CN107369827B - Preparation method of lithium vanadium phosphate/carbon composite positive electrode material with flower-like structure - Google Patents
Preparation method of lithium vanadium phosphate/carbon composite positive electrode material with flower-like structure Download PDFInfo
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Abstract
The invention particularly relates to a preparation method of a lithium vanadium phosphate/carbon composite anode material with a flower-like structure, which comprises the steps of adding a soluble lithium compound, a vanadium compound, phosphate and citric acid into deionized water according to a proper proportion to prepare a solution, then adding a proper amount of sodium citrate, fully stirring to form a transparent solution, placing a substrate with a vanadium compound on the surface into the transparent solution, dipping for a plurality of days, taking out and drying, then calcining the substrate at 500-1000 ℃ in a protective atmosphere for a period of time, taking out and cooling, repeating the steps for a plurality of times on the calcined substrate, wherein the same transparent solution needs to be prepared again for each dipping, and sequentially carrying out low-temperature carbonization treatment and high-temperature synthesis on the finally obtained substrate under the protective atmosphere to obtain the flower-like lithium vanadium phosphate/carbon composite anode material. The lithium vanadium phosphate anode material disclosed by the invention has the advantages of high specific capacity, good cycle performance, good rate performance and the like, and integrates the advantages of low cost, environmental friendliness and the like.
Description
Technical Field
The invention belongs to the technical field of battery anode composite materials, and particularly relates to a preparation method of a lithium vanadium phosphate/carbon composite anode material with a flower-shaped structure.
Background
As a novel green storage battery, the lithium ion battery has the advantages of high working voltage, light weight, large specific energy, small self-discharge rate,The battery has the advantages of long cycle life, no memory effect, no environmental pollution and the like, and gradually replaces the traditional secondary battery to become an ideal power supply for small and light electronic devices such as cameras, mobile phones, notebook computers, portable measuring instruments and the like and environment-friendly electric automobiles. The development of the lithium ion power battery industry is promoted, a huge green industry cluster can be driven to grow up rapidly, and the method has great strategic significance and pulling effect on national economy. Meanwhile, the lithium ion power battery belongs to the field of energy conservation and new energy, and meets the development requirements of national policies. For a long time, the united states supports a number of national laboratories and enterprises to undertake the development work of automotive lithium ion batteries together. The european union has made a development plan of high specific energy storage batteries and has continuously produced stage results. Since japan has been the leading country in lithium ion power battery technology and since the successful development and marketing of lithium ion batteries in japan in 1990, a hot line of research on lithium ion batteries has been developed at home and abroad due to their unique properties. The lithium ion battery is a high-energy secondary battery which is developed very rapidly and has very wide application prospect in the current rechargeable battery. In the lithium ion battery, the amount of the cathode material used is large, which increases the production cost of the lithium ion battery. Currently, substances used as positive electrode materials for lithium ion batteries are mainly lithium-containing transition metal oxides, including layered-structured LiMO (M = Co, Ni, Mn) and spinel-type LiMn2O4. However, these materials are due to price (LiCoO)2) Safety (LiNiO)2) High temperature electrochemical performance (LiMn)2O4) And the like, so that they are subjected to many restrictions in the application of high-capacity batteries. Therefore, the search for new cathode materials with low cost and excellent performance is the focus of research on lithium ion batteries.
Since Goodenough and the like put forward a polyanionic lithium battery anode material lithium iron phosphate for the first time, researchers have developed a great deal of research on polyanionic phosphates, wherein the most successful is to realize the industrial production of the polyanionic lithium iron phosphate anode material, but people have not reported many research on lithium vanadium phosphate, and the industrial production is still not realized at present. However, lithium vanadium phosphate is a material with better performance than lithium iron phosphate, and has the following advantages: a. the lithium iron phosphate has excellent thermal stability, and is only slightly lower than lithium iron phosphate in the currently researched anode material; b. the lithium ion battery has high discharge voltage and a plurality of discharge voltage platforms, the average discharge voltage is 4.1V, which is higher than the 3.4V discharge voltage of lithium iron phosphate, and 3.5V, 3.6V, 4.1V and 4.6V 4 discharge platforms are arranged; c. excellent cycling stability and high discharge capacity, and the theoretical capacity is 197 mAh/g and is higher than that of 170 mAh/g of lithium iron phosphate. It can be seen that the research space for lithium vanadium phosphate is large.
