Modified nickel-cobalt-aluminum ternary positive electrode material and preparation method therefor, and lithium battery

Abstract

Provided in the present disclosure are a modified nickel-cobalt-aluminum ternary positive electrode material and a preparation method therefor, and a lithium battery. The modified nickel-cobalt-aluminum ternary positive electrode material provided by the present disclosure comprises a bulk phase material and a coating layer that coats the surface of the bulk phase material, wherein the coating layer is composed of boric acid and at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide. In the present disclosure, boric acid and at least one of a binary compound containing an effective metal and an aluminum-containing metal oxide are used as a composite coating source to perform composite coating, such that the coating effect of the nickel-cobalt-aluminum ternary positive electrode material is optimized, and an ultrahigh-nickel-content nickel-cobalt-aluminum ternary positive electrode material having relatively good physical and chemical properties is prepared. Moreover, the problems of poor structural stability, a high residual alkali content, a relatively low capacity and unsatisfactory rate and cycle performance of the material are ameliorated.

Description

A modified nickel-cobalt-aluminum ternary cathode material, its preparation method, and a lithium battery.

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202411929064.X, filed on December 25, 2024, entitled "A Modified Nickel-Cobalt-Aluminum Ternary Cathode Material and Its Preparation Method and Lithium Battery", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of lithium battery materials technology, and more specifically, to a modified nickel-cobalt-aluminum ternary cathode material, its preparation method, and a lithium battery. Background Technology

[0004] Nickel-cobalt-aluminum (NCA) ternary cathode materials have become a popular choice for power lithium-ion batteries due to their significant advantages in energy density, cost, and safety. However, a key challenge of this high-nickel material lies in the unique characteristics of its surface, which easily triggers unwanted side reactions, and electrochemical reactions often preferentially occur at the material surface. Therefore, ensuring the stability of the material's surface structure is crucial for improving the overall electrochemical performance of the electrode material. Unfortunately, the widely used lithium nickel-cobalt-aluminum (NCA) ternary cathode materials often exhibit decreased cycle stability during charge-discharge cycling due to surface instability.

[0005] To address the aforementioned issues, it is of great importance to develop a modified nickel-cobalt-aluminum ternary cathode material that can overcome the shortcomings of existing nickel-cobalt-aluminum ternary cathode materials, such as poor cycle stability, high residual alkali content, low capacity, and unsatisfactory rate and cycle performance. This material, along with its preparation method and lithium battery, is of particular interest. Summary of the Invention

[0006] The purpose of this disclosure is to overcome the defects of the prior art by providing a modified nickel-cobalt-aluminum ternary cathode material, a method for preparing the same, and a lithium battery.

[0007] The technical problem solved by this disclosure is achieved by the following technical solution.

[0008] This disclosure provides a modified nickel-cobalt-aluminum ternary cathode material, which includes a bulk material and a coating layer covering the surface of the bulk material. The coating layer is composed of at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide, and boric acid.

[0009] This disclosure also provides a method for preparing the modified nickel-cobalt-aluminum ternary cathode material according to the above, comprising the following steps: mixing a bulk material with at least one of a transition metal nitride and an aluminum-containing metal oxide and boric acid, and then sintering the mixture to obtain the modified nickel-cobalt-aluminum ternary cathode material.

[0010] This disclosure also provides a lithium battery, wherein the positive electrode of the lithium battery comprises the modified nickel-cobalt-aluminum ternary positive electrode material described above or the modified nickel-cobalt-aluminum ternary positive electrode material prepared by the above preparation method.

