CN106450308A - High-capacity mesoporous carbon nanofiber for lithium-ion battery and preparation method of high-capacity mesoporous carbon nanofiber - Google Patents

Abstract

A high-capacity mesoporous carbon nanofiber for lithium-ion batteries and a preparation method thereof belong to the technical field of nanomaterials and new energy. The method of the invention adopts fibrous calcium citrate as a raw material, and can obtain mesoporous carbon nanofibers through carbonization and removal of templates, without adding an activator, and has simple operation procedures. The mesoporous carbon nanofiber of the present invention has a large specific surface area, and a large number of pores and channel structures are uniformly distributed inside the fiber. The mesoporous carbon nanofibers of the present invention are used as negative electrode materials for lithium-ion batteries. Compared with traditional negative electrode materials and existing carbon fiber materials, they have obvious advantages in specific capacity, cycle stability and rate performance, and can satisfy the rapidly developing power Lithium-ion battery requirements.

Description

A kind of high-capacity mesoporous carbon nanofiber for lithium ion battery and preparation method thereof

technical field

The invention relates to a high-capacity mesoporous carbon nanofiber for lithium ion batteries and a preparation method thereof, belonging to the technical field of nanomaterials and new energy.

Background technique

Lithium-ion battery is a secondary battery (rechargeable battery), which has the characteristics of high working voltage, large specific energy, long service life, and no memory effect. In recent years, the industrial research and development of lithium-ion batteries has developed rapidly. As the negative electrode material of lithium-ion batteries, metallic lithium was first applied, followed by alloys; however, they could not solve the safety performance of lithium-ion batteries, so the company was born. Lithium-ion battery with carbon material as negative electrode.

Since the commercialization of lithium-ion batteries, carbon materials have dominated the anode materials. As a special carbon-based material, carbon nanofibers have high material utilization, high lithium storage capacity, large electrode/electrolyte contact area, and electronic and Li ⁺ ion conduction path is short, high output power and many other advantages, used as lithium ion battery anode material, can effectively improve the specific capacity, cycle stability and rate performance.

Chinese patent 201410244910.4 discloses a method for preparing a mesoporous carbon material and its application as an electrode material. Chinese patent 201210050636.8 discloses a carbon material with a hierarchical pore structure for the negative electrode of a power lithium-ion battery and its preparation method. Plate-shaped magnesium aluminum hydrotalcite and metal sources are used as templates, and the process flow is complicated. Chinese patent 201010581833.3 discloses a mesoporous carbon nanofiber anode material for lithium-ion batteries and its preparation method. The fiber is obtained by electrospinning and further carbonized to obtain carbon nanofibers, but there are problems such as inconspicuous pore structure. After 20 cycles of battery negative electrode material, the specific capacity is only maintained at 400mAh/g, which is relatively small compared with traditional graphite (~372mAh/g).

This patent is based on calcium citrate as raw material, mesoporous carbon nanofibers can be prepared only by carbonization and template removal, no need to add activators, calcium oxide and other decomposition products can be directly used as in-situ templates, the prepared mesoporous carbon nanofibers Carbon nanofibers have a high specific surface area and a pore size suitable for the intercalation and extraction of lithium ions. They are used as anode materials for lithium-ion batteries, and have significantly improved and improved specific capacity, cycle life, and rate performance.

Contents of the invention

The technical problem to be solved by the present invention is to provide a high-capacity mesoporous carbon nanofiber for lithium-ion batteries and its preparation method. The method does not need to add an activator, the process is simple, and the prepared mesoporous carbon nanofiber has abundant pores. structure and high specific surface area.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A kind of high-capacity mesoporous carbon nanofiber for lithium ion battery and preparation method thereof, the specific steps are as follows:

(1) Put uniformly dispersed fibrous calcium citrate in a horizontal tube furnace, and under the protection of inert gas, raise the furnace temperature to the activation temperature of 500~1000°C at a rate of 2~8°C/min, and keep it warm for 2 After ~5h, cool down to room temperature naturally.

(2) Then the carbonized product obtained in step (1) is taken out, the template is removed by rinsing with hydrochloric acid solution, deionized and cleaned to neutrality, and the cleaned product is placed in a freeze dryer for drying treatment, and finally the mesoporous carbon is obtained. Nanofibers.

