CN115821243A - Method for exciting liquid plasma surface modified metal lithium - Google Patents
Method for exciting liquid plasma surface modified metal lithium Download PDFInfo
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- CN115821243A CN115821243A CN202210439451.XA CN202210439451A CN115821243A CN 115821243 A CN115821243 A CN 115821243A CN 202210439451 A CN202210439451 A CN 202210439451A CN 115821243 A CN115821243 A CN 115821243A
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Abstract
The invention relates to a method for exciting liquid plasma surface modification of metal lithium, and belongs to the technical field of metal lithium material processing. The method comprises the steps of firstly placing metal lithium in a plasma reactor, adding a certain amount of organic solvent to immerse the metal lithium, sealing, starting a direct-current power supply, forming plasma between metal electrodes positioned at two sides of a liquid solvent, providing energy for the reaction between the organic solvent and the metal lithium, and constructing a uniform and compact protective layer on the surface of the metal lithium. The uniform and compact protective layer can isolate the metal lithium from air, so that the corrosion of the air to the metal lithium is prevented, and in addition, through the selection of the types of the liquid solvents, the protective layer which is favorable for the metal lithium to exert the electrochemical performance can be constructed on the surface of the metal lithium, so that the charging and discharging performance of the metal lithium is improved while the air stability is improved. The method is simple to operate, low in cost, rapid and efficient, and has the potential of large-scale production.
Description
Technical Field
The invention relates to a method for exciting liquid plasma surface modification of metal lithium, and belongs to the technical field of metal lithium material processing.
Technical Field
The metal lithium has the advantages of high theoretical specific capacity, low potential, small density, large energy density and the like, so the metal lithium is an ideal negative electrode material for assembling a novel lithium battery. However, in the production and storage processes of metal lithium, once contacting with air, the metal lithium is corroded by the air, reacts with water, oxygen, carbon dioxide and the like in the air, and impurities such as lithium oxide, lithium carbonate, lithium hydroxide and the like are formed on the surface of the metal lithium, and the distribution of the impurities on the surface of the metal lithium is uneven, which further influences the exertion of the electrochemical performance of the metal lithium. Therefore, the poor air stability of the lithium metal is a big problem which hinders the practical application of the lithium metal, and is a key problem to be solved urgently in the field.
The plasma is composed of electrons, ions, and non-ionized neutral particles and has a certain energy. A plasma can be formed between the metal electrode and the liquid anode by a dc power supply to provide energy to the system. In addition, the liquid phase plasma active particles have a stronger permeation effect than the gas phase plasma active particles, and can be more uniformly contacted with the reactant, thereby facilitating uniform occurrence of the reaction. The invention provides a method for modifying metal lithium on the surface of liquid-excited plasma, aiming at the problem of poor air stability of the metal lithium, and the method is characterized in that the plasma formed between metal electrodes on two sides of a liquid solvent is used for providing energy for the reaction between the metal lithium and the liquid solvent, promoting the rapid reaction, forming a uniform and compact protective layer on the surface of the metal lithium, improving the air stability of the metal lithium, and further improving the electrochemical performance of the metal lithium by selecting the type of the liquid solvent.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a method for exciting liquid plasma to modify metal lithium on the surface, which is rapid, efficient, low in cost and simple to operate.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for exciting liquid plasma to modify metallic lithium on the surface comprises the following steps:
s1: placing metallic lithium in a plasma reactor under an inert atmosphere;
s2: adding an organic solvent capable of immersing the metallic lithium, and sealing the plasma reactor;
s3: and generating plasma in the plasma reactor, and reacting for a certain time to obtain the surface modified metal lithium.
Preferably, the metallic lithium in step S1 of the preparation method is in the form of powder, block, strip, or the like, and more preferably, the metallic lithium is at least one of lithium powder, lithium block, lithium ribbon, and lithium sheet.
Preferably, the above-described production method step S1 places metallic lithium in a plasma reactor in a glove box filled with an inert atmosphere.
Preferably, the plasma reactor is sealed after the organic solvent is added in step S2 of the above preparation method.
