Modified nickel-based positive electrode material, preparation method therefor, and lithium-ion battery

Abstract

A modified nickel-based positive electrode material, a preparation method therefor, and a lithium-ion battery. The modified nickel-based positive electrode material comprises a nickel-based positive electrode material matrix and a doping element doped in the nickel-based positive electrode material matrix, the electronegativity of the doping element being higher than the electronegativity of lithium and a transition metal element in the nickel-based positive electrode material matrix, and the porosity of the material being 10% to 20%. In the modified nickel-based positive electrode material, part of the doping element enters a lattice body of the nickel-based positive electrode material matrix, and the electronegativity of the doping element is greater than that of lithium and the transition metal element; thus, the nickel-based positive electrode material has stronger covalent properties, higher bonding strength, higher oxidation potential, stable lattice oxygen in the structure, and a reduction in the precipitation of lattice oxygen, thereby improving the structural stability of the material.

Description

A modified nickel-based positive electrode material, a preparation method thereof, and a lithium-ion battery

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311830412.3, filed on December 27, 2023, entitled “A modified nickel-based positive electrode material, a preparation method thereof, and a lithium-ion battery”, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to the field of lithium-ion batteries, and in particular to a modified nickel-based positive electrode material, a preparation method thereof, and a lithium-ion battery. Background Art

[0004] To meet the growing demand for longer driving range in the new energy vehicle market, competition for high-energy-density batteries has intensified, leading to significant development of high-energy lithium-ion batteries. In this race to meet this demand, the development of lithium-ion battery materials with higher energy density and cycle life is becoming increasingly urgent. Nickel-based cathode materials have garnered widespread attention due to their high capacity and high voltage platforms.

[0005] The development of nickel-based cathode materials tends to be high nickel and high voltage. Increasing nickel content and operating voltage is the most direct way to increase specific capacity. However, there are also problems such as high residual lithium, unstable bulk structure, severe lithium-nickel mixing, surface side reactions, long lithium ion transmission distance, and poor ion conductivity, which affect capacity, rate and long-term cycle performance. Currently, there are existing technologies that use modification methods such as doping and coating to solve the above problems, but the doping modification effect is still poor. Problems such as unstable bulk structure, surface side reactions, long lithium ion transmission distance, and poor ion conductivity still exist, affecting the electrochemical performance of nickel-based cathode materials. Summary of the Invention

[0006] The present application provides a modified nickel-based positive electrode material with good rate performance and cycle performance and high capacity, a preparation method thereof, and a lithium-ion battery.

[0007] In order to solve the above technical problems, the technical solutions proposed in this application are:

[0008] The first aspect of the present application provides a modified nickel-based positive electrode material, comprising a nickel-based positive electrode material matrix and an doping element doped in the nickel-based positive electrode material matrix, wherein the doping element includes a high-electronegativity doping element L, and the electronegativity of the doping element L is higher than the electronegativity of lithium and transition metal elements in the nickel-based positive electrode material matrix, and the porosity of the modified nickel-based positive electrode material is 10% to 20%.

[0009] The doping element L has a greater electronegativity than the lithium and transition metal elements in the nickel-based cathode material matrix, resulting in stronger covalency, higher bond strength, and higher oxidation potential. This stabilizes the lattice oxygen in the structure and reduces its precipitation, thereby improving the structural stability of the material. A portion of the doping element L enters the lattice of the nickel-based cathode material matrix, while the remaining portion adheres to the gaps between the primary particles within the matrix, forming an intercalated structure. The intercalated material in the gaps between the primary particles is removed through a specific water washing process, achieving pore formation and forming a highly porous material.

[0010] In any embodiment, the electronegativity value of the doping element L is greater than 2.0.

[0011] In any embodiment, the doping element L includes at least one of B, C, N, S, F, Cl, Br or I.

[0012] In any embodiment, the mass of the doping element L accounts for 0.05% to 0.2% of the mass of the modified nickel-based positive electrode material.

[0013] In any embodiment, the specific surface area of ​​the modified nickel-based positive electrode material is 0.8 m 2 / g~1.5m 2 / g, and the total residual lithium on its surface is 1000ppm~1800ppm.