Further, the diameter of the mesoporous carbon nanofibers in the step (2) is 10-1000 nm.

Further, the mesoporous carbon nanofibers in the step (2) have a large number of pores and channels evenly distributed inside, and the pore size distribution is 3-20nm.

Further, the specific surface area of the mesoporous carbon nanofibers in the step (2) is 500-2000m ² /g.

Further, the mesoporous carbon nanofibers in the step (2) are used as negative electrode materials for lithium-ion batteries, and the first discharge specific capacity is 1000mAh/g~1500mAh/g, and after 50 cycles, the specific capacity remains above 600mAh/g, Significantly improved specific capacity and cycle stability.

The beneficial effects of the present invention are as follows:

The calcium citrate precursor is directly carbonized, and the decomposition products such as calcium oxide are used as in-situ templates to form pores, without adding an additional activator, and the process is simple; mesoporous carbon nanofibers have a large specific surface area, fiber There are a large number of pores and channel structures evenly distributed inside. When used as a negative electrode material for lithium-ion batteries, it has obvious advantages in specific capacity, cycle stability and rate performance compared with traditional negative electrode materials and existing carbon fiber materials. Requirements for power lithium-ion batteries on capacity, cycle life and cycle stability.

Description of drawings

Fig. 1 is the SEM figure of the mesoporous carbon nanofiber of embodiment 1 of the present invention;

Fig. 2 is the TEM picture of the mesoporous carbon nanofiber in Example 1 of the present invention;

Fig. 3 is the N of the mesoporous carbon nanofiber in Example ₁ of the present invention Adsorption-desorption curve;

Fig. 4 is the XRD pattern of mesoporous carbon nanofibers in Example 1 of the present invention;

Fig. 5 is the Raman diagram of the mesoporous carbon nanofiber in Example 1 of the present invention;

Fig. 6 is the EDS result of mesoporous carbon nanofiber in Example 1 of the present invention;

7 is a cycle performance curve of mesoporous carbon nanofibers at a current density of 100mA/g in Example 1 of the present invention;

FIG. 8 is a rate performance curve of mesoporous carbon nanofibers under different current densities in Example 1 of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1

Put uniformly dispersed fibrous calcium citrate in a tube furnace, under the protection of inert gas, raise the temperature of the furnace to the activation temperature of 700°C at a rate of 5°C/min, keep it warm for 2 hours, and then cool it down to room temperature naturally; The obtained carbonized products were taken out, and templates such as calcium oxide were removed by immersion in 1mol/L dilute hydrochloric acid solution, and washed with deionization several times to neutrality, and the cleaned products were placed in a freeze dryer for drying treatment, and finally obtained Mesoporous carbon nanofibers, and the morphology and structure of the obtained mesoporous carbon nanofibers were tested for physical and chemical properties.

Further, the mesoporous carbon nanofiber is used as the active material for battery assembly. Firstly, the mass ratio of active material: binder: conductive agent is 8:1:1 and mixed evenly, then an appropriate amount of N-methylpyrrolidone is added, and stirred Stirring with a mixer to make a uniform slurry; the slurry is evenly coated on the rough surface of the copper foil, baked under vacuum at 80°C for 24 hours, and then cut into pieces to obtain a Φ14 pole piece, and a lithium piece is used for the counter electrode, in a vacuum glove box Assemble and obtain the button-type lithium battery of model CR2032.

Figure 1 is an SEM image of the mesoporous carbon nanofibers obtained by the method of this embodiment. As shown in the figure, the mesoporous carbon nanofibers are evenly distributed, have a high aspect ratio, and have a fiber diameter of about 10-1000 nm.

Fig. 2 is a TEM image of mesoporous carbon nanofibers obtained by the method of this embodiment. It can be seen from Fig. 2 that the fiber skeleton structure of mesoporous carbon nanofibers contains a large number of pores and channels.

Fig. ₃ is the N adsorption-desorption curve of the mesoporous carbon nanofiber obtained by the method of this embodiment, it can be seen that the curve has an obvious IV type hysteresis loop at a relative pressure of 0.4 to 0.9, indicating that the mesoporous carbon nanofiber has pores Structure and certain adsorption performance; From the pore size distribution diagram, it can be seen that there are a large number of mesoporous structures in mesoporous carbon nanofibers, and the pore size is mainly distributed in the range of 5-20nm; the specific surface area is 1472m ² /g by BET algorithm.

