In-situ construction alloying interface protection negative electrode and preparation method and application thereof

Abstract

The invention relates to the technical field of solid-state batteries, in particular to an in-situ construction alloying interface protection negative electrode and a preparation method and application thereof. The negative electrode comprises a current collector, and a metal lithium layer, a lithium-loving material layer and a polymer layer are sequentially arranged on the current collector; the lithium-loving material layer comprises a first lithium-loving material and a second lithium-loving material, the second lithium-loving material comprises a lithium magnesium alloy, and the polymer layer comprises vinylene carbonate. The preparation method comprises the following steps: S1, compounding a metal lithium layer with a current collector to obtain a first matrix material; s2, compounding a first lithium-loving material onto the first base material to obtain a second base material; and S3, dropwise adding a reagent containing VC, Mg (TFSI) 2, LiTFSI and an initiator onto the second substrate material, and carrying out heating polymerization, thereby obtaining the composite material. The negative electrode provided by the invention can effectively reduce the probability of short circuit in the battery and improve the safety performance and cycling stability of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to an in-situ constructed alloyed interface protection negative electrode and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of the modern electronics industry, the application scope of energy storage devices is becoming increasingly broad. Batteries, as electrochemical energy storage devices, are widely used in various fields, including portable smart devices and electric vehicles. Among the many electrode materials, lithium has an extremely low density, extremely high capacity, and extremely low electrochemical potential, making lithium batteries widely used. Since the last century, the commercialization of lithium-ion batteries has increased. They generally use lithium iron phosphate, lithium cobalt oxide, and other materials as positive electrode materials and graphite as negative electrode materials.

[0003] With the rapid development of electronic devices, higher requirements are being placed on battery capacity density. The theoretical energy density of existing lithium-ion batteries based on graphite anodes is difficult to meet the growing social needs. In the next generation of battery systems, metallic lithium anodes have extremely high capacity density (3860 mAh g -1 ) and the lowest electrode potential (-3.040 V vs. standard hydrogen electrode), is considered the holy grail in the field of energy storage devices.

[0004] Currently, lithium metal batteries suffer from low cycle life and poor safety. This is primarily due to the growth of lithium dendrites, which form a loose, mossy lithium layer. During charge and discharge, the mossy lithium forms a surface SEI film, which continuously forms, peels off, and accumulates, resulting in low battery charge and discharge efficiency and increased interfacial impedance. Furthermore, the growth of lithium dendrites and the resulting "dead lithium" create safety issues and lead to loss of active electrode material. Dendrite formation is closely related to current density. At very low current densities (<0.1 mA / cm²), the lithium anode is typically very stable, with virtually no dendrite formation. However, as current density increases, the stress generated by the rapid deposition of lithium easily ruptures the SEI film on the anode surface, inducing dendrite growth. Higher current density leads to poor surface stability and faster dendrite formation.

[0005] In recent years, an increasing number of researchers have employed composite lithium metal anode technology to improve battery performance. These researchers have attempted to incorporate lithium as the active material into high-surface-area porous electrodes to create composite lithium anodes. These researchers have employed methods such as composite coating and composite materials, lithium-affinity modification of the skeleton material, and functionalization of the skeleton surface. The use of a highly conductive porous substrate to reduce the true current density on the electrode surface inhibits lithium dendrite growth. Skeletal material modification can induce uniform and dense deposition of lithium ions at the skeleton interface, thereby altering the growth state of lithium dendrites. Furthermore, the presence of a skeleton support structure on the surface can reduce the anode expansion rate and reduce internal stress in the battery, significantly improving the battery's cycle performance and safety. However, the traditional "electrolyte-diaphragm" system uses low-boiling-point toxic organic solvents, which pose a risk of electrolyte leakage, combustion, and explosion, posing a serious safety hazard.

[0006] Compared with liquid batteries, all-solid-state batteries do not have the risk of leakage due to the lack of liquid, and the batteries have higher thermal stability and a wider operating temperature range; however, with the development of the skeleton structure, the interface problem between the surface of the composite lithium negative electrode and the electrolyte has become increasingly prominent, becoming an important factor affecting lithium metal batteries. The poor contact between the electrolyte and the composite negative electrode material will lead to high interfacial resistance and uneven lithium ion (Li + ) flow, further leading to uneven growth of lithium dendrites, and ultimately battery failure. Therefore, developing lithium anodes for next-generation solid-state lithium batteries with high energy density and high safety performance is the key to efficient and safe energy storage.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The first purpose of the present invention is to provide an in-situ constructed alloyed interface protection negative electrode, the interface of which is controllable. When used as a negative electrode of a lithium battery, it can induce uniform lithium deposition, significantly reduce the interface impedance, inhibit dendrite growth, and avoid direct contact between the solid electrolyte and lithium metal, thereby avoiding the occurrence of side reactions; thereby effectively reducing the probability of short circuit in the battery and improving the safety performance and cycle stability of the battery.

