A negative electrode of a lithium ion battery, a negative electrode material, a manganese-based bimetallic MOFs material, and a preparation method and application thereof

Abstract

The application discloses a kind of negative electrode of lithium ion battery, negative electrode material, manganese series bimetallic MOFs material and its preparation method and application, belong to lithium ion battery field. Organic ligand of formula (1) structure and composite metal source containing divalent metal source and manganese source are carried out coordination reaction, and the bimetallic MOFs material containing divalent metal-trivalent manganese is prepared;Divalent metal element in divalent metal source includes at least one of Ni, Zn, Co, Cu, R1 and R2 are each independently selected from one of -COOM, -SO3M, -PO3H2 and -COOR3, M is H, Na, K, R3 is C1~C6 alkyl group. The reversible specific capacity, rate performance, cycle stability and conductivity of lithium ion battery are improved by the mutual cooperation between the introduced trivalent manganese and divalent metal and organic ligand, and the preparation method is simple, and it is convenient for industrial production.

Description

Technical Field

[0001] This invention relates to a negative electrode for lithium-ion batteries, a negative electrode material, a manganese-based bimetallic MOF material, its preparation method and application, and belongs to the field of lithium-ion battery technology. Background Technology

[0002] With the overuse of fossil fuels in the 20th century, we urgently need to find a clean energy source to replace traditional fossil fuels. Among them, electricity is considered a highly efficient and safe clean energy source, and lithium-ion batteries (LIBs), which can be used to efficiently store electricity, have also received widespread attention.

[0003] However, the performance bottlenecks of current commercial lithium-ion batteries are becoming increasingly prominent. Among these bottlenecks, graphite is commonly used as the anode material, but its theoretical specific capacity is relatively low (only 374 mAh g⁻¹). -1 This severely restricts further improvements in battery energy density, becoming one of the key bottlenecks hindering the development of LIBs. At the same time, the problems with cathode materials are equally significant, especially in reversible capacity and rate performance, where their deficiencies have become a core bottleneck restricting the overall performance improvement of lithium-ion batteries.

[0004] Regarding anode materials, although researchers have developed various high-capacity alternative systems such as silicon-based, tin-based, and MOF-derived materials, these materials still face a series of shortcomings in practical applications. For example, the initial coulombic efficiency is relatively low. During the first charge-discharge cycle, novel high-capacity anode materials (such as silicon-based, tin-based, and some MOF-derived materials) suffer from electrolyte decomposition forming a solid electrolyte interphase (SEI) film, irreversible lithium capture, and irreversible consumption of lithium ions by structural defect sites, resulting in a large amount of lithium ions being consumed and unable to participate in subsequent cycles. While pre-lithiation technologies (such as electrochemical pre-lithiation and the addition of stable lithium metal powder) can effectively improve the initial efficiency to over 90%, the pre-lithiation process has extremely stringent requirements for environmental humidity, complex operating procedures, and the introduced active lithium powder poses safety hazards, thus large-scale application still faces many challenges.

[0005] Secondly, the rate performance is insufficient. High-capacity anode materials generally have low intrinsic conductivity, and the diffusion coefficient of lithium ions within their crystal lattice is also very limited. Under the conditions of high current density during rapid charging and discharging, electrons cannot be transported to the active sites in time, and lithium ions also have difficulty quickly inserting into or extracting from the electrode material. This leads to a sharp increase in the polarization voltage inside the electrode, a significant decrease in the utilization rate of the active material, and a severe reduction in the actual reversible capacity.

[0006] Therefore, it is necessary to explore a new type of lithium-ion battery anode material. Summary of the Invention

[0007] To address the problems existing in the prior art, one of the objectives of this invention is to provide a method for preparing manganese-based bimetallic MOFs materials. This invention is the first to prepare bimetallic MOFs materials containing divalent metal and trivalent manganese. By introducing trivalent manganese and divalent metal and the interaction between organic ligands, the HOMO-LUMO energy level difference of organic ligands is reduced, thereby improving the reversible specific capacity, rate performance, cycle stability and conductivity of lithium-ion batteries. Moreover, the preparation method is simple, easy to industrialize, and has a high yield.

