Lithium nickel manganate positive electrode material, preparation method, and lithium-ion battery

Abstract

Provided in the present application are a lithium nickel manganate positive electrode material, a preparation method, and a lithium-ion battery. In the lithium nickel manganate positive electrode material provided by the present application, the positive electrode material comprises, from interior to exterior, an internal ordered phase and a surface disordered phase, wherein the internal ordered phase comprises a doping element, and is of an ordered spinel structure; the surface disordered phase comprises a doping element, and is of a disordered spinel structure; and the mass proportion of the surface disordered phase in the positive electrode material is 0%<m<1%. In the lithium nickel manganate positive electrode material provided by the present application, the internal ordered phase provides a high working voltage and a high energy density, the surface disordered phase improves the cycling stability of the positive electrode material and provides a higher capacity and a faster lithium-ion diffusion rate, and the doping element lowers the content of unstable lattice oxygen and reduces lattice distortion; and such a material design strategy provides a new possibility for the development of high-performance lithium-ion batteries.

Description

A lithium nickel manganese oxide cathode material, its preparation method, and a lithium-ion battery.

[0001] This application claims priority to Chinese Patent Application No. 202410906988.1, filed on July 8, 2024, entitled "A Lithium Nickel Manganese Oxide Cathode Material, Preparation Method and Lithium-ion Battery", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of lithium-ion battery technology, and more specifically, to a lithium nickel manganese oxide cathode material, its preparation method, and a lithium-ion battery. Background Technology

[0003] Lithium-ion batteries, due to their excellent performance, high energy density, and long cycle life, are currently one of the main energy storage options and are widely used in electric vehicles and portable electronic devices. However, range anxiety and long charging times are major obstacles to the development of electric vehicles. Therefore, developing cathode materials with higher energy density and higher rate performance is crucial.

[0004] The key to achieving higher energy density and rate performance lies primarily in increasing the capacity of the cathode material or raising the operating voltage. Compared to lithium iron phosphate and layered lithium cobalt oxide, spinel lithium nickel manganese oxide boasts higher operating voltage and energy density, along with a stable 3D lithium-ion transport channel. These advantages make lithium nickel manganese oxide one of the most promising cathode materials in the industry. However, despite these advantages, lithium nickel manganese oxide suffers from structural instability, leading to unsatisfactory commercial applications as a cathode material. Major issues include drastic capacity reduction, severe interfacial reactions, and electrolyte incompatibility at high voltages. Summary of the Invention

[0005] To address the aforementioned problems, this application provides a lithium nickel manganese oxide cathode material, a preparation method, and a lithium-ion battery. The lithium nickel manganese oxide cathode material provided in this application combines high operating voltage, energy density, and cycle stability.

[0006] Therefore, the primary objective of this application is to provide a lithium nickel manganese oxide cathode material.

[0007] The second objective of this application is to provide a method for preparing lithium nickel manganese oxide cathode material.

[0008] A third objective of this application is to provide a lithium-ion battery.

[0009] To achieve the first objective of this application, the technical solution of this application provides a lithium nickel manganese oxide cathode material, which includes an internal ordered phase and a surface disordered phase from the inside out; the internal ordered phase is an ordered spinel structure; the surface disordered phase is a disordered spinel structure; wherein, the mass ratio of the surface disordered phase to the cathode material is 0% < m ≤ 1%.

[0010] Compared with existing technologies, the technical advantages achieved by this solution are as follows: The internal ordered phase of the lithium nickel manganese oxide cathode material provided in this application is an ordered spinel structure, with manganese existing in a tetravalent form and nickel-manganese cations arranged in an orderly manner. The internal ordered phase provides high operating voltage and energy density. The surface disordered phase is a disordered spinel structure, with manganese ions existing in a trivalent form, which is beneficial to the cycle stability of lithium nickel manganese oxide and provides higher capacity and faster lithium-ion diffusion rate. Therefore, the lithium nickel manganese oxide cathode material provided in this application combines high operating voltage, energy density, and cycle stability. This material design strategy provides new possibilities for the development of high-performance lithium-ion batteries.

[0011] Furthermore, in related technologies, disordered and ordered phases of nickel manganese cations typically coexist in lithium nickel manganese oxide (LiMO). These phases possess different structures and electrochemical properties, and the ratio of disordered to ordered phases significantly impacts the electrochemical performance of LiMO. The disordered phase, caused by oxygen vacancies resulting from high-temperature calcination, allows manganese to exist in a trivalent form within the crystal structure, which is beneficial for the cycle stability of LiMO and provides higher capacity and a faster lithium-ion diffusion rate. However, excessive disordered phase leads to an overabundance of trivalent manganese ions, resulting in the Jan Taylor effect and manganese dissolution. In ordered phases, manganese exists in a tetravalent form, and nickel manganese cations are arranged in an orderly manner. While ordered LiMO provides a high operating voltage, lithium-ion deintercalation during cycling causes a phase transition in the crystal, leading to severe grain breakage, increased contact between phase surfaces and the electrolyte, numerous side reactions, accelerated capacity reduction, and severe gas generation. This application significantly improves the electrochemical performance, structural stability, and surface properties of the material by optimizing the mass ratio of the disordered phase in the lithium-ion battery cathode material.

