Full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries

Abstract

The invention relates to the technical field of resource recycling of waste lithium iron phosphate batteries, in particular to a waste lithium iron phosphate battery full-cycle low-carbon slag-free recycling method which comprises the following steps: S1, pretreatment: sorting out lithium iron phosphate black powder and carrying out heat treatment, S2, copper recycling: preparing basic copper carbonate and copper extraction slag by using the lithium iron phosphate black powder, and S3, recycling copper from the copper extraction slag. The method comprises the following steps: S1, preparing copper extraction slag, S2, preparing sodium phosphate, S3, recycling lithium: preparing battery-grade lithium carbonate and lithium extraction slag from the copper extraction slag, S4, recycling phosphorus and aluminum: preparing aluminum phosphate, trisodium phosphate dodecahydrate and phosphorus extraction slag from the lithium extraction slag, S5, recycling iron: preparing iron phosphate and graphite slag from the phosphorus extraction slag, and S6, recycling graphite: preparing a regenerated graphite negative electrode material from the graphite slag. According to the method, all the component elements in the lithium iron phosphate black powder are comprehensively recycled, the total recycling efficiency of all the component elements is greatly improved, the output of pollutants is reduced, and the green production level is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recovery of waste lithium iron phosphate batteries, and in particular to a full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries. Background Art

[0002] As new energy development technology matures, lithium-ion batteries have attracted much attention for their high specific energy, high voltage, long cycle life, good safety, and environmental friendliness, and are widely used in electronic communications, electric vehicles, and other fields. The service life of lithium batteries is only 3-5 years, and recycling a large number of lithium batteries that are no longer in use is a problem that must be faced.

[0003] At present, most recycling technologies are mainly aimed at the recycling of a series of precious metals such as cobalt and nickel in waste lithium batteries, but the recycling of lithium iron phosphate black powder is slightly insufficient; in the existing recycling methods, the recovery of various elements in lithium iron phosphate black powder is not comprehensive, and the unrecycled part is directly wasted, resulting in incomplete and low efficiency recycling, and will produce additional solid waste pollution, which is not friendly to the environment. Summary of the invention

[0004] In response to the above problems, the present invention provides a full-cycle, low-carbon, slag-free recycling method for waste lithium iron phosphate batteries to solve the problems in the prior art of insufficient recycling of lithium iron phosphate black powder, incomplete recovery of various elements, low efficiency, and generation of additional solid waste pollution.

[0005] To achieve the above object, the present invention provides a full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries, comprising the following steps:

[0006] S1 pretreatment: discharge, crush and disassemble the waste lithium iron phosphate batteries, separate the diaphragm, shell and lithium iron phosphate black powder from the waste lithium iron phosphate batteries, and heat treat the lithium iron phosphate black powder;

[0007] S2 copper recovery: using ammonia-ammonium mixed solution to leach copper from the heat-treated lithium iron phosphate black powder, filtering and separating to obtain copper-containing liquid and copper-extracting slag, heating the copper-containing liquid for deammoniation, filtering and drying the residue to obtain basic copper carbonate;

[0008] S3 lithium recovery: using oxidation-acid leaching method, extracting lithium from copper extraction slag with a mixed solution of hydrogen peroxide and sulfuric acid, filtering and separating to obtain lithium-containing liquid and lithium extraction slag; removing heavy metal impurities from the lithium-containing liquid by precipitation, extracting lithium with an extractant, and stripping with sulfuric acid to obtain a lithium sulfate solution, adding sodium carbonate precipitant to the lithium sulfate solution to react and generate lithium carbonate precipitate, washing and drying to obtain battery-grade lithium carbonate;

