CN116053461B

CN116053461B - Electrochemical device and electronic device including the same

Info

Publication number: CN116053461B
Application number: CN202310330945.9A
Authority: CN
Inventors: 刘俊飞; 彭谢学; 张世军
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2023-03-30
Filing date: 2023-03-30
Publication date: 2023-06-23
Anticipated expiration: 2043-03-30
Also published as: CN116053461A

Abstract

The present application provides an electrochemical device and an electronic device including the same, the electrochemical device including a positive electrode including a current collector and a positive electrode active material layer including a positive electrode active material Li _1+x M _1‑y Mg _y O ₂ M is selected from one or more of Ni, co, mn, al, fe, cu, ru, nb, W, cr, zr, mo, V, ti, la, Y, x is more than 0 and less than or equal to 2, and y is more than 0 and less than or equal to 0.02; the electrolyte comprises a compound of formula I:

formula IX is selected from Si, ti, and Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ At least one of (a) comprises at least one C _2‑8 Alkenyl or C _2‑8 Alkynyl, Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ Independently selected from H, halogen, and substituted or unsubstituted groups of: c (C) _1‑8 Alkyl, C _2‑8 Alkenyl, C _2‑8 Alkynyl, C _6‑12 Aryl, C _1‑8 Alcohol group, C _2‑8 Ester groups of (a) are present.

Description

Electrochemical device and electronic device including the same

Technical Field

The present disclosure relates to the field of energy storage technologies, and in particular, to an electrochemical device and an electronic device including the same.

Background

Lithium ion batteries are used as portable chemical energy sources, and are widely used in the fields and industries of consumer electronic products (such as mobile phones, notebooks, cameras and the like), energy storage products (household energy storage, energy storage power stations, UPS power supplies and the like), new energy automobiles and the like due to the advantages of high energy density, high working voltage platform, small self-discharge, long service life, environmental friendliness and the like. As the market for products continues to expand, higher demands are placed on the performance and production costs of the batteries. Lithium-rich materials have received more market attention because of their high gram-volume and reduced production costs due to lower cobalt and nickel element usage.

Although the lithium-rich material has higher capacity, the structure of the battery is damaged relatively more when the battery is charged to a higher voltage range due to oxygen activation in the high voltage range, and the capacity of the battery can be attenuated rapidly.

The prior art solves the disadvantages of the lithium-rich materials by using a secondary particle structure or doping Mg element in the positive electrode active material, however, this introduces new problems, for example, mg in the positive electrode active material increases the stability of the internal structure of the material but causes a lower battery capacity. Accordingly, there is a need in the art to reduce the negative impact of Mg element in lithium-rich materials on battery cycling performance while taking advantage of the high capacity characteristics of lithium-rich materials.

Disclosure of Invention

In a first aspect of the present application, there is provided an electrochemical device comprising a positive electrode and an electrolyte, wherein the positive electrode comprises a positive electrode current collector and a positive electrode active material layer comprising a positive electrode active material Li _1+x M _1-y Mg _y O ₂ Wherein M is selected from one or more of Ni, co, mn, al, fe, cu, ru, nb, W, cr, zr, mo, V, ti, la, Y, and 0 < x is less than or equal to 2, and 0 < y is less than or equal to 0.02;

and wherein the electrolyte comprises a compound of formula I:

i is a kind of

Wherein X is selected from one of Si and Ti,

Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ at least one of (a) comprises at least one C _2-8 Alkenyl or C _2-8 Alkynyl, Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ Independently selected from H, halogen, and substituted or unsubstituted groups of: c (C) _1-8 Alkyl, C _2-8 Alkenyl, C _2-8 Alkynyl, C _6-12 Aryl, C _1-8 Alcohol group, C _2-8 Ester groups of (a) are present.

By introducing Mg into the lithium-rich positive electrode active material in the positive electrode active material layer, the stability of the material structure is improved, so that the structure of the lithium-rich positive electrode active material is not easily damaged, and meanwhile, as the compound of the formula I contains alkenyl or alkynyl, a protective film with binding force can be formed on the surface of the lithium-rich positive electrode active material, therefore, by using the electrolyte containing the compound of the formula I in the electrochemical device, on one hand, the using amount of Mg can be reduced, the capacity exertion reduction possibly caused by the high content of excessive Mg can be avoided, and on the other hand, the occurrence of material particle breakage can be reduced as much as possible, thereby greatly prolonging the cycle life of the battery and reducing the volume expansion caused by the long-term use process.

In a second aspect of the present application, there is provided an electrochemical device comprising a positive electrode and an electrolyte, wherein the positive electrode active material has a secondary particle structure formed of primary crystal grains, particularly agglomerated, by means of which ion transport and battery rate properties can be obtained,

and wherein the electrolyte comprises a compound of formula I:

i is a kind of

Wherein X is selected from one of Si and Ti,

The compound of the formula I contains alkenyl or alkynyl and can be polymerized on the surface of the positive electrode to form a film so as to form stronger binding force, so that the electrolyte containing the compound of the formula I is used in the electrochemical device, and the outward expansion of secondary particles and the breakage of material particles are reduced, so that the cycle life of the battery is remarkably prolonged and the volume expansion caused by long-term use is reduced.

