CN115799471A - Doped coating modified nickel cobalt lithium manganate material, preparation method and application thereof - Google Patents
Doped coating modified nickel cobalt lithium manganate material, preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a doped coated modified nickel cobalt lithium manganate material, a preparation method and application thereof a Ni b Co c Mn d Ta e O 2 /Nb f A, b, c, d, e, f are sufficientThe following requirements are set: a is more than or equal to 1.0 and less than or equal to 1.2, b is more than or equal to 0.5 and less than or equal to 1, c is more than 0 and less than or equal to 0.2, d is more than 0 and less than or equal to 0.3, e is more than 0 and less than or equal to 0.01, and f is more than 0 and less than or equal to 0.01. Doping a doping element Ta into the nickel cobalt lithium manganate material through one-time sintering; and coating the coating element Nb on the surface of the Ta-doped nickel cobalt lithium manganate material by secondary sintering. The 0.1C specific discharge capacity of the doped and coated modified nickel cobalt lithium manganate material is more than 212mAh/g in a voltage range of 3-4.3V, and the circulating capacity retention rate reaches more than 91.21% at a constant temperature of 25 ℃ for 100 weeks.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a doped coated modified nickel cobalt lithium manganate material, a preparation method and application thereof.
Background
The rapid development of the new energy automobile industry puts higher requirements on the performance of the lithium ion battery. Lithium ion batteries are widely used in the fields of 3C, electric vehicles, and the like due to their advantages of high energy density, high capacity, good cycle performance, and the like. The lithium ion battery is composed of main parts such as a positive electrode material, a negative electrode material, a diaphragm, electrolyte and the like, wherein the positive electrode material has a dominant position in action and cost, and the performance of the positive electrode material directly influences the performance of the battery. The core component of the new energy automobile is the battery, the cost of the battery accounts for about 40% of the whole automobile, and the quality of the battery directly influences the endurance, safety and the like of the automobile.
The positive electrode materials of lithium batteries used at the present stage mainly include lithium iron phosphate, lithium manganate, lithium cobaltate, ternary lithium and the like. Currently, in the field of new energy automobiles, lithium ion batteries are mainly applied to lithium iron phosphate batteries and ternary lithium batteries. The lithium iron phosphate battery does not contain precious metal materials, and has low cost, long cycle life and high safety. The ternary lithium battery has higher energy density and high charging and discharging speed, but has higher irreversible capacity loss during first charging and discharging, poorer cycle performance, lower safety performance and higher cost. In order to increase the gram volume of the material, the nickel content is generally increased, but the increase of the nickel content increases the cost on one hand and also reduces the safety performance of the material on the other hand.
In addition, most of the nickel-cobalt-manganese ternary positive electrode materials are modified by adopting single element doping or cladding, the doping mode is single, the effect is limited, only one performance of the material is improved, the other performances are not obviously improved, and some of the materials can even generate negative effects.
Therefore, a modification method is needed, so that the gram capacity, rate capability, cycle life, safety performance and the like of the material are obviously improved.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a doped coated modified nickel cobalt lithium manganate material, a preparation method and application thereof, wherein in the preparation method, tantalum ions are doped into the material through one-time sintering, so that the internal structure of the material is stabilized, and the thermal stability of the material is improved; and then, niobium ions are coated on the surface of the doped material through secondary sintering, so that the surface coating property of the material is improved, the lithium ion loss is reduced, the first effect is improved, and the electrical property and the safety performance of the material can be obviously improved under the synergistic effect of the two elements.
In order to achieve the above object, the present invention adopts the following technical solutions.
A doped coated modified lithium nickel cobalt manganese oxide material is a doped Ta coated Nb modified lithium nickel cobalt manganese oxide material with a general formula of Li a Ni b Co c Mn d Ta e O 2 /Nb f The values of a, b, c, d, e and f meet the following requirements: a is more than or equal to 1.0 and less than or equal to 1.2, b is more than or equal to 0.5 and less than or equal to 1, c is more than 0 and less than or equal to 0.2, d is more than 0 and less than or equal to 0.3, e is more than 0 and less than or equal to 0.01, and f is more than 0 and less than or equal to 0.01.
As a preferable embodiment, the doped coated modified nickel cobalt lithium manganate material has e more than 0 and less than or equal to 0.002, and f more than 0 and less than or equal to 0.004.
