Isolating piece of lithium thermal battery and preparation method of isolating piece

Abstract

The invention discloses a lithium thermal battery separator and a preparation method thereof, the separator is a composite fiber membrane containing inorganic powder and electrolyte salt, and the separator is prepared by an electrostatic spinning technology. According to the isolation piece disclosed by the embodiment of the invention, the isolation piece is high in mechanical strength, relatively good in electrolyte retention capability and relatively thin in thickness, and the lithium thermal battery prepared from the isolation piece is relatively high in working stability and high in battery energy density.

Description

Technical Field

[0001] This invention relates to the field of lithium thermal battery technology, and in particular to a separator for a lithium thermal battery and its preparation method. Background Technology

[0002] Lithium-ion batteries are disposable storage batteries that rely on internal heat sources for activation. They have outstanding advantages such as extremely long storage life (up to 20 years or more), high instantaneous power, and good environmental adaptability (can work from -50℃ to +70℃). They are widely used in military and high-end civilian fields such as aerospace, missile weapons, and deep-sea exploration.

[0003] The separator is one of the core components of a lithium-ion battery, serving to isolate the positive and negative electrodes, prevent physical short circuits that could lead to electron conduction, and absorb and retain the molten electrolyte, providing a transport channel for lithium ions. Currently, traditional lithium-ion battery separators are mainly produced by powder compression molding, which involves mixing ceramic powders such as MgO and SiO2 with electrolyte salts (such as LiCl-KCl eutectic salts) and then pressing them into shape. This type of separator has the following inherent defects: poor mechanical strength and high brittleness, making it prone to cracking under battery assembly, transportation, or activation impacts, leading to short circuits; limited electrolyte retention capacity, with insufficient adsorption and retention of molten electrolyte, affecting the long-term stability of the battery; and difficulty in achieving a thinner profile, limiting further improvements in battery energy density. Therefore, improvements are needed. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a separator for a lithium thermal battery, which has high mechanical strength, good electrolyte retention ability, thin thickness, and results in a lithium thermal battery with high working stability and high energy density.

[0005] The present invention also proposes a method for preparing the above-mentioned separator.

[0006] The present invention also proposes a lithium thermal battery having the above-mentioned separator.

[0007] According to a first aspect of the present invention, a separator for a lithium-ion battery is a composite fiber membrane comprising inorganic powder and electrolyte salt, wherein the separator is prepared by electrospinning technology.

[0008] According to embodiments of the present invention, the separator for a lithium-ion battery is prepared by electrospinning inorganic powder and electrolyte salt to form a composite fiber membrane with a three-dimensional network structure. The composite fiber membrane is used as a separator in a lithium-ion battery. The three-dimensional network structure of the composite fiber membrane has good flexibility and tensile strength, which can overcome the fragility of ceramic sheets and give the separator high mechanical strength. The composite fiber membrane has high porosity and good pore connectivity, which can better adsorb molten electrolyte salt under high temperature conditions, providing sufficient channels for lithium-ion transport and improving the ionic conductivity of the lithium-ion battery. By controlling the electrospinning process time, separators with thicknesses of tens to hundreds of micrometers can be prepared, which is conducive to the thinning of the separator, reducing the space ratio of the separator in the lithium-ion battery, thereby improving the energy density of the lithium-ion battery.

[0009] According to some embodiments of the present invention, the polymer of the composite fiber membrane is one of polyacrylonitrile, polyvinylidene fluoride, polyimide or its derivatives.

[0010] According to some embodiments of the present invention, the inorganic powder includes at least one of magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide.

[0011] According to some embodiments of the present invention, the electrolyte salt is a LiCl-KCl eutectic salt or a LiF-LiCl-LiBr ternary electrolyte.

[0012] A method for preparing a separator for a lithium-ion battery according to a second aspect of the present invention, wherein the separator is the separator described in the first aspect of the present invention, the preparation method comprising the following steps: Step (1): Dissolve the polymer in an organic solvent to prepare a polymer solution; Step (2): Add inorganic powder and electrolyte salt to the polymer solution, and after stirring and ultrasonic treatment, obtain a uniform spinning precursor solution; Step (3): Electrospin the spinning precursor solution to obtain a composite fiber membrane; Step (4): Dry the composite fiber membrane to obtain the separator sheet.

