A coated material and its preparation method, a composite electrode and its application, and a capacitive deionization lithium extraction system and method.

Abstract

This invention belongs to the field of lithium extraction technology, specifically relating to a coated material and its preparation method, a composite electrode and its application, and a capacitive deionization lithium extraction system and method. This invention utilizes retired NCM cathode materials, which are surface-modified with LTO to form an NCM@LTO coated material, and then applied to a capacitive deionization lithium extraction system to achieve lithium extraction from brine in salt lakes through electrochemical drive. + The technology enables targeted enrichment of lithium. It balances material reuse with lithium extraction functionalization. Microstructurally, the LTO layer provides stable Ti-O-Li bond sites and electrochemical pseudocapacitive behavior, forming a "selective lithium intercalation interface." Macroscopically, the capacitive deionization system allows for reversible adsorption and desorption through potential control. In terms of resource recycling, it enables the direct high-value utilization of retired battery materials and the green development of lithium resources in salt lakes.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology, specifically relating to a coating material and its preparation method, a composite electrode and its application, and a capacitive deionization lithium extraction system and method. Background Technology

[0002] With the rapid development of the new energy industry, lithium-ion batteries have been widely used in electric vehicles, energy storage systems, and portable electronic devices. Global demand for lithium resources is experiencing explosive growth, and lithium prices are fluctuating significantly, creating an urgent need for efficient and sustainable lithium resource extraction. Currently, the main sources of lithium include spodumene, lepidolite, and salt lake brines. Among these, salt lake brines are considered one of the most promising lithium resource sources due to their abundant reserves and stable grades. However, lithium extraction from salt lake brines faces significant technical challenges. High concentrations of sodium (Na) are often present in salt lake brine systems. + K + Mg 2+ Ca 2+ Coexisting cations, Li + The relatively low lithium content, small hydration radius, and difficulty in desolvation make it difficult for traditional physicochemical separation methods to achieve high-selectivity lithium extraction. Currently, the most commonly used lithium extraction processes in industrial applications include chemical precipitation, solvent extraction, membrane separation, and solid-phase adsorption. However, existing lithium extraction technologies from salt lakes generally suffer from drawbacks such as high energy consumption, low efficiency, poor selectivity, or poor renewability, making the development of an efficient, reversible, and environmentally friendly lithium extraction technology urgently needed.

[0003] In recent years, capacitive deionization (CDI) has attracted widespread attention as an emerging electrochemical separation and water treatment technology. CDI achieves desalination or enrichment of specific ions by applying a low voltage (typically 1.0–1.6 V) between two electrodes, causing ions in the solution to migrate and adsorb onto the electrode surface under the influence of an electric field, forming an electrical double layer or embedding into the electrode material's lattice. Its advantages include: mild operating conditions and low energy consumption; no chemical reagents involved, no secondary pollution; controllable and reversible adsorption and desorption processes; and easily adjustable and reusable electrode materials.

[0004] However, traditional CDI electrode materials are mainly carbon-based (activated carbon, carbon aerogel, carbon nanotubes, MXene, etc.), and their adsorption mechanisms mainly rely on electrostatic interactions or physical adsorption, which are not suitable for Li. + Na + Mg 2+ The ability to distinguish between monovalent and polyvalent cations is limited. In salt lake brine systems, high concentrations of Na... + Mg 2+ The presence of it will seriously interfere with Li + The migration and adsorption of Li leads to the migration and adsorption of Li+ The enrichment efficiency is low and the selectivity is poor. Recent studies have attempted to introduce pseudocapacitive or intercalation electrode materials (such as TiO2, LiMn2O4, Li4Ti5O4). 12 (etc.) to improve selectivity, but their electrode preparation is complex, costly, and lacks stability, and most are based on native materials, which is not sustainable.

[0005] On the other hand, a large number of power batteries have entered their peak retirement period. Among retired lithium-ion batteries, nickel-cobalt-manganese (NCM) ternary cathode materials are the main rich source of metal resources. They have stable chemical composition, ordered layered lattice structure, and reversible lithium insertion / extraction characteristics. Traditional recycling methods are mostly hydrometallurgy (acid leaching-precipitation-extraction) or high-temperature roasting (reduction-leaching) to recover metal elements such as Ni, Co, and Mn. However, these processes are complex, energy-intensive, and difficult to treat waste liquid, and they fail to fully utilize the potential of NCM itself as a functional material. Summary of the Invention

[0006] The purpose of this invention is to provide a coated material and its preparation method, a composite electrode and its application, and a capacitive deionization lithium extraction system and method.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing a coated material from retired ternary cathode material, comprising the following steps:

[0009] The retired ternary cathode material was sequentially lithium-added and calcined to obtain a ternary cathode material with reconstructed crystal lattice.

[0010] A titanium source, a lithium source, a solvent, and a dispersion of a ternary cathode material with lattice reconstruction are mixed, and then subjected to liquid-phase reaction, drying, and sintering in sequence to obtain the coated material; the coated material is a ternary cathode material coated with a LiTiO2 layer.

