阅读说明：本技术 一种热电池电解质用多孔llzo陶瓷粉体抑制剂及其制备方法 (Porous LLZO ceramic powder inhibitor for thermal battery electrolyte and preparation method thereof ) 是由 温兆银 吴梅芬 郑楚均 常强 于 2021-07-20 设计创作，主要内容包括：本发明公开一种热电池电解质用多孔LLZO陶瓷粉体抑制剂及其制备方法。所述热电池电解质用多孔LLZO陶瓷粉体抑制剂包括多级复合孔结构的多孔LLZO陶瓷粉体和原位修饰于所述多孔LLZO陶瓷粉体表面的金属氧化物保护膜；所述金属氧化物为SiO-2、Al-2O-3、TiO-2、ZrO-2、SnO-2、MgO中的至少一种；其中多孔LLZO陶瓷粉体和金属氧化物保护膜的质量比为10：1-100：1。所述多孔LLZO陶瓷粉体抑制剂能够抑制热电池电解质的溢出并减少惰性抑制剂的使用,实现提高热电池电解质的电导率、提升电池的功率密度和延长电池寿命。(The invention discloses a porous LLZO ceramic powder inhibitor for a thermal battery electrolyte and a preparation method thereof. The porous LLZO ceramic powder inhibitor for the thermal battery electrolyte comprises porous LLZO ceramic powder with a multi-stage composite pore structure and a metal oxide protective film which is in-situ modified on the surface of the porous LLZO ceramic powder; the metal oxide is SiO 2 、Al 2 O 3 、TiO 2 、ZrO 2 、SnO 2 At least one of MgO; wherein the mass ratio of the porous LLZO ceramic powder to the metal oxide protective film is 10:1-100: 1. the porous LLZO ceramic powder inhibitor can inhibit overflow of the electrolyte of the thermal battery and reduce the use of inert inhibitors, thereby realizing the purposes of improving the conductivity of the electrolyte of the thermal battery, improving the power density of the battery and prolonging the service life of the battery.)

1. The porous LLZO ceramic powder inhibitor for the thermal battery electrolyte is characterized by comprising porous LLZO ceramic powder with a multi-stage composite pore structure and a metal oxide protective film which is in-situ modified on the surface of the porous LLZO ceramic powder; the metal oxide is SiO₂、Al₂O₃、TiO₂、ZrO₂、SnO₂At least one of MgO; wherein the mass ratio of the porous LLZO ceramic powder to the metal oxide protective film is 10:1-100: 1.

2. the porous LLZO ceramic powder suppressor for battery electrolyte according to claim 1, wherein the thickness of the metal oxide protective film is 1 to 100 nm.

3. The porous LLZO ceramic powder inhibitor for a thermal battery electrolyte according to claim 1 or 2, wherein said porous LLZO ceramic powder comprises undoped porous LLZO ceramic powder and/or doped elemental porous LLZO ceramic powder; preferably, the doping element comprises at least one of Ta, Al, Zr, F, Nb, Ga, Ca, Mg.

4. The porous LLZO ceramic powder inhibitor for a thermal battery electrolyte according to any one of claims 1 to 3, wherein said porous LLZO ceramic powder has a multi-level pore structure of a composite of mesopores, micropores and macropores.

5. The porous LLZO ceramic powder inhibitor for thermal battery electrolyte as claimed in claim 4, wherein the porous LLZO ceramic powder has a pore size of 1nm-5 μm, a porosity of more than 50%, and a pore volume of 0.5-0.9cm³(ii)/g; preferably, the mesoporous aperture of the porous LLZO ceramic powder is 2-50 nm; the aperture of the micropores is 1-2 nm; the aperture of the big hole is 0.1-10 μm.

6. The preparation method of the porous LLZO ceramic powder inhibitor for thermal battery electrolyte according to any one of claims 1 to 5, wherein the preparation method forms a coating layer on the surface of the porous LLZO ceramic powder through the mutual electrostatic adsorption of a metal oxide precursor and a surface passivation film of the porous LLZO ceramic powder, and then the coating layer is calcined to obtain the porous LLZO ceramic powder inhibitor for thermal battery electrolyte.

7. The method of claim 6, comprising the steps of:

(1) surface treatment to form a passivation film: calcining the porous LLZO ceramic powder with the multi-level composite pore structure in an air atmosphere at the temperature of 450-650 ℃ for 2-5h, collecting the powder, and adjusting the temperature and humidity to form a passivation film on the surface of the porous LLZO ceramic powder;

(2) the metal oxide precursor and the porous LLZO ceramic powder after surface treatment have mutual electrostatic adsorption effect: adding a metal oxide precursor solution into porous LLZO ceramic powder with a passivation film formed on the surface, adjusting the pH of the solution to 8-9, stirring for reaction, separating and drying;

(3) modifying the metal oxide protective film: calcining the reaction product in the step (2) for 2-5h at the temperature of 300-500 ℃ in the air atmosphere to obtain the porous LLZO ceramic powder inhibitor for the electrolyte of the thermal battery.

