CN113020589A - Stable metal lithium powder and preparation method and application thereof - Google Patents
Stable metal lithium powder and preparation method and application thereof Download PDFInfo
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- CN113020589A CN113020589A CN202110220591.3A CN202110220591A CN113020589A CN 113020589 A CN113020589 A CN 113020589A CN 202110220591 A CN202110220591 A CN 202110220591A CN 113020589 A CN113020589 A CN 113020589A
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- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
- B22F1/102—Metallic powder coated with organic material
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- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H01M4/02—Electrodes composed of, or comprising, active material
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/381—Alkaline or alkaline earth metals elements
- H01M4/382—Lithium
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Abstract
The invention relates to stable metallic lithium powder and a preparation method and application thereof. The preparation method provided by the invention has the advantages that the metal lithium powder is not required to be pretreated, the slight oxidation on the surface of the metal lithium powder is directly utilized to carry out chemical substitution reaction with the coating liquid, a compact and light and thin composite silicate coating layer can be formed on the surface of the metal lithium powder, the process is simple, the operability is strong, the prepared stable metal lithium powder has high stability and storage life, the safe transportation, the storage and the use are convenient, and the stable metal lithium powder can be widely used as a lithium pre-supplement additive of a lithium battery electrode material, so that the comprehensive performances of the lithium battery such as the capacity, the cycle life and the like are improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to stable metal lithium powder and a preparation method and application thereof.
Background
Lithium ion batteries are widely used because of their advantages of high operating voltage, large specific energy, small volume, light weight, long cycle life, low self-discharge, no memory effect, no pollution, etc. In recent years, with the rapid development of new energy automobiles, smart grids and distributed energy storage, higher requirements are put forward on the energy density of lithium ion batteries. The cathode material of the traditional lithium ion battery is graphite and carbon material, and the anode material comprises lithium cobaltate, lithium manganate, lithium iron phosphate and other materials. At present, most commercial lithium ion batteries adopt a carbonaceous negative electrode, generally adopt a graphite-based material, and have low lithium intercalation capacity (372 mAh/g). During the charging and discharging processes, the consumption of lithium ions and the decomposition coupling of the electrolyte form a passivation protective layer on the surface of the graphite negative electrode, which is generally called as a solid electrolyte interface, and is called as an SEI film for short. In theory, the SEI film only transmits lithium ions, but blocks the transmission of electrons, thereby preventing further degradation of the electrolyte and enabling stable cycling of a lithium ion battery with a carbonaceous negative electrode. The SEI film is mainly formed during the first several charging processes, especially during the first charging process, resulting in rapid reduction of the battery capacity. As the battery charge and discharge progresses, the graphite negative electrode material undergoes a volume change of about 10% due to the intercalation and deintercalation of lithium ions. The SEI film may be broken due to a change in volume, causing the lithiated graphite to contact and react with the electrolyte, thereby consuming the electrolyte and lithium ions. This results in the continuous generation and thickening of the SEI film, resulting in the contact and reaction of lithiated graphite with the electrolyte, thereby consuming the electrolyte and lithium ions, and the available capacity and internal resistance of the battery are continuously decreased and increased.
In recent years, silicon-based negative electrode batteries have been developed rapidly. The silicon-based negative electrode material has the advantages of high specific capacity (up to 4200mAh/g, which is far higher than 372mAh/g of graphite), low cost, low embedded potential and the like, and is considered to be one of the most promising negative electrode materials of next-generation high-specific-energy lithium ion batteries. Since the potential is outside the electrolyte stability window, an SEI film is also formed, resulting in low initial cycle coulombic efficiency. 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, resulting in a low first cycle coulombic efficiency (ICE), and reducing the capacity and energy density of the lithium ion battery. In addition, during the lithiation process, the silicon can expand greatly by 300-400%, which may cause the subsequent SEI film generation and active material pulverization, resulting in the active material peeling off on the current collector. Further, since the conductivity is poor and the capacity cannot be sufficiently utilized, the power density is also poor. Therefore, many researchers have been devoted to the study of silicon/carbon composite anode materials to improve the service life and rate performance thereof.
