A composite-doped modified nickel-based cathode material and its preparation method

Abstract

The present invention discloses a composite-doped modified nickel-based cathode material, which comprises a nickel-based cathode material matrix and doping elements doped in the nickel-based cathode material matrix. The doping elements include element K, element L and element M. Element K includes at least one of Al, Mg, Zr or Co. Element L is a high-valence small-radius element, and element M is a low-valence large-radius element. The present invention also provides a preparation method of the above-mentioned composite-doped modified nickel-based cathode material. Through the synergistic co-doping of multiple doping elements, the present invention improves the cycle stability of the cathode material, and improves the capacity and rate performance of the cathode material.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and particularly relates to a cathode material and a preparation method thereof. Background Art

[0002] In order to meet the increasing demand for driving range in the new energy vehicle market, the competition for high-energy density batteries has increased, and high-energy lithium-ion batteries have been greatly developed. In the race for energy density, the development of ternary cathode materials tends to be high-nickel and high-voltage. As the ultimate goal of ternary cathode materials, ultra-high nickel cathode materials have great energy density and cost advantages, but at the same time, there are problems of poor cycle performance and safety performance.

[0003] Regarding the above problems existing in high-nickel cathode materials, currently, they are mainly improved by using single crystallization. However, high-nickel single crystals bring problems such as high residual lithium, unstable bulk structure, single crystal aggregation, and relatively serious lithium-nickel mixing, which have an impact on capacity, rate, and long-term cycle performance. Currently, in the existing technology, doping and coating and other modification means are used to solve the above problems, but the doping modification effect is still poor, and problems such as unstable bulk structure, single crystal aggregation, and lithium-nickel mixing still exist, affecting the electrochemical performance of high-nickel cathode materials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background art, and provide a composite-doped and modified nickel-based cathode material with good bulk structure stability, good single crystal dispersion, and low lithium-nickel mixing, and a preparation method thereof. To solve the above technical problem, the technical solution proposed by the present invention is as follows:

[0005] A composite-doped and modified nickel-based cathode material, comprising a nickel-based cathode material matrix and doping elements doped in the nickel-based cathode material matrix, the doping elements comprising element K, element L, and element M, wherein element K comprises at least one of Al, Mg, Zr, or Co, element L is a high-valence and small-radius element, and element M is a low-valence and large-radius element.

[0006] In the above composite-doped and modified nickel-based cathode material, preferably, the high-valence and small-radius element comprises at least one of W, Ta, Nb, Ti, or Mo, and the low-valence and large-radius element comprises at least one of Y, Ce, Ca, Ba, or Sr.

[0007] In the above composite-doped and modified nickel-based cathode material, preferably, the doping molar ratio of element K, element L, and element M is 1:(0.8 - 1.2):(1.8 - 2.4). The present invention needs to control the doping ratio of each element, control the growth and dispersion of primary particle single crystals, form well-dispersed single crystal particles, and can solve the problem of single crystal particle aggregation, which is beneficial to the improvement of electrochemical performance.

[0008] In the above nickel-based cathode material modified by composite doping, preferably, elements L and M are doped into the lattice of the nickel-based cathode material matrix to form a cubic ABO3 perovskite structure, and element K enters the A-site and / or B-site in the ABO3 perovskite structure to form a composite doping structure.

[0009] The nickel-based cathode material modified by composite doping of the present invention is co-doped with three types of element additives having a stable lattice and a combination of fluxing effect and dissolution inhibition effect. Elements L and M are doped into the lattice of the nickel-based cathode material matrix during sintering to form a cubic ABO3 perovskite structure, and element K enters the A-site and / or B-site in the ABO3 perovskite structure during sintering to form a composite doping structure. The composite doping structure plays a strut effect, relieves lattice displacement, eliminates grain boundary stress, improves the stability of the NMC layered lattice structure, increases the oxygen vacancy concentration while stabilizing the perovskite cubic structure, and improves the lithium ion diffusion rate and cycle stability. At the same time, by controlling the doping molar ratio of each doping element, the present invention can form single crystal particles with good dispersibility, further improving the electrochemical performance of the nickel-based cathode material.

[0010] In the above nickel-based cathode material modified by composite doping, preferably, there is also a coating element N outside the nickel-based cathode material matrix, and the chemical general formula of the nickel-based cathode material is Li z Ni 1-x-y Co x Me y K u L v M w N r O 2-s , where 0.9 ≤ z ≤ 1.1, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, 0 < u ≤ 0.05, 0 < v ≤ 0.05, 0 < w ≤ 0.05, 0 ≤ r ≤ 0.05, -0.05 ≤ s ≤ 0.05, Me is at least one of Mn and Al, and the coating element N includes at least one of Mg, Ca, B, Ce, Co, Al, Zr, or F.

