Electrode, preparation method thereof and lithium extraction method

Abstract

The invention relates to the technical field of electrochemistry, in particular to an electrode, a preparation method thereof and a lithium extraction method. The preparation method of the electrode comprises the following steps that lithium manganate and terbium salt are calcined to obtain a first active substance, the first active substance is LiMn2-XTbXO4, and X is larger than or equal to 0.005 and smaller than or equal to 0.02; stirring the first active material, the conductive agent, the binder and the solvent to obtain electrode slurry; covering a graphite sheet with the electrode slurry, and drying to obtain a pre-electrode; in a lithium removal three-electrode system, the pre-electrode is used as a first working electrode, voltage is applied to the first working electrode, so that lithium ions in the first active substance are removed to form a second active substance with a lithium vacancy, and the electrode is obtained. The method provided by the embodiment of the invention is high in process controllability and simple, and the cycling stability of the second active substance in the obtained electrode and the selectivity to Li < + > are relatively excellent.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrode and its preparation method and lithium extraction method. Background Technology

[0002] Lithium is a core material for new energy vehicles and energy storage systems, and its demand is growing rapidly year by year. my country has abundant lithium resources, but they mainly exist in the form of salt lake brines and ores. During lithium ore processing, a large amount of lithium-containing waste is generated, and the leachate from this waste has a low lithium concentration and contains a high concentration of sodium. + K + Mg 2+ Ca 2+ Due to impurity ions, traditional chemical precipitation methods are difficult to achieve highly selective lithium extraction.

[0003] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of protection of this application. Summary of the Invention

[0004] This application provides an electrode and its preparation method, as well as a lithium extraction method, to solve or alleviate one or more of the technical problems mentioned above.

[0005] A first aspect of this application provides a method for preparing an electrode, comprising the following steps: Lithium manganese oxide and terbium salt are calcined to obtain a first active material, which is LiMn. 2-x Tb X O4, 0.005≤X≤0.02; The first active material, conductive agent, binder and solvent are stirred to obtain electrode slurry; The electrode slurry is coated onto a graphite sheet and dried to obtain a pre-electrode; In the lithium removal three-electrode system, the pre-electrode is used as the first working electrode. A voltage is applied to the first working electrode to remove lithium ions from the first active material to form a second active material with lithium vacancies, thus obtaining the electrode.

[0006] The method and process described in this application are highly controllable and simple. The obtained electrode, by doping terbium ions into the stable spinel structure of lithium manganese oxide, effectively suppresses the Jahn-Teller effect and manganese dissolution, significantly improving the cycle stability of the second active material in the electrode and its resistance to Li. + This electrode exhibits high selectivity and is particularly suitable for lithium extraction from complex systems such as lithium slag leachate and salt lake brine.

[0007] Specifically, rare earth elements replace part of Mn 3+The subsequent generation of lattice stress restricts local distortion of the Mn-O bonds, suppressing C-axis elongation and structural collapse caused by the Jahn-Teller effect; after terbium occupies the octahedral sites of lithium manganese oxide, it reduces the surface Mn content. 3+ The ratio reduces the disproportionation reaction, that is, it reduces the reaction 2Mn 3+ →Mn 2+ +Mn 4+ The process of Mn leads to the 2+ Reduced dissolution significantly improves the cycling stability of the second active substance and its resistance to Li. + The method improves selectivity by adjusting electrochemical parameters to control the amount of lithium removal, resulting in a higher concentration of lithium vacancies. These uniformly distributed lithium vacancies serve as channels for lithium-ion transport, facilitating lithium extraction from lithium-containing solutions. In summary, this method is simpler, and the second active material in the electrode has uniformly doped terbium and uniformly distributed lithium vacancies, thus improving the electrode's lithium extraction performance in complex systems. This allows the electrode to be used for lithium extraction from complex systems such as lithium slag leachate and brine from salt lakes.

[0008] According to embodiments of this application, the mass ratio of lithium manganese oxide to terbium salt is 1:(0.013-0.052); the mass ratio of the first active material, the conductive agent, the binder, and the solvent is 8:(0.5-1.5):(0.5-2.0):(35-50); the terbium salt includes at least one of terbium nitrate, terbium oxide, and terbium acetate; the conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; and the solvent includes N-methylpyrrolidone.

[0009] According to an embodiment of this application, the calcination temperature is 600℃-1000℃; the stirring time is 12h-20h; and the stirring speed is 600rpm-1000rpm.

[0010] According to an embodiment of this application, the covering method includes coating; the areal density of the pre-electrode is 0.5 mg / cm³. 2 -2.7mg / cm 2 .

[0011] According to an embodiment of this application, the drying is carried out under vacuum conditions, the drying temperature is 65℃-110℃, and the drying time is 8h-14h.

[0012] According to an embodiment of this application, the delithiation three-electrode system further includes: a first reference electrode comprising a silver electrode and / or a silver chloride electrode; a first pair of electrodes comprising a silver sheet electrode; and an electrolyte comprising a lithium salt solution with a concentration of 0.05 mol / L to 1 mol / L, wherein the lithium salt comprises at least one of lithium chloride, lithium sulfate, lithium nitrate, and lithium acetate.

