CN112928248A - Positive active material of lithium battery, preparation method and preparation method of lithium battery - Google Patents

Positive active material of lithium battery, preparation method and preparation method of lithium battery Download PDF

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Publication number
CN112928248A
CN112928248A CN202011285546.8A CN202011285546A CN112928248A CN 112928248 A CN112928248 A CN 112928248A CN 202011285546 A CN202011285546 A CN 202011285546A CN 112928248 A CN112928248 A CN 112928248A
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lithium
positive active
vanadium phosphate
lithium battery
additive
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俞晓峰
刘慧洁
杨淑娟
顾志华
宋帅
韩晓亚
李丹
高良秋
周宏�
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Fengfan 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M4/131—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
    • H01M4/36—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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • 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 positive active material of the lithium battery is a composite material of a ternary material and lithium vanadium phosphate, and comprises the following components in percentage by weight: 80-99.9% of ternary material, 0.1-20% of lithium vanadium phosphate, 0-1% of additive and 0-5% of conductive agent, wherein the additive accounts for 0-1% of the total amount of the ternary material and the lithium vanadium phosphate. According to the invention, the vanadium lithium phosphate is mixed and added into the layered ternary material, so that the rate discharge performance of the ternary material under low SOC (state of charge) is effectively improved, and the lithium battery prepared by using the positive active material has excellent power performance and wide high-power working SOC range.

Description

Positive active material of lithium battery, preparation method and preparation method of lithium battery
Technical Field
The invention relates to a positive active material of a high-power lithium battery, a preparation method and a preparation method of the lithium battery, and belongs to the technical field of batteries.
Background
The lithium ion battery as a secondary battery has the characteristics of high energy density, long cycle life, relatively low price, no memory effect and the like, and is widely applied to the fields of digital products, vehicle power batteries and energy storage.
Under the increasing double pressure of fossil energy and environmental protection all over the world, policy and regulation of various countries and regions put higher and higher requirements on automobile exhaust emission and oil consumption, so that the development of energy-saving and new energy automobiles becomes an important task and development direction of various host plants. Typical energy-saving and new energy vehicles are mainly classified into pure electric vehicles, plug-in hybrid vehicles and hybrid vehicles according to the types of vehicle driving sources. The electric automobile takes electric energy in a battery as energy, and the electric energy stored in the battery is converted into mechanical energy through a motor, so that the automobile is driven to run, and the concept of zero-pollution automobile running is achieved. Therefore, electric vehicles have been rapidly developed as a good solution to the problems of resource shortage, environmental pollution, and the like. The lithium ion battery is used as an electric energy storage unit of the electric automobile, and because the factors such as energy density, safety and cost cannot meet the requirements of the automobile on mileage, cost, safety and the like, the traditional automobile using fuel oil as a main power source is still the main choice for a long time. Therefore, in order to improve the exhaust emission and fuel consumption of fuel-powered vehicles, hybrid vehicles will become a better choice in recent times.
Hybrid vehicles are a good choice for energy-saving vehicles, and have been developed greatly because of their ability to reduce fuel consumption effectively. Hybrid systems have the following performance requirements for batteries: the lithium ion battery has the advantages of low-temperature instant starting capability, large-current high-power charging and discharging capability, wide temperature use range, wider SOC range meeting high-power charging and discharging requirements, long cycle life and the like, and the requirements provide greater performance challenges for materials, designs and the like of the conventional lithium ion battery. The ternary cathode material is used as one of the cathode materials of the lithium ion battery, has good performances in the aspects of energy density, power, circulation, safety and the like, and is widely applied to power batteries. Although the ternary material with the layered structure has good power and safety performance, the ternary material is found to have good power under high SOC in the application process, but in a low SOC interval, the power is sharply reduced due to the increase of the internal resistance of the ternary material, so that the power value fluctuation in the whole battery SOC range is large, and the high-power available SOC range is reduced. To address this problem, patent 201380031782.9 proposes to combine a ternary material with LiFePO4The (LFP) material is mixed and used in the slurry mixing process, so that the power performance of the ternary material battery at low SOC is improved. But due to the ternary material and LiFePO4The working voltage difference of the two materials is large, the situation that the working voltage in the mixed anode battery is changed rapidly exists, and the LFP is not easy to disperse due to the fact that the ternary material and the LFP are different in particle shape, large in specific surface area and the like in the mixed material in the slurry mixing process, so that the processing difficulty in the production process is increased.
