Modified iron phosphate material and lithium iron phosphate material, and preparation methods therefor and use thereof

Abstract

The present invention belongs to the technical field of lithium iron phosphate materials, and provides a modified iron phosphate material and a lithium iron phosphate material, and preparation methods therefor and the use thereof. The modified iron phosphate material is integrally in a sheet shape and comprises zirconium phosphate of a lamellar structure, wherein elemental silver and lithium oxide are loaded between lamellas of the zirconium phosphate, and iron phosphate is formed on the outer surface of the zirconium phosphate. The modified iron phosphate material can be further prepared into a lithium iron phosphate material for use in a battery, and can improve the rate capability, coulombic efficiency, capacity and conductivity of the battery. The preparation methods for the modified iron phosphate material and the lithium iron phosphate material are simple and can realize industrial production.

Description

A modified iron phosphate material, lithium iron phosphate material and preparation method and application thereof Technical Field

[0001] The present disclosure relates to the technical field of lithium iron phosphate materials, and in particular to a modified iron phosphate material, a lithium iron phosphate material, and a preparation method and application thereof. Background Art

[0002] Since their introduction, lithium-ion batteries have seen rapid growth and adoption due to their high specific energy, long lifespan, and pollution-free properties. Their applications have gradually shifted from traditional digital products to power supplies, continuing their positive growth trajectory. The performance of cathode materials directly impacts the performance of lithium-ion batteries, and their cost also directly determines the cost of the battery. Therefore, the research and development of cathode materials for lithium batteries is crucial for improving their performance.

[0003] The low electronic conductivity and ion mobility of LiFePO4 hinder its large-scale application in high-power and low-temperature environments. Furthermore, batteries currently made from lithium iron phosphate exhibit poor performance in terms of first-cycle coulombic efficiency and battery capacity.

[0004] In view of this, the present disclosure is proposed.

[0005] Summary of the Invention

[0006] The purpose of the present disclosure includes providing a modified iron phosphate material, a lithium iron phosphate material, and a preparation method and application thereof to solve or improve the above-mentioned technical problems.

[0007] The present disclosure can be implemented as follows:

[0008] In a first aspect, the present disclosure provides a modified iron phosphate material, which is in the form of a sheet as a whole. The modified iron phosphate material includes zirconium phosphate with a lamellar structure, wherein elemental silver and lithium oxide are loaded between the layers of the zirconium phosphate, and iron phosphate is formed on the outer surface of the zirconium phosphate.

[0009] In an optional embodiment, the modified ferric phosphate material has at least one of the following characteristics:

[0010] Feature 1: The diameter of the modified iron phosphate material is 1μm-2μm;

[0011] Feature 2: The thickness of the modified iron phosphate material is 180nm-220nm.

[0012] In a second aspect, the present disclosure provides a method for preparing a modified iron phosphate material as described in the aforementioned embodiment, comprising the following steps: mixing a zirconium phosphate precursor loaded with silver and organic lithium between layers with an iron source and a phosphate source in a solution system to obtain iron phosphate with zirconium phosphate as the core; and calcining the above-mentioned iron phosphate in a reducing atmosphere to obtain a modified iron phosphate material.

[0013] In an optional embodiment, the ratio of the zirconium phosphate precursor to the iron source is 2 g:1 mol to 5 g:1 mol; and / or the molar ratio of the phosphate in the phosphate source to the iron ion in the iron source is 0.98:1 to 1.05:1.

[0014] In an alternative embodiment, the iron ions in the iron source are ferric ions.

[0015] In an alternative embodiment, the iron source comprises at least one of ferric nitrate and ferric chloride.

[0016] In an alternative embodiment, the phosphate source includes at least one of ammonium hydrogen phosphate, ammonium phosphate, and ammonium dihydrogen phosphate.

[0017] In an optional embodiment, the mixing reaction includes at least one of the following features:

[0018] Feature 1: The reaction pH is 1.2-2.2;

[0019] Feature 2: Reaction temperature is 60℃-90℃;

[0020] Feature 3: Reaction time is 2h-5h;

[0021] Feature 4: The reaction is carried out under stirring conditions.

[0022] In an optional embodiment, the pH adjuster used to adjust the pH value includes at least one of ammonia, NaOH and urea;

[0023] And / or, the stirring speed is 500 rpm-900 rpm.

[0024] In an optional embodiment, the preparation of the zirconium phosphate precursor includes: mixing and reacting silver-loaded zirconium phosphate and organic lithium under acidic conditions.

[0025] In an alternative embodiment, the molar ratio of the organolithium to the silver-loaded zirconium phosphate is 5:100 to 10:100.

