CN108808150A - A method for comprehensive recycling and reuse of waste ternary electrode materials - Google Patents

Abstract

The invention discloses a kind of methods that synthetical recovery recycles waste and old ternary electrode material, utilize the design feature of stratiform ternary electrode material, selectively lithium ion is deviate from from tertiary cathode active material under the driving of extra electric field, recycling is precipitated using precipitating reagent；In addition, the tertiary cathode material for lacking lithium state is used as the catalyst of oxygen evolution reaction.Recovery method of the present invention not only can effectively recycle elemental lithium, but can functional whole utilization electrode material used as catalyst, and it is simple for process, easy to implement, be conducive to promote and apply.

Description

A method for comprehensive recycling and reuse of waste ternary electrode materials

technical field

The invention relates to a method for comprehensively recycling waste ternary electrode materials, and belongs to the technical field of recycling lithium ion batteries.

Background technique

With the advancement of science and technology and the rapid development of social economy, the process of industrialization and urbanization is accelerating, and the demand for energy has been showing a growing trend. Human traditional energy fuels such as coal, oil and natural gas have been exploited and used in large quantities, making the non-renewable energy represented by fossil energy gradually exhausted, and the energy crisis facing the world is becoming increasingly severe. The use of renewable energy sources such as solar, wind and nuclear energy requires stable energy storage carriers. Due to the advantages of high specific energy, long cycle life, no memory effect and light weight, lithium-ion batteries have become the most promising high-efficiency secondary batteries and the fastest-growing chemical energy storage power sources.

Nickel-cobalt-manganese composite ternary material combines the common advantages of three layered materials such as LiCoO ₂ , LiNiO ₂ and LiMnO ₂ , and its performance is superior to that of a single component. It is similar to LiCoO ₂ , but has the advantages of low cost and environmental friendliness. As a high-capacity cathode material, it has become a research hotspot. The nickel-cobalt-manganese composite ternary material lithium-ion battery has been put into commercial application. According to statistics, in 2017, the installed capacity of nickel-cobalt-manganese composite ternary material lithium-ion batteries in China's electric vehicle market reached 15GWh, and the installed capacity of ternary material lithium-ion batteries increased by 134.4% year-on-year. The power battery route is transforming to ternary materials, and ternary materials are replacing lithium iron phosphate as the cathode material with the highest growth rate in 2017. However, as the service time increases, the performance of lithium-ion batteries, such as capacity, discharge efficiency, and safety, will decline significantly, making it difficult to meet application requirements. The service life of lithium-ion batteries is generally 2 to 4 years, and the cycle of use is about 500 to 1000 times. The number of retired lithium-ion batteries is increasing rapidly year by year. It is predicted that by 2020, the number of waste lithium-ion batteries in my country will reach 25 billion, with a total weight of 500,000 tons, of which lithium-ion batteries made of ternary materials account for a considerable proportion. The average content of lithium in discarded ternary material lithium-ion batteries is 1.9%, nickel is 12.1%, and cobalt is 2.3%. Lithium metal is a scarce resource, and cobalt itself is relatively expensive, and the content in waste batteries is higher than that of raw ore. It is an important strategic material. From another point of view, if the scrapped lithium batteries are not recycled, they will cause serious pollution to the environment. At present, the imbalance between supply and demand of transition metal resources required for the production of lithium-ion batteries is gradually becoming prominent. Domestic power battery manufacturers have expanded the production capacity of lithium-ion ternary batteries in the past two years. It is expected to recover cobalt, nickel, manganese, The market value created by metals such as lithium and iron and aluminum will reach 5.2 billion yuan in 2018. Therefore, recycling waste lithium batteries not only has economic value, but also has good social and environmental benefits. It has attracted extensive attention from scholars at home and abroad.

