Carbon powder and method for recycling carbon powder from waste lithium iron phosphate black powder and application thereof, porous carbon material

Abstract

The present invention relates to the field of battery recycling and discloses a method for recovering carbon powder from waste lithium iron phosphate black powder. The method is performed in a circulation device comprising an aeration device and a circulation barrel connected thereto. The method comprises: (1) introducing a first raw material into the aeration device for a first aeration treatment, and introducing a mixed stream I obtained after the first aeration treatment into the circulation barrel for a first contact reaction to obtain a solid substance as an intermediate material I; (2) introducing a second raw material into the aeration device for a second aeration treatment, and introducing a mixed stream II obtained after the second aeration treatment into the circulation barrel for a second contact reaction to obtain an intermediate material II; and (3) drying the intermediate material II to obtain the carbon powder. The carbon powder recovered by the method provided by the present invention has a higher purity and can be widely used in the field of carbon materials.

Description

Technical Field

[0001] The present invention relates to the field of battery recycling, and in particular to carbon powder, a method for recycling carbon powder from waste lithium iron phosphate black powder, applications thereof, and porous carbon materials. Background Art

[0002] Thanks to strong support from national policies in recent years, lithium-ion battery production has steadily increased year by year. Statistics show that by 2016, China alone had produced 7.84 billion lithium-ion batteries. The lifespan of lithium-ion batteries is typically three to five years, meaning a significant number of these batteries have already been scrapped, and the number of scrapped batteries is increasing. If these scrapped batteries are not properly handled, they will pose a serious threat to the ecological environment. Therefore, recycling lithium-ion batteries has become increasingly urgent.

[0003] In recent years, there has been considerable research both domestically and internationally on the recycling of materials from used batteries. However, this research has generally focused on the recovery of precious metals like lithium and cobalt, or non-ferrous metals like copper foil. Research on the recovery of relatively low-value graphite has been limited. Essentially, carbon materials recovered from lithium batteries possess excellent electrical conductivity, a defined particle size distribution, and a high degree of graphitization. If high-purity carbon materials can be recovered, they could be used as conductive pigments for conductive coatings, as fillers in plastics and rubber, and even more so, as negative electrode materials for lithium batteries.

[0004] CN1758478A discloses a method for recovering positive and negative electrode materials from waste and old electrode sheets. This method involves collecting negative electrode sheets containing copper foil and then calcining them in a high-temperature furnace to decompose the binder, thereby separating the carbon powder and copper foil. While this method achieves separation, it consumes a lot of energy and fails to consider that recycled lithium battery negative electrode materials often contain some lithium-carbon compounds, which are highly flammable and difficult to guarantee safety.

[0005] CN101710632A discloses a method for recovering and repairing graphite, a waste lithium-ion battery anode material. This method uses cellulose acetate as a surface modifier to modify the graphite surface at high temperatures, thereby repairing the graphite negative electrode. While this method improves the performance of the graphite material, it is complex, the raw materials are expensive, and the repair performance is limited.

[0006] In summary, finding a new method to recover high-purity and practical negative electrode materials from waste lithium iron phosphate batteries so that they can be recycled and reused is of great significance for enterprises to improve their economic benefits. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems of low purity and practicality of carbon powder recovered from waste lithium iron phosphate batteries in the prior art.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for recovering carbon powder from waste lithium iron phosphate black powder. The method is performed in a circulation device comprising an aeration device and a circulation barrel connected thereto. The method comprises:

[0009] (1) introducing a first raw material into the aeration device for a first aeration treatment, and introducing a mixed flow I obtained after the first aeration treatment into the circulation barrel for a first contact reaction to obtain a solid as an intermediate material I; the first raw material contains waste lithium iron phosphate black powder and an acid solution I; the waste lithium iron phosphate black powder contains copper and aluminum elements;

[0010] (2) introducing a second raw material into the aeration device for a second aeration treatment, and introducing the mixed flow II obtained after the second aeration treatment into the circulation barrel for a second contact reaction to obtain an intermediate material II; the second raw material contains the acid solution II and the intermediate material I obtained in step (1); the conditions of the second contact reaction at least meet the following requirements: the temperature is not less than 40° C.; the weight ratio of the intermediate material I to the acid solution II is 1:1-5;

[0011] (3) Drying the intermediate material II to obtain the carbon powder.

[0012] The second aspect of the present invention provides carbon powder prepared by the method described in the first aspect; the purity of the carbon powder is higher than 70%.