[0011] The effects and benefits of this disclosure include:

[0012] This disclosure provides a modified nickel-cobalt-aluminum ternary cathode material, its preparation method, and a lithium battery. The modification is achieved through a coating process using at least one of a binary nitride containing an effective metal or an aluminum-containing metal oxide, combined with boric acid. This surface coating not only enhances interfacial kinetics, giving the modified nickel-cobalt-aluminum ternary cathode material good ion diffusion capabilities, but also prevents direct contact between the bulk material and the electrolyte, reducing side reactions between the bulk material and the electrolyte. This results in a modified nickel-cobalt-aluminum ternary cathode material with high conductivity and high lithium-ion content. + The high diffusion rate, high stability, low residual alkali content, high discharge capacity, and better rate and cycle performance enable lithium-ion batteries prepared using the above-mentioned modified nickel-cobalt-aluminum ternary cathode material to have better electrical performance. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 is a SEM image of the sample prepared in Example 1;

[0015] Figure 2 shows the XRD diffraction pattern of the sample prepared in Example 1;

[0016] Figure 3 shows the first charge-discharge performance of the button batteries of Example 1 and Comparative Example 1.

[0017] Figure 4 shows the charge-discharge cycle performance of the button batteries of Example 1 and Comparative Example 1 at 45°C. Detailed Implementation

[0018] The embodiments of this disclosure will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this disclosure. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0019] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0020] The following provides a detailed description of a modified nickel-cobalt-aluminum ternary cathode material, its preparation method, and a lithium battery, as provided in the embodiments of this disclosure.

[0021] In a first aspect, embodiments of this disclosure provide a modified nickel-cobalt-aluminum ternary cathode material, which includes a bulk material and a coating layer covering the surface of the bulk material. The coating layer is composed of at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide, and boric acid.

[0022] Studies have shown that, with increasing nickel content, ultra-high nickel ternary cathode materials exhibit poorer cycle stability and safety compared to higher nickel ternary cathode materials. Their production conditions are also more demanding, requiring stricter control over equipment sealing, temperature, humidity, and CO2 levels. The ultra-high nickel content results in higher Li... + / Ni 2+ Mixed arrangement, increased lattice distortion, microcracks and lattice oxygen release, more severe surface side reactions, and higher residual lithium content all affect the safety and cycle performance of ultra-high nickel ternary materials. This disclosure optimizes the coating and sintering process of ternary materials by using at least one of a binary compound containing an effective metal or an aluminum-containing metal oxide as a coating source, along with boric acid, to achieve optimal coating effect for the nickel-cobalt-aluminum ternary cathode material. This results in a nickel-cobalt-aluminum ternary cathode material with better physicochemical properties. Simultaneously, it improves the problems of low material structural stability, high residual lithium, low capacity, and poor rate and cycle performance.

[0023] In some alternative embodiments, the bulk material is composed of LiNi. x Co y M 1-x-yO2, where: 0.90≤x≤0.98, 0≤y<0.8, and M is at least two elements selected from Mn, Ti, Zr, Sr, Mo, Mg, Sb, V, Ta, Sn, Nb, B, Sc, Y, Mo, La, and W.

[0024] This disclosure provides a modified nickel-cobalt-aluminum ternary cathode material, in which the inner layer of the matrix cathode material is doped with the dopant element M, and when Zr with a high valence state is used... 4+ With Y 4+ Modification and doping not only broadened the sintering temperature range of the material, but also allowed for the appropriate addition of Li... + / Ni 2+ While mixing, a small amount of Ni is effectively placed 3+ Reduced to Ni 2+ Or it may induce the formation of Li vacancies, greatly promoting the formation of Li. + Diffusion transport, part of Li + The atoms migrate to the nickel layer and serve as atomic pillars to prevent the collapse of the layered plane during charging and discharging. Doping also mitigates the anisotropic volume change caused by the H2-H3 phase transition in the material and suppresses the loss of lattice oxygen, ensuring the structural stability of the inner matrix of the invented cathode material.

[0025] In some alternative embodiments, the aluminum-containing metal oxide includes at least one of cerium aluminate, lanthanum strontium aluminate, and magnesium aluminate, and the transition metal nitride includes at least one of molybdenum nitride, cobalt nitride, and tungsten nitride.

[0026] In some optional embodiments, the particle size of the modified nickel-cobalt-aluminum ternary cathode material is 3 μm to 15 μm, and the thickness of the coating layer is 3 nm to 10 nm.

