Electro-chemical apparatus and electronic apparatus

Abstract

To provide an electro-chemical apparatus and an electronic apparatus having improved performance.SOLUTION: An electro-chemical apparatus according to an aspect of the present invention includes a positive electrode, a negative electrode, and an electrolytic solution. The negative electrode includes a negative electrode collector and a negative mixture layer formed in the negative electrode collector. The negative electrode collector includes tin. The negative electrode collector further includes silver. The content of silver relative to the weight of the negative electrode collector is 0.01% to 0.2%. The electrolytic solution includes a compound containing a sulfur-oxygen double bond.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to the field of energy storage, and more specifically, to electrochemical devices and electronic devices, particularly lithium-ion batteries.

Background Art

[0002] With the development of technology and the increasing demand for mobile devices, the demand for electrochemical devices (e.g., lithium-ion batteries) under different usage conditions has increased significantly. As a result, higher requirements are being placed on the performance of lithium-ion batteries, including high capacity, long cycle life, high temperature resistance, high rate discharge performance, and overcharge resistance.

[0003] During the use of a lithium-ion battery, if the charge control circuit fails, the lithium-ion battery is prone to overcharge, which causes an irreversible reduction reaction of lithium ions in the negative electrode and reduces the charge-discharge cycle efficiency of the lithium-ion battery. When the charging voltage reaches the decomposition voltage of the electrolyte, the electrolyte decomposes at the positive electrode of the lithium-ion battery, generating gas, increasing the pressure and temperature inside the lithium-ion battery, and reducing its stability. This has a serious impact on the high-temperature cycle characteristics, swelling characteristics, and safety of the lithium-ion battery, and may even lead to the complete failure of the lithium-ion battery. In view of this, there is a need to provide electrochemical devices and electronic devices with improved performance.

Summary of the Invention

[0004] Embodiments of the present invention provide electrochemical devices and electronic devices having improved high-temperature cycle characteristics and overcharge resistance, thereby solving at least one safety problem existing in the related art to some extent.

[0005] In one aspect of the present invention, there is provided 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 negative electrode current collector contains tin, and the electrolytic solution contains a compound containing a sulfur-oxygen double bond.

[0006] According to an embodiment of the present invention, the negative electrode current collector contains copper.

[0007] According to an embodiment of the present invention, when the content of tin is a% with respect to the weight of the negative electrode current collector, a is in the range of 0.01 to 0.2.

[0008] According to an embodiment of the present invention, the negative electrode current collector further contains silver, and the content of silver is 0.01% to 0.2% with respect to the weight of the negative electrode current collector.

[0009] According to an embodiment of the present invention, the negative electrode current collector 1) has an average surface roughness of 0.05 μm to 1.5 μm, 2) has a tensile strength of 100 N / mm 2 or more, 3) has a 0.2% proof stress of 30 N / mm 2 or more, 4) has a thickness of 1 μm to 100 μm, and satisfies at least one of the above.

[0010] According to an embodiment of the present invention, the negative electrode mixture layer a) has a reflectance Ra at a wavelength of 550 nm of 7% to 15%, b) has a density da of 1.3 g / cm 3 to 1.9 g / cm 3 or more, c) has a weight La per unit area of 4.5 mg / cm 2 to 12.5 mg / cm 2 or more, d) has a porosity Pa of 20% to 40%, and satisfies at least one of the above.

[0011] According to an embodiment of the present invention, the compound containing the sulfur-oxygen double bond includes at least one of cyclic sulfate, linear sulfate, linear sulfonate, cyclic sulfonate, linear sulfite, and cyclic sulfite.

[0012] According to an embodiment of the present invention, the compound containing the sulfur-oxygen double bond includes the compound of Formula 1, [Chemical formula] W is [Chemical formula] selected from, L is independently selected from a single bond and a methylene group, and two Ls in the same ring structure do not simultaneously form a single bond, m is 1, 2, 3 or 4, n is 0, 1 or 2, and p is 0, 1, 2, 3, 4, 5, or 6.

[0013] According to an embodiment of the present invention, the compound of Formula 1 includes [Chemical formula] at least one of.

[0014] According to an embodiment of the present invention, when the content of the compound containing the sulfur-oxygen double bond is b% based on the weight of the electrolyte, b is in the range of 0.01 to 10.

[0015] According to an embodiment of the present invention, the electrolyte further includes a propionate ester, and the propionate ester includes the compound of Formula 2, [Chemical formula] R 1 is selected from ethyl and ethyl halide, R 2is selected from C1-C6 alkyl and C1-C6 halogenated alkyl, and Based on the weight of the electrolyte, the content of the propionate ester is in the range of 10% to 60%.

[0016] According to an embodiment of the present invention, when the content of the compound containing the sulfur-oxygen double bond is b% based on the weight of the electrolyte, b is in the range of 0.01 to 10, and 1 ≤ b / a ≤ 100 is satisfied.

[0017] According to an embodiment of the present invention, the reaction area d m of the negative electrode mixture layer 2 and the content b% of the compound containing the sulfur-oxygen double bond satisfy 0.5 ≤ d / b ≤ 30.

[0018] In another aspect of the present invention, the present invention provides an electronic device including the electrochemical device described in the present invention.

[0019] Further aspects and advantages of the embodiments of the present invention will be partially described, shown, or interpreted by the implementation of the embodiments of the present invention in the following description.

Mode for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described in detail. The embodiments of the present invention should not be construed as limiting the present invention.

[0021] Unless otherwise specified, the following terms used in this specification have the meanings shown below.

[0022] In specific embodiments and claims, the term "at least one of" in connection with a list of items means any combination of the listed items. For example, if items A and B are listed, "at least one of A and B" means only A, only B, or A and B. In other examples, if items A, B, and C are listed, "at least one of A, B, and C" means only A, or only B, only C, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may include a single element or a plurality of elements. Item B may include a single element or a plurality of elements. Item C may include a single element or a plurality of elements. The term "at least one kind of" has the same meaning as the term "at least one of".

[0023] As used herein, the term "alkyl" is expected to be a straight-chain saturated hydrocarbon structure having 1 to 20 carbon atoms. Also, "alkyl" is expected to be a branched-chain or cyclic hydrocarbon structure having 3 to 20 carbon atoms. When specifying an alkyl group having a specific number of carbon atoms, all geometric isomers having that number of carbon atoms are expected to be included. Thus, for example, "butyl" means including n-butyl, sec-butyl, isobutyl, tert-butyl, and cyclobutyl, and "propyl" means including n-propyl, isopropyl, and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, etc.

[0024] As used herein, the term "halogenated" means that some or all of the hydrogen atoms in a group are replaced by halogen atoms (e.g., fluorine, chlorine, bromine, or iodine).

[0025] During the use of a lithium-ion battery, if the charge control circuit fails, the lithium-ion battery is prone to overcharging and overheating, which will seriously affect the performance of the lithium-ion battery. Generally, to avoid this problem, physical methods (e.g., integrated circuit protection method) and chemical methods (e.g., overcharge protection additive method) can be used. The integrated circuit method has the advantages of being reliable, fast, and widely applied, but it requires a complex structure (e.g., a plastic exterior is required) and is expensive. The overcharge protection additive method can use additives based on polymerization reactions (e.g., biphenyl, cyclohexylbenzene, etc.) or additives based on repeated redox reactions (e.g., lithium halide, metallocene and its derivatives, benzene derivatives, etc.). However, biphenyl and cyclohexylbenzene increase the internal resistance of the lithium-ion battery and reduce the performance of the lithium-ion battery. When a high charging current flows through the lithium-ion battery, lithium halide, metallocene and its derivatives, and benzene derivatives cannot exert a protective effect, and at the same time, they may reduce the cycle characteristics of the lithium-ion battery.

[0026] The present invention solves the above problems by combining a negative electrode current collector containing tin and an electrolytic solution containing a compound containing a sulfur-oxygen double bond, and significantly improves the high-temperature characteristics and overcharge resistance characteristics of the lithium-ion battery. When the electrochemical device of the present invention is in a high-temperature or overcharged state, the generated lithium-containing reductant spreads thinly over the entire surface of the negative electrode and is uniformly deposited, thereby reducing the irreversible capacity and helping to improve the discharge capacity, thereby improving the high-temperature cycle characteristics and overcharge resistance characteristics of the electrochemical device, and can maintain good performance without deformation of the electrochemical device.

[0027] In one embodiment, the present invention provides an electrochemical device including a positive electrode, a negative electrode, and an electrolyte as follows.

[0028] I. Negative electrode The negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on one or both sides of the negative electrode current collector.

[0029] 1. Negative electrode current collector One feature of the electrochemical device of the present invention is that the negative electrode current collector contains tin. The presence of tin helps to improve the strength and processability of the negative electrode current collector, suppress the expansion or contraction of the negative electrode during the charge and discharge process of the electrochemical device, and can significantly improve the high-temperature cycle characteristics and overcharge resistance characteristics of the electrochemical device.

[0030] In some embodiments, when the content of tin is a% based on the weight of the negative electrode current collector, a is in the range of 0.01 to 0.2. In some embodiments, a is in the range of 0.05 to 0.15. In some embodiments, a is in the range of 0.08 to 0.10. In some embodiments, a is 0.01, 0.03, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, or 0.2, or within the range consisting of any two of the above numerical values.

[0031] In some embodiments, the negative electrode current collector further contains silver. The presence of silver helps to further improve the high-temperature cycle characteristics and overcharge resistance characteristics of the electrochemical device.

[0032] In some embodiments, based on the weight of the negative electrode current collector, the silver content is from 0.01% to 0.2%. In some embodiments, based on the weight of the negative electrode current collector, the silver content is from 0.05% to 0.15%. In some embodiments, based on the weight of the negative electrode current collector, the silver content is from 0.08% to 0.10%. In some embodiments, based on the weight of the negative electrode current collector, the silver content is 0.01%, 0.03%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, or 0.2%, or within the range consisting of any two of the above numerical values.

[0033] When the content of tin or silver in the negative electrode current collector is within the range of 0.01% to 0.2%, it helps to suppress the oxidation of the surface of the negative electrode current collector, endows the negative electrode current collector with good electrical conductivity, and during the process of preparing the negative electrode, the negative electrode current collector can recrystallize during the drying step after coating the negative electrode mixture layer, and the high-temperature cycle characteristics and overcharge resistance characteristics of the electrochemical device can be further improved.

[0034] In some embodiments, the form of the negative electrode current collector includes, but is not limited to, metal foil, metal cylinder, metal strip coil, metal plate, metal film, expanded metal, punched metal, foam metal, etc. In some embodiments, the negative electrode current collector is a metal foil. In some embodiments, the metal foil is in a mesh shape.

[0035] In some embodiments, the negative electrode current collector contains copper.

[0036] In some embodiments, the negative electrode current collector is a copper foil. As used herein, the term "copper foil" includes copper alloy foils.

