CN116825995A - Composite coated positive electrode material and preparation method and application thereof - Google Patents

Composite coated positive electrode material and preparation method and application thereof Download PDF

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CN116825995A
CN116825995A CN202310800369.XA CN202310800369A CN116825995A CN 116825995 A CN116825995 A CN 116825995A CN 202310800369 A CN202310800369 A CN 202310800369A CN 116825995 A CN116825995 A CN 116825995A
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lithium
positive electrode
lithium cobaltate
electrode material
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马晓丽
芦佳雪
尚美
郭建
高秀玲
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Tianjin EV Energies Co Ltd
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    • B60—VEHICLES IN GENERAL
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    • H01M4/00—Electrodes
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • 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
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    • H01M4/00—Electrodes
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes

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Abstract

The invention provides a composite coated positive electrode material, a preparation method and application thereof, wherein the composite coated positive electrode material comprises lithium cobaltate and a composite coating layer coated on the surface of the lithium cobaltate, and the composite coating layer comprises ferric phosphate and scandium oxide; by selecting lithium cobaltate as a matrix material and selecting ferric phosphate and scandium oxide to be matched with the matrix material as a material of a composite coating layer, a compact coating layer is formed on the surface of the lithium cobaltate, so that side reaction caused by direct contact of the lithium cobaltate and electrolyte can be effectively prevented, and further, the structural stability of the composite coating anode material is improved, meanwhile, ferric phosphate in the composite coating layer can interact with polymer components in an SEI film to form an interface layer favorable for lithium ion transmission, and further, the interface transmissibility of the composite coating anode material is improved, so that a lithium ion battery comprising the composite coating anode material has higher discharge capacity and excellent cycle performance.

Description

Composite coated positive electrode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a composite coated positive electrode material, and a preparation method and application thereof.
Background
Layered lithium cobaltate is one of the most commonly used positive electrode materials of commercial lithium ion batteries, and has higher theoretical specific capacity and working voltage, so that the energy density is higher, but because of electrostatic repulsion existing between transition metals, when more than 50% of lithium ions are separated from the lithium cobaltate, the stability of the crystal structure is destroyed, and therefore, the actual specific capacity of the lithium cobaltate is only half of the theoretical specific capacity. At present, in order to improve the discharge specific capacity of a lithium cobaltate battery, on one hand, the charge cut-off voltage of the lithium cobaltate battery is gradually increased from 4.20V to 4.45V at the earliest commercialization, and even higher, but the higher charge cut-off voltage can cause irreversible phase change of the lithium cobaltate, so that the layered crystal structure of the lithium cobaltate battery is easy to collapse, release oxygen and dissolve cobalt, the cycle life of the battery is shortened, the safety is deteriorated and the like; on the other hand, a ternary material (LiNi) is formed by substituting a nickel element and a manganese element for part of cobalt element in lithium cobaltate 1-y-z Mn y Co z ) The structure can be more stable, and the capacity can be improved.
CN111540890a discloses a nickel cobalt lithium manganate ternary positive electrode material and a preparation method thereof. Wherein, the preparation method comprises the following steps: 1) Preparation of nickel cobalt lithium manganate ternary material carbonate precursor Ni by coprecipitation method x Co y Mn 1-x- y CO 3 Wherein x is more than or equal to 0.6 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 0.2, and 0 is more than or equal to 1-x-y is more than or equal to 0 and less than or equal to 0.22); 2) Mixing the carbonate precursor of the nickel cobalt lithium manganate ternary material prepared in the step 1), lithium salt and additives, sintering in an oxygen furnace, cooling, crushing and screening to obtain the single crystal nickel cobalt lithium manganate ternary positive electrode material of the lithium ion battery, wherein the positive electrode material prepared by the method is compared with the traditional secondary particle type positive electrode materialThe rolling mill has higher compaction density, can effectively avoid the phenomenon of ball cracking in the rolling process, improves the energy density and ensures the integrity of particles.
However, the ionic radii of lithium ions and nickel ions in the crystal lattice of the nickel cobalt lithium manganate ternary material are close, element mixing is easy to occur, and the reversibility of the material is reduced; and the nickel cobalt lithium manganate ternary material can be directly connected with electrolyte in the charge-discharge cycle process, so that transition metal ions are dissolved in the electrolyte and undergo side reaction, the cycle performance of the nickel cobalt lithium manganate ternary material is reduced, and the discharge capacity and the cycle performance of a lithium ion battery prepared from the nickel cobalt manganese ternary material can be improved.
