CN114421013B - Electrochemical device and electronic device - Google Patents
Electrochemical device and electronic device Download PDFInfo
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- CN114421013B CN114421013B CN202210238399.1A CN202210238399A CN114421013B CN 114421013 B CN114421013 B CN 114421013B CN 202210238399 A CN202210238399 A CN 202210238399A CN 114421013 B CN114421013 B CN 114421013B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract
The application provides an electrochemical device, which comprises an electrolyte and a positive plate; the electrolyte comprises a compound shown in formula I; based on the mass of the electrolyte, the mass percentage content of the compound shown in the formula I is A%, and A is more than or equal to 0.5 and less than or equal to 20; the electrolyte also comprises fluoroethylene carbonate, and the mass percentage of the fluoroethylene carbonate is B% based on the mass of the electrolyte; the positive plate comprises a positive active material, the positive active material comprises metal elements, the mass percentage of the metal elements is X% based on the mass of the positive active material, and the metal elements comprise at least one of Al, Mg and Ti; the A, the B and the X satisfy the following relational expression: 5000 XX is more than or equal to B; 0<X/A is less than or equal to 6. The electrochemical device can remarkably improve the cycle performance and the storage stability of the electrochemical device.
Description
Technical Field
The present disclosure relates to the field of electrochemistry, and more particularly, to an electrochemical device and an electronic device.
Background
The lithium ion battery has the advantages of high working voltage, high energy density, low self-discharge rate, small volume, light weight, environmental friendliness and the like, and is widely applied to the fields of intelligent wearable equipment, smart phones, unmanned aerial vehicles, notebook computers and other consumer electronics and the fields of electric automobiles and the like. With the increasing complexity of the service environment of various products, higher requirements are put forward on the cycle performance and the high-temperature storage performance of the lithium ion battery.
Disclosure of Invention
In view of the problems of the background art, it is an object of the present application to provide an electrochemical device and an electronic device.
In order to achieve the above object, the present application provides an electrochemical device including an electrolyte and a positive electrode sheet;
the electrolyte comprises a compound shown in formula I;
Wherein R is1-R6Each independently selected from hydrogen, halogen, cyano, nitro, sulfonic acid, aldehyde, carboxyl, silicon, substituted or unsubstituted C1-6Alkoxy, substituted or unsubstituted C1-6Alkyl, substituted or notSubstituted C2-6Alkenyl, substituted or unsubstituted C2-6Alkynyl, or substituted or unsubstituted C6-12At least one of aryl groups; wherein, when substituted, the substituent is halogen;
based on the mass of the electrolyte, the mass percentage content of the compound shown in the formula I is A%, and A is more than or equal to 0.5 and less than or equal to 20;
the electrolyte also comprises fluoroethylene carbonate, and the mass percentage of the fluoroethylene carbonate is B% based on the mass of the electrolyte;
the positive plate comprises a positive active material, the positive active material comprises metal elements, the mass percentage of the metal elements is X% based on the mass of the positive active material, and the metal elements comprise at least one of Al, Mg and Ti;
the A, the B and the X satisfy the following relational expression: 5000 XX is more than or equal to B; X/A is more than 0 and less than or equal to 6.
In some embodiments, the compound of formula I comprises at least one of formula I-1 through compound I-16:
In some embodiments, the electrolyte further includes a first additive including at least one of 1, 3-propane sultone and a polynitrile compound.
In some embodiments, the polynitrile compound comprises at least one of a dinitrile compound or a trinitrile compound.
In some embodiments, the dinitrile compound comprises succinonitrile, glutaronitrile, adiponitrile, 1, 5-dicyanopentane, 1, 6-dicyanohexane, tetramethylsuccinonitrile, ethylene glycol bis (propionitrile) ether.
In some embodiments, the nitrile compound comprises 1,3, 5-pentanitrile, 1,2, 3-propanetrimethylnitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 3-tris (2-cyanoethoxy) propane.
In some embodiments, the mass percent of the compound shown in the formula I is A%, the mass percent of the first additive is C%, and the mass percent of the first additive is not less than 0.5 and not more than 10 based on the mass of the electrolyte.
In some embodiments, said a and said C satisfy the following relationship: C/A is more than or equal to 0.2 and less than or equal to 16.
In some embodiments, the electrochemical device further comprises a negative electrode sheet;
in some embodiments, the negative electrode sheet includes a negative active material;
in some embodiments, the negative active material includes silicon-based particles, with at least 2 graphite particles surrounding each silicon-based particle.