At present, the recycling methods for lithium-ion batteries are mainly divided into two categories, namely pyrometallurgy and hydrometallurgy. The so-called pyrometallurgy method is a method of treating waste lithium batteries under high temperature conditions and purifying metals or metal compounds. The main process of hydrometallurgical recycling of lithium-ion ternary battery electrode materials is: discharge and dismantling of waste batteries → material pretreatment → alkali leaching and acid leaching treatment to recover metal ions → step-by-step precipitation separation or synthesis transformation, the main purpose is to enrich Transition metal elements in electrode materials are used to re-prepare related metal compounds or ternary electrode materials to achieve recycling. The above method has the disadvantages of complex process, difficult disposal of subsequent waste liquid, and low recovery rate.

The current recovery and treatment methods only recover and purify metal elements such as lithium and manganese in electrode materials through dissolution-enrichment-precipitation and other separation processes to become basic chemical raw materials, rather than recycle and process them in a targeted manner for the application process. Reasonable utilization is obviously not economically feasible. It is necessary to explore effective recycling methods and technologies to provide an effective and reasonable way to solve the environmental pollution and resource waste caused by waste lithium-ion batteries, so as to truly realize the best use of materials and turn waste into treasure.

Contents of the invention

The purpose of the present invention is to provide a method for comprehensively recycling waste ternary electrode materials. This method utilizes the structural characteristics of the layered ternary electrode material, drives the external electric field to selectively remove lithium ions from the ternary positive electrode active material, and uses a precipitant such as sodium phosphate or sodium carbonate to precipitate and recover; in addition, the lithium ion in the delithiated state Ternary electrode materials can serve as excellent catalysts for the oxygen evolution reaction (OER). The recovery method of the invention can not only effectively recover the lithium element, but also can use the electrode material as a catalyst in a functional whole, and the process is simple and easy to implement, which is beneficial to popularization and application.

The present invention comprehensively recycles and reuses the method for waste and old ternary electrode materials, comprising the following steps:

Step 1: Use N-methylpyrrolidone solvent to soak and dissolve the binder (PVDF) in the waste ternary electrode material, peel off the electrode material and the aluminum foil of the current collector, and peel off the waste ternary positive electrode active material LiNi _x Co _y Mn _z O ₂ (x+y+z=1) mixed with a binder (polyvinylidene fluoride PVDF, or polytetrafluoroethylene PTFE) is coated on a conductive substrate, and after vacuum drying, a ternary cathode material composite film is obtained ; With the obtained ternary cathode material composite film as the anode, the inert electrode as the cathode, and the supporting electrolyte solution as the electrolyte, build an electrolytic cell, apply an electric field potential of 0.5 to 5V, and maintain it for 1 to 20h, using the layered ternary electrode material Structural features, selectively extract lithium ions from the ternary positive electrode active material into the electrolyte;

The waste ternary cathode active material is LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM111), LiNi _0.4 Co _0.2 Mn _0.4 O ₂ (NCM424), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523) , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622), LiNi _0.7 Co _0.1 Mn _0.2 O ₂ (NCM712), LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811) and so on.

The waste ternary electrode material also includes LiCoO ₂ , LiNiO ₂ , Li ₂ MnO ₄ , LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.75 Mn _0.25 O ₂ , LiNi _0.5 Mn _1.5 O ₄ , LiNi _0.7 Co _0.3 O ₂ , etc. Electrode material (considering that the value of any one or both of x, y, and _z in LiNi _x Co _y Mnz O ₂ can be zero). Similarly, this method is also applicable to the comprehensive recovery of nLi ₂ MnO ₃ ·(1-n)Li(Nix Co _y Mn _{z )} O ₂ (n=0～1, x+y+z=1) lithium-rich electrode materials .

The inert electrode is one of non-metal electrodes such as graphite and carbon fiber cloth, or metal electrodes such as platinum electrodes and titanium mesh.

The supporting electrolyte solution is one or more of metal ion compound solutions such as sodium chloride, potassium chloride and lithium chloride; the concentration range of the supporting electrolyte solution is 0.1-2mol/L.

The conductive substrate is one of carbon fiber cloth, titanium mesh and graphite paper.

