A method for regenerating waste lithium iron phosphate powder doped with titanium dioxide by fire process

Abstract

The application discloses a method for repairing and regenerating lithium iron phosphate waste powder doped with titanium dioxide by a fire method, and comprises the following steps: loading lithium iron phosphate waste pole pieces into an atmosphere furnace to remove impurities, and performing vibration screening to obtain lithium iron phosphate pole powder; adding the lithium iron phosphate pole powder into a rotary kiln to perform deep defluorination, and obtaining deep defluorination pole powder; blending the deep defluorination pole powder, and performing two-stage ball milling by doping with titanium dioxide to obtain ball-milled mixture; performing spray drying on the ball-milled mixture to obtain lithium iron phosphate precursor; and adding the lithium iron phosphate precursor into the atmosphere furnace to perform sintering, and obtaining lithium iron phosphate product. The application creatively modifies the lithium iron phosphate waste material by doping titanium dioxide and combining with a carbon coating method in the process of repairing the lithium iron phosphate waste material, and greatly improves the material performance and electrochemical performance of the product.

Description

TECHNICAL FIELD

[0001] The application relates to a resource green and environment-friendly recycling technology field, in particular to a method for repairing and regenerating waste lithium iron phosphate powder doped with titanium dioxide by a fire method. BACKGROUND

[0002] As a new type of lithium ion battery positive electrode material, lithium iron phosphate (LiFePO4 or LFP) has excellent characteristics such as wide source, low price, high theoretical specific capacity, good thermal stability, environmental friendliness, safety and reliability, and the like. The lithium iron phosphate battery made of lithium iron phosphate is widely used in new energy power batteries. Since May 2021, lithium iron phosphate batteries have first reversed the output of ternary lithium batteries, and then surpassed ternary lithium batteries in the vehicle-mounted quantity in July; by September, the output of lithium iron phosphate batteries was 1.4 times that of ternary lithium batteries, and the installed capacity was 1.6 times that of ternary lithium batteries, and the gap between the two is widening, showing a trend of lithium iron phosphate replacing ternary batteries. At present, lithium ion batteries have the highest comprehensive cost performance, especially lithium iron phosphate batteries. Therefore, the rapid development of power batteries and storage batteries cannot be separated from lithium iron phosphate, and with the rapid increase in demand for power batteries and storage batteries, the demand for lithium iron phosphate also increases.

[0003] With the rapid development of the new energy automobile industry, the production and sales of new energy power batteries in China are increasing year by year, but power batteries have a service life. According to the data released by the China Automotive Technology Research Center, the cumulative retired quantity of power batteries in China in 2020 was about 200,000 tons, and the cumulative retired quantity in 2025 was about 780,000 tons. The power batteries equipped in early electric vehicles are mainly lithium iron phosphate batteries, especially in the use of batteries in electric buses, the lithium iron phosphate positive material reaches more than 85%, and the waste lithium iron phosphate resources available for recycling are relatively sufficient, and the effective recovery of metals and the utilization of residual energy will bring considerable economic benefits

[0004] At present, the recycling technology of waste LFPBs materials is mainly divided into solid phase recycling technology and wet recycling technology according to different recycling principles. The solid phase recycling of waste LFPBs materials generally removes organic binders by calcination to separate LFP powder from aluminum foil, obtains LFP waste, and then obtains the required molar ratio of lithium, iron and phosphorus by batching, and synthesizes new LFP positive materials by a solid phase method to complete the repair of the materials.

[0005] Patent CN201810887735.9 (A method for preparing battery-grade lithium iron phosphate by directly repairing lithium iron phosphate waste powder by fire method) directly repairs battery-grade lithium iron phosphate by oxidation roasting, batching, drying and sintering, and iron removal by screening, but this method has certain limitations, the requirements for raw materials are high, the electrochemical performance of the repaired product fluctuates greatly, and only the standard of energy storage type lithium iron phosphate battery can be met. The dispersing agent used is alcohol, which has certain safety risks.

