Organic nanometer negative electrode based on insertion layer type pseudo-capacitor and preparation method and application thereof
阅读说明：本技术 一种基于插层式赝电容的有机纳米负极及其制备方法和应用 (Organic nanometer negative electrode based on insertion layer type pseudo-capacitor and preparation method and application thereof ) 是由 张力 刘建军 胡忠利 赵晓琳 于 2020-06-30 设计创作，主要内容包括：本发明公开了一种基于插层式赝电容的有机纳米负极,它包括活性材料、导电剂和粘结剂,所述活性材料为有机分子晶体材料。本发明使用纳米化有机分子晶体材料作为锂离子电池或锂离子混合电容器等的负极材料,使得有机纳米晶体能够充分与电极中的导电剂接触,具有良好的电子导电性,可显著提升锂离子电池的可逆容量和锂离子混合电容器的能量密度。(The invention discloses an organic nanometer negative electrode based on an insertion layer type pseudocapacitance, which comprises an active material, a conductive agent and a binder, wherein the active material is an organic molecular crystal material. The invention uses the nano organic molecular crystal material as the cathode material of the lithium ion battery or the lithium ion hybrid capacitor, and the like, so that the organic nano crystal can be fully contacted with the conductive agent in the electrode, has good electronic conductivity, and can remarkably improve the reversible capacity of the lithium ion battery and the energy density of the lithium ion hybrid capacitor.)
1. An organic nanometer negative electrode based on an insertion layer type pseudocapacitance comprises an active material, a conductive agent and a binder, and is characterized in that: the active material is an organic molecular crystal material, the crystal structure of the organic molecular crystal material is a hexagonal or monoclinic layered structure, and the interlayer distance is 0.2-0.6 nm.
2. The organic nanometer negative electrode based on the insertion layer type pseudocapacitance of claim 1 is characterized in that: the organic molecular crystal material is a mixture consisting of one or more of 2,2 '-bipyridyl-4, 4' -dicarboxylic acid, fumaric acid, sodium citrate, cyclohexadecanone, organic conjugated micromolecule carboxylic acid, organic micromolecule carboxylic acid lithium salt, organic micromolecule carboxylic acid sodium salt, organic micromolecule carboxylic acid potassium salt, organic conjugated acid anhydride, organic conjugated quinones, organic conjugated sulfur, organic conjugated azobenzene and organic conductive polymers.
3. The organic nanometer negative electrode based on the insertion layer type pseudocapacitance of claim 2 is characterized in that: the organic molecular crystal material is a mixture consisting of one or more of 2,2' -bipyridyl-3, 3' -dicarboxylic acid, 2' -bipyridyl-5, 5' -dicarboxylic acid, maleic acid, itaconic acid, terephthalic acid, naphthalene tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, dilithium rhodizonate, tetralithium rhodizonate, hexalithium rhodizonate, sodium rhodizonate, lithium terephthalate, 2, 4-dienyl lithium adipate, azobenzene, sodium 4- (phenylazo) benzoate, sodium azobenzene-4, 4' -dicarboxylate, polydopamine and polymer PQL.
4. The organic nanometer negative electrode based on the insertion layer type pseudocapacitance of claim 1 is characterized in that: the mass ratio of the active material to the conductive agent to the binder is 5-8: 1-4: 1.
5. The organic nanometer negative electrode based on the insertion layer type pseudocapacitance of claim 1 is characterized in that: the binder is a mixture consisting of one or more of polyvinylidene fluoride, carboxymethyl cellulose, sodium alginate, LA132, lignocellulose and polytetrafluoroethylene.
6. The method for preparing the organic nanometer negative electrode based on the insertion layer type pseudocapacitance is characterized by comprising the following steps:
(a) mixing the active material, the conductive agent and the binder, adding a solvent, and performing ball milling to obtain viscous slurry;
(b) coating the viscous slurry on a metal foil, and drying to obtain a pole piece;
(c) and rolling and punching the pole piece.
7. The method for preparing the organic nanometer negative electrode based on the insertion layer type pseudocapacitance is characterized in that: in the step (a), the solvent is a mixture of one or more selected from N-methyl pyrrolidone, water and ethanol.
