Modified lithium-rich manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrode materials, and provides a modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof.The modified lithium-rich manganese-based positive electrode material comprises an inner core and a coating layer coating the inner core; the inner core comprises a molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material, and the coating layer comprises aluminum oxide. Molybdenum and lanthanum elements are synergistically doped into a material body phase, so that the layered structure is effectively stabilized, a three-phase interface is constructed, the rate capability of the material is remarkably improved, and voltage attenuation is delayed. On the basis, aluminum oxide coating is further adopted, side reaction between the material and electrolyte is inhibited, dissolution of transition metal ions is reduced, the structural stability of the material is enhanced, and therefore the cycle life of the material is greatly prolonged, and the safety of the material is greatly improved. According to the method, through the synergistic effect of bulk phase doping and surface coating, an effective strategy is provided for high performance of the lithium-rich manganese-based positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the field of electrode technology and relates to a modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof. Background Art

[0002] As a key path to decarbonizing the transportation sector, electric vehicles are experiencing unprecedented rapid growth. Global lithium-ion battery market demand is projected to reach 4,700GWh by 2030, with a compound annual growth rate (CAGR) of 29.5%. Power battery demand will account for over 75% of this total, with energy storage batteries experiencing the fastest growth. This explosive growth is placing higher demands on power batteries' energy density, cycle life, and cost control. As the mainstream power source for electric vehicles, improved performance of lithium-ion batteries is directly related to their range, safety, and market competitiveness.

[0003] Among the four core materials of lithium-ion batteries, cathode materials are the key factor in determining battery energy density and cost, accounting for approximately 40% of the total battery cost. Currently, the most widely commercialized cathode materials for lithium-ion batteries include lithium cobalt oxide (LCO), lithium iron phosphate (LFP), and ternary materials (NCM / NCA). However, these materials are approaching their theoretical limits in terms of energy density (generally below 300Wh / kg) and cost control, making it difficult to meet the high-energy-density, low-cost power battery requirements of next-generation electric vehicles.

[0004] Against this backdrop, lithium-rich manganese-based cathode materials, also known as lithium-rich manganese oxides (LRMOs), are becoming a research hotspot for the next generation of high-energy-density lithium-ion battery cathode materials due to their unique structural and performance advantages. These materials have a theoretical specific capacity of up to 250 mAh / g, more than 1.5 times that of traditional layered cathode materials, and can operate at a voltage of up to 4.8V, promising to increase the energy density of lithium-ion batteries to over 400 Wh / kg. Furthermore, lithium-rich manganese-based materials use abundant manganese as their primary active element, and their raw material costs are approximately 30% lower than those of traditional ternary materials, offering significant economic advantages.

[0005] However, the high specific capacity of lithium-rich manganese-based cathode materials mainly comes from the additional capacity provided by the irreversible redox of oxygen anions at high voltage (>4.5V), but this leads to a decrease in its first coulombic efficiency (ICE) and severe capacity and voltage decay. At the same time, the loss of lattice oxygen and the migration of transition metals (TM) can easily lead to a harmful phase transition from a layered structure to a spinel phase in lithium-rich manganese-based cathode materials and a decrease in cycle performance. In addition, the poor lithium ion diffusion kinetics of the lithium-rich manganese-based cathode materials themselves lead to poor rate performance.

[0006] To solve these technical difficulties, it is still necessary to comprehensively consider and apply multiple aspects such as size control, structural design, element doping and surface modification, so as to develop better high-performance lithium-rich manganese-based positive electrode materials through synergistic effects, thereby laying the foundation for their large-scale commercial application. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a modified lithium-rich manganese-based positive electrode material and its preparation method and use, wherein the modified lithium-rich manganese-based positive electrode material includes a core and a coating layer coating the core; the core includes a molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material, and the coating layer includes aluminum oxide. By synergistically doping molybdenum and lanthanum elements into the bulk phase of the material, its layered structure is effectively stabilized and a three-phase interface is constructed, which significantly improves the rate performance of the material and delays voltage decay. On this basis, aluminum oxide coating is further used to inhibit the side reactions between the material and the electrolyte, reduce the dissolution of transition metal ions, enhance the structural stability of the material, and thus greatly improve its cycle life and safety. This method provides an effective strategy for the high performance of lithium-rich manganese-based positive electrode materials through the synergistic effect of bulk doping and surface coating.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a modified lithium-rich manganese-based positive electrode material, comprising a core and a coating layer coating the core; the core comprises a molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material, and the coating layer comprises aluminum oxide.