[0013] According to the method for preparing the separator of the lithium thermal battery according to the embodiments of the present invention, by adding inorganic powder and electrolyte salt to the polymer solution to obtain a uniform spinning precursor solution, it is beneficial to make the composite fiber membrane obtained during electrospinning more uniform. Drying the composite fiber membrane allows the organic solvent and polymer in the composite fiber membrane to volatilize, which is beneficial to improving the porosity of the composite fiber membrane. Under high temperature conditions, the composite fiber membrane is more likely to adsorb molten electrolyte. When the composite fiber membrane is used in the lithium thermal battery, it can provide sufficient channels for lithium ion transport, thereby improving the ionic conductivity of the lithium thermal battery.

[0014] According to some embodiments of the present invention, the organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and acetone.

[0015] According to some embodiments of the present invention, in step (3), the parameters of the electrospinning are: voltage 10-30kV, receiving distance 10-20cm, and spinning solution propulsion rate 0.5-2.0mL / h.

[0016] According to a third aspect of the present invention, the lithium thermal battery includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, wherein the separator is the separator described in the first aspect of the present invention.

[0017] According to embodiments of the present invention, a lithium-ion battery is provided with a separator as described in the first aspect of this invention. An inorganic powder and electrolyte salt are electrospinned to form a composite fiber membrane with a three-dimensional network structure, which is then used as a separator in the lithium-ion battery. The three-dimensional network structure of the composite fiber membrane exhibits good flexibility and tensile strength, overcoming the fragility of ceramic sheets and giving the separator high mechanical strength, thereby enhancing the mechanical reliability and stability of the lithium-ion battery. The composite fiber membrane has high porosity and good pore connectivity, enabling better adsorption of molten electrolyte salts under high-temperature conditions, providing sufficient channels for lithium-ion transport and improving the ionic conductivity of the lithium-ion battery. By controlling the electrospinning process time, separators with thicknesses ranging from tens to hundreds of micrometers can be prepared, facilitating the thinning of the separator and reducing its space ratio within the lithium-ion battery, thereby increasing the energy density of the lithium-ion battery.

[0018] According to some embodiments of the present invention, the positive electrode includes at least one of FeS2, CoS2, NiS2, NiCl2, VS2, and MoS2.

[0019] According to some embodiments of the present invention, the negative electrode comprises at least one of a boron-lithium alloy, a lithium-silicon alloy, and a lithium-aluminum alloy. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic flowchart illustrating a method for preparing a separator for a lithium-ion battery according to some embodiments of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] The following is for reference. Figure 1 A separator for a lithium-ion thermal battery according to an embodiment of the present invention is described.

[0023] According to a first aspect of the present invention, the separator of a lithium-ion battery is a composite fiber membrane comprising inorganic powder and electrolyte salt, and the separator is prepared by electrospinning technology.

[0024] Electrospinning is a process that uses a high-voltage electrostatic field to prepare micro / nanofibers. Electrospinning is a special form of electrostatic atomization of polymer fluids. In this process, the atomized material is not split into tiny droplets, but rather into tiny polymer jets that eventually solidify into fibers. The polymer solution or melt is jetted into fibers under a strong electric field. Under the influence of the electric field, the droplets at the needle tip change from a spherical shape to a conical shape, and then extend from the tip of the cone to obtain fine filaments, thus enabling the production of polymer filaments with nanoscale diameters. Electrospinning technology is simple, controllable, and easily scalable for large-area, continuous production.

[0025] Electrospinning technology produces composite fiber membranes with a three-dimensional network structure from inorganic powders and electrolyte salts. These composite fiber membranes are then used as separators in lithium-ion batteries. The three-dimensional network structure of the composite fiber membranes provides excellent flexibility and tensile strength, overcoming the fragility of ceramic sheets. This results in higher mechanical strength for the separators and improves the yield and reliability of battery assembly.

