A high-safety solid-state lithium metal battery and a preparation method thereof

Abstract

The application discloses a high-safety solid-state lithium metal battery, which comprises a negative electrode, a solid-state electrolyte and a positive electrode, and further comprises a hetero-interface layer between the negative electrode and the solid-state electrolyte, wherein the hetero-interface layer is a double-layer composite structure composed of a passivation layer and a polymer / semiconductor, and the passivation layer is at least one of a nitride layer, an oxide layer, a nitrogen chemical layer, a carbon-based layer, a phosphate layer, a fluoride layer and a metal-based protective layer. By introducing the hetero-interface layer between the lithium metal negative electrode and the solid-state electrolyte, the physical contact between the lithium metal negative electrode and the solid-state electrolyte can be effectively improved, the growth of lithium dendrites is prevented, the interface reaction between the lithium metal and the solid-state electrolyte is reduced, the problem of thermal runaway fire combustion under high temperature is effectively inhibited, and the stability, safety and cycle performance of the solid-state lithium metal battery under room temperature and high temperature are enhanced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, particularly to high-safety solid-state lithium metal batteries and their preparation methods. Specifically, this invention provides a technical solution to improve the safety, thermal stability, and cycle life of lithium metal batteries by constructing a heterogeneous interface layer. Background Technology

[0002] With the global energy transition and the rapid development of the new energy vehicle industry, battery technology, especially in improving battery safety and energy density, has become an important direction for global technological innovation. Solid-state lithium batteries, due to their higher energy density and better safety, are widely considered a strong contender for next-generation battery technology.

[0003] Currently, the rapid development of solid-state battery technology is driven by demands from multiple sectors, including new energy vehicles and grid energy storage. Several companies have disclosed their product development progress and mass production plans. China is accelerating the industrialization process of solid-state batteries, committed to meeting the growing market demand from new energy vehicles and other application areas.

[0004] Despite the numerous theoretical advantages of solid-state lithium batteries, several technical bottlenecks remain, particularly the interfacial stability between the lithium metal anode and the solid electrolyte. Due to its high energy density, the lithium metal anode is prone to reacting with the solid electrolyte during use, leading to increased interfacial resistance and lithium dendrite growth. This negatively impacts overall battery performance and can potentially trigger thermal runaway under extreme conditions. Especially at high current densities and high temperatures, poor interfacial contact between the solid electrolyte and the electrode exacerbates the instability of chemical and electrochemical reactions, significantly increasing the risk of thermal runaway. This accelerates electrolyte thermal degradation, ultimately resulting in a sharp decline in battery performance and even safety incidents such as short circuits and explosions.

[0005] To address these issues in existing technologies, current research largely focuses on improving the interfacial stability between the electrode and the solid electrolyte by introducing protective layers (such as fluorides or oxides). However, a search by the inventors revealed that some publicly available technologies attempt to suppress lithium dendrite growth and improve battery cycle life through the introduction of metal mesh frameworks, including composites of lithium metal anodes and metal mesh frameworks, and passivation films (such as LiCl or LiF films). This approach focuses more on suppressing lithium dendrite growth. While the metal mesh framework can improve the uniformity of lithium metal deposition, its effect is limited to physical support, with limited improvement on interfacial chemical stability, especially under high-temperature conditions. Currently, single-layer interfacial modification materials such as fluorides or oxides are also used. These passivation films reduce interfacial side reactions to some extent, but they cannot buffer the volume changes of lithium metal. Under high current density or high-temperature environments, their ability to suppress lithium dendrites and their interfacial stability remain insufficient. Similarly, their effect on improving thermal stability under high-temperature conditions is limited, and they still cannot effectively solve safety problems such as fires caused by thermal runaway.

[0006] Therefore, most of the existing technologies mentioned above rely on a single interface layer, which cannot effectively meet the requirements for stability, low resistance, and long lifespan under high current density in extreme environments such as high temperatures. Existing technologies still have significant limitations when facing safety and stability issues under extreme conditions such as high temperatures.

[0007] In summary, it is urgent to overcome the numerous technical challenges of the existing technologies. Summary of the Invention

[0008] To address the problems existing in the prior art, this application improves the safety and stability of solid-state lithium metal batteries by constructing a heterogeneous interface layer in the battery structure, effectively suppressing interface reactions and thermal runaway, and improving the safety, cycle life and stability performance of existing batteries under extreme conditions.

