Liquid metal-based monatomic catalyst, dynamic self-adaptive solid-solid catalytic sulfur positive electrode, solid-state lithium-sulfur battery and preparation method

Abstract

The invention belongs to the technical field of solid-state lithium-sulfur batteries, and particularly relates to a liquid metal-based monatomic catalyst, a dynamic self-adaptive solid-solid catalytic sulfur positive electrode, a solid-state lithium-sulfur battery and a preparation method. The invention provides a liquid metal-based monatomic catalyst. The liquid metal-based monatomic catalyst comprises liquid metal and transition metal monatomic dispersed in the liquid metal, the liquid metal comprises Ga or a Ga-based alloy, and the Ga-based alloy comprises a GaIn alloy or a GaInSn alloy. The fluidity of Ga or Ga-based alloy at the working temperature of the battery is utilized, a catalytic activity center (transition metal single atoms such as Cu and Fe) is dynamically conveyed to a reaction interface, self-adaptive contact and efficient catalysis are achieved, the interface contact and reaction kinetics problems are synchronously solved, the prepared solid-state lithium-sulfur battery is stable in coulombic efficiency and high in charge-discharge specific capacity, and the service life of the solid-state lithium-sulfur battery is prolonged. The cycling stability is good.

Description

Technical Field

[0001] This invention belongs to the field of solid-state lithium-sulfur battery technology, specifically relating to a liquid metal-based single-atom catalyst, a dynamic adaptive solid-solid catalytic sulfur cathode, a solid-state lithium-sulfur battery, and its preparation method. Background Technology

[0002] With the accelerated global energy structure transformation, high-energy-density and high-safety energy storage technologies have become a research focus. Traditional lithium-ion batteries, due to their theoretical energy density limit (<400Wh / kg) and constraints on key metal resources, struggle to meet the energy density requirements of emerging fields such as electric vehicles and smart grids, which demand >500Wh / kg. Lithium-sulfur batteries, with their high theoretical specific capacity (1675mAh / g) and energy density (2600Wh / kg) of sulfur cathodes, as well as the environmental friendliness and low cost advantages of sulfur, are widely considered strong candidates for next-generation energy storage systems. However, traditional liquid lithium-sulfur batteries suffer from inherent problems such as polysulfide shuttle effect, lithium dendrite growth, and electrolyte flammability, severely limiting their practical application. To overcome these challenges, researchers have turned to all-solid-state lithium-sulfur battery systems, using solid electrolytes to replace organic electrolytes, fundamentally solving the safety and shuttle effect problems.

[0003] Currently, research on solid-state lithium-sulfur batteries mainly focuses on three major types of electrolyte systems: (1) inorganic solid-state electrolytes (such as sulfide-type Li) 10 GeP2S 12 Oxide-type LLZO: has high ionic conductivity (10). -4 ~10 -2 (2) Polymer electrolytes (such as PEO-based systems): have good flexibility, but low room temperature ionic conductivity (usually <10 S / cm), but poor solid-solid interface contact, and volume changes during charging and discharging can easily lead to interface peeling; -4 S / cm), and the strong coordination between ether oxygen bond and lithium ion limits the migration efficiency; (3) Composite electrolyte: by introducing inorganic filler or constructing three-dimensional ion channels, we try to improve the performance in a synergistic way, but we still face challenges such as interface compatibility and complex preparation process.

[0004] Recently, the academic community has attempted to optimize the performance of solid-state lithium-sulfur batteries through various strategies, such as interface engineering: using deep eutectic / carbon composite modification layers to improve interfacial contact, or constructing carbon-sulfur-catalyst molecular-level contact interfaces through micropore confinement strategies to enhance reaction kinetics; catalytic modification: introducing single-atom catalysts or metal compounds to catalyze sulfur conversion reactions; and structural design: constructing integrated electrode-electrolyte structures through in-situ polymerization to reduce interfacial impedance. Despite these advancements, the results are still far from theoretically expected. Current lithium-sulfur batteries still suffer from poor solid-solid interface contact and slow reaction kinetics, leading to poor cycle stability. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a liquid metal-based single-atom catalyst, a dynamically adaptive solid-solid catalytic sulfur cathode, a solid-state lithium-sulfur battery, and a preparation method thereof. Using the liquid metal-based single-atom catalyst of this invention to prepare a sulfur cathode followed by a solid-state lithium-sulfur battery results in a battery with stable coulombic efficiency, high charge-discharge specific capacity, and good cycle stability.

[0006] This invention provides a liquid metal-based single-atom catalyst, comprising a liquid metal and transition metal single atoms dispersed in the liquid metal; The liquid metal includes Ga or a Ga-based alloy, and the Ga-based alloy includes a GaIn alloy or a GaInSn alloy. The transition metal single atom includes one or more of Cu, Fe, Co, and Pt.

[0007] Preferably, the mass fraction of transition metal single atoms in the liquid metal-based single-atom catalyst is 0.5-5%.

[0008] This invention also provides a method for preparing the liquid metal-based single-atom catalyst described in the above technical solution, comprising the following steps: Under a protective atmosphere, transition metal powder and liquid metal are mixed and heated to melt, yielding a liquid metal-based single-atom catalyst.

[0009] The present invention also provides a dynamic adaptive solid-solid catalytic sulfur cathode, comprising a cathode sheet and a cathode material supported on the cathode sheet; The cathode material includes the liquid metal-based single-atom catalyst described in the above technical solution or the liquid metal-based single-atom catalyst obtained by the above preparation method, an active material, an ion conductor, and a binder.