Disclosure of Invention
The invention provides a positive active material of a high-power lithium battery, a preparation method and a lithium battery preparation method for overcoming the defects of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the positive active material of the lithium battery is a composite material of a ternary material and lithium vanadium phosphate, and comprises the following components in percentage by weight: 80-99.9% of ternary material, 0.1-20% of lithium vanadium phosphate, 0-1% of additive and 0-5% of conductive agent, and the sum of the weight ratios of the ternary material and the lithium vanadium phosphate is one hundred%.
According to the positive active substance of the lithium battery, the positive active substance is of a spherical core-shell composite structure, the ternary material is a core of a main material, and the lithium vanadium phosphate and the additive distributed in an island-shaped manner on the surface and the continuously distributed conductive agent are jointly formed into a shell.
The particle size D50 of the ternary material of the positive active material of the lithium battery is 2-20 mu m and comprises LiNi1/3Co1/ 3Mn1/3O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.6Co0.2Mn0.2O2One kind of (1).
In the positive active material of the lithium battery, the particle size D50 of the lithium vanadium phosphate is less than 200 nm.
In the positive active material of the lithium battery, the ratio of the particle size of the ternary material to the particle size of the lithium vanadium phosphate is 50: 1 or more.
The additive is Al2O3、Al(OH)3、TiO2MgO, MnO and ZrO2One or more of (a).
The conductive agent is one or more of conductive carbon black, acetylene black, ketjen black and graphene.
A preparation method of a positive active material of a lithium battery comprises a dry preparation method and a wet preparation method, wherein the dry preparation method comprises the following steps: adding 80-99.9% of ternary material, 0.1-20% of lithium vanadium phosphate and 0-1% of additive into a mechanical fusion machine, mixing for 30-60min, uniformly coating the lithium vanadium phosphate and the additive on the surface of the ternary material by external mechanical force, then adding 0-5% of conductive agent, continuing to start fusion and mixing for 30-90min to obtain a composite anode active substance of ternary/lithium vanadium phosphate/conductive agent/additive;
the wet preparation method comprises the following steps: a. adding 0-1% of additive into a stirrer, adding alcohol, controlling the solid content to be 10-50%, starting stirring and dispersing to obtain additive dispersion liquid; b. adding 80-99.9% of ternary material and 0.1-20% of lithium vanadium phosphate into a three-dimensional mixer, adding 30-100% of the additive dispersion liquid and alcohol, starting mixing for 10-60min, adding 0-5% of conductive agent, and mixing for 10-120 min; c. and after mixing, starting vacuum, keeping the vacuum degree at-0.1 MPa, heating at 50-70 ℃, and drying to obtain the composite cathode active substance with uniformly mixed ternary/lithium vanadium phosphate/conductive agent/additive.
In the dry method and the wet method, the ternary material, the lithium vanadium phosphate and the additive are mixed, and the island-shaped surface coating is easily formed on the surface of the ternary main material due to the large particle size of the lithium vanadium phosphate material. The conductive agent has small particles and large specific surface area, and can easily form uniform continuous distribution. The composite positive active substance structure comprises a core taking a ternary material as a main material, a shell formed by taking lithium vanadium phosphate and additives distributed in an island shape on the surface and a continuously distributed conductive agent as a common body, and the three materials form a core-shell structure of the composite material together.
A manufacturing method of a lithium battery is used for manufacturing the lithium battery by using the prepared positive electrode composite material, and comprises the following steps:
(1) premixing the prepared composite positive active substance and the conductive agent in a powerful mixer for 2-15min to obtain a premix, wherein the mass ratio of the composite positive active substance is 90-97%, and the mass ratio of the conductive agent is 1-5%;
(2) adding PVDF into an NMP solvent according to the proportion of 1-3%, stirring and dispersing to obtain PVDF glue solution with the solid content of 7%;
(3) adding the premix obtained in the step (1) into PVDF glue solution in a planetary mixer through a feeding port, controlling the revolution speed of the double planetary mixer to be 10-30 r/min, after the addition of the materials is finished, adjusting the revolution speed to be 25-35 r/min, adjusting the revolution speed of a dispersion disc to be 1500-2000 r/min, stirring for 30-90min, vacuumizing and continuously stirring for 60-150 min;
(4) testing the viscosity after stirring is finished, and obtaining the anode slurry after the viscosity is proper;
(5) coating the obtained anode slurry on an aluminum foil to obtain an anode plate;
(6) and assembling the positive plate and the corresponding negative plate, and then injecting, forming and grading to obtain the lithium ion battery.