Currently, lithium can be supplemented to an electrode material through prelithiation to offset irreversible lithium loss caused by the formation of an SEI film, so as to improve the total capacity and energy density of a battery. The addition amount of the anode material is increased, the prelithiation additive is used, the electrochemical prelithiation is adopted, the electrode prelithiation is carried out in a contact short circuit mode and the like, the irreversible capacity loss of the first circulation can be compensated to a certain extent, and the economic cost is increased or the complexity of the experimental process is enhanced. Aiming at the problems in the lithium ion battery, the best solution is to add extra active lithium in the negative pole piece, and the common method is to directly spray metal lithium powder to the negative pole piece through a lithium supplement device to supplement lithium, so that the purposes of improving the first coulombic efficiency and the battery capacity are achieved. On one hand, the lithium metal powder belongs to high-reactivity alkali metal, belongs to dangerous articles, and is very easy to cause serious accidents such as explosion, fire and the like, and on the other hand, the lithium metal powder has a large specific surface area, light weight, and is easy to scatter, so that the lithium supplement operation is difficult. Therefore, researchers have developed various methods for preparing stable lithium metal powders.
CN110767884A discloses an inert metal lithium powder with a core-shell structure, and the preparation method comprises the following steps: (1) putting pure lithium metal powder with the particle size of 5-100 mu m into a reactor filled with inert gas, introducing a certain amount of oxygen, reacting the surface of the pure lithium metal powder with the oxygen to generate a layer of lithium oxide shell, and preparing the lithium/Li alloy lithium powder2O inert lithium powder A with a core-shell structure; (2) putting inert metal lithium powder A into a reactor filled with inert gas, then introducing a certain amount of carbon dioxide, heating the reactor to 100 ℃ and 160 ℃, reacting the carbon dioxide with lithium oxide to generate a lithium carbonate shell, and preparing the lithium/lithium carbonate shell2CO3Inert metal lithium powder B with a core-shell structure; (3) adopting polyaniline as a polymer shell to carry out secondary coating on the inert metal lithium powder B prepared in the step (2) to obtain the lithium/Li-doped lithium ion battery2CO3The inert lithium powder C with the PANI three-layer core-shell structure. The preparation method of the stable metal lithium powder is complex in operation, difficult to control and not suitable for large-scale popularization and use.
CN111725515A discloses a stable lithium powder, a preparation method and an application thereof, wherein the preparation method comprises the following steps: mixing and reacting fluorine-containing acid salt, lithium powder and an organic solvent to form a lithium fluoride passivation layer on the surface of the lithium powder so as to obtain stable lithium powder, wherein the mass ratio of the lithium fluoride passivation layer to the lithium powder in the stable lithium powder is (0.5-1.8): 1. The stable lithium powder prepared by the preparation method has a large mass ratio of the lithium fluoride passivation layer, causes waste of active lithium, and is not suitable for large-scale popularization and use.
CN110369711A discloses a stabilized lithium powder and a preparation method thereof, the preparation method comprises: (1) performing ball milling treatment on the lithium powder to obtain ball-milled lithium powder; (2) mixing the ball-milled lithium powder with the composite reaction solution and carrying out stabilization treatment to obtain a stabilized lithium powder precursor; the composite reaction liquid comprises an organic solvent and hydrogen chloride; (3) and drying the stabilized lithium powder precursor to obtain the stabilized lithium powder. The preparation method of the stable metal lithium powder is complex in operation, difficult to control and not suitable for large-scale popularization and use.
In summary, there is a need to develop a novel stable lithium metal powder and a preparation method thereof, which not only simplifies the preparation process, but also enables the prepared stable lithium metal powder to have very high stability and storage life, is convenient for safe transportation, storage and use, and can be widely used as a lithium pre-supplement additive for lithium battery electrode materials, and is used for solving the problem of low first efficiency of lithium batteries, thereby improving the capacity, cycle life and other comprehensive properties of lithium batteries.
Disclosure of Invention
In view of the problems in the prior art, the invention provides stable metallic lithium powder and a preparation method and application thereof. The preparation method provided by the invention has the advantages that the metal lithium powder is not required to be pretreated, the slight oxidation on the surface of the metal lithium powder is directly utilized to carry out chemical substitution reaction with the coating liquid, and a compact and light and thin composite silicate coating layer can be formed on the surface of the metal lithium powder.