[0012] In one technical solution of this application, the chemical formula of the cathode material is: Li a Ni b Mn c M d O 4-h Wherein, M is a doping element, and the doping element is selected from at least one of Ta, Nb, P, Al, Ti, Cr, Mo, Sb, Te, V, Ce, W and La, 1.0≤a≤1.04, 0.45≤b≤0.50, 1.45≤c≤1.50, 0≤d≤0.059, and 0.01<h<0.05.

[0013] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: In the lithium nickel manganese oxide cathode material provided in this application, the lithium content ratio is crucial to ensuring sufficient lithium ions participate in the insertion and extraction during battery charging and discharging. An appropriate amount of lithium can improve the battery's energy density and cycle performance. The nickel content ratio helps to improve the battery's operating voltage and energy density, while also improving the material's conductivity and structural stability. Manganese is one of the main elements constituting the spinel structure, and its content ratio improves the electronic structure and thermal stability of the cathode material. Doping elements enter the 8a and 16c sites of the lithium nickel manganese oxide spinel crystal or replace Ni and Mn in the lattice, reducing the oxygen content in the unstable lattice. The generated MO bond energy is greater than Mn / Ni-O, reducing lattice distortion. Appropriate doping element content can further improve the material's performance, such as reducing lattice distortion and improving cycle stability. Oxygen is a key element constituting the spinel structure of the cathode material, and its content directly affects the material's crystal structure and electrochemical performance. Therefore, the cathode material of this application aims to improve the performance of lithium-ion batteries by optimizing element ratios and doping strategies.

[0014] In one technical solution of this application, the thickness of the surface disordered phase is 30nm-70nm.

[0015] Compared with existing technologies, the technical effects achieved by this solution are as follows: the ideal thickness of the disordered surface phase can provide sufficient active material to participate in electrochemical reactions, improve the diffusion rate of lithium ions, and maintain structural stability; while protecting the core material from direct erosion by the electrolyte, the disordered surface phase can also reduce internal stress caused by volume expansion. The thickness of the disordered surface phase is between 30nm and 70nm, which helps to better absorb and disperse these stresses, prevent material cracking or peeling, and thus extend the battery's lifespan.

[0016] In one technical solution of this application, the doping rate of the doping element in the cathode material is 1.5%-3%.

[0017] Compared with existing technologies, the technical effects achieved by this technology are as follows: the amount of dopant added affects the crystal structure of the cathode material, and the material performance is optimized by changing the lattice constant and cell volume, stabilizing lattice oxygen, improving the kinetic performance and thermodynamic stability of lithium nickel manganese oxide, and realizing the bulk oxygen-locking function; an appropriate amount of dopant improves the order and disorder inside nickel manganese spinel, avoiding severe bulk distortion during cycling.

[0018] To achieve the second objective of this application, the technical solution of this application provides a method for preparing lithium nickel manganese oxide cathode material, used to prepare lithium nickel manganese oxide cathode material as described in any of the above technical solutions, the preparation method comprising:

[0019] S100. Mix the nickel-manganese precursor, lithium salt, and dopant evenly to obtain a mixture.

[0020] S200, The mixture is sintered for the first time to obtain a green body;

[0021] S300, The blank is sintered a second time to obtain the cathode material;

[0022] The second sintering process includes a first-stage sintering and a second-stage sintering. The temperature of the first-stage sintering is no higher than that of the second-stage sintering, and the sintering time of the first-stage sintering is longer than that of the second-stage sintering.

[0023] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: The preparation method of lithium nickel manganese oxide cathode material provided in this application introduces doping elements into the cathode material through the first sintering. Due to the charge compensation mechanism, the doping of high-valence elements will increase the concentration of Mn in the bulk phase. 4+ Transform into Mn 3+ This process improves the order and disorder of the cathode material, preventing severe bulk distortion during cycling. A second sintering stage, performed at a lower temperature, repairs oxygen-deficient structures, resulting in a high-purity, ordered spinel structure. The high-temperature, rapid tempering during the second sintering stage facilitates rapid oxygen desorption from the nickel-manganese spinel surface, forming a disordered phase where manganese is present as Mn. 3+ Having a larger lattice constant will improve capacity and lithium-ion transport rate, and reduce lattice strain and repeated construction of CEI film during charging and discharging.

[0024] In one technical solution of this application, the temperature of the first sintering in S200 is 800℃-1000℃; and / or the time of the first sintering in S200 is 10h-20h.

[0025] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: the first sintering in the temperature range of 800℃-1000℃ can effectively promote the full reaction between raw materials, which helps to introduce doping elements into the cathode material and promotes the uniform distribution of doping elements in the bulk structure of the cathode material; if the time is too short, the raw material reaction may be insufficient and the bulk structure of the cathode material may not develop completely; if the time is too long, it may increase energy consumption, reduce production efficiency, and may cause unnecessary side reactions.