[0011] In the above nickel-based cathode material modified by composite doping, preferably, the specific surface area of the nickel-based cathode material is 0.4 - 1.0 m 2 / g, and the residual lithium amount on the surface of the nickel-based cathode material is 800 - 1400 ppm of the mass of the nickel-based cathode material.

[0012] In the above nickel-based cathode material modified by composite doping, preferably, the doping elements are a combination of Zr, Mo, and Ba or a combination of Mg, Ta, and Sr. Combining the high-temperature co-doping of the above three elements, the doped cathode material has better electrochemical performance.

[0013] Among the above-mentioned composite-doped and modified nickel-based cathode materials, preferably, in the DQ / DV discharge curve of the nickel-based cathode material at a rate of 0.1C, there is a small reduction peak protruding between 3.4V and 3.6V, indicating that the cathode material has a good kinetic diffusion rate, low polarization internal resistance and power loss, and can exhibit higher capacity and better cycling performance.

[0014] As a general technical concept, the present invention also provides a preparation method of the above-mentioned composite-doped and modified nickel-based cathode material, comprising the following steps:

[0015] S1. Mix a nickel-cobalt-manganese hydroxide precursor, a lithium source and a dopant containing a doping element evenly, and then perform a sintering treatment to obtain a sintered product;

[0016] S2. Crush and dissociate the sintered product in step S1, then mix it with a coating agent containing a coating element N, and after mixing evenly, perform a sintering treatment to obtain the composite-doped and modified nickel-based cathode material.

[0017] In the above preparation method, preferably, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium fluoride or lithium phosphate, and the molar ratio of lithium element in the lithium source to the nickel-cobalt-manganese hydroxide precursor is (1.05 - 1.08):1.

[0018] In the above preparation method, preferably, in step S1, the sintering treatment includes two-stage sintering. The sintering temperature of the first-stage sintering is 400 - 600°C, and the heat preservation time is 2 - 5h. The sintering temperature of the second-stage sintering is 700 - 900°C, and the heat preservation time is 8 - 20h;

[0019] In step S2, the sintering temperature of the sintering treatment is 300 - 700°C, and the heat preservation time is 4 - 10h.

[0020] In the above preparation method, preferably, the dopant is a substance containing element K, a substance containing element L and a substance containing element M, and the coating agent is a compound containing a coating element N.

[0021] When the present invention prepares the ternary cathode material, through the crushing and dissociation process, the dissociation effect of single crystal particles is controlled, and the integrity of single crystal particles is ensured while dissociating, forming particles with uniform, narrow distribution and good dispersibility, improving the dispersibility of particle size, obtaining a narrower particle range, and improving the consistency of material use.

[0022] Through the selection of appropriate small-particle precursors and a relatively high lithium ratio, combined with element doping, coating modification, and a dry sintering process, the present invention modifies the crystal structure and morphology of single-crystal particles of ternary cathode materials, alleviates lattice displacement, eliminates grain boundary stress, improves the stability of the NMC layered lattice structure, reduces the interfacial energy barrier, simultaneously reduces lithium-nickel mixing, stabilizes lattice oxygen, reduces oxygen loss, and repairs the surface Li / O defects generated during the high-temperature sintering of high-nickel materials, reduces the surface stress of the materials, can react with the residual lithium on the surface at the same time, reduces the residual lithium, protects the surface of the materials, reduces side reactions with the electrolyte during cycling, improves the cycling stability of the materials, and alleviates the common problems of high residual lithium and poor cycling performance of high-nickel cathode materials, alleviates the irreversible phase change of high-nickel materials, improves the mechanical strength of the materials, and at the same time has a stable crystal structure, enabling the battery to have the performance of high safety, high capacity, and long cycling, meeting the safety and high-performance usage requirements of long-endurance high-end vehicle models and being applicable to the needs of EV long-endurance vehicle batteries.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] 1. The nickel-based cathode material with composite doping modification of the present invention uses elements K, L, and M with stable lattices and a combination of fluxing and dissolution-inhibiting effects for co-doping. Among them, element K enters the lattice to occupy the transition metal site or lithium site, provides a pillar effect and forms strong K-O bonds to stabilize the crystal structure; element L is a high-valence element with a relatively small ionic radius. At high temperatures, after a part of the ions enter the lattice, due to valence balance, the lithium intercalation and embedding are slightly inhibited, the crystal growth is inhibited while promoting the orderly entry of lithium into the lithium layer, promoting the directional growth of primary particles, and reducing lithium-nickel mixing in the lithium layer. Another part remains on the crystal surface to form a lithium-ion conductor; element M has a relatively large cation radius and is difficult to enter the lattice. It adheres to the grain boundaries, reduces the interfacial surface energy, promotes the fusion growth of primary particles, and improves the grain morphology. The three types of doping elements co-dope synergistically to form a simple cubic structure of ABO3 perovskite type in the crystal structure of the material, playing a pillar effect, alleviating lattice displacement, eliminating grain boundary stress, improving the stability of the NMC layered lattice structure, reducing the interfacial energy barrier, simultaneously reducing lithium-nickel mixing, stabilizing lattice oxygen, reducing oxygen loss, reducing polarization internal resistance, and improving the cycling stability of the materials, and improving the capacity and rate performance of the materials.

