CN112542571A - Novel lithium ion battery positive pole piece and preparation method and application thereof - Google Patents

Novel lithium ion battery positive pole piece and preparation method and application thereof Download PDF

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CN112542571A
CN112542571A CN201910900995.XA CN201910900995A CN112542571A CN 112542571 A CN112542571 A CN 112542571A CN 201910900995 A CN201910900995 A CN 201910900995A CN 112542571 A CN112542571 A CN 112542571A
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active material
material layer
lithium
pole piece
positive pole
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曾家江
李素丽
李俊义
徐延铭
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Zhuhai Cosmx Battery Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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

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  • Chemical Kinetics & Catalysis (AREA)
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  • Materials Engineering (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The invention provides a novel lithium ion battery positive pole piece and a preparation method and application thereof, wherein the positive pole piece comprises a positive current collector layer, a first active material layer and a second active material layer; wherein the first active material layer includes a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent, and a binder; the second active material layer includes a lithium composite metal oxide active material, a conductive agent, and a binder. By using the novel structure design of the two-layer coating pole piece, the pole piece has higher ionic conductivity and electronic conductivity than the pole piece with the conventional one-layer coating structure; the lithium ion battery can be applied to a lithium ion battery system, the surface resistance of the positive pole piece can be effectively improved, the internal resistance of the battery is reduced, and the lithium ion battery obtained by assembling the novel positive pole piece can obviously improve the low-temperature discharge performance of the battery, reduce EIS impedance, and improve the rate capability and the cycle performance.

Description

Novel lithium ion battery positive pole piece and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a novel lithium ion battery positive pole piece, a preparation method thereof and application thereof in a lithium ion battery.
Background
Power batteries and high voltage digital batteries are currently rapidly developing and widely used in the 3C consumer digital field such as mobile phones, notebook computers, tablet computers, bluetooth small batteries and the like and in the electric vehicle field. Lithium ion batteries are increasingly demanding in terms of performance, whether in the digital or power domain. In recent years, the volume energy density development of the digital lithium ion battery is fast reaching the limit of materials, which directly limits the application of the lithium ion battery in the field of high-voltage digital batteries, and the mass energy density requirement of the power lithium ion battery is very high.
In order to obtain higher volume or mass energy density, the pole piece surface density of the positive and negative active materials is designed to be higher, and the requirement on the compaction density of the positive and negative pole pieces is higher; however, in both cases, the electrolyte is difficult to absorb, the cycle performance is poor, the positive and negative active materials cannot be fully utilized, the gram-capacity performance efficiency is low, the first charging efficiency is reduced, the diffusion of the electrolyte from the liquid phase to the inside of the positive electrode plate is difficult, and particularly, the diffusion of the electrolyte from the liquid phase to particles inside the positive electrode plate through the solid-liquid interface between the positive electrode plate and the electrolyte at low temperature is more difficult, so the discharge polarization at low temperature is large, and the performance is poor.
In order to improve the liquid absorption of the positive pole piece, the porosity of the pole piece is increased to improve the liquid absorption in the industry at present, which is an effective means; however, the improvement of the liquid absorption property also affects the energy density of the battery.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a lithium ion battery positive pole piece and a preparation method and application thereof, wherein the positive pole piece comprises a positive current collector layer, a first active material layer and a second active material layer; the first active material layer and the second active material layer are sequentially arranged on at least one side surface of the positive current collector layer; or the second active material layer and the first active material layer are sequentially arranged on at least one side surface of the positive current collector layer; the first active material layer includes a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent, and a binder; the second active material layer includes a lithium composite metal oxide active material, a conductive agent, and a binder. The positive pole piece with the structure, especially the positive pole piece with the total coating thickness of 160-210 mu m, can solve the problem that the diffusion of electrolyte from a liquid phase to particles in the positive pole piece is slow through a solid-liquid interface of the positive pole piece and the electrolyte at low temperature, and can reduce the internal polarization resistance of the lithium ion battery discharging at low temperature, namely improve the polarization problem of the positive pole piece in the application process. The high conductivity of the conductive agent and the high ionic conductivity of the fast ionic conductor material are utilized, and the two-layer coating technology is used, so that the electronic conductivity and the ionic conductivity of the positive pole piece are improved, and the low-temperature discharge performance, the multiplying power performance and the cycle performance of the lithium ion battery can be effectively improved while the energy density is ensured.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention provides a lithium ion battery positive pole piece, wherein the positive pole piece comprises a positive current collector layer, a first active material layer and a second active material layer;
the first active material layer and the second active material layer are sequentially arranged on at least one side surface of the positive current collector layer; or the second active material layer and the first active material layer are sequentially arranged on at least one side surface of the positive current collector layer;
wherein the first active material layer includes a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent, and a binder; the second active material layer includes a lithium composite metal oxide active material, a conductive agent, and a binder.