8. The preparation method according to claim 7, wherein in the step (1), the temperature and humidity of the mixture are adjusted to 20-30 ℃, the humidity of the mixture is 20-40%, and the standing time is 6-12 h.

9. The production method according to claim 7 or 8, wherein in the step (2), the concentration of the metal oxide precursor solution is 0.01 to 1 g/mL; the metal oxide precursor contains at least one of metal alkoxide, metal ester salt and metal organic complex; the mass ratio of the metal oxide precursor to the porous LLZO ceramic powder is 1:100-1: 10.

10. The preparation method according to any one of claims 6 to 9, wherein the nano LLZO ceramic powder is spray-dried with a pore former to form a porous LLZO ceramic powder with a multi-stage composite pore structure.

Technical Field

The invention relates to a porous LLZO ceramic powder inhibitor for a thermal battery electrolyte and a preparation method thereof, belonging to the field of chemical power sources.

Background

The thermal battery is a molten salt electrolyte reserve type battery, and is widely applied to the military fields of electronic countermeasure, aerospace, missile and the like due to the advantages of long storage time, quick and reliable activation, wide working temperature range, high specific power and the like. In recent years, with the development of weaponry technology, higher requirements are put on the performance of a thermal battery in service conditions of high power, rapid activation and the like. The thermal battery consists of positive and negative electrodes and a molten salt electrolyte. The electrolyte is solid-state insulated at normal temperature, and becomes liquid when the temperature exceeds the melting point of the electrolyte during working, thereby having higher lithium ion conductivity (usually 1S cm)^-1Above), the battery is activated. However, the liquid molten electrolyte has fluidity and is easily spilled in practical use, which accelerates self-discharge of the thermal battery, and may even cause short circuit of the battery in severe cases, thereby adversely affecting the service life and safety of the thermal battery. In order to inhibit the electrolyte from flowing, MgO and SiO with high specific surface are generally required to be added into the electrolyte₂、Al₂O₃、TiO₂、ZrO₂、MgF₂Etc. to inhibit electrolyte overflow. However, these inert chemicals do not have an ion conducting function by themselves, and the higher the content in the electrolyte sheet, the higher the electrolyte sheet resistivity, and the lower the battery performance.

LLZO ceramics (lithium lanthanum zirconium oxide ceramics) is used as one of preferable materials for electrolytes of lithium metal solid-state batteries because of its advantages of high safety, wide electrochemical window, high thermal stability, stability to lithium metal, etc. However, the conductivity of the LLZO ceramic is 2-3 orders of magnitude lower than that of molten salt electrolyte, and the instantaneous high-power output requirement of the thermal battery cannot be met.The LiCl-LiBr-LiF molten salt electrolyte with different proportions is adopted by equal Liuhai to dope the LLZO to obtain the high-conductivity composite electrolyte (the conductivity is 2.802 multiplied by 10 at the temperature of 550℃)^-2S cm^-1) And is successfully applied to thermal batteries (Ionics,26(2020), 3875-3882). The single particle of the LLZO powder has no adsorption function on the molten salt electrolyte, and the doping of the LLZO in the molten salt electrolyte can improve the conductivity of the molten salt electrolyte but cannot prevent the molten salt electrolyte from dissolving out. Chinese patent CN 201910145492.6 establishes rapid Li by doping small amount of alkali metal halide eutectic salt in porous loose structure LLZO⁺A transmission channel to increase the LLZO conductivity. However, the LLZO porosity of the porous loose structure is limited, so that the amount of doped molten salt electrolyte salt is small (the mass fraction of molten salt is 5-15%), which is far lower than the requirement of the content of molten salt electrolyte in the electrolyte of a military thermal battery (the content of molten salt electrolyte is more than or equal to 40%), which influences the power performance of the thermal battery.

Therefore, how to improve the conductivity of the electrolyte of the thermal battery, improve the power output characteristics of the thermal battery, effectively inhibit the flow of the electrolyte, and reduce or avoid the use of inert inhibitors becomes a hotspot and difficulty of the current research on the electrolyte of the thermal battery.

