Electrochemical and Electronic Devices

Abstract

The present invention relates to an electrochemical device and an electronic device. Specifically, the present invention provides an electrochemical device including a positive electrode, a negative electrode, and an electrolyte, the positive electrode including a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, the positive electrode active material including elemental tungsten, and the electrolyte including fluoroethylene carbonate. The electrochemical device of the present invention has improved low-temperature rate characteristics and high-temperature and high-pressure safety.

Description

[Technical field]

[0001] The present invention relates to the field of energy storage, and in particular to electrochemical and electronic devices, especially lithium-ion batteries. [Background technology]

[0002] With the development of technology and the increasing demand for mobile devices, the demands on electrochemical devices (e.g., lithium ion batteries) under different usage conditions have increased significantly, which has placed higher requirements on the properties of lithium ion batteries, such as high capacity, suitable cycle life, good high temperature properties, good low temperature properties, good high rate discharge properties, overcharge resistance properties and safety.

[0003] The potential difference between the positive and negative active materials used in lithium-ion batteries is generally more than 2 V, so only organic solvent electrolyte systems with a wider electrochemical window can be selected. However, these lithium-ion batteries are not suitable for use under extreme operating conditions (e.g., low temperature) and have potential safety issues.

[0004] In view of this, there is a need to provide electrochemical and electronic devices with improved low temperature properties and safety. Summary of the Invention

[0005] SUMMARY OF THE DISCLOSURE Embodiments of the present invention address, in part, problems existing in the prior art by providing electrochemical and electronic devices having improved low temperature properties and safety.

[0006] In one aspect of the present invention, the present invention provides an electrochemical device including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes elemental tungsten, and the electrolyte includes fluoroethylene carbonate.

[0007] According to an embodiment of the present invention, when the content of the tungsten element is x% based on the mass of the positive electrode active material, and the content of the fluoroethylene carbonate is a% based on the mass of the electrolyte, x and a satisfy 1≦a / x≦70.

[0008] According to an embodiment of the present invention, when the content of the tungsten element is x% based on the mass of the positive electrode active material, x satisfies 0.05≦x≦1.

[0009] According to an embodiment of the present invention, when the content of the fluoroethylene carbonate is a% based on the mass of the electrolyte, a satisfies 0.1≦a≦7.

[0010] According to an embodiment of the present invention, the electrolyte further comprises a compound having a sulfur-oxygen double bond, and the content of the compound having a sulfur-oxygen double bond relative to the mass of the electrolyte is b%, where b satisfies 0.01≦b≦5.

[0011] According to an embodiment of the present invention, when the content of the tungsten element is x% based on the mass of the positive electrode active material, b and x satisfy 1≦b / x≦50.

[0012] According to an embodiment of the present invention, the positive electrode further includes an insulating layer, and the insulating layer is formed on the positive electrode current collector and overlaps with the positive electrode active material layer in a portion thereof, or the insulating layer is formed on the positive electrode current collector and does not overlap with the positive electrode active material layer.

[0013] According to an embodiment of the present invention, the insulating layer includes a compound containing an aluminum element, and the content of the aluminum element is y1% relative to the mass of the insulating layer, and the content of the tungsten element is x% relative to the mass of the positive electrode active material, where y1 and x satisfy 50≦y1 / x≦650.

[0014] According to an embodiment of the present invention, the value of y1 ranges from 30-65.

[0015] According to an embodiment of the present invention, the positive electrode further includes an undercoat layer formed between the positive electrode current collector and the positive electrode active material layer.

[0016] According to an embodiment of the present invention, the undercoat layer contains aluminum elements, and the content of the aluminum elements is y2% relative to the mass of the undercoat layer, and the content of the tungsten elements is x% relative to the mass of the positive electrode active material, where y2 and x satisfy 20≦y2 / x≦550.

[0017] According to an embodiment of the present invention, the value of y2 is in the range of 20-50.

[0018] According to an embodiment of the present invention, the electrolyte further includes at least one of succinonitrile, adiponitrile, ethylene glycol bis(2-cyanoethyl)ether, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,3-propane sultone, ethylene sulfate, vinylene carbonate, and 1-propylphosphoric acid cyclic anhydride.

[0019] According to an embodiment of the present invention, the positive active material includes lithium nickel cobalt manganese oxide.

[0020] In another aspect, the present invention provides an electronic device comprising an electrochemical device according to the present invention.

[0021] The tungsten-containing positive electrode active material used in the present invention has high lattice stability and can significantly improve the safety of electrochemical devices at high temperatures and high pressures. At the same time, by using an electrolyte containing fluoroethylene carbonate in combination with the positive electrode active material, the low-temperature rate characteristics of the electrochemical devices can be significantly improved.

[0022] Additional aspects and advantages of embodiments of the invention will be set forth in, and in part are set forth in, the following description, or may be learned by practice of the embodiments of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the present invention will be described in detail with reference to the examples, which should not be construed as limiting the present invention.

[0024] Unless expressly stated otherwise, the following terms used herein have the meanings indicated below.

[0025] In the detailed description and claims, a list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if item A and item B are listed, the short phrase "at least one of A and B" means A only, B only, or A and B. In another example, if item A, item B, and item C are listed, the short phrase "at least one of A, B, and C" means A only, B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements. The term "at least one of" has the same meaning as the term "at least one of."

[0026] The organic solvent electrolyte system used in conventional electrochemical devices (e.g., lithium ion batteries) is prone to combustion under extreme operating conditions (e.g., overcharging and discharging, overheating, or overcooling), which poses serious safety problems. In addition, the negative electrode active material of lithium ion batteries is generally graphite-based materials, silicon carbon composite materials, or silicon monoxide materials, which have poor dynamic properties under low temperature or high rate operating conditions, which seriously deteriorates the properties of lithium ion batteries. In addition, conventional lithium ion batteries have poor low-temperature discharge properties, and their properties deteriorate seriously below -10°C, making them unable to even be discharged. Conventional lithium ion batteries also have poor high-rate properties, and when continuously discharged at a rate of 5C, the delayed heat dissipation leads to a high temperature rise, which poses the risk of thermal runaway. In addition, overuse of user terminals can also lead to overcharging of lithium ion batteries, which can cause safety accidents such as combustion and explosion.