[0008] The second objective of this invention is to provide a manganese-based bimetallic MOF material.

[0009] The third objective of this invention is to provide the application of manganese-based bimetallic MOF materials in the preparation of lithium-ion battery anode materials. These materials exhibit excellent reversible specific capacity, rate performance, cycle stability, and conductivity when used in the preparation of lithium-ion battery anode materials.

[0010] The fourth objective of this invention is to provide a negative electrode material for lithium-ion batteries.

[0011] The fifth objective of this invention is to provide a negative electrode for a lithium-ion battery.

[0012] To achieve the above objectives, a first aspect of the present invention provides a method for preparing manganese-based bimetallic MOFs materials, the method comprising:

[0013] By coordinating an organic ligand with the structure of formula (1) and a composite metal source containing a divalent metal source and a manganese source, a bimetallic MOF material containing a divalent metal-trivalent manganese is prepared; the divalent metal source contains at least one of Ni, Zn, Co, and Cu.

[0014] Equation (1);

[0015] In formula (1), R1 and R2 are each independently selected from one of -COOM, -SO3M, -PO3H2 and -COOR3, where M is H, Na or K, and R3 is a C1~C6 alkyl group.

[0016] Metal-organic frameworks (MOFs) are porous materials composed of metal centers and organic ligands, possessing advantages such as high porosity, large specific surface area, high thermal stability, and ordered crystal structure. Compared with conventional electrode materials, the functional tunability and porosity of MOFs make them excellent charge storage electrodes. Porphyrins are a class of aromatic compounds with high π-π conjugation stability, and their abundant active centers are very suitable for use in electrochemical devices. Although porphyrins have broad application prospects in lithium-ion batteries, issues such as ionic conductivity and structural stability still limit their application development. This invention uses a porphyrin ring in a large conjugated system as the backbone. The groups introduced into the porphyrin structure by this invention not only provide additional structural stability, helping to buffer volume expansion and contraction during cycling, but also enhance electron transfer and improve electrochemical performance. Furthermore, divalent metals and trivalent manganese ions are introduced into the ligand, and metalloporphyrins are prepared through coordination chelation between porphyrin and metal ions, thereby preparing bimetallic MOF materials. The bimetallic MOFs provided by this invention reduce the HOMO-LUMO energy level difference of the ligand by introducing metal ions, thus improving their conductivity. The organic ligands provided by this invention also have abundant redox active sites, which are more conducive to interaction with Li. + This allows for the combination of substances, thereby enhancing electrochemical performance.

[0017] As a preferred option, R1 and R2 are each independently selected from one of -COOH, -SO3H, -PO3H2 and -COOCH3.

[0018] As a more preferred embodiment, the organic ligand has the structure of formula (A):

[0019] Formula (A)

[0020] In formula (A), R1 and R2 are the same, being either -COOH or -COOCH3. Modification at positions 5 and 15 using the functional groups R1 and R2 can further improve the electrochemical performance of lithium-ion batteries.

[0021] As a preferred embodiment, in manganese-based bimetallic MOFs materials, the molar ratio of divalent metal to organic ligand is 1.3~1.8:1, and the molar ratio of trivalent manganese to the organic ligand is 1~1.2:1. Reducing the amount of trivalent manganese will lead to a decrease in the conductivity of the material.

[0022] As a more preferred embodiment, the molar ratio of divalent metal to organic ligand is 1.5:1, and the molar ratio of trivalent manganese to the organic ligand is 1:1. It has been found that, under this preferred condition, the prepared lithium-ion anode material exhibits superior electrochemical performance.

[0023] As a preferred embodiment, in formula (A), R1 and R2 are identical, both being -COOCH3. Compared to existing carboxyphenyl ligands, this ligand has a lower energy level difference and exhibits superior charge transport potential as an electrochemical energy storage MOF ligand.

[0024] As a preferred embodiment, the divalent metal is nickel. When Ni 2+ With Mn 3+ When used in combination, the synergistic effect between the bimetals can effectively improve the electronic structure of the material and exhibit better electrochemical performance.

[0025] As a preferred embodiment, the coordination reaction process includes:

[0026] (1) In the presence of organic solvent I, the organic ligand is mixed with manganese source and refluxed in the dark to obtain a precipitate. The precipitate is then dissolved in organic solvent II and the organic solvent II is evaporated under a protective atmosphere to obtain Mn-ligand complex.

