CN103474658B - Flexible lithium ion secondary battery negative pole of a kind of lithium niobate composite carbon nanometer tube and preparation method thereof and application - Google Patents

Abstract

The flexible lithium ion secondary battery negative pole of a kind of lithium niobate composite carbon nanometer tube provided by the invention, described electrode is the pyrene of the load lithium niobate of polymer overmold or the carbon nano tube flexible electrode of pyrene derivatives modification.Additionally provide preparation method and the application of this electrode.Preparation technology is simple in this pole, with low cost, this electrode adopts the method for liquid phase growth in situ by lithium niobate material load coated with conductive polymer on the carbon nano tube network of high conductivity and thereon, utilize carbon nano-tube and conducting polymer compound system to have good flexible feature and prepare the flexible electrode film with certain mechanical strength, the flexibility of electrode can be realized well and improve the chemical property of lithium niobate material, this electrode have apparently higher than the charge/discharge capacity of lithium titanate anode and good cycle performance and close to 100% coulombic efficiency, mechanical property is good, excellent electrochemical performance, safe and reliable.

Description

A lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode and its preparation method and application

technical field

The invention belongs to the field of battery material science, and particularly relates to a lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode, a preparation method of the electrode, and a lithium ion secondary battery including the electrode.

Background technique

Carbonate electrolyte is currently the most commonly used electrolyte in lithium-ion secondary battery systems. This type of electrolyte will decompose when the discharge voltage is lower than 1.0V (vs Li ⁺ /Li ⁰ ), forming an SEI film, which affects Battery safety and cycle stability. The current commercial carbon-based negative electrode materials and the silicon-based and tin-based negative electrode materials under development all have the above-mentioned problems in use due to their low redox potential.

As an emerging negative electrode material, Li ₄ Ti ₅ O ₁₂ has an oxidation-reduction potential of about 1.5V (vs Li ⁺ /Li ⁰ ), which can effectively avoid the above problems. But the theoretical specific capacity of Li ₄ Ti ₅ O ₁₂ is only 175mAh/g, far lower than carbon-based, silicon-based or tin-based negative electrode materials. Therefore, there is an urgent need for a new type of anode material with a redox potential of 1.0 V (vs Li ⁺ /Li ⁰ ), good safety, good cycle stability, and high specific capacity.

The flexible design of lithium-ion secondary batteries has also received extensive attention from the academic community. This kind of battery adopts a simple self-supporting negative electrode-electrolyte and separator layer-self-supporting positive electrode sandwich structure design. Due to the omission of current collectors, steel shells and a large amount of perfused organic electrolyte, the specific energy density and safety of the battery are improved. It has been greatly improved and the application field has become wider.

Lithium niobate material is a well-known photoelectric material. According to the existing reports, this material also has the potential as a negative electrode material for lithium-ion secondary batteries, and the applied electrochemical window can be controlled at 1.0V (vs Li ⁺ / Li ⁰ ) above, so as to avoid the decomposition of the electrolyte during use.

Contents of the invention

Purpose of the invention: The first purpose of the present invention is to provide a lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode with good safety, good cycle stability and high specific capacity.

The second object of the present invention is to provide a method for preparing the above-mentioned negative electrode.

A third object of the present invention is to provide a lithium ion secondary battery including the electrode.

Technical solution: The invention provides a lithium niobate composite carbon nanotube flexible lithium-ion secondary battery negative electrode, the electrode is a polymer coated lithium niobate-loaded pyrene or pyrene derivative modified carbon nanotube flexible electrode .

Preferably, the polymer is a pyrrole polymer.

The present invention also provides a preparation method for the above-mentioned lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode, comprising the following steps:

(1) Preparation of carbon nanotubes modified by pyrene or pyrene derivatives: placing carbon nanotubes in pyrene solution or pyrene derivative solution, stirring and reacting to obtain carbon nanotubes modified by pyrene or pyrene derivatives;

(2) Preparation of carbon nanotubes modified with pyrene or pyrene derivatives loaded with lithium niobate: Add a mixed aqueous solution of niobium source and lithium source to the solution of carbon nanotubes modified with pyrene or pyrene derivatives, stir for reaction, and nitrogen after reaction Heat treatment under atmosphere to obtain carbon nanotubes modified with pyrene or pyrene derivatives loaded with lithium niobate;

(3) Preparation of the electrode precursor slurry: Add the carbon nanotubes modified with pyrene or pyrene derivatives loaded with lithium niobate into the pyrrole monomer solution, and stir to make the pyrrole monomers in the pyrene or pyrene derivatives loaded with lithium niobate Surface polymerization of modified carbon nanotubes to obtain electrode precursor slurry;

(4) Preparation of flexible lithium-ion secondary battery negative electrode: compound the electrode precursor slurry on the substrate by coating, spin coating or suction filtration, dry to separate the substrate, and heat-treat to obtain the finished product.

