Passivated lithium powder, method for preparing the same, negative electrode sheet, battery, and electric device

Abstract

The application provides a kind of passivated lithium powder and its preparation method, negative electrode sheet, battery and electric equipment, the first aspect of the application provides a kind of passivated lithium powder, the passivated lithium powder includes lithium powder and the passivation layer coated on the surface of the lithium powder;The passivation layer includes the product generated by the in-situ reaction of the compound shown in formula 1 with the lithium powder;C n H x (OH) y F z Formula 1, in formula 1, 2≤n≤50, y≥1, z≥1, x≥1;The product includes LiF and C n H x (OLi) y The passivated lithium powder has excellent air stability, anti-hygroscopicity, and can stabilize the SEI film on the surface of the electrode sheet when applied to the electrode sheet.

Description

Technical Field

[0001] This invention relates to a passivated lithium powder, and more particularly to a passivated lithium powder and its preparation method, negative electrode sheet, battery and electrical equipment, belonging to the field of secondary batteries. Background Technology

[0002] During the first charge and discharge cycle of a lithium-ion battery, the organic electrolyte undergoes reduction and decomposition on the surface of the negative electrode, forming a solid electrolyte layer that irreversibly consumes the Li₂ from the positive electrode. + This results in a low coulombic efficiency for the first cycle of the battery.

[0003] Passivated lithium powder, a lithium-ion additive for negative electrodes, is a multifunctional, high-energy-density lithium-ion material compatible with various negative electrodes, including graphite and silicon-based anodes. Passivated lithium powder uses metallic lithium as its raw material. Metallic lithium has high chemical reactivity, and when processed into powder, it has a larger specific surface area and even higher reactivity. In practical applications, a series of passivation measures are used to construct a passivation layer on the surface of the lithium powder particles to reduce the reactivity of metallic lithium in air.

[0004] However, current methods for producing and passivating passivated lithium powder focus more on the simplicity and ease of the preparation process. Further research is needed to develop passivated lithium powders with superior air stability, deliquescence resistance, and positive impact on the SEI film on the electrode surface. Summary of the Invention

[0005] This invention provides a passivated lithium powder that has excellent air stability and deliquescence resistance, and when applied to electrodes, it can stabilize the SEI film on the electrode surface.

[0006] The present invention also provides a method for preparing passivated lithium powder, which is simple in process and can prepare the above-mentioned passivated lithium powder.

[0007] The present invention also provides a negative electrode sheet comprising the above-mentioned passivated lithium powder.

[0008] The present invention also provides a battery comprising the aforementioned negative electrode.

[0009] The present invention also provides an electrical device comprising the aforementioned battery.

[0010] The present invention provides a passivated lithium powder, the passivated lithium powder comprising lithium powder and a passivation layer coated on the surface of the lithium powder;

[0011] The passivation layer comprises the product generated by the in-situ reaction of the compound shown in Formula 1 with the lithium powder;

[0012] C n H x (OH) y Fz Formula 1

[0013] In Equation 1, 2≤n≤50, y≥1, z≥1, x≥1;

[0014] The products include LiF and C. n H x (OLi) y .

[0015] The passivated lithium powder described above further includes Li2CO3 in the passivation layer.

[0016] As described above, for passivated lithium powder, 7 ≤ n ≤ 50.

[0017] The passivated lithium powder described above has a melting point ≤100℃ and a boiling point ≥220℃ for the compound shown in Formula 1.

[0018] The passivated lithium powder described above includes one or more of 4-fluoro-2-isopropoxyphenol and 4,5-difluoro-2-methylphenol.

[0019] The passivated lithium powder described above has a D50 particle size of 30 μm to 60 μm.

[0020] And / or, the thickness of the passivation layer is 150 nm to 400 nm.

[0021] In another aspect, the present invention provides a method for preparing the passivated lithium powder as described above, comprising the following steps:

[0022] Under an argon atmosphere, the compound shown in Formula 1 is mixed with an inert solvent to obtain a mixed system; lithium powder is added to the mixed system and reacted at 180℃~210℃ to obtain the passivated lithium powder.

[0023] In the preparation method described above, the inert solvent includes liquid paraffin;

[0024] And / or, the volume ratio of the inert solvent to the compound shown in Formula 1 is 70:30 to 99:1, preferably 95:5 to 98:2;

[0025] And / or, the reaction is carried out under stirring conditions, wherein the stirring rate is 5000~20000 rpm, preferably 8000~11000 rpm;

[0026] And / or, the reaction time is 0.5 to 24 hours, preferably 0.5 to 1.5 hours.