[0009] The second object of the present invention is to provide a method for preparing the in-situ alloyed interface protective negative electrode as described above.

[0010] The third object of the present invention is to provide a lithium-ion all-solid-state battery, comprising the in-situ constructed alloyed interface protection negative electrode as described above.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: An in-situ alloyed interface protection negative electrode comprises a current collector, on which a metallic lithium layer, a lithium-philic material layer and a polymer layer are sequentially provided; The lithium-philic material layer includes a first lithium-philic material and a second lithium-philic material, the second lithium-philic material includes a lithium-magnesium alloy, and the polymer layer includes polyvinylene carbonate and an ion conductor.

[0012] Preferably, the current collector includes at least one of copper ball, copper wire, zinc wire, aluminum wire, nickel wire, iron wire, titanium wire, iron-nickel alloy wire, copper foil, zinc foil, aluminum foil, nickel foil, iron foil, titanium foil, iron-nickel alloy foil, carbon film, carbon cloth, carbon paper, carbon fiber, graphene, MXene, conductive polymer non-metallic material, foam copper, foam zinc, foam nickel, foam aluminum, foam iron, foam titanium, foam iron-nickel alloy, and carbon nanotubes.

[0013] Preferably, the first lithium-philic material includes at least one of C65, amorphous carbon black, carbon nanotubes, Super P and acetylene black.

[0014] Preferably, the ion conductor comprises LiTFSI.

[0015] A method for preparing an in-situ alloyed interface protection negative electrode according to any one of the aforementioned embodiments comprises the following steps: S1. The metallic lithium layer and the current collector are composited to obtain a first matrix material; S2. The slurry containing the first lithium-philic material is coated on the first base material and dried to obtain a second base material; S3. Add a reagent containing VC, Mg(TFSI)2, LiTFSI and an initiator dropwise onto the second base material, and heat and polymerize to obtain.

[0016] Preferably, in step S1, the thickness of the metallic lithium layer is 5-75 μm.

[0017] Preferably, in step S1, the compounding method includes at least one of mechanical pressure compounding, hot melt compounding, and electrochemical compounding.

[0018] Preferably, in step S2, the coating thickness of the slurry is 90-200 μm.

[0019] Preferably, in step S2, the slurry includes a first lithium-philic material, a binder and a solvent, the mass ratio of the first lithium-philic material to the binder is 70:30~99:1, and the mass ratio of the total mass of the first lithium-philic material and the binder to the solvent is 10:1~2.

[0020] Preferably, after coating the slurry, a mechanical pressure compounding step is further included.

[0021] Preferably, in step S3, the mass concentration of Mg(TFSI)2 in the reagent is 2% to 6%.

[0022] Preferably, in step S3, the mass concentration of the initiator in the reagent is 0.05% to 0.2%; Preferably, in step S3, the initiator includes at least one of azobisisobutyronitrile, dibenzoyl peroxide, ammonium persulfate, and sodium bisulfite.

[0023] Preferably, in step S3, the molar concentration of LiTFSI in the reagent is 0.5-1.5 mol / L.

[0024] Preferably, in step S3, the amount of the reagent added is 10-30 μL.

[0025] Preferably, in step S3, the temperature of the heating polymerization is 50-65° C., and the time of the heating polymerization is 1-3 hours.