[0006] Patent CN201811109955.5 (Preparation method of high-tapping high-capacity composite positive electrode material for lithium battery) dopes titanium dioxide by two-stage ultrasonic dispersion of graphene oxide in water or ethanol, two-stage ball milling or stirring mixing, and then prepares the precursor by microwave and calcination, and then prepares the composite positive electrode material by two-stage forming treatment, sintering and mixing dispersion. The preparation method of this method is complex, and ethanol is used, which has certain safety risks. At the same time, this method dopes titanium dioxide, changes the morphology of lithium iron phosphate, shortens the diffusion path of lithium, and improves the diffusion speed of lithium, but this method is a performance improvement processing method for commercially available lithium iron phosphate products, not a repair and regeneration method for lithium iron phosphate waste.

[0007] Patent CN114024055A (A method for short-process recovery of waste lithium iron phosphate battery material) is a method for recovering lithium iron phosphate / carbon powder by washing and drying the positive electrode material obtained by separating waste lithium iron phosphate, adding lithium source, phosphorus source and vanadium pentoxide, and then mechanically activating, drying and calcining to obtain regenerated lithium iron phosphate material. Although this method is simple, the ball milling medium used is ethanol, which has certain safety risks. Importantly, the specific discharge capacity of the regenerated material is low, about 142mAh / g and 136mAh / g at 0.1C and 1C respectively.

[0008] In summary, it is of great significance to study the method of doping titanium dioxide and combining with carbon coating during the regeneration and repair process of lithium iron phosphate waste to improve the electrochemical performance, conductivity and physical properties of regenerated lithium iron phosphate positive electrode material. SUMMARY

[0009] The present application aims to overcome the shortcomings of existing lithium iron phosphate waste powder regeneration and repair technology, and develop a method for improving the performance of doped titanium dioxide lithium iron phosphate positive electrode material. This method removes fluorine by two steps of electrode separation and deep impurity removal, completely removing the influence of impurity F on product performance. The high-temperature spraying strengthens the conductivity of semiconductor titanium dioxide, which itself acts as a conductive agent, while reducing the content of carbon as a coated conductive agent, thereby improving the compaction density of the product and strengthening the electrochemical performance of the product.

[0010] In order to achieve the above object, the technical scheme of the present application is: a method for repairing and regenerating waste lithium iron phosphate powder doped with titanium dioxide by fire method, comprising the following steps:

[0011] (1) Separation of pole piece and impurity removal: the waste lithium iron phosphate pole piece is loaded into an atmosphere furnace, the oxygen concentration in the atmosphere furnace is controlled to be 500-1000 ppm, the hearth pressure is 50-300 Pa, the impurity removal temperature is 560-640 DEG C, the impurity removal time is 3-5 h, the impurity-removed lithium iron phosphate pole piece is subjected to vibration screening to obtain lithium iron phosphate pole powder;

[0012] (2) Deep defluorination: the lithium iron phosphate pole powder obtained in step (1) is added into a rotary kiln for deep defluorination, the defluorination oxygen concentration is 19-50%, the defluorination temperature is 450-500 DEG C, the defluorination time is 5-8 h, and deep defluorinated pole powder is obtained;

[0013] (3) Ball milling: the deep defluorinated pole powder obtained in step (2) and doped titanium dioxide added according to the molar ratio Li:Fe:P=1.0-1.05:0.97-1:1 and the mass percentage of 0.5-3% are subjected to two-stage ball milling to obtain ball-milled mixture;

[0014] (4) Spray drying: the ball-milled mixture obtained in step (3) is subjected to spray drying by using a spray dryer, the spray inlet air temperature is 310-340 DEG C, the outlet air temperature is set to be 95-105 DEG C, and the atomization frequency is 42-50 HZ to obtain lithium iron phosphate precursor;

[0015] (5) Sintering: the lithium iron phosphate precursor obtained in step (4) is added into an atmosphere furnace for sintering under the protection of inert gas, the sintering and purifying temperature is 750-820 DEG C, the sintering and purifying time is 8-12 h, and lithium iron phosphate product with high compactness and high electrochemical performance is obtained.