In some embodiments, the compound of formula I comprises at least one of the following compounds:

，

，

。

in some embodiments, the compound of formula I is present in an amount of a, and a is 0.01 wt.% or less and 5 wt.% or less, based on the total weight of the electrolyte.

In some embodiments, the compound of formula I is present in an amount of a, and a is 0.01 wt.% 3 wt.% or less, based on the total weight of the electrolyte.

In some embodiments, the electrolyte further comprises an additive a selected from LiBF ₄ 、LiPO ₂ F ₂ At least one of 4, 5-dicyano-2-trifluoromethylimidazole Lithium (LiTDI), difluoro-bis (oxalate) lithium phosphate (LiDFBP), tetrafluoro-oxalato-phosphate (LiTfOP), difluoro-oxalato-borate (LiDFOB) or bis-oxalato-borate (LiBOB), and wherein the additive A is contained in an amount of b and 0.01 wt.% or more and 5 wt.% or less based on the total weight of the electrolyte.

In some embodiments, the compound of formula I content a and additive a content b satisfy: a is less than or equal to 2b.

In some embodiments, the electrolyte further comprises an additive B having the structure of formula II,

II (II)

Wherein X is ₁ To X ₅ Is a nitrogen atom (N) or a substituent-containing carbon atom (C-R), whichThe substituents attached at the positions of the carbon atoms are independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, amino, nitrile, halogen, ether, pyridyl or carbonyl-containing groups.

In some embodiments, the additive B is present in an amount of 0.01 wt% to 5 wt% based on the total weight of the electrolyte.

In some embodiments, the additive B is selected from at least one of the following compounds of formula II-1 to formula II-19:

，

，

，

，

。

in some embodiments, the positive electrode active material includes secondary particles formed of primary grains, and Dv of the secondary particles ₉₀ The shortest diameter d of the primary crystal grain is as follows: dv ₉₀ ≥2d。

In some embodiments, dv of the secondary particles ₉₀ From 5 μm to 20. Mu.m.

In some embodiments, dv of the secondary particles ₅₀ From 2 μm to 10 μm.

In some embodiments, the positive electrode active material layer further comprises a conductive material comprising carbon nanotubes having a raman spectrum at 1350cm ^-1 Peak intensity at I _D1 And at 1580cm ^-1 Peak intensity at I _G1 The ratio of (C) is I _D1 /I _G1 And I _D1 /I _G1 ≤2。

In some embodiments, the positive electrode active material layer further comprises a conductive material comprising carbon nanotubes having a raman spectrum at 1350cm ^-1 Peak intensity at I _D1 And at 1580cm ^-1 Peak intensity at I _G1 The ratio of (C) is I _D1 /I _G1 And I _D1 /I _G1 ≤1。

In some embodiments, the positive electrode active material layer further comprises LiCoO ₂ 、LiNiCoMnO ₂ 、LiFePO ₄ 、LiMn ₂ O ₄ At least one of them.

In a third aspect of the present application, the present application provides an electronic device comprising an electrochemical device according to the first aspect of the present application.

Detailed Description

Embodiments of the present application will be described in detail below. The examples of the present application should not be construed as limiting the scope of the claims of the present application. The following terms used herein have the meanings indicated below, unless explicitly indicated otherwise.

As used herein, the term "about" is used to describe and illustrate small variations. When used in connection with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely and instances where it occurs to the close approximation. For example, when used in connection with a numerical value, the term can refer to a range of variation of less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

In the detailed description and claims, a list of items connected by the term "one of" may mean any of the listed items. For example, if items a and B are listed, the phrase "one of a and B" means either only a or only B. In another example, if items A, B and C are listed, one of the phrases "A, B and C" means only a; only B; or only C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.

In the detailed description and claims, a list of items connected by the terms "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, the phrase "at least one of a and B" or "at least one of a or B" means only a; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" or "at least one of A, B or 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 A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.

In the description and in the claims, the number following the expression concerning the number of carbons, i.e. the capital letter "C", for example "C ₁ -C ₁₀ ”、“C ₃ -C ₁₀ In "etc., the number following" C "such as" 1"," 3 "or" 10 "represents the number of carbons in a particular functional group. That is, the functional groups may include 1 to 10 carbon atoms and 3 to 10 carbon atoms, respectively. For example, "C ₁ -C ₄ Alkyl "or" C _1-4 Alkyl "means an alkyl group having 1 to 4 carbon atoms, e.g. CH ₃ -、CH ₃ CH ₂ -、CH ₃ CH ₂ CH ₂ -、(CH ₃ ) ₂ CH-、CH ₃ CH ₂ CH ₂ CH ₂ -、CH ₃ CH ₂ CH(CH ₃ ) -or (CH) ₃ ) ₃ C-。