[0010] The main performance disadvantages of LRMOs include low initial coulombic efficiency, severe capacity and voltage decay, and poor rate performance. The direct causes of these disadvantages are mainly the detachment of lattice oxygen from the material during the cycle, adverse phase transitions, and side reactions with the electrolyte. The present invention effectively regulates the crystal field distortion of lithium-rich manganese-based materials by co-doping molybdenum and lanthanum in the bulk phase, thereby enhancing the covalent nature of the Mn-O bond and Mo 6+ The high valence state characteristics of La not only significantly improve the intrinsic electronic conductivity of the material, but also stabilize the crystal framework structure through strong dp orbital hybridization. 3+The large ion radius effect effectively expands the dimensional space of the lithium ion transmission channel and significantly reduces the degree of cation mixing. The synergistic doping of the two reconstructs the defective chemical environment of the material at the atomic scale, optimizes the oxygen vacancy concentration, and achieves the best balance between lithium ion transmission kinetics and structural stability. At the same time, the uniformly distributed oxygen vacancy network formed on the surface provides ordered nucleation sites for the alumina coating, promotes the densification and thickness uniformity of the coating, and effectively inhibits the crack initiation of the coating under cyclic stress. During the formation of the alumina coating, some aluminum ions migrate to the bulk phase through the oxygen vacancy network, and form Mo-O-Al and La-O-Al composite interface phases with molybdenum and lanthanum elements, buffering Li through reversible lattice distortion. + The volume change during intercalation and deintercalation further improves the transport kinetics of lithium ions at the interface. At the same time, the interfacial hydroxyl group (-OH) reacts with the electrolyte HF to form an AlF3 passivation layer, which protects the lithium-rich positive electrode material from the side effects of the electrolyte by providing a physical barrier. Ultimately, the "electronic pinning effect" of molybdenum and lanthanum co-doping on the layered structure and the dual protection of aluminum oxide coating against HF corrosion are achieved. The two work synergistically to build a multiple protection network from the bulk to the surface, significantly improving the material's structural stability, electrochemical reversibility and cycle performance.

[0011] It needs to be explained again that the "three-phase interface" formed in the lithium-rich manganese-based positive electrode material by co-doping molybdenum and lanthanum in the present invention refers to the coherent interface structure of the layered phase (C2 / m), the spinel phase (Fd-3m) and the rock salt phase (Fm-3m): the layered phase serves as the main body to maintain the lithium ion deintercalation channel and high capacity; molybdenum doping induces the spinel phase to form a three-dimensional ion diffusion network to improve the rate performance; lanthanum doping inhibits oxygen release and resists electrolyte corrosion by stabilizing the surface rock salt phase. The three phases achieve synergistic coupling through atomic-level lattice continuity and uniform distribution of doping elements. The oxygen vacancy channels spontaneously formed at the interface further enhance ion transport, thereby constructing a "layered-spinel-rock salt" continuous charge network, which enables the material to have both high rate performance and cycle stability, and significantly delays voltage decay.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] As a preferred technical solution of the present invention, the chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material includes Li x Mn a Ni b Co c Mo y La zO2, wherein 1.08≤x≤1.512, for example, x can be 1.08, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5 or 1.1512; 0.4<a<0.7, for example, a can be 0.42, 0.45, 0.48, 0.5, 0.53, 0.55, 0.58, 0.6, 0.63, 0.65, 0.65 or 0.68; 0<b<0.3, for example, b can be 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.24, 0.26 or 0.28; 0<c<0.3, for example, c can be 0.05 , 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.24, 0.26 or 0.28, etc.; 0.0027≤y≤0.027, for example, y can be 0.0027, 0.005, 0.008, 0.01, 0.013, 0.015, 0.018, 0.02, 0.023, 0.025 or 0.027, etc.; 0.0027≤z≤0.027, for example, z can be 0.0027, 0.005, 0.008, 0.01, 0.013, 0.015, 0.018, 0.02, 0.023, 0.025 or 0.027, etc.; and a+b+c+x+y+z=2.

