CN113764641B - Cathode material, preparation method thereof and lithium ion battery - Google Patents
Cathode material, preparation method thereof and lithium ion battery Download PDFInfo
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- H01M4/00—Electrodes
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- 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
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract
The invention relates to the technical field of lithium ion electrode materials, in particular to a positive electrode material, a preparation method thereof and a lithium ion battery. The positive electrode material comprises an electrode base material and a coating layer coated on the surface of the electrode base material; wherein the chemical formula of the electrode base material is LiNi x Mn y O 2 X is more than or equal to 0.50 and less than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.50; the chemical formula of the coating layer is M a Nb b O c Wherein the mass fraction of Nb in the coating layer is 0.1-0.5%, and M is at least one selected from Ti, zr, mg, B, al, W, ta, sn, Y, sr, ca and Ba. The invention adopts a coating layer M with good conductivity a Nb b O c The DCR of the positive electrode material (namely the direct current internal resistance of the battery) can be reduced, and the cycle performance of the positive electrode material is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion electrode materials, in particular to a positive electrode material, a preparation method thereof and a lithium ion battery.
Background
Lithium ion batteries are widely used in the fields of automobiles, electronic industries, and the like because of their advantages of high energy density, excellent cycle performance, and the like. The performance of the positive electrode material as the core component of the lithium ion batteryThe quality of the lithium ion battery is directly influenced. Commercially common positive electrode materials include lithium cobaltate, lithium iron phosphate, lithium manganate, lithium nickelate, and the like. Among them, the ternary positive electrode material has a good development prospect due to its advantages such as high energy density and good cycle life, such as NCM (Ni) x Co y Mn z )，NCA(Ni x Co y Al z ) And the like. However, cobalt is a strategic resource, which is not only expensive, but also easily pollutes the environment, and these adverse factors directly limit the development of ternary materials.
The cobalt-free layered cathode material not only gets rid of the restriction of cobalt element, but also has the advantages of higher reversible specific capacity, low price and the like, so that the cobalt-free layered cathode material is more and more favored by the energy industry. However, the absence of cobalt element, on one hand, reduces the ionic conductivity of the material, increases the DCR, and deteriorates the electrical performance of the battery; on the other hand, the structural stability of the material is lowered, and the service life of the battery is reduced.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The first purpose of the present invention is to provide a positive electrode material using a coating layer M having good conductivity a Nb b O c The DCR of the cathode material (namely the direct current internal resistance of the battery) can be reduced, and the cycle performance of the cathode material is improved.
The second purpose of the present invention is to provide the preparation method of the positive electrode material, wherein the dry mixing coating is adopted to mix the material of the coating layer and the electrode substrate material, such that the advantages of good coating effect, uniform coating layer, and the like are provided, such that the mechanical strength, the conductivity and the cycle performance of the positive electrode material are improved. And the method also has the advantages of simple operation, mild conditions, suitability for mass production and the like.
The third purpose of the invention is to provide a lithium ion battery, which has the advantages of good conductivity and cycle performance, long service life and the like.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
the positive electrode material comprises an electrode base material and a coating layer coated on the surface of the electrode base material;
wherein the chemical formula of the electrode base material is LiNi x Mn y O 2 ，0.50≤x≤0.95，0.05≤y≤0.50；
The chemical formula of the coating layer is M a Nb b O c Wherein the mass fraction of Nb in the coating layer is 0.1-0.5%, and M is at least one selected from Ti, zr, mg, B, al, W, ta, sn, Y, sr, ca and Ba.
The invention provides a positive electrode material, which is prepared by coating an electrode substrate material with M with good conductivity a Nb b O c The DCR of the positive electrode material (namely the direct current internal resistance of the battery) can be reduced, and the cycle performance of the positive electrode material is improved.
The invention provides a cobalt-free anode material, which is a layered structure material with a single crystal morphology, wherein the size of the single crystal material is 1-5 mu m.
Preferably, the mass of the coating layer is 0.1% to 3% of the mass of the electrode base material, including but not limited to the point of any one of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 2%, 2.5%, 2.7%, 2.9%, or a range between any two.