[0026] In one technical solution of this application, the sintering temperature of one stage is 500℃-700℃, and / or the sintering time of one stage is 5h-15h.

[0027] Compared with existing technologies, the technical effects achieved by this technical solution are: by performing a sintering process at a lower temperature, oxygen defect structures can be repaired, resulting in a high-purity ordered spinel structure.

[0028] In one technical solution of this application, the temperature of the two-stage sintering is 800℃-1000℃; and / or the time of the two-stage sintering is 0.5h-2h.

[0029] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: the high-temperature rapid tempering of the two-stage sintering helps the nickel-manganese spinel surface to rapidly lose oxygen and form a disordered phase. The disordered phase on the nickel-manganese spinel surface can effectively improve the morphology of lithium nickel manganese oxide, improve the sphericity of the grains, prevent grain breakage during the electrode rolling process, increase the compaction density of the material, and effectively reduce the specific surface area of ​​lithium nickel manganese oxide, thus reducing the occurrence of side reactions.

[0030] In one technical solution of this application, the process before S300 includes sequentially crushing and sieving the green body.

[0031] Compared with existing technologies, the technical effects achieved by this solution are as follows: Through crushing and sieving, this application can effectively remove large particles or agglomerates that may form during sintering, thus ensuring a uniform particle size distribution in the final product. The treated green body has a higher specific surface area, which helps to enhance the reactivity during sintering, allowing the material to more fully complete lattice restructuring and uniform distribution of dopant elements during the second sintering. Furthermore, it helps to improve material utilization and consistency, reducing the scrap rate due to substandard materials, thereby improving production efficiency. By optimizing these pretreatment steps, the dependence on subsequent second sintering can be reduced while ensuring material quality, helping to lower overall production costs and improve the efficiency and feasibility of the entire preparation process.

[0032] To achieve the third objective of this application, the technical solution of this application provides a lithium-ion battery, which includes the lithium nickel manganese oxide cathode material of any of the above technical solutions.

[0033] Compared with the prior art, the technical effects achieved by adopting this technical solution are as follows: The lithium-ion battery of this technical solution includes the lithium nickel manganese oxide cathode material of any technical solution of this application, and therefore has all the beneficial effects of the lithium nickel manganese oxide cathode material of any technical solution of this application, which will not be repeated here.

[0034] The technical solution provided in this application can achieve at least one of the following effects:

[0035] (1) The lithium nickel manganese oxide cathode material provided in this application has an internal ordered phase that provides high working voltage and energy density, and a surface disordered phase that improves the cycle stability of the cathode material and provides higher capacity and faster lithium-ion diffusion rate. The doping elements reduce the oxygen content of unstable lattice and reduce lattice distortion. This material design strategy provides new possibilities for the development of high-performance lithium-ion batteries.

[0036] (2) The method for preparing lithium nickel manganese oxide cathode material provided in this application involves sintering the cathode material and then rapidly tempering it at high temperature in two stages to construct a disordered phase on its surface. The surface of the lithium nickel manganese oxide crystal is oxygen-deficient, forming oxygen defects. The short tempering time allows the surface of the lithium nickel manganese oxide to form a disordered phase constructed by trivalent manganese ions, and oxygen defects will not occur inside the crystal. At the same time, the dopant in the S100 mixing stage plays a stabilizing role in the lattice of lithium nickel manganese oxide during the subsequent sintering process, making it easier for trivalent manganese ions to form on the surface of lithium nickel manganese oxide, improving the lithium-ion conduction rate of lithium nickel manganese oxide and reducing the phase change that occurs during the lithium-ion insertion and extraction process. It can also improve the morphology of lithium nickel manganese oxide and reduce the specific surface area, reduce the contact with the electrolyte, and inhibit the dissolution of manganese and the occurrence of interfacial side reactions. Attached Figure Description

[0037] Figure 1 is a scanning electron microscope image of the lithium nickel manganese oxide cathode material provided in Embodiment 1 of this application;

[0038] Figure 2 is a scanning electron microscope image of the lithium nickel manganese oxide cathode material provided in Comparative Example 3 of this application;

[0039] Figure 3 is a scanning electron microscope image of the lithium nickel manganese oxide cathode material provided in Comparative Example 2 of this application. Detailed Implementation

[0040] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. Many specific details are set forth in the following description to provide a thorough understanding of this application; however, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0041] The technical solutions of some embodiments of this application are described below with reference to Figures 1 and 2.

[0042] The embodiments of this application provide a lithium nickel manganese oxide cathode material, which includes an internal ordered phase and a surface disordered phase from the inside out; the internal ordered phase is an ordered spinel structure; the surface disordered phase is a disordered spinel structure; wherein, the mass ratio of the surface disordered phase to the cathode material is 0% < m ≤ 1%.

