CN114665095A - Battery with a battery cell - Google Patents

Battery with a battery cell Download PDF

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Publication number
CN114665095A
CN114665095A CN202210322987.3A CN202210322987A CN114665095A CN 114665095 A CN114665095 A CN 114665095A CN 202210322987 A CN202210322987 A CN 202210322987A CN 114665095 A CN114665095 A CN 114665095A
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carbonate
lithium
mass
active layer
positive
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彭冲
张保海
李涛
李俊义
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated solvents

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Secondary Cells (AREA)

Abstract

The invention provides a battery, which comprises a positive plate and electrolyte, wherein the positive plate comprises a positive current collector and a positive active layer positioned on at least one surface of the positive current collector, the positive active layer comprises an additive, and the additive is selected from one or more of lithium nitrate, lithium nitrite, lithium borate, lithium phosphate and lithium fluoroborate; the electrolyte comprises an organic solvent and a lithium salt, wherein the organic solvent comprises a fluorine-containing organic solvent, and/or the lithium salt comprises a fluorine-containing lithium salt. According to the invention, the lithium-containing additive is added into the positive active layer and acts with the fluorine ions in the electrolyte, so that the volume expansion of the battery is relieved, and the cycle life of the battery is prolonged.

Description

Battery with a battery cell
Technical Field
The invention relates to a battery, and relates to the technical field of electrochemistry.
Background
With the continuous development of the related technology of the battery, people put higher demands on the energy density and the quick charge performance of the battery.
However, as the energy density and the quick charge performance of the battery are improved, the cycle performance of the battery is reduced to different degrees, for example, the compaction density of the negative electrode plate is necessarily required to be improved to improve the energy density of the battery, but the dynamic performance of the battery is reduced, the cycle expansion is large, and the cycle life is reduced; in order to improve the quick charge performance of the battery, a negative electrode active material with better dynamic performance and smaller particle size needs to be used, and the surface density of the negative electrode plate is reduced, so that the compaction density of the negative electrode plate is reduced, the energy density of the battery is reduced, the cyclic expansion is increased, and the cyclic life is reduced, therefore, the problem of how to relieve the cyclic expansion and cyclic life reduction of the battery is paid more and more attention.
Disclosure of Invention
The invention provides a battery for alleviating the problems of increased cycle expansion and reduced cycle life of the battery.
The invention provides a battery, which comprises a positive plate, wherein the positive plate comprises a positive current collector and a positive active layer positioned on at least one surface of the positive current collector, the positive active layer comprises an additive, and the additive is selected from one or more of lithium nitrate, lithium nitrite, lithium borate, lithium phosphate and lithium fluoroborate;
the electrolyte comprises an organic solvent and a lithium salt, wherein the organic solvent comprises a fluorine-containing organic solvent, and/or the lithium salt comprises a fluorine-containing lithium salt.
The battery provided by the invention comprises a positive plate, a negative plate and electrolyte, wherein the positive plate and the negative plate are used for carrying out electrochemical reaction and providing capacity for the battery, the electrolyte provides a conducting medium for the electrochemical reaction, and in order to relieve the problems of increase of battery cycle expansion and reduction of cycle life, the invention improves the materials used by the positive plate and the electrolyte, and the following details are set forth:
fig. 1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present invention, as shown in fig. 1, the positive electrode sheet includes a positive electrode current collector 100 and a positive electrode active layer 200 located on at least one surface of the positive electrode current collector, where the positive electrode current collector 100 may be a conventional material such as an aluminum foil, and the positive electrode active layer 200 includes an additive specifically selected from one or more of lithium nitrate, lithium nitrite, lithium borate, lithium phosphate, and lithium fluoroborate, and during a battery charge-discharge cycle, the additive is continuously dissolved out from the positive electrode active layer, where lithium ions may supplement lithium for the positive electrode, so as to improve an energy density of the battery, and anions, lithium ions, and fluoride ions in an electrolyte act together to form a smooth, dense, electrically conductive, mechanically high, and non-breakable SEI film, and ensure that F, O elements in the SEI film are uniformly distributed, so as to help to improve a protection effect of the SEI film on a negative electrode active material, the cycle expansion of the battery is relieved, and the cycle life of the battery is prolonged; especially for lithium ion batteries, the components in the SEI film formed (e.g., Li)3N、LiF、LiNxOy) Contribute to Li+The diffusion along the horizontal direction and the migration along the vertical direction of the interface improve the ion transport performance of the SEI film, so that lithium ions are uniformly deposited and rapidly diffused on the negative electrode plate, and the generation of lithium dendrites is prevented; meanwhile, because the solubility of the additive in the electrolyte is poor, the additive is helpful for continuous dissolution in the battery cycle process, and Li is continuously provided+And anions are used to repair the SEI film so that the repaired SEI film still has the composition and function of a fresh SEI film.
