A lithium nickel manganese oxide spinel positive electrode material, a preparation method and application thereof

Abstract

This invention discloses a lithium nickel manganese oxide spinel cathode material, its preparation method, and its application, belonging to the field of battery material technology. The lithium nickel manganese oxide spinel cathode material includes a lithium nickel manganese oxide bulk, the molecular formula of which is Li. x Ni y Mn 2‑y O4, where x = 0.8–1.2 and y = 0.4–0.6; the lithium nickel manganese oxide substrate is doped with dopant elements, a modified layer is formed on the surface of the lithium nickel manganese oxide substrate, and a coating layer is formed on the surface of the modified layer; the dopant elements include at least two selected from Ta, Nb, La, Y, Te, Fe, Ti, W, Mo, Ge, and Na; the modified layer contains at least two selected from Mg, Al, P, Zr, Cl, and F; the coating layer contains a soft conductive material. This lithium nickel manganese oxide spinel cathode material has high initial charge-discharge capacity and capacity retention, and can be further used to prepare cathode sheets and batteries with better performance.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a lithium nickel manganese oxide spinel cathode material, its preparation method, and its application. Background Technology

[0002] Spinel-phase lithium nickel manganese oxide (LiMO) is a lithium-ion battery cathode with ultra-high plateau voltage, theoretical capacity, and energy density. For example, its plateau voltage can reach 4.7V, its theoretical capacity can reach 147mAh / g, and its energy density can reach ≥650Wh / kg. From the perspective of energy density and cost, this material has great market potential. Furthermore, spinel-structured LiMO also has the advantages of very stable thermochemical structure and good rate performance. However, LiMO performs poorly in cycle storage, mainly because during charging, the Ni element in the material is oxidized to +4, resulting in an extremely high delithiation voltage and strong electropositivity, which causes electrolyte decomposition and induces a series of failure reactions.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium nickel manganese oxide spinel cathode material, its preparation method and application, in order to solve or improve the above-mentioned technical problems.

[0005] This invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a lithium nickel manganese oxide spinel cathode material, comprising a lithium nickel manganese oxide substrate, wherein the molecular formula of the lithium nickel manganese oxide substrate is Li. x Ni y Mn 2-y O4, where x = 0.8~1.2, y = 0.4~0.6;

[0007] The lithium nickel manganese oxide body is doped with doping elements, and a modified layer is formed on the surface of the lithium nickel manganese oxide body. The surface of the modified layer has a coating layer.

[0008] The doping elements include at least two of Ta, Nb, La, Y, Te, Fe, Ti, W, Mo, Ge, and Na; the modifying elements contained in the modified layer include at least two of Mg, Al, P, Zr, Cl, and F;

[0009] The coating layer contains a soft conductive material.

[0010] In an optional embodiment, the lithium nickel manganese oxide spinel further includes at least one of the following characteristics:

[0011] Feature 1: D of lithium nickel manganese oxide spinel cathode material v10 The range is 1μm to 4μm, D v50 The diameter is 4μm~8μm, Dv90 The thickness ranges from 6μm to 20μm.

[0012] Feature 2: The content of each doping element in the lithium nickel manganese oxide spinel cathode material is 500ppm~10000ppm;

[0013] Feature 3: The content of each modifying element in the lithium nickel manganese oxide spinel cathode material is 500ppm~50000ppm;

[0014] Feature 4: The mass of the coating layer is 0.5%~5% of that of the lithium nickel manganese oxide spinel cathode material;

[0015] Feature 5: In lithium nickel manganese oxide spinel cathode materials, the area in direct contact with the electrolyte is less than 10% of the total surface area of ​​the lithium nickel manganese oxide spinel cathode material;

[0016] Feature 6: The 0.1C discharge specific capacity of the lithium nickel manganese oxide spinel cathode material is not less than 138 mAh / g.

[0017] In a second aspect, the present invention provides a method for preparing a lithium nickel manganese oxide spinel cathode material as described in the foregoing embodiments, comprising the following steps: modifying a lithium nickel manganese oxide substrate doped with doping elements to form a modified layer on the surface of the lithium nickel manganese oxide substrate doped with doping elements; and preparing a coating layer on the surface of the modified layer.

[0018] In an optional embodiment, the preparation of the lithium nickel manganese oxide body doped with the dopant element includes: mixing a nickel manganese precursor, a lithium source, and a dopant that provides the dopant element to obtain a first mixture; and performing a first sintering on the first mixture to obtain the lithium nickel manganese oxide body doped with the dopant element.

[0019] In an optional embodiment, the temperature of the first sintering is 600℃~1000℃, and / or the time of the first sintering is 5h~20h.

[0020] In an optional embodiment, modifying the lithium nickel manganese oxide bulk doped with doped elements includes: mixing the lithium nickel manganese oxide bulk doped with doped elements with a modifier that provides the modifying elements to obtain a second mixture; and subjecting the second mixture to a second sintering.