At present, there are various methods for synthesizing lithium vanadium phosphate/carbon composite materials, and the common methods include: high temperature solid phase method, sol-gel method, microwave method, hydrothermal method. However, the high-temperature solid phase method is complicated to operate and high in cost, and the obtained material particles are large and uneven and are easy to generate impurities; although the microwave method has low energy consumption, the heating time and temperature are not easy to control, and the product performance is influenced; the concentration of a hydrothermal method is not easy to control, and the product performance is influenced; the lithium vanadium phosphate prepared by the existing sol-gel method has larger particles, and influences the charge capacity and the cycle performance of the product. Meanwhile, from the research, the particle morphology has great influence on the performance of the lithium vanadium phosphate material, and the lithium vanadium phosphate material with uniform and porous particles has larger specific surface area and can improve the electrochemical performance.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art and provide the Li with the advantages of simplicity, environmental protection, stable structure, good cycle performance and low production cost3V2（PO3）4A preparation method of a/C composite positive electrode material.
The invention also provides a lithium vanadium phosphate/carbon composite cathode material with a flower-like structure.
The purpose of the invention is realized by the following technical scheme:
in particular to a preparation method of a lithium vanadium phosphate/carbon composite anode material with a flower-shaped structure, which comprises the following steps:
s1, mixing soluble lithium compounds, vanadium compounds and phosphates according to a proper proportion, putting the mixture into deionized water, adding a proper amount of citric acid, and stirring at a certain temperature to form a clear and transparent mixed solution;
s2, horizontally placing the substrate with the vanadium compound attached to the surface into the transparent mixed solution obtained in the step S1 for soaking for several days, taking out the soaked substrate for drying, then carrying out high-temperature calcination for a period of time in a protective atmosphere, and then taking out and cooling;
s3, repeating the steps S1 and S2 for a plurality of times by taking the calcined and cooled substrate as an object;
and S4, sequentially carrying out low-temperature carbonization treatment and high-temperature synthesis treatment on the matrix obtained in the step S3 in a protective atmosphere to obtain the lithium vanadium phosphate/carbon composite cathode material with the flower-like structure.
The invention creatively puts the matrix with the vanadium compound attached to the surface into the mixed solution containing lithium ions, vanadium ions, phosphorus ions and citric acid to be soaked for several days, the vanadium compound attached to the surface of the matrix can be used as a seed crystal, so that lithium vanadium phosphate/carbon grows and grows around the seed until a composite material with excellent performance is formed, and the formed Li3V2（PO3）4the/C composite material has excellent performance, and the preparation method has the advantages of simple process, easy operation and lower cost.
Preferably, the soluble lithium compound, the soluble vanadium compound and the soluble phosphate in the step S1 are mixed according to the atomic ratio of lithium, vanadium and phosphorus of 3:2:3, the mass fraction of the added citric acid is 2-20%, and the mixture is stirred for 0.5-2 hours at the temperature of 30-70 ℃.
Preferably, the substrate in step S2 is a metal-based material or a carbon-based material, such as: stainless steel, titanium plates, copper plates, carbonized oroxylum seeds and carbonized rush.
Preferably, the number of days for soaking the substrate with the vanadium pentoxide on the surface in the transparent mixed solution in the step S2 is 5-15 days; the high-temperature calcination is carried out in a tubular furnace, the temperature is 500-1000 ℃, the calcination time is 2-6 hours, and the protective atmosphere is one of nitrogen, argon, helium and carbon dioxide.
Preferably, the repetition frequency in the step S3 is 2-7 times.
Preferably, in step S4, the specific parameters of the low-temperature carbonization treatment are: carbonizing at the temperature of 200-400 ℃ for 2-8 h, preferably at the temperature of 350 ℃ for 5 h; the specific parameters of the high-temperature synthesis treatment are as follows: the high-temperature synthesis is carried out at 600-850 ℃ for 3-15 h, preferably at 750 ℃ for 10 h.
Preferably, the method for preparing the substrate with the vanadium compound attached to the surface comprises the following steps: mixing a proper amount of vanadium compound and pure water to form solution or suspension, uniformly spraying the solution or suspension on the surface of a matrix in a spraying mode, then drying the matrix sprayed with the vanadium compound solution in vacuum, putting the matrix into a tubular furnace, and calcining the matrix in an inert atmosphere at a certain temperature for a certain time.