[0027] (2) After dissolving the Mn-ligand complex in organic solvent III, an acid solution is added for protonation to obtain the protonated product; when the organic ligand contains a -COOR3 group, alkaline hydrolysis is performed in an alkaline solution before protonation, and then protonation is performed.

[0028] (3) The protonated product is reacted with a divalent metal source by a solvothermal reaction to obtain the product.

[0029] As a preferred embodiment, the temperature of the light-shielded reflux is 120~140℃, and the time is 4~8h.

[0030] As a preferred approach, alkaline hydrolysis has a pH of 13-14, and protonation has a pH of 2-4.

[0031] As a preferred embodiment, the temperature of the solvothermal reaction is 140~180℃ and the time is 12~36h.

[0032] It should be noted that the present invention does not have any special requirements for the preparation method of the organic ligand; conventional preparation methods in the field can be used, or commercially available organic ligands can be used.

[0033] As a preferred embodiment, in step (2), the alkaline hydrolysis is performed at a temperature of 50-70°C for 20-30 hours.

[0034] As a preferred approach, protonation is performed after alkaline hydrolysis followed by evaporation of 40-60% by volume of organic solvent III under a protective atmosphere.

[0035] As a preferred embodiment, in step (1), the method further includes: dissolving the precipitate in organic solvent II, washing it with hydrochloric acid solution, retaining the organic layer, drying it, and then evaporating the organic solvent II under a protective atmosphere to obtain the Mn-ligand complex.

[0036] As a preferred embodiment, the protective atmosphere is an oxygen-free atmosphere. More preferably, a nitrogen atmosphere and / or an argon atmosphere is used.

[0037] As a preferred embodiment, organic solvent I is N,N-dimethylformamide, organic solvent II is chloroform, and organic solvent III is a combination of tetrahydrofuran and methanol in a volume ratio of 1:0.8~1.2.

[0038] As a preferred embodiment, the solvent for the solvothermal reaction is tetrahydrofuran.

[0039] It should be noted that the present invention does not have special requirements on the amount of each solvent used, and any solvent known in the art can be used.

[0040] A third aspect of the present invention is to provide the application of manganese-based bimetallic MOFs materials in the preparation of lithium battery anode materials.

[0041] A fourth aspect of the present invention is to provide a negative electrode material for a lithium-ion battery, comprising a negative electrode active material, wherein the negative electrode active material is the manganese-based bimetallic MOF material described in the second aspect above.

[0042] As a preferred embodiment, the negative electrode active material comprises manganese-based bimetallic MOFs, a conductive agent, and a binder.

[0043] As a preferred embodiment, based on the total mass of the lithium battery anode material, the content of the manganese-based bimetallic MOF material is 50-70 wt%, the content of the conductive agent is 25-35 wt%, and the content of the binder is 5-15 wt%.

[0044] As a preferred embodiment, the manganese source is a soluble salt of divalent manganese. More preferably, it is at least one selected from manganese nitrate, manganese chloride, and manganese acetate.

[0045] As a preferred embodiment, the divalent metal source is selected from at least one of soluble nickel salts, soluble zinc salts, soluble cobalt salts, and soluble copper salts.

[0046] As a more preferred embodiment, the divalent metal source is selected from at least one of nickel nitrate, nickel chloride, nickel acetate, and nickel sulfate.

[0047] As a preferred embodiment, the conductive agent is carbon black and the binder is polyvinylidene fluoride.

[0048] A fifth aspect of the present invention is to provide a negative electrode for a lithium-ion battery, comprising a current collector and a negative electrode material loaded thereon, wherein the negative electrode material is the negative electrode material for the lithium-ion battery described in the third aspect above.