[0021] In an optional embodiment, the temperature of the second sintering is 600℃~700℃, and / or the time of the second sintering is 5h~10h.

[0022] In an optional implementation, the lithium nickel manganese oxide body doped with doped elements is first subjected to roller crushing and airflow crushing to obtain crushed material; then the crushed material is sintered a second time.

[0023] In an optional implementation, the roller spacing is 1mm to 3mm during the roller crushing process.

[0024] In an optional embodiment, the preparation of the coating layer includes: directly fusing and coating the lithium nickel manganese oxide body with doped elements having a modified layer with the coating material, and without sintering and / or carbonization after coating.

[0025] In an optional embodiment, the coating material is fused and coated in the form of a semi-solid liquid or a highly viscous liquid.

[0026] In an optional embodiment, the coating material is a soft conductive material.

[0027] In an optional embodiment, the soft conductive material includes at least one of conductive asphalt and conductive polymer.

[0028] In an optional embodiment, the conductive polymer includes at least one of polyaniline conductive agent, polypyrrole conductive agent, and PEDOT:PSS conductive agent.

[0029] In an optional embodiment, the particle size of the coated material is less than or equal to 2 μm.

[0030] In an optional embodiment, the fusion coating temperature is 30°C to 120°C, and / or the fusion coating is performed at a rotation speed of 1000 rpm to 5000 rpm.

[0031] Thirdly, the present invention provides a positive electrode sheet, wherein the active material in the positive electrode sheet includes the lithium nickel manganese oxide spinel positive electrode material of the aforementioned embodiments.

[0032] Fourthly, the present invention provides a battery comprising the positive electrode sheet of the aforementioned embodiments.

[0033] The beneficial effects of this invention include:

[0034] The method for preparing lithium nickel manganese oxide spinel cathode material provided by this invention uses lithium nickel manganese oxide as the bulk material and dops it with doping elements. On the one hand, this is beneficial to enhance the single-crystallization morphology of the lithium nickel manganese oxide bulk material, thereby changing the bulk phase and improving the internal lattice stability of the material. On the other hand, it is beneficial to reduce the content of trivalent manganese. In addition, it is also beneficial to improve the conductivity of the material. Surface modification of the lithium nickel manganese oxide bulk material doped with doping elements to form a modification layer is beneficial to improve the particle dispersion of the lithium nickel manganese oxide bulk material. P in this layer is also beneficial to improve the discharge capacity and first-time efficiency of the lithium nickel manganese oxide bulk material and promote the appearance of the (100) cross section. By coating the surface of the modified layer with a soft conductive material, the positive electrode and the electrolyte can be completely isolated. This prevents the high-valence transition metal of the positive electrode from contacting the electrolyte during full-charge storage, thereby mitigating the high-voltage decomposition of the electrolyte. This not only effectively isolates the contact between the electrolyte and the positive electrode material and alleviates the occurrence of side reactions, but also effectively improves the structural stability, conductivity, initial efficiency, capacity, and high-temperature cycling capacity retention of the lithium nickel manganese oxide spinel positive electrode material. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 The XRD crystal diffraction pattern of the two sintered materials in Example 1;

[0037] Figure 2 The image shows the SEM (Scanning Electron Microscope) morphology of the lithium nickel manganese oxide spinel cathode material in Example 1.

[0038] Figure 3 The image shows the SEM (scanning electron microscope) morphology of the lithium nickel manganese oxide spinel cathode material in Comparative Example 2.

[0039] Figure 4 The above are the charge-discharge curves of lithium nickel manganese oxide spinel cathode materials in Example 1 and Comparative Example 4. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0041] The following is a detailed description of the lithium nickel manganese oxide spinel cathode material, its preparation method, and its application provided by the present invention.

[0042] This invention proposes a lithium nickel manganese oxide spinel cathode material, comprising a lithium nickel manganese oxide bulk, the molecular formula of which is Li. x Ni y Mn 2-y O4, where x = 0.8~1.2, y = 0.4~0.6;

[0043] The aforementioned lithium nickel manganese oxide substrate is doped with doping elements, and a modified layer is formed on the surface of the aforementioned lithium nickel manganese oxide substrate, with a coating layer on the surface of the modified layer.

[0044] The doping elements include at least two of Ta, Nb, La, Y, Te, Fe, Ti, W, Mo, Ge, and Na; the modifying elements contained in the modified layer include at least two of Mg, Al, P, Zr, Cl, and F.

[0045] The coating layer contains a soft conductive material.