[0010] Preferably, the active material is a sulfur / carbon composite material; the ion conductor includes one or more of LiAl-LDH, LiPSCl, LiInCl, LATP, and LLZTO.

[0011] Preferably, the positive electrode material further includes conductive carbon material, and the positive electrode material comprises the following components in the following proportions: sulfur / carbon composite material 70~85wt%, LiAl-LDH 10~20wt%, liquid metal-based single-atom catalyst 0.5~5wt%, binder 3~8wt%, and conductive carbon material 1~10wt%.

[0012] This invention also provides a method for preparing the dynamic adaptive solid-solid catalytic sulfur cathode described in the above technical solution, comprising the following steps: A positive electrode slurry is obtained by mixing a liquid metal-based single-atom catalyst, an active material, an ionic conductor, a binder, and an organic solvent. The positive electrode slurry is coated onto the positive electrode sheet and dried to obtain a dynamic adaptive solid-solid catalytic sulfur positive electrode.

[0013] The present invention also provides a solid-state lithium-sulfur battery, comprising the dynamic adaptive solid-solid catalytic sulfur cathode described in the above technical solution or the dynamic adaptive solid-solid catalytic sulfur cathode obtained by the above preparation method, an in-situ polymerized solid electrolyte, a lithium metal anode, and a separator.

[0014] This invention also provides a method for preparing a solid-state lithium-sulfur battery, comprising the following steps: A battery is assembled from a dynamically adaptive solid-solid catalytic sulfur cathode, a lithium metal anode, and a separator. An electrolyte is injected into the battery to carry out an in-situ polymerization reaction to form an in-situ polymerized solid electrolyte, thereby obtaining a solid lithium-sulfur battery. The electrolyte includes a polymer precursor, a lithium salt, and an additive. The polymer precursor is 1,3-dioxolane and / or hexachlorocyclotriphosphazene, and the additive is lithium nitrate.

[0015] Preferably, the in-situ polymerization reaction is followed by a step-type formation, which includes an initial activation stage, a deep activation stage, an interface stabilization stage, and a channel optimization stage. The initial activation stage is: discharging to 1.5V with a high current pulse of 3~5C, followed by charging to 3.0V with a low current of 0.05~0.1C. The deep activation stage is: cycling 2~5 times at a rate of 0.05C. The interface stabilization stage is: cycling 3~5 times at a rate of 0.1C. The channel optimization stage is: cycling 5~10 times at a rate of 0.2C.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a liquid metal-based single-atom catalyst, comprising a liquid metal and transition metal single atoms dispersed in the liquid metal; the liquid metal comprises Ga or a Ga-based alloy, the Ga-based alloy comprising a GaIn alloy or a GaInSn alloy; the transition metal single atoms comprise one or more of Cu, Fe, Co, and Pt. This invention utilizes the fluidity of Ga or Ga-based alloys at battery operating temperatures (e.g., 30°C) to dynamically transport catalytic active centers (Cu, Fe, and other transition metal single atoms) to the reaction interface, achieving "adaptive" contact and efficient catalysis, simultaneously solving the problems of interface contact and reaction kinetics. The resulting solid-state lithium-sulfur battery exhibits stable coulombic efficiency, high charge-discharge specific capacity, and good cycle stability.

[0017] This invention also provides a solid-state lithium-sulfur battery and its preparation method. Through ring-opening polymerization of 1,3-dioxolane and / or hexachlorocyclotriphosphazene, a three-dimensional cross-linked polymer electrolyte network is formed inside the electrode (lithium salt-initiated polymerization achieves in-situ polymerization transformation of the liquid-phase precursor to the solid electrolyte), constructing an integrated interface that effectively reduces interfacial impedance and enhances interfacial stability. The step-by-step formation method of this invention gradually activates the electrode interface and forms a stable SEI film, optimizing ion transport channels and improving battery cycle stability.

[0018] Compared with existing technologies, the solid-state lithium-sulfur battery prepared by this invention also has the following beneficial effects: 1. Improve electrochemical performance (1) High discharge capacity and high utilization rate of active materials The solid-state lithium-sulfur battery prepared by this invention exhibits a discharge capacity greater than 900 mAh / g at room temperature and 0.1C. This value is significantly higher than that of conventional solid-state lithium-sulfur batteries, indicating extremely high utilization of the active material (sulfur). The main reason is the synergistic effect of the liquid metal-based single-atom catalyst and in-situ polymerization. The catalyst directly acts on the solid-to-solid sulfur conversion reaction, lowering the reaction energy barrier and improving reaction kinetics, allowing more sulfur to participate in the reaction, thereby increasing the capacity. The liquid-phase precursor fully wets the voids in the electrode particles, and the solid polymer electrolyte formed by in-situ polymerization achieves integrated and close contact with the sulfur electrode, greatly expanding the effective ion transport interface and ensuring that lithium ions can efficiently reach the surface of the active material, jointly promoting the improvement of utilization.

[0019] (2) Excellent rate performance and fast charging potential High initial capacity and good interfacial contact indicate that the battery possesses excellent rate performance and is expected to achieve fast charging. The main reasons include: the catalyst accelerates the intrinsic kinetics of the sulfur redox reaction; the low-torsion ion channels formed by in-situ polymerization and LiAl-LDH promote lithium salt dissociation and improve conductivity, together constructing an ultrafast ion transport pathway, which enables the battery to maintain low polarization even at high current densities, thus supporting rapid charge and discharge.

