Battery interface buffer layer and flexible battery

Abstract

The utility model belongs to the field of flexible batteries, and particularly discloses a battery interface buffer layer and a flexible battery. The battery interface buffer layer comprises a polyethylene film and silicon dioxide layers coating the two surfaces of the polyethylene film; the thickness of the polyethylene film ranges from 0.4 mm to 1.5 mm, and the total thickness of the silicon dioxide layers wrapping the two faces ranges from 22 nm to 68 nm. The flexible battery comprises a positive electrode layer, a negative electrode layer and an electrolyte layer, the battery interface buffer layer is arranged between the positive electrode layer and the electrolyte layer and / or between the negative electrode layer and the electrolyte layer. As the polyethylene film coated with the silicon dioxide layers on the two sides is used as the interface buffer layer, the bonding strength at the grain boundary is increased through mutual diffusion between oxygen atoms provided by silicon dioxide and sulfur atoms in the electrolyte, and the growth of the lithium dendrites is subjected to larger resistance.

Description

Technical Field

[0001] The present application belongs to the technical field of flexible batteries, and more specifically, relates to a battery interface buffer layer and a flexible battery. Background Art

[0002] Lithium-ion batteries have become one of the necessities of human life and play an important role in many fields such as consumer electronics, electric vehicles, and aerospace products. At present, with the continuous growth of electrification demand, the use rate of lithium-ion batteries has also increased exponentially. Therefore, safe batteries with high energy density are in great demand. The current lithium-ion batteries containing liquid electrolytes have a significant risk of fire or even explosion due to the use of highly flammable organic solvents. Replacing liquid electrolytes with solid electrolytes will definitely improve the safety of batteries, because solid electrolytes do not have the problems of flammability and electrolyte leakage. In addition, solid electrolytes make it possible to use lithium metal anodes, which will greatly increase the energy density of batteries. Therefore, all-solid-state batteries are regarded as one of the key technologies in the future and have received widespread attention in recent years. However, unlike liquid electrolytes, solid electrolytes cannot flow or penetrate into the gaps in all-solid-state batteries, resulting in poor physical contact between particles. Since all components in all-solid-state batteries are solid, the manufacture of all-solid-state batteries requires stacking the positive electrode, electrolyte, and negative electrode in sequence, thereby forming multiple interfaces, and there are serious interface contact problems. In particular, the interface between the solid electrolyte and the metallic lithium negative electrode, the point-to-point solid-solid contact interface, often causes a large interfacial contact resistance and uneven current distribution, which brings about the problem of lithium dendrites. In addition, lithium metal has an extremely low reduction potential, which can reduce most of the solid electrolyte, leading to the occurrence of side reactions.

[0003] Patent document CN116864689A discloses a lithium battery interface buffer layer and a preparation method thereof, which can alleviate stress accumulation and volume expansion during lithium deposition; however, since the stress generated by the interface buffer layer prepared by it during the deposition process is converted into an electric field, the converted electric field is unstable and the deposition behavior of lithium cannot be regulated, which will still cause uneven deposition of lithium and lead to dendrite growth. Summary of the invention

[0004] In response to the defects of the existing technology, the applicant studied the mechanism of the interface reaction process and added an interface buffer layer between the electrode and the electrolyte to solve the application difficulties of flexible solid-state batteries.

[0005] To achieve the above objectives, the present application provides a battery interface buffer layer, comprising a polyethylene film and a silicon dioxide layer coated on both sides of the polyethylene film; the thickness of the polyethylene film is 0.4mm~1.5mm, and the total thickness of the silicon dioxide layer coated on both sides is 22nm~68nm.

[0006] Preferably, the polyethylene film has a thickness of 0.8 mm to 1.2 mm.

[0007] Preferably, the total thickness of the silicon dioxide layer coated on both sides of the polyethylene film is 30 nm to 50 nm.

[0008] Preferably, in the silicon dioxide layers coated on both sides of the polyethylene film, the silicon dioxide layer on one side is thicker than that on the other side.

[0009] As further preferred, the thicker silicon dioxide layer on the one side accounts for more than 75% of the total thickness of the silicon dioxide layers coated on the two sides.

[0010] Another object of the present application is to provide a flexible battery, comprising a positive electrode layer, a negative electrode layer and an electrolyte layer;

[0011] The battery interface buffer layer is provided between the positive electrode layer and the electrolyte layer, and / or between the negative electrode layer and the electrolyte layer.

[0012] Preferably, the negative electrode layer is metallic lithium and has a thickness of 100 μm to 200 μm.

[0013] Preferably, the positive electrode layer is nickel cobalt lithium manganese oxide, and has a thickness of 50 μm to 100 μm.

[0014] As a further preferred embodiment, the chemical formula of the lithium nickel cobalt manganese oxide is LiNi x Co y Mn (1-x-y) O 2 ; Among them, 0.3 <x<0.65,0.15<y<0.25。

[0015] Preferably, the electrolyte layer is a sulfide all-solid electrolyte with a thickness of 1 μm to 100 μm.

[0016] As a further preferred embodiment, the chemical formula of the sulfide all-solid electrolyte is Li (6+z) M z As (1-z) S 5 I; wherein M is Si or Sn, 0 <z<0.4。

[0017] Preferably, among the silicon dioxide coated on both sides of the polyethylene film, the silicon dioxide layer on the side facing the electrolyte layer is thicker than that on the other side.

