A high-capacity high-nickel ternary cathode material and its preparation method

Abstract

The present invention provides a high-capacity high-nickel ternary cathode material. Compared with the prior art, the present invention uses elements with large ionic radii to form surface-doped ionic compounds, which can isolate the high-nickel multi-element cathode from contact with water, inhibit the occurrence of Li+ / H+ exchange reactions, reduce the lithium extraction of the high-nickel multi-element material during the water washing process, and reduce the formation of spinel nickel oxide or rock salt phase nickel oxide, which is beneficial to the uniform concentration of Li during the subsequent construction of the concentration gradient layered material by secondary firing; at the same time, a cobalt-rich coating layer is constructed on the surface of the cathode material, which can effectively solve a series of problems such as poor cycle performance, deteriorated gas generation, and high residual alkali caused by the instability of Ni3+ on the surface of the high-nickel material; the combined action of the doping of elements with large ionic radii and the cobalt-rich coating layer solves a series of problems caused by the instability of Ni3+ in the high-nickel multi-element cathode material, improves the interfacial characteristics of the material, and enhances the electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and particularly relates to a high-capacity high-nickel ternary cathode material and a preparation method thereof. Background Art

[0002] High-nickel multi-component cathode materials are considered to be the most promising cathode materials for new energy vehicle batteries due to their high capacity, excellent rate performance and low cost. However, during the synthesis of high-nickel ternary materials, some Ni 2+ tends to occupy the Li + site. Therefore, to avoid cation mixing, an excessive amount of Li source must be inevitably added. In addition, due to the instability of Ni 3+ , the structure lithium leaches out when the cathode is stored in humid air. These adverse factors together result in a relatively high residual alkali Li2CO3 / LiOH in the high-nickel multi-component cathode material. The formation of Li2CO3 / LiOH on the surface is considered to be the main reason for the poor storage performance of high-nickel materials. Even worse, LiOH reacts with LiPF6 in the electrolyte to generate HF. At 100% SOC state, HF dissolves the transition metal ions in the cathode, resulting in the phase change of the material from layered to spinel, causing battery pack swelling and cycle attenuation.

[0003] To remove the residual alkali on the surface of the high-nickel multi-component cathode material, currently, mainstream cathode factories usually add a water washing and drying process after the first sintering of the high-nickel multi-component cathode material. However, since the high-nickel material is prone to Li + / H + exchange reaction in water, the structural lithium is lost, resulting in the formation of NiOOH phase. The NiOOH substance is converted into spinel nickel oxide or rock salt phase nickel oxide through drying or heat treatment at a certain second sintering temperature. This structure affects the migration of lithium and is not conducive to the subsequent construction of a surface concentration gradient layered material during the second sintering. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a high-capacity high-nickel ternary cathode material with high discharge capacity and good cycle performance and a preparation method thereof.

[0005] The present invention provides a high-capacity high-nickel ternary cathode material, wherein the high-capacity high-nickel ternary cathode material is a secondary particle formed by aggregation of primary particles; a coating layer is provided on the surface of the secondary particle; the coating layer contains lithium element and cobalt element;

[0006] The general formula of the secondary particle is: Li a Ni 1-x-y-z Co x M y A z O 2+e ;

[0007] Among them, 0 ≤ x ≤ 0.35, 0 ≤ y ≤ 0.35, 0 < z ≤ 0.10, 0.95 < a < 1.30, 0 ≤ e ≤ 0.2;

[0008] The M is selected from Mn and / or Al; the A is an alkaline earth metal element and / or a lanthanide metal element; the ionic radius of the A is 90 - 135 pm;

[0009] The atomic ratio of A in all other metals except the Li element obtained by X-ray photoelectron spectroscopy test after the high-capacity high-nickel ternary cathode material is ion-etched is C A1 , and the atomic ratio of A in all other metals except the Li element obtained by using inductively coupled plasma technology to test the high-capacity high-nickel ternary cathode material is C A2 , 20% ≤ (C A2 - C A1 ) / C A2 .

[0010] Preferably, the ion used for the ion etching is an Ar + ion; the energy of the ion etching is 4 - 8 keV; the time of the ion etching is 20 - 40 min; the angle of the ion etching is 2 degrees; the rotation speed of the ion etching is 1 - 2 rpm.

[0011] Preferably, the alkaline earth metal element is selected from Ba and / or Sr; the lanthanide metal element is selected from one or more of La, Sm, Ce, and Y.

