CN113059167A - Preparation method of passivated lithium microspheres and device and application thereof - Google Patents
Preparation method of passivated lithium microspheres and device and application thereof Download PDFInfo
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Abstract
The invention provides a preparation method of passivated lithium microspheres and a device and application thereof. The preparation method of the passivated lithium microspheres provided by the invention comprises the following steps: 1) dispersing the molten metal lithium jet flow by using a fluid vibrating nozzle to obtain metal lithium liquid drops; 2) applying static electricity to the metal lithium droplets to obtain metal lithium microspheres; 3) and (3) placing the metal lithium microspheres in a passivation solution, and stirring to obtain the passivated lithium microspheres. According to the preparation method, the microcapsule granulation technology is adopted, the superimposed vibration principle and the specific passivation process are utilized, and the passivated lithium microspheres with small size, adjustable size, narrow particle size distribution, adjustable composition and thickness of the passivation layer and high coating rate can be prepared.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a preparation method of passivated lithium microspheres and a device and application thereof.
Background
Lithium ion batteries have the advantages of high voltage, high specific energy, good safety performance, and the like, and have been widely used in portable electronic products and electric vehicles. With the rapid development of new energy automobiles, smart grids and distributed energy storage, higher requirements are put forward on the energy density of new energy devices, and high-capacity electrode materials are urgently needed to be researched. The negative electrode of the current commercial lithium ion battery is mainly made of graphite and silicon carbon materials. However, the potentials of the graphite and the silicon-carbon material are outside the electrolyte voltage stabilizing window, and the electrolyte is reduced to generate a Solid Electrolyte Interface (SEI) on the surface of the negative electrode during charging, wherein the SEI is composed of lithium oxide, lithium fluoride, an organic lithium salt compound and the like, and consumes lithium ions of the positive electrode, so that active lithium ions of the positive electrode are lost (7-15 wt%), and the initial cycle coulomb efficiency is low. The increasing thickness of the SEI film also results in irreversible loss of lithium ions, permanently consuming a large amount of lithium from the positive electrode, and reducing the capacity and energy density of the lithium ion battery.
The prelithiation technology is an effective method for reducing irreversible capacity loss and improving coulombic efficiency, and lithium is supplemented to an electrode material through prelithiation to offset the irreversible lithium loss caused by the formation of an SEI film so as to improve the total capacity and energy density of a battery. Researchers increase the addition amount of the anode material, use the prelithiation additive, adopt the electrochemical prelithiation, adopt the contact short circuit and other ways to prelithiate the electrode, can compensate the irreversible capacity loss of the first cycle to a certain extent, wherein the chemical lithium supplement taking the lithium powder as the lithium supplement agent does not need extra preassembling and disassembling process, has high compatibility with the lithium ion battery assembly process flow, and is a very effective lithium supplement means. However, the lithium metal powder has high activity and is difficult to use directly, and it is necessary to produce a stable lithium metal powder particle, in which the inner layer of the particle is lithium metal and the outer layer is a protective layer having good lithium ion conductivity and electron conductivity. In the prelithiation process, the prelithiated negative electrode sheet may be obtained by mixing passivated lithium powder into the battery slurry or dispersing the passivated lithium powder in an organic solvent, then coating or spraying the dispersion on the negative electrode sheet, and then drying the residual organic solvent on the negative electrode sheet. During formation, lithium powder on the negative electrode is consumed in the formation of an SEI film, so that lithium ions deintercalated from the positive electrode are retained to the maximum extent, and the first cycle efficiency and the capacity of the lithium ion battery are improved.
At present, a method for preparing passivated lithium powder mainly adopts a strong mechanical shearing micro-emulsification method reported by FMC company, specifically, an inert high-boiling-point organic solvent is used as a protective solvent, metal lithium is melted at a higher temperature, the melted metal lithium is micro-emulsified through high shearing force generated by high-speed stirring, and a passivation additive is added to obtain passivated lithium powder.