As a preferred embodiment, the doped coated modified lithium nickel cobalt manganese oxide material is prepared by doping a doping element Ta into the lithium nickel cobalt manganese oxide material through one-time sintering; coating a coating element Nb on the surface of the Ta-doped nickel cobalt lithium manganate material by secondary sintering, preferably, the nickel cobalt lithium manganate before modification is LiNi 0.83 Co 0.12 Mn 0.05 O 2 。
According to the invention, ta element is doped into the lithium nickel cobalt manganese oxide material through one-time sintering, and the Ta element doping can stabilize the crystal structure of the lithium nickel cobalt manganese oxide material, improve the cycle performance of the material and improve the thermal stability of the material. Through the surface of secondary sintering with the nickel cobalt lithium manganate material after the doping of Nb element cladding, the remaining lithium carbonate in material surface can be consumed to the Nb cladding to form one deck nanometer coating on the material surface, this kind of nanometer coating can effectively reduce the production of material surface miscellaneous phase, has reduced lithium ion's loss, makes lithium ion's transmission process more unobstructed simultaneously.
In addition, a small amount of Nb permeates into a nickel cobalt lithium manganate material phase in the coating process and generates a synergistic effect with Ta element, so that the crystal structure of the material can be better stabilized, and the cycle performance of the material is improved. Therefore, the existence of the Nb coating layer can improve the discharge capacity and rate performance of the material, reduce the surface resistance, improve the lithium ion transmission rate and reduce the formation of the surface impurity phase of the material.
In a preferred embodiment, the doped coated modified lithium nickel cobalt manganese oxide material contains a doping element Ta in an amount of 1000ppm to 5000ppm (for example, 1500ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500 ppm).
In a preferred embodiment of the above-mentioned doped, coated and modified lithium nickel cobalt manganese oxide material, the content of the coating element Nb in the doped, coated and modified lithium nickel cobalt manganese oxide material is 1000ppm to 5000ppm (for example, 1500ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500 ppm).
The invention also provides a preparation method of the doped coated modified nickel cobalt lithium manganate material, which adopts the following technical scheme.
A preparation method of a doped coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) Uniformly mixing a nickel-cobalt-manganese ternary positive electrode precursor, a lithium source and a tantalum (Ta) compound for doping to obtain a mixture A;
(2) Sintering the mixture A for the first time to obtain doped modified nickel cobalt lithium manganate;
(3) Mixing the doped and modified nickel cobalt lithium manganate with water, stirring, dehydrating and drying to obtain dried doped and modified nickel cobalt lithium manganate;
(4) Uniformly mixing the dried doped and modified nickel cobalt lithium manganate obtained in the step (3) with a niobium (Nb) compound for coating to obtain a mixture B;
(5) And (4) carrying out secondary sintering on the mixture obtained in the step (4) to obtain the doped, coated and modified nickel cobalt lithium manganate.
According to the invention, a secondary sintering process is adopted, the doped elements can better enter a nickel cobalt lithium manganate material phase, the coating elements can more uniformly cover the surface of the material, and the prepared material has better gram volume performance, rate capability, cycle life and safety performance.
In the above preparation method, as a preferred embodiment, in the step (1), the ternary positive electrode precursor is Ni x Co y Mn z (OH) 2 X is more than or equal to 0.5 and less than 1, y is more than 0 and less than or equal to 0.2, z is more than 0 and less than or equal to 0.3, x + y + z =1; more preferably Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 。
In the above production method, as a preferred embodiment, in the step (1), the molar ratio of the lithium element in the lithium source to the sum of the nickel, cobalt, and manganese elements in the nickel-cobalt-manganese ternary positive electrode precursor is 1.0 to 1.2 (for example, 1.03.
In the above preparation method, as a preferred embodiment, in the step (1), the lithium source is at least one of lithium carbonate, anhydrous lithium hydroxide and monohydrate lithium hydroxide.
In the above production method, as a preferable embodiment, in the step (1), the Ta compound for doping is Ta 2 O 5 And tantalate (C) 2 H 2 O 4 X 'Ta, the value of x' being in the range of 1 to 3).
In the above production method, as a preferred embodiment, in the step (1), the Ta compound for doping is added in such a manner that the molar ratio of the lithium element in the lithium source to the metal element for doping Ta in the Ta compound for doping is 1. That is, in the step (1), the Ta compound for doping is added in such a manner that the mass ratio of the lithium element in the lithium source to the doping metal element Ta in the Ta compound for doping is 1.
In the above preparation method, as a preferred embodiment, in the step (1), the nickel-cobalt-manganese ternary positive electrode precursor and the lithium source are mixed, and then the Ta compound for doping is added to the mixture of the nickel-cobalt-manganese ternary positive electrode precursor and the lithium source.
In the above preparation method, as a preferred embodiment, in the step (3), the water is pure water.
In the step (3) of the invention, the doped and modified nickel cobalt lithium manganate obtained in the step (2) is mixed with water, and lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material are washed away, so that the surface residual alkali is reduced. Because residual alkali affects battery manufacturing and battery performance, such as homogenate jelly caused by too high alkali content, poor thermal stability of batteries caused by too high lithium carbonate and the like, washing the residual alkali with water is beneficial to ensuring the performance of batteries assembled by the material.
In the above production method, as a preferable embodiment, in the step (4), the Nb compound for coating is Nb 2 O 5 And NbX 5 At least one of (niobium pentahalide), wherein X is one of F, cl, br, I, at and Ts.
In the above production method, as a preferred embodiment, in the step (4), the molar ratio of the lithium element in the lithium source to the coating metal element in the coating compound is 1. That is, in the step (4), the mass ratio of the lithium element in the lithium source to the coating metal element in the coating compound is 1.
In the above preparation method, as a preferred embodiment, in the step (2), the calcination atmosphere for the primary sintering is oxygen, and preferably, the concentration of the oxygen is greater than or equal to 80%.
Because the high-nickel ternary precursor is easy to generate the cation mixed-discharging phenomenon in the sintering process, the pure oxygen sintering can ensure that the sintering is more sufficient, and the cation mixed-discharging phenomenon is reduced.
In the above-mentioned production method, as a preferable embodiment, in the step (2), the calcination temperature in the primary sintering is 700 to 890 ℃ (700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃), preferably 750 to 850 ℃ (for example, 760 ℃, 780 ℃, 800 ℃, 820 ℃, 840 ℃), and the calcination time is 18 to 26 hours (for example, 19 hours, 20 hours, 22 hours, 24 hours, 25 hours).
In the present invention, the primary sintering is mainly aimed at reacting the precursor with the lithium source and infiltrating the doping element into the bulk material phase.
In the above preparation method, as a preferred embodiment, in the step (2), the doped lithium nickel cobalt manganese oxide obtained by primary sintering needs to be crushed and then screened, so as to obtain doped lithium nickel cobalt manganese oxide product particles with a particle size D50 of 3 to 4.5 μm. The particle size D50 here means that the proportion of particles having a particle size greater than 50% is greater than this and the proportion of particles having a particle size less than this is also 50%.
In the above preparation method, as a preferred embodiment, the nickel cobalt lithium manganate doped in the step (3) is mixed with water in a mass ratio of 1 (0.6 to 1.2) (e.g., 1.
In the above preparation method, as a preferred embodiment, in the step (5), the calcination atmosphere for the secondary sintering is oxygen, and preferably, the oxygen concentration is greater than or equal to 90%.
In the present invention, the secondary sintering is mainly to coat the coating material on the surface of the material more uniformly, but to prevent the content of residual alkali on the surface of the material from increasing, the sintering is required to be performed under a high oxygen concentration to prevent the sintering from reacting with H in the air 2 O and CO 2 Contacting to generate residual alkali; sintering with pure oxygen is better without considering the cost.
In the above-mentioned preparation method, as a preferable embodiment, in the step (5), the calcination temperature of the secondary sintering is 200 ℃ to 400 ℃ (e.g., 220 ℃, 250 ℃, 280 ℃, 300 ℃, 350 ℃, 400 ℃), and the calcination time is 12 to 20h (e.g., 13h, 15h, 16h, 18 h).
The invention also provides application of the doped coated modified nickel cobalt lithium manganate material as a positive electrode material in a lithium ion battery.
In the invention, the technical characteristics can be freely combined to form a new technical scheme under the condition of not conflicting with each other.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the doped and coated modified nickel cobalt lithium manganate material has the specific discharge capacity of 0.1C of more than 212mAh/g in a voltage range of 3-4.3V, and the gram capacity is improved by about 6mAh/g compared with that of the unmodified nickel cobalt lithium manganate material; the retention rate of the circulation capacity at the constant temperature of 25 ℃ for 100 weeks is more than 91.21 percent, and is improved by about 5 percent compared with the unmodified lithium nickel cobalt manganese oxide material;
2. the DSC thermal decomposition temperature of the doped coated modified lithium nickel cobalt manganese oxide material is increased by about 12 ℃ compared with that of the unmodified lithium nickel cobalt manganese oxide material;
3. the method has high process stability, the doping elements can be stably doped into the bulk phase by adopting a secondary sintering process, the coating elements can be uniformly coated on the surface of the material, and the gram capacity, cycle life, safety performance and the like of the prepared nickel cobalt lithium manganate material are obviously improved.
Drawings
FIG. 1 is an SEM image of a doped coated modified nickel cobalt lithium manganate material prepared in example 1 of the present invention.
Fig. 2 is an enlarged view of the SEM image of fig. 1.
FIG. 3 is a graph showing the first charge-discharge curves of the lithium nickel cobalt manganese oxide materials prepared in examples 1 to 3 of the present invention and comparative examples 1 to 4.
Detailed Description
The present invention will be described in detail with reference to examples. The various examples are provided by way of explanation of the invention, and not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. It is therefore intended that the present invention encompass such modifications and variations as fall within the scope of the appended claims and their equivalents.
In the present invention, the reagents and materials are commercially available, unless otherwise specified.
The doped coated modified lithium nickel cobalt manganese oxide material Li prepared by the invention a Ni b Co c Mn d Ta e O 2 /Nb f The values of a, b, c, d, e and f meet the following requirements: a is more than or equal to 1.0 and less than or equal to 1.2, b is more than or equal to 0.5 and less than or equal to 1, c is more than 0 and less than or equal to 0.2, d is more than 0 and less than or equal to 0.3, e is more than 0 and less than or equal to 0.01, and f is more than 0 and less than or equal to 0.01. Wherein a, b, c, d, e and f are atomic numbers or mole numbers of corresponding elements.
Ternary precursor Ni x Co y Mn z (OH) 2 X is more than or equal to 0.5 and less than 1, y is more than 0 and less than or equal to 0.2, z is more than 0 and less than or equal to 0.3, and x + y + z =1, wherein x, y and z are atomic numbers or mole numbers of corresponding elements.
Example 1
A preparation method of a doped and coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04 blend, ta 2 O 5 The adding amount is that the molar ratio of the lithium element to the tantalum element is 1:0.000763 (namely, the mass ratio is 1;
(2) Performing primary sintering on the mixture obtained in the step (1), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 800 ℃, and the calcining time is 22h; crushing, sieving, mixing with water, washing to remove lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain doped modified nickel cobalt lithium manganate;
(3) According to the molar ratio of lithium element to niobium element of 1:0.001857 (namely, the mass ratio is 1 2 O 5 Adding the mixture into the doped modified nickel cobalt lithium manganate obtained in the step (2), uniformly mixing, and performing secondary sintering, wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 400 ℃, and the calcining time is 16 hours, so as to obtain the doped coated modified nickel cobalt lithium manganate with the general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.000763 O 2 /Nb 0.001857 . Fig. 1 and 2 show SEM images of the doped coated modified lithium nickel cobalt manganese oxide prepared in this example.
Example 2
A preparation method of a doped and coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04 blend, ta 2 O 5 The adding amount is that the molar ratio of the lithium element to the tantalum element is 1:0.001144 (namely, the mass ratio is 1;
(2) Performing primary sintering on the mixture obtained in the step (1), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 800 ℃, and the calcining time is 22h; crushing, sieving, mixing with water, washing to remove lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain doped modified nickel cobalt lithium manganate;
(3) According to the molar ratio of the lithium element to the niobium element of 1:0.002600 (namely, the mass ratio is 1 2 O 5 Adding the lithium nickel cobalt manganese oxide into the doped and modified lithium nickel cobalt manganese oxide obtained in the step (2), and uniformly mixing; carrying out secondary sintering under the condition that the sintering atmosphere is oxygen, the oxygen concentration is 90 percent, the calcining temperature is 400 ℃ and the calcining time is 16h to obtain the doping coating modified nickel cobalt lithium manganate with the general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001144 O 2 /Nb 0.002600 。
Example 3
A preparation method of a doped and coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04 blend, ta 2 O 5 The adding amount is that the molar ratio of the lithium element to the tantalum element is 1:0.001526 (namely, the mass ratio is 1;
(2) Performing primary sintering on the mixture obtained in the step (1), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 800 ℃, and the calcining time is 22h; crushing, sieving, mixing with water, washing to remove lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain doped modified nickel cobalt lithium manganate;
(3) According to the molar ratio of the lithium element to the niobium element of 1:0.003342 (namely, the mass ratio is 1 2 O 5 Adding the mixture into the doped modified nickel cobalt lithium manganate obtained in the step (2), uniformly mixing, and performing secondary sintering, wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 400 ℃, and the calcining time is 16 hours, so as to obtain the doped coated modified nickel cobalt lithium manganate with the general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001526 O 2 /Nb 0.003342 。
Example 4
A preparation method of a doping-coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04 mixing, tantalum oxalate salt (C) 2 H 2 O 4 xTa) is added in a molar ratio of lithium element to tantalum element of 1:0.000763 (namely, the mass ratio is 1;
(2) Performing primary sintering on the mixture obtained in the step (1), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 800 ℃, and the calcining time is 22h; crushing, sieving, mixing with water, washing to remove lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain doped modified nickel cobalt lithium manganate;
(3) According to the molar ratio of lithium element to niobium element of 1:0.001857 Niobium pentahalide (NbX) was weighed (i.e., mass ratio of 1 5 X is one of F, cl, br, I, at and Ts), adding the mixture into the doped modified nickel cobalt lithium manganate obtained in the step (2), uniformly mixing, and performing secondary sintering, wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 400 ℃, and the calcination time is 16h, so as to obtain the doped coated modified nickel cobalt lithium manganate with the general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.000763 O 2 /Nb 0.001857 。
Comparative example 1
A preparation method of a nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04, and carrying out primary sintering under the condition that the sintering atmosphere is oxygen, the oxygen concentration is 90 percent, the calcination temperature is 800 ℃, and the calcination time is 22 hours;
(2) Crushing and sieving the product sintered in the step (1), mixing the product with water, washing away lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, dehydrating and drying to obtain a product, and performing secondary sintering on the product, wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 400 ℃, and the calcination time is 16 hours to obtain the nickel cobalt lithium manganate material with the general formula of LiNi 0.83 Co 0.12 Mn 0.05 O 2 。
In the comparative example, the lithium nickel cobalt manganese oxide material is not subjected to tantalum doping and niobium coating modification.
Comparative example 2
A preparation method of a doped modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And hydrogen monohydrateLithium oxide is added according to a molar ratio of 1:1.04 mixing, ta 2 O 5 The adding amount is that the molar ratio of the lithium element to the tantalum element is 1:0.000763, adding into the mixture of the ternary anode precursor and the lithium hydroxide monohydrate, and mixing uniformly;
(2) Performing primary sintering on the mixture obtained in the step (1), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 800 ℃, and the calcining time is 22h; crushing, sieving, mixing with water, washing to remove lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain doped modified nickel cobalt lithium manganate;
(3) And (3) carrying out secondary sintering on the doped modified nickel cobalt lithium manganate obtained in the step (2), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 400 ℃, and the calcining time is 16h, so as to obtain the doped nickel cobalt lithium manganate with the general formula of LiNi 0.83 Co 0.1 2 Mn 0.05 Ta 0.000763 O 2 。
In this comparative example, the lithium nickel cobalt manganese oxide material was not niobium-coated.
Comparative example 3
A preparation method of a coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04, and carrying out primary sintering under the condition that the sintering atmosphere is oxygen, the oxygen concentration is 90 percent, the calcination temperature is 800 ℃, and the calcination time is 22 hours; crushing, sieving, mixing with water, washing away lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain the nickel cobalt lithium manganate;
(2) According to the molar ratio of the lithium element to the niobium element of 1:0.001857 weighing Nb 2 O 5 Adding the mixture into the nickel cobalt lithium manganate obtained in the step (1) after being crushed and sieved, and uniformly mixing; performing secondary sintering, wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 400 ℃, and the calcining time is 16h; obtaining the coated and modified nickel cobalt lithium manganate with the general formula of LiNi 0.83 Co 0.12 Mn 0.05 O 2 /Nb 0.001857 。
In the comparative example, the lithium nickel cobalt manganese oxide material was not modified by tantalum doping.
Comparative example 4
A preparation method of a doping-coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04 blend, ta 2 O 5 The adding amount is that the molar ratio of the lithium element to the tantalum element is 1:0.001144, adding the weighed materials into a mixture of a ternary positive electrode precursor and lithium hydroxide monohydrate, and uniformly mixing;
(2) Performing primary sintering on the mixture obtained in the step (1), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 900 ℃, and the calcining time is 22h; crushing, sieving, mixing with water, washing away lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain the doped and modified nickel cobalt lithium manganate;
(3) According to the molar ratio of the lithium element to the niobium element of 1:0.002600 weighing Nb 2 O 5 Adding the mixture into the nickel cobalt lithium manganate obtained in the step (2) after doping modification, and uniformly mixing; carrying out secondary sintering under the condition that the sintering atmosphere is oxygen, the oxygen concentration is 90 percent, the calcining temperature is 400 ℃, and the calcining time is 16h to obtain the doping-coated modified nickel cobalt lithium manganate with the general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001144 O 2 /Nb 0.002600 。
In this comparative example, the calcination temperature for one-time sintering was too high.