[0027] The preparation method described above further includes, after the reaction is completed: cooling the temperature of the reaction system to below the melting point of lithium metal, and then subjecting the reaction system to vacuum drying.

[0028] The temperature of the vacuum drying process is ≤180℃, preferably 130~140℃.

[0029] The preparation method described above, after the vacuum drying process is completed, further includes: introducing CO2 gas into the reaction system at a temperature of 120~179℃, preferably 130~140℃.

[0030] In another aspect, the present invention provides a negative electrode sheet, comprising the passivated lithium powder as described above or the passivated lithium powder prepared by the preparation method described above.

[0031] In another aspect, the present invention provides a battery comprising the negative electrode sheet as described above.

[0032] In another aspect, the present invention provides an electrical device comprising the battery described above.

[0033] The passivated lithium powder provided by this invention includes lithium powder and a passivation layer coated on the surface of the lithium powder. The passivation layer of this invention is derived from a compound with a specific composition, including LiF and lithium alkoxide. It not only leverages the excellent resistance of LiF to the corrosion of the passivated lithium powder by substances such as H2O and O2 in the air and is not prone to moisture absorption and deliquescence, but also, as a strong nucleophile, lithium alkoxide is conducive to the generation of Li2CO3 in the passivation layer after the subsequent CO2 is introduced. At the same time, the presence of the nucleophile lithium alkoxide helps to form a dense SEI layer on the lithium-filled electrode. Under the synergistic effect of LiF and lithium alkoxide, the passivated lithium powder has excellent air stability and deliquescence resistance. Moreover, after the passivated lithium powder is applied to the electrode, it can stabilize the SEI film on the surface of the electrode. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0035] Figure 1 This is a schematic diagram of the structure of passivated lithium powder provided in a specific embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] a-Passivation layer, b-Lithium powder.

[0038] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] Figure 1 This is a schematic diagram of the structure of passivated lithium powder provided in a specific embodiment of the present invention, as shown below. Figure 1 As shown, one aspect of the present invention provides a passivated lithium powder, comprising lithium powder b and a passivation layer a coated on the surface of the lithium powder; the passivation layer a comprises a product generated by the in-situ reaction of the compound shown in Formula 1 with the lithium powder; C n H x (OH) y F z Equation 1; In Equation 1, 2≤n≤50, x+y+z=2n, y≥1, z≥1; The products include LiF and C n H x (OLi) y .

[0041] In detail, the passivated lithium powder provided by the present invention has a core-shell structure, wherein the lithium powder is the core structure and the passivation layer covering the surface of the lithium powder is the outer layer structure.

[0042] The compound shown in Formula 1 acts as a passivating agent and reacts in situ with lithium powder on the surface of the lithium powder to obtain a passivation layer, wherein the passivation layer includes LiF and C. n H x (OLi) y In the in-situ reaction process, the products between the compound shown in Formula 1 and lithium powder, in addition to LiF and C, are... n H x (OLi) y In addition, it also includes lithium-carbon alloys formed by the reaction of metallic lithium with partially coked fluorinating agents.

[0043] The specific components in the passivation layer can be detected using common detection methods in the field. For example, after preparing the passivation lithium powder sample in a glove box, it can be vacuum transferred to the XPS test chamber for XPS testing.

[0044] In the compounds represented by Formula 1, n includes, but is not limited to, a range of 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or any two of these ranges.

[0045] In one specific embodiment, the compound represented by Formula 1 in this invention is a fluorinated phenol, wherein the fluorinated phenol, as a fluorinating agent for lithium metal, has the advantages of low cost and easy availability, high temperature stability, and controllable degree of fluorination.

[0046] The passivated lithium powder provided by this invention exhibits excellent air stability and deliquescence resistance. Furthermore, when applied to electrodes, it stabilizes the SEI film on the electrode surface. The inventors believe the reasons for this are as follows: Passivating the lithium powder with the compound shown in Formula 1 allows for control of the -F position, which enhances the activity of the CF bond and its reactivity with Li, thereby controlling the distribution and content of LiF within the passivation layer. LiF possesses good resistance to corrosion from substances such as H2O and O2 in the air, and is not easily hygroscopic, ensuring the flowability and stability of the passivated lithium powder when used in a dew point chamber. As an important component of the SEI, LiF exhibits stable mechanical properties and a wide electrochemical window, contributing to SEI stability. Simultaneously, the phenolic hydroxyl hydrogen exhibits a certain degree of reactivity, reacting with metallic lithium, with the Li atom replacing H to generate lithium alkoxide -OLi. Lithium alkoxide, as a nucleophile, readily reacts with the nucleophile CO2 to generate Li2CO3. The unsaturated bonds in the benzene ring provide sufficient electron cloud to ensure the reactivity of the C-OH and CF bonds. Compared to directly coating LiF / Li2CO3 onto the surface of lithium metal powder using physical methods, the passivation layer constructed by combining a passivating agent with the reaction of CO2 and lithium metal has a closer contact with the lithium metal and a more uniform coating.