According to the invention, the thickness of the first active substance layer is <70 μm, preferably 30-50 μm, for example 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 60 μm, 70 μm.
According to the invention, the thickness of the second active substance layer is <70 μm, preferably 30-50 μm, for example 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 60 μm, 70 μm.
According to the present invention, in the first active material layer, the mass of the lithium composite metal oxide active material accounts for 90 to 99 wt%, preferably 90 to 95 wt%, for example, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt% of the total mass of the first active material layer; the mass of the fast ion conductor material is 1 to 10 wt%, preferably 1 to 5 wt%, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt% of the total mass of the first active material layer.
According to the present invention, the mass ratio of the conductive agent to the binder in the first active material layer is 1.0 to 3.0: 1.0.
According to the present invention, the mass of the lithium composite metal oxide active material in the second active material layer accounts for 90 to 99 wt%, preferably 94 to 98 wt%, for example, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt% of the total mass of the second active material layer; the mass of the conductive agent is 1 to 4 wt%, preferably 2 to 3 wt%, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt% of the total mass of the second active material layer; the mass of the binder accounts for 1 to 4 wt%, preferably 2 to 3 wt%, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt% of the total mass of the second active material layer.
The invention provides a preparation method of the lithium ion battery positive pole piece, which comprises the following steps:
(1) mixing a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent and a binder to prepare slurry, and coating the slurry on the surface of a positive current collector to prepare a coated positive pole piece containing a first active material layer;
mixing a lithium composite metal oxide active material, a conductive agent and a binder to prepare slurry, coating the slurry on the surface of a first active material layer, and preparing a coating positive pole piece containing a second active material layer and the first active material layer; or,
(1') mixing a lithium composite metal oxide active material, a conductive agent and a binder to prepare slurry, and coating the slurry on the surface of a positive current collector to prepare a coated positive pole piece containing a second active material layer;
mixing a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent and a binder to prepare slurry, and coating the slurry on the surface of a second active material layer to prepare a coating positive pole piece containing a first active material layer and a second active material layer;
(2) and (3) rolling the coated positive pole piece obtained in the step (1) or the step (1') to obtain a rolled positive pole piece.
According to the invention, the coating can be, for example, extrusion coating, spraying, or the like.
According to the invention, the positive current collector is selected from aluminium foil. The thickness of the positive current collector layer is 8-12 μm.
According to the invention, the conductive agent is selected from one or more of carbon black, acetylene black, carbon nanotubes (such as single-walled carbon nanotubes and multi-walled carbon nanotubes), nanofibers and graphene, and is preferably graphene.
According to the invention, the binder is chosen from the binders commonly used in the art, such as HSV900, 5130 binders, PVDF, and the like, as known in the art.
