Medium-nickel polycrystalline ternary positive electrode material and preparation method therefor, composite positive electrode material and preparation process therefor, and battery

Abstract

Provided are a medium-nickel polycrystalline ternary positive electrode material and a preparation method therefor, a composite positive electrode material and a preparation process therefor, and a battery. The medium-nickel polycrystalline ternary positive electrode material comprises secondary particles composed of multiple polycrystalline primary particles. The medium-nickel polycrystalline ternary positive electrode material further comprises a stabilizer. The stabilizer is not only distributed at grain boundaries inside the polycrystalline primary particles, but also coats the surfaces of the polycrystalline primary particles and the surfaces of the secondary particles. The stabilizer comprises a modifying element, the modifying element including any one of or a combination of at least two of Co, Mg, Zn, W, Al, Nb, Sr, or Ba. The medium-nickel polycrystalline ternary positive electrode material not only has a relatively high withstand voltage, but also has a relatively high gram capacity and a relatively low impedance. A battery prepared from the medium-nickel polycrystalline ternary positive electrode material not only exhibits a relatively high gram capacity and a relatively low impedance at an application voltage of greater than 4.25 V, but also exhibits excellent cycle stability.

Description

A medium-nickel polycrystalline ternary cathode material and its preparation method, a composite cathode material and its preparation process, and a battery.

[0001] This application claims priority to Chinese Patent Application No. 202511432913.5, filed with the Chinese Patent Office on September 30, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to a medium-nickel polycrystalline ternary cathode material and its preparation method, a composite cathode material and its preparation process, and a battery. Background Technology

[0003] In the field of new energy vehicles, the market demand for long driving range, ultra-fast charging and long life cycle warranty is becoming increasingly urgent, which directly drives the rapid development of lithium-ion batteries towards high energy density, low impedance and high long-term reliability.

[0004] The performance of lithium-ion batteries largely depends on their cathode materials. Therefore, there is an increasing demand for lithium-ion battery cathode materials in terms of specific capacity, low ion diffusion resistance, long cycle performance, and high storage performance.

[0005] Currently, ternary cathode materials are one of the important research directions in the field of lithium-ion batteries. Among them, medium-nickel ternary cathode materials (50%≤Ni≤70%) exhibit unique performance characteristics: compared with low-nickel ternary cathode materials (30%≤Ni≤50%), they have a higher capacity advantage; and compared with high-nickel ternary cathode materials (Ni>70%), they have superior long-cycle characteristics. Furthermore, from the perspective of particle morphology, ternary cathode materials can be divided into two types: single-crystal and polycrystalline. Compared with single-crystal ternary cathode materials, polycrystalline ternary cathode materials, due to their smaller primary particle size and shorter lithium-ion transport path, have lower charge transfer impedance and ion diffusion impedance, better meeting the requirements of ultra-fast charging and low impedance development in lithium-ion batteries.

[0006] Therefore, medium-nickel polycrystalline ternary cathode materials are promising ternary cathode materials; however, the medium-nickel polycrystalline ternary cathode materials disclosed in related technologies have performance defects. Due to the anisotropy of its primary particles, the grain boundary bonding strength at the primary particle joints is weak, which makes the material unable to withstand full-cell application voltage systems above 4.25V. During long-term cycling, the grain boundaries of this material are prone to cracking, leading to an increase in side reactions and a deterioration in the cycle performance of the battery.

[0007] CN115911300A discloses a method for preparing a high-voltage ternary cathode material, comprising the following steps: Step 1: Mixing lithium salt, a ternary precursor containing nickel, cobalt, and manganese, and a dopant uniformly, followed by a first sintering, to obtain a first-sintered material; Step 2: Crushing the first-sintered material and mixing it with a coating agent A for coating, followed by a second sintering, to obtain a first-coated material with a first coating layer; the coating agent A is one or more combinations of compounds containing the corresponding elements Li, Al, Ti, Mg, Co, Sr, Ba, B, Na, Sn, P, F, and Sm. Step 3: Crushing the first-coated material and mixing it with a coating agent B for coating, followed by a third sintering, to obtain a ternary cathode material with a second coating layer; the coating agent B is one or more combinations of compounds containing the corresponding elements Ti, Al, B, Ti, Zr, W, Y, P, F, Li, and B. The high-voltage ternary cathode material disclosed in this document improves the integrity of the surface coating and simultaneously enhances the power performance and cycle performance of the material.

[0008] CN113620352A discloses a method for preparing a high-voltage single-crystal ternary cathode material, belonging to the field of battery material technology. The method includes the following steps: uniformly mixing lithium salt, ternary precursor, and metal compound to obtain a mixture; sintering the mixture once and then pulverizing it to obtain a powder; adding the powder to an ethanol solution containing a pre-coating agent, stirring and mixing, evaporating the ethanol, and drying to obtain a powder; sintering the powder a second time and then sieving it to obtain the high-voltage single-crystal ternary cathode material. This application incorporates a dopant that can form a lithium-ion conductor on its surface, improving the electrochemical performance of the material and effectively preventing the dissolution of lattice lithium during wet coating; using aluminum hydroxide as a pre-coating agent ensures uniform reaction during the second sintering process; and employing a calcination method with four heat-preserving platforms improves the dispersion and roundness of the single-crystal particles.

[0009] Technical issues

[0010] The medium-nickel polycrystalline ternary cathode materials disclosed in related technologies all have certain drawbacks, such as low withstand voltage and the inability to simultaneously possess high specific capacity and low impedance. Therefore, it is crucial to develop and design a novel medium-nickel polycrystalline ternary cathode material and its preparation method, as well as composite cathode materials and their preparation processes and batteries.

[0011] Technical solutions

[0012] This application provides a medium-nickel polycrystalline ternary cathode material and its preparation method, a composite cathode material and its preparation process, and a battery. The medium-nickel polycrystalline ternary cathode material not only has a high withstand voltage, but also a high specific capacity and a low impedance. The battery prepared with the medium-nickel polycrystalline ternary cathode material exhibits both high specific capacity and low impedance, as well as excellent cycle stability at an application voltage >4.25V.

[0013] In one aspect, this application provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles;

[0014] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer. The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0015] The stabilizer contains a modifying element, which includes any one or a combination of at least two of Co, Mg, Zn, W, Al, Nb, Sr or Ba.

[0016] Secondly, this application provides a method for preparing the nickel polycrystalline ternary cathode material of the first aspect, the method comprising:

[0017] (1) Using the modified element source and the medium-nickel ternary polycrystalline precursor as raw materials, hydrothermal treatment was carried out to obtain the modified precursor;

[0018] (2) The modified precursor obtained in step (1) is mixed with the lithium source and then subjected to heat treatment to obtain a medium-nickel polycrystalline ternary cathode material.

[0019] Thirdly, this application provides a composite cathode material, which includes the medium-nickel polycrystalline ternary cathode material of the first aspect, and a coating layer covering the outside of the medium-nickel polycrystalline ternary cathode material.

[0020] Fourthly, this application provides a preparation process for a third-party composite cathode material, the preparation process including:

[0021] The first aspect involves mixing the medium-nickel polycrystalline ternary cathode material with a coating agent and then sintering it to obtain the medium-nickel polycrystalline ternary cathode material.

[0022] Fifthly, this application provides a battery comprising a medium-nickel polycrystalline ternary cathode material of the first aspect and / or a composite cathode material of the third aspect.

[0023] Beneficial effects

[0024] Compared with related technologies, this application has the following advantages:

[0025] The medium-nickel polycrystalline ternary cathode material provided in this application includes a stabilizer that is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the secondary particles composed of polycrystalline primary particles. The presence of the stabilizer can suppress the generation of cracks at the grain boundaries during battery cycling, and can also improve the interfacial stability between polycrystalline primary particles and between secondary particles in the secondary particles, so that the medium-nickel polycrystalline ternary cathode material has a higher withstand voltage.