[0049] Compared with the prior art, the present invention has at least the following advantages:

[0050] This invention utilizes specific porphyrin-based organic ligands and introduces bimetallic ions, particularly manganese ions with variable valence states, at the center of the porphyrin ring to achieve improved electrode specific capacity and enhanced rate performance when prepared as a lithium-ion battery anode material. Its specific capacity is [not specified in the original text]. -1 It still has 1160 mAh g after 150 cycles at a current density. -1 Its high reversible specific capacity means that even with a 10-fold increase in current density, it retains 588 mAh g⁻¹ after 800 cycles. -1 The specific capacity indicates that it has good cycling stability. Attached Figure Description

[0051] Figure 1 The image shows the 1H NMR spectrum of dipyrrolemethane prepared in the preparation example.

[0052] Figure 2 This is the 1H NMR spectrum of 5,15-bis(4-methoxycarbonylphenyl)porphyrin MeODBP prepared by the preparation example.

[0053] Figure 3 This is the mass spectrum of MeODBP(Mn) prepared in Example 1.

[0054] Figure 4 The 1H NMR spectrum of 5,15-bis(4-carboxyphenyl)porphyrin H2DBP prepared in Example 1.

[0055] Figure 5 The mass spectrum of H2DBP(Mn) prepared in Example 1 is shown.

[0056] Figure 6 The XRD diffraction patterns of DBP(Mn)-Ni prepared in Example 1 and DBP-Ni prepared in Comparative Example 1 are shown. They indicate that both DBP(Mn)-Ni and DBP-Ni in Comparative Example 1 have ordered crystal structures, and their crystal structures are similar.

[0057] Figure 7 The image shown is a scanning electron microscope (SEM) image of DBP(Mn)-Ni prepared in Example 1. Figure 7 This indicates that the morphology of DBP(Mn)-Ni is 2D nanosheets.

[0058] Figure 8 The image shown is a transmission electron microscope (TEM) image of DBP(Mn)-Ni prepared in Example 1. Figure 8 This indicates that the morphology of DBP-Ni is 2D nanosheets.

[0059] Figure 9 The XPS results and elemental peak fitting curves for DBP(Mn)-Ni and DBP-Ni are shown in the figure. As can be seen from the figure, the successful introduction of manganese ions with variable valence states into DBP(Mn)-Ni, compared to Ni 2p in Comparative Example 1, shows that the Ni 2p binding energy in DBP(Mn)-Ni is larger, indicating that the introduction of manganese ions with variable valence states enhances the oxidation ability of the Ni-COO group.

[0060] Figure 10 The image shows the cyclic voltammetry (CV) diagrams of half-cells prepared from the MOFs materials of Example 1 and Comparative Example 1.

[0061] Figure 11 The image shows the constant current charge-discharge diagrams of half-cells prepared from MOFs materials of Example 1, Comparative Example 1, and Comparative Example 2.

[0062] Figure 12 The graph shows the rate performance of half-cells prepared from MOFs materials of Example 1, Comparative Example 1, and Comparative Example 2.

[0063] Figure 13 The graph shows the long-cycle performance of half-cells prepared from MOFs materials of Example 1, Comparative Example 1, and Comparative Example 2.

[0064] Figure 14 The images show cyclic voltammetry diagrams of half-cells prepared from MOFs materials in Example 1 at different scan rates.

[0065] Figure 15 The graph shows the proportions of diffusion control and capacitance control of the half-cells prepared from the MOFs material in Example 1 at different scan rates.

[0066] Figure 16 Schematic diagram of the synthesis of Example 1 and Comparative Example 1.

[0067] Figure 17 The image shows the constant current charge-discharge diagram of the half-cell prepared from the MOFs material in Comparative Example 3. Detailed Implementation

[0068] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0069] In this invention, room temperature refers to 25±2℃.

[0070] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0071] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0072] The preparation example is used to prepare 5,15-bis(4-methoxycarbonylphenyl)porphyrin (MeODBP).

[0073] (1) Synthesis of dipyrrolemethane:

[0074] Add 250 mL of freshly evaporated pyrrole and 0.87 g of polyoxymethylene to a 500 mL round-bottom flask. Heat to 60 °C under argon protection to dissolve all raw materials. Stir for 30 min and cool to room temperature. Slowly add 0.27 mL of trifluoroacetic acid (TFA) to the solution and stir continuously for 1 h. Then add 410 mg of sodium hydroxide and stir continuously for 1 h. Distill the remaining pyrrole under vacuum. Extract the remaining solid with dichloromethane / water. Purify the crude product in chloroform. The pure product is a brown crystal, yielding dipyrrolemethane.