According to the present invention, the lithium composite metal oxide active material may be lithium cobaltate having a chemical formula of LicCo1-a-bMaNbO2(ii) a C is more than or equal to 0.95 and less than or equal to 1.05, a is more than or equal to 0 and less than or equal to 0.1, B is more than or equal to 0 and less than or equal to 0.1, the M, N elements can be the same or different and are at least independently selected from one or more of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, B and F elements; the lithium composite metal oxide active material may be lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminate,of the formula LiwNi1-x-y-zCoxMnyAzO2(ii) a Wherein w is more than or equal to 0.95 and less than or equal to 1.05, x is more than or equal to 0.05 and less than or equal to 0.3, Y is more than or equal to 0 and less than or equal to 0.3, z is more than or equal to 0 and less than or equal to 0.05, and the element A is selected from one or more of Al, Mg, Ti, Zr, Y, La, Sr, B and F.
According to the invention, the fast ion conductor material is selected from one or more of lithium titanium aluminum phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium aluminum germanium phosphate, boron trioxide doped lithium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum aluminum zirconium oxide, niobium doped lithium lanthanum zirconium oxide, tantalum doped lithium lanthanum zirconium oxide and niobium doped lithium lanthanum zirconium oxide.
According to the invention, the particle size D of the fast ion conductor material50Is 0.5 to 4 μm, preferably 0.6 to 1 μm.
According to the present invention, the particle diameter D of the lithium composite metal oxide active material50Is 3 to 18 μm, and illustratively, the particle diameter D of lithium cobaltate50D of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminate of 10-18 mu m50The particle size is 3-12 μm.
According to the invention, the surface density of the positive pole piece is 17-27mg/cm2The porosity of the positive pole piece is 14-30%, and the compaction density of the positive pole piece is 3.2-4.3g/cm3。
The invention provides a lithium ion battery which comprises the positive pole piece.
According to the invention, the lithium ion battery also comprises a negative pole piece, a diaphragm and electrolyte.
According to the invention, the negative electrode plate comprises a negative active material, and the negative active material comprises a graphite material and/or a silicon material.
According to the present invention, the separator is a separator known in the art, for example, a separator for a commercial lithium ion battery known in the art.
According to the present invention, the graphite material is at least one of artificial graphite, natural graphite, and the like.
According to the invention, the silicon material is, for example, Si, SiC and SiOx(0<x<2) One or more of (a).
According to the invention, the silicon material accounts for 0-20 wt% of the total mass of the graphite material and the silicon material, and the pure graphite material is preferably used as a negative electrode.
According to the present invention, the nonaqueous electrolytic solution is a conventional electrolytic solution known in the art, and the solvent contains ethylene carbonate (abbreviated as EC), diethyl carbonate (abbreviated as DEC), propylene carbonate (abbreviated as PC), fluoroethylene carbonate (abbreviated as FEC), and the like.
The invention provides a preparation method of the lithium ion battery, which comprises the step of assembling the positive electrode, the negative electrode, the non-aqueous electrolyte and the diaphragm into the lithium ion battery.
The invention has the beneficial effects that:
the invention provides a lithium ion battery positive pole piece and a preparation method and application thereof, wherein the positive pole piece comprises a positive current collector layer, a first active material layer and a second active material layer; the first active material layer and the second active material layer are sequentially arranged on at least one side surface of the positive current collector layer; or the second active material layer and the first active material layer are sequentially arranged on at least one side surface of the positive current collector layer; wherein the first active material layer includes a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent, and a binder; the second active material layer includes a lithium composite metal oxide active material, a conductive agent, and a binder. By using the novel structure design of the two-layer coating pole piece, the pole piece has higher ionic conductivity and electronic conductivity than the pole piece with the conventional one-layer coating structure; the lithium ion battery can be applied to a lithium ion battery system, the surface resistance of the positive pole piece can be effectively improved, the internal resistance of the battery is reduced, and the lithium ion battery obtained by assembling the novel positive pole piece can obviously improve the low-temperature discharge performance of the battery, reduce EIS impedance, and improve the rate capability and the cycle performance.
Drawings
FIG. 1 is a schematic view of the structure of a positive electrode plate according to the present invention; wherein 1 is a positive electrode current collector layer, 2 is a first active material layer, and 3 is a second active material layer.
