Method for preparing catalyst from waste lithium ion battery conductive agent and application thereof

Abstract

The application relates to the field of green energy storage and energy conversion, in particular to a method for preparing a catalyst from a recycled conductive agent of a waste lithium ion battery and application. The preparation method comprises treating a recycled conductive agent of a waste lithium nickel cobalt manganese oxide (NCM) positive electrode by low-pressure nitrogen-containing cold plasma to prepare a (Ni, Co, Mn) and N atom co-doped conductive carbon black catalyst, and the catalyst has ORR / OER performance and is used for green energy storage and energy conversion of fuel cells, metal air batteries, water electrolysis and super (pseudo) capacitors. The N atom and transition metal (Ni, Co, Mn) co-doped conductive carbon black has excellent ORR / OER dual-function catalytic activity and other advantages.

Description

Technical Field

[0001] This application relates to the field of green energy storage and energy conversion, and more specifically, it relates to a method for preparing catalysts by recycling conductive agents from waste lithium-ion batteries and their application. Background Technology

[0002] Based on a lifespan of 5-8 years for lithium-ion batteries (LIBs), the first wave of retired power batteries is imminent. Currently, LIB recycling methods mainly include pyrometallurgy, hydrometallurgy, and biometallurgy, among which hydrometallurgy offers the widest variety of recyclable materials and the highest recovery rate. For example, ternary nickel-cobalt-manganese (NCM) lithium battery cathode materials can be recovered by acid leaching, yielding Li, Co, Ni, and Mn, with the leaching residue primarily consisting of conductive agents.

[0003] The conductive agents in LIBs differ from ordinary carbon black, requiring high oil absorption value and low metal impurity content, making them a high-value auxiliary material. Ordinary carbon black typically has an oil absorption value of 180 mLg. -1 Conductive carbon black (SuperP, Ketjen black) can reach at least 250 mLg. -1 Furthermore, their branched structure increases the number of conductive contact points. Novel conductive agents such as carbon nanotubes and graphene contact the cathode material via line-to-point and surface-to-point methods, which are superior to the point-to-point contact of conductive carbon black. Therefore, they have lower impedance and require less addition, but are more expensive. To reduce costs, novel composite conductive pastes combining conductive carbon black with carbon nanotubes or graphene have recently been developed and will gradually be applied to LIB manufacturing.

[0004] After multiple charge-discharge cycles of liquid intracellular blocks (LIBs), the recovered conductive agents often contain varying degrees of metallic impurities, making them difficult to reuse in LIB manufacturing. Therefore, conductive agents are currently often treated as solid waste or plastic fillers and have not yet been reused for high-value purposes. However, with the rapid increase in the scale of decommissioned LIBs and the use of new conductive agents, the recyclable value of conductive agents will continue to grow. Summary of the Invention

[0005] This disclosure provides a method and application for preparing catalysts by recycling conductive agents from waste lithium-ion batteries, achieving co-doping of conductive carbon black with N atoms and transition metals (Ni, Co, Mn), thus giving it advantages such as excellent ORR / OER bifunctional catalytic activity.

[0006] In a first aspect, this disclosure provides a method for preparing a catalyst by recycling conductive agents from waste lithium-ion batteries. The preparation method includes treating the conductive agent of a waste lithium-ion battery nickel-cobalt-manganese (NCM) cathode with low-pressure nitrogen-containing cold plasma to obtain carbon black co-doped with N atoms and transition metals on carbon materials. The carbon black is used as an ORR / OER bifunctional catalyst for green energy storage and energy conversion in fuel cells, metal-air batteries, water electrolysis, and supercapacitors (pseudocapacitors).

[0007] Conductive carbon materials possess large specific surface areas, high electronic conductivity, and multi-layered porous structures. Active sites can be formed through heteroatoms (such as N, P, S, and B) doping and topological defects. Nitrogen species in doped carbon materials include graphitic nitrogen, pyridine nitrogen, pyrrole nitrogen, and pyridine nitrides. Dai Liming et al. reported that vertically aligned nitrogen-doped carbon nanotubes exhibit better electrocatalytic activity, long-term operational stability, and tolerance than Pt. Utilizing the lone pair electrons of the doped nitrogen atoms, transition metals (such as Ni, Co, Mn, and Fe) can be further introduced to form metal-nitrogen-carbon (MNC) coordination structures, which can further enhance electrocatalytic performance.

[0008] Cold plasma treatment methods are characterized by fast processing speed and environmental friendliness, and are easy to implement in industrial applications.

[0009] Preferably, the carbon material is one of activated carbon, amorphous carbon black, bio-derived carbon, carbon nanotubes, graphene, and carbon aerogel, and the nitrogen species in the doped carbon material are mainly one of graphitic nitrogen, pyridine nitrogen, pyrrole nitrogen, and pyridine nitride.

[0010] Preferably, the preparation method includes the following steps:

[0011] S1: Dismantling and pretreatment of waste lithium-ion batteries, grinding to obtain NCM powder;

[0012] S2: Leaching of lithium nickel cobalt manganese oxide (NCM) cathode material, followed by filtration to obtain filtrate and filter residue;

[0013] S3: Cold plasma treatment of filter residue. The filter residue powder is placed in a special sealed container, and after evacuation, pure N2 is introduced. Then, the vacuum is continued to 50-150 Pa. The sample in the vacuum container is subjected to low-pressure nitrogen-containing cold plasma bombardment treatment for different durations using a Tesla coil to obtain ORR / OER bifunctional catalysts with different doping levels.

[0014] Preferably, the preparation step of S1 includes:

[0015] After the waste ternary lithium battery is fully discharged, it is manually disassembled to obtain the cathode material. Then, the cathode powder is heated in a muffle furnace at 200-600℃ to remove the organic binder contained in the cathode material, and then ground to obtain NCM powder.

[0016] Preferably, the preparation step of S2 includes:

[0017] Place 2-3g of NCM powder into a three-necked flask for acid leaching. Add 100-150mL of 0.50mol / L H2SO4 solution at a fixed NCM powder to H2SO4 solution ratio (solid-liquid ratio) of 5-60g / L. -1H2SO4 was added, followed by 2-4 mL of 30 vol% H2O2. The water bath temperature was 50-90℃, and the mixture was stirred continuously at 300-500 rpm for 1-1.5 h. After acid leaching, the mixture was filtered to separate the filtrate from the filter residue. The obtained filtrate can be further purified to recover valuable metals such as Li, Ni, Co, and Mn. The obtained filter residue was heated in an oven at 30-80℃ for 8-10 h to dry the surface filtrate. After cooling, it was ground into a fine powder for later use.

[0018] Preferably, the characterization analysis of the bifunctional catalyst includes the following steps:

[0019] The morphology of the unbombarded material was characterized by scanning electron microscopy (SEM), the composition and crystal structure of the sample were characterized by X-ray diffraction (XRD), the structure of the carbon material sample was characterized by Raman spectroscopy, and the surface chemical analysis of the sample was performed by X-ray electron spectroscopy (XPS). The catalytic activity of the sample was characterized by an electrochemical workstation, and the analytical methods included cyclic voltammetry (CV), linear sweep voltammetry (LSV), and rotating disk electrode analysis (RDE).

[0020] Secondly, this disclosure provides an application of a catalyst prepared from recycled conductive agents from spent lithium-ion batteries. The catalyst is used in flexible zinc-air batteries and aqueous zinc-air batteries, specifically including:

[0021] PBC, PBC-15, and PBC-30 catalysts were used as air cathodes, with zinc metal sheets as anodes, and a solution containing 6 mol / L... -1 A flexible solid electrolyte consisting of polyvinyl alcohol (PVA) in KOH solution is used to form a "sandwich" type zinc-air battery.

[0022] PBC, PBC-15, and PBC-30 catalysts were used as air cathodes, with zinc foil as the anode, and a 6 mol / L electrolyte was used. -1 KOH and 0.2 mol L -1 A mixed solution of Zn(Ac)2. The battery assembly starts from the negative electrode, and from left to right, the sequence is: negative electrode plate - zinc plate - electrolyte - positive electrode - positive electrode plate.

[0023] The catalyst preparation method is simple and low in cost; the catalyst has excellent ORR and OER catalytic activity and stability, and can be used for energy electrochemical storage and conversion.

[0024] Preferably, the catalyst is used in flexible zinc-air batteries and aqueous zinc-air batteries, and the specific preparation steps include:

[0025] Weigh 20 mg of PBC-305 and add 25-100 μL of 5% Nafion solution as a raw material. Then add 500-1500 μL of isopropanol and 500-1500 μL of deionized water. Sonicate for 30-60 min to obtain the cathode slurry. Use a pipette to evenly coat the prepared slurry onto 1.5 cm × 2 cm carbon cloth, with a loading of 0.2-0.6 mg / cm² on each piece of carbon cloth. -2 The mixture is then dried at 60-80℃ for 6-8 hours to obtain the air cathode of the flexible zinc-air battery.