[0037] In some embodiments, the negative electrode current collector contains at least one of tough pitch copper and oxygen-free copper. As used herein, the term "tough pitch copper" includes copper alloy foils based on tough pitch copper, and the term "oxygen-free copper" includes copper alloy foils based on oxygen-free copper.

[0038] In some embodiments, the tough pitch copper complies with the JIS-H3100-C1100 standard. In some embodiments, the oxygen-free copper complies with the JIS-H3100-C1100 standard. The composition of the tough pitch copper or oxygen-free copper that meets the above criteria is close to pure copper, has good electrical conductivity, and is particularly suitable as a negative electrode current collector.

[0039] In some embodiments, the oxygen content (based on copper) in the tough pitch copper is 0.01% to 0.02%. In some embodiments, the oxygen content (relative to copper) in the oxygen-free copper is 0.001% or less.

[0040] In some embodiments, the copper foil contains impurities, and the impurities include at least one of P, Fe, Zr, Mg, S, Ge, and Ti. In some embodiments, the content of the impurities is 20 ppm or less based on the weight of the copper foil. When the content of the impurities in the copper foil is within the above range, it is difficult for the copper foil to undergo bending deformation, so the rotation of the crystal orientation is reduced, the generation of shear bands is avoided, and it contributes to the improvement of the fracture resistance of the negative electrode current collector.

[0041] According to an embodiment of the present invention, the negative electrode current collector has at least one of the following features (1) to (4).

[0042] (1) Average surface roughness In some embodiments, the average surface roughness of the negative electrode current collector is 0.05 μm to 1.5 μm. In some embodiments, the average surface roughness of the negative electrode current collector is 0.1 μm to 1.3 μm. In some embodiments, the average surface roughness of the negative electrode current collector is 0.15 μm to 1.0 μm. In some embodiments, the average surface roughness of the negative electrode current collector is 0.2 μm to 0.8 μm. In some embodiments, the average surface roughness of the negative electrode current collector is 0.3 μm to 0.5 μm. In some embodiments, the average surface roughness of the negative electrode current collector is 0.05 μm, 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.3 μm, or 1.5 μm, or within a range consisting of any two of the above numerical values. When the average surface roughness of the negative electrode current collector is within the above range, the interfacial area between the negative electrode current collector and the negative electrode binder layer increases, the adhesion between the negative electrode current collector and the negative electrode active material improves, contributing to the improvement of the high-temperature cycle characteristics and overcharge resistance characteristics of the electrochemical device.

[0043] The average surface roughness of the negative electrode current collector can be measured by the method described in ISO 1302:2002.

[0044] (2) Tensile strength As used herein, the term "tensile strength" means the ratio of the maximum tensile force required for a sample to break to the cross-sectional area of the sample.

[0045] In some embodiments, the tensile strength of the negative electrode current collector is 100 N / mm 2 or more. In some embodiments, the tensile strength of the negative electrode current collector is 150 N / mm 2 or more. In some embodiments, the tensile strength of the negative electrode current collector is 200 N / mm 2 or more. In some embodiments, the tensile strength of the negative electrode current collector is 250 N / mm 2 or more. In some embodiments, the tensile strength of the negative electrode current collector is 300 N / mm 2 or more. In some embodiments, the tensile strength of the negative electrode current collector is 350 N / mm 2The above is the case. In some embodiments, the tensile strength of the negative electrode current collector is 400 N / mm 2 The above is the case. In some embodiments, the tensile strength of the negative electrode current collector is 450 N / mm 2 The above is the case. In some embodiments, the tensile strength of the negative electrode current collector is 500 N / mm 2 The above is the case. When the tensile strength of the negative electrode current collector is within the above range, cracking of the negative electrode current collector due to expansion or contraction of the negative electrode mixture layer during charging and discharging of the electrochemical device can be suppressed, so that the high-temperature cycle characteristics and overcharge resistance characteristics of the electrochemical device can be improved.

[0046] The tensile strength of the negative electrode current collector can be measured by the same apparatus and method as those for measuring elongation (refer to GB-228-87 for the test method).

[0047] (3) 0.2% proof stress As used herein, the term "0.2% proof stress" means the magnitude of the load required to cause a 0.2% plastic deformation (i.e., permanent deformation) in the sample. In other words, after applying the load to cause a 0.2% plastic deformation in the sample and then removing the load, the sample still maintains a 0.2% plastic deformation.

[0048] In some embodiments, the 0.2% proof stress of the negative electrode current collector is 30 N / mm 2 The above is the case. In some embodiments, the 0.2% proof stress of the negative electrode current collector is 50 N / mm 2 The above is the case. In some embodiments, the 0.2% proof stress of the negative electrode current collector is 100 N / mm 2 The above is the case. In some embodiments, the 0.2% proof stress of the negative electrode current collector is 150 N / mm 2 The above is the case. In some embodiments, the 0.2% proof stress of the negative electrode current collector is 200 N / mm 2 The above is the case. In some embodiments, the 0.2% proof stress of the negative electrode current collector is 300 N / mm 2The above is the case. When the 0.2% proof stress of the negative electrode current collector is within the above range, cracking of the negative electrode current collector due to expansion or contraction of the negative electrode mixture layer during charging and discharging of the electrochemical device can be suppressed, so that the high-temperature cycle characteristics and overcharge resistance characteristics of the electrochemical device can be improved.

[0049] The 0.2% proof stress of the negative electrode current collector can be measured by the same apparatus and method as those for the measurement of elongation (refer to GB-228-87 for the test method).

[0050] (4) Thickness In some embodiments, the thickness of the negative electrode current collector is 1 μm to 100 μm. In some embodiments, the thickness of the negative electrode current collector is 3 μm to 80 μm. In some embodiments, the thickness of the negative electrode current collector is 5 μm to 50 μm. In some embodiments, the thickness of the negative electrode current collector is 10 μm to 30 μm. In some embodiments, the thickness of the negative electrode current collector is 15 μm to 20 μm. In some embodiments, the thickness of the negative electrode current collector is 1 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 440 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm, or within a range consisting of any two of the above numerical values. When the thickness of the negative electrode current collector is within the above range, the negative electrode current collector has high strength, is easy to coat, and is less likely to be deformed such as curled in the negative electrode shape.

[0051] 2. Negative electrode mixture layer The negative electrode mixture layer includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active material. The negative electrode mixture layer may be a single layer or multiple layers, and each layer in the multiple-layer negative electrode active material may contain the same or different negative electrode active materials. The negative electrode active material is any material that can reversibly occlude and release metal ions such as lithium ions. In some embodiments, in order to prevent lithium metal from being inadvertently deposited on the negative electrode during charging, the chargeable capacity of the negative electrode active material is larger than the discharge capacity of the positive electrode active material.

[0052] In some embodiments, the negative electrode binder layer has at least one of the following characteristics (a) to (d).

[0053] (a) Reflectivity The reflectivity of the negative electrode binder layer can reflect the smoothness of the surface of the negative electrode binder layer and the surface compression state of the negative electrode active material in the negative electrode binder layer. The reflectivity of the negative electrode binder layer can be controlled by the type of the negative electrode active material, the molding conditions of the negative electrode active material layer, and the post-treatment process after molding. It can also be controlled by the pressing pressure, the number of pressing times, the heating conditions during pressing, the material and surface shape of the pressing plate and pressing roll used during pressing.

[0054] In some embodiments, the reflectivity Ra of the negative electrode binder layer at a wavelength of 550 nm is 7% to 15%. In some embodiments, the reflectivity Ra of the negative electrode binder layer at a wavelength of 550 nm is 8% to 14.8%. In some embodiments, the reflectivity Ra of the negative electrode binder layer at a wavelength of 550 nm is 10% to 12%. In some embodiments, the reflectivity Ra of the negative electrode binder layer at a wavelength of 550 nm is 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, or within a range consisting of any two of the above numerical values. When the reflectivity of the negative electrode binder layer is within the above range, side reactions on the surface of the negative electrode binder layer can be suppressed, and the permeability of the electrolyte from the surface of the negative electrode binder layer to the inside of the negative electrode binder layer can be increased, so that the rapid charging characteristics of the electrochemical device can be improved.

[0055] The reflectivity of the negative electrode binder layer can be measured using a spectrophotometer (for example, SPECTRO PHOTOMETER CM-5 manufactured by KONICA MINOLTA).

[0056] (b) Density In some embodiments, the density da of the negative electrode binder layer is 1.3 g / cm 3 ~1.9 g / cm 3 is. In some embodiments, the density da of the negative electrode binder layer is 1.35 g / cm 3~1.62 g / cm 3 is. In some embodiments, the density da of the negative electrode binder layer is 1.4 g / cm 4 ~1.6 g / cm 3 is. In some embodiments, the density da of the negative electrode binder layer is 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , or 1.9 g / cm 3 is, or within the range consisting of any two of the above numerical values.

[0057] (c) Weight In some embodiments, the weight La per unit area of the negative electrode binder layer is 4.5 mg / cm 2 ~12.5 mg / cm 2 is. In some embodiments, the weight La per unit area of the negative electrode binder layer is 6.0 mg / cm 2 ~12.0 mg / cm 2 is. In some embodiments, the weight La per unit area of the negative electrode binder layer is 4.5 mg / cm 2 , 5 mg / cm 2 , 5.5 mg / cm 2 , 6 mg / cm 2 , 6.5 mg / cm 2 , 7 mg / cm 2 , 7.5 mg / cm 2 , 8 mg / cm 2 , 8.5 mg / cm 2 , 9 mg / cm 2 , 9.5 mg / cm 2 , 10 mg / cm 2 , 10.5 mg / cm 2 , 11 mg / cm 2 , 11.5 mg / cm 2 , 12 mg / cm 2 , or 12.5 mg / cm 2 is, or within the range consisting of any two of the above numerical values.

[0058] The weight per unit area of the negative electrode binder layer in the present invention is the ratio of the mass (mg) of the negative electrode binder layer to the area (cm 2 ) of the binder layer. The mass and area of the negative electrode binder layer are obtained by the following method. A test piece of an appropriate size is cut out from the negative electrode, and after measuring its area S1 and mass W0, the negative electrode current collector is peeled off from the negative electrode, the mass W1 of the negative electrode current collector is measured, and the mass of the negative electrode binder layer is calculated from (W0 - W1), and the weight per unit area = (W0 - W1) / S1. When the selected negative electrode is a double-sided binder layer, the weight per unit area = (W0 - W1) / S1 / 2.

[0059] As a method for peeling the negative electrode binder layer, for example, the negative electrode binder layer can be immersed in a solvent that can dissolve or swell the negative electrode binder layer, and the binder layer can be wiped off with a cloth or the like.

[0060] The weight per unit area of the negative electrode binder layer can be adjusted by a known method. For example, when forming the negative electrode binder layer by coating, it can be adjusted by changing the solid content concentration of the coating solution used for forming the negative electrode binder layer, the number of coating times, the gap of the coating solution inlet of the coater, etc. The weight per unit area of the negative electrode binder layer can be increased by increasing the solid content concentration, increasing the number of coating times, or increasing the gap. The weight per unit area of the negative electrode binder layer can be reduced by decreasing the solid content concentration, decreasing the number of coating times, or decreasing the gap.

