阅读说明：本技术 一种改性氟化碳及其制备方法和应用 (Modified carbon fluoride and preparation method and application thereof ) 是由 李烨 刘超 杨敏 李明书 张鹏 陈少云 焦文慧 方治文 于 2021-08-12 设计创作，主要内容包括：本发明涉及锂电池技术领域,具体涉及一种改性氟化碳及其制备方法和应用。制备方法包括：1)将氟化碳、氨水和乙醇混合,搅拌形成悬浊液,使氟化碳分散均匀；2)步骤1)所得悬浊液反应后洗涤过滤,得到氟化碳滤渣；3)将步骤2)所得氟化碳滤渣干燥,得到目标产物改性氟化碳；该改性氟化碳可用作电极材料；锂电池为以该改性氟化碳作为正极材料的锂电池。本发明成功使用氨水改性了氟化碳,降低了氟化碳中游离氟的含量,得到了具有低温和大倍率环境下优良放电性能的氟化碳材料。(The invention relates to the technical field of lithium batteries, in particular to modified carbon fluoride and a preparation method and application thereof. The preparation method comprises the following steps: 1) mixing carbon fluoride, ammonia water and ethanol, and stirring to form a suspension so as to uniformly disperse the carbon fluoride; 2) washing and filtering the suspension obtained in the step 1) after reaction to obtain carbon fluoride filter residues; 3) drying the carbon fluoride filter residue obtained in the step 2) to obtain a target product modified carbon fluoride; the modified fluorocarbon can be used as an electrode material; the lithium battery is a lithium battery using the modified carbon fluoride as a positive electrode material. According to the invention, ammonia water is successfully used for modifying the carbon fluoride, the content of free fluorine in the carbon fluoride is reduced, and the carbon fluoride material with excellent discharge performance in low-temperature and high-rate environments is obtained.)

1. A preparation method of modified carbon fluoride is characterized by comprising the following steps:

1) mixing carbon fluoride, ammonia water and ethanol, and stirring to form a suspension so as to uniformly disperse the carbon fluoride;

2) washing and filtering the suspension obtained in the step 1) after reaction to obtain carbon fluoride filter residues;

3) drying the carbon fluoride filter residue obtained in the step 2) to obtain the target product modified carbon fluoride.

2. The method of claim 1, wherein the mass-to-volume ratio of carbon fluoride to aqueous ammonia is 1: 0.01-20 g/mL.

3. The method according to claim 1, wherein the concentration of the aqueous ammonia is 1% to 28%.

4. The method of claim 1, wherein the mass to volume ratio of carbon fluoride to ethanol is 1: 0.01-20 g/mL.

5. The method according to claim 1, wherein the reaction time of the suspension in step 2) is 0.01 to 24 hours.

6. The method according to claim 1, wherein the drying temperature in the step 3) is 20 to 200 ℃.

7. A modified fluorocarbon produced by the production method according to any one of claims 1 to 6.

8. Use of the modified fluorocarbon according to claim 7 as an electrode material.

9. The use according to claim 8, wherein the modified fluorocarbon is used as a positive electrode material for lithium batteries.

Technical Field

The invention relates to the technical field of lithium batteries, in particular to modified carbon fluoride and a preparation method and application thereof.

Background

The carbon fluoride material is an important derivative of a carbon material, has extremely low surface energy and interlayer energy, excellent chemical stability and thermal stability and high theoretical specific capacity, and therefore, has important application in the fields of solid lubrication, corrosion and pollution prevention, battery electrode materials and the like. Particularly in the field of battery electrode materials, the lithium/carbon fluoride battery draws wide attention by virtue of high specific energy, and meanwhile, the working temperature range of the lithium/carbon fluoride battery is-60-180 ℃, so that the lithium/carbon fluoride battery is very suitable for the requirements of extreme environments such as aerospace and the like.

The core of the development of lithium/carbon fluoride batteries is the properties of carbon fluoride materials. Due to the strong covalent property of the C-F bond, the conductivity of the carbon fluoride is poor, the surface energy of the carbon fluoride is low, and the permeability of the carbon fluoride and electrolyte is poor, so that when the carbon fluoride is used as an electrode, polarization is easily caused, the multiplying power performance of the lithium/carbon fluoride battery is poor, the discharge platform is low and far inferior to the theoretical discharge platform, and the high-power discharge requirement cannot be met.

