The present disclosure belongs to the technical field of resource recycling, and specifically relates to a method for recycling iron phosphate waste and use thereof.
Compared with traditional batteries (energy storage materials), lithium-ion batteries (LIBs) have the advantages of high voltage, large specific capacity, long cycling life, and prominent safety performance. LIBs are widely used in portable electronic equipment, electric vehicle, aerospace, military engineering, and other fields, which have promising application prospects and huge economic benefits. Lithium iron phosphate (LFP) batteries are widely used in portable batteries, electric vehicles, and other fields due to their advantages such as environmental friendliness, low price, and long cycling life.
Since 2010, LFP batteries have been used in electric taxis and electric buses. More and more LFP batteries have been decommissioned, and it is difficult to recover the performance of LFP only by simple physical methods. Decommissioned LFP batteries are first subjected to lithium extraction, and the remaining part is often discharged as industrial waste, which causes a series of environmental pollution problems such as water eutrophication and also causes a serious waste of phosphorus and iron resources. In related art, a recycling method of LFP positive and negative electrode sheets is disclosed, where lithium is recovered from the electrode sheets, and then lithium is complemented to prepare LFP. However, the method has problems such as cumbersome technological procedures, high cost, high impurity content, and low compacted density. With the technical development, the performance of a regenerated LFP material can fully meet the commercial application standards. It is particularly important to develop a simple, low-cost, easily-controlled, and environmentally-friendly method for recycling iron phosphate, which is also of great significance for building a true closed-loop industrial chain.
The present disclosure is intended to solve at least one of the technical problems existing in the prior art. In view of this, the present disclosure provides a method for recycling iron phosphate waste and use thereof. The method involves simple preparation process, high product consistency, low cost, high production capacity, and low energy consumption, and is environmentally friendly and suitable for large-scale industrial production.
According to one aspect of the present disclosure, a method for recycling iron phosphate waste is provided, including the following steps:
In some implementations of the present disclosure, the iron phosphate waste may include one or more from the group consisting of an iron phosphate scrap, a waste obtained after subjecting LFP to lithium extraction, an iron-phosphorus residue obtained after subjecting an LFP electrode sheet to lithium extraction, and an iron-phosphorus residue obtained after subjecting an LFP battery to disassembly and lithium extraction.
In some implementations of the present disclosure, in S1, the acid liquid may include one or more from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.
In some implementations of the present disclosure, in S1, a molar ratio of acid anions in the acid liquid to iron ions in the iron phosphate waste may be (1.1-1.5):1.
In some implementations of the present disclosure, in S1, the mixing of the iron phosphate waste with the acid liquid for dissolution may include: adding the acid liquid with stirring, where the stirring may be conducted at a speed of 100 r/min to 400 r/min for 3 h to 5 h.
In some implementations of the present disclosure, in S2, the alkali liquid may include one or more from the group consisting of ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, diammonium phosphate (DAP), sodium bicarbonate, and potassium bicarbonate; and the alkali liquid may be added at a speed of 0.1 L/min to 6 L/min.
In some implementations of the present disclosure, in S2, the pH may be adjusted to 0.5 to 2.5.
In some implementations of the present disclosure, in S2 and S3, the stirring may be conducted at a speed of 200 rpm/min to 600 rpm/min, the heating may be conducted at 80° C. to 100° C., and the reaction may be conducted for 2 h to 8 h.
In some implementations of the present disclosure, in S2, a filtrate obtained after the filtering may be added to the remaining portion of the iron-phosphorus solution in S3. Because there is still a small amount of Fe3+ in the filtrate, direct discharge of the filtrate goes against the original intention of the present disclosure, and the addition of the filtrate to the remaining portion of the iron-phosphorus solution in S3 can achieve the purpose of recycling.
In some implementations of the present disclosure, in S3, a filtrate obtained after the filtering may be used for the dissolution of the iron phosphate waste in S1, which can reduce the consumption of acid liquid.
In some implementations of the present disclosure, in S3, a mass of the iron phosphate dihydrate precipitate kept may account for 5% to 40% of a total mass of the iron phosphate dihydrate precipitate produced.
In some implementations of the present disclosure, in S3, the drying may be conducted at 110° C. to 150° C. by a manner of flash evaporation or rake drying.
The present disclosure also provides use of the method for recycling iron phosphate waste described above in the preparation of an LFP battery.
According to a preferred implementation of the present disclosure, the present disclosure at least has the following beneficial effects:
1. In the present disclosure, an iron phosphate precipitating agent is added to make a produced iron phosphate precipitate have uniform particle size distribution, high crystallinity, and prominent compactness.
2. In the combined process where a small amount of a precipitate is added for cycling provided by the present disclosure, an iron phosphate precipitating agent is prepared and used for the subsequent preparation of iron phosphate, and iron phosphate obtained in each preparation can be used for the next preparation of iron phosphate. The preparation process is simple, and involves an alkali liquid only in the preparation of a precipitating agent and does not involve the use of an alkali liquid in the subsequent production, which is environmentally friendly. Moreover, the method of the present disclosure involves high product consistency, low cost, high production capacity, and low energy consumption, and is suitable for large-scale industrial production.
