CN117043977A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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Publication number
CN117043977A
CN117043977A CN202280021200.8A CN202280021200A CN117043977A CN 117043977 A CN117043977 A CN 117043977A CN 202280021200 A CN202280021200 A CN 202280021200A CN 117043977 A CN117043977 A CN 117043977A
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China
Prior art keywords
protective layer
positive electrode
electrochemical device
inorganic particles
binder
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韩冬冬
刘晓欠
张青文
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology 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
    • 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
    • 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
    • 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

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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)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The present application discloses an electrochemical device, comprising: and the positive electrode comprises a positive electrode current collector, a protective layer and a positive electrode active material layer. The protective layer is disposed between the positive electrode current collector and the positive electrode active material layer. The protective layer comprises inorganic particles, and the inorganic particles meet the requirement that Dv5 is less than or equal to 0.5 mu m when tested by a laser particle sizer, wherein Dv5 represents the particle size corresponding to the cumulative volume distribution number of the inorganic particles reaching 5%, so that the electrochemical device can have excellent safety.

Description

Electrochemical device and electronic device Technical Field
The present application relates to the field of energy storage, and in particular, to an electrochemical device and an electronic device.
Background
With the popularity of electronic products such as notebook computers, mobile phones, palm game players, tablet computers, etc., the safety requirements of electrochemical devices (e.g., lithium ion batteries) are becoming more stringent. At present, safety accidents such as ignition, explosion and the like caused by external impact or extrusion and the like still exist in the use process of the lithium ion battery, so that the wide application of the lithium ion battery is hindered. Among them, a short circuit between the positive electrode current collector and the negative electrode active material layer is one of the most likely to cause an accident. Therefore, a technical means capable of improving the safety performance of the lithium ion battery is needed.
Disclosure of Invention
According to an aspect of the present application, there is provided an electrochemical device including: and the positive electrode comprises a positive electrode current collector, a protective layer and a positive electrode active material layer. The protective layer is disposed between the positive electrode current collector and the positive electrode active material layer. The protective layer comprises inorganic particles, and the inorganic particles meet the requirement that Dv5 is less than or equal to 0.5 mu m when tested by a laser particle sizer, wherein Dv5 represents the particle size corresponding to the cumulative volume distribution number of the inorganic particles reaching 5%. Inorganic particles in the protective layer are controlled to meet the requirement that Dv5 is less than or equal to 0.5um, so that the inorganic particles can cover the positive electrode current collector more uniformly and comprehensively, and particularly, the corners of the winding structure can be filled with the inorganic particles with sufficient small particle sizes, so that the positive electrode current collector at the corners can be covered better; when the electrochemical device is extruded by the side edges, the protective layer has internal stress along with the bending of the pole piece, particularly at the corner of the winding structure, the stress is more concentrated when the electrochemical device is extruded by the side edges because the corner is bent, small-particle-size inorganic particles in the protective layer can promote the sliding among the inorganic particles, reduce the internal stress and inhibit the protective layer from falling off, so that the risk of short circuit between the positive current collector and the negative active material layer is reduced, and the safety performance of the electrochemical device is improved.
In some embodiments, the protective layer has a thickness H1 μm, satisfying Dv 50/H1.ltoreq.0.4, where Dv50 represents the particle size in μm corresponding to a cumulative volume distribution of the inorganic particles up to 50% as tested using a laser particle sizer. At this time, when the electrochemical device is impacted or pressed by external force, the inorganic particles can slide mutually in the thickness direction of the protective layer, so that the stress in the protective layer is further reduced, the falling of the protective layer is inhibited, the risk of short circuit between the positive electrode current collector and the negative electrode active material layer is reduced, and the safety performance of the electrochemical device is further improved.
In some embodiments, dv90/H1 < 1 is satisfied, where Dv90 represents the particle size in μm corresponding to a cumulative volume distribution number of the inorganic particles up to 90%. At this time, the inorganic particles have smaller particle numbers with excessively large particle diameters, so that when the electrochemical device is impacted or extruded by external force, the stress in the protective layer can be further reduced, and the falling of the protective layer is restrained, so that the risk of short circuit between the positive electrode current collector and the negative electrode active material layer is reduced, and the safety performance of the electrochemical device is further improved.
In some embodiments, 0.5.ltoreq.H1.ltoreq.10 is satisfied.
In some embodiments, the inorganic particles comprise first particles and second particles.
In some embodiments, the first particles comprise an element a comprising at least one of Al, mg, si, ca, ti, ce, zn, Y, hf, zr, ba or Sn.
In some embodiments, the second particles comprise Li element and M element, the M element comprising at least one of Mn or Fe.
In some embodiments, the first particles comprise at least one of aluminum oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium silicate, diaspore, barium sulfate, calcium sulfate, or calcium silicate.
In some embodiments, the second particles comprise at least one of lithium iron phosphate, lithium manganese iron phosphate, or lithium manganate.
