A five-element doped lithium nickel manganese oxide cathode material and a precursor and a preparation method thereof

Abstract

This invention belongs to the technical field of lithium-ion battery cathode materials, specifically disclosing a five-element doped lithium nickel manganese oxide cathode material, its precursor, and preparation method. The chemical formula of the cathode material is LiNi. 0.5 Mn 1.5‑x M x O4, where x is the total doping amount, 0.01≤x≤0.10; M is a mixture of any five elements selected from Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Sb, and W, with a molar ratio of 1:1:1:1:1. The cathode material has a spinel structure with regular octahedral particles, predominantly exposed on the (111) crystal face, while the exposure of the (100) and (110) crystal faces is suppressed. A precursor was prepared by co-precipitation under constant temperature and pH conditions in a water bath. A precursor with a nano-flower-like hierarchical structure was obtained by three-stage control of the feed rate and stirring rate. After lithiation and calcination, a regular octahedron with uniform particles, no agglomeration, and predominantly exposed on the (111) crystal face was obtained, significantly improving rate performance and cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to a five-element doped lithium nickel manganese oxide cathode material, its precursor, and preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and large-scale energy storage, the market is placing increasingly higher demands on the energy density, cycle stability, and high-temperature safety of lithium-ion batteries. As a core component of lithium-ion batteries, the cathode material directly determines the overall performance of the battery; therefore, the development of high-performance cathode materials has become a research hotspot in the current lithium-ion battery field.

[0003] Lithium nickel manganese oxide (LNMO), as a spinel-type cathode material with great application potential, boasts a high operating voltage plateau of approximately 4.7V, high theoretical energy density, abundant manganese ore resources, low cost, and environmental friendliness. Based on its significant advantages, LNMO is widely considered one of the ideal cathode materials for next-generation high-energy-density lithium-ion batteries, with broad application prospects in high-end power batteries and energy storage batteries, providing longer driving range under the same volume or weight constraints.

[0004] However, existing lithium nickel manganese oxide (LNMO) materials still have room for further optimization in terms of rate performance, high-temperature cycling stability, and interface stability. This is mainly because manganese ions undergo irreversible structural phase transitions during charge and discharge, leading to capacity decay. Secondly, the high-voltage plateau of LNMO makes the electrolyte prone to oxidative decomposition on the cathode material surface, accelerating interfacial side reactions.

[0005] To address the aforementioned issues, researchers have primarily attempted to improve the overall performance of lithium nickel manganese oxide through methods such as elemental doping, particle morphology control, or calcination optimization. For example, introducing transition metal elements with ionic radii similar to Ni and Mn to replace some manganese sites effectively suppresses spinel framework distortion. In recent years, multi-element high-entropy doping technology has received widespread attention. By introducing multiple elements at equimolar or near-equimolar levels into the same lattice sites, the synergistic effect and configurational entropy increase among the elements can significantly improve the structural stability and electrochemical performance of the material, thereby enhancing its overall stability.

[0006] Coprecipitation is widely used in precursor preparation due to its homogeneous composition and controllable process. However, in multi-element doping processes, the homogeneity and controllability of coprecipitation are greatly challenged due to the differences in chemical properties of the different ions. This is because conventional coprecipitation processes employ constant feed flow rates and constant stirring speeds, often focusing on obtaining relatively regular spherical secondary particles, lacking staged kinetic control over nucleation, growth, and subsequent agglomeration. Such processes have limited ability to control the evolution of microstructure and the final crystal surface structure at the precursor level, making it difficult to simultaneously achieve particle homogeneity, surface crystal state, and material structural stability.

[0007] Therefore, how to reshape the precursor formation path through the staged regulation of the co-precipitation process while maintaining the advantages of multi-element doping, and further achieve synergistic optimization of the final lithium nickel manganese oxide octahedral crystal state and electrochemical performance, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing lithium nickel manganese oxide cathode materials, such as poor rate performance, poor high-temperature cycling stability, and poor controllability of surface crystal exposure. In particular, conventional co-precipitation processes cannot simultaneously achieve phased control of precursor morphology, control of particle uniformity, and optimization of final crystal surface exposure.

[0009] This invention provides a novel preparation strategy that can simultaneously achieve the advantages of multi-element doping and synergistic optimization of particle morphology and crystal face exposure state.

[0010] To achieve the above-mentioned objectives, the following technical solution is provided:

[0011] The first aspect of this invention provides a five-element doped lithium nickel manganese oxide cathode material, which overcomes the shortcomings of lithium nickel manganese oxide cathode materials in terms of rate performance, high-temperature cycling stability and surface crystal exposure.

[0012] A five-element doped lithium nickel manganese oxide cathode material with the chemical formula LiNi 0.5 Mn 1.5-x M x O4, x represents the total doping amount, with a value ranging from 0.01 to x ≤ 0.10. Wherein, M is a mixture of five elements selected from Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Sb and W, and the molar ratio between the five elements is 1:1:1:1:1, and the molar ratio of each element M is allowed to have a deviation of ±10%. The cathode material has a spinel structure with regular octahedral particles. The (111) crystal face is the dominant exposed crystal face, while the exposure of the (100) and (110) crystal faces is suppressed.

[0013] Furthermore, the cathode material is prepared by co-precipitation, during which the feed rate and stirring rate are controlled to vary in multiple stages.

