A lithium-rich lithium-iron-phosphate material, a preparation method and application thereof

Abstract

The application discloses a lithium-rich lithium-iron material and a preparation method and application thereof. The lithium-rich lithium-iron material comprises lithium-rich lithium-iron particles and rare earth metal oxide particles coated on surfaces of the lithium-rich lithium-iron particles, and a heterostructure is formed between interfaces of the lithium-rich lithium-iron and the rare earth metal oxide particles. The application adopts the rare earth metal oxide to construct a hetero-interface, reduces resistance of electron migration, and increases electron mobility; microwave sintering is adopted to reduce a temperature and time required by a reaction, and lithium-rich lithium-iron composite material particles are prepared with small defects; small particles and low defect concentration are beneficial to reduce polarization, improve capacity, and improve particle size matching degree with positive electrode material.

Description

Technical Field

[0001] This application belongs to the field of batteries and relates to a positive electrode lithium replenishment material, specifically a lithium-rich lithium iron phosphate material and its preparation method and application. Background Technology

[0002] With the rapid development of electronic technology, mobile phones, laptops, cameras, electric bicycles, and electric vehicles are becoming increasingly common and indispensable parts of daily life. As the demand for portability increases, the requirements for energy storage batteries are also rising. Therefore, developing an energy storage battery with high capacity, good safety performance, and long service life is an urgent task. Compared to lead-acid and nickel-cadmium batteries, lithium-ion batteries have been widely used due to their advantages such as high energy density, high power density, long lifespan, good safety, low self-discharge, and wide temperature adaptability.

[0003] During the first charge and discharge cycle of a lithium-ion battery, a solid electrolyte interphase (SEI) film forms on the negative electrode surface. This film converts a significant amount of active lithium into lithium carbonate, lithium fluoride, and alkyl lithium, resulting in lithium loss from the positive electrode material and reducing the battery's initial coulombic efficiency and capacity. In lithium-ion battery systems using graphite negative electrodes, approximately 10% of the lithium source is consumed during the first charge. When using high-specific-capacity negative electrode materials, such as alloys (silicon, tin, etc.), oxides (silicon oxide, tin oxide), and amorphous carbon negative electrodes, the consumption of positive electrode lithium source is further aggravated.

[0004] To further improve the energy density of lithium-ion batteries, pre-lithiation of the positive or negative electrode is an effective method. However, current negative electrode lithium replenishment materials have the following drawbacks: excessively high activity, making long-term stable storage impossible, thus increasing operational difficulty and production risks. Positive electrode lithium replenishment materials have high potential, good compatibility with existing lithium-ion battery processing technologies, and are safer and easier to handle, thus attracting increasing attention from academia and industry. However, existing positive electrode lithium replenishment materials (such as lithium L-ascorbate, lithium D-isoascorbate, lithium metabisulfite, lithium sulfite, and lithium phytate) are easily oxidized in air and are difficult to synthesize in large quantities, which is detrimental to large-scale industrial production. Summary of the Invention

[0005] One of the purposes of this application is to provide a lithium-rich lithium iron ferrite material.

[0006] The lithium iron ferrite material provided in this application comprises lithium iron ferrite particles and rare earth metal oxide particles coated on the surface of the lithium iron ferrite particles, wherein a heterogeneous structure is formed at the interface between the lithium iron ferrite and the rare earth metal oxide particles.

[0007] The rare earth metal oxide is selected from one or more of the following: Y2O3, Sc2O3, La2O3, Ce2O3, Rb2O, and Yb2O3;

[0008] The mass ratio of the rare earth metal oxide to the lithium iron ferrite particles is 1:(99.5-99.9), specifically 1:99.5, 1:99.7 or 1:99.9, and more specifically 1:99.5.

[0009] This application also provides a method for preparing the above-mentioned lithium-rich lithium iron ferrite material.