Specifically, fig. 2 is a schematic structural diagram of a positive electrode sheet according to still another embodiment of the present invention, and as shown in fig. 2, the positive electrode active layer 200 includes a first positive electrode active layer 201 and a second positive electrode active layer 202, the first positive electrode active layer 201 is disposed on at least one surface of the positive electrode current collector 100, the second positive electrode active layer 202 is disposed on a surface of the first positive electrode active layer 201 away from the positive electrode current collector 100, and a mass of the additive in the first positive electrode active layer is smaller than a mass of the additive in the second positive electrode active layer, during a battery charge and discharge cycle, the additive in the second positive electrode active layer 202 is first dissolved out, reacts with the electrolyte and forms an SEI film on a surface of the negative electrode, and the additive in the first positive electrode active layer 201 continuously dissolves and supplements the additive in a later period of the cycle, the composition and function of the SEI film are ensured.
The positive active layer comprises a positive active material, a conductive agent and a binder besides an additive, taking a lithium ion battery as an example, the positive active material is a lithium-containing active material, such as one or more of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate and lithium nickel cobalt aluminate, the mass of the additive is 1-8% of the mass of the positive active material, and when the positive active layer comprises a first positive active layer and a second positive active layer, the mass fraction of the additive is in the above range, which is beneficial to giving consideration to the functions of the additive and the performance of the battery.
The conductive agent may include one or more of conductive carbon black, carbon nanotubes, conductive graphite, graphene, and the binder may include one or more of polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride-hexafluoropropylene, a polyamide, polyacrylonitrile, a polyacrylate, a polyacrylic acid, a polyacrylate, a polyvinylpyrrolidone, a polyvinyl ether, a polymethyl methacrylate, a polytetrafluoroethylene, a polyhexafluoropropylene, and Styrene Butadiene Rubber (SBR).
Because the additive is insoluble in a conventional organic solvent, such as an NMP solvent, and is easily precipitated at the bottom of the slurry in the slurry preparation process, the function of the additive cannot be effectively exerted, in the positive plate preparation process, a positive active material, a conductive agent and a binder are firstly dissolved in the NMP solvent according to a certain mass fraction, the additive is added after the positive active material, the conductive agent and the binder are uniformly stirred, the positive active material, the conductive agent and the binder are uniformly coated on at least one surface of a positive current collector as positive active layer slurry to obtain a positive active layer, and the positive plate is obtained through drying and rolling.
The electrolyte comprises an organic solvent and a lithium salt, wherein the organic solvent comprises a fluorine-containing organic solvent, and/or the lithium salt comprises a fluorine-containing lithium salt, namely the molecular structure of at least one of the organic solvent and the lithium salt comprises fluorine.
The fluorine-containing organic solvent can be one or more of fluoro-carbonate and fluoro-carboxylic ester, and in addition, the organic solvent also comprises a conventional organic solvent, namely the molecular structure does not contain fluorine, and specifically, the organic solvent comprises one or more of non-fluoro-carbonate, non-fluoro-carboxylic ester and fluoro-carboxylic ester;
the non-fluoro carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate and propylene carbonate;
the fluoro carbonate comprises one or two of fluoro chain carbonates and fluoro cyclic carbonates, wherein the fluoro chain carbonates are selected from one or more of fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, trifluoroethyl methyl carbonate and bis (trifluoroethyl) carbonate, ethyl fluoroacetate, ethyl heptafluorobutyrate, ethyl 4,4, 4-trifluorobutyrate, propyl trifluoroacetate, 2-trifluoromethyl ethyl acetate, methyl difluoroacetate and methyl difluoropropionate;
the fluorinated cyclic carbonate is selected from the group consisting of fluoroethylene carbonate, 4-difluoroethylene carbonate, 4, 5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4, 5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4, 5-dimethylethylene carbonate, one or more of 4, 5-difluoro-4, 5-dimethyl ethylene carbonate, 4-difluoro-5, 5-dimethyl ethylene carbonate, difluoroethylene carbonate and trifluoromethyl propylene carbonate;
the non-fluorinated carboxylic ester is selected from one or more of methyl propionate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate and ethyl butyrate;
the fluorocarboxylic acid ester is selected from one or more of ethyl difluoroacetate, ethyl heptafluorobutyrate, ethyl 4,4, 4-trifluorobutyrate, propyl trifluoroacetate, 2-trifluoromethyl ethyl acetate, methyl difluoroacetate and methyl difluoropropionate.
