An interfacial protective layer for lithium metal anodes, its preparation method and application

Abstract

This invention relates to the field of battery technology, specifically to an interface protective layer for a lithium metal anode, its preparation method, and its application. The interface protective layer for the lithium metal anode includes a first flexible layer, a nano-silicon layer, and a second flexible layer. The first flexible layer is disposed on one side of the nano-silicon layer, and the second flexible layer is disposed on the other side of the nano-silicon layer. The first flexible layer contains at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum. The nano-silicon layer contains nano-silicon particles with a particle size D50 of 20-500 nm. The second flexible layer contains at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum. The interface protective layer of this invention can improve the deposition uniformity on the lithium metal anode deposition surface, induce uniform lithium metal deposition during charging, improve the density of the lithium metal anode deposition surface, increase the resistance to dendrite growth, improve the rate performance and cycle performance of the battery, and reduce the risk of short circuits.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an interface protective layer for a lithium metal anode, its preparation method, and its application. Background Technology

[0002] Lithium metal has an extremely high theoretical specific capacity (3860 mAh / g) and the lowest lithium potential (0 V vs Li / Li). + Lithium-ion batteries (Li-O-S) are the ideal negative electrode form for lithium-ion batteries. However, their application in lithium-ion rechargeable batteries is severely limited because they are prone to lithium dendrite defects during charging and discharging, which can penetrate the separator and cause short circuits. Solid-state batteries, due to the use of dense solid electrolytes, have a certain degree of inhibition against lithium dendrite penetration. However, in practice, it has been found that lithium dendrites can still grow along grain boundaries in dense solid electrolytes, causing short circuits. Therefore, suppressing the generation and growth of lithium dendrites in solid-state batteries is an urgent problem to be solved. Current technologies improve dendrite generation and growth through interface engineering design, electrolyte layer mechanics and structural design, and electrolyte material design. However, existing methods still have limitations in suppressing the generation and growth of lithium metal anode dendrites in solid-state batteries, making it difficult to achieve good cycle performance under high areal loading and room temperature (20~30℃) conditions.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] One objective of this invention is to provide an interface protection layer for lithium metal anodes that can effectively suppress the generation and growth of dendrites in solid-state lithium metal anodes, enabling long-term cycling under high load conditions.

[0005] Another objective of this invention is to provide a method for preparing an interface protective layer for a lithium metal anode.

[0006] Another object of the present invention is to provide a negative electrode.

[0007] Another object of the present invention is to provide a battery.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] An interface protective layer for a lithium metal anode includes a first flexible layer, a nano-silicon layer, and a second flexible layer. The first flexible layer is disposed on one side surface of the nano-silicon layer, and the second flexible layer is disposed on the other side surface of the nano-silicon layer. The first flexible layer contains at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum. The nano-silicon layer contains nano-silicon particles with a particle size D50 of 20-500 nm. The second flexible layer contains at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum.

[0010] In some embodiments, the surface of the first flexible layer away from the nano-silicon layer is in contact with the electrolyte layer, and the first flexible layer comprises at least two of magnesium, indium, zinc, tin, lead, gold, silver and aluminum.

[0011] In some embodiments, the thickness of the first flexible layer is 5~10 μm.

[0012] In some embodiments, the first flexible layer further comprises lithium.

[0013] In some embodiments, the areal loading of the silicon nanoparticles is 0.1~4 mg / cm³. 2 .

[0014] In some embodiments, the thickness of the nano-silicon layer is 1~500 μm.

[0015] In some embodiments, the nano-silicon layer further includes a binder, the binder comprising less than 5% by mass in the nano-silicon layer.

[0016] In some embodiments, at least one surface of the first flexible layer is further provided with an ion-conducting adhesive layer, the thickness of which is 1~2μm.

[0017] In some embodiments, the surface of the second flexible layer away from the nano-silicon layer is in contact with the lithium metal anode.

[0018] In some embodiments, the thickness of the second flexible layer is 5~10 μm.

[0019] The method for preparing the interface protective layer of the lithium metal anode as described above includes the following steps:

[0020] Obtain a first flexible layer; combine nano-silicon powder with the first flexible layer by coating or powder pressing to form a nano-silicon layer; obtain a second flexible layer, and bring the second flexible layer into contact with the nano-silicon layer and press them together to obtain an interface protective layer.

[0021] In some embodiments, the method for obtaining the first flexible layer and the method for obtaining the second flexible layer each independently include: obtaining a single-element film of any one of magnesium, indium, zinc, tin, lead, gold, silver and aluminum, or performing a laminated composite or eutectic composite of at least two of magnesium, indium, zinc, tin, lead, gold, silver and aluminum.