As used herein, the term "alkyl" refers to a straight chain saturated hydrocarbon structure having 1 to 10 carbon atoms. "alkyl" is also intended to be a branched or cyclic hydrocarbon structure having 3 to 10 carbon atoms. For example, the alkyl group may be an alkyl group of 1 to 10 carbon atoms, an alkyl group of 1 to 8 carbon atoms, an alkyl group of 1 to 6 carbon atoms, or an alkyl group of 1 to 4 carbon atoms. When alkyl groups having a specific carbon number are specified, all geometric isomers having that carbon number are contemplated; thus, for example, reference to "butyl" is intended to include 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, and the like. In addition, the alkyl group may be optionally substituted.

The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that may be straight or branched and has at least one and typically 1,2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl group typically contains 2 to 10 carbon atoms, for example, can be 2 to 8 carbon atoms, 2 to 6 carbon atoms, or 2 to 4 carbon atoms. Representative alkenyl groups include, for example, vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like. In addition, alkenyl groups may be optionally substituted.

The term "alkynyl" refers to a monovalent unsaturated hydrocarbon group that may be straight or branched and has at least one and typically 1,2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group typically contains an alkynyl group of 2 to 10, 2 to 8, 2 to 6, or 2 to 4 carbon atoms. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like. In addition, alkynyl groups may be optionally substituted.

The term "aryl" encompasses both monocyclic and polycyclic systems. The polycyclic ring may have two or more rings in common in which two carbons are two adjoining rings (the rings being "fused"), wherein at least one of the rings is aromatic, e.g., the other rings may be cycloalkyl, cycloalkenyl, aryl, heterocyclic, and/or heteroaryl. For example, an aryl group may contain an aryl group of 6 to 12 carbon atoms or 6 to 10 carbon atoms. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl, and the like. In addition, aryl groups may be optionally substituted.

When the above substituents are substituted, they are substituted with one or more halogens unless otherwise indicated.

As used herein, the term "halogen" encompasses F, cl, br and I, preferably F or Cl.

The term "positive electrode active material" refers to a material capable of reversibly intercalating and deintercalating lithium ions. In some embodiments of the present application, the positive electrode active material includes, but is not limited to, lithium-containing transition metal oxides.

1. Electrochemical device

The electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery or a sodium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, a sodium ion secondary battery, a sodium polymer secondary battery, a sodium ion polymer secondary battery. In some embodiments, an electrochemical device of the present application comprises a positive electrode and an electrolyte. In some embodiments, an electrochemical device of the present application comprises a positive electrode, a negative electrode, a separator, and an electrolyte.

Positive electrode

In some embodiments, a positive electrode includes a current collector and a positive electrode active material layer on the current collector, the positive electrode active material layer including a positive electrode active material.

The positive electrode active material includes at least one lithiated intercalation compound that reversibly intercalates and deintercalates lithium ions. In some embodiments of the present application, the positive electrode active material layer comprises a lithium-containing transition metal oxide. In some embodiments, the positive electrode active material layer comprises a composite oxide. In some embodiments, the composite oxide contains lithium and at least one element selected from cobalt, manganese, magnesium, and nickel, and in particular, the composite oxide contains magnesium.

In some embodiments, the positive electrode active material layer comprises positive electrode active material Li _1+x M _1-y Mg _y O ₂ Wherein M is selected from one or more of Ni, co, mn, al, fe, cu, ru, nb, W, cr, zr, mo, V, ti, la, Y, and 0 < x.ltoreq.2, and 0 < y.ltoreq.0.02. By introducing Mg element into the positive electrode active material, stability of the material structure is increased, however, when y exceeds 0.02, the introduction of excessive Mg element will cause a decrease in capacity exertion of the positive electrode material.

In some embodiments, wherein the positive electrode active material comprises secondary particles, the secondary particle structure is formed by agglomeration of primary grains, dv of the secondary particles ₉₀ The shortest diameter d of the primary crystal grain is as follows: dv ₉₀ And (3) not less than 2d. When Dv is ₉₀ Below 2d, the diameter of the secondary particles is too small and the diameter of the primary crystal grains is too large, which results in deterioration of stability to make the secondary particle structure more easily broken.

In some embodiments, dv of the secondary particles ₅₀ From 2 μm to 10 μm.

The positive electrode active material layer further includes a binder, and optionally includes a conductive material. The binder enhances the bonding of the positive electrode active material particles to each other, and also enhances the bonding of the positive electrode active material to the current collector.

In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like.

