A mixed solvent and method for leaching metals in a lithium-ion battery positive electrode under ultraviolet radiation

Abstract

The present invention belongs to the field of recycling waste lithium-ion batteries, and provides a mixed solvent and method for leaching metals in the positive electrode of a lithium-ion battery under ultraviolet radiation. The mixed solvent includes 10 to 60 parts of acetonitrile by volume; 3 to 20 parts of hydrogen peroxide solution; and 3 to 20 parts of dichloromethane. The present invention uses ultraviolet light as an energy source to activate hydrogen peroxide and oxygen in the air to produce electrons and holes, thereby producing a series of highly active hydroxyl radicals and superoxide radicals, which further catalyze acetonitrile and dichloromethane to undergo oxidation-reduction reactions to produce methyl radicals, and these oxidizing radicals act together on the positive electrode material of the waste lithium-ion battery to leach and oxidize the low-valent metal ions therein. The interaction between the mixed solvent and the photochemical reaction can significantly shorten the time of the leaching reaction, can ensure the efficient leaching of metals in the waste positive electrode material, and has an ideal treatment effect on waste batteries.

Description

Technical Field

[0001] The invention belongs to the field of recycling waste lithium-ion batteries, and in particular relates to a mixed solvent and a method for leaching metals in a positive electrode of a lithium-ion battery under ultraviolet radiation. Background Art

[0002] As the demand for energy from rechargeable lithium-ion batteries continues to increase, the accelerated production of these devices will soon translate into a large amount of waste. Since the lifespan of lithium-ion batteries in small electronic products (such as mobile phones, power banks, etc.) is less than 3 years, and the lifespan of lithium-ion batteries in electric vehicles is only 5-10 years, these devices will generate a large amount of waste lithium-ion batteries over time. The large accumulation of waste batteries will affect health and the environment. Therefore, the development of recycling methods specific to lithium-ion batteries can minimize the impact of these waste batteries on human production and life, and can also ease the constraints on the supply chain of battery manufacturers.

[0003] Effectively recovering raw materials from waste batteries is economically and environmentally beneficial, but existing recycling technologies still face some practical problems. Most of the recoverable value of waste batteries is in the positive electrode, mainly extracting the transition metal elements contained in the active lithium oxide. Common methods are based on pyrometallurgy, hydrometallurgy, biometallurgy, mechanical methods or some combination of the four methods. But these methods usually involve high energy costs caused by extreme temperatures (up to 1400 degrees Celsius or higher), rampant harmful smoke emissions, and corrosive reagents such as hydrochloric acid, nitric acid and sulfuric acid, which can cause certain hazards to workers' health and the natural environment.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0005] The present invention is made to solve the above-mentioned problems, and aims to provide a mixed solvent and method for leaching metals in the positive electrode of a lithium ion battery under ultraviolet radiation. The mixed solvent can efficiently leach metals in the positive electrode of waste lithium ion batteries under ultraviolet light; the method can leach metal ions in the positive electrode material in a short time under normal temperature and pressure conditions without using high temperature and high pressure, strong acid and strong alkali, and only requires ultraviolet light, an oxidant and an organic solvent.

[0006] The invention provides a mixed solvent for leaching metals in a positive electrode of a lithium ion battery under ultraviolet radiation, which has the following characteristics: the mixed solvent comprises the following components by volume: 10 to 60 parts of acetonitrile; 3 to 20 parts of a hydrogen peroxide solution; and 3 to 20 parts of dichloromethane; wherein the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is ≥30%.

[0007] The present invention also provides a method for leaching metals in a positive electrode of a lithium ion battery under ultraviolet radiation, which has the following characteristics and comprises the following steps: step S1, disassembling a positive electrode sheet from a waste lithium ion battery and grinding the positive electrode sheet into a positive electrode powder; step S2, mixing the positive electrode powder and a mixed solvent together, and irradiating with ultraviolet light to start a leaching reaction; step S3, after the leaching reaction is completed, filtering and separating the residual solid and the leachate and collecting the leachate; wherein the mixed solvent comprises 10 to 60 parts by volume of acetonitrile, 3 to 20 parts by volume of a hydrogen peroxide solution, and 3 to 20 parts by volume of dichloromethane; the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is ≥30%; in step 2, 20 to 100 parts by weight of the positive electrode powder, 10 to 60 parts by volume of acetonitrile, 3 to 20 parts by volume of a hydrogen peroxide solution, and 3 to 20 parts by volume of dichloromethane are mixed together.