[0014] In any embodiment, the chemical formula of the modified nickel-based cathode material is Li z Ni 1-x- y Co x Me y L u M v N w O 2-t , wherein, 0.9≤z≤1.1, 0≤x≤0.2, 0≤y≤0.2, 0<u≤0.007, 0≤v≤0.01, 0≤w≤0.01, -0.05≤t≤0.05, Me includes one or more of Mn and Al, M includes one or more of Na, K, Mg, Ca, Sr, Ba, Zr, Ti, and Y, and N includes one or more of B, La, Ce, Al, Co, Ti, or W.

[0015] The second aspect of the present application provides a method for preparing the above-mentioned modified nickel-based positive electrode material, comprising the following steps:

[0016] (1) mixing a positive electrode material precursor, a lithium source, and a dopant uniformly and then sintering the mixture to obtain a sintered product;

[0017] (2) washing the sintered product obtained in step (1) with water and drying it to obtain a washed product;

[0018] (3) The washed product obtained in step (2) is evenly mixed with a coating agent containing elemental N, and then sintered to obtain a modified nickel-based positive electrode material.

[0019] In the preparation method of the present application, part of the element L enters the lattice of the nickel-based positive electrode material matrix, and the other part is attached to the gaps between the primary particles inside the matrix to form an intercalation structure. The intercalation material existing in the gaps between the primary particles is removed through a specific water washing process, which can achieve the effect of pore formation and form a modified nickel-based positive electrode material with high porosity.

[0020] In any embodiment, in step (1), the dopant is a dopant containing element L, and the mass ratio of the dopant added to the positive electrode material precursor is denoted as a, where a is 2% to 8%. The present application forms a high-porosity material by combining a high amount of an intercalation compound containing the dopant element L with a specific water washing process, thereby shortening the diffusion distance of lithium ions, increasing the diffusion rate of lithium ions, and exerting a higher capacity while improving the rate performance of the material.

[0021] In any embodiment, in step (1), the dopant containing element L is an inorganic acid salt, and its solubility s at 20° C. is greater than 10 g / 100 g water.

[0022] In any embodiment, in step (2), during the water washing process, the solid-liquid mass ratio is recorded as b, b≤s(1+a) / 500a, to ensure that the intercalated materials in the gaps between the primary particles inside the matrix can be removed during the water washing process, thereby achieving the purpose of pore formation.

[0023] In any embodiment, in step (2), during the water washing process, the solid-liquid mass ratio b is 0.5 to 1.8.

[0024] In any embodiment, in step (2), during the water washing process, the water washing temperature is 5° C. to 25° C., and the stirring speed is 500 rpm / min to 900 rpm / min.

[0025] In any embodiment, in step (1), the sintering treatment includes two stages of sintering, the sintering temperature of the first stage is 400°C to 600°C, and the holding time is 2h to 5h, and the sintering temperature of the second stage is 700°C to 900°C, and the holding time is 8h to 20h.

[0026] In any embodiment, in step (3), the sintering temperature is 300° C. to 700° C., and the sintering and holding time is 4 h to 10 h.

[0027] In any embodiment, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium phosphate.

[0028] In any embodiment, the dopant is an inorganic acid salt containing elements M and L at the same time.

[0029] The third aspect of the present application provides a lithium-ion battery, wherein the positive electrode material used in the lithium-ion battery includes the modified nickel-based positive electrode material of the first aspect of the present application or the modified nickel-based positive electrode material prepared by the preparation method of the second aspect of the present application.

[0030] Compared with the prior art, the advantages of this application are:

[0031] (1) The modified nickel-based positive electrode material of the present application adopts a high electronegativity doping element L to dope and modify the nickel-based positive electrode material. A portion of the doping element L enters the lattice of the nickel-based positive electrode material matrix. Its electronegativity is greater than that of lithium and transition metal elements in the material matrix. It has stronger covalency, higher bond strength, higher oxidation potential, stabilizes the lattice oxygen in the structure, reduces the precipitation of lattice oxygen, and thus improves the structural stability of the material.

