A kind of ultra-high nickel single crystal cathode material, its preparation method and application

Abstract

The present invention provides a high-nickel single-crystal cathode material, a preparation method thereof, and an application thereof. The high-nickel single-crystal cathode material includes a high-nickel single-crystal cathode material main body and a composite coating layer coated on the surface of the high-nickel single-crystal cathode material main body; the composite coating layer includes an inner coating layer and an outer coating layer; the inner coating layer is coated on the surface of the high-nickel single-crystal cathode material main body in a dot shape, the inner coating layer includes a first coating element, and the first coating element includes Zr element and Co element; the outer coating layer is coated on the surface of the inner coating layer in a film shape, the outer coating layer includes a second coating element, and the second coating element includes B element. By sequentially performing dot coating and film coating on the material main body, the present invention effectively suppresses the residual alkali amount on the material surface and improves the sieving speed of the material. Moreover, the high-nickel single-crystal cathode material has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a high-nickel single-crystal cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of the new energy industry, lithium-ion batteries have become the focus of attention.

[0003] Based on the increasing requirements of consumers for lithium-ion batteries, high-nickel cathode materials have gradually come into view. High-nickel cathode materials have a relatively high specific capacity and excellent cycle life. However, with the increase in nickel content, especially for the single-crystal lithium nickel cobalt manganate cathode material with ultra-high nickel, the residual alkali is relatively high, resulting in poor fluidity of the material, and thus poor processability of the cathode material. For example, during pipeline transportation, the pipeline is blocked, and too much material adheres to the inner wall of the classification bin of the air classifier during material pulverization, making it difficult to pass through the sieve and resulting in low production efficiency.

[0004] To this end, CN114524468A provides a preparation method for a modified single-crystal ultra-high-nickel quaternary NCMA cathode material, and the preparation method includes the following steps: (1) uniformly mixing an ultra-high-nickel precursor, a lithium source, and a nano-oxide in a mixer; (2) obtaining a first-fired material; (3) subjecting the first-fired material obtained in step (2) to jaw crushing, roll crushing, pulverization, and sieving; (4) uniformly mixing the single-crystal ultra-high-nickel quaternary NCMA cathode material obtained in step (3) with a strontium source and a tungsten source in a mixer; (5) performing secondary sintering, and screening to obtain the cathode material. CN112194196A discloses a composite coating agent for a high-nickel single-crystal ternary cathode material, a preparation method thereof, and an application, including at least one of a metal and / or non-metal oxide, an ammonium salt compound, and a solvent, and is prepared by at least one process of ball milling, air flow pulverization, calcination, wet mixing, and spray drying. CN112310389A discloses a preparation method for a high-nickel single-crystal cathode material, including the following steps: S1. Mixing a ternary precursor and lithium hydroxide at a lithium-to-metal molar ratio of 1.01-1.10:1, adding a doping agent, and calcining in an oxygen atmosphere to obtain a first-calcined material; S2. Subjecting the first-calcined material to coarse crushing, fine crushing, sieving, and demagnetization to obtain a pulverized material; S3. Adding the pulverized material and water at a water-to-material ratio of 0.5:1-5:1 to a reaction kettle, controlling the temperature of the reaction kettle, adding a reagent to react, and drying after the reaction is completed to obtain a mixed material; S4. Mixing the mixed material with a modified coating agent and placing it in an atmosphere furnace for secondary calcination, and then performing coarse crushing, fine crushing, sieving, and demagnetization to obtain the ternary cathode material.

[0005] However, although the above methods can reduce the residual alkali amount of the cathode material to a certain extent, they are all island-shaped coatings, and there is a problem of difficult sieving of the finished product.

[0006] Therefore, how to effectively suppress the residual alkali content of the ultra-high nickel single crystal cathode material, improve the sieving speed of the ultra-high nickel single crystal cathode material, and at the same time improve the electrochemical performance of the ultra-high nickel single crystal cathode material are technical problems that need to be solved urgently. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an ultra-high nickel single crystal cathode material, its preparation method and application. By sequentially performing dot coating and film coating on the ultra-high nickel single crystal cathode material body, while improving the conductivity, the contact between the ultra-high nickel single crystal cathode material body and the electrolyte is isolated. The inner coating layer effectively suppresses the residual alkali content on the surface of the ultra-high nickel single crystal cathode material, and the outer coating layer effectively improves the sieving speed of the ultra-high nickel single crystal cathode material. Moreover, the ultra-high nickel single crystal cathode material has excellent electrochemical performance.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides an ultra-high nickel single crystal cathode material, which includes an ultra-high nickel single crystal cathode material body and a composite coating layer coated on the surface of the ultra-high nickel single crystal cathode material body;

[0010] The composite coating layer includes an inner coating layer and an outer coating layer;

[0011] The inner coating layer is dot-coated on the surface of the ultra-high nickel single crystal cathode material body. The inner coating layer includes a first coating element, and the first coating element includes Zr element and Co element;

[0012] The outer coating layer is film-coated on the surface of the inner coating layer. The outer coating layer includes a second coating element, and the second coating element includes B element.