Preferably, the specific surface area of the cathode material is 0.2-0.9m 2 (iv) g; including but not limited to 0.25m 2 /g、0.3m 2 /g、0.35m 2 /g、0.4m 2 /g、0.45m 2 /g、0.5m 2 /g、0.55m 2 /g、0.6m 2 /g、0.7m 2 /g、0.75m 2 /g、0.8m 2 /g、0.85m 2 A point value of any one of/g or a range value between any two.
Preferably, the particle size of the cathode material is 1-5 μm.
Preferably, the mass ratio of Nb to metal M in the cladding is 1-3, and can be selected from the following ratio of 1.
Preferably, the content of free water in the cathode material is <200ppm.
The invention also provides a preparation method of the cathode material, which comprises the following steps:
and mixing the material of the coating layer with the electrode base material, coating, and then annealing to obtain the cathode material.
The preparation method provided by the invention adopts dry mixing coating to mix the material of the coating layer and the electrode matrix material, and has the advantages of good coating effect, uniform coating layer and the like, thereby improving the mechanical strength, the conductivity and the cycle performance of the anode material. And the method also has the advantages of simple operation, mild conditions, suitability for mass production and the like.
Preferably, the preparation method of the material of the coating layer comprises the following steps: and (3) grinding the oxide of the Nb and the oxide or the salt of the metal M to obtain the material of the coating layer.
Preferably, the milling time is 1-2h, and can be selected from 1.2h, 1.4h, 1.5h, 1.6h or 1.8h.
In some preferred embodiments of the present invention, the method for preparing the electrode base material comprises: after uniformly mixing LiOH and a precursor material, reacting in an oxidizing atmosphere, cooling and crushing after the reaction is finished to obtain the electrode matrix material; wherein the chemical formula of the precursor material is Ni x Mn y (OH) 2 ，0.50≤x≤0.95，0.05≤y≤0.50。
Preferably, the mixing time is 10-20min and stirring is carried out at 2000-3000rpm during the mixing.
Wherein the time of mixing includes, but is not limited to, the point value of any one of 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, or a range value between any two.
The rotational speeds include, but are not limited to, values in any one of 2100rpm, 2200rpm, 2300rpm, 2400rpm, 2500rpm, 2600rpm, 2700rpm, 2800rpm, 2900rpm, or a range of values between any two.
Preferably, the gas used for the oxidizing atmosphere comprises oxygen and/or air.
More preferably, the oxygen mass concentration in the oxidizing atmosphere is >90%.
Preferably, the flow rate of the gas is 2-20L/min, including but not limited to 3L/min, 4L/min, 5L/min, 6L/min, 7L/min, 8L/min, 9L/min, 10L/min, 11L/min, 12L/min, 13L/min, 14L/min, 15L/min, 16L/min, 17L/min, 18L/min, 19L/min, or a range value between any two.
Preferably, the temperature of the mixed materials in the reaction process is 800-1000 ℃, and the reaction time is 8-12h.
Wherein the temperature includes, but is not limited to, any one of 810 ℃, 820 ℃, 830 ℃, 850 ℃, 865 ℃, 880 ℃, 900 ℃, 920 ℃, 950 ℃ and 980 ℃, or a range between any two thereof.
The reaction time includes, but is not limited to, any of 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, or a range of values therebetween.
Preferably, during the mixing, the stirring is performed at a speed of 2000-3000rpm, including but not limited to a point value of any one of 2100rpm, 2200rpm, 2300rpm, 2400rpm, 2500rpm, 2600rpm, 2700rpm, 2800rpm, 2900rpm, or a range value between any two.
More preferably, the stirring time is 10-20min, including but not limited to any one of 12min, 14min, 15min, 17min, 18min, 19min or a range between any two.
Preferably, during the mixing, the annealing treatment includes: heating the coated material at 200-500 deg.C in oxygen-containing atmosphere; including but not limited to, a point value of any one of 250 deg.C, 300 deg.C, 350 deg.C, 400 deg.C, 450 deg.C, 480 deg.C, or a range of values between any two. More preferably, the heat treatment is performed at 300 to 400 ℃.
Preferably, the time of the heat treatment is 4 to 8 hours, including but not limited to the dot value of any one of 4.5 hours, 5 hours, 5.5 hours, 5.8 hours, 6 hours, 6.5 hours, 7 hours, 7.2 hours, 7.5 hours or the range value between any two.