[0046] In this invention, doping elements are beneficial in two ways: firstly, they enhance the single-crystal morphology of lithium nickel manganese oxide, thereby altering the bulk phase and improving the internal lattice stability of the material; secondly, they reduce oxygen loss during synthesis, lowering the content of trivalent manganese; and thirdly, they improve the conductivity of the material. Modifying elements are beneficial in improving the particle dispersion of lithium nickel manganese oxide, with P being particularly beneficial in improving the discharge capacity and first-time efficiency of the lithium nickel manganese oxide, promoting the appearance of the (100) cross section. The soft conductive material in the coating layer can completely isolate the positive electrode from the electrolyte, thus preventing the high-valence transition metal of the positive electrode from contacting the electrolyte during full-charge storage, thereby alleviating the high-voltage decomposition of the electrolyte.

[0047] In some embodiments, under a scanning electron microscope, the lithium nickel manganese oxide spinel cathode material exhibits a dispersed morphology, and the D of the lithium nickel manganese oxide spinel cathode material powder is shown. v50 It can be 4μm to 8μm, such as 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm or 8μm, or any other value within the range of 4μm to 8μm.

[0048] The lithium nickel manganese oxide spinel cathode material with the above-mentioned particle size has good dispersibility and a relatively regular morphology, which is conducive to having a uniform coating layer, better isolating the electrolyte and cathode material from contact and mitigating side reactions.

[0049] In some embodiments, the content of each dopant element in the lithium nickel manganese oxide spinel cathode material can be 500ppm to 10000ppm, such as 500ppm, 1000ppm, 2000ppm, 4000ppm, 6000ppm, 8000ppm or 10000ppm, or any other value in the range of 500ppm to 10000ppm.

[0050] If the amount of dopant is too high, it will hinder the dopant from entering the material, and the uniformity and the material's specific capacity will be affected.

[0051] In some embodiments, the content of each modified element in the lithium nickel manganese oxide spinel cathode material can be 500ppm to 50000ppm, such as 500ppm, 1000ppm, 2000ppm, 5000ppm, 8000ppm, 10000ppm, 15000ppm, 20000ppm, 25000ppm, 30000ppm, 35000ppm, 40000ppm, 45000ppm or 50000ppm, or any other value within the range of 500ppm to 50000ppm.

[0052] The mass of the coating layer can be 0.5% to 5% of the lithium nickel manganese oxide spinel cathode material, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, or any other value within the range of 0.5% to 5%.

[0053] If the coating layer has too much mass, the interfacial impedance of the material surface may increase significantly, and the mass of the modifying element itself has no electrochemical activity, which will greatly affect the capacity.

[0054] The aforementioned coating layer contains a soft conductive material. This type of material is relatively soft and viscous, and has good flexibility and ductility. It can be directly coated onto the surface of the modified layer by mechanical fusion to obtain the finished product without the need for additional sintering operations.

[0055] In some embodiments, the area in the lithium nickel manganese oxide spinel cathode material that is in direct contact with the electrolyte is less than 10% of the total surface area of ​​the lithium nickel manganese oxide spinel cathode material. For example, the area in the lithium nickel manganese oxide spinel cathode material that is in direct contact with the electrolyte is almost zero.

[0056] In some embodiments, the 0.1C discharge specific capacity of the lithium nickel manganese oxide spinel cathode material is not less than 138 mAh / g.

[0057] As mentioned above, the lithium nickel manganese oxide spinel cathode material provided by this invention has advantages such as high conductivity, high initial efficiency, high capacity, and high-temperature cycle capacity retention.

[0058] Accordingly, the present invention provides a method for preparing a lithium nickel manganese oxide spinel cathode material as described in the foregoing embodiments, comprising the following steps: modifying a lithium nickel manganese oxide substrate doped with doping elements to form a modified layer on the surface of the lithium nickel manganese oxide substrate doped with doping elements; and preparing a coating layer on the surface of the modified layer.

[0059] In some embodiments, the preparation of a lithium nickel manganese oxide body doped with a dopant element may include: mixing a nickel manganese precursor, a lithium source, and a dopant that provides the dopant element to obtain a first mixture; and subjecting the first mixture to a first sintering to obtain a lithium nickel manganese oxide body doped with a dopant element.

[0060] The aforementioned nickel-manganese precursor can be a precursor in the form of hydroxide, an precursor in the form of oxide, or a precursor in the form of carbonate.

[0061] The preparation of the nickel-manganese precursor mentioned in this invention can be carried out by referring to the usual preparation methods of related precursors, or it can be purchased directly.

[0062] By way of example, the lithium source may include, but is not limited to, at least one of lithium hydroxide, lithium carbonate, lithium sulfate and lithium acetate.

[0063] The molar ratio of the lithium source to the transition metal element in the nickel-manganese precursor can be from 0.48:1 to 0.55:1, such as 0.48:1, 0.49:1, 0.5:1, 0.51:1, 0.52:1, 0.53:1, 0.54:1 or 0.55:1, etc.

[0064] Dopant can be in the form of oxides, chlorides, fluorides, phosphates, or elemental forms corresponding to the dopant element. The amount of dopant used should be such that the content of each dopant element in the lithium nickel manganese oxide spinel cathode material is 500ppm to 10000ppm.

