A composite modified lithium-rich manganese-based positive electrode material, a preparation method and application thereof

Abstract

The application provides a composite modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof, and the preparation method of the composite modified lithium-rich manganese-based positive electrode material comprises the following steps: S1, mixing a lanthanum source and a tungsten source with a solvent to obtain a mixture A; the molar ratio of La to W in the lanthanum source and the tungsten source is 1:(1.9-2.1); S2, dispersing a lithium-rich manganese-based matrix in the mixture A, drying and sintering to obtain the composite modified lithium-rich manganese-based positive electrode material. The preparation method of the composite modified lithium-rich manganese-based positive electrode material provided by the application uses a lanthanum source and a tungsten source to convert a residual alkali (Li2CO3 / LiOH) on the surface of the positive electrode material into a coating layer in situ through sintering, which not only eliminates the risk of swelling and slurry gelation caused by the residual alkali, but also avoids the waste of active lithium, significantly improves the initial coulomb efficiency of the lithium-rich manganese-based positive electrode material by reducing the formation of dead lithium.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, specifically to a composite modified lithium-rich manganese-based cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-rich manganese-based cathode materials (LRMO) are considered core cathode materials for next-generation high-energy-density power batteries due to their high specific capacity (over 250 mAh / g) and significant cost advantages. However, this material faces severe challenges in commercial applications: under deep delithiation conditions (>4.5V), irreversible lattice oxygen evolution and transition metal ion migration lead to the degradation of the layered structure towards the spinel / rock salt phase, resulting in severe voltage decay and capacity loss; simultaneously, the electrolyte is easily catalytically decomposed at high voltages, forming a high-impedance interface film and generating acidic substances such as HF; furthermore, the material has low intrinsic ionic conductivity, and the low-conductivity phase generated on the surface during cycling further hinders lithium-ion transport, resulting in limited rate performance.

[0003] To overcome the above problems, existing technologies mainly employ modification methods such as metal oxide coating (e.g., Al2O3, WO3) and bulk doping (e.g., Na, Mg, F), but each has obvious drawbacks. Among these, WO3 coating, while able to utilize W... O-bonds pin lattice oxygen, but oxygen itself is a lithium-ion insulator. A slightly thicker coating layer leads to a sharp increase in interfacial charge transfer impedance, making it difficult to meet application requirements in terms of rate performance and cycle stability. Simple physical coating cannot consume residual alkali on the surface, which continues to generate gas during cycling, resulting in persistently high residual alkali content and deteriorating processing performance. While rare earth element doping (such as La and Ce) can widen the interlayer spacing, the limited solid solubility of large-radius ions makes them prone to segregation to the surface during high-temperature sintering, forming uncontrollable impurity phases that hinder lithium-ion transport. This results in low initial coulombic efficiency, insufficient discharge capacity, and rapid capacity decay during cycling. Furthermore, conventional water washing dealkali removal processes can cause H... + / Li + Exchange causes damage to the surface structure and capacity loss; while existing coatings The doping combination process lacks the in-situ conversion and utilization of residual lithium on the surface, and has always been unable to simultaneously solve the problems of residual alkali, increased interfacial impedance and structural degradation.

[0004] Therefore, there is an urgent need for a method that can effectively reduce the content of residual alkali (Li2CO3 / LiOH) on the surface, improve the initial coulombic efficiency and discharge capacity, improve rate performance, and achieve long-term stable cycle retention, thereby comprehensively improving the electrochemical performance and processing adaptability of lithium-rich manganese-based cathode materials. Summary of the Invention

[0005] This invention provides a composite modified lithium-rich manganese-based cathode material, its preparation method, and its application, in order to solve the above-mentioned problems.

[0006] In a first aspect, the present invention provides a method for preparing a composite modified lithium-rich manganese-based cathode material, comprising the following steps: S1, mix the lanthanum source, tungsten source and solvent to obtain mixture A; The molar ratio of La to W in the lanthanum source and tungsten source is 1:(1.9-2.1). S2, the lithium-rich manganese-based matrix is ​​mixed with mixture A, dried and sintered to obtain the composite modified lithium-rich manganese-based cathode material.

