CN114148998B

CN114148998B - Precise fluorinated ginkgo leaf, purification method and functional application of lithium primary battery

Info

Publication number: CN114148998B
Application number: CN202111480392.2A
Authority: CN
Inventors: 简贤; 李金耀; 侯佳; 王晓辉; 刘一凡; 王俊伟
Original assignee: Yangtze River Delta Research Institute of UESTC Huzhou
Current assignee: Yangtze River Delta Research Institute of UESTC Huzhou
Priority date: 2021-12-06
Filing date: 2021-12-06
Publication date: 2023-08-04
Anticipated expiration: 2041-12-06
Also published as: GB202217450D0; GB2616099A; CN114148998A

Abstract

The invention discloses a fluorinated ginkgo She Zhengji material for a lithium primary battery, which comprises the purification treatment of natural ginkgo leaves and micro-oxidation grafting of-OH and-COOH in the air, and the impurities are converted into oxides while the carbon material in the ginkgo leaves is reserved. In addition, the carbonized ginkgo leaves are washed by dilute acid solution to remove impurities. Annealing at 900-1100 deg.c to obtain purified carbonized ginkgo leaf. Further, the fluorinated ginkgo leaf is prepared by adopting a precise fluorination process. Therefore, the lithium fluorocarbon battery obtained based on the accurate fluorinated ginkgo leaf and purification method and the lithium primary battery preparation has certain electrical properties, and lays an important foundation for various preparation methods of the fluorocarbon and popularization and application of the lithium/fluorocarbon battery.

Description

Precise fluorinated ginkgo leaf, purification method and functional application of lithium primary battery

Technical Field

The invention belongs to the technical field of new fluorocarbon materials and lithium primary batteries, and particularly relates to a precise fluorinated ginkgo leaf and a purification process method, and the purified fluorinated ginkgo leaf material is used as a positive electrode material of the lithium primary battery to prepare the lithium primary battery.

Background

The rapid development of new materials into new energy lithium batteries brings many opportunities and advances. Unlike lithium ion secondary batteries, lithium primary batteries play an irreplaceable role in extreme environments, difficult to detach, no charge, and other extreme conditions. Among them, lithium/carbon fluoride primary batteries are receiving attention for their excellent performance. The lithium/fluorocarbon battery has the advantages of large specific energy, high working voltage, wide working temperature range, excellent storage performance (small self-discharge), convenient use and carrying and the like, can meet the application requirements of power supplies in the fields of military, aviation, medicine and the like, and has great market potential. The theoretical energy density of the lithium/carbon fluoride battery (Li/(CFx) n) system is as high as 2189Wh/kg, which is the first commercial lithium primary battery worldwide using solid positive electrode materials. The positive electrode of the lithium/fluorocarbon primary battery Li/(CFx) n is a fluorocarbon material (CFx) n, and the negative electrode is metallic lithium. The performance of lithium fluorocarbon batteries is primarily dependent on the fluorocarbon cathode material, including the crystallinity, conductivity, particle size distribution, interfacial wettability, etc. of the fluorocarbon. These properties are in turn closely related to the carbon source and the precision fluorination technique. The carbon sources reported at present are carbon nanotubes, graphene, fullerene, hard carbon and the like. For example, chinese patent 202011245792.0 discloses a core-shell structure fluorocarbon material, a preparation method thereof and a lithium battery. The developed fluorination techniques include antimony pentafluoride, hydrofluoric acid, fluorine gas and other fluorination processes. The method for preparing the carbon fluoride by combining the fluorine gas with the high-temperature environment has the advantages of relatively low cost and good controllability, and is popularized. Therefore, finding new carbon sources and combining precise fluorination processes is one of the important directions of lithium/carbon fluoride batteries at present.

There are many difficulties in the current practice that limit the wide application of lithium/carbon fluoride batteries, the cost of carbon materials and the fluorination process result in relatively high price of carbon fluoride, and the preparation of carbon materials also causes certain pollution to the environment. Therefore, seeking carbon sources in nature and optimizing the fluorination process are expected to open up a new idea for the development of the fluorocarbon materials.

Disclosure of Invention

The invention aims at overcoming the defects in the background technology and provides a precise fluorinated ginkgo leaf and purification process method and lithium primary battery preparation. According to the invention, ginkgo leaves are used as a natural carbon source, and a purification process and a precise fluorination process are combined, so that impurities such as Ca and Mg contained in the fluorocarbon material are well removed, and meanwhile, a small amount of-OH and-COOH are grafted to the surface functional group modified carbon source, and the activity of fluorocarbon bonds is regulated and controlled; the lithium/carbon fluoride battery which is derived from natural ginkgo leaves, high in specific capacity and stable in voltage platform is obtained by adopting the precise fluorinated ginkgo leaves and the purification process method for preparing the carbon fluoride as the positive electrode material.

