CN112701276A - Quaternary polycrystalline positive electrode material and preparation method and application thereof - Google Patents

Abstract

The invention provides a quaternary polycrystalline anode material and a preparation method and application thereof, wherein the anode material comprises a main body and a dopant, and the dopant is uniformly doped into the main body, wherein the main body has a chemical general formula of LiNi_xCo_yMn_zAl_{(1‑x‑y‑z)}O₂The dopant comprises selenium oxide andcalcium oxide and Se/Ca are uniformly doped into the material main body, so that the structural stability of the layered positive electrode material is enhanced, and Li is reduced⁺/Ni²⁺Cationic shuffling effect, inhibition of O^2‑To O₂And the phase transition of the material from delamination to spinel is hindered to a certain extent, so that the electrochemical performance of the cathode material is improved.

Description

Quaternary polycrystalline positive electrode material and preparation method and application thereof

Technical Field

The invention belongs to the field of lithium ion batteries, and relates to a quaternary polycrystalline anode material, and a preparation method and application thereof.

Background

With the wide application of lithium ion batteries in the fields of mobile phones, computers, automobiles, energy storage and the like, people have higher and higher requirements on the safety, energy density and cycle stability of the batteries. The most representative of such batteries are lithium secondary batteries (LIBs) in which lithium ions in a positive electrode and a negative electrode generate electric energy due to a change in chemical potential upon intercalation and deintercalation. The positive electrode material has a direct leading effect on the performance of LIBs, and therefore, many researchers are dedicated to realizing a positive electrode material which has a large capacity, a fast charge/discharge speed and a long cycle life and can reversibly intercalate and deintercalate lithium ions.

The particles of the current quaternary polycrystalline positive electrode material are secondary particle spheres formed by agglomeration of primary particles, the diameter of the secondary particle spheres is usually between several micrometers and tens of micrometers, and the size of the primary particles is generally several hundred nanometers. With the increase of the cycle times, as the primary particles in the secondary spheres have different crystal plane orientations, the anisotropy of the expansion and contraction of crystal lattices among the crystal grains causes the secondary particles to be broken, a large amount of oxygen is released, and microcracks are generated among the primary particles. At present, high-valence metal ions, such as Mo⁶⁺(radius)

)、Se⁶⁺(radius)

) Etc. as a dopant can significantly affect the structure of the positive electrode material and improve electrochemical performance. The main reason is that the d band of the transition metal is fixed on the top of the oxygen p band in the transition metal oxide by regulating O₂The evolution of gas thus affects the structural stability of the oxide. However, because the introduction of high valence state elements will inevitably lead to the increase of divalent nickel in the material bulk, which will increase Li⁺/Ni²⁺And (4) cation mixing and draining effect.

CN109437339A discloses a high-nickel quaternary positive electrode material precursor, a high-nickel quaternary positive electrode material, a preparation method and application thereof, wherein the chemical formula of the high-nickel quaternary positive electrode material is as shown in the formula Li_a(Ni_1-x-y-zCo_xAl_yMn_z)O₂(ii) a x, y, z and a are mole fractions, x is more than 0.03 and less than or equal to 0.15, y is more than 0.01 and less than 0.05, z is more than 0.01 and less than 0.05, and x is more than 0.6 and less than 1? y is less than 0.9, a is more than or equal to 1 and less than or equal to 1.1. Soluble nickel salt, soluble cobalt salt, soluble aluminum salt and soluble manganese salt are prepared into solution, the nickel salt, the cobalt salt, the aluminum salt and the manganese salt can be uniformly distributed in the solution, and the high-nickel quaternary anode material precursor is prepared by adopting the solution in which the nickel salt, the cobalt salt, the aluminum salt and the manganese salt are uniformly distributed. And then mixing the high-nickel quaternary positive electrode material precursor with lithium salt, and sintering for four times to obtain the high-nickel quaternary positive electrode material. Different particles of the material have different crystal face orientations and the anisotropy of crystal lattice expansion and contraction among the crystal grains, so that secondary particles can be broken and a large amount of oxygen can be released at the later stage of circulation.