Preferably, in step S2 of the above preparation method, the organic solvent is at least one of ethylene carbonate, fluoroethylene carbonate, propylene trifluorocarbonate, bis trifluoroethyl carbonate, and the like.
Preferably, in step S3 of the preparation method, by turning on the direct current, electrons between the anode and the cathode of the plasma reactor are subjected to the action of the electric field force to form a plasma; more preferably, the DC power is 10 to 1000W and the reaction time is 10 to 600min.
Preferably, the surface-modified metallic lithium in step S3 is surface-modified by forming a uniform dense protective layer on the surface of the metallic lithium, wherein the uniform dense protective layer is one or more of lithium carbonate, lithium fluoride, lithium oxide, and the like.
Preferably, step S3 of the above preparation process is carried out at room temperature.
Preferably, the inert atmosphere in the present invention is argon.
Preferably, the method specifically comprises the following steps:
s1: placing metallic lithium in a plasma reactor in a glove box filled with an inert atmosphere;
s2: adding a certain amount of organic solvent into the plasma reactor to ensure that the metal lithium is completely immersed in the organic solvent and sealed;
s3: and starting a direct current power supply, adjusting power, closing the direct current power supply after reacting for a certain time, and opening the sealing cover to obtain the modified metal lithium.
The invention provides a simple method for exciting liquid plasma to modify metallic lithium on the surface, which comprises the following steps: firstly, placing metal lithium in a plasma reactor, adding a certain amount of organic solvent, sealing, starting a direct current power supply, forming plasma between metal electrodes positioned at two sides of a liquid solvent, providing energy for the reaction between the organic solvent and the metal lithium, and constructing a uniform and compact protective layer on the surface of the metal lithium. The method is simple to operate, low in cost, rapid and efficient, and has the potential of large-scale production.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the plasma formed between the metal electrodes on the two sides of the liquid solvent provides energy for the reaction of the liquid solvent and the metal lithium, so that the reaction is promoted to be rapidly generated, and a uniform and compact protective layer is constructed on the surface of the metal lithium. The even compact protective layer can be isolated with metal lithium and air to prevent the corrosion of air to metal lithium, in addition, through the kind selection of liquid solvent, can also construct the protective layer that is favorable to its performance electrochemistry on metal lithium surface, improve its charge-discharge performance when improving air stability, reduce its production, storage cost, avoid the production of safety problem simultaneously. The method has the advantages of simple process, simple and convenient operation, rapidness, high efficiency and remarkable economic benefit.
Drawings
FIG. 1 is a graph comparing unmodified lithium metal (left), modified lithium metal of example 1 (middle) and modified lithium metal of comparative example (right) after 5min (top) and 30min (bottom) exposure to air.
FIG. 2 is an SEM image of modified lithium metal of example 1.
FIG. 3 is an XPS plot of modified lithium metal of example 1.
Fig. 4 is a graph comparing cycle performance of a ternary battery assembled using modified lithium metal of example 1, unmodified lithium metal, and modified lithium metal of comparative example, respectively.
Fig. 5 is a graph comparing the cycle performance of a ternary battery assembled using modified lithium metal of example 1, unmodified lithium metal and modified lithium metal of comparative example after exposure to air, respectively.
FIG. 6 is an XPS spectrum of example 2.
Detailed Description
The technical solution of the present invention is further illustrated by the following embodiments and the accompanying drawings, but the scope of the present invention is not limited thereto. The room temperature in the present invention is 15 to 40 ℃ and more preferably 25 to 30 ℃.
Example 1:
a method for exciting liquid plasma to modify metallic lithium on the surface comprises the following steps:
s1: placing a metal lithium sheet with the length of 20mm and the width of 15mm in a glove box filled with argon in a plasma reactor;
s2: adding 20mL of fluoroethylene carbonate into the reactor to completely immerse the metal lithium sheet, and removing the reactor out of the glove box after sealing;
s3: and starting a direct current power supply, adjusting the power to be 50W, closing the direct current power supply after reacting for 300min, and opening a sealing cover to obtain the modified metal lithium with the surface attached with the lithium carbonate and lithium fluoride compact protective layer.