In some embodiments, the electrochemical device satisfies at least one of the following conditions:
(1) the A satisfies the following conditions: a is more than or equal to 0.5 and less than or equal to 10;
(2) the X/A satisfies: X/A is more than or equal to 0.01 and less than or equal to 4;
(3) the C satisfies: c is more than or equal to 0.5 and less than or equal to 6;
(4) the C/A satisfies 0.5-10.
In some embodiments, the present application also provides an electronic device comprising the electrochemical device described above.
The application at least comprises the following beneficial effects:
the electrochemical device can remarkably improve the cycle performance and the high-temperature storage performance of the electrochemical device.
Detailed Description
Exemplary embodiments are described more fully below, however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.
In the description of the present application, unless otherwise expressly specified or limited, the terms "formula I", "first additive", and the like are used for illustrative purposes only and are not to be construed as indicating or implying relative importance or relationship to one another.
[ electrochemical device ]
The electrochemical device of the present application is not particularly limited, and may include any device in which electrochemical reactions occur. In some embodiments, the electrochemical device may include, but is not limited to, a lithium ion battery.
In some embodiments, an electrochemical device includes a positive electrode tab, a negative electrode tab, a separator, an electrolyte, and a casing.
< electrolyte solution >
In some embodiments, the electrolyte comprises a compound of formula I;
Wherein R is1-R6Each independently selected from hydrogen, halogen, cyano, nitro, sulfonic acid, aldehyde, carboxyl, silicon, substituted or unsubstituted C1-6Alkoxy, substituted or unsubstituted C1-6Alkyl, substituted or unsubstituted C2-6Alkenyl, substituted or unsubstituted C2-6Alkynyl, or substituted or unsubstituted C6-12At least one of aryl groups; wherein, when substituted, the substituent is halogen.
In some embodiments, the mass percent of the compound shown in the formula I is A%, and A is more than or equal to 0.5 and less than or equal to 20 based on the mass of the electrolyte. In some embodiments, the mass percentage a% of the compound of formula I may be 0.5%, 1.0%, 5.0%, 10%, 15%, 20%, or any range therebetween, based on the mass of the electrolyte. The compound shown in the formula I in the content range can form an interface protective film on the surface of the positive electrode, and the stability of the positive electrode interface is improved.
In some embodiments, the electrolyte further comprises fluoroethylene carbonate in an amount of B% by mass based on the mass of the electrolyte. In some embodiments, the fluoroethylene carbonate has a mass percentage content B% ranging from 1% to 30% based on the mass of the electrolyte.
The fluoroethylene carbonate can act with active lithium at a cathode interface to generate LiF and an organic polymer protective layer, so that the decomposition of electrolyte at the cathode interface is effectively inhibited, the expansion of generated gas is reduced, and meanwhile, the fluoroethylene carbonate is easy to decompose at a high-temperature environment to generate an HF etched anode interface CEI layer and an anode active material, the corrosion resistance of an anode material can be improved by doping metal elements into the anode, and meanwhile, a compound shown in formula I is added into the electrolyte to form a protective film at the anode interface to inhibit the etching of HF on the CEI layer.
In some embodiments, the compound of formula I comprises at least one of formula I-1 through compound I-16:
In some embodiments, the electrolyte further includes a first additive including at least one of 1, 3-propane sultone and a polynitrile compound. The addition of the first additive on the basis of the formula I can further improve the cycle performance and the high-temperature storage performance of the electrochemical device.
In some embodiments, the polynitrile compound comprises at least one of a dinitrile compound or a trinitrile compound.
In some embodiments, the dinitrile compound comprises succinonitrile, glutaronitrile, adiponitrile, 1, 5-dicyanopentane, 1, 6-dicyanohexane, tetramethylsuccinonitrile, ethylene glycol bis (propionitrile) ether.
In some embodiments, the tricyanide compound comprises 1,3, 5-pentanitrile, 1,2, 3-propanetricitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 3-tris (2-cyanoethoxy) propane.
