CN104538207B - TiNb2O7The preparation method of/carbon nano tube compound material and using the material as the lithium-ion capacitor of negative pole - Google Patents

Abstract

The invention provides a kind of preparation method of titanium niobate/carbon nano tube compound material and using the material as the lithium-ion capacitor of negative pole, the composite is mixed by adding titanium source, niobium source and CNT, obtained after carrying out solvent heat treatment, drying process and two step bakings processing, simple production process, easily expands large-scale production.Obtained titanium niobate/carbon nano tube compound material improves the overall electrical conductance of material again while increasing product specific surface area.The capacitor being made using the composite for negative pole, operating voltage is high, have extended cycle life, and specific energy is far above general electrochemical capacitor, up to 50 WhKg^‑1More than, with very high practical value.

Description

Preparation method of TiNb2O7/carbon nanotube composite material and use the material as negative electrode lithium ion capacitor

technical field

The invention relates to the fields of electrochemical material preparation and energy fields, in particular to a preparation method of a TiNb ₂ O ₇ /carbon nanotube composite material and a lithium ion capacitor using the material as a negative electrode.

Background technique

With the continuous development of the world economy, the depletion of fossil energy, the intensification of environmental pollution, and the increasingly significant global greenhouse effect, the development of new energy development, environmental protection, energy conservation and emission reduction has become an extremely important and urgent issue for human beings. Chemical energy storage devices are an important part of the energy system, among which electrochemical supercapacitors and lithium-ion batteries have attracted much attention due to their excellent performance.

With the development of hybrid electric vehicles and the demand for energy storage devices with high power density and high energy density, lithium-ion capacitors that combine the advantages of electric double-layer capacitors and lithium-ion secondary batteries have attracted much attention. Due to the simultaneous use of electrode materials for lithium batteries and electric double-layer capacitors, lithium-ion capacitors have the dual properties of both, which are higher in power density than lithium-ion batteries and higher in energy density than electric double-layer capacitors. Therefore, lithium-ion capacitors are expected to be used in high-energy and high-power electronic products such as new energy vehicles, electrical equipment, military and aerospace facilities.

Recently, lithium-ion hybrid capacitors using a battery-type electrode material (energy source) for one pole and an electric double-layer capacitor-type electrode material (power source) for the other pole have been widely reported. In 2001, Amatucci et al. reported for the first time a hybrid energy storage system in a non-aqueous system with an energy density greater than 10 Wh Kg in Journal of The Electrochemical Society 148 (2001) A930-A939 (An asymmetric hybrid nonaqueous energy storage cell). ^-1 , the negative electrode is lithium titanate (LTO), and the positive electrode material is activated carbon (AC). With this report, more hybrid energy storage systems under organic systems have been extensively studied. For example, Ni et al reported a _method using _AC / _{LiPF 6} /LTO-C system, its energy density reaches 20Wh·Kg ^-1 . Wang et al reported a carbon nanotube (CNT)/LiPF ₆ / _{TiO 2 -B} The system has an energy density of 12.5 Wh·Kg ^-1 at a current density of 10 C in the voltage range of 0-2.8 V. Cericola et al reported a ₂ O in Journal ofPower Sources 196(2011) 10305-10313 (Hybridization of electrochemical capacitors and rechargeable batteries: An experimental analysis of the different possible approaches utilizing activated carbon, Li ₄ Ti ₅ O _{12 andLi4Mn )} The mixed system of O ₄ /LiClO ₄ /AC has an energy density of 45 Wh·Kg ^{-1 at a power density of 30 W·Kg -1 .} Li et al. used Ni-doped LiMn ₂ O ₄ as the negative electrode, such as the system of LiNi _0.5 Mn _1.5 O ₄ /LiPF ₆ /AC, the working voltage is as high as 4.7 V, and the energy density has reached more than 50 Wh·Kg ^-1 (Electrochemical and Solid State Letters 8 (2005) A433-A436 (A hybrid electrochemical supercapacitor based on a 5 V Li-ion battery cathode and active carbon)). The hybrid capacitor can make full use of the voltage difference between the positive and negative electrodes to provide the highest output working voltage, thus maximizing the energy density of the hybrid capacitor. The goal of lithium-ion hybrid capacitors is to increase energy density while sacrificing minimal power density and cycle times.