[0013] According to an embodiment of this application, the voltage is 0.6V-1V, and the voltage application time is 1h-3h.

[0014] A second aspect of this application provides an electrode obtained using the preparation method described in the first aspect.

[0015] A third aspect of this application provides a lithium extraction method, comprising the following steps: The second electrode is placed in a lithium-containing solution; In the lithium extraction three-electrode system, the electrode is used as the second working electrode, and a reduction potential is applied to the electrode to insert lithium into the second active material, thereby obtaining a lithium-intercalated electrode.

[0016] The lithium extraction method of this application embodiment uses an electrode with lithium vacancies as the working electrode and performs electrochemical lithium intercalation at a controllable reduction potential to achieve efficient, highly selective, and reversible extraction of lithium ions from complex lithium-containing solutions.

[0017] According to an embodiment of this application, the lithium extraction method further includes: applying an oxidation potential to the lithium intercalation electrode in a desorption three-electrode system to extract lithium from the lithium intercalation electrode.

[0018] According to embodiments of this application, the lithium-containing solution includes lithium slag leachate, salt lake brine, or lithium-containing wastewater, wherein the lithium-containing solution contains Li... + The concentration is 10 mg / L-200 mg / L, and the pH is 2.0-11.0. Attached Figure Description

[0019] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0020] Figure 1 This is a morphology diagram of the second active material on the LTMO-1 electrode in Example 1; Figure 2 This is the elemental distribution diagram of the energy dispersive X-ray spectroscopy (EDS) of the second active material on the LTMO-1 electrode in Example 1; Figure 3 These are X-ray diffraction patterns of the second active material in the electrodes of Examples 1-3; Figure 4 This is a cyclic voltammetry curve of the LTMO-1 electrode in Example 1 at different scan rates; Figure 5 This is a constant current discharge curve of the electrode in Example 1; Figure 6 This is a bar chart of the discharge capacity of the electrode in Example 1 after 6 consecutive cycles; Figure 7 This is a cyclic voltammetry curve of the electrode prepared in Example 1 under different electrolytes; Figure 8 This is a constant current discharge curve of the electrode prepared in Example 1 in different electrolytes; Figure 9 These are cyclic voltammetry results of the electrode prepared in Example 1 at different pH values; Figure 10 This is a graph showing the lithium extraction capacity versus time for the electrodes of Examples 1-3 and Comparative Example 1 over 120 min. Figure 11 This is a graph showing the relationship between the electrode lithium extraction capacity and lithium concentration for Examples 1-3 and Comparative Example 1; Figure 12 This is a graph showing the relationship between the electrode of Example 1 and the concentration of each ion after lithium extraction, under different cycles in a simulated lithium slag leachate. Detailed Implementation

[0021] The embodiments of this application are described in detail below, with examples of the embodiments shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0022] In this application, when numerical intervals (i.e., numerical ranges) are involved, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0023] Spinel-type lithium manganese oxide (LiMn2O4, LMO) is due to its three-dimensional Li... +With its diffusion channels, high theoretical capacity (148 mAh / g), and low cost, LMO has become one of the most promising lithium-ion sieve electrode materials. The lithium extraction mechanism of LMO is based on reversible lithium-ion insertion and extraction reactions. However, traditional LMO electrodes suffer from poor cycle stability; during repeated charge-discharge processes, Mn... 3+ The Jahn-Teller effect easily occurs, leading to lattice distortion and causing the structure of active materials to collapse; at the same time, Mn 3+ A disproportionation reaction occurs to generate soluble Mn. 2+ Dissolution leads to rapid capacity decay. The LMO electrode retains only about 75% of its capacity after 6 cycles. The LMO electrode also suffers from insufficient ion selectivity; in high-salt, multi-ion coexisting systems, Mg... 2+ Ca 2+ The hydrated ionic radius of divalent ions and Li + Close to, easy to be with Li + Competitive adsorption occurs, reducing the selectivity and purity of lithium extraction.

[0024] Accordingly, a first aspect of the present application provides a method for preparing an electrode, comprising the following steps: (1) Lithium manganese oxide and terbium salt are calcined to obtain a first active material, wherein the first active material is LiMn. 2-X Tb X O4, 0.005≤X≤0.02; (2) Stir the first active material, conductive agent, binder and solvent to obtain electrode slurry; (3) The electrode slurry is coated onto a graphite sheet and dried to obtain a pre-electrode; (4) In the delithiation three-electrode system, the pre-electrode is used as the first working electrode, and a voltage is applied to the first working electrode to cause lithium ions in the first active material to be delithiated to form a second active material with lithium vacancies, thereby obtaining the electrode.

[0025] The method and process described in this application are highly controllable and simple. The obtained electrode, by doping terbium ions into the stable spinel structure of lithium manganese oxide, effectively suppresses the Jahn-Teller effect and manganese dissolution, significantly improving the cycle stability of the second active material in the electrode and its resistance to Li. + This electrode exhibits high selectivity and is particularly suitable for lithium extraction from complex systems such as lithium slag leachate and salt lake brine.

