Method and system for electrochemically recycling lithium ions in ternary lithium battery leachate

Abstract

The invention belongs to the field of lithium recovery, and particularly relates to a method and a system for electrochemically recovering lithium ions in ternary lithium battery leachate. The method comprises the following steps: (1) leaching the cathode material of the waste ternary battery to obtain a ternary leachate; (2) performing lithium ion enrichment in a capacitive deionization device by taking the ternary leaching solution obtained in the step (1) as a lithium source to obtain a lithium-rich receiving solution and a lithium-removed recycling solution; (3) recovering the lithium-rich receiving liquid to obtain recovered lithium; and performing non-lithium metal element recovery on the lithium-removed recovery liquid. According to the technical scheme, the rocking chair type capacitive deionization RCDI system adopts a waste ternary battery cathode material (SNCM) as an electrode material, the extraction quantity of a single reaction cycle can reach 4.90 mM g <-1 >, continuous and selective lithium extraction is realized, and meanwhile, the cost and the environmental influence are reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium recovery, and particularly relates to a method and system for electrochemically recovering lithium ions in a leaching solution of a ternary lithium battery. BACKGROUND

[0002] Lithium-ion batteries are widely used due to their high energy density, good cycle performance, environmental friendliness and other advantages. In 2024 alone, the total amount of retired power batteries worldwide exceeded one million tons, and the amount of recovered power batteries was less than 30% of the total amount of retired power batteries. On the other hand, the leakage of heavy metals (especially Ni, Co, and Mn in ternary lithium batteries) and plastics in waste batteries will seriously harm the natural environment and human health. Efficient recovery of lithium-ion batteries and reduction of environmental impact have become one of the technologies that need to be developed.

[0003] The current mainstream lithium-ion battery recovery methods include physical recovery, pyrometallurgical recovery, and hydrometallurgical recovery. The physical recovery technology does not involve chemical reactions, and the process is simple, can be combined with automatic full-component, full-automatic, and pollution-free disassembly, and is economical; but the recovery purity is low, the resolution is poor, and impurities may be introduced, affecting the quality and performance of the recovered materials. The pyrometallurgical recovery technology is simple and efficient, but has high energy consumption, low elemental recovery rate, and may produce toxic and harmful gases, causing environmental pollution. The hydrometallurgical recovery technology is mature, has high recovery efficiency and high product purity, and has low requirements for equipment. Compared with the first two processes, the hydrometallurgical recovery has a superior recovery rate and low secondary pollution.

[0004] However, further recovery of lithium in the leaching solution using traditional hydrometallurgical methods faces many challenges. Currently, conventional separation methods involve extraction, chemical precipitation, and ion exchange technologies. These methods usually extract transition metal ions first, and then recover lithium ions from the remaining solution. However, this strategy has obvious defects: on the one hand, the priority recovery of transition metal ions leads to a decrease in the priority of lithium recovery, resulting in a high loss rate during the extraction process; on the other hand, the ion exchange principle used in the precipitation or extraction process will introduce a large amount of impurity cations such as Na + These coexisting impurity cations will reduce the purity of the final Li2CO3 precipitate. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a method and system for electrochemically recovering lithium ions in a leaching solution of a ternary lithium battery.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A method for electrochemically recovering lithium ions in a leaching solution of a ternary lithium battery, comprising the following steps:

[0008] (1) leaching of the waste ternary battery cathode material, adding the waste ternary battery cathode material into a leaching solution for leaching to obtain a ternary leaching solution;

[0009] (2) lithium ion enrichment in a capacitive deionization device using the ternary leaching solution of step (1) as a lithium source to obtain a lithium-enriched receiving solution and a lithium-removed recovery solution;

[0010] (3) recovering lithium from the lithium-enriched receiving solution and recovering non-lithium metal elements from the lithium-removed recovery solution.

[0011] The cathode and the anode of the capacitive deionization device are independently prepared using the waste ternary battery cathode material.

[0012] The anode is prepared by adding the waste ternary lithium battery cathode material, a binder, and a conductive agent into NMP to obtain an electrode slurry, and coating the electrode slurry onto a substrate to obtain the anode after drying.

[0013] Preferably, the mass ratio of the waste ternary lithium battery cathode material, the binder, and the conductive agent is (6-8) : (1-2) : (1-2).

[0014] Preferably, the binder is PVDF, and the conductive agent is carbon black.

