Disclosure of Invention
The invention mainly aims to solve the problems and provides a preparation method of a carbon/selenium doped titanium dioxide lithium sulfur battery positive electrode material with simplicity, high efficiency, low cost and low energy consumption and assembly of a lithium sulfur battery, which specifically comprise the following steps:
(1) cleaning and shearing mulberry leaves, adding deionized water, grinding, further crushing by repeated ultrasound, transferring the mulberry leaves into a mixed solution of absolute ethyl alcohol and concentrated sulfuric acid, performing hydrothermal treatment to carbonize the mulberry leaves, washing with deionized water, filtering, washing to be neutral, and drying at 60-80 ℃ overnight to obtain the biochar prepared based on the mulberry leaves, which is named as P1 for later use;
(2) uniformly mixing glycerol and isopropanol under magnetic stirring, adding triethanolamine and stirring for 5-10min, adding titanyl sulfate and stirring for 5-10min until a white sol solution is formed, then adding P1 and continuously stirring for 30min under magnetic stirring, carrying out microwave heating, washing, filtering and drying a product to obtain a carbon-doped titanium dioxide material, and naming the carbon-doped titanium dioxide material as P2 for later use;
(3) and (2) putting the P2 into sulfuric acid, adding selenium chloride under magnetic stirring, stirring for 10-20min, transferring to a reaction kettle for hydrothermal reaction, and washing, filtering and drying a product to obtain the carbon/selenium-doped titanium dioxide material.
(4) Firstly, uniformly mixing the prepared carbon/selenium-doped titanium dioxide material with 10-40% of sulfur powder, then transferring the mixture into a tube furnace, heating the mixture to 120 ℃ at the heating rate of 2 ℃/min, and heating the mixture for 2 hours; weighing the product, the super conductive carbon and the polyvinylidene fluoride according to the mass ratio of 7:2:1 after heating, dissolving the product in N-methyl pyrrolidone, grinding the product into uniform slurry, coating the slurry on copper foil, drying the slurry at low temperature, placing the slurry in a vacuum drying oven for drying for 12 hours, and finally cutting the slurry into wafers by a slicer; then assembling the positive plate, the gasket, the lithium sheet, the electrolyte, the diaphragm, the electrolyte, the carbon/selenium-doped titanium dioxide lithium sulfur battery positive plate, the gasket and the negative plate in turn in an argon glove box, and finally sealing the battery by using a battery pressing machine.
Preferably, the hydrothermal treatment in step (1) is heating at a temperature of 120-200 ℃ for 6-24 h.
Preferably, the mass-to-volume ratio of the glycerol, the isopropanol, the triethanolamine and the titanyl sulfate in the step (2) is (5-10) mL, (15-50) mL, (0.05-0.5) mL and (1-8) g.
Preferably, the microwave heating in the step (2) is heating for 1-3h under the power condition of 500-.
Preferably, the P1 in step (2) is added in an amount of 1-5% of P2.
Preferably, the selenium chloride in the step (3) is added in an amount of 0.5-10% of the total mass of the carbon/selenium-doped titanium dioxide.
Preferably, the hydrothermal reaction in step (3) is heating at 150-200 ℃ for 12-24 h.
Further, the prepared carbon/selenium-doped titanium dioxide material is used as a positive electrode material of a lithium-sulfur battery and is applied to the field of lithium-sulfur batteries.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) the invention provides a preparation method of a carbon/selenium-doped titanium dioxide lithium sulfur battery anode material, which has the advantages of easiness in preparation, energy conservation, low cost and the like.
(2) The carbon/selenium-doped titanium dioxide lithium sulfur battery positive electrode material prepared by the invention is a titanium dioxide material doped with biological carbon and selenium, and the participation of the titanium dioxide material and the titanium dioxide material not only improves the conductivity of the material, but also increases the specific surface area of the material, increases active sites for electrochemical reaction, enables sulfur atoms to be uniformly distributed in the structure, avoids sulfur agglomeration and polysulfide interaction, improves the utilization rate of sulfur, and is beneficial to the improvement of electrochemical performance.