[0075] (2) Synthesis of 5,15-bis(4-methoxycarbonylphenyl)porphyrin (MeODBP):

[0076]

[0077] Take 1.2 g of 4-(methoxycarbonyl)benzaldehyde, add 1.07 g of dipyrrolemethane and 1000 mL of anhydrous dichloromethane (DCM) to a round-bottom flask, stir thoroughly to dissolve, and then slowly add 340 μL of TFA dropwise to the solution. Stir at room temperature in the dark for 4 h. After the reaction is complete, add 2.49 g of 2,3-dichloro-5,6-dicyano-1,4-dibenzoquinone (DDQ) to the reaction mixture, stir for another 30 min, add an equimolar amount of triethylamine (TEA) to neutralize the reaction mixture, and distill the remaining solvent under vacuum. Use chloroform as the mobile phase and purify the crude product of MeODBP by column chromatography.

[0078] Example 1

[0079] (1) Synthesis of MeODBP(Mn):

[0080] Weigh 434 mg MeODBP and 1.9 g MnCl2·4H2O into a 250 mL round-bottom flask, add 100 mL N,N-dimethylformamide (DMF), reflux at 140 °C in the dark for 6 h, cool to room temperature, add 100 mL H2O, let stand overnight, filter and collect the precipitate. Then, dissolve the precipitate in chloroform, wash twice with 1 M HCl, and then wash three times with H2O to retain the organic layer. After drying with anhydrous magnesium sulfate, evaporate the chloroform under a nitrogen atmosphere to give a purple-red product.

[0081] (2) Synthesis of H2DBP(Mn):

[0082] Weigh 400 mg MeODBP(Mn) into a 250 mL round-bottom flask, add 45 mL of anhydrous tetrahydrofuran (THF) and 45 mL of methanol. After the solid is completely dissolved, add 14 mL of 2 M potassium hydroxide aqueous solution (pH=13.5) and reflux at 60 °C for 24 h. After cooling to room temperature, evaporate half the volume of solvent under a nitrogen atmosphere. Adjust the pH of the remaining solution to 3 using TFA / NaHCO3. Collect the precipitate by centrifugation, wash three times with water and ether, and dry overnight in a vacuum oven at 60 °C.

[0083] (3) Synthesis of DBP(Mn)-Ni:

[0084] 0.25 mmol H₂DBP(Mn) and 1.25 mmol NiCl₂·6H₂O were dissolved separately in 20 mL of N,N-dimethylformamide (DMF). After the two solutions were mixed thoroughly, they were transferred to a reaction vessel lined with polytetrafluoroethylene and reacted at 150 °C for 48 h. After cooling to room temperature, the cooled product was collected by vacuum filtration, washed three times with DMF, and dried overnight in a vacuum oven at 60 °C to obtain DBP(Mn)-Ni.

[0085] Figures 1 to 5 This demonstrates that DBP(Mn)-Ni has been successfully synthesized, and that Ni in DBP(Mn)-Ni... 2+ and Mn 3+ It has been successfully introduced and does not contain Mn. 2+ , where Ni 2+ The molar ratio of Mn to the organic ligand is 1.5:1. 3+ The molar ratio with the organic ligand is 1:1.

[0086] Comparative Example 1

[0087] (1) Synthesis of H2DBP:

[0088] Weigh 400 mg MeODBP into a 250 mL round-bottom flask, add 45 mL of anhydrous tetrahydrofuran (THF) and 45 mL of methanol. After the solid is completely dissolved, add 14 mL of 2 M potassium hydroxide aqueous solution (pH=13.5) and reflux at 60 °C for 24 h. After cooling to room temperature, evaporate half the volume of solvent in a reducing atmosphere. Adjust the pH of the remaining solution to 3 using TFA / NaHCO3. Collect the precipitate by centrifugation, wash three times with water and ether, and dry overnight in a vacuum oven at 60 °C.