In general, a certain amount of free fluorine is contained in a carbon fluoride material, the free fluorine does not contribute to capacity in a chemical reaction of a battery, an electrolyte reacts with the free fluorine to generate substances such as hydrogen fluoride and the like in an electrochemical reaction process, and the substances corrode the battery. Generally, a water washing method is adopted to remove free fluorine from a carbon fluoride material, but the water washing method cannot effectively remove the free fluorine and cannot significantly improve the electrochemical performance of the material, and since the modification can significantly affect the performance of the carbon fluoride, a modified carbon fluoride capable of significantly improving the performance of the carbon fluoride and a preparation method thereof are needed.

Disclosure of Invention

The invention provides modified carbon fluoride and a preparation method and application thereof, aiming at the technical problem that a common lithium/carbon fluoride battery cannot meet the high-rate discharge requirement. According to the invention, ammonia water is successfully used for modifying the carbon fluoride, the content of free fluorine in the carbon fluoride is reduced, and the carbon fluoride material with excellent discharge performance in low-temperature and high-rate environments is obtained.

In a first aspect, the present invention provides a method for preparing a modified fluorocarbon, comprising the steps of:

1) mixing carbon fluoride, ammonia water and ethanol, and stirring to form a suspension so as to uniformly disperse the carbon fluoride;

2) washing and filtering the suspension obtained in the step 1) after reaction to obtain carbon fluoride filter residues;

3) drying the carbon fluoride filter residue obtained in the step 2) to obtain the target product modified carbon fluoride.

Further, the mass volume ratio of the carbon fluoride to the ammonia water is 1: 0.01-20 g/mL.

Further, the concentration of the ammonia water is 1-28%.

Further, the mass volume ratio of the carbon fluoride to the ethanol is 1: 0.01-20 g/mL.

Further, the reaction time of the suspension in the step 2) is 0.01-24 h.

Further, the reaction of the suspension in the step 2) is carried out under at least one condition of standing, ultrasound, heating, hydrothermal treatment, vacuum pumping and pressurization;

step 2), washing and filtering adopt at least one of centrifugation, suction filtration or other existing washing and filtering methods;

and 3) drying by at least one of water bath heating evaporation, drying in a drying oven, vacuum drying, natural air drying or other existing drying methods.

Further, the drying temperature in the step 3) is 20-200 ℃.

In a second aspect, the present invention provides a modified fluorocarbon prepared by the above method.

In a third aspect, the present invention provides a use of the modified fluorocarbon as an electrode material, preferably a lithium battery positive electrode material.

The beneficial effect of the invention is that,

the preparation method of the modified carbon fluoride is simple, low in cost and strong in controllability, and can reduce the content of free fluorine in the carbon fluoride and improve the electrochemical performance of the material;

the prepared modified carbon fluoride is micron-sized powder, has high purity, and has a high discharge platform, good rate performance and good low-temperature performance.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a scanning electron microscope photograph of the material of example 1;

FIG. 2 is a graph of the discharge performance of a lithium battery of example 4;

FIG. 3 is a graph of the discharge performance of a lithium battery of example 5;

fig. 4 is a graph of the discharge performance of the lithium battery of comparative example 1.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

And (3) uniformly dispersing 8g of carbon fluoride in 10mL of ethanol, adding 10mL of 25% ammonia water, mixing, uniformly stirring, standing for reaction for 2 hours, carrying out suction filtration on the suspension, putting the filter residue into a drying oven, and drying at 100 ℃ for 12 hours to obtain the modified carbon fluoride. Free fluorine content tests are respectively carried out on the carbon fluoride materials before and after ammonia water modification, the content of the unmodified free fluorine in the carbon fluoride is 1.98%, and the content of the modified free fluorine in the carbon fluoride is 0.0042%. The scanning electron microscope picture of the material obtained in this example is shown in FIG. 1.