[0007] In one optional embodiment, the total mass of the lanthanum source and the tungsten source is 0.5 wt% to 4.5 wt% of the mass of the lithium-rich manganese-based matrix. Optionally, the total mass of the lanthanum source and the tungsten source is 2.0 wt% of the mass of the lithium-rich manganese-based matrix. In one optional embodiment, the amount of solvent used is sufficient to completely dissolve the tungsten source and the lanthanum source and to uniformly disperse the lithium-rich manganese-based matrix into a slurry. In one alternative embodiment, the solvent includes an organic solvent and water; Optionally, the ratio of the organic solvent to water is 100:(4-6). Optionally, the organic solvent includes at least one of anhydrous ethanol, ethylene glycol, propylene glycol, and dimethylformamide.

[0008] In one optional embodiment, the drying includes at least one of spray drying and rotary evaporation; In one alternative embodiment, the drying temperature is 60-80°C.

[0009] Understandably, as the solvent evaporates, the tungsten and lanthanum sources will deposit on the surface of the lithium-rich manganese-based matrix particles along with the distribution of surface residual alkali (Li2CO3 / LiOH), forming a uniform precursor film.

[0010] In one optional embodiment, the sintering temperature is 300℃-900℃, the time is 1-12h, the heating rate is 2-5℃ / min, and the atmosphere is an oxygen-containing atmosphere. Optionally, the oxygen-containing atmosphere includes at least one of air and oxygen. It can be understood that the reaction mechanism during the sintering process involves the decomposition of the lanthanum and tungsten sources, releasing gases (NH3, NO). x The remaining highly reactive La and W oxide intermediates rapidly undergo the following in-situ reaction with Li₂CO₃ / LiOH on the matrix surface: Li2CO3+ La2O3+ 4WO3→ 2LiLa(WO4)2+ CO2; 2LiOH+ La2O3+ 4WO3→ 2LiLa(WO4)2+ H2O.

[0011] It can be understood that this temperature range is sufficient to drive the surface solid-phase reaction to generate a highly crystalline scheelite phase, while being below the temperature at which the matrix material undergoes bulk phase rearrangement or excessive lithium volatilization.

[0012] Optionally, the sintering temperature is 600℃-750℃, and the holding time is 4-6 hours; Optionally, the sintering includes pre-firing at 300℃-500℃ for 1-3 hours, followed by sintering at 550℃-800℃ for 2-8 hours; In one optional embodiment, in step S1, the mixing temperature is 40-70°C, and the mixing time is sufficient to form a transparent and homogeneous solution, and the method includes stirring. In one optional embodiment, in step S2, the mixing temperature is 40-70°C and the time is 15-30 minutes. Optionally, the mixing includes ultrasound and stirring; It is understood that the mixing is intended to ensure that the agglomerated secondary particles are opened up, and that mixture A, as a modifier, can adequately wet the micropores and grain boundaries on the particle surface.

[0013] In one alternative embodiment, the tungsten source includes soluble tungsten salts, tungsten oxides, and tungsten-containing compounds. Optionally, the soluble tungsten salt includes at least one of ammonium tungstate, ammonium metatungstate, ammonium paratungstate, sodium paratungstate, and sodium tungstate; Optionally, the tungsten oxide includes tungsten oxide.

[0014] In one alternative embodiment, the lanthanum source includes a soluble lanthanum salt or an oxide of lanthanum; Optionally, the soluble lanthanum salt includes at least one of lanthanum nitrate hexahydrate, lanthanum chloride heptahydrate, lanthanum acetate trihydrate, lanthanum sulfate octahydrate, lanthanum carbonate octahydrate, and lanthanum oxide; Optionally, the oxide of lanthanum includes lanthanum oxide.

[0015] In one optional embodiment, the general chemical formula of the lithium-rich manganese-based matrix includes xLi2MnO3·(1-x)LiMO2, wherein 0.3≤x≤0.7, and M is a transition metal element; Optionally, the transition metal element includes at least one of Mn, Co, and Ni; In one alternative embodiment, the Dv50 of the lithium-rich manganese-based matrix is ​​0.2-20µm.

[0016] Secondly, the present invention also provides a composite modified lithium-rich manganese-based cathode material prepared by the above preparation method.