8. The use of the organic nano-anode based on the intercalation pseudocapacitance as claimed in any one of claims 1 to 5, wherein: the lithium ion battery is used for assembling a lithium ion hybrid capacitor with a positive electrode and an electrolyte.
9. The application of the organic nanometer negative electrode based on the insertion layer type pseudocapacitance as claimed in claim 8, wherein: the active material of the positive electrode is commercial porous activated carbon, S-doped porous carbon, N-doped porous carbon, P-doped porous carbon, biomass-derived porous activated carbon or metal organic framework-derived porous carbon.
Technical Field
The invention belongs to the field of energy devices, relates to an organic nano negative electrode, and particularly relates to a nano organic negative electrode with ultrahigh intercalation type pseudocapacitance lithium ion storage specific capacity, and a preparation method and application thereof.
Background
Currently, electrochemical energy storage devices, such as lithium ion batteries and supercapacitors, have been widely used in people's daily life and transportation, and have also triggered further pursuits of high energy density/power density. The lithium ion battery is a system with higher energy density in the currently practical battery, but the power density is relatively lower; in contrast, supercapacitors have excellent power density and cycle life, but there are severe shortboards in energy density. The performance difference is mainly determined by the difference of the two working mechanisms.
In order to overcome the disadvantages of the above systems in terms of energy and power density, a novel electrochemical energy storage device has been proposed in recent years, in which a capacitive positive electrode material and a battery-type negative electrode material are integrated into a system to construct lithium-ion hybrid capacitors (LICs). The lithium-ion hybrid capacitor effectively combines the advantages of a lithium-ion battery and a super capacitor, and therefore has high energy density, long endurance and fast storage/discharge speed. Lithium ion hybrid capacitor when charging, Li+Ions are embedded into a battery type negative electrode material through electrolyte under the action of an external electric field to generate a Faraday reaction; meanwhile, anions are adsorbed to the surface of the capacitance type anode in a non-Faraday reaction, and meanwhile, equal amount of electrons flow from the anode to the cathode through an external circuit; upon discharge, Li+Ions are released from the battery-type negative electrode, anions are desorbed from the capacitive-type positive electrode, and electrons in an external circuit flow from the negative electrodeAnd forming current to the positive electrode to realize energy output.
In 2001, Amatucci et al used LiPF for the first time6Acetonitrile as electrolyte, respectively AC (activated carbon) and lithium titanium oxide (such as Li)4Ti5O12) Lithium ion hybrid capacitors were assembled as the positive and negative electrode materials. Research shows that the system can keep 90% of capacity under low multiplying power under the condition of high charging/discharging multiplying power of 10C, and the capacity retention rate can reach 85-90% after 500 cycles. Therefore, the lithium ion hybrid capacitor has good rate performance and cycling stability, and the service life is considerable, which is the first report about the lithium ion hybrid capacitor. Thereafter, Hatozaki of fuji co, japan used activated carbon as a positive electrode material and pre-intercalated lithium graphite or the like as a negative electrode material to prepare a hybrid capacitor, and was formally named a lithium-ion hybrid capacitor. Subsequently, the lithium ion hybrid capacitor has undergone a vigorous development process, and various lithium ion hybrid capacitors having excellent properties have been developed so far.