[0012] Preferably, the mass of cobalt element in the coating layer is 0.02% - 2% of the mass of the secondary particles.

[0013] The present invention also provides a preparation method of the above-mentioned high-capacity high-nickel ternary cathode material, including the following steps:

[0014] S1) Mix the ternary precursor material, the raw material containing the A element and the lithium source, and perform the first sintering to obtain a primary sintered material;

[0015] S2) Wash the primary sintered material, and after drying, obtain a dried material;

[0016] S3) Mix the dried material with a cobalt salt, and perform the second sintering to obtain a high-capacity high-nickel ternary cathode material.

[0017] Preferably, the raw material containing the A element is selected from one or more of an oxide, a carbonate compound, a sulfate compound, and a hydroxide containing the A element;

[0018] The lithium source is selected from one or more of lithium hydroxide, lithium carbonate, and lithium nitrate;

[0019] The cobalt salt is selected from one or more of cobalt oxides, carbonate compounds, sulfate compounds, hydroxy oxides and hydroxides.

[0020] Preferably, the first sintering in the step S1) is specifically: sintering at 400 °C to 600 °C for 2 to 8 h, and then heating to 650 °C to 1000 °C and continuing to sinter for 10 to 14 h.

[0021] Preferably, the water-to-material ratio for water washing in the step S2) is (0.5 to 5):1; the time for water washing is 0.5 to 30 min; the drying temperature is 80 °C to 200 °C.

[0022] Preferably, the temperature of the second sintering is 150 °C to 750 °C; the time of the second sintering is 2 to 20 h.

[0023] Preferably, the mass of the cobalt salt is 0.02% to 2% of the mass of the dried material.

[0024] The present invention provides a high-capacity high-nickel ternary cathode material, which is a secondary particle formed by aggregation of primary particles; a coating layer is provided on the surface of the secondary particle; the coating layer contains lithium element and cobalt element; the general formula of the secondary particle is: Li a Ni 1-x-y-z Co x M y A z O 2+e ; wherein, 0 ≤ x ≤ 0.35, 0 ≤ y ≤ 0.35, 0 < z ≤ 0.10, 0.95 < a < 1.30, 0 ≤ e ≤ 0.2; the M is selected from Mn and / or Al; the A is an alkaline earth metal element and / or a lanthanide metal element; the ionic radius of the A is 90 to 135 pm. Compared with the prior art, the present invention uses an element with a large ionic radius to form a surface-doped ionic compound, which can isolate the contact between the high-nickel multi-element cathode and water, inhibit the occurrence of the Li + / H + exchange reaction, reduce the lithium extraction of the high-nickel multi-element material during water washing, reduce the formation of spinel nickel oxide or rock salt phase nickel oxide, facilitate the Li concentration homogenization during the subsequent construction of the concentration gradient layered material by secondary sintering, and the reconstruction of the surface layered structure of the high-nickel multi-element cathode material, improve its discharge capacity and also improve the cycle performance of the material; at the same time, a cobalt-rich coating layer is constructed on the surface of the cathode material, which can effectively solve a series of problems such as poor cycle performance, gas production deterioration and high residual alkali caused by the instability of Ni 3+ on the surface of the high-nickel material; the combined action of the element doping with a large ionic radius and the cobalt-rich coating layer solves a series of problems caused by the instability of Ni 3+ on the high-nickel multi-element cathode material, improves the interfacial characteristics of the material, and enhances the electrochemical performance.

[0025] The experimental results show that in Ni2p of the high-capacity high-nickel ternary cathode material prepared by the present invention, the proportion of the peak area of Ni 3+ can reach 91.1%. Description of the Drawings

[0026] Figure 1 It is a comparative diagram of charge-discharge curves at 0.2C of the high-nickel ternary cathode material obtained in Example 1 and Comparative Example 1 of the present invention. Detailed Embodiments

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] The present invention provides a high-capacity high-nickel ternary cathode material. The high-capacity high-nickel ternary cathode material is secondary particles formed by aggregation of primary particles; a coating layer is provided on the surface of the secondary particles; the coating layer contains lithium element and cobalt element; the general formula of the secondary particles is: Li a Ni 1-x-y-z Co x M y A z O 2+e ; wherein, 0≤x≤0.35, 0≤y≤0.35, 0<z≤0.10, 0.95<a<1.30, 0≤e≤0.2; M is selected from Mn and / or Al; A is an alkaline earth metal element and / or a lanthanide metal element; the ionic radius of A is 90-135 pm. In the present invention, preferably 0.05≤x≤0.3, more preferably 0.05≤x≤0.2, still more preferably 0.08≤x≤0.15, and most preferably 0.1≤x≤0.12.