[0013] The third aspect of the present invention provides use of the carbon powder described in the second aspect in the field of carbon materials.

[0014] The fourth aspect of the present invention provides a porous carbon material, and the preparation method of the porous carbon material includes: in the presence of a protective gas, mixing and reacting the carbon powder described in the second aspect with an activator to obtain a porous carbon material precursor, and sequentially acid-washing and drying the porous carbon material precursor to obtain the porous carbon material.

[0015] The solution of the present invention has at least the following advantages over the prior art:

[0016] 1. The purity of the carbon powder recovered by the method provided by the present invention is as high as 81%, and can be widely used in the field of carbon materials.

[0017] 2. The carbon material provided by the present invention has a developed microporous / mesoporous structure, which increases its specific surface area. In addition, since the waste lithium iron phosphate black powder is leached with inorganic acid and circulated aeration, a small amount of oxygen-containing or nitrogen-containing groups are inevitably introduced into the obtained carbon powder. When the carbon material with the above characteristics is used as a supercapacitor material, on the one hand, its developed pore structure greatly shortens the ion transmission distance in the electrolyte, thereby having better ion transmission capacity; on the other hand, the high oxygen content on its surface improves the wettability of the material surface, which can further improve the ion transmission capacity in the electrolyte; at the same time, these oxygen-containing or nitrogen-containing functional groups can provide high pseudocapacitance for the carbon material, and the high specific surface area provides the carbon material with high double-layer capacitance.

[0018] In particular, the porous carbon material prepared by using the carbon powder provided by the present invention has a well-developed mesoporous structure and a specific surface area of ​​up to 1413m 2 / g, with a pore volume of up to 0.93 cm 2 / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow diagram of a method for recovering carbon powder from waste lithium iron phosphate black powder according to a preferred embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of a process flow chart for preparing a porous carbon material according to a preferred embodiment of the present invention;

[0021] Figure 3 These are scanning electron microscope images of the porous carbon material prepared from the carbon powder recovered in Example 1 and Comparative Example 3 provided by the present invention, wherein a and b represent scanning electron microscope images of the porous carbon material prepared from the carbon powder recovered in Comparative Example 3, and c and d represent scanning electron microscope images of the porous carbon material prepared from the carbon powder recovered in Example 1.

[0022] Description of Reference Numerals

[0023] 1. Air 2. First circulation sub-barrel 3. Second circulation sub-barrel

[0024] 4. Venturi tube 5. Circulation pump DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0026] As mentioned above, the first aspect of the present invention provides a method for recovering carbon powder from waste lithium iron phosphate black powder. The method is performed in a circulation device, wherein the circulation device includes an aeration device and a circulation barrel connected thereto. The method comprises:

[0027] (1) introducing a first raw material into the aeration device for a first aeration treatment, and introducing a mixed flow I obtained after the first aeration treatment into the circulation barrel for a first contact reaction to obtain a solid as an intermediate material I; the first raw material contains waste lithium iron phosphate black powder and an acid solution I; the waste lithium iron phosphate black powder contains copper and aluminum elements;

[0028] (2) introducing a second raw material into the aeration device for a second aeration treatment, and introducing the mixed flow II obtained after the second aeration treatment into the circulation barrel for a second contact reaction to obtain an intermediate material II; the second raw material contains the acid solution II and the intermediate material I obtained in step (1); the conditions of the second contact reaction at least meet the following requirements: the temperature is not less than 40° C.; the weight ratio of the intermediate material I to the acid solution II is 1:1-5;

[0029] (3) Drying the intermediate material II to obtain the carbon powder.

[0030] Preferably, the waste lithium iron phosphate black powder contains 1-2 wt% of copper and 1-2 wt% of aluminum.

[0031] More preferably, the waste lithium iron phosphate black powder contains 2-4.2wt% of lithium, 16.14-33.89wt% of iron, 8.93-18.76wt% of phosphorus, 1-2wt% of copper, 1-2wt% of aluminum, 30-45wt% of carbon, 0.01-0.1wt% of nickel, 0.01-0.1wt% of cobalt, 0.01-0.1wt% of manganese and 0.1-20wt% of other components.

[0032] It should be noted that the composition of waste lithium iron phosphate black powder is extremely complex and contains many types of elements. The other components are any one or more elements known in the art in addition to the above-mentioned elements. The present invention will not go into details here, and those skilled in the art should not understand this as a limitation of the present invention.

