An interface bonding layer of lithium and a solid-state electrolyte, an interface bonding method and application

Abstract

The application belongs to the technical field of energy storage materials, and relates to an interface bonding layer of lithium and a solid-state electrolyte, an interface bonding method and application. A bonding layer is deposited on the surface of a solid-state electrolyte base material through magnetron sputtering. The bonding layer can be composed of tin-lead alloy, tin-silver-copper ternary alloy and the like, and is suitable for NASICON type, garnet type, sulfide and halide and the like solid-state electrolytes. The bonding process is carried out at 70 DEG C and under a pressure of 200 MPa, which significantly improves the interface stability of the battery, reduces the interface impedance, and thus effectively improves the energy density and cycle life. In addition, the composition of the bonding layer has a certain solubility with lithium, can form a binary or multi-component alloy, promotes uniform deposition of lithium, inhibits formation of lithium dendrites, and reduces the risk of battery failure. The application not only improves the safety and stability of the battery, but also optimizes the overall electrochemical performance, and provides strong support for practical application of the solid-state metal lithium battery.

Description

Technical Field

[0001] This invention belongs to the field of energy storage materials technology, and relates to an interfacial bonding layer between lithium and solid electrolyte, an interfacial bonding method, and its application. Background Technology

[0002] Solid-state lithium metal batteries, as an energy storage technology, have attracted widespread attention due to their high energy density, excellent safety, and long cycle life. Compared with traditional liquid batteries, solid-state lithium metal batteries use solid electrolytes, which significantly reduces the risk of leakage and combustion, solving many safety hazards of traditional batteries.

[0003] However, the commercialization of this technology still faces many challenges, among which the instability of the interface between solid electrolyte and lithium metal is particularly critical. In solid-state lithium metal batteries, solid electrolytes typically include various materials such as NASICON-type oxides, garnet-type electrolytes, sulfides, and halides. Each type of solid electrolyte may exhibit different forms of interfacial instability when in contact with lithium metal. For example, (1) when NASICON-type oxide solid electrolytes come into contact with lithium metal, they are prone to chemical reactions, generating non-conductive lithium compounds, thereby reducing the overall performance of the battery. In addition, the significant volume change of lithium metal during charging and discharging may induce mechanical stress, leading to the formation of interfacial cracks, which further affects ionic conductivity. (2) Garnet-type solid electrolytes are favored due to their excellent ionic conductivity, but their interfacial impedance with lithium metal is relatively high, which directly affects the cycle performance and energy efficiency of the battery. Studies have found that as the temperature increases, garnet-type electrolytes may undergo a phase transition with lithium metal, leading to interfacial instability and thus accelerating the degradation of battery performance. (3) Sulfide solid electrolytes generally have good conductivity, but at high temperatures they may react with lithium metal to form low-conductivity lithium sulfides, affecting the battery's conductivity. Furthermore, the corrosion of lithium metal at the sulfide electrolyte interface needs to be addressed; this corrosion not only leads to interface degradation but may also cause battery cycling instability. (4) Halide solid electrolytes, such as chlorides and iodides, also face chemical instability issues when in contact with metallic lithium. They may react with lithium metal during battery operation, forming non-conductive byproducts that affect ion migration efficiency. Simultaneously, lithium deposition and stripping processes in halide electrolytes may also lead to non-uniform lithium distribution, further affecting battery performance.

[0004] Therefore, solid-state lithium metal batteries have enormous development potential, but their interfacial instability remains a bottleneck restricting their commercial application. In-depth research into the interfacial interaction between solid electrolytes and lithium metal will pave the way for the future development of solid-state batteries, enabling high-performance, safe, and reliable energy storage solutions. Summary of the Invention

[0005] This invention addresses the instability of the interface between solid-state electrolyte and lithium metal in solid-state lithium metal batteries by providing a universal method for bonding the lithium metal interface with the solid-state electrolyte and its application in solid-state lithium batteries. The method involves depositing a bonding layer on the surface of a solid-state electrolyte substrate material via magnetron sputtering. The bonding layer is composed of materials such as tin-lead alloys or tin-silver-copper ternary alloys. The solid-state electrolyte can be NASICON-type, garnet-type, sulfide, or halide. The bonding process is carried out at 70°C and 200 MPa pressure, and is suitable for the preparation of solid-state lithium symmetric batteries or solid-state lithium metal full cells. This method is universal and significantly improves the interface stability of the battery, reduces interface impedance, and thus effectively improves the battery's energy density and cycle life. Furthermore, the modification and enhancement techniques of the interface bonding layer further optimize the battery's ion conductivity and improve overall electrochemical performance, resulting in solid-state lithium metal batteries with better safety and high efficiency.

