A lanthanum-doped nickel-manganese-based sodium-ion battery positive electrode material, a preparation method and application thereof

Abstract

This invention discloses a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, its preparation method, and its application, belonging to the field of electrode material technology. The chemical formula of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material is Na. 0.67 Ni 0.33‑x Mn 0.67 La x O2, where x ranges from 0.005 to 0.01; this invention achieves the precipitation of lanthanum in Na through a controllable alkaline co-precipitation process. 0.67 Ni 0.33 Mn 0.67 Atomic-level uniform solid solution in the O2 lattice. This highly uniform doped structure positively modulates the material's band structure; DFT simulations show a significant reduction in the downspin band gap from 2.9 eV to 1.1 eV, effectively lowering the electronic transition barrier and enhancing the material's electronic conductivity. Electrochemical testing results demonstrate that this modification strategy significantly improves the material's high-rate cycling stability.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, and in particular relates to a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] Due to the continuous rise in lithium salt prices and the uneven distribution of resources (especially those with lower extraction costs), there are potential geopolitical risks. Sodium salt, on the other hand, is priced at less than 2,700 yuan / ton, with abundant and readily available reserves. It is expected that once the industry achieves large-scale production, the cost of sodium-ion batteries will drop below 500 yuan / kWh. Therefore, considering both short-term cost reduction and long-term strategic resource reserves, sodium-ion batteries are a preferred complementary solution for cost reduction and ensuring supply chain security in the new energy battery system. In the layered cathode structure of sodium ions, the layered oxide Na... 0.67 (Mn) 0.67 Ni 0.33 O2 is easy to synthesize, has a simple process, and is suitable for large-scale industrial production, but it has problems such as poor rate performance and low cycle stability.

[0003] Lanthanum (La), due to its large ionic radius, can significantly increase the d-spacing of layered structures when doped into sodium-ion battery cathode materials. This optimization of lattice parameters effectively reduces the diffusion barrier of sodium ions during charge and discharge, thereby improving ion mobility. Simultaneously, the "pillar effect" of lanthanum can suppress irreversible phase transitions in the high-voltage region above 4.2V, making the discharge plateau more stable and thus enhancing the structural stability of the battery. Currently, existing technologies utilize the sol-gel method to prepare iron-containing ternary systems (Na(Ni)... 0.33 Fe 0.33 Mn 0.33 ) 1-x La x The patent CN106848288A provides a lanthanum-doped sodium-ion battery cathode material and its preparation method. In this prior art, the main purpose of introducing iron is to reduce raw material costs by utilizing inexpensive iron sources, and to attempt to utilize Fe... 3+ / Fe 4+Redox couples contribute additional specific capacity. However, the introduction of iron is a double-edged sword: iron ions are prone to migration during charge and discharge, leading to lattice structure distortion, and high-valence iron ions are extremely unstable at high voltages, easily triggering lattice oxygen release and electrolyte side reactions, which in turn limits the rate performance and long-cycle stability of the material. Furthermore, the sol-gel method used in this existing technology has significant limitations in practical applications: it relies on expensive sodium citrate as a chelating agent, increasing preparation costs; the gelation process is extremely sensitive to parameters such as pH, temperature, and time, making it difficult to ensure batch consistency; and the lengthy gelation cycle also results in low production efficiency, making it difficult to meet the demands of rapid industrial response. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, its preparation method, and its applications. This invention employs a nickel-manganese binary system with iron removed and innovatively utilizes an alkaline co-precipitation method to prepare the lanthanum-doped cathode material. This invention eliminates unstable iron, avoiding the structural degradation risk caused by iron migration, and instead further stabilizes the Ni-Mn framework through precise lanthanum doping. Experimental data confirms that even with iron removal, the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material obtained by this invention exhibits significantly better capacity retention and cycle stability at a high rate of 10C than existing iron-containing systems. Furthermore, this invention employs a co-precipitation process, achieving uniform co-precipitation of metal ions at the atomic level through precise control of reaction conditions. This not only ensures high uniformity of the precursor composition but also significantly reduces process costs and control complexity, providing a highly competitive technical path for the large-scale manufacturing of high-performance sodium-ion batteries.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, wherein the chemical formula of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material is Na. 0.67 Ni 0.33-x Mn 0.67 La x O2, where x ranges from 0.005 to 0.01.