In some embodiments, the protective layer comprises a binder. In some embodiments, the binder is an aqueous binder. The aqueous binder can improve the binding force between the protective layer and the positive electrode current collector and the positive electrode active material layer, and improve the internal resistance growth rate of the electrochemical device in high-temperature storage.
In some embodiments, the binder comprises a polymer formed from at least one of acrylic acid, an acrylate salt, acrylonitrile, acrylamide, or an acrylate ester.
In some embodiments, the binder comprises at least one of a carboxymethyl cellulose salt or a nitrile rubber.
In some embodiments, the binder has a weight average molecular weight of 18 to 220 tens of thousands.
In some embodiments, the protective layer further comprises a conductive agent. In some embodiments, the conductive agent comprises at least one of a lamellar, network, wire-like, or particulate conductive agent. In some embodiments, the conductive agent is 0.3% to 20% by mass based on the mass of the protective layer.
In some embodiments, 0.1.ltoreq.Dv50.ltoreq.1.5. In some embodiments, 0.4.ltoreq.Dv90.ltoreq.3.5.
In some embodiments, the protective layer further comprises a leveling agent. In some embodiments, the leveling agent is greater than 0% and less than or equal to 6% by mass based on the mass of the protective layer.
In some embodiments, the leveling agent comprises at least one of a siloxane-based compound, a siloxane-based derivative, an oxy-olefin polymer, an acrylate-based polymer, an alcohol-based compound, an ether-based compound, or a fluorocarbon compound.
In some embodiments, the resistance of the positive electrode is RΩ, satisfying 1+.R+. 10 in the fully charged state of the electrochemical device.
According to another aspect of the present application, there is provided an electronic device comprising the electrochemical device according to any one of the preceding embodiments.
Detailed Description
Hereinafter, the present application will be described in detail. It should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present application on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Thus, the description shown in the embodiments described in the specification is merely a specific example for the purpose of illustration and is not intended to show all technical aspects of the application, and it is to be understood that various alternative equivalents and variants may be made thereto at the time of filing the present application.
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" means only a; only B; or A and B. In another example, if items A, B and C are listed, then the phrase "at least one of A, B and C" means only a; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.
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.
1. Electrochemical device
The present application provides an electrochemical device, comprising: and the positive electrode comprises a positive electrode current collector, a protective layer and a positive electrode active material layer. The protective layer is disposed between the positive electrode current collector and the positive electrode active material layer. The protective layer comprises inorganic particles, and the inorganic particles meet the requirement that Dv5 is less than or equal to 0.5 mu m when tested by a laser particle sizer, wherein Dv5 represents the particle size corresponding to the cumulative volume distribution number of the inorganic particles reaching 5%.
On the one hand, by arranging the protective layer between the positive electrode current collector and the positive electrode active material layer, the risk of short circuit between the positive electrode current collector and the negative electrode active material layer when the electrochemical device is impacted or extruded by external force can be reduced, and the safety performance of the electrochemical device is improved. On the other hand, inorganic particles in the protective layer are controlled to meet the requirement that Dv5 is less than or equal to 0.5um, so that the inorganic particles can cover the positive electrode current collector more uniformly and comprehensively, and particularly at the corners of the winding structure, the inorganic particles with sufficient small particle size can be filled, so that the positive electrode current collector at the corners can be covered better; when the electrochemical device is extruded by the side edges, the protective layer has internal stress along with the bending of the pole piece, particularly at the corner of the winding structure, the stress is more concentrated when the electrochemical device is extruded by the side edges because the corner has bending stress, small-particle-size inorganic particles in the protective layer can promote the sliding among the inorganic particles, reduce the internal stress and inhibit the protective layer from falling off, thereby reducing the risk of short circuit between the positive current collector and the negative active material layer and further improving the safety performance of the electrochemical device.
In some embodiments, dv5 is 0.05 μm, 0.08 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, or a range between any two of the foregoing.
In some embodiments, the protective layer has a thickness of H1 μm, satisfying Dv 50/H1.ltoreq.0.4, where Dv50 represents the particle size in μm corresponding to a cumulative volume distribution of the inorganic particles up to 50% as tested using a laser particle sizer. At this time, when the electrochemical device is impacted or pressed by external force, the inorganic particles can slide mutually in the thickness direction of the protective layer, so that the stress in the protective layer is further reduced, the falling of the protective layer is inhibited, the risk of short circuit between the positive electrode current collector and the negative electrode active material layer is reduced, and the safety performance of the electrochemical device is further improved. In some embodiments, the Dv50/H1 value is 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, or a range between any two of the foregoing values.
In some embodiments, the protective layer satisfies Dv90/H1 < 1, wherein Dv90 represents the particle size corresponding to a cumulative volume distribution of the inorganic particles up to 90% as tested using a laser particle sizer. At this time, the inorganic particles have smaller particle numbers with excessively large particle diameters, so that when the electrochemical device is impacted or extruded by external force, the stress in the protective layer can be further reduced, and the falling of the protective layer is restrained, so that the risk of short circuit between the positive electrode current collector and the negative electrode active material layer is reduced, and the safety performance of the electrochemical device is further improved. In some embodiments, the Dv90/H1 has a value of 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or a range between any two of the foregoing values.