The invention has the beneficial effects that:
the surface of the layered ternary material of the positive active substance is coated with the lithium vanadium phosphate, and the lithium vanadium phosphate material has higher lithium ion diffusion coefficient, so that the positive active substance has good power and low-temperature performance; the lithium vanadium phosphate improves the discharge internal resistance of the ternary material under low SOC, and improves the SOC range of the high-power use of the anode material; meanwhile, the higher working voltage (3.6/4.1V) of the lithium vanadium phosphate is closer to the discharge voltage platform of the ternary material, and the voltage sudden change caused by the larger difference of the voltage platform is avoided when the lithium vanadium phosphate is compounded with the ternary material; and the lithium vanadium phosphate material has more stable structure and better safety performance.
Drawings
Fig. 1 is a schematic view of the structure of a composite positive electrode active material particle of the present invention;
FIG. 2 is a comparative plot of internal DC resistance at different SOCs for the lithium ion batteries prepared in example 1 and comparative example 1;
FIG. 3 is a graph comparing HPPC discharge power at different SOCs for lithium ion batteries prepared in example 1 and comparative example 1;
fig. 4 is a graph of the charge-discharge cycle at 45C for the lithium ion battery prepared in example 1.
In the figure: 1. a continuously distributed conductive agent layer in the cladding layer; 2. additive and lithium vanadium phosphate material distributed in an island mode; 3. a ternary host material; the coordinate DCR represents the direct current internal resistance; SOC represents battery state of charge; power represents power; capacity ret represents capacity retention; cycle No represents the number of cycles.
Detailed Description
According to the invention, the island-type distributed lithium vanadium phosphate is coated on the surface of the layered ternary material of the positive active substance, and the lithium vanadium phosphate material has a high lithium ion diffusion coefficient, so that the positive active substance has good power and low-temperature performance; the lithium vanadium phosphate improves the discharge internal resistance of the ternary material under low SOC, and improves the SOC range of high-power use; meanwhile, the higher working voltage (3.6/4.1V) of the lithium vanadium phosphate is closer to the discharge voltage platform of the ternary material, and when the lithium vanadium phosphate is compounded with the ternary material for use, voltage mutation caused by larger difference of the voltage platform is avoided; and the lithium vanadium phosphate material has more stable structure and better safety performance.
The addition of the additive in the positive active substance reduces the side reaction of the ternary material and the electrolyte, and improves the service life and the storage performance of the ternary material. The electronic conductivity of the positive electrode composite material is further improved by the continuously distributed conductive agent, and the consumption of the conductive agent in the positive electrode slurry formula is reduced by the good dispersion effect of the conductive agent.
The ternary material is a polycrystal or monocrystal spherical particle with the particle size D50 of about 10 mu m conventionally, the lithium vanadium phosphate is power type lithium vanadium phosphate and is a nano-scale particle generally, the morphology and specific surface area of the ternary material and the lithium vanadium phosphate are greatly different, and compared with simple stirring and mixing in a conventional slurry mixing process, the slurry prepared by the lithium battery anode slurry mixing method is more uniform and has excellent performance; in addition, the invention carries out premixing of the anode active substance and the conductive agent in the material preparation stage, thereby effectively avoiding uneven mixing caused by inconsistent particle size and specific surface area of each material.
The present invention will be further described with reference to the following examples.
Example 1
Preparation of composite positive electrode active material:
according to the weight ratioLiNi with D50 particle size of 5 mu m0.5Co0.2Mn0.3O2(NCM 523) ternary material 90.0%, Lithium Vanadium Phosphate (LVP) material with D50 particle size of 50nm 10.0%, and Al 0.15% of the total weight of the active substances (NCM 523+ LVP)2O3Adding the materials into a mechanical fusion machine, starting mixing for 30min, then adding conductive carbon black super-P accounting for 0.5 percent of the total weight of the materials, starting equipment for dispersing and mixing for 30min, and taking out powder to obtain the composite positive active substance.
