Research progress on recovery technology for waste phosphate ion battery recovery technology

　　Author ：Iflowpower – Portable Power Station Supplier

In 2010, my country began to promote new energy vehicles. In 2014, the emergence of burst rises, 2017 sales of approximately 770,000 vehicles. Bus, bus, etc.

, based on lithium iron phosphate ion batteries, life expectancy is about 8 years. The continued rise in new energy vehicles will have a burst of dynamic lithium battery in the future. If a large number of eliminated batteries do not have a proper resolution, it will bring serious environmental pollution and energy waste, how to solve the waste battery Is a major problem that people care.

According to the statistics of my country's lithium-powered lithium battery industry, the demand for global dynamic lithium battery in 2016 is 41.6GW H, where LFP, NCA, NCM and LMO's four important types of dynamic lithium-ion batteries are 23.9GW · h, respectively.

5.5GW · h, 10.5GW · h and 1.

7GW · h, Lifepo4 battery occupy 57.4% of the market, NCA and NCM two major three-dimensional system power lithium battery total demand accounted for 38.5% of total demand.

Due to the high-energy density of the three-yuan material, the 2017 Sanyuan Power Lithium Battery is 45%, and the lithium iron battery is 49% of the lithium battery. At present, the pure electric passenger car is all lithium iron phosphate ion batteries, and the iron phosphate dynamic lithium battery is the most mainstreaming battery system in the early industry. Therefore, the decommissioning period of the lithium iron phosphate ion battery will be first arrived.

The recycling of LifePo4 waste batteries can not only reduce the environmental pressure caused by a large amount of waste, but will bring considerable economic benefits, which will contribute to the continued development of the entire industry. This article will resolve the country's current policy, the important price of the waste, LifePo4 batteries, etc. On this basis, a variety of recycling, re-use methods, electrolyte, electrolyte, electrolyte, electrolyte and negative electrode materials, and refer to the scale recovery supply reference for LIFEPO4 batteries.

1 Waste Battery Recycling Policy With the development of my country's lithium-ion battery industry, the effective recycling and solving of used batteries is a healthy problem that the industry can continue to develop. The Notice of "Energy Saving and New Energy Automobile Industry Development Plan (2012-2020)" is clearly mentioned that enhanced dynamic lithium battery step utilization and recovery management, the development of dynamic lithium battery recycling management method, guiding power lithium battery processing Company enhances recycling of waste batteries. With the increasing problem of dynamic lithium battery recovery, countries and places have announced the development of relevant policies, norms and supervision of recycling industry in recent years.

The country's important policy in battery recycling in the country is shown in Table 1. 2 Waste LifePO4 Battery Recycling Important Component Lithium Ion Battery Structure Generally includes a positive electrode, a negative electrode, an electrolyte, a diaphragm, a housing, a cover, and the like, wherein the positive electrode material is the core of the lithium ion battery, and the positive electrode material accounted for more than 30% of the battery cost. Table 2 is the material of a batch of 5A · h wound LifePO4 batteries in Guangdong Province (1% solid content in the table).

It can be seen from Table 2, the lithium positive electrode phosphate, the negative graphite, the electrolyte, the diaphragm is the largest, copper foil, aluminum foil, carbon nanotubes, acetylene black, conductive graphite, PVDF, CMC. According to Shanghai colored net offer (June 29, 2018), aluminum: 1.4 million yuan / ton, copper: 51,400 yuan / ton, lithium iron phosphate: 72,500 yuan / ton; according to my country's energy storage network and battery network According to reports, general graphite negative electrode material is (6-7) million / ton, the price of electrolyte is (5-5.

5) million / ton. A large amount of material, high price, is an important component of the current recycling of used batteries, and recycled the solution to consider economic benefits and environmental benefits. 3 Waste LifePO4 Material Recycling Technology 3.

1 Chemical Precipitation Law Recycling Technology At present, chemical precipitate wet recovery is a tight way of recycling of waste batteries. The oxides or salts of Li, Co, Ni, etc. are recovered by co-precipitation, and then chemical raw materials.