Disclosure of Invention

Aiming at the problems, the invention provides a porous LLZO ceramic powder inhibitor for a thermal battery electrolyte and a preparation method thereof, wherein the porous LLZO ceramic powder inhibitor can inhibit the overflow of the thermal battery electrolyte and reduce the use of an inert inhibitor, thereby realizing the purposes of improving the conductivity of the thermal battery electrolyte, improving the power density of the battery and prolonging the service life of the battery.

In a first aspect, the present invention provides a porous LLZO ceramic powder suppressor for a thermal battery electrolyte. The porous LLZO ceramic powder inhibitor for the thermal battery electrolyte comprises porous LLZO ceramic powder with a multi-stage composite pore structure and a metal oxide protective film which is in-situ modified on the surface of the porous LLZO ceramic powder. On one hand, the porous LLZO ceramic powder inhibitor for the thermal battery electrolyte effectively prevents the molten salt electrolyte from dissolving out by utilizing a multi-stage pore structure, and the multi-stage pore structure can also ensure the high adsorption content of the molten salt electrolyte so as to improve the conductivity of the electrolyte; on the other hand, the surface of the porous LLZO ceramic powder is modified with the metal oxide protective film, so that the room-temperature chemical stability of the LLZO ceramic powder can be improved, the LLZO ceramic powder is prevented from reacting with impurities in the air, the room-temperature self-discharge reaction caused by a thermal battery in the storage process is prevented, and the storage life is prolonged.

Preferably, the metal oxide includes, but is not limited to, SiO₂、Al₂O₃、TiO₂、ZrO₂、SnO₂And at least one of MgO. The metal oxide has good compatibility with molten salt electrolyte, does not have lithium ion conductivity at room temperature, can improve the chemical stability of LLZO, prevent the self-discharge of a thermal battery at room temperature, and prolong the storage life of the battery.

Preferably, the mass ratio of the porous LLZO ceramic powder to the metal oxide protective film is 10:1-100: 1. the quality ratio of the metal oxide protective film is too high, so that the conductivity of the electrolyte is improved; too low does not provide a good protective effect, and does not effectively improve the chemical stability of LLZO and prevent the room temperature self-discharge reaction of the thermal battery.

Preferably, the thickness of the metal oxide protective film is 1-100 nm. Because the lithium ion conductivity of the metal oxide protective film is lower than that of the thermal battery molten salt electrolyte and the LLZO electrolyte, the thickness of the metal oxide protective film is controlled within the range, and the reduction of the lithium ion conductivity of the overall composite electrolyte of the thermal battery in the working process of the thermal battery can be avoided.

Preferably, the porous LLZO ceramic powder includes undoped porous LLZO ceramic powder and/or porous LLZO ceramic powder doped with an element. The doping element may comprise at least one of Ta, Al, Zr, F, Nb, Ga, Ca, Mg.

Preferably, the porous LLZO ceramic powder has a multi-level pore structure with composite mesopores, micropores and macropores.

Preferably, the pore diameter of the porous LLZO ceramic powder is 1nm-5 μm, the porosity is more than 50%, and the pore volume is 0.5-0.9cm³(ii) in terms of/g. In some technical schemes, the mesoporous aperture of the porous LLZO ceramic powder is 2-50 nm; the aperture of the micropores is 1-2 nm; big holeThe diameter is 0.1-10 μm.

In a second aspect, the present invention provides a method for preparing the porous LLZO ceramic powder suppressor for a thermal battery electrolyte as defined in any one of the above. The preparation method comprises the steps of forming a coating layer on the surface of the porous LLZO ceramic powder through the mutual electrostatic adsorption effect of a metal oxide precursor and a surface passivation film of the porous LLZO ceramic powder, and then calcining to obtain the porous LLZO ceramic powder inhibitor for the thermal battery electrolyte.

Preferably, the preparation method of the porous LLZO ceramic powder inhibitor for the thermal battery electrolyte comprises the following steps:

(1) surface treatment to form a passivation film: calcining the porous LLZO ceramic powder with the multi-level composite pore structure in an air atmosphere at the temperature of 450-650 ℃ for 2-5h, collecting the powder, and adjusting the temperature and humidity to form a passivation film on the surface of the porous LLZO ceramic powder for later use;

(2) the metal oxide precursor and the porous LLZO ceramic powder after surface treatment have mutual electrostatic adsorption effect: adding a metal oxide precursor solution into porous LLZO ceramic powder with a passivation film formed on the surface, adjusting the pH of the solution to 8-9, stirring for reaction, separating and drying;

(3) modifying the metal oxide protective film: calcining the reaction product in the step (2) for 2-5h at the temperature of 300-500 ℃ in the air atmosphere to obtain the porous LLZO ceramic powder inhibitor for the electrolyte of the thermal battery.