[0025] 2. When preparing the composite-doped and modified nickel-based cathode material by the preparation method of the present invention, a surface coating and dry sintering process are adopted to repair the surface Li / O defects generated during the high-temperature sintering process of the high-nickel material, reduce the surface stress of the material, and at the same time can react with the residual lithium on the surface to reduce the residual lithium, and protect the surface of the material, reduce the side reactions with the electrolyte during the cycle, improve the cycle stability of the material, solve the common problem of high residual lithium in the ultra-high-nickel material, avoid the problem of damaged surface structure introduced by the water washing process to remove residual lithium, and at the same time can establish a lithium ion transmission channel, fix the oxygen atoms on the surface, inhibit the generation of nickel oxide phase in the side reaction during the cycle of the high-nickel component on the surface of the high-nickel material, and improve the cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for description in the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 SEM diagram of the composite-doped and modified nickel-based cathode material for Example 1.

[0028] Figure 2 EPMA diagram of the composite-doped and modified nickel-based cathode material for Example 1.

[0029] Figure 3 XRD diagram of the cathode materials of Example 1 and Comparative Example 1.

[0030] Figure 4 DQ / DV curve diagram of the cathode materials of Example 1 and Comparative Example 1.

[0031] Figure 5 High-temperature cycle performance diagram of the cathode materials of Example 1 and Comparative Example 1.

[0032] Figure 6 SEM diagram of the cathode material for Comparative Example 4. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] For the convenience of understanding the present invention, the following will describe the present invention more comprehensively and in detail in combination with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0034] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0035] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0036] Example 1:

[0037] A composite-doped modified nickel-based cathode material with the chemical formula Li 1.0 Ni 0.926 Co 0.030 Mn 0.040 Zr 0.001 Mo 0.001 Ba 0.002 B 0.001 O2, where Zr, Mo, and Ba are doping elements, and B is a coating element. The nickel-based cathode material consists of primary single-crystal small particles with a particle D50 size of 4.0 μm and a specific surface area of 0.73 m 2 / g, and the total residual lithium is 1251 ppm.

[0038] The preparation method of the above composite-doped modified nickel-based cathode material includes the following steps:

[0039] 1) The purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium hydroxide monohydrate, zirconium oxide, molybdenum trioxide, and barium carbonate are added to a high-speed mixing blender according to a molar ratio of 1:1.07:0.001:0.001:0.002, stirred at a speed of 1800 r / min for 30 min, and then in a box furnace with an oxygen concentration ≥ 96%, heated at a heating rate of 3 °C / min to 500 °C and held for 2 h, then heated to 786 °C and held for 12 h, and naturally cooled to room temperature to obtain a sintered material.

[0040] 2) The sintered material is first crushed by a jaw crusher and a pair-roll crusher, and then pulverized by a jet mill. The air pressure is controlled at 0.35 MPa, the classification frequency is 45 Hz, and the air extraction frequency is 40 Hz, which can effectively dissociate the sintered agglomerated particles and control the particle size.

[0041] 3) The pulverized material and boric acid are added to a high-speed mixing blender according to a molar ratio of 1:0.001, stirred at a speed of 1800 r / min for 30 min, and then in a box furnace under an oxygen atmosphere, heated at a heating rate of 3 °C / min to 320 °C and held for 8 h, and naturally cooled to room temperature to obtain a sintered material. The sintered material is screened using a 300-mesh sieve to obtain the composite-doped modified nickel-based cathode material of this example.

[0042] The SEM image of the above ternary cathode material is as shown in Figure 1As shown, it can be seen from the figure that the ternary cathode material is in the form of small granular spherical, with a relatively round single crystal morphology and good dispersibility. Through EPMA( Figure 2 ), elemental analysis shows that Zr / Mo / Ba elements are doped into the interior of the single crystal particles, and through XRD( Figure 3 ) data analysis, a BaMoO3 phase (Pm3m cubic type: ABO3 perovskite-like structure) is formed.