[0017] Thirdly, the present invention also provides a lithium-ion battery comprising the above-mentioned composite modified lithium-rich manganese-based cathode material.

[0018] Those skilled in the art will understand that the lithium-ion battery provided by the present invention may include structural components such as an electrolyte, a positive electrode, a negative electrode, a separator, and a casing. During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor between the positive and negative electrode. The separator is disposed between the positive and negative electrode, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing lithium ions to pass through.

[0019] As an example, the positive electrode sheet includes a positive current collector and a positive active layer. The positive current collector has two opposing surfaces in its own thickness direction, and the positive active layer is disposed on either or both of the opposing surfaces of the positive current collector. The material of the positive electrode sheet used in the lithium-ion battery of the present invention is a composite modified lithium-rich manganese-based positive electrode material prepared by the preparation method provided in the present invention.

[0020] As an example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer. The negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode active layer is disposed on either or both of the opposing surfaces of the negative electrode current collector. The materials, composition, and manufacturing methods of the negative electrode sheet used in the lithium-ion battery of the present invention may include any techniques disclosed in the prior art.

[0021] The material and shape of the separator used in the lithium-ion battery of the present invention are not particularly limited, and may include any technology disclosed in the prior art.

[0022] The electrolyte used in the lithium-ion battery of the present invention may also include any technology disclosed in the prior art.

[0023] This invention does not specifically limit the preparation method of lithium-ion batteries; lithium-ion batteries can be prepared using conventional preparation methods in the art. For example, positive electrode sheets, separators, and negative electrode sheets are stacked sequentially, with the separator located between the positive and negative electrode sheets. A cell is obtained through stacking or winding processes, and then the lithium-ion battery of this invention is obtained through baking, electrolyte injection, formation, and packaging.

[0024] Fourthly, the present invention also provides an electrical device comprising the aforementioned lithium-ion battery.

[0025] It is understood that in the electrical equipment provided by the present invention, the lithium-ion battery can be used as a power source for the electrical equipment, or as an energy storage unit for the electrical equipment. The electrical equipment may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The method for preparing composite modified lithium-rich manganese-based cathode material provided by this invention uses lanthanum and tungsten sources to utilize the surface residual alkali (Li2CO3 / LiOH) on the cathode material surface as raw material, which is then converted into a coating layer in situ through sintering. This eliminates the risks of gas expansion and slurry gelation caused by residual alkali, and avoids the waste of active lithium. By reducing the formation of dead lithium, the initial coulombic efficiency of the material is significantly improved. The molar ratio of La to W in the lanthanum and tungsten sources is 1:(1.9-2.1) to ensure the formation of pure-phase LiLa(WO4)2 and avoid the formation of insulating La2O3 or WO3 impurities. The generated LiLa(WO4)2 is an excellent lithium-ion conductor, solving the drawback of traditional inert coating layers hindering lithium-ion transport and significantly improving rate performance. At the same time, the "pillar effect" generated by the strong WO bonds and La ions greatly enhances the surface lattice rigidity, effectively suppressing lattice oxygen release and layer-to-spinel phase transition under high voltage, thereby significantly improving cycle stability and voltage decay.

[0027] 2. The preparation method of the composite modified lithium-rich manganese-based cathode material provided by the present invention has a sintering temperature of 300℃-900℃. This temperature range is sufficient to drive the surface solid-phase reaction to generate a highly crystalline scheelite phase, while being lower than the temperature at which the matrix material undergoes bulk phase rearrangement or excessive lithium volatilization. Detailed Implementation