[0032] (2) The modified nickel-based positive electrode material of the present application adopts a highly electronegative doping element L to dope and modify the nickel-based positive electrode material. Another part of the doping element L adheres to the gaps between the primary particles inside the matrix, inhibiting the growth of the primary particles and forming an intercalation structure. The intercalation material existing in the gaps between the primary particles is removed through a subsequent specific water washing process to achieve the effect of pore formation, forming a high-porosity material, reducing the diffusion distance of lithium ions, and thus exerting a higher capacity.

[0033] (3) When preparing the modified nickel-based positive electrode material, the preparation method of the present application adopts a specific water washing process. In addition to washing away the high-solubility intercalation material from the matrix to achieve the pore-forming function and form a high-porosity material matrix, it can also wash away the residual alkali on the surface of the material matrix to form a low-impedance surface layer, shorten the diffusion distance of lithium ions, increase the diffusion speed of lithium ions, exert a higher capacity, and improve the rate performance of the material.

[0034] (4) The preparation method of the present application adopts surface coating and dry sintering processes to repair the surface structural defects generated during the water washing process of the high-nickel material, reduce the surface stress of the material, and react with the residual lithium on the surface to further reduce the residual lithium and reduce the specific surface area of ​​the material to form an ion conductor layer, protect the surface of the material, reduce the side reaction with the electrolyte during the cycle, and improve the cycle stability of the material; while establishing the lithium ion transmission channel, it can also fix the oxygen atoms on the surface, inhibit the formation of the side reaction nickel oxide phase during the cycle of the high-nickel component on the surface of the high-nickel material, and improve the cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0036] FIG1 is a SEM image of the sintered product obtained in step (1) of Example 1 of the present application;

[0037] Figure 2 is a SEM image of the washed product obtained in step (2) of Example 1 of the present application;

[0038] FIG3 is a SEM image of the modified nickel-based positive electrode material prepared in Example 1 of the present application;

[0039] FIG4 is a cross-sectional view of the modified nickel-based positive electrode material prepared in Example 1 of the present application;

[0040] FIG5 is a SEM image of the modified nickel-based positive electrode material prepared in Comparative Example 1 of the present application;

[0041] FIG6 is a cross-sectional view of the modified nickel-based positive electrode material prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0042] To facilitate understanding of the present application, the following will provide a more comprehensive and detailed description of the present application in conjunction with the accompanying drawings and preferred embodiments of the specification, but the scope of protection of the present application is not limited to the following specific embodiments.

[0043] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this application.

[0044] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0045] Example 1:

[0046] A modified nickel-based cathode material of the present application comprises a nickel-based cathode material matrix and an impurity doped in the nickel-based cathode material matrix, and its chemical formula is Li 1.0 Ni 0.900 Co 0.045 Mn 0.055 S 0.0056 B 0.001 O 1.9944, where S is the doping element and B is the coating element. The modified nickel-based cathode material is composed of secondary spherical polycrystals with a particle size D50 of 9.83 μm and a specific surface area of ​​1.04 m 2 / g, the total residual lithium is 1418ppm, the porosity of the modified nickel-based positive electrode material is 12.21%, and the mass of the doping element S accounts for 0.17% of the total mass of the modified nickel-based positive electrode material.

[0047] The method for preparing the modified nickel-based positive electrode material of this embodiment comprises the following steps:

[0048] (1) Ni-Co-Mn hydroxide precursor Ni 0.90 Co 0.045 Mn 0.055 (OH)2, lithium hydroxide monohydrate, and lithium sulfate were added to a high-speed mixer in a molar ratio of 1:1.05:0.03, stirred at a speed of 1800 r / min for 30 minutes, and then heated to 500°C at a heating rate of 3°C / min in a box furnace with an oxygen concentration of ≥96%, and kept warm for 2 hours, and then heated to 754°C for 11 hours, and naturally cooled to room temperature, crushed, and passed through a 300-mesh sieve to obtain a sintered product; the SEM image of the sintered product is shown in Figure 1, which shows that the material is composed of secondary spherical crystals composed of primary particles, and lithium sulfate is inserted into the gaps between the primary particles in a lamellar manner, presenting an intercalated structure;