[0043] The lithium nickel manganese oxide cathode material provided in this application has an ordered spinel structure in its internal phase, with manganese existing in a tetravalent form and nickel and manganese cations arranged in an orderly manner. This ordered internal phase provides high operating voltage and energy density. The disordered surface phase is also a disordered spinel structure, with manganese ions existing in a trivalent form, which is beneficial to the cycle stability of lithium nickel manganese oxide and provides higher capacity and faster lithium-ion diffusion rate. Therefore, the lithium nickel manganese oxide cathode material provided in this application combines high operating voltage, energy density, and cycle stability. This material design strategy provides new possibilities for the development of high-performance lithium-ion batteries.

[0044] Specifically, in related technologies, disordered and ordered phases of nickel manganese cations typically coexist in lithium nickel manganese oxide (LiMO). These phases possess different structures and electrochemical properties, and the ratio of disordered to ordered phases significantly impacts the electrochemical performance of LiMO. The disordered phase, caused by oxygen vacancies resulting from high-temperature calcination, allows manganese to exist in a trivalent form within the crystal structure, which is beneficial for the cycle stability of LiMO and provides higher capacity and a faster lithium-ion diffusion rate. However, excessive disordered phase leads to an overabundance of trivalent manganese ions, resulting in the Jan Taylor effect and manganese dissolution. In the ordered phase of LiMO, manganese exists in a tetravalent form, and nickel manganese cations are arranged in an orderly manner. While the ordered phase structure provides a high operating voltage, lithium-ion deintercalation during cycling causes a phase transition in the crystal, leading to severe grain breakage, increased contact between phase surfaces and the electrolyte, numerous side reactions, accelerated capacity reduction, and severe gas generation. This application significantly improves the electrochemical performance, structural stability, and surface properties of the material by optimizing the mass ratio of the disordered phase in the lithium-ion battery cathode material.

[0045] In one embodiment of this application, the chemical formula of the positive electrode material is: Li a Ni b Mn c M d O 4-h Wherein, M is a doping element, and the doping element is selected from at least one of Ta, Nb, P, Al, Ti, Cr, Mo, Sb, Te, V, Ce, W and La, 1.0≤a≤1.04, 0.45≤b≤0.50, 1.45≤c≤1.50, 0≤d≤0.059, and 0.01<h<0.05.

[0046] In the lithium nickel manganese oxide cathode material provided in this application, the lithium content ratio is crucial for ensuring sufficient lithium ions participate in the insertion and extraction during battery charging and discharging. An appropriate amount of lithium can improve the battery's energy density and cycle performance. The nickel content ratio helps improve the battery's operating voltage and energy density, while also improving the material's conductivity and structural stability. Manganese is one of the main elements constituting the spinel structure, and its content ratio improves the electronic structure and thermal stability of the cathode material. Doping elements enter the 8a and 16c sites of the lithium nickel manganese oxide spinel crystal or replace Ni and Mn in the lattice, reducing the oxygen content in the unstable lattice. The generated MO bond energy is greater than Mn / Ni-O, reducing lattice distortion. Appropriate doping element content can further improve the material's performance, such as reducing lattice distortion and improving cycle stability. Oxygen is a key element constituting the spinel structure of the cathode material, and its content directly affects the material's crystal structure and electrochemical performance. Therefore, the cathode material provided in this application aims to improve the performance of lithium-ion batteries by optimizing element ratios and doping strategies.

[0047] In one embodiment of this application, the thickness of the surface disordered phase is 30nm-70nm.

[0048] An ideal surface disordered phase thickness can provide sufficient active material to participate in electrochemical reactions, improve the diffusion rate of lithium ions, and maintain structural stability. While protecting the core material from direct erosion by the electrolyte, the surface disordered phase can also mitigate internal stress caused by volume expansion. A surface disordered phase thickness between 30nm and 70nm helps to better absorb and disperse these stresses, prevent material cracking or peeling, and thus extend the battery's lifespan.

[0049] In one embodiment of this application, the doping rate of the doping element in the cathode material is 1.5%-3%.

[0050] The amount of dopant added affects the crystal structure of the cathode material. By changing the lattice constant and cell volume, the material performance can be optimized, the lattice oxygen can be stabilized, and the kinetic performance and thermodynamic stability of lithium nickel manganese oxide can be improved, thus achieving the bulk oxygen-locking function. Appropriate dopant elements can improve the order and disorder inside nickel manganese spinel, avoiding severe bulk distortion during cycling.

[0051] This application provides a method for preparing lithium nickel manganese oxide cathode material, used to prepare lithium nickel manganese oxide cathode material as described in any of the above embodiments. The preparation method includes:

[0052] S100. Mix the nickel-manganese precursor, lithium salt, and dopant evenly to obtain a mixture.

[0053] S200, The mixture is sintered for the first time to obtain a green body;

[0054] S300, The blank is sintered a second time to obtain the cathode material;

[0055] The second sintering process includes a first-stage sintering and a second-stage sintering. The temperature of the first-stage sintering is no higher than that of the second-stage sintering, and the sintering time of the first-stage sintering is longer than that of the second-stage sintering.