[0006] The technical solution adopted by this invention to solve the technical problem is: an interfacial bonding layer between lithium and a solid electrolyte, wherein the interfacial bonding layer is formed by depositing a bonding layer alloy on the surface of a solid electrolyte substrate material using radio frequency magnetic sputtering; the bonding layer alloy includes: tin-lead alloy, tin-silver-copper ternary alloy, tin-silver alloy, tin-copper alloy, and Wood's alloy; the solid electrolyte includes: NASICON-type oxide solid electrolyte, garnet-type solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte; the interfacial bonding layer is formed by depositing the bonding layer alloy on one or both surfaces of the solid electrolyte substrate material using radio frequency magnetic sputtering. The components in this bonding layer have a certain solubility with lithium and can form binary or multi-component alloys with lithium. This alloy can not only effectively bond the solid electrolyte to the lithium metal anode, improving the interfacial physical contact behavior between the solid electrolyte and the lithium metal anode, but also induce the nucleus growth of lithium metal by adjusting the interfacial characteristics, promoting its uniform deposition. This process helps to suppress the formation of lithium dendrites, thereby reducing the risk of damage and failure of the solid electrolyte caused by lithium dendrites. This optimized interface bonding technology not only improves the safety and stability of the battery, but also enhances its electrochemical performance and extends its cycle life.

[0007] The thickness of the interface bonding layer is 0.5–5 μm. The thickness of the interface modification layer affects battery performance. An excessively thick interface modification layer will increase the interface impedance, i.e., increase the resistance to lithium-ion transport. An excessively thin interface modification layer is easily damaged and fails during battery charging and discharging. Therefore, it is necessary to balance the above two factors and select the optimal thickness.

[0008] Preferably, the NASICON-type solid electrolyte comprises: Li 1+x Al x Ti 2-x (PO4)3 (x = 0.3–0.5) and Li1+x Al x Ge 2-x (PO4)3 (x = 0.3–0.5); Garnet-type solid electrolytes include: Li7La3Zr2O 12 Li 3+x La 2 / 3- x TiO3, Li5La3Nb2O 12 and Li 6.25 La3Zr 1.75 Ta 0.25 O 12 Sulfide solid electrolytes include: Li₂S-P₂S₅, Li 10 GeP2S 12 Li7P3S 11 And Li2S-Sb2S3; halide solid electrolytes include: Li3MX6 (M=Y, Er, Sc, In, X=F, Cl, Br) and Li2MCl6 (M=Zr, Cd, Ti).

[0009] More preferably, the combination method of the interface bonding layer includes: Li 1+x Al x Ti 2-x (PO4)3 solid electrolyte and tin-lead alloy bonding layer combination, Li7La3Zr2O 12 Solid-state electrolytes and tin-silver-copper ternary alloy bonding layers are combined; Li₂S-P₂S₅ solid-state electrolytes and tin-lead alloy bonding layers are combined; Li₃MX₆ solid-state electrolytes and Wood's alloy bonding layers are combined; and Li₂MCl₄ solid-state electrolytes and tin-copper alloy bonding layers are combined. When preparing bonding layers on different solid-state electrolyte surfaces, the metals contained in multiple bonding layers can be used as targets for co-sputtering, or a single bonding layer alloy metal can be prepared as an alloy target for sputtering.

[0010] Preferably, the composition ratio of the tin-lead alloy is: Sn / Pb=x / (1-x), x=0.3~0.7; the composition ratio of the tin-silver-copper ternary alloy is: Sn / Ag / Cu=x / y / (1-xy), x=0~0.1, y=0~0.1; the composition ratio of the tin-silver alloy is: Sn / Ag=x / (1-x), x=0.3~0.7; the composition ratio of the tin-copper alloy is: Sn / Cu=x / (1-x), x=0.3~0.7; and the composition ratio of the Wood alloy is: Pb / Sn / Bi / Cd, (0~0.25) / (0~0.125) / (0~0.5) / (0~0.125).