[0008] In the method for leaching metals in the positive electrode of a lithium ion battery under ultraviolet radiation provided by the present invention, it can also have the following characteristics: wherein, in step 2, 10 mg of positive electrode powder is placed in a test tube, and then a mixed solvent consisting of 10 ml of H2O2, 10 ml of dichloromethane and 30 ml of acetonitrile is added, and the test tube is placed in a photochemical reactor, the light source of the photochemical reactor is a 15WUVC lamp, and the leaching reaction is carried out under ultraviolet light for 4 to 24 hours.

[0009] The method for leaching metals from a positive electrode of a lithium-ion battery under ultraviolet radiation provided by the present invention may also have the following characteristics: wherein the main component of the positive electrode sheet is NCM523 or LCO.

[0010] In the method for leaching metals in the positive electrode of a lithium ion battery under ultraviolet radiation provided by the present invention, it can also have the following characteristics: wherein, the specific operation of step S1 is: immersing the waste lithium ion battery in a 5% by mass NaCl solution for 12 hours to consume the remaining power, and then drying it in an oven at 60°C for 12 hours. After drying, disassembling and collecting the positive electrode sheet, rinsing the positive electrode sheet with double distilled water, and then soaking it in a 5% by mass NaOH solution in a fume hood for 1 hour to dissolve the aluminum foil, and then rinsing the positive electrode sheet with double distilled water again and drying it in a vacuum drying oven at 60°C for 12 hours. The dried positive electrode sheet is ground in a crusher and passed through a 100-mesh sieve to obtain positive electrode powder for standby use.

[0011] Functions and Effects of the Invention

[0012] The mixed solvent provided by the present invention contains acetonitrile, hydrogen peroxide solution and dichloromethane, uses ultraviolet light as energy, activates hydrogen peroxide and oxygen in the air to generate electrons and holes, and then generates a series of highly active hydroxyl radicals and superoxide radicals, these active radicals further catalyze acetonitrile and dichloromethane to undergo oxidation-reduction reaction to generate methyl radicals, these oxidative free radicals act together on the positive electrode material of waste lithium ion batteries to leach and oxidize the low-valent metal ions therein. The interaction between the mixed solvent and the photochemical reaction can significantly shorten the leaching reaction time, can ensure the efficient leaching of metals in the waste positive electrode material, and has an ideal treatment effect on waste batteries.

[0013] The method for leaching metals in the positive electrode of a lithium-ion battery under ultraviolet radiation provided by the present invention can leach metal ions in the positive electrode material in a short time under normal temperature and pressure conditions without using high temperature and high pressure, strong acid or strong alkali, and only requires ultraviolet light, an oxidant and an organic solvent. The method has the characteristics of mild reaction conditions, low energy consumption, simple operation, high efficiency and no harmful emissions. DETAILED DESCRIPTION

[0014] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following is a detailed description of the mixed solvent and method for leaching metals in the positive electrode of a lithium-ion battery under ultraviolet radiation in combination with an embodiment of the present invention.

[0015] Unless otherwise specified, the raw materials and reagents used in the present invention are all from common commercial products. The waste lithium-ion battery packs are from Shanghai SEG Electronics Market, and the main components of the positive electrode are LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523) or LCO.

[0016] The mixed solvent provided by the present invention for leaching metals in the positive electrode of a lithium ion battery under ultraviolet radiation comprises the following components by volume:

[0017] 10-60 parts of acetonitrile;

[0018] 3-20 parts of hydrogen peroxide solution;

[0019] 3 to 20 parts of dichloromethane.

