A positive electrode lithium supplementing agent material, a preparation method and application thereof

Abstract

This invention relates to the field of battery technology, specifically to a cathode lithium replenishment agent material, its preparation method, and its application. The preparation method of the cathode lithium replenishment agent material of this invention includes the following steps: stirring and milling a mixture of a first lithium source, an iron source, a first carbon source, a dopant containing element M, and a solvent, wherein element M is selected from at least one of nickel, zirconium, and manganese, to obtain a mixed slurry; drying the mixed slurry and performing a first sintering treatment to obtain a first material; mixing the first material with a second lithium source and then performing a second sintering treatment to obtain a second material; mixing the second material with a titanium source and a second carbon source and then performing a third sintering treatment. The method of this invention can reduce the residual alkali content of the material and the degree of corrosion to the crucible, resulting in a cathode lithium replenishment agent material with excellent electrochemical performance, which can improve the initial charge capacity of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a positive electrode lithium replenishing agent material, its preparation method, and its application. Background Technology

[0002] Significant progress has been made in the research of lithium-ion batteries, with improvements in specific capacity, cycle stability, and rate performance. However, many problems remain. Among them, irreversible capacity loss limits the application of many high-energy materials, and most of this irreversible capacity loss comes from the lithium ions consumed during the formation of the solid electrolyte film during the first charge.

[0003] During the first charge of a lithium-ion battery, the organic solvents in the electrolyte (such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and propylene carbonate (PC)) readily decompose on the surface of the negative electrode after drawing lithium ions from the positive electrode, forming a passivation film called the solid electrolyte interphase (SEI) film. The SEI film insulates against electron passage while allowing lithium ions to pass through; it is an electronic insulator but an excellent ionic conductor, effectively inhibiting further electrolyte decomposition and preventing the formation of a thicker SEI film after the first cycle. The SEI film mainly consists of organic components such as RCOOLi, ROLi, and ROCO2Li, as well as inorganic components such as Li2CO3, Li2O, LiOH, and LiF. The formation of these lithium-containing components is irreversible, thus permanently consuming a portion of the lithium from the positive electrode. + This reduces the coulombic efficiency (ICE) of the first cycle and results in lower energy and capacity density of lithium-ion batteries.

[0004] Graphite, currently the most widely used commercial lithium-ion battery anode material, experiences an initial irreversible capacity loss of around 10%, while some high-capacity anode materials suffer even higher losses, such as silicon-based and tin-based anode materials, which can exceed 30%. To address this initial irreversible capacity loss and improve initial coulombic efficiency, researchers have developed lithium replenishment technology. This technology adds a new primary lithium source to the electrode material to compensate for the loss of active lithium caused by the formation of the SEI film during the first cycle. However, the traditional high-temperature solid-state reaction method for preparing lithium ferrite replenishment materials often leads to severe corrosion of the crucible, resulting in the introduction of impurities into the material, reducing its purity, and ultimately affecting its performance.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One object of the present invention is to provide a method for preparing a positive electrode lithium replenishing agent material, which can improve the initial charging capacity of the positive electrode lithium replenishing agent material, while reducing the residual alkali content and the degree of corrosion of the crucible.

[0007] Another object of the present invention is to provide a positive electrode lithium replenishing agent material with excellent electrochemical performance.

[0008] Another object of the present invention is to provide a positive electrode material.

[0009] Another object of the present invention is to provide a battery.

[0010] Another object of the present invention is to provide an electrical device.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0012] A method for preparing a positive electrode lithium replenishing agent material includes the following steps:

[0013] A mixture of a first lithium source, an iron source, a first carbon source, a dopant containing element M, and a solvent is stirred and milled to obtain a mixed slurry. The mixed slurry is then dried and subjected to a first sintering treatment to obtain a first material. The first material is mixed with a second lithium source and then subjected to a second sintering treatment to obtain a second material. The second material is then mixed with a titanium source and a second carbon source and then subjected to a third sintering treatment.

[0014] In one embodiment, the first lithium source includes at least one of lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium dihydrogen phosphate, lithium chloride, lithium acetate, and lithium carbonate.

[0015] In one embodiment, the iron source includes at least one of ferric oxide, ferric chloride, ferric nitrate, ferric sulfate, ferric bromide, and ferric hydroxide.

[0016] In one embodiment, the dopant includes at least one of a nickel source, a zirconium source, and a manganese source.

[0017] In one embodiment, the nickel source in the dopant includes at least one of nickel suboxide, nickel sulfate, and nickel powder.

