A lithium-halogen reversible interphase layer, a solid-state battery lithium metal negative electrode and a preparation method thereof and a full solid-state battery

Abstract

The application discloses a lithium-halogen reversible interface layer, a solid-state battery lithium metal negative electrode and a preparation method and a full solid-state battery, and belongs to the technical field of solid-state battery electrode materials. The interface layer is directly covered on the lithium metal surface of the solid-state lithium metal negative electrode, and the chemical formula is Li(Cl 1‑a‑b Br a I b ), wherein 0<=a<=0.4, 0<=b<=0.4 and a+b<=0.6; the thickness of the interface layer is 5nm-30nm; the ion conductivity of the interface layer at 25 DEG C is >=2*10 ‑4 S*cm ‑1 ; when the battery temperature is increased to 80 DEG C-110 DEG C, the halogen element X2 partial pressure in the interface layer is >=10kPa, the ion conductivity is decreased by >=50%, reversible thermal shutdown is formed; when the temperature falls back to 25 DEG C, the ion conductivity of the interface layer recovers to >=90% of the initial value. The application is particularly suitable for a sulfide solid-state electrolyte system, the needle temperature rise rate is reduced by >=65%, and the retention rate is >=90% after 500 cycles.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state lithium metal batteries, and particularly to an all-solid-state battery suitable for sulfide solid electrolyte or high-nickel ternary cathode systems. Background Technology

[0002] All-solid-state batteries use non-flammable solid electrolytes, offering significantly superior intrinsic safety compared to liquid batteries. However, when sulfide solid electrolyte systems are paired with high-nickel ternary cathodes, the intense heat generated by interfacial side reactions under abuse conditions exposes the following bottlenecks in existing technologies: First, insufficient passive protection: Sulfide electrolytes are flammable in air and easily decompose and generate gas at the interface with cathode materials (such as NCM811) under high voltage. The thermal runaway initiation temperature is approximately 163°C, with a temperature rise rate as high as 8-10°C / s, far exceeding that of oxide systems. Traditional solid electrolyte layers lack active thermal management functions and cannot achieve reversible blocking of ion transport in the early stages of the aforementioned thermal runaway (80-110°C). Second, the risk of dendrite accumulation: Although solid electrolytes have high mechanical strength (>1GPa), interfacial contact degradation during long-term cycling can lead to localized current density concentrations. Lithium dendrites may still slowly penetrate along grain boundaries or pore defects, and the accumulation of micro-short circuits can cause a significant drop in capacity. Existing technologies attempt to introduce rigid ceramic layers such as Al2O3 and LLZO onto the surface of the negative electrode, but these coatings lack reversible phase transition capabilities, have thermal response temperatures exceeding 300℃, and are irreparable once cracked. Therefore, there is an urgent need for a smart interface material that combines active thermal shutdown and dendrite self-healing, providing redundant safety assurance, especially for the extreme operating conditions of sulfide systems. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a lithium-halogen reversible interface layer, which can utilize... The reversible reaction forms a dynamic protective layer at the negative electrode-electrolyte interface, achieving the dual functions of low-temperature thermal shutdown and dendrite self-healing.

[0004] The second objective of this invention is to provide a solid-state battery lithium metal anode that significantly improves the safety threshold of the high-nickel / sulfide system by constructing the halogen interface layer between the anode and the sulfide solid electrolyte.

[0005] The third objective of this invention is to provide a method for preparing the solid-state battery lithium metal anode, which is compatible with existing ALD or in-situ electrochemical formation equipment.

[0006] The fourth objective of this invention is to provide an all-solid-state battery that uses a sulfide solid electrolyte (such as Li6PS5Cl) and a high-nickel cathode. Through the interface layer, the battery surface temperature rise rate under needle penetration abuse is reduced by ≥65%, the capacity retention rate is ≥90% after 500 cycles, the energy density is increased by 8%-12%, and the cycle life is >500 cycles.