[0020] The mass fraction of hydrogen peroxide is ≥30%, the purity of dichloromethane used is ≥99.5% (AR), and the purity of acetonitrile is ≥99.9% (AR).

[0021] The above-mentioned mixed solvent is used to leach the metal in the positive electrode of the lithium-ion battery under ultraviolet radiation, and the specific method is as follows:

[0022] Step S1, dismantle the positive electrode sheet from the waste lithium-ion battery and grind the positive electrode sheet into positive electrode powder. The specific operation is as follows:

[0023] The used battery pack was immersed in a 5% NaCl solution for 12 hours to consume the remaining power to prevent short circuit and fire, and then dried in an oven at 60°C for 12 hours. After drying, a small hole was cut at the edge of the battery pack with scissors, and the battery pack was manually disassembled to collect the positive electrode, negative electrode, diaphragm and other components. Among them, the positive electrode was rinsed with double distilled water, and then soaked in a 5% NaOH solution in a fume hood for 1 hour to dissolve the aluminum foil. The positive electrode was then rinsed with double distilled water again and dried in a vacuum drying oven at 60°C for 12 hours. The dried positive electrode was ground in a crusher and passed through a 100-mesh sieve, and the powder (positive electrode powder) was collected for later use.

[0024] Step S2, the positive electrode powder and the mixed solvent are mixed together, and irradiated with ultraviolet light to start the leaching reaction. The specific operation is as follows:

[0025] The positive electrode powder is placed in a test tube and added to a mixed solvent consisting of H2O2, dichloromethane (DCM) and acetonitrile (MeCN). The test tube is placed in a photochemical reactor, which includes a reaction dark box, a light controller, a light source and a magnetic stirrer. The light source selected in the present invention is 15W (≥20μW / cm 2 ) UVC lamp provides 254nm ultraviolet radiation. The leaching experiment was carried out in a reaction dark box, under ultraviolet light irradiation, at a stirring speed of 300 rpm for 4 hours. Samples were taken every 30 minutes to 60 minutes during the leaching process.

[0026] Step S3, after the leaching reaction is completed, the residual solid and the leachate are separated by filtration and the leachate is collected. The concentration of metal ions in the liquid during the leaching process is determined by atomic absorption spectrophotometry (AAS).

[0027] The calculation process of leaching efficiency is as follows:

[0028] A portion of the positive electrode powder obtained in step S1 is taken out for digestion to confirm the content of all metal elements therein. The ratio of the metal ion concentration after digestion to the ion concentration of the leached ion is converted into the leaching efficiency calculation formula:

[0029] Where E1 (%) is the leaching efficiency of the target metal; c1 (μg / mL) is the metal concentration measured in the leaching solution; v1 (ml) is the volume of the leaching solution after constant volume (fixed volume); c2 (μg / ml) is the metal concentration in the solution after complete digestion with nitric acid; v2 (ml) is the volume of the digestion solution after constant volume.

[0030] The digestion process is as follows: 7 ml of concentrated nitric acid (65% to 68% HNO3) and 5 mg of positive electrode powder are placed in a 10 ml digestion tube, and decomposed in a fully automatic microwave digestion instrument set at a temperature of 110°C for 24 hours to prepare three sets of parallel digestion experiments. After the digestion is completed, the volume is fixed in a 100 ml volumetric flask. After the volume is fixed, 3 ml of each set of parallel samples is taken with a rubber-tipped pipette and filtered through a 0.22 μm membrane. The concentrations of metal ions of lithium, nickel, cobalt and manganese after digestion are measured by atomic absorption spectrophotometry (AAS) and the average is taken. The total amount of metal ions in the positive electrode material per unit mass is obtained by proportional calculation.

[0031] <Example 1>

[0032] This example uses the above-mentioned mixed solvent and method to leach metal ions from waste lithium-ion batteries (the main component of the positive electrode sheet is NCM523). The addition ratio of positive electrode powder and mixed solvent is: one part of positive electrode powder (part by mass), one part of H2O2 (part by volume), three parts of CH3CN (parts by volume), and one part of CH2Cl2 (part by volume).

