A method for preparing lithium sulfide from waste lithium-ion batteries as raw materials

Abstract

The present invention discloses a method for preparing lithium sulfide from waste lithium-ion batteries, comprising: (1) selectively leaching lithium from waste lithium-ion batteries; (2) purifying and removing impurities from the obtained lithium-rich leaching solution through a two-stage precipitation process to obtain a high-purity lithium sulfate refined solution; (3) mixing the high-purity lithium sulfate refined solution with a carbon source to obtain a lithium sulfide precursor solution; (4) obtaining a lithium sulfide precursor by spray pyrolysis of the precursor solution; (5) sintering the lithium sulfide precursor to obtain high-purity lithium sulfide. The present invention recovers and prepares high-value lithium sulfide materials from waste lithium-ion batteries. The method is simple. Selectively extracting the lithium sulfate refined solution from waste lithium-ion batteries reduces the preparation cost of lithium sulfate. The two-stage precipitation impurity removal process reduces reagent consumption and lithium ion loss. The one-step synthesis of lithium sulfide has a simple method and a short cycle, and finally obtains high-purity lithium sulfide with a purity of over 99%.

Description

Technical Field

[0001] The present invention belongs to the field of recycling of waste lithium-ion batteries, and relates to a method for preparing lithium sulfide from waste lithium-ion batteries as raw materials. Technical Background

[0002] The demand for new energy vehicles and their core components - lithium-ion batteries has surged. However, the energy density of lithium-ion batteries has approached its theoretical limit, and all-solid-state batteries based on sulfide solid electrolytes have become a new direction for improving energy density. Lithium sulfide is a key material for synthesizing sulfide solid electrolytes.

[0003] At present, the methods for preparing lithium sulfide mainly include solid-phase synthesis and liquid-phase synthesis. Solid-phase synthesis mainly includes three methods: carbothermal reduction, magnesiothermal reduction, and ball milling of a mixture of elemental lithium and elemental sulfur. Magnesiothermal reduction mainly uses magnesium as a reducing agent to react with lithium sulfate at 550 °C to prepare lithium sulfide. However, since the reaction temperature can reach 1500 °C instantaneously, it is prone to explosion and has great potential safety hazards. The method of ball milling a mixture of elemental lithium and elemental sulfur is a simple synthesis method, but it has the disadvantages of expensive raw materials, frequent loading and unloading during ball milling, low synthesis conversion rate, and long reaction time. Liquid-phase synthesis is mainly the solvent method, with sufficient reaction and easy product purification, but organic solvents are flammable, explosive, and volatile, causing serious environmental pollution and being difficult to recycle. Carbothermal reduction of lithium sulfate is a relatively common commercial method for preparing lithium sulfide at present due to its low cost, low process cost, and difficulty in emitting toxic gases.

[0004] Patent CN112678781A discloses a new method for preparing lithium sulfide, which is known for its practicability, safety, and environmental friendliness. Different from traditional processes, this new technology avoids the use of high-risk materials, reduces energy consumption, has relatively loose requirements for production equipment, ensures batch-to-batch production consistency, and does not release toxic gases during the process, effectively preventing secondary pollution. Specifically, after sulfur powder and lithium hydroxide monohydrate are mixed and ground, an oxidation-reduction reaction occurs in the atmosphere of the reducing agent hydrazine hydrate, and a lithium sulfide product is obtained after spray drying, and its main content can reach more than 90%, but high-purity lithium sulfide products cannot be prepared.

[0005] The price fluctuation of lithium metal and the limited global lithium resources have promoted the development of waste lithium-ion battery recycling technology. Lithium in waste batteries is generally recycled into lithium sulfate and then converted into lithium compounds such as lithium carbonate for reuse in preparing the cathode materials of lithium-ion batteries. The long recycling process and complex phase conversion process of traditional recycling processes increase the recycling cost, and new processes for directly preparing high-value-added lithium resources based on the leaching solution of lithium battery recycling need to be developed. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing lithium sulfide from waste lithium-ion batteries to solve the deficiencies in the prior art. The method of the present invention is simple, which can not only efficiently recover lithium in waste lithium-ion batteries, but also propose a simple preparation process to prepare lithium sulfide. While the unit preparation cost is significantly reduced, high-purity lithium sulfide can be obtained.