[0007] One of the objectives of this invention is achieved through the following technical solution:

[0008] A lithium-halogen reversible interface layer, wherein the interface layer directly covers the lithium metal surface of a solid lithium metal anode, has the chemical formula Li(Cl) 1-a-b Br a I b The interface layer has a thickness of 5nm-30nm and an ionic conductivity of ≥2×10⁻⁶ at 25°C. The ionic conductivity of the interface layer at 25°C is ≥2×10⁻⁶. -4 S·cm -1 When the battery temperature rises to 80℃-110℃, the partial pressure of halogen element X2 in the interface layer is ≥10kPa, and the ionic conductivity decreases by ≥50%, forming a reversible thermal shutdown; when the temperature drops back to 25℃, the ionic conductivity of the interface layer recovers to ≥90% of its initial value.

[0009] Furthermore, the halogen vacancy concentration is ≥5×10 13 cm -2 The halogen vacancy is introduced in any of the following ways:

[0010] (a) In-situ electrochemical halogen precipitation, with an application of 0.05-0.2 mA·cm -2 The pulsed current causes the halogen salts in the electrolyte to be reduced and release X. - ;

[0011] (b) Atomic layer deposition (ALD) using trimethylaluminum vapor (TMA) and HX (X = Cl, Br, I) as precursors, cyclically 20-200 times at 100-200 °C.

[0012] Furthermore, the interface layer passes through within 30 seconds after dendrite penetration. The reaction completes self-healing, and the interfacial impedance increases by <5% after healing.

[0013] The second objective of this invention is achieved by the following technical solution:

[0014] A solid-state battery lithium metal anode, comprising:

[0015] Lithium metal;

[0016] A three-dimensional porous carbon host, wherein the host has a mesoporous structure with a pore size of 2-50 nm and a porosity of 60%-85%;

[0017] The lithium-halogen reversible interface layer covers the space between lithium metal and the sulfide solid electrolyte.

[0018] Furthermore, the three-dimensional porous carbon host is selected from mesoporous carbon nanotubes, graphene aerogels, or hierarchical porous carbon, with a specific surface area ≥800 m². 2 ·g -1 .

[0019] Furthermore, the lithium metal is composited with the three-dimensional porous carbon host through melt lithium injection or electrochemical pre-lithiation, with a lithium metal filling rate ≥80%.

[0020] The third objective of this invention is achieved by the following technical solution:

[0021] A method for preparing the lithium metal anode of the solid-state battery, characterized by comprising the following steps:

[0022] S1. Provide the three-dimensional porous carbon host;

[0023] S2. Fill the lithium metal into the three-dimensional porous carbon host to obtain a Li / C composite.

[0024] S3. Constructing a lithium-halogen reversible interface layer on the surface of the Li / C composite: in-situ electrochemical halogen evolution: applying 0.1 mA·cm during the initial formation stage. -2 Square wave pulse for 10 min, electrolyte is tetrahydrofuran solution of 1M LiTFSI + 0.1M LiX; or ALD deposition: TMA and HX precursor, cycled 50-120 times at 150℃ to obtain the lithium metal anode of the solid battery.

[0025] S4. Assemble the solid-state battery lithium metal anode, the sulfide solid electrolyte (Li6PS5Cl), and the cathode into an all-solid-state battery.

[0026] Furthermore, the lithium metal is composited with the three-dimensional porous carbon host through melt lithium injection or electrochemical pre-lithiation, with a lithium metal filling rate ≥80%.

[0027] The fourth objective of this invention is achieved by the following technical solution:

[0028] An all-solid-state battery, comprising:

[0029] (a) The solid lithium metal anode described above;

[0030] (b) A sulfide solid electrolyte, selected from one of Li6PS5Cl and LPSCl; or LLZTO or polyoxyethylene-bis(trifluoromethanesulfonyl)imide lithium PEO-LiTFSI composite electrolyte;

[0031] (c) Positive electrode, selected from either high-nickel ternary positive electrode (NCM811) or sulfur-carbon composite positive electrode;

[0032] The all-solid-state battery exhibits a surface temperature rise rate reduction of ≥65% under nail penetration abuse and a capacity retention rate of ≥90% after 500 cycles.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The present invention provides a lithium-halogen reversible interface layer, a lithium metal anode for solid-state batteries, and an all-solid-state battery. 1. Independent technical value for sulfide systems: The present invention is particularly applicable to sulfide solid electrolyte systems such as Li6PS5Cl. Experimental data show that under abusive needle penetration, the surface temperature rise rate of the battery decreases from 8.5℃ / s to 1.8℃ / s, a reduction of 78.8%; after 500 cycles, the capacity retention rate increases from 68.3% to 91.2%, a relative increase of 33.5%, and the effective cycle life is extended by more than 250%. This function has independent and irreplaceable technical value in the high reactivity scenario of sulfide systems.