[0033] The leaching process specifically includes the following steps:

[0034] Step S1, discharging, disassembling, peeling and grinding the waste battery pack to obtain positive electrode powder for standby use.

[0035] Step S2, hydrogen peroxide, acetonitrile and dichloromethane solution are mixed in a volume ratio of 1:3:1; then the mixed solvent is added to a test tube and placed in a photoreactor, the battery positive electrode powder is added, and the ultraviolet lamp and the stirrer are turned on and the timing is started. Samples are taken every 30 minutes, and the metal ion concentration is measured using AAS.

[0036] Step S3, the reaction is completed in about 4 hours, and the leaching rates of Ni and Co reach the highest, namely 99% and 97% respectively. The leaching rate of manganese ions is 22.54%. After the leaching reaction is completed, the residue solid and the leachate are separated by filtration and the leachate is collected.

[0037] <Example 2>

[0038] This embodiment uses the above-mentioned mixed solvent and method to leach metal ions from waste lithium-ion batteries (the main component of the positive electrode is LCO). The addition ratio of positive electrode powder and mixed solvent is: two parts (mass parts) of positive electrode powder, one part (volume parts) of H2O2, three parts (volume parts) of CH3CN, and one part (volume parts) of CH2Cl2.

[0039] The leaching process specifically includes the following steps:

[0040] Step S1, discharging, disassembling, peeling and grinding the waste battery pack to obtain positive electrode powder for standby use.

[0041] Step S2, hydrogen peroxide, acetonitrile and dichloromethane solution are mixed in a volume ratio of 1:3:1; then the mixed solvent is added to a test tube and placed in a photoreactor, the battery positive electrode powder is added, and the ultraviolet lamp and the stirrer are turned on and the timing is started. Samples are taken every 60 minutes, and the metal ion concentration is measured using AAS.

[0042] Step S3, the reaction is completed in about 24 hours, and the leaching rate of Co can reach 95%. After the leaching reaction is completed, the residual solid and the leachate are separated by filtration and the leachate is collected.

[0043] In this embodiment, after the pretreatment, the positive electrode material has no other metal ions except Co.

[0044] <Example 3>

[0045] This example uses the above-mentioned mixed solvent and method to leach metal ions from waste lithium-ion batteries (the main component of the positive electrode sheet is NCM523). The addition ratio of positive electrode powder and mixed solvent is: two parts (mass parts) of positive electrode powder, one part (volume parts) of H2O2, two parts (volume parts) of CH3CN, and two parts (volume parts) of CH2Cl2.

[0046] The leaching process specifically includes the following steps:

[0047] Step S1, discharging, disassembling, peeling and grinding the waste battery pack to obtain positive electrode powder for standby use.

[0048] Step S2, hydrogen peroxide, acetonitrile and dichloromethane solution are mixed in a volume ratio of 1:2:2; then the mixed solvent is added to a test tube and placed in a photoreactor, the battery positive electrode powder is added, and the ultraviolet lamp and the stirrer are turned on and the timing is started. Samples are taken every 30 minutes, and the metal ion concentration is measured using AAS.

[0049] Step S3, the reaction is completed in about 4 hours, and the Ni and Co are 53.9% and 51.2% respectively. The manganese ion leaching rate is 18.5%. After the leaching reaction is completed, the residual solid and the leachate are separated by filtration and the leachate is collected.

[0050] Functions and Effects of the Embodiments

[0051] The mixed solvent provided in the above embodiment contains acetonitrile, hydrogen peroxide solution and dichloromethane, and ultraviolet light is used as energy to activate hydrogen peroxide and oxygen in the air to produce electrons and holes, thereby generating a series of highly active hydroxyl radicals and superoxide radicals, which further catalyze acetonitrile and dichloromethane to undergo oxidation-reduction reactions to produce methyl radicals, and these oxidizing radicals act together on the cathode material of waste lithium-ion batteries to leach and oxidize the low-valent metal ions therein. The interaction between the mixed solvent and the photochemical reaction can significantly shorten the leaching reaction time, ensure the efficient leaching of metals in the waste cathode material, and have an ideal treatment effect on waste batteries.

