Lithium-sulfur battery and manufacturing method thereof, and electric device

Abstract

This application relates to the field of lithium-sulfur battery technology, providing a lithium-sulfur battery, its manufacturing method, and an electrical device, which can at least improve the performance of the lithium-sulfur battery. The manufacturing method includes: preparing an initial battery cell; injecting a first electrolyte comprising lithium salt, lithium nitrate, and an ether solvent into the initial battery cell and performing a first formation process; injecting a second electrolyte comprising a zinc ion source, 2-methylimidazole, and an organic solvent into the initial battery cell, wherein the concentration of the zinc ion source in the second electrolyte is 0.005 mol / L to 0.5 mol / L, and the molar ratio of 2-methylimidazole to zinc ions in the zinc ion source is 2:1 to 20:1; performing an in-situ activation process on the initial battery cell, holding the initial battery cell at a preset temperature for a preset time to allow the zinc ion source and 2-methylimidazole to react and generate ZIF-8 nanocrystals; and performing a second formation process on the initial battery cell to form a lithium-sulfur battery.

Description

Technical Field

[0001] This application relates to the field of lithium-sulfur battery technology, and in particular to a lithium-sulfur battery, its manufacturing method, and electrical equipment. Background Technology

[0002] Lithium-sulfur (Li-S) batteries are considered one of the most promising high-energy-density energy storage systems due to their extremely high theoretical energy density (approximately 2600 Wh / kg) and the low cost, environmental friendliness, and abundant reserves of sulfur as the active material. Lithium-sulfur batteries demonstrate broad application prospects and are expected to break through the energy density limits of lithium-ion batteries, meeting the needs of next-generation high-energy-density energy storage devices.

[0003] However, the commercialization of lithium-sulfur batteries is severely hampered by their inherent drawbacks. The most critical issue is the "polysulfide shuttle effect": during charge and discharge, the intermediate product of the sulfur cathode—soluble lithium polysulfide (Li₂S₂)—is generated. n Sulfur (n=4~8) dissolves in the electrolyte and migrates freely between the positive and negative electrodes. It is reduced at the negative electrode and oxidized at the positive electrode, forming a parasitic reaction cycle that leads to irreversible loss of active material, rapid capacity decay, low coulombic efficiency, and corrosion and instability of the lithium metal negative electrode. Furthermore, the poor electronic and ionic conductivity of sulfur and its final discharge product, lithium sulfide (Li2S), also limits sulfur utilization and battery rate performance. Summary of the Invention

[0004] This application provides a lithium-sulfur battery, a method for manufacturing the same, and an electrical device thereof, which can at least improve the performance of the lithium-sulfur battery.

[0005] According to some embodiments of this application, one aspect of this application provides a method for manufacturing a lithium-sulfur battery, comprising: providing a sulfur-containing positive electrode, a lithium metal negative electrode, and a separator; winding or stacking the sulfur-containing positive electrode, the separator, and the lithium metal negative electrode and then placing them into a casing to form an initial battery cell, wherein the separator is located between the sulfur-containing positive electrode and the lithium metal negative electrode; injecting a first electrolyte into the initial battery cell, the components of the first electrolyte comprising: 8 wt% to 23 wt% lithium salt, 0.5 wt% to 10 wt% lithium nitrate, and an ether solvent; performing a first formation process on the initial battery cell; and further... A second electrolyte is injected into the initial battery cell. The components of the second electrolyte include a zinc ion source, 2-methylimidazole, and an organic solvent. The concentration of the zinc ion source in the second electrolyte is 0.005 mol / L to 0.5 mol / L, and the molar ratio of 2-methylimidazole to zinc ions in the zinc ion source is 2:1 to 20:1. The initial battery cell undergoes an in-situ activation process, in which the initial battery cell is held at a preset temperature for a preset time to allow the zinc ion source and 2-methylimidazole to react and generate ZIF-8 nanocrystals. The initial battery cell then undergoes a second formation process to form a lithium-sulfur battery.

[0006] In some embodiments, the preset temperature is 50°C to 80°C; the preset time is 2 hours to 24 hours.

[0007] In some embodiments, the average particle size of ZIF-8 nanocrystals is 50 nm to 500 nm.

[0008] In some embodiments, the zinc ion source is selected from one or more of zinc nitrate, zinc acetate, zinc chloride, zinc sulfate, zinc bis(trifluoromethanesulfonyl)imide, or zinc bis(fluorosulfonyl)imide.

[0009] In some embodiments, the total molar concentration of zinc ions in the second electrolyte from 2-methylimidazole and the zinc ion source is less than or equal to 0.3 mol / L.

[0010] In some embodiments, the organic solvent in the second electrolyte is composed of a mixture of N,N-dimethylformamide and tetrahydrofuran, and the mass ratio of N,N-dimethylformamide to tetrahydrofuran is 1:1 to 3:1; or, the organic solvent is composed of ethanol and tetrahydrofuran, and the mass ratio of ethanol to tetrahydrofuran is 1:1 to 2:1.

[0011] In some embodiments, the ether solvent is a mixture of 1,3-dioxolane and 1,2-dimethoxyethane, and the mass ratio of 1,3-dioxolane to 1,2-dimethoxyethane is 2:8 to 8:2.

[0012] In some embodiments, the concentration of lithium salt in the first electrolyte is 0.5 mol / L to 2.5 mol / L.

[0013] In some embodiments, the second electrolyte further includes a lithium salt, and the lithium salt in the second electrolyte is the same as the lithium salt in the first electrolyte, and the lithium salt concentration in the second electrolyte is the same as the lithium salt concentration in the first electrolyte.

[0014] In some embodiments, the second electrolyte further includes 1 wt% to 2 wt% of auxiliary additives, including graphene oxide or its derivatives or phosphate ester compounds.

[0015] In some embodiments, the first electrolyte further includes 0.1 wt% to 5 wt% of a negative electrode additive.

[0016] In some embodiments, the negative electrode additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, phosphorus pentasulfide, vinylene carbonate, or 1,3-propane sulpholactone.

[0017] According to some embodiments of this application, another aspect of this application also provides a lithium-sulfur battery, which is prepared using the manufacturing method of the lithium-sulfur battery in the above embodiments.

[0018] According to some embodiments of this application, in another aspect, this application also provides an electrical device, which includes the lithium-sulfur battery and load in the above embodiments; or, the electrical device includes an energy storage system and load, the energy storage system including the lithium-sulfur battery in the above embodiments.

[0019] The technical solution provided in this application has at least the following advantages:

[0020] In the lithium-sulfur battery manufacturing method provided in this application embodiment, after preparing the initial cell, a first electrolyte comprising lithium salt, lithium nitrate, and ether solvent is injected into the initial cell, followed by a first formation process. This aims to utilize the good compatibility of the ether solvent with the lithium metal anode and the optimization effect of lithium nitrate on the SEI film to construct a stable basic interface on the lithium metal anode surface, providing a stable electrochemical environment for the subsequent in-situ formation of ZIF-8. Then, a second electrolyte comprising a zinc ion source, 2-methylimidazole, and an organic solvent is injected into the initial cell. An in-situ activation process is performed before the second formation process. The zinc ion source and 2-methylimidazole act as precursors, directionally penetrating and reacting in situ. ZIF-8 nanocrystals are formed in the region with the highest polysulfide concentration, constituting a barrier network and enhancing the polysulfide suppression effect.

