Truncated lithium nickel manganese oxide positive electrode material with coating layer as well as preparation method and application of truncated lithium nickel manganese oxide positive electrode material

Abstract

The invention relates to the technical field of lithium batteries, in particular to a truncated lithium nickel manganese oxide positive electrode material with a coating layer and a preparation method and application of the truncated lithium nickel manganese oxide positive electrode material with the coating layer, and the truncated lithium nickel manganese oxide positive electrode material with the coating layer comprises spinel lithium nickel manganese oxide particles with single-crystal structures and truncated octahedral morphology, an inorganic solid electrolyte coating layer with a coating structure is formed on the surface of the spinel lithium nickel manganese oxide particle; and the inorganic solid electrolyte coating layer is used as a lithium ion conductor. LNMO particles with a single-crystal structure and regular truncated octahedral morphology are used as a core, the morphology mainly exposes a {111} crystal face and a {100} crystal face which are stable in thermodynamics, the LNMO particles have higher chemical inertness, and a solid foundation is laid for improving the interface stability; the ultrathin, continuous and compact inorganic solid electrolyte coating layer is coated on the surface of the core, can be used as a physical barrier to isolate electrolyte, and provides a rapid migration channel for lithium ions due to high intrinsic lithium ion conductivity.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a truncated lithium nickel manganese oxide cathode material with a coating layer, its preparation method, and its application. Background Technology

[0002] Spinel-type LiNi 0.5 Mn 1.5 O4 (LNMO) cathode material is valued for its high operating voltage (approximately 4.7V vs. Li). + The cobalt-free and cobalt-free properties of the Li₂O₃ / Li₂O₃ have attracted much attention; however, their commercial application is limited by severe interfacial instability. At a high voltage of 4.7V, the electrolyte undergoes severe oxidative decomposition, forming an unstable CEI film; manganese on the material surface is easily dissolved and poisons the negative electrode; and lattice oxygen loss may cause safety hazards. Traditional modification strategies, such as single-element doping or surface coating, struggle to improve interfacial stability while simultaneously maintaining ionic conductivity and rate performance, and issues such as coating uniformity, adhesion, and large-scale preparation remain prominent.

[0003] Specifically, traditional modification strategies cannot economically and efficiently construct a protective layer on active particles with complex morphologies that simultaneously possesses "excellent chemical stability," "high lithium-ion conductivity," and "excellent mechanical stability." Either the coating quality (uniformity, density, and adhesion) is substandard, or the properties of the coating layer itself (such as insulation) introduce new performance limitations, or the preparation process cannot be scaled up.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a truncated lithium nickel manganese oxide cathode material with a coating layer, its preparation method and application, aiming to solve the problems of poor electrochemical performance and substandard coating quality of existing cathode materials.

[0006] The technical solution of the present invention is as follows: A truncated lithium nickel manganese oxide cathode material with a coating layer includes spinel lithium nickel manganese oxide particles having a single crystal structure and a truncated octahedral morphology, and an inorganic solid electrolyte coating layer with a coating structure formed on the surface of the spinel lithium nickel manganese oxide particles; the inorganic solid electrolyte coating layer serves as a lithium-ion conductor.

[0007] The truncated lithium nickel manganese oxide cathode material with a coating layer, wherein the particle size D50 of the spinel lithium nickel manganese oxide particles is between 1.0 μm and 5.0 μm.

[0008] The truncated lithium nickel manganese oxide cathode material with a coating layer, wherein the thickness of the inorganic solid electrolyte coating layer is 1nm-20nm.

[0009] The truncated nickel manganese oxide cathode material with a coating layer, wherein the inorganic solid electrolyte coating layer is made of one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, and lithium phosphorus oxynitride.

[0010] The truncated lithium nickel manganese oxide cathode material with a coating layer, wherein the mass of the inorganic solid electrolyte coating layer accounts for 0.5wt%-3wt% of the total mass of the truncated lithium nickel manganese oxide cathode material.

[0011] A method for preparing a truncated lithium nickel manganese oxide cathode material with a coating layer includes the following steps: A mixture is obtained by mixing lithium source, nickel source and manganese source; The mixture is subjected to pre-sintering and sintering treatments in sequence, and then ground to obtain single-crystal truncated lithium nickel manganese oxide; or, the mixture is mixed with a eutectic salt, calcined, and then ground to obtain single-crystal truncated lithium nickel manganese oxide. Inorganic solid electrolytes are mixed with solvents to obtain precursor sols; After coating the single-crystal truncated lithium nickel manganese oxide with the precursor sol, the material is heat-treated to obtain a truncated lithium nickel manganese oxide cathode material with a coating layer.

[0012] The method for preparing the truncated lithium nickel manganese oxide cathode material with a coating layer, wherein the lithium source is selected from one or more of Li2CO3, LiCH3COO, Li2C2O4, LiOH·H2O, and LiOH; the nickel source is selected from one or more of NiO, Ni(NO3)2·6H2O, Ni(CH3COO)2, Ni(OH)2, and NiCO3; and the manganese source is selected from one or more of MnO2, Mn2O3, MnCO3, Mn(NO3)2·4H2O, and Mn(CH3COO)2.