[0089] (2) Synthesis of DBP-Ni:

[0090] 0.25 mmol H₂DBP and 1.25 mmol NiCl₂·6H₂O were dissolved in 20 mL of N,N-dimethylformamide (DMF), respectively. After the two solutions were mixed thoroughly, they were transferred to a reaction vessel lined with polytetrafluoroethylene and reacted at 150 °C for 48 h. After cooling to room temperature, the cooled product was collected by vacuum filtration, washed three times with DMF, and dried overnight in a vacuum oven at 60 °C to obtain DBP-Ni.

[0091] Comparative Example 2

[0092] (1) Synthesis of MeODBP(Zn):

[0093] Weigh 434 mg MeODBP and 1.8 g ZnCl2 into a 250 mL round-bottom flask, add 100 mL N,N-dimethylformamide (DMF), reflux at 140 °C in the dark for 6 h, cool to room temperature, add 100 mL H2O, let stand overnight, filter and collect the precipitate. Then, dissolve the precipitate in chloroform, wash twice with 1 M HCl, and then wash three times with H2O to retain the organic layer. After drying with anhydrous magnesium sulfate, evaporate the chloroform under a nitrogen atmosphere to give a purple-red product.

[0094] (2) Synthesis of H2DBP(Zn):

[0095] Weigh 400 mg MeODBP(Zn) into a 250 mL round-bottom flask, add 45 mL of anhydrous tetrahydrofuran (THF) and 45 mL of methanol. After the solid is completely dissolved, add 14 mL of 2 M potassium hydroxide aqueous solution (pH=13.5) and reflux at 60 °C for 24 h. After cooling to room temperature, evaporate half the volume of solvent under a nitrogen atmosphere. Adjust the pH of the remaining solution to 3 using TFA / NaHCO3. Collect the precipitate by centrifugation, wash three times with water and ether, and dry overnight in a vacuum oven at 60 °C.

[0096] (3) Dissolve 0.25 mmol H2DBP(Zn) and 1.25 mmol NiCl2·6H2O in 20 mL N,N-dimethylformamide (DMF), respectively. After mixing the two solutions thoroughly, transfer them to a reaction vessel lined with polytetrafluoroethylene and react at 150 °C for 48 h. After cooling to room temperature, collect the cooled product by vacuum filtration, wash three times with DMF, and dry overnight in a vacuum oven at 60 °C to obtain DBP(Zn)-Ni.

[0097] Comparative Example 3

[0098] (1) Preparation of MeOTCPP (tetra(4-methoxycarbonylphenyl)porphyrin)

[0099] Weigh 3.0 g of pyrrole and 6.9 g of methyl paraformylbenzoate into a 500 mL three-necked flask, add 100 mL of propionic acid to completely dissolve them, and reflux at 140 °C for 12 h. After the mixture cools to room temperature, filter to obtain a purple-black product, wash with acetone, and the resulting purple crystals are denoted as MeOTCPP.

[0100] (2) Preparation of MeOTCPP(Mn)

[0101] 0.854 g MeOTCPP and 1.25 g MnCl2·4H2O were added to a 500 mL three-necked flask, and 100 mL of LDM was added. The mixture was refluxed for 6 h. After cooling to room temperature, 100 mL of water was added. The resulting precipitate was filtered and washed twice with 50 M LH2O. The resulting solid was dissolved in chloroform, washed three times with 1 M HCl, and washed twice with water. After separation, the organic layer was evaporated using a rotary evaporator to remove the organic solvent. The resulting crystals were designated as MeOTCPP(Mn).

[0102] (3) Preparation of TCPP(Mn)

[0103] Weigh 0.75 g of MeOTCPP(Mn) into a 100 mL flask, add 25 mL of tetrahydrofuran and 25 mL of methanol to dissolve it, and then add 25 mL of KOH aqueous solution (mKOH = 2.63 g). Reflux the mixture at 60 °C for 12 h. After cooling to room temperature, remove the tetrahydrofuran and methanol using a rotary evaporator. Adjust the pH of the remaining solution to approximately 3 with HCl, collect the precipitate through filtration, and wash with water. The resulting crystals are denoted as TCPP(Mn).

[0104] (4) Preparation of TCPP(Mn)-Ni

[0105] 1.25 mmol NiCl₂·6H₂O and 0.25 mmol TCPP(Mn) were dissolved in 40 mL LDM. After stirring until homogeneous, the mixture was transferred to a 100 mL stainless steel PTFE hydrothermal reactor and heated at 140 °C for 48 h. After cooling, the resulting product was collected at room temperature and washed three times with H₂O / ethanol. The product was designated as TCPP(Mn)-Ni.