[0061] (d) Porosity In some embodiments, the porosity Pa of the negative electrode binder layer is 20% - 40%. In some embodiments, the porosity Pa of the negative electrode binder layer is 26.5% - 31.3%. In some embodiments, the porosity Pa of the negative electrode binder layer is 26% - 31%. In some embodiments, the porosity Pa of the negative electrode binder layer is 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, or 40%, or within a range consisting of any two of the above numerical values.

[0062] The porosity of the negative electrode mixture layer can be measured by punching the negative electrode into 13-mm pieces using a punching machine and measuring the thickness of the pieces using a micrometer with an accuracy of one ten-thousandth. A certain number of pieces are placed in the sample compartment of an AccuPyc 1340 device. After purging the sample 30 times with helium gas, the pressure inside the sample compartment is tested by passing helium gas through the sample in accordance with the procedure, and the true volume inside the sample bottle is calculated using Boyle's law PV = nRT. After the test, the number of pieces is counted, and the apparent volume of the sample is calculated. The porosity of the sample is calculated by the following formula. Porosity = 1 - true volume / apparent volume.

[0063] In some embodiments, the negative electrode mixture layer simultaneously has the density and porosity as described above. In this case, excessive immersion of the electrolyte from the surface of the negative electrode mixture layer into the interior of the negative electrode mixture layer can be suppressed, diffusion of the electrolyte into the interior of the negative electrode mixture layer can be enhanced, the reactivity of the negative electrode mixture layer can be increased, side reactions of the negative electrode mixture layer can be suppressed, and the high-temperature characteristics and overcharge resistance characteristics of the electrochemical device can be improved.

[0064] The thickness of the negative electrode mixture layer refers to the thickness of the negative electrode mixture layer coated on one side of the negative electrode current collector. In some embodiments, the thickness of the negative electrode mixture layer is 15 μm or more. In some embodiments, the thickness of the negative electrode mixture layer is 20 μm or more. In some embodiments, the thickness of the negative electrode mixture layer is 30 μm or more. In some embodiments, the thickness of the negative electrode mixture layer is 150 μm or less. In some embodiments, the thickness of the negative electrode mixture layer is 120 μm or less. In some embodiments, the thickness of the negative electrode mixture layer is 100 μm or less. In some embodiments, the thickness of the negative electrode mixture layer is within the range consisting of any two of the above numerical values. When the thickness of the negative electrode mixture layer is within the above range, the electrolyte can penetrate near the interface of the negative electrode current collector, and the charge-discharge characteristics at a high current density of the electrochemical device can be improved. At the same time, when the volume ratio of the negative electrode current collector to the negative electrode active material is within an appropriate range, the capacity of the electrochemical device can be ensured.

[0065] The ratio of the thickness of the negative electrode active material layer to the thickness of the negative electrode current collector is the thickness of the single-sided negative electrode active material layer divided by the thickness of the negative electrode current collector, and the numerical value is not particularly limited. In some embodiments, the ratio of the thickness is 50 or less. In some embodiments, the ratio of the thickness is 30 or less. In some embodiments, the ratio of the thickness is 20 or less. In some embodiments, the ratio of the thickness is 10 or less. In some embodiments, the ratio of the thickness is 1 or more. In some embodiments, the ratio of the thickness is within the range consisting of any two of the above numerical values. When the ratio of the thickness is within the above range, the capacity of the electrochemical device can be ensured, and the heat dissipation of the negative electrode current collector during charge and discharge at a high current density can be suppressed.

[0066] Negative electrode active material In some embodiments, the negative electrode active material includes carbon materials such as graphite, hard carbon, soft carbon, and MCMB, silicon, SiO x Silicon-containing compounds such as silicon oxides represented by (0 < x < 2), metallic lithium, metals that form alloys with lithium, and their alloys, amorphous compounds mainly composed of oxides such as tin dioxide, and lithium titanate (Li4Ti5O 12 ) are included, but not limited thereto.

[0067] In some embodiments, the negative electrode active material includes a carbon material. In some embodiments, the negative electrode active material contains a carbon material having a graphite structure. In some embodiments, the negative electrode active material is at least one of artificial graphite and natural graphite.

[0068] In some embodiments, the metals that form alloys with metallic lithium include, but are not limited to, aluminum, silicon, tin, and germanium.

[0069] In some embodiments, the negative electrode active material contains different components mainly composed of a carbon material having a graphite structure. In some embodiments, the content of the carbon material having a graphite structure is 70.0% or more based on the weight of the negative electrode binder layer. In some embodiments, the content of the carbon material having a graphite structure is 90.0% or more based on the weight of the negative electrode binder layer. The content of the carbon material having a graphite structure is 95.0% or more based on the weight of the negative electrode binder layer.

[0070] In some embodiments, the negative electrode active material, which is a metal or semi-metal that forms an alloy with lithium represented by silicon, and their alloys, has a high charge-discharge capacity.

[0071] In some embodiments, the negative electrode active material contains a mixture of a metal or semi-metal that forms an alloy with lithium represented by silicon, and their alloys, and a carbon material having a graphite structure.

[0072] Binder In some embodiments, the negative electrode binder layer further includes a negative electrode binder. The negative electrode binder can enhance the bonding between the negative electrode active material particles and the bonding between the negative electrode binder layer and the negative electrode current collector. The type of the negative electrode binder is not particularly limited as long as it is a material stable to the electrolytic solution or the solvent used during the manufacture of the electrode.

[0073] Examples of the negative electrode binder include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and cellulose nitrate; rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber; thermoplastic elastomer-like polymers such as styrene-butadiene-styrene block copolymer or its hydride, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymer, and styrene-isoprene-styrene block copolymer or its hydride; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer; and polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions), but are not limited thereto. The above negative electrode binder may be used alone or in any combination.

[0074] In some embodiments, based on the weight of the negative electrode mixture layer, the content of the negative electrode binder is 0.1% or more, 0.5% or more, or 0.6% or more. In some embodiments, based on the weight of the negative electrode mixture layer, the content of the negative electrode binder is 10% or less, 8% or less, 5% or less, or 4% or less. In some embodiments, the content of the negative electrode binder is within the range consisting of any two of the above numerical values. When the content of the negative electrode binder is within the above range, the capacity of the electrochemical device and the strength of the negative electrode can be sufficiently ensured.

[0075] When the negative electrode active material layer contains a rubbery polymer (for example, SBR), in some embodiments, based on the weight of the negative electrode active material layer, the content of the negative electrode binder is more than 0.1%, more than 0.5%, or more than 0.6%. In some embodiments, based on the weight of the negative electrode active material layer, the content of the negative electrode binder is less than 5%, less than 3%, or less than 2%. In some embodiments, based on the weight of the negative electrode active material layer, the content of the negative electrode binder is within the range consisting of any two of the above numerical values.

[0076] When the negative electrode active material layer contains a fluorine-based polymer (for example, polyvinylidene fluoride), in some embodiments, based on the weight of the negative electrode active material layer, the content of the negative electrode binder is more than 1%, more than 2%, or more than 3%. In some embodiments, based on the weight of the negative electrode active material layer, the content of the negative electrode binder is less than 15%, less than 10%, or less than 8%. Based on the weight of the negative electrode active material layer, the content of the negative electrode binder is within the range consisting of any two of the above numerical values.

[0077] Thickening agent The thickening agent is usually used to adjust the viscosity of the negative electrode slurry. The type of the thickening agent is not particularly limited, and examples thereof include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. The above thickening agents may be used alone or in any combination.

[0078] In some embodiments, based on the weight of the negative electrode active material layer, the content of the thickening agent is more than 0.1%, more than 0.5%, or more than 0.6%. In some embodiments, based on the weight of the negative electrode active material layer, the content of the thickening agent is less than 5%, less than 3%, or less than 2%. When the content of the thickening agent is within the above range, it is possible to suppress a decrease in the capacity and an increase in the resistance of the electrochemical device, and to ensure good coatability of the negative electrode slurry.

[0079] Solvent The type of solvent used for forming the negative electrode slurry is not particularly limited, and any solvent that can dissolve or disperse the negative electrode active material, the negative electrode binder, and the thickener and conductive material used as needed may be used. In some embodiments, as the solvent used for forming the negative electrode slurry, either an aqueous solvent or an organic solvent can be used. Examples of the aqueous solvent include, but are not limited to, water, alcohol, etc. Examples of the organic solvent include, but are not limited to, N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. The above solvents may be used alone or in any combination.

[0080] Preparation of the negative electrode The negative electrode in the electrochemical device of the present invention can be prepared using any known method. For example, a binder, a solvent, a thickener added as needed, a conductive material, a filler, etc. are added to the negative electrode active material to form a slurry, and this slurry is applied to the negative electrode current collector and dried, and then the electrode is formed by pressing. The negative electrode active material may be made into a sheet-like electrode by roll forming or a pellet electrode by compression molding.

[0081] II. Electrolyte The electrolyte used in the electrochemical device of the present invention includes an electrolyte and a solvent for dissolving the electrolyte. In some embodiments, the electrolyte used in the electrochemical device of the present invention further includes an additive.

[0082] Another main feature of the electrochemical device of the present invention is that the electrolyte contains a compound containing a sulfur-oxygen double bond.

[0083] In some embodiments, the compound containing the sulfur-oxygen double bond includes at least one of a cyclic sulfate, a linear sulfate, a linear sulfonate, a cyclic sulfonate, a linear sulfite, and a cyclic sulfite.

[0084] In some embodiments, the cyclic sulfate includes, but is not limited to, one or more of 1,2-ethylene sulfate, 1,2-propylene sulfate, 1,3-propylene sulfate, 1,2-butylene sulfate, 1,3-butylene sulfate, 1,4-butylene sulfate, 1,2-pentylene sulfate, 1,3-pentylene sulfate, 1,4-pentylene sulfate, and 1,5-pentylene sulfate.

[0085] In some embodiments, the linear sulfate includes, but is not limited to, one or more of dimethyl sulfate, methyl ethyl sulfate, and diethyl sulfate.

[0086] In some embodiments, the linear sulfonate includes, but is not limited to, one or more of fluorosulfonic acid esters such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl dimethylsulfonate, methyl 2-(methanesulfonyloxy)propionate, and ethyl 2-(methanesulfonyloxy)propionate.

[0087] In some embodiments, the cyclic sulfonic acid ester includes, but is not limited to, one or more of 1,3-propanesultone, 1-fluoro-1,3-propanesultone, 2-fluoro-1,3-propanesultone, 3-fluoro-1,3-propanesultone, 1-methyl-1,3-propanesultone, 2-methyl-1,3-propanesultone, 3-methyl-1,3-propanesultone, 1-propene-1,3-sultone, 2-propylene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro-2-propene-1,3-sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 2-methyl-1-propene-1,3-sultone, 3-methyl-1-propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3-methyl-2-propene-1,3-sultone, 1,4-butanestultone, 1,5-pentanesultone, methylene methanedisulfonate, ethylene methanedisulfonate, and the like.