[0018] In one embodiment, the zirconium source in the dopant includes at least one of zirconium dioxide, zirconium hydroxide, zirconium nitrate, zirconium phosphate, and zirconium chloride.

[0019] In one embodiment, the manganese source in the dopant includes at least one of manganese oxalate, manganese oxide, manganese sulfate, and manganese carbonate.

[0020] In one embodiment, the first carbon source includes an organic carbon source and / or an inorganic carbon source; the organic carbon source includes at least one of polyethylene glycol, polypropylene, phenolic resin, epoxy resin, polyimide, polycarbonate, glucose, citric acid, and ascorbic acid; the inorganic carbon source includes at least one of conductive carbon black, graphite, and carbon nanotubes.

[0021] In one embodiment, the molar ratio of the first lithium source, iron source, first carbon source, and dopant, based on lithium, iron, carbon, and M elements, is (1-2):1:(0.04-0.08):(0.002-0.006).

[0022] In one embodiment, the stirring time is 1 to 3 hours.

[0023] In one embodiment, the grinding speed is 1500-2500 rpm, and the grinding time is 1-5 hours.

[0024] In one embodiment, the drying includes spray drying; the feed rate of the spray dryer is 15-30 rpm; and the outlet air temperature is 90-135°C.

[0025] In one embodiment, the temperature of the first sintering treatment is 600-800°C, and the holding time of the first sintering treatment is 2-10 hours.

[0026] In one embodiment, the heating rate of the first sintering treatment is 1 to 3 °C / min, and the first sintering treatment is carried out under protective gas conditions.

[0027] In one embodiment, the molar ratio of the first material to the lithium element in the second lithium source is 1:(4-5).

[0028] In one embodiment, the second lithium source includes at least one of lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium dihydrogen phosphate, lithium chloride, lithium acetate, and lithium carbonate.

[0029] In one embodiment, the temperature of the second sintering treatment is 750–900°C, and the holding time of the second sintering treatment is 10–25 h.

[0030] In one embodiment, the heating rate of the second sintering treatment is 1 to 3 °C / min, and the second sintering treatment is carried out under protective gas conditions.

[0031] In one embodiment, the mass ratio of the second material, the titanium element in the titanium source, and the carbon element in the second carbon source is 1:(0.001~0.01):(0.01~0.1).

[0032] In one embodiment, the second carbon source includes an organic carbon source and / or an inorganic carbon source; the organic carbon source includes at least one of polyethylene glycol, polypropylene, phenolic resin, epoxy resin, polyimide, polycarbonate, glucose, citric acid, and ascorbic acid; the inorganic carbon source includes at least one of conductive carbon black, graphite, and carbon nanotubes.

[0033] In one embodiment, the titanium source includes at least one of titanium oxide and titanium tetrachloride.

[0034] In one embodiment, the temperature of the third sintering treatment is 400–600°C, and the holding time of the third sintering treatment is 2–6 hours.

[0035] In one embodiment, the heating rate of the third sintering process is 1 to 3 °C / min, and the third sintering process is carried out under protective gas conditions.

[0036] A positive electrode lithium replenishing agent material is prepared by the method described above.

[0037] A positive electrode material includes a positive electrode active material and a positive electrode lithium supplement material; the positive electrode active material includes lithium iron phosphate; the positive electrode lithium supplement material accounts for 5% to 20% of the mass of the positive electrode active material.

[0038] A battery comprising the aforementioned positive electrode lithium replenishing agent material or the aforementioned positive electrode material.

[0039] An electrical device, including the battery.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) The present invention reduces the degree of corrosion of the crucible by adding lithium source in two steps. After titanium coating, it reacts with the residual alkali on the surface of the material to form lithium titanate, which can reduce the residual alkali content of the material. Carbon coating plays a synergistic role and can increase the conductivity of the material. The method of the present invention can reduce the degree of corrosion of the crucible, reduce the residual alkali content of the lithium replenishing agent material, and improve the first week charging capacity of the battery.

[0042] (2) The positive electrode lithium replenishing agent material obtained by the method of the present invention has excellent electrochemical performance. Further preparation of batteries can improve the battery capacity, cycle performance and safety performance. Detailed Implementation

[0043] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0044] According to one aspect of the present invention, the present invention relates to a method for preparing a positive electrode lithium replenishing agent material, comprising the following steps:

[0045] A mixture of a first lithium source, an iron source, a carbon source, a dopant containing element M, and a solvent is stirred and milled, wherein element M is selected from at least one of nickel, zirconium, and manganese, to obtain a mixed slurry; the mixed slurry is dried and subjected to a first sintering treatment to obtain a first material; the first material is mixed with a second lithium source and then subjected to a second sintering treatment to obtain a second material; the second material is mixed with a titanium source and a carbon source and then subjected to a third sintering treatment.