[0010] The method for preparing the lithium iron ferrite-rich material provided in this application includes the following steps:

[0011] 1) The lithium source and iron source are mixed in a high-temperature mixture and microwave sintered to obtain lithium iron ferrite rich in lithium. The obtained lithium iron ferrite rich in lithium is then pulverized to obtain lithium iron ferrite rich in lithium powder.

[0012] 2) The obtained lithium iron ferrite powder is ball-milled and mixed with rare earth metal oxides. The resulting mixture is then sieved, and the undersize material is retained.

[0013] 3) The obtained sieved material is microwave sintered under a protective atmosphere to obtain lithium iron ferrite material coated with rare earth metal oxides.

[0014] In step 1) of the above method, the lithium source includes one or more of Li2O, LiOH, Li2C2O4, and Li2CO3;

[0015] The iron source includes one or more of Fe2O3, Fe2(C2O4)3, and Fe(NO3)3;

[0016] The lithium source and iron source are added at a lithium to iron molar ratio of (5.0-5.5):1.

[0017] The high-speed mixing can be 500-800 rpm, and the high-speed mixing time can be 5-10 min;

[0018] Preferably, the lithium source and iron source have a particle size D50 of 0.5-1 μm.

[0019] The microwave sintering temperature can be 400-600℃, the time can be 5-10h, the microwave power can be 1-3kW, and the heating rate can be 5-10℃ / min;

[0020] The microwave sintering is carried out under the protection of an inert gas; the inert gas can be either nitrogen or argon.

[0021] The pulverization process can specifically be airflow pulverization.

[0022] The particle size D50 of the lithium iron ferrite powder obtained after pulverization can be 3-5μm;

[0023] In step 2) of the above method, the rare earth metal oxide is selected from one or more of the following: Y2O3, Sc2O3, La2O3, Ce2O3, Rb2O, and Yb2O3;

[0024] Preferably, the particle size D50 of the rare earth metal oxide is 0.5-3 μm;

[0025] The rare earth metal oxide is added at a mass ratio of rare earth metal oxide to lithium iron ferrite powder of 1:(99.5-99.9), specifically 1:99.5, 1:99.7 or 1:99.9, more specifically 1:99.5;

[0026] In the ball milling process, the ball-to-material ratio is 5-10:1, specifically 5:1, 7:1, or 10:1, more specifically 5:1; the rotation speed is 200-500 rpm; and the time is 2-6 hours; specifically 300 rpm for 2 hours, 400 rpm for 4 hours, or 500 rpm for 6 hours; preferably 300 rpm for 2 hours.

[0027] The sieve used for sieving has a mesh size of 300-500.

[0028] In step 3) of the above method, the microwave sintering temperature can be 400-600℃, and the time can be 5-10h, such as 400℃ for 5h, 500℃ for 7h, or 600℃ for 10h; the microwave power can be 1-3kW, and the heating rate can be 5-10℃ / min.

[0029] The microwave sintering is carried out under the protection of an inert gas; the inert gas can be either nitrogen or argon.

[0030] The application of the above-mentioned lithium-rich lithium iron ferrite material or the lithium-rich lithium iron ferrite material prepared by the above method in the preparation of lithium-ion batteries is also within the scope of protection of this invention.

[0031] In the aforementioned application, the lithium-rich lithium iron phosphate material is used as a positive electrode lithium replenisher in lithium-ion batteries.

[0032] The present invention also provides a lithium-ion battery containing the above-mentioned lithium iron phosphate material.

[0033] The present invention has the following beneficial effects: The present invention designs a method of coating the surface of lithium-rich lithium ferrite with rare earth metal oxides to form a heterostructure between the lithium-rich lithium ferrite material and the rare earth metal element interface, that is, an interface region formed between two materials with different conductivity. Its advantages are:

[0034] (1) Using rare earth metal oxides to construct heterogeneous interfaces reduces the resistance to electron migration and increases electron mobility.

