Method for recovering lithium from spent lithium iron phosphate battery

Abstract

The present invention provides a method for recovering lithium from a spent lithium iron phosphate battery, comprising: subjecting the positive electrode black powder of the spent lithium iron phosphate battery to a roasting reaction in a roasting furnace filled with a protective gas, and simultaneously adjusting, on the basis of the mixture in the roasting furnace, the input flow rate of chlorine gas to control the temperature of the roasting reaction, wherein the temperature of the roasting reaction is 50-300 °C; subjecting the product of the roasting reaction to water leaching to obtain a solution of the product; subjecting the solution of the product to suction filtration to obtain a filtrate; and concentrating the filtrate by means of evaporation and then drying the residue to obtain a lithium chloride crystal. In the present invention, one-step roasting is carried out at a low temperature, and the temperature of the roasting reaction is controlled by adjusting the input flow rate of chlorine gas, so that the lithium element in the spent lithium iron phosphate battery can be converted into lithium chloride, which is soluble in water, and a lithium chloride crystal can be further prepared. The method has a simple process, high reaction efficiency, low energy consumption, and a lithium element recovery rate as high as 95%; the method has great industrial application value.

Description

A method for recovering lithium from spent lithium iron phosphate batteries Technical Field

[0001] This invention relates to the field of battery recycling, and in particular to a method for recovering lithium from waste lithium iron phosphate batteries. Background Technology

[0002] With the development of China's new energy industry, a large number of batteries have been produced and put into use. After a certain period of use, the capacity of these batteries gradually decreases, failing to meet the needs of various applications, and thus they are discarded and become industrial waste. With the expansion of new energy vehicle sales, the number of retired power batteries and their raw materials is increasing, making waste battery recycling an urgent industry need. At the same time, waste batteries contain a large number of metal elements such as nickel, lithium, and iron, which have significant recycling value. Through advanced and reasonable extraction methods, the cost may be lower than smelting from ore, and it can also reduce damage to the natural environment.

[0003] Currently, the recycling of waste lithium-ion batteries mainly uses wet processes, supplemented by pyrometallurgical processes to treat the electrolyte, separator, and binder. However, the current wet and pyrometallurgical processes have the following drawbacks: 1. The process flow is long and complex, resulting in high costs; 2. The lithium recovery rate in waste lithium iron phosphate batteries is low, leading to poor economic benefits. Technical issues

[0004] To address the aforementioned technical problems, this invention aims to provide a method for recovering lithium from spent lithium iron phosphate batteries that is simple in process, highly efficient in reaction, low in energy consumption, and has a high recovery rate. Technical solutions

[0005] This invention is achieved through the following scheme:

[0006] A method for recovering lithium from spent lithium iron phosphate batteries, the method comprising:

[0007] The cathode black powder of waste lithium iron phosphate batteries is placed in a roasting furnace filled with protective gas for roasting reaction. At the same time, the flow rate of chlorine gas input is adjusted according to the mixture in the roasting furnace to control the roasting reaction temperature, which is controlled at 50-300℃.

[0008] The roasting product after the roasting reaction was soaked in water to obtain a roasting product solution;

[0009] The calcined product solution was filtered to obtain the filtrate;

[0010] The filtrate was evaporated, concentrated, and then dried to obtain lithium chloride crystals;

[0011] The method of adjusting the input chlorine flow rate based on the mixture in the calcination furnace to control the calcination reaction temperature is expressed by the following formula:

[0012]

[0013] In the formula, The conversion factor between molar quantity and volume. =11.2; This indicates the heat dissipation of the roasting furnace per minute, and it is related to the roasting furnace. This indicates the amount of heat generated per minute by the chemical reaction of one mole of lithium iron phosphate during the roasting process. This indicates the total mass of the mixture in the calcination furnace; This indicates the specific heat capacity of the mixture in the calcination furnace; This indicates the maximum allowable temperature deviation of the calcination reaction temperature, which is generally set between 10-30℃. This indicates the chlorine flow rate input into the roasting furnace per minute;

[0014] In actual production, data under different conditions is first measured using appropriate measuring equipment and stored in a corresponding database within the control system. Then, the database is queried based on the real-time status to calculate the chlorine flow rate. Specifically, the equipment is first fixed, and the heat dissipation rate under different conditions is measured to form... The database is used to retrieve values ​​from the table based on the current status. It is obtained by directly measuring the heat of reaction. The specific heat capacity of each individual substance is measured first, and then calculated according to the mass ratio; based on the total mass of the mixture in the current roasting furnace and the conversion factor. The maximum allowable temperature deviation of the calcination reaction and what was obtained , and The value can be used to calculate the chlorine flow rate control range input into the roasting furnace per minute. Since the reaction in the roasting furnace is continuous, the chlorine flow rate will continuously change according to the reaction time. The roasting reaction time is related to the capacity of the roasting furnace, its heat dissipation capacity, and the amount of material. Generally speaking, the roasting reaction time is controlled to be 20-50 minutes.