[0035] 2. The complementarity of active thermal management and passive protection: through... This invention utilizes a reversible phase transition reaction to actively block ion transport in the early stages of thermal runaway (80-110℃), compared to traditional solid electrolyte layers that only exhibit thermal response at temperatures above 300℃, thus improving the safety margin by over 200℃. This active thermal management function complements the intrinsic safety of solid electrolytes without increasing system complexity.

[0036] 3. Dynamic self-healing mechanism suppresses micro-short circuit accumulation: Within 30 seconds after dendrite penetration, the interface impedance recovery rate is >96%, and the pore size healing rate is >85%, compared to the polarization recovery rate of only 18% for the interface-free scheme. The micro-short circuit accumulation effect is fundamentally suppressed. This mechanism prevented the battery from experiencing early capacity drop after 500 cycles, significantly outperforming the performance of Comparative Example 1, which failed due to micro-short circuit at week 142.

[0037] 4. Narrow temperature window reversible response: This invention achieves a decrease in ion conductivity of ≥50% within a narrow temperature range of 80-110℃, and a recovery rate of >90% after the temperature drops back to 25℃. This avoids false triggering (normal operating conditions <60℃) and ensures rapid response under abusive conditions, thus balancing safety and reliability.

[0038] 5. Differences in applicability to oxide systems: In oxide solid electrolyte systems such as LLZTO, although the role of this invention is relatively minor (due to higher intrinsic safety), it still provides redundancy safety enhancement, reduces needle penetration temperature rise by about 30%, and improves cycle retention by about 5%, thus expanding the applicability of the technical solution.

[0039] 6. Process compatibility and cost advantages: The preparation method is compatible with existing ALD or roll-to-roll electrochemical formation equipment, requiring no new production line investment. The interface layer thickness is only 5-30nm, and the material cost increases by <0.5%, making it economically feasible for industrial-scale implementation. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments. It should be noted that, without conflict, the embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0041] Example 1

[0042] This embodiment provides a lithium-halogen reversible interface layer, which directly covers the lithium metal surface of a solid lithium metal anode, and has the chemical formula Li(Cl₂)₂. 1-a-b Br a I b The interface layer has the following properties: 0 ≤ a ≤ 0.4, 0 ≤ b ≤ 0.4, and a + b ≤ 0.6; the interface layer thickness is 5 nm - 30 nm; and the ionic conductivity of the interface layer at 25 °C is ≥ 2 × 10⁻⁶. -4 S·cm-1; When the battery temperature rises to 80℃-110℃, the partial pressure of halogen element X2 in the interface layer is ≥10kPa, the ionic conductivity decreases by ≥50%, and a reversible thermal shutdown is formed; When the temperature drops back to 25℃, the ionic conductivity of the interface layer recovers to ≥90% of the initial value.

[0043] A method for producing a lithium metal anode for solid-state batteries includes the following steps:

[0044] S1 provides a three-dimensional porous carbon host, specifically CNTs;

[0045] S2. Fill lithium metal into a three-dimensional porous carbon host to obtain a Li / C composite. The specific method is as follows: Take a mesoporous CNT film with a pore size of 10 nm and a porosity of 75%, and treat it with lithium foil at 250 °C for 10 min by melt lithium implantation to obtain a Li / CNT composite with a lithium filling rate of 85% and a thickness of 50 μm.

[0046] S3. A lithium-halogen reversible interface layer, replacing the thermosensitive membrane, is constructed on the surface of the Li / C composite, wherein the method of introducing halogen vacancies by in-situ electrochemical halogen evolution is as follows:

[0047] S31. Preparation of temporary electrolyte (in Ar glove box)

[0048] Solvent: Tetrahydrofuran (THF) or 1,3-dioxolane (DOL), with water and oxygen content <0.5ppm;

[0049] Lithium salt preparation:

[0050] Main salt: Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 1 M concentration, provides lithium ions (Li... + ).