[0015] Preferably, the substrate is a two-dimensional titanium sheet or a three-dimensional graphite felt.

[0016] The cathode is prepared by pre-lithium removal treatment of the anode in a three-electrode system.

[0017] Preferably, the three-electrode system includes the anode as a working electrode, a platinum mesh as a counter electrode, and silver / silver chloride as a reference electrode.

[0018] Preferably, the specific steps of the pre-lithium removal treatment are: in a 5-20 mM, preferably 10 mM lithium sulfate solution, lithium is removed at a constant current for 1-3 h, preferably 1.5 h, to obtain the cathode; preferably, the constant current is 0.1-0.2 mA mg -1 , preferably 0.115 mA mg -1 .

[0019] Preferably, the method of lithium ion enrichment in step (2) includes the following steps:

[0020] (21) preliminary purification of lithium salt:

[0021] (211) the ternary leaching solution is introduced into the cathode chamber of the first capacitive deionization device, and the Li2SO4 solution is introduced into the anode chamber; the anode and the cathode of the capacitive deionization device are connected with the positive electrode and the negative electrode of an external power source, respectively; and the first capacitive deionization device is first charged with a constant current, and when the voltage rises to the cut-off voltage, the constant voltage under the voltage is switched, and when the current is less than the cut-off current, the reaction is ended;

[0022] Preferably, the cut-off voltage ranges from 0.5 V to 0.7 V, and is preferably 0.7 V; and the cut-off current ranges from 0.2 mA to 0.5 mA, and is preferably 0.3 mA.

[0023] (212) the solutions in the cathode chamber and the anode chamber are pumped out, and deionized water is injected into the chambers for flushing until the conductivity of the water out of the chambers is reduced to 20 μS cm -1 The following;

[0024] (213) the solution pumped out of the anode chamber in step (212) is introduced into the cathode chamber, the solution pumped out of the cathode chamber is introduced into the anode chamber, the anode is connected with the negative electrode of an external power source, the cathode is connected with the positive electrode of the external power source, and the capacitive deionization device is charged with a constant current, and when the voltage rises to a predetermined value, the constant voltage under the voltage is switched, and when the current is less than the cut-off current, the reaction is ended;

[0025] Preferably, the cut-off voltage ranges from 0.5 V to 0.7 V, and is preferably 0.7 V; and the cut-off current ranges from 0.2 mA to 0.5 mA, and is preferably 0.3 mA.

[0026] (214) steps (211) to (213) are repeated to obtain a first lithium-rich receiving solution and a first lithium-removed recovery solution; and steps (211) to (213) are regarded as one cycle.

[0027] Preferably, the method further comprises: (22) re-purification of lithium: the first lithium-rich receiving solution obtained in step (214) is introduced into the cathode chamber of a second capacitive deionization device identical to the first capacitive deionization device, and steps (211) to (214) are performed to re-purify the lithium to obtain a second lithium-rich receiving solution and a second lithium-removed recovery solution.

[0028] Preferably, the cut-off voltage in step (22) is greater than the cut-off voltage in step (211), and the cut-off current in step (22) is less than the cut-off current in step (211); and preferably, the cut-off voltage in step (22) is 0.8 V, and the constant current is 0.25 mA.

[0029] After 40 cycles are independently performed on the first capacitive deionization device and the second capacitive deionization device, the cathodes and the anodes of the first capacitive deionization device and the second capacitive deionization device are recovered;

[0030] The recycling method is to add the cathode and the anode as working electrodes to a three-electrode system for pre-lithium removal treatment. The specific steps of the pre-lithium removal treatment are as follows: in a 5-20 mM, preferably 10 mM lithium sulfate solution, lithium is removed at a constant current for 1-3 h, preferably 1.5 h; preferably, the constant current is 0.1-0.2 mA mg -1 , preferably 0.15 mA mg -1 ; the recovered lithium-rich lithium sulfate solution is used as a third lithium-rich receiving solution;

[0031] The recycled cathode and anode are added to the leaching solution for leaching to obtain a third lithium-removed recycling solution.

[0032] The leaching solution is a mixture of an H2SO4 solution and an H2O2 solution;

[0033] Preferably, the solid-liquid ratio of the waste ternary battery cathode material to the leaching solution is 1:(5-20); preferably, the solid-liquid ratio is 1:10;

[0034] Preferably, the mass ratio of the H2SO4 solution to the H2O2 solution is 2.5:1; preferably, the concentration of the H2O2 solution is 30%; and the concentration of the H2SO4 solution is 98%.