[0027] Adding additives such as aromatic compounds such as fluorobenzene and biphenyl to the electrolyte is one of the ways to solve the safety problems of lithium-ion batteries, but these additives not only increase the impedance of the battery, but also cause a decrease in low-temperature characteristics. Safety can also be improved by providing an inorganic coating layer on the surface of the pole piece, but it still leads to a loss of energy density or a decrease in low-temperature characteristics. In the industry, tungsten element is sometimes added to the positive electrode material to change the surface energy of the microscopic structure of the material and greatly improve the cycle stability of the material. However, there is still no report that adding tungsten element to the positive electrode material improves safety. In addition, it is generally believed that the use of fluoroethylene carbonate in the electrolyte is to form a film on the negative electrode and reduce side reactions between the negative electrode and the electrolyte. Based on existing knowledge, it is not possible to predict how the simultaneous use of a positive electrode active material containing tungsten element and an electrolyte containing fluoroethylene carbonate will affect the low-temperature rate and safety characteristics of the electrochemical device.

[0028] The present invention solves the problems related to low-temperature rate and safety characteristics of electrochemical devices by using a positive electrode active material containing tungsten element and an electrolyte containing fluoroethylene carbonate. Doping the positive electrode active material with tungsten element can effectively suppress lattice distortion and improve lattice stability, thereby suppressing particle volume change during charge-discharge cycles at high or low temperatures, so as to reduce particle cracking and crushing, and improving interface stability. Using an electrolyte containing fluoroethylene carbonate can significantly reduce the ionic resistance and electronic resistance of the surface of the positive electrode active material. The specific combination of the positive electrode active material and electrolyte of the present invention can not only effectively improve the low-temperature rate characteristics of the electrochemical device, but also significantly improve the safety (such as short circuit safety and thermal abuse safety) of the electrochemical device.

[0029] I, positive electrode The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The positive electrode active material layer may be a single layer or multiple layers. The positive electrode active material layer includes a positive electrode active material, and each layer in the multiple layers of the positive electrode active material may include the same or different positive electrode active materials.

[0030] One main feature of the electrochemical device of the present invention is that the positive electrode active material comprises elemental tungsten.

[0031] In some embodiments, when the content of the tungsten element is x% with respect to the mass of the positive electrode active material, x satisfies 0.05≦x≦1. In some embodiments, x satisfies 0.01≦x≦0.5. In some embodiments, x may be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1. Or, x may be in a range consisting of any two of the above values. When the content of the tungsten element in the positive electrode active material is within the above range, the low-temperature rate characteristic and high-temperature and high-pressure safety of the electrochemical device can be further improved.

[0032] In some embodiments, the positive electrode further includes an insulating layer, and the insulating layer is formed on the positive electrode current collector and overlaps the positive electrode active material layer in some areas, or the insulating layer is formed on the positive electrode current collector and does not overlap the positive electrode active material layer.

[0033] In some embodiments, the insulating layer includes a compound containing an aluminum element. In some embodiments, the compound containing an aluminum element includes an alumina ceramic. When the insulating layer includes a compound containing an aluminum element, the low-temperature rate characteristic and high-temperature and high-pressure safety of the electrochemical device can be further improved.

[0034] In some embodiments, when the content of the aluminum element is y1% with respect to the mass of the insulating layer, y1 and x satisfy 50≦y1 / x≦650. In some embodiments, y1 and x satisfy 60≦y1 / x≦600. In some embodiments, y1 and x satisfy 100≦y1 / x≦500. In some embodiments, y1 and x satisfy 200≦y1 / x≦400. In some embodiments, y1 / x may be 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, or 650. Or, y1 / x may be in a range consisting of any two of the above numerical values. When the aluminum element content in the insulating layer and the tungsten element content in the positive electrode active material satisfy the above relationship, the surface defects of the crystal structure of the positive electrode active material can be reduced, the continuous destruction of the surface passivation layer of the positive electrode active material during the charge-discharge cycle of the electrochemical device can be effectively suppressed, and the number of repairs can be reduced. As a result, the interface stability of the positive electrode active material layer can be sufficiently improved, and the low-temperature rate characteristics and high-temperature and high-pressure safety of the electrochemical device can be further improved.

[0035] In some embodiments, the value of y1 is in the range of 30 to 65. In some embodiments, the value of y1 is in the range of 40 to 60. In some embodiments, y1 may be 30, 35, 40, 45, 50, 55, 60, or 65. Or, y1 may be in the range consisting of any two of the above values. When the content of aluminum element in the insulating layer is within the above range, the low temperature rate characteristic and high temperature and high pressure safety of the electrochemical device can be further improved.

[0036] In some embodiments, the positive electrode further includes an undercoat layer formed between the positive electrode current collector and the positive electrode active material layer.

[0037] In some embodiments, the undercoat layer includes an aluminum element. In some embodiments, the undercoat layer includes an alumina ceramic. When the undercoat layer includes a compound containing an aluminum element, the low-temperature rate characteristic and the high-temperature and high-pressure safety of the electrochemical device can be further improved.

[0038] In some embodiments, when the content of the aluminum element is y2% based on the mass of the undercoat layer, y2 and x satisfy 20≦y2 / x≦550. In some embodiments, y2 and x satisfy 50≦y2 / x≦500. In some embodiments, y2 and x satisfy 100≦y2 / x≦400. In some embodiments, y2 and x satisfy 200≦y2 / x≦400. In some embodiments, y2 / x may be 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, or 550. Or, y2 / x may be in a range consisting of any two of the above numerical values. When the content of aluminum element in the undercoat layer and the content of tungsten element in the positive electrode active material satisfy the above relationship, the positive electrode interface stability during the charge / discharge cycle of the electrochemical device can be effectively improved, and as a result, the low-temperature rate characteristics and high-temperature / high-pressure safety of the electrochemical device can be further improved.

[0039] In some embodiments, the value of y2 is in the range of 20 to 50. In some embodiments, the value of y2 is in the range of 20 to 35. In some embodiments, y2 may be 20, 25, 30, 35, 40, 45, or 50. Or, y2 may be in the range consisting of any two of the above values. When the content of aluminum element in the undercoat layer is within the above range, the low temperature rate characteristic and high temperature and high pressure safety of the electrochemical device can be further improved.

[0040] In some embodiments, the positive active material comprises lithium cobalt oxide. In some embodiments, the positive active material comprises lithium nickel cobalt manganese oxide. Compared with lithium cobalt oxide, lithium nickel cobalt manganese oxide has a more stable crystal structure after doping with tungsten, and the low-temperature rate characteristics and high-temperature and high-pressure safety of the electrochemical device are more significantly improved.