[0020] (3) Significantly improved cycle stability Tight solid-solid interface contact and catalysis help maintain the stability of the electrode structure during long-term cycling, thus promising extremely long cycle life. The main reasons include: the catalyst fills voids, improves interfacial mechanical contact, and helps buffer volume change stress during charge and discharge. The integrated electrode-electrolyte structure formed by in-situ polymerization, and the robust inorganic-organic composite electrolyte network, can effectively adapt to volume changes during cycling and prevent interfacial contact failure, which is key to achieving long cycle life.

[0021] 2. Enhance security Intrinsic safety is improved: the thermal stability and flame retardancy of the battery system are significantly enhanced. The main reason is that the phosphazene polymer backbone (formed by the polymerization of HCCP / DOL) itself has good thermal stability and flame retardancy, replacing the volatile and flammable liquid electrolyte, thus fundamentally improving the intrinsic safety of the battery.

[0022] 3. Optimize interface and ion transport Low interfacial impedance and high ionic conductivity result in a battery with low overall impedance, which is beneficial for improved performance. The main reasons include: the excellent wettability of the liquid precursor ensures perfect contact with all active materials, forming continuous and dense ion transport channels after polymerization, significantly reducing solid-solid interface resistance; and the Lewis acid sites and nitrogen atoms in the composite electrolyte formed by LiAl-LDH and the polymer synergistically promote lithium salt dissociation, thereby increasing lithium-ion transference number and high ionic conductivity.

[0023] In summary, this invention systematically solves the core challenges of solid-state lithium-sulfur batteries in terms of interface, kinetics, and safety through the ingenious design and synergistic effect of three core technologies: dynamic adaptive catalyst, in-situ polymerization interface construction, and composite electrolyte optimization. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a microstructure diagram of the dynamic adaptive solid-solid catalytic sulfur electrode of Example 2; Figure 2 A flowchart illustrating in-situ solid-state and stepped formation of batteries; Figure 3 This is a comparison graph showing the cycle performance of the battery in Example 2 and the battery in Comparative Example 1 at 0.1C. Figure 4 The results show the rate cycling performance of the in-situ solid-state battery in Example 2. Figure 5 The charge-discharge curves of the in-situ solid-state battery in Example 2 at 0.1C are shown. Figure 6 The EIS test results are for the in-situ solid-state battery of Example 2 and the liquid battery of Comparative Example 2. Figure 7 The LSV test results are for the in-situ solid-state battery in Example 2; Figure 8The rate cycling performance results are for Comparative Example 1 battery; Figure 9 The charge-discharge curves of the battery in Comparative Example 1 at 0.1C are shown. Figure 10 The charge-discharge curves of Comparative Example 3 battery at 0.1C are shown. Figure 11 Rate cycling performance of in-situ solid-state batteries after different solid electrolytes are used in the positive electrode slurry; Figure 12 Rate cycling performance of in-situ solid-state batteries after Ga and its alloys are used as conductive agents in the positive electrode slurry adjustment. Detailed Implementation

[0026] This invention provides a liquid metal-based single-atom catalyst, comprising a liquid metal and transition metal single atoms dispersed in the liquid metal; The liquid metal includes Ga or a Ga-based alloy, and the Ga-based alloy includes a GaIn alloy or a GaInSn alloy. The transition metal single atom includes one or more of Cu, Fe, Co, and Pt.

[0027] In this invention, the mass fraction of transition metal single atoms in the liquid metal-based single-atom catalyst is preferably 0.5-5%, specifically 1%, 2%, 3%, or 4%. The mass fraction described in this invention yields an atomically dispersed liquid metal-based single-atom catalyst without agglomeration.

[0028] In this invention, the composition of the GaIn alloy preferably includes: Ga 75.5 wt% and In 24.5 wt%; the composition of the GaInSn alloy preferably includes: Ga 68.5 wt%, In 21.5 wt% and Sn 10.0 wt%.

[0029] The catalyst described in this invention is in a molten state at the battery operating temperature, and can flow and fill the gaps between the positive electrode particles to form a dynamically adaptive electron / ion hybrid conductive network.

[0030] This invention provides a method for preparing the liquid metal-based single-atom catalyst described above, comprising the following steps: Under a protective atmosphere, transition metal powder and liquid metal are mixed and heated to melt, yielding a liquid metal-based single-atom catalyst.

[0031] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0032] In this invention, the protective atmosphere is preferably an argon-hydrogen mixture, wherein the volume fraction of hydrogen in the argon-hydrogen mixture is preferably 5-10%, and the volume fraction of argon is preferably 90-95%.

[0033] In this invention, the preferred heating and melting temperature is 800~1000℃, specifically 900℃, and the preferred holding time is 5~20h, specifically 10h; the preferred heating rate from room temperature to the heating and melting temperature is 5℃ / min. During the heating and melting process, the metal diffuses to form a uniformly dispersed dynamic metal-based single-atom catalyst. If the heating and melting temperature is too low, insufficient atomic dispersion may occur; if the temperature is too high, Ga or the alloy may volatilize.

[0034] In this invention, the process of heating and melting preferably includes cooling, and the cooling is preferably natural cooling.

[0035] The present invention provides a dynamic adaptive solid-solid catalytic sulfur cathode, comprising a cathode sheet and a cathode material supported on the cathode sheet; The cathode material includes the liquid metal-based single-atom catalyst described in the above technical solution or the liquid metal-based single-atom catalyst obtained by the above preparation method, an active material, an ion conductor, and a binder.

[0036] In this invention, the active material is preferably a sulfur / carbon composite material, which is preferably S / Super P (carbon black), S / AC (activated carbon), or S / Graphene (graphene). The mass ratio of S to Super P in the S / Super P mixture is preferably 3:1. The sulfur / carbon composite material is preferably a homogeneous composite formed by a melt diffusion method, specifically: mixing and grinding carbon material and sulfur, heating at 155°C for 10 hours, and then heating at 250°C for 2.5 hours.