[0056] The method for preparing lithium nickel manganese oxide cathode material provided in this application introduces doping elements into the cathode material through a first sintering process. Due to the charge compensation mechanism, the doping of high-valence elements will increase the concentration of Mn in the bulk phase. 4+ Transform into Mn 3+ This process improves the order and disorder of the cathode material, preventing severe bulk distortion during cycling. A second sintering stage, performed at a lower temperature, repairs oxygen-deficient structures, resulting in a high-purity, ordered spinel structure. The high-temperature, rapid tempering during the second sintering stage facilitates rapid oxygen desorption from the nickel-manganese spinel surface, forming a disordered phase where manganese is present as Mn. 3+ Having a larger lattice constant will improve capacity and lithium-ion transport rate, and reduce lattice strain and repeated construction of CEI film during charging and discharging.

[0057] For example, the nickel-manganese precursor in the embodiments of this application is selected from nickel-manganese composite hydroxide.

[0058] For example, the lithium salt in the embodiments of this application is selected from at least one of lithium carbonate (Li2CO3), lithium oxalate, and lithium hydroxide (LiOH).

[0059] For example, the dopant in the embodiments of this application is selected from at least one of Ta2O5, Nb2O5, P2O5, Al2O3, TiO2, Cr2O3, Mo2O3, Sb2O3, TeO2 and La2O3.

[0060] In one embodiment of this application, in S200, the temperature of the first sintering is 800°C-1000°C; and / or in S200, the time of the first sintering is 10h-20h.

[0061] The first sintering at a temperature range of 800℃-1000℃ can effectively promote the full reaction between raw materials, which helps to introduce doping elements into the cathode material and promotes the uniform distribution of doping elements in the bulk structure of the cathode material. If the time is too short, the raw material reaction may be insufficient and the bulk structure of the cathode material may not be fully developed. If the time is too long, it may increase energy consumption, reduce production efficiency, and may cause unnecessary side reactions.

[0062] In one embodiment of this application, the sintering temperature of one stage is 500℃-700℃; and / or the sintering time of one stage is 5h-15h.

[0063] By performing a sintering process at a lower temperature, oxygen defect structures can be repaired, resulting in a high-purity, ordered spinel structure.

[0064] In one embodiment of this application, the temperature of the two-stage sintering is 800℃-1000℃; and / or the time of the two-stage sintering is 0.5h-2h.

[0065] Specifically, the high-temperature rapid tempering of the two-stage sintering helps the nickel-manganese spinel surface to rapidly lose oxygen and form a disordered phase. This disordered phase on the nickel-manganese spinel surface can effectively improve the morphology of lithium nickel manganese oxide, improve the sphericity of the grains, prevent grain breakage during the electrode rolling process, increase the compaction density of the material, and effectively reduce the specific surface area of ​​lithium nickel manganese oxide, thus reducing the occurrence of side reactions.

[0066] In one embodiment of this application, the process before S300 includes sequentially crushing and sieving the billet.

[0067] This application utilizes crushing and sieving to effectively remove large particles or agglomerates that may form during sintering, ensuring a uniform particle size distribution in the final product. The treated green body has a higher specific surface area, which helps enhance the reactivity during sintering, allowing for more complete lattice restructuring and uniform distribution of dopant elements during the second sintering. Furthermore, it improves material utilization and consistency, reducing scrap rates due to substandard materials, thereby increasing production efficiency. By optimizing these pretreatment steps, reliance on subsequent second sintering can be reduced while maintaining material quality, contributing to lower overall production costs and improving the efficiency and feasibility of the entire preparation process.

[0068] The embodiments of this application provide a lithium-ion battery, which includes the lithium nickel manganese oxide cathode material of any of the above embodiments.

[0069] The lithium-ion battery of this embodiment includes the lithium nickel manganese oxide cathode material of any embodiment of this application, and therefore has all the beneficial effects of the lithium nickel manganese oxide cathode material of any embodiment of this application, which will not be repeated here.

[0070]

Example 1

[0071] This embodiment provides a lithium nickel manganese oxide cathode material, and the specific operation is as follows.

[0072] S100, 100g of Ni 0.5 Mn 1.5 (OH)4, 23.03g of Li2CO3, 0.615g of WO3, and 3.25g of NH4H2PO4 were added to a high-speed mixer and mixed at 600rpm for 30min to obtain a mixture.

[0073] S200: Heat the mixture to 1030℃ at 2℃ / min, hold for 15h, and perform the first sintering to obtain the green body;

[0074] S300: The blank is heated to 750℃ at 2℃ / min and held for 10h for first-stage sintering; then the temperature is rapidly increased to 900℃ at 5℃ / min and held for 1h for second-stage sintering to obtain lithium nickel manganese oxide cathode material.

[0075]

Example 2

[0076] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 1.17g of Ta2O5, and 3.25g of NH4H2PO4.

[0077]

Example 3

[0078] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.765g of MoO3 and 3.25g of NH4H2PO4.

[0079]

Example 4

[0080] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.84g of TeO2 and 3.25g of NH4H2PO4.

