Electrochemical device and electronic device comprising the same

Abstract

The present application relates to an electrochemical device and an electronic device comprising the same. The present application provides an electrochemical device comprising: an electrode comprising a current collector, an active material layer on at least one surface of the current collector, a tab on the current collector, and a tab protection layer on the tab, the tab protection layer comprising a first polymer layer, the first polymer layer having a melting point of T A ℃, 110≤T A ≤136.5; and an electrolyte comprising ethylene carbonate and propylene carbonate; wherein the sum of the weight percentages of the ethylene carbonate and the propylene carbonate is Y% based on the weight of the electrolyte, Y is 20-80; and Y and T A satisfy: 0.147 A The electrochemical device of the present application has improved hot box performance and high temperature storage performance.

Description

[0001] This invention patent application is a divisional application of the invention patent application with application number 202080020239.9, application date November 18, 2020, and invention title "Electrochemical Device and Electronic Device Containing the Thereof". Technical Field

[0002] This application relates to the field of energy storage, specifically to an electrochemical device and an electronic device comprising the same, particularly a lithium-ion battery. Background Technology

[0003] With the widespread adoption of smart products, the demand for electronic devices such as mobile phones, laptops, and cameras is increasing year by year. Electrochemical devices, such as lithium-ion batteries, serve as the power source for these electronic products, featuring high energy density, no memory effect, and high operating voltage, and are gradually replacing traditional Ni-Cd and MH-Ni batteries. However, as electronic products become increasingly thinner and more portable, the requirements for lithium-ion batteries are constantly rising. Developing lithium-ion batteries with good cycle stability, low impedance, low self-discharge, and safety is one of the main market demands. Summary of the Invention

[0004] This application provides an electrochemical device to attempt to solve at least one problem existing in the relevant field to some extent. This application also provides an electronic device incorporating the electrochemical device.

[0005] In one embodiment, this application provides an electrochemical device comprising electrodes and an electrolyte.

[0006] In one embodiment, the electrode includes a current collector, an active material layer on at least one surface of the current collector, a tab on the current collector, and a tab protection layer on the tab. The tab protection layer includes a first polymer layer having a melting point of T. A ℃, 110≤T A ≤136.5.

[0007] In one embodiment, the electrolyte comprises ethylene carbonate and propylene carbonate; wherein, based on the weight of the electrolyte, the sum of the weight percentages of the ethylene carbonate and the propylene carbonate is Y%, where Y is 20-80; and Y and T A Satisfy: 0.147 < Y / T A <0.7.

[0008] In some embodiments, the tab protection layer further includes a second polymer layer, the second polymer layer having a melting point of T. B ℃, T B ≤160, and T Aand T B Satisfy: 0 < T B -T A ≤50.

[0009] In some embodiments, the first polymer layer comprises at least one of maleic anhydride-grafted modified polypropylene, acidified polyolefin resin, or polyethylene.

[0010] In some embodiments, the second polymer layer comprises at least one of polypropylene or a polypropylene-modified resin.

[0011] In some embodiments, the electrolyte further comprises propionate, wherein the weight percentage of the propionate is 10%-60% based on the weight of the electrolyte.

[0012] In some embodiments, the propionate ester includes at least one of methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, methyl fluoropropionate, ethyl fluoropropionate, propyl fluoropropionate, butyl fluoropropionate, or pentyl fluoropropionate, wherein fluoro means that at least one hydrogen atom is replaced by a fluorine atom.

[0013] In some embodiments, the electrolyte further comprises a trimethylacetic acid compound.

[0014] In some embodiments, the structural formula of the trimethylacetate compound is: ;

[0015] Where R is C1-C 10 Alkyl, C2-C 10 alkenyl, C1-C 10 Haloalkyl, C2-C 10 Halogenated alkenyl, halogen, aryl or amide.

[0016] In some embodiments, the trimethylacetic acid compound includes at least one of methyl trimethylacetate or ethyl trimethylacetate.

[0017] In some embodiments, the electrolyte further comprises at least one of a dinitrile compound or a trinitrile compound.

[0018] The dinitrile compound includes at least one of the following compounds:

[0019] Butadionitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanonane, 1,10-dicyanodecane, 1,12-dicyandodecane, tetramethylbutadionitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile or ethylene glycol bis(propionitrile) ether;

[0020] The trinitrile compound includes at least one of the following compounds:

[0021] 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane or 1,2,5-tris(cyanoethoxy)pentane.

[0022] In another embodiment, this application provides an electronic device that includes the electrochemical device described in the embodiments of this application.

[0023] The electrochemical device provided in this application has improved hot box performance and high-temperature storage performance.

[0024] Additional aspects and advantages of the embodiments of this application will be described and shown in part in the following description, or illustrated by practice of the embodiments of this application. Attached Figure Description

[0025] The accompanying drawings, necessary for describing embodiments of this application or the prior art, will be briefly described below to facilitate the depiction of embodiments of this application. It is obvious that the drawings described below represent only a portion of the embodiments in this application. Those skilled in the art will be able to derive other embodiments from the structures illustrated in these drawings without requiring inventive effort.