Fig. 4 is the XRD pattern of the mesoporous carbon nanofiber obtained by the method of this embodiment, it can be seen that the mesoporous carbon nanofiber is in an amorphous state, and the weak diffraction peak at 2θ=24° is unique to carbon materials (002 )peak.

Figure 5 is the Raman diagram of the mesoporous carbon nanofibers obtained by the method of this embodiment. It can be seen that the characteristic peaks at the wavenumbers of 1330cm ^-1 and 1580cm ^-1 are the D peak and G peak of the carbon material, respectively.

Figure 6 is the EDS result of the mesoporous carbon nanofibers obtained by the method of this embodiment, as can be seen from Figure 6, there is no other intermediate product, and the carbon content is greater than 92.13at %, indicating that the intermediate process flow has better feasibility .

Fig. 7 is that the mesoporous carbon nanofiber obtained by the method of this embodiment is used as the lithium ion battery negative electrode material, and the current density is 100mA/g cycle performance curve, the first discharge specific capacity is 1025mAh/g, and the first charge specific capacity is 729mAh/g. g, the Coulombic efficiency reaches 71%; after 50 cycles, the specific capacity remains above 600mAh/g, with high specific capacity and cycle stability.

Figure 8 is the rate performance curves at different current densities of the mesoporous carbon nanofibers obtained by the method of this embodiment as the negative electrode material of the lithium ion battery. When the current density is 50mA/g, the discharge specific capacity is 754mAh/g, 100mA/g The discharge specific capacity is 623mAh/g at 200mA/g, 526mAh/g at 200mA/g, 436mAh/g at 500mA/g, and 378mAh/g at 1000mA/g. Good rate characteristics.

Example 2

Put uniformly dispersed fibrous calcium citrate in a tube furnace, under the protection of inert gas, raise the temperature of the furnace to the activation temperature of 800°C at a rate of 5°C/min, keep it warm for 2 hours, and then cool it down to room temperature naturally; The obtained carbonized products were taken out, and templates such as calcium oxide were removed by immersion in 1mol/L dilute hydrochloric acid solution, and washed with deionization several times to neutrality, and the cleaned products were placed in a freeze dryer for drying treatment, and finally obtained Mesoporous carbon nanofibers, and the morphology and structure of the obtained mesoporous carbon nanofibers were tested for physical and chemical properties.

Further, the mesoporous carbon nanofiber is used as the active material for battery assembly. Firstly, the mass ratio of active material: binder: conductive agent is 8:1:1 and mixed evenly, then an appropriate amount of N-methylpyrrolidone is added, and stirred Stirring with a mixer to make a uniform slurry; the slurry is evenly coated on the rough surface of the copper foil, baked under vacuum at 80°C for 24 hours, and then cut into pieces to obtain a Φ14 pole piece, and a lithium piece is used for the counter electrode, in a vacuum glove box Assemble and obtain the button-type lithium battery of model CR2032.

The method of this embodiment is basically the same as that of Embodiment 1, except that the carbonization temperature is set to 800°C. The mesoporous carbon obtained by this method has a specific surface area of 658m ² /g, and at a current density of 100mA/g, the initial discharge specific capacity is 1050mAh/g, and after 50 cycles, the capacity remains at 621mAh/g.

Example 3

Put uniformly dispersed fibrous calcium citrate in a tube furnace, and under the protection of inert gas, raise the temperature of the furnace to the activation temperature of 700°C at a rate of 5°C/min, keep it warm for 4 hours, and then cool it down to room temperature naturally; The obtained carbonized products were taken out, and templates such as calcium oxide were removed by immersion in 1mol/L dilute hydrochloric acid solution, and washed with deionization several times to neutrality, and the cleaned products were placed in a freeze dryer for drying treatment, and finally obtained Mesoporous carbon nanofibers, and the morphology and structure of the obtained mesoporous carbon nanofibers were tested for physical and chemical properties.