[0028] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0032] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0033] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0034] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0035] Example 1 This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: S1, Lanthanum source (lanthanum nitrate hexahydrate) and tungsten source (ammonium metatungstate) are dissolved in a composite solvent (the ratio of anhydrous ethanol to water is 100:5), and the mixture is magnetically stirred in a water bath at 40°C for 30 min to obtain mixture A; the molar ratio of La to W in the lanthanum source and tungsten source is 1:2.01; S2, lithium-rich manganese-based matrix (Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O2 (Dv50 of 10µm) was dispersed in mixture A and treated with an ultrasonic disperser for 20 min. The mixture was then transferred to a rotary evaporator and dried under a 70℃ water bath and negative pressure (-2MPa). After drying, the mixture was placed in a high-purity alumina crucible and then placed in a box-type muffle furnace. The furnace was heated to 600℃ at a heating rate of 5℃ / min under an air atmosphere and held at that temperature for 5 h. After the holding period, the mixture was allowed to cool naturally to room temperature and passed through a 400-mesh sieve to obtain the composite modified lithium-rich manganese-based cathode material. The total mass of the lanthanum source and tungsten source was 2.95 wt% of the mass of the lithium-rich manganese-based matrix.

[0036] Example 2 This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: S1, Lanthanum source (lanthanum nitrate hexahydrate) and tungsten source (ammonium metatungstate) are dissolved in a composite solvent (the ratio of anhydrous ethanol to water is 100:5), and the mixture is magnetically stirred in a water bath at 40°C for 30 min to obtain mixture A; the molar ratio of La to W in the lanthanum source and tungsten source is 1:2. S2, lithium-rich manganese-based matrix (Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O2 (Dv50 of 10µm) was dispersed in mixture A and treated with an ultrasonic disperser for 20 min. The mixture was then transferred to a rotary evaporator and dried under a 70℃ water bath and negative pressure (-2MPa). After drying, the mixture was placed in a high-purity alumina crucible and then placed in a box-type muffle furnace. The furnace was heated to 600℃ at a heating rate of 5℃ / min under an air atmosphere and held at that temperature for 5 h. After the holding period, the mixture was allowed to cool naturally to room temperature and passed through a 400-mesh sieve to obtain the composite modified lithium-rich manganese-based cathode material. The total mass of the lanthanum source and tungsten source was 1.47 wt% of the mass of the lithium-rich manganese-based matrix.

[0037] Example 3 This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: S1, Lanthanum source (lanthanum nitrate hexahydrate) and tungsten source (ammonium metatungstate) are dissolved in a composite solvent (the ratio of anhydrous ethanol to water is 100:5), and the mixture is magnetically stirred in a water bath at 40°C for 30 min to obtain mixture A; the molar ratio of La to W in the lanthanum source and tungsten source is 1:2. S2, lithium-rich manganese-based matrix (Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O2 (Dv50 of 10µm) was dispersed in mixture A and treated with an ultrasonic disperser for 20 min. The mixture was then transferred to a rotary evaporator and dried under a 70℃ water bath and negative pressure (-2MPa). After drying, the mixture was placed in a high-purity alumina crucible and then placed in a box-type muffle furnace. The furnace was heated to 600℃ at a heating rate of 5℃ / min under an air atmosphere and held at that temperature for 5 h. After the holding period, the mixture was allowed to cool naturally to room temperature and passed through a 400-mesh sieve to obtain the composite modified lithium-rich manganese-based cathode material. The total mass of the lanthanum source and tungsten source was 4.42 wt% of the mass of the lithium-rich manganese-based matrix.

[0038] Example 4 This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: S1, lanthanum source (lanthanum chloride heptahydrate) and tungsten source (ammonium tungstate) are dissolved in a composite solvent (ethylene glycol to water ratio of 100:5), and the mixture is magnetically stirred in a water bath at 50°C for 30 min to obtain mixture A; the molar ratio of La to W in the lanthanum source and tungsten source is 1:1.95; S2, lithium-rich manganese-based matrix (Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O2 (Dv50 of 5µm) was dispersed in mixture A and treated with an ultrasonic disperser for 20 min. The mixture was then transferred to a rotary evaporator and dried under a 75℃ water bath and negative pressure (-2MPa). After drying, the mixture was placed in a high-purity alumina crucible and then placed in a box-type muffle furnace. The furnace was heated to 700℃ at a heating rate of 3℃ / min under an air atmosphere and held at that temperature for 6 h. After the holding period, the mixture was allowed to cool naturally to room temperature and passed through a 400-mesh sieve to obtain the composite modified lithium-rich manganese-based cathode material. The total mass of the lanthanum source and tungsten source was 3 wt% of the mass of the lithium-rich manganese-based matrix.

