A doped coating modified lithium nickel cobalt manganese oxide material, a preparation method and applications thereof

Abstract

The application discloses a doped coating modified lithium nickel cobalt manganese oxide material, a preparation method and application thereof, and the lithium nickel cobalt manganese oxide material is a doped Ta coating Nb modified lithium nickel cobalt manganese oxide material, and a general formula is Li a Ni b Co c Mn d Ta e O2 / Nb f , values of a, b, c, d, e and f meet the following requirements: 1.0<=a<=1.2, 0.5<=b<1, 0 The application dopes a doped element Ta into the inside of the lithium nickel cobalt manganese oxide material through primary sintering; and coats a coating element Nb to the surface of the lithium nickel cobalt manganese oxide material after the Ta doping through secondary sintering. The doped coating modified lithium nickel cobalt manganese oxide material has a 0.1C discharge specific capacity of 212mAh / g or more in a 3-4.3V voltage interval, and a 25 DEG C constant temperature 100-week cycle capacity retention rate reaches 91.21% or more.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a doped and coated modified lithium nickel cobalt manganese oxide material, a preparation method and application thereof. BACKGROUND

[0002] The rapid development of the new energy vehicle industry puts forward higher requirements for the performance of lithium ion batteries. Lithium ion batteries are widely used in 3C, electric vehicles and other fields due to their high energy density, high capacity and good cycle performance. A lithium ion battery is composed of a positive electrode material, a negative electrode material, a separator and an electrolyte, among which the positive electrode material occupies a dominant position in terms of function and cost. The performance of the positive electrode material directly affects the performance of the battery. The core component of a new energy vehicle is a battery, and the cost of the battery accounts for about 40% of the entire vehicle. The performance of the battery directly affects the endurance and safety of the vehicle.

[0003] The positive electrode materials of the lithium battery used at the present stage mainly include lithium iron phosphate, lithium manganate, lithium cobaltate and ternary lithium. At present, in the field of new energy vehicles, lithium ion batteries mainly use lithium iron phosphate batteries and ternary lithium batteries. The lithium iron phosphate battery does not contain noble metal materials, has low cost, long cycle life and high safety. The ternary lithium battery has high energy density and fast charging and discharging speed, but has high irreversible capacity loss in the first charging and discharging, poor cycle performance, low safety performance and high cost. In order to improve the specific capacity of the material, the nickel content is usually increased. However, the increase of the nickel content increases the cost and reduces the safety performance of the material.

[0004] In addition, the modification of the nickel cobalt manganese ternary positive electrode material at the present stage mostly adopts single-element doping or coating. The doping method is single and has limited effect, and often only improves a certain performance of the material, has no obvious improvement effect on other performances, and even has a negative effect.

[0005] Therefore, a modification method is needed to significantly improve the specific capacity, rate performance, cycle life and safety performance of the material. SUMMARY

[0006] In view of the problems in the prior art, the application provides a doped and coated modified lithium nickel cobalt manganese oxide material, a preparation method and application thereof. The preparation method first dopes tantalum ions into the material through primary sintering to stabilize the internal structure of the material and improve the thermal stability of the material. Then, niobium ions are coated on the surface of the doped material through secondary sintering to improve the surface coating property of the material, reduce the loss of lithium ions and improve the initial efficiency. The synergistic effect of the two elements can significantly improve the electrical performance and safety performance of the material.

[0007] In order to achieve the above-mentioned purpose, the application adopts the following technical solutions.

[0008] A doped coating modified lithium nickel cobalt manganese oxide material is a Ta-doped Nb-coated modified lithium nickel cobalt manganese oxide material, and the general formula is Li a Ni b Co c Mn d Ta e O2 / Nb f , the values of a, b, c, d, e, and f meet the following requirements: 1.0≤a≤1.2, 0.5≤b<1, 0<c≤0.2, 0<d≤0.3, 0<e≤0.01, and 0<f≤0.01.

[0009] As a preferred embodiment of the above-mentioned doped coating modified lithium nickel cobalt manganese oxide material, 0<e≤0.002, and 0<f≤0.004.

[0010] As a preferred embodiment of the above-mentioned doped coating modified lithium nickel cobalt manganese oxide material, the doped element Ta is doped into the interior of the lithium nickel cobalt manganese oxide material through primary sintering; the coating element Nb is coated onto the surface of the lithium nickel cobalt manganese oxide material after the Ta doping through secondary sintering, and preferably, the modified lithium nickel cobalt manganese oxide is LiNi 0.83 Co 0.12 Mn 0.05 O2.

