A lithium-rich manganese-based positive electrode material, a preparation method thereof and a battery

Abstract

This invention relates to the field of lithium battery technology, and more particularly to a lithium-rich manganese-based cathode material, its preparation method, and a battery thereof. The lithium-rich manganese-based cathode material comprises a lithium-rich core: the lithium-rich core includes a lithium-rich manganese-based matrix and a non-metallic element-doped structure located on the surface of the lithium-rich manganese-based matrix; and a composite modification layer coating the surface of the lithium-rich core: the composite modification layer contains an oxygen-deficient transition metal oxide and an amorphous lithium salt glass phase; the transition metal element in the oxygen-deficient transition metal oxide is selected from one or more of Mo, W, V, Ti, Nb, Ce, and Zr, and the amorphous lithium salt glass phase is selected from one or more of lithium sulfate, lithium phosphate, lithium silicate, lithium borate, and lithium aluminate. The lithium-rich manganese-based cathode material provided by this invention can improve the interfacial stability and cycle performance of the material through the synergistic effect of near-surface doping and the composite modification layer.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a lithium-rich manganese-based cathode material, its preparation method, and a battery thereof. Background Technology

[0002] Lithium-ion batteries, as important energy storage devices, are widely used in electronic devices, electric vehicles, and renewable energy storage. With the increasing demand for energy, all-solid-state batteries are considered the optimal solution to balance high energy density and high safety performance. High-capacity cathode materials are one of the key factors affecting all-solid-state batteries. In particular, lithium-rich manganese-based cathode materials have attracted much attention from the scientific and industrial communities due to their high theoretical specific capacity and superior high voltage stability. However, lithium-rich manganese-based cathode materials face several key problems in practical applications, mainly in long-cycle stability and performance degradation under high voltage.

[0003] In existing technologies, to improve the performance of lithium-rich manganese-based cathode materials, researchers generally employ coating techniques to enhance the interfacial stability of the materials. Common coating materials include metal oxides, fluorides, and phosphates. These coating materials reduce side reactions and improve the cycle stability of the material by isolating the electrolyte from direct contact with the cathode. However, existing composite coating technologies still have some limitations. For example, Chinese patent application CN109713260A mainly uses single phosphate coating—while it can improve stability, its function as an ion / electron conduction / interface layer is singular: it neither considers providing good electron / ion conduction nor includes structural gradient or interface buffer design. Meanwhile, in existing technologies, besides coating modification, non-metallic element doping is also an important means to improve the structural stability and interfacial performance of lithium-rich manganese-based cathode materials, with sulfur doping being a typical example. For instance, the sulfur doping method used in Chinese patent application CN111430703A typically involves high-temperature treatment, which may cause changes in the lattice structure of the material, thus affecting the overall performance of the battery. Therefore, optimizing the structure of the coating layer and improving the long-term stability and interfacial compatibility of lithium-rich manganese-based cathode materials remain key to solving these problems.

[0004] Furthermore, solid-state batteries, as a novel energy storage technology, have become a research hotspot in recent years due to their higher safety and longer lifespan. However, improving the performance of solid-state batteries still faces many challenges, particularly in terms of the interfacial stability and ionic conductivity between the cathode and the solid electrolyte. Existing lithium-rich manganese-based cathode materials still face problems such as interfacial reactions, material expansion, and capacity decay in solid-state batteries. Although existing research has focused on the coating or modification of lithium-rich manganese-based cathode materials, and methods for optimizing the coating layer structure for traditional liquid lithium-ion batteries exist, few publications or patent applications specifically address the systematic study of the interfacial compatibility between lithium-rich cathode materials and solid electrolytes. In particular, how to solve problems such as high voltage, lithium-rich reactive oxygen release, interfacial side reactions, ion / electron conduction, and interfacial stability has been almost entirely undisclosed and optimized in existing published patent applications. Currently, there is an urgent need to provide a novel lithium-rich manganese-based cathode material and its preparation method. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a lithium-rich manganese-based cathode material with a multi-level interface buffer composite layer, its preparation method, and a battery. By introducing a non-metallic element doping structure into the near-surface layer of the lithium-rich manganese-based substrate and constructing a composite modification layer containing oxygen-deficient transition metal oxides and amorphous lithium salt glass phases on its outer surface, the interfacial stability and cycle performance of the material can be improved without significantly damaging the main layered structure.

[0006] In a first aspect, the lithium-rich manganese-based cathode material provided by the present invention comprises: Lithium-rich core: The lithium-rich core includes a lithium-rich manganese matrix and a non-metallic element doping structure located on the surface of the lithium-rich manganese matrix.

