A lithium manganese oxide microsheet material and its preparation method

Abstract

This invention discloses a lithium manganese oxide microsheet material and its preparation method. The lithium manganese oxide microsheet material is a two-dimensional sheet structure composed of tightly packed spinel-structured crystalline nanoparticles of lithium manganese oxide, exhibiting uniform thickness, good continuity, and high stability. The preparation method involves uniformly mixing a nitrogen-rich / oxygen-rich covalent organic polymer with manganese salt, lithium compound, and doped metal salt, followed by melt calcination to obtain the lithium manganese oxide microsheet material. Alternatively, the nitrogen-rich / oxygen-rich organic polymer can be uniformly mixed with manganese salt, lithium compound, and doped metal salt, and dried; then calcined at high temperature under an active atmosphere to obtain the lithium manganese oxide microsheet material. The lithium manganese oxide microsheet material prepared by this invention possesses a large, continuous two-dimensional sheet structure, exhibiting high conductivity and high specific capacity. Furthermore, the small amount of metals doped into the microsheets, such as Al and Ni, further improves its stability and suppresses structural deformation, making it suitable for applications in lithium-ion batteries, capacitor energy storage, electrochemical lithium extraction, and lithium-ion adsorption.

Description

Technical Field

[0001] This invention relates to a lithium manganese oxide micron sheet material and its preparation method, which can be used for lithium-ion battery energy storage, electrochemical lithium extraction, and lithium-ion sieve adsorption. Background Technology

[0002] Lithium manganese oxide, as an emerging electrode material, possesses advantages such as a unique spinel structure, three-dimensional ion channels facilitating rapid ion transport, high redox reactivity, and abundant lithium adsorption active sites, resulting in excellent performance in lithium-ion batteries and electrochemical lithium extraction applications. It has wide applications in supercapacitors, lithium-ion batteries, electrochemical lithium extraction, and lithium-ion sieve adsorption. The main preparation methods for lithium manganese oxide include precipitation-thermal crystallization, microwave methods, rheological phase methods, sol-gel methods, hydrothermal methods, and high-temperature solid-state sintering. High-temperature solid-state sintering yields lithium manganese oxide materials with high crystallinity, good electrochemical activity, and can be mass-produced. Currently, commercially available lithium manganese oxide is mainly prepared using the high-temperature solid-state sintering method. However, lithium manganese oxide materials prepared by this traditional method generally have irregular morphologies and are prone to agglomeration. Furthermore, it is difficult to avoid the inherent problems of lithium manganese oxide, such as poor conductivity, structural distortion, capacity decay, and decreased stability, which are detrimental to its application in lithium-ion battery energy storage and electrochemical lithium extraction. Two-dimensional lithium manganese oxide materials possess inherent advantages in energy storage due to their high specific surface area, abundant exposed active sites, and non-stacked structure (J. Mater. Chem. 22 (2012), 20952-20957; Chem. Rev. 120 (2020), 6684-6737). Furthermore, the continuously arranged spinel two-dimensional structure significantly promotes electron and ion transport and mitigates structural deformation caused by ion insertion / extraction. On the other hand, large-scale micron-sheet lithium manganese oxide materials offer significant advantages in lithium-ion sieve adsorption applications. For example, compared to nanopowder structures, large-scale micron-sheet lithium-ion sieves are easier to wash, regenerate, and recycle, saving energy.

[0003] The structure control of common lithium manganese oxide materials (such as one-dimensional, two-dimensional, and three-dimensional structures) mainly adopts the template method (ChemElectroChem 7 (2020), 105-111; J. Power Sources 328 (2016), 345-354; J. Electroanal. Chem. 928 (2023), 117090). However, conventional template agents are prone to decomposition or deformation at high temperatures, leading to the collapse of the entire structure. The resulting nanomaterials have poor uniformity and continuity, making it difficult to scale up and apply the preparation method. Moreover, the resulting two-dimensional sheets are difficult to scale up. This is mainly because the preparation of high-performance lithium manganese oxide generally requires high-temperature operation to improve its crystallinity and lithium intercalation / deintercalation activity. Therefore, improving the electrochemical performance of lithium manganese oxide by controlling its microstructure to improve structural stability and charge transport remains a challenging problem. There is an urgent need to design and prepare materials with a simple method, abundant active sites, high electrochemical activity, and excellent cycle stability for use in supercapacitors and electrochemical lithium extraction.

