A method for combined modification of carbon monofluoride by hybrid plasma and in situ compounding

Abstract

The present application belongs to the technical field of new materials and lithium primary battery, and provides a method for modifying carbon fluoride by combined plasma and in-situ compounding, and a lithium primary battery prepared by using the modified carbon fluoride as a positive electrode material. The present application uses mixed plasma to control the C-F bond type of carbon fluoride, and the fluorocarbon bond is selectively broken to form an amorphous carbon layer on the surface of the carbon fluoride in-situ. Potassium permanganate is used as a manganese source to react with the surface carbon and organic source to generate ultra-fine manganese dioxide particles in-situ, and form a CF x / MnO2 composite material, which is used as a positive electrode material of a lithium / carbon fluoride primary battery. The residual carbon layer on the surface of the carbon fluoride and the composite manganese dioxide particles can effectively improve the conductivity of the carbon fluoride, slow down the electrochemical polarization in the discharge process of the primary battery, reduce the voltage hysteresis effect in the initial stage of discharge, and further improve the rate performance of the lithium / carbon fluoride battery, which is of great significance to promote the application and popularization of the lithium / carbon fluoride battery.

Description

Technical Field

[0001] This invention belongs to the field of new materials and lithium primary battery technology, and relates to a method for the joint modification of fluorinated carbon materials. Specifically, it provides a method for the joint modification of fluorinated carbon by mixed plasma and in-situ composite, and uses the modified fluorinated carbon as a positive electrode material to prepare a lithium primary battery. Background Technology

[0002] Common primary lithium batteries include lithium / manganese dioxide batteries, lithium / sulfur dioxide batteries, lithium / thionyl chloride batteries, and lithium / carbon fluoride batteries. Among these, lithium / carbon fluoride batteries (Li / CF4) are particularly important. x Compared to other solid-state cathode batteries, it has the highest theoretical energy density (2180 Wh / kg), and its practical specific energy can reach 250–800 Wh / kg. Meanwhile, Li / CF... x The battery also has many advantages: 1) Wide operating temperature range: Fluorinated carbon materials are stable and can be used in a wide temperature range of -20 to 80℃; 2) Stable operating voltage: After the fluorinated carbon in the positive electrode reacts, it becomes LiF and C, and the utilization rate of active materials can reach almost 100%. The operating voltage remains basically stable until the end of the discharge; 3) Low self-discharge rate: The self-discharge rate of lithium / fluorinated carbon batteries is very low (annual self-discharge rate <1%), so it has an ultra-long storage life of more than ten years.

[0003] Currently, lithium / carbon fluoride batteries are widely used in aerospace, deep-sea exploration, military, and medical fields, and have broad development prospects; however, due to the limited application of their cathode material, carbon fluoride (CF2), they face challenges. x The poor intrinsic conductivity and strong covalent CF bond energy of lithium-ion / carbon fluoride batteries lead to severe polarization in the initial discharge phase, resulting in significant voltage hysteresis and substantial capacity decay at high discharge rates, approximately 30% of the theoretical capacity. This greatly limits the further development and utilization of lithium-ion / carbon fluoride primary batteries. To compensate for the voltage hysteresis and poor rate performance of lithium-ion / carbon fluoride batteries, patent document CN110707313A discloses a V2O5-carbon fluoride composite cathode material. This material utilizes the high voltage plateau and good rate performance of V2O5 to compensate for the poor rate performance of lithium-ion / carbon fluoride batteries; however, the voltage hysteresis effect still exists. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing lithium / carbon fluoride (Li / CF) batteries. x To address the shortcomings of existing methods, a combined approach of hybrid plasma and in-situ composite modification of fluorinated carbon is proposed. First, hybrid plasma technology is used to carbonize the surface of the fluorinated carbon material, followed by composite bonding with ultrafine manganese dioxide particles to prepare a high-rate performance CF2. x / C / MnO2 composite cathode material is used in lithium primary batteries to effectively improve the specific capacity of lithium / carbon fluoride batteries, while also improving the problem of voltage hysteresis in the early stage of discharge.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for combined modification of fluorinated carbon using hybrid plasma and in-situ composite processes, characterized by comprising the following steps:

[0007] Step 1: Place the fluorinated carbon into the tubular furnace chamber of the plasma-enhanced chemical vapor deposition (PECVD) equipment and remove all air and moisture from the tubular furnace chamber;

[0008] Step 2: Vacuum the cavity and introduce induction gas at a total flow rate of 100-200 ml / min. Maintain the cavity pressure in the range of 20-100 Pa for 15-30 min. Then, start the plasma excitation source and perform plasma treatment at a power of 50-400 W for 5-60 min to obtain carbon-coated fluorinated carbon.