[0009] This application provides a high-safety solid-state lithium metal battery, comprising a lithium metal anode, a solid electrolyte, and a cathode, characterized in that: it further comprises a heterogeneous interface layer located between the anode and the solid electrolyte, the heterogeneous interface layer being a bilayer composite structure composed of a passivation layer and a polymer / semiconductor, wherein the passivation layer includes, but is not limited to, one of a nitride layer, an oxide layer, a nitrogen chemical layer, a carbon base layer, a phosphate layer, a fluoride layer, and a metal-based protective layer; the semiconductor includes, but is not limited to, Si, Ge, or their composite alloys.

[0010] Preferably, the heterogeneous interface layer is located between the lithium metal anode and the solid electrolyte.

[0011] Preferably, the metal-based protective layer is made of metals such as In, Sn, Ti, Al, or their alloys.

[0012] Preferably, the solid electrolyte is, but is not limited to, Li. 1.5 Al 0.5 Ge 1.5 (PO4)3 (LAGP), Li 1.3 AI O.3 Ti 1.7 (PO4)3 (LATP), Li 6.4 La3Zr 1.4 Ta 0.6 O 12 (LLTO), Li7La3Zr2O 12 Solid electrolytes of oxides such as (LLZO) possess excellent ionic conductivity and chemical stability.

[0013] This invention also provides a method for preparing a high-safety solid-state lithium metal battery, characterized by comprising the following steps:

[0014] Step 1: Synthesis of solid electrolytes

[0015] Oxide-coated solid electrolytes were synthesized using conventional solid-state reaction methods.

[0016] The second step is to prepare the heterogeneous interface layer.

[0017] First, an atomic layer deposition (ALD) technique is used to deposit a passivation layer on the surface of a solid electrolyte.

[0018] Subsequently, a polymer / semiconductor layer is deposited on the passivation layer by magnetron sputtering, spin coating or plasma-enhanced chemical vapor deposition (PECVD) to form a heterogeneous interface layer.

[0019] Step 3: Preparation of ionic liquids

[0020] Lithium salt, potassium salt, and cesium salt are mixed in a predetermined ratio and heated until melted to form an ionic liquid;

[0021] Step 4: Preparation of the positive electrode

[0022] Ru nanoparticles were directly assembled on a carbon fiber substrate using DC reactive magnetron sputtering technology, and an ionic liquid was added between the cathode and the solid electrolyte to improve the contact between the electrode and the solid electrolyte.

[0023] Step 5: Battery Assembly

[0024] A battery is assembled from a lithium metal anode, a solid electrolyte containing a heterogeneous interface layer, and a Ru cathode.

[0025] Preferably, the passivation layer has a thickness of 1-10 nm, and the polymer / semiconductor layer has a thickness of 50-200 nm. More preferably, the alumina has a thickness of 6-7 nm, and the amorphous silicon has a thickness of 60-70 nm.

[0026] This invention also provides applications of the aforementioned high-safety solid-state lithium metal batteries, which are applicable to a variety of solid electrolyte materials and can operate stably under high temperature and high current density conditions, providing high-energy-density safety solutions for electric vehicles, energy storage systems, aerospace, military equipment and deep-sea exploration.

[0027] The technical solution provided in this application has at least the following technical effects or advantages:

[0028] 1. This invention introduces a heterogeneous interface layer between the lithium metal anode and the solid electrolyte, which can effectively improve the physical contact between the lithium metal anode and the solid electrolyte, prevent the growth of lithium dendrites, reduce the interface reaction between lithium metal and solid electrolyte, effectively suppress the problem of thermal runaway and combustion at high temperature, and enhance the stability, safety and cycle performance of solid lithium metal batteries at room temperature and high temperature.

[0029] 2. By precisely controlling the composition and thickness of the heterogeneous interface layer, this invention not only solves the interface stability problem in the prior art, but also significantly improves the overall performance of the battery under high temperature and high current density, significantly improves the cycle life of the battery, and solves the problem of easy degradation of traditional batteries under high current density and high temperature environments. Compared with the single interface layer solution in the prior art, the heterogeneous interface layer of this invention has higher and better thermal stability and chemical stability, improves the charge and discharge capability of the battery under high current density, significantly improves the rate performance of the battery, and provides a more reliable technical guarantee for the high safety and high efficiency of solid-state lithium batteries.