In some embodiments, the mass percentage of the first additive is C%, and C is more than or equal to 0.5 and less than or equal to 10 based on the mass of the electrolyte. In some embodiments, C% may be 0.5%, 3%, 5%, 10%. In some embodiments, said a and said C satisfy the following relationship: C/A is more than or equal to 0.2 and less than or equal to 16. In some embodiments, C/a may be 0.2, 1.0, 2.0, 6.0, 10, 14, 16. The first additive can form a CEI layer on the positive electrode interface to inhibit side reaction of electrolyte on the positive electrode interface, but when the addition amount is too low, the structure of the formed CEI layer is unstable, and when the addition amount is too high, the resistance of the positive electrode interface is increased and the electrolyte is decomposed on the positive electrode interface, so that the cycle performance and the high-temperature storage stability of the electrochemical device are influenced. Meanwhile, the relation between C and A is required to be more than or equal to 0.2 and less than or equal to 16, the additive in the formula I and the first additive can form a CEI layer on the positive electrode interface to inhibit the side reaction of the positive electrode interface, and when the two satisfy the above relation, the electrochemical device can have better cycle performance and high-temperature storage performance.
In some embodiments, at least one of the following conditions is met:
(1) the A satisfies the following conditions: a is more than or equal to 0.5 and less than or equal to 10;
(2) the X/A satisfies: X/A is more than or equal to 0.01 and less than or equal to 4;
(3) the C satisfies the following conditions: c is more than or equal to 0.5 and less than or equal to 6;
(4) the C/A satisfies that C/A is more than or equal to 0.5 and less than or equal to 10.
In some embodiments, the electrolyte further comprises a lithium salt. The lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt comprisesLiPF6、LiBF4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、LiSiF6At least one of LiBOB or LiDFOB.
In some embodiments, the electrolyte further comprises an organic solvent. The organic solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound, and a sulfone compound. The organic solvent includes, but is not limited to, at least one of Ethylene Carbonate (EC), Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Butylene Carbonate (BC), Methyl Formate (MF), Methyl Acetate (MA), Ethyl Acetate (EA), Propyl Acetate (PA), Methyl Propionate (MP), Ethyl Propionate (EP), Propyl Propionate (PP), Methyl Butyrate (MB), Ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), Sulfolane (SF), dimethylsulfone (MSM), methylethylsulfone (EMS), diethylsulfone (ESE), 1, 3-Dioxolan (DOL), dimethyl ether (DME).
< Positive electrode sheet >
In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode sheet disposed on at least one surface of the positive electrode current collector. The positive electrode membrane typically includes a positive electrode active material and optionally a positive electrode binder and a conductive agent.
In some embodiments, the structure of the positive electrode tab is a structure of a positive electrode tab that can be used in an electrochemical device, which is well known in the art.
In some embodiments, the positive electrode collector may be a metal foil or a porous metal plate, for example, a foil or a porous plate using a metal such as aluminum, copper, nickel, titanium, silver, or an alloy thereof. As an example, the positive electrode collector may be an aluminum foil.
In some embodiments, the positive electrode active material comprises a metal element, the metal element is contained in an amount of X% by mass based on the mass of the positive electrode active material, and the metal element comprises at least one of Al, Mg, and Ti. The metal element is contained in an amount of 0.05 to 5% by mass based on the mass of the positive electrode active material. The metal element can improve the structural stability of the positive active material, improve the corrosion resistance of the positive active material in circulation, reduce side reactions between the positive active material and electrolyte, and improve the cycle performance and high-temperature storage performance of the electrochemical device.
In some embodiments, the positive active material may include at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or lithium nickel manganate.
In some embodiments, the A, the B, and the X satisfy the following relationship: 5000 XX is more than or equal to B; X/A is more than 0 and less than or equal to 6. In some embodiments, X/a may be 0.0002, 0.1, 0.2, 0.025, 0.05, 0.01, 0.02, 0.03, 0.04, 0.005, 0.003, 0.0025, 0.24, 0.4, 1,2, 4, 6. The proportional relation between the doping amount and the additive is regulated and controlled, the stability of the positive interface can be improved while the negative interface is protected, and the cycle performance and the high-temperature storage performance of the electrochemical device are further improved.
In some embodiments, the positive electrode binder is used to improve the binding properties of the positive electrode active material particles to each other and to the current collector. In some embodiments, the positive electrode binder comprises at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon.
In some embodiments, the conductive agent comprises at least one of conductive graphite, superconducting carbon, acetylene black, conductive carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the method for preparing the positive electrode sheet is a method for preparing a positive electrode sheet that can be used for an electrochemical device, which is well known in the art. In some embodiments, the positive electrode active material, and optionally the binder and the conductive agent are generally dissolved and dispersed in a solvent to prepare a uniform positive electrode slurry, and the positive electrode slurry is coated on a positive electrode current collector and subjected to drying, cold pressing and other processes to obtain a positive electrode sheet. The solvent is a solvent known in the art that can be used as the positive electrode active material layer, and is, for example, but not limited to, N-methylpyrrolidone (NMP).