[0015] This application controls the roasting reaction temperature in the roasting furnace by controlling the chlorine flow rate. This not only effectively controls the roasting reaction temperature but also reduces the need for other temperature control equipment in the roasting furnace, thereby lowering production costs.

[0016] The chemical reaction formula for the calcination reaction is as follows:

[0017] LiFePO4 + 0.5Cl2 LiCl + FePO4

[0018] This roasting reaction converts lithium in the cathode black powder of spent lithium iron phosphate batteries into water-soluble lithium chloride, and iron and phosphorus into water-insoluble iron phosphate. The lithium content of the roasted product can reach over 95% of the lithium content in the spent lithium iron phosphate cathode black powder. Therefore, after water immersion, the water-soluble lithium chloride and iron phosphate can be separated from the roasted product. After filtration, evaporation, concentration, and drying, lithium chloride crystals are obtained, thus realizing the recovery of lithium from spent lithium iron phosphate batteries. The filtration and evaporation / concentration drying processes are existing technologies and will not be described in detail here.

[0019] The weight of lithium iron phosphate in the cathode black powder is calculated based on the mass content of lithium, iron, and phosphorus in the cathode black powder of waste lithium iron phosphate batteries. Under normal circumstances, the lithium and phosphorus content will be slightly higher than the iron content because the electrolyte also contains a small amount of lithium and phosphorus. The mass content of lithium in the cathode black powder is ≥4.0%, and the mass content of iron is ≥30%.

[0020] Furthermore, after the roasting reaction is completed in the roasting furnace, a protective gas is first introduced into the roasting furnace to completely replace the remaining chlorine gas in the roasting furnace, and then the roasting product is taken out. It should be noted that the replaced chlorine gas needs to be transported to an external tail gas absorption device for recovery treatment.

[0021] Furthermore, the water soaking of the roasted product specifically involves adding pure water to the roasted product obtained from the roasting reaction and heating it to a preset temperature while stirring until the roasted product is completely soaked.

[0022] Furthermore, the amount of pure water used is calculated based on the requirement of 10 to 50 grams of pure water per gram of roasted product.

[0023] Furthermore, the preset temperature is controlled at 40–70°C, and the stirring time is controlled at 2 hours or more.

[0024] Furthermore, the protective gas is nitrogen or an inert gas. The inert gas is typically argon or helium. Beneficial effects

[0025] This invention provides a method for recovering lithium from spent lithium iron phosphate batteries. This method controls the roasting reaction temperature in a roasting furnace by controlling the chlorine gas flow rate. This effectively controls the roasting reaction temperature and reduces the need for other temperature control equipment in the roasting furnace, thereby lowering production costs. Furthermore, the roasting temperature is relatively low, employing a one-step chlorine-filled roasting method to convert lithium from spent lithium iron phosphate batteries into water-soluble lithium chloride. The roasted product is then subjected to water leaching, filtration, evaporation, concentration, and drying to obtain lithium chloride crystals, thus achieving lithium recovery from spent lithium iron phosphate batteries. This method is simple, highly efficient, energy-efficient, and achieves a lithium recovery rate of over 95%. Moreover, it effectively meets environmental protection requirements and has significant industrial application value. Attached Figure Description

[0026] Figure 1 shows the phase qualitative analysis spectrum of the calcination reaction product in Example 1 of this application.

[0027] Figure 2 shows the phase qualitative analysis spectrum of the calcination reaction product in Example 2 of this application.

[0028] Figure 3 shows the phase qualitative analysis spectrum of the calcination reaction product in Example 3 of this application. The best embodiment of the present invention

[0029] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the description of the embodiments. Example 1

[0030] Take 100kg of waste lithium iron phosphate battery cathode black powder raw material, in which the lithium iron phosphate content is 86.4%, the graphite content is 11.8%, and the rest are impurities such as copper, aluminum, fluorine, and titanium. Place the waste lithium iron phosphate battery cathode black powder raw material in a vacuum oven and bake at 150℃ for 2 hours. Then, let it cool naturally to room temperature to obtain dried waste lithium iron phosphate battery cathode black powder.

[0031] The dried waste lithium iron phosphate battery cathode black powder was added to a roasting furnace and heated to the reaction temperature of 180°C. Chlorine gas with a purity of 99.99% was introduced to carry out a selective reaction. During the roasting reaction, the maximum allowable temperature deviation of the roasting reaction was controlled by adjusting the chlorine gas flow rate to 30°C. The roasting reaction time was 30 minutes. After the roasting reaction was completed, the mixture was allowed to cool naturally. The chlorine gas flow rate was controlled at 210-220 L / min.