CN111640928A discloses an NCMA quaternary system material and a preparation method thereof, a lithium battery anode material and a lithium battery. The NCMA quaternary system material comprises an NCMA quaternary positive electrode material and a coating layer, and the coating layer comprises Co₃O₄And V₂O₅. By Co₃O₄And V₂O₅The Co-coating layer not only can solve the problem of residual alkali on the surface of the material, but also can inhibit the dissolution of transition metal in the NCMA quaternary anode material and Co₃O₄And V₂O₅The mutual synergistic effect of the components is used for further improving the charge transmission rate of the material body and the ion transmission rate between the material and the electrolyte, thereby promoting the insertion and extraction of lithium ions, reducing the residual lithium and the side reaction on the surface of the NCMA quaternary anode material, and further improving the electrochemical properties of the NCMA quaternary anode material, such as capacity, stability and the like. But Li thereof⁺/Ni²⁺The cation-shuffling effect also causes deterioration in cycle performance and rate performance.

The scheme has the problems of poor cycle performance and rate performance and the like, so that the development of the quaternary anode material with good cycle performance and excellent rate performance is necessary.

Disclosure of Invention

The invention aims to provide a quaternary polycrystalline positive electrode material and a preparation method and application thereof, wherein the positive electrode material comprises a main body and a dopant, and the dopant is uniformly doped into the main body, wherein the main body has a chemical general formula of LiNi_xCo_yMn_zAl_(1-x-y-z)O₂The dopant comprises selenium oxide and calcium oxide, and Se/Ca is uniformly doped into the material main body, so that the structural stability of the layered cathode material is enhanced, and Li is reduced⁺/Ni²⁺Cationic shuffling effect, inhibition of O^2-To O₂And the phase transition of the material from delamination to spinel is hindered to a certain extent, so that the electrochemical performance of the cathode material is improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a quaternary polycrystalline positive electrode material, which comprises a main body and a dopant, wherein the dopant is uniformly doped into the main body, and the chemical general formula of the main body is LiNi_xCo_yMn_zAl_(1-x-y-z)O₂0.8 < x < 1, for example: 0.8, 0.85, 0.9, 0.95 or 1, etc., 0 < y < 0.1, e.g.: 0.01, 0.03, 0.05, 0.07, or 0.09, etc., 0 < z < 0.1, e.g.: 0.01, 0.03, 0.05, 0.07, or 0.09, etc., and the dopant includes selenium oxide and calcium oxide.

According to the invention, the doping agent is added into the main material to promote the lithium ion insertion and extraction, the structural stability of the layered anode material is enhanced, and Li is reduced⁺/Ni²⁺The positive ion mixed discharging effect reduces the oxygen release amount, improves the lithium ion diffusion coefficient, and hinders the phase change of the material from delamination to spinel to a certain extent, thereby improving the electrochemical performance of the positive electrode material.

In a second aspect, the present invention provides a method for preparing a quaternary polycrystalline positive electrode material according to the first aspect, the method comprising the steps of:

(1) pre-sintering, cooling, crushing and sieving the nickel-cobalt-manganese-aluminum hydroxide to obtain nickel-cobalt-manganese-aluminum oxide;

(2) and (2) carrying out dry mixing on a lithium source, a selenium source and a calcium source and the nickel-cobalt-manganese-aluminum oxide obtained in the step (1), and then calcining, cooling, crushing and sieving to obtain the quaternary polycrystalline anode material.

According to the invention, the quaternary polycrystalline precursor is subjected to presintering treatment and a selenium/calcium co-doping mechanism to promote lithium ion insertion and extraction, the presintering treatment enables the surface amorphous layer after the precursor treatment to be removed, the surface holes are increased, lithium salt diffusion is facilitated, and Se/Ca is uniformly doped into the material main body, the selenium/calcium co-doping mechanism can enhance the structural stability of the layered anode material, and the Li content is reduced⁺/Ni²⁺The cation mixed discharging effect reduces the oxygen release amount.

Preferably, the temperature of the pre-sintering in the step (1) is 150-500 ℃, for example: 150 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃ or 500 ℃ and the like.

Preferably, the pre-burning time is 6-10 h, for example: 6h, 7h, 8h, 9h or 10h and the like.

Preferably, the atmosphere of the pre-firing of step (1) comprises air.