[0037] In this invention, the ion conductor is preferably a solid electrolyte, which preferably includes one or more of layered bimetallic hydroxides, LiPSCl (lithium phosphorus-sulfur-chloride), LiInCl (lithium indium chloride), LATP (lithium aluminum titanium phosphate), and LLZTO (lithium lanthanum zirconium tantalum oxide). The layered bimetallic hydroxide can be lithium aluminum layered bimetallic hydroxide (LiAl-LDH). The solid electrolyte of this invention not only conducts lithium ions and enhances lithium ion conduction within the positive electrode, but also improves the electrolyte's mechanical strength and adsorbs impurities. The solid electrolyte of this invention can effectively reduce the interfacial contact impedance between the electrolyte and the sulfur positive electrode, optimizing the interfacial contact between the solid electrolyte and the electrode, thereby significantly improving the lithium ion transport kinetics.

[0038] In this invention, the positive electrode material preferably further includes a conductive carbon material (electronic conductor), and the conductive carbon material is preferably Super P, acetylene black or carbon nanotubes.

[0039] In this invention, the binder is preferably polyvinylidene fluoride, which ensures the stability of the electrode structure.

[0040] In this invention, the cathode material preferably comprises the following components in the following proportions: 70-85 wt% sulfur / carbon composite material, 10-20 wt% LiAl-LDH, 0.5-5 wt% liquid metal-based single-atom catalyst, 3-8 wt% binder, and 1-10 wt% conductive carbon material. In the embodiments of this invention, the mass ratio of sulfur / carbon composite material, LiAl-LDH, liquid metal-based single-atom catalyst, and binder in the cathode material is 8:1:0.5:0.5. The sulfur electrode has a composite structure, and the liquid metal-based single-atom catalyst adaptively regulates the adsorption and conversion of polysulfides during charge and discharge, realizing a solid-solid reaction-dominated sulfur chemical reaction.

[0041] This invention also provides a method for preparing the dynamic adaptive solid-solid catalytic sulfur cathode described in the above technical solution, comprising the following steps: A positive electrode slurry is obtained by mixing a liquid metal-based single-atom catalyst, an active material, an ionic conductor, a binder, and an organic solvent. The positive electrode slurry is coated onto the positive electrode sheet and dried to obtain a dynamic adaptive solid-solid catalytic sulfur positive electrode.

[0042] In this invention, the organic solvent preferably includes N-methylpyrrolidone (NMP).

[0043] In this invention, the positive electrode sheet is preferably aluminum foil (current collector), and the coating amount of the positive electrode slurry is preferably 2 mg / cm³. 2 .

[0044] In this invention, the drying temperature is preferably 50~80℃, specifically 60℃, and the drying time is preferably 8~15h, specifically 12h.

[0045] The present invention also provides a solid-state lithium-sulfur battery, comprising the dynamic adaptive solid-solid catalytic sulfur cathode described in the above technical solution or the dynamic adaptive solid-solid catalytic sulfur cathode obtained by the above preparation method, an in-situ polymerized solid electrolyte, a lithium metal anode, and a separator.

[0046] In this invention, the in-situ polymerized solid electrolyte is obtained by in-situ polymerization of a polymer precursor, a lithium salt, and an additive. The polymer precursor includes 1,3-dioxolane (DOL) and / or hexachlorocyclotriphosphazene (HCCP), where DOL and HCCP are monomers capable of ring-opening polymerization. The lithium salt preferably includes lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(fluoromethanesulfonyl)imide (LiTFSI), or lithium hexafluorophosphate (LiPF6), which provides lithium ions. The additive preferably includes lithium nitrate (LiNO3), which acts as a film-forming additive to promote the formation of a stable SEI. DOL and HCCP polymerize under the initiation of the lithium salt to form a polyphosphazene-polyether composite electrolyte, forming a cross-linked network; the initiator (lithium salt) added to the electrolyte initiates cationic ring-opening polymerization, forming a three-dimensional ion-conducting network.

[0047] In this invention, the thickness of the lithium metal anode is preferably 50-150 μm, and a Li3N / LiF mixed SEI layer is formed on the surface by the decomposition of LiNO3 added to the electrolyte, which inhibits dendrite growth. During the in-situ polymerization process, an interface modification layer is also formed. This interface modification layer is preferably a dynamic interface layer formed on the positive electrode side by a liquid metal single-atom catalyst, which works synergistically with the solid electrolyte to reduce interfacial impedance.

[0048] This invention also provides a method for preparing the solid-state lithium-sulfur battery described above, comprising the following steps: A battery is assembled from a dynamically adaptive solid-solid catalytic sulfur cathode, a lithium metal anode, and a separator. An electrolyte is injected into the battery to carry out an in-situ polymerization reaction to form an in-situ polymerized solid electrolyte, thereby obtaining a solid lithium-sulfur battery. The electrolyte includes a polymer precursor, a lithium salt, and an additive. The polymer precursor is 1,3-dioxolane and / or hexachlorocyclotriphosphazene, and the additive is lithium nitrate.

[0049] In this invention, the concentration of lithium salt in the electrolyte is preferably 0.8~1.5 mol / L, specifically 1 mol / L; the concentration of additive (lithium nitrate) is preferably 0.01~0.1 mol / L, specifically 0.05 mol / L.

[0050] In this invention, the preferred temperature for the in-situ polymerization reaction is 40~100℃, specifically 60℃, and the preferred time is 2~12h, specifically 4h. This invention enables the in-situ solidification of lithium-sulfur batteries through in-situ polymerization.

