CN113078290A - Positive pole piece and electrochemical device and electronic device comprising same - Google Patents

Positive pole piece and electrochemical device and electronic device comprising same Download PDF

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Publication number
CN113078290A
CN113078290A CN202110325366.6A CN202110325366A CN113078290A CN 113078290 A CN113078290 A CN 113078290A CN 202110325366 A CN202110325366 A CN 202110325366A CN 113078290 A CN113078290 A CN 113078290A
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conductive
membrane layer
conductive oxide
oxide
membrane
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CN113078290B (en
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谷风
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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
    • 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
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The application relates to a positive pole piece, and an electrochemical device and an electronic device comprising the positive pole piece. The positive pole piece comprises a current collector and a membrane layer arranged on the surface of the current collector, wherein the membrane layer comprises a conductive agent, the conductive agent comprises a conductive oxide, the thickness of the membrane layer is H, and the mass percentage of the conductive oxide is a based on the mass of a first membrane area A1 from the surface of the membrane layer adjacent to the current collector to a first membrane area A1 at a position which is away from the surface H/2 of the membrane layer adjacent to the current collector along the thickness direction of the membrane layer; in a second membrane area A2 from the surface of the membrane layer far away from the current collector to the surface H/2 of the membrane layer far away from the current collector along the thickness direction of the membrane layer, based on the mass of the second membrane area A2, the mass percentage content of the conductive oxide is b, and the following conditions are met: a > b. The positive pole piece provided by the application can obviously improve the high-temperature storage performance of an electrochemical device under high voltage.

Description

Positive pole piece and electrochemical device and electronic device comprising same
Technical Field
The application relates to the technical field of energy storage, in particular to a positive pole piece, an electrochemical device comprising the positive pole piece and an electronic device comprising the positive pole piece.
Background
In order to pursue higher energy density, lithium ion batteries have been developed in a direction of increasing voltage and increasing delithiation amount, and problems of the positive electrode are also sufficiently revealed at high voltage and high delithiation amount: the surface of the anode material releases oxygen, the conductive network is oxidized and the like, thereby bringing the problems of battery cycle water jump, gas generation and the like. The conductive agents used in the market at present are mostly conductive carbon black or carbon conductive agents in other forms of carbon, such as carbon nanotubes, graphene, ketjen black and the like, and the conductive agents have the advantages of large specific surface area, high conductivity and the like. However, under high voltage, especially after the voltage is greater than 4.2V, on one hand, the carbon conductive agent is easy to oxidize to generate gas, on the other hand, the electron conductivity close to the current collector side is better, and the electric potential close to the current collector under the high voltage is higher, so that the oxidation gas generation of the carbon conductive agent is accelerated, the conductive network is damaged, the impedance is increased, and the cycle is attenuated.
Disclosure of Invention
The positive pole piece can obviously improve the high-temperature storage gas production of the electrochemical device under high voltage. The present application also relates to electrochemical devices and electronic devices comprising such positive electrode sheets.
The first aspect of the application provides a positive pole piece, positive pole piece include the mass flow body and set up in the diaphragm layer on the mass flow body surface, the diaphragm layer includes the conducting agent, the conducting agent includes conductive oxide, wherein, the thickness on diaphragm layer is H, along the thickness direction on diaphragm layer, from diaphragm layer with the adjacent surface of mass flow body to the distance in the first diaphragm region A1 of diaphragm layer with the adjacent surface H/2 department of mass flow body, based on the quality in first diaphragm region A1, conductive oxide's mass percent is a; in a second membrane area A2 from the surface of the membrane layer far away from the current collector to the position H/2 away from the surface of the membrane layer far away from the current collector along the thickness direction of the membrane layer, based on the mass of the second membrane area A2, the mass percentage content of the conductive oxide is b, and the following conditions are met: a > b.
The method starts with replacing the conductive agent, and replaces the carbon conductive agent with the conductive oxide with higher conductivity and smaller specific surface area completely or partially, so that the electronic conductivity of the lithium ion battery close to one side of the current collector is high, the potential in the positive pole piece is higher, on one hand, the positive pole material can release oxygen under high voltage, and on the other hand, the conductive carbon can be oxidized to cause failure of the conductive network. And the cation of the conductive oxide has higher valence, so that the conductive oxide is more stable in an oxidation environment. Through making the diaphragm layer in be close to the regional content of electrically conductive oxide in mass flow body one side higher in this application, can improve the inboard stability of diaphragm layer that has higher voltage, restrain the emergence of side reaction such as inboard oxidation gas production, maintain good electrically conductive network to restrain the increase of diaphragm layer impedance, promote battery performance.