According to the invention, the quaternary polycrystalline precursor is firstly pre-sintered, the pre-sintered material is uniformly dry-mixed with a lithium source, a selenium source and a calcium source and then is high-temperature calcined again, the diffusion of lithium salt in the process of synthesizing the quaternary polycrystalline anode material by high-temperature calcination is promoted by forming more pores and large specific surface area after pre-sintering, and selenium/calcium ions are uniformly doped into a material main body, so that the structural stability of the layered anode material is enhanced, and the Li is reduced⁺/Ni²⁺Cationic shuffling effect, inhibition of O^2-To O₂And the phase transition of the material from delamination to spinel is hindered to a certain extent, so that the electrochemical performance of the cathode material is improved.

Preferably, the lithium source of step (2) comprises any one of lithium hydroxide, lithium carbonate or lithium oxide or a combination of at least two thereof.

Preferably, the selenium source comprises selenium oxide and/or selenium chloride.

Preferably, the calcium source comprises any one or a combination of at least two of calcium oxide, calcium hydroxide or calcium carbonate.

Preferably, the molar ratio of the lithium source to the nickel-cobalt-manganese-aluminum oxide in the step (2) is 1-1.5: 1, such as: 1:1, 1.1: 1. 1.2:1, 1.3:1, 1.4:1 or 1.5:1, etc.

Preferably, the mass content of the selenium source is 0.3-0.5% by mass of the quaternary polycrystalline positive electrode material, such as: 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, etc.

Preferably, the mass content of the calcium source is 0.3-0.5%, such as: 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, etc.

Selenium/calcium codoping is carried out on the presintered precursor, and the selenium doping can enhance the structural stability of the layered anode material and inhibit O^2-To O₂Oxidation process of (2), and Ca²⁺And Ni²⁺The ionic radius is close, and the Li position is occupied but the electrochemical reaction does not occur, thereby reducing the Li⁺/Ni²⁺The positive ion mixed-discharging effect improves the lithium ion diffusion coefficient, and hinders the phase change of the material from delamination to spinel to a certain extent, thereby improving the electrochemical performance of the positive electrode material.

Preferably, the temperature of the calcination in the step (2) is 600-800 ℃, for example: 600 deg.C, 620 deg.C, 650 deg.C, 680 deg.C, 700 deg.C, 750 deg.C or 800 deg.C, etc.

Preferably, the calcination time is 6-10 h, such as: 6h, 7h, 8h, 9h or 10h and the like.

Preferably, the atmosphere of the calcination is oxygen.

As a preferable scheme of the invention, the preparation method comprises the following steps:

(1) pre-burning the nickel-cobalt-manganese-aluminum hydroxide at 150-500 ℃ for 6-10 h, cooling, crushing and sieving to obtain nickel-cobalt-manganese-aluminum oxide;

(2) and (2) carrying out dry mixing on a lithium source, a selenium source and a calcium source and the nickel-cobalt-manganese-aluminum oxide obtained in the step (1), calcining at 600-800 ℃ for 6-10 h, cooling, crushing and sieving to obtain the quaternary polycrystalline anode material.

In a third aspect, the present invention provides a positive electrode plate, wherein the positive electrode plate comprises the quaternary polycrystalline positive electrode material according to the first aspect.

In a fourth aspect, the invention further provides a lithium ion battery, where the lithium ion battery includes the positive electrode sheet described in the third aspect.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, the doping agent is added into the main material to promote the lithium ion insertion and extraction, the structural stability of the layered anode material is enhanced, and Li is reduced⁺/Ni²⁺The positive ion mixed discharging effect reduces the oxygen release amount, improves the lithium ion diffusion coefficient, and hinders the phase change of the material from delamination to spinel to a certain extent, thereby improving the electrochemical performance of the positive electrode material.

(2) According to the invention, the quaternary polycrystalline precursor is subjected to presintering treatment and a selenium/calcium co-doping mechanism to promote lithium ion insertion and extraction, the presintering treatment enables the surface amorphous layer after the precursor treatment to be removed, the surface holes are increased, lithium salt diffusion is facilitated, and Se/Ca is uniformly doped into the material main body, the selenium/calcium co-doping mechanism can enhance the structural stability of the layered anode material, and the Li content is reduced⁺/Ni²⁺The cation mixed discharging effect reduces the oxygen release amount.

Drawings

Fig. 1 is a first charge-discharge curve diagram of a quaternary polycrystalline positive electrode material according to example 1 of the present invention.

Fig. 2 is a graph showing the first charge and discharge curves of the quaternary polycrystalline positive electrode material according to comparative example 1 of the present invention.