[0022] In some embodiments, the method for obtaining the first flexible layer includes: laminating or eutectic bonding of any one of magnesium, indium, zinc, tin, lead, gold, silver and aluminum with lithium.

[0023] In some embodiments, the pressure of the powder pressing method is 45~300MPa.

[0024] In some embodiments, the pressure of the pressing process is 45~300MPa.

[0025] A negative electrode sheet includes the aforementioned interface protection layer and a lithium metal negative electrode, wherein a second flexible layer of the interface protection layer is in contact with the lithium metal negative electrode.

[0026] A battery includes an interface protective layer, a lithium metal negative electrode, a positive electrode, and an electrolyte layer. A second flexible layer in the interface protective layer is in contact with the lithium metal negative electrode, a first flexible layer is in contact with the electrolyte layer, and the positive electrode is disposed on the surface of the electrolyte layer away from the first flexible layer.

[0027] The battery preparation method described above includes the following steps:

[0028] After the electrolyte layer and the positive electrode sheet are stacked, a first compaction is performed; a first flexible layer, a nano-silicon layer and a second flexible layer are sequentially stacked on the surface of the electrolyte layer and compacted respectively, or the prepared interface protection layer is compacted with the electrolyte layer to obtain an interface protection layer; a lithium metal sheet and a negative electrode current collector are sequentially stacked on the surface of the interface protection layer and a second compaction is performed.

[0029] In some embodiments, the pressure of the first compaction is 100~320MPa.

[0030] In some embodiments, the total compaction pressure during the preparation of the interface protective layer is 100~1000MPa.

[0031] In some embodiments, the pressure of the second compaction is 5 to 500 MPa.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The interface protection layer of the lithium metal anode of the present invention comprises a first flexible layer made of a metal or alloy material with low elastic modulus, high plasticity and reversible alloying with lithium metal, such as magnesium, indium, zinc, tin, lead, gold, silver, aluminum and other elements and their binary or multi-element alloys, to increase the density and contact area of ​​this contact layer and suppress dendrites from penetrating through the voids. The intermediate layer uses nano-silicon particles to form an ion transport channel with high density and high ion conductivity and eliminates the generation of lithium dendrites through the reaction of silicon and lithium. The second flexible layer uses a high-density metal layer to block dendrites from entering the powder layer, and at the same time, the good plasticity and flexibility of the low elastic modulus metal increases the contact area with the nano-powder layer, reducing dendrite growth caused by interface cracking during cycling. The interface protective layer of this invention can improve the deposition uniformity on the lithium metal anode deposition surface, induce uniform lithium metal deposition during charging, improve the density of the lithium metal anode deposition surface, and increase the resistance to dendrite growth. The intermediate layer absorbs lithium dendrites through reaction consumption, eliminating lithium dendrites in the intermediate layer. It improves the bonding strength with the electrolyte contact layer, reduces the phenomenon of electrolyte layer and anode layer contact separation caused by electrode material expansion and contraction during charge and discharge cycles, and improves the rate performance and cycle performance of the battery. It increases the potential between the electrolyte layer and the lithium metal anode interface, increases the electrochemical barrier for lithium dendrite precipitation at this interface position, makes dendrite precipitation at this position more difficult, reduces the tendency of dendrite formation from the source, and reduces the risk of battery short circuit.

[0034] (2) The method for preparing the interface protective layer of the lithium metal anode of the present invention is simple and easy to implement, which can ensure the uniformity of the interface protective layer, have a suitable bonding strength, and is conducive to improving the deposition uniformity on the lithium metal anode deposition surface, inducing uniform deposition of lithium metal during charging; improving the density of the lithium metal anode deposition surface, increasing the resistance to dendrite growth, improving the rate performance and cycle performance of the battery, and achieving long cycle under high load.

[0035] (3) The battery of the present invention has excellent rate performance, cycle performance and safety performance. Detailed Implementation

[0036] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0037] According to one aspect of the present invention, the present invention relates to an interface protective layer for a lithium metal anode, comprising a first flexible layer, a nano-silicon layer, and a second flexible layer, wherein the first flexible layer is disposed on one side surface of the nano-silicon layer, and the second flexible layer is disposed on the other side surface of the nano-silicon layer; the first flexible layer comprises at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum; the nano-silicon layer comprises nano-silicon particles, wherein the particle size D50 of the nano-silicon particles is 20~500nm (e.g., 20nm, 50nm, 100nm, 150nm, 200nm, 300nm, 400nm, 500nm, etc.); and the second flexible layer comprises at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum.

