Defect element doped double modified lithium-rich manganese-based layered oxide positive electrode material and preparation method and application thereof

Abstract

The application discloses a defect element doped double modified lithium-rich manganese-based layered oxide positive electrode material and a preparation method and application thereof. 1.12 (Mn 0.54 Ni 0.13 Co 0.13 ) x Zn 1‑x O2, wherein x=0.0025~0.01. A solution containing manganese source, nickel source, cobalt source and lithium source is slowly dropped into a solution containing citric acid, and after mixing, the pH is adjusted, and then heat treatment is performed, so that the positive electrode material is obtained. The prepared positive electrode material is induced to generate a spinel phase in the material through lithium defect engineering, so that the migration rate of Li + is improved, sites are provided for Zn 2+ doping, and the strong bonding strength of Zn-O improves the stability of the structure. The migration rate of Li + is significantly improved, and excellent cycle performance is exhibited.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material preparation technology, specifically relating to a lithium-rich manganese-based layered oxide cathode material with defect element doping and double modification, its preparation method, and its application. Background Technology

[0002] In recent years, driven by new energy vehicles, electric light vehicles, power tools, and new energy storage, the global market for lithium batteries has maintained a rapid growth trend. However, breakthroughs in next-generation lithium-ion batteries face challenges, primarily due to limitations in cathode material development. Among various cathode materials, layered lithium-rich manganese-based cathode materials xLi2MnO3 (1-x)LiTMO2 (TM = Co, Mn, Ni, etc.) are considered one of the most promising due to their high capacity (>250 mAh / g), low cost, low environmental toxicity, good safety, and ease of processing. However, the commercial application of lithium-rich materials still faces several challenges. First, low initial coulombic efficiency, meaning that during the first charge, some oxygen ions in the lattice are over-oxidized, resulting in incomplete lithium ion recovery. The second problem is capacity and voltage decay, mainly due to the escape of lattice oxygen and the transformation of the layered structure into the spinel phase. Furthermore, the migration and valence state changes of transition metal ions during cycling are also involved. Third, the layered structure of lithium-rich manganese-based cathode materials in the physical phase leads to poor performance across multiple parameters. This structure hinders the diffusion of lithium ions within the material perpendicular to the layer, significantly limiting the kinetics and multiple properties of the electrochemical reaction.

[0003] To overcome these problems, researchers have conducted extensive studies and found that doping with exogenous elements and enhancing surface stability are two effective strategies. Among these, doping with elements that are not highly electrochemically active and have stable valence states (e.g., Zn) is particularly effective. 2+ Zr 4+ Ti 4+ 、Nb 5+ W 6+Spinel (etc.) can often stabilize anionic redox reactions and inhibit the shedding of lattice oxygen. As for enhancing surface stability, spinel structure is considered one of the most effective surface coating materials. It not only has the great advantage of compatibility with lithium-rich layered phases, but also releases the stress at the lattice interface during rapid lithium-ion insertion and extraction; at the same time, it can provide a three-dimensional lithium-ion diffusion path, enhancing the multiple properties of the material. Currently, common methods for generating spinel coatings include (1) surface treatment with acid, carbon reducing agent or other chemical reagents, and (2) adjusting the calcination temperature or heat treatment time to induce the spinel phase in situ. Among these methods, the use of chemical reagents to treat materials can easily lead to material contamination and increase costs. Changing the calcination temperature or heat treatment time makes it difficult to ensure good dispersion of lithium-rich manganese materials, thus keeping them some distance from practical applications. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, the present invention provides a lithium-rich manganese-based base oxide cathode material with defect element doping and double modification, its preparation method and application.

[0005] This invention discloses a lithium-rich manganese-based layered oxide cathode material with defect element doping and dual modification, wherein the chemical formula of the cathode material is Li. 1.12 (Mn 0.54 Ni 0.13 Co 0.13 ) x Zn 1-x O2, where x = 0.0025~0.01.

[0006] Furthermore, the defect element-doped double-modified lithium-rich manganese-based base oxide cathode material is obtained by lithium defect-induced transformation of the Li2MnO3 phase into the spinel phase LiMn2O4.

[0007] The method for preparing the defect element-doped, dual-modified lithium-rich manganese-based layered oxide cathode material of the present invention is as follows:

[0008] According to the chemical formula Li 1.12 (Mn 0.54 Ni 0.13 Co 0.13 ) x Zn 1-x The dosage of O2 is determined by adding aqueous solutions of manganese, nickel, cobalt, lithium, and zinc sources dropwise into a citric acid solution, mixing them uniformly to form a mixture, adjusting the pH to 6-7, adding NH4OH, and stirring the mixture to obtain a homogeneous gel. The obtained homogeneous gel is then heat-treated to obtain a precursor. This precursor is further heat-treated to obtain the lithium-rich manganese-based layered oxide cathode material. The lithium source is selected according to the chemical formula Li... 1.12 (Mn 0.54 Ni0.13 Co 0.13 ) x Zn 1-x 98% of the 1.12% of O2 was added.