[0026] In addition, the presence of stabilizers can improve the structural stability of medium-nickel polycrystalline ternary cathode materials, reduce the collapse of lithium-ion channels caused by lattice expansion / contraction during charging and discharging, stabilize the redox reversibility of transition metal ions, reduce the irreversible migration of transition metal ions or the formation of inert phases, and retain more complete interlayer diffusion channels, thereby enabling medium-nickel polycrystalline ternary cathode materials to have higher specific capacity.

[0027] In addition, as a chemically inert barrier, the stabilizer can not only isolate the secondary particles from the electrolyte and reduce side reactions, but also improve the defects at the grain boundaries within the polycrystalline primary particles, thereby giving the medium-nickel polycrystalline ternary cathode material a lower impedance.

[0028] In summary, the medium-nickel polycrystalline ternary cathode material provided in this application not only has a high withstand voltage, but also a high specific capacity and a low impedance. The battery prepared with the medium-nickel polycrystalline ternary cathode material exhibits both high specific capacity and low impedance at an application voltage >4.25V, and also demonstrates excellent cycle stability.

[0029] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0030] Figure 1 is a SEM image of the composite cathode material provided in Example 1.

[0031] Figure 2 is a SEM image of the composite cathode material provided in Comparative Example 2.

[0032] Figure 3 shows the capacity retention rate of the batteries prepared with the composite cathode materials provided in Example 1 and Comparative Example 2 as a function of the number of cycles under cycling conditions from 4.25V to 2.8V.

[0033] Figure 4 shows the capacity retention rate of the batteries prepared with the composite cathode materials provided in Example 1 and Comparative Example 2 as a function of the number of cycles under cycling conditions from 4.30V to 2.8V.

[0034] Figure 5 shows the capacity retention rate of the batteries prepared with the composite cathode materials provided in Example 1 and Comparative Example 2 as a function of the number of cycles under cycling conditions from 4.35V to 2.8V.

[0035] Embodiments of the present invention

[0036] In one aspect, this application provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles;

[0037] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer. The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0038] The stabilizer contains a modifying element, which includes any one or a combination of at least two of Co, Mg, Zn, W, Al, Nb, Sr or Ba.

[0039] In this application, the modifying element includes any one or at least two combinations of Co, Mg, Zn, W, Al, Nb, Sr or Ba. Typical but non-limiting combinations include combinations of Co and Mg, Zn and W, Al and Nb, Sr and Ba, or Co, Mg, Zn and W.

[0040] The medium-nickel polycrystalline ternary cathode material provided in this application includes a stabilizer that is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the secondary particles composed of polycrystalline primary particles. The presence of the stabilizer can suppress the generation of cracks at the grain boundaries during battery cycling, and can also improve the interfacial stability between polycrystalline primary particles and between secondary particles in the secondary particles, so that the medium-nickel polycrystalline ternary cathode material has a higher withstand voltage.

[0041] In addition, the presence of stabilizers can improve the structural stability of medium-nickel polycrystalline ternary cathode materials, reduce the collapse of lithium-ion channels caused by lattice expansion / contraction during charging and discharging, stabilize the redox reversibility of transition metal ions, reduce the irreversible migration of transition metal ions or the formation of inert phases, and retain more complete interlayer diffusion channels, thereby enabling medium-nickel polycrystalline ternary cathode materials to have higher specific capacity.

[0042] In addition, as a chemically inert barrier, the stabilizer can not only isolate the secondary particles from the electrolyte and reduce side reactions, but also improve the defects at the grain boundaries within the polycrystalline primary particles, thereby giving the medium-nickel polycrystalline ternary cathode material a lower impedance.

[0043] In summary, the medium-nickel polycrystalline ternary cathode material provided in this application not only has a high withstand voltage, but also a high specific capacity and a low impedance. The battery prepared with the medium-nickel polycrystalline ternary cathode material exhibits both high specific capacity and low impedance at an application voltage >4.25V, and also demonstrates excellent cycle stability.

[0044] Optionally, the polycrystalline primary particles are formed by stacking several medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0045] Optionally, the stabilizer material includes any one or a combination of at least two of oxides, hydroxides, or hydroxy oxides containing a modifying element. Typical but non-limiting combinations include combinations of oxides and hydroxides, combinations of hydroxides and hydroxy oxides, combinations of oxides and hydroxy oxides, or combinations of oxides, hydroxides, and hydroxy oxides.

[0046] Optionally, taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 500ppm to 10000ppm, for example, it can be 500ppm, 1000ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 9000ppm or 10000ppm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0047] In the medium-nickel polycrystalline ternary cathode material provided in this application, the mass fraction of the stabilizer affects the performance of the medium-nickel polycrystalline ternary cathode material and the battery. When the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 200ppm to 20000ppm, the medium-nickel polycrystalline ternary cathode material and the battery have better performance. This is because when the mass fraction of the stabilizer is within this range, the stabilizer can uniformly cover the surface of the polycrystalline primary and secondary particles and fill the grain boundaries within the polycrystalline primary particles. This avoids both the increase in insulating phase caused by excessive stabilizer, which would lead to increased impedance, and the insufficient performance enhancement effect caused by insufficient stabilizer content.

[0048] Optionally, the medium-nickel polycrystalline ternary cathode material also includes doping elements, which are doped into the lattice of the medium-nickel ternary material single crystal.

[0049] In the medium-nickel polycrystalline ternary cathode material provided in this application, the doping elements doped in the lattice of the medium-nickel ternary material single crystal are beneficial to improving the performance of the medium-nickel polycrystalline ternary cathode material and the battery. This is because after the doping elements enter the single crystal lattice, they can adjust the lattice parameters, expand the lithium-ion diffusion channels, and reduce the migration energy barrier. At the same time, they can also stabilize the valence state of transition metal ions through valence compensation, suppress the irreversible migration and dissolution of transition metal ions during charging and discharging, reduce lattice distortion, and thus improve the performance of the medium-nickel polycrystalline ternary cathode material and the battery.

[0050] Optionally, the doping elements include Zr and / or Al.

[0051] Optionally, based on 100% of the mass of the medium-nickel polycrystalline ternary positive electrode material, the mass fraction of the doping element in the medium-nickel polycrystalline ternary positive electrode material is 500 ppm to 10000 ppm, for example, may be 500 ppm, 800 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm, 9000 ppm or 10000 ppm, but is not limited to the enumerated values, and other unrecited values within this numerical range are also applicable.

[0052] In the medium-nickel polycrystalline ternary positive electrode material provided by the present application, the mass fraction of the doping element doped in the crystal lattice of the single crystal of the medium-nickel ternary material will affect the performance of the medium-nickel polycrystalline ternary positive electrode material and the battery; when based on 100% of the mass of the medium-nickel polycrystalline ternary positive electrode material, and the mass fraction of the doping element in the medium-nickel polycrystalline ternary positive electrode material is 500 ppm to 10000 ppm, the medium-nickel polycrystalline ternary positive electrode material and the battery have better performance, which is because the doping element within this mass fraction range can uniformly enter the crystal lattice, which can not only optimize the diffusion of lithium ions by adjusting the lattice parameters, but also sufficiently stabilize the valence state of the transition metal and inhibit migration and dissolution; an excessive amount is liable to cause intensified lattice distortion, while an insufficient amount cannot exert a stabilizing effect.

[0053] Optionally, the chemical formula of the medium-nickel polycrystalline ternary positive electrode material is LiNi x Co y Mn 1-x-y-z-w M z N w O2, where 0.5≤x≤0.7, 0<y≤0.3, 0.001≤z≤0.04, 0.001≤w≤0.04, M is a modifying element, and N is a doping element.