Detailed Description
Example 1
The preparation of the carbon/selenium doped titanium dioxide lithium sulfur battery anode material and the assembly of the lithium sulfur battery comprise the following steps:
(1) cleaning and shearing mulberry leaves, adding deionized water, grinding, further crushing by repeated ultrasound, transferring the mulberry leaves into a mixed solution of absolute ethyl alcohol and concentrated sulfuric acid, performing hydrothermal treatment for 4 hours at 150 ℃ to carbonize the mulberry leaves, washing with deionized water, filtering, washing to neutrality, and drying overnight at 60 ℃ to obtain biochar prepared based on the mulberry leaves, which is named as P1 for later use;
(2) under magnetic stirring, uniformly mixing 10mL of glycerol and 20mL of isopropanol, adding 0.5mL of triethanolamine, stirring for 10min, adding 6g of titanyl sulfate, stirring for 10min until a white sol solution is formed, then adding P1 under magnetic stirring, continuously stirring for 30min, carrying out microwave heating for 1h under the condition of 700W power, and then washing, filtering and drying a product to obtain a carbon-doped titanium dioxide material; microwave heating for 1h under the power condition of 700W, and then washing, filtering and drying the product to obtain a carbon-doped titanium dioxide material which is named as P2 for later use;
(3) 4g P2 is put into sulfuric acid, then 0.3g of selenium chloride is added under magnetic stirring and stirred for 20min, the mixture is transferred into a reaction kettle and undergoes hydrothermal reaction for 12h at 180 ℃, and then the product is washed, filtered and dried, thus obtaining the carbon/selenium doped titanium dioxide material.
(4) Firstly, uniformly mixing the carbon/selenium-doped titanium dioxide material prepared in the embodiment 1 with 30% of sulfur powder, then transferring the mixture into a tube furnace, heating the mixture to 120 ℃ at a heating rate of 2 ℃/min, and heating the mixture for 2 hours; weighing the product, the super conductive carbon and the polyvinylidene fluoride according to the mass ratio of 7:2:1 after heating, dissolving the product in N-methyl pyrrolidone, grinding the product into uniform slurry, coating the slurry on copper foil, drying the slurry at low temperature, placing the slurry in a vacuum drying oven for drying for 12 hours, and finally cutting the slurry into wafers by a slicer; then assembling the positive plate, the gasket, the lithium sheet, the electrolyte, the diaphragm, the electrolyte, the carbon/selenium-doped titanium dioxide lithium sulfur battery positive plate, the gasket and the negative plate in turn in an argon glove box, and finally sealing the battery by using a battery pressing machine.
Example 2
The preparation of the carbon/selenium doped titanium dioxide lithium sulfur battery anode material and the assembly of the lithium sulfur battery comprise the following steps:
(1) cleaning and shearing mulberry leaves, adding deionized water, grinding, further crushing by repeated ultrasound, transferring the mulberry leaves into a mixed solution of absolute ethyl alcohol and concentrated sulfuric acid, performing hydrothermal treatment for 4 hours at 150 ℃ to carbonize the mulberry leaves, washing with deionized water, filtering, washing to neutrality, and drying overnight at 60 ℃ to obtain biochar prepared based on the mulberry leaves, which is named as P1 for later use;
(2) under magnetic stirring, uniformly mixing 10mL of glycerol and 20mL of isopropanol, adding 0.5mL of triethanolamine, stirring for 10min, adding 6g of titanyl sulfate, stirring for 10min until a white sol solution is formed, then adding P1 under magnetic stirring, continuously stirring for 30min, carrying out microwave heating for 1h under the condition of 700W power, and then washing, filtering and drying a product to obtain a carbon-doped titanium dioxide material; microwave heating for 1h under the power condition of 700W, and then washing, filtering and drying the product to obtain a carbon-doped titanium dioxide material which is named as P2 for later use;
(3) placing 5g P2 in sulfuric acid, adding 0.15g of selenium chloride under magnetic stirring, stirring for 20min, transferring to a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 12h, washing, filtering and drying the product to obtain the carbon/selenium doped titanium dioxide material.