[0011] Preferably, the retired ternary cathode material includes at least one of NCM111, NCM523, and NCM622;

[0012] The lithium replenishment process includes: mixing retired ternary cathode material and lithium source solution, and sequentially performing stirring, soaking, and hydrothermal reaction; the lithium source solution includes at least one of lithium hydroxide solution and lithium acetate solution; the concentration of the lithium source solution is 0.3~0.5 mol / L, and the ratio of retired ternary cathode material to lithium source solution is 1g:50~70mL;

[0013] The stirring and soaking time is 6-12 hours;

[0014] The hydrothermal reaction is carried out at a temperature of 160~200℃ for 2~6 hours.

[0015] The roasting temperature is 700~850℃, and the holding time is 2~4h; the roasting atmosphere is air.

[0016] Preferably, the titanium source includes at least one of tetrabutyl titanium, tetraisopropyl titanate, and tetraethyl titanate;

[0017] The lithium source includes at least one of lithium hydroxide, lithium carbonate, and lithium acetate;

[0018] The molar ratio of the titanium source to the lithium source is 1:1 to 1.05, and the mass ratio of the titanium source to the lattice-reconstructed ternary cathode material is 0.02:0.54 to 0.64, based on the amount of titanium and lithium.

[0019] The solid-liquid ratio of the dispersion of the ternary cathode material containing lattice reconstruction is 1g:10~15mL;

[0020] The solvent includes a mixture of ethanol and water; the volume ratio of ethanol to water in the mixture is 9~10:1.

[0021] The mixing process is as follows: after premixing the titanium source, lithium source and solvent, the resulting premixed liquid is added dropwise to the dispersion of the ternary cathode material containing lattice reconstruction under stirring conditions.

[0022] Preferably, the liquid-phase reaction is carried out under stirring conditions, and the stirring time is 3 hours;

[0023] The drying temperature is 70~90℃, and the time is 12~24h;

[0024] The sintering temperature is 700~850℃, the holding time is 2~4h, and the sintering is carried out in an air atmosphere.

[0025] The present invention also provides a coated material prepared by the method described above, wherein the coated material is a ternary cathode material coated with a LiTiO2 layer.

[0026] Preferably, the thickness of the LiTiO2 layer is 5~10nm.

[0027] The present invention also provides a composite electrode, comprising a current collector and an electrode material on the surface of the current collector, wherein the electrode material comprises an active material, a conductive agent and a binder, and the active material is the coating material described in the above technical solution.

[0028] The present invention also provides the application of the composite electrode described above in lithium batteries or capacitor deionization lithium extraction.

[0029] The present invention also provides a capacitive deionization lithium extraction system, wherein the working electrode of the capacitive deionization lithium extraction system is the composite electrode described in the above technical solution.

[0030] The present invention also provides a method for lithium extraction by capacitive deionization, which uses the capacitive deionization lithium extraction system described in the above technical solution.

[0031] This invention provides a method for preparing a coated material from retired ternary cathode material, comprising the following steps: sequentially subjecting the retired ternary cathode material to lithium supplementation and calcination to obtain a ternary cathode material with lattice reconstruction; mixing a titanium source, a lithium source, a solvent, and a dispersion of the ternary cathode material with lattice reconstruction, and sequentially performing a liquid-phase reaction, drying, and sintering to obtain the coated material; wherein the coated material is a LiTiO2 layer coated ternary cathode material.

[0032] This invention utilizes retired NCM cathode materials, modified with LiTiO2 (LTO) to form NCM@LTO coated materials, and then applies them to a capacitor deionization system to electrochemically drive the recovery of Li in brine from salt lakes. + The targeted enrichment of lithium is achieved through a technology that balances material reuse with lithium extraction functionalization. Microstructurally, the LTO layer provides stable Ti-O-Li bond sites and electrochemical pseudocapacitive behavior, forming a "selective lithium intercalation interface." Macroscopically, the capacitive deionization system allows for reversible adsorption and desorption through potential control. In terms of resource recycling, it enables the direct high-value utilization of retired battery materials and the green development of brine lake lithium resources. Specific beneficial effects include:

[0033] (1) Direct functional recycling of retired battery materials: For the first time, retired NCM cathode materials are transformed from the traditional metal smelting recycling route into a functional material reuse path, retaining their layered structure and reversible lithium insertion and extraction characteristics, which greatly simplifies the recycling process and reduces energy consumption.

[0034] (2) Interface regulation mechanism of LiTiO2 coating layer: After the introduction of LTO layer, a "Ti-O-Li" interface channel is formed on the NCM surface, which enhances the Li + Intercalation / deintercalation kinetics and effectively suppress other cations (such as Na) + Mg 2+ The LTO coating enhances selectivity through co-intercalation. This interface also imparts excellent cycling stability and chemical resistance to the electrode. The LTO coating inhibits the structural collapse and dissolution of the NCM material in high-salt environments, and the electrode retains over 90% capacity after more than 30 adsorption-desorption cycles.