In order to achieve the purpose, the invention adopts the following technical scheme:
one of the objects of the present invention is to provide a method for preparing stable lithium metal powder, comprising the steps of:
(1) uniformly mixing metal lithium powder and coating liquid, heating and stirring, wherein the coating liquid comprises mercaptosilane compounds and alkoxysilane compounds;
(2) and (2) sequentially filtering, washing and drying the product obtained in the step (1) to obtain the stable lithium metal powder coated by the composite silicate.
The preparation method of the invention does not need to pretreat the lithium metal powder, and directly utilizes the slight oxidation on the surface of the lithium metal powder to carry out chemical substitution reaction with the coating liquid, and LiO on the surface of the lithium metal powder2And/or LiOH can be bonded with-SH bond of mercaptosilane compound to form-S-Li+Followed by the functional group-Si-OCH of the mercaptosilane compounds3Can be reacted with a functional group-Si-OCH of an alkoxysilane compound2CH3Hydrolysis and condensation reactions occur, and then a compact and light composite silicate coating layer is formed on the surface of the metal lithium powder, wherein the composite silicate coating layer not only comprises inorganic silicate with high hardness and can effectively inhibit the growth of lithium dendrites, but also comprises organosilane with low hardness and can effectively improve the toughness of the composite silicate coating layer; the preparation method of the invention not only simplifies the preparation process and has strong operability, but also can ensure that the prepared stable metal lithium powder has high stability and long storage life, is convenient for safe transportation, storage and use, can be widely used as a pre-lithium supplement additive of a lithium battery electrode material, and is used for solving the problem of low first efficiency of the lithium battery, thereby improving the capacity, cycle life and other comprehensive properties of the lithium battery.
As a preferable embodiment of the present invention, the surface of the lithium metal powder in the step (1) contains Li2O and/or LiOH, because the lithium metal powder in the prior art is generally stored in an argon atmosphere and is active in chemical property, an oxide layer is formed on the surface of the lithium metal powder used as the pre-lithium supplement additive, but the oxidation degrees of different batches of lithium metal powder are not greatly different.
Preferably, the particle size of the lithium metal powder in step (1) is 20 to 100 μm, for example, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, but is not limited to the enumerated values, and other non-enumerated values within the above numerical range are also applicable.
Preferably, the step (1) is carried out in an ultra-low dew point room with the dew point less than or equal to-70 ℃, because a thin oxide layer is formed on the surface layer of the lithium metal powder, and the stability of the lithium metal powder can be effectively ensured only by limiting the water content in the environment as much as possible.
As a preferable technical scheme of the invention, the mercaptosilane compounds in the step (1) comprise 2-trimethylsilane ethanol mercaptan and/or 3-mercaptopropyltrimethoxysilane.
Preferably, the alkoxysilane compound in step (1) includes any one or a combination of at least two of tetraethoxysilane, 1, 2-diethoxy-1, 1,2, 2-tetramethyldisilane, 1, 3-diethoxy-1, 1,3, 3-tetramethyldisiloxane, or 1, 2-bis (2-methoxyphenyl) -1,1,2, 2-tetramethyldisilane, and the combination is typically, but not limited to: a combination of tetraethoxysilane and 1, 2-diethoxy-1, 1,2, 2-tetramethyldisilane, a combination of 1, 2-diethoxy-1, 1,2, 2-tetramethyldisilane and 1, 3-diethoxy-1, 1,3, 3-tetramethyldisiloxane, a combination of 1, 3-diethoxy-1, 1,3, 3-tetramethyldisiloxane and 1, 2-bis (2-methoxyphenyl) -1,1,2, 2-tetramethyldisilane, or a combination of tetraethoxysilane and 1, 2-bis (2-methoxyphenyl) -1,1,2, 2-tetramethyldisilane, and the like.
As a preferable technical solution of the present invention, the preparation method of the coating solution in the step (1) comprises: and (2) uniformly mixing the mercaptosilane compound, the alkoxysilane compound and the organic solvent in a protective gas atmosphere to obtain a coating solution, wherein the coating solution is a uniform solution.