[0009] S4 Phosphorus and aluminum recovery: adopt alkali leaching method, use alkali solution to separate phosphorus and iron from lithium extraction slag, filter and separate to obtain phosphorus-containing liquid and phosphorus extraction slag; use sulfuric acid to adjust the pH of phosphorus-containing liquid to generate aluminum phosphate precipitate, filter and separate to obtain crude aluminum phosphate and phosphorus-containing purified liquid, wash, filter and dry the crude aluminum phosphate to obtain aluminum phosphate; use phosphoric acid to adjust the pH of phosphorus-containing purified liquid, cool and crystallize to generate sodium phosphate trihydrate precipitate, centrifuge and filter, and then dry at low temperature to obtain sodium phosphate trihydrate;

[0010] S5 iron recovery: dissolving the phosphorus extraction slag with sulfuric acid, filtering and separating to obtain iron-containing liquid and graphite slag; dissolving the trisodium phosphate dodecahydrate prepared in step S4 and adding it to the iron-containing liquid, adjusting the pH of the iron-containing liquid, reacting under high temperature to generate crude iron phosphate, filtering, washing, and drying to obtain an iron phosphate product;

[0011] S6 Graphite Recovery: The graphite slag is subjected to purification, coating and graphitization processes in sequence to produce recycled graphite negative electrode material.

[0012] Furthermore, in step S1, the heat treatment temperature of the lithium iron phosphate black powder is 450-600° C., and the heat treatment time is 2-5 hours.

[0013] Furthermore, in step S2, the ammonia-ammonium mixed solution is a mixed solution of ammonia and ammonium carbonate or ammonium bicarbonate, the ammonium concentration in the ammonia-ammonium mixed solution is 1-5 mol / L, the ratio of the ammonia-ammonium mixed solution to lithium iron phosphate black powder is 2-5:1, the copper leaching temperature is 30-50°C, and the leaching time is 2-4h; the heating deammoniation temperature of the copper-containing solution is 90-110°C, the filter residue drying temperature is 70°C, and the drying time is 2h.

[0014] Furthermore, in step S3, the concentration of sulfuric acid in the mixed solution of hydrogen peroxide and sulfuric acid is 0.4-1 mol / L, the temperature is controlled at 50-80° C. during the oxidation-acid leaching process to extract lithium, and the extraction time is 4-8 hours.

[0015] Furthermore, in step S3, in the process of removing heavy metal impurities by precipitation, the pH value of the lithium-containing liquid is adjusted to 10-12 to precipitate the heavy metal impurities in the lithium-containing liquid; in the process of extracting lithium using an extractant, a diketone lithium extractant is used, and the volume ratio of the extractant to the lithium-containing liquid is 1:1; in the process of obtaining a lithium sulfate solution by back extraction using sulfuric acid, the sulfuric acid concentration is 1 mol / L, and the volume ratio of sulfuric acid to the lithium-containing liquid is 10:1; the sodium carbonate concentration in the sodium carbonate precipitant is 250 g / L, and the molar ratio of the amount of sodium carbonate added to the lithium content in the lithium sulfate solution is 1-1.5:1, and the reaction temperature of sodium carbonate and lithium sulfate is controlled to be 90°C, and the reaction time is 2h.

[0016] Furthermore, in step S4, the alkali solution is a sodium hydroxide solution with a concentration of 10-32%, the liquid-solid ratio of the alkali solution to the lithium extraction slag is 2-5:1, the temperature of the ferrophosphorus separation process is controlled at 50-90°C, and the control time is 2-4h.

[0017] Furthermore, in step S4, sulfuric acid is used to adjust the pH of the phosphorus-containing liquid to 4-7 to generate aluminum phosphate precipitate, and 0.1-0.5 mol / L phosphoric acid is used to wash the crude aluminum phosphate; phosphoric acid is used to adjust the pH of the phosphorus-containing purified liquid to 12-12.5, and the temperature is lowered to 5° C. to generate trisodium phosphate dodecahydrate precipitate.