[0027] Secondly, this disclosure also provides a method for preparing the modified nickel-cobalt-aluminum ternary cathode material according to the above, comprising the following steps: mixing a bulk material with at least one of a transition metal nitride containing an effective metal and an aluminum metal oxide and boric acid, and then sintering the mixture to obtain the modified nickel-cobalt-aluminum ternary cathode material.

[0028] In some alternative embodiments, the preparation of the bulk material includes the following steps: proportionally mixing Ni... x Co y (OH)₂ precursor A, lithium source B, aluminum source C, and source M are mixed to obtain mixture D. Mixture D is then sintered once to obtain bulk material E; wherein:

[0029] The mixing machine speed during the mixing process is 900 rpm to 1200 rpm, the mixing temperature is 25℃ to 45℃, and the time is 40 min to 60 min. The molar ratio of lithium source to precursor A in the mixed material D, Li / (Ni+Co) = 1.04 to 1.07. Aluminum source C includes at least one of aluminum hydroxide, aluminum oxide, aluminum nitrate, aluminum isopropoxide, and aluminum sulfate. The mass fraction of Al element in aluminum source C in precursor A is 1000 ppm to 5000 ppm. M source includes at least one of oxides, nitrates, and sulfates of element M. The mass fraction of element M in M ​​source in precursor A is 1000 ppm to 10000 ppm. Element M includes at least two elements selected from Mn, Ti, Zr, Sr, Mo, Mg, Sb, V, Ta, Sn, Nb, B, Sc, Y, Mo, La, and W. Lithium source B includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate.

[0030] In some optional embodiments, the conditions for primary sintering include: placing the mixture D into a box furnace, heating it to 450°C to 600°C at a rate of 2°C / min to 10°C / min under an oxygen-containing atmosphere, holding it at that temperature for 2-4 hours, then continuing to heat it to 650°C to 750°C, holding it at that temperature for 10-15 hours, and then cooling, crushing, sieving, washing with water, and vacuum drying to obtain bulk material E.

[0031] In some optional embodiments, the preparation of the modified nickel-cobalt-aluminum ternary cathode material includes: mixing bulk material E with at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide and boric acid to obtain a mixture F; and subjecting the mixture F to secondary sintering to obtain the modified nickel-cobalt-aluminum ternary cathode material; wherein:

[0032] The mixing machine speed during the mixing process is 800 rpm to 1000 rpm, the mixing temperature is 20℃ to 45℃, and the time is 20 min to 40 min; boric acid accounts for 1000 ppm of the total mass of bulk material E, and the metal elements in aluminum metal oxides and / or transition metal nitrides account for 200 ppm to 2000 ppm of the total mass of bulk material E; the aluminum metal oxides include at least one of cerium aluminate, lanthanum strontium aluminate, and magnesium aluminate, and the transition metal nitrides include at least one of molybdenum nitride, cobalt nitride, and tungsten nitride.

[0033] In some optional embodiments, the conditions for secondary sintering include: placing the mixture F into a box furnace, heating it to 250°C to 400°C at a rate of 2°C / min to 10°C / min under an oxygen-containing atmosphere, holding it at that temperature for 5h to 12h, then cooling, pulverizing, and sieving to obtain the modified nickel-cobalt-aluminum ternary cathode material, wherein the Li element in the modified nickel-cobalt-aluminum ternary cathode material accounts for 6.6wt% to 7.4wt% of the total mass of the modified nickel-cobalt-aluminum ternary cathode material.