Preferably, the shielding gas comprises any one of argon, helium or neon, or a combination of at least two of these, typical but non-limiting examples being: a combination of argon and helium, a combination of helium and neon, or a combination of argon and neon, and the like.
Preferably, the organic solvent comprises any one of hexadecene, tetradecene, dodecaene or an oil hydrocarbon or a combination of at least two of these, typical but non-limiting examples being: hexadecene and tetradecene in combination, tetradecene and dodecaene in combination, dodecaene and oil hydrocarbon in combination, hexadecene and oil hydrocarbon in combination, or the like.
Preferably, the mass ratio of the mercaptosilane compound to the alkoxysilane compound in step (1) is 1 (1-3), for example, 1:1, 1:1.5, 1:2, 1:2.5, or 1:3, but not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the mass ratio of the lithium metal powder to the coating liquid in the step (1) is (0.5-2.0):98, for example, 0.5:98, 0.8:98, 1.0:98, 1.2:98, 1.5:98, 1.7:98 or 2.0:98, but not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.
As a preferred embodiment of the present invention, the temperature of the heating and stirring in the step (1) is 25 to 120 ℃, for example, 25 ℃, 35 ℃, 50 ℃, 75 ℃, 90 ℃, 100 ℃, 110 ℃ or 120 ℃, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
Preferably, the stirring speed of the heating and stirring in step (1) is 500-1200rpm, such as 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, 1100rpm or 1200rpm, etc., but not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.
Preferably, the heating and stirring time in step (1) is 50-180min, such as 50min, 60min, 80min, 100min, 120min, 140min, 150min or 180min, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
As a preferable technical scheme of the invention, the filtering device adopted in the filtering in the step (2) comprises a Buchner funnel and/or a filter screen.
Preferably, the solvent used for the washing in step (2) is an alkane and/or alkene with a boiling point below 100 ℃.
Preferably, the drying temperature in step (2) is 60-100 ℃, such as 60 ℃, 70 ℃, 80 ℃, 90 ℃ or 100 ℃, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the drying time in step (2) is 2-12h, such as 2h, 4h, 6h, 8h, 10h or 12h, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the drying of step (2) is performed in a vacuum drying oven.
As a preferred technical scheme of the invention, the preparation method comprises the following steps:
(1) under the protective gas atmosphere, uniformly mixing mercaptosilane compounds, alkoxy silane compounds and organic solvent, controlling the mass ratio of the mercaptosilane compounds to the alkoxy silane compounds to be 1 (1-3) to obtain uniform coating liquid, and then in an ultra-low dew point room with the dew point of less than or equal to-70 ℃, enabling the particle size to be 20-100 mu m and the surface to contain Li2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the mass ratio of the metal lithium powder to the coating liquid to be (0.5-2.0):98, controlling the heating and stirring temperature to be 25-120 ℃, the stirring speed to be 500-1200rpm, and the time to be 50-180 min;
(2) and (2) filtering the product obtained in the step (1) by using a Buchner funnel and/or a filter screen, washing by using alkane and/or alkene with the boiling point lower than 100 ℃, and drying in a vacuum drying oven at the drying temperature of 60-100 ℃ for 2-12h to obtain the stable lithium metal powder coated by the composite silicate.
The second purpose of the invention is to provide stable lithium metal powder which is obtained by the preparation method of the first purpose.
In a preferred embodiment of the present invention, the particle size of the stabilized lithium metal powder is 20 to 100. mu.m, for example, 20. mu.m, 40. mu.m, 50. mu.m, 60. mu.m, 70. mu.m, 80. mu.m, or 100. mu.m, but the particle size is not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable.
Preferably, the mass of the composite silicate coating layer is 0.5-2% of the total mass of the stable lithium metal powder, for example, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, or 2%, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
It is worth saying that the content of the lithium metal in the stable lithium metal powder is more than or equal to 98 wt% by controlling the mass of the composite silicate coating layer to be 0.5-2% of the total mass of the stable lithium metal powder, so as to ensure the electrical properties required by the pre-lithium supplement additive.
Preferably, the thickness of the composite silicate coating layer is 5-100nm, such as 5nm, 10nm, 30nm, 50nm, 70nm, 90nm or 100nm, but not limited to the recited values, and other values not recited in the range of values are also applicable.