< negative electrode sheet >
In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on a surface of the negative electrode current collector. The anode active material layer includes an anode active material.
In some embodiments, the structure of the negative electrode sheet is a structure of a negative electrode sheet that may be used in an electrochemical device, as is well known in the art.
The negative electrode current collector has two surfaces opposite in a thickness direction thereof, and a negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.
The negative electrode collector may be a metal foil or a porous metal plate, for example, a foil or a porous plate made of a metal such as copper, nickel, titanium, or iron, or an alloy thereof. As an example, the negative current collector is a copper foil.
In some embodiments, the negative active material comprises silicon-based particles and graphite particles, and at least 2 graphite particles surround each silicon-based particle, so that the electrochemical device has good cycle performance and high-temperature storage performance. Graphite particles around the silicon-based particles can be used as a buffer layer to relieve the expansion of the silicon-based particles in the circulation process of the electrochemical device and avoid the phenomenon of falling and inactivation of the negative active material after lithium intercalation expansion; and side reactions caused by direct contact between the silicon-based particles and the electrolyte can be reduced, and the cycle performance and the high-temperature storage performance of the electrochemical device are improved. The number of graphite particles around the silicon-based particles can be adjusted by adjusting the compaction density of the negative electrode sheet or the particle size of the negative electrode active material.
In some embodiments, the anode active material layer further includes an anode binder and an anode conductive agent. In some embodiments, the negative electrode binder comprises at least one of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon.
In some embodiments, the specific kind of the negative electrode conductive agent is not limited and may be selected as desired. As an example, the conductive agent includes, but is not limited to, at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the anode active material layer further includes a thickener. The specific kind of the thickener is not limited and may be selected as required. By way of example, thickeners include, but are not limited to, sodium carboxymethylcellulose (CMC).
In some embodiments, the method of preparing the negative electrode sheet is a method of preparing a negative electrode sheet that may be used in an electrochemical device, which is well known in the art. In some embodiments, the negative active material and optionally the conductive agent, the binder and the thickener are generally dispersed in a solvent to form a uniform negative slurry, the negative slurry is coated on a negative current collector, and the negative pole piece is obtained through procedures of drying, cold pressing and the like. The solvent is a solvent known in the art, such as, but not limited to, water, which can be used as the negative electrode active material layer. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but the present application is not limited thereto.
< isolation film >
The separator is a separator known in the art that can be used for an electrochemical device, such as, but not limited to, polyolefin-based microporous membranes. In some embodiments, the release film comprises at least one of Polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl methacrylate copolymer.
In some embodiments, the separator is a single layer separator or a multilayer separator.
In some embodiments, the release film is coated with a coating. In some embodiments, the coating comprises at least one of an organic coating comprising at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethylacrylate, acrylic acid-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, sodium carboxymethylcellulose, and an inorganic coating comprising SiO, and a method of making a coating comprising a mixture of a copolymer of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethylacrylate, acrylic acid-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, and sodium carboxymethylcellulose2、Al2O3、CaO、TiO2、ZnO2、MgO、ZrO2、SnO2At least one of them.
The form and thickness of the separator are not particularly limited. The method for preparing the separator is a method for preparing a separator that can be used in an electrochemical device, which is well known in the art.
< housing >
The case serves to enclose the electrode assembly. In some embodiments, the housing may be a hard shell housing or a flexible housing. The hard shell is made of metal, for example. The flexible housing is, for example, a metal plastic film, such as an aluminum plastic film, a steel plastic film, or the like.
In some embodiments, the positive electrode plate, the separator and the negative electrode plate may be manufactured into an electrode assembly through a winding process or a lamination process, the electrode assembly is placed in a casing, an electrolyte is injected into the casing, and the electrochemical device is obtained after vacuum packaging, standing, formation, shaping, capacity grading and the like.
In other embodiments, the cells are stacked.
In other embodiments, the electrochemical device is used in conjunction with a circuit protection board.
[ electronic device ]
The present application also provides an electronic device comprising the above electrochemical device, the electronic device of the present application being any electronic device such as, but not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric power tool, a flashlight, a camera, a large-sized household battery, a lithium ion capacitor. Note that the electrochemical device of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-exemplified electronic devices. The air transport carrier device comprises an air transport carrier device in the atmosphere and an air transport carrier device outside the atmosphere.
The present application is further illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.
