CN103887495A - Lithium vanadium phosphate nanometer material modified by three dimensional porous classification carbon, preparation method and application thereof - Google Patents

Abstract

The invention relates to a preparation method of a Li3V2(PO4)3 (lithium vanadium phosphate) nanometer material modified by three dimensional porous classification carbon, wherein the Li3V2(PO4)3 nanometer material has an obvious porous structure, the sizes of particles are 10-50 micrometers, and each particle is formed by a plurality of small particles of Li3V2(PO4)3, the size of each small particle is 0.2-0.5 micrometer, the surface of each small particle is wrapped by a uniform carbon layer, and the small particles are connected each other by virtue of carbon nanometer particles of which the size is 10-20 nanometer, the carbon nanometer particles form a three dimensional carbon web, so that the small particles are wrapped in the three dimensional carbon web. The preparation method of the lithium vanadium Li3V2(PO4)3 (lithium vanadium phosphate) nanometer material modified by three dimensional porous classification carbon provided by the invention has the beneficial effects that by virtue of a simple and easy solution method combined with a solid state sintering method, the Li3V2(PO4)3 nanometer material modified by three dimensional porous classification carbon is prepared, and when the Li3V2(PO4)3 nanometer material is used as a positive active material of a lithium battery, the Li3V2(PO4)3 nanometer material has the characteristics of high power, good cycling stability and good high-and-low temperature performance; secondly, the invention is simple in technology, strong in feasibility and easy to amplify, meets the characteristic of green chemistry, and facilitates the market extension.

Description

Three-dimensional porous hierarchical carbon-modified lithium vanadium phosphate nanomaterial and its preparation method and application

technical field

The invention belongs to the technical field of nanomaterials and electrochemistry, and in particular relates to a preparation method of a three-dimensional porous hierarchical carbon modified _Li3V2 ( _PO4 ) _{3nanomaterial} , which can _be used as a positive electrode active material of a lithium ion battery.

Background technique

Today, in order to further promote the rapid development of the field of electric vehicles, the study of high-capacity, high-power, high-stability, good temperature adaptability and low-cost lithium-ion batteries based on new nanostructures is the frontier of lithium-ion battery research in the current low-carbon economy era and one of the hotspots. Li ₃ V ₂ (PO4) ₃ has good structural stability, high potential, good thermal stability and high capacity, and is considered to be one of the most potential cathode materials for lithium-ion batteries. Since the monoclinic Li ₃ V ₂ (PO4) ₃ is a sodium fast ion conductor structure (NASICON), it can provide a three-dimensional channel for lithium ion intercalation/extraction, so it has a high lithium ion diffusion coefficient (10 ^-9 ～10 ^-10 cm ² s ^-1 ). However, the low electronic conductivity of Li ₃ V ₂ (PO ₄ ) ₃ ultimately limits its application as a high-power electrode material.

In recent years, researchers have explored many methods to try to solve the shortcomings of the low electronic conductivity of Li ₃ V ₂ (PO ₄ ) ₃ , including carbon coating, nanonization and doping. Among the many strategies, carbon coating is a more economical and convenient method. However, the simple carbon coating of Li ₃ V ₂ (PO ₄ ) ₃ cannot greatly improve the electronic conductivity of electrode materials. The three-dimensional bicontinuous channel carbon framework can provide dual transport channels for electrons and ions, reduce the transport path of ions, and increase the contact area between the electrolyte and the electrode material. However, Li ₃ V ₂ (PO ₄ ) ₃ electrode materials decorated with three-dimensional porous hierarchical carbon have not been reported yet. Therefore, the three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ electrode material has the advantages of large specific surface area, low charge and mass transfer resistance, and significantly improved electronic conductivity. In addition, the carbon network between Li ₃ V ₂ (PO ₄ ) ₃ particles can limit the particle growth and agglomeration of Li ₃ V ₂ (PO ₄ ) ₃ particles during high-temperature calcination, and also act as a buffer layer to effectively prevent The structural destruction of the electrode material due to volume changes when lithium ions are intercalated/extracted effectively improves the cycle stability of the electrode material. At the same time, the three-dimensional bicontinuous carbon framework can significantly increase the diffusion rate of lithium ions in the electrode and reduce its diffusion path, thereby reducing the polarization of lithium-ion batteries at low temperatures, and finally realizing Li ₃ V ₂ (PO ₄ ) ₃ electrode materials In the field of high power, long life and high and low temperature electrode materials, the excellent low temperature makes it a potential application material for lithium ion batteries.