[0026] Weigh 20 mg of PBC-305 and add 25-100 μL of 5% Nafion solution as a raw material. Then add 500-1500 μL of isopropanol and 500-1500 μL of deionized water. Sonicate for 30-60 minutes to obtain the cathode slurry. Use a pipette to evenly spread the prepared slurry onto 1.5 cm × 2 cm carbon paper, with a loading of 0.2-0.6 mg / cm² on each sheet. -2 The mixture is then dried at 60-80℃ for 6-8 hours to obtain the air cathode of the flexible zinc-air battery.

[0027] In summary, this application has the following beneficial effects:

[0028] 1. Due to the large specific surface area, high electronic conductivity, and multi-level porous structure of the conductive carbon material in this application, active sites can be formed through heteroatoms (such as N, P, S, B, etc.) doping and topological defects. The nitrogen species in the doped carbon material include graphitic nitrogen, pyridine nitrogen, pyrrole nitrogen, and pyridine nitride, etc. Dai Liming et al. reported that vertically arranged nitrogen-doped carbon nanotubes have better electrocatalytic activity, long-term operating stability and tolerance than Pt (Science, 2009, 323:760-764.). By utilizing the lone pair electrons of the doped nitrogen atoms, transition metals (such as Ni, Co, Mn, Fe, etc.) can be further introduced to form metal-nitrogen-carbon (MNC) coordination structure active sites, which can further enhance the electrocatalytic performance. The cold plasma treatment method has the characteristics of fast processing speed and environmental friendliness, and is easy to realize industrial application.

[0029] 2. The catalyst preparation method in this application is simple and low-cost. The preparation method can "turn waste into treasure" and realize high-value utilization. The conductive agent of the waste ternary lithium battery is separated by hydrometallurgical technology, and then treated with low-pressure nitrogen-containing cold plasma to achieve N atom and (Ni, Co, Mn) co-doped conductive carbon black, thus obtaining a catalyst with excellent ORR and OER performance.

[0030] 3. The catalyst of this application has excellent ORR and OER catalytic activity and stability, and can be used for energy electrochemical storage and conversion.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the scope of protection of this disclosure. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process for preparing the catalyst of the present invention;

[0033] Figure 2 This is the PBC diagram of the present invention;

[0034] Figure 3 This is a SEM image of the PBC-30 of the present invention;

[0035] Figure 4 Raman diagrams for PBC, PBC-15, and PBC-30 of this invention;

[0036] Figure 5 This is a heat treatment diagram of the cathode material of the present invention;

[0037] Figure 6 These are XRD diagrams of PBC, PBC-15, and PBC-30 of the present invention;

[0038] Figure 7 This is the full spectrum of the PBC-30XPS of the present invention;

[0039] Figure 8 This is the XPS narrow spectrum C-plot of the present invention;

[0040] Figure 9 This is a Ni diagram of the present invention;

[0041] Figure 10 This is the Co diagram of the present invention;

[0042] Figure 11 This is the Mn diagram of the present invention;

[0043] Figure 12 The CV test results of PBC, PBC-15, and PBC-30 of this invention in 0.1 MkOH are shown.

[0044] Figure 13 The ORR test result of PBC-30 of the present invention in 0.1 MkOH is shown in the figure.

[0045] Figure 14 This is the Koutecky-Levic fitting diagram of the present invention;

[0046] Figure 15 The ORR test results of PBC, PBC-15, and PBC-30 of this invention at 1600 rpm in 0.1 MkOH are shown. Figure 16 This is the Tafel fitting plot of the present invention;

[0047] Figure 17 OER test results of PBC, PBC-15, and PBC-30 of this invention in 0.1 MkOH;

[0048] Figure 18 For Tafel fitting plot;

[0049] Figure 19 The bifunctional electrocatalytic activity of PBC, PBC-15, and PBC-30 for ORR and OER in this invention;

[0050] Figure 20 A schematic diagram illustrating the assembly of a flexible zinc-air battery using the recycled conductive agent catalyst prepared according to this invention.