According to some embodiments of the present application, a.gtoreq.0.3%. According to some embodiments of the present application, 0.3% ≦ a ≦ 4.5%.
According to some embodiments of the present application, 0 ≦ b ≦ 1.0%. According to some embodiments of the present application, 0 ≦ b ≦ 0.75%.
According to some embodiments of the present application, the conductive oxide includes a material having P42Conductive oxide of/mnm structure or having P63At least one of the conductive oxides of mc structure. Aspect P42Conductive oxides at/mnm such as antimony tin oxide and P63The conducting oxide with the mc structure, such as zinc aluminum oxide, has zero band gap and high electronic conductivity; on the other hand, the two structures have high real density, relatively lower specific surface and small contact area with the electrolyte.
According to some embodiments of the application, the polymer has a P42The XRD pattern of the conductive oxide with the structure of/mnm has diffraction peaks in at least one of the following ranges: 25-27 degrees, 32.5-34.5 degrees and 50.5-52.5 degrees. According to some embodiments of the application, the polymer has a P63The XRD pattern of the mc-structured conductive oxide has diffraction peaks in at least one of the following ranges: 31 degrees to 32 degrees, 33.5 degrees to 34.5 degrees and 35.5 degrees to 36.5 degrees.
According to some embodiments of the present application, the conductive oxide has an average particle size Dv50 ≦ 1 μm. According to some embodiments of the present application, the conductive oxide has an average particle size of 50nm Dv50 ≦ 1 μm.
According to some embodiments, the powder conductivity of the conductive oxide is ≧ 1 × 106μ S/cm. According to some embodiments, the powder conductivity of the conductive oxide is ≧ 2 × 106μS/cm。
According to some embodiments of the present application, the conductive oxide has a specific surface area of 20m or more2(ii) in terms of/g. According to some embodiments of the present application, the conductive oxide has a specific surface area of 20m2G to 50m2/g。
According to some embodiments of the present application, the conductive oxide comprises at least one of the elements tin, antimony, indium, zinc, aluminum, zirconium, platinum, palladium, chromium. According to some embodiments of the present application, the conductive oxide comprises at least one of tin antimony oxide, indium tin oxide, zinc aluminum oxide.
According to some embodiments of the present application, the conductive agent further includes a carbon-based conductive agent having a mass percentage of c1 in the a1 based on the mass of the first membrane area a 1; the mass percentage of the carbon-based conductive agent in the a2 based on the mass of the second membrane region a2 is c 2; satisfies the following conditions: c1< c 2. The content of the carbon conductive agent in the area, close to the current collector, on the membrane layer is lower, so that the impedance increase caused by oxidation of the carbon conductive agent on the inner side of the membrane layer with higher voltage can be reduced or avoided, and side reactions such as gas generation caused by oxidation on the inner side are reduced. According to some embodiments of the present application, c1 ≦ 0.5%.
According to some embodiments of the present application, c2 ≦ 1.5%.
According to some embodiments of the present application, the carbon-based conductive agent includes at least one of conductive carbon black, conductive graphite, acetylene black, ketjen black, graphene, and carbon nanotubes.
According to some embodiments of the application, the thickness H of the membrane layer satisfies: h is more than or equal to 10um and less than or equal to 200 um. According to some embodiments of the application, the thickness H of the membrane layer satisfies: h is more than or equal to 10um and less than or equal to 100 um.
According to some embodiments of the present application, the membrane layer further comprises a positive electrode material comprising at least one of a lithium transition metal composite oxide or a lithium transition metal phosphate compound, and a binder.
According to some embodiments of the present application, the lithium transition metal composite oxide comprises Lix1Niy1Coz1MnkMqOb-aTaWherein M comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, or Ce, T is a halogen, and x, Y, z, k, q, a, and B satisfy, respectively: 0.2<x1 is less than or equal to 1.2, y1 is less than or equal to 0 and less than or equal to 1, z1 is less than or equal to 1, k is less than or equal to 0 and less than or equal to 1, q is less than or equal to 0 and less than or equal to 1, b is less than or equal to 1 and less than or equal to 2, and a is less than or equal to 0 and less than or equal to 1, and y1, z. In some embodiments, 0.6 ≦ x1 ≦ 1.2, 0 ≦ y1 ≦ 1, 0<z1 is less than or equal to 1, k is less than or equal to 0 and less than or equal to 1, q is less than or equal to 0 and less than or equal to 1, b is less than or equal to 1.5 and less than or equal to 2, and a is less than or equal to 0 and less than or equal to 0.5.
