CN115092902A - Method for preparing lithium manganese iron phosphate cathode material by utilizing iron-rich manganese slag - Google Patents

Abstract

The method for preparing the lithium manganese iron phosphate anode material by utilizing the iron-rich manganese slag comprises the following steps of: (1) recovering iron-rich manganese slag to prepare mineral powder; (2) adding sulfuric acid into the mineral powder obtained in the step (1), carrying out two-stage leaching, and combining two leaching solutions to obtain a mixed leaching solution; (3) purifying and removing impurities from the mixed leaching solution obtained in the step (2) to obtain a ferric manganese phosphate coprecipitation product; (4) and (4) sintering and dehydrating the ferric manganese phosphate coprecipitation product obtained in the step (3), and calcining the product matched with lithium to obtain the lithium ferric manganese phosphate anode material. The method adopts sectional leaching to recover the iron and manganese elements in the manganese slag, the leaching effect of the iron and manganese elements is good, and then phosphoric acid and hydrogen peroxide are adopted to synthesize an iron and manganese phosphate coprecipitation product, so that the obtained product can be directly utilized and recovered, and the method is low in energy consumption, economic and efficient; the lithium ferric manganese phosphate anode material provided by the invention has excellent electrochemical performance and excellent long cycle performance.

Description

Method for preparing lithium iron manganese phosphate cathode material by using iron and manganese-rich slag

technical field

The invention relates to a method for preparing a cathode material of iron manganese phosphate lithium salt, in particular to a method for preparing an iron manganese lithium phosphate cathode material by using iron-rich manganese slag.

Background technique

At present, the battery industry is mainly synthesized directly from mineral resources. The batteries produced in industry include alkaline batteries, zinc batteries, lead-acid batteries and lithium-ion batteries. Among them, lithium-ion batteries rely on their high energy density, chemical stability and good cycle. Performance and other advantages have been widely used. However, the rapid development of lithium-ion batteries has led to a substantial increase in the demand for mineral resources, raising concerns about the supply of battery materials. In addition, the shortage of mineral resources and the rising price of raw materials have hindered the rapid development of the battery industry.

Wet leaching and recovery of iron and manganese from iron and manganese-rich slag to produce lithium iron manganese phosphate is a technology completely different from the traditional production process. Because metallurgical waste slag usually contains lithium, cobalt, nickel, rare earth and other elements, the content is usually higher than that in primary ore, so metallurgical waste slag is also an important secondary resource for battery materials, and the leached iron and manganese elements can be directly It is used to synthesize lithium iron manganese phosphate material, which is easy for large-scale production. But at the same time, because the elements contained in the iron-manganese-rich slag are complex, the operation of extracting iron and manganese elements is complicated and the yield is not high.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art, and to provide a method for preparing phosphoric acid by using iron-rich manganese slag, which is easy to operate, has a good recovery effect of iron and manganese elements, and has excellent electrochemical performance of the obtained lithium iron manganese phosphate cathode material. A method for iron manganese lithium cathode material.

The technical solution adopted by the present invention to solve the technical problem is to use the iron-manganese-rich slag to prepare the iron manganese lithium phosphate positive electrode material, comprising the following steps:

(1) Recycle the iron-manganese-rich slag to make mineral powder;

(2) adding sulfuric acid to the mineral powder obtained in step (1), carrying out two-stage leaching, and combining two leaching solutions to obtain a mixed leaching solution;

(3) purifying and removing impurities from the mixed leachate obtained in step (2) to obtain a co-precipitated product of iron and manganese phosphate;

(4) sintering and dehydrating the iron manganese phosphate coprecipitated product obtained in step (3) at a low temperature, and calcining with lithium to obtain a lithium iron manganese phosphate cathode material.

Further, in step (1), the content of iron in the iron-rich manganese slag is 20-40 wt %, and the average content of manganese is 3-5 wt %.

Further, in step (1), the iron-manganese-rich slag is recovered by drying treatment, the drying temperature is 100~150°C, preferably 120°C, and the drying time is 5~30h, preferably 10~20h.

