Regeneration method of lithium iron phosphate material based on raw material recycling

Abstract

The invention provides a regeneration method of a lithium iron phosphate material based on raw material recycling. The regeneration method comprises the following steps: crushing a lithium iron phosphate positive plate disassembled from a waste battery, and screening to obtain positive powder; calcining the positive electrode powder in a mixed atmosphere of chlorine and inert gas to decompose the lithium iron phosphate into LiCl and FePO4 to obtain a calcined substance, dissolving the calcined substance in water, and performing solid-liquid separation to obtain filtrate and filter residue; the filtrate is electrolyzed, the filtrate is placed in an anode chamber, the same amount of water is injected into a cathode chamber, lithium hydroxide is collected in the cathode chamber after electrolysis, and chlorine capable of being used for calcination leaching in the step (2) is collected in the anode chamber; and mixing the filter residue and lithium hydroxide according to the same molar ratio of lithium to iron, adding a reducing organic matter, mixing, carrying out ball milling, and roasting to obtain the LiFePO4 material. According to the regeneration method, separation of Li < + > and FePO4 can be realized through a low-temperature sintering reaction, so that the regeneration rate is relatively high, and input-output full closed loop of raw materials in the whole regeneration process can be realized.

Claims

1. A method for regenerating lithium iron phosphate material based on raw material recycling, characterized in that: include: (1) Preparation of positive electrode powder The lithium iron phosphate cathode sheets removed from waste batteries are crushed and screened to obtain cathode powder; (2) Calcination and leaching The positive electrode powder is calcined in a mixed atmosphere of chlorine and an inert gas to decompose lithium iron phosphate into LiCl and FePO4 to obtain a calcined product, and the calcined product is dissolved in water and then solid-liquid separated to obtain a filtrate and a filter residue, wherein the volume ratio of the chlorine and the inert gas in the mixed atmosphere is 10-25:75-90, and the calcination temperature is 180-250°C; (3) Electrolysis The filtrate is electrolyzed and the concentration of LiCl in the filtrate is controlled to be less than 50 g / L. The device used for the electrolysis uses graphite plates as cathode plates and anode plates, and is divided into a cathode chamber and an anode chamber using a cation exchange membrane. The filtrate is placed in the anode chamber, and an equal amount of water is injected into the cathode chamber. After the electrolysis, lithium hydroxide is collected in the cathode chamber, and chlorine gas that can be used for calcination and leaching in step (2) is collected in the anode chamber. (4) Regeneration The filter residue and the lithium hydroxide are mixed in a molar ratio of lithium to iron, and then a reducing organic matter is added, the mixture is ball-milled, and then calcined to obtain LiFePO4 material.

2. The regeneration method of lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The lithium iron phosphate-based positive electrode sheet includes a positive electrode active material, a binder, and a conductive agent. The chemical formula of the positive electrode active material is LiFe x M 1-x PO4, where M is at least one of Mg, Al, Mn, Co, Si, V, and Ti, 0.9 < x ≤ 1.0, the binder includes PVDF, and the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube, and graphene.

3. The regeneration method of lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The lithium iron phosphate positive electrode sheets are mechanically crushed to a particle size of 70-90 μm, and then screened using a sieve coupled with a vibration stirrer.

4. The regeneration method of lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The reducing organic matter includes at least one of pyromellitic acid, glycine, alanine, glucose and fructose.

5. The regeneration method of lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The voltage applied during the electrolysis is 3.5-4.0V.

6. The method for regenerating lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The lithium hydroxide is evaporated and crystallized to obtain LiOH•H2O crystals.

7. The method for regenerating lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The reducing organic matter accounts for 8-12% of the sum of the mass of the filter residue and the lithium hydroxide.

8. The method for regenerating lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The ball milling speed is 200-400 rpm, and the ball milling time is 3-5 h.

9. The method for regenerating lithium iron phosphate material based on raw material recycling according to claim 1, characterized in that: The calcination is carried out under an inert atmosphere, and the calcination includes pre-calcination and secondary calcination.

10. The method for regenerating lithium iron phosphate material based on raw material recycling according to claim 9, characterized in that: The pre-calcination temperature is 300-400° C., and the pre-calcination time is 10-15 hours. After the pre-calcination, reducing organic matter accounting for 8-12% of the sum of the mass of the filter residue and the lithium hydroxide is added and then the secondary calcination is performed. The secondary calcination temperature is 600-700° C., and the secondary calcination time is 10-15 hours.

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