[0014] Furthermore, in the co-precipitation process, the parameters for controlling the multi-stage variation of feed rate and stirring speed are as follows: The first stage uses a metal salt solution feed rate of 10-15 mL / min and a stirring rate of 1000-1500 r / min. The second stage uses a metal salt solution feed rate of 5-10 mL / min and a stirring rate of 500-1000 r / min. The third stage uses a metal salt solution feed rate of 1-5 mL / min and a stirring rate of 100-500 r / min.

[0015] Furthermore, the precipitation reaction is carried out at a temperature of 50-60℃.

[0016] Furthermore, the pH of the reaction system is 8.0-11.0.

[0017] The second aspect of the present invention provides a precursor preparation method, which controls the precipitation of five-element doped elements to form a precursor according to the design expectation by continuously changing the feed rate and stirring rate in three stages, thereby ensuring that the multiple elements of the five-element doped elements are converted into the target precursor in the cathode material in the expected proportion.

[0018] A method for preparing a precursor of a five-element doped lithium nickel manganese oxide cathode material includes the following steps: S1. Prepare a mixed metal salt solution with Ni and Mn as the main elements and the other five elements M as dopants, with a total metal ion concentration of 0.1~3 mol / L; at the same time, prepare a complexing agent solution with a concentration of 0.2~6 mol / L and a precipitant solution with a concentration of 0.2~6 mol / L.

[0019] S2. The mixed metal salt solution, complexing agent solution, and precipitant solution are added to a reaction vessel for co-precipitation reaction at a temperature of 50-60°C and a pH of 8.0-11.0. The solution feeding process is divided into three continuous stages. First stage: The feed rate of the mixed metal salt solution is 10~15 mL / min, and the stirring rate is 1000~1500 r / min; Second stage: The feed rate of the mixed metal salt solution is 5~10 mL / min, and the stirring rate is 500~1000 r / min; The third stage: the feed rate of the mixed metal salt solution is 1~5 mL / min, and the stirring rate is 100~500 r / min.

[0020] The feed rate of the complexing agent solution is consistent with the feed rate of the mixed metal salt solution, and the feed rate of the precipitant solution is adjusted in real time according to the change of pH value of the reaction system; after the reaction is completed, a precursor suspension is obtained.

[0021] S3. The precursor suspension is washed and dried to obtain precursor powder.

[0022] In the preparation method of this invention, the feeding rate of the complexing agent solution and the mixed metal salt solution are kept consistent, meaning that both are fed according to the reaction equivalent ratio to ensure that the various materials meet the reaction equivalent ratio during the co-precipitation process.

[0023] Furthermore, in S1, the raw materials used to prepare the mixed metal salt solution are as follows: the Ni source is selected from at least one of nickel sulfate, nickel nitrate, and nickel acetate.

[0024] Preferably, the Mn source is selected from at least one of manganese sulfate, manganese nitrate, and manganese acetate; Preferably, other transition metal salts are also selected from one or more of sulfates, nitrates, acetates and ammonium salts.

[0025] Other transition metal salts refer to metal salts of M doped with five elements.

[0026] M is a mixture of five elements selected from Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Sb and W.

[0027] Specifically, the metal salts used for doping element M can be: titanium sulfate, ferric sulfate, ferrous sulfate, copper sulfate pentahydrate, zinc sulfate heptahydrate, cobalt sulfate heptahydrate, chromium sulfate hexahydrate, zirconium sulfate, ferric nitrate, cobalt nitrate, copper nitrate, zinc nitrate, silver nitrate, cadmium nitrate, copper acetate, zinc acetate, ferric acetate, cobalt acetate, chromium acetate, palladium acetate, ammonium metavanadate, ammonium tetramolybdate, ammonium tungstate, ferrous ammonium sulfate, and ammonium chromate. These are just typical examples of salts for doping metal elements and are not limited to the above range. Salts of sulfate, nitrate, and ammonium salt types are preferred.

[0028] Five elements are selected from the above metal salts to form other transition metal salts, and a mixed metal salt solution is prepared.

[0029] Furthermore, in S1, the complexing agent is at least one of ammonia, citric acid, sodium gluconate, urea, and ethylenediaminetetraacetic acid; the precipitant is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, or ammonium bicarbonate.

[0030] Furthermore, in S3, the washing process uses deionized water and / or anhydrous ethanol.

[0031] Preferably, the washing process involves sequentially washing with deionized water and anhydrous ethanol.

[0032] Furthermore, in S2, the coprecipitation reaction time is 6~24 h, and after the reaction is completed, an aging step is also included, with an aging time of 8~24 h.

[0033] The third aspect of the present invention provides a method for preparing a five-element doped lithium nickel manganese oxide cathode material, which is based on the aforementioned precursor powder raw material and obtained by segmented temperature calcination to obtain a five-element doped lithium nickel manganese oxide material with uniform particle size, regular morphology, and predominantly exposed (111) crystal plane, thereby achieving a synergistic improvement in rate performance, high-temperature performance and cycle stability.

[0034] A method for preparing a five-element doped lithium nickel manganese oxide cathode material involves mixing the aforementioned precursor powder with a lithium source and then performing segmented temperature calcination to obtain the five-element doped lithium nickel manganese oxide cathode material.

[0035] Furthermore, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate, and the molar ratio of lithium element to the total transition metal elements in the precursor is 1.00-1.10:2.

