CN111261969A - A method for recycling and regenerating cathode material of waste lithium iron phosphate battery - Google Patents

Abstract

The invention provides a method for recycling and regenerating positive electrode materials of waste lithium iron phosphate batteries, which comprises the following steps: disassembling the recycled waste lithium iron phosphate batteries after being completely discharged, and taking out positive electrode sheets; cleaning the positive electrode sheets with organic solvents to remove Residual electrolyte, dry; immerse the dried positive electrode sheet in a dispersion formed by organic acid and water, heat and stir; sieve the mixture from the previous step, separate the current collector, and obtain a suspension, which is evaporated under stirring Dry, vacuum-dry to obtain recycled material powder; measure the content of element Li and Fe, supplement lithium, mix well, and roast the mixed material in an inert atmosphere to obtain a recycled positive electrode material. The present invention uses the above-mentioned dispersion liquid to separate the current collector and the positive electrode active material, which greatly improves the recovery rate of aluminum and lithium iron phosphate and the separation efficiency of the two. The step of recycling aluminum reduces costs and avoids secondary pollution to the environment.

Description

A method for recycling and regenerating cathode material of waste lithium iron phosphate battery

technical field

The invention relates to the field of recycling waste lithium iron phosphate batteries, in particular to a method for recycling and regenerating positive electrode materials of waste lithium iron phosphate batteries.

Background technique

Since the commercial launch of lithium-ion batteries in the 1990s, they have received widespread attention and attention. Due to the advantages of high operating voltage, easy portability, and high energy density, lithium-ion batteries have been widely used in mobile phones, notebook computers, cameras, etc. In modern electronic devices such as electric vehicles. With the advancement of technology, the production and demand of lithium-ion batteries are increasing day by day. For example, from 2000 to 2010, the global growth rate increased by 800%, and with its further potential applications in electric vehicles and smart grids, the demand for lithium-ion batteries is even greater. increasingly intensified. According to estimates of industrial demand and growth, the market value of lithium-ion batteries will rapidly increase from US$31.4 billion in 2015 to US$53.7 billion in 2020, which will inevitably lead to a strong demand for lithium metal worldwide and a shortage of lithium metal.

As we all know, after a certain number of charges and discharges, the capacity of lithium-ion batteries will gradually lose until they are scrapped. The service life of lithium-ion batteries is generally 1-3 years, and the life of power lithium batteries is longer. If a large number of scrapped lithium-ion batteries are generated, if they are not disposed of, landfill will seriously pollute the environment and affect human health. It will also cause waste of resources, increase the pressure on the utilization of existing resources on the earth, and limit the longer-term development of lithium batteries. Therefore, whether from an environmental or economic point of view, the recycling of used lithium-ion batteries is imperative, and there is an urgent need to increase the efforts to promote the recycling industry.