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

a method for preparing a fluorocarbon material by using accurate fluorinated ginkgo leaf and a purification process method is characterized by comprising the following steps:

step 1, collecting 500-5000g of natural ginkgo leaves, washing dust and sandy soil with deionized water for 3-5 times, and then airing.

And 2, placing 500-2000g of dried ginkgo leaves in a CVD furnace, heating to 100-120 ℃ at a speed of 10 ℃/min under an air atmosphere, continuously heating to 600-900 ℃ at a speed of 10 ℃/min under a nitrogen atmosphere, maintaining at 600-900 ℃ for 30-60min, and naturally cooling to obtain carbonized ginkgo leaves.

And 3, placing the carbonized ginkgo leaves in a suction filtration device, washing for 2-3 times by using a dilute acid solution, washing for 5-8 times by using deionized water, and then placing in a 50-80 ℃ oven for 30-60min to obtain the carbonized ginkgo leaves after washing.

And 4, placing the washed carbonized ginkgo leaves in a CVD furnace again, heating to 900-1100 ℃ at a speed of 10 ℃/min under the nitrogen atmosphere, keeping for 4-6 hours, regulating and controlling the graphitization degree and the surface defect structure of carbon, and naturally cooling to obtain a carbon source prepared from the purified ginkgo leaves.

And 5, placing a carbon source prepared from ginkgo leaves in a mixed gas of fluorine and nitrogen, and performing fluorination at 200-450 ℃ for 30-90 min to obtain the prepared carbon fluoride material taking the ginkgo leaves as raw materials.

Further, in the step 3, the dilute acid solution is prepared from acetic acid, nitric acid, hydrochloric acid and deionized water according to the volume ratio of 0.05-0.1:1.

Further, the mass ratio of the carbonized ginkgo leaf to the dilute acid solution in the step 3 is 1: (2-8)

Further, in the step 4, the mixed gas is fluorine gas, and the concentration ratio of the fluorine gas to the nitrogen gas is 5% -10%.

The invention also provides a precise fluorinated ginkgo leaf and a purification method and functional application of the lithium-carbon fluoride primary battery, wherein the lithium-carbon fluoride primary battery comprises a carbon fluoride anode material, a lithium metal cathode, electrolyte and a diaphragm.

Further, the carbon fluoride positive electrode material is formed by coating a mixed slurry of a fluorinated ginkgo leaf material, SP and PVDF on an aluminum foil current collector.

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

the invention provides a precise fluorinated ginkgo leaf, a purification method and functional application of a lithium primary battery, wherein natural components of natural ginkgo leaf are utilized to perform micro-oxidation grafting on-OH and-COOH in air, and impurities are converted into oxides while carbon materials in the ginkgo leaf are reserved. Washing carbonized ginkgo leaves with dilute acid solution to remove impurities. And purifying the carbonized ginkgo leaves at 900-1100 ℃. Therefore, the lithium fluorocarbon battery obtained based on the accurate fluorinated ginkgo leaf and purification method and the lithium primary battery preparation has certain electrical properties, and lays an important foundation for various preparation methods of the fluorocarbon and popularization and application of the lithium/fluorocarbon battery.

Drawings

FIG. 1 is an SEM image of a sample of the ginkgo leaf obtained in example 1 after carbonization at 700 ℃, wherein (a) and (b) are SEM images at different magnifications;

FIG. 2 is an SEM image of a sample of the ginkgo leaf obtained in example 2 after carbonization at 800 ℃, wherein (a) and (b) are SEM images at different magnifications;

FIG. 3 is an SEM image of a sample of the ginkgo leaf obtained in example 3 after carbonization at 900 ℃, wherein (a) and (b) are SEM images at different magnifications;

FIG. 4 is a graph of the Raman of the sample obtained in example 6 after fluorination at 400 ℃;

FIG. 5 is an XRD pattern for a sample obtained in example 6 after fluorination at 400 ℃;

FIG. 6 is an SEM image of a sample obtained in example 5 after fluorination at 350 ℃;

FIG. 7 is an SEM image of a sample obtained in example 5 after fluorination at 375 ℃;

FIG. 8 is an SEM image of a sample obtained in example 4 after fluorination at 375 ℃;

FIG. 9 is an SEM image of a sample obtained in example 4 after fluorination at 400 ℃;

FIG. 10 is an SEM image of a sample obtained in example 6 after fluorination at 400 ℃;

FIG. 11 is a Mapping graph of a sample obtained in example 5 after fluorination at 375 ℃. Wherein, (a) is an SEM image, (b) is an element total spectrogram, and (c), (d), (e) and (f) are element spectrograms of carbon, fluorine, calcium and magnesium respectively;

FIG. 12 is an XPS plot of samples obtained in example 5 after fluorination at 375 ℃.

FIG. 13 is a TEM image of samples obtained in example 5 after fluorination at 375℃wherein (a), (b), (c) (d), (e), (f) are TEM images of samples at different magnifications after accurate fluorination;

FIG. 14 is a graph showing the discharge curves of the assembled batteries of example 4 after fluorination at 350℃at different discharge rates;

FIG. 15 is a graph showing the discharge curves of the sample assembled battery obtained in example 5 after fluorination at 375℃at different discharge rates;

fig. 16 is a graph showing the discharge curves of the assembled batteries of the sample obtained in example 6 after fluorination at 400 c at different discharge rates.

Detailed Description

The technical scheme of the invention is further described in detail below with reference to the accompanying drawings and specific examples.

Example 1

The accurate fluorinated ginkgo leaf and purification method and the functional application of the lithium primary battery are characterized by comprising the following steps:

and step 1, collecting 500g of natural ginkgo leaves, washing dust and sandy soil with deionized water for 5 times, and then airing.

And 2, placing 500g of dried ginkgo leaves in a CVD furnace, heating to 120 ℃ at a speed of 10 ℃/min under an air atmosphere, continuously heating to 700 ℃ at a speed of 10 ℃/min under a nitrogen atmosphere, maintaining at 700 ℃ for 60min, and naturally cooling to obtain carbonized ginkgo leaves.

And 3, placing the carbonized ginkgo leaves in a suction filtration device, washing for 3 times by using a dilute acid solution, washing for 8 times by using deionized water, and then placing in a 50 ℃ oven for 60min to obtain the carbonized ginkgo leaves after washing.

Example 2

This embodiment differs from embodiment 1 in that: the process of step 2 is adjusted as follows: and (3) placing 500g of dried ginkgo leaves in a CVD furnace, heating to 120 ℃ at a speed of 10 ℃/min under an air atmosphere, then continuously heating to 800 ℃ at a speed of 10 ℃/min under a nitrogen atmosphere, maintaining at 800 ℃ for 60min, and naturally cooling to obtain carbonized ginkgo leaves.

Example 3

This embodiment differs from embodiment 1 in that: the process of step 2 is adjusted as follows: and (3) placing 500g of dried ginkgo leaves in a CVD furnace, heating to 120 ℃ at a speed of 10 ℃/min under an air atmosphere, then continuously heating to 900 ℃ at a speed of 10 ℃/min under a nitrogen atmosphere, maintaining at 900 ℃ for 60min, and naturally cooling to obtain carbonized ginkgo leaves.

Example 4

and step 1, collecting 500g of natural ginkgo leaves, washing dust and sandy soil with deionized water for-5 times, and then airing.

And 2, placing 500g of dried ginkgo leaves in a CVD furnace, heating to 120 ℃ at a speed of 10 ℃/min under an air atmosphere, continuously heating to 900 ℃ at a speed of 10 ℃/min under a nitrogen atmosphere, maintaining at 900 ℃ for 60min, and naturally cooling to obtain carbonized ginkgo leaves.

And 4, placing the washed carbonized ginkgo leaves in a CVD furnace again, heating to 1000 ℃ at a speed of 10 ℃/min under the nitrogen atmosphere, keeping for 4 hours, regulating and controlling the graphitization degree and the surface defect structure of carbon, and naturally cooling to obtain a carbon source prepared from the purified ginkgo leaves.

And 5, placing a carbon source prepared from ginkgo leaves in a mixed gas of fluorine and nitrogen, and carrying out fluorination for 60min at the temperature of 350 ℃ to obtain the carbon fluoride material prepared from the ginkgo leaves.

Example 5

This embodiment differs from embodiment 4 in that: the process of step 5 is adjusted as follows: and (3) placing a carbon source prepared from ginkgo leaves in a mixed gas of fluorine and nitrogen, and carrying out fluorination at 375 ℃ for 60min to obtain the carbon fluoride material prepared from ginkgo leaves.

