Method for flash preparation of lithium manganese iron phosphate through cooperation of ferrophosphorus tailings and waste lithium manganate

Abstract

The invention discloses a method for preparing lithium manganese iron phosphate through cooperation of ferrophosphorus tailings and waste lithium manganate in a flash mode, and the method comprises the steps that the ferrophosphorus tailings and the waste lithium manganate are subjected to multiple times of pulse synthesis through a flash heating method to obtain the lithium manganese iron phosphate. According to the method, the waste lithium iron phosphate battery and the waste lithium manganate are recycled to synthesize a new positive electrode material, so that a perfect closed loop of recycling of the waste battery and remanufacturing of the new battery is realized, and a plurality of steps in purification, leaching and synthesis during traditional treatment of the ferrophosphorus tailings and recycling of the lithium manganate are omitted; more importantly, complex procedures such as long-time high-temperature sintering required for manufacturing the lithium manganese iron phosphate are greatly shortened, the time cost and the labor cost are effectively saved, the purity of the synthesized lithium manganese iron phosphate reaches 99.97%, large consumption of strong acid and strong base and long-time high-temperature energy waste are avoided, and the method is suitable for industrial production. And an efficient and economical closed-loop method is provided for waste lithium battery recovery and new battery preparation.

Description

Technical field:

[0001] The present invention relates to the technical field of waste lithium battery recycling, and in particular to a method for flash-preparing lithium ferromanganese phosphate using ferrophosphorus tailings and waste lithium manganate. Background technology:

[0002] The most widely used process in the lithium battery recycling industry is hydrometallurgical recycling, particularly for lithium iron phosphate batteries (LIFP) from retired electric vehicles. The established process prioritizes lithium extraction, while iron is oxidized to insoluble ferrous phosphate (FePO), which is then deposited in large quantities as tailings. However, these leached ferrous phosphate tailings cannot be directly used in commercial ferrous phosphate materials due to their high impurities and large lattice defects, and there is currently no effective solution. Purifying these ferrous phosphate tailings requires lengthy steps. Meanwhile, with the widespread adoption of convenient electronic devices and smart appliances, a common feature of these electronic products is that most of them contain lithium manganese oxide (LMO) batteries. However, LMO batteries have a low value, making recycling uneconomical and leading to widespread disposal. Therefore, the disposal of these two types of lithium battery waste is particularly important. Currently, LMOF is considered a next-generation cathode material to replace LMOF due to its low cost, high safety, excellent low-temperature performance, and high energy density. Currently, reported methods for preparing LMOF mainly include liquid phase methods, high-temperature solid-phase methods, and spray drying. For example, Chinese patent CN115215315 uses a hydrothermal method to recover iron and manganese from stainless steel slag to prepare lithium iron manganese phosphate. The hydrothermal method for preparing lithium iron manganese phosphate needs to be carried out under high temperature and high pressure, and the use of a large amount of organic solvents will cause serious environmental pollution, making it unsuitable for mass production. At the same time, the content of iron and manganese elements in stainless steel slag is relatively low, and the yield of preparing lithium iron manganese phosphate using it is not high. Chinese patent CN115231541 publicly reports the use of a spray drying method to prepare lithium iron manganese phosphate, but the equipment cost required for this method is relatively high and the operation is complicated. It is difficult to cope with the vast power battery market today. CN110396598A discloses a method for recycling lithium manganese oxide positive electrode materials of waste lithium-ion batteries, which uses a mixed solution of sulfuric acid and hydrogen peroxide for leaching, and then performs a hydrothermal reaction. However, the strong acid discharges high-salt wastewater, and the lengthy process conditions of leaching + hydrothermal reaction will greatly reduce production capacity and increase costs. CN119551645A discloses a high-density lithium manganese iron phosphate material, its preparation method, and its use. This method involves first preparing a large-particle raw material, then compounding it into a precursor, and finally adding a lithium salt to synthesize the lithium manganese iron phosphate. While the resulting cathode material has high electrochemical performance, the long reaction steps and the need for precise control of each process step significantly increase costs and pose the risk of poor cyclic stability.

