RU2554940C2 - Method of obtaining hybrid material (versions) for rechargeable chemical sources of current - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to cathode organic-inorganic hybrid material for secondary lithium-ionic sources of current with composition (C₆H₄N)*xV₂O₅*yH₂O, where x=0.10-0.12, y=0.7-0.9 in form of nanorolls from 100 to 500 nm long and diameter from 10 to 20 nm with surface area 60 m²/g and pore diameter 20-30 nm. Invention also relates to versions of material obtaining.

EFFECT: claimed material possesses improved mechanical properties, high specific capacity and stability in time.

3 cl, 2 ex, 4 dwg

Description

FIELD OF THE INVENTION

The invention relates to inorganic chemistry and can be used as an active material of the cathode composition (C ₅ H ₄ N) * xY ₂ O ₅ * yH ₂ O, where x = 0.10-0.12, y = 0.7-0.9. The advantage of the obtained material is that it provides stable electrochemical characteristics of the secondary lithium-ion current source with a high value of the electrochemical capacity for lithium.

State of the art

One approach to obtaining the cathode active material is to use hybrid materials from conductive polymers embedded in an inorganic layered structure.

The formation of hybrid materials from conductive polymers embedded in a V ₂ O ₅ matrix occurs when molecules of the corresponding monomers are intercalated into an inorganic layered structure. The strong oxidizing nature of the oxide causes the redox polymerization of organic molecules. It should be noted that while the embedded polymer undergoes partial oxidation, V ₂ O _{5 is} partially reduced, as a result of which it turns into an oxide with a mixed oxidation state of vanadium V ^IV / V ^V , the electronic conductivity of which is higher than that of the original V ₂ O ₅ .

The affinity of V ₂ O ₅ for intercalated nitrogen-containing coordination compounds and organic ligands is well known. In order to use an organic additive to improve the electrochemical response, two characteristics are required: (1) the additive must contain a nitrogen-containing group to ensure interaction with the vanadium oxide layers and lead to the separation of the layers, and (2) contain a functional group that stimulates polymerization, for example sulfonic acid group.

In work (Wong, HP, Dave, V.S., Leroux, F., Harreld, J „Dunn, B., & Nazar, LF Synthesis and characterization of polypyrrole / vanadium pentoxide nanocomposite aerogels. Journal Of Materials Chemistry, 8 ( 4), 1019-1027, 1998) the use of hybrid materials based on nonmmppona / V ₂ O _{5 is considered} . The composite was obtained by polymerization of pyrrole using V ₂ O ₅ dispersed in a solution of perchloric acid HClO ₄ acting as an oxidizing agent. In this case, the simultaneous polymerization and precipitation of the hybrid material occurs, and the charge-discharge capacity is also significantly increased in comparison with hybrid materials obtained without the use of acid. The discharge capacity in the first cycle using acid is 135 mAh / g, while the discharge capacity of the hybrid material polypyrrole / V ₂ O ₅ obtained without using acid is 98 mAh / g. This production method differs from the present invention both in the chemical nature of the product (composition) and in the production method.

US Patent No. 8,148,455 Hybrid two- and three-component host-guest nanocomposites and method for manufacturing the same) describes a method for producing a hybrid material based on V ₂ O ₅ and an electrically conductive polyaniline polymer for use as a cathode for lithium-ion current sources . The pre-obtained xerogel V ₂ O ₅ is mixed with an aqueous solution of aniline chloride, the final mixture is milled in a planetary mill for 8 hours, followed by washing and drying. The disadvantage of this technique, from the present invention, is the inability to obtain a material with a porous morphology necessary to increase the contact area of the cathode material with liquid electrolyte.

The closest to the proposed technical essence and the number of matching features is the work (F. Leroux, V.E. Konene, LF Nazar, Electrochemical Lithium Intercalation into a Polyaniline / V ₂ O ₅ Nanocomposite. Journal Of The Electrochemical Society, 143 (9) , L181, 1996) on the synthesis of the polyaniline _{V 2} O ₅ nanocomposite for use in secondary lithium-ion current sources. The pre-obtained xerogel V ₂ O ₅ is mixed with the precursor to obtain polyaniline, as a result, H ₂ O _{2 is} added to the resulting polyaniline / V ₂ O ₅ solution. The differences between this technique and the proposed one are the need for step-by-step synthesis and the inability to form nanowires that create the necessary hierarchy of macro- and micropores.