[0036] Furthermore, the calcination process includes a pre-calcination process, a main calcination process, and a cooling process. Specifically: the pre-calcination process involves heating from room temperature to 300-500℃ at a heating rate of 5-10℃ / min and holding at that temperature for 3-6 hours; the main calcination process involves heating to 700-900℃ at a heating rate of 1-3℃ / min and holding at that temperature for 10-18 hours; and the cooling process involves cooling to 50℃ at a cooling rate of 1-5℃ / min and then cooling with the furnace to room temperature.

[0037] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention prepares a lithium nickel manganese oxide precursor through high-entropy synergistic doping of five elements and three-stage co-precipitation kinetic control, and then prepares the final five-element-doped lithium nickel manganese oxide cathode material through calcination process control. Through three-stage co-precipitation kinetic control, continuous control of the nucleation, growth, and subsequent agglomeration processes is achieved, obtaining a precursor with a nano-flower-like / sheet-like self-assembled hierarchical structure. Compared with the dense and irregular agglomerated structure of conventional co-precipitation, this structure has a larger specific surface area and more abundant reactive sites, breaking through the limitations of conventional co-precipitation processes in controlling the morphology and structure of the precursor. This forms channels that facilitate the uniform diffusion of lithium ions and the directional growth of crystals during subsequent lithiation.

[0038] 2. Due to differences in the preparation process, the five-element doped lithium nickel manganese oxide cathode material of this invention exhibits a precursor formation characteristic that is more conducive to the homogenization of the final lithium nickel manganese oxide particles and the formation of a regular octahedral morphology compared to the conventional co-precipitation process. The calcined cathode material exhibits a regular octahedral particle morphology, with the (111) crystal plane, which has excellent electrochemical stability, as the dominant exposed surface. The exposure of the (100) and (110) crystal planes is effectively suppressed, thereby significantly reducing interfacial side reactions caused by differences in crystal plane activity under high voltage.

[0039] 3. The five-element doped lithium nickel manganese oxide cathode material of this invention exhibits excellent rate performance and excellent cycle stability under both room temperature and high temperature conditions. This is due to the stabilizing effect of five-element doping on the spinel lattice structure, the optimization of electronic conductivity through multi-element synergy, and the improved interface stability resulting from the exposure of the (111) crystal plane. Even at extremely high rates, the material can still maintain a very high discharge specific capacity, and even at 10C and 20C rates, it still has considerable capacity output.

[0040] 4. The five-element doped lithium nickel manganese oxide cathode material of this invention exhibits excellent cycle stability, with a capacity retention of 90.3% after 600 cycles at room temperature, a significant improvement compared to undoped / conventional process samples (67.4%). After 200 cycles at 55℃ and 1C, the capacity retention reaches 91.2%, significantly better than conventional constant-rate co-precipitation processes and samples without five-element doping, indicating that the material of this invention possesses excellent cycle stability at both room temperature and high temperature. Attached Figure Description

[0041] Figure 1 This is a SEM image of the precursor of the material prepared in Example 1.

[0042] Figure 2 The image shows the SEM image of the precursor of the material prepared in Comparative Example 1.

[0043] Figure 3 The image shows a SEM image of the material prepared in Example 1.

[0044] Figure 4The image shows the SEM image of the material prepared in Comparative Example 1.

[0045] Figure 5 This is a comparison chart of the rate performance of electrodes prepared from the materials of Example 1 and Comparative Example 1.

[0046] Figure 6 This is a comparison graph showing the room temperature cycling stability of electrodes prepared from the materials of Example 1 and Comparative Example 1.

[0047] Figure 7 This is a comparison chart of the high-temperature cycling stability at 55°C for electrodes prepared using materials from Example 1 and Comparative Example 1.

[0048] Figure 8 The SEM and EDS spectra of the material prepared in Example 1 are shown.

[0049] Figure 9 The graph shows a comparison of the stability of electrodes prepared from the materials of Example 1 and Comparative Example 1 under 2C cycling at 25°C. Detailed Implementation

[0050] The following provides a more detailed description of the present invention: a five-element doped lithium nickel manganese oxide cathode material, with the chemical formula LiNi. 0.5 Mn 1.5 -xM x O4, wherein M is a mixture of five elements selected from Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Sb and W, and the molar ratio of the five elements is 1:1:1:1:1; x is the total doping amount, ranging from 0.01 to 0.1; the preferred ratio of the five doping elements is 1:1:1:1:1.

[0051] Furthermore, the five elements are a combination of Cr, Cu, Zn, Nb, and Mo, that is, M is a combination of Cr, Cu, Zn, Nb, and Mo.

[0052] Preferably, the total doping amount x ranges from 0.02 to 0.08, and preferably x = 0.06.

[0053] The present invention also provides a precursor of the cathode material, wherein the precursor is composed of Ni and Mn as the main elements and contains the five doping elements, and has a nanoflower-like / sheet-like self-assembled hierarchical structure.