[0018] Furthermore, in the step S5, in the process of dissolving the phosphorus extraction slag with sulfuric acid, the concentration of sulfuric acid is 2-5 mol / L, the liquid-solid ratio of sulfuric acid to phosphorus extraction slag is 5-10:1, the dissolution temperature is controlled to be 20-50°C, and the dissolution time is 2-4h; trisodium phosphate dodecahydrate is added to the iron-containing liquid at an iron-phosphorus molar ratio of 1-1.1:1, and the pH of the iron-containing liquid is adjusted to 1.8-2.2, and the reaction is carried out at a high temperature of 90°C for 4h to generate crude iron phosphate.

[0019] Furthermore, in step S6, in the purification process, the graphite slag is acid-leached with one or more of nitric acid, hydrochloric acid and sulfuric acid, the acid concentration is 5-10 mol / L, the purification temperature is controlled at 50-90°C, and the purification time is 2-4h; in the coating process, the purified graphite slag is solid-phase coated with asphalt at high temperature, and the asphalt dosage is 5-10% of the mass of the graphite slag; in the graphitization process, the asphalt-coated graphite slag is graphitized at 3000°C.

[0020] Beneficial effects of the present invention:

[0021] The present invention comprehensively recycles and utilizes each component element in the lithium iron phosphate black powder, greatly improves the total recovery efficiency of each component element, and reduces the amount of pollutants generated;

[0022] The present invention adopts a low-cost, highly selective reagent combination to carry out targeted leaching of different elements, and can selectively separate different elements in different steps, and greatly improve the recovery efficiency of different elements, and the recovery efficiency of different elements can reach more than 95%;

[0023] In the present invention, according to the composition of lithium iron phosphate black powder, the added value of different components is comprehensively considered, and the valuable components therein, including lithium, iron, phosphorus, copper, aluminum and graphite carbon, are fully and efficiently recovered;

[0024] The present invention adopts an alkaline leaching method to efficiently separate phosphorus and iron, greatly improving the efficiency of phosphorus and iron separation;

[0025] Each process in the present invention has extremely high selectivity for the recovery of valuable elements, the entire process is relatively gentle, the recovery process is greatly shortened, the energy consumption is greatly reduced, and it is beneficial to reduce carbon emissions; the valuable elements are efficiently and selectively separated and recovered, which greatly improves the recovery rate, and no residual slag is generated throughout the process, avoiding secondary pollution and improving the level of green production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1

[0030] A method for recycling waste lithium iron phosphate batteries in a full-cycle, low-carbon and slag-free manner comprises the following steps:

[0031] S1. Discharging, crushing and disassembling the waste lithium iron phosphate batteries, separating the diaphragm, the shell and the lithium iron phosphate black powder from the waste lithium iron phosphate batteries, and heat treating the lithium iron phosphate black powder at 550° C. for 5 hours;

[0032] S2, using a 2.5 mol / L ammonia-ammonium carbonate mixed solution to leach copper from the heat-treated lithium iron phosphate black powder, the liquid-solid ratio of the ammonia-ammonium carbonate mixed solution to the lithium iron phosphate black powder is 5:1, the process control temperature of leaching copper is 50 ° C, after 4 hours, the copper-containing liquid and the copper-extracting slag are separated after filtration, the copper-containing liquid is heated to 90 ° C for heating deamination, and the filter residue is dried at 70 ° C for 2 hours after filtration to obtain basic copper carbonate;

[0033] S3, using oxidation-acid leaching method, extracting lithium from the copper extraction slag by a sulfuric acid-hydrogen peroxide mixed solution with a sulfuric acid concentration of 0.1 mol / L, the liquid-solid ratio of the sulfuric acid-hydrogen peroxide mixed solution to the copper extraction slag is 5:1, the process temperature of lithium extraction is controlled at 60°C, and after 5 hours, the lithium-containing liquid and the lithium extraction slag are obtained by filtration and separation;