[0011] This invention also discloses a method for interfacial bonding of lithium to a solid electrolyte, wherein the interfacial bonding method is used to prepare the above-mentioned interfacial bonding layer, and the interfacial bonding method includes the following steps:

[0012] Step S1: Remove impurities from the surface of the solid electrolyte matrix material and polish it;

[0013] Step S2: Using the bonding layer alloy as the target material, sputtering deposition is performed on the solid electrolyte substrate material polished in step S1 to form an interface bonding layer;

[0014] Step S3: Bond the lithium metal anode to the solid electrolyte with the bonding layer at 70-150°C and a pressure of 50-200 MPa.

[0015] The sputtering conditions for the interface bonding method include: a background vacuum of 0.1 × 10⁻⁶. -4 ~9.9×10 -4 The working pressure is 0.30 to 0.55 Pa, and the purity of the bonding layer alloy as the target material is ≥99.99%.

[0016] Preferably, the target-to-electrode distance of the interface bonding method is 8-12 cm, the sputtering power is 70-90 W, the sputtering temperature is 20-30 °C, the sample tray transfer speed is 0.5-1 cm / s, and the sputtering time is 10-30 min.

[0017] Preferably, the target-to-electrode distance of the interface bonding method is 8-12 cm, the sputtering power is 70-90 W, the sputtering temperature is 20-30 °C, the sample tray transfer speed is 0.5-1 cm / s, and the sputtering time is 10-30 min.

[0018] The present invention also discloses an application of a lithium-solid electrolyte interface bonding layer. The application uses the above-mentioned interface bonding layer and includes using the interface bonding layer to prepare lithium batteries, including: solid-state lithium symmetric batteries and solid-state lithium metal full batteries.

[0019] Preferably, when the lithium battery is a solid-state lithium symmetric battery, the interface bonding layer is deposited on both sides of the solid electrolyte matrix material, and then the metallic lithium anode is bonded to both sides of the electrolyte by hot-press bonding, thus preparing a solid-state lithium symmetric battery in the battery case.

[0020] Preferably, when the lithium battery is a solid lithium metal full battery, the interface bonding layer is deposited on both sides of the solid electrolyte matrix material, and then the lithium metal negative electrode is bonded to one side of the electrolyte by hot pressing bonding method, while the other side is matched with the positive electrode material.

[0021] The beneficial effects of this invention are:

[0022] 1. The interfacial bonding method provided by this invention has wide applicability. It is not only applicable to different types of solid electrolytes (such as NASICON type, garnet type, sulfide, halide), but can also be applied to the preparation of solid lithium batteries. The method of this invention can adapt to various material systems and has extremely strong adaptability.

[0023] 2. This invention significantly improves the interfacial physical contact behavior between the solid electrolyte and metallic lithium by depositing a bonding layer on the surface of the solid electrolyte, thereby enhancing the stability of the interface. The good solubility and alloying properties of the bonding layer and metallic lithium avoid electrochemical instability at the interface and reduce interfacial impedance.

[0024] 3. The bonding layer of this invention can induce uniform deposition of metallic lithium, avoiding the disorderly growth of lithium dendrites, thereby effectively reducing the risk of lithium dendrites piercing the solid electrolyte, preventing battery failure, and improving battery safety.

[0025] 4. The bonding layer of this invention not only provides a strong interface connection, but also optimizes the lithium ion conduction path and reduces interface impedance. This invention improves the ion conductivity of the battery, effectively improves the battery's energy density and cycle life, and significantly enhances the overall electrochemical performance.

[0026] 5. The magnetron sputtering method of the present invention is carried out in a vacuum environment, the process parameters are controllable, the thickness and uniformity of the bonding layer are easy to adjust, the preparation process is stable, the method of the present invention has mild conditions, the bonding temperature and pressure are moderate, and it is easy to realize in large-scale production.