[0009] Further, the manganese source is at least one of manganese acetate, manganese sulfate, and manganese nitrate; the nickel source is at least one of nickel acetate, nickel sulfate, and nickel nitrate; the cobalt source is at least one of cobalt acetate, cobalt sulfate, and cobalt nitrate; the lithium source is at least one of lithium acetate, lithium sulfate, and lithium nitrate; and the zinc source is at least one of zinc acetate, zinc sulfate, and zinc nitrate.

[0010] Furthermore, the heat treatment conditions for obtaining the precursor by heat treatment of the obtained homogeneous gel are to heat to 110-130°C at a rate of 4-6°C / min and heat treat for 10-14 hours.

[0011] Furthermore, the heat treatment of the precursor is carried out in two stages:

[0012] First stage: Heat to 350-450℃ at a rate of 2-5℃ / min, and heat treat for 3-5 hours;

[0013] Second stage: Heat to 750-850℃ at a rate of 2-5℃ / min, and heat treat for 7-9 hours.

[0014] Furthermore, the heat treatment of the precursor is carried out in an inert gas atmosphere.

[0015] Furthermore, the inert gas is at least one of argon and nitrogen.

[0016] Furthermore, the citric acid solution has a mass concentration of 0.2-0.315 g / mL.

[0017] The present invention relates to the application of a defect element-doped, double-modified lithium-rich manganese-based layered oxide cathode material, which is used to prepare lithium batteries.

[0018] The present invention has the following beneficial effects:

[0019] The cathode material prepared by this invention, through lithium defect engineering-induced formation of the spinel phase in the material, not only improves the Li-... + The migration rate of Zn 2+ Doping provides sites. Furthermore, the stronger Zn-O bonding enhances structural stability. This significantly improves the Li... + It exhibits a high migration rate and excellent cycling performance.

[0020] The lithium-rich manganese-based layered oxide prepared in this invention exhibits several advantages. Firstly, a suitable amount of lithium defects induces the transformation of the Li₂MnO₃ phase to the more stable spinel phase LiMn₂O₄. This process leads to a decrease in the average valence state of manganese and suppresses the phase transition from layered structure to defective spinel and then to disordered rock salt, thereby enhancing battery stability. Secondly, lithium defects cause some zinc ions to permeate into the lithium layer. During lithium ion insertion / extraction, the strong Zn-O bonding stabilizes the lattice oxygen, further enhancing stability.

[0021] The preparation method provided by this invention is simple and can be prepared by simple solution mixing to obtain sol-gel and calcination in an air atmosphere. Attached Figure Description

[0022] Figure 1 The images shown are scanning transmission electron microscope (SEM) images of lithium-rich manganese-based layered oxide cathode materials for Comparative Example 1, Example 1, and Example 2; the SEM scale bar is 1 µm; where a and b are SEM images of different positions of LNCM in Comparative Example 1; c is an SEM image of LNCM-Z in Example 1; d is an LvMNC-Z image in Example 2; and e to g are high-resolution transmission electron microscope images of LvMNC-Z material.

[0023] Figure 2 The X-ray powder diffraction patterns of the lithium-rich manganese-based layered oxide cathode materials in Comparative Example 1, Example 1, and Example 2 are shown from left to right as the original lithium-rich manganese-based layered metal oxide cathode material, the zinc-doped lithium-rich manganese-based layered metal oxide cathode material, and the zinc-doped lithium defect-modified lithium-rich manganese-based layered metal oxide cathode material.

[0024] Figure 3 The following figures illustrate the electrochemical performance tests of lithium-ion batteries assembled from lithium-rich manganese-based layered oxide cathode materials in Comparative Example 1, Example 1, and Example 2, under a constant temperature of 30°C and a voltage range of 2.0-4.8V. Figure a shows the rate performance of the lithium-rich manganese-based layered metal oxide cathode materials in Comparative Example 1, Example 1, and Example 2; Figure b shows the cycle performance of the lithium-rich manganese-based layered metal oxide cathode materials in Comparative Example 1, Example 1, and Example 2 at a current density of 0.2C; and Figure c shows the cycle performance of the lithium-rich manganese-based layered metal oxide cathode materials in Comparative Example 1, Example 1, and Example 2 at a current density of 5C. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the spirit of the contents disclosed in the present invention will be described in detail below. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0026] The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0027] Comparative Example 1