According to some embodiments of the present application, the lithium transition metal phosphate compound comprises Lix2Ry2Qz2PO4Wherein R comprises at least one of Fe or Mn; q comprises at least one of Al, Ti, V, Cr, Co, Ni, Cu, Zn, Mg, Ga, Zr, Nb and Si; wherein x2 is more than or equal to 0.6 and less than or equal to 1.2, y2 is more than or equal to 0.95 and less than or equal to 1, and z2 is more than or equal to 0 and less than or equal to 0.05.
The positive pole piece provided by the application can inhibit impedance increase under high voltage, and improves high-temperature storage performance of an electrochemical device under high voltage.
A second aspect of the present application provides an electrochemical device comprising the positive electrode sheet of the first aspect.
A third aspect of the present application provides an electronic device comprising the electrochemical device according to the second aspect.
Drawings
FIG. 1 compares the BET and powder conductivity of conventional conductive carbon black (Super P) and nano tin antimony oxide.
FIG. 2 shows P42XRD diffraction peak of tin antimony oxide with/nm structure.
FIG. 3 shows P63XRD diffraction peak of zinc aluminum oxide with mc structure.
Detailed Description
To make the purpose, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below with reference to the embodiments, and it is obvious that the described embodiments are a part of the embodiments of the present application, and not all of the embodiments. The embodiments described herein are illustrative and are provided to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application. All other embodiments obtained by a person skilled in the art based on the technical solutions provided in the present application and the given embodiments belong to the scope of protection of the present application.
For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each separately disclosed point or individual value may itself, as a lower or upper limit, be combined with any other point or individual value or with other lower or upper limits to form ranges not explicitly recited.
In the description herein, "above" and "below" include the present numbers unless otherwise specified.
Unless otherwise indicated, terms used in the present application have well-known meanings that are commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters mentioned in the present application can be measured by various measurement methods commonly used in the art (for example, the test can be performed according to the methods given in the examples of the present application).
The term "about" is used to describe and illustrate minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs in close proximity. For example, when used in connection with a numerical value, the term can refer to a range of variation that is less than or equal to ± 10% of the numerical value, such as less than or equal to
Plus or minus 5%, less than or equal to plus or minus 4%, less than or equal to plus or minus 3%, less than or equal to plus or minus 2%, less than or equal to plus or minus 1%, less than or equal to plus or minus 0.5%, less than or equal to plus or minus 0.1%, or less than or equal to plus or minus 0.05%. Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
A list of items to which the term "at least one of," "at least one of," or other similar term is connected may imply 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 a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; 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.
First, positive pole piece
The first aspect of this application provides a positive pole piece, positive pole piece including the mass flow body and set up in the diaphragm layer on mass flow body surface, the diaphragm layer includes the conducting agent, the conducting agent includes conductive oxide. The membrane layer comprises a positive electrode material, a conductive agent and a binder, wherein the conductive agent comprises a conductive oxide. The thickness of the membrane layer is H, and in a first membrane area A1 from the surface of the membrane layer adjacent to the current collector to a position H/2 away from the surface of the membrane layer adjacent to the current collector along the thickness direction of the membrane layer, the mass percentage of the conductive oxide is a based on the mass of the first membrane area A1; in a second membrane area A2 from the surface of the membrane layer far away from the current collector to the position H/2 away from the surface of the membrane layer far away from the current collector along the thickness direction of the membrane layer, based on the mass of the second membrane area A2, the mass percentage content of the conductive oxide is b, and the following conditions are met: a > b.
It will be appreciated that the current collector has two opposite surfaces in its thickness direction, and the membrane layer may be laminated on either or both of the two opposite surfaces of the current collector.
According to some embodiments of the present application, a.gtoreq.0.3%. For example, a is 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and any value in between. In some embodiments of the present application, 0.3% ≦ a ≦ 2.0%.
According to some embodiments of the present application, the conductive oxide includes a material having P42Conductive oxide of/mnm structure or having P63At least one of the conductive oxides of mc structure.