[0006] Secondly, the present invention provides a method for preparing the above-mentioned lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, comprising the following steps: weighing raw materials according to the stoichiometric ratio of the chemical formula; adding soluble nickel salt, soluble manganese salt and soluble lanthanum salt to water and mixing them to obtain a mixed salt solution; adding sodium hydroxide aqueous solution to the mixed salt solution; adjusting the pH value of the solution; performing a water bath reaction; filtering and centrifuging to obtain a precursor; mixing the precursor and soluble sodium salt; performing a first grinding and pre-sintering; a second grinding and high-temperature solid-state sintering to obtain the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material.

[0007] Furthermore, the soluble nickel salt is selected from nickel nitrate, nickel chloride, nickel sulfate, or nickel acetate.

[0008] Furthermore, the soluble manganese salt is selected from manganese nitrate, manganese sulfate, manganese acetate, or manganese chloride.

[0009] Furthermore, the soluble lanthanum salt is selected from lanthanum nitrate or lanthanum chloride; the soluble sodium salt is selected from sodium carbonate, sodium nitrate or sodium chloride.

[0010] Furthermore, the pH value is 10-11.

[0011] Furthermore, the water bath reaction is carried out at a temperature of 60°C for 4 hours.

[0012] Furthermore, the pre-sintering temperature is 500°C and the time is 4 hours.

[0013] Furthermore, the high-temperature solid-state sintering temperature is 900℃ and the time is 12h.

[0014] The preparation principle of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material provided by this invention is as follows: First, soluble nickel salt, soluble lanthanum salt, and soluble manganese salt are dissolved in deionized water according to stoichiometric ratio to obtain a Ni-containing cathode material. 2+ La 3+ Mn 2 + A mixed cation solution was prepared. Sodium hydroxide was then added, followed by ammonia as a complexing agent under stirring in a medium-temperature water bath. In the reaction system, transition metal ions TM... 2+ It preferentially undergoes a complexation reaction with ammonia (NH3) to form a stable metal ammonia complex [TM(NH3)]. n ] 2+ The formation of this complex effectively reduced the amount of free TM in the reaction system. 2+ The concentration of [certain substances] slows down the nucleation rate of the crystals, which is beneficial for subsequent grain growth control. Subsequently, the metal-ammonia complex [TM(NH3)]... n ] 2+Reacting with hydroxide ions under high pH conditions, the TM(OH)₂ crystal nuclei gradually dissociate and precipitate. Due to the high surface free energy of the initially formed nuclei, they tend to aggregate and grow on the surface of the existing particles, forming larger micron-sized secondary particle precursors by reducing the total energy of the system. Finally, the obtained precursor is dried and pre-sintered at 500℃ in air to remove impurities such as C and H; after grinding, it is then subjected to high-temperature solid-state sintering at 900℃ to finally obtain Na. 0.67 Ni 0.33- x Mn 0.67 La x O2 cathode material.

[0015] The core design concept of this invention lies in utilizing the large ionic radius of lanthanum (La) to "pin" the transition metal layer. This micro-substitution strategy not only maintains the integrity of the layered structure but, more importantly, significantly enhances the thermodynamic stability of the material under high desodiumization conditions, fundamentally suppressing lattice distortion and structural collapse during cycling. To achieve this design, this invention developed an improved co-precipitation-high-temperature sintering process, ensuring the uniform distribution of lanthanum at the atomic scale. VASP simulations further reveal that lanthanum doping effectively modulates the electronic structure near the Fermi level, not only improving rate performance but also significantly extending the cycle life of the material by enhancing chemical bonding forces. Experiments show that this material maintains extremely high capacity retention even under high voltage and high current density, solving the problem of rapid cycle decay in traditional nickel-manganese-based materials. Furthermore, the process is simple and low-cost, making it highly valuable for industrial applications.