[0028] The chemical composition of the lithium-rich manganese-based layered oxide cathode material (LNCM) in this comparative example is: Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, its preparation method is as follows: Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 (LNCM) was synthesized via a simple sol-gel method. Metal salts Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, and Ni(CH3COO)2·4H2O, along with an excess of 5% LiNO3, were weighed according to specific stoichiometric ratios. These metal salts were dissolved in 50 mL of deionized water to prepare salt solution A. 4.2239 g of citric acid was weighed and added to 50 mL of deionized water, and stirred thoroughly to form solution B. Salt solution A was slowly added dropwise to citric acid solution B, and the mixture was stirred thoroughly to form solution C. The pH of the mixture in solution C was adjusted to 6–7. The mixture was stirred with NH4OH until it became a homogeneous gel. Subsequently, it was dried at 120°C to obtain the polymer precursor. The polymer precursor was heated in air at 400°C for 4 hours and then at 800°C for 8 hours. After cooling, the material is ground into homogeneous powder in a furnace to obtain LNCM material.

[0029] refer to Figure 1 (a) and (b) are scanning electron microscope (SEM) images showing that Comparative Example 1 has well-regulated particles with diameters ranging from 100 to 150 nm.

[0030] refer to Figure 2 The XRD patterns of the lithium-rich manganese-based layered oxide cathode materials synthesized in Comparative Example 1 show that the main diffraction peaks in the XRD patterns are in good agreement with the standard pattern 70-4313 (belonging to the R-3m space group), indicating that all materials have a typical layered α-NaFeO2 structure, corresponding to the LiTMO2 phase. Furthermore, some weaker diffraction peaks appear at 2θ = 20°~25°. These peaks correspond to the Li2MnO3 phase, which is characteristic of lithium-rich manganese-based materials. They are formed by the LiMn6 superlattice arrangement in the transition metal layer.

[0031] refer to Figure 3Cyclic testing was conducted at a current density of 0.2 C, with the voltage range set between 2.0 and 4.8 V. The LMNC material exhibited rapid capacity decay during cycling, decreasing from 246.2 mAh / g to 157.2 mAh / g after 100 cycles, representing a capacity retention of 63.8%. At a current density of 5 C, the initial discharge specific capacity of LMNC was only 102.4 mAh / g, decreasing to 47.3 mAh / g after 800 cycles, with a capacity retention of only 46.1%.

[0032] Example 1

[0033] The chemical formula of the zinc-doped lithium-rich manganese-based layered oxide cathode material (LNCM-Z) in this embodiment is: Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Zn 0.005 O2, its preparation method is as follows: Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 (LNCM) was synthesized via a simple sol-gel method. Metal salts Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, and Ni(CH3COO)2·4H2O, along with excess 5% LiNO3 and Zn(NO3)2 according to the above molar amounts, were weighed according to specific stoichiometric ratios. These metal salts were dissolved in 50 mL of deionized water to prepare salt solution A. 4.2239 g of citric acid was weighed and added to 50 mL of deionized water, and stirred thoroughly to form solution B. Salt solution A was slowly added dropwise to citric acid solution B, and the mixture was stirred thoroughly to form solution C. The pH of the mixture in solution C was adjusted to 6–7. The mixture was stirred with NH4OH until it became a homogeneous gel. Subsequently, it was dried at 120°C to obtain the polymer precursor. The polymer precursor was heated in air at 400°C for 4 hours and then at 800°C for 8 hours. After cooling, the material is ground into homogeneous powder in a furnace to obtain LMNC-Z material.

[0034] refer to Figure 1 (c) SEM images show that the LMNC-Z material has slightly smaller particles, a smoother and more uniform morphology, and clearer boundaries. This indicates that the modification maintained good crystallinity.

[0035] refer to Figure 2The XRD pattern of the zinc-doped lithium-rich manganese-based layered oxide cathode material synthesized in Example 1 shows that the main diffraction peaks in the XRD pattern are in good agreement with the standard pattern 70-4313 (belonging to the R-3m space group), indicating that all materials have a typical layered α-NaFeO2 structure, corresponding to the LiTMO2 phase. Furthermore, some weaker diffraction peaks appear at 2θ = 20°~25°. These peaks correspond to the Li2MnO3 phase, which is characteristic of lithium-rich manganese-based materials. They are formed by the LiMn6 superlattice arrangement in the transition metal layer.