Preferably, in the step (1), the temperature and humidity of the mixture are adjusted to 20-30 ℃, the humidity is 20-40%, and the standing time is 6-12 h. The purpose of temperature and humidity regulation is to form LiOH and/or Li on the surface of the LLZO ceramic powder₂CO₃The passivation film of (1).

Preferably, in the step (2), the concentration of the metal oxide precursor solution is 0.01-1 g/mL; the metal oxide precursor contains at least one of metal alkoxide, metal ester salt and metal organic complex; the mass ratio of the metal oxide precursor to the porous LLZO ceramic powder is 1:100-1: 10.

Preferably, the nano-LLZO ceramic powder is subjected to spray drying by means of a pore-forming agent to form the porous LLZO ceramic powder with the multi-stage composite pore structure.

PreferablyUniformly stirring nano LLZO ceramic powder, a pore-forming agent, a dispersing agent, a binder, a pH regulator, a solvent and a pore-forming agent to form slurry, and then spray-drying the slurry to obtain the porous LLZO ceramic powder. The solid content (mass percent Korean content) of the slurry is 30-60%. The pH of the slurry is 10-12. Preferably, the pH adjuster comprises LiOH, Li₂CO₃And ammonia, the solvent comprises at least one of water, ethanol, methanol and isopropanol, and the dispersing agent and the binder comprise at least one of polyvinyl alcohol, polyethylene glycol, polyvinyl butyral and polyethylene oxide.

Preferably, the pore-forming agent includes, but is not limited to, at least one of inorganic carbon powder, polystyrene, polymethyl methacrylate, and functionalized polystyrene. Functionalization includes, but is not limited to, sulfonation, carboxylation, hydroxylation, amination, and thiolation. Preferably, the morphology of the pore-forming agent is spherical, and the particle size is 50nm-1 μm. The content of the pore-forming agent can be 10-50% of the mass of the nano LLZO ceramic powder.

Preferably, the slurry for spray drying is fed at a rate of 10-50mL/min, the inlet temperature is 180-210 ℃, and the outlet temperature is 70-90 ℃.

Has the advantages that:

1. the porous LLZO ceramic powder inhibitor for the thermal battery electrolyte has a multi-level pore structure with high porosity and different pore size distribution, can effectively improve the adsorption performance and the adsorption content of a molten salt electrolyte, can improve the chemical stability of the LLZO by a metal oxide protective film on the surface, avoids the reaction of the LLZO and impurities in the air, effectively prevents the lithium ion conduction between a positive electrode and a negative electrode at room temperature, inhibits the self-discharge reaction in the storage process of the thermal battery, and thus prolongs the service life and the storage time of the thermal battery;

2. the porous LLZO ceramic powder inhibitor for the thermal battery electrolyte has higher lithium ion conductivity when the thermal battery works, and the instantaneous power output performance of the thermal battery is obviously improved;

3. the preparation method of the porous LLZO ceramic powder inhibitor for the thermal battery electrolyte has the advantages of simple and convenient operation, low cost and environmental protection.

Drawings

FIG. 1 is a schematic view showing the preparation of a porous LLZO ceramic powder inhibitor for a thermal battery electrolyte;

FIG. 2 is a microscopic morphology of porous LLZO ceramic powder made with different pore former contents of an unmodified metal oxide protective film;

FIG. 3 is a pore size distribution curve of porous LLZO ceramic powder prepared with different pore former contents for an unmodified metal oxide protective film.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative of, and not restrictive on, the present invention. Unless otherwise specified, each percentage means a mass percentage.

The invention provides a porous LLZO ceramic powder inhibitor for a thermal battery electrolyte, which can also be called as porous LLZO ceramic powder with a surface modified with a metal oxide protective film. The porous LLZO ceramic powder inhibitor for the thermal battery electrolyte comprises porous LLZO ceramic powder with a multi-stage composite pore structure (also called as 'porous LLZO powder') and a metal oxide protective film (also called as 'metal oxide modification layer') which is modified on the surface of the porous LLZO ceramic powder in situ.