[0041] In some embodiments, the surface of the positive electrode active material may have a material attached thereto that is different in composition. Examples of the surface-attached material may include, but are not limited to, 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; and carbon. By attaching a material to the surface of the positive electrode active material, the oxidation reaction of the electrolyte on the surface of the positive electrode active material can be suppressed, and the life of the electrochemical device can be increased. If the amount of material attached to the surface is too small, the effect cannot be fully observed. If the amount of material attached to the surface is too large, the ingress and egress of lithium ions may be hindered, and the resistance may increase. In the present invention, a positive electrode active material having a material attached to the surface of the positive electrode active material that is different in composition from the positive electrode active material is also referred to as a "positive electrode active material".

[0042] In some embodiments, the shapes of the positive electrode active material particles include, but are not limited to, block-like, polyhedral, spherical, ellipsoidal, plate-like, needle-like, and columnar shapes. 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.

[0043] The type of the positive electrode conductive material is not limited, and any known conductive material may be used. Examples of the positive electrode conductive material may include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; carbon nanotubes; graphene, etc. The positive electrode conductive material may be used alone or in any combination.

[0044] The type of positive electrode binder used in the manufacture of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material may be used as long as it is soluble or dispersible in the liquid medium used in the manufacture of the electrode. Examples of positive electrode binders 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, butadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or their hydrogenated products, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-ethylene copolymers, and styrene-isoprene rubber. The positive electrode binder may include, but is not limited to, one or more of the following: thermoplastic elastomer-like polymers such as ethylene block copolymers or their hydrides; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; ion-conductive polymer compositions having alkali metal ions (especially lithium ions), etc. The positive electrode binder may be used alone or in any combination.

[0045] The type of solvent used to form the positive electrode slurry is not limited, and may be any solvent capable of dissolving or dispersing the positive electrode active material, the conductive material, the positive electrode binder, and the thickener used as necessary. Examples of the solvent used to form the positive electrode slurry may include either an aqueous solvent or an organic solvent. Examples of the aqueous medium may include, but are not limited to, water, a mixed medium of alcohol and water, and the like. Examples of organic media may include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene, etc.; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, cyclohexanone, etc.; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, tetrahydrofuran (THF), etc.; amides such as N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, etc.; aprotic polar solvents such as hexamethylphosphamide and dimethylsulfoxide, etc.

[0046] The thickener is usually used to adjust the viscosity of the slurry. When an aqueous medium is used, the slurry can be made using a thickener and a styrene butadiene rubber (SBR) emulsion. The type of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. The thickener may be used alone or in any combination.

[0047] The type of the positive electrode current collector is not particularly limited, and may be any known material suitable for use as a positive electrode current collector. Examples of the positive electrode current collector may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating layer, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum.

[0048] In order to reduce the electrical contact resistance between the positive electrode current collector and the positive electrode active material layer, the surface of the positive electrode current collector may include a conductive additive. Examples of the conductive additive may include, but are not limited to, carbon and precious metals such as gold, platinum, and silver.

[0049] The positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The positive electrode using the positive electrode active material can be produced by a normal method. That is, the positive electrode active material, the binder, and, if necessary, a conductive material and a thickener are dry-mixed to form a sheet, and the sheet obtained is pressed against the positive electrode current collector; alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, and the slurry is applied to the positive electrode current collector and dried, thereby forming a positive electrode active material layer on the current collector. This allows the positive electrode to be obtained.

[0050] In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 95%, preferably 96%, more preferably 97%. In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 98%. In some embodiments, the mass fraction of the positive electrode active material in the positive electrode active material layer is 99%. When the mass fraction of the positive electrode active material in the positive electrode active material layer is within the above range, the energy density of the electrochemical device can be significantly increased.

[0051] When the positive electrode active material is in the form of primary particles, the average particle size of the positive electrode active material refers to the primary particle size of the positive electrode active material particles. When the positive electrode active material primary particles are aggregated to form secondary particles, the average particle size of the positive electrode active material particles refers to the secondary particle size of the positive electrode active material particles.

[0052] In some embodiments, when the average particle size of the positive electrode active material is D μm, the value of D is in the range of 5 to 30. In some embodiments, the value of D is in the range of 10 to 25. In some embodiments, the value of D is in the range of 12 to 20. In some embodiments, D may be 5, 7, 9, 10, 12, 15, 18, 20, 25, or 30. Or, D may be in the range consisting of any two of the above numerical values.

[0053] When the average particle size of the positive electrode active material is within the above range, a positive electrode active material having a high tap density can be obtained, and the deterioration of the characteristics of the electrochemical device can be suppressed, and problems such as the occurrence of streaks can be prevented in the process of preparing the positive electrode of the electrochemical device (i.e., when the positive electrode active material, conductive material, binder, etc. are slurried with a solvent and applied in the form of a film). By mixing two or more positive electrode active materials having different average particle sizes, the filling property during the preparation of the positive electrode can be further improved.

[0054] The average particle size of the positive electrode active material can be measured using a laser diffraction / scattering type particle size distribution measuring device. When using HORIBA's LA-920 as a particle size distribution measuring device, a 0.1% sodium hexametaphosphate aqueous solution is used as the dispersion medium used during measurement, and the measurement refractive index is set to 1.24 after ultrasonic dispersion for 5 minutes. The average particle size of the positive electrode active material can also be measured using a laser diffraction type particle size distribution measuring device (Shimadzu Corporation SALD-2300) and a scanning electron microscope (ZEISS EV018, 100 or more samples).

[0055] II, electrolyte The electrolytic solution used in the electrochemical device of the present invention contains an electrolyte and a solvent that dissolves the electrolyte. Another main feature of the electrochemical device of the present invention is that the electrolytic solution contains fluoroethylene carbonate.

[0056] In some embodiments, when the content of the fluoroethylene carbonate is a% with respect to the mass of the electrolyte, x and a satisfy 1≦a / x≦70. In some embodiments, x and a satisfy 2≦a / x≦60. In some embodiments, x and a satisfy 5≦a / x≦50. In some embodiments, x and a satisfy 10≦a / x≦30. In some embodiments, a / x may be 1, 2, 3, 5, 8, 10, 20, 30, 40, 50, 60, or 70. Or, a / x may be in a range consisting of any two of the above numerical values. When the content of fluoroethylene carbonate in the electrolyte and the content of tungsten element in the positive electrode active material satisfy the above relationship, the surface defects of the crystal structure of the positive electrode active material can be reduced, the continuous destruction of the surface passivation layer of the positive electrode active material during the charge-discharge cycle of the electrochemical device can be effectively suppressed, and the number of repairs can be reduced. As a result, the interface stability of the positive electrode active material layer can be sufficiently improved, and the low-temperature rate characteristics and high-temperature and high-pressure safety of the electrochemical device can be further improved.