[0054] In the present application, 0.5≤x≤0.7, and the value of x may be, for example, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68 or 0.70, but is not limited to the enumerated values, and other unrecited values within this numerical range are also applicable.

[0055] In the present application, 0<y≤0.3, and the value of y may be, for example, 0.05, 0.10, 0.15, 0.20, 0.25 or 0.30, but is not limited to the enumerated values, and other unrecited values within this numerical range are also applicable.

[0056] In this application, 0.001≤z≤0.04, and the value of z can be, for example, 0.001, 0.005, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035 or 0.040, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] In this application, 0.001≤w≤0.04, and the value of w can be, for example, 0.001, 0.005, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035 or 0.040, but is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0058] Optionally, the D1 particle size of the medium-nickel polycrystalline ternary cathode material is 0.5 μm to 7.0 μm, for example, it can be 0.5 μm, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm or 7.0 μm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0059] Optionally, the D10 particle size of the medium-nickel polycrystalline ternary cathode material is 1.0 μm to 12.0 μm, for example, it can be 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm or 12.0 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] Optionally, the D50 particle size of the medium-nickel polycrystalline ternary cathode material is 2.0 μm to 15.0 μm, for example, it can be 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm or 15.0 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0061] Optionally, the D90 particle size of the medium-nickel polycrystalline ternary cathode material is 10.0 μm to 20.0 μm, for example, it can be 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm or 20.0 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] Optionally, the D99 particle size of the medium-nickel polycrystalline ternary cathode material is 16.0 μm to 30.0 μm, for example, it can be 16.0 μm, 18.0 μm, 20.0 μm, 22.0 μm, 24.0 μm, 26.0 μm, 28.0 μm or 30.0 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] Optionally, the span value of the particle size of the medium-nickel polycrystalline ternary cathode material is 0.1 to 1.5, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] Optionally, the powder impedance of the medium-nickel polycrystalline ternary cathode material is 10 Ω·cm to 500 Ω·cm, for example, it can be 10 Ω·cm, 50 Ω·cm, 100 Ω·cm, 150 Ω·cm, 200 Ω·cm, 250 Ω·cm, 300 Ω·cm, 350 Ω·cm, 400 Ω·cm, 450 Ω·cm or 500 Ω·cm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] Optionally, the compaction density of the medium-nickel polycrystalline ternary cathode material is 2.80 g / cm³. 3 ~3.70g / cm 3 For example, it can be 2.80g / cm³, 2.90g / cm³, 3.00g / cm³, 3.10g / cm³, 3.20g / cm³, 3.30g / cm³, 3.40g / cm³, 3.50g / cm³, 3.60g / cm³, or 3.70g / cm³, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] Optionally, the specific surface area of ​​the medium-nickel polycrystalline ternary cathode material is 0.1 m². 2 / g~2.0m 2 / g, for example, can be 0.1m² / g, 0.2m² / g, 0.3m² / g, 0.4m² / g, 0.5m² / g, 0.6m² / g, 0.7m² / g, 0.8m² / g, 0.9m² / g, 1.0m² / g, 1.2m² / g, 1.4m² / g, 1.6m² / g, 1.8m² / g, or 2.0m² / g, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0067] In a second aspect, the present application provides a preparation method of the nickel-containing polycrystalline ternary positive electrode material in the first aspect, and the preparation method includes:

[0068] (1) Using a modifying element source and a medium-nickel ternary polycrystalline precursor as raw materials, performing a hydrothermal treatment to obtain a modified precursor;

[0069] (2) mixing the modified precursor obtained in step (1) with a lithium source, and then performing a heat treatment to obtain the medium-nickel polycrystalline ternary positive electrode material.

[0070] Optionally, in the coating process of step (1), the mass ratio of the modifying element source to the medium-nickel ternary polycrystalline precursor used is (2~15):100, for example, it may be 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 12:100 or 15:100, but is not limited to the enumerated values, and other unenumerated values within this numerical range are also applicable.

[0071] Optionally, the modifying element source in step (1) includes any one or a combination of at least two of a Co source, a Mg source, a Zn source, a W source, an Al source, a Nb source, a Sr source or a Ba source. Typical but non-limiting combinations include a combination of a Co source and a Mg source, a combination of a Zn source and a W source, a combination of an Al source and a Nb source, a combination of a Sr source and a Ba source, or a combination of a Co source, a Mg source, a Zn source and a W source.

[0072] Optionally, the Co source, Mg source, Zn source, W source, Al source, Nb source, Sr source and Ba source each independently include a sulfate and / or a hydroxide.

[0073] Optionally, the chemical formula of the medium-nickel ternary polycrystalline precursor in step (1) is Ni x Co y Mn 1-x-y (OH)₂, where 0.5≤x≤0.7, 0<y≤0.3.

[0074] In the present application, 0.5≤x≤0.7, and the value of x may be, for example, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68 or 0.70, but is not limited to the enumerated values, and other unenumerated values within this numerical range are also applicable.

[0075] In the present application, 0<y≤0.3, and the value of y may be, for example, 0.05, 0.10, 0.15, 0.20, 0.25 or 0.30, but is not limited to the enumerated values, and other unenumerated values within this numerical range are also applicable.

[0076] Optionally, step (1) hydrothermal treatment includes: using a medium-nickel ternary polycrystalline precursor, a source of modifying elements, a precipitant and water as raw materials to prepare a mixed slurry, and then carrying out a hydrothermal reaction by heating to prepare the modified precursor.

[0077] Optionally, the mass ratio of the medium-nickel ternary polycrystalline precursor to the precipitant is 1:(0.0002~0.02), for example, it can be 1:0.0002, 1:0.0005, 1:0.001, 1:0.002, 1:0.005, 1:0.008, 1:0.01, 1:0.015 or 1:0.02, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0078] Optionally, the solid-liquid ratio of the medium-nickel ternary polycrystalline precursor to water is (0.4~0.8):1, for example, it can be 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1 or 0.8:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The unit of solid-liquid ratio is g / mL.

[0079] Optionally, the precipitant may include an alkaline solution.

[0080] Optionally, the alkaline solution includes a LiOH solution with a concentration of 0.05 g / mL to 0.15 g / mL, such as 0.05 g / mL, 0.06 g / mL, 0.07 g / mL, 0.08 g / mL, 0.09 g / mL, 0.10 g / mL, 0.11 g / mL, 0.12 g / mL, 0.13 g / mL, 0.14 g / mL, or 0.15 g / mL, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0081] Optionally, the heating temperature in the hydrothermal reaction is 20℃~100℃, and the time is 2h~10h.

[0082] In this application, the heating temperature in the hydrothermal reaction is 20℃~100℃, for example, it can be 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0083] In this application, the heating time in the hydrothermal reaction is 2h to 10h, for example, it can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] In the preparation method of the medium-nickel polycrystalline ternary cathode material provided in this application, the heating time during the hydrothermal reaction affects the performance of the medium-nickel polycrystalline ternary cathode material and the battery. When the heating time during the hydrothermal reaction is 2h to 10h, the medium-nickel polycrystalline ternary cathode material and the battery have better performance. This is because when the hydrothermal reaction time is within this range, the modifying elements can fully diffuse and uniformly coat the surface of the precursor and penetrate to the grain boundary to form a stable modified material. This avoids excessive particle growth or agglomeration caused by excessive time. It can ensure the modification effect to enhance structural stability and maintain a suitable particle size and dispersion, thereby improving the performance of the medium-nickel polycrystalline ternary cathode material and the battery.

[0085] Optionally, stirring may be performed during the heating process.