In some embodiments, the positive electrode active material layer further comprises a conductive material including, but 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, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from the group consisting of metal powder, metal fiber, copper, nickel, aluminum, silver. In some embodiments, the conductive polymer is a polyphenylene derivative. In some preferred embodiments, the conductive material comprises carbon nanotubes and the carbon nanotubes have a diameter of 5nm to 50nm. In some preferred embodiments, the conductive material comprises carbon nanotubes having a Raman spectrum at 1350cm ^-1 Peak intensity at I _D1 And at 1580cm ^-1 Peak intensity at I _G1 The ratio of (C) is I _D1 /I _G1 And I _D1 /I _G1 Less than or equal to 2, preferably I _D1 /I _G1 And is less than or equal to 1. By adding carbon nanotubes in the positive electrode active material layer, the increase in interfacial resistance of the electrode due to the introduction of additive B in the electrolyte can be effectively balanced, further, I _D1 /I _G1 And when the temperature is less than or equal to 1, the defects of the carbon nano tube are fewer, so that better conductive performance can be provided for the pole piece.

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

The positive electrode may be prepared by a preparation method well known in the art. For example, the positive electrode can be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include N-methylpyrrolidone, etc., but is not limited thereto.

In some embodiments, the positive electrode is manufactured by forming a positive electrode material using a positive electrode active material layer including a lithium transition metal-based compound powder and a binder on a current collector.

In some embodiments, the positive electrode active material layer may be generally fabricated by: the positive electrode material and the binder (conductive material and thickener, etc. as needed) are dry-mixed to form a sheet, the obtained sheet is pressed against the positive electrode current collector, or 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.

Negative electrode

The materials, compositions, and methods of making the negative electrode used in the electrochemical devices of the present application may include any of the 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 by reference herein in its entirety.

In some embodiments, the anode includes a current collector and an anode active material layer on the current collector. The anode active material includes a material that reversibly intercalates/deintercalates lithium ions. In some embodiments, the material that reversibly intercalates/deintercalates lithium ions includes a carbon material. In some embodiments, the carbon material may be any carbon-based negative electrode active material commonly used in lithium ion rechargeable batteries. In some embodiments, the carbon material includes, but is not limited to: crystalline carbon, amorphous carbon, or mixtures thereof. The crystalline carbon may be amorphous, platelet-shaped, spherical or fibrous natural graphite or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and the like.

In some embodiments, the anode active material layer includes an anode active material. The specific kind of the anode active material is not particularly limited, and may be selected according to the need. In some embodiments, the negative electrode active material includes, but is not limited to: lithium metal, structured lithium metal, natural graphite, artificial graphite, intermediate phase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composites, li-Sn alloys, li-Sn-O alloys, sn, snO, snO ₂ Lithiated TiO of spinel structure ₂ -Li ₄ Ti ₅ O ₁₂ A Li-Al alloy, or any combination thereof. Wherein the silicon-carbon composite means that it comprises at least about 5 wt% silicon based on the weight of the silicon-carbon anode active material.

When the anode includes a silicon carbon compound, silicon: carbon=about 1:10 to 10:1, median particle diameter Dv of the silicon carbon compound ₅₀ About 0.1 microns to 20 microns. When the anode includes an alloy material, the anode active material layer may be formed using a method such as vapor deposition, sputtering, plating, or the like. When the anode includes lithium metal, for example, an anode active material layer is formed with a conductive skeleton having a spherical twisted shape and metal particles dispersed in the conductive skeleton. In some embodiments, the spherical twisted conductive backbone may have a porosity of about 5% to about 85%. In some embodiments, a protective layer may also be provided on the lithium metal anode active material layer.

In some embodiments, the anode active material layer may include a binder, and optionally, a conductive material. The binder enhances the bonding of the anode active material particles to each other and the bonding of the anode active material to the current collector. 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, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like.

In some embodiments, the conductive material includes, but is not limited to: a carbon-based material, a metal-based material, a conductive polymer, or a mixture thereof. In some embodiments, the carbon-based material is selected from natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from the group consisting of metal powder, metal fiber, copper, nickel, aluminum, silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

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, conductive metal coated polymeric substrates, and any combination thereof.

The negative electrode may be prepared by a preparation method well known in the art. For example, the anode may be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include water or the like, but is not limited thereto.

Isolation film

In some embodiments, the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application.

For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from 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 can be selected. The substrate layer may be one or more layers, and when the substrate layer is a plurality of layers, the compositions of the polymers of different substrate layers may be the same or different, and the weight average molecular weights of the polymers of different substrate layers are not completely the same; when the substrate layer is a multilayer, the polymers of different substrate layers differ in closed cell temperature.

In some embodiments, the surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic material.

In some embodiments, the separator includes a porous substrate and a coating layer including inorganic particles and a binder.

In some embodiments, the coating layer thickness is from about 0.5 microns to about 10 microns, from about 1 micron to about 8 microns, or from about 3 microns to about 5 microns.

In some embodiments, the inorganic particles are selected from the group consisting of SiO ₂ 、Al ₂ O ₃ 、CaO、TiO ₂ 、ZnO ₂ 、MgO、ZrO ₂ 、SnO ₂ 、Al(OH) ₃ Or AlOOH. In some embodiments, the particle size of the inorganic particles is from about 0.001 microns to about 3 microns.