[0038] The interface protective layer of the lithium metal anode of this invention comprises a first flexible layer made of a metal or alloy material with low elastic modulus, high plasticity, and reversible alloying ability with lithium metal, such as magnesium, indium, zinc, tin, lead, gold, silver, aluminum, and their binary or multi-element alloys. This increases the density and contact area of ​​the contact layer, inhibiting dendrite penetration through voids. The intermediate layer uses nano-silicon particles to form ion transport channels with high density and high ion conductivity, and eliminates lithium dendrite formation through the reaction between silicon and lithium. The second flexible layer uses a high-density metal layer to block dendrites from entering the powder layer. At the same time, the good plasticity and flexibility of the low elastic modulus metal increase the contact area with the nano-powder layer, reducing dendrite growth caused by interface cracking during cycling. The interface protective layer of this invention can improve the deposition uniformity on the lithium metal anode deposition surface, induce uniform lithium metal deposition during charging, improve the density of the lithium metal anode deposition surface, and increase the resistance to dendrite growth. The intermediate layer absorbs lithium dendrites through reaction consumption, eliminating lithium dendrites in the intermediate layer. It improves the bonding strength with the electrolyte contact layer, reduces the phenomenon of electrolyte layer and anode layer contact separation caused by electrode material expansion and contraction during charge and discharge cycles, and improves the rate performance and cycle performance of the battery. It increases the potential between the electrolyte layer and the lithium metal anode interface, increases the electrochemical barrier for lithium dendrite precipitation at this interface position, makes dendrite precipitation at this position more difficult, reduces the tendency of dendrite formation from the source, and reduces the risk of battery short circuit.

[0039] After the first round of charge-discharge activation, the first and second flexible layers become lithium alloy layers, which have good electrical and ion conduction capabilities. The middle nano-silicon powder particle layer becomes a lithium-silicon alloy layer, which also has good electronic and ion conductivity. Due to the high density of the upper and lower alloy layers, the penetration of lithium dendrites is blocked, ensuring that there is only silicon alloy and no metallic lithium component in the middle silicon particle layer. This ensures that the lithium ion potential in the silicon alloy layer is higher than the lithium ion potential in the lithium metal layer. In other words, the lithium ion potential in the silicon alloy layer is higher than the lithium dendrite formation potential. The existence of this potential difference eliminates the prerequisite for lithium dendrite formation from the perspective of electrochemical energy.

[0040] In some embodiments, the surface of the first flexible layer away from the nano-silicon layer is in contact with the electrolyte layer. The first flexible layer contains at least two of magnesium, indium, zinc, tin, lead, gold, silver and aluminum, and can be a laminated composite or a mixed molten alloy, such as a laminated composite of magnesium and indium, a molten alloy of zinc and tin, etc.

[0041] In some embodiments, the thickness of the first flexible layer is 5-10 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. This thickness can balance flexibility and strength, improving the dendrite suppression effect.

[0042] In some embodiments, the first flexible layer further comprises lithium. In some embodiments, the first flexible layer is a composite layer of at least one of magnesium, indium, zinc, tin, lead, gold, silver and aluminum with lithium. The mass ratio of at least one of magnesium, indium, zinc, tin, lead, gold, silver and aluminum to lithium is (7~8):(2~3).

[0043] In some embodiments, the areal loading of the silicon nanoparticles is 0.1~4 mg / cm³. 2 For example, 0.1 mg / cm 2 0.4 mg / cm 2 0.45 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 1mg / cm 2 2mg / cm 2 3mg / cm 2 4mg / cm 2 This areal loading is beneficial for optimizing the lithium-ion transport path, allowing for better absorption of lithium dendrites through reaction consumption.

[0044] In some embodiments, the thickness of the nano-silicon layer is 1~500μm, for example, 1μm, 2μm, 5μm, 10μm, 15μm, 20μm, 30μm, 40μm, 50μm, 80μm, 100μm, 200μm, 300μm, 400μm, 500μm, etc. The present invention uses a nano-silicon layer of suitable thickness, which is more conducive to improving the performance of the interface protective layer, effectively suppressing the generation and growth of dendrites in the lithium metal anode, and achieving long cycling under high loading.