[0035] (3) Electrochemical selective adsorption mechanism of composite electrode: This invention utilizes the synergistic effect of the pseudocapacitance and intercalation reaction of LTO to form an electrochemical selective adsorption mechanism: Li +Na is fixed to lattice sites through an intercalation reaction. + K + Plasma is difficult to penetrate due to the size-charge density mismatch, hindering the realization of Li in complex saline lake systems. + Targeted enrichment of Li. The composite electrode provided by this invention has highly selective lithium extraction performance; the NCM@LTO electrode is effective for the targeted enrichment of Li. + Li has preferential adsorption capacity + / Na + The selectivity coefficient is as high as 64 times, Li + / Na + The selectivity coefficient is close to 20 times.

[0036] (4) Green, reversible, and low-energy lithium extraction system: Compared with methods such as chemical precipitation, extraction, and membrane separation, this invention adopts low-voltage electrochemical drive, requires no chemical reagents, has low energy consumption, and the process is controllable. Electrode regeneration can be achieved through voltage reversal, eliminating the need for acid washing or high-temperature calcination. The lithium extraction process relies solely on low-voltage drive, requiring no chemical precipitants or organic extractants. The entire system does not generate secondary pollution, aligning with the direction of green chemical engineering and clean energy development. The material preparation process is based on mature battery processing and coating technologies, and the equipment is highly versatile, compatible with existing retired battery recycling systems and electrochemical separation devices, possessing excellent industrialization prospects.

[0037] (5) Significant synergistic effect of resource recycling and environment: This method solves two major problems at the same time: recycling of retired power battery resources and development of salt lake lithium resources, realizing a closed-loop recycling path of "from waste battery to salt lake lithium extraction", which is of great significance to promoting the sustainable supply of lithium resources. Attached Figure Description

[0038] Figure 1 Here is a SEM image of the positive electrode powder obtained in Example 1;

[0039] Figure 2 SEM image of the NCM material with lattice reconstruction obtained in Example 1;

[0040] Figure 3 The image shows the SEM image of NCM@LTO obtained in Example 1.

[0041] Figure 4 The XRD patterns of the lattice-reconstructed NCM material and NCM@LTO obtained in Example 1 are shown.

[0042] Figure 5 XPS characterization images of the lattice-reconstructed NCM material and NCM@LTO obtained in Example 1;

[0043] Figure 6The cyclic voltammetry curves of the NCM@LTO electrode in test example 2 in one mole of lithium chloride, sodium chloride and magnesium chloride solution are shown.

[0044] Figure 7 To test the lithium electroadsorption recovery capacity of the NCM@LTO electrode in Example 3 under different applied current densities;

[0045] Figure 8 To compare the cycle stability of the NCM electrode and the NCM@LTO electrode in Test Example 4;

[0046] Figure 9 To test the partition coefficient of the NCM@LTO electrode in Example 5 for different cations in the simulated salt lake brine;

[0047] Figure 10 This test was conducted to examine the gradual accumulation concentration changes of various ions in the electrolyte at the receiving end of the NCM@LTO electrode in Test Example 5. Detailed Implementation

[0048] This invention provides a method for preparing a coated material from retired ternary cathode material, comprising the following steps:

[0049] The retired ternary cathode material was sequentially lithium-added and calcined to obtain a ternary cathode material with reconstructed crystal lattice.

[0050] A titanium source, a lithium source, a solvent, and a dispersion of a ternary cathode material with lattice reconstruction are mixed, and then subjected to liquid-phase reaction, drying, and sintering in sequence to obtain the coated material; the coated material is a ternary cathode material coated with a LiTiO2 layer.

[0051] This invention involves sequentially replenishing lithium and calcining retired ternary cathode materials to obtain ternary cathode materials with reconstructed crystal lattice.

[0052] In this invention, the retired ternary cathode material preferably includes NCM111 (LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2), NCM523 (LiNi) 0.5 Co 0.2 Mn 0.3 O2) and NCM622 (LiNi 0.6 Co 0.2 Mn 0.2At least one of O2). The present invention does not specifically limit the source or process of obtaining the retired ternary cathode material; any method well known to those skilled in the art can be used. In a specific embodiment of the present invention, the process of obtaining the retired ternary cathode material preferably includes: discharging the battery to 0V under an inert atmosphere, disassembling the battery, and removing the cathode sheet; soaking the cathode sheet in N-methylpyrrolidone (1-Methyl-2-pyrrolidinone, NMP) for 24 hours to remove the binder, washing and drying to obtain cathode powder; calcining the cathode powder to remove residual carbon and organic matter; the calcination temperature is preferably 550~600℃, the holding time is preferably 3 hours, and the calcination is preferably carried out in an air atmosphere.