The set of essential features of the invention

The task was to obtain hybrid inorganic-organic materials with a porous structure that have improved mechanical properties based on gels of vanadium (V) oxide and an electrically conductive pro-polymer material - polyaniline, which will allow them to be used to create new materials for secondary lithium-ion current sources.

This problem was solved by the present invention, in particular the production of a hybrid electrode material of the formula (C ₆ H ₄ N) * xV ₂ O ₅ * yH ₂ O, where x = 0.10-0.12, y = 0.7-0.9, in the form of nanowires with a porous structure .

A hybrid material was obtained by adding V ₂ O ₅ and anilinium sulfate to a solution of H ₂ O ₅ (10-20 wt.%) With stirring, followed by heating the mixture to 40 ° C and keeping at this temperature for 1 hour, thereby, in the synthesis process, a uniform distribution of polyaniline in the V ₂ O ₅ interlayer space occurs and the mechanical properties of the final product are improved.

Technical result

At low labor costs and simple technical performance, a hybrid cathode material (C ₆ H ₄ N) * xV ₂ O ₅ * yH ₂ O was obtained, where x = 0.10-0.12, y = 0.7-0.9 in the form of nanowires with a porous structure, which, due to the high surface area makes it easy to contact with liquid electrolyte, thereby facilitating the intercalation of lithium ions in the interlayer space of vanadium pentoxide. The use of an electrically conductive polymer material allows to improve the mechanical and transport properties of the material during cycling, and thereby a high specific electrochemical capacity and its stability over time are achieved.

A detailed description of the method of obtaining

Hybrid material (C ₆ H ₄ N) * xV ₂ O ₅ * yH ₂ O (x = 0.10-0.12, y = 0.7-0.9) in the form of nanorods with a porous structure was obtained by adding V ₂ O ₅ and aniline sulfate to the solution H ₂ O ₂ (15% wt.) With stirring, followed by heating the mixture to 40 ° C and maintaining at this temperature for 1 hour.

The order of addition of the components can be changed by preparing a gel from vanadium pentoxide by dissolving V ₂ O ₅ powder in H ₂ O ₂ (15 wt%), followed by the addition of aniline sulfate, with stirring, heating the mixture to 40 ° C and keeping at this temperature for 1 hour

As a result of synthesis, after filtration, washing of the product and drying at a temperature of 60 ° C, a product was formed with a porous microstructure in the form of nanoswitches with a length of 100 to 500 nm and a diameter of 10 to 20 nm (Fig. 1a, b) with a surface area of 60 m ² / g and a pore diameter of 20-30 nm (Fig. 2).

X-ray phase analysis data show (Fig. 3) that the (001) peaks of layered V ₂ O ₅ indicate an increase in the interlayer space from 11 to 13.5 A, which corresponds to the intercalation of polyaniline in the interlayer space of V ₂ O ₅ with the formation of a hybrid organo-inorganic composite.

According to TG-DTA (Fig. 3), the primary mass loss occurs in the temperature range from 55-120 ° C, which is responsible for the dehydration of the sample, the second - when heated to 360 ° C and corresponds to the decomposition of polyaniline with subsequent crystallization of the inorganic component. The total mass loss in the sample is 9-12 wt.%, The composition of the composite can be estimated as (C ₆ H ₄ N) * xV ₂ O ₅ * yH ₂ O, where x = 0.10-0.12, y = 0.7-0.9.

For electrochemical studies, the active mass for working electrodes was prepared by mixing 75% of the active material, 20% of the electrically conductive additive (acetylene black, oxidized graphite, carbon nanotubes) and 5% polyvinylidene difluoride (Aldrich) dissolved in N-methylpyrrolidone (Aldrich).

Homogenization of the electrode mass was carried out by ultrasonic treatment for 10 minutes The finished mass was applied evenly on one side of the current lead made of stainless steel mesh (0.05 mm thick mesh). To remove N-methylpyrrolidone, the electrodes were dried in an oven at 90 ° C for 5 hours. Next, the electrodes were pressed with a force of 500 kg / cm ² for 30 seconds, after which they were re-dried in vacuum at a temperature of 120 ° C-240 ° C for 8-12 hours to remove traces of water. The amount of active substance on the electrodes measuring 1.0 cm × 1.0 cm was 20–25 mg.

A counter electrode and a reference electrode were prepared by rolling thin lithium strips (lithium grade LE-1) onto a nickel grid with a nickel foil current lead welded to it.

