Molybdenum-doped and LFP-coated modified positive electrode material and preparation method thereof

Abstract

The invention relates to a molybdenum-doped and LFP-coated modified positive electrode material and a preparation method thereof. The positive electrode material comprises an inner core and a coating layer coating the inner core, the inner core is internally provided with a Mo element doped with a bulk phase; and the coating layer is lithium iron phosphate. The high valence state of Mo < 6 + > is utilized to realize dual stability of electrons and crystal structure layers, lattice oxygen loss under high voltage is inhibited, thermal safety is improved, and meanwhile, lithium and nickel mixed discharge can be inhibited; in addition, a better dynamic environment can be provided for lithium ion migration. The coating layer can inhibit interface side reaction and generation of a high-impedance phase, and also has good lithium ion conductivity, so that the interface impedance is greatly reduced; in addition, Mo doping provides structural support for the coating layer, so that the coating layer is prevented from cracking due to inner core distortion; and the stability is enhanced by matching protection of the coating layer with Mo doping, so that the material has high capacity, long cycle life and high safety, and is suitable for a solid-state battery system.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a cathode material, particularly a molybdenum-doped and LFP-coated cathode material and its preparation method. Background Technology

[0002] Nickel-rich layered oxide cathode materials are key materials for achieving high-energy-density lithium-ion batteries, but their commercialization has been hampered by two inherent and insurmountable stability problems. In terms of bulk structure, these materials are prone to a series of detrimental bulk phase changes during charge-discharge cycling, including characteristic phase transition reactions, irreversible loss of lattice oxygen, and severe Li-induced oxidation. + / Ni 2+ Cation mixing occurs, and these bulk-level instabilities directly lead to the continuous degradation of battery capacity and a significant decline in voltage plateau, severely impacting the battery's cycle life. Regarding interfacial properties, the highly active Ni present on the material surface... 4+ Species readily undergo violent interfacial side reactions with battery electrolytes. The reaction products form an unstable cathode electrolyte interfacial (CEI) film on the material surface. This film not only significantly increases interfacial impedance and reduces ion transport efficiency, but may also cause safety hazards such as thermal runaway under long-term cycling or high-temperature environments.

[0003] To alleviate the aforementioned stability issues, the industry has widely researched and applied single-element doping or surface coating modification strategies. However, these single strategies all have significant functional limitations. More importantly, existing research lacks effective synergistic design between the doping element and the surface coating layer, failing to achieve comprehensive optimization of material properties. Element doping strategies, through lattice site doping, can optimize the bulk crystal structure of materials to some extent, enhancing lattice stability and having a certain effect on suppressing bulk phase transitions and cation mixing. However, this strategy only acts on the bulk phase and cannot reach the interfacial reaction region between the material surface and the electrolyte. Therefore, it has almost no effect on improving the interfacial instability caused by surface side reactions. While traditional surface coating strategies can reduce direct contact between the material surface and the electrolyte through physical isolation, suppressing interfacial side reactions to some extent, the coating layer is often an ion-insulating or low-ionic-conductivity inert material, which severely hinders Li... + The lack of transport channels between the material surface and the electrolyte leads to a significant sacrifice in the rate performance of the battery, making it difficult to meet the application requirements of high power density batteries. More importantly, even when doping and coating are used simultaneously in existing technologies, they are often simply superimposed. The doping elements and the coating layer do not form a synergistic effect of functional complementarity. In fact, the poor compatibility between the coating layer and the bulk structure after doping may further aggravate the ion transport resistance or structural stability risks.

[0004] To overcome the limitations of single modification strategies, the industry has recently begun exploring composite modification approaches that combine phase stabilization and interface optimization, attempting to combine doping with surface coating. However, these attempts still suffer from numerous technical shortcomings because they have not resolved the core issue of the synergistic effect between the two. Some studies have attempted to use fast ion conductors as surface coating layers, combined with conventional dopants, hoping to leverage the high ion conductivity of fast ion conductors to achieve both protection and ion transport, while simultaneously stabilizing the bulk phase through doping. However, these fast ion conductor materials exhibit significant mismatches in thermal expansion coefficients with nickel-rich cathode materials and the doped bulk structure, leading to problems such as coating layer cracking and detachment during high-temperature synthesis or cycling. Furthermore, there is no synergistic design between the dopants and the coating layer, and the synthesis process is usually quite complex, making large-scale production difficult.

[0005] Therefore, the existing technology lacks a synergistic design approach that enables doping elements and surface coating layers to form functional complementarity and structural compatibility, resulting in composite modification effects that fall far short of expectations. In this regard, it is necessary to provide a new cathode material with synergistic doping and coating and its preparation method. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a molybdenum-doped and LFP-coated cathode material and its preparation method, particularly a molybdenum-doped and LFP-coated cathode material suitable for solid-state batteries and its preparation method. The present invention utilizes Mo... 6+ The high valence state achieves dual stability at both the electronic and crystal structure levels, suppressing lattice oxygen loss under high voltage and improving thermal safety. It also suppresses lithium-nickel mixing and provides a better kinetic environment for lithium-ion migration. The coating layer suppresses interfacial side reactions and the formation of high-resistivity phases, while also exhibiting good lithium-ion conductivity, significantly reducing interfacial impedance. Furthermore, Mo doping provides structural support for the coating layer, preventing cracking due to core distortion. The protective coating layer combined with Mo doping enhances stability, resulting in a material with high capacity, long cycle life, and high safety, suitable for solid-state battery systems.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a molybdenum-doped and LFP-coated modified cathode material, the cathode material comprising a core and a coating layer covering the core;

[0009] The core contains bulk-doped Mo elements;

[0010] The coating layer is lithium iron phosphate (LFP).