[0026] The composite fiber membrane obtained by electrospinning has a porosity of over 80%. The composite fiber membrane with high porosity and good pore connectivity can better adsorb molten electrolyte salts under high temperature conditions, providing sufficient channels for lithium-ion transport, improving the ionic conductivity of lithium-ion batteries, and thus improving the discharge power of lithium-ion batteries.

[0027] The electrospinning process time is controllable. For example, the electrospinning process time can be shortened to prepare separators with thicknesses ranging from tens to hundreds of micrometers, which is beneficial for thinning the separators and reducing their space ratio within the battery, thereby increasing the battery's energy density. Alternatively, the electrospinning process time can be extended to prepare thicker separators, increasing the selectivity for separators of different thicknesses.

[0028] According to embodiments of the present invention, the separator for a lithium-ion battery is prepared by electrospinning inorganic powder and electrolyte salt to form a composite fiber membrane with a three-dimensional network structure. The composite fiber membrane is used as a separator in a lithium-ion battery. The three-dimensional network structure of the composite fiber membrane has good flexibility and tensile strength, which can overcome the fragility of ceramic sheets and give the separator high mechanical strength. The composite fiber membrane has high porosity and good pore connectivity, which can better adsorb molten electrolyte salt under high temperature conditions, providing sufficient channels for lithium-ion transport and improving the ionic conductivity of the lithium-ion battery. By controlling the electrospinning process time, separators with thicknesses of tens to hundreds of micrometers can be prepared, which is conducive to the thinning of the separator, reducing the space ratio of the separator in the lithium-ion battery, thereby improving the energy density of the lithium-ion battery.

[0029] According to some embodiments of the present invention, the polymer of the composite fiber membrane is one of polyacrylonitrile, polyvinylidene fluoride, polyimide or its derivatives.

[0030] For example, the polymer of the composite fiber membrane can be one of polyacrylonitrile, polyvinylidene fluoride, and polyimide, or it can be a derivative of polyacrylonitrile, polyvinylidene fluoride, and polyimide. For example, the polymer of the composite fiber membrane can be a copolymer of polyacrylonitrile.

[0031] By using polyacrylonitrile, polyvinylidene fluoride, polyimide, or their derivatives as the polymer for the composite fiber membrane, it is beneficial to assist the inorganic powder spinning process during electrospinning. Furthermore, polyacrylonitrile, polyvinylidene fluoride, polyimide, and their derivatives are easily volatilized by drying or heating after the composite fiber membrane is formed, which helps to increase the porosity of the composite fiber membrane. Under high temperature conditions, the composite fiber membrane is more likely to adsorb molten electrolyte. When the composite fiber membrane is used in lithium-ion batteries, it can provide sufficient channels for lithium-ion transport, thereby improving the ionic conductivity of the lithium-ion battery.

[0032] According to some embodiments of the present invention, the inorganic powder includes at least one of magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide.

[0033] For example, the inorganic powder includes at least one of magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide. It can be one of the inorganic powders including magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide, or it can be multiple of the inorganic powders including magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide.

[0034] By using inorganic powders including at least one of magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide, the high-temperature resistance properties of magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide can be utilized to enable the composite fiber membrane prepared to maintain high mechanical strength even under high-temperature conditions.

[0035] According to some embodiments of the present invention, the electrolyte salt is a LiCl-KCl eutectic salt or a LiF-LiCl-LiBr ternary electrolyte. Both the LiCl-KCl eutectic salt and the LiF-LiCl-LiBr ternary electrolyte have relatively low melting points. By using a LiCl-KCl eutectic salt or a LiF-LiCl-LiBr ternary electrolyte as the electrolyte salt, when used in a lithium-ion battery, the electrolyte salt remains in a molten state during discharge, which is beneficial for improving the ionic conductivity of the lithium-ion battery, thereby achieving high-power discharge.

