High-entropy doped LiMn0. 85Fe0. 15PO4 positive electrode material and preparation method thereof

Abstract

The molecular general formula of the positive electrode material is Li < x > Mn < 0.85 > Fe < 0.15-y > M < 1 > a M < 2 > b M < 3 > c M < 4 > d M < 5 > e M < 6 > f P < z > O < 4 >, M < 1 > is a + 1 valence metal element, M < 2 > is a + 2 valence metal element, M < 3 > is a + 3 valence metal element, M < 4 > is a + 4 valence metal element, M < 5 > is a + 5 valence metal element, M < 6 > is a + 6 valence metal element, x is larger than or equal to 0.90 and smaller than 1.10, y is larger than or equal to 0.01 and smaller than 0.06, z is larger than or equal to 0.90 and smaller than 1.10, and a + b + c + d + e + f is equal to y. According to the method, spray drying is adopted to assist high-temperature solid-phase reaction for high-entropy doping, and through combination of multiple main elements, entropy can be configured to the maximum extent, and performance improvement is achieved. The stability and the rate capability of the battery material are improved, and the charge-discharge specific capacity is relatively high. And the preparation process is simple, low in production cost and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy battery materials, specifically relating to a high-entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material and its preparation method. Technical Background LiMn 0.85 Fe 0.15 Both PO4 and LiFePO4 have an olivine structure, and their theoretical capacity, thermal stability, and safety performance are comparable to those of LiFePO4, but PO4 has a higher voltage plateau (4.1V) and a theoretical specific energy of 684 Wh·kg. -1 It is 17% higher than LiFePO4, therefore, LiMn 0.85 Fe 0.15 PO4 is considered a next-generation cathode material for lithium-ion batteries. However, LiMn, which has a high manganese content... 0.85 Fe 0.15 PO4 exhibits poor structural stability, leading to deterioration in battery cycle and rate performance. After manganese and iron become miscible, the material undergoes crystal structure distortion, potentially causing manganese leaching during battery cycling and reacting with the electrolyte, thus affecting cycle life. Simultaneously, the material has poor electrical conductivity and ion diffusion coefficient, further impacting rate performance. A combined doping and coating modification strategy can effectively address the issues associated with LiMn. 0.85 Fe 0.15 The problem with PO4.

[0002] High-entropy materials are a new type of multi-principal-element materials composed of multiple elements in equimolar (or near-equimolar) ratios, and are currently one of the most important research hotspots in the international materials science community. Unlike traditional materials, multi-principal-element high-entropy materials have complex compositions, with the constituent element atoms randomly and disorderedly distributed in lattice positions. Therefore, high-entropy materials exhibit a high-entropy effect thermodynamically, a hysteresis diffusion effect kinetically, a lattice distortion effect structurally, and a cocktail effect in terms of performance.

[0003] Inspired by the concept of entropy stability in high-entropy alloys, high-entropy doping strategies have rapidly expanded into the field of battery materials. High-entropy doping is a special doping method that typically involves introducing three or more types of atoms to replace the original atoms. In recent years, research on high-entropy doped battery materials has surged, with significant progress made in exploring new systems and understanding composition-structure-performance relationships. However, its application in lithium-ion battery materials is currently limited, particularly in the field of lithium manganese iron phosphate cathode materials. Therefore, exploring its application in LiMn... 0.85 Fe 0.15 The application of PO4 cathode materials has great scientific and commercial value. Summary of the Invention

[0004] The purpose of this invention is to provide a high-entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material and its preparation method: This method uses spray drying-assisted high-temperature solid-state reaction to prepare multi-element high-entropy doped and modified LiMn. 0.85 Fe 0.15 PO4 cathode material achieves high electronic and ionic conductivity, thereby improving cycle performance and rate performance.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material, wherein the general molecular formula of the cathode material is Li x Mn 0.85 Fe 0.15-y M1 a M2 b M3 c M4 d M5 e M6 f P z O4, where M1 is a metal element with a +1 valence, M2 is a metal element with a +2 valence, M3 is a metal element with a +3 valence, M4 is a metal element with a +4 valence, M5 is a metal element with a +5 valence, M6 is a metal element with a +6 valence, 0.90≤x<1.10, 0.01≤y<0.06, 0.90≤z<1.10, and a+b+c+d+e+f=y.

[0006] Furthermore, the +1 valence metal element is one or more of Na and K, the +2 valence metal element is one or more of Mg, Ca, Ba, Co, Ni, Cu and Zn, the +3 valence metal element is one or more of V, Al, Cr, Y, La and Ce, the +4 valence metal element is one or more of Ti and Zr, the +5 valence metal element is one or more of Nb and Ta, and the +6 valence metal element is one or more of Mo and W.

[0007] A high-entropy doped LiMn 0.85 Fe 0.15 The preparation method of PO4 cathode material includes the following steps: a) Add Li to an aqueous solution of carbon source and surfactant. x Mn 0.85 Fe 0.15-y M1 a M2 b M3 c M4 d M5 e M6 f Pz O4 is added in stoichiometric proportions to manganese source, iron source, compound M1, compound M2, compound M3, compound M4, compound M5 and compound M6, mixed evenly, then phosphorus source and lithium source are added, and the mixture is ground to obtain a mixture. b) The mixture was subjected to sand milling and a first spray drying process to obtain spherical precursors; c) The spherical precursor is subjected to a first high-temperature sintering to obtain an intermediate; d) Add intermediates to an aqueous solution containing nano-sized oxides and different carbon sources from step a), and perform a second spray drying; e) The material after the second spray drying is subjected to a second high-temperature sintering to obtain highly entropy-doped LiMn. 0.85 Fe 0.15 PO4 cathode material.