[0051] Additive: Lithium chloride (LiCl), 0.1 M, as a source of chloride ions (Cl⁻).

[0052] Pretreatment requirements: LiCl must be vacuum dried at 120 °C for 12 hours before use.

[0053] Key additive: 3wt% FEC (fluoroethylene carbonate), used to pre-form a film on the Li surface to prevent Li from being corroded before halogen precipitation;

[0054] S32. Negative electrode-electrolyte contact method: The Li / CNT composite is used as the negative electrode. The Li / CNT composite negative electrode is immersed in the above temporary electrolyte, and the liquid level submerges the negative electrode surface by 2 mm. A three-electrode system is adopted: the negative electrode is the working electrode, the lithium foil is the counter electrode, and the double lithium foil is the reference electrode to avoid polarization misjudgment.

[0055] Apply a square wave pulse: 0.1 mA·cm at 25℃. -2 A square wave pulse was applied for 10 minutes at a frequency of 0.1 Hz, with a 5-second on / off cycle, for a total of 10 minutes and 30 cycles. The purpose was to apply the square wave pulse to Cl... - Sufficient time is allowed for diffusion to the Li surface, while a continuous current results in an excessively thick and cracked LiCl layer. In-situ precipitation of Cl... - It reacts with Li to form an 8 nm LiCl layer with a halogen vacancy concentration of 6 × 10⁻⁶. 13 cm -2 .

[0056] S33. Post-reaction treatment (to prevent residual liquid from damaging the solid electrolyte):

[0057] Remove the negative electrode and rinse it three times with pure DOL solvent, each time for 10 seconds at a flow rate of 50 mL / min, to remove residual LiTFSI.

[0058] Vacuum drying: In the vacuum chamber of the glove box, the negative electrode is left to stand at room temperature for 2 hours, and then dried at 60 ℃ for 1 hour to ensure complete solvent evaporation (mass loss <0.1 wt%).

[0059] S34. Quality Inspection: Randomly sample 3 pieces, and use XPS to detect the intensity of the Cl2p peak (198.5 eV), confirming that the LiCl layer thickness is 8±2 nm and the halogen vacancy concentration is ≥5×10⁻⁶. 13 cm -2 (by Cl) - (Calculation of O1s satellite peak shift due to vacancy).

[0060] S35, Transfer to solid-state battery assembly: The negative electrode that has undergone the above treatment has a LiCl interface layer. At this time, it is cold-pressed with Li6PS5Cl solid electrolyte, with a relative density of 96%. The solid electrolyte will not react with the residual temporary electrolyte because the solvent has completely evaporated, leaving only the inorganic LiCl layer.

[0061] S4. Assemble the solid-state battery lithium metal anode, solid-state electrolyte, and positive electrode into an all-solid-state battery. Specifically, stack it with an NCM811 positive electrode to form a 2Ah pouch battery.

[0062] Example 2

[0063] This embodiment provides a lithium-halogen reversible interface layer, which directly covers the lithium metal surface of a solid lithium metal anode, and has the chemical formula Li(Cl₂)₂. 1-a-b Br a I b The interface layer has the following properties: 0 ≤ a ≤ 0.4, 0 ≤ b ≤ 0.4, and a + b ≤ 0.6; the interface layer thickness is 5 nm - 30 nm; and the ionic conductivity of the interface layer at 25 °C is ≥ 2 × 10⁻⁶. -4 S·cm -1 When the battery temperature rises to 80℃-110℃, the partial pressure of halogen element X2 in the interface layer is ≥10kPa, and the ionic conductivity decreases by ≥50%, forming a reversible thermal shutdown; when the temperature drops back to 25℃, the ionic conductivity of the interface layer recovers to ≥90% of its initial value.

[0064] A method for manufacturing a lithium metal anode for solid-state batteries includes the following steps:

[0065] S1 provides a three-dimensional porous carbon host, specifically CNTs;

[0066] S2. Fill lithium metal into a three-dimensional porous carbon host to obtain a Li / C composite. The specific method is as follows: Take a mesoporous CNT film with a pore size of 10 nm and a porosity of 75%, and treat it with lithium foil at 250 °C for 10 min by melt lithium implantation to obtain a Li / CNT composite with a lithium filling rate of 85%.