[0036] refer to Figure 1 According to a second aspect of the present invention, a method for preparing a separator for a lithium-ion battery, wherein the separator is the same as that according to a first aspect of the present invention, the preparation method includes the following steps: Step (1): Dissolve the polymer in an organic solvent to prepare a polymer solution, so that the polymer is fully dissolved in the organic solvent, which facilitates the subsequent processing steps. Step (2): Add inorganic powder and electrolyte salt to the polymer solution, and after stirring and ultrasonic treatment, obtain a uniform spinning precursor solution. Obtaining a uniform spinning precursor solution through stirring and ultrasonic treatment is beneficial to obtaining a more uniform product during electrospinning. Step (3): Electrospin the spinning precursor solution and collect the composite fiber membrane. Step (4): Dry the composite fiber membrane to obtain the separator. For example, the composite fiber membrane can be dried in a vacuum chamber at 80°C for 24 hours.

[0037] According to the method for preparing the separator of the lithium thermal battery according to the embodiments of the present invention, by adding inorganic powder and electrolyte salt to the polymer solution to obtain a uniform spinning precursor solution, it is beneficial to make the composite fiber membrane obtained during electrospinning more uniform. Drying the composite fiber membrane allows the organic solvent and polymer in the composite fiber membrane to volatilize, which is beneficial to improving the porosity of the composite fiber membrane. Under high temperature conditions, the composite fiber membrane is more likely to adsorb molten electrolyte. When the composite fiber membrane is used in the lithium thermal battery, it can provide sufficient channels for lithium ion transport, thereby improving the ionic conductivity of the lithium thermal battery.

[0038] According to some embodiments of the present invention, the organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and acetone.

[0039] For example, the organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and acetone, or it can be one of N,N-dimethylformamide, N-methylpyrrolidone, and acetone, or it can be multiple of N,N-dimethylformamide, N-methylpyrrolidone, and acetone.

[0040] By using an organic solvent including at least one of N,N-dimethylformamide, N-methylpyrrolidone, and acetone, it is beneficial to dissolve the polymer in the organic solvent, which facilitates subsequent stirring and ultrasonic treatment after the addition of inorganic powder and electrolyte salt, making it easier to obtain a uniform spinning precursor solution. Furthermore, N,N-dimethylformamide, N-methylpyrrolidone, and acetone are volatile, which facilitates the drying of the composite fiber membrane after electrospinning.

[0041] According to some embodiments of the present invention, in step (3), the parameters of electrospinning are: voltage 10-30kV, receiving distance 10-20cm, and spinning solution propulsion rate 0.5-2.0mL / h.

[0042] For example, the voltage parameters for electrospinning can be 10kV, 15kV, 20kV, 25kV, 30kV, etc.; the receiving distance for electrospinning can be 10cm, 12cm, 14cm, 16cm, 18cm, 20cm, etc.; and the propulsion rate of the spinning solution for electrospinning can be 0.5mL / h, 1mL / h, 1.5mL / h, 2mL / h, etc. If the voltage parameters of electrospinning are too high or too low, or if the propulsion rate of the electrospinning solution is too fast, the jetting of the precursor solution will be unstable, affecting the uniformity of the resulting composite fiber membrane. If the propulsion rate of the electrospinning solution is too slow, the composite fiber membrane will be generated too slowly, reducing the efficiency of electrospinning. If the receiving distance of electrospinning is too short, the amount of organic solvent evaporation during electrospinning will be low, and the jetting of the precursor solution will remain viscous during deposition, easily leading to fiber adhesion or the formation of a flattened structure in the composite fiber membrane, resulting in low uniformity of the composite fiber membrane. If the receiving distance of electrospinning is too long, the accuracy of the jetting deposition of the precursor solution will be reduced, which will also easily lead to low uniformity of the composite fiber membrane.

[0043] By setting the electrospinning parameters in step (3) to 10-30kV, 10-20cm receiving distance, and 0.5-2.0mL / h spinning solution propulsion rate, the jet of the spinning precursor solution is made more stable, and the uniformity of the composite fiber membrane formed during the electrospinning process is improved.

[0044] According to a third aspect embodiment of the present invention, the lithium thermal battery includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, wherein the separator is the separator described in the first aspect embodiment of the present invention.