In some embodiments, the binder is selected from at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoroethylene copolymer (PVDF-HFP), polyvinylpyrrolidone (PVP), polyacrylate, pure acrylic emulsion (anionic acrylic emulsion copolymerized from acrylate and special function monomers), styrene-acrylic emulsion (styrene-acrylate emulsion) obtained by emulsion copolymerization of styrene and acrylate monomers, and styrene-butadiene emulsion (SBR obtained by emulsion copolymerization of butadiene and styrene).

Electrolyte solution

In some embodiments, the electrolyte includes a lithium salt, an organic solvent, and a compound of formula I,

i is a kind of

Wherein X is selected from Si, ti, Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ At least one of (a) comprises at least one C _2-8 Alkenyl or C _2-8 Alkynyl, Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ Independently selected from H, halogen, and substituted or unsubstituted groups of: c (C) _1-8 Alkyl, C _2-8 Alkenyl, C _2-8 Alkynyl, C _6-12 Aryl, C _1-8 Alcohol group, C _2-8 Ester groups of (a) are present.

，

，

。

in some embodiments, the compound of formula I is present in an amount of a.ltoreq.a.ltoreq.5% by weight, preferably 0.1.ltoreq.a.ltoreq.3.0% by weight, e.g. 0.1.ltoreq.a.ltoreq.1.0% by weight, based on the total weight of the electrolyte, the compound of formula I may be present in an amount of, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%. When a is less than 0.01 wt%, too small a content may not sufficiently exert an effect of the compound of formula I, and when a is more than 5 wt%, too large a content may increase the impedance of the positive electrode interface.

In some embodiments, the electrolyte further comprises an additive a, preferably an ionic additive and selected from LiBF ₄ 、LiPO ₂ F ₂ At least one of 4, 5-dicyano-2-trifluoromethylimidazole Lithium (LiTDI), difluoro-bis (oxalato) lithium phosphate (LiDFBP), tetrafluoro-oxalato-phosphate (LiTfOP), difluoro-oxalato-borate (LiDFOB) or bis-oxalato-borate (LiBOB), and wherein the additive A is contained in an amount of b and 0.01 wt% or less b 5 wt%, preferably 0.1 wt% or less b 3.0 wt%, for example 0.1 wt% or less b 1.0 wt%, and the additive A may be contained in an amount of, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, or 1.0 wt%, based on the total weight of the electrolyte. When the content of the additive A is greater than the range defined hereinLimited by the solubility and dissociation degree of additive a, an excess of additive a can negatively affect the conductivity of the electrolyte.

In some embodiments, the compound of formula I content a and additive a content b satisfy: a is less than or equal to 2b. By introducing the additive A, an inorganic compound of lithium can be formed on the positive electrode film, so that the lithium ion conduction capacity is improved, and in addition, the electrode surface protection film formed by the additive A and an organic component formed by polymerization of unsaturated bonds of the compound of the formula I has enhanced toughness, so that the electrode surface film has good ion conduction and strong stability.

II (II)

Wherein X is ₁ To X ₅ Is a nitrogen atom (N) or a substituent-containing carbon atom (C-R), wherein the substituent attached to the position of the carbon atom is independently selected from H, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an amino group, a nitrile group, a halogen atom, an ether group, a pyridyl group, or a carbonyl-containing group; wherein the substituents attached at the position of the nitrogen atom are independently selected from substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted silane groups, amine groups, or carbonyl-containing groups.

By introducing the additive B into the electrolyte, a film can be formed on the positive electrode and the negative electrode, further improving the SEI structure of the electrochemical device.

In some embodiments, the additive B is present in an amount of 0.01 wt% to 5 wt%, preferably 0.1 wt% to 3.0 wt%, for example 0.1 wt% to 1.0 wt%, and the additive B may be present in an amount of, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, based on the total weight of the electrolyte. When the content of the additive B exceeds 5 wt%, an excessive amount of the additive B will cause an increase in resistance and increase the risk of lithium precipitation.

，

，/>

，

，

。

in some embodiments, the lithium salt is selected from one or more of an inorganic lithium salt and an organic lithium salt. In some embodiments, the lithium salt contains at least one of a fluorine element, a boron element, or a phosphorus element. In some embodiments, the lithium salt is selected from one or more of the following lithium salts: lithium hexafluorophosphate LiPF ₆ Lithium bis (trifluoromethanesulfonyl) imide LiN (CF) ₃ SO ₂ ) ₂ (abbreviated as LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO) ₂ F) ₂ ) (abbreviated as LiFSI), lithium hexafluoroarsenate LiAsF ₆ Lithium perchlorate LiClO ₄ Or lithium triflate LiCF ₃ SO ₃ 。

In some embodiments, the concentration of the lithium salt is 0.3 mol/L to 1.5 mol/L. In some embodiments, the concentration of the lithium salt is 0.5 mol/L to 1.3 mol/L or about 0.8 mol/L to 1.2 mol/L. In some embodiments, the concentration of the lithium salt is about 1.10mol/L.