[0046] This invention reduces the corrosion of the crucible by adding a lithium source in two steps. After titanium coating, it reacts with the residual alkali on the material surface to form lithium titanate, which reduces the residual alkali content of the material. Carbon coating plays a synergistic role and can increase the conductivity of the material. The method of this invention can reduce the corrosion of the crucible, reduce the residual alkali content of the lithium replenishing agent material, and improve the first-cycle charging capacity of the battery.

[0047] In one embodiment, the total mass ratio of the first lithium source, iron source, carbon source, and dopant containing element M to the solvent is (0.25–0.45):1, for example, 0.3:1, 0.35:1, 0.4:1, 0.45:1, etc. In one embodiment, the solvent is water.

[0048] In one embodiment, the first material is LiFeO2 material doped with element M; the second material has the chemical formula Li5FeO4. The final cathode lithium replenishing agent material is a titanium and carbon co-coated lithium ferrite replenishing material.

[0049] In one embodiment, the first lithium source includes at least one selected from lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium dihydrogen phosphate, lithium chloride, lithium acetate, and lithium carbonate. The first lithium source of the present invention can be any one or a combination of at least two of the above, such as a combination of lithium chloride and lithium acetate, or a combination of anhydrous lithium hydroxide and lithium dihydrogen phosphate.

[0050] In one embodiment, the iron source includes at least one selected from ferric oxide, ferric chloride, ferric nitrate, ferric sulfate, ferric bromide, and ferric hydroxide. The iron source of the present invention can be any combination of one or more of the above, such as a combination of ferric nitrate, ferric sulfate, and ferric bromide, or a combination of ferric oxide and ferric chloride.

[0051] In one embodiment, the dopant includes at least one of a nickel source, a zirconium source, and a manganese source. The nickel source includes at least one of nickel(II) oxide, nickel sulfate, and nickel powder. The zirconium source includes at least one of zirconium dioxide, zirconium hydroxide, zirconium nitrate, zirconium phosphate, and zirconium chloride. The manganese source includes at least one of manganese oxalate, manganese oxide, manganese sulfate, and manganese carbonate. The dopant of the present invention can be any combination of one or more of the above, such as a combination of nickel sulfate, zirconium nitrate, and manganese sulfate, or a combination of nickel(II) oxide, zirconium hydroxide, and manganese oxalate.

[0052] In one embodiment, the first carbon source includes an organic carbon source and / or an inorganic carbon source; the organic carbon source includes at least one selected from polyethylene glycol, polypropylene, phenolic resin, epoxy resin, polyimide, polycarbonate, glucose, citric acid, and ascorbic acid; the inorganic carbon source includes at least one selected from conductive carbon black, graphite, and carbon nanotubes. The first carbon source of the present invention can be an organic carbon source or an inorganic carbon source, or a combination of both, such as a combination of glucose and ascorbic acid, or a combination of polyethylene glycol and epoxy resin, etc.

[0053] In one embodiment, the titanium source includes at least one of titanium oxide and titanium tetrachloride.

[0054] In one embodiment, the molar ratio of the first lithium source, iron source, first carbon source, and dopant, based on lithium, iron, carbon, and M elements, is (1-2):1:(0.04-0.08):(0.002-0.006), for example, 1:1:0.04:0.002, 1.5:1:0.05:0.005, 2:1:0.08:0.006, etc. The present invention employs a suitable molar ratio of the first lithium source, iron source, first carbon source, and dopant to ensure the physicochemical properties of the first material.

[0055] In one embodiment, the stirring time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. By using an appropriate stirring time, the materials are thoroughly mixed.

[0056] In one embodiment, the grinding speed is 1500-2500 rpm, such as 1500 rpm, 1800 rpm, 2000 rpm, 2200 rpm, 2500 rpm, etc., and the grinding time is 1-5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, etc.

[0057] In one embodiment, the drying includes spray drying; the spray drying is carried out in a spray dryer with a feed rate of 15–30 rpm, such as 15 rpm, 18 rpm, 20 rpm, 25 rpm, etc., and an outlet air temperature of 90–135°C, such as 90°C, 100°C, 110°C, 120°C, 135°C, etc. Suitable drying conditions ensure the particle size and properties of the material.