[0047] Furthermore, in one specific embodiment of the present invention, the passivation layer further includes Li2CO3.

[0048] The Li2CO3 in the passivation layer can be obtained by removing the solvent by vacuum drying after the in-situ reaction is completed, and then introducing a certain amount of CO2 and reacting it under high temperature conditions.

[0049] Li2CO3 is stable in air and does not easily absorb H2O from the air to form agglomerates, which can improve the stability of passivated lithium powder in air to a certain extent.

[0050] In this invention, the presence of Li2CO3 and LiF, C in the passivation layer is not limited. n H x (OLi) y The quality relationship between components can be selected according to actual needs to better leverage the synergistic effect between the various components in the passivation layer.

[0051] In one specific embodiment, the passivation layer contains 25.2% Li₂CO₃ by mass, 48.3% LiF by mass, and C... n H x (OLi)y The mass percentage content is 20.5%.

[0052] Furthermore, in one specific embodiment of the present invention, 7 ≤ n ≤ 50.

[0053] In detail, n includes, but is not limited to, a range of 10, 15, 20, 25, 30, 35, 40, 45, 50, or any two of these.

[0054] The more carbon atoms in the compound shown in Formula 1, the higher the boiling point of the compound shown in Formula 1, which ensures that the compound shown in Formula 1 will not vaporize during the coating process, thus allowing it to fully participate in the reaction.

[0055] Furthermore, in one specific embodiment of the present invention, the compound shown in Formula 1 has a melting point ≤100℃ and a boiling point ≥210℃.

[0056] In detail, the melting point includes, but is not limited to, 100°C, 95°C, 90°C, 85°C, 80°C, 75°C, 70°C, or any range not exceeding 100°C.

[0057] Boiling point includes, but is not limited to, 210℃, 215℃, 220℃, 225℃, 230℃, 235℃, 240℃, 245℃ or any range ≥210℃.

[0058] When the melting point and boiling point of the compound shown in Formula 1 are within the above range, it not only has high stability and can avoid the adverse effects on the efficiency and effect of the in-situ reaction caused by phase transformation during the in-situ reaction, but also the compound with the above melting point and boiling point can better react with lithium powder in situ, and the passivation layer formed is more tightly bonded to the lithium powder as the core, and has excellent stability.

[0059] Furthermore, in a specific embodiment of the present invention, the compound shown in Formula 1 includes one or more of 4-fluoro-2-isopropoxyphenol and 4,5-difluoro-2-methylphenol.

[0060] The compounds of the above types not only have melting and boiling points within a suitable range, but are also available through commercial channels, reducing the difficulty of preparation. At the same time, they can better achieve in-situ reactions with lithium powder, improve the stability and deliquescence resistance of passivated lithium powder, and when applied to electrodes, they are conducive to the formation of a stable SEI film.

[0061] Furthermore, in one specific embodiment of the present invention, the D50 particle size of the passivated lithium powder is 20 μm to 50 μm;

[0062] And / or, the thickness of the passivation layer is 100 nm to 800 nm.

[0063] In detail, the D50 particle size of passivated lithium powder can be detected using common detection methods in the field, such as laser particle size analyzer, sieving method, scanning electron microscope, etc.

[0064] Specifically, the D50 particle size of the passivated lithium powder includes, but is not limited to, a range of 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any combination thereof.

[0065] When the D50 particle size of passivated lithium powder is within the above range, it can be adapted to different lithium replenishment scenarios. For example, graphite anodes require less lithium replenishment, and using passivated lithium powder products with smaller D50 can improve the uniformity of lithium replenishment. Silicon-carbon anodes require a large amount of lithium replenishment, and using passivated lithium powder products with larger D50 can improve the lithium replenishment efficiency.

[0066] In this invention, the thickness of the passivation layer refers to the average thickness of the passivation layer, which can also be detected using common detection methods in the field, such as scanning electron microscopy, transmission electron microscopy, atomic force microscopy, etc.

[0067] Specifically, the thickness of the passivation layer includes, but is not limited to, a range of 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, or any combination thereof.