[0026] Figure 1 The diagram illustrates the tab and packaging bag encapsulation structure in one embodiment of this application.

[0027] Figure 2 The structure of the tab protection layer in one embodiment of this application is shown.

[0028] Figure 3 The structure of the tab protection layer in another embodiment of this application is shown.

[0029] Figure 4 The battery structure and the location of the tab protection layer in one embodiment of this application are shown. Detailed Implementation

[0030] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0031] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0032] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0033] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "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 contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0034] As used herein, the term "alkyl" is intended to refer to a straight-chain saturated hydrocarbon structure having 1 to 20 carbon atoms. "alkyl" is also intended to refer to a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. For example, an alkyl group can be an alkyl group with 1-20 carbon atoms, an alkyl group with 1-10 carbon atoms, an alkyl group with 1-5 carbon atoms, an alkyl group with 5-20 carbon atoms, an alkyl group with 5-15 carbon atoms, or an alkyl group with 5-10 carbon atoms. When an alkyl group with a specific number of carbon atoms is specified, it is intended to cover all geometric isomers having that number of carbon atoms; thus, for example, "butyl" means including n-butyl, sec-butyl, isobutyl, tert-butyl, and cyclobutyl; "propyl" includes 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. Additionally, the alkyl group may optionally be substituted.

[0035] As used herein, the term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that may be straight-chain or branched and has at least one, typically one, two, or three carbon-carbon double bonds. Unless otherwise defined, the alkenyl group typically contains 2-20 carbon atoms, for example, it may be an alkenyl group with 2-20 carbon atoms, an alkenyl group with 6-20 carbon atoms, an alkenyl group with 2-12 carbon atoms, or an alkenyl group with 2-6 carbon atoms. Representative alkenyl groups include, for example, vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, etc. Additionally, the alkenyl group may optionally be substituted.

[0036] As used herein, the term "aryl" encompasses both monocyclic and polycyclic systems. A polycyclic system may have two or more rings in which two carbons are shared by two adjacent rings (the rings are "fused"), wherein at least one of the rings is aromatic; for example, the other rings may be cycloalkyl, cycloalkenyl, aryl, heterocyclic, and / or heteroaryl. For example, an aryl group may be C6-C. 50 Aryl, C6-C 40 Aryl, C6-C 30 Aryl, C6-C 20 Aryl or C6-C 10 Aryl groups. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphth-1-yl, naphth-2-yl, etc. Additionally, the aryl group may be optionally substituted.

[0037] As used herein, the term "haloalkyl" refers to an alkyl group in which at least one hydrogen atom is replaced by a halogen atom. The term "haloalkenyl" refers to an alkenyl group in which at least one hydrogen atom is replaced by a halogen atom.

[0038] As used in this article, the term "halogen" encompasses F, Cl, Br, and I.

[0039] When the above substituents are substituted, their substituents can be independently selected from the following group: halogen, alkyl, alkenyl, aryl.

[0040] As used in this article, the content of each component is based on the weight of the electrolyte.

[0041] As used herein, the terms “substituted” or “substituted” mean that the substance can be substituted by one or more (e.g., two or three) substituents. For example, “fluorinated” means that the substance can be substituted by one or more (e.g., two or three) F groups.

[0042] I. Electrochemical Device

[0043] In some embodiments, this application provides an electrochemical device comprising electrodes and an electrolyte:

[0044] In some embodiments, the electrode includes a current collector, an active material layer on at least one surface of the current collector, a tab on the current collector, and a tab protection layer on the tab, the tab protection layer including a first polymer layer having a melting point of T. A ℃, 110≤T A ≤136.5.

[0045] In some embodiments, the electrolyte comprises ethylene carbonate and propylene carbonate; wherein, based on the weight of the electrolyte, the sum of the weight percentages of the ethylene carbonate and the propylene carbonate is Y%, where Y is 20-80; and Y and T A Satisfy: 0.147 < Y / T A <0.7. Y / T A Within this range, the thermal stability of the electrochemical system of the electrochemical device is improved, thereby improving the performance of the thermal chamber, and at the same time, the high-temperature storage performance of the lithium-ion battery is significantly enhanced.

[0046] In some embodiments, T A The range is 110, 115, 120, 125, 130, 135, 136, 136.5, or any combination of these values. T A Within this range, the safety performance of electrochemical devices can be significantly improved.

[0047] In some embodiments, Y is a range of 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, or any combination of these values.

[0048] In some embodiments, Y / T A The value is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7, or a range of any two of these values.

[0049] In some embodiments, the tab protection layer further includes a second polymer layer, the second polymer layer having a melting point of T. B ℃, T B ≤160, and T A and T B Satisfy: 0 < T B -T A ≤50. T B -T A Within this range, electrochemical devices offer superior safety performance.