Therefore, development of a composite coated positive electrode material with high discharge capacity and excellent cycle performance is a technical problem which needs to be solved in the field.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a composite coated positive electrode material, a preparation method and application thereof, wherein the composite coated positive electrode material is prepared by adopting ferric phosphate and scandium oxide to coat the surface of lithium cobaltate, so that the interface transmissibility of the composite coated positive electrode material is improved, and side reactions caused by direct contact of the lithium cobaltate and electrolyte can be effectively prevented, so that a lithium ion battery containing the composite coated positive electrode material has excellent cycle performance, rate capability and higher discharge specific capacity.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a composite coated positive electrode material, which comprises lithium cobaltate and a composite coating layer coated on the surface of the lithium cobaltate, wherein the material of the composite coating layer comprises ferric phosphate and scandium oxide.
The composite coated positive electrode material provided by the invention comprises lithium cobaltate, wherein the surface of the lithium cobaltate is uniformly coated with a compact composite coating layer formed by ferric phosphate and scandium oxide; on one hand, the ferric phosphate in the composite coating layer can interact with the polymer component in the SEI film to form an interface layer which is favorable for lithium ion transmission, so that the dynamic performance of the composite coated anode material is improved, the occurrence of electrode polarization reaction is reduced, and the discharge capacity and the multiplying power performance of the material are improved; on the other hand, scandium oxide and ferric phosphate are matched for composite coating, so that the structural stability of the composite coating is higher, side reactions caused by direct contact of electrode materials and electrolyte can be further avoided, and the cycle stability of the materials is improved.
In conclusion, the invention adopts the iron phosphate and scandium oxide to be matched and clad on the surface of lithium cobaltate, thereby greatly improving the first discharge specific capacity of the material and simultaneously ensuring the material to have excellent cycle stability.
Preferably, the lithium cobaltate has the chemical formula LiCo x M 1-x O 2 ；
Wherein 0.9.ltoreq.x.ltoreq.0.99 (e.g. 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97 or 0.98 etc.), M is selected from any one or a combination of at least two of B, mg, al, ca, ti, V, cr, mn, fe, ni, cu, zn, Y, zr, nb, mo, ru, sn, sb, te, ir or Bi.
As a preferable technical scheme of the invention, M and M are doped in the lithium cobaltate material, and can be used as a 'pillar' to stabilize the crystal structure of lithium cobaltate in a lithium removal state, inhibit the structural change of the lithium cobaltate in a high voltage state, improve the stability of the material in the high voltage state, adapt to the change of local interaction of lithium ions in the removal and intercalation processes, increase the interlayer spacing of a lithium ion layer by doping M, improve the diffusion rate of lithium ions in the crystal structure, and finally ensure that the lithium cobaltate material shows good structural stability, excellent long-cycle performance and excellent multiplying power performance.
Preferably, the M is selected from a combination of at least 5 of B, mg, al, ca, ti, V, cr, mn, fe, ni, cu, zn, Y, zr, nb, mo, ru, sn, sb, te, ir or Bi.
As the preferable technical scheme of the invention, the at least 5M elements are doped in the lithium cobaltate material, so that the crystal structure of the lithium cobaltate material can be further stabilized, the charge and discharge capacity of the lithium cobaltate material can be improved, and the obtained composite coated positive electrode material has ultrahigh long-cycle stability and excellent rate capability.
Preferably, the M is selected from the group consisting of Ni, cu, mg, mn and Ti.
As a preferable technical scheme of the invention, the stability and electrochemical performance of the composite coated cathode material can be better improved by selecting the 5 elements to be matched in a coordinated manner to dope the lithium cobaltate; wherein, ni, cu and Co are matched for charge compensation, effective capacity is provided, mg, mn and Ti are used for regulating and controlling the electronic structure of the initial material to improve the charge-discharge voltage of the material, and stabilizing the crystal structure of the frame in the process of releasing/embedding lithium ions.
Preferably, the lithium cobaltate has the chemical formula LiCo 0.95 Ni 0.01 Mn 0.01 Ti 0.005 Mg 0.005 Al 0.02 O 2 、LiCo 0.96 Ni 0.01 Mn 0.01 Ti 0.005 Mg 0.005 Al 0.01 O 2 Or LiCo 0.96 Ni 0.01 Mn 0.01 Y 0.005 Mg 0.005 Al 0.01 O 2 。
Preferably, the lithium cobaltate is obtained by co-sintering a cobalt source, a lithium source and an M source;
wherein M is selected from any one or a combination of at least two of B, mg, al, ca, ti, V, cr, mn, fe, ni, cu, zn, Y, zr, nb, mo, ru, sn, sb, te, ir and Bi.
