Anthraquinone conjugated coordination polymer electrode material for secondary battery as well as preparation method and application of anthraquinone conjugated coordination polymer electrode material

Abstract

The invention belongs to the field of preparation of secondary battery electrode materials, and particularly relates to an anthraquinone conjugated coordination polymer electrode material for a secondary battery as well as a preparation method and application of the anthraquinone conjugated coordination polymer electrode material. The structure of the anthraquinone conjugated coordination polymer is shown as a formula # imgabs0 #, R1 and R2 are respectively and independently selected from O, S or NH, and R1 and R2 are not O at the same time; r3 and R4 are independently selected from a hydrogen atom, an amino group, a hydroxyl group or a sulfydryl group; m is a transition metal ion. The anthraquinone conjugated coordination polymer is used as a positive electrode of a secondary battery, the anthraquinone conjugated coordination polymer, a conductive agent and a binder are uniformly mixed in a dispersion liquid, then a current collector is uniformly coated with the mixture, and then vacuum drying is performed to obtain the positive electrode of the secondary battery. The technical problems of low specific capacity, low energy density and rapid degradation of capacity and cycle performance of the secondary battery are solved.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of secondary battery electrode materials. Specifically, it relates to an anthraquinone-based conjugated coordination polymer electrode material for secondary batteries, its preparation method and application. Background Art

[0002] Secondary batteries have occupied a dominant position in the fields of electronic devices, electric vehicles, large-scale energy storage power stations, etc. due to their advantages such as high energy density, portability and strong environmental adaptability. As the current mainstream secondary battery, the cathode material of lithium-ion batteries, as the main body of the electrochemical reaction, directly determines the upper limit of the energy density and the comprehensive cost of the battery. However, commercial inorganic cathode materials (such as layered LiCoO2, ternary lithium battery materials) are composed of elements such as lithium, cobalt and nickel, and the scarcity (low crustal abundance, Co: 0.003%, Ni: 0.008%) and unsustainability of their resources are becoming increasingly apparent. Secondly, the rigid crystal structure is prone to lattice volume changes during the ion insertion / extraction process, resulting in the reconstruction of the electrode / electrolyte interface, leading to irreversible capacity loss and cycle stability problems.

[0003] To solve the above problems, researchers have focused on developing organic electrode materials with both structural tunability and sustainability. Generally speaking, organic electrode materials (such as quinone-based, imine-based compounds) can obtain high theoretical specific capacity through multi-electron redox reactions, which is significantly better than traditional inorganic cathodes. However, the low electronic conductivity of organic materials leads to the need to add a high proportion of conductive agents during the electrode preparation process, resulting in a serious decline in the actual energy density. Secondly, the dissolution of most organic small molecule active substances in organic electrolytes will cause rapid decline in capacity and cycle performance. These bottleneck problems have slowed down the industrialization process of organic electrode materials.

[0004] To break through the limitations of the existing electrode material system, conjugated coordination polymers, as a new type of organic-inorganic hybrid material, exhibit unique energy storage potential. Conjugated coordination polymers self-assemble into ordered crystalline materials through the coordination bonding of conjugated organic ligands and metal ions. Structurally, the good conjugated structure of conjugated coordination polymers endows them with excellent conductivity. At the same time, the inherent redox activity and multi-electron storage performance make them have a high theoretical capacity. More importantly, the flexible porous structure of conjugated coordination polymers allows rapid ion insertion / extraction without causing serious material volume changes, ensuring the cycle life of the battery. Therefore, conjugated coordination polymer materials are very promising as secondary battery electrode materials.

[0005] However, there are still some defects that cannot be ignored in the reported conjugated coordination polymer electrode materials. The electron delocalization degree of some existing conjugated coordination polymers is limited, resulting in poor electron transport performance and restricting their battery performance (Cheng L, Yu J, Chen L, et al. Immobilizing Quinone-Fused Aza-Phenazine into π-d Conjugated Coordination Polymers with Multiple-Active Sites for Sodium-Ion Batteries[J]. Small, 2023, 19(35): 2301578.). The actual capacity of some conjugated coordination polymers is much lower than the theoretical value because their unique redox potential or active sites cannot be fully utilized (Chen Y, Zhu Q, Fan K, et al. Successive storage of cations and anions by ligands of π–d-conjugated coordination polymers enabling robust sodium-ion batteries[J]. Angewandte Chemie, 2021, 133(34): 18917-18924.). More notably, the electron delocalization degree of conjugated coordination polymers constructed with ligands having a relatively small conjugated system or only a single coordination atom is limited, and the intermolecular π-π stacking interaction is relatively weak, which leads to poor chemical and electrochemical stability of such coordination polymers (Luo Y, Liu J, Zhang L. A Monocrystalline Coordination Polymer with Multiple Redox Centers as a High-Performance Cathode for Lithium-Ion Batteries[J]. Angewandte Chemie, 2022, 134(38): e202209458.). Therefore, how to design novel ligands to construct conjugated coordination polymer electrode materials with excellent conductivity, high capacity, and good cycle stability is worthy of in-depth study. Summary of the Invention