The lithium ion batteries of examples 1-1 to 1-26, examples 2-1 to 2-12, examples 3-1 to 3-2, comparative examples 1-1 to 1-10, and comparative example 3-1 were each prepared as follows:
(1) preparation of the electrolyte
Mixing ethylene carbonate and diethyl carbonate in a ratio of 3: 7, mixing the raw materials in a mass ratio, uniformly mixing the raw materials to obtain a base solvent, and adding dry lithium hexafluorophosphate (LiPF) into the base solvent6) Mixing uniformly to obtain electrolyte, wherein, LiPF6The mass percentage content of the active carbon is 12.5 percent; adding a certain content of the additive in the application into the electrolyte to obtain the required electrolyte;
(2) preparation of positive plate
The preparation method comprises the following steps of mixing positive electrode active materials of lithium cobaltate (the molecular formula is LiCoO 2), polyvinylidene fluoride (PVDF) and Super-P according to a mass ratio of 96: 2: 2 dissolving in N-methyl pyrrolidone (NMP), and mixing to obtain positive slurry; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 12 mu m, baking for 1h at 120 ℃, and then compacting and cutting to obtain a positive electrode plate; when the anode active material is prepared, mixing different types or contents of metal oxides into an anode active material precursor, and then calcining for a certain time at high temperature to obtain the anode active material containing various metal elements;
(3) preparation of the separator
Taking a polypropylene film with the thickness of 12 mu m as a separation film;
(4) preparation of negative plate
Preparing a negative electrode active material comprising silicon-based particles and graphite particles, sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber according to a mass ratio of 85: 2: dissolving the mixture 13 in water, fully mixing and stirring to obtain negative electrode slurry, uniformly coating the negative electrode slurry on a negative electrode current collector copper foil with the thickness of 12 mu m, baking for 1h at 120 ℃ to obtain a negative electrode membrane, and then compacting and cutting to obtain a negative electrode sheet;
(5) preparation of lithium ion battery
Stacking the positive plate, the isolating membrane and the negative plate in sequence to enable the isolating membrane to be positioned between the positive plate and the negative plate to play an isolating role, and then winding the positive plate, the isolating membrane and the negative plate into a square bare cell; and (2) filling the naked battery cell into an aluminum plastic film packaging bag, baking at 80 ℃ to remove water to obtain a dry battery cell, injecting corresponding electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to complete the preparation of the lithium ion battery.
And then testing the performance of the lithium ion battery.
(1) The number test method of graphite particles around silicon-based particles comprises the following steps: cutting the cold-pressed negative plate into test samples with the size of 6mm multiplied by 6mm, placing a sample table on a heater for heating, wherein the heating temperature is 150-160 ℃, then coating paraffin on the sample table, after the paraffin is melted, placing the negative plate test sample, slightly protruding the test sample out of the edge of the sample table, then cutting the test sample by using an ion polisher, and then observing the cut cross section by using a Scanning Electron Microscope (SEM), wherein in an electron microscope (in an electron microscope image, the color of silicon-based particles is lightest, and the color of graphite particles is slightly dark), the longest line segment between any two points on a certain silicon-based particle is taken as a diameter to be a circle, and the number of the graphite particles in the circle is defined as the number of the graphite particles around the silicon-based particle, wherein when any part of the graphite particles is in the circle, the graphite particles all belong to the graphite particles around the silicon-based particle.
(2) And (3) testing the normal-temperature cycle performance: and charging the lithium ion battery to 4.45V at a constant current of 0.5C at 25 ℃, standing for 30min, discharging to 3.0V at a constant current of 0.5C, standing for 30min, wherein the process is a cyclic charge-discharge process, and the discharge capacity at the moment is recorded, namely the first-cycle discharge capacity. And (3) carrying out a cyclic charge-discharge test on the lithium ion battery according to the method, recording the discharge capacity after each cycle until the cycle reaches 300 cycles, stopping the test, and recording the discharge capacity at the moment, namely the discharge capacity at the 300 th cycle.
Capacity retention ratio (%) of the lithium ion battery is 300 cycles of discharge capacity/first cycle of discharge capacity x 100%.
(3) And (3) testing the high-temperature storage performance: charging the lithium ion battery to 3.95V at a constant current of 0.5C at 25 ℃, then charging at a constant voltage until the current is 0.5C, wherein the lithium ion battery is in a half-charging state, and recording the thickness of the battery at the moment as t mm; and then charging to 4.45V at a constant current of 0.5C, then charging at a constant voltage until the current is 0.025C, and the lithium ion battery is in a full charge state, placing the battery in a constant temperature box at 60 ℃ for high-temperature storage, storing for 15 days, taking out, cooling to 25 ℃, performing thickness test on the lithium ion battery, and recording the thickness of the battery at the moment, namely T mm.
