Superfine metal lithium powder as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of metal material processing, and discloses superfine metal lithium powder as well as a preparation method and application thereof. The preparation method comprises the following steps: heating metal lithium in a vacuum environment to obtain metal lithium steam; carrying out inert gas injection on the metal lithium steam; and separating and screening the product obtained by blowing to obtain the superfine metal lithium powder. According to the preparation scheme, heating, melting and evaporation are carried out in a vacuum environment, introduction of impurities is avoided, and the purity of the obtained lithium powder is higher; meanwhile, lithium metal is evaporated in a vacuum environment, the needed evaporation temperature is lower, and energy consumption is small. And moreover, the metal lithium does not react with argon, so that other byproducts are not generated, and the yield is higher. The obtained superfine lithium powder has the characteristics of small particle size, high purity, high yield, low cost and the like, can be applied to lithium supplement of a negative electrode of a lithium ion battery, and can improve the initial coulombic efficiency and the energy density of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material processing, and in particular to an ultrafine lithium metal powder and a preparation method and application thereof. Background Art

[0002] Lithium metal is often used as the negative electrode of primary lithium batteries or secondary lithium batteries. -1 The theoretical specific capacity and the lowest electrochemical potential make it the most promising negative electrode material for lithium-ion batteries. However, during the first few cycles of use, a SEI film will form on lithium-ion batteries, which will cause the battery capacity to decay. To solve the above problems, the current method is mainly to supplement the electrode material with lithium through pre-lithiation technology. This method can offset the irreversible lithium loss caused by the formation of the SEI film to increase the total capacity and energy density of the battery.

[0003] Negative electrode lithium replenishment is one of the main directions of pre-lithiation technology. The current lithium replenishment methods mainly include: (1) composite metal lithium strip lithium replenishment; (2) lithium powder lithium replenishment. The specific process of lithium powder replenishment is: directly spreading metal lithium powder on the surface of the negative electrode. The method of lithium powder replenishment is simple and easy, and has a significant effect on improving battery capacity. One of the key factors affecting the pre-lithiation effect is the particle size of lithium powder. The smaller the particle size of lithium powder, the tighter the bond with the negative electrode, and the better the effect on improving battery capacity. Therefore, the preparation of ultrafine lithium powder has become a hot topic in current research.

[0004] At present, the methods for preparing lithium powder mainly include stirring method and atomization method. The stirring method is to put metallic lithium into an inert organic solvent, stir it after melting to disperse it, and obtain metallic lithium powder after cooling. Although the stirring method is convenient to operate and the lithium powder obtained has good particle size uniformity, the waste generated during its preparation and treatment process will cause harm to production personnel, and the lithium powder needs to be processed again after preparation. The atomization method is to melt the metallic lithium, use the pressure of an inert gas such as argon, spray the molten lithium into a mist, and obtain lithium powder after cooling. Although the atomization method is simple to operate and is not easy to produce other pollutants, the controllability of the overall process is low, and the particle size of the lithium powder prepared by atomization is uneven, and lithium powder with small particle size and good uniformity cannot be prepared. Summary of the invention

[0005] The purpose of the present invention is to provide an ultrafine metallic lithium powder and a preparation method and application thereof, so as to solve the problem that the existing method for preparing lithium powder cannot have a uniform particle size of lithium powder products, the solution is safer and does not require further treatment.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing ultrafine metallic lithium powder, comprising the following steps:

[0008] In a vacuum environment, metallic lithium is heated to obtain metallic lithium vapor;

[0009] The metallic lithium vapor is sprayed with an inert gas; the sprayed product is separated and sieved to obtain ultrafine metallic lithium powder.

[0010] Preferably, in the method for preparing the ultrafine metallic lithium powder, the purity of the metallic lithium is ≥99.90%.

[0011] Preferably, in the method for preparing ultrafine lithium metal powder, the vacuum degree of the vacuum environment is ≤1×10 -1 Pa.