Due to electrochemical hysteresis, the battery-type negative electrode tends to be a main cause of limiting the output power and high energy density of the lithium-ion hybrid capacitor. In contrast to the surface-controlled charge storage of positive porous electrodes (typically high specific surface active carbon, graphene and carbon nanotubes and other carbon-based materials), negative electrodes are primarily limited by the inherent semi-infinite diffusion process within the bulk of the electrode material. Therefore, research on lithium-ion hybrid capacitors has been focused on battery-type negative electrode materials, mainly including carbon-based materials and lithium intercalation compounds (Li)4Ti5O12、Nb2O5Etc.), alloying materials, conversion materials, etc. F.B Reguin et al used commercial graphite as the negative electrode and commercial activated carbon as the positive electrode, with 1M LiPF6DMC (1: 1) as electrolyte, assembling a lithium-ion hybrid capacitor. Under a wide voltage window of 1.5-5.0V, the maximum energy density and the maximum power density of the device can respectively reach 145.8Wh kg-1And 10kW kg-1(ii) a However, under the voltage window, the attenuation of the capacitor is obvious, and the capacity retention rate is 60% after 10000 circles. Xiahui of Nanjing university of rational Industrial and Chinese scienceThe technical university remnants and the like take commercial bacterial cellulose membranes as initial materials to prepare a boron and nitrogen double-doped three-dimensional porous carbon nanofiber network structure (BNC); and the BNC is successfully used for the high-performance BNC// BNC lithium ion capacitor. The results show that the power density is 225W kg-1The symmetric double-carbon lithium ion capacitor is 220Wh kg-1High energy density of (2); and 104Wh kg at the energy density-1Then the power density of the LICs can reach 22500W kg-1The performance of the compound is far better than that of the reported LICs. Lucun peak and hero et al, the university of harbin industry, reported a lithium ion capacitor assembled from high concentration nitrogen doped carbon nanospheres (ANCS). The nitrogen doping optimizes the stacking parameters of the carbon microcrystal structure, improves the active points of the carbon material, and further improves the Li content of the anode and cathode materials+And PF6 -The storage capacity of (2). The ANCS and the pre-lithiated ANCS are combined to obtain the all-carbon mixed ion capacitor with the potential window reaching 4.5V, the all-carbon mixed ion capacitor has extremely excellent electrochemical performance, and the maximum energy density can reach 206.7Wh kg-1The maximum power density can reach 22.5kW kg-1(ii) a It has outstanding high-rate cycle stability, and can be
Compared with carbon material negative electrodes, alloying materials, conversion materials and other embedded bulk materials generally have the common problems of poor electronic conductivity, slow reaction kinetics, poor electrochemical performance and the like. For these types of negative electrode materials, people usually adopt nanocrystallization technology and carbon coating technology to improve their electrochemical properties. Preparing nitrogen-doped carbon-coated Co by pyrolyzing a bimetallic organic framework (ZnCo-ZIF) step by step in Nanjing university gold bell and the like3ZnC nano polyhedral particle (Co)3ZnC @ NC) serving as a negative electrode material is combined with a microporous carbon (MPC) positive electrode material with high specific surface area derived from biomass pine needles to obtain the lithium ion hybrid capacitor with high energy density. The working voltage range of the lithium ion hybrid capacitor is 1.0-4.5V, and the voltage of the lithium ion hybrid capacitor is 275Wkg-1The energy density is up to 141.4Wh kg-1And at 15.2Wh kg-1At energy density of (2), its power densityThe degree can reach 10.3kW kg-1. The LTO/graphene composite material is prepared by combining an atomic layer deposition breeding technology with subsequent heat treatment lithiation, such as Wangchun university of Hebei industry. The lithium ion mixed capacitor is assembled by matching with an active carbon anode material, and the maximum energy density of the lithium ion mixed capacitor is 52Wh kg-1The maximum power density can reach 57.6kW kg-1And at 25A g-1The capacity retention rate is up to 97% after 2000 cycles under the current density.
At present, the lithium ion hybrid capacitor cathode material is mainly concentrated on inorganic metal oxide/nitride and other materials, and is restricted by the problems of theoretical specific capacity, oxidation-reduction potential, insufficient metal mineral deposit, great environmental pollution and the like, so that the green and high-energy requirements of next-generation pure energy devices are difficult to meet. Compared with the traditional inorganic material, the organic material has the advantages of low price, environmental protection, high theoretical specific capacity and the like. More importantly, the organic material has the advantages of variety diversity, designability of structure, adjustable oxidation-reduction potential and the like, and can provide rich choices for selecting the cathode of the lithium-ion hybrid capacitor, so that the organic material has wide research and development and application prospects. However, the application of organic materials to the negative electrode of lithium ion hybrid capacitors has been recently reported. This is mainly due to three reasons: the organic material has electronic insulation property, is easy to dissolve in an organic solvent and has defects in a synthetic method for preparing the organic nano material.