The porous LLZO ceramic powder can be porous LLZO powder, and also can be porous LLZO powder doped with different elements. The doping element includes but is not limited to at least one of Ta, Al, Zr, F, Nb, Ga, Ca, Mg. In some embodiments, the porous LLZO powder has a pore size distribution of 1nm to 5 μm, a porosity of greater than 50%, and a pore volume of 0.5 to 0.9cm³(ii) in terms of/g. The porous LLZO ceramic powder has particle diameter of 1-20 μm and tap density of 0.5-1g/cm³. The green body formed by the porous LLZO ceramic powder can have a room temperature resistance of more than 10⁷Ω.cm。

The metal oxide protective film is positioned inside and on the surface of the pore structure, so that the LLZO chemical stability can be improved, the self-discharge reaction of the thermal battery can be inhibited, and the storage life of the battery can be prolonged. In some embodiments, the thickness of the metal oxide protective film is 1-100 nm. The metal oxide may be SiO₂、Al₂O₃、TiO₂、ZrO₂、MgO、SnO₂At least one of them.

Preferably, in the porous LLZO ceramic powder inhibitor for a thermal battery electrolyte, the mass ratio of the porous LLZO ceramic powder to the metal oxide protective film is 10:1-100: 1. the LLZO ceramic powder with the surface containing the metal oxide modification layer and various pore structures is used as a thermal battery electrolyte inhibitor and can replace the currently common molten salt electrolyte adsorbent such as SiO₂MgO and the like, on one hand, the conductivity of the electrolyte of the thermal battery can be improved, the multiplying power performance of the battery is improved, on the other hand, the chemical stability of the LLZO is improved through the coating of the metal oxide modification layer, the side reaction that the thermal battery generates self-discharge due to the fact that the LLZO conducts lithium ions at room temperature is avoided, and the storage life of the thermal battery is prolonged.

In the prior art, a lithium-containing compound is generally coated on the surface of the LLZO powder to establish a pure lithium ion conductive intermediate transition layer between a metallic lithium negative electrode and an interface of the LLZO solid electrolyte, and the transition layer has high lithium ion conductivity and no electron conductivity, so that the growth of lithium dendrite is effectively inhibited. The metal oxide modification layer coated on the surface of the porous LLZO ceramic powder with the multi-stage composite pore structure in situ does not have room-temperature lithium ion conductivity. Just because it does not have lithium ion conduction ability, can avoid leading to the thermal battery storage process self-discharge reaction by LLZO room temperature conduction lithium ion, also avoid simultaneously LLZO stores in the process and contacts with the impurity of air and produce the side reaction to promote the chemical stability of LLZO and improve the storage life of thermal battery.

The porous LLZO ceramic powder inhibitor for the thermal battery electrolyte not only has a layer of metal oxide protective film on the surface, but also has a porous structure with composite mesopores, micropores and macropores. The overflow of molten salt electrolyte in the working process of the thermal battery can be inhibited through the cooperation of the two, the use of inert inhibitors is reduced, the conductivity of the electrolyte of the thermal battery is improved, the power density of the thermal battery is improved, and the storage time and the service life of the thermal battery are prolonged.

The invention also discloses a preparation method of the porous LLZO ceramic powder inhibitor for the thermal battery electrolyte. The porous LLZO ceramic powder is firstly pretreated to form the powder containing LiOH and/or Li₂CO₃The passivation film is prepared by inducing the metal oxide precursor to coat the surface of the LLZO ceramic powder by utilizing the electrostatic adsorption effect between the passivation film component and the metal oxide precursor, and finally calcining to form the metal oxide protective film. The metal oxide protective film is coated on the surface of the porous LLZO ceramic powder, does not participate in the sintering process of the LLZO ceramic, is not used as a component of a LLZO solid ceramic electrolyte, and is only used as a surface modification layer of the LLZO powder, so that the effects of improving the chemical stability of the LLZO powder and preventing the self-discharge of a thermal battery at room temperature are achieved.

By way of example, the preparation method comprises the steps of preparing mesoporous, microporous and macroporous composite porous LLZO ceramic powder by adopting a spraying method, performing mutual electrostatic adsorption between a metal oxide precursor and a surface passivation film of the porous LLZO ceramic powder, and then calcining to form the porous LLZO ceramic powder coated with a surface modified metal oxide protective film.

And (3) carrying out nano treatment on the LLZO ceramic powder. Preparing the LLZO powder and a solvent into slurry, and performing ball milling and refining to form the nano LLZO ceramic powder. For example, LLZO powder and isopropyl alcohol are mixed in a mass ratio of 1:10 grinding the mixture by adopting a high-speed ball mill after preparing the mixture into slurry, collecting the slurry, placing the slurry in a blast oven for drying, and sieving the dried slurry by using a 80-mesh sieve for later use. The grain diameter of the nano LLZO ceramic powder can be D₅₀Up to 200-300nm, D₉₀Up to 500-700 nm. The grinding speed of the high-speed ball mill can be 1200-2000r/min, and the ball milling time can be 2-4 h. The drying temperature of the blast oven can be 70-100 ℃, and the drying time can be 8-12 h.