[0049] (2) According to the mass ratio a of the dopant lithium sulfate to the nickel cobalt manganese hydroxide precursor of 5.6% and the dopant solubility s of 25g / 100g water, the solid-liquid mass ratio of the washing process is calculated to be less than 0.94, and then the sintered product is washed with deionized water, and the solid-liquid mass ratio of the washing is controlled to b=0.9. The temperature of the deionized water is 8°C, the stirring speed is 700rpm, and the washing is carried out for 10min. After washing, the sample is placed in a vacuum oven and vacuum-dried at 140°C for 6h, then naturally cooled to room temperature, and passed through a 300-mesh sieve to obtain a washed product; the electron microscope image of the washed product is shown in Figure 2, and the flaky lithium sulfate in the matrix disappears and is dissolved in water and washed away;

[0050] (3) The washed product and boric acid were added to a high-speed mixing mixer at a molar ratio of 1:0.001, stirred at a speed of 1800 r / min for 30 min, and then heated to 300°C at a heating rate of 3°C / min in a box furnace in an oxygen atmosphere and kept warm for 6 h. The mixture was naturally cooled to room temperature and sieved using a 300-mesh sieve to obtain the modified nickel-based positive electrode material of this embodiment. The electron microscope image is shown in Figure 3, and the cross-sectional view is shown in Figure 4. It can be seen from the figure that the porosity of the material is large, and uniform pores are present between the primary particles. The porosity is calculated by image processing and is 12.21%.

[0051] Example 2:

[0052] A modified nickel-based cathode material of the present application comprises a nickel-based cathode material matrix and an impurity doped in the nickel-based cathode material matrix, and its chemical formula is Li 0.9956 Na 0.0044 Ni 0.900 Co 0.045 Mn 0.055 Cl 0.0044 B 0.001 O 1.9956 , wherein Na and Cl are doping elements and B is a coating element. The modified nickel-based cathode material is composed of secondary spherical polycrystals with a particle size D50 of 9.73 μm and a specific surface area of ​​0.94 m 2 / g, the total residual lithium is 1258ppm, the porosity of the modified nickel-based positive electrode material is 15.99%, and the mass of the doping element Cl accounts for 0.15% of the total mass of the modified nickel-based positive electrode material.

[0053] The method for preparing the modified nickel-based positive electrode material of this embodiment comprises the following steps:

[0054] (1) Ni-Co-Mn hydroxide precursor Ni 0.90 Co 0.045 Mn 0.055 (OH)2, lithium hydroxide monohydrate, and sodium chloride were added into a high-speed mixer in a molar ratio of 1:1.05:0.03, stirred at a speed of 1800 r / min for 30 min, and then heated to 500°C at a heating rate of 3°C / min in a box furnace with an oxygen concentration of ≥96%, and kept warm for 2 h, and then heated to 754°C and kept warm for 11 h, and naturally cooled to room temperature, crushed, and passed through a 300-mesh sieve to obtain a sintered product;

[0055] (2) According to the mass ratio a of the dopant sodium chloride to the nickel cobalt manganese hydroxide precursor of 3.0%, the solubility s of the dopant is 36 g / 100 g water, and the solid-liquid mass ratio of the washing process is calculated to be less than 2.4. Then, the sintered product is washed with deionized water, and the solid-liquid mass ratio b of the washing process is controlled to be 1.0. The temperature of the deionized water is 8°C, the stirring speed is 700 rpm, and the washing is carried out for 10 minutes. After washing, the sample is placed in a vacuum oven and vacuum-dried at 140°C for 6 hours. Then, it is naturally cooled to room temperature and passed through a 300 mesh sieve to obtain a washed product.

[0056] (3) The washed product and boric acid were added to a high-speed mixing mixer in a molar ratio of 1:0.001, stirred at a speed of 1800 r / min for 30 min, and then heated to 300°C at a heating rate of 3°C / min in a box furnace under an oxygen atmosphere for 6 h, naturally cooled to room temperature, and sieved using a 300-mesh sieve to obtain the modified nickel-based positive electrode material of this embodiment.