[0033] Preferably, in step (1), the method further comprises: subjecting the product obtained from the first contact reaction to solid-liquid separation treatment to obtain the solid as the intermediate material I.

[0034] Preferably, the solid content of the intermediate material I includes: 0.005-0.05wt% lithium, 0.04-0.4wt% iron, 0.02-0.2wt% phosphorus, 0.1-0.5wt% copper, 0.1-0.5wt% aluminum and 60-70wt% carbon.

[0035] More preferably, the method further comprises: in step (3), before performing the drying process, performing a solid-liquid separation process on the intermediate material II.

[0036] In the present invention, there are no special requirements for the operating method used for solid-liquid separation treatment. Those skilled in the art can adopt the solid-liquid separation treatment technology known in the art for the present invention. The present invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of the present invention.

[0037] Preferably, both the first and second aeration treatments are performed in the presence of a gaseous stream, and the conditions for each of the first and second aeration treatments independently satisfy at least: an oxygen content in the gaseous stream of 15-30 V / V% and a flow rate of 300-800 sccm. Exemplarily, the oxygen content in the gaseous stream is 15%, 21%, and 30%, and the flow rates of the gaseous stream are 300 sccm, 500 sccm, 600 sccm, 700 sccm, and 800 sccm. The inventors have discovered that under this preferred embodiment, the carbon powder provided by the present invention has a higher purity.

[0038] This application utilizes a single acid leaching and a high-temperature pickling process, while simultaneously exposing the material to an oxygen-containing gas, to efficiently extract various impurity elements from waste lithium iron phosphate black powder, thereby producing high-purity carbon powder. The carbon material produced using the carbon powder obtained in this invention exhibits improved electrical properties. In light of this, the inventors completed the present invention.

[0039] Preferably, the circulation equipment also includes a circulation pump, the circulation barrel includes a first circulation sub-barrel and a second circulation sub-barrel arranged downstream of the first circulation sub-barrel, there is a height difference of not less than 100 mm between the first circulation sub-barrel and the second circulation sub-barrel, and the second circulation sub-barrel and the aeration device are connected through the circulation pump.

[0040] Preferably, the first circulating sub-barrel and the second circulating sub-barrel of the present invention may be the same or different, and the ratio of the inner diameter to the height of the first circulating sub-barrel and the second circulating sub-barrel is independently 1:1.5-2.

[0041] It should be noted that the inner diameters of the first circulating sub-barrel and the second circulating sub-barrel in the present invention refer to the diameters inside the barrel.

[0042] Preferably, the aeration device is a negative pressure device with a gas phase flow introduction function.

[0043] Preferably, the aeration device is a connection combination of a venturi injection tube and a venturi suction tube (hereinafter collectively referred to as a venturi tube), wherein the gas phase flow can be introduced into the venturi suction tube through at least one opening, the liquid phase flow can be introduced into the venturi injection tube through at least one opening for aeration treatment, and the mixed flow obtained after the aeration treatment can be introduced downstream through at least one opening.

[0044] Preferably, a stirring device and a heating device are independently provided in the first circulating sub-barrel and the second circulating sub-barrel.

[0045] Preferably, the oxygen content in the gaseous stream in the first aeration treatment is 20-25 V / V%, and the flow rate of the gaseous stream in the second aeration treatment is 500-700 sccm. The inventors have found that under this preferred embodiment, the carbon powder provided by the present invention has a higher purity.

[0046] More preferably, the gaseous stream is air.

[0047] Preferably, in step (1), the conditions of the first contact reaction are controlled so that when the first contact reaction is completed, the content of lithium ions in the material at the bottom of the second circulation sub-barrel is less than 100 ppm.

[0048] More preferably, the first contact reaction is carried out under stirring conditions, and the conditions of the first contact reaction also include: a stirring speed of 200-600 rpm and a temperature of 25-80°C.

[0049] It should be noted that the temperature of the first contact reaction is the temperature initially set for the reaction, and the first contact reaction is an exothermic reaction. The temperature of the reaction system varies in the range of 40-80°C during the reaction. The present invention will not be elaborated here, and those skilled in the art should not understand it as a limitation of the present invention.

[0050] Preferably, the weight ratio of the waste lithium iron phosphate black powder to the acid solution I is 1:2-4.

[0051] More preferably, the concentration of the acid solution I is 2-4 mol / L.