Different fluorine-containing organic solvents can provide fluoride ions, but the influence on the performance of the battery is different due to different groups for providing the fluoride ions, further, the organic solvents comprise fluorinated chain carbonate and fluorinated carboxylic ester, and/or the organic solvents comprise fluorinated cyclic carbonate, further, the volume of the fluorinated chain carbonate and the fluorinated carboxylic ester is 25-98% of the total volume of the organic solvents, and the volume of the fluorinated cyclic carbonate is 20-65% of the total volume of the organic solvents.
The fluorine-containing lithium salt comprises one or more of lithium hexafluorophosphate, bis (trifluoromethyl) sulfonyl imide and bis (fluorosulfonyl) imide lithium, and further comprises three of lithium hexafluorophosphate, bis (trifluoromethyl) sulfonyl imide and bis (fluorosulfonyl) imide lithium, wherein the mass of lithium hexafluorophosphate is 8-15% of the total mass of the organic solvent, the mass of bis (trifluoromethyl) sulfonyl imide is 0.3-6% of the total mass of the organic solvent, and the mass of bis (fluorosulfonyl) imide lithium is 0.3-6% of the total mass of the organic solvent.
In addition, the electrolyte also comprises other additives, such as anode additives, cathode additives and other auxiliary additives, thereby further improving the performance of the battery, and particularly, the electrolyte also comprises a positive electrode additive, the positive electrode additive is selected from one or more of 1,2, 3-tri (2-cyanoethoxy) propane, 1,2, 4-tri (2-cyanoethoxy) butane, 1,1, 1-tri (cyanoethoxymethylene) ethane, 1,1, 1-tri (cyanoethoxymethylene) propane, 3-methyl-1, 3, 5-tri (cyanoethoxy) pentane, 1,2, 7-tri (cyanoethoxy) heptane, 1,2, 6-tri (cyanoethoxy) hexane and 1,2, 5-tri (cyanoethoxy) pentane;
further, the mass of the positive electrode additive is 2-9% of the total mass of the organic solvent.
The negative electrode additive is selected from one or more of vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, ethylene carbonate, ethylene sulfate, ethylene sulfite, methylene methane disulfonate and vinyl ethylene carbonate;
further, the mass of the negative electrode additive is 0.3-25% of the total mass of the organic solvent.
The auxiliary additive comprises one or more of vinyl sulfate (DTD), fluoro-phosphazene, 2, 6-di-tert-butylpyridine, 4-methylpyridine, 4-ethylpyridine, 4 '-dimethyl-2, 2' -bipyridine, 2-hydroxyethylpyridine, 3-hydroxy-2-methylpyridine, 2-hydroxy-5-methylpyridine and 2-hydroxy-4-methylpyridine;
the DTD can be used as a low-impedance additive, the fluoro-phosphazene can be used as a wetting additive, the performance of the battery is further improved, and furthermore, the mass of the auxiliary additive is 1-8.5% of the total mass of the organic solvent.
The preparation method of the electrolyte comprises the following steps: the electrolyte is prepared by mixing the fluorine-containing organic solvent according to a certain proportion, adding the fluorine-containing lithium salt and necessary additives, and uniformly mixing.
The negative plate comprises a negative current collector and a negative active layer arranged on at least one surface of the negative current collector, the negative active layer comprises a negative active material, a conductive agent, a binder and a thickening agent, the negative active material can comprise one or two of a graphite-based active material and a silicon-based active material, the selection of the conductive agent and the binder is the same as that of the positive plate, and the thickening agent can be sodium carboxymethyl cellulose (CMC-Na) and the like.
It is understood that the battery further includes a separator between the positive and negative electrode tabs for preventing the positive and negative electrode tabs from contacting and short-circuiting, which may be a material conventional in the art, and the present invention is not further limited thereto.
The battery provided by the invention can be prepared according to the conventional method in the field, for example, the battery can be prepared by sequentially stacking the positive plate, the diaphragm and the negative plate, assembling into a battery core, then packaging, baking, injecting electrolyte, performing hot pressing, forming and other procedures.