In some embodiments, 0.1.ltoreq.Dv50.ltoreq.1.5. In some embodiments, dv50 is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 1, 1.05, 1.15, 1.2, 1.4, 1.5, or a range between any two of the foregoing values.
In some embodiments, 0.4.ltoreq.Dv90.ltoreq.3.5. In some embodiments, dv90 is 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, or a range between any two of the foregoing values.
In some embodiments, H1 is 0.5 μm to 10 μm. In some embodiments, H1 is 0.5 μm, 0.8 μm, 1.2 μm, 1.6 μm, 2 μm, 2.4 μm, 2.8 μm, 3.2 μm, 3.6 μm, 4 μm, 4.4 μm, 4.8 μm, 5.2 μm, 5.6 μm, 6 μm, 6.4 μm, 6.8 μm, 7.2 μm, 7.6 μm, 8 μm, 8.4 μm, 9.4 μm, 9.8 μm, 10 μm, or a range between any two of the foregoing values.
In some embodiments, the inorganic particles comprise first particles and/or second particles. In some embodiments, the inorganic particles comprise first particles and second particles.
In some embodiments, the first particles comprise an element a, which may comprise at least one of Al, mg, si, ca, ti, ce, zn, Y, hf, zr, ba or Sn. In some embodiments, the first particles comprise at least one of aluminum oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium silicate, diaspore, barium sulfate, calcium sulfate, or calcium silicate. In some embodiments, the Al is derived from at least one of boehmite, alumina, aluminum hydroxide, diaspore. In some embodiments, the Si is derived from at least one of kaolin or calcium silicate. In some embodiments, ba is derived from barium sulfate. In some embodiments, the Ca is derived from at least one of calcium oxide, calcium sulfate, or calcium silicate. In some embodiments, the Mg is derived from at least one of magnesium oxide or magnesium hydroxide.
In some embodiments, the first particles are 0% to 93.5% by mass based on the mass of the protective layer. In some embodiments, the first particle is 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 93.5% by mass or a range between any two of the foregoing.
In some embodiments, the second particles comprise Li element and M element, the M element comprising at least one of Mn or Fe. In some embodiments, the second particles comprise at least one of lithium iron phosphate (abbreviated LFP), lithium manganese iron phosphate (abbreviated LFMP), or lithium manganate (abbreviated LMO). In some embodiments, li is derived from at least one of lithium iron phosphate (abbreviated LFP), lithium manganese iron phosphate (abbreviated LFMP), or lithium manganate (abbreviated LMO). In some embodiments, the Mn is derived from at least one of lithium manganese iron phosphate (LFMP) or Lithium Manganate (LMO). In some embodiments, the Fe is derived from at least one of lithium iron phosphate (LFP) or lithium manganese iron phosphate (LFMP).
In some embodiments, the mass percent of the second particles is 0% to 98.5% based on the mass of the protective layer. In some embodiments, the mass percent of the second particle is 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98.5%, or a range between any two of the foregoing.
In some embodiments, the protective layer comprises a first binder. In some embodiments, the first binder is an aqueous binder. The aqueous binder can improve the binding force between the protective layer and the positive electrode current collector and the positive electrode active material layer, and improve the internal resistance growth rate of the electrochemical device in high-temperature storage.
In some embodiments, the first binder comprises a polymer formed from at least one of acrylic acid, an acrylate salt, acrylonitrile, acrylamide, or an acrylate ester.
In some embodiments, the first binder comprises at least one of a carboxymethyl cellulose salt or a nitrile rubber.
In some embodiments, the first binder comprises an acrylate and a polymer formed from at least one of acrylic acid, acrylonitrile, and an acrylate.
In some embodiments, the first binder has a weight average molecular weight of 18 to 220 tens of thousands. In some embodiments, the first binder has a weight average molecular weight of 20 to 180 ten thousand. In some embodiments, the first binder has a weight average molecular weight of 20 to 160 tens of thousands. In some embodiments, the first binder has a weight average molecular weight of 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 220 or a range between any two of the foregoing.
In some embodiments, the first binder is 0.5% to 21% by mass based on the mass of the protective layer. In some embodiments, the first binder is 0.5%, 1%, 2%, 3%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21% by mass or a range between any two of the foregoing.
In some embodiments, the protective layer comprises a first conductive agent. In some embodiments, the first conductive agent may comprise at least one of a lamellar, network, wire-like, or particulate conductive agent. In some embodiments, the first conductive agent comprises at least one of graphene (abbreviated GN), graphite fiber, carbon nanotube (abbreviated CNT), ketjen black, or conductive carbon (abbreviated SP).