[0021] The first electrolyte injection uses a basic electrolyte suitable for lithium-sulfur battery systems. Its main purpose is to complete the initial cell wetting and electrochemical activation (formation) process, and to form a basic, functional SEI film on the lithium metal anode surface. This step ensures that the initial cell possesses the basic working capabilities of a lithium-sulfur battery and provides a relatively stable internal environment for subsequent in-situ reactions. The second electrolyte injection is carried out after the initial cell has undergone preliminary formation or stabilization cycling. At this time, a specific solution containing the ZIF-8 precursor (i.e., zinc ion source and 2-methylimidazole) is injected, avoiding the risk of the ZIF-8 precursor solution interfering with the initial SEI formation. If the ZIF-8 precursor (especially metal ions) is present during the critical stage of SEI film formation during the first charge of the initial cell, it may participate in the interfacial reaction, interfering with the formation of the normal SEI film, and even adversely affecting the lithium metal anode. Stepwise electrolyte injection can protect the integrity of the initial process. Secondly, stepwise electrolyte injection can improve the selectivity and efficiency of in-situ reactions. Introducing the precursor after the initial cell internal environment has stabilized is more conducive to controlling the in-situ formation of ZIF-8 under specific conditions (such as heating), avoiding interference with the initial electrochemical process. Furthermore, the stepwise electrolyte injection strategy provides process flexibility, allowing for functional enhancement steps after a preliminary assessment of the initial cell's basic electrochemical performance, facilitating quality control during production. Attached Figure Description

[0022] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The flowchart corresponds to the manufacturing method of the lithium-sulfur battery provided in the embodiments of this application. Detailed Implementation

[0024] In traditional lithium-ion batteries, the SEI film (Solid Electrolyte Interface membrane) is a complex composite thin layer that naturally forms during the first charge-discharge process due to the electrochemical reduction and decomposition of electrolyte components (solvents, salts, additives) on the negative electrode surface. Its typical components include inorganic salts (such as Li₂CO₃, LiF, Li₂O) and organic / polymeric substances (such as alkyl lithium carbonate, polyethylene oxide, etc.). This passively formed SEI film is usually rigid or semi-rigid, lacking sufficient mechanical toughness and elasticity to adapt to the drastic deformation of the negative electrode.

[0025] To address this issue, related technologies mainly focus on the following aspects: First, by using nano- or composite designs of electrode materials (such as porous silicon and silicon / carbon composites) to accommodate volume changes and alleviate stress; second, by developing highly elastic polymer binders (such as polyacrylic acid PAA, crosslinked polymers, etc.) to maintain the integrity of the electrode structure; and third, by using film-forming additives (such as vinylene carbonate FEC and vinylene carbonate VC) to optimize the chemical composition and initial morphology of the SEI, aiming to form a more stable or slightly flexible interface layer.

[0026] However, these methods primarily provide external buffering or confinement, or improve the initial SEI properties, failing to fundamentally address the problem of physical rupture of the SEI film under enormous, repeated stress and its subsequent repair. The SEI inherently lacks the ability to actively respond to stress damage and self-repair, which limits the interfacial stability of the battery during long-cycle operation.

[0027] Effectively suppressing polysulfide shuttling while ensuring efficient ion and electron transport is key to achieving high-performance lithium-sulfur batteries. To address the polysulfide shuttling problem in lithium-sulfur batteries, a series of strategies and methods have been developed. These methods mainly focus on four aspects: cathode material design, electrolyte optimization, separator modification, and anode protection.

[0028] In cathode material design, two main mechanisms are employed to suppress the dissolution and migration of polysulfides: physical confinement and chemisorption. Physical confinement strategies typically trap sulfur or lithium sulfides within the pores of various microporous or mesoporous conductive substrates (such as porous carbon, carbon nanotubes, and graphene), utilizing the spatial confinement effect to reduce polysulfide dissolution. Chemisorption strategies involve introducing polar materials (such as metal oxides, sulfides, and nitrogen-doped carbon) as a substrate or additive. These materials enhance adsorption through chemical interactions with polysulfides, reducing their free migration in the electrolyte.

[0029] In terms of electrolyte optimization, the main aspects include: (1) using high-concentration electrolytes to reduce the solubility of polysulfides; (2) adding additives that can react with or complex with polysulfides (such as LiNO3, P2S5, etc.) to form a protective interface layer or a stable complex; and (3) developing novel solvent systems with low polysulfide solubility (such as ether-carbonate mixed solvents, ionic liquids, high-concentration salt solutions, etc.). These strategies aim to reduce the solubility of polysulfides or limit their migration ability at the source.

[0030] In terms of separator modification, traditional separators (such as polypropylene and polyethylene) only physically separate the positive and negative electrodes and cannot effectively block polysulfide shuttle. Therefore, functional layers (such as carbon layers, polymer layers, metal oxide layers, or metal-organic framework (MOF) layers) can be coated onto traditional separators to physically block or chemically adsorb polysulfides. These functional layers typically possess a certain degree of ion selectivity, allowing lithium ions to pass through while blocking polysulfide anions, thereby suppressing the shuttle effect while ensuring normal battery operation.

[0031] In terms of negative electrode protection, the main focus is on the adverse reactions between lithium metal negative electrodes and polysulfides. By constructing artificial SEI films, using protective additives, or optimizing electrolyte formulations, a stable interface layer is formed on the lithium metal surface, reducing direct contact and side reactions with polysulfides, thereby inhibiting the corrosion and dendrite growth of the lithium negative electrode.

[0032] In the field of separator modification or electrolyte additives, metal-organic frameworks (MOFs) have been explored for suppressing polysulfide shuttle due to their high specific surface area, regular and tunable pore structure, and potential chemical functionality. Related technologies involve applying pre-synthesized MOF powders to the separator surface via coating or dispersing them directly into the electrolyte as additives. For example, MOF materials such as ZIF-8 (zeolite imidazolium ester framework-8), UiO-66 (1,4-dicarboxylated phenylzirconium MOF), or HKUST-1 (1,3,5-comymethylenetricarboxylate copper) are combined with carbon materials or polymers and coated onto the separator surface to form a functional layer; or nanoscale MOF particles are directly dispersed in the electrolyte as polysulfide scavengers. While these methods have achieved some success, they also have some drawbacks. For instance, direct addition of pre-synthesized MOF powders can easily lead to agglomeration, reducing effectiveness; the uniformity of the separator coating process, the bonding strength, and the impact on separator porosity are difficult to control precisely, and may significantly increase the battery's internal resistance.

[0033] Despite significant progress in suppressing polysulfide shuttle in lithium-sulfur batteries, numerous challenges remain, hindering the practical application of high-performance lithium-sulfur batteries.

[0034] First, the physical confinement and chemisorption strategies of cathode materials often exhibit limitations under high sulfur loading (crucial for achieving high energy density) and long-term cycling conditions. The physically confined structure may be disrupted by volume changes during long-term cycling, and the chemisorption sites may gradually become saturated or deactivated, leading to a significant decrease in the ability to suppress polysulfide shuttle with increasing cycle number. Furthermore, the large amount of inactive materials (such as porous carbon supports) introduced to improve confinement or adsorption effects reduces the battery's mass energy density and volumetric energy density, contradicting practical application requirements.

[0035] While electrolyte additive strategies are simple to implement, they often involve the irreversible consumption of the additives themselves, requiring continuous replenishment to maintain their effectiveness. Some additives (such as LiNO3) may also undergo side reactions with electrode materials or adversely affect the stability of the lithium metal anode, especially under low charge or low temperature conditions. Furthermore, increasing the type and concentration of electrolyte additives may alter their physicochemical properties (such as viscosity and ionic conductivity), thereby affecting the battery's rate performance and low-temperature performance.

[0036] The main challenge in employing pre-synthesized MOFs for separator coating or as electrolyte additives is achieving a uniform, efficient, and stable distribution and integration of MOF materials within the battery, particularly in critical areas such as separator and cathode pores. When pre-synthesized MOF powder is added to the electrolyte, it tends to agglomerate and precipitate, exhibiting poor dispersion stability. When used for separator coating, it struggles to penetrate deeply into the separator's internal pore network, primarily forming a surface layer and limiting its polysulfide blocking efficiency. Furthermore, the adhesion between the coated functional layer and the separator substrate is typically weak, potentially leading to peeling or cracking during long-term battery operation, thus weakening the protective effect. Residual binders or solvents used in the coating process can also clog pores or increase thickness, increasing ion transport resistance and impacting battery performance.

[0037] Furthermore, integrating these modification steps into existing battery manufacturing processes cost-effectively is also a challenge. Traditional MOF coating or addition processes typically require additional processing steps, increasing manufacturing complexity and cost, which is detrimental to large-scale applications. The synthesis conditions of some MOF materials (including ZIF-8) may not be fully compatible with the battery manufacturing environment, such as requiring specific solvents, long-term heat treatment, or precise pH control, all of which increase the difficulty of process integration.

[0038] Therefore, developing a structural layer with polysulfide suppression function that can be uniformly constructed in situ at key locations within lithium-sulfur batteries is considered a more promising and potentially more effective solution. This method should overcome the limitations of pre-synthesized MOF materials in application while maintaining the stability of the internal electrochemical environment of the battery and not affecting the fundamental processes of ion transport and electrochemical reactions.