[0013] The method for preparing the truncated lithium nickel manganese oxide cathode material with a coating layer includes the following steps: the pre-sintering temperature is 400℃-650℃, and the pre-sintering time is 4h-6h; the sintering temperature is 850℃-950℃, and the sintering time is 10h-20h; the calcination temperature is 800℃-900℃, and the calcination time is 8h-15h.

[0014] The method for preparing the truncated lithium nickel manganese oxide cathode material with a coating layer, wherein the coating treatment includes one of the following: fluidized bed method, sol-gel method, mechanical ball milling solid phase method, and co-precipitation method.

[0015] Application of a truncated lithium nickel manganese oxide cathode material with a coating layer in lithium-ion batteries.

[0016] Beneficial Effects: This invention provides a truncated lithium nickel manganese oxide cathode material with a coating layer, its preparation method, and its application. The truncated lithium nickel manganese oxide cathode material with a coating layer includes spinel lithium nickel manganese oxide particles with a single-crystal structure and a truncated octahedral morphology, and an inorganic solid electrolyte coating layer with a coating structure formed on the surface of the spinel lithium nickel manganese oxide particles; the inorganic solid electrolyte coating layer serves as a lithium-ion conductor. This invention uses LNMO particles with a single-crystal structure and a truncated octahedral morphology as the core. This morphology mainly exposes the thermodynamically stable {111} and {100} crystal planes, which have higher chemical inertness, laying a solid foundation for improving interface stability. At the same time, an ultra-thin, continuous, and dense inorganic solid electrolyte coating layer is used to coat the surface of the core. This coating layer not only acts as a physical barrier to isolate the electrolyte, but also provides a fast migration channel for lithium ions due to its high intrinsic lithium-ion conductivity, rather than the "barrier" of traditional insulating coating layers. Furthermore, this truncated nickel manganese oxide cathode material with a coating layer possesses excellent long cycle life, superior high-rate performance, enhanced thermal integrity, and a feasible industrialization path, providing a key material solution for advancing the practical application of next-generation lithium-ion batteries with high energy density, long life, and high safety. Attached Figure Description

[0017] Figure 1 SEM image of the single-crystal truncated lithium nickel manganese oxide cathode material prepared in Example 1; Figure 2 This is a TEM image of the single-crystal truncated lithium nickel manganese oxide cathode material prepared in Example 1; Figure 3 XRD pattern; Figure 4 SEM image of the cathode material with a coating amount of 0.5 wt%; Figure 5 SEM image of the cathode material with a coating amount of 1 wt%; Figure 6 TEM image of the cathode material with a coating amount of 1 wt%; Figure 7 TEM image of the cathode material with a coating amount of 2wt%; Figure 8 This is a discharge rate diagram; Figure 9 This is a long cycle life diagram; Figure 10 Microscopic characterization of cathode materials obtained by coating LATP using the traditional sol-gel method; Figure 11SEM image of the single-crystal truncated octahedral LNMO matrix material in Comparative Example 1; Figure 12 This is a SEM image of the single-crystal truncated octahedral LNMO matrix material of Comparative Example 1 at another magnification. Figure 13 SEM image of single-crystal LNMO coated with LATP oxide, Comparative Example 2. Detailed Implementation

[0018] This invention provides a truncated lithium nickel manganese oxide cathode material with a coating layer, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0019] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0020] Spinel-type LiNi 0.5 Mn 1.5 O4 (LNMO) cathode materials are a highly attractive research direction in the field of lithium-ion batteries. Their core value lies in their high voltage of approximately 4.7V (compared to Li). + The operating voltage of the / Li electrolyte is high. Its cobalt-free, manganese-rich composition also gives it the potential for low cost and high resource sustainability. However, this ultra-high operating voltage is a double-edged sword, pushing it to the limits of the electrochemical stability of conventional materials and bringing severe technical challenges. The fundamental problem is that the voltage of 4.7V far exceeds the thermodynamic stability window of conventional organic carbonate-based electrolytes (usually below 4.3V), leading to violent and irreversible side reactions at the cathode-electrolyte interface, triggering a series of chain degradation effects, which severely restricts its practical application.

[0021] To address these challenges, researchers have primarily proposed two strategies: elemental doping and surface coating. However, these existing techniques all have significant limitations. Elemental doping involves introducing small amounts of heterogeneous elements (such as Al) into the LNMO lattice. 3 + Mg 2+ F - (etc.), replacing the original Ni, Mn, or O sites, aiming to stabilize the crystal structure, suppress phase transitions, or reduce Mn.3+ The content is used to alleviate Jahn-Teller distortion. However, the configurational entropy gain introduced by traditional single or binary doping is limited, making it difficult to fundamentally suppress elemental segregation and harmful phase transition processes thermodynamically. The improvement effect is often local and incomplete, and it cannot simultaneously solve multiple problems such as manganese dissolution, oxygen loss, and interfacial side reactions. Moreover, different dopants may target different problems, but simple superposition is unlikely to produce a synergistic effect of "1+1>2", and may instead introduce new imbalances.