[0006] In view of the above deficiencies or improvement requirements of the prior art, the present invention provides an anthraquinone-based conjugated coordination polymer electrode material for secondary batteries, its preparation method and application, aiming to obtain an anthraquinone-based conjugated coordination polymer with [MX4] (M is a transition metal ion, X is O, S or NH) as the coordination unit, thereby solving the technical problems of low specific capacity, low energy density of secondary batteries in the prior art, and rapid decline of capacity and cycling performance.

[0007] To achieve the above object, according to one aspect of the present invention, an anthraquinone-based conjugated coordination polymer electrode material is provided, and the structural general formula of the anthraquinone-based conjugated coordination polymer is selected from one of the structures of formula (1) or formula (2):

[0008]

[0009] Wherein, R1 and R2 are each independently selected from O, S or NH, and R1 and R2 are not both O at the same time; R3 and R4 are each independently selected from hydrogen, amino group, hydroxyl group or mercapto group; M is a transition metal ion.

[0010] Preferably, the transition metal ion is selected from Cu 2+ , Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ , Fe 2+ , Fe 3+ One or more of them.

[0011] According to another aspect of the present invention, a preparation method of an anthraquinone-based conjugated coordination polymer electrode material is provided,

[0012] (1) Add a transition metal salt to a solvent and dissolve it to obtain a transition metal salt solution;

[0013] (2) Use the product after substituting the hydrogen atoms at the 1 and 4 carbon positions, or 5 and 8 carbon positions, or 1 and 5 carbon positions, or 4 and 8 carbon positions on anthraquinone with coordination groups as the ligand, and add the ligand to the transition metal salt solution to obtain a reaction solution; the coordination group is selected from amino group, hydroxyl group or mercapto group;

[0014] (3) After heating and reacting the reaction solution, make the oxygen atom on anthraquinone and the coordination group both form a six-membered ring structure with the transition metal ion in the transition metal salt through coordination bonding to obtain the anthraquinone-based conjugated coordination polymer.

[0015] Preferably, the solvent is selected from one or more of ethanol, water, N,N-dimethylformamide or dimethyl sulfoxide.

[0016] Preferably, the molar ratio of the transition metal salt to the ligand is 1 to 2; the concentration of the transition metal salt solution is 0.005 mol / L - 4 mol / L.

[0017] Preferably, in step (3), the heating conditions are as follows: hydrothermal or heating reaction at a temperature of 60 - 180 °C for 6 - 72 h.

[0018] According to another aspect of the present invention, there is provided an application of the anthraquinone-based conjugated coordination polymer electrode material, which is used as a positive electrode material for secondary batteries.

[0019] According to another aspect of the present invention, there is provided a positive electrode for a secondary battery, which includes a conductive agent, a binder, and the anthraquinone-based conjugated coordination polymer.

[0020] According to another aspect of the present invention, there is provided a method for preparing a positive electrode for a secondary battery, in which the anthraquinone-based conjugated coordination polymer, the conductive agent, and the binder are uniformly mixed in a dispersion liquid, and then uniformly coated on a current collector, and then vacuum dried to obtain the positive electrode for the secondary battery.

[0021] Preferably, the conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, and graphene;

[0022] Preferably, the binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, and polyvinyl alcohol.