[0011] In the present application, the Ta element is doped into the interior of the lithium nickel cobalt manganese oxide material through primary sintering, the doping of the Ta element 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. The Nb element is coated onto the surface of the doped lithium nickel cobalt manganese oxide material through secondary sintering, and the Nb coating can consume the residual lithium carbonate on the surface of the material and form a nano-coating layer on the surface of the material. This nano-coating layer can effectively reduce the generation of impurities on the surface of the material, reduce the loss of lithium ions, and make the transmission process of lithium ions more smooth.

[0012] In addition, a small amount of Nb will penetrate into the bulk phase of the lithium nickel cobalt manganese oxide material during the coating process, and will have a synergistic effect with the Ta element, which can better stabilize the crystal structure of the material and improve the cycle performance of the material. Therefore, the existence of the Nb coating layer can improve the discharge capacity, rate performance, and surface resistance of the material, improve the lithium ion transmission rate, and reduce the formation of impurities on the surface of the material.

[0013] As a preferred embodiment of the above-mentioned doped coating modified lithium nickel cobalt manganese oxide material, the content of the doped element Ta in the doped coating modified lithium nickel cobalt manganese oxide material is 1000ppm~5000ppm (for example, 1500ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm).

[0014] As a preferred embodiment, in the doped and coated modified lithium nickel cobalt manganese oxide material, the content of the coating element Nb is 1000 ppm to 5000 ppm (for example, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm).

[0015] The application also provides a preparation method of the above-mentioned doped and coated modified lithium nickel cobalt manganese oxide material, which adopts the following technical scheme.

[0016] A preparation method of a doped and coated modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0017] (1) uniformly mixing a ternary positive electrode precursor, a lithium source and a tantalum (Ta) compound for doping to obtain a mixture A;

[0018] (2) sintering the mixture A once to obtain a doped and modified lithium nickel cobalt manganese oxide;

[0019] (3) mixing the doped and modified lithium nickel cobalt manganese oxide with water, stirring and then dehydrating and drying to obtain a dried doped and modified lithium nickel cobalt manganese oxide;

[0020] (4) uniformly mixing the dried doped and modified lithium nickel cobalt manganese oxide obtained in step (3) with a niobium (Nb) compound for coating to obtain a mixture B;

[0021] (5) sintering the mixture obtained in step (4) twice to obtain a doped and coated modified lithium nickel cobalt manganese oxide.

[0022] The application adopts a two-sintering process, the doping element can better enter the bulk phase of the lithium nickel cobalt manganese oxide material, and the coating element can more uniformly cover the surface of the material, so that the prepared material has good specific capacity performance, rate performance, cycle life and safety performance.

[0023] As a preferred embodiment in the above preparation method, in step (1), the ternary positive electrode precursor is Ni x Co y Mn z (OH)2, 0.5≤x<1, 0<y≤0.2, 0<z≤0.3, x+y+z=1; more preferably Ni 0.83 Co 0.12 Mn 0.05 (OH)2.

[0024] In the above production method, as a preferred embodiment, in the step (1), the molar ratio of lithium element in the lithium source to the sum of nickel, cobalt and manganese elements in the nickel-cobalt-manganese ternary positive electrode precursor is 1.0-1.2:1 (for example, 1.03:1, 1.05:1, 1.1:1, 1.15:1).

[0025] In the above production method, as a preferred embodiment, in the step (1), the lithium source is at least one of lithium carbonate, anhydrous lithium hydroxide and lithium hydroxide monohydrate.

[0026] In the above production method, as a preferred embodiment, in the step (1), the doping Ta compound is at least one of Ta2O5 and tantalum oxalate (C2H2O4·x'Ta, x' is in the range of 1-3).

[0027] In the above production method, as a preferred embodiment, in the step (1), the doping Ta compound is added in a manner that the molar ratio of lithium element in the lithium source to the doping metal element Ta in the doping Ta compound is 1:0.00076-0.0016 (for example, 1:0.0008, 1:0.0010, 1:0.0011, 1:0.0012, 1:0.0013, 1:0.0014, 1:0.0015). That is, in the step (1), the doping Ta compound is added in a manner that the mass ratio of lithium element in the lithium source to the doping metal element Ta in the doping Ta compound is 1:0.02-0.04 (for example, 1:0.025, 1:0.03, 1:0.035, 1:0.04).

[0028] In the above production 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 doping Ta compound is added to the mixture of the nickel-cobalt-manganese ternary positive electrode precursor and the lithium source.

[0029] In the above production method, as a preferred embodiment, in the step (3), the water is pure water.