[0043] Example 2:

[0044] A composite-doped and modified nickel-based cathode material with the chemical formula Li 1.0 Ni 0.926 Co 0.030 Mn 0.040 Al 0.001 Nb 0.001 Ce 0.002 B 0.001 O2, where Al, Nb, and Ce are doping elements, and B is a coating element. It is composed of primary single crystal small particles, with a relatively round single crystal morphology and good dispersibility. The D50 particle size is 4.3 μm, the specific surface area is 0.75 m 2 / g, and the total residual lithium is 1282 ppm.

[0045] The preparation method of the above composite-doped and modified nickel-based cathode material includes the following steps:

[0046] 1) The purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium monohydrate hydroxide, aluminum oxide, niobium pentoxide, and cerium oxide are added to a high-speed mixing blender according to a molar ratio of 1:1.07:0.0005:0.0005:0.002, stirred at a speed of 1800 r / min for 30 min, and then in a box furnace with an oxygen concentration ≥ 96%, heated at a heating rate of 3 °C / min to 500 °C and held for 2 h, then heated to 786 °C and held for 12 h, and naturally cooled to room temperature to obtain a sintered material.

[0047] 2) The sintered material is first crushed by a jaw crusher and a pair of roll crushers in sequence, and then crushed by a jet mill. The air pressure is controlled at 0.35 MPa, the classification frequency is 45 Hz, and the air extraction frequency is 40 Hz, which can effectively dissociate the sintered agglomerated particles and control the particle size.

[0048] 3) Add the crushed material and boric acid into a high-speed mixing blender at a molar ratio of 1:0.001, stir for 30 min at a rotation speed of 1800 r / min, then in a box furnace under an oxygen atmosphere, heat it up to 320 °C at a heating rate of 3 °C / min and hold for 8 h, and naturally cool to room temperature to obtain the sintered material. Screen the sintered material with a 300-mesh sieve to obtain the composite-doped and modified nickel-based cathode material of this example.

[0049] Example 3:

[0050] A composite-doped and modified nickel-based cathode material with the chemical formula Li 1.0 Ni 0.926 Co 0.030 Mn 0.040 Mg 0.001 Ta 0.001 Sr 0.002 B 0.001 O2, where Mg, Ta, and Sr are doping elements, and B is a coating element. It consists of primary single-crystal small particles, with a D50 particle size of 4.5 μm, a specific surface area of 0.80 m 2 / g, and the total residual lithium is 1176 ppm.

[0051] The preparation method of the above composite-doped and modified nickel-based cathode material includes the following steps:

[0052] 1) Add the purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium hydroxide monohydrate, magnesium oxide, tantalum pentoxide, and strontium oxide into a high-speed mixing blender at a molar ratio of 1:1.07:0.001:0.0005:0.002, stir for 30 min at a rotation speed of 1800 r / min, then in a box furnace with an oxygen concentration ≥ 96%, heat it up to 500 °C at a heating rate of 3 °C / min and hold for 2 h, then heat it up to 786 °C and hold for 12 h, and naturally cool to room temperature to obtain the sintered material.

[0053] 2) First, coarsely crush the sintered material with a jaw crusher and a pair of roller mills in sequence, and then crush it with a jet mill. Control the air pressure at 0.35 MPa, the classification frequency at 45 Hz, and the air extraction frequency at 40 Hz, which can effectively dissociate the sintered agglomerated particles and control the particle size.

[0054] 3) Add the crushed material and boric acid to a high-speed mixing blender at a molar ratio of 1:0.001, stir at a speed of 1800 r / min for 30 min, then in a box furnace under an oxygen atmosphere, heat it at a heating rate of 3 °C / min to 320 °C and hold for 8 h, and naturally cool to room temperature to obtain the sintered material. Screen the sintered material using a 300-mesh sieve to obtain the composite-doped and modified nickel-based cathode material of this example.

[0055] Example 4:

[0056] A composite-doped and modified nickel-based cathode material with the chemical formula Li 1.0 Ni 0.926 Co 0.030 Mn 0.040 Zr 0.001 W 0.00 1Ca 0.002 B 0.001 O2, where Zr, W, and Ca are doping elements, and B is a coating element. It consists of primary single-crystal small particles, with a D50 particle size of 3.8 μm, a specific surface area of 0.69 m 2 / g, and the total residual lithium is 1209 ppm.

[0057] The preparation method of the above composite-doped and modified nickel-based cathode material includes the following steps:

[0058] 1) Add the purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium hydroxide monohydrate, zirconium oxide, tungsten oxide, and calcium hydroxide to a high-speed mixing blender at a molar ratio of 1:1.07:0.001:0.001:0.002, stir at a speed of 1800 r / min for 30 min, then in a box furnace with an oxygen concentration ≥ 96%, heat it at a heating rate of 3 °C / min to 500 °C and hold for 2 h, then heat it to 786 °C and hold for 12 h, and naturally cool to room temperature to obtain the sintered material.