Lithium-ion batteries are mainly composed of four main components: positive electrode, negative electrode, electrolyte and separator. The cost of active material on the positive electrode accounts for about 30-50% of the manufacturing cost of the entire lithium-ion battery, and is the most valuable component in lithium-ion batteries. It is also the focus and difficulty of lithium-ion battery recycling. Among the technologies for recycling or re-utilizing positive active materials of ion batteries, hydrometallurgy is the more mature technology. The process is simple and easy to control, and the recovery efficiency is high. Therefore, it has received extensive attention. The battery treatment and recycling method is mainly to firstly discharge and disassemble the battery, separate the active material through high temperature sintering, organic solvent such as NMP ultrasonic or NaOH corrosion current collector and other pretreatment methods, and then immerse the active material through acid leaching, alkali leaching or mixing. The leaching method selectively or completely leaches the metal elements in the active material, and finally obtains the metal element, metal compound, positive electrode material, etc. through extraction, precipitation, replacement, distillation and other methods. Relevant patents include patent CN107706480A, which discloses a silica gel extractant for lithium battery recovery and its preparation method and application method. A silica gel extractant is designed, which has different binding rates to metal ions at different temperatures. High efficiency, high efficiency, environmental protection and pollution-free separation of metal ions can be achieved. CN102368560B discloses a method for recycling electrode materials of a battery. The ionic liquid is used as a solvent to selectively dissolve active substances, and the active substances dissolved in the ionic liquid are recovered by simple high temperature treatment to recover metallic lithium and heavy metal elements therein. CN107419096B discloses a preparation method for recycling and regenerating ternary positive electrode materials from waste lithium batteries. After leaching metal elements in waste positive electrodes with inorganic acid, after removing copper, aluminum and iron, co-precipitate under alkaline conditions to obtain ternary material precursors, and finally combine with The lithium carbonate is ball-milled and then calcined to obtain a regenerated ternary cathode material. CN106921001B discloses a method for recovering lithium cobalt oxide batteries by using power ultrasound. The efficient leaching of lithium and cobalt is realized by H ₂ S ₂ O ₄ -H ₂ O ₂ combined with intermittent ultrasonic assistance, and the subsequent precipitation is recovered separately. Lithium and cobalt. CN109449522A discloses a method for recovering metal ions in waste batteries and applying them to all-solid-state lithium batteries. The recovery of metal ions is realized by using organic acids, and the recovered products are nanosized and used as inert fillers to increase polymer-lithium salts. The shaping area, thereby improving the ionic conductivity, realizes the recovery and reuse of resources.

Analyzing the prior art, the following problems exist in the recovery process of hydrometallurgy: 1. There are many process steps, and the process parameters need to be strictly controlled; 2. A large amount of reagents are consumed, a large amount of impurity ions are introduced, and the cost of recovery is increased; 3. , the treatment and recovery process usually produces secondary pollution such as waste liquid and exhaust gas, and it needs to be equipped with another device for collection and treatment.

In view of the shortcomings of the prior art, the object of the present invention is to provide a low-cost, short-range and environmentally friendly closed-loop recovery and regeneration method for the positive electrode material of a lithium iron phosphate waste battery, utilizing the acidity and carbon elements of naturally occurring organic acids to recover The pretreatment separation and subsequent resynthesis are integrated in the process to prepare a carbon-coated recycled cathode material. The whole process uses less reagents, high recovery efficiency, and no secondary pollution.

SUMMARY OF THE INVENTION

The invention provides a method for recycling and regenerating positive electrode materials of waste lithium iron phosphate batteries. The method is environmentally friendly and has no pollution, simple process steps, low cost, high recycling efficiency, and no secondary pollution.

A method for recycling and regenerating positive electrode materials of waste lithium iron phosphate batteries, comprising the following steps:

1) Disassemble the recycled lithium iron phosphate waste battery after fully discharging, and take out the positive electrode sheet;

2) cleaning the positive electrode sheet with an organic solvent, removing the residual electrolyte on the positive electrode sheet, and drying;

3) immersing the dried positive electrode sheet in step 2) in the dispersion formed by organic acid and water, heating and stirring;

4) sieving the mixture finally obtained in step 3), separating the current collector to obtain a suspension containing the positive active material, evaporating the suspension to dryness under stirring, and vacuum drying to obtain the recovered material powder;

5) Determination of element Li and Fe content, adding lithium source to the recycled material powder to supplement lithium, mixing the mixed material mechanically or manually, and roasting the obtained mixed material in an inert atmosphere to obtain a recycled positive electrode material.

Step 3) The organic acid is a fatty acid or a biomass acid, and the number of carbon atoms of the organic acid is 12-20, including but not limited to at least one of stearic acid and linoleic acid; The mass fraction of acid is 1-5%.

The organic acid in the dispersion, on the one hand, accelerates the peeling of the positive electrode active material from the current collector, and on the other hand provides a carbon source for the carbon coating of lithium iron phosphate.

Step 3) The solid-liquid ratio of the positive electrode sheet to the dispersion liquid is 10-100 g/L; preferably, the solid-liquid ratio of the positive electrode sheet to the dispersion liquid in step 3) is 30 g/L-60 g/L.