[0008] Furthermore, the carbon source is one or more of sucrose, glucose, citric acid, polyvinyl alcohol, soluble starch, ascorbic acid, carbon black, acetylene black, carbon nanotubes, polyethylene glycol, and graphene.

[0009] Furthermore, the carbon source is at least two of sucrose, glucose, citric acid, polyvinyl alcohol, polyethylene glycol, carbon nanotubes, and graphene. Furthermore, the carbon coating content of the mixture in step a) is high-entropy doped LiMn. 0.85 Fe 0.15 The carbon coating content of the material after the second spray drying in step d) is 0.5wt%~10wt% of the PO4 cathode material, and is high-entropy doped LiMn. 0.85 Fe 0.15 The PO4 cathode material is 0.5 wt% to 10 wt% of its weight.

[0010] Furthermore, the carbon coating is high-entropy doped LiMn. 0.85 Fe 0.15 The PO4 cathode material accounts for 0.5 wt% to 6 wt% of its weight.

[0011] Furthermore, the surfactant is one or more selected from polyvinylpyrrolidone, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, cyclohexane, fluoroalkyl quaternary ammonium salt, oleic acid, sodium 4-styrene sulfonate, and silane coupling agents. The amount of surfactant added is 0.1wt% to 8wt% of the intermediate.

[0012] Furthermore, the surfactant mentioned in step a) is PVP, DTAB, CTAB, SDBS, SDS, oleic acid, or a silane coupling agent.

[0013] Furthermore, the amount of the surfactant added is 1wt% to 5wt% of the intermediate.

[0014] Furthermore, the manganese source is one or more of manganese powder, manganese dioxide, manganese trioxide, manganese tetroxide, manganese carbonate, manganese oxalate, manganese acetate, and manganese nitrate; The iron source is one or more of the following: iron powder, ferric oxide, ferric oxide, ferric oxide, ferrous oxalate, ferric sulfate, ferric chloride, ferric phosphate, ferric nitrate, and ferric hydroxide. The compounds M1, M2, M3, M4, M5, and M6 are one or more of the following: carbonates, oxalates, acetates, sulfates, nitrates, halides, oxides, and hydroxides. Furthermore, the manganese source is manganese dioxide, manganese tetroxide, manganese carbonate, or manganese acetate; The iron source is ferric oxide, ferric oxide, ferrous oxalate, or ferric phosphate.

[0015] Preferably, the compounds M1, M2, M3, M4, M5 and M6 are the corresponding oxides, hydroxides, acetates or oxalates.

[0016] Furthermore, the phosphorus source is one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, lithium phosphate, and lithium dihydrogen phosphate; The lithium source is one or more of lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium dihydrogen phosphate. Furthermore, the phosphorus source is phosphoric acid, ammonium dihydrogen phosphate, or lithium dihydrogen phosphate; The lithium source is lithium hydroxide, lithium carbonate, or lithium dihydrogen phosphate.

[0017] Furthermore, the ball milling speed is 200~1200 rpm, and the ball milling time is 1~12 h; Furthermore, the ball milling speed is 300~1000 rpm, and the ball milling time is 4~8 hours.

[0018] Furthermore, the grinding speed is 500~3000 rpm, and the grinding time is 1~6 hours; Furthermore, the grinding speed is 800~2600 rpm, and the grinding time is 3~5 hours.

[0019] Furthermore, the spray drying temperature is 150~350℃, and the feeding rate is 10~80mL / min; the nano-sized oxide is one or more of Al2O3, MgO, TiO2, ZnO, ZrO2 and SiO2.

[0020] The amount of the nano-sized oxide added is 1 wt% to 6 wt% of the intermediate.

[0021] Furthermore, the spray drying temperature described in steps b) and d) is 200~320°C, and the feed rate is 30~60mL / min.

[0022] Furthermore, the nanoscale oxide is Al2O3, MgO, TiO2 or ZrO2.

[0023] Furthermore, the first sintering temperature is 500~800℃, the sintering time is 4~20h, and the heating rate is 1-10℃ / min; the second sintering temperature is 300~600℃, the sintering time is 10~120min, and the heating rate is 1-10℃ / min.

[0024] Furthermore, the first sintering temperature is 550~750℃, the sintering time is 6~12h, and the heating rate is 2~6℃ / min; Furthermore, the second sintering temperature is 350~550℃, the sintering time is 20~120min, and the heating rate is 2~6℃ / min.