The spray drying method is also a common method for preparing passivated lithium powder, and the method adopts a dry lithium melting tank to melt solid metal lithium into liquid metal lithium, atomizes the liquid metal lithium into fine metal lithium droplets in the dry passivation tank to enable the fine metal lithium droplets to fall in a dispersing manner, meets cooling passivation air flow in the falling process, is cooled and solidified into metal lithium microspheres, reacts with a passivating agent to form a passivation film on the surfaces of the metal lithium microspheres, and obtains passivated metal lithium microspheres.
Disclosure of Invention
The invention provides a preparation method of passivated lithium microspheres, which can prepare passivated lithium microspheres with small size, adjustable size, narrow particle size distribution, adjustable composition and thickness of a passivation layer and high coating rate by adopting a microcapsule granulation technology and a superposition vibration principle of a fluid vibration nozzle and a specific passivation process.
The invention also provides a passivated lithium microsphere which is prepared by the preparation method, on one hand, the passivated lithium microsphere has the advantages of small size and narrow particle size distribution, is easy to disperse in lithium supplement slurry, and is beneficial to obtaining a compact and uniform lithium supplement layer, on the other hand, the passivated lithium microsphere has the advantage of high coating rate, and the passivation layer can completely coat the internal lithium metal, so that the lithium metal is not influenced by moisture and oxidizing gas in the air, and can be stably stored in the air for a long time.
The invention also provides a preparation device of the passivated lithium microspheres, which is simple and easy to operate, can realize continuous production of the passivated lithium microspheres, and is beneficial to industrial production and application of the passivated lithium microspheres.
The invention also provides a negative plate, wherein the lithium supplement layer of the negative plate comprises the passivated lithium microspheres prepared by the invention, and the negative plate can slowly release metallic lithium when being applied to a lithium ion battery, so that irreversible lithium loss caused by an SEI (solid electrolyte interphase) film formed on the surface of the negative electrode is effectively counteracted.
The invention also provides a lithium ion battery which comprises the negative plate and has the advantages of high first-time charge and discharge efficiency (first effect), high discharge capacity and good cycle performance.
The invention provides a preparation method of passivated lithium microspheres in a first aspect, which comprises the following steps:
1) dispersing the molten metal lithium jet flow by using a fluid vibrating nozzle to obtain metal lithium liquid drops;
2) applying static electricity to the metal lithium droplets to obtain metal lithium microspheres;
3) and (3) placing the metal lithium microspheres in a passivation solution, and stirring to obtain the passivated lithium microspheres.
The invention adopts microcapsule granulation technology to prepare the passivated lithium microsphere with a core-shell structure, wherein the core is the metallic lithium microsphere, and the shell is a passivation layer coated on the surface of the metallic lithium microsphere. Firstly, dispersing molten metal lithium jet flow through a fluid vibration nozzle, wherein the fluid vibration nozzle can vibrate and break the molten metal lithium jet flow flowing in a laminar flow manner through a superimposed vibration principle to disperse the molten metal lithium jet flow into metal lithium droplets with uniform particle size, and the fluid vibration nozzle with smaller nozzle diameter can be selected to obtain the metal lithium microspheres with smaller size; secondly, in order to avoid the agglomeration phenomenon of the metallic lithium droplets, static electricity can be applied to the metallic lithium droplets to disperse the metallic lithium droplets to obtain metallic lithium microspheres; and finally, placing the metal lithium microspheres in a passivation solution, stirring to form a passivation coating layer on the surfaces of the metal lithium microspheres, and specifically, obtaining the passivation lithium microspheres with high coating rate, adjustable thickness of the passivation layer and uniform particle size by adjusting the stirring speed and the concentration of the passivation solution.
In order to enable the molten metal lithium to be more convenient to transport and use, a lithium melting tank can be used for heating a solid metal lithium ingot to a molten state, then the solid metal lithium ingot is conveyed to a fluid vibration nozzle in a mode of air pressure pumping of the liquid lithium, the temperature of the vibration nozzle is heated and kept at 300 ℃ all the time, and the metal lithium is kept in a molten state all the time.
