A method for preparing lithium iron phosphate using ferrous phosphide as raw material and the product thereof

Abstract

The application discloses a method for preparing lithium iron phosphate by taking ferrous phosphide as raw material and a product, relates to the technical field of green and sustainable development of the steel industry and new energy materials, and comprises the following steps: preparing ferrous phosphide by taking steel slag and phosphorus tailings as raw materials, using nitric acid to leach the ferrous phosphide, controlling the pH of leaching to be 2.5-3, and controlling the leaching time to be 2-5 hours; adding phosphoric acid in the leaching solution, controlling the Fe / P molar ratio in the solution after adding the phosphoric acid to be 0.6-0.8; filtering the leaching solution, and roasting the filtered precipitate in an air atmosphere at 700-900 DEG C for 10-12 hours; mixing the roasted product with lithium hydroxide and glucose, and mixing the raw materials according to the molar ratio of FePO4:LiOH.H2O:C6H 12 O6 being 1:1.06:0.18-0.21; pressing the mixed raw materials into blocks, and roasting the blocks under an inert atmosphere at 700 DEG C for 10 hours, so that lithium iron phosphate is obtained. The application realizes bidirectional green development of the steel industry and the new energy industry by preparing lithium iron phosphate materials by using steel slag recovery products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of green and sustainable development of the steel industry and new energy materials, and particularly relates to a method for preparing lithium iron phosphate from ferrous phosphide as a raw material and a product. BACKGROUND

[0002] In recent years, with the rapid development of new energy automobile industry, lithium iron phosphate (LiFePO4) is widely used in new generation lithium ion batteries as a positive electrode material without using cobalt, nickel and other rare metals.

[0003] In addition, the preparation of traditional lithium iron phosphate uses high-grade phosphate rock as a raw material, and the production process is long and energy-consuming. The depletion of high-grade phosphate rock further increases the supply risk and ecological cost of lithium iron phosphate. SUMMARY

[0004] In view of the above-mentioned deficiencies in the existing lithium iron phosphate production process, the purpose of the present application is to provide a method for preparing lithium iron phosphate from ferrous phosphide as a raw material, and a product. First, steel slag and phosphate tailings are used as raw materials, the mixture ratio is controlled, the calcination time and temperature are adjusted, and high-purity ferrous phosphide is directly prepared by using a one-step carbon thermal reduction method combined with a multi-stage wet magnetic separation method. Then, lithium iron phosphate is prepared from the prepared ferrous phosphide as a raw material by combining acid leaching with a pyro-reduction method. The process flow is short and the energy consumption is low. The steel slag recovery product is used to prepare lithium iron phosphate materials, realizing the two-way green development of the steel industry and the new energy industry.

[0005] According to the first aspect of the technical scheme of the present application, a method for preparing lithium iron phosphate from ferrous phosphide as a raw material is provided, comprising the following steps:

[0006] S1: preparing ferrous phosphide from steel slag and phosphate tailings, using nitric acid to leach the ferrous phosphide, controlling the pH to be 2.5-3, and the leaching time to be 2-5 hours; adding phosphoric acid in the leaching solution, and controlling the Fe / P molar ratio in the solution after adding the phosphoric acid to be 0.6-0.8;

[0007] S2: filtering the leaching solution obtained in S1, and calcining the filtered precipitate in an air atmosphere at 700-900℃ for 10-12 hours;

[0008] S3: mixing the calcined product obtained in S2 with lithium hydroxide and glucose, and mixing them according to the molar ratio of FePO4:LiOH·H2O:C6H 12 O6 being 1:1.06:0.18-0.21;

[0009] S4: pressing the mixed raw materials in S3 into blocks, and calcining them at 700℃ for 10 hours in an inert atmosphere, thereby obtaining lithium iron phosphate.

[0010] As a preferred scheme of the method for preparing ferrous phosphide by taking steel slag and phosphorus tailings as raw materials according to the application, in the step S1, the preparation method of the ferrous phosphide is as follows:

[0011] S11, mixing the steel slag and the phosphorus tailings, a reducing agent to obtain a mixture;

[0012] S12, after the mixture is pressed and formed, calcination is carried out under an inert gas atmosphere, the calcination temperature is 1200-1300 DEG C, and the calcination time is 4-6 h;

[0013] S13, the product obtained in S12 is cooled to room temperature, and after crushing and magnetic separation, the ferrous phosphide is obtained.