[0053] In this invention, the lithium replenishment process preferably includes: mixing retired ternary cathode material and lithium source solution, and sequentially performing stirring soaking and hydrothermal reaction; the lithium source solution preferably includes at least one of lithium hydroxide solution and lithium acetate solution; the concentration of the lithium source solution is preferably 0.3~0.5 mol / L, specifically 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L; the ratio of retired ternary cathode material to lithium source solution is preferably 1 g: 50~70 mL, specifically 1 g: 60 mol / L; the stirring soaking time is preferably 6~12 h, specifically 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, or 12 h; the hydrothermal reaction temperature is preferably 160~200℃, specifically 160℃, 170℃, 180℃, 190℃, or 200℃; and the time is preferably 2~6 h, specifically 2 h, 3 h, 4 h, 5 h, or 6 h. In this invention, the roasting temperature is 700~850℃, specifically 700℃, 750℃, 800℃, or 850℃; the holding time is 2~4 hours, specifically 3 hours; and the roasting atmosphere is preferably air.

[0054] In this invention, the material structure can be regenerated and the layered Li(Ni) structure restored by combining lithium replenishment and calcination. x Co y Mn z O2 crystal lattice structure.

[0055] After obtaining the ternary cathode material with lattice reconstruction, the present invention mixes a titanium source, a lithium source, a solvent and a dispersion of the ternary cathode material with lattice reconstruction, and sequentially performs liquid-phase reaction, drying and sintering to obtain the coated material.

[0056] In this invention, the titanium source preferably includes at least one selected from tetrabutyl titanium, tetraisopropyl titanate, and tetraethyl titanate; the lithium source preferably includes at least one selected from lithium hydroxide, lithium carbonate, and lithium acetate; the molar ratio of the titanium source to the lithium source, based on the amount of titanium and lithium, is preferably 1:1 to 1.05; the mass ratio of the titanium source to the lattice-reconstructed ternary cathode material is preferably 0.02:0.54 to 0.64; the solid-liquid ratio of the dispersion containing the lattice-reconstructed ternary cathode material is preferably 1 g:10 to 15 mL; and the solvent of the dispersion is preferably deionized water. In this invention, the solvent preferably includes a mixed solvent of ethanol and water; the volume ratio of ethanol to water in the mixed solvent is preferably 9 to 10:1. This invention does not impose a special limitation on the amount of solvent used, as long as it ensures uniform dispersion of all substances.

[0057] In this invention, the mixing process is preferably as follows: after premixing the titanium source, lithium source and solvent, the resulting premixed liquid is added dropwise to the dispersion of the ternary cathode material containing lattice reconstruction under stirring conditions; the dropwise addition rate is preferably 5~8 mL / min, specifically 5 mL / min, 6 mL / min, 7 mL / min, or 8 mL / min.

[0058] In this invention, the liquid-phase reaction is preferably carried out under stirring conditions, and the stirring time is preferably 3 hours (referring to the reaction time after the droplet addition is completed). In this invention, the drying temperature is preferably 70~90℃, and the drying time is preferably 12~24 hours; the solvent can be removed by drying to obtain a dry powder.

[0059] In this invention, the sintering temperature is preferably 700~850℃, specifically 700℃, 750℃, 800℃, or 850℃; the holding time is preferably 2~4h, specifically 3h; and the sintering is preferably carried out in an air atmosphere.

[0060] This invention also provides a coated material prepared by the method described in the above technical solution, wherein the coated material is a ternary cathode material coated with a LiTiO2 layer. In this invention, the thickness of the LiTiO2 layer is preferably 5-10 nm. In this invention, the thickness of the LiTiO2 layer is controlled to ensure that stable lithium insertion sites are provided without affecting the electron conduction path.

[0061] The present invention also provides a composite electrode, comprising a current collector and an electrode material on the surface of the current collector, wherein the electrode material comprises an active material, a conductive agent and a binder, and the active material is the coating material described in the above technical solution.

[0062] In this invention, the conductive agent comprises at least one of conductive carbon black and conductive graphite; the binder preferably comprises PVDF; the mass ratio of the active material, conductive agent, and binder is preferably 8:1:1. In this invention, the current collector preferably comprises at least one of titanium foil, carbon paper, and carbon cloth. In this invention, the loading of the active material on the composite electrode is preferably 5 mg / cm³. 2 .

[0063] In this invention, the preferred method for preparing the composite electrode includes: mixing an active material, a conductive agent, a binder, and a solvent to obtain a slurry; coating the slurry onto the current collector; and sequentially drying and pressing. In this invention, the solvent preferably includes NMP; the amount of solvent used is not particularly limited, and any solvent well-known to those skilled in the art can be used. In this invention, the coating thickness is preferably 100 μm. In this invention, the drying temperature is preferably 80°C, and the drying time is preferably 12 h; the pressing pressure is preferably 10 MPa, and the pressing time is preferably 2 min. In this invention, the specific surface area of ​​the composite electrode is preferably 25 m². 2 / g, with a pore size preferably of 10~50nm. In this invention, the composite electrode possesses excellent ion transport channels.

