CN115020677A - Positive active material and preparation method thereof, positive pole piece and lithium ion battery - Google Patents

Positive active material and preparation method thereof, positive pole piece and lithium ion battery Download PDF

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CN115020677A
CN115020677A CN202210821289.8A CN202210821289A CN115020677A CN 115020677 A CN115020677 A CN 115020677A CN 202210821289 A CN202210821289 A CN 202210821289A CN 115020677 A CN115020677 A CN 115020677A
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lithium ion
positive electrode
active material
ion battery
electrode active
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袁长福
李�根
黄东海
王荟
吴承仁
李进
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GAC Aion New Energy Automobile Co Ltd
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GAC Aion New Energy Automobile 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

The application relates to the technical field of battery manufacturing, in particular to a positive active material and a preparation method thereof, a positive pole piece and a lithium ion battery. A method for preparing a positive electrode active material, comprising: reacting LiNi 0.5 Mn 1.5 O 4 Mixing the first material and the second material and then sintering; wherein the first material comprises LiFePO 4 And LiFe x Mn 1‑x PO 4 0 < x < 1; the second material comprises B 2 O 3 And H 3 BO 3 At least one of (1). The preparation method of the positive active material is beneficial to simultaneously improving the interface stability of the cathode and the anode of the lithium ion battery, and further beneficial to improving the cycle performance of the lithium ion battery.

Description

Positive active material and preparation method thereof, positive pole piece and lithium ion battery
Technical Field
The application relates to the technical field of battery manufacturing, in particular to a positive active material and a preparation method thereof, a positive pole piece and a lithium ion battery.
Background
Currently, the positive active materials of lithium ion batteries mainly include two types, lithium iron phosphate (LFP) and lithium nickel cobalt manganese oxide ternary (NCM). The LFP does not contain high-cost elements such as nickel and cobalt and the like, has the cost advantage compared with NCM, and has the characteristics of good safety and excellent cycle performance, but also has the obvious defects of poor low-temperature performance and low energy density. While the NCM material has high energy density and good low-temperature performance, the NCM material needs to adopt nickel or cobalt with higher proportion, has high cost and poor safety. Therefore, research and development of a cathode material with low cost, high energy density and high safety is a focus of industrial attention.
Material LiNi having spinel structure 0.5 Mn 1.5 O 4 The composite material has the advantages of high energy density, high thermal stability, electrochemical stability, high safety, low cost, excellent rate performance and the like. LiNi 0.5 Mn 1.5 O 4 The theoretical reversible capacity of the lithium ion battery is 147mAh/g, the actual reversible capacity can reach 135mAh/g, the voltage platform of the lithium ion battery is up to 4.7V, and the energy density of the prepared lithium ion battery can reach over 230 wh/kg.
However, the decomposition voltage of the conventional electrolyte is generally less than 4.5V, and it is difficult to withstand a high voltage of 4.7V, the electrolyte is easily decomposed by oxidation at the cathode interface, and a stable SEI film (solid electrolyte interface film) is difficult to form on the anode surface, so that LiNi is used 0.5 Mn 1.5 O 4 The lithium ion battery as the anode material is difficult to form a stable cathode-anode interface, so that the cycle performance of the lithium ion battery is difficult to meet the requirement, and LiNi 0.5 Mn 1.5 O 4 The application of (A) has limitation, and cannot be applied to industrial mass production.
Disclosure of Invention
The application aims to provide a positive active material, a preparation method thereof, a positive pole piece and a lithium ion battery, and aims to improve the existing LiNi adopted 0.5 Mn 1.5 O 4 The lithium ion battery as the anode material has the technical problem that a stable cathode-anode interface is difficult to form.
In a first aspect, the present application provides a method for preparing a positive electrode active material, comprising: reacting LiNi 0.5 Mn 1.5 O 4 Mixing the first material and the second material and then sintering; wherein the first material comprises LiFePO 4 And LiFe x Mn 1-x PO 4 0 < x < 1; the second material comprises B 2 O 3 And H 3 BO 3 At least one of (1).