[0081]

Example 5

[0082] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.675g of Nb2O5 and 3.25g of NH4H2PO4.

[0083]

Example 6

[0084] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.27g of Al2O3 and 3.25g of NH4H2PO4.

[0085]

Example 7

[0086] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.765g of Sb2O3 and 3.25g of NH4H2PO4.

[0087]

Example 8

[0088] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.405g of Cr2O3 and 3.25g of NH4H2PO4.

[0089]

Example 9

[0090] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.855g of La2O3 and 3.25g of NH4H2PO4.

[0091]

Example 10

[0092] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.42g of TiO2 and 3.25g of NH4H2PO4.

[0093]

Example 11

[0094] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.956g of V2O5 and 3.25g of NH4H2PO4.

[0095]

Example 12

[0096] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that in S100, the mixture includes: 100g of Ni 0.5 Mn 1.5 (OH)4, 22.59g of Li2CO3, 0.905g of CeO2 and 3.25g of NH4H2PO4.

[0097]

Example 13

[0098] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1. The difference is that in S300, the temperature of the second-stage sintering is 950°C and the time of the second-stage sintering is 0.5h.

[0099]

Example 14

[0100] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1. The difference is that in S300, the temperature of the second-stage sintering is 925°C and the time of the second-stage sintering is 0.75h.

[0101]

Example 15

[0102] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1. The difference is that in S300, the temperature of the second-stage sintering is 875°C and the time of the second-stage sintering is 1.25h.

[0103]

Example 16

[0104] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1. The difference is that in S300, the temperature of the second-stage sintering is 850°C and the time of the second-stage sintering is 1.5h.

[0105]

Example 17

[0106] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1. The difference is that in S300, the temperature of the second-stage sintering is 825°C and the time of the second-stage sintering is 2 hours.

[0107]

Example 18

[0108] This embodiment provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1. The difference is that in S300, the temperature of the second-stage sintering is 800°C and the time of the second-stage sintering is 2.5h.

[0109] Comparative Example 1

[0110] This comparative example provides a lithium nickel manganese oxide cathode material, and the specific operation is as follows.

[0111] S100, 100g of Ni 0.5 Mn 1.5 (OH)4 and 20.73g of Li2CO3 were added to a high-speed mixer and mixed at 600rpm for 30min to obtain a mixture.

[0112] S200: Heat the mixture to 1030℃ at 2℃ / min, hold for 15h, and perform the first sintering to obtain the green body;

[0113] S300: The blank is heated to 750℃ at 2℃ / min and held for 10h to perform a first-stage sintering to obtain lithium nickel manganese oxide cathode material.

[0114] Comparative Example 2

[0115] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that step S300 is omitted.

[0116] Comparative Example 3

[0117] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 1, except that only one sintering stage is performed in S300.

[0118] Comparative Example 4

[0119] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is the same as in Example 2, except that only one sintering stage is performed in S300.

[0120] Comparative Example 5

[0121] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 3. The difference is that in S300, only one sintering stage is performed.

[0122] Comparative Example 6

[0123] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 4. The difference is that in S300, only one sintering stage is performed.

[0124] Comparative Example 7

[0125] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 5. The difference is that in S300, only one sintering stage is performed.

[0126] Comparative Example 8

[0127] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 6. The difference is that in S300, only one sintering stage is performed.

[0128] Comparative Example 9

[0129] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 7. The difference is that in S300, only one sintering stage is performed.

[0130] Comparative Example 10

[0131] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 8. The difference is that in S300, only one sintering stage is performed.

[0132] Comparative Example 11

[0133] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 9. The difference is that in S300, only one sintering stage is performed.

[0134] Comparative Example 12

[0135] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 10. The difference is that in S300, only one sintering stage is performed.

[0136] Comparative Example 13

[0137] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 11. The difference is that in S300, only one sintering stage is performed.

[0138] Comparative Example 14

[0139] This comparative example provides a lithium nickel manganese oxide cathode material, the preparation method of which is described in Example 12. The difference is that in S300, only one sintering stage is performed.

[0140] Lithium-manganese oxide cathode materials from Examples 1-18 and Comparative Examples 1-14 were used as cathode materials to prepare lithium-ion batteries. The lithium-ion batteries mainly consist of a cathode sheet, a cathode sheet, a separator, and an electrolyte. The cathode material, as the active material, is mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1 to obtain the cathode sheet. The separator is a PP or PE film. The cathode sheet is a lithium sheet. The electrolyte consists of lithium salt (such as LiPF6), solvent (such as carbonates), and additives (such as stabilizers). The cathode sheet, separator, and cathode sheet are sequentially stacked, and a cell is obtained through a stacking or winding process. The lithium-ion battery is then obtained through baking, electrolyte injection, formation, and packaging processes.

[0141] Furthermore, the electrochemical performance of lithium-ion batteries prepared using the lithium nickel manganese oxide cathode materials of Examples 1-18 and Comparative Examples 1-14 as active materials was tested, and the results are shown in Tables 1 and 2. Specifically, the test steps were as follows: first, two cycles of charge and discharge at a current of 0.1C were performed; then, one cycle of charge and discharge was performed at currents of 0.33C and 1C respectively; then, 100 cycles of charge and discharge were performed at a current of 2C; and finally, 5 cycles of charge and discharge were performed at a current of 3C.