[0014] As a preferred scheme of the method for preparing ferrous phosphide by taking steel slag and phosphorus tailings as raw materials according to the application, in the step S11, the chemical composition of the steel slag is as follows: 41.34wt% CaO, 30.8wt% TFe, 13.45wt% SiO2, 4.88wt% MgO, 2.23wt% P2O5, 2.58wt% Al2O3, 2.84wt% MnO, 0.59wt% TiO2 and 0.78wt% other.

[0015] As a preferred scheme of the method for preparing ferrous phosphide by taking steel slag and phosphorus tailings as raw materials according to the application, in the step S11, the chemical composition of the phosphorus tailings is as follows: 35.45wt% CaO, 1.01wt% TFe, 30.67wt% SiO2, 13.78wt% MgO, 8.97wt% P2O5, 1.36wt% Al2O3, 4.89wt% C, 0.51wt% F, 1.52wt% SO3 and 1.84wt% other.

[0016] As a preferred scheme of the method for preparing ferrous phosphide by taking steel slag and phosphorus tailings as raw materials according to the application, in the step S11, the steel slag and the phosphorus tailings are respectively crushed to below 0.074 mm before mixing.

[0017] As a preferred scheme of the method for preparing ferrous phosphide by taking steel slag and phosphorus tailings as raw materials according to the application, in the step S11, the steel slag and the phosphorus tailings, a reducing agent are mixed in a proportion of 1:1:4 according to the molar ratio of Fe:P:C.

[0018] As a preferred scheme of the method for preparing ferrous phosphide by taking steel slag and phosphorus tailings as raw materials according to the application, in the step S11, the reducing agent is a carbonaceous reducing agent;

[0019] The carbonaceous reducing agent is powdered graphite or activated carbon with a particle size of 10-74 μm.

[0020] As a preferred scheme of the method for preparing ferrous phosphide by using steel slag and phosphorous tailings as raw materials according to the application, in the step S12, the block formed after the mixture is pressed is in a cylindrical shape, a block shape or a spherical shape.

[0021] The cross-sectional diameter of the cylindrical block is 6-10 mm, the maximum diameter of the spherical block is 6-10 mm, and the maximum dimension of the edge length of the block-shaped block is 6-10 mm.

[0022] As a preferred scheme of the method for preparing ferrous phosphide by using steel slag and phosphorous tailings as raw materials according to the application, in the step S12, the inert gas is argon.

[0023] As a preferred scheme of the method for preparing ferrous phosphide by using steel slag and phosphorous tailings as raw materials according to the application, in the step S12, the calcination temperature is 1300 DEG C and the calcination time is 5 h.

[0024] As a preferred scheme of the method for preparing ferrous phosphide by using steel slag and phosphorous tailings as raw materials according to the application, in the step S13, the magnetic separation method is a multi-stage wet magnetic separation method, the magnetic separation strength is 100 mT, the single magnetic separation time is 1 min, and the magnetic separation times is 5.

[0025] As a preferred scheme of the method for preparing ferrous phosphide by using steel slag and phosphorous tailings as raw materials according to the application, in the step S1, the concentration of the nitric acid is 1 mol / L and the concentration of the phosphoric acid is 1 mol / L.

[0026] As a preferred scheme of the method for preparing ferrous phosphide by using steel slag and phosphorous tailings as raw materials according to the application, in the step S2, the calcination temperature is 700 DEG C and the calcination time is 10 h.

[0027] As a preferred scheme of the method for preparing ferrous phosphide by using steel slag and phosphorous tailings as raw materials according to the application, in the step S4, the calcination temperature is 700 DEG C and the calcination time is 10 h.

[0028] According to the second aspect of the technical scheme of the application, a lithium iron phosphate is provided, which is prepared by the method according to any one of the above aspects.

[0029] The application has the following advantages:

[0030] (1) The application uses steel slag and phosphorous tailings as raw materials, controls the proportion of the mixture, adjusts the calcination time and temperature, and directly prepares ferrous phosphide with a purity of more than 85% by using a one-step carbon thermal reduction method combined with a multi-stage wet magnetic separation method.