[0064] The present invention also provides the application of the composite electrode described above in lithium batteries or capacitor deionization lithium extraction.

[0065] The present invention also provides a capacitive deionization lithium extraction system, wherein the working electrode of the capacitive deionization lithium extraction system is the composite electrode described in the above technical solution.

[0066] In this invention, the reference electrode of the capacitive deionization lithium extraction system is preferably an Ag / AgCl electrode, the counter electrode is preferably a platinum sheet electrode or an activated carbon cloth electrode, and the separator is preferably a polypropylene separator. This invention does not impose any particular limitation on the construction method of the capacitive deionization lithium extraction system; any method well-known to those skilled in the art can be used.

[0067] This invention also provides a capacitive deionization lithium extraction method, which employs the capacitive deionization lithium extraction system described in the above technical solution. In this invention, the preferred conditions for the capacitive deionization lithium extraction method include: an influent flow rate of 15-40 mL / min and an applied electric field of 10-30 mA·g. -1 The extraction time is 0.2~0.5 hours. In this invention, during the lithium extraction process, a low current is applied to allow the Li in the salt lake brine to be extracted. + Selectively migrate and adsorb onto the working electrode.

[0068] In this invention, after lithium extraction using the capacitive deionization method, a desorption process is preferably also included. In this invention, the desorption stage achieves lithium extraction through reverse voltage or short-circuit discharge. + The lithium is released, thus obtaining a lithium-rich solution. The system provided by this invention can be cyclically operated, enabling continuous lithium extraction.

[0069] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0070] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0071] Example 1

[0072] Retired electric vehicle lithium-ion batteries (model NCM523) were selected as raw materials. After being discharged to 0V in an inert atmosphere, the batteries were disassembled and the positive electrode sheets were removed. The PVDF binder was removed by soaking in N-methylpyrrolidone for 24 hours. After washing and drying, the positive electrode powder was obtained. The positive electrode powder was calcined at 600℃ for 3 hours in air atmosphere to obtain the retired ternary positive electrode material.

[0073] 1g of the decommissioned ternary cathode material obtained above and 60mL of 0.3mol / L LiOH solution were placed in a hydrothermal reactor. The mixture was first stirred and soaked for 12h, then hydrothermally reacted at 180℃ for 4h. After lithium supplementation, the mixture was calcined at 700℃ for 2h in air atmosphere to obtain the NCM material with lattice reconstruction.

[0074] Tetrabutyl titanium and lithium carbonate were dissolved in an ethanol-deionized water (volume ratio 9:1) mixture at a Ti:Li molar ratio of 1:1. Under stirring, the solution was slowly added dropwise at a rate of 5 mL / min to an aqueous dispersion of NCM material containing lattice reconstruction (where the solid-liquid ratio of the dispersion was 1 g:10 mL, and the mass ratio of tetrabutyl titanium to NCM material was 0.02:0.54). The mixture was stirred for 3 h. Then, it was dried at 80 °C for 12 h to obtain a dry powder. The dried powder was then kept at 850 °C for 2 h in air to obtain LiTiO2-coated NCM (denoted as NCM@LTO).

[0075] NCM@LTO, Super P conductive carbon black, and PVDF were mixed in a mass ratio of 8:1:1, and NMP was added to form a uniform slurry. The slurry was then uniformly coated onto conductive titanium foil using a doctor blade coating method to a thickness of approximately 100 μm. After vacuum drying at 80 °C for 12 h, the electrode was pressed into a sheet under a pressure of 10 MPa for 2 min to obtain the composite electrode (denoted as NCM@LTO composite electrode, with an electrode specific surface area (BET) of approximately 25 m²). 2 / g, with pore sizes concentrated in the 10~50nm range, and the loading of active material on the composite electrode is 5mg / cm³. 2 ).

[0076] Performance testing

[0077] Test Example 1

[0078] Figure 1 The image shows the SEM image of the positive electrode powder obtained in Example 1. Figure 1 It can be seen that the particles are of different sizes and have rough, uneven surfaces, and even nanoscale flocculent or granular deposits are visible.

[0079] Figure 2 The image shows a SEM image of the NCM material with lattice reconstruction obtained in Example 1. Figure 2 It can be seen that it repaired the surface rock salt phase, and the NCM particles after lattice reconstruction have a clean, smooth and dense surface.

[0080] Figure 3 The image shows the SEM image of NCM@LTO obtained in Example 1. Figure 3 It can be seen that the main structure of NCM remains intact and has not been damaged by the coating process; the LTO coating layer forms a uniform, dense and continuous nanofilm structure; the interface has good bonding and a certain roughness, which is beneficial to improving electrochemical activity.