[0009] Step 3: Disperse the carbon-coated fluorinated carbon in a mixture of ethanol and deionized water, add potassium permanganate solution, react at room temperature for 30-120 minutes, and finally obtain the fluorinated carbon composite cathode material after centrifugation and drying.

[0010] Furthermore, in step 1, the amount of fluorinated carbon used is 1g to 200g.

[0011] Furthermore, in step 1, the specific process of purging all air and moisture from the tubular furnace cavity is as follows: a protective gas is introduced into the furnace at a rate of 50-100 ml / min, and the cavity temperature is heated to 80-120°C and held for 30-60 minutes.

[0012] Furthermore, in step 2, the inducing gas is any two of nitrogen, argon, acetylene, methane, propylene, hydrogen, and oxygen, and the gas ratio between the two is 1:1 to 4. It should be noted that, taking nitrogen and argon as an example, the ratio can be either nitrogen:argon 1:1 to 4 or argon:nitrogen 1:1 to 4.

[0013] Furthermore, in step 3, the concentration of the potassium permanganate solution is 0.01–0.5 mol / L, and the ratio of carbon-coated fluorinated carbon to potassium permanganate is 1 g: 0.001–0.004 mol, that is, each gram of carbon-coated fluorinated carbon reacts with 0.001–0.004 mol of potassium permanganate.

[0014] The present invention also provides a lithium / carbon fluoride primary battery, comprising: a carbon fluoride positive electrode, a lithium metal negative electrode, an electrolyte, and a separator, characterized in that the carbon fluoride positive electrode is a combined modified carbon fluoride material of the above-mentioned mixed plasma and in-situ composite.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention employs a hybrid plasma and in-situ composite modification technique to treat fluorinated carbon: First, hybrid plasma is used to regulate the CF bond type of fluorinated carbon, while selective fluorine-carbon bond breaking occurs in situ to form "amorphous carbon" coating the surface of the fluorinated carbon; second, potassium permanganate is used as a manganese source to react with the surface carbon and organic source to generate ultrafine manganese dioxide particles in situ, forming CF... x A C / MnO2 composite material was used as the positive electrode material for lithium / carbon fluoride primary batteries. The residual carbon layer on the surface of the fluoride and the composite manganese dioxide particles effectively improve the conductivity of the fluoride, mitigate electrochemical polarization during primary battery discharge, and reduce the voltage hysteresis effect in the early stage of discharge, thereby improving the rate performance of the lithium / carbon fluoride battery. Therefore, this invention, based on the combined modification technology of mixed plasma-MnO2 in-situ composite, produces fluoride with good rate performance and no obvious voltage hysteresis effect, which is of great significance for improving the performance of lithium / carbon fluoride batteries and promoting their application. Attached Figure Description

[0017] Figure 1 SEM images of commercial fluorocarbon raw materials and the modified fluorocarbon material obtained in Example 3; wherein, (a) is the SEM image of commercial fluorocarbon raw materials; and (b) is the SEM image of the modified fluorocarbon material obtained in Example 3.

[0018] Figure 2 TEM images of commercial fluorocarbon raw materials and the modified fluorocarbon material obtained in Example 3; wherein, (a) is a TEM image of commercial fluorocarbon raw materials; and (b) is a TEM image of the modified fluorocarbon material obtained in Example 3.

[0019] Figure 3 Raman spectra of the modified fluorocarbon materials obtained from commercial fluorocarbon raw materials, Examples 1, 2, and 3.

[0020] Figure 4 The XRD patterns of the modified fluorocarbon materials obtained from commercial fluorocarbon raw materials, Examples 1, 2, and 3 are shown.

[0021] Figure 5 Discharge curves of batteries assembled using commercial fluorinated carbon raw materials as cathode materials at different discharge rates.

[0022] Figure 6 The discharge curves of the battery assembled using the modified fluorinated carbon material obtained in Example 1 as the positive electrode material at different discharge rates are shown.

[0023] Figure 7 The discharge curves of the battery assembled using the modified fluorinated carbon material obtained in Example 2 as the positive electrode material at different discharge rates are shown.

[0024] Figure 8 The discharge curves of the battery assembled using the modified fluorinated carbon material obtained in Example 3 as the positive electrode material at different discharge rates are shown.

