Electrochemical desalination method using retired lithium ion battery cathode and application thereof

Abstract

The application discloses an electrochemical desalination method for retired lithium ion batteries, and relates to the technical field of resources and environment.The electrochemical desalination method comprises the following steps: mixing positive electrode powder of the retired lithium ion battery in a modified solution, performing reaction, filtering a solid-liquid suspension system after the reaction, obtaining lithium-containing filtrate and precipitate, washing and drying the precipitate, and obtaining an electrochemical desalination electrode material; mixing the obtained electrochemical desalination electrode material, a conductive agent and a binder in an organic solvent, then dropping the mixture onto carbon cloth, drying to obtain an electrochemical desalination electrode; placing the obtained electrochemical desalination electrode in a double-electrode desalination system to perform desalination; wherein, saturated sodium carbonate solution is added to the lithium-containing filtrate, and lithium is recovered through a precipitation method; the modified solution comprises ferricyanide solution and / or ferrocyanide solution; and the modified solution is an acidic solution.

Description

Technical Field

[0001] This invention relates to the field of resource and environmental technology, and in particular to an electrochemical desalination method using the positive electrode of a retired lithium-ion battery and its application. Background Technology

[0002] Desalination of brackish water or wastewater recycling is an important way to solve the shortage of freshwater resources. Currently, the main method for desalination of brackish water is electrochemical desalination, which is mainly divided into two types: capacitive deionization (CDI) and battery deionization (BDI). Battery deionization (BDI) relies on phase modulation mediated by the redox process between anions / cations in the brackish water and the electrode active material to achieve ion removal. Therefore, it has high selectivity and relatively low energy consumption. However, there is still a lack of relatively low-cost active reaction materials for battery deionization processes, which limits the large-scale application of this technology.

[0003] On the other hand, with the increasing demand for new energy sources, the production of retired lithium-ion batteries is also gradually increasing. Improper disposal not only wastes resources but also poses a significant threat to the environment. Therefore, recycling or comprehensively utilizing retired lithium-ion batteries is an essential path for the development of an environmentally friendly society. Existing pyrometallurgical or hydrometallurgical processes for recycling retired lithium-ion batteries often suffer from drawbacks such as high acid / alkali consumption and long process flows, and typically generate large amounts of high-salinity wastewater. The complete treatment of this high-salinity wastewater is also a problem that must be solved.

[0004] Therefore, how to prepare highly reactive electrode materials based on retired lithium-ion battery resources for the desalination treatment of high-salt wastewater, so as to achieve green closed-loop recycling in the retired lithium-ion battery recycling industry, is a problem that urgently needs to be solved. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the objective of the present invention is to provide an electrochemical desalination method using the positive electrode of a retired lithium-ion battery. This method involves reacting the retired lithium-ion battery positive electrode material with (ferrous) ferrocyanide to obtain an electrochemical desalination electrode material, which is then used in electrochemical desalination, thereby combining the recycling of retired lithium-ion batteries with the desalination of saline water or the recovery of wastewater.

[0006] A second aspect of the present invention provides an application of an electrochemical desalination method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of this invention provides an electrochemical desalination method using the positive electrode of a retired lithium-ion battery, comprising the following steps:

[0009] S1. Prepare a modified solution, mix retired lithium-ion battery cathode powder in the modified solution, and react. After the reaction, filter the solid-liquid suspension system to obtain lithium-containing filtrate and precipitate. After purifying the precipitate, obtain electrochemical desalting electrode material.

[0010] S2. The electrochemical desalination electrode material obtained in step S1 is mixed with a conductive agent and a binder in an organic solvent and then dropped onto carbon cloth. After drying, an electrochemical desalination electrode is obtained.

[0011] S3. Place the electrochemical desalination electrode obtained in step S2 into a two-electrode desalination system to perform desalination;

[0012] In step S1, a saturated sodium carbonate solution is added to the lithium-containing filtrate, and lithium is recovered by precipitation.

[0013] The modified solution in step S1 includes a ferricyanide solution and / or a ferrousyanide solution; the modified solution is an acidic solution.

[0014] The basic principle of this invention is as follows: Under acidic conditions, the transition metal in the positive electrode of a retired ion battery reacts with (non-)ferrocyanide, transforming into a Prussian blue-like basic structure, which precipitates as stardust. Simultaneously, lithium ions remain in the lithium-containing filtrate. This Prussian blue-like basic structure can combine with sodium ions migrating in the desalted salt solution under electrochemical conditions, undergoing a redox reaction, thereby reducing the salt content in the solution.