[0067] S3. A lithium-halogen reversible interface layer, replacing the thermosensitive membrane, is constructed on the surface of the Li / C composite, wherein the method of introducing halogen vacancies by in-situ electrochemical halogen evolution is as follows:

[0068] S31, Lithium metal surface pre-protection:

[0069] A 2 nm amorphous carbon (aC) layer was pre-sputtered onto the surface of the Li / CNT composite anode, or a 1 nm AlF3 layer was evaporated by electron beam, using a Kurt J. Lesker PVD system. This protective layer serves two purposes: ① to isolate water and oxygen; ② to be extremely thin (<2 nm), thus not hindering the Li… + ③ The ALD process can be etched through by hydrogen halide (HCl) without affecting the subsequent formation of LiX.

[0070] S32 and ALD equipment retrofit: Use Beneq TFS-200 or Savannah S200 and install a lithium metal-specific intake manifold: the precursor HX (HCl, HBr) and TMA are introduced separately to avoid HX condensation and corrosion in the pipeline;

[0071] Substrate temperature: reduced to 100–120 ℃ (conventional ALD is 150–200 ℃), balancing deposition rate and lithium metal stability; deposition rate: 0.05 nm / cycle, 50–120 cycles yield 5–10 nm LiX;

[0072] S33, ALD in-situ etching and deposition are synchronized: Each cycle: TMA pulse (0.1s) → N2 purging (10s) → HX pulse (0.2s) → N2 purging (10s);

[0073] Mechanism: HX serves as both a halogen source and a slightly etched pre-protective layer (aC or AlF3), instantly generating LiX on the exposed fresh Li surface, thus achieving selective deposition.

[0074] Example 3

[0075] This embodiment provides a lithium-halogen reversible interface layer with gradient vapor doping.

[0076] The Li / CNT composite was treated in 0.5 kPa Br2 vapor at 200 °C for 20 min to obtain Li(Cl) 0.7 Br 0.3 The gradient layer has a high Br content in the outer layer and a high Cl content in the inner layer.

[0077] The shutdown response time at 80℃ is shortened to 15 seconds, and there is no micro-short circuit after 1000 cycles.

[0078] Comparative Example 1

[0079] Comparative Example 1 provides a solid-state battery lithium metal anode without a lithium-halogen reversible interface layer, and is otherwise the same as Example 1.

[0080] At 80℃, the polarization voltage increased by 0.35V, causing thermal runaway in the needle penetration experiment, and short circuit after 120 cycles.

[0081] Comparative Example 2

[0082] Comparative Example 1 provides a solid-state battery lithium metal anode, using an oxide solid electrolyte LLZTO, and is otherwise the same as Comparative Example 1.

[0083] Industrial applicability

[0084] The lithium-halogen interface layer of this invention is thin (<30nm), and the preparation process is compatible with existing battery production lines (ALD or solution method), requiring no additional equipment. Applicable to:

[0085] High-nickel / lithium metal solid-state batteries for electric vehicles;

[0086] High-rate batteries for drones;

[0087] Grid-level energy storage system.

[0088] It can improve battery safety levels (by passing nail penetration, overcharge, and hot box tests) while maintaining high cycle life, and has significant industrialization prospects.

[0089] Experimental Example

[0090] 1. Experimental Methods

[0091] Solid-state battery lithium metal anode preparation

[0092] Example 1 (In-situ Electrochemical Halogen Evolution): 50 5×5cm solid-state battery lithium metal anode plates were prepared according to the manufacturing method of Example 1. 2 The Li / CNT anodes were constructed, with 25 sheets having an 8nm LiCl interface layer (experimental group) and 25 sheets without an interface layer (comparative example 1).

[0093] Example 2 (ALD): Twenty Li / CNT anodes of the same size were prepared according to the manufacturing method of solid-state battery lithium metal anode in Example 2, with a LiCl thickness of 10 nm.

[0094] Stacking sequence: negative electrode | electrolyte | positive electrode, apply 20MPa isostatic pressure for 1 minute, and vacuum seal with aluminum-plastic film.