[0057] In some embodiments, a satisfies 0.1≦a≦7. In some embodiments, a satisfies 0.1≦a≦5. In some embodiments, a satisfies 0.5≦a≦3. In some embodiments, a satisfies 1≦a≦2. In some embodiments, a may be 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, or 7. Or, a may be in a range consisting of any two of the above numerical values. When the content of fluoroethylene carbonate in the electrolyte is within the above range, the low temperature rate characteristic and high temperature and high pressure safety of the electrochemical device can be further improved.

[0058] In some embodiments, the electrolyte further comprises a compound having a sulfur-oxygen double bond.

[0059] In some embodiments, when the content of the compound having a sulfur-oxygen double bond is b% relative to the mass of the electrolyte, b satisfies 0.01≦b≦5. In some embodiments, b satisfies 0.01≦b≦2. In some embodiments, b satisfies 0.05≦b≦1. In some embodiments, b satisfies 0.1≦b≦0.5. In some embodiments, b may be 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5. Or, b may be in a range consisting of any two of the above values. When the content of the compound having a sulfur-oxygen double bond in the electrolyte is within the above range, the low-temperature rate characteristic and high-temperature and high-pressure safety of the electrochemical device can be further improved.

[0060] In some embodiments, b and x satisfy 1≦b / x≦50. In some embodiments, b and x satisfy 2≦b / x≦20. In some embodiments, b and x satisfy 5≦b / x≦10. In some embodiments, b / x may be 1, 2, 3, 5, 8, 10, 20, 30, 40, 50. Or, b / x may be in a range consisting of any two of the above values. When the content of the compound having a sulfur-oxygen double bond in the electrolyte and the content of the tungsten element in the positive electrode active material satisfy the above relationship, the surface defects of the crystal structure of the positive electrode active material can be reduced, and the continuous destruction of the surface passivation layer of the positive electrode active material during the charge-discharge cycle of the electrochemical device can be effectively suppressed, and the number of repairs can be reduced, thereby sufficiently improving the interface stability of the positive electrode active material layer, and as a result, the low temperature rate characteristic and high temperature and high pressure safety of the electrochemical device can be further improved.

[0061] In some embodiments, the compound having a sulfur-oxygen double bond includes at least one of a cyclic sulfate, a chain sulfate, a chain sulfonate, a cyclic sulfonate, a chain sulfite, and a cyclic sulfite.

[0062] In some embodiments, the cyclic sulfate may include, 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.

[0063] In some embodiments, the linear sulfate esters include, but are not limited to, one or more of dimethyl sulfate, methyl ethyl sulfate, and diethyl sulfate.

[0064] In some embodiments, the linear sulfonate esters include, but are not limited to, one or more of fluorosulfonate esters such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl dimethylsulfonate, methyl 2-(methanesulfonyloxy)propionate, and ethyl 2-(methanesulfonyloxy)propionate.

[0065] In some embodiments, the cyclic sulfonate ester is 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 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, The sultone may be one or more of, but is not limited to, 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-butane sultone, 1,5-pentane sultone, methylene methane disulfonate, and ethylene methane disulfonate.

[0066] In some embodiments, the linear sulfite ester may include, but is not limited to, one or more of dimethyl sulfite, methyl ethyl sulfite, and diethyl sulfite.

[0067] In some embodiments, the cyclic sulfites include, but are 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.

[0068] In some embodiments, the compound having a sulfur-oxygen double bond comprises a compound of formula I: [ka] Where: W is [ka] is selected from Each L is independently a single bond or a methylene group; m is 1, 2, 3, or 4; n is 0, 1, or 2, and p is 0, 1, 2, 3, 4, 5, or 6.

[0069] In some embodiments, the compound of formula I is [ka] The composition includes at least one of the following:

[0070] In some embodiments, the dicyclosultone comprises a compound of formula II: [ka] wherein A1, A2, A3 and A4 are each independently selected from a substituted or unsubstituted C1-3 alkylene group, and if substituted, the substituents are selected from a C1-5 alkyl group, a halogen, and a halogenated C1-5 alkyl group.

[0071] In some embodiments, the compound of formula II is [ka] The composition includes at least one of the following:

[0072] In some embodiments, the electrolyte further comprises at least one of succinonitrile, adiponitrile, ethylene glycol bis(2-cyanoethyl)ether, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,3-propane sultone, ethylene sulfate, vinylene carbonate, and 1-propylphosphoric acid cyclic anhydride. In some embodiments, the content of the compound is 0.1% to 6% based on the mass of the electrolyte. In some embodiments, the content of the compound is 0.5% to 5% based on the mass of the electrolyte. In some embodiments, the content of the compound is 1% to 3% based on the mass of the electrolyte. These compounds help stabilize the interface between the positive electrode and the electrolyte, thereby further improving the overcharge resistance and safety of the electrochemical device at high temperature and pressure.

[0073] In some embodiments, the electrolyte further comprises any non-aqueous solvent that can be used as a solvent for electrolytes known in the prior art.

[0074] In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0075] In some embodiments, examples of the cyclic carbonate ester may include, but are not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonate ester has 3 to 6 carbon atoms.

[0076] In some embodiments, examples of the chain carbonate ester may include, but are 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, and di-n-propyl carbonate. Examples of the fluorine-substituted chain carbonate ester include, but are not limited to, one or more of bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethylmethylcarbonate, 2,2-difluoroethylmethylcarbonate, and 2,2,2-trifluoroethylmethylcarbonate.

[0077] In some embodiments, examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of γ-butyrolactone and γ-valerolactone. In some embodiments, a portion of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.

[0078] In some embodiments, examples of the chain carboxylic acid ester may include, but are 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. In some embodiments, some of the hydrogen atoms of the chain carboxylic acid ester may be substituted with fluorine. In some embodiments, examples of the fluorine-substituted chain carboxylic acid ester may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate.

[0079] In some embodiments, examples of the cyclic ethers may include, but are not limited to, one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0080] In some embodiments, examples of the linear ether may include, but are 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.

[0081] In some embodiments, examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of trimethyl phosphate, triethyl phosphate, dimethylethyl phosphate, methyldiethyl phosphate, ethylenemethyl phosphate, ethyleneethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tri(2,2,2-trifluoroethyl)phosphate, and tri(2,2,3,3,3-pentafluoropropyl)phosphate, and the like.