Step 1) The complete discharge is that the open circuit voltage of the final waste lithium iron phosphate battery is less than 2V.

Step 2) The organic solvent is not particularly limited, and the solvent in the commonly used lithium iron phosphate battery electrolyte can be used, including but not limited to at least one of dimethyl carbonate, 1,3-dioxolane, and diethyl carbonate. A sort of.

Step 3) The stirring speed is 300-800r/min, the heating temperature is 20-60°C, and the stirring time is 5-10min

Step 4) The aperture of the sieve is 40-80 mesh, the stirring speed is 300-800r/min, the heating temperature is 80-100°C, and the vacuum condition is -0.5-(-0.1)MPa.

Step 5) The lithium source includes but is not limited to at least one of lithium hydroxide, lithium carbonate, and lithium iron phosphate; the molar ratio of Li and Fe after lithium supplementation is 1-1.08:1, and the mixing method For mechanical ball milling, the ball milling time is 1-5h.

Step 5) The precise determination method of each element content includes but is not limited to at least one of ICP-AES, ICP-OES, and ICP-MS.

Step 5) The inert gas includes but not limited to nitrogen or argon, the calcination temperature is 300-800°C, and the calcination time is 2-10h.

Compared with the prior art, the beneficial effects of the present invention are:

1. The present invention uses the mixed solution of organic acid and water to separate the current collector and the positive electrode active material, which greatly improves the recovery rate of aluminum and lithium iron phosphate and the separation efficiency of the two. The process is simple and fast, saving mechanical methods, acid Complicated aluminum recovery steps such as leaching or alkali leaching reduce costs and avoid secondary pollution to the environment.

2. The inventors also unexpectedly found that the recycled cathode material finally obtained by adjusting the concentration and dosage of organic acid has excellent electrochemical performance, which is close to the battery performance index of the newly prepared lithium iron phosphate cathode material, showing that in industrial advantage.

3. The organic acid and the residual conductive additives and binders used in the present invention are used as the carbon source in the subsequent positive electrode material regeneration process to prepare a carbon-coated regenerated positive electrode material whose electrochemical performance meets the requirements of the lithium-lithium battery for the positive electrode material. The recycling and reuse of the cathode material in the waste lithium iron phosphate battery is realized, the cost is saved and the environment is protected.

Fourth, the process of the present invention integrates the separation and regeneration of the positive electrode material, the process is simplified, the reagents used are few and pollution-free, and at the same time, the carbon coating of the positive electrode material can be realized, and the electrochemical performance of the recycled material can be improved; the present invention requires equipment Not high, suitable for industrialized lithium battery recycling, regeneration and amplification operations.

Description of drawings

Fig. 1 is the SEM image of the vacuum-drying recovery material powder of Example 3 of the present invention;

Fig. 2 is the SEM image of the cathode material recovered and regenerated after roasting in Example 3 of the present invention

Fig. 3 is the XRD pattern of the vacuum-drying recovery material powder of Example 3 of the present invention;

Fig. 4 is the XRD pattern of the positive electrode material that obtains recovery and regeneration after roasting in Example 3 of the present invention;

Fig. 5 is the first charge-discharge curve of the button battery of Application Example 3 of the present invention;

FIG. 6 is a cycle curve of a button battery in Application Example 3 of the present invention.

Detailed ways

The present invention is further described below in conjunction with specific embodiments, but is not limited to the contents in the description. Unless otherwise specified, the "parts" described in the examples of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

Example 1

1) First, fully discharge the recycled lithium iron phosphate waste battery, and the open circuit voltage after discharge is 0.8V, then disassemble, and take out the positive electrode sheet (the content of lithium iron phosphate is 84.6%, and the content of aluminum is 12.1%);

2) Clean the positive electrode sheet with dimethyl carbonate, remove the residual electrolyte on the positive electrode sheet, and place the positive electrode sheet with the residual electrolyte removed in an 80°C vacuum oven to dry;