[0007] The composite modified layer coating the surface of the lithium-rich core contains an oxygen-deficient transition metal oxide and an amorphous lithium salt glass phase; the transition metal element in the oxygen-deficient transition metal oxide is selected from one or more of Mo, W, V, Ti, Nb, Ce, and Zr, and the amorphous lithium salt glass phase is selected from one or more of lithium sulfate, lithium phosphate, lithium silicate, lithium borate, and lithium aluminate.

[0008] This invention provides a lithium-rich manganese-based cathode material with a multi-level interface buffer composite layer. Through gradient doping of non-metallic elements, synergistic modification with oxygen-deficient transition metal oxides and amorphous lithium salt glass phases, the high-voltage stability, interfacial compatibility, and cycle performance of the lithium-rich manganese-based cathode material are significantly improved. This invention enhances the uniformity and stability of the composite layer while improving the material's conductivity and interfacial reaction inhibition capabilities. This structure exhibits excellent electrochemical performance in both solid-state and liquid lithium-ion batteries, demonstrating outstanding performance under high voltage and long-cycle operation.

[0009] Preferably, the general chemical formula of the lithium-rich manganese-based matrix is ​​xLi₂MnO₃·(1-x)LiMO₂, where M is selected from one or more of Mn, Ni, and Co, 0 < x < 1, and preferably 0.4 ≤ x ≤ 0.6; the non-metallic element doping structure is preferably a sulfur gradient doping structure. For example, in Embodiment 1 of the present invention, the sulfur content in the near-surface region of the lithium-rich manganese-based matrix is ​​higher than that in the deeper regions; combined with the XPS depth profile results, it can be seen that the S 2p spectrum under unetched (0 s) conditions mainly shows characteristic peaks located in the higher binding energy region, corresponding to sulfate (SO₄) in the amorphous lithium salt glass phase on the surface. 2- The high-valence sulfur-containing species, such as S, are observed. However, after etching for a certain period (e.g., 100 s), as the surface layer is gradually removed, in the near-surface region close to the substrate, in addition to the weakening of the signal of the aforementioned high-valence sulfur species, a new peak appears in the region with a lower binding energy. This peak can be attributed to S... 2- It is dominated by low-valence sulfur species, which are associated with lattice or near-surface structures.

[0010] The above is composed of surface high-valence sulfur (SO4) 2- ) to the inner layer of low-valence sulfur (S) 2- The transformation of sulfur indicates that sulfur not only exists on the particle surface in the form of lithium salt glass phase, but also enters the lattice or near-surface structure of lithium-rich manganese matrix as a dopant, forming a sulfur chemical environment and distribution gradient that gradually changes from the outside to the inside. This result proves the real existence and gradient characteristics of sulfur-doped structures from both the valence state and spatial distribution perspectives, and is an important basis for the construction of non-metallic element gradient doping structures in this invention.

[0011] Preferably, the general chemical formula of the oxygen-deficient transition metal oxide is M'O. n-δ Wherein, M' is selected from one or more of Mo, W, V, Ti, Nb, Ce, and Zr, n is the number of oxygen atoms in the common oxides corresponding to the stoichiometric ratio of M', and δ is the amount of oxygen vacancies, satisfying 0.02≤δ≤0.5. In the preferred Mo or W system of the embodiments of the present invention, n is 3.

[0012] Preferably, the amorphous lithium salt glass phase is selected from one or more of Li2SO4, Li3PO4, Li2SiO3, LiBO2, LiPO3, and Li4P2O7.

[0013] Preferably, the non-metallic element is one of S, P, Si, and B, and sulfur is the most preferred element.

[0014] Preferably, the oxygen-deficient transition metal oxide and the amorphous lithium salt glass phase form a composite distribution structure in the composite modification layer; in some embodiments, the two can be spatially interwoven. In this invention, detection results from scanning electron microscopy (EDS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and aberration-corrected transmission electron microscopy (AC-TEM) show that the oxygen-deficient transition metal oxide and the amorphous lithium salt glass phase are mainly distributed on the material surface, and together with the near-surface doped region, constitute the composite modification interface. This structure helps to improve surface stability, interfacial compatibility, and cycling performance.

[0015] Secondly, the present invention provides a method for preparing the lithium-rich manganese-based cathode material, comprising: 1) A transition metal precursor was prepared by co-precipitation method; the transition metal precursor was mixed with a lithium source and calcined to obtain lithium-rich manganese-based matrix powder.

[0016] 2) The lithium-rich manganese-based matrix powder is mixed with a metal sulfide precursor to obtain a precursor composite powder.

[0017] 3) The precursor composite powder is subjected to a two-stage heat treatment to obtain a composite powder with a lithium-rich core and an oxygen-deficient transition metal oxide coating.

[0018] 4) The composite powder is mixed with a lithium salt glass precursor, heat-treated and then rapidly cooled to obtain a lithium-rich manganese-based cathode material containing a surface composite modification layer and a non-metallic element doping structure.