[0051] Figure 21 The open-circuit voltage of the PBC-30 of this invention applied to flexible zinc-air batteries;

[0052] Figure 22 The present invention relates to the application of PBC, PBC-15, and PBC-30 in flexible zinc-air batteries at a current density of 1 mA / cm². -2 Discharge specific capacity test results at that time;

[0053] Figure 23 The present invention provides PBC, PBC-15, and PBC-30 for application in flexible zinc-air batteries at a current density of 1 mA / cm². -2 Constant current charge-discharge cycle test results at that time;

[0054] Figure 24 The polarization and power density curves of PBC, PBC-15, and PBC-30 of this invention applied to flexible zinc-air batteries;

[0055] Figure 25 A schematic diagram illustrating the assembly of the recycled conductive agent catalyst prepared in this invention in an aqueous zinc-air battery;

[0056] Figure 26 The open-circuit voltage of the PBC-30 of this invention applied to aqueous zinc-air batteries;

[0057] Figure 27 The present invention relates to the application of PBC, PBC-15, and PBC-30 in aqueous zinc-air batteries at a current density of 5 mA / cm². -2 Constant current charge-discharge cycle test results at that time;

[0058] Figure 28 The results of discharge tests of the PBC, PBC-15, and PBC-30 of this invention applied to aqueous zinc-air batteries at different current densities are shown. Detailed Implementation

[0059] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0060] Example

[0061] Example 1

[0062] A method for preparing PBC-15 catalyst by recycling conductive agents from waste lithium-ion batteries includes the following steps:

[0063] (1) Leaching treatment of lithium nickel cobalt manganese oxide cathode material from waste lithium batteries

[0064] The cathode material from discarded lithium-ion batteries was disassembled and removed. First, the NCM cathode material was separated from the aluminum foil. Then, it was heat-treated in a muffle furnace at 400°C for 6 hours to remove the binder contained in the cathode material. The heat-treated cathode material was then ground to a 200-mesh fineness to obtain NCM powder.

[0065] 2.5 g of NCM powder was placed in a three-necked flask for acid leaching, and 125 mL of 0.50 mol / L solution was added according to a solid-liquid ratio of 20 g / L. - 1 In H2SO4, 3 mL of 30 vol% H2O2 was added, and the mixture was heated in a water bath at 75°C and stirred continuously at 450 rpm for 1 hour. After acid leaching, the mixture was filtered to separate the filtrate from the filter residue. The filtrate could be further purified to obtain valuable metals Li, Ni, Co, and Mn. The filter residue was dried and ground into a fine powder.

[0066] (2) Cold plasma treatment of filter residue

[0067] The filter residue powder was placed in a special sealed container, and after evacuation, pure N2 was introduced. The evacuation was then continued to 100 Pa, and the sample inside the vacuum container was bombarded with low-pressure nitrogen-containing cold plasma for 15 minutes using a Tesla coil (35 kW) to achieve co-doped conductive carbon black containing N atoms and transition metals (Ni, Co, Mn). Figure 1 ).

[0068] Compared with recycled conductive carbon black raw materials, Raman analysis ( Figure 4 The data shows that the disorder peak (D) and the graphite peak (G) are located at 1347 cm⁻¹. -1 and 1588cm -1 The ratio of the D peak to the G peak intensity (I) after cold plasma treatment. D / I G The impact is not significant. XRD analysis shows that ( Figure 5 , Figure 6The surface of the recovered conductive carbon black (PBC) contains a small amount of lithium nickel cobalt manganese oxide, the composition of which is similar to that of LiNi. 0.8 Co 0.1 Mn 0.1 The O2 (NCM811) concentration was consistent. After 15 min of cold plasma treatment, the peak value of the NCM compound decreased.

[0069] (3) Analysis of the electrochemical performance of the catalyst

[0070] Cyclic voltammetry (CV) and rotating disk electrode (RDE, LSV) analyses were performed using a CHI760 electrochemical workstation. A 0.1 MkOH solution was used as the electrolyte. Before testing, the KOH solution was allowed to stand for 30 minutes under oxygen-purified conditions to saturate the alkaline solution with O2. The working electrode was a catalyst-modified glassy carbon electrode, the counter electrode was a platinum wire, and the reference electrode was a Hg / HgO electrode. The working electrode was modified with a pre-prepared PBC-15 slurry. 4 mg of PBC-15 was weighed into a clean glass vial, and 800 μL of deionized water, 200 μL of ethanol, and 100 μL of 5% Nafion solution were added using a pipette. The vial was then sonicated in an ice-water bath for 30 minutes to prepare the working electrode modification slurry. 8 mL of the modified working electrode slurry was pipetted onto the glassy carbon electrode and allowed to air dry for later use. A similar process could be used to prepare the PBC working electrode modification slurry.

[0071] During cyclic voltammetry testing, the voltage window was set to -0.8 to 0.2 V, and the scan rate was 10 mV / s. -1 The CV curves compared the performance of two catalysts, PBC and PBC-15. Figure 12 Significant cathodic reduction peaks were observed near -0.18V (vs. Hg / HgO, the same below), with ORR current densities of 0.58 mA / cm². -2 0.42mAcm -2 .