Preferably, the cobalt source comprises tricobalt tetraoxide.
Preferably, the lithium source comprises lithium carbonate and/or lithium hydroxide.
Preferably, the M source comprises a sulfate of M and/or an oxide of M.
Preferably, the sintering temperature is 500 to 1200 ℃, for example 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃, etc., more preferably 800 to 1100 ℃.
Preferably, the sintering time is 4 to 20 hours, for example, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours, 15 hours, 17 hours, 19 hours, or the like, and more preferably 8 to 15 hours.
Preferably, the iron phosphate is 0.2 to 10% by mass, for example, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9% by mass, based on 100% by mass of the lithium cobaltate.
Preferably, the particle size of the iron phosphate is not higher than 500nm, for example 450nm, 400nm, 350nm, 300nm, 250nm, 200nm, 150nm or 100nm, etc.
As a preferable technical scheme of the invention, the particle size of the ferric phosphate is limited to be not higher than 500nm, so that the cycle performance and the discharge capacity of the composite coated positive electrode material can be better improved, and if the particle size of the ferric phosphate is too large, effective coating cannot be formed and lithium ion transmission can be blocked, so that the charge and discharge performance and the cycle performance of the finally obtained composite coated positive electrode material are affected.
Preferably, the iron phosphate is prepared by a process comprising: and mixing ferric salt and phosphate in an organic solvent, and reacting to obtain the ferric phosphate.
Preferably, the iron salt comprises any one or a combination of at least two of ferric chloride, ferric nitrate or ferric sulfate.
Preferably, the phosphate salt comprises sodium dihydrogen phosphate.
Preferably, the organic solvent comprises any one or a combination of at least two of ethanol, ethylene glycol, isopropanol, propylene glycol or glycerol.
Preferably, the temperature of the mixing is 30 to 80 ℃, e.g. 40 ℃, 50 ℃, 60 ℃, or 70 ℃, etc.
Preferably, the mixing time is 2 to 12 hours, for example 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or 11 hours, etc.
Preferably, the temperature of the reaction is 100 to 200 ℃, for example 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, etc.
Preferably, the reaction time is 2 to 15 hours, for example 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours or 14 hours, etc.
Preferably, the reaction further comprises a drying step after completion.
Preferably, the drying temperature is 60 to 100 ℃, for example 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, or the like.
Preferably, the drying time is 6 to 12 hours, for example 7 hours, 8 hours, 9 hours, 10 hours or 11 hours, etc.
Preferably, the scandium oxide is 0.2 to 8% by mass, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6% or 7% by mass, based on 100% by mass of the lithium cobaltate.
In a second aspect, the present invention provides a method for preparing the composite coated cathode material according to the first aspect, the method comprising: and mixing scandium source, ferric phosphate and lithium cobaltate in water, and drying and calcining to obtain the composite coated anode material.
Preferably, the scandium source comprises scandium nitrate.
Preferably, the temperature of the mixing is 30 to 80 ℃, for example 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, or the like.
Preferably, the mixing time is 3 to 8 hours, such as 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, or 7.5 hours, etc.
Preferably, the drying temperature is 80 to 120 ℃, for example 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, or the like.
Preferably, the drying time is 8 to 12 hours, for example 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours or 11.5 hours, etc.
Preferably, the temperature of the calcination is 200 to 1000 ℃, for example 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, or the like.
Preferably, the calcination time is 4 to 12 hours, for example 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or 11 hours, etc.
As a preferable technical scheme of the invention, the preparation method of the composite coated positive electrode material comprises the following steps:
(1) Dissolving a scandium source in deionized water to obtain 0.01-0.1 mol/L scandium source aqueous solution;
(2) And (3) adding ferric phosphate and lithium cobaltate into the scandium source water solution obtained in the step (1), and drying and calcining to obtain the composite coated positive electrode material.
In a third aspect, the present invention provides a lithium ion battery comprising a composite coated positive electrode material according to the first aspect.
In a fourth aspect, the invention provides an application of the lithium ion battery in a new energy automobile.