[0023] Preferably, the mass ratio of the anthraquinone-based conjugated coordination polymer, the conductive agent, and the binder is (1 - 9):(8 - 0.5):(1 - 0.5)

[0024] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0025] 1. Based on low-cost and easily available anthraquinone-based industrial materials and their derivatives, the present invention prepares a series of novel conjugated coordination polymers through their coordination reaction with transition metal ions by a one-pot method. Such materials have a highly ordered crystal structure and excellent chemical stability. Their six-membered ring metal coordination centers and extended π-d conjugated systems endow them with excellent electron transport characteristics and electrochemical stability, enabling reversible storage of monovalent and multivalent ions. Compared with traditional conjugated coordination polymers with five-membered ring coordination centers, the anthraquinone-based conjugated coordination polymers provided by the present invention all have six-membered ring coordination structures, and the larger coordination active centers greatly improve the structural stability during multi-electron storage.

[0026] 2. The present invention replaces anthraquinone with heteroatom coordination groups (independently selected from amino, hydroxyl or mercapto groups, and R1 and R2 are not both O at the same time). Compared with anthraquinone substituted with pure hydroxyl groups (i.e., when R1 and R2 are both O at the same time) as the coordination group, the structure of the present invention has better atomic orbital overlap with metal ions, thus improving the electron transport performance and electrochemical stability of the conjugated coordination polymer. At the same time, the conjugated coordination polymer formed by the heteroatom coordination group-substituted anthraquinone has a stronger π-d conjugation effect, which can stimulate the multi-electron storage of the coordination center. When used as an electrode material, the assembled secondary battery has excellent capacity release and cycle life.

[0027] 3. The conjugated coordination polymer material provided by the present invention has stable redox activity and multi-electron storage ability, and can stably store a variety of monovalent and polyvalent ions. Thereby, the energy density of the electrode material is improved, which is suitable for the field of secondary batteries. The sodium-ion battery assembled with the anthraquinone-based conjugated coordination polymer of the present invention as the positive electrode material has a maximum discharge capacity of 325 mAh g -1 , and has a capacity retention of 85% after cycling 100 times at a current density of 100 mA g -1 . These performances are superior to most of the reported conjugated coordination polymer positive electrode materials, revealing the unique advantages of anthraquinone-based conjugated coordination polymers in new secondary battery systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. is the cycling performance diagram of the anthraquinone-based conjugated coordination polymer material P-1 (M = Cu 2+ ) assembled into a battery at a current density of 100 mA g -1 in Example 1 of the present invention.

[0029] Figure 2 FIG. is the charge-discharge curve of the anthraquinone-based conjugated coordination polymer material P-2 (M = Cu 2+ ) assembled into a battery at a current density of 100 mA g -1 in Example 2 of the present invention.

[0030] Figure 3 FIG. is the charge-discharge curve of the anthraquinone-based conjugated coordination polymer material P-3 (M = Cu 2+ ) assembled into a battery at a current density of 100 mA g -1 in Example 3 of the present invention.

[0031] Figure 4 FIG. is the scanning electron microscope image of the anthraquinone-based conjugated coordination polymer P-4 (M = Cu 2+ ) described in Example 4 of the present invention.

[0032] Figure 5This is the powder XRD comparison chart of the conjugated coordination polymer composite electrode material and the conjugated coordination polymer P-4 (M = Cu) in Example 5 of the present invention. 2+ )

[0033] Figure 6 This is the cycling performance chart of the conjugated coordination polymer composite electrode material assembled into a battery at a current density of 100 mA g -1 . Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] To achieve the above objective, according to one aspect of the present invention, an anthraquinone-based conjugated coordination polymer electrode material is provided, and the structural general formula of the anthraquinone-based conjugated coordination polymer is selected from one of the following structures:

[0036]

[0037] Wherein, R1 and R2 are independently selected from O, S or NH, and R1 and R2 are not both O at the same time; R3 and R4 are independently selected from hydrogen, amino group, hydroxyl group or mercapto group; M is a transition metal ion.

[0038] Preferably, the transition metal ion is selected from 2+ Cu 2+ , Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ , Fe 3+ or one or more of them.

[0039] According to another aspect of the present invention, a preparation method of an anthraquinone-based conjugated coordination polymer electrode material is provided.

[0040] (1) Add a transition metal salt to a solvent to dissolve it to obtain a transition metal salt solution;

[0041] (2) Use the product obtained by substituting the hydrogen atoms at the 1- and 4-carbon positions, or 5- and 8-carbon positions, or 1- and 5-carbon positions, or 4- and 8-carbon positions of anthraquinone with a coordination group as a ligand, and add the ligand to the transition metal salt solution to obtain a reaction solution; the coordination group is selected from an amino group, a hydroxyl group or a mercapto group.