[0054] A method for preparing a precursor, wherein the precursor is prepared by coprecipitation and three-stage kinetic regulation is implemented during the coprecipitation process, specifically including the following steps: S1. Prepare a mixed metal salt solution with Ni and Mn as the main elements and transition metal elements as dopants, with a concentration of 0.1-3 mol / L. At the same time, prepare a complexing agent solution with a concentration of 0.2-6 mol / L and a precipitant solution with a concentration of 0.2-6 mol / L. S2. The mixed metal salt solution, complexing agent solution, and precipitant solution from S1 are added to the reactor for co-precipitation reaction. The co-precipitation reaction temperature is 50-60℃, and the pH of the reaction system is 8.0-11.0. The above solution feeding process is divided into three continuous stages: the first stage uses a metal salt solution feed rate of 10-15 mL / min and a stirring rate of 1000-1500 r / min; the second stage uses a metal salt solution feed rate of 5-10 mL / min and a stirring rate of 500-1000 r / min; and the third stage uses a metal salt solution feed rate of 1-5 mL / min and a stirring rate of 100-500 r / min. The flow rate of the complexing agent is the same as that of the metal salt solution, and the flow rate of the precipitant is adjusted in real time according to the pH change. After the reaction is completed, a precursor suspension is obtained. S3. The precursor suspension is washed and dried to obtain precursor powder.

[0055] Furthermore, the precursor exhibits a nanoflower-like / sheet-like self-assembled hierarchical structure.

[0056] Furthermore, the concentration of the mixed metal salt solution is 0.3~1.5 mol / L, the concentration of the complexing agent solution is 0.5~3 mol / L, and the concentration of the precipitant solution is 0.5~3 mol / L; the temperature of the coprecipitation reaction is 52~58℃, and the pH value of the reaction system is 9.2~10.5.

[0057] The core of the preparation method of this invention lies in the three-stage kinetic control during the co-precipitation process: In the first stage, a high feed rate (10~15 mL / min) and a high stirring rate (1000~1500 r / min) promote rapid nucleation, generating a large number of fine and uniformly distributed crystal nuclei; in the second stage, a reduced feed rate (5~10 mL / min) and a stirring rate (500~1000 r / min) control the directional growth of crystal nuclei, forming a lamellar primary structure; in the third stage, an even lower feed rate (1~5 mL / min) and a stirring rate (100~500 r / min) promote the self-assembly and stacking of the lamellar structure, forming a nanoflower-like hierarchical structure. Through the differentiated kinetic control of the above three stages, a unique precursor morphology is constructed that is conducive to the formation of regular octahedral particles with (111) crystal plane as the dominant exposed surface during the subsequent lithiation calcination process.

[0058] Furthermore, in S2, the proportions of the reaction time of the three consecutive stages to the total reaction time are as follows: the first stage 10%~25%, the second stage 30%~40%, and the third stage 40%~50%.

[0059] The present invention also provides a method for preparing the five-element doped lithium nickel manganese oxide cathode material, including the preparation of mixed metal salt solution, three-stage co-precipitation, precursor washing and drying, lithiation mixing, and pre-calcination-main calcination-slow cooling treatment.

[0060] Based on the above method for preparing precursors, the following steps are also included: S4. Mix the precursor powder with a lithium source; S5. The mixed powder is calcined in stages at different temperatures to obtain a five-element doped lithium nickel manganese oxide cathode material.

[0061] Furthermore, the molar ratio of lithium element in the lithium source to the total transition metal elements in the precursor powder is (1.01~1.10):2.

[0062] Furthermore, the mixed powder is subjected to segmented temperature calcination. First, it is pre-calcined at 400-600℃ for 2-8 hours with a heating rate of 1-10℃ / min, then calcined at 700-900℃ for 6-20 hours with a heating rate of 0.5-5℃ / min, and finally cooled to 30-80℃ with the furnace to room temperature to obtain the five-element doped lithium nickel manganese oxide cathode material.

[0063] Furthermore, the segmented temperature calcination includes three stages: pre-calcination, main calcination, and cooling.

[0064] The heating rate of the pre-firing process is 3~8℃ / min, the pre-firing temperature is 450~550℃, and the pre-firing time is 3~6h.

[0065] The heating rate of the main calcination process is 1~3℃ / min, the main calcination temperature is 750~850℃, and the main calcination time is 8~16 h.

[0066] The cooling process has a cooling rate of 1~5℃ / min, cooling to 40~60℃.

[0067] Furthermore, the pre-calcination process is carried out in an air atmosphere, and the main calcination is carried out in an air atmosphere or an oxygen atmosphere.

[0068] The above preparation method is based on the precipitation sequence and ratio of five-element doped lithium nickel manganese oxide precursors controlled by three-stage co-precipitation kinetics. This method aims to address the shortcomings of existing lithium nickel manganese oxide cathode materials in terms of rate performance, high-temperature cycling stability, and controllable exposure of surface crystal planes. It achieves precursor morphology control, particle uniformity, and final crystal surface structure optimization, which are difficult to achieve simultaneously by conventional co-precipitation processes.

[0069] By controlling the feed rate and stirring rate of the transition metal salt solution in stages during the co-precipitation process, differentiated kinetic control is implemented for the nucleation, growth, and later agglomeration processes, constructing a special structure different from the precursor obtained by conventional co-precipitation processes. After lithiation and calcination, a five-element doped lithium nickel manganese oxide material with uniform particles, regular morphology, and predominantly exposed (111) crystal plane can be obtained, while effectively suppressing the exposure of (100) and (110) crystal planes, thereby achieving a synergistic improvement in rate performance, high-temperature performance, and cycle stability.

[0070] The present invention may also include a positive electrode sheet and a lithium-ion battery.

[0071] A positive electrode sheet, the positive electrode sheet comprising a current collector and a positive active material layer coated on the surface of the current collector, the positive active material layer comprising the aforementioned five-element doped lithium nickel manganese oxide positive electrode material, a conductive agent and a binder.