The form is carried out, and the chemical precipitation method is an important approach to the current industrialized recovery of lithium cobaltate and the three-dimensional waste battery. With regard to LiFePO4 materials, separating the precipitation method by high temperature calcination, alkali dissolution, acid leaching, etc., to recover the most economic value of Li elements, and can simultaneously recover metal and other metals, use NaOH alkali solution to dissolve the positive electrode, so The collective aluminum foil enters the solution in NaalO2, filtered, the filtrate is neutralized with a sulfuric acid solution to obtain Al (OH) 3, and the recovery of Al.

The filter residue is LiFePO4, conductive agent carbon black and LiFePO4 material surface coated carbon, etc. There are two ways to recycle LifePO4: The method is used to dissolve the slag with hydrogen sulfuric acid to dissolve the slag with hydroxide, so that the solution in Fe2 (SO4) 3 and Li2SO4, the filtrate after separation of carbon impurities is adjusted with NaOH and ammonia water, first make iron Fe (OH) 3 precipitate, residue Na2CO3 solution precipitate Li2CO3; method 2 is based on FEPO4 microolysis in nitric acid, dissolve the positive electrode material filter residue with nitric acid and hydrogen peroxide, first forming the FEPO4 precipitate, and finally precipitate in Fe (OH) 3, The residual acid solution precipitates Li2CO3 for saturated Na2CO3 solution, and the respective precipitation of Al, Fe, and Li. Li et al [6], based on LIFEPO4 in H2SO4 + H2O2 mixed solution, Fe2 + is oxidized into Fe3 +, and forming FEPO4 precipitate with PO43-binding, recovering metal Fe and separated from Li, further based on 3LI2SO4 + 2NA3PO4 → 3NA2SO4 + 2Li3PO4 ↓, generate precipitation, separation, collect, realize the recovery of metal Li.

The oxidizing material is more easily dissolved in the HCl solution, WANG, etc., the LiFePO4 / C mixed material powder is calcined at 600 ° C, ensuring that the ferri ions are completely oxidized, and the solubility of LiFePO4 is dissolved in acid, and the recovery of Li is 96%. Recycled LifePO4 analysis After obtaining precursor FePO4 · 2H2O and Li source, synthesizing LiFepo4 material is a research hot spot, ZHENG et al [8] high temperature solutions to electrode sheets, removes the binder and carbon to oxidize LIFEPO4 Fe2 + to Fe3 +, screen The powder obtained was dissolved in sulfuric acid, and the dissolved filtrate was adjusted pH to 2 to obtain FEPO4 hydrate, and 5 h was obtained at 700 ° C for 5 hours to obtain a FEPO4 recovery product, and the filtrate was concentrated with Na2CO3 solution to precipitate Li2CO3, and realize metals.

Recycle. Bian et al. after pyrochlorination by phosphoric acid by phosphoric acid, it is used to obtain FEPO4 · 2H2O, and as a precursor, a Li2CO3 and a glucose carbon thermal reduction method to form a LIFEPO4 / C composite, and Li in recovery material is precipitated in LIH2PO4.

, Realize the recovery of materials, and then use. The chemical precipitation method can be used for mixing the positive recovery of useful metals, and the preamble requires low before the waste positive, which is the advantage of this type of method. However, there is a LifePO4 material that does not contain cobalt and other precious metals, the above method often has a long, and a lot of birth Disadvantages of high acid and alkali waste liquid, high recovery cost.

3.2 High Temperature solid phase repair technology based on the decay mechanism of LIFEPO4 battery and the charge and discharge characteristics of the positive electrode material, the structure of the positive LIFEPO4 material is stable, and the loss of activity Li is one of the important facts of the battery capacity attenuation, so the LIFEPO4 material is considered to be replenished LI and other losses of elements straight repair potential. At present, the important fix method has a straight high temperature to solve and add the corresponding element source.

High temperature is solved, and the use of electrochemical properties of recovery materials by amurging, supplemental element sources, etc. Xie Yinghao, etc. After dismantling the waste battery, separating the positive electrode, after the binder is carbonized by heating under nitrogen protection, the phosphate-lithium iron-based positive material.