[0042] (3) After heating and reacting the reaction solution, the oxygen atom on the anthraquinone and the coordination group both form a six-membered ring structure with the transition metal ions in the transition metal salt through coordination bonding to obtain the anthraquinone-based conjugated coordination polymer.

[0043] In some embodiments, the solvent is selected from one or more of ethanol, water, N,N-dimethylformamide, or dimethyl sulfoxide.

[0044] In some embodiments, the molar ratio of the transition metal salt to the ligand is 1-2; the concentration of the transition metal salt solution is 0.005 mol / L - 4 mol / L.

[0045] In some embodiments, the metal salt is one or more of nitrates, sulfates, tetrafluoroborates, perchlorates, acetates, and chlorides.

[0046] In some embodiments, in step (3), the conditions for the reaction are: hydrothermal or heating reaction at a temperature of 60 - 180 °C for 6 - 72 h.

[0047] In some embodiments, in step (3), after the reaction is completed, the reaction solution is filtered, washed, and dried to obtain the conjugated coordination polymer powder.

[0048] In some embodiments, the washing is specifically carried out by washing with N,N-dimethylformamide, water, and ethanol in sequence.

[0049] According to another aspect of the present invention, there is provided an application of the anthraquinone-based conjugated coordination polymer electrode material as described above, which is used as a positive electrode material for secondary batteries.

[0050] In some embodiments, the secondary battery is a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, a dual-ion battery, a magnesium-ion battery, an aluminum-ion battery, or a zinc-ion battery.

[0051] According to another aspect of the present invention, there is provided a positive electrode for a secondary battery, including a conductive agent, a binder, and the conjugated coordination polymer as described above.

[0052] In some embodiments, the conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, and graphene.

[0053] In some embodiments, the binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, and polyvinyl alcohol.

[0054] In some embodiments, the mass ratio of the conjugated coordination polymer, the conductive agent, and the binder is (1 - 9):(8 - 0.5):(1 - 0.5).

[0055] According to another aspect of the present invention, there is provided a method for preparing a positive electrode of a secondary battery, wherein the conjugated coordination polymer, the conductive agent, and the binder are uniformly mixed in a dispersion liquid, and then uniformly coated on a current collector, and then vacuum dried to obtain the positive electrode of the secondary battery.

[0056] Example 1

[0057] Based on the present invention, the preparation of the conjugated coordination polymer material P-1 (M = Cu 2+ ) includes the following steps:

[0058] (1) Add 0.252 mmol of Cu(NO3)2·3H2O to 20 mL of ethanol;

[0059] (2) Disperse 0.252 mmol of 1,4-diaminoanthraquinone (purchased from Macklin Reagent) in the copper nitrate solution of step (1), and ultrasonicate for 5 minutes to obtain a uniform mixture;

[0060] (3) Transfer the mixture of step (2) to a pressure-resistant reaction tube and seal the pressure-resistant reaction tube. Then place it in an oven at 80 °C for three days. After the reaction, slowly cool the temperature to room temperature through a program;

[0061] (4) Collect and filter the reaction solution, and wash the obtained solid product with a small amount of N,N-dimethylformamide (DMF) multiple times until the filtrate is colorless, and then wash the solid product with water and ethanol in sequence. Collect the solid product and dry it in a vacuum oven at 80 °C for 12 hours. The obtained purple solid powder is the conjugated coordination polymer P-1 (M = Cu 2+ ), and the yield is 66% (based on the ligand).

[0062] Mix 30 mg of the conjugated coordination polymer material P-1 (M = Cu 2+ ), 15 mg of small particle conductive carbon black (Super-P), and 5 mg of sodium carboxymethylcellulose evenly, add 1 mL of deionized water in three portions, and grind thoroughly to obtain a uniform slurry. Coat it evenly on an aluminum foil (the active material loading is 1 - 1.5 mg / cm 2 ), and vacuum dry it at 80 °C for 12 hours to prepare an electrode film. In an argon glove box that is almost anhydrous and oxygen-free, cut the electrode film into electrode pieces with a diameter of 14 mm as the positive electrode, use metallic sodium as the negative electrode, separate the two with a polypropylene (PP) separator and glass fiber, use 1 M sodium hexafluorophosphate (NaPF6) and ethylene glycol dimethyl ether (DME) as the electrolyte, and then assemble it into a button cell. The assembled battery is subjected to a constant current charge-discharge test at a current density of 100 mA g -1 , the voltage range is 0.8 - 3.6 V, and the cycle performance is as Figure 1As shown

[0063] It can be seen from Figure 1 that the assembled battery has less capacity decay after 30 cycles and has a discharge specific capacity of 224 mAh g -1 after 30 cycles. Therefore, when the conjugated coordination polymer P-1 (M = Cu 2+ ) is used as the cathode material of the sodium-ion battery, it has good reversibility of sodium-ion storage.