In a specific embodiment, when the flow rate of the molten metal lithium entering the fluid vibrating nozzle is set to be 5-50mL/min, the molten metal lithium can be ensured to be smoothly sprayed out after passing through the nozzle through vibration.
The particle size of the lithium metal microspheres can be controlled by controlling the nozzle diameter of the fluid vibrating nozzle. For example, when the diameter of the nozzle is controlled to be 0.01 to 0.15mm, metallic lithium microspheres having a uniform particle diameter and a distribution range of 5 to 150 μm can be prepared.
The number of the generated metal lithium liquid drops can be controlled by controlling the vibration frequency of the fluid vibration nozzle, when the vibration frequency of the fluid vibration nozzle is set to be 40-6000Hz, 40-6000 metal lithium liquid drops can be generated per second, and the specific vibration frequency can be selected according to different required metal lithium microsphere numbers.
In order to prevent the lithium droplets from reacting with active components in the air at high temperatures, the metallic lithium droplets are controlled to be dispersed in an inert atmosphere, such as argon.
Further, the electrostatic application of the lithium metal droplets in the step 2) can be realized through the electrode control unit, and after the electrostatic application is finished, the lithium metal droplets are cooled to 40-150 ℃, so that the lithium metal droplets are gradually solidified to form a solid before entering the passivation solution, and the coating treatment in the passivation solvent is better. The cooling may be achieved by controlling the temperature inside the dispersion chamber, for example, when the temperature of the dispersion chamber is set to 60 ℃, the lithium metal droplets may be cooled to 60 ℃.
The passivating agent used in the present invention may be selected from at least one of natural polymers and synthetic polymers, specifically, the natural polymers may be selected from gelatin, carrageenan, agar, agarose, chitosan, cellulose, whey protein, collagen, and latex, and the synthetic polymers may be selected from polyurethane, polymethyl methacrylate, polyethylene terephthalate, epoxy resin, polystyrene, polycarbonate, polyimide, polyether ether ketone, and polybenzimidazole. Different passivating solvents can be selected according to different required dispersion systems or use characteristics to specifically coat the lithium metal microspheres.
Further, in the step 3), the stirring speed is 350-1500 rpm; and/or the concentration of the passivation solution is 0.1-2mol/L, the passivation layer with high coating rate and uniform coating can be obtained by adopting the stirring speed and the concentration of the passivation solution, and the stirring speed and the concentration of the passivation solution can be adjusted within the range according to the difference of the thickness of the required passivation layer.
And after the passivation is finished, obtaining a passivated lithium microsphere solution, wherein the obtained passivated lithium microsphere solution can be directly coated on a negative electrode active material layer as a lithium supplement slurry to form a lithium supplement layer, or the passivated lithium microsphere solution can be collected and dried, a rotary evaporator or a freeze drying mode can be selected for drying, and the powdered passivated lithium microsphere solid can be obtained after drying.
In a second aspect, the invention provides a passivated lithium microsphere obtained by the preparation method provided in the first aspect. The passivated lithium microsphere provided by the invention has a core-shell structure with a passivating layer coated on the surface of metallic lithium, has the advantages of small size and narrow particle size distribution, is easy to disperse in lithium supplement slurry, and is beneficial to obtaining a compact and uniform lithium supplement layer, and has the advantage of high coating rate.
Furthermore, the diameter of a vibrating nozzle and a passivation process in the preparation process of the passivated lithium microspheres can be controlled, the passivated lithium microspheres with the particle size of 5-40 mu m are prepared, the particle size range distribution is extremely narrow, the size of the passivated lithium microspheres is extremely small, and the passivated lithium microspheres have a better lithium supplementing effect when applied to lithium ion batteries.
In a third aspect, the present invention provides an apparatus for preparing passivated lithium microspheres, the apparatus comprising: the device comprises a fluid vibrating nozzle and an electrode control unit, wherein the jet direction of the fluid vibrating nozzle faces the electrode control unit.