[0034] This disclosure provides a method for preparing the modified nickel-cobalt-aluminum ternary cathode material described above. The method involves coating and modifying the surface of the bulk material with at least one of a binary nitride containing an effective metal or an aluminum-containing metal oxide, and boric acid. On one hand, the metal compounds used in this disclosure not only possess good electrical and thermal conductivity and chemical stability against acid and alkali corrosion, but also exhibit high melting points and high mechanical strength. Furthermore, and more importantly, by heat-treating the bulk material with cerium aluminate at a specific temperature, a portion of the cerium aluminate, boric acid, and residual lithium in the bulk material undergoes high-temperature heat treatment. This process consumes the residual lithium while forming a mixed fast-ion conductor composite coating layer of lithium borate, lithium aluminate, and lithium cerate, significantly reducing the surface residual lithium content of the bulk material. This improves the interfacial transport kinetics of Li and suppresses parasitic side reactions, thereby improving the electrochemical performance of the bulk material. Cerium aluminate's resistance to acid and alkali corrosion effectively inhibits the dissolution of Ni in the coated bulk material and prevents direct contact corrosion between the bulk material surface and the electrolyte, reducing side reactions in the electrolyte and improving the cycling stability of the bulk material. Cerium aluminate's high mechanical strength also effectively inhibits particle breakage in the coated bulk material and prevents direct contact corrosion between the internal particle surfaces and the electrolyte after particle breakage, reducing side reactions in the electrolyte, improving the material's cycling stability, and reducing capacity loss. On the other hand, Ce surface doping lowers the bond energy of the Li-O bonds, and the resulting Li vacancies can accelerate Li... + Transmission rate; in addition, Ce 4+ It has a strong oxidizing ability and can oxidize Ni on the material surface. 2+ Oxidized to Ni 3+ This reduces the formation of surface salt phases, further maintaining the integrity and stability of the crystal structure. Surface coating not only enhances interfacial dynamics, giving the composite material excellent ion diffusion capabilities, but also prevents direct contact between the bulk material and the electrolyte, reducing side reactions between the bulk material and the electrolyte. Based on this structure, the bulk material exhibits high electrical conductivity and Li... + It has high diffusion rate, high stability, low residual lithium, high discharge capacity, and better rate and cycle performance.

[0035] The modified nickel-cobalt-aluminum ternary cathode material preparation method disclosed herein is simple, highly operable, and the sintering conditions can be adjusted on existing mature production line processes, making it suitable for large-scale production. It provides a feasible strategy for preparing lithium-ion battery cathode materials with high energy density and superior safety performance.

[0036] Thirdly, this disclosure provides a lithium battery, wherein the positive electrode of the lithium battery includes the modified nickel-cobalt-aluminum ternary positive electrode material described above or the modified nickel-cobalt-aluminum ternary positive electrode material prepared by the above preparation method.

[0037] As can be seen from the above, this disclosure provides a modified nickel-cobalt-aluminum ternary cathode material, its preparation method, and a lithium battery. It employs a combination of multi-element doping and surface modification to improve defects such as low material structural stability, severe particle breakage, high residual lithium, low capacity, and poor rate and cycle performance. The internal composition of the modified nickel-cobalt-aluminum ternary cathode material is LiNi. x Co y M 1-x-y O2, wherein: 0.90≤x≤0.98, 0≤y<0.8, and M is at least two elements selected from Mn, Ti, Zr, Sr, Mo, Mg, Sb, V, Ta, Sn, Nb, B, Sc, Y, Mo, La, and W. The outer layer is a composite coating layer consisting of a binary nitride containing an effective metal or an aluminum metal oxide and boric acid.

[0038] The following detailed description, in conjunction with embodiments, illustrates a modified nickel-cobalt-aluminum ternary cathode material, its preparation method, and a lithium battery provided by this disclosure. However, these descriptions should not be construed as limiting the scope of protection of this disclosure.

[0039] A method for preparing a modified nickel-cobalt-aluminum ternary cathode material includes the following steps:

[0040] 1. Weigh out Ni according to the lithium source to precursor molar ratio of Li / (Ni+Co) = 1.07. 0.96 Co 0.04 (OH)2 precursor A and battery-grade lithium hydroxide B, and separately weigh 4000 ppm aluminum hydroxide C (accounting for 4000 ppm of the precursor mass) and 3500 ppm of nano-sized additives zirconium oxide (2500 ppm) and yttrium oxide (1000 ppm) in total. Mix them evenly using a high-speed mixer at 1000 rpm for 45 min and at a temperature of 25–45 °C to obtain mixture D;

[0041] 2. Place the mixture D obtained in step 1 into a box furnace, and heat it to 550°C at a rate of 3°C / min under an oxygen atmosphere. After heat treatment for 3 hours, continue to heat it to 725°C and sinter it for 13 hours. Then cool, crush, sieve, wash with water, and vacuum dry to obtain bulk material E.