[0014] Preferably, the mass of the coating layer accounts for 1% to 3% of the mass of the core, for example, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%.

[0015] In a second aspect, the present invention provides a method for preparing the modified lithium-rich manganese-based positive electrode material according to the first aspect, comprising the following steps:

[0016] A nickel source, a cobalt source, and a manganese source are prepared into a mixed salt solution A; a molybdenum salt and a lanthanum salt are prepared into a mixed salt solution B; and a base solution containing a precipitant and a complexing agent is prepared;

[0017] Adding the mixed salt solution A, mixed salt solution B, precipitant and complexing agent to the base liquid in parallel, continuing the coprecipitation reaction to obtain a precursor;

[0018] The precursor is mixed with a lithium compound and then subjected to a first calcination to obtain a molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material;

[0019] The molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material is mixed with a solution containing an aluminum source, dried, and then subjected to a second calcination to form a coating layer to obtain a modified lithium-rich manganese-based positive electrode material.

[0020] The preparation method of the present invention adopts a one-step co-precipitation method to achieve the simultaneous doping of manganese, nickel, cobalt with molybdenum and lanthanum elements, which solves the problem of uneven element distribution in the traditional step-by-step doping process, significantly improves the electrochemical performance of the material, and is more suitable for large-scale industrial production, is environmentally friendly and reduces production costs.

[0021] As a preferred technical solution of the present invention, the nickel source, cobalt source and manganese source include sulfates of the corresponding metal elements; the lanthanum salt includes sodium lanthanate; and the molybdenum salt includes sodium molybdate.

[0022] Preferably, the total metal concentration in the mixed salt solution A is 1 to 3 mol / L, for example, 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L or 3 mol / L.

[0023] Preferably, the total metal concentration in the mixed salt solution B is 0.1 to 1 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L.

[0024] Preferably, the molar amount of the molybdenum element in the molybdenum salt accounts for 0.5% to 5% of the molar amount of the manganese element in the manganese source, for example, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0025] Preferably, the molar amount of lanthanum in the lanthanum salt accounts for 0.5% to 5% of the molar amount of manganese in the manganese source, for example, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0026] As a preferred technical solution of the present invention, the complexing agent includes aqueous ammonia with a concentration of 16% to 20%, for example, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5% or 20%, and the precipitant includes liquid alkali with a concentration of 20% to 24%, for example, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5% or 24%, etc.

[0027] Preferably, the concentration of the complexing agent in the base solution is 2-4 g / L, for example, 2 g / L, 2.3 g / L, 2.5 g / L, 2.8 g / L, 3 g / L, 3.3 g / L, 3.5 g / L, 3.8 g / L or 4 g / L.

[0028] Preferably, the pH of the base solution is 10-11, for example, 10, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.

[0029] As a preferred technical solution of the present invention, the parallel flow rate of the mixed salt solution A is 5 to 10 L / h, for example, 5 L / h, 5.5 L / h, 6 L / h, 6.5 L / h, 7 L / h, 7.5 L / h, 8 L / h, 8.5 L / h, 9 L / h, 9.5 L / h or 10 L / h; the parallel flow rate of the mixed salt solution B is 1 to 5 L / h, for example, 1 L / h, 1.5 L / h, 2 L / h, 2.5 L / h, 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h or 5 L / h, etc.; the parallel flow rate of the complexing agent is 1 to 5 L / h, such as 1 L / h, 1.5 L / h, 2 L / h, 2.5 L / h, 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h or 5 L / h, etc.; the parallel flow rate of the precipitant is 10 to 15 L / h, such as 10 L / h, 10.5 L / h, 11 L / h, 11.5 L / h, 12 L / h, 12.5 L / h, 13 L / h, 13.5 L / h, 14 L / h, 14.5 L / h or 15 L / h, etc.