[0036] refer to Figure 3 Under a current density of 5 C and a high charging cutoff voltage of 2-4.8V, the discharge specific capacity of LMNC-Z obtained in Example 1 decreased from 151.7 mAh / g to 84.7 mAh / g after 800 cycles, with a capacity retention of 55.8%. The corresponding lithium-rich manganese-based layered oxide cathode material LMNC had an initial discharge specific capacity of only 102.4 mAh / g, which decreased to 47.3 mAh / g after 800 cycles, with a capacity retention of only 46.1%.

[0037] Example 2

[0038] The chemical composition of the lithium-defect zinc-doped dual-modified lithium-rich manganese-based layered oxide cathode material (LMNC-Z) in this embodiment is: Li 1.12 Mn 0.54 Ni 0.13 Co 0.13 Zn 0.005 O2 is prepared as follows: it is synthesized via a simple sol-gel method. Metal salts Mn(CH3COO)2·4H2O, Co(CH3COO)2·4H2O, Ni(CH3COO)2·4H2O, and Zn(NO3) are weighed according to specific stoichiometric ratios. 2， The molar ratio of lithium sources was reduced to 98% of the theoretical stoichiometry. Salt solution A was prepared by dissolving these metal salts in 50 mL of deionized water. 4.2239 g of citric acid was weighed and added to 50 mL of deionized water, and stirred evenly to form solution B. Salt solution A was slowly added dropwise to citric acid solution B, and the mixture was stirred evenly to form solution C. The pH of the mixture in solution C was adjusted to 6–7. The mixture was stirred with NH4OH until it became a homogeneous gel. Subsequently, it was dried at 120°C to obtain the polymer precursor. The polymer precursor was heated in air at 400°C for 4 hours and then at 800°C for 8 hours. After cooling, it was ground into a homogeneous powder in an oven to obtain the LvMNC-Z material.

[0039] refer to Figure 1 (d) The LvMNC-Z material has slightly smaller particles, a smoother and more uniform morphology, and clearer boundaries. This indicates that the modification maintained good crystallinity. (Reference) Figure 1 Images (e)-(g) are high-resolution transmission electron microscopy (HR-TEM) images of the LvMNC-Z material. At the 20 nm microscale, the three samples are clearly composed primarily of regularly arranged hexahedral sheets. Upon further magnification, the lattice striations are clearly visible, indicating a well-developed crystal structure. Specifically, as... Figure 1 As shown in (f), two distinct structures can be observed: the 0.406 nm interlayer spacing matches the (-111) crystal plane of the Li₂MnO₃ phase, while the 0.246 nm interlayer spacing clearly corresponds to the (111) crystal plane of the spinel phase. This result is consistent with the findings of the aforementioned X-ray diffraction (XRD) analysis, providing more intuitive evidence that the lithium defect-induced spinel phase is effectively coated on the material surface. Energy dispersive spectroscopy (EDS) mapping shows that the distribution of zinc (Zn) is consistent with the distribution of manganese (Mn), cobalt (Co), and nickel (Ni). Zinc does not form localized aggregates in the material but rather forms a homogeneous mixed system with the other elements. This homogeneous distribution ensures that each part of the material exhibits similar chemical and physical properties, thus enabling the LvMN-CZ material to demonstrate superior performance in practical applications.

[0040] refer to Figure 2 The XRD pattern of the double-modified lithium-rich manganese-based substrate oxide cathode material synthesized in Example 2 shows that, compared with Comparative Example 1 and Example 1, two distinct shoulder peaks can be clearly seen near the (003) and (101) diffraction peaks in the local magnified region of LvMNC-Z. These peaks are the result of reflection from the (111) and (220) crystal planes of the spinel phase, respectively, and are labeled as Its space group is Fd-3m. This result proves that lithium defects successfully induced the spinel phase on the sample surface. Another observation in the XRD spectrum is the obvious splitting of the (006) / (102) and (108) / (110) peaks, which indicates that the synthesized material has a good layered structure.

[0041] refer to Figure 3At a current density of 0.2 C, the LvMNC-Z material exhibits the highest cycling stability, maintaining a discharge specific capacity of 237.0 mAh / g after 100 cycles, with a capacity retention of 91.6%. The corresponding lithium-rich manganese-based substrate oxide shows rapid capacity decay, decreasing from 246.2 mAh / g to 157.2 mAh / g, with a capacity retention of only 63.8%. The discharge specific capacities of LvMNC-Z at current densities of 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 10 C are 268.9, 217, 185.6, 158, 123.8, and 94.5 mAh / g, respectively, all higher than those of LMNC at the corresponding current densities. At a current density of 5C, LvMNC-Z exhibits an initial discharge specific capacity of 145 mAh / g, which decreases to only 92.3 mAh / g after 800 cycles, demonstrating a capacity retention of 63.7%. In contrast, the corresponding lithium-rich manganese-based layered oxide cathode material has an initial discharge specific capacity of only 102.4 mAh / g, decreasing to 47.3 mAh / g after 800 cycles, with a capacity retention of only 46.1%. The corresponding zinc-doped lithium-rich manganese-based layered oxide cathode material shows a discharge specific capacity decrease from 151.7 mAh / g to 84.7 mAh / g after the same number of cycles, with a capacity retention of 55.8%.