[0095] 2. Testing Methods

[0096] Only the puncture abuse and cycle life tests used full cells; other critical functional tests used symmetric cells, such as ion conductivity, thermal shutdown response, and dendrite penetration-self-healing.

[0097] Test conditions and results

[0098] Ionic conductivity: The conductivity was determined according to GB / T 36376-2018 Solid Electrolytes AC Impedance Method, using a Solartron 1260+1287. The conditions were: frequency 1MHz-0.1Hz, amplitude 10mV, temperature increments of 5℃ from 25-120℃, and a holding time of 30 min before testing. The results are shown in Table 1.

[0099] Thermal shutdown response: Binder MK120 incubator, heating rate 2℃ / min -1 The real part of the impedance Z'@1kHz was recorded. The measurement results are shown in Table 1.

[0100] Table 1. Dynamics of thermal shutdown response

[0101] Group Thermal shutdown start temperature (°C) <![CDATA[25℃σ(S·cm -1 )]]> <![CDATA[80℃σ(S·cm -1 )]]> Decrease rate Thermal shutdown response time (s) Example 1 82 <![CDATA[2.1×10 -4 ]]> <![CDATA[0.90×10 -4 ]]> 57% 15 Example 2 85 <![CDATA[1.9×10 -4 ]]> <![CDATA[0.78×10 -4 ]]> 59% 18 Comparative Example 1 No response <![CDATA[1.8×10 -4 ]]> <![CDATA[1.7×10 -4 ]]> 6% -

[0102] As can be seen from Table 1, the response temperature of Example 1 is lower than the thermal runaway initiation temperature of the sulfide system (163°C), providing a safety margin of 81°C. The ALD coating of Example 2 responds slightly slower, but has excellent reversibility. Comparative Example 1 has no thermal shutdown function and cannot be actively intervened. Its impedance at 80°C is slightly reduced, and the ionic conductivity decreases only slightly.

[0103] Problems encountered during full-cell (Li|Li6PS6Cl|NCM) testing: Too many sources of polarization: the negative electrode LiX layer, positive electrode CEI, electrolyte grain boundaries, contact resistance, etc. are mixed together, with a total polarization ΔV_total=0.5 V, but the negative electrode only accounts for 0.05 V; the puncture signal is overwhelmed: when the needle punctures the negative electrode, ΔV_total may only change by 0.02 V (<5%), making it impossible to determine whether it is self-healing of the negative electrode or creep of the positive electrode material; the life test is too slow: full cells need to be cycled 500 times to observe capacity decay in order to indirectly infer whether the negative electrode has self-healed; symmetric cells can be tested 100 times per day for puncture-healing, directly quantifying the process.

[0104] Dendrite puncture-self-healing: In-situ SEM (PhenomXLAr) + micro-force probe, 5µN puncture applied to simulate dendrite puncture. Continuous imaging was performed from 0-600s after the micro-force probe was withdrawn. The puncture pore diameter was 1.2 μm, and the healing rate η(t) was recorded: η(t) = 1 - Dt / D0, where D0 = initial pore diameter, Dt = pore diameter at time t; a 1mA cm-force was applied to the battery. -2 Constant current discharge (or charging) was used to force lithium deposition from one side and dissolution from the other; the polarization voltage of the symmetrical cell (Li|Li6PS5Cl|Li) was recorded simultaneously. The measurement results are shown in Table 2.

[0105] Table 2. Quantitative analysis of dendrite puncture-self-healing in situ using SEM.

[0106] Group Initial pore size (µm) Remaining pore size (µm) after 600s Healing rate % Symmetric cell polarization recovery % Example 1 1.2±0.1 0.15±0.05 87% 96% Example 2 1.1±0.1 0.10±0.03 91% 98% Comparative Example 1 1.3±0.1 1.25±0.1 4% 20% Comparative Example 2 1.1±0.1 0.70±0.08 39.1% 45%

[0107] As can be seen from Table 2, the LiX layer on the pore wall of the membrane in Example 1 is dynamically chemically bonded (Li ⁺ (+½X2→LiX) achieves a high healing rate; the ALD coating in Example 2 is denser and has a more uniform distribution of halogen vacancies, resulting in a slightly better healing effect; Comparative Example 1 has no dynamic repair mechanism and relies solely on passive filling by a semi-solid electrolyte, with the pore size remaining almost unchanged; Comparative Example 2, due to the intrinsic stability of LLZTO, shows better performance than the anode scheme under the sulfide system, even though the anode scheme fails more slowly. The healing rates of Examples 1 and 2 differ from those of Comparative Example 1 by 83-87 percentage points, far exceeding the measurement error range (±3-5%), proving that the interface layer is a necessary condition for self-healing function. The healing rates of Examples 1 and 2 differ from those of Comparative Example 1 by 47.9%.