[0059] 2) First crush the sintered material with a jaw crusher and a pair of roller mills in sequence, and then crush it with a jet mill. Control the air pressure at 0.35 MPa, the classification frequency at 45 Hz, and the air extraction frequency at 40 Hz, which can effectively dissociate the sintered agglomerated particles and control the particle size.

[0060] 3) Add the crushed material and boric acid to a high-speed mixing blender at a molar ratio of 1:0.001, stir at a speed of 1800 r / min for 30 min, then in a box furnace under an oxygen atmosphere, heat it up to 320 °C at a heating rate of 3 °C / min and keep it warm for 8 h, and naturally cool it to room temperature to obtain the sintered material. Screen the sintered material using a 300-mesh sieve to obtain the composite-doped and modified nickel-based cathode material of this example.

[0061] Example 5:

[0062] A composite-doped and modified nickel-based cathode material with the chemical formula Li 1.0 Ni 0.926 Co 0.030 Mn 0.040 Zr 0.001 Mo 0.001 Ba 0.002 Al 0.001 O2, where Zr, Mo, and Ba are doping elements, and Al is a coating element. It consists of primary single-crystal small particles, with a D50 particle size of 4.0 μm, a specific surface area of 0.73 m 2 / g, and the total residual lithium is 1251 ppm.

[0063] The preparation method of the above composite-doped and modified nickel-based cathode material includes the following steps:

[0064] 1) Add the purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium hydroxide monohydrate, zirconium oxide, molybdenum trioxide, and barium carbonate to a high-speed mixing blender at a molar ratio of 1:1.07:0.001:0.001:0.002, stir at a speed of 1800 r / min for 30 min, then in a box furnace with an oxygen concentration ≥ 96%, heat it up to 500 °C at a heating rate of 3 °C / min and keep it warm for 2 h, then heat it up to 786 °C and keep it warm for 12 h, and naturally cool it to room temperature to obtain the sintered material.

[0065] 2) First, coarsely crush the sintered material with a jaw crusher and a pair of roll crushers in sequence, and then crush it with a jet mill. Control the air pressure at 0.35 MPa, the classification frequency at 45 Hz, and the air draft frequency at 40 Hz, which can effectively dissociate the sintered agglomerated particles and control the particle size.

[0066] 3) Add the crushed material and alumina to a high-speed mixing blender at a molar ratio of 1:0.0005, stir at a speed of 1800 r / min for 30 min, then in a box furnace under an oxygen atmosphere, heat it at a heating rate of 3 °C / min to 320 °C, hold for 8 h, and naturally cool to room temperature to obtain the sintered material. Screen the sintered material using a 300-mesh sieve to obtain the composite-doped and modified nickel-based cathode material of this example.

[0067] Example 6:

[0068] A composite-doped and modified nickel-based cathode material with the chemical formula Li 1.0 Ni 0.926 Co 0.030 Mn 0.040 Zr 0.001 W 0.000 4Mo 0.0004 Ca 0.0022 B 0.001 O2, where Zr, W, Mo, and Ca are doping elements, and B is a coating element. It consists of primary single-crystal small particles, with a D50 particle size of 4.1 μm, a specific surface area of 0.62 m 2 / g, and the total residual lithium is 1137 ppm.

[0069] The preparation method of the above composite-doped and modified nickel-based cathode material includes the following steps:

[0070] 1) Add the purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium hydroxide monohydrate, zirconium oxide, tungsten oxide, molybdenum trioxide, and calcium hydroxide to a high-speed mixing blender at a molar ratio of 1:1.07:0.001:0.0004:0.0004:0.0022, stir at a speed of 1800 r / min for 30 min, then in a box furnace with an oxygen concentration ≥ 96%, heat it at a heating rate of 3 °C / min to 500 °C, hold for 2 h, then heat it to 786 °C, hold for 12 h, and naturally cool to room temperature to obtain the sintered material.

[0071] 2) First, coarsely crush the sintered material using a jaw crusher and a pair of roller mills, then crush it using a jet mill. Control the air pressure at 0.35 MPa, the classification frequency at 45 Hz, and the air extraction frequency at 40 Hz, which can effectively dissociate the sintered agglomerated particles and control the particle size.

[0072] 3) Add the crushed material and boric acid to a high-speed mixing blender at a molar ratio of 1:0.001, stir at a speed of 1800 r / min for 30 min, then in a box furnace under an oxygen atmosphere, heat at a rate of 3 °C / min to 320 °C and hold for 8 h, and naturally cool to room temperature to obtain the sintered material. Screen the sintered material using a 300-mesh sieve to obtain the composite-doped and modified nickel-based cathode material of this example.