[0035] (2) Microwave sintering is used to reduce the temperature and time required for the reaction, resulting in the preparation of lithium-rich lithium iron ferrite composite materials with small particles and few defects.

[0036] (3) Small particles and low defect concentration are beneficial to reduce polarization, increase capacity, and improve the compatibility with the particle size of the cathode material. Attached Figure Description

[0037] Figure 1 AE shows a comparison of the charging curves between different embodiments and comparative examples.

[0038] Figure 2 Figures A and B show a comparison of SEM images of the materials prepared in Example 1 and Comparative Example 1, where A is the material prepared in Example 1 and B is the material prepared in Comparative Example 1. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0040] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0041] Typically, lithium-rich additives have poor conductivity, and their high polarity affects the electrochemical performance of battery materials, including voltage plateau increase and capacity decrease. However, by uniformly distributing rare earth metal oxides on the surface of lithium iron ferrite materials, a heterostructure is formed between the lithium iron ferrite material and the rare earth metal oxide interface. The advantages are: (1) Using rare earth oxides to construct the heterostructure interface reduces the resistance to electron migration and increases electron mobility; (2) Using microwave sintering reduces the temperature and time required for the reaction, and the LFO composite material has small particles and fewer defects; (3) Small particles and low defect concentration are conducive to reducing polarization, increasing capacity, and improving the compatibility with the particle size of the cathode material.

[0042] Example 1

[0043] Step 1: Lithium hydroxide (D50 0.5-1μm) and iron oxide (D50 0.5-1μm) were mixed in a high-speed mixer at an elemental molar ratio of 5.2:1 (800 rpm, 10 min). After mixing, microwave sintering was performed in a nitrogen atmosphere at a power of 1 kW, a temperature of 400℃, a sintering time of 5 h, a heating rate of 5℃ / min, and a ventilation rate of 10 m³ / min. 3 / h; After sintering, lithium iron ferrite solid is obtained. The solid is coarsely crushed and then subjected to air jet milling to obtain lithium iron ferrite powder (D50 is 3-5μm).

[0044] Step 2: Take Y2O3 (D50 is 0.5-1μm) and lithium iron ferrite powder in a ball mill jar with a mass ratio of Y2O3 to lithium iron ferrite of 1:99.5, the ball-to-material ratio is 5:1, the speed is set to 300rpm, and the mixture is ball-milled for 2 hours. Pass the mixture through a 400-mesh sieve and keep the undersize material.

[0045] Step 3: The sieved material is microwave sintered in a nitrogen atmosphere. The microwave sintering power is 1kW, the sintering temperature is 400℃, the sintering time is 5h, and the heating rate is 5℃ / min. After sintering, lithium iron ferrite material coated with Y2O3 is obtained.

[0046] Step 4: Mix and grind 1.6g of the prepared lithium iron phosphate material, 0.2g of PVDF, and 0.2g of SP in a mass ratio of 8:1:1. Then, coat the mixture to a thickness of 300μm onto a 250mm×100mm aluminum foil as the positive electrode of the lithium-ion battery. Assemble CR2032 coin cells in an argon-filled glove box. The negative electrode is a lithium metal sheet, the separator is a polypropylene microporous membrane, and the electrolyte is a 1mol / L LiPF6 solution with an electrolyte solvent ratio of EC:DMC:EMC = 1:1:1 (v / v / v). The measured voltage range of the coin cell is 2V-4.5V, and the charge / discharge current is 0.05C.

[0047] Example 2

[0048] Step 1: Lithium hydroxide (D50 0.5-1μm) and iron oxide (D50 0.5-1μm) were mixed in a high-speed mixer at an elemental molar ratio of 5.2:1 (800 rpm, 10 min). After mixing, microwave sintering was performed in a nitrogen atmosphere at a power of 1 kW, a temperature of 400℃, a sintering time of 5 h, a heating rate of 5℃ / min, and a ventilation rate of 10 m³ / min. 3 / h; After sintering, lithium iron ferrite solid is obtained. The solid is coarsely crushed and then subjected to air jet milling to obtain lithium iron ferrite powder (D50 is 3-5μm).