3. The anhydrous iron phosphate prepared by the present disclosure meets the standards of iron phosphate used for LFP and shows further-optimized performance, which has an initial specific charge capacity of 162 mAh/g at 1 C and an initial coulombic efficiency of more than 96%. The anhydrous iron phosphate can be directly used as a precursor for preparing LFP.
The present disclosure is further described below with reference to accompanying drawings and examples.
The concepts and technical effects of the present disclosure are clearly and completely described below in conjunction with examples, so as to allow the objectives, features and effects of the present disclosure to be fully understood. Apparently, the described examples are merely some rather than all of the examples of the present disclosure. All other examples obtained by those skilled in the art based on the examples of the present disclosure without creative efforts should fall within the protection scope of the present disclosure.
Iron phosphate was prepared in this example by a specific process including the following steps:
Iron phosphate was prepared in this example by a specific process including the following steps:
Iron phosphate was prepared in this example by a specific process including the following steps:
Iron phosphate was prepared in this example by a specific process including the following steps:
Iron phosphate was prepared in this Comparative Example by a specific process including the following steps:
The anhydrous iron phosphate initially prepared and the anhydrous iron phosphate obtained after 3 cycles in Examples 1 to 4 were tested for physical and chemical indexes, and the physical and chemical indexes of the anhydrous iron phosphate initially prepared were compared with that of the anhydrous iron phosphate obtained after 3 cycles. Results were shown in Table 1 below.
It can be seen from Table 1 that, for both the anhydrous iron phosphate initially prepared and the anhydrous iron phosphate obtained after 3 cycles in the method of the present disclosure, various physical and chemical indexes are in line with the standards for LFP cathode materials, indicating that the anhydrous iron phosphate prepared by the cycle process has stable quality and the process is reliable.
The anhydrous iron phosphate initially prepared and the anhydrous iron phosphate obtained after 3 cycles in Example 3 and the commercially-available anhydrous iron phosphate (purchased from Langfang Nabo Chemical Technology Co., Ltd.) were used to prepare LFP according to the following method: 2,800 ml of water, 1,000 g of iron phosphate, 80 g of glucose, and 80 g of PEG dispersed in 200 g of hot water were mixed, where a final solid-to-liquid ratio was controlled at 35%; the mixture was dispersed with a high-speed disperser for 30 min and then poured into a sand mill for fine grinding, where a slurry D50 was controlled at 500 nm to 550 nm during the fine grinding; a resulting material was spray-dried at an air outlet temperature controlled at 100° C. to 110° C.; and the material was sintered at 750° C. for 10 h in a sagger introduced with nitrogen as an inert protective gas to obtain highly-compacted LFP. The prepared LFP was tested for performance indexes of all aspects, and results were shown in Table 2 below:
It can be seen from Table 2 that the compacted density and specific surface area (SSA) of the LFP powder synthesized from anhydrous iron phosphate in the examples of the present disclosure are higher than that of the LFP synthesized from the commercially-available iron phosphate, and the electrochemical performance of the LFP powder synthesized from anhydrous iron phosphate in the examples of the present disclosure is also slightly better than that of the LFP synthesized from the commercially-available iron phosphate, indicating that the anhydrous iron phosphate prepared by the present disclosure has reached the standards of iron phosphate used for LFP and shows further-optimized performance, and thus can be directly used as a precursor for the production of LFP. In addition, the anhydrous iron phosphate initially prepared has comparable properties to the anhydrous iron phosphate obtained after 3 cycles, indicating that the anhydrous iron phosphate prepared by the cycle process has stable quality and the process is very stable.
The present disclosure also compares Example 3 with Comparative Example 1 in terms of alkali consumption, specifically as shown in Table 3.
It can be seen from Table 3 that, in Example 3, alkali liquid is used only in the initial preparation, and an alkali liquid consumption in the initial preparation only accounts for about ¼ of an alkali liquid consumption in Comparative Example 1; and in Example 3, after the iron phosphate precipitate is recycled, the subsequent process does not involve the use of alkali liquid, but in Comparative Example 1, the alkali liquid consumption will increase with the increase in the treatment capacity of iron-phosphorus residue, indicating that the method of the present disclosure is more environmentally friendly and more economical than the conventional method.
The examples of present disclosure are described in detail with reference to the accompanying drawings, but the present disclosure is not limited to the above examples. Within the scope of knowledge possessed by those of ordinary skill in the technical field, various changes can also be made without departing from the purpose of the present disclosure. In addition, the examples in the present disclosure and features in the examples may be combined with each other in a non-conflicting situation.
Number | Date | Country | Kind |
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202110365978.8 | Apr 2021 | CN | national |
The present application is a continuation application of PCT application No. PCT/CN2021/142510 filed on Dec. 29, 2021, which claims the benefit of Chinese Patent Application No. 202110365978.8 filed on Apr. 6, 2021. The contents of all of the aforementioned applications are incorporated by reference herein in their entirety.
Number | Date | Country | |
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Parent | PCT/CN2021/142510 | Dec 2021 | US |
Child | 18373966 | US |