[0082] In some embodiments, examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethylsulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In some embodiments, some of the hydrogen atoms of the sulfur-containing organic solvent may be replaced with fluorine.

[0083] 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.

[0084] In some embodiments, the solvent used in the electrolyte of the present invention includes a cyclic carbonate ester, a chain carbonate ester, a cyclic carboxylate ester, a chain carboxylate ester, 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.

[0085] In some embodiments, the electrolyte is not particularly limited, and any known electrolyte can be used. In the case of a lithium secondary battery, a lithium salt is usually used.Examples of electrolytes include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, and LiWF7; lithium tungstates such as LiWOF5; lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, and CF3CF2CF2CF2CO2Li; FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, and CF3CF2SO Lithium sulfonates such as 3Li, CF3CF2CF2SO3Li, and 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 bissulfonylimide, lithium cyclic 1,3-perfluoropropane bissulfonylimide, and LiN(CF3SO2)(C4F9SO2); LiC(FSO2)3, LiC(CF3SO2)3 , LiC(C2F5SO2)3; (maronite)borate lithium salts such as lithium bis(maronite)borate and lithium difluoro(maronite)borate; (maronite)phosphate lithium salts such as lithium tris(maronite)phosphate, lithium difluorobis(maronite)phosphate, and lithium tetrafluoro(maronite)phosphate; and LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiB The lithium salts may include, but are not limited to, fluorine-containing organic lithium salts such as F3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2; lithium oxalate borate salts such as lithium difluoro(oxalate)borate, lithium bis(oxalate)borate; lithium oxalate phosphate salts such as lithium tetrafluoro(oxalate)phosphate, lithium difluorobis(oxalate)phosphate, lithium tris(oxalate)phosphate, and the like.

[0086] 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 bissulfonylimide lithium, cyclic 1,3-perfluoropropane bissulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, and lithium difluorobis(oxalato)phosphate, which helps improve the power output characteristics, high rate charge / discharge characteristics, high temperature storage characteristics, and cycle characteristics of the electrochemical device.

[0087] The content of the electrolyte is not particularly limited as long as it does not impair the effect of the present invention. In some embodiments, the total molar concentration of lithium in the electrolyte 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 is less than 3 mol / L, less than 2.5 mol / L, or less than 2.0 mol / L. In some embodiments, the total molar concentration of lithium in the electrolyte is in a range consisting of any two of the above values. When the concentration of the electrolyte is in the above range, the amount of lithium, which is a charged particle, is not too small, and the viscosity can be set to an appropriate range, making it easier to ensure good electrical conductivity.

[0088] When two or more electrolytes are used, the electrolyte comprises at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte comprises a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate. In some embodiments, the electrolyte comprises a lithium salt. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is greater than 0.01% or greater than 0.1% by weight of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is less than 20% or less than 10% by weight of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is in the range consisting of any two of the above values.

[0089] In some embodiments, the electrolyte includes one or more salts selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, 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 bissulfonylimide lithium, cyclic 1,3-perfluoropropane bissulfonylimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. In some embodiments, the other salt is LiPF6.

[0090] In some embodiments, the content of the other salts is greater than 0.01%, or greater than 0.1%, by weight of the electrolyte. In some embodiments, the content of the other salts is less than 20%, less than 15%, or less than 10%, by weight of the electrolyte. In some embodiments, the content of the other salts is in a range consisting of any two of the above values. The other salts in the above amounts help balance the electrical conductivity and viscosity of the electrolyte.

[0091] III, negative electrode The negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material. The negative electrode active material layer may be a single layer or multiple layers, and each layer of the multiple layers of the negative electrode active material may include the same or different negative electrode active materials. The negative electrode active material is any material that can reversibly absorb and release metal ions, such as lithium ions. In some embodiments, the chargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional deposition of lithium metal on the negative electrode during charging.

[0092] Any known current collector can be used as the current collector that holds the negative electrode active material. Examples of the negative electrode current collector include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.

[0093] When the negative electrode current collector is a metal material, the form of the negative electrode current collector may include, but is not limited to, a metal foil, a metal cylinder, a metal strip roll, a metal plate, a metal film, a metal lath, a stamped metal, a metal foam, etc. In some embodiments, the negative electrode current collector is a metal film. In some embodiments, the negative electrode current collector is a copper foil. In some embodiments, the negative electrode current collector is a rolled copper foil by a rolling method or an electrolytic copper foil by an electrolytic method.

[0094] In some embodiments, the thickness of the negative electrode current collector is greater than 1 μm or greater than 5 μm. In some embodiments, the thickness of the negative electrode current collector is less than 100 μm or less than 50 μm. In some embodiments, the thickness of the negative electrode current collector is in a range consisting of any two of the above values.

[0095] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions. Examples of the negative electrode active material include, but are not limited to, carbon materials such as natural graphite and artificial graphite, metals such as silicon (Si) and tin (Sn), and oxides of metal elements such as Si and Sn. The negative electrode active material may be used alone or in any combination.

[0096] The negative electrode active material layer may further include a negative electrode binder. The negative electrode binder can improve the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. The type of the negative electrode binder is not particularly limited, and may be a material that is stable against the electrolyte and the solvent used in the manufacture of the electrode. In some embodiments, the negative electrode binder includes a resin binder. Examples of the resin binder may include, but are not limited to, fluororesin, polyacrylonitrile (PAN), polyimide resin, acrylic acid-based resin, polyolefin resin, and the like. When the negative electrode mixture slurry is prepared using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethylcellulose (CMC) or a salt thereof, styrene butadiene rubber (SBR), polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, and the like.

[0097] The negative electrode can be prepared by applying a negative electrode mixture slurry containing a negative electrode active material and a resin binder to a negative electrode current collector, drying the slurry, and then rolling the slurry to form a negative electrode active material layer on both sides of the negative electrode current collector.

[0098] IV, separator In order to prevent short circuits, a separator is usually provided between the positive electrode and the negative electrode, and in this case, the electrolyte of the present invention is usually used by permeating the separator.

[0099] The material and shape of the separator are not particularly limited as long as they do not significantly impair the effects of the present invention. The separator may be a resin, glass fiber, inorganic material, etc., made of a material stable to the electrolyte of the present invention. In some embodiments, the separator includes a porous sheet with excellent liquid retention, or a material in the form of a nonwoven fabric. Examples of materials for the resin or glass fiber separator may 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 materials for the separator may be used alone or in any combination.