[0019] Preferably, in step 1), the lithium source is selected from at least one of Li2CO3, LiOH·H2O, LiCl, LiNO3, LiC2H3O2, and Li2SO4.

[0020] Preferably, in step 1), the precipitant used in the co-precipitation method is selected from one or more of NaOH, KOH, Na2CO3, and K2CO3.

[0021] Preferably, in step 1), the transition metal precursor is prepared by co-precipitation of a transition metal salt, wherein the transition metal salt is selected from one or more of sulfates, nitrates, chlorides, and acetates, and is preferably NiSO4, MnSO4, or CoSO4.

[0022] Further preferably, in step 1), the reaction temperature of the co-precipitation method is 40-60℃, the pH is 9.5-12.5, and the reaction time is 2-24h; preferably, in step 1), the calcination includes a first stage sintering and a second stage sintering, wherein the first stage sintering is performed at 350-650℃ for 2-10h, and the second stage sintering is performed at 750-980℃ for 5-30h.

[0023] Preferably, the calcination atmosphere is an oxygen-containing atmosphere.

[0024] Preferably, in step 2), the metal element M in the metal sulfide precursor is selected from one or more of Mo, W, V, Ti, Nb, Ce, and Zr; and the metal sulfide is selected from one or more of MoS2, WS2, VS2, TiS2, NbS2, Ce2S3, and ZrS2.

[0025] Further preferably, in step 2), the method of introducing the metal sulfide precursor is selected from one or more of dry mixing, ball milling coating, solution impregnation, and spray drying, preferably ball milling coating; preferably, the amount of the metal sulfide precursor added is 0.05-10 wt% of the mass of the lithium-rich manganese-based matrix, preferably 2-8 wt%, and more preferably 3-4 wt%, based on the metal element.

[0026] Preferably, in step 3), the first stage of the two-stage heat treatment includes the following conditions: under an inert atmosphere, the temperature is 200-500℃, preferably 300-400℃, and the time is 0.2-10h, preferably 3-4h; the second stage of the heat treatment includes: under an oxygen-containing atmosphere, the temperature is 250-650℃, preferably 500-600℃, more preferably 500-550℃, and the time is 0.2-20h, preferably 5-6h; thereby enabling the metal sulfide to undergo in-situ transformation, where the metal element M' is oxidized and forms a compound with the general formula M'O. n-δ The oxygen-deficient transition metal oxide coating layer. As can be seen from the examples and comparative examples, this combination of conditions helps to improve the initial discharge specific capacity, initial coulombic efficiency, and cycle retention.

[0027] Further preferably, the atmosphere of the second heat treatment stage is an oxygen-containing gas or a controllable oxygen partial pressure atmosphere, such as air, or a mixture of oxygen and an inert gas, with an oxygen volume fraction of 1%-80%.

[0028] Preferably, in step 4), the lithium salt glass precursor is selected from one or more of Li2SO4, Li3PO4, Li2SiO3, LiBO2, and LiPO3, preferably Li2SO4, Li3PO4, and LiBO2, and the mass loading of the lithium salt glass precursor is 0.1-15 wt% of the mass of the lithium-rich manganese-based matrix. Preferably, the non-metallic element is one of S, P, Si, B, and Al, preferably sulfur.

[0029] Preferably, in step 4), the heat treatment temperature is 100-650℃, preferably 300-700℃, for example, 400℃, 500℃, 600℃, 700℃, etc., more preferably 500-550℃, and the time is 0.2-10h, preferably 2-9h, for example 3h, 5h, 8h, 9h, etc., more preferably 7-8h.

[0030] Preferably, in step 4), the rapid cooling is gas flow quenching, liquid nitrogen assisted cooling, or natural rapid heat dissipation, with a cooling rate ≥10℃ / min, such as 15℃ / min, 20℃ / min, 25℃ / min, 30℃ / min, etc., preferably 20-30℃ / min.

[0031] In this invention, a lithium salt glass precursor (selected from Li2SO4, Li3PO4, Li2SiO3, LiBO2, LiPO3) is introduced and an amorphous lithium salt glass component is constructed. After heat treatment (temperature 100-650℃, time 0.2-10h), a cooling process is used to cool the lithium salt glass precursor at a cooling rate ≥10℃ / min, so that the lithium salt glass precursor is rapidly transformed into an amorphous glass phase and solidified on the particle surface to construct a doped structure, which significantly improves the overall performance of the product. The effect is even better under the preferred conditions.

[0032] Further preferred, the coating layer formed by steps 3) and 4) is a composite coating layer, and the mass ratio of the composite coating layer in the lithium-rich manganese-based cathode material is not zero and is less than 30 wt%; for example, 1 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 28 wt%, etc.