[0011] The cathode material provided by this invention utilizes Mo 6+Mo achieves dual stability at both the electronic and crystal structure levels due to its high valence state characteristics. 6+ Mo forms a strong covalent bond with oxygen (Mo-O), significantly increasing the oxygen evolution barrier and fundamentally suppressing lattice oxygen loss under high voltage, thus improving thermal safety. Simultaneously, to balance the charge, Mo... 6+ Doping forces some Ni 2+ Oxidized to Ni 3+ This directly reduces the ease with Li + Ni undergoing mixing 2+ The concentration effectively suppresses cation mixing and ensures unobstructed lithium layer channels; in addition, the strong Mo-O bond energy moderately supports and widens the lithium layer spacing, providing a suitable environment for Li... + Migration provides a better kinetic environment; moreover, the coating layer first acts as a dense physical barrier, isolating the highly active material from direct contact with the electrolyte, fundamentally suppressing interfacial side reactions and the formation of high-resistivity phases. More importantly, unlike traditional insulating coatings, LFP itself has good lithium-ion conductivity, enabling the construction of high-speed ion transport channels on the particle surface, greatly reducing interfacial impedance, perfectly balancing interfacial protection and high-speed ion transport, and solving the bottleneck problem of rate performance degradation caused by traditional coatings; therefore, Mo bulk doping can stabilize the core lattice, suppress phase transitions, lattice oxygen loss, and Li + / Ni 2+ Mixed arrangement; the LFP coating can isolate the core from the electrolyte, suppress interfacial side reactions, and ensure Li + The two work synergistically, using Mo doping to provide structural support for the LFP coating layer, preventing it from cracking due to core distortion; LFP interface protection combined with Mo doping enhances stability, giving the material high capacity, long cycle life and high safety, making it suitable for solid-state battery systems.

[0012] In some embodiments, the chemical formula of the kernel is , where 0.02≤x≤0.1, 0.05≤y≤0.15, 0.05≤z≤0.15, and x+y+z=1.

[0013] Where x is 0.02 to 0.1, for example, it can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Where y is 0.05 to 0.15, for example, it can be 0.05, 0.06, 0.08, 0.09, 0.1, 0.12, 0.14 or 0.15, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Where z is 0.05 to 0.15, for example, it can be 0.05, 0.06, 0.08, 0.09, 0.1, 0.12, 0.14 or 0.15, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] In some embodiments, the chemical formula of the kernel is , where 0.02≤x≤0.1.

[0017] Secondly, the present invention provides a method for preparing a molybdenum-doped and LFP-coated modified cathode material, the preparation method comprising the following steps:

[0018] (1) Provides a bulk Mo-doped core;

[0019] (2) A lithium iron phosphate coating layer is coated on the surface of the core described in step (1) to obtain the cathode material described in the first aspect.

[0020] In some embodiments, the method of coating with lithium iron phosphate includes:

[0021] A phosphorus source, an iron source, and a first lithium source are mixed in a solvent to obtain a mixture; then the core described in step (1) is dispersed in the mixture; after removing the solvent, heat treatment is performed in a protective atmosphere to achieve the coating of lithium iron phosphate.

[0022] In some embodiments, the phosphorus source includes ammonium dihydrogen phosphate.

[0023] In some embodiments, the iron source includes ferric nitrate.

[0024] In some embodiments, the first lithium source includes lithium acetate.

[0025] A suitable mixture has a high solids content that provides both fluidity and appropriate concentration, ensuring that the LFP precursor can be uniformly deposited on the surface of the core during solvent removal.

[0026] In some embodiments, the solid content of the mixture is 10wt% to 30wt%, for example, it can be 10wt%, 15wt%, 20wt%, 25wt% or 30wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] A suitable solid-liquid ratio allows LFP precursor ions to fully contact the core surface, which is beneficial for forming a continuous and uniform nano-coating layer.

[0028] In some embodiments, the solid-liquid ratio of the core to the mixture is 1:5 to 1:10, wherein the dimension of the solid-liquid ratio is g / mL, and it can be, for example, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] In some embodiments, the solvent may be water or anhydrous ethanol.

[0030] In some embodiments, the solvent removal method includes rotary evaporation or spray drying.

[0031] In some embodiments, the heat treatment temperature is 500°C to 700°C, for example, it can be 500°C, 520°C, 540°C, 550°C, 560°C, 580°C, 600°C, 620°C, 640°C, 650°C, 660°C, 680°C or 700°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] In some embodiments, the protective atmosphere may include nitrogen and / or an inert gas.