[0013] In the present invention, by sequentially performing dot coating and film coating on the ultra-high nickel single crystal cathode material body, the dot coating can react with the residual alkali on the surface of the cathode material to suppress the residual alkali content on the surface of the ultra-high nickel single crystal cathode material. Lithium zirconate in the inner coating layer can improve the conductivity of the cathode material, and lithium cobaltate can improve the discharge specific capacity of the cathode material. The synergistic effect of the two can further improve the discharge specific capacity of the cathode material; the B-containing film coating can improve the smoothness of the cathode material surface and accelerate the sieving speed. Therefore, under the dual action of dot coating and film coating, not only the conductivity of the ultra-high nickel single crystal cathode material is improved, the contact between the ultra-high nickel single crystal cathode material body and the electrolyte is isolated, and the residual alkali content on the surface of the ultra-high nickel single crystal cathode material is effectively suppressed, but also the sieving speed of the ultra-high nickel single crystal cathode material is effectively improved. Moreover, the ultra-high nickel single crystal cathode material has excellent electrochemical performance.

[0014] As a preferred technical solution of the present invention, the average coating thickness of the composite coating layer satisfies the following conditions:

[0015] W = [(A + B) 1 / 2 / 0.6 / 70% + C / 0.6] / 1000 Formula I

[0016] wherein, W is the average coating thickness of the composite coating layer, g / cm 2 ; A is the content of Zr element, ppm; B is the content of Co element, ppm; C is the content of B element.

[0017] In the present invention, 0.6 in Formula I represents the specific surface area of the ultra-high nickel single crystal cathode material, with the unit of m 2 / g, and 70% represents that the inner coating layer can coat about 70% of the surface of the ultra-high nickel single crystal cathode material.

[0018] In the present invention, when the average coating thickness of the composite coating layer satisfies Formula I, the conductivity of the coating layer of the cathode material can be improved, which is beneficial to the transfer of lithium ions. At the same time, the residual alkali on the surface of the cathode material can be reduced, and the main body of the cathode material can be effectively isolated from the electrolyte to reduce gas generation and improve the cycle performance.

[0019] Preferably, the W is 1.05 - 1.3 g / cm 2 , for example, it can be 1.05 g / cm 2 , 1.1 g / cm 2 , 1.15 g / cm 2 , 1.2 g / cm 2 , 1.25 g / cm 2 or 1.3 g / cm 2 etc.

[0020] In the present invention, if the value of W is too large, it will lead to too thick composite coating layer, which is not conducive to the transfer of lithium ions; if the value of W is too small, the coating agent cannot react fully with the residual alkali on the surface of the cathode material, and cannot effectively isolate the main body of the cathode material from the electrolyte, resulting in higher gas generation and poorer cycle performance.

[0021] As a preferred technical solution of the present invention, the chemical formula of the ultra-high nickel single crystal cathode material main body is Li m Ni a Co b Mn c O 2 , wherein, 1 ≤ m ≤ 1.06, 0.94 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.04, 0.01 ≤ c ≤ 0.4, a + b + c = 1.

[0022] In the present invention, 1 ≤ m ≤ 1.06, for example, it can be 1, 1.01, 1.02, 1.03, 1.04, 1.05 or 1.06, etc.; 0.94 ≤ a ≤ 0.99, for example, it can be 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, etc.; 0.01 ≤ b ≤ 0.04, for example, it can be 0.01, 0.02, 0.03 or 0.04, etc.; 0.01 ≤ c ≤ 0.4, for example, it can be 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4, etc.

[0023] In a second aspect, the present invention provides a method for preparing the ultra-high nickel single crystal cathode material as described in the first aspect, and the preparation method includes the following steps:

[0024] (1) Mix the precursor of the ultra-high nickel single crystal cathode material and a lithium source, and after primary sintering, obtain the ultra-high nickel single crystal cathode material main body, and then pulverize it;

[0025] (2) Mix the pulverized ultra-high nickel single crystal cathode material main body, a Zr source and a Co source, and after secondary sintering, obtain the ultra-high nickel single crystal cathode material main body coated with an inner coating layer, and then pulverize it;

[0026] (3) Mix the pulverized ultra-high nickel single crystal cathode material main body coated with the inner coating layer and a B source, and after tertiary sintering, obtain the ultra-high nickel single crystal cathode material.

[0027] The present invention adopts a three-sintering process to achieve dot-shaped and film-shaped coating on the ultra-high nickel single crystal cathode material main body, improves the conductivity of the ultra-high nickel single crystal cathode material, and isolates the contact between the cathode material main body and the electrolyte, thereby improving the discharge specific capacity and cycling performance. The film-shaped coating can improve the fluidity of the cathode material and increase the sieving speed.

[0028] As a preferred technical solution of the present invention, the chemical formula of the precursor of the ultra-high nickel single crystal cathode material in step (1) is Ni a Co b Mn c O 2 , where 0.94 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.04, 0.01 ≤ c ≤ 0.4, and a + b + c = 1.

[0029] Preferably, the lithium source in step (1) includes any one or a combination of at least two of lithium hydroxide, lithium carbonate or lithium nitride.

[0030] Preferably, the molar ratio of the precursor of the ultra-high nickel single crystal cathode material to the lithium source in step (1) is 1:(1 - 1.06), and for example, it can be 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05 or 1:1.06, etc.

[0031] Preferably, the first sintering in step (1) is carried out in an oxygen-containing atmosphere.

[0032] Preferably, the oxygen concentration in the oxygen-containing atmosphere is greater than or equal to 95%, and for example, it can be 95%, 96%, 97%, 98%, 99%, 99.5%, 99.8% or 99.9%, etc.

[0033] Preferably, the temperature of the first sintering in step (1) is 780 - 800 °C, and for example, it can be 780 °C, 785 °C, 790 °C, 795 °C or 800 °C, etc.

[0034] Preferably, the time of the first sintering in step (1) is 8 - 12 h, and for example, it can be 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h, etc.