In general, designing and preparing battery-type anode materials with excellent performance is the key to obtaining high performance of hybrid capacitors. Usually, the cycle life of hybrid capacitors is significantly attenuated due to the poor cycle stability of battery-type electrode materials. Therefore, anode materials with stable structure, high energy density and fast charge-discharge capability are urgently needed to be developed. So far, many different kinds of anode materials have been extensively studied, such as LTO. However, the low specific capacity (175 mAh·g ^-1 ) and poor electronic conductivity of LTO greatly limit its high rate capability. Therefore, it is particularly urgent to find new electrode materials to replace LTO.

TiNb ₂ O ₇ with a layered monoclinic crystal structure was recently proposed by the Goodenough group as a new type of anode material for lithium-ion batteries, with a theoretical capacity of 387.6 mAh g ^-1 and 5 electron transfer reactions during charge and discharge (Ti ⁴⁺ /Ti ³⁺ , Nb ⁵⁺ /Nb ³⁺ ), which is twice that of LTO materials, and the charge and discharge potentials are not much different, which can effectively avoid the formation of solid electrolyte interfacial film (SEI) and ensure that the electrodes However, the intrinsic electronic conductivity of TiNb ₂ O ₇ material is not high, which restricts its application in actual production.

Contents of the invention

In order to solve the problems of the prior art, the present invention provides a preparation method of a TiNb ₂ O ₇ /carbon nanotube composite material and a lithium ion capacitor using the material as a negative electrode. The production process is simple, easy to realize industrialization, and has a high use value.

The preparation method provided by the invention comprises the following steps:

1) Add the titanium source and the niobium source into the dispersant to disperse and mix to obtain a mixture of Ti and Nb, wherein the molar ratio of Ti to Nb is 1:2;

2) Add carbon nanotubes to the mixture of Ti and Nb obtained in step 1) and stir, and the obtained new mixture is ready for use, wherein the mass ratio of carbon nanotubes to the mixture of Ti and Nb is 2:3. The concentration in tube dispersant is about 11.5 mg·mL ^-1 ;

3) Pour the final mixture obtained in step 2) into the reactor for solvent heat treatment, the reaction temperature is 160-220 ℃, keep warm for 12-36h and then cool to room temperature;

4) The sample obtained in step 3) was centrifuged and dried, and then placed in a porcelain boat for two-step roasting treatment. The first roasting temperature was 300 °C, the heating rate was 2 °C·min ^-1 , and the holding time was 1 -2 h, the sintering atmosphere is air; the second-step calcination temperature is 700 ℃, the heating rate is 3 ℃·min ^-1 , the holding time is 1-2 h, and the sintering atmosphere is nitrogen.

As a further improvement, the titanium source in step 1) is one or more of isopropyl titanate, tetrabutyl titanate or titanium ethoxide.

As a further improvement, the niobium source in step 1) is one or both of niobium chloride or niobium oxyethoxide.

As a further improvement, the dispersant in step 1) is one or both of ethanol or dimethylformamide.

The present invention also provides a lithium-ion capacitor. The capacitor uses TiNb ₂ O ₇ /carbon nanotube composite material as the negative electrode material, and aluminum foil coated with activated carbon as the positive electrode. The electrolyte is an organic electrolyte containing lithium hexafluorophosphate and quaternary ammonium salt. , Polypropylene porous film is used as the diaphragm to assemble lithium-ion capacitors. Wherein, the mass ratio of the positive electrode active material to the negative electrode active material is 5.