[0004] Existing literature methods and related published patents have the following drawbacks:

[0005] (1) Application No. 201410221391.X uses sugarcane bagasse as a template and prepares it under high temperature calcination through processes such as treatment, adsorption, calcination and cleaning. The synthesis process is very complicated, and the resulting porous lithium manganese oxide nanosheets are small in size, with poor continuity and overall uniformity, and cannot obtain micron sheet structure.

[0006] (2) Application No. 201410221391.X used lithium manganese oxide precursor prepared by hydrogen peroxide and tetramethylammonium hydroxide as template, and then prepared ultrathin two-dimensional morphology nanosheets with hierarchical structure lithium manganese oxide through subsequent stirring, drying and high temperature calcination. The synthesis steps are complicated, the nanosheets are small and the layer continuity is poor, and the structure is irregular.

[0007] (3) Application No. 201710188919.1 uses phenol as an additive and polyethylene film as a two-dimensional template. The precursor is first synthesized hydrothermally and then calcined at high temperature. The synthesis steps are complicated. Moreover, the obtained two-dimensional lithium manganese oxide has poor continuity, poor crystallinity, loose structure and irregularity. Summary of the Invention

[0008] The technical problem to be solved by this invention is that the lithium manganese oxide materials used in existing lithium-ion batteries, electrochemical lithium extraction and lithium-ion sieve technologies have problems such as small particle size, disordered structure, serious agglomeration, low electrochemical activity, poor structural stability, and high difficulty in operation and processing.

[0009] To address the aforementioned problems, this invention provides a lithium manganese oxide microsheet material, wherein the lithium manganese oxide microsheet material is a two-dimensional sheet structure composed of tightly packed lithium manganese oxide spinel-structured crystalline nanoparticles, and the specific surface area of ​​the lithium manganese oxide microsheet material is 5-100 m². 2 / g, with a thickness of 20-500nm, a length of 1-200μm, and a width of 1-200μm; the lithium manganese oxide microsheet material is doped with one or more of lanthanum, aluminum, and nickel metals, and the atomic ratio of the doped metal to manganese is 0:1-0.1:1.

[0010] Preferably, the lithium manganese oxide microsheet has a thickness of 20-80 nm, a length of 5-100 μm, and a width of 5-100 μm.

[0011] Preferably, the atomic ratio of the doped metal to manganese in the lithium manganese oxide microsheet is 0.01:1 to 0.1:1.

[0012] The present invention also provides a method for preparing the above-mentioned lithium manganese oxide microsheet material: a nitrogen-rich / oxygen-rich covalent organic polymer is uniformly mixed with manganese salt, lithium compound, and doped metal salt; then the mixture is melted and calcined under an active atmosphere to obtain lithium manganese oxide microsheet material.

[0013] Preferably, the nitrogen-rich / oxygen-rich covalent organic polymer comprises any one or more of 1,3,5-tricarboxychloroglucosamine-4,4',4”-(1,3,5-triazine-2,4,6-triacyl)triphenylamine, melamine cyanurate polymer, 2,3,6,7,10,11-hexahydroxytriphenyl, 1,2,4,5-tetrahydroxybenzene, and 2,6-diaminoanthraquinone-1,3,5-tricarboxychloroglucosamine; the manganese salt is manganese nitrate, manganese acetate, or manganese carbonate. The mixture contains one or more of manganese, manganese sulfate, and manganese chloride; the lithium compound contains one or more of lithium hydroxide, lithium chloride, lithium acetate, lithium nitrate, and lithium carbonate; the doped metal salt contains one or more of aluminum salt, iron salt, nickel salt, and lanthanum salt; the mass of the nitrogen-rich / oxygen-rich covalent organic polymer is 10-50% of the total mass of the mixture; the lithium-manganese molar ratio of the lithium compound to the manganese salt is 1:1-1:3, and the molar ratio of the doped metal salt to the manganese salt is 0:1-0.1:1.

[0014] Preferably, the doped metal salt is an aluminum salt.

[0015] Preferably, the active atmosphere is any one or more of oxygen, ammonia and carbon dioxide, and the melting and calcination temperature is 400-1000℃.

[0016] Preferably, the melting and calcination temperature is 700-750℃.

[0017] The present invention also provides an electrochemical lithium extraction electrode, characterized in that the electrode contains the lithium manganese oxide microsheet material as described in claim 1, as well as a conductive agent and a binder.

[0018] Preferably, the conductive agent is any one or more of conductive carbon black, conductive graphite, graphene, and carbon nanofibers; the binder is any one or more of polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), and polyvinylidene fluoride (PVDF).