[0033] Thirdly, the present invention provides a lithium-ion battery or a solid-state battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator; the positive electrode comprises a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector, the positive electrode active layer comprising the lithium-rich manganese-based positive electrode material or the lithium-rich manganese-based positive electrode material obtained by the preparation method; the electrolyte is a solid electrolyte in a solid-state battery or a liquid electrolyte in a lithium-ion battery.

[0034] The beneficial effects of this invention are at least as follows: The novel lithium-rich manganese-based cathode material provided by this invention employs a multi-level interface buffer composite layer, combining an oxygen-deficient transition metal oxide and an amorphous lithium salt glass phase into a composite structure, while simultaneously incorporating non-metallic element doping. This significantly improves the material's high-voltage stability, interfacial compatibility, and cycle performance. Through this structure, the uniformity and stability of the composite layer are effectively enhanced, while the introduction of non-metallic element doping improves the material's conductivity and interfacial reaction inhibition capability. This innovative structure exhibits excellent electrochemical performance in both solid-state and liquid lithium-ion batteries, particularly excelling in high-voltage and long-cycle operation. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. Without creative effort, those skilled in the art can further obtain other drawings based on the drawings of this application.

[0036] Figure 1 This is a SEM image in BSE mode of Embodiment 1 of the present invention.

[0037] Figure 2 These are (a) TEM images and (b) AC-TEM images of Example 1 of this invention.

[0038] Figure 3 This is the EDS diagram of Embodiment 1 in this invention.

[0039] Figure 4 This is an XPS image of molybdenum and sulfur in Example 1 of this invention.

[0040] Figure 5 This is an EPR diagram of Embodiment 1 in this invention.

[0041] Figure 6 These are XRD patterns of Example 1 and Comparative Example 1 in this invention.

[0042] Figure 7 This is a charge-discharge curve diagram for the first week of Embodiment 1 of the present invention.

[0043] Figure 8 This is a SEM image in BSE mode for Comparative Example 1 of this invention.

[0044] Figure 9 This is the charge-discharge curve of Comparative Example 1 in this invention during the first week. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0046] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0047] Unless otherwise specified, the techniques or conditions described in the embodiments of this invention shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Devices, instruments, reagents, etc., without specified manufacturers, are all conventional products that can be purchased through legitimate channels. All experimental reagents and raw materials involved are commercially available products, and all reagents are analytical grade products.

[0048] In this embodiment of the invention, the xLi2MnO3·(1-x)LiMO2 matrix powder was prepared by co-precipitation. The specific value of x was 0.5; the molar ratio of Mn, Ni, and Co in M ​​was 0.54:0.13:0.13; the transition metal salts used were NiSO4·6H2O, MnSO4·H2O, and CoSO4·7H2O. The lithium source was lithium carbonate (99.9% purity), the co-precipitation reaction temperature was 50℃, pH=10, and the reaction time was 10h; the first stage of the sintering procedure was treatment at 500℃ for 5h, followed by treatment at 900℃ for 15h.

[0049] Example 1 This embodiment provides a lithium-rich manganese-based cathode material, which uses the standard co-precipitation method described above to prepare xLi₂MnO₃·(1-x)LiMO₂ matrix powder. Subsequently, a MoS₂ precursor is introduced onto the matrix surface by ball milling at an addition amount of 3 wt%. The material undergoes two stages of heat treatment: the first stage is at 300°C in an inert atmosphere for 3 h, and the second stage is at 500°C in an oxygen-containing atmosphere for 5 h, forming a molybdenum oxide layer containing oxygen vacancies. Then, Li₂SO₄ is introduced as a lithium salt glass precursor, and the material is heat-treated at 500°C for 8 h, followed by cooling at a cooling rate of 20°C / min to obtain an amorphous lithium salt glass and a sulfur-doped composite layer.

[0050] SEM images in backscattered (BSE) mode are as follows: Figure 1 As shown, a continuous outer layer with higher contrast can be observed on the particle surface. Since BSE is more sensitive to atomic numbers, the brightness difference of the outer layer in the figure indicates the presence of a coating phase on the particle surface that differs from the bulk component; combined with the annotation results, this can be attributed to the surface-constructed MoO₂. 3-xThe composite coating with Li2SO4 was formed. The composite layer was evenly distributed, continuous and dense along the particle surface, with no obvious exposed matrix or large-area peeling, indicating that the coating layer was successfully formed and had good coverage and integrity.