[0026] In an alternative embodiment, the organolithium includes at least one of lithium hydroxypyruvate hydrate, lithium citrate, lithium salicylate, and lithium octanoate.

[0027] In an alternative embodiment, the acidic conditions are provided by hydrochloric acid.

[0028] In an alternative embodiment, the preparation of the silver-loaded zirconium phosphate comprises mixing a silver source, a layered zirconium phosphate, and a gap adjuster under acidic conditions.

[0029] In an optional embodiment, the layered zirconium phosphate has at least one of the following characteristics:

[0030] Feature 1: The diameter of the layered zirconium phosphate is 200nm-600nm;

[0031] Feature 2: The thickness of the layered zirconium phosphate is 20nm-50nm.

[0032] In an optional embodiment, the mass ratio of the silver source to the layered zirconium phosphate is 0.1:100 to 3:100.

[0033] In an alternative embodiment, the molar ratio of the gap adjuster to the silver element in the silver source is 3:1 to 6:1.

[0034] In an alternative embodiment, the gap adjuster includes at least one of methylamine, ethylamine, butylamine, and tetrabutylammonium bromide.

[0035] In an alternative embodiment, the acidic conditions during the preparation of the silver-loaded zirconium phosphate are provided by nitric acid.

[0036] In an optional embodiment, the calcination temperature is 500° C.-800° C.; and / or the calcination time is 3 h-6 h.

[0037] In a third aspect, the present disclosure provides a lithium iron phosphate material, the raw materials for preparing the lithium iron phosphate material include the modified iron phosphate material of the aforementioned embodiment.

[0038] In an optional embodiment, the lithium iron phosphate material is carbon-coated lithium iron phosphate.

[0039] In a fourth aspect, the present disclosure provides a method for preparing the lithium iron phosphate material as described in the aforementioned embodiment, comprising the following steps: mixing a modified iron phosphate material, a lithium source, and a carbon source, and calcining the mixture.

[0040] In an optional embodiment, the modified ferric phosphate material is mixed with a lithium source and a carbon source and calcined.

[0041] In a fifth aspect, the present disclosure provides a battery, the raw materials for preparing the battery include the lithium iron phosphate material of the aforementioned embodiment.

[0042] The beneficial effects of the present disclosure include:

[0043] In the present disclosure, the flaky modified iron phosphate material can shorten the lithium ion transmission path. By introducing silver and lithium between the layers of zirconium phosphate, elemental silver can increase the activity of lithium oxide as a lithium supplement. At the same time, since elemental silver has better conductivity, the electrical conductivity of the material can be improved. In addition, the layered structure of layered zirconium phosphate itself is conducive to the transmission of lithium ions, improves the transmission speed of lithium ions, and the layered structure also helps to induce the formation of flaky iron phosphate. The present disclosure not only effectively utilizes the interlayer space of zirconium phosphate by placing lithium oxide in the intercalation layer of zirconium phosphate, but also forms iron phosphate on the outer surface of zirconium phosphate, thereby effectively avoiding the contact of lithium oxide in the layer with air, which is conducive to reducing the generation of residual alkali by-products.

[0044] By preparing the modified iron phosphate material into lithium iron phosphate and further preparing it into a battery, the performance of the battery in terms of the first-cycle coulombic efficiency and battery capacity can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0046] FIG1 is a SEM image of the modified iron phosphate material prepared in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0047] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0048] The modified iron phosphate material, lithium iron phosphate material, and preparation methods and applications of the present invention are described in detail below.

[0049] The present disclosure provides a modified iron phosphate material, which is in a flaky shape. The modified iron phosphate material includes zirconium phosphate with a lamellar structure, wherein elemental silver and lithium oxide are loaded between the layers of the zirconium phosphate, and iron phosphate is formed on the outer surface of the zirconium phosphate.

[0050] The above-mentioned elemental silver can improve the conductivity of the modified iron phosphate material; moreover, the above-mentioned elemental silver can also promote lithium oxide to play its role as a lithium replenishing agent, thereby improving the lithium replenishing capacity of the material.

[0051] In some embodiments, the elemental silver is nanosized.

[0052] In the present disclosure, the sheet-like modified iron phosphate material can shorten the lithium ion transmission path. By introducing silver and lithium between the layers of zirconium phosphate, elemental silver can increase the activity of lithium oxide as a lithium supplement. At the same time, since elemental silver has good conductivity, it can improve the conductivity of the material. In addition, the layered structure of layered zirconium phosphate is conducive to the transmission of lithium ions, increases the transmission speed of lithium ions, and the layered structure also helps to induce the formation of sheet-like iron phosphate. It should be noted that lithium oxide, as a lithium supplement of binary lithium compounds, easily absorbs moisture and CO2 in the air and degenerates into LiOH and Li2CO3. Contact with water will generate highly alkaline lithium hydroxide. Therefore, lithium oxide is usually used as a lithium supplement. It needs to be separated from the air by a carbon layer or the like; and the present disclosure places it in the intercalation layer of zirconium phosphate, which not only effectively utilizes the interlayer space of zirconium phosphate, but also forms iron phosphate on the outer surface of zirconium phosphate, thereby effectively avoiding the contact of lithium oxide in the layer with air, which is conducive to reducing the generation of residual alkali byproducts.