[0035] The step of recovering lithium from the lithium-rich receiving solution in step (3) is as follows: after the lithium-containing receiving solution is evaporated and concentrated, lithium is recovered by precipitation with sodium carbonate;

[0036] Preferably, the step of recovering non-lithium metal elements from the lithium-removed recycling solution is as follows: using the extraction strategy of Niklas Jantunen, under the conditions of a pH value of 2.50 and a phase ratio (S / F) of 0.8, 0.8 M D2EHPA is used to extract manganese, and then manganese sulfate is obtained by purifying with sulfuric acid after the extraction of manganese is completed. Cyanex 272 is used to extract cobalt from the remaining solution.

[0037] The present application also includes a system for electrochemically recycling lithium ions in a ternary lithium battery leaching solution for the method, comprising:

[0038] A capacitive deionization device: for preliminary extraction and repurification of lithium;

[0039] A liquid supply system: for supplying or discharging ternary leaching solution, lithium-rich receiving solution and lithium-removed recycling solution to the capacitive deionization device;

[0040] A control system: for controlling the current, voltage and liquid flow rate.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] The technical scheme of the application develops a method and system for electrochemically recovering lithium ions in leaching solution of ternary lithium battery, which is used for efficiently and preferentially recovering lithium from leaching solution of waste ternary lithium battery. The system is a rocking chair capacitive deionization (RCDI) system, adopts waste ternary battery cathode material (SNCM) as electrode material, and the amount of lithium extracted in a single reaction cycle can reach 4.90mMg -1 , realizes continuous and selective lithium extraction, and reduces cost and environmental impact.

[0043] Compared with traditional capacitive deionization (CDI) and extraction methods, the technical scheme of the application has lower energy consumption, higher efficiency and more excellent cycle stability. The purity of Li + in the second lithium-rich receiving solution obtained through re-purification can reach 95.82%, and the lithium recovery rate of the whole solution extraction system is about 90.09%.

[0044] In summary, the method and system for electrochemically recovering lithium ions in leaching solution of ternary lithium battery are designed and proposed, which can realize the "double-effect" utilization and recovery of SNCM. Economic analysis shows that the process has positive profit, which highlights its feasibility and sustainability. The electrochemical recovery method and closed-loop recovery strategy of ternary lithium battery involved in the application conform to the concept of circular economy and sustainable development, and provide a feasible solution for efficient recovery and resource recycling of waste batteries. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 It is a lithium extraction principle diagram of the "SLNCM / / SNCM" RCDI system in embodiment 1;

[0046] Figure 2 It is a leaching solution recovery flowchart based on the "SLNCM / / SNCM" RCDI system in embodiment 1;

[0047] Figure 3 It is the lithium extraction result of one preliminary lithium extraction cycle and one re-purification lithium extraction cycle when the electrode active site load of the "SLNCM / / SNCM" RCDI system in embodiment 1 is 0.36g;

[0048] Figure 4 It is the purity of lithium ions received after one preliminary lithium extraction cycle and one re-purification lithium extraction cycle when the electrode active site load of the "SLNCM / / SNCM" RCDI system in embodiment 1 is 0.36g;

[0049] Figure 5 It is the Li + / Ni in the process of one preliminary lithium extraction cycle and one re-purification lithium extraction cycle when the electrode active site load of the "SLNCM / / SNCM" RCDI system in embodiment 1 is 0.36g;2+ Co 2+ Mn 2+ separation factor of Co

[0050] Figure 6 Capacity fade results of SNCM electrodes in Li2SO4 solution for 40 charge-discharge cycles

[0051] Figure 7 Flow chart of ternary lithium battery "closed loop" recycling strategy based on "SLNCM / / SNCM" RCDI system in Example 1. DETAILED DESCRIPTION

[0052] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in combination with the drawings and the best embodiments.