[0030] Preferably, the coprecipitation reaction is carried out under stirring, and the stirring speed is 300-500 rpm, for example, 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm, 420 rpm, 450 rpm, 480 rpm or 500 rpm.

[0031] Preferably, the pH of the coprecipitation reaction is 8.5 to 11.5, for example, 8.5, 8.8, 9, 9.2, 9.5, 9.8, 10, 10.3, 10.5, 10.8, 11, 11.2 or 11.5.

[0032] Preferably, the coprecipitation reaction time is 24 to 60 h, for example, 24 h, 28 h, 30 h, 34 h, 38 h, 42 h, 46 h, 50 h, 52 h, 54 h, 56 h, 58 h or 60 h.

[0033] As a preferred technical solution of the present invention, the precursor is washed, filtered, dried and pre-calcined before being mixed with the lithium compound.

[0034] Preferably, the drying temperature is 70-90°C, for example, 70°C, 73°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C or 90°C; and the drying time is 10-14h, for example, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h or 14h.

[0035] Preferably, the pre-calcination temperature is 400-500°C, for example, 400°C, 410°C, 430°C, 450°C, 480°C or 500°C; and the pre-calcination time is 3-7h, for example, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h or 7h.

[0036] As a preferred technical solution of the present invention, the lithium compound includes lithium carbonate.

[0037] Preferably, the molar ratio of the manganese source in the precursor to the molar ratio of the lithium element in the lithium compound is 1:(2-2.8), for example, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7 or 1:28.

[0038] Preferably, the first calcination has a heating rate of 3-8°C / min, a temperature of 800-900°C, and a time of 10-14h, for example, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h or 14h.

[0039] As a preferred technical solution of the present invention, the aluminum source includes aluminum nitrate; and the solvent in the solution containing the aluminum source includes ethanol.

[0040] Preferably, the temperature of the second calcination is 400-600°C, for example, 400°C, 430°C, 450°C, 480°C, 500°C, 520°C, 550°C, 580°C or 600°C; and the time is 3-7h, for example, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h or 7h.

[0041] In a third aspect, the present invention provides a battery comprising the modified lithium-rich manganese-based positive electrode material described in the first aspect.

[0042] It should be noted that due to space limitations and to avoid redundancy, the present invention does not exhaustively list all point values ​​within the above numerical range, but is not limited to the listed values. Other unlisted values ​​within the above numerical range are also applicable.

[0043] Compared with the existing technical solutions, the present invention has at least the following beneficial effects:

[0044] In the modified lithium-rich manganese-based material described in the present invention, the multi-dimensional performance improvement of the lithium-rich manganese-based positive electrode material is achieved through the synergistic effect of molybdenum-lanthanum co-doping and aluminum oxide coating. The high valence characteristics of the molybdenum element play a dual function in the crystal framework: first, by activating the delocalized electron network, it significantly enhances the intrinsic electronic conductivity of the material, providing a fast charge transfer path for high-rate charging and discharging; second, it utilizes its strong dp orbital hybridization ability to form a stable chemical bond with oxygen atoms, inhibiting the irreversible loss of lattice oxygen under high voltage, thereby maintaining the integrity of the layered structure. The introduction of lanthanum reconstructs the lithium ion transmission environment through spatial effects - its large ionic radius produces a controllable expansion effect in the lattice, expands the lithium layer spacing and constructs a three-dimensional through-diffusion channel, while reducing the stress between transition metal layers through charge screening, significantly reducing the probability of the formation of lithium-nickel mixed arrangement defects. The innovative nature of the molybdenum-lanthanum synergistic system lies in its synergistic mechanism of atomic-level charge compensation and lattice matching: the high electronegativity of molybdenum and the charge buffering properties of lanthanum form a dynamic balance, which not only avoids lattice distortion caused by high-valence doping, but also suppresses the obstruction of lithium diffusion caused by large-radius ions. The two form a stable [Mo-O-La] bonding network in the lattice, and through bond energy redistribution, the oxygen vacancy concentration is precisely controlled, thereby improving the lithium ion migration rate while blocking the chain reaction of structural collapse. The design of the alumina coating further achieves a gradient upgrade of the interface function - its surface chemical modification induces the formation of a composite interface phase with both high ionic conductivity and electron blocking properties, while the physical barrier effect isolates the active material from the corrosion of the electrolyte, forming a closed-loop protection from the two dimensions of bulk stability and interface dynamics.