[0052] Particularly preferably, the acid solution I is selected from at least one of hydrochloric acid, sulfuric acid and phosphoric acid.

[0053] Preferably, the second contact reaction is carried out under stirring conditions, wherein the second contact reaction conditions include: a stirring speed of 200-600 rpm, a temperature of 60-80° C., and a time of 6-12 hours. The inventors have found that under this preferred embodiment, the carbon powder provided by the present invention has a higher purity.

[0054] Preferably, the weight ratio of the intermediate material I to the acid solution II is 1:2-4. The inventors have found that under this preferred embodiment, the carbon powder provided by the present invention has a higher purity.

[0055] More preferably, the concentration of the acid solution II is 2-4 mol / L.

[0056] Particularly preferably, the acid solution II is selected from at least one of hydrochloric acid, sulfuric acid and phosphoric acid.

[0057] Preferably, in step (3), the drying treatment conditions include: temperature of 80-105° C., time of 12-24 h, and pressure of 0.01-0.1 MPa.

[0058] The following combination Figure 1 Preferred embodiments of the present invention are described in detail, but the present invention is not limited thereto.

[0059] exist Figure 1 The method of the present invention comprises:

[0060] (1) adding waste lithium iron phosphate black powder and acid solution I into a first circulating sub-barrel 2, turning on the circulation device and the stirring device of the first circulating sub-barrel 2 and the second circulating sub-barrel 3, so that the logistics in the first circulating sub-barrel 2 can be introduced into the second circulating sub-barrel 3 by gravity, the logistics in the second circulating sub-barrel 3 is circulated back to the venturi tube 4 through a pipeline with a circulating pump 5, and is subjected to a first aeration treatment with air 1, and the logistics after the aeration treatment is introduced into the circulating barrel, and a first contact reaction is carried out to obtain a product, and the product is subjected to solid-liquid separation to obtain a solid as the intermediate material I;

[0061] (2) adding the acid solution II and the intermediate material I into the first circulating sub-barrel 2, turning on the circulation device and the stirring device and heating device of the first circulating sub-barrel 2 and the second circulating sub-barrel 3, so that the logistics in the first circulating sub-barrel 2 can be introduced into the second circulating sub-barrel 3 by gravity, and the logistics in the second circulating sub-barrel 3 is circulated back to the venturi tube 4 through the pipeline with the circulating pump 5, and is subjected to a second aeration treatment with the air 1, and the logistics after the aeration treatment is introduced into the circulating barrel to undergo a second contact reaction to obtain the intermediate material II;

[0062] (3) The intermediate material II is subjected to solid-liquid separation and drying treatment in sequence to obtain carbon powder.

[0063] As mentioned above, the second aspect of the present invention provides carbon powder prepared by the method described in the first aspect; the purity of the carbon powder is higher than 70%.

[0064] It should be noted that the purity of the carbon powder refers to mass purity.

[0065] As mentioned above, the third aspect of the present invention provides the use of the carbon powder described in the second aspect in the field of carbon materials.

[0066] As mentioned above, the fourth aspect of the present invention provides a porous carbon material, and the preparation method of the porous carbon material includes: in the presence of a protective gas, mixing the carbon powder described in the second aspect with an activator to obtain a porous carbon material precursor, and sequentially acid-washing and drying the porous carbon material precursor to obtain the porous carbon material.

[0067] Preferably, the protective gas is selected from at least one of nitrogen and argon.

[0068] Preferably, the activator is selected from at least one of potassium hydroxide and sodium hydroxide.

[0069] Preferably, the mixing reaction conditions include: temperature of 450-800° C. and time of 2-4 h.

[0070] More preferably, the specific surface area of ​​the porous carbon material is greater than 1231m 2 / g.

[0071] Particularly preferably, the pore volume of the porous carbon material is greater than 0.77 cm 3 / g.

[0072] The carbon material provided by the present invention has a developed microporous / mesoporous structure, which increases its specific surface area. In addition, since the waste lithium iron phosphate black powder is leached with inorganic acid and circulated aeration, a small amount of oxygen-containing or nitrogen-containing groups are inevitably introduced into the obtained carbon powder. When the carbon material with the above characteristics is used as a supercapacitor material, on the one hand, its developed pore structure greatly shortens the ion transmission distance in the electrolyte, thereby having better ion transmission capacity. On the other hand, the high oxygen content on its surface improves the wettability of the material surface, which can further improve the ion transmission capacity in the electrolyte. At the same time, these oxygen-containing or nitrogen-containing functional groups can provide high pseudocapacitance for the carbon material, and the high specific surface area provides the carbon material with high double-layer capacitance.