[0053] Example 1 Figure 7 Flow chart of ternary lithium battery "closed loop" recycling strategy based on "SLNCM / / SNCM" RCDI system

[0054] 1. Preparation of cathode and anode of capacitive deionization device

[0055] 1.1 The anode described above is prepared in the following manner: waste ternary lithium battery cathode material, binder and conductive agent are added to NMP to obtain electrode slurry; the electrode slurry is coated on the substrate and dried to obtain the anode; the mass ratio of the waste ternary lithium battery cathode material, binder and conductive agent is (6-8) : (1-2) : (1-2); specifically, it can be 6:2:2 or 8:1:1; in this application, 8:1:1 is taken as an illustrative example; the binder is PVDF; the conductive agent is carbon black; preferably, the substrate is a two-dimensional titanium sheet or a three-dimensional graphite felt;

[0056] For the anode with two-dimensional titanium sheet as the substrate, the electrode slurry is uniformly coated on the surface of the cut titanium sheet with a thickness of about 20-50 μm using a doctor blade, and then dried in a drying oven at 60°C for 12 hours;

[0057] For the anode with three-dimensional graphite felt as the substrate, the electrode slurry is uniformly dropped into the graphite felt, and then dried in a drying oven at 60°C for 12 hours, and the step is repeated 3-5 times to ensure that the electrode has an observable active material loading.

[0058] In this embodiment, the anode with two-dimensional titanium sheet as the substrate is used for subsequent illustrative description.

[0059] 1.2 The cathode is prepared by pre-lithiation of the anode of step 1.1 in a three- electrode system; the three-electrode system includes the anode as the working electrode, a platinum mesh as the counter electrode, and a silver / silver chloride as the reference electrode; the specific steps of pre-lithiation are as follows: in 10 mM lithium sulfate solution, the anode is pre-lithiated at a constant current for 1.5 h to obtain the cathode; preferably, the constant current is 0.115 mA, and it should be noted that the current applied in this application is referred to the mg of the active material of the cathode of the spent ternary lithium battery; for example, a constant current of 0.115 mA is a current of 0.115 mA / mg.

[0060] 2. A method for electrochemically recycling lithium ions from a ternary lithium battery leaching solution

[0061] (1) Leaching of the spent ternary battery cathode material, 1 kg of the spent ternary battery cathode material is added to the leaching solution for leaching to obtain a ternary leaching solution; sulfuric acid is used as the leaching acid, and the cathode is leached at 85°C with 10 liters of 2.5 M sulfuric acid and 1 liter of hydrogen peroxide (30%); the leaching is performed for 2 hours, and the solid-liquid ratio is 1:10;

[0062] (2) The ternary leaching solution of step (1) is used as a lithium source for lithium ion enrichment in a capacitive deionization device to obtain a lithium-enriched receiving solution and a lithium-removed recovery solution;

[0063] (21) Preliminary purification of lithium salt Figure 1 The lithium extraction principle diagram of the "SLNCM / / SNCM" RCDI system is shown, which is mainly based on the reversible redox reaction of lithium deintercalation in LNCM and NCM;

[0064] (211) The ternary leaching solution is introduced into the cathode chamber 1 of the first capacitive deionization device, and the Li2SO4 solution is introduced into the anode chamber 2; the anode and the cathode of the capacitive deionization device are connected to the positive and negative electrodes of an external power source, respectively; and the first capacitive deionization device is first applied with a constant current, and when the voltage rises to the cutoff voltage, it is switched to constant voltage application at this voltage, and when the current is less than the cutoff current, the reaction is ended; preferably, the cutoff voltage is in the range of 0.5 V-0.7 V; preferably, 0.7 V; and the cutoff current is 0.2 mA-0.5 mA, preferably 0.3 mA.

[0065] In this embodiment, the ternary leaching solution is introduced into the cathode chamber 1, and the 5 mM Li2SO4 solution is introduced into the anode chamber 2 for lithium enrichment. Both are circulated at a flow rate of 30 mL min -1 -1 through a double-channel peristaltic pump. A constant current of 0.0750 mA mg -1 -1 is applied between the anode and the cathode until the battery potential rises to 0.7 V, and then a constant voltage is maintained until the current drops to 0.3 mA.

[0066] (212) Extract the solution from the cathode chamber and anode chamber, and flush the chambers with deionized water until the conductivity of the effluent drops to 20 μS / cm. -1 the following;

[0067] (213) The solution extracted from the anode chamber in step (212) is introduced into the cathode chamber, and the solution exported from the cathode chamber is introduced into the anode chamber. The anode is connected to the negative terminal of the external power supply, and the cathode is connected to the positive terminal of the external power supply. The capacitor deionization device is then energized with a constant current. When the voltage rises to a predetermined value, the constant voltage energization at that voltage is switched. When the current is less than the cutoff current, the reaction ends. Specifically, in this embodiment, the cutoff voltage is 0.7V and the cutoff current is 0.3mA.