In addition, the solution method used to prepare three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterials is simple and easy, and does not need to add other organic substances, and only needs to change the concentration of reactants to control the shape and size of the material Size, and the prepared material has high yield, high purity and good dispersibility.

Contents of the invention

The technical problem to be solved by the present invention is to provide a three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ /C and its preparation method in view of the above-mentioned prior art. The process is simple, meets the requirements of green chemistry and is easy to scale up On this basis, the three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ also has excellent electrochemical performance.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: three-dimensional porous hierarchical carbon-modified lithium vanadium phosphate nanomaterial, which has obvious porous structure, and the particle size is 10-50 _μm , and the particle size is 0.2-0.5 μm by many Li ₃ V ₂ (PO ₄ ) ₃ small particles, the surface of Li ₃ V ₂ (PO ₄ ) ₃ small particles is covered with a uniform carbon layer, and the Li ₃ V ₂ (PO ₄ ) ₃ /C small particles are composed of The carbon nanoparticles of 10-20nm are connected to each other, and the carbon nanoparticles form a three-dimensional carbon network, so that small Li ₃ V ₂ (PO ₄ ) ₃ particles are wrapped in the three-dimensional carbon network, which is the product obtained by the following method, including: The following steps:

1) Add vanadium source vanadium pentoxide and oxalic acid into distilled water, wherein the molar ratio of V ₂ O ₅ to oxalic acid is 1:5-1:7, stir and dissolve to obtain VOC ₂ O ₄ blue solution;

2) Measure the phosphorus source with a molar ratio of 1:1.5 to the vanadium source, add it to the VOC ₂ O ₄ blue solution obtained in step 1), and stir evenly;

3) Weigh the lithium source with a molar ratio of 1:1.5 to the vanadium source, dissolve it in distilled water, and drop it into the solution obtained in step 2) after dissolving;

4) Weigh glucose as the carbon source, wherein the molar ratio of vanadium source to glucose is 2:0.5-2:1.2, dissolve in distilled water, add dropwise to the solution obtained in step 3), and stir evenly to obtain a precursor solution;

5) Dry the precursor solution in a drying oven to obtain a dark brown solid, grind the solid and place it in a vacuum drying oven at 140-160°C to dry, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined in a nitrogen atmosphere, and the pre-calcined product was slightly ground and then calcined to finally obtain a black three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial.

The preparation method of the described three-dimensional porous hierarchical carbon-modified lithium vanadium phosphate nanomaterial comprises the following steps:

1) Add vanadium source vanadium pentoxide and oxalic acid into distilled water, wherein the molar ratio of V ₂ O ₅ to oxalic acid is 1:5-1:7, stir and dissolve to obtain VOC ₂ O ₄ blue solution;

2) Measure the phosphorus source with a molar ratio of 1:1.5 to the vanadium source, add it to the VOC ₂ O ₄ blue solution obtained in step 1), and stir evenly;

3) Weigh the lithium source with a molar ratio of 1:1.5 to the vanadium source, dissolve it in distilled water, and drop it into the solution obtained in step 2) after dissolving;

4) Weigh glucose as the carbon source, wherein the molar ratio of vanadium source to glucose is 2:0.5-2:1.2, dissolve in distilled water, add dropwise to the solution obtained in step 3), and stir evenly to obtain a precursor solution;

5) Dry the precursor solution in a drying oven to obtain a dark brown solid, grind the solid and place it in a vacuum drying oven at 140-160°C to dry, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined in a nitrogen atmosphere, and the pre-calcined product was slightly ground and then calcined to finally obtain a black three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial.

According to the above scheme, the phosphorus source in step 2) is any one of H ₃ PO ₄ and NH ₄ H ₂ PO ₄ or a mixture thereof.