This application is directed to the synthesis of a peptide by the passage of LiNi 0.5 Mn 1.5 O 4 Comprising LiFePO 4 And LiFe x Mn 1-x PO 4 (0 < x < 1) and a first material comprising B 2 O 3 And H 3 BO 3 The second material of at least one of the two materials is mixed and sintered, so that the first material and the second material can be coated on the LiNi 0.5 Mn 1.5 O 4 To effectively block LiNi 0.5 Mn 1.5 O 4 Contact with the electrolyte, inhibit the decomposition of the electrolyte at the interface of negative pole; and the lithium removal degree under a low potential can be effectively increased, so that the reduction degree of the anode potential is increased, and a stable SEI film is formed at the anode. Therefore, the preparation method of the cathode active material provided by the application is beneficial to simultaneously improving the cathode and anode interface stability of the lithium ion battery, is further beneficial to improving the cycle performance of the lithium ion battery, and greatly expands the LiNi 0.5 Mn 1.5 O 4 The range of application of (1).
In some embodiments of the first aspect of the present application, LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material is (85-98): (1.5-10): 0.5-5).
LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material is (85-98) to (1.5-10) to (0.5-5), which is beneficial to further improving the interface stability of the cathode and the anode of the lithium ion battery and further improving the cycle performance of the battery; the energy density of the lithium ion battery can be ensured.
Alternatively, LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material is (86-93), (5-9.5) and (2-4.5).
In some embodiments of the first aspect of the present application, the sintering temperature is 350-.
Under the sintering condition, the first material and the second material are favorably and uniformly and fully coated on the LiNi 0.5 Mn 1.5 O 4 Of the first and second materials to LiNi 0.5 Mn 1.5 O 4 Barrier effect with electrolyte.
Optionally, the sintering temperature is 450-600 ℃, and the sintering time is 4-6 h.
In some embodiments of the first aspect of the present application, LiFe x Mn 1-x PO 4 Is LiFe 0.24 Mn 0.76 PO 4 。
LiFe x Mn 1-x PO 4 Is LiFe 0.24 Mn 0.76 PO 4 And the method is favorable for further improving the cycle performance of the lithium ion battery.
In some embodiments of the first aspect of the present application, the step of mixing comprises: stirring at 10-100rpm for 2-10min, and stirring at 350-750rpm for 10-45 min.
LiNi 0.5 Mn 1.5 O 4 The first material and the second material are stirred for 2-10min at 10-100rpm, so that the first material and the second material can be preliminarily dispersed in a mixed system, and the method is favorable forAvoid the uneven dispersion of the mixed system in the macroscopic view. Stirring at 350- 0.5 Mn 1.5 O 4 So as to realize that the first material and the second material are fully and uniformly coated on the LiNi 0.5 Mn 1.5 O 4 Of (2) is provided.
In some embodiments of the first aspect of the present application, after sintering further comprises: crushing and screening the sintered product D 50 Is a crushed product of 5-13 μm.
In a second aspect, the present application provides a positive electrode active material, which is prepared by the method for preparing the positive electrode active material provided in the first aspect.
The cathode active material provided by the application is beneficial to simultaneously improving the interface stability of the cathode and the anode of the lithium ion battery, and further is beneficial to improving the cycle performance of the lithium ion battery.
In a third aspect, the present application provides a positive electrode sheet, including the positive electrode active material provided in the second aspect.
The positive pole piece provided by the application is beneficial to improving the stability of the cathode and anode interfaces of the lithium ion battery at the same time, and further is beneficial to improving the cycle performance of the lithium ion battery.
In a fourth aspect, the present application provides a lithium ion battery, which includes a separator, an electrolyte, a negative electrode plate, and the positive electrode plate provided in the third aspect. The electrolyte contains a film forming additive, and the reduction potential of the film forming additive is greater than or equal to 0.9V.