[0031] (2) The high-purity ferrous phosphide obtained by the above process is used as a raw material, and an acid leaching and fire reduction method is combined to prepare lithium iron phosphate, and the product has no crystal structure defects and has structural characteristics as an electrode material. In the process, iron phosphate is used as an intermediate product, and an acid leaching and co-precipitation method is used to obtain iron phosphate material without impurities, so that the prepared lithium iron phosphate can be used for the preparation of lithium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 The flowchart of the method for preparing lithium iron phosphate from ferrous phosphide according to the present application.

[0034] Figure 2 The XRD analysis diagram of lithium iron phosphate prepared in the embodiment of the present application.

[0035] The implementation, functional characteristics and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] Steel slag is a large solid waste in the steel industry, and its annual output gradually increases with the increase of steel production, which brings environmental pollution and safety problems. In addition, the development of new energy vehicle industry makes the supply of phosphorus resources increasingly tight. The technical scheme of the present application uses ferrous phosphide as a substitute for traditional phosphorus resources to produce lithium iron phosphate, which not only realizes the recovery of valuable elements in steel slag, but also greatly alleviates the phosphorus resource supply crisis. Specifically, the technical scheme of the present application uses high-purity ferrous phosphide as raw material to produce lithium iron phosphate, which can not only reduce the pretreatment process of raw materials such as phosphate rock, but also can flexibly control the process to obtain high-purity lithium iron phosphate product. Combining the production technology of ferrous phosphide and lithium iron phosphate from steel slag recovery products is a green and low-carbon new preparation process based on secondary resources, which is of great significance to guarantee the supply of lithium iron phosphate. The construction of an efficient value-added regeneration technology system for directly preparing industrial phosphorus products from phosphorus secondary resources in steel slag can further improve the utilization efficiency of steel slag resources. It promotes the green and sustainable development in the process of steel production.

[0038] The technical scheme of the present application first provides a method for preparing lithium iron phosphate from ferrous phosphide as raw material, as shown in Figure 1 The technical scheme of the present application first provides a method for preparing lithium iron phosphate from ferrous phosphide as raw material, as shown in

[0039] S1: Using 1 mol / L nitric acid to leach ferrous phosphide, controlling pH=2.5-3, and leaching time 2-5h; adding 1 mol / L phosphoric acid in the leaching solution, and controlling the amount of phosphoric acid added to Fe / P=0.6-0.8(mole ratio) in the solution after adding.

[0040] Here, since nitric acid has oxidizing property, it can ensure that Fe is oxidized to Fe3+ ion in the leaching process.

[0041] In addition, during the leaching process, when pH<2.5, Fe(OH)3 precipitate will be preferentially produced, and too high pH value will waste more reagents in the pH control stage, and the alkaline environment is more conducive to the precipitation of Fe(OH)3, so the leaching pH is controlled at 2.5-3.

[0042] In a preferred embodiment, the preparation method of the ferrous phosphide is as follows:

[0043] S11, mixing steel slag, phosphorus tailings and reducing agent to obtain a mixture;

[0044] S12, after the mixture is pressed into shape, calcination is carried out under inert gas atmosphere, the calcination temperature is 1200-1300℃, and the calcination time is 4-6h;

[0045] S13, cooling the product obtained in S12 to room temperature, crushing and magnetic separation to obtain ferrous phosphide.

[0046] In a preferred embodiment, in the step S11, the chemical composition of the steel slag is: 41.34wt% CaO, 30.8wt% TFe, 13.45wt% SiO2, 4.88wt% MgO, 2.23wt% P2O5, 2.58wt% Al2O3, 2.84wt% MnO, 0.59wt% TiO2, and 0.78wt% others; and the chemical composition of the phosphorite tailings is: 35.45wt% CaO, 1.01wt% TFe, 30.67wt% SiO2, 13.78wt% MgO, 8.97wt% P2O5, 1.36wt% Al2O3, 4.89wt% C, 0.51wt% F, 1.52wt% SO3, and 1.84wt% others.

[0047] Here, in the step S1, the high iron content in the steel slag is conducive to its capturing of phosphorus in the environment, and reacting with the reduced phosphorus to generate ferrous phosphide, thereby reducing the loss of phosphorus caused by the volatilization of phosphorus in the reaction, and thus improving the recovery rate of phosphorus in the steel slag and the phosphorite tailings.

[0048] In a preferred embodiment, in the step S11, the steel slag and the phosphorite tailings are respectively crushed to below 0.074mm before being mixed.