[0039] Example 5 This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: S1, Lanthanum source (lanthanum nitrate hexahydrate) and tungsten source (ammonium metatungstate) are dissolved in a composite solvent (the ratio of anhydrous ethanol to water is 100:5), and the mixture is magnetically stirred in a water bath at 40°C for 30 min to obtain mixture A; the molar ratio of La to W in the lanthanum source and tungsten source is 1:2.01; S2, lithium-rich manganese-based matrix (Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O2 (Dv50 of 10µm) was dispersed in mixture A and treated with an ultrasonic disperser for 20 min. The mixture was then transferred to a rotary evaporator and dried under a 70℃ water bath and negative pressure (-2MPa). The dried material was then placed in a high-purity alumina crucible and placed in a box-type muffle furnace. Under air atmosphere, the temperature was increased to 400℃ at a rate of 3℃ / min and held for 2 h. The temperature was then further increased to 800℃ at a rate of 5℃ / min and held for 6 h. The material was then allowed to cool naturally to room temperature in the furnace and passed through a 400-mesh sieve to obtain the composite modified lithium-rich manganese-based cathode material. The total mass of the lanthanum and tungsten sources was 2.95 wt% of the mass of the lithium-rich manganese-based matrix.

[0040] Example 6 This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: S1, Lanthanum source (lanthanum acetate trihydrate) and tungsten source (ammonium paratungstate) are dissolved in a composite solvent (the ratio of propylene glycol to water is 100:5), and the mixture is magnetically stirred in a water bath at 70°C for 30 min to obtain mixture A; the molar ratio of La to W in the lanthanum source and tungsten source is 1:1.9; S2, lithium-rich manganese-based matrix (Li 1.7 Mn 0.7 Co 0.3 Ni 0.3 O 2.7 The lanthanum source (Dv50 of 0.2µm) was dispersed in mixture A and treated with an ultrasonic disperser for 20 min. It was then transferred to a rotary evaporator and dried under a water bath at 80℃ and a negative pressure (-2MPa). After drying, it was placed in a high-purity alumina crucible and then placed in a box-type muffle furnace. Under an air atmosphere, it was heated to 900℃ at a heating rate of 3℃ / min and held at that temperature for 1 h. After the holding period, it was allowed to cool naturally to room temperature with the furnace and passed through a 400-mesh sieve to obtain the composite modified lithium-rich manganese-based cathode material. The total mass of the lanthanum source and the tungsten source was 4.5wt% of the mass of the lithium-rich manganese-based matrix.

[0041] Example 7 This embodiment provides a composite modified lithium-rich manganese-based cathode material, and the specific steps and parameter settings are as follows: S1, Lanthanum source (lanthanum sulfate octahydrate) and tungsten source (sodium tungstate) are dissolved in a composite solvent (the ratio of dimethylformamide to water is 100:5), and the mixture is magnetically stirred in a water bath at 50°C for 30 min to obtain mixture A; the molar ratio of La to W in the lanthanum source and tungsten source is 1:2.1; S2, lithium-rich manganese-based matrix (Li 1.3 Mn 0.3 Co 0.7 Ni 0.7 O 2.3 The lanthanum source (Dv50 of 20µm) was dispersed in mixture A and treated with an ultrasonic disperser for 20 min. It was then transferred to a rotary evaporator and dried under a water bath at 60℃ and negative pressure (-2MPa). After drying, it was placed in a high-purity alumina crucible and then placed in a box-type muffle furnace. Under an air atmosphere, it was heated to 300℃ at a heating rate of 5℃ / min and held at that temperature for 12 h. After the holding period, it was allowed to cool naturally to room temperature with the furnace and passed through a 400-mesh sieve to obtain the composite modified lithium-rich manganese-based cathode material. The total mass of the lanthanum source and tungsten source was 0.5wt% of the mass of the lithium-rich manganese-based matrix.

[0042] Comparative Example 1 This comparative example provides a composite modified lithium-rich manganese-based cathode material, which differs from Example 1 only in that the tungsten source is replaced with an equal mass of lanthanum source. The rest is the same as in Example 1.