[0027] 6. The thickness of the bonding layer in this invention has been optimized so that it neither increases the resistance to lithium-ion transport nor causes the battery to fail during cycling due to being too thin, thus achieving the best interface enhancement effect. Detailed Implementation

[0028] The relevant technologies of this invention will be clearly and completely described below with reference to the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] This embodiment provides a universal method for interfacial bonding of lithium metal to a solid electrolyte and its application in solid-state lithium batteries, including a solid electrolyte substrate and an interfacial bonding layer; the solid electrolyte is one of NASICON-type oxide solid electrolyte, garnet-type solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte. The bonding layer is composed of one of tin-lead alloy, tin-silver-copper ternary alloy, tin-silver alloy, tin-copper alloy, and Wood's alloy. The bonding method is hot-press bonding.

[0030] The interfacial bonding method between lithium metal and solid electrolyte of this invention exhibits significant advantages in the fabrication of solid-state lithium symmetric batteries and solid-state lithium metal full batteries. Using magnetron sputtering, a bonding layer is deposited on the surface of the solid electrolyte to form an effective interfacial bonding layer, primarily composed of materials such as tin-lead alloys and tin-silver-copper ternary alloys. This bonding layer design not only enhances the physical contact between the solid electrolyte and lithium metal and reduces interfacial impedance, but also induces uniform lithium deposition, thereby effectively suppressing the formation of lithium dendrites. By optimizing the bonding process and bonding layer composition, this method significantly improves interfacial stability, reduces performance degradation caused by interfacial instability, and ultimately improves the energy density and cycle life of the battery. Its broad applicability allows this method to be adapted to different types of solid electrolytes, providing strong support for the future development of high-performance, safe, and reliable solid-state lithium batteries.

[0031] The specific preparation steps are as follows:

[0032] The solid electrolyte was fixed within the magnetron sputtering chamber and covered with a baffle. A suitable target (purity ≥99.99%) was selected based on the pre-determined bonding alloy elements. Before use, the target was cleaned with acetone and dried. Subsequently, pre-sputtering was performed for 5–10 minutes to remove oxides and other impurities from the target surface, ensuring the material deposited on the solid electrolyte during subsequent sputtering is pure and free of impurities. Then, the baffle of the sample tray was opened, and sputtering began. The process parameters for RF magnetron sputtering were set as follows: background vacuum (0.1–9.9) × 10⁻⁶. -4 The sputtering parameters were: working pressure 0.30–0.55 Pa, target distance 8–12 cm, sputtering power 70–90 W, sputtering temperature 20–30 °C, sample tray transfer speed 0.5–1 cm / s, and sputtering time 10–30 minutes. Optimized sputtering time, power, and pressure were selected based on the target material. A solid electrolyte sheet with a uniformly attached bonding layer was then obtained, with the bonding layer thickness approximately 0.5–5 μm. Subsequently, a lithium metal anode was bonded to the solid electrolyte sheet with the bonding layer, and hot-pressed at 70–150 °C and a pressure of 50–200 MPa. This bonding process was carried out in a drying chamber with a dew point of -50 °C.

[0033] This invention utilizes the aforementioned solid electrolyte to prepare solid-state lithium symmetric batteries and solid-state lithium metal full batteries. (1) The solid-state lithium symmetric battery is prepared by placing a solid electrolyte with a lithium metal negative electrode bonded on both sides into a standard CR2032 coin cell to assemble the solid-state symmetric battery. (2) The solid-state lithium metal full battery is prepared by matching a solid electrolyte with a lithium metal negative electrode bonded on one side with a positive electrode, placing it into a standard CR2032 coin cell to assemble the solid-state lithium metal full battery.

[0034] Example

[0035] Example 1 provides a Sn / Ag alloy bonded Li 1.5 Al 0.5 Ti 1.5 Methods involving (PO4)3 solid electrolytes and lithium metal