Further, the mesoporous carbon nanofiber is used as the active material for battery assembly. Firstly, the mass ratio of active material: binder: conductive agent is 8:1:1 and mixed evenly, then an appropriate amount of N-methylpyrrolidone is added, and stirred Stirring with a mixer to make a uniform slurry; the slurry is evenly coated on the rough surface of the copper foil, baked under vacuum at 80°C for 24 hours, and then cut into pieces to obtain a Φ14 pole piece, and a lithium piece is used for the counter electrode, in a vacuum glove box Assemble and obtain the button-type lithium battery of model CR2032.

The method of this embodiment is basically the same as that of Embodiment 1, except that after high-temperature carbonization, the holding time is set to 4 hours. The mesoporous carbon obtained by this method has a specific surface area of 1596m ² /g, and at a current density of 100mA/g, the initial discharge specific capacity is 1223mAh/g, and after 50 cycles, the capacity remains at 653mAh/g.

Example 4

Put uniformly dispersed fibrous calcium citrate in a tube furnace, and under the protection of an inert gas, raise the temperature of the furnace to the activation temperature of 700°C at a rate of 3°C/min, keep it warm for 2 hours, and then cool it down to room temperature naturally; The obtained carbonized products were taken out, and templates such as calcium oxide were removed by immersion in 1mol/L dilute hydrochloric acid solution, and washed with deionization several times to neutrality, and the cleaned products were placed in a freeze dryer for drying treatment, and finally obtained Mesoporous carbon nanofibers, and the physical and chemical properties of the obtained mesoporous carbon nanofibers were tested for their morphology and structure.

Further, the mesoporous carbon nanofiber is used as the active material for battery assembly. Firstly, the mass ratio of active material: binder: conductive agent is 8:1:1 and mixed evenly, then an appropriate amount of N-methylpyrrolidone is added, and stirred Stirring with a mixer to make a uniform slurry; the slurry is evenly coated on the rough surface of the copper foil, baked under vacuum at 80°C for 24 hours, and then cut into pieces to obtain a Φ14 pole piece, and a lithium piece is used for the counter electrode, in a vacuum glove box Assemble and obtain the button-type lithium battery of model CR2032.

The method of this embodiment is basically the same as that of Embodiment 1, except that the heating rate is set to 3° C./min. The mesoporous carbon obtained by this method has a specific surface area of 1956m ² /g, and at a current density of 100mA/g, the initial discharge specific capacity is 1459mAh/g, and after 50 cycles, the capacity remains at 679mAh/g.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in other related technologies fields, all of which are equally included in the scope of patent protection of the present invention.

Claims (5)

1. a kind of lithium ion battery with mesoporous carbon nano-fiber of high power capacity and preparation method thereof it is characterised in that concrete steps such as Under：

(1) by finely dispersed threadiness calcium citrate be placed in tube furnace, under inert gas shielding, by furnace temperature with 2 ~ 8 DEG C/ The heating rate of min rises to 500 ~ 1000 DEG C of activation temperature, and after insulation 2 ~ 5h, Temperature fall is to room temperature；

(2) and then by the carbonized product of step (1) gained take out, respectively removing template, deionization are embathed by hydrochloric acid solution Clean to neutrality, the product after cleaning is positioned in freeze drier and is dried process, finally obtain mesoporous carbon nano-fiber.

2. a kind of lithium ion battery according to claim 1 mesoporous carbon nano-fiber of high power capacity and preparation method thereof, its It is characterised by：Mesoporous carbon nanofiber diameter described in step (2) is 10 ~ 1000nm.

3. lithium ion battery according to claim 1 mesoporous carbon nano-fiber of high power capacity and preparation method thereof, its feature It is：The inner homogeneous of the mesoporous carbon nano-fiber described in step (2) are distributed with substantial amounts of hole and passage, pore-size distribution 3 ~ 20nm.

4. lithium ion battery according to claim 1 mesoporous carbon nano-fiber of high power capacity and preparation method thereof, its feature It is：Mesoporous carbon nano-fiber specific surface area described in step (2) is 500 ~ 2000m²/g.

5. lithium ion battery according to claim 1 mesoporous carbon nano-fiber of high power capacity and preparation method thereof, its feature It is：Mesoporous carbon nano-fiber described in step (2) is used as lithium ion battery negative material, and first discharge specific capacity is 1000mAh/g ~ 1500mAh/g, after circulating 50 times, specific capacity is maintained at more than 600mAh/g, significantly improves specific capacity and follows Ring stability.