[0034] The pH of the lithium-containing solution is adjusted to 12, heavy metal impurities are removed by precipitation, lithium is extracted by using a diketone lithium extracting agent at a volume ratio of 1:1, and a lithium sulfate solution is obtained by back-extraction using 1 mol / L sulfuric acid at a volume ratio of 10:1, and a 250 mg / L sodium carbonate solution is added to the lithium sulfate solution, the molar ratio of the amount of sodium carbonate added to the lithium content in the lithium sulfate solution is 1:1, and the reaction is carried out at 90° C. for 2 hours to generate a lithium carbonate precipitate, which is washed and dried to obtain a battery-grade lithium carbonate;

[0035] S4, using alkaline leaching method, using 10% sodium hydroxide solution, at a liquid-solid ratio of 5:1, at 90°C, to separate phosphorus and iron from lithium extraction slag, the phosphorus and iron separation time is 4h, filtering and separating to obtain phosphorus-containing liquid and phosphorus extraction slag; using sulfuric acid to adjust the pH of the phosphorus-containing liquid to 7 to generate aluminum phosphate precipitate, filtering and separating to obtain crude aluminum phosphate and phosphorus-containing purified liquid, washing the crude aluminum phosphate with 0.2mol / L phosphoric acid, filtering and drying to obtain aluminum phosphate; using phosphoric acid to adjust the pH of the phosphorus-containing purified liquid to 12.5, cooling to 5°C to crystallize to generate trisodium phosphate dodecahydrate precipitate, centrifugally filtering and low-temperature drying to obtain trisodium phosphate dodecahydrate;

[0036] S5, using 5 mol / L sulfuric acid at a liquid-to-solid ratio of 5:1 to dissolve the phosphorus extraction slag, dissolving it at 50°C for 4 hours, filtering and separating to obtain iron-containing liquid and graphite slag; dissolving the trisodium phosphate dodecahydrate prepared in step S4 and adding it to the iron-containing liquid at an iron-phosphorus molar ratio of 1:0, adjusting the pH of the iron-containing liquid to 1.8, reacting at 90°C for 4 hours to generate crude iron phosphate, filtering, washing, and drying to obtain an iron phosphate product;

[0037] S6. Purify the graphite slag by acid leaching for 4 hours at 90°C with a mixed acid of hydrochloric acid and sulfuric acid at a concentration of 5 mol / L, perform high-temperature solid-phase coating on the purified graphite slag with 5% asphalt, and then graphitize the asphalt-coated graphite slag at 3000°C to obtain a regenerated graphite negative electrode material.

[0038] Embodiment 2

[0039] A method for recycling waste lithium iron phosphate batteries in a full-cycle, low-carbon and slag-free manner comprises the following steps:

[0040] S1. Discharging, crushing and disassembling the waste lithium iron phosphate batteries, separating the diaphragm, the shell and the lithium iron phosphate black powder from the waste lithium iron phosphate batteries, and heat treating the lithium iron phosphate black powder at 550° C. for 5 hours;

[0041] S2, using a 1 mol / L ammonia-ammonium carbonate mixed solution to leach copper from the heat-treated lithium iron phosphate black powder, the liquid-solid ratio of the ammonia-ammonium carbonate mixed solution to the lithium iron phosphate black powder is 5:1, the process control temperature of leaching copper is 50°C, and after 4 hours, the copper-containing liquid and the copper-extracting slag are separated after filtration, the copper-containing liquid is heated to 90°C for heating deamination, and the filter residue is dried at 70°C for 2 hours after filtration to obtain basic copper carbonate;

[0042] S3, using oxidation-acid leaching method, extracting lithium from the copper extraction slag by a sulfuric acid-hydrogen peroxide mixed solution with a sulfuric acid concentration of 0.4 mol / L, the liquid-solid ratio of the sulfuric acid-hydrogen peroxide mixed solution to the copper extraction slag is 5:1, the process temperature of lithium extraction is controlled at 60°C, and after 5 hours, the lithium-containing liquid and the lithium extraction slag are obtained by filtration and separation;