[0016] 2、As a further improvement of the present application, in step (1), the waste lithium iron phosphate pole piece includes waste pole piece disassembled from waste lithium iron phosphate battery, lithium iron phosphate pole piece or edge material generated in the process of preparing lithium iron phosphate battery, and also includes lithium iron phosphate pole powder generated in the process of preparing various lithium iron phosphate and qualified pole powder obtained by powdering from the battery.

[0017] 3、As a further improvement of the present application, in step (2), the pressure in the rotary kiln for deep defluorination is 99400-99500 Pa, so that C is burned into carbon dioxide, the material is activated, fluorine is deeply removed, and LiFePO4 is oxidized into Fe2O3 and Li3Fe2PO4.

[0018] 4. As a further improvement to the present invention, in step (3), the ingredients include a lithium source, a carbon source, a phosphorus source, and an activator. The lithium source is one of lithium carbonate, lithium oxalate, or lithium hydroxide; the iron source is one of iron oxide, iron hydroxide, or ferrous oxide; the phosphorus source is one of ammonium dihydrogen phosphate or iron phosphate; the carbon source is one or a mixture of glucose, starch, etc.; and the activator is DOS305. The ball milling temperature is 5-20℃, the rotation speed is 1200-1600 r / min, and the time is 3-5 h to ensure thorough mixing.

[0019] 5. As a further improvement to the present invention, in step (3), the amount of carbon source added is 8%-10% of the mass percentage of the deep defluorination electrode powder, the amount of activator DOS305 added is 0.5%-1% of the mass percentage of the deep defluorination electrode powder, and the order of material addition is deionized water, activator, lithium source, phosphorus source, titanium dioxide, carbon source, and then deep defluorination electrode powder is added.

[0020] 6. As a further improvement to the present invention, step (4) activates titanium dioxide and reduces its adhesion by high-temperature spraying, while improving the semiconductor properties of titanium dioxide, thereby obtaining a lithium iron phosphate precursor.

[0021] 7. As a further improvement to the present invention, the sintering in step (5) is carried out in an atmosphere furnace, wherein the inert gas is one or more of nitrogen, helium or argon; the heating rate is 2.5-3℃ / min, the high-temperature synthesis time of lithium iron phosphate material at 420-450℃ is 3-6h, the furnace pressure is 25-75Pa and the oxygen concentration is 5-50ppm during the entire sintering process.

[0022] Since titanium dioxide itself is a semiconductor, its conductivity is improved through high-temperature spray modification, thereby increasing the conductivity of the recycled material lithium iron phosphate. Under high current conditions, the electron conductivity is greatly improved, while the addition of coating carbon can be reduced. The incorporation of impurity titanium ions increases the lithium ion conduction channels, promotes the insertion and extraction of lithium ions, and thus improves the electrochemical properties such as charge and discharge performance and rate performance, as well as the physical properties such as compaction density.

[0023] Beneficial effects:

[0024] 1. This invention removes fluoride from lithium iron phosphate electrode powder containing impurities between 5-8% by mass through two steps: electrode separation and impurity removal, and deep impurity removal. This process directly removes the impurity F from lithium iron phosphate electrode powder to below 0.1%, while simultaneously causing an oxidation-decomposition reaction in lithium iron phosphate, oxidizing the original LiFePO4 (iron in divalent form) into Fe2O3 and Li3Fe2PO4. This lays the foundation for the high electrochemical performance and high specific capacitance of lithium iron phosphate, and also creatively provides the possibility of doping titanium dioxide in a new process.

[0025] 2、The application is the preparation principle of synthesizing lithium iron phosphate positive material by solid phase method Fe2O3+Li3Fe2PO4, direct repair by fire method, and doping titanium dioxide in the ball milling process while combining with carbon coating method for modification, so that titanium-doped and carbon-coated lithium iron phosphate is obtained, directional doping of titanium into iron site and uniform coating of carbon are realized, the compaction density is high, the energy density is high, and the lithium iron phosphate positive material is suitable for power battery.