Fig. 2 is a graph showing discharge retention at different rates of the batteries of example 1 and comparative example 3 according to the present invention.
Detailed Description
The preparation method of the present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Example 1:
the preparation method of the positive pole piece comprises the following steps: the method comprises the following steps of 3;
(1) mixing lithium cobaltate, titanium aluminum lithium phosphate (LATP) serving as a fast ion conductor material, PVDF and carbon nano tubes in a weight ratio of 94% to 3% to 2% to 1%, dispersing the mixture in NMP, and stirring by double planets to obtain positive slurry. Coating the slurry on the front side and the back side of an aluminum foil current collector with the thickness of 12 mu m, drying after coating, and coating the slurry on one side with the thickness of 40 mu m to obtain the positive pole piece coated with the first active substance layer.
(2) Mixing 96% to 1.5% to 0.5% to 2% of lithium cobaltate, carbon nano-tubes, conductive graphene and PVDF in weight ratio, dispersing the mixture in NMP, and stirring through double planets to obtain the anode slurry. And coating the slurry on the positive pole piece coated with the first active material layer, drying after coating, and coating the slurry on one side to obtain the positive pole piece coated with the second active material layer, wherein the thickness of the coating on one side is 40 mu m.
(3) Rolling the positive pole piece coated with the second active material layer, wherein the compaction density is 4.0g/cm3And rolling to obtain a positive pole piece, wherein the prepared positive pole piece has a structure as shown in figure 1, and a first active material layer 2 and a second active material layer 3 are respectively arranged on two sides of the surface of a positive current collector 1.
(4) The lithium ion battery is prepared and tested by the following steps:
similarly, a negative electrode active material, styrene diene rubber (SBR), sodium carboxymethylcellulose, and conductive carbon black were mixed in a weight ratio of 94% to 3% to 2% to 1%, and the mixture was dispersed in water and mixed by double planetary to obtain a negative electrode slurry. And coating the slurry on a copper current collector, and then rolling and drying to prepare a negative plate with a negative material for later use.
The nonaqueous electrolytic solution used is a conventional electrolytic solution known in the art, and the solvent contains ethylene carbonate (abbreviated as EC), diethyl carbonate (abbreviated as DEC), propylene carbonate (abbreviated as PC), fluoroethylene carbonate (abbreviated as FEC), and the like.
And then winding in a winding mode to obtain a winding core, packaging in an aluminum plastic bag, performing hot pressing to obtain a soft package battery core, and testing the capacity of the soft package battery core to be 2400 mAh.
The capacity retention rate of the soft package cell in each cycle is measured (test conditions are that under the conditions of 0.7C charging and 0.7C discharging, the charging and discharging temperature is 25 ℃, and the voltage range is 3.0-4.45V), the capacity retention rate of the soft package cell at-20 ℃ for 0.25C discharging (the ratio of the capacity of 0.25C discharging at the normal temperature of 25 ℃) is tested, the EIS curve of the soft package cell at the normal temperature of 50% SOC is tested, and the rate discharge capacity of the soft package cell at the normal temperature of 0.2C, 0.5C, 1.0C and 2.0C is tested (0.2C capacity is taken as 100% of initial comparative capacity retention rate).
Example 2:
the rest of the preparation method of the positive pole piece in the embodiment 2 is the same as the embodiment 1, except that the thickness of the coating in the step 1 is changed from 40 μm to 50 μm, and the thickness of the coating in the step 2 is changed from 40 μm to 30 μm; the lithium ion battery is prepared and the testing steps are the same.
Example 3:
the rest of the preparation method of the positive pole piece in the embodiment 3 is the same as that in the embodiment 1, except that the proportion of each component in the step 2 is from 90% to 5% to 3% to 2%; the lithium ion battery is prepared and the testing steps are the same.
Example 4:
the rest of the preparation method of the positive electrode plate in the embodiment 4 is the same as that in the embodiment 1, except that the graphene component in the step 1 is replaced by the single-walled carbon nanotube, and the component contents are the same; the lithium ion battery is prepared and the testing steps are the same.