The beneficial effects of the present invention are:

(1) The present invention adopts a relatively mild wet chemical method, supplemented by short-term calcination to obtain pure phase TiNb ₂ O ₇ , the production process is simple, and it is easy to expand scale production.

(2) The present invention obtains TiNb ₂ O ₇ /carbon nanotube composite material, TiNb ₂ O ₇ has small particle size, uniform distribution, good product stability and consistency, and TiNb ₂ O ₇ nanoparticles are evenly distributed in carbon nanotubes The periphery of the tube is closely combined with carbon nanotubes, and its rich pore structure can completely infiltrate the active material with the electrolyte, while the nanoscale particles can effectively shorten the transmission distance of lithium ions and electrons during charge and discharge, and increase the While increasing the specific surface area of the product, it also improves the overall electrical conductivity of the material.

(3) In the process of assembling lithium-ion capacitors, the present invention adopts TiNb ₂ O ₇ /carbon nanotube composite material as the battery-type negative electrode material for the first time, uses activated carbon as the electric double-layer capacitor-type positive electrode material, and selects the electrolyte containing lithium hexafluorophosphate and quaternary ammonium salt Organic electrolyte, polypropylene porous membrane as separator, the assembled lithium ion capacitor has excellent performance, high working voltage, long cycle life (2000 cycles, capacity retention rate greater than 97%), and the specific energy is much higher than that of ordinary capacitors. Chemical capacitors, which can reach more than 50 Wh·Kg ^-1 , have high practical value.

Description of drawings

Fig. 1 is the XRD pattern of TiNb ₂ O ₇ / carbon nanotube composite material prepared by the present invention;

Fig. 2 is the SEM picture of the TiNb ₂ O ₇ /carbon nanotube composite material prepared by the present invention;

Fig. 3 is the charging and discharging curve at 0.1 C of the TiNb ₂ O ₇ /carbon nanotube composite material prepared by the present invention;

Fig. 4 prepared by the present invention uses TiNb ₂ O ₇ / carbon nanotubes as the negative electrode and activated carbon as the electrochemical curve diagram of the hybrid capacitor under different current densities;

Fig. 5 is a life curve of 2000 cycles at 1A·g ^-1 for a TiNb ₂ O ₇ /carbon nanotube hybrid capacitor prepared by the present invention as the negative electrode and activated carbon as the positive electrode.

detailed description

The present invention will be further described below in conjunction with accompanying drawing.

The above content of the present invention will be further described in detail below through specific examples. However, it should not be construed that the content of the present invention is limited to the following examples.

Example 1

At room temperature, 1 mmol of niobium pentachloride and 2 mmol of isopropyl titanate were added to 20 mL of ethanol to disperse and mix, after stirring for 30 min, 230 mg of carbon nanotubes were added, and after stirring again for 30 min, the The mixed solution was poured into the inner lining of the reactor for solvothermal reaction. The reaction temperature was 200 °C, and the holding time was 24 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying treatment. 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature is 700 ℃, the heating rate is 3 ℃·min ^-1 , the holding time is 2h, and the sintering atmosphere is nitrogen.

Fig. 1 is an XRD pattern of the TiNb ₂ O ₇ /carbon nanotube composite material obtained in this embodiment.

Fig. 2 is a SEM image of the TiNb ₂ O ₇ /carbon nanotube composite material obtained in this embodiment.

It is not difficult to see from the above drawings that the TiNb ₂ O ₇ /carbon nanotube composite material obtained in this embodiment has a small particle size, is closely combined with carbon nanotubes, and has good product stability and consistency.

Weigh the TiNb ₂ O ₇ /carbon nanotube composite material, acetylene black, and binder polyvinylidene fluoride obtained in this example with a mass ratio of 8:1:1. After grinding evenly, use N-methylpyrrolidone as the Solvent, fully stirred into a paste, and then evenly coated on the copper foil with a film coating machine, fully dried at 110 ℃ for 12 hours, and cut into appropriate size electrode sheets. The assembly of the half-cell uses metal lithium as the negative electrode, polypropylene porous membrane as the diaphragm, and 1M LiPF ₆ EC/DMC (volume ratio 1:1) as the electrolyte, and is assembled into a button-type in an argon-filled glove box. The battery is then charged and discharged on the Land battery test system.