[0142] Table 1

[0143] Specifically, under the same d value, Li a Ni b Mn c M d O 4-h The charging capacity below 4.4V in the first cycle is defined as X1, and Li a Ni b Mn c M d O 4-h If the initial charging capacity is defined as X2, then the overall disorder degree is Y1 = X1 / X2. Let Li... a Ni b Mn c M d O 4-h The surface disorder is defined as Y2, where Y2 = the difference between Y1 of the lithium nickel manganese oxide cathode material obtained by two-stage sintering and Y1 of the lithium nickel manganese oxide obtained by only one-stage sintering (for example, in Example 1, Y2 is the difference between Y1 in Example 1 and Y1 in Comparative Example 3, 9.54 - 7.02 = 2.52); the Li obtained by only one-stage sintering a Ni b Mn c M d O 4-hThe overall disorder is defined as Y1', and the Li obtained by only one sintering stage a Ni b Mn c O 4-h The overall disorder is defined as Y1”, and the doping rate Ф = Y1' - Y1 (for example, in Example 1, Ф is the difference between Y1 in Comparative Example 3 and Y1 in Comparative Example 1, 7.02 - 4.67 = 2.35). The surface disorder phase mass ratio W = 1 - Y2.

[0144] Table 2

[0145] In this application, the 4V plateau percentage of a battery refers to the proportion of time or capacity during the discharge process when the battery voltage is maintained at 4V. When the 4V plateau percentage of a battery meets the requirement of 8%-10%, the battery possesses high operating voltage, energy density, and cycle stability. As can be seen from the embodiments and comparative examples, the battery in the embodiments of the present invention possesses high operating voltage, energy density, and cycle stability.

[0146] Specifically, as shown in Tables 1-2, in Examples 1-18, the element doping rate was approximately 1.5%-3.0%, and the molar ratio of elements in the chemical formula of the prepared lithium nickel manganese oxide was also roughly within the range of element doping rates described above. The doping elements are incorporated into the crystal lattice, but may also agglomerate on the surface of lithium nickel manganese oxide due to factors such as larger atomic radii, resulting in different doping rates for different elements. Element doping can significantly improve the disorder of lithium nickel manganese oxide, enhancing its 4V plateau and rate performance. Furthermore, doping elements in the bulk phase of lithium nickel manganese oxide can significantly increase its lattice constant, which is the main reason for the improved rate performance. However, compared to Comparative Examples 1-14, their cathode materials do not include the surface disordered phase, and the lithium nickel manganese oxide exhibits an overall ordered / disordered homogeneous material. The P-doped samples showed significantly poor rate performance, with P being more readily absorbed by PO4. 4- It exists in the nickel-manganese spinel bulk phase, hindering lithium-ion diffusion.

[0147] In addition, the two-stage sintering and high-temperature tempering form a nickel-manganese spinel structure with surface oxygen defects, which accounts for 8%-10% of the 4V charging platform, while the 4V charging platform of ordinary calcination process accounts for 6%-7%. By constructing a surface disordered phase without spinel structure on the surface of the cathode material through two-stage sintering, the 4V platform of lithium nickel manganese oxide with low-temperature oxygen repair can be raised again.

[0148] Furthermore, the presence of a disordered phase can effectively extend the lifespan of lithium nickel manganese oxide. Specifically, due to the presence of the disordered phase, stress deformation caused by phase transformation during lithium ion charging and discharging is reduced, the formation of exposed crystal faces is decreased, and the cycle performance of lithium nickel manganese oxide is improved. However, excessive disordered phase is detrimental to the cycle performance of lithium nickel manganese oxide, as a higher proportion of disordered phase will result in more Mn. 3+ Due to the Jan Taylor effect, Mn 3+ The presence of [unspecified substance] is detrimental to lattice stability, making lithium nickel manganese oxide prone to lattice distortion, leading to severe side reactions and reducing its cycle performance. Therefore, this scheme aims to obtain a lithium nickel manganese oxide cathode material with excellent performance by rationally constructing the ordered / disordered ratio and distribution of lithium nickel manganese oxide.

[0149] As can be seen from Figure 1 and the test data in the table of Example 1, after two-stage sintering, the obtained lithium nickel manganese oxide has a D50 value of 12.16 μm and a BET value of 0.40 μm. 2 The lithium nickel manganese oxide (LiMO) exhibits a smooth, octahedral structure without truncated corners, with good particle dispersion and no excessive large particles or agglomeration. The assembled button cell demonstrates a high 2C discharge specific capacity of 129.3 mAh / g, a 2C / 0.1C discharge rate specific capacity ratio of 101.1%, a 3C discharge specific capacity of 117.4 mAh / g, and a 4V discharge plateau percentage of 9.54%. After 100 cycles at 2C, the assembled button cell retains 94.0% of its capacity, as shown in Table 1. The increased 4V plateau percentage and improved rate performance demonstrate that the disordered phase proportion of the lithium nickel manganese oxide prepared by the two-stage sintering process is increased.