Example 5:
the rest of the preparation method of the positive pole piece in the embodiment 5 is the same as that in the embodiment 1, except that the sequence of the step 1 and the step 2 is adjusted; the lithium ion battery is prepared and the testing steps are the same.
Comparative example 1:
the rest of the positive electrode sheet of comparative example 1 was prepared in the same manner as in example 1, except that step 1 was omitted, the positive electrode sheet was coated with only one layer, and the thickness of the coated layer was equal to the total thickness of the first active material layer and the second active material layer in example 1; the lithium ion battery is prepared and the testing steps are the same.
Comparative example 2:
the rest of the positive electrode sheet of comparative example 2 was prepared in the same manner as in example 1, except that step 2 was omitted, the positive electrode sheet was coated with only one layer, and the thickness of the coated layer was equal to the total thickness of the first active material layer and the second active material layer in example 1; the lithium ion battery is prepared and the testing steps are the same.
Comparative example 3:
the preparation method of the positive pole piece of the comparative example 3 comprises the following steps:
mixing 93 percent to 3 percent to 2 percent to 1.5 percent to 0.5 percent of lithium cobaltate, fast ion conductor lithium titanium aluminum phosphate (LATP), PVDF, carbon nano tubes and conductive graphene in weight ratio, dispersing the mixture in NMP, and stirring through double planets to obtain positive slurry. Coating the slurry on an aluminum foil current collector with the thickness of 12 mu m, drying after coating, wherein the thickness of the coated pole piece is equal to the total thickness of the first active material layer and the second active material layer in the example 1, and the obtained positive pole piece is rolled and has the compaction density of 4.0g/cm3And rolling to obtain the positive pole piece. The lithium ion battery was prepared and the test procedure was the same as in comparative example 1.
TABLE 1 results of Performance test of lithium ion batteries of examples 1 to 5 and comparative examples 1 to 3
Figure BDA0002211806390000091
As can be seen from Table 1, the internal resistance of the battery assembled by the positive pole piece with the three coating layers is greatly reduced, and the high-low temperature performance and the capacity retention rate are greatly improved. Specifically, the method comprises the following steps:
based on the example 1 and the comparative example 1, it can be seen that the introduction of the fast ion layer is beneficial to improving the electrical property of the battery and reducing the internal resistance, mainly because the fast ion material can effectively improve the overall lithium ion conductivity of the pole piece and improve the lithium ion migration rate.
Based on the example 1 and the comparative example 2, it can be seen that the surface resistance of the pole piece can be effectively improved by properly adding the conductive agent in the active material layer, the conductivity of the pole piece is improved, the internal resistance increase in the pole piece circulation process is improved, and the circulation performance and the rate performance are improved.
Based on example 1 and comparative example 3, it can be seen that the ionic conductance and electronic conductance of the pole piece can be effectively improved due to the difference of the design of different layer materials in the two-layer coating, thereby improving the cycle performance.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A positive pole piece of a lithium ion battery comprises a positive current collector layer, a first active material layer and a second active material layer;
the first active material layer and the second active material layer are sequentially arranged on at least one side surface of the positive current collector layer; or the second active material layer and the first active material layer are sequentially arranged on at least one side surface of the positive current collector layer;
wherein the first active material layer includes a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent, and a binder; the second active material layer includes a lithium composite metal oxide active material, a conductive agent, and a binder.
2. The positive electrode sheet according to claim 1, wherein the thickness of the first active material layer is <70 μ ι η, preferably 30-50 μ ι η;
preferably, the thickness of the second active material layer is <70 μm, preferably 30-50 μm.
3. The positive electrode sheet according to claim 1 or 2, wherein,
in the first active material layer, the mass of the lithium composite metal oxide active material accounts for 90-99 wt% of the total mass of the first active material layer; the mass of the fast ion conductor material accounts for 1-10 wt% of the total mass of the first active material layer;
in the first active material layer, the mass ratio of the conductive agent to the binder is 1.0-3.0: 1.0.