[0030] In the step (3) of the present application, the lithium nickel cobalt manganese oxide after doping modification obtained in the step (2) is mixed with water to wash away the residual lithium carbonate, lithium hydroxide, free lithium on the surface of the material and reduce the residual alkali on the surface. Since the residual alkali affects battery production and battery performance, such as high alkali content leading to homogenate jelly and high lithium carbonate content leading to poor battery thermal stability, therefore, washing away the residual alkali with water is beneficial to ensure the performance of the battery assembled with the material.

[0031] In the above preparation method, as a preferred embodiment, in the step (4), the Nb compound for coating is at least one of Nb2O5 and NbX5 (pentahalide niobium), wherein X is one of F, Cl, Br, I, At, Ts.

[0032] In the above preparation method, as a preferred embodiment, in the step (4), the Nb compound for coating is at least one of Nb2O5 and NbX5 (pentahalide niobium), wherein X is one of F, Cl, Br, I, At, Ts.

[0033] In the above preparation method, as a preferred embodiment, in the step (2), the calcination atmosphere of the primary sintering is oxygen, preferably, the concentration of the oxygen is ≥80%.

[0034] Because the high-nickel ternary precursor is prone to cation disordering during sintering, pure oxygen sintering can make the sintering more sufficient and reduce the cation disordering phenomenon.

[0035] In the above preparation method, as a preferred embodiment, in the step (2), the calcination temperature of the primary sintering is 700-890℃ (700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃), preferably 750-850℃ (for example, 760℃, 780℃, 800℃, 820℃, 840℃), and the calcination time is 18-26h (for example, 19h, 20h, 22h, 24h, 25h).

[0036] In the present application, the main purpose of the primary sintering is to make the precursor and the lithium source react and make the doping elements penetrate into the material body phase.

[0037] In the preparation method, as a preferred embodiment, in the step (2), the doped lithium nickel cobalt manganese oxide obtained by the first sintering needs to be crushed and sieved to obtain doped lithium nickel cobalt manganese oxide product particles with a particle size D50 of 3-4.5 μm. Here, the particle size D50 means that the particles with a particle size greater than it account for 50%, and the particles with a particle size less than it also account for 50%.

[0038] In the preparation method, as a preferred embodiment, in the step (3), the doped lithium nickel cobalt manganese oxide and water are mixed in a mass ratio of 1:(0.6-1.2) (for example, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1).

[0039] In the preparation method, as a preferred embodiment, in the step (5), the calcination atmosphere of the second sintering is oxygen, and preferably, the oxygen concentration is ≥90%.

[0040] In the present application, the second sintering is mainly to make the coating more uniformly coated on the material surface, but also to prevent the content of residual alkali on the material surface from rising, so it is necessary to sinter in a high oxygen concentration to prevent contact with H2O and CO2 in the air to generate residual alkali; it is better to sinter with pure oxygen without considering the cost.

[0041] In the preparation method, as a preferred embodiment, in the step (5), the calcination temperature of the second sintering is 200-400°C (for example, 220°C, 250°C, 280°C, 300°C, 350°C, 400°C), and the calcination time is 12-20 h (for example, 13 h, 15 h, 16 h, 18 h).

[0042] The present application also provides a use of the above-mentioned doped and coated modified lithium nickel cobalt manganese oxide material as a positive electrode material in a lithium ion battery.

[0043] In the present application, the above technical features can be freely combined to form new technical solutions under the condition of not conflicting with each other.

[0044] Compared with the prior art, the present application has the following beneficial technical effects:

[0045] 1. The doped and coated modified lithium nickel cobalt manganese oxide material has a 0.1C discharge specific capacity of 212 mAh / g or more in the voltage range of 3-4.3 V, which is about 6 mAh / g higher than that of the unmodified lithium nickel cobalt manganese oxide material; and the capacity retention rate after 100 cycles at a constant temperature of 25°C is 91.21% or more, which is about 5% higher than that of the unmodified lithium nickel cobalt manganese oxide material.

[0046] 2. The DSC thermal decomposition temperature of the doped and coated modified lithium nickel cobalt manganese oxide material is also about 12°C higher than that of the unmodified lithium nickel cobalt manganese oxide material.

[0047] 3、The process of the present application has high stability, and the doping elements can be stably doped into the bulk phase by using the two-burning process, and the coating elements can be uniformly coated on the surface of the material, so that the prepared nickel-cobalt-manganese lithium material has obvious improvement in specific capacity, cycle life and safety performance. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 SEM image of the doped and coated modified nickel-cobalt-manganese lithium material prepared in Example 1 of the present application.

[0049] Figure 2 SEM image of the doped and coated modified nickel-cobalt-manganese lithium material prepared in Example 1 of the present application. Figure 1 SEM image of the doped and coated modified nickel-cobalt-manganese lithium material prepared in Example 1 of the present application.