In some embodiments, the first conductive agent is 0.3% to 20% by mass based on the mass of the protective layer. In some embodiments, the first conductive agent is 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 10%, 12%, 14%, 16%, 18%, 20% or a range between any two of the foregoing values.
In some embodiments, the protective layer further comprises a leveling agent. In some embodiments, the leveling agent may include at least one of a siloxane-based compound, a siloxane-based derivative, an oxygen-containing olefin polymer, an acrylate-based polymer, an alcohol-based compound, an ether-based compound, or a fluorocarbon-based compound. In some embodiments, the leveling agent comprises at least one of polydimethylsiloxane, ethoxypropylene-propoxypropylene polymer, or fluorocarbon modified polyacrylate.
In some embodiments, the mass percent of the leveling agent is greater than 0% and less than or equal to 6% based on the mass of the protective layer. In some embodiments, the leveling agent is 0.001%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% or a range between any two of the foregoing values by mass. The leveling agent is favorable for forming a uniform and smooth protective layer, and increasing the contact area of the protective layer, the current collector and the positive electrode active material layer, thereby inhibiting the increase of the internal resistance of the electrochemical device in high-temperature storage.
In some embodiments, the positive electrode active material layer includes an active material, a second binder, and a second conductive agent.
In some embodiments, the active material comprises lithium cobaltate (abbreviated LCO). In some embodiments, the mass percentage of the active material is 94% to 99% based on the mass of the positive electrode active material layer. In some embodiments, the mass percent of active material is 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99% or a range between any two of the foregoing, based on the mass of the positive electrode active material layer.
In some embodiments, the second binder comprises at least one of polyvinylidene fluoride (abbreviated as PVDF), nitrile rubber, or polyacrylate. In some embodiments, the second binder is 0.5% to 2.5% by mass based on the mass of the positive electrode active material layer. In some embodiments, the mass percent of the second binder is 0.5%, 1%, 1.5%, 2%, 2.5%, or a range between any two of the foregoing values, based on the mass of the positive electrode active material layer.
In some embodiments, the second conductive agent comprises at least one of graphene, graphite fibers, carbon nanotubes, ketjen black, or conductive carbon. In some embodiments, the mass percentage of the second conductive agent is 0.5% to 3.5% based on the total mass of the positive electrode active material layer. In some embodiments, the mass percent of the second conductive agent is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or a range between any two of the foregoing values, based on the mass of the positive electrode active material layer.
According to the application, the protective layer is arranged between the positive electrode current collector and the positive electrode active material layer of the electrochemical device, so that the risk of short circuit between the positive electrode current collector and the negative electrode active material layer when the electrochemical device is impacted or extruded by external force can be reduced, and the safety performance of the electrochemical device is improved. Meanwhile, the application realizes that by controlling the material of the protective layer to contain inorganic particles and controlling the material to be tested by a laser particle sizer, when the inorganic particles meet the requirement that Dv5 is less than or equal to 0.5 mu m (wherein Dv5 represents the particle diameter corresponding to the cumulative volume distribution number of the inorganic particles reaching 5 percent), the inorganic particles can cover the positive electrode current collector more uniformly and comprehensively, particularly at the corners of a winding structure, the inorganic particles with sufficient small particle diameters can be filled, so that the positive electrode current collector at the corners can be covered better; when the electrochemical device is extruded by the side edges, the protective layer has internal stress along with the bending of the pole piece, particularly at the corner of the winding structure, the stress is more concentrated when the electrochemical device is extruded by the side edges because the corner has bending stress, small-particle-size inorganic particles in the protective layer can promote the sliding among the inorganic particles, reduce the internal stress and inhibit the protective layer from falling off, thereby reducing the risk of short circuit between the positive current collector and the negative active material layer and further improving the safety performance of the electrochemical device.
The electrochemical device of the present application further includes a separator, an electrolyte, and a negative electrode.
In some embodiments, the electrochemical device of the present application includes, but is not limited to: primary or secondary batteries of all kinds. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, lithium secondary batteries include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.
2. Method for preparing the electrochemical device
The method of manufacturing the electrochemical device of the present application is described in detail below by taking a lithium ion battery as an example.
Preparation of the negative electrode: dispersing a negative electrode active substance (at least one of carbon material, silicon material or lithium titanate) and a negative electrode binder, and optionally a conductive material in a solvent system according to a certain mass ratio, fully stirring and uniformly mixing, coating the mixture on a negative electrode current collector, and drying and cold pressing the mixture to obtain the negative electrode.