[0025] Compared with the prior art, the present invention has the following beneficial effects: This invention is based on LiMn 0.85 Fe 0.15 High-entropy doping of PO4 cathode materials allows six or more elements to share the same elemental sites. By adjusting the maximum configurational entropy within the crystal and forming a complex chemical bond network within the material, it greatly enhances the interaction between transition metals and O, forming a structurally stable high-entropy solid solution and improving the LiMn content. 0.85 Fe 0.15 The intrinsic conductivity of PO4 cathode material is beneficial for improving plateau voltage and rate performance. The use of spray drying assisted by high-temperature solid-state reaction to obtain spherical particles increases tap density. Secondary carbon coating and secondary sintering processes form a uniform thin carbon layer on the material surface, which is beneficial for improving electronic conductivity and capacity utilization. The nano-oxide coating further inhibits manganese dissolution, improves structural stability during cycling, and thus enhances cycle performance. The process is simple, easy to operate, has a short production cycle, and low production cost, making it suitable for large-scale production. Samples prepared according to this invention were assembled into batteries and subjected to charge-discharge tests. The results show that the high-entropy doping strategy significantly improves the cycle performance and rate performance of the material. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The high-entropy doped LiMn in Example 1 of this invention 0.85 Fe 0.15 SEM image of PO4; Figure 2 The high-entropy doped LiMn in Example 1 of this invention 0.85 Fe 0.15 Particle size distribution diagram of PO4; Figure 3 The high-entropy doped LiMn in Example 1 of this invention 0.85 Fe 0.15 Charge-discharge curves of PO4; Figure 4 LiMn in Comparative Example 1 of this invention 0.85 Fe 0.15 Charge-discharge curve of PO4 at 0.1C; Figure 5 This is a comparison chart of the cycle performance of Example 1 and Comparative Example 1 in this invention. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0028] Embodiments of the present invention provide a high-entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material and its preparation method, including highly entropy-doped LiMn 0.85 Fe 0.15 The chemical formula of PO4 cathode material is Li x Mn 0.85 Fe 0.15- y M1 a M2 b M3 c M4 d M5 e M6 f P zO4, where M1 is a metal element with a +1 valence, M2 is a metal element with a +2 valence, M3 is a metal element with a +3 valence, M4 is a metal element with a +4 valence, M5 is a metal element with a +5 valence, M6 is a metal element with a +6 valence, 0.90≤x<1.10, 0.01≤y<0.06, 0.90≤z<1.10, a+b+c+d+e+f=y; The +1 valence metal element includes one or more of Na and K; the +2 valence metal element includes one or more of Mg, Ca, Ba, Co, Ni, Cu, and Zn; the +3 valence metal element includes one or more of V, Al, Cr, Y, La, and Ce; the +4 valence metal element includes one or more of Ti and Zr; the +5 valence metal element includes one or more of Nb and Ta; and the +6 valence metal element includes one or more of Mo and W.

[0029] A high-entropy doped LiMn 0.85 Fe 0.15 The preparation method of PO4 cathode material includes the following steps: a) Add the carbon source and surfactant to deionized water, stir to dissolve, and then proceed according to LiMn 0.85 Fe 0.15 PO4 was added sequentially in stoichiometric proportions to manganese source, iron source, and compounds M1, M2, M3, M4, M5, and M6. After thorough mixing, phosphorus source and lithium source were added, and the mixture was ball-milled to obtain a final product. The surfactant improved the dispersibility of the material, ensuring that the carbon source was uniformly coated onto the particles. b) The mixture obtained in step a) is further milled and spray-dried for the first time to obtain spherical precursors; c) Add the precursor from step b) to an atmosphere furnace for the first high-temperature sintering, cool to room temperature, grind and sieve to obtain the intermediate; d) Add the carbon source and nano-sized oxide to deionized water, mix thoroughly, then add the intermediate obtained in step c), and perform a second spray drying to obtain the spray-dried material. Secondary carbon coating and nano-sized oxide coating can effectively improve the carrier activity in LiMn. 0.85 Fe 0.15 Dynamic transport processes in PO4; e) The spray-dried material from step d) is added to an atmosphere furnace for a second high-temperature sintering. After cooling to room temperature, it is ground and sieved to obtain highly entropy-doped LiMn. 0.85 Fe 0.15 PO4 cathode material. Secondary sintering can better coat the carbon source and nano-sized oxides from step d) onto the material surface, and the resulting material structure and properties are more stable.

[0030] In steps a) and d), the carbon source is one or more selected from sucrose, glucose, citric acid, polyvinyl alcohol, soluble starch, ascorbic acid, carbon black, acetylene black, carbon nanotubes, polyethylene glycol, and graphene. Preferably, the carbon source is at least two selected from sucrose, glucose, citric acid, polyvinyl alcohol, polyethylene glycol, carbon nanotubes, and graphene, and each substance has the same mass ratio, and at least two carbon sources can form a stable carbon network; LiMn with high entropy carbon coating 0.85 Fe 0.15 The carbon coating is 0.5 wt% to 10 wt% of the PO4 cathode material. Preferably, the carbon coating is high-entropy doped LiMn. 0.85 Fe 0.15 The PO4 cathode material accounts for 0.5 wt% to 6 wt% of its weight.

[0031] In step a), the surfactant is one or more of the following: polyvinylpyrrolidone (PVP), dodecyltrimethylammonium bromide (DTAB), hexadecyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfonate (SDS), cyclohexane, fluoroalkyl quaternary ammonium salts, oleic acid, sodium 4-styrene sulfonate, and silane coupling agents (such as KH550). Preferably, the surfactant in step a) is PVP, DTAB, CTAB, SDBS, SDS, oleic acid, or a silane coupling agent; the amount of surfactant added is 0.1 wt% to 8 wt% of the intermediate. Preferably, the amount of surfactant added is 1 wt% to 5 wt% of the intermediate.

[0032] The manganese source mentioned in step a) is one or more of manganese powder, manganese dioxide, manganese trioxide, manganese tetroxide, manganese carbonate, manganese oxalate, manganese acetate, and manganese nitrate; preferably, the manganese source is manganese dioxide, manganese tetroxide, manganese carbonate, or manganese acetate.

[0033] The iron source mentioned in step a) is one or more of iron powder, ferric oxide, ferric oxide, ferric tetroxide, ferrous oxalate, ferric sulfate, ferric chloride, ferric phosphate, ferric nitrate, and ferric hydroxide; preferably, the iron source is ferric oxide, ferric tetroxide, ferrous oxalate, or ferric phosphate.