[0045] In some embodiments, the nano-silicon layer further includes a binder, the binder comprising less than 5% by mass in the nano-silicon layer, for example, 1%, 2%, 3%, 4%, 4.5%, etc. Adhesive binders may be added depending on the manufacturing process and thickness requirements.

[0046] In some embodiments, by heat-treating the first flexible layer and / or the second flexible layer, the grain size is reduced by recrystallization, thereby reducing the cracks caused by grain expansion after lithium ions are embedded in the metal layer, thus reducing the growth path of lithium dendrites in the metal layer and inhibiting dendrite growth.

[0047] In some embodiments, at least one surface of the first flexible layer is further provided with an ion-conducting adhesive layer, the thickness of which is 1~2μm, such as 1μm, 1.2μm, 1.5μm, 1.8μm, or 2μm. Applying the ion-conducting adhesive layer further enhances the adhesion to the electrolyte layer interface and the nano-silicon interface, reducing interfacial contact detachment caused by electrode expansion and contraction during charging and discharging.

[0048] In some embodiments, the surface of the second flexible layer away from the nano-silicon layer is in contact with the lithium metal anode. In some embodiments, the thickness of the second flexible layer is 5~10μm, for example, 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm. This thickness balances flexibility and strength, improving the dendrite suppression effect.

[0049] According to another aspect of the present invention, the present invention also relates to a method for preparing an interface protective layer for a lithium metal anode as described above, comprising the following steps:

[0050] Obtain the first flexible layer.

[0051] Nano-silicon powder is combined with the first flexible layer by coating or powder pressing to form a nano-silicon layer.

[0052] A second flexible layer is obtained, and the second flexible layer is brought into contact with the nano-silicon layer and pressed together to obtain an interface protection layer.

[0053] The method for preparing the interface protective layer of the lithium metal anode of the present invention is simple and easy to implement, which can ensure the uniformity of the interface protective layer, have suitable bonding strength, and help improve the deposition uniformity on the lithium metal anode deposition surface, induce uniform deposition of lithium metal during charging, improve the density of the lithium metal anode deposition surface, increase the resistance to dendrite growth, improve the rate performance and cycle performance of the battery, and achieve long cycle under high load.

[0054] In some embodiments, the method for obtaining the first flexible layer and the method for obtaining the second flexible layer each independently include: obtaining a single-element film of any one of magnesium, indium, zinc, tin, lead, gold, silver and aluminum, or performing a laminated composite or eutectic composite of at least two of magnesium, indium, zinc, tin, lead, gold, silver and aluminum.

[0055] In some embodiments, the method for obtaining the first flexible layer includes: laminating or eutectic bonding of any one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum with lithium. In some embodiments, the pressure of the powder pressing method is 45~300MPa, for example 45MPa, 80MPa, 90MPa, 100MPa, 110MPa, 120MPa, 150MPa, 200MPa, 300MPa, etc. This suitable pressure is beneficial for fully bonding the first flexible layer and the nano-silicon layer, improving the interfacial bonding performance.

[0056] In some embodiments, the pressure of the pressing process is 45~300MPa, such as 45MPa, 80MPa, 90MPa, 100MPa, 110MPa, 120MPa, 150MPa, 300MPa, etc. This suitable pressure is conducive to fully bonding the second flexible layer and the nano-silicon layer and improving the interfacial bonding performance.

[0057] According to another aspect of the present invention, the present invention also relates to a negative electrode sheet, comprising the aforementioned interface protective layer and a lithium metal negative electrode, wherein a second flexible layer of the interface protective layer is in contact with the lithium metal negative electrode. The negative electrode sheet of the present invention, through the modification effect of the interface protective layer, can improve the deposition uniformity on the lithium metal negative electrode deposition surface, induce uniform deposition of lithium metal during charging, and increase the resistance to dendrite growth.

[0058] According to another aspect of the present invention, the present invention also relates to a battery comprising the aforementioned interface protective layer, a lithium metal negative electrode, a positive electrode, and an electrolyte layer, wherein a second flexible layer in the interface protective layer is in contact with the lithium metal negative electrode, a first flexible layer is in contact with the electrolyte layer, and the positive electrode is disposed on the surface of the electrolyte layer away from the first flexible layer.

[0059] The battery of this invention has excellent rate performance, cycle performance, and safety performance.