The invention also provides a negative plate, and the preparation method of the negative plate comprises the following steps: and carrying out pre-lithiation on the stable lithium metal powder obtained by the second purpose or the stable lithium metal powder obtained by the preparation method of the first purpose.
Preferably, the negative plate is a silicon-based negative plate.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) according to the preparation method, the metal lithium powder is not required to be pretreated, the slight oxidation on the surface of the metal lithium powder is directly utilized to carry out chemical substitution reaction with the coating liquid, and a compact and light and thin composite silicate coating layer can be formed on the surface of the metal lithium powder, so that the preparation process is simplified, the operability is strong, and the large-scale popularization and use are facilitated;
(2) the stable lithium metal powder prepared by the preparation method has high stability and long storage life, is convenient for safe transportation, storage and use, can be widely used as a pre-lithium supplement additive of a lithium battery electrode material, and is used for solving the problem of low first effect of the lithium battery, thereby improving the capacity, cycle life and other comprehensive properties of the lithium battery.
Drawings
FIG. 1 is a flow chart of a method of making stabilized lithium metal powder according to the present invention;
FIG. 2 is a scanning electron micrograph of the stabilized lithium metal powder prepared in example 1 of the present invention.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, typical but non-limiting examples of the invention are as follows:
as shown in fig. 1, the preparation method of the stable lithium metal powder according to the present invention comprises the following steps:
(1) uniformly mixing metal lithium powder and coating liquid, heating and stirring, wherein the coating liquid comprises mercaptosilane compounds and alkoxysilane compounds;
(2) and (2) sequentially filtering, washing and drying the product obtained in the step (1) to obtain the stable lithium metal powder coated by the composite silicate.
Example 1
The embodiment provides a preparation method of stable lithium metal powder, which comprises the following steps:
(1) adding 1g of 3-mercaptopropyl-trimethoxysilane and 1g of tetraethoxysilane into a glass three-necked flask in an argon atmosphere, controlling the mass ratio of the mercaptosilane compound to the alkoxysilane compound to be 1:1, then adding 100mL of hexadecene solvent into the flask to obtain uniform coating liquid, and then in an ultra-low dew point room with the dew point being less than or equal to-70 ℃, adding 0.5g of a room with the particle size of 20 mu m and the surface containing Li2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the heating and stirring temperature to be 25 ℃, the stirring speed to be 1000rpm, and the time to be 120 min;
(2) and (2) in a glove box under the argon atmosphere, performing suction filtration on the product obtained in the step (1) by using a Buchner funnel, washing by using n-hexane, filtering for three times to remove residual hexadecene, and then drying in a vacuum drying box at the drying temperature of 80 ℃ for 8 hours to obtain the stable lithium metal powder coated by the composite silicate.
Example 2
The embodiment provides a preparation method of stable lithium metal powder, which comprises the following steps:
(1) under argon atmosphere, 1g of 3-mercaptopropyltrimethoxysilane and 3g of tetraethoxysilane are added into a glass three-necked flask, and the mercaptosilanes are controlledThe mass ratio of the compound to the alkoxysilane compound is 1:3, then 100mL of hexadecene solvent is added into a bottle to obtain a uniform coating solution, and then 0.5g of a coating solution with a particle size of 20 μm and Li on the surface is added in an ultralow dew point room with a dew point of less than or equal to-70 DEG C2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the heating and stirring temperature to be 25 ℃, the stirring speed to be 1000rpm, and the time to be 120 min;
(2) and (2) in a glove box under the argon atmosphere, performing suction filtration on the product obtained in the step (1) by using a Buchner funnel, washing by using n-hexane, filtering for three times to remove residual hexadecene, and then drying in a vacuum drying box at the drying temperature of 80 ℃ for 8 hours to obtain the stable lithium metal powder coated by the composite silicate.