Preparation of positive electrode:
(1) Adding inorganic particles, a first conductive agent, a first binder and optionally a leveling agent into a solvent, and uniformly mixing to obtain a slurry (hereinafter referred to as a "first slurry") of the protective layer;
(2) Coating the first slurry in the step (1) on a target area of the positive electrode current collector;
(3) Drying the positive electrode current collector containing the first slurry obtained in the step (2) to remove the solvent, thereby obtaining a positive electrode current collector coated with a protective layer;
(4) Dispersing the active material, the second conductive agent and the second binder in a solvent system according to a certain mass ratio, and fully stirring and uniformly mixing to obtain slurry (hereinafter referred to as "second slurry") of the positive electrode active material;
(5) Coating the second slurry on the target area of the positive electrode current collector coated with the protective layer, which is obtained in the step (3);
(6) And (3) drying the positive electrode current collector containing the second slurry in the step (5) to remove the solvent, thereby obtaining the required positive electrode.
The types of the inorganic particles, the first conductive agent, the first binder, the active material, the second conductive agent, and the second binder are as described above.
In some embodiments, examples of the solvent include, but are not limited to, N-methylpyrrolidone, acetone, or water. In some embodiments, the amount of solvent may be appropriately adjusted.
In some embodiments, the current collector has a thickness in the range of 3 micrometers to 20 micrometers, although the disclosure is not limited thereto. The current collector is not particularly limited as long as the current collector is conductive without causing adverse chemical changes in the fabricated battery. Examples of the current collector include copper, stainless steel, aluminum, nickel, titanium, or an alloy (e.g., copper-nickel alloy), but the disclosure is not limited thereto. In some embodiments, fine irregularities (e.g., surface roughness) may be included on the surface of the current collector to enhance adhesion of the surface of the current collector to the active material. In some embodiments, the current collector may be used in a variety of forms, examples of which include a film, sheet, foil, mesh, porous structure, foam, or jeopardy, but the present disclosure is not limited thereto.
Isolation film: in some embodiments, a porous polymeric film of polyethylene (abbreviated PE) is used as the separator. In some embodiments, the material of the isolation film may include fiberglass, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof. In some embodiments, the pores in the separator have diameters in the range of 0.01 microns to 1 micron, and the thickness of the separator is in the range of 5 microns to 500 microns.
Electrolyte solution: in some embodiments, the electrolyte includes an organic solvent, a lithium salt, and an additive. In some embodiments, the organic solvent includes at least one of ethylene carbonate (abbreviated EC), propylene carbonate (abbreviated PC), diethyl carbonate (abbreviated DEC), ethylmethyl carbonate (abbreviated EMC), dimethyl carbonate (abbreviated DMC), propylene carbonate, or ethyl propionate. In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF 6 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium difluorophosphate (LiPO) 2 F 2 ) Lithium bis (trifluoromethanesulfonyl) imide LiN (CF) 3 SO 2 ) 2 (LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO) 2 F) 2 ) (LiLSI), lithium bisoxalato borate LiB (C) 2 O 4 ) 2 (LiBOB) or lithium difluorooxalato borate LiBF 2 (C 2 O 4 ) At least one of (LiDFOB).
And stacking the positive electrode, the isolating film and the negative electrode in sequence, so that the isolating film is positioned in the middle of the positive electrode and the negative electrode to play a role in isolation, and winding to obtain the bare cell. And placing the wound bare cell in an outer package, injecting electrolyte, packaging, and performing technological processes such as formation, degassing, trimming and the like to obtain the lithium ion battery.
3. Electronic device
The present application provides an electronic device comprising an electrochemical device according to the foregoing.
According to some embodiments of the application, 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.
4. Detailed description of the preferred embodiments
The present application will be described in further detail with reference to examples. However, it should be understood that the following embodiments are merely examples, and the embodiment modes of the present application are not limited thereto.
Examples 1 to 38 and comparative examples 1 to 2
Manufacturing of positive electrode
Step (1): adding inorganic particles, a first binder, a first conductive agent and an optional leveling agent into water, and uniformly mixing to obtain a slurry (hereinafter referred to as a "first slurry") of the protective layer;
step (2), coating the first slurry in the step (1) on a target area of the positive electrode current collector;
step (3), drying the positive electrode current collector containing the first slurry obtained in the step (2) to remove the solvent, thereby obtaining a positive electrode current collector coated with a protective layer;
dispersing an active substance (lithium cobaltate, 97.3 mass percent), a second conductive agent (conductive carbon (trade name Super P) with the mass percent of 0.6 percent and carbon nano tube (abbreviated as CNT) with the mass percent of 0.5 percent) and a second binder (polyvinylidene fluoride (abbreviated as PVDF) with the mass percent of 1.6 percent) in an N-methylpyrrolidone solvent system, and fully stirring and uniformly mixing to obtain a slurry (hereinafter referred to as a second slurry) of a positive electrode active substance;
step (5) coating the second slurry on the target area of the positive electrode current collector coated with the protective layer, which is obtained in the step (3);
and (6) drying the positive electrode current collector containing the second slurry in the step (5) to remove the solvent, thereby obtaining the required positive electrode.
Table 1 below specifically shows the difference in protective layer in the positive electrodes in examples 1 to 38 and comparative examples 1 to 2.