[0029] In the present invention, preferably 0.005≤y≤0.3, more preferably 0.005≤y≤0.2, still more preferably 0.008≤y≤0.1, still more preferably 0.01≤y≤0.05, still more preferably 0.01≤y≤0.03, still more preferably 0.01≤y≤0.02, and most preferably y = 0.016.

[0030] In the present invention, preferably 0.001 ≤ z ≤ 0.1, more preferably 0.001 ≤ z ≤ 0.08, still more preferably 0.001 ≤ z ≤ 0.05, still more preferably 0.002 ≤ z ≤ 0.01, still more preferably 0.003 ≤ z ≤ 0.006, still more preferably 0.003 ≤ z ≤ 0.006, and most preferably z = 0.004.

[0031] In the present invention, preferably 1 ≤ a ≤ 1.25, more preferably 1.01 ≤ a ≤ 1.2, still more preferably 1.01 ≤ a ≤ 1.15, still more preferably 1.01 ≤ a ≤ 1.1, still more preferably 1.02 ≤ a ≤ 1.06, and most preferably a = 1.025.

[0032] The average particle size of the secondary particles in the high-capacity high-nickel ternary cathode material provided by the present invention is preferably 5 - 30 μm, more preferably 8 - 20 μm, and still more preferably 10 - 15 μm.

[0033] The atomic ratio of A to all other metals except Li in the high-capacity high-nickel ternary cathode material provided by the present invention after ion etching and tested by X-ray photoelectron spectroscopy is C A1 , and the atomic ratio of A to all other metals except Li in the high-capacity high-nickel ternary cathode material tested by inductively coupled plasma technology is C A2 , 20% ≤ (C A2 - C A1 ) / C A2 ; in the present invention, the ions used for the ion etching are preferably Ar + ions; the energy of the ion etching is preferably 4 - 8 keV, more preferably 6 keV; the time of the ion etching is preferably 20 - 40 min, more preferably 25 - 35 min, still more preferably 30 min; the angle of the ion etching is preferably 2 degrees; the rotation speed of the ion etching is preferably 1 - 2 rpm; in the present invention, preferably, 20% ≤ (C A2 - C A1 ) / C A2 ≤ 60%, more preferably, 25% ≤ (C A2 - C A1 ) / C A2 ≤ 58%, still more preferably, 28% ≤ (C A2 - C A1 ) / C A2 ≤ 57.5%.

[0034] The A is an alkaline earth metal element and / or a lanthanide metal element; the alkaline earth metal element is preferably Ba and / or Sr; the lanthanide metal element is preferably one or more of La, Sm, Ce, and Y.

[0035] The high-capacity high-nickel ternary cathode material is secondary particles formed by aggregation of primary particles; a coating layer is provided on the surface of the secondary particles; the coating layer contains lithium element and cobalt element; the mass of cobalt element in the coating layer is preferably 0.02% to 2% of the mass of the secondary particles, more preferably 0.05% to 1.5%, still more preferably 0.1% to 1.3%, still more preferably 0.4% to 1%, and most preferably 0.5% to 0.6%.

[0036] In the present invention, a surface-doped ionic compound formed by elements with large ionic radii can isolate the high-nickel multi-element cathode from contact with water, inhibiting the occurrence of Li + / H + exchange reaction, reducing the lithium extraction of the high-nickel multi-element material during the water washing process, generating less spinel nickel oxide or rock salt phase nickel oxide, facilitating the concentration homogenization of Li during the subsequent process of constructing a concentration gradient layered material by secondary sintering, reconstructing the surface layered structure of the high-nickel multi-element cathode material, improving its discharge capacity and also improving the cycle performance of the material; at the same time, a cobalt-rich coating layer is constructed on the surface of the cathode material, and this coating layer can effectively solve a series of problems such as poor cycle performance, deteriorated gas generation and high residual alkali caused by the instability of Ni 3+ on the surface of the high-nickel material; the combined action of the doping of elements with large ionic radii and the cobalt-rich coating layer solves a series of problems caused by the instability of Ni 3+ on the high-nickel multi-element cathode material, improves the interfacial characteristics of the material, and enhances the electrochemical performance.