[0049] In a preferred embodiment, in the step S11, the steel slag and the phosphorite tailings, and the reducing agent are mixed in a molar ratio of Fe:P:C of 1:1:4.

[0050] Here, too low a content of C will result in insufficient reduction of Fe and P in the steel slag and the phosphorite tailings, thereby affecting the preparation of Fe2P, and there is a competitive relationship between the dissolution of C and P in elemental iron, and too high a content of C will inhibit the dissolution of phosphorus in iron, thereby resulting in insufficient recovery of phosphorus. Since P will be partially volatilized or react with CaO in the slag phase during the reaction, an excess of P needs to be used to ensure the generation of ferrous phosphide. Through research and analysis, it is found that the mixing of the steel slag and the phosphorite tailings, and the reducing agent in a molar ratio of Fe:P:C of 1:1:4 is the best range of the mixing ratio.

[0051] In a preferred embodiment, in the step S11, the reducing agent is a carbonaceous reducing agent. In a preferred embodiment, the carbonaceous reducing agent is powdered graphite or activated carbon with a particle size of 10-74μm.

[0052] Here, in the step S12, the reason why the calcination temperature is set to 1200-1300℃ and the calcination time is set to 4-6h is that: the reaction rate is slow when the calcination temperature is low and the reaction cannot be ensured to be completed, 1200-1300℃ can ensure the reaction to be completed, and a too high temperature will lead to a too high energy consumption and a risk of phosphorus volatilization; 4-6h can ensure the reaction to be completed, and a reaction time less than 4h will lead to an incomplete reaction and thus the phosphorus oxide cannot be completely reduced and cannot be fully recovered, and a too long reaction time will reduce the process efficiency and increase the energy consumption.

[0053] In a preferred embodiment, in the step S12, the mixed material after being pressed into a block is in a cylindrical shape, a block shape or a spherical shape; wherein the cross-sectional diameter of the cylindrical block is 6-10mm, the maximum diameter of the spherical block is 6-10mm, and the maximum dimension of the edge length of the block-shaped block is 6-10mm.

[0054] In a preferred embodiment, in the step S12, the inert gas is argon.

[0055] In a preferred embodiment, in the step S12, the calcination temperature is 1300℃ and the calcination time is 5h.

[0056] In a preferred embodiment, in the step S13, the magnetic separation method is a multi-stage wet magnetic separation method, the magnetic separation strength is 100mT, the single magnetic separation time is 1min, and the magnetic separation number is 5.

[0057] Here, the combination of the multi-stage wet magnetic separation method and the one-step carbon thermal reduction method makes the process flow shorter and the Fe and P recovery rates higher, thereby achieving the purposes of reducing the cost and improving the production efficiency.

[0058] S2: filtering the leaching solution in step 1, and calcining the filtered precipitate in an air atmosphere at 700-900℃ for 10-12h.

[0059] As a preferred scheme of the method for preparing ferrous phosphide from steel slag and phosphorus tailings, in the step S2, the calcination temperature is 700℃ and the calcination time is 10h.

[0060] Here, the calcination temperature of 700-900℃ is the temperature at which the iron phosphate crystals are formed and stably exist, and at a too low temperature, the crystal structure of the iron phosphate is unstable; and the calcination time of 10-12h ensures the complete growth of the crystals and the formation of a product without defects in the crystal structure, thereby ensuring that the crystal structure of the obtained lithium iron phosphate is also free of defects and thus has the structural characteristics as an electrode material.

[0061] S3: mixing the calcined product (iron phosphate, FePO4) obtained in S2 with lithium hydroxide (LiOH·H2O) and glucose (C6H 12O6) mixing, and mixing the raw materials in a molar ratio of FePO4:LiOH-H2O:C6H 12 O6) mixing, and mixing the raw materials in a molar ratio of FePO4:LiOH-H2O:C6H

[0062] S4: pressing the mixed raw materials in S3 into a block, and calcining the block under an inert atmosphere at 700°C for 10 hours.

[0063] Here, the calcination temperature of 700°C is a temperature at which iron phosphate crystals are formed and stably exist, and at a lower temperature, the crystals grow slowly, and the crystal structure of the generated product has defects, while the calcination time of 10 hours can ensure complete growth of the crystals, and the product formed has a crystal structure without defects, and thus the crystal structure of the lithium iron phosphate obtained finally also does not have defects, thereby having the structural characteristics as an electrode material.