TABLE 1
The positive electrode active material layers, positive electrode current collectors, and the like of the positive electrodes in examples 1 to 38 and comparative examples 1 to 2 were prepared by the foregoing processes, except for the above-described differences.
Manufacturing of lithium ion battery
The positive electrode of the lithium ion battery is manufactured as described above.
And (3) a negative electrode: and (3) fully and uniformly stirring active substances of artificial graphite, a conductive agent of acetylene black, a binder of styrene-butadiene rubber (SBR for short) and a thickener of sodium carboxymethylcellulose (CMC for short) in a deionized water solvent system according to the mass ratio of 95:2:2:1, coating the mixture on a Cu foil, and drying and cold pressing the mixture to obtain the negative electrode.
Electrolyte solution: in an argon atmosphere glove box with a water content of < 10ppm, ethylene carbonate (abbreviated as EC), diethyl carbonate (abbreviated as DEC), propylene carbonate (abbreviated as PC) and lithium salt LiPF6 which is fully dried are uniformly mixed according to the weight ratio of 2:6:2, and then the lithium salt LiPF6 is dissolved in the solvent, wherein the content of the LiPF6 is 12.5 percent, and 1.5 percent of 1, 3-propane sultone, 3 percent of fluoroethylene carbonate and 2 percent of adiponitrile are added. Wherein the content of each substance is based on the total weight of the electrolyte.
Isolation film: a porous polymeric film of Polyethylene (PE) was used as a separator.
And stacking the anode, the isolating film and the cathode in sequence, enabling the isolating film to be positioned in the middle of the anode and the cathode to play a role of isolation, winding, placing in an outer package, injecting the prepared electrolyte, packaging, and carrying out processes such as formation, degassing, trimming and the like to obtain the lithium ion battery.
Performance test method
Particle size
The test was performed using a laser particle sizer (malvern 3000): after the instrument is started, deionized water is added into the sample bin, blank background testing is performed first, and inorganic particle granularity is tested when no obvious characteristic peak exists in the blank background. And adding the inorganic particle aqueous dispersion liquid with uniform ultrasonic dispersion into a sample bin to start a test, thus obtaining the granularity distribution condition of inorganic particles, automatically outputting the granularity distribution of materials by related software, and calculating to obtain Dv5/Dv50/Dv90 (the particle sizes corresponding to the cumulative volume distribution numbers of the samples respectively reaching 5%/50%/90%).
Thickness of protective layer
1) The positive electrode coated with the protective layer was removed from the lithium ion battery in an environment of (25.+ -.3). Degree.C. Wiping the electrolyte remained on the surface of the positive electrode by using dust-free paper;
2) Cutting the positive electrode coated with the protective layer under plasma to obtain the cross section of the positive electrode;
3) The cross section of the positive electrode obtained in 2) was observed under a Scanning Electron Microscope (SEM), and the thickness of the protective layer was tested, with adjacent test points being spaced 0.5mm to 1mm apart, at least 10 different points were tested, and the average value of all test points was recorded as the thickness H1 μm of the protective layer.
Internal resistance of lithium ion battery
And using a resistor to test the alternating current internal resistance of the lithium ion battery by adopting sine and 1000Hz frequency waves.
High temperature storage internal resistance increase rate
Storage conditions (85 ℃ C. For 6 h):
in an environment of 25+/-3 ℃, the lithium ion battery is charged to 4.45V at a constant current of 0.5C and then is charged to 0.025C at a constant voltage of 4.45V, and the initial internal resistance of the lithium ion battery is tested to be IMP0. And (3) putting the lithium ion battery into a high-temperature furnace at 85+/-3 ℃ for 6 hours, taking out, and testing the internal resistance of the lithium ion battery as IMP6 hours after the temperature of the lithium ion battery is reduced to 25+/-3 ℃. High-temperature storage internal resistance increase rate= (IMP 6h-IMP 0)/imp0×100%.
Positive electrode resistance in full charge state
1) Constant-current charging is carried out to 4.45V of full charge design voltage at a multiplying power of 0.05C, and then constant-voltage charging is carried out to 0.025C (cut-off current) at the full charge design voltage of 4.45V, so that the lithium ion battery reaches a full charge state;
2) Disassembling the lithium ion battery to obtain a positive electrode;
3) Placing the positive electrode obtained in the step 2) in an environment with the humidity of 5-15% for 30min, and then sealing and transferring to a resistance test site;
4) Testing the resistance of the positive electrode obtained in 3) by using a BER1200 type diaphragm resistance tester, wherein the intervals between adjacent test points are 2mm to 3mm, at least 15 different points are tested, the average value of the resistance of all the test points is recorded as the resistance RΩ of the positive electrode in a full charge state, and the test parameters are as follows: the ram area was 153.94mm2, the pressure 3.5t, and the hold time 50s.