Fig. 1 is a schematic structural diagram of a passivated lithium microsphere preparation apparatus according to an embodiment of the present invention, and as shown in fig. 1, the preparation apparatus includes a lithium melting tank 1, a fluid vibrating nozzle 2, an electrode control unit 3, a dispersion bin 4, a passivation tank 5, and a collection tank 6.
The lithium melting tank 1 is connected with the fluid vibrating nozzle 2 through a conveying pipeline, the conveying pipeline is provided with a heat insulation structure, molten metal lithium can be kept in a liquid state in the conveying process, and an integrated heater is also arranged in the fluid vibrating nozzle 2 and can be heated to 300 ℃, so that the heat insulation requirement of the molten metal lithium is met; an electrode control unit 3 is arranged below the fluid vibration nozzle 2, and can control the static electrification of the metal lithium droplets coming out of the fluid vibration nozzle 2 to avoid agglomeration; then, after passing through the electrode control unit 3, the metallic lithium droplets are further dispersed in a dispersion bin 4, and the temperature in the dispersion bin can be set to be 40-150 ℃, so that the metallic lithium liquid is gradually solidified into solid metallic lithium microspheres in the falling process of the dispersion bin 4; a passivation pool 5 is arranged below the dispersion bin, and a stirring paddle is arranged at the bottom of the passivation pool, so that the metal lithium microspheres falling into the passivation pool can be uniformly dispersed in the passivation solution, and the uniformly coated passivation lithium microsphere solution is obtained; the passivation pool 5 and the collection tank 6 are connected with a conveying pipeline, the passivation lithium microsphere solution can enter the collection tank 6 through the conveying pipeline, and the metal lithium microsphere solution in the collection tank 6 can be directly used or further dried into solid powdery passivation lithium microspheres for storage.
The preparation device of the passivated lithium microspheres provided by the invention is simple and easy to operate, can realize continuous production of the passivated lithium microspheres, and has important industrial application value.
The invention provides a negative plate, which comprises a negative current collector, a negative active material layer and a lithium supplement layer which are arranged in a stacked manner, wherein the material of the lithium supplement layer comprises the passivated lithium microspheres provided by the second aspect of the invention. The negative plate is applied to a lithium ion battery, and the passivated lithium microspheres in the lithium supplement layer can slowly release metallic lithium, so that irreversible lithium loss caused by an SEI (solid electrolyte interphase) film formed on the surface of the negative electrode is effectively counteracted.
The fifth aspect of the invention provides a lithium ion battery, which comprises the negative electrode sheet provided by the third aspect of the invention. The lithium ion battery can well replenish lost active lithium in the charging and discharging process, so the lithium ion battery has the advantages of high first-time charging and discharging efficiency, high discharging capacity and good cycling stability.
Compared with the prior art, the invention at least has the following beneficial effects:
1. the preparation method of the passivated lithium microspheres adopts a microcapsule granulation technology, and can prepare the passivated lithium microspheres with small size, adjustable size, narrow particle size distribution, adjustable composition and thickness of the passivation layer and high coating rate by the superposition vibration principle of the fluid vibration nozzle and the control of the passivation process.
2. The passivated lithium microsphere provided by the invention has the advantages of small size and narrow particle size distribution, is easy to disperse in lithium supplement slurry, and is beneficial to obtaining a compact and uniform lithium supplement layer, and has the advantage of high coating rate.
3. The preparation device of the passivated lithium microspheres provided by the invention can realize continuous production of the passivated lithium microspheres and is beneficial to industrial production and application of the passivated lithium microspheres.
4. When the negative plate provided by the invention is applied to a lithium ion battery, the passivated lithium microspheres in the lithium supplement layer can slowly release metallic lithium, and irreversible lithium loss caused by an SEI (solid electrolyte interphase) film formed on the surface of the negative electrode is effectively counteracted.
5. The lithium ion battery provided by the invention has the advantages of high first efficiency, high discharge capacity and good cycle performance.