[0073] The following combination Figure 2 A preferred embodiment of the method for preparing a porous carbon material of the present invention is provided, the method comprising:

[0074] (1) subjecting waste lithium iron phosphate black powder (i.e., waste LFP black powder) to a first contact reaction (i.e., a single acid leaching) with an acid solution I, followed by filtration and separation to obtain a solid as an intermediate material I;

[0075] (2) subjecting the acid solution II to a second contact reaction with the intermediate material I (i.e., secondary acid washing) to obtain the intermediate material II;

[0076] (3) subjecting the intermediate material II to solid-liquid separation (i.e., filtration separation) and drying treatment in sequence to obtain the carbon powder;

[0077] (4) The carbon powder is mixed with an activator for reaction (i.e., high-temperature calcination) to obtain a porous carbon material precursor, and the porous carbon material precursor is sequentially acid-washed and dried to obtain the porous carbon material (i.e., graded porous carbon).

[0078] The present invention will be described in detail below by way of examples, but the present invention is not limited thereby. In the following examples, unless otherwise specified, the experimental instruments, reagents and raw materials involved are all commercially available, and the reagents are all analytically pure products.

[0079] Waste lithium iron phosphate black powder: containing 2.5wt% lithium, 20.1wt% iron, 11.16wt% phosphorus, 1wt% copper, 1.5wt% aluminum, 45wt% carbon, 0.1wt% nickel, 0.1wt% cobalt, 0.1wt% manganese and 18.44% other components;

[0080] Diaphragm: water-based cellulose diaphragm;

[0081] Electrolyte: 6 mol / L potassium hydroxide solution.

[0082] The structure of the circulation equipment used in the following example is: it includes a connected Venturi tube and a circulation barrel, the circulation barrel includes a first circulation sub-barrel with an inner diameter of 2m and a height of 3m and a second circulation sub-barrel with an inner diameter of 2m and a height of 3m arranged downstream of the first circulation sub-barrel, the bottom of the second circulation sub-barrel and the upper part of the Venturi tube are maintained in communication through a pipeline with a circulation pump; the first circulation sub-barrel and the second circulation sub-barrel are both provided with a stirring device and a heating device; the height difference between the first circulation sub-barrel and the second circulation sub-barrel is adjustable.

[0083] Taking the first contact reaction as an example, the circulation process of the logistics in the circulation equipment is: adding the logistics to the first circulation sub-barrel, turning on the circulation equipment and the stirring device, so that the logistics in the first circulation sub-barrel can be introduced into the second circulation sub-barrel by gravity, the logistics in the second circulation sub-barrel is circulated back to the Venturi tube through a pipeline with a circulation pump, and undergoes a first aeration treatment with the air, and the logistics obtained after the first aeration treatment is introduced into the first circulation sub-barrel to undergo a first contact reaction.

[0084] In the following examples, the performance testing methods involved are as follows:

[0085] 1. The purity of carbon powder is tested with a carbon-sulfur analyzer;

[0086] 2. The specific surface area and pore volume were determined by using a Micromeritics ASAP2460 volumetric adsorption analyzer to obtain nitrogen adsorption / desorption isotherms at 77 K. The specific surface area and pore volume were then calculated using the BET and DFT methods, respectively, based on the test data.

[0087] Example 1

[0088] This embodiment is used to recover carbon powder from waste lithium iron phosphate black powder. The specific formula and process parameters are shown in Table 1, and the carbon powder is prepared according to the method described below.

[0089] The method for recovering carbon powder from waste lithium iron phosphate black powder comprises the following steps:

[0090] (1) adding 2 tons of waste lithium iron phosphate black powder and 2.5 mol / L sulfuric acid solution into a first circulation sub-barrel, starting the circulation equipment and the stirring device, performing a first aeration treatment with air, completing a first contact reaction, obtaining a product, and performing solid-liquid separation on the product to obtain a solid as intermediate material I;

[0091] The height difference between the first circulating sub-barrel and the second circulating sub-barrel in the circulating device is 500 mm;

[0092] (2) adding 2 t of the intermediate material I and a 2.5 mol / L sulfuric acid solution into the first circulation sub-barrel, starting the circulation device, the stirring device, and the heating device, performing a second aeration treatment with air, completing a second contact reaction, and obtaining the intermediate material II;

[0093] In this step, the height difference between the first circulation sub-barrel and the second circulation sub-barrel in the circulation device is adjusted to 1000 mm;

[0094] (3) The intermediate material II is subjected to solid-liquid separation and drying treatment in sequence to obtain carbon powder.