[0026] A lithium-ion all-solid-state battery comprises the in-situ constructed alloyed interface protection negative electrode described in any one of the aforementioned embodiments or a negative electrode prepared by the preparation method of the in-situ constructed alloyed interface protection negative electrode described in any one of the aforementioned embodiments.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an in-situ constructed alloyed interface layer to protect the negative electrode, in-situ polymerizes vinylene carbonate to form a polymer layer containing an ion conductor, buffers the interface volume change, and reduces the interface impedance; uses a graphitized carbon material as the first lithium-philic material, and Mg(TFSI)2 is reduced by metallic lithium to form a lithium-magnesium alloy in situ as the second lithium-philic material, and the two together constitute a lithium-philic material layer. The lithium-magnesium alloy increases the diffusion coefficient of lithium ions to the bulk phase at the interface; the graphitized carbon material increases the lithium-philic characteristics and structural stability of the interface. The negative electrode interface is controllable, and when used as a lithium battery negative electrode, it can induce uniform lithium deposition and inhibit dendrite growth, thereby effectively reducing the probability of short circuits in the battery and improving the safety performance of the battery; the polymer layer on the negative electrode can avoid direct contact between the solid electrolyte and lithium metal to cause a reaction. The method of the present invention has a simple preparation process, and the negative electrode prepared by this method can uniformly control the deposition of lithium ions, significantly reduce the interface impedance, inhibit the growth of dendrites, and improve the cycle performance and safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A schematic diagram of the negative electrode structure provided by an embodiment of the present invention; Figure 2 This is a charge-discharge curve diagram of the 10th cycle of the all-solid-state battery assembled with the negative electrode in Example 1 of the present invention and Comparative Example 1 under the conditions of Test Example 1; Figure 3 This is a cycle performance diagram of the all-solid-state battery assembled with the negative electrode in Example 1 of the present invention and Comparative Example 1 under the conditions of Test Example 1. DETAILED DESCRIPTION

[0030] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0031] like Figure 1 As shown, the first aspect of the present invention provides an in-situ constructed alloyed interface protection negative electrode, comprising a current collector 4, on which a metallic lithium layer 3, a lithium-philic material layer 2 and a polymer layer 1 are sequentially provided; The lithium-philic material layer 2 includes a first lithium-philic material and a second lithium-philic material, the second lithium-philic material includes a lithium-magnesium alloy, and the polymer layer 1 includes polyvinylene carbonate and an ion conductor.

[0032] In the negative electrode material provided by the present invention, a lithium-magnesium alloy is formed in situ by reducing Mg(TFSI)2 with metallic lithium, and a polymer layer is formed by in situ polymerization of vinylene carbonate. The present invention utilizes the polymer layer to buffer interfacial volume changes and reduce interfacial impedance. The lithium-magnesium alloy increases the diffusion coefficient of lithium ions to the bulk phase at the interface, and the first lithium-philic material increases the interfacial lithium-philic properties and structural stability. The negative electrode interface is controllable. When used as a negative electrode in a lithium battery, it can induce uniform lithium deposition, significantly reduce interfacial impedance, inhibit dendrite growth, and avoid direct contact between the solid electrolyte and lithium metal, thus preventing the occurrence of side reactions. This can effectively reduce the probability of short circuits within the battery and improve the battery's safety performance and cycle stability.

[0033] In some specific embodiments of the present invention, the current collector 4 used includes at least one of copper ball, copper wire, zinc wire, aluminum wire, nickel wire, iron wire, titanium wire, iron-nickel alloy wire, copper foil, zinc foil, aluminum foil, nickel foil, iron foil, titanium foil, iron-nickel alloy foil, carbon film, carbon cloth, carbon paper, carbon fiber, graphene, MXene, conductive polymer non-metallic material, foam copper, foam zinc, foam nickel, foam aluminum, foam iron, foam titanium, foam iron-nickel alloy, and carbon nanotubes.

[0034] In some specific embodiments of the present invention, the first lithiophilic material includes at least one of C65, amorphous carbon black, carbon nanotubes, Super P, and acetylene black, preferably carbon nanotubes. Graphitized carbon materials can increase interfacial lithiophilic properties and structural stability.

[0035] In some embodiments of the present invention, the ion conductor comprises LiTFSI.

[0036] A second aspect of the present invention provides a method for preparing an in-situ alloyed interface protection negative electrode according to any one of the aforementioned embodiments, comprising the following steps: S1. The metallic lithium layer and the current collector are composited to obtain a first matrix material; S2. The slurry containing the first lithium-philic material is coated on the first base material and dried to obtain a second base material; S3. Add a reagent containing VC, Mg(TFSI)2, LiTFSI and an initiator dropwise onto the second substrate material, and heat and polymerize to obtain.