[0068] When the passivation layer thickness of the passivated lithium powder is within the above range, it can be adapted to different lithium replenishment scenarios. For example, a thicker passivation layer can be used when the dew point environment is high, while a thinner passivation layer can be used when the lithium replenishment requirement is high.

[0069] In another aspect, the present invention provides a method for preparing the passivated lithium powder as described above, comprising the following steps:

[0070] Under an argon atmosphere, the compound shown in Formula 1 was mixed with an inert solvent to obtain a mixed system; lithium powder was added to the mixed system and reacted at 180℃~210℃ to obtain passivated lithium powder.

[0071] In this invention, an inert solvent refers to a solvent that does not react with metallic lithium or lithium alloys, or with the compounds shown in Formula 1.

[0072] In detail, the compound shown in Formula 1 is mixed with an inert solvent. After stirring, the compound is uniformly dispersed in the mixture, which promotes the subsequent reaction. The inert solvent provides a stable medium for the subsequent reaction. Subsequently, lithium powder is added to the inert system. At 180℃-210℃, the lithium powder reacts in situ with the compound shown in Formula 1, forming a passivation layer on the surface of the lithium powder, thus obtaining passivated lithium powder.

[0073] Specifically, the reaction temperature includes, but is not limited to, a range of 180°C, 190°C, 200°C, 210°C, 220°C, or any combination thereof.

[0074] The preparation method provided by the present invention can prepare passivated lithium powder with excellent stability and deliquescence resistance. At the same time, when the passivated lithium powder is used as an electrode, it can form a stable SEI film.

[0075] Furthermore, in one specific embodiment of the present invention, the inert solvent includes liquid paraffin;

[0076] And / or, the volume ratio of the inert solvent to the compound shown in Formula 1 is 70:30 to 99:1, preferably 95:5 to 98:2;

[0077] And / or, the reaction is carried out under stirring conditions, with a stirring rate of 5000~20000 rpm, preferably 8000~11000 rpm;

[0078] And / or, the reaction time is 0.5~24h, preferably 0.5~1.5h.

[0079] Specifically, based on the total volume of the mixture consisting of the inert solvent and the compound shown in Formula 1, the volume mass fraction of the compound shown in Formula 1 includes, but is not limited to, 1%, 5%, 10%, 15%, 20%, 25%, 30%, or any combination thereof. When the volumes of the inert solvent and the compound shown in Formula 1 are in the above-mentioned relationship, the inert solvent can effectively dilute the reactants, control the reaction rate, and improve the uniformity of various components in the passivation layer.

[0080] Preferably, the volume mass fraction of the compound shown in Formula 1 includes, but is not limited to, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any combination thereof. When the volume of the inert solvent and the compound shown in Formula 1 are related as described above, the dispersing effect of the inert solvent can be better utilized.

[0081] The reaction is carried out under stirring conditions, with stirring rates including but not limited to 5000 rpm, 6000 rpm, 8000 rpm, 10000 rpm, 12000 rpm, 14000 rpm, 16000 rpm, 18000 rpm, 20000 rpm, or any combination thereof. Preferably, the stirring rate includes but is not limited to 8000, 8500, 9000, 9500, 10000, 10500, 11000 rpm, or any combination thereof. When the reaction is carried out under stirring at the above-mentioned stirring rates, the reaction rate can be increased, the uniformity of the passivation layer can be improved, and thus the stability of the passivated lithium powder can be enhanced.

[0082] The reaction time includes, but is not limited to, a range of 0.5h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any two of these ranges; preferably, the reaction time is a range of 0.5h, 0.6h, 0.8h, 1.0h, 1.2h, 1.4h, 1.5h, or any two of these ranges.

[0083] When the reaction time is controlled within the above range, the thickness of the passivation layer in the passivation lithium powder can be effectively controlled, so that the thickness is within a suitable range, which can play both the role of the passivation layer and the effect of lithium replenishment.

[0084] Furthermore, in a specific embodiment of the present invention, after the reaction is completed, the method further includes: cooling the temperature of the reaction system to below the melting point of lithium metal, and then performing vacuum drying on the reaction system; the temperature of the vacuum drying treatment is ≤180°C, preferably 130~140°C.

[0085] After the reaction is complete, the surface of the passivated lithium powder may have residual inert solvent or other impurities. In order to improve the purity and stability of the final passivated lithium powder product, the temperature of the reaction system is lowered to below the melting point of lithium metal, and then the reaction system is vacuum dried at a temperature not exceeding 180°C.