The amount of FEC2O4 · 2H2O, Li2CO3, (NH4) 2HPO4 regulated Li, Fe, and the P molar ratio were added to 1.05: 1: 1, and the carbon content of the calcined reactant was adjusted to 3%, 5%. And 7%, adding an appropriate amount of anhydrous ethanol in the material (600R / min) ball milling for 4 h, and the nitrogen atmosphere is warmed to 700 ° C constant temperature 24H roast LIFEPO4 material for 10 ° C / min.

As a result, the repair material having a carbon content of 5% has optimal electrochemical properties, and the first discharge ratio of 148.0mA · h / g; 1C under 0.1 C is 50 times, the capacity retention ratio is 98.

9%, and the recovery is Solution Process See Figure 4. Song et al. Takes the solid phase high temperature use of the straight mixed LifePo4, when the mass ratio of the doped new material and the waste recovery material is 3: 7,700 ° C high temperature 8h after 8h repair material electrochemical performance is good.

Li et al. Used to add Li Source Li2CO3 to recycled LIFEPO4 materials at 600 ° C, 650 ° C, 700 ° C, 750 ° C, 800 ° C in argon / hydrogen mixed gas. The first discharge capacity of the material is 142.

9mA · h / g, the optimum repair temperature is 650 ° C, the first discharge capacity of the repair material is 147.3mA · h / g, which is slightly improved, and the magnification and cycle performance improved. The study of 都 成, declare that Li2CO3 supplemented by 10% to waste positive electrode materials can effectively compensate for the loss of recyclant lithium, and the reduced material after the repair material is 157 mA, respectively.

H / g and 73mA · h / g, the capacity is almost no attenuation after 200 cycles under 0.5C. The addition of 20% of Li2CO3 will cause oligants such as Li2CO3 Meng Li2O during the baking repair process, resulting in a lower coulombic efficiency.

High temperature solid phase repair technology only adds a small amount of Li, Fe, P element, do not have a large amount of acid-base reagent, the sprouting waste acid waste alkali, the process flow is simple, environmentally friendly, but the purity requirements of the recovery raw materials are high. The presence of impurities reduces electrochemical properties of repair materials. 3.

3 High temperature solid phase regeneration technology is different from high-temperature solid phase pen direct repair technology, and high temperature regeneration techniques will first solve the recovery material to have a precursor with reaction activity, and each element can be re-crystallized, and then realizes the reproduction of the material. 都 成 等 保 3 极 片 分 分 3 分 分 3 2 2 分 分 2 2 2 2 2 2 2 正 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 材料 材料 2 材料 2 2 And the mass fraction is 25% glucose (based on the lithium iron phosphate), the regenerated LIFEPO4 / C positive electrode material is obtained at 650 ° C, and the material is in 0.1c and 20c and the discharge ratio is respectively.

It is 159.6mA · h / g and 86.9mA · h / g, after 10C magnification, after 1000 cycles, the capacity reservoir reservoir regeneration of LIFEPO4 positive electrode material is 91%.

With the above literature, the author of this article conducted a waste of LifePO4 materials in the early stage, "oxidation-carbon-thermal reduction" regeneration method. The regeneration method is important based on Co reduction FEPO4 and LiOH precursor synthesis of LiFePO4 materials for Li3FE2 (PO4) 3 and Fe2O3, while LIFEPO4 oxidation is also Li3FE2 (PO4) 3 and Fe2O3, and therefore, the thermal solution will be recovered. The positive electrode is removed from the binder and also realizes the oxidation of LIFEPO4.

As the regenerative reaction material, it is glucose, a hydrated citric acid, polyethylene glycol, 650--750 ° C high-temperature carbon heat reduction regeneration LIFEPO4, three reduction Both regeneration LIFEPO4 / C materials without impurities can be obtained. High temperature solid phase regeneration technology, the recovered LIFEPO4 material is oxidized to the reaction intermediate, and the regeneration LIFEPO4 material is obtained by carbon thermal reduction, and the material has a uniform oxidation and carbon thermal reduction thermodynamic process, and the regenerative material can regulate resistance, process flow Simple, but, similar to high temperature solid phase repair technology, this method is high in recovery materials, and the recovery material is solved before the recovery materials is necessary. 3.

4 Biological leaching technology Biological leaching technology In the recovery of the old battery, the first use of nickel-cadmium waste batteries recovered cadmium, nickel, iron, Cerruti, etc., dissolved, decreased waste nickel-cadmium battery, recovery, 100%, respectively. Nickel 96.