Preferably, the total amount of lithium carbonate and lithium hydroxide in the positive electrode material is less than 0.3wt%.
In some specific embodiments of the present invention, the content of residual alkali in the positive electrode material is less than 0.3wt%.
Preferably, the pH of the cathode material is less than or equal to 12.
The invention also provides a lithium ion battery which comprises the cathode material or a battery cathode prepared from the cathode material prepared by the preparation method.
The lithium ion battery provided by the invention has the advantages of good conductivity and cycle performance, long service life and the like.
Compared with the prior art, the invention has the beneficial effects that:
(1) The positive electrode material provided by the invention adopts the coating layer M with good conductivity a Nb b O c The DCR of the anode material (namely the direct current internal resistance of the battery) is reduced, and the cycle performance of the anode material is improved.
(2) The anode material provided by the invention does not contain cobalt element, is a layered structure material with a single crystal morphology, and the size of the single crystal material is 1-5 mu m.
(3) The preparation method provided by the invention adopts dry mixing coating to mix the material of the coating layer and the electrode matrix material, and has the advantages of good coating effect, uniform coating layer and the like, thereby improving the mechanical strength, the conductivity and the cycle performance of the anode material. And the method also has the advantages of simple operation, mild conditions, suitability for mass production and the like.
(4) The lithium ion battery provided by the invention has the advantages of good conductivity and cycle performance, long service life and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 shows LiNi, an electrode base material, according to example 4 of the present invention 0.75 Mn 0.25 O 2 A scanning electron microscope image with a magnification of 2000;
FIG. 2 shows LiNi, an electrode base material, provided in example 4 of the present invention 0.75 Mn 0.25 O 2 A scanning electron microscope image with a magnification of 5000;
fig. 3 is a scanning electron microscope image with a magnification of 2000 of the cathode material provided in example 4 of the present invention;
fig. 4 is a scanning electron microscope image with a magnification of 20000 of the cathode material provided in example 4 of the present invention.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and the detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.
Example 1
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) LiOH and a precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 10min, and the stirring rotating speed is 2000rpm; then the mixed materials are reacted for 12 hours at the high temperature of 800 ℃ in an oxygen atmosphere (the oxygen concentration is more than 90 percent, the oxygen flow is 2L/min) in an atmosphere furnace, and the reaction is naturalAnd crushing by using crushing equipment after cooling to obtain the electrode base material.
(b) And Nb 2 O 5 And TiO 2 (the mass ratio of Nb to Ti is 1; adding the composite material A (with the Nb element content of 0.1%) and the electrode substrate material into a mixing device for mixing, wherein the mixing time is 10 minutes, and the stirring speed is 2000; then annealing the mixed and coated mixed material for 8h at the high temperature of 300 ℃ in an oxygen environment, and screening by a 300-mesh sieve to obtain the anode material.
Example 2
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) Mixing LiOH and precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 20min, and the stirring speed is 3000rpm; and then reacting the mixed material at 1000 ℃ in an oxygen atmosphere (the oxygen concentration is more than 90 percent, and the oxygen flow is 10L/min) in an atmosphere furnace for 8, naturally cooling, and crushing by using crushing equipment to obtain the electrode base material.
(b) Nb in a reaction vessel 2 O 4 And MgCO 3 (Nb: mg element mass ratio 1; adding the composite material A (with the Nb element content of 0.5%) and the electrode base material into mixing equipment for mixing, wherein the mixing time is 20 minutes, and the stirring speed is 3000rpm; and then annealing the mixed and coated mixed material in an oxygen environment at a high temperature of 500 ℃ for 4, and screening by a 400-mesh sieve to obtain the cathode material.
Example 3
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) Mixing LiOH and precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 15min, and the stirring rotating speed is 2500rpm; then placing the mixed materials in an oxygen atmosphere (the oxygen concentration is more than 90 percent, and the oxygen flow is 20L/min) and an atmosphere furnace with the temperature of 900 ℃ highAnd (3) carrying out warm reaction for 10 hours, naturally cooling, and then crushing by using crushing equipment to obtain the electrode matrix material.