[0050] In some embodiments, T B It is a range of 138, 140, 145, 150, 155, 160, or any combination of these values.

[0051] In some embodiments, T B -T A The value is 0.1, 0.5, 1, 3, 5, 10, 20, 30, 40, 50, or a range of any two of these values.

[0052] In some embodiments, the first polymer layer comprises at least one of maleic anhydride-grafted modified polypropylene, acidified polyolefin resin, or polyethylene.

[0053] In some embodiments, the first polymer layer comprises at least one of Mitsui Chemicals' QE840, QFF551, DuPont Rough 0910, DuPont Elvax, Samsung E093A, or Mitsubishi Chemical's P546.

[0054] In some embodiments, the second polymer layer comprises at least one of polypropylene resins.

[0055] In some embodiments, the second polymer layer comprises at least one of Samsung CF330, TPC FS5611, or ExxonMobil 6102FL.

[0056] In some embodiments, the tab protective layer is a single-layer, double-layer, or triple-layer structure.

[0057] In some embodiments, the tab protection layer comprises a first polymer layer. In some embodiments, the tab protection layer comprises a first polymer layer and a second polymer layer. In some embodiments, the tab protection layer comprises two first polymer layers and a second polymer layer located between the two first polymer layers.

[0058] In some embodiments, the electrolyte further comprises a propionate ester, wherein the weight percentage of the propionate ester is 10%-60% based on the weight of the electrolyte. In some embodiments, the weight percentage of the propionate ester is 10%, 20%, 30%, 40%, 50%, 60%, or a range of any two of these values, based on the weight of the electrolyte.

[0059] In some embodiments, the propionate ester includes at least one of methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, methyl fluoropropionate, ethyl fluoropropionate, propyl fluoropropionate, butyl fluoropropionate, or pentyl fluoropropionate, wherein fluoro means that at least one hydrogen atom is replaced by a fluorine atom.

[0060] In some embodiments, the electrolyte further comprises a trimethylacetic acid compound.

[0061] In some embodiments, the structural formula of the trimethylacetate compound is: ;

[0062] Where R is C1-C 10 Alkyl, C2-C 10 alkenyl, C1-C 10 Haloalkyl, C2-C 10 Halogenated alkenyl, halogen, aryl or amide.

[0063] In some embodiments, R is a C1-C6 alkyl, C2-C6 alkenyl, C1-C6 haloalkyl, C2-C6 haloalkenyl, halogen, aryl, or amide.

[0064] In some embodiments, the trimethylacetic acid compound includes at least one of methyl trimethylacetate or ethyl trimethylacetate.

[0065] In some embodiments, the electrolyte further comprises at least one of a dinitrile compound or a trinitrile compound.

[0066] The dinitrile compound includes at least one of the following compounds:

[0067] Butadionitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanonane, 1,10-dicyanodecane, 1,12-dicyandodecane, tetramethylbutadionitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile or ethylene glycol bis(propionitrile) ether;

[0068] The trinitrile compound includes at least one of the following compounds:

[0069] 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane or 1,2,5-tris(cyanoethoxy)pentane.

[0070] In some embodiments, the content of the dinitrile compound is 1%-5% based on the weight of the electrolyte. In some embodiments, the content of the dinitrile compound is 1%, 2%, 3%, 3.5%, 4.0%, 5.0%, or any combination of these values, based on the weight of the electrolyte.

[0071] In some embodiments, the content of the trinitrile compound is 1%-5% based on the weight of the electrolyte. In some embodiments, the content of the trinitrile compound is 1%, 2%, 3%, 3.5%, 4.0%, 5.0%, 6.0%, or any combination of these values, based on the weight of the electrolyte.

[0072] In some embodiments, the electrolyte comprises a trinitrile compound and ethylene glycol bis(propionitrile) ether, wherein the weight percentage of the trinitrile compound is a% based on the weight of the electrolyte, and the content of the ethylene glycol bis(propionitrile) ether is b%, satisfying 1.0 ≤ a + b ≤ 6.0. In some embodiments, a + b is a range of 1.0, 2.0, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, or any combination of these values.

[0073] In some embodiments, 1.2 ≤ a / b ≤ 20. In some embodiments, a / b is a range of 2.0, 3.0, 3.3, 4.0, 5.5, 7.0, 8.5, 9.5, 12.0, 14.5, 16.5, 18.5, 20.0, or any combination of these values.

[0074] In some embodiments, the electrolyte further comprises fluoroethylene carbonate and 1,3-propanesulfonyl lactone, wherein the weight percentage of fluoroethylene carbonate is c%, and the weight percentage of 1,3-propanesulfonyl lactone is d%, based on the weight of the electrolyte, satisfying 6.0 ≤ c + d ≤ 15.0. In some embodiments, c + d is a range of 6.0, 7.0, 8.0, 8.5, 9.0, 9.5, 10.0, 11.0, 11.5, 12.0, 13.0, 14.0, 15.0, or any combination of these values.