The electrolyte contains the film forming additive, so that the lithium removal degree of the anode material under a low potential platform can be further reduced, the potential of the anode is effectively reduced, the stability of an SEI film formed at the anode is further improved, and the cycle performance of the lithium ion battery is further improved.
The lithium ion battery provided by the application can improve the interface stability of the cathode and the anode of the lithium ion battery, and further improve the cycle performance of the lithium ion battery.
In some embodiments of the fourth aspect of the present disclosure, the film-forming additive comprises at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, propylene sulfite, lithium bis (oxalato) borate, and lithium difluorophosphate.
Optionally, the mass fraction of the film forming additive in the electrolyte is 1-10%.
Optionally, the film-forming additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate; the mass fraction of the film forming additive in the electrolyte is 2-5%.
Drawings
To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 shows a graph of cycle performance for the lithium ion batteries of examples 1-3 and comparative examples 1-3 provided herein.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The decomposition voltage of the current electrolyte is generally less than 4.5V, and the high voltage of 4.7V is difficult to resist, so that LiNi is adopted 0.5 Mn 1.5 O 4 The lithium ion battery as the anode material is difficult to form a stable cathode-anode interface, so that the cycle performance of the lithium ion battery is difficult to meet the requirement.
In order to solve the above problems, the present application provides a method for preparing a positive electrode active material, comprising: reacting LiNi 0.5 Mn 1.5 O 4 A first material andmixing the second material and sintering; wherein the first material comprises LiFePO 4 And LiFe x Mn 1-x PO 4 0 < x < 1; the second material comprises B 2 O 3 And H 3 BO 3 At least one of (1).
This application is directed to the synthesis of a peptide by the passage of LiNi 0.5 Mn 1.5 O 4 The first material and the second material are mixed and sintered, so that the first material and the second material can be coated on the LiNi 0.5 Mn 1.5 O 4 To effectively block LiNi 0.5 Mn 1.5 O 4 Contact with the electrolyte, inhibit the decomposition of the electrolyte at the interface of negative pole; and the lithium removal degree under a low potential can be effectively increased, so that the reduction degree of the anode potential is increased, and a stable SEI film is formed at the anode.
Therefore, the preparation method of the cathode active material provided by the application is beneficial to simultaneously improving the cathode and anode interface stability of the lithium ion battery, is further beneficial to improving the cycle performance of the lithium ion battery, and greatly expands the LiNi 0.5 Mn 1.5 O 4 The range of application of (1).
It is understood that in the present application, LiFePO can be used as the first material 4 And LiFe x Mn 1-x PO 4 (0 < x < 1), or only LiFePO can be selected 4 Or LiFe x Mn 1-x PO 4 (x is more than 0 and less than 1). The second material can be selected from B 2 O 3 And H 3 BO 3 Alternatively, only B may be used 2 O 3 Or H 3 BO 3 。
By way of illustration, LiFe x Mn 1-x PO 4 In the above, x may be 0.1, 0.2, 0.5, 0.7, or 0.9.
In the application, the first material and the second material are both in a nanometer scale, so that the first material and the second material can be effectively coated on LiNi 0.5 Mn 1.5 O 4 Of the surface of (a).
Illustratively, in the present application, LiNi 0.5 Mn 1.5 O 4 D of (A) 50 4-12 μm, D of the first material 50 Less than 1.2 μm, D of the second material 50 Less than 1.0 μm.
By way of illustration, LiFe x Mn 1-x PO 4 Is LiFe 0.24 Mn 0.76 PO 4 。
In the present application, LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material is (85-98): (1.5-10): 0.5-5).
LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material is (85-98) to (1.5-10) to (0.5-5), which is beneficial to further improving the interface stability of the cathode and the anode of the lithium ion battery and further improving the cycle performance of the battery; the energy density of the lithium ion battery can be ensured. If the content of the first material and the second material is too high, the energy density of the battery is adversely affected; if the content of the first material and the second material is too low, the stability of the cathode and anode interface of the lithium ion battery is not favorably improved.
As an example, LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material may be 85:10:5, 90:8:2, 92:5:3, or 98:1.5:0.5, etc.