[0035] Preferably, the mesh number of the ultra-high nickel single crystal cathode material body after crushing in step (1) is 300 - 400 mesh, and for example, it can be 300 mesh, 325 mesh, 350 mesh, 375 mesh or 400 mesh, etc.

[0036] As a preferred technical solution of the present invention, the Zr source in step (2) includes zirconia and / or zirconium hydroxide.

[0037] Preferably, the Co source in step (2) includes cobalt oxide and / or cobalt hydroxide.

[0038] Preferably, the content of the Zr source in step (2) is 1500 - 2500 ppm, and for example, it can be 1500 ppm, 1700 ppm, 1900 ppm, 2100 ppm, 2300 ppm or 2500 ppm, etc.

[0039] In the present invention, if the content of the Zr source is too low, the surface conductivity of the cathode material is poor; if the content of the Zr source is too high, the coating layer is too thick, which is not conducive to lithium ion transfer.

[0040] Preferably, the content of the Co source in step (2) is 8000 - 12000 ppm, and for example, it can be 8000 ppm, 8500 ppm, 9000 ppm, 9500 ppm, 10000 ppm, 10500 ppm, 11000 ppm, 11500 ppm or 12000 ppm, etc.

[0041] In the present invention, if the content of the Co source is too low, the residual alkali cannot be effectively reduced, the coating layer is relatively thin, and the main body of the cathode material cannot be effectively isolated from the electrolyte, resulting in a high gas generation and poor cycle performance; if the content of the Co source is too high, the coating layer will be too thick, which is not conducive to the transfer of lithium ions.

[0042] Preferably, the secondary sintering in step (2) is carried out in an oxygen-containing atmosphere, and the oxygen concentration in the oxygen-containing atmosphere is greater than or equal to 95%, for example, it can be 95%, 96%, 97%, 98%, 99%, 99.5%, 99.8% or 99.9%, etc.

[0043] Preferably, the temperature of the secondary sintering in step (2) is 700 - 750 °C, for example, it can be 700 °C, 710 °C, 720 °C, 730 °C, 740 °C or 750 °C, etc.

[0044] Preferably, the time of the secondary sintering in step (2) is 4 - 8 h, for example, it can be 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h or 8 h, etc.

[0045] Preferably, the mesh number of the main body of the ultra-high nickel single crystal cathode material coated with the inner layer coating layer after being crushed in step (2) is 300 - 400 meshes, for example, it can be 300 meshes, 325 meshes, 350 meshes, 375 meshes or 400 meshes, etc.

[0046] As a preferred technical solution of the present invention, the B source in step (3) includes boric acid and / or boron oxide.

[0047] Preferably, the content of the B source in step (3) is 500 - 600 ppm, for example, it can be 500 ppm, 520 ppm, 540 ppm, 560 ppm, 580 ppm or 600 ppm, etc.

[0048] In the present invention, if the content of the B source is too low, it cannot be uniformly coated on the surface of the cathode material and cannot significantly improve the sieving speed; if the content of the B source is too high, the coating layer is too thick, and since B is an inert coating layer, it is not conducive to the transfer of lithium ions.

[0049] Preferably, the tertiary sintering in step (3) is carried out in an oxygen-containing atmosphere, and the oxygen concentration in the oxygen-containing atmosphere is greater than or equal to 95%, for example, it can be 95%, 96%, 97%, 98%, 99%, 99.5%, 99.8% or 99.9%, etc.

[0050] Preferably, the temperature of the tertiary sintering in step (3) is 250 - 300 °C, for example, it can be 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C, etc.

[0051] Preferably, the time for the three - stage sintering in step (3) is 4 - 8 h, for example, it can be 700 °C, 710 °C, 720 °C, 730 °C, 740 °C or 750 °C, etc.

[0052] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0053] (1) Mix the precursor Ni a Co b Mn c O 2 of the ultra - high nickel single - crystal cathode material and the lithium source by dry mixing in a molar ratio of 1:(1 - 1.06), and conduct primary sintering at 780 - 800 °C for 8 - 12 h in an oxygen atmosphere with a purity of 99.99% to obtain the ultra - high nickel single - crystal cathode material body, and then pulverize it so that the mesh number of the ultra - high nickel single - crystal cathode material body is 300 - 400 mesh;

[0054] Among them, 0.94 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.04, 0.01 ≤ c ≤ 0.4, and a + b + c = 1;

[0055] (2) Dry - mix the pulverized ultra - high nickel single - crystal cathode material body, Zr source and Co source, and conduct secondary sintering at 700 - 750 °C for 4 - 8 h in an oxygen atmosphere with a purity of 99.99% to obtain the ultra - high nickel single - crystal cathode material body coated with an inner coating layer, and then pulverize it so that the mesh number of the ultra - high nickel single - crystal cathode material body coated with the inner coating layer is 300 - 400 mesh;

[0056] Among them, the content of the Zr source is 1500 - 2500 ppm, and the content of the Co source is 8000 - 12000 ppm;

[0057] (3) Mix the pulverized ultra - high nickel single - crystal cathode material body coated with the inner coating layer and the B source, and conduct tertiary sintering at 250 - 300 °C for 4 - 8 h in an oxygen atmosphere with a purity of 99.99% to obtain the ultra - high nickel single - crystal cathode material;

[0058] Among them, the content of the B source is 500 - 600 ppm.

[0059] In the third aspect, the present invention provides a positive electrode sheet, and the positive electrode sheet includes the ultra - high nickel single - crystal cathode material as described in the first aspect.

[0060] In the fourth aspect, the present invention provides a lithium - ion battery, and the lithium - ion battery includes the positive electrode sheet as described in the third aspect.