According to the above scheme, the lithium source in step 3) is any one of LiAc, Li ₂ CO ₃ , LiNO ₃ and LiCl or a mixture thereof.

According to the above scheme, the pre-calcination temperature in step 6) is 350° C. for 5 hours, and the calcination temperature is 750-850° C. for 8 hours.

The application of the three-dimensional porous hierarchical carbon-modified lithium vanadium phosphate nanometer material as a positive electrode active material of a lithium ion battery.

The beneficial effects of the present invention are: the present invention mainly prepares a three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanometer material through a simple and easy solution method combined with a solid-phase sintering method, which is active as the positive electrode of a lithium-ion battery When used as a material, it shows the characteristics of high power, good cycle stability, and good high and low temperature performance; secondly, the process of the present invention is simple, and the precursor solution can be obtained by simple and easy stirring, and the solution is dried and solidified under an inert atmosphere. After sintering, a three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanometer material can be obtained. The method is highly feasible, easy to scale up, conforms to the characteristics of green chemistry, and is conducive to market promotion.

Description of drawings

Figure 1 is the XRD pattern of the three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial of Example 1 of the present invention;

Fig. 2 is the Raman diagram of the three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial in Example 1 of the present invention;

3 is an SEM image of the three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial of Example 1 of the present invention;

4 is a TEM image of the three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial of Example 1 of the present invention;

Fig. 5 is a normal temperature battery cycle performance graph of the three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial in Example 1 of the present invention;

Fig. 6 is a high-temperature battery cycle performance graph of the three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial in Example 1 of the present invention;

Fig. 7 is a diagram of the temperature-variable battery cycle performance of the three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial in Example 1 of the present invention.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Example 1:

A method for preparing a three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanometer material, comprising the following steps:

1) Add 0.637g vanadium pentoxide (V ₂ O ₅ ) and 2.646g oxalic acid (C ₂ H ₂ O ₄ ) into 20mL distilled water (the molar ratio of V ₂ O ₅ to oxalic acid is 1:6), at 80℃ Mix and stir for 10 minutes to obtain VOC ₂ O ₄ blue solution;

2) Measure 85% phosphoric acid (H ₃ PO ₄ ) solution (0.716mL) with a molar ratio of 1:1.5 to the vanadium source, drop phosphoric acid into the blue solution obtained in step 1), and stir evenly;

3) Weigh 1.125g of lithium acetate dihydrate (LiAc, the actual amount of lithium source is 1.05 times the required reaction amount) powder, dissolve it in 5mL of distilled water, and drop it into the blue solution obtained in step 2);

4) Weigh 0.5g of glucose (C ₆ H ₁₂ O ₆ ) powder (the molar ratio of vanadium source to glucose is 2:0.79), dissolve it in 5mL of distilled water, add it dropwise to the solution obtained in step 3), and stir for 5h. Obtain the precursor blue solution;

5) Dry the precursor solution in a 120°C drying oven to obtain a dark brown solid, grind the solid and dry it in a 140°C vacuum oven for 8 hours, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined at 350°C for 5 hours under a nitrogen atmosphere, and the pre-fired product was slightly ground and then calcined at 800°C for 8 hours to obtain a black three-dimensional porous dual-channel continuous Li ₃ V ₂ (PO ₄ ) ₃ nanomaterials.

Taking the three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanomaterial of the present invention as an example, its structure is determined by X-ray diffractometer and Raman spectrometer. As shown in Figure 1, the X-ray diffraction pattern (XRD) shows that the three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ phase and Li ₃ V ₂ (PO ₄ ) with card number 01-072-7074 ₃ The standard sample is completely consistent, the sample is a monoclinic structure, the space group is P2 ₁ /n, and there is no impurity peak and C peak. Although the _ID / _IG of the Raman spectrum (Fig. 2) is 0.98, it indicates that the carbon contained in the sample has a high degree of graphitization, but because the graphitized carbon is not a long-range ordered structure, but is dispersed in the amorphous Carbon, so XRD cannot detect the peak of crystallized graphite.