[0051] The microstructure of Example 1 was analyzed using transmission electron microscopy (TEM) (see [link]). Figure 2 The figure shows a crystal plane spacing of 0.218 nm, confirming the formation of an oxygen-vacancy molybdenum oxide layer. A layer spacing of d(003) = 0.49 nm further indicates a distinct layered structure, slightly larger than the d(003) = 0.47 nm of normal lithium-rich materials, suggesting the introduction of sulfur doping. This increased layer spacing is typically associated with lattice expansion caused by sulfur doping, demonstrating that sulfur doping successfully alters the material's structure and improves the battery's interfacial compatibility. Furthermore, the TEM image reveals the presence of amorphous materials on the surface, indicating the formation of an amorphous Li₂SO₄ layer, further enhancing the material's interfacial stability. The TEM images verify the high-quality crystal structure and uniformity of the composite layer, demonstrating the successful introduction of sulfur doping, the oxygen-vacancy molybdenum oxide layer, and amorphous lithium sulfate, consistent with the designed composite layer structure.

[0052] Furthermore, aberration-corrected transmission electron microscopy (AC-TEM) was employed (see... Figure 2 The surface structure of the material was characterized with high resolution, allowing for a clearer distinction between crystalline and amorphous regions. Crystalline MoO₂ can be observed on the surface in the figure. 3-x The nanostructure exhibits clearly discernible lattice fringes, while its outer or adjacent regions display an amorphous structure without obvious lattice fringes, corresponding to the amorphous Li₂SO₄ phase; the two are in close contact at the nanoscale and exhibit an interwoven distribution. This result further directly proves that a crystalline oxygen-deficient transition metal oxide (MoO₂) is constructed on the surface of the material of this invention. 3-x A composite coating structure consisting of amorphous lithium salt glass phase (Li₂SO₄) and an amorphous lithium salt glass phase. Figure 2 It can be seen that the composite layer not only uniformly covers the particle surface on a macroscopic scale, but also forms a crystalline / amorphous synergistic composite structure on a microscopic scale, thus fully demonstrating the construction method and structural characteristics of the "oxygen-deficient transition metal oxide-amorphous lithium salt glass phase" composite modified layer proposed in this invention. This structure can achieve a synergistic improvement in interface stability and ion / electron transport performance while maintaining the stability of the main layered structure, thereby providing a structural basis for improving material performance.

[0053] For the EDS image of Example 1 (see Figure 3The image shows a uniform distribution of molybdenum (Mo), sulfur (S), cobalt (Co), manganese (Mn), and nickel (Ni), demonstrating the successful formation of the composite layer. The uniform distribution of molybdenum indicates that the oxygen-vacancy molybdenum oxide composite layer has been effectively coated on the surface of the cathode material, and the presence of sulfur further verifies the formation of lithium sulfate and sulfur-doped layers, which helps to improve the interfacial compatibility between the material and the solid electrolyte.

[0054] The XPS depth profiling results of Example 1 are as follows: Figure 4 As shown, Mo 3d can be fitted into two partial peaks under both 0s and 100s etching conditions. One set is located in the high binding energy region, corresponding to Mo... 6+ The other group is located in a relatively low binding energy region, corresponding to Mo 5 + / Mo 4+ The bimodal characteristic of the coexistence of high-valence and low-valence Mo indicates that the surface molybdenum oxide is not stoichiometric MoO3, but rather contains MoO. 3-x The reduced state component in this form is direct evidence of surface oxygen vacancies. In the unetched state (0s), S 2p mainly exhibits a peak at a high binding energy, which can be attributed to SO4 in the amorphous Li2SO4 on the surface. 2- The signal; after 100 seconds of etching, the SO4 2- While the peak significantly weakened, a new weak peak appeared on the side with lower binding energy, corresponding to sulfur-doped species (S) in the lattice / near-surface layer. 2- (or containing sulfoxy groups). Therefore, the changes in Mo 3d and S 2p before and after etching together prove that an oxygen-vacancy-rich MoO2 was constructed on the surface of the material in this embodiment. 3-x A Li₂SO₄ composite coating layer was formed, and a distinct sulfur-doped region was established on the side near the substrate. Furthermore, the defect structure in the material was characterized by electron paramagnetic resonance (EPR) testing (see [link to ECR]). Figure 5 A distinct characteristic signal was observed at g≈2.003, which is typically attributed to oxygen vacancies or related defect centers. Compared to Comparative Example 1, Example 1 exhibits a higher signal intensity at this g value, indicating the presence of more oxygen vacancy defects on its surface or near-surface region. This result is consistent with the oxygen-deficient transition metal oxides (MoO2) observed in the aforementioned TEM and aberration-corrected electron microscopy. 3-x The consistent structure further confirms the successful construction of oxygen vacancies in the composite coating layer of this invention, thus providing a structural basis for improving interface stability and electrochemical performance.