[0019] The present invention also provides a method for preparing the above-mentioned electrochemical lithium extraction electrode: the lithium manganese oxide micron sheet material, the conductive agent, and the binder are mixed evenly, and then the mixture is pressed on a conductive current collector to obtain the electrochemical lithium extraction electrode.

[0020] Preferably, the lithium manganese oxide microsheet material, conductive agent, and binder are in a mass ratio of (6.5-9.5):(0.15-2.5):(0.25-2.5).

[0021] The present invention also provides an application of the above-mentioned lithium manganese oxide microsheet material for lithium adsorption in aqueous solution.

[0022] The present invention also provides an application of the above-mentioned electrochemical lithium extraction electrode in electroadsorption lithium extraction, lithium-ion batteries or capacitor energy storage.

[0023] The lithium manganese oxide micron sheet material provided by this invention is a sheet structure composed of ordered arrangement of nano-sized spinel crystal particles. It has the characteristics of uniform thickness, good continuity of crystal particles, no stacking, and ultra-large planar structure. In the electrode, it is conducive to electron transport and ion migration, which can effectively increase the conductivity and electrochemical activity of the material. At the same time, the interaction between spinel particles reduces the phase transformation stress of spinel, thereby greatly improving the structural stability during lithium insertion / extraction cycling.

[0024] The method provided by this invention is simple, and the prepared lithium manganese oxide microsheet material has a large, continuous two-dimensional sheet structure with high conductivity and high specific capacity. Furthermore, the small amount of metals doped into the microsheet, such as Al and Ni, further improves its stability and suppresses structural deformation. The microsheets prepared by this invention can be widely used in lithium-ion batteries, capacitor energy storage, electrochemical lithium extraction, and lithium-ion adsorption.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) The present invention prepares lithium manganese oxide microsheet material, which is composed of a single layer of ordered spinel-structured crystalline nanoparticles, with a robust adjacent structure, good continuity and uniform thickness. This compact structure can improve stability.

[0027] (2) The small size of the lithium manganese oxide crystal particles that make up the micron sheet facilitates the exposure of more active sites, greatly improving the electron transfer and ion transport performance of lithium manganese oxide, increasing conductivity, electrochemical activity and specific capacitance characteristics; and the small phase transition stress during the redox process improves the structural stability of lithium manganese oxide and enhances the electrochemical stability of the material.

[0028] (3) The lithium manganese oxide microsheet material contains trace amounts of doped metal, which further suppresses structural distortion, reduces manganese dissolution, and improves structural stability.

[0029] (4) The preparation method is simple, environmentally friendly, and can be produced in batches. The micron-sized sheets are large and easy to operate and recycle in practical applications.

[0030] (5) The electrode assembly of the present invention, which uses lithium manganese oxide microsheets as active material, has a large lithium adsorption capacity, good selectivity and high stability. Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope (SEM) image of the lithium manganese oxide microsheet material in Example 1;

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the Al-doped lithium manganese oxide microsheet material in Example 2;

[0033] Figure 3 The image shows a scanning electron microscope (SEM) image of the lithium manganese oxide particle agglomerate material in Comparative Example 1.

[0034] Figure 4 Cyclic voltammetry of lithium manganese oxide microsheet electrode prepared in Example 1 and lithium manganese oxide particle electrode prepared in Comparative Example 1 in 1 mol / L LiCl.

[0035] Figure 5 The AC impedance diagrams of the lithium manganese oxide microsheet electrode prepared in Example 1 and the lithium manganese oxide particle electrode prepared in Comparative Example 1 in 1 mol / L LiCl.

[0036] Figure 6 The adsorption capacity changes of the lithium manganese oxide microsheet electrode prepared in Example 1, the Al-doped lithium manganese oxide microsheet electrode prepared in Example 2, and the lithium manganese oxide particle electrode prepared in Comparative Example 1 were observed during 100 lithium adsorption-desorption cycles in 10 mM LiCl.

[0037] Figure 7 Adsorption / desorption curves of Al-doped lithium manganese oxide micron-sized sheet electrodes prepared in Example 2 for different cations in 10 mM solutions of different metal salts; Detailed Implementation

[0038] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0039] Example 1

[0040] This embodiment provides a method for preparing lithium manganese oxide microsheet material, as detailed below:

[0041] The covalent organic polymer melamine cyanurate, lithium acetate, and manganese acetate were uniformly mixed in a mass ratio of 2:1:5 and placed in a muffle furnace. The mixture was gradually heated to 750°C and maintained for 10 hours. After natural cooling, lithium manganese oxide microsheet material was obtained.