According to some embodiments of the application, the polymer has a P42The XRD pattern of the conductive oxide with the structure of/mnm has diffraction peaks in at least one of the following ranges: 25-27 degrees, 32.5-34.5 degrees and 50.5-52.5 degrees. Described in this application with P42The conductive oxide with a/mnm structure comprises a bulk phase structure P42A conductive oxide of a/mnm space group. According to some embodiments of the application, the polymer has a P42The XRD pattern of the conductive oxide with the/mnm structure simultaneously comprises diffraction peaks respectively positioned in the ranges of 25-27 degrees, 32.5-34.5 degrees and 50.5-52.5 degrees.
According to some embodiments of the application, the polymer has a P63The XRD pattern of the mc-structured conductive oxide has diffraction peaks in at least one of the following ranges: 31 degrees to 32 degrees, 33.5 degrees to 34.5 degrees and 35.5 degrees to 36.5 degrees. Described in this application with P63The conductive oxide with mc structure comprises a bulk phase structure of P63A conductive oxide of mc structural space group. According to some embodiments of the application, the polymer has a P63The XRD pattern of the conductive oxide with the mc structure simultaneously comprises diffraction peaks respectively positioned in the ranges of 31-32 degrees, 33.5-34.5 degrees and 35.5-36.5 degrees.
According to some embodiments of the present application, the conductive oxide has an average particle size Dv50 ≦ 1 μm. According to some embodiments of the present application, the conductive oxide has an average particle size of 50nm Dv50 ≦ 1 μm.
According to some embodiments, the powder conductivity of the conductive oxide is ≧ 1 × 106μ S/cm. According to some embodiments, the powder conductivity of the conductive oxide is ≧ 2 × 106μS/cm。
According to some embodiments of the present application, the conductive oxide has a specific surface area of 20m or more2(ii) in terms of/g. According to some embodiments of the present application, the conductive oxide has a specific surface area of 20m2G to 50m2/g。
According to some embodiments of the present application, the conductive oxide comprises at least one of the elements tin, antimony, indium, zinc, aluminum, zirconium, platinum, palladium, chromium. According to some embodiments of the present application, the conductive oxide comprises at least one of tin antimony oxide, indium tin oxide, zinc aluminum oxide.
According to some embodiments of the application, the thickness H of the membrane layer satisfies: h is more than or equal to 10um and less than or equal to 200 um. According to some embodiments of the application, the thickness H of the membrane layer satisfies: h is more than or equal to 10um and less than or equal to 100 um.
According to some embodiments of the present application, b ≧ 0, e.g., b is 0.2%, 0.5%, 0.7%, 1.0%, 1.3%, 1.5%, 2.0%, and any value therebetween. According to some embodiments of the present application, 0 ≦ b ≦ 1.0%. According to some embodiments of the present application, 0 ≦ b ≦ 0.75%.
According to some embodiments of the present application, the conductive agent further includes a carbon-based conductive agent having a mass percentage of c1 in the a1 based on the mass of the first membrane area a 1; the mass percentage of the carbon-based conductive agent in the a2 based on the mass of the second membrane region a2 is c 2; satisfies the following conditions: c1< c 2.
According to some embodiments of the present application, c1 ≦ 0.5%. For example, c1 is 0, 0.2%, 0.3%, 0.4%, 0.5%, and any value in between.
According to some embodiments of the present application, c2 ≦ 1.5%, e.g., c2 is 0.3%, 0.5%, 0.7%, 1.2%, and any value therebetween.
In some embodiments, the carbon-based conductive agent includes at least one of conductive carbon black, conductive graphite, acetylene black, ketjen black, graphene, carbon nanotubes.
According to some embodiments of the present application, the membrane layer further comprises a positive electrode material comprising at least one of a lithium transition metal composite oxide or a lithium transition metal phosphate compound, and a binder.
According to some embodiments of the present application, the lithium transition metal composite oxide comprises Lix1Niy1Coz1MnkMqOb-aTaWherein M comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, or Ce, T is a halogen, and x, Y, z, k, q, a, and B satisfy, respectively: 0.2<x1 is less than or equal to 1.2, y1 is less than or equal to 0 and less than or equal to 1, z1 is less than or equal to 1, k is less than or equal to 0 and less than or equal to 1, q is less than or equal to 0 and less than or equal to 1, b is less than or equal to 1 and less than or equal to 2, and a is less than or equal to 0 and less than or equal to 1, and y1, z. In some embodiments, 0.6 ≦ x1 ≦ 1.2, 0 ≦ y1 ≦ 1, 0<z1 is less than or equal to 1, k is less than or equal to 0 and less than or equal to 1, q is less than or equal to 0 and less than or equal to 1, b is less than or equal to 1.5 and less than or equal to 2, and a is less than or equal to 0 and less than or equal to 0.5.