[0033] In some embodiments, the method for preparing the kernel includes:

[0034] A bulk Mo-doped precursor was prepared by co-precipitation; the precursor was mixed with a second lithium source and calcined in an oxygen-containing atmosphere to obtain the core.

[0035] In some embodiments, the molar ratio of lithium in the second lithium source to the precursor is 1.05:1 or higher to compensate for the loss of the second lithium source during calcination.

[0036] In some embodiments, the calcination includes a first calcination and a second calcination performed sequentially;

[0037] The first calcination includes heating to 480°C to 550°C at a heating rate of 3°C / min to 5°C / min, and holding at that temperature for 5 hours to 7 hours;

[0038] The second calcination involves heating to 700℃~800℃ at a heating rate of 2℃ / min~3℃ / min and holding at that temperature for 10h~15h.

[0039] The heating rate of the first calcination is 3℃ / min to 5℃ / min, for example, it can be 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] The temperature for the first calcination is 480℃~550℃, for example, it can be 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃ or 550℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] The holding time for the first calcination is 5h to 7h, for example, it can be 5h, 5.5h, 6h, 6.5h or 7h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] The heating rate of the second calcination is 2℃ / min to 3℃ / min, for example, it can be 2℃ / min, 2.1℃ / min, 2.4℃ / min, 2.5℃ / min, 2.7℃ / min, 2.8℃ / min or 3℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] The second calcination temperature is 700℃~800℃, for example, it can be 700℃, 720℃, 750℃, 760℃, 780℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] The holding time for the second calcination is 10h to 15h, for example, it can be 10h, 11h, 12h, 13h, 14h or 15h, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] In some embodiments, the co-precipitation includes: adding a molybdenum salt solution, a sodium hydroxide solution, and ammonia water in a co-current manner to a mixed salt solution of nickel, cobalt, and manganese to obtain a bulk-doped Mo precursor.

[0046] In the mixed salt solution, the nickel salt can be nickel sulfate, the cobalt salt can be cobalt sulfate, and the manganese salt can be manganese sulfate.

[0047] The molybdenum salt in the molybdenum salt solution can be any one or a combination of at least two of ammonium molybdate, sodium molybdate, or potassium molybdate.

[0048] The concentration of the sodium hydroxide solution can be 35wt% to 40wt%, for example, 35wt%, 36wt%, 37wt%, 38wt%, 39wt% or 40wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] The concentration of ammonia water can be 20wt% to 25wt%, for example, 20wt%, 21wt%, 22wt%, 23wt%, 24wt% or 25wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] In some embodiments, the pH value of the coprecipitation is 10.5 to 11.5, for example, it can be 10.5, 10.8, 11, 11.2 or 11.5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0051] In some embodiments, the coprecipitation temperature is 50°C to 65°C, for example, 50°C, 52°C, 55°C, 56°C, 58°C, 60°C, 63°C, 64°C or 65°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] In some embodiments, the stirring speed of the coprecipitation is 400 rpm to 550 rpm, for example, 400 rpm, 410 rpm, 420 rpm, 440 rpm, 450 rpm, 460 rpm, 480 rpm, 500 rpm, 520 rpm, 540 rpm or 550 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0053] In some embodiments, the median particle size D50 of the kernel is 5μm to 12μm, for example, it can be 5μm, 6μm, 8μm, 9μm, 10μm, 11μm or 12μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] As a preferred embodiment of the preparation method described in the second aspect, the preparation method includes the following steps:

[0055] (1) A bulk Mo-doped precursor was prepared by co-precipitation; a second lithium source was mixed with the precursor and calcined in an oxygen atmosphere to obtain a bulk Mo-doped core with a median particle size D50 of 5 μm to 12 μm.

[0056] The coprecipitation process involves adding a molybdenum salt solution, a sodium hydroxide solution with a concentration of 35wt%~40wt%, and ammonia water with a concentration of 20wt%~25wt% to a mixed salt solution composed of nickel sulfate, cobalt sulfate, and manganese sulfate in parallel flow to obtain a bulk Mo-doped precursor. The coprecipitation process is carried out at a pH of 10.5~11.5, a temperature of 50℃~65℃, and a stirring speed of 400rpm~550rpm.

[0057] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is greater than 1.05:1;

[0058] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 480℃~550℃ at a heating rate of 3℃ / min~5℃ / min and holding at that temperature for 5h~7h; the second calcination includes heating to 700℃~800℃ at a heating rate of 2℃ / min~3℃ / min and holding at that temperature for 10h~15h.

[0059] (2) A phosphorus source, an iron source and a first lithium source are mixed in a solvent to obtain a mixture with a solid content of 10wt%~30wt%; then the core described in step (1) is dispersed in the mixture, wherein the solid-liquid ratio of the core to the mixture is 1:5~1:10, and the dimension of the solid-liquid ratio is g / mL; after removing the solvent, a heat treatment of 500℃~700℃ is performed in a nitrogen atmosphere to achieve the coating of lithium iron phosphate;

[0060] The phosphorus source is ammonium dihydrogen phosphate, the iron source is ferric nitrate, and the first lithium source is lithium acetate;

[0061] The methods for removing solvents include rotary evaporation or spray drying.