[0072] Figure 15 The LSV curves of PBC and PBC-15 at 1600 rpm were compared. The results showed that the ORR onset potential of PBC-15 was -0.06V, and the half-wave potential (E) was... 1 / 2 The initial potential of PBCORR is -0.17V; the initial potential of E is -0.06V. 1 / 2 The value is -0.18V. At a test voltage of -0.8V, the ORR limiting current density of the PBC-15 is 4.8 mA / cm². -2 The limiting current density of the PBC is 3.6 mA / cm². -2 Tafel curve fitting was further performed on the two catalysts (…). Figure 16 The values ​​are 94.61 mVdec. -1and 81.92mVdec -1 The above results indicate that bombardment with cold plasma for 15 min improves the ORR catalytic activity for recovering the conductive agent and enhances the ORR process kinetics.

[0073] OER performance was also tested in a 0.1 MkOH solution saturated with N2. Figure 17 The test voltage range is 0.2V-1V, and the scan rate is 5mVs. -1 PBC and PBC-15 at 10 mAcm -2 The overpotentials at these times were 437mV and 427mV, respectively. At a voltage of 1.0V, the current densities of PBC and PBC-15 reached 29.5 mA / cm², respectively. -2 33.5mAcm -2 Tafel slopes of PBC and PBC-15 ( Figure 18 The values ​​are 222.56 mVdec. -1 and 139.84mVdec -1 .

[0074] The OER current density is 10 mA / cm². -2 The potential difference ΔE between the potential corresponding to the peak value and the half-wave potential corresponding to the ORR peak was used to evaluate the overall ORR / OER activity of the sample. After analysis, it was found that ΔE = 0.97V and 0.95V for PBC and PBC-15, respectively. Figure 19 ).

[0075] Example 2

[0076] A method for preparing PBC-30 catalyst by recycling conductive agents from waste lithium-ion batteries includes the following steps:

[0077] (1) Leaching treatment of lithium nickel cobalt manganese oxide cathode material from waste lithium batteries

[0078] The cathode material from discarded lithium-ion batteries was disassembled and removed. First, the NCM cathode material was separated from the aluminum foil. Then, it was heat-treated in a muffle furnace at 400°C for 6 hours to remove the binder contained in the cathode material. The heat-treated cathode material was then ground to a 200-mesh fineness to obtain NCM powder.

[0079] 2.5 g of NCM powder was placed in a three-necked flask for acid leaching, and 125 mL of 0.50 mol / L solution was added according to a solid-liquid ratio of 20 g / L. - 1 In H2SO4, 3 mL of 30 vol% H2O2 was added, and the mixture was heated in a water bath at 75°C and stirred continuously at 450 rpm for 1 hour. After acid leaching, the mixture was filtered to separate the filtrate from the filter residue. The filtrate could be further purified to obtain valuable metals Li, Ni, Co, and Mn. The filter residue was dried and ground into a fine powder.

[0080] (2) Cold plasma treatment of filter residue

[0081] The filter residue powder was placed in a special sealed container, and after evacuation, pure N2 was introduced. The evacuation was then continued to 100 Pa, and the sample inside the vacuum container was bombarded with low-pressure nitrogen-containing cold plasma for 30 minutes using a Tesla coil (35 kW) to achieve co-doped conductive carbon black containing N atoms and transition metals (Ni, Co, Mn). Figure 1 ).

[0082] Compared with recycled conductive carbon black raw materials, SEM analysis showed that the carbon black discharged for 30 minutes exhibited a loose and porous structure. Figure 2 , Figure 3 Raman Figure 4 Analysis showed that the disorder peak (D) and the graphite peak (G) were located at 1347 cm⁻¹. -1 and 1588cm -1 The ratio of the D peak to the G peak intensity (I) after cold plasma treatment. D / I G The impact is not significant. XRD analysis shows that ( Figure 5 , Figure 6 The surface of the recovered conductive carbon black (PBC) contains a small amount of lithium nickel cobalt manganese oxide, the composition of which is similar to that of LiNi. 0.8 Co 0.1 Mn 0.1 The O2 (NCM811) peak value was consistent. After 30 min of cold plasma treatment, the peak value of the NCM compound decreased. X-ray electron spectroscopy (XPS) analysis of the sample (PBC-30) treated with cold plasma for 30 min further showed that C, Ni, Co, Mn, and O elemental signals were present in the full spectrum. C1s peak fitting ( Figure 8 The data shows the presence of C-C bonds, CO bonds, CN bonds, and C=O bonds; Ni 2p Peak fitting ( Figure 9 The data shows the presence of Ni–O bonds and corresponding satellite peaks; Co 2p Peak fitting ( Figure 10 The results show the presence of Co-O and Co-Co bonds, along with accompanying peaks; while Mn... 2p The fit only shows one Mn-O bond ( Figure 11 The cold plasma treatment indicates that the recovered carbon black underwent a chemical change in the residual NCM compounds.