[0053] In some embodiments, the diameter of the modified ferric phosphate material may be 1 μm-2 μm, such as 1 μm, 1.5 μm or 2 μm, etc. In some embodiments, the thickness of the modified ferric phosphate material may be 180 nm-220 nm, such as 180 nm, 190 nm, 200 nm, 210 nm or 220 nm, etc.

[0054] Accordingly, the present disclosure also provides a method for preparing the above-mentioned modified iron phosphate material, which may include the following steps: mixing a zirconium phosphate precursor loaded with silver and organic lithium between layers with an iron source and a phosphate source in a solution system to obtain iron phosphate with zirconium phosphate as the core; and then placing it in a reducing atmosphere and calcining it to obtain a modified iron phosphate material.

[0055] In the present disclosure, the preparation of the zirconium phosphate precursor may include: mixing and reacting silver-loaded zirconium phosphate and organic lithium under acidic conditions.

[0056] The preparation of the silver-loaded zirconium phosphate may include: mixing a silver source, layered zirconium phosphate, and a gap adjuster under acidic conditions.

[0057] The diameter of the layered zirconium phosphate may be 200 nm to 600 nm, such as 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm or 600 nm, etc. The thickness of the layered zirconium phosphate may be 20 nm to 50 nm, such as 20 nm, 25 nm, 30 nm, 35 nm, 40 nm or 50 nm, etc.

[0058] The mass ratio of the silver source to the layered zirconium phosphate can be 0.1:100 to 3:100, such as 0.1:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100 or 3:100, or any other value within the range of 0.1:100 to 3:100.

[0059] The molar ratio of the gap adjuster to the silver element in the silver source can be 3:1 to 6:1, such as 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, or 6:1, or any other value within the range of 3:1 to 6:1. The gap adjuster used can illustratively, but not limited to, include at least one of methylamine, ethylamine, butylamine, and tetrabutylammonium bromide.

[0060] In some embodiments, the acidic condition in the process of preparing the silver-loaded zirconium phosphate can be provided by a nitric acid solution, the concentration of which can be 1 mol / L. In other embodiments, other acidic substances can also be used.

[0061] In some specific embodiments, the preparation of silver-loaded zirconium phosphate can be achieved by mixing silver and layered zirconium phosphate in a preset mass ratio in a 1 mol / L nitric acid solution at room temperature, adding a preset amount of a gap regulator, stirring for 2 hours, filtering, washing, and drying to obtain the silver-loaded zirconium phosphate.

[0062] As mentioned above, the layered structure of zirconium phosphate is rich in hydroxyl groups. When it is mixed with silver in a solution under stirring conditions, the silver ions can be replaced with the hydroxyl groups in the zirconium phosphate, that is, the hydrogen in the hydroxyl groups is replaced with silver ions, thereby obtaining zirconium phosphate loaded with silver ions.

[0063] In the present disclosure, during the preparation of the zirconium phosphate precursor, the molar ratio of the organic lithium to the silver-loaded zirconium phosphate can be 5:100 to 10:100, such as 5:100, 5.5:100, 6:100, 6.5:100, 7:100, 7.5:100, 8:100, 8.5:100, 9:100, 9.5:100 or 10:100, or any other value within the range of 5:100 to 10:100.

[0064] The organic lithium may illustratively but not limitatively include at least one of lithium hydroxypyruvate hydrate, lithium citrate, lithium salicylate and lithium octanoate.

[0065] In some embodiments, the acidic condition during the preparation of the zirconium phosphate precursor may be provided by hydrochloric acid, and the concentration of the hydrochloric acid solution may be 1 mol / L. In other embodiments, other acidic substances may also be used.

[0066] In some specific embodiments, the zirconium phosphate precursor can be prepared by placing silver-loaded zirconium phosphate in deionized water, adding 1 mol / L hydrochloric acid, adding organic lithium, stirring continuously for 1 hour, filtering, and washing to obtain the zirconium phosphate precursor.

[0067] As described above, organic lithium is reacted with zirconium phosphate loaded with silver. The organic lithium can interact with or attract the hydroxyl groups between the zirconium phosphate layers, thereby introducing it into the zirconium phosphate layers, so that there are both silver ions and organic lithium between the zirconium phosphate layers.