[0022] Surface coating is a more direct method of interface modification, aiming to construct a physical barrier to isolate the active material from direct contact with the electrolyte. However, different coating techniques each face their own bottlenecks. For example, wet chemical methods (such as sol-gel and precipitation methods) involve immersing LNMO particles in a solution containing a coating precursor, followed by drying and heat treatment to form a coating layer on the particle surface. This method struggles to achieve nanoscale thickness, continuous and dense coatings on particle surfaces with complex morphologies (such as truncated octahedrons). The coating layer tends to be too thick at particle edges and too thin or even missing at planar areas. More commonly, the coating material itself agglomerates, forming isolated island-like structures rather than a complete film. Furthermore, coating layers formed through solution adsorption and subsequent heat treatment often have only physical adhesion or weak chemical bonding with the substrate. Under the volumetric stress of long-term electrochemical cycling, they are prone to peeling or cracking, losing their protective function. At the same time, the subsequent high-temperature heat treatment process may induce unfavorable interfacial diffusion or chemical reactions between the coating layer and the LNMO substrate, which may damage the electrochemical performance of the substrate. Physical vapor deposition methods (such as atomic layer deposition, ALD) achieve precise deposition at the atomic layer level by alternately pulsedly introducing gaseous precursors into the reaction chamber, causing a self-limiting surface reaction on the substrate surface. However, they are extremely expensive, have extremely slow deposition rates, and face challenges in covering complex three-dimensional structures. In addition, the choice of coating material is limited. Common coating materials are mostly insulating or low ionic conductivity oxides, such as Al2O3, ZrO2, MgO, etc. While these insulating coatings provide physical isolation, they will seriously hinder the transport of lithium ions and significantly increase the interfacial impedance, resulting in a sharp decline in the rate performance and high current discharge capability of the material, forming a sharp contradiction between "stability" and "kinetic performance".

[0023] Based on this, the present invention provides a truncated lithium nickel manganese oxide cathode material with a coating layer, comprising spinel lithium nickel manganese oxide particles having a single crystal structure and a truncated octahedral morphology, and an inorganic solid electrolyte (SSE) coating layer forming a coating structure on the surface of the spinel lithium nickel manganese oxide particles; the inorganic solid electrolyte coating layer serves as a lithium-ion conductor.

[0024] In this embodiment, the present invention uses LNMO particles with a single-crystal structure and a regular truncated octahedral morphology as the core. This morphology mainly exposes the thermodynamically stable {111} and {100} crystal planes, which inherently possess higher chemical inertness, laying a solid foundation for improving interface stability. Simultaneously, an ultra-thin, continuous, and dense inorganic solid electrolyte coating layer is used to coat the core surface. This coating layer not only acts as a physical barrier to isolate the electrolyte but also provides a rapid migration channel for lithium ions due to its high intrinsic lithium-ion conductivity, rather than the "barrier" of traditional insulating coating layers. Furthermore, this truncated nickel-manganese lithium oxide cathode material with the coating layer exhibits excellent long cycle life, superior high-rate performance, enhanced thermal integrity, and a feasible industrialization path, providing a key material solution for advancing the practical application of next-generation lithium-ion batteries with high energy density, long life, and high safety.

[0025] Specifically, the truncated lithium nickel manganese oxide cathode material with a coating layer provided by this invention produces a synergistically enhanced overall technical effect, fundamentally breaking through the application bottleneck of high-voltage LNMO cathodes, including: 1) Exceptional long cycle life: The high ion conductivity SSE coating effectively suppresses electrolyte decomposition and manganese dissolution, while the single-crystal matrix eliminates degradation sources such as grain boundaries. The synergy of these two factors enables the material to exhibit extremely stable cycling performance at a high voltage of 4.7V. After 1000 cycles at a 1C rate, the capacity retention can exceed 95%, which is far superior to uncoated materials (~85%) and traditional coated materials (~89%).

[0026] 2) Excellent high-rate performance: The high ionic conductivity of the SSE coating layer ensures the rapid transport of lithium ions, enabling the material to retain more than 85% of the 0.1C discharge capacity at a high rate of 5C. This successfully solves the core contradiction of traditional coating technology sacrificing rate performance in pursuit of stability.

[0027] 3) Enhanced thermal safety: The dense SSE coating and the stable single crystal substrate together suppress oxygen loss during cycling, thereby improving the thermal safety of the battery from the source.

[0028] In this embodiment, a truncated lithium nickel manganese oxide cathode material with a coating layer is obtained by constructing a core-shell synergistic system of "external stability and internal solidity". "Internal solidity" is achieved by constructing a single-crystal truncated octahedral core, fundamentally eliminating bulk defects such as grain boundaries, and utilizing its stable low-index crystal facets to enhance intrinsic chemical inertness, thereby strengthening the intrinsic stability of the core. "External stability" is achieved by introducing a high-ionic-conductivity inorganic solid electrolyte (SSE) as a shell layer, providing a physical barrier while ensuring high-speed lithium-ion transport, breaking the constraint of traditional coating technology's "prioritizing stability at the expense of speed". Utilizing the synergistic effect between "internal solidity" and "external stability", comprehensive strengthening from the bulk phase to the interface is achieved.