[0003] Therefore, it is necessary to develop a method for flash preparation of lithium iron manganese phosphate positive electrode material by using ferrophosphorus tailings and waste lithium manganese oxide. Summary of the invention:

[0004] The purpose of the present invention is to provide a method for flash preparing lithium ferromanganese phosphate by using ferrophosphorus tailings in conjunction with waste lithium manganate, which solves the problems that the tailings discharged from waste lithium iron phosphate batteries recycled by the hydrometallurgical industry cannot be utilized at a high value, the recovery value of waste lithium manganate is low, and the lithium ferromanganese phosphate synthesis steps are long.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for flash-preparing lithium ferromanganese phosphate by using ferrophosphorus tailings and waste lithium manganate. The method comprises the following steps: uniformly mixing the ferrophosphorus tailings and waste lithium manganate at a mass ratio of 151:181 to 154:185 in a tumbling oscillator under tumbling oscillation conditions to obtain a mixed waste material; placing the mixed waste material in a graphite boat and rapidly heating the mixed waste material by pulse heating in an argon atmosphere of a high-pressure reactor; and rapidly cooling the sample after the heating is completed to obtain the lithium ferromanganese phosphate. The ferrophosphorus tailings mainly contain ferrophosphate, and may include ferrophosphorus tailings obtained by hydrometallurgical recovery of waste lithium ferrophosphate batteries (see US10741890B2, CN108899601B, CN107381604B), phosphorus-containing slag obtained by producing ferrophosphorus in a blast furnace (see JP5569174B2), or byproduct slag obtained by producing yellow phosphorus in an electric furnace (see CN115286433B).

[0007] The waste lithium manganese oxide comes from waste lithium manganese oxide battery positive electrode materials.

[0008] Preferably, the rotation speed of the tumbling oscillation is 15 to 40 rpm / min, and the oscillation frequency is 3 to 18 Hz.

[0009] Preferably, the current density is 2000-4500A / m 2 , voltage density is 40-55V / m 2 .

[0010] Preferably, the argon gas pressure is 0.8-1.3 MPa.

[0011] Preferably, the rapid heating rate is 10-60° C. / ms.

[0012] Preferably, the pulse frequency of the pulse heating is fixed at 1000 Hz.

[0013] Preferably, the pulse heating has a pulse number of 1 to 50 times and a duration of 1 to 50 ms.

[0014] Preferably, the rapid cooling is water cooling or liquid nitrogen freezing.

[0015] Preferably, the cooling rate of the rapid cooling is 200 to 2.2×10 3 ℃ / s.

[0016] The flash heating method of the present invention is a constant current density pulse heating method, which uses a constant current density or constant voltage density power supply to electrically heat the ferrophosphorus tailings and waste lithium manganese oxide. The flash heating method is based on the principle of Joule heating. The graphite boat is heated, and the heat is transferred to the ferrophosphorus tailings and waste lithium manganese oxide for flash heating. By controlling the area of ​​the mixed raw materials stacked in the graphite boat, the high-pressure reactor is filled with argon gas and the current density, voltage density, and number of pulses are adjusted to heat the mixed raw materials. After heating, the outside of the high-pressure reactor is cooled by water or by injecting liquid nitrogen into the argon gas inlet to cool the mixture.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. Compared with traditional pickling and repairing of ferrophosphorus tailings to other compounds, the flash heating method used in the present invention can omit the lengthy impurity removal and purification steps, reduce the wastewater and waste residue discharged in these steps, and flash heating to high temperature can repair the lattice of ferrophosphorus tailings, avoiding the range defects caused by lattice defects when synthesizing lithium battery positive electrode materials.

[0019] 2. Compared with the traditional synthesis of lithium battery positive electrode materials, which requires ball milling, high-temperature sintering, grinding and screening, which takes more than ten hours, the present invention has obvious advantages in time, can effectively solve the problem of lengthy preparation time of lithium manganese iron phosphate, and effectively improve the synthesis efficiency of lithium manganese iron phosphate.

[0020] 3. The present invention can recycle waste lithium manganese oxide with low value, effectively saving time and labor costs, and significantly improving industrial benefits.

[0021] In summary, the present invention synthesizes lithium iron manganese phosphate from ferrophosphorus tailings and waste lithium manganese oxide by multiple pulses using a flash heating method, simultaneously removes impurities and repairs the lattice of the ferrophosphorus tailings, and recovers the waste lithium iron phosphate batteries and waste lithium manganese oxide to synthesize new positive electrode materials, thereby realizing a perfect closed loop of old battery recycling and new battery remanufacturing, eliminating multiple steps of purification, leaching, and synthesis in traditional treatment of ferrophosphorus tailings and recovery of lithium manganese oxide. More importantly, it greatly shortens the complex processes such as long-term high-temperature sintering required for the manufacture of lithium iron manganese phosphate, effectively saving time and labor costs. The purity of the synthesized lithium iron manganese phosphate reaches 99.97%, which not only avoids the large-scale consumption of strong acids and alkalis and the waste of energy at long-term high temperatures, but also accurately and directionally synthesizes the two lithium battery wastes into the next-generation power battery positive electrode material, providing an efficient and economical closed-loop method for the recycling of waste lithium batteries and the preparation of new batteries. Description of the drawings:

[0022] Figure 1 This is the XRD pattern of the lithium manganese iron phosphate material obtained in Example 2;

[0023] Figure 2This is a long cycle performance diagram of the positive electrode material of lithium manganese iron phosphate prepared in Example 2 and Comparative Examples 1-2. Specific implementation method:

[0024] The following is a further description of the present invention, but not a limitation of the present invention.