[0068] In the present disclosure, the usage ratio of the zirconium phosphate precursor to the iron source can be 2g:1mol to 5g:1mol, such as 2g:1mol, 2.5g:1mol, 3g:1mol, 3.5g:1mol, 4g:1mol, 4.5g:1mol or 5g:1mol, or it can be any other value within the range of 2g:1mol to 5g:1mol.

[0069] The molar ratio of phosphate in the phosphate source to iron ions in the iron source can be 0.98:1 to 1.05:1, such as 0.98:1, 0.99:1, 1.00:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1, or any other value within the range of 0.98:1 to 1.05:1.

[0070] In some embodiments, the iron ions in the iron source may be ferric ions. In other embodiments, the iron ions in the iron source may be ferrous ions. If ferrous ions are used, an oxidizing agent is required to oxidize the ferrous ions to ferric ions. In some specific embodiments, the iron source may be, by way of example but not limitation, at least one of ferric nitrate and ferric chloride.

[0071] The phosphate source may illustratively but not limitatively include at least one of ammonium hydrogen phosphate, ammonium phosphate, and ammonium dihydrogen phosphate.

[0072] In some embodiments, the iron source may be prepared into an iron source solution, and the phosphate source may be prepared into a phosphate solution. Then, the zirconium phosphate precursor loaded with silver and organic lithium between layers is mixed with the iron source solution and the phosphate solution for reaction.

[0073] The concentration of the iron source solution can be, by way of example but not limitation, 1 mol / L, and the concentration of the phosphate solution can be, by way of example but not limitation, 1 mol / L. It should be noted that the concentrations of the iron source solution and the phosphate solution can be adjusted accordingly based on actual conditions and are not further limited herein.

[0074] For reference, the pH value of the reaction between the above-mentioned zirconium phosphate precursor loaded with silver and organic lithium between the layers and the iron source and the phosphate source can be 1.2-2.2, such as 1.2, 1.4, 1.6, 1.8, 2.0 or 2.2, or any other value within the range of 1.2-2.2. Exemplarily, the pH adjuster used to adjust the pH value may include at least one of ammonia water, NaOH and urea. In some specific embodiments, ammonia water can be used to adjust the pH value. The concentration of the ammonia water used can be, for example, 1 mol / L, and can also be adjusted according to actual needs.

[0075] The reaction temperature of the zirconium phosphate precursor loaded with silver and organic lithium between the above layers with the iron source and the phosphate source can be 60°C-90°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, or any other value within the range of 60°C-90°C.

[0076] The reaction temperature of the above-mentioned zirconium phosphate precursor loaded with silver and organic lithium between the layers with the iron source and the phosphate source can be 2h-5h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, or any other value within the range of 2h-5h.

[0077] In some embodiments, the reaction of the silver- and organolithium-loaded zirconium phosphate precursor with the iron source and the phosphate source is performed under stirring. The stirring speed may be, for example, 500 rpm to 900 rpm, such as 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, or 900 rpm.

[0078] After the reaction is completed, iron phosphate with zirconium phosphate as the core can be obtained by filtering, washing and drying.

[0079] As mentioned above, due to the large negative charge density on the surface of zirconium phosphate, it can adsorb trivalent iron ions, inducing phosphate to react with it to form iron phosphate, which can form iron phosphate with zirconium phosphate loaded with silver and organic lithium between the layers as the core.

[0080] In the present disclosure, the calcination temperature may be 500°C-800°C, such as 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, or any other value within the range of 500°C-800°C.

[0081] The calcination time can be 3 h to 6 h, such as 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, or any other value within the range of 3 h to 6 h.

[0082] The reducing atmosphere used for calcination may be, for example but not limited to, a carbon monoxide atmosphere or a hydrogen atmosphere.

[0083] Continuing from the above, the calcination process reduces the silver ions in the zirconium phosphate to elemental silver in situ, and the organic lithium is calcined to produce lithium oxide, thereby forming elemental silver and lithium oxide between the zirconium phosphate layers. The metallic silver nanoparticles formed by the calcination process are sufficiently small to enable the lithium oxide to function as a lithium replenisher, improving its lithium replenishment capacity. The metallic silver also improves the material's electrical conductivity.

[0084] In addition, the present disclosure also provides a lithium iron phosphate material, the raw materials for preparing the lithium iron phosphate material include the above-mentioned modified iron phosphate material.

[0085] In some embodiments, the lithium iron phosphate material is carbon-coated lithium iron phosphate.