[0026] 3、The application utilizes high-temperature spray drying, through high-temperature spray, titanium dioxide is activated and its adhesion is reduced, and the semiconductor performance of titanium dioxide is improved, titanium dioxide not only dopes metal ions, but also acts as a conductive performance like carbon coating, so that the addition of carbon source is reduced, the carbon content in the product is reduced, and the compaction density of the product exceeds 2.52 g / cm 3 .

[0027] 4、The process flow is short, the pollution problem of traditional wet recovery solvent is avoided, and there is no need for leaching, extraction, precipitation and other operations, the recovery rate of lithium, iron and phosphorus exceeds 98%; at the same time, the incorporation of titanium occupies the Fe 2+ site in the lithium iron phosphate phase, forms lithium titanium phosphate, is conducive to the formation of dense crystal lattices of lithium titanium phosphate, lithium titanium phosphate and titanium dioxide, and due to the introduction of titanium dioxide, the agglomeration phenomenon of the powder is reduced, and the electrochemical performance of the regenerated lithium iron phosphate material is improved.

[0028] At present, the electrochemical performance of the common repair products reported can only meet the requirements of energy storage type lithium iron phosphate batteries, but the electrochemical performance of the lithium iron phosphate battery material prepared by the process meets the requirements of the market for power type lithium iron phosphate batteries, and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a direct repair regeneration principle flow chart of titanium dioxide-doped lithium iron phosphate waste cathode sheet;

[0030] Figure 2 It is an XRD detection diagram of lithium iron phosphate products of example 1 and comparative example 1;

[0031] Figure 3 It is an element mapping image (EDS) analysis diagram of titanium dioxide-doped lithium iron phosphate repair regeneration products;

[0032] Figure 4 It is an X-ray photoelectron spectroscopy (XPS) analysis diagram of titanium dioxide-doped lithium iron phosphate repair regeneration products;

[0033] Figure 5 It is a first charge-discharge curve diagram under different rate conditions. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application, and the present application includes other embodiments and variations within the technical idea thereof.

[0035] The embodiment of the present application provides a method for repairing and regenerating waste lithium iron phosphate powder doped with titanium dioxide by a fire method

[0036] Please refer to Figure 1 . The present application will be further described below through specific embodiments.

[0037] Case 1

[0038] (1) Separation of pole piece and impurity removal: the un-liquid-injected lithium iron phosphate waste pole piece is loaded into an atmosphere furnace, the oxygen concentration in the atmosphere furnace is controlled to be 500 ppm, the furnace pressure is 50 Pa, the impurity removal temperature is 640 DEG C, and the impurity removal time is 3 h, the impurity-removed lithium iron phosphate pole piece is subjected to vibration screening to obtain lithium iron phosphate pole powder;

[0039] (2) Deep defluorination: the lithium iron phosphate pole powder obtained in step (1) is added into a rotary kiln for deep defluorination, the defluorination pressure is 99500 Pa, the defluorination oxygen concentration is 50%, the defluorination temperature is 450 DEG C, and the defluorination time is 5 h, to obtain a mixture of deep defluorinated Fe2O3 and Li3Fe2PO4;

[0040] (3) Ball milling: the deep defluorinated pole powder obtained in step (2) and the calculated ingredients according to the molar ratio Li:Fe:P = 1.0:0.97:1 are added, the mass percentage of the added product equivalent to the doping titanium dioxide is 1%, the added amount of the carbon source is 10% of the mass percentage of the deep defluorinated pole powder, and the added amount of the activator DOS305 is 1% of the mass percentage of the deep defluorinated pole powder, to perform two-stage ball milling to obtain a ball-milled mixture;

[0041] (4) Spray drying: the ball-milled mixture obtained in step (3) is subjected to spray drying by using a spray dryer, the spray inlet air temperature is 310 DEG C, the outlet air temperature is set to be 95 DEG C, and the atomization frequency is 42 HZ, to obtain a lithium iron phosphate precursor;

[0042] (5) Sintering: the lithium iron phosphate precursor obtained in step (4) is added into an atmosphere furnace for sintering under nitrogen protection, the heating speed is 3 DEG C / min, the high-temperature synthesis time of the lithium iron phosphate material at 420 DEG C is 6 h, the sintering and purifying temperature is 750 DEG C, the sintering and purifying time is 12 h, the furnace pressure is 25 Pa, and the oxygen concentration is 50 ppm during the whole sintering process, to obtain a lithium iron phosphate product.