[0015] Taking the reaction process of potassium ferrocyanide and lithium cobalt oxide as an example, the specific chemical reaction process is as follows:

[0016] LiCoO2+[Fe(CN)6] 4- +4H + +K + =KCoFe(CN)6·0.5H2O+Li + +1.5H2O

[0017] KCoFe(CN)6·0.5H2O+e -1 +Na+=KNaCoFe(CN)6+0.5H2O

[0018] In some embodiments of the present invention, the retired lithium-ion battery cathode powder in step S1 is one or more of lithium iron phosphate cathode, lithium manganese oxide cathode, lithium nickel cobalt manganese oxide cathode, and lithium cobalt oxide cathode.

[0019] In some embodiments of the present invention, the lithium nickel cobalt manganese oxide cathode includes LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2.

[0020] In some embodiments of the present invention, the modified solution in step S1 is one or more of sodium ferricyanide, potassium ferricyanide, sodium ferrocyanide, and potassium ferrocyanide.

[0021] In some embodiments of the present invention, the modified solution in step S1 contains sulfuric acid.

[0022] The sulfuric acid in the modified solution can provide acidic conditions, which can better promote the reaction between the cathode material of retired ion batteries and the modified solution.

[0023] In some embodiments of the present invention, the concentration of the modified solution in step S1 is 0.2 to 6 mol / L.

[0024] The concentration of the modified solution affects the desalination capability of the resulting electrochemical desalination electrode.

[0025] In some embodiments of the present invention, the concentration of the modified solution in step S1 is 0.2 to 0.4 mol / L.

[0026] When the concentration of the modified solution is 0.2–0.4 mol / L, the desalination capacity of the electrochemical desalination electrode is not less than 45 mg / g, and the desalination capacity does not significantly increase when the concentration of the modified solution continues to increase.

[0027] In some embodiments of the present invention, the concentration of sulfuric acid in the modified solution of step S1 is 0.1 to 10 mol / L.

[0028] In some embodiments of the present invention, the concentration of sulfuric acid in the modified solution of step S1 is 0.5 to 5 mol / L.

[0029] In some specific embodiments of the present invention, the concentration of sulfuric acid in the modified solution of step S1 is 0.5 to 1 mol / L.

[0030] In some examples of the present invention, the concentration of sulfuric acid in the modified solution of step S1 is 0.6 to 0.8 mol / L.

[0031] In some embodiments of the present invention, the volume-to-mass ratio of the modified solution to the retired lithium-ion battery cathode powder in step S1 is (1-100) mL:1 g.

[0032] In some embodiments of the present invention, the volume-to-mass ratio of the modified solution to the retired lithium-ion battery cathode powder in step S1 is (40-70) mL:1 g.

[0033] In some specific embodiments of the present invention, the volume-to-mass ratio of the modified solution to the retired lithium-ion battery cathode powder in step S1 is (50-65) mL:1 g.

[0034] In some embodiments of the present invention, the mixing in step S1 is carried out under stirring conditions, with a stirring speed of 100 to 1000 rpm.

[0035] In some embodiments of the present invention, the stirring speed in step S1 is 500-800 rpm.

[0036] In some embodiments of the present invention, the reaction temperature in step S1 is 5–95°C; the reaction time is 0.5–12 h.

[0037] In some embodiments of the present invention, the reaction temperature in step S1 is 10–60°C; the reaction time is 1–5 h.

[0038] In some specific embodiments of the present invention, the reaction temperature in step S1 is 25-45°C; the reaction time is 2-3 hours.

[0039] In some embodiments of the present invention, the conductive agent in step S2 includes conductive carbon black.

[0040] In some embodiments of the present invention, the adhesive in step S2 includes polyvinylidene fluoride.

[0041] In some embodiments of the present invention, the organic solvent in step S2 includes at least one of dimethylacetamide, dimethylformamide, and ethanol.

[0042] In some embodiments of the present invention, the mass ratio of the electrochemical desalination electrode material to the conductive agent and binder in step S2 is (5-9):1:1.

[0043] In some embodiments of the present invention, the mass ratio of the electrochemical desalination electrode material to the conductive agent and binder in step S2 is (7-8):1:1.

[0044] In some embodiments of the present invention, the mass-to-volume ratio of the electrochemical desalination electrode material to the organic solvent in step S2 is (1-20) mg:(5-20) mL.