[0016] Thirdly, the present invention provides an application of the above-mentioned lanthanum-doped nickel-manganese-based sodium-ion battery cathode material in the preparation of sodium-ion batteries.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects: Existing technologies mostly employ the sol-gel method, which suffers from problems such as complex processes and component segregation. This invention achieves the precipitation of lanthanum in Na+ through a controllable alkaline co-precipitation process. 0.67 Ni 0.33 Mn 0.67 Atomic-level uniform solid solution in the O2 lattice. This highly uniform doped structure positively modulates the material's band structure; DFT simulations show a significant reduction in the downspin band gap from 2.9 eV to 1.1 eV, effectively lowering the electronic transition barrier and enhancing the material's electronic conductivity. Electrochemical testing results demonstrate that this modification strategy significantly improves the material's high-rate cycling stability. Under a high current density shock of 10C, the prepared Na... 0.67 Ni 0.33-x Mn 0.67 Lax The O2 cathode material exhibits excellent structural tolerance, maintaining a capacity retention of 93.6% after 700 cycles, a significant improvement compared to the 69.4% retention of the nickel-iron-manganese system under the same conditions. This invention achieves a qualitative leap in material performance through a simple process, paving a new path for the practical application of high-power sodium-ion batteries. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 SEM image of NML0.005 prepared in Example 1; Figure 2 EDS image of NML0.01 prepared in Example 2; Figure 3 XRD pattern of NM prepared for Comparative Example 1; Figure 4 The first charge-discharge curves of NML0.005 prepared in Example 1 at 2.0-4.4V and 0.1C current density; Figure 5 SEM image of NML0.005 prepared in Example 1 after cycling at 1C / 50 cycles; Figure 6 The rate discharge curves of NML0.005 prepared in Example 1 at different current densities in the range of 2.0-4.4V; Figure 7 Long-term cycling curve of NML0.005 prepared in Example 1 at 2.0-4.4V and 10C; Figure 8 The rate discharge curves of NML0.01 prepared in Example 2 at different current densities in the range of 2.0-4.4V; Figure 9 The long-cycle diagram of NML0.01 prepared in Example 2 at 2.0-4.4V and 10C; Figure 10 Charge-discharge curves of the NM prepared for Comparative Example 1 at current densities of 2.0–4.4 V and 10 C; Figure 11 This is a comparison diagram of the density of states of NML0.005 in Example 1 and NM in Comparative Example 1; Figure 12 Charge-discharge curves of the NFML prepared for Comparative Example 2 at current densities of 2.0-4.4V and 10C. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] This invention provides a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, wherein the chemical formula of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material is Na. 0.67 Ni 0.33-x Mn 0.67 La x O2, where x ranges from 0.005 to 0.01.

[0026] This invention provides a theoretical research method for electrode structures. The theoretical research scheme adopted to achieve the above objective is as follows: A Na… 0.67 Ni 0.33-x Mn 0.67 Lax The positive electrode structure of O2 has a supercell size of 3×3×1. The structure was optimized using the VASP software package, and its density of states was calculated considering a strongly electron-correlated system. The U value of Mn is 3.9 eV, the U value of Ni is 6.0 eV, and the U value of La is 7.5 eV.

[0027] This invention simulates the lanthanum-doped cathode structure using first-principles density functional theory. The calculation results show that lanthanum doping can improve and reduce the downspin bandgap of the cathode structure, decreasing it from 2.9 eV to 1.1 eV, thus confirming the material's good conductivity. Furthermore, it exhibits high cycling stability at 10C rate, overcoming the limitations of transition metal oxides like Na+. 0.67 (Mn) 0.67 Ni 0.33 The application of O2 in sodium-ion battery cathode materials has problems such as poor cycle stability and low rate performance. O2 has advantages such as excellent cycle performance, stable structure, abundant raw material sources, low cost, and good repeatability.

[0028] This invention also provides a method for preparing the above-mentioned lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, comprising the following steps: adding soluble nickel salt, soluble manganese salt and soluble lanthanum salt to water and mixing them to obtain a mixed salt solution; adding sodium hydroxide aqueous solution to the mixed salt solution, then adjusting the pH value of the solution, performing a water bath reaction, filtering and centrifuging to obtain a precursor; mixing the precursor and soluble sodium salt, and then performing a first grinding, pre-sintering, a second grinding and high-temperature solid-state sintering to obtain the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material.

[0029] In some preferred embodiments, the soluble nickel salt is selected from nickel nitrate, nickel chloride, nickel sulfate, or nickel acetate; the soluble manganese salt is selected from manganese nitrate, manganese sulfate, manganese acetate, or manganese chloride; the soluble lanthanum salt is selected from lanthanum nitrate or lanthanum chloride; and the soluble sodium salt is selected from sodium carbonate, sodium nitrate, or sodium chloride.

[0030] In some preferred embodiments, the pH value is 10-11.

[0031] In some preferred embodiments, the water bath reaction is carried out at a temperature of 60°C for 4 hours.

[0032] In some preferred embodiments, the pre-sintering temperature is 500°C and the time is 4 hours.

[0033] In some preferred embodiments, the high-temperature solid-state sintering temperature is 900°C and the time is 12 hours.