[0050] Figure 3 First charge-discharge curve of the nickel-cobalt-manganese lithium material prepared in Examples 1-3 and Comparative Examples 1-4 of the present application. DETAILED DESCRIPTION

[0051] The present application will be described in detail below with reference to examples. Each example is provided by way of explanation of the present application and is not intended to limit the present application. In fact, those skilled in the art will appreciate that modifications and variations to the present application can be made without departing from the scope or spirit of the present application. For example, features shown or described as one embodiment can be used in another embodiment to produce yet another embodiment. It is, therefore, desired that the present application contain all such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0052] In the present application, the reagents and materials, unless otherwise specified, can be obtained from commercial channels.

[0053] The doped and coated modified nickel-cobalt-manganese lithium material Li a Ni b Co c Mn d Ta e O2 / Nb f , the values of a, b, c, d, e and f meet the following requirements: 1.0≤a≤1.2, 0.5≤b<1, 0<c≤0.2, 0<d≤0.3, 0<e≤0.01, 0<f≤0.01. Wherein a, b, c, d, e and f are the atomic number or the mole number of the corresponding element.

[0054] The ternary precursor Ni x Co y Mn z (OH)2, 0.5≤x<1, 0<y≤0.2, 0<z≤0.3, x+y+z=1, wherein x, y and z are the atomic number or the mole number of the corresponding element.

[0055] Example 1

[0056] A preparation method of a doped coated modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0057] (1) A ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2and lithium hydroxide monohydrate are mixed in a molar ratio of 1:1.04, Ta2O5 is added in an amount according to a molar ratio of lithium element to tantalum element of 1:0.000763 (i.e., a mass ratio of 1:0.02), and is added to the mixture of the ternary positive electrode precursor and lithium hydroxide monohydrate, and is uniformly mixed;

[0058] (2) The mixture obtained in step (1) is subjected to primary sintering, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 800°C, and the calcination time is 22h; after crushing and sieving, the mixture is mixed with water to wash away the residual lithium carbonate, lithium hydroxide, and free lithium on the surface of the material, and is dehydrated and dried to obtain a doped modified lithium nickel cobalt manganese oxide;

[0059] (3) Nb2O5 is weighed according to a molar ratio of lithium element to niobium element of 1:0.001857 (i.e., a mass ratio of 1:0.025), and is added to the doped modified lithium nickel cobalt manganese oxide obtained in step (2), and is uniformly mixed, and is subjected to secondary sintering, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 400°C, and the calcination time is 16h, to obtain a doped coated modified lithium nickel cobalt manganese oxide, with a general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.000763 O2 / Nb 0.001857 . Figure 1 and Figure 2 An SEM image of the doped coated modified lithium nickel cobalt manganese oxide prepared in this embodiment is shown.

[0060] Example 2

[0061] A preparation method of a doped coated modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0062] (1) A ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2and lithium hydroxide monohydrate are mixed in a molar ratio of 1:1.04, Ta2O5 is added in an amount according to a molar ratio of lithium element to tantalum element of 1:0.001144 (i.e., a mass ratio of 1:0.03), and is added to the mixture of the ternary positive electrode precursor and lithium hydroxide monohydrate, and is uniformly mixed;

[0063] (2) the mixture obtained in step (1) is subjected to one-time sintering, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 800°C, the calcination time is 22h; after crushing and sieving, the mixture is mixed with water to wash away lithium carbonate, lithium hydroxide and free lithium remaining on the surface of the material, and then dehydrated and dried to obtain doped modified lithium nickel cobalt manganese oxide;

[0064] (3) Nb2O5 is weighed according to a molar ratio of lithium element to niobium element of 1:0.002600 (i.e., a mass ratio of 1:0.035), and then added to the doped modified lithium nickel cobalt manganese oxide obtained in step (2) and uniformly mixed; two-time sintering is performed, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 400°C, the calcination time is 16h, and doped coated modified lithium nickel cobalt manganese oxide is obtained, with a general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001144 O2 / Nb 0.002600 .