Further preferably, the vanadium compound on the substrate is V2O5、NH4VO3、V2O3The concentration of the vanadium compound prepared into an aqueous solution or a suspension is 0.01-0.1 mmol/ml; the vacuum drying operation is to place the matrix in a vacuum drying oven at the temperature of 80-120 ℃ for drying for 1-5 hours; the calcining temperature in the tubular furnace is 300-600 ℃, the calcining time is 1-8 hours, and the inert gas is one of nitrogen, argon, helium and carbon dioxide.
The lithium vanadium phosphate/carbon composite cathode material is prepared according to the preparation method of the composite cathode material.
Preferably, the lithium vanadium phosphate/carbon composite positive electrode material is in a flower-like spherical structure, the diameter of the flower-like spherical structure is 30-50 μm, and the petal spacing is 5-15 μm.
Compared with the prior art, the invention has the advantages that:
(1) flower-like structured Li synthesized by the invention3V2（PO3）4the/C composite anode material has the characteristic of multi-pore channel, and the structure can allow the electrolyte to enter easily, so that the electrolyte and Li are increased3V2（PO3）4The contact area of the/C composite material greatly shortens the transmission path of lithium ions and improves the transmission efficiency of the lithium ions, thereby obtaining good electrochemical performance. Such Li3V2（PO3）4When the/C composite material is charged and discharged at 5C multiplying power, the first charging and discharging specific capacity at room temperature can reach 163mAh/g to the maximum, and after 50 cycles, the capacity retention rate can reach 95.3% to the maximum.
(2) When the matrix with the vanadium compound on the surface is prepared, the vanadium compound is creatively prepared into the aqueous solution, the aqueous solution of the vanadium compound is uniformly sprayed on the specific surface by a spraying method, the vanadium compound on the surface of the matrix is the seed crystal, when the matrix is immersed in the mixed solution, the existence of the seed crystal is beneficial to the formation of the lithium vanadium phosphate crystal, and the formed particles are uniformly distributed on the matrix, so that the formed Li is formed3V2（PO3）4The performance of the/C composite material is more excellent.
(3) The lithium vanadium phosphate/carbon cathode composite material disclosed by the invention has the advantages of high specific capacity, good cycle performance, good rate performance and the like, and integrates the advantages of low cost, environmental friendliness and the like. Meanwhile, the preparation method of the lithium vanadium phosphate/carbon cathode composite material has the advantages of simple process, easy operation and lower cost, and the Li with excellent performance is obtained3V2（PO3）4the/C composite cathode material provides an effective way.
Drawings
FIG. 1 is Li having a flower-like structure in example 13V2（PO3）4XRD diffraction pattern of the/C composite positive electrode material.
FIG. 2 is Li having a flower-like structure in example 43V2（PO3）4SEM image of 3000 times magnification of/C composite cathode material.
Detailed Description
The invention is further illustrated by the following specific examples. The following examples are illustrative only and are not to be construed as unduly limiting the invention which may be embodied in many different forms as defined and covered by the summary of the invention. Reagents, compounds and apparatus employed in the present invention are conventional in the art unless otherwise indicated.
Example 1
Having a surface V2O5Preparation of the matrix of (1): will V2O5Dissolving in pure water to prepare 0.1mmol/ml V2O5The aqueous solution is uniformly sprayed on a stainless steel substrate by a simple spraying device, then the stainless steel substrate is placed in a vacuum drying oven to be dried for 1 hour at 120 ℃, then the stainless steel substrate is placed in a tube furnace to be calcined for 5 hours at 400 ℃ in nitrogen atmosphere, and the surface V is obtained2O5The stainless steel substrate of (1).
S1, dissolving lithium acetate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 15% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid and the vanadium pentoxide to form a transparent mixed solution;
s2, horizontally placing the substrate with the vanadium pentoxide on the surface into the transparent mixed solution obtained in the step S1 for soaking for 5 days, taking out the soaked substrate, placing the substrate into a vacuum drying oven for drying, then placing the substrate into a tubular furnace for calcining at 750 ℃ for 3 hours under the nitrogen protection atmosphere, and then taking out the substrate for cooling;
s3, repeating the steps S1 and S22 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 350 ℃ for 5 hours, heating to 750 ℃, synthesizing at a high temperature for 10 hours, and finally obtaining the lithium vanadium phosphate/carbon composite cathode material with a flower-shaped structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 120 mAh/g; after 50 cycles, the capacity retention rate was 94%.