[0061] The numerical ranges described in the present invention not only include the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the described ranges.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] In the present invention, the main body of the ultra-high nickel single crystal cathode material is sequentially subjected to dot coating and film coating. The dot coating can react with the residual alkali on the surface of the cathode material to inhibit the amount of residual alkali on the surface of the ultra-high nickel single crystal cathode material. Lithium zirconate in the inner coating layer can improve the conductivity of the cathode material, and lithium cobaltate can improve the discharge specific capacity of the cathode material. The synergistic effect of the two can further improve the discharge specific capacity of the cathode material; the film coating containing B can improve the smoothness of the surface of the cathode material and accelerate the sieving speed. Therefore, under the dual action of dot coating and film coating, not only the conductivity of the ultra-high nickel single crystal cathode material is improved, the contact between the main body of the ultra-high nickel single crystal cathode material and the electrolyte is isolated, and the amount of residual alkali on the surface of the ultra-high nickel single crystal cathode material is effectively inhibited, but also the sieving speed of the ultra-high nickel single crystal cathode material is effectively improved. Moreover, the ultra-high nickel single crystal cathode material has excellent electrochemical performance. Description of the Drawings

[0064] Figure 1 SEM image of the ultra-high nickel single crystal cathode material prepared in Example 1 of the present invention. Detailed Embodiments

[0065] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0066] Example 1

[0067] This example provides an ultra-high nickel single crystal cathode material, which includes an ultra-high nickel single crystal cathode material main body Li 1.04 Ni 0.95 Co 0.03 Mn 0.02 O 2 , and a composite coating layer coated on the surface of the ultra-high nickel single crystal cathode material main body; the composite coating layer includes an inner coating layer and an outer coating layer; the inner coating layer is dot-coated on the surface of the ultra-high nickel single crystal cathode material main body, and the inner coating layer includes a first coating element, and the first coating element includes Zr element and Co element; the outer coating layer is film-coated on the surface of the inner coating layer, and the outer coating layer includes a second coating element, and the second coating element includes B element.

[0068] The average coating thickness of the composite coating layer satisfies the following conditions:

[0069] W = [(A + B) 1 / 2 / 0.6 / 70% + C / 0.6] / 1000 Formula I

[0070] wherein, W is the average coating thickness of the composite coating layer, g / cm 2 ; A is the content of Zr element, ppm; B is the content of Co element, ppm; C is the content of B element;

[0071] The said W is 1.115 g / cm 2 .

[0072] This embodiment also provides a preparation method of a high-nickel single-crystal cathode material, and the preparation method includes the following steps:

[0073] (1) According to a molar ratio of 1:1.04, dry-mix the precursor Ni a Co b Mn c O 2 of the high-nickel single-crystal cathode material and lithium hydroxide, and perform a first sintering at 795°C for 10 h in an oxygen atmosphere with a purity of 99.99% to obtain the main body of the high-nickel single-crystal cathode material, and then crush it so that the mesh number of the main body of the high-nickel single-crystal cathode material is 350 meshes;

[0074] wherein, a is 0.95, b is 0.03, and c is 0.02;

[0075] (2) Dry-mix the crushed main body of the high-nickel single-crystal cathode material, Zr source and Co source, and perform a second sintering at 700°C for 5 h in an oxygen atmosphere with a purity of 99.99% to obtain the main body of the high-nickel single-crystal cathode material coated with an inner coating layer, and its chemical formula is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 , and then crush it so that the mesh number of the main body of the high-nickel single-crystal cathode material coated with the inner coating layer is 350 meshes;

[0076] wherein, the Zr source is zirconia with a content of 2000 ppm, and the Co source is cobalt oxide with a content of 12000 ppm;

[0077] (3) Mix the crushed ultra-high nickel single crystal cathode material body coated with the inner coating layer and the B source, and conduct three sinterings at 300 °C for 5 h in an oxygen atmosphere with a purity of 99.99% to obtain the ultra-high nickel single crystal cathode material, whose chemical formula is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0046 ;

[0078] Among them, the B source is boron oxide, and the content is 500 ppm.

[0079] Figure 1 The SEM image of the ultra-high nickel single crystal cathode material prepared in this example is shown. As can be seen from the figure, the morphology of this material is irregular, and its particle size is in the range of 1 - 2.5 μm.

[0080] Example 2

[0081] This example provides an ultra-high nickel single crystal cathode material. The ultra-high nickel single crystal cathode material includes an ultra-high nickel single crystal cathode material body LiNi 0.97 Co 0.02 Mn 0.01 O 2 , and a composite coating layer coated on the surface of the ultra-high nickel single crystal cathode material body; the composite coating layer includes an inner coating layer and an outer coating layer; the inner coating layer is coated on the surface of the ultra-high nickel single crystal cathode material body in a dot shape, and the inner coating layer includes a first coating element, and the first coating element includes Zr element and Co element; the outer coating layer is coated on the surface of the inner coating layer in a film shape, and the outer coating layer includes a second coating element, and the second coating element includes B element.

[0082] The average coating thickness of the composite coating layer satisfies the following conditions:

[0083] W = [(A + B) 1 / 2 / 0.6 / 70% + C / 0.6] / 1000 Formula Ⅰ

[0084] Among them, W is the average coating thickness of the composite coating layer, g / cm 2 ; A is the content of Zr element, ppm; B is the content of Co element, ppm; C is the content of B element;

[0085] The W is 1.05 g / cm 2 .

