阅读说明：本技术 一种紫外辐射改性氟化碳的方法及在锂一次电池中的应用 (Method for modifying carbon fluoride by ultraviolet radiation and application of carbon fluoride in lithium primary battery ) 是由 简贤 马俊 刘一凡 于 2021-01-29 设计创作，主要内容包括：一种紫外辐射改性氟化碳的方法,属于新材料、一次电池技术领域。包括：1)称取氟化碳均匀平铺于透明容器中,使氟化碳在容器内的平均厚度为1～5mm,然后将容器置于磁力搅拌机上搅拌；2)保持搅拌的同时,开启紫外灯,辐射改性氟化碳材料,辐射功率为5W～500W,辐射时间为1h以上。本发明采用紫外辐射对氟化碳进行改性,紫外线的能量与氟化碳表面的碳氟键匹配,改变了氟化碳的表面结构,并在表面接枝碳氧基团,有效改善了氟化碳材料的导电性；改性后的氟化碳作为正极材料应用于锂一次电池中,大幅提高了电池的倍率性能。(A method for modifying carbon fluoride by ultraviolet radiation belongs to the technical field of new materials and primary batteries. The method comprises the following steps: 1) weighing carbon fluoride, uniformly spreading the carbon fluoride in a transparent container to enable the average thickness of the carbon fluoride in the container to be 1-5 mm, and then placing the container on a magnetic stirrer for stirring; 2) and (3) keeping stirring, simultaneously, starting the ultraviolet lamp, and radiating the modified carbon fluoride material, wherein the radiation power is 5-500W, and the radiation time is more than 1 h. According to the invention, the carbon fluoride is modified by adopting ultraviolet radiation, the energy of ultraviolet rays is matched with the carbon-fluorine bond on the surface of the carbon fluoride, the surface structure of the carbon fluoride is changed, and the carbon-oxygen group is grafted on the surface, so that the conductivity of the carbon fluoride material is effectively improved; the modified carbon fluoride is used as a positive electrode material to be applied to a lithium primary battery, so that the rate capability of the battery is greatly improved.)

1. A method of modifying carbon fluoride by ultraviolet radiation, comprising the steps of:

step 1, weighing carbon fluoride, uniformly paving the carbon fluoride in a container to enable the average thickness of the carbon fluoride in the container to be 1-5 mm, then placing the container on a magnetic stirrer, and adjusting the rotating speed to enable the carbon fluoride in the container to uniformly receive the radiation of ultraviolet light;

and 2, keeping magnetic stirring, simultaneously turning on an ultraviolet lamp, radiating the modified carbon fluoride material, wherein the radiation power of the ultraviolet lamp is 5-500W, and the radiation time is more than 1h, and taking out after the radiation is finished to obtain the modified carbon fluoride.

2. The method for modifying carbon fluoride through ultraviolet radiation according to claim 1, wherein the rotation speed of the magnetic stirring in the step 1 is 100-500 rpm.

3. The method of claim 1, wherein the gas atmosphere in the container of step 1 is air.

4. The method for modifying carbon fluoride through ultraviolet radiation according to claim 1, wherein the wavelength of the ultraviolet lamp in the step 2 is 200-400 nm.

5. The method for modifying fluorocarbon by ultraviolet radiation as claimed in claim 1, wherein the step 2 ultraviolet radiation process is performed under a light-shielding condition.

6. Use of the modified fluorocarbon obtained by the process of any one of claims 1 to 5 as a positive electrode material for lithium fluorocarbon primary cells.

Technical Field

The invention belongs to the technical field of new materials and primary batteries, and particularly relates to a method for modifying carbon fluoride by ultraviolet radiation and application of the modified carbon fluoride as a positive electrode material in a lithium primary battery.

Background

In the face of global energy crisis, people are eagerly seeking clean, safe and renewable energy sources, such as wind energy, geothermal energy and the like, and if the energy sources are convenient to use, the energy sources need to be converted into electric energy, so that high-capacity electrochemical power sources need to be utilized for energy storage. Lithium primary batteries are common energy storage devices and include primarily lithium/sulfur dioxide batteries, lithium/manganese dioxide batteries, lithium/thionyl chloride batteries, lithium/carbon fluoride batteries, and the like. At present, the most widely used lithium primary battery is a lithium/manganese dioxide battery, but the defects of low specific energy, limited applicable temperature and the like of the lithium/manganese dioxide battery cannot meet the requirements of high-rate discharge and work under severe temperature environment conditions. The lithium/carbon fluoride battery is used as a primary battery with the highest specific capacity at present, and the specific capacity of the lithium/carbon fluoride battery is 2-3 times that of the lithium/manganese dioxide battery. Moreover, under the condition of meeting the discharge requirement, the lithium/carbon fluoride battery has the obvious advantages of smaller volume, lighter weight, excellent high-low temperature performance (the working temperature is minus 40 ℃ to 170 ℃), stable working voltage, environmental protection, high safety, small self-discharge and the like, so the lithium/carbon fluoride battery has important application in aerospace, military, medical treatment and life. However, the carbon fluoride material serving as the cathode active material of the lithium/carbon fluoride battery has extremely strong covalent property, so that the intrinsic conductivity of the lithium/carbon fluoride battery is poor, the electrode kinetic process is slow, the lithium/carbon fluoride battery can only discharge at a low rate, and the initial discharge voltage hysteresis phenomenon is serious. In order to improve the performance of carbon fluoride, the carbon fluoride material is usually modified by a method of mixing a positive electrode. Zhang et al (DOI:10.1016/j. jpowsour.2009.10.096) have found that a carbon-coated carbon fluoride material obtained by mixing carbon fluoride with acetone and heat-treating the mixture at a high temperature of 600 ℃ in a protective atmosphere can discharge at a high rate of 2C, but acetone as a carbon source is harmful to the human body; zhang et al (DOI:10.1016/j. popowour.2008.12.007) similarly obtained carbon fluoride with better rate capability by heat treating carbon fluoride with citric acid at a temperature (400-500 ℃) lower than the decomposition temperature of carbon fluoride. Furthermore, hydrothermal methods are also common methods for modifying fluorocarbons, but the yield of hydrothermal methods is low. The method has the problems of high energy consumption, complex operation, high requirement on equipment, treatment at high temperature and high pressure, certain danger and the like. Therefore, how to obtain a simple method for modifying the carbon fluoride with low energy consumption has important significance.

Disclosure of Invention

The invention aims to provide a method for modifying carbon fluoride by ultraviolet radiation and application of the carbon fluoride in a lithium primary battery, aiming at the defects in the prior art. According to the invention, the surface of the carbon fluoride is modified by adopting ultraviolet radiation, so that the surface of the carbon fluoride is fragmented and grafted with carbon-oxygen groups, and the conductivity of the carbon fluoride is effectively improved; the modified carbon fluoride material is used as a positive electrode material to be applied to a lithium primary battery, so that the lithium carbon fluoride primary battery with high rate performance is obtained.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method of modifying carbon fluoride by ultraviolet radiation, comprising the steps of:

step 1, weighing carbon fluoride, uniformly paving the carbon fluoride in a transparent container to enable the average thickness of the carbon fluoride in the container to be 1-5 mm, then placing the container on a magnetic stirrer, and adjusting the rotating speed to enable the carbon fluoride in the container to uniformly receive the radiation of ultraviolet light;

and 2, keeping magnetic stirring, simultaneously turning on an ultraviolet lamp, radiating the modified carbon fluoride material, wherein the radiation power of the ultraviolet lamp is 5-500W, and the radiation time is more than 1h, and taking out after the radiation is finished to obtain the modified carbon fluoride.

Further, the rotating speed of the magnetic stirring in the step 1 is 100-500 rpm.

Further, the gas atmosphere in the container in the step 1 is air.

Further, the wavelength of the ultraviolet lamp in the step 2 is 200-400 nm.

Further, the step 2 ultraviolet radiation process is performed under a shading condition to prevent ultraviolet radiation from hurting people.