[0083] (3) Analysis of the electrochemical performance of the catalyst

[0084] Cyclic voltammetry (CV) and rotating disk electrode (RDE, LSV) analyses were performed using a CHI760 electrochemical workstation. A 0.1 MkOH solution was used as the electrolyte. Before testing, the KOH solution was allowed to stand for 30 minutes under oxygen-purified conditions to saturate the alkaline solution with O2. The working electrode was a catalyst-modified glassy carbon electrode, the counter electrode was a platinum wire, and the reference electrode was a Hg / HgO electrode. The working electrode was modified with a pre-prepared PBC-30 slurry. 4 mg of PBC-30 was weighed into a clean glass vial, and 800 μL of deionized water, 200 μL of ethanol, and 100 μL of 5% Nafion solution were added using a pipette. The vial was then sonicated in an ice-water bath for 30 minutes to prepare the working electrode modification slurry. 8 mL of the modified working electrode slurry was pipetted onto the glassy carbon electrode and allowed to air dry for later use. A similar modification slurry for the PBC working electrode could be prepared.

[0085] During cyclic voltammetry testing, the voltage window was set to -0.8 to 0.2 V, and the scan rate was 10 mV / s. -1 The CV curves compared the performance of two catalysts, PBC and PBC-30. Figure 12 Significant cathodic reduction peaks were observed near -0.18V (vs. Hg / HgO, the same below), with ORR current densities of 0.58 mA / cm². -2 0.32mAcm -2 The highest reduction current density was observed in the recovered conductive carbon black after 30 minutes of cold plasma treatment.

[0086] The LSV curves of the PBC-30 modified electrode were measured using a rotating disk electrode (RDE) at 400, 625, 900, 1225, and 1600 rpm, with a test voltage range of -0.8V to 0.2V and a scan rate of 5 mVs. -1 ( Figure 13 Furthermore, using KL curve fitting, the number of electrons transferred by the catalyst was found to be 4.07, or 4e. - ORR process of the path ( Figure 14 ).

[0087] Figure 15 The LSV curves of PBC and PBC-30 at 1600 rpm were compared. The results showed that the ORR onset potential of PBC-30 was -0.04V, and the half-wave potential (E) was... 1 / 2 The initial potential of PBCORR is -0.15V; the initial potential of E is -0.06V. 1 / 2 The value is -0.18V. At a test voltage of -0.8V, the ORR limiting current density of the PBC-30 is 5.7 mA / cm². -2 The limiting current density of the PBC is 3.6 mA / cm². -2Tafel curve fitting was further performed on the two catalysts (…). Figure 16 The values ​​are 94.61 mVdec. -1 and 75.29mVdec -1 The above results indicate that cold plasma bombardment for 30 min significantly improves the ORR catalytic activity for recovering the conductive agent and enhances the ORR process kinetics.

[0088] OER performance was also tested in a 0.1 MkOH solution saturated with N2. Figure 17 The test voltage range is 0.2-1V, and the scan rate is 5mVs. -1 PBC and PBC-30 at 10 mAcm -2 The overpotentials at these times were 437mV and 378mV, respectively. At a voltage of 1.0V, the current densities of PBC and PBC-30 reached 29.5 mA / cm², respectively. -2 43.4mAcm -2 Tafel slopes of PBC and PBC-30 ( Figure 18 The values ​​are 222.56 mVdec. -1 and 113.63mVdec -1 .

[0089] The OER current density is 10 mA / cm². -2 The potential difference ΔE between the potential corresponding to the peak value and the half-wave potential corresponding to the ORR peak was used to evaluate the overall ORR / OER activity of the sample. After analysis, it was found that ΔE for PBC and PBC-30 was 0.97V and 0.88V respectively. Figure 19 ).

[0090] Application examples

[0091] Application Example 1

[0092] A flexible zinc-air battery application using a catalyst prepared from recycled conductive agents from spent lithium-ion batteries, comprising the following specific steps:

[0093] Weigh 10 mg of PBC-30 and add 50 μL of 5% Nafion solution as a raw material. Then add 975 μL of isopropanol and 975 μL of deionized water, and sonicate for 30 min to obtain the cathode slurry. Use a pipette to evenly spread the prepared slurry onto a 1.5 cm × 2 cm carbon cloth, with a loading of 0.4 mg / cm² on each piece of carbon cloth. -2 The cathode was then dried at 60°C for 6 hours, thus obtaining the air cathode for a flexible zinc-air battery. Similarly, PBC and PBC-15 air cathodes can be prepared.