The measured charging and discharging curves of the TiNb ₂ O ₇ /carbon nanotube composite material obtained in Example 1 at 0.1 C are shown in FIG. 3 .

The assembly of lithium-ion capacitors is similar to that of half-cells, except that the positive electrode uses a mixture of activated carbon, acetylene black, and a binder (mass ratio of 8:1:1). The electrolyte is an organic electrolyte containing lithium hexafluorophosphate and quaternary ammonium salt. The matching of the positive and negative electrode materials has a great influence on the final performance of the ionic capacitor. According to the formula of charge conservation, the preferred mass ratio of the positive active material to the negative active material in this patent is 5.

The measured electrochemical curves of the TiNb ₂ O ₇ /carbon nanotube composite material obtained in Example 1 at different current densities and the life of 2000 cycles at 1 A g ^-1 The curves are shown in Figure 4 and Figure 5 respectively. It can be seen from the figure that the lithium-ion capacitor assembled in this patent has a high energy density, as high as 51.35 Wh·Kg ^{-1 at a current density of 0.15 A·g -1 .} The cycle performance is also quite excellent, and the capacity fading is only 2.3% after 2000 cycles at a current density of 1 A g ^-1 .

Example 2

At room temperature, 1 mmol of niobium pentachloride and 2 mmol of isopropyl titanate were added to 20 mL of dimethyl sulfoxide to disperse and mix. After stirring for 30 min, 230 mg of carbon nanotubes were added and stirred again for 30 min. After 1 min, the mixed solution was poured into the lining of the reactor for solvothermal reaction. The reaction temperature was 200 °C, and the holding time was 24 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying at 60 °C. , and the drying time was 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was nitrogen.

Example 3

At room temperature, add 1 mmol of niobium ethoxide and 2 mmol of isopropyl titanate into 20 mL of dimethyl sulfoxide to disperse and mix, stir for 30 min, add 230 mg of carbon nanotubes, and stir again for 30 min Finally, the mixed solution was poured into the inner lining of the reactor for solvothermal reaction, the reaction temperature was 200 °C, and the holding time was 24 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying treatment, and the drying temperature was 60 °C. The drying time is 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was nitrogen.

Example 4

At room temperature, add 1 mmol of niobium ethoxide and 2 mmol of tetrabutyl titanate into 20 mL of dimethyl sulfoxide to disperse and mix, stir for 30 min, add 230 mg of carbon nanotubes, and stir again for 30 min Finally, the mixed solution was poured into the inner lining of the reactor for solvothermal reaction, the reaction temperature was 200 °C, and the holding time was 24 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying treatment, and the drying temperature was 60 °C. The drying time is 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was nitrogen.

Example 5

At room temperature, add 1 mmol of niobium pentachloride and 2 mmol of titanyl ethoxide to 20 mL of dimethyl sulfoxide for dispersion and mixing. After stirring for 30 min, add 230 mg of carbon nanotubes and stir again for 30 min. , pour the mixed liquid into the inner lining of the reactor to carry out solvothermal reaction, the reaction temperature is 200 °C, and the holding time is 24 h. The time is 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was nitrogen.

Example 6

At room temperature, 1 mmol of niobium pentachloride and 2 mmol of isopropyl titanate were added to 20 mL of ethanol to disperse and mix, after stirring for 30 min, 230 mg of carbon nanotubes were added, and after stirring again for 30 min, the The mixed solution was poured into the inner lining of the reactor for solvothermal reaction. The reaction temperature was 160 °C, and the holding time was 36 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying treatment. 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature is 700 ℃, the heating rate is 3 ℃·min ^-1 , the holding time is 2h, and the sintering atmosphere is nitrogen.