[0036] The pre-prepared Li 1.5 Al 0.5 Ti 1.5 The (PO4)3 solid electrolyte sheet was placed in the sputtering chamber and covered with a baffle. A Sn / Ag target with a purity of 99.99% was cleaned and dried with acetone, then pre-sputtered for 5 minutes to remove surface oxides and other impurities, ensuring a pure Sn / Ag bonding layer is deposited on the surface of the solid electrolyte. The process parameters for RF magnetron sputtering were: a base vacuum of 5.0 × 10⁻⁶. -4 Argon gas with a purity of 99.99% was introduced at a working pressure of 0.35 Pa, a target distance of 10 cm, a sputtering power of 70 W, a sputtering temperature of 25 °C, a sample disk transfer speed of 1 cm / s, and a sputtering time of 20 min to prepare Li-type materials modified with a Sn / Ag bonding layer. 1.5 Al 0.5 Ti 1.5 (PO4)3 solid electrolyte. The bonding layer prepared in this example is approximately 100 nm. A lithium metal anode is bonded to a Li₂ electrode with a Sn / Ag bonding layer. 1.5 Al 0.5 Ti 1.5 (PO4)3 solid electrolyte is bonded at 150℃ and 150MPa.

[0037] Example 2 provides a Sn / Ag / Cu ternary alloy bonded to Li7La3Zr2O 12 Methods involving solid electrolytes and metallic lithium

[0038] The pre-prepared Li7La3Zr2O 12 The solid electrolyte sheet was placed in the sputtering chamber and covered with a baffle. The Sn / Ag / Cu target material with a purity of 99.99% was cleaned and dried with acetone, then pre-sputtered for 5 minutes to remove surface oxides and other impurities, ensuring a pure Sn / Ag / Cu bonding layer deposited on the surface of the solid electrolyte. The process parameters for RF magnetron sputtering were: a base vacuum of 5.0 × 10⁻⁶. -4 Argon gas with a purity of 99.99% was introduced at a working pressure of 0.35 Pa, a target distance of 10 cm, a sputtering power of 75 W, a sputtering temperature of 25 °C, a sample disk transfer speed of 1 cm / s, and a sputtering time of 30 min to prepare Li7La3Zr2O modified with a Sn / Ag / Cu bonding layer. 12Solid electrolyte. The bonding layer prepared in this embodiment is approximately 150 nm thick. A lithium metal anode is bonded to a Li7La3Zr2O electrode with a Sn / Ag / Cu bonding layer. 12 Solid electrolytes are bonded at 120°C and 130 MPa.

[0039] Example 3 provides a Sn / Pb alloy bonded to Li5La3Nb2O 12 Methods involving solid electrolytes and metallic lithium

[0040] The pre-prepared Li5La3Nb2O 12 The solid electrolyte sheet was placed in the sputtering chamber and covered with a baffle. A 99.99% pure Sn / Pb target was cleaned and dried with acetone, then pre-sputtered for 5 minutes to remove surface oxides and other impurities, ensuring a pure Sn / Pb bonding layer was deposited on the surface of the solid electrolyte. The process parameters for RF magnetron sputtering were: a base vacuum of 5.0 × 10⁻⁶. -4 Argon gas with a purity of 99.99% was introduced at a working pressure of 0.35 Pa, a target distance of 10 cm, a sputtering power of 80 W, a sputtering temperature of 25 °C, a sample disk transfer speed of 0.5 cm / s, and a sputtering time of 15 min to prepare Li5La3Nb2O modified with a Sn / Pb bonding layer. 12 Solid electrolyte. The bonding layer prepared in this embodiment is approximately 120 nm thick. A lithium metal anode is bonded to a Li₅La₃Nb₂O₄ electrode with a Sn / Pb bonding layer. 12 Solid electrolytes are bonded at 150°C and 150 MPa.

[0041] Example 4 provides a method for bonding a Sn / Cu alloy to a Li3InCl6 solid electrolyte and metallic lithium.

[0042] The pre-prepared Li3InCl6 solid electrolyte sheet was placed in the sputtering chamber and covered with a baffle. A Sn / Cu target with a purity of 99.99% was cleaned and dried with acetone, then pre-sputtered for 5 minutes to remove surface oxides and other impurities, ensuring a pure Sn / Cu bonding layer deposited on the surface of the solid electrolyte. The process parameters for RF magnetron sputtering were: a base vacuum of 5.0 × 10⁻⁶. -4 Argon gas with a purity of 99.99% was introduced at a working pressure of 0.35 Pa, a target-to-electrode distance of 10 cm, a sputtering power of 80 W, a sputtering temperature of 25 °C, a sample tray transfer speed of 1 cm / s, and a sputtering time of 20 min to prepare a Sn / Cu bonded layer modified Li3InCl6 solid electrolyte. The bonded layer prepared in this example was approximately 150 nm thick. The lithium metal anode was then bonded to the Li3InCl6 solid electrolyte with the Sn / Cu bonded layer at 170 °C and a pressure of 120 MPa.