[0094] PBC, PBC-15, and PBC-30 catalysts were used as air cathodes, with zinc metal sheets as anodes, and a solution containing 6 mol / L... -1 A flexible solid electrolyte, polyvinyl alcohol (PVA) in KOH solution, forms a "sandwich" type zinc-air battery, the structure of which is as follows: Figure 20 As shown.

[0095] Test results show that the open-circuit voltage of the zinc-air battery using PBC-30 as the positive electrode is 1.32V; during full discharge, based on the mass of zinc sheet consumed, the specific capacities of PBC, PBC-15, and PBC-30 are 564 mAh g. 1 615mAhg 1 688mAhg 1 During constant current charge-discharge testing, the charge-discharge voltage difference was 0.88V, and the energy utilization efficiency was 53.4%. Figure 21 , 22 ,twenty three); Figure 24 The results show that the PBC-30 flexible zinc-air battery is less affected by the discharge current in terms of discharge voltage compared to batteries using PBC and PBC-15, and has a flatter polarization curve. Its energy density (17.38 mW / cm³) is also higher. -2 ), higher than using PBC (6.00mWcm) -2 ) and PBC-15 (11.75mWcm -2 A flexible zinc-air battery was constructed. It is evident that using PBC-30 as the cathode performs better than using PBC or PBC-15.

[0096] Application Example 2

[0097] An application of a catalyst prepared from recycled conductive agents from spent lithium-ion batteries in an aqueous zinc-air battery, comprising the following specific steps:

[0098] Weigh 10 mg of PBC-30 and add 50 μL of 5% Nafion solution as a raw material. Then add 975 μL of isopropanol and 975 μL of deionized water, and sonicate for 30 min to obtain the cathode slurry. Use a pipette to evenly spread the prepared slurry onto 1.5 cm × 2 cm carbon paper, with a loading of 0.4 mg / cm² on each sheet. -2 The cathode was then dried at 60°C for 6 hours, thus obtaining the air cathode for an aqueous zinc-air battery. Similarly, PBC and PBC-15 air cathodes can be prepared.

[0099] PBC, PBC-15, and PBC-30 catalysts were used as air cathodes, and polished zinc sheets were used as anodes. A 6 mol / L electrolyte was employed. -1KOH and 0.2 mol L -1 A mixed solution of Zn(Ac)₂. Battery assembly begins with the negative electrode, proceeding from left to right as follows: negative electrode plate - zinc plate - electrolyte - positive electrode - positive electrode plate. A schematic diagram of the structure is shown below. Figure 25 As shown.

[0100] Test results show that the open-circuit voltage of the zinc-air battery using PBC-30 as the air cathode is 1.45V; during constant current charge-discharge testing, the zinc-air battery using PBC-30 as the air cathode can stably charge and discharge for 110 hours, while the charge-discharge potential of zinc-air batteries using PBC and PBC-15 as the air cathodes decreases significantly after about 90 hours. Figure 26 , 27 ); Figure 28 The display shows that at 1C, 5C, 10C, 20C, 30C, and 5C (1C = 1mA / cm²), -2 At different discharge rates, the PBC-30-based battery exhibited a higher discharge voltage than the PBC-15 and PBC-based batteries, indicating that the PBC-30 has excellent rate performance.

[0101] The above description is merely an exemplary embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for preparing a catalyst by recycling conductive agents from waste lithium-ion batteries, characterized in that, The catalyst preparation method includes treating the conductive agent of the cathode of waste lithium-ion battery nickel cobalt manganese oxide with low-pressure nitrogen-containing cold plasma to obtain a catalyst with N atoms and Ni, Co, and Mn co-doped conductive carbon black. The catalyst is used as an ORR / OER bifunctional catalyst for green energy storage and energy conversion in fuel cells, metal-air batteries, water electrolysis and supercapacitors. The method for preparing the catalyst includes the following steps: S1: Dismantling and pretreatment of waste lithium-ion batteries, grinding to obtain NCM powder; S2: Leaching of lithium nickel cobalt manganese oxide cathode material, followed by filtration to obtain filtrate and filter residue; S3: Cold plasma treatment of filter residue. The filter residue powder is placed in a special sealed container, and pure N2 is introduced after vacuuming. Then, the vacuum is continued to 50-150 Pa. The sample in the sealed container is bombarded with low-pressure nitrogen-containing cold plasma for different durations under the condition of 35 kW power using a Tesla coil to obtain ORR / OER bifunctional catalysts with different doping levels.