[0086] Optionally, the stirring speed is 60 r / min to 100 r / min, for example, it can be 60 r / min, 65 r / min, 70 r / min, 75 r / min, 80 r / min, 85 r / min, 90 r / min, 95 r / min or 100 r / min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0087] Optionally, the hydrothermal treatment in step (1) may be followed by drying.

[0088] Optionally, the drying temperature is 60℃~100℃, for example, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0089] Optionally, the drying time is 8h to 10h, for example, 8h, 8.5h, 9h, 9.5h or 10h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0090] Optionally, in step (2), the mass ratio of the modified precursor to the lithium source in the mixing process is 1:(1.01~1.06), for example, it can be 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05 or 1:1.06, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0091] Optionally, the lithium source in step (2) includes lithium hydroxide and / or lithium carbonate.

[0092] Optionally, step (2) of mixing may also include the incorporation of a dopant.

[0093] Optionally, in step (2), the mass ratio of the modified precursor to the dopant in the mixing process is 1:(0.0002~0.01), for example, it can be 1:0.0002, 1:0.0005, 1:0.001, 1:0.002, 1:0.003, 1:0.004, 1:0.005, 1:0.006, 1:0.007, 1:0.008, 1:0.009 or 1:0.01, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0094] Optionally, the dopant may include a Zr source and / or an Al source.

[0095] Optionally, the Zr source includes ZrO2.

[0096] Optionally, the Al source includes Al2O3 and / or AlOOH.

[0097] Optionally, the heat treatment temperature in step (2) is 840℃~860℃ and the time is 24.5h~25.5h.

[0098] In this application, the temperature of the heat treatment in step (2) is 840℃~860℃, for example, it can be 840℃, 842℃, 844℃, 846℃, 848℃, 850℃, 852℃, 854℃, 856℃, 858℃ or 860℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0099] In this application, the heat treatment time in step (2) is 24.5h to 25.5h, for example, it can be 24.5h, 24.6h, 24.7h, 24.8h, 24.9h, 25.0h, 25.1h, 25.2h, 25.3h, 25.4h or 25.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0100] Optionally, the preparation method of medium-nickel polycrystalline ternary cathode material includes:

[0101] (1) Mixed nickel ternary polycrystalline precursor (chemical formula Ni) x Co y Mn 1-x-y(OH)₂, wherein 0.5≤x≤0.7, 0<y≤0.3), a modifying element source (Co source, Mg source, Zn source, W source, Al source, Nb source, Sr source or Ba source, sulfate and / or hydroxide), a precipitant (LiOH solution with a concentration of 0.05 g / mL to 0.15 g / mL) and water to obtain a mixed slurry, then performing a hydrothermal reaction while heating at 20°C to 100°C for 2 h to 10 h and stirring at a rotation speed of 60 r / min to 100 r / min, followed by drying at 60°C to 100°C for 8 h to 10 h, to prepare a modified precursor;

[0102] The mass ratio of the modifying element source to the medium-nickel ternary polycrystalline precursor is (2~15):100, the mass ratio of the medium-nickel ternary polycrystalline precursor to the precipitant is 1:(0.0002~0.02), and the solid-liquid ratio of the medium-nickel ternary polycrystalline precursor to water is (0.4~0.8):1, and the unit of the solid-liquid ratio is g / mL;

[0103] (2) mixing the modified precursor obtained in step (1), a lithium source (lithium hydroxide and / or lithium carbonate) and a dopant (Zr source and / or Al source) at a mass ratio of 1:(1.01~1.06):(0.0002~0.01), and then performing a heat treatment at 840°C to 860°C for 24.5 h to 25.5 h to obtain the medium-nickel polycrystalline ternary cathode material.

[0104] In a third aspect, the present application provides a composite cathode material, which comprises the medium-nickel polycrystalline ternary cathode material according to the first aspect, and a cladding layer coated on the outside of the medium-nickel polycrystalline ternary cathode material.

[0105] Optionally, the thickness of the cladding layer is 0.1 μm to 0.6 μm.

[0106] Optionally, the material of the cladding layer comprises any one or a combination of at least two of metal oxides, phosphates, non-metal oxides or fast ion conductors, typical but non-limiting combinations include a combination of a metal oxide and a phosphate, a combination of a non-metal oxide and a fast ion conductor, a combination of a phosphate and a non-metal oxide, or a combination of a metal oxide, a phosphate and a fast ion conductor.

[0107] In the present application, the metal oxide in the cladding layer comprises Al₂O₃ and / or ZrO₂.

[0108] In the present application, the phosphate in the cladding layer comprises Li₃PO₄, AlPO₄, Mg₃(PO₄)₂ or FePO₄, typical but non-limiting combinations include a combination of Li₃PO₄ and AlPO₄, a combination of Mg₃(PO₄)₂ and FePO₄, a combination of Li₃PO₄ and Mg₃(PO₄)₂, or a combination of Li₃PO₄, AlPO₄ and FePO₄.

[0109] In this application, the non-metallic oxides in the coating layer include SiO2, P2O5, B2O3 or GeO2, and typical but non-limiting combinations include combinations of SiO2 and P2O5, combinations of B2O3 and GeO2, combinations of SiO2 and B2O3, or combinations of SiO2, P2O5 and GeO2.

[0110] In this application, the fast ion conductor in the coating layer includes Li7La3Zr2O 12 Li3BO3, Li2SiO3, or LiAlO2, with typical but non-limiting combinations including Li7La3Zr2O 12 Combinations with Li3BO3, combinations of Li2SiO3 and LiAlO2, Li7La3Zr2O 12 Combinations with Li3BO3, or Li7La3Zr2O 12 The combination of Li3BO3 and LiAlO2.

[0111] Fourthly, this application provides a preparation process for a third-party composite cathode material, the preparation process including:

[0112] The first aspect involves mixing the medium-nickel polycrystalline ternary cathode material with a coating agent and then sintering it to obtain the medium-nickel polycrystalline ternary cathode material.

[0113] Optionally, before mixing, the process also includes: sequentially crushing, sieving, and demagnetizing the medium-nickel polycrystalline ternary cathode material.

[0114] Optionally, the mass ratio of medium-nickel polycrystalline ternary cathode material to coating agent in the mixture is 1:(0.0005~0.002), for example, it can be 1:0.0005, 1:0.0007, 1:0.0009, 1:0.001, 1:0.0012, 1:0.0014, 1:0.0016, 1:0.0018 or 1:0.002, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0115] Optionally, the coating agent includes any one or a combination of at least two of metal oxides, phosphates, non-metal oxides, or fast ion conductors. Typical but non-limiting combinations include combinations of metal oxides and phosphates, combinations of non-metal oxides and fast ion conductors, combinations of phosphates and non-metal oxides, or combinations of metal oxides, phosphates, and fast ion conductors.

[0116] Optionally, the sintering temperature is 290℃~310℃ and the time is 8h~10h.

[0117] In this application, the sintering temperature is 290℃~310℃, for example, it can be 290℃, 292℃, 294℃, 296℃, 298℃, 300℃, 302℃, 304℃, 306℃, 308℃ or 310℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0118] In this application, the sintering time is 8h to 10h, for example, it can be 8h, 8.2h, 8.4h, 8.6h, 8.8h, 9h, 9.2h, 9.4h, 9.6h, 9.8h or 10h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0119] Optionally, after sintering, the process further includes: sequentially crushing, pulverizing, batch mixing, and demagnetizing the sintered material to obtain a medium-nickel polycrystalline ternary cathode material.

[0120] Fifthly, this application provides a battery comprising a medium-nickel polycrystalline ternary cathode material of the first aspect and / or a composite cathode material of the third aspect.

[0121] The numerical range of this application includes not only the listed point values, but also any point values ​​between the unlisted numerical ranges. Due to space limitations and for the sake of brevity, this application will not exhaustively list all the specific point values ​​included in the range.