In the delithiation process driven by an external electric field, the temperature range of the electrolyte is 0-90° C., and the pH range is 1-12.

Step 2: Take out the lithium-deficient ternary cathode material composite film obtained in step 1, and wash it with distilled water and ethanol in turn to remove impurities such as chloride ions remaining on the surface; then place the composite film in NMP (N-methyl pyrrolidone) solvent, dissolve and remove the binder, remove the lithium-deficient ternary positive electrode material from carbon fiber cloth or titanium mesh, centrifuge, wash and dry to obtain lithium-deficient nickel-cobalt-manganese composite metal oxide powder; The lithium-state nickel-cobalt-manganese composite metal oxide powder can be directly used as a catalyst for oxygen evolution reaction (OER).

Step 3: Add a precipitating agent to the electrolyte obtained in step 1 to precipitate lithium ions therein to obtain lithium carbonate or lithium phosphate; the obtained lithium carbonate or lithium phosphate can be used as a lithium source to grind and mix with raw materials such as iron phosphate and glucose, and then undergo solidification phase calcination to synthesize lithium iron phosphate electrode material, which can be recycled and reused.

The precipitation agent is selected from sodium bicarbonate, sodium carbonate or sodium phosphate and the like.

The lithium-deficient nickel-cobalt-manganese composite metal oxide powder prepared by the present invention is coated on a glassy carbon rotating disc electrode to perform an OER catalytic performance test, or the OER catalytic performance test is performed after being treated by the following treatment methods:

Take out the lithium-deficient ternary cathode material composite membrane obtained in step 1, and wash it with distilled water and ethanol in order to remove impurities such as chloride ions remaining on the surface; then cut the composite membrane into an electrode sheet of a certain area, and the electrode The sheet is prepared as a sample to be tested for OER, and is directly clamped on the working electrode of an oxygen evolution reaction (OER) test instrument for OER catalytic performance testing. The problem of poor electrical conductivity of materials can be well solved by integrating catalytic materials and conductive substrates (such as carbon cloth).

The present invention first disassembles and sorts the waste ternary lithium-ion batteries, soaks the positive electrode sheet in an organic solvent and undergoes ultrasonic treatment to peel off the positive electrode material and the aluminum foil of the current collector, and regenerates the waste ternary positive electrode active material and binder The ternary cathode material composite film formed by mixing and coating on carbon fiber cloth or titanium mesh is used as the anode, the inert electrode is used as the cathode, and a certain concentration of supporting electrolyte solution is used as the electrolyte to construct an electrolytic cell. Driven by an external DC electric field, the lithium ions embedded in the layered nickel-cobalt-manganese ternary electrode material layer are extracted and dissolved in the aqueous solution to realize the nickel-cobalt-manganese composite ternary material LiNi _x Co _y Mn _z O ₂ (x+y+ z=1) In-situ conversion to prepare delithiated Li _1-δ Ni _x Co _{y Mnz} O ₂ (δ≤1). Based on the good electrocatalytic properties of nickel-cobalt-manganese composite metal oxides, the nickel-cobalt-manganese layered composite metal oxides obtained after delithiation were used as catalysts for oxygen evolution reaction (OER). At the same time, adding sodium phosphate or sodium carbonate as a precipitant to the delithiated solution can precipitate and recover lithium phosphate or lithium carbonate. Lithium carbonate is a commonly used recovery form of lithium element, and lithium phosphate can be used as an electrode material for re-synthesis of lithium iron phosphate important raw materials.

Description of drawings

Fig. 1 is a comparison chart of X-ray diffraction (XRD) test of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM111) waste ternary cathode material before and after delithiation treatment in Example 1 of the present invention.

Fig. 2 is a scanning electron microscope (SEM) comparison diagram of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM111) waste ternary cathode material before and after delithiation treatment in Example 1 of the present invention. a is before delithiation, b is after delithiation.

Fig. 3 is a comparison chart of catalytic performance of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM111) spent ternary cathode material before and after delithiation treatment in Example 1 of the present invention in oxygen evolution reaction (OER).