[0042] 3. Next, weigh 1000 ppm of nano-sized cerium aluminate and 1000 ppm of boric acid, which account for 1000 ppm of the total mass of bulk material E, and add them to the bulk material E obtained in step 2. Mix them evenly using a high-speed mixer at a speed of 1000 rpm for 30 min and a mixing temperature of 20-45℃ to obtain mixture F.

[0043] 4. Place the mixture F obtained in step 3 into a box furnace, heat it to 325°C at a rate of 3°C / min under an oxygen atmosphere, hold it at that temperature for 9 hours, then cool it down, crush it, and sieve it.

[0044] Figure 1 is a SEM image of the surface morphology of the product prepared in Example 1. The product particles are relatively uniformly coated, and there is no obvious agglomeration of additives on the particle surface, with only a few additives remaining. Figure 2 is an XRD diffraction pattern of the product prepared in Example 1. Compared with the standard card, no other impurity peaks were found, indicating that the coating layer did not affect the structure of the bulk material E itself.

[0045] Example 2

[0046] 1. Perform the operation according to steps 1 to 2 of Example 1;

[0047] 2. Next, weigh 1000 ppm of nano-sized cobalt nitride and 1000 ppm of boric acid, which account for 1000 ppm of the total mass of bulk material E, and mix them evenly with bulk material E to obtain material F. The relevant parameters are consistent with step 3 in Example 2. The difference between this step and step 1 in Example 1 is that the types of metal compounds are different in step 3.

[0048] 3. Subsequent operations shall be carried out in step 4 of Example 1.

[0049] Example 3

[0050] 1. Perform the operation according to steps 1 to 2 of Example 1;

[0051] 2. Next, weigh 1000 ppm of nano-sized lanthanum strontium aluminate and 1000 ppm of boric acid, which account for 1000 ppm of the total mass of bulk material E, and mix them evenly with bulk material E to obtain material F. The relevant parameters are consistent with step 3 in Example 2. The difference between this step and step 1 in Example 1 is that the types of metal compounds are different in step 3.

[0052] 3. Subsequent operations shall be carried out in step 4 of Example 1.

[0053] Example 4

[0054] 1. Perform the operation according to steps 1 to 2 of Example 1;

[0055] 2. Next, 1000 ppm of nano-sized tungsten nitride and 1000 ppm of boric acid, which account for 1000 ppm of the total mass of bulk material E, are weighed and mixed evenly with bulk material E to obtain material F. The relevant parameters are consistent with step 3 in Example 2. The difference between this step and step 1 in Example 1 is that the types of metal compounds are different in step 3.

[0056] 3. Subsequent operations shall be carried out in step 4 of Example 1.

[0057] Comparative Example 1

[0058] Perform the operation according to steps 1-2 of Example 1, but without adding the nano-scale additives zirconium oxide and yttrium oxide;

[0059] The remaining steps are prepared according to steps 3-4 in Example 1, but boric acid and metal compounds are not added in step 3.

[0060] Comparative Example 2

[0061] 1. Perform the operation according to steps 1 to 2 of Example 1;

[0062] 2. The remaining operation steps are prepared according to steps 3 to 4 in Example 1, but boric acid and the metal compound cerium aluminate are not added in step 3.

[0063] Comparative Example 3

[0064] 1. Perform the operation according to steps 1 to 2 of Example 1;

[0065] 2. The remaining operation steps are prepared according to steps 3 to 4 in Example 1, but in step 3, only boric acid is added and not the metal compound cerium aluminate.

[0066] Comparative Example 4

[0067] 1. Perform the operation according to steps 1 to 2 of Example 1;

[0068] 2. The remaining operation steps are prepared according to steps 3 to 4 in Example 1, but in step 3, only cerium aluminate is added and boric acid is not added.