SEM images (Fig. 3) and TEM images (Fig. 4) show that the prepared Li ₃ V ₂ (PO ₄ ) ₃ /C has a three-dimensional porous hierarchical structure. The size of individual Li ₃ V ₂ (PO ₄ ) ₃ /C particles is 0.2-0.5 μm, and the surface of the small particles is covered with a uniform layer of carbon. micron particles. There are obvious gaps between the particles, and many carbon particles fill the gaps, connecting the dispersed Li ₃ V ₂ (PO ₄ ) ₃ /C small particles.

The three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ prepared by the invention is used as the positive electrode active material of the lithium ion battery, and the remaining steps of the lithium ion battery preparation method are the same as the usual preparation method. The preparation method of the positive electrode sheet is as follows, using three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ as the active material, acetylene black as the conductive agent, polytetrafluoroethylene as the binder, the active material, acetylene black, polytetrafluoroethylene The mass ratio of ethylene is 70:20:10; after fully mixing them in proportion, add a small amount of isopropanol, grind evenly, and press the electrode sheet with a thickness of about 0.5mm on the roller machine; the pressed positive electrode sheet is placed at 80°C Dry in the oven for 24 hours before use. 1M LiPF ₆ was dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC) as electrolyte, lithium sheet was used as negative electrode, Celgard2325 was used as separator, and CR2025 stainless steel was used as battery case to assemble a button-type lithium-ion battery.

Taking the three-dimensional porous hierarchical carbon modified Li ₃ V ₂ (PO ₄ ) ₃ obtained in this example as an example, as shown in Figure 5a, at current densities of 1C, 5C, 20C and 30C, the three-dimensional porous hierarchical carbon modified Li ₃ V The initial discharge specific capacity of ₂ (PO ₄ ) ₃ can reach 126, 124, 122 and 121mAh/g, respectively. The rate performance of the material is excellent (Figure 5b). After charging and discharging at different current densities from 0.5C to 20C, the discharge capacity of the material at a current density of 30C can still reach 118.2mAh/g. After experiencing the above rapid charge and discharge, the capacity of the material at 1C current density can be recovered to 120.5mAh/g, indicating that the material has good structural stability. In addition, the cycle stability of the material is also very prominent (Figure 5c). At a current density of 20C, the specific capacity of the material after 4000 cycles is still 94mAh/g, and the sub-capacity decay rate is only 0.0065%. At the same time, we also characterized the performance of the samples under high and low temperature conditions. Under the test condition of 60°C (Figure 6), the discharge specific capacities of the samples at 5C and 20C current densities were 132.1 and 130.1mAh/g, respectively. After 1000 cycles, the capacity retention rate of the material at 20C current density is 85%, which shows that the structure of the material is very stable at high temperature. After lowering the test temperature to -20°C, the first discharge specific capacity of the material can still reach 106.2mAh/g (Figure 7, 1C charge/5C discharge), and the capacity retention rate can still reach 87.6% after 450 cycles. Subsequently, the test temperature was set at 25°C, and the discharge specific capacity of the material could rapidly increase to 117.3mAh/g (5C charge/5C discharge). When the temperature increased to 60°C, the specific capacity of the sample further increased to 125.1mAh/g. Even after being tested at different temperatures from -20°C to 60°C, when the temperature returns to room temperature, the discharge specific capacity of the material can still reach 108.3mAh/g. The above properties indicate that the three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ has excellent electrochemical performance and is a potential cathode material for lithium-ion batteries.

Example 2:

A method for preparing a three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanometer material, comprising the following steps:

1) Add 0.637g vanadium pentoxide (V ₂ O ₅ ) and 2.205g oxalic acid (C ₂ H ₂ O ₄ ) into 20mL distilled water (the molar ratio of V ₂ O ₅ to oxalic acid is 1:5), at 80℃ Mix and stir for 10 minutes to obtain VOC ₂ O ₄ blue solution;

2) Measure 1.209g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) powder with a molar ratio of 1:1.5 to the vanadium source, dissolve it in distilled water and drop it into the blue solution obtained in step 1) , stir evenly;

3) Weigh 0.406g of lithium carbonate (Li ₂ CO ₃ , the actual amount of lithium source is 1.05 times the required reaction amount) powder, dissolve it in 5mL of distilled water, and drop it into the blue solution obtained in step 2);