[0026] Specifically, rare earth elements replace part of Mn 3+ The subsequent generation of lattice stress restricts local distortion of the Mn-O bonds, suppressing C-axis elongation and structural collapse caused by the Jahn-Teller effect; after terbium occupies the octahedral sites of lithium manganese oxide, it reduces the surface Mn content. 3+The ratio reduces the disproportionation reaction, that is, it reduces the reaction 2Mn 3+ →Mn 2+ +Mn 4+ The process of Mn leads to the 2+ Reduced dissolution significantly improves the cycling stability of the second active substance and its resistance to Li. + The method improves selectivity by adjusting electrochemical parameters to control the amount of lithium removal, resulting in a higher concentration of lithium vacancies. These uniformly distributed lithium vacancies serve as channels for lithium-ion transport, facilitating lithium extraction from lithium-containing solutions. In summary, this method is simpler, and the second active material in the electrode has uniformly doped terbium and uniformly distributed lithium vacancies, thus improving electrode consistency and enabling the electrode to be used for lithium extraction from complex systems such as lithium slag leachate and salt lake brine.

[0027] According to an embodiment of this application, lithium manganese oxide and terbium salt are calcined to obtain a first active material, wherein the first active material is LiMn. 2-X Tb X O4, 0.005≤X≤0.02. In this step, terbium is incorporated into the octahedral lattice of lithium manganese oxide through high-temperature solid-state doping, forming LiMn with controllable stoichiometry and a complete crystal structure. 2-X Tb X O4 powder.

[0028] In some embodiments, lithium manganese oxide serves as the matrix material, forming the basis for lithium intercalation and deintercalation in the electrode; terbium ions from the terbium salt enter the lattice of lithium manganese oxide, achieving doping. Optionally, the calcination temperature is 600℃-1000℃, such as 600℃, 700℃, 780℃, 800℃, 900℃, 1000℃, etc. This further enhances the doping effect, yielding the first active material.

[0029] In some embodiments, LiMn 2-X Tb X In O4, 0.005 ≤ X ≤ 0.02, for example, 0.005, 0.01, 0.02, etc. X within the aforementioned range can be obtained by substituting Mn³. + The introduction of lattice prestress effectively suppresses Jahn-Teller distortion and manganese ion dissolution, significantly enhancing the structural stability and cycle life of the second active material in complex electrolytes; it also ensures that the rapid diffusion of lithium ions in the spinel framework is not hindered, maintaining the high ionic conductivity of the electrode.

[0030] In some embodiments, the mass ratio of lithium manganese oxide to terbium salt is 1:(0.013-0.052).

[0031] According to an embodiment of this application, a first active material, a conductive agent, a binder, and a solvent are stirred to obtain an electrode slurry.

[0032] In some embodiments, a conductive agent is used to improve the electronic conductivity of the electrode, promoting uniform current distribution during lithium insertion / extraction; a binder is used to fix the first active material onto the graphite sheet. Optionally, the mass ratio of the first active material, the conductive agent, the binder, and the solvent is 8:(0.5-1.5):(0.5-2.0):(35-50). Thus, the aforementioned formulation balances electrode conductivity, structural strength, doping effect, and process operability, making it suitable for the preparation of highly efficient and selective lithium extraction electrodes.

[0033] Optionally, the terbium salt includes at least one of terbium nitrate, terbium oxide, and terbium acetate.

[0034] Optionally, the conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; wherein the carbon black includes acetylene black.

[0035] Optionally, the solvent includes N-methylpyrrolidone.

[0036] In some embodiments, the stirring time is 12h-20h, such as 12h, 15h, 18h, 20h, etc. The stirring speed is 600rpm-1000rpm, such as 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, etc. This improves the uniformity of the electrode slurry.

[0037] According to an embodiment of this application, the electrode slurry is coated onto a graphite sheet and dried to obtain a pre-electrode.

[0038] In some embodiments, the covering method includes coating.

[0039] In some embodiments, the areal density of the pre-electrode is 0.5 mg / cm³. 2 -2.7mg / cm 2 For example, 0.5 mg / cm 2 1mg / cm 2 2mg / cm 2 2.7 mg / cm 2 Within this areal density range, the film forms uniformly and has a stable structure, effectively preventing the shedding of active substances.

[0040] In some embodiments, drying is carried out under vacuum conditions, with a drying temperature of 65°C-110°C, such as 65°C, 75°C, 85°C, 95°C, 110°C, etc., and a drying time of 8h-14h, such as 8h, 9h, 10h, 11h, 12h, 13h, 14h, etc. Therefore, low-temperature, long-term drying facilitates slow solvent evaporation, preventing cracking of the dried graphite sheet.

[0041] According to an embodiment of this application, in a lithium removal three-electrode system, the pre-electrode is used as the first working electrode. A voltage is applied to the first working electrode to cause lithium ions in the first active material to be removed, forming a second active material with lithium vacancies, thus obtaining the electrode. The chemical reaction occurring during the lithium removal process is LiMn... 2-X Tb X O4-0.5e - →Li 0.5 Mn 2-X Tb X O4+0.5Li + Li 0.5 Mn 2-X Tb X O4-e - →2λ-MnO2(Tb)+0.5Li + After delithiation, a second active material with lithium vacancies (λ-MnO2(Tb)) is formed.