[0029] In some embodiments, the D50 particle size of the spinel lithium nickel manganese oxide is in the range of 1.0 μm to 5.0 μm. Controlling the D50 particle size of the spinel lithium nickel manganese oxide within the above range can balance the lithium ion diffusion path and the tap density of the electrode, thereby improving the rate performance and the volumetric energy density. Moreover, the lithium nickel manganese oxide particles have a disordered spinel structure (space group Fd3m), and an appropriate degree of Ni / Mn disorder helps to improve the electronic conductivity and the rate performance; at the same time, the lithium nickel manganese oxide particles have a regular truncated octahedron morphology, and this morphology mainly exposes the thermodynamically most stable {111} crystal plane and {100} crystal plane, followed by the {100} crystal plane. These low surface energy crystal planes have higher chemical inertness and can effectively resist the erosion of the electrolyte, providing a first line of defense for the material.

[0030] In some embodiments, the thickness of the inorganic solid electrolyte coating layer is 1 nm - 20 nm. Controlling the thickness of the inorganic solid electrolyte coating layer within the above range is sufficient to effectively isolate the electrolyte and thin enough to minimize the hindrance to lithium ion transport; moreover, the coating layer and the core are bonded by chemical bonds, with a strong bond and are not prone to peeling or cracking during long-term cycling.

[0031] In a preferred embodiment, the thickness of the inorganic solid electrolyte coating layer is 5 nm - 15 nm.

[0032] In some embodiments, the material of the inorganic solid electrolyte coating layer includes lithium aluminum titanium phosphate (LATP, such as Li 1+x Al x Ti 2-x (PO4)3, 0.1 < x < 0.5), lithium lanthanum zirconium oxide (LLZO, such as cubic phase Li7La3Zr2O 12 ), lithium phosphorus oxynitride (LiPON), or one or more of them. The above materials themselves have a wide electrochemical window (>5V) and a high bulk lithium ion conductivity (usually better than 10 -4 S cm -1 ) at room temperature. As a coating layer, they are firmly bonded to the core by chemical bonds, can effectively isolate the direct contact between the core and the electrolyte, and at the same time provide an ultra-fast migration channel for lithium ions.

[0033] In some embodiments, the mass of the inorganic solid electrolyte coating layer accounts for 0.5 wt% - 3 wt% of the total mass of the truncated lithium nickel manganese oxide cathode material.

[0034] In this embodiment, the truncated nickel-manganese oxide cathode material with the above-described structure, due to the single-crystal core avoiding grain boundary degradation of polycrystalline materials, and the SSE coating layer effectively suppressing electrolyte decomposition and transition metal dissolution, exhibits extremely stable cycle performance at a high voltage of 4.7V. After 1000 cycles at 1C rate, the capacity retention rate can exceed 95%, far superior to the uncoated material (approximately 85%), achieving an ultra-long cycle life. Furthermore, the high ion conductivity SSE coating layer provides an ultra-fast migration channel for lithium ions, rather than the transport barrier of traditional insulating coating layers. Therefore, the capacity retention rate of this material at a high rate of 5C can still reach more than 85% of the 0.1C discharge capacity, successfully solving the historical problem of the difficulty in achieving both high stability and high rate, and achieving excellent high rate performance. At the same time, the dense SSE coating layer and the stable single-crystal substrate jointly suppress oxygen loss during cycling, improving the thermal safety of the battery from the source.

[0035] In addition, the present invention also provides a method for preparing a truncated lithium nickel manganese oxide cathode material with a coating layer, comprising the following steps: Step S10: Mix the lithium source, nickel source, and manganese source to obtain a mixture; Step S20: The mixture is subjected to pre-sintering and sintering treatments in sequence, and then ground to obtain single-crystal truncated lithium nickel manganese oxide; or, the mixture is mixed with a eutectic salt, calcined, and then ground to obtain single-crystal truncated lithium nickel manganese oxide. Step S30: Mix the inorganic solid electrolyte with a solvent to obtain a precursor sol; Step S40: After coating the single-crystal truncated lithium nickel manganese oxide with the precursor sol, heat treatment is performed to obtain a truncated lithium nickel manganese oxide cathode material with a coating layer.

[0036] In this embodiment, a preparation process combining stepwise synthesis and coating treatment is employed. First, a high-quality single-crystal truncated octahedral matrix is ​​synthesized via high-temperature solid-state sintering or molten salt method. Then, a coating treatment is used to ensure that each matrix particle, in a suspended state, fully contacts and reacts with the coating precursor, ultimately generating a uniform SSE coating layer in situ on the particle surface. This method perfectly resolves the contradiction between coating uniformity and large-scale preparation. Furthermore, this preparation process is easily scaled up to continuous production, providing a reliable and economical technical solution for the large-scale preparation of high-performance cathode materials.