[0045] In some embodiments of the present invention, the drying temperature in step S2 is 60–90°C.

[0046] In some embodiments of the present invention, the drying temperature in step S2 is 80-90°C.

[0047] In some embodiments of the present invention, the drying time of step S2 is 1 to 12 hours.

[0048] In some embodiments of the present invention, the drying time of step S2 is 10 to 12 hours.

[0049] In some embodiments of the present invention, the mixing in step S2 is carried out under stirring; the stirring speed is 200 to 1500 rpm.

[0050] In some embodiments of the present invention, the stirring speed in step S2 is 800–900 rpm.

[0051] In some embodiments of the present invention, during the desalination process in step S3, the applied current density is 20 to 320 mA / g.

[0052] In some embodiments of the present invention, the current density in step S3 is 20 to 160 mA / g.

[0053] In some specific embodiments of the present invention, the current density in step S3 is 20-80 mA / g.

[0054] In some examples of the present invention, the current density in step S3 is 20 to 40 mA / g.

[0055] By controlling the current density during the desalination process, the desalination capability of the electrochemical desalination electrode can be further improved.

[0056] In some embodiments of the present invention, the concentration of sodium chloride in the desalted salt solution of step S3 is 100-1000 mg / L.

[0057] In some embodiments of the present invention, the concentration of sodium chloride in the desalted salt solution of step S3 is 200-1000 mg / L.

[0058] In some specific embodiments of the present invention, the concentration of sodium chloride in the desalted salt solution of step S3 is 500-1000 mg / L.

[0059] In some examples of the present invention, the concentration of sodium chloride in the salt solution desalted in step S3 is 900-1000 mg / L.

[0060] By controlling the initial concentration of sodium chloride solution during the desalination process, the desalination capacity of the electrochemical desalination electrode can be further improved, and when the concentration of sodium chloride is 900-1000 mg / L, the desalination capacity is not less than 35 mg / g.

[0061] In some embodiments of the present invention, the pH of the salt solution desalted in step S3 is 2 to 12.

[0062] In some embodiments of the present invention, the pH of the salt solution desalted in step S3 is 4 to 12.

[0063] In some specific embodiments of the present invention, the pH of the salt solution desalted in step S3 is 6 to 10.

[0064] In some embodiments of the present invention, the amount of saturated sodium carbonate solution added is 10 to 40% of the volume of lithium-containing filtrate.

[0065] In some embodiments of the present invention, the amount of saturated sodium carbonate solution added is 20-40% of the volume of lithium-containing filtrate.

[0066] In some embodiments of the present invention, the reaction temperature of the precipitation method is 80–100°C; the reaction time is 0.5–6 h.

[0067] In some embodiments of the present invention, the reaction temperature of the precipitation method is 90-95°C; the reaction time is 3-6 hours.

[0068] In some embodiments of the present invention, the precipitation reaction is carried out under stirring at a speed of 50 to 500 rpm.

[0069] In some embodiments of the present invention, the stirring speed of the precipitation method is 200-300 rpm.

[0070] A second aspect of the present invention is to provide an application of the electrochemical desalination method described in the first aspect of the present invention in brackish water desalination or wastewater recycling.

[0071] Compared with the prior art, the present invention has at least the following beneficial effects:

[0072] The electrochemical desalination method of this invention uses the positive electrode of a retired lithium-ion battery to prepare an electrochemical desalination electrode and applies it to electrochemical desalination. While realizing the recycling of retired lithium-ion battery resources, it reduces the cost of battery deionization electrochemical desalination and can ensure the desalination capacity of the electrochemical desalination electrode. It is conducive to the large-scale application of battery deionization technology and has good economic, social and environmental benefits. It is suitable for saline water desalination or wastewater recycling, and can also be used for the treatment and reuse of high-salt wastewater in the recycling process of retired lithium-ion batteries. Attached Figure Description

[0073] Figure 1 This is a process flow diagram of an embodiment of the present invention.

[0074] Figure 2The XRD patterns are shown for the cathode and electrochemical desalination electrode materials of retired lithium-ion batteries in Examples 1, 6, and 10-11 of this invention; wherein... Figure 2 a is the XRD pattern of the positive electrode of a retired lithium-ion battery. Figure 2 b is the XRD pattern of the electrochemical desalination electrode material; the horizontal axis is the diffraction angle and the vertical axis is the diffraction intensity.