[0049] Step 2: Take Sc2O3 (D50 is 0.5-1μm) and lithium iron ferrite powder in a ball mill jar with a mass ratio of Sc2O3 to lithium iron ferrite of 1:99.5, the ball-to-material ratio is 5:1, the speed is set to 300rpm, and the mixture is ball-milled for 2 hours. Pass the mixture through a 400-mesh sieve and keep the undersize material.

[0050] Step 3: The sieved material is microwave sintered in a nitrogen atmosphere. The microwave sintering power is 1kW, the sintering temperature is 400℃, the sintering time is 5h, and the heating rate is 5℃ / min. After sintering, lithium iron ferrite material coated with Y2O3 is obtained.

[0051] Step 4: Mix and grind 1.6g of the prepared lithium iron phosphate material, 0.2g of PVDF, and 0.2g of SP in a mass ratio of 8:1:1. Then, coat the mixture to a thickness of 300μm onto a 250mm×100mm aluminum foil as the positive electrode of the lithium-ion battery. Assemble CR2032 coin cells in an argon-filled glove box. The negative electrode is a lithium metal sheet, the separator is a polypropylene microporous membrane, and the electrolyte is a 1mol / L LiPF6 solution with an electrolyte solvent ratio of EC:DMC:EMC = 1:1:1 (v / v / v). The measured voltage range of the coin cell is 2V-4.5V, and the charge / discharge current is 0.05C.

[0052] Example 3

[0053] Step 1: Lithium hydroxide (D50 0.5-1μm) and iron oxide (D50 0.5-1μm) were mixed in a high-speed mixer at an elemental molar ratio of 5.2:1 (800 rpm, 10 min). After mixing, microwave sintering was performed in a nitrogen atmosphere at a power of 1 kW, a temperature of 400℃, a sintering time of 5 h, a heating rate of 5℃ / min, and a ventilation rate of 10 m³ / min. 3 / h; After sintering, lithium iron ferrite solid is obtained. The solid is coarsely crushed and then subjected to air jet milling to obtain lithium iron ferrite powder (D50 is 3-5μm).

[0054] Step 2: Take La2O3 (D50 is 0.5-1μm) and lithium iron ferrite powder in a ball mill jar with a mass ratio of 1:99.5 and a ball-to-material ratio of 5:1. Set the speed to 300 rpm and ball mill for 2 hours. Pass the mixture through a 400-mesh sieve and keep the undersize material.

[0055] Step 3: The sieved material is microwave sintered in a nitrogen atmosphere. The microwave sintering power is 1kW, the sintering temperature is 400℃, the sintering time is 5h, and the heating rate is 5℃ / min. After sintering, lithium iron ferrite material coated with Y2O3 is obtained.

[0056] Step 4: Mix and grind 1.6g of the prepared lithium iron phosphate material, 0.2g of PVDF, and 0.2g of SP in a mass ratio of 8:1:1. Then, coat the mixture to a thickness of 300μm onto a 250mm×100mm aluminum foil as the positive electrode of the lithium-ion battery. Assemble CR2032 coin cells in an argon-filled glove box. The negative electrode is a lithium metal sheet, the separator is a polypropylene microporous membrane, and the electrolyte is a 1mol / L LiPF6 solution with an electrolyte solvent ratio of EC:DMC:EMC = 1:1:1 (v / v / v). The measured voltage range of the coin cell is 2V-4.5V, and the charge / discharge current is 0.05C.