[0073] Comparative Example 1:

[0074] A high-nickel single-crystal cathode material with the chemical formula Li 1.0 Ni 0.93 Co 0.03 Mn 0.04 O2, which is composed of primary single-crystal small particles, has a relatively serious phenomenon of single-crystal particle agglomeration, a D50 particle size of 4.1 μm, a specific surface area of 0.77 m 2 / g, and a total residual lithium of 4119 ppm.

[0075] The preparation method of the above high-nickel single-crystal cathode material includes the following steps:

[0076] 1) Add the purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2 and lithium hydroxide monohydrate to a high-speed mixing blender at a molar ratio of 1:1.07, stir at a speed of 1800 r / min for 30 min, then in a box furnace with an oxygen concentration ≥ 96%, heat at a rate of 3 °C / min to 500 °C and hold for 2 h, then heat to 786 °C and hold for 12 h, and naturally cool to room temperature to obtain the sintered material.

[0077] 2) First crush the sintered material successively with a jaw crusher and a pair-roll crusher, and then crush it with a jet mill. The air pressure is controlled at 0.35 MPa, the classification frequency is 45 Hz, and the air draft frequency is 40 Hz.

[0078] 3) Screen the crushed material using a 300-mesh sieve to obtain the ternary cathode material.

[0079] Figure 4 It is the DQ / DV curve graph of the cathode materials prepared in Example 1 and Comparative Example 1 at a 0.1C rate. As can be seen from the figure, the overall reduction peak of Comparative Example 1 is relatively short, and there is no reduction peak at about 3.5 V, with a relatively large polarization and a relatively low discharge capacity; while the overall reduction peak of Example 1 is relatively high, especially the H2-H3 phase transition peak at about 4.2 V and the H1-M reduction peak at about 3.5 V, indicating that Example 1 alleviates the irreversible phase transitions of H1-M and H2-H3 and has a higher specific capacity.

[0080] Figure 5 It is the high-temperature cycle performance graph of the cathode materials prepared in Example 1 and Comparative Example 1. As can be seen from the graph, through co-doping and coating layer design, the high-temperature cycle performance of Example 1 is far superior to that of Comparative Example 1.

[0081] Comparative Example 2:

[0082] A high-nickel single-crystal cathode material with the chemical formula Li 1.01 Ni 0.93 Co 0.03 Mn 0.04 B 0.001 O2, where B is the coating element, which consists of primary single-crystal small particles, and the single-crystal particles have a relatively serious agglomeration phenomenon. The D50 particle size is 4.2 μm, the specific surface area is 0.73 m 2 / g, and the total residual lithium is 1399 ppm.

[0083] The preparation method of the above high-nickel single-crystal cathode material includes the following steps:

[0084] 1) Add the purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2 and lithium hydroxide monohydrate into a high-speed mixing blender according to a molar ratio of 1:1.07, stir at a speed of 1800 r / min for 30 min, then in a box furnace with an oxygen concentration ≥ 96%, heat up to 500 °C at a heating rate of 3 °C / min and hold for 2 h, then heat up to 786 °C and hold for 12 h, and naturally cool to room temperature to obtain a sintered material.

[0085] 2) First crush the sintered material with a jaw crusher and a pair-roller crusher in sequence, and then crush it with a jet mill. The air pressure is controlled at 0.35 MPa, the classification frequency is 45 Hz, and the air draft frequency is 40 Hz.

[0086] 3) Add the crushed material and boric acid into a high-speed mixing blender according to a molar ratio of 1:0.001, stir at a speed of 1800 r / min for 30 min, then in a box furnace under an oxygen atmosphere, heat up to 320 °C at a heating rate of 3 °C / min and hold for 8 h, and naturally cool to room temperature to obtain a sintered material. Screen the sintered material with a 300-mesh sieve to obtain a ternary cathode material.

[0087] Comparative Example 3:

[0088] A high-nickel single-crystal cathode material with the chemical formula Li 1.0 Ni 0.927 Co 0.030 Mn 0.040 Mo 0.001 Ba 0.002 B 0.001O2, where Mo and Ba are doping elements, B is a coating element, which consists of primary single-crystal small particles, the D50 particle size is 4.2 μm, the specific surface area is 0.78 m 2 / g, and the total residual lithium is 1292 ppm.

[0089] The preparation method of the above-mentioned composite-doped and modified nickel-based cathode material includes the following steps:

[0090] 1) The purchased nickel-cobalt-manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium hydroxide monohydrate, molybdenum trioxide, and barium carbonate are added to a high-speed mixing blender according to a molar ratio of 1:1.07:0.001:0.002, stirred at a rotation speed of 1800 r / min for 30 min, and then in a box furnace with an oxygen concentration ≥ 96%, heated at a heating rate of 3 °C / min to 500 °C and held for 2 h, then heated to 786 °C and held for 12 h, and naturally cooled to room temperature to obtain a sintered material.