[0037] Specifically, this invention utilizes the aforementioned preparation method to obtain a lithium nickel manganese oxide cathode material with a "core-shell synergistic" stabilization system. A single-crystal truncated octahedron is used as the core, and the single-crystal structure avoids defects such as grain boundaries common in polycrystalline materials, fundamentally reducing the active sites for side reactions. The regular truncated octahedral morphology primarily exposes the thermodynamically stable {111} and {100} crystal planes, which have low surface energy and high chemical inertness, significantly enhancing the material's intrinsic resistance to electrolyte corrosion. This design provides a solid foundation for long-term stable cycling under high voltage. Furthermore, this invention abandons the traditional approach of using insulating oxide coating layers, employing an inorganic solid electrolyte with high lithium-ion conductivity as the shell material (such as LATP or LLZO). This shell layer not only acts as a physical barrier, effectively isolating the positive electrode material from direct contact with the electrolyte and suppressing side reactions and manganese dissolution, but more importantly, it provides a "highway" for the rapid migration of lithium ions. This achieves ultimate interface protection while perfectly resolving the core contradiction of traditional coatings that severely sacrifice rate performance due to low ionic conductivity. Furthermore, the core and shell layers of this invention are not simply superimposed, but rather generate a synergistic enhancement effect of "1+1>2". The stable single-crystal core provides a robust and flat substrate for the ultra-thin shell layer, ensuring the continuity and strong bonding of the coating layer; while the highly conductive shell layer creates a safe interface environment for the core to operate stably under high voltage. Together, they comprehensively improve the structural integrity and electrochemical stability of the material from the bulk phase to the interface.

[0038] In some embodiments, the lithium source is selected from, but not limited to, one or more of Li2CO3, LiCH3COO, Li2C2O4, LiOH·H2O, and LiOH; the nickel source is selected from, but not limited to, one or more of NiO, Ni(NO3)2·6H2O, Ni(CH3COO)2, Ni(OH)2, and NiCO3; and the manganese source is selected from, but not limited to, one or more of MnO2, Mn2O3, MnCO3, Mn(NO3)2·4H2O, and Mn(CH3COO)2.

[0039] In some embodiments, the pre-sintering treatment temperature is 400℃-650℃ and the pre-sintering treatment time is 4h-6h; the sintering treatment temperature is 850℃-950℃ and the sintering treatment time is 10h-20h; the calcination treatment temperature is 800℃-900℃ and the calcination treatment time is 8h-15h.

[0040] In some embodiments, before calcination, the mixture and the eutectic salt mixture are kept at 400-650°C for 1-2 hours in an air or oxygen atmosphere to complete dehydration and nitrate decomposition.

[0041] In some embodiments, the mass ratio of the mixture to the eutectic salt is 1:(3-5).

[0042] In some embodiments, the eutectic salt includes, but is not limited to, NaCl-KCl eutectic salt, KCl-ZnCl2 eutectic salt, NaCl-KCl-ZnCl2 eutectic salt, and MgCl2-KCl-NaCl eutectic salt.

[0043] Specifically, lithium, nickel, and manganese sources are thoroughly ground and mixed with a eutectic salt in stoichiometric ratios. The mixture is then placed in a corundum crucible, covered, and heated to 400-650℃ for 1-2 hours in an air or oxygen atmosphere to complete dehydration and nitrate decomposition. The temperature is then increased to 850-950℃ and held for 10-20 hours. This temperature range and sufficiently long holding time facilitate the dissolution and re-precipitation of metal ions in the molten salt medium, resulting in preferential growth along specific crystal faces to form a truncated octahedral morphology composed of 8 {111} triangular facets and 6 {100} tetrahedrons. Increasing the molten salt ratio or introducing trace amounts of surfactants such as citric acid can further regulate the crystal facet exposure behavior. After the reaction, the mixture is naturally cooled to room temperature and repeatedly washed with boiling water to thoroughly remove the eutectic salt. After centrifugation or filtration, it is vacuum dried at 60℃. The final LNMO is a single-crystal truncated octahedral particle with a particle size of 1-5 μm and a D50 of approximately 3 μm, exhibiting a smooth surface and clear edges.

[0044] In some embodiments, the concentration of the precursor sol corresponds to the final coating amount.

[0045] In some embodiments, the coating process includes one of the following: fluidized bed method, sol-gel method, mechanical ball milling solid phase method, and coprecipitation method.

[0046] In some embodiments, step S40 specifically involves: coating the single-crystal lithium nickel manganese oxide with the precursor sol using a fluidized bed method, including the following steps: Step S41: Perform pre-fluidization treatment on the single-crystal lithium nickel manganese oxide; Step S42: After spraying the pre-fluidized single-crystal lithium nickel manganese oxide with the precursor sol, perform fluidized drying treatment.

[0047] In some embodiments, the parameters of the pre-fluidization treatment include: inlet air temperature of 80-85℃ and air volume of 80-100m³. 3 The pre-fluidization time is 5-8 minutes, and the airflow can be determined according to the equipment, so that the particles circulate in a clear fountain-like manner within the Wurster pipe. Pre-fluidization removes adsorbed water from the surface of the single-crystal lithium nickel manganese oxide, eliminates static electricity, and breaks up soft agglomerates, ensuring that each particle is independently exposed in the spray zone.

[0048] In some embodiments, the precursor sol needs to be maintained at 30-35°C and continuously magnetically stirred, with the viscosity controlled between 8-15 mPa·s. The spray gun uses a two-fluid atomizing nozzle with an atomization pressure of 1.8-2.2 bar to ensure that the average droplet diameter is between 15-30 μm.

[0049] In some embodiments, the parameters of the spray treatment include: spray treatment time of 35-45 min, inlet air temperature of 78-82℃, outlet air temperature of 48-55℃, spraying speed of 2.5-4.5 g / min, and distance between the Wurster pipe and the air distribution plate of 15-25 mm.