Example 7

At room temperature, 1 mmol of niobium pentachloride and 2 mmol of isopropyl titanate were added to 20 mL of ethanol to disperse and mix, after stirring for 30 min, 230 mg of carbon nanotubes were added, and after stirring again for 30 min, the The mixed solution was poured into the lining of the reactor for solvothermal reaction. The reaction temperature was 220 °C, and the holding time was 12 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying treatment. 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature is 700 ℃, the heating rate is 3 ℃·min ^-1 , the holding time is 2h, and the sintering atmosphere is nitrogen.

Example 8

At room temperature, 1 mmol of niobium pentachloride and 2 mmol of isopropyl titanate were added to 20 mL of ethanol to disperse and mix, after stirring for 30 min, 230 mg of carbon nanotubes were added, and after stirring again for 30 min, the The mixed solution was poured into the lining of the reactor for solvothermal reaction. The reaction temperature was 200 °C, and the holding time was 20 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying treatment. 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 1 h, and the sintering atmosphere was air; The internal firing temperature is 700 ℃, the heating rate is 3 ℃·min ^-1 , the holding time is 2h, and the sintering atmosphere is nitrogen.

Example 9

At room temperature, 1 mmol of niobium pentachloride and 2 mmol of isopropyl titanate were added to 20 mL of ethanol to disperse and mix, after stirring for 30 min, 230 mg of carbon nanotubes were added, and after stirring again for 30 min, the The mixed solution was poured into the lining of the reactor for solvothermal reaction. The reaction temperature was 200 °C, and the holding time was 20 h. After the reaction was completed and cooled to room temperature, the product was subjected to centrifugal drying treatment. 10 h. Afterwards, the dried samples were placed in a porcelain boat for two-step calcination treatment. The first calcination temperature was 300 ℃, the heating rate was 2 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was air; The internal firing temperature was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 1 h, and the sintering atmosphere was nitrogen.

There are many specific application approaches of the present invention, and the above description is only a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements can also be made without departing from the principles of the present invention. Improvements should also be regarded as the protection scope of the present invention.

Claims (4)

1. A preparation method of TiNb ₂ O ₇ /carbon nanotube composite material, it is characterized in that comprising the following steps: 1) Add titanium source and niobium source to the dispersant to disperse and mix to obtain a mixture of Ti and Nb, wherein the molar ratio of Ti to Nb is 1:2; 2) Add carbon nanotubes to the mixture of Ti and Nb obtained in step 1) and stir, and the obtained new mixture is ready for use, wherein the mass ratio of carbon nanotubes to the mixture of Ti and Nb is 2:3, and the carbon nanotubes The concentration in the dispersant is about 11.5mg·mL ^-1 ; 3) Pour the mixture finally obtained in step 2) into a reaction kettle for solvent heat treatment at a reaction temperature of 160-220°C, keep it warm for 12-36h and then cool to room temperature; 4) The sample obtained in step 3) was centrifuged and dried, and then placed in a porcelain boat for two-step roasting treatment. The temperature of the first roasting treatment was 300 °C, the heating rate was 2 °C·min ^-1 , and the holding time was 1 -2 h, the sintering atmosphere is air; the second-step calcination temperature is 700 ℃, the heating rate is 3 ℃·min ^-1 , the holding time is 1-2 h, and the sintering atmosphere is nitrogen. 2. The TiNb ₂ O ₇ /carbon nanotube composite material according to claim 1, characterized in that: the titanium source in step 1) is isopropyl titanate, tetrabutyl titanate or titanium ethoxide one or more. 3. The TiNb ₂ O ₇ /carbon nanotube composite material according to claim 1, characterized in that: the niobium source in step 1) is one or both of niobium chloride or niobium ethoxide. 4. The TiNb ₂ O ₇ /carbon nanotube composite material according to claim 1, characterized in that: the dispersant in step 1) is one or both of ethanol or dimethylformamide.