Further, in step (2), the two-stage leaching is to use sulfuric acid to continuously leaching the mineral powder twice, and the solid-to-liquid ratio of the mineral powder and the leaching agent in the first leaching is controlled to be 1:5～15, preferably 1:1: 10. The concentration of leaching agent sulfuric acid is 0.5~1.5mol/L, preferably 1.0mol/L, the temperature of leaching is 70~90℃, preferably 85℃, the time of leaching is 2~5h, preferably 3h, and the intensity of stirring is 100°C. ~500r/min, preferably 200r/min, wash the mineral powder with deionized water after leaching.

Further, in step (2), after the ore powder is leached for the first time, solid-liquid separation is performed to obtain filter residue, and the filter residue is leached for the second time, and the solid-liquid ratio of filter residue and leaching agent during the second leaching is controlled to be 1: 5～15, preferably 1:10, the concentration of leaching agent sulfuric acid is 5～10mol/L, preferably 6mol/L, the temperature of leaching is 70～90 ℃, preferably 85 ℃, the time of leaching is 10～30h, preferably 20h, The intensity of stirring is 100~500r/min, preferably 85°C, and the filter residue is acid washed with sulfuric acid after leaching.

Further, in step (3), the phosphoric acid is 0.05~0.15mol/L, preferably 0.1.mol/L.

Further, in step (3), the purification and removal of impurities is to adjust the pH value of the leachate to 1.8-2.3, control the concentration of phosphoric acid to be 0.1-0.3 mol/L, and the concentration of hydrogen peroxide to be 0.1-0.2 mol/L, so that P The /M value (the ratio of phosphoric acid to metal elements) is 1.00~1.05:1, preferably 1.03:1, to synergistically remove aluminum, barium and magnesium elements in the mixed leaching solution.

Further, in step (3), the co-precipitated product of iron and manganese phosphate is white.

Further, in step (4), the temperature of the sintering and dehydration is 200-400°C, preferably 300°C.

Further, in step (4), the temperature for calcining the lithium compounding is 600-900°C, preferably 800°C, and the amount of lithium compounding is that Li:M is 1.00-1.05:1, preferably 1.03:1.

The study found that it is difficult to achieve the highest leaching rate of iron and manganese elements by only one leaching of iron and manganese slag, because the leaching rate of manganese will decrease when the leaching rate of iron element increases. In the present invention, by adding excess sulfuric acid as a leaching agent, two-stage leaching is performed, firstly, mild conditions are adopted to obtain the best manganese leaching rate, and the filter residue is subsequently subjected to a second step of strengthening leaching to achieve the highest iron leaching rate. The iron and manganese elements in the iron-manganese-rich slag are separated and recovered into the leachate, and the leachate is collected twice for directional precipitation.

The invention has low energy consumption, does not need high temperature and pure oxygen sintering, directly adopts wet method to recover manganese slag resources, has low cost and is suitable for large-scale production. The lithium iron manganese phosphate material synthesized by the invention forms a special electrode material doped with various rare elements such as lithium, cobalt, nickel, etc., which enhances the electronic conductivity and abundant active sites, provides high reversible capacity, And maintain excellent long-term cycling performance at a high current density of 0.5C.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention adopts staged leaching to recover iron and manganese elements in manganese slag, and the leaching effect of iron and manganese elements is good, then phosphoric acid and hydrogen peroxide are used to synthesize iron-manganese phosphate co-precipitated products, and the recovered products are directly utilized, which consumes less energy. Low energy and cost-effective.

(2) The lithium iron manganese phosphate cathode material obtained in the present invention has excellent electrochemical performance and excellent long cycle performance.

(3) The present invention is easy to operate, and has a short technological process, which is beneficial to large-scale production.

Description of drawings

1 is the XRD pattern of the lithium iron manganese phosphate cathode material obtained in Example 1.

2 is a test diagram of the electrochemical performance of the lithium iron manganese phosphate cathode material obtained in Example 1.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

In the following examples, the leaching rate of iron and manganese elements was detected by ICP, and the electrochemical data was detected by electrochemical workstation.

Unless otherwise specified, all materials are common commercial products.