[0045] The preparation method described in this paper employs a simultaneous coprecipitation synthesis strategy, achieving in-situ uniform compounding of the molybdenum and lanthanum doping elements with the host material through precise molecular-level control. This innovative process overcomes the technical limitations of traditional post-doping methods, achieving spatially homogenous distribution of the doping elements in the solution phase and fundamentally addressing key technical challenges such as element segregation and lattice distortion.

[0046] The innovative process revealed by the preparation method described in the present invention has wide parameter adaptability and a simplified operating process, which significantly reduces production costs while improving raw material utilization. This technical route exhibits excellent engineering characteristics, including good process scalability, experimental reproducibility, and product batch consistency. The prepared material system exhibits excellent electrochemical performance and provides key material solutions for strategic emerging fields such as power batteries, large-scale energy storage systems, and next-generation electric vehicles. It has broad market application prospects and significant economic benefits, and is expected to promote technological upgrading and sustainable development of related industries. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0048] It should be apparent to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0049] Example 1

[0050] This embodiment provides a modified lithium-rich manganese-based positive electrode material, including a core and a coating layer covering the core; the core is a molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material, and the coating layer is aluminum oxide. The chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2, the mass of the coating layer accounts for 2% of the mass of the core.

[0051] The method for preparing the modified lithium-rich manganese-based positive electrode material comprises the following steps:

[0052] Step S1: Dissolve the nickel source NiSO4·6H2O, the cobalt source CoSO4·7H2O, and the manganese source MnSO4·H2O in deionized water at a Ni:Co:Mn molar ratio of 0.13:0.13:0.54 to obtain a mixed salt solution A with a total metal concentration of 2.0M. Prepare a mixed solution B of soluble molybdenum salt and lanthanum salt, each comprising a combination of sodium molybdate and sodium lanthanate, with a total metal concentration of 0.35M required for doping. The soluble molybdenum salt and lanthanum salt are prepared in an amount of 1% of the amount of manganese, and the lanthanum salt is prepared in an amount of 1% of the amount of manganese. Then, prepare a base solution, which is a mixed solution of pure water, a precipitant, and a complexing agent, ammonia, with a pH of 10.8 and an ammonia concentration of 3g / L.

[0053] Step S2: 30% of the total volume of the reactor was added to the reactor. At the same time, the manganese, nickel, and cobalt mixed salt solution A, the molybdenum and lanthanum salt mixed solution B, ammonia water (concentration of 18%), and liquid alkali (concentration of 22%) were added to the reactor simultaneously through a metering pump. The materials in the reactor were stirred by a stirring paddle at a stirring speed of 400 rpm. The flow rate of the mixed salt solution A was controlled to 7 L / h, the flow rate of the mixed solution B was 3 L / h, the flow rate of the ammonia water was 3 L / h, and the flow rate of the liquid alkali was 10 L / h. The reaction temperature was 60°C, the pH value of the reaction system (i.e., the solution in the reactor) was 10.5, and the coprecipitation reaction was carried out for 48 hours to obtain a precursor.

[0054] Step S3: After washing, filtering, drying, and pre-calcining the precursor, the precursor is mixed with the lithium compound by ball milling, and then the first calcination is carried out at a high temperature, wherein the drying temperature is 80°C and the drying time is 12 hours; the pre-calcination temperature is 480°C and the pre-calcination time is 5 hours; the first calcination heating rate is 5°C / min, the temperature is 880°C, and the time is 12 hours. The ratio of the precursor to the lithium compound is 1:2.4 in terms of the molar ratio of Mn to Li, and the lithium compound is Li2CO3, and the chemical formula is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material.

[0055] Step S4: Add a certain amount of aluminum source Al(NO3)3·9H2O to the ethanol solution to dissolve and evenly disperse it to obtain a solution containing the aluminum source, and then take a certain amount of Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 was added to the solution, the coating amount was controlled to 2%, and ultrasonic treatment was performed for 1 hour to make it evenly dispersed in the solution. Subsequently, the above solution was placed on a magnetic stirrer and stirred at 60°C until the alcohol was completely evaporated. Finally, the sample was moved to a muffle furnace and calcined for a second time at 500°C for 5 hours to form a coating layer, and the modified lithium-rich manganese-based positive electrode material Al2O3@Li was obtained. 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2.