[0057] Example 4

[0058] Step 1: Lithium hydroxide (D50 0.5-1μm) and iron oxide (D50 0.5-1μm) were mixed in a high-speed mixer at an elemental molar ratio of 5.2:1 (800 rpm, 10 min). After mixing, microwave sintering was performed in a nitrogen atmosphere at a power of 1 kW, a temperature of 400℃, a sintering time of 5 h, a heating rate of 5℃ / min, and a ventilation rate of 10 m³ / min. 3 / h; After sintering, lithium iron ferrite solid is obtained. The solid is coarsely crushed and then subjected to air jet milling to obtain lithium iron ferrite powder (D50 is 3-5μm).

[0059] Step 2: Take Ce2O3 (D50 is 0.5-1μm) and lithium iron ferrite powder in a ball mill jar with a mass ratio of Ce2O3 to lithium iron ferrite of 1:99.5 and a ball-to-material ratio of 5:1. Set the speed to 300 rpm and ball mill for 2 hours. Pass the mixture through a 400-mesh sieve and keep the material passing through the sieve.

[0060] Step 3: The sieved material is microwave sintered in a nitrogen atmosphere. The microwave sintering power is 1kW, the sintering temperature is 400℃, the sintering time is 5h, and the heating rate is 5℃ / min. After sintering, lithium iron ferrite material coated with Y2O3 is obtained.

[0061] Step 4: Mix and grind 1.6g of the prepared lithium iron phosphate material, 0.2g of PVDF, and 0.2g of SP in a mass ratio of 8:1:1. Then, coat the mixture to a thickness of 300μm onto a 250mm×100mm aluminum foil as the positive electrode of the lithium-ion battery. Assemble CR2032 coin cells in an argon-filled glove box. The negative electrode is a lithium metal sheet, the separator is a polypropylene microporous membrane, and the electrolyte is a 1mol / L LiPF6 solution with an electrolyte solvent ratio of EC:DMC:EMC = 1:1:1 (v / v / v). The measured voltage range of the coin cell is 2V-4.5V, and the charge / discharge current is 0.05C.

[0062] Example 5

[0063] Step 1: Lithium hydroxide (D50 0.5-1μm) and iron oxide (D50 0.5-1μm) were mixed in a high-speed mixer at an elemental molar ratio of 5.2:1 (800 rpm, 10 min). After mixing, microwave sintering was performed in a nitrogen atmosphere at a power of 1 kW, a temperature of 400℃, a sintering time of 5 h, a heating rate of 5℃ / min, and a ventilation rate of 10 m³ / min. 3 / h; After sintering, lithium iron ferrite solid is obtained. The solid is coarsely crushed and then subjected to air jet milling to obtain lithium iron ferrite powder (D50 is 3-5μm).

[0064] Step 2: Take Rb2O (D50 is 0.5-1μm) and lithium iron ferrite powder in a ball mill jar with a mass ratio of Rb2O to lithium iron ferrite of 1:99.5, the ball-to-material ratio is 5:1, the speed is set to 300rpm, and the mixture is ball-milled for 2 hours. Pass the mixture through a 400-mesh sieve and keep the undersize material.

[0065] Step 3: The sieved material is microwave sintered in a nitrogen atmosphere. The microwave sintering power is 1kW, the sintering temperature is 400℃, the sintering time is 5h, and the heating rate is 5℃ / min. After sintering, lithium iron ferrite material coated with Y2O3 is obtained.

[0066] Step 4: Mix and grind 1.6g of the prepared lithium iron phosphate material, 0.2g of PVDF, and 0.2g of SP in a mass ratio of 8:1:1. Then, coat the mixture to a thickness of 300μm onto a 250mm×100mm aluminum foil as the positive electrode of the lithium-ion battery. Assemble CR2032 coin cells in an argon-filled glove box. The negative electrode is a lithium metal sheet, the separator is a polypropylene microporous membrane, and the electrolyte is a 1mol / L LiPF6 solution with an electrolyte solvent ratio of EC:DMC:EMC = 1:1:1 (v / v / v). The measured voltage range of the coin cell is 2V-4.5V, and the charge / discharge current is 0.05C.