[0064] Example 2

[0065] Based on the present invention, the preparation of the conjugated coordination polymer material P-2 (M = Cu 2+ ) includes the following steps:

[0066] (1) Dissolve 0.412 mmol of 1,5-diaminoanthraquinone (purchased from Macklin Reagent) in 10 mL of DMF, and obtain a ligand solution after ultrasonic homogenization;

[0067] (2) Disperse 0.412 mmol of copper acetate in 10 mL of DMF, and obtain a copper acetate solution after ultrasonic homogenization;

[0068] (3) Dropwise add the copper salt solution described in step (2) into the ligand solution, and maintain reflux at 120 °C for 24 hours; after the reaction is completed, filter, wash, and dry the reaction solution to obtain the conjugated coordination polymer material P-2 (M = Cu 2+ ), and the yield is 75% (based on the ligand).

[0069] Mix 30 mg of the conjugated coordination polymer material P-2 (M = Cu 2+ ) with 15 mg of Super-P and 5 mg of sodium carboxymethyl cellulose uniformly, add 1 mL of water in three portions, and obtain a uniform slurry after sufficient grinding. Coat it uniformly on aluminum foil (the active material loading is 1 - 1.3 mg / cm 2 ), and dry it in vacuum at 80 °C for 12 hours to prepare an electrode film. In an argon glove box with nearly anhydrous and oxygen-free conditions, cut the electrode film into electrode pieces with a diameter of 14 mm as the positive electrode, use metallic sodium as the negative electrode, separate the two with a pp separator and glass fiber, use 1 M NaPF6 and DME as the electrolyte, and then assemble a coin cell. The assembled battery is subjected to constant current charge and discharge at a current density of 100 mA g -1 , and the voltage range is 0.8 - 3.6 V. The charge and discharge curves are as Figure 2 shown.

[0070] It can be seen from Figure 2 that the conjugated coordination polymer material P-2 (M = Cu 2+ ) has a relatively high discharge specific capacity (191 mAh g-1 ) This fully demonstrates that when the anthraquinone-based conjugated coordination polymer provided by the present invention is used as the positive electrode material of a secondary battery, it has excellent sodium ion storage performance.

[0071] Example 3

[0072] Based on the present invention, the preparation of the conjugated coordination polymer material P-3 (M = Cu 2+ ) includes the following steps:

[0073] (1) Add 0.25 mmol of Cu(NO3)2·3H2O to a mixed solution of 4 mL of ethanol and 1 mL of deionized water, and ultrasonically treat for 5 min until the copper salt is fully dissolved to obtain a copper salt solution;

[0074] (2) Add 0.25 mmol of 1-amino-4-hydroxyanthraquinone (purchased from Macklin Reagent) to the copper salt solution in step (1), and ultrasonically treat for 5 minutes to obtain a uniform mixed solution of ligand and metal ions;

[0075] (3) Transfer the mixed solution in step (2) to a pressure-resistant reaction tube, seal the pressure-resistant reaction tube, and place it in an oven at 80 °C for reaction for three days;

[0076] (4) After the reaction is completed, collect and filter the reaction solution. The obtained solid product is washed with a small amount of DMF multiple times until the filtrate is colorless, and then the solid product is washed with water and ethanol in sequence. Collect the solid product and dry it in a vacuum oven at 80 °C for 12 hours. The obtained black-brown powder is the conjugated coordination polymer.

[0077] Mix 30 mg of the conjugated coordination polymer material P-3 (M = Cu 2+ )、15 mg of Super-P and 5 mg of sodium carboxymethylcellulose evenly, add 1 mL of deionized water in three portions, and grind thoroughly to obtain a uniform slurry. Coat it evenly on an aluminum foil (the active material loading is 1 - 1.5 mg / cm 2 ), and dry it in a vacuum at 80 °C for 12 hours to obtain an electrode film. In an argon glove box that is nearly anhydrous and oxygen-free, cut the electrode film into electrode pieces with a diameter of 14 mm as the positive electrode, use metallic sodium as the negative electrode, separate the two with a pp separator and glass fiber, use 1 M NaPF6 and DME as the electrolyte, and then assemble a button cell. The assembled battery is subjected to constant current charge and discharge at a current density of 100 mA g -1 , and the voltage range is 0.8 - 3.6 V. The charge-discharge curve is as Figure 3 shown.