Example 3
The embodiment provides a preparation method of stable lithium metal powder, which comprises the following steps:
(1) adding 5g of 3-mercaptopropyl-trimethoxysilane and 5g of tetraethoxysilane into a glass three-necked flask in an argon atmosphere, controlling the mass ratio of the mercaptosilane compound to the alkoxysilane compound to be 1:1, then adding 100mL of hexadecene solvent into the flask to obtain uniform coating liquid, and then in an ultra-low dew point room with the dew point of less than or equal to-70 ℃, adding 0.5g of a room with the particle size of 20 mu m and the surface containing Li2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the heating and stirring temperature to be 25 ℃, the stirring speed to be 1000rpm, and the time to be 120 min;
(2) and (2) in a glove box under the argon atmosphere, performing suction filtration on the product obtained in the step (1) by using a Buchner funnel, washing by using n-hexane, filtering for three times to remove residual hexadecene, and then drying in a vacuum drying box at the drying temperature of 80 ℃ for 8 hours to obtain the stable lithium metal powder coated by the composite silicate.
Example 4
The embodiment provides a preparation method of stable lithium metal powder, which comprises the following steps:
(1) adding 5g of 3-mercaptopropyl-trimethoxysilane and 10g of tetraethoxysilane into a glass three-necked flask in an argon atmosphere, controlling the mass ratio of the mercaptosilane compound to the alkoxysilane compound to be 1:2, then adding 100mL of hexadecene solvent into the flask to obtain uniform coating liquid, and then in an ultra-low dew point room with the dew point of less than or equal to-70 ℃, adding 0.5g of a room with the particle size of 20 mu m and the surface containing Li2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the heating and stirring temperature to be 25 ℃, the stirring speed to be 1000rpm, and the time to be 120 min;
(2) and (2) in a glove box under the argon atmosphere, performing suction filtration on the product obtained in the step (1) by using a Buchner funnel, washing by using n-hexane, filtering for three times to remove residual hexadecene, and then drying in a vacuum drying box at the drying temperature of 80 ℃ for 8 hours to obtain the stable lithium metal powder coated by the composite silicate.
Example 5
The embodiment provides a preparation method of stable lithium metal powder, which comprises the following steps:
(1) adding 1g of 2-trimethylsilylethanethiol and 1g of 1, 2-diethoxy-1, 1,2, 2-tetramethyldisilane into a glass three-neck flask under the atmosphere of helium, controlling the mass ratio of the mercaptosilane compound to the alkoxysilane compound to be 1:1, then adding 100mL of tetradecyl solvent into the flask to obtain a uniform coating solution, and then in an ultra-low dew point room with the dew point of less than or equal to-70 ℃, adding 2g of a room with the particle size of 50 mu m and the surface containing Li into the room2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the heating and stirring temperature to be 120 ℃, the stirring speed to be 500rpm, and the time to be 180 min;
(2) and (2) in a glove box under helium atmosphere, performing suction filtration on the product obtained in the step (1) by using a Buchner funnel, washing by using n-hexane, filtering for three times to remove the residual tetradecene, and then drying in a vacuum drying box at the drying temperature of 60 ℃ for 12 hours to obtain the stable lithium metal powder coated by the composite silicate.
Example 6
The embodiment provides a preparation method of stable lithium metal powder, which comprises the following steps:
(1) adding 1g of 2-trimethylsilylethylthiol and 1g of 1, 2-bis (2-methoxyphenyl) -1,1,2, 2-tetramethyldisilane into a glass three-neck flask under the atmosphere of neon, controlling the mass ratio of the mercaptosilane compounds to the alkoxysilane compounds to be 1:1, then adding 100mL of dodecalute solvent into the flask to obtain a uniform coating solution, and then adding 2g of a room with an ultralow dew point of less than or equal to-70 ℃ and a particle size of 100 mu m and a surface containing Li into the room2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the heating and stirring temperature to be 50 ℃, the stirring speed to be 1200rpm, and the time to be 50 min;
(2) and (2) in a glove box under the atmosphere of neon, performing suction filtration on the product obtained in the step (1) by using a Buchner funnel, washing by using n-hexane, filtering for three times to remove residual dodecathin, and then drying in a vacuum drying box at the drying temperature of 100 ℃ for 2 hours to obtain the stable metal lithium powder coated by the composite silicate.
Comparative example 1
This comparative example provides a method for preparing stable lithium metal powder, except that 1g of 3-mercaptopropyltrimethoxysilane was replaced with 1g of tetraethoxysilane, that is, the coating liquid included only alkoxysilane-based compounds, and the conditions were exactly the same as in example 1.