[0088] In some embodiments, the linear sulfite ester includes, but is not limited to, one or more of dimethyl sulfite, methyl ethyl sulfite, and diethyl sulfite.

[0089] In some embodiments, the cyclic sulfite ester includes, but is not limited to, one or more of 1,2-ethylene sulfite, 1,2-propylene sulfite, 1,3-propylene sulfite, 1,2-butylene sulfite, 1,3-butylene sulfite, 1,4-butylene sulfite, 1,2-pentylene sulfite, 1,3-pentylene sulfite, 1,4-pentylene sulfite, and 1,5-pentylene sulfite.

[0090] In some embodiments, the compound containing a sulfur-oxygen double bond includes the compound of Formula 1,

Chemical formula

Chem.

[0091] In some embodiments, the compound of formula 1 is

Chem.

[0092] In some embodiments, when the content of the compound containing the sulfur-oxygen double bond is b% based on the weight of the electrolyte, b is in the range of 0.01 to 10. In some embodiments, b is in the range of 0.1 to 8. In some embodiments, b is in the range of 0.5 to 5. In some embodiments, b is in the range of 1 to 3. In some embodiments, b is 0.01, 0.05, 0.1, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10, or is within the range consisting of any two of the above numerical values. When the content of the compound containing the sulfur-oxygen double bond in the electrolyte is within the above range, it helps to further improve the high-temperature characteristics and overcharge resistance of the electrochemical device.

[0093] In some embodiments, the content b% of the compound containing a sulfur-oxygen double bond in the electrolytic solution and the content a% of tin in the negative electrode current collector satisfy 1 ≤ b / a ≤ 100. In some embodiments, 5 ≤ b / a ≤ 80. In some embodiments, 10 ≤ b / a ≤ 50. In some embodiments, 20 ≤ b / a ≤ 30. In some embodiments, b / a is 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100, or within the range consisting of any two of the above numerical values. When the content b% of the compound containing a sulfur-oxygen double bond in the electrolytic solution and the content a% of tin in the negative electrode current collector satisfy the above relationship, it helps to further improve the high-temperature characteristics and overcharge resistance characteristics of the electrochemical device.

[0094] In some embodiments, the reaction area d m of the negative electrode mixture layer 2 and the content b% of the compound containing a sulfur-oxygen double bond in the electrolytic solution satisfy 0.5 ≤ d / b ≤ 30. In some embodiments, 1 ≤ d / b ≤ 25. In some embodiments, 5 ≤ d / b ≤ 20. In some embodiments, 10 ≤ d / b ≤ 15. In some embodiments, d / b is 0.5, 1, 5, 10, 15, 20, 25, or 30, or within the range consisting of any two of the above numerical values. The reaction area d m of the negative electrode mixture layer 2 and the content b% of the compound containing a sulfur-oxygen double bond in the electrolytic solution satisfy the above relationship, which helps to further improve the high-temperature characteristics and overcharge resistance characteristics of the electrochemical device.

[0095] In some embodiments, the reaction area of the negative electrode mixture layer is 0.005 m 2 ~300 m 2 In some embodiments, the reaction area of the negative electrode mixture layer is 0.01 m 2 ~250 m 2 In some embodiments, the reaction area of the negative electrode mixture layer is 0.05 m 2 ~200 m 2 In some embodiments, the reaction area of the negative electrode mixture layer is 0.1 m 2 ~150 m2 It is. In some embodiments, the reaction area of the negative electrode mixture layer is 0.5 m 2 ~100 m 2 It is. In some embodiments, the reaction area d of the negative electrode mixture layer is 1 m 2 ~50 m 2 It is. In some embodiments, the reaction area of the negative electrode mixture layer is 5 m 2 ~30 m 2 It is. In some embodiments, the reaction area of the negative electrode mixture layer is 10 m 2 ~20 m 2 It is. In some embodiments, the reaction area of the negative electrode mixture layer is 0.005 m 2 , 0.01 m 2 , 0.05 m 2 , 0.1 m 2 , 0.5 m 2 , 1 m 2 , 5 m 2 , 10 m 2 , 50 m 2 , 100 m 2 , 150 m 2 , 200 m 2 , 250 m 2 , or 300 m 2 It is, or within the range consisting of any two of the above numerical values.

[0096] The reaction area of the negative electrode mixture layer can be measured by the nitrogen adsorption BET one-point method using the gas flow method with a nitrogen-helium mixed gas in which the relative pressure value of nitrogen gas with respect to atmospheric pressure is accurately adjusted to 0.3 after pre-drying the sample at 350 °C for 15 minutes under nitrogen gas flow using a surface area meter (fully automatic surface area measuring device manufactured by Okura Riken). The specific surface area of the negative electrode mixture layer is measured according to this method. The specific surface area of the negative electrode mixture layer refers to the specific surface area of the entire negative electrode mixture layer including the negative electrode active material and additives (such as binder, conductive agent, thickening agent, and filler). The weight of the negative electrode mixture layer, that is, the total weight of the negative electrode mixture layer including the negative electrode active material and additives (such as binder, conductive agent, thickening agent, and filler) is measured. The reaction area of the negative electrode mixture layer is calculated by the following formula. Reaction area = Specific surface area of the negative electrode mixture layer × Weight of the negative electrode mixture layer.

[0097] In some embodiments, the electrolytic solution further includes at least one of the following compounds. (i) Propionic acid ester (ii) Organic compound having a cyano group (iii) Lithium difluorophosphate (iv) Compound of formula 3

Chemical formula

[0098] (i) Propionic acid ester In some embodiments, the propionic acid ester includes a compound of formula 2,

Chemical formula

[0099] In some embodiments, the propionate ester includes, but is not limited to, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, amyl propionate, methyl halopropionate, ethyl halopropionate, propyl halopropionate, butyl halopropionate, and amyl halopropionate. In some embodiments, the propionate ester is at least one selected from methyl propionate, ethyl propionate, propyl propionate, butyl propionate, and amyl propionate. In some embodiments, the halogen group in methyl halopropionate, ethyl halopropionate, propyl halopropionate, butyl halopropionate, and amyl halopropionate is one or more selected from a fluorine group (-F), a chlorine group (-Cl), a bromine group (-Br), and an iodine group (-I). In some embodiments, the halogen group is a fluorine group (-F), and better effects can be achieved.

[0100] In some embodiments, based on the weight of the electrolyte, the content of the propionate ester is 10% - 60%. In some embodiments, based on the weight of the electrolyte, the content of the propionate ester is 20% - 50%. In some embodiments, based on the weight of the electrolyte, the content of the propionate ester is 30% - 40%. In some embodiments, based on the weight of the electrolyte, the content of the propionate ester is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%, or within a range consisting of any two of the above values. When the content of the propionate ester in the electrolyte is within the above range, it helps to further improve the high-temperature characteristics and overcharge resistance characteristics of the electrochemical device.

[0101] (ii) A compound having a cyano group In some embodiments, the compound having a cyano group includes, but is not limited to, one or more of 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-dioxapimelonitrile, 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, and 1,2,5-tris(cyanoethoxy)pentane.

[0102] The compounds having a cyano group may be used alone or in any combination. When the electrolyte contains two or more compounds having a cyano group, the content of the compounds having a cyano group means the total content of two or more compounds having a cyano group. In some embodiments, based on the weight of the electrolyte, the content of the compounds having a cyano group is 0.1% to 15%. In some embodiments, based on the weight of the electrolyte, the content of the compounds having a cyano group is 0.5% to 10%. In some embodiments, based on the weight of the electrolyte, the content of the compounds having a cyano group is 1% to 8%. In some embodiments, based on the weight of the electrolyte, the content of the compounds having a cyano group is 3% to 5%. In some embodiments, based on the weight of the electrolyte, the content of the compounds having a cyano group is 0.1%, 0.5%, 1%, 3%, 5%, 8%, 10%, 13%, or 15%, or within the range consisting of any two of the above numerical values.

[0103] (iii) Lithium difluorophosphate (LiPO2F2) In some embodiments, based on the weight of the electrolyte, the content of lithium difluorophosphate is 0.01% to 1.5%. In some embodiments, based on the weight of the electrolyte, the content of lithium difluorophosphate is 0.05% to 1.2%. In some embodiments, based on the weight of the electrolyte, the content of lithium difluorophosphate is 0.1% to 1.0%. In some embodiments, based on the weight of the electrolyte, the content of lithium difluorophosphate is 0.5% to 0.8%. In some embodiments, based on the weight of the electrolyte, the content of lithium difluorophosphate is 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.8%, 1%, or 1.5%, or within the range consisting of any two of the above numerical values.

[0104] (iv) Compound of Formula 3 In some embodiments, the compound of Formula 3 is

Chemical

[0105] In some embodiments, the content of the compound of Formula 3 is 0.01% to 5% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 3 is 0.05% to 3% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 3 is 0.1% to 2% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 3 is 0.5% to 1% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 3 is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, or 5% based on the weight of the electrolyte, or is within the range consisting of any two of the above numerical values.

[0106] solvent In some embodiments, the electrolyte further includes any non-aqueous solvent that can be used as a solvent for electrolytes known in the prior art.

[0107] In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of cyclic carbonates, linear carbonates, cyclic carboxylic acid esters, linear carboxylic acid esters, cyclic ethers, linear ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0108] In some embodiments, the cyclic carbonate includes, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonate has 3 to 6 carbon atoms.

[0109] In some embodiments, the chain carbonate ester includes, but is not limited to, one or more of chain carbonate esters such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, etc. The fluorine-substituted chain carbonate ester includes, but is not limited to, one or more of bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, and 2,2,2-trifluoroethyl methyl carbonate, etc.

[0110] In some embodiments, the cyclic carboxylic acid ester includes, but is not limited to, one or more of γ-butyrolactone and γ-valerolactone. In some embodiments, a part of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.

[0111] In some embodiments, the chain carboxylic acid ester includes, but is not limited to, one or more of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-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, etc. In some embodiments, a part of the hydrogen atoms of the chain carboxylic acid ester may be substituted with fluorine. In some embodiments, the fluorine-substituted chain carboxylic acid ester includes, but is not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate, etc.

[0112] In some embodiments, the cyclic ether includes, but is not limited to, one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0113] In some embodiments, the chain ether includes, but is not limited to, one or more of dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane.

[0114] In some embodiments, the phosphorus-containing organic solvent includes, but is not limited to, one or more of trimethyl phosphate, triethyl phosphate, dimethylethyl phosphate, methyldiethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,3,3,3-pentafluoropropyl) phosphate.