Further, LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material is (86-93) to (5-9.5) to (2-4.5), and the lithium ion battery has better cathode and anode interface stability and better energy density.
In the present application, LiNi 0.5 Mn 1.5 O 4 The step of mixing the first material and the second material comprises the following steps: stirring at 10-100rpm for 2-10min, and stirring at 350-750rpm for 10-45 min.
LiNi 0.5 Mn 1.5 O 4 The first material and the second material are stirred at 10-100rpm for 2-10min, so that the first material and the second material with smaller granularity and lower content can be primarily dispersed in a mixed system, and the mixed system is favorably prevented from being dispersed unevenly macroscopically. Stirring at 350-750rpm for 10-45min to disperse the first material and the second material in the mixed systemThe material was further uniformly adhered to the large-particle LiNi 0.5 Mn 1.5 O 4 So as to realize that the first material and the second material are fully and uniformly coated on the LiNi 0.5 Mn 1.5 O 4 Of (2) is provided.
In order to ensure that the first material and the second material are uniformly and fully coated on the LiNi 0.5 Mn 1.5 O 4 To the first material and the second material, LiNi 0.5 Mn 1.5 O 4 And the barrier effect of the electrolyte, in the application, the sintering temperature is 350-900 ℃, and the sintering time is 2-10 h.
As an example, the temperature of sintering may be 350 ℃, 400 ℃, 450 ℃, 550 ℃, 600 ℃, 800 ℃, 900 ℃ or the like; the sintering time can be 2h, 3h, 5h, 7h or 10h, etc.
Furthermore, the sintering temperature is 450-600 ℃, the sintering time is 4-6h, so that the sintering effect is better, and the first material and the second material are more uniformly and fully coated on the LiNi 0.5 Mn 1.5 O 4 Of (2) is provided.
In the present application, the method of preparing the positive active material further includes: after sintering, the sintered product is crushed and screened D 50 Is a broken product of 5-13 mu m, is beneficial to the subsequent positive active material to better exert LiNi in the positive pole piece 0.5 Mn 1.5 O 4 The advantages of (1).
Illustratively, D of the crushed product obtained by crushing the sintered product and then screening 50 May be 5 μm, 7 μm, 10 μm or 13 μm, etc.
In the embodiment of the application, before the step of crushing the sintered product and the step of sieving, the method further comprises the step of demagnetizing the crushed product to remove magnetic foreign matters such as elemental iron.
It should be noted that in other possible implementations, the sintering may be performed without crushing, demagnetizing, or screening.
The application also provides a positive active material which is prepared by the preparation method of the positive active material.
The cathode active material provided by the application is beneficial to simultaneously improving the interface stability of the cathode and the anode of the lithium ion battery, and further is beneficial to improving the cycle performance of the lithium ion battery.
The application also provides a positive pole piece, which comprises the positive active material.
The positive pole piece provided by the application is beneficial to improving the stability of the cathode and anode interfaces of the lithium ion battery at the same time, and further is beneficial to improving the cycle performance of the lithium ion battery.
The application also provides a lithium ion battery, which comprises a diaphragm, electrolyte, a negative pole piece and the positive pole piece.
In the present application, the electrolyte contains a film-forming additive, the reduction potential (VS Li) of which + and/Li) is more than or equal to 0.9V, the lithium removal degree of the anode material under a low potential platform can be further reduced, so that the potential of the anode is effectively reduced, the stability of an SEI film formed at the anode is further improved, and the cycle performance of the lithium ion battery is further improved.
The mass fraction of the film forming additive in the electrolyte is 1-10%, so that the lithium removal degree of the anode material under a low potential platform can be effectively reduced, and the anode potential is further effectively reduced.
As an example, the mass fraction of the film forming additive in the electrolyte may be 1%, 2%, 5%, 7%, 10%, or the like.
In the present application, the film-forming additive having a reduction potential of 0.9V or more may be selected from the group consisting of Vinylene Carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), Propylene Sulfite (PS), lithium bis (LiBOB) oxalate, and lithium difluorophosphate (LiPO) 2 F 2 ) At least one of (1).