[0030] 3. This invention is applicable to a variety of solid electrolyte materials, including oxides, sulfides, phosphates, polymers, fluorides, nitrides and halides, and can provide broad technical support for different types of battery applications.

[0031] 4. The battery of the present invention is particularly suitable for stable operation under high temperature conditions above 150 °C, and is applicable to electric vehicles, energy storage systems, aerospace, military equipment and other fields.

[0032] 5. The solid-state lithium metal battery of the present invention can not only provide high energy density and excellent performance under normal temperature conditions, but also work stably under extreme conditions (such as high temperature environment or high current density), and has important practical application value. Attached Figure Description

[0033] Figure 1This is a schematic diagram of the structure of a solid-state lithium metal battery in an embodiment of the present invention.

[0034] Figure 2 This is a flowchart of the silicon-based heterostructure interface layer preparation process for solid-state lithium batteries in this embodiment of the invention, and SEM images of LAGP after each process.

[0035] Figure 3 This is a comparison of high-temperature thermal runaway experiments before and after the introduction of a heterogeneous interface layer into the LAGP solid electrolyte in this embodiment of the invention. Detailed Implementation

[0036] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods. Example

[0037] This embodiment provides a highly safe solid-state lithium metal battery, such as... Figure 1 As shown, it includes:

[0038] Lithium metal anode (Li): As the negative electrode of the battery, it provides lithium ions and has a high energy density.

[0039] Solid oxide electrolytes (SSEs): As lithium-ion transport media, they possess excellent ionic conductivity and chemical stability, making them suitable for stable operation under high temperature and high current density conditions.

[0040] Heterogeneous interface layer: Located between the lithium metal anode and the solid electrolyte, this layer combines alumina (Al2O3) and amorphous silicon (a-Si) layers. By optimizing interfacial contact, it suppresses side reactions and effectively prevents thermal runaway at high temperatures. Alumina, acting as a passivation material, forms LiAlO2 during charge / discharge. LiAlO2 is a fast ion conductor with a high lithium-ion diffusion coefficient, promoting lithium-ion insertion and extraction. During charge / discharge, LiAlO2 ion channels are formed, improving lithium-ion transport characteristics. This ion channel formation contributes to improved battery charge / discharge efficiency and cycle stability. Amorphous Si, in direct contact with Li, forms Li... x The Si alloy improves the solid-solid contact and increases the battery's conductivity. Simultaneously, because Si does not undergo side reactions with Li, it also isolates the oxygen generated at high temperatures from the direct contact between Li and LAGP, thus preventing potential thermal runaway. Through the design of this heterogeneous interface layer, this invention effectively optimizes the interfacial contact between the lithium metal anode and the solid electrolyte, suppresses side reactions, and effectively prevents the growth of lithium dendrites.

[0041] In this embodiment, the heterogeneous interface layer is a bilayer composite structure composed of alumina (Al₂O₃) and amorphous silicon (a-Si), wherein the alumina thickness is 6 nm and the amorphous silicon thickness is 70 nm. This heterogeneous interface effectively prevents thermal runaway caused by interfacial reactions.

[0042] This embodiment also discloses a method for preparing the above-mentioned solid-state lithium metal battery, including the following steps:

[0043] Step 1: Synthesis of solid electrolyte (LAGP)

[0044] 1) Raw material preparation: First, Li2CO3 (99%, Alfa Aesar), Al2O3 (99%, Aladdin), NH4H2PO4 (AR, Nanjing Chemical Reagent Co., Ltd.) and GeO2 (99.999%, China National Pharmaceutical Chemical Reagent, Beijing) are mixed in proportion to obtain a uniform powder.

[0045] 2) Ball milling: Place the mixed powder into a high-energy ball mill, set the ball milling speed to 400 rpm, and the ball milling time to 4.5 hours to ensure that the raw materials are fully and evenly mixed.

[0046] 3) Sintering process: The ball-milled mixture powder is placed in a muffle furnace and sintered at 600 °C for 1 hour, then ball-milled again at 400 rpm for 4.5 hours, and then sintered at 900 °C for 6 hours. The sintered powder is then ball-milled again for 4 hours to ensure its uniformity.

[0047] 4) Pressing and final sintering: The obtained powder is pressed into a disc with a diameter of 18 mm and a thickness of 0.9 mm, and then sintered at 900 °C for 6 hours to finally obtain the required LAGP solid electrolyte sheet.