[0056] Example 2

[0057] This embodiment provides a modified lithium-rich manganese-based positive electrode material. By adjusting the amount of molybdenum salt and lanthanum salt in step S1 of the preparation method to change the doping ratio of molybdenum to lanthanum, the chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material as the core is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 adjusted to Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0013 La 0.0095O2, except for the above, other conditions are exactly the same as those in Example 1.

[0058] Example 3

[0059] This embodiment provides a modified lithium-rich manganese-based positive electrode material. By adjusting the amount of molybdenum salt and lanthanum salt in step S1 of the preparation method to change the doping ratio of molybdenum to lanthanum, the chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material as the core is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 adjusted to Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0027 La 0.0081 O2, except for the above, other conditions are exactly the same as those in Example 1.

[0060] Example 4

[0061] This embodiment provides a modified lithium-rich manganese-based positive electrode material. By adjusting the amount of molybdenum salt and lanthanum salt in step S1 of the preparation method to change the doping ratio of molybdenum to lanthanum, the chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material as the core is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 adjusted to Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0095 La 0.0013 O2, except for the above, other conditions are exactly the same as those in Example 1.

[0062] Example 5

[0063] This embodiment provides a modified lithium-rich manganese-based positive electrode material. By adjusting the amount of aluminum source in step S4 of the method, the coating amount is adjusted from 2% to 0.2%. Except for the above, other conditions are exactly the same as those in Example 1.

[0064] Example 6

[0065] This embodiment provides a modified lithium-rich manganese-based positive electrode material. By adjusting the amount of aluminum source in step S4 of the preparation method, the coating amount is adjusted from 2% to 1%. Except for the above, other conditions are exactly the same as those in Example 1.

[0066] Example 7

[0067] This embodiment provides a modified lithium-rich manganese-based positive electrode material. By adjusting the amount of aluminum source in step S4 of the preparation method, the coating amount is adjusted from 2% to 3%. Except for the above, other conditions are exactly the same as those in Example 1.

[0068] Example 8

[0069] This embodiment provides a modified lithium-rich manganese-based positive electrode material. By adjusting the amount of aluminum source in step S4 of the preparation method, the coating amount is adjusted from 2% to 4%. Except for the above, other conditions are exactly the same as those in Example 1.

[0070] Comparative Example 1

[0071] This comparative example provides a modified lithium-rich manganese-based positive electrode material. In step S1 of the preparation method, only molybdenum salt is used, that is, part of the lanthanum salt is replaced by an equal amount of molybdenum salt, so that the chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material as the core is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 adjusted to Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0108 O2, except for the above, other conditions are exactly the same as those in Example 1.

[0072] Comparative Example 2

[0073] This comparative example provides a modified lithium-rich manganese-based positive electrode material, by using only lanthanum salt in step S1 of the preparation method, that is, replacing part of the molybdenum salt with an equal amount of lanthanum salt, so that the chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material as the core is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 adjusted to Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 La 0.0108 O2, except for the above, other conditions are exactly the same as those in Example 1.

[0074] Comparative Example 3

[0075] This comparative example provides a modified lithium-rich manganese-based positive electrode material, wherein the molybdenum salt and the lanthanum salt are removed in step S1 of the preparation method, that is, no co-doping is performed, so that the chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material as the core is Li 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 adjusted to Li 1.3 Mn 0.5446 Ni 0.1331 Co 0.1331 O2, except for the above, other conditions are exactly the same as those in Example 1.

[0076] Comparative Example 4

[0077] This comparative example provides a lithium-rich manganese-based positive electrode material, wherein the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material Li obtained in step S3 is prepared without step S4 and coating. 1.3 Mn 0.54 Ni 0.13 Co 0.13 Mo 0.0054 La 0.0054 O2 was used for subsequent testing. Except for the above, other conditions were exactly the same as those in Example 1.