[0050] In some embodiments, in step S42, immediately after the spraying process is completed, the inlet air temperature is increased to 90°C and the air volume is increased to 120 m³ / h. 3 Continue fluidizing for 20-30 minutes per hour until the outlet air temperature stabilizes above 75℃ and the material moisture content drops below 0.1%.

[0051] In some embodiments, in step S40, the heat treatment temperature is 650℃-750℃, and the heat treatment time is 6h-8h. Preferably, the heat treatment temperature is 750℃, and the heat treatment time is 6h.

[0052] In addition, the present invention also provides the application of a truncated lithium nickel manganese oxide cathode material with a coating layer in lithium-ion batteries.

[0053] In this embodiment, when the truncated nickel-manganese oxide cathode material with the coating layer is applied to a lithium-ion battery, the single-crystal truncated octahedral core provides excellent intrinsic structural stability, while the high-ionic-conductivity solid electrolyte shell provides superior interfacial stability. The synergistic effect of these two components achieves comprehensive enhancement from the bulk phase to the interface. Furthermore, the high-ionic-conductivity coating layer, while suppressing electrolyte decomposition and manganese dissolution, ensures rapid lithium-ion transport, enabling the material to simultaneously possess ultra-long cycle life (e.g., capacity retention >95% after 1000 cycles at 1C) and excellent high-rate performance. Simultaneously, the material exhibits clear single-crystallinity, specific crystal face exposure, and a nanoscale uniform coating layer structure, demonstrating good performance repeatability and providing a reliable raw material foundation for the manufacture of high-performance batteries.

[0054] In some embodiments, the lithium-ion battery includes a positive electrode sheet; the positive electrode sheet contains the truncated lithium nickel manganese oxide positive electrode material with a coating layer.

[0055] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

[0056] Example 1: This embodiment provides a single-crystal truncated lithium nickel manganese oxide cathode material, as detailed below: Single-crystal truncated octahedral LNMO matrix synthesized by high-temperature molten salt method Li2CO3 (5wt% excess), NiO, MnO2 and LiCl-KCl eutectic salt were mixed and calcined at 880℃ for 12 hours in an Ar atmosphere. After cooling, the mixture was washed and dried to obtain a single-crystal truncated octahedral LNMO matrix with a particle size of 2-3 μm.

[0057] The single-crystal truncated lithium nickel manganese oxide cathode material prepared in this embodiment was characterized, and its SEM image is shown below. Figure 1 As shown, the TEM image is as follows Figure 2 As shown, the particle morphology remains intact, exhibiting a single-crystal structure and a regular truncated octahedral morphology. The XRD pattern is shown below. Figure 3 As shown, this embodiment successfully prepared a single-crystal truncated lithium nickel manganese oxide cathode material.

[0058] Example 2 This embodiment investigates the effect of coating thickness on cathode materials, as detailed below: The single-crystal truncated octahedral LNMO core prepared in Example 1 was coated using a fluidized bed method, including the following steps: Powder pre-fluidization: Add 1kg of single-crystal truncated octahedral LNMO core into the fluidized bed, set the inlet air temperature to 83℃, the air volume to 90m³ / h, and pre-fluidize for 7min. The purpose is to remove surface adsorbed water, eliminate static electricity, and break up soft agglomerates to ensure that each particle can be independently exposed in the spray zone.

[0059] Preparation of the spray sol: Prepare approximately 650 mL of LATP precursor sol in advance. The sol should be maintained at 30–35°C and continuously stirred magnetically, with a viscosity of 10 mPa·s. Use a two-fluid atomizing nozzle for the spray gun, with an atomization pressure of 2 bar to ensure an average droplet diameter of 25 μm.

[0060] Formal spraying: 40 minutes, inlet air temperature 80℃, outlet air temperature 50℃, spraying speed 3.0g / min; distance between Wurster guide tube and air distribution plate is 20mm; After spraying, continue fluidized drying: immediately after spraying, increase the inlet air temperature to 90℃ and the air volume to 120m³ / h, and continue fluidization for 20-30 minutes until the outlet air temperature stabilizes above 75℃ and the material moisture content drops below 0.1%, thus obtaining the LATP-coated lithium nickel manganese oxide cathode material precursor.

[0061] Heat treatment: The LATP-coated lithium nickel manganese oxide cathode material precursor was annealed at 750°C in an oxygen atmosphere for 6 hours to obtain the LATP-coated lithium nickel manganese oxide cathode material.

[0062] Specifically, the amounts of LATP precursor sol used correspond to a coating amount of 0.5 wt% (Example 2a), 1 wt% (Example 2b), 2 wt% (Example 2c), and 3 wt% (Example 2d).

[0063] The cathode materials obtained in Examples 2a and 2b were characterized by microstructure, and their SEM images are shown below. Figure 4 and Figure 5 As shown. TEM images of the cathode materials obtained in Examples 2b and 2c are shown respectively. Figure 6 and Figure 7 As shown in the image; SEM images show that the particle morphology remains intact after coating. TEM images show that a uniform (approximately 8±2 nm) and continuous dense coating layer has formed on the particle surface. XRD patterns are shown below. Figure 3 As shown, XRD and SAED confirmed that the coating layer is a NASICON-type LATP phase. Furthermore, TEM measurements showed that the average thicknesses of the coating layers with coating amounts of 0.5 wt%, 1 wt%, 2 wt%, and 3 wt% were 5 nm, 8 nm, 15 nm, and 23 nm, respectively.