[0043] The pH of the lithium-containing solution is adjusted to 12, heavy metal impurities are removed by precipitation, lithium is extracted by using a diketone lithium extracting agent at a volume ratio of 1:1, and a lithium sulfate solution is obtained by back-extraction using 1 mol / L sulfuric acid at a volume ratio of 10:1, and a 250 mg / L sodium carbonate solution is added to the lithium sulfate solution, the molar ratio of the amount of sodium carbonate added to the lithium content in the lithium sulfate solution is 1:1, and the reaction is carried out at 90° C. for 2 hours to generate a lithium carbonate precipitate, which is washed and dried to obtain a battery-grade lithium carbonate;

[0044] S4, using alkaline leaching method, using 32% sodium hydroxide solution, at a liquid-solid ratio of 5:1, at 90°C, to separate phosphorus and iron from lithium extraction slag, the phosphorus and iron separation time is 4h, filtering and separating to obtain phosphorus-containing liquid and phosphorus extraction slag; using sulfuric acid to adjust the pH of the phosphorus-containing liquid to 7 to generate aluminum phosphate precipitate, filtering and separating to obtain crude aluminum phosphate and phosphorus-containing purified liquid, washing the crude aluminum phosphate with 0.1mol / L phosphoric acid, filtering and drying to obtain aluminum phosphate; using phosphoric acid to adjust the pH of the phosphorus-containing purified liquid to 12.5, cooling to 5°C to crystallize to generate trisodium phosphate dodecahydrate precipitate, centrifugally filtering and low-temperature drying to obtain trisodium phosphate dodecahydrate;

[0045] S5, using 5 mol / L sulfuric acid at a liquid-to-solid ratio of 5:1 to dissolve the phosphorus extraction slag, dissolving it at 50°C for 4 hours, filtering and separating to obtain iron-containing liquid and graphite slag; dissolving the trisodium phosphate dodecahydrate prepared in step S4 and adding it to the iron-containing liquid at an iron-phosphorus molar ratio of 1:0, adjusting the pH of the iron-containing liquid to 1.8, reacting at 90°C for 4 hours to generate crude iron phosphate, filtering, washing, and drying to obtain an iron phosphate product;

[0046] S6. Purify the graphite slag by acid leaching for 4 hours at 90°C with a mixed acid of hydrochloric acid and sulfuric acid at a concentration of 5 mol / L, perform high-temperature solid-phase coating on the purified graphite slag with 5% asphalt, and then graphitize the asphalt-coated graphite slag at 3000°C to obtain a regenerated graphite negative electrode material.

[0047] Embodiment 3

[0048] A method for recycling waste lithium iron phosphate batteries in a full-cycle, low-carbon and slag-free manner comprises the following steps:

[0049] S1. Discharging, crushing and disassembling the waste lithium iron phosphate batteries, separating the diaphragm, the shell and the lithium iron phosphate black powder from the waste lithium iron phosphate batteries, and heat treating the lithium iron phosphate black powder at 550° C. for 5 hours;

[0050] S2, using a 2.5 mol / L ammonia-ammonium carbonate mixed solution to leach copper from the heat-treated lithium iron phosphate black powder, the liquid-solid ratio of the ammonia-ammonium carbonate mixed solution to the lithium iron phosphate black powder is 5:1, the process control temperature of leaching copper is 50 ° C, after 4 hours, the copper-containing liquid and the copper-extracting slag are separated after filtration, the copper-containing liquid is heated to 90 ° C for heating deamination, and the filter residue is dried at 70 ° C for 2 hours after filtration to obtain basic copper carbonate;

[0051] S3, using oxidation-acid leaching method, extracting lithium from the copper extraction slag by a sulfuric acid-hydrogen peroxide mixed solution with a sulfuric acid concentration of 0.4 mol / L, the liquid-solid ratio of the sulfuric acid-hydrogen peroxide mixed solution to the copper extraction slag is 5:1, the process temperature of lithium extraction is controlled at 60°C, and after 5 hours, the lithium-containing liquid and the lithium extraction slag are obtained by filtration and separation;