[0058] In one embodiment, the temperature of the first sintering treatment is 600–800°C, such as 600°C, 650°C, 680°C, 700°C, 720°C, 750°C, or 800°C. The holding time of the first sintering treatment is 2–10 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or 10 hours. The heating rate of the first sintering treatment is 1–3°C / min, such as 2°C / min or 3°C / min. The first sintering treatment is carried out under a protective gas condition, such as nitrogen. This invention ensures that the first material has a specific microstructure by employing suitable first sintering treatment conditions.

[0059] In one embodiment, the molar ratio of the first material to the lithium element in the second lithium source is 1:(4-5), such as 1:4, 1:4.5, 1:5, etc. This invention uses a suitable molar ratio of the first material to the second lithium source, which can reduce the corrosion of the crucible and ensure the lithium replenishment effect.

[0060] In one embodiment, the second lithium source includes at least one selected from lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium dihydrogen phosphate, lithium chloride, lithium acetate, and lithium carbonate. The second lithium source can be any one or a combination of the above, such as a combination of lithium chloride and lithium acetate, or a combination of lithium dihydrogen phosphate, lithium chloride, and lithium carbonate.

[0061] In one embodiment, the temperature of the second sintering treatment is 750–900°C, for example, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, 900°C, etc., and the holding time of the second sintering treatment is 10–25 hours, for example, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours, 25 hours, etc. In one embodiment, the heating rate of the second sintering treatment is 1–3°C / min, for example, 2°C / min, 3°C / min, etc., and the second sintering treatment is carried out under a protective gas condition, such as nitrogen.

[0062] In one embodiment, the second carbon source includes an organic carbon source and / or an inorganic carbon source; the organic carbon source includes at least one selected from polyethylene glycol, polypropylene, phenolic resin, epoxy resin, polyimide, polycarbonate, glucose, citric acid, and ascorbic acid; the inorganic carbon source includes at least one selected from conductive carbon black, graphite, and carbon nanotubes; the second carbon source of the present invention can be an organic carbon source or an inorganic carbon source, or a combination of both, such as a combination of phenolic resin, epoxy resin, and polyimide, or a combination of polycarbonate and carbon nanotubes, etc. The titanium source includes at least one selected from titanium oxide and titanium tetrachloride.

[0063] In one embodiment, the mass ratio of the second material, the titanium element in the titanium source, and the carbon element in the second carbon source is 1:(0.001~0.01):(0.01~0.1), for example, 1:0.001, 1:0.01, 1:0.005:0.02, 1:0.008:0.05, 1:0.01:0.01, etc. This invention uses a suitable proportion of titanium source, which can react with the residual alkali on the surface of the coated material to form lithium titanate, reducing the residual alkali content of the material. Simultaneously, using a suitable proportion of the second carbon source can synergistically increase the conductivity of the material, reduce the corrosion of the crucible, reduce the residual alkali content of the material, and improve the first-cycle charging capacity of the cathode material.

[0064] In one embodiment, the temperature of the third sintering treatment is 400–600°C, for example, 400°C, 450°C, 500°C, 600°C, etc.; the holding time of the third sintering treatment is 2–6 hours, for example, 2 hours, 3 hours, 3.5 hours, 4 hours, 5 hours, or 6 hours; the heating rate of the third sintering treatment is 1–3°C / min, for example, 2 / min, 3°C / min, etc.; and the third sintering treatment is carried out under a protective gas condition, such as nitrogen. This invention, through suitable third sintering conditions, ensures the electrochemical performance of the final obtained positive electrode lithium replenishment material.

[0065] According to another aspect of the present invention, the present invention also relates to a positive electrode lithium replenishing agent material, which is prepared by the method for preparing the positive electrode lithium replenishing agent material.

[0066] The positive electrode lithium replenishing agent material of the present invention has excellent electrochemical performance. As a lithium replenishing agent material for positive electrode active material, it can improve the battery capacity and enhance its cycle performance.

[0067] According to another aspect of the present invention, the present invention also relates to a positive electrode material, comprising a positive electrode active material and the aforementioned positive electrode lithium supplement material; the positive electrode active material comprises lithium iron phosphate; the mass of the positive electrode lithium supplement material accounts for 5% to 20% of the mass of the positive electrode active material, for example 5%, 8%, 10%, 12%, 15%, 18% or 20%, etc.

[0068] In one embodiment, the positive electrode active material, positive electrode lithium supplement material, conductive agent, binder, and solvent of the present invention are mixed to obtain a positive electrode slurry, which is further coated on at least one side of the positive electrode current collector, dried, and rolled to obtain a positive electrode sheet. In one embodiment, the solvent includes an organic solvent, such as N-methylpyrrolidone, the conductive agent includes acetylene black, the binder includes polyvinylidene fluoride, and the positive electrode active material includes lithium iron phosphate. In one embodiment, the mass ratio of the positive electrode active material, conductive agent, and binder is (88-93):(3-6):(3-6). In one embodiment, the mixing is carried out in a vacuum mixer for 20-40 minutes. In one embodiment, the drying temperature is 100-130°C, and the drying time is 8-15 hours.