[0108] Abuse of needle pricks: Measured according to GB / T31485-2015, using a Ø3mm steel needle at a speed of 10mm·s. -1 The thermocouple was placed on the surface of the lithium metal negative electrode of the solid-state battery. The test was conducted according to UL-9540A §6.3 Test Method for Assessing the Spread of Thermal Runaway Fires in Battery Energy Storage Systems, and the results are shown in Table 3.

[0109] Table 3 Needle prick abuse test (2Ah soft pack)

[0110] Group Maximum temperature (°C) Temperature rise rate (°C / s) Voltage drop (mV) Has it passed UL-9540A? Example 1 108 1.8 320 yes Example 2 102 2.0 290 yes Comparative Example 1 168 8.5 ＞2000 no Comparative Example 2 85 1.2 180 yes

[0111] As shown in Table 3, the interface layer in Example 1 initiates thermal shutdown at 90℃, reducing conductivity by 52%, effectively suppressing short-circuit current, and lowering the temperature rise rate by 65%. Example 2 exhibits better ALD coating uniformity, with effects comparable to Example 1; however, it lacks thermal shutdown functionality, and the continuous heat generation from the short-circuit current triggers the decomposition and combustion of the sulfide electrolyte. The oxide's inherent thermal stability is high, resulting in a naturally lower temperature rise rate, making the interface layer's role relatively minor. For sulfide solid electrolyte systems, the halogen interface layer reduces the needle penetration temperature rise rate from 8.5℃ / s to 1.8℃ / s, a reduction of 78.8%, demonstrating its independent technical value in highly reactive systems.

[0112] Cycle life: Tested according to GB / T 31484-2015, using an Arbin BT-2000 equipment, under the following conditions: 25℃, 0.5C charge / discharge, voltage range 2.8-4.3V. The test results are shown in Table 4.

[0113] Table 4 Long-cycle data and interface stability (0.5C, 25℃)

[0114] Group First week discharge capacity (mAh) 12-week retention rate % Interface impedance growth rate (0→4 weeks)% Example 1 2015 91.2 ＋12 Example 2 1998 90.5 ＋8 Comparative Example 1 1980 68.3 ＋85 Comparative Example 2 1950 89.0 ＋15

[0115] As shown in Table 4, in Example 1, the interface layer suppressed dendrite penetration, and no micro-short circuits were observed after 12 weeks; the impedance increase was due to normal interface aging. In Example 2, the ALD coating had higher density and slower impedance increase. In Comparative Example 1, the dendrite impedance increased dramatically without protection. In Comparative Example 2, the oxide system had a strong intrinsic ability to suppress dendrites, and the effect of the interface layer was relatively minor. In the sulfide system, the interface layer increased the cycle life by 33%, the 12-week retention rate increased from 68% to 91%, and significantly suppressed the deterioration of interface impedance.

[0116] Experimental conclusions

[0117] 1. Independent value for sulfide systems: For sulfide solid electrolyte systems such as Li6PS5Cl, the halogen interface layer reduces the temperature rise rate under needle puncture abuse by 78.8% and increases cycle life by 33%, demonstrating that its active thermal management function in highly reactive systems has independent technical value.

[0118] 2. Differences from oxide systems: Oxide solid electrolytes have higher intrinsic safety and the role of the interface layer is relatively minor, but this invention is also applicable and provides redundant safety enhancement.

[0119] 3. This invention achieves active blocking of ion transport in the early stage of thermal runaway (80-110℃) through a reversible phase transition reaction, which complements the intrinsic safety of solid electrolytes without increasing the complexity of the system.

[0120] 4. The interface layer is accessed through... The reversible reaction heals 87-92% of dendrite punctures within 600 seconds, restoring >96% of the polarization of the symmetrical cell, and preventing the accumulation of micro-short circuits during daily cycles.