[0122] The technical solution of this application will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of this application and should not be construed as specific limitations thereof.

[0123] Example 1

[0124] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0125] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (Co2O3). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0126] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 1000 ppm.

[0127] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0128] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 1000 ppm.

[0129] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.196 Co 0.002 Zr 0.002 O2;

[0130] The preparation methods of medium-nickel polycrystalline ternary cathode materials include:

[0131] (1) Mixed nickel ternary polycrystalline precursor (chemical formula Ni) 0.6 Co 0.2 Mn 0.2 The mixture of (OH)2, cobalt sulfate powder, precipitant (LiOH solution with a concentration of 0.1 g / mL) and water was used to obtain a mixed slurry. The slurry was then subjected to a hydrothermal reaction by heating at 40 °C for 6 h while stirring at 80 r / min. The slurry was then dried at 80 °C for 8 h to obtain the modified precursor.

[0132] The mass ratio of cobalt sulfate powder to medium-nickel ternary polycrystalline precursor is 2:100, the mass ratio of medium-nickel ternary polycrystalline precursor to precipitant is 1:0.01, and the solid-liquid ratio of medium-nickel ternary polycrystalline precursor to water (excluding water in LiOH solution) is 0.6:1. The unit of solid-liquid ratio is g / mL.

[0133] (2) The modified precursor obtained in step (1), lithium hydroxide and dopant (ZrO2) are mixed in a mass ratio of 1:1.03:0.002 and then subjected to heat treatment at 850°C for 25 hours to obtain a medium-nickel polycrystalline ternary cathode material.

[0134] This embodiment also provides a composite cathode material, which includes the medium-nickel polycrystalline ternary cathode material provided in this embodiment, and a Li3PO4 coating layer with a thickness of 0.4 μm covering the outside of the medium-nickel polycrystalline ternary cathode material;

[0135] The preparation process of composite cathode materials includes:

[0136] The medium-nickel polycrystalline ternary cathode material provided in this embodiment is sequentially crushed, sieved, and demagnetized. Then, the demagnetized medium-nickel polycrystalline ternary cathode material with a mass ratio of 1:0.0012 is mixed with a coating agent (Li3PO4) and sintered at 300°C for 9 hours. The sintered material is then sequentially crushed, pulverized, batch-mixed, and demagnetized to obtain the medium-nickel polycrystalline ternary cathode material.

[0137] Example 2

[0138] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0139] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (MgO). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0140] Based on the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 500 ppm.

[0141] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0142] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 2000 ppm.

[0143] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.195 Mg 0.001 Zr 0.004 O2;

[0144] In the preparation method of the medium-nickel polycrystalline ternary cathode material, except that the cobalt sulfate powder in step (1) is replaced with magnesium sulfate powder, and the mass ratio of magnesium sulfate powder to medium-nickel ternary polycrystalline precursor is 5:100, and the hydrothermal reaction is carried out by heating at 60°C for 4 hours while stirring at the same speed, the rest is the same as in Example 1.

[0145] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0146] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0147] Example 3

[0148] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0149] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (ZnO). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0150] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 2000 ppm.

[0151] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0152] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 3000 ppm.

[0153] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.189 Zn 0.006 Zr 0.005 O2;

[0154] In the preparation method of the medium-nickel polycrystalline ternary cathode material, except that the cobalt sulfate powder in step (1) is replaced with zinc sulfate powder, and the mass ratio of zinc sulfate powder to medium-nickel ternary polycrystalline precursor is 8:100, and the hydrothermal reaction is carried out by heating at 80°C for 2 hours while stirring at the same speed, the rest is the same as in Example 1.

[0155] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0156] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0157] Example 4

[0158] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0159] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (Ba(OH)2). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0160] Based on the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 500 ppm.

[0161] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0162] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 4000 ppm.

[0163] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.191 Ba 0.002 Zr 0.007 O2;

[0164] In the preparation method of the medium-nickel polycrystalline ternary cathode material, except that the cobalt sulfate powder in step (1) is replaced with barium sulfate powder, and the mass ratio of barium sulfate powder to the medium-nickel ternary polycrystalline precursor is 10:100, and the hydrothermal reaction is carried out by heating at 100°C for 5 hours while stirring at the same speed, the rest is the same as in Example 1.

[0165] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0166] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0167] Example 5

[0168] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0169] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (W2O5). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0170] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 5000 ppm.

[0171] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0172] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 4000 ppm.

[0173] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.183 W 0.009 Zr 0.008 O2;

[0174] In the preparation method of the medium-nickel polycrystalline ternary cathode material, except that the cobalt sulfate powder in step (1) is replaced with tungsten hydroxide powder, and the mass ratio of tungsten hydroxide powder to medium-nickel ternary polycrystalline precursor is 15:100, and the hydrothermal reaction is carried out by heating at 60°C for 8 hours while stirring at the same speed, the rest is the same as in Example 1.

[0175] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0176] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0177] Example 6

[0178] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0179] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (Al₂O₃). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0180] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 2000 ppm.

[0181] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0182] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 6000ppm.

[0183] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.185 Al 0.005 Zr 0.01 O2;

[0184] In the preparation method of the medium-nickel polycrystalline ternary cathode material, except that the cobalt sulfate powder in step (1) is replaced with aluminum sulfate powder, and the mass ratio of aluminum sulfate powder to medium-nickel ternary polycrystalline precursor is 12:100, and the hydrothermal reaction is carried out by heating at 70°C for 10 hours while stirring at the same speed, the rest is the same as in Example 1.

[0185] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0186] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0187] Example 7

[0188] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0189] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (SrO2). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0190] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 10000 ppm.

[0191] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0192] Based on the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 500 ppm.

[0193] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co0.2 Mn 0.181 Sr 0.018 Zr 0.001 O2;

[0194] In the preparation method of the medium-nickel polycrystalline ternary cathode material, except that the cobalt sulfate powder in step (1) is replaced with strontium sulfate powder, and the mass ratio of strontium sulfate powder to the medium-nickel ternary polycrystalline precursor is 10:100, and the hydrothermal reaction is carried out by heating at 20°C for 4 hours while stirring at the same speed, the rest is the same as in Example 1.

[0195] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0196] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0197] Example 8

[0198] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0199] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (MgO). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0200] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 1000 ppm.

[0201] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Al), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0202] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 10000ppm.

[0203] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.179 Mg 0.003 Zr 0.018 O2;

[0204] The preparation methods of medium-nickel polycrystalline ternary cathode materials include:

[0205] (1) Mixed nickel ternary polycrystalline precursor (chemical formula Ni) 0.5 Co 0.3 Mn 0.2 The mixture of (OH)2, magnesium hydroxide powder, precipitant (LiOH solution with a concentration of 0.05 g / mL) and water was used to obtain a mixed slurry. The slurry was then subjected to a hydrothermal reaction by heating at 100 °C for 2 h while stirring at 100 r / min. The slurry was then dried at 60 °C for 10 h to obtain the modified precursor.

[0206] The mass ratio of magnesium hydroxide powder to medium-nickel ternary polycrystalline precursor is 2:100, the mass ratio of medium-nickel ternary polycrystalline precursor to precipitant is 1:0.02, and the solid-liquid ratio of medium-nickel ternary polycrystalline precursor to water is 0.8:1. The unit of solid-liquid ratio is g / mL.

[0207] (2) The modified precursor obtained in step (1), lithium carbonate and dopant (Al2O3) with a mass ratio of 1:1.06:0.01 are mixed and then heat-treated at 860℃ for 24.5h to obtain a medium-nickel polycrystalline ternary cathode material.