[0007] To achieve the above object, a method for preparing lithium sulfide from waste lithium-ion batteries, the waste lithium-ion batteries include waste ternary lithium-ion batteries and waste lithium iron phosphate batteries, and the method includes the following steps:

[0008] (1) Selectively leach the waste lithium iron phosphate batteries to obtain a lithium-rich leaching solution; roast the waste ternary lithium-ion batteries and then leach with water to obtain a lithium-rich leaching solution;

[0009] (2) Remove impurity ions from the lithium-rich leaching solution obtained in step (1) through a two-stage precipitation process to obtain a high-purity lithium sulfate refining solution;

[0010] (3) Mix the high-purity lithium sulfate refining solution with a soluble carbon source to obtain a lithium sulfide precursor solution;

[0011] (4) Obtain a lithium sulfide precursor through spray pyrolysis of the precursor solution;

[0012] (5) Sinter the lithium sulfide precursor powder under a specific atmosphere and temperature to prepare lithium sulfide.

[0013] In the present invention, the waste lithium iron phosphate batteries are from the waste powder obtained by disassembling the positive and negative electrodes together, which contains 3.5 - 4.0 wt% of lithium, 25 - 27 wt% of iron, 14 - 16 wt% of phosphorus, 3.4 - 3.7 wt% of copper, and 2 - 2.5 wt% of aluminum.

[0014] In a preferred embodiment, an acid-containing impregnating agent is added during the selective leaching of the waste lithium iron phosphate batteries, and the acid-containing impregnating agent contains an acid and an oxidant; wherein, the acid is selected from one or more of sulfuric acid, hydrochloric acid, and phosphoric acid, and the concentration of the acid is 0.6 - 1 mol / L, preferably 0.6 - 0.7 mol / L. The oxidant is H 2 O 2 wherein the addition amount of H 2 O 2 is 2.0 - 3.0 times the theoretical amount for oxidizing Fe 2+ in the old lithium iron phosphate black powder.

[0015] In a preferred embodiment, the solid-liquid mass-volume ratio of the waste lithium iron phosphate batteries to the acid-containing impregnating agent is 1 g: 3 - 10 mL, preferably 1 g: 5 - 8 mL;

[0016] In the present invention, the waste ternary lithium-ion battery comes from the waste powder obtained by disassembling the positive and negative electrodes together, which contains 4.1-5.2wt% lithium, 13-19wt% nickel, 6-9wt% cobalt and 9-15wt% manganese.

[0017] A preferred solution is to add a roasting agent when roasting the waste ternary lithium-ion battery, wherein the roasting agent is selected from one or more of ammonium sulfate, sodium bisulfate, and concentrated sulfuric acid, wherein the amount of the roasting agent added is equal to the amount of Li in the waste ternary lithium-ion battery. + The amount of the reaction is 0.9 to 2.0 times, preferably 0.9 to 1.5 times; the calcination temperature is 500 to 700°C, the calcination time is 1.0 to 4.0 hours, preferably the calcination temperature is 550 to 650°C.

[0018] In a preferred embodiment, the water immersion is carried out under stirring, and the reaction is carried out in a water bath at a constant stirring rate of 300 rpm and 25° C. for 1 hour.

[0019] In a preferred embodiment, during the precipitation reaction of step (2), a pH adjusting agent is added, and the pH adjusting agent is selected from one of sodium hydroxide and sodium carbonate. In the two-stage precipitation process, the pH value of the first-stage impurity removal process system is 4-8, the system temperature is 25-50°C, and the precipitation time is 10-30 min; the pH value of the second-stage impurity removal process system is 8-10, the system temperature is 30-60°C, and the precipitation time is 30-60 min. Preferably, the pH value of the first-stage impurity removal process system is 7.5, the system temperature is 25-50°C, and the precipitation time is 10-30 min; the pH value of the second-stage impurity removal process system is 9.5, the system temperature is 30-60°C, and the precipitation time is 30-60 min. By adopting a two-stage impurity removal process, the impurity ions in the lithium-rich solution can be well removed. The first-stage impurity removal mainly removes Al in the solution. 3+ and Cu 2+ The main component of the precipitated product is Al(OH) 3 and Cu(OH) 2 The two-stage impurity removal process can deeply remove the impurity ions in the solution, among which Ni 2+ and Co 2 + Completely removed, the main component of the precipitated product is Ni(OH) 2 、Co(OH) 2 、Mn(OH) 2 and Mg(OH) 2 .