[0121] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A lithium-halogen reversible interface layer, characterized in that, The interface layer directly covers the lithium metal surface of the solid lithium metal anode, and its chemical formula is Li(Cl). 1-a-b Br a I b The interface layer has a thickness of 5nm-30nm and an ionic conductivity of ≥2×10⁻⁶ at 25°C. The ionic conductivity of the interface layer at 25°C is ≥2×10⁻⁶. -4 S·cm -1 When the battery temperature rises to 80℃-110℃, the partial pressure of the halogen element X2 in the interface layer is ≥10kPa, and the ionic conductivity decreases by ≥50%, forming a reversible thermal shutdown; when the temperature drops back to 25℃, the ionic conductivity of the interface layer recovers to ≥90% of its initial value. The halogen vacancy concentration in the interface layer is ≥5×10 13 cm -2 .

2. The lithium-halogen reversible interface layer as described in claim 1, characterized in that, The halogen vacancy is introduced in any of the following ways: In-situ electrochemical halogen precipitation: Apply 0.05-0.2 mA·cm -2 The pulsed current causes the halogen salts in the electrolyte to be reduced and release X⁻. Atomic layer deposition: using trimethylaluminum vapor and HX (X=Cl, Br, I) as precursors, cycling 20-200 times at 100-200℃.

3. The lithium-halogen reversible interface layer as described in claim 1, characterized in that, The interface layer undergoes self-healing within 30 seconds after dendrite penetration via the Li+1 / 2X2⇌LiX reaction, and the interface resistance increases by <5% after healing.

4. A lithium metal anode for a solid-state battery, characterized in that, include: Lithium metal; A three-dimensional porous carbon host, wherein the three-dimensional porous carbon host has a mesoporous structure with a pore size of 2-50 nm and a porosity of 60%-85%, and accommodates the lithium metal to form a Li / C complex; The lithium-halogen reversible interface layer according to any one of claims 1-3, wherein the interface layer covers the space between the lithium metal anode and the sulfide solid electrolyte of the solid-state battery.

5. A solid-state battery lithium metal anode as described in claim 4, characterized in that, The three-dimensional porous carbon host is selected from mesoporous carbon nanotubes, graphene aerogels, or hierarchical porous carbon, with a specific surface area ≥ 800 m². 2 ·g -1 .

6. A solid-state battery lithium metal anode as described in claim 4, characterized in that, The lithium metal is combined with the three-dimensional porous carbon host through melt lithium injection or electrochemical pre-lithiation, and the lithium metal filling rate is ≥80%.

7. A method for preparing a solid-state battery lithium metal anode according to any one of claims 4-6, characterized in that, Includes the following steps: S1. Provide the three-dimensional porous carbon host; S2. Fill the lithium metal into the three-dimensional porous carbon host to obtain the Li / C composite; S3. Constructing a lithium-halogen reversible interface layer as described in any one of claims 1-3 on the surface of the Li / C composite: In-situ electrochemical halogen evolution: Applying a square wave pulse current of 0.05-0.2 mA·cm-2 for 10 min to reduce the halogen salt in the electrolyte and release X-, wherein the electrolyte is a tetrahydrofuran solution of 1 M LiTFSI and 0.1 M LiX, and X = at least one of Cl, Br, and I; or atomic layer deposition: using trimethylaluminum vapor and HX (X = Cl, Br, I) as precursors, cycling at 100-200 °C for 20-200 times, with the thickness controlled at 10 nm ± 2 nm, to obtain the lithium metal anode of the solid-state battery; S4. Assemble the solid-state battery lithium metal anode, sulfide solid electrolyte, and cathode into an all-solid-state battery.

8. An all-solid-state battery, characterized in that, include: The solid-state battery lithium metal anode according to any one of claims 4-6; A sulfide solid electrolyte, selected from either Li6PS5Cl or LPSCl; The cathode is selected from either a high-nickel ternary cathode or a sulfur-carbon composite cathode. The all-solid-state battery exhibits a surface temperature rise rate reduction of ≥65% under nail penetration abuse and a capacity retention rate of ≥90% after 500 cycles.