The lithium ion battery thickness growth rate (%) = (T-T)/T × 100%.
TABLE 1 parameters of examples 1-1 to 1-26 and comparative examples 1-1 to 1-10
| Examples | Formula I | A(%) | B(%) | Metallic element | X(%) | Whether 5X 10^ 3X ≧ B | X/A | Capacity retention ratio (%) | Thickness growth rate (%) |
| Example 1-1 | Formula I-1 | 0.5 | 3 | Al | 0.05 | Is that | 0.1 | 53 | 81 |
| Examples 1 to 2 | Formula I-1 | 1 | 3 | Al | 0.05 | Is that | 0.05 | 58 | 76 |
| Examples 1 to 3 | Formula I-1 | 5 | 3 | Al | 0.05 | Is that | 0.01 | 64 | 59 |
| Examples 1 to 4 | Formula I-1 | 10 | 3 | Al | 0.05 | Is that | 0.005 | 62 | 60 |
| Examples 1 to 5 | Formula I-1 | 15 | 3 | Al | 0.05 | Is that | 0.003 | 57 | 67 |
| Examples 1 to 6 | Formula I-1 | 20 | 3 | Al | 0.05 | Is that | 0.0025 | 54 | 72 |
| Examples 1 to 7 | Formula I-1 | 0.5 | 3 | Al | 0.1 | Is that | 0.2 | 61 | 69 |
| Examples 1 to 8 | Formula I-1 | 0.5 | 3 | Al | 0.2 | Is that | 0.4 | 60 | 71 |
| Examples 1 to 9 | Formula I-1 | 0.5 | 3 | Al | 0.5 | Is that | 1 | 58 | 72 |
| Examples 1 to 10 | Formula I-1 | 0.5 | 3 | Al | 1 | Is that | 2 | 55 | 74 |
| Examples 1 to 11 | Formula I-1 | 0.5 | 3 | Al | 2 | Is that | 4 | 53 | 75 |
| Examples 1 to 12 | Formula I-1 | 0.5 | 3 | Al | 3 | Is that | 6 | 52 | 77 |
| Examples 1 to 13 | Formula I-3 | 0.5 | 3 | Al | 0.1 | Is that | 0.2 | 60 | 68 |
| Examples 1 to 14 | Formula I-5 | 1 | 5 | Al | 0.1 | Is that | 0.1 | 66 | 58 |
| Examples 1 to 15 | Formula I-7 | 5 | 5 | Al | 0.1 | Is that | 0.1 | 69 | 52 |
| Examples 1 to 16 | Formula I-13 | 1 | 5 | Al | 0.1 | Is that | 0.1 | 64 | 61 |
| Examples 1 to 17 | Formula I-1+ formula I-3 | 2+2 | 5 | Al | 0.1 | Is that | 0.025 | 65 | 59 |
| Examples 1 to 18 | Formula I-3+ formula I-11 | 2+3 | 5 | Al | 0.1 | Is that | 0.02 | 67 | 57 |
| Examples 1 to 19 | Formula I-7 | 5 | 5 | Al+Mg | 0.1+0.1 | Is that | 0.04 | 71 | 49 |
| Examples 1 to 20 | Formula I-7 | 5 | 5 | Al+Ti | 0.05+0.1 | Is that | 0.03 | 70 | 48 |
| Examples 1 to 21 | Formula I-7 | 5 | 5 | Ti+Mg | 0.05+0.1 | Is that | 0.03 | 69 | 51 |
| Examples 1 to 22 | Formula I-7 | 5 | 5 | Al+Mg+Ti | 0.1+0.1+1 | Is that | 0.24 | 68 | 53 |
| Examples 1 to 23 | Formula I-1 | 5 | 3 | Al | 0.001 | Is that | 0.0002 | 60 | 67 |
| Examples 1 to 24 | Formula I-1 | 5 | 10 | Al | 0.1 | Is that | 0.02 | 58 | 70 |
| Examples 1 to 25 | Formula I-3 | 5 | 5 | Al | 0.1 | Is that | 0.02 | 69 | 55 |
| Examples 1 to 26 | Formula I-11 | 5 | 5 | Al | 0.1 | Is that | 0.02 | 68 | 56 |
| Comparative examples 1 to 1 | / | / | 3 | / | / | / | / | 38 | 115 |
| Comparative examples 1 to 2 | / | / | / | Al | 0.05 | Is that | / | 37 | 108 |
| Comparative examples 1 to 3 | Formula I-1 | 5 | / | / | / | / | / | 35 | 103 |
| Comparative examples 1 to 4 | / | / | 3 | Al | 0.05 | Is that | / | 40 | 98 |
| Comparative examples 1 to 5 | Formula I-1 | 5 | 3 | / | / | / | / | 45 | 95 |
| Comparative examples 1 to 6 | Formula I-1 | 5 | / | Al | 0.05 | Is that | 0.01 | 42 | 90 |
| Comparative examples 1 to 7 | Formula I-1 | 0.3 | 3 | Al | 0.05 | Is that | 0.16 | 50 | 86 |
| Comparative examples 1 to 8 | Formula I-1 | 25 | 3 | Al | 0.05 | Is that | 0.002 | 48 | 89 |