The organic solvent includes at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), ethylmethyl carbonate (DEC), dimethyl carbonate (DMC), sulfolane (SF), γ -butyrolactone (γ -BL), propylethyl carbonate, methyl Formate (MF), ethyl formate (MA), ethyl Acetate (EA), ethyl Propionate (EP), propylpropionate (PP), methyl propionate, methyl butyrate, ethyl butyrate, methylethyl fluorocarbonate, dimethylfluorocarbonate, or diethyl fluorocarbonate, etc.

In some embodiments, wherein the solvent comprises 70 wt% to 95 wt% of the electrolyte.

In some embodiments, the organic solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof. The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof. Examples of chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC) and combinations thereof. Examples of fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, trifluoromethyl ethylene carbonate, and combinations thereof. Examples of carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decalactone, valerolactone, mevalonic acid lactone, caprolactone, and combinations thereof. Examples of ether compounds are dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

In some embodiments, examples of other organic solvents are dimethyl sulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphoric acid esters, and combinations thereof.

The electrolyte used in the electrochemical device of the present application is any of the electrolytes described above in the present application. The electrolyte used in the electrochemical device of the present application may also include other electrolytes within a range not departing from the gist of the present application.

2. Electronic device

The electronic device of the present application may be any device using the electrochemical device of the present application.

In some embodiments, the electronic device includes, but is not limited to: notebook computers, pen-input computers, mobile computers, electronic book players, portable telephones, portable facsimile machines, portable copiers, portable printers, headsets, video recorders, liquid crystal televisions, hand-held cleaners, portable CD-players, mini-compact discs, transceivers, electronic notebooks, calculators, memory cards, portable audio recorders, radios, stand-by power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, watches, electric tools, flash lamps, cameras, household large-sized batteries or lithium-ion capacitors, and the like.

To achieve the above objects and to enable those skilled in the art to understand the present invention, the following examples are given by way of illustration of specific embodiments in which the invention may be practiced, and it is intended that the described examples be merely illustrative of some, not all, of the examples.

3. Test method

1. Lithium ion battery cycle performance test

And placing the lithium ion battery in a 45 ℃ incubator, and standing for 30 minutes to keep the lithium ion battery at a constant temperature. The lithium ion battery which reached the constant temperature was charged to a voltage of 4.28V at a constant current of 5C, then charged to a current of 0.05C at a constant voltage of 4.28V, and then discharged to a voltage of 3.0V at a constant current of 10C, which is described as one charge-discharge cycle. The charge-discharge cycle was repeated for 600 cycles with the capacity of the first discharge being 100%. As an index for evaluating the cycle performance of the lithium ion battery, the cycle capacity retention rate was calculated by:

cycling capacity retention = capacity at 600 cycles +.capacity at first discharge.

2. Lithium ion battery low-temperature discharge capacity retention rate test

Placing a lithium ion battery in a high-low temperature box with adjustable temperature, setting the temperature at 25 ℃, standing for 60min, discharging to 3.0V at 0.2 ℃, standing for 15min, charging to 4.28V at 1C constant current, charging to 0.05C at constant voltage, standing for 15min, discharging to 3.0V at 0.2C, and recording that the discharge capacity at this step is C ₂₅ The method comprises the steps of carrying out a first treatment on the surface of the Regulating the temperature of the high-low temperature box to minus 20 ℃, repeating the charging and discharging processes, and recording the discharge capacity as C _-20 。

Low-temperature discharge capacity retention rate c=c _-20 /C ₂₅ 。

Examples 1-1 to 1-28

Preparation of the negative electrode: mixing negative active material artificial graphite, thickener sodium carboxymethylcellulose (CMC) and binder styrene-butadiene rubber (SBR) according to a weight ratio of 97:1:2, adding deionized water, and obtaining negative slurry under the action of a vacuum stirrer, wherein the solid content of the negative slurry is 54 weight percent; uniformly coating the negative electrode slurry on a negative electrode current collector copper foil; and drying the coated copper foil at 85 ℃, cold pressing, cutting, slitting and drying for 12 hours under the vacuum condition of 120 ℃ to obtain the negative electrode.

Preparation of positive electrode: positive electrode active material Li _1.12 (Ni _0.44 Co _0.001 Mn _0.559 ) _1-y Mg _y O ₂ Mixing a conductive agent Super P and a binder polyvinylidene fluoride according to a weight ratio of 97:1.4:1.6, adding N-methylpyrrolidone (NMP), and uniformly stirring under the action of a vacuum stirrer to obtain positive electrode slurry, wherein the solid content of the positive electrode slurry is 72 wt%; uniformly coating the anode slurry on an anode current collector aluminum foil; drying the coated aluminum foil at 85 ℃, then cold pressing, cutting and slitting,drying under vacuum at 85 ℃ for 4 hours gave a positive electrode, and the numerical value of y in the chemical formula of the positive electrode active material is shown in table 1.