[0078] From Figure 3 it can be seen that the conjugated coordination polymer material P-3 (M = Cu 2+) has a discharge specific capacity of 235 mAh g -1 The charging and discharging voltages are 2.48 V and 1.53 V respectively, and the voltage plateau is obvious, which fully demonstrates that the anthraquinone-based conjugated coordination polymer material provided by the present invention has excellent sodium ion storage performance.

[0079] Example 4

[0080] Based on the present invention, the preparation of the conjugated coordination polymer material P-4 (M = Cu 2+ ) includes the following steps:

[0081] (1) Add 0.148 mmol of Cu(NO3)2·3H2O to a mixed solution of 5 mL of ethanol and deionized water (ethanol: water = 1:2, volume ratio), and obtain a copper salt solution after ultrasonic dissolution is complete;

[0082] (2) Disperse 0.148 mmol of 1,5-diamino-4,8-dihydroxy-9,10-anthraquinone (purchased from Macklin Reagent) in the copper salt solution of step (1), and ultrasonically treat for 5 minutes to obtain a uniform mixed solution;

[0083] (3) Transfer the mixed solution of step (2) to a pressure-resistant reaction tube and seal the pressure-resistant reaction tube. Then place it in an oven at 120 °C for three days. After the reaction is completed, slowly lower the temperature to room temperature through a program;

[0084] (4) After the reaction is completed, collect and filter the reaction solution. The obtained solid product is washed with a small amount of DMF multiple times until the filtrate is colorless, and then the solid product is washed with water and ethanol in sequence. Collect the solid product and dry it in a vacuum oven at 80 °C for 12 hours. The obtained purple-black solid powder is the conjugated coordination polymer, and the yield is 63% (based on the ligand).

[0085] Figure 4 This is the scanning electron microscope image of the conjugated coordination polymer crystal obtained in this example. The SEM image shows that P-4 (M = Cu 2+ ) is a uniform rod-like structure with regular morphology, and the length range is 1-4 microns.

[0086] Example 5

[0087] Based on the present invention, the preparation method of the conjugated coordination polymer P-4 (M = Cu 2+ ) composite electrode material in this example includes the following steps:

[0088] (1) 0.248 mmol of 1,5-diamino-4,8-dihydroxy-9,10-anthraquinone (purchased from Macklin Reagent) and 0.248 mmol of Cu(NO3)2·3H2O were added to a mixed solution of 20 mL of water and DMF (water:DMF = 1:1, volume ratio). It was ultrasonically dispersed for 10 minutes to completely dissolve it;

[0089] (2) 42 mg of single-walled carbon nanotubes were added to the reaction solution described in step (1) and stirred for 2 hours. Subsequently, the reaction solution was ultrasonically treated for 2 hours to ensure good dispersion of the carbon nanotubes;

[0090] (3) The solution obtained in step (2) was placed in a 100 mL round-bottom flask and reacted at 80 °C for 24 hours under stirring;

[0091] (4) After the reaction was completed, the reaction solution was collected and filtered. The obtained solid product was washed with a small amount of DMF multiple times until the filtrate was colorless, and then washed with water and ethanol in sequence. It was placed in a vacuum oven at 80 °C and dried for 12 hours. The obtained fluffy black powder was the conjugate coordination polymer P-4 (M = Cu 2+ ) composite electrode material. As Figure 5 shown, the XRD diffraction analysis patterns of the conjugate coordination polymer P-4 (M = Cu 2+ ) and the conjugate coordination polymer P-4 (M = Cu 2+ ) composite electrode material are respectively. It can be seen from the figure that except for the diffraction peak of carbon nanotubes at 26.1 degrees, the XRD diffraction pattern of the conjugate coordination polymer P-4 (M = Cu 2+ ) composite electrode material is consistent with that of the conjugate coordination polymer P-4 (M = Cu 2+ ). Therefore, the conjugate coordination polymer composite electrode material obtained in this example was successfully synthesized.