[0042] The surface morphology of the material was observed using a scanning electron microscope, and the electron microscope images are as follows: Figure 1 As shown, lithium manganese oxide microsheets maintain a large length, width, and unique two-dimensional sheet structure, composed of ordered arrangements of nano-spinel particles, with a uniform thickness of approximately 200 nm.

[0043] This embodiment also provides a method for preparing a lithium manganese oxide microsheet electrode: active material, conductive agent, and binder are mixed and ground in a mass ratio of 8:1:1, and then pressed into sheets on a titanium mesh using a press to obtain the lithium manganese oxide microsheet electrode. In 1M LiCl solution, the lithium manganese oxide microsheet material (LMO-NS) electrode prepared in this embodiment exhibits excellent electrochemical activity (e.g., ...). Figure 4 (As shown). AC impedance spectroscopy analysis was employed, such as... Figure 5 As shown, the lithium manganese oxide microsheet material (LMO-NS) prepared in this embodiment exhibits a low charge transfer resistance (only 7Ω) and good conductivity, which is highly beneficial for its application in lithium-ion battery ion storage and electrochemical lithium extraction. LMO-NS and activated carbon (AC) electrodes were placed in parallel to form a capacitor (LMO-NS‖AC) for capacitive lithium extraction. The electrode has a high capacity; in 10 mM LiCl, the lithium adsorption capacity reaches 1.65 mmol / g. Figure 6 The results show that after 100 cycles in a capacitive deionization device, the LMO-NS electrode still retains 78.1% of its lithium-ion adsorption capacity, indicating that the lithium manganese oxide microsheet material has high adsorption capacity and good cycle stability.

[0044] Example 2

[0045] The functional group-rich covalent organic polymer melamine cyanurate, lithium acetate, and manganese acetate were mixed in a mass ratio of 2:1:5, with a small amount of Al salt added. The molar ratio of Al to Mn was 1:39. The mixture was placed in a muffle furnace and treated at 700°C for 10 hours. After natural cooling, Al-doped lithium manganese oxide microsheet material (LAMO-NS) was obtained.

[0046] The surface morphology of the material was observed using a scanning electron microscope, and the electron microscope images are as follows: Figure 2 As shown, Al-doped lithium manganese oxide microsheets still maintain large length, width, and a unique two-dimensional sheet structure, composed of ordered arrangements of nano-spinel particles, with a uniform thickness of approximately 200 nm.

[0047] The active material, conductive agent, and binder were mixed and ground in a mass ratio of 8:1:1, and then pressed onto a titanium mesh to obtain an Al-doped lithium manganese oxide microsheet electrode. LAMO-NS and AC electrodes were placed in parallel to form a capacitor, LAMO-NS‖AC, for lithium extraction via capacitor operation. Figure 6 The results show that the LAMO-NS electrode has a high capacity, achieving a lithium adsorption capacity of 1.68 mmol / g in 10 mM LiCl. After 100 cycles in a capacitive deionization device, the LAMO-NS electrode still retains 91.8% of its lithium-ion adsorption capacity, indicating that this lithium manganese oxide microsheet material possesses high adsorption capacity and excellent cycling stability. Furthermore, the adsorption capacity of the LAMO-NS microsheet electrode for LiCl was investigated in 10 mM solutions of different metal salts. + The selectivity of the LAMO-NS microsheet electrode prepared in this embodiment is shown to be good for Li. + It exhibits excellent selectivity (e.g.) Figure 7 (As shown).

[0048] Example 3

[0049] The functional group-rich covalent organic polymer 1,3,5-tricarboxychloroglucosamine-4,4′,4″-(1,3,5-triazine-2,4,6-triacyl)triphenylamine, lithium nitrate, and manganese acetate were uniformly mixed in a mass ratio of 2:1:5 and placed in a muffle furnace. The mixture was slowly heated to 700°C and held at that temperature for 10 hours. After natural cooling, lithium manganese oxide microsheet material was obtained.

[0050] Example 4

[0051] The functional group-rich covalent organic polymer 2,6-diaminoanthraquinone-1,3,5-tricarboxymethylchloroglucosamine, lithium acetate, and manganese acetate were uniformly mixed in a mass ratio of 2:1:5. A small amount of Ni salt was added, and the molar ratio of Ni to Mn was 1:39. After uniform mixing, the mixture was placed in a muffle furnace and treated at 700℃ for 10 hours. After natural cooling, Ni-doped lithium manganese oxide microsheet material was obtained.