[0042] In some embodiments, the lithium vacancy rate in the second active material is 71%-99%.

[0043] In some embodiments, in the delithiation three-electrode system, the first reference electrode includes a silver electrode and / or a silver chloride electrode; the first pair of electrodes includes a silver sheet electrode; the electrolyte includes a lithium salt solution with a concentration of 0.05 mol / L to 1 mol / L, wherein the lithium salt includes at least one of lithium chloride, lithium sulfate, lithium nitrate, and lithium acetate. Mild delithiation in the electrolyte yields a second active material with uniform lithium vacancies.

[0044] Furthermore, the voltage is 0.6V-1V, and the voltage application time is 1h-3h. An electrode is prepared by optimizing the voltage application process conditions. The second active material in the electrode not only contains a terbium-doped spinel framework but also contains a large number of uniformly distributed lithium vacancies.

[0045] A second aspect of this application provides an electrode prepared using the method of the first aspect. The electrode includes a graphite sheet and an active material layer on the graphite sheet. The active material layer includes a second active material having lithium vacancies. The second active material in the electrode has uniformly doped terbium and uniformly distributed lithium vacancies, thereby improving the electrode's consistency. This allows the electrode to be used for lithium extraction from complex systems such as lithium slag leachate and brine from salt lakes. During extraction, lithium from the lithium-containing solution is embedded into the electrode to achieve lithium extraction.

[0046] In some embodiments, the crystal structure of the second active material is a spinel structure maintaining the Fd-3m space group, Tb 3+It occupies 16d octahedral sites; its morphological characteristics are octahedral or truncated octahedral morphology. The particle size range of the second active substance is 92nm-640nm.

[0047] In some embodiments, the second active material has an initial discharge specific capacity of not less than 110 mAh / g and a capacity retention of ≥85% after 6 cycles; when the electrode is used for lithium extraction, the lithium extraction capacity after continuous immersion in a 50 mg / L LiCl solution for 120 min is not less than 25 mg / g, where mg / g refers to the lithium content of the LiCl solution. + The ratio between the content of [substance name] (mg) and the content of active substance (g).

[0048] A third aspect of this application provides an electrochemical lithium extraction method, which includes the following steps: The electrode described in the second aspect is placed in a lithium-containing solution; In the lithium extraction three-electrode system, the electrode is used as the second working electrode, and a reduction potential is applied to the electrode to cause the second active material to intercalate lithium, thus obtaining a lithium-intercalated electrode.

[0049] The lithium extraction method of this application embodiment uses an electrode with lithium vacancies and performs electrochemical lithium intercalation at a controllable reduction potential to insert lithium ions from the lithium-containing solution into the electrode, thereby obtaining a lithium-intercalated electrode. This initially achieves efficient, highly selective, and reversible extraction of lithium ions from complex lithium-containing solutions.

[0050] In some embodiments, in the lithium extraction three-electrode system, the second pair of electrodes is a silver sheet or platinum sheet electrode, and the second reference electrode is a silver / silver chloride electrode or a saturated calomel electrode. During lithium extraction, a reduction potential is applied to the electrodes under constant current conditions to cause lithium ions in the lithium-containing solution to intercalate into the second active material.

[0051] In some embodiments, the lithium extraction method further includes: applying an oxidation potential to the lithium-intercalated electrode in a desorption three-electrode system to extract lithium from the lithium-intercalated electrode. In this step, an oxidation potential is applied under constant current conditions to extract lithium intercalated into the second active material, and the extracted lithium is then enriched to complete the lithium extraction.

[0052] In some embodiments, in the desorption three-electrode system, the third pair of electrodes is a silver sheet or a platinum sheet electrode, and the third reference electrode is a silver / silver chloride electrode or a saturated calomel electrode.

[0053] In some embodiments, preset steps can be repeatedly performed, the preset steps including: in a lithium extraction three-electrode system, using the electrode as the second working electrode, applying a reduction potential to the electrode to intercalate lithium into the second active material, obtaining a lithium-intercalated electrode; and in a desorption three-electrode system, applying an oxidation potential to the lithium-intercalated electrode to remove lithium from the lithium-intercalated product. This enables the recycling of the electrode and the complete extraction of lithium from lithium-containing solutions.

[0054] In some embodiments, the lithium-containing solution includes lithium slag leachate, salt lake brine, or lithium-containing wastewater, wherein the lithium-containing solution contains Li + The concentration of Tb ranged from 10 mg / L to 200 mg / L, and the pH ranged from 2.0 to 11.0. Therefore, the electrode exhibited good electrochemical activity under acidic, neutral, and alkaline conditions. This is attributed to Tb. 3+ Doping enhances the chemical stability of the second active material's lattice, suppressing Mn dissolution and structural collapse under extreme pH conditions. Its wide pH adaptability allows the electrode to treat lithium-containing wastewater from various sources. Furthermore, the electrode is also suitable for lithium extraction from high-salt solutions.