Further, the film forming additive having a reduction potential of 0.9V or more is selected from Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), and lithium difluorophosphate (LiPO) 2 F 2 ) Can further effectively realize the reduction of the anode material under a low potential platformThe degree of delithiation effectively lowers the anode potential.
The film forming additive having a reduction potential of 0.9V or more is selected from Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), and lithium difluorophosphate (LiPO) 2 F 2 ) At least one of them, the mass fraction of the film-forming additive in the electrolyte is 2-5%.
In other possible embodiments, the film-forming additive is not limited to the above-mentioned one, and may be any film-forming additive that satisfies a reduction potential of 0.9V or more.
The lithium ion battery provided by the application at least has the following advantages:
the lithium ion battery provided by the application can improve the interface stability of the cathode and the anode of the lithium ion battery, and further improve the cycle performance of the lithium ion battery (the cycle life of the lithium ion battery is prolonged from 300 weeks to over 1000 weeks, and the capacity retention rate is up to over 80%).
The characteristics and properties of the positive electrode active material, the preparation method thereof, the positive electrode sheet, and the lithium ion battery provided by the present application are further described in detail with reference to the embodiments below.
Example 1
The embodiment provides a lithium ion battery, which is prepared by the following method:
(1) 174.687kg of LiNi 0.5 Mn 1.5 O 4 17.469kg of nanoscale LiFePO 4 7.856kg of nanoscale B 2 O 3 Adding into 500L high speed mixer, stirring at 50rpm for 5min, and then at 600rpm for 25 min. Loading the uniformly mixed materials into mullite saggers with the size of 330mm multiplied by 100mm (L multiplied by W multiplied by H), loading 2.5kg of the mixed materials into each sagger, placing the saggers into a sintering furnace filled with dry air, sintering the saggers for 4 hours at the temperature of 450 ℃, removing magnetism after crushing, and screening to obtain D 50 The product was 10 μm, and a positive electrode active material was obtained.
(2) 8000g of the positive electrode active material obtained in the step (1), 83g of conductive carbon black (super-P), 83g of Carbon Nano Tube (CNT) and 166g of polyvinylidene fluoride (PVDF) are added into 3100mL of N-methyl pyrrolidone (NMP), and stirred and mixed uniformly by a vacuum stirrer to obtain positive electrode slurry.
And (3) uniformly coating the positive electrode slurry on two surfaces of a current collector of an aluminum foil (with the thickness of 13 mu m), and drying, cold pressing and die cutting to obtain the positive electrode piece.
(3) 5000g of graphite, 105g of conductive carbon black (super-P), 60g of sodium carboxymethylcellulose (CMC) and 211g of styrene butadiene rubber emulsion (containing 45% of SBR) are added into 5000mL of deionized water, and the mixture is stirred and mixed uniformly by a vacuum stirrer to obtain negative electrode slurry.
And (3) uniformly coating the negative electrode slurry on two surfaces of a copper foil (with the thickness of 8 mu m) current collector, and drying, cold pressing and die cutting to obtain the negative electrode plate.
(4) And (3) placing a diaphragm with the thickness of 12 micrometers between the positive pole piece obtained in the step (2) and the negative pole piece obtained in the step (3), preparing a naked battery cell in a lamination mode, manufacturing a packaging bag by using an aluminum plastic film composite material, placing the naked battery cell into the packaging bag, packaging to obtain a dry battery cell, baking the dry battery cell to remove water to ensure that the water content is lower than 250ppm, injecting electrolyte into the dry battery cell, wherein the injection coefficient is 2.7g/Ah, and then carrying out the procedures of sealing, standing, formation, degassing packaging, capacity grading and the like to obtain the soft package lithium ion battery with the capacity of about 1.6 Ah.