[0208] This embodiment also provides a composite cathode material, which includes the medium-nickel polycrystalline ternary cathode material provided in this embodiment, and a 0.6 μm thick Li7La3Zr2O coating on the outside of the medium-nickel polycrystalline ternary cathode material. 12 Coating layer;

[0209] The preparation process of composite cathode materials includes:

[0210] The medium-nickel polycrystalline ternary cathode material provided in this embodiment is sequentially crushed, sieved, and demagnetized. Then, the demagnetized medium-nickel polycrystalline ternary cathode material with a mass ratio of 1:0.002 is mixed with a coating agent (Li7La3Zr2O). 12 After mixing, the materials are sintered at 290℃ for 10 hours. The sintered materials are then crushed, pulverized, batch-mixed, and demagnetized in sequence to obtain medium-nickel polycrystalline ternary cathode material.

[0211] Example 9

[0212] This embodiment provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of a plurality of polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of a plurality of medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0213] The medium-nickel polycrystalline ternary cathode material also includes a stabilizer (ZnO). The stabilizer is not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles.

[0214] Based on the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 500 ppm.

[0215] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Al), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0216] Taking the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 6000ppm.

[0217] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.189 Zn 0.001 Zr 0.01 O2;

[0218] The preparation methods of medium-nickel polycrystalline ternary cathode materials include:

[0219] (1) Mixed nickel ternary polycrystalline precursor (chemical formula Ni) 0.7 Co 0.1 Mn 0.2 The mixture of (OH)2, zinc sulfate powder, precipitant (LiOH solution with a concentration of 0.15 g / mL) and water was used to obtain a mixed slurry. The slurry was then subjected to hydrothermal reaction by heating at 20°C for 10 h while stirring at 60 r / min. The slurry was then dried at 100°C for 8 h to obtain the modified precursor.

[0220] The mass ratio of zinc sulfate powder to medium-nickel ternary polycrystalline precursor is 15:100, the mass ratio of medium-nickel ternary polycrystalline precursor to precipitant is 1:0.0002, and the solid-liquid ratio of medium-nickel ternary polycrystalline precursor to water is 0.4:1. The unit of solid-liquid ratio is g / mL.

[0221] (2) The modified precursor obtained in step (1) with a mass ratio of 1:1.01:0.0002, lithium carbonate and dopant (AlOOH) are mixed and then heat-treated at 840℃ for 25.5h to obtain a medium-nickel polycrystalline ternary cathode material.

[0222] This embodiment also provides a composite cathode material, which includes the medium-nickel polycrystalline ternary cathode material provided in this embodiment, and a Li3BO3 coating layer with a thickness of 0.1μm covering the outside of the medium-nickel polycrystalline ternary cathode material;

[0223] The preparation process of composite cathode materials includes:

[0224] The medium-nickel polycrystalline ternary cathode material provided in this embodiment is sequentially crushed, sieved, and demagnetized. Then, the demagnetized medium-nickel polycrystalline ternary cathode material with a mass ratio of 1:(0.0005~0.002) is mixed with a coating agent (Li3BO3) and sintered at 310℃ for 8 hours. The sintered material is then sequentially crushed, pulverized, batch-mixed, and demagnetized to obtain the medium-nickel polycrystalline ternary cathode material.

[0225] Example 10

[0226] This embodiment provides a medium-nickel polycrystalline ternary cathode material. The mass fraction of the medium-nickel polycrystalline ternary cathode material is 200 ppm, and the mass fraction of the dopant element is 4000 ppm.

[0227] In the preparation method of medium-nickel polycrystalline ternary cathode material, except for the mass ratio of cobalt sulfate powder to medium-nickel ternary polycrystalline precursor in step (1) which is 0.5:100, all other steps are the same as in Example 1.

[0228] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0229] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0230] Example 11

[0231] This embodiment provides a medium-nickel polycrystalline ternary cathode material. The mass fraction of the medium-nickel polycrystalline ternary cathode material is 18,000 ppm, and the mass fraction of the dopant element is 500 ppm.

[0232] In the preparation method of medium-nickel polycrystalline ternary cathode material, except for the mass ratio of cobalt sulfate powder to medium-nickel ternary polycrystalline precursor in step (1) which is 20:100, all other steps are the same as in Example 1.

[0233] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0234] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0235] Example 12

[0236] This embodiment provides a medium-nickel polycrystalline ternary cathode material, except that the doping element (Zr) in the medium-nickel polycrystalline ternary cathode material is omitted.

[0237] Except for omitting the dopant (ZrO2) in step (2) of the preparation method of medium-nickel polycrystalline ternary cathode material, the rest is the same as in Example 1.

[0238] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0239] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0240] Example 13

[0241] This embodiment provides a medium-nickel polycrystalline ternary cathode material. Dividing by the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 4500 ppm, and the mass fraction of the dopant element is 200 ppm.

[0242] In the preparation method of medium-nickel polycrystalline ternary cathode material, except for step (2) where the mass ratio of the modified precursor to the dopant (ZrO2) is 1:0.0002, all other steps are the same as in Example 1.

[0243] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0244] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0245] Example 14

[0246] This embodiment provides a medium-nickel polycrystalline ternary cathode material. Dividing by the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 800 ppm, and the mass fraction of the dopant element is 18000 ppm.

[0247] In the preparation method of medium-nickel polycrystalline ternary cathode material, except for step (2) where the mass ratio of the modified precursor to the dopant (ZrO2) is 1:0.03, all other steps are the same as in Example 1.

[0248] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0249] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0250] Example 15

[0251] This embodiment provides a medium-nickel polycrystalline ternary cathode material. Except for step (1) of the preparation method of the medium-nickel polycrystalline ternary cathode material, in which the heating time during the hydrothermal reaction is 0.5h, the rest is the same as in Example 1.

[0252] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0253] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0254] Example 16

[0255] This embodiment provides a medium-nickel polycrystalline ternary cathode material. Except for step (1) of the preparation method of the medium-nickel polycrystalline ternary cathode material, in which the heating time during the hydrothermal reaction is 15h, the rest are the same as in Example 1.

[0256] This embodiment also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this embodiment;

[0257] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this embodiment, everything else is the same as in Example 1.

[0258] Comparative Example 1

[0259] This comparative example provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of several polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of several medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0260] The medium-nickel polycrystalline ternary cathode material also includes a doping element (Zr), which is doped into the lattice of the medium-nickel ternary material single crystal;

[0261] Based on the mass of the medium-nickel polycrystalline ternary cathode material as 100%, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 2500 ppm.

[0262] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.196 Zr 0.004 O2;

[0263] The preparation method of medium-nickel polycrystalline ternary cathode material is as follows:

[0264] A medium-nickel ternary polycrystalline precursor (chemical formula Ni) with a mass ratio of 1:1.03:0.002 was used. 0.6 Co 0.2 Mn 0.2 After mixing (OH)2, lithium hydroxide and dopant (ZrO2), the mixture is subjected to heat treatment at 850℃ for 25 hours to obtain a medium-nickel polycrystalline ternary cathode material.

[0265] This comparative example also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this comparative example;

[0266] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this comparative example, everything else is the same as in Example 1.

[0267] Comparative Example 2

[0268] This comparative example provides a medium-nickel polycrystalline ternary cathode material, which includes secondary particles composed of several polycrystalline primary particles; the polycrystalline primary particles are formed by the stacking of several medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

[0269] The chemical formula of the medium-nickel polycrystalline ternary cathode material is LiNi. 0.6 Co 0.2 Mn 0.2 O2;

[0270] The preparation methods of medium-nickel polycrystalline ternary cathode materials include:

[0271] A medium-nickel ternary polycrystalline precursor (chemical formula Ni) with a mass ratio of 1:1.03 was used. 0.6 Co 0.2 Mn 0.2 After mixing (OH)2 with lithium hydroxide, the mixture is subjected to heat treatment at 850℃ for 25 hours to obtain a medium-nickel polycrystalline ternary cathode material.