And (3) spray forming the LLZO powder to prepare the porous LLZO ceramic powder with the multi-stage composite pore structure. Preparing nano LLZO ceramic powder, a pore-forming agent, a dispersing agent, a binder, a pH regulator and a solvent into slurry according to a certain solid content ratio. The solids content of the slurry may be 30-60%. Wherein the pH regulator includes but is not limited to LiOH, ammonia water, Li₂CO₃At least one of (1); solvents include, but are not limited to, water, ethanol, methanol,At least one of isopropyl alcohol; the dispersing agent and the binder can be at least one selected from polyvinyl alcohol, polyethylene glycol, polyvinyl butyral and polyethylene oxide; the pore-forming agent includes, but is not limited to, at least one of inorganic carbon powder, polystyrene, polymethyl methacrylate, and functionalized polystyrene. The functionalization may be one or more of sulfonation, carboxylation, hydroxylation, amination, and thiolation. In some technical schemes, the shape of the pore-forming agent is spherical, and the particle size is 50nm-1 μm. The content of the pore-forming agent can be 10-50% of the mass of the LLZO powder. Composite porous structures of different porosities can be formed by adding pore formers of different contents and/or different particle sizes. And then, injecting the uniformly stirred slurry by adopting spraying equipment according to a certain flow rate, controlling the temperature of an inlet and an outlet, and collecting the sprayed porous LLZO ceramic powder with the multi-stage composite pore structure. The nozzle diameter may be 1 mm. In some embodiments, the flow rate of the sprayed slurry is 10 to 50 mL/min; the inlet temperature is 180 ℃ and 210 ℃; the outlet temperature is 70-90 ℃. In the method, the LLZO powder is subjected to nanocrystallization and spray drying (secondary granulation) to obtain the LLZO ceramic powder with the multi-stage composite pore structure.

Calcining the spray-dried powder in an air atmosphere for a period of time, collecting the calcined powder, and storing the calcined powder in an air atmosphere with certain temperature and humidity for a period of time. The purpose of calcination is to remove the binder and pore former. The calcination temperature can be 450-650 ℃, and the calcination time can be 2-5 h. The calcined powder can be stored at the environment temperature of 20-30 ℃ and the humidity of 20-40% for 6-12 h. The long-term storage in the above environment is intended to form a product containing LiOH and/or Li₂CO₃The passivation film of (3) is coated with an inducing metal oxide precursor. The thickness of the surface passivation film can be 1-100 nm. The above realizes surface treatment of the porous LLZO powder to form a passivation film on the surface thereof.

And (3) performing electrostatic adsorption on the porous LLZO powder with the passivation film formed on the surface and the metal oxide precursor to form the metal oxide protective film. The metal oxide (precursor composition) is electrostatically adsorbed and fixed on the surface of the LLZO powder through the components of the passivation film to form a precursor coating layer of the metal oxide, so that the metal oxide coating layer can be conveniently formed through subsequent calcination treatment. If the metal oxide precursor is directly acted by the LLZO, on one hand, basic acting groups cannot be provided and the fixing effect on the metal oxide precursor is not firm, and on the other hand, the metal oxide precursor is directly acted by the LLZO, and the metal oxide can react with the LLZO component to obtain a second-phase electrolyte after the calcination treatment, so that the LLZO component is changed and the conductivity of the LLZO is influenced.

Preparing a metal oxide precursor solution with a certain concentration, adding the porous LLZO powder after surface treatment, adjusting the pH value of the solution to 8-9, stirring for a certain time, filtering, washing and drying. The metal oxide precursor includes, but is not limited to, at least one of metal oxide organic alkoxide, ester salt and organic metal complex. The concentration of the metal oxide precursor solution is 0.01-1 g/mL. The mass ratio of the porous LLZO powder to the metal oxide precursor is 10:1-100:1, which is realized by the mass ratio of the powder after surface treatment to the metal oxide precursor solution. The solution pH regulator includes but is not limited to at least one of ammonia, triethylamine, diethylamine and methylamine. The stirring speed can be 100-400r/min, and the stirring time can be 1-3 h. Thus, the metal oxide protective film is formed by the electrostatic adsorption interaction between the porous LLZO powder and the metal oxide precursor, the surface of which forms the passivation film.

And drying the ceramic powder subjected to electrostatic adsorption, and calcining the dried ceramic powder in an air atmosphere for a period of time to obtain the porous LLZO ceramic powder inhibitor for the electrolyte of the thermal battery. The calcination temperature is 300-500 ℃, and the calcination time is 2-5 h.