[0037] The present invention also provides a preparation method of the above high-capacity high-nickel ternary cathode material, including the following steps: S1) mixing a ternary precursor material, a raw material containing element A and a lithium source, and performing a first sintering to obtain a first sintered material; S2) washing the first sintered material, and drying to obtain a dried material; S3) mixing the dried material with a cobalt salt, and performing a second sintering to obtain the high-capacity high-nickel ternary cathode material.

[0038] Among them, the present invention does not have special restrictions on the sources of all raw materials, and they can be commercially available.

[0039] Mixing the ternary precursor material, the raw material containing element A and the lithium source; the ternary precursor material is Ni 1-x-y- z Co x M y(OH)2; The raw material containing element A is preferably one or more of an oxide, a carbonate, a sulfate, and a hydroxide containing element A, more preferably one or more of an oxide, a carbonate, and a hydroxide containing element A; The lithium source can be any lithium source well-known to those skilled in the art without special limitations. In the present invention, it is preferably one or more of lithium hydroxide, lithium carbonate, and lithium nitrate; The molar ratio of lithium element in the lithium source to the total molar number of Ni + Co + M + A is a:1; The a is the same as described above and will not be elaborated here; The present invention has no special limitations on the mixing method, and it is only necessary to mix evenly.

[0040] After mixing, the first sintering is carried out to obtain a primary sintered material; In the present invention, the first sintering is preferably specifically: sintering at 400°C to 600°C for 2 to 8 hours, and then heating up to 650°C to 1000°C and continuing to sinter for 10 to 14 hours; More preferably specifically: sintering at 450°C to 550°C for 2 to 6 hours, and then heating up to 650°C to 900°C and continuing to sinter for 10 to 14 hours; Still more preferably specifically: sintering at 500°C for 2 to 4 hours, and then heating up to 700°C to 800°C and continuing to sinter for 10 to 14 hours; Most preferably specifically: sintering at 500°C for 2 to 4 hours, and then heating up to 740°C to 760°C and continuing to sinter for 11 to 14 hours; The heating rate of the first sintering is preferably 1 to 10°C / min, more preferably 1 to 6°C / min, still more preferably 2 to 4°C / min; The atmosphere of the first sintering is preferably an oxygen atmosphere, a nitrogen atmosphere, or a vacuum condition, more preferably an oxygen atmosphere.

[0041] The primary sintered material is washed with water and then dried to obtain a dried material; The water-to-material ratio of the water washing is preferably (0.5 to 5):1, more preferably (0.8 to 2):1, still more preferably (1 to 1.5):1; The time of the water washing is preferably 0.5 to 30 minutes, more preferably 1 to 15 minutes, still more preferably 5 to 10 minutes; After water washing, it is preferably dehydrated and then dried; The dehydration is preferably carried out using a solid-liquid separation device; The drying temperature is preferably 80°C to 200°C, more preferably 110°C to 180°C, still more preferably 140°C to 160°C, and most preferably 150°C; The atmosphere of the drying is preferably an oxygen atmosphere, a nitrogen atmosphere, or a vacuum condition, more preferably a vacuum condition; The drying is preferably carried out in a drying device, and the drying device used is preferably a double-cone dryer, a plow knife dryer, a centrifugal spray dryer, a vibrating dryer, a drum dryer, a tray dryer, etc. The drying device includes but is not limited to the above devices.

[0042] Mix the dried material with a cobalt salt; the cobalt salt can be any cobalt salt well-known to those skilled in the art without special limitations. In the present invention, it is preferably one or more of cobalt oxides, carbonate compounds, sulfate compounds, hydroxyoxides, and hydroxides. To avoid introducing anionic impurities, it is more preferably one or more of cobalt oxides, carbonate compounds, hydroxyoxides, and hydroxides; the particle size of the cobalt salt is preferably 100 - 500 nm, more preferably 100 - 400 nm, still more preferably 200 - 300 nm; the mass of the cobalt salt is preferably 0.02% - 2% of the mass of the dried material, more preferably 0.05% - 1.5%, still more preferably 0.1% - 1.3%, still more preferably 0.4% - 1%, and most preferably 0.5% - 0.6%; the rotation speed of the mixing is preferably 500 - 1000 r / min, more preferably 600 - 900 r / min, still more preferably 700 - 800 r / min; the mixing time is preferably 5 - 20 min, more preferably 10 - 20 min, still more preferably 15 min.