[0065] For example, the temperature for the first sintering can be 600℃~1000℃, such as 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, or any other value within the range of 600℃~1000℃.

[0066] The first sintering time can be 5h to 20h, such as 5h, 8h, 10h, 12h, 15h, 18h or 20h, or any other value within the range of 5h to 20h.

[0067] In this invention, modifying a lithium nickel manganese oxide substrate doped with doped elements may include: mixing the lithium nickel manganese oxide substrate doped with doped elements with a modifier that provides the modifying elements to obtain a second mixture; and subjecting the second mixture to a second sintering.

[0068] Modifiers can be various forms that can form a uniform surface dispersion, such as fluorides, oxides, elements, chlorides, sulfides, and sulfates corresponding to the modifying elements. The amount of modifier used should be sufficient to ensure that the content of each modifying element in the lithium nickel manganese oxide spinel cathode material is 500ppm to 50000ppm.

[0069] For example, the temperature for the second sintering can be 600℃~700℃, such as 600℃, 620℃, 650℃, 680℃ or 700℃, or any other value within the range of 600℃~700℃.

[0070] The second sintering time can be 5h to 10h, such as 5h, 6h, 7h, 8h, 9h or 10h, or any other value within the range of 5h to 10h.

[0071] In some implementations, the lithium nickel manganese oxide body doped with doped elements can first be subjected to roller crushing and airflow crushing to obtain crushed material; then the crushed material can be sintered a second time.

[0072] During the coarse crushing process of double rollers, the roller spacing can be 1mm to 3mm, such as 1mm, 1.5mm, 2mm, 2.5mm or 3mm.

[0073] By first crushing and then sintering a second time, it is beneficial to better mix the lithium nickel manganese oxide bulk material with the modifier, resulting in a better modification effect.

[0074] As an example, the preparation of the coating layer may include: directly fusing and coating the lithium nickel manganese oxide substrate with doped elements and the coating material, without sintering and / or carbonization after coating.

[0075] For example, the soft conductive material may include at least one of conductive bitumen and conductive polymer. The conductive polymer may, by way of example but not limitation, include at least one of polyaniline conductive agent, polypyrrole conductive agent, and PEDOT:PSS conductive agent.

[0076] In some implementations, the particle size of the coating material is less than or equal to 2 μm to achieve a better coating effect, such as more uniform coating.

[0077] For example, the coating material is fused and coated in a semi-solid liquid form.

[0078] The fusion coating temperature can be 30℃~120℃, such as 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃, or other values ​​within the range of 30℃~120℃.

[0079] Fusion coating can be performed at speeds of 1000 rpm to 5000 rpm (e.g., 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm, or 5000 ppm).

[0080] The soft conductive material used in this invention can be uniformly coated onto the material surface using a mechanical method. This process is a physical process, which avoids the reaction between the coating material and the doped lithium nickel manganese oxide substrate with the modified layer at high temperatures, thus preventing damage to the crystal lattice of the lithium nickel manganese oxide substrate. Furthermore, the soft conductive material with sufficiently high viscosity is indistinguishable from a solid when no external force is applied, but it will exhibit an extremely viscous liquid state under mechanical force. Therefore, it is only necessary to fuse and coat the material in a semi-solid liquid or high-viscosity liquid form according to the equipment and material characteristics.

[0081] It should be noted that in existing coating processes, achieving uniform coating typically requires a reaction between the coating material and the surface of the material to be coated. However, coating materials that cannot be uniformly dispersed on the surface of the material are unlikely to form a uniform coating layer. This invention, by employing specific coating materials combined with mechanical fusion, achieves simple, rapid, low-cost, and uniform coating. Furthermore, it eliminates the need for the carbonization and sintering steps required in existing technologies after coating, thus avoiding the reduction of spinel lithium nickel manganese oxide materials.

[0082] Continuing from the above, the preparation method of lithium nickel manganese oxide spinel cathode material provided by the present invention uses micron-sized lithium nickel manganese oxide particles as the substrate. First, doping elements are doped into the lithium nickel manganese oxide substrate. Then, a modifier is used to modify the surface of the lithium nickel manganese oxide substrate with doped elements. Finally, a soft conductive material (such as conductive asphalt and conductive polymer) is uniformly coated onto the surface of the lithium nickel manganese oxide substrate with the modified layer through mechanical fusion coating. This method can not only effectively isolate the contact between the electrolyte and the cathode material and alleviate the occurrence of side reactions, but also effectively improve the structural stability, conductivity, first-time efficiency, capacity, and high-temperature cycling capacity retention of the lithium nickel manganese oxide spinel cathode material.

[0083] In addition, the present invention also provides a positive electrode sheet, wherein the active material in the positive electrode sheet includes the lithium nickel manganese oxide spinel positive electrode material of the aforementioned embodiments.