(b) And Nb 2 O 5 And ZrO 2 Carrying out ball milling for 2h (Nb: zr element mass ratio 3); adding the composite material A (with the Nb element content of 0.3%) and the electrode substrate material into a mixing device for mixing, wherein the mixing time is 15 minutes, and the stirring speed is 2500rpm; and then annealing the mixed and coated mixed material in an oxygen environment at the high temperature of 400 ℃ for 6h, and screening by a 300-mesh sieve to obtain the cathode material.
Example 4
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) LiOH and a precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 15min, and the stirring rotating speed is 2500rpm; then the mixed materials are put into an atmosphere furnace (the oxygen concentration is more than 90 percent, the oxygen flow is 18L/min) for high-temperature reaction at 950 ℃ for 10 hours, and after natural cooling, crushing is carried out by using crushing equipment to obtain the electrode substrate material LiNi 0.75 Mn 0.25 O 2 。
(b) And Nb 2 O 5 And Ti (OH) 4 (Nb: ti element mass ratio 1); adding the composite material A (with the Nb element content of 0.2%) and the electrode base material into a mixing device for mixing, wherein the mixing time is 15 minutes, and the stirring speed is 2500rpm; and then annealing the mixed and coated mixed material in an oxygen environment at the high temperature of 400 ℃ for 6h, and screening by a 300-mesh sieve to obtain the cathode material.
Example 5
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) LiOH and a precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 15min, and the stirring rotating speed is 3000rpm; then the mixed materials are put in oxygen atmosphere(the oxygen concentration is more than 90 percent, the oxygen flow is 18L/min), reacting for 10 hours at the high temperature of 950 ℃ in an atmosphere furnace, naturally cooling, and crushing by using crushing equipment to obtain an electrode matrix material LiNi 0.75 Mn 0.25 O 2 。
(b) The electrode base material and zirconium oxide ZrO 2 And Nb 2 O 5 (Nb: zr element mass ratio 3) and simultaneously adding into a mixing device for mixing, wherein the mixing time is 15 minutes, and the stirring speed is 2500rpm; then annealing the mixed and coated mixed material in an oxygen environment at the high temperature of 400 ℃ for 6h, sieving by a 300-mesh sieve to obtain the cathode material.
Example 6
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) Mixing LiOH and precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 15min, and the stirring rotating speed is 2500rpm; and then reacting the mixed material at the high temperature of 900 ℃ in an oxygen atmosphere (the oxygen concentration is more than 90 percent, and the oxygen flow is 20L/min) in an atmosphere furnace for 10 hours, naturally cooling, and crushing by using crushing equipment to obtain the electrode base material.
(b) Nb in a reaction vessel 2 O 5 And Al 2 O 3 (Nb: al element mass ratio 3; adding the composite material A (with the Nb element content of 0.3%) and the electrode base material into a mixing device for mixing, wherein the mixing time is 15 minutes, and the stirring speed is 2500rpm; and then annealing the mixed and coated mixed material in an oxygen environment at the high temperature of 400 ℃ for 6h, and screening by a 300-mesh sieve to obtain the cathode material.
Comparative example 1
EXAMPLE 4 electrode base Material LiNi prepared in step (a) 0.75 Mn 0.25 O 2 。
Comparative example 2
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) Mixing LiOH and precursor materialNi material 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 15min, and the stirring rotating speed is 3000rpm; then the mixed materials are put into an atmosphere furnace (the oxygen concentration is more than 90 percent, the oxygen flow is 18L/min) for high-temperature reaction at 950 ℃ for 10 hours, and after natural cooling, crushing is carried out by using crushing equipment to obtain the electrode substrate material LiNi 0.75 Mn 0.25 O 2 。
(b) Mixing the electrode base material with zirconium oxide (ZrO) 2 ) Are added into a mixing device together for mixing, and the addition amount of the Zr element is the sum of the masses of Zr and Nb in example 5, wherein the mixing time is 15 minutes, and the stirring speed is 2500rpm; and then annealing the mixed and coated mixed material in an oxygen environment at the high temperature of 400 ℃ for 6h, and screening by a 300-mesh sieve to obtain the cathode material.