The invention also provides application of the ultraviolet radiation modified fluorocarbon as a positive electrode material of a lithium fluorocarbon primary battery.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention provides a method for modifying carbon fluoride by ultraviolet radiation and application of the carbon fluoride in a lithium primary battery, wherein the carbon fluoride is modified by ultraviolet radiation, the energy of ultraviolet rays is matched with a carbon-fluorine bond on the surface of the carbon fluoride, the surface structure of the carbon fluoride is changed, and a carbon-oxygen group is grafted on the surface of the carbon fluoride, so that the conductivity of the carbon fluoride material is effectively improved; the modified carbon fluoride is used as a positive electrode material to be applied to a lithium primary battery, so that the rate capability of the battery is greatly improved.

2. Compared with the traditional carbon fluoride modification method, such as high-temperature carbon coating, hydrothermal coating, conductive polymer coating and the like, the method for modifying carbon fluoride by ultraviolet radiation provided by the invention is simple to operate, does not need complex equipment and environment, can realize modification at normal temperature and normal pressure, reduces the cost, and can realize large-scale batch production.

Drawings

FIG. 1 is an SEM image of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 1; wherein a is SEM of an original carbon fluoride sample before modification, and b is SEM of the carbon fluoride sample after modification for 72h under the radiation of an ultraviolet lamp with the power of 5W in example 1;

FIG. 2 is an SEM image of a sample of carbon fluoride obtained by modification with ultraviolet radiation of example 2;

FIG. 3 is an XRD pattern of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 1; wherein a is the XRD pattern of the original carbon fluoride sample before modification, and b is the XRD pattern of the sample after ultraviolet radiation modification in example 1;

FIG. 4 is an XRD pattern of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 2; wherein a is the XRD pattern of the original carbon fluoride sample before modification, and b is the XRD pattern of the sample after ultraviolet radiation modification in example 2;

FIG. 5 is a thermogravimetric plot of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 1; wherein a is a thermogravimetric curve of an original carbon fluoride sample before modification, and b is a thermogravimetric curve of a sample after ultraviolet radiation modification in example 1;

FIG. 6 is a thermogravimetric plot of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 2; wherein a is a thermogravimetric curve of an original carbon fluoride sample before modification, and b is a thermogravimetric curve of a sample after ultraviolet radiation modification in example 2;

FIG. 7 is a graph comparing the impedance curves of the fluorocarbon samples before and after modification by ultraviolet radiation of example 1; wherein a is the impedance curve of the original carbon fluoride sample before modification, and b is the impedance curve of the sample after ultraviolet radiation modification in example 1;

FIG. 8 is a graph comparing the impedance curves of the fluorocarbon samples before and after modification by ultraviolet radiation of example 2; wherein a is the impedance curve of the original carbon fluoride sample before modification, and b is the impedance curve of the sample after ultraviolet radiation modification in example 2;

FIG. 9 is a discharge curve at 0.1C rate for a sample of carbon fluoride before and after modification by ultraviolet radiation for example 1; wherein a is the discharge curve of the original carbon fluoride sample before modification, and b is the discharge curve after ultraviolet radiation modification in example 1;

fig. 10 is a discharge curve of the uv modified fluorocarbon sample obtained in example 1 at 1C high rate performance.

Detailed Description

The technical scheme of the invention is detailed below by combining the accompanying drawings and the embodiment.

Example 1

A method for modifying carbon fluoride by ultraviolet radiation specifically comprises the following steps:

step 1, weighing 3g of carbon fluoride powder sample (original carbon fluoride sample), uniformly paving the carbon fluoride powder sample in a beaker to ensure that the average thickness of the original carbon fluoride sample in the beaker is 2mm, then placing a magnetic rotor in the beaker, transferring the sample to a magnetic stirrer for stirring, and adjusting the stirring speed to be 100 revolutions per minute;

and 2, keeping magnetic stirring, simultaneously turning on an ultraviolet lamp, radiating the modified carbon fluoride material under the shielding of shading cloth, wherein the radiation power of the ultraviolet lamp is 5W, the wavelength of the ultraviolet lamp is 350nm, and the radiation time is 3h, and after the radiation is finished, taking out the modified carbon fluoride material to obtain the modified carbon fluoride.