[0084] The present invention also provides a battery cell comprising the above-mentioned positive electrode sheet.

[0085] For example, the aforementioned battery cells can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft.

[0086] The present invention also provides a battery comprising the above-described battery cells.

[0087] The present invention also provides an electrical device comprising the aforementioned battery cell and / or battery. As examples, the electrical device may include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0088] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0089] Example 1

[0090] This embodiment provides a lithium nickel manganese oxide spinel cathode material, which comprises lithium nickel manganese oxide spinel with the molecular formula LiNi 0.5 Mn 1.5 The lithium nickel manganese oxide substrate of O4 is doped with doping elements, and a modified layer is formed on the surface of the lithium nickel manganese oxide substrate. The surface of the modified layer has a coating layer.

[0091] The preparation method of this lithium nickel manganese oxide spinel cathode material includes:

[0092] Step (1): Prepare lithium nickel manganese oxide substrate doped with doped elements.

[0093] Nickel-manganese hydroxide containing nickel and manganese in a molar ratio of 1:3 is thoroughly mixed with a lithium source and a dopant providing the doping elements in a high-speed mixer at a speed of 1500 rpm to obtain a first mixture; the first mixture is sintered in a box furnace at a temperature of 930°C for 10 hours to obtain a lithium nickel manganese oxide body doped with the doping elements (hereinafter referred to as "first sintered material").

[0094] The nickel-manganese hydroxide was purchased directly, with a Ni to Mn molar ratio of 1:3. The lithium source was lithium carbonate, with a Li to transition metal molar ratio of 0.51:1. The doping elements were Nb and Ta, with corresponding dopants of Nb₂O₅ and Ta₂O₅. The Nb doping amount was 4000 ppm, and the Ta doping amount was also 4000 ppm, for the lithium nickel manganese oxide spinel cathode material.

[0095] Step (2): Prepare crushed material.

[0096] The sintered material obtained in step (1) is subjected to roller crushing and airflow crushing and classification to obtain crushed material.

[0097] The roller spacing is 1.5 mm, and the crushing air pressure is 4 atmospheres.

[0098] Step (3): Prepare the modified layer.

[0099] The crushed material obtained in step (2) is mixed with the modifier to obtain a second mixture; the second mixture is sintered in a kiln at a temperature of 600°C for 6 hours to obtain a lithium nickel manganese oxide body with a modified layer and doped elements (hereinafter referred to as "second sintered material").

[0100] The modifier is AlF3, and the content of F in the lithium nickel manganese oxide spinel cathode material is 2000 ppm.

[0101] Step (4): Prepare the coating layer.

[0102] The sintered material obtained in step (3) and the coating material are fused and coated in a mechanical fusion coating machine at a temperature of 60°C for 1.5 hours. After discharge, the finished lithium nickel manganese oxide spinel cathode material is obtained directly.

[0103] The coating material is D. v50 The basic conductivity of <2μm is 10. -9 The conductive asphalt has a strength of S / m, and the mass of the coating layer is 2% of that of the lithium nickel manganese oxide spinel cathode material.

[0104] In this lithium nickel manganese oxide spinel cathode material, the area in direct contact with the electrolyte is less than 10% of the total surface area of ​​the lithium nickel manganese oxide spinel cathode material.

[0105] In step (3) above, the XRD crystal diffraction pattern of the two sintered materials is as follows: Figure 1 As shown, in step (4), the SEM scanning electron microscope morphology of the lithium nickel manganese oxide spinel cathode material is as follows: Figure 2 As shown.

[0106] Depend on Figure 1 It can be seen that the material has good crystallinity and basically no impurities.

[0107] Depend on Figure 2 It can be seen that the coating agent is coated very evenly on the surface of the object to be coated to form a coating layer.

[0108] Example 2

[0109] The difference between this embodiment and embodiment 1 is that step (2) is not performed.

[0110] Example 3

[0111] This embodiment provides a lithium nickel manganese oxide spinel cathode material, whose structure is the same as that in Embodiment 1. The preparation method of this lithium nickel manganese oxide spinel cathode material includes:

[0112] Step (1): Prepare lithium nickel manganese oxide substrate doped with doped elements.

[0113] Nickel-manganese hydroxide containing nickel and manganese in a molar ratio of 1:3 is thoroughly mixed with a lithium source and a dopant providing the doping elements in a high-speed mixer at a speed of 1500 rpm to obtain a first mixture. The first mixture is then sintered in a box furnace at a temperature of 600°C for 20 hours to obtain a lithium nickel manganese oxide bulk material doped with the doping elements (hereinafter referred to as "first sintering material").