Comparative example 5
A preparation method of a doping-coated modified nickel cobalt lithium manganate material comprises the following steps:
(1) The ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 And lithium hydroxide monohydrate in a molar ratio of 1:1.04 blend, ta 2 O 5 The adding amount is that the molar ratio of the lithium element to the tantalum element is 1:0.001144, adding the weighed materials into a mixture of a ternary positive electrode precursor and lithium hydroxide monohydrate, and uniformly mixing;
(2) Performing primary sintering on the mixture obtained in the step (1), wherein the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcining temperature is 800 ℃, and the calcining time is 22h; crushing, sieving, mixing with water, washing to remove lithium carbonate, lithium hydroxide and free lithium remained on the surface of the material, and dehydrating and drying to obtain doped modified nickel cobalt lithium manganate;
(4) (3) according to the molar ratio of the lithium element to the niobium element of 1:0.002600 weighing Nb 2 O 5 Adding the lithium nickel cobalt manganese oxide into the doped and modified lithium nickel cobalt manganese oxide obtained in the step (2), and uniformly mixing; carrying out secondary sintering under the condition that the sintering atmosphere is oxygen, the oxygen concentration is 90 percent, the calcining temperature is 500 ℃, and the calcining time is 16h to obtain doped coating modified nickel cobalt lithium manganate or LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001144 O 2 /Nb 0.002600 。
In this comparative example, the calcination temperature of the secondary sintering was too high.
Battery assembly and performance testing
Manufacturing a positive plate: mixing an active material (the nickel cobalt lithium manganate material obtained in examples 1-4 and comparative examples 1-5), superP and PVDF according to a mass ratio of 90: 5, adding a proper amount of NMP, uniformly stirring, uniformly coating electrode slurry on an aluminum foil, drying, rolling, slicing, and vacuum-drying at 120 ℃ for 24 hours.
Assembling the battery: placing a positive electrode shell, placing an elastic sheet in the shell, placing a metal sheet on the elastic sheet, and placing a metal sheet on the metal sheet
The surface of the anode plate coated with the anode material faces upwards, is soaked by the electrolyte and is covered by the electrolyte
A diaphragm (a battery-grade polypropylene microporous film) is soaked by electrolyte, and a metal lithium sheet is placed; and assembling the button cell into a CR2032 type button cell. The electrolyte used is 1.15mol/LLIPF 6 The EC + DEC + EMC (volume ratio is 1: 1), and the additive DFP is less than or equal to 2 percent.
And performing electrochemical performance test by using the assembled CR2032 type button cell. The test conditions were as follows: the charging and discharging voltage interval is 3V-4.3V; the test temperature was 25 ℃; the button cell was charged to 4.3V at 0.1C and was held constant for 30min, and the capacity of the button cell was tested at 0.1C rate.
After the first circulation is finished, the button cell is fully charged, then the button cell is disassembled in the glove box, the positive electrode material on the positive plate is scraped and transferred into a high-pressure crucible, and the positive electrode material is used as a sample for DSC test. DSC tests were carried out at 25 ℃ on the lithium nickel cobalt manganese oxide materials obtained in examples 1 to 4 and comparative examples 1 to 5, and the respective temperature increase rates were 5 ℃/min.
Table 1 lists the cycling performance and capacity data (0.1C, 3-4.3V @25 deg.C) and DSC thermal decomposition temperatures for examples 1-4 and comparative examples 1-5. FIG. 3 shows the first charge-discharge curves of the lithium nickel cobalt manganese oxide materials prepared in examples 1 to 3 of the present invention and comparative examples 1 to 4.
TABLE 1 cycle performance (0.1C3-4.3V @25 ℃) and DSC pyrolysis temperature of the cathode material
As can be seen from Table 1 and FIG. 3, in example 1, the first discharge capacity of the obtained doped and coated modified nickel cobalt lithium manganate material reaches 212.2mAh/g, the capacity retention rate reaches 91.21% after being cycled at 25 ℃ under normal temperature for 100 weeks, and the DSC thermal decomposition temperature reaches 230 ℃.