According to some embodiments of the present application, the lithium transition metal phosphate compound comprises Lix2Ry2Qz2PO4Wherein R comprises at least one of Fe or Mn; q comprises at least one of Al, Ti, V, Cr, Co, Ni, Cu, Zn, Mg, Ga, Zr, Nb and Si; wherein x2 is more than or equal to 0.6 and less than or equal to 1.2, y2 is more than or equal to 0.95 and less than or equal to 1, and z2 is more than or equal to 0 and less than or equal to 0.05.
According to some embodiments of the present application, the current collector may employ a metal foil or a composite current collector. For example, aluminum foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, or the like) on a polymer base material.
Two, electrochemical device
The electrochemical device of the present application includes any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, an electrochemical device of the present application includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.
1. Positive pole piece
The positive electrode plate in the electrochemical device of the present application is the positive electrode plate described in the first aspect.
2. Negative pole piece
The materials, compositions, and methods of making the negative electrode sheets used in the electrochemical devices of the present application can include any of the techniques disclosed in the prior art.
According to some embodiments of the present application, the negative electrode tab includes a negative electrode current collector and a negative active material layer disposed on at least one surface of the negative electrode current collector. According to some embodiments of the present application, the negative active material layer includes a negative active material, and the negative active material may include a material capable of reversibly intercalating/deintercalating lithium ions, a lithium metal alloy, a material capable of doping/dedoping lithium, or a transition metal oxide. According to some embodiments of the present application, the negative active material layer includes a binder, and the binder may include various binder polymers. According to some embodiments of the present application, the negative active material layer further includes a conductive material to improve electrode conductivity. Any conductive material may be used as the conductive material as long as it does not cause a chemical change.
3. Electrolyte solution
The electrolyte that may be used in the embodiments of the present application may be an electrolyte known in the art.
In some embodiments, the electrolyte includes an organic solvent, a lithium salt, and an additive. The organic solvent of the electrolyte according to the present application may be any organic solvent known in the art that can be used as a solvent of the electrolyte. In some embodiments, the organic solvent includes, but is not limited to: ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate.
The lithium salt according to the present application includes, but is not limited to: lithium hexafluorophosphate (LiPF)6) Lithium tetrafluoroborate (LiBF)4) Lithium difluorophosphate (LiPO)2F2) Lithium bis (trifluoromethanesulfonylimide) LiN (CF)3SO2)2(LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO)2F)2) (LiFSI), lithium bis (oxalato) borate LiB (C)2O4)2(LiBOB) or lithium difluorooxalato borate LiBF2(C2O4) (LiDFOB). In some embodiments, the concentration of lithium salt in the electrolyte is: about 0.5 to 3mol/L, about 0.5 to 2mol/L, or about 0.8 to 1.5 mol/L.
The additive of the electrolyte according to the present application may be any additive known in the art as an additive of electrolytes. According to some embodiments of the present application, the additive comprises a polynitrile compound containing at least two cyano groups, such as 1,2, 3-tris- (2-cyanoethoxy) propane, 1,3, 6-hexanetrinitrile, adiponitrile, or succinonitrile.
4. Diaphragm
The material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance or the like formed of a material stable to the electrolyte of the present application.
For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.
At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.
The inorganic layer includes inorganic particles selected from at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate, and a binder. The binder is at least one selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
The polymer layer comprises a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).
Electronic device
The present application further provides an electronic device comprising an electrochemical device according to the second aspect of the present application.
The electronic device of the present application is not particularly limited. In some embodiments, the electronic device of the present application includes, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a cellular phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a flashlight, a camera, a large household battery, a lithium ion capacitor, and the like.