Comparative example:
s1: placing a metal lithium sheet with the length of 20mm and the width of 15mm in a glove box filled with argon into a reactor;
s2: adding 20mL of fluoroethylene carbonate into the reactor to completely immerse the metal lithium sheet, and removing the reactor out of the glove box after sealing;
s3: and opening the sealing cover after the metal lithium in the reactor reacts with the fluoroethylene carbonate for 300min to obtain the modified metal lithium with the lithium carbonate and the lithium fluoride attached to the surface.
FIG. 1 is a graph comparing unmodified lithium metal (left), modified lithium metal of example 1 (middle) and modified lithium metal of comparative example (with) after 5min (top) and 30min (bottom) exposure to air. After 5min of air exposure, the modified metallic lithium of example 1 and the comparative example still maintained metallic luster, while the surface of the unmodified metallic lithium became black; after the air is exposed for 30min, the surfaces of the comparative example modified metal lithium and the unmodified metal lithium are blackened and are completely oxidized and corroded, while the modified metal lithium in the embodiment 1 still keeps the metallic luster, and the air stability of the modified metal lithium is obviously improved.
FIG. 2 is an SEM of modified lithium metal of example 1. It can be seen that the protective layer product is uniformly distributed on the surface of the modified lithium metal of example 1.
FIG. 3 is XPS of modified lithium metal of example 1. As can be seen from the Li 1s spectrum, the modified lithium metal of this example has lithium carbonate and lithium fluoride on the surface. Therefore, it is understood that the modified lithium of this example has a uniform and dense protective layer of lithium carbonate and lithium fluoride attached to the surface.
The modified metal lithium of example 1, the unmodified metal lithium and the modified metal lithium of comparative example were used as a negative electrode, a ternary positive electrode (NCM 811) and an electrolyte (1M LiPF), respectively 6 /(EC + DMC)) were assembled into cells, and fig. 4 is a graph comparing the cycling performance of the three cells. Example 1 modified lithium Metal assembled batteries have a capacity of 180.2mA hr g after 50 cycles -1 The capacity of the battery assembled by unmodified metal lithium after 50 cycles is 175.5mA h g -1 While the comparative example modified lithium metal assembled cell had a capacity of 173.6mA hr g after 50 cycles -1 Example 1 modified lithium metal battery not only overcomes the problem of capacity reduction caused by modification of lithium metal in the prior art, but also enables the battery to exert larger capacity, which exceeds the capacity of battery assembled by unmodified lithium metal.
Fig. 5 is a graph comparing the cycle performance of the ternary batteries assembled with the modified metallic lithium of example 1 and the unmodified metallic lithium and the modified metallic lithium of comparative example, respectively, after being exposed to air for 5 min. Examples1 the capacity of the battery assembled after the modified metal lithium is exposed to air after 50 cycles is 175.9mA h g -1 The lithium ion battery can still stably circulate and exert larger capacity, the circulation performance and the capacity value of the lithium ion battery are not greatly changed compared with the battery without exposed air, the capacity of the battery assembled after the unmodified metal lithium is exposed to the air is quickly attenuated, and only 140.9mA h g of capacity is left after 50 circles of circulation -1 The electrochemical performance is seriously deteriorated, and in addition, the capacity of the assembled battery after the modified metallic lithium of the comparative example is exposed to air is only 154.2mA h g after 50 cycles -1 And the cycle stability is poor, and the electrochemical performance is also seriously deteriorated.
Example 2:
a method for exciting liquid plasma to modify metallic lithium on the surface comprises the following steps:
s1: winding a metal lithium belt into a metal lithium coil in a glove box filled with argon, and then placing the metal lithium coil in a plasma reactor;
s2: adding 30mL of ethylene carbonate into the reactor to completely immerse the metal lithium roll, sealing, and then removing the glove box;
s3: and starting a direct current power supply, adjusting the power to be 10W, closing the direct current power supply after reacting for 600min, and opening a sealing cover to obtain the modified metal lithium with lithium carbonate attached to the surface.