[0012] Preferably, in the method for preparing ultrafine metallic lithium powder, the heating temperature is 500-600°C.

[0013] Preferably, in the method for preparing ultrafine metallic lithium powder, the inert gas used in the inert gas blowing includes argon or helium; and the purity of the inert gas used in the inert gas blowing is ≥99.99%.

[0014] Preferably, in the method for preparing ultrafine metallic lithium powder, the gas pressure of the inert gas blowing is ≥3 MPa.

[0015] The present invention also provides ultrafine metal lithium powder prepared by the method for preparing the ultrafine metal lithium powder.

[0016] Preferably, in the ultrafine metal lithium powder, the particle size D of the ultrafine metal lithium powder is 90 ≤30μm.

[0017] The present invention also provides an application of the ultrafine metallic lithium powder in replenishing lithium at the negative electrode of a lithium ion battery.

[0018] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) In the preparation scheme of the present invention, the heating, melting and evaporation are carried out in a vacuum environment, which avoids the introduction of impurities and the obtained lithium powder has a higher purity; at the same time, the evaporation temperature required for evaporating metallic lithium in a vacuum environment is lower and the energy consumption is small. In addition, metallic lithium does not react with argon gas and does not produce other by-products, and its yield is higher.

[0020] (2) The scheme of the present invention is to evaporate the liquid metal lithium melt into a gaseous state, and the gaseous metal lithium is cooled and solidified into a solid powder after being sprayed with an inert gas. The obtained powder has a more uniform size and a smaller particle size. The atomization powder making mainly uses gas to break a larger liquid melt into a smaller liquid melt, and then solidifies to form a solid powder. The size of the broken droplets is uneven. Compared with the lithium powder obtained by the present invention, the powder particle size after the solidification of the droplets obtained by the atomization powder making scheme is larger. Therefore, the ultrafine lithium powder obtained by the present invention has the characteristics of small particle size, high purity, high yield, low cost, etc., and can be used for lithium supplementation of the negative electrode of lithium-ion batteries, which can improve the battery's initial coulomb efficiency and energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0022] Figure 1 A schematic diagram of the process for preparing ultrafine lithium metal powder;

[0023] Figure 2 It is a front structural schematic diagram of the flour making equipment used in the present invention;

[0024] Among them, 1: evaporation chamber, 2: heating and melting device, 3: bell mouth, 4: crucible, 5: induction coil, 6: cyclone separation tower, 7: collection tank. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing ultrafine metallic lithium powder, comprising the following steps:

[0026] In a vacuum environment, metallic lithium is heated to obtain metallic lithium vapor;

[0027] The metallic lithium vapor is sprayed with an inert gas; the sprayed product is separated and sieved to obtain ultrafine metallic lithium powder.

[0028] In the present invention, the purity of the metallic lithium is preferably ≥99.90%.

[0029] In the present invention, the vacuum degree of the vacuum environment is preferably ≤1×10 -1 Pa, preferably ≤3×10 -2 Pa, preferably ≤5×10 -3 Pa.

[0030] In the present invention, the heating temperature is preferably 500 to 600°C, more preferably 500 to 540°C, and even more preferably 520 to 530°C.

[0031] In the present invention, the inert gas used in the inert gas blowing preferably includes argon or helium, and more preferably argon.

[0032] In the present invention, the purity of the inert gas used for the inert gas blowing is preferably ≥ 99.99%, and more preferably ≥ 99.999%.

[0033] In the present invention, the gas pressure of the inert gas blowing is preferably ≥3 MPa, more preferably ≥3.5 MPa, and even more preferably ≥4 MPa.

[0034] In the present invention, the separation is preferably multi-stage cyclone separation.

[0035] In the present invention, the separation conditions are not limited, and any method known to those skilled in the art may be used.

[0036] In the present invention, the powder making equipment used in the method for preparing ultrafine metallic lithium powder preferably comprises an evaporation chamber 1, a cyclone separation tower 6, and a collection tank 7 connected in sequence.