Drawings
FIG. 1 is a schematic structural diagram of a passivated lithium microsphere preparation apparatus according to an embodiment of the invention;
FIG. 2 is a scanning electron micrograph of passivated lithium microspheres according to example 1 of the present invention;
FIG. 3 is a graph showing the capacity fade of the passivated lithium microspheres of example 1 and comparative example 1 of the present invention after storage in a dry environment (temperature 22 ℃ C., humidity < 5%) for various periods of time.
Description of reference numerals:
1: a lithium melting tank;
2: a fluid vibrating nozzle;
3: an electrode control unit;
4: a dispersion bin;
5: a passivation pool;
6. and (4) a collection tank.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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
This example, using the apparatus of fig. 1, was used to prepare passivated lithium microspheres comprising the following steps:
1) a metallic lithium ingot with a purity of more than 99.9 percent is heated to a molten state at 260 ℃ in a stainless steel lithium melting tank 1 under the protection of inert gas.
2) The molten lithium metal is delivered to the fluid vibrating nozzle 2 by pneumatic pumping, the delivery flow rate is 25mL/min, and the diameter of the fluid vibrating nozzle is 0.04 mm.
3) The laminar-flow lithium metal jet is dispersed into lithium metal droplets by superimposed vibration at the fluid vibrating nozzle 2, with the vibration frequency set at 2000 Hz.
4) The metallic lithium liquid drops enter the electrode control unit 3 and are charged with static electricity, and are gradually solidified into metallic lithium microspheres in the dispersion bin 4 filled with argon, and the temperature of the dispersion bin 4 is set to be 60 ℃.
5) And the metal lithium microspheres fall into a passivation tank 5, are continuously stirred with the chitosan propylene carbonate solution in the passivation tank, are rapidly cooled and quickly coated on the surfaces of the metal lithium microspheres to form a passivation layer, so that a passivated lithium microsphere solution is obtained, the stirring speed is set to be 800rpm, and the concentration of the chitosan propylene carbonate solution is 0.5 mol/L.
6) The passivated lithium microsphere solution was transferred to a collection tank 6 and freeze dried to obtain solid powdered passivated lithium microspheres, labeled a 1.
The passivated lithium microspheres obtained in example 1 are characterized by using a scanning electron microscope, and fig. 2 is a scanning electron microscope image of the passivated lithium microspheres obtained in example 1 of the invention, and as shown in fig. 2, the particles of the passivated lithium microspheres are round and smooth, and the particle size is 15-30 μm.
Example 2
This example, using the apparatus of fig. 1, was used to prepare passivated lithium microspheres comprising the following steps:
1) a metallic lithium ingot with a purity of more than 99.9 percent is heated to a molten state at 260 ℃ in a stainless steel lithium melting tank 1 under the protection of inert gas.
2) The molten lithium metal is delivered to the fluid vibrating nozzle 2 by pneumatic pumping, the delivery flow rate is 10mL/min, and the diameter of the fluid vibrating nozzle is 0.15 mm.
3) The laminar flowing lithium metal jet is dispersed into lithium metal droplets by superimposed vibration at the fluid vibrating nozzle 2, with the vibration frequency set at 4000 Hz.
4) The metallic lithium liquid drops enter the electrode control unit 3 and are charged with static electricity, and are gradually solidified into metallic lithium microspheres in the dispersion bin 4 filled with argon, and the temperature of the dispersion bin 4 is set to be 80 ℃.
5) And the metal lithium microspheres fall into a passivation tank 5, are continuously stirred with a chitosan dimethylformamide solution in the passivation tank, are rapidly cooled and quickly coated on the surfaces of the metal lithium microspheres to form a passivation layer, so that a passivated lithium microsphere solution is obtained, the stirring speed is set to 1200rpm, and the concentration of the chitosan dimethylformamide solution is 1.0 mol/L.
6) The passivated lithium microsphere solution was transferred to a collection tank 6 and freeze dried to obtain solid powdered passivated lithium microspheres, labeled a 2.