[0051] In this invention, the in-situ polymerization reaction preferably further includes a step-type formation process, which activates the cell and forms a stable interface. The step-type formation includes an initial activation stage, a deep activation stage, an interface stabilization stage, and a channel optimization stage, as follows: The initial activation stage specifically involves: using a large current pulse discharge of 3~5C to 1.5V, followed by charging with a small current of 0.05~0.1C to 3.0V; to promote the decomposition of LiNO3 to form a stable SEI film and trigger the initial construction of the internal ion network of the positive electrode. The deep activation stage (stage 1) specifically involves cycling at a rate of 0.05C 2 to 5 times to focus on activating the sulfur cathode and forming a Li3N / LiF mixed SEI. The interface stabilization stage (stage 2) specifically involves cycling at a rate of 0.1C for 3 to 5 times to stabilize the lithium anode interface and further suppress dendrite growth. The channel optimization stage (stage 3) specifically involves cycling at a rate of 0.2C for 5 to 10 cycles to optimize the solid-solid interface ion channels and improve battery rate performance.

[0052] The solid-state lithium-sulfur battery of the present invention has a multi-level structure and spatial configuration, as detailed below: (1) Atomic / molecular structure: In a liquid metal-based single-atom catalyst, transition metal atoms (M) are anchored in a gallium alloy liquid matrix in single-atom form, forming an "M-Ga" dynamic coordination structure. This structure can reversibly adjust the adsorption energy for polysulfides during charge and discharge, achieving adaptive reconstruction of the catalytic active sites.

[0053] In the solid electrolyte, the polyphosphazene backbone (-P=N-) and polyether segments (-CH2-CH2-O-) form a hybrid cross-linked network, with LiAl-LDH serving as a nanofiller to enhance ionic conductivity (up to 10 at room temperature). -4 ~10 -3 S / cm).

[0054] (2) Electrode and battery stage structure: The cathode features a three-phase continuous design: a sulfur / carbon conductive phase, a LiAl-LDH ion-conducting phase, and a liquid metal-based single-atom catalytic phase intertwine in three-dimensional space to form an electron-ion-catalytic synergistic transport channel, enabling the solid-solid conversion reaction of sulfur.

[0055] In-situ polymerization interface: After the electrolyte precursor penetrates into the electrode pores, it polymerizes to form an integrated electrode-electrolyte interface, which effectively inhibits polysulfide shuttle and alleviates volume expansion (>80%).

[0056] Soft-pack battery configuration: It adopts a stacked Z-type structure and aluminum-plastic film vacuum packaging to ensure high energy density (>500 Wh / kg) and safety.

[0057] This invention overcomes the three major bottlenecks of traditional solid-state lithium-sulfur batteries, as follows: (1) High interfacial contact resistance: A tight solid-solid interface is constructed by combining the fluidity of the liquid metal-based catalyst with the wettability of in-situ polymerization; (2) Slow sulfur conversion kinetics: Utilize the high active sites of single-atom catalysts to lower the reaction energy barrier (e.g., reduce the activation energy from 0.16 eV to 0.07 eV). (3) Interface failure caused by volume effect: Through dynamic adaptive interface design and the flexibility of polymer network, the stress and strain during the cycling process are buffered, and the stability of electrode structure is improved.

[0058] This invention provides a new path for achieving high energy density (>500 Wh / kg) and long lifespan solid-state lithium-sulfur batteries through the synergy of multiple technologies, combining innovation with engineering application potential.

[0059] To further illustrate the present invention, the liquid metal-based single-atom catalyst, dynamic adaptive solid-solid catalytic sulfur cathode, solid lithium-sulfur battery, and preparation method provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1: Preparation of liquid metal-based single-atom catalyst (Ga / Cu) In an argon-filled glove box, 2g of copper powder was weighed and added to 98g of liquid Ga. The mixture was placed in an alumina crucible and transferred to a tube furnace. A mixture of argon (95% by volume) and hydrogen (5% by volume) was introduced, and the temperature was increased to 900℃ at 5℃ / min and maintained at this temperature for 10h. After natural cooling to room temperature, a homogeneous liquid Ga / Cu single-atom catalyst was obtained.

[0061] Example 2 1. Dynamically adaptive sulfur cathode Preparation of S / Super P composite material: Super P (carbon black conductive agent) and sublimed sulfur were mixed and ground at a mass ratio of 1:3, heat-treated at 155℃ for 10h, and then heated at 250℃ for 2.5h.

[0062] Preparation of positive electrode slurry: The above-mentioned S / Super P composite material, LiAl-LDH solid electrolyte, PVDF binder and Ga / Cu liquid single-atom catalyst prepared in Example 1 were ground into a uniform slurry in NMP solvent at a mass ratio of 80:10:5:5.

[0063] Coating and drying: The prepared slurry is coated onto aluminum foil (active material 2 mg / cm²). 2 The cathode material was dried under vacuum at 60℃ for 12 hours and then cut to obtain the positive electrode sheet.

[0064] 2. Battery assembly, in-situ solidification and activation Battery assembly: In an argon glove box, the obtained positive electrode, lithium metal negative electrode, and polyolefin separator are assembled into a button cell.

[0065] Electrolyte injection and polymerization: A DOL solution containing 1M LiFSI and 0.05M LiNO3 was injected into both sides of the separator in the assembled battery. The battery was then placed in a 60℃ oven and allowed to stand for 4 hours to complete the in-situ polymerization.

[0066] Step-by-step transformation: Initial activation: Discharge at 5C to 1.5V, then charge at 0.1C to 3.0V.