Side extrusion pass rate
And (3) constant-current charging the lithium ion battery to be tested to the designed full charge voltage of 4.45V at the multiplying power of 0.05C, and then constant-voltage charging to the current of 0.025C (cut-off current) at the full charge design voltage of 4.45V, so that the lithium ion battery reaches the full charge state, and recording the appearance of the lithium ion battery before the test. And (3) performing side extrusion test on the battery in an environment of 25+/-3 ℃, wherein the diameter of a steel nail is 5mm, the extrusion speed is 150mm/s, starting extrusion from the side of the lithium ion battery perpendicular to one side of the tab, stopping the test after the surface temperature of the lithium ion battery is reduced to 50 ℃ for 3min, taking 20 lithium ion batteries as a group, observing the state of the lithium ion battery in the test process, and taking the fact that the lithium ion battery is not burnt and does not explode as passing standards. Note side crush pass = pass number/20.
Table 2 below shows the properties of examples 1 to 38 and comparative examples 1 to 2.
TABLE 2
1. The influence of the presence or absence of a protective layer and the particle diameter of inorganic particles on the performance of an electrochemical device was examined
As can be seen from the foregoing tables 1 and 2, the side crush passing rate of the lithium ion batteries of examples 1 to 38 having the protective layer and comparative example 2 having the protective layer was significantly better than that of the lithium ion battery of comparative example 1 having no protective layer. Therefore, the protective layer added between the positive electrode current collector and the positive electrode active material layer can obviously improve the safety performance of the lithium ion battery.
As is apparent from the comparison of examples 1 to 38 in the foregoing tables 1 and 2 with comparative example 2, when the inorganic particles of the protective layer satisfy Dv 5.ltoreq.0.5 μm (where Dv5 represents the particle diameter corresponding to when the cumulative volume distribution number of the inorganic particles reaches 5%), the lithium ion battery can have a higher side crush passing rate (70% or more), since by controlling the inorganic particles in the protective layer satisfy Dv 5.ltoreq.0.5 μm, the inorganic particles can be made to cover the positive electrode current collector more uniformly and comprehensively, particularly at the corners of the wound structure, the inorganic particles can be filled with sufficiently small particle diameters, thereby better covering the positive electrode current collector at the corners; and when the lithium ion battery is extruded by the side edges, the protective layer has internal stress along with the bending of the pole piece, particularly at the corner of the winding structure, the stress is more concentrated when the lithium ion battery is extruded by the side edges because the corner has bending stress, small-particle-size inorganic particles in the protective layer can promote the sliding among the inorganic particles, and the internal stress is reduced, so that the protective layer is inhibited from falling off, the risk of short circuit between the positive current collector and the negative active material layer is reduced, and the side edge extrusion passing rate of the lithium ion battery is improved.
Further, as is evident from the comparison of examples 1 to 36 and 37 in the foregoing tables 1 and 2, the lithium ion battery can have a more excellent side crush passing rate (90% or more) when the inorganic particles of the protective layer satisfy Dv 50/H1.ltoreq.0.4. This is because, when the lithium ion battery receives the side extrusion, can have sufficient inorganic particle mutually to slide in the thickness direction of protective layer to further reduce the inside stress of protective layer, restrain the drop of protective layer, thereby reduce the risk of short circuit between positive pole current collector and the negative pole active material layer, and then further improve the side extrusion rate of passing through of lithium ion battery.
2. The influence of the composition of the protective layer on the performance of the electrochemical device was examined
2.1 inorganic particles
The inorganic particles used for the protective layer in embodiments 1 to 38 of the present application may include the first particles and/or the second particles. The first particles comprise at least one of boehmite, alumina, barium sulfate, calcium sulfate, or calcium silicate. The second particles include at least one of lithium iron phosphate, lithium manganese iron phosphate, and lithium manganate. However, it should be understood that the inorganic particles used for the protective layer of the present application are not limited to the kind exemplified in the specific examples, and may contain the analogues thereof.
2.2 first adhesive
The first binder used for the protective layer in embodiments 1 to 38 of the present application may include at least one of acrylonitrile-lithium acrylate-acrylamide polymer, polyacrylic acid, sodium carboxymethyl cellulose, sodium polyacrylate, polyacrylonitrile, or nitrile rubber. However, it should be understood that the first binder used for the protective layer of the present application is not limited to the kind exemplified in the specific examples, and may include a polymer formed of at least one of acrylic acid, acrylamide, acrylate, acrylonitrile, or acrylate.
As can be seen from the comparison of examples 1 to 37 and 38 and comparative example 2 in the foregoing tables 1 and 2, when the first binder included in the protective layer is an aqueous binder, it can significantly improve the high-temperature storage internal resistance increase rate of the lithium ion battery compared to polytetrafluoroethylene and polyvinylidene fluoride.
2.3 leveling agent
The leveling agent used for the protective layer in embodiments 1 to 38 of the present application may include at least one of ethoxypropylene-propoxypropylene copolymer, polydimethylsilane, acrylate polymer, sodium acrylate polymer, or fluorocarbon modified polyacrylate. However, it should be understood that the leveling agent used for the protective layer of the present application is not limited to the kind exemplified in the specific examples, and may contain the analogues thereof.