Compared with the prior art, the invention has the following beneficial effects:
the composite coated positive electrode material provided by the invention comprises lithium cobaltate and a composite coating layer coated on the surface of the lithium cobaltate, wherein the material of the composite coating layer comprises ferric phosphate and scandium oxide; by selecting lithium cobaltate as a matrix material and selecting ferric phosphate and scandium oxide to be matched with the matrix material as a material of a composite coating layer, a compact coating layer is formed on the lithium cobaltate, so that side reaction caused by direct contact of the lithium cobaltate and electrolyte can be effectively prevented, the structural stability of the composite coating anode material is further improved, meanwhile, the ferric phosphate in the composite coating layer can interact with polymer components in an SEI film to form an interface layer favorable for lithium ion transmission, and further the interface transmissibility of the composite coating anode material is improved, so that a lithium ion battery comprising the composite coating anode material has higher discharge capacity and excellent cycle performance.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Preparation example 1
A lithium cobalt oxide powder has a chemical formula of LiCo 0.95 Ni 0.01 Mn 0.01 Ti 0.005 Mg 0.005 Al 0.02 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 、Mn 2 O 3 、NiO、MgO、TiO 2 And Al 2 O 3 Mixing uniformly according to stoichiometric ratio, roasting for 9h in air atmosphere at 1050 ℃ to obtain theLithium cobaltate powder.
Preparation example 2
A lithium cobalt oxide powder has a chemical formula of LiCo 0.96 Ni 0.01 Mn 0.01 Ti 0.005 Mg 0.005 Al 0.01 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 、Mn 2 O 3 、NiO、MgO、TiO 2 And Al 2 O 3 Mixing evenly according to stoichiometric ratio, and roasting for 8 hours in an air atmosphere at 1100 ℃ to obtain the lithium cobaltate powder.
Preparation example 3
A lithium cobalt oxide powder has a chemical formula of LiCo 0.96 Ni 0.01 Mn 0.01 Y 0.005 Mg 0.005 Al 0.01 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 、Mn 2 O 3 、NiO、MgO、Y 3 O 2 And Al 2 O 3 Mixing evenly according to the stoichiometric ratio, and roasting for 15 hours in an air atmosphere at 950 ℃ to obtain the lithium cobaltate powder.
Preparation example 4
A lithium cobalt oxide powder has a chemical formula of LiCo 0.955 Ni 0.01 Mn 0.01 Ti 0.005 Al 0.02 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 、Mn 2 O 3 、NiO、TiO 2 And Al 2 O 3 Mixing evenly according to stoichiometric ratio, and roasting for 9 hours in air atmosphere at 1050 ℃ to obtain the lithium cobaltate powder.
Preparation example 5
A lithium cobalt oxide powder has a chemical formula of LiCo 0.955 Ni 0.01 Mn 0.01 Mg 0.005 Al 0.02 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 、Mn 2 O 3 NiO, mgO and Al 2 O 3 Mixing evenly according to stoichiometric ratio, and roasting for 9 hours in air atmosphere at 1050 ℃ to obtain the lithium cobaltate powder.
Preparation example 6
A lithium cobalt oxide powder has a chemical formula of LiCo 0.96 Ni 0.01 Mn 0.01 Al 0.02 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 、Mn 2 O 3 、NiO、MgO、TiO 2 And Al 2 O 3 Mixing evenly according to stoichiometric ratio, and roasting for 9 hours in air atmosphere at 1050 ℃ to obtain the lithium cobaltate powder.
Preparation example 7
A lithium cobalt oxide powder has a chemical formula of LiCo 0.98 Ni 0.01 Mn 0.01 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 、Mn 2 O 3 Mixing with NiO uniformly according to stoichiometric ratio, and roasting for 9 hours in air atmosphere at 1050 ℃ to obtain the lithium cobalt oxide powder.
Preparation example 8
A lithium cobalt oxide powder has a chemical formula of LiCo 0.99 Ni 0.01 O 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 、Li 2 CO 3 Mixing with NiO uniformly according to stoichiometric ratio, and roasting for 9 hours in air atmosphere at 1050 ℃ to obtain the lithium cobalt oxide powder.
Preparation example 9
A lithium cobalt oxide powder has a chemical formula of LiCoO 2 ；
The preparation method comprises the following steps: co is to be 3 O 4 And Li (lithium) 2 CO 3 Uniformly mixing according to stoichiometric ratio, and roasting for 9 hours in air atmosphere at 1050 ℃ to obtain the lithium cobaltate powder.