Example 3
This example, using the apparatus of fig. 1, was used to prepare passivated lithium microspheres comprising the following steps:
1) a metallic lithium ingot with a purity of more than 99.9 percent is heated to a molten state at 260 ℃ in a stainless steel lithium melting tank 1 under the protection of inert gas.
2) The molten lithium metal is delivered to the fluid vibrating nozzle 2 by pneumatic pumping, the delivery flow rate is 30mL/min, and the diameter of the fluid vibrating nozzle is 0.06 mm.
3) The laminar flowing lithium metal jet is dispersed into lithium metal droplets at the fluid vibrating nozzle 2 by superimposed vibration, with the vibration frequency set at 1500 Hz.
4) The metallic lithium liquid drops enter the electrode control unit 3 and are charged with static electricity, and are gradually solidified into metallic lithium microspheres in the dispersion bin 4 filled with argon, and the temperature of the dispersion bin 4 is set to be 50 ℃.
5) And the metal lithium microspheres fall into a passivation tank 5, are continuously stirred with the polymethyl methacrylate dimethyl sulfoxide solution in the passivation tank, are rapidly cooled and quickly coated on the surfaces of the metal lithium microspheres to form a passivation layer, so that a passivated lithium microsphere solution is obtained, the stirring speed is set to be 500rpm, and the concentration of the polymethyl methacrylate dimethyl sulfoxide solution is 1.2 mol/L.
6) The passivated lithium microsphere solution was transferred to a collection tank 6 and by rotary evaporation solid powdered passivated lithium microspheres, labeled a3, were obtained.
Example 4
This example, using the apparatus of fig. 1, was used to prepare passivated lithium microspheres comprising the following steps:
1) a metallic lithium ingot with a purity of more than 99.9 percent is heated to a molten state at 260 ℃ in a stainless steel lithium melting tank 1 under the protection of inert gas.
2) The molten lithium metal is delivered to the fluid vibrating nozzle 2 by pneumatic pumping, the delivery flow rate is 35mL/min, and the diameter of the fluid vibrating nozzle is 0.08 mm.
3) The laminar flowing lithium metal jet is dispersed into lithium metal droplets by superimposed vibration at the fluid vibrating nozzle 2, with the vibration frequency set at 1000 Hz.
4) The metallic lithium liquid drops enter the electrode control unit 3 and are charged with static electricity, and are gradually solidified into metallic lithium microspheres in the dispersion bin 4 filled with argon, and the temperature of the dispersion bin 4 is set to be 50 ℃.
5) And (3) the metal lithium microspheres fall into a passivation tank 5, are continuously stirred with the polystyrene acetone solution in the passivation tank, are rapidly cooled and quickly coated on the surfaces of the metal lithium microspheres to form a passivation layer, so that a passivated lithium microsphere solution is obtained, the stirring speed is set to be 800rpm, and the concentration of the polystyrene acetone solution is 1.5 mol/L.
6) The passivated lithium microsphere solution was transferred to a collection tank 6 and by rotary evaporation solid powdered passivated lithium microspheres, labeled a4, were obtained.
Comparative example 1
The comparative example, in which the apparatus of fig. 1 was used to prepare passivated lithium microspheres and the fluid vibrating nozzle was replaced with a common atomizing apparatus, included the following steps:
1) a metallic lithium ingot with a purity of more than 99.9 percent is heated to a molten state at 260 ℃ in a stainless steel lithium melting tank 1 under the protection of inert gas.
2) Molten lithium metal is conveyed to the position of the pneumatic dropping nozzle 2 through pneumatic pumping, the conveying flow rate is 25mL/min, and the diameter of the pneumatic dropping nozzle is 0.04 mm.
3) And (3) dispersing the laminar-flow lithium metal jet into lithium metal liquid drops at the fluid vibrating nozzle 2 through air flow atomization, wherein the air flow rate is set to be 80L/min.
4) The metallic lithium liquid drops enter the electrode control unit 3 and are charged with static electricity, and are gradually solidified into metallic lithium microspheres in the dispersion bin 4 filled with argon, and the temperature of the dispersion bin 4 is set to be 60 ℃.