[0115] In some embodiments, the sulfur-containing organic solvent includes, but is not limited to, one or more of sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In some embodiments, a part of the hydrogen atoms of the sulfur-containing organic solvent may be substituted with fluorine.

[0116] In some embodiments, the aromatic fluorine-containing solvent includes, but is not limited to, one or more of fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0117] In some embodiments, the solvent used in the electrolyte of the present invention includes cyclic carbonates, chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present invention includes an organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, ethyl acetate, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present invention includes ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, and combinations thereof.

[0118] Additive In some embodiments, examples of the additive include, but are not limited to, one or more of fluorocarbonate, vinyl carbonate containing a carbon-carbon double bond, and acid anhydride.

[0119] In some embodiments, the content of the additive is 0.01% to 15%, 0.1% to 10%, or 1% to 5% based on the weight of the electrolyte.

[0120] According to an embodiment of the present invention, the content of the propionate ester is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times that of the additive based on the weight of the electrolyte.

[0121] In some embodiments, the additive includes one or more fluorocarbonates. During charging and discharging of the lithium-ion battery, the fluorocarbonate can cooperate with the propionate to form a stable protective film on the surface of the negative electrode, so that the decomposition reaction of the electrolyte can be suppressed.

[0122] In some embodiments, the fluorocarbonate has the formula C=O(OR x )(OR y ), where R x and R y are each independently selected from an alkyl group and a halogenated alkyl group having 1 to 6 carbon atoms, and at least one of R x and R y is selected from a fluoroalkyl group having 1 to 6 carbon atoms, and R x and R y optionally form a 5- to 7-membered ring together with the atoms to which they are attached.

[0123] In some embodiments, examples of the fluorocarbonate include, but are not limited to, one or more of 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, trifluoromethyl methyl carbonate, trifluoroethyl methyl carbonate, and ethyl trifluoroethyl carbonate.

[0124] In some embodiments, the additive includes one or more vinyl carbonates containing a carbon-carbon double bond. Examples of the vinyl carbonate containing a carbon-carbon double bond include, but are not limited to, vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, 1,2-diethyl vinylene 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 ethylene carbonate, 1,1-divinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1,1-dimethyl-2-methylidene ethylene carbonate, and 1,1-diethyl-2-methylidene ethylene carbonate. In some embodiments, the vinyl carbonate containing a carbon-carbon double bond includes vinylene carbonate, which is easily obtained and can achieve better effects.

[0125] In some embodiments, the additive is a combination of a fluorocarbonate and a vinyl carbonate containing a carbon-carbon double bond. 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 a fluorocarbonate and a cyclic phosphate anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a sulfonic anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic sulfonic anhydride.

[0126] electrolyte The electrolyte is not particularly limited, and any known electrolyte can be arbitrarily used. In the case of a lithium secondary battery, a lithium salt is usually used.Examples of electrolytes include, but are not limited to, inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiWF7; lithium tungstates such as LiWOF5; lithium carboxylate salts such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li; lithium sulfonate salts such as FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li; lithium imide salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethane bis-sulfonylimide, lithium cyclic 1,3-perfluoropropane bis-sulfonylimide, LiN(CF3SO2)(C4F9SO2); methylated lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3; lithium (malonate) borate salts such as lithium bis(malonate) borate salt, lithium difluoro(malonate) borate salt; lithium (malonate) phosphate salts such as tris(malonate) lithium phosphate, lithium difluorobis(malonate) phosphate, lithium tetrafluoro(malonate) phosphate salt; and fluorine-containing organic lithium salts such as LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2; lithium oxalate borate salts such as lithium difluorooxalate borate, lithium bis(oxalate) borate; lithium oxalate phosphate salts such as lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium tris(oxalate) phosphate, etc.

[0127] In some embodiments, the electrolyte is selected from LiPF6, LiSbF6, FSO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane bis-sulfonylimide lithium, cyclic 1,3-perfluoropropane bis-sulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, lithium difluorooxalate borate, lithium bis(oxalate) borate, and lithium difluorobis(oxalate) phosphate, and helps to improve output power characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc. of the electrochemical device.

[0128] The content of the electrolyte is not particularly limited as long as the effects of the present invention are not impaired. In some embodiments, the total molar concentration of lithium in the electrolyte solution is more than 0.3 mol / L, more than 0.4 mol / L, or more than 0.5 mol / L. In some embodiments, the total molar concentration of lithium in the electrolyte solution 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 solution is within the range consisting of any two of the above numerical values. When the electrolyte concentration is within the above range, there is not too little lithium, which is a charged particle, and the viscosity can be adjusted to an appropriate range, so it is easy to ensure good electrical conductivity.

[0129] When using two or more electrolytes, the electrolyte contains at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte contains a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte contains a lithium salt. In some embodiments, based on the weight of the electrolyte, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is more than 0.01% or more than 0.1%. In some embodiments, based on the weight of the electrolyte, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is less than 20% or less than 10%. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is within the range consisting of any two of the above numerical values.

[0130] In some embodiments, the electrolyte contains one or more substances selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate, and one or more other salts. The other salts include the lithium salts exemplified above. In some embodiments, the other salts are LiPF6, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane bis-sulfonylimide lithium, cyclic 1,3-perfluoropropane bis-sulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3. In some embodiments, the other salt is LiPF6.

[0131] In some embodiments, the content of other salts is more than 0.01% or more 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 the range consisting of any two of the above numerical values. Other salts having the above content help to balance the electrical conductivity and viscosity of the electrolytic solution.

[0132] In addition to the above solvents, additives, and electrolyte salts, the electrolytic solution can contain additional additives such as a negative electrode film-forming agent, a positive electrode protective agent, and an overcharge prevention agent as required. As the additives, those generally used in non-aqueous electrolyte secondary batteries can be used, and examples thereof include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluoroanisole, 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 according to the type of the additive and the like. In some embodiments, the content of the additive is less than 5% based on the weight of the electrolyte, or is within the range of 0.01% to 5% or within the range of 0.2% to 5%.

[0133] III. Positive Electrode The positive electrode includes a positive electrode current collector and a positive electrode mixture layer provided on one or both sides of the positive electrode current collector.

[0134] 1. Positive Electrode Mixture Layer The positive electrode includes a positive electrode mixture layer, and the positive electrode mixture layer includes a positive electrode active material. The positive electrode mixture layer may be a single layer or multiple layers. Each layer in the multilayer positive electrode active material can contain the same or different positive electrode active materials. The positive electrode active material is any material that can reversibly occlude and release metal ions such as lithium ions.

[0135] The type of the positive electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions (for example, lithium ions). In some embodiments, the positive electrode active material is a substance containing lithium and at least one transition metal. Examples of the positive electrode active material include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

[0136] In some embodiments, the transition metals in the lithium transition metal composite oxide include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some embodiments, the lithium transition metal composite oxide is a lithium cobalt composite oxide such as LiCoO2, a lithium nickel composite oxide such as LiNiO2, a lithium manganese composite oxide such as LiMnO2, LiMn2O4, Li2MnO4, etc., LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, etc., lithium nickel manganese cobalt composite oxides, etc., and a part of the transition metal atoms that are the main body of these lithium transition metal composite oxides are substituted by other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W. Examples of the lithium transition metal composite oxide are LiNi 0.5 Mn 0.5 O2, LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.45 Co 0.10 Al 0.45 O2, LiMn 1.8 Al 0.2 O4 and LiMn 1.5 Ni 0.5including, but not limited to, O4. Examples of combinations of lithium transition metal composite oxides include, but are not limited to, the combination of LiCoO2 and LiMn2O4, and part of the Mn in LiMn2O4 may be replaced by a transition metal (e.g., LiNi 0.33 Co 0.33 Mn 0.33 O2), and part of the Co in LiCoO2 may be replaced by a transition metal.

[0137] In some embodiments, the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some embodiments, the lithium-containing transition metal phosphate compound includes iron phosphates such as LiFePO4, Li3Fe2(PO4)3, LiFeP2O7, and cobalt phosphates such as LiCoPO4, and part of the transition metal atoms that are the main body of these lithium-containing transition metal phosphate compounds are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si.

[0138] In some embodiments, the positive electrode active material includes lithium phosphate that improves the continuous charging characteristics of the electrochemical device. There is no limitation on the use of lithium phosphate. In some embodiments, the positive electrode active material and lithium phosphate are mixed and used. In some embodiments, with respect to the weight of the positive electrode active material and lithium phosphate, the content of lithium phosphate is more than 0.1%, more than 0.3%, or more than 0.5%. In some embodiments, with respect to the weight of the positive electrode active material and lithium phosphate, the content of lithium phosphate is less than 10%, less than 8%, or less than 5%. In some embodiments, the content of lithium phosphate is within the range consisting of any two of the above numerical values.

[0139] Surface coating A substance different from the composition may adhere to the surface of the positive electrode active material. Examples of the surface-adhering substance include oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; carbon, etc., but are not limited thereto.

[0140] These surface-adhering substances can adhere to the surface of the positive electrode active material by the following methods. A method of dissolving or suspending the surface-adhering substance in a solvent, infiltrating the positive electrode active material, and drying; a method of dissolving or suspending a precursor of the surface-adhering substance in a solvent, infiltrating the positive electrode active material, and then reacting by heating or the like; and a method of firing while adding to a precursor of the positive electrode active material. When attaching carbon, a method of mechanically attaching a carbon material (for example, activated carbon) may be used.

[0141] In some embodiments, the content of the surface-adhering substance is more than 0.1 ppm, more than 1 ppm, or more than 10 ppm with respect to the weight of the positive electrode binder layer. In some embodiments, the content of the surface-adhering substance is less than 10%, less than 5%, or less than 2% with respect to the weight of the positive electrode binder layer. In some embodiments, the content of the surface-adhering substance is within a range consisting of any two of the above numerical values with respect to the weight of the positive electrode binder layer.

[0142] By attaching a substance to the surface of the positive electrode active material, the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material can be suppressed, and the life of the electrochemical device can be extended. If the amount of the surface-adhering substance is too small, the effect will not appear sufficiently. If the amount of the surface-adhering substance is too large, the entry and exit of lithium ions may be inhibited, and the resistance may increase.

[0143] In the present invention, the positive electrode active material with a substance different from its composition adhering to the surface of the positive electrode active material is also referred to as the "positive electrode active material".

[0144] Shape In some embodiments, the shape of the positive electrode active material particles includes, but is not limited to, block shape, polyhedron shape, spherical shape, ellipsoidal shape, plate shape, needle shape, columnar shape, etc. In some embodiments, the positive electrode active material particles include primary particles, secondary particles, or a combination thereof. In some embodiments, the primary particles may aggregate to form secondary particles.