In conclusion, the development of high-performance organic nano-electrode materials as negative electrode materials of lithium ion hybrid capacitors is a key supporting technology for developing next generation of high-performance green sustainable lithium ion batteries/hybrid capacitors.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a nano organic negative electrode with ultrahigh insertion layer type pseudocapacitance lithium ion storage specific capacity.
The invention provides an organic nanometer negative electrode based on an insertion layer type pseudocapacitance, which comprises an active material, a conductive agent and a binder, wherein the active material is an organic molecular crystal material, the crystal structure of the organic molecular crystal material is a hexagonal or monoclinic layered structure, and the interlayer distance is 0.2-0.6 nm.
Further, the organic molecular crystal material is a mixture of one or more selected from 2,2 '-bipyridyl-4, 4' -dicarboxylic acid, fumaric acid, sodium citrate, cyclohexadecanone, organic conjugated small molecular carboxylic acid, organic small molecular carboxylic acid lithium salt, organic small molecular carboxylic acid sodium salt, organic small molecular carboxylic acid potassium salt, organic conjugated acid anhydride, organic conjugated quinones, organic conjugated sulfur, organic conjugated azobenzene and organic conductive polymers.
Still further, the organic molecular crystal material is a mixture of one or more selected from the group consisting of 2,2' -bipyridine-3, 3' -dicarboxylic acid, 2' -bipyridine-5, 5' -dicarboxylic acid, maleic acid, itaconic acid, terephthalic acid, naphthalene tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, dilithium rhodizonate, tetralithium rhodizonate, hexalithium rhodizonate, sodium rhodizonate, lithium terephthalate,
Optimally, the mass ratio of the active material to the conductive agent to the binder is 5-8: 1-4: 1.
Preferably, the binder is a mixture of one or more of polyvinylidene fluoride, carboxymethyl cellulose, sodium alginate, LA132, lignocellulose and polytetrafluoroethylene.
The invention also aims to provide a preparation method of the organic nanometer negative electrode based on the insertion layer type pseudocapacitance, which comprises the following steps:
(a) mixing the active material, the conductive agent and the binder, adding a solvent, and performing ball milling to obtain viscous slurry;
(b) coating the viscous slurry on a metal foil, and drying to obtain a pole piece;
(c) and rolling and punching the pole piece.
Preferably, in the step (a), the solvent is a mixture of one or more selected from the group consisting of N-methylpyrrolidone, water and ethanol.
The invention further aims to provide application of the organic nanometer negative electrode based on the insertion layer type pseudocapacitance, which is used for assembling a lithium ion hybrid capacitor with a positive electrode and an electrolyte.
Optimally, the active material of the positive electrode is commercial porous activated carbon, S-doped porous carbon, N-doped porous carbon, P-doped porous carbon, biomass-derived porous activated carbon or metal organic framework-derived porous carbon.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:
(1) the invention uses the nano organic molecular crystal material as the cathode material of the lithium ion battery or the lithium ion hybrid capacitor, and the like, so that the organic nano crystal can be fully contacted with the conductive agent in the electrode, has good electronic conductivity, and can remarkably improve the reversible capacity of the lithium ion battery and the energy density of the lithium ion hybrid capacitor. As exemplified by 2,2 '-bipyridine-4, 4' -dicarboxylic acid: 2,2 '-bipyridine-4, 4' -dicarboxylic acid has an-OH, -C ═ O, and-C ═ N group in the molecular structure, and during the first discharge, the-OH group undergoes an irreversible lithiation reaction first, followed by redox reactions of the-C ═ O and-C ═ N functional groups. Compared with the conventional carbonyl compound, the 2,2 '-bipyridine-4, 4' -dicarboxylic acid has two reversible electroactive functional groups and a lower molecular weight, and thus has a higher reversible capacity.