[0081] Figure 4 The XRD patterns of the lattice-reconstructed NCM material and NCM@LTO obtained in Example 1 are shown below. Figure 4 It can be seen that the XRD pattern of the NCM material after lithium replenishment exhibits a typical α-NaFeO2 layered structure (space group R-3m), with characteristic diffraction peaks located near 18°, 37°, 44°, 48°, and 65° (denoted by 2θ), corresponding to the (003), (101), (104), (105), and (110) crystal planes, respectively. The sharp peaks and small half-widths indicate that the NCM maintains high crystal integrity after lithium replenishment. The XRD pattern of the coated NCM@LTO material maintains the same layered diffraction characteristics as the original NCM, with no shift in the positions of the main peaks. Only slight changes in peak intensity and peak width are observed, indicating that the low-temperature coating process did not destroy the main crystal lattice framework of the NCM.

[0082] Figure 5 The XPS characterization images of the lattice-reconstructed NCM material and NCM@LTO obtained in Example 1 show that the Ti 2p peak of the uncoated NCM is almost invisible, only showing background signal. The coated NCM@LTO material clearly exhibits the Ti 2p peak. 3 / 2 With Ti 2p 1 / 2 The peaks are located at 458.5–459.2 eV and 464.3–465.0 eV, respectively, corresponding to Ti 4+ The characteristic binding energy was demonstrated. This result proves that the Ti-based coating was successfully formed on the NCM surface. The coating can significantly improve the chemical environment of the NCM surface, reduce defects, enhance stability, and inhibit metal dissolution.

[0083] Test Example 2

[0084] The composite electrode obtained in Example 1 was characterized.

[0085] The pseudocapacitance and lithium intercalation potential window were characterized using an electrochemical workstation in a three-electrode system (working electrode: NCM@LTO composite electrode; reference electrode: Ag / AgCl; counter electrode: platinum sheet electrode). The potential range was 0–1.1 V, and the scan rate was 5 mV·s. -1 Cyclic voltammetry curves were performed in 1 mol / L lithium chloride, sodium chloride, and magnesium chloride solutions, respectively.

[0086] The results are as follows Figure 6 As shown, in a 1 mol / L lithium chloride solution, the NCM@LTO electrode exhibits the most typical and strong reversible lithium insertion / deintercalation peak pair. A significant oxidation peak is observed in the 0.55–0.65 V (oxidation region), corresponding to Li... + Deintercalation from the NCM@LTO interlayer structure; a matching reduction peak appears at 0.4~0.5V (reduction region), representing Li + The reversible intercalation reaction is observed; sharp peaks, high peak currents, and small inter-peak potential differences (ΔE) indicate rapid lithium intercalation kinetics. Furthermore, the CV curves exhibit a broad and continuous pseudocapacitive region, reflecting the rapid intercalation of Li. + Rapid surface adsorption / reaction behavior was observed in the LiTiO2 thin layer. The overall current density was significantly higher than that in sodium chloride and magnesium chloride solutions, indicating that this electrode material exhibits rapid adsorption / reaction behavior on LiTiO2. + The interface activity is optimal.

[0087] NCM@LTO electrodes exhibit significantly higher performance than Na in lithium chloride. + Mg 2+ The NCM@LTO composite electrode exhibits excellent electrochemical activity and reversible intercalation behavior, characterized by clear peaks, high peak currents, and strong reversibility. The test results directly confirm the electrochemical activity and reversible intercalation behavior of Li. +Its selective adsorption / intercalation ability is superior to that of Na. + and Mg 2+ This is one of the key mechanisms underlying the selective lithium extraction from salt lake systems in this invention.

[0088] Test Example 3

[0089] Construction and operation of capacitive deionization (CDI) lithium extraction system

[0090] The NCM@LTO electrode obtained in Example 1 was used as the working electrode, and the activated carbon electrode was used as the counter electrode, with a spacing of 0.5 mm, separated by a polypropylene membrane; first, pure 1 g·L -1 We used lithium chloride solution to test the lithium ion recovery capability of the NCM@LTO electrode under different current conditions.

[0091] At room temperature (25℃), at 10~30 mA·g -1 The system was run under constant current until the voltage of the CDI system reached 1.2V, and the changes in ion concentration in the solution were recorded. During the desorption phase, a reverse constant current (10~30 mA·g) was used. -1 The system operates until the voltage of the CDI system reaches 1.0V, at which point the lithium-rich liquid is released.