[0037] In the present invention, the evaporation chamber 1 preferably includes: a heating and melting device 2 , a bell mouth 3 , a crucible 4 , and an induction coil 5 .

[0038] In the present invention, the heating and melting device 2 is preferably fixed to the upper part of the inner cavity of the evaporation chamber 1 .

[0039] In the present invention, the heating and melting device 2 is preferably fixed by bolts.

[0040] In the present invention, the bell mouth 3 is preferably placed on the crucible 4 .

[0041] In the present invention, the upper end of the tube body of the bell mouth 3 is preferably bell-mouth-shaped, and the lower end of the tube body is preferably cylindrical.

[0042] In the present invention, the diameter of the lower end of the tube body of the bell mouth 3 is preferably smaller than the diameter of the crucible 4. The purpose is to ensure that the lower end of the tube body of the bell mouth 3 can be placed on the crucible 4.

[0043] In the present invention, the crucible 4 is preferably placed on a bracket fixed to the bottom of the inner cavity of the evaporation chamber 1 .

[0044] In the present invention, the induction coil 5 is spirally wrapped around the outer wall of the crucible 4 .

[0045] In the present invention, the material of the induction coil 5 is preferably copper.

[0046] In the present invention, the front structural schematic diagram of the flour making equipment is as follows Figure 2 shown.

[0047] The invention also provides an ultrafine metallic lithium powder.

[0048] In the present invention, the particle size D of the ultrafine lithium metal powder is 90 It is preferably ≤30 μm, more preferably ≤28 μm, and even more preferably ≤25 μm.

[0049] The present invention also provides an application of ultrafine metallic lithium powder in replenishing lithium at the negative electrode of a lithium ion battery.

[0050] In the present invention, the application method is not limited, and any method known to those skilled in the art may be used.

[0051] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] This embodiment provides a method for preparing ultrafine lithium metal powder, and its flow diagram is as follows: Figure 1 As shown, the following steps are included:

[0054] 3 kg of metallic lithium with a purity of 99.90% was added to a stainless steel crucible and vacuumed to 8 × 10 -2 Pa, heated and evaporated at 500°C, to obtain metallic lithium vapor;

[0055] Argon gas with a purity of 99.99% was introduced, and the valve of the argon gas pipeline was opened. The metallic lithium vapor was cooled and solidified by argon gas injection. The gas pressure of the argon gas injection was 3MPa, and lithium powder was obtained. The lithium powder was subjected to multi-stage cyclone separation in the induced draft fan, and the lithium powder entered the collection tank. The lithium powder in the collection tank was sieved through a vibrating screen to obtain 2.921kg of ultrafine lithium powder with a purity of 99.135% and a particle size of: D 10 =5.492μm, D 50 =14.167μm, D 90 =28.169μm.

[0056] Example 2

[0057] This embodiment provides a method for preparing ultrafine lithium metal powder, comprising the following steps:

[0058] Add 3 kg of metallic lithium with a purity of 99.90% into a stainless steel crucible and evacuate to 3 × 10 -2 Pa, heated and evaporated at 530°C, to obtain metallic lithium vapor;

[0059] Argon gas with a purity of 99.99% was introduced, and the valve of the argon gas pipeline was opened. The metallic lithium vapor was cooled and solidified by argon gas injection. The gas pressure of the argon gas injection was 4MPa, and lithium powder was obtained. The lithium powder was subjected to multi-stage cyclone separation in the induced draft fan, and the lithium powder entered the collection tank. The lithium powder in the collection tank was sieved through a vibrating screen to obtain 2.917kg of ultrafine lithium powder, with a purity of 99.296% and a particle size of: D 10 =4.954μm, D 50 =18.523μm, D 90 =29.590μm.