[0067] Example 6

[0068] Step 1: Lithium hydroxide (D50 0.5-1μm) and iron oxide (D50 0.5-1μm) were mixed in a high-speed mixer at an elemental molar ratio of 5.2:1 (800 rpm, 10 min). After mixing, microwave sintering was performed in a nitrogen atmosphere at a power of 1 kW, a temperature of 400℃, a sintering time of 5 h, a heating rate of 5℃ / min, and a ventilation rate of 10 m³ / min. 3 / h; After sintering, lithium iron ferrite solid is obtained. The solid is coarsely crushed and then subjected to air jet milling to obtain lithium iron ferrite powder (D50 is 3-5μm).

[0069] Step 2: Take Yb2O3 (D50 is 0.5-1μm) and lithium iron ferrite powder in a ball mill jar with a mass ratio of Yb2O3 to lithium iron ferrite of 1:99.5 and a ball-to-material ratio of 5:1. Set the speed to 300 rpm and ball mill for 2 hours. Pass the mixture through a 400-mesh sieve and keep the material passing through the sieve.

[0070] Step 3: The sieved material is microwave sintered in a nitrogen atmosphere. The microwave sintering power is 1kW, the sintering temperature is 400℃, the sintering time is 5h, and the heating rate is 5℃ / min. After sintering, lithium iron ferrite material coated with Y2O3 is obtained.

[0071] Step 4: Mix and grind 1.6g of the prepared lithium iron phosphate material, 0.2g of PVDF, and 0.2g of SP in a mass ratio of 8:1:1. Then, coat the mixture to a thickness of 300μm onto a 250mm×100mm aluminum foil as the positive electrode of the lithium-ion battery. Assemble CR2032 coin cells in an argon-filled glove box. The negative electrode is a lithium metal sheet, the separator is a polypropylene microporous membrane, and the electrolyte is a 1mol / L LiPF6 solution with an electrolyte solvent ratio of EC:DMC:EMC = 1:1:1 (v / v / v). The measured voltage range of the coin cell is 2V-4.5V, and the charge / discharge current is 0.05C.

[0072] Example 7

[0073] Using the method of Example 1, the mass ratio of Y2O3 to lithium iron ferrite was 1:99.7.

[0074] Example 8

[0075] Using the method of Example 1, the mass ratio of Y2O3 to lithium iron ferrite was 1:99.9.

[0076] Example 9

[0077] The method of Example 1 was used, with a ball-to-material ratio of 7:1.

[0078] Example 10

[0079] The method of Example 1 was used, with a ball-to-material ratio of 10:1.

[0080] Example 11

[0081] Using the method of Example 1, the ball milling time was 4 hours and the rotation speed was 400 rpm.

[0082] Example 12

[0083] The method of Example 1 was used, with a ball milling time of 6 hours and a rotation speed of 500 rpm.

[0084] Example 13

[0085] Using the method of Example 1, the microwave sintering temperature was 500℃, and the sintering time was 7 hours (referring to the sintering temperature and time after mixing with rare earth metal oxides in step 3).

[0086] Example 14

[0087] Using the method of Example 1, the microwave sintering temperature was 600℃, and the sintering time was 10h (referring to the sintering temperature and time after mixing with rare earth metal oxides in step 3).

[0088] Comparative Example 1

[0089] Step 1: Lithium hydroxide (D50 0.5-1μm) and iron oxide (D50 0.5-1μm) were mixed in a high-speed mixer at an elemental molar ratio of 5.2:1 (800 rpm, 10 min). After mixing, microwave sintering was performed in a nitrogen atmosphere at a power of 1 kW, a temperature of 400℃, a sintering time of 5 h, a heating rate of 5℃ / min, and a ventilation rate of 10 m³ / min. 3 / h; After sintering, lithium iron ferrite solid is obtained. The solid is coarsely crushed and then subjected to air jet milling to obtain lithium iron ferrite powder (D50 is 3-5μm).