Preparing a lithium ion battery:
the prepared composite positive active material 94.5% and the conductive agent 2.5% are premixed in a strong mixer for 5min according to the weight percentage to obtain the premix.
Adding 3wt% of PVDF into an NMP solvent, and controlling the weight ratio of PVDF: NMP = 7: 93 stirring and dispersing to obtain PVDF glue solution.
Adding the premix into PVDF glue solution in a planetary mixer through a feeding port, regulating revolution speed to 20 rpm, regulating revolution speed to 30 rpm after adding the premix, regulating rotation speed of a dispersion disc to 1500 rpm, stirring for 60min, vacuumizing, continuously stirring for 90min, and regulating viscosity to 4000 +/-1000 mPa & s (solid content is 66.5%) to obtain the anode slurry. Coating the slurry on an aluminum foil according to the designed surface density to obtain a positive plate; and then assembling the lithium ion battery with a negative electrode, a diaphragm and the like, and performing liquid injection, formation and capacity grading to obtain the lithium ion battery.
Example 2
Preparation of composite positive electrode active material:
LiNi with D50 particle size of 4 mu m according to weight ratio1/3Co1/3Mn1/3O293.0% of (NCM111) ternary material, 7.0% of Lithium Vanadium Phosphate (LVP) material with D50 particle size of 50nm and 0.3% of TiO (titanium oxide) based on the total weight of the active substances (NCM 523+ LVP)2Adding the materials into a mechanical fusion machine, starting mixing for 30min, then adding conductive carbon black super-P accounting for 0.5 percent of the total weight of the materials, starting equipment for dispersing and mixing for 30min, and taking out powder to obtain the composite positive active substance.
Preparing a lithium ion battery:
and premixing 93% of the prepared composite positive electrode active substance and 4% of a conductive agent in a strong mixer for 5min according to the weight percentage to obtain a premix.
Adding 3wt% of PVDF into an NMP solvent, and controlling the weight ratio of PVDF: NMP = 7: 93 stirring and dispersing to obtain PVDF glue solution.
Adding the premix into PVDF glue solution in a planetary mixer through a feeding port, wherein the revolution speed is 25 r/min, after the addition of the premix is finished, adjusting the revolution speed to 30 r/min, adjusting the rotation speed of a dispersion disc to 2000 r/min, stirring for 60min, vacuumizing and continuously stirring for 90min, and adjusting the viscosity to 4000 +/-1000 mPa & s (the solid content is 66%) to obtain the anode slurry. Coating the slurry on an aluminum foil according to the designed surface density to obtain a positive plate; and then assembling the lithium ion battery with a negative electrode, a diaphragm and the like, and performing liquid injection, formation and capacity grading to obtain the lithium ion battery.
Comparative example 1
94 percent of NCM523 ternary material with the grain diameter of 5 mu m of D50 and P3 percent of conductive carbon black are premixed for 5min in an intensive mixer according to weight percentage to obtain the premix.
Adding 3wt% of PVDF into an NMP solvent, and controlling the weight ratio of PVDF: NMP = 7: 93 stirring and dispersing to obtain PVDF glue solution.
Adding the premix into PVDF glue solution in a planetary mixer through a feeding port, wherein the revolution speed is 25 r/min, after the addition of the premix is finished, adjusting the revolution speed to 30 r/min, adjusting the rotation speed of a dispersion disc to 2000 r/min, stirring for 60min, vacuumizing and continuously stirring for 90min, and adjusting the viscosity to 4000 +/-1000 mPa & s (the solid content is 68.0%) to obtain the anode slurry. Coating the slurry on an aluminum foil according to the designed surface density to obtain a positive plate; and then assembling the lithium ion battery with a negative electrode, a diaphragm and the like, and performing liquid injection, formation and capacity grading to obtain the lithium ion battery.
Comparative example 2
90.0% of NCM523 ternary material with the grain size of D50 being 5 mu m, 10.0% of LVP material with the grain size of D50 being 50nm and the components (NCM 523+ LVP) according to the weight percentage: carbon black = 94: 3, adding conductive carbon black super P, and premixing for 5min in a powerful mixer to obtain the premix.