Preparation example 10
An iron phosphate powder having a particle size of about 200nm;
the preparation method comprises the following steps: adding 60mL of ethylene glycol solution into a 100mL beaker, placing the beaker into a constant temperature water bath at 45 ℃, adding 0.03mol of anhydrous ferric chloride under continuous stirring, dripping 3mL of 2mol/L sodium dihydrogen phosphate aqueous solution after the anhydrous ferric chloride is completely dissolved, stirring at a constant temperature of 40 ℃ for 2 hours, transferring the solution into a 100mL polytetrafluoroethylene-lined reaction kettle, reacting for 5 hours in a constant temperature oven at 120 ℃, naturally cooling the reaction kettle to room temperature after the reaction is completed, pouring out supernatant, transferring the precipitate into a centrifuge tube for centrifugal separation, washing with ultrapure water and absolute ethyl alcohol in sequence, and placing the product into a vacuum drying oven at 80 ℃ for drying for 6 hours to obtain the ferric phosphate powder.
PREPARATION EXAMPLE 11
An iron phosphate powder having a particle size of about 500nm;
the preparation method comprises the following steps: adding 60mL of ethylene glycol solution into a 100mL beaker, placing the beaker into a constant temperature water bath at 45 ℃, adding 0.03mol of anhydrous ferric chloride under continuous stirring, dripping 3mL of 2mol/L sodium dihydrogen phosphate aqueous solution after the anhydrous ferric chloride is completely dissolved, stirring at a constant temperature of 40 ℃ for 2 hours, transferring the solution into a 100mL polytetrafluoroethylene-lined reaction kettle, reacting for 10 hours in a constant temperature oven at 120 ℃, naturally cooling the reaction kettle to room temperature after the reaction is completed, pouring out supernatant, transferring the precipitate into a centrifuge tube for centrifugal separation, washing with ultrapure water and absolute ethyl alcohol in sequence, and placing the product into a vacuum drying oven at 80 ℃ for drying for 6 hours to obtain the ferric phosphate powder.
Preparation example 12
An iron phosphate powder having a particle size of about 700nm;
the preparation method comprises the following steps: adding 60mL of ethylene glycol solution into a 100mL beaker, placing the beaker into a constant temperature water bath at 45 ℃, adding 0.03mol of anhydrous ferric chloride under continuous stirring, dripping 3mL of 2mol/L sodium dihydrogen phosphate aqueous solution after the anhydrous ferric chloride is completely dissolved, stirring at a constant temperature of 40 ℃ for 2 hours, transferring the solution into a 100mL polytetrafluoroethylene-lined reaction kettle, reacting for 16 hours in a constant temperature oven at 120 ℃, naturally cooling the reaction kettle to room temperature after the reaction is completed, pouring out supernatant, transferring the precipitate into a centrifuge tube for centrifugal separation, washing with ultrapure water and absolute ethyl alcohol in sequence, and placing the product into a vacuum drying oven at 80 ℃ for drying for 6 hours to obtain the ferric phosphate powder.
Example 1
A composite coated positive electrode material comprises lithium cobaltate (preparation example 1), wherein the surface of the lithium cobaltate is coated with ferric phosphate (preparation example 10) and scandium oxide;
wherein, calculated by taking the mass of lithium cobaltate as 100%, the mass of ferric phosphate is 1%, and the mass of scandium oxide is also 1%;
the preparation method of the composite coated positive electrode material provided by the embodiment comprises the following steps:
(1) Scandium nitrate (Sc (NO) 3 )·6H 2 O) dissolving in deionized water to obtain scandium nitrate solution with the molar concentration of 0.1 mol/L;
(2) Dispersing lithium cobaltate and nano ferric phosphate in the scandium nitrate solution obtained in the step (1), stirring for 4 hours in a constant-temperature water bath at 30 ℃, drying for 8 hours in a baking oven at 90 ℃, and finally calcining for 6 hours in a muffle furnace at 600 ℃ to obtain the composite coated anode material.