Example 2

This example is different from example 1 in that: the process of step 2 is adjusted as follows: and (3) while keeping magnetic stirring, turning on the ultraviolet lamp, radiating the modified carbon fluoride material under the shielding of shading cloth, wherein the radiation power of the ultraviolet lamp is 15W, the wavelength of the ultraviolet lamp is 350nm, the radiation time is 3h, and after the completion, taking out the carbon fluoride material to obtain the modified carbon fluoride.

Example 3

This example is different from example 1 in that: the process of step 2 is adjusted as follows: and (3) while keeping magnetic stirring, turning on the ultraviolet lamp, radiating the modified carbon fluoride material under the shielding of shading cloth, wherein the radiation power of the ultraviolet lamp is 300W, the wavelength of the ultraviolet lamp is 350nm, the radiation time is 5h, and after the completion, taking out the carbon fluoride material to obtain the modified carbon fluoride.

Example 4

This example is different from example 1 in that: the process of step 2 is adjusted as follows: and (3) while keeping magnetic stirring, starting the ultraviolet lamp, radiating the modified carbon fluoride material under the shielding of shading cloth, wherein the radiation power of the ultraviolet lamp is 500W, the wavelength of the ultraviolet lamp is 350nm, the radiation time is 1.5h, and after the completion, taking out the modified carbon fluoride material to obtain the modified carbon fluoride.

Example 5

This example is different from example 1 in that: the wavelength of the ultraviolet light used in step 2 was 260 nm.

Example 6

This example is different from example 1 in that: the ultraviolet wavelength used in step 2 was 390 nm.

Example 7

This example is different from example 1 in that: the process of step 1 is adjusted as follows: weighing 5g of carbon fluoride powder sample (original carbon fluoride sample), placing the sample in a beaker, wherein the average thickness of the original carbon fluoride sample in the beaker is 3mm, placing the sample in the beaker into a magnetic rotor, transferring the sample to a magnetic stirrer for stirring, and adjusting the stirring speed to 200 revolutions per minute.

Example 8

This example is different from example 1 in that: the process of step 1 is adjusted as follows: weighing 8g of carbon fluoride powder sample (original carbon fluoride sample), placing the sample in a beaker, wherein the average thickness of the original carbon fluoride sample in the beaker is 5mm, placing the sample in the beaker into a magnetic rotor, transferring the sample to a magnetic stirrer for stirring, and adjusting the stirring speed to 400 rpm.

FIG. 1 is an SEM image of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 1, wherein a is an SEM of an original carbon fluoride sample before modification, the original carbon fluoride material is in a sheet-like layer shape, and edges of the material are partially destroyed due to fluorination; b is SEM of a sample of the fluorinated carbon of example 1 after modification for 72h under irradiation of an ultraviolet lamp with a power of 5W, and it can be seen that the surface of the fluorinated carbon is fragmented by the ultraviolet energy.

FIG. 2 is an SEM image of a sample of carbon fluoride obtained by modification with ultraviolet radiation of example 2; it can be seen that the carbon fluoride material modified by ultraviolet radiation is fragmented.

FIG. 3 is an XRD pattern of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 1; wherein, a is the XRD pattern of the original carbon fluoride sample before modification, and b is the XRD pattern of the sample after ultraviolet radiation modification in example 1. As can be seen from fig. 3, before and after the modification by ultraviolet radiation, the crystal structure of the fluorocarbon fluoride was not changed, and the diffraction peaks were present at 2 θ ═ 14.8 °,40.8 °, and 73.5 °, where the diffraction peaks at 2 θ ═ 40.8 ° and 73.5 ° correspond to the (001) plane and the (100) plane of the fluorocarbon C — C, respectively; when 2 θ is 14.8 °, a (002) plane diffraction peak of C — F is present.