Example 2
Having NH on the surface4VO3Preparation of the matrix of (1): reacting NH4VO3Dissolving in pure water to prepare 0.1mmol/ml NH4VO3The aqueous solution is uniformly sprayed on the titanium plate substrate by a simple spraying device, then the titanium plate substrate is placed in a vacuum drying oven to be dried for 1 hour at 100 ℃, and then the stainless steel substrate is placed in a tube furnace to be calcined at 300 ℃ in the nitrogen atmosphereBurning for 6 hours to obtain NH on the surface4VO3The titanium plate substrate of (1).
S1, dissolving lithium dihydrogen phosphate and ammonium metavanadate in a molar ratio of 3:2 in deionized water, adding 15% citric acid, and stirring at 70 ℃ on a magnetic stirrer to completely dissolve the citric acid and the ammonium metavanadate to form a transparent mixed solution;
s2, horizontally placing the substrate with the ammonium metavanadate on the surface into the transparent mixed solution obtained in the step S1 for soaking for 5 days, taking out the soaked substrate for drying, then placing the substrate into a tube furnace for calcination at 800 ℃ for 2 hours in a protective atmosphere, and then taking out and cooling;
s3, repeating the steps S1 and S22 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 350 ℃ for 5 hours, heating to 750 ℃, synthesizing at a high temperature for 10 hours, and finally obtaining the lithium vanadium phosphate/carbon composite cathode material with a flower-shaped structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 131 mAh/g; after 50 cycles, the capacity retention rate was 92.8%.
Example 3
Having a surface V2O5Preparation of the matrix of (1): will V2O5Dissolving in pure water to prepare 0.05 mmol/ml V2O5The aqueous solution is uniformly sprayed on the oroxylum indicum matrix by a simple spraying device, then the stainless steel matrix is placed in a vacuum drying oven to be dried for 4 hours at the temperature of 80 ℃, then the oroxylum indicum matrix is placed in a tube furnace to be calcined for 2 hours at the temperature of 500 ℃ in the argon atmosphere, and the surface V is obtained2O5The semen oroxyli matrix.
S1, dissolving lithium acetate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 15% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid and the vanadium pentoxide to form a transparent mixed solution;
s2, horizontally placing the substrate with the vanadium pentoxide on the surface into the transparent mixed solution obtained in the step S1 for soaking for 5 days, taking out the soaked substrate, placing the substrate into a vacuum drying oven for drying, then placing the substrate into a tubular furnace for calcining for 6 hours at 1000 ℃ under the argon protective atmosphere, and then taking out the substrate for cooling;
s3, repeating the steps S1 and S24 times for the calcined and cooled substrate obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 400 ℃ for 5 hours, heating to 800 ℃ for high-temperature synthesis for 10 hours, and finally obtaining the lithium vanadium phosphate/carbon composite anode material with a flower-shaped structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 153 mAh/g; after 50 cycles, the capacity retention rate was 94.2%.
Example 4
Having a surface V2O5Preparation of the matrix of (1): will V2O5Dissolving in pure water to prepare 0.1mmol/ml V2O5The aqueous solution is uniformly sprayed on the rush substrate by a simple spraying device, then the rush substrate is placed in a vacuum drying box and dried for 5 hours at the temperature of 80 ℃, then the rush substrate is placed in a tube furnace and calcined for 8 hours at the temperature of 300 ℃ in the nitrogen atmosphere to obtain the aqueous solution with V on the surface2O5The rush substrate.
S1, dissolving lithium acetate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 18% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid and the vanadium pentoxide to form a transparent mixed solution;
s2, horizontally placing the substrate with the vanadium pentoxide on the surface into the transparent mixed solution obtained in the step S1 for soaking for 10 days, taking out the soaked substrate, placing the substrate into a vacuum drying oven for drying, then placing the substrate into a tubular furnace for calcining at 900 ℃ for 2 hours under the nitrogen protection atmosphere, and then taking out the substrate for cooling;
s3, repeating the steps S1 and S24 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 200 ℃ for 8 hours, heating to 800 ℃ for high-temperature synthesis for 15 hours, and finally obtaining the lithium vanadium phosphate/carbon composite anode material with a flower-shaped structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 163 mAh/g; after 50 cycles, the capacity retention rate was 95.3%.