[0069] According to another aspect of the invention, the invention also relates to a battery comprising the aforementioned positive electrode lithium replenishing agent material or the aforementioned positive electrode material.

[0070] The battery of this invention has excellent initial efficiency, cycle performance, and high safety performance.

[0071] In one embodiment, the battery of the present invention includes a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode contains the aforementioned positive electrode lithium replenishing agent material.

[0072] According to another aspect of the invention, the invention also relates to an electrical device comprising the aforementioned battery.

[0073] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0074] Example 1

[0075] A method for preparing a positive electrode lithium replenishing agent material includes the following steps:

[0076] (a) A mixture of a first lithium source, an iron source, a first carbon source, a dopant, and water is stirred for 2 hours. The total mass ratio of the first lithium source, iron source, first carbon source, and dopant to water is 0.35:1. The mixture is then placed in a sand mill for sand milling at a speed of 2000 rpm for 2 hours to obtain a mixed slurry. The first lithium source is lithium carbonate, the iron source is ferric nitrate, the first carbon source is glucose, and the dopant is zirconium dioxide. The molar ratio of the first lithium source, iron source, first carbon source, and dopant is 1.5:1:0.06:0.005 for lithium, iron, carbon, and zirconium. The number of moles of the first lithium source is 7.5 mol.

[0077] (b) The above mixed slurry was spray-dried using a spray dryer and then placed in an atmosphere furnace for a first sintering treatment to obtain the first material. The feed rate of the spray dryer was 20 rpm; the outlet air temperature was 105°C; the first sintering treatment was carried out under a protective gas condition, the temperature of the first sintering treatment was 690°C, the holding time was 4.5 h, and the heating rate of the first sintering treatment was 2°C / min.

[0078] (c) The first material and lithium carbonate are mixed evenly in a high-speed mixer and then subjected to a second sintering process to obtain the second material; wherein the molar ratio of the first material to lithium in lithium carbonate is 1:4.5; the second sintering process is carried out in a nitrogen atmosphere, the temperature of the second sintering process is 800℃, the holding time is 15h, and the heating rate of the second sintering process is 2℃ / min.

[0079] (d) The second material is mixed with the titanium source and the second carbon source, and a third sintering treatment is carried out in a box-type atmosphere furnace; wherein the titanium source is titanium tetrachloride, the second carbon source is glucose, and the mass ratio of titanium element in the second material and the titanium source to carbon element in the second carbon source is 1:0.005:0.05; the third sintering treatment is carried out under protective gas conditions, the temperature of the third sintering treatment is 510℃, the holding time is 3h, and the heating rate of the third sintering treatment is 2℃ / min.

[0080] Example 2

[0081] A method for preparing a positive electrode lithium replenishing agent material includes the following steps:

[0082] (a) A mixture of a first lithium source, an iron source, a first carbon source, a dopant, and water is stirred for 1 hour. The total mass ratio of the first lithium source, iron source, first carbon source, and dopant to water is 0.35:1. The mixture is then placed in a sand mill for sand milling at a speed of 1500 rpm for 5 hours to obtain a mixed slurry. The first lithium source is lithium carbonate, the iron source is ferric nitrate, the first carbon source is glucose, and the dopant is zirconium dioxide. The molar ratio of the first lithium source, iron source, first carbon source, and dopant is 1.5:1:0.06:0.005 for lithium, iron, carbon, and zirconium. The number of moles of the first lithium source is 7.5 mol.

[0083] (b) The above mixed slurry was spray-dried using a spray dryer and then placed in an atmosphere furnace for a first sintering treatment to obtain the first material. The feed rate of the spray dryer was 15 rpm; the outlet air temperature was 90°C; the first sintering treatment was carried out under a protective gas condition, the temperature of the first sintering treatment was 600°C, the holding time was 10 h, and the heating rate of the first sintering treatment was 2°C / min.

[0084] (c) The first material and lithium carbonate are mixed evenly in a high-speed mixer and then subjected to a second sintering process to obtain the second material; wherein the molar ratio of the first material to lithium in lithium carbonate is 1:4.5; the second sintering process is carried out in a nitrogen atmosphere, the temperature of the second sintering process is 750°C, the holding time is 20h, and the heating rate of the second sintering process is 2°C / min.