[0045] According to embodiments of the present invention, a lithium-ion battery is provided with a separator as described in the first aspect of this invention. An inorganic powder and electrolyte salt are electrospinned to form a composite fiber membrane with a three-dimensional network structure, which is then used as a separator in the lithium-ion battery. The three-dimensional network structure of the composite fiber membrane exhibits good flexibility and tensile strength, overcoming the fragility of ceramic sheets and giving the separator high mechanical strength, thereby enhancing the mechanical reliability and stability of the lithium-ion battery. The composite fiber membrane has high porosity and good pore connectivity, enabling better adsorption of molten electrolyte salts under high-temperature conditions, providing sufficient channels for lithium-ion transport and improving the ionic conductivity of the lithium-ion battery. By controlling the electrospinning process time, separators with thicknesses ranging from tens to hundreds of micrometers can be prepared, facilitating the thinning of the separator and reducing its space ratio within the lithium-ion battery, thereby increasing the energy density of the lithium-ion battery.

[0046] According to some embodiments of the present invention, the positive electrode includes at least one of FeS2, CoS2, NiS2, NiCl2, VS2, and MoS2.

[0047] For example, the positive electrode includes at least one of FeS2, CoS2, NiS2, NiCl2, VS2, and MoS2, or it can be one of FeS2, CoS2, NiS2, NiCl2, VS2, and MoS2, or it can be multiple of FeS2, CoS2, NiS2, NiCl2, VS2, and MoS2.

[0048] By including at least one of FeS2, CoS2, NiS2, NiCl2, VS2, and MoS2 in the positive electrode, the characteristic that divalent metals are not prone to dendrite formation can be utilized to prevent the metal in the positive electrode from generating dendrites that pierce the separator during discharge, thereby enhancing the stability of the lithium-ion battery during discharge.

[0049] According to some embodiments of the present invention, the negative electrode comprises at least one of a boron-lithium alloy, a lithium-silicon alloy, and a lithium-aluminum alloy. For example, the negative electrode may contain at least one of boron-lithium alloy, lithium-silicon alloy, and lithium-aluminum alloy. It may contain one of boron-lithium alloy, lithium-silicon alloy, and lithium-aluminum alloy, or it may contain multiple of boron-lithium alloy, lithium-silicon alloy, and lithium-aluminum alloy.

[0050] Among them, boron-lithium alloys, lithium-silicon alloys, and lithium-aluminum alloys are all inexpensive and readily available. By including at least one of these alloys in the negative electrode, it is possible to provide lithium for lithium-ion batteries while reducing production costs.

[0051] The following examples further illustrate the separator of the lithium thermal battery of the present invention, its preparation method, and the lithium thermal battery.

[0052] Example 1, Preparation of spinning solution: Dissolve 1.2g of polyacrylonitrile (PAN) powder in 10mL of N,N-dimethylformamide (DMF) and stir at 60℃ for 6 hours until completely dissolved. Then add 3g of magnesium oxide (MgO) powder and 3g of LiCl-KCl eutectic salt powder, continue stirring for 12 hours, and sonicate for 2 hours to obtain a uniform suspension.

[0053] Electrospinning: The spinning solution was loaded into a syringe, the injection rate was set to 1.0 mL / h, the distance between the needle tip (inner diameter 0.6 mm) and the roller collector was 15 cm, and the applied voltage was 18 kV. The spun fibers were collected on the aluminum foil roller for 8 hours.

[0054] Post-processing: The collected fiber membrane is peeled off the aluminum foil and dried in an 80°C vacuum oven for 24 hours to obtain the final composite fiber separator.

[0055] Battery assembly: The above-mentioned separator, LiSi alloy negative electrode, and FeS2 positive electrode were assembled into an experimental lithium thermal battery unit in an argon glove box.