[0037] In the present invention, the reagent is obtained by dispersing LiTFSI, Mg(TFSI)2 and an initiator in VC (vinylene carbonate). The method of the present invention composites a first lithium-philic material on the surface of the lithium metal layer, and utilizes the first lithium-philic material to increase the interfacial lithium-philic properties and structural stability; the reagent containing VC, Mg(TFSI)2, LiTFSI and an initiator is dropwise added onto a second base material, and Mg(TFSI)2 is reduced by metallic lithium to form a lithium-magnesium alloy as a second lithium-philic material, and the lithium-magnesium alloy is utilized to increase the diffusion coefficient of lithium ions at the interface to the bulk phase; in the presence of an initiator and under heating conditions, vinylene carbonate is in situ polymerized to form a polymer layer containing an ion conductor, which buffers interfacial volume changes, reduces interfacial impedance, and can avoid direct contact between the solid electrolyte and metallic lithium, thereby avoiding the occurrence of side reactions; the preparation process of the method of the present invention is simple, and the negative electrode prepared by the method can uniformly control the deposition of lithium ions, significantly reduce interfacial impedance, inhibit the growth of dendrites, and can improve the cycle performance and safety performance of the battery.

[0038] In some specific embodiments of the present invention, step S1 further includes a step of cleaning the current collector before compounding. As an example, the cleaning includes the following steps: The current collector was soaked in ethanol and deionized water successively, and ultrasonic treatment was performed during the soaking process. The current collector was taken out and dried.

[0039] In some specific embodiments of the present invention, in step S1, the thickness of the metallic lithium layer is 5-75 μm, for example, any value among 5 μm, 25 μm, 50 μm, 75 μm, or a range consisting of any two values.

[0040] In some specific embodiments of the present invention, in step S1, the compounding method includes at least one of mechanical pressure compounding, hot melt compounding, and electrochemical compounding; preferably, mechanical pressure compounding.

[0041] In some specific embodiments of the present invention, in step S2, the coating thickness of the slurry is 90-200 μm, for example, any value among 90 μm, 120 μm, 150 μm, 180 μm, 200 μm, or a range consisting of any two values.

[0042] In some specific embodiments of the present invention, in step S2, the slurry includes a first lithium-philic material, a binder and a solvent; wherein the mass ratio of the first lithium-philic material to the binder is 70:30~99:1, for example, it can be any point value among 70:30, 80:20, 90:10, 92:8, 96:4, and 99:1, or a range value consisting of any two point values; the mass ratio of the total mass of the first lithium-philic material and the binder to the solvent is 10:1~2, for example, it can be any point value among 10:1, 10:1.2, 10:1.5, 10:1.8, and 10:2, or a range value consisting of any two point values; as an example, the binder used can be PVDF and the solvent used can be NMP.

[0043] In some specific embodiments of the present invention, after coating the slurry, a mechanical pressure compounding step is also included; the mechanical pressure compounding can be performed before dropping the reagent or after the reagent is dropped to form a polymer layer, preferably before dropping the reagent.

[0044] In some specific embodiments of the present invention, in step S3, the mass concentration of Mg(TFSI)2 in the reagent is 2% to 6%, for example, it can be any one of 2%, 3%, 4%, 5%, 6% or a range consisting of any two of the values.

[0045] In some specific embodiments of the present invention, in step S3, the mass concentration of the initiator in the reagent is 0.05% to 0.2%, for example, it can be any point value among 0.05%, 0.1%, 0.15%, 0.2%, or a range value consisting of any two point values.

[0046] In some specific embodiments of the present invention, in step S3, the initiator used includes at least one of azobisisobutyronitrile, dibenzoyl peroxide, ammonium persulfate, and sodium bisulfite.

[0047] In some specific embodiments of the present invention, in step S3, the molar concentration of LiTFSI in the reagent is 0.5-1.5 mol / L, for example, any one of 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, and 1.5 mol / L, or a range consisting of any two of these values.

[0048] In some specific embodiments of the present invention, in step S3, the amount of the reagent added is 10-30 μL, for example, any value among 10 μL, 15 μL, 20 μL, 25 μL, 30 μL, or a range consisting of any two values.

[0049] In some specific embodiments of the present invention, in step S3, the temperature of the heating polymerization is 50-65°C, for example, it can be any point value among 50°C, 55°C, 60°C, and 65°C, or a range value consisting of any two points; the time of the heating polymerization is 1-3 h, for example, it can be any point value among 1 h, 1.5 h, 2 h, 2.5 h, and 3 h, or a range value consisting of any two points.

[0050] The third aspect of the present invention provides a lithium-ion all-solid-state battery, comprising the in-situ constructed alloyed interface protection negative electrode described in any one of the aforementioned embodiments or a negative electrode prepared by the preparation method of the in-situ constructed alloyed interface protection negative electrode described in any one of the aforementioned embodiments.