[0043] Example 5 provides a Pb / Sn / Sb / Cd alloy bonded to Li 6.25 La3Zr 1.75 Ta 0.25 O 12 Methods involving solid electrolytes and metallic lithium

[0044] The pre-prepared Li 6.25 La3Zr 1.75 Ta 0.25 O 12 The solid electrolyte sheet was placed in the sputtering chamber and covered with a baffle. The 99.99% pure Pb / Sn / Sb / Cd target was cleaned and dried with acetone, then pre-sputtered for 5 minutes to remove surface oxides and other impurities, ensuring a pure Pb / Sn / Sb / Cd bonding layer was deposited on the surface of the solid electrolyte. The process parameters for RF magnetron sputtering were: a base vacuum of 5.0 × 10⁻⁶. -4 Argon gas with a purity of 99.99% was introduced at a working pressure of 0.35 Pa, a target distance of 10 cm, a sputtering power of 70 W, a sputtering temperature of 25 °C, a sample disk transfer speed of 1 cm / s, and a sputtering time of 20 min to prepare Li-type materials modified with a Sn / Ag bonding layer. 6.25 La3Zr 1.75 Ta 0.25 O 12 Solid electrolyte. The bonding layer prepared in this embodiment is approximately 100 nm thick. A lithium metal anode is bonded to a Li₂ electrode with a Pb / Sn / Sb / Cd bonding layer. 6.25 La3Zr 1.75 Ta 0.25 O 12 Solid electrolytes are bonded at 1100℃ and 200MPa.

[0045] Example 6 provides a Sn / Pb alloy bonded Li 1.5 Al 0.5 Ge 1.5 Methods involving (PO4)3 solid electrolytes and lithium metal

[0046] The pre-prepared Li 1.5 Al 0.5 Ge 1.5 The (PO4)3 solid electrolyte sheet was placed in the sputtering chamber and covered with a baffle. A Sn / Pb target with a purity of 99.99% was cleaned and dried with acetone, then pre-sputtered for 5 minutes to remove surface oxides and other impurities, ensuring a pure Sn / Pb bonding layer is deposited on the surface of the solid electrolyte. The process parameters for RF magnetron sputtering were: a base vacuum of 5.0 × 10⁻⁶. -4Argon gas with a purity of 99.99% was introduced at a working pressure of 0.30 Pa, a target distance of 8 cm, a sputtering power of 90 W, a sputtering temperature of 25 °C, a sample disk transfer speed of 1 cm / s, and a sputtering time of 15 min to prepare Li with a Sn / Pb bonded layer. 1.5 Al 0.5 Ge 1.5 (PO4)3 solid electrolyte. The bonding layer prepared in this embodiment is approximately 90 nm. A lithium metal anode is bonded to a Li₂ electrode with a Sn / Pb bonding layer. 1.5 Al 0.5 Ge 1.5 (PO4)3 solid electrolyte is bonded at 150℃ and 100MPa.

[0047] Example 7 provides a method for bonding a Sn / Ag / Cu ternary alloy with a Li2ZrCl4 solid electrolyte and metallic lithium.

[0048] The pre-prepared Li₂ZrCl₄ solid electrolyte sheet was placed in the sputtering chamber and covered with a baffle. A Sn / Ag / Cu target with a purity of 99.99% was cleaned and dried with acetone, then pre-sputtered for 5 minutes to remove surface oxides and other impurities, ensuring a pure Sn / Ag / Cu bonding layer deposited on the surface of the solid electrolyte. The process parameters for RF magnetron sputtering were: a background vacuum of 5.0 × 10⁻⁶. -4 Argon gas with a purity of 99.99% was introduced at a working pressure of 0.30 Pa, a target-to-electrode distance of 12 cm, a sputtering power of 85 W, a sputtering temperature of 25 °C, a sample tray transfer speed of 0.5 cm / s, and a sputtering time of 30 min to prepare a Sn / Ag / Cu bonded layer modified Li₂ZrCl₄ solid electrolyte. The bonded layer prepared in this example was approximately 150 nm thick. The lithium metal anode was then bonded to the Li₂ZrCl₄ solid electrolyte with the Sn / Ag / Cu bonded layer at 150 °C and a pressure of 150 MPa.