Example 6

This embodiment differs from embodiment 4 in that: the process of step 5 is adjusted as follows: and (3) placing a carbon source prepared from ginkgo leaves in a mixed gas of fluorine and nitrogen, and carrying out fluorination at 400 ℃ for 60min to obtain the carbon fluoride material prepared from the ginkgo leaves.

FIGS. 1-3 SEM pictures of ginkgo leaves after carbonization at 700, 800, 900℃ in examples 1-3. SEM images of the fluorocarbon raw material before induction treatment at different magnifications show that the carbonized ginkgo leaves are porous in microstructure, and the flaky characteristic can provide active sites for lithium ion reaction.

FIG. 4 is a Raman diagram of a 400℃fluorinated carbon material treated in example 6. In FIG. 4, 1341cm ^-1 And 1587cm ^-1 The peak appearing at the position is the characteristic peak of carbon, corresponds to the D peak and the G peak respectively, and I _D /I _G A value of 0.97, indicating that the structure of the fluorinated carbon material is still ordered.

Fig. 5 is an XRD pattern of the carbon material after fluorination at 400 ℃ obtained by the treatment of example 6. Fig. 5 shows that the fluorinated carbon material has more diffraction peaks, wherein the diffraction peaks at 2θ=13.28° and 40.4 ° correspond to the (001) plane and the (100) plane of the carbon fluoride C-C, respectively; diffraction peaks at 2θ=28.2 °, 46.96 °, 55.72 °, 68.52 ° and 75.76 ° all represent CaF ₂ 。

FIG. 6 is an SEM image of a carbon material after fluorination at 350℃and treatment of example 4. As shown in the figure, when fluorination is carried out at 350 ℃, the fluorination effect is not ideal because the temperature is too low.

FIGS. 7 and 8 are SEM images of a 375℃fluorinated carbon material obtained by the treatment of example 6. It is shown that after the treatment of example 6, the morphology of the material collapses due to the increase of the temperature, resulting in the increase of the density of the material and the decrease of the specific surface area, and finally affecting the specific energy and specific power of the battery.

Fig. 9 and 10 are SEM images of the carbon material after fluorination at 400 ℃ obtained by the treatment of example 5. It is shown that the material substantially maintains a flaky morphology after the treatment of example 5, while the conductivity of the material decreases after fluorination, resulting in the aggregation of secondary electrons and the picture becoming brighter.

FIG. 11 is a Mapping graph of a carbon material fluorinated at 400℃obtained by the treatment of example 6. Mapping analysis of samples of ginkgo leaves fluorinated at 400 degrees celsius found that: the material contains elements such as carbon, fluorine, magnesium, calcium and the like because of the residual raw materials caused by incomplete purification process.

FIG. 12 is an XPS chart of a carbon material fluorinated at 400℃after the treatment of example 6. XPS analysis of samples of ginkgo leaves fluorinated at 400 degrees Celsius found that: high resolution scanning of C1s shows that there are 6 peaks with binding energies 284.7ev,285.6ev,287.1ev,288.7ev,290.3ev,293.3ev, which are represented by C-C bonds, c=c bonds, semi-ionic C-F bonds, covalent C-F bonds, C-F3 bonds. In particular, at a binding energy of 290.3eV, corresponds to the element C in calcium carbonate and acetic acid adsorbed on MgO. It can be seen that some Mg and Ca elements are present in the sample.

Fig. 13 is a TEM image at various magnifications of the 400 c fluorocarbon material obtained by the treatment of example 6. The whole appearance is sheet-shaped, and the material can be seen to have good crystallinity locally, so that carbon with large-area crystal morphology can appear, and a good basis can be provided for the following accurate fluorination process and the improvement of battery performance.

Assembling a battery:

the fluorinated ginkgo leaf samples obtained in the examples 4, 5 and 6, ketjen black serving as a conductive agent and PVDF serving as a binder are prepared into slurry according to the mass ratio of 8:1:1, uniformly coated on aluminum foil serving as a current collector, and dried in vacuum at 80 ℃ for 12 hours to obtain a positive plate. Then in a glove box, taking metal lithium as a negative electrode, taking an electrode slice prepared by fluoridized ginkgo leaf as a positive electrode, assembling the electrode slice into a button cell in the glove box, and then standing for 24 hours for testing.