FIG. 4 is an XRD pattern of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 2; wherein a is the XRD pattern of the original carbon fluoride sample before modification, and b is the XRD pattern of the sample after ultraviolet radiation modification in example 2; as can be seen from fig. 4, the crystal structure of the carbon fluoride material is still not changed under the modification of the larger power radiation.

FIG. 5 is a thermogravimetric plot of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 1; wherein a is a thermogravimetric curve of an original carbon fluoride sample before modification, and b is a thermogravimetric curve of a sample after ultraviolet radiation modification in example 1; as can be seen from fig. 5, the uv-modified fluorocarbon sample had a structure with a fragmented surface, which was less thermally stable than the original fluorocarbon sample, and the decomposition started at a lower temperature.

FIG. 6 is a thermogravimetric plot of a sample of carbon fluoride before and after modification by ultraviolet radiation of example 2; wherein a is a thermogravimetric curve of an original carbon fluoride sample before modification, and b is a thermogravimetric curve of a sample after ultraviolet radiation modification in example 2; as can be seen from fig. 6, the sample modified by uv radiation starts to decompose at a lower temperature, and the larger power does not bring about a larger change.

Assembling the battery:

the sample obtained in the example 1 and the example 2 after the ultraviolet radiation modification, the conductive agent Keqin black and the adhesive PVDF are dissolved in NMP according to the mass ratio of 7:2:1, the mixture is stirred uniformly to prepare positive electrode slurry, the positive electrode slurry is uniformly coated on a current collector aluminum foil by a coating machine, the current collector aluminum foil is dried in vacuum at the temperature of 80 ℃ for 12 hours, and then the positive electrode sheet is obtained by cutting and tabletting. And (3) adopting metal lithium as a negative electrode material, assembling the lithium fluorocarbon button cell in a glove box, and standing for 24h for testing.

FIG. 7 is a graph comparing impedance curves for lithium fluorocarbon cells with the fluorocarbon sample as the positive electrode material before and after UV radiation modification of example 1; wherein a is the impedance curve of the original carbon fluoride sample before modification, and b is the impedance curve of the sample after ultraviolet radiation modification in example 1; the semicircle appearing in the curve represents the insertion resistance of Li +, and the slope of the straight line represents the diffusion resistance of Li +. As can be seen from fig. 7, the carbon fluoride material modified by uv radiation has smaller impedance when used as the positive electrode material of the lithium carbon fluoride battery.

FIG. 8 is a graph comparing impedance curves for lithium fluorocarbon cells with a sample of fluorocarbon before and after UV radiation modification as the positive electrode material in example 2; wherein a is the impedance curve of the original carbon fluoride sample before modification, and b is the impedance curve of the sample after ultraviolet radiation modification in example 2; as can be seen from fig. 8, the sample modified by ultraviolet radiation has a lower impedance.

FIG. 9 is the discharge curve at 0.1C rate for a lithium fluorocarbon cell with a sample of fluorocarbon before and after UV radiation modification as the positive electrode material of example 1; wherein a is the discharge curve of the original carbon fluoride sample before modification, and b is the discharge curve after ultraviolet radiation modification in example 1; as can be seen from fig. 9, although there is not much difference in specific capacity before and after the uv modification, the discharge curve of the fluorocarbon sample after the uv modification has a higher and more stable discharge plateau, which is about 2.5V, while the discharge curve of the original fluorocarbon has a certain fluctuation due to poor conductivity, and the discharge plateau is unstable. The carbon fluoride sample modified by ultraviolet radiation has better conductivity and shows better rate performance.

Fig. 10 is a discharge curve of 1C high rate performance of a lithium fluorocarbon cell with the uv modified fluorocarbon sample obtained in example 1 as the positive electrode material. As can be seen from fig. 10, at a high rate of 1C, the original sample could not discharge at such a high rate, but the uv radiation modified fluorocarbon sample could sustain a discharge plateau around 2.0V, and also had a specific discharge capacity of 750 mAh/g.