In the charge-discharge cycle process of the battery, the additive is continuously dissolved out of the positive active layer, wherein lithium ions can supplement lithium for the positive electrode, the energy density of the battery is improved, anions, the lithium ions and fluoride ions in electrolyte act together to form a smooth, compact, high-conductivity, high-mechanical-performance and non-cracking SEI film, F, O elements in the SEI film are uniformly distributed, the protection effect on a negative active material is improved, the cycle expansion of the battery is relieved, and the cycle performance of the battery is improved; while components (e.g., Li) in the SEI film formed3N、LiF、LiNxOy) Contribute to Li+The ion transport performance of the SEI film is improved by horizontal diffusion and vertical migration along the interface, so that lithium ions are uniformly deposited and rapidly diffused on the negative electrode plate, and lithium dendrite is prevented from being generated; meanwhile, because the solubility of the additive in the electrolyte is poor, the additive is beneficial to continuous dissolution in the battery circulation process, and Li is continuously provided+And anions are used to repair the SEI film so that the repaired SEI film still has the composition and function of a fresh SEI film.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a positive electrode sheet according to another embodiment of the present invention.
Description of reference numerals:
100-positive current collector;
200-positive active layer;
201-a first positive active layer;
202-second positive active layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention is explained in detail by taking a lithium ion battery as an example:
example 1
The lithium ion battery provided by the embodiment comprises a positive plate, a negative plate and electrolyte, wherein,
the positive plate comprises a positive current collector aluminum foil and a positive active layer arranged on the surface of the positive current collector copper foil, wherein the positive active layer comprises 97.2 parts by mass of positive active substance lithium cobaltate, 1.5 parts by mass of conductive agent carbon black, 1.3 parts by mass of binder polyvinylidene fluoride and 0.972 part by mass of lithium nitrate (the mass of the lithium nitrate is 1 percent of the mass of the lithium cobaltate);
the negative plate comprises a negative current collector copper foil and a negative active layer arranged on the surface of the negative current collector copper foil, wherein the negative active layer comprises 96.9 parts by mass of negative active substance artificial graphite, 1.5 parts by mass of conductive agent carbon black, 1.3 parts by mass of binder styrene butadiene rubber and 1.3 parts by mass of thickener sodium carboxymethyl cellulose;
the electrolyte is electrolyte 1.
Example 2
The lithium ion battery provided in this example can be referred to example 1 except that the mass of lithium nitrate in the positive electrode active layer is 2% of the mass of lithium cobaltate.
Example 3
The lithium ion battery provided in this example can be referred to example 1 except that the mass of lithium nitrate in the positive electrode active layer was 3% of the mass of lithium cobaltate.
Example 4
The lithium ion battery provided in this example can be referred to example 1 except that the mass of lithium nitrate in the positive electrode active layer is 5% of the mass of lithium cobaltate.
Example 5
The lithium ion battery provided in this example can be referred to example 1 except that the mass of lithium nitrate in the positive electrode active layer was 7% of the mass of lithium cobaltate.
Example 6
The lithium ion battery provided in this embodiment can refer to embodiment 1, and the difference is that the positive plate includes a positive electrode current collector aluminum foil and a first positive electrode active layer and a second positive electrode active layer sequentially stacked on the surface of the positive electrode current collector copper foil, where:
the first positive electrode active layer comprises 97.2 parts by mass of a positive electrode active substance lithium cobaltate, 1.5 parts by mass of a conductive agent carbon black, 1.3 parts by mass of a binder polyvinylidene fluoride and 0.972 parts by mass of lithium nitrate (the mass of the lithium nitrate is 1% of the mass of the lithium cobaltate);
the second positive electrode active layer included 97.2 parts by mass of a positive electrode active material lithium cobaltate, 1.5 parts by mass of a conductive agent carbon black, 1.3 parts by mass of a binder polyvinylidene fluoride, and 4.86 parts by mass of lithium nitrate (the mass of lithium nitrate was 5% of the mass of lithium cobaltate).
Example 7
The lithium ion battery provided in this example can be referred to example 6 except that the mass of lithium nitrate in the first positive electrode active layer was 1.5% of the mass of lithium cobaltate.
Example 8
The lithium ion battery provided in this example can be referred to example 6, except that the mass of lithium nitrate in the first positive electrode active layer is 2% of the mass of lithium cobaltate; the mass of lithium nitrate in the second positive electrode active layer was 7% of the mass of lithium cobaltate.
Example 9
The lithium ion battery provided in this example can be referred to example 6 except that the mass of lithium nitrate in the first positive electrode active layer was 3% of the mass of lithium cobaltate.
Example 10
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 2.