In the step (1), in the step (1), the pyrene solution or the pyrene derivative solution is an aqueous solution or an ethanol solution, and its molar concentration is 0.02-1mol/L, and the mass ratio of the pyrene or pyrene derivative to the carbon nanotube is 1: (0.5-10); the reaction time is 6-48h.

In step (2), the niobium source is niobium oxalate, the lithium source is lithium acetate, and the molar ratio between the niobium source and the lithium source is 1:1; the mass ratio of carbon nanotubes to lithium acetate is (2-10): 1. The reaction temperature is 50-70°C, preferably 60°C, and the reaction time is 8-24h, preferably 12h; the heat treatment temperature is 500-900°C, preferably 700°C, and the heat treatment time is 4-6h, preferably 5h.

In step (3), the stirring temperature is 0-40° C., and the stirring time is 6-15 hours; the mass ratio of the pyrrole monomer to the carbon nanotube is (0.5-5):1.

In step (4), the drying temperature is 80-110°C, and the drying time is 4-12h; the heat treatment temperature is 120-180°C, preferably 155°C, and the heat treatment time is 1-3h, preferably 2h; the substrate is polyvinylidene fluoride substrate or silicon wafer.

The present invention also provides the application of the lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode in the preparation of lithium ion secondary batteries.

Beneficial effects: the lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode provided by the present invention has a simple preparation process and low cost. The nanotube network is coated with a conductive polymer on it, and a flexible electrode film with a certain mechanical strength is prepared by using the characteristics of the carbon nanotube and conductive polymer composite system to have good flexibility, which can well realize the electrode. Flexibility and improve the electrochemical performance of lithium niobate material, the electrode has significantly higher charge and discharge capacity than lithium titanate negative electrode and good cycle performance and close to 100% coulombic efficiency, good mechanical properties, excellent electrochemical performance, safe reliable.

Similar to Li ₄ Ti ₅ O ₁₂ , lithium niobate also has the disadvantage of poor electrical conductivity. In the present invention, the overall electrical conductivity of the electrode can be significantly improved by combining lithium niobate with carbon nanotubes with high electrical conductivity. , which is conducive to the excellent electrochemical performance of the electrode during use.

The invention utilizes the unique mechanical properties of carbon nanotubes and conductive polymers to prepare flexible electrodes, and the prepared flexible self-supporting electrodes have excellent mechanical properties.

Since the preparation method of the electrode material adopts a solution phase reaction method, the experiment has strong operability and the experiment process is relatively simple.

Description of drawings

Figure 1 is an SEM photo of the lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode.

Fig. 2 is a TEM photograph of a carbon nanotube composite modified with pyrene or pyrene derivatives loaded with lithium niobate.

Fig. 3 is the charging and discharging curve of the lithium battery using the negative electrode of the flexible lithium ion secondary battery of the present invention.

Fig. 4 is the cycle performance of the lithium battery using the negative electrode of the flexible lithium ion secondary battery of the present invention.

Detailed ways

The present invention can be better understood from the following examples. However, those skilled in the art will readily understand that the specific material ratios, process conditions and results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims .

Example 1

Lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode, i.e. pyrrole polymer-coated pyrene derivative loaded lithium niobate modified carbon nanotube flexible electrode, the preparation method comprising the following steps:

1. Add pyrene derivatives in the reactor, use ethanol as solvent, configure the ethanol solution of pyrene derivatives of 0.5mol/L, leave standstill after ultrasonic waves; add carbon nanotubes, the mass of the pyrene derivatives and carbon nanotubes Ratio of 1:5, strong ultrasonic stirring reaction for 12h, to get pyrene derivatives modified carbon nanotubes;

2. Under the condition of maintaining strong ultrasonic stirring, slowly add the mixed solution containing niobium oxalate and lithium acetate with a molar ratio of 1:1 in the reactor containing the carbon nanotubes modified by pyrene derivatives, the mass of carbon nanotubes and lithium acetate The ratio is 6:1, after reacting in a water bath at 60°C for 12 hours, put it into a tube furnace filled with nitrogen atmosphere, and heat-treat at 700°C for 5 hours to obtain carbon nanotubes modified with pyrene derivatives loaded with lithium niobate;