[0020] In a preferred embodiment, the soluble carbon source includes one or more of glucose, sucrose, fructose, maltose and citric acid.

[0021] Preferably, the atomization method of spray pyrolysis is one of pressure spraying and centrifugal spraying; the inlet air temperature is between 180 and 240 °C, and the outlet air temperature is set between 100 and 150 °C. This inlet air temperature can preliminarily decompose the organic carbon source to reduce the emission of reaction waste gas and improve the product yield.

[0022] Preferably, the inert atmosphere is nitrogen atmosphere, argon atmosphere or vacuum; the heating rate of sintering is 2 - 4 °C / min, and it is kept at 700 - 1000 °C for 2 - 10 h.

[0023] The beneficial effects of the present invention are as follows:

[0024] In the inorganic acid and oxidant system, the oxidant oxidizes Fe 2+ into Fe that is difficult to leach 3+ , selectively leaches lithium from waste lithium iron phosphate batteries, and efficiently leaches lithium element; during the heating process, it can melt and decompose to produce SO 2 Moreover, ammonium sulfate, which is cheap and easily available, is used as a metal sulfating reagent, and at the same time, the negative electrode carbon with reduction activity and wide source is selected as an auxiliary roasting agent. After static roasting - simple water leaching treatment, lithium in waste ternary lithium batteries is selectively extracted; for the lithium-rich leaching solution containing Al 3+ , Cu 2+ , Ni 2+ , Co 2+ , Mn 2+ , and Mg 2+ , a two-stage precipitation impurity removal process is adopted to deeply remove impurity ions; the soluble carbon source is directly dissolved in the lithium sulfate refining solution, and the spray drying process is used. In the form of spray granulation, lithium sulfate particles are tightly wrapped on the surface of water-insoluble carbon particles to achieve the effect of uniform mixing and sufficient contact of the reaction surface; lithium sulfide is prepared by carbothermal reduction method. The present invention makes the process of selective recovery of lithium from waste lithium-ion batteries simpler. The two-stage impurity removal process is adopted to ensure a high impurity removal rate while reducing the loss of lithium; the preparation of lithium sulfide by carbothermal reduction method produces fewer by-products, fundamentally improves the purity of lithium sulfide, and the crystallinity of lithium sulfide is higher, the output is higher, and it has good performance in battery applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Flow schematic diagram of the method for preparing lithium sulfide from waste lithium-ion batteries as raw materials in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the purpose and method of the present invention clearer, the following further details the present invention in combination with the implementation examples. The examples described here are only used to explain the invention and cannot limit the invention.

[0027] Example 1

[0028] Step (1): The waste lithium iron phosphate battery contains 3.62 wt% lithium, 26.5 wt% iron, 14.8 wt% phosphorus, 3.65 wt% copper and 2.07 wt% aluminum. The above waste lithium iron phosphate is subjected to oxidative leaching in a 0.667 mol / L dilute sulfuric acid with a solid-liquid ratio of 1:7 g / mL, adding 2.85 times the theoretical value of hydrogen peroxide. The leaching temperature is 25 °C, the leaching time is 1 h, and the stirring speed is 300 rpm / min. The waste ternary lithium-ion battery contains 4.17 wt% lithium, 13.45 wt% nickel, 6.27 wt% cobalt and 9.19 wt% manganese. At 650 °C, 1.3 times the theoretical value of ammonium sulfate is added for carbon anode-assisted sulfation roasting to carry out roasting conversion of the waste ternary lithium-ion battery, and the roasting time is 2 h. After roasting, the material is taken out and subjected to lithium removal water leaching. The water leaching process is stirred in a water bath at 25 °C at a stirring rate of 300 rpm for 1 h. After solid-liquid separation, leaching residue and lithium-rich leaching solution are obtained.

[0029] Step (2): Sodium hydroxide is added step by step to the lithium-rich leaching solution obtained in step (1). In the first-stage impurity removal, the pH value is adjusted to 7.5, stirred in a water bath at 35 °C for 20 min, filtered to obtain a filtrate. In the second-stage impurity removal, the pH value is adjusted to 9.5, stirred in a water bath at 45 °C for 50 min, filtered to obtain a filtrate, and finally a lithium sulfate refining solution with a concentration of 124 g / L is obtained.