[0042] As can be seen from this embodiment, the lithium-defect zinc-doped lithium-rich manganese-based basal oxide cathode material provided by the present invention has better long-cycle stability at high charging cut-off voltage compared with the unmodified lithium-rich manganese-based basal oxide cathode material.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that any changes or modifications made by those skilled in the art without departing from the scope of the technical solution disclosed above are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A lithium-rich manganese-based layered oxide cathode material with defect element doping and dual modification, characterized in that, The chemical formula of the positive electrode material is Li 1.12 (Mn 0.54 Ni 0.13 Co 0.13 ) x Zn 1-x O2, where x = 0.0025~0.

01.

2. The lithium-rich manganese-based substrate oxide cathode material with defect element doping and dual modification according to claim 1, characterized in that, The defect element-doped double-modified lithium-rich manganese-based base oxide cathode material is obtained by lithium defect-induced transformation of the Li2MnO3 phase into the spinel phase LiMn2O4.

3. A method for preparing a lithium-rich manganese-based substrate oxide cathode material with defect element doping and dual modification as described in claim 1, characterized in that, The preparation method is as follows: According to the chemical formula Li 1.12 (Mn 0.54 Ni 0.13 Co 0.13 ) x Zn 1-x The dosage of O2 is determined by adding aqueous solutions of manganese, nickel, cobalt, lithium, and zinc sources dropwise into a citric acid solution, mixing them uniformly to form a mixture, adjusting the pH to 6-7, adding NH4OH, and stirring the mixture to obtain a homogeneous gel. The obtained homogeneous gel is then heat-treated to obtain a precursor. This precursor is further heat-treated to obtain the lithium-rich manganese-based layered oxide cathode material. The lithium source is selected according to the chemical formula Li... 1.12 (Mn 0.54 Ni 0.13 Co 0.13 ) x Zn 1-x 98% of the 1.12% of O2 was added.

4. The method for preparing a lithium-rich manganese-based substrate oxide cathode material with defect element doping and dual modification according to claim 3, characterized in that, The manganese source is at least one of manganese acetate, manganese sulfate, and manganese nitrate; the nickel source is at least one of nickel acetate, nickel sulfate, and nickel nitrate; the cobalt source is at least one of cobalt acetate, cobalt sulfate, and cobalt nitrate; the lithium source is at least one of lithium acetate, lithium sulfate, and lithium nitrate; and the zinc source is at least one of zinc acetate, zinc sulfate, and zinc nitrate.

5. The method for preparing a lithium-rich manganese-based substrate oxide cathode material with defect element doping and dual modification according to claim 3, characterized in that, The heat treatment conditions for obtaining the precursor by heat treatment of the obtained homogeneous gel are: heating to 110-130℃ at a rate of 4-6℃ / min, and heat treatment for 10-14h.

6. The method for preparing a lithium-rich manganese-based layered oxide cathode material with defect element doping and dual modification according to claim 3, characterized in that, The heat treatment of the precursor is carried out in two stages: First stage: Heat to 350-450℃ at a rate of 2-5℃ / min, and heat treat for 3-5 hours; Second stage: Heat to 750-850℃ at a rate of 2-5℃ / min, and heat treat for 7-9 hours.

7. A method for preparing a lithium-rich manganese-based layered oxide cathode material with defect element doping and dual modification according to claim 3 or 6, characterized in that, The heat treatment of the precursor is carried out in an inert gas atmosphere.

8. The method for preparing a lithium-rich manganese-based layered oxide cathode material with defect element doping and dual modification according to claim 7, characterized in that, The inert gas is at least one of argon and nitrogen.

9. The method for preparing a lithium-rich manganese-based layered oxide cathode material with defect element doping and dual modification according to claim 3, characterized in that, The citric acid solution has a mass concentration of 0.2-0.315 g / mL.

10. The application of the defect element-doped, dual-modified lithium-rich manganese-based layered oxide cathode material as described in claim 1 or 2, characterized in that, The cathode material is used to prepare lithium batteries.

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