[0090] Step 2: Take lithium iron ferrite powder into a ball mill jar with a ball-to-powder ratio of 5:1 and a rotation speed of 300 rpm. Grind the powder in the ball mill for 2 hours, then pass it through a 400-mesh sieve and keep the undersize material.

[0091] Step 3: The sieved material is microwave sintered in a nitrogen atmosphere. The microwave sintering power is 1kW, the sintering temperature is 400℃, the sintering time is 5h, and the heating rate is 5℃ / min. After sintering, lithium-rich lithium iron ore material is obtained.

[0092] Step 4: Mix and grind 1.6g of the prepared lithium iron phosphate material, 0.2g of PVDF, and 0.2g of SP in a mass ratio of 8:1:1. Then, coat the mixture to a thickness of 300μm onto a 250mm×100mm aluminum foil as the positive electrode of the lithium-ion battery. Assemble CR2032 coin cells in an argon-filled glove box. The negative electrode is a lithium metal sheet, the separator is a polypropylene microporous membrane, and the electrolyte is a 1mol / L LiPF6 solution with an electrolyte solvent ratio of EC:DMC:EMC = 1:1:1 (v / v / v). The measured voltage range of the coin cell is 2V-4.5V, and the charge / discharge current is 0.05C.

[0093] Comparative Example 2

[0094] Using the method of Example 1, the mass ratio of Y2O3 to lithium iron ferrite was 1:99.0.

[0095] Comparative Example 3

[0096] The method of Example 1 was used, with a ball-to-material ratio of 2:1.

[0097] Comparative Example 4

[0098] Using the method of Example 1, the ball milling speed was 100 rpm and the time was 6 hours.

[0099] Comparative Example 5

[0100] Using the method of Example 1, the microwave sintering temperature was 700℃ and the sintering time was 12h.

[0101] Table 1 shows a comparison of the electrical performance and voltage plateau of Examples 1-14 and Comparative Examples 1-5.

[0102]

[0103]

[0104] Figure 1 AE shows a comparison of the charging curves between different embodiments.

[0105] Figure 2 Figure AB shows a comparison of SEM images of Example 1 and Comparative Example 1.

[0106] As can be seen from Table 1, there are differences in the capacity of the doped materials, and for the same materials, the voltage plateau is reduced.

[0107] Figure 1 Figure A illustrates the effect of different doping elements on the capacity of lithium-ion additive materials. As can be seen from the figure, Y₂O₃ exhibits advantages in both average voltage and capacity. This may be because the coating layers formed by different elements have varying electron migration efficiencies.

[0108] Figure 1 Figure B illustrates the effects of different ball milling times and rotation speeds on material properties. As shown in the figure, the optimal conditions are a rotation speed of 300 rpm and ball milling for 2 hours. Too low a ball milling time and rotation speed will lead to uneven mixing, while too long a mixing time will result in partial deterioration of the lithium-rich lithium iron ferrite.

[0109] Figure 1 Figure C illustrates the effect of different Y₂O₃ addition amounts on material performance. As can be seen from the figure, excessive Y₂O₃ addition results in only a small increase in capacity, while excessive addition has a certain impact on capacity. The optimal mass ratio of Y₂O₃ to lithium-rich lithium iron phosphate is 1:99.5. Too little Y₂O₃ leads to insufficient coating, while excessive addition results in an overly thick coating layer, affecting conductivity.

[0110] Figure 1 Figure D illustrates the effect of different ball-to-material ratios in ball milling on material properties. As shown in the figure, a low ball-to-material ratio leads to uneven mixing, while an excessive ball-to-material ratio compacts the main material, also affecting the mixing effect. The optimal ball-to-material ratio is 5:1.

[0111] Figure 1 Figure E illustrates the effect of different microwave sintering conditions on material properties. As shown in the figure, the optimal sintering condition is 400℃ for 5 hours. Excessive sintering time leads to larger grain sizes, affecting capacity utilization. During battery charging and discharging, only the surface reacts, leaving no residual reaction inside, resulting in reduced capacity.