[0055] Furthermore, the pH of the lithium-containing solution is 4-10.

[0056] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. It should be understood that these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. Embodiment 1 Step 1: Electrode paste preparation 4g of lithium manganese oxide powder (LiMn2O4, purity ≥99%) and 0.104g of terbium nitrate heptahydrate (Tb(NO3)3·7H3O, purity ≥99.9%) were weighed and calcined at 780℃ to obtain LiMn 1.99 Tb 0.01 O4.

[0057] 0.8g LiMn 1.99 Tb 0.01 O4, 0.1g of superconducting carbon black (specific surface area ≥250m²) 2 0.1 g of polyvinylidene fluoride (PVDF, molecular weight approximately 534,000) and 4 g of N-methylpyrrolidone (NMP, anhydrous, purity ≥99.5%) were added and stirred in a mechanical stirrer at 900 rpm for 16 h to obtain a uniform electrode slurry.

[0058] Step 2: Slurry Coating The prepared electrode paste was uniformly coated onto a graphite sheet (0.1 mm thick, purity ≥ 99.5%) using a doctor blade, with a coating area of ​​6 cm². 2 .

[0059] Step 3: Vacuum drying The coated graphite sheets were placed in a vacuum drying oven and dried at 65°C and a vacuum degree <10Pa for 12 hours to allow the NMP solvent to fully evaporate, resulting in a sheet with an areal density of 2 mg / cm³. 2 The pre-electrode.

[0060] Step 4: Electrochemical delithiation A three-electrode system was constructed: the initial electrode obtained in step 3 was used as the working electrode, a silver sheet (20mm × 30mm × 0.1mm) as the counter electrode, and a silver / silver chloride electrode as the reference electrode. The electrolyte was 80 mL of a 1 mol / L LiCl solution (pH approximately 6.5). A constant voltage of 1.0 V was applied to the working electrode using an electrochemical workstation for 2 hours to perform lithium removal. During this process, LiMn... 1.99 Tb 0.01 O4 is gradually oxidized to λ-MnO2(Tb), and Li can be detected in the solution. + The concentration gradually increased.

[0061] After delithiation, the electrode surface is gently rinsed with deionized water and air-dried naturally. The resulting electrode is labeled LTMO-1.

[0062] Example 2 The electrode was prepared according to the method of Example 1, except that step 1: electrode slurry preparation: The amount of terbium nitrate heptahydrate used was 0.052 g, yielding LiMn. 1.995 Tb 0.005 The resulting electrode was labeled LTMO-0.5 using O4.

[0063] Example 3 The electrode was prepared according to the method of Example 1, except that step 1: electrode slurry preparation: The amount of terbium nitrate heptahydrate used was 0.208 g, yielding LiMn. 1.98 Tb 0.02 The resulting electrode was labeled LTMO-2 using O4.

[0064] Comparative Example 1 The electrode was prepared according to the method of Example 1, except that step 1: electrode slurry preparation: 0.8g of lithium manganese oxide powder (LiMn2O4) and 0.1g of superconducting carbon black (specific surface area ≥250m²) were weighed. 2 0.1 g of polyvinylidene fluoride (PVDF, molecular weight approximately 534,000) and 4 g of N-methylpyrrolidone (NMP, anhydrous, purity ≥99.5%) were added and stirred in a mechanical stirrer at 900 rpm for 16 h to obtain a uniform electrode slurry. The prepared electrode paste was uniformly coated onto a graphite sheet (0.1 mm thick, purity ≥ 99.5%) using a doctor blade, with a coating area of ​​6 cm². 2 .

[0065] The coated graphite sheets were placed in a vacuum drying oven and dried at 65°C and a vacuum degree <10Pa for 12 hours to allow the NMP solvent to fully evaporate, resulting in a sheet with an areal density of 2 mg / cm³. 2 The electrode is labeled LMO.

[0066] Test Case A Figure 1 This is a morphology image of the second active material on the LTMO-1 electrode in Example 1, obtained using a field emission scanning electron microscope (accelerating voltage 5kV). Figure 1 The second active material exhibits a typical octahedral or truncated octahedral morphology, with a particle size of approximately 92.23 nm to 636.1 nm. The particles are uniformly distributed and show no obvious agglomeration, indicating that the crystal structure remains intact after Tb doping.

[0067] Figure 2 This is the energy dispersive X-ray spectroscopy (EDS) elemental distribution diagram of the second active material on the LTMO-1 electrode of Example 1. The Tb element is uniformly distributed on the particle surface, confirming that Tb was successfully incorporated into the lithium manganese oxide lattice.