3) Accurately step 2) Weigh 3 g of the obtained positive electrode sheet, and put it into 100 ml of an aqueous dispersion with a mass fraction of 1% stearic acid. In order to further accelerate mass transfer, the positive electrode sheet is cut into a size of 2 cm × 2 cm, and the rotational speed is adjusted to be 500r/min, stirring at 25°C for 5min;

4) The final obtained mixture in step 3) is sieved out of the current collector aluminum using a 40 mesh sieve to obtain a suspension containing the positive active material, and the aluminum foil is cleaned with deionized water and dried, and 2mol/L of nitric acid is used for sampling. After the solution was dissolved, the purity of the obtained aluminum foil was analyzed by ICP-OES, and the recovery rate of aluminum was calculated. The suspension was evaporated to dryness at a stirring speed of 400 r/min and a temperature of 80 °C, stirred for 6 h, and dried in a vacuum drying oven with a vacuum degree of -0.2 MPa to obtain the recovered material powder, and the recovery rate was calculated. The results are shown in Table 1. ;

5) Using ICP-OES to measure the Li and Fe content in the recovered material powder in step 4), the molar ratio of Li and Fe is 0.8:1, and adding lithium source lithium carbonate to supplement lithium, so that both Li and Fe are added. The molar ratio is 1.05:1, the mixing method is high-energy ball milling, and the ball milling time is 3h.

Example 2

The rest are the same as in Example 1, except that the mass fraction of stearic acid is 3%.

Example 3

The rest are the same as in Example 1, except that the mass fraction of stearic acid is 5%.

Example 4

The rest are the same as in Example 1, except that the amount of the positive electrode sheet in step 3 is 1 g.

Example 5

The rest are the same as in Example 1, except that the amount of the positive electrode sheet in step 3 is 6 g.

Example 6

The rest are the same as in Example 1, except that the amount of the positive electrode sheet in step 3 is 10 g.

Example 7

The rest are the same as in Example 1, except that the amount of the positive electrode sheet in step 3 is 11 g.

Example 8

The rest are the same as in Example 1, except that the organic acid used is linoleic acid.

Comparative Example 1

The rest are the same as in Example 1, except that the organic acid used is oxalic acid.

Comparative Example 2

The recycling of aluminum and lithium iron phosphate cathode active materials is carried out using the prior art.

Take 100g of waste lithium iron phosphate cathode material (content of lithium iron phosphate 84.6%, content of aluminum 12.1%) and 1.2L of sodium hydroxide solution (0.4mol/L), mix and stir, heat to 90°C, react for 2h, and carry out alkali leaching. Aluminum was filtered, and the filtrate was neutralized with a sulfuric acid solution to pH=9.0 to precipitate aluminum in the form of aluminum hydroxide. The aluminum hydroxide precipitate was washed with deionized water and dried. The weight was 31.89 g, and the yield of aluminum was 78.53%. Sampling was dissolved in 2mol/L nitric acid solution, and the purity of the obtained aluminum hydroxide was analyzed by ICP-OES. The purity was 96.78%. The lithium iron phosphate filter residue after aluminum removal was calcined at 600 ° C for 6 hours in a nitrogen atmosphere to obtain lithium iron phosphate powder. The material was 82.65 g, and the recovery rate of lithium iron phosphate was 97.69%.

Application example

The positive electrode materials obtained in the above examples and comparative examples are respectively tested by battery assembly according to the following steps, corresponding to application examples 1-8, and comparative application examples 1 and 2,

Electrode sheet preparation: The obtained recovered lithium iron phosphate, carbon black and binder (PVDF) were mixed and made into a slurry in a mass ratio of 8:1:1, and the slurry was uniformly coated on the carbon-coated aluminum foil current collector. After drying in a blast oven at 80°C, a positive electrode sheet was prepared by vacuum drying at 80°C for 8 hours. Lithium sheet is used as the counter electrode, PP separator (celgard2500) is used, an appropriate amount of electrolyte (1M LiPF ₆ is dissolved in an organic solvent with a volume ratio of EC:DEC:DMC=1:1:1) is added, and gloves under the protection of argon A 2032 button cell was assembled in the box, and the following electrochemical performance tests were performed:

First charge and discharge performance:

The first charge-discharge voltage specific capacity at 0.1C (1C=170mA/g), the results are shown in Figure 5 and Table 1.