[0067] Phase 1: Two charge-discharge cycles at 0.05C.

[0068] Phase 2: 3 cycles of 0.1C charge and discharge.

[0069] Phase 3: 5 cycles of 0.2C charge and discharge.

[0070] Performance testing: After formation, the battery was tested at room temperature and 0.1C rate. The initial discharge capacity reached 920mAh / g, demonstrating excellent electrochemical performance.

[0071] Comparative Example 1 The only difference from Example 2 is that no liquid single-atom catalyst is added when preparing the sulfur cathode. The mass ratio of sulfur-carbon material (S / Super P composite material), carbon black conductive agent, and PVDF binder is 8:1:1, resulting in a conventional sulfur cathode.

[0072] Comparative Example 2 The only difference from Example 2 is that the electrolyte is replaced with a commercial lithium-sulfur electrolyte.

[0073] Comparative Example 3 The only difference from Example 2 is that the in-situ solidified electrolyte formulation does not contain LiNO3 (i.e., a DOL solution containing 1M LiFSI).

[0074] Comparative Examples 1 and 3 were both subjected to in-situ solidification and activation of the batteries according to the method of Example 2, and then their performance was tested at room temperature and 0.1C rate.

[0075] Figure 1 This is a microstructure diagram of the dynamic adaptive solid-solid catalytic sulfur electrode in Example 2. The spherical structure represents liquid Ga, the sheet-like structure represents Li-Al LDH, and the granular structure represents S / SP material. It can be seen that the liquid catalyst fills the spaces between the sulfur / carbon solid material particles.

[0076] Figure 2The flowchart shows the in-situ solidification and step-formation process of batteries. The in-situ polymerization process can convert liquid precursors into solid polymers inside the battery. The liquid precursors can fully wet the gaps between the positive electrode particles, retaining the advantage of close contact between the liquid and solid interfaces. After in-situ polymerization, an integrated solid-solid interface is formed, which ensures good contact between the polymer electrolyte and the electrode, so as to achieve the purpose of rapid ion transport.

[0077] Figure 3 The graph shows a comparison of the cycle performance of the battery in Example 2 (Ga-modified electrode) and the battery in Comparative Example 1 (ordinary electrode) at 0.1C. It can be seen that the battery with modified positive electrode has a higher charge-discharge specific capacity, better efficiency, and slower degradation.

[0078] Batteries with in-situ solidification and cathode modification were tested, and the results were compared with those with liquid state (Comparative Example 2) and in-situ solidification. This further demonstrates that the batteries using the in-situ solidification method exhibit superior ionic conductivity and electrochemical performance. Furthermore, the batteries with modified cathodes showed stable coulombic efficiency, higher charge-discharge specific capacity, and better cycle performance.

[0079] Figure 4 The results show the rate cycling performance of the in-situ solid-state battery in Example 2. Figure 5 The charge / discharge curve of this battery is shown. Figure 6 The EIS test results for this battery are as follows. Figure 7 The LSV test results for this battery are shown.

[0080] Figure 4 The results show that as the current rate gradually increases from 0.1C (0.2C, 0.5C, 1C) to 2C, the battery discharge capacity exhibits the expected decreasing trend. At the 2C rate, the battery can still maintain 259 mAh g⁻¹. -1 The discharge capacity. When the rate is reduced from 2C back to 0.5C for long-term cycling, the capacity can be restored to 454 mAh g. -1 The capacity performance was not significantly different from that before the rate switching. From cycle 25 to 40, the capacity decay was relatively gradual, with a final capacity retention of 39.7%. This result indicates that the main structure and reaction interface of the battery were maintained after high-rate cycling, demonstrating the positive effect of the in-situ solid-state strategy on maintaining electrode stability. The coulombic efficiency remained at a high level throughout the test, confirming the battery's good reversibility.

[0081] Figure 5 The image shows the charge-discharge curve of the battery in Example 2 during the second cycle at a 0.1C rate. During discharge, its discharge capacity was 1143.33 mAh·g. -1The curves show two distinct voltage plateaus. The first plateau is located in the approximately 2.10–2.30 V range, corresponding to the reduction of solid-state S8 to soluble long-chain polysulfides (Li2S8, Li2S6). Subsequently, the curves show a plateau at a discharge capacity of approximately 362 mAh·g. -1 An inflection point appears, followed by a second, longer voltage plateau (approximately 2.05–2.15 V). This plateau corresponds to the further reduction of the long-chain polysulfide to the insoluble short-chain Li₂S₂ / Li₂S. The clear distinction between the two plateaus demonstrates the stepwise progression of the multi-step reduction reaction. During charging, the charging capacity is 1010.93 mAh·g. -1 The curves primarily exhibit a relatively long charging plateau, centered in the approximately 2.20–2.30 V range. This corresponds to the oxidation of Li₂S₂ / Li₂S back to polysulfides until S₈. The voltage difference (polarization) between the charge and discharge curves is relatively small. The coulombic efficiency in the second cycle is 88.4%. This efficiency value is consistent with common phenomena in lithium-sulfur batteries, such as the initial formation of a solid-liquid interface and the unavoidable loss of some active materials. The clear reaction plateau in the discharge curves indicates that the dynamic single-atom catalyst and in-situ solidification technology used in this embodiment can effectively maintain the intrinsic electrochemical pathway and kinetics of the sulfur species conversion reaction while stabilizing the electrode structure.

[0082] By fitting the diameter of the semicircle, it was found that the charge transfer resistance of Example 2 (5.08Ω) was lower than that of Comparative Example 2 (9.09Ω), which reflects a smaller energy barrier between ions and the solid surface at the interface, demonstrating the development potential of this method. Figure 6 ).