[0052] The pH of the lithium-containing solution is adjusted to 12, heavy metal impurities are removed by precipitation, lithium is extracted by using a diketone lithium extracting agent at a volume ratio of 1:1, and a lithium sulfate solution is obtained by back-extraction using 1 mol / L sulfuric acid at a volume ratio of 10:1, and a 250 mg / L sodium carbonate solution is added to the lithium sulfate solution, the molar ratio of the amount of sodium carbonate added to the lithium content in the lithium sulfate solution is 1:1, and the reaction is carried out at 90° C. for 2 hours to generate a lithium carbonate precipitate, which is washed and dried to obtain a battery-grade lithium carbonate;

[0053] S4, using alkaline leaching method, using 15% sodium hydroxide solution, at a liquid-solid ratio of 5:1, at 90°C, to separate phosphorus and iron from lithium extraction slag, the phosphorus and iron separation time is 4h, filtering and separating to obtain phosphorus-containing liquid and phosphorus extraction slag; using sulfuric acid to adjust the pH of the phosphorus-containing liquid to 7 to generate aluminum phosphate precipitate, filtering and separating to obtain crude aluminum phosphate and phosphorus-containing purified liquid, washing the crude aluminum phosphate with 0.4mol / L phosphoric acid, filtering and drying to obtain aluminum phosphate; using phosphoric acid to adjust the pH of the phosphorus-containing purified liquid to 12.5, cooling to 5°C to crystallize to generate trisodium phosphate dodecahydrate precipitate, centrifugally filtering and low-temperature drying to obtain trisodium phosphate dodecahydrate;

[0054] S5, using 5 mol / L sulfuric acid at a liquid-solid ratio of 5:1 to dissolve the phosphorus extraction slag, dissolving it at 50°C for 4 hours, filtering and separating to obtain iron-containing liquid and graphite slag; dissolving the trisodium phosphate dodecahydrate prepared in step S4 and adding it to the iron-containing liquid according to the iron-phosphorus ratio, adjusting the pH of the iron-containing liquid to 1.8, reacting at 90°C for 4 hours to generate crude iron phosphate, filtering, washing, and drying to obtain an iron phosphate product;

[0055] S6. Purify the graphite slag by acid leaching for 4 hours at 90°C with a mixed acid of hydrochloric acid and sulfuric acid at a concentration of 5 mol / L, perform high-temperature solid-phase coating on the purified graphite slag with 5% asphalt, and then graphitize the asphalt-coated graphite slag at 3000°C to obtain a regenerated graphite negative electrode material.

[0056] Experiments were conducted according to the steps of Examples 1 to 3 above, all using 100 g of lithium iron phosphate black powder as the raw material. The final recovered products are shown in Table 1 below, and the recovery rates of each valuable component are shown in Table 2 below.

[0057] Table 1 Recovered product status table Unit: g

[0058]

[0059] Table 2 Recovery rate of each valuable component

[0060]

[0061] The index analysis of the recovered products in the above Examples 1 to 3 was carried out, and compared with relevant national or industry standards. The detailed analysis of the index of each recovered product is shown in Tables 3 to 8 below.

[0062] Table 3 Basic copper carbonate index analysis

[0063]

[0064] Table 4 Lithium carbonate index analysis

[0065]

[0066]

[0067] Table 5 Analysis of aluminum phosphate indicators

[0068]

[0069] Table 6 Analysis of indicators of trisodium phosphate dodecahydrate

[0070]

[0071]

[0072] Table 7 Analysis of iron phosphate indicators

[0073]

[0074] Table 8 Analysis of indicators of recycled graphite negative electrode materials

[0075]

[0076]

[0077] In summary, according to the relevant data in Table 1 and Table 2 above, it can be seen that Examples 1 to 3 all achieve high levels of recovery for each valuable component, among which the recovery rate of lithium is as high as 94.9%, close to 95%, the recovery rate of iron can exceed 95%, the recovery rate of phosphorus exceeds 96%, and can reach up to 97.3%, the recovery rate of copper is as high as 94.7%, the recovery rate of aluminum is as high as 97.8%, and the recovery rate of graphite is as high as 89.7%, close to 90%;

[0078] According to the relevant data in Tables 3 to 8 above, it can be seen that the relevant indicators of the recovered products in Examples 1 to 3 are in line with the relevant national or industry standards.