4) Weigh 0.631g of glucose (C ₆ H ₁₂ O ₆ ) powder (the molar ratio of vanadium source to glucose is 2:1), dissolve it in 5mL of distilled water, add it dropwise to the solution obtained in step 3), and stir for 5h. Obtain the precursor blue solution;

5) Dry the precursor solution in a 120°C drying oven to obtain a dark brown solid, grind the solid and dry it in a 140°C vacuum oven for 8 hours, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined at 350°C for 5 hours under a nitrogen atmosphere, and the pre-fired product was slightly ground and then calcined at 750°C for 8 hours to obtain a black three-dimensional porous dual-channel continuous Li ₃ V ₂ (PO ₄ ) ₃ nanomaterials.

Taking the Li ₃ V ₂ (PO ₄ ) ₃ /C obtained in this example as an example, at a current density of 5C, the initial discharge specific capacity of Li ₃ V ₂ (PO ₄ ) ₃ /C can reach 116mAh/g, 300 The discharge specific capacity after the second cycle is 106.2mAh/g, and the capacity retention rate is 91.5%.

Example 3:

A method for preparing a three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanometer material, comprising the following steps:

1) Add 0.637g of vanadium pentoxide (V ₂ O ₅ ) and 3.087g of oxalic acid (C ₂ H ₂ O ₄ ) into 20mL of distilled water (the molar ratio of V ₂ O ₅ to oxalic acid is 1:7), at 80℃ Mix and stir for 10 minutes to obtain VOC ₂ O ₄ blue solution;

2) Measure 85% phosphoric acid (H ₃ PO ₄ ) solution (0.716mL) with a molar ratio of 1:1.5 to the vanadium source, drop phosphoric acid into the blue solution obtained in step 1), and stir evenly;

3) Weigh 0.406g of lithium carbonate (Li ₂ CO ₃ , the actual amount of lithium source is 1.05 times the required reaction amount) powder, dissolve it in 5mL of distilled water, and drop it into the blue solution obtained in step 2);

4) Weigh 0.315g of glucose (C ₆ H ₁₂ O ₆ ) powder (the molar ratio of vanadium source to glucose is 2:0.5), dissolve it in 5mL of distilled water, add it dropwise to the solution obtained in step 3), and stir for 5h. Obtain the precursor blue solution;

5) Dry the precursor solution in a 120°C drying oven to obtain a dark brown solid, grind the solid and dry it in a 160°C vacuum oven for 8 hours, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined at 350°C under a nitrogen atmosphere for 5 hours, the pre-fired product was slightly ground and then calcined at 850°C for 8 hours, and finally a black three-dimensional porous dual-channel continuous Li ₃ V ₂ (PO ₄ ) ₃ was obtained nanomaterials.

Taking the Li ₃ V ₂ (PO ₄ ) ₃ /C obtained in this example as an example, at a current density of 5C, the initial discharge specific capacity of Li ₃ V ₂ (PO ₄ ) ₃ /C can reach 117.3mAh/g, respectively. After 300 cycles, the discharge specific capacity is 103.3mAh/g, and the capacity retention rate is 88%.

Example 4:

A method for preparing a three-dimensional porous hierarchical carbon-modified Li ₃ V ₂ (PO ₄ ) ₃ nanometer material, comprising the following steps:

1) Add 0.637g vanadium pentoxide (V ₂ O ₅ ) and 2.205g oxalic acid (C ₂ H ₂ O ₄ ) into 20mL distilled water (the molar ratio of V ₂ O ₅ to oxalic acid is 1:5), at 80℃ Mix and stir for 10 minutes to obtain VOC ₂ O ₄ blue solution;

2) Measure 85% phosphoric acid (H ₃ PO ₄ ) solution (0.716mL) with a molar ratio of 1:1.5 to the vanadium source, drop phosphoric acid into the blue solution obtained in step 1), and stir evenly;

3) Weigh 0.466g of lithium chloride (LiCl, the actual amount of lithium source is 1.05 times the required reaction amount) powder, dissolve it in 5mL of distilled water, and drop it into the blue solution obtained in step 2);