3. Add the carbon nanotubes modified by pyrene derivatives loaded with lithium niobate into the pyrrole monomer solution, the mass ratio of the pyrrole monomer to the carbon nanotubes is 2.5:1, stir at 20°C for 9h, and make the pyrrole monomer Surface polymerization of carbon nanotubes modified by pyrene derivatives loaded with lithium niobate to obtain electrode precursor slurry;

4. Coat the electrode precursor slurry on the polyvinylidene fluoride substrate, dry at 100°C for 8 hours, and use the difference in surface tension during the drying process to separate the coated flexible electrode sheet from the polyvinylidene fluoride substrate;

5. Heat-treat the obtained flexible electrode sheet at a temperature of 155° C. for 2 hours to obtain it.

The electrode of the present invention is directly applied to the lithium-ion secondary battery; and various performance parameters of the prepared flexible lithium-sulfur battery electrode are tested, and the results are shown in Fig. 1 to Fig. 4 .

Figure 1 is the SEM photo of the negative electrode of lithium niobate composite carbon nanotube flexible lithium ion secondary battery. touch. Figure 2 shows the TEM photos of carbon nanotube composites modified with pyrene or pyrene derivatives loaded with lithium niobate to further support this phenomenon.

Fig. 3 is the charging and discharging curve of the lithium battery using the negative electrode of the flexible lithium ion secondary battery of the present invention. It can be seen from Fig. 3 that the charging and discharging capacity of the battery is always maintained above 200mAh/g, which is obviously higher than that of the current commercialized or under research and development. A Li ₄ Ti ₅ O ₁₂ electrode material. In the figure, the 1st-a curve represents the first charge curve, the 1st-b curve represents the first discharge curve, the 2st-a curve represents the second charge curve, the 2st-b curve represents the second discharge curve, and the 3st-a curve represents the second discharge curve. The curve represents the third charge curve, and the 3st-b curve represents the third discharge curve.

Figure 4 is the cycle performance curve of the lithium battery using the negative electrode of the flexible lithium ion secondary battery of the present invention. It can be seen from Figure 4 that the electrode is applied to the battery except that the capacity has a certain attenuation in the initial charge and discharge process, and the subsequent During the charge and discharge process, it shows a relatively stable charge and discharge capacity and the Coulombic efficiency is close to 100%.

In summary, the present invention has the advantages of simple process and easy operation in the production of flexible negative electrodes, and the prepared composite battery electrodes of carbon nanotubes and lithium niobate materials have significantly higher charge-discharge capacity and Good cycle performance and close to 100% coulombic efficiency have the potential to become anodes for new lithium-ion secondary batteries.

Example 2

Lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode, i.e. pyrrole polymer-coated pyrene derivative loaded lithium niobate modified carbon nanotube flexible electrode, the preparation method comprising the following steps:

1. Add pyrene derivatives in the reactor, use water as a solvent, configure a 0.02mol/L ethanol solution of pyrene derivatives, and put it aside after ultrasonic waves; add carbon nanotubes, the mass of the pyrene derivatives and carbon nanotubes The ratio is 1:0.5, and the strong ultrasonic stirring reaction is carried out for 48 hours, and the carbon nanotubes modified by pyrene derivatives are obtained;

2. Under the condition of maintaining strong ultrasonic stirring, slowly add the mixed solution containing niobium oxalate and lithium acetate with a molar ratio of 1:1 in the reactor containing the carbon nanotubes modified by pyrene derivatives, the mass of carbon nanotubes and lithium acetate The ratio is 2:1, after reacting in a water bath at 70°C for 8 hours, put it into a tube furnace filled with nitrogen atmosphere, and heat-treat at 500°C for 6 hours to obtain carbon nanotubes modified with pyrene derivatives loaded with lithium niobate;

3. Add the carbon nanotubes modified by pyrene derivatives loaded with lithium niobate into the pyrrole monomer solution, the mass ratio of the pyrrole monomer to the carbon nanotubes is 0.5:1, and stir at 40°C for 6h, so that the pyrrole monomer is Surface polymerization of carbon nanotubes modified by pyrene derivatives loaded with lithium niobate to obtain electrode precursor slurry;