The technical solution of the present application is exemplarily described below by specific embodiments:
1. preparation of lithium ion battery
Example 1
(1) Preparation of positive pole piece
Two kinds of sizing agents are prepared, and the sizing agent A is used as a base coating: the positive electrode material LiNi0.8Co0.1Mn0.1O2(average particle diameter: 10 μm), conductive oxide P42Antimony tin oxide of the/nm type (average particle diameter of 200nm, specific surface area of 29 m)2Per gram), carbon nano tube CNT, adhesive polyvinylidene fluoride (PVDF) according to the mass ratio of 96.9: 1.0: 0.1: 2, fully stirring and uniformly mixing in an N-methyl pyrrolidone solvent system; top coating B slurry: the positive electrode material LiNi0.8Co0.1Mn0.1O2(average particle diameter: 10 μm), conductive oxide P42Antimony tin oxide of the/nm type (average particle diameter of 200nm, specific surface area of 29 m)2Per gram), carbon nano tube CNT, adhesive polyvinylidene fluoride (PVDF) according to the mass ratio of 96.9: 0.5: 0.4: 2.2 fully stirring and mixing the mixture evenly in an N-methyl pyrrolidone solvent system.
Uniformly coating the slurry A on two sides of an aluminum foil of a positive current collector, drying at 110 ℃, and controlling the thickness of a coating layer to be 100 mu m by controlling the coating outlet of the slurry A; and uniformly coating the slurry B on two sides of the dried membrane, drying at 110 ℃, and controlling the thickness of the coating layer to be 100 mu m by controlling the coating outlet of the slurry B.
And (4) cold pressing, cutting and welding the lug to obtain the positive pole piece, wherein the thickness H of the membrane layer on the single surface of the positive current collector is 50 microns.
(2) Preparation of negative pole piece
Mixing artificial graphite serving as a negative electrode active material, a conductive agent Super P, a thickening agent sodium carboxymethyl cellulose (CMC) and Styrene Butadiene Rubber (SBR) serving as a binder according to the weight ratio of 96.4: 1.5: 0.5: 1.6, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer, wherein the solid content of the negative electrode slurry is 54 wt%; uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector; and then drying at 85 ℃, cold pressing, cutting and welding a tab to obtain the negative pole piece.
(3) Preparation of the electrolyte
Gloves under dry argon atmosphereIn the tank, Ethylene Carbonate (EC), Propylene Carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC: PC: DEC of 3: 4, followed by addition of lithium salt LiPF6And mixing uniformly to obtain the electrolyte. Wherein, LiPF6The concentration of (2) is 1 mol/L.
(4) Preparation of the separator
A Polyethylene (PE) film having a thickness of 7 μm was selected as the separator.
(5) Preparation of lithium ion battery
Stacking the positive pole piece, the diaphragm and the negative pole piece in sequence to enable the diaphragm to be positioned between the positive pole piece and the negative pole piece to play a role in isolation, and then winding to obtain a winding assembly; and (3) placing the winding assembly in an outer packaging aluminum-plastic film, injecting the prepared electrolyte, and performing vacuum packaging, standing, formation, shaping, capacity test and other procedures to obtain the lithium ion battery.
Example 2
The difference from example 1 is that: in the preparation of the positive pole piece, the conductive oxide is P63mc type zinc aluminum oxide (average particle diameter 100nm, specific surface area 40 m)2/g)。
Example 3
The difference from example 1 is that: in the preparation of the anode plate, the conductive oxide is indium tin oxide (with an average particle size of 50nm and a specific surface area of 50 m)2/g)。
Example 4 example 8
The difference from example 1 is that: conductive oxide P42The average grain sizes of the/nm type tin antimony oxide are different and are respectively 10nm, 50nm, 100nm, 500nm and 1000 nm.
Example 9-example 10
The difference from example 1 is that: conductive oxide P42The percentage of antimony tin oxide/mnm in the area of the membrane layer a1 varied, 2% and 4.5% respectively.
Example 11 example 12
The difference from example 1 is that: conductive oxide P42The percentage of antimony tin oxide/mnm in the area of the membrane layer a2 varied, 0% and 0.2% respectively.
Example 13 example 15
The difference from example 1 is that: the percentage of the carbon-based conductive agent in the area of the membrane layer a1 was varied and was 0%, 0.3%, and 0.4%, respectively.
Example 16-example 18
The difference from example 1 is that: the percentage of the carbon-based conductive agent in the area of the membrane layer a2 was varied and was 0.1%, 1%, and 1.4%, respectively.
Example 19 example 21
The difference from example 1 is that: the thickness H of the membrane layer is different and is respectively as follows: 10 μm, 100 μm, 200 μm.