[0064] The technical scheme of the present application also provides a lithium iron phosphate prepared by the method according to the above aspect.

[0065] Embodiment

[0066] The lithium iron phosphate preparation method of the present example includes the following steps:

[0067] (1) mixing steel slag and phosphorus tailings, and graphite to obtain a mixture; the chemical composition of the steel slag is: 41.34wt% CaO, 30.8wt% TFe, 13.45wt% SiO2, 4.88wt% MgO, 2.23wt% P2O5, 2.58wt% Al2O3, 2.84wt% MnO, 0.59wt% TiO2, and 0.78wt% other. The chemical composition of the phosphorus tailings is: 35.45wt% CaO, 1.01wt% TFe, 30.67wt% SiO2, 13.78wt% MgO, 8.97wt% P2O5, 1.36wt% Al2O3, 4.89wt% C, 0.51wt% F, 1.52wt% SO3, and 1.84wt% other. The steel slag and the phosphorus tailings are crushed before mixing, and the size after crushing is ≤0.074mm; the powdered steel slag and the phosphorus tailings, and the graphite with a particle size of 10μm are mixed in a molar ratio of Fe:P:C of 1:1:4; the mixture is pressed into a shape, and then calcined under an argon atmosphere, the block after the mixture is pressed into a shape is cylindrical, the cross-sectional diameter is 8mm, the calcination temperature is 1300°C, the calcination time is 5h, and then cooled to room temperature, and after crushing and magnetic separation, ferrous phosphide is obtained;

[0068] (2) The obtained ferrous phosphide is leached with 1 mol / L nitric acid, and 1 mol / L H3PO4 is added after leaching, and the amount of H3PO4 added is to ensure that the Fe / P in the solution is 0.6 (mole ratio), and the pH titrator is used to control the pH value to be 3 during the leaching process, and the leaching time is 3 h; since Fe(OH)3 is very easy to precipitate, therefore, the Fe / P is controlled to be 0.6 (mole ratio), and too much P can ensure that all the precipitates are FePO4. At the same time, the pH value is 3, which is also to avoid the precipitation of Fe(OH)3, and at the pH value of 3, FePO4 is precipitated in preference to Fe(OH)3;

[0069] (3) The leaching system in (1) is filtered by using a suction filter, and the filtrate is calcined in air for 10 hours, and the calcination temperature is 700°C;

[0070] (4) The calcined product (iron phosphate, FePO4, and ferrous phosphide is completely converted into iron phosphate) in (3) is mixed with lithium hydroxide (LiOH-H2O) and glucose (C6H 12 O6), and the mixture is mixed according to the molar ratio of FePO4:LiOH-H2O:C6H 12 O6 is 1:1.06:0.18;

[0071] (5) The mixture in (4) is pressed into a block with a diameter of 1 cm;

[0072] (6) The block-shaped raw material in (5) is calcined at 700°C for 10 hours in an inert atmosphere.

[0073] (7) After the reaction is completed, the sample of lithium iron phosphate is obtained after cooling to room temperature.

[0074] Figure 2 The XRD analysis diagram of lithium iron phosphate prepared by using steel slag and hot reduction in the examples shows that the diffraction peaks of lithium iron phosphate in the sample can be indexed to the LiFePO4 (JCPDS No. 81-1173) of the orthorhombic system structure, which indicates that the prepared product has the structural framework of lithium iron phosphate.

[0075] Comparative Example 1

[0076] The lithium iron phosphate preparation method of the present comparative example comprises the following steps:

[0077] (1) The ferrous phosphide is leached with 1 mol / L nitric acid, and the pH titrator is used to control the pH value to be 3 during the leaching process, and the leaching time is 3 h;

[0078] (2) The leaching system in (1) is filtered by using a suction filter, and the filtrate is calcined in air for 10 hours, and the calcination temperature is 700°C;

[0079] (3) The detection result of the calcined product in (2) is Fe3PO7, and no peak corresponding to iron phosphate appears. When the pH is controlled at 3, Fe / P = 3:1 in the solution due to no H3PO4 being added, so FePO4 and Fe(OH)3 are precipitated at the same time, and Fe3PO7 is generated by reaction in the high-temperature stage in (2). The precipitate in the solution is Fe(OH)3 precipitate. Therefore, the preparation of lithium iron phosphate cannot be continued.