[0075] Figure 3 The figures show the electrochemical performance of the electrochemical desalination electrodes obtained in Examples 1-3 of this invention; wherein... Figure 3 a is the CV curve of the electrochemical desalting electrode prepared in Example 1 in 1000 mg / L sodium chloride solution. The horizontal axis is the potential and the vertical axis is the current density. Figure 3 b is a graph showing the cycling performance of the electrochemical desalination electrode prepared in Example 3 in a 1000 mg / L sodium chloride solution with a current intensity of 60 mA / g. The horizontal axis in the graph represents the number of cycles, the left vertical axis represents the desalination performance, and the right vertical axis represents the coulombic efficiency (red represents the discharge performance, blue represents the charging performance, and green represents the coulombic efficiency). Figure 3 c is a graph showing the charge / discharge performance of the electrochemical desalting electrode prepared in Example 1 in a 1000 mg / L sodium chloride solution at a rate of 20–320 mA / g. The lower horizontal axis represents the number of cycles, the upper horizontal axis represents the current density during the corresponding rate change process, the left vertical axis represents the desalting performance, and the right vertical axis represents the coulombic efficiency. Figure 3 Figure d shows the desalination capacity of the electrochemical desalination electrode prepared in Example 2 under different current intensities (sodium chloride concentration 1000 mg / L). The horizontal axis represents the current intensity, and the vertical axis represents the desalination performance.

[0076] Figure 4 The diagram shows the desalination capacity of the electrochemical desalination electrodes of Examples 3-4 of this invention under desalination conditions; wherein... Figure 4 a is a graph showing the desalination capacity of the electrochemical desalination electrode in Example 3 at different initial concentrations of sodium chloride solution; Figure 4 b is a graph showing the desalination capacity of the electrochemical desalination electrode in Example 4 under different initial pH values ​​of sodium chloride solutions.

[0077] Figure 5 This refers to the desalination capability of the electrochemical desalination electrode under different potassium ferrocyanide concentrations in Example 5 of the present invention.

[0078] Figure 6 The electrochemical performance diagrams are shown for the electrochemical desalination electrodes obtained in Examples 6-8 of this invention; wherein... Figure 6 a is the CV curve of the electrochemical desalting electrode prepared in Example 6 in 1000 mg / L sodium chloride solution. The horizontal axis is the potential and the vertical axis is the current density. Figure 6b is a graph showing the cycling performance of the electrochemical desalination electrode prepared in Example 8 in a 1000 mg / L sodium chloride solution with a current intensity of 60 mA / g. The horizontal axis represents the number of cycles, the left vertical axis represents the desalination performance, and the right vertical axis represents the coulombic efficiency (red represents the discharge performance, blue represents the charging performance, and green represents the coulombic efficiency). Figure 6 c is a graph showing the charge / discharge performance of the electrochemical desalination electrode prepared in Example 6 in a 1000 mg / L sodium chloride solution at a rate of 20–320 mA / g. The lower horizontal axis represents the number of cycles, the upper horizontal axis represents the current density during the corresponding rate change process, the left vertical axis represents the desalination performance, and the right vertical axis represents the coulombic efficiency. Figure 6 Figure d shows the desalination capacity of the electrochemical desalination electrode prepared in Example 7 under different current intensities (sodium chloride concentration 1000 mg / L). The horizontal axis represents the current intensity, and the vertical axis represents the desalination performance.

[0079] Figure 7 The diagram shows the desalination capacity of the electrochemical desalination electrodes of Examples 8-9 of this invention under desalination conditions; wherein... Figure 7 a is a graph showing the desalination capacity of the electrochemical desalination electrode in Example 8 at different initial concentrations of sodium chloride solution; Figure 7 b is a graph showing the desalination capacity of the electrochemical desalination electrode in Example 9 under different initial pH values ​​of sodium chloride solutions. Detailed Implementation

[0080] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0081] The desalination capacity in the following embodiments of the present invention is calculated as follows: Desalination capacity (mg / g) = (C0 - C) / (mg / g) t )V / m, where C0 is the initial sodium chloride concentration (mg / L), C t V is the sodium chloride concentration (mg / L) after the desalination reaction, V is the volume of the target desalination solution (L), and m is the mass (g) of the desalination active electrode powder (i.e., the electrochemical desalination electrode material).

[0082] The process flow of this invention embodiment is as follows: Figure 1 As shown.