[0145] Tap density In some embodiments, the tap density of the positive electrode active material is 0.5 g / cm 3 greater than, 0.8 g / cm 3 greater than, or 1.0 g / cm 3 greater than. When the tap density of the positive electrode active material is within the above range, the amount of dispersion medium required during the formation of the positive electrode mixture layer and the required amounts of the conductive material and the positive electrode binder can be suppressed, thereby ensuring the filling rate of the positive electrode active material and the capacity of the electrochemical device. By using a composite oxide powder with a high tap density, a positive electrode mixture layer with a high density can be formed. Generally, the higher the tap density, the more preferable it is, and there is no particular upper limit. In some embodiments, the tap density of the positive electrode active material is 4.0 g / cm 3 less than, 3.7 g / cm 3 less than, or 3.5 g / cm 3 less than. When the tap density of the positive electrode active material has an upper limit as described above, a decrease in load characteristics can be suppressed.

[0146] The tap density of the positive electrode active material can be calculated by putting 5 g to 10 g of the positive electrode active material powder into a 10 mL glass graduated cylinder, performing 200 strokes of vibration with a 20 mm amplitude, and obtaining the powder packing density (tap density).

[0147] 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 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.

[0148] In some embodiments, the median diameter (D50) of the positive electrode active material particles is greater than 0.3 μm, greater than 0.5 μm, greater than 0.8 μm, or greater than 1.0 μm. In some embodiments, the median diameter (D50) of the positive electrode active material particles is less than 30 μm, less than 27 μm, less than 25 μm, or less than 22 μm. In some embodiments, the median diameter (D50) of the positive electrode active material particles is within the range consisting of any two of the above numerical values. When the median diameter (D50) of the positive electrode active material particles is within the above range, a positive electrode active material having a high tap density can be obtained, and a decrease in the performance of the electrochemical device can be suppressed. On the other hand, in the process of preparing the positive electrode of the electrochemical device (that is, when the positive electrode active material, the conductive material, the binder, etc. are slurried with a solvent and coated in a film form), problems such as streak generation can be prevented. Here, by mixing two or more types of positive electrode active materials having different median diameters, the fillability during positive electrode preparation can be further enhanced.

[0149] The median diameter (D50) of the positive electrode active material particles can be measured using a laser diffraction / scattering particle size distribution measuring device. When using LA-920 manufactured by HORIBA as the particle size distribution meter, a 0.1% aqueous sodium hexametaphosphate solution is used as the dispersion medium for measurement, and after ultrasonic dispersion for 5 minutes, the refractive index for measurement is set to 1.24 for measurement.

[0150] Average primary particle diameter When the primary particles of the positive electrode active material particles aggregate to form secondary particles, in some embodiments, the average primary particle diameter of the positive electrode active material is greater than 0.05 μm, greater than 0.1 μm, or greater than 0.5 μm. In some embodiments, the average primary particle diameter 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 some embodiments, the average primary particle diameter of the positive electrode active material is within the range consisting of any two of the above numerical values. When the average primary particle diameter of the positive electrode active material is within the above range, powder fillability and specific surface area can be ensured, a decrease in battery performance can be suppressed, and appropriate crystallinity can be obtained, thereby ensuring the charge-discharge reversibility of the electrochemical device.

[0151] The average primary particle diameter of the positive electrode active material can be obtained by observing an image obtained with a scanning electron microscope (SEM). Among the SEM images at a magnification of 10,000 times, for any 50 primary particles, the maximum value of the slice obtained from the left and right boundary lines of the primary particles with respect to a horizontal straight line is obtained, and the average value of these is obtained to obtain the average primary particle diameter.

[0152] Specific surface area (BET) In some embodiments, the specific surface area (BET) of the positive electrode 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 some embodiments, the specific surface area (BET) of the positive electrode active material is less than 50 m 2 / g, less than 40 m 2 / g, or less than 30 m 2 / g. In some embodiments, the specific surface area (BET) of the positive electrode active material is within the range consisting of any two of the above numerical values. When the specific surface area (BET) of the positive electrode active material is within the above range, the performance of the electrochemical device can be ensured and good coatability can be imparted to the positive electrode active material.

[0153] The specific surface area (BET) of the positive electrode active material can be measured by the nitrogen adsorption BET one-point method using the gas flow method using a nitrogen-helium mixed gas in which the relative pressure value of nitrogen gas with respect to atmospheric pressure is accurately adjusted to 0.3 after pre-drying the sample at 150 °C for 30 minutes under nitrogen gas flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken).

[0154] Positive electrode conductive material The type of the positive electrode conductive material is not limited, and any known conductive material can be used. Examples of the positive electrode conductive material include carbon materials such as natural graphite and artificial graphite; carbon black such as acetylene black; amorphous carbon such as acicular coke; carbon nanotubes; graphene, etc., but are not limited thereto. The above positive electrode conductive materials may be used alone or in any combination.

[0155] In some embodiments, the content of the positive electrode conductive material is more than 0.01%, more than 0.1%, or more than 1% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode conductive material is less than 10%, less than 8%, or less than 5% based on the weight of the positive electrode active material layer. When the content of the positive electrode conductive material is within the above range, sufficient conductivity and the capacity of the electrochemical device can be ensured.

[0156] Positive electrode binder The type of the positive electrode binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, it may be a material that can be dissolved or dispersed in the liquid medium used during the production of the electrode. Examples of the positive electrode binder include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and cellulose nitrate; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; thermoplastic elastomer-like polymers such as styrene-butadiene-styrene block copolymer or its hydrogenated product, ethylene-propylene-diene terpolymer (EPDM), styrene-ethylene-butadiene-ethylene copolymer, and styrene-isoprene-styrene block copolymer or its hydrogenated product; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer; and polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions), etc., but are not limited thereto. The above positive electrode binders may be used alone or in any combination.

[0157] In some embodiments, with respect to the weight of the positive electrode active material layer, the content of the positive electrode binder is more than 0.1%, more than 1%, or more than 1.5%. In some embodiments, with respect to the weight of the positive electrode active material layer, the content of the positive electrode binder is less than 10%, less than 5%, less than 4%, or less than 3%. When the content of the positive electrode binder is within the above range, the positive electrode can have good conductivity and sufficient mechanical strength, and the capacity of the electrochemical device can be guaranteed.

[0158] Solvent The type of solvent used for forming the positive electrode slurry is not limited, and any solvent that can dissolve or disperse the positive electrode active material, conductive material, positive electrode binder, and thickener used as required may be used. Examples of the solvent used for forming the positive electrode slurry may include either an aqueous solvent or an organic solvent. Examples of the aqueous medium include, but are not limited to, water, a mixed medium of alcohol and water, etc. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene; heterocyclic compounds such as quinoline, pyridine; ketones such as acetone, methyl ethyl ketone, cyclohexanone; esters such as methyl acetate, methyl acrylate; amines such as diethylenetriamine, N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide, dimethyl sulfoxide, etc., but are not limited thereto.

[0159] Thickener Thickeners are usually used to adjust the viscosity of slurries. When using an aqueous medium, the slurry can be formed using a thickener and a styrene-butadiene rubber (SBR) emulsion. The type of thickener is not particularly limited, and examples thereof include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. The above thickeners may be used alone or in any combination.

[0160] In some embodiments, based on the weight of the positive electrode mixture layer, the content of the thickener is more than 0.1%, more than 0.2%, or more than 0.3%. In some embodiments, based on the weight of the positive electrode mixture layer, the content of the thickener is less than 5%, less than 3%, or less than 2%. In some embodiments, based on the weight of the positive electrode mixture layer, the content of the thickener is within the range consisting of any two of the above numerical values. When the content of the thickener is within the above range, good coatability can be imparted to the positive electrode slurry, and a decrease in the capacity and an increase in the resistance of the electrochemical device can be suppressed.

[0161] Content of the positive electrode active material In some embodiments, based on the weight of the positive electrode mixture layer, the content of the positive electrode active material is more than 80%, more than 82%, or more than 84%. In some embodiments, based on the weight of the positive electrode mixture layer, the content of the positive electrode active material is less than 99% or less than 98%. In some embodiments, based on the weight of the positive electrode mixture layer, the content of the positive electrode active material is within the range consisting of any two of the above numerical values. When the content of the positive electrode active material is within the above range, the electrical capacity of the positive electrode active material in the positive electrode mixture layer can be ensured, and the strength of the positive electrode can be maintained.

[0162] Density of the positive electrode active material layer For the positive electrode mixture layer obtained by coating and drying, in order to increase the packing density of the positive electrode active material, pressing treatment can be performed by means of manual pressing or roll pressing, etc. In some embodiments, the density of the positive electrode mixture layer is 1.5 g / cm3 Greater than 2 g / cm 3 Greater than or 2.2 g / cm 3 It is greater than. In some embodiments, the density of the positive electrode mixture layer is 5 g / cm 3 Less than, 4.5 g / cm 3 Less than, or 4 g / cm 3 Less than. In some embodiments, the density of the positive electrode mixture layer is within the range consisting of any two of the above numerical values. When the density of the positive electrode mixture layer is within the above range, the electrochemical device can be provided with good charge and discharge characteristics, and at the same time, an increase in resistance can be suppressed.

[0163] Thickness of the positive electrode mixture layer The thickness of the positive electrode mixture layer refers to the thickness of the positive electrode mixture layer on either side of the positive electrode current collector. In some embodiments, the thickness of the positive electrode mixture layer is greater than 10 μm, or greater than 20 μm. In some embodiments, the thickness of the positive electrode mixture layer is less than 500 μm, or less than 450 μm.

[0164] Method for manufacturing the positive electrode active material The positive electrode active material can be manufactured using a general method for manufacturing an inorganic compound. In order to produce a spherical or ellipsoidal positive electrode active material, a raw material substance of a transition metal is dissolved or pulverized and dispersed in a solvent such as water, the pH is adjusted while stirring, a spherical precursor is produced and recovered, and after drying if necessary, an Li-containing substance such as LiOH, Li2CO3, LiNO3, etc. is added, and a manufacturing method of firing at a high temperature to obtain the positive electrode active material can be adopted.

[0165] 2. Positive electrode current collector The type of the positive electrode current collector is not particularly limited, and any known material suitable as the positive electrode current collector may be used. Examples of the positive electrode current collector include metal materials such as aluminum, stainless steel, nickel plating layer, titanium, tantalum, etc.; carbon materials such as carbon cloth and carbon paper, but are not limited thereto. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum.

[0166] The form of the positive current collector is not particularly limited. When the positive current collector is a metal material, the form of the positive current collector includes, but is not limited to, metal foil, metal cylinder, metal strip coil, metal plate, metal foil, expanded metal, punched metal, foamed metal, etc. When the positive current collector is a carbon material, the form of the positive current collector includes, but is not limited to, carbon plate, carbon film, carbon cylinder, etc. In some embodiments, the positive current collector is metal foil. In some embodiments, the metal foil is in a mesh shape. The thickness of the metal foil is not particularly limited. In some embodiments, the thickness of the metal foil is greater than 1 μm, greater than 3 μm, or greater than 5 μm. In some 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 the range composed of any two of the above numerical values.