[0034] This invention also provides an application of the above-mentioned lanthanum-doped nickel-manganese-based sodium-ion battery cathode material in the preparation of sodium-ion batteries.

[0035] To facilitate understanding, the following explanations will first cover several technical terms.

[0036] Example 1: A method for preparing a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material The chemical formula of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material prepared in this embodiment is Na. 0.67 Ni 0.325 Mn 0.670 La 0.005 The specific preparation method of O2 includes the following steps: Dissolve 3 g (17.75 mmol) manganese sulfate monohydrate, 2.233 g (8.50 mmol) nickel sulfate hexahydrate, and 60 mg (0.14 mmol) lanthanum nitrate hexahydrate in 10 g of deionized water. Stir until homogeneous to obtain a mixed salt solution. Add 13 mL of a 4% concentration solution to the resulting mixed salt solution. A sodium hydroxide solution of mol / mL was prepared, and the pH of the solution was adjusted to 11 with ammonia (25 wt.%). The mixture was then reacted in a water bath at 60 °C for 4 h, followed by static precipitation for 12 h to obtain a precursor precipitate. The precursor precipitate was centrifuged and dried three times (25 °C, 10 min) to obtain the precursor. The precursor was dried at 100 °C for 16 h, then mixed with 0.92 g (8.68 mmol) of sodium carbonate, first ground into powder, and first calcined (in air, 500 °C, 4 h). After removal, it was ground a second time and calcined a second time (in air, 900 °C, 12 h) to obtain a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, denoted as NML0.005. Figure 1 The SEM image of NML0.005 prepared in Example 1 is shown below. Figure 1 It can be seen that it has a regular layered or blocky structure, and there are irregular particles on the surface.

[0037] Example 2: A method for preparing a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material The chemical formula of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material prepared in this embodiment is Na. 0.67 Ni 0.32 Mn 0.67 La 0.01 The specific preparation method of O2 includes the following steps: 4 g (23.67 mmol) manganese sulfate monohydrate, 3.111 g (11.84 mmol) nickel sulfate hexahydrate, and 153.73 mg (0.36 mmol) lanthanum nitrate hexahydrate were dissolved in 20 g of deionized water and stirred until homogeneous to obtain a mixed salt solution. 18 mL of 4 mol / mL sodium hydroxide solution was added dropwise to the resulting mixed salt solution. The pH of the solution was then adjusted to 11 with ammonia (25 wt.%), and the reaction was carried out in a water bath at 60 °C for 4 h. The mixture was then allowed to stand and precipitate for 12 hours. h, a precursor precipitate was obtained; the precursor precipitate was centrifuged and dried three times (25℃, 10min) to obtain a precursor; the precursor was dried at 100℃ for 16h, then mixed with 1.27g (12.0mmol) sodium carbonate, ground into powder for the first time, calcined for the first time (in air, 500℃, 4h), then taken out, ground a second time, and calcined a second time (in air, 900℃, 12h) to obtain a lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, denoted as NML0.01. Figure 2 The EDS image of NML0.01 prepared in Example 2 is shown below. Figure 2 As can be seen, the lanthanum element on its surface can be uniformly distributed in the material structure.

[0038] Comparative Example 1 The chemical formula of the sodium-ion battery cathode material prepared in this comparative example is Na. 0.67 Ni 0.33 Mn 0.67 O2, its specific preparation method includes the following steps: 3g of manganese sulfate monohydrate and 2.233g of nickel sulfate hexahydrate were dissolved in 10g of deionized water and stirred until homogeneous to obtain a mixed salt solution. 2.5g of sodium hydroxide solution with a concentration of 0.2g / mL was added dropwise to the obtained mixed salt solution. Then, the pH of the solution was adjusted to 11 with ammonia water (25wt.%). The solution was then reacted in a water bath at 55℃ for 4h and precipitated overnight for 12h to obtain a precursor precipitate. The obtained precursor precipitate was centrifuged and dried three times (25℃, 10min) to obtain a precursor. The obtained precursor was dried at 100℃ for 16h and then mixed with 0.92g of sodium carbonate. The mixture was first ground into powder, first calcined (in air, 500℃, 4h), and then removed. It was then ground a second time and calcined a second time (in air, 900℃, 12h) to obtain a sodium-ion battery cathode material, denoted as NM.