[0075] In some embodiments, 1.2 ≤ c / d ≤ 20. In some embodiments, c / d is 1.2, 2.0, 3.0, 3.3, 4.0, 5.5, 7.0, 8.5, 9.5, 12.0, 14.5, 16.5, 18.5, 20.0, or a range of any two of these values.

[0076] In some embodiments, the electrolyte may further comprise allyl nitrile.

[0077] In some embodiments, the electrochemical device includes any device in which an electrochemical reaction occurs.

[0078] In some embodiments, the electrode includes a negative electrode having a negative electrode active material capable of adsorbing and releasing metal ions; and a positive electrode having a positive electrode active material capable of adsorbing and releasing metal ions.

[0079] In some embodiments, the electrochemical device further includes a separating membrane located between the positive and negative electrodes.

[0080] In some embodiments, the electrochemical device is a lithium secondary battery.

[0081] In some embodiments, the lithium secondary battery includes, but is not limited to: lithium metal secondary battery, lithium-ion secondary battery, lithium polymer secondary battery or lithium-ion polymer secondary battery, and all-solid-state secondary lithium battery.

[0082] Figure 1 The illustration shows the packaging structure of the tabs and the packaging bag in one embodiment of this application. The packaging bag 1-1 is bonded to the metal strip 1-3 by the tab protective layer 1-2, and the packaging bag 1-5 is bonded to the metal strip 1-3 by the tab protective layer 1-4, wherein the tab protective layers 1-2 and 1-4 are both single-layer structures, that is, composed of a first polymer layer.

[0083] Figure 2 The structure of the tab protection layer in one embodiment of this application is shown. The tab protection layer has a double-layer structure, wherein the tab protection layer above the metal strip 2-3 is composed of a first polymer layer 2-1 and a second polymer layer 2-2, and the tab protection layer below the metal strip 2-3 is composed of a first polymer layer 2-5 and a second polymer layer 2-4.

[0084] Figure 3 The structure of the tab protection layer in another embodiment of this application is shown. The tab protection layer has a three-layer structure. The tab protection layer above the metal strip 3-4 consists of first polymer layers 3-1 and 3-3 and a second polymer layer 3-2 located between them. The tab protection layer below the metal strip 3-4 consists of first polymer layers 3-5 and 3-6 and a second polymer layer 3-6 located between them.

[0085] The main function of the tab protective layer is to adhere to the tabs of the lithium-ion battery, thereby heat-sealing the tabs to the inner polypropylene layer of the polymer battery packaging bag. Currently, commonly used tab protective layers generally have a melting point above 140℃. This invention mainly uses a tab protective layer with a lower melting point to achieve early heat dissipation of the battery and thus improve battery thermal safety.

[0086] negative electrode

[0087] The materials, composition, and manufacturing methods of the negative electrode used in the electrochemical device of this application may include any techniques disclosed in the prior art. In some embodiments, the negative electrode is the negative electrode described in U.S. Patent Application US9812739B, which is incorporated herein by reference in its entirety.

[0088] In some embodiments, the negative electrode includes a current collector and a negative electrode active material layer located on the current collector. In some embodiments, the negative electrode active material layer includes a negative electrode active material. In some embodiments, the negative electrode active material includes, but is not limited to: lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, silicon-oxygen materials, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Li-Al alloys or any combination thereof.

[0089] In some embodiments, the negative electrode active material layer includes an adhesive. In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0090] In some embodiments, the negative electrode active material layer includes a conductive material. In some embodiments, the conductive material includes, but is not limited to: natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver, or polyphenylene derivatives.

[0091] In some embodiments, the current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal.

[0092] In some embodiments, the negative electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then coating the active material composition onto a current collector.

[0093] In some embodiments, the solvent may include, but is not limited to, deionized water and N-methylpyrrolidone.

[0094] In some embodiments, the negative electrode in an all-solid-state secondary lithium battery is a metallic lithium foil.

[0095] positive electrode

[0096] The material of the positive electrode used in the electrochemical device of this application can be prepared using materials, structures, and manufacturing methods known in the art. In some embodiments, the positive electrode of this application can be prepared using the techniques described in US9812739B, which is incorporated herein by reference in its entirety.

[0097] In some embodiments, the positive electrode includes a current collector and a layer of positive electrode active material on the current collector. The positive electrode active material includes at least one lithiation intercalation compound that reversibly inserts and deintercalates lithium ions. In some embodiments, the positive electrode active material includes a composite oxide. In some embodiments, the composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel.

[0098] In some embodiments, the positive electrode active material is selected from lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese (NCM) ternary materials, lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), or any combination thereof.