[0095] Unless otherwise specified, the remaining examples were carried out using a process similar to that of Example 1, except that the formulations and process parameters used in each example were different. For details, see Table 1 (Note: the parameters not listed in Table 1 are the same as the corresponding parameters in Example 1).

[0096] Table 1

[0097]

[0098]

[0099] Example 4

[0100] This embodiment is carried out in a similar manner to that of embodiment 1, except that in step (2), the weight ratio of the intermediate material I to the 2.5 mol / L sulfuric acid solution is 1:1.

[0101] The rest are the same as in Example 1.

[0102] Carbon powder S4 is recovered.

[0103] Example 5

[0104] This example was carried out in a similar manner to that of Example 1, except that in step (2), the conditions for the second contact reaction were: temperature of 40° C., stirring speed of 300 rpm, and time of 6 h.

[0105] The rest are the same as in Example 1.

[0106] Carbon powder S5 is recovered.

[0107] Example 6

[0108] This embodiment is carried out in a similar manner to that of embodiment 1, except that in step (2), the condition for the second aeration treatment is: the air flow rate is 300 sccm.

[0109] The rest are the same as in Example 1.

[0110] Carbon powder S6 is recovered.

[0111] Comparative Example 1

[0112] This comparative example was carried out in a similar manner to Example 1, except that in step (2), the weight ratio of the intermediate material I to the 2.5 mol / L sulfuric acid solution was 1:0.5.

[0113] The rest are the same as in Example 1.

[0114] Carbon powder DS1 was recovered.

[0115] Comparative Example 2

[0116] This comparative example was carried out in a similar manner to Example 1, except that in step (2), the conditions for the second contact reaction were: temperature of 25° C., stirring speed of 300 rpm, and time of 6 h.

[0117] The rest are the same as in Example 1.

[0118] Carbon powder DS2 is recovered.

[0119] Comparative Example 3

[0120] This embodiment is carried out in a similar manner to that of embodiment 1, except that in step (2), only the logistics is circulated without aeration treatment. Specifically, the method is as follows:

[0121] (1) The same operation as in Example 1 was used to obtain a solid substance as intermediate material I;

[0122] (2) adding 2 t of the intermediate material I and a 2.5 mol / L sulfuric acid solution into the first circulating sub-barrel, starting the circulation device, the stirring device, and the heating device to complete the second contact reaction and obtain the intermediate material II;

[0123] In this step, the height difference between the first circulation sub-barrel and the second circulation sub-barrel in the circulation device is adjusted to 1000 mm;

[0124] (3) The intermediate material II is subjected to solid-liquid separation and drying treatment in sequence to obtain carbon powder DS3.

[0125] Test Case

[0126] 1. The carbon powder recovered in the examples and comparative examples was tested for purity. The results are shown in Table 2.

[0127] 2. 100 g of high-purity carbon powder recovered in the examples and comparative examples was ground and mixed with potassium hydroxide in a weight ratio of 1:4, and then placed in a corundum ark and placed in a tube furnace. Under argon protection, the mixture was reacted at 600° C. for 2 h to obtain a porous material precursor I. The porous material precursor I was washed twice with 0.5 mol / L dilute sulfuric acid and deionized water, respectively, and then dried in a vacuum drying oven to obtain a porous carbon material. The porous carbon material was subjected to performance tests, including specific surface area and pore volume. The results are shown in Table 2.

[0128] 0.5 mg of the above-mentioned porous carbon material, polytetrafluoroethylene and carbon black were added to 0.1 mL of anhydrous ethanol in a mass ratio of 8:1:1 and mixed evenly to obtain a slurry. The slurry was applied to a circular nickel foam and dried to obtain a material. The diaphragm, electrolyte and the material were combined into a button-type supercapacitor. The electrochemical performance was tested on a Neware tester. The voltage window was 0-1 V and the current density was 0.5 A / g. The test results are shown in Table 2.