Fig. 4 is a comparison chart of X-ray diffraction (XRD) test of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523) waste ternary cathode material before and after delithiation treatment in Example 2 of the present invention.

5 is a scanning electron microscope (SEM) comparison diagram of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523) waste ternary cathode material before and after delithiation treatment in Example 2 of the present invention. a is before delithiation, b is after delithiation.

Fig. 6 is a comparison chart of catalytic performance of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523) spent ternary cathode material before and after delithiation treatment in Example 2 of the present invention in oxygen evolution reaction (OER).

Detailed ways

Example 1: Comprehensive recovery of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM111) type waste ternary materials

Use N-methylpyrrolidone solvent to soak and dissolve the binder (PVDF) therein to peel off the electrode material and the aluminum foil of the current collector, and obtain the positive electrode active material and the binder polyvinylidene fluoride PVDF and the conductive agent acetylene black after peeling according to 8: 1:1 ratio mixed into a slurry and coated on carbon fiber cloth, placed in a vacuum oven to dry for 10 hours to form a composite film as the anode, blank carbon cloth as the cathode, and a sodium chloride solution with a concentration of 0.8mol/L as the electrolysis solution to build an electrolytic cell. The applied electric field voltage was 2V and maintained for 6h. The delithiated electrolyte was tested by inductively coupled plasma spectrometer (ICP-MS) to obtain the lithium ion concentration in the electrolyte, and the calculated delithiation rate reached 97.6%, as shown in Table 1.

The composite film coated with the lithium-deficient NCM111 ternary positive electrode material obtained above was removed, and washed several times with distilled water and ethanol solution to remove impurities such as chloride ions remaining on the surface. The composite film was characterized by X-ray diffraction (XRD), and compared with the XRD of the NCM111 active material that was not delithiated and recovered. The results are shown in Figure 1. The comparison of morphology before and after delithiation and recovery is shown in Figure 2 by scanning electron microscope (SEM) test. It can be seen that after delithiation driven by electric field, the composition and morphology of the sample changed greatly. The composite film is reasonably cut into 1cm×1cm electrode sheet, and the electrode sheet is prepared as a sample to be tested for OER test, which is directly sandwiched on the working electrode for the catalyst performance test of oxygen evolution reaction (OER), and the performance before and after delithiation recovery As shown in Figure 3, the NCM111 ternary cathode material recovered after delithiation has an overpotential of 246mV at 10mA/cm ² , showing excellent performance.

Example 2: Comprehensive recovery of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523) waste ternary materials

Use N-methylpyrrolidone solvent to soak and dissolve the binder (PVDF) therein to peel off the electrode material and the aluminum foil of the current collector, and obtain the positive electrode active material and the binder polyvinylidene fluoride PVDF and the conductive agent acetylene black after peeling according to 8: 1:1 ratio mixed into a slurry and coated on carbon fiber cloth, placed in a vacuum oven to dry for 10 hours to form a composite film as the anode, blank carbon cloth as the cathode, and a sodium chloride solution with a concentration of 0.8mol/L as the electrolysis solution to build an electrolytic cell. The applied electric field voltage was 2V and maintained for 6h. The delithiated electrolyte was tested by inductively coupled plasma spectrometer (ICP-MS) to obtain the concentration of lithium ions in the electrolyte, and the calculated delithiation rate reached 96.5%, as shown in Table 1.

The composite film coated with the lithium-deficient NCM523 ternary positive electrode material obtained above was removed, and washed several times with distilled water and ethanol solution to remove impurities such as chloride ions remaining on the surface. The composite film was characterized by X-ray diffraction (XRD), and compared with the XRD of the NCM111 active material that was not delithiated and recovered. The results are shown in Figure 4. A large change; the scanning electron microscope (SEM) test shows the morphology comparison before and after delithiation and recovery as shown in Figure 5. It can be seen that after delithiation driven by electric field, the composition and morphology of the sample changed greatly. The composite film is reasonably cut into 1cm×1cm electrode sheet, and the electrode sheet is prepared as a sample for OER test, which is directly sandwiched on the working electrode for the catalytic performance test of oxygen evolution reaction (OER). For example, as shown in Figure 6, the NCM523 ternary cathode material recovered after delithiation has an overpotential of 179mV at 10mA/cm ² , showing excellent performance.