[0099] In some embodiments, the positive electrode active material may have a coating on its surface, or may be mixed with another compound having a coating. The coating may include at least one coating element compound selected from oxides of the coating element, hydroxides of the coating element, hydroxyoxides of the coating element, oxycarbonates of the coating element, and hydroxycarbonates of the coating element. The compound used for the coating may be amorphous or crystalline.

[0100] In some embodiments, the coating elements contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or any combination thereof. The coating may be applied by any method, as long as the method does not adversely affect the performance of the positive electrode active material. For example, the method may include any coating method known in the art, such as spraying, dipping, etc.

[0101] The positive electrode active material layer also includes a binder and optionally a conductive material. The binder improves the bonding between the positive electrode active material particles and also improves the bonding between the positive electrode active material and the current collector.

[0102] In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0103] In some embodiments, the conductive material includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, and silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0104] In some embodiments, the current collector may be aluminum, but is not limited thereto.

[0105] The positive electrode can be prepared by methods known in the art. For example, the positive electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then coating the active material composition onto a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone, etc.

[0106] In some embodiments, the positive electrode is made by forming a positive electrode material using a layer of positive electrode active material comprising lithium transition metal compound powder and a binder on a current collector.

[0107] In some embodiments, the positive electrode active material layer can typically be fabricated by: dry mixing the positive electrode material and a binder (conductive material and thickener, etc., as needed) to form a sheet, pressing the resulting sheet onto the positive electrode current collector, or dissolving or dispersing these materials in a liquid medium to form a slurry, coating it onto the positive electrode current collector, and drying it. In some embodiments, the material of the positive electrode active material layer includes any material known in the art.

[0108] Separating membrane

[0109] In some embodiments, the electrochemical device of this application includes a separator between the positive and negative electrodes to prevent short circuits. The material and shape of the separator used in the electrochemical device of this application are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application.

[0110] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be selected.

[0111] A surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0112] The inorganic layer comprises inorganic particles and a binder. The inorganic particles are selected from one or more of the following: alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is selected from one or more of the following: polyvinylidene fluoride, copolymers of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, the polymer material of which includes at least one of the following: polyamide, polyacrylonitrile, acrylate polymers, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0113] electrolytes

[0114] The electrolyte used in the embodiments of this application can be any electrolyte known in the prior art, including, but not limited to: inorganic lithium salts, such as LiClO4, LiAsF6, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, etc.; fluorinated organic lithium salts, such as LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropane disulfonylimide lithium, cyclic 1,2-tetrafluoroethane disulfonylimide lithium, LiN(CF3SO2)(CF3SO2), etc. 2) LiC(CF3SO2), LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2; lithium salts containing dicarboxylic acid complexes, such as lithium bis(oxalate)borate, lithium difluorooxalate borate, lithium tri(oxalate)phosphate, lithium difluorobis(oxalate)phosphate, lithium tetrafluoro(oxalate)phosphate, etc. Furthermore, the above electrolytes can be used alone, or two or more can be used simultaneously. For example, in some embodiments, the electrolyte includes a combination of LiPF6 and LiBF4. In some embodiments, the electrolyte comprises an inorganic lithium salt such as LiPF6 or LiBF4 and a combination of a fluorinated organic lithium salt such as LiCF3SO3, LiN(CF3SO2)2, or LiN(C2F5SO2)2. In some embodiments, the concentration of the electrolyte is in the range of 0.8-3 mol / L, for example, in the range of 0.8-2.5 mol / L, 0.8-2 mol / L, 1-2 mol / L, 0.5-1.5 mol / L, 0.8-1.3 mol / L, 0.5-1.2 mol / L, or, for example, 1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0115] II. Electronic Devices

[0116] The electronic device of this application can be any device that uses the electrochemical device according to the embodiments of this application.

[0117] In some embodiments, the electronic device includes, but is not limited to: laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0118] The following uses a lithium-ion battery as an example and combines specific embodiments to illustrate the preparation of a lithium-ion battery. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0119] Example

[0120] The following describes the performance evaluation based on the embodiments and comparative examples of the lithium-ion battery of this application.

[0121] I. Preparation of Lithium-ion Batteries

[0122] (1) Preparation of electrolyte

[0123] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and other organic solvents are mixed in a specific ratio. The other organic solvents are selected from at least one of diethyl carbonate (DEC), ethyl propionate (EP), or propyl propionate (PP). LiPF6 is then added and stirred until homogeneous to form a basic electrolyte, wherein the concentration of LiPF6 is 1.15 mol / L. Different amounts of the substances shown in the tables below are added to the basic electrolyte to obtain electrolytes for different examples and comparative examples. The content of each substance in the electrolytes described in this application is calculated based on the weight of the electrolyte.

[0124] The contents of EC and PC are shown in Table 1, and the remaining organic solvent is DEC.

[0125] (2) Preparation of the positive electrode

[0126] Lithium cobalt oxide (LiCoO2), carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 95:2:3. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto aluminum foil as a positive electrode current collector. After drying at 85°C, the foil was cold-pressed, cut, and slit, and then dried under vacuum at 85°C for 4 hours to obtain the positive electrode.