[0091] 2) The sintered material is initially crushed by a jaw crusher and a pair-roll crusher in sequence, and then pulverized by a jet mill, with the air pressure controlled at 0.35 MPa, the classification frequency at 45 Hz, and the air draft frequency at 40 Hz.

[0092] 3) The pulverized material and boric acid are added to a high-speed mixing blender according to a molar ratio of 1:0.001, stirred at a rotation speed of 1800 r / min for 30 min, and then in a box furnace under an oxygen atmosphere, heated at a heating rate of 3 °C / min to 320 °C and held for 8 h, and naturally cooled to room temperature to obtain a sintered material. The sintered material is sieved using a 300-mesh sieve to obtain a ternary cathode material.

[0093] Comparative Example 4:

[0094] A high-nickel single-crystal cathode material with the chemical formula Li 1.0 Ni 0.925 Co 0.030 Mn 0.040 Zr 0.001 Mo 0.002 Ba 0.002 B 0.00 1O2, where Zr, Mo, and Ba are doping elements, B is a coating element, which consists of primary single-crystal small particles, with very serious particle agglomeration, the D50 particle size is 4.9 μm, the specific surface area is 0.94 m 2 / g, and the total residual lithium is 7204 ppm.

[0095] The preparation method of the above-mentioned high-nickel single-crystal cathode material includes the following steps:

[0096] 1) Add the purchased nickel cobalt manganese hydroxide precursor Ni 0.93 Co 0.03 Mn 0.04 (OH)2, lithium hydroxide monohydrate, zirconium oxide, molybdenum trioxide, and barium carbonate into a high-speed mixing blender according to a molar ratio of 1:1.07:0.001:0.002:0.002, stir at a speed of 1800 r / min for 30 min, then in a box furnace with an oxygen concentration ≥ 96%, heat up at a rate of 3 °C / min to 500 °C and hold for 2 h, then heat up to 786 °C and hold for 12 h, and naturally cool to room temperature to obtain a sintered material.

[0097] 2) First crush the sintered material with a jaw crusher and a pair-roll crusher in sequence, and then crush it with a jet mill. The air pressure is controlled at 0.35 MPa, the classification frequency is 45 Hz, and the air extraction frequency is 40 Hz.

[0098] 3) Add the crushed material and boric acid into a high-speed mixing blender according to a molar ratio of 1:0.001, stir at a speed of 1800 r / min for 30 min, then in a box furnace under an oxygen atmosphere, heat up at a rate of 3 °C / min to 320 °C and hold for 8 h, and naturally cool to room temperature to obtain a sintered material. Screen the sintered material with a 300-mesh sieve to obtain a ternary cathode material.

[0099] The SEM image of the above ternary cathode material is as Figure 6 shown. It can be seen from the figure that the ternary cathode material is composed of primary single-crystal small particles. The grain size of the primary particles is small, the agglomeration phenomenon is very serious, the residual lithium is also extremely high, and the primary particles do not grow sufficiently.

[0100] Performance test:

[0101] Use CR2032 coin cells to study the electrochemical performance of the cathode materials in the above examples and comparative examples.

[0102] Positive electrode sheet: Stir and disperse the cathode materials of Examples 1-6 and Comparative Examples 1-4, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) in a mass ratio of 92.5:5:2.5 with the solvent NMP, coat it on an aluminum foil substrate, and roll it to obtain a positive electrode sheet.

[0103] Negative electrode sheet: Lithium metal sheet.

[0104] Electrolyte: 1 mol / L LiPF6 solution, the solvent is a mixed solvent of EC and DMC, the ratio of the two is 1:2, and the additive is 1% VC.

[0105] Assemble into CR2032 coin cells for battery testing. The charging cut-off voltage is 4.3 V, and the discharging cut-off voltage is 3.0 V.

[0106] The following are the test results of the electrical properties of the cathode materials prepared in Examples 1-6 and Comparative Examples 1-4. The test results of the electrical properties are shown in Table 1.

[0107] Table 1: Test Results of the Electrical Properties of the Cathode Materials in Examples 1-6 and Comparative Examples 1-4

[0108]

[0109] As can be seen from Table 1, the ultra-high nickel single-crystal cathode materials prepared in Examples 1-6 not only have a simple preparation method, but also can significantly improve the first discharge capacity and rate performance, and can significantly improve the high-temperature cycle. To a great extent, it solves the common problems of high residual lithium, poor rate and cycle performance of high-nickel materials in the industry. In Comparative Examples 1-3, the doping and coating design of the present invention was not adopted, the surface residual lithium was relatively high, the lithium-nickel mixing ratio was relatively serious, the polarization internal resistance was relatively large, and the capacity, rate and cycle performance were relatively poor. Compared with the examples, the overall electrochemical performance was relatively poor. In Comparative Example 4, the doping ratio of the doping element was not controlled, the primary particle grains agglomerated seriously, the residual lithium was extremely high, and the electrochemical performance was poor.