2. The method for preparing a catalyst by recycling the conductive agent of waste lithium-ion batteries according to claim 1, characterized in that, The conductive carbon black is SuperP, and the nitrogen species in the conductive carbon black are mainly one of graphitic nitrogen, pyridine nitrogen, pyrrole nitrogen and pyridine nitrogen oxides.

3. The method for preparing a catalyst by recycling the conductive agent of waste lithium-ion batteries according to claim 1, characterized in that, The preparation steps of S1 include: After the waste ternary lithium battery is fully discharged, it is manually disassembled to obtain the cathode material. Then, the cathode powder is heated in a muffle furnace at 200-600℃ to remove the organic binder contained in the cathode material, and then ground to obtain NCM powder.

4. The method for preparing a catalyst by recycling the conductive agent of waste lithium-ion batteries according to claim 1, characterized in that, The preparation steps of S2 include: Place 2-3g of NCM powder into a three-necked flask for acid leaching. Add 100-150mL of 0.50mol / L H2SO4 solution at a solid-liquid ratio of 5-60g / L NCM powder to H2SO4 solution. -1 H2SO4 was added, followed by 2-4 mL of 30 vol% H2O2. The water bath temperature was 50-90℃, and the mixture was stirred continuously at 450-600 rpm for 1-1.5 h. After acid leaching, the mixture was filtered to separate the filtrate from the filter residue. The filtrate was then purified to recover valuable metals such as Li, Ni, Co, and Mn. The filter residue was heated in an oven at 30-80℃ for 8-10 h to dry the surface filtrate. After cooling, the residue was ground into a fine powder for later use.

5. The method for preparing a catalyst by recycling the conductive agent of waste lithium-ion batteries according to claim 1, characterized in that, The characterization analysis of the bifunctional catalyst includes the following steps: The morphology of the unbombarded material was characterized by scanning electron microscopy, the composition and crystal structure of the sample were characterized by X-ray diffraction, the structure of the carbon material sample was characterized by Raman spectroscopy, and the surface chemical analysis of the sample was performed by X-ray electron spectroscopy. The catalytic activity of the sample was characterized by an electrochemical workstation, and the analytical methods included cyclic voltammetry, linear sweep spectroscopy, and rotating disk electrode.

6. The application of a catalyst for preparing conductive agents from recycled waste lithium-ion batteries, obtained according to any one of claims 1-5, characterized in that, The catalyst is used in flexible zinc-air batteries or aqueous zinc-air batteries, specifically including: PBC, PBC-15, and PBC-30 catalysts were used as air cathodes, with zinc metal sheets as anodes, and a solution containing 6 mol / L... - 1 A flexible solid electrolyte of polyvinyl alcohol in KOH solution is used to form a "sandwich" type zinc-air battery; or PBC, PBC-15, and PBC-30 catalysts were used as air cathodes, with zinc foil as the anode, and a 6 mol / L electrolyte was used. - 1 KOH and 0.2 mol L -1 The Zn(Ac)2 mixed solution is used to assemble the battery, starting from the negative electrode. From left to right, the order is negative electrode plate - zinc sheet - electrolyte - positive electrode - positive electrode plate.

7. The application of the catalyst prepared from recycled waste lithium-ion battery conductive agent according to claim 6, characterized in that, The catalyst is used in flexible zinc-air batteries or aqueous zinc-air batteries, and the specific preparation steps include: Weigh 20 mg of PBC-305 and add 25-100 μL of 5% Nafion solution as a raw material. Then add 500-1500 μL of isopropanol and 500-1500 μL of deionized water, and sonicate for 30 min to obtain the cathode slurry. Use a pipette to evenly spread the prepared slurry onto a 1.5 cm × 2 cm carbon cloth, with a loading of 0.2-0.6 mg / cm² on each piece of carbon cloth. -2 Subsequently, it is dried at 30-80℃ for 6-8 hours to obtain the air cathode of the flexible zinc-air battery; or Weigh 20 mg of PBC-305 and add 25-100 μL of 5% Nafion solution as a raw material. Then add 500-1500 μL of isopropanol and 500-1500 μL of deionized water, and sonicate for 30 min to obtain the cathode slurry. Use a pipette to evenly spread the prepared slurry onto 1.5 cm × 2 cm carbon paper, with a loading of 0.2-0.6 mg / cm² on each sheet. -2 The cathode of the aqueous zinc-air battery is then dried at 30-80℃ for 6-8 hours to obtain the air cathode.

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