[0025] Figure 9 EIS curves of batteries assembled using commercial fluorinated carbon raw materials and modified fluorinated carbon materials obtained in Examples 1, 2, and 3 as cathode materials. Detailed Implementation

[0026] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] Example 1

[0028] This embodiment provides a method for jointly modifying fluorinated carbon using hybrid plasma and in-situ composite methods, comprising the following steps:

[0029] Step 1: Place 5g of fluorinated carbon into the tubular furnace chamber of the plasma-enhanced chemical vapor deposition equipment, then introduce argon gas into the furnace at a rate of 100ml / min, and control the temperature at 100℃ for 30min to ensure that all air and moisture are removed.

[0030] Step 2: Start the vacuum pump to evacuate the cavity, and introduce acetylene and argon gas, adjusting the gas ratio of the mixed plasma to 1:1, maintaining a total flow rate of 100 ml / min, and keeping the cavity pressure within the range of 20–50 Pa for 30 minutes; then start the plasma excitation source and perform plasma treatment at a power of 200 W for 15 minutes to obtain carbon-coated fluorinated carbon (CF₂). x -P);

[0031] Step 3: Disperse the fluorinated carbon (1g) obtained in Step 2 in 20ml of ethanol and 20ml of deionized water, and add 20ml of potassium permanganate solution (0.01mol / L). React at room temperature for 30min. Finally, after centrifugation and drying, the fluorinated carbon composite cathode material (CF) is obtained. x -P-1).

[0032] Example 2

[0033] The difference between this embodiment and Embodiment 1 is that:

[0034] The specific process of step 3 is as follows: Disperse the fluorinated carbon (1g) obtained in step 2 in 20ml of ethanol and 20ml of deionized water, and add 20ml of potassium permanganate solution (0.05mol / L). React at room temperature for 30min. Finally, after centrifugation and drying, the fluorinated carbon composite cathode material (CF) is obtained. x -P-2).

[0035] Example 3

[0036] The difference between this embodiment and Embodiment 1 is that:

[0037] The specific process of step 3 is as follows: Disperse the fluorinated carbon (1g) obtained in step 2 in 20ml of ethanol and 20ml of deionized water, and add 20ml of potassium permanganate solution (0.1mol / L). React at room temperature for 30min. Finally, after centrifugation and drying, the fluorinated carbon composite cathode material (CF) is obtained. x -P-3).

[0038] The modified fluorocarbon materials obtained in Examples 1 to 3 above, as well as commercial fluorocarbon raw materials, were tested, and the results are as follows: Figures 1-4 As shown, the details are as follows.

[0039] Figure 1 SEM images of commercial fluorocarbon raw materials and the modified fluorocarbon material obtained in Example 3, by [the source text is missing]. Figure 1 It is known that commercial fluorocarbon raw materials have a layered structure and a smooth surface, and the modified fluorocarbon material obtained in Example 3 has fine MnO2 particles on its surface.

[0040] Figure 2 TEM images of commercial fluorocarbon raw materials and the modified fluorocarbon material obtained in Example 3, by [the source text is missing]. Figure 2 It can be seen that commercial fluorinated carbon raw materials do not have obvious lattice stripes and are in a disordered state overall. The modified fluorinated carbon material obtained in Example 3 has MnO2 lattice stripes, but the lattice stripes are not obvious, which indicates that the composite MnO2 is amorphous.

[0041] Figure 3 Raman spectra of commercial fluorocarbon raw materials and modified fluorocarbons obtained in Examples 1, 2, and 3; by Figure 3 It can be seen that fluorinated carbon has a distinct carbon D peak (1315 cm⁻¹). -1 ) and G peak (1584cm) -1 According to the intensity ratio of the D peak and the G peak (I) D / I G It can determine the degree of defect in the material; Figure 3In the sample, as the concentration of potassium permanganate solution increases, the I... D / I G The values ​​were 0.524, 0.645, 1.028, and 1.158, respectively, indicating that increasing the concentration of potassium permanganate solution further damages the structure of fluorinated carbon and its surface carbon layer, leading to an increase in defects in the fluorinated carbon; and, at 639 cm⁻¹... -1 The appearance of the stretching vibration peak of Mn-O indicates the successful recombination of MnO2.

[0042] Figure 4 XRD patterns of commercial fluorocarbon raw materials and modified fluorocarbons obtained in Examples 1, 2, and 3; by Figure 4 It can be seen that as the potassium permanganate solution increases, the characteristic peaks of fluorinated carbon weaken, indicating that the potassium permanganate solution has a certain destructive effect on the lattice of fluorinated carbon. Furthermore, weak MnO2 characteristic peaks appear at 2θ = 37.1° and 2θ = 66.2°, indicating that the composite MnO2 is amorphous.