4) Weigh 0.757g of glucose (C ₆ H ₁₂ O ₆ ) powder (the molar ratio of vanadium source to glucose is 2:1.2), dissolve it in 5mL of distilled water, add it dropwise to the solution obtained in step 3), and stir for 5h. Obtain the precursor blue solution;

5) Dry the precursor solution in a 120°C drying oven to obtain a dark brown solid, grind the solid and dry it in a 140°C vacuum oven for 8 hours, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined at 350°C for 5 hours under a nitrogen atmosphere, and the pre-fired product was slightly ground and then calcined at 800°C for 8 hours to obtain a black three-dimensional porous dual-channel continuous Li ₃ V ₂ (PO ₄ ) ₃ nanomaterials.

Taking the Li ₃ V ₂ (PO ₄ ) ₃ /C obtained in this example as an example, at a current density of 5C, the initial discharge specific capacity of Li ₃ V ₂ (PO ₄ ) ₃ /C can reach 117.5mAh/g, respectively. After 300 cycles, the discharge specific capacity is 110.3mAh/g, and the capacity retention rate is 93.9%.

Example 5:

The preparation method of three-dimensional double continuous channel Li ₃ V ₂ (PO ₄ ) ₃ nanometer material, it comprises the following steps:

1) Add 0.637g of vanadium pentoxide (V ₂ O ₅ ) and 3.087g of oxalic acid (C ₂ H ₂ O ₄ ) into 20mL of distilled water (the molar ratio of V ₂ O ₅ to oxalic acid is 1:7), at 80℃ Mix and stir for 10 minutes to obtain VOC ₂ O ₄ blue solution;

2) Measure 1.209g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) powder with a molar ratio of 1:1.5 to the vanadium source, dissolve it in distilled water and drop it into the blue solution obtained in step 1) , stir evenly;

3) Weigh 1.125g of lithium acetate dihydrate (LiAc, the actual amount of lithium source is 1.05 times the required reaction amount) powder, dissolve it in 5mL of distilled water, and drop it into the blue solution obtained in step 2);

4) Weigh 0.442g of glucose (C ₆ H ₁₂ O ₆ ) powder (the molar ratio of vanadium source to glucose is 2:0.7), dissolve it in 5mL distilled water, add it dropwise to the solution obtained in step 3), and stir for 5h. Obtain the precursor blue solution;

5) Dry the precursor solution in a 120°C drying oven to obtain a dark brown solid, grind the solid and dry it in a 140°C vacuum oven for 8 hours, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined at 350°C for 5 hours under a nitrogen atmosphere, and the pre-fired product was slightly ground and then calcined at 800°C for 8 hours to obtain a black three-dimensional porous dual-channel continuous Li ₃ V ₂ (PO ₄ ) ₃ nanomaterials.

Taking Li ₃ V ₂ (PO ₄ ) ₃ /C obtained in this example as an example, at a current density of 5C, the initial discharge specific capacity of Li ₃ V ₂ (PO ₄ ) ₃ /C can reach 118.1mAh/g, respectively. After 300 cycles, the discharge specific capacity is 105.9mAh/g, and the capacity retention rate is 89.7%.

Embodiment 6:

The preparation method of three-dimensional double continuous channel Li ₃ V ₂ (PO ₄ ) ₃ nanometer material, it comprises the following steps:

1) Add 0.637g vanadium pentoxide (V ₂ O ₅ ) and 2.646g oxalic acid (C ₂ H ₂ O ₄ ) into 20mL distilled water (the molar ratio of V ₂ O ₅ to oxalic acid is 1:6), at 80℃ Mix and stir for 10 minutes to obtain VOC ₂ O ₄ blue solution;

2) Measure 85% phosphoric acid (H ₃ PO ₄ ) solution (0.716mL) with a molar ratio of 1:1.5 to the vanadium source, drop phosphoric acid into the blue solution obtained in step 1), and stir evenly;

3) Weigh 0.406g of lithium carbonate (Li ₂ CO ₃ , the actual amount of lithium source is 1.05 times the required reaction amount) powder, dissolve it in 5mL of distilled water, and drop it into the blue solution obtained in step 2);