(2) The crystal structure of the selected nano organic molecular crystal is a hexagonal or monoclinic layered structure, and the interlayer distance is 0.2-0.6 nm, so that the layered structure is very favorable for lithium ions to be embedded into the layers of the molecular crystal at high speed without being influenced by diffusion control, and the ultrahigh intercalation pseudocapacitance capacity is obtained. Continuing with the nanocrystal structure of 2,2 '-bipyridine-4, 4' -dicarboxylic acid as an example: lithium ions are rapidly inserted into an intercrystalline channel of 2,2 '-bipyridine-4, 4' -dicarboxylic acid during charging; during discharging, the lithium ions entering the molecular crystal layers can return to the electrolyte again, and the stored charges are released through an external circuit. The process of charge/discharge is a reversible process of intercalation and deintercalation of lithium ions between molecular crystal layers; the 2,2 '-bipyridine-4, 4' -dicarboxylic acid molecular crystal has larger interlayer spacing, so that lithium ions can be more favorably and rapidly inserted and removed between the layers, and the lithium ion hybrid capacitor has higher energy density and power density;
(3) the nanometer organic molecular crystal with proper crystal face and space is used as the cathode active material of the lithium ion battery and the lithium ion hybrid capacitor, and the nanometer organic molecular crystal generally has lower oxidation-reduction potential, so that the working voltage window of the lithium ion hybrid capacitor can be obviously improved.
(4) The nano organic molecular crystal generally has excellent anti-dissolving capacity in ester and ether electrolytes, does not dissolve in the circulating process, and can be used for preparing a stable negative pole piece.
(5) The nano organic molecular crystal generally has insulating property, but the nano organic molecular crystal is beneficial to fully combining with a conductive network formed by a binder and a conductive agent, so that the overall conductivity of an electrode cannot be reduced when the nano organic molecular crystal is used as a negative electrode material, and the rate performance cannot be influenced.
(6) The nano organic molecular crystals generally have a higher melting point. For example, the melting point of 2,2 '-bipyridyl-4, 4' -dicarboxylic acid is as high as 310 ℃, which is obviously higher than that of electrolytic solution solvents such as DEC, DMC and EMC, and the like, and when the lithium ion battery cathode can be used as a cathode, the safety of lithium ion batteries and lithium ion hybrid capacitors can be effectively ensured.
(7) The lithium ion battery and the lithium ion hybrid capacitor based on the nano organic molecular crystal cathode have high energy density, excellent power characteristics and excellent cycle performance, and the electrochemical performance of the lithium ion battery and the lithium ion hybrid capacitor is remarkably superior to that of the existing lithium ion hybrid capacitor at present;
(8) the invention initiates a preparation method of the nano organic molecular crystal, namely a dissolving and drying recrystallization process based on high-energy ball milling, and has simple process and low cost.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image of a 2,2 '-bipyridine-4, 4' -dicarboxylic acid-based electrode sheet prepared in example 1;
FIG. 2 is a Transmission Electron Microscope (TEM) image of a pole piece based on 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1;
FIG. 3 is a graph of the rate performance of a lithium-ion battery cell based on 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1;
FIG. 4 is a graph of the cycle performance of a lithium ion battery based on 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1;
FIG. 5 is a graph of the ratio of intercalated pseudocapacitances based on 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1: (a) a pseudocapacitance effect map, (b) an insertion layer pseudocapacitance ratio map;
fig. 6 is an SEM image of a P (VDF-HFP) porous film prepared in example 1: (a) the scale bar is 20 μm; (b) the scale is 2 μm;
FIG. 7 is a physical photograph of a P (VDF-HFP) gel electrolyte membrane prepared in example 1;
FIG. 8 is a graph showing energy density at different mass ratios of positive and negative electrode active materials in a lithium ion capacitor containing 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1;
FIG. 9 is a constant current charge/discharge curve diagram of a lithium ion capacitor containing 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1 under the condition of an optimal mass ratio of positive and negative electrode active materials;
FIG. 10 is a graph of energy density versus power density for an optimum positive and negative electrode active material mass ratio for a lithium ion capacitor containing 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1;
FIG. 11 is a photograph of a flexible lithium ion hybrid capacitor of 2,2 '-bipyridine-4, 4' -dicarboxylic acid prepared in example 1 in real life and a practical example.
Detailed Description
The following provides a detailed description of preferred embodiments of the invention.