[0043] After mixing, perform a second sintering to obtain a high-capacity high-nickel ternary cathode material; the temperature of the second sintering is preferably 150°C - 750°C, more preferably 250°C - 700°C, still more preferably 350°C - 700°C, still more preferably 450°C - 700°C, still more preferably 550°C - 700°C, still more preferably 600°C - 700°C, and most preferably 630°C; the time of the second sintering is preferably 2 - 20 h, more preferably 5 - 15 h, still more preferably 8 - 12 h, and most preferably 10 h; the atmosphere of the second sintering is preferably an oxygen atmosphere, a nitrogen atmosphere, or a vacuum condition, and more preferably an oxygen atmosphere.

[0044] To further illustrate the present invention, the following provides a detailed description of a high-capacity high-nickel ternary cathode material and its preparation method in combination with examples.

[0045] All reagents used in the following examples are commercially available.

[0046] Example 1

[0047] The mother material of the primary sintered cathode material powder is mixed by nickel-cobalt composite hydroxide, Sr element-containing oxide (SrO), and lithium hydroxide in a molar ratio of Li / (Ni + Co + M + A) of 1.025 and heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and kept at a constant temperature for 2 h, then heated to 740°C at a rate of 2°C / min and kept at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Sr 0.004 O2. The average particle size of the primary sintered cathode material powder is 12.53 μm.

[0048] Wash 3000 g of the once-sintered cathode material and deionized water for 10 min at a weight ratio of 1:1, and filter and dehydrate the material liquid through a Buchner suction flask for 30 min. Mash the filter cake and dry it in a double-cone dryer under vacuum conditions at a temperature of 150 °C. Mix the obtained dried material with Co(OH)2 having an average particle size of about 200 nm at a weight ratio of 159 / 1 in a 10 L high-speed mixer at a rotation speed of 800 r / min for 15 min to mix evenly. Finally, place the evenly mixed mixture under an oxygen atmosphere and sinter it at a target temperature of 630 °C for 10 h for the second sintering treatment to obtain a high-capacity high-nickel ternary cathode material with an average particle size of 12.43 μm.

[0049] Example 2

[0050] The once-sintered cathode material powder base material is mixed with nickel-cobalt composite hydroxide, a barium-containing carbonate compound (BaCO3), and lithium hydroxide at a molar ratio of Li / (Ni + Co + M + A) of 1.025 and heated to 500 °C at a rate of 2 °C / min under an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740 °C at a rate of 2 °C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Ba 0.004 O2. Except for this, a multi-component high-nickel material is obtained in the same manner as in Example 1. The average particle size of the once-sintered cathode material powder is 12.53 μm. Except for this, a high-capacity high-nickel ternary cathode material is obtained in the same manner as in Example 1, and the average particle size of the obtained high-capacity high-nickel ternary cathode material is 12.41 μm.

[0051] Example 3

[0052] The once-sintered cathode material powder base material is mixed with nickel-cobalt composite hydroxide, a lanthanum-containing oxide (La2O3), and lithium hydroxide at a molar ratio of Li / (Ni + Co + M + A) of 1.025 and heated to 500 °C at a rate of 2 °C / min under an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740 °C at a rate of 2 °C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co 0.10 Al 0.016 La 0.004 O2. The average particle size of the once-sintered cathode material powder is 12.52 μm. Except for this, a high-capacity high-nickel ternary cathode material is obtained in the same manner as in Example 1, and the average particle size of the obtained high-capacity high-nickel ternary cathode material is 12.39 μm.

[0053] Example 4

[0054] The mother material of the primary sintered cathode material powder is mixed with nickel-cobalt composite hydroxide, an oxide containing Y element (Y2O3), and lithium hydroxide at a molar ratio of Li / (Ni+Co+M+A) of 1.025 and heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740°C at a rate of 2°C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Y 0.004 O2. The average particle size of the primary sintered cathode material powder is 12.50 μm. In addition, a high-capacity high-nickel ternary cathode material is obtained in the same manner as in Example 1, and the average particle size of the obtained high-capacity high-nickel ternary cathode material is 12.41 μm.

[0055] Example 5

[0056] The mother material of the primary sintered cathode material powder is mixed with nickel-cobalt composite hydroxide, an oxide containing Sm element (Sm2O3), and lithium hydroxide at a molar ratio of Li / (Ni+Co+M+A) of 1.025 and heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740°C at a rate of 2°C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Sm 0.004 O2. The average particle size of the primary sintered cathode material powder is 12.51 μm. In addition, a high-capacity high-nickel ternary cathode material is obtained in the same manner as in Example 1, and the average particle size of the obtained high-capacity high-nickel ternary cathode material is 12.38 μm.