[0086] This embodiment also provides a method for preparing a high-nickel single-crystal cathode material, and the preparation method includes the following steps:

[0087] (1) According to a molar ratio of 1:1, the precursor Ni of the high-nickel single-crystal cathode material a Co b Mn c O 2 and lithium hydroxide are dry-mixed, and primary sintering is carried out at 790 °C for 8 h in an oxygen atmosphere with a purity of 99.99%, to obtain the main body of the high-nickel single-crystal cathode material, and then it is pulverized so that the mesh number of the main body of the high-nickel single-crystal cathode material is 400 mesh;

[0088] wherein, a is 0.97, b is 0.02, and c is 0.01;

[0089] (2) The pulverized main body of the high-nickel single-crystal cathode material, Zr source and Co source are dry-mixed, and secondary sintering is carried out at 720 °C for 8 h in an oxygen atmosphere with a purity of 99.99% to obtain the main body of the high-nickel single-crystal cathode material coated with an inner coating layer, and its chemical formula is LiNi 0.97 Co 0.02 Mn 0.01 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 , and then it is pulverized so that the mesh number of the main body of the high-nickel single-crystal cathode material coated with the inner coating layer is 400 mesh;

[0090] wherein, the Zr source is zirconium hydroxide with a content of 2000 ppm, and the Co source is cobalt hydroxide with a content of 12000 ppm;

[0091] (3) The pulverized main body of the high-nickel single-crystal cathode material coated with the inner coating layer and the B source are mixed, and tertiary sintering is carried out at 270 °C for 6 h in an oxygen atmosphere with a purity of 99.99% to obtain the high-nickel single-crystal cathode material, and its chemical formula is LiNi 0.97 Co 0.02 Mn 0.01 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0046 ;

[0092] Among them, the B source is boric acid with a content of 500 ppm.

[0093] Example 3

[0094] This example provides a high-nickel single-crystal cathode material, and the high-nickel single-crystal cathode material includes a high-nickel single-crystal cathode material main body Li 1.06 Ni 0.98 Co 0.01 Mn 0.01 O 2 , and a composite coating layer coated on the surface of the high-nickel single-crystal cathode material main body; the composite coating layer includes an inner coating layer and an outer coating layer; the inner coating layer is dot-coated on the surface of the high-nickel single-crystal cathode material main body, and the inner coating layer includes a first coating element, and the first coating element includes Zr element and Co element; the outer coating layer is film-coated on the surface of the inner coating layer, and the outer coating layer includes a second coating element, and the second coating element includes B element.

[0095] The average coating thickness of the composite coating layer satisfies the following conditions:

[0096] W = [(A + B) 1 / 2 / 0.6 / 70% + C / 0.6] / 1000 Equation Ⅰ

[0097] Among them, W is the average coating thickness of the composite coating layer, g / cm 2 ; A is the content of Zr element, ppm; B is the content of Co element, ppm; C is the content of B element;

[0098] The W is 1.3 g / cm 2 .

[0099] This example also provides a preparation method of a high-nickel single-crystal cathode material, and the preparation method includes the following steps:

[0100] (1) According to a molar ratio of 1:1.06, the precursor Ni a Co b Mn c O 2 of the high-nickel single-crystal cathode material and lithium hydroxide are dry-mixed, and primary sintering is carried out at 780 °C for 12 h in an oxygen atmosphere with a purity of 99.99%, to obtain a high-nickel single-crystal cathode material main body, and then it is pulverized so that the mesh number of the high-nickel single-crystal cathode material main body is 325 mesh;

[0101] Among them, a is 0.98, b is 0.01, and c is 0.01;

[0102] (2) The crushed main body of the ultra-high nickel single crystal cathode material, Zr source and Co source are dry-mixed and then subjected to secondary sintering at 750 °C for 4 h in an oxygen atmosphere with a purity of 99.99% to obtain the main body of the ultra-high nickel single crystal cathode material coated with an inner coating layer, and its chemical formula is Li 1.06 Ni 0.98 Co 0.01 Mn 0.01 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 , and then it is crushed so that the mesh number of the main body of the ultra-high nickel single crystal cathode material coated with the inner coating layer is 325 mesh;

[0103] Among them, the Zr source is zirconium hydroxide with a content of 2000 ppm, and the Co source is cobalt oxide with a content of 12000 ppm;

[0104] (3) The crushed main body of the ultra-high nickel single crystal cathode material coated with the inner coating layer and the B source are mixed and then subjected to tertiary sintering at 250 °C for 8 h in an oxygen atmosphere with a purity of 99.99% to obtain the ultra-high nickel single crystal cathode material, and its chemical formula is Li 1.06 Ni 0.98 Co 0.01 Mn 0.01 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0046 ;

[0105] Among them, the B source is boron oxide with a content of 500 ppm.

[0106] Example 4

[0107] The difference between this example and Example 1 is that the W value is 1.198, and the content of boron oxide in step (3) is 550 ppm, then the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 ·(B 2 O3 ) 0.0051 。

[0108] The remaining preparation methods and parameters are the same as those in Example 1.

[0109] Example 5

[0110] The difference between this example and Example 1 is that the value of W is 1.282, and the content of boron oxide in step (3) is 600 ppm. Then the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0055 。

[0111] The remaining preparation methods and parameters are the same as those in Example 1.

[0112] Example 6

[0113] The difference between this example and Example 5 is that the value of W is 1.071, and the content of cobalt oxide in step (2) is 8000 ppm. Then the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0045 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0055 。

[0114] The remaining preparation methods and parameters are the same as those in Example 5.

[0115] Example 7

[0116] The difference between this example and Example 5 is that the value of W is 1.094, and the content of cobalt oxide in step (2) is 10000 ppm. Then the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co3 O 4 ) 0.0056 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0055 。

[0117] The remaining preparation methods and parameters are the same as those in Example 5.

[0118] Example 8

[0119] The difference between this example and Example 7 is that the value of W is 1.11, and the content of zirconia in step (2) is 1500 ppm. Then the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0056 ·(ZrO 2 ) 0.0016 ·(B 2 O 3 ) 0.0055 。

[0120] The remaining preparation methods and parameters are the same as those in Example 7.

[0121] Example 9

[0122] The difference between this example and Example 7 is that the value of W is 1.12, and the content of zirconia in step (2) is 2500 ppm. Then the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0056 ·(ZrO 2 ) 0.0027 ·(B 2 O 3 ) 0.0055 。

[0123] The remaining preparation methods and parameters are the same as those in Example 7.

[0124] Example 10

[0125] The difference between this embodiment and Embodiment 1 is that the Co content of the cobalt oxide described in step (2) is adjusted to 2900 ppm, so that the average coating thickness W of the composite coating is 1 g / cm 2 .

[0126] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0127] Embodiment 11

[0128] The difference between this embodiment and Embodiment 1 is that the Co content of the cobalt oxide described in step (2) is adjusted to 45000 ppm, so that the average coating thickness W of the composite coating is 1.35 g / cm 2 .

[0129] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0130] Embodiment 12

[0131] The difference between this embodiment and Embodiment 1 is that the content of zirconia described in step (2) is 1000 ppm, and the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0011 ·(B 2 O 3 ) 0.0046 .

[0132] The remaining preparation methods and parameters are the same as those in Embodiment 1.

[0133] Embodiment 13

[0134] The difference between this embodiment and Embodiment 1 is that the content of zirconia described in step (2) is 3000 ppm, and the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0033 ·(B 2 O 3 ) 0.0046 .

[0135] The remaining preparation methods and parameters are the same as those in Example 1.

[0136] Example 14

[0137] The difference between this example and Example 1 is that the content of cobalt oxide in step (2) is 7000 ppm, and the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0040 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0046 。

[0138] The remaining preparation methods and parameters are the same as those in Example 1.

[0139] Example 15

[0140] The difference between this example and Example 1 is that the content of cobalt oxide in step (2) is 13000 ppm, and the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0074 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0046 。

[0141] The remaining preparation methods and parameters are the same as those in Example 1.

[0142] Example 16

[0143] The difference between this example and Example 1 is that the content of boron oxide in step (3) is 400 ppm, and the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 ·(B2 O 3 ) 0.0037 。

[0144] The remaining preparation methods and parameters are the same as those in Example 1.

[0145] Example 17

[0146] The difference between this example and Example 1 is that the content of boron oxide in step (3) is 700 ppm, and the chemical formula of the obtained ultra-high nickel single crystal cathode material is Li 1.04 Ni 95 Co 3 Mn 2 O 2 ·(Co 3 O 4 ) 0.0068 ·(ZrO 2 ) 0.0022 ·(B 2 O 3 ) 0.0064 。

[0147] The remaining preparation methods and parameters are the same as those in Example 1.

[0148] Comparative Example 1

[0149] The difference between this comparative example and Example 1 is that a composite coating layer is not coated on the surface of the ultra-high nickel single crystal cathode material Li 1.04 Ni 95 Co 3 Mn 2 O 2 , that is, steps (2) and (3) are not carried out.

[0150] The remaining preparation methods and parameters are the same as those in Example 1.

[0151] Comparative Example 2

[0152] The difference between this comparative example and Example 1 is that only the inner coating layer is coated on the surface of the ultra-high nickel single crystal cathode material Li 1.04 Ni 95 Co 3 Mn 2 O 2 , that is, step (3) is not carried out.

[0153] The remaining preparation methods and parameters are the same as those in Example 1.

[0154] Comparative Example 3

[0155] The difference between this comparative example and Example 1 is that only the inner coating layer is coated on the surface of the ultra-high nickel single crystal cathode material Li 1.04 Ni 95Co 3 Mn 2 O 2 The surface of the outer coating layer is coated with the main body of the ultra-high nickel single crystal cathode material after pulverization, that is, instead of performing step (2), the pulverized main body of the ultra-high nickel single crystal cathode material and the B source are directly mixed.

[0156] The remaining preparation methods and parameters are the same as those in Example 1.

[0157] Performance Test

[0158] The ultra-high nickel single crystal cathode materials prepared in Examples 1-17 and Comparative Examples 1-3 were made into positive electrode sheets, and were combined with negative electrode sheets (i.e., the main material is graphite), PP separators and electrolytes (1M LiPF 6 (EC:EMC:DMC = 1 vol%:1 vol%:1 vol%) + 3% FEC) to make lithium ion batteries.

[0159] The above lithium ion batteries were subjected to electrochemical performance tests, including capacity tests, rate tests, first efficiency and cycle performance tests. In addition, the test of residual alkali content was also carried out.

[0160] 1) Conditions for the first cycle capacity test: 0.1C charge / 0.1C discharge.

[0161] 2) Conditions for the rate test: 0.5C charge / 1C discharge.

[0162] 3) Conditions for the first efficiency test: First efficiency = the capacity of the first cycle of 0.1C discharge divided by the capacity of the first cycle of 0.1C discharge.

[0163] 4) Conditions for the cycle performance test: 0.5C charge / 1C discharge, cycle 50 times.

[0164] 5) Test method for residual alkali content: Dissolve the sample with ultrapure water, titrate the alkaline substances in the sample with a hydrochloric acid standard solution, and confirm the titration endpoints of LiOH and Li 2 CO 3 respectively by the potential change, and calculate the contents of LiOH and Li 2 CO 3 respectively.

[0165] Table 1

[0166]

[0167]

[0168] Analysis:

[0169] As can be seen from the above table, in the present invention, the main body of the ultra-high nickel single crystal cathode material is subjected to dot coating and film coating in sequence. The dot coating can react with the residual alkali on the surface of the cathode material, reducing the amount of residual alkali on the surface of the ultra-high nickel single crystal cathode material. Lithium zirconate in the inner coating layer can improve the conductivity of the cathode material, and lithium cobaltate can improve the discharge specific capacity of the cathode material. The synergistic effect of the two can further improve the discharge specific capacity of the cathode material; the film coating containing B can improve the smoothness of the surface of the cathode material and accelerate the sieving speed. Under the dual action of dot coating and film coating, the ultra-high nickel single crystal cathode material has excellent electrochemical performance.

[0170] As can be seen from the data results of Examples 1-9, the ultra-high nickel single crystal cathode material provided by the present invention within the parameter protection range has a relatively fast sieving speed, and both the discharge specific capacity and the cycling performance are relatively high.

[0171] As can be seen from the comparison of the data results of Example 1 and Examples 10-11, if the average coating thickness W of the composite coating layer is too small, the coating layer is too thin to effectively reduce the residual alkali on the surface of the cathode material, resulting in a large contact area between the cathode material and the electrolyte, an increase in side reactions, a lower discharge specific capacity, and a deterioration in cycling performance; if the average coating thickness W of the composite coating layer is too large, the coating layer is too thick. Although it can reduce the residual alkali, the thick coating layer is not conducive to the transfer of lithium ions, resulting in poor electrical performance.

[0172] As can be seen from the comparison of the data results of Example 1 and Examples 12-13, if the content of the Zr source is too low, the conductivity of the surface of the cathode material is poor, which is not conducive to the transfer of lithium ions, resulting in poor electrical performance; if the content of the Zr source is too high, the Zr-containing coating layer is too thick, which is also not conducive to the transfer of lithium ions and will also result in poor electrical performance.

[0173] As can be seen from the comparison of the data results of Example 1 and Examples 14-15, if the content of the Co source is too low, the coating layer is too thin and the small amount of cobalt cannot effectively reduce the residual alkali on the surface of the cathode material, resulting in a large contact area between the cathode material and the electrolyte, an increase in side reactions, a lower discharge specific capacity, and a deterioration in cycling performance; if the content of the Co source is too high, the coating layer is too thick. Although it can reduce the residual alkali, the thick coating layer is not conducive to the transfer of lithium ions, resulting in poor electrical performance.

[0174] As can be seen from the comparison of the data results of Example 1 and Examples 16-17, if the content of the B source is too low, the B coating layer is too thin to be evenly coated on the surface of the main body of the cathode material, thus unable to effectively accelerate the sieving speed; if the content of the B source is too high, the B coating layer is too thick, which is not conducive to the transfer of lithium ions and affects the electrical performance.

[0175] As can be seen from the comparison of the data results of Example 1 and Comparative Example 1, if only the conventional ultra-high nickel single crystal cathode material Li 1.04 Ni95 Co 3 Mn 2 O 2 As a cathode material, there is a large amount of residual alkali on the surface of the material, the sieving speed is slow, and the electrochemical performance of the material is poor.

[0176] From the comparison of the data results between Example 1 and Comparative Example 2, it can be seen that if only on the surface of the ultra-high nickel single crystal cathode material Li 1.04 Ni 95 Co 3 Mn 2 O 2 the inner coating layer is coated, so that only dot-like coating exists on the surface of the ultra-high nickel single crystal cathode material, which will increase the surface roughness of the cathode material, resulting in a slower sieving speed and poor electrochemical performance of the material.

[0177] From the comparison of the data results between Example 1 and Comparative Example 3, it can be seen that if only on the surface of the ultra-high nickel single crystal cathode material Li 1.04 Ni 95 Co 3 Mn 2 O 2 the outer coating layer is coated, it cannot effectively reduce the residual alkali, and the cathode material cannot be separated from the electrolyte after assembling into an electric core, resulting in poor electrical performance.

[0178] The applicant declares that the present invention uses the above embodiments to illustrate the process method of the present invention, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the raw materials selected by the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A high-nickel single-crystal cathode material, characterized in that, the high-nickel single-crystal cathode material includes a high-nickel single-crystal cathode material main body and a composite coating layer coated on the surface of the high-nickel single-crystal cathode material main body; the composite coating layer includes an inner coating layer and an outer coating layer; the inner coating layer is coated on the surface of the high-nickel single-crystal cathode material main body in a dot shape, and the inner coating layer includes a first coating element, and the first coating element includes Zr element and Co element; the outer coating layer is coated on the surface of the inner coating layer in a film shape, and the outer coating layer includes a second coating element, and the second coating element includes B element; The average coating thickness W of the composite coating layer is 1.05 - 1.3 g / cm 2 .

2. The high-nickel single-crystal cathode material according to claim 1, characterized in that, the average coating thickness of the composite coating layer satisfies the following conditions: W = [(A + B) 1 / 2 / 0.6 / 70% + C / 0.6] / 1000 Formula I Among them, W is the average coating thickness of the composite coating, g / cm 2 ; A is the content of Zr element, ppm; B is the content of Co element, ppm; C is the content of B element.