Table 1 is an inductively coupled plasma spectrometer (ICP-MS) test result table of the electrolyte solution after delithiation in Example 1 and Example 2.

Table 1

electrode material Electric field voltage/V Active substance mass/g Lithium ion concentration in electrolyte after delithiation (mg/L) Delithiation rate/% NCM111 2.0 0.1071 37.37 97.6 NCM523 2.0 0.1226 42.34 96.5

Claims (8)

1. A method for comprehensive recycling and reuse of waste ternary electrode materials, characterized in that: Utilizing the structural characteristics of layered ternary electrode materials, lithium ions are selectively extracted from the ternary positive electrode active material under the drive of an external electric field, and the precipitant is used to precipitate and recover; in addition, the lithium-deficient ternary positive electrode material is used as A catalyst for the oxygen evolution reaction is used. 2. The method according to claim 1, characterized in that comprising the steps of: Step 1: Use N-methylpyrrolidone solvent to soak and dissolve the binder in the waste ternary electrode material, peel off the electrode material and the aluminum foil of the current collector, and mix and coat the waste ternary positive electrode active material obtained after stripping with the binder Cover it on a conductive substrate, and obtain a ternary cathode material composite film after vacuum drying; use the obtained ternary cathode material composite film as an anode, use an inert electrode as a cathode, and use a supporting electrolyte solution as an electrolyte to construct an electrolytic cell, and apply an electric field to drive desorption Lithium, using the structural characteristics of layered ternary electrode materials, selectively extracts lithium ions from the ternary positive electrode active material into the electrolyte; Step 2: Take out the lithium-deficient ternary cathode material composite film obtained in step 1, and wash it with distilled water and ethanol in order to remove impurities such as chloride ions remaining on the surface; then place the composite film in NMP to dissolve and remove the sticky material. As a binder, the lithium-deficient ternary positive electrode material is removed from carbon fiber cloth or titanium mesh, centrifuged, washed and dried to obtain lithium-deficient nickel-cobalt-manganese composite metal oxide powder; the resulting lithium-deficient nickel-cobalt-manganese composite metal Oxide powder can be directly used as a catalyst for oxygen evolution reaction; Step 3: adding a precipitant to the electrolyte obtained in step 1 to precipitate lithium ions therein to obtain lithium carbonate or lithium phosphate; the obtained lithium carbonate or lithium phosphate is used as a lithium source to prepare lithium iron phosphate electrode materials, which can then be recycled and reused. The precipitation agent is selected from sodium bicarbonate, sodium carbonate or sodium phosphate and the like. 3. The method according to claim 2, characterized in that: The waste ternary positive electrode active material is LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.4 Co _0.2 Mn _0.4 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.7 Co _0.1 Mn _0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ or more. 4. The method according to claim 2, characterized in that: The inert electrode is one of non-metal electrodes such as graphite and carbon fiber cloth, or metal electrodes such as platinum electrodes and titanium mesh. 5. The method according to claim 2, characterized in that: The supporting electrolyte solution is one or more of metal ion compound solutions such as sodium chloride, potassium chloride and lithium chloride; the concentration range of the supporting electrolyte solution is 0.1-2mol/L. 6. The method according to claim 2, characterized in that: The conductive substrate is one of carbon fiber cloth, titanium mesh and graphite paper. 7. The method of claim 2, characterized in that: In the delithiation process driven by an external electric field, the temperature range of the electrolyte is 0-90° C., and the pH range is 1-12. 8. The method of claim 2, wherein: During the delithiation process driven by an external electric field, the potential of the external electric field is 0.5-5V and maintained for 1-20h.