[0127] (3) Preparation of negative electrode

[0128] The negative electrode active material graphite, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in an appropriate amount of deionized water solvent at a weight ratio of 95:2:3 to form a uniform negative electrode slurry. This slurry is then coated onto the negative electrode current collector Cu foil, dried, and cold-pressed to obtain the negative electrode.

[0129] (4) Preparation of the separating membrane

[0130] Polyethylene (PE) membrane was selected as the separator.

[0131] (5) Preparation of lithium-ion batteries

[0132] The tab protective layer and metal strip are bonded together using flat plate heating or high-frequency heating to create a tab containing the tab protective layer. This tab is then welded to the positive and negative electrodes. The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The stack is then wound and placed in outer packaging foil. The prepared electrolyte is injected into the dried battery. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is complete.

[0133] II. Testing Methods

[0134] 1. Hot box test:

[0135] At 25°C, the lithium-ion battery was charged at a constant current of 0.7C to 4.45V, and then charged at a constant voltage of 4.45V to a current of 0.05C. The battery was then placed in a high-temperature chamber at 5±2°C. o The battery was heated to 135°C at a temperature rise rate of C / min and held for 1 hour (hr). Changes in battery voltage, temperature, and chamber temperature were recorded. The battery passed the test if it did not catch fire or explode. Ten batteries were tested in each group, and the number of batteries that passed the test was recorded.

[0136] 2. High-temperature storage test:

[0137] At 25℃, the lithium-ion battery was left to stand for 30 minutes; then it was charged at a constant current rate of 0.5C to 4.45V, and then charged at a constant voltage of 4.45V to 0.05C. After standing for 5 minutes, the thickness of the lithium-ion battery was measured and recorded as h0; then the lithium-ion battery was placed in a constant temperature chamber at 85℃ for 24 days, and the thickness of the lithium-ion battery was measured and recorded as h1. The thickness expansion rate of the lithium-ion battery was calculated using the following formula: Thickness expansion rate (%) = (h1-h0) / h0×100%.

[0138] 3. Low-temperature discharge test

[0139] At 25℃, the lithium-ion battery was charged at a constant current of 0.7C to 4.45V, and then charged at a constant voltage of 4.45V to a current of 0.05C. Afterwards, the lithium-ion battery was left to stand at different temperatures (25℃, 0℃, -10℃) for 4 hours, and then discharged at 0.2C to 3.0V. After each discharge, it was left to stand for 5 minutes, and the discharge capacity of the lithium-ion battery was recorded. Using the discharge capacity at 25℃ as a baseline, the discharge capacity ratio of the lithium-ion battery at different temperatures was obtained.

[0140] The discharge capacity ratio (%) of lithium-ion batteries at different temperatures = discharge capacity at different temperatures (0℃, -10℃) / discharge capacity at 25℃ × 100%

[0141] 4. High-temperature storage test

[0142] At 25°C, the lithium-ion battery was left to stand for 30 minutes, then charged at a constant current rate of 0.5C to 4.45V, and then charged at a constant voltage rate of 4.45V to 0.05C. After standing for 5 minutes, the battery was stored at 85°C for 24 days. The thickness of the battery was then measured, and the battery thickness expansion rate was calculated using the following formula:

[0143] Thickness expansion rate = [(thickness after storage - thickness before storage) / thickness before storage] × 100%.

[0144] A. Table 1 shows the composition and performance test results of the lithium-ion batteries in the relevant embodiments. The tab protective layer used in comparative examples D1-1 to D1-2 consists of a second polymer layer with a melting point of T. B The second polymer layer is selected from Samsung CF330 block copolymer polypropylene. The tab protection layers of Comparative Examples D1-3 to D1-5 and Examples S1-1 to S1-7 consist of a first polymer layer with a melting point of T. A The first polymer layer is selected from Bayer 50E632 (melting point 136.5℃), Bayer 50E631 (melting point 136℃), Bayer 40E529 (melting point 135℃), Bayer 50E662 (melting point 130℃), and Bayer 4104 (melting point 125℃). o C), Baiqi 4208 (melting point 110℃), Laokao 0910 (melting point 100℃) o C).

[0145] Table 1

[0146] The “—” indicates that the substance in that layer is not present.

[0147] As shown in Table 1, the lithium-ion batteries in Comparative Examples D1-1 and D1-2 only passed the 130℃ hot chamber test, while the pass rates for the 132℃ and 135℃ hot chamber tests were very low. This is because the melting point of the tab protection layer in Comparative Examples D1-1 and D1-2 is relatively high. During abuse tests such as the hot chamber, the gas cannot quickly open the gas bag, and the generated heat gradually accumulates inside the battery, which can easily lead to battery fire or even explosion. Adjusting the total amount of EC+PC or adjusting the melting point of the polymer layer can significantly improve the hot chamber performance. However, when the EC+PC content is low, even adjusting the melting point will not have a good effect; when the EC+PC content is high, adjusting the melting point has an effect on the hot chamber, but the electrical performance is relatively poor. Therefore, both methods must be used within a certain reasonable range to achieve good results.