[0051] The embodiments of the present invention will be described in detail below with reference to specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0052] Example 1 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 192:8:3 to form a slurry and coated to a coating thickness of 150 μm, dried, and rolled on the lithium metal side to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. 20 μL of the above reagent was dropped onto the second substrate material and heated at 60 °C for 2 h to polymerize to obtain a negative electrode protected by an alloyed interface layer.

[0053] Example 2 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 184:16:3 to form a slurry and coated to a coating thickness of 150 μm, dried, and rolled on the lithium metal side to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. 20 μL of the above reagent was dropped onto the second substrate material and heated at 60 °C for 2 h to polymerize to obtain a negative electrode protected by an alloyed interface layer.

[0054] Example 3 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 180:20:3 to form a slurry and coated to a coating thickness of 150 μm, dried, and rolled on the lithium metal side to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. 20 μL of the above reagent was dropped onto the second substrate material and heated at 60 °C for 2 h to polymerize to obtain a negative electrode protected by an alloyed interface layer.

[0055] Example 4 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 192:8:3 to form a slurry and coated to a coating thickness of 150 μm and dried to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. S4. Add 20 μL of the above reagent dropwise onto the second substrate material and heat at 60°C for 2 h to polymerize. After polymerization, roll-press the substrate onto the lithium metal side to obtain a negative electrode protected by an alloyed interface layer.

[0056] Example 5 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 184:16:3 to form a slurry and coated to a coating thickness of 150 μm and dried to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. 20 μL of the above reagent was dropped onto the second substrate material and heated at 60 °C for 2 h for polymerization. After polymerization, it was rolled onto the metal lithium side to obtain a negative electrode protected by an alloyed interface layer.

[0057] Example 6 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 180:20:3 to form a slurry and coated to a coating thickness of 150 μm and dried to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. 20 μL of the above reagent was dropped onto the second substrate material and heated at 60 °C for 2 h for polymerization. After polymerization, it was rolled onto the metal lithium side to obtain a negative electrode protected by an alloyed interface layer.

[0058] Example 7 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 192:8:3 to form a slurry and coated to a coating thickness of 150 μm, dried, and rolled on the lithium metal side to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. 10 μL of the reagent was dropped onto the second substrate material and heated at 60 °C for 2 h to polymerize to obtain a negative electrode protected by an alloyed interface layer.

[0059] Example 8 S1. Soak the current collector in ethanol and then deionized water to remove impurities. Ultrasonication was performed for 10 minutes during the soaking process. The current collector was then dried at 80°C for 4 hours. A 50 μm lithium metal and a 9 μm current collector were cut into 5 cm × 8 cm sheets, stacked, and roll-pressed into sheets. The total thickness was reduced by 1–2 μm after rolling, obtaining the first substrate material. S2 carbon nanotubes, PVDF and NMP were mixed in a mass ratio of 192:8:3 to form a slurry and coated to a coating thickness of 150 μm, dried, and rolled on the lithium metal side to obtain a second base material; S3. Prepare a reagent by adding Mg(TFSI)2 and azobisisobutyronitrile (AIBN) to a 1 mol / L LiTFSI solution in VC. The concentration of Mg(TFSI)2 is 4 wt % and the concentration of AIBN is 0.1 wt %. 30 μL of the above reagent was dropped onto the second substrate material and heated at 60 °C for 2 h to polymerize to obtain a negative electrode protected by an alloyed interface layer.

[0060] Comparative Example 1 Comparative Example 1 is similar to Example 1, except that steps S2 and S3 are not performed, and the remaining conditions are the same as those of Example 1.

[0061] Comparative Example 2 Comparative Example 2 is similar to Example 1, except that step S3 is not performed, and the other conditions are the same as those of Example 1.

[0062] Comparative Example 3 Comparative Example 3 is similar to Example 1, except that in step S3, the added reagent does not contain Mg(TFSI)2, and the other conditions are the same as those in Example 1.

[0063] Test Example 1 The negative electrodes prepared in the examples and comparative examples were respectively connected to the NCM9 series sulfide positive electrode (2 mAh / cm 2 ), LPSC electrolyte matching, assembled all-solid-state mold batteries, and carried out electrochemical testing at an operating voltage of 2.8-4.3 V and a procedure of 0.3 C-4.3 V-0.3 C. The test results are shown in Table 1, where the average median discharge voltage refers to the average value of the median discharge voltage of each cycle; the cycle life refers to the number of charge and discharge cycles when a short circuit occurs or the capacity decays to 80%.