Example 2
A composite coated positive electrode material comprises lithium cobaltate (preparation example 2), wherein the surface of the lithium cobaltate is coated with nano ferric phosphate (preparation example 10) and scandium oxide;
wherein, calculated by taking the mass of lithium cobaltate as 100%, the mass of ferric phosphate is 0.5%, and the mass of scandium oxide is 2%;
the preparation method of the composite coated positive electrode material provided by the embodiment comprises the following steps:
(1) Scandium nitrate (Sc (NO) 3 )·6H 2 O) dissolving in deionized water to obtain scandium nitrate solution with the molar concentration of 0.1 mol/L;
(2) Dispersing lithium cobaltate and nano ferric phosphate in the scandium nitrate solution obtained in the step (1), stirring for 4 hours in a constant-temperature water bath at 30 ℃, drying for 8 hours in a baking oven at 90 ℃, and finally calcining for 6 hours in a muffle furnace at 600 ℃ to obtain the composite coated anode material.
Example 3
A composite coated positive electrode material comprises lithium cobaltate (preparation example 3), wherein the surface of the lithium cobaltate is coated with nano ferric phosphate (preparation example 10) and scandium oxide;
wherein, calculated by taking the mass of lithium cobaltate as 100%, the mass of ferric phosphate is 2%, and the mass of scandium oxide is 0.2%;
the preparation method of the composite coated positive electrode material provided by the embodiment comprises the following steps:
(1) Scandium nitrate (Sc (NO) 3 )·6H 2 O) dissolving in deionized water to obtain scandium nitrate solution with the molar concentration of 0.1 mol/L;
(2) Dispersing lithium cobaltate and nano ferric phosphate in the scandium nitrate solution obtained in the step (1), stirring for 4 hours in a constant-temperature water bath at 30 ℃, drying for 8 hours in a baking oven at 90 ℃, and finally calcining for 6 hours in a muffle furnace at 600 ℃ to obtain the composite coated anode material.
Example 4
The composite coated cathode material was different from example 1 only in that the mass of iron phosphate was 10% and the mass of scandium oxide was 0.2% calculated as 100% of the mass of lithium cobaltate, and other substances, parameters and production methods were the same as in example 1.
Example 5
The composite coated cathode material was different from example 1 only in that the mass of iron phosphate was 0.2% and the mass of scandium oxide was 8% calculated as 100% of the mass of lithium cobaltate, and other substances, parameters and production methods were the same as in example 1.
Example 6
The composite coated cathode material was different from example 1 only in that the mass of iron phosphate was 15% and the mass of scandium oxide was 0.1% calculated as 100% of the mass of lithium cobaltate, and other substances, parameters and production methods were the same as in example 1.
Example 7
The composite coated cathode material was different from example 1 only in that the mass of iron phosphate was 0.1% and the mass of scandium oxide was 10% calculated as 100% of the mass of lithium cobaltate, and other substances, parameters and production methods were the same as in example 1.
Examples 8 to 13
The composite coated cathode material was different from example 1 only in that lithium cobaltates obtained in preparation examples 4 to 9 were used instead of lithium cobaltate obtained in preparation example 1, respectively, and other substances, parameters and preparation methods were the same as in example 1.
Examples 14 to 15
A composite coated cathode material was different from example 1 only in that the iron phosphate powder obtained in preparation example 10 was replaced with the iron phosphate powder obtained in preparation examples 11 and 12, respectively, and other substances, parameters and preparation methods were the same as in example 1.
Comparative example 1
A lithium cobalt oxide positive electrode material was only the lithium cobalt oxide powder obtained in preparation example 1.
Comparative example 2
A coated positive electrode material comprising lithium cobaltate (preparation example 1), the surface of which is coated with only iron phosphate (preparation example 10);
wherein, calculated by taking the mass of lithium cobaltate as 100%, the mass of the ferric phosphate is 2%;
the preparation method of the composite coated positive electrode material provided in the comparative example comprises the following steps: dispersing lithium cobaltate and ferric phosphate in deionized water, stirring for 4 hours in a constant-temperature water bath at 30 ℃, drying for 8 hours in an oven at 90 ℃, and finally calcining for 6 hours in a muffle furnace at 600 ℃ to obtain the coated anode material.
Comparative example 3
A coated positive electrode material comprising lithium cobaltate (preparation example 1), the surface of which is coated with scandium oxide only;
wherein the mass of scandium oxide is 2% calculated by taking the mass of lithium cobaltate as 100%;
the preparation method of the composite coated positive electrode material provided by the comparative example comprises the following steps:
(1) Scandium nitrate (Sc (NO) 3 )·6H 2 O) dissolving in deionized water to obtain scandium nitrate solution with the molar concentration of 0.5 mol/L;
(2) Dispersing lithium cobaltate in the scandium nitrate solution obtained in the step (1), stirring for 4 hours in a constant-temperature water bath at 30 ℃, drying for 8 hours in a baking oven at 90 ℃, and finally calcining for 6 hours in a muffle furnace at 600 ℃ to obtain the coated anode material.