[0114] The nickel-manganese hydroxide was purchased directly, with a nickel to manganese molar ratio of 1:3. The lithium source was lithium hydroxide, and the molar ratio of Li in lithium carbonate to the transition metal in the nickel-manganese hydroxide was 0.51:1. The doping elements were W and Mo, with dopants WO3 and MoO3 respectively. The W doping amount was 2000 ppm, and the Mo doping amount was 4000 ppm, similar to that of lithium nickel manganese oxide spinel cathode materials.

[0115] Step (2): Prepare crushed material.

[0116] The sintered material obtained in step (1) is subjected to roller crushing and airflow crushing and classification to obtain crushed material.

[0117] The roller spacing between the two rollers is 1 mm, and the crushing air pressure is 3 atmospheres.

[0118] Step (3): Prepare the modified layer.

[0119] The crushed material obtained in step (2) is mixed with the modifier to obtain a second mixture; the second mixture is sintered in a kiln at a temperature of 650°C for 10 hours to obtain a lithium nickel manganese oxide body with a modified layer and doped elements (hereinafter referred to as "second sintered material").

[0120] The modifier is ZrF4, and the content of Zr in the lithium nickel manganese oxide spinel cathode material is 500 ppm.

[0121] Step (4): Prepare the coating layer.

[0122] The sintered material obtained in step (3) and the coating material are fused and coated in a mechanical fusion coating machine at a temperature of 30°C for 1 hour. After discharge, the finished lithium nickel manganese oxide spinel cathode material is obtained directly.

[0123] The coating material is polyaniline conductive agent, and the mass of the coating layer is 0.5% of the lithium nickel manganese oxide spinel cathode material.

[0124] Example 4

[0125] This embodiment provides a lithium nickel manganese oxide spinel cathode material, whose structure is the same as that in Embodiment 1. The preparation method of this lithium nickel manganese oxide spinel cathode material includes:

[0126] Step (1): Prepare lithium nickel manganese oxide substrate doped with doped elements.

[0127] A nickel-manganese hydroxide with a molecular formula containing nickel and manganese in a molar ratio of 1:3 is thoroughly mixed with a lithium source and a dopant providing the doping elements in a high-speed mixer at a speed of 1500 rpm to obtain a first mixture. The first mixture is then sintered in a box furnace at a temperature of 1000°C for 5 hours to obtain a lithium nickel manganese oxide bulk material doped with the doping elements (hereinafter referred to as "first sintering material").

[0128] The nickel-manganese hydroxide was purchased directly, with a Ni to Mn molar ratio of 1:3. The lithium source was lithium carbonate, with a Li to transition metal molar ratio of 0.55:1. The doping elements were Ti and Ge, with TiO2 and GeO2 as the corresponding dopants. The Ti doping amount was 4000 ppm for the lithium nickel manganese oxide spinel cathode material, and the Ge doping amount was 5000 ppm for the same material.

[0129] Step (2): Prepare crushed material.

[0130] The sintered material obtained in step (1) is subjected to roller crushing and airflow crushing and classification to obtain crushed material.

[0131] The roller spacing between the two rollers is 3mm, and the crushing air pressure is 5 atmospheres.

[0132] Step (3): Prepare the modified layer.

[0133] The crushed material obtained in step (2) is mixed with the modifier to obtain a second mixture; the second mixture is sintered in a kiln at a temperature of 700°C for 5 hours to obtain a lithium nickel manganese oxide body with a modified layer and doped elements (hereinafter referred to as "second sintered material").

[0134] The modifier is Li3PO4, and the content of P in the lithium nickel manganese oxide spinel cathode material is 10000ppm.

[0135] Step (4): Prepare the coating layer.

[0136] The sintered material obtained in step (3) and the coating material are fused and coated in a mechanical fusion coating machine at a temperature of 120°C for 1 hour. After discharge, the finished lithium nickel manganese oxide spinel cathode material is obtained directly.

[0137] The coating material is polypyrrole conductive agent, and the mass of the coating layer is 5% of the lithium nickel manganese oxide spinel cathode material.

[0138] Comparative Example 1

[0139] The difference between this comparative example and Example 1 is that in step (4), the coating material is ordinary small-particle asphalt with a particle size of 3 micrometers.

[0140] Comparative Example 2

[0141] The difference between this comparative example and Example 1 is that in step (4), the coating process is carried out in a high-speed mixer at a speed of 1500 rpm.

[0142] The SEM (Scanning Electron Microscopy) morphology of the lithium nickel manganese oxide spinel cathode material obtained in this comparative example is as follows: Figure 3 As shown.

[0143] Depend on Figure 3 It can be seen that the soft coating agent is still dispersed in particulate form on the surface of the object to be coated.

[0144] Comparative Example 3

[0145] The difference between this comparative example and Example 1 is that in step (3), the modifier is a solid electrolyte lithium lanthanum titanium aluminum LLTO, and the mass of the modifier is 2000 ppm of the lithium nickel manganese oxide spinel cathode material.