[0039] This application provides a lithium-sulfur battery, its manufacturing method, and an electrical device thereof. The manufacturing method employs a two-step injection and an in-situ reaction to construct a zeolite imidazole ester framework-8 (ZIF-8) confined structure inside the lithium-sulfur battery. This allows the ZIF-8 nanomaterials to be distributed more uniformly and deeply within the porous structure of the lithium-sulfur battery, thereby effectively suppressing the migration of polysulfides.

[0040] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0041] In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0042] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0043] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included.

[0044] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0045] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0046] Figure 1 The flowchart corresponds to the manufacturing method of the lithium-sulfur battery provided in the embodiments of this application.

[0047] refer to Figure 1 The method for manufacturing a lithium-sulfur battery provided in this application includes:

[0048] S101 provides a sulfur-containing positive electrode, a lithium metal negative electrode, and a separator.

[0049] S102. After the sulfur-containing positive electrode, separator and lithium metal negative electrode are wound or stacked, they are placed into the casing to form the initial cell. The separator is located between the sulfur-containing positive electrode and the lithium metal negative electrode.

[0050] S103. Inject a first electrolyte into the initial battery cell. The components of the first electrolyte include: 8wt% to 23wt% lithium salt, 0.5wt% to 10wt% lithium nitrate, and ether solvent.

[0051] S104. Perform the first formation process on the initial battery cell.

[0052] S105. Inject a second electrolyte into the initial cell. The components of the second electrolyte include: a zinc ion source, 2-methylimidazole, and an organic solvent. The concentration of the zinc ion source in the second electrolyte is 0.005 mol / L to 0.5 mol / L, and the molar ratio of 2-methylimidazole to zinc ions in the zinc ion source is 2:1 to 20:1.

[0053] S106. Perform an in-situ activation process on the initial battery cell, keeping the initial battery cell at a preset temperature for a preset time so that the zinc ion source and 2-methylimidazole react to generate ZIF-8 nanocrystals.

[0054] S107. Perform a second formation process on the initial cell to form a lithium-sulfur battery.

[0055] In the lithium-sulfur battery manufacturing method provided in this application embodiment, after preparing the initial cell, a first electrolyte comprising lithium salt, lithium nitrate, and ether solvent is injected into the initial cell, followed by a first formation process. This aims to utilize the good compatibility of the ether solvent with the lithium metal anode and the optimization effect of lithium nitrate on the SEI film to construct a stable basic interface on the lithium metal anode surface, providing a stable electrochemical environment for the subsequent in-situ formation of ZIF-8. Then, a second electrolyte comprising a zinc ion source, 2-methylimidazole, and an organic solvent is injected into the initial cell. An in-situ activation process is performed before the second formation process. The zinc ion source and 2-methylimidazole act as precursors, directionally penetrating and reacting in situ. ZIF-8 nanocrystals are formed in the region with the highest polysulfide concentration, constituting a barrier network and enhancing the polysulfide suppression effect.

[0056] The first electrolyte injection uses a basic electrolyte suitable for lithium-sulfur battery systems. Its main purpose is to complete the initial cell wetting and electrochemical activation (formation) process, and to form a basic, functional SEI film on the lithium metal anode surface. This step ensures that the initial cell possesses the basic working capabilities of a lithium-sulfur battery and provides a relatively stable internal environment for subsequent in-situ reactions. The second electrolyte injection is carried out after the initial cell has undergone preliminary formation or stabilization cycling. At this time, a specific solution containing the ZIF-8 precursor (i.e., zinc ion source and 2-methylimidazole) is injected, avoiding the risk of the ZIF-8 precursor solution interfering with the initial SEI formation. If the ZIF-8 precursor (especially metal ions) is present during the critical stage of SEI film formation during the first charge of the initial cell, it may participate in the interfacial reaction, interfering with the formation of the normal SEI film, and even adversely affecting the lithium metal anode. Stepwise electrolyte injection can protect the integrity of the initial process. Secondly, stepwise electrolyte injection can improve the selectivity and efficiency of in-situ reactions. Introducing the precursor after the initial cell internal environment has stabilized is more conducive to controlling the in-situ formation of ZIF-8 under specific conditions (such as heating), avoiding interference with the initial electrochemical process. Furthermore, the stepwise electrolyte injection strategy provides process flexibility, allowing for functional enhancement steps after a preliminary assessment of the initial cell's basic electrochemical performance, facilitating quality control during production.

[0057] In S101, the sulfur-containing cathode may include a cathode current collector and a cathode material layer covering the surface of the cathode current collector.

[0058] The positive current collector can be made of aluminum foil or aluminum foil with surface treatment, such as carbon-coated aluminum foil or oxide-coated aluminum foil.

[0059] The positive electrode material layer includes positive electrode active material, binder and conductive agent.

[0060] Positive electrode active materials can be organic sulfides such as polyacrylonitrile (SPAN), diphenyl disulfide, and thiophene polymers. These materials can effectively inhibit the dissolution of polysulfides by covalently binding sulfur atoms.

[0061] Positive electrode active materials can also be composed of sulfur-based active materials, including elemental sulfur, sulfur / carbon composites, sulfur / conductive polymer composites, organic polysulfide materials, and pre-lithiated sulfur materials. Among these, sulfur / carbon composites are the most important technical route, which can be further subdivided into sulfur / porous carbon composites, sulfur / graphene composites, sulfur / carbon nanotube composites, sulfur / carbon fiber composites, and sulfur / biomass carbon composites. The carbon carriers in sulfur / porous carbon composites include activated carbon, mesoporous carbon, microporous carbon, hierarchical porous carbon, ordered mesoporous carbon prepared by template methods, and metal-organic framework-derived porous carbon, etc. Sulfur / graphene composites utilize the high conductivity and large specific surface area of ​​graphene, and can be composited using various methods such as graphene oxide reduction coating, graphene encapsulation of sulfur particles, and graphene / sulfur sandwich structures. Sulfur / carbon nanotube composites achieve physical confinement and electronic conduction of sulfur by filling sulfur into the interior of carbon nanotubes or coating it on the surface of carbon nanotubes. Pre-lithiated sulfur materials improve coulombic efficiency and capacity utilization during the first charge and discharge cycle by pre-introducing lithium ions.

[0062] The binder can be selected from polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC), sodium alginate, etc.

[0063] The conductive agent can be selected from carbon black, Super P, acetylene black, carbon nanotubes, graphene, etc.

[0064] Lithium metal anodes consist of anodes made of pure lithium metal, typically existing in the form of lithium foil with thicknesses ranging from 50 to 500 micrometers to ultrathin 10 to 50 micrometers. Ultrathin lithium foil designs help improve battery energy density and reduce dead lithium formation. Surface-structured lithium metals, through the construction of specific micro / nano structures such as columnar arrays, honeycomb structures, and porous structures, can effectively reduce local current density and promote uniform deposition. Three-dimensional lithium metals include porous lithium sponges and lithium-filled conductive frameworks (such as nickel foam, carbon felt, and graphene frameworks), which can accommodate volume changes during lithium deposition.

[0065] Artificial SEI film technology significantly improves interfacial stability by pre-constructing a protective layer on the surface of lithium foil. Protective layer materials include organic protective layers (such as conductive polymers, polymer electrolyte membranes), inorganic protective layers (such as lithium fluoride, lithium nitride, alumina, zinc oxide, etc.), and organic / inorganic composite protective layers.

[0066] Lithium metal anodes also include lithium alloy anodes, such as lithium-silicon alloys, lithium-tin alloys, and lithium-aluminum alloys. Alloying reactions can alleviate lithium dendrite growth and provide additional capacity contributions.

[0067] Lithium metal anodes also include coated anodes, such as those containing lithium metal powder, lithium alloy powder, and other anode active materials, combined with conductive agents (carbon black, carbon nanotubes, graphene, etc.) and binders (PVDF, CMC, SBR, etc.) to form an anode material layer coated on the surface of the anode current collector. The anode current collector is typically made of copper foil, but surface-modified copper foil, such as carbon-coated copper foil, oxide-coated copper foil, and three-dimensional copper current collectors, can also be used to optimize lithium deposition behavior and interface stability.