[0068] (214) Repeat steps (211)-(213) to obtain a first lithium-rich receiving liquid and a first lithium-removed recovery liquid; steps (211)-(213) form a cycle.

[0069] (22) Lithium repurification:

[0070] The first lithium-rich receiving solution obtained in step (214) is added to the anode chamber of the second capacitor deionization device, which is the same as in step (211). Figure 2 (As shown), steps (211)-(214) are performed to purify lithium to obtain a second lithium-rich receiving solution and a second lithium-removed recovery solution; the cutoff voltage in step (22) is greater than the cutoff voltage in step (211), and the cutoff current in step (22) is less than the cutoff current in step (211); preferably, the cutoff voltage in step (22) is 0.8V and the cutoff current is 0.25mA.

[0071] Specifically, in this embodiment, the difference from the preliminary purification in step (21) is as follows: in step (211), the first lithium-rich receiving solution obtained from the first capacitor deionization device is input into the cathode chamber 1 of the second capacitor deionization device, and at the same time, 25mM Li2SO4 solution is input into the anode chamber 2 of the second capacitor deionization device. The solution is circulated at a flow rate of 60mL / min, and a constant current of 0.075mA / mg is applied until the battery potential rises to 0.8V, and then continues until the current drops to 0.25mA; in step (213), the cutoff voltage is 0.8V and the cutoff current is 0.25mA; the second lithium-rich receiving solution and the second lithium-removed recovery solution are obtained.

[0072] During the process of feeding the first lithium-rich receiving solution into the second capacitor deionization unit, a ternary leaching solution can continue to be fed into the first capacitor deionization unit to ensure continuous lithium extraction production.

[0073] Figure 3The lithium extraction results of one primary purification cycle and one re-purification lithium extraction cycle of the "SLNCM / / SNCM" RCDI system with an electrode active site loading of 0.36 g are shown. In the initial lithium extraction process, the lithium ion (Li + ) concentration in the first lithium-rich receiving solution increased by 35.26 mM compared to the ternary leaching solution, while the nickel ion (Ni 2+ ), cobalt ion (Co 2+ ), and manganese ion (Mn 2+ ) concentrations in the first lithium-removing recovery solution increased by 2.74 mM, 2.97 mM, and 1.29 mM, respectively, compared to the ternary leaching solution. The lithium ion (Li + ) extraction amount per cycle was 4.90 mmol g -1 .

[0074] In the re-purification process, the lithium ion (Li + ) concentration in the second lithium-rich receiving solution increased by 32.19 mM compared to the first lithium-rich receiving solution, while the nickel ion (Ni 2+ ), cobalt ion (Co 2+ ), and manganese ion (Mn 2+ ) concentrations in the second lithium-removing recovery solution increased by 0.66 mM, 0.59 mM, and 0.16 mM, respectively, compared to the first lithium-removing recovery solution. The lithium ion (Li + ) extraction amount per cycle was 4.02 mmol g -1 .

[0075] Figure 4 The purity of the received lithium ions after one primary lithium extraction cycle and one re-purification lithium extraction cycle of the "SLNCM / / SNCM" RCDI system with an electrode active site loading of 0.36 g is shown. After the two extraction steps, the purity of the lithium ions first increased from 52.88% to 83.43%, and then further increased to 95.82%.

[0076] Figure 5 The separation coefficients of Li + / Ni 2+ , Co 2+ , Mn 2+ during one primary lithium extraction cycle and one re-purification lithium extraction cycle of the "SLNCM / / SNCM" RCDI system with an electrode active site loading of 0.36 g are shown. In the primary purification process, the separation coefficients of lithium ions with respect to nickel, cobalt, and manganese ions were 3.60, 3.62, and 8.38, respectively; in the re-purification process, the separation coefficients of lithium ions with respect to nickel, cobalt, and manganese ions were 2.96, 3.62, and 5.73, respectively.

[0077] 3. Recovery of the electrode

[0078] After 40 cycles of the first and second capacitive deionization devices independently, the electrode capacity decayed, and the cathode and anode of the first and second capacitive deionization devices were recovered;

[0079] Figure 6 The capacity decay results of the SNCM electrode in 40 charge-discharge cycles in Li2SO4 solution were as follows: the cycle stability and capacity decay of the SNCM electrode in 40 charge-discharge processes were tested in 0.5M Li2SO4 solution, the current density was ±0.15mA mg -1 , and the voltage range was 0.1-1V. The results showed that after 40 cycles, the discharge capacity of SNCM decreased from the peak value of 96.56mAh g -1 to 72.74mAh g -1 , and the capacity retention rate was 75.33%. Therefore, the SNCM electrode (cathode) and SLNCM electrode (anode) after 40 charge-discharge cycles were recovered in the present application.