Charge-discharge cycle stability:

The cycle life curve under 0.5C (1C=170mA/g) charge-discharge mode, the discharge capacity retention rate after 150 cycles, the results are shown in Figure 6 and Table 1.

Table 1

Comparative Example 2 ^a refers to the recovery of aluminum in the form of aluminum hydroxide, and the purity of aluminum refers to the purity of aluminum hydroxide.

Fig. 1 and Fig. 2 are respectively embodiment 3 step 4) reclaimed material after vacuum drying and step 5) carry out SEM test result of the positive electrode material reclaimed after roasting There is obvious agglomeration phenomenon, the prepared lithium iron phosphate/carbon particles are relatively uniform, and the surface of the particles has obvious coated carbon particles, which achieves the purpose of coating.

FIG. 3 and FIG. 4 are respectively X-ray diffraction (XRD) results of the recovered material after step 4) vacuum drying in Example 3 and the recovered and regenerated cathode material obtained after step 5) roasting. For the vacuum-dried lithium iron phosphate after separation in step 4), compared with the commercialized Lithium iron phosphate P198-S13, it can be seen from the XRD in Figure 3 that its main diffraction peak is consistent with the commercial material, that is, the surface iron phosphate The crystal structure of lithium is not destroyed, and the existence of some impurity phases of iron phosphate is presumed to be caused by the lack of active lithium ions during cycling.

For the cathode material recovered in step 5) Fig. 4, comparing the lithium iron phosphate of commercial material and the impurity phase of iron phosphate in Fig. 3, there is no impurity peak, indicating that lithium enters the crystal lattice during the roasting process, repairing the Lattice-defective lithium iron phosphate structure. At the same time, it was also found that the peak shape of the XRD pattern of the recovered cathode material was sharp and narrow, indicating that it had a good crystal structure, and no diffraction peak of crystalline carbon was observed, indicating that the carbon-coated carbon existed in an amorphous form.

Fig. 5 is the first charge-discharge curve of the button battery in Application Example 3 of the present invention. Combining with Fig. 4 and the data in Table 1, it can be seen that the first charge specific capacity of the lithium iron phosphate cathode material prepared by the present invention is higher than 160mAh at a rate of 0.1C. /g, the first discharge specific capacity is higher than 130mAh/g, the first discharge specific capacity of the preferred application example is higher than 150mAh/g, the first charge and discharge efficiency is higher than 90%, reaching the level of general lithium iron phosphate cathode material, that is, it satisfies phosphoric acid Requirements for cathode materials of iron-lithium batteries.

Fig. 6 is the cycle curve of the button battery of application example 3 of the present invention. It can be seen from Fig. 5 and the data in Table 1 that the lithium iron phosphate cathode material recovered and regenerated by the present invention can maintain more than 80% of the capacity of the first discharge after 150 cycles. , the highest can reach 91.55%, indicating that the lithium iron phosphate cathode material recovered and regenerated by the present invention has good charge-discharge cycle stability.

It can be seen from the data in Table 1 that the performance of the cathode material obtained by the recovery method of the present invention is close to that of the newly prepared lithium iron phosphate cathode material, showing satisfactory performance and having industrial advantages.

In addition to the excellent electrochemical performance of the obtained positive electrode material, the method for recycling the positive electrode material of the waste battery provided by the present invention also shows good economical efficiency, and the recovery rates of the main substances in the positive electrode material, that is, aluminum and lithium iron phosphate, are both high. to a very satisfactory degree. In particular, the recovery rate of aluminum is more than 97%, while according to the general method in the prior art, the recovery rate of aluminum can only be 78%. The recovery rate of the positive electrode active material lithium iron phosphate is close to that of the prior art. However, since the present invention adopts a specific concentration of organic acid and a specific solid-liquid feeding ratio, the electrochemical performance of the positive electrode material is significantly improved.