[0064] Table 1

[0065] Test Example 2 The negative electrodes prepared in the examples and comparative examples were respectively connected to the NCM9 series sulfide positive electrode (2 mAh / cm 2 ), LPSC electrolyte matching, assembled all-solid-state mold batteries, and carried out electrochemical tests at an operating voltage of 2.8-4.3 V and a procedure of 0.1 C-4.3 V-0.1 C. The test results are shown in Table 2.

[0066] Table 2

[0067] From Table 1, Table 2 and Figure 2 、 Figure 3 It can be seen from the data in that compared with the comparative example, the all-solid-state battery assembled from the negative electrode material prepared in the embodiment has better cycle stability and safety, indicating that the negative electrode prepared by the method of the present invention can improve the cycle performance and safety performance of the battery.

[0068] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. An in-situ alloyed interface protection negative electrode, characterized in that: The method comprises a current collector, wherein a metallic lithium layer, a lithium-philic material layer and a polymer layer are sequentially provided on the current collector; The lithium-philic material layer includes a first lithium-philic material and a second lithium-philic material, the second lithium-philic material includes a lithium-magnesium alloy, and the polymer layer includes polyvinylene carbonate and an ion conductor.

2. The in-situ alloyed interface protection negative electrode according to claim 1, characterized in that: The current collector includes at least one of copper balls, copper wires, zinc wires, aluminum wires, nickel wires, iron wires, titanium wires, iron-nickel alloy wires, copper foils, zinc foils, aluminum foils, nickel foils, iron foils, titanium foils, iron-nickel alloy foils, carbon films, carbon cloths, carbon paper, carbon fibers, graphene, MXene, conductive polymer non-metallic materials, copper foam, zinc foam, nickel foam, aluminum foam, iron foam, titanium foam, iron-nickel alloy foam, and carbon nanotubes.

3. The in-situ alloyed interface protection negative electrode according to claim 1, characterized in that: The first lithiophilic material includes at least one of C65, amorphous carbon black, carbon nanotubes, Super P and acetylene black; and / or the ion conductor includes LiTFSI.

4. The method for preparing an in-situ alloyed interface protection negative electrode according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. The metallic lithium layer and the current collector are composited to obtain a first matrix material; S2. The slurry containing the first lithium-philic material is coated on the first base material and dried to obtain a second base material; S3. Add a reagent containing VC, Mg(TFSI)2, LiTFSI and an initiator dropwise onto the second base material, and heat and polymerize to obtain.

5. The method for preparing an in-situ alloyed interface protection negative electrode according to claim 4, wherein: In step S1, the thickness of the metallic lithium layer is 5 to 75 μm; And / or, the compounding method includes at least one of mechanical pressure compounding, hot melt compounding, and electrochemical compounding.

6. The method for preparing an in-situ alloyed interface protection negative electrode according to claim 4, characterized in that: In step S2, at least one of the following characteristics is met: (1) The coating thickness of the slurry is 90-200 μm; (2) The slurry includes a first lithium-philic material, a binder, and a solvent, wherein the mass ratio of the first lithium-philic material to the binder is 70:30 to 99:1, and the mass ratio of the total mass of the first lithium-philic material and the binder to the solvent is 10:1 to 2; (3) After coating the slurry, a mechanical pressure compounding step is also included.

7. The method for preparing an in-situ alloyed interface protection negative electrode according to claim 4, characterized in that: In step S3, at least one of the following characteristics is met: In the reagent, the mass concentration of Mg(TFSI)2 is 2% to 6%; In the reagent, the mass concentration of the initiator is 0.05% to 0.2%; The initiator includes at least one of azobisisobutyronitrile, dibenzoyl peroxide, ammonium persulfate, and sodium bisulfite; In the reagent, the molar concentration of LiTFSI is 0.5-1.5 mol / L.

8. The method for preparing an in-situ alloyed interface protective negative electrode according to claim 4, wherein: In step S3, the amount of the reagent added is 10-30 μL.

9. The method for preparing an in-situ alloyed interface protective negative electrode according to claim 4, wherein: In step S3, the temperature of the heating polymerization is 50-65° C., and the time of the heating polymerization is 1-3 h.

10. A lithium-ion all-solid-state battery, characterized in that: The invention comprises the in-situ constructed alloyed interface protection negative electrode as described in any one of claims 1 to 3 or the negative electrode prepared by the preparation method of the in-situ constructed alloyed interface protection negative electrode as described in any one of claims 4 to 9.

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