Preparation of electrolyte: in a dry argon atmosphere glove box, ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC) were mixed in mass ratio EC: PC: EMC: dec=20:10:30:40, followed by addition of additives according to the additives shown in table 1, dissolution and thorough stirring, and addition of lithium salt LiPF ₆ And (5) uniformly mixing to obtain the electrolyte. Wherein, liPF ₆ The concentration of (C) was 1.10mol/L. The additives used in the electrolyte and the contents thereof are shown in table 1.

Preparation of a separation film: selecting Polyethylene (PE) isolating film with thickness of 9 mu m, passing through polyvinylidene fluoride (PVDF) slurry and Al ₂ O ₃ And (5) coating and drying the slurry to obtain the final isolating film.

Assembling a lithium ion battery: and sequentially stacking the positive electrode, the isolating film and the negative electrode, enabling the isolating film to be positioned between the positive electrode sheet and the negative electrode sheet, then placing the isolating film in an outer packaging foil aluminum plastic film after winding and welding the electrode lugs, injecting the electrolyte, and obtaining the soft package lithium ion battery after vacuum packaging, standing, formation, shaping and capacity testing.

Examples 1 to 29

50% LiNi for the cathode material using a hybrid cathode _0.5 Co _0.2 Mn _0.3 O ₂ + 50% Li _1.12 (Ni _0.44 Co _0.001 Mn _0.559 ) _1-y Mg _y O ₂ ) Except for the positive electrode material, other materials and processes were exactly the same as those of examples 1 to 2.

Comparative examples 1-1 to 1-3

Comparative examples 1-1 to 1-3 were carried out with reference to example 1, wherein additives used in comparative examples 1-1 to 1-3 are shown in table 1.

The soft-pack lithium ion batteries obtained from comparative examples 1-1 to 1-3 and examples 1-1 to 1-29 were subjected to a first discharge capacity test and a capacity retention test, respectively, the results of the tests are shown in table 1, and the contents of the compound of formula I, the additive a, and the additive B are shown based on the total weight of the electrolyte.

As can be seen from the test results of examples 1-1 to 1-19 and comparative examples 1-1 to 4, although the doping of Mg element in the positive electrode active material can improve the cycle performance of the battery, the excessive Mg element in the positive electrode active material deteriorates the first discharge capacity of the positive electrode mainly because the doping of Mg tends to enter the transition metal position of the positive electrode active material and can play a role in stabilizing the positive electrode structure, but the doping of Mg also passivates the connected Li ⁺ And further reduce the discharge capacity.

As shown by the test results of examples 1-1 to 1-29, the lithium ion battery according to the present application not only has excellent first discharge capacity, but also obtains improved cycle capacity retention. In examples 1-1 to 1-29, the compound of formula I having an unsaturated bond was used in the electrolyte, and it was possible to efficiently polymerize the compound into a film on the positive electrode, thereby forming a stable elastic CEI and protecting the positive electrode. Therefore, when the proper content of Mg element in the positive electrode active material is combined with the proper amount of the compound in the formula I in the electrolyte, the improvement of the battery cycle performance caused by the Mg element can be maintained, the influence of the battery cycle performance on the first discharge capacity can be reduced, and in addition, the consumption of the Mg element can be reduced by the combined use, so that the influence of the Mg on the discharge capacity is further reduced.

Examples 1-20 to 1-28 in comparison with examples 1-2 demonstrate that the addition of additive A, B alone or A and B together with the electrolyte can further enhance the cycle life of the battery. This is mainly because the additive a can form a film on the positive electrode and the negative electrode, and a lower film formation resistance is achieved; the additive B can form a film on the positive electrode and the negative electrode, can play a role in removing hydrofluoric acid to a certain extent, and can play a better role in using the additives A and B.

Examples 2-1 to 2-5

Examples 2-1 to 2-5 were carried out with reference to examples 1-23, with the differences shown in Table 2.

As can be seen from comparing examples 2-1 to 2-3 with examples 1 to 23, when the secondary particle size of the positive electrode material is larger than twice the primary grain size, the secondary particle has sufficient stress release, and good ion transport is maintained while maintaining the stability of the structure, thereby achieving improvement of the battery cycle performance and low-temperature discharge performance.

Examples 3-1 to 3-6

Examples 3-1 to 3-6 were carried out with reference to examples 1-23, except that the preparation of the positive electrode was completed by the following method: positive electrode active material Li _1.12 (Ni _0.44 Co _0.001 Mn _0.559 ) _1-y Mg _y O ₂ Specific I shown in Table 3 _D1 /I _G1 Mixing a conductive agent carbon nano tube and a binder polyvinylidene fluoride according to a weight ratio of 97:1.4:1.6, adding N-methyl pyrrolidone (NMP), and uniformly stirring under the action of a vacuum stirrer to obtain positive electrode slurry, wherein the solid content of the positive electrode slurry is 72 weight percent; uniformly coating the anode slurry on an anode current collector aluminum foil; and drying the coated aluminum foil at 85 ℃, cold pressing, cutting and slitting, and drying for 4 hours under the vacuum condition at 85 ℃ to obtain the anode.