[0083] Example 1

[0084] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery, comprising the following steps:

[0085] S1. Select NCM111(LiNi) 0.33 Co0.33 Mn 0.33 After discharging and dismantling retired lithium-ion batteries of type O2, waste NCM111 powder was obtained. 1g of NCM111 powder was weighed and added to 50mL of 0.2mol / L potassium ferrocyanide solution with a sulfuric acid concentration of 0.6mol / L. The mixture was stirred continuously at 500rpm for 2h at a reaction temperature of 25℃. After the reaction was completed, the mixture was filtered to obtain a lithium-containing filtrate and a precipitate of the reaction product. The reaction product was washed and dried to obtain an electrochemical desalination electrode material with a Prussian blue-like structure (NCM111-PBA).

[0086] S2. Weigh 8 mg of the electrochemical desalination electrode material obtained in step S1, and add it, along with 1 mg of conductive carbon black and 1 mg of polyvinylidene fluoride, to 10 mL of dimethylformamide. After stirring evenly at 800 rpm, add the mixture dropwise to a 2 × 2 cm³ volumetric precipitate. 2 An electrochemical desalination electrode was obtained by drying the carbon cloth at 80°C for 12 hours.

[0087] S3. The electrochemical desalting electrode obtained in step S3 and the counter electrode containing activated carbon were placed in a 1000 mg / L sodium chloride solution with a pH of 12. The desalting reaction was carried out at a current intensity of 20 mA / g. The desalting capacity was tested to reach 46.87 mg / g.

[0088] In this embodiment, 10 mL (20% of the volume of the lithium-containing filtrate) of saturated sodium carbonate solution is added to the lithium-containing filtrate in step S1 above, and the mixture is heated to 95°C with continuous stirring to precipitate and recover lithium. The precipitation reaction time is 3 hours and the stirring speed is 300 rpm. After precipitation, the mixture is filtered while hot at 95°C and repeatedly washed with deionized water at 95°C to recover lithium carbonate.

[0089] Example 2

[0090] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery. Based on Example 1, the current intensity for desalination in step S3 is changed. The current intensity is set to 40mA / g, 80mA / g, 160mA / g and 320mA / g respectively, while other conditions remain unchanged.

[0091] The desalination capacity of this embodiment was tested, and the results are as follows: Figure 3 As shown in d, when the current intensity is 40mA / g, 80mA / g, 160mA / g and 320mA / g, the desalination capacity is 40.38mg / g, 37.12mg / g, 30.89mg / g and 28.25mg / g, respectively.

[0092] Example 3

[0093] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery. Based on Example 1, the current intensity of the desalination process in step S3 is controlled to be 60 mA / g, and the initial sodium chloride concentration is changed to 100 mg / L, 200 mg / L, 500 mg / L and 1000 mg / L.

[0094] like Figure 4 As shown in Figure a, when the initial sodium chloride concentrations are 100 mg / L, 200 mg / L, 500 mg / L, and 1000 mg / L, the desalination capabilities of the electrochemical desalination electrode are 20.67 mg / g, 27.48 mg / g, 34.01 mg / g, and 35.72 mg / g, respectively.

[0095] Example 4

[0096] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery. Based on Example 1, the current intensity in the desalination process in step S3 is controlled to be 60 mA / g and the initial sodium chloride concentration is 1000 mg / L, while the initial pH value of the sodium chloride solution is changed.

[0097] like Figure 4 As shown in b, as the initial pH of the sodium chloride solution increases from 2 to 12, the desalination capacity of the electrochemical desalination electrode obtained in this embodiment increases from 26.32 mg / g to 46.21 mg / g.

[0098] Example 5

[0099] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery. Based on Example 1, the concentration of potassium ferrocyanide solution in step S1 is controlled to be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L and 0.4 mol / L, while other preparation and reaction conditions remain unchanged.

[0100] like Figure 5 As shown, when the concentrations of potassium ferrocyanide solution are 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, and 0.4 mol / L, the corresponding desalination capacities of the electrochemical desalination electrodes are 10.98 mg / g, 24.73 mg / g, 46.87 mg / g, 47.28 mg / g, and 48.13 mg / g, respectively.