5) And the metal lithium microspheres fall into a passivation tank 5, are continuously stirred with the chitosan propylene carbonate solution in the passivation tank, are rapidly cooled and quickly coated on the surfaces of the metal lithium microspheres to form a passivation layer, so that a passivated lithium microsphere solution is obtained, the stirring speed is set to be 800rpm, and the concentration of the chitosan propylene carbonate solution is 0.5 mol/L.
6) The passivated lithium microsphere solution was transferred to a collection tank 6 and freeze dried to obtain solid powdered passivated lithium microspheres, labeled a 5.
Preparation example:
1. preparation of negative plate
SiOC500 is taken as a negative electrode, the passivated lithium microspheres A1-A5 are prepared into slurry and coated on a negative electrode sheet, and the coating surface density is 2g/m2And after drying and rolling, the pre-lithium negative plate is marked as N1-N5.
2. Preparation of lithium ion battery
Using NCM811 as a positive electrode, respectively matching with negative electrode sheets of N1-N5, performing single-layer lamination, assembling a soft package full cell, wherein the diaphragm uses a single-side ceramic coating diaphragm, and the electrolyte is lithium hexafluorophosphate (LiPF)6): ethylene Carbonate (EC): diethyl carbonate (DEC): polypropylene (PP) ═ 1: 1.78: 3.57: and 1.4, standing for 72 hours after liquid injection, and forming to obtain the lithium ion battery C1-C5.
Test examples
1. Particle size and thickness testing
Testing the particle size and the thickness of the passivation layer of the passivated lithium microspheres A1-A5, and testing the particle size by adopting a particle size analyzer; and testing the thickness of the passivation layer by adopting a transmission electron microscope. The test results are shown in table 1.
2. Effective metallic lithium and specific capacity testing
The test method comprises the following steps: respectively paving the passivated lithium microspheres prepared in example 1 and comparative example 1 in a culture dish, standing in a drying room with the humidity of less than 5%, uniformly mixing 20mg of the passivated lithium microsphere powder of example 1 and comparative example 1 with carbon black and polyvinylidene fluoride in N-methyl pyrrolidone according to the ratio of 7:2:1 at different standing time points to prepare lithium powder electrode slurry, coating the electrode slurry on copper foil by scraping, drying, cutting, weighing to prepare a lithium powder electrode, assembling a button cell by taking a smooth copper foil as a counter electrode, and using electrolyte as mixed solution of ethylene carbonate and dimethyl carbonate (EC: DMC ═ 1:1) containing 1M LiPF 6; and standing for 10 hours, carrying out constant current charging at 0.05 ℃ with the cut-off voltage of 2V, testing and recording the charging capacity, and calculating the effective gram capacity of the passivated lithium microspheres according to the mass of the lithium powder deposited on the smooth copper foil. And drawing a graph of the capacity fading change condition of the passivating agent microspheres after standing for different times according to the calculated effective gram capacity of the passivating agent microspheres after different standing times.
Fig. 3 is a graph showing the capacity fading change of the passivated lithium microspheres of example 1 and comparative example 1 after being stored in a dry environment (temperature 22 ℃, humidity < 5%) for different times, as shown in fig. 3, compared with comparative example 1, the passivated lithium microspheres prepared in example 1 have lower capacity loss after being stored in dry air for a long time, which shows that the passivated lithium microspheres prepared by the preparation method of the present invention have better lithium utilization rate and stability.
3. First Effect test
The first-effect test is carried out on the lithium ion battery C1-C5, and the test method comprises the following steps: charging an unformed lithium ion battery to 4.25V at constant current of 0.2C, then charging at constant voltage until the current is reduced to 0.02C, standing for 5min, discharging the battery to 2.5V at constant current of 0.2C, recording the first charging capacity Qcharge and the first discharging capacity Qdischarge of the battery, and calculating the first charging and discharging efficiency eta of the battery, namely Edischarge/Echarge multiplied by 100%. The test results are shown in table 2.