[0080] The recovery method was to add the cathode and anode as working electrodes to a three-electrode system for pre-lithium removal treatment. The specific steps of pre-lithium removal treatment were as follows: in 10mM lithium sulfate solution, lithium was removed for 1.5h at a constant current, preferably, the constant current was 0.115mA; the lithium-rich lithium sulfate solution obtained by recovery was used as the third lithium-rich receiving solution; the recovered cathode and anode were added to the leaching solution for leaching to obtain the third lithium-removed recovery solution.

[0081] (3) The lithium-rich receiving solution was recovered to obtain recovered lithium; and the lithium-removed recovery solution was recovered for non-lithium metal elements.

[0082] The first, second and third lithium-rich receiving solutions were recovered for lithium salt. The specific method was as follows: after lithium extraction, the purity of the receiving solution was about 93.5%, Li + concentration was about 11.71g L -1 (from 10.85g L -1 from SNCM electrode, 0.86g L -1 , calculated at 80% recovery rate). In order to prepare industrial-grade Li2CO3, the solution needed to be evaporated and concentrated to Li + concentration >20g L -1 , which required evaporation of about 3L. In the receiving solution, the amount of Li + was about 11.81mol. In order to achieve complete precipitation, about 0.68kg Na2CO3 was needed, and the lithium recovery rate was 80%, which could produce about 0.349kg Li2CO3.

[0083] The first, second and third lithium-removed recovery solutions are subjected to non-lithium metal salt recovery to recover nickel, cobalt and manganese. Under the conditions of a pH value of 2.50 and a phase ratio (S / F) of 0.8, manganese is extracted using 0.8M D2EHPA, and then purified by washing with sulfuric acid to obtain manganese sulfate. After manganese extraction is completed, cobalt is extracted from the remaining solution using Cyanex272.

[0084] Example 2

[0085] Example 2 differs from Example 1 in that the cutoff voltage of the constant current stage in step (211) is 0.5V.

[0086] Example 3

[0087] Example 3 differs from Example 1 in that the cutoff voltage of the constant current stage in step (211) is 0.6V.

[0088] Example 4

[0089] Example 4 differs from Example 1 in that the cutoff current in step (211) is 0.5mA.

[0090] Example 5

[0091] Example 5 differs from Example 1 in that the cutoff current in step (211) is 0.18mA.

[0092] Comparative Example 1

[0093] Comparative Example 1 differs from Example 1 in that the Li in the leach solution is recovered using an extraction (Cyanex301) method. + From a simulated leach solution containing cobalt, lithium, nickel, copper, aluminum and other metals, cobalt is preferentially extracted, and lithium in the raffinate is further recovered. Simulated waste lithium-ion battery leach solution: Li+350mg / L, Co 2+ 1000mg / L, Cu 2+ 400mg / L, Al 3+ 100mg / L, Ni 2+ 100mg / L; Extractant Cyanex301 concentration 0.1M; Diluent: kerosene; Phase ratio (O / A): 1:1; Temperature: 25-55°C (warming is conducive to extraction); Extraction time: 30 minutes; pH: 7.2.

[0094] Comparative Example 2

[0095] Comparative Example 2 differs from Example 1 in that the Li in the leach solution is recovered using an extraction (D2EHPA) method. +Extraction agent: 40% D2EHPA (P204) + 60% sulfonated kerosene (pre-neutralization: 60% D2EHPA converted to sodium salt); extraction conditions: pH: 3.5 (Li co-extraction increases when pH < 3.5, Ni / Co extraction is insufficient when pH > 3.5); extraction time: 6 minutes; phase ratio (O / A): 1:1; temperature: 25°C.

[0096] Comparative Example 3

[0097] Comparative Example 3 differs from Example 1 in that the acid leaching and advanced oxidation process (AOP-CLPs) are used to selectively recover Li from spent ternary lithium batteries + AOPs (advanced oxidation processes): strong oxidizing free radicals (SO4 - · and ·OH) are generated in situ by using heat-activated sodium persulfate (Na2S2O8) to selectively oxidize the positive electrode material, promote the release of lithium, and inhibit the leaching of cobalt (Co 2+ ), manganese (Mn 2+ ).