[0049] Table 1. Performance Comparison of Solid-State Lithium Symmetric Batteries between Examples and Control Examples

[0050]

[0051] Table 2. Performance Comparison of Solid-State Lithium Full Batteries between Examples and Control Examples

[0052]

[0053] Table 1 shows a performance comparison between Examples 1 to 7 and the control example, highlighting the advantages of solid-state lithium metal full cells with bonding layers in several key parameters. At 30°C and a current density of 0.1 mA cm⁻², the overpotentials of these cells were all below 100 mV, indicating that the bonding layer significantly reduced energy loss and improved energy efficiency. Furthermore, the interface impedance was less than 100 Ω / cm. 2 This further demonstrates that the bonding layer optimizes the contact between the electrolyte and lithium metal, improving ionic conductivity. This low impedance state is a key factor in ensuring high battery efficiency. Table 2 further illustrates the performance under higher rate conditions. Solid-state lithium metal full cells with bonding layers exhibit good cycle performance and high capacity retention at 30°C and 0.2C rate. After long-term cycle testing, the discharge capacity of these batteries remained at a high level, showing that the introduction of the bonding layer effectively enhances the cycle stability of the battery. Overall, these data indicate that the application of the bonding layer not only improves the immediate performance of the battery but also ensures its reliability in long-term use, providing strong support for the practical application of solid-state lithium metal batteries.

[0054] The introduction of the bonding layer significantly improves the performance of solid-state lithium metal batteries, mainly in the following aspects: (1) Interface stability: The bonding layer effectively enhances the physical contact between the solid electrolyte and lithium metal, reduces interface instability, and reduces the occurrence of interface reactions. (2) Reduced interface impedance: The presence of the bonding layer reduces the interface impedance of the battery, improves ionic conductivity, and enables lithium ions to migrate more quickly, thereby increasing the power density of the battery. (3) Uniform lithium deposition: The bonding layer helps to induce uniform deposition of lithium metal, inhibits the formation of lithium dendrites, reduces the risk of damage to the solid electrolyte, and extends the battery's lifespan. (4) Extended cycle life: The optimized design and modification technology of the bonding layer improves the overall cycle stability of the battery, enabling it to maintain higher performance during multiple charge-discharge cycles. In summary, the introduction of the bonding layer not only improves the safety and stability of solid-state lithium metal batteries, but also significantly improves their electrochemical performance, laying the foundation for their commercial application.

[0055] The ultimate goal of this invention is to improve the interfacial contact between the solid electrolyte and the lithium anode, while fundamentally preventing interfacial instability between the solid electrolyte and metallic lithium. This avoids irreversible consumption of active lithium and the solid electrolyte, and consequently prevents capacity loss and early failure of the solid-state battery caused by dendrite penetration of the solid electrolyte. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention. Clearly, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Thus, if these modifications and variations of the invention fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0056] In summary, this invention fundamentally avoids interfacial instability between the solid electrolyte and metallic lithium, preventing irreversible consumption of both active lithium and the solid electrolyte, and thus avoiding capacity loss and early failure of solid-state batteries caused by dendrite penetration of the solid electrolyte. Therefore, this invention has broad application prospects in the field of energy storage materials technology.