[0043] The lithium iron phosphate positive electrode material is detected, and the compaction density is 2.52 g / cm 3 The rest of the detection is respectively as Figure 2 、 Figure 3 、 Figure 4 and Figure 5 It can be seen from Figure 2 that the XRD characteristic diffraction peak of the sample prepared by doping 1% of titanium dioxide is completely matched with the standard characteristic peak of LiFePO4, and the XRD peak type of the sample is sharp, which indicates that the obtained sample has a complete LiFePO4 olivine structure, and also indicates that the small amount of TiO2 doping does not change the crystal structure of LiFePO4; it can be seen from Figure 3 that the mapping images of Fe, C and Ti are closely matched with the corresponding images of LiFePO4 / C composite material, and are uniformly distributed on the same spherical material, and the carbon atoms in the mapping image of C are almost uniformly distributed in all areas, which indicates the formation of an ultra-thin carbon film, and the mapping image of Ti obviously appears a dot-like feature, which is consistent with the overall outline of the material, indicating that the Ti element is uniformly distributed and coated on the surface of the composite spherical material; it can be seen from Figure 4 that the iron in the LiFePO4 / C composite material is in divalent state, and the 2p3 / 2 and 2p1 / 2 bond energies of Ti element are near 458.5 eV and 464.5 eV respectively, which are consistent with the characteristics of Ti 4+ , indicating that Ti in the composite material still exists in the form of TiO2; it can be seen from Figure 5 that the charge-discharge curve of the sample prepared by doping 1% of titanium dioxide has a pair of charge-discharge voltage platforms of 3.5 V and 3.4 V in the voltage range of 2.5-4.0 V at 0.1 C (17 mAh·g-1) rate, which corresponds to the Fe 2+ / Fe 3+ redox reaction of LiFePO4 in the charge-discharge process, indicating that the doping of TiO2 effectively improves the difference of the charge-discharge voltage platform of the material, and the small amount of TiO2 doping reduces the polarization in the charge-discharge process of the material, and the 1C discharge capacity is 146.8 mAh / g.

[0044] Case 2

[0045] (1) The separated and impurity-removed lithium iron phosphate electrode sheet is loaded into an atmosphere furnace, the oxygen concentration in the atmosphere furnace is controlled to be 1000 ppm, the furnace pressure is 300 Pa, the impurity removal temperature is 560℃, and the impurity removal time is 5h, and the impurity-removed lithium iron phosphate electrode sheet is subjected to vibration screening to obtain lithium iron phosphate electrode powder;

[0046] (2) Deep defluorination: the lithium iron phosphate powder obtained in step (1) is added into a rotary kiln for deep defluorination, the defluorination pressure is 99400 Pa, the defluorination oxygen concentration is 19%, the defluorination temperature is 500°C, and the defluorination time is 8h, to obtain a mixture of deep defluorinated Fe2O3 and Li3Fe2PO4;

[0047] (3) Ball milling: the deep defluorinated powder obtained in step (2) and the calculated amount of raw materials according to the molar ratio of Li:Fe:P=1.05:1:1 are added for secondary ball milling, and 0.5% of the product in terms of mass percentage is added as titanium dioxide for doping, the amount of carbon source added is 8% of the mass percentage of the deep defluorinated powder, and the amount of activator DOS305 added is 0.5% of the mass percentage of the deep defluorinated powder, to obtain a ball-milled mixture;