[0083] Figure 7 LSV testing was conducted on the battery of Example 2 to evaluate its electrochemical stability in the high potential region. The test results showed that when the voltage was scanned to approximately 4 V (vs. Li), the electrochemical stability remained stable. + When the anode current approaches the vicinity of (Li), it begins to increase sharply. This sharp increase in current corresponds to the electrochemical oxidation and decomposition reaction of the electrolyte components on the cathode surface. This phenomenon defines the upper limit of the electrochemical stability window of this battery system. This oxidation onset potential is consistent with the theoretical expectation of conventional ether-based electrolyte systems, indicating that under the in-situ solidification conditions described in this invention, the battery module still follows basic electrochemical laws when reaching high voltage.

[0084] This series of performance tests proves that the in-situ solidification method obtained through the above operations has better cycle stability and rate performance than the original method.

[0085] Figure 8To compare the rate cycling performance of the battery in Example 1, an in-situ solid-state battery using a traditional cathode slurry formulation (with conductive agent C as the sole conductive medium) was tested for rate performance. This battery exhibited significant deficiencies in its rate cycling performance. After undergoing the same rate test as Example 2, its capacity decreased drastically. After 40 cycles, its capacity retention (relative to the first cycle capacity) was only about 15%, indicating that most of the active material had failed. More importantly, its capacity-cycle count curve fluctuated wildly and showed very poor stability, indicating that side reactions continued to occur inside the battery, and the electrode interface was in an extremely unstable state. The results of Comparative Example 1 demonstrate that relying solely on in-situ solid-state technology without simultaneously optimizing the conductive medium and electrolyte composition of the cathode cannot yield a high-performance, long-life lithium-sulfur battery. Its low capacity retention and poor cycle stability highlight the necessity and significant advancement of the core technical solution of this invention: replacing the conductive agent from C with Ga (a dynamic single-atom system) and introducing a specific solid electrolyte to synergistically optimize the interface.

[0086] Figure 9 Comparing the charge-discharge curves of Comparative Example 1 at 0.1C rate in the second cycle with that of Example 2, it was found that the charge-discharge plateau voltage and polarization degree of Example 2 were similar to those of the conventional Comparative Example 1, indicating that their initial reaction overpotentials were at the same level. However, under these conditions, Example 2 exhibited higher discharge specific capacity and charge specific capacity. This result demonstrates that the present invention significantly improves the utilization rate of active materials. This is mainly due to the introduction of a Ga-based dynamic single-atom catalytic system, which may reduce irreversible loss of active materials by more effectively anchoring and catalyzing the conversion of polysulfides and constructing a better conductive network, thereby allowing more sulfur species to participate in the electrochemical reaction. The effective increase in capacity improves the energy density of the battery and has potential advantages in maintaining capacity over long cycles.

[0087] Figure 10 The charge-discharge curve for Comparative Example 3 at a 0.1C rate in the second cycle shows a charging capacity of up to 4721 mAh·g. -1 The discharge specific capacity is only 490 mAh·g -1 The battery exhibited severe overcharging and extremely low coulombic efficiency. Although it used a Ga-based dynamic single-atom catalyst cathode, the lack of LiNO3 in the in-situ solid-state formulation led to abnormal charge-discharge processes. This result indicates that the battery system cannot form an effective interface protection mechanism in the absence of LiNO3 additives in the in-situ solid-state formulation. This comparative result strongly demonstrates the indispensable key role of LiNO3 additives in suppressing side reactions and stabilizing the electrode interface in this invention, further confirming the importance of the synergistic design of the catalytic system and interface modifiers in this invention.

[0088] Compared to the original lithium-sulfur battery cathode slurry preparation method (Comparative Example 1), this invention solves the problems of poor cycle stability and low reversible capacity caused by solid-state interface contact. It can be seen that Comparative Example 1 ( Figure 8 The degradation of the original positive electrode slurry preparation method (C is the conductive agent) is quite obvious, with a basic capacity retention of about 15% and very poor stability after rate cycling; while Figure 4 Example 2: The battery with modified positive electrode exhibits higher charge-discharge specific capacity and more stable battery cycle life. Simultaneously, through... Figure 5 and Figure 9 The charge-discharge curves (second cycle at 0.1C) show that the initial specific capacity of the original positive electrode slurry conditioning method is not high, while the charge-discharge specific capacity of Example 2 is higher. Figure 10 The original in-situ solidification formulation without LiNO3 showed overcharging, while the in-situ solidification method with LiNO3 did not show overcharging and had better cycle stability.

[0089] Example 3 The difference from Example 2 is that the LiAl-LDH solid electrolyte was adjusted to LiPSCl, LiInCl, LATP, and LLZTO, respectively.

[0090] Figure 11 To assess the rate cycling performance of in-situ solid-state batteries after different solid electrolytes were used in cathode slurry preparation, a comparison was made of cathode modifications with different solid electrolytes. LiAl-LDH solid electrolyte exhibited the best performance in terms of interfacial compatibility, resulting in a significantly improved charge / discharge specific capacity (initial specific capacity reached 1397 mAh / g) in the assembled batteries, and demonstrating high discharge specific capacity at various rates. LiAl-LDH can adsorb polysulfides, improving the ion conduction efficiency of lithium-sulfur batteries.

[0091] Example 4 The difference from Example 1 is that Ga is replaced with GaIn alloy and GaInSn alloy, respectively.