[0068] Figure 3 This is the X-ray diffraction pattern of the second active material on the electrodes of Examples 1-3. The pattern was created using an X-ray diffractometer (Cu rays, λ=1.5406Å, scanning range 10~80°) to analyze the crystal structure of the second active material on the electrodes of Examples 1-3. The pattern shows that all samples exhibit characteristic diffraction peaks of spinel LiMn2O4, with the main peaks located at 2θ=18.6°, 36.2°, 44.2°, 48.3°, 58.5°, and 64.4°, corresponding to the (111), (311), (400), (331), (511), and (440) crystal planes, respectively, conforming to the Fd-3m space group. The diffraction peaks of the second active material in LTMO-1 and LTMO-2 are slightly shifted to a lower angle relative to LiMn2O4 (Δ2θ≈0.1°~0.2°), indicating that Tb 3+ (ionic radius 0.923 Å) substituted Mn 3+ / Mn 4+The lattice parameters increased after doping; no impurity phase diffraction peaks were observed in the second active material of all electrodes, indicating that a single spinel phase was maintained after Tb doping; the diffraction peaks were sharp and the half-peak width was small, indicating that the crystallinity of the second active material in the electrode was good. The lattice parameters were calculated according to the Bragg equation and the peak position of (311): LiMn2O4 was 8.248 Å, LTMO-1 was 8.256 Å, and LTMO-2 was 8.262 Å, confirming that Tb doping caused lattice expansion, which in turn gave the electrode a wider lithium-ion diffusion channel and stronger structural stability, reduced the diffusion resistance of lithium ions in the lattice, and improved the cycle stability of the electrode.

[0069] Figure 4 This is a cyclic voltammetry curve of the electrode from Example 1 at different scan rates. The tests were conducted at room temperature using an electrochemical workstation. The electrode (LTMO-1) prepared in Example 1 was used as the working electrode, a silver sheet as the counter electrode, and Ag / AgCl as the reference electrode. Cyclic voltammetry was performed in 80 mL of a 1 mol / L LiCl solution. At scan rates of 0.1 mV / s, 0.2 mV / s, 0.3 mV / s, 0.5 mV / s, and 1 mV / s, the potential window was 0.2 V–1.1 V. The results show that distinct oxidation and reduction peaks appeared at different scan rates. The oxidation peak current increased with increasing scan rate, indicating that the electrode possesses excellent electrochemical reversibility and rapid response capability.

[0070] Figure 5 This is a constant current discharge curve of the electrode (LTMO-1) in Example 1. From... Figure 5 It can be seen that at currents of 25 mA / g, 50 mA / g, 100 mA / g, 250 mA / g, 500 mA / g, and 1000 mA / g, the corresponding discharge capacities are 138.06 mAh / g, 135.97 mAh / g, 124.03 mAh / g, 132.15 mAh / g, 125.46 mAh / g, and 125.11 mAh / g, respectively. The figure shows a clear voltage plateau in the discharge curve, corresponding to the reduction peak position of the cyclic voltammetry curve. Furthermore, when the current density increases from 25 mA / g to 1000 mA / g (a 40-fold increase), the capacity only decreases from 138.06 mAh / g to 125.11 mAh / g, maintaining a capacity retention of 90.6%, indicating that the electrode exhibits excellent rate performance and low electrochemical polarization.

[0071] Figure 6This is a bar chart of the discharge capacity of the electrode in Example 1 after 6 cycles. The results are as follows: 1st cycle: 116 mAh / g; 2nd cycle: 114 mAh / g; 3rd cycle: 111 mAh / g; 4th cycle: 108 mAh / g; 5th cycle: 106 mAh / g; 6th cycle: 104 mAh / g. The capacity retention rate after six cycles is 104 / 116 × 100% = 89.7%. This indicates that the electrode has good electrochemical stability.

[0072] Test Case B The effects of different coexisting ions on the lithium extraction performance of the electrode prepared in Example 1 were investigated using cyclic voltammetry and constant current discharge testing. The electrode from Example 1 was used as the working electrode, the silver sheet electrode as the counter electrode, and the silver / silver chloride electrode as the reference electrode. Three-electrode systems were constructed using electrolytes with different compositions. The electrolytes included: a 1 mol / L pure LiCl solution (in... Figure 7 and Figure 8 A 1 mol / L LiCl and 1 mol / L NaCl mixed solution (denoted as Li) Figure 7 and Figure 8 (denoted as Li+Na), a 1 mol / L LiCl and 1 mol / L KCl mixed solution (in...) Figure 7 and Figure 8 A 1 mol / L solution of LiCl and MgCl (denoted as Li+K) containing 1 mol / L of LiCl and MgCl. Figure 7 and Figure 8 (denoted as Li+Mg), a 1 mol / L LiCl and 1 mol / L SrCl mixed solution (in... Figure 7 and Figure 8 (denoted as Li+Sr), a 1 mol / L LiCl and 1 mol / L BaCl mixed solution (in) Figure 7 and Figure 8 (denoted as Li+Ba), a 1 mol / L LiCl and 1 mol / L CaCl mixed solution (in... Figure 7 and Figure 8 (denoted as Li+Ca). In this system, cyclic voltammetry was performed at a scan rate of 1 mV / s within a voltage range of 0.2 V to 1.1 V.

[0073] Figure 7 The figure shows the cyclic voltammetry curves of the electrode prepared in Example 1 under different electrolytes. It can be seen from the figure that the redox potential of the mixed solution is slightly shifted to a higher potential compared with the pure LiCl solution, but it still shows obvious redox peaks, which further illustrates that the electrode of this application can be used for the extraction of lithium from high salt solutions.