Example 1

The method for preparing lithium iron manganese phosphate cathode material by utilizing iron-rich manganese slag, comprises the following steps:

(1) After the iron-manganese-rich slag is dried in an oven at 120°C for 20h, it is crushed and ground and passed through a 200-mesh sieve to make mineral powder;

(2) carry out two-stage leaching to the 10g mineral powder obtained in step (1), add 100ml of 1mol/L sulfuric acid solution to the first stage of leaching, the leaching temperature is 85°C, the time is 3h, the stirring intensity is 200r/min, and the The solution after the leaching is filtered, washed with deionized water, to obtain the leaching solution and the leaching residue; the leaching residue is transferred into the sulfuric acid of 100ml of 6mol/L to carry out the second stage leaching, the leaching temperature is 85 ° C, and the time is 20h, using 6mol /L sulfuric acid solution washing to obtain a leachate, which is combined with the first-stage leachate to obtain a mixed iron-manganese leachate;

(3) Prepare 0.1 mol/L leaching solution and 0.1 mol/L phosphoric acid solution so that the P/M ratio is 1.03:1, add 0.13 mol/L hydrogen peroxide, adjust the pH of the mixture to 1.8, react for 15 min, and filter Dry to obtain amorphous iron manganese phosphate hydrate co-precipitated product;

(4) The amorphous iron manganese phosphate hydrate coprecipitated product obtained in step (3) was sintered and dehydrated at 300°C, and then calcined with lithium at a ratio of 1.4:1. The calcination temperature was 800°C, and the calcination time For 8h, the cathode material of lithium iron manganese phosphate is obtained.

After testing, the leaching rate of iron in the iron-rich manganese slag of the present embodiment is 95%, and the leaching rate of manganese element is 98%.

Assembly of the battery: Weigh 0.08 g of the lithium iron manganese phosphate cathode material obtained in Example 1 of the present invention, add 0.01 g of acetylene black as a conductive agent, 0.01 g of polyvinylidene fluoride as a binder, and N-methylpyrrolidone as a dispersant. After mixing evenly, coat it on aluminum foil to make a positive electrode sheet. In a vacuum glove box, the metal lithium sheet is used as the negative electrode, and the composite film of PE and PP is used as the separator. 1mol/L LiPF6/DMC:EC (volume ratio 1:1) is The electrolyte is assembled into a CR2032 button battery.

After testing, the assembled battery has a discharge gram capacity of 157.8mAh/g in the voltage range of 2-4.2 V and a rate of 0.5 C (1C=158.7mAh/g). The discharges at 2C and 5C are 175.6, 170.5, 163.4, 147.8, and 133.9mAh/g, respectively; the capacity retention rate after 200 cycles at a rate of 0.5 C is 95.1%.

Comparative ratio

The method for preparing lithium iron manganese phosphate cathode material by utilizing iron-rich manganese slag, comprises the following steps:

(1) After the iron-manganese-rich slag is dried in an oven at 120°C for 20h, it is crushed and ground and passed through a 200-mesh sieve to make mineral powder;

(2) carry out one-stage leaching to the 10g mineral powder obtained in step (1), add 100ml of 3mol/L sulfuric acid solution to the leaching, the leaching temperature is 85°C, the time is 23h, and the stirring intensity is 200r/min. Filter and wash with deionized water to obtain leaching solution and leaching residue.

(3) Prepare 0.1 mol/L leaching solution and 0.1 mol/L phosphoric acid solution so that the P/M ratio is 1.03:1, add 0.13 mol/L hydrogen peroxide, adjust the pH of the mixture to 1.8, react for 15 minutes, filter Dry to obtain amorphous iron manganese phosphate hydrate co-precipitated product;

(4) The amorphous iron manganese phosphate hydrate coprecipitated product obtained in step (3) was sintered and dehydrated at 300°C, and then calcined with lithium at a ratio of 1.4:1. The calcination temperature was 800°C, and the calcination time For 8h, the cathode material of lithium iron manganese phosphate is obtained.

After testing, the leaching rate of iron in the iron-manganese-rich slag of this comparative example is only 40%, and the leaching rate of manganese element is 90%.