[0101] Example 6

[0102] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery, comprising the following steps:

[0103] S1. NCM622(LiNi 0.6 Co 0.2 Mn 0.2 After discharging and dismantling retired lithium-ion batteries of type O2, waste NCM622 powder was obtained. 0.8g of NCM622 powder was weighed and added to 50mL of 0.4mol / L potassium ferrocyanide solution with a sulfuric acid concentration of 0.8mol / L. The mixture was stirred continuously at 800rpm for 3 hours at a reaction temperature of 45℃. After the reaction was completed, the lithium-containing filtrate and the reaction product precipitate were obtained by filtration. After washing and drying, the reaction product was used to obtain an electrochemical desalination electrode material with a Prussian blue-like structure (NCM622-PBA).

[0104] S2. Weigh 7 mg of the electrochemical desalination electrode material obtained in step S1, and add it, along with 1 mg of conductive carbon black and 1 mg of polyvinylidene fluoride, to 12 mL of dimethylformamide. After stirring evenly at 900 rpm, add the mixture dropwise to a 2 × 2 cm³ volumetric precipitate. 2 An electrochemical desalting electrode was obtained by drying the carbon cloth at 90°C for 12 hours.

[0105] S3. The electrochemical desalting electrode obtained in step S2 and the counter electrode containing activated carbon were placed in a 1000 mg / L sodium chloride solution with a pH of 10. The desalting reaction was carried out at a current intensity of 20 mA / g. The desalting capacity of the electrochemical desalting electrode was tested to be 38.72 mg / g.

[0106] In this embodiment, 20 mL (40% of the volume of the lithium-containing filtrate) of saturated sodium carbonate solution was added to the lithium-containing filtrate obtained in step S1 above, and the mixture was heated to 90°C with continuous stirring to precipitate and recover lithium. The precipitation reaction time was 6 h, and the stirring speed was 200 rpm. After precipitation was completed, the mixture was filtered while hot at 90°C and repeatedly rinsed with deionized water at 90°C. After drying, high-purity lithium carbonate was recovered.

[0107] Example 7

[0108] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery. Based on Example 6, the current intensity for desalination in step S3 is changed to 40 mA / g, 80 mA / g, 160 mA / g, and 320 mA / g, while other conditions remain unchanged.

[0109] like Figure 6 As shown in d, when the current intensity is increased to 40mA / g, 80mA / g, 160mA / g, and 320mA / g, the desalination capacity of the electrochemical desalination electrode decreases to 35.82mg / g, 32.61mg / g, 28.98mg / g, and 24.85mg / g, respectively.

[0110] Example 8

[0111] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery. Based on Example 6, the current intensity of the desalination process in step S3 is controlled at 60 mA / g, and only the initial sodium chloride concentration is changed. The sodium chloride concentrations are 100 mg / L, 200 mg / L, 500 mg / L and 1000 mg / L.

[0112] like Figure 7 As shown in Figure a, when the initial sodium chloride concentration is increased to 100 mg / L, 200 mg / L, 500 mg / L and 1000 mg / L, the desalination capacity of the electrochemical desalination electrode is 22.62 mg / g, 25.18 mg / g, 34.13 mg / g and 37.58 mg / g, respectively.

[0113] Example 9

[0114] This embodiment provides an electrochemical desalination method using the positive electrode of a retired ion battery. Based on Example 6, the current intensity in the desalination process in step S3 is controlled to be 60 mA / g and the initial sodium chloride concentration is 1000 mg / L, only the initial solution pH value is changed.

[0115] like Figure 7 As shown in b, as the initial pH of the solution increases from 2 to 10, the desalination capacity of the electrochemical desalination electrode increases from 26.57 mg / g to 35.18 mg / g. When the pH continues to increase to 12, the desalination capacity decreases to 18.49 mg / g.

[0116] Example 10

[0117] This embodiment provides an electrochemical desalination method using the positive electrode of a retired lithium-ion battery. Based on Example 1, the retired lithium-ion battery NCM111 is replaced with NCM811.

[0118] Example 11

[0119] This embodiment provides an electrochemical desalination method using the positive electrode of a retired lithium-ion battery. Based on Example 1, the retired lithium-ion battery NCM111 is replaced with NCM523.

[0120] The results from Examples 1-9 show that the concentration of potassium ferrocyanide solution, the current intensity during desalination, the concentration of sodium chloride solution, and the initial pH value of sodium chloride solution all have a significant impact on the desalination capacity of the electrochemical desalination electrode.