4. Cycle performance test
The cycle performance test method for the lithium ion battery C1-C5 comprises the following steps: charging the lithium ion battery to 4.25V at constant current of 1C, then charging at constant voltage until the current is reduced to 0.02C, standing for 5min, discharging the battery to 2.5V at constant current of 1C, wherein the discharge and charge cycles are carried out for 100 times, the initial capacity of the battery and the battery capacity after 100 charge and discharge cycles are recorded, and the capacity retention rate of the battery is calculated by the following calculation formula: capacity retention ratio is battery capacity after 100 charge and discharge cycles/initial capacity of the battery 100%. The test results are shown in table 2.
TABLE 1
| Passivated lithium microspheres | A1 | A2 | A3 | A4 | A5 |
| Particle diameter (D50)/μm | <23 | <11 | <45 | <68 | <36 |
| Thickness of passivation layer/mum | 0.5 | 0.2 | 1.5 | 2.6 | 0.9 |
TABLE 2
| Battery with a battery cell | C1 | C2 | C3 | C4 | C5 |
| First effect | 87.5％ | 88.4％ | 85.8％ | 84.8％ | 84.6％ |
| Capacity retention rate | 95.6％ | 96.2％ | 95.1％ | 94.3％ | 94.1％ |
As can be seen from the data in Table 1, the particle size controllable and coating layer controllable passivated lithium microspheres can be prepared by the microcapsule granulation technology, the passivated lithium microspheres with smaller size and narrow particle size distribution can be prepared by controlling the process parameters, and the passivated lithium powder is uniformly coated and has a thinner coating layer, so that the gram capacity of the lithium powder can be better exerted. Comparing A1 and A5, the particle size of the passivated lithium microsphere prepared by the preparation method of the invention is obviously smaller and the thickness of the passivated layer can be thinner compared with the existing atomization device by adopting the vibrating nozzle technology.
The passivated lithium microspheres are arranged on the surface of a negative plate to prepare a pre-lithiated negative electrode, and as can be seen from data in table 2, the passivated lithium microspheres with small particle sizes are beneficial to exerting capacity, the first efficiency of the battery is high, and the cycle performance is excellent.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A preparation method of passivated lithium microspheres is characterized by comprising the following steps:
1) dispersing the molten metal lithium jet flow by using a fluid vibrating nozzle to obtain metal lithium liquid drops;
2) applying static electricity to the metal lithium droplets to obtain metal lithium microspheres;
3) and (3) placing the metal lithium microspheres in a passivation solution, and stirring to obtain the passivated lithium microspheres.
2. The method of claim 1, wherein the flow rate of the molten lithium metal into the fluid vibrating nozzle is 5-50 mL/min.
3. The method of claim 2, wherein the fluid vibrating nozzle has a diameter of 0.01 to 0.15 mm; and/or the presence of a gas in the gas,
the vibration frequency of the fluid vibration nozzle is 40-6000 Hz.
4. The method according to any one of claims 1 to 3, wherein the metallic lithium microspheres are obtained by cooling the metallic lithium droplets to 40 to 150 ℃ after applying static electricity to the metallic lithium droplets in step 2).
5. The method according to claim 1, wherein in step 3), the stirring speed is 350-1500 rpm; and/or the presence of a gas in the gas,
the concentration of the passivating agent in the passivating solution is 0.1-2 mol/L.
6. Passivated lithium microspheres, characterized in that said passivated lithium microspheres are obtained according to the method of preparation according to any one of claims 1 to 5.
7. The passivated lithium microspheres of claim 6, wherein the particle size of the passivated lithium microspheres is between 5 and 40 μm.
8. A production apparatus for carrying out the production method according to any one of claims 1 to 7, characterized by comprising: the device comprises a fluid vibrating nozzle and an electrode control unit, wherein the jet direction of the fluid vibrating nozzle faces to the electrode control unit.
9. A negative electrode sheet comprising the passivated lithium microspheres of claim 6 or 7.
10. A lithium ion battery comprising the negative electrode sheet according to claim 9.
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