The preparation method of the invention prepares the porous ceramic powder containing LiOH and/or Li on the surface by a pretreatment mode₂CO₃The passivation film induces (the precursor composition of) metal oxide to coat the surface of the porous ceramic powder by utilizing the electrostatic adsorption effect between the passivation film component and the metal oxide precursor, and then the metal oxide protective layer is obtained by calcining.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

Mixing LLZO ceramic powder and an anhydrous isopropanol solvent according to a mass ratio of 1:10, grinding for 3 hours at the speed of 1800r/min by adopting a high-speed ball mill, drying in a blast oven at 70 ℃, and screening and refining by using a 80-mesh sieve for later use. Preparing the refined ceramic powder, polyethylene glycol, lithium hydroxide and water into slurry with the solid content of 20%, adjusting the pH of the slurry to 11, adding a carbon powder pore-forming agent with the mass fraction of 10% and the diameter of 500nm, and uniformly stirring. Injecting sample by using a spraying device with a nozzle diameter of 1mm, controlling the feeding flow rate to be 0.5mL/min, the inlet temperature to be 200 ℃, and the outlet temperature to be 82 ℃. Collecting the sprayed powder, calcining the powder for 3h at 600 ℃ in an air atmosphere, taking out the powder, and placing the powder for 6h in an air atmosphere with the temperature of 25 ℃ and the humidity of 30 percent to obtain the powder after surface treatment. Preparing 0.5g/mL alcoholic solution of aluminum triethoxide, adjusting the pH value to 8.5 by using triethylamine, stirring and mixing the alcoholic solution and the powder after surface treatment according to the mass ratio of 1:20, controlling the stirring speed to be 300r/min and the stirring time to be 2h, and then filtering, washing and drying. Calcining the dried powder for 3h at 450 ℃ in an air atmosphere to obtain the porous LLZO ceramic powder (LLZO inhibitor) with the surface modified with the metal oxide protective film.

The composite powder obtained by uniformly mixing porous LLZO ceramic powder and molten salt electrolyte LiCl-KCl in a mass ratio of 1:1 by a dry method is used as the electrolyte of a thermal battery, the positive electrode is iron disulfide, the negative electrode is LiB alloy, the thermal battery is assembled by a powder tabletting method, and the temperature is kept at 500 ℃ and is 100mA/cm²The discharge was carried out until the discharge cut-off voltage became 0.01V. Compared with a thermal battery electrolyte adopting MgO as an inhibitor, the thermal battery adopting the composite electrolyte of the porous LLZO ceramic powder has the advantages that the discharge specific capacity is improved by 2-10% under the same test condition, and the impedance of the thermal battery is reduced after dischargeThe reduction is 10-40%. Compared with the porous LLZO ceramic powder, when the composite electrolyte prepared by the porous LLZO inhibitor for modifying the metal oxide protective film and the molten salt electrolyte under the same condition is used as the thermal battery electrolyte, the discharge specific capacity and impedance are not obviously reduced under the same test condition, and the room-temperature storage life is prolonged by 10-50%.

Example 2

Mixing LLZO ceramic powder and an anhydrous isopropanol solvent according to a mass ratio of 1:10, grinding for 3 hours at the speed of 1800r/min by adopting a high-speed ball mill, drying in a blast oven at 70 ℃, and screening and refining by using a 80-mesh sieve for later use. Preparing the refined ceramic powder, polyethylene glycol, lithium hydroxide and water into slurry with the solid content of 20%, adjusting the pH of the slurry to 11, adding a carbon powder pore-forming agent with the mass fraction of 20% and the diameter of 500nm, and uniformly stirring. The sample is injected by a spraying device with a nozzle diameter of 1mm, the feeding flow rate is controlled to be 0.5mL/min, the inlet temperature is 200 ℃, and the outlet temperature is 82 ℃. Collecting the sprayed powder, calcining the powder for 3h at 600 ℃ in an air atmosphere, taking out the powder, and placing the powder for 6h in an air atmosphere with the temperature of 25 ℃ and the humidity of 30 percent to obtain the powder after surface treatment. Preparing 0.5g/mL of an alcohol solution of aluminum triethoxide, adjusting the pH value to 8.5 by using triethylamine, stirring and mixing the alcohol solution and the powder after surface treatment according to the mass ratio of 1:20, controlling the stirring speed to be 300r/min and the stirring time to be 2h, and then filtering, washing and drying. Calcining the dried powder for 3h at 450 ℃ in an air atmosphere to obtain the porous LLZO ceramic powder with the surface modified with the metal oxide protective film.