[0085] (d) The second material is mixed with the titanium source and the second carbon source, and a third sintering treatment is carried out in a box-type atmosphere furnace; wherein the titanium source is titanium tetrachloride, the second carbon source is glucose, and the mass ratio of titanium element in the second material and the titanium source to carbon element in the second carbon source is 1:0.008:0.01; the third sintering treatment is carried out under protective gas conditions, the temperature of the third sintering treatment is 400℃, the holding time is 6h, and the heating rate of the third sintering treatment is 2℃ / min.

[0086] Example 3

[0087] A method for preparing a positive electrode lithium replenishing agent material includes the following steps:

[0088] (a) A mixture of a first lithium source, an iron source, a first carbon source, a dopant, and water is stirred for 3 hours. The total mass ratio of the first lithium source, iron source, first carbon source, and dopant to water is 0.35:1. The mixture is then placed in a sand mill for sand milling at a speed of 2500 rpm for 1 hour to obtain a mixed slurry. The first lithium source is lithium carbonate, the iron source is ferric nitrate, the first carbon source is glucose, and the dopant is zirconium dioxide. The molar ratio of the first lithium source, iron source, first carbon source, and dopant is 1.5:1:0.06:0.005 for lithium, iron, carbon, and zirconium. The number of moles of the first lithium source is 7.5 mol.

[0089] (b) The above mixed slurry was spray-dried using a spray dryer and then placed in an atmosphere furnace for the first sintering treatment to obtain the first material. The feed rate of the spray dryer was 30 rpm; the outlet air temperature was 135°C; the first sintering treatment was carried out under protective gas conditions, the temperature of the first sintering treatment was 800°C, the holding time was 2 h, and the heating rate of the first sintering treatment was 2°C / min.

[0090] (c) The first material and lithium carbonate are mixed evenly in a high-speed mixer and then subjected to a second sintering process to obtain the second material; wherein the molar ratio of the first material to lithium in lithium carbonate is 1:4.5; the second sintering process is carried out in a nitrogen atmosphere, the temperature of the second sintering process is 900℃, the holding time is 10h, and the heating rate of the second sintering process is 2℃ / min.

[0091] (d) The second material is mixed with the titanium source and the second carbon source, and a third sintering treatment is carried out in a box-type atmosphere furnace; wherein the titanium source is titanium tetrachloride, the second carbon source is glucose, and the mass ratio of titanium element in the second material and the titanium source to carbon element in the second carbon source is 1:0.002:0.1; the third sintering treatment is carried out under protective gas conditions, the temperature of the third sintering treatment is 600℃, the holding time is 2h, and the heating rate of the third sintering treatment is 2℃ / min.

[0092] Example 4

[0093] A method for preparing a positive electrode lithium replenishing agent material, except that the mass ratio of titanium in the second material and titanium source to carbon in the second carbon source is 1:0.007:0.04, and other conditions are the same as in Example 1.

[0094] Example 5

[0095] A method for preparing a positive electrode lithium replenishing agent material, except that the mass ratio of titanium in the second material and titanium source to carbon in the second carbon source is 1:0.004:0.06, other conditions are the same as in Example 1.

[0096] Example 6

[0097] A method for preparing a positive electrode lithium replenishing agent material includes the following steps:

[0098] (a) A mixture of a first lithium source, an iron source, a first carbon source, a dopant, and water is stirred for 2 hours, and then placed in a sand mill for sand milling at a speed of 2200 rpm for 2 hours to obtain a mixed slurry; wherein the first lithium source is lithium dihydrogen phosphate, the iron source is ferric sulfate, the first carbon source is citric acid, and the dopant is manganese sulfate, nickel sulfate, and zirconium dioxide, and the molar ratio of the first lithium source, iron source, first carbon source, manganese sulfate, nickel sulfate, and zirconium phosphate based on lithium, iron, carbon, manganese, nickel, and zirconium elements is 1.5:1:0.06:0.001:0.002:0.002;

[0099] (b) The above mixed slurry was spray-dried using a spray dryer and then placed in an atmosphere furnace for a first sintering treatment to obtain the first material. The feed rate of the spray dryer was 25 rpm; the outlet air temperature was 95°C; the first sintering treatment was carried out under a protective gas condition, the temperature of the first sintering treatment was 730°C, the holding time was 3.5 h, and the heating rate of the first sintering treatment was 2°C / min.