4. Coat the electrode precursor slurry on the polyvinylidene fluoride substrate, dry at 80°C for 12 hours, and use the difference in surface tension during the drying process to separate the coated flexible electrode sheet from the polyvinylidene fluoride substrate;

5. Heat-treat the obtained flexible electrode sheet at 180°C for 1 hour to obtain it.

Example 3

Lithium niobate composite carbon nanotube flexible lithium ion secondary battery negative electrode, i.e. pyrrole polymer-coated pyrene-modified carbon nanotube flexible electrode loaded with lithium niobate, the preparation method comprising the following steps:

1. Add pyrene to the reactor, use ethanol as solvent, configure a 1mol/L pyrene ethanol solution, put it aside after ultrasonication; add carbon nanotubes, the mass ratio of pyrene to carbon nanotubes is 1:10, strong Ultrasonic stirring was carried out for 6 hours to obtain pyrene-modified carbon nanotubes;

2. Under the condition of maintaining strong ultrasonic stirring, slowly add a mixed solution containing niobium oxalate and lithium acetate with a molar ratio of 1:1 in the reactor containing pyrene-modified carbon nanotubes, the mass ratio of carbon nanotubes to lithium acetate is 10:1, after reacting in a water bath at 50°C for 24 hours, put it into a tube furnace filled with nitrogen atmosphere, and heat-treat at 900°C for 4 hours to obtain pyrene-modified carbon nanotubes loaded with lithium niobate;

3. Add the pyrene-modified carbon nanotubes loaded with lithium niobate into the pyrrole monomer solution, the mass ratio of the pyrrole monomers to the carbon nanotubes is 5:1, stir at 0° C. for 15 h, so that the pyrrole monomers are loaded with niobium Surface polymerization of pyrene-modified carbon nanotubes of lithium acid lithium to obtain electrode precursor slurry;

4. Coat the electrode precursor slurry on a flat silicon wafer, dry at 110°C for 4 hours, and use the difference in surface tension during the drying process to separate the coated flexible electrode sheet from the flat silicon wafer;

5. Heat-treat the obtained flexible electrode sheet at a temperature of 120°C for 3 hours to obtain it.

Claims (1)

1. a preparation method for the flexible lithium ion secondary battery negative pole of lithium niobate composite carbon nanometer tube, is characterized in that: comprise the following steps:

(1) preparation of the carbon nano-tube of pyrene or pyrene derivatives modification: carbon nano-tube is placed in pyrene solution or pyrene derivatives solution, stirs and make reaction, obtains the carbon nano-tube of pyrene or pyrene derivatives modification; Pyrene solution or pyrene derivatives solution are the aqueous solution or ethanolic solution, and its molar concentration is 0.02-1mol/L, and the mass ratio of described pyrene or pyrene derivatives and carbon nano-tube is 1:(0.5-10); Reaction time is 6-48h;

(2) preparation of the pyrene of load lithium niobate or the carbon nano-tube of pyrene derivatives modification: are added niobium source and lithium source mixed aqueous solution in the carbon nano-tube solution that pyrene or pyrene derivatives are modified, stirring makes reaction, heat treatment under blanket of nitrogen after reaction, obtains the pyrene of load lithium niobate or the carbon nano-tube of pyrene derivatives modification; Described niobium source is niobium oxalate, and lithium source is lithium acetate, and the mol ratio in described niobium source, lithium source is 1:1; Carbon nano-tube and lithium acetate mass ratio are (2-10): 1, and reaction temperature is 50-70 DEG C, and the reaction time is 8-24h; Heat treatment temperature is 500-900 DEG C, and heat treatment time is 4-6h;

(3) preparation of electrode precursor slurry: the carbon nano-tube that the pyrene of load lithium niobate or pyrene derivatives are modified is added in pyrrole monomer solution, stir the carbon nano tube surface polymerization that pyrrole monomer is modified at pyrene or the pyrene derivatives of load lithium niobate, obtain electrode precursor slurry; Whipping temp is 0-40 DEG C, and mixing time is 6-15h; The mass ratio of described pyrrole monomer and carbon nano-tube is (0.5-5): 1;

(4) preparation of flexible lithium ion secondary battery negative pole: electrode precursor slurry is adopted coating, the mode of spin coating or suction filtration is compounded on substrate, drying makes substrate separation, heat treatment, to obtain final product; Heat treatment temperature is 120-180 DEG C, and heat treatment time is 1-3h; Substrate is Kynoar substrate or silicon chip.