[0146] Comparative Example 4

[0147] The difference between this comparative example and Example 1 is that step (4) is not performed.

[0148] Test case

[0149] The lithium nickel manganese oxide spinel cathode materials obtained in Examples 1-4 and Comparative Examples 1-4 were subjected to the following tests:

[0150] ① The particle size distribution of lithium nickel manganese oxide spinel cathode materials obtained in each embodiment and comparative example was measured using a laser particle size analyzer.

[0151] ② The lithium nickel manganese oxide spinel cathode materials obtained in each embodiment and each comparative example were used to prepare coin cells with lithium metal anodes, and the initial charge and discharge capacity of 3.0V~4.95V was tested.

[0152] The preparation method of the coin cell includes: preparing a positive electrode slurry by mixing lithium nickel manganese oxide positive electrode material, conductive carbon black, and PVDF in a ratio of 90:5:5; adjusting the slurry concentration using NMP; coating the slurry onto aluminum foil using an automatic coating machine; and drying at 120℃. Afterwards, rolling is performed to control the positive electrode compaction to 3.0±0.2. Subsequently, it is assembled with a lithium metal negative electrode separator to form a 2032 coin cell. The electrolyte used is a commercially available electrolyte with EC and DMC as the main components, suitable for voltages above 4.8V.

[0153] ③ The lithium nickel manganese oxide spinel cathode materials obtained in each embodiment and comparative example were used to make coin cells with commercial graphite anodes. The cells were cycled 50 times at 45°C and a voltage range of 3.0V to 4.9V to test the capacity retention rate.

[0154] The preparation method of the coin cell includes: preparing a positive electrode slurry by mixing lithium nickel manganese oxide positive electrode material, conductive carbon black, and PVDF in a ratio of 94.5:2.5:3; adjusting the slurry concentration using NMP; coating the slurry onto aluminum foil using an automatic coating machine; and drying at 120℃. The positive electrode is then rolled to control its density to 3.0±0.2. Subsequently, a graphite negative electrode is prepared based on the areal density and theoretical capacity of the positive electrode. Finally, the coin cell is assembled with a separator to form a 2032 coin cell. The electrolyte is a commercially available electrolyte suitable for voltages above 4.8V, primarily composed of EC and DMC.

[0155] The test results are shown in Table 1 and Figure 4 As shown.

[0156] Table 1 Performance Comparison Results

[0157]

[0158] As shown in Table 1, the lithium nickel manganese oxide spinel cathode materials obtained by the methods provided in Examples 1-4 of this invention all exhibit superior performance. Specifically, the lithium nickel manganese oxide spinel cathode material of Example 1, using the process of this invention, has a capacity >139 mAh / g, a remaining capacity higher than 115 mAh / g after 50 cycles at 45°C, and a high-temperature cycling retention rate greater than 94.5%. Example 2, which did not involve a crushing process compared to Example 1, resulted in a lithium nickel manganese oxide spinel cathode material with inferior performance.

[0159] As can be seen from Example 1 and Comparative Example 1, the conductivity of the soft coating agent plays an important role. Example 1, with its better surface conductivity, exhibits better capacity and higher initial efficiency. High conductivity is also more conducive to the performance of the full cell, with Example 1 showing significantly superior capacity and long-term cycle performance compared to Comparative Example 1.

[0160] Comparative Example 2 did not employ mechanical fusion coating; instead, it used a conventional high-speed mixer to mix the coating agent. Figure 3 As can be seen, in Comparative Example 2, the soft coating agent is still dispersed in particulate form on the surface of the object to be coated, while... Figure 2 It can be seen that in Example 1, the coating agent was coated very uniformly on the surface of the object to be coated to form a coating layer. Table 1 shows that there is a significant difference in performance between Comparative Example 2 and Example 1, indicating that the coating agent in Comparative Example 2 did not function effectively. This demonstrates that the mechanical fusion method of the present invention has a significant impact. The Example 1 also shows a significant performance advantage.

[0161] Comparative Example 3 uses other types of surface modifiers, and its overall performance is worse than that of Example 1, but significantly better than that of Comparative Example 4. The modifying elements in Example 1 and Comparative Example 3 are significantly different, and the soft conductive coating is compatible with these modifying elements, demonstrating the compatibility of the process of this invention.

[0162] Comparative Example 4, which did not have a coating layer, produced the worst-performing lithium nickel manganese oxide spinel cathode material.

[0163] In summary, the preparation method of lithium nickel manganese oxide spinel cathode material provided by this invention uses micron-sized lithium nickel manganese oxide particles as the substrate. First, doping elements are applied to the lithium nickel manganese oxide substrate. Then, a modifier is used to modify the surface of the lithium nickel manganese oxide substrate with doped elements. Finally, a soft conductive material (such as conductive asphalt and conductive polymer) is uniformly coated onto the surface of the modified lithium nickel manganese oxide substrate with doped elements through mechanical fusion coating. This method can not only effectively isolate the contact between the electrolyte and the cathode material and alleviate the occurrence of side reactions, but also effectively improve the structural stability, conductivity, initial efficiency, capacity, and high-temperature cycling capacity retention of the lithium nickel manganese oxide spinel cathode material.