[0055] The XRD patterns of Example 1 and Comparative Example 1 are as follows: Figure 6As shown, the diffraction peaks maintain the characteristic peak positions and relative intensities of the lithium-rich layered structure, indicating that the composite coating / treatment process did not damage the main crystal structure. Meanwhile, at the low-angle characteristic peaks (enlarged area in the right figure), Example 1 shows a significant leftward shift (2θ decrease) compared to Comparative Example 1. According to Bragg's law, a decrease in 2θ corresponds to an increase in interplanar spacing, indicating a slight lattice expansion. This lattice expansion can be attributed to the local structural modulation caused by the introduction of sulfur doping into the surface / near-surface layer, further confirming the successful introduction of sulfur doping in Example 1 from an XRD perspective.

[0056] Solid-state battery fabrication: The lithium-rich manganese-based cathode material prepared in Example 1, a solid electrolyte, and carbon nanotubes were mixed to form a composite cathode. A lithium sheet was used as the anode, and Li6PS5Cl was used as the solid electrolyte. During assembly, the solid electrolyte, the cathode and anode sheets, and a separator were pressed together to form a battery cell, which was then assembled in a glove box to obtain the solid-state battery.

[0057] The electrochemical performance of the solid-state battery in Example 1 was tested using an electrochemical testing instrument at a temperature of 25°C. At a current density of 0.1C (1C = 200 mAh / g), the charging voltage range was 2–4.8V. The initial charge-discharge performance of the battery was tested as follows: Figure 7 As shown in Table 1, the detailed results of the cycle performance are as follows.

[0058] Example 2 This embodiment provides a lithium-rich manganese-based cathode material, prepared using a standard co-precipitation method to obtain xLi₂MnO₃·(1-x)LiMO₂ matrix powder. Subsequently, a MoS₂ precursor was introduced onto the matrix surface via ball milling at an addition amount of 3 wt%. The material underwent two heat treatments: the first stage was at 300°C in an inert atmosphere for 3 h, and the second stage was at 600°C in an oxygen-containing atmosphere for 5 h, forming a molybdenum oxide layer with oxygen vacancies. Then, Li₂SO₄ was introduced as a lithium salt glass precursor, followed by heat treatment at 500°C for 8 h and cooling at a rate of 30°C / min to obtain an amorphous lithium salt glass and sulfur-doped composite layer. The material was applied to a solid-state battery using the method of Example 1, employing a Li₆PS₅Cl solid electrolyte. The electrochemical test results are shown in Table 1.

[0059] Example 3 This embodiment provides a lithium-rich manganese-based cathode material, prepared using a standard co-precipitation method to obtain xLi₂MnO₃·(1-x)LiMO₂ matrix powder. Subsequently, a MoS₂ precursor was introduced onto the matrix surface via ball milling at an addition amount of 3 wt%. The material underwent two heat treatments: the first stage was at 300°C in an inert atmosphere for 3 h, and the second stage was at 500°C in an oxygen-containing atmosphere for 5 h, forming a molybdenum oxide layer with oxygen vacancies. Then, Li₂SO₄ was introduced as a lithium salt glass precursor, followed by heat treatment at 500°C for 8 h and cooling at a rate of 30°C / min to obtain an amorphous lithium salt glass and sulfur-doped composite layer. The material was applied to a solid-state battery using the method of Example 1, employing a Li₆PS₅Cl solid electrolyte. The electrochemical test results are shown in Table 1.

[0060] Example 4 This embodiment provides a lithium-rich manganese-based cathode material, prepared using a standard co-precipitation method to obtain xLi₂MnO₃·(1-x)LiMO₂ matrix powder. Subsequently, a MoS₂ precursor was introduced onto the matrix surface via ball milling at an addition amount of 3 wt%. The material underwent two heat treatments: the first stage was at 300°C in an inert atmosphere for 3 h, and the second stage was at 500°C in an oxygen-containing atmosphere for 5 h, forming an oxygen-vacancy molybdenum oxide layer. Then, Li₃PO₄ was introduced as a lithium salt glass precursor, followed by heat treatment at 500°C for 8 h and cooling at a rate of 20°C / min to obtain an amorphous lithium salt glass and phosphorus-doped composite layer. The material was applied to a solid-state battery using the method of Example 1, employing a Li₆PS₅Cl solid electrolyte. The electrochemical test results are shown in Table 1.

[0061] Example 5 In this embodiment, the lithium-rich manganese-based cathode material was prepared using a standard co-precipitation method to obtain xLi2MnO3·(1-x)LiMO2 matrix powder. A MoS2 precursor was introduced onto the surface of the matrix powder at a concentration of 3 wt% using a solution impregnation method. After two stages of heat treatment—the first stage at 300°C in an inert atmosphere for 3 h, and the second stage at 500°C in an oxygen-containing atmosphere for 5 h—an oxygen-vacancy molybdenum oxide composite layer was formed. Subsequently, LiBO2 was added as a lithium salt glass precursor, and the mixture was heat-treated at 500°C for 5 h, followed by cooling at a rate of 20°C / min to form an amorphous lithium salt glass and a boron-doped layer. The material was applied to a solid-state battery using the method of Example 1, employing a Li6PS5Cl solid electrolyte. The electrochemical test results are shown in Table 1.