[0092] Figure 12 The rate cycle performance of in-situ solid-state batteries with Ga and its alloys as conductive agents in the positive electrode slurry was investigated. The results showed that the rate performance of solid-state lithium-sulfur batteries with Ga in the positive electrode was more stable and the charge-discharge specific capacity was higher.

[0093] The battery prepared according to the embodiments of the present invention has the following excellent effects: (1) Excellent interface contact and self-adaptation capability: Liquid metal-based single-atom catalysts can flow at the battery operating temperature and can dynamically fill the voids caused by sulfur volume changes, achieving "self-adaptive" tight solid-solid interface contact and significantly reducing interface impedance.

[0094] (2) LiAl-LDH and the in-situ polymerized phosphazene polymer together form a rigid-flexible ion conduction network, which effectively inhibits the degradation of the electrode structure.

[0095] (3) Highly efficient solid-solid reaction kinetics: The single-atom catalyst provides highly active catalytic sites, which greatly accelerates the conversion reaction between solid Li2S and sulfur, solving the problem of its inherently slow kinetics. Experiments show that the solid lithium-sulfur battery prepared in this invention can maintain a discharge capacity of more than 900 mAh / g at room temperature and 0.1C, which is far superior to ordinary solid lithium-sulfur batteries (around 800 mAh / g, and unstable).

[0096] (4) Excellent structural stability and safety: The three-dimensional cross-linked polymer skeleton formed by in-situ polymerization (derived from HCCP / DOL) has good mechanical strength and flame retardancy. Combined with the "anchoring" effect of LiAl-LDH, it stabilizes the electrode structure and greatly improves the thermal safety of the battery.

[0097] (5) Integrated preparation process: The present invention prepares batteries through positive electrode preparation, in-situ electrolyte polymerization and interface formation, which synergistically improves battery performance. The process is simple, has good compatibility with existing battery manufacturing processes, and has the potential for large-scale production.

[0098] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A liquid metal-based single-atom catalyst, characterized in that, Includes liquid metal, and transition metal single atoms dispersed in the liquid metal; The liquid metal includes Ga or a Ga-based alloy, and the Ga-based alloy includes a GaIn alloy or a GaInSn alloy. The transition metal single atom includes one or more of Cu, Fe, Co, and Pt.

2. The liquid metal-based single-atom catalyst according to claim 1, characterized in that, The mass fraction of transition metal single atoms in the liquid metal-based single-atom catalyst is 0.5-5%.

3. The method for preparing the liquid metal-based single-atom catalyst according to claim 1 or 2, characterized in that, Includes the following steps: Under a protective atmosphere, transition metal powder and liquid metal are mixed and heated to melt, yielding a liquid metal-based single-atom catalyst.

4. A dynamic adaptive solid-solid catalytic sulfur cathode, characterized in that, It includes a positive electrode sheet and a positive electrode material loaded on the positive electrode sheet; The cathode material includes the liquid metal-based single-atom catalyst as described in claim 1 or 2, or the liquid metal-based single-atom catalyst obtained by the preparation method described in claim 3, an active material, an ion conductor, and a binder.

5. The dynamic adaptive solid-solid catalytic sulfur cathode according to claim 4, characterized in that, The active material is a sulfur / carbon composite material; the ion conductor includes one or more of LiAl-LDH, LiPSCl, LiInCl, LATP, and LLZTO.

6. The dynamic adaptive solid-solid catalytic sulfur cathode according to claim 5, characterized in that, The cathode material also includes conductive carbon material, and the cathode material comprises the following components in the following proportions: 70-85 wt% sulfur / carbon composite material, 10-20 wt% LiAl-LDH, 0.5-5 wt% liquid metal-based single-atom catalyst, 3-8 wt% binder and 1-10 wt% conductive carbon material.

7. The method for preparing the dynamic adaptive solid-solid catalytic sulfur cathode according to any one of claims 4 to 6, characterized in that, Includes the following steps: A positive electrode slurry is obtained by mixing a liquid metal-based single-atom catalyst, an active material, an ionic conductor, a binder, and an organic solvent. The positive electrode slurry is coated onto the positive electrode sheet and dried to obtain a dynamic adaptive solid-solid catalytic sulfur positive electrode.

8. A solid-state lithium-sulfur battery, characterized in that, Includes the dynamic adaptive solid-solid catalytic sulfur cathode as described in any one of claims 4 to 6, or the dynamic adaptive solid-solid catalytic sulfur cathode obtained by the preparation method described in claim 7, the in-situ polymerized solid electrolyte, the lithium metal anode, and the separator.

9. The method for preparing a solid-state lithium-sulfur battery according to claim 8, characterized in that, Includes the following steps: A battery is assembled from a dynamically adaptive solid-solid catalytic sulfur cathode, a lithium metal anode, and a separator. An electrolyte is injected into the battery to carry out an in-situ polymerization reaction to form an in-situ polymerized solid electrolyte, thereby obtaining a solid lithium-sulfur battery. The electrolyte includes a polymer precursor, a lithium salt, and an additive. The polymer precursor is 1,3-dioxolane and / or hexachlorocyclotriphosphazene, and the additive is lithium nitrate.

10. The preparation method according to claim 9, characterized in that, The in-situ polymerization reaction is followed by a step-type formation, which includes an initial activation stage, a deep activation stage, an interface stabilization stage, and a channel optimization stage. The initial activation stage involves discharging to 1.5V with a high current pulse of 3-5C, followed by charging to 3.0V with a low current of 0.05-0.1C. The deep activation stage involves cycling 2-5 times at a rate of 0.05C. The interface stabilization stage involves cycling 3-5 times at a rate of 0.1C. The channel optimization stage involves cycling 5-10 times at a rate of 0.2C.

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