[0068] Membranes can be made from a variety of materials, including polyolefin membranes, ceramic-coated membranes, high-strength polymer membranes, and functionalized composite membranes. Polyolefin membranes, including polypropylene (PP) membranes, polyethylene (PE) membranes, and PP / PE composite membranes, possess good mechanical strength and chemical stability. Ceramic-coated membranes coat a polyolefin substrate with ceramic materials such as alumina, zirconium oxide, and titanium oxide, improving the membrane's high-temperature resistance, wettability, and safety. High-strength polymer membranes, including aramid fiber membranes, polyimide membranes, and polytetrafluoroethylene (PTFE) membranes, exhibit excellent thermal stability and mechanical strength.

[0069] The separator can also be a functionalized composite separator, designed to meet the specific needs of lithium-sulfur batteries, such as barrier, adsorption, or ion selection functions. A functionalized composite separator can include a separator substrate and a functional layer coated on the surface of the substrate. The functional layer material can be selected from carbon materials (such as carbon black, graphene, and carbon nanotubes), polar materials (such as metal oxides and metal sulfides), or polymer materials. These materials facilitate the functionalization of the separator, further enhancing the polysulfide suppression effect.

[0070] In S102, according to battery type, the casing can be divided into cylindrical battery casing, square battery casing, and pouch battery casing. Cylindrical battery casing is usually made of steel or aluminum alloy; square battery casing is usually made of aluminum or steel; pouch battery casing is usually made of aluminum-plastic composite film, which includes an outer layer (nylon / PET), a middle layer (aluminum foil), and an inner layer (PP heat-sealing layer).

[0071] In S102, the initial cell refers to the dry cell assembly formed by assembling a sulfur-containing positive electrode, a lithium metal negative electrode, and a separator into a housing.

[0072] In some embodiments, prior to S103, the process further includes: high-temperature baking and moisture testing. The high-temperature baking temperature ranges from 80°C to 120°C, and the baking time ranges from 12 hours to 48 hours. In the moisture testing, the initial moisture content inside the battery cell is less than 50 ppm.

[0073] In S103, the first electrolyte is mainly used to form an initial and stable SEI film on the surface of the lithium metal anode.

[0074] The lithium salt in the first electrolyte can be selected from one or more compounds that can dissolve in ether solvents and provide a sufficient lithium ion concentration. Lithium salts include, but are not limited to, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), and lithium difluorooxalate borate (LiDFOB).

[0075] Preferably, the lithium salt in the first electrolyte is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or a mixture of the two, all of which have good thermal and chemical stability and help to form a high-quality SEI film on the surface of the lithium metal anode.

[0076] The specific mass fraction of lithium salt in the first electrolyte can be 5 wt%, 8 wt%, 10 wt%, 12 wt%, 13 wt%, 15 wt%, 18 wt%, 20 wt%, or 23 wt%. The mass fraction of lithium salt refers to the proportion of the mass of lithium salt to the total mass of the first electrolyte.

[0077] In some embodiments, the concentration of lithium salt in the first electrolyte is 0.5 mol / L to 2.5 mol / L. For example, it can be 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.3 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.3 mol / L, or 2.5 mol / L.

[0078] Lithium nitrate (LiNO3) is a key additive in the first electrolyte. It is used to form a protective passivation layer on the surface of the lithium metal anode, inhibit the growth of lithium dendrites, reduce the direct reaction between lithium metal and polysulfides, and improve coulombic efficiency.

[0079] The specific mass fraction of lithium nitrate in the first electrolyte can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.4wt%, 4wt%, 4.3wt%, 5wt%, 5.6wt%, 6wt%, 6.8wt%, 7wt%, 7.4wt%, 8wt%, 8.3wt%, 9wt%, 9.5wt%, or 10wt%. The mass fraction of lithium nitrate refers to the proportion of lithium nitrate by mass to the total mass of the first electrolyte.

[0080] In the first electrolyte, ether solvents exhibit good stability to the lithium metal anode and moderate solubility for polysulfides. Ether solvents include, but are not limited to, one or more of 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), ethylene glycol diethyl ether, diethylene glycol dimethyl ether (DEGDME or G2), triethylene glycol dimethyl ether (TEGDME or G3), tetraethylene glycol dimethyl ether (TETRAGLYME or G4), and their derivatives.

[0081] Preferably, the ether solvent is a mixture of 1,3-dioxolane and 1,2-dimethoxyethane. This combination of ether solvents helps to balance the formation quality of the SEI film, ionic conductivity, and the dissolution behavior of polysulfides. The mass ratio of 1,3-dioxolane to 1,2-dimethoxyethane is 2:8 to 8:2, specifically 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, or 8:2.

[0082] In some embodiments, the first electrolyte further includes 0.1 wt% to 5 wt% of a negative electrode additive, specifically 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, 1.3 wt%, 1.6 wt%, 2 wt%, 2.4 wt%, 2.8 wt%, 3 wt%, 3.3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0083] Negative electrode additives include one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), phosphorus pentasulfide (P2S5), vinylene carbonate (VC), or 1,3-propane sulpholactone (PS). FEC or DFEC helps form a lithium fluoride (LiF)-rich SEI film; P2S5, as a polysulfide stabilizer, can participate in the formation of a sulfur-containing SEI film, further stabilizing the lithium metal anode interface; VC or PS, as commonly used film-forming additives, help form a stable SEI film.

[0084] In some embodiments, before S104, the method further includes: placing the initial cell at 40°C to 60°C for 12 to 48 hours to allow the first electrolyte to fully wet the sulfur-containing positive electrode, the lithium metal negative electrode, and the separator.

[0085] In S104, the rate current of the first formation process can be 0.05C to 0.1C, and the cutoff voltage is 1.5V to 2.8V. Based on the special requirements of lithium-sulfur batteries, a low rate current of 0.05C to 0.1C is used in the initial formation stage. Low rate formation is conducive to the uniform formation of the SEI film on the surface of the lithium metal anode, avoiding lithium dendrite growth caused by excessive current density; at the same time, it allows additives such as lithium nitrate in the first electrolyte to fully participate in the construction of the SEI film, forming a stable interface layer; in addition, the mild electrochemical process is conducive to the gradual activation of the sulfur-containing cathode, avoiding structural damage caused by rapid volume changes.

[0086] To ensure that the first electrolyte additive fully generates a stable SEI film and provides a stable foundation for the subsequent in-situ generation of ZIF-8, the first formation process can be controlled to charge to more than 60% of the initial cell's SOC (State of Charge).

[0087] Following S104, the process also includes allowing the initial battery cell to stand at room temperature for 2 to 24 hours.

[0088] In S105, the purpose of the second electrolyte is to introduce the precursor that can generate ZIF-8 into the initial cell, allowing it to fully penetrate the separator and electrodes (especially the separator region facing the sulfur-containing cathode and the sulfur-containing cathode pores), while the other components of the second electrolyte should be compatible with the lithium-sulfur battery system.

[0089] The ZIF-8 precursor comprises a zinc ion source and 2-methylimidazole. The zinc ion source can be selected from one or more of zinc nitrate, zinc acetate, zinc chloride, zinc sulfate, zinc bis(trifluoromethanesulfonyl)imide (Zn(TFSI)2), or zinc bis(fluorosulfonyl)imide (Zn(FSI)2). Zn(TFSI)2 is preferred because its anion TFSI- is the same as the anion of the preferred lithium salt LiTFSI in the first electrolyte, thus maximizing the electrochemical compatibility of the electrolyte system and avoiding the introduction of new anion species.

[0090] The concentration of the zinc ion source in the second electrolyte can be 0.005 mol / L, 0.008 mol / L, 0.01 mol / L, 0.015 mol / L, 0.02 mol / L, 0.03 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.15 mol / L, 0.18 mol / L, 0.2 mol / L, 0.23 mol / L, 0.26 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.44 mol / L, or 0.5 mol / L. The preferred concentration range of the zinc ion source in the second electrolyte is 0.01 mol / L to 0.2 mol / L.

[0091] 2-Methylimidazole (H2mIM or 2-MIM) is an essential organic ligand for the formation of ZIF-8, and its concentration is typically maintained in excess relative to the zinc ion source. The molar ratio of 2-methylimidazole to zinc ions in the zinc ion source is 2:1 to 20:1, specifically 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1. The preferred molar ratio of 2-methylimidazole to zinc ions in the zinc ion source is 4:1 to 10:1.

[0092] In some embodiments, the total molar concentration of zinc ions in the 2-methylimidazole and zinc ion source in the second electrolyte is less than or equal to 0.3 mol / L to ensure a reasonable amount of ZIF-8 generated without negatively impacting the performance of the lithium-sulfur battery. This is to avoid key factors such as excessive ZIF-8 clogging ion transport channels, preventing the precursor from reacting or precipitating prematurely during electrolyte injection or storage, and ensuring the uniform distribution of ZIF-8 in the separator and electrode pores.