Fig. 3 is a graph of the cycle capacity retention rate of the quaternary polycrystalline positive electrode material according to example 1 of the present invention.

Fig. 4 is a graph of cycle capacity retention of a quaternary polycrystalline positive electrode material according to comparative example 1 of the present invention.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

The embodiment provides a quaternary polycrystalline anode material, which is prepared by the following specific steps:

(1) pre-burning nickel-cobalt-manganese-aluminum hydroxide (molar ratio: Ni: Co: Mn: Al: 88:6:3:3) in an air atmosphere at 450 ℃ in a common box furnace for 8 hours, cooling, crushing and sieving to obtain nickel-cobalt-manganese-aluminum oxide;

(2) and (2) mixing the nickel-cobalt-manganese-aluminum oxide obtained in the step (1) with LiOH, selenium oxide and calcium oxide in a molar ratio of 1:1.025:0.001:0.001 by a dry method in a mixer, calcining the dry-mixed material in an oxygen atmosphere at 700 ℃ in a common box furnace for 8 hours, cooling, crushing and sieving to obtain the quaternary polycrystalline anode material.

The first charge-discharge curve diagram of the quaternary polycrystalline positive electrode material is shown in figure 1.

The cycle capacity retention rate graph of the quaternary polycrystalline positive electrode material is shown in fig. 3, and the positive electrode material prepared from the quaternary polycrystalline positive electrode material shows excellent cycle stability as can be seen from fig. 3.

Example 2

The embodiment provides a quaternary polycrystalline anode material, which is prepared by the following specific steps:

(1) pre-burning nickel-cobalt-manganese-aluminum hydroxide (molar ratio: Ni: Co: Mn: Al: 88:6:3:3) in an air atmosphere at 300 ℃ in a common box furnace for 7 hours, cooling, crushing and sieving to obtain nickel-cobalt-manganese-aluminum oxide;

(2) and (2) mixing the nickel-cobalt-manganese-aluminum oxide obtained in the step (1) with lithium carbonate, selenium oxide and calcium oxide in a molar ratio of 1:1.2:0.001:0.001 by a dry method in a mixer, calcining the dry-mixed material in an oxygen atmosphere at 750 ℃ in a common box furnace for 6.5 hours, cooling, crushing and sieving to obtain the quaternary polycrystalline anode material.

Example 3

This example is different from example 1 only in that the temperature of the calcination in step (1) is 150 ℃ and other conditions and parameters are exactly the same as those in example 1.

Example 4

This example is different from example 1 only in that the temperature of the calcination in step (1) is 500 ℃, and other conditions and parameters are exactly the same as those in example 1.

Example 5

This example is different from example 1 only in that the temperature of the calcination in step (1) is 120 ℃ and other conditions and parameters are exactly the same as those in example 1.

Example 6

This example is different from example 1 only in that the temperature of the calcination in step (1) is 600 ℃, and other conditions and parameters are exactly the same as those in example 1.

Comparative example 1

This comparative example differs from example 1 only in that no calcium oxide was added in step (2) and the other conditions and parameters were exactly the same as in example 1.

The first charge and discharge curve of the cathode material prepared in this comparative example is shown in fig. 2.

The cycle capacity retention rate graph of the cathode material prepared in the comparative example is shown in fig. 4.

Comparative example 2

This comparative example differs from example 1 only in that no selenium oxide was added in step (2) and the other conditions and parameters were exactly the same as in example 1.

And (3) performance testing:

the positive electrode materials obtained in examples 1 to 6 and comparative examples 1 to 3 were uniformly mixed with the positive electrode material, the carbon black conductive agent, the binder PVDF and NMP in a mass ratio of 95:2.5:2.5:5 to prepare a battery positive electrode slurry. Coating the slurry on an aluminum foil with the thickness of 20-40 mu M, performing vacuum drying and rolling to prepare a positive electrode plate, taking a lithium metal plate as a negative electrode, and proportioning 1.15M LiPF electrolyte₆EC: DMC (1:1 vol%), and assembling the button cell.