Comparative example 1
The difference from example 1 is that: in the preparation of the positive pole piece, a positive pole material (LiNi)0.8Co0.1Mn0.1O2) The conductive agent SuperP, the carbon nano tube CNT and the binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97: 0.5: 0.5: 2, fully stirring and uniformly mixing in an N-methyl pyrrolidone solvent system, and coating on two surfaces of an aluminum foil of the positive current collector.
2. Test method
(1) Specific discharge capacity test
And (3) placing the lithium ion battery in a constant temperature box at 25 ℃, and standing for 5 minutes to keep the temperature of the lithium ion battery constant. Charging the lithium ion battery reaching the constant temperature to 4.25V at a constant current of 0.2C, then charging the lithium ion battery at a constant voltage of 4.25V until the current is 0.025C, and standing for 5 minutes; then, the discharge was performed at a constant current of 0.2C until the voltage became 2.8V, and the discharge capacity at 1 st time was obtained by leaving the cell to stand for 3 minutes.
Specific discharge capacity (mAh/g) 1 st discharge capacity/quality of positive electrode material
(2) High temperature storage Performance test
Charging the lithium ion battery to 4.25V at a constant current of 0.7C at 25 ℃, charging the lithium ion battery to a constant voltage of 0.05C at 4.25V, testing by a micrometer, and recording the thickness of the battery as H11; the cells were fully stored at 85 ℃ for 24 hours and after 24 hours the thickness of the cells was measured and recorded with a micrometer and recorded as H12.
Thickness expansion ratio (H12-H11)/H11X 100%
(3) XRD test
And placing the sample in a sample groove to keep the surface flat, placing the sample in a sample table of an XRD testing instrument, and obtaining an XRD spectrum by using a scanning speed of 2 degrees/min and a scanning angle range of 10 degrees to 80 degrees.
3. Test results
Table 1 shows the effect of conductive oxide species on the specific discharge capacity and 24h thickness expansion rate at 85 ℃ storage of lithium ion batteries.
Table 2 shows the effect of the average particle size of the conductive oxide on the specific discharge capacity and the 24h thickness expansion rate at 85 ℃ storage of the lithium ion battery.
Table 3 shows the effect of the mass percent a of the conductive oxide in the first membrane region a1 on the specific discharge capacity and 24h thickness expansion rate at 85 ℃ storage of the lithium ion battery.
Table 4 shows the effect of the mass percentage b of the conductive oxide in the second membrane region a2 on the specific discharge capacity and 24h thickness expansion rate at 85 ℃ storage of the lithium ion battery.
Table 5 shows the effect of the mass percentage content c1 of the carbon-based conductive agent in the first membrane area a1 on the specific discharge capacity and the 24-hour thickness expansion rate in 85 ℃.
Table 6 shows the effect of the mass percentage content c2 of the carbon-based conductive agent in the second membrane region a2 on the specific discharge capacity and the 24-hour thickness expansion rate in 85 ℃.
The effect of the membrane layer thickness H on the specific discharge capacity and the 24H thickness expansion rate at 85 ℃ storage of the lithium ion battery is shown in table 7.
The thickness of the membrane layer is H, the area within H/2 of the surface of the current collector along the thickness direction is a first membrane area A1, and the area within H/2 of the surface of the membrane layer along the thickness direction is a second membrane area A2.
TABLE 1
Figure BDA0002994432380000121
As can be seen from the data in table 1, the use of the conductive oxide instead of the carbon-based conductive agent in the film layer can reduce the oxidation and gassing of the carbon-based conductive agent at high voltage, thereby reducing the thickness expansion rate of high-temperature storage, and can improve the stability of the conductive network at high voltage, thereby improving the capacity performance.
TABLE 2
Figure BDA0002994432380000131
As can be seen from the data in table 2, as the average particle size of the conductive oxide decreases, the capacity increases and then decreases, and the high-temperature storage improvement effect increases and then decreases, because the particle size of the conductive oxide is too small to be uniformly dispersed, which results in deterioration of the conductive network, and the specific surface area of the conductive oxide increases, and the side reactions occurring on the surface increase.
TABLE 3
Figure BDA0002994432380000132
As can be seen from the data in table 3, as the percentage a of the oxide conductive agent in the a1 region increases, capacity improvement and high-temperature storage gassing improvement effect decrease.