[0057] Example 3:

[0058] A modified nickel-based cathode material of the present application comprises a nickel-based cathode material matrix and an impurity doped in the nickel-based cathode material matrix, and its chemical formula is Li 0.9957 K 0.0043 Ni 0.900 Co 0.045 Mn 0.055 F 0.0043 B 0.001 O 1.9957 , where K and F are doping elements and B is a coating element. The modified nickel-based cathode material is composed of secondary spherical polycrystals with a particle size of 9.78 μm and a specific surface area of ​​0.94 m 2 / g, the total residual lithium is 1304ppm, the porosity of the modified nickel-based positive electrode material is 17.82%, and the mass of the doping element F accounts for 0.08% of the total mass of the nickel-based positive electrode material.

[0059] The method for preparing the modified nickel-based positive electrode material of this embodiment comprises the following steps:

[0060] (1) Ni cobalt manganese hydroxide precursor Ni 0.90 Co 0.045 Mn 0.055 (OH)2, lithium hydroxide monohydrate, and potassium fluoride were added into a high-speed mixer in a molar ratio of 1:1.05:0.03, stirred at a speed of 1800 r / min for 30 minutes, and then heated to 500°C at a heating rate of 3°C / min in a box furnace with an oxygen concentration of ≥96%, and kept warm for 2 hours, and then heated to 754°C and kept warm for 11 hours, and naturally cooled to room temperature, crushed, and passed through a 300-mesh sieve to obtain a sintered product;

[0061] (2) According to the mass ratio a of the dopant potassium fluoride to the nickel cobalt manganese hydroxide precursor of 2.9% and the dopant solubility s of 95g / 100g water, the solid-liquid mass ratio of the washing process is calculated to be less than 6.52, and then the sintered product is washed with deionized water, and the solid-liquid mass ratio of the washing is controlled to be b=1.0. The temperature of the deionized water is 8°C, the stirring speed is 700rpm, and the washing is carried out for 10min. After washing, the sample is placed in a vacuum oven and vacuum dried at 140°C for 6h, then naturally cooled to room temperature, and passed through a 300-mesh sieve to obtain a washed product;

[0062] (3) The washed product and boric acid were added to a high-speed mixing mixer in a molar ratio of 1:0.001, stirred at a speed of 1800 r / min for 30 min, and then heated to 300°C at a heating rate of 3°C / min in a box furnace under an oxygen atmosphere for 6 h, naturally cooled to room temperature, and sieved using a 300-mesh sieve to obtain the modified nickel-based positive electrode material of this embodiment.

[0063] Comparative Example 1:

[0064] The modified nickel-based positive electrode material of this comparative example has the chemical formula Li 1.0 Ni 0.90 Co 0.045 Mn 0.055 B 0.001 O2, composed of secondary spherical polycrystals, with a particle D50 diameter of 9.8 μm and a specific surface area of ​​0.48 m 2 / g, the total residual lithium is 1150ppm, and the porosity of the nickel-based positive electrode material is 1.2%.

[0065] The preparation method of the modified nickel-based positive electrode material of this comparative example differs from that of Example 1 only in that lithium sulfate dopant is not introduced. The preparation steps are as follows:

[0066] (1) Ni cobalt manganese hydroxide precursor Ni 0.90 Co 0.045 Mn 0.055 (OH)2 and lithium hydroxide monohydrate were added into a high-speed mixer at a molar ratio of 1:1.05, stirred at a speed of 1800 r / min for 30 min, and then heated to 500°C at a heating rate of 3°C / min in a box furnace with an oxygen concentration of ≥96%, and kept warm for 2 h, and then heated to 754°C and kept warm for 11 h, and naturally cooled to room temperature, crushed, and passed through a 300-mesh sieve to obtain a primary sintered material;

[0067] (2) The primary sintered material was washed with deionized water at a solid-liquid mass ratio of 1.0, the temperature of the deionized water was controlled at 8°C, the stirring speed was 700 rpm, and the washing time was 10 min. After washing, the sample was placed in a vacuum oven and vacuum-dried at 140°C for 6 h, then naturally cooled to room temperature and passed through a 300-mesh sieve to obtain the washed material;

[0068] (3) The washed material and boric acid were added into a high-speed mixer at a molar ratio of 1:0.001, stirred at a speed of 1800 r / min for 30 min, and then heated to 300°C at a heating rate of 3°C / min in a box furnace under an oxygen atmosphere and kept warm for 6 h. The material was naturally cooled to room temperature and sieved using a 300-mesh sieve to obtain a modified nickel-based positive electrode material.