[0079] The iron and phosphorus contents and leaching rates in the phosphorus-containing liquid and the phosphorus extraction slag during step S4 of Examples 1 to 3 were detected and analyzed, as shown in Table 3 below.

[0080] Table 3 Iron and phosphorus content and leaching rate in phosphorus-containing liquid

[0081]

[0082] Based on the leaching solution, the phosphorus and iron separation efficiency was calculated according to the following formula. The phosphorus and iron separation efficiency in step S4 of Examples 1 to 3 is shown in Table 4.

[0083]

[0084] Table 4 Phosphorus and iron separation efficiency

[0085] project Embodiment 1 Embodiment 2 Embodiment 3 Separation efficiency % 95.29 96.69 97.49

[0086] According to Table 4 above, the phosphorus-iron separation efficiency can reach over 97%.

[0087] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries, characterized in that: The steps include: S1 pretreatment: discharge, crush and disassemble the waste lithium iron phosphate batteries, separate the diaphragm, shell and lithium iron phosphate black powder from the waste lithium iron phosphate batteries, and heat treat the lithium iron phosphate black powder; S2 copper recovery: using ammonia-ammonium mixed solution to leach copper from the heat-treated lithium iron phosphate black powder, filtering and separating to obtain copper-containing liquid and copper-extracting slag, heating the copper-containing liquid for deammoniation, filtering and drying the residue to obtain basic copper carbonate; S3 lithium recovery: using oxidation-acid leaching method, extracting lithium from copper slag with a mixed solution of hydrogen peroxide and sulfuric acid, filtering and separating to obtain lithium-containing liquid and lithium-extracting slag; The lithium-containing liquid is sequentially subjected to precipitation to remove heavy metal impurities, lithium is extracted using an extractant, and a lithium sulfate solution is obtained by back-extraction using sulfuric acid, sodium carbonate precipitant is added to the lithium sulfate solution to react and generate lithium carbonate precipitate, and battery-grade lithium carbonate is obtained after washing and drying; S4 Phosphorus and aluminum recovery: adopt alkali leaching method, use alkali solution to separate phosphorus and iron from lithium extraction slag, filter and separate to obtain phosphorus-containing liquid and phosphorus extraction slag; use sulfuric acid to adjust the pH of phosphorus-containing liquid to generate aluminum phosphate precipitate, filter and separate to obtain crude aluminum phosphate and phosphorus-containing purified liquid, wash, filter and dry the crude aluminum phosphate to obtain aluminum phosphate; use phosphoric acid to adjust the pH of phosphorus-containing purified liquid, cool and crystallize to generate sodium phosphate trihydrate precipitate, centrifuge and filter, and then dry at low temperature to obtain sodium phosphate trihydrate; S5 iron recovery: dissolving the phosphorus extraction slag with sulfuric acid, filtering and separating to obtain iron-containing liquid and graphite slag; dissolving the trisodium phosphate dodecahydrate prepared in step S4 and adding it to the iron-containing liquid, adjusting the pH of the iron-containing liquid, reacting under high temperature to generate crude iron phosphate, filtering, washing, and drying to obtain an iron phosphate product; S6 Graphite Recovery: The graphite slag is subjected to purification, coating and graphitization processes in sequence to produce recycled graphite negative electrode material.

2. According to claim 1, a full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries is characterized in that: In the step S1, the heat treatment temperature of the lithium iron phosphate black powder is 450-600° C., and the heat treatment time is 2-5 hours.