[0106] Test case

[0107] Electrochemical performance tests were performed on the MOFs materials prepared in the above examples. Specifically, the MOFs materials prepared in the above examples were added to N-methylpyrrolidone in a mass ratio of 6:3:1 with conductive carbon black and polyvinylidene fluoride. After stirring evenly, the mixture was coated onto a pretreated conductive copper foil substrate and dried in a vacuum drying oven for 12 hours to form a negative electrode. In a glove box, it was combined with a lithium foil to form a button half-cell CR2016. The electrolyte was a 1 M LiPF6 solution containing ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl carbonate (EMC) (1:1:1, vol.%). The separator was a Celgard 2500 membrane. The specific test results are shown in Table 1.

[0108] The assembled battery underwent constant current charge-discharge experiments using a Newware CT2001A tester from Shenzhen Newware Electronics Co., Ltd. The constant current charge-discharge test current density was 100 mA g.-1 The rate testing current densities were 100, 500, 1000, 1500, 2000, 2500, and 3000 mA g. -1 The long-cycle test current density is 1000 mA g -1 .

[0109] Cyclic voltammetry and AC impedance spectroscopy were performed on the assembled battery using a Gamry Instruments Interface 1010E electrochemical workstation. Cyclic voltammetry scan rates were 0.2, 0.4, 0.6, 0.8, and 1 mV s. -1 The cutoff voltages were 0.01V and 2.99756V, respectively. The initial frequency of the AC impedance test was 100000Hz, and the cutoff frequency was 0.01Hz.

[0110]

[0111] The battery prepared in Comparative Example 2 was tested at 100 mA g. -1 After 50 cycles, it contained only 551.1 mAh g. -1 Even with a 10-fold increase in current density and 700 cycles, its specific capacity is only 195.02 mAh g. -1 The electrochemical performance of DBP(Zn)-Ni is worse than that of monometallic DBP-Ni, proving that Mn 3 +-Ni 2+ The synergistic effect between them effectively improved the electrochemical performance of the materials. As can be seen from the results of Comparative Example 3, TCPP(Mn)-Ni exhibited significantly lower performance than DBP(Mn)-Ni, which was lower at 100 mA g. -1 After 60 cycles at the specified current density, it only exhibited 455.63 mAh g⁻¹. -1 The capacity.

[0112] Figure 10 The figures show the cyclic voltammetry (CV) curves of half-cells prepared from the MOFs materials of Example 1 and Comparative Example 1. As can be seen from the figures, the first CV curve differs significantly from subsequent cycles. This change is likely due to some irreversible reactions and the formation of the solid-electrolyte-interphase (SEI) layer. The integral area of ​​the CV curve for DBP(Mn)-Ni is larger than that for DBP-Ni in Comparative Example 1, indicating that the DBP(Mn)-Ni anode has better specific capacity and reversibility.

[0113] Figure 11The figures show the galvanostatic charge-discharge curves of half-cells prepared from the MOFs materials of Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from the figures, DBP(Mn)-Ni exhibits better reversibility and superior performance during cycling compared to DBP-Ni in Comparative Example 1 and DBP(Zn)-Ni in Comparative Example 2.

[0114] Figure 12 The graph shows the rate performance of half-cells prepared from MOFs materials of Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from the graph, the DBP(Mn)-Ni anode provides higher capacity at all current densities than the DBP-Ni in Comparative Example 1 and the DBP(Zn)-Ni in Comparative Example 2, indicating its superior rate performance.

[0115] Figure 13 The graph shows the long-cycle performance of half-cells prepared from MOF materials of Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from the graph, the DBP(Mn)-Ni anode exhibits a higher specific capacity after long-cycle operation at high current densities compared to the DBP-Ni in Comparative Example 1 and the DBP(Zn)-Ni in Comparative Example 2, indicating its good cycle stability. The manganese-based bimetallic MOFs provided by this invention, as anode materials for lithium-ion batteries, can improve the cycle stability of lithium-ion batteries, extend battery life, and maintain a high specific capacity even at high current densities.