Comparative example 2
This comparative example provides a method for preparing stable lithium metal powder, except that 1g of tetraethoxysilane was replaced with 1g of 3-mercaptopropyltrimethoxysilane, that is, the coating liquid included only the mercaptosilane-based compound, and the conditions were exactly the same as in example 1.
And (3) testing electrical properties:
respectively dispersing the lithium metal powder prepared in the above examples and comparative examples in N-methylpyrrolidone (NMP) solution containing 5% polyvinylidene fluoride (PVDF), and stirring to obtain lithium powder with solid content of 5%The lithium powder slurry of (1) was prepared in such a manner that the areal density was 11mg/cm2Uniformly coating the lithium powder slurry on SiOxVacuum drying and rolling the negative plate of the/C to obtain a pre-lithiated negative plate, wherein the positive plate is NCM, and the pre-lithiated negative plate is manufactured into a single-layer laminated soft package battery of 0.5Ah, and is kept stand for 24h for electrical property test; wherein, electrolyte: LiPF 6: EC: DEC: PP: FEC ═ 1:1.78:3.57:1.4: 8; SiO 2xC, negative electrode proportion: PAA 3.0%, SP 1.0%, CMC 3.0%; and (3) anode proportioning: NCM: SP: PVDF 97:1.0: 2.0; the specific test results are shown in table 1.
TABLE 1
Stabilizing the content (wt%) of metallic lithium in the lithium powder:
taking 10g of each of the lithium metal powders prepared in the above examples and comparative examples, and measuring the content (wt%) of the lithium metal in the stable lithium powder by using a relevant instrument; the specific test results are shown in table 2.
And (3) gram capacity test:
the lithium metal powder prepared in the above examples and comparative examples is stabilized lithium powder according to the mass ratio: polyvinylidene fluoride (PVDF): carbon Nanotube (CNT): n-methylpyrrolidone (NMP) 1.5:2:2:100 was slurried and then processed to an areal density of 11mg/cm2Coating the copper foil with the thickness of 12 mu m on the copper foil, drying the copper foil to be used as a working electrode, selecting an inert copper foil as a counter electrode, assembling the prepared working electrode and the counter electrode into a half cell, adopting a charging process step to charge the counter electrode at a low multiplying power, wherein the charging multiplying power is 0.02C, the cut-off voltage is 2.0V, and then testing the gram capacity of the half cell respectively; the specific test results are shown in table 2.
25℃&Stability test in 50% environment:
respectively placing the lithium metal powder prepared in the above embodiments and comparative examples in a constant temperature and humidity chamber and starting timing, controlling the conditions to be 50% at 25 ℃ (no fire or smoke), and judging the stability of the lithium metal powder in the air by observing the time required for the color of the lithium metal powder to change from silver gray to black; the specific test results are shown in table 2.
TABLE 2
In conclusion, the preparation method provided by the invention does not need to pretreat the metal lithium powder, and directly utilizes the slight oxidation of the surface of the metal lithium powder to carry out chemical substitution reaction with the coating liquid containing the mercaptosilane compound and the alkoxysilane compound, so that a compact, light and thin composite silicate coating layer can be formed on the surface of the metal lithium powder, the preparation process is simplified, the operability is strong, and the preparation method is convenient for large-scale popularization and use; in addition, the stable lithium metal powder prepared by the preparation method has high stability and long storage life, is convenient for safe transportation, storage and use, can be widely used as a lithium pre-supplement additive of a lithium battery electrode material, and is used for solving the problem of low first effect of the lithium battery, thereby improving the capacity, cycle life and other comprehensive properties of the lithium battery.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (10)
1. A method for preparing stable lithium metal powder, which is characterized by comprising the following steps:
(1) uniformly mixing metal lithium powder and coating liquid, heating and stirring, wherein the coating liquid comprises mercaptosilane compounds and alkoxysilane compounds;
(2) and (2) sequentially filtering, washing and drying the product obtained in the step (1) to obtain the stable lithium metal powder coated by the composite silicate.