3. The high-nickel single-crystal cathode material according to claim 1 or 2, characterized in that, The chemical formula of the main body of the ultra-high nickel single crystal cathode material is Li m Ni a Co b Mn c O 2 , where 1 ≤ m ≤ 1.06, 0.94 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.04, 0.01 ≤ c ≤ 0.4, and a + b + c = 1.

4. A preparation method of the high-nickel single-crystal cathode material according to any one of claims 1-3, characterized in that, the preparation method includes the following steps: (1) Mix the precursor of the high-nickel single-crystal cathode material and a lithium source, and obtain the high-nickel single-crystal cathode material main body after primary sintering, and pulverize it; (2) Mix the pulverized high-nickel single-crystal cathode material main body, a Zr source and a Co source, and obtain the high-nickel single-crystal cathode material main body coated with the inner coating layer after secondary sintering, and pulverize it; (3) Mix the pulverized high-nickel single-crystal cathode material main body coated with the inner coating layer and a B source, and obtain the high-nickel single-crystal cathode material after tertiary sintering.

5. The preparation method according to claim 4, characterized in that, The chemical formula of the precursor of the ultra-high nickel single crystal cathode material described in step (1) is Ni a Co b Mn c O 2 , where 0.94 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.04, 0.01 ≤ c ≤ 0.4, and a + b + c = 1.

6. The preparation method according to claim 4, characterized in that, the lithium source in step (1) includes any one or a combination of at least two of lithium hydroxide, lithium carbonate or lithium nitride.

7. The preparation method according to claim 4, characterized in that, the molar ratio of the precursor of the high-nickel single-crystal cathode material to the lithium source in step (1) is 1:(1-1.06).

8. The preparation method according to claim 4, characterized in that, the primary sintering in step (1) is carried out in an oxygen-containing atmosphere.

9. The preparation method according to claim 4, characterized in that, the temperature of the primary sintering in step (1) is 780-800 °C.

10. The preparation method according to claim 4, characterized in that, the time of the primary sintering in step (1) is 8-12 h.

11. The preparation method according to claim 4, characterized in that, the mesh number of the pulverized high-nickel single-crystal cathode material main body in step (1) is 325-400 mesh.

12. The preparation method according to claim 4, characterized in that, the Zr source in step (2) includes zirconia and / or zirconium hydroxide.

13. The preparation method according to claim 4, characterized in that, the Co source in step (2) includes cobalt oxide and / or cobalt hydroxide.

14. The preparation method according to claim 4, characterized in that, the content of the Zr source in step (2) is 1500-2500 ppm.

15. The preparation method according to claim 4, characterized in that the content of the Co source in step (2) is 8000 - 12000 ppm.

16. The preparation method according to claim 4, characterized in that the secondary sintering in step (2) is carried out in an oxygen-containing atmosphere.

17. The preparation method according to claim 4, characterized in that the temperature of the secondary sintering in step (2) is 700 - 750 °C.

18. The preparation method according to claim 4, characterized in that the time of the secondary sintering in step (2) is 4 - 8 h.

19. The preparation method according to claim 4, characterized in that the mesh number of the ultra-high nickel single crystal cathode material main body coated with the inner coating layer after being pulverized in step (2) is 325 - 400 mesh.

20. The preparation method according to claim 4, characterized in that the B source in step (3) includes boric acid and / or boron oxide.

21. The preparation method according to claim 4, characterized in that the content of the B source in step (3) is 500 - 600 ppm.

22. The preparation method according to claim 4, characterized in that the tertiary sintering in step (3) is carried out in an oxygen-containing atmosphere.

23. The preparation method according to claim 4, characterized in that the temperature of the tertiary sintering in step (3) is 250 - 300 °C.

24. The preparation method according to claim 4, characterized in that the time of the tertiary sintering in step (3) is 4 - 8 h.

25. The preparation method according to any one of claims 4 - 24, characterized in that the preparation method includes the following steps: (1) Mix the precursor Ni of the ultra-high nickel single crystal cathode material and the lithium source by dry method in a molar ratio of 1:(1 - 1.06), and perform a primary sintering at 780 - 800 °C for 8 - 12 h in an oxygen atmosphere with a purity of 99.99% to obtain the main body of the ultra-high nickel single crystal cathode material, and then crush it so that the mesh number of the main body of the ultra-high nickel single crystal cathode material is 300 - 400 mesh; a Co b Mn c O 2 ​ wherein, 0.94 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.04, 0.01 ≤ c ≤ 0.4, and a + b + c = 1; (2) The pulverized ultra-high nickel single crystal cathode material main body, Zr source and Co source are dry-mixed, and secondary sintering is carried out at 700 - 750 °C for 4 - 8 h in an oxygen atmosphere with a purity of 99.99% to obtain the ultra-high nickel single crystal cathode material main body coated with the inner coating layer, and then it is pulverized so that the mesh number of the ultra-high nickel single crystal cathode material main body coated with the inner coating layer is 300 - 400 mesh; wherein, the content of the Zr source is 1500 - 2500 ppm, and the content of the Co source is 8000 - 12000 ppm; (3) The pulverized ultra-high nickel single crystal cathode material main body coated with the inner coating layer and the B source are mixed, and tertiary sintering is carried out at 250 - 300 °C for 4 - 8 h in an oxygen atmosphere with a purity of 99.99% to obtain the ultra-high nickel single crystal cathode material; wherein, the content of the B source is 500 - 600 ppm.

26. A positive electrode plate, characterized in that the positive electrode plate includes the ultra-high nickel single crystal cathode material according to any one of claims 1 - 3.

27. A lithium-ion battery, characterized in that the lithium-ion battery includes the positive electrode plate according to claim 26.

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