[0086] The preferred temperature for vacuum drying is 130-140℃. For example, the temperature for vacuum drying includes, but is not limited to, 130℃, 131℃, 132℃, 133℃, 134℃, 135℃, 136℃, 137℃, 138℃, 139℃, 140℃, or any combination thereof.

[0087] When the temperature of the vacuum drying process is within the above range, it can not only effectively avoid the damage to the structure of the passivated lithium powder due to excessive temperature, but also improve the efficiency of the vacuum drying process.

[0088] Furthermore, in a specific embodiment of the present invention, after the vacuum drying process is completed, the method further includes: introducing CO2 gas into the reaction system at a temperature of 120~179°C, preferably 130~140°C.

[0089] After vacuum drying, carbon dioxide is introduced into the reaction system. The carbon dioxide reacts with the lithium alkoxide in the passivation layer to form lithium carbonate. The lithium carbonate can further improve the stability of the passivated lithium powder.

[0090] In detail, the temperature after CO2 is introduced includes, but is not limited to, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 179°C, or any combination thereof.

[0091] In another aspect, the present invention provides a negative electrode sheet, comprising the passivated lithium powder as described above or the passivated lithium powder prepared by the preparation method described above.

[0092] In detail, since the negative electrode includes passivated lithium powder as described above or passivated lithium powder prepared by the method described above, it helps to stabilize the SEI structure of the negative electrode and play a role in lithium replenishment.

[0093] It is understood that the negative electrode sheet of the present invention specifically includes a negative electrode current collector and a negative electrode active layer formed of a negative electrode active material disposed on the surface of the negative electrode current collector.

[0094] In the specific preparation of the negative electrode, the negative electrode active material, conductive agent, and binder can be dispersed in an appropriate amount of deionized water and thoroughly stirred to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the negative electrode current collector, and after drying, rolling, and slitting, a negative electrode sheet is obtained. In one specific embodiment, the negative electrode active layer comprises, by weight percentage, 70-99 wt% of negative electrode active material, 0.5-15 wt% of conductive agent, and 0.5-15 wt% of binder; more specifically, it comprises 80-98 wt% of negative electrode active material, 1-10 wt% of conductive agent, and 1-10 wt% of binder.

[0095] The negative electrode current collector layer can be made of at least one of copper foil, nickel foam, and copper foam; the conductive agent can be made of at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and graphene; the binder can be made of at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate; and the negative electrode active material can be made of at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon suboxide and silicon-carbon negative electrodes), and tin-based negative electrode materials (mainly including tin and tin alloys).

[0096] In another aspect, the present invention provides a battery comprising the negative electrode sheet as described above.

[0097] It is conceivable that, in addition to the aforementioned negative electrode, the battery of the present invention also includes a positive electrode, an electrolyte, and a separator.

[0098] This invention does not strictly limit the positive electrode active material in the positive electrode sheet. For example, it can be at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate (LFP), lithium nickel manganese oxide, lithium-rich manganese-based material, etc.

[0099] This invention does not strictly limit the choice of electrolyte, and may include one or more solvents commonly used in current battery electrolytes, as well as lithium salts commonly used in current electrolytes. For example, the solvent may be ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, methyl ethyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, γ-butyrolactone, etc.; the lithium salt may be one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0100] This invention does not strictly limit the choice of separator material. It can be one of the separator materials commonly used in batteries, such as polypropylene separator (PP), polyethylene separator (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polyimide electrospun separator (PI), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), cellulose nonwoven separator, and separator with ceramic coating.

[0101] In the preparation of lithium-ion batteries, the positive electrode, separator, and negative electrode are wound or stacked to obtain a bare cell, which is then packaged into a pre-stamped aluminum-plastic film bag. After the packaged battery is dried at 85°C, the electrolyte is injected into the dried battery. The battery undergoes resting, formation, and secondary sealing to complete the preparation of the lithium-ion battery.

[0102] In another aspect, the present invention provides an electrical device comprising the battery described above.

[0103] This invention does not limit the specific type of electrical equipment, and may include any device that requires a battery to power it, such as electric vehicles, mobile phones, smart home devices, robots, drones, e-cigarettes, and speakers.

[0104] The electrical device provided by this invention includes the aforementioned battery, and therefore has good electrochemical performance and stability.

[0105] The passivated lithium powder provided by the present invention will be described in detail below through specific embodiments.