[0078] The lithium-rich manganese-based cathode materials obtained in the Examples and Comparative Examples were prepared as positive electrodes. A lithium metal sheet was used as the negative electrode, Celgard 2400 was used as the separator, and 1 mol / L LiPF6 was used as the electrolyte. These cells were assembled into CR2032 button-type batteries. Electrochemical performance was then tested under the following conditions: a voltage range of 2–4.8 V, a current density of 1 C, and 200 cycles. The results are reported in Table 1.

[0079] Table 1

[0080]

[0081] As can be seen from Table 1:

[0082] Compared with the comparative example 1 (only Mo doping), the first discharge capacity and cycle retention rate of Example 1 (Mo-La co-doping + 2% Al2O3 coating) are significantly improved, mainly due to the formation of MoO4 2- -La 3+ The composite site inhibits the Li / Ni mixing and stabilizes the oxygen framework, while the single Mo doping leads to lattice stress concentration. Compared with the comparative example 2 (only La doping), the capacity retention rate of Example 1 is 8.9% higher because La 3+ Excessive amounts will block Li +Diffusion channel, and co-doping optimizes the interlayer electrostatic potential through charge balance. Compared with Comparative Example 3 (no doping), the first capacity of Example 1 is increased by 43mAh / g, because co-doping suppresses irreversible oxygen release under high voltage. Compared with Comparative Example 4 (no coating), the capacity retention rate of Example 1 is increased by 24.3%, because the Al2O3 coating layer (2%) is chemically inert to isolate the electrolyte corrosion and generate a fast ion conductor LiAlO2 interface phase, while the uncoated material causes the CEI layer to thicken due to surface side reactions.

[0083] The comparison between Example 1 (Mo:La=1:1) and Examples 2-4 (different Mo / La ratios) shows that the unbalanced doping ratio will significantly affect the performance. 3+ Excessive addition leads to lattice expansion, the Li interlayer spacing increases, but Li + Diffusion is hindered, and the capacity retention rate decreases by 4.2%; in Example 3 (Mo:La=1:3), the rigidity of La-O bond is enhanced, which inhibits phase transition but sacrifices reversible capacity (the first capacity decreases by 8 mAh / g); in Example 4 (Mo:La=7:1), due to Mo 6+ Excessive Li occupies the Li site to form Li2MoO4 impurity phase, resulting in a sudden drop in capacity of 20mAh / g. The equimolar ratio (1:1) of Example 1 balances the Mo 6+ The improvement of electronic conductivity of La 3+ The oxygen framework stabilization effect, while avoiding lattice distortion, is the optimal solution for the doping threshold.

[0084] Comparison of Example 1 (2% Al2O3) with Examples 5-8 of different coating amounts shows that the coating amount needs to be precisely controlled: Example 5 (0.2%) cannot effectively suppress the Mn 3+ The capacity retention rate dropped by 8.3% due to dissolution. In Example 6 (1%), the coating thickness was insufficient (~2nm), and the interface was easily peeled off at high temperature, and the retention rate dropped by 2.8%. In Example 7 (3%), the coating was too thick (~8nm), which improved the stability in the later stage of the cycle, but the Li + The extended diffusion path resulted in an initial capacity loss of 9 mAh / g. Example 8 (4%) further reduced its capacity by 16 mAh / g due to the accumulation of an insulating "dead layer" of Al2O3, which increased the interfacial impedance. The 2% coating (~5 nm) of Example 1 achieved an optimal balance between physical protection and ion transport by completely covering the active sites and forming a LiAlO2-Li2MoO4 composite interface phase.

[0085] In summary, the modified lithium-rich manganese-based cathode material described in the present invention can effectively overcome the problems of poor rate performance and rapid voltage decay of lithium-rich manganese-based cathode materials through the synergistic effect of molybdenum and lanthanum co-doping and aluminum oxide coating. The preparation method adopts a synchronous co-precipitation synthesis strategy, and through molecular-level precise control, it achieves in-situ uniform recombination of molybdenum and lanthanum dual doping elements with the main material, achieving spatially homogenized distribution of doping elements, fundamentally solving key technical problems such as element segregation and lattice distortion, and is conducive to ensuring the acquisition of high-performance modified lithium-rich manganese-based cathode materials.