[0100] 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.

[0101] Examples of inorganic materials may include, but are not limited to, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, sulfates (e.g., barium sulfate, calcium sulfate, etc.) The form of the inorganic material may include, but is not limited to, particulate or fibrous.

[0102] The separator may be in the form of a film, examples of which include, but are not limited to, nonwoven fabric, woven fabric, microporous film, etc. In the form of a film, the separator has a pore size of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm. In addition to the above-mentioned 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 negative electrode using a resin-based binder, for example, a separator formed by forming a porous layer on both sides of the positive electrode using alumina particles with a 90% particle size of less than 1 μm using a fluororesin as a binder, can also be used.

[0103] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is more than 1 μm, more than 5 μm, or more 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 in a range consisting of any two of the above numerical values. When the thickness of the separator is in the above range, insulation and mechanical strength are ensured, and the rate characteristics and energy density of the electrochemical device are ensured.

[0104] When a porous material such as a porous sheet or a nonwoven fabric is used as the separator, the porosity of the separator is arbitrary. In some embodiments, the porosity of the separator is more than 10%, more than 15%, or more 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 in a range consisting of any two of the above values. When the porosity of the separator is in the above range, the insulation and mechanical strength are ensured, and the sheet resistance is suppressed, so that the electrochemical device has good safety characteristics.

[0105] The average pore size of the separator is also arbitrary. In some embodiments, the average pore size of the separator is less than 0.5 μm, or less than 0.2 μm. In some embodiments, the average pore size of the separator is greater than 0.05 μm. In some embodiments, the average pore size of the separator is in the range consisting of any two of the above values. If the average pore size of the separator exceeds the above range, short circuits are likely to occur. If the average pore size of the separator is in the above range, the electrochemical device has good safety characteristics.

[0106] V. Electrochemical device assembly The electrochemical device assembly includes an electrode group, a current collecting structure, an outer casing, and a protective element.

[0107] The electrode group may be any one of a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, and a structure in which the positive electrode and the negative electrode are spirally wound 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 rate) is more than 40% or more than 50%. In some embodiments, the electrode group occupancy rate is less than 90% or less than 80%. In some embodiments, the electrode group occupancy rate is in a range consisting of any two of the above numerical values. When the electrode group occupancy rate is in the above range, the capacity of the electrochemical device can be secured, and deterioration of characteristics such as repeated charge / discharge characteristics and high-temperature storage characteristics caused by an increase in internal pressure can be suppressed.

[0108] The current collecting structure is not particularly limited. In some embodiments, the current collecting structure is a structure that reduces the resistance of the wiring portion and the joint portion. When the electrode group has the laminated structure, a structure formed by bundling the metal core parts of each electrode layer and welding them to a terminal is preferably used. When the electrode area is large, the internal resistance increases, so it is also preferably used to reduce the resistance by providing two or more terminals in the electrode. When the electrode group has the wound structure, the internal resistance can be reduced by providing two or more lead structures on each of the positive electrode and the negative electrode and bundling them to a terminal.

[0109] The material of the outer case is not particularly limited, and may be any material that is stable against the electrolyte used. The outer case may be made of metals such as nickel-plated steel, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminated film of resin and aluminum foil, but is not limited thereto. In some embodiments, the outer case is made of metal such as aluminum or aluminum alloy, or a laminated film.

[0110] 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 formed by using the metals via a resin gasket. The laminated film exterior case includes, but is not limited to, a sealed structure formed by heat-sealing resin layers together. In order to improve the sealing property, a resin different from the resin used in the laminated film may be interposed between the resin layers. When the resin layer is heat-sealed via the current collecting terminal to form a sealed structure, the metal is bonded to the resin, so that a resin having a polar group or a modified resin into which a polar group has been introduced is used as the interposed resin. The shape of the exterior case is also arbitrary, and may be, for example, any one of a cylindrical shape, a rectangular shape, a laminate type, a button type, a large size, etc.

[0111] The protective element may be a positive temperature coefficient (PTC) whose resistance increases when abnormal heat is generated or an excessive current flows, a thermal fuse, a thermistor, a current valve (current cutoff valve) that cuts off the current flowing in the electric circuit by suddenly increasing the internal pressure or temperature of the battery when abnormal heat is generated, etc. The protective element may be selected so that it does not function during normal use at high current, or it may be designed in such a way that abnormal heat generation or thermal runaway does not occur even if the protective element is not present.

[0112] The electrochemical device of the present invention includes any device in which an electrochemical reaction occurs, specific examples of which include a lithium metal secondary battery or a lithium ion secondary battery.

[0113] The present invention further provides an electronic device comprising an electrochemical device according to the present invention.

[0114] The application of the electrochemical device of the present invention is not particularly limited, and can be used in any electronic device known in the prior art.In some embodiments, the electrochemical device of the present invention can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, mobile phones, portable facsimiles, portable copy machines, portable printers, stereo headsets, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power sources, motors, automobiles, motorcycles, auxiliary bicycles, bicycles, lighting equipment, toys, game consoles, watches, power tools, flashlights, cameras, large household storage batteries, and lithium ion capacitors.

[0115] The following takes lithium ion battery as an example, and describes the preparation of lithium ion battery with reference to specific examples.Those skilled in the art should understand that the preparation method described in the present invention is only illustrative, and any other suitable preparation method is within the scope of the present invention. Working Example

[0116] 1. Preparation of lithium-ion batteries 1. Preparation of the negative electrode Artificial graphite, styrene butadiene rubber, and sodium carboxymethylcellulose were mixed with deionized water in a mass ratio of 96%:2%:2% and stirred uniformly to obtain anode slurry. This anode slurry was applied to a 9μm copper foil, dried, cold rolled, punched, and tab-welded to obtain anode.

[0117] 2. Preparation of the positive electrode (1) Preparation of lithium nickel cobalt manganese oxide containing elemental tungsten as the positive electrode active material Anhydrous ethanol and deionized water were mixed in a volume ratio of 7:3, and 0.05 mol of nickel nitrate hexahydrate, 0.02 mol of cobalt nitrate hexahydrate, and 0.03 mol of manganese acetate tetrahydrate were added thereto, and the mixture was completely dissolved by ultrasonic stirring. The mixture was transferred to a 500 mL autoclave, 0.6 mol of ammonium bicarbonate was added thereto, heated to 120 ° C, held for 8 hours, cooled, centrifuged, the precipitate was collected, washed three times with anhydrous ethanol, and vacuum dried at 60 ° C for 8 hours to obtain a nickel cobalt manganese hydroxide precursor. Subsequently, lithium carbonate, tungsten oxide, and the prepared nickel cobalt manganese hydroxide precursor were thoroughly mixed and ground, calcined in a tubular furnace at 900 ° C for 20 hours, cooled, and then ground again to obtain lithium nickel cobalt manganese oxide containing tungsten element as a positive electrode active material.