[0052] The method for leaching metals in the positive electrode of a lithium-ion battery under ultraviolet radiation provided in the above embodiment can leach metals in the positive electrode material in a short time under normal temperature and pressure conditions without using high temperature and high pressure, strong acid and strong alkali, and only requires ultraviolet light, an oxidant and an organic solvent. It has the characteristics of mild reaction conditions, low energy consumption, simple operation, high efficiency and no harmful emissions.

[0053] It can be seen from the above Examples 1-3 that the volume ratio of hydrogen peroxide, acetonitrile and dichloromethane of 1:3:1 is the optimal leaching ratio.

[0054] The above embodiments are preferred cases of the present invention and are not intended to limit the scope of protection of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention; at the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A mixed solvent for leaching metals in a lithium-ion battery cathode under ultraviolet radiation, characterized in that: The following components are included by volume: 10-60 parts of acetonitrile; 3-20 parts of hydrogen peroxide solution; 3-20 parts of dichloromethane; Wherein, the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is ≥30%.

2. The mixed solvent for leaching metals in the positive electrode of a lithium-ion battery under ultraviolet radiation according to claim 1, characterized in that: in, The following components are included by volume: 3 parts of acetonitrile; 1 part hydrogen peroxide solution; 1 part of dichloromethane.

3. A method for leaching metals from a lithium-ion battery cathode under ultraviolet radiation, characterized in that: The following steps are involved: Step S1, disassembling a positive electrode sheet from a waste lithium-ion battery and grinding the positive electrode sheet into a positive electrode powder; Step S2, mixing the positive electrode powder and the mixed solvent together, and irradiating with ultraviolet light to start a leaching reaction; Step S3, after the leaching reaction is completed, filtering and separating the residual solid and the leachate and collecting the leachate; Wherein, the mixed solvent comprises 10 to 60 parts of acetonitrile, 3 to 20 parts of hydrogen peroxide solution, and 3 to 20 parts of dichloromethane by volume; the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is ≥30%; In step 2, 20 to 100 parts by weight of the positive electrode powder, 10 to 60 parts by volume of the acetonitrile, 3 to 20 parts by volume of the hydrogen peroxide solution, and 3 to 20 parts by volume of the dichloromethane are mixed together.

4. The method for leaching metal from a positive electrode of a lithium-ion battery under ultraviolet radiation according to claim 3, characterized in that: in, In step 2, 10 mg of the positive electrode powder is placed in a test tube, and then the mixed solvent consisting of 10 ml H2O2, 10 ml dichloromethane and 30 ml acetonitrile is added, and the test tube is placed in a photochemical reactor, the light source of the photochemical reactor is a 15WUVC lamp, and the leaching reaction is carried out under ultraviolet light for 4 to 24 hours.

5. The method for leaching metal from a positive electrode of a lithium-ion battery under ultraviolet radiation according to claim 3, characterized in that: in, The main component of the positive electrode sheet is NCM523 or LCO.

6. The method for leaching metal from a positive electrode of a lithium-ion battery under ultraviolet radiation according to claim 3, characterized in that: in, The specific operation of step S1 is: immersing the waste lithium-ion battery in a 5% by mass NaCl solution for 12 hours to consume the remaining power, and then drying it in an oven at 60°C for 12 hours. After drying, disassembling and collecting the positive electrode sheet, rinsing the positive electrode sheet with double distilled water, and then soaking it in a 5% by mass NaOH solution in a fume hood for 1 hour to dissolve the aluminum foil, and then rinsing the positive electrode sheet with double distilled water again and drying it in a vacuum drying oven at 60°C for 12 hours. The dried positive electrode sheet is ground in a crusher and passed through a 100-mesh sieve to obtain the positive electrode powder for standby use.

Images