[0065] Example 3

[0066] A preparation method of doped coated modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0067] (1) ternary positive electrode precursor Li 0.83 Co 0.12 Mn 0.05 (OH)2 and lithium hydroxide monohydrate are mixed according to a molar ratio of 1:1.04, and Ta2O5 is weighed according to a molar ratio of lithium element to tantalum element of 1:0.001526 (i.e., a mass ratio of 1:0.04), and then added to the mixture of the ternary positive electrode precursor and lithium hydroxide monohydrate and uniformly mixed;

[0068] (2) the mixture obtained in step (1) is subjected to one-time sintering, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 800°C, the calcination time is 22h; after crushing and sieving, the mixture is mixed with water to wash away lithium carbonate, lithium hydroxide and free lithium remaining on the surface of the material, and then dehydrated and dried to obtain doped modified lithium nickel cobalt manganese oxide;

[0069] (3) Nb2O5 is weighed according to a molar ratio of lithium element to niobium element of 1:0.003342 (i.e., a mass ratio of 1:0.045), and then added to the doped modified lithium nickel cobalt manganese oxide obtained in step (2) and uniformly mixed; two-time sintering is performed, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 400°C, the calcination time is 16h, and doped coated modified lithium nickel cobalt manganese oxide is obtained, with a general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001526 O2 / Nb 0.003342 .

[0070] Example 4

[0071] A preparation method of a doped coated modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0072] (1) mixing ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2and lithium hydroxide monohydrate according to a molar ratio of 1:1.04, adding tantalum oxalate salt (C2H2O4·xTa) in an amount according to a molar ratio of lithium element to tantalum element of 1:0.000763 (i.e., a mass ratio of 1:0.02), and adding the tantalum oxalate salt into the mixture of the ternary positive electrode precursor and the lithium hydroxide monohydrate, and mixing uniformly;

[0073] (2) performing first sintering on the mixture obtained in step (1), the sintering atmosphere being oxygen, the oxygen concentration being 90%, the calcination temperature being 800°C, and the calcination time being 22h; after crushing and sieving, mixing with water to wash away lithium carbonate, lithium hydroxide, free lithium remaining on the surface of the material, and dehydrating and drying to obtain a doped modified lithium nickel cobalt manganese oxide;

[0074] (3) weighing niobium pentahalide (NbX5, X being one of F, Cl, Br, I, At, and Ts) according to a molar ratio of lithium element to niobium element of 1:0.001857 (i.e., a mass ratio of 1:0.025), adding the niobium pentahalide into the doped modified lithium nickel cobalt manganese oxide obtained in step (2), mixing uniformly, performing second sintering, the sintering atmosphere being oxygen, the oxygen concentration being 90%, the calcination temperature being 400°C, and the calcination time being 16h, to obtain a doped coated modified lithium nickel cobalt manganese oxide, the general formula being LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.000763 O2 / Nb 0.001857 .

[0075] Comparative Example 1

[0076] A preparation method of a lithium nickel cobalt manganese oxide material, comprising the following steps:

[0077] (1) mixing ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2and lithium hydroxide monohydrate according to a molar ratio of 1:1.04, and performing first sintering, the sintering atmosphere being oxygen, the oxygen concentration being 90%, the calcination temperature being 800°C, and the calcination time being 22h;

[0078] (2) The product after step (1) is crushed and sieved, then mixed with water to wash away the lithium carbonate, lithium hydroxide, and free lithium remaining on the surface of the material. After dehydration and drying, the obtained product is subjected to secondary sintering in an oxygen atmosphere with an oxygen concentration of 90% at a calcination temperature of 400°C for 16h to obtain a lithium nickel cobalt manganese oxide material with a general formula of LiNi 0.83 Co 0.12 Mn 0.05 O2.

[0079] In the present comparative example, the lithium nickel cobalt manganese oxide material is not subjected to tantalum doping and niobium coating modification.

[0080] Comparative Example 2

[0081] A method for preparing a doped modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0082] (1) A ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2 and lithium hydroxide monohydrate are mixed in a molar ratio of 1:1.04. Ta2O5 is added in an amount of 1:0.000763 of the molar ratio of lithium element to tantalum element, and is added to the mixture of the ternary positive electrode precursor and lithium hydroxide monohydrate, and is uniformly mixed;

[0083] (2) The mixture obtained in step (1) is subjected to primary sintering in an oxygen atmosphere with an oxygen concentration of 90% at a calcination temperature of 800°C for 22h. After crushing and sieving, the mixture is mixed with water to wash away the lithium carbonate, lithium hydroxide, and free lithium remaining on the surface of the material. After dehydration and drying, a doped modified lithium nickel cobalt manganese oxide is obtained;

[0084] (3) The doped modified lithium nickel cobalt manganese oxide obtained in step (2) is subjected to secondary sintering in an oxygen atmosphere with an oxygen concentration of 90% at a calcination temperature of 400°C for 16h to obtain a doped lithium nickel cobalt manganese oxide with a general formula of LiNi 0.83 Co 0.1 2Mn 0.05 Ta 0.000763 O2.

[0085] In the present comparative example, the lithium nickel cobalt manganese oxide material is not subjected to niobium coating modification.