5%, iron 95%, dissolved leaching time is 93 days. XIN et al. It uses sulfur-sulfide thiobacillus, Caucite-Rotel hook-side spiral bacteria and (sulfur + yellow iron ore - sulfur sulfurium) mixing system to solve LiFepo4, LiMn2O4, LiniXCoyMN1- X-YO2, wherein the thiosidide thiobacillus system on LiFePO4 is 98%, and the leaching rate of LiMn2O4 in LiFePO4 is 95%, and the leaching rate of Mn is 96%, and the Mn is optimized.

The mixture is above 95% of the uniform leaching rate of Li, Ni, Co, and Mn in terms of Li, Ni, Co, and Mn in terms of term of material. The dissolution of Li is important due to the dissolution of H2SO4, and the dissolution of Ni, Co, and Mn is Fe2 + reduction and acid dissolution composite use. In biological leaching technology, the cycle of biofushes should be cultivated, and the dissolution leaching time is long, and during the dissolution process, the flora is easily inactivated, limiting the technology in industrial use.

Therefore, further improve the culture velocity of strains, adsorbing metal ion speed, etc., improve the leaching rate of metal ions. 3.

5 Mechanical activation Solve Recycling Technical chemical activation can cause physical and chemical changes in normal temperature constant pressure, including phase change, structural defect, strain, amorphization, or even straight reactions. In use in waste battery recovery, it is possible to improve recovery efficiency under room temperature conditions. Fan et al.

, Uses a battery fully discharge in the NaCl solution, and the recovered LIFEPO4 is high for 5 hours by 700 ° C to remove organic impurities. Mechanically activation with the blend of the recovery material for the mixture with the grass acid. The mechanical activation process is important to include three steps: particle size decrease, chemical bond break, new chemical bond.

After grinding mechanical activation, the mixed raw materials and zirconia beads were rinsed with deionized water and soaked for 30 min, and the filtrate was stirred at 90 ° C to evaporate until Li + had a concentration of greater than 5 g / L, and the pH to 4 of the filtrate was adjusted with 1 mol / L of NaOH solution. And continue to stir up until the concentration of Fe2 + is less than 4 mg / L, thereby obtaining high purity filtrate. After filtration, the purified lithium solution was adjusted to 8, stirred at 90 ° C for 2 h, and the precipitate was collected and dried at 60 ° C for Li recovery product.

The recovery rate of Li can reach 99%, and Fe is recovered in FEC2O4 · 2H2O. The recovery rate is 94%. YANG et al.

Under ultrasonic auxiliary use, the positive electrode material is separated from the positive electrode powder and the sodium ethylenediamine tetracetate (EDTA-2NA), which uses a planetary ball mill for mechanical activation. After further leaching of the activated sample with dilute phosphoric acid, the leaching is completed, and the cellulose membrane is vacuum filtration with acetate film, the liquid filtrate containing lithium, iron metal ions, Fe, Li in phosphoric acid can reach 97.67%, 94.

29, respectively. %. The filtrate was refluxed at 90 ° C for 9 h, and the metal Fe was precipitated in the form of FEPO4 · 2H2O, Li, and the precipitate was collected and dried.

Zhu et al. Is blended with lecithin by recovered LiFePO4 / C. After mechanical ball is chemically activated, 4 h is sintered at 600 ° C under AR-H2 (10%) mixed atmosphere, obtained (C + N + P) Coated regeneration LifePO4 composite.

In the regenerative material, the N-C key and the P-C key are covered with LiFePO4 to form a stable C + N + P co-clad coated layer, and the regeneration material is small, which can shorten Li + and the diffusion path of LI + and electrons. When the amount of the lecithin is 15%, the capacity of the regeneration material reaches 164.9mA · h / g during the low rate of 0.

2c. 3.6 Other Recycling Solutions - An Electrochemical Recycling Solution Technology Yang Zeheng et al, use 1-methyl-2 pyrrolidone (NMP) to dissolve waste LIFEPO4 (NMP), collect recovered LIFEPO4 materials, recovering materials and conductive agents, binders Preparation to the electrode to be repaired, the metal lithium film is an negative electrode, produce a buckle battery.