[0030] Step (3): 100 g of sucrose is added to the lithium sulfate refining solution obtained in step (2) and stirred to obtain a clear slurry.

[0031] Step (4): The clear slurry obtained in step (3) is pumped into a spray dryer by a peristaltic pump. The inlet air temperature is set at 205 °C, the outlet air temperature is set at 150 °C, and the precursor powder is obtained by spraying.

[0032] Step (5): All the precursor powder obtained in step (4) is loaded into a crucible. Under a flowing nitrogen atmosphere, it is heated to 825 °C at a heating rate of 2.5 °C / min, held for 2 h, cooled down, and high-purity lithium sulfide powder is obtained.

[0033] Example 2

[0034] Step (1): The waste lithium iron phosphate battery contains 3.62 wt% lithium, 26.5 wt% iron, 14.8 wt% phosphorus, 3.65 wt% copper, and 2.07 wt% aluminum. The above waste lithium iron phosphate is subjected to oxidative leaching in a 0.92 mol / L dilute sulfuric acid with a solid-liquid ratio of 1:5 g / mL, adding 3.0 times the theoretical value of hydrogen peroxide. The leaching temperature is 25 °C, the leaching time is 1 h, and the stirring speed is 300 rpm / min; the waste ternary lithium-ion battery contains 4.17 wt% lithium, 13.45 wt% nickel, 6.27 wt% cobalt, and 9.19 wt% manganese. At 600 °C, 1.1 times the theoretical value of concentrated sulfuric acid is added for carbon anode-assisted sulfation roasting to convert the waste ternary lithium-ion battery. The roasting time is 1 h. After roasting, the material is taken out and subjected to lithium removal water leaching. The water leaching process is stirred in a water bath at 25 °C at a stirring rate of 300 rpm for 1 h; after solid-liquid separation, a leaching residue and a lithium-rich leaching solution are obtained.

[0035] Step (2): Sodium hydroxide is added step by step to the lithium-rich leaching solution obtained in Step (1). In the first-stage impurity removal, the pH value is adjusted to 6.0, stirred in a water bath at 35 °C for 20 min, filtered to obtain a filtrate; in the second-stage impurity removal, the pH value is adjusted to 8.0, stirred in a water bath at 45 °C for 50 min, filtered to obtain a filtrate, and finally a refined lithium sulfate solution with a concentration of 119 g / L is obtained.

[0036] Step (3): 100 g of citric acid is added to the refined lithium sulfate solution obtained in Step (2) and stirred to obtain a clear slurry.

[0037] Step (4): The clear slurry obtained in Step (3) is pumped into a spray dryer using a peristaltic pump. The inlet air temperature is set to 190 °C, the outlet air temperature is set to 110 °C, and the precursor powder is obtained by spraying.

[0038] Step (5): All the precursor powder obtained in Step (4) is loaded into a crucible. Under a flowing nitrogen atmosphere, it is heated to 900 °C at a heating rate of 1.5 °C / min, held for 8 h, cooled, and high-purity lithium sulfide powder is obtained.

[0039] Example 3

[0040] Step (1): The waste lithium iron phosphate battery contains 3.62 wt% lithium, 26.5 wt% iron, 14.8 wt% phosphorus, 3.65 wt% copper, and 2.07 wt% aluminum. The above waste lithium iron phosphate is subjected to oxidative leaching in 0.6 mol / L dilute sulfuric acid with a solid-liquid ratio of 1:10 g / mL and a hydrogen peroxide system of 2.85 times the theoretical value. The leaching temperature is 25°C, the leaching time is 1 h, and the stirring speed is 300 rpm / min. The waste ternary lithium-ion battery contains 4.17 wt% lithium, 13.45 wt% nickel, 6.27 wt% cobalt, and 9.19 wt% manganese. At 550°C, 0.9 times the theoretical value of sodium bicarbonate is added for carbon anode-assisted sulfation roasting to convert the waste ternary lithium-ion battery. The roasting time is 2 h. After roasting, the material is taken out and subjected to lithium removal water leaching. The water leaching process is stirred in a water bath at 25°C at a stirring rate of 300 rpm for 1 h. After solid-liquid separation, the leaching residue and lithium-rich leaching solution are obtained.

[0041] Step (2): Sodium hydroxide is added step by step to the lithium-rich leaching solution obtained in step (1). In the first-stage impurity removal, the pH value is adjusted to 7.0, and it is stirred in a water bath at 35°C for 20 min, and then filtered to obtain a filtrate. In the second-stage impurity removal, the pH value is adjusted to 8.5, and it is stirred in a water bath at 45°C for 50 min, and then filtered to obtain a filtrate. Finally, a lithium sulfate refined solution with a concentration of 111 g / L is obtained.

[0042] Step (3): 120 g of glucose is added to the lithium sulfate refined solution obtained in step (2) and stirred to obtain a clear slurry.

[0043] Step (4): The clear slurry obtained in step (3) is pumped into a spray dryer using a peristaltic pump. The inlet air temperature is set at 220°C, and the outlet air temperature is set at 120°C to obtain precursor powder by spraying.

[0044] Step (5): All the precursor powder obtained in step (4) is loaded into a crucible. Under a flowing nitrogen atmosphere, it is heated to 960°C at a heating rate of 2.0°C / min, held for 8 h, and then cooled to obtain high-purity lithium sulfide powder.

[0045] Comparative Example 1:

[0046] This comparative example is basically the same as Example 1. Steps (1), (3), and (4) remain unchanged. The difference is only in step (2): The two-stage precipitation impurity removal process is changed to a one-stage precipitation impurity removal process, and the pH value of the solution is adjusted to 9.5, and the other conditions are the same as those in Example 1.

[0047] Comparative Example 2:

[0048] This comparative example is basically the same as Example 1. Steps (1), (3), and (4) remain unchanged. The difference lies only in step (2): the two-stage precipitation impurity removal process is changed to a step-by-step sequential precipitation impurity removal process. The pH value of the first-stage impurity removal system is adjusted to 4.0 to remove Al 3+ ; the pH value of the second-stage impurity removal system is adjusted to 6.2 to remove Cu 2+ ; the pH value of the third-stage impurity removal system is adjusted to 7.0 to remove Ni 2+ ; the pH value of the fourth-stage impurity removal system is adjusted to 8.4 to remove Co 2+ ; the pH value of the fifth-stage impurity removal system is adjusted to 9.1 to remove Mn 2+ ; the pH value of the sixth-stage impurity removal system is adjusted to 9.5 to remove Mg 2+ , and the other conditions are the same as those in Example 1.

[0049] The lithium sulfide prepared in the examples and comparative examples was made into an electrolyte and characterized. The specific methods for preparing and characterizing the electrolyte are as follows: Lithium sulfide, phosphorus pentasulfide, and lithium chloride were added to a zirconia ball milling tank according to the designed ratio, and ball milled for 1 h at a ball-to-material ratio of 40:1 to obtain electrolyte raw powder; the raw powder was sintered at 500 °C for 8 h to obtain electrolyte powder. A certain amount of electrolyte powder was made into a blocking cell with a diameter of 10 mm under a pressure of 300 MPa, and then the impedance spectrum was measured in the frequency range of 1 - 1 MHz using the impedance test module of an electrochemical workstation to obtain the electrolyte impedance, and the conductivity was calculated according to the thickness.

[0050] The detection results of each example and comparative example are shown in Table 1:

[0051] Table 1 Detection results of each example and comparative example

[0052]

[0053] As can be seen from Table 1, the lithium recovery rate in Examples 1 - 3 is higher than that in Comparative Example 2, and the purity of lithium sulfide is higher than that in Comparative Example 1; it shows that the effect of two-stage impurity removal is better than that of one-stage impurity removal and step-by-step sequential impurity removal. When performing one-stage impurity removal, when the pH value of the system is too high, some of the precipitates generated first will undergo a dissolution reaction, resulting in a rise in the concentration of impurity ions in the system and affecting the impurity removal effect; while for multi-step impurity removal, after multiple filtration and washing, the loss rate of lithium increases significantly.

[0054] It can also be seen that the present invention can prepare high-purity lithium sulfide from waste lithium-ion batteries. The raw material cost source is extensive, the product purity can reach more than 98%, and the conductivity of the prepared electrolyte can reach more than 3.8 mS / cm.

[0055] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

[0056] The materials, reagents, etc. used in the above embodiments can be obtained from commercial channels without special instructions.

Claims

1. A method for preparing lithium sulfide using waste lithium-ion batteries as raw materials, characterized in that: The waste lithium-ion batteries include waste ternary lithium-ion batteries and waste lithium iron phosphate batteries, and the method includes the following steps: (1) Add 0.6-1 mol / L sulfuric acid and an oxidant to selectively leach waste lithium iron phosphate batteries to obtain a lithium-rich leachate; roast waste ternary lithium ion batteries and then leach them in water to obtain a lithium-rich leachate, wherein the waste lithium iron phosphate batteries come from waste powder obtained by disassembling the positive and negative electrodes together, which contains 3.5-4.0 wt% lithium, 25-27 wt% iron, 14-16 wt% phosphorus, 3.4-3.7 wt% copper, and 2-2.5 wt% aluminum; the waste ternary lithium ion batteries come from waste powder obtained by disassembling the positive and negative electrodes together, which contains 4.1-5.2 wt% lithium, 13-19 wt% nickel, 6-9 wt% cobalt, and 9-15 wt% manganese; when selectively leaching the waste lithium iron phosphate batteries, the solid-liquid mass volume ratio is 1 g: 3-10 mL; (2) The lithium-rich leaching solution obtained in step (1) is subjected to a two-stage precipitation process to remove impurity ions to obtain a high-purity lithium sulfate refined solution, wherein the pH value of the first stage impurity removal process system in the two-stage precipitation process is 6-8, and the Al in the solution is mainly removed. 3+ and Cu 2+ The pH value of the two-stage impurity removal process system is 8~10, which deeply removes impurity ions in the solution, including Ni 2+ and Co 2+ Completely removed, the main components of the precipitation product are Ni(OH)2, Co(OH)2 and Mn(OH)2; (3) mixing a high-purity lithium sulfate refined solution and a soluble carbon source to obtain a lithium sulfide precursor solution; (4) obtaining a lithium sulfide precursor by spray pyrolysis of the precursor solution. Specifically, the atomization method of the spray pyrolysis is one of pressure spray and centrifugal spray; the inlet air temperature is between 180 and 240° C., and the outlet air temperature is set between 100 and 150° C.; (5) Sintering a lithium sulfide precursor powder at 700-1000° C. in a specific atmosphere to prepare lithium sulfide, wherein the purity of the lithium sulfide reaches more than 98%, and the conductivity of the electrolyte prepared from the lithium sulfide reaches more than 3.8 mS / cm; wherein the specific atmosphere is a nitrogen atmosphere, an argon atmosphere or a vacuum.

2. The method according to claim 1, characterized in that The oxidant is H2O2, and the amount of H2O2 added is sufficient to oxidize Fe in the waste lithium iron phosphate battery. 2+ 2.0~3.0 times the theoretical dosage.

3. The method according to claim 2, characterized in that The leaching temperature of the waste lithium iron phosphate battery is 25-85° C., the leaching time is 1.0-2.5 h, and the stirring speed is 300 r / min-400 r / min.

4. The method according to claim 1, characterized in that When the waste ternary lithium-ion battery is roasted, a roasting agent is added, wherein the roasting agent is selected from one or more of ammonium sulfate, sodium bisulfate, and concentrated sulfuric acid, wherein the amount of the roasting agent added is equal to the amount of Li in the waste ternary lithium-ion battery. + The reaction amount is 0.9~2.0 times of the theoretical amount; the calcination temperature is 500~700℃, and the calcination time is 1.0~4.0 h.

5. The method according to claim 1 or 4, characterized in that: The water immersion was carried out in a water bath at a constant stirring rate of 300 rpm and 25° C. for 1 h.

6. The method according to claim 1, characterized in that In the two-stage precipitation process, the temperature of the first-stage impurity removal process system is 25~50°C and the precipitation time is 10~30 min; the temperature of the second-stage impurity removal process system is 30~60°C and the precipitation time is 30~60 min; the pH adjuster is selected from one of sodium hydroxide and sodium carbonate.

7. The method according to claim 1, characterized in that The soluble carbon source includes one or more of glucose, sucrose, fructose, maltose and citric acid.

8. The method according to claim 1, characterized in that The sintering heating rate is 2~4℃ / min, and the insulation time is 2~10h.

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