[0092] The obtained conjugate coordination polymer composite electrode material was dried in an oven at 80 °C for 12 hours. Subsequently, the conjugate coordination polymer composite electrode material, carbon nanotubes, and sodium carboxymethylcellulose were mixed evenly according to a mass ratio of 6:3:1 (the total content of carbon nanotubes was controlled at 30%). After adding a small amount of water, it was ground into a uniform slurry, which was coated on aluminum foil and dried at 80 °C for 12 hours, and then transferred to a glove box and cut into a pole piece with a diameter of 14 mm for standby. A 2032-type button battery was used, with the above-mentioned pole piece as the positive electrode and metallic sodium as the negative electrode. The positive and negative electrodes were separated by glass fiber, and 1M NaPF6 and DME were used as the electrolyte. Encapsulation was carried out in a glove box with an oxygen content and a water content less than 1 ppm, and a constant current charge-discharge test was carried out on a Blue Electric system, and the voltage range was 0.5 - 3.6 V.

[0093] As Figure 6The cyclic performance graph of the battery assembled with the conjugate coordination polymer composite electrode material at a current density of 100 mA g -1 The current density. After cycling 100 times at a current density of 100 mA g -1 , the battery still has a capacity retention of 85%, indicating that the coordination polymer has excellent cycling stability when used in sodium-ion batteries.

[0094] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An anthraquinone conjugated coordination polymer electrode material, characterized in that: The general structural formula of the anthraquinone conjugated coordination polymer is selected from one of the structures of formula (1) or formula (2): Wherein, R1 and R2 are independently selected from O, S or NH, and R1 and R2 are not O at the same time; R3 and R4 are independently selected from hydrogen, amino, hydroxyl or thiol; M is a transition metal ion.

2. The anthraquinone conjugated coordination polymer electrode material according to claim 1, characterized in that: The transition metal ion is selected from Cu 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ , Mn 2+ , Fe 2+ , Fe 3+ One or more of .

3. The method for preparing an anthraquinone conjugated coordination polymer electrode material according to any one of claims 1 to 2, characterized in that: (1) adding a transition metal salt into a solvent and dissolving it to obtain a transition metal salt solution; (2) using a coordination group to replace the hydrogen atoms at the 1 and 4 carbon positions, or the 5 and 8 carbon positions, or the 1 and 5 carbon positions, or the 4 and 8 carbon positions on anthraquinone as a ligand, and adding the ligand to the transition metal salt solution to obtain a reaction solution; the coordination group is selected from amino, hydroxyl or thiol; (3) heating the reaction solution so that the oxygen atoms and the coordination groups on the anthraquinone react with the transition metal ions in the transition metal salt to form a six-membered ring structure through coordination bonding, thereby obtaining the anthraquinone conjugated coordination polymer.

4. The method for preparing an anthraquinone conjugated coordination polymer electrode material according to claim 3, characterized in that: The solvent is selected from one or more of ethanol, water, N,N-dimethylformamide or dimethyl sulfoxide; the molar ratio of the transition metal salt to the ligand is 1 to 2; and the concentration of the transition metal salt solution is 0.005 mol / L to 4 mol / L.

5. The method for preparing an anthraquinone conjugated coordination polymer electrode material according to claim 3, characterized in that: In step (3), the heating conditions are: hydrothermal or heating reaction at a temperature of 60-180° C. for 6-72 hours.

6. The use of the anthraquinone conjugated coordination polymer electrode material according to any one of claims 1 to 2, characterized in that: It is used as a positive electrode material for secondary batteries.

7. A positive electrode of a secondary battery, characterized in that: The invention comprises a conductive agent, a binder and the anthraquinone conjugated coordination polymer according to any one of claims 1 to 2.

8. A method for preparing a positive electrode of a secondary battery, characterized in that: The anthraquinone conjugated coordination polymer according to any one of claims 1 to 2, a conductive agent and a binder are uniformly mixed in a dispersion, and then uniformly coated on a current collector, followed by vacuum drying to obtain the positive electrode of the secondary battery.

9. The method for preparing a positive electrode of a secondary battery according to claim 8, characterized in that: The conductive agent is selected from one or more of conductive carbon black, carbon nanotubes, and graphene; The binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose and polyvinyl alcohol.

10. The method for preparing a positive electrode of a secondary battery according to claim 8, characterized in that: The mass ratio of the anthraquinone conjugated coordination polymer, the conductive agent and the binder is (1-9): (8-0.5): (1-0.5).

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