The electrical property test of the material adopts a blue battery test system to test at 25 ℃, and the test voltage range is 3V-4.3; capacity, 1 week, 20 weeks and 50 weeks capacity and capacity retention were tested. The test results are shown in table 1:

TABLE 1

As can be seen from table 1, in examples 1 to 6, the specific charge capacity of the quaternary polycrystalline positive electrode material of the present invention can be 229.3mAh/g or more, the specific discharge capacity can be 200.8mAh/g or more, the primary battery efficiency can be 88.5% or more, and the 50-cycle retention rate can be 96.1% or more.

Compared with the embodiment 1 and the embodiments 3-6, in the invention, the temperature of the pre-sintering in the step (1) is controlled to be 150-500 ℃, so that the nickel-cobalt-manganese-aluminum hydroxide can be completely oxidized and the appearance of the oxide can be prevented from being damaged, the prepared quaternary polycrystalline anode material has higher specific discharge capacity and higher 50-turn cycle retention rate, if the temperature is lower than 150 ℃, the nickel-cobalt-manganese-aluminum hydroxide can not be completely oxidized, and if the temperature is higher than 500 ℃, the appearance of the oxide is damaged, so that the specific discharge capacity and 50-turn cycle retention rate of the corresponding quaternary polycrystalline anode material are reduced.

Compared with the comparative examples 1 and 2, the method disclosed by the invention has the advantages that the selenium oxide and the calcium oxide are simultaneously added in the step (2) of preparing the quaternary polycrystalline positive electrode material, so that more excellent specific discharge capacity and higher cycle retention rate can be obtained.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims (10)

1. A quaternary polycrystalline positive electrode material, characterized in that the positive electrode material comprises a host and a dopant, wherein the dopant is uniformly doped into the host;

wherein the chemical general formula of the main body is LiNi_xCo_yMn_zAl_(1-x-y-z)O₂X is more than 0.8 and less than 1, y is more than 0 and less than 0.1, z is more than 0 and less than 0.1, and the dopant comprises oxideSelenium and calcium oxide.

2. A method of making the quaternary polycrystalline positive electrode material of claim 1, comprising the steps of:

(1) pre-sintering, cooling, crushing and sieving the nickel-cobalt-manganese-aluminum hydroxide to obtain nickel-cobalt-manganese-aluminum oxide;

(2) and (2) carrying out dry mixing on a lithium source, a selenium source and a calcium source and the nickel-cobalt-manganese-aluminum oxide obtained in the step (1), and then calcining, cooling, crushing and sieving to obtain the quaternary polycrystalline anode material.

3. The preparation method according to claim 2, wherein the pre-firing temperature in the step (1) is 150 to 500 ℃;

preferably, the pre-burning time is 6-10 h;

preferably, the pre-firing atmosphere comprises air.

4. The method of claim 2 or 3, wherein the lithium source of step (2) comprises any one of lithium hydroxide, lithium carbonate, or lithium oxide, or a combination of at least two thereof.

5. The method of any one of claims 2-4, wherein the selenium source comprises selenium oxide and/or selenium chloride;

preferably, the calcium source comprises any one or a combination of at least two of calcium oxide, calcium hydroxide or calcium carbonate.

6. The method of any one of claims 2-5, wherein the molar ratio of the lithium source to the nickel cobalt manganese aluminum oxide in step (2) is 1 to 1.5: 1;

preferably, the mass content of the selenium source is 0.3-0.5% by taking the mass of the quaternary polycrystalline positive electrode material as 100%;

preferably, the mass content of the calcium source is 0.3-0.5%.

7. The method according to any one of claims 2 to 6, wherein the temperature of the calcination in the step (2) is 600 to 800 ℃;

preferably, the calcining time is 6-10 h;

preferably, the atmosphere of the calcination is oxygen.

8. The method of any one of claims 2 to 7, comprising the steps of:

(1) pre-burning the nickel-cobalt-manganese-aluminum hydroxide at 150-500 ℃ for 6-10 h, cooling, crushing and sieving to obtain nickel-cobalt-manganese-aluminum oxide;

(2) and (2) carrying out dry mixing on a lithium source, a selenium source and a calcium source and the nickel-cobalt-manganese-aluminum oxide obtained in the step (1), calcining at 600-800 ℃ for 6-10 h, cooling, crushing and sieving to obtain the quaternary polycrystalline anode material.

9. A positive electrode sheet comprising the quaternary polycrystalline positive electrode material of claim 1.

10. A lithium ion battery comprising the positive electrode sheet of claim 9.

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