[0060] According to another aspect of the present invention, the present invention also relates to a method for preparing a battery as described above, comprising the following steps:

[0061] After the electrolyte layer and the positive electrode sheet are stacked, a first compaction is performed; a first flexible layer, a nano-silicon layer and a second flexible layer are sequentially stacked on the surface of the electrolyte layer and compacted respectively, or the prepared interface protection layer is compacted with the electrolyte layer to obtain an interface protection layer; a lithium metal sheet and a negative electrode current collector are sequentially stacked on the surface of the interface protection layer and a second compaction is performed.

[0062] The battery preparation method of the present invention, through the coordinated operation of each step, is conducive to improving structural stability, effectively suppressing dendrite generation and growth, and achieving long cycle life under high load.

[0063] In some embodiments, the first compaction pressure is 100~320 MPa, for example, 100 MPa, 240 MPa, 250 MPa, 280 MPa, 300 MPa, 320 MPa, etc. In some embodiments, the total compaction pressure during the preparation of the interface protective layer is 100~1000 MPa, for example, 100 MPa, 240 MPa, 250 MPa, 300 MPa, 320 MPa, 360 MPa, 500 MPa, 800 MPa, 1000 MPa, etc. In some embodiments, the second compaction pressure is 5~500 MPa, for example, 5 MPa, 10 MPa, 50 MPa, 100 MPa, 200 MPa, 300 MPa, 390 MPa, 400 MPa, 410 MPa, 420 MPa, 440 MPa, 450 MPa, 500 MPa, etc. Using appropriate compaction pressure at different stages helps to ensure the bonding strength of each layer and the overall structural stability, and optimizes interface performance.

[0064] In some embodiments, the pressure of the first compaction is less than or equal to the total compaction pressure during the preparation of the interface protective layer, and less than the pressure of the second compaction. Using appropriate compaction pressures in each step in a coordinated manner can optimize interface performance and improve the structural stability of the battery.

[0065] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0066] Example 1

[0067] A method for preparing an interface protective layer for a lithium metal anode includes the following steps:

[0068] (1) Preparation of the first flexible layer: a lithium-indium alloy (Li-In) film is used, which is obtained by stacking lithium film and indium film together and then thinning by rolling; the mass ratio of lithium to indium is 2:8 and the thickness is 5μm.

[0069] (2) Preparation of the nano-silicon layer: The silicon powder was pressed onto the surface of the first flexible layer by powder pressing at a pressure of 100 MPa. The particle size D50 of the nano-silicon powder was 50 nm, and the surface loading was 0.5 mg / cm². 2 The thickness is 5μm.

[0070] (3) Preparation of the second flexible layer: An indium metal film with a thickness of 5 μm was pressed onto the other side of the nano-silicon layer at a pressure of 100 MPa.

[0071] Example 2

[0072] A method for preparing an interface protective layer for a lithium metal anode includes the following steps:

[0073] (1) Preparation of the first flexible layer: a lithium-tin alloy (Li-Sn) film is used, which is obtained by stacking lithium film and tin film together and then thinning by rolling; the mass ratio of lithium to tin is 3:7 and the thickness is 5μm.

[0074] (2) Preparation of the nano-silicon layer: The silicon powder was pressed onto the surface of the first flexible layer of the alloy film by powder pressing at a pressure of 100 MPa. The particle size D50 of the nano-silicon powder was 20 nm, and the surface loading was 0.5 mg / cm³. 2 The thickness is 5μm.

[0075] (3) Preparation of the second flexible layer: A tin metal film with a thickness of 5 μm is pressed onto the other side of the nano-silicon layer at a pressure of 100 MPa.

[0076] Example 3

[0077] A method for preparing an interface protective layer for a lithium metal anode includes the following steps:

[0078] (1) Preparation of the first flexible layer: A lithium-zinc alloy (Li-Zn) film is used. The lithium film and zinc film are stacked together and then thinned by rolling. The mass ratio of lithium to zinc is 3:7 and the thickness is 5μm.

[0079] (2) Preparation of the nano-silicon layer: Silicon powder was pressed onto the first flexible layer by powder pressing at a pressure of 100 MPa. The particle size D50 of the nano-silicon powder was 100 nm, and the surface loading was 0.5 mg / cm². 2 .

[0080] (3) Preparation of the second flexible layer: A zinc metal film with a thickness of 5 μm was pressed onto the other side of the nano-silicon layer at a pressure of 100 MPa.

[0081] Example 4

[0082] A method for preparing a battery includes the following steps:

[0083] (1) The positive electrode sheet includes a positive current collector and a positive electrode material layer, the positive electrode material layer including nickel-cobalt-manganese (LiNi) 0.9 Co 0.05 Mn 0.05 O2) ternary cathode materials, sulfide electrolytes (Li) 10 GeP2S 12 The conductive carbon black has a mass ratio of 70:25:5, and the positive current collector is aluminum foil with a surface loading of 30 mg / cm³. 2 The positive electrode is punched into a 9mm diameter disc for use as the positive electrode.