[0056] Example 2, Preparation of spinning solution: Dissolve 1.2g of polyacrylonitrile (PAN) powder in 10mL of N,N-dimethylformamide (DMF) and stir at 60℃ for 6 hours until completely dissolved. Then add 4g of lithium lanthanum oxide (LLZO) powder and 4g of LiCl-LiBr-LiF eutectic salt powder, continue stirring for 12 hours, and sonicate for 2 hours to obtain a homogeneous suspension.

[0057] Electrospinning: The spinning solution was loaded into a syringe, the injection rate was set to 1.0 mL / h, the distance between the needle tip (inner diameter 0.6 mm) and the roller collector was 15 cm, and the applied voltage was 18 kV. The spun fibers were collected on the aluminum foil roller for 8 hours.

[0058] Post-processing: The collected fiber membrane is peeled off the aluminum foil and dried in an 80°C vacuum oven for 24 hours to obtain the final composite fiber separator.

[0059] Battery assembly: The above-mentioned separator, LiB alloy negative electrode, and FeS2 positive electrode were assembled into an experimental lithium thermal battery unit in an argon glove box.

[0060] Example 3, Preparation of spinning solution: Dissolve 1.2g of polyacrylonitrile (PAN) powder in 10mL of N,N-dimethylformamide (DMF) and stir at 60℃ for 6 hours until completely dissolved. Then add 4g of MgO powder and 4g of LiCl-LiBr-LiF eutectic salt powder, continue stirring for 12 hours, and sonicate for 2 hours to obtain a uniform suspension.

[0061] Electrospinning: The spinning solution was loaded into a syringe, the injection rate was set to 1.0 mL / h, the distance between the needle tip (inner diameter 0.6 mm) and the roller collector was 15 cm, and the applied voltage was 18 kV. The spun fibers were collected on the aluminum foil roller for 8 hours.

[0062] Post-processing: The collected fiber membrane is peeled off the aluminum foil and dried in an 80°C vacuum oven for 24 hours to obtain the final composite fiber separator.

[0063] Battery assembly: The above-mentioned separator, LiB alloy negative electrode, and FeS2 positive electrode were assembled into an experimental lithium thermal battery unit in an argon glove box.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0065] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A separator for a lithium-ion battery, characterized in that, The separator is a composite fiber membrane containing inorganic powder and electrolyte salt, and it is prepared by electrospinning technology.

2. The isolation sheet according to claim 1, characterized in that, The polymer of the composite fiber membrane is one of polyacrylonitrile, polyvinylidene fluoride, polyimide, or their derivatives.

3. The isolation sheet according to claim 1, characterized in that, The inorganic powder includes at least one of magnesium oxide, silicon dioxide, aluminum oxide, titanium dioxide, and lithium lanthanum zirconium oxide.

4. The isolation sheet according to claim 1, characterized in that, The electrolyte salt is a LiCl-KCl eutectic salt or a LiF-LiCl-LiBr ternary electrolyte.

5. A method for preparing a separator for a lithium-ion thermal battery according to any one of claims 1-4, characterized in that, Includes the following steps: Step (1): Dissolve the polymer in an organic solvent to prepare a polymer solution; Step (2): Add inorganic powder and electrolyte salt to the polymer solution, and after stirring and ultrasonic treatment, obtain a uniform spinning precursor solution; Step (3): Electrospin the spinning precursor solution to obtain a composite fiber membrane; Step (4): Dry the composite fiber membrane to obtain the separator sheet.

6. The preparation method according to claim 5, characterized in that, The organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and acetone.

7. The preparation method according to claim 5, characterized in that, In step (3), the parameters of the electrospinning are: voltage 10-30kV, receiving distance 10-20cm, and spinning solution propulsion rate 0.5-2.0mL / h.

8. A lithium-ion thermal battery, comprising a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, characterized in that, The isolation sheet is the isolation sheet according to any one of claims 1-4.

9. The lithium thermal battery according to claim 8, characterized in that, The positive electrode includes at least one of FeS2, CoS2, NiS2, NiCl2, VS2, and MoS2.

10. The lithium thermal battery according to claim 8, characterized in that, The negative electrode comprises at least one of a boron-lithium alloy, a lithium-silicon alloy, and a lithium-aluminum alloy.

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