After multiple charge and discharge, lithium is embedded from the negative electrode into a positive electrode material, making the positive electrode from the lithium state to a lithically, achieved the effect of repair. However, the repaired electrode is then assembled into a full battery difficulty, it is difficult to direct scale use. 4 Electrolytic solution recovery technology Progress.

SUN et al, solve the electrolyte while using a vacuum pyrolysis method to recover the waste battery. Place the split positive electrode material in a vacuum furnace, the system is less than 1 kPa, the cooling temperature of the cold trap is 10 ° C. The vacuum furnace was heated at 10 ° C / min, and was allowed at 600 ° C for 30 min, the volatiles entered the condenser and condensed, and the noncompled gas was extracted through the vacuum pump, and finally collect by the gas collector.

The binder and electrolyte are volatilized or analyzed as a low molecular weight product, and most of the pyrolysis products are organic fluorocarbon compounds for enrichment and recovery. The organic solvent extraction method is to transfer the electrolyte to the extractant by adding a suitable organic solvent to the extractant. After extraction, distillation or fractionation, collect or separate the electrolytic solution after extracting different boiling points of each component in the extraction product.

Tongdong leather, under liquid nitrogen protection, cut the waste battery, remove the active substance, put the active material in the organic solvent for a period of time to leach the electrolyte. The extraction efficiency of the electrolytic solution was compared, and the results declare the declaration of the PC, DEC and DME, and the extraction rate of the PC was the fastest, and the electrolyte can be completely detached after 2 hours, and the PC can be repeatedly used multiple times, which may be because of the opposite PCs with large electromalities are more conducive to the dissolution of lithium salts. Supercritical CO2 recycled waste-free lithium ion battery electrolyte refers to the process of electrolytic solution adsorbed in a supercritical CO2 as an extractant, separating a lithium ion battery diaphragm and an active material.

Gruetzke et al. Study the extraction effect of liquid CO2 and supercritical CO2 on electrolyte. Regarding the electrolyte system containing LiPF6, DMC, EMC and EC, when liquid CO2 is used, the recovery rate of DMC and EMC is high, and the recovery of EC is low, and the total recovery rate is high when the recovery of EC is low.

The extraction efficiency of the electrolytic solution is highest in the liquid CO2, and the extraction efficiency of the electrolyte can be achieved (89.1 ± 3.4)% (mass fraction).

LIU et al, supercritical CO2 extractive electrolyte combined with dynamic extraction after first static extraction, and 85% extraction rate can be obtained. Vacuum pyrolysis technology recovers the electrolytic solution to achieve the peeling of the active material and the current fluid, simplify the recovery process, but the recovery process has a higher energy consumption, and further solves the fluorocarbon organic compound; the organic solvent extraction process can be recovered An important component of the electrolyte, but there is a problem of high extraction solvent cost, separation difficult and subsequent sprouts, etc.; Supercritical CO2 extraction technology has no solvent residue, simple solvent separation, good product reduction, etc.

, is a lithium ion battery One of the research directions of the electrolyte recycling, but there is also a large amount of CO2 consumption, and the entrained agent may affect the reuse of electrolyte. 5 Negative electrode material recovery techniques Decompose from LIFEPO4 battery failure mechanism, the degree of recession in the negative graphite performance is greater than the positive LiFePO4 material, and due to the relatively low price of the negative electrode graphite, the amount of amount is relatively small, the recovery and then economical is weak, currently Recycling research on the negative electrode of the waste battery is relatively small. In the negative electrode, the copper foil is expensive and the recovery process is simple.

It has high recovery value. The recovered graphite powder is expected to circulate in battery processing by modification. Zhou Xu et al, the vibration screening, the vibration screening and the airflow sorting combination process separates and recovered wastely lithium ion battery negative electrode materials.

The process process is pulverized into the hammer rupture machine to a particle diameter of less than 1 mm, and the rupture is placed on the fluidized bed distribution plate to form a fixed bed; opening the fan adjusting gas flow rate, allowing the particulate bed to fix the bed, The bed is loose, and the initial fluid is until sufficient fluidization, the metal is separated from the non-metal particles, wherein the light component is collected by the airflow, collecting the cyclone separator, and the recombination is retained at the bottom of the fluidized bed. The results declare that after the negative electrode material is screened, the particle size is 92.4% in a rupture of the particle size of more than 0.