[0100] (c) The first material and lithium dihydrogen phosphate are mixed evenly in a high-speed mixer and then subjected to a second sintering process to obtain the second material; wherein the molar ratio of the first material to lithium in lithium dihydrogen phosphate is 1:4.8; the second sintering process is carried out in a nitrogen atmosphere, the temperature of the second sintering process is 850°C, the holding time is 12h, and the heating rate of the second sintering process is 2°C / min.

[0101] (d) The second material is mixed with the titanium source and the second carbon source, and a third sintering treatment is carried out in a box-type atmosphere furnace; wherein the titanium source is titanium tetrachloride, the second carbon source is ascorbic acid and conductive carbon black, and the mass ratio of titanium element in the second material, titanium element in the titanium source, carbon element in ascorbic acid and conductive carbon black is 1:0.006:0.03:0.03; the third sintering treatment is carried out under protective gas conditions, the temperature of the third sintering treatment is 560℃, the holding time is 2.5h, and the heating rate of the third sintering treatment is 2℃ / min.

[0102] Comparative Example 1

[0103] A method for preparing a positive electrode lithium replenishing agent material, except that the lithium replenishment operation in step (c) is not performed, and the equal amount of the second lithium source in step (c) is combined into the addition in step (a), and other conditions are the same as in Example 1.

[0104] Comparative Example 2

[0105] A method for preparing a positive electrode lithium replenishing agent material, except that a titanium source is not added in step (d), and other conditions are the same as in Example 1.

[0106] Comparative Example 3

[0107] A method for preparing a positive electrode lithium replenishing agent material, except that a second carbon source is not added in step (d), and the other conditions are the same as in Example 1.

[0108] Experimental Example

[0109] 1. The positive electrode lithium replenishing agent materials obtained in the examples and comparative examples were subjected to crucible corrosion experiments. The test method included: crushing the positive electrode lithium replenishing agent materials prepared in each example and comparative example together with their corresponding corroded crucibles, and then performing ICP testing; the crucibles were the crucibles used to hold the positive electrode lithium replenishing agent materials during the preparation process, and the crucibles used in each example and comparative example were the same.

[0110] The specific results are shown in Table 1.

[0111] Table 1. Aluminum content in various cathode lithium replenishment materials

[0112] Group Aluminum content (ppm) Example 1 226 Example 2 258 Example 3 261 Example 4 243 Example 5 279 Example 6 263 Comparative Example 1 1550 Comparative Example 2 809 Comparative Example 3 655

[0113] As shown in Table 1, the aluminum content in the positive electrode lithium replenishment material obtained by the method of the present invention is relatively low.

[0114] II. The positive electrode lithium replenishing agent materials obtained in the examples and comparative examples were used to prepare coin cells. The preparation methods included: taking positive electrode active material (lithium iron phosphate), conductive agent (acetylene black), and binder (polyvinylidene fluoride), adding them to an appropriate amount of solvent (N-methylpyrrolidone, abbreviated as NMP) at a mass ratio of 90:5:5, then adding the positive electrode lithium replenishing agent material at a mass of 10% of the positive electrode active material, stirring in a vacuum mixer for 0.5 hours to obtain a positive electrode slurry; uniformly coating the positive electrode active material onto the surface of the positive electrode current collector (aluminum foil), drying it in a vacuum drying oven at 120°C for 12 hours, and then rolling and cutting it to obtain a circular positive electrode sheet with a diameter of 12 mm; the negative electrode sheet was a lithium sheet; the separator was a microporous polypropylene film; the electrolyte included LiPF6 and an organic solvent, with a molar concentration of LiPF6 of 1 mol / L; the coin cell was a CR2032 type.

[0115] The performance of each battery was tested, and the results are shown in Table 2. Test conditions: 3.0-4.3V. A coin cell battery was prepared using pure lithium iron phosphate (LFP) as the cathode material according to the above method. The 0.1C charging capacity was 162.0 mAh / g, and the 0.1C discharging capacity was 152.0 mAh / g.

[0116] Table 2 Battery performance test results

[0117]