Example 3

Mixing LLZO ceramic powder and an anhydrous isopropanol solvent according to a mass ratio of 1:10, grinding for 3 hours at the speed of 1800r/min by adopting a high-speed ball mill, drying in a blast oven at 70 ℃, and screening and refining by using a 80-mesh sieve for later use. Preparing the refined ceramic powder, polyethylene glycol, lithium hydroxide and water into slurry with the solid content of 20%, adjusting the pH of the slurry to 11, adding a carbon powder pore-forming agent with the mass fraction of 30% and the diameter of 500nm, and uniformly stirring. The sample is injected by a spraying device with a nozzle diameter of 1mm, the feeding flow rate is controlled to be 0.5mL/min, the inlet temperature is 200 ℃, and the outlet temperature is 82 ℃. Collecting the sprayed powder, calcining the powder for 3h at 600 ℃ in an air atmosphere, taking out the powder, and placing the powder for 6h in an air atmosphere with the temperature of 25 ℃ and the humidity of 30 percent to obtain the powder after surface treatment. Preparing 0.5g/mL of an alcohol solution of aluminum triethoxide, adjusting the pH value to 8.5 by using triethylamine, stirring and mixing the alcohol solution and the powder after surface treatment according to the mass ratio of 1:20, controlling the stirring speed to be 300r/min and the stirring time to be 2h, and then filtering, washing and drying. Calcining the dried powder for 3h at 450 ℃ in an air atmosphere to obtain the porous LLZO ceramic powder with the surface modified with the metal oxide protective film.

Example 4

Mixing LLZO ceramic powder and an anhydrous isopropanol solvent according to a mass ratio of 1:10, grinding for 3 hours at the speed of 1800r/min by adopting a high-speed ball mill, drying in a blast oven at 70 ℃, and screening and refining by using a 80-mesh sieve for later use. Preparing the refined ceramic powder, polyethylene glycol, lithium hydroxide and water into slurry with the solid content of 20%, adjusting the pH of the slurry to 11, adding a carbon powder pore-forming agent with the mass fraction of 40% and the diameter of 500nm, and uniformly stirring. The sample is injected by a spraying device with a nozzle diameter of 1mm, the feeding flow rate is controlled to be 0.5mL/min, the inlet temperature is 200 ℃, and the outlet temperature is 82 ℃. Collecting the sprayed powder, calcining the powder for 3h at 600 ℃ in an air atmosphere, taking out the powder, and placing the powder for 6h in an air atmosphere with the temperature of 25 ℃ and the humidity of 30 percent to obtain the powder after surface treatment. Preparing 0.5g/mL of an alcohol solution of aluminum triethoxide, adjusting the pH value to 8.5 by using triethylamine, stirring and mixing the alcohol solution and the powder after surface treatment according to the mass ratio of 1:20, controlling the stirring speed to be 300r/min and the stirring time to be 2h, and then filtering, washing and drying. Calcining the dried powder for 3h at 450 ℃ in an air atmosphere to obtain the porous LLZO ceramic powder with the surface modified with the metal oxide protective film.

Example 5

Mixing LLZO ceramic powder and an anhydrous isopropanol solvent according to a mass ratio of 1:10, grinding for 3 hours at the speed of 1800r/min by adopting a high-speed ball mill, drying in a blast oven at 70 ℃, and screening and refining by using a 80-mesh sieve for later use. Preparing the refined ceramic powder, polyethylene glycol, lithium hydroxide and water into slurry with the solid content of 20%, adjusting the pH of the slurry to 11, adding a carbon powder pore-forming agent with the mass fraction of 50% and the diameter of 500nm, and uniformly stirring. The sample is injected by a spraying device with a nozzle diameter of 1mm, the feeding flow rate is controlled to be 0.5mL/min, the inlet temperature is 200 ℃, and the outlet temperature is 82 ℃. Collecting the sprayed powder, calcining the powder at 600 ℃ for 3h in an air atmosphere, taking out the powder, and placing the powder in an air atmosphere with the temperature of 25 ℃ and the humidity of 30% for 6h to obtain the powder after surface treatment. Preparing 0.5g/mL of an alcohol solution of aluminum triethoxide, adjusting the pH value to 8.5 by using triethylamine, stirring and mixing the alcohol solution and the powder after surface treatment according to the mass ratio of 1:20, controlling the stirring speed to be 300r/min and the stirring time to be 2h, and then filtering, washing and drying. Calcining the dried powder for 3h at 450 ℃ in an air atmosphere to obtain the porous LLZO ceramic powder with the surface modified with the metal oxide protective film.