[0069] An SEM image of the modified nickel-based cathode material of this comparative example is shown in Figure 5 , which shows that the material is composed of secondary spherical crystals composed of primary particles. A cross-sectional view of the material is shown in Figure 6 , which shows that the overall porosity of the matrix material is relatively low, calculated through image processing, and its porosity is 1.2%. Compared with Example 1, the internal porosity of the matrix of this comparative example is relatively low, and the capacity, rate, and cycle performance are generally poor.

[0070] Comparative Example 2:

[0071] The modified nickel-based positive electrode material of this comparative example has the chemical formula Li 1.0 Ni 0.90 Co 0.045 Mn 0.055 S 0.0012 B 0.001 O 0.9988 The nickel-based cathode material is composed of secondary spherical polycrystals with a particle size of 9.83 μm and a specific surface area of ​​0.70 m 2 / g, the total residual lithium is 1432ppm, the porosity of the nickel-based positive electrode material is 2.16%, and the mass of the doping element S accounts for 0.03% of the total mass of the modified nickel-based positive electrode material.

[0072] The preparation method of the modified nickel-based positive electrode material of this comparative example comprises the following steps:

[0073] (1) Ni cobalt manganese hydroxide precursor Ni 0.90 Co 0.045 Mn 0.055 (OH)2, lithium hydroxide monohydrate, and lithium sulfate are added into a high-speed mixer in a molar ratio of 1:1.05:0.005, stirred at a speed of 1800 r / min for 30 minutes, and then heated to 500°C at a heating rate of 3°C / min in a box furnace with an oxygen concentration of ≥96%, and kept warm for 2 hours, and then heated to 754°C and kept warm for 11 hours, and naturally cooled to room temperature, crushed, and passed through a 300-mesh sieve to obtain a primary sintered material;

[0074] (2) The primary sintered material was washed with deionized water at a solid-liquid mass ratio of 1.0, the temperature of the deionized water was controlled at 8°C, the stirring speed was 700 rpm, and the washing time was 10 min. After washing, the sample was placed in a vacuum oven and vacuum-dried at 140°C for 6 h, then naturally cooled to room temperature and passed through a 300-mesh sieve to obtain the washed material;

[0075] (3) The washed material and boric acid were added to a high-speed mixer at a molar ratio of 1:0.001, stirred at a speed of 1800 r / min for 30 min, and then heated to 300°C at a heating rate of 3°C / min in a box furnace under an oxygen atmosphere and kept warm for 6 h. The material was naturally cooled to room temperature and sieved using a 300-mesh sieve to obtain a modified nickel-based positive electrode material.

[0076] Comparative Example 3:

[0077] The nickel-based positive electrode material of this comparative example has the chemical formula Li 1.0 Ni 0.89 Co 0.045 Mn 0.055 S 0.014 B 0.001 O 0.986The nickel-based cathode material is composed of secondary spherical polycrystals with a particle size of 9.94 μm and a specific surface area of ​​0.51 m 2 / g, the total residual lithium is 2227ppm, the porosity of the nickel-based positive electrode material is 3.83%, and the mass of the doping element S accounts for 0.45% of the total mass of the nickel-based positive electrode material.