| Comparative examples 1 to 9 | Formula I-1 | 5 | 10 | Al | 0.001 | Whether or not | 0.0002 | 49 | 93 |
| Comparative examples 1 to 10 | Formula I-1 | 0.5 | 3 | Al | 3.2 | Is that | 6.4 | 45 | 91 |
In table 1, it can be seen from examples 1-1 to 1-26 and comparative examples 1-1 to 1-10 that when the relationship among the content of fluoroethylene carbonate, the content of the compound represented by formula I, and the content of the metal element satisfies the present application, that is, the mass percentage content of the compound represented by formula I-1 is 0.5% to 20%, the mass percentage content a% of the compound represented by formula I-1 and the mass percentage content X% of the metal element satisfy 0< X/a ≦ 6, and the mass percentage content B% of fluoroethylene carbonate and the mass percentage content X% of the metal element satisfy 5000 × X ≧ B, the cycle performance and the high-temperature storage performance of the lithium ion battery can be significantly improved.
It can be seen from examples 1-13 to examples 1-26 that the cycle performance and high-temperature storage performance of the lithium ion battery can be improved by adjusting the type of the compound represented by formula I and the type of the metal element, and therefore, the various substances in formula I can be used alone or in combination; the metal elements doped in the three anode materials can be doped with one to three of the metal elements, and the cycle performance and the high-temperature storage performance of the lithium ion battery can be improved.
TABLE 2 parameters for examples 1-7 and examples 2-1 to 2-12
| Examples | First additive | C（%） | C/A | Capacity retention ratio (%) | Thickness growth rate (%) |
| Examples 1 to 7 | / | / | / | 61 | 69 |
| Example 2-1 | Adiponitrile | 0.5 | 1 | 62 | 66 |
| Examples 2 to 2 | Adiponitrile | 1 | 2 | 65 | 61 |
| Examples 2 to 3 | Adiponitrile | 3 | 6 | 67 | 58 |
| Examples 2 to 4 | Adiponitrile | 5 | 10 | 68 | 56 |
| Examples 2 to 5 | Adiponitrile | 7 | 14 | 66 | 55 |
| Examples 2 to 6 | Succinonitrile and its use | 1 | 2 | 67 | 68 |
| Examples 2 to 7 | 1, 6-dicyanohexane | 1 | 2 | 69 | 60 |
| Examples 2 to 8 | Ethylene glycol bis (propionitrile) ether | 1 | 2 | 60 | 56 |
| Examples 2 to 9 | 1,3, 5-Pentamitril | 1 | 2 | 70 | 45 |
| Examples 2 to 10 | 1,3, 6-hexanetricarbonitrile | 1 | 2 | 71 | 44 |
| Examples 2 to 11 | 1,2, 3-tris (2-cyanoethoxy) propane | 1 | 2 | 74 | 42 |
| Examples 2 to 12 | 1,3 propane sultone +1,3, 6-hexanetricarbonitrile | 0.5+0.5 | 2 | 71 | 48 |
In the above table, examples 1 to 7 were used as the base electrolyte, to which the first additive was added.
As can be seen from examples 1 to 7 and examples 2 to 1 to 2 to 12, when the first additive is added to the electrolyte, the cycle performance and the high-temperature storage performance of the electrochemical device can be improved when the content of the first additive is 0.5% to 10%. When the compound shown in the formula I, the mass percent of A% and the mass percent of C% of the first additive satisfy the relation that C/A is more than or equal to 0.2 and less than or equal to 16, the electrochemical device has better cycle performance and high-temperature storage performance.