[0039] XRD analysis was performed on the sodium-ion battery cathode material prepared in Comparative Example 1. A Shimadzu XRD6100 X-ray diffractometer was used to characterize the crystal structure of the material. The test conditions were: Cu target, Kα radiation, 40 kV, 30 mA, step size 0.02°, scan range 3–80 nm. ° The sample is a powder. The sample is placed in the groove of the sample stage, flattened, and then directly tested. Figure 3 The XRD pattern of NM prepared for Comparative Example 1 shows that the material has a good crystal structure.

[0040] Comparative Example 2 This comparative example prepares a sodium-ion battery cathode material according to Example 1 described in patent CN106848288A, with the chemical formula Na(Ni) 0.33 Fe 0.33 Mn0.33) 0.98 La 0.02 The specific preparation method for O2 materials includes the following steps: 3.88g manganese acetate tetrahydrate, 3.94g nickel acetate tetrahydrate, 6.397g ferric nitrate nonahydrate, 0.433g lanthanum nitrate hexahydrate, and 4.419g sodium nitrate were dissolved in 300g deionized water and stirred until homogeneous. 100g of citric acid solution with a concentration of 0.12g / mL was added dropwise, and the mixture was reacted in a water bath at 50℃ for 2 hours. The pH was then adjusted to 5.5 with ammonia, and the water bath temperature was increased to 70℃. The reaction was continued for 8 hours to obtain a wet gel, which is the precursor gel. The gel was then dried at 100℃ for 16 hours, ground into powder, and finally calcined in air at 500℃ for 6 hours. The powder was then removed, ground again, and calcined in air at 950℃ for 12 hours to obtain the final product, denoted as NFML.

[0041] Application Example 1 The lanthanum-doped nickel-manganese-based sodium-ion battery cathode material prepared in Example 1 was mixed with conductive carbon black and binder polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. Then, 0.6 g of N-methylpyrrolidone (NMP) was added and stirred evenly. The mixture was coated onto aluminum foil and dried in a vacuum oven at 90°C. The electrode sheets were then cut on a die-cutting machine to obtain electrode sheets of the material. The obtained electrode sheets were used as the positive electrode, and the sodium metal sheet was used as the negative electrode. The electrolyte was composed of solute NaClO4 (1 mol / L) and solvents DEC (diethyl carbonate), EC (ethylene carbonate), and FEC (fluoroethylene carbonate) at a volume ratio of 1:1:0.05. The separator was made of glass fiber. The cells were assembled into 2032 coin cells in a glove box filled with argon (Ar). The charge and discharge performance was then tested using a BTS51800 battery testing system from Shenzhen Xinwei Electronics Co., Ltd.

[0042] Figure 4 The first charge-discharge curves of NML0.005 prepared in Example 1 at 2.0-4.4V and 0.1C current density are shown below. Figure 4 It can be seen that the discharge specific capacity can reach 119 mAh / g at a current density of 0.1C and at 2.0-4.4V, and there is a reversible charge-discharge plateau above 4.2V, which provides the material with high specific capacity. Figure 5SEM image of NML0.005 prepared in Example 1 after cycling at 1C / 50 cycles; from Figure 5 As can be seen, the particles on it are reaction particles of the electrolyte, and its main structure is still a layered structure, indicating that its structure is stable.

[0043] Figure 6 The discharge curves of NML0.005 prepared in Example 1 at different current densities and in the range of 2.0-4.4V are shown below. Figure 6 As shown, the material maintains a discharge specific capacity of 128.64 mAh / g, 105.68 mAh / g, 83.4 mAh / g, and 71.38 mAh / g at current densities of 0.2C, 1C, 2C, and 5C, respectively, in the range of 2.0-4.4V. Furthermore, when the current density returns to 0.2C, the specific capacity remains at 108.94 mAh / g. This demonstrates that the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material prepared in this invention possesses excellent reversible cycling performance. Further testing of its long-term cycling performance at a high current density of 10C further confirms this. Figure 7 The long-cycle graph of NML0.005 prepared in Example 1 at 2.0-4.4V and 10C shows that the capacity retention rate is 78.0% after 700 cycles.

[0044] Application Example 2 The electrochemical performance of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material prepared in Example 2 was tested using the same method as in Application Example 1. Figure 8 The discharge curves of NML0.01 prepared in Example 2 at different current densities and in the range of 2.0-4.4V are shown below. Figure 8 As shown, the material maintains a discharge specific capacity of 118.65 mAh / g, 91.82 mAh / g, 86.55 mAh / g, and 73.19 mAh / g at current densities of 0.2C, 1C, 2C, and 5C, respectively, in the range of 2.0-4.4V. Furthermore, when the current density returns to 0.2C, the specific capacity remains at 108.31 mAh / g. This demonstrates that the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material prepared in this invention possesses excellent reversible cycling performance. Further testing of its long-term cycling performance at a high current density of 10C further confirms this. Figure 9 The image shows the long-cycle chromatogram of NML0.01 prepared in Example 2 at 2.0-4.4V and 10C. Figure 9 As can be seen, the capacity retention rate reached 93.6% after 700 cycles.