[0062] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] The cathode material provided by this invention utilizes Mo 6+ Mo achieves dual stability at both the electronic and crystal structure levels due to its high valence state characteristics. 6+ Mo forms a strong covalent bond with oxygen (Mo-O), significantly increasing the oxygen evolution barrier and fundamentally suppressing lattice oxygen loss under high voltage, thus improving thermal safety. Simultaneously, to balance the charge, Mo... 6+ Doping forces some Ni 2+ Oxidized to Ni 3+ This directly reduces the ease with Li + Ni undergoing mixing 2+ The concentration effectively suppresses cation mixing and ensures unobstructed lithium layer channels; in addition, the strong Mo-O bond energy moderately supports and widens the lithium layer spacing, providing a suitable environment for Li... +Migration provides a better kinetic environment; moreover, the coating layer first acts as a dense physical barrier, isolating the highly active material from direct contact with the electrolyte, fundamentally suppressing interfacial side reactions and the formation of high-resistivity phases. More importantly, unlike traditional insulating coatings, LFP itself has good lithium-ion conductivity, enabling the construction of high-speed ion transport channels on the particle surface, greatly reducing interfacial impedance, perfectly balancing interfacial protection and high-speed ion transport, and solving the bottleneck problem of rate performance degradation caused by traditional coatings; therefore, Mo bulk doping can stabilize the core lattice, suppress phase transitions, lattice oxygen loss, and Li + / Ni 2+ Mixed arrangement; the LFP coating can isolate the core from the electrolyte, suppress interfacial side reactions, and ensure Li + The two work synergistically, using Mo doping to provide structural support for the LFP coating layer, preventing it from cracking due to core distortion; LFP interface protection combined with Mo doping enhances stability, giving the material high capacity, long cycle life and high safety, making it suitable for solid-state battery systems. Detailed Implementation

[0065] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0066] The "range" disclosed in this invention can be defined in the form of 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. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0067] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0068] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0069] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0070] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can 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.

[0071] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0072] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0073] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0074] Example 1

[0075] This embodiment provides a molybdenum-doped and LFP-coated modified cathode material, comprising a core and a coating layer covering the core; wherein the core has the chemical formula LiNi. 0.75 Co 0.1 Mn 0.1 Mo 0.05 O2, with a coating of lithium iron phosphate;

[0076] The method for preparing the cathode material provided in this embodiment includes the following steps:

[0077] (1) A bulk Mo-doped precursor was prepared by co-precipitation; a second lithium source was mixed with the precursor and calcined in an oxygen atmosphere to obtain a bulk Mo-doped core with a median particle size D50 of 8 μm.

[0078] The coprecipitation process involves adding sodium molybdate solution, 40 wt% sodium hydroxide solution, and 22 wt% ammonia solution in parallel to a mixed salt solution consisting of nickel sulfate, cobalt sulfate, and manganese sulfate to obtain a bulk Mo-doped precursor. The coprecipitation process is carried out at a pH of 11, a temperature of 60°C, and a stirring speed of 500 rpm.

[0079] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is 1.05:1;

[0080] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 500°C at a heating rate of 4°C / min and holding at that temperature for 6 hours; the second calcination includes heating to 750°C at a heating rate of 2.5°C / min and holding at that temperature for 12 hours.

[0081] (2) A phosphorus source, an iron source and a first lithium source are mixed in water to obtain a mixture with a solid content of 20 wt%; then the core described in step (1) is dispersed in the mixture, wherein the solid-liquid ratio of the core to the mixture is 1:8 and the dimension of the solid-liquid ratio is g / mL; after removing water, heat treatment is performed at 600℃ in a nitrogen atmosphere to achieve the coating of lithium iron phosphate;

[0082] The phosphorus source is ammonium dihydrogen phosphate, the iron source is ferric nitrate, and the first lithium source is lithium acetate; the molar ratio of iron, lithium and phosphorus in the mixture is 1:1:1.

[0083] The method for removing water is spray drying.

[0084] Example 2

[0085] This embodiment provides a molybdenum-doped and LFP-coated modified cathode material, comprising a core and a coating layer covering the core; wherein the core has the chemical formula LiNi. 0.75 Co 0.1 Mn 0.1 Mo 0.05 O2, with a coating of lithium iron phosphate;

[0086] The method for preparing the cathode material provided in this embodiment includes the following steps:

[0087] (1) A bulk Mo-doped precursor was prepared by co-precipitation; a second lithium source was mixed with the precursor and calcined in an oxygen atmosphere to obtain a bulk Mo-doped core with a median particle size D50 of 8 μm.

[0088] The coprecipitation process involves adding sodium molybdate solution, 40 wt% sodium hydroxide solution, and 22 wt% ammonia solution in parallel to a mixed salt solution consisting of nickel sulfate, cobalt sulfate, and manganese sulfate to obtain a bulk Mo-doped precursor. The coprecipitation process is carried out at a pH of 10.5, a temperature of 50°C, and a stirring speed of 400 rpm.

[0089] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is 1.05:1;

[0090] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 480°C at a heating rate of 3°C / min and holding at that temperature for 7 hours; the second calcination includes heating to 700°C at a heating rate of 2°C / min and holding at that temperature for 15 hours.