[0069] Comparative Example 5

[0070] 1. Weigh Ni according to step 1 of Example 1. 0.96 Co 0.04 (OH)2 precursor A and battery-grade lithium hydroxide B, and separately weigh aluminum hydroxide C (5000 ppm of precursor mass) and nano-sized additives zirconium oxide (3000 ppm) and yttrium oxide (2000 ppm) (total amount of 5000 ppm) are mixed. The mixing process is the same as step 1 in Example 1 to obtain mixture D.

[0071] 2. Place the mixture D obtained in step 1 into a box furnace, and heat it to 550°C at a rate of 3°C / min under an oxygen atmosphere. After heat treatment for 3 hours, continue to heat it to 750°C and sinter it for 15 hours. Then cool, crush, sieve, wash with water, and vacuum dry to obtain bulk material E.

[0072] 3. Next, weigh 2000 ppm of nano-sized cerium aluminate and 2000 ppm of boric acid, which account for the total mass of bulk material E, and add them to the bulk material E obtained in step 2. Mix them evenly using a high-speed mixer. The mixing process is the same as step 3 in Example 1 to obtain mixture F.

[0073] 4. Place the mixture F obtained in step 3 into a box furnace, heat it to 400°C at a rate of 3°C / min under an oxygen atmosphere, hold it at that temperature for 12 hours, then cool it down, crush it, and sieve it.

[0074] Comparative Example 6

[0075] 1. Weigh the relevant materials according to Example 1 in step 1, and mix them evenly using a high-speed mixer. The speed of the high-speed mixer is 1200 rpm, the mixing time is 45 min, and the mixing temperature is 50℃ to obtain mixture D;

[0076] 2. Perform the operation according to step 2 in Example 1 to obtain bulk material E;

[0077] 3. Weigh the modified additive according to step 2 in Example 1, add it to the bulk material E obtained in step 2, and mix it evenly using a high-speed mixer. The speed of the high-speed mixer is 1200 rpm, the mixing time is 30 min, and the mixing temperature is 50℃ to obtain the mixture F.

[0078] 4. Perform the operation as described in step 4 of Example 1.

[0079] Electrochemical performance testing:

[0080] The products obtained in Examples 1-4 and Comparative Examples 1-6 were used as positive electrode materials to fabricate coin cells for electrochemical performance testing. The fabrication method was as follows:

[0081] a. The products obtained in the examples and comparative examples were stirred in a ratio of positive electrode material powder: conductive agent (SP): adhesive (PVDF) = 90:5:5 to form a uniformly dispersed positive electrode slurry. The slurry was then coated, punched, and vacuum dried. A lithium metal sheet was used as the negative electrode material for the counter electrode, and a polypropylene film with micropores was used as the battery separator. Ethylene carbonate (EC) / dimethyl carbonate (DMC) with a solvent volume ratio of 1:1 and 1 mol / L LiPF6 were used as the electrolyte. The batteries were assembled into 2032 button batteries in a glove box filled with dry high-purity argon gas and left to stand for 8 hours.

[0082] b. After the button batteries have been left to stand, charge and discharge them at an ambient temperature of 25°C, at a voltage of 3.0–4.3V, and at a current rate of 0.2C. Perform electrochemical performance tests on Examples 1–4 and Comparative Example 1. Calculate the initial discharge efficiency, i.e.: Initial efficiency = Initial discharge specific capacity / Initial charge specific capacity * 100%.

[0083] c. At 45°C, charge / discharge at 3.0–4.3V with 1C, and perform cycle performance tests on Examples 1–4 and Comparative Examples 1–6. Calculate the capacity retention rate after 50 cycles using the following formula: Capacity retention rate = Specific capacity at 50th discharge / Specific capacity at first discharge * 100%.

[0084] Please refer to Table 1 for specific test data.