[0084] (2) 100mg of electrolyte powder is loaded into the battery sleeve mold (Ф10mm) and pressed into a dense electrolyte layer by a press. The pressure is 200MPa and the holding time is 10min. After the positive electrode is loaded into one side of the electrolyte layer, it is compacted under high pressure. The pressure is 300MPa and the holding time is 10min.

[0085] (3) A lithium-indium alloy (Li-In) film is used, which is obtained by stacking lithium film and indium film together and then thinning by rolling. The mass ratio of lithium to indium is 2:8 and the thickness is 5μm. The Li-In alloy film is punched into a Ф10mm disc, inserted into the other side of the electrolyte layer, and a pressure of 100MPa is applied to it to make it tightly bonded to the electrolyte layer.

[0086] (4) Spread 0.5 mg of nano-silicon powder evenly on the Li-In alloy side. The particle size D50 of the nano-silicon powder is 50 nm, and the surface loading is 0.5 mg / cm². 2 A pressure of 100 MPa is applied to initially densify the material and allow it to adhere tightly to the Li-In alloy layer.

[0087] (5) A Ф10mm round piece is punched out from an indium metal sheet with a thickness of 5μm and placed on the nano silicon layer. A pressure of 100MPa is applied to make it adhere tightly to the nano silicon layer.

[0088] (6) A Ф10mm round piece is punched out from a 50μm thick negative lithium metal sheet and placed on top of an indium metal sheet. A Ф10mm copper foil is placed as a current collector. A pressure of 400MPa is applied and held for 1 minute to densify each layer of the entire cell.

[0089] (7) The positive and negative terminals of the battery mold were sealed with steel plungers and tightened with bolts. Then, the mold was placed in an inert gas atmosphere for charge and discharge testing. The bolt torque was 1.2 Nm, corresponding to a pressure of about 10 MPa.

[0090] Example 5

[0091] A method for preparing a battery includes the following steps:

[0092] (1) The positive electrode sheet includes a positive current collector and a positive electrode material layer, the positive electrode material layer including nickel-cobalt-manganese (LiNi) 0.9 Co 0.05 Mn 0.05 O2) ternary cathode materials, sulfide electrolytes (Li) 10 GeP2S 12 The conductive carbon black has a mass ratio of 70:25:5, and the positive current collector is aluminum foil with a surface loading of 30 mg / cm³. 2 The positive electrode is punched into a 9mm diameter disc for use as the positive electrode.

[0093] (2) 100mg of electrolyte powder is loaded into the battery sleeve mold (Ф10mm) and pressed into a dense electrolyte layer by a press. The pressure is 200MPa and the holding time is 10min. After the positive electrode is loaded into one side of the electrolyte layer, it is compacted under high pressure. The pressure is 300MPa and the holding time is 10min.

[0094] (3) A lithium-tin alloy (Li-Sn) film is used, which is obtained by stacking lithium film and tin film together and then thinning by rolling. The mass ratio of lithium to tin is 3:7 and the thickness is 5μm. The Li-Sn alloy film is punched into a Ф10mm round piece, inserted into the other side of the electrolyte layer, and a pressure of 100MPa is applied to it to make it tightly pressed together with the electrolyte layer.

[0095] (4) Spread 0.5 mg of nano-silicon powder evenly on the side of the Li-Sn alloy. The particle size D50 of the nano-silicon powder is 20 nm, and the surface loading is 0.5 mg / cm². 2 A pressure of 100 MPa is applied to initially densify the material and allow it to adhere tightly to the Li-Sn alloy layer.

[0096] (5) A tin metal sheet with a thickness of 5μm is punched out into a Ф10mm round piece and placed on the nano-silicon layer. A pressure of 100MPa is applied to make it adhere tightly to the nano-silicon layer.

[0097] (6) A Φ10mm round piece is punched out from a 50μm thick negative electrode lithium metal sheet and placed on a tin metal sheet. A Φ10mm copper foil is placed as a current collector. A pressure of 400MPa is applied and held for 1 minute to densify each layer of the entire cell.

[0098] (7) The positive and negative terminals of the battery mold were sealed with steel plungers and tightened with bolts. Then, the mold was placed in an inert gas atmosphere for charge and discharge testing. The bolt torque was 1.2 Nm, corresponding to a pressure of about 10 MPa.