[0150] As can be seen from the test data in Figure 2 and Comparative Example 3, the lithium nickel manganese oxide obtained after two-stage sintering oxygen repair has a D50 value of 11.43 μm and a BET value of 0.40 μm. 2 The lithium nickel manganese oxide (LiMO) exhibits an octahedral spinel structure, but shows some agglomeration. The assembled coin cell has a 2C discharge specific capacity of 128 mAh / g, a 2C / 0.1C discharge rate specific capacity ratio of 97.0%, a 3C discharge specific capacity of 114.6 mAh / g, and a 4V discharge plateau percentage of 7.02%. After 100 cycles at 2C, the assembled coin cell retains 92% of its capacity, as shown in Table 1. The low contribution of the 4V plateau discharge, along with the relatively low rate and cycle performance, demonstrates that the prepared lithium nickel manganese oxide after oxygen remediation exists primarily as an ordered phase.

[0151] As can be seen from Figure 3 and the test data in the table of Comparative Example 2, after a sintering process, the obtained lithium nickel manganese oxide has a D50 value of 9.86 μm and a BET value of 0.39 μm. 2The lithium nickel manganese oxide (LiNCO) exhibits a smooth, truncated octahedral structure with good particle dispersion, exhibiting minimal large particles and agglomeration. The assembled button cell demonstrates a high 2C discharge specific capacity of 128.6 mAh / g, a 3C discharge specific capacity of 117.4 mAh / g, and a 4V discharge plateau percentage of 12.79%. After 100 cycles at 2C, the capacity retention of the assembled button cell is 91.5%, as shown in Table 1. The excessively high 4V plateau capacity contribution and rate performance demonstrate that the lithium nickel manganese oxide obtained from single-stage sintering possesses a high proportion of disordered phase. However, the excessively high Mn content in the disordered phase... 3+ The Ginger-Taylor effect can occur, leading to a severe decline in cycle performance. Therefore, this solution addresses this by rationally designing the ordered / disordered phase ratio of lithium nickel manganese oxide.

[0152] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0153] The use of terms such as "S100", "S200", and "S300" in this specification is for the convenience of describing the embodiments of this application. This application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited by the order of the specific embodiments described above.

[0154] While this application discloses the above information, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application shall be determined by the scope defined in the claims.

Claims

1. A lithium nickel manganese oxide cathode material, wherein, The cathode material comprises an internal ordered phase and a surface disordered phase from the inside out; The internal ordered phase is an ordered spinel structure; The disordered phase on the surface has a disordered spinel structure; The surface disordered phase accounts for 0% < m ≤ 1% of the mass of the cathode material.

2. The lithium nickel manganese oxide cathode material according to claim 1, wherein, The chemical formula of the cathode material is: Li a Ni b Mn c M d O 4-h ; Wherein, M is a doping element, and the doping element is selected from at least one of Ta, Nb, P, Al, Ti, Cr, Mo, Sb, Te, V, Ce, W and La, with 1.0≤a≤1.04, 0.45≤b≤0.50, 1.45≤c≤1.50, 0≤d≤0.059, and 0.01<h<0.

05.

3. The lithium nickel manganese oxide cathode material according to claim 1 or 2, wherein, The thickness of the disordered phase on the surface is 30nm-70nm.

4. The lithium nickel manganese oxide cathode material according to claim 2, wherein, The doping rate of the doping element in the cathode material is 1.5%-3%.

5. A method for preparing a lithium nickel manganese oxide cathode material, used to prepare the lithium nickel manganese oxide cathode material as described in any one of claims 1-4, wherein, The preparation method includes: S100. Mix the nickel-manganese precursor, lithium salt, and dopant evenly to obtain a mixture. S200. The mixture is sintered for the first time to obtain a green body; S300: The blank is sintered a second time to obtain the positive electrode material; The second sintering includes a first-stage sintering and a second-stage sintering. The temperature of the first-stage sintering is not higher than that of the second-stage sintering, and the time of the first-stage sintering is longer than that of the second-stage sintering.

6. The preparation method according to claim 5, wherein, In S200, the temperature of the first sintering is 800℃-1000℃; and / or In S200, the first sintering time is 10h-20h.

7. The preparation method according to claim 5 or 6, wherein, The sintering temperature of the first section is 500℃-700℃; and / or The sintering time for the first stage is 5-15 hours.

8. The preparation method according to any one of claims 5-7, wherein, The sintering temperature for the two stages is 800℃-1000℃; and / or The sintering time for the two stages is 0.5h-2h.

9. The preparation method according to any one of claims 5-8, wherein, Before S300, the blank is also subjected to crushing and sieving processes in sequence.

10. A lithium-ion battery, wherein, The lithium-ion battery includes the lithium nickel manganese oxide cathode material as described in any one of claims 1-4.

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