[0085] Table 1 Electrical performance test results

[0086] As can be seen from Table 1 and Figures 3-4 above, compared with Comparative Example 1, the electrical performance (initial efficiency and discharge specific capacity) and high-temperature cycle stability of the cathode materials prepared in the embodiments of this disclosure are significantly improved. The method of this embodiment effectively improves the initial efficiency of the material and enhances its charge-discharge performance; simultaneously, it exhibits good cycle performance at a high temperature of 45°C and a 1C rate, further demonstrating improved rate performance. This indicates that the composite coating of cerium aluminate and boric acid effectively avoids direct contact reaction between the cathode material surface and the electrolyte, preventing electrolyte decomposition side reactions, improving the cycle stability of the cathode material, and significantly increasing the cycle life of the lithium battery. The possible reasons are as follows: the strong acid and alkali corrosion resistance of the transition metal nitrides and / or aluminum metal oxides containing effective metals in the modified nickel-cobalt-aluminum ternary cathode material enables the coated cathode material to effectively reduce the dissolution of nickel; in addition, the reaction of boric acid with the residual lithium in the cathode material to form a lithium borate coating layer that is a fast ion conductor gives the modified nickel-cobalt-aluminum ternary cathode material excellent electrochemical performance.

[0087] Comparative Examples 1-6 show significantly reduced electrical performance (initial efficiency and discharge specific capacity) and high-temperature cycling stability compared to the products prepared in the embodiments of this disclosure. Comparative Examples 1-4 either did not undergo coating or used a single coating agent, resulting in relatively poor performance of the lithium batteries prepared using the products from Comparative Examples 1-4. The higher dopant and coating agent content in Comparative Example 5 is expected to require a higher sintering temperature, greatly deteriorating the physicochemical properties of the material. The high dopant and coating agent content reduces the active lithium content and hinders Li-1 production. + Transport. Higher sintering temperatures disrupt the crystal structure of the material, increasing cation mixing and further reducing its physicochemical properties. In Comparative Example 6, the higher coating speed and temperature significantly reduced the uniformity of dopant and coating agent coating, failing to achieve the desired coating effect. High speeds also caused particle breakage, resulting in reduced electrochemical performance. Furthermore, excessively high coating temperatures led to localized deterioration of additives and coating agents, ultimately reducing material performance.

[0088] The above description is only a preferred embodiment of this disclosure. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principles of this disclosure, and these improvements and modifications should also be considered within the scope of protection of this disclosure. Industrial applicability

[0089] This disclosure provides a modified nickel-cobalt-aluminum ternary cathode material, its preparation method, and a lithium battery. The modified nickel-cobalt-aluminum ternary cathode material provided by this disclosure includes a bulk material and a coating layer covering the surface of the bulk material. The coating layer is composed of at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide, and boric acid. This composite coating optimizes the coating effect of the nickel-cobalt-aluminum ternary cathode material, resulting in a modified nickel-cobalt-aluminum ternary cathode material with high conductivity and high lithium-ion content. + With high diffusion rate, high stability, low residual alkali content, high discharge capacity, and better rate and cycle performance, lithium-ion batteries prepared using the above-mentioned modified nickel-cobalt-aluminum ternary cathode material have better electrical performance, expanding the application scope of high-nickel cathode materials in the field of lithium-ion batteries.

Claims

1. A modified nickel-cobalt-aluminum ternary cathode material, characterized in that, The modified nickel-cobalt-aluminum ternary cathode material includes a bulk material and a coating layer covering the surface of the bulk material. The coating layer is composed of at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide, and boric acid. 2.The modified nickel-cobalt-aluminum ternary cathode material of claim 1, characterized in that, The bulk material is composed of LiNi x Co y M 1-x-y O2, where: 0.90≤x≤0.98, 0≤y<0.8, and M is at least two elements selected from Mn, Ti, Zr, Sr, Mo, Mg, Sb, V, Ta, Sn, Nb, B, Sc, Y, Mo, La, and W. 3.The modified nickel-cobalt-aluminum ternary cathode material of claim 1, characterized in that, The aluminum-containing metal oxide includes at least one of cerium aluminate, lanthanum strontium aluminate, and magnesium aluminate, and the transition metal nitride includes at least one of molybdenum nitride, cobalt nitride, and tungsten nitride.