[0093] In the second electrolyte, the organic solvent should be able to dissolve the zinc ion source and 2-methylimidazole well, have good wettability to the sulfur-containing cathode, facilitate the formation of ZIF-8 in polysulfide-rich areas (such as near the sulfur-containing cathode and the membrane), and have reasonable compatibility with the first injected electrolyte. At the same time, the use of aqueous systems should be avoided or the water content should be strictly controlled.

[0094] Based on the above functional zoning considerations, the organic solvent in the second electrolyte can be a mixture of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF). DMF has excellent solubility for polar compounds (such as zinc ion sources and 2-methylimidazole) and good wettability for sulfur-containing cathodes, which is beneficial for precursor penetration into the cathode pores. THF helps ensure compatibility with the first electrolyte ether system and reduces the overall viscosity. The relatively high boiling point of DMF (153°C) helps maintain solvent stability during the formation of ZIF-8.

[0095] The mass ratio of N,N-dimethylformamide to tetrahydrofuran is 1:1 to 3:1, and can be 1:1, 1.5:1, 2:1, 2.3:1, 2.6:1 or 3:1.

[0096] Alternatively, the organic solvent in the second electrolyte can be composed of ethanol and tetrahydrofuran. Ethanol is one of the classic solvents for ZIF-8 synthesis, and it can dissolve the precursor well. Mixing it with THF helps to balance the solubility and compatibility with the first electrolyte.

[0097] The mass ratio of ethanol to tetrahydrofuran is 1:1 to 2:1, for example, it can be 1:1, 1.1:1, 1.3:1, 1.5:1, 1.8:1 or 2:1.

[0098] In some embodiments, the organic solvent can be tetrahydrofuran (THF). THF has advantages such as better chemical compatibility with the ether system of the first electrolyte, relatively lower sensitivity to trace amounts of moisture, better process tolerance, a moderate boiling point (approximately 66°C) facilitating temperature control for subsequent ZIF-8 formation, and potentially less solubility or damage to the already formed SEI film. If THF is used as the main solvent, a small amount of highly polar co-solvent (such as a small amount of DMF or ethanol) can be added to enhance the solubility of the precursor.

[0099] In some embodiments, to maintain the continuity of ionic conductivity and electrochemical environment inside the lithium-sulfur battery, the second electrolyte may further include a lithium salt. The lithium salt in the second electrolyte may be the same as the lithium salt in the first electrolyte, and the concentration of the lithium salt in the second electrolyte may be the same as the concentration of the lithium salt in the first electrolyte.

[0100] In some embodiments, the second electrolyte may further include 1 wt% to 2 wt% of auxiliary additives, specifically 1 wt%, 1.1 wt%, 1.3 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, or 2 wt%. The content of auxiliary additives in the range of 1 wt% to 2 wt% can avoid interfering with the homogeneous nucleation and growth of ZIF-8.

[0101] Auxiliary additives include graphene oxide or its derivatives, or phosphate esters. Graphene oxide or its derivatives (such as reduced graphene oxide), with its large specific surface area and functional groups, can assist in the adsorption of polysulfides during or after the formation of the ZIF-8 network; phosphate esters act as flame retardants.

[0102] Before S106, the process also includes letting the initial cell stand at 40°C to 60°C for 12 to 48 hours to allow the second electrolyte to fully wet the sulfur-containing positive electrode, the separator, and the lithium metal negative electrode.

[0103] In S106, the preset temperature is 50℃~80℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, preferably 60℃~70℃; the preset time is 2 hours~24 hours, for example, it can be 2 hours, 3 hours, 5 hours, 8 hours, 10 hours, 13 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, preferably 4 hours~12 hours.

[0104] The particle size of ZIF-8 nanocrystals can be adjusted by modifying process parameters such as precursor concentration, solvent, preset activation temperature, and preset time. ZIF-8 nanocrystal particles refer to particulate matter composed of ZIF-8 crystal grains. In some embodiments, the average particle size of ZIF-8 nanocrystals is 50 nm to 500 nm, specifically 50 nm, 60 nm, 80 nm, 100 nm, 130 nm, 160 nm, 180 nm, 200 nm, 250 nm, 300 nm, 340 nm, 360 nm, 400 nm, 450 nm, or 500 nm.

[0105] ZIF-8, as a target MOF material, is primarily chosen based on its unique structural and chemical properties. ZIF-8 possesses a precise and narrow pore window size (approximately 0.34 nm), which is significantly larger than the radius of a bare lithium ion (approximately 0.076 nm). This allows lithium ions with a solvation sheath (effectively sized around 0.4 nm or larger, but with some flexibility to pass through the pore window) to pass relatively easily, thus ensuring the necessary ion transport channels for lithium-sulfur batteries. However, polysulfide anions (S... n 2- (n≥4), especially polysulfides with longer chain lengths (such as S6). 2- S8 2- These larger polysulfide anions are typically larger (e.g., with an effective diameter exceeding 0.6 nm and a larger solvation layer). Therefore, the pore structure of ZIF-8 can significantly hinder or sieve these larger polysulfide anions, acting like a "molecular fence" to greatly reduce their chances of passing through the membrane to the negative electrode. At the same time, the Lewis acidic sites of zinc ions provide strong chemisorption sites for polysulfides.

[0106] Besides physical barriers, Zn exposed in the ZIF-8 framework 2+ As Lewis acid sites, the ions can chemically interact with electron-rich sulfur atoms (Lewis bases) in polysulfides (e.g., through coordination or strong adsorption). This chemical anchoring further enhances ZIF-8's ability to capture polysulfides and is another important mechanism for suppressing the shuttle effect. Furthermore, ZIF-8 exhibits good chemical stability in ether electrolytes, and its precursors are readily available and the synthesis conditions are mild, all of which support its application in this technical solution.

[0107] In other embodiments, other MOF materials such as ZIF-67 and UiO-66 can also be constructed in situ by adjusting the precursor in the second electrolyte to improve polysulfide capture capability and interfacial compatibility.

[0108] In S107, the rate current of the second formation process is greater than that of the first formation process. Appropriately increasing the formation rate helps activate more sulfur active sites, improving sulfur utilization, and simultaneously verifying the stability of the ZIF-8 nanocrystal network under dynamic electrochemical conditions.

[0109] The rate current for the second formation process is 0.1C to 0.2C, and the cutoff voltage is 1.5V to 2.8V.

[0110] The second formation process charges the battery to over 90% of its initial state of charge (SOC).

[0111] The voltage window for the first and second formation processes is set to 1.5V to 2.8V, which is consistent with the typical operating range of lithium-sulfur batteries. The lower limit of 1.5V ensures the full conversion of polysulfides to lithium sulfide, while the upper limit of 2.8V balances the integrity of the sulfur oxidation reaction and the stability of the electrolyte under the protection of the ZIF-8 network.

[0112] The temperatures of the first and second formation processes can be controlled between 40°C and 60°C, which not only facilitates full electrolyte wetting but also provides suitable conditions for the structural optimization of ZIF-8.

[0113] In some embodiments, the first electrolyte accounts for 70% to 90% of the total mass ratio of the first electrolyte and the second electrolyte. If the initial electrolyte injection volume is insufficient, the initial cell may not be adequately wetted, easily leading to insufficient capacity or poor cycle performance after the first formation process. If the initial electrolyte injection volume is too large, the precursor concentration in the second electrolyte may be excessively diluted, affecting the formation effect and distribution uniformity of ZIF-8. Preferably, the injection volume of the first electrolyte is controlled within the range of 75% to 85% of the total electrolyte volume, ensuring sufficient electrochemical activity while leaving appropriate space for functional enhancement in the second stage.

[0114] The mainstream method for suppressing polysulfide shuttle in related technologies relies on introducing pre-synthesized metal-organic framework (MOF) materials into lithium-sulfur battery systems through physical mixing, coating, or direct addition. This "pre-synthesis followed by addition" approach is a passive material introduction strategy, limited by the morphology, size distribution, and interfacial bonding strength between the pre-synthesized material and the lithium-sulfur battery module. The synthesis, processing, and application of MOF materials are separate processes, and the final functional performance of the material is often negatively affected by intermediate processing steps. Furthermore, pre-synthesized MOF materials face inherent problems during application, such as poor dispersibility, severe agglomeration, and weak bonding with the substrate. The root cause of these problems lies in the fact that the physical dispersion of solid particles in a liquid medium is essentially a thermodynamically unstable process.