FIG. 6 is an XPS spectrum of example 2. From the Li 1s spectrum, it can be seen that the modified lithium surface of example 2 contains lithium carbonate and lithium, wherein lithium is the metallic lithium itself. From this, it is understood that the modified lithium metal of example 2 has a lithium carbonate protective layer on the surface.
Example 3:
a method for exciting liquid plasma to modify metallic lithium on the surface comprises the following steps:
s1: placing a lithium metal sheet in a plasma reactor in a glove box filled with argon;
s2: adding 40mL of propylene carbonate trifluoride into the reactor to completely immerse the lithium metal powder, sealing, and removing the glove box;
s3: and starting a direct current power supply, adjusting the power to be 1000W, closing the direct current power supply after reacting for 10min, and opening a sealing cover to obtain the modified metal lithium with the surface attached with lithium carbonate and lithium fluoride.
Example 4:
a method for exciting liquid plasma to modify metallic lithium on the surface comprises the following steps:
s1: placing a lithium metal sheet in a plasma reactor in a glove box filled with argon;
s2: adding 50mL of bis (trifluoroethyl carbonate) into the reactor to completely immerse the lithium metal, sealing and then removing the glove box;
s3: and starting a direct current power supply, adjusting the power to 800W, closing the direct current power supply after reacting for 30min, and opening a sealing cover to obtain the modified metal lithium with the lithium carbonate and the lithium fluoride attached to the surface.
The preparation parameters and the performance results for the examples are shown in Table 1.
TABLE 1 preparation parameters and Performance results for the examples
In conclusion, the modified metal lithium obtained by the method can improve the air stability, improve the electrochemical stability of the lithium battery and improve the capacity of the battery; the method has the advantages of simple process, simple and convenient operation, rapidness, high efficiency and remarkable economic benefit.
The above-described embodiments are merely preferred embodiments of the present invention, which is not intended to be limiting in any way, and other variations and modifications are possible without departing from the scope of the invention as set forth in the appended claims.
Claims (9)
1. A method for exciting liquid plasma to modify metallic lithium on the surface is characterized by comprising the following steps:
s1: placing metallic lithium in a plasma reactor under an inert atmosphere;
s2: adding an organic solvent capable of immersing the metallic lithium, and sealing the plasma reactor;
s3: and generating plasma in the plasma reactor, and reacting for a certain time to obtain the surface modified metal lithium.
2. The method for surface modification of metallic lithium by exciting liquid plasma according to claim 1, wherein the metallic lithium in step S1 is at least one of lithium powder, lithium block, lithium ribbon and lithium sheet.
3. The method for exciting liquid plasma to modify the surface of the metallic lithium according to claim 1, wherein the organic solvent in the step S2 is at least one of ethylene carbonate, fluoroethylene carbonate, propylene trifluorocarbonate and bis-trifluoroethyl carbonate.
4. The method for exciting liquid plasma to modify the surface of the metallic lithium according to the claim 1, wherein in the step S3, by turning on a direct current, a plasma is formed in the plasma reactor; the power of the direct current is 10-1000W.
5. The method for exciting liquid plasma to modify the surface of the metallic lithium as claimed in claim 4, wherein the reaction time is 10-600 min.
6. The method for exciting liquid plasma to surface modify the metallic lithium according to claim 1, wherein the surface modified metallic lithium in the step S3 is surface modified by forming a uniform and dense protective layer on the surface of the metallic lithium.
7. The method for exciting liquid plasma to surface modify metallic lithium according to claim 6, wherein the uniform dense protective layer is one or more of lithium carbonate, lithium fluoride and lithium oxide.
8. The method for exciting liquid plasma to surface modify metallic lithium according to claim 1, wherein the inert atmosphere is argon.
9. The method for exciting liquid plasma to surface modify metallic lithium according to claim 1, wherein the step S3 is performed at room temperature.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210439451.XA CN115821243A (en) | 2022-04-25 | 2022-04-25 | Method for exciting liquid plasma surface modified metal lithium |
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| CN202210439451.XA CN115821243A (en) | 2022-04-25 | 2022-04-25 | Method for exciting liquid plasma surface modified metal lithium |
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