Example 5
Having a surface V2O3Preparation of the matrix of (1): will V2O3Dissolving in pure water to prepare 0.05 mmol/ml V2O3The aqueous solution is uniformly sprayed on a stainless steel substrate by a simple spraying device, then the stainless steel substrate is placed in a vacuum drying oven to be dried for 1 hour at 120 ℃, then the stainless steel substrate is placed in a tube furnace to be calcined for 2 hours at 400 ℃ in nitrogen atmosphere, and the surface V is obtained2O3The stainless steel substrate of (1).
S1, dissolving lithium acetate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 16% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid and the vanadium pentoxide to form a transparent mixed solution;
s2, horizontally placing the substrate with the vanadium trioxide on the surface into the transparent mixed solution obtained in the step S1 for soaking for 15 days, taking out the soaked substrate, placing the substrate into a vacuum drying oven for drying, then placing the substrate into a tubular furnace for 850 ℃ calcination for 3 hours under the argon protective atmosphere, and then taking out and cooling;
s3, repeating the steps S1 and S24 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 300 ℃ for 5 hours, heating to 600 ℃, and synthesizing at a high temperature for 10 hours to obtain the lithium vanadium phosphate/carbon composite cathode material with a flower-like structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 132 mAh/g; after 50 cycles, the capacity retention rate was 93.1 %。
Example 6
Having a surface V2O5Preparation of the matrix of (1): will V2O5Dissolving in pure water to prepare 0.01 mmol/ml V2O5The aqueous solution is uniformly sprayed on a stainless steel substrate by a simple spraying device, then the stainless steel substrate is placed in a vacuum drying oven to be dried for 3 hours at the temperature of 80 ℃, and then the stainless steel substrate is placed in a tube furnace to be calcined for 1 hour at the temperature of 400 ℃ in the nitrogen atmosphere to obtain the aqueous solution with V on the surface2O5The stainless steel substrate of (1).
S1, dissolving lithium gluconate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 20% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid and the citric acid to form a transparent mixed solution;
s2, horizontally placing the substrate with the vanadium pentoxide on the surface into the transparent mixed solution obtained in the step S1 for soaking for 5 days, taking out the soaked substrate, placing the substrate into a vacuum drying oven for drying, then placing the substrate into a tubular furnace for calcining at 950 ℃ for 4 hours under the argon protective atmosphere, and then taking out the substrate for cooling;
s3, repeating the steps S1 and S22 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 350 ℃ for 2 hours, heating to 750 ℃, synthesizing at a high temperature for 3 hours, and finally obtaining the lithium vanadium phosphate/carbon composite cathode material with a flower-shaped structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 126 mAh/g; after 50 cycles, the capacity retention rate was 91.4%.
Example 7
Having NH on the surface4VO3Preparation of the matrix of (1): reacting NH4VO3Dissolving in pure water to prepare 0.1mmol/ml NH4VO3The aqueous solution is uniformly sprayed on the copper plate matrix by a simple spraying device, then the copper plate matrix is placed in a vacuum drying oven to be dried for 1 hour at the temperature of 120 ℃, and then the copper plate matrix is driedThe copper plate matrix is placed in a tube furnace and calcined for 1 hour at 600 ℃ in the nitrogen atmosphere to obtain the copper plate matrix with V on the surface2O5The copper plate base body.
S1, dissolving lithium formate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 13% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid, so as to form a transparent mixed solution;
s2, horizontally placing the substrate with the ammonium metavanadate on the surface into the transparent mixed solution obtained in the step S1 for soaking for 5 days, taking out the soaked substrate, placing the substrate into a vacuum drying box for drying, then placing the substrate into a tubular furnace for 700-DEG calcination for 3 hours under the helium protective atmosphere, and then taking out and cooling;
s3, repeating the steps S1 and S27 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 300 ℃ for 3h, heating to 700 ℃ for high-temperature synthesis for 8h, and finally obtaining the lithium vanadium phosphate/carbon composite anode material with a flower-shaped structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 136 mAh/g; after 50 cycles, the capacity retention rate was 92.4%.