250 mm, and the grade of the toner is 96.6% in the fragment of less than 0.125 mm, and it can be recovered; Among the ruptures of 0.

125--0.250mm, the grade of copper is low, and the effective separation and recovery of copper and toner can be achieved by gas flow sorting. At present, the negative electrode is mainly based on the aqueous binder, and the binder can be dissolved in aqueous solution, the negative electrode material and the collector copper foil can be separated by simple processes.

Zhu Xiaohui, etc., developed a method of using secondary ultrasonic ancillary acidification and wet recovery. The negative electrode sheet is placed in a dilute hydrochloric acid solution, and the straight graphite sheet and the collector copper foil are separated, and the collector is washed, and the recovery is achieved.

The graphite material is filtered, dried, and sieved separation to obtain recovered graphite crude product. The crude product is solved in an oxidizing agent such as nitric acid, oxidic acid, removing the metal compound in the material, the binder, and the graphite surface germination functionalized group, resulting in a secondary purification graphite material after collecting drying. After the secondary purified graphite material is immersed in a reducing aqueous solution of ethylenediamine or diviniscin, then the nitrogen protection is thermally resolved to repair the graphite material, and the modified graphite powder for battery can be obtained.

The negative electrode of the waste battery tends to use aqueous bonding, so the active material and the concentrate copper foil can be peeled off through a simple method, and the conventional recovery of high-value copper foils, the graphite material is discarded will result in a great waste of materials. Therefore, developing the modification and repair technology of graphite materials, realizing the reuse of waste graphite materials in the battery industry or other industrial categories. 6 Economic benefits of recycling economic decomposition of lithium iron phosphate waste battery recovery is greatly affected by raw material prices, including waste batteries recovery price, raw carbonate price, lithium iron phosphate price, etc.

Using the currently used wet recycling technology route, the most recovered economic value of the waste phosphate ion battery is lithium, the recovery revenue is about 7800 yuan / ton, and the recovery cost is about 8,500 yuan / ton, and the recovery income cannot be overturned. Recycling cost, where the lithium iron phosphate recovery costs of the original material costs account for 27%, and the cost of the excipient cost is 35%. The cost of excipients is important including hydrochloric acid, sodium hydroxide, hydrogen peroxide, etc.

(above data from the battery alliance and competition) Di consultation). Using wet technology routes, lithium cannot achieve complete recovery (lithium recovery is often 90% or less), phosphorus, iron recovery effect is poor, and use a large number of excipients, etc., it is important to use wet technical route difficult to achieve profitability Original.

The lithium iron phosphate waste battery uses high temperature solid phase method repair or regeneration technology route, compared with the wet technical route, the recovery process does not alkali dissolve the fluid aluminum foil and the acid dissolved positive electrode material lithium iron phosphate and other process steps, so the amount of use of the accessories is large. Reduce, and high temperature solid phase repair or regenerative technology route, high recovery of lithium, iron and phosphorus elements can have higher recovery benefits, according to the expectations of Beijing Saidmy, using high temperature repair law Component recycling technology route, will be able to achieve approximately 20% net profit. 7 When the recovery material is a complex mixed recovery material, it is suitable for the recovery of metal by chemical precipitation method or biological leaching technology, and the chemical material that can be reused, but with respect to LiFePO4 materials, the wet recovery is longer, To use more acid-base reagents and solve a large number of acid-base waste liquid, there is a shortcomings of high recovery costs and low economic value.

Compared with the chemical precipitation method, high temperature repair and high temperature regeneration techniques have a short period of short, and the amount of acid-base reagent is small, and the amount of waste acid waste alkali is less, but the approach is required to resolve or regenerate resolution. Strict intrinsic to prevent electrochemical properties of impurities remain affecting materials. Impurities include a small amount of aluminum foil, copper foil, etc.

In addition to the problem, it is a straightforward problem, and the regeneration process has been studied in large-scale use but is not a desire problem. In order to improve the economic value of waste batteries, low-cost electrolyte and negative electrode material recovery techniques should be further developed, and the useful substances in the waste battery are maximized to maximize recovery.