Example 2

And (3) uniformly dispersing 10g of carbon fluoride in 20mL of ethanol, adding 20mL of 25% ammonia water, mixing, uniformly stirring, performing ultrasonic treatment for 4h, performing suction filtration on the suspension, putting the filter residue in a drying oven, and drying at 100 ℃ for 12h to obtain the modified carbon fluoride. Free fluorine content tests are respectively carried out on the carbon fluoride materials before and after ammonia water modification, the content of the unmodified free fluorine in the carbon fluoride is 1.98%, and the content of the modified free fluorine in the carbon fluoride is 0.0028%.

Example 3

And (2) uniformly dispersing 500g of carbon fluoride in 10L of ethanol, adding 10L of 25% ammonia water, mixing, stirring uniformly, standing, soaking for 2h, carrying out suction filtration on the suspension, putting the filter residue in a drying oven, and drying at 120 ℃ for 24h to obtain the modified carbon fluoride. Free fluorine content tests are respectively carried out on the carbon fluoride materials before and after ammonia water modification, the content of the unmodified free fluorine in the carbon fluoride is 5.65%, and the content of the modified free fluorine in the carbon fluoride is 0.00097%.

Example 4

Taking the modified carbon fluoride material prepared in the example 1 as a positive electrode material, mixing the obtained modified carbon fluoride positive electrode material, conductive carbon black and PVDF in a ratio of 80:10:10 into N-methyl pyrrolidone, grinding into paste, and coating the paste on an aluminum foil; vacuum drying at 120 deg.C for 12 hr, and cutting into electrode sheet with diameter of 12 mm; preparing the weighed electrode slice into a positive electrode, taking metal lithium as a negative electrode, taking a polyethylene microporous membrane as a diaphragm and taking 1M LiClO₄(DME + PC) is used as electrolyte and assembled into a lithium battery in a glove box filled with argon.

Example 5

The modified carbon fluoride material prepared in example 2 was used as a positive electrode material, and the remaining materials were selected from the same material as in example 4, and assembled into a lithium battery in a glove box filled with argon gas.

Comparative example 1

A lithium battery was assembled in a glove box filled with argon gas, using the raw material of fluorocarbon of example 1 as a positive electrode material, and selecting the remaining materials as in example 4.

The lithium batteries of examples 4 and 5 were tested for electrochemical performance under a lower voltage limit of 1.5V. As shown in FIG. 2, the lithium battery in example 4 has a specific discharge capacity of 762mAh/g at a discharge current of 50mA/g and a discharge platform of 3.12V above 1.5V; under the discharge current of 4A/g, the specific discharge capacity of more than 1.5V is 634.2mAh/g, the discharge platform reaches 2.74V, and the high-power-factor-performance lithium battery has good power performance; under the environment of minus 40 ℃, the discharge is carried out by the current of 50mA/g, the specific discharge capacity of more than 1.5V is 517.5mAh/g, the discharge platform is 2.65V, and the low-temperature discharge performance is good.

As shown in FIG. 3, in the lithium battery of example 5, under a discharge current of 50mA/g, the discharge specific capacity of more than 1.5V is 719.2mAh/g, and the discharge platform reaches 3.10V; under the discharge current of 4A/g, the specific discharge capacity of more than 1.5V is 625.2mAh/g, the discharge platform reaches 2.73V, and the high-power-factor-performance lithium battery has good power performance; under the environment of minus 40 ℃, the discharge is carried out by the current of 50mA/g, the specific discharge capacity of more than 1.5V is 462.1mAh/g, the discharge platform is 2.59V, and the low-temperature discharge performance is good.

The lithium battery of comparative example 1 was tested for electrochemical performance, and the results are shown in fig. 4, where the specific discharge capacity of more than 1.5V was 717.6mAh/g and the discharge plateau reached 3.12V at a discharge current of 50 mA/g; under the discharge current of 4A/g, the specific discharge capacity of more than 1.5V is 617.8mAh/g, the discharge median voltage is 2.21V, and the platform slides seriously; under the environment of-40 ℃, the discharge is carried out by the current of 50mA/g, the specific discharge capacity of more than 1.5V is 360.7mAh/g, and the discharge platform is 2.32V.

Although the present invention has been described in detail by referring to the drawings in connection with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention.