CN104538207A - Method for preparing titanium niobate and carbon nanotube composite material and lithium ion capacitor with material as negative electrode - Google Patents

Abstract

The invention provides a preparation method of a titanium niobate/carbon nanotube composite material and a lithium ion capacitor using the material as a negative electrode. The composite material is mixed by adding titanium source, niobium source and carbon nanotube, and subjected to solvent heat treatment, It is obtained after drying treatment and two-step baking treatment, the production process is simple, and it is easy to expand scale production. The obtained titanium niobate/carbon nanotube composite material not only increases the specific surface area of the product, but also improves the overall electrical conductivity of the material. The capacitor made of this composite material as the negative electrode has high working voltage and long cycle life, and the specific energy is much higher than that of general electrochemical capacitors, which can reach more than 50 Wh·Kg ^-1 , which has high practical value.

Description

Preparation method of titanium niobate/carbon nanotube composite material and lithium ion capacitor using the material as negative electrode

technical field

The present invention relates to the fields of preparation of electrochemical materials and energy, in particular to a preparation method of a titanium niobate/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 nonaqueous system with an energy density greater than 10 Wh in Journal of The Electrochemical Society 148 (2001) A930-A939 (An asymmetric hybrid nonaqueous energy storage cell). ·Kg ^-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 reached 20 Wh·Kg ^-1 . Wang et al reported a carbon nanotube (CNT)/ _{LiPF 6 /} TiO ₂ -B system, its energy density is 12.5 Wh·Kg ^-1 under the current density of 10 C in the voltage range of 0-2.8 V. Cericola et al reported in Journal of Power 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 and Li 4Mn) _{2 O} A LiMn ₂ O ₄ /LiClO ₄ /AC hybrid system has an energy density as high as 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.

Titanium niobate (TiNb ₂ O ₇ ) with a layered monoclinic structure was recently proposed by the Goodenough group as a new type of anode material for lithium-ion batteries. Its theoretical capacity is 387.6 mAh·g ^-1 . There are 5 electron transfer reactions (Ti ⁴⁺ /Ti ³⁺ , Nb ⁵⁺ /Nb ³⁺ ), twice that of LTO materials, and the charge and discharge potentials are not much different, which can effectively avoid the solid electrolyte interface film (SEI) 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 titanium niobate/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 high application efficiency. 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 titanium niobate mixture, wherein the molar ratio of Ti to Nb is 1:2;

2) Add carbon nanotubes to the titanium niobate mixture obtained in step 1) and stir, and the obtained new mixture is ready for use, wherein the ratio of carbon nanotubes to titanium niobate mixture is 2:3, and the concentration in the dispersant About 11.5 mg·mL ^-1 ;

3) Pour the mixture 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 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 titanium niobate/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 a separator 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 titanium niobate, the production process is simple, and it is easy to expand scale production.

(2) What the present invention obtains is the titanium niobate/carbon nanotube composite material, the titanium niobate particle size is small, the distribution is uniform, the product stability and consistency are good, and the titanium niobate nano-particles are evenly distributed in the periphery of the carbon nanotube , closely combined with carbon nanotubes, its rich pore structure allows the electrolyte to completely infiltrate the active material, while nanoscale particles can effectively shorten the transmission distance of lithium ions and electrons during charge and discharge, increasing the product ratio While increasing the surface area, the electrical conductivity of the material as a whole is increased.

(3) In the process of assembling lithium-ion capacitors, the present invention adopts titanium niobate/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 general electrochemical capacitors. Capacitors, up to 50 Wh·Kg ^-1 or more, have high practical value.

Description of drawings

Fig. 1 is the XRD figure of the titanium niobate/carbon nanotube composite material prepared by the present invention;

Fig. 2 is the SEM figure of the titanium niobate/carbon nanotube composite material prepared by the present invention;

Fig. 3 is the charge-discharge curve figure at 0.1 C of the titanium niobate/carbon nanotube composite material prepared by the present invention;

Fig. 4 prepared by the present invention takes titanium niobate/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 of a hybrid capacitor prepared by the present invention with titanium niobate/carbon nanotubes as the negative electrode and activated carbon as the positive electrode at 1 A·g ^-1 .

Detailed ways

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 was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was nitrogen.

Fig. 1 is an XRD pattern of the titanium niobate/carbon nanotube composite material obtained in this embodiment.

Fig. 2 is an SEM image of the titanium niobate/carbon nanotube composite material obtained in this embodiment.

It is not difficult to see from the above drawings that the titanium niobate/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 titanium niobate/carbon nanotube composite material, acetylene black, and binder polyvinylidene fluoride obtained in this example at a mass ratio of 8:1:1, grind them evenly, and use N-methylpyrrolidone as a 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 electrode sheets of appropriate size. 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 charge and discharge curves of the titanium niobate/carbon nanotube composite material obtained in Example 1 at 0.1 C are shown in Figure 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 electrochemical curves of the lithium-ion capacitors obtained in Example 1 with titanium niobate/carbon nanotube composites as negative electrodes at different current densities and the life curves of 2000 cycles at 1 A g ^-1 Respectively shown in Figure 4, Figure 5. 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 was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was 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 was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was 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 was 700 ℃, the heating rate was 3 ℃·min ^-1 , the holding time was 2 h, and the sintering atmosphere was 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 (6)

1. a preparation method for titanium niobate/carbon nano tube compound material, is characterized in that comprising the following steps:

1) titanium source and niobium source are added dispersion mixing in dispersant, obtain titanium niobate mixture, wherein Ti and Nb mol ratio is 1:2;

2) carbon nano-tube joined in step 1) and stir in gained titanium niobate mixture, the new mixture of acquisition is stand-by, and wherein the ratio of carbon nano-tube and titanium niobate mixture is 2:3, and the concentration in dispersant is about 11.5 mgmL ^-1;

3) by step 2) in mixture pour in reactor and carry out solvent heat treatment, reaction temperature is 160-220 DEG C, is cooled to room temperature after insulation 12-36h;

4) by the sample centrifugal drying obtained in step 3), be placed in porcelain boat and carry out two one-step baking process, first step calcination process temperature is 300 DEG C, and heating rate is 2 DEG C of min ^-1, temperature retention time is 1-2 h, and sintering atmosphere is air; Second sintering temperature is 700 DEG C, and heating rate is 3 DEG C of min ^-1, temperature retention time is 1-2 h, and sintering atmosphere is nitrogen.

2. titanium niobate/carbon nano tube compound material according to claim 1, is characterized in that: the titanium source described in step 1) is one or more in isopropyl titanate, butyl titanate or ethanol oxygen titanium.

3. titanium niobate/carbon nano tube compound material according to claim 1, is characterized in that: the niobium source described in step 1) is one or both in niobium chloride or ethanol oxygen niobium.

4. titanium niobate/carbon nano tube compound material according to claim 1, is characterized in that: the dispersant described in step 1) is one or both in ethanol or dimethyl formamide.

5. a lithium-ion capacitor, is characterized in that: the negative material of capacitor is titanium niobate/carbon nano tube compound material.

6. a kind of lithium-ion capacitor according to claim 5, is characterized in that: in described negative material active material quality and positive active material with than being 1:5.