[0086] Accordingly, the present disclosure also provides a method for preparing the above-mentioned lithium iron phosphate material, which may include the following steps: mixing the modified iron phosphate material, a carbon source, and a lithium source, and calcining the mixture.

[0087] When the lithium iron phosphate material has a carbon coating layer, the modified iron phosphate material is mixed with a lithium source and a carbon source and then calcined during preparation.

[0088] For reference, the lithium source may be, for example but not limited to, lithium carbonate, and the carbon source may be, for example but not limited to, glucose.

[0089] In some specific embodiments, the lithium iron phosphate material can be prepared by referring to the following method: the modified iron phosphate material provided by the present disclosure is mixed with Li2CO3 in a molar ratio of 1.02:1, and glucose is added, and anhydrous ethanol is added, and the glucose is 5% of the total mass of the modified iron phosphate material and Li2CO3. After ball milling for 4 hours, it is dried at 80°C for 12 hours, taken out and ground evenly again, and then placed under nitrogen flow protection, and calcined at 650°C for 6 hours to obtain a carbon-coated lithium iron phosphate material. It should be noted that in other embodiments, the lithium source, carbon source, and solvent commonly used in the preparation of lithium iron phosphate materials can also be used, and the process conditions of the preparation process can also be adjusted according to actual conditions.

[0090] Furthermore, the present disclosure also provides a battery, the raw materials for preparing the battery include the above-mentioned lithium iron phosphate material.

[0091] It should be noted that the preparation of the battery can refer to the conventional technology of preparing batteries using lithium iron phosphate material as the positive electrode material, and no further details or limitations are given here.

[0092] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0093] Example 1

[0094] This embodiment provides a modified iron phosphate material, the preparation process of which includes:

[0095] S1: In a 1 mol / L nitric acid solution, silver and layered zirconium phosphate were mixed in a mass ratio of 1:100, and ethylamine was added as a gap regulator. The molar ratio of ethylamine to silver was 4:1. The mixture was stirred at room temperature for 2 h. After filtration, washing, and drying, silver-loaded zirconium phosphate was obtained.

[0096] S2: Place the above-mentioned silver-loaded zirconium phosphate in deionized water, add 1 mol / L hydrochloric acid, mix lithium salicylate and silver-loaded zirconium phosphate in a molar ratio of 7:100, and continue stirring for 1 hour. After filtering, washing, and drying, a zirconium phosphate precursor with silver and organic lithium loaded between layers is obtained.

[0097] S3: Place a zirconium phosphate precursor loaded with silver and organic lithium in water, add 1 mol / L ferric nitrate solution, the mass molar ratio of zirconium phosphate to ferric nitrate is 4g:1mol, stir evenly, add 1 mol / L ammonium hydrogen phosphate solution, and ensure that the molar ratio of phosphate and trivalent iron is 1:1. Adjust the pH to 1.2-2.2 with ammonia water, react for 4 hours at a stirring speed of 700 rpm and a reaction temperature of 85°C, filter the precipitate, wash, and dry to obtain iron phosphate with zirconium phosphate as the core.

[0098] S4: calcining the iron phosphate with the zirconium phosphate as the core in a hydrogen atmosphere at 700° C. for 6 h to obtain a modified iron phosphate material, the SEM image of which is shown in FIG1 .

[0099] The modified iron phosphate material has a diameter of about 1.5 μm and a thickness of about 200 nm.

[0100] Example 2

[0101] The difference between this embodiment and embodiment 1 is that in S1, the mass ratio of silver to layered zirconium phosphate is 3:100. In S2, the molar ratio of lithium salicylate to silver-loaded zirconium phosphate is 5:100.

[0102] The remaining steps and conditions are the same as in Example 1.

[0103] Example 3

[0104] The difference between this embodiment and embodiment 1 is that in S1, the mass ratio of silver to layered zirconium phosphate is 0.1:100. In S2, the molar ratio of lithium salicylate to silver-loaded zirconium phosphate is 10:100.

[0105] The remaining steps and conditions are the same as in Example 1.

[0106] Example 4

[0107] The difference between this embodiment and embodiment 1 is that in S3, the mass molar ratio of zirconium phosphate to ferric nitrate is 2g:1mol.

[0108] The remaining steps and conditions are the same as in Example 1.

[0109] Example 5

[0110] The difference between this embodiment and embodiment 1 is that in S3, the mass molar ratio of zirconium phosphate to ferric nitrate is 5g:1mol.

[0111] The remaining steps and conditions are the same as in Example 1.