[0072] A lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode is the aforementioned positive electrode sheet.

[0073] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0074] Example 1 This embodiment provides a five-element doped lithium nickel manganese oxide cathode material, the accurate chemical formula of which is: LiNi 0.5 Mn 1.44 Cr 0.012 Cu 0.012 Zn 0.012 Nb 0.012 Mo 0.012 O4 Weigh out the metal salts according to the target stoichiometric ratio to prepare a mixed metal salt solution with a concentration of 0.5 mol / L. Simultaneously, prepare a 1 mol / L ammonia solution and a 1 mol / L sodium hydroxide solution. Conduct a co-precipitation reaction at 55℃ and pH 9.8-10.0, using three consecutive stages: The first stage feed rate and stirring rate are 12 mL / min and 1200 r / min, respectively. The feed rate and stirring rate for the second stage are 8 mL / min and 800 r / min, respectively. The third stage had a feed rate of 4 mL / min and a stirring rate of 400 r / min, and the mixture was aged for 16 h after the reaction was completed.

[0075] The obtained precursor was washed and dried at 60°C for 16 h, then mixed with lithium hydroxide at a molar ratio of lithium to total transition metals of 1.07:2. The mixture was then pre-calcined at 5°C / min to 500°C for 5 h, then calcined at 2°C / min to 800°C for 12 h, and finally cooled in the furnace at 3°C / min to 50°C to obtain a five-element doped lithium nickel manganese oxide cathode material.

[0076] Example 2 The only difference between this embodiment and Example 1 is that the chemical formula of the target product is adjusted to: LiNi 0.5 Mn 1.48 Cr 0.004 Cu 0.004 Zn 0.004 Nb 0.004 Mo 0.004 O4 That is, the total doping amount is 0.02; the other coprecipitation process parameters, aging conditions, lithiation conditions and calcination regime are the same as in Example 1.

[0077] Example 3 The only difference between this embodiment and Example 1 is that the chemical formula of the target product is adjusted to: LiNi 0.5 Mn 1.40 Cr 0.02 Cu 0.02 Zn 0.02 Nb 0.02 Mo 0.02 O4 That is, the total doping amount is 0.10; the other coprecipitation process parameters, aging conditions, lithiation conditions and calcination regime are the same as in Example 1.

[0078] Comparative Example 1 This comparative example is an undoped pure nickel-manganese lithium oxide cathode material, prepared using a conventional co-precipitation process with constant flow rate and constant stirring speed. The difference from Example 1 is that in step one, the five doping materials (Cr, Cu, Zn, Nb, and Mo) are not added; only a mixed metal salt solution is prepared using nickel and manganese sources. In step two, the metal salt feed flow rate is constant at 8 mL / min, and the stirring speed is constant at 800 r / min. All other reaction temperatures, pH, aging conditions, lithiation conditions, and calcination regimes are the same as in Example 1. This sample is used as a baseline control.

[0079] Comparative Example 2 The only difference between this comparative example and Example 1 is that the three-stage kinetic control in the co-precipitation stage is removed, and a constant process is used instead, i.e., the metal salt feed flow rate is constant at 8 mL / min, and the stirring rate is constant at 800 r / min; the remaining raw material system, doping system, reaction temperature, pH, aging conditions, lithiation conditions, and calcination regime are the same as in Example 1. In other words, this comparative example maintains the five-element doping system unchanged, only eliminating the three-stage co-precipitation process.

[0080] Comparative Example 3 The only difference between this comparative example and Example 1 is that in step one, the five doping materials Cr, Cu, Zn, Nb, and Mo are not added; only a mixed metal salt solution is prepared using nickel and manganese sources. The remaining three-stage co-precipitation process parameters, reaction temperature, pH, aging conditions, lithiation conditions, and calcination regime are the same as in Example 1. In other words, this comparative example maintains the three-stage co-precipitation process unchanged, only removing the doping elements to form the original nickel-manganese cathode material.

[0081] Comparative Example 4 The only difference between this comparative example and Example 1 is that the total substitution amount in step one is the same as in Example 1, that is, the total doping amount is still 0.06, but only Cu doping source is added for single element substitution, and Cr, Zn, Nb and Mo are not added; the other three stages of co-precipitation process parameters, reaction temperature, pH, aging conditions, lithiation conditions and calcination regime are the same as in Example 1.

[0082] Comparative Example 5 The only difference between this comparative example and Example 1 is that the total substitution amount in step one is the same as in Example 1, that is, the total doping amount is still 0.06, but only Nb doping source is added for single element substitution, and Cr, Cu, Zn and Mo are not added; the other three stages of co-precipitation process parameters, reaction temperature, pH, aging conditions, lithiation conditions and calcination regime are the same as in Example 1.

[0083] The precursors and cathode materials prepared in the above embodiments and comparative examples were characterized and tested according to the following methods.

[0084] The morphology of the precursor and cathode material was observed using a scanning electron microscope (SEM) with an accelerating voltage of 5~20kV.

[0085] The crystal structure was characterized using X-ray diffraction (XRD) with Cu Kα (λ=0.15406 nm) as the radiation source and a scanning range of 10° to 80°.