[0078] The preparation method of the modified nickel-based positive electrode material of this comparative example comprises the following steps:

[0079] (1) Ni-Co-Mn hydroxide precursor Ni 0.90 Co 0.045 Mn 0.055 (OH)2, lithium hydroxide monohydrate, and lithium sulfate were added into a high-speed mixer in a molar ratio of 1:1.05:0.03, stirred at a speed of 1800 r / min for 30 minutes, and then heated to 500°C at a heating rate of 3°C / min in a box furnace with an oxygen concentration of ≥96%, and kept warm for 2 hours, and then heated to 754°C and kept warm for 11 hours, and naturally cooled to room temperature, crushed, and passed through a 300-mesh sieve to obtain a primary sintered material;

[0080] (2) The primary sintered material was washed with deionized water at a solid-liquid mass ratio of 3.0. The temperature of the deionized water was controlled at 8°C, the stirring speed was 700 rpm, and the washing time was 10 min. After washing, the sample was placed in a vacuum oven and vacuum-dried at 140°C for 6 h. It was then naturally cooled to room temperature and passed through a 300-mesh sieve to obtain the washed material.

[0081] (3) The washed material and boric acid were added into a high-speed mixer at a molar ratio of 1:0.001, stirred at a speed of 1800 r / min for 30 min, and then heated to 300°C at a heating rate of 3°C / min in a box furnace under an oxygen atmosphere and kept warm for 6 h. The material was naturally cooled to room temperature and sieved using a 300-mesh sieve to obtain a modified nickel-based positive electrode material.

[0082] Performance testing:

[0083] The electrochemical properties of the positive electrode materials in the above embodiments and comparative examples were studied using CR2032 button cells.

[0084] Positive electrode sheet: The positive electrode materials of Examples 1-3 and Comparative Examples 1-3, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) were stirred and dispersed with the solvent NMP in a mass ratio of 92.5:5:2.5, coated on an aluminum foil substrate, and roll-pressed to obtain a positive electrode sheet.

[0085] Negative electrode: lithium metal sheet.

[0086] Electrolyte: 1 mol / L LiPF6 solution, the solvent is a mixed solvent of EC and DMC, the mass ratio of the two is 1:2, and the additive is 1% by mass VC.

[0087] The battery was assembled into a CR2032 button battery for battery testing. The charging cut-off voltage was 4.35V, and the discharging cut-off voltage was 3.0V. The test results of the electrical performance are shown in Table 1.

[0088] Table 1: Electrical performance test results of the positive electrode materials in Examples 1-3 and Comparative Examples 1-3

[0089] As can be seen from Table 1, the modified nickel-based positive electrode materials in Examples 1 to 3 can significantly improve the initial discharge capacity and rate performance of the materials, and can significantly improve high-temperature cycles, which to a large extent solves the common problems of high residual lithium, poor rate and cycle performance of high-nickel positive electrode materials in the industry. Comparative Example 1 does not use lithium sulfate for intercalation and pore formation, so the porosity is low, and the capacity, rate and cycle performance are overall poor; in Comparative Example 2, the amount of intercalation additive added is small, resulting in a small porosity, and the capacity, rate and cycle performance are also overall poor; during the water washing process of Comparative Example 3, the solid-liquid mass is relatively large, the intercalation material is not fully removed, and a large amount remains in the primary particle gap, resulting in a small porosity, and the capacity, rate and cycle performance are also overall poor. It can be seen that the materials of Comparative Examples 1 to 3 have a relatively low porosity as a whole, a long lithium ion transmission distance, a relatively large polarization internal resistance, and relatively poor capacity, rate and cycle performance. Compared with the overall electrochemical performance of the embodiments, they are relatively poor.

[0090] In summary, this application modifies the matrix structure and morphology of nickel-based positive electrode materials by adopting high electronegativity and high solubility inorganic acid salt doping combined with a water washing process, thereby realizing intercalation pore modification and forming a low residual lithium, high porosity and high stability material, shortening the diffusion distance of lithium ions and increasing the diffusion rate of lithium ions, while eliminating grain boundary stress, reducing lithium-nickel mixing, exerting higher capacity, and having better rate performance. High electronegative element doping stabilizes lattice oxygen, reduces oxygen loss, and has a higher oxidation potential, thereby improving the structural stability of the material. At the same time, combined with the coating process, it repairs the surface structural defects generated during the water washing process, reduces the surface stress of the material, forms an ion conductor layer, protects the surface of the material, reduces side reactions with the electrolyte during the cycle, improves the cycle stability of the material, and achieves high capacity, high rate, and long cycle performance, which is suitable for the needs of EV long-range vehicle battery materials.