[0112] Example 6

[0113] This embodiment provides a modified iron phosphate material, the preparation process of which includes:

[0114] S1: In a 1 mol / L nitric acid solution, silver and layered zirconium phosphate were mixed in a mass ratio of 1.5:100, and tetrabutylammonium bromide was added as a gap regulator. The molar ratio of tetrabutylammonium bromide to silver was 3:1. The mixture was stirred at room temperature for 2 h. After filtration, washing, and drying, silver-loaded zirconium phosphate was obtained.

[0115] S2: Place the above-mentioned silver-loaded zirconium phosphate in deionized water, add 1 mol / L hydrochloric acid, mix lithium citrate and silver-loaded zirconium phosphate in a molar ratio of 5:100, and continue stirring for 1 hour. After filtering, washing, and drying, a zirconium phosphate precursor with silver and organic lithium loaded between layers is obtained.

[0116] S3: Place a zirconium phosphate precursor loaded with silver and organic lithium in water, add 1 mol / L ferric chloride solution, the mass molar ratio of zirconium phosphate and ferric chloride is 3.5g:1mol, stir evenly, add 1 mol / L ammonium phosphate solution, and ensure that the molar ratio of phosphate and trivalent iron is 0.98:1. Adjust the pH to 1.2-2.2 with NaOH solution, react for 5 hours at a stirring speed of 500 rpm and a reaction temperature of 60°C, filter the precipitate, wash, and dry to obtain iron phosphate with zirconium phosphate as the core.

[0117] S4: calcining the iron phosphate with the zirconium phosphate as the core in a carbon monoxide atmosphere at 500° C. for 6 hours to obtain a modified iron phosphate material.

[0118] Example 7

[0119] This embodiment provides a modified iron phosphate material, the preparation process of which includes:

[0120] S1: In a 1 mol / L nitric acid solution, silver and layered zirconium phosphate were mixed in a mass ratio of 2:100, and butylamine was added as a gap regulator. The molar ratio of butylamine to silver was 6:1. The mixture was stirred at room temperature for 2 h. After filtration, washing, and drying, silver-loaded zirconium phosphate was obtained.

[0121] S2: Place the above-mentioned silver-loaded zirconium phosphate in deionized water, add 1 mol / L hydrochloric acid, mix lithium octanoate and silver-loaded zirconium phosphate in a molar ratio of 10:100, and continue stirring for 1 hour. After filtering, washing, and drying, a zirconium phosphate precursor with silver and organic lithium loaded between layers is obtained.

[0122] S3: Place a zirconium phosphate precursor loaded with silver and organic lithium in water, add 1 mol / L ferric chloride solution, the mass molar ratio of zirconium phosphate to ferric chloride is 4.5g:1mol, stir evenly, add 1 mol / L ammonium dihydrogen phosphate solution, and ensure that the molar ratio of phosphate to trivalent iron is 1.05:1. Adjust the pH to 1.2-2.2 with urea solution, react for 2 hours at a stirring speed of 900 rpm and a reaction temperature of 90°C, filter the precipitate, wash, and dry to obtain iron phosphate with zirconium phosphate as the core.

[0123] S4: calcining the iron phosphate with the zirconium phosphate as the core in a hydrogen atmosphere at 800° C. for 6 hours to obtain a modified iron phosphate material.

[0124] Example 8

[0125] This embodiment provides a carbon-coated lithium iron phosphate material, and its preparation process is as follows: the modified iron phosphate material provided in Example 1 is mixed with Li2CO3 in a molar ratio of 1.02:1, and glucose is added, and anhydrous ethanol is added, and the glucose is 5% of the total mass of the modified iron phosphate material and Li2CO3. After ball milling for 4 hours, it is dried at 80°C for 12 hours, taken out and ground evenly again, and then placed under nitrogen flow protection and calcined at 650°C for 6 hours.

[0126] Comparative Example 1

[0127] The difference between this comparative example and Example 1 is:

[0128] S1: In a 1 mol / L nitric acid solution, silver and layered zirconium phosphate were mixed in a mass ratio of 1:100, stirred at room temperature for 2 h, and filtered, washed, and dried to obtain silver-loaded zirconium phosphate.

[0129] S2: Same as Example 1.

[0130] S3: Same as Example 1.

[0131] S4: Same as Example 1.

[0132] That is, no gap regulator was used in this comparative example.

[0133] Comparative Example 2

[0134] The difference between this comparative example and Example 1 is:

[0135] S1: None.

[0136] S2: None.

[0137] S3: Mix 1 mol / L ferric nitrate solution and 1 mol / L ammonium hydrogen phosphate solution to ensure that the molar ratio of phosphate to ferric iron is 1:1, adjust the pH to 1.2-2.2 with aqueous ammonia, and react at a stirring speed of 700 rpm and a reaction temperature of 85°C for 4 hours. Filter the precipitate, wash, and dry.

[0138] S4: Same as Example 1.