[0118] (2) Preparation of lithium cobalt oxide containing tungsten, which is the positive electrode active material A certain amount of Co3O4 and LiOH powder was measured out, thoroughly mixed in an agate mortar, ground, and then fired at 900°C for 10 hours. A certain amount of sodium tungstate was added to the fired mixture, which was then ball-milled for 10 hours using ethanol as a solvent, and then fired at 800°C for 10 hours to obtain lithium cobalt oxide containing tungsten element, which is the positive electrode active material.

[0119] Alumina, carbon nanotubes, and polypropionate were mixed with deionized water in a mass ratio of 65:25:10 and stirred uniformly to obtain an insulating layer or undercoat layer slurry, which was then applied to an aluminum foil of 12 μm.

[0120] The positive electrode active material, carbon nanotubes, and polyvinylidene fluoride were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 97:1:2 and stirred uniformly to obtain a positive electrode active material layer slurry. This positive electrode active material layer slurry was applied to an undercoat layer or an aluminum foil, dried, cold rolled, punched, and tab-welded to obtain a positive electrode.

[0121] 3. Preparation of electrolyte In a dry argon gas atmosphere, EC, PC, PP, and DEC (weight ratio 1:1:1:1) were mixed, LiPF6 was added, and mixed uniformly to form a base electrolyte solution with a LiPF6 concentration of 12.5%. By adding additives with different contents to the base electrolyte solution, electrolyte solutions of different examples and comparative examples were obtained.

[0122] The abbreviations and names of the components in the electrolyte are shown in the table below.

[0123] [Table 1A]

[0124] 4. Preparation of the separator A polyethylene porous polymer film served as the separator.

[0125] 5. Preparation of Lithium-ion Battery The obtained positive electrode, separator, and negative electrode were wound in order, placed in an exterior foil, and an inlet was left. An electrolyte was injected through the inlet, and the battery was packaged. The battery was then subjected to processes such as formation and capacity grading to manufacture a lithium-ion battery.

[0126] 2.Measurement method 1. Measurement method for overcharge deformation rate of lithium-ion batteries After leaving the lithium ion battery at 25°C for 30 minutes, it was charged at a constant current of 0.5C to 4.45V, and then charged at a constant voltage of 0.05C at 4.45V, left to stand for 60 minutes, and the thickness 1 was measured. After that, the step of charging at a constant current of 0.1C for 60 minutes and leaving to stand for 30 minutes was repeated five times, and the lithium ion battery was brought to a state of charge (SOC) of 150%, and the thickness 2 was measured. The overcharge deformation rate of the lithium ion battery was calculated by the following formula.

[0127]

number

[0128] 2. Measurement method for high temperature short circuit deformation rate of lithium ion batteries After leaving the lithium ion battery at 25°C for 30 minutes, it was charged at a constant current of 0.5C to 4.7V, and then charged at a constant voltage of 0.05C at 4.7V, and left to stand for 60 minutes, and the thickness T1 of the lithium ion battery was measured. Next, the lithium ion battery was short-circuited at 100mΩ for 10 seconds, and the thickness T2 of the lithium ion battery was measured. The high-temperature short-circuit deformation rate of the lithium ion battery was calculated using the following formula.

[0129]

number

[0130] 3. Measurement method for low-temperature rate characteristics of lithium-ion batteries At -20°C, the lithium ion battery was discharged at 0.2C to 3.0V, left to stand for 5 minutes, charged at 0.5C to 4.7V, charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharge measurements were performed at 0.2C and 5.0C to obtain discharge capacity 1 and discharge capacity 2. The low temperature rate of the lithium ion battery was calculated using the following formula.

[0131]

number

[0132] 3. Measurement results Table 1B shows the effects of the positive electrode active material and the electrolyte on the low-temperature rate characteristics and high-temperature and high-pressure safety of the lithium-ion battery. In Examples 1-1 to 1-19 and Comparative Examples 1-1 to 1-3, lithium nickel cobalt manganese oxide containing / not containing tungsten element was used as the positive electrode active material. In Example 1-20 and Comparative Examples 1-4, 1-5, and 1-6, lithium cobalt oxide containing / not containing tungsten element was used as the positive electrode active material.

[0133] [Table 1B]

[0134] As shown in Comparative Example 1-1, when the positive electrode active material is undoped lithium nickel cobalt manganese oxide and the electrolyte does not contain FEC, the lithium ion battery has a high overcharge deformation rate and a low short circuit deformation rate. As shown in Comparative Example 1-2, when the positive electrode active material is lithium nickel cobalt manganese oxide containing tungsten element but the electrolyte does not contain FEC, the lithium ion battery has a high overcharge deformation rate and a low short circuit deformation rate. As shown in Comparative Example 1-3, when the electrolyte contains FEC but the positive electrode active material is undoped lithium nickel cobalt manganese oxide, the lithium ion battery has a high overcharge deformation rate and a low short circuit deformation rate.

[0135] As shown in Examples 1-1 to 1-19, when the positive electrode active material is lithium nickel-cobalt manganese oxide containing tungsten element and the electrolyte contains FEC, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be significantly reduced and the low temperature rate can be significantly increased.

[0136] When the content of FEC in the electrolyte (a%) and the content of tungsten element in the positive electrode active material (x%) satisfy 1≦a / x≦70, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly improved.

[0137] When the content of FEC in the electrolyte is in the range of 0.1% to 7%, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly increased.

[0138] When the content of tungsten element in the positive electrode active material is 0.05% to 1%, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly increased.

[0139] In addition, as shown in Comparative Examples 1-4 to 1-6 and Example 1-20, when the positive electrode active material is lithium cobalt oxide containing tungsten element and the electrolyte contains FEC, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be significantly reduced and the low temperature rate can be significantly increased. Compared with lithium cobalt oxide containing tungsten element, lithium nickel cobalt manganese oxide containing tungsten element has a more obvious effect of improving the properties of the lithium ion battery.