[0074] Figure 8 The figures show the constant current discharge curves of the electrode prepared in Example 1 in different electrolytes. The results show that, compared with pure lithium solution, the discharge plateau of the electrode in various mixed solutions shifts to higher potentials as a whole. This is basically consistent with the trend of the redox peak shifting to higher potentials observed in the cyclic voltammetry curves, further indicating that the electrode of this application can be used for lithium extraction from high-salt lithium-containing solutions.

[0075] Test Case C The electrochemical performance of the electrode prepared in Example 1 at different pH values ​​was investigated by performing cyclic voltammetry tests. The electrode from Example 1 was used as the working electrode, the silver sheet electrode as the counter electrode, and the silver / silver chloride electrode as the reference electrode. Three-electrode systems were constructed using electrolytes with different pH values. The electrolytes included 1 mol / L LiCl solutions at pH=2, pH=4, pH=6, pH=8, pH=9, pH=10, and pH=11. The pH of the LiCl solution was adjusted using HCl and LiOH. Cyclic voltammetry was performed in this system at a scan rate of 1 mV / s within a voltage window of 0.2 V–1.1 V. Figure 9 The results show that the CV curves at different pH values ​​maintain a clear redox peak within the pH range of 4-10, with little change in peak shape and peak current, indicating that the electrode has good electrochemical stability within this pH range. At pH 2.0 or 11, the redox peaks are significantly weakened, and the peak current decreases by about 80%, which may be due to the intensified dissolution of Mn ions under strong acid conditions. At pH 11.0, the oxidation peak weakens, and the reduction peak almost disappears, indicating that an irreversible chemical reaction occurred on the electrode surface under strong alkaline conditions.

[0076] Under the same conditions (50 mg / L LiCl solution, discharge current density of 50 mA / g, adsorption time of 120 min), the lithium extraction capacity of the electrodes of Example 1 (LTMO-1), Example 2 (LTMO-0.5), Example 3 (LTMO-2), and Comparative Example 1 (LMO) was measured. Specifically, each electrode was immersed in 80 mL of 50 mg / L LiCl solution; a discharge current density of 50 mA / g was applied for 120 min; samples were taken at 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min, and the LiCl concentration in the solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). + Concentration; based on Li +Calculation of lithium extraction capacity (mgLi) based on concentration reduction and electrode active material mass + / g active material), the lithium extraction capacity is calculated according to formula (1): Formula (1); q represents the electrode pair with Li + The extraction capacity is used to evaluate the lithium extraction performance of the electrode, expressed in mg / g; C0 represents the initial concentration of lithium ions in the solution before lithium extraction begins, expressed in mg / L; C t The value represents the lithium ion concentration in the solution after time t of the lithium extraction reaction, in mg / L; V represents the volume of the lithium-containing solution, in L; and m represents the mass of the active material on the electrode, in g.

[0077] Figure 10 The lithium extraction capacities of the electrodes in Examples 1 (LTMO-1), 2 (LTMO-0.5), 3 (LTMO-2), and Comparative Example 1 (LMO) at 120 min were 25.73 mg / g, 20.04 mg / g, 20.06 mg / g, and 14.10 mg / g, respectively. These results indicate that terbium doping significantly improves lithium extraction performance, with Example 1 exhibiting the highest lithium extraction capacity.

[0078] Figure 11 This is a graph showing the relationship between lithium extraction capacity and lithium concentration for the electrodes of Examples 1 (LTMO-1), 2 (LTMO-0.5), 3 (LTMO-2), and Comparative Example 1 (LMO). The graph was obtained after lithium extraction in LiCl solutions of 10 mg / L, 25 mg / L, 50 mg / L, 100 mg / L, and 200 mg / L for 120 min. It can be seen that, under the same initial concentration and reaction time, the electrode prepared in Example 1 exhibits the highest lithium extraction capacity. There is a certain degree of positive correlation between the lithium extraction capacity of the electrodes prepared in Examples 1, 2, 3, and Comparative Example 1 and the initial concentration of the lithium solution. This indicates that a higher initial concentration can improve the lithium extraction capability of the electrode. A possible reason is that a higher concentration of electrolyte can increase the collision frequency between lithium ions and the electrode surface and strengthen the electrostatic attraction, thereby improving the electrode's efficiency in extracting lithium ions.

[0079] Test case D Simulated solution preparation: Based on the actual composition of a lithium slag leachate, the following ion concentrations were prepared in a simulated solution: Li + 100 mg / L, Na + It is 11700 mg / L, K + The concentration was 483 mg / L, Mg 2+ It is 158 mg / L, Ca 2+ The concentration was 1219 mg / L, Sr 2+ It is 600 mg / L, Ba2+ The concentration was 1264 mg / L, and the pH was 6.5. Experimental steps: (1) Immerse the LTMO-1 electrode prepared in Example 1 into 80 mL of simulated solution; (2) Discharge adsorption was performed for 1 h at a current density of 50 mA / g within a voltage range of 0.2 V-1.1 V to complete the Li adsorption. + Extraction; (3) Transfer the electrode to 65 mL of 0.1 mol / L KCl solution, and charge and desorb at a current density of 50 mA / g for 1 h within a voltage range of 0.2 V-1.1 V to complete the Li desorption process. + Elution was performed for a total of 6 cycles; after each cycle, the concentration of each element in the desorption solution was determined by ICP-OES.