3. According to claim 1, a full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries is characterized in that: In the step S2, the ammonia-ammonium mixed solution is a mixed solution of ammonia and ammonium carbonate or ammonium bicarbonate, the ammonium concentration in the ammonia-ammonium mixed solution is 1-5 mol / L, the ratio of the ammonia-ammonium mixed solution to the lithium iron phosphate black powder is 2-5:1, the copper leaching temperature is 30-50°C, and the leaching time is 2-4h; the heating deammoniation temperature of the copper-containing solution is 90-110°C, the filter residue drying temperature is 70°C, and the drying time is 2h.

4. According to claim 1, a full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries is characterized in that: In step S3, the concentration of sulfuric acid in the mixed solution of hydrogen peroxide and sulfuric acid is 0.4-1 mol / L, the temperature is controlled at 50-80° C. during the oxidation-acid leaching process to extract lithium, and the extraction time is 4-8 hours.

5. According to claim 1, a full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries is characterized in that: In the step S3, in the process of removing heavy metal impurities by precipitation, the pH value of the lithium-containing liquid is adjusted to 10-12 to precipitate the heavy metal impurities in the lithium-containing liquid; in the process of extracting lithium by using an extractant, a diketone lithium extractant is used, and the volume ratio of the extractant to the lithium-containing liquid is 1:1; in the process of obtaining a lithium sulfate solution by back extraction with sulfuric acid, the sulfuric acid concentration is 1 mol / L, and the volume ratio of sulfuric acid to the lithium-containing liquid is 10:1; the sodium carbonate concentration in the sodium carbonate precipitant is 250 g / L, and the molar ratio of the amount of sodium carbonate added to the lithium content in the lithium sulfate solution is 1-1.5:1, and the reaction temperature of sodium carbonate and lithium sulfate is controlled to be 90° C., and the reaction time is 2 hours.

6. A full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries according to claim 1, characterized in that: In step S4, the alkali solution is a sodium hydroxide solution with a concentration of 10-32%, the liquid-solid ratio of the alkali solution to the lithium extraction slag is 2-5:1, the temperature of the ferrophosphorus separation process is controlled at 50-90° C., and the control time is 2-4 hours.

7. A full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries according to claim 1, characterized in that: In the step S4, sulfuric acid is used to adjust the pH of the phosphorus-containing liquid to 4-7 to generate aluminum phosphate precipitate, and 0.1-0.5 mol / L phosphoric acid is used to wash the crude aluminum phosphate; phosphoric acid is used to adjust the pH of the phosphorus-containing purified liquid to 12-12.5, and the temperature is lowered to 5° C. to generate trisodium phosphate dodecahydrate precipitate.

8. A full-cycle low-carbon slag-free recycling method for waste lithium iron phosphate batteries according to claim 1, characterized in that: In the step S5, in the process of dissolving the phosphorus extraction slag with sulfuric acid, the concentration of sulfuric acid is 2-5 mol / L, the liquid-solid ratio of sulfuric acid to phosphorus extraction slag is 5-10:1, the dissolution temperature is controlled to be 20-50°C, and the dissolution time is 2-4 hours; trisodium phosphate dodecahydrate is added to the iron-containing liquid at a molar ratio of iron to phosphorus of 1-1.1:1, and the pH of the iron-containing liquid is adjusted to 1.8-2.2, and the reaction is carried out at a high temperature of 90°C for 4 hours to generate crude iron phosphate.

9. A full-cycle low-carbon slag-free recovery method for waste lithium iron phosphate batteries according to claim 1, characterized in that: In the step S6, in the purification process, the graphite slag is acid-leached with one or more of nitric acid, hydrochloric acid and sulfuric acid, the acid concentration is 5-10 mol / L, the purification temperature is controlled at 50-90°C, and the purification time is 2-4 hours; in the coating process, the purified graphite slag is solid-phase coated with asphalt at high temperature, and the asphalt dosage is 5-10% of the mass of the graphite slag; in the graphitization process, the graphite slag coated with asphalt is graphitized at 3000°C.

Images