[0112] Figure 2 Figures A and B show SEM comparisons of Example 1 and Comparative Example 1, respectively. The small particles are Y₂O₃, and the large particles are lithium iron ferrite material. As can be seen from the figures, in Figure A, Y₂O₃ is uniformly coated on the surface of the lithium iron ferrite material. Furthermore, a heterogeneous structure is formed at the interface between Y₂O₃ and lithium iron ferrite.

[0113] By ball milling and mixing iron source, lithium source and rare earth metal oxide, and then using microwave sintering, lithium-rich lithium iron ferrite material is prepared, which has higher capacity and better polarization. At the same time, the microwave sintering synthesis method reduces the synthesis cost of the material. This type of lithium-rich lithium iron ferrite material provides a better lithium supplementation additive for lithium-ion batteries.

[0114] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A lithium iron ferrite material, comprising lithium iron ferrite particles and rare earth metal oxide particles coated on the surface of the lithium iron ferrite particles, wherein a heterostructure is formed at the interface between the lithium iron ferrite and the rare earth metal oxide particles. in, The rare earth metal oxide is selected from one of Y2O3 and Sc2O3; The mass ratio of the rare earth metal oxide to the lithium iron ferrite particles is 1:(99.5-99.9). The method for preparing the lithium iron ferrite-rich material includes the following steps: 1) The lithium source and iron source are mixed in a high-temperature mixture and microwave sintered to obtain lithium iron ferrite rich in lithium. The obtained lithium iron ferrite rich in lithium is then pulverized to obtain lithium iron ferrite rich in lithium powder. 2) The obtained lithium iron ferrite powder is ball-milled and mixed with the rare earth metal oxide, and the resulting mixture is sieved, with the undersize material retained. 3) The obtained sieved material is microwave sintered under a protective atmosphere to obtain lithium iron ferrite material coated with rare earth metal oxides. In the ball milling process, the ball-to-material ratio is 5:1, the rotation speed is 300 rpm, and the time is 2 hours. In step 3), the microwave sintering temperature is 400℃ and the time is 5h.

2. The lithium-rich lithium iron phosphate material according to claim 1, characterized in that: In step 1), the lithium source includes one or more of the following: Li2O, LiOH, Li2C2O4, and Li2CO3; The iron source includes one or more of Fe2O3, Fe2(C2O4)3, and Fe(NO3)3; The lithium source and iron source are added at a lithium to iron molar ratio of (5.0-5.5):

1.

3. The lithium iron ferrite material according to claim 1, characterized in that: In step 1), the microwave sintering temperature is 400-600℃, the time is 5-10h, the microwave power is 1-3kW, and the heating rate is 5-10℃ / min. In step 3), the microwave power is 1-3kW and the heating rate is 5-10℃ / min; In steps 1) and 3), the microwave sintering is carried out under inert gas protection; In step 1), the pulverization is air jet milling, and the particle size D50 of the lithium iron ferrite powder obtained after pulverization is 3-5 μm.

4. The lithium iron ferrite material according to claim 1, characterized in that: In step 2), the rare earth metal oxide is added at a mass ratio of rare earth metal oxide to lithium iron ferrite powder of 1:(99.5-99.9).

5. The lithium iron ferrite material according to claim 1, characterized in that: The sieve used for sieving has a mesh size of 300-500.

6. The application of the lithium-rich lithium iron phosphate material of claim 1 as a lithium supplement material in the preparation of lithium-ion batteries.

7. The application according to claim 6, characterized in that: The lithium-rich lithium iron phosphate material is used as a positive electrode lithium replenisher in lithium-ion batteries.

8. A lithium-ion battery, characterized in that: The lithium-ion battery contains the lithium-rich lithium iron phosphate material as described in claim 1.

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