Example 8
Having a surface V2O5Preparation of the matrix of (1): will V2O5Dissolving in pure water to prepare 0.1mmol/ml V2O5The aqueous solution is uniformly sprayed on the rush substrate by a simple spraying device, then the rush substrate is placed in a vacuum drying box and dried for 1 hour at 120 ℃, then the rush substrate is placed in a tube furnace and calcined for 1 hour at 400 ℃ in nitrogen atmosphere to obtain the solution with V on the surface2O5The rush substrate.
S1, dissolving lithium acetate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 16% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid and the vanadium pentoxide to form a transparent mixed solution;
s2, horizontally placing the substrate with the vanadium pentoxide on the surface into the transparent mixed solution obtained in the step S1 for soaking for 10 days, taking out the soaked substrate, placing the substrate into a vacuum drying oven for drying, then placing the substrate into a tubular furnace for 850 ℃ calcination for 3 hours under the nitrogen protection atmosphere, and then taking out the substrate for cooling;
s3, repeating the steps S1 and S25 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at low temperature of 250 ℃ for 5 hours, heating to 650 ℃, synthesizing at high temperature for 5 hours, and finally obtaining the lithium vanadium phosphate/carbon composite cathode material with a flower-like structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 150 mAh/g; after 50 cycles, the capacity retention rate was 93.3%.
Example 9
Having a surface V2O5Preparation of the matrix of (1): will V2O5Dissolving in pure water to prepare 0.1mmol/ml V2O5The aqueous solution is uniformly sprayed on the oroxylum indicum matrix by a simple spraying device, then the oroxylum indicum matrix is placed in a vacuum drying oven to be dried for 2 hours at the temperature of 80 ℃, then the oroxylum indicum matrix is placed in a tube furnace to be calcined for 1 hour at the temperature of 600 ℃ in the nitrogen atmosphere, and V is obtained on the surface2O5The semen oroxyli matrix.
S1, dissolving lithium acetate, vanadium pentoxide and ammonium dihydrogen phosphate in a molar ratio of 3:1:3 in deionized water, adding 19% of citric acid, and stirring on a magnetic stirrer at 60 ℃ to completely dissolve the citric acid and the vanadium pentoxide to form a transparent mixed solution;
s2, horizontally placing the substrate with the vanadium pentoxide on the surface into the transparent mixed solution obtained in the step S1 for soaking for 5 days, taking out the soaked substrate, placing the substrate into a vacuum drying oven for drying, then placing the substrate into a tubular furnace for 650 ℃ calcination for 5 hours under the argon protective atmosphere, and then taking out and cooling;
s3, repeating the steps S1 and S27 times for the calcined and cooled matrix obtained in the step S2;
and S4, placing the matrix obtained in the step S3 in a tubular furnace filled with protective gas, carbonizing at a low temperature of 350 ℃ for 5 hours, heating to 750 ℃, synthesizing at a high temperature for 10 hours, and finally obtaining the lithium vanadium phosphate/carbon composite cathode material with a flower-shaped structure.
Obtained Li3V2（PO3）4When the/C composite positive electrode material is charged and discharged at 5C multiplying power, the first discharge specific capacity at room temperature can reach 160 mAh/g; after 50 cycles, the capacity retention rate was 93.1%.
The inventor states that the invention is illustrated by the above embodiments, but the invention is not limited to the above detailed process equipment and process flow, i.e. the invention is not meant to be dependent on the above detailed process equipment and process flow. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (9)
1. The preparation method of the lithium vanadium phosphate/carbon composite cathode material with the flower-like structure is characterized by comprising the following steps of:
s1, mixing soluble lithium compounds, vanadium compounds and phosphates according to a proper proportion, placing the mixture into deionized water, adding a proper amount of citric acid, and stirring at a certain temperature to form a clear and transparent mixed solution;
s2, horizontally placing the substrate with the vanadium compound attached to the surface in the transparent mixed solution obtained in the step S1 for soaking for several days, taking out the soaked substrate for drying, then carrying out high-temperature calcination for a period of time in a protective atmosphere, taking out the substrate for cooling, wherein the preparation method of the substrate with the vanadium compound attached to the surface comprises the following steps: mixing a proper amount of vanadium compound and pure water to form a solution or a suspension, uniformly spraying the solution or the suspension on the surface of a matrix in a spraying mode, then drying the matrix sprayed with the vanadium compound solution in vacuum, putting the matrix into a tubular furnace, and calcining the matrix in an inert gas at a certain temperature for a certain time;
s3, repeating the steps S1 and S2 for a plurality of times by taking the calcined and cooled substrate as an object;
and S4, sequentially carrying out low-temperature carbonization treatment and high-temperature synthesis treatment on the matrix obtained in the step S3 under a protective atmosphere to obtain the lithium vanadium phosphate/carbon composite anode material with the flower-like structure.