[0034] The compounds M1, M2, M3, M4, M5 and M6 mentioned in step a) are one or more of the corresponding carbonates, oxalates, acetates, sulfates, nitrates, halides, oxides and hydroxides; Preferably, the compound M1 is sodium hydroxide, sodium carbonate, sodium chloride, potassium hydroxide, or potassium chloride; The compounds of M2 are magnesium oxide, magnesium chloride, magnesium hydroxide, calcium carbonate, barium carbonate, cobalt sulfate, cobalt oxide, nickel sulfate, nickel oxide, copper oxide, copper sulfate, zinc oxide, or zinc chloride. The compounds of M3 are ammonium metavanadate, vanadium pentoxide, aluminum oxide, aluminum hydroxide, chromium oxide, yttrium oxide, lanthanum oxide, lanthanum nitrate, cerium oxide, or cerium nitrate; The compound of M4 is titanium dioxide, titanium tetrachloride, or zirconium oxide; The compound of M5 is niobium pentoxide, niobium oxalate, or tantalum pentoxide; The compounds of M6 are molybdenum oxide, ammonium molybdate, or tungsten oxide.

[0035] The phosphorus source mentioned in step a) is one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, lithium phosphate, and lithium dihydrogen phosphate; preferably, the phosphorus source is phosphoric acid, ammonium dihydrogen phosphate, or lithium dihydrogen phosphate.

[0036] The lithium source mentioned in step a) is one or more of lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate and lithium dihydrogen phosphate; preferably, the lithium source is lithium hydroxide, lithium carbonate or lithium dihydrogen phosphate.

[0037] In step a), the ball milling speed is 200~1200 rpm and the ball milling time is 1~12 h; preferably, the ball milling speed is 300~1000 rpm and the ball milling time is 4~8 h.

[0038] In step b), the grinding speed is 500~3000 rpm and the grinding time is 1~6h; preferably, the grinding speed is 800~2600 rpm and the grinding time is 3~5h.

[0039] The temperature of the first spray drying treatment in step b) and the second spray drying treatment in step d) is 150~350℃, and the feed rate is 10~80mL / min; preferably, the temperature of the first spray drying treatment in step b) and the second spray drying treatment in step d) is 200~320℃, and the feed rate is 30~60mL / min.

[0040] In step c), the first high-temperature sintering temperature is 500~800℃, the sintering time is 4~20h, and the heating rate is 1-10℃ / min; preferably, the first high-temperature sintering temperature is 550~750℃, the sintering time is 6~12h, and the heating rate is 2~6℃ / min.

[0041] The nanoscale oxide mentioned in step d) is one or more of Al2O3, MgO, TiO2, ZnO, ZrO2 and SiO2; preferably, the nanoscale oxide is Al2O3, MgO, TiO2 or ZrO2.

[0042] In step e), the second high-temperature sintering temperature is 300~600 ℃, the sintering time is 10~120 min, and the heating rate is 1-10 ℃ / min. Preferably, the second high-temperature sintering temperature is 350~550 ℃, the sintering time is 20~120 min, and the heating rate is 2~6 ℃ / min.

[0043] Example 1 1) Citric acid, polyethylene glycol, and SDBS were added to deionized water and stirred until dissolved. Then, manganese carbonate, ferrous oxalate, sodium hydroxide, magnesium hydroxide, ammonium metavanadate, zirconium dioxide, niobium pentoxide, and molybdenum trioxide were added sequentially and mixed evenly. Ammonium dihydrogen phosphate and lithium hydroxide were then added, and the mixture was ground thoroughly at 800 rpm for 6 hours in a ball mill to obtain a mixture. Citric acid and polyethylene glycol served as carbon sources, with a carbon content of 3 wt%. SDBS served as a surfactant with a content of 1 wt%. The stoichiometric ratio of Li:Mn:Fe:Na:Mg:V:Zr:Nb:Mo:P = 1.02:0.85:0.12:0.005:0.005:0.005:0.005:0.005:1.01. 2) After ball milling, the mixture was transferred to a sand mill and milled at 2000 rpm for 2 hours. Then, it was spray dried at a temperature of 250℃ and a feed rate of 50 mL / min to obtain spherical precursors. 3) The precursor was sintered at 650°C for 8 hours in a nitrogen or argon atmosphere furnace at a heating rate of 2°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add glucose and nano-SiO2 to deionized water and mix evenly. The concentration of glucose is 0.5wt% and the concentration of nano-SiO2 is 2wt%. Add intermediate, continue stirring and carry out a second spray drying. The spray drying temperature is 200℃ and the feed rate is 50mL / min. 5) The material obtained from the second spraying is sintered at 400℃ for 60 min in a nitrogen or argon atmosphere furnace at a heating rate of 2℃ / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material Li. 1.02 Mn 0.85 Fe 0.12 Na 0.005 Mg 0.005 V 0.005 Zr 0.005 Nb 0.005 Mo 0.005 P 1.01 O4.

[0044] See Figure 1 As can be seen, the cathode materials obtained in Example 1 are all secondary spherical particles, and the primary particles are of uniform size.

[0045] See Figure 2 As can be seen, the average particle size of the cathode material obtained in Example 1 is 2.38 μm, and the largest spherical particle has a particle size of no more than 10 μm.

[0046] See Figure 3 As can be seen, the cathode material obtained in Example 1 exhibits excellent capacity and rate performance when assembled into a battery. The capacities of the material at rates of 0.1C, 0.2C, 1C, 2C, 3C, 5C, 8C, 10C, 20C, 30C, and 50C are 153.2, 152.8, 143.9, 140.6, 135.1, 132.9, 126.5, 118.3, 114.6, 102.3, and 89.2 mAh g, respectively. -1 .