2. The method according to claim 1, wherein the surface of the lithium metal powder of step (1) contains Li2O and/or LiOH;
preferably, the particle size of the lithium metal powder in the step (1) is 20-100 μm;
preferably, step (1) is carried out in an ultra low dew point chamber having a dew point of ≦ 70 ℃.
3. The production method according to claim 1 or 2, wherein the mercaptosilane-based compound of step (1) comprises 2-trimethylsilylethylthiol and/or 3-mercaptopropyltrimethoxysilane;
preferably, the alkoxysilane compound in step (1) includes any one or a combination of at least two of tetraethoxysilane, 1, 2-diethoxy-1, 1,2, 2-tetramethyldisilane, 1, 3-diethoxy-1, 1,3, 3-tetramethyldisiloxane, or 1, 2-bis (2-methoxyphenyl) -1,1,2, 2-tetramethyldisilane.
4. The method according to any one of claims 1 to 3, wherein the coating solution of step (1) is prepared by a method comprising: under the atmosphere of protective gas, uniformly mixing the mercaptosilane compound, the alkoxysilane compound and an organic solvent to obtain a coating solution;
preferably, the shielding gas comprises any one of argon, helium or neon or a combination of at least two of the same;
preferably, the organic solvent comprises any one of hexadecene, tetradecene, dodecaene or oil hydrocarbon or a combination of at least two of the same;
preferably, the mass ratio of the mercaptosilane compound to the alkoxysilane compound in the step (1) is 1 (1-3);
preferably, the mass ratio of the lithium metal powder to the coating liquid in the step (1) is (0.5-2.0): 98.
5. The method according to any one of claims 1 to 4, wherein the temperature of the heating and stirring in step (1) is 25 to 120 ℃;
preferably, the stirring speed of the heating and stirring in the step (1) is 500-1200 rpm;
preferably, the heating and stirring time of the step (1) is 50-180 min.
6. The method according to any one of claims 1 to 5, wherein the filtration in step (2) is carried out using a filtration device comprising a Buchner funnel and/or a filter screen;
preferably, the solvent used in the washing in the step (2) is alkane and/or alkene with the boiling point lower than 100 ℃;
preferably, the temperature for drying in the step (2) is 60-100 ℃;
preferably, the drying time of the step (2) is 2-12 h;
preferably, the drying of step (2) is performed in a vacuum drying oven.
7. The production method according to any one of claims 1 to 6, characterized by comprising the steps of:
(1) under the protective gas atmosphere, uniformly mixing mercaptosilane compounds, alkoxy silane compounds and organic solvent, controlling the mass ratio of the mercaptosilane compounds to the alkoxy silane compounds to be 1 (1-3) to obtain uniform coating liquid, and then in an ultra-low dew point room with the dew point of less than or equal to-70 ℃, enabling the particle size to be 20-100 mu m and the surface to contain Li2Uniformly mixing O and/or LiOH metal lithium powder with the coating liquid, heating and stirring, controlling the mass ratio of the metal lithium powder to the coating liquid to be (0.5-2.0):98, controlling the heating and stirring temperature to be 25-120 ℃, the stirring speed to be 500-1200rpm, and the time to be 50-180 min;
(2) and (2) filtering the product obtained in the step (1) by using a Buchner funnel and/or a filter screen, washing by using alkane and/or alkene with the boiling point lower than 100 ℃, and drying in a vacuum drying oven at the drying temperature of 60-100 ℃ for 2-12h to obtain the stable lithium metal powder coated by the composite silicate.
8. A stabilized lithium metal powder obtained by the production method according to any one of claims 1 to 7.
9. The stabilized lithium metal powder of claim 8, wherein the particle size of the stabilized lithium metal powder is 20-100 μ ι η;
preferably, the mass of the composite silicate coating layer accounts for 0.5-2% of the total mass of the stable lithium metal powder;
preferably, the thickness of the composite silicate coating layer is 5-100 nm.
10. The negative plate is characterized in that the preparation method of the negative plate comprises the following steps: prelithiation with the stabilized lithium metal powder according to claim 8 or 9 or with the stabilized lithium metal powder obtained by the preparation process according to any one of claims 1 to 7;
preferably, the negative plate is a silicon-based negative plate.
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