[0043] Comparative Example 2 This comparative example provides a composite modified lithium-rich manganese-based cathode material, which differs from Example 1 only in that the lanthanum source is replaced with an equal mass of tungsten source. The rest is the same as in Example 1.

[0044] Comparative Example 3 This comparative example provides a composite modified lithium-rich manganese-based cathode material, which differs from Example 7 only in that the molar ratio of La to W in the lanthanum source and tungsten source is 1:1. The rest is the same as in Example 7.

[0045] Comparative Example 4 This comparative example provides a composite modified lithium-rich manganese-based cathode material, which differs from Example 7 only in that the molar ratio of La to W in the lanthanum source and tungsten source is 1:3; The rest is the same as in Example 7.

[0046] Comparative Example 5 This comparative example provides a composite modified lithium-rich manganese-based cathode material, which differs from Example 7 only in that the lanthanum source is replaced with an equimolar amount of cerium source. The rest is the same as in Example 7.

[0047] Comparative Example 6 This comparative example provides a composite modified lithium-rich manganese-based cathode material, which differs from Example 7 only in that the tungsten source is replaced with an equimolar amount of molybdenum source. The rest is the same as in Example 7.

[0048] Experimental Example 1 According to GB / T 41704-2022 "Determination of Magnetic Foreign Matter Content and Residual Alkali Content in Lithium-ion Cathode Materials", the surface residual alkali of the composite modified lithium-rich manganese-based cathode materials obtained in Examples 1-7 and Comparative Examples 1-6 was tested, and the results are shown in Table 1: Table 1 Surface residual alkali data

[0049] As shown in Table 1, La-W co-doping significantly reduces residual alkali on the surface of lithium-rich manganese-based cathode materials. The residual alkali of the co-doped sample in Example 1 is much lower than that of Comparative Example 1 (La-doped only) and Comparative Example 2 (W-doped only), indicating that the synergistic effect of La-W co-doping in reducing alkali is far superior to that of single doping. This is because La... 3+ With W 6+ Stable composite oxides can be generated, consuming free lithium on the surface and inhibiting the formation of alkaline substances. Furthermore, Examples 1-6 demonstrate that the La / W molar ratio and total doping amount need to be controlled within a suitable range; samples with imbalanced ratios or low doping amounts will affect the residual alkali content on the surface. Example 5, which uses two-stage calcination, shows relatively better control over residual alkali. Comparative Examples 3 and 4 with abnormal ratios, and Comparative Examples 5 and 6 with replaced dopants, all showed significantly higher residual alkali values, demonstrating the unique modifying properties of the La-W doping combination.

[0050] Experiment Example 2 The composite modified lithium-rich manganese-based cathode materials obtained in Examples 1-7 and Comparative Examples 1-6 were used as cathode active materials and were homogenized with polyvinylidene fluoride (PVDF) and acetylene black in a ratio of 80:10:10, with the areal density controlled at 4 g / cm³. 2 Electrode compaction density 2 g / cm³ 3 The electrode was fabricated using a lithium metal sheet as the counter electrode and a glass fiber separator. A 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC to DMC volume ratio of 1:1) was used as the electrolyte. The CR2032 coin cell was assembled in an argon-filled glove box and finally placed in the Blue Electric testing system for electrical performance testing.

[0051] The electrical performance test conditions are as follows: (1) First charge-discharge performance test: The charge and discharge voltage range for cyclic testing is 2.0V-4.8V, and the test temperature is 25℃. After the open circuit voltage stabilizes, the battery's first charge and discharge performance is tested by cycling at 0.1C / 0.1C for one week. The initial charge capacity is defined as the capacity when the battery is charged at a constant current of 0.1C until the voltage reaches 4.8V, and the initial discharge capacity is defined as the capacity when the battery is discharged at a constant current of 0.1C until the cutoff voltage reaches 2.0V. The initial coulombic efficiency is then calculated. The Coulomb efficiency for the first lap is calculated as follows: ; Where: ICE is the initial Coulomb efficiency; D1 is the initial discharge capacity at a specified rate (e.g., 0.1C); C1 represents the initial charging capacity at the same rate.