[0121] Figure 2The images show the XRD patterns of the cathode and electrochemical desalination electrode materials of retired lithium-ion batteries in Examples 1, 6, and 10-11. Figure 2 a is the XRD pattern of the cathode of a retired lithium-ion battery. The XRD patterns of each retired cathode powder conform to the relevant standard cathode card. Figure 2 b is the XRD pattern of the electrochemical desalting electrode material. According to the spectrum analysis, the desalting electrodes all have a Prussian blue-like structure.

[0122] In summary, the electrochemical desalination method of this invention enables the recycling of retired lithium-ion battery resources, reduces the cost of electrochemical desalination of batteries, and ensures the desalination capacity of the resulting electrochemical desalination electrode. Furthermore, by adjusting the solubility of the modified solution, the current intensity during the desalination process, the concentration of the sodium chloride solution, or the initial pH of the sodium chloride solution, the desalination capacity of the electrochemical desalination electrode can be further improved, reaching a maximum of 48.13 mg / g.

[0123] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An electrochemical desalination method using the positive electrode of a retired lithium-ion battery, characterized in that, Includes the following steps: S1. Prepare a modified solution, mix retired lithium-ion battery cathode powder in the modified solution, and react. After the reaction, filter the solid-liquid suspension system to obtain lithium-containing filtrate and precipitate. After purifying the precipitate, obtain electrochemical desalting electrode material. S2. The electrochemical desalination electrode material obtained in step S1 is mixed with a conductive agent and a binder in an organic solvent and then dropped onto carbon cloth. After drying, an electrochemical desalination electrode is obtained. S3. Place the electrochemical desalination electrode obtained in step S2 into a two-electrode desalination system to perform desalination; In step S1, a saturated sodium carbonate solution is added to the lithium-containing filtrate to recover lithium by precipitation. The modified solution in step S1 includes a ferricyanide solution and / or a ferrocyanide solution; The modified solution is an acidic solution; In step S2, the mass ratio of the electrochemical desalination electrode material to the conductive agent and binder is (5~9):1:1; During the desalination process in step S3, a current density of 20~160mA / g is applied; The concentration of sodium chloride in the desalting solution in step S3 is 500~1000 mg / L; The pH of the salt solution desalted in step S3 is 4~12; The retired lithium-ion battery cathode powder in step S1 is LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2 or LiNi 0.33 Co 0.33 Mn 0.33 O2.

2. The electrochemical desalination method according to claim 1, characterized in that, The modified solution in step S1 is one or more of sodium ferricyanide, potassium ferricyanide, sodium ferrocyanide, and potassium ferrocyanide. And / or, the modified solution in step S1 contains sulfuric acid.

3. The electrochemical desalination method according to claim 1 or 2, characterized in that, The concentration of the modified solution in step S1 is 0.2~6 mol / L; And / or, the concentration of sulfuric acid in the modified solution of step S1 is 0.1~10 mol / L; And / or, in step S1, the volume-to-mass ratio of the modified solution to the retired lithium-ion battery cathode powder is (1~100) mL:1 g.

4. The electrochemical desalination method according to claim 1, characterized in that, The mixing in step S1 is carried out under stirring conditions, with a stirring speed of 100~1000 rpm; And / or, the reaction temperature in step S1 is 5~95℃; the reaction time is 0.5~12h.

5. The electrochemical desalination method according to claim 1, characterized in that, The conductive agent in step S2 includes conductive carbon black. And / or, the adhesive in step S2 includes polyvinylidene fluoride; And / or, the organic solvent in step S2 includes at least one of dimethylacetamide, dimethylformamide, and ethanol.

6. The electrochemical desalination method according to claim 1 or 5, characterized in that, In step S2, the mass-to-volume ratio of the electrochemical desalination electrode material to the organic solvent is (1~20) mg:(5~20) mL.

7. The electrochemical desalination method according to claim 1, characterized in that, The drying temperature in step S2 is 60~90℃; And / or, the drying time in step S2 is 1~12h; And / or, the mixing in step S2 is carried out under stirring; the stirring speed is 200~1500 rpm.

8. The electrochemical desalination method according to claim 1, characterized in that, The amount of saturated sodium carbonate solution added is 10-40% of the volume of the lithium-containing filtrate; And / or, the reaction temperature of the precipitation method is 80~100℃; the reaction time is 0.5~6h; And / or, the precipitation reaction is carried out under stirring at a speed of 50 to 500 rpm.

9. The application of the electrochemical desalination method according to any one of claims 1 to 8 in brackish water desalination or wastewater recycling.

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