[0167] In order to reduce the electrical contact resistance between the positive current collector and the positive electrode active material layer, the surface of the positive current collector can include a conductive aid. The conductive aid includes, but is not limited to, carbon and precious metals such as gold, platinum, and silver.

[0168] The ratio of the thickness of the positive electrode active material layer to the thickness of the positive current collector is the thickness of the positive electrode active material layer on one side divided by the thickness of the positive current collector, and the numerical value is not particularly limited. In some embodiments, the ratio of the thickness is less than 50, less than 30, or less than 20. In some embodiments, the ratio of the thickness is greater than 0.5, greater than 0.8, or greater than 1. In some embodiments, the ratio of the thickness is within the range composed of any two of the above numerical values. When the ratio of the thickness is within the above range, the heat dissipation of the positive current collector during charge and discharge at a high current density can be suppressed, and the capacity of the electrochemical device can be ensured.

[0169] 3. Method for manufacturing the positive electrode The positive electrode can be manufactured by forming a positive electrode mixture layer containing a positive electrode active material and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be carried out by an ordinary method. That is, the positive electrode active material, the binder, and, if necessary, a conductive material, a thickening agent, etc. are dry-mixed into a sheet shape, and the obtained sheet-like material is pressure-bonded to the positive electrode current collector; alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, and this slurry is applied to the positive electrode current collector and dried to form a positive electrode active material layer on the current collector, thereby obtaining a positive electrode.

[0170] IV. Separator In order to prevent short circuit, a separator is usually provided between the positive electrode and the negative electrode. In this case, the electrolytic solution of the present invention is usually impregnated into the separator and used.

[0171] The material and shape of the separator are not particularly limited as long as the effects of the present invention are not significantly impaired. The separator may be a resin, glass fiber, inorganic substance, etc. formed of a material stable to the electrolytic solution of the present invention. In some embodiments, the separator includes a porous sheet or non-woven fabric excellent in liquid retention property, etc. Examples of the material of the resin or glass fiber separator include, but are not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, etc. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned separator materials may be used alone or in any combination.

[0172] 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.

[0173] Examples of inorganic materials include, but are not limited to, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). The form of the inorganic material includes, but is not limited to, particulate or fibrous forms.

[0174] The separator may be in the form of a film, and examples thereof include, but are not limited to, non-woven fabrics, woven fabrics, microporous membranes, etc. In the form of a film, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the independent film-like separator, a separator formed by forming a composite porous layer containing the inorganic particles on the surface of the positive electrode and / or the negative electrode using a resin binder can also be used. For example, a separator formed by using a fluororesin as a binder to form a porous layer on both sides of the positive electrode with alumina particles having a particle size of less than 1 μm accounting for 90% can also be used.

[0175] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. In some embodiments, the thickness of the separator is within the range consisting of any two of the above values. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and the rate characteristics and energy density of the electrochemical device can be ensured.

[0176] When using a porous material such as a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary. In some embodiments, the porosity of the separator is greater than 10%, greater than 15%, or greater than 20%. In some embodiments, the porosity of the separator is less than 60%, less than 50%, or less than 45%. In some embodiments, the porosity of the separator is within the range consisting of any two of the above numerical values. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, the resistance of the membrane can be suppressed, and the electrochemical device can be given good safety characteristics.

[0177] The average pore diameter of the separator is also arbitrary. In some embodiments, the average pore diameter of the separator is less than 0.5 μm or less than 0.2 μm. In some embodiments, the average pore diameter of the separator is greater than 0.05 μm. In some embodiments, the average pore diameter of the separator is within the range consisting of any two of the above numerical values. When the average pore diameter of the separator exceeds the above range, a short circuit is likely to occur. When the average pore diameter of the separator is within the above range, the electrochemical device can be given good safety characteristics.

[0178] V. Electrochemical device assembly The electrochemical device assembly includes an electrode group, a current collecting structure, an exterior case, and a protection element.

[0179] Electrode group The electrode group may have any one of a laminated structure formed by laminating the positive electrode and the negative electrode with the separator interposed therebetween, and a structure formed by winding the positive electrode and the negative electrode in a spiral shape with the separator interposed therebetween. In some embodiments, the ratio of the mass of the electrode group to the internal volume of the battery (electrode group occupancy) is more than 40% or more than 50%. In some embodiments, the electrode group occupancy is less than 90% or less than 80%. In some embodiments, the electrode group occupancy is within the range consisting of any two of the above numerical values. When the electrode group occupancy is within the above range, the capacity of the electrochemical device can be ensured, and the deterioration of characteristics such as repeated charge and discharge characteristics and high-temperature storage accompanying the increase in internal pressure can be suppressed.

[0180] Current collection structure The current collection structure is not particularly limited. In some embodiments, the current collection structure is a structure that reduces the resistance of the wiring portion and the joint portion. When the electrode group has the above laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to the terminal is preferably used. Since the internal resistance increases as the electrode area increases, it is also preferably used to provide two or more terminals in the electrode to reduce the resistance. When the electrode group has the above winding structure, two or more lead structures are provided for the positive electrode and the negative electrode, respectively, and bundled to the terminal, whereby the internal resistance can be lowered.

[0181] Outer case The material of the outer case is not particularly limited, and any material that is stable with respect to the electrolytic solution used may be used. The outer case may be made of metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, magnesium alloys, or a laminated film of resin and aluminum foil, but is not limited thereto. In some embodiments, the outer case is a metal of aluminum or aluminum alloy, or a laminated film.

[0182] The metal exterior case includes, but is not limited to, a sealed structure formed by welding metals together by laser welding, resistance welding, or ultrasonic welding, or a rivet structure using the above metals via a resin gasket. The exterior case using the laminated film includes, but is not limited to, a sealed structure formed by heat-sealing resin layers together. In order to improve the sealing performance, a resin different from the resin used for the laminated film may be interposed between the above resin layers. When the resin layer is heat-sealed through the current collector terminal to form a sealed structure, since the metal is joined to the resin, a resin having a polar group or a modified resin into which a polar group is introduced is used as the interposed resin. Note that the shape of the exterior case is also arbitrary, and may be any one of, for example, a cylindrical shape, a rectangular shape, a laminated type, a button type, a large size, etc.

[0183] Protection element As the protection element, a positive temperature coefficient (PTC) whose resistance increases when abnormal heat generation or an excessive current flows, a thermal fuse, a thermistor, a valve (current cutoff valve) that shuts off the current flowing through the electric circuit by rapidly increasing the internal pressure or internal temperature of the battery during abnormal heat generation, etc. are used. As the above protection element, an element that does not function during normal use at high current can be selected, or the design can be such that abnormal heat generation or thermal runaway does not occur even without a protection element.

[0184] VI. Applications The electrochemical device of the present invention includes any device in which an electrochemical reaction occurs, and specific examples thereof include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, this electrochemical device is a lithium secondary battery including a lithium metal secondary battery or a lithium ion secondary battery.

[0185] The present invention further provides an electronic device including the electrochemical device according to the present invention.

[0186] The use of the electrochemical device of the present invention is not particularly limited and may be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of the present invention is a laptop, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disk, a transceiver, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an assist bicycle, a bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a flash, a camera, a large household battery, and a lithium ion capacitor, etc., but not limited thereto.

[0187] Hereinafter, a lithium ion battery is taken as an example, and the preparation of the lithium ion battery will be described with reference to specific examples. Those skilled in the art should understand that the preparation method described in the present invention is merely illustrative, and any other appropriate preparation method is within the scope of the present invention.

[0188] Examples The performance of the examples and comparative examples of the lithium ion battery of the present invention will be evaluated below.

[0189] I. Preparation of Lithium Ion Battery

[0190] 1. Preparation of Negative Electrode Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed with deionized water at a mass ratio of 96%:2%:2%, stirred uniformly to obtain a slurry for the negative electrode. This slurry for the negative electrode was applied to a current collector of 12 μm. After drying, cold rolling, further punching, and welding tabs, a negative electrode was obtained.

[0191] 2. Preparation of Positive Electrode Lithium cobalt oxide (LiCoO2), a conductive material (Super-P), and polyvinylidene fluoride (PVDF) were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 95%:2%:3% and stirred uniformly to obtain a slurry for the positive electrode. This slurry for the positive electrode was coated on a 12-μm aluminum foil, dried, cold-rolled, further punched, and tabs were welded to obtain a positive electrode.

[0192] 3. Preparation of the electrolyte In a dry argon gas atmosphere, EC, PC, and DEC (weight ratio 1:1:1) were mixed, LiPF6 was added, and they were uniformly mixed to form a base electrolyte, where the concentration of LiPF6 was 1.15 mol / L. By adding additives with different contents to the base electrolyte, electrolytes for different examples and comparative examples were obtained.

[0193] The abbreviations and names of the components in the electrolyte are shown in Table 8 below.

Table 8

[0194] 4. Preparation of the separator A polyethylene (PE) porous polymer film was used as the separator.

[0195] 5. Preparation of the lithium-ion battery The obtained positive electrode, separator, and negative electrode were wound in order and placed in an outer packaging foil, leaving a liquid injection port. The electrolyte was injected through the liquid injection port, sealed, and after processes such as formation and capacity measurement, a lithium-ion battery was obtained.

[0196] II. Measurement method

[0197] 1. Measurement method for the high-temperature cycle capacity retention rate of the lithium-ion battery At 65°C, the lithium-ion battery was charged at a constant current of 1C until 4.45V, and then charged at a constant voltage of 4.45V until the current reached 0.05C, and further discharged at a constant current of 1C until 3.0V. This was taken as the first cycle. According to the above conditions, 200 cycles were performed on the lithium-ion battery. "1C" refers to the value of the current that completely discharges the battery capacity within 1 hour. The high-temperature cycle capacity retention rate of the lithium-ion battery was calculated by the following formula. High-temperature cycle capacity retention rate = (Discharge capacity after cycle / Discharge capacity of the first cycle) × 100%.