[0025] The ferrophosphorus tailings in the following examples were derived from ferrophosphorus resources recovered from waste lithium iron phosphate batteries via sulfuric acid pickling. ICP analysis revealed a molar ratio of phosphorus to iron in the ferrophosphorus residue of approximately 1:1. The waste lithium manganese oxide was derived from the positive electrode material of waste lithium manganese oxide batteries.

[0026] Example 1: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0027] The steps include:

[0028] Add 151g of ferrophosphorus tailings and 181g of waste lithium manganate to the tumbling oscillator, set the tumbling oscillation speed to 15rpm / min, the tumbling oscillation frequency to 3Hz, place the mixture in a graphite boat, and then place the graphite boat in a high-pressure reactor. Set the current density to 2000A / m 2 , voltage density is 40V / m 2 The autoclave was closed, and the argon pressure was set to 0.8 MPa, the heating rate to 10°C / ms, the pulse frequency to 1, the duration to 1ms, and the cooling rate to 200°C / s. After the above treatment, the two waste particles fused, and the atoms rearranged under the drive of thermal energy to synthesize lithium manganese iron phosphate.

[0029] Example 2: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0030] The process comprises the following steps: adding 151 g of ferrophosphorus tailings and 181 g of waste lithium manganate to a tumbling oscillator, setting the tumbling oscillation speed to 40 rpm / min and the tumbling oscillation frequency to 18 Hz, placing the mixture in a graphite boat, and then placing the graphite boat in a high-pressure reactor, and setting the current density to 4500 A / m 2 , voltage density is 55V / m 2 The autoclave was closed, the argon pressure was set to 1.3 MPa, the heating rate to 60°C / ms, the number of pulses to 50, the duration to 50 ms, and the cooling rate to 2200°C / s. After the above treatment, the two waste particles fused, and the atoms rearranged under the drive of thermal energy to synthesize lithium manganese iron phosphate.

[0031] Example 3: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0032] The process comprises the following steps: adding 151 g of ferrophosphorus tailings and 181 g of waste lithium manganate to a tumbling oscillator, setting the tumbling oscillation speed to 20 rpm / min and the tumbling oscillation frequency to 6 Hz, placing the mixture in a graphite boat, and then placing the graphite boat in a high-pressure reactor, and setting the current density to 2500 A / m 2 , voltage density is 43V / m 2 The autoclave was closed, and the argon pressure was set to 0.9 MPa, the heating rate to 20°C / ms, the pulse frequency to 10 times, the duration to 10 ms, and the cooling rate to 600°C / s. After the above treatment, the two waste particles fused, and the atoms rearranged under the drive of thermal energy to synthesize lithium manganese iron phosphate.

[0033] Example 4: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0034] The process comprises the following steps: adding 151 g of ferrophosphorus tailings and 181 g of waste lithium manganate to a tumbling oscillator, setting the tumbling oscillation speed to 35 rpm / min and the tumbling oscillation frequency to 15 Hz, placing the mixture in a graphite boat, and then placing the graphite boat in a high-pressure reactor, setting the current density to 4000 A / m 2 , voltage density is 52V / m 2 The autoclave was closed, the argon pressure was set to 1.2 MPa, the heating rate was 50°C / ms, the number of pulses was 40, the duration was 40 ms, and the cooling rate was 1800°C / s. After the above treatment, the two waste particles fused, and the atoms rearranged under the drive of thermal energy to synthesize lithium manganese iron phosphate.

[0035] Example 5: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0036] The process comprises the following steps: adding 151 g of ferrophosphorus tailings and 181 g of waste lithium manganate to a tumbling oscillator, setting the tumbling oscillation speed to 25 rpm / min and the tumbling oscillation frequency to 9 Hz, placing the mixture in a graphite boat, and then placing the graphite boat in a high-pressure reactor, setting the current density to 3000 A / m 2 , voltage density is 46V / m 2 The autoclave was closed, the argon pressure was set to 1 MPa, the heating rate to 30°C / ms, the number of pulses to 20, the duration to 20ms, and the cooling rate to 1000°C / s. After the above treatment, the two waste particles fused, and the atoms rearranged under the drive of thermal energy to synthesize lithium manganese iron phosphate.