[0091] (2) A mixture of phosphorus source, iron source and first lithium source is mixed in water to obtain a mixture with a solid content of 10 wt%; then the core described in step (1) is dispersed in the mixture, wherein the solid-liquid ratio of the core to the mixture is 1:5 and the dimension of the solid-liquid ratio is g / mL; after removing water, heat treatment is performed at 500℃ in a nitrogen atmosphere to achieve the coating of lithium iron phosphate coating layer;

[0092] The phosphorus source is ammonium dihydrogen phosphate, the iron source is ferric nitrate, and the first lithium source is lithium acetate; the molar ratio of iron, lithium and phosphorus in the mixture is 1:1:1.

[0093] The method for removing water is spray drying.

[0094] Example 3

[0095] This embodiment provides a molybdenum-doped and LFP-coated modified cathode material, comprising a core and a coating layer covering the core; wherein the core has the chemical formula LiNi. 0.75 Co 0.1 Mn 0.1 Mo 0.05 O2, with a coating of lithium iron phosphate;

[0096] The method for preparing the cathode material provided in this embodiment includes the following steps:

[0097] (1) A bulk Mo-doped precursor was prepared by co-precipitation; a second lithium source was mixed with the precursor and calcined in an oxygen atmosphere to obtain a bulk Mo-doped core with a median particle size D50 of 8 μm.

[0098] The coprecipitation process involves adding sodium molybdate solution, 40 wt% sodium hydroxide solution, and 22 wt% ammonia solution in parallel to a mixed salt solution consisting of nickel sulfate, cobalt sulfate, and manganese sulfate to obtain a bulk Mo-doped precursor. The coprecipitation process is carried out at a pH of 11.5, a temperature of 65°C, and a stirring speed of 550 rpm.

[0099] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is 1.05:1;

[0100] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 550°C at a heating rate of 5°C / min and holding at that temperature for 5 hours; the second calcination includes heating to 800°C at a heating rate of 3°C / min and holding at that temperature for 10 hours.

[0101] (2) A phosphorus source, an iron source and a first lithium source are mixed in water to obtain a mixture with a solid content of 30 wt%; then the core described in step (1) is dispersed in the mixture, wherein the solid-liquid ratio of the core to the mixture is 1:10 and the dimension of the solid-liquid ratio is g / mL; after removing water, heat treatment is performed at 700℃ in a nitrogen atmosphere to achieve the coating of lithium iron phosphate;

[0102] The phosphorus source is ammonium dihydrogen phosphate, the iron source is ferric nitrate, and the first lithium source is lithium acetate; the molar ratio of iron, lithium and phosphorus in the mixture is 1:1:1.

[0103] The method for removing water is spray drying.

[0104] Example 4

[0105] This embodiment provides a molybdenum-doped and LFP-coated modified cathode material. Besides changing the molybdenum doping amount, the core chemical formula is LiNi. 0.7 Co 0.1 Mn 0.1 Mo 0.1 Except for O2, everything else is the same as in Example 1.

[0106] Example 5

[0107] This embodiment provides a molybdenum-doped and LFP-coated modified cathode material. Besides changing the molybdenum doping amount, the core chemical formula is LiNi. 0.78 Co 0.1 Mn 0.1 Mo 0.02 Except for O2, everything else is the same as in Example 1.

[0108] Example 6

[0109] This embodiment provides a molybdenum-doped and LFP-coated modified cathode material. Besides changing the molybdenum doping amount, the core chemical formula is LiNi. 0.6 Co 0.1 Mn 0.1 Mo 0.2 Except for O2, everything else is the same as in Example 1.

[0110] Comparative Example 1

[0111] This comparative example provides an LFP-coated modified cathode material, comprising a core and a coating layer covering the core; wherein the core has the chemical formula LiNi. 0.8 Co 0.1 Mn 0.1 O2, with a coating of lithium iron phosphate;

[0112] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0113] (1) Precursor preparation by co-precipitation; the second lithium source and the precursor are mixed and calcined in an oxygen atmosphere to obtain a core with a median particle size D50 of 8 μm;

[0114] The coprecipitation process involves adding a 40 wt% sodium hydroxide solution and a 22 wt% ammonia solution in parallel to a mixed salt solution consisting of nickel sulfate, cobalt sulfate, and manganese sulfate to obtain a precursor. The coprecipitation process is carried out at a pH of 11, a temperature of 60°C, and a stirring speed of 500 rpm.

[0115] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is 1.05:1;

[0116] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 500°C at a heating rate of 4°C / min and holding at that temperature for 6 hours; the second calcination includes heating to 750°C at a heating rate of 2.5°C / min and holding at that temperature for 12 hours.

[0117] (2) A phosphorus source, an iron source and a first lithium source are mixed in water to obtain a mixture with a solid content of 20 wt%; then the core described in step (1) is dispersed in the mixture, wherein the solid-liquid ratio of the core to the mixture is 1:8 and the dimension of the solid-liquid ratio is g / mL; after removing water, heat treatment is performed at 600℃ in a nitrogen atmosphere to achieve the coating of lithium iron phosphate;

[0118] The phosphorus source is ammonium dihydrogen phosphate, the iron source is ferric nitrate, and the first lithium source is lithium acetate; the molar ratio of iron, lithium and phosphorus in the mixture is 1:1:1.