Similarly, in example 2, the first discharge capacity of the obtained doped lithium nickel cobalt manganese oxide material reaches 216.3mAh/g, the capacity retention rate is 94.45% after being cycled at 25 ℃ for 100 weeks, and the DSC thermal decomposition temperature is 239 ℃.
In example 3, the first discharge capacity of the doped and coated lithium nickel cobalt manganese oxide material reaches 214.9mAh/g, the capacity retention rate is 93.24% after the material is cycled at 25 ℃ under normal temperature for 100 weeks, and the DSC thermal decomposition temperature is 235 ℃.
In example 4, the first discharge capacity of the doped and coated lithium nickel cobalt manganese oxide material reaches 214.1mAh/g, the capacity retention rate is 92.89% after the material is cycled at 25 ℃ under normal temperature for 100 weeks, and the DSC thermal decomposition temperature is 234 ℃.
In the comparative example 1, the first discharge capacity of the obtained nickel cobalt lithium manganate material reaches 206.5mAh/g, the capacity retention rate is 86.7 percent after the material is cycled at the normal temperature of 25 ℃ for 100 weeks, and the DSC thermal decomposition temperature is 218 ℃.
In the comparative example 2, the first discharge capacity of the doped and modified nickel cobalt lithium manganate material reaches 207.3mAh/g, the capacity retention rate is 87.5 percent after the material is cycled at the normal temperature of 25 ℃ for 100 weeks, and the DSC thermal decomposition temperature is 225 ℃.
In comparative example 3, the first discharge capacity of the obtained coated and modified lithium nickel cobalt manganese oxide material reaches 208.8mAh/g, the capacity retention rate is 88.6 percent after the lithium nickel cobalt manganese oxide material is circulated at the normal temperature of 25 ℃ for 100 weeks, and the DSC thermal decomposition temperature is 220 ℃.
In comparative example 4, the first discharge capacity of the obtained coated and modified lithium nickel cobalt manganese oxide material reaches 205.3mAh/g, the capacity retention rate is 88.1 percent after the material is cycled at 25 ℃ and normal temperature for 100 weeks, and the DSC thermal decomposition temperature is 215 ℃.
In comparative example 5, the first discharge capacity of the obtained coated and modified nickel cobalt lithium manganate material reaches 206.1mAh/g, the capacity retention rate is 88.9 percent after being cycled at 25 ℃ and normal temperature for 100 weeks, and the DSC thermal decomposition temperature is 217 ℃.
In conclusion, the doped and coated modified nickel cobalt lithium manganate material has the specific discharge capacity of 0.1C of more than 212mAh/g in the voltage range of 3-4.3V and the first efficiency of more than 90 percent, and compared with the unmodified (or only doped or only coated) nickel cobalt lithium manganate material, the gram capacity of the doped and coated modified nickel cobalt lithium manganate material is improved by about 6mAh/g, and the first efficiency is improved; the circulation capacity retention rate reaches more than 91.21 percent at the constant temperature of 25 ℃ for 100 weeks, and is improved by about 5 percent compared with the nickel cobalt lithium manganate material which is not modified (or is only doped and modified or is only coated and modified);
in addition, the DSC thermal decomposition temperature of the doped and coated modified lithium nickel cobalt manganese oxide material is increased by about 12 ℃ compared with that of the unmodified lithium nickel cobalt manganese oxide material, and is correspondingly increased compared with the lithium nickel cobalt manganese oxide material which is only doped and modified or only coated and modified.
Claims (10)
1. A doped coated modified lithium nickel cobalt manganese oxide material is characterized in thatThe doped and coated modified nickel cobalt lithium manganate material is a Ta-doped and coated Nb-doped modified nickel cobalt lithium manganate material, and has a general formula of Li a Ni b Co c Mn d Ta e O 2 /Nb f The values of a, b, c, d, e and f meet the following requirements: a is more than or equal to 1.0 and less than or equal to 1.2, b is more than or equal to 0.5 and less than or equal to 1, c is more than 0 and less than or equal to 0.2, d is more than 0 and less than or equal to 0.3, e is more than 0 and less than or equal to 0.01, and f is more than 0 and less than or equal to 0.01.
2. The doped and coated modified lithium nickel cobalt manganese oxide material according to claim 1, wherein a doping element Ta is doped into the lithium nickel cobalt manganese oxide material through one-time sintering; coating the coating element Nb on the surface of the Ta-doped nickel cobalt lithium manganate material through secondary sintering; and/or the presence of a gas in the atmosphere,
in the doped and coated modified nickel cobalt lithium manganate material, the content of a doping element Ta is 1000 ppm-5000 ppm; the content of the coating element Nb is 1000ppm to 5000ppm.