[0052] Comparative Example 1

[0053] Lithium acetate and manganese acetate were uniformly mixed at a mass ratio of 1:5 and placed in a muffle furnace. The mixture was then treated at 750℃ for 10 hours, followed by natural cooling to obtain lithium manganese oxide nanoparticle aggregates. Scanning electron microscope images of the material are shown below. Figure 3As shown.

[0054] The active material, conductive agent, and binder were mixed and ground in a mass ratio of 8:1:1, and then pressed onto a titanium mesh to obtain a lithium manganese oxide microsheet electrode. In 1M LiCl solution, the lithium manganese oxide (LMO) electrode prepared in this comparative example exhibited poor electrochemical activity (e.g., ...). Figure 4 (As shown). AC impedance spectroscopy analysis was employed, such as... Figure 5 As shown, the LMO material prepared in this embodiment exhibits a large charge transfer resistance (15Ω) and poor conductivity, which is detrimental to its application in lithium-ion battery ion storage and electrochemical lithium extraction. A capacitor (LMO‖AC) was constructed by paralleling LMO with an AC electrode for capacitive lithium extraction. In 10 mM LiCl, the lithium adsorption capacity was only 1.05 mmol / g. Figure 6 This indicates that the LMO electrode retains only 48.5% of its adsorption capacity after 100 cycles in the capacitive deionization device, indicating poor stability.

Claims

1. A method for preparing a lithium manganate microsheet material, characterized by, The specific surface area of the lithium manganate microsheet material is 5-100 m 2 / g, the thickness is 20-500 nm, the length is 1-200 μm, and the width is 1-200 μm; one or more of lanthanum, aluminum and nickel is doped in the lithium manganate microsheet material, and the molar ratio of the doped metal to manganese is 0:1-0.1:

1. The preparation method of the lithium manganate microsheet material is: uniformly mixing nitrogen / oxygen-rich covalent organic polymers with manganese salt, lithium compound and doped metal salt; then melting and calcining the mixture under an active atmosphere to obtain the lithium manganate microsheet material, wherein the active atmosphere is any one or several of oxygen, ammonia and carbon dioxide gas, and the melting and calcining temperature is 400-1000℃.

2. The lithium manganate microparticle material of claim 1, wherein, The nitrogen / oxygen-rich covalent organic polymer includes any one or several of 1,3,5-triformylchloroglucopyranoside-4,4',4"-(1,3,5-triazine-2,4,6-triacyl) triphenylamine, melamine cyanuric acid polymer, 2,3,6,7,10,11-hexahydroxytriphenyl, 1,2,4,5-tetrahydroxybenzene, and 2,6-diaminoanthraquinone-1,3,5-triformylchloroglucopyranoside; the manganese salt is any one or several of manganese nitrate, manganese acetate, manganese carbonate, manganese sulfate and manganese chloride; the lithium compound is any one or several of lithium hydroxide, lithium chloride, lithium acetate, lithium nitrate and lithium carbonate; the doped metal salt is any one or several of aluminum salt, iron salt, nickel salt and lanthanum salt; the mass of the nitrogen / oxygen-rich covalent organic polymer is 10-50% of the total mass of the mixture; the lithium-manganese molar ratio of the lithium compound to the manganese salt is 1:1-1:3, and the molar ratio of the doped metal salt to the manganese salt is 0:1-0.1:

1.

3. An electrode for electrochemical lithium extraction, characterized in that, The electrode contains the lithium manganate microsheet material of claim 1 and a conductive agent and a binder.

4. The electrode for electrochemically extracting lithium according to claim 3, wherein The conductive agent is any one or several of conductive carbon black, conductive graphite, graphene and nanocarbon fiber; and the binder is any one or several of polyvinyl alcohol, polytetrafluoroethylene, carboxymethyl cellulose and polyvinylidene fluoride.

5. The method for preparing the electrochemical lithium extraction electrode according to claim 3 or 4, characterized in that, The lithium manganate microsheet material, the conductive agent and the binder are uniformly mixed, and then the mixture is pressed on a conductive current collector to obtain the electrochemical lithium extraction electrode.

6. The method for preparing the electrochemical lithium extraction electrode as described in claim 5, characterized in that, The mass ratio of the lithium manganate microsheet material, the conductive agent and the binder is (6.5-9.5):(0.15-2.5):(0.25-2.5).

7. Use of the lithium manganate microparticle material according to claim 1, characterized in that The lithium manganate microsheet material is used for lithium adsorption in aqueous solution.

8. Use of the electrochemical lithium extraction electrode of claim 3 or 4 in electroadsorption lithium extraction, lithium ion batteries or capacitor energy storage.

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