[0064] The discharge rate curve and long cycle life curve are shown below. Figure 8 and Figure 9 As shown, the cycling stability (93% after 1000 cycles) of Example 2a (5 nm) was lower than that of Example 2b (8 nm), indicating that an excessively thin coating layer may lead to insufficient local protection. Example 2c (15 nm) showed a significant decrease in initial capacity (132 mAh / g) and a drop in 5C rate performance to 80%, indicating that an excessively thick coating layer increased ion transport impedance. This demonstrates that 5-15 nm, especially 8-10 nm, is the optimal thickness range.

[0065] Example 3 This embodiment explores the comparison of different solid electrolyte coatings. This embodiment is largely the same as Example 2, except that it uses a LiPON coating (Example 3a) and an LLZO (lithium lanthanum zirconium oxide, cubic phase) coating (Example 3b). All three coating layers achieved uniform coverage. However, the precursor of LATP (Example 1) was easier to obtain and control. The discharge rate diagram and long cycle life diagram are shown below. Figure 8 and Figure 9 As shown, all three materials significantly improve cycling stability (capacity retention >92% after 1000 cycles). However, the LATP-coated material (Example 1) exhibits the best overall performance, thanks to the excellent stability of LATP in air and its high bulk ionic conductivity.

[0066] Example 4 This embodiment studies the effect of core particle size on material properties. By adjusting the molten salt ratio, matrices with different particle sizes were prepared, and then the same LATP coating was performed to obtain cathode materials with core particle size of 3-4 μm (Example 4a) and cathode materials with core particle size of 1-2 μm (Example 4b).

[0067] Characterization revealed that Example 4a (large particle size) outperformed Example 4b (small particle size) at high magnification (e.g., 5C) because the small particle size resulted in more surface side reactions. Furthermore, Example 4b (large particle size) exhibited a higher tap density. Therefore, particle sizes in the range of 1.0–5.0 μm can be selected based on specific application requirements (power or energy density).

[0068] Example 5 This embodiment studies the effects of different coating methods on material properties, using the sol-gel method (Example 5a), mechanical ball milling method (Example 5b), and co-precipitation method (Example 5c).

[0069] The traditional sol-gel method for encapsulating LATP is as follows: The same truncated LNMO matrix as in Example 1 was used. It was immersed in LATP sol containing lithium, aluminum, titanium and phosphorus sources, and the dip-coating method was used. After drying, it was calcined in air at 700°C for 2 hours.

[0070] Microscopic characterization of cathode materials obtained by traditional sol-gel coating of LATP is shown in the figure. Figure 10 As shown, all three coating methods can achieve a certain degree of coverage. However, fluidized bed coating makes it easier to control the thickness and uniformity of the coating layer. A uniform coating layer can form a complete protective film on the surface of LNMO particles. This coating layer can act as a "bridge" for rapid lithium-ion migration and ensure the continuity of electron conduction. In contrast, non-uniform coating results in a large number of exposed areas on the particle surface. The discontinuity of the coating layer can obstruct the lithium-ion transport path and even form local electronic insulation regions, significantly reducing the rate performance and cycle stability of the material.

[0071] Comparative Example 1 This comparative example provides an uncoated single-crystal LNMO octahedral matrix as a benchmark for performance comparison, directly using single-crystal truncated octahedral LNMO matrix material synthesized in the same batch as in Example 1 without any coating treatment.

[0072] The SEM images at different magnifications are as follows: Figure 11 and Figure 12 As shown, the voltage scaling factor chart and long-cycle lifetime chart are respectively as follows: Figure 8 and Figure 9 As shown; half-cell testing revealed that its capacity decayed the fastest, with a capacity retention rate of only 84.5% after 1000 cycles.

[0073] Comparative Example 2 This comparative example provides a single-crystal octahedral LNMO coated with LATP oxide. The LATP coating was performed using a fluidized bed method, with the process identical to that in Example 2. SEM images of the obtained LATP oxide-coated single-crystal octahedral LNMO are shown below. Figure 13 As shown.

[0074] The material exhibits significantly lower cycle stability (approximately 62% after 1000 cycles) compared to Example 2b, and its rate performance is poor (75% capacity retention at 5C), demonstrating that the large interfacial impedance differences at sharp locations easily lead to localized Li-C degradation. + Excessive flux can cause concentration polarization, affecting rate performance. During cycling, stress concentration at sharp apex can directly tear the coating layer, causing it to lose its interfacial protection function.

[0075] Comparative Example 3 This comparative example provides a single-crystal octahedral LNMO coated with LLZO oxide. The LLZO coating was performed using a fluidized bed method, and the process was the same as in Example 2.

[0076] The material's cycling stability (approximately 58% after 1000 cycles) is significantly lower than that of Examples 2b and 3b, and its rate performance is poor (5C capacity retention rate of 65%). The vertices and edges of the regular octahedron are weak areas of stress concentration. During cycling, these areas are prone to microcracks first. The cracks will extend along the crystal plane and penetrate the coating layer, eventually leading to electrolyte intrusion, dissolution of transition metals, and accelerated material performance degradation.