2. The method for preparing the composite cathode material according to claim 1, wherein the soluble lithium compound, the soluble vanadium compound and the soluble phosphate are mixed in step S1 according to an atomic ratio of lithium, vanadium and phosphorus of 3:2:3, the mass fraction of the added citric acid is 2-20%, and the mixture is stirred at 30-70 ℃ for 0.5-2 hours.
3. The method for preparing a composite positive electrode material according to claim 1, wherein the substrate in step S2 is a metal-based material or a carbon-based material.
4. The method for preparing the composite cathode material according to claim 1, wherein the number of days for which the substrate having vanadium pentoxide on the surface is immersed in the transparent mixed solution in step S2 is 5 to 15 days; the high-temperature calcination is carried out in a tubular furnace, the temperature is 500-1000 ℃, the calcination time is 2-6 hours, and the protective atmosphere is one of nitrogen, argon, helium and carbon dioxide.
5. The method for preparing the composite positive electrode material according to claim 1, wherein the repetition number in the step S3 is 2 to 7.
6. The method for preparing the composite cathode material according to claim 1, wherein in step S4, the specific parameters of the low-temperature carbonization treatment are as follows: carbonizing at 200-400 ℃ for 2-8 h, preferably at 350 ℃ for 5 h; the specific parameters of the high-temperature synthesis treatment are as follows: high-temperature synthesis is carried out at 600-850 ℃ for 3-15 h, preferably at 750 ℃ for 10 h.
7. The method of claim 1The preparation method of the composite cathode material is characterized in that the vanadium compound on the substrate is V2O5、NH4VO3、V2O3The concentration of the vanadium compound prepared into an aqueous solution or a suspension is 0.01-0.1 mmol/ml; the vacuum drying operation is to place the matrix in a vacuum drying oven at the temperature of 80-120 ℃ for drying for 1-5 hours; the calcining temperature in the tubular furnace is 300-600 ℃, the calcining time is 1-8 hours, and the inert gas is one of nitrogen, argon, helium and carbon dioxide.
8. The lithium vanadium phosphate/carbon composite cathode material prepared by the preparation method of the composite cathode material according to any one of claims 1 to 7.
9. The lithium vanadium phosphate/carbon composite positive electrode material according to claim 8, wherein the lithium vanadium phosphate/carbon composite positive electrode material has a flower-like spherical structure, the diameter of the flower-like spherical structure is 30 to 50 μm, and the petal spacing is 5 to 15 μm.
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| CN107845507A (en) * | 2017-12-22 | 2018-03-27 | 株洲市智汇知识产权运营服务有限责任公司 | Fluorophosphoric acid vanadium lithium/application of the fluorinated graphene composite positive pole in lithium-ion capacitor |
| CN108054025A (en) * | 2017-12-22 | 2018-05-18 | 湖南工业大学 | Use the preparation method of the lithium-ion capacitor of LiFePO4/expansion micro crystal graphite/carbon composite |
| CN107895657A (en) * | 2017-12-23 | 2018-04-10 | 株洲市智汇知识产权运营服务有限责任公司 | A kind of preparation method of lithium-ion capacitor using spherical microcrystalline graphite material |
| CN108155022B (en) * | 2017-12-23 | 2020-04-03 | 林荣铨 | Preparation method of lithium ion capacitor using microcrystalline graphite material |
| CN108039284A (en) * | 2017-12-23 | 2018-05-15 | 湖南工业大学 | Use the preparation method of the lithium-ion capacitor of phosphoric acid vanadium lithium/expansion micro crystal graphite/carbon composite |
| CN108448098B (en) * | 2018-03-30 | 2020-08-07 | 合肥师范学院 | Positive electrode material Na of sodium-ion battery with flower-shaped structure2CoFe(CN)6Preparation method of (1) |
| CN113036114B (en) * | 2021-02-04 | 2022-05-31 | 浙江大学 | Nano-sheet flower-like sodium vanadium fluorophosphate electrode material and preparation method and application thereof |
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