[0080] Comparative Example 2

[0081] The lithium iron phosphate preparation method of the present comparative example comprises the following steps:

[0082] (1) The ferrous phosphide is leached using 1 mol / L nitric acid, the pH titrator is used to control the pH = 3 during the leaching process, and the leaching time is 3 h;

[0083] (2) The leaching system in (1) is filtered using a suction filter, and the filtrate is calcined in air for 10 hours, and the calcination temperature is 700 DEG C;

[0084] (3) The detection result of the calcined product in (2) is Fe3PO7, and no peak corresponding to iron phosphate appears. The pH is controlled at 2, and the precipitate in the solution is Fe(OH)3 precipitate. Therefore, the preparation of lithium iron phosphate cannot be continued.

[0085] In summary, the present application uses steel slag and phosphorus tailings as raw materials, controls the proportion of the mixture, adjusts the calcination time and temperature, uses the one-step carbon thermal reduction method combined with the multi-stage wet magnetic separation method to directly prepare ferrous phosphide with a purity of more than 85%, and uses the acid leaching and fire reduction method to quickly produce high-purity lithium iron phosphate. The preparation process is simple and realizes high-value utilization of steel slag.

[0086] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made according to the content of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A method for preparing lithium iron phosphate using ferrous phosphide as a raw material, characterized by, Comprising the following steps: S1: using steel slag and phosphorus tailings as raw materials to prepare ferrous phosphide with a purity of more than 85% by using a one-time carbon thermal reduction method combined with a multi-stage wet magnetic separation method, using nitric acid to leach the ferrous phosphide, the leaching control pH=2.5~3, the leaching time is 2~5h; add phosphoric acid in the leaching solution, the amount of phosphoric acid added is controlled at Fe / P=0.6~0.8 molar ratio in the solution after adding; The preparation method of the ferrous phosphide is as follows: S11, mix the steel slag and phosphorus tailings, and the carbonaceous reducing agent according to the molar ratio of Fe:P:C being 1:1:4 to obtain a mixture; wherein the chemical composition of the steel slag is: 41.34 wt% CaO, 30.8 wt% TFe, 13.45 wt% SiO2, 4.88 wt% MgO, 2.23 wt% P2O5, 2.58 wt% Al2O3, 2.84 wt% MnO, 0.59 wt% TiO2 and 0.78 wt% other; the chemical composition of the phosphorus tailings is: 35.45 wt% CaO, 1.01 wt% TFe, 30.67 wt% SiO2, 13.78 wt% MgO, 8.97 wt% P2O5, 1.36 wt% Al2O3, 4.89 wt% C, 0.51 wt% F, 1.52 wt% SO3 and 1.84 wt% other; S12, after the mixture is pressed into shape, calcination is carried out under an inert gas atmosphere, the calcination temperature is 1200~1300℃, and the calcination time is 4~6h; S13, cool the product obtained in S12 to room temperature, crush, and then carry out multi-stage wet magnetic separation to obtain ferrous phosphide; S2: filter the leaching solution obtained in S1, and calcine the filtered precipitate in an air atmosphere at 700~900℃ for 10~12h; S3: The calcined product obtained in S2 is mixed with lithium hydroxide and glucose, and mixed in a molar ratio of FeP04: LiOH-H20: C6H 12 06 of 1 : 1.06: 0.18 ~ 0.21; S4: press the mixed raw materials in S3 into blocks, and carry out calcination under an inert atmosphere at 700℃ for 10h to obtain lithium iron phosphate.

2. The method of claim 1, wherein, In the step S11, the reducing agent is a carbonaceous reducing agent; The carbonaceous reducing agent is powdered graphite or activated carbon with a particle size of 10~74μm.

3. The method of claim 1, wherein, In the step S12, the calcination temperature is 1300℃, and the calcination time is 5h.

4. The method of claim 1, wherein, In the step S13, the magnetic separation strength is 100mT, the single magnetic separation time is 1min, and the number of magnetic separations is 5.

5. The method of claim 1, wherein, In the S1, the concentration of the nitric acid is 1mol / L, and the concentration of the phosphoric acid is 1mol / L.

6. The method of claim 1, wherein, In the S2, the calcination temperature is 700℃, and the calcination time is 10h; in the S4, the calcination temperature is 700℃, and the calcination time is 10h.

7. A lithium iron phosphate prepared by the method according to any one of claims 1 to 6.

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