[0115] The lithium-sulfur battery manufacturing method provided in this application adopts an "in-situ generation" technical route. Through staged electrolyte injection, the ZIF-8 precursor undergoes a chemical reaction at specific locations and times within the initial battery cell, directly constructing a nanoscale polysulfide barrier network in the areas where functionality is required. During the in-situ generation process, precursor molecules are uniformly dispersed at the molecular level in the electrolyte, and then directly nucleate and grow at interfacial sites through chemical reactions. The resulting ZIF-8 nanocrystals exhibit stronger chemical bonding and a more uniform spatial distribution with their surrounding environment. This "molecular-level dispersion-in-situ reaction-interfacial growth" mechanism ensures that the functional material can precisely form an effective barrier network in areas with the highest polysulfide concentration (such as near the positive electrode and in the membrane pores).

[0116] Traditional single-filling electrolyte process introduces all electrolyte components into the battery system at the same time, which leads to competitive reactions and mutual interference between different functional additives, making it difficult to achieve the optimal expression of the functions of each component.

[0117] The lithium-sulfur battery manufacturing method provided in this application adopts a staged liquid injection strategy. The first liquid injection stage focuses on constructing a stable basic SEI film on the lithium anode surface using ether solvents and lithium nitrate, providing a stable electrochemical environment for subsequent in-situ reactions. The second liquid injection stage introduces a ZIF-8 precursor on the already stabilized interface, avoiding interference from the precursor to the initial SEI formation process while ensuring efficient ZIF-8 generation in the cathode region and separator. This time-separated strategy decouples the mutual constraint between lithium metal anode stability and polysulfide suppression function. The in-situ generated ZIF-8 forms an organic combination with the internal structure of the lithium-sulfur battery, providing not only a physical barrier effect but also enhancing the polysulfide fixation effect through a chemical adsorption mechanism, achieving a synergistic improvement in lithium-sulfur battery performance.

[0118] According to some embodiments of this application, another aspect of this application also provides a lithium-sulfur battery, which is prepared using the manufacturing method of the lithium-sulfur battery in the above embodiments.

[0119] According to some embodiments of this application, in another aspect, this application also provides an electrical device, which includes the lithium-sulfur battery and load in the above embodiments; or, the electrical device includes an energy storage system and load, the energy storage system including the lithium-sulfur battery in the above embodiments.

[0120] The following are specific embodiments of this application.

[0121] Example 1 was prepared using the following steps.

[0122] (1) Provide sulfur-containing positive electrode, lithium metal negative electrode and separator.

[0123] The cathode slurry formulation consists of a sulfur / carbon composite material, a conductive agent SuperP, conductive carbon nanotubes (CNTs), and a binder polyvinylidene fluoride (PVDF) in a mass ratio of 85:8:2:5. A sulfur-containing cathode is prepared through a coating process, followed by drying and roll pressing. The sulfur / porous carbon composite material has a sulfur content of 70 wt% and a sulfur loading of 3.2 ± 0.2 mg / cm³. 2 The lithium metal anode is a 100-micrometer-thick lithium foil; the separator is a polypropylene separator.

[0124] (2) The sulfur-containing positive electrode, separator, and lithium metal negative electrode are stacked in sequence and wound into a core and packaged with aluminum-plastic film to form the initial battery cell; the initial battery cell is baked at 80°C for 24 hours to remove moisture so that the moisture content of the initial battery cell is less than 50ppm. The theoretical capacity of the initial battery cell is 5.0Ah.

[0125] (3) Inject the first electrolyte into the initial cell. The components of the first electrolyte include: 13 wt% LiTFSI, 2.35 wt% lithium nitrate, and 84.65 wt% ether solvent, wherein the ether solvent is composed of DOL and DME in a mass ratio of 1:1. The mass of the first electrolyte accounts for 85% of the total electrolyte required.

[0126] (4) After the initial cell is left to stand at 45°C for 36 hours, the initial cell is subjected to the first formation process. The cell assembly is charged to 60% SOC using a 0.05C rate current and then discharged. The upper limit voltage is 2.8V and the temperature is 40°C.

[0127] (5) After allowing the initial battery cell to stand at room temperature for 12 hours, inject a second electrolyte into the initial battery cell. The components of the second electrolyte include: 0.33 mol / L Zn(TFSI)2, 1.33 mol / L 2-methylimidazole, 13 wt% LiTFSI, and the balance organic solvent, wherein the organic solvent consists of DMF and THF in a mass ratio of 2:1. The mass of the second electrolyte accounts for 15% of the total electrolyte required.

[0128] (6) After the initial cell is left to stand at 45°C for 36 hours, the initial cell is activated in situ by holding it at 80°C for 12 hours to allow the zinc ion source and 2-methylimidazole to react and generate ZIF-8 nanocrystals. The average particle size of the ZIF-8 nanocrystals is 200 nm to 300 nm.

[0129] (7) The initial cell is subjected to a second formation process. The initial cell is charged to 85% SOC using a 0.1C rate current and then discharged. The upper limit voltage is 2.8V and the temperature is 40℃ to form a lithium-sulfur battery.

[0130] The difference between Example 2 and Example 1 is that the concentration of Zn(TFSI)2 in the second electrolyte is 0.17 mol / L and the concentration of 2-methylimidazole is 0.67 mol / L.

[0131] The difference between Example 3 and Example 1 is that the concentration of Zn(TFSI)2 in the second electrolyte is 0.5 mol / L and the concentration of 2-methylimidazole is 2 mol / L.

[0132] The difference between Comparative Example 1 and Example 1 is that both the first electrolyte and the second electrolyte consist of 13 wt% LiTFSI, 2 wt% lithium nitrate and 85 wt% ether solvent, wherein the ether solvent is composed of DOL and DME in a mass ratio of 1:1.

[0133] The difference between Comparative Example 2 and Example 1 is that both the first electrolyte and the second electrolyte consist of 13 wt% LiTFSI, 2 wt% lithium nitrate, 0.5 wt% pre-synthesized ZIF-8, and 84.5 wt% ether solvent, wherein the ether solvent is composed of DOL and DME in a mass ratio of 1:1.

[0134] The pre-synthesized ZIF-8 was prepared as follows: 0.297 g of Zn(NO3)2·6H2O and 1.315 g of 2-methylimidazole were dissolved in 20 mL of methanol, respectively. The mixture was rapidly mixed and stirred at room temperature for 2 hours, followed by standing at room temperature for 24 hours to complete crystallization. After the reaction was complete, the product was centrifuged (8000 rpm, 10 minutes), washed three times with methanol, and finally dried under vacuum at 80 °C for 12 hours to obtain a white pre-synthesized ZIF-8 powder. The pre-synthesized ZIF-8 exhibited a regular rhombic dodecahedral morphology, with a particle size range of 200 nm to 300 nm and a specific surface area of ​​1380 m². 2 / g, pore volume 0.64cm 3 / g, average pore size is

[0135] The difference between Comparative Example 3 and Comparative Example 1 is that the surface of the diaphragm is coated with pre-synthesized ZIF-8. The preparation method is as follows: 0.5 g of pre-synthesized ZIF-8 powder is added to 10 mL of N-methylpyrrolidone (NMP) solvent containing 0.05 g of polyvinylidene fluoride (PVDF) binder. After ultrasonic dispersion for 30 minutes, the mixture is stirred on a magnetic stirrer for 12 hours to obtain a uniform slurry. The slurry is then coated onto both sides of the polypropylene diaphragm using a doctor blade coating process, with the coating amount controlled at 0.8 ± 0.1 mg / cm². 2 The coated diaphragm was dried at 60°C for 4 hours, and then treated under vacuum at 120°C for 12 hours to completely remove the solvent. The thickness of the pre-synthesized ZIF-8 was 5 μm.

[0136] The difference between Comparative Example 4 and Example 1 is that the first electrolyte consists of 13 wt% LiTFSI, 2 wt% lithium nitrate, 0.05 mol / L Zn(TFSI)2, 0.2 mol / L 2-methylimidazole and the balance solvent, which consists of DOL, DME, DMF and THF in a mass ratio of 42.5:42.5:10:5, and steps (5) and (6) are removed.