[0119] The method for removing water is spray drying.

[0120] Comparative Example 2

[0121] This comparative example provides a niobium-doped cathode material modified with LFP coating. Except for replacing molybdenum with niobium, it is identical to Example 1, including a core and a coating layer covering the core; wherein the core has the chemical formula LiNi. 0.75 Co 0.1 Mn 0.1 Nb 0.05 O2, with a coating of lithium iron phosphate;

[0122] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0123] (1) A precursor of bulk Nb-doped element was prepared by co-precipitation; the second lithium source was mixed with the precursor and calcined in an oxygen atmosphere to obtain a bulk Nb-doped element core with a median particle size D50 of 8 μm.

[0124] The coprecipitation process involves adding niobium pentachloride solution, 40 wt% sodium hydroxide solution, and 22 wt% ammonia solution in parallel to a mixed salt solution consisting of nickel sulfate, cobalt sulfate, and manganese sulfate to obtain a bulk Nb-doped precursor. The coprecipitation process is carried out at a pH of 11, a temperature of 60°C, and a stirring speed of 500 rpm.

[0125] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is 1.05:1;

[0126] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 500°C at a heating rate of 4°C / min and holding at that temperature for 6 hours; the second calcination includes heating to 750°C at a heating rate of 2.5°C / min and holding at that temperature for 12 hours.

[0127] (2) A phosphorus source, an iron source and a first lithium source are mixed in water to obtain a mixture with a solid content of 20 wt%; then the core described in step (1) is dispersed in the mixture, wherein the solid-liquid ratio of the core to the mixture is 1:8 and the dimension of the solid-liquid ratio is g / mL; after removing water, heat treatment is performed at 600℃ in a nitrogen atmosphere to achieve the coating of lithium iron phosphate;

[0128] The phosphorus source is ammonium dihydrogen phosphate, the iron source is ferric nitrate, and the first lithium source is lithium acetate; the molar ratio of iron, lithium and phosphorus in the mixture is 1:1:1.

[0129] The method for removing water is spray drying.

[0130] Comparative Example 3

[0131] This comparative example provides an aluminum-doped cathode material modified with LFP coating. Except for replacing molybdenum with aluminum, it is identical to Example 1, including a core and a coating layer covering the core; wherein the core has the chemical formula LiNi. 0.75 Co 0.1 Mn 0.1 Al 0.05 O2, with a coating of lithium iron phosphate;

[0132] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0133] (1) A bulk Al-doped precursor was prepared by co-precipitation; a second lithium source was mixed with the precursor and calcined in an oxygen atmosphere to obtain a bulk Al-doped core with a median particle size D50 of 8 μm.

[0134] The coprecipitation process involves adding aluminum sulfate solution, 40 wt% sodium hydroxide solution, and 22 wt% ammonia solution in parallel to a mixed salt solution consisting of nickel sulfate, cobalt sulfate, and manganese sulfate to obtain a bulk Al-doped precursor. The coprecipitation process is carried out at a pH of 11, a temperature of 60°C, and a stirring speed of 500 rpm.

[0135] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is 1.05:1;

[0136] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 500°C at a heating rate of 4°C / min and holding at that temperature for 6 hours; the second calcination includes heating to 750°C at a heating rate of 2.5°C / min and holding at that temperature for 12 hours.

[0137] (2) A phosphorus source, an iron source and a first lithium source are mixed in water to obtain a mixture with a solid content of 20 wt%; then the core described in step (1) is dispersed in the mixture, wherein the solid-liquid ratio of the core to the mixture is 1:8 and the dimension of the solid-liquid ratio is g / mL; after removing water, heat treatment is performed at 600℃ in a nitrogen atmosphere to achieve the coating of lithium iron phosphate;

[0138] The phosphorus source is ammonium dihydrogen phosphate, the iron source is ferric nitrate, and the first lithium source is lithium acetate; the molar ratio of iron, lithium and phosphorus in the mixture is 1:1:1.

[0139] The method for removing water is spray drying.

[0140] Comparative Example 4

[0141] This comparative example provides a molybdenum-doped modified cathode material with the chemical formula LiNi. 0.75 Co 0.1 Mn 0.1 Mo 0.05 O2;

[0142] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0143] A bulk Mo-doped precursor was prepared by co-precipitation; a second lithium source was mixed with the precursor and calcined in an oxygen atmosphere to obtain a cathode material with a median particle size D50 of 8 μm.

[0144] The coprecipitation process involves adding sodium molybdate solution, 40 wt% sodium hydroxide solution, and 22 wt% ammonia solution in parallel to a mixed salt solution consisting of nickel sulfate, cobalt sulfate, and manganese sulfate to obtain a bulk Mo-doped precursor. The coprecipitation process is carried out at a pH of 11, a temperature of 60°C, and a stirring speed of 500 rpm.

[0145] The second lithium source is lithium hydroxide, and the molar ratio of lithium to precursor in the second lithium source is 1.05:1;

[0146] The calcination includes a first calcination and a second calcination performed sequentially; the first calcination includes heating to 500°C at a heating rate of 4°C / min and holding at that temperature for 6 hours; the second calcination includes heating to 750°C at a heating rate of 2.5°C / min and holding at that temperature for 12 hours.