[0045] Comparative Application Example 1 The electrochemical performance of the battery cathode material prepared in Comparative Example 1 was tested using the same method as in Application Example 1. Figure 10 Charge-discharge curves of the NM prepared for Comparative Example 1 at current densities of 2.0–4.4 V and 10 C; from Figure 10 As can be seen, the material has a discharge capacity of 76.44 mAh / g at a current density of 10C and a capacity retention rate of 68.1% after 700 cycles.

[0046] Based on first-principles calculations, the electronic structures of the NM and NML0.005 systems were calculated using density functional theory (DFT). Figure 11 The density of states (DOS) of NML0.005 in Example 1 is shown in comparison with that of NM in Comparative Example 1. From... Figure 11 It can be seen that the introduction of lanthanum (La) atoms introduces new electronic states near the Fermi level, thereby effectively reducing the band gap of the material. A narrower band gap means that the energy required for electrons to transition from the valence band to the conduction band is reduced, lowering the potential barrier for electron migration within the crystal lattice. In terms of macroscopic electrochemical performance, this manifests as a significant increase in the intrinsic electronic conductivity of the material, which is beneficial for reducing polarization during high-current charge and discharge processes, and improving the rate performance and kinetic characteristics of the battery.

[0047] Comparative Application Example 2 Na(Ni) prepared in Comparative Example 2 0.33 Fe 0.33 Mn 0.33 ) 0.98 La 0.02 The electrochemical performance of the O2 material was tested using the same method as in Application Example 1. Figure 12 The charge-discharge curves of the NFML prepared for Comparative Example 2 at current densities of 2.0–4.4 V and 10 C are shown below. Figure 12 It can be seen that the capacity retention rate of this material after 700 cycles at 2.0-4.4V and 10C current density is only 69.4%, which is much lower than that of Example 1 (78.0%) and Example 2 (93.6%). This proves that compared with the nickel-iron-manganese system of the prior art, the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material prepared by this invention has better cycle performance at high voltage.

[0048] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A lanthanum-doped nickel-manganese-based sodium-ion battery cathode material, characterized in that, The chemical formula of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material is Na. 0.67 Ni 0.33-x Mn 0.67 La x O2, where x ranges from 0.005 to 0.01; The preparation method of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material includes the following steps: weighing raw materials according to the stoichiometric ratio of the chemical formula; adding soluble nickel salt, soluble manganese salt and soluble lanthanum salt to water and mixing them to obtain a mixed salt solution; adding sodium hydroxide aqueous solution to the mixed salt solution; adjusting the pH value of the solution to alkaline; carrying out a water bath reaction; filtering and centrifuging to obtain a precursor; mixing the precursor and soluble sodium salt; and performing a first grinding, pre-sintering, second grinding and high-temperature solid-state sintering to obtain the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material. The pH value is 10-11; The pre-sintering temperature is 500℃ and the time is 4 hours; The high-temperature solid-state sintering temperature is 900℃ and the time is 12h.

2. The lanthanum-doped nickel-manganese-based sodium-ion battery cathode material according to claim 1, characterized in that, The soluble nickel salt is selected from nickel nitrate, nickel chloride, nickel sulfate, or nickel acetate.

3. The lanthanum-doped nickel-manganese-based sodium-ion battery cathode material according to claim 1, characterized in that, The soluble manganese salt is selected from manganese nitrate, manganese sulfate, manganese acetate, or manganese chloride.

4. The lanthanum-doped nickel-manganese-based sodium-ion battery cathode material according to claim 1, characterized in that, The soluble lanthanum salt is selected from lanthanum nitrate or lanthanum chloride; the soluble sodium salt is selected from sodium carbonate, sodium nitrate or sodium chloride.

5. The lanthanum-doped nickel-manganese-based sodium-ion battery cathode material according to claim 1, characterized in that, The water bath reaction was carried out at a temperature of 60°C for 4 hours.

6. The application of the lanthanum-doped nickel-manganese-based sodium-ion battery cathode material according to any one of claims 1-5 in the preparation of sodium-ion batteries.

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