Application example 1
A lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte;
wherein the materials of the positive electrode comprise 90%, 5%, 2.5% and 2.5% of composite coated positive electrode materials (example 1), PVDF, multi-wall carbon tubes and SP;
the material of the negative electrode comprises graphite, SBR, CMC and SP with the percentage content of 95.5%, 1.4%, 1.1% and 2% respectively;
the diaphragm is a ceramic diaphragm;
the electrolyte comprises EC, PC, EMC, VC and PS with the volume ratio of 35:5:60:1:1, and then LiPF is added 6 So that LiPF 6 The concentration of (2) is 1mol/L;
the preparation process of the lithium ion battery provided by the application example comprises the following steps:
(1) Mixing a material of the positive electrode with NMP to obtain positive electrode slurry with the solid content of 50%, and performing coating, rolling and die cutting to obtain a positive electrode plate;
mixing the material of the negative electrode with water to obtain negative electrode slurry with the solid content of 48%, and performing coating, rolling and die cutting to obtain a negative electrode plate;
(2) And (3) assembling the positive electrode plate, the negative electrode plate and the diaphragm obtained in the step (1), injecting electrolyte, and carrying out capacity division and formation to obtain the lithium ion battery.
Application examples 2 to 15
A lithium ion battery was different from application example 1 only in that the composite coated cathode materials obtained in examples 2 to 15 were used in place of the composite coated cathode material obtained in example 1, respectively, and other substances, amounts and preparation methods were the same as those of application example 1.
Comparative application example 1
A lithium ion battery was different from application example 1 only in that the lithium cobaltate material obtained in comparative example 1 was used instead of the composite coated cathode material obtained in example 1, and other substances, amounts and preparation methods were the same as those of application example 1.
Comparative application examples 2 to 3
A lithium ion battery was different from application example 1 only in that the composite coated cathode materials obtained in example 1 were replaced with the coated cathode materials obtained in comparative examples 2 to 3, respectively, and other substances, amounts and preparation methods were the same as application example 1.
Performance test:
(1) First discharge capacity: discharging with a multiplying power of 1C in a voltage range of 3.0-4.5V, and testing discharge capacity;
(2) Cycle performance: the 1C cycle was performed at 45℃and capacity retention rates were recorded for 20 weeks, 30 weeks and 50 weeks for the cycle.
The lithium ion batteries provided in application examples 1 to 15 and comparative application examples 1 to 3 were tested according to the above test methods, and the test results are shown in table 1:
TABLE 1
From the data in table 1, it can be seen that:
the lithium ion batteries obtained in application examples 1 to 15 have a first discharge capacity up to 190.6 to 197.5mAh/g, and cycle performance shows that the capacity retention rate in 20 cycles is 93.3 to 98.2%, the capacity retention rate in 30 cycles is 91.3 to 97.4%, and the capacity retention rate in 50 cycles is 87.2 to 96.3%, and have excellent cycle performance.
As can be seen from the data of comparative application examples 1 and 1 to 3, the positive electrode material was only lithium cobaltate powder, and the non-coating layer (comparative application example 1), the coating layer was only iron phosphate (comparative application example 2), and the coating layer was only scandium oxide (comparative application example 3) all resulted in a decrease in the first discharge capacity of the resulting lithium ion battery, and the cycle performance was deteriorated.
It was found from the data of application example 1 and application examples 6 to 7 that the addition amount of iron phosphate and scandium oxide in the coating layer also affects the cycle performance of the final lithium ion battery.
Further, according to the data of application example 1 and application examples 8 to 13, it can be seen that the lithium ion battery prepared from the lithium cobaltate material obtained by matching five elements with cobalt has the optimal comprehensive performance.
Finally, as can be seen from the data of application example 1 and application examples 14 to 15, too large particle size of the coated iron phosphate powder also affects the first discharge capacity and cycle performance of the obtained lithium ion battery.
The applicant states that the present invention describes a composite coated positive electrode material and a method for preparing the same and applications thereof by the above examples, but the present invention is not limited to the above examples, i.e. it does not mean that the present invention must be practiced by relying on the above examples. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.