[0048] (4) Spray drying: the ball-milled mixture obtained in step (3) is spray dried by a spray dryer, the spray inlet temperature is 340°C, the outlet temperature is set to 105°C, and the atomization frequency is 50HZ, to obtain a lithium iron phosphate precursor;

[0049] (5) Sintering: the lithium iron phosphate precursor obtained in step (4) is added into an atmosphere furnace for sintering under argon protection, the heating rate is 2.5°C / min, the lithium iron phosphate material is synthesized at a high temperature of 450°C for 3h, the sintering and purification temperature is 820°C, the sintering and purification time is 8h, the furnace pressure is 75Pa, and the oxygen concentration is 5ppm during the whole sintering process, to obtain a lithium iron phosphate product.

[0050] The lithium iron phosphate positive electrode material is detected, and the tap density is 2.51g / cm 3 , and the 1C discharge capacity is 145.3mAh / g.

[0051] Case 3

[0052] (1) Separation of electrode sheet and removal of impurities: the qualified electrode powder obtained by powdering from the battery is loaded into an atmosphere furnace, the oxygen concentration in the atmosphere furnace is controlled to be 800ppm, the furnace pressure is 100Pa, the removal temperature is 600°C, and the removal time is 4h, to obtain lithium iron phosphate powder;

[0053] (2) Deep defluorination: the lithium iron phosphate powder obtained in step (1) is added into a rotary kiln for deep defluorination, the defluorination pressure is 99450 Pa, the defluorination oxygen concentration is 30%, the defluorination temperature is 480°C, and the defluorination time is 6h, to obtain a mixture of deep defluorinated Fe2O3 and Li3Fe2PO4;

[0054] (3) Ball milling: the deep defluorination powder obtained in step (2) and ingredients calculated according to the molar ratio of Li:Fe:P = 1.02:0.98-1:1 are added for two-stage ball milling, and 3% of the product in terms of mass percentage is added as titanium dioxide for doping; the amount of carbon source added is 9% of the mass percentage of the deep defluorination powder, and the amount of activator DOS305 added is 0.8% of the mass percentage of the deep defluorination powder, for two-stage ball milling to obtain a ball milling mixture;

[0055] (4) Spray drying: the ball milling mixture obtained in step (3) is subjected to spray drying by using a spray dryer, the spray inlet air temperature is 320°C, the outlet air temperature is set to 100°C, and the atomization frequency is 45HZ to obtain a lithium iron phosphate precursor;

[0056] (5) Sintering: the lithium iron phosphate precursor obtained in step (4) is added into an atmosphere furnace, and sintering is performed under helium protection, the heating rate is 2.8°C / min, the lithium iron phosphate material is synthesized at a high temperature of 440°C for 4h, the sintering purification temperature is 780°C, the sintering purification time is 10h, the furnace pressure is 55Pa, and the oxygen concentration is 20ppm during the whole sintering process, to obtain a lithium iron phosphate product.

[0057] The lithium iron phosphate positive electrode material is detected, and the tap density is 2.54g / cm 3 , and the 1C discharge capacity is 148.7mAh / g.

[0058] Comparative Example 1

[0059] (1) Separation of electrode sheet and removal of impurities: the un-liquid-injected lithium iron phosphate waste electrode sheet is loaded into an atmosphere furnace, the oxygen concentration in the atmosphere furnace is controlled to be 500ppm, the furnace pressure is 50Pa, the removal of impurities is performed at a temperature of 640°C for 3h, and the lithium iron phosphate electrode sheet after removal of impurities is subjected to vibration screening to obtain a lithium iron phosphate electrode powder;

[0060] (2) Deep defluorination: the lithium iron phosphate electrode powder obtained in step (1) is added into a rotary kiln for deep defluorination, the defluorination pressure is 99500Pa, the defluorination oxygen concentration is 50%, the defluorination temperature is 450°C, and the defluorination time is 5h to obtain a mixture of deep defluorination Fe2O3 and Li3Fe2PO4;