[0148] The test results from Examples S1-1 to S1-11 show that when the tab protection layer prepared by the second polymer layer is replaced by the tab protection layer prepared by the first polymer layer, and the melting point value T of the first polymer layer is... A The value Y, which contains EC+PC, satisfies the following condition: 0.147 < Y / T A When the temperature is less than 0.7, the pass rate of the thermal chamber test for lithium-ion batteries is significantly improved. On one hand, introducing a first polymer layer into the tab protection layer allows the gas inside the battery to break through the gas pocket in advance, facilitating timely heat dissipation and thus significantly improving the thermal chamber test results. On the other hand, the improved thermal stability of the entire electrochemical system further enhances the thermal chamber performance and significantly improves the high-temperature storage performance of lithium-ion batteries.

[0149] Tables 2 and 3 show the composition and performance test results of the lithium-ion batteries in the relevant embodiments. The tab protection layer in embodiments S2-1 to S2-3 has a double-layer structure, comprising a first polymer layer and a second polymer layer. The tab protection layer in embodiment S3-1 has a triple-layer structure, i.e., a second polymer layer between two first polymer layers. The melting point T of the first polymer layer is... A Both were at 125°C. The first polymer layer mentioned above was selected from Bayer 4104 (125°C). o C), the second polymer layer is selected from Samsung CF330 block copolymer polypropylene.

[0150] Table 2

[0151] The “—” indicates that the substance in that layer is not present.

[0152] Table 3

[0153] As can be seen from the test results in Tables 2 and 3, replacing the tab protective layer made of the second polymer layer in Comparative Example D1-2 with the aforementioned double-layer and triple-layer tab protective layers also improves the thermal test performance of lithium-ion batteries. This is because, regardless of whether it is a double-layer or triple-layer structure, as long as it contains a low-melting-point layer, heat can be dissipated from the battery in a timely manner at a lower temperature, thus preventing thermal runaway.

[0154] C. Table 4 shows the composition and performance test results of the lithium-ion batteries in the relevant embodiments. The preparation of the lithium-ion batteries in Examples S4-1 and S4-2 is similar to that in Examples S1-2, except that the electrolyte composition is different, as detailed in Table 4.

[0155] Table 4

[0156] As can be seen from the test results in Table 4, the melting point T of the first polymer layer A The content of EC+PC Y satisfies the following relationship: 0.147 < Y / T A When the temperature is less than 0.7, adding a certain amount of propyl propionate or ethyl propionate to the electrolyte can further improve the low-temperature performance of lithium-ion batteries.

[0157] D. Table 5 shows the composition and performance test results of the lithium-ion batteries in the relevant embodiments. The preparation process of the lithium-ion batteries in Examples S5-1 to S5-3 is similar to that in Examples S1-2, except that the electrolyte composition is different, as detailed in Table 5.

[0158] Table 5

[0159] As can be seen from the test results in Table 5, the melting point T of the first polymer layer is... A The content of EC+PC Y satisfies the following relationship: 0.147 < Y / T A When the concentration is less than 0.7, adding a certain amount of trimethylacetate to the electrolyte can further improve the thermal performance of lithium-ion batteries.

[0160] E. Table 6 shows the composition and performance test results of the lithium-ion batteries in the relevant embodiments. The preparation process of the lithium-ion batteries in Examples S6-1 to S6-16 is similar to that in Examples S1-2, except that the electrolyte composition is different, as detailed in Table 6.

[0161] Table 6

[0162] As can be seen from the test results in Table 6, the melting point T of the first polymer layer is...A The content of EC+PC Y satisfies the following relationship: 0.147 < Y / T A When the concentration is less than 0.7, adding a certain amount of dinitrile and trinitrile compounds to the electrolyte can further improve the thermal performance of lithium-ion batteries.

[0163] F: Table 7 shows the composition and performance test results of the lithium-ion batteries in the relevant embodiments. The preparation process of the lithium-ion batteries in Examples S7-1 to S7-11 is similar to that in Examples S1-2, except that the composition of the electrolyte is different, as detailed in Table 7.

[0164] Table 7

[0165] The “—” indicates that the substance in that layer is not present.

[0166] As can be seen from the test results in Table 7, the melting point T of the first polymer layer A The content of EC+PC Y satisfies the following relationship: 0.147 < Y / T A When the concentration is <0.7, adding a certain amount of fluoroethylene carbonate to the electrolyte deteriorates the battery's thermal performance to some extent. Adding 1,3-propane sulpholol has no significant effect on the thermal performance, but the simultaneous presence of both can further improve the thermal performance of the lithium-ion battery, presumably related to their co-forming properties. When both are present, the optimal effect is achieved by simultaneously adding dinitrile and trinitrile compounds.