Claims (10)

1. The composite coated positive electrode material is characterized by comprising lithium cobalt oxide and a composite coating layer coated on the surface of the lithium cobalt oxide, wherein the material of the composite coating layer comprises ferric phosphate and scandium oxide.
2. The composite coated positive electrode material according to claim 1, wherein the lithium cobaltate has a chemical formula of LiCo x M 1-x O 2 ；
Wherein x is more than or equal to 0.9 and less than or equal to 0.99, and M is selected from any one or a combination of at least two of B, mg, al, ca, ti, V, cr, mn, fe, ni, cu, zn, Y, zr, nb, mo, ru, sn, sb, te, ir and Bi;
preferably, the M is selected from a combination of at least 5 of B, mg, al, ca, ti, V, cr, mn, fe, ni, cu, zn, Y, zr, nb, mo, ru, sn, sb, te, ir or Bi;
preferably, said M is selected from the group consisting of Ni, cu, mg, mn and Ti;
preferably, the lithium cobaltate has the chemical formula LiCo 0.95 Ni 0.01 Mn 0.01 Ti 0.005 Mg 0.005 Al 0.02 O 2 、LiCo 0.96 Ni 0.01 Mn 0.01 Ti 0.005 Mg 0.005 Al 0.01 O 2 Or LiCo 0.96 Ni 0.01 Mn 0.01 Y 0.005 Mg 0.005 Al 0.01 O 2 。
3. The composite coated positive electrode material according to claim 1 or 2, wherein the lithium cobaltate is obtained by co-sintering a cobalt source, a lithium source and an M source;
wherein M is selected from any one or a combination of at least two of B, mg, al, ca, ti, V, cr, mn, fe, ni, cu, zn, Y, zr, nb, mo, ru, sn, sb, te, ir and Bi;
preferably, the cobalt source comprises tricobalt tetraoxide;
preferably, the lithium source comprises lithium carbonate and/or lithium hydroxide;
preferably, the M source comprises a sulfate of M and/or an oxide of M;
preferably, the sintering temperature is 500-1200 ℃, and more preferably 800-1100 ℃;
preferably, the sintering time is 4 to 20 hours, more preferably 8 to 15 hours.
4. The composite coated positive electrode material according to any one of claims 1 to 3, wherein the mass percentage of the iron phosphate is 0.2 to 10% based on 100% of the mass of the lithium cobaltate;
preferably, the particle size of the iron phosphate is not higher than 500nm.
5. The composite coated positive electrode material according to any one of claims 1 to 4, wherein the iron phosphate is prepared by a method comprising: mixing ferric salt and phosphate in an organic solvent, and reacting to obtain the ferric phosphate;
preferably, the iron salt comprises any one or a combination of at least two of ferric chloride, ferric nitrate or ferric sulfate;
preferably, the phosphate comprises sodium dihydrogen phosphate;
preferably, the organic solvent comprises any one or a combination of at least two of ethanol, ethylene glycol, isopropanol, propylene glycol or glycerol;
preferably, the temperature of the mixing is 30-80 ℃;
preferably, the mixing time is 2-12 hours;
preferably, the temperature of the reaction is 100-200 ℃;
preferably, the reaction time is 2-15 hours;
preferably, the reaction further comprises a step of drying after completion;
preferably, the drying temperature is 60-100 ℃;
preferably, the drying time is 6 to 12 hours.
6. The composite coated positive electrode material according to any one of claims 1 to 5, wherein the scandium oxide is 0.2 to 8% by mass based on 100% by mass of the lithium cobaltate.
7. A method for preparing the composite coated positive electrode material according to any one of claims 1 to 6, comprising: and mixing scandium source, ferric phosphate and lithium cobaltate in water, and drying and calcining to obtain the composite coated anode material.
8. The method of producing according to claim 7, wherein the scandium source comprises scandium nitrate.
Preferably, the temperature of the mixing is 30-80 ℃;
preferably, the mixing time is 3-8 hours;
preferably, the drying temperature is 80-120 ℃;
preferably, the drying time is 8-12 hours;
preferably, the temperature of the calcination is 200-1000 ℃;
preferably, the calcination time is 4 to 12 hours.
9. A lithium ion battery comprising the composite coated positive electrode material according to any one of claims 1 to 6.
10. Use of the lithium ion battery of claim 9 in a new energy automobile.
CN202310800369.XA 2023-06-30 2023-06-30 Composite coated positive electrode material and preparation method and application thereof Pending CN116825995A (en)

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