[0086] Electrochemical performance testing was conducted using CR2032 coin cells. The positive electrode active material, acetylene black conductive agent, and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 8:1:1, and a slurry was prepared using N-methylpyrrolidone (NMP) as a solvent. This slurry was uniformly coated onto an aluminum foil current collector, vacuum dried at 100°C for 12 h, and then punched into positive electrode sheets with a diameter of 12 mm. A lithium metal sheet was used as the negative electrode, a Celgard 2500 polypropylene membrane as the separator, and a 1 mol / L LiPF6 EC / DMC / EMC solution (volume ratio 1:1:1) as the electrolyte. The coin cells were assembled in an argon glove box (water and oxygen content <0.1 ppm). The constant current charge-discharge test voltage range was 3.5–4.95 V.

[0087] Characterized by scanning electron microscopy, the precursor obtained in Example 1 was as follows: Figure 1 As shown in the scanning electron microscope (SEM) image, the precursor exhibits a distinct nanoflower-like / sheet-like self-assembled hierarchical structure.

[0088] The precursor obtained in Comparative Example 1 is as follows Figure 2 As shown, the scanning electron microscope (SEM) images show that the precursor obtained in Comparative Example 1 mainly exhibits a relatively dense and irregular aggregate structure, without forming an obvious nanoflower-like hierarchical sheet self-assembly morphology.

[0089] After calcination, the five-element doped lithium nickel manganese oxide cathode material obtained in Example 1 is as follows: Figure 3 As shown, the scanning electron microscope (SEM) image shows that the material has a regular octahedral particle morphology with uniform particle distribution. No obvious truncated corner and truncated edge structures were observed, indicating that the material surface mainly exposes the (111) crystal plane.

[0090] The scanning electron microscope (SEM) image of the undoped lithium nickel manganese oxide cathode material obtained in Comparative Example 1 is as follows: Figure 4 As shown, there are obvious truncated and truncated edges at the top and side edges of the particles, indicating that in addition to the (111) crystal plane, the (100) and (110) crystal planes are also exposed. From this, it can be seen that... Figure 3 and Figure 4 It can be seen that the (100) and (110) crystal planes in the lithium nickel manganese oxide material of the present invention are present in very small amounts or even none. They are also submerged in the baseline in the XRD pattern and only slightly affect the relative intensity of the (111) crystal plane.

[0091] like Figure 8As shown, the five-element doped lithium nickel manganese oxide cathode material prepared in Example 1 was analyzed using SEM morphology and EDS spectra. The SEM morphology images show that the particles exhibit a clear cubic / quasi-cubic crystal structure with sharp edges and smooth surfaces, indicating excellent crystallinity. This suggests that the crystal growth of the material is relatively complete, without obvious agglomeration or breakage. The EDS layered images show that the Nb, Mo, Cu, Ni, and Mn dopants are uniformly dispersed without segregation. The five-element co-doping exhibits high entropy characteristics, resulting in good capacity and cycle stability of the cathode material.

[0092] Electrochemical tests on all samples obtained in the examples and comparative examples were performed using the same method. The positive electrode active material, acetylene black, and polyvinylidene fluoride were mixed uniformly at a mass ratio of 8:1:1. N-methylpyrrolidone was added to form a slurry, which was then uniformly coated onto the surface of an aluminum foil current collector. The slurry was dried at 100°C for 12 h, and then die-cut to form the positive electrode sheet. A coin cell was assembled using a lithium metal sheet as the negative electrode in a glove box. Rate performance was tested using a constant current charge-discharge method. The test voltage range was 3.5-4.95V, with rates of 0.2C, 0.5C, 1C, 2C, 5C, 10C, 15C, and 20C, finally returning to 0.2C, to evaluate the high-rate performance and capacity recovery capability of the samples.

[0093] The results of the rate performance test are as follows: Figure 5 As shown in the figure, the discharge specific capacity of Example 1 and Comparative Example 1 at different rates is compared. Example 1 maintains a high reversible capacity under conditions of 0.2C, 0.5C, 1C, 2C, 5C, 10C, 15C and 20C. Under 10C conditions, it still has a discharge specific capacity of about 120 mAh / g (measured range of 119-121 mAh / g). After recovering to 0.2C, the capacity recovers to about 138-143 mAh / g. Comparative Example 1 is not much different from Example 1 at low rates, but the capacity decays rapidly with increasing rate. Under 10C conditions, it drops to about 50 mAh / g. At rates above 10C, it decays even more significantly, almost becoming inactive.

[0094] The results of the loop test are as follows Figure 6 The figure shows a comparison of the cycling performance of Example 1 and Comparative Example 1 under room temperature (25°C). Cycling tests were conducted at room temperature (25°C). Example 1 showed a slower discharge capacity decay during cycling, retaining 90.3% of its capacity after 600 cycles, while Comparative Example 1 only retained 67.4% of its capacity after 534 cycles.

[0095] High-temperature cycling performance test results are as follows Figure 7As shown, high-temperature cycling tests were conducted at 55°C and 1°C. The results showed that the capacity retention rate of the cathode material in Example 1 was 91.2% after 200 cycles (95.3% after 100 cycles, see Table 1), while the capacity of Comparative Example 1 decreased rapidly during cycling, with a capacity retention rate of only 43.1% after 115 cycles (50.4% after 100 cycles, see Table 1). This indicates that conventional co-precipitation processes and undoped materials are more prone to structural degradation and interfacial side reactions under high-temperature conditions, ultimately leading to rapid capacity decay.