Adding 3wt% of PVDF into an NMP solvent, and controlling the weight ratio of PVDF: NMP = 7: 93 stirring and dispersing to obtain PVDF glue solution.
Adding the premix into PVDF glue solution in a planetary mixer through a feeding port, wherein the revolution speed is 25 r/min, after the addition of the premix is finished, adjusting the revolution speed to 30 r/min, adjusting the rotation speed of a dispersion disc to 2000 r/min, stirring for 60min, vacuumizing and continuously stirring for 90min, and adjusting the viscosity to 4000 +/-1000 mPa & s (the solid content is 65.0%) to obtain the anode slurry. Coating the slurry on an aluminum foil according to the designed surface density to obtain a positive plate; and then assembling the lithium ion battery with a negative electrode, a diaphragm and the like, and performing liquid injection, formation and capacity grading to obtain the lithium ion battery.
Comparing the direct current internal resistances of the lithium ion battery prepared by the method of the present invention (example 1) and the lithium ion battery prepared by compounding without adding lithium vanadium phosphate to the positive electrode active material (comparative example 1) under different SOCs, referring to fig. 2, the difference of the discharging internal resistances of the two batteries is not significant under high SOC, but the direct current internal resistance of the comparative example 1 is 4.2m Ω under 20% SOC, which is significantly larger than the direct current internal resistance of the battery prepared by the example 1 of the present invention by 2.6m Ω, and the battery performance of the comparative example 1 under low SOC is inferior to the battery performance of the present invention under low SOC.
Comparing the HPPC power at different SOCs of the lithium ion battery (example 1) prepared by the method of the present invention with the HPPC power at different SOCs of the lithium battery (comparative example 1) prepared by compounding lithium vanadium phosphate without adding lithium vanadium phosphate to the positive electrode active material, referring to fig. 3, the power difference between the two batteries at high SOC is small, but at 20% SOC, the HPPC discharge power of the battery of example 1 is 770W, which is significantly higher than the discharge power of 480W of comparative example 1, and is more advantageous for high power use at 20% SOC. Compared with comparative example 1, the positive electrode material of the present invention can improve the SOC working range and has better power performance.
Comparing the charge and discharge stability at 45 ℃ of 2C cycles of the lithium ion battery prepared by the method (example 1) and the lithium ion battery prepared by compounding the positive active material without adding lithium vanadium phosphate (comparative example 1), referring to FIG. 4, the high temperature cycle life of the battery prepared by the positive active material compounded by the ternary material and the lithium vanadium phosphate is higher than that of the comparative example 1, and the high temperature cycle capacity retention rate is obviously better than that of the comparative example 1, which shows that the composite positive active material of the invention has better stability at high temperature.
Compared with the preparation process (comparative example 2) in which the ternary material and the lithium vanadium phosphate material are not compounded, the solid content (66.5%) of the cathode slurry in the embodiment 1 in the lithium battery preparation process is 1.5% higher than that (65.0%) of the cathode slurry in the comparative example 2, and the slurry processing performance in the coating process is better.

Claims (9)

1. A positive electrode active material for a lithium battery, characterized in that: the positive active substance is a composite material of a ternary material and lithium vanadium phosphate, and comprises the following components in percentage by weight: 80-99.9% of ternary material, 0.1-20% of lithium vanadium phosphate, 0-1% of additive and 0-5% of conductive agent, and the sum of the weight ratios of the ternary material and the lithium vanadium phosphate is one hundred%.
2. The positive active material for a lithium battery as claimed in claim 1, wherein: the positive active substance is of a spherical core-shell composite structure, the ternary material is a core of a main material, and the lithium vanadium phosphate and the additive distributed in an island shape on the surface and the continuously distributed conductive agent are jointly formed into a shell.
3. The positive active material for a lithium battery as claimed in claim 2, wherein: the particle size D50 of the ternary material is 2-20 μm and comprises LiNi1/3Co1/3Mn1/3O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.6Co0.2Mn0.2O2One kind of (1).
4. The positive active material for a lithium battery as claimed in claim 3, wherein: the particle size D50 of the lithium vanadium phosphate is less than 200 nm.
5. The positive active material for a lithium battery as claimed in claim 4, wherein: the ratio of the particle size of the ternary material to the particle size of the lithium vanadium phosphate is 50: 1 or more.
6. The positive active material for a lithium battery as claimed in claim 5, wherein: the additive is Al2O3、Al(OH)3、TiO2MgO, MnO and ZrO2One or more of (a).
7. The positive active material for a lithium battery as claimed in claim 6, wherein: the conductive agent is one or more of conductive carbon black, acetylene black, Ketjen black and graphene.
8. A method of preparing a positive active material for a lithium battery according to any one of claims 1 to 7, characterized in that: the preparation method comprises a dry preparation method and a wet preparation method, wherein the dry preparation method comprises the following steps: adding 80-99.9% of ternary material, 0.1-20% of lithium vanadium phosphate and 0-1% of additive into a mechanical fusion machine, mixing for 30-60min, then adding 0-5% of conductive agent, continuing to start fusion and mixing for 30-90min to obtain a composite positive active substance of ternary/lithium vanadium phosphate/conductive agent/additive;
the wet preparation method comprises the following steps: a. adding 0-1% of additive into a stirrer, adding alcohol, controlling the solid content to be 10-50%, starting stirring and dispersing to obtain additive dispersion liquid; b. adding 80-99.9% of ternary material and 0.1-20% of lithium vanadium phosphate into a three-dimensional mixer, adding 30-100% of the additive dispersion liquid and alcohol, starting mixing for 10-60min, adding 0-5% of conductive agent, and mixing for 10-120 min; c. and after mixing, starting vacuum, keeping the vacuum degree at-0.1 MPa, heating at 50-70 ℃, and drying to obtain the composite cathode active substance with uniformly mixed ternary/lithium vanadium phosphate/conductive agent/additive.
9. A manufacturing method of a lithium battery is characterized by comprising the following steps: a lithium battery fabricated using the composite positive active material prepared according to claim 8, the fabrication method comprising the steps of:
(1) premixing the prepared composite positive active substance and the conductive agent in a powerful mixer for 2-15min to obtain a premix, wherein the mass ratio of the positive composite material is 90-97%, and the mass ratio of the conductive agent is 1-5%;
(2) adding PVDF into an NMP solvent according to the proportion of 1-3wt%, stirring and dispersing to obtain a PVDF glue solution with the solid content of 7%;
(3) adding the premix obtained in the step (1) into PVDF glue solution in a planetary mixer through a feeding port, controlling the revolution speed of the double planetary mixer to be 10-30 r/min, after the addition of the materials is finished, adjusting the revolution speed to be 25-35 r/min, adjusting the revolution speed of a dispersion disc to be 1500-2000 r/min, stirring for 30-90min, vacuumizing and continuously stirring for 60-150 min;
(4) testing the viscosity after stirring is finished, and obtaining the anode slurry after the viscosity is proper;
(5) coating the obtained anode slurry on an aluminum foil to obtain an anode plate;
(6) and assembling the positive plate and the corresponding negative plate, and then injecting, forming and grading to obtain the lithium ion battery.
CN202011285546.8A 2020-11-17 2020-11-17 Positive active material of lithium battery, preparation method and preparation method of lithium battery Pending CN112928248A (en)

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CN105185974A (en) * 2015-07-15 2015-12-23 湖南杉杉能源科技股份有限公司 Cathode material for lithium ion batteries and preparation method thereof
CN107204428A (en) * 2017-06-16 2017-09-26 中南大学 A kind of method of phosphoric acid vanadium lithium coated lithium ion battery ternary material
CN107293727A (en) * 2017-07-24 2017-10-24 广州市云通磁电股份有限公司 A kind of positive electrode, lithium ion battery comprising the positive electrode and preparation method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104692352A (en) * 2013-12-05 2015-06-10 中国电子科技集团公司第十八研究所 Method for surface coating of lithium ion battery anode material with nanoscale iron phosphate
CN105185974A (en) * 2015-07-15 2015-12-23 湖南杉杉能源科技股份有限公司 Cathode material for lithium ion batteries and preparation method thereof
CN107204428A (en) * 2017-06-16 2017-09-26 中南大学 A kind of method of phosphoric acid vanadium lithium coated lithium ion battery ternary material
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Application publication date: 20210608