[0086] Comparative Example 3

[0087] A method for preparing a coated modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0088] (1) A ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05(OH)2 and lithium hydroxide monohydrate were mixed at a molar ratio of 1:1.04 and sintered once. The sintering atmosphere was oxygen with an oxygen concentration of 90%. The calcination temperature was 800℃ and the calcination time was 22h. After being crushed and sieved, the mixture was mixed with water to wash away the residual lithium carbonate, lithium hydroxide and free lithium on the surface of the material. The material was then dehydrated and dried to obtain lithium nickel cobalt manganese oxide.

[0089] (2) Weigh Nb₂O₅ according to a lithium to niobium molar ratio of 1:0.001857, add it to the pulverized and sieved lithium nickel cobalt manganese oxide obtained in step (1), and mix evenly; perform secondary sintering, with an oxygen atmosphere of 90%, a calcination temperature of 400℃, and a calcination time of 16h; to obtain coated and modified lithium nickel cobalt manganese oxide, with the general formula LiNi 0.83 Co 0.12 Mn 0.05 O2 / Nb 0.001857 .

[0090] In this comparative example, the lithium nickel cobalt manganese oxide material was not modified with tantalum doping.

[0091] Comparative Example 4

[0092] A method for preparing a doped and coated modified lithium nickel cobalt manganese oxide material includes the following steps:

[0093] (1) Ni, a ternary cathode precursor 0.83 Co 0.12 Mn 0.05 (OH)2 and lithium hydroxide monohydrate are mixed in a molar ratio of 1:1.04. The amount of Ta2O5 added is weighed according to the molar ratio of lithium to tantalum of 1:0.001144. It is added to the mixture of ternary cathode precursor and lithium hydroxide monohydrate and mixed evenly.

[0094] (2) The mixture obtained in step (1) is sintered once. The sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 900℃, and the calcination time is 22h. After crushing and sieving, it is mixed with water to wash away the residual lithium carbonate, lithium hydroxide, and free lithium on the surface of the material. After dehydration and drying, the doped and modified lithium nickel cobalt manganese oxide is obtained.

[0095] (3) Weigh Nb₂O₅ according to a lithium to niobium molar ratio of 1:0.002600, add it to the doped and modified lithium nickel cobalt manganese oxide obtained in step (2), and mix evenly; perform secondary sintering in an oxygen atmosphere with an oxygen concentration of 90%, a calcination temperature of 400℃, and a calcination time of 16h to obtain doped and modified lithium nickel cobalt manganese oxide with the general formula LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001144 O2 / Nb 0.002600 .

[0096] In the present comparative example, the calcination temperature of the first sintering is too high.

[0097] Comparative Example 5

[0098] A preparation method of a doped coated modified lithium nickel cobalt manganese oxide material, comprising the following steps:

[0099] (1) A ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2and lithium hydroxide monohydrate are mixed in a molar ratio of 1:1.04, and Ta2O5 is added in an amount of 1:0.001144 of the molar ratio of lithium element to tantalum element, and is added to the mixture of the ternary positive electrode precursor and lithium hydroxide monohydrate, and is uniformly mixed;

[0100] (2) The mixture obtained in step (1) is subjected to first sintering, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 800°C, and the calcination time is 22h; after crushing and sieving, the mixture is mixed with water to wash away the residual lithium carbonate, lithium hydroxide, and free lithium on the surface of the material, and is dehydrated and dried to obtain a doped modified lithium nickel cobalt manganese oxide;

[0101] (4) Nb2O5 is weighed according to the molar ratio of lithium element to niobium element of 1:0.002600, and is added to the doped modified lithium nickel cobalt manganese oxide obtained in step (2), and is uniformly mixed; second sintering is carried out, the sintering atmosphere is oxygen, the oxygen concentration is 90%, the calcination temperature is 500°C, and the calcination time is 16h, to obtain a doped coated modified lithium nickel cobalt manganese oxide, LiNi 0.83 Co 0.12 Mn 0.05 Ta 0.001144 O2 / Nb 0.002600 .

[0102] In the present comparative example, the calcination temperature of the second sintering is too high.

[0103] Battery assembly and performance test

[0104] Positive electrode sheet production: the active material (lithium nickel cobalt manganese oxide material obtained by Examples 1-4 and Comparative Examples 1-5), SuperP and PVDF are mixed in a mass ratio of 90:5:5, an appropriate amount of NMP is added and stirred uniformly, the electrode slurry is uniformly coated on an aluminum foil, and after drying, rolling, slicing, and vacuum drying at 120°C for 24h.