4. The modified nickel-cobalt-aluminum ternary cathode material according to any one of claims 1-3, characterized in that, The particle size of the modified nickel-cobalt-aluminum ternary cathode material is 3μm to 15μm, and the thickness of the coating layer is 3nm to 10nm.

5. A method for preparing the modified nickel-cobalt-aluminum ternary cathode material according to any one of claims 1-4, characterized in that, The process includes the following steps: mixing a bulk material with at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide and boric acid, and then sintering the mixture to obtain a modified nickel-cobalt-aluminum ternary cathode material.

6. The production method according to claim 5, characterized by, The preparation of the bulk material includes the following steps: Ni x Co y mixing a precursor A, a lithium source B, an aluminum source C and an M source to obtain a mixture D, and then sintering the mixture D once to obtain a bulk material E; wherein: The mixing machine speed during the mixing process is 900 rpm to 1200 rpm, the mixing temperature is 25℃ to 45℃, and the time is 40 min to 60 min; the molar ratio of the lithium source to the precursor A in the mixed material D, Li / (Ni+Co) = 1.04 to 1.07; the aluminum source C includes at least one of aluminum hydroxide, aluminum oxide, aluminum nitrate, aluminum isopropoxide, and aluminum sulfate, and the Al element in the aluminum source C accounts for 1000 ppm to 5000 ppm of the mass fraction of the precursor A; the M source includes at least one of oxides, nitrates, and sulfates of the M element, and the M element in the M source accounts for 1000 ppm to 10000 ppm of the mass fraction of the precursor A, and the M element includes at least two elements selected from Mn, Ti, Zr, Sr, Mo, Mg, Sb, V, Ta, Sn, Nb, B, Sc, Y, Mo, La, and W; the lithium source B includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate.

7. The production method according to claim 6, wherein The conditions for the first sintering include: placing the mixture D into a box furnace, heating it to 450℃~600℃ at a rate of 2℃ / min~10℃ / min under an oxygen-containing atmosphere, holding it at that temperature for 2h-4h, then continuing to heat it to 650℃~750℃, holding it at that temperature for sintering for 10h~15h, followed by cooling, crushing, sieving, washing with water, and vacuum drying to obtain bulk material E.

8. The preparation method according to claim 7, characterized in that, The preparation of the modified nickel-cobalt-aluminum ternary cathode material includes: mixing bulk material E with at least one of a transition metal nitride containing an effective metal and an aluminum-containing metal oxide, and boric acid to obtain a mixture F; and subjecting the mixture F to secondary sintering to obtain the modified nickel-cobalt-aluminum ternary cathode material; wherein: The mixing machine speed during the mixing process is 800 rpm to 1000 rpm, the mixing temperature is 20℃ to 45℃, and the time is 20 min to 40 min; the boric acid accounts for 1000 ppm of the total mass of the bulk material E, and the metal element in the aluminum-containing metal oxide and / or the transition metal nitride accounts for 200 ppm to 2000 ppm of the total mass of the bulk material E; the aluminum-containing metal oxide includes at least one of cerium aluminate, lanthanum strontium aluminate, and magnesium aluminate, and the transition metal nitride includes at least one of molybdenum nitride, cobalt nitride, and tungsten nitride.

9. The preparation method according to claim 8, characterized in that, The conditions for the secondary sintering include: placing the mixture F into a box furnace, heating it to 250℃~400℃ at a rate of 2℃ / min~10℃ / min under an oxygen-containing atmosphere, holding it at that temperature for 5h~12h, then cooling, pulverizing, and sieving to obtain the modified nickel-cobalt-aluminum ternary cathode material, wherein the Li element in the modified nickel-cobalt-aluminum ternary cathode material accounts for 6.6wt%~7.4wt% of the total mass of the modified nickel-cobalt-aluminum ternary cathode material.

10. A lithium battery, characterized by, The lithium battery cathode comprises the modified nickel-cobalt-aluminum ternary cathode material as described in any one of 1 to 4, or the modified nickel-cobalt-aluminum ternary cathode material prepared by any one of 5 to 9.

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