(4) Firstly, uniformly mixing the carbon/selenium-doped titanium dioxide material prepared in the embodiment 2 with 20% of sulfur powder, then transferring the mixture into a tube furnace, heating the mixture to 120 ℃ at a heating rate of 2 ℃/min, and heating the mixture for 2 hours; weighing the product, the super conductive carbon and the polyvinylidene fluoride according to the mass ratio of 7:2:1 after heating, dissolving the product in N-methyl pyrrolidone, grinding the product into uniform slurry, coating the slurry on copper foil, drying the slurry at low temperature, placing the slurry in a vacuum drying oven for drying for 12 hours, and finally cutting the slurry into wafers by a slicer; then assembling the positive plate, the gasket, the lithium sheet, the electrolyte, the diaphragm, the electrolyte, the carbon/selenium-doped titanium dioxide lithium sulfur battery positive plate, the gasket and the negative plate in turn in an argon glove box, and finally sealing the battery by using a battery pressing machine.
Example 3
The preparation of the carbon/selenium doped titanium dioxide lithium sulfur battery anode material and the assembly of the lithium sulfur battery comprise the following steps:
(1) cleaning and shearing mulberry leaves, adding deionized water, grinding, further crushing by repeated ultrasound, transferring the mulberry leaves into a mixed solution of absolute ethyl alcohol and concentrated sulfuric acid, performing hydrothermal treatment for 4 hours at 150 ℃ to carbonize the mulberry leaves, washing with deionized water, filtering, washing to neutrality, and drying overnight at 60 ℃ to obtain biochar prepared based on the mulberry leaves, which is named as P1 for later use;
(2) under magnetic stirring, uniformly mixing 10mL of glycerol and 20mL of isopropanol, adding 0.5mL of triethanolamine, stirring for 10min, adding 6g of titanyl sulfate, stirring for 10min until a white sol solution is formed, then adding P1 under magnetic stirring, continuously stirring for 30min, carrying out microwave heating for 1h under the condition of 700W power, and then washing, filtering and drying a product to obtain a carbon-doped titanium dioxide material; microwave heating for 1h under the power condition of 700W, and then washing, filtering and drying the product to obtain a carbon-doped titanium dioxide material which is named as P2 for later use;
(3) placing 5g P2 in sulfuric acid, adding 0.03g of selenium chloride under magnetic stirring, stirring for 20min, transferring to a reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 12h, washing, filtering and drying the product to obtain the carbon/selenium doped titanium dioxide material.
(4) Firstly, uniformly mixing the carbon/selenium-doped titanium dioxide material prepared in the embodiment 3 with 20% of sulfur powder, then transferring the mixture into a tube furnace, heating the mixture to 120 ℃ at a heating rate of 2 ℃/min, and heating the mixture for 2 hours; weighing the product, the super conductive carbon and the polyvinylidene fluoride according to the mass ratio of 7:2:1 after heating, dissolving the product in N-methyl pyrrolidone, grinding the product into uniform slurry, coating the slurry on copper foil, drying the slurry at low temperature, placing the slurry in a vacuum drying oven for drying for 12 hours, and finally cutting the slurry into wafers by a slicer; then assembling the positive plate, the gasket, the lithium sheet, the electrolyte, the diaphragm, the electrolyte, the carbon/selenium-doped titanium dioxide lithium sulfur battery positive plate, the gasket and the negative plate in turn in an argon glove box, and finally sealing the battery by using a battery pressing machine.
Comparative example 1
The difference between comparative example 1 and example 1 is that a carbon-doped carbon dioxide material is prepared without adding selenium chloride in the preparation process.
Comparative example 2
The difference between the comparative example 2 and the example 1 is that selenium chloride and carbide prepared from mulberry leaves are not added in the preparation process, namely, a carbon dioxide material is prepared.
Comparative example 3
Comparative example 3 of the present invention uses commercial titanium dioxide as a comparison.
(1) Nitrogen adsorption and desorption test
The materials prepared in examples 1 to 3 of the invention and comparative examples 1 to 3 were subjected to a nitrogen adsorption and desorption test to characterize the specific surface area of the material, and the specific steps thereof were as follows: firstly, loading the material into a test tube, then installing the test tube on a degasser, and degassing for 12 hours at 110 ℃; after the degassing of the sample is finished, fixing the sample on a nitrogen adsorption and desorption instrument, and then starting the automatic nitrogen adsorption and desorption test in a liquid nitrogen environment. After the test is finished, the data of the specific surface area of the material can be obtained, and is specifically shown in table 1.