[0272] This comparative example also provides a composite cathode material, except that the medium-nickel polycrystalline ternary cathode material is replaced with the medium-nickel polycrystalline ternary cathode material provided in this comparative example;

[0273] Except for replacing the medium-nickel polycrystalline ternary cathode material used in the preparation process of the composite cathode material with the medium-nickel polycrystalline ternary cathode material provided in this comparative example, everything else is the same as in Example 1.

[0274] The composite cathode materials provided in Example 1 and Comparative Example 2 were tested using an electron microscope. The SEM image of the composite cathode material provided in Example 1 is shown in Figure 1, and the SEM image of the composite cathode material provided in Comparative Example 2 is shown in Figure 2.

[0275] The particle size of the composite cathode materials provided in the examples and comparative examples was tested. The particle size test method was as follows: the composite cathode materials were tested using a laser particle size analyzer, and the D1 particle size, D10 particle size, D50 particle size, D90 particle size, and D99 particle size of the composite cathode materials were obtained as shown in Table 1. Then, the Span value was calculated, and the Span value was obtained as shown in Table 1.

[0276]

[0277] The coin cell specific capacity of the composite cathode materials provided in the examples and comparative examples was tested. The test method was as follows: using the Blue Electric test system, charge and discharge tests were performed at a current density of 0.2C within the voltage ranges of 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V respectively. Before the test, the materials were allowed to stand for 10 minutes, and the temperature was controlled at 25±2℃. The initial discharge capacity was recorded, and the specific capacity was calculated based on the mass of the active material. The average value of 5 samples in each test group was taken. The coin cell specific capacities at 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V are shown in Table 2.

[0278]

[0279] The composite cathode materials provided in the examples and comparative examples were tested for powder impedance. The test method was as follows: the powder was pressed into a disc with a diameter of 10 mm and a thickness of 2 mm at a pressure of 195 MPa; the powder impedance of the material was tested using a powder resistance meter, and the obtained powder impedance is shown in Table 1.

[0280] The compaction density of the composite cathode materials provided in the examples and comparative examples was tested. The test method was as follows: a certain mass of composite cathode material was taken, poured into a mold with an inner diameter of 10 mm, and pressed with a tablet press at a pressure of 195 MPa for 30 seconds to form a disc. The thickness was then measured with calipers, and the volume was calculated. The compaction density of the composite cathode material was calculated according to the formula "mass / volume" as shown in Table 3.

[0281] The specific surface area of ​​the composite cathode materials provided in the examples and comparative examples was tested. The test method was as follows: 0.5g of composite cathode material was taken and degassed under vacuum at 300℃ for 3 hours. Then, using a specific surface area analyzer, with nitrogen as the adsorbate, adsorption-desorption test was performed at -196℃. The specific surface area was calculated by the multi-point BET equation. The specific surface area of ​​the composite cathode material is shown in Table 3.

[0282]

[0283] The composite positive electrode material provided in the examples and comparative examples was used to prepare the positive electrode sheet. The method for preparing the positive electrode sheet is as follows: the composite positive electrode material, conductive carbon black and PVDF are mixed in a mass ratio of 95:3:2, NMP is added to adjust the solid content to 50%, and the mixture is stirred for 3 hours until the slurry is uniform; the mixture is coated on a 12μm aluminum foil using a 200μm gap coater, dried at 120℃ for 2 hours, rolled to a compaction density of 3.6g / cm³, cut into 5cm×5cm electrode sheets, and dried under vacuum at 80℃ for 12 hours to obtain the positive electrode sheet.

[0284] A battery was prepared using the obtained positive electrode sheet. The method for preparing the battery was as follows: In an argon glove box, a CR2032 coin cell was assembled using the positive electrode sheet as the positive electrode, a lithium metal sheet as the negative electrode, Celgard 2400 as the separator, and a 1 mol / L LiPF6 EC / DMC / EMC (1:1:1) solution as the electrolyte. The battery was then left to stand for 12 hours to obtain the battery.

[0285] The specific capacity of the obtained batteries was tested using the Blue Electric testing system. Initial charge-discharge tests were conducted at a current density of 0.1C within the voltage ranges of 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V, respectively, and the discharge capacity was recorded. The test temperature was 25℃, and the batteries were allowed to stand for 5 minutes before cycling began. The specific capacities at 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V were calculated and are shown in Table 4.

[0286]

[0287] The obtained battery was subjected to high-voltage impedance testing. The testing method was as follows: at 25℃, an electrochemical workstation was used to test the battery with an AC signal of 5mV at a frequency of 1MHz-0.01Hz. The impedance spectrum was recorded, and the impedance of the battery is shown in Table 5.

[0288]

[0289] The obtained batteries were subjected to high-voltage cycle performance testing. The test method was as follows: using the Blue Electric test system, the batteries were charged and discharged 1000 times at a current density of 0.5C within voltage ranges of 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V, respectively, at 25℃. The capacity retention rates at 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V were calculated and are shown in Table 6. Among them, Example 1 and the... Figure 3 shows the capacity retention rate of the battery prepared with the composite cathode material provided in Example 2 as a function of the number of cycles under cycling conditions of 4.25V~2.8V; Figure 4 shows the capacity retention rate of the battery prepared with the composite cathode material provided in Example 1 and Comparative Example 2 as a function of the number of cycles under cycling conditions of 4.30V~2.8V; Figure 5 shows the capacity retention rate of the battery prepared with the composite cathode material provided in Example 1 and Comparative Example 2 as a function of the number of cycles under cycling conditions of 4.35V~2.8V.

[0290]

[0291] From Tables 1 to 6 and Figures 1 to 5, we can see that:

[0292] (1) The composite cathode materials provided in Examples 1 to 9 all exhibited high coin cell capacity at 4.25V~2.8V, 4.30V~2.8V and 4.35V~2.8V, and had low powder impedance, high compaction density and large specific surface area.

[0293] The batteries prepared using the composite cathode materials provided in Examples 1-9 also exhibited high specific capacity and low impedance at 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V, and also showed high cycle stability at 4.25V~2.8V, 4.30V~2.8V, and 4.35V~2.8V.

[0294] (2) By comparing Example 1 with Examples 10 and 11, it can be seen that the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material provided in this application affects the performance of the medium-nickel polycrystalline ternary cathode material and the battery. When the mass fraction of the medium-nickel polycrystalline ternary cathode material is 500ppm to 10000ppm, the medium-nickel polycrystalline ternary cathode material and the battery have better performance. This is because when the mass fraction of the stabilizer is in this range, the stabilizer can uniformly cover the surface of the polycrystalline primary particles and secondary particles and fill the grain boundaries in the polycrystalline primary particles. This avoids the increase of the insulating phase caused by excessive amount, which leads to increased impedance, and also avoids insufficient performance enhancement due to insufficient stabilizer content.

[0295] (3) By comparing Example 1 and Example 12, it can be seen that in the medium-nickel polycrystalline ternary cathode material provided in this application, the doping elements doped in the lattice of the medium-nickel ternary material single crystal are beneficial to improving the performance of the medium-nickel polycrystalline ternary cathode material and the battery. This is because after the doping elements enter the single crystal lattice, they can adjust the lattice parameters, expand the lithium-ion diffusion channel, and reduce the migration energy barrier. At the same time, they can also stabilize the valence state of transition metal ions through valence compensation, suppress the irreversible migration and dissolution of transition metal ions during charging and discharging, reduce lattice distortion, and thus improve the performance of the medium-nickel polycrystalline ternary cathode material and the battery.