[0137] The above embodiments and comparative examples were subjected to 25°C cycling performance tests, 45°C cycling performance tests, first-week coulombic efficiency tests, internal resistance tests, and 60°C storage performance tests.

[0138] 25℃ and 45℃ Cyclic Performance Tests: Cyclic tests were conducted at 25℃±2℃ using a constant current constant voltage (CCCV) charging mode. The specific charging procedure was as follows: first, constant current charging at 0.2C was used to reach the upper limit voltage of 2.8V, then constant voltage charging at 2.8V was used until the charging current decayed to C / 20 (approximately 0.05C) or the charging time reached 8 hours, whichever came first. Discharge was performed using a constant current of 0.2C to reach the lower limit voltage of 1.5V. The same CCCV charging mode was applied to the 0.5C rate test, i.e., constant current charging at 0.5C to 2.8V, then constant voltage charging until the current decayed to C / 20 or the time limit was reached. 45℃ Cyclic Performance Test: The 0.2C CCCV charge-discharge test was repeated at 45℃±2℃. The discharge capacity was recorded for the 200th and 300th cycles, and the capacity retention rate was calculated as (Nth discharge capacity / 3rd discharge capacity) × 100%. The third cycle was used as a baseline to eliminate the influence of the battery activation process in the first two cycles. During the test, a constant temperature chamber was used to ensure that the ambient temperature fluctuation did not exceed ±2℃, and a 5-minute rest period was set between each cycle to ensure the battery condition was stable.

[0139] First-week coulombic efficiency test: Under various temperature conditions and rate combinations, the first-week efficiency was measured using the standard CCCV charging mode. The charging process was as follows: constant current charging at the set rate (0.2C or 0.5C) to 2.8V, then constant voltage charging until the current decayed to C / 20 or the charging time reached 8 hours, whichever came first. Discharging was performed using the same rate with constant current to 1.5V. The first-week coulombic efficiency was calculated as (first discharge capacity / first charge capacity) × 100%. To ensure data accuracy, pretreatment was performed before the first formal test: constant current charging at 0.05C to 2.5V, followed by resting for 2 hours and then constant current discharging at 0.05C to 1.7V to complete the initial activation of the lithium-sulfur battery, before the formal first-week efficiency test.

[0140] Internal resistance testing: A DC internal resistance testing method was used, charging the battery to 50% SOC under various temperature conditions. The charging process was as follows: charging to 50% of the theoretical capacity at 0.2C CCCV mode, and allowing it to stand for 30 minutes to reach electrochemical equilibrium. Then, a 1C discharge current pulse was applied for 10 seconds, and the voltage drop ΔV was measured. The DC internal resistance R = ΔV / ΔI was calculated. Each sample was tested three times under the same conditions, and the average value was taken to ensure the repeatability of the test results. During the test, the ambient temperature was kept stable, and the battery surface temperature variation did not exceed ±1℃.

[0141] 60℃ Storage Performance Test: First, the lithium-sulfur battery was charged to 100% SOC using a 0.2C CCCV mode. Specifically, it was charged at a constant current of 0.2C to 2.8V, then switched to constant voltage charging until the current decayed to C / 20, ensuring the battery was fully charged. The discharge capacity at this point was recorded as the initial capacity C1 (obtained by discharging at a constant current of 0.2C to 1.5V). The fully charged lithium-sulfur battery was then sealed and stored at 60℃±2℃ for 28 days. During storage, the battery appearance and voltage were checked weekly to ensure no abnormalities. After storage, the lithium-sulfur battery was moved to room temperature (25℃±2℃) and left to stand for 4 hours to allow the battery temperature to equalize. Then, it was discharged at a constant current of 0.2C to 1.5V, and the discharge capacity C2 was recorded. The capacity retention rate was calculated as (C2 / C1)×100%. A capacity recovery test was then conducted: the battery was recharged in CCCV mode at 0.2C. Specifically, it was charged at a constant current to 2.8V, then charged at a constant voltage until the current decayed to C / 20, and finally discharged at a constant current of 0.2C to 1.5V. The recovered capacity C3 was recorded, and the capacity recovery rate was calculated as (C3 / C1) × 100%. The capacity recovery rate reflects the degree of reversible performance loss of the lithium-sulfur battery after high-temperature storage.

[0142] All electrochemical tests were performed using a multi-channel battery testing system with the following accuracy: voltage ±0.1mV, current ±0.1%FS. Temperature control was achieved using a constant temperature chamber with an accuracy of ±1℃ and a temperature uniformity of ±2℃. The ambient humidity was controlled at 45% ±10%RH. All tests were conducted in an electromagnetically shielded testing chamber to avoid external interference.

[0143] At least three parallel samples were tested under each test condition, and data are expressed as mean ± standard deviation. When the standard deviation exceeds 5% of the mean, the number of samples was increased or the test was repeated to ensure data reliability. All capacity data were standardized based on the discharge capacity of the third cycle to eliminate the effects of initial battery activation.

[0144] The test results are shown in Tables 1 to 4.

[0145] Table 1

[0146]

[0147] Table 2

[0148]

[0149] Table 3

[0150]

[0151] Table 4

[0152]

[0153] By comparing Comparative Example 1 (blank control group) with Examples 1 to 3, the manufacturing method of the lithium-sulfur battery provided in this application clearly demonstrates the significant improvement in lithium-sulfur battery performance achieved by the ZIF-8 confined structure constructed within the lithium-sulfur battery through secondary liquid injection and in-situ reaction. Under 25°C and 0.2C charge-discharge conditions, Comparative Example 1 showed capacity retention of 58.2% and 41.3% after 200 and 300 cycles, respectively, with a first-cycle coulombic efficiency of 74.5%. In contrast, Example 1, prepared using the manufacturing method of the lithium-sulfur battery provided in this application, achieved capacity retention of 82.6% and 68.9% after 200 and 300 cycles, respectively, representing improvements of 24.4 and 27.6 percentage points, with the first-cycle efficiency also increasing to 85.7%. This significant improvement fully validates the effectiveness of the strategy of achieving in-situ ZIF-8 generation through staged liquid injection. Under conditions of 0.5C rate and 45°C high temperature, Example 1 also showed consistent performance advantages compared to Comparative Example 1, further confirming the universality and stability of the lithium-sulfur battery manufacturing method provided in this application.

[0154] Compared with two conventional MOF application methods, Comparative Example 2 (pre-synthesized ZIF-8 directly added to the electrolyte) and Comparative Example 3 (pre-synthesized ZIF-8 coated on the separator), the capacity retention rates of Comparative Example 2 and Comparative Example 3 after 200 cycles at 25°C and 0.2C charge-discharge conditions were 63.5% and 68.7%, respectively. Although these were improvements of 5.3 and 10.5 percentage points compared to the blank control group, Comparative Example 1, they were significantly lower than the 82.6% of Example 1. This comparative result confirms the technical advantages of the in-situ generation mechanism. The inherent problems faced by pre-synthesized MOF materials during application, such as poor dispersibility, severe agglomeration, and weak bonding with the substrate, are directly reflected in the performance data. In the lithium-sulfur battery manufacturing method provided in this application embodiment, the in-situ generation strategy enables ZIF-8 nanocrystals to be more uniformly and deeply constructed in the pore structure of the separator and electrode through the mechanism of "molecular-level dispersion-in-situ reaction-interface growth", forming a continuous and effective polysulfide barrier network, thereby achieving a performance improvement of 14.3 to 19.1 percentage points compared with the traditional method.

[0155] Comparative Example 4 employed a one-time mixed electrolyte injection method, simultaneously introducing all electrolyte components into the battery system. Under conditions of 25°C and 0.2C, its capacity retention rate after 200 cycles was 71.8%, and its first-cycle efficiency was 80.2%. While this performance was superior to the pre-synthesized ZIF-8 groups (Comparative Examples 2 and 3), it was still significantly lower than the scheme in Example 1. This performance difference strongly demonstrates the necessity and advancement of the staged electrolyte injection strategy. Staged electrolyte injection, through sequential functional separation, solves the problem of competitive reactions and mutual interference between different functional additives in traditional one-time electrolyte injection. The first electrolyte injection stage focuses on the stable construction of the lithium metal anode SEI film, avoiding interference from the ZIF-8 precursor on the initial SEI formation process. The second electrolyte injection stage introduces the precursor on the basis of a stable interface, ensuring that ZIF-8 is generated in the most suitable electrochemical environment, achieving synergistic optimization of lithium metal anode stability and polysulfide suppression function.