[0105] Battery assembly: first place the positive electrode shell, place the spring sheet inside the shell, place the metal sheet on the spring sheet, place the positive electrode sheet produced above on the metal sheet, the side coated with the positive electrode material faces up, and the electrolyte is soaked and covered The diaphragm (a battery grade polypropylene microporous film) was soaked with electrolyte and a piece of lithium metal was placed on it. A CR2032 button cell was assembled. The electrolyte used was 1.15 mol / L LiPF6 in EC+DEC+EMC (volume ratio 1:1:1) with an additive DFP of less than or equal to 2%.

[0106] The assembled CR2032 button cell was used for electrochemical performance testing. The test conditions were as follows: the charge and discharge voltage range was 3-4.3 V; the test temperature was 25°C; the button cell was charged at 0.1 C to 4.3 V and held at constant voltage for 30 min, and the capacity of the button cell at 0.1 C rate was tested.

[0107] After the first cycle, the button cell was disassembled and the positive electrode material on the positive electrode sheet was scraped off and transferred to a high-pressure crucible. The positive electrode material was used as a sample for DSC testing. The lithium nickel cobalt manganese oxide materials obtained in Examples 1-4 and Comparative Examples 1-5 were subjected to DSC testing at 25°C, and the heating rate was 5°C / min.

[0108] Table 1 lists the cycle performance and capacity data (0.1 C, 3-4.3 V @ 25°C) and DSC thermal decomposition temperature of the lithium nickel cobalt manganese oxide materials of Examples 1-4 and Comparative Examples 1-5. Figure 3 The first charge-discharge curve of the lithium nickel cobalt manganese oxide material prepared in Example 1-3 and Comparative Example 1-4 is shown.

[0109] Table 1 Cycle performance (0.1 C, 3-4.3 V @ 25°C) and DSC thermal decomposition temperature of the positive electrode material

[0110]

[0111]

[0112] From Table 1 and Figure 3 It can be seen that in Example 1, the first discharge capacity of the doped and coated modified lithium nickel cobalt manganese oxide material reached 212.2 mAh / g, the capacity retention rate was 91.21% after 100 cycles at 25°C, and the DSC thermal decomposition temperature was 230°C.

[0113] Similarly, in Example 2, the first discharge capacity of the doped and coated lithium nickel cobalt manganese oxide material reached 216.3 mAh / g, the capacity retention rate was 94.45% after 100 cycles at 25°C, and the DSC thermal decomposition temperature was 239°C.

[0114] In Example 3, the first discharge capacity of the doped and coated lithium nickel cobalt manganese oxide material reached 214.9 mAh / g, the capacity retention rate was 93.24% after 100 cycles at 25°C, and the DSC thermal decomposition temperature was 235°C.

[0115] In Example 4, the obtained doped coated lithium nickel cobalt manganese oxide material has a first discharge capacity of 214.1 mAh / g, a capacity retention rate of 92.89% after 100 cycles at 25 DEG C, and a DSC thermal decomposition temperature of 234 DEG C.

[0116] In Comparative Example 1, the obtained lithium nickel cobalt manganese oxide material has a first discharge capacity of 206.5 mAh / g, a capacity retention rate of 86.7% after 100 cycles at 25 DEG C, and a DSC thermal decomposition temperature of 218 DEG C.

[0117] In Comparative Example 2, the obtained doped modified lithium nickel cobalt manganese oxide material has a first discharge capacity of 207.3 mAh / g, a capacity retention rate of 87.5% after 100 cycles at 25 DEG C, and a DSC thermal decomposition temperature of 225 DEG C.

[0118] In Comparative Example 3, the obtained coated modified lithium nickel cobalt manganese oxide material has a first discharge capacity of 208.8 mAh / g, a capacity retention rate of 88.6% after 100 cycles at 25 DEG C, and a DSC thermal decomposition temperature of 220 DEG C.

[0119] In Comparative Example 4, the obtained coated modified lithium nickel cobalt manganese oxide material has a first discharge capacity of 205.3 mAh / g, a capacity retention rate of 88.1% after 100 cycles at 25 DEG C, and a DSC thermal decomposition temperature of 215 DEG C.

[0120] In Comparative Example 5, the obtained coated modified lithium nickel cobalt manganese oxide material has a first discharge capacity of 206.1 mAh / g, a capacity retention rate of 88.9% after 100 cycles at 25 DEG C, and a DSC thermal decomposition temperature of 217 DEG C.

[0121] In summary, the doped coated modified lithium nickel cobalt manganese oxide material has a specific capacity of 212 mAh / g or more at 0.1C in the voltage range of 3-4.3V, a first efficiency of 90% or more, a capacity retention rate of 91.21% or more after 100 cycles at 25 DEG C, and a DSC thermal decomposition temperature of 234 DEG C or more.