[0106] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0107] Example 1

[0108] The method for preparing passivated lithium powder provided in this embodiment includes the following steps:

[0109] 1. Under an argon atmosphere, liquid paraffin and 4-fluoro-2-isopropoxy-phenol (liquid at room temperature, boiling point 231.1℃) are mixed evenly at a volume ratio of 97:3 to obtain a mixed system;

[0110] 2. Add lithium powder to the mixture at a solid-liquid ratio of 10:1, heat to 187°C at 5°C / min, and after the temperature stabilizes, turn on low-speed stirring. After the temperature stabilizes at 187°C again, turn on high-speed stirring to 11000 rpm and maintain for 10 min, then stir at low speed for 300 rpm and maintain at 187°C for 30 min.

[0111] 3. After the system temperature is naturally cooled to 130℃, it is injected into the filter to remove excess solvent, and then transferred to a vacuum dryer to remove excess solvent. The vacuum is maintained at 130℃ for 30 minutes.

[0112] 4. Use high-purity CO2 (99.996% purity) to break the vacuum and maintain the system in a CO2 atmosphere for 60 min at a temperature of 130℃. After cooling, passivated lithium powder containing LiF, Li2CO3, lithium alkoxide, and organic matter is obtained. The organic matter here comes from some inert organic solvents and coking fragments of passivating agent molecules during the molten emulsification of metallic lithium.

[0113] Example 2

[0114] The method for preparing passivated lithium powder provided in this embodiment includes the following steps:

[0115] 1. Under an argon atmosphere, liquid paraffin and 4-fluoro-2-isopropoxy-phenol (liquid at room temperature, boiling point 231.1℃) are mixed evenly at a volume ratio of 97:3 to obtain a mixed system;

[0116] 2. Add lithium powder to the mixture at a solid-liquid ratio of 10:1, heat to 195°C at 5°C / min, and after the temperature stabilizes, turn on low-speed stirring. After the temperature stabilizes at 195°C again, turn on high-speed stirring to 11000 rpm and maintain for 10 min, then stir at low speed for 300 rpm and maintain at 195°C for 30 min.

[0117] 3. After the system temperature is naturally cooled to 135℃, it is injected into the filter to remove excess solvent, and then transferred to a vacuum dryer to remove excess solvent. The vacuum is maintained at 135℃ for 30 minutes.

[0118] 4. Use high-purity CO2 (99.996% purity) to break the vacuum and maintain the system in a CO2 atmosphere for 60 minutes at a temperature of 130℃. After cooling, passivated lithium powder containing LiF, Li2CO3, lithium alkoxides, and organic matter is obtained.

[0119] Example 3

[0120] The method for preparing passivated lithium powder provided in this embodiment includes the following steps:

[0121] 1. Under an argon atmosphere, liquid paraffin and 4,5-difluoro-2-methylphenol (liquid at room temperature, boiling point 210℃) are mixed evenly at a volume ratio of 97:3 to obtain a mixed system;

[0122] 2. Add lithium powder to the mixture at a solid-liquid ratio of 10:1, heat to 187°C at 5°C / min, and after the temperature stabilizes, turn on low-speed stirring. After the temperature stabilizes at 187°C again, turn on high-speed stirring to 9000 rpm and maintain for 10 min, then stir at low speed for 500 rpm and maintain at 187°C for 30 min.

[0123] 3. After the system temperature is naturally cooled to 130℃, it is injected into the filter to remove excess solvent, and then transferred to a vacuum dryer to remove excess solvent. The vacuum is maintained at 130℃ for 30 minutes.

[0124] 4. Use high-purity CO2 (99.996% purity) to break the vacuum and maintain the system in a CO2 atmosphere for 60 min at a temperature of 130℃. After cooling, passivated lithium powder containing LiF, Li2CO3, lithium alkoxides, and organic matter is obtained.

[0125] Example 4

[0126] The method for preparing passivated lithium powder provided in this embodiment includes the following steps:

[0127] 1. Under an argon atmosphere, liquid paraffin and 4,5-difluoro-2-methylphenol (liquid at room temperature, boiling point 210℃) are mixed evenly at a volume ratio of 97:3 to obtain a mixed system;

[0128] 2. Add lithium powder to the mixture at a solid-liquid ratio of 10:1, heat to 195°C at 5°C / min, and after the temperature stabilizes, turn on low-speed stirring. After the temperature stabilizes at 195°C again, turn on high-speed stirring to 9000 rpm and maintain for 10 min, then stir at low speed for 500 rpm and maintain at 195°C for 30 min.

[0129] 3. After the system temperature is naturally cooled to 130℃, it is injected into the filter to remove excess solvent, and then transferred to a vacuum dryer to remove excess solvent. The vacuum is maintained at 130℃ for 30 minutes.