[0198] 2. Method for measuring the high-temperature cycle thickness expansion rate of a lithium-ion battery At 65°C, the lithium-ion battery was left standing for 30 minutes, then charged at a constant current of 0.5C until 4.45V, and further charged at a constant voltage of 4.45V until 0.05C. After standing for 5 minutes, the thickness of the lithium-ion battery was measured. According to the above conditions, 100 cycles were performed on the lithium-ion battery, and then the thickness of the lithium-ion battery was measured again. The high-temperature cycle thickness expansion rate of the lithium-ion battery was calculated by the following formula. High-temperature cycle thickness expansion rate = [(Thickness after cycle - Thickness before cycle) / Thickness before cycle] × 100%

[0199] 3. Method for measuring the overcharge deformation rate of a lithium-ion battery At 25°C, the lithium-ion battery was left standing for 30 minutes, and then charged at a constant current of 0.5C until 4.45V, and further charged at a constant voltage of 4.45V until 0.05C. After standing for 60 minutes, the thickness T1 of the lithium-ion battery was measured. Then, the step of charging at a constant current of 0.1C for 60 minutes and standing for 30 minutes was repeated 5 times to bring the lithium-ion battery to a 150% state of charge (SOC), and the thickness T2 of the lithium-ion battery was measured. The overcharge deformation rate of the lithium-ion battery was calculated by the following formula. Overcharge deformation rate = [(T2 - T1) / T1] × 100%

[0200] 4. Method for measuring the discharge capacity retention rate of a lithium-ion battery The lithium-ion battery was discharged at a constant current of 0.5C until 3.0V, allowed to stand for 5 minutes, then charged at a constant current of 0.5C until 4.45V, and charged at a constant voltage until the cut-off current reached 0.05C, allowed to stand for 5 minutes, and then discharged at constant currents of 0.2C and 5C respectively until the cut-off voltage of 3.0V. The discharge capacity at 5C was recorded as D1, and the discharge capacity at 0.2C was recorded as D0. According to the following formula, the discharge capacity retention rate of the lithium-ion battery at 5C based on the discharge capacity at 0.2C was calculated. Discharge capacity retention rate = [(D1 - D0) / D0]×100% For each example or comparative example, five samples were measured and their average values were taken.

[0201] III. Measurement Results Table 1 shows the effects of the compound containing sulfur-oxygen double bond in the negative electrode current collector and the electrolyte on the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, and overcharge deformation rate of the lithium-ion battery.

[0202]

Table 1

[0203] As can be seen from the results, when the negative electrode current collector of the lithium-ion battery contains tin and the electrolyte contains a compound containing sulfur-oxygen double bond, tin can suppress the expansion and contraction of the negative electrode during the charge and discharge process, and the compound containing sulfur-oxygen double bond helps to stabilize the surface structure of the negative electrode, the interface between the negative electrode binder layer and the negative electrode current collector, and the interface between the negative electrode binder layer and the electrolyte. Thereby, the high-temperature cycle capacity retention rate of the lithium-ion battery can be significantly improved, and the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery can be significantly reduced.

[0204] When the tin content in the negative electrode current collector is within the range of 0.01% to 0.2%, the improvement in the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, and overcharge deformation rate of the lithium-ion battery is particularly significant.

[0205] Table 2 shows the effects of the presence of silver in the negative electrode current collector on the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, and overcharge deformation rate of the lithium-ion battery. The differences between Examples 2-1 to 2-9 and Example 1-1 are only the parameters shown in Table 2.

[0206]

Table 2

[0207] From the results, it was found that when the negative electrode current collector of the lithium-ion battery contains tin and the electrolyte contains a compound containing a sulfur-oxygen double bond, and the negative electrode current collector further contains 0.01% to 0.2% of silver, the high-temperature cycle capacity retention rate of the lithium-ion battery can be further improved, and the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery can be further reduced.

[0208] Table 3 shows the effects of the thickness, tensile strength, and 0.2% proof stress of the negative electrode current collector on the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, and overcharge deformation rate of the lithium-ion battery. The differences between Examples 3-1 to 3-5 and Example 1-1 are only the parameters shown in Table 3.

[0209]

Table 3

[0210] As shown in Table 3, the negative electrode current collector can have properties such that the tensile strength is 100 N / mm 2 or more, the 0.2% proof stress is 30 N / mm 2 or more, and / or the thickness is 1 μm to 100 μm. When the negative electrode current collector has a tensile strength, 0.2% proof stress, and / or thickness within the above ranges, it helps to further improve the high-temperature cycle capacity retention rate of the lithium-ion battery and further reduce the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery.

[0211] Table 4 shows the effects of different negative electrode active materials and the reflectance Ra at a wavelength of 550 nm of the negative electrode binder layer on the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, overcharge deformation rate, and discharge capacity retention rate of the lithium-ion battery. The differences between Examples 4-1 to 4-6 and Example 1-1 are only the parameters shown in Table 4.

[0212]

Table 4

[0213] From the results, by using different negative electrode active materials and making the reflectance Ra at a wavelength of 550 nm of the negative electrode binder layer 7% - 15%, the high-temperature cycle capacity retention rate of the lithium-ion battery can be further improved, the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery can be further reduced, and at the same time, the discharge capacity retention rate of the lithium-ion battery can be significantly improved.

[0214] Table 5 shows the effects of the electrolyte components on the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, and overcharge deformation rate of the lithium-ion battery. The differences between Examples 5-1 to 5-31 and Example 1-1 are only the parameters shown in Table 5.

[0215]

Table 5

[0216] From the results, it was found that when the negative electrode current collector of the lithium-ion battery contains tin and the electrolyte contains a compound containing a sulfur-oxygen double bond, and the electrolyte further contains propionate, an organic compound having a cyano group, lithium difluorophosphate, and / or the compound of Formula 3, the high-temperature cycle capacity retention rate of the lithium-ion battery can be further significantly improved, and the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery can be further significantly reduced.

[0217] Table 6 shows the effects of the content b% of the compound containing sulfur-oxygen double bond in the electrolyte and the tin content a% in the negative electrode current collector on the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, and overcharge deformation rate of the lithium-ion battery. The differences between Examples 6-1 to 6-7 and Example 1-1 are only the parameters shown in Table 6.

[0218]

Table 6

[0219] As can be seen from the results, when the content of the compound containing sulfur-oxygen double bond in the electrolyte is 0.01% to 10%, it helps to further improve the high-temperature cycle capacity retention rate of the lithium-ion battery and reduce the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery.

[0220] When b and a further satisfy 1 ≤ b / a ≤ 100, it is particularly advantageous to increase the high-temperature cycle capacity retention rate of the lithium-ion battery and lower the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery.

[0221] Table 7 shows the effects of the content b% of the compound containing sulfur-oxygen double bond in the electrolyte and the reaction area d m of the negative electrode mixture layer 2 on the high-temperature cycle capacity retention rate, high-temperature cycle expansion rate, and overcharge deformation rate of the lithium-ion battery. The differences between Examples 7-1 to 7-5 and Example 1-1 are only the parameters shown in Table 7.

[0222]

Table 7

[0223] From the results, the content b% of the compound containing sulfur-oxygen double bond in the electrolyte and the reaction area d m of the negative electrode mixture layer 2When 0.5 ≦ d / b ≦ 30 is satisfied, it has been found that it is useful for further improving the high-temperature cycle capacity retention rate of the lithium-ion battery and reducing the high-temperature cycle expansion rate and overcharge deformation rate of the lithium-ion battery.

[0224] Throughout the specification, references by "Example", "Some Examples", "One Example", "Another Example", "Example", "Specific Example", or "A Part of the Example" mean that at least one example or embodiment of the present invention includes the specific features, structures, materials, or characteristics described in the said example or embodiment. Therefore, references described at various places throughout the specification, such as "In some embodiments", "In an embodiment", "In one embodiment", "In another example", "In one example", "In a specific example", or "Example" do not necessarily refer to the same embodiment or example in the present invention. Also, the specific features, structures, materials, or characteristics of this specification can be combined in any suitable way in one or more embodiments or examples.

[0225] Exemplary embodiments have been described and explained, but those skilled in the art should understand that the above-described embodiments should not be construed as limiting the present invention, and that modifications, substitutions, and changes to the embodiments are possible without departing from the technical idea, principle, and scope of the present invention.

Claims

1. An electrochemical device comprising 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 negative electrode current collector contains tin, the negative electrode current collector further contains silver, and the content of the silver is 0.01% to 0.2% based on the weight of the negative electrode current collector, the electrolytic solution contains a compound containing a sulfur-oxygen double bond, the electrochemical device.

2. The electrochemical device according to claim 1, wherein the negative electrode current collector contains copper.

3. The electrochemical device according to claim 1, wherein when the content of the tin is a% based on the weight of the negative electrode current collector, a is in the range of 0.01 to 0.

2.

4. The electrochemical device according to claim 1, wherein the average surface roughness of the negative electrode current collector is 0.05 μm to 1.5 μm.

5. The tensile strength of the negative electrode current collector is 100 N / mm ２ or more, the electrochemical device according to claim 1.

6. The 0.2% proof stress of the negative electrode current collector is 30 N / mm ２ or more. The electrochemical device according to claim 1.

7. The electrochemical device according to claim 1, wherein the thickness of the negative electrode current collector is 1 μm to 100 μm.

8. The electrochemical device according to claim 1, wherein the reflectance Ra of the negative electrode mixture layer at a wavelength of 550 nm is 7% to 15%.

9. The density da of the negative electrode mixture layer is 1.3 g / cm ３ to 1.9 g / cm ３ The electrochemical device according to claim 1, wherein the density is as described above.

10. The weight La per unit area of the negative electrode mixture layer is 4.5 mg / cm ２ to 12.5 mg / cm ２ The electrochemical device according to claim 1, wherein the weight La per unit area of the negative electrode mixture layer is 4.5 mg / cm to 12.5 mg / cm.

11. The electrochemical device according to claim 1, wherein the porosity Pa of the negative electrode mixture layer is 20% to 40%.

12. The electrochemical device according to claim 1, wherein the compound containing a sulfur-oxygen double bond includes at least one of a cyclic sulfate ester, a chain sulfate ester, a chain sulfonate ester, a cyclic sulfonate ester, a chain sulfite ester, and a cyclic sulfite ester.

13. The electrochemical device according to claim 1, wherein the compound containing a sulfur-oxygen double bond includes a compound of Formula 1, 【Chemical 11】 W is, 【Chemical Formula 12】 selected from, L is independently selected from a single bond and a methylene group respectively, m is 1, 2, 3 or 4, n is 0, 1 or 2, and, p is 0, 1, 2, 3, 4, 5, or 6, the electrochemical device according to claim 1.

14. The electrochemical device according to claim 13, wherein the compound of Formula 1 includes, 【Chemical 13】 at least one of, the electrochemical device according to claim 13.

15. The electrochemical device according to claim 1, wherein when the content of the compound containing a sulfur-oxygen double bond is b% based on the weight of the electrolytic solution, b is in the range of 0.01 to 10.

16. The electrolytic solution further contains a propionate ester, and the propionate ester includes a compound of Formula 2, 【Chemical 14】 R １ is selected from ethyl and ethyl halide, R ２ is selected from C １ -C ６ alkyl and C １ -C ６ haloalkyl, and The electrochemical device according to claim 1, wherein the content of the propionate ester is in the range of 10% to 60% with respect to the weight of the electrolyte solution.

17. The electrochemical device according to claim 3, wherein when the content of the compound containing the sulfur-oxygen double bond is b% with respect to the weight of the electrolyte solution, b is in the range of 0.01 to 10, and 1 ≤ b / a ≤ 100 is satisfied.

18. The reaction area d m of the negative electrode mixture layer ２ The electrochemical device according to claim 15, wherein the content b% of the compound containing the sulfur-oxygen double bond satisfies 0.5 ≤ d / b ≤ 30.

19. An electronic device including the electrochemical device according to any one of claims 1 to 18.

Images