Comparative example 3
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) LiOH and a precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 15min, and the stirring rotating speed is 3000rpm; then the mixed materials are put into an atmosphere furnace (the oxygen concentration is more than 90 percent, the oxygen flow is 18L/min) for high-temperature reaction at 950 ℃ for 10 hours, and after natural cooling, crushing is carried out by using crushing equipment to obtain the electrode substrate material LiNi 0.75 Mn 0.25 O 2 。
(b) The electrode base material and alumina (Al) 2 O 3 ) The Al elements are added into a mixing device together for mixing, and the addition amount of the Al elements is the sum of the mass of Al and Nb in example 6, wherein the mixing time is 15 minutes, and the stirring speed is 2500rpm; and then annealing the mixed and coated mixed material in an oxygen environment at the high temperature of 400 ℃ for 6h, and screening by a 300-mesh sieve to obtain the cathode material.
Comparative example 4
The preparation method of the cathode material in the embodiment comprises the following steps:
(a) LiOH and a precursor material Ni 0.75 Mn 0.25 (OH) 2 Mixing by adopting high-speed mixing equipment, wherein the mixing time is 15min, and the stirring speed is 3000rpm; then the mixed materials are put into an atmosphere furnace (the oxygen concentration is more than 90 percent, the oxygen flow is 18L/min) for high-temperature reaction at 950 ℃ for 10 hours, and after natural cooling, crushing is carried out by using crushing equipment to obtain the electrode substrate material LiNi 0.75 Mn 0.25 O 2 。
(b) The electrode base material and ZrO 2 And TiO 2 Simultaneously adding the mixed solution into a mixing device for mixing, wherein the mass sum of the Zr element and the Ti element is the same as that of the Nb element and the Ti element in the example 4, the mixing time is 15 minutes, and the stirring speed is 2500rpm; then annealing the mixed and coated mixed material in an oxygen environment at the high temperature of 400 ℃ for 6h, sieving by a 300-mesh sieve to obtain the cathode material.
Comparative example 5
(a) Same as in step (a) of example 4;
(b) Same as in step (b) of example 4, except that only Nb was added at the time of mixing 2 O 5 However, the mass sum of the Nb element remains the same as that of the Nb and Ti elements in example 4.
Test example 1
The electrode base material LiNi prepared in step (a) of example 4 was used 0.75 Mn 0.25 O 2 The positive electrode materials finally prepared in step (b) of comparative example 1 and example 4 were respectively subjected to scanning electron microscope examination, and the results thereof are shown in fig. 1 to 4.
As can be seen from fig. 1 to 4, after the treatment of step (b), the surface of the particles of the positive electrode material is successfully coated with a uniform coating substance.
Test example 2
The positive electrode materials obtained in examples 1 to 6 and comparative examples 1 to 5 of the present application were analyzed for electrochemical properties, and the results are shown in table 1 below.
TABLE 1 analysis of electrochemical Properties of electrode base Material and cathode Material
As can be seen from table 1, the 0.1C discharge capacity of the positive electrode material provided in example 4 of the present application was increased by up to about 5mAh/g and the 1C discharge capacity was increased by up to 8mAh/g, as compared to the uncoated positive electrode material (comparative example 1). Therefore, the conductive performance of the material is improved by coating the coating layer with better conductive performance. Meanwhile, the coating effect of the anode material is good, a uniform coating layer is formed, the mechanical strength of the anode material is enhanced, the contact of the anode material and electrolyte is effectively prevented by the coating agent, the occurrence of side reactions is reduced, and the cycle performance of the material is improved.
In comparative example 2, as compared with example 5, the coating layer composed of Zr metal and Nb was used as the coating layer, and the electrode base material (LiNi) was used as the counter electrode 0.75 Mn 0.25 O 2 ) The improvement of the discharge capacity of the coating is better than that of the oxide coating layers of Zr and Al which are coated separately. Comparative example 4 in comparison with example 4, a counter electrode base material (LiNi) using a coating layer in which Nb and Ti are compounded 0.75 Mn 0.25 O 2 ) The improvement of the discharge capacity of the coating is better than that of a coating layer which adopts Zr and Ti in composite matching. Comparative example 5 compared with example 4, the coating layer only adopts Nb oxide, and the electrical property of the cathode material is not improved as much as that of the composite coating layer formed by adding the metal additive-Nb.