[0118] As shown in Table 2, the batteries obtained from the positive electrode lithium replenishment materials in each embodiment of the present invention have high charging capacity. The charging capacity of the batteries in each embodiment is increased by 14.69% or more compared to the charging capacity of the batteries prepared from pure LFP. The charging capacity increase of the batteries in the comparative examples compared to the batteries prepared from pure LFP is relatively low.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a positive electrode lithium replenishing agent material, characterized in that, Includes the following steps: A mixture of a first lithium source, an iron source, a first carbon source, a dopant containing element M, and a solvent is stirred and milled, wherein element M is selected from zirconium, manganese, or at least two of nickel, zirconium, and manganese to obtain a mixed slurry; the mixed slurry is dried and subjected to a first sintering treatment to obtain a first material; the first material is mixed with a second lithium source and then subjected to a second sintering treatment to obtain a second material; the second material is mixed with a titanium source and a second carbon source and then subjected to a third sintering treatment. The molar ratio of the first lithium source, iron source, first carbon source, and dopant, based on lithium, iron, carbon, and M elements, is (1~2):1:(0.04~0.08):(0.002~0.006). The molar ratio of the first material to the lithium element in the second lithium source is 1:(4~5); The mass ratio of titanium in the second material and carbon in the second carbon source is 1:(0.001~0.01):(0.01~0.1). The stirring time is 1-3 hours; the milling speed is 1500-2500 rpm; and the milling time is 1-5 hours. The drying process includes spray drying; the feed rate for spray drying is 15~30 rpm; and the outlet air temperature is 90~135℃. The first material is LiFeO2 material doped with element M, the second material is Li5FeO4 doped with element M, and the positive electrode lithium replenishing agent material is Li5FeO4 lithium replenishing material co-coated with titanium and carbon doped with element M. After being coated with titanium, it reacts with the residual alkali on the surface of the positive electrode lithium replenishing agent material to form lithium titanate.

2. The method for preparing the positive electrode lithium replenishing agent material according to claim 1, characterized in that, It includes at least one of the following features (1) to (6): (1) The first lithium source includes at least one of lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium dihydrogen phosphate, lithium chloride, lithium acetate and lithium carbonate; (2) The iron source includes at least one of ferric oxide, ferric chloride, ferric nitrate, ferric sulfate, ferric bromide and ferric hydroxide; (3) The nickel source in the dopant includes at least one of nickel suboxide, nickel sulfate and nickel powder; (4) The zirconium source in the dopant includes at least one of zirconium dioxide, zirconium hydroxide, zirconium nitrate, zirconium phosphate and zirconium chloride; (5) The manganese source in the dopant includes at least one of manganese oxalate, manganese oxide, manganese sulfate and manganese carbonate; (6) The first carbon source includes an organic carbon source and / or an inorganic carbon source; the organic carbon source includes at least one of polyethylene glycol, polypropylene, phenolic resin, epoxy resin, polyimide, polycarbonate, glucose, citric acid and ascorbic acid; the inorganic carbon source includes at least one of conductive carbon black, graphite and carbon nanotubes.

3. The method for preparing the positive electrode lithium replenishing agent material according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The temperature of the first sintering treatment is 600~800℃, and the holding time of the first sintering treatment is 2~10h; (2) The heating rate of the first sintering treatment is 1~3℃ / min, and the first sintering treatment is carried out under protective gas conditions.

4. The method for preparing the positive electrode lithium replenishing agent material according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) The second lithium source includes at least one of lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium dihydrogen phosphate, lithium chloride, lithium acetate and lithium carbonate; (2) The temperature of the second sintering treatment is 750~900℃, and the holding time of the second sintering treatment is 10~25h; (3) The heating rate of the second sintering treatment is 1~3℃ / min, and the second sintering treatment is carried out under protective gas conditions.

5. The method for preparing the positive electrode lithium replenishing agent material according to claim 1, characterized in that, It includes at least one of the following features (1) to (4): (1) The second carbon source includes an organic carbon source and / or an inorganic carbon source; the organic carbon source includes at least one of polyethylene glycol, polypropylene, phenolic resin, epoxy resin, polyimide, polycarbonate, glucose, citric acid and ascorbic acid; the inorganic carbon source includes at least one of conductive carbon black, graphite and carbon nanotubes. (2) The titanium source includes at least one of titanium oxide and titanium tetrachloride; (3) The temperature of the third sintering treatment is 400~600℃, and the holding time of the third sintering treatment is 2~6h; (4) The heating rate of the third sintering treatment is 1~3℃ / min, and the third sintering treatment is carried out under protective gas conditions.

6. A positive electrode lithium replenishing agent material, characterized in that, It is prepared by the method for preparing the positive electrode lithium replenishing agent material according to any one of claims 1 to 5.

7. A positive electrode material, characterized in that, It includes a positive electrode active material and a positive electrode lithium supplement material as described in claim 6; the positive electrode active material includes lithium iron phosphate; the mass of the positive electrode lithium supplement material accounts for 5% to 20% of the mass of the positive electrode active material.

8. A battery, characterized in that, It includes the positive electrode lithium replenishing agent material as described in claim 6 or the positive electrode material as described in claim 7.

9. An electrical appliance, characterized in that, Includes the battery as described in claim 8.

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