[0060] Example 3

[0061] This embodiment provides a method for preparing ultrafine metallic lithium powder, comprising the following steps:

[0062] 5 kg of metallic lithium with a purity of 99.90% was added to a stainless steel crucible and vacuumed to 8 × 10 -3 Pa, heated and evaporated at 520°C, to obtain metallic lithium vapor;

[0063] Argon gas with a purity of 99.99% was introduced, and the valve of the argon gas pipeline was opened. The metallic lithium vapor was cooled and solidified by argon gas injection. The gas pressure of the argon gas injection was 3MPa, and lithium powder was obtained. The lithium powder was subjected to multi-stage cyclone separation in the induced draft fan, and the lithium powder entered the collection tank. The lithium powder in the collection tank was sieved through a vibrating screen to obtain 4.862kg of ultrafine lithium powder with a purity of 99.315% and a particle size of: D 10 =5.739μm, D 50 =16.937μm, D 90 =27.523μm.

[0064] Example 4

[0065] This embodiment provides a method for preparing ultrafine metallic lithium powder, comprising the following steps:

[0066] Add 3 kg of metallic lithium with a purity of 99.90% into a stainless steel crucible and evacuate to 5 × 10 -3 Pa, heated and evaporated at 540°C, to obtain metallic lithium vapor;

[0067] Argon gas with a purity of 99.99% was introduced, and the valve of the argon gas pipeline was opened. The metallic lithium vapor was cooled and solidified by argon gas injection. The gas pressure of the argon gas injection was 4MPa, and lithium powder was obtained. The lithium powder was subjected to multi-stage cyclone separation in the induced draft fan, and the lithium powder entered the collection tank. The lithium powder in the collection tank was sieved through a vibrating screen to obtain 2.918kg of ultrafine lithium powder with a purity of 99.362% and a particle size of: D 10 =4.168μm, D 50 =15.934μm, D90 =29.185μm.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing lithium metal powder by atomization, comprising the following steps:

[0070] Add 5 kg of metallic lithium with a purity of 99.90% into a stainless steel crucible and evacuate to 3 × 10 -2 Pa, heated at 350 ° C for 60 min to obtain completely molten metallic lithium liquid;

[0071] The nozzle angle of the spray plate was adjusted to 45°, and argon gas with a purity of 99.99% was introduced at a pressure of 5 MPa. The valve of the guide nozzle was opened, and the metal blocking rod at the bottom of the stainless steel crucible was lifted to allow the metallic lithium liquid to flow into the spray plate through the guide nozzle at 250°C, and then the metallic lithium liquid was broken and atomized by argon spraying to obtain metallic lithium droplets;

[0072] The metallic lithium droplets were passed into a cooling chamber whose cooling medium was cosmetic grade white oil and cooled to 23°C to obtain metallic lithium powder; the metallic lithium powder was cyclone separated in an induced draft fan and then entered a collecting tank, and the metallic lithium powder in the collecting tank was sieved through a vibrating screen to obtain 4.896 kg of lithium powder product with a purity of 97.689% and a particle size of: D 10 =24.584μm, D 50 =66.194μm, D 90 =134.558μm.

[0073] Comparative Example 2

[0074] This comparative example provides a method for preparing lithium metal powder by atomization, comprising the following steps:

[0075] Add 5 kg of metallic lithium with a purity of 99.90% into a stainless steel crucible and evacuate to 5 × 10 -2 Pa, heated at 400 °C for 60 min to obtain completely molten metallic lithium liquid;

[0076] The nozzle angle of the spray plate was adjusted to 45°, and argon gas with a purity of 99.99% was introduced at a pressure of 5 MPa. The valve of the guide nozzle was opened, and the metal blocking rod at the bottom of the stainless steel crucible was lifted to allow the metallic lithium liquid to flow into the spray plate through the guide nozzle at 250°C, and then the metallic lithium liquid was broken and atomized by argon spraying to obtain metallic lithium droplets;