[0129] 3. Cycle performance test: This paper intends to use the LAND battery test system with a charge and discharge voltage range of 0.01 to 1 V. In order to allow the electrolyte to infiltrate the active material and fully stimulate the activity of the electrode material, the button-type supercapacitor assembled above needs to be allowed to stand for 12 hours in advance, and then charged and discharged at a constant current of 500 mA / g. The specific results are shown in Table 2.

[0130] Table 2

[0131]

[0132] Table 2 (Continued)

[0133]

[0134]

[0135] It can be seen from the results in Table 2 that the carbon powder recovered from waste lithium iron phosphate black powder using the method of the present invention has higher purity, and the prepared porous carbon material has a higher specific surface area and pore volume, and has higher specific capacitance and better cycle performance when applied to capacitors.

[0136] The present invention provides an exemplary scanning electron microscope image of the porous carbon material prepared by recycling the carbon powder obtained in Example 1 and Comparative Example 3 of the present invention, see Figure 3 .

[0137] from Figure 3 It can be seen that the porous carbon material prepared from carbon powder with higher purity has a more developed pore structure, a larger specific surface area, and is more conducive to electron transmission.

[0138] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for recovering carbon powder from waste lithium iron phosphate black powder, characterized in that: The method is carried out in a circulation device comprising an aeration device and a circulation barrel connected thereto; the method comprises: (1) introducing a first raw material into the aeration device for a first aeration treatment, and introducing a mixed flow I obtained after the first aeration treatment into the circulation barrel for a first contact reaction to obtain a solid as an intermediate material I; the first raw material contains waste lithium iron phosphate black powder and an acid solution I; the waste lithium iron phosphate black powder contains 1-2 wt% of copper and 1-2 wt% of aluminum; (2) introducing a second raw material into the aeration device for a second aeration treatment, and introducing the mixed flow II obtained after the second aeration treatment into the circulation barrel for a second contact reaction to obtain an intermediate material II; the second raw material contains the acid solution II and the intermediate material I obtained in step (1); the conditions of the second contact reaction at least meet the following requirements: the temperature is not less than 40° C.; the weight ratio of the intermediate material I to the acid solution II is 1:1-5; (3) Drying the intermediate material II to obtain the carbon powder; The first aeration treatment and the second aeration treatment are both carried out in the presence of a gaseous phase flow, and the conditions of the first aeration treatment and the second aeration treatment each independently at least satisfy: the oxygen content in the gaseous phase flow is 15-30 V / V%, and the flow rate of the gaseous phase flow is 300-800 sccm.

2. The method for recovering carbon powder from waste lithium iron phosphate black powder according to claim 1, wherein the circulation equipment further comprises a circulation pump, the circulation barrel comprises a first circulation sub-barrel and a second circulation sub-barrel arranged downstream of the first circulation sub-barrel, the first circulation sub-barrel and the second circulation sub-barrel having a height difference of not less than 100 mm, and the second circulation sub-barrel and the aeration device are connected via the circulation pump.

3. The method for recovering carbon powder from waste lithium iron phosphate black powder according to claim 2, wherein: The oxygen content in the gas phase flow in the first aeration treatment is 20-25 V / V%, and the flow rate of the gas phase flow in the second aeration treatment is 500-700 sccm.

4. The method for recovering carbon powder from waste lithium iron phosphate black powder according to claim 3, wherein: In step (1), the conditions of the first contact reaction are controlled so that the content of lithium ions in the material at the bottom of the second circulation sub-barrel is less than 100 ppm at the end of the first contact reaction; And / or, the first contact reaction is carried out under stirring conditions, and the conditions of the first contact reaction also include: a stirring speed of 200-600 rpm and a temperature of 25-80°C.

5. The method for recovering carbon powder from waste lithium iron phosphate black powder according to claim 1 or 2, characterized in that: The weight ratio of the waste lithium iron phosphate black powder to the acid solution I is 1:2-4; And / or, the concentration of the acid solution I is 2-4 mol / L.

6. The method for recovering carbon powder from waste lithium iron phosphate black powder according to claim 1 or 2, characterized in that: The second contact reaction is carried out under stirring conditions, and the conditions for the second contact reaction include: a stirring speed of 200-600 rpm, a temperature of 60-80° C., and a time of 6-12 hours.

7. The method for recovering carbon powder from waste lithium iron phosphate black powder according to claim 1 or 2, characterized in that: The weight ratio of the intermediate material I to the acid solution II is 1:2-4; And / or, the concentration of the acid solution II is 2-4 mol / L.

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