[0032] The exhaust gas generated by the roasting reaction is absorbed by alkaline solution spraying and purified to meet the standards before being discharged.

[0033] Nitrogen gas is introduced into the roasting furnace to completely replace the remaining chlorine gas inside the furnace, and the replaced chlorine gas is then transported to an external tail gas absorption device for recovery.

[0034] Take out the roasted product, add pure water to the roasted product and heat to 60℃ and stir for 8 hours to obtain the roasted product solution. The amount of pure water used is calculated as 20g of pure water is required for 1g of roasted product.

[0035] The calcined product solution was filtered to obtain the filtrate;

[0036] The filtrate was placed in an evaporating dish and boiled until all the water vapor was evaporated to obtain an evaporation and concentration product. The evaporation and concentration product was dried at 60°C for 4 hours to obtain lithium chloride crystals. Example 2

[0037] Take 100kg of waste lithium iron phosphate battery cathode black powder raw material, in which the lithium iron phosphate content is 93.2%, the graphite content is 5.3%, and the rest are impurities such as copper, aluminum, fluorine, and titanium. Place the waste lithium iron phosphate battery cathode black powder raw material in a vacuum oven and bake at 150℃ for 2 hours. Then, let it cool naturally to room temperature to obtain dried waste lithium iron phosphate battery cathode black powder.

[0038] The dried waste lithium iron phosphate battery cathode black powder was added to a roasting furnace and heated to a reaction temperature of 300°C. Chlorine gas with a purity of 99.99% was introduced to carry out a selective reaction. During the roasting reaction, the maximum allowable temperature deviation of the roasting reaction was controlled by adjusting the flow rate of chlorine gas to 20°C. The roasting reaction time was 20 minutes. After the roasting reaction was completed, the mixture was allowed to cool naturally. The chlorine gas flow rate was controlled at 345-365 L / min.

[0039] The exhaust gas generated by the roasting reaction is absorbed by alkaline solution spraying and purified to meet the standards before being discharged.

[0040] Nitrogen gas is introduced into the roasting furnace to completely replace the remaining chlorine gas inside the furnace, and the replaced chlorine gas is then transported to an external tail gas absorption device for recovery.

[0041] Take out the roasted product, add pure water to the roasted product and heat to 50℃ and stir for 4 hours to obtain the roasted product solution. The amount of pure water used is calculated based on 40g of pure water required for 1g of roasted product.

[0042] The calcined product solution was filtered to obtain the filtrate;

[0043] The filtrate was boiled in an evaporating dish until all the water vapor was evaporated to obtain an evaporation concentrate. The evaporation concentrate was then dried at 80°C for 2 hours to obtain lithium chloride crystals. Example 3

[0044] Take 100kg of waste lithium iron phosphate battery cathode black powder raw material, in which the lithium iron phosphate content is 52.3%, the graphite content is 41.2%, and the rest are impurities such as copper, aluminum, fluorine, and titanium. Place the waste lithium iron phosphate battery cathode black powder raw material in a vacuum oven and bake at 150℃ for 2 hours. Then, let it cool naturally to room temperature to obtain dried waste lithium iron phosphate battery cathode black powder.

[0045] The dried waste lithium iron phosphate battery black powder was added to the roasting reactor and heated to the reaction temperature of 50°C. Chlorine gas with a purity of 99.99% was introduced to carry out selective reaction. During the roasting reaction, the maximum allowable temperature deviation of the roasting reaction was controlled by adjusting the chlorine gas flow rate to 10°C. The roasting reaction time was 50 minutes. After the roasting reaction was completed, the mixture was allowed to cool naturally. The chlorine gas flow rate was 130-140 L / min.

[0046] The exhaust gas generated by the roasting reaction is absorbed by alkaline solution spraying and purified to meet the standards before being discharged.

[0047] Nitrogen gas is introduced into the roasting furnace to completely replace the remaining chlorine gas inside the furnace, and the replaced chlorine gas is then transported to an external tail gas absorption device for recovery.

[0048] Take out the roasted product, add pure water to the roasted product and heat to 55℃ and stir for 3 hours to obtain the roasted product solution. The amount of pure water used is calculated based on 50g of pure water required for 1g of roasted product.

[0049] The calcined product solution was filtered to obtain the filtrate;

[0050] The filtrate was placed in an evaporating dish and boiled until all the water vapor was evaporated to obtain an evaporation and concentration product. The evaporation and concentration product was dried at 70°C for 3 hours to obtain lithium chloride crystals.