As can be seen from the comparison of examples 31 to 35 and example 36 in the foregoing tables 1 and 2, when the protective layer contains the leveling agent, the effect of improving the increase rate of the internal resistance in high-temperature storage is more remarkable than that in the case of not containing the leveling agent.
In summary, the electrochemical device of the present application has a high side extrusion passing rate, i.e., excellent safety; and the high-temperature storage internal resistance increase rate can be kept within a certain range, and the high-temperature storage internal resistance increase rate has good high-temperature stability.
Reference throughout this specification to "some embodiments," "one embodiment," "another example," "an example," "a particular example," or "a partial example" means that at least one embodiment or example in the present application includes the particular feature, structure, material, or characteristic described in the embodiment or example. Thus, descriptions appearing throughout the specification, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "example," which do not necessarily reference the same embodiments or examples in the application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
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 application, and that changes, substitutions and alterations may be made herein without departing from the spirit, principles and scope of the application.

Claims (10)

  1. An electrochemical device, comprising: the positive electrode comprises a positive electrode current collector, a protective layer and a positive electrode active material layer, wherein the protective layer is arranged between the positive electrode current collector and the positive electrode active material layer; the protective layer comprises inorganic particles, and the inorganic particles meet the requirement that Dv5 is less than or equal to 0.5 mu m when tested by a laser particle sizer, wherein Dv5 represents the particle size corresponding to the cumulative volume distribution number of the inorganic particles reaching 5%.
  2. The electrochemical device according to claim 1, wherein a thickness of the protective layer is H1 μm, at least one of the following conditions being satisfied:
    (a) Dv50/H1 is less than or equal to 0.4, wherein Dv50 represents the particle size corresponding to the cumulative volume distribution number of the inorganic particles reaching 50 percent, and the unit is mu m;
    (b) Dv90/H1 < 1, wherein Dv90 represents a particle diameter corresponding to the cumulative volume distribution number of the inorganic particles reaching 90%, and the unit is mu m;
    (c)0.5≤H1≤10。
  3. the electrochemical device of claim 1, wherein the inorganic particles comprise first particles and/or second particles that satisfy at least one of the following conditions:
    (1) The first particles comprise an element a comprising at least one of Al, mg, si, ca, ti, ce, zn, Y, hf, zr, ba or Sn;
    (2) The second particles contain a Li element and an M element, the M element containing at least one of Mn or Fe.
  4. The electrochemical device of claim 3, which satisfies at least one of the following conditions:
    (i) The first particles comprise at least one of alumina, magnesia, titania, hafnia, tin oxide, ceria, zinc oxide, calcium oxide, zirconia, yttria, boehmite, aluminum hydroxide, magnesium hydroxide, calcium silicate, diaspore, barium sulfate, calcium sulfate, or calcium silicate;
    (ii) The second particles comprise at least one of lithium iron phosphate, lithium manganese iron phosphate, or lithium manganate.
  5. The electrochemical device of claim 1, wherein the protective layer comprises a binder that satisfies at least one of the following characteristics:
    (I) The binder is an aqueous binder;
    (II) the binder comprises a polymer formed from at least one of acrylic acid, an acrylate salt, acrylonitrile, acrylamide, or an acrylate ester;
    (III) the binder comprises at least one of a carboxymethyl cellulose salt or a nitrile rubber;
    (IV) the weight average molecular weight of the binder is 18 to 220 tens of thousands.
  6. The electrochemical device of claim 1, wherein the protective layer further comprises a conductive agent that satisfies at least one of the following characteristics:
    (1) The conductive agent comprises at least one of lamellar, network, linear or granular conductive agents;
    (2) The conductive agent is 0.3 to 20% by mass based on the mass of the protective layer.
  7. The electrochemical device of claim 2, wherein at least one of the following conditions is satisfied:
    (1)0.1≤Dv50≤1.5；
    (2)0.4≤Dv90≤3.5。
  8. the electrochemical device of claim 1, wherein the protective layer further comprises a leveling agent that satisfies at least one of the following characteristics:
    (1) Based on the mass of the protective layer, the mass percentage of the leveling agent is more than 0% and less than or equal to 6%;
    (2) The leveling agent comprises at least one of siloxane compounds, siloxane derivatives, oxygen-containing olefin polymers, acrylic ester polymers, acrylic acid salt polymers, alcohol compounds, ether compounds or fluorocarbon compounds.
  9. The electrochemical device according to claim 1, wherein the resistance of the positive electrode is rΩ in a full charge state, satisfying 1.ltoreq.r.ltoreq.10.
  10. An electronic device comprising the electrochemical device according to any one of claims 1-9.
CN202280021200.8A 2022-03-30 2022-03-30 Electrochemical device and electronic device Pending CN117043977A (en)

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