[0296] (4) By comparing Example 1 with Examples 13 and 14, it can be seen that in the medium-nickel polycrystalline ternary cathode material provided in this application, the mass fraction of the doping element in the lattice of the medium-nickel ternary material single crystal affects the performance of the medium-nickel polycrystalline ternary cathode material and the battery. When the mass fraction of the doping element in the medium-nickel polycrystalline ternary cathode material is 500ppm~10000ppm, the medium-nickel polycrystalline ternary cathode material and the battery have better performance. This is because the doping element in this mass fraction range can enter the lattice uniformly, which can optimize lithium-ion diffusion by adjusting the lattice parameters and fully stabilize the transition metal valence state, suppressing migration and dissolution. If the amount is too large, it will easily cause the lattice distortion to intensify, and if the amount is insufficient, it will be difficult to play a stabilizing role.

[0297] (5) By comparing Example 1 with Examples 15 and 16, it can be seen that in the preparation method of medium-nickel polycrystalline ternary cathode material provided in this application, the heating time during hydrothermal reaction will affect the performance of medium-nickel polycrystalline ternary cathode material and battery. When the heating time during hydrothermal reaction is 2h to 10h, the medium-nickel polycrystalline ternary cathode material and battery have better performance. This is because when the hydrothermal reaction time is within this range, the modifying elements can fully diffuse and uniformly coat the surface of the precursor and penetrate to the grain boundary to form a stable modified material. It also avoids excessive particle growth or agglomeration caused by excessive time. It can ensure the modification effect to enhance structural stability and maintain appropriate particle size and dispersion, thereby improving the performance of medium-nickel polycrystalline ternary cathode material and battery.

[0298] (6) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the medium-nickel polycrystalline ternary cathode material provided in this application includes stabilizers that are not only distributed at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the secondary particles composed of polycrystalline primary particles. The presence of stabilizers can suppress the generation of cracks at the grain boundaries during battery cycling, and can also improve the interface stability between polycrystalline primary particles and between secondary particles in the secondary particles, so that the medium-nickel polycrystalline ternary cathode material has a higher withstand voltage.

[0299] In addition, the presence of stabilizers can improve the structural stability of medium-nickel polycrystalline ternary cathode materials, reduce the collapse of lithium-ion channels caused by lattice expansion / contraction during charging and discharging, stabilize the redox reversibility of transition metal ions, reduce the irreversible migration of transition metal ions or the formation of inert phases, and retain more complete interlayer diffusion channels, thereby enabling medium-nickel polycrystalline ternary cathode materials to have higher specific capacity.

[0300] In addition, as a chemically inert barrier, the stabilizer can not only isolate the secondary particles from the electrolyte and reduce side reactions, but also improve the defects at the grain boundaries within the polycrystalline primary particles, thereby giving the medium-nickel polycrystalline ternary cathode material a lower impedance.

[0301] In summary, the medium-nickel polycrystalline ternary cathode material provided in this application not only has a high withstand voltage, but also a high specific capacity and a low impedance. The battery prepared with the medium-nickel polycrystalline ternary cathode material exhibits both high specific capacity and low impedance at an application voltage >4.25V, and also demonstrates excellent cycle stability.

Claims

1. A medium-nickel polycrystalline ternary cathode material, comprising secondary particles composed of a plurality of polycrystalline primary particles; The medium-nickel polycrystalline ternary cathode material also includes a stabilizer, which is distributed not only at the grain boundaries inside the polycrystalline primary particles, but also coated on the surface of the polycrystalline primary particles and the surface of the secondary particles. The stabilizer contains a modifying element, which includes any one or a combination of at least two of Co, Mg, Zn, W, Al, Nb, Sr, or Ba.

2. The medium-nickel polycrystalline ternary cathode material of claim 1, wherein, The polycrystalline primary particles are formed by the stacking of several medium-nickel ternary material single crystals, and grain boundaries are formed between the medium-nickel ternary material single crystals within the polycrystalline primary particles.

3. The medium-nickel polycrystalline ternary cathode material according to claim 1 or 2, wherein, The stabilizer material includes any one or a combination of at least two of the oxides, hydroxides or hydroxy oxides containing the modifying element; Optionally, based on the mass of the medium-nickel polycrystalline ternary cathode material, the mass fraction of the stabilizer in the medium-nickel polycrystalline ternary cathode material is 500ppm to 10000ppm.

4. The medium-nickel polycrystalline ternary cathode material of claim 2, wherein, The medium-nickel polycrystalline ternary cathode material also includes doping elements, which are doped into the crystal lattice of the medium-nickel ternary material single crystal. Optionally, the doping element includes Zr and / or Al; Optionally, based on the mass of the medium-nickel polycrystalline ternary cathode material, the mass fraction of the doping elements in the medium-nickel polycrystalline ternary cathode material is 500ppm to 10000ppm.

5. The medium-nickel polycrystalline ternary cathode material according to any one of claims 1-4, wherein, The chemical formula of the medium-nickel polycrystal ternary positive electrode material is LiNi x Co y Mn 1-x-y-z-w M z N w O2, wherein, 0.5≤x≤0.7, 0 Optionally, the D50 particle size of the medium-nickel polycrystalline ternary cathode material is 2μm~15μm; Optionally, the Span value of the particle size of the medium-nickel polycrystalline ternary cathode material is 0.1~1.

5.

6. The medium-nickel polycrystalline ternary cathode material according to any one of claims 1-5, wherein, The powder impedance of the medium-nickel polycrystalline ternary cathode material is 10 Ω·cm to 500 Ω·cm. Optionally, the compaction density of the medium-nickel polycrystalline ternary positive electrode material is 2.80 g·cm 3 3.70 g·cm 3 ; Optionally, the specific surface area of the medium-nickel polycrystalline ternary positive electrode material is 0.10 m 2 / g~2.00 m 2 / g.

7. A method for preparing the medium-nickel polycrystalline ternary cathode material according to any one of claims 1 to 6, comprising: (1) Using the modified element source and the medium-nickel ternary polycrystalline precursor as raw materials, hydrothermal treatment was carried out to obtain the modified precursor; (2) The modified precursor obtained in step (1) is mixed with the lithium source and then subjected to heat treatment to obtain a medium-nickel polycrystalline ternary cathode material.

8. The production method according to claim 7, wherein In step (1) of coating, the mass ratio of the source of the modifying element to the medium-nickel ternary polycrystalline precursor is (2~15):100; Optionally, the hydrothermal treatment in step (1) includes: preparing a mixed slurry using a medium-nickel ternary polycrystalline precursor, a source of modifying elements, a precipitant and water as raw materials, and then carrying out a hydrothermal reaction by heating to obtain a modified precursor; Optionally, the heating temperature in the hydrothermal reaction is 20℃~100℃, and the heating time is 2h~10h.

9. The production method according to claim 7 or 8, wherein In step (2), the mass ratio of the modified precursor to the lithium source in the mixture is 1:(1.01~1.06); Optionally, the mixing in step (2) may further include the incorporation of a dopant; Optionally, the dopant includes a Zr source and / or an Al source; Optionally, the heat treatment in step (2) is performed at a temperature of 840℃~860℃ for a time of 24.5h~25.5h.

10. A composite cathode material comprising the medium-nickel polycrystalline ternary cathode material as described in any one of claims 1 to 6, and a coating layer covering the outside of the medium-nickel polycrystalline ternary cathode material.

11. A process for preparing the composite cathode material according to claim 10, comprising: The medium-nickel polycrystalline ternary cathode material described in any one of claims 1 to 6 is mixed with a coating agent and then sintered to obtain the medium-nickel polycrystalline ternary cathode material.

12. A battery comprising the medium-nickel polycrystalline ternary cathode material according to any one of claims 1 to 6 and / or the composite cathode material according to claim 10.

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