[0061] (3) Ball milling: the deep defluorination powder obtained in step (2) and ingredients calculated according to the molar ratio of Li:Fe:P = 1.0:0.97:1 are added for two-stage ball milling, the amount of carbon source added is 10% of the mass percentage of the deep defluorination powder, and the amount of activator DOS305 added is 1% of the mass percentage of the deep defluorination powder to obtain a ball milling mixture;

[0062] (4) Spray drying: the ball-milling mixture obtained in step (3) is subjected to spray drying by using a spray dryer, the spray inlet temperature is 310°C, the outlet temperature is set to 95°C, the atomization frequency is 42HZ, and a lithium iron phosphate precursor is obtained;

[0063] (5) Sintering: the lithium iron phosphate precursor obtained in step (4) is added into an atmosphere furnace, and sintering is performed under nitrogen protection, the heating speed is 3°C / min, the lithium iron phosphate material is synthesized at a high temperature of 420°C for 6h, the sintering purification temperature is 750°C, the sintering purification time is 12h, the furnace pressure is 25Pa, and the oxygen concentration is 50ppm during the whole sintering process, and a lithium iron phosphate product is obtained.

[0064] The lithium iron phosphate positive electrode material is detected, and the tap density is 2.43g / cm 3 , the 1C discharge capacity is 142.5mAh / g, and from Figure 2 It can be seen that the XRD characteristic diffraction peak of the sample prepared by not doping titanium dioxide is completely matched with the standard characteristic peak of LiFePO4, and the XRD peak type of the sample is sharp, which indicates that the obtained sample has a complete LiFePO4 olivine structure.

[0065] Comparative Example 2

[0066] (1) Oxidation roasting: the qualified cathode powder obtained by powdering from the battery is directly added into a rotary kiln for oxidation roasting, the roasting pressure is 99450Pa, the roasting oxygen concentration is 30%, the roasting temperature is 480°C, and the roasting time is 6h, and a mixture of Fe2O3 and Li3Fe2PO4 is obtained;

[0067] (2) Ball milling: the deep defluorination cathode powder obtained in step (1) and the ingredients calculated according to the molar ratio Li:Fe:P=1.02:0.98-1:1 are added, and 3% of the mass percentage of the product is added for doping titanium dioxide for two-stage ball milling to obtain a ball-milling mixture; the addition amount of the carbon source is 9% of the mass percentage of the deep defluorination cathode powder, and the addition amount of the activator DOS305 is 0.8% of the mass percentage of the deep defluorination cathode powder, and two-stage ball milling is performed to obtain a ball-milling mixture

[0068] (4) Spray drying: the ball-milling mixture obtained in step (3) is subjected to spray drying by using a spray dryer, the spray inlet temperature is 310°C, the outlet temperature is set to 95°C, the atomization frequency is 42HZ, and a lithium iron phosphate precursor is obtained;

[0069] (5) sintering: the lithium iron phosphate precursor obtained in step (4) is added into an atmosphere furnace, and sintering is carried out under the protection of helium, the heating speed is 2.8 ℃ / min, the lithium iron phosphate material is synthesized at a high temperature of 440 ℃ for 4 h, the sintering purification temperature is 780 ℃, the sintering purification time is 10 h, the furnace pressure is 55 Pa, the oxygen concentration is 20 ppm during the whole sintering process, and the lithium iron phosphate product is obtained.

[0070] The lithium iron phosphate positive electrode material is detected, and the compaction density is 2.38 g / cm 3 , the 1C discharge capacity is 126.3 mAh / g, and the F content in the product is more than 1%.