[0116] Figure 14 The figures show cyclic voltammetry diagrams of half-cells prepared from the MOFs materials in the examples at different scan rates. The peaks represent the characteristic peaks of the DBP(Mn)-Ni anode, with the peak positions changing slightly with increasing scan rate.

[0117] Figure 15 The graph shows the proportions of diffusion-controlled and capacitance-controlled processes in the half-cells prepared from the MOFs material of Example 1 at different scan rates. The graph shows the changes in the capacitance-controlled and diffusion-controlled proportions of the DBP(Mn)-Ni anode at different scan rates, indicating that capacitance control dominates the electrochemical reaction of this material.

[0118] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a manganese-based bimetallic MOF material, characterized in that: By coordinating an organic ligand with the structure of formula (1) and a composite metal source containing a divalent metal source and a manganese source, a bimetallic MOF material containing a divalent metal-trivalent manganese is prepared; the divalent metal source contains at least one of Ni, Zn, Co, and Cu. Equation (1); In formula (1), R1 and R2 are each independently selected from one of -COOM, -SO3M, -PO3H2 and -COOR3, where M is H, Na or K, and R3 is a C1~C6 alkyl group.

2. The method for preparing a manganese-based bimetallic MOF material according to claim 1, characterized in that: R1 and R2 are each independently selected from one of -COOH, -SO3H, -PO3H2 and -COOCH3; Preferably, the organic ligand has the structure of formula (A): Formula (A) In formula (A), R1 and R2 are the same, being either -COOH or -COOCH3.

3. The method for preparing a manganese-based bimetallic MOF material according to claim 1 or 2, characterized in that: In manganese-based bimetallic MOF materials, the molar ratio of divalent metal to organic ligand is 1.3~1.8:1, and the molar ratio of trivalent manganese to the organic ligand is 1~1.2:

1. Preferably, the molar ratio of divalent metal to organic ligand is 1.5:1, and the molar ratio of trivalent manganese to organic ligand is 1:

1.

4. A method for preparing a manganese-based bimetallic MOF material according to claim 1 or 2, characterized in that: In equation (A), R1 and R2 are the same, both being -COOCH3; And / or, the divalent metal is nickel.

5. A method for preparing a manganese-based bimetallic MOF material according to claim 1 or 2, characterized in that: The coordination reaction process includes: (1) In the presence of organic solvent I, the organic ligand is mixed with manganese source and refluxed in the dark to obtain a precipitate. The precipitate is then dissolved in organic solvent II and the organic solvent II is evaporated under a protective atmosphere to obtain Mn-ligand complex. (2) After dissolving the Mn-ligand complex in organic solvent III, an acid solution is added for protonation to obtain the protonated product; when the organic ligand contains a -COOR3 group, alkaline hydrolysis is performed in an alkaline solution before protonation, and then protonation is performed. (3) The protonated product is reacted with a divalent metal source by a solvothermal reaction to obtain the product.

6. The method for preparing manganese-based bimetallic MOFs materials according to claim 5, characterized in that: The temperature for the light-protected reflux is 120~140℃, and the time is 4~8h; And / or, the pH value for alkaline hydrolysis is 13-14, and the pH value for protonation is 2-4; And / or, the temperature of the solvothermal reaction is 120~140℃ and the time is 12~36h; And / or, the organic solvent I is N,N-dimethylformamide, the organic solvent II is chloroform, and the organic solvent III is a combination of tetrahydrofuran and methanol in a volume ratio of 1:0.8~1.2; And / or, the solvent for the solvothermal reaction is tetrahydrofuran.

7. Manganese-based bimetallic MOFs materials prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the manganese-based bimetallic MOFs material according to claim 7 in the preparation of lithium battery anode materials.

9. A negative electrode material for a lithium-ion battery, comprising a negative electrode active material, characterized in that: The negative electrode active material comprises the manganese-based bimetallic MOFs material as described in claim 8.

10. A negative electrode for a lithium-ion battery, comprising a current collector and a negative electrode material loaded thereon, characterized in that: The negative electrode material is the negative electrode material of the lithium-ion battery as described in claim 9.

Images