[0098] CLPs (chemical leaching processes): coupling sulfuric acid (H2SO4) enhances the leaching efficiency of lithium, addressing the incomplete lithium release problem when AOPs are used alone.

[0099] Positive electrode material: NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O2) or mixed positive electrode waste (containing Li, Co, Ni, Mn). Slurry preparation: waste particles are mixed with deionized water to form a uniform slurry. Oxidant dosage: [S2O8 2- ] / [transition metal M] molar ratio = 0.30; temperature: 85°C; solid-liquid ratio (slurry density): 400 g / L; acidity control: final pH ≈ 3.0; reaction time: 240 minutes.

[0100] Table 1 shows the adsorption capacity at constant pressure and constant current stages under different reaction conditions, and Table 2 shows the lithium loss rate and purity of different methods.

[0101] Table 1

[0102]

[0103] Table 2

[0104]

[0105] As can be seen from Table 1-2, when the absolute value of the cut-off voltage of the constant current process is less than 0.7V, the reaction will be insufficient, resulting in low capacity utilization and affecting the efficiency of the recovery process; under the condition of ensuring sufficient reaction in the constant current stage, i.e. the absolute value of the cut-off voltage is 0.7V, when the reaction time in the constant voltage stage is too long, the phenomenon of lithium ion reverse extraction will occur, and when the constant voltage time is too short, the reaction will be insufficient, so the lithium extraction process needs a sufficient constant current process and a proper constant voltage process, i.e. the relatively optimal reaction condition in Example 1. Under this condition, the lithium extraction amount in a single reaction cycle in the preliminary lithium extraction process can reach 4.90mMg -1 , the lithium extraction amount in a single reaction cycle in the purification process can reach 4.02mmol g -1 , the purity of Li + in the receiving solution 3 can reach 95.82%, and the lithium recovery rate of the whole solution extraction system is about 90.09%.

[0106] In summary, the method and system for electrochemically recovering lithium ions in the leaching solution of ternary lithium batteries are designed and proposed, which can realize the "double-effect" utilization and recovery of SNCM. Economic analysis shows that the process has a positive profit, highlighting its feasibility and sustainability. The electrochemical recovery method and closed-loop recovery strategy of ternary lithium batteries in the present application conform to the concept of circular economy and sustainable development, and provide a feasible solution for efficient recovery and resource reuse of waste batteries.

[0107] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery, characterized in that, Includes the following steps: (1) Leaching of waste ternary battery cathode material: The waste ternary battery cathode material is added to the leaching solution for leaching to obtain ternary leaching solution. (2) The ternary leachate from step (1) is used as a lithium source to enrich lithium ions in a capacitor deionization device to obtain a lithium-rich receiving liquid and a lithium-removed recovery liquid. (3) The lithium-rich receiving liquid is recycled to obtain recovered lithium; The lithium-removed recovery solution is used to recover non-lithium metal elements.

2. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 1, characterized in that, The cathode and anode of the capacitor deionization device are independently prepared using cathode materials from waste ternary batteries.

3. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 2, characterized in that, The anode is prepared by mixing waste ternary lithium battery cathode material, binder, and conductive agent with NMP to obtain an electrode slurry; the electrode slurry is then coated onto a substrate and dried to obtain the anode. Preferably, the mass ratio of the waste ternary lithium battery cathode material, binder, and conductive agent is (6-8):(1-2):(1-2); Preferably, the binder is PVDF; the conductive agent is carbon black; Preferably, the substrate is a two-dimensional titanium sheet or a three-dimensional graphite felt.

4. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 3, characterized in that, The cathode is prepared by pre-delithiation treatment of the anode in a three-electrode system to obtain the cathode; Preferably, the three-electrode system includes the anode as the working electrode, the platinum mesh as the counter electrode, and silver / silver chloride as the reference electrode; Preferably, the specific steps of the pre-delithiation treatment are as follows: in a 5-20 mM; preferably 10 mM lithium sulfate solution, delithiation is performed at a constant current for 1-3 hours, preferably 1.5 hours, to obtain a cathode; preferably, the constant current density is 0.1-0.2 mA mg. -1 Preferably 0.115 mA mg -1 .

5. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 1, wherein the lithium ion enrichment method in step (2) includes the following steps: (21) Preliminary purification of lithium salts: (211) A ternary leachate is introduced into the cathode chamber of the first capacitor deionization device, and a Li2SO4 solution is introduced into the anode chamber. The anode and cathode of the capacitor deionization device are connected to the positive and negative terminals of an external power supply, respectively. The first capacitor deionization device is first energized with a constant current. When the voltage rises to a predetermined value, it is switched to constant voltage energization at that voltage. When the current is less than the cutoff current, the reaction ends. Preferably, the cutoff voltage range is 0.5V-0.7V; more preferably, it is 0.7V. The cutoff current is 0.2mA-0.5mA, preferably 0.3mA. (212) Extract the solution from the cathode chamber and anode chamber, and flush the chambers with deionized water until the conductivity of the effluent drops to 20 μS / cm. -1 the following; (213) The solution extracted from the anode chamber in step (212) is introduced into the cathode chamber, the solution exported from the cathode chamber is introduced into the anode chamber, and the anode is connected to the negative terminal of the external power supply, the cathode is connected to the positive terminal of the external power supply, and the capacitor deionization device is energized with constant current. When the voltage rises to a predetermined value, it is switched to constant voltage energization at that voltage. When the current is less than the cutoff current, the reaction ends. Preferably, the cutoff voltage is 0.5V-0.7V; more preferably 0.7V. The cutoff current is 0.2mA-0.5mA, preferably 0.3mA. (214) Repeat steps (211)-(213) to obtain a first lithium-rich receiving liquid and a first lithium-removed recovery liquid; steps (211)-(213) form a cycle.

6. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 5, characterized in that, Also includes: (22) Lithium repurification: The first lithium-rich receiving solution obtained in step (214) is added to the cathode chamber of the second capacitor deionization device, which is the same as in step (211), and lithium is repurified in steps (211)-(214) to obtain the second lithium-rich receiving solution and the second lithium-removed recovery solution. Preferably, the cutoff voltage in step (22) is greater than the cutoff voltage in step (211), and the cutoff current in step (22) is less than the cutoff current in step (211); preferably, the cutoff voltage in step (22) is 0.8V, and the cutoff current is 0.25mA.

7. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 6, characterized in that, After the first capacitor deionization unit and the second capacitor deionization unit have been independently operated for 40 cycles, the cathodes and anodes of the first capacitor deionization unit and the second capacitor deionization unit are recovered. The recovery method involves adding the cathode and anode as working electrodes to a three-electrode system for pre-lithiation treatment. The specific steps of the pre-lithiation treatment are as follows: in a 5-20 mM, preferably 10 mM, lithium sulfate solution, delithiation is performed at a constant current for 1-3 hours, preferably 1.5 hours; preferably, the constant current is 0.1-0.2 mA mg. -1 Preferably 0.15 mA mg -1 The recovered lithium-rich lithium sulfate solution was used as the third lithium-rich receiving solution. The recovered cathode and anode are added to a leaching solution for leaching to obtain a third lithium-removing recovery solution.

8. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 1, characterized in that, The leachate is a mixture of H2SO4 solution and H2O2 solution; Preferably, the solid-liquid ratio of the waste ternary battery cathode material to the leachate is 1:(5-20); more preferably, it is 1:

10. Preferably, the mass ratio of H2SO4 solution to H2O2 solution is 2.5:1; preferably, the concentration of H2O2 solution is 30%; and the concentration of H2SO4 solution is 98%.

9. The method for electrochemically recovering lithium ions from the leachate of a ternary lithium battery according to claim 1, characterized in that, The steps for recovering lithium from the lithium-rich receiving liquid in step (3) are as follows: after evaporating and concentrating the lithium-containing receiving liquid, it is recovered by precipitation with sodium carbonate; Preferably, the steps for recovering non-lithium metal elements from the lithium-removed recovery solution are as follows: using Niklas Jantunen's extraction strategy, manganese is extracted with 0.8M D2EHPA under conditions of pH 2.50 and a relative ratio S / F of 0.8, followed by purification with sulfuric acid to obtain manganese sulfate. After the manganese extraction is completed, cobalt is extracted from the remaining solution using Cyanex 272.

10. A system for the electrochemical recovery of lithium ions from ternary lithium battery leachate using the method described in any one of claims 1-9, characterized in that, include: Capacitor deionization unit: used for the initial extraction and repurification of lithium; Liquid supply system: used to supply or discharge ternary leachate, lithium-rich receiving liquid, and lithium-removed recovery liquid to the capacitor deionization unit; Control system: Used to control current, voltage, and liquid flow rate.

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