[0140] Table 2 shows the effect of the compound having a sulfur-oxygen double bond in the electrolyte and the relationship between the compound and the content of tungsten element in the positive electrode active material on the low temperature rate characteristics and high temperature and high pressure safety of the lithium ion battery. Other than the parameters listed in Table 2, Examples 2-1 to 2-25 were set in the same manner as Example 1-1.

[0141] [Table 2]

[0142] As can be seen from the results, by adding 0.01% to 5% of a compound having a sulfur-oxygen double bond to the electrolyte in addition to containing FEC, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly increased.

[0143] When the content b% of the compound having a sulfur-oxygen double bond in the electrolyte and the content x% of the tungsten element in the positive electrode active material satisfy 1≦b / x≦50, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly increased.

[0144] Table 3 shows the effect of the aluminum element content in the insulating layer and the tungsten element content in the positive electrode active material on the low temperature rate characteristics and high temperature and high pressure safety of the lithium ion battery. Other than the parameters listed in Table 3, Examples 3-1 to 3-16 were set the same as Example 1-1.

[0145] [Table 3]

[0146] As can be seen from the results, when the aluminum content y1% in the positive electrode insulating layer and the tungsten content x% in the positive electrode active material satisfy 50≦y1 / x≦650, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly improved.

[0147] When the aluminum content in the positive electrode insulating layer is 30% to 65%, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly increased.

[0148] Table 4 shows the effect of the aluminum element content in the undercoat layer and the tungsten element content in the positive electrode active material on the low temperature rate characteristics and high temperature and high pressure safety of the lithium ion battery. Other than the parameters listed in Table 4, Examples 4-1 to 4-15 were set the same as Example 1-1.

[0149] [Table 4]

[0150] As can be seen from the results, when the aluminum content y2% in the positive electrode undercoat layer and the tungsten content x% in the positive electrode active material satisfy 20≦y2 / x≦550, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly improved.

[0151] When the content of aluminum element in the positive electrode undercoat layer is 20% to 50%, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced, and the low temperature rate can be further significantly increased.

[0152] Table 5 shows the effect of adding additional compounds to the electrolyte on the low-temperature rate characteristics and high-temperature and high-pressure safety of the lithium-ion battery. Other than the parameters listed in Table 5, Examples 5-1 to 5-15 were set to the same as Example 1-1.

[0153] [Table 5]

[0154] As can be seen from the results, when the electrolyte contains a dinitrile compound and further contains at least one of succinonitrile, adiponitrile, ethylene glycol bis(2-cyanoethyl)ether, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,3-propane sultone, ethylene sulfate, vinylene carbonate, and 1-propylphosphoric acid cyclic anhydride, the overcharge deformation rate and short circuit deformation rate of the lithium ion battery can be further reduced while improving the low temperature rate.

[0155] Throughout the specification, references to "an embodiment," "some of the embodiments," "one embodiment," "another example," "example," "embodiment," or "some of the examples" mean that at least one embodiment or example of the invention includes a particular feature, structure, material, or characteristic described in that embodiment or example. Thus, the appearances of, for example, "in some embodiments," "in an embodiment," "in another example," "in one example," "in a particular example," or "example" in various places throughout the specification do not necessarily refer to the same embodiment or example of the invention. Furthermore, particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

[0156] Although exemplary embodiments have been described and illustrated, those skilled in the art should understand that the above-described embodiments are not to be construed as limiting the present invention, and that modifications, substitutions, and alterations to the embodiments are possible without departing from the spirit, principles, and scope of the present invention.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, The positive electrode active material layer contains a positive electrode active material, The positive electrode active material contains elemental tungsten, and The electrochemical device, wherein the electrolyte comprises fluoroethylene carbonate.

2. 2. The electrochemical device according to claim 1, wherein, when the content of the tungsten element is x% with respect to the mass of the positive electrode active material, and the content of the fluoroethylene carbonate is a% with respect to the mass of the electrolyte, x and a satisfy 1≦a / x≦70.

3. 2. The electrochemical device according to claim 1, wherein when the content of the tungsten element is x % relative to the mass of the positive electrode active material, x satisfies 0.05≦x≦1.

4. 2. The electrochemical device according to claim 1, wherein when the content of the fluoroethylene carbonate is a % relative to the mass of the electrolyte, a satisfies 0.1≦a≦7.

5. 2. The electrochemical device according to claim 1, wherein the electrolyte further contains a compound having a sulfur-oxygen double bond, and when the content of the compound having a sulfur-oxygen double bond relative to the mass of the electrolyte is b%, b satisfies 0.01≦b≦5.

6. 6. The electrochemical device according to claim 5, wherein when the content of the tungsten element is x% with respect to the mass of the positive electrode active material, b and x satisfy 1≦b / x≦50.

7. The positive electrode further comprises an insulating layer; and the insulating layer is formed on the positive electrode current collector and overlaps the positive electrode active material layer in a partial region; or The electrochemical device according to claim 1 , wherein the insulating layer is formed on the positive electrode current collector and does not overlap the positive electrode active material layer.

8. the insulating layer includes a compound containing an aluminum element, The content of the aluminum element with respect to the mass of the insulating layer is y １ %, and the content of the tungsten element relative to the mass of the positive electrode active material is x%, then y １ and x is 50≦y １ The electrochemical device according to claim 7 , wherein x≦650.

9. y １ The electrochemical device of claim 8, wherein the value of is in the range of 30 to 65.

10. The electrochemical device according to claim 1 , wherein the positive electrode further comprises an undercoat layer formed between the positive electrode current collector and the positive electrode active material layer.

11. The undercoat layer contains an aluminum element, The content of the aluminum element relative to the mass of the undercoat layer is y ２ %, and the content of the tungsten element relative to the mass of the positive electrode active material is x%, then y ２ and x is 20≦y ２ The electrochemical device according to claim 10, wherein x≦550.

12. y ２ The electrochemical device of claim 11, wherein the value of is in the range of 20 to 50.

13. 2. The electrochemical device of claim 1, wherein the electrolyte further comprises at least one of succinonitrile, adiponitrile, ethylene glycol bis(2-cyanoethyl)ether, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,3-propane sultone, ethylene sulfate, vinylene carbonate, and 1-propylphosphoric acid cyclic anhydride.

14. 10. The electrochemical device of claim 1, wherein the positive electrode active material comprises lithium nickel cobalt manganese oxide.

15. An electronic device comprising an electrochemical device according to any one of claims 1 to 14.

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