[0086] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0087] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0088] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A modified lithium-rich manganese-based positive electrode material, characterized in that: It comprises a core and a coating layer covering the core; the core comprises a molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material, and the coating layer comprises aluminum oxide.

2. The modified lithium-rich manganese-based positive electrode material according to claim 1, characterized in that The chemical formula of the molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material includes Li x Mn a Ni b Co c Mo y La z O2, where 1.08≤x≤1.512, 0.4<a<0.7, 0.01<b<0.3, 0.01<c<0.3, 0.0027≤y≤0.027, 0.0027≤z≤0.027, and a+b+c+x+y+z=2; Preferably, the mass of the coating layer accounts for 1% to 3% of the mass of the core.

3. A method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 1 or 2, characterized in that: The steps include: A nickel source, a cobalt source, and a manganese source are prepared into a mixed salt solution A; a molybdenum salt and a lanthanum salt are prepared into a mixed salt solution B; and a base solution containing a precipitant and a complexing agent is prepared; Adding the mixed salt solution A, mixed salt solution B, precipitant and complexing agent to the base liquid in parallel, continuing the coprecipitation reaction to obtain a precursor; The precursor is mixed with a lithium compound and then subjected to a first calcination to obtain a molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material; The molybdenum-lanthanum co-doped lithium-rich manganese-based positive electrode material is mixed with a solution containing an aluminum source, dried, and then subjected to a second calcination to form a coating layer to obtain a modified lithium-rich manganese-based positive electrode material.

4. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 3, characterized in that: The nickel source, cobalt source and manganese source include sulfates of the corresponding metal elements; the lanthanum salt includes sodium lanthanate; and the molybdenum salt includes sodium molybdate; Preferably, the total metal concentration in the mixed salt solution A is 1 to 3 mol / L; Preferably, the total metal concentration in the mixed salt solution B is 0.1 to 1 mol / L; Preferably, the molar amount of the molybdenum element in the molybdenum salt accounts for 0.5% to 5% of the molar amount of the manganese element in the manganese source; Preferably, the molar amount of the lanthanum element in the lanthanum salt accounts for 0.5% to 5% of the molar amount of the manganese element in the manganese source.

5. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The complexing agent includes aqueous ammonia with a concentration of 16% to 20%; the precipitant includes liquid alkali with a concentration of 20% to 24%; Preferably, the concentration of the complexing agent in the base solution is 2 to 4 g / L; Preferably, the pH of the base solution is 10-11.

6. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The parallel flow rate of the mixed salt solution A is 5 to 10 L / h; the parallel flow rate of the mixed salt solution B is 1 to 5 L / h; the parallel flow rate of the complexing agent is 1 to 5 L / h; the parallel flow rate of the precipitant is 10 to 15 L / h; Preferably, the coprecipitation reaction is carried out under stirring, and the stirring speed is 300-500 rpm; Preferably, the pH of the coprecipitation reaction is 8.5 to 11.5; Preferably, the coprecipitation reaction time is 24 to 60 hours.

7. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The precursor is washed, filtered, dried and pre-calcined before being mixed with the lithium compound; Preferably, the drying temperature is 70-90°C and the drying time is 10-14 hours; Preferably, the pre-firing temperature is 400-500° C. and the pre-firing time is 3-7 hours.

8. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The lithium compound includes lithium carbonate; Preferably, the ratio of the molar amount of the manganese source in the precursor to the molar amount of the lithium element in the lithium compound is 1:(2-2.8); Preferably, the first calcination has a heating rate of 3 to 8°C / min, a temperature of 800 to 900°C, and a time of 10 to 14 hours.

9. The method for preparing the modified lithium-rich manganese-based positive electrode material according to claim 4, characterized in that: The aluminum source includes aluminum nitrate; the solvent in the solution containing the aluminum source includes ethanol; Preferably, the second calcination is performed at a temperature of 400 to 600° C. and for a time of 3 to 7 hours.

10. A battery, characterized in that: Contains the modified lithium-rich manganese-based positive electrode material according to claim 1 or 2.

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