Wherein the electrolyte is LiPF solution 6 And a solvent; the solvent is selected from Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), Vinylene Carbonate (VC) and lithium difluorophosphate (LiPO) 2 F 2 ) Composition is carried out; ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), vinylene acid (VC), and lithium difluorophosphate (LiPO) 2 F 2 ) In a mass ratio of 30:65:3:2, LiPF 6 The concentration in the electrolyte was 1M.
Example 2
This embodiment provides a lithium ion battery, and the difference between this embodiment and embodiment 1 is the difference in step (1). Step (1) of example 2 is as follows:
189.125kg of LiNi 0.5 Mn 1.5 O 4 9.456kg of nanoscale LiFe 0.24 Mn 0.76 PO 4 2.519kg of nanoscale H 3 BO 3 Adding into 500L high speed mixer, stirring at 50rpm for 5min, and stirring at 600rpmAnd (5) 25 min. Loading the uniformly mixed materials into mullite saggers with the size of 330mm multiplied by 100mm (L multiplied by W multiplied by H), loading 2.5kg of the mixed materials into each sagger, placing the saggers into a sintering furnace filled with nitrogen, sintering the saggers for 4 hours at the temperature of 600 ℃, crushing, demagnetizing and screening to obtain D 50 The product was 10 μm, and a positive electrode active material was obtained.
Example 3
This example provides a lithium ion battery, and differs from example 1 in the quality of the raw material for preparing the positive electrode active material in step (1); in this example, LiNi 0.5 Mn 1.5 O 4 Has a mass of 189.125kg, LiFePO 4 Has a mass of 9.456kg, B 2 O 3 Mass of (1.418 kg).
Example 4
This example provides a lithium ion battery, and differs from example 1 in the quality of the raw material for preparing the positive electrode active material in step (1); in this example, LiNi 0.5 Mn 1.5 O 4 Has a mass of 160kg, LiFePO 4 Has a mass of 30kg, B 2 O 3 The mass of (2) is 10 kg.
Example 5
This example provides a lithium ion battery, and differs from example 1 in the difference in the sintering temperature in step (1); in this example, the sintering temperature was 300 ℃.
Example 6
This example provides a lithium ion battery, and the difference between this example and example 1 is that LiNi is used in step (1) 0.5 Mn 1.5 O 4 、LiFePO 4 And B 2 O 3 Different mixing steps; in this example, LiNi 0.5 Mn 1.5 O 4 、LiFePO 4 And B 2 O 3 Directly stirring at 600rpm for 30 min.
Comparative example 1
This example provides a lithium ion battery, and this comparative example differs from example 1 in that the raw material for preparing the positive electrode active material in step (1) is different; in this comparative example, the raw material of the positive electrode active material was 190.476kg of LiNi 0.5 Mn 1.5 O 4 And 9.524kg of nanoscale LiFePO 4 。
Comparative example 2
This example provides a lithium ion battery, and this comparative example differs from example 1 in that the raw material for preparing the positive electrode active material in step (1) is different; in this comparative example, the raw material of the positive electrode active material was 198.511kg of LiNi 0.5 Mn 1.5 O 4 And 1.489kg of nanoscale B 2 O 3 。
Comparative example 3
This example provides a lithium ion battery, and this comparative example differs from example 1 in the difference of the electrolyte in step (4); in this comparative example, the electrolyte was composed of solute LiPF 6 And a solvent; the solvent consists of Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC); the mass ratio of Ethylene Carbonate (EC) to Ethyl Methyl Carbonate (EMC) was 31.58:68.42, LiPF 6 The concentration in the electrolyte was 1M.
Examples of the experiments
The lithium ion batteries provided in examples 1 to 3 and comparative examples 1 to 3 were subjected to cycle performance tests, and the test results are shown in fig. 1; the lithium ion batteries provided in examples 1 to 6 and comparative examples 1 to 3 were subjected to cycle life and specific capacity tests of the positive electrode, and the test results are shown in table 1.
TABLE 1
Figure BDA0003744594110000121
Description of the drawings: the cycle life in table 1 means: the number of cycles at which the capacity of the lithium ion battery decays to 80%.