[0077] The metallic lithium droplets were passed into a cooling chamber whose cooling medium was cosmetic grade white oil and cooled to 25°C to obtain metallic lithium powder; the metallic lithium powder was cyclone separated in an induced draft fan and then entered a collecting tank, and the metallic lithium powder in the collecting tank was sieved through a vibrating screen to obtain 4.779 kg of lithium powder product with a purity of 98.035% and a particle size of: D 10=27.631μm, D 50 =70.072μm, D 90 =145.224μm.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing lithium metal powder by atomization, comprising the following steps:

[0080] Add 10 kg of metallic lithium with a purity of 99.90% into a stainless steel crucible and evacuate to 5 × 10 -2 Pa, heated at 400 °C for 60 min to obtain completely molten metallic lithium liquid;

[0081] The nozzle angle of the spray plate was adjusted to 45°, argon gas with a purity of 99.99% was introduced at a pressure of 3 MPa, the guide nozzle valve was opened, and the metal blocking rod at the bottom of the stainless steel crucible was lifted to allow the metallic lithium liquid to flow into the spray plate through the guide nozzle at 250°C, and then the metallic lithium liquid was broken and atomized by argon spraying to obtain metallic lithium droplets;

[0082] The metallic lithium droplets were passed into a cooling chamber whose cooling medium was cosmetic grade white oil and cooled to 25°C to obtain metallic lithium powder; the metallic lithium powder was cyclone separated in an induced draft fan and then entered a collecting tank, and the metallic lithium powder in the collecting tank was sieved through a vibrating screen to obtain 9.632 kg of lithium powder product with a purity of 97.186% and a particle size of: D 10 =31.435μm, D 50 =82.274μm, D 90 =163.744μm.

[0083] By comparison, it can be known that compared with the atomization method, the ultrafine lithium powder prepared by the preparation scheme of the present invention has the characteristics of small particle size, high purity, high yield and low cost, and is more suitable for negative electrode lithium supplementation. The main principle of negative electrode lithium supplementation is to supplement metallic lithium at the negative terminal to make up for the loss of lithium during the first charge and discharge of the battery. Theoretically, the smaller the size of the lithium powder, the smaller the interval between the powders after the powder is spread on the negative electrode sheet, the denser the powder adheres to the negative electrode surface, and the surface area of ​​the negative electrode sheet in contact with lithium per unit area is larger, that is, the available lithium content per unit area is higher. Therefore, compared with lithium powder with large-sized particles, the smaller the particle size of the lithium powder, the better the effect of lithium supplementation.

[0084] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine lithium metal powder, characterized in that: The following steps are involved: In a vacuum environment, metallic lithium is heated to obtain metallic lithium vapor; The metallic lithium vapor is sprayed with an inert gas; the sprayed product is separated and sieved to obtain ultrafine metallic lithium powder.

2. The method for preparing ultrafine lithium metal powder according to claim 1, characterized in that: The purity of the metallic lithium is ≥99.90%.

3. The method for preparing ultrafine lithium metal powder according to claim 1 or 2, characterized in that: The vacuum degree of the vacuum environment is ≤1×10 -1 Pa.

4. The method for preparing ultrafine lithium metal powder according to claim 3, characterized in that: The heating temperature is 500-600°C.

5. The method for preparing ultrafine lithium metal powder according to claim 1, characterized in that: The inert gas used in the inert gas blowing includes argon or helium; the purity of the inert gas used in the inert gas blowing is ≥99.99%.

6. The method for preparing ultrafine lithium metal powder according to claim 1 or 5, characterized in that: The gas pressure of the inert gas blowing is ≥3MPa.

7. Ultrafine lithium metal powder obtained by the method for preparing ultrafine lithium metal powder according to any one of claims 1 to 6.

8. The ultrafine lithium metal powder according to claim 7, characterized in that: The particle size D of the ultrafine lithium metal powder 90 ≤30μm.

9. Use of the ultrafine metallic lithium powder according to claim 7 or 8 in replenishing lithium at the negative electrode of a lithium ion battery.

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