[0057] Example 6

[0058] The mother material of the primary sintered cathode material powder is mixed with nickel-cobalt composite hydroxide, an oxide containing Ce element (CeO2), and lithium hydroxide at a molar ratio of Li / (Ni+Co+M+A) of 1.025 and heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740°C at a rate of 2°C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Ce 0.004 O2. The average particle size of the primary sintered cathode material powder is 12.53 μm. In addition, a high-capacity high-nickel ternary cathode material is obtained in the same manner as in Example 1, and the average particle size of the obtained high-capacity high-nickel ternary cathode material is 12.42 μm.

[0059] Comparative Example 1

[0060] The mother material of the primary sintered cathode material powder is mixed with nickel-cobalt composite hydroxide and lithium hydroxide in a molar ratio of Li / (Ni+Co+M+A) of 1.025 and heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740°C at a rate of 2°C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.884 Co 0.10 Al 0.016 O2. The average particle size of the primary sintered cathode material powder is 12.50 μm. 3000 g of the primary sintered cathode material and deionized water are washed in a weight ratio of 1:1 for 10 min, and the slurry is filtered and dehydrated through a Buchner filter flask for 30 min. The filter cake is crushed and dried in a double-cone dryer under vacuum at a temperature of 150°C. The obtained dried material is mixed with nano-Co(OH)2 in a weight ratio of 159 / 1 using a 10 L high-speed mixer at a rotation speed of 800 r / min for 15 min for uniform mixing. Finally, the uniformly mixed mixture is placed in an oxygen atmosphere and sintered at a target temperature of 630°C for 10 h for secondary firing treatment to obtain a high-nickel ternary cathode material, with an average particle size of 12.43 μm.

[0061] Comparative Example 2

[0062] The mother material of the primary sintered cathode material powder is mixed with nickel-cobalt composite hydroxide, Sr element-containing oxide (SrO) and lithium hydroxide in a molar ratio of Li / (Ni+Co+M+A) of 1.025 and heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740°C at a rate of 2°C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Sr 0.004 O2. The average particle size of the primary sintered cathode material powder is 12.53 μm. The obtained first-fired material is mixed with Co(OH)2 in a weight ratio of 159 / 1 using a 10 L high-speed mixer at a rotation speed of 800 r / min for 15 min for uniform mixing. Finally, the uniformly mixed mixture is placed in an oxygen atmosphere and sintered at a target temperature of 630°C for 10 h for secondary firing treatment to obtain a high-nickel ternary cathode material, with an average particle size of 12.54 μm.

[0063] Comparative Example 3

[0064] The mother material of the primary sintered cathode material powder is mixed with nickel-cobalt composite hydroxide, Sr element-containing oxide (SrO) and lithium hydroxide in a molar ratio of Li / (Ni+Co+M+A) of 1.025 and heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held at a constant temperature for 2 h, then heated to 740°C at a rate of 2°C / min and held at a constant temperature for 11 h for firing, represented by Li 1.025 Ni 0.88 Co0.10 Al 0.016 Sr 0.004 It is represented by O₂. The average particle size of the primary sintered cathode material powder is 12.53 μm. 3000 g of the primary sintered cathode material and deionized water are washed for 10 min at a weight ratio of 1:1, and the material liquid is filtered and dehydrated for 30 min through a Buchner filter flask. The filter cake is mashed and dried in a double-cone dryer under vacuum conditions at a temperature of 150 °C to obtain a dried material, which is sintered at a target temperature of 630 °C for 10 h under an oxygen atmosphere for secondary sintering treatment to obtain a high-nickel ternary cathode material with an average particle size of 12.40 μm.

[0065] Comparative Example 4

[0066] The primary sintered cathode material powder base material is mixed by nickel-cobalt composite hydroxide, an oxide containing Mg element (MgO) and lithium hydroxide in a molar ratio of Li / (Ni + Co + M + A) of 1.025 and heated to 500 °C at a rate of 2 °C / min and held at a constant temperature for 2 h in an oxygen atmosphere, then heated to 740 °C at a rate of 2 °C / min and held at a constant temperature for 11 h for firing, using Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Mg 0.004 It is represented by O₂. The average particle size of the primary sintered cathode material powder is 12.50 μm. 3000 g of the primary sintered cathode material and deionized water are washed for 10 min at a weight ratio of 1:1, and the material liquid is filtered and dehydrated for 30 min through a Buchner filter flask. The filter cake is mashed and dried in a double-cone dryer under vacuum conditions at a temperature of 150 °C. The obtained dried material is mixed with Co(OH)₂ at a weight ratio of 15 / 1 using a 10 L high-speed mixer at a rotation speed of 800 r / min for 15 min for uniform mixing, and finally the uniformly mixed mixture is placed under an oxygen atmosphere and sintered at a target temperature of 630 °C for 10 h for secondary sintering treatment to obtain a high-nickel ternary cathode material with an average particle size of 12.40 μm.