TABLE 4
Figure BDA0002994432380000141
As can be seen from the data in table 4, as the percentage b of the oxide conductive agent in the a2 region increases, capacity improvement and high-temperature storage gassing improvement effect decrease.
TABLE 5
Figure BDA0002994432380000142
As can be seen from the data in table 5, as the percentage of the conductive carbon in the a1 region, c1, increases, an increase in capacity is exhibited, and the improvement effect of the high-temperature storage gassing decreases.
TABLE 6
Figure BDA0002994432380000143
As can be seen from the data in table 6, as the percentage of the conductive carbon in the a2 region, c2, increases, the capacity improvement is exhibited, and the high temperature storage gas evolution does not change much.
TABLE 7
Figure BDA0002994432380000151
As can be seen from the data in table 7, as the film layer thickness H is decreased, an increase in capacity can be exhibited and high temperature storage is improved.

Claims (10)

1. A positive pole piece comprises a current collector and a membrane layer arranged on the surface of the current collector, wherein the membrane layer comprises a conductive agent, the conductive agent comprises a conductive oxide, the thickness of the membrane layer is H, and the mass percentage of the conductive oxide is a based on the mass of a first membrane area A1 in a first membrane area A1 from the surface, adjacent to the current collector, of the membrane layer to a position H/2 away from the surface, adjacent to the current collector, of the membrane layer along the thickness direction of the membrane layer; in a second membrane area A2 from the surface of the membrane layer far away from the current collector to the position H/2 away from the surface of the membrane layer far away from the current collector along the thickness direction of the membrane layer, based on the mass of the second membrane area A2, the mass percentage content of the conductive oxide is b, and the following conditions are met: a > b.
2. The positive electrode plate according to claim 1, wherein a is not less than 0.3%.
3. The positive electrode sheet according to claim 1, wherein the conductive oxygenThe compound comprises a compound having P42Conductive oxide of/mnm structure or having P63At least one of the conductive oxides of mc structure.
4. The positive electrode sheet according to claim 3, wherein the sheet has a P42The XRD pattern of the conductive oxide with the structure of/mnm has diffraction peaks in at least one of the following ranges: 25-27 degrees, 32.5-34.5 degrees and 50.5-52.5 degrees; said has P63The XRD pattern of the mc-structured conductive oxide has diffraction peaks in at least one of the following ranges: 31 degrees to 32 degrees, 33.5 degrees to 34.5 degrees and 35.5 degrees to 36.5 degrees.
5. The positive electrode sheet according to claim 1, wherein the conductive oxide has at least one of the following characteristics a) to e):
a) the average particle size Dv50 of the conductive oxide is less than or equal to 1 μm;
b) the powder conductivity of the conductive oxide is more than or equal to 1 x 106μS/cm；
c) The specific surface area of the conductive oxide is more than or equal to 20m2/g；
d) The conductive oxide comprises at least one of tin, antimony, indium, zinc, aluminum, zirconium, platinum, palladium and chromium elements;
e) the conductive oxide comprises at least one of tin antimony oxide, indium tin oxide and zinc aluminum oxide.
6. The positive electrode sheet according to claim 1, wherein the conductive agent further comprises a carbon-based conductive agent, and the mass percentage of the carbon-based conductive agent in the a1 is c1 based on the mass of the first membrane region a 1; the mass percentage of the carbon-based conductive agent in the a2 based on the mass of the second membrane region a2 is c 2; satisfies the following conditions: c1< c 2.
7. The positive electrode plate of claim 6, wherein c1 is 0.5% or less and/or c2 is 1.5% or less.
8. The positive electrode sheet of claim 1, wherein the membrane layer further comprises a positive electrode material and a binder, the positive electrode material comprising at least one of a lithium transition metal composite oxide or a lithium transition metal phosphate compound.
9. An electrochemical device comprising the positive electrode sheet as set forth in any one of claims 1 to 8.
10. An electronic device comprising the electrochemical device as claimed in claim 9.
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CN110854387A (en) * 2019-11-04 2020-02-28 宁德新能源科技有限公司 Positive electrode, and electrochemical device and electronic device comprising same
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CN105742637A (en) * 2014-12-12 2016-07-06 苏州宝时得电动工具有限公司 Positive material and battery containing same
CN111200109A (en) * 2018-11-16 2020-05-26 宁德时代新能源科技股份有限公司 Battery with a battery cell
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