[0062] Example 6 This embodiment provides a lithium-rich manganese-based cathode material, prepared using a standard co-precipitation method to obtain xLi₂MnO₃·(1-x)LiMO₂ matrix powder. Subsequently, a WS₂ precursor was introduced onto the matrix surface via ball milling at an addition amount of 3 wt%. The material underwent two heat treatments: the first stage was at 300°C in an inert atmosphere for 3 h, and the second stage was at 500°C in an oxygen-containing atmosphere for 5 h, forming an oxygen-vacancy tungsten oxide layer. Then, Li₂SO₄ was introduced as a lithium salt glass precursor, followed by heat treatment at 500°C for 5 h and cooling at a rate of 20°C / min to obtain an amorphous lithium salt glass and a sulfur-doped layer. The method of Example 1 was used to apply this material in a solid-state battery using a Li₆PS₅Cl solid electrolyte. The electrochemical test results are shown in Table 1.

[0063] Example 7 The same method as in Example 1 was used, except that the amount of MoS2 added, calculated as metal element, was adjusted to 2 wt% to verify the rationality of the preferred range of precursor addition in step 2). The electrochemical test results are shown in Table 1.

[0064] Example 8 The same method as in Example 1 was used, except that the second heat treatment temperature in step 3) was adjusted to 550°C. The electrochemical test results are shown in Table 1.

[0065] Example 9 The same method as in Example 1 was used, except that in step 4), the lithium salt glass precursor was replaced with Li3PO4, and the heat treatment time was adjusted to 5 hours. The electrochemical test results are shown in Table 1.

[0066] Comparative Example 1 In this comparative experiment, a basic lithium-rich manganese-based cathode material without any coating or doping treatment was used. This material was prepared by a conventional co-precipitation method, and the resulting xLi₂MnO₃·(1-x)LiMO₂ matrix powder underwent no surface treatment or hierarchical structure modification. The material was applied to a solid-state battery using the method described in Example 1, with a Li₆PS₅Cl solid electrolyte. The electrochemical test results are shown in Table 1. Figure 9 The charge-discharge curve for Comparative Example 1 shows the initial capacity of the material at 189.1 mAh / g, with an initial efficiency of 61.69%, and a capacity retention of only 56.23% after 300 cycles. The lack of a base material employing sulfur doping, an oxygen-vacancy molybdenum oxide composite layer, or an amorphous lithium salt glass coating results in significantly lower electrochemical performance compared to other modified materials.

[0067] Figure 8The image shows the SEM image of the material in Comparative Example 1 in backscattered electron (BSE) mode. The image illustrates the morphology of the lithium-rich manganese-based cathode material particles, which exhibit a relatively smooth surface and no obvious coating layer. Since backscattered electrons are more sensitive to elements with higher atomic numbers, the material surface displays uniform low contrast, indicating the absence of any high-atomic-number coating layer or composite.

[0068] Comparative Example 2 In this comparative experiment, the lithium-rich manganese-based cathode material did not incorporate an oxygen-vacancy molybdenum oxide composite layer. The same material preparation method as in Example 1 was used in this comparative experiment, but the step of forming the oxygen-vacancy molybdenum oxide layer was omitted. Electrochemical test results are shown in Table 1. This material exhibits poor high-rate performance and high internal resistance, which affects its long-term stability. The lack of an oxygen-vacancy molybdenum oxide composite layer leads to a decline in battery performance during long-term use, especially at high voltages where degradation is likely to occur.

[0069] Comparative Example 3 The lithium-rich manganese-based cathode material used in this comparative experiment was not treated with an amorphous lithium salt glass coating. The same material synthesis method as in Example 1 was applied to this experiment, but the lithium salt glass coating step was omitted. Electrochemical test results are shown in Table 1. The results indicate that the absence of the amorphous lithium salt glass layer reduces the overall stability of the battery, especially during charge and discharge, where battery performance significantly degrades. The amorphous lithium salt glass coating is crucial for improving battery stability and extending cycle life.

[0070] Table 1

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, include: Lithium-rich core: The lithium-rich core includes a lithium-rich manganese matrix and a non-metallic element doping structure located on the surface of the lithium-rich manganese matrix; The composite modified layer coating the surface of the lithium-rich core contains an oxygen-deficient transition metal oxide and an amorphous lithium salt glass phase; the transition metal element in the oxygen-deficient transition metal oxide is selected from one or more of Mo, W, V, Ti, Nb, Ce, and Zr, and the amorphous lithium salt glass phase is selected from one or more of lithium sulfate, lithium phosphate, lithium silicate, lithium borate, and lithium aluminate.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The general chemical formula of the lithium-rich manganese-based matrix is ​​xLi2MnO3·(1-x)LiMO2, where M is selected from one or more of Mn, Ni, and Co, and 0 < x < 1.

3. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The non-metallic element doping structure is a sulfur gradient doping structure.

4. The lithium-rich manganese-based cathode material according to any one of claims 1-3, characterized in that, The general chemical formula of the oxygen-deficient transition metal oxide is M'O. n-δ Where M' is selected from one or more of Mo, W, V, Ti, Nb, Ce, and Zr, n is the number of oxygen atoms in the oxide corresponding to the stoichiometric ratio of M', and δ is the amount of oxygen vacancies, 0.02≤δ≤0.5; And / or, the amorphous lithium salt glass phase is selected from one or more of Li2SO4, Li3PO4, Li2SiO3, LiBO2, LiPO3, and Li4P2O7; the oxygen-deficient transition metal oxide and the amorphous lithium salt glass phase form a composite structure in the composite modification layer; And / or, the nonmetallic element is one of S, P, Si, and B.

5. The method for preparing the lithium-rich manganese-based cathode material according to any one of claims 1-4, characterized in that, include: 1) A transition metal precursor was prepared by co-precipitation; the transition metal precursor was mixed with a lithium source and calcined to obtain a lithium-rich manganese-based matrix powder; 2) The lithium-rich manganese-based matrix powder is mixed with a metal sulfide precursor to obtain a precursor composite powder; 3) The precursor composite powder is subjected to a two-stage heat treatment to obtain a composite powder coated with oxygen-deficient transition metal oxides. 4) The composite powder is mixed with a lithium salt glass precursor, heat-treated and then rapidly cooled to obtain a lithium-rich manganese-based cathode material containing a surface composite modification layer and a non-metallic element doping structure.

6. The method for preparing lithium-rich manganese-based cathode material according to claim 5, characterized in that, In step 1), the lithium source is selected from at least one of Li2CO3, LiOH·H2O, LiCl, LiNO3, LiC2H3O2, and Li2SO4; And / or, in step 1), the precipitant used in the co-precipitation method is selected from one or more of NaOH, KOH, Na2CO3, and K2CO3.

7. The method for preparing lithium-rich manganese-based cathode material according to claim 6, characterized in that, In step 1), the reaction temperature of the co-precipitation method is 40-60℃, the pH is 9.5-12.5, and the reaction time is 2-24h; and / or, the calcination includes a first-stage sintering and a second-stage sintering, wherein the first-stage sintering is performed at 350-650℃ for 2-10h, and the second-stage sintering is performed at 750-980℃ for 5-30h.

8. The method for preparing lithium-rich manganese-based cathode material according to claim 5, characterized in that, In step 2), the metal element M in the metal sulfide precursor is selected from one or more of Mo, W, V, Ti, Nb, Ce, and Zr; the metal sulfide is selected from one or more of MoS2, WS2, VS2, TiS2, NbS2, Ce2S3, and ZrS2. And / or, the metal sulfide precursor is introduced by one or more of the following methods: dry mixing, ball milling coating, solution impregnation, and spray drying; and / or, based on metal elements, the amount of the metal sulfide precursor added is 0.05-10 wt% of the mass of the lithium-rich manganese-based matrix.

9. The method for preparing the lithium-rich manganese-based cathode material according to any one of claims 5-8, characterized in that, In step 3), the conditions for the first heat treatment stage include: in an inert atmosphere, the temperature is 200-500℃ and the time is 0.2-10h; the conditions for the second heat treatment stage include: in an oxygen-containing atmosphere, the temperature is 250-650℃ and the time is 0.2-20h.

10. The method for preparing the lithium-rich manganese-based cathode material according to any one of claims 5-8, characterized in that, In step 4), the lithium salt glass precursor is selected from one or more of Li2SO4, Li3PO4, Li2SiO3, LiBO2, and LiPO3, and the mass loading of the lithium salt glass precursor is 0.1-15 wt% of the mass of the lithium-rich manganese-based matrix. And / or, the heat treatment temperature is 100-650℃, and the time is 0.2-10h; And / or, the rapid cooling is gas flow quenching, liquid nitrogen-assisted cooling, or natural rapid heat dissipation, with a cooling rate ≥10℃ / min.

11. A lithium-ion battery or solid-state battery, characterized in that, The battery includes a positive electrode, a negative electrode, an electrolyte, and a separator; the positive electrode includes a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector, the positive electrode active layer comprising the lithium-rich manganese-based positive electrode material according to any one of claims 1-4 or the lithium-rich manganese-based positive electrode material obtained by the preparation method of the lithium-rich manganese-based positive electrode material according to any one of claims 5-10; the electrolyte is a solid electrolyte in a solid-state battery or a liquid electrolyte in a lithium-ion battery.

Images