[0048] The second step is the preparation of the heterogeneous interface layer, such as... Figure 2 As shown:

[0049] 1) Deposition of alumina layer: Using atomic layer deposition (ALD) technology, an Al2O3 layer of about 6 nm thick was deposited on the obtained LAGP surface to improve interface stability.

[0050] 2) Deposition of amorphous silicon layer: A layer of amorphous silicon (a-Si) about 70 nm thick is deposited on the Al2O3 layer by plasma enhanced chemical vapor deposition (PECVD) technology to form a heterogeneous interface layer with high ionic conductivity, which effectively avoids thermal runaway.

[0051] Step 3: Preparation of Ionic Liquids

[0052] Lithium nitrate (99.99% purity), potassium nitrite (99.99% purity), and cesium nitrate (99.99% purity) were mixed in a molar ratio of 37:39:24 and heated to 120 °C until the mixture was completely melted to obtain the desired ionic liquid.

[0053] Step 4: Preparation of the positive electrode

[0054] Ru nanoparticles were deposited on a carbon fiber substrate using DC reactive magnetron sputtering technology. The sputtering time was 0.5 to 3 minutes, the working pressure was 0.2 Pa, the power was 100 W, and the current density was 0.3 A.

[0055] After the positive electrode is prepared, 20 μl of the ionic liquid is added between the solid electrolyte and the positive electrode using a pipette to ensure good contact between the electrolyte and the electrode.

[0056] Step 5: Battery Assembly

[0057] A lithium metal anode, a solid electrolyte containing a heterogeneous interface layer, and a Ru cathode are assembled into a battery. The battery is packaged using standard battery packaging technology to ensure that the battery will not leak due to temperature changes or other external factors during use.

[0058] In this embodiment, the combined use of atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD) techniques during battery fabrication allows for precise control of the thickness and composition of the heterogeneous interface layer. This results in a more uniform interface layer with lower conductivity loss. This refined fabrication process ensures that the battery will not experience performance degradation due to interface instability during long-term use, improves the battery's thermal stability, suppresses lithium dendrite growth, and significantly extends the battery's cycle life.

[0059] like Figure 3 As shown, a thermal runaway experiment was conducted at 260°C on the solid electrolyte before and after the introduction of the heterogeneous interface layer in an inert gas atmosphere, specifically demonstrating the improvement of battery stability under extreme high temperature conditions after the introduction of the heterogeneous interface layer.

[0060] The experimental results above demonstrate that the present invention successfully prepared a solid-state lithium metal battery with high safety and stability, and the introduced heterogeneous interface layer significantly improved the cycle stability of the battery.

[0061] Specifically, through testing, a Li-symmetric cell with a heterogeneous interface layer introduced using the same method achieved a current of 0.1 mA cm⁻¹ at room temperature. -2 The battery cycled for over 560 hours at a current density, while the cycle life of batteries without an interface layer was significantly reduced. The introduction of the heterogeneous interface layer greatly improved the cycle life of the battery. Furthermore, the Li-CO2 battery with this heterogeneous interface layer achieved a cycle life of over 560 hours at 150 °C with a current density of 500 mA g⁻¹.-1 Current density and 500 mAh g -1 Under capacity constraints, it can stably cycle for more than 150 cycles, demonstrating excellent high-temperature performance and the versatility of this heterogeneous interface layer.

[0062] Comparative experiments demonstrate that the innovative heterogeneous interface layer design significantly improves battery safety, stability, and high-temperature adaptability, while also increasing battery life and cycle performance. Experimental results validate the effectiveness of this invention, particularly highlighting its significant advantages in high-temperature stability and cycle life.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A high-safety solid-state lithium metal battery, comprising a lithium metal anode, a solid electrolyte, and a cathode, characterized in that: It also includes a heterogeneous interface layer located between the lithium metal anode and the solid electrolyte to suppress thermal runaway at high temperatures. The heterogeneous interface layer is a bilayer composite structure composed of an alumina layer and an amorphous silicon layer. The amorphous silicon layer is located between the lithium metal anode and the alumina layer. The alumina layer has a thickness of 6-7 nm, the amorphous silicon layer has a thickness of 60-70 nm, and the solid electrolyte is LAGP or LATP.

Images