4. The positive electrode sheet according to any one of claims 1 to 3,
in the second active material layer, the mass of the lithium composite metal oxide active material accounts for 90-99 wt% of the total mass of the second active material layer; the mass of the conductive agent accounts for 1-4 wt% of the total mass of the second active material layer; the mass of the binder accounts for 2-3 wt% of the total mass of the second active material layer.
5. The positive electrode sheet according to any one of claims 1 to 4, wherein the lithium composite metal oxide active material may be lithium cobaltate having a chemical formula of LicCo1-a-bMaNbO2(ii) a C is more than or equal to 0.95 and less than or equal to 1.05, a is more than or equal to 0 and less than or equal to 0.1, B is more than or equal to 0 and less than or equal to 0.1, the M, N elements can be the same or different and are at least independently selected from one or more of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, B and F elements; the lithium composite metal oxide active material can be lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminate, and the chemical formula of the lithium composite metal oxide active material is LiwNi1-x-y-zCoxMnyAzO2(ii) a Wherein w is more than or equal to 0.95 and less than or equal to 1.05, x is more than or equal to 0.05 and less than or equal to 0.3, Y is more than or equal to 0 and less than or equal to 0.3, z is more than or equal to 0 and less than or equal to 0.05, and the element A is selected from one or more of Al, Mg, Ti, Zr, Y, La, Sr, B and F;
particle diameter D of the lithium composite metal oxide active material50Is 3 to 18 μm, and illustratively, the particle diameter D of lithium cobaltate50D of lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminate of 10-18 mu m50The particle size is 3-12 μm.
6. The positive electrode plate according to any one of claims 1 to 5, wherein the fast ion conductor material is selected from one or more of titanium aluminum lithium phosphate, lanthanum lithium titanate, lanthanum lithium tantalate, germanium aluminum lithium phosphate, boron trioxide doped lithium phosphate, lithium lanthanum zirconium oxygen, lanthanum zirconium aluminum lithium oxygen, niobium doped lithium lanthanum zirconium oxygen, tantalum doped lithium lanthanum zirconium oxygen, niobium doped lithium lanthanum zirconium oxygen;
the particle diameter D of the fast ion conductor material50Is 0.5 to 4 μm, preferably 0.6 to 1 μm.
7. The positive electrode plate according to any one of claims 1 to 6, wherein the areal density of the positive electrode plate is 17 to 27mg/cm2The porosity of the positive pole piece is 14-30%, and the compaction density of the positive pole piece is 3.2-4.3g/cm3。
8. The method for preparing the positive pole piece of the lithium ion battery of any one of claims 1 to 7, which comprises the following steps:
(1) mixing a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent and a binder to prepare slurry, and coating the slurry on the surface of a positive current collector to prepare a coated positive pole piece containing a first active material layer;
mixing a lithium composite metal oxide active material, a conductive agent and a binder to prepare slurry, coating the slurry on the surface of a first active material layer, and preparing a coating positive pole piece containing a second active material layer and the first active material layer; or,
(1') mixing a lithium composite metal oxide active material, a conductive agent and a binder to prepare slurry, and coating the slurry on the surface of a positive current collector to prepare a coated positive pole piece containing a second active material layer;
mixing a lithium composite metal oxide active material, a fast ion conductor material, a conductive agent and a binder to prepare slurry, and coating the slurry on the surface of a second active material layer to prepare a coating positive pole piece containing a first active material layer and a second active material layer;
(2) and (3) rolling the coated positive pole piece obtained in the step (1) or the step (1') to obtain a rolled positive pole piece.
9. A lithium ion battery comprising the positive electrode sheet of any one of claims 1 to 7.
10. The lithium ion battery of claim 9, wherein the lithium ion battery further comprises a negative electrode sheet, a separator, and an electrolyte.
CN201910900995.XA 2019-09-23 2019-09-23 Novel lithium ion battery positive pole piece and preparation method and application thereof Pending CN112542571A (en)

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