[0156] By comparing the three precursor concentration gradients—Example 2 (low concentration 0.17 mol / L), Example 1 (standard concentration 0.33 mol / L), and Example 3 (high concentration 0.5 mol / L)—the precise balance between ZIF-8 formation and lithium-sulfur battery performance was revealed. Under conditions of 25°C and 0.2C, the capacity retention rates after 200 cycles for the three examples were 74.3%, 82.6%, and 79.1%, respectively, exhibiting a significant concentration effect. The relatively low performance of Example 2 indicates that insufficient precursor concentration prevents the formation of a continuous and effective polysulfide barrier network. While Example 3 is superior to Example 2, it is inferior to Example 1. Combined with its relatively high internal resistance (125 mΩ vs. 118 mΩ in Example 1), this suggests that excessive precursor may lead to excessive ZIF-8 formation, resulting in an overly dense structure in the separator and electrode pores, adversely affecting lithium-ion transport. The 0.33 mol / L concentration used in Example 1 ensured sufficient ZIF-8 formation to effectively suppress polysulfide shuttle while avoiding the negative impact of excessive formation on ion transport.

[0157] At 25°C and 0.2°C, Comparative Example 1 exhibited the lowest internal resistance (95 mΩ), while the pre-synthesized ZIF-8 groups (Comparative Examples 2 and 3) had resistances of 108 mΩ and 112 mΩ, respectively. The internal resistance range of Examples 1 to 3 was 118 mΩ to 125 mΩ. Although the introduction of ZIF-8 led to a moderate increase in internal resistance, this change has a reasonable technical mechanism. The in-situ generated ZIF-8 forms a functional composite interface that allows selective lithium ion passage while effectively blocking polysulfide anions. This moderate increase in internal resistance (approximately 20 mΩ to 30 mΩ) resulted in a significant improvement in cycle stability (20 to 25 percentage points), demonstrating excellent cost-effectiveness. More importantly, at 45°C and 0.2°C, the internal resistance of Example 1 decreased to 108 mΩ, indicating that ZIF-8 exhibits better ion transport performance at actual operating temperatures.

[0158] At 45°C and 0.2°C, the capacity retention rates of Example 1 after 200 and 300 cycles reached 87.3% and 74.2%, respectively, which were improved compared to the 25°C condition, demonstrating excellent high-temperature cycling stability. This phenomenon is closely related to the enhanced polysulfide suppression effect and improved ion transport performance of ZIF-8 at high temperatures.

[0159] The results of the 60°C high-temperature storage test showed that Example 1 exhibited a capacity retention rate of 76.4% and a capacity recovery rate of 84.2%, which were significantly improved compared to the 48.3% and 62.5% of the control group (Comparative Example 1). This indicates that the in-situ generated ZIF-8, through its Lewis acidic Zn... 2+ The chemical anchoring effect of the sites and polysulfides effectively reduces parasitic reactions and loss of active substances during high-temperature storage, providing excellent interfacial chemical stability.

[0160] The improved coulombic efficiency in the first week indicates optimization of the initial interface; the significant enhancement in cycle stability confirms effective suppression of polysulfide shuttle; and the substantial improvement in high-temperature storage performance reflects improved interfacial chemical stability. The staged liquid injection strategy avoids inter-component interference through sequential functional separation, the in-situ generation mechanism ensures uniform distribution and strong interfacial bonding of ZIF-8, and precise precursor concentration control achieves the optimal balance between barrier effect and ion transport. These three factors work synergistically to solve the core problem of polysulfide shuttle while comprehensively improving the overall performance of lithium-sulfur batteries. The lithium-sulfur battery manufacturing method provided in this application demonstrates significant advantages over existing pre-synthesized ZIF-8 technologies, verifying the technical value of the "in-situ generation" mechanism in terms of material distribution uniformity and interfacial bonding. Simultaneously, the staged liquid injection strategy, through sequential functional separation, achieves synergistic optimization of lithium metal anode stability and polysulfide suppression, providing a feasible technical path for the industrial application of lithium-sulfur batteries.

[0161] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for manufacturing a lithium-sulfur battery, characterized by, include: It provides sulfur-containing cathodes, lithium metal anodes, and separators; The sulfur-containing positive electrode, the separator, and the lithium metal negative electrode are wound or stacked and then placed into a housing to form an initial battery cell, with the separator located between the sulfur-containing positive electrode and the lithium metal negative electrode. A first electrolyte is injected into the initial battery cell. The components of the first electrolyte include: 8 wt% to 23 wt% lithium salt, 0.5 wt% to 10 wt% lithium nitrate, and ether solvent. After the first electrolyte is injected, the initial cell undergoes a first formation process; After the first formation process, a second electrolyte is injected into the initial cell. The components of the second electrolyte include: a zinc ion source, 2-methylimidazole, and an organic solvent. The concentration of the zinc ion source in the second electrolyte is 0.005 mol / L to 0.5 mol / L, and the molar ratio of 2-methylimidazole to zinc ions in the zinc ion source is 2:1 to 20:

1. After the second electrolyte is injected, the initial cell is activated in situ by holding the initial cell at a preset temperature for a preset time so that the zinc ion source and 2-methylimidazole react to generate ZIF-8 nanocrystals. Following the in-situ activation process, the initial cell undergoes a second formation process to form a lithium-sulfur battery.

2. The method for manufacturing a lithium-sulfur battery according to claim 1, characterized by, The preset temperature is 50℃~80℃; the preset time is 2 hours~24 hours.

3. The method of manufacturing a lithium-sulfur battery according to claim 1, characterized by, The average particle size of the ZIF-8 nanocrystals is 50nm~500nm.

4. The method of manufacturing a lithium-sulfur battery according to claim 1, characterized by, The zinc ion source is selected from one or more of zinc nitrate, zinc acetate, zinc chloride, zinc sulfate, bis(trifluoromethanesulfonyl)imide zinc, or bis(fluorosulfonyl)imide zinc.

5. The method of manufacturing a lithium-sulfur battery according to claim 1, wherein The total molar concentration of 2-methylimidazole and zinc ions from the zinc ion source in the second electrolyte is less than or equal to 0.3 mol / L.

6. The method of manufacturing a lithium-sulfur battery according to claim 1, wherein In the second electrolyte, the organic solvent is composed of a mixture of N,N-dimethylformamide and tetrahydrofuran, and the mass ratio of N,N-dimethylformamide to tetrahydrofuran is 1:1 to 3:1; or, the organic solvent is composed of ethanol and tetrahydrofuran, and the mass ratio of ethanol to tetrahydrofuran is 1:1 to 2:

1.

7. The method of manufacturing a lithium-sulfur battery according to claim 1, wherein The ether solvent is a mixture of 1,3-dioxolane and 1,2-dimethoxyethane, and the mass ratio of 1,3-dioxolane to 1,2-dimethoxyethane is 2:8 to 8:

2.

8. The method of manufacturing a lithium-sulfur battery according to claim 1, wherein In the first electrolyte, the concentration of lithium salt is 0.5 mol / L to 2.5 mol / L.

9. The method of manufacturing a lithium-sulfur battery according to claim 8, wherein The second electrolyte also includes lithium salt, and the lithium salt in the second electrolyte is the same as the lithium salt in the first electrolyte, and the lithium salt concentration in the second electrolyte is the same as the lithium salt concentration in the first electrolyte.

10. The method of manufacturing a lithium-sulfur battery according to claim 1, wherein The second electrolyte also includes 1wt% to 2wt% of auxiliary additives, which include graphene oxide or its derivatives or phosphate ester compounds.

11. The method of manufacturing a lithium-sulfur battery according to claim 1, wherein The first electrolyte also includes 0.1wt% to 5wt% of a negative electrode additive.

12. The method of manufacturing a lithium-sulfur battery according to claim 11, wherein The negative electrode additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, phosphorus pentasulfide, vinylene carbonate, or 1,3-propane sulphol.

13. A lithium-sulfur battery, characterized by, It is prepared by the manufacturing method of lithium-sulfur battery as described in any one of claims 1 to 12.

14. An electrical device, characterized by The electrical equipment includes the lithium-sulfur battery and load as described in claim 13; or, the electrical equipment includes an energy storage system and load, wherein the energy storage system includes the lithium-sulfur battery as described in claim 13.

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