[0096] The cathode materials of Example 1 and Comparative Example 1 were subjected to a 2C cycle test at 25°C, and the results are as follows: Figure 9 As shown, the cathode material of Example 1 maintained a capacity retention of 88.2% after 1000 2C cycles, while that of Comparative Example 1 was only 36.1%.

[0097] As can be seen from Examples 1-3 and Comparative Examples 1-5, the technical effect of the present invention stems from the synergistic effect of three-stage co-precipitation kinetic regulation and pentagonal doping. Comparative Example 1, as a basic sample of "conventional process + no doping," reflects the structure and performance level of traditional lithium nickel manganese oxide materials. Comparative Example 2 keeps the pentagonal doping system unchanged, only removing the three-stage co-precipitation process, demonstrating that three-stage kinetic regulation plays a crucial role in the precursor formation path, final particle morphology, and crystal face exposure state. Comparative Example 3 keeps the three-stage co-precipitation process unchanged, only removing the doping element, indicating that process optimization alone cannot fully achieve the comprehensive performance improvement of the present invention. Comparative Examples 4 and 5 further illustrate that while using only single Cu doping or single Nb doping can improve some performance to a certain extent, it is difficult to achieve the comprehensive optimization effect of pentagonal high-entropy synergistic doping in rate performance, cycle stability, and high-temperature performance.

[0098] Example 4 This embodiment uses a different pentagonal doping combination than Example 1, and the target product has the chemical formula LiNi. 0.5 Mn 1.44 Fe 0.012 Co 0.012 Zr 0.012 Sn 0.012 W 0.012 O4, which is to select five elements, Fe, Co, Zr, Sn and W, in an equimolar ratio for doping, with a total doping amount of x=0.06.

[0099] Weigh out NiSO4·6H2O, MnSO4·H2O, FeSO4·7H2O, CoSO4·7H2O, ZrOCl2·8H2O, SnCl4·5H2O, and (NH4) according to the corresponding stoichiometric ratios. 10 W 12 O 41·xH2O, the rest of the preparation method and coprecipitation parameters are the same as in Example 1.

[0100] Example 5 The difference between this embodiment and Example 1 lies in the adjustment of the concentration of the prepared solutions. The concentration of the mixed metal salt solution was adjusted to 1.5 mol / L, the concentration of the ammonia complexing agent was adjusted to 3.0 mol / L, and the concentration of the NaOH precipitant was adjusted to 3.0 mol / L. The corresponding feed rates during the co-precipitation process were adjusted as follows: 10 mL / min, 1200 r / min in the first stage; 6 mL / min, 700 r / min in the second stage; and 2 mL / min, 300 r / min in the third stage, to compensate for the kinetic differences caused by the increased solution concentration. The remaining parameters and operations were the same as in Example 1.

[0101] Example 6 This embodiment follows the raw material system and doping composition of Example 1. The three-stage time allocation is adjusted as follows: the first stage accounts for 30% of the total reaction time (approximately 2.1 h), the second stage accounts for 40% (approximately 2.8 h), and the third stage accounts for 30% (approximately 2.1 h), with the total reaction time remaining at 7 h. The feed rate and stirring rate for each stage remain consistent with Example 1. The remaining operations are the same as in Example 1.

[0102] Example 7 The difference between this embodiment and Embodiment 1 is that the segmented calcination process is adjusted as follows: pre-calcination is carried out at 3℃ / min to 550℃ for 4 hours, followed by main calcination at 1℃ / min to 850℃ for 10 hours, and then cooling is carried out at 2℃ / min to 60℃. The remaining operations are the same as in Embodiment 1.

[0103] Example 8 The difference between this embodiment and Example 1 is that the precipitant is replaced by Na2CO3 instead of NaOH, and the complexing agent is replaced by ethylenediaminetetraacetic acid (EDTA) instead of ammonia. The pH value of the coprecipitation reaction is adjusted to 8.0~8.5 (the suitable pH range for carbonate systems). The three-stage feed rate and stirring rate are the same as in Example 1. After the reaction, the mixture is aged in the reactor for 20 h. The resulting precursor is a carbonate precursor. A low-temperature pre-decomposition step of 300℃ / 3 h is added before the pre-calcination in step five to promote the complete decomposition of carbonates. The remaining operations are the same as in Example 1.

[0104] Table 1: Summary Analysis of Results from Comparative Examples and Embodiments

[0105] Multiple examples, along with comparative examples, were used to verify the significant and unpredictable performance differences between single-element doping and five-element doping. As shown in the table above, only when the three-stage co-precipitation kinetics regulation and five-element doping work in synergy can the construction of precursor nanoflower-like morphology, exposure of the (111) crystal plane advantage of the calcined product, excellent rate performance, and high-temperature cycling stability be simultaneously achieved. A comprehensive performance improvement cannot be obtained by using either technique alone.

[0106] The decomposition temperature of lithium nickel manganese oxide exceeds 300 degrees Celsius. The improved high-temperature cycle stability mainly stems from the suppression of the JT effect and surface side reactions after high-entropy doping modification. Furthermore, the obtained cathode material can be tested at 2C for 1000 cycles, and the test results are consistent with the conclusions in the table above.