FIG. 14 is a graph showing the discharge curves of the assembled batteries of example 4 after fluorination at 350℃at different discharge rates; it can be seen that the discharge curves of the fluorinated ginkgo leaf samples fluorinated at 350 ℃ are complete at discharge rates of 0.01, 0.05, 0.1, 0.5 and 1C, and the voltage plateau decreases with increasing rate. The fluorinated ginkgo leaf sample fluorinated at 350 ℃ exhibits the best discharge performance at a discharge rate of 0.5C, with a specific capacity of about 300mAh/g at a cutoff of 1.5V.

FIG. 15 is a graph showing the discharge curves of the sample assembled battery obtained in example 5 after fluorination at 375℃at different discharge rates; it can be seen that the discharge curves of 375 deg.c fluorinated ginkgo leaf samples were complete at discharge rates of 0.01, 0.05, 0.1, 0.5, 1C and compared to fig. 14. The fluorinated ginkgo leaf sample fluorinated at 375 ℃ has more excellent specific capacity at different multiplying powers. And exhibits an optimal discharge performance at a discharge rate of 0.5C, with a specific capacity of about 400mAh/g at a cutoff of 1.5V.

FIG. 16 is a graph showing the discharge curves of the assembled batteries of the sample obtained in example 6 after fluorination at 400℃at different discharge rates; it can be seen that the discharge curves of the fluorinated ginkgo leaf samples fluorinated at 400 ℃ are complete at discharge rates of 0.01, 0.05, 0.1, 0.5 and 1C. However, in contrast to fig. 14 and 15, the discharge curve at a larger discharge rate of 0.5 and 1C has no obvious voltage plateau due to the larger fluorination depth of the fluorinated ginkgo leaf sample at 400 ℃. The fluorinated ginkgo leaf sample fluorinated at 400 ℃ has more excellent specific capacity at a lower magnification. The best discharge performance is shown under the discharge multiplying power of 0.05C, and the specific capacity is more than 400mAh/g when the discharge multiplying power is cut off to 1.5V.

Claims

1. The precise fluorinated ginkgo leaf and purification method is characterized by comprising the following steps:

step 1, collecting natural ginkgo leaves, washing dust and sandy soil with deionized water, and airing;

step 2, placing the dried ginkgo leaves in a CVD furnace, heating to 100-120 ℃ in an air atmosphere for pre-carbonization treatment, then continuously heating to 600-900 ℃ in a nitrogen atmosphere, keeping at 600-900 ℃ for 30-60min for carbonization, and naturally cooling to obtain carbonized ginkgo leaves;

step 3, alternately washing carbonized ginkgo leaves with dilute acid solution and deionized water, filtering with a suction filtration device, and then drying in a baking oven at 50-80 ℃ to obtain carbonized ginkgo leaves after washing and impurity removal;

step 4, placing the washed carbonized ginkgo leaves in a CVD furnace again, heating to 900-1100 ℃ at a speed of 10 ℃/min under the nitrogen atmosphere, keeping for 4-6 hours, regulating and controlling the graphitization degree and the surface defect structure of carbon, and naturally cooling to obtain a carbon source prepared from purified ginkgo leaves;

step 5, placing a carbon source prepared from ginkgo leaves in a mixed gas of fluorine and nitrogen for fluorination to obtain a prepared fluorocarbon material taking the ginkgo leaves as a raw material;

and 6, taking the fluorinated ginkgo leaf obtained in the step 3 as a positive electrode material of the lithium primary battery to assemble the battery.

2. The method for precise fluorination of ginkgo leaves and purification according to claim 1, wherein the dilute acid solution in the step 3 is a solution prepared by mixing acetic acid, nitric acid, hydrochloric acid and deionized water in a volume ratio of (0.05-0.1): 1.

3. The precise fluorinated ginkgo leaf and purification method according to claim 1, wherein the mass ratio of the carbonized ginkgo leaf to the dilute acid solution in the step 3 is 1: (2-8).

4. The method for precisely fluorinating ginkgo leaf and purifying according to claim 1, wherein the mixed gas in the step 5 is fluorine gas with a concentration ratio of 5% -10% of the mixed gas of fluorine gas and nitrogen gas.

5. The method of claim 1, wherein the fluorination temperature in step 5 is 200-450 ℃ and the fluorination time is 30-90 min.

6. The method of claim 1, wherein the positive electrode material of the lithium primary battery in step 6 is prepared from the following materials: conductive agent: binder=8:1:1 mass ratio.

7. Use of the fluorinated ginkgo leaf obtained by the method according to any one of claims 1 to 6 as a positive electrode material for lithium primary batteries.