The organic acid, the residual conductive additive and the binder used in the present invention are used as the carbon source in the subsequent regeneration process of the cathode material, and the carbon-coated regeneration cathode material whose electrochemical performance meets the requirements of the lithium-lithium battery for the cathode material is prepared. The recycling and reuse of cathode materials in waste lithium iron phosphate batteries saves costs and protects the environment.

The process of the invention integrates the separation and regeneration of the positive electrode material, the process is simplified, the used reagents are few and pollution-free, and at the same time, the carbon coating of the positive electrode material can be realized, and the electrochemical performance of the recycled material can be improved.

The preparation process of the invention is simple, the equipment requirements are not high, and the invention is suitable for the recovery, regeneration and amplification operation of the industrialized lithium battery.

The above detailed description is a specific description of one of the feasible embodiments of the present invention, which is not intended to limit the scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention shall be included in the present invention. within the scope of the technical solution.

Claims (10)

1. A method for recycling and regenerating a lithium iron phosphate waste battery anode material comprises the following steps:

1) completely discharging the recovered waste lithium iron phosphate battery, disassembling the waste lithium iron phosphate battery, and taking out the positive plate;

2) cleaning the positive plate by using an organic solvent, removing the residual electrolyte on the positive plate, and drying;

3) immersing the positive plate dried in the step 2) into a dispersion liquid formed by organic acid and water, heating and stirring;

4) sieving the mixture finally obtained in the step 3), separating out a current collector to obtain a suspension containing the positive active substance, evaporating the suspension to dryness under stirring, and drying in vacuum to obtain recovered material powder;

5) and (3) measuring the content of the elements Li and Fe, adding a lithium source into the recycled material powder for lithium supplement, mechanically or manually mixing the mixed material, and roasting the obtained mixed material in an inert atmosphere to obtain the recycled and regenerated cathode material.

2. The recycling method according to claim 1, wherein the organic acid in step 3) is fatty acid or biological acid, the number of carbon atoms of the organic acid is 12-20, and the organic acid includes but is not limited to at least one of stearic acid and linoleic acid.

3. The recovery and regeneration method according to claim 2, wherein the mass fraction of the organic acid in the dispersion is 1 to 5%.

4. The recycling method according to claim 1, wherein the feeding solid-liquid ratio of the positive electrode sheet and the dispersion liquid in step 3) is 10-100 g/L.

5. The recycling method according to claim 4, wherein the feeding solid-liquid ratio of the positive electrode sheet and the dispersion liquid in the step 3) is 30g/L-60 g/L.

6. The recycling method according to claim 1, wherein the organic solvent in step 2) is at least one selected from the group consisting of dimethyl carbonate, 1, 3-dioxolane, and diethyl carbonate.

7. The recycling method as set forth in claim 1, wherein the stirring speed in step 3) is 800r/min, the heating temperature is 20-60 ℃, and the stirring time is 5-10 min.

8. The recycling method of claim 1, wherein the mesh size of the sieve in step 4) is 40-80 mesh, the stirring speed is 800r/min, the heating temperature is 80-100 ℃, and the vacuum condition is-0.5- (-0.1) MPa.

9. The recycling method according to claim 1, wherein the lithium source in step 5) is at least one selected from the group consisting of lithium hydroxide, lithium carbonate, and lithium iron phosphate; the molar ratio of Li to Fe after lithium supplement is 1-1.08:1, the mixing mode is mechanical ball milling, and the ball milling time is 1-5 h.

10. The recycling method as claimed in claim 1, wherein the inert gas in step 5) includes but is not limited to nitrogen or argon, the calcination temperature is 300-800 ℃, and the calcination time is 2-10 h.

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