[0147] Performance Characterization

[0148] Li₂S, P₂S₅, LiCl, and zirconia balls with an average particle size of 10 mm were mixed in a zirconia pot and ball-milled at 500 rpm for 14 h. The ball-milled material was then annealed at 450 °C for 8 h in a nitrogen atmosphere to obtain the solid electrolyte Li₆PS₅Cl. The positive electrode material prepared in the above example and comparative example, along with the solid electrolyte Li₆PS₅Cl and carbon black, were mixed in a mass ratio of 69:30:1 to serve as the positive electrode material for the solid-state battery. Graphite was used as the negative electrode, and the solid-state battery was assembled in an argon-filled glove box.

[0149] A charge-discharge test system was used to activate the device twice in the 3V~4.6V range at a 0.1C rate, and then cycle it 500 times at a 0.5C rate. The discharge capacity of the first and 500th cycles was recorded. The percentage of the discharge capacity of the 500th cycle to the discharge capacity of the first cycle was taken as the capacity retention rate at room temperature (25℃).

[0150] In addition, the assembled solid-state battery was placed in a 60°C constant temperature chamber for 4 hours and cycled 300 times at a 0.5C rate in the range of 3V~4.6V. The discharge capacity of the 1st and 300th cycles was recorded. The percentage of the discharge capacity of the 300th cycle to the discharge capacity of the 1st cycle was taken as the high temperature (60°C) cycle capacity retention rate.

[0151] The electrochemical impedance spectroscopy (EIS) of the solid-state battery was tested using an electrochemical workstation at a frequency band of 10 GHz. -2 The EIS spectra of the solid-state battery after activation were measured at Hz and with an amplitude of 5mV. After one cycle and 200 cycles, the interfacial impedance between the positive electrode and the solid electrolyte was extracted by equivalent circuit fitting. The percentage increase in impedance after 200 cycles relative to the impedance after one cycle was taken as the interfacial impedance growth rate.

[0152] The characterization results are shown in Table 1.

[0153] Table 1

[0154]

[0155] As can be seen from Examples 1 to 5 in Table 1, the molybdenum-doped and LFP-coated modified cathode material provided by the present invention has excellent comprehensive performance.

[0156] A comparison of Examples 1, 4, 5, and 6 shows that the Mo doping amount is a key factor affecting material performance; it only achieves optimal results within a reasonable range, while excessive doping leads to performance degradation. This is because an appropriate amount of Mo... 6+ The formation of strong Mo-O bonds can raise the oxygen evolution energy barrier and force Ni to evolve. 2+ Oxidized to Ni 3+ To suppress cation mixing and appropriately widen the lithium interlayer spacing; however, when the Mo doping amount is too high, excessive Mo... 6+ It will disrupt the lattice charge balance, leading to lattice distortion, which in turn undermines the stability of the bulk structure. At the same time, excessive Mo may accumulate at grain boundaries, hindering Li + migrate.

[0157] A comparison between Comparative Example 1 and Example 1 shows that Mo bulk doping is a core prerequisite for ensuring the bulk stability of the material; without Mo doping, the material performance deteriorates significantly. This is because the lack of Mo... 6+ The inability to form strong Mo-O bonds to suppress lattice oxygen loss under high voltage significantly reduces thermal safety; simultaneously, it cannot reduce Ni through charge compensation. 2+ Concentration, Li + / Ni 2+ Severe cation mixing and blockage of lithium layer channels led to Li + Migration kinetics deteriorate, bulk phase transitions intensify, ultimately resulting in low cycle capacity retention and poor thermal stability.

[0158] A comparison of Comparative Examples 2 and 3 with Example 1 shows that Mo doping has advantages over Nb and Al doping. This is because: Nb 5+ The valence state is lower than Mo 6+ The charge compensation effect is weak, suppressing Ni 2+ The mixing effect is insufficient, and the Nb-O bond strength is weaker than the Mo-O bond, resulting in limited inhibition of oxygen loss; Al 3+ As low-valence ions, Ni ions cannot be controlled by charge compensation, and can only slightly support the lattice. They cannot solve the problems of oxygen loss and cation mixing. At the same time, their synergy with the LFP coating layer is not as good as that of Mo.

[0159] A comparison of Comparative Example 4 and Example 1 shows that the LFP coating layer is crucial for ensuring the material's interfacial performance; the material performance is poor without LFP coating. This is because the lack of a dense physical barrier provided by LFP allows the highly reactive Ni on the nickel-rich core surface to penetrate more readily. 4+It will undergo violent side reactions with the electrolyte, forming a high-impedance CEI film, and the interfacial impedance will increase sharply; at the same time, it lacks the high-speed ion transport channels constructed by LFP, and the interfacial Li + Transport is hindered, rate performance drops significantly, and thermal safety issues become prominent. This contrasts sharply with the characteristics of Mo doping, which can only ensure bulk stability but cannot solve interface problems, highlighting the core role of LFP coating in interface protection and ion transport.

[0160] A comprehensive comparison of Example 1 and all comparative examples shows that the synergistic effect of Mo bulk doping and LFP surface coating is key to achieving high capacity, long cycle life, and high safety in the material. Mo doping provides structural support for the LFP coating layer through bulk stabilization, preventing it from cracking due to core distortion; the LFP coating layer reduces the exposure of active sites on the core surface through interface protection, while the high ionic conductivity of LFP and the lithium layer channels broadened by Mo doping form a synergistic mass transfer effect, perfectly solving the defects of traditional single modification.

[0161] In summary, the cathode material provided by this invention utilizes Mo 6+ Mo achieves dual stability at both the electronic and crystal structure levels due to its high valence state characteristics. 6+ Mo forms a strong covalent bond with oxygen (Mo-O), significantly increasing the oxygen evolution barrier and fundamentally suppressing lattice oxygen loss under high voltage, thus improving thermal safety. Simultaneously, to balance the charge, Mo... 6+ Doping forces some Ni 2+ Oxidized to Ni 3+ This directly reduces the ease with Li + Ni undergoing mixing 2+ The concentration effectively suppresses cation mixing and ensures unobstructed lithium layer channels; in addition, the strong Mo-O bond energy moderately supports and widens the lithium layer spacing, providing a suitable environment for Li... + Migration provides a better kinetic environment; moreover, the coating layer first acts as a dense physical barrier, isolating the highly active material from direct contact with the electrolyte, fundamentally suppressing interfacial side reactions and the formation of high-resistivity phases. More importantly, unlike traditional insulating coatings, LFP itself has good lithium-ion conductivity, enabling the construction of high-speed ion transport channels on the particle surface, greatly reducing interfacial impedance, perfectly balancing interfacial protection and high-speed ion transport, and solving the bottleneck problem of rate performance degradation caused by traditional coatings; therefore, Mo bulk doping can stabilize the core lattice, suppress phase transitions, lattice oxygen loss, and Li + / Ni 2+ Mixed arrangement; the LFP coating can isolate the core from the electrolyte, suppress interfacial side reactions, and ensure Li +The two work synergistically, using Mo doping to provide structural support for the LFP coating layer, preventing it from cracking due to core distortion; LFP interface protection combined with Mo doping enhances stability, giving the material high capacity, long cycle life and high safety, making it suitable for solid-state battery systems.

[0162] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A molybdenum-doped and LFP-coated cathode material, characterized in that, The cathode material includes a core and a coating layer covering the core; The core contains bulk-doped Mo elements; The coating layer is lithium iron phosphate.

2. The cathode material according to claim 1, characterized in that, The chemical formula of the kernel is , where 0.02≤x≤0.1, 0.05≤y≤0.15, 0.05≤z≤0.15, and x+y+z=1.

3. A method for preparing a molybdenum-doped and LFP-coated modified cathode material, characterized in that, The preparation method includes the following steps: (1) Provides a bulk Mo-doped core; (2) The surface of the core described in step (1) is coated with a lithium iron phosphate coating layer to obtain the cathode material described in claim 1 or 2.

4. The preparation method according to claim 3, characterized in that, The method for coating with a lithium iron phosphate coating layer includes: A phosphorus source, an iron source, and a first lithium source are mixed in a solvent to obtain a mixture; then the core described in step (1) is dispersed in the mixture; after removing the solvent, heat treatment is performed in a protective atmosphere to achieve the coating of lithium iron phosphate.

5. The preparation method according to claim 4, characterized in that, The phosphorus source includes ammonium dihydrogen phosphate; And / or, the iron source includes ferric nitrate; And / or, the first lithium source includes lithium acetate; And / or, the solid content of the mixture is 10wt%~30wt%.

6. The preparation method according to claim 4 or 5, characterized in that, The solid-liquid ratio of the core to the mixture is 1:5 to 1:10, wherein the dimension of the solid-liquid ratio is g / mL; And / or, the method for removing the solvent includes rotary evaporation or spray drying; And / or, the temperature of the heat treatment is 500℃~700℃; And / or, the protective atmosphere may include nitrogen and / or an inert gas.

7. The preparation method according to any one of claims 3 to 6, characterized in that, The method for preparing the kernel includes: A bulk Mo-doped precursor was prepared by co-precipitation; the precursor was mixed with a second lithium source and calcined in an oxygen-containing atmosphere to obtain the core.

8. The preparation method according to claim 7, characterized in that, The molar ratio of lithium in the second lithium source to the precursor is 1.05:1 or higher.

9. The preparation method according to claim 7 or 8, characterized in that, The calcination includes a first calcination and a second calcination performed sequentially. The first calcination includes heating to 480°C to 550°C at a heating rate of 3°C / min to 5°C / min, and holding at that temperature for 5 hours to 7 hours; The second calcination involves heating to 700℃~800℃ at a heating rate of 2℃ / min~3℃ / min and holding at that temperature for 10h~15h.

10. The preparation method according to any one of claims 7 to 9, characterized in that, The pH value of the coprecipitate is 10.5~11.5; And / or, the co-precipitation temperature is 50℃~65℃; And / or, the stirring speed for the co-precipitation is 400 rpm to 550 rpm; And / or, the median particle size D50 of the kernel is 5μm~12μm.

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