Table 1: specific surface area of the materials prepared in inventive examples 1-3 and comparative examples 1-3
As can be seen from Table 1, the carbon/selenium-doped titanium dioxide materials prepared in examples 1 to 3 of the present invention have a larger specific surface area, which is 1.2 to 2.9 times that of the materials prepared in comparative examples 1 to 3, and this is attributable to the carbon and selenium doping, which increases the specific surface area of the titanium dioxide and also provides more reactive sites.
(2) Electrochemical cycle Performance test
The battery is placed in a battery channel of a blue battery tester, program parameters of the blue battery tester are set, the theoretical specific capacity of the material is set to 1672mAh/g, the voltage testing interval is set to 1.5-3V, the current density is set to 167.2mA/g, and the charging and discharging testing times are set to 500 times. After the test is finished, the data information of the cycle number and the specific capacity of the battery can be obtained from the blue battery system, and the specific data is shown in table 2.
Table 2: cycle Performance tables for materials prepared in inventive examples 1-2 and comparative examples 1-3
As can be seen from the data in table 2, the specific discharge capacities of the first coils of the lithium-sulfur batteries prepared in examples 1 and 2 of the present invention were 894.4mAh/g and 851.4mAh/g, respectively; the discharge specific capacity of 100 circles is 758.9mAh/g and 746.5mAh/g respectively; the discharge specific capacity of 300 circles is 693.4mAh/g and 701.5mAh/g respectively; the discharge specific capacity of 500 circles is 672.3mAh/g and 672.5mAh/g respectively; from this, it can be calculated that the capacity loss rates of the lithium sulfur batteries prepared in example 1 and example 2 were 15.1% and 12.3% at 100 cycles, 22.9% and 18.3% at 300 cycles, and 25.9% and 22.4% at 500 cycles, respectively. It can be seen that the capacity loss of the materials prepared in examples 1 and 2 is high in the first 100 cycles, and when the materials are circulated to 300 cycles, the material circulation is in a stable circulation state, and the capacity loss rate is low; it was also found that the sulfur doping ratio of example 1 was 30% and the sulfur doping ratio of example 2 was 15%, but both showed similar cycle capacities, and there was no great difference due to the different sulfur doping ratios, since the carbon/selenium doping in example 1 was more, thereby increasing the sulfur utilization.
It can also be observed from the data of table 2 that the first-turn specific discharge capacities of inventive example 1, comparative example 2 and comparative example 3 were 894.4mAh/g, 516.4mAh/g, 152.8mAh/g and 145.6 mAh/g; the 100-turn specific discharge capacities of the lithium ion battery are 758.9mAh/g, 416.7mAh/g, 79.3mAh/g and 76.5mAh/g respectively, so that the material prepared in the embodiment 1 of the invention has higher lithium storage capacity compared with the materials prepared in the comparative examples 1-3. The pure titania materials prepared in comparative examples 2 and 3 could not be recycled to 500 th cycle or even 300 th cycle due to the large capacity reduction, while the carbon/selenium-doped titania prepared in example 1 could be recycled for 500 cycles smoothly and maintain good recycling efficiency, because the carbon/selenium doping provides more reactive sites for the intercalation and deintercalation of lithium ions and sulfur atoms and reduction products thereof.
(3) Electrochemical impedance spectroscopy test
The cell was placed in the cell holder of an Auto Lab electrochemical workstation, set to a voltage test interval of 1.5-3V, and then tested at a scan rate of 0.5mV/s, with specific resistance data as shown in Table 3.
Table 3: electrochemical impedance table of examples 1-3 of the present invention and comparative examples 1-3
Item
|
Example 1
|
Example 2
|
Example 3
|
Comparative example 1
|
Comparative example 2
|
Comparative example 3
|
Resistance (RC)
|
73Ω
|
69Ω
|
77Ω
|
132Ω
|
174Ω
|
152Ω |
As can be seen from table 3, the batteries prepared in examples 1 to 3 have a smaller impedance value, which is because the carbon/selenium doping accelerates the electron transport, improves the conductivity of the material, and further makes the material have excellent electrochemical properties, thereby further verifying that the carbon/selenium doped titanium dioxide lithium sulfur battery cathode material has better electrochemical cycle performance.
While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. Such modifications and variations are considered to be within the scope of the invention.