TABLE 3 parameters for example 2-2, example 3-1, example 3-2 and comparative example 3-1
| Item | First addition Agent for treating cancer | C（%） | C/A | Whether the negative plate contains silicon Base particle | Graphite around silicon-based particles Number of particles | Capacity retention (%) | Thickness growth rate (%) |
| Examples 2 to 2 | Adiponitrile | 1 | 2 | Is that | 5 | 65 | 61 |
| Example 3-1 | Adiponitrile | 1 | 2 | Is that | 7 | 70 | 60 |
| Examples 3 to 2 | Adiponitrile | 1 | 2 | Is that | 6 | 68 | 58 |
| Comparative example 3-1 | Adiponitrile | 1 | 2 | Is that | 1 | 54 | 77 |
In the above table, the number of graphite particles around the silicon-based particles in the negative electrode active material was adjusted based on example 2-2.
As can be seen from examples 2-2, 3-1 to 3-2, and 3-1, when the negative active material includes silicon-based particles and the number of graphite particles around the silicon-based particles is 2 or more, the electrochemical device has better cycle performance and high-temperature storage performance.
The above-disclosed features are not intended to limit the scope of practice of the present disclosure, and therefore, all equivalent variations that are described in the claims of the present disclosure are intended to be included within the scope of the claims of the present disclosure.
Claims (9)
1. An electrochemical device includes an electrolyte and a positive electrode sheet;
the electrolyte comprises a lithium salt and a compound shown in formula I;
Wherein R is1-R6Each independently selected from hydrogen, halogen, cyano, nitro, sulfonic acid, aldehyde, carboxyl, silicon, substituted or unsubstituted C1-6Alkoxy, substituted or unsubstituted C1-6Alkyl, substituted or unsubstituted C2-6Alkenyl, substituted or unsubstituted C2-6Alkynyl, or substituted or unsubstituted C6-12At least one of aryl groups; wherein, when substituted, the substituent is halogen;
based on the mass of the electrolyte, the mass percentage content of the compound shown in the formula I is A%, and A is more than or equal to 0.5 and less than or equal to 20;
the electrolyte also comprises fluoroethylene carbonate, and the mass percentage of the fluoroethylene carbonate is B% based on the mass of the electrolyte;
the positive plate comprises a positive active material, the positive active material comprises metal elements, the mass percentage of the metal elements is X% based on the mass of the positive active material, and the metal elements comprise at least one of Al, Mg and Ti;
the A, the B and the X satisfy the following relational expression: 5000 XX is more than or equal to B; X/A is more than 0 and less than or equal to 6.
2. The electrochemical device of claim 1, wherein the compound of formula I comprises at least one of formula I-1 to compound I-16:
3. The electrochemical device according to claim 1,
the electrolyte also includes a first additive including at least one of 1, 3-propane sultone and a polynitrile compound.
4. The electrochemical device according to claim 3,
the polynitrile compound comprises at least one of a dinitrile compound or a trinitrile compound;
the dinitrile compounds include succinonitrile, glutaronitrile, adiponitrile, 1, 5-dicyanopentane, 1, 6-dicyanohexane, tetramethylsuccinonitrile, ethylene glycol bis (propionitrile) ether;
the trinitrile compound comprises 1,3, 5-pentanetrimethylnitrile, 1,2, 3-propanetrinitrile, 1,3, 6-hexanetricarbonitrile, 1,2, 6-hexanetricarbonitrile and 1,2, 3-tris (2-cyanoethoxy) propane.
5. The electrochemical device according to claim 3,
based on the mass of the electrolyte, the mass percentage of the compound shown in the formula I is A%, the mass percentage of the first additive is C%, and C is more than or equal to 0.5 and less than or equal to 10.
6. The electrochemical device according to claim 5,
the A and the C satisfy the following relational expression: C/A is more than or equal to 0.2 and less than or equal to 16.
7. The electrochemical device according to claim 1,
the electrochemical device further comprises a negative electrode sheet;
the negative electrode sheet includes a negative active material;
the negative active material comprises silicon-based particles, and at least 2 graphite particles are arranged around each silicon-based particle.
8. The electrochemical device according to any one of claims 1 to 7, satisfying at least one of the following conditions:
(1) the A satisfies the following conditions: a is more than or equal to 0.5 and less than or equal to 10;
(2) the X/A satisfies: X/A is more than or equal to 0.01 and less than or equal to 4;
(3) the C satisfies: c is more than or equal to 0.5 and less than or equal to 6;
(4) the C/A satisfies 0.5-10.
9. An electronic device comprising the electrochemical device of any one of claims 1-8.
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