Example 11
The lithium ion battery provided in this example can be referred to as example 7, except that the electrolyte is the electrolyte 3.
Example 12
The lithium ion battery provided in this example can be referred to as example 7, except that the electrolyte is electrolyte 4.
Example 13
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is electrolyte 5.
Example 14
The lithium ion battery provided in this example can be referred to as example 7, except that the electrolyte is the electrolyte 6.
Example 15
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is the electrolyte 7.
Example 16
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 8.
Example 17
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 9.
Example 18
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 10.
Example 19
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 11.
Example 20
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 12.
Example 21
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 13.
Example 22
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is electrolyte 14.
Example 23
The lithium ion battery provided in this embodiment can be referred to as embodiment 7, except that the electrolyte is an electrolyte 16.
Comparative example 1
The lithium ion battery provided by the present comparative example can be referred to example 1 except that the positive electrode active layer includes 97.2 parts by mass of a positive electrode active material lithium cobaltate, 1.5 parts by mass of a conductive agent carbon black, and 1.3 parts by mass of a binder polyvinylidene fluoride, i.e., does not include lithium nitrate;
the electrolyte is electrolyte 14.
Comparative example 2
The lithium ion battery provided by the present comparative example can be referred to comparative example 1 except that the electrolyte is the electrolyte 15.
Comparative example 3
The lithium ion battery provided by the present comparative example can be referred to comparative example 1 except that the electrolyte is the electrolyte 16.
The lithium ion batteries provided by examples 1-23 and comparative examples 1-3 are further cycled at 25 ℃, the cycle schedule 2C-4.45V is cut to 0.025C/0.7C-3.0V, and the volume expansion rate (%), the capacity retention rate (%) and the lithium precipitation condition on the surface of the negative plate of the lithium ion battery are tested, the specific analysis and test methods are as follows, the test results are shown in tables 1-2, and the components and the content of the used electrolyte are shown in table 3:
1. lithium precipitation on the surface of the negative plate: after the cycle is cycled for 300T according to the cycle system, the lithium ion battery is disassembled, the lithium separation condition on the surface of the negative plate is observed, the lithium separation condition on the surface of the negative plate is classified into five grades according to the lithium separation condition of the lithium ion battery, and the grades are represented by 0, 1,2,3, 4 and 5, wherein 0 represents no lithium separation, 5 represents serious lithium separation, 1,2,3 and 4 represent different lithium separation degrees, and the larger the number is, the more serious the lithium separation degree is;
2. testing of capacity retention: testing initial capacity Q of lithium ion battery1And the capacity of the lithium ion battery is tested to be Q after the lithium ion battery is circulated for 800T according to the circulation system2Capacity retention (%) ═ Q2/Q1*100％；
3. Testing of expansion ratio: testing the thickness P of the lithium ion battery1And testing the thickness P of the lithium ion battery after the lithium ion battery is cycled for 800T according to the cycle system2The cycle expansion ratio (%) (P2-P1)/P1 × 100%.
TABLE 1
Figure BDA0003571102130000111
TABLE 2
Figure BDA0003571102130000112
According to the data provided in table 1-2, it can be known that the expansion rate of the lithium ion battery is favorably relieved, the problem of lithium precipitation of the lithium ion battery is relieved, and the capacity retention rate of the lithium ion battery is improved by adding the lithium-containing additive into the positive active layer and coacting with the fluorine ions in the electrolyte; compared with a single-layer positive active layer, the double-layer positive active layer is beneficial to further improving the capacity retention rate of the lithium ion battery; in addition, the lithium-containing additive content is too much, the cycle expansion rate of the lithium ion battery is increased on the contrary, and in the actual preparation process, the content of the additive and the components and the content of the electrolyte need to be reasonably selected, so that the lithium ion battery has better cycle performance.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Figure BDA0003571102130000131
Figure BDA0003571102130000141

Claims (10)

1. A battery comprising a positive electrode sheet and an electrolyte, wherein:
the positive plate comprises a positive current collector and a positive active layer positioned on at least one surface of the positive current collector, wherein the positive active layer comprises an additive, and the additive is selected from one or more of lithium nitrate, lithium nitrite, lithium borate, lithium phosphate and lithium fluoroborate;
the electrolyte comprises an organic solvent and a lithium salt, wherein the organic solvent comprises a fluorine-containing organic solvent, and/or the lithium salt comprises a fluorine-containing lithium salt.
2. The battery of claim 1, wherein the positive active layers comprise a first positive active layer and a second positive active layer, wherein the first positive active layer is disposed on at least one surface of the positive current collector, wherein the second positive active layer is disposed on a surface of the first positive active layer away from the positive current collector, and wherein a mass of the additive in the first positive active layer is less than a mass of the additive in the second positive active layer.
3. The battery according to claim 1 or 2, wherein the positive electrode active layer further comprises a positive electrode active material, and the mass of the additive is 1-8% of the mass of the positive electrode active material.
4. The cell defined in any one of claims 1-3, wherein the organic solvent comprises one or more of a non-fluorinated carbonate, a non-fluorinated carboxylate, a fluorinated carboxylate;
the non-fluoro carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate and propylene carbonate;
the fluoro carbonate comprises one or two of fluoro chain carbonate and fluoro cyclic carbonate, wherein the fluoro chain carbonate is selected from one or more of fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, trifluoroethyl methyl carbonate and bis (trifluoroethyl) carbonate, ethyl fluoroacetate, ethyl heptafluorobutyrate, ethyl 4,4, 4-trifluorobutyrate, propyl trifluoroacetate, 2-trifluoromethyl ethyl acetate, methyl difluoroacetate and methyl difluoropropionate;
the fluorinated cyclic carbonate is selected from the group consisting of fluoroethylene carbonate, 4-difluoroethylene carbonate, 4, 5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4, 5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4, 5-dimethylethylene carbonate, 4, 5-difluoro-4, 5-dimethyl ethylene carbonate, 4-difluoro-5, 5-dimethyl ethylene carbonate, difluoroethylene carbonate and trifluoromethyl propylene carbonate;
the non-fluorinated carboxylic ester is selected from one or more of methyl propionate, ethyl acetate, propyl acetate, ethyl propionate, propyl propionate and ethyl butyrate;
the fluorocarboxylic acid ester is selected from one or more of ethyl difluoroacetate, ethyl heptafluorobutyrate, ethyl 4,4, 4-trifluorobutyrate, propyl trifluoroacetate, 2-trifluoromethyl ethyl acetate, methyl difluoroacetate and methyl difluoropropionate.
5. The battery according to claim 4, wherein the volume of the fluorinated chain carbonate and the fluorinated carboxylic acid ester is 25 to 98% of the total volume of the organic solvent, and the volume of the fluorinated cyclic carbonate is 20 to 65% of the total volume of the organic solvent.
6. The cell of claim 1, wherein the lithium salt comprising fluorine comprises one or more of lithium hexafluorophosphate, bis (trifluoromethylsulfonyl) imide, and lithium bis (fluorosulfonyl) imide.
7. The battery according to claim 6, wherein the mass of the lithium hexafluorophosphate is 8 to 15% of the total mass of the organic solvent, the mass of the bis (trifluoromethylsulfonyl) imide is 0.3 to 6% of the total mass of the organic solvent, and the mass of the lithium bis (fluorosulfonyl) imide is 0.3 to 6% of the total mass of the organic solvent.
8. The cell defined in claim 1, wherein the electrolyte further comprises a positive electrode additive selected from one or more of 1,2, 3-tris (2-cyanoethoxy) propane, 1,2, 4-tris (2-cyanoethoxy) butane, 1,1, 1-tris (cyanoethoxymethylene) ethane, 1,1, 1-tris (cyanoethoxymethylene) propane, 3-methyl-1, 3, 5-tris (cyanoethoxy) pentane, 1,2, 7-tris (cyanoethoxy) heptane, 1,2, 6-tris (cyanoethoxy) hexane, 1,2, 5-tris (cyanoethoxy) pentane;
and/or the mass of the positive electrode additive is 2-9% of the total mass of the organic solvent.
9. The battery of claim 1, wherein the electrolyte further comprises a negative electrode additive selected from one or more of vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, ethylene carbonate, ethylene sulfate, ethylene sulfite, methylene methane disulfonate, vinyl ethylene carbonate;
and/or the mass of the negative electrode additive is 0.3-25% of the total mass of the organic solvent.
10. The battery of claim 1, wherein the electrolyte further comprises an auxiliary additive comprising one or more of vinyl sulfate, fluoro phosphazene, 2, 6-di-tert-butylpyridine, 4-methylpyridine, 4-ethylpyridine, 4 '-dimethyl-2, 2' -bipyridine, 2-hydroxyethylpyridine, 3-hydroxy-2-methylpyridine, 2-hydroxy-5-methylpyridine, 2-hydroxy-4-methylpyridine;
and/or the mass of the auxiliary additive accounts for 1-8.5% of the total mass of the organic solvent.
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