[0139] That is, zirconium phosphate was not used in this comparative example.

[0140] Comparative Example 3

[0141] The difference between this comparative example and Example 1 is:

[0142] S1: None.

[0143] S2: Place nano-layered zirconium phosphate in deionized water, add 1 mol / L hydrochloric acid, mix lithium salicylate and zirconium phosphate in a molar ratio of 7:100, and continue stirring for 1 hour. After filtering, washing, and drying, a zirconium phosphate precursor with organic lithium loaded between layers is obtained.

[0144] S3 is the same as Example 1.

[0145] S4 is the same as Example 1.

[0146] That is, no silver was used in this comparative example.

[0147] Comparative Example 4

[0148] The difference between this comparative example and Example 1 is:

[0149] S1: Same as Example 1.

[0150] S2: None.

[0151] S3: Place the silver-loaded zirconium phosphate in water, then add 1 mol / L ferric nitrate solution, the mass molar ratio of zirconium phosphate to ferric nitrate is 4g:1mol, stir evenly and add 1 mol / L ammonium hydrogen phosphate solution, while ensuring that the molar ratio of phosphate and trivalent iron is 1:1, adjust the pH to 1.2-2.2 with ammonia water, stir at 700 rpm, reaction temperature at 85°C, and react for 4 hours.

[0152] S4: Same as Example 1.

[0153] That is, no organic lithium was used in this comparative example.

[0154] Test example

[0155] The modified iron phosphate materials of Examples 1-7 and the iron phosphate materials of Comparative Examples 1-4 were prepared into carbon-coated lithium iron phosphate materials according to the method and conditions of Example 8, and were further prepared into button batteries according to the following methods: a binder (polyvinylidene fluoride), a conductive agent (acetylene black) and LiFePO4 were mixed in a mass ratio of 1:1:8, N-methylpyrrolidone was added to form a slurry, and the slurry was evenly coated on an aluminum foil. After vacuum drying, the slurry was taken out, rolled and punched into circular electrode sheets, and the button batteries were assembled in a glove box.

[0156] The constant current charge and discharge cycle test of the above button batteries was carried out, and the charge and discharge voltage was 2.5-4.2V.

[0157] In addition, the rate specific capacity at 1C, 3C and 10C, as well as the first discharge specific capacity and first coulombic efficiency at 1C rate were tested; and the electrical conductivity of the material was tested by direct voltammetry.

[0158] The test results are shown in Table 1.

[0159] Table 1 Test results

[0160] By comparing Example 1 and Example 2, it can be seen that the increase in silver loaded on zirconium phosphate will increase conductivity, but the reduction in the loading amount of organic lithium will reduce the lithium replenishment effect, resulting in a relative decrease in the first-week coulombic efficiency and battery capacity.

[0161] By comparing Example 1 and Example 3, it can be seen that the conductivity is relatively reduced as the silver loading of zirconium phosphate is reduced, but the lithium replenishment effect is improved due to the increased loading of organic lithium, so that the first-week coulombic efficiency and battery capacity are relatively improved.

[0162] By comparing Example 1 and Example 4, it can be seen that a decrease in the content of zirconium phosphate will relatively reduce the conductivity and lithium replenishment effect.

[0163] By comparing Example 1 and Example 5, it can be seen that an increase in the zirconium phosphate content will reduce the capacity.

[0164] By comparing Example 1 and Comparative Example 1, it can be seen that if the gap regulator is not used, the interlayer intercalation material will be reduced, and the corresponding battery performance effect will be poor.

[0165] By comparing Example 1 and Comparative Example 2, it can be seen that without using zirconium phosphate, the corresponding battery performance is poor.

[0166] By comparing Example 1 and Comparative Example 3, it can be seen that without using silver, the conductivity is low and the lithium replenishment effect is poor;

[0167] By comparing Example 1 and Comparative Example 4, it can be seen that: using only silver ions without adding organic lithium, although the conductivity is good, the first coulombic efficiency is poor. Industrial Applicability

[0168] The flaky modified iron phosphate material provided in this disclosure has high electrical conductivity and lithium ion transport speed, reducing the generation of residual alkali. The modified iron phosphate material can be used to prepare a lithium iron phosphate cathode material and further fabricate a battery, thereby improving the battery's performance in terms of initial coulombic efficiency and battery capacity.

Claims

1. A modified iron phosphate material, characterized in that, The modified iron phosphate material is in a flaky shape as a whole. The modified iron phosphate material includes zirconium phosphate with a lamellar structure, and elemental silver and lithium oxide are loaded between the layers of the zirconium phosphate, and iron phosphate is formed on the outer surface of the zirconium phosphate.

