode, a negative electrode and an electrolyte,
The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector, and the negative electrode mixture layer includes a negative electrode active material.
When the yield point elongation of the negative electrode mixture layer is X% and the median diameter of the negative electrode active material is Y μm, X and Y satisfy 0.1≦X/Y≦30,
The electrolyte includes a compound having a cyano group,
The compound having a cyano group includes a dinitrile compound and a trinitrile compound having an ether bond, and the content of the dinitrile compound is greater than the content of the trinitrile compound having an ether bond with respect to the weight of the electrolytic solution. Device. The electrochemical device according to claim 1, wherein the X is within the range of 10-30 and the Y is within the range of 1-50. The electrochemical device according to claim 1, wherein the content of the compound having a cyano group is Z% based on the weight of the electrolytic solution, and Z is within a range of 0.1 to 10. The electrochemical device according to claim 3, wherein the X and the Z satisfy 2≦X/Z≦100. The negative electrode mixture layer includes rubber, and the rubber includes at least one of styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluoro rubber, acrylonitrile-butadiene rubber, and styrene-propylene rubber. Electrochemical device. 6. The electrochemical device according to claim 5, wherein the rubber further includes at least one of an acrylic acid functional group, a chlorotrifluoroethylene functional group, and a hexafluoropropylene functional group. The negative electrode active material is
(i): Contains at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, amorphous carbon, silicon-containing material, tin-containing material, and alloy material;
(ii): Contains a metal, the metal includes at least one of molybdenum, iron, or copper, and the content of the metal is 0.05% or less based on the weight of the negative electrode mixture layer. The electrochemical device according to claim 1, which satisfies at least one of the following. The compounds having a cyano group include succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethyl Glutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, ethylene glycol bis( propionitrile) ether, 3,5-dioxa-pimeronitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis( 2-cyanoethyl) ether, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethoxy)pentane, ethylene glycol bis(4 -cyanobutyl) ether, 1,4-dicyano-2-butene, 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 , 3,5-pentane tricarbonitrile, 1,2,3-propane tricarbonitrile, 1,3,6-hexane tricarbonitrile, 1,2,6-hexane tricarbonitrile, 1,2,3-tris (2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane , 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane or 1,2,5- The electrochemical device according to claim 1, comprising at least one type of tris(cyanoethoxy)pentane. The compound having a cyano group contains a dinitrile compound not containing an ether bond and a dinitrile compound containing an ether bond, and the content of the dinitrile compound not containing an ether bond is greater than the content of the dinitrile compound containing an ether bond. , The electrochemical device according to claim 1. The electrochemical device according to claim 1, wherein the compound having a cyano group includes a dinitrile compound and a trinitrile compound, and the content of the dinitrile compound is greater than the content of the trinitrile compound. The electrolyte further includes at least one compound selected from compounds a) and d),
a) fluoroethylene carbonate,
b) a compound containing a sulfur-oxygen double bond,
c) lithium difluorophosphate,
d) Compound represented by formula 1

However, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently hydrogen or a C ₁ to C ₁₀ alkyl group,
L ₁ and L ₂ are each independently -(CR ⁷ R ⁸ ) _n -,
R ⁷ and R ⁸ are each independently hydrogen or a C ₁ -C ₁₀ alkyl group, and
The electrochemical device according to claim 1, wherein n is 1, 2 or 3. The compound represented by the formula 1 is:

The electrochemical device according to claim 11, comprising at least one of the following. The electrochemical device according to claim 11, wherein the content of the compound represented by formula 1 is within the range of 0.01% to 5% with respect to the weight of the electrolytic solution. The electrochemical device according to claim 11, wherein the content of the fluoroethylene carbonate is b% based on the weight of the electrolytic solution, and b is in the range of 0.1 to 10. The electrochemical device according to claim 14, wherein the Y and the b satisfy 4≦Y×b≦200. An electronic device comprising the electrochemical device according to any one of claims 1 to 15.