[0077] Specifically, the key performance of the embodiments and comparative examples is summarized in Table 1: Table 1

[0078] Through the above systematic examples and comparative cases, the superiority of the "fluidized bed preparation of inorganic solid electrolyte coating layer" technology provided by this invention is fully demonstrated from multiple dimensions such as coating layer thickness, type, core particle size, and preparation method. This technology can construct a uniform, dense, ultrathin, and highly ionicly conductive protective layer on the surface of single-crystal truncated octahedral LNMO, perfectly solving the interface stability problem of high-voltage cathodes, and the process has the potential for large-scale application.

[0079] In summary, this invention provides a truncated lithium nickel manganese oxide cathode material with a coating layer, its preparation method, and its application. The truncated lithium nickel manganese oxide cathode material with a coating layer comprises spinel lithium nickel manganese oxide particles with a single-crystal structure and a regular truncated octahedral morphology, and an inorganic solid electrolyte coating layer with a coating structure formed on the surface of the spinel lithium nickel manganese oxide particles; the inorganic solid electrolyte coating layer serves as a lithium-ion conductor. This invention uses LNMO particles with a single-crystal structure and a regular truncated octahedral morphology as the core. This morphology mainly exposes the thermodynamically stable {111} and {100} crystal planes, which inherently possess higher chemical inertness, laying a solid foundation for improving interface stability. Simultaneously, an ultra-thin, continuous, and dense inorganic solid electrolyte coating layer is used to coat the core surface. This coating layer not only acts as a physical barrier to isolate the electrolyte but also provides a rapid migration channel for lithium ions due to its high intrinsic lithium-ion conductivity, rather than acting as a "barrier" of traditional insulating coating layers. Furthermore, this truncated nickel manganese oxide cathode material with a coating layer possesses excellent long cycle life, superior high-rate performance, enhanced thermal integrity, and a feasible industrialization path, providing a key material solution for advancing the practical application of next-generation lithium-ion batteries with high energy density, long life, and high safety.

[0080] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A truncated lithium nickel manganese oxide cathode material with a coating layer, characterized in that, It includes spinel lithium nickel manganese oxide particles with a single crystal structure and a truncated octahedral morphology, and an inorganic solid electrolyte coating layer with a coating structure formed on the surface of the spinel lithium nickel manganese oxide particles; the inorganic solid electrolyte coating layer serves as a lithium-ion conductor.

2. The truncated lithium nickel manganese oxide cathode material with a coating layer according to claim 1, characterized in that, The particle size D50 of the spinel lithium nickel manganese oxide particles is between 1.0 μm and 5.0 μm.

3. The truncated lithium nickel manganese oxide cathode material with a coating layer according to claim 1, characterized in that, The thickness of the inorganic solid electrolyte coating layer is 1nm-20nm.

4. The truncated lithium nickel manganese oxide cathode material with a coating layer according to claim 1, characterized in that, The inorganic solid electrolyte coating layer is made of one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, and lithium phosphorus oxynitride.

5. The truncated lithium nickel manganese oxide cathode material with a coating layer according to claim 1, characterized in that, The inorganic solid electrolyte coating layer accounts for 0.5wt%-3wt% of the total mass of the truncated lithium nickel manganese oxide cathode material.

6. A method for preparing a truncated lithium nickel manganese oxide cathode material with a coating layer as described in any one of claims 1-5, characterized in that, Including the following steps: A mixture is obtained by mixing lithium source, nickel source and manganese source; The mixture was subjected to pre-sintering and sintering treatments in sequence, and then ground to obtain single-crystal truncated lithium nickel manganese oxide. Alternatively, the mixture can be mixed with a eutectic salt, calcined, and then ground to obtain single-crystal truncated lithium nickel manganese oxide; Inorganic solid electrolytes are mixed with solvents to obtain precursor sols; After coating the single-crystal truncated lithium nickel manganese oxide with the precursor sol, the material is heat-treated to obtain a truncated lithium nickel manganese oxide cathode material with a coating layer.

7. The method for preparing the truncated lithium nickel manganese oxide cathode material with a coating layer according to claim 6, characterized in that, The lithium source is selected from one or more of Li2CO3, LiCH3COO, Li2C2O4, LiOH·H2O, and LiOH; the nickel source is selected from one or more of NiO, Ni(NO3)2·6H2O, Ni(CH3COO)2, Ni(OH)2, and NiCO3; and the manganese source is selected from one or more of MnO2, Mn2O3, MnCO3, Mn(NO3)2·4H2O, and Mn(CH3COO)2.

8. The method for preparing the truncated lithium nickel manganese oxide cathode material with a coating layer according to claim 6, characterized in that, The pre-sintering treatment temperature is 400℃-650℃, and the pre-sintering treatment time is 4h-6h; the sintering treatment temperature is 850℃-950℃, and the sintering treatment time is 10h-20h; the calcination treatment temperature is 800℃-900℃, and the calcination treatment time is 8h-15h.

9. The method for preparing the truncated lithium nickel manganese oxide cathode material with a coating layer according to claim 6, characterized in that, The coating process includes one of the following: fluidized bed method, sol-gel method, mechanical ball milling solid phase method, and coprecipitation method.

10. The application of a truncated lithium nickel manganese oxide cathode material with a coating layer as described in any one of claims 1-5 in a lithium-ion battery.

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