4) Weigh 0.757g of glucose (C ₆ H ₁₂ O ₆ ) powder (the molar ratio of vanadium source to glucose is 2:1.2), dissolve it in 5mL of distilled water, add it dropwise to the solution obtained in step 3), and stir for 5h. Obtain the precursor blue solution;

5) Dry the precursor solution in a 120°C drying oven to obtain a dark brown solid, grind the solid and dry it in a 140°C vacuum oven for 8 hours, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined at 350°C for 5 hours under a nitrogen atmosphere, and the pre-fired product was slightly ground and then calcined at 800°C for 8 hours to obtain a black three-dimensional porous dual-channel continuous Li ₃ V ₂ (PO ₄ ) ₃ nanomaterials.

Taking the Li ₃ V ₂ (PO ₄ ) ₃ /C obtained in this example as an example, at a current density of 5C, the initial discharge specific capacity of Li ₃ V ₂ (PO ₄ ) ₃ /C can reach 122mAh/g, 300 After one cycle, the discharge specific capacity is 115mAh/g, and the capacity retention rate is 94.3%.

Embodiment 7:

The preparation method of three-dimensional double continuous channel Li ₃ V ₂ (PO ₄ ) ₃ nanometer material, it comprises the following steps:

1) Add 0.637g vanadium pentoxide (V ₂ O ₅ ) and 2.646g oxalic acid (C ₂ H ₂ O ₄ ) into 20mL distilled water (the molar ratio of V ₂ O ₅ to oxalic acid is 1:6), at 80℃ Mix and stir for 10 minutes to obtain VOC ₂ O ₄ blue solution;

2) Measure 85% phosphoric acid (H ₃ PO ₄ ) solution (0.716mL) with a molar ratio of 1:1.5 to the vanadium source, drop phosphoric acid into the blue solution obtained in step 1), and stir evenly;

3) Weigh 0.758g of lithium nitrate (LiNO ₃ , the actual amount of lithium source is 1.05 times the required reaction amount) powder, dissolve it in 5mL of distilled water, and drop it into the blue solution obtained in step 2);

4) Weigh 0.442g of glucose (C ₆ H ₁₂ O ₆ ) powder (the molar ratio of vanadium source to glucose is 2:0.7), dissolve it in 5mL distilled water, add it dropwise to the solution obtained in step 3), and stir for 5h. Obtain the precursor blue solution;

5) Dry the precursor solution in a 120°C drying oven to obtain a dark brown solid, grind the solid and dry it in a 140°C vacuum oven for 8 hours, and finally obtain the precursor powder;

6) The precursor powder was pre-calcined at 350°C for 5 hours under a nitrogen atmosphere, and the pre-fired product was slightly ground and then calcined at 750°C for 8 hours to obtain a black three-dimensional porous dual-channel continuous Li ₃ V ₂ (PO ₄ ) ₃ nanomaterials.

Taking Li ₃ V ₂ (PO ₄ ) ₃ /C obtained in this example as an example, at a current density of 5C, the first discharge specific capacity of Li ₃ V ₂ (PO ₄ ) ₃ /C can reach 120mAh/g, 300 After the first cycle, the discharge specific capacity is 111mAh/g, and the capacity retention rate is 92.5%.

Claims (9)

1. three-dimensional porous classification carbon is modified phosphoric acid vanadium lithium nano material, and it has obvious loose structure, and granular size is 10-50 μ m, and particle is the Li of 0.2-0.5 μ m by many sizes ₃v ₂(PO ₄) ₃granule composition, Li ₃v ₂(PO ₄) ₃granule surface is all surrounded by uniform carbon-coating, Li ₃v ₂(PO ₄) ₃between/C granule, interconnected by the carbon nano-particle of 10-20nm, this carbon nano-particle has formed three-dimensional carbon net, thereby by Li ₃v ₂(PO ₄) ₃granule is wrapped in three-dimensional carbon net, and it is following method products therefrom, includes following steps:

1) vanadium source vanadic oxide and oxalic acid are joined in distilled water to wherein V ₂o ₅with the mol ratio of oxalic acid be 1:5-1:7, stirring and dissolving, obtains VOC ₂o ₄blue solution;