[0043] Furthermore, the modified fluorinated carbon materials obtained in Examples 1-3 of this invention and commercial fluorinated carbon raw materials were used as positive electrode materials for battery assembly: A slurry was prepared by mixing commercial fluorinated carbon raw materials, the modified fluorinated carbon materials obtained in Examples 1-3, conductive additives (SP), and binders (PVDF) at a mass ratio of 8:1:1. This slurry was uniformly coated onto current collector aluminum foil and dried in a vacuum drying oven at 80°C for 12 hours to obtain a positive electrode sheet. Using lithium metal as the negative electrode and the fluorinated carbon electrode sheet as the positive electrode, a button cell was assembled in a glove box and then left to stand for 24 hours for electrochemical performance testing. The results are as follows: Figures 5-9 As shown.

[0044] Figure 5 Discharge curves of batteries assembled using commercially available fluorinated carbon raw materials as cathode materials at different discharge rates; Figure 5 It is known that commercial fluorocarbon raw materials have poor rate performance, exhibit severe voltage hysteresis in the initial stage of discharge, and cannot discharge at rates greater than 3C.

[0045] Figure 6 The discharge curves of the battery assembled using the modified fluorinated carbon material obtained in Example 1 as the positive electrode material at different discharge rates are shown below. Figure 6 It can be seen that the modified fluorinated carbon material has significantly improved voltage hysteresis effect in the early stage of discharge, and can also discharge at 6C rate with a specific capacity of 430mAh / g.

[0046] Figure 7 The discharge curves of the battery assembled using the modified fluorinated carbon material obtained in Example 2 as the positive electrode material at different discharge rates are shown. Figure 7It can be seen that the modified fluorinated carbon material significantly improves the voltage hysteresis effect in the early stage of discharge, improves the voltage plateau at high rates, and can achieve a specific capacity of 420mAh / g at a 10C rate.

[0047] Figure 8 The discharge curves of the battery assembled using the modified fluorinated carbon material obtained in Example 3 as the positive electrode material at different discharge rates are shown. Figure 8 It can be seen that the modified fluorinated carbon material significantly improves the voltage hysteresis effect in the early stage of discharge, improves the voltage plateau at high rates, and can achieve a specific capacity of 410mAh / g at a 10C rate.

[0048] Figure 9 EIS curves of batteries assembled using commercial fluorinated carbon raw materials and modified fluorinated carbon materials obtained in Examples 1, 2, and 3 as cathode materials are shown. The diameter of the half-circle in the high-frequency portion represents the charge transfer resistance of the battery, and the slope of the straight line in the low-frequency portion is related to the lithium-ion diffusion rate. Figure 9 It can be seen that the charge transfer impedance of the modified fluorinated carbon is significantly reduced.

[0049] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for combined modification of fluorinated carbon using hybrid plasma and in-situ composite processes, characterized in that, Includes the following steps: Step 1: Place the fluorinated carbon into the tubular furnace chamber of the plasma-enhanced chemical vapor deposition (PECVD) equipment and remove all air and moisture from the tubular furnace chamber; Step 2: Vacuum the cavity and introduce induction gas at a total flow rate of 100-200 ml / min. Maintain the cavity pressure within the range of 20-100 Pa for 15-30 min. Then, start the plasma excitation source and perform plasma treatment at a power of 50-400 W for 5-60 min to obtain carbon-coated fluorinated carbon. The induction gas is acetylene and argon, and the gas ratio is adjusted to 1:

1. Step 3: Disperse the carbon-coated fluorinated carbon in a mixture of ethanol and deionized water, and add potassium permanganate solution (concentration 0.01–0.5 mol / L). The ratio of carbon-coated fluorinated carbon to potassium permanganate is 1 g: 0.001–0.004 mol. React at room temperature for 30–120 min. Finally, after centrifugation and drying, the fluorinated carbon composite cathode material is obtained. The fluorinated carbon composite cathode material is denoted as CF. x / C / MnO2.

2. The method for combined modification of fluorinated carbon by mixed plasma and in-situ composite as described in claim 1, characterized in that, In step 1, the amount of fluorinated carbon used is 1g to 200g.

3. The method for combined modification of fluorinated carbon by mixed plasma and in-situ composite as described in claim 1, characterized in that, In step 1, the specific process of removing all air and moisture from the tubular furnace cavity is as follows: a protective gas is introduced into the furnace at a rate of 50-100 ml / min, and the cavity temperature is heated to 80-120℃ and held for 30-60 minutes.

4. A lithium / carbon fluoride primary battery, comprising: The fluorinated carbon cathode, lithium metal anode, electrolyte, and separator are characterized in that the fluorinated carbon cathode is a fluorinated carbon composite cathode material obtained by the combined modification of fluorinated carbon using the mixed plasma and in-situ composite method described in claim 1.

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