[0047] Example 2 1) Add sucrose, polyvinyl alcohol, carbon nanotubes, and PVP to deionized water and stir until dissolved. Then, add manganese tetroxide, ferric oxide, potassium hydroxide, calcium carbonate, aluminum oxide, titanium dioxide, niobium pentoxide, and molybdenum trioxide in sequence. After mixing evenly, add phosphoric acid and lithium carbonate, and grind thoroughly in a ball mill at 600 rpm for 8 hours to obtain a mixture. Sucrose, polyvinyl alcohol, and carbon nanotubes are the carbon sources, with a carbon content of 2 wt%. PVP is used as a surfactant with a content of 2 wt%. The stoichiometric ratio Li:Mn:Fe:K:Ca:Al:Ti:Nb:Mo:P = 1.03:0.85:0.10:0.005:0.005:0.01:0.01:0.01:0.01:1.0; 2) After ball milling, the mixture was transferred to a sand mill and milled at 1800 rpm for 3 hours. Then, it was spray dried at a temperature of 300℃ and a feed rate of 60 mL / min to obtain spherical precursors. 3) The precursor was sintered at 700°C for 6 hours in a nitrogen or argon atmosphere furnace at a heating rate of 5°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add glucose and nano ZrO2 to deionized water, mix well, the concentration of glucose is 1wt%, the concentration of nano ZrO2 is 1wt%, add intermediate, continue stirring and carry out a second spray drying, the spray drying temperature is 250℃, and the feed rate is 50mL / min. 5) The material obtained from the second spraying is sintered at 500℃ for 40 min in a nitrogen or argon atmosphere furnace at a heating rate of 2℃ / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material Li. 1.03 Mn 0.85 Fe 0.10 K 0.005 Ca 0.005Al 0.01 Ti 0.01 Nb 0.01 Mo 0.01 PO4.

[0048] Example 3 1) Glucose, polyethylene glycol, and silane coupling agent KH550 were added to deionized water and stirred until dissolved. Then, manganese tetroxide, ferric phosphate, sodium carbonate, barium carbonate, yttrium oxide, zirconium dioxide, tantalum pentoxide, and molybdenum trioxide were added sequentially and mixed evenly. Phosphoric acid and lithium carbonate were then added, and the mixture was ground thoroughly at 600 rpm for 8 hours in a ball mill to obtain a mixture. Sucrose, polyvinyl alcohol, and carbon nanotubes were used as carbon sources, with a carbon content of 3 wt%. KH550 was used as a surfactant with a content of 1 wt%. The stoichiometric ratio Li:Mn:Fe:Na:Ba:Y:Zr:Ta:Mo:P = 1.05:0.85:0.11:0.01:0.01:0.005:0.005:0.005:0.005:1.02; 2) After ball milling, the mixture was transferred to a sand mill and milled at 2000 rpm for 2.5 h. Then, it was spray dried at a temperature of 240 ℃ and a feed rate of 40 mL / min to obtain spherical precursors. 3) The precursor was sintered at 600°C for 12 hours in a nitrogen or argon atmosphere furnace at a heating rate of 3°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add graphene and nano MgO to deionized water and mix evenly. The concentration of graphene is 0.5wt% and the concentration of nano MgO is 3wt%. Add intermediate, continue stirring and carry out a second spray drying. The spray drying temperature is 200℃ and the feed rate is 40mL / min. 5) The material obtained from the second spraying is sintered at 400℃ for 20 min in a nitrogen or argon atmosphere furnace at a heating rate of 3℃ / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material Li. 1.05 Mn 0.85 Fe 0.11 Na 0.01 Ba 0.01 Y 0.005 Zr 0.005 Ta 0.005 Mo 0.005 P 1.02 O4.

[0049] Example 4 1) Citric acid, polyvinyl alcohol, carbon nanotubes, and oleic acid were added to deionized water and stirred until dissolved. Then, manganese acetate, ferric phosphate, sodium chloride, copper oxide, yttrium oxide, titanium tetrachloride, niobium oxalate, and tungsten trioxide were added sequentially and mixed evenly. Phosphoric acid and lithium carbonate were then added, and the mixture was ground thoroughly at 300 rpm for 8 hours in a ball mill to obtain a mixture. Citric acid, polyvinyl alcohol, and carbon nanotubes were used as carbon sources, with a carbon content of 4 wt%. Oleic acid was used as a surfactant with a content of 5 wt%. The stoichiometric ratio of Li:Mn:Fe:Na:Cu:Y:Ti:Nb:W:P = 1.05:0.85:0.03:0.02:0.02:0.02:0.02:0.02:0.02:1. 2) After ball milling, the mixture was transferred to a sand mill and milled at 800 rpm for 5 hours. Then, it was spray dried at a temperature of 320℃ and a feed rate of 60 mL / min to obtain spherical precursors. 3) The precursor was sintered at 750°C for 6 hours in a nitrogen or argon atmosphere furnace at a heating rate of 6°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add sucrose and nano ZrO2 to deionized water and mix evenly. The concentration of sucrose is 2wt% and the concentration of nano ZrO2 is 2wt%. Add the intermediate and continue stirring before carrying out a second spray drying. The spray drying temperature is 320℃ and the feed rate is 60mL / min. 5) The material obtained from the second spraying is sintered at 600℃ for 10 min in a nitrogen or argon atmosphere furnace at a heating rate of 6℃ / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material Li. 1.05 Mn 0.85 Fe 0.03 Na 0.02 Cu 0.02 Y 0.02 Ti 0.02 Nb 0.02 W 0.02 PO4.

[0050] Example 5 1) Soluble starch, carbon black, and polyvinylpyrrolidone were added to deionized water and stirred until dissolved. Then, manganese carbonate, ferrous oxalate, sodium hydroxide, magnesium hydroxide, ammonium metavanadate, zirconium dioxide, niobium pentoxide, and molybdenum trioxide were added sequentially and mixed evenly. Ammonium dihydrogen phosphate and lithium hydroxide were then added, and the mixture was ground thoroughly at 800 rpm for 6 hours in a ball mill to obtain a mixture. Soluble starch and carbon black were used as carbon sources, with a carbon content of 3 wt%. Polyvinylpyrrolidone was used as a surfactant, with a content of 1 wt%. The stoichiometric ratio of Li:Mn:Fe:Na:Mg:V:Zr:Nb:Mo:P = 1.02:0.85:0.12:0.005:0.005:0.005:0.005:0.005:1.01. 2) After ball milling, the mixture was transferred to a sand mill and milled at 2000 rpm for 2 hours. Then, it was spray dried at a temperature of 250℃ and a feed rate of 50 mL / min to obtain spherical precursors. 3) The precursor was sintered at 650°C for 8 hours in a nitrogen or argon atmosphere furnace at a heating rate of 2°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add glucose and nano-Al2O3 to deionized water and mix well. The concentration of glucose is 0.5wt% and the concentration of nano-Al2O3 is 5wt%. Add intermediate and continue stirring before a second spray drying. The spray drying temperature is 200℃ and the feed rate is 50mL / min. 5) The material obtained from the second spraying is sintered at 400℃ for 60 min in a nitrogen or argon atmosphere furnace at a heating rate of 2℃ / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material Li. 1.02 Mn 0.85 Fe 0.12 Na 0.005 Mg 0.005 V 0.005 Zr 0.005 Nb 0.005 Mo 0.005 P 1.01 O4.

[0051] Example 6 1) Citric acid, polyethylene glycol, and SDBS were added to deionized water and stirred until dissolved. Then, manganese carbonate, ferrous oxalate, potassium chloride, cobalt oxide, lanthanum oxide, zirconium dioxide, niobium oxalate, and ammonium molybdate were added sequentially and mixed thoroughly. Lithium dihydrogen phosphate was then added, and the mixture was ground thoroughly at 1000 rpm for 4 hours in a ball mill to obtain a mixture. Citric acid and polyethylene glycol served as carbon sources, with a carbon content of 3 wt%. SDBS served as a surfactant, with a content of 1 wt%. The stoichiometric ratio of Li:Mn:Fe:K:Co:La:Zr:Nb:Mo:P = 1:0.85:0.12:0.005:0.005:0.005:0.005:0.005:0.005:1. 2) After ball milling, the mixture was transferred to a sand mill and milled at 3000 rpm for 1 hour. Then, it was spray dried at a temperature of 200℃ and a feed rate of 30 mL / min to obtain spherical precursors. 3) The precursor was sintered at 550°C for 12 hours in a nitrogen or argon atmosphere furnace at a heating rate of 2°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add polyethylene glycol and nano-SiO2 to deionized water and mix evenly. The concentration of polyethylene glycol is 10wt% and the concentration of nano-SiO2 is 1wt%. Add intermediate, continue stirring and carry out a second spray drying. The spray drying temperature is 300℃ and the feed rate is 30mL / min. 5) The material obtained from the second spraying is sintered at 350℃ for 120 min in a nitrogen or argon atmosphere furnace at a heating rate of 2℃ / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material LiMn. 0.85 Fe 0.12 K 0.005 Co 0.00 5La 0.005 Zr 0.005 Nb 0.005 Mo 0.005 PO4.

[0052] The cathode materials prepared in Examples 2 to 6 have similar morphologies to the cathode material prepared in Example 1.

[0053] Example 7 1) Ascorbic acid, acetylene black, and DTAB were added to deionized water and stirred until dissolved. Then, manganese carbonate, ferrous oxalate, sodium hydroxide, magnesium hydroxide, ammonium metavanadate, zirconium dioxide, niobium pentoxide, and molybdenum trioxide were added sequentially and mixed evenly. Ammonium dihydrogen phosphate and lithium hydroxide were then added and milled thoroughly at 1200 rpm for 1 hour to obtain a mixture. Citric acid and polyethylene glycol were used as carbon sources, with a carbon content of 3 wt%. SDBS was used as a surfactant with a content of 1 wt%. The stoichiometric ratio of Li:Mn:Fe:Na:Mg:V:Zr:Nb:Mo:P = 1.02:0.85:0.12:0.005:0.005:0.005:0.005:0.005:1.01; 2) After ball milling, the mixture was transferred to a sand mill and milled at 500 rpm for 6 hours. Then, it was spray dried at a temperature of 320℃ and a feed rate of 60 mL / min to obtain spherical precursors. 3) The precursor was sintered at 550°C for 12 hours in a nitrogen or argon atmosphere furnace at a heating rate of 10°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add glucose and nano ZrO2 to deionized water and mix well. The concentration of glucose is 0.5 wt% and the concentration of nano ZrO2 is 2 wt%. Add intermediate, continue stirring and carry out a second spray drying. The spray drying temperature is 150℃ and the feed rate is 80 mL / min. 5) The material obtained from the second spray is sintered at 550°C for 20 min in a nitrogen or argon atmosphere furnace at a heating rate of 5°C / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material.

[0054] Example 8 1) Citric acid, graphene, and CTAB were added to deionized water and stirred until dissolved. Then, manganese carbonate, ferrous oxalate, sodium hydroxide, magnesium hydroxide, ammonium metavanadate, zirconium dioxide, niobium pentoxide, and molybdenum trioxide were added sequentially and mixed evenly. Ammonium dihydrogen phosphate and lithium hydroxide were then added, and the mixture was ground thoroughly at 200 rpm for 12 hours to obtain a mixture. Citric acid and polyethylene glycol were used as carbon sources, with a carbon content of 3 wt%. SDBS was used as a surfactant with a content of 1 wt%. The stoichiometric ratio of Li:Mn:Fe:Na:Mg:V:Zr:Nb:Mo:P = 1.02:0.85:0.12:0.005:0.005:0.005:0.005:0.005:1.01; 2) After ball milling, the mixture was transferred to a sand mill and milled at 3000 rpm for 1 hour. Then, it was spray dried at a temperature of 200℃ and a feed rate of 80 mL / min to obtain spherical precursors. 3) The precursor was sintered at 750°C for 6 hours in a nitrogen or argon atmosphere furnace at a heating rate of 1°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add glucose and nano-Al2O3 to deionized water and mix well. The concentration of glucose is 0.5wt% and the concentration of nano-Al2O3 is 2wt%. Add intermediate and continue stirring before a second spray drying. The spray drying temperature is 320℃ and the feed rate is 30mL / min. 5) The material obtained from the second spray is sintered at 350°C for 100 min in a nitrogen or argon atmosphere furnace at a heating rate of 2°C / min. After cooling to room temperature, it is ground and sieved to obtain a high-entropy doped cathode material.

[0055] Example 9 1) Citric acid, polyvinyl alcohol, and SDBS were added to deionized water and stirred until dissolved. Then, manganese carbonate, ferrous oxalate, sodium hydroxide, magnesium hydroxide, ammonium metavanadate, zirconium dioxide, niobium pentoxide, and molybdenum trioxide were added sequentially and mixed evenly. Ammonium dihydrogen phosphate and lithium hydroxide were then added, and the mixture was ground thoroughly at 1000 rpm for 4 hours to obtain a mixture. Citric acid and polyethylene glycol were used as carbon sources, with a carbon content of 3 wt%. SDBS was used as a surfactant with a content of 1 wt%. The stoichiometric ratio of Li:Mn:Fe:Na:Mg:V:Zr:Nb:Mo:P = 1.02:0.85:0.12:0.005:0.005:0.005:0.005:0.005:1.01; 2) After ball milling, the mixture was transferred to a sand mill and milled at 800 rpm for 5 hours. Then, it was spray dried at a temperature of 350℃ and a feed rate of 30 mL / min to obtain spherical precursors. 3) The precursor was sintered at 800°C for 4 hours in a nitrogen or argon atmosphere furnace at a heating rate of 6°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add glucose and nano TiO2 to deionized water and mix well. The concentration of glucose is 0.5 wt% and the concentration of nano TiO2 is 2 wt%. Add intermediate and continue stirring before a second spray drying. The spray drying temperature is 350℃ and the feed rate is 60 mL / min. 5) The material obtained from the second spray is sintered at 600°C for 10 min in a nitrogen or argon atmosphere furnace at a heating rate of 6°C / min, cooled to room temperature, ground and sieved to obtain high-entropy doped cathode material.

[0056] Example 10 1) Citric acid, ascorbic acid, and SDS were added to deionized water and stirred until dissolved. Then, manganese carbonate, ferrous oxalate, sodium hydroxide, magnesium hydroxide, ammonium metavanadate, zirconium dioxide, niobium pentoxide, and molybdenum trioxide were added sequentially and mixed evenly. Ammonium dihydrogen phosphate and lithium hydroxide were then added, and the mixture was ground thoroughly at 300 rpm for 8 hours to obtain a mixture. Citric acid and polyethylene glycol were used as carbon sources, with a carbon content of 3 wt%. SDBS was used as a surfactant with a content of 1 wt%. The stoichiometric ratio of Li:Mn:Fe:Na:Mg:V:Zr:Nb:Mo:P = 1.02:0.85:0.12:0.005:0.005:0.005:0.005:0.005:1.01; 2) After ball milling, the mixture was transferred to a sand mill and milled at 2600 rpm for 3 hours. Then, it was spray dried at a temperature of 150℃ and a feed rate of 10 mL / min to obtain spherical precursors. 3) The precursor was sintered at 500°C for 20 hours in a nitrogen or argon atmosphere furnace at a heating rate of 2°C / min, cooled to room temperature, and then ground and sieved to obtain the intermediate. 4) Add glucose and nano ZnO to deionized water and mix well. The concentration of glucose is 0.5 wt% and the concentration of nano ZnO is 2 wt%. Add intermediate and continue stirring before a second spray drying. The spray drying temperature is 320℃ and the feed rate is 80 mL / min. 5) The material obtained from the second spray is sintered at 300°C for 120 min in a nitrogen or argon atmosphere furnace at a heating rate of 2°C / min. After cooling to room temperature, it is ground and sieved to obtain the high-entropy doped cathode material.

[0057] Comparative Example 1 Comparative Example 1: LiMn was prepared using a conventional solid-state method. 0.85 Fe 0.15 Lithium hydroxide, manganese carbonate, ferrous oxalate, and ammonium dihydrogen phosphate were weighed according to the molar ratio of Li:Mn:Fe:P = 1:0.85:0.15:1. Citric acid and polyethylene glycol were used as carbon sources, and the carbon content was 3 wt%. The mixture was ball-milled at 800 rpm for 6 hours, then dried in an oven. After grinding and sieving, it was sintered at 650℃ for 8 hours under a nitrogen or argon atmosphere at a heating rate of 2℃ / min. After cooling to room temperature, it was ground and sieved again to obtain LiMn. 0.85 Fe 0.15 PO4 cathode material.

[0058] See Figure 4 As can be seen, the discharge specific capacity of the cathode material obtained in Comparative Example 1 at a 0.1C rate is only 128.5 mAh g. -1The capacity differs by 20 mAh g from that of other embodiments at 0.1C. -1 above.

[0059] The positive electrode material powder obtained by this invention is assembled into a battery. The positive electrode is made by mixing positive electrode material, conductive agent and binder in a certain proportion, coating, rolling, cutting and pressing. The negative electrode is a lithium metal sheet. The electrolyte is 1mol / L LiPF6, EC / EMC / DMC (1:1:1, v / v / v). The separator is a polypropylene microporous membrane. The battery performance is tested on a charge and discharge test platform.

[0060] See Figure 5 As can be seen, the cycling performance of Example 1 and Comparative Example 1 is significantly different. At 3C rate, after 100 cycles, the capacity retention rate of the battery in Example 1 is 100.2%, while that of the battery in Comparative Example 1 is only 61.3%. In addition, the coulombic efficiency of the battery in Example 1 is also higher than that of Comparative Example 1.

[0061] Table 1. Comparison of electrochemical performance between Examples 1-3 and Comparative Example 1

[0062] Table 1 shows a comparison of the electrochemical performance of the cathode materials obtained in different embodiments and Comparative Example 1. The results indicate that the embodiments show significant improvements in capacity, rate capability, and cycle stability compared to Comparative Example 1.

[0063] This invention employs spray drying-assisted high-temperature solid-state reaction for high-entropy doping. By combining multiple main elements, the configuration entropy can be maximized, thereby improving performance. This battery material effectively solves the problem of LiMn using a high-entropy doping strategy. 0.85 Fe 0.15 The low electronic and ionic conductivity of PO4 cathode material improves its stability and rate performance, while also exhibiting high charge-discharge specific capacity, reaching an above-average level in the industry. The preparation process of this invention is simple, with low production costs, making it suitable for large-scale production.

[0064] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A high-entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material characterized by, The positive electrode material has a general formula of Li x Mn 0.85 Fe 0.15-y M1 a M2 b M3 c M4 d M5 e M6 f P z O4, wherein M1 is a +1 valence metal element, M2 is a +2 valence metal element, M3 is a +3 valence metal element, M4 is a +4 valence metal element, M5 is a +5 valence metal element, M6 is a +6 valence metal element, 0.90≤x<1.10, 0.01≤y<0.06, 0.90≤z<1.10, and a+b+c+d+e+f=y.

2. The high-entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material according to claim 1, characterized in that, The +1 valence metal element is one or more of Na and K, the +2 valence metal element is one or more of Mg, Ca, Ba, Co, Ni, Cu and Zn, the +3 valence metal element is one or more of V, Al, Cr, Y, La and Ce, the +4 valence metal element is one or more of Ti and Zr, the +5 valence metal element is one or more of Nb and Ta, and the +6 valence metal element is one or more of Mo and W.

3. A high entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material according to any one of claims 1 to 2, wherein the material is prepared by a method comprising the steps of: The method comprises the following steps: a) adding manganese source, iron source, compound of M1, compound of M2, compound of M3, compound of M4, compound of M5 and compound of M6 to the aqueous solution of carbon source and surfactant in a stoichiometric ratio of Mn:Fe:M1:M2:M3:M4:M5:M6, mixing uniformly, then adding phosphorus source and lithium source, grinding to obtain a mixture; x Mn 0.85 Fe 0.15-y M1 a M2 b M3 c M4 d M5 e M6 f P z O4 ; b) sand milling and first spray drying of the mixture to obtain spherical precursors; c) first high-temperature sintering of the spherical precursors to obtain intermediates; d) adding the intermediates to an aqueous solution containing nanoscale oxides and a carbon source different from that in step a) to perform second spray drying. e) high temperature sintering of the second spray dried material to obtain high entropy doped LiMn 0.85 Fe 0.15 PO4 cathode material.

4. The production method according to claim 3, characterized by, The carbon source is one or more of sucrose, glucose, citric acid, polyvinyl alcohol, soluble starch, ascorbic acid, carbon black, acetylene black, carbon nanotubes, polyethylene glycol and graphene.

5. The preparation method according to claim 3, characterized in that, The mixture in step a) has a carbon-coated content of 0.5wt%-10wt% of the high-entropy-doped LiMn 0.85 Fe 0.15 PO4 cathode material, and the carbon-coated content in the material after the second spray drying in step d) is 0.5wt%-10wt% of the high-entropy-doped LiMn 0.85 Fe 0.15 PO4 cathode material.

6. The preparation method according to claim 3, characterized in that, The surfactant is one or more of polyvinylpyrrolidone, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, cyclohexane, fluorinated alkyl quaternary ammonium salt, oleic acid, sodium 4-styrene sulfonate and silane coupling agent. The amount of the surfactant added is 0.1wt%-8wt% of the intermediates.

7. The preparation method according to claim 3, characterized in that, The manganese source is one or more of manganese powder, manganese dioxide, manganese sesquioxide, manganese trioxide, manganese carbonate, manganese oxalate, manganese acetate and manganese nitrate; The iron source is one or more of iron powder, iron monoxide, iron sesquioxide, iron trioxide, ferrous oxalate, iron sulfate, iron chloride, iron phosphate, iron nitrate and iron hydroxide; The compound of M1, the compound of M2, the compound of M3, the compound of M4, the compound of M5 and the compound of M6 are one or more of carbonates, oxalates, acetates, sulfates, nitrates, halides, oxides and hydroxides.

8. The preparation method according to claim 3, characterized in that, The phosphorus source is one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, lithium phosphate and lithium dihydrogen phosphate; The lithium source is one or more of lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate and lithium dihydrogen phosphate.

9. The preparation method according to claim 3, characterized in that, The temperature of the spray drying is 150-350℃, and the feeding speed is 10-80mL / min; the nanoscale oxide is one or more of Al2O3, MgO, TiO2, ZnO, ZrO2 and SiO2; and the amount of the nanoscale oxide added is 1wt%-6wt% of the intermediates.

10. The method of claim 3, wherein, The first sintering temperature is 500-800℃, the sintering time is 4-20h, and the heating rate is 1-10℃ / min; the second sintering temperature is 300-600℃, the sintering time is 10-120min, and the heating rate is 1-10℃ / min.

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