Test example 3
The materials obtained in examples 1 to 6 and comparative examples 1 to 5 were respectively subjected to half-cell fabrication, and the DCR of the cell at normal temperature under 0.1C charge and 0.1C discharge was calculated by performing a test on the charge-discharge system. The results are shown in Table 2.
TABLE 2 DCR test results for cells
| Group of | |
Buckle electricity 2 | Buckle electricity 3 |
| Example 1 (m.OMEGA.) | 16.6 | 17.1 | 16.3 |
| Example 2 (m.OMEGA.) | 17.2 | 16.4 | 16.2 |
| Example 3 (m.OMEGA.) | 16.1 | 16.5 | 16.1 |
| Example 4 (m.OMEGA.) | 12.6 | 10.1 | 11.7 |
| Example 5 (m.OMEGA.) | 16.9 | 19.4 | 18.8 |
| Example 6 (m.OMEGA.) | 15.8 | 15.8 | 16.2 |
| COMPARATIVE EXAMPLE 1 (m.OMEGA.) | 41.2 | 39.7 | 38.2 |
| COMPARATIVE EXAMPLE 2 (m.OMEGA.) | 20.5 | 19.2 | 21.3 |
| COMPARATIVE EXAMPLE 3 (m.OMEGA.) | 25.9 | 23.9 | 22.6 |
| COMPARATIVE EXAMPLE 4 (m.OMEGA.) | 22.9 | 23.2 | 23.5 |
| COMPARATIVE EXAMPLE 5 (m.OMEGA.) | 21.2 | 21.7 | 22.2 |
As can be seen from table 2, the cathode material provided by the present invention significantly reduces DCR of the material by introducing a coating layer with good conductivity.
While particular embodiments of the present invention have been illustrated and described, it will be appreciated that the above embodiments are only intended to illustrate the technical solution of the present invention and not to limit it; those of ordinary skill in the art will understand that: modifications may be made to the teachings of the foregoing embodiments without departing from the spirit or scope of the present invention, or equivalents may be substituted for some or all of the features thereof; the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention; it is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
Claims (10)
1. The positive electrode material is characterized by comprising an electrode base material and a coating layer coated on the surface of the electrode base material;
wherein the chemical formula of the electrode base material is LiNi x Mn y O 2 ，0.50≤x≤0.95，0.05≤y≤0.50；
The chemical formula of the coating layer is M a Nb b O c Wherein the mass fraction of Nb in the coating layer is 0.1-0.5%, and M is selected from Ta;
the preparation method of the material of the coating layer comprises the following steps: grinding the oxide of Nb and the oxide or salt of the metal M to obtain a material of the coating layer;
the positive electrode material does not contain cobalt element;
the mass of the coating layer is 0.1-3% of that of the electrode base material;
the mass ratio of Nb to metal M in the cladding layer is 1-3;
the preparation method of the cathode material comprises the following steps: mixing the material of the coating layer with the electrode base material, coating, and then annealing to obtain the anode material;
the annealing treatment comprises the following steps: and heating the coated material at 200-350 ℃ in an oxygen-containing atmosphere.
2. The positive electrode material according to claim 1, wherein the specific surface area of the positive electrode material is 0.2 to 0.9m 2 /g。
3. The positive electrode material according to claim 1, wherein the particle diameter of the positive electrode material is 1 to 5 μm.
4. The positive electrode material according to claim 1, wherein the time for the milling is 1 to 2 hours.
5. The positive electrode material according to claim 1, wherein the stirring speed during the mixing is 2000 to 3000rpm.
6. The positive electrode material according to claim 5, wherein the stirring time is 10 to 20min.
7. The positive electrode material according to claim 1, wherein the time of the heat treatment is 4 to 8 hours.
8. The positive electrode material according to claim 1, wherein the total amount of lithium carbonate and lithium hydroxide in the positive electrode material is less than 0.3wt%.
9. The positive electrode material as claimed in claim 1, wherein the positive electrode material has a pH of 12 or less.
10. A lithium ion battery comprising the positive electrode material as claimed in any one of claims 1 to 9.
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