[0130] 4. Use high-purity CO2 (99.996% purity) to break the vacuum and maintain the system in a CO2 atmosphere for 100 min at a temperature of 130℃. After cooling, passivated lithium powder containing LiF, Li2CO3, lithium alkoxides, and organic matter is obtained.

[0131] Example 5

[0132] The preparation method of passivated lithium powder provided in this embodiment is basically the same as that in Example 1, except that:

[0133] In step 1, the volume ratio of liquid paraffin to 4-fluoro-2-isopropoxyphenol is 95:5, resulting in passivated lithium powder containing LiF, Li2CO3, lithium alkoxide and organic matter in the passivation layer.

[0134] Example 6

[0135] The preparation method of passivated lithium powder provided in this embodiment is basically the same as that in Example 1, except that:

[0136] In step 1, the volume ratio of liquid paraffin to 4,5-difluoro-2-methylphenol is 95:5, resulting in passivated lithium powder containing LiF, Li2CO3, lithium alkoxide and organic matter in the passivation layer.

[0137] Example 7

[0138] The preparation method of passivated lithium powder provided in this embodiment is basically the same as that in Example 1, except that:

[0139] In step 2, lithium powder is added to the mixture at a solid-liquid ratio of 10:1, and heated to 187°C at 5°C / min. After the temperature stabilizes, low-speed stirring is started. After the temperature stabilizes at 187°C again, high-speed stirring is started at 8000 rpm and maintained for 10 min. Then, low-speed stirring is started at 300 rpm and maintained at 187°C for 30 min.

[0140] Comparative Example 1

[0141] The method for preparing passivated lithium powder provided in this comparative example includes the following steps:

[0142] 1. Under an argon atmosphere, add liquid paraffin and lithium powder to lithium powder at a solid-liquid ratio of 10:1, heat to 187°C at 5°C / min, and after the temperature stabilizes, start low-speed stirring. After the temperature stabilizes at 187°C again, turn on high-speed stirring to 11000 rpm and maintain for 10 min, then stir at low speed for 500 rpm and maintain at 187°C for 30 min.

[0143] 3. After the system temperature is naturally cooled to 130℃, it is injected into a filter to remove excess solvent, and then transferred to a vacuum dryer to remove excess solvent. After maintaining the vacuum at 130℃ for 30 minutes, an inert gas such as Ar is used to break the vacuum to obtain unpassivated lithium powder.

[0144] Comparative Example 2

[0145] The method for preparing passivated lithium powder provided in this comparative example includes the following steps:

[0146] The unpassivated lithium powder obtained in Comparative Example 1 was placed in an ALD device, and then LiF was deposited on the surface of the lithium powder as a raw material to obtain non-in-situ passivated LiF-coated passivated lithium powder.

[0147] Comparative Example 3

[0148] The preparation method of the passivated lithium powder provided in this comparative example is basically the same as that in comparative example 11, except that:

[0149] In step 3, after maintaining a vacuum at 130°C for 30 minutes, CO2 is used to break the vacuum to obtain non-in-situ passivated Li2CO3-coated passivated lithium powder.

[0150] Comparative Example 4

[0151] The method for preparing passivated lithium powder provided in this comparative example includes the following steps:

[0152] The unpassivated lithium powder obtained in Comparative Example 1 was placed in an ALD device, and LiF and Li2CO3 were deposited on the surface of the lithium powder as raw materials to obtain non-in-situ passivated lithium powder coated with LiF and Li2CO3.

[0153] Test case

[0154] 1. The passivated lithium powder provided in all embodiments and comparative examples was tested, including the following steps:

[0155] 1) Particle size test: Dedicated Malvern laser particle size analyzer.

[0156] 2) Passivation layer thickness test: frozen FIB combined with SEM.

[0157] 3) Passivation layer composition test: After the above passivation lithium powder sample is prepared in a glove box, it is transferred under vacuum to the XPS test chamber for XPS test.

[0158] The specific test results are shown in Table 1.

[0159] Note: The contents of LiF, Li2CO3, and lithium alcohols here refer to the proportions of the passivation layer. The effective lithium content mentioned below refers to the proportion of active lithium to the total lithium powder particles.

[0160] Table 1

[0161]

[0162] 2. Passivated lithium powder air exposure test

[0163] All passivated lithium powder samples provided in the examples and comparative examples were sampled in 100 mg units and then sealed and transferred to a constant temperature and humidity test chamber. The test chamber was pre-set to a dew point of -20°C and an air environment of 20°C. The samples were placed in the test chamber for air exposure experiments, and samples were taken at different times. The test results are shown in Table 2.