[0092] The lithium extraction efficiency of NCM@LTO under different current densities is as follows: Figure 7 As shown in the figure. This figure illustrates the NCM@LTO composite electrode at 10, 20, and 30 mA·g. -1 Electroadsorption recovery performance at three current densities. The overall trend shows that the higher the current density, the lower the lithium recovery capacity, but the decrease is relatively mild, reflecting the excellent rate stability of the electrode. At 10 mA·g... -1 At this time, the electrode exhibited the highest lithium recovery capacity, approximately 26–27 mg·g. -1 This indicates that at lower currents, ion migration and intercalation processes are more complete, and the electrode can approach its intrinsic adsorption / intercalation capacity. The current was increased to 20 mA·g. -1 Afterwards, the volume decreased slightly to approximately 24-25 mg / g. -1 This indicates that the electrode structure can still maintain a high lithium-ion adsorption efficiency, even at 30 mA·g. -1 Even at higher current densities, the capacity remains at 20~21 mg·g. -1The limited decrease in lithium adsorption capacity indicates that the NCM@LTO composite electrode effectively reduces interfacial impedance and alleviates diffusion limitations under high-rate conditions. Error bars show good repeatability between different tests, further demonstrating the structural stability and reproducibility of the reaction process of the composite electrode. Overall, these results demonstrate that the NCM@LTO composite electrode not only possesses high lithium adsorption capacity at low current densities but also maintains good lithium recovery performance at high current densities, making it suitable for rapid electroadsorption recovery scenarios and indicating its practical application potential in large-scale lithium resource recovery systems with high rate requirements.

[0093] Test Example 4

[0094] Comparative experiment

[0095] The NCM material with lattice reconstruction obtained in Example 1 was used as the active material to prepare an electrode according to the preparation method of NCM@LTO composite electrode, which is denoted as NCM electrode;

[0096] NCM electrode and NCM@LTO composite electrode were used as working electrodes, respectively, and activated carbon cloth electrode was used as counter electrode, with a spacing of 0.5 mm, separated by a polypropylene diaphragm; first, pure 1 g·L -1 Lithium chloride solution, at 30 mA·g -1 The current density was used to test and compare the cycle stability of NCM electrode and NCM@LTO composite electrode during lithium recovery.

[0097] like Figure 8 As shown, during the first cycle, the lithium recovery capacity of the NCM@LTO composite electrode was significantly higher than that of the NCM electrode. Specifically, the initial capacity of the NCM@LTO composite electrode reached 23.4 mg·g⁻¹. -1 The initial capacity of the NCM electrode was only about 19.7 mg·g. -1 This indicates that the LTO coating effectively enhances the initial lithium-ion insertion / extraction capability of the material. After 30 complete cycles, the NCM@LTO composite electrode retained more than 90% of its capacity, while the NCM electrode retained less than 70%, fully demonstrating the stability advantage of the material of this invention during long-term cycling.

[0098] The LTO coating effectively suppresses side reactions between the NCM material and the electrolyte, reducing the increase in interfacial impedance. The core-shell structure design mitigates the volume change of the NCM material during cycling, preventing the pulverization and shedding of the active material. The LTO layer provides additional lithium-ion transport channels, improving the material's kinetic properties. Through the material structure design and preparation method provided in this invention, the obtained NCM@LTO composite material can effectively improve lithium recovery capacity and significantly enhance its electrochemical stability during long-term cycling, demonstrating significant industrial application value and promising prospects.

[0099] Test Example 5

[0100] Lithium extraction verification from raw salt lake water

[0101] A capacitive deionization lithium extraction system was constructed using an NCM@LTO composite electrode as the working electrode and an activated carbon cloth electrode as the counter electrode, with a spacing of 0.5 mm and separated by a polypropylene membrane.

[0102] To verify practical feasibility, a simulation of the brine from the Xitaijinaier Salt Lake in Qinghai (Li + 0.1 g / L, Na + 102.4 g / L, Mg 2 + 15.4 g / L, K + 8.5 g / L, Ca 2+ The NCM@LTO electrode was tested at 0.2 g / L. During a lithium extraction process, the partition coefficient of multiple coexisting ions in a simulated salt lake solution was measured. K d Comparison Figure 9 As shown. The results clearly demonstrate that the electrode material is effective for Li + Its adsorption / intercalation capacity is far higher than that of other coexisting ions. First, Li + The partition coefficient is as high as approximately 3200 mL·g -1 The order of magnitude is 1-2 orders of magnitude higher than that of other ions, indicating that the electrode is effective against Li. + It possesses extremely strong affinity and preferential embedding ability. This remarkable... K d The difference means that the electrode can still effectively enrich Li in a competitive and complex electrolyte environment. + This is a key foundation for achieving highly selective lithium extraction. In contrast, Na... + and K + of K d The value is only in the tens to hundreds of mL·g -1 Within the range; Mg 2+ and Ca 2+ of K d Although slightly higher, it's only at the hundred-level, similar to Li. + There is still a gap of at least one order of magnitude compared to the former. Low-valence cations (Na₂) + K + ) and high-valence hard acid-base ions (Mg 2+ Ca 2+None of the samples showed a significant adsorption trend, indicating that the adsorption preference of NCM@LTO is not simply controlled by charge or hydration energy, but is related to the reversible lithium-ion insertion channels in the material structure, surface charge regulation, and the quasi-sieving effect of the LTO coating layer. Overall, this figure clearly demonstrates that NCM@LTO materials have excellent lithium selectivity in the simulated highly competitive ion environment of a salt lake. Its partition coefficient advantage indicates that the material has extremely strong selective lithium extraction potential in the adsorption-capacitive deionization-regeneration cycle, providing crucial quantitative evidence for its engineering applications.