[0051] The calcination products from Examples 1, 2, and 3 were taken and subjected to XRD phase qualitative analysis, as shown in Figures 1, 2, and 3. The analysis results show that the main components of the calcination products taken from the three examples are lithium iron phosphate and lithium chloride. In Figures 1, 2, and 3, the horizontal axis represents the 2θ diffraction angle, which is the angle between the extension of the incident X-ray and the reflected X-ray, and the vertical axis represents the intensity after diffraction.

[0052] In addition, the products after evaporation, concentration and drying in Examples 1, 2 and 3 were analyzed by ICP elemental analysis, and the results are shown in Table 1:

[0053] Table 1. Detection and analysis results of the products after evaporation, concentration and drying in Examples 1-3.

[0054] Example 1 Example 2 Example 3 Lithium Chloride Purity (%) 99.6 99.5 2 99.7 Lithium Extraction Rate (%) 96.7 96.0 95.6

[0055] As can be seen from Table 1, the purity of lithium chloride in the three examples is all above 99.5%, and the lithium extraction rate is all above 95%. Specifically, the impurity elements in the evaporation and concentration product of Example 1 are as follows: Fe content 20ppm, P content 12ppm, F content 2ppm, Cu content 3ppm, Al content 4ppm, Ti content 0.6ppm, and Ca content 2ppm; the impurity elements in the evaporation and concentration product of Example 2 are as follows: Fe content 12ppm, P content 6ppm, F content 1ppm, Cu content 0.5ppm, Al content 2ppm, Ti content 0.5ppm, and Ca content 1ppm; the impurity elements in the evaporation and concentration product of Example 3 are as follows: Fe content 67ppm, P content 38ppm, F content 8ppm, Cu content 16ppm, Al content 15ppm, Ti content 0.8ppm, and Ca content 3ppm. Therefore, it can be seen that the impurity element content in the three embodiments all reached the ppm level. Thus, the lithium recovery rate of the lithium recovery method in the waste lithium iron phosphate battery provided by the present invention is high, the recovered lithium chloride product has high purity, and the method is simple, energy-efficient, and can well meet environmental protection requirements, and has great industrial application value. Embodiments of the present invention

[0056] Type the description paragraph of embodiments of the present invention here. Industrial applicability

[0057] Type the industrial utility description paragraph here. Sequence List Free Content

[0058] Type the free content description paragraph for the sequence list here.

Claims

1. A method for recovering lithium from a spent lithium iron phosphate battery, the method comprising: The method comprises: ​ The positive electrode black powder of the waste lithium iron phosphate battery is placed in a roasting treatment furnace filled with a protective gas for roasting reaction, and the flow of input chlorine gas is adjusted based on the mixture in the roasting treatment furnace to control the roasting reaction temperature, which is controlled to be 50-300 DEG C; The roasting product after the roasting reaction is subjected to water immersion to obtain a roasting product solution; The roasting product solution is filtered to obtain a filtrate; The filtrate is evaporated and concentrated, and then dried to obtain lithium chloride crystals; The formula for adjusting the flow of input chlorine gas based on the mixture in the roasting treatment furnace to control the roasting reaction temperature is as follows: ； In the formula, represents the conversion factor of molar mass to volume, represents the heat dissipation amount per minute of the roasting treatment furnace, represents the heat of chemical reaction per one mole of lithium iron phosphate per minute of the roasting reaction, Mtotal represents the total mass of the mixture in the roasting treatment furnace, Cp represents the specific heat capacity of the mixture in the calcination treatment furnace, represents the maximum temperature deviation allowed for the calcination reaction temperature, The flow of chlorine gas input into the roasting treatment furnace per minute is represented by F.

2. The method of claim 1, wherein the method is characterized by: After the roasting reaction in the roasting treatment furnace is completed, the remaining chlorine gas in the roasting treatment furnace is completely replaced by filling the roasting treatment furnace with a protective gas, and then the roasting product is taken out.

3. The method of recovering lithium from a spent lithium iron phosphate battery of any one of claims 1-2, wherein: The water immersion of the roasting product specifically comprises adding pure water to the roasting product obtained by the roasting reaction and stirring at a preset temperature until the roasting product is completely soaked.

4. The method of recovering lithium from spent lithium iron phosphate batteries of claim 3, wherein: The amount of pure water is calculated to be 10-50 g of pure water per 1 g of roasting product.

5. The method of recovering lithium from spent lithium iron phosphate batteries of claim 4, wherein: The preset temperature is controlled to be 40-70 DEG C, and the stirring time is controlled to be more than 2 h.

6. The method of recovering lithium from a spent lithium iron phosphate battery of any one of claims 1-2, wherein: The protective gas is nitrogen or an inert gas.

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