[0164] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium nickel manganese oxide spinel cathode material, characterized in that, The lithium nickel manganese oxide spinel cathode material includes a lithium nickel manganese oxide bulk, the molecular formula of which is Li. x Ni y Mn 2-y O4, where x = 0.8~1.2, y = 0.4~0.6; The lithium nickel manganese oxide body is doped with doping elements, and a modified layer is formed on the surface of the lithium nickel manganese oxide body. The surface of the modified layer has a coating layer. The doping element is selected from at least two of Ta, Nb, La, Y, Te, Fe, Ti, W, Mo, Ge and Na; the modifying element contained in the modified layer is composed of one of Mg, Al and Zr and one of Cl and F; The preparation of the coating layer includes: directly fusing and coating a lithium nickel manganese oxide substrate with a modified layer and doped elements with a coating material, without sintering and / or carbonization after coating; the coating material is a soft conductive material; the soft conductive material includes at least one of conductive asphalt and conductive polymer; The content of each doping element in the lithium nickel manganese oxide spinel cathode material is 500ppm to 10000ppm; the content of each modifying element in the lithium nickel manganese oxide spinel cathode material is 500ppm to 50000ppm; and the mass of the coating layer is 0.5% to 5% of the lithium nickel manganese oxide spinel cathode material.

2. The lithium nickel manganese oxide spinel cathode material according to claim 1, characterized in that, The lithium nickel manganese oxide spinel cathode material also includes at least one of the following characteristics: Feature 1: The D of the lithium nickel manganese oxide spinel cathode material v10 The range is 1μm to 4μm, D v50 The diameter is 4μm~8μm, D v90 The thickness ranges from 6μm to 20μm. Feature 2: The area in direct contact with the electrolyte in the lithium nickel manganese oxide spinel cathode material is less than 10% of the total surface area of ​​the lithium nickel manganese oxide spinel cathode material; Feature 3: The 0.1C discharge specific capacity of the lithium nickel manganese oxide spinel cathode material is not less than 138 mAh / g.

3. A method for preparing the lithium nickel manganese oxide spinel cathode material as described in claim 1 or 2, characterized in that, Includes the following steps: The lithium nickel manganese oxide substrate doped with dopant elements is modified to form the modified layer on the surface of the lithium nickel manganese oxide substrate doped with dopant elements; the coating layer is prepared on the surface of the modified layer.

4. The preparation method according to claim 3, characterized in that, The preparation of the lithium nickel manganese oxide body doped with the doped element includes: mixing a nickel manganese precursor, a lithium source, and a dopant that provides the doping element to obtain a first mixture; and performing a first sintering on the first mixture to obtain the lithium nickel manganese oxide body doped with the doped element.

5. The preparation method according to claim 4, characterized in that, The temperature of the first sintering is 600℃~1000℃, and / or the time of the first sintering is 5h~20h.

6. The preparation method according to claim 4, characterized in that, Modifying a lithium nickel manganese oxide bulk doped with a dopant element includes: mixing the lithium nickel manganese oxide bulk doped with the dopant element with a modifier that provides the modifier element to obtain a second mixture; and subjecting the second mixture to a second sintering.

7. The preparation method according to claim 6, characterized in that, The temperature of the second sintering is 600℃~700℃, and / or the time of the second sintering is 5h~10h.

8. The preparation method according to claim 6, characterized in that, First, the lithium nickel manganese oxide body doped with doped elements is subjected to coarse crushing by roller crushing and airflow crushing to obtain crushed material; then the crushed material is subjected to a second sintering.

9. The preparation method according to claim 8, characterized in that, During the coarse crushing process of double rollers, the roller spacing is 1mm~3mm.

10. The preparation method according to claim 3, characterized in that, The coating material is fused and coated in the form of a semi-solid liquid or a highly viscous liquid.

11. The preparation method according to claim 3, characterized in that, The conductive polymer includes at least one of polyaniline conductive agent, polypyrrole conductive agent, and PEDOT:PSS conductive agent.

12. The preparation method according to claim 3, characterized in that, The particle size of the coating material is less than or equal to 2 μm.

13. The preparation method according to claim 3, characterized in that, The fusion coating temperature is 30℃~120℃, and / or the fusion coating is carried out at a rotation speed of 1000rpm~5000rpm.

14. A positive electrode plate, characterized in that, The active material in the positive electrode sheet includes the lithium nickel manganese oxide spinel positive electrode material as described in claim 1 or 2.

15. A battery, characterized in that, The battery contains the positive electrode sheet as described in claim 14.

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