[0091] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0092] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A modified nickel-based cathode material, comprising a nickel-based cathode material matrix and a doping element doped in the nickel-based cathode material matrix, wherein the doping element includes a doping element L with high electronegativity, and the electronegativity of the doping element L is higher than that of lithium and transition metal elements in the nickel-based cathode material matrix, and the porosity of the modified nickel-based cathode material is 10% to 20%.

2. The modified nickel-based cathode material according to claim 1, wherein, The electronegativity value of the doping element L > 2.

0.

3. The modified nickel-based cathode material according to claim 1 or 2, wherein, The doping element L includes one or more of B, C, N, S, F, Cl, Br, or I.

4. The modified nickel-based cathode material according to any one of claims 1 to 3, wherein, The mass of the doping element L accounts for 0.05% to 0.2% of the total mass of the modified nickel-based cathode material.

5. The modified nickel-based cathode material according to any one of claims 1 to 4, wherein, The specific surface area of the modified nickel-based cathode material is 0.8 m 2 / g to 1.5 m 2 / g, and the total residual lithium on its surface is 1000 ppm to 1800 ppm.

6. The modified nickel-based cathode material according to any one of claims 1 to 5, wherein, The chemical general formula of the modified nickel-based cathode material is Li z Ni 1-x-y Co x Me y L u M v N w O 2-t , where 0.9 ≤ z ≤ 1.1, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, 0 < u ≤ 0.007, 0 ≤ v ≤ 0.01, 0 ≤ w ≤ 0.01, -0.05 ≤ t ≤ 0.05, Me includes one or more of Mn and Al, M includes one or more of Na, K, Mg, Ca, Sr, Ba, Zr, Ti, and Y, and N includes one or more of B, La, Ce, Al, Co, Ti, or W.

7. A preparation method of the modified nickel-based cathode material according to any one of claims 1 to 6, comprising the following steps: (1) Mix the cathode material precursor, lithium source, and dopant evenly and then perform a sintering treatment to obtain a sintered product; (2) Wash and dry the sintered product obtained in step (1) to obtain a washed product; (3) Mix the washed product obtained in step (2) evenly with a coating agent containing element N, and then perform a sintering treatment to obtain the modified nickel-based cathode material.

8. The preparation method of the modified nickel-based cathode material according to claim 7, wherein, In step (1), the dopant includes a dopant containing element L, and the mass ratio of its addition amount to the cathode material precursor is denoted as a, and a is 2% to 8%.

9. The preparation method of the modified nickel-based cathode material according to claim 8, wherein, The dopant containing element L is an inorganic acid salt, and its solubility s at 20°C is greater than 10 g / 100 g of water.

10. The preparation method of the modified nickel-based cathode material according to claim 9, wherein, In step (2), during the washing process, the solid-liquid mass ratio is denoted as b, and b ≤ s(1 + a) / 500a.

11. The preparation method of the modified nickel-based cathode material according to claim 10, wherein, In step (2), during the washing process, the solid-liquid mass ratio b is 0.5 to 1.

8.

12. The preparation method of the modified nickel-based cathode material according to any one of claims 7 to 11, wherein, In step (2), the washing temperature is 5°C to 25°C, and the stirring speed is 500 rpm to 900 rpm.

13. The preparation method of the modified nickel-based cathode material according to any one of claims 7 to 12, wherein, In step (1), the sintering treatment includes two-stage sintering. First, heat up to 400°C to 600°C for the first-stage sintering, and the holding time for the first-stage sintering is 2 h to 5 h. Then, heat up to 700°C to 900°C for the second-stage sintering, and the holding time for the second-stage sintering is 8 h to 20 h.

14. The preparation method of the modified nickel-based cathode material according to any one of claims 7 to 13, wherein, In step (3), the temperature of the sintering treatment is 300°C to 700°C, and the sintering holding time is 4 h to 10 h.

15. A lithium-ion battery, wherein the cathode material used in the lithium-ion battery includes the modified nickel-based cathode material according to any one of claims 1 to 6 or the modified nickel-based cathode material prepared by the preparation method according to any one of claims 7 to 14.

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