[0080] Figure 12 This is a graph showing the relationship between the electrode in Example 1 and the concentration of each ion after different cycles in the simulated lithium slag leachate. The results indicate that after 6 cycles, the simulated leachate ( Figure 12 The right-hand vertical axis records the Li content in the feed liquid. + The lithium ion concentration in the extract decreased from 91.07 mg / L to 59.41 mg / L (as shown in the bars in the figure), while the lithium concentration in the extract increased from 0 to 23.58 mg / L, as shown by the black line, while the concentrations of other ions (as shown by the colored lines in the figure) remained almost unchanged. The lithium purity was calculated using formula (2). Formula (2); where, The purity of lithium in the extract is expressed in %; C Li This indicates the lithium ion concentration in the extract, expressed in mg / L. The total concentration of all detected metal ions in the extract is expressed in mg / L. Calculations show that the lithium purity in the extract reaches 99.04%, indicating that the electrode prepared in Example 1 can still accurately identify and capture Li in simulated wastewater with complex composition. + It rejects other coexisting cations, exhibiting extremely high selectivity.

[0081] In summary, the electrode of this application achieved high-purity, high-selectivity, and high-stability lithium extraction in a simulated lithium slag leachate system with high salt content and multiple ion interference, which has significant industrial application value.

[0082] It should also be noted that the terms "some embodiments," "other embodiments," and "embodiments" used in this application refer to specific features, structures, or characteristics described in connection with those embodiments, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0083] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0084] It should also be noted that the above are merely preferred embodiments of this application and do not limit the scope of protection of this application. Any equivalent structural or procedural transformations made based on the content of this application’s specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of protection of this application.

Claims

1. A method for preparing an electrode, characterized in that, Includes the following steps: Lithium manganese oxide and terbium salt are calcined to obtain a first active material, which is LiMn. 2- X Tb X O4, 0.005≤X≤0.02; The first active material, conductive agent, binder and solvent are stirred to obtain electrode slurry; The electrode slurry is coated onto a graphite sheet and dried to obtain a pre-electrode; In the lithium removal three-electrode system, the pre-electrode is used as the first working electrode. A voltage is applied to the first working electrode to remove lithium ions from the first active material to form a second active material with lithium vacancies, thus obtaining the electrode.

2. The preparation method according to claim 1, characterized in that, The mass ratio of lithium manganese oxide to terbium salt is 1:(0.013-0.052); The mass ratio of the first active substance, the conductive agent, the binder, and the solvent is 8:(0.5-1.5):(0.5-2.0):(35-50); The terbium salt includes at least one of terbium nitrate, terbium oxide, and terbium acetate; The conductive agent includes at least one of carbon black, carbon nanotubes, and graphene; The solvent includes N-methylpyrrolidone.

3. The preparation method according to claim 1, characterized in that, The calcination temperature is 600℃-1000℃; The stirring time is 12h-20h, and the stirring speed is 600rpm-1000rpm.

4. The preparation method according to claim 1, characterized in that, The covering method includes coating; The areal density of the pre-electrode is 0.5 mg / cm³. 2 -2.7mg / cm 2 .

5. The preparation method according to claim 1, characterized in that, The drying is carried out under vacuum conditions, the drying temperature is 65℃-110℃, and the drying time is 8h-14h.

6. The preparation method according to claim 1, characterized in that, In the lithium removal three-electrode system, the first reference electrode includes a silver electrode and / or a silver chloride electrode; The first pair of electrodes includes silver sheet electrodes; The electrolyte comprises a lithium salt solution with a concentration of 0.05 mol / L to 1 mol / L, wherein the lithium salt comprises at least one of lithium chloride, lithium sulfate, lithium nitrate, and lithium acetate.

7. The preparation method according to claim 1 or 6, characterized in that, The voltage is 0.6V-1V, and the voltage is applied for 1h-3h.

8. An electrode, characterized in that, It is obtained by the preparation method according to any one of claims 1-7.

9. A method for lithium extraction, characterized in that, Includes the following steps: The electrode according to claim 8 is placed in a lithium-containing solution; In the lithium extraction three-electrode system, the electrode is used as the second working electrode, and a reduction potential is applied to the electrode to insert lithium into the second active material, thereby obtaining a lithium-intercalated electrode.

10. The lithium extraction method according to claim 9, characterized in that, Also includes: In the desorption three-electrode system, an oxidation potential is applied to the lithium intercalation electrode to remove lithium from the lithium intercalation electrode.

11. The lithium extraction method according to claim 9 or 10, characterized in that, The lithium-containing solution includes lithium slag leachate, salt lake brine, or lithium-containing wastewater. The lithium-containing solution contains Li... + The concentration is 10 mg / L-200 mg / L, and the pH is 2.0-11.0.

Images