Examples 3-1 to 3-6 and examples 1-23 show that the addition of carbon nanotubes can improve the first discharge capacity, the cyclic capacity retention rate and the low temperature discharge capacity retention rate of the battery by improving the electron conductivity of the electrode sheet. Comparison with comparative example 3-1 shows that when the carbon nanotubes are I _D1 /I _G1 When the value is not more than 2, it is possible toBetter battery performance is achieved.

Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the present application and that changes, substitutions and alterations of the embodiments may be made without departing from the spirit, principles and scope of the present application, which also fall within the scope of the present application.

Claims

1. An electrochemical device comprising a positive electrode and an electrolyte, wherein,

the positive electrode includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material Li _1+x M _1-y Mg _y O ₂ Wherein M is selected from one or more of Ni, co, mn, al, fe, cu, ru, nb, W, cr, zr, mo, V, ti, la, Y, x is more than or equal to 0.12 and less than or equal to 2, and y is more than or equal to 0 and less than or equal to 0.02; and wherein the first and second heat sinks are disposed,

the electrolyte comprises a compound of formula I:

i is a kind of

Wherein X is selected from one of Si and Ti, Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ At least one of (a) comprises at least one C _2-8 Alkenyl or C _2-8 Alkynyl, Y ₁ 、Y ₂ 、Y ₃ 、Y ₄ Independently selected from H, halogen, and substituted or unsubstituted groups of: c (C) _1-8 Alkyl, C _2-8 Alkenyl, C _2-8 Alkynyl, C _6-12 Aryl, C _1-8 Alcohol group, C _2-8 Ester groups of (a) are present.

2. The electrochemical device of claim 1, wherein the compound of formula I comprises at least one of the following compounds:

。

3. the electrochemical device according to claim 1 or 2, wherein the compound of formula I is present in an amount of a, and a is 0.01 wt.% or more and 5 wt.% or less, based on the total weight of the electrolyte.

4. The electrochemical device according to claim 1 or 2, wherein the compound of formula I is contained in an amount of a and 0.01 wt.% or more a or less than 3 wt.% based on the total weight of the electrolyte.

5. The electrochemical device according to claim 1 or 2, characterized in that the electrolyte further comprises an additive a selected from LiBF ₄ 、LiPO ₂ F ₂ At least one of 4, 5-dicyano-2-trifluoromethyl imidazole lithium, difluoro-bis (oxalate) phosphate lithium, tetrafluoro-oxalato phosphate lithium, difluoro-oxalato-borate lithium or bis-oxalato-borate lithium, and wherein the additive A content is b and 0.01 wt% or more and 5 wt% or less based on the total weight of the electrolyte.

6. The electrochemical device of claim 5, wherein the compound of formula I content a and the additive a content b satisfy, based on the total weight of the electrolyte: a is less than or equal to 2b.

7. The electrochemical device of claim 1, wherein the electrolyte further comprises an additive B having a structure of formula II,

II (II)

Wherein X is ₁ To X ₅ Is a nitrogen atom or a carbon atom containing a substituent, wherein the substituents attached at the positions of the carbon atoms are independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, amino, nitrile,a halogen atom, an ether group, a pyridyl group or a carbonyl-containing group.

8. The electrochemical device of claim 7, wherein the additive B is selected from at least one of the following compounds of formula II-1 to formula II-19:

。

9. the electrochemical device of claim 7, wherein the additive B is present in an amount of 0.01 to 5 wt%, based on the total weight of the electrolyte.

10. The electrochemical device according to claim 1, wherein the positive electrode active material includes secondary particles formed of primary crystal grains, and Dv of the secondary particles ₉₀ The shortest diameter d with the primary crystal grain satisfies: dv ₉₀ Not less than 2d; and/or Dv of the secondary particles ₉₀ From 5 μm to 20. Mu.m.

11. The electrochemical device of claim 1, wherein the positive electrode active material layer further comprises a conductive material comprising carbon nanotubes having a raman spectrum at 1350cm ^-1 Peak intensity at I _D1 And at 1580cm ^-1 Peak intensity at I _G1 The ratio of (C) is I _D1 /I _G1 And I _D1 /I _G1 ≤2。

12. The electrochemical device of claim 1, wherein the positive electrode active material layer further comprises a conductive material comprising carbon nanotubes having a raman spectrum at 1350cm ^-1 Peak intensity at I _D1 And at 1580cm ^-1 Peak intensity at I _G1 The ratio of (C) is I _D1 /I _G1 And I _D1 /I _G1 ≤1。

13. An electronic device characterized in that it comprises the electrochemical device according to any one of claims 1 to 12.