[0103] After multiple electrochemical lithium extraction cycles, the gradual accumulation concentration changes of various ions in the receiving electrolyte are as follows: Figure 10 As shown. Li + The concentration increases rapidly and linearly with the number of cycles, starting from approximately 30 mL / g in the first cycle. -1 Gradually increase to 100 mL·g in the 5th cycle. -1 220 mL·g in the 10th cycle -1 Finally, it reached nearly 360 mL·g on the 15th lap. -1 This continuously increasing trend indicates that the electrode can effectively release the enriched Li in each cycle. + This demonstrates that the material possesses stable and reproducible reversible intercalation / deintercalation capabilities. The linear growth characteristic indicates that the electrode structure did not exhibit significant degradation, and the interfacial reactions and kinetics remained well maintained. In contrast, Na... + K + Mg 2+ and Ca 2+ The concentration remained almost constant at 0–15 mL·g throughout the cycle. -1 The levels of these ions are low and the variation is minimal. This indicates that the material exhibits almost no adsorption behavior for these competing ions; even under multiple cycles, these ions do not accumulate or release significantly. The material's selectivity stems from the NCM and LTO's preference for intercalation to monovalent small-radius ions, and the further enhancement of the Li by the NCM@LTO composite structure after interface modification. + The transmission channel and interface affinity.

[0104] Overall, the figure clearly demonstrates the effect of the NCM@LTO electrode on Li + Its high selectivity and excellent cycling stability provide key evidence for achieving efficient lithium recovery in complex water systems containing multiple competing ions.

[0105] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A capacitor-based deionization lithium extraction system, characterized in that, The working electrode of the capacitor deionization lithium extraction system is a composite electrode. The composite electrode includes a current collector and an electrode material on the surface of the current collector. The electrode material includes an active material, a conductive agent, and a binder. The active material is a coating material. The preparation method of the coating material includes the following steps: The retired ternary cathode material was sequentially lithium-added and calcined to obtain a ternary cathode material with reconstructed crystal lattice. A titanium source, a lithium source, a solvent, and a dispersion of a ternary cathode material with lattice reconstruction are mixed, and then subjected to liquid-phase reaction, drying, and sintering in sequence to obtain the coated material; the coated material is a ternary cathode material coated with a LiTiO2 layer.

2. The capacitor deionization lithium extraction system according to claim 1, characterized in that, The retired ternary cathode material includes at least one of NCM111, NCM523 and NCM622; The lithium replenishment process includes: mixing retired ternary cathode material and lithium source solution, and sequentially performing stirring, soaking, and hydrothermal reaction; the lithium source solution includes at least one of lithium hydroxide solution and lithium acetate solution; the concentration of the lithium source solution is 0.3~0.5 mol / L, and the ratio of retired ternary cathode material to lithium source solution is 1g:50~70mL; The stirring and soaking time is 6-12 hours; The hydrothermal reaction is carried out at a temperature of 160~200℃ for 2~6 hours. The roasting temperature is 700~850℃, and the holding time is 2~4h; the roasting atmosphere is air.

3. The capacitor deionization lithium extraction system according to claim 1, characterized in that, The titanium source includes at least one of tetrabutyl titanium, tetraisopropyl titanate, and tetraethyl titanate. The lithium source includes at least one of lithium hydroxide, lithium carbonate, and lithium acetate; The molar ratio of the titanium source to the lithium source is 1:1 to 1.05, and the mass ratio of the titanium source to the lattice-reconstructed ternary cathode material is 0.02:0.54 to 0.64, based on the amount of titanium and lithium. The solid-liquid ratio of the dispersion of the ternary cathode material containing lattice reconstruction is 1g:10~15mL; The solvent includes a mixture of ethanol and water; the volume ratio of ethanol to water in the mixture is 9~10:

1. The mixing process is as follows: after premixing the titanium source, lithium source and solvent, the resulting premixed liquid is added dropwise to the dispersion of the ternary cathode material containing lattice reconstruction under stirring conditions.

4. The capacitive deionization lithium extraction system according to claim 1 or 3, characterized in that, The liquid-phase reaction is carried out under stirring conditions for 3 hours; The drying temperature is 70~90℃, and the time is 12~24h; The sintering temperature is 700~850℃, the holding time is 2~4h, and the sintering is carried out in an air atmosphere.

5. The capacitor deionization lithium extraction system according to claim 1, characterized in that, The thickness of the LiTiO2 layer is 5~10nm.

6. A method for lithium extraction by capacitive deionization, characterized in that, The process is carried out using the capacitive deionization lithium extraction system described in any one of claims 1 to 5.

Images