[0067] Comparative Example 5

[0068] The primary sintered cathode material powder base material is mixed by nickel-cobalt composite hydroxide, an oxide containing Sr element (SrO) and lithium hydroxide in a molar ratio of Li / (Ni + Co + M + A) of 1.025 and heated to 500 °C at a rate of 2 °C / min and held at a constant temperature for 2 h in an oxygen atmosphere, then heated to 740 °C at a rate of 2 °C / min and held at a constant temperature for 11 h for firing, using Li 1.025 Ni 0.88 Co 0.10 Al 0.016 Sr 0.004 It is represented by O₂. The average particle size of the primary sintered cathode material powder is 12.52 μm, and the specific surface area is 0.29 m 2 / g. Wash 500 g of the once-sintered cathode material and deionized water for 10 min at a weight ratio of 1:1, and filter and dehydrate the slurry through a Buchner filter flask for 30 min. Mash the filter cake and dry it in a double-cone dryer under vacuum conditions at a temperature of 150 °C. Mix the obtained dried material with Co(OH)2 at a weight ratio of 15.9 / 1 in a 10 L high-speed mixer at a rotation speed of 800 r / min for 15 min to mix evenly. Finally, place the evenly mixed mixture in an oxygen atmosphere and sinter it at a target temperature of 630 °C for 10 h for the second sintering treatment to obtain a high-nickel ternary cathode material with an average particle size of 12.46 μm.

[0069] Test method:

[0070] 1. BET: Test using the N2 adsorption method, model: Micromeritics ASAP2460;

[0071] 2. Half-cell test: Mix and make a slurry according to active material: conductive carbon black SP (particle size 40 nm): PVDF (molecular weight 900,000) = 90%: 5%: 5%, control the areal density at 17 mg / cm 2 , after rolling, control the compaction at 3.4 mg / cm 3 , assemble into a 2430 button cell, and test the battery by charging and discharging at 0.2C for the specific capacity, and the test voltage range is 2.5 V to 4.25 V;

[0072] 3. Full-cell test: Mix and make a positive electrode slurry according to active material: SP (particle size 40 nm): KS-6: PVDF (molecular weight 900,000) = 94.5%: 2%: 1%: 2.5%, make a positive electrode plate through the coating and rolling processes, control the areal density of the electrode plate at 16 mg / cm 2 , use artificial graphite for the negative electrode, make a slurry according to the ratio of graphite: SP: CMC: SBR = 95.5%: 1%: 1.5%: 2%, control the coating areal density at 10 mg / cm 2 , use a 20 μm dry PP / PE / PP separator (Ube UP3074, Japan), use a carbonate (EC / DMC / DEC volume ratio 3:3:4) solution of 1 mol / L LiPF6 as the electrolyte, assemble into a 503048 model battery with a battery capacity of about 800 mAh, and use it for testing, the voltage range is 3.0 to 4.20 V; Compare the capacity retention rate by cycling at 1C for 300 weeks at 45 °C;

[0073] 4. XPS test: Scanning X-ray photoelectron spectrometer (XPS), model: Thermo ESCALAB 250XI;

[0074] 5. Cross-section etching: Use the Gatan 697Ilion II for the etching equipment, use Ar+ Etch the ion pair powder material under the test conditions of 6 keV, 30 min, an angle of 2 degrees, and a sample stage rotation speed of 1 rpm;

[0075] 6. ICP test: Weigh 0.4 g of the positive electrode material sample into a 250 ml beaker, add 7.5 mL of high-grade pure hydrochloric acid and 2.5 mL of high-grade pure nitric acid, and heat and dissolve at 195 °C for 30 min. Transfer the heated liquid to a volumetric flask, make up the volume with pure water, and dilute to within the measurable range for measurement using an ICP instrument.

[0076] The above-mentioned examples and comparative examples were subjected to physical and chemical property tests and electrochemical tests under the same test conditions, and the test results are shown in Table 1; the charge-discharge curve comparison diagram of Example 1 and Comparative Example 1 at 0.2C is as Figure 1 shown.