Assembly of the battery: Weigh 0.08 g of the lithium iron manganese phosphate cathode material obtained in the comparative example of the present invention, add 0.01 g of acetylene black as a conductive agent, 0.01 g of polyvinylidene fluoride as a binder, and N-methylpyrrolidone as a dispersant. After uniformly coating it on aluminum foil to make a positive electrode sheet, in a vacuum glove box, the metal lithium sheet is used as the negative electrode, the composite film of PE and PP is used as the separator, and 1mol/L LiPF6/DMC:EC (volume ratio 1:1) is used as the electrolytic liquid, assembled into a CR2032 button battery.

After testing, the assembled battery has a discharge gram capacity of 115.7mAh/g in the voltage range of 2-4.2 V and a rate of 0.5 C; at 0.1C, 0.2C, 0.5C, 2C, and 5C, the discharge capacity is 121.6, 118.5, 113.4, 112.9, 111.4mAh/g; the capacity retention rate after 200 cycles at 0.5 C rate is 27.4%, and the overall performance of the battery is poor.

Claims (7)

1. The method for preparing the lithium ferric manganese phosphate anode material by utilizing the iron-rich manganese slag is characterized by comprising the following steps of:

(1) recovering iron-rich manganese slag to prepare mineral powder;

(2) adding sulfuric acid into the mineral powder obtained in the step (1), carrying out two-stage leaching, and combining two leaching solutions to obtain a mixed leaching solution;

(3) purifying and removing impurities from the mixed leaching solution obtained in the step (2) to obtain a ferric manganese phosphate coprecipitation product;

(4) and (4) sintering and dehydrating the iron manganese phosphate coprecipitation product obtained in the step (3), and calcining the product matched with lithium to obtain the lithium iron manganese phosphate anode material.

2. The method for preparing the lithium ferric manganese phosphate cathode material by using the iron-rich manganese slag according to claim 1, wherein in the step (1), the content of iron in the iron-rich manganese slag is 20-40wt%, and the average content of manganese is 3-5 wt%.

3. The method for preparing the lithium manganese iron phosphate cathode material by using the iron-rich manganese slag according to claim 1 or 2, wherein in the step (2), the ore powder is leached twice continuously by using sulfuric acid in the two-stage leaching, the solid-to-liquid ratio of the ore powder and the leaching agent in the first leaching is controlled to be 1: 5-15, the concentration of the sulfuric acid in the leaching agent is 0.5-1.5 mol/L, the leaching temperature is 70-90 ℃, the leaching time is 2-5 h, the stirring strength is 100-500 r/min, and the ore powder is washed by using deionized water after leaching.

4. The method for preparing the lithium manganese iron phosphate cathode material by using the iron-rich manganese slag according to any one of claims 1 to 3, wherein in the step (2), after the mineral powder is subjected to primary leaching, solid-liquid separation is performed to obtain filter residue, the filter residue is subjected to secondary leaching, the solid-liquid ratio of the filter residue to a leaching agent in the secondary leaching is controlled to be 1: 5-15, the concentration of sulfuric acid in the leaching agent is 5-10 mol/L, the leaching temperature is 70-90 ℃, the leaching time is 10-30 h, the stirring intensity is 100-500 r/min, and the filter residue is subjected to acid pickling by using sulfuric acid after the leaching.

5. The method for preparing lithium manganese iron phosphate cathode material from iron-rich manganese slag according to any one of claims 1 to 4, wherein in the step (3), the purification and impurity removal are performed to adjust the pH value of the leachate to 1.8-2.3, the concentration of phosphoric acid is controlled to 0.1-0.3mol/L, the concentration of hydrogen peroxide is controlled to 0.1-0.2mol/L, the P/M value is 1.00-1.05: 1, and the aluminum, barium and magnesium elements in the mixed leachate are synergistically removed.

6. The method for preparing the lithium manganese iron phosphate cathode material by using the iron-rich manganese slag according to any one of claims 1 to 5, wherein the sintering dehydration temperature in the step (4) is 200 to 400 ℃.

7. The method for preparing the lithium manganese iron phosphate cathode material by using the iron-rich manganese slag according to any one of claims 1 to 6, wherein in the step (4), the temperature for calcining the lithium is 600 to 900 ℃, and the amount of the lithium is Li: m is 1.00-1.05: 1.

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