[0071] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A pyrometallurgical remediation and regeneration method for lithium iron phosphate waste powder doped with titanium dioxide, characterized in that, The method comprises the following steps: (1) separating and removing impurities from the lithium iron phosphate pole piece: loading the lithium iron phosphate waste pole piece into an atmosphere furnace, controlling the oxygen concentration in the atmosphere furnace to be 500-1000 ppm, the furnace pressure to be 50-300 Pa, the impurity removal temperature to be 560-640 DEG C, and the impurity removal time to be 3-5 h, and then performing vibration screening after impurity removal to obtain lithium iron phosphate pole powder; (2) deep fluorine removal: adding the lithium iron phosphate pole powder obtained in step (1) into a rotary kiln for deep fluorine removal, the fluorine removal oxygen concentration being 19-50%, the fluorine removal temperature being 450-500 DEG C, and the fluorine removal time being 5-8 h, to obtain deep fluorine removal pole powder; (3) ball milling: performing two-stage ball milling on the deep fluorine removal pole powder obtained in step (2) and ingredients calculated according to the molar ratio Li:Fe:P=1.0-1.05:0.97-1:1 and 0.5-3% of titanium dioxide added for doping, to obtain ball-milled mixture; (4) spray drying: performing spray drying on the ball-milled mixture obtained in step (3) by using a spray dryer, the spray inlet air temperature being 310-340 DEG C, the outlet air temperature being set to 95-105 DEG C, and the atomization frequency being 42-50 HZ, to obtain lithium iron phosphate precursor; (5) sintering: adding the lithium iron phosphate precursor obtained in step (4) into an atmosphere furnace for sintering under the protection of inert atmosphere, the sintering and purifying temperature being 750-820 DEG C, and the sintering and purifying time being 8-12 h, to obtain lithium iron phosphate product with high compactness and high electrochemical performance.

2. The method for regenerating waste lithium iron phosphate powder doped with titanium dioxide by pyrogenic process according to claim 1, characterized in that, In step (1), the lithium iron phosphate waste pole piece includes waste pole pieces disassembled from retired lithium iron phosphate batteries, lithium iron phosphate pole pieces, or edge scraps generated in the process of preparing lithium iron phosphate batteries, and also includes lithium iron phosphate pole powder generated in the process of preparing various lithium iron phosphate batteries and qualified pole powder obtained by beating the batteries.

3. The method of claim 1, wherein the method is characterized by: In step (2), the pressure in the rotary kiln for deep fluorine removal is 99400-99500 Pa, so that C is burned into carbon dioxide, the material is activated, fluorine is deeply removed, LiFePO4 is oxidized into Fe2O3 and Li3Fe2(PO4)3.

4. The method of claim 1, wherein the method is characterized by: In step (3), the ingredients include a lithium source, an iron source, a carbon source, a phosphorus source, and an activator, the lithium source is one of lithium carbonate, lithium oxalate, or lithium hydroxide, the iron source is one of iron oxide, iron hydroxide, or ferrous oxide, the phosphorus source is one of ammonium dihydrogen phosphate or iron phosphate, the carbon source is one or a mixture of several of glucose, starch, etc., and the activator is DOS305; the ball milling temperature is 5-20 DEG C, the rotating speed is 1200-1600 r / min, and the time is 3-5 h, so that the ingredients are fully mixed.

5. The method of claim 1, wherein the method is characterized by: In step (3), the amount of the carbon source added is 8%-10% of the mass percentage of the deep fluorine removal pole powder, the amount of the activator DOS305 added is 0.5%-1% of the mass percentage of the deep fluorine removal pole powder, and the material is added in the following order: deionized water, the activator, the lithium source, the phosphorus source, titanium dioxide, the carbon source, and then the deep fluorine removal pole powder.

6. The method of claim 1, wherein the method is characterized by: In step (4), high-temperature spraying is performed to activate titanium dioxide, reduce the adhesion of titanium dioxide, improve the semiconductor performance of titanium dioxide, and obtain lithium iron phosphate precursor.

7. The method of claim 1, wherein the method is characterized by: The sintering in the step (5) is carried out in an atmosphere furnace, wherein the inert atmosphere is one or more of nitrogen, helium or argon; the temperature rising speed is 2.5-3 ℃ / min, the high temperature synthesis time of the lithium iron phosphate material is 3-6 h at 420-450 ℃, the furnace pressure is 25-75 Pa and the oxygen concentration is 5-50 ppm during the whole sintering process.

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