2) the phosphorus source that to measure with vanadium source mol ratio be 1:1.5, is joined the VOC of step 1) gained ₂o ₄in blue solution, stir;

3) the lithium source that to take with vanadium source mol ratio be 1:1.5, is dissolved in distilled water, splashes into step 2 after dissolving) in gained solution;

4) take glucose as carbon source, wherein the mol ratio of vanadium source and glucose is 2:0.5-2:1.2, is dissolved in distilled water, dropwise joins in step 3) gained solution, stirs, and obtains precursor solution;

5) precursor solution is dried at drying box, obtain pitchy solid, solid abrasive is placed in 140-160 DEG C of vacuum drying chamber and is dried, finally obtain precursor powder;

6) by precursor powder pre-burning under nitrogen atmosphere, after being ground a little, calcines again pre-burning product, and finally obtain the three-dimensional porous classification carbon of black and modify Li ₃v ₂(PO ₄) ₃nano material.

2. three-dimensional porous classification carbon as claimed in claim 1 is modified phosphoric acid vanadium lithium nano material, it is characterized in that step 2) described phosphorus source is H ₃pO ₄and NH ₄h ₂pO ₄in the mixing of any one or they.

3. three-dimensional porous classification carbon as claimed in claim 1 is modified phosphoric acid vanadium lithium nano material, it is characterized in that, the lithium source described in step 3) is LiAc, Li ₂cO ₃, LiNO ₃mixing with any one or they in LiCl.

4. three-dimensional porous classification carbon as claimed in claim 1 is modified phosphoric acid vanadium lithium nano material, it is characterized in that, the calcined temperature described in step 6) is 350 DEG C, and the time is 5 hours, and calcining heat is 750-850 DEG C, and the time is 8 hours.

5. three-dimensional porous classification carbon claimed in claim 1 is modified the preparation method of phosphoric acid vanadium lithium nano material, includes following steps:

1) vanadium source vanadic oxide and oxalic acid are joined in distilled water to wherein V ₂o ₅with the mol ratio of oxalic acid be 1:5-1:7, stirring and dissolving, obtains VOC ₂o ₄blue solution;

2) the phosphorus source that to measure with vanadium source mol ratio be 1:1.5, is joined the VOC of step 1) gained ₂o ₄in blue solution, stir;

3) the lithium source that to take with vanadium source mol ratio be 1:1.5, is dissolved in distilled water, splashes into step 2 after dissolving) in gained solution;

4) take glucose as carbon source, wherein the mol ratio of vanadium source and glucose is 2:0.5-2:1.2, is dissolved in distilled water, dropwise joins in step 3) gained solution, stirs, and obtains precursor solution;

5) precursor solution is dried at drying box, obtain pitchy solid, solid abrasive is placed in 140-160 DEG C of vacuum drying chamber and is dried, finally obtain precursor powder;

6) by precursor powder pre-burning under nitrogen atmosphere, after being ground a little, calcines again pre-burning product, and finally obtain the three-dimensional porous classification carbon of black and modify Li ₃v ₂(PO ₄) ₃nano material.

6. three-dimensional porous classification carbon as claimed in claim 5 is modified phosphoric acid vanadium lithium nano material, it is characterized in that step 2) described phosphorus source is H ₃pO ₄and NH ₄h ₂pO ₄in the mixing of any one or they.

7. three-dimensional porous classification carbon as claimed in claim 5 is modified the preparation method of phosphoric acid vanadium lithium nano material, it is characterized in that, the lithium source described in step 3) is LiAc, Li ₂cO ₃, LiNO ₃mixing with any one or they in LiCl.

8. three-dimensional porous classification carbon as claimed in claim 5 is modified the preparation method of phosphoric acid vanadium lithium nano material, it is characterized in that, the calcined temperature described in step 6) is 350 DEG C, and the time is 5 hours, and calcining heat is 750-850 DEG C, and the time is 8 hours.

9. three-dimensional porous classification carbon claimed in claim 1 is modified the application of phosphoric acid vanadium lithium nano material as anode active material of lithium ion battery.

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