[0122] In addition, the DSC thermal decomposition temperature of the doped coated modified lithium nickel cobalt manganese oxide material is 12 DEG C or more higher than that of the unmodified lithium nickel cobalt manganese oxide material, and is also higher than that of the doped modified or coated modified lithium nickel cobalt manganese oxide material.

Claims

1. A doped cladding modified lithium nickel cobalt manganese oxide material, characterized in that, The doped coating modified lithium nickel cobalt manganese oxide material is a doped Ta coating Nb modified lithium nickel cobalt manganese oxide material, with a general formula of LiNi 0.83 Co 0.12 Mn 0.05 Ta e O2 / Nb f , the values of e and f meet the following requirements: 0 < e < 0.002, e < f < 0.004; The doping element Ta is doped into the inside of the lithium nickel cobalt manganese oxide material by primary sintering; the coating element Nb is coated onto the surface of the lithium nickel cobalt manganese oxide material after the Ta doping by secondary sintering. The calcination temperature of the primary sintering is 700-890°C, and the calcination temperature of the secondary sintering is 200-400°C.

2. A method of producing the doped coating-modified lithium nickel cobalt manganese oxide material according to claim 1, characterized by, The method comprises 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; the ternary positive electrode precursor is Ni 0.83 Co 0.12 Mn 0.05 (OH)2; (2) The mixture A is subjected to primary sintering to obtain doped and modified lithium nickel cobalt manganese oxide; (3) The doped and modified lithium nickel cobalt manganese oxide is mixed with water, stirred, and then dehydrated and dried to obtain dried doped and modified lithium nickel cobalt manganese oxide; (4) The dried doped and modified lithium nickel cobalt manganese oxide obtained in step (3) is mixed with a Nb compound for coating to obtain a mixture B; (5) The mixture obtained in step (4) is subjected to secondary sintering to obtain doped and coated modified lithium nickel cobalt manganese oxide.

3. The method for preparing the doped and coated modified lithium nickel cobalt manganese oxide material according to claim 2, characterized in that, in step (1), the lithium source is at least one of lithium carbonate, anhydrous lithium hydroxide, and monohydrate lithium hydroxide; and / or, in step (1), the Ta compound for doping is at least one of Ta2O5 and tantalum oxalate; and / or, in step (4), the Nb compound for coating is at least one of Nb2O5 and NbX5, wherein X is one of F, Cl, Br, I, At, and Ts.

4. The method for preparing the doped and coated modified lithium nickel cobalt manganese oxide material according to claim 2, characterized in that, in step (2), the calcination atmosphere of the primary sintering is oxygen, and the calcination time of the primary sintering is 18-26 h; and / or, in step (5), the calcination atmosphere of the secondary sintering is oxygen, and the calcination time of the secondary sintering is 12-20 h.

5. The method for preparing the doped and coated modified lithium nickel cobalt manganese oxide material according to claim 2, characterized in that, in step (1), the molar ratio of lithium elements in the lithium source to the sum of nickel, cobalt, and manganese elements in the lithium nickel cobalt manganese ternary positive electrode precursor is 1.0-1.2:1; and / or, in step (1), the Ta compound for doping is added in a manner that the molar ratio of lithium elements in the lithium source to the doping metal element Ta in the Ta compound for doping is 1:0.00076-0.0016; and / or, in step (3), the doped lithium nickel cobalt manganese oxide is mixed with water in a mass ratio of 1:(0.6-1.2); and / or, in step (4), the molar ratio of lithium elements in the lithium source to the coating metal elements in the Nb compound for coating is 1:0.0014-0.0037.

6. The method of claim 2, wherein the doped, cladding-modified nickel-cobalt- manganese lithium oxide material is prepared by a process comprising: In step (1), the lithium 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 lithium nickel cobalt manganese ternary positive electrode precursor and the lithium source. ​ 7. The method of claim 2, wherein the doped, cladding-modified nickel-cobalt- manganese lithium oxide material is prepared by a process comprising: providing a lithium nickel cobalt manganese oxide material; and coating the lithium nickel cobalt manganese oxide material with a coating comprising a dopant. In step (2), the doped lithium nickel cobalt manganese oxide obtained by primary sintering needs to be crushed and sieved to obtain doped lithium nickel cobalt manganese oxide product particles with a particle size D50 of 3-4.5 μm.

8. Use of the doped-coated modified lithium nickel cobalt manganese oxide material according to claim 1 or the doped-coated modified lithium nickel cobalt manganese oxide material prepared according to the preparation method of any one of claims 3-7 as a cathode material in a lithium ion battery.

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