3. The preparation method of the doped coated modified nickel cobalt lithium manganate material according to claim 1 or 2, characterized by comprising the following steps:
(1) Uniformly mixing a nickel-cobalt-manganese ternary positive electrode precursor, a lithium source and a Ta compound for doping to obtain a mixture A;
(2) Performing primary sintering on the mixture A to obtain doped modified nickel cobalt lithium manganate;
(3) Mixing the doped and modified nickel cobalt lithium manganate with water, stirring, dehydrating and drying to obtain dried doped and modified nickel cobalt lithium manganate;
(4) Uniformly mixing the dried doped and modified nickel cobalt lithium manganate obtained in the step (3) with a Nb compound for coating to obtain a mixture B;
(5) And (4) carrying out secondary sintering on the mixture obtained in the step (4) to obtain the doped, coated and modified nickel cobalt lithium manganate.
4. The preparation method of the doped coated modified lithium nickel cobalt manganese oxide material according to claim 3, wherein in the step (1), the doped coated modified lithium nickel cobalt manganese oxide material is preparedThe ternary positive electrode precursor is Ni x Co y Mn z (OH) 2 X is more than or equal to 0.5 and less than 1, y is more than 0 and less than or equal to 0.2, z is more than 0 and less than or equal to 0.3, x + y + z=1; and/or the presence of a gas in the gas,
in the step (1), the lithium source is at least one of lithium carbonate, anhydrous lithium hydroxide and monohydrate lithium hydroxide; and/or the presence of a gas in the gas,
in the step (1), the Ta compound for doping is Ta 2 O 5 And tantalate oxalate; and/or the presence of a gas in the gas,
in the step (4), the Nb compound for cladding is Nb 2 O 5 And NbX 5 Wherein, X is one of F, cl, br, I, at and Ts.
5. The method for preparing the doped coated modified nickel cobalt lithium manganate material of claim 3, wherein the ternary positive electrode precursor is Ni 0.83 Co 0.12 Mn 0.05 (OH) 2 。
6. The preparation method of the doped coated modified nickel cobalt lithium manganate material of claim 3, characterized in that,
in the step (2), the calcining atmosphere of the primary sintering is oxygen, the calcining temperature of the primary sintering is 700-890 ℃, and the calcining time is 18-26 h; and/or the presence of a gas in the gas,
in the step (5), the calcination atmosphere of the secondary sintering is oxygen, the calcination temperature of the secondary sintering is 200-400 ℃, and the calcination time is 12-20 h.
7. The preparation method of the doped coated modified nickel cobalt lithium manganate material of claim 3, characterized in that,
in the step (1), the molar ratio of the lithium element in the lithium source to the sum of the nickel, cobalt and manganese elements in the nickel-cobalt-manganese ternary positive electrode precursor is 1.0-1.2; and/or the presence of a gas in the atmosphere,
in the step (1), the Ta compound for doping is added in a manner that the molar ratio of lithium element in the lithium source to the Ta element for doping in the Ta compound for doping is 1; and/or the presence of a gas in the gas,
mixing the nickel cobalt lithium manganate doped in the step (3) with water according to the mass ratio of (0.6-1.2) of 1; and/or the presence of a gas in the atmosphere,
in the step (4), the coating Nb compound is in a molar ratio of the lithium element in the lithium source to the coating metal element in the coating Nb compound of 1.
8. The preparation method of the doping coating modified lithium nickel cobalt manganese oxide material according to claim 3, wherein in the step (1), a nickel cobalt manganese ternary positive electrode precursor and a lithium source are mixed, and then a Ta compound for doping is added to the mixture of the nickel cobalt manganese ternary positive electrode precursor and the lithium source.
9. The method for preparing doped coated modified lithium nickel cobalt manganese oxide material according to claim 3, wherein in the step (2), the doped lithium nickel cobalt manganese oxide obtained by primary sintering needs to be crushed and then screened, so as to obtain doped lithium nickel cobalt manganese oxide product particles with the particle size D50 of 3-4.5 μm.
10. Use of the doped coated modified lithium nickel cobalt manganese oxide material according to claim 1 or 2 or the doped coated modified lithium nickel cobalt manganese oxide material prepared by the preparation method according to any one of claims 3 to 9 as a positive electrode material in a lithium ion battery.
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