2. The iron phosphate material according to claim 1, wherein The modified iron phosphate material has at least one of the following characteristics: Characteristic 1: The diameter of the modified iron phosphate material is 1 μm - 2 μm; Characteristic 2: The thickness of the modified iron phosphate material is 180 nm - 220 nm.

3. A method for preparing the modified iron phosphate material as described in claim 1 or 2, characterized in that, It includes the following steps: Mix and react a zirconium phosphate precursor loaded with silver and organolithium with an iron source and a phosphate source in a solution system to obtain iron phosphate with zirconium phosphate as the core; calcine the iron phosphate with zirconium phosphate as the core in a reducing atmosphere to obtain the modified iron phosphate material.

4. The preparation method according to claim 3, wherein, The dosage ratio of the zirconium phosphate precursor to the iron source is 2 g:1 mol to 5 g:1 mol; and / or, the molar ratio of phosphate in the phosphate source to iron ions in the iron source is 0.98:1 to 1.05:

1.

5. The preparation method according to claim 3 or 4, characterized in that, The iron ions in the iron source are trivalent iron ions.

6. The preparation method according to claim 5, characterized in that, The iron source includes at least one of iron nitrate and iron chloride.

7. The preparation method according to any one of claims 3-6, characterized in that, The phosphate source includes at least one of ammonium hydrogen phosphate, ammonium phosphate, and ammonium dihydrogen phosphate.

8. The preparation method according to any one of claims 3-7, characterized in that, The mixing reaction includes at least one of the following characteristics: Characteristic 1: The reaction pH value is 1.2 - 2.2; Characteristic 2: The reaction temperature is 60°C - 90°C; Characteristic 3: The reaction time is 2 h - 5 h; Characteristic 4: The reaction is carried out under stirring conditions.

9. The preparation method according to claim 8, characterized in that, The pH regulator used to adjust the pH value includes at least one of ammonia water, NaOH, and urea; and / or, the stirring speed is 500 rpm - 900 rpm.

10. The preparation method according to any one of claims 4-9, characterized in that, The preparation of the zirconium phosphate precursor includes: mixing and reacting zirconium phosphate loaded with silver and organolithium under acidic conditions.

11. The preparation method according to claim 10, characterized in that, The molar ratio of the organolithium to the zirconium phosphate loaded with silver is 5:100 to 10:

100.

12. The preparation method according to claim 10 or 11, characterized in that, The organolithium includes at least one of lithium hydroxy pyruvate hydrate, lithium citrate, lithium salicylate, and lithium octanoate.

13. The preparation method according to claim 10, characterized in that, The acidic condition is provided by hydrochloric acid.

14. The preparation method according to any one of claims 10-13, characterized in that, The preparation of the zirconium phosphate loaded with silver includes: mixing a silver source, layered zirconium phosphate, and an interlayer regulator under acidic conditions.

15. The preparation method according to claim 14, characterized in that, The layered zirconium phosphate has at least one of the following characteristics: Characteristic 1: The diameter of the layered zirconium phosphate is 200 nm - 600 nm; Characteristic 2: The thickness of the layered zirconium phosphate is 20 nm - 50 nm.

16. The preparation method according to claim 14 or 15, characterized in that, The mass ratio of the silver source to the layered zirconium phosphate is 0.1:100 to 3:

100.

17. The preparation method according to any one of claims 14-16, characterized in that, The molar ratio of the interlayer regulator to silver element in the silver source is 3:1 to 6:

1.

18. The preparation method according to any one of claims 14-17, characterized in that, The interlayer regulator includes at least one of methylamine, ethylamine, butylamine, and tetrabutylammonium bromide.

19. The preparation method according to any one of claims 14-18, characterized in that, The acidic condition in the process of preparing the zirconium phosphate loaded with silver is provided by nitric acid.

20. The preparation method according to any one of claims 3-19, characterized in that, The calcination temperature is 500°C - 800°C; and / or, the calcination time is 3 h - 6 h.

21. A lithium iron phosphate material, characterized in that, The preparation raw materials of the lithium iron phosphate material include the modified iron phosphate material described in claim 1 or 2.

22. The lithium iron phosphate material according to claim 21, characterized in that, The lithium iron phosphate material is carbon-coated lithium iron phosphate.

23. A method for preparing the lithium iron phosphate material as described in claim 21 or 22, characterized in that, It includes the following steps: Mix the modified iron phosphate material with a lithium source and roast.

24. The preparation method according to claim 23, characterized in that, Mix the modified iron phosphate material with a lithium source and a carbon source, and then calcine.

25. A battery, characterized in that, The raw materials for preparing the battery include the lithium iron phosphate material described in claim 21 or 22.

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