[0167] Throughout this specification, references to "some embodiments," "partial embodiments," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics described herein can be combined in any suitable manner in one or more embodiments or examples.

[0168] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrochemical device comprising: An electrode, the electrode comprising a current collector, an active material layer on at least one surface of the current collector, and a tab on the current collector; and a tab protection layer located on the tab, the tab protection layer comprising a first polymer layer having a melting point of T A °C, 110 < T A ≤ 136.5; and The electrolyte comprises ethylene carbonate and propylene carbonate; Based on the weight of the electrolyte, the sum of the weight percentages of ethylene carbonate and propylene carbonate is Y%, where Y is 20-70; and Y and T A Satisfy: 0.147 < Y / T A <0.

7.

2. The electrochemical device according to claim 1, wherein the tab protective layer further comprises a second polymer layer, the melting point of the second polymer layer being T B ℃, T B ≤160, and T A and T B Satisfy: 0 < T B -T A ≤50.

3. The electrochemical device according to claim 1, wherein the first polymer layer comprises at least one of maleic anhydride-grafted modified polypropylene, acidified polyolefin resin, or polyethylene.

4. The electrochemical device according to claim 2, wherein the second polymer layer comprises polypropylene resin.

5. The electrochemical device of claim 1, wherein the electrolyte further comprises a propionate ester, wherein the propionate ester comprises 10%-60% by weight based on the weight of the electrolyte.

6. The electrochemical device according to claim 5, wherein the propionate comprises at least one of methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, methyl fluoropropionate, ethyl fluoropropionate, propyl fluoropropionate, butyl fluoropropionate, or pentyl fluoropropionate, wherein fluoro means that at least one hydrogen atom is replaced by a fluorine atom.

7. The electrochemical device according to claim 1, wherein the electrolyte further comprises a trimethylacetic acid compound.

8. The electrochemical device according to claim 7, wherein the trimethylacetate compound has the following structural formula: ； in, R is C1-C 10 Alkyl, C2-C 10 alkenyl, C1-C 10 Haloalkyl, C2-C 10 Halogenated alkenyl, halogen, aryl or amide.

9. The electrochemical device according to claim 7, wherein the trimethylacetic acid compound comprises at least one of methyl trimethylacetate or ethyl trimethylacetate.

10. The electrochemical device according to claim 1, wherein the electrolyte further comprises at least one of a dinitrile compound or a trinitrile compound. The dinitrile compound includes at least one of the following compounds: Butadionitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanonane, 1,10-dicyanodecane, 1,12-dicyandodecane, tetramethylbutadionitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile or ethylene glycol bis(propionitrile) ether; The trinitrile compound includes at least one of the following compounds: 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane or 1,2,5-tris(cyanoethoxy)pentane.

11. The electrochemical device according to claim 10, wherein the weight percentage of the dinitrile compound is 0.3%-3% based on the weight of the electrolyte.

12. The electrochemical device according to claim 10, wherein the weight percentage of the trinitrile compound is 0.5%-3% based on the weight of the electrolyte.

13. The electrochemical device according to claim 1, wherein the electrolyte comprises adiponitrile, and the weight percentage of adiponitrile is 1%-3% based on the weight of the electrolyte.

14. The electrochemical device according to claim 1, wherein the electrolyte comprises succinate, and the succinate is present in a weight percentage of 1%-3% based on the weight of the electrolyte.

15. The electrochemical device according to claim 1, wherein the electrolyte comprises 1,3,6-hexanetricarbonyl nitrile, and the weight percentage of the 1,3,6-hexanetricarbonyl nitrile is 0.5%-3% based on the weight of the electrolyte, preferably, the weight percentage of the 1,3,6-hexanetricarbonyl nitrile is 1.5%-3%.

16. The electrochemical device according to claim 1, wherein the electrolyte comprises ethylene glycol bis(propionitrile) ether, and the weight percentage of the ethylene glycol bis(propionitrile) ether is 0.3%-3.5% based on the weight of the electrolyte, preferably, the weight percentage of the ethylene glycol bis(propionitrile) ether is 1.5%-3.5%.

17. The electrochemical device according to claim 1, wherein the electrolyte comprises fluoroethylene carbonate, and the weight percentage of the fluoroethylene carbonate is 3%-6% based on the weight of the electrolyte, preferably 4%-5% by weight.

18. The electrochemical device of claim 1, wherein the electrolyte comprises 1,3-propanesulfonyl lactone, and the weight percentage of the 1,3-propanesulfonyl lactone is 1%-3% based on the weight of the electrolyte.

19. The electrochemical device according to claim 1, wherein 0.147 < Y / T A <0.

59.

20. The electrochemical device according to claim 1, wherein Y is 20-50.

21. An electronic device, wherein the electronic device comprises an electrochemical device according to any one of claims 1-20.

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