[0057] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An interfacial bonding layer between lithium and a solid electrolyte, characterized in that, The interface bonding layer is a bonding layer formed by depositing a bonding layer alloy onto the surface of a solid electrolyte matrix material using radio frequency magnetic sputtering. The bonding layer alloys include: tin-lead alloy, tin-silver-copper ternary alloy, tin-silver alloy, tin-copper alloy, and Wood's alloy; the solid electrolytes include: NASICON-type oxide solid electrolyte, garnet-type solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte. The thickness of the interface bonding layer is 90 nm to 0.5 μm; The NASICON-type solid electrolyte includes: Li 1+x Al x Ti 2-x (PO4)3 (x = 0.3–0.5) and Li 1+x Al x Ge 2-x (PO4)3 (x = 0.3–0.5); the garnet-type solid electrolyte includes: Li7La3Zr2O 12 Li 3+x La 2 / 3-x TiO3, Li5La3Nb2O 12 and Li 6.25 La3Zr 1.75 Ta 0.25 O 12 The sulfide solid electrolyte includes: Li₂S-P₂S₅, Li 10 GeP2S 12 Li7P3S 11 And Li2S-Sb2S3; the halide solid electrolyte includes: Li3MX6 (M=Y,Er,Sc,In,X=F,Cl,Br) and Li2MCl6 (M=Zr,Cd,Ti); The combination methods of the interface bonding layer include: Li 1+x Al x Ti 2-x (PO4)3 solid electrolyte and tin-lead alloy bonding layer combination, Li7La3Zr2O 12 Solid electrolyte and tin-silver-copper ternary alloy bonding layer combination, Li2S-P2S5 solid electrolyte and tin-lead alloy bonding layer combination, Li3MX6 solid electrolyte and Wood's alloy bonding layer combination, Li2MCl4 solid electrolyte and tin-copper alloy bonding layer. The composition ratio of the tin-lead alloy is: Sn / Pb = x / (1-x), x = 0.3~0.7; the composition ratio of the tin-silver-copper ternary alloy is: Sn / Ag / Cu = x / y / (1-xy), x = 0~0.1, y = 0~0.1; the composition ratio of the tin-silver alloy is: Sn / Ag = x / (1-x), x = 0.3~0.7; the composition ratio of the tin-copper alloy is: Sn / Cu = x / (1-x), x = 0.3~0.7; the composition ratio of the Wood alloy is: Pb / Sn / Bi / Cd, (0~0.25) / (0~0.125) / (0~0.5) / (0~0.125).

2. A method for interfacial bonding of lithium with a solid electrolyte, characterized in that, The interface bonding method is used to prepare the interface bonding layer according to claim 1, and the interface bonding method includes the following steps: Step S1: Remove impurities from the surface of the solid electrolyte matrix material and polish it; Step S2: Using the bonding layer alloy as the target material, sputtering deposition is performed on the solid electrolyte substrate material polished in step S1 to form an interface bonding layer; Step S3: Bond the lithium metal anode to the solid electrolyte with the bonding layer at 70-150°C and a pressure of 50-200 MPa. The sputtering conditions for the interface bonding method include: a base vacuum of 0.1×10⁻⁴ to 9.9×10⁻⁴ Pa, a working pressure of 0.30 to 0.55 Pa, and a purity of ≥99.99% for the bonding layer alloy as the target material.

3. The method for interfacial bonding of lithium and solid electrolyte according to claim 2, characterized in that, The target-to-electrode distance of the interface bonding method is 8–12 cm, the sputtering power is 70–90 W, the sputtering temperature is 20–30 °C, the sample tray transfer speed is 0.5–1 cm / s, and the sputtering time is 10–30 min.

4. The method for interfacial bonding of lithium and solid electrolyte according to claim 2, characterized in that, The target-to-electrode distance of the interface bonding method is 8–12 cm, the sputtering power is 70–90 W, the sputtering temperature is 20–30 °C, the sample tray transfer speed is 0.5–1 cm / s, and the sputtering time is 10–30 min.

5. An application of a lithium-solid electrolyte interface bonding layer, characterized in that, The application employs the interface bonding layer as described in claim 1, and the application includes using the interface bonding layer to prepare a lithium battery, the lithium battery including: a solid-state lithium symmetric battery and a solid-state lithium metal full battery.

6. The application of the lithium-solid electrolyte interface bonding layer according to claim 5, characterized in that, When the lithium battery is a solid-state lithium symmetric battery, the interface bonding layer is deposited on both sides of the solid electrolyte matrix material, and then the metallic lithium anode is bonded to both sides of the electrolyte by hot-press bonding, thus preparing a solid-state lithium symmetric battery in the battery case.

7. The application of the lithium-solid electrolyte interface bonding layer according to claim 5, characterized in that, When the lithium battery is a solid-state lithium metal full battery, the interface bonding layer is deposited on both sides of the solid electrolyte matrix material, and then the lithium metal negative electrode is bonded to one side of the electrolyte by hot-press bonding, while the other side is matched with the positive electrode material.

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