[0077] Table 1 Performance test results of high-nickel ternary positive electrode materials

[0078]

[0079]

[0080] From the above data, it can be seen that the obtained primary sintered materials doped with elements with large ionic radii (La, Ba, Sm, Sr, Ce, Y) show higher discharge capacities after water washing, cobalt coating, and secondary sintering. Their relatively large (C A2 -C A1 ) / C A2 indicates that there are fewer doped elements in the bulk phase, and most of the doped elements are aggregated on the surface of the positive electrode particles. Moreover, the relatively high proportion of the Ni 3+ peak area indicates the presence of a relatively low content of spinel nickel oxide or rock salt phase nickel oxide. The good layered structure of the water-washed and dried material is conducive to the homogenization of lithium concentration during the secondary sintering process, providing a lithium source for the subsequent conversion of coated Co into lithium cobalt layered compounds. The good layered structure on the surface is beneficial to the performance of the capacity. At the same time, such positive electrode materials rich in cobalt on the surface also show better cycle performance. However, doping elements such as Mg with ionic radii similar to those of the main elements of the positive electrode have similar effects to those of undoped ones, with a relatively low proportion of the Ni 3+ peak area, and they do not show a relatively low discharge capacity after water washing, cobalt coating, and secondary sintering.

Claims

1. A high-capacity, high-nickel ternary cathode material, characterized in that: The high-capacity high-nickel ternary cathode material is secondary particles formed by aggregation of primary particles; a coating layer is provided on the surface of the secondary particles; the coating layer contains lithium element and cobalt element; The general formula of the secondary particles is: Li a Ni 1-x-y-z Co x M y A z O 2+e ; wherein, 0≤x≤0.35, 0≤y≤0.35, 0<z≤0.10, 0.95<a<1.30, 0≤e≤0.2; the M is selected from Mn and / or Al; the A is an alkaline earth metal element and / or a lanthanide metal element; the ionic radius of the A is 90-135 pm; The high-capacity high-nickel ternary positive electrode material is ion-etched and then tested by X-ray photoelectron spectroscopy to obtain an atomic ratio of A to all metals except Li. A1 The high-capacity high-nickel ternary cathode material is tested using inductively coupled plasma technology. The atomic ratio of A in all metals except Li is C. A2 , 20%≤(C A2 -C A1 ) / C A2 ; the alkaline earth metal element is selected from Ba and / or Sr; the lanthanide metal element is selected from one or more of La, Sm, Ce and Y; the mass of cobalt element in the coating layer is 0.02%-2% of the mass of the secondary particles.

2. The high-capacity high-nickel ternary cathode material according to claim 1, wherein The ions used in the ion etching are Ar + ions; the ion etching energy is 4~8 keV; the ion etching time is 20~40 min; the ion etching angle is 2 degrees; the ion etching speed is 1~2 rpm.

3. A method for preparing the high-capacity high-nickel ternary cathode material according to claim 1, characterized in that, It includes the following steps: S1) Mix a ternary precursor material, a raw material containing element A and a lithium source, and perform a first sintering to obtain a first sintered material; S2) Wash the first sintered material, and after drying, obtain a dried material; S3) Mix the dried material with a cobalt salt, and perform a second sintering to obtain a high-capacity high-nickel ternary cathode material.

4. The preparation method according to claim 3, characterized in that, The raw material containing element A is selected from one or more of an oxide, a carbonate compound, a sulfate compound and a hydroxide containing element A; The lithium source is selected from one or more of lithium hydroxide, lithium carbonate and lithium nitrate; The cobalt salt is selected from one or more of an oxide, a carbonate compound, a sulfate compound, a hydroxyoxide and a hydroxide of cobalt.

5. The preparation method according to claim 3, characterized in that, The first sintering in the step S1) is specifically: sinter at 400°C to 600°C for 2 to 8 h, and then raise the temperature to 650°C to 1000°C and continue sintering for 10 to 14 h.

6. The preparation method according to claim 3, wherein In the step S2), the water-to-material ratio of the water washing is (0.5-5):1; the time of the water washing is 0.5 to 30 min; the drying temperature is 80°C to 200°C.

7. The preparation method according to claim 3, wherein The temperature of the second sintering is 150°C to 750°C; the time of the second sintering is 2 to 20 h.

8. The preparation method according to claim 3, characterized in that The mass of the cobalt salt is 0.02%-2% of the mass of the dried material.

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