[0107] In summary, this invention achieves joint control of the precursor formation path and the final crystal plane state through the synergistic effect of three-stage co-precipitation kinetic regulation and five-element doping. Through the synergistic cooperation of five-element doping, a precursor with a nano-flower-like / lamellar self-assembled hierarchical structure was successfully constructed, resulting in a regular octahedral five-element doped lithium nickel manganese oxide cathode material with the (111) crystal plane as the dominant exposed surface. This material exhibits significant improvements in rate performance, high-temperature stability, and cycle life, and can be widely applied in high-energy-density lithium-ion power batteries, energy storage batteries, and consumer electronics batteries. The preparation method has a wide process parameter window, is simple to operate, and is easy to scale up for production. The raw materials used are all common raw materials in the field of lithium-ion battery cathode materials, and can be directly modified and applied to existing co-precipitation production lines without special equipment, demonstrating good industrial application prospects and economic value.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. All equivalent substitutions, improvements, and modifications 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 five-element doped lithium nickel manganese oxide cathode material, characterized in that, Its chemical formula is LiNi 0.5 Mn 1.5-x M x O4, x represents the total doping amount, with a value ranging from 0.01 to x ≤ 0.

10. Wherein, M is a mixture of five elements selected from Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Sb and W, and the molar ratio between the five elements is 1:1:1:1:1, and the molar ratio of each element M is allowed to have a deviation of ±10%. The cathode material has a spinel structure with regular octahedral particles. The (111) crystal face is the dominant exposed crystal face, while the exposure of the (100) and (110) crystal faces is suppressed. The cathode material is prepared by co-precipitation, during which the feed rate and stirring speed are controlled in multiple stages. The parameters for controlling the multi-stage changes in feed rate and stirring speed during the co-precipitation reaction are as follows: The first stage uses a metal salt solution feed rate of 10-15 mL / min and a stirring rate of 1000-1500 r / min. The second stage uses a metal salt solution feed rate of 5-10 mL / min and a stirring rate of 500-1000 r / min. The third stage uses a metal salt solution feed rate of 1-5 mL / min and a stirring rate of 100-500 r / min.

2. The five-element doped lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The precipitation reaction occurs at a temperature of 50-60℃.

3. The five-element doped lithium nickel manganese oxide cathode material according to claim 2, characterized in that, The pH of the reaction system is 8.0-11.

0.

4. A method for preparing a precursor for a five-element doped lithium nickel manganese oxide cathode material, characterized in that, Includes the following steps: S1. Prepare a mixed metal salt solution with Ni and Mn as the main elements and the other five elements M as dopants, with a total metal ion concentration of 0.1~3 mol / L; at the same time, prepare a complexing agent solution with a concentration of 0.2~6 mol / L and a precipitant solution with a concentration of 0.2~6 mol / L. S2. The mixed metal salt solution, complexing agent solution, and precipitant solution are added to a reaction vessel for co-precipitation reaction at a temperature of 50-60°C and a pH of 8.0-11.

0. The solution feeding process is divided into three continuous stages. First stage: The feed rate of the mixed metal salt solution is 10~15 mL / min, and the stirring rate is 1000~1500 r / min; Second stage: The feed rate of the mixed metal salt solution is 5~10 mL / min, and the stirring rate is 500~1000 r / min; The third stage: the feed rate of the mixed metal salt solution is 1~5 mL / min, and the stirring rate is 100~500 r / min; The feeding rate of the complexing agent solution is consistent with the feeding rate of the mixed metal salt solution, and the feeding rate of the precipitant solution is adjusted in real time according to the change of pH value of the reaction system. After the reaction is complete, a precursor suspension is obtained; S3. The precursor suspension is washed and dried to obtain precursor powder.

5. The preparation method according to claim 4, characterized in that, In S1, the raw materials used to prepare the mixed metal salt solution are as follows: The Ni source is selected from at least one of nickel sulfate, nickel nitrate, and nickel acetate; The Mn source is selected from at least one of manganese sulfate, manganese nitrate, and manganese acetate; Other transition metal salts are selected from one or more of sulfates, nitrates, acetates, and ammonium salts.

6. The preparation method according to claim 4, characterized in that, In S1, the complexing agent is at least one of ammonia, citric acid, sodium gluconate, urea, and ethylenediaminetetraacetic acid; the precipitant is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, or ammonium bicarbonate. In S3, washing is performed using deionized water and / or anhydrous ethanol.

7. The preparation method according to claim 4, characterized in that, In S2, the coprecipitation reaction time is 6~24 h, and after the reaction is completed, an aging step is also included, with an aging time of 8~24 h.

8. A method for preparing the five-element doped lithium nickel manganese oxide cathode material according to any one of claims 1-3, characterized in that, The precursor powder described in any one of claims 4-7 is mixed with a lithium source and then subjected to segmented temperature calcination to obtain a five-element doped lithium nickel manganese oxide cathode material.

9. The method according to claim 8, characterized in that, The lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium nitrate or lithium acetate, and the molar ratio of lithium to the total transition metal elements in the precursor is 1.00-1.10:

2.

10. The method according to claim 8, characterized in that, The calcination process includes a pre-calcination process, a main calcination process, and a cooling process. The pre-firing process involves raising the temperature from room temperature to 300-500℃ at a rate of 5-10℃ / min and holding it at that temperature for 3-6 hours. The main calcination process involves heating to 700-900℃ at a rate of 1-3℃ / min and holding at that temperature for 10-18 hours. The cooling process involves reducing the temperature to 50°C at a rate of 1-5°C / min, and then cooling it to room temperature along with the furnace.

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