[0099] Example 6

[0100] A method for preparing a battery includes the following steps:

[0101] (1) The positive electrode sheet includes a positive current collector and a positive electrode material layer, the positive electrode material layer including nickel-cobalt-manganese (LiNi) 0.9 Co 0.05 Mn 0.05 O2) ternary cathode materials, sulfide electrolytes (Li) 10 GeP2S 12 The conductive carbon black has a mass ratio of 70:25:5, and the positive current collector is aluminum foil with a surface loading of 30 mg / cm³. 2 The positive electrode is punched into a 9mm diameter disc for use as the positive electrode.

[0102] (2) 100mg of electrolyte powder is loaded into the battery sleeve mold (Ф10mm) and pressed into a dense electrolyte layer by a press. The pressure is 200MPa and the holding time is 10min. After the positive electrode is loaded into one side of the electrolyte layer, it is compacted under high pressure. The pressure is 300MPa and the holding time is 10min.

[0103] (3) A lithium-zinc alloy (Li-Zn) film is used, which is obtained by stacking lithium film and zinc film together and then thinning by rolling. The mass ratio of lithium to zinc is 3:7 and the thickness is 5μm. The Li-Zn alloy film is punched into a Ф10mm round piece, inserted into the other side of the electrolyte layer, and a pressure of 100MPa is applied to it to make it tightly pressed together with the electrolyte layer.

[0104] (4) Spread 0.5 mg of nano-silicon powder evenly on the side of the Li-Zn alloy. The particle size D50 of the nano-silicon powder is 100 nm, and the surface loading is 0.5 mg / cm². 2 A pressure of 100 MPa is applied to initially densify the material and allow it to adhere tightly to the Li-Zn alloy layer.

[0105] (5) A zinc metal sheet with a thickness of 5μm is punched into a Ф10mm round piece and placed on the nano silicon layer. A pressure of 100MPa is applied to make it adhere tightly to the nano silicon layer.

[0106] (6) A Ф10mm round piece is punched out from a 50μm thick negative lithium metal sheet and placed on a zinc metal sheet. A Ф10mm copper foil is placed as a current collector. A pressure of 400MPa is applied and held for 1 minute to densify each layer of the entire cell.

[0107] (7) The positive and negative terminals of the battery mold were sealed with steel plungers and tightened with bolts. Then, the mold was placed in an inert gas atmosphere for charge and discharge testing. The bolt torque was 1.2 Nm, corresponding to a pressure of about 10 MPa.

[0108] Example 7

[0109] A method for preparing a battery differs from that in Example 4 in that:

[0110] The pressure in step (3) is 105 MPa.

[0111] The pressure in step (4) is 115 MPa.

[0112] The pressure in step (5) is 105 MPa.

[0113] The pressure in step (6) is 390 MPa.

[0114] Example 8

[0115] A method for preparing a battery differs from that in Example 4 in that:

[0116] The particle size D50 of the nano-silicon powder is 500 nm.

[0117] The pressure in step (3) is 80 MPa.

[0118] The pressure in step (4) is 120 MPa.

[0119] The pressure in step (5) is 80 MPa.

[0120] Comparative Example 1

[0121] A method for preparing a battery differs from that in Example 4 in that:

[0122] Steps (4), (5), and (6) are not included, meaning that the battery does not have an interface protection layer.

[0123] Comparative Example 2

[0124] A method for preparing a battery differs from that in Example 4 in that:

[0125] The particle size D50 of the nano-silicon powder is 600nm.

[0126] Experimental Example

[0127] The batteries in Examples 4-7 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Table 1.

[0128] The testing methods include:

[0129] Charge and discharge steps: 1. Perform one charge and discharge cycle using a constant current charge and discharge rate of 0.1C, with a cutoff voltage of 2.5~4.3V; 2. Perform a charge and discharge cycle test using a constant current rate of 0.5C, continuously charging and discharging 2000 cycles.

[0130] First-cycle efficiency calculation formula: First-cycle efficiency = (0.1C first-cycle discharge capacity / 0.1C first-cycle charging capacity) × 100%.

[0131] The formula for calculating the discharge rate is: 1C / 0.1C discharge rate = (0.5C first discharge capacity / 0.1C discharge capacity) × 100%.

[0132] Cycle count: The number of cycles in which the capacity retention rate is 80% of the discharge capacity in the first cycle at 0.5C.