[0037] Example 6: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0038] The process comprises the following steps: adding 151 g of ferrophosphorus tailings and 181 g of waste lithium manganate to a tumbling oscillator, setting the tumbling oscillation speed to 30 rpm / min and the tumbling oscillation frequency to 12 Hz, placing the mixture in a graphite boat, and then placing the graphite boat in a high-pressure reactor, and setting the current density to 3500 A / m 2 , voltage density is 49V / m 2 The autoclave was closed, and the argon pressure was set to 1.1 MPa, the heating rate to 40°C / ms, the number of pulses to 30, the duration to 30 ms, and the cooling rate to 1400°C / s. After the above treatment, the two waste particles fused, and the thermally driven atomic rearrangement caused the synthesis of lithium manganese iron phosphate.

[0039] Comparative Example 1: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0040] Refer to Example 2, the difference is that the number of pulses is not set, and the rest of the process and parameters are the same as those in Example 2.

[0041] Since the number of pulses was not set during heating in Comparative Example 1, the temperature was always maintained at a relatively high temperature, causing the material to dissociate into a mixture of various iron / manganese compounds after synthesis, and failing to achieve the simultaneous synthesis of lithium manganese iron phosphate while disposing of the waste.

[0042] Comparative Example 2: A method for flash preparation of positive electrode materials using waste leaching residue and waste lithium manganese oxide

[0043] Refer to Example 2, the difference is that the cooling method is natural cooling, and the other processes and parameters are the same as Example 2.

[0044] Since the cooling speed in Comparative Example 2 is slow, the lithium element undergoes gasification and biochemical transformation at a relatively high temperature, and the lithium content in the synthesized material is extremely low, and the synthesis of lithium iron manganese phosphate positive electrode material cannot be achieved.

[0045] The purity of the lithium manganese iron phosphate products synthesized in Examples 1 to 6 and Comparative Examples 1 to 2 is shown in Table 1:

[0046] Table 1

[0047]

[0048] The positive electrode materials of lithium manganese iron phosphate prepared in Example 2 and Comparative Example 1-2 were subjected to charge and discharge tests. Figure 2 , showing that Example 2 has a longer cycle number and a more stable cycle.

[0049] The description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for flash-producing lithium ferromanganese phosphate by using ferrophosphorus tailings and waste lithium manganate, characterized in that: The method comprises the following steps: mixing ferrophosphorus tailings and waste lithium manganate in a mass ratio of 151:181 to 154:185 in a tumbling oscillator under tumbling oscillation conditions to obtain mixed waste, placing the mixed waste in a graphite boat, and rapidly heating the mixed waste by pulse heating in an argon atmosphere of a high-pressure reactor using a flash heating method, and rapidly cooling the sample after the heating is completed to obtain lithium ferromanganese phosphate; the ferrophosphorus tailings mainly contain ferrophosphate, including ferrophosphorus tailings obtained by hydrometallurgical recovery of waste lithium ferrophosphate batteries, or phosphorus-containing slag produced by a blast furnace process to produce ferrophosphorus, or slag produced as a byproduct of electric furnace production of yellow phosphorus.

2. The method according to claim 1, characterized in that The waste lithium manganese oxide comes from waste lithium manganese oxide battery positive electrode materials.

3. The method according to claim 1, characterized in that The rotation speed of the tumbling oscillation is 15 to 40 rpm / min, and the oscillation frequency is 3 to 18 Hz.

4. The method according to claim 1, wherein Current density is 2000-4500A / m 2 , voltage density is 40-55V / m 2 .

5. The method according to claim 1, wherein The argon gas pressure is 0.8-1.3 MPa.

6. The method according to claim 1, characterized in that The rapid heating rate is 10-60°C / ms.

7. The method according to claim 1, characterized in that The pulse frequency of the pulse heating is fixed at 1000 Hz.

8. The method according to claim 1, characterized in that The pulse heating has a pulse number of 1 to 50 times and a duration of 1 to 50 ms.

9. The method according to claim 1, characterized in that The rapid cooling is water cooling or liquid nitrogen freezing.

10. The method according to claim 1, characterized in that The cooling rate of the rapid cooling is 200~2.2×10 3 ℃ / s.

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