[0110] The present invention modifies the crystal structure and morphology of the single-crystal particles of the ternary cathode material by selecting a suitable high-nickel small-particle precursor, combining element doping and coating modification with a dry sintering process, relieving lattice displacement, eliminating grain boundary stress, improving the stability of the NMC layered lattice structure, reducing the interfacial energy barrier, while reducing lithium-nickel mixing, stabilizing lattice oxygen, reducing oxygen loss, and repairing the surface Li / O defects generated during the high-temperature sintering process of high-nickel materials, reducing the surface stress of the material, while being able to react with the surface residual lithium, reducing the residual lithium, and protecting the material surface, reducing the side reaction with the electrolyte during the cycle, improving the cycle stability of the material, improving the common problems of high residual lithium and poor cycle performance of high-nickel cathode materials, relieving the irreversible phase transformation of high-nickel materials, improving the mechanical strength of the material, while the crystal structure is stable, enabling the battery to have the performance of high safety, high capacity and long cycle, meeting the safety and high-performance use requirements of long-endurance high-end models, and being applicable to the needs of EV long-endurance vehicle batteries.

Claims

1. A composite doped and modified nickel-based cathode material, comprising a nickel-based cathode material matrix and doping elements doped in the nickel-based cathode material matrix, characterized in that, The doping elements include element K, element L, and element M. Element K includes at least one of Al, Mg, and Zr. Element L is a high-valence and small-radius element, and element M is a low-valence and large-radius element; The high-valence and small-radius elements include at least one of W, Ta, Nb, Ti, or Mo, and the low-valence and large-radius elements include at least one of Y, Ce, Ca, Ba, or Sr; The doping molar ratio of element K, element L, and element M is 1:(0.8 - 1.2):(1.8 - 2.4); In addition to the matrix of the nickel-based cathode material, there is a coating element N, and the chemical general formula of the nickel-based cathode material is Li z Ni 1-x- y Co x Me y K u L v M w N r O 2-s , where 0.9 ≤ z ≤ 1.1, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, 0 < u ≤ 0.05, 0 < v ≤ 0.05, 0 < w ≤ 0.05, 0 ≤ r ≤ 0.05, -0.05 ≤ s ≤ 0.05, Me is Mn, and the coating element N includes at least one of Mg, Ca, B, Ce, Co, Al, Zr, or F.

2. The composite-doped and modified nickel-based cathode material according to claim 1, wherein Element L and element M are doped into the lattice of the nickel-based cathode material matrix to form a perovskite-type cubic structure of ABO3. Element K enters the A-site and / or B-site in the perovskite-type cubic structure of ABO3 to form a composite doping structure.

3. The composite-doped and modified nickel-based cathode material according to claim 1, wherein The specific surface area of the nickel-based cathode material is 0.4 - 1.0 m 2 / g, and the residual lithium content on the surface of the nickel-based cathode material is 800 - 1400 ppm of the mass of the nickel-based cathode material.

4. The composite-doped and modified nickel-based cathode material according to claim 1, characterized in that, In the 0.1C rate DQ / DV discharge curve of the nickel-based cathode material, there is a convex reduction peak between 3.4V and 3.6V.

5. A method for preparing a composite-doped modified nickel-based cathode material as described in any one of claims 1-4, characterized in that, It includes the following steps: S1. Mix the nickel-cobalt-manganese hydroxide precursor, lithium source, and dopant containing doping elements evenly and then perform sintering treatment to obtain a sintered product; S2. Crush and dissociate the sintered product in step S1, then mix it with a coating agent containing coating element N, and after mixing evenly, perform sintering treatment to obtain a nickel-based cathode material with composite doping modification.

6. The preparation method according to claim 5, wherein The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium fluoride, or lithium phosphate. The molar ratio of lithium element in the lithium source to the nickel-cobalt-manganese hydroxide precursor is (1.05 - 1.08):

1.

7. The preparation method according to claim 5, characterized in that, In step S1, the sintering treatment includes two-stage sintering. The sintering temperature of the first stage is 400 - 600°C, and the holding time is 2 - 5h. The sintering temperature of the second stage is 700 - 900°C, and the holding time is 8 - 20h; In step S2, the sintering temperature of the sintering treatment is 300 - 700°C, and the holding time is 4 - 10h.

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