[0133] Table 1 Test Results

[0134]

[0135] As shown in Table 1, the battery obtained by the method of the present invention has high initial efficiency, high rate performance and high cycle performance. The initial efficiency is 82% or higher, the rate performance is 79% or higher, and the capacity retention rate is 80% in the first discharge cycle at 0.5C for more than 800 cycles.

[0136] The batteries obtained by the methods in Comparative Examples 1 and 2 had low initial efficiency, poor rate performance, and poor cycle performance.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An interface protective layer for a lithium metal anode, characterized in that, It includes a first flexible layer, a nano-silicon layer, and a second flexible layer. The first flexible layer is disposed on one side surface of the nano-silicon layer, and the second flexible layer is disposed on the other side surface of the nano-silicon layer. The first flexible layer comprises at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum; the surface of the first flexible layer away from the nano-silicon layer is in contact with the electrolyte layer in the solid-state battery; the nano-silicon layer is composed of nano-silicon particles with a particle size D50 of 20-500 nm; the areal loading of the nano-silicon particles is 0.1-4 mg / cm³. 2 ; The second flexible layer is at least one of magnesium, indium, zinc, tin, lead, gold, silver, and aluminum; the surface of the second flexible layer away from the nano-silicon layer is in contact with the lithium metal negative electrode. The method for preparing the interface protective layer of the lithium metal anode includes the following steps: Obtain the first flexible layer; Nano-silicon powder is composited with the first flexible layer by powder pressing to form a nano-silicon layer; A second flexible layer is obtained, and the second flexible layer is brought into contact with the nano-silicon layer and pressed together to obtain an interface protection layer. The pressure for the powder pressing method is 80~300MPa; The pressure for the pressing process is 80~300MPa.

2. The interface protective layer of the lithium metal anode according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) The first flexible layer comprises at least two of magnesium, indium, zinc, tin, lead, gold, silver and aluminum; (2) The thickness of the first flexible layer is 5~10μm; (3) The first flexible layer also contains lithium.

3. The interface protective layer of the lithium metal anode according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) The thickness of the nano-silicon layer is 1~500μm; (2) The nano-silicon layer further comprises a binder, wherein the mass content of the binder in the nano-silicon layer is less than 5%; (3) At least one side surface of the first flexible layer is further provided with an ion-conducting adhesive layer, the thickness of which is 1~2μm.

4. The interface protective layer of the lithium metal anode according to claim 1, characterized in that, The thickness of the second flexible layer is 5~10μm.

5. The interface protective layer of the lithium metal anode according to claim 1, characterized in that, It includes any one of the following features (1) to (2): (1) The method for obtaining the first flexible layer and the method for obtaining the second flexible layer each independently include: obtaining a single-element film of any one of magnesium, indium, zinc, tin, lead, gold, silver and aluminum, or performing a laminated composite or co-melted composite of at least two of magnesium, indium, zinc, tin, lead, gold, silver and aluminum; (2) The method for obtaining the first flexible layer includes: laminating or eutectic bonding of any one of magnesium, indium, zinc, tin, lead, gold, silver and aluminum with lithium.

6. A negative electrode sheet, characterized in that, It includes an interface protection layer as described in any one of claims 1 to 5 and a lithium metal anode, wherein the second flexible layer of the interface protection layer is in contact with the lithium metal anode.

7. A battery, characterized in that, The device comprises an interface protective layer, a lithium metal anode, a cathode, and an electrolyte layer as described in any one of claims 1 to 5, wherein a second flexible layer in the interface protective layer is in contact with the lithium metal anode, a first flexible layer is in contact with the electrolyte layer, and the cathode is disposed on the surface of the electrolyte layer away from the first flexible layer.

8. The method for preparing a battery as described in claim 7, characterized in that, Includes the following steps: After the electrolyte layer and the positive electrode sheet are stacked, the first compaction is performed; A first flexible layer, a nano-silicon layer, and a second flexible layer are sequentially stacked on the surface of the electrolyte layer and compacted respectively, or the interface protection layer of any one of claims 1 to 5 is compacted with the electrolyte layer to obtain an interface protection layer; Lithium metal sheets and negative electrode current collectors are sequentially stacked on the surface of the interface protective layer, and then a second compaction is performed.

9. The method for preparing a battery according to claim 8, characterized in that, It includes at least one of the following features (1) to (3): (1) The pressure of the first compaction is 100~320MPa; (2) The total compaction pressure during the preparation of the interface protective layer is 100~1000MPa; (3) The pressure of the second compaction is 5~500MPa.

Images