[0164] 3. Effective lithium test

[0165] Weigh approximately 40 mg of the passivation powder provided in all examples and comparative examples into a specially made crucible, and quickly place it into the chamber of a differential scanning calorimeter. Tests are conducted under an Ar protective atmosphere: the heating range is 30–200 °C, and the heating rate is 5 °C / min. After obtaining the test curves, the effective lithium content is determined by comparing the sample's enthalpy of melting with the standard enthalpy of melting of metallic lithium. The test results are shown in Table 2.

[0166] 4. Lithium replenishment capacity test of passivated lithium powder

[0167] The passivated lithium powders provided in all examples and comparative examples were prepared at 2 mg / cm³. 2 The lithium powder was evenly distributed on the surface of the artificial graphite negative electrode, and a force of ~10 MPa was applied to crush the lithium powder particles, releasing the inner metallic lithium. After standing, a battery was assembled using the graphite electrode as the negative electrode to test the lithium powder replenishment capacity. The test conditions for capacity testing were a test window of 0~0.6V and a charging current of 0.1C. The test results are shown in Table 2.

[0168] 5. Battery cycle life test after lithium replenishment with passivated lithium powder

[0169] The passivated lithium powders provided in all examples and comparative examples were prepared at 2 mg / cm³. 2 The lithium powder was evenly sprinkled on the surface of the artificial graphite negative electrode, and a force of ~10 MPa was applied to crush the lithium powder particles and release the inner layer of metallic lithium. After standing, the graphite electrode was used as the negative electrode to assemble the battery and test the battery cycle life.

[0170] The battery prepared above was subjected to cycle performance testing at room temperature of 25°C. The test process is as follows: first, it was charged to 4.2V at 3C constant current, then charged at constant voltage with a cutoff current of 0.05C, and finally discharged to 2.5V at 1C constant current. This cycle test was repeated until the capacity decayed to 80%. The test results are shown in Table 2.

[0171] Table 2

[0172]

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passivated lithium powder, characterized in that, The passivated lithium powder comprises lithium powder and a passivation layer coated on the surface of the lithium powder; The passivation layer comprises a product generated by in-situ reaction of 4-fluoro-2-isopropoxyphenol and / or 4,5-difluoro-2-methylphenol with the lithium powder at 180-220℃; The product comprises LiF and lithium alcoholate.

2. The passivated lithium powder of claim 1, wherein, The passivation layer further comprises Li2CO3.

3. The passivated lithium powder of claim 1 or 2, wherein, The D50 particle size of the passivated lithium powder is 30-60 μm; And / or, the thickness of the passivation layer is 150-400 nm.

4. A process for the preparation of the passivated lithium powder according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Under an argon atmosphere, 4-fluoro-2-isopropoxyphenol and / or 4,5-difluoro-2-methylphenol is mixed with an inert solvent to obtain a mixed system; lithium powder is added to the mixed system, and the reaction is carried out at 180-220℃ to obtain the passivated lithium powder.

5. The preparation method according to claim 4, characterized in that, The inert solvent comprises liquid paraffin; And / or, the volume ratio of the inert solvent to the 4-fluoro-2-isopropoxyphenol and / or 4,5-difluoro-2-methylphenol is 70:30-99:1; And / or, the reaction is carried out under stirring, and the stirring rate is 5000-20000 rpm; And / or, the reaction time is 0.5-24 h.

6. The preparation method according to claim 5, characterized in that, The volume ratio of the inert solvent to the 4-fluoro-2-isopropoxyphenol and / or 4,5-difluoro-2-methylphenol is 95:5-98:2; and / or, The stirring rate is 8000-11000 rpm; and / or, The reaction time is 0.5-1.5 h.

7. The method of any one of claims 4-6, wherein, After the reaction is completed, the temperature of the reaction system is lowered to below the melting point of metallic lithium, and the reaction system is subjected to vacuum drying treatment; The temperature of the vacuum drying treatment is ≤180℃.

8. The preparation method according to claim 7, characterized in that, The temperature of the vacuum drying treatment is 130-140℃.

9. The preparation method according to claim 7, characterized in that, After the vacuum drying treatment is completed, CO2 gas is introduced into the reaction system at a temperature of 120-179℃.

10. The method of claim 9, wherein, CO2 gas is introduced into the reaction system at a temperature of 130-140℃.

11. A negative electrode sheet characterized by comprising: The passivated lithium powder of claims 1-3 or prepared by the method of any one of claims 4-10.

12. A battery, characterized by The negative electrode sheet of claim 11.

13. An electrical device, characterized by The battery of claim 12.

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