[0052] (2) Ratio performance test: The assembled button cells were charged and discharged at constant currents of 0.1 C and 1 C within a voltage range of 2V to 4.8V, with a cutoff condition of 4.5V. (3) Cyclic stability test: Charge the battery at a constant current of 1C to 4.8V, then discharge it at a constant current of 1C until the cutoff voltage is 2.0V. Repeat this charge-discharge cycle 200 times. Calculate the cycle capacity retention rate (%) of the battery after 200 cycles: Cycle capacity retention rate = Discharge capacity of the 200th cycle / Discharge capacity of the 1st cycle × 100%.

[0053] The specific test results are shown in Table 2: Table 2 Electrical performance data

[0054] As shown in Table 2, Examples 1-6 exhibited high first-cycle coulombic efficiency, charge / discharge capacity, rate performance, and cycle retention due to lanthanum-tungsten co-doping. Example 5 demonstrated the best overall performance due to its excellent compatibility with the formulation and calcination process; Example 7, with its lower doping amount, saw a decline in all performance aspects. Comparative Examples 1 (single lanthanum doping) and 2 (single tungsten doping) showed significantly inferior performance compared to the co-doped samples. Comparative Examples 3 and 4, with lanthanum-tungsten ratios deviating from the appropriate range, showed further deterioration in their performance. Comparative Examples 5 and 6, where lanthanum and tungsten were replaced with cerium and molybdenum respectively, showed the largest decline in electrochemical performance, fully demonstrating that lanthanum-tungsten co-doping can effectively reduce irreversible capacity loss and stabilize the material lattice. Only a reasonable formulation and process can achieve the optimal modification effect; element replacement, single-component doping, and parameter imbalances are all insufficient to achieve the same results.

[0055] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a composite modified lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: S1, mix the lanthanum source, tungsten source and solvent to obtain mixture A; The molar ratio of La to W in the lanthanum source and tungsten source is 1:(1.9-2.1). S2, the lithium-rich manganese-based matrix is ​​mixed with mixture A, dried and sintered to obtain the composite modified lithium-rich manganese-based cathode material.

2. The preparation method according to claim 1, characterized in that, The total mass of the lanthanum source and tungsten source is 0.5 wt% to 4.5 wt% of the mass of the lithium-rich manganese-based matrix.

3. The preparation method according to claim 1 or 2, characterized in that, The solvent includes organic solvents and water; Optionally, the ratio of the organic solvent to water is 100:(4-6).

4. The preparation method according to any one of claims 1-3, characterized in that, The sintering temperature is 300℃-900℃, the time is 1-12h, the heating rate is 2-5℃ / min, and the atmosphere is an oxygen-containing atmosphere.

5. The preparation method according to any one of claims 1-4, characterized in that, The general chemical formula of the lithium-rich manganese-based matrix includes xLi2MnO3·(1-x)LiMO2, where 0.3≤x≤0.7 and M is a transition metal element; Optionally, the transition metal element includes at least one of Mn, Co, and Ni; And / or, the Dv50 of the lithium-rich manganese-based matrix is ​​0.2-20µm.

6. The preparation method according to any one of claims 1-5, characterized in that, The tungsten source includes soluble tungsten salts, tungsten oxides, and tungsten-containing compounds; Optionally, the soluble tungsten salt includes at least one of ammonium tungstate, ammonium metatungstate, ammonium paratungstate, sodium paratungstate, and sodium tungstate; Optionally, the tungsten oxide includes tungsten oxide.

7. The preparation method according to any one of claims 1-6, characterized in that, The lanthanum source includes soluble lanthanum salts and lanthanum oxides; Optionally, the soluble lanthanum salt includes at least one of lanthanum nitrate hexahydrate, lanthanum chloride heptahydrate, lanthanum acetate trihydrate, lanthanum sulfate octahydrate, lanthanum carbonate octahydrate, and lanthanum oxide; Optionally, the oxide of lanthanum includes lanthanum oxide.

8. A composite modified lithium-rich manganese-based cathode material prepared by the preparation method according to any one of claims 1-7.

9. A lithium-ion battery, characterized in that, It includes the composite modified lithium-rich manganese-based cathode material as described in claim 8.

10. An electrical appliance, characterized in that, It includes the lithium-ion battery as described in claim 9.

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