As can be seen from table 1 and fig. 1, the cycle life of the lithium ion batteries prepared in examples 1 to 6 is significantly longer than that of the lithium ion batteries prepared in comparative examples 1 to 3, which indicates that the preparation method of the positive electrode active material and the film-forming additive in the electrolyte of the lithium ion battery provided in the examples of the present application can effectively improve the cycle life of the lithium ion battery.
Lithium ion batteries prepared in examples 2 to 3 and examples 5 to 6The cycle life of the lithium ion batteries prepared in example 1 was slightly shorter than that of the lithium ion batteries prepared in example 1, indicating that the first material and the second material were selected and LiNi was used 0.5 Mn 1.5 O 4 The proportion of the first material to the second material, the sintering temperature and the stirring and mixing speed can all influence the cycle life of the lithium ion battery.
The cycle life of the lithium ion battery prepared in example 4 is higher than that of the lithium ion battery prepared in example 1, but the specific capacity of the lithium ion battery prepared in example 4 is much lower than that of the lithium ion battery prepared in example 1, which indicates that when the content of the first material and the second material is too high, the energy density of the battery is adversely affected.
In conclusion, the preparation method of the cathode active material provided by the application is beneficial to simultaneously improving the interface stability of the cathode and the anode of the lithium ion battery, and is further beneficial to improving the cycle performance of the lithium ion battery.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. A method for producing a positive electrode active material, comprising:
reacting LiNi 0.5 Mn 1.5 O 4 Mixing the first material and the second material and then sintering;
wherein the first material comprises LiFePO 4 And LiFe x Mn 1-x PO 4 0 < x < 1; the second material comprises B 2 O 3 And H 3 BO 3 At least one of (1).
2. The method for producing a positive electrode active material according to claim 1, comprising the LiNi 0.5 Mn 1.5 O 4 The first material and the second materialThe mass ratio of the materials is (85-98): (1.5-10): 0.5-5);
optionally, the LiNi 0.5 Mn 1.5 O 4 The mass ratio of the first material to the second material is (86-93): (5-9.5): 2-4.5).
3. The method for preparing a positive electrode active material according to claim 1, wherein the sintering temperature is 350-900 ℃, and the sintering time is 2-10 h;
optionally, the sintering temperature is 450-600 ℃, and the sintering time is 4-6 h.
4. The method for producing a positive electrode active material according to claim 1, wherein the LiFe is x Mn 1-x PO 4 Is LiFe 0.24 Mn 0.76 PO 4 。
5. The method for preparing a positive electrode active material according to claim 1, wherein the mixing step comprises: stirring at 10-100rpm for 2-10min, and then at 350-750rpm for 10-45 min.
6. The method for producing a positive electrode active material according to any one of claims 1 to 5, further comprising, after the sintering: crushing the sintered product and screening D 50 Is a crushed product of 5-13 μm.
7. A positive electrode active material, characterized in that it is produced by the method for producing a positive electrode active material according to any one of claims 1 to 6.
8. A positive electrode sheet, characterized in that a coating layer of the positive electrode sheet comprises the positive electrode active material according to claim 7.
9. A lithium ion battery comprising a separator, an electrolyte, a negative electrode sheet, and the positive electrode sheet of claim 8;
the electrolyte contains a film forming additive, and the reduction potential of the film forming additive is greater than or equal to 0.9V.
10. The lithium ion battery of claim 9, wherein the film forming additive comprises at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, propylene sulfite, lithium bis (oxalato) borate, and lithium difluorophosphate;
optionally, the mass fraction of the film forming additive in the electrolyte is 1-10%;
optionally, the film-forming additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate; the mass fraction of the film forming additive in the electrolyte is 2-5%.
CN202210821289.8A 2022-07-13 2022-07-13 Positive active material and preparation method thereof, positive pole piece and lithium ion battery Pending CN115020677A (en)

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CN107256979A (en) * 2017-06-22 2017-10-17 北京圣比和科技有限公司 A kind of 3V level lithium-ion-power cells and its preparation based on lithium titanate anode
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