Testing of the electrodes (recording charge-discharge curves and cyclic voltammograms) was carried out in sealed Teflon cells of plane-parallel design containing a working electrode, one or two counter electrodes and a reference electrode. All operations for the assembly of prototypes of elements were carried out in a glove box with argon atmosphere Labconco Protector CA. The content of water and oxygen vapor in the atmosphere of the box did not exceed 5 ppm. A 1 M solution of LiClO ₄ (Aldrich, battery grade) in a mixture of propylene carbonate (Aldrich, anhydrous) and 1,2-dimethoxyethane (Aldrich, anhydrous) (7: 3 by volume) was used as an electrolyte. The water content in these electrolytes, measured according to Fisher (684 KF-Coulometer, Metrohm), did not exceed 50 ppm. All electrodes were separated by separators made of porous polypropylene of the PORP brand (NPO Ufim, Moscow).

The charge / discharge current was 20 mA / g. The potential sweep rate was 130 μV / s. The range of cell cycling potentials was 2.0–4.0 V (in comparison with Li / Li ⁺ ).

The initial discharge capacity of the electrode was about 240 mAh / g. The rate of decrease in specific capacity after the 20th cycle decreases to 1.3 mAh / g per cycle and is caused by the occurrence of a change in the structure of the substance and the formation of a “parasitic layer” on the surface of the cathode material (Fig. 4).

The invention is illustrated by the following figures and examples.

Fig. 1. Micrographs of the resulting hybrid material.

Fig. 2. Pore size distribution for the sample, calculated from the data of capillary nitrogen adsorption.

Fig. 3. Diffraction pattern of the hybrid material (C ₆ H ₄ N) * xV ₂ O ₅ * yH ₂ O. Insert: thermal analysis curves obtained by polythermal heating of the starting products of the synthesis.

Fig. 4. The capacity of the hybrid material during cycling. Insert: cyclic voltammogram, potential sweep speed 130 μV / s.

Example 1

A mixture of V ₂ O ₅ broaches and anilinium sulfate taken in a molar ratio of 1: 0.1-0.5 is added to a H ₂ O ₂ solution (15 wt%) with stirring, followed by heating the mixture to 40 ° C and keeping at this temperature for 1 hour After cooling to room temperature, the dark green flakes of the precipitate are filtered off, washed with distilled water and dried at 60 ° C for one day in air. The properties of the obtained material are presented in Fig. 1-4.

Example 2

To 30 ml of a solution of H ₂ O ₂ (10-20% wt.) Is added with stirring 0.5 g of powder of vanadium pentoxide. After the formation of the V ₂ O ₅ gel, aniline sulfate in a molar ratio of 1: 0.1-0.5 mol is slowly added to the solution. The mixture is heated to 40 ° C and maintained at this temperature for 1 hour. After cooling to room temperature, the dark green flakes of the precipitate are filtered off, washed with distilled water and dried at 60 ° C for one day in air. The properties of the obtained material are presented in Fig. 1-4.

The material proposed in the present invention is of great interest for use as an active cathode material for secondary lithium-ion current sources. Interest is determined by high electrochemical properties with a capacity of more than 240 mAh / g and stability during cycling.

Claims (3)

1. Cathode organo-inorganic hybrid material for secondary lithium-ion current sources of the composition (C ₆ H ₄ N) * xV ₂ O ₅ * yH ₂ O, where x = 0.10-0.12, y = 0.7-0.9 in the form of nanorotations with a length of 100 to 500 nm and a diameter of 10 to 20 nm with a surface area of 60 m ² / g and a pore diameter of 20-30 nm. 2. A method of obtaining a hybrid material according to claim 1, comprising dissolving in H ₂ O ₂ (15 wt.%) A mixture of V ₂ O ₅ and anilinium sulfate taken in a molar ratio of 1: 0.1-0.5 with stirring, followed by heating to 40 ° C, keeping at this temperature for 1 hour, filtering, washing the product and drying at 60 ° C. 3. The method of producing a hybrid material according to claim 1, comprising the formation of a gel from vanadium pentoxide by dissolving the V ₂ O ₅ powder in H ₂ O ₂ (10-20 wt.%), Followed by the addition of aniline sulfate in a molar ratio of 1 mol V ₂ O ₅ - 0.1-0.5 mol of aniline sulfate, heating to 40 ° C, keeping at this temperature for 1 hour, filtering, washing the product and drying at 60 ° C.

Images