[0018] In general, compared with the prior art, the above technical scheme conceived by the present application uses a polyethylene film coated with a silicon dioxide layer on both sides as an interface buffer layer. The mutual diffusion between the oxygen atoms provided by the silicon dioxide and the sulfur atoms in the electrolyte increases the bonding strength at the grain boundary, making the growth of lithium dendrites encounter greater resistance. At the same time, the sulfide solid electrolyte doped with oxygen atoms will react with the metal lithium electrode to generate lithium oxide during the charge and discharge process, thereby forming a stable passivation layer at the interface between the two, thereby achieving the purpose of inhibiting the growth of lithium dendrites. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the battery interface buffer layer provided in this application;

[0020] Figure 2 This is a schematic diagram of the structure of a flexible battery provided in Example 1 of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] Additionally, references throughout this specification to "one embodiment," "one embodiment," "some embodiments," "one example," "some examples," or similar language indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, appearances of the phrase "in one embodiment," "in one embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0023] The present application discloses a battery interface buffer layer, comprising a polyethylene film and a silicon dioxide layer coated on both sides of the polyethylene film, such as Figure 1 As shown; the thickness of the polyethylene film is 0.4mm~1.5mm, and the total thickness of the silicon dioxide layers coated on both sides of the polyethylene film is 22nm~68nm; in some embodiments, the thickness of the polyethylene film is 0.8mm~1.2mm, and in other embodiments, the total thickness of the silicon dioxide layers coated on both sides of the polyethylene film is 30nm~50nm; in some embodiments, the silicon dioxide layer on one side is thicker than that on the other side; wherein the thicker silicon dioxide layer on the side preferably accounts for more than 75% of the total thickness.

[0024] The present application also discloses a flexible battery including the above-mentioned battery interface buffer layer; the flexible battery can be a lithium metal battery, an all-solid-state battery or any other type of flexible battery. The flexible battery includes a positive electrode layer, a negative electrode layer and an electrolyte layer; the above-mentioned battery interface buffer layer is arranged between the positive electrode layer and the electrolyte layer, and / or between the negative electrode layer and the electrolyte layer. When the above-mentioned battery interface buffer layer is arranged between the positive electrode layer and the electrolyte layer, and between the negative electrode layer and the electrolyte layer, the flexible battery is composed of a positive electrode layer, a first buffer layer, an electrolyte layer, a second buffer layer and a negative electrode layer stacked in sequence.

[0025] In some embodiments, the flexible battery is a lithium metal battery, that is, the negative electrode layer is metallic lithium with a thickness of 100 μm to 200 μm; in other embodiments, the positive electrode layer is lithium nickel cobalt manganese oxide with a thickness of 50 μm to 100 μm; that is, the chemical formula of the positive electrode layer is LiNi x Co y Mn (1-x-y) O 2 ; Among them, 0.3 <x<0.65,0.15<y<0.25。

[0026] In some embodiments, the electrolyte layer is a sulfide all-solid electrolyte with a thickness of 1 μm to 100 μm; that is, the chemical formula of the electrolyte layer is Li (6+z) M z As (1-z) S 5 I; wherein M is Si or Sn, 0 <z<0.4。

[0027] In some embodiments, when the silicon dioxide layer on one side is thicker than the other side, the thicker silicon dioxide layer on the side should be placed toward the electrolyte layer when stacked, that is, the thinner silicon dioxide layer on the side should be placed toward the positive electrode layer or the negative electrode layer when stacked.

[0028] Example 1

[0029] Example 1 A flexible lithium metal battery was prepared, such as Figure 2 As shown in the figure, from right to left, it is composed of a positive electrode, a first buffer layer, a sulfide all-solid electrolyte, a second buffer layer, and a negative electrode. The negative electrode is a 150μm thick lithium metal, and the sulfide all-solid electrolyte is a 50μm thick Li 6.8 Si 0.8 As 0.2 S 5 I, the positive electrode is LiNi with a thickness of 75μm 0.6 Co 0.2 Mn 0.2 O 2 .

[0030] The first buffer layer and the second buffer layer both include a stacked polyethylene film with a thickness of 0.9 mm and a silicon dioxide layer with a total thickness of 40 nm on both sides.

[0031] The preparation method of the lithium metal battery comprises the following steps:

[0032] (1) Prepare the substrate: Select metal foil to support the sulfide all-solid electrolyte and the positive and negative electrode materials;

[0033] (2) Preparation of electrode materials: In a vacuum environment, the electrode active material is melted at high temperature and evaporated onto the selected substrate to form a solid film. In this embodiment, the temperature used for the positive electrode is 450 degrees Celsius, and the electrode active material used is LiNi 0.6 Co 0.2 Mn 0.2 O 2 , the temperature used for the negative electrode is 1340 degrees Celsius, and the electrode active material used is metallic lithium;

[0034] (3) Preparation of electrolyte materials: The chemical reaction is Li2S (99.98%, Sigma

[0035] Aldrich), As2S5 (99%, Mucklin), Al2S3 (99%, Alfa Aesar), Sn (99.9%, Aladdin), S (99.99%, Sigma Aldrich), LiBr (99.8%, Alfa Aesar), LiI (99.9%, Alfa Aesar). Each sample was divided into the finished product Li 6.8 Si 0.8 As 0.2 S 5 The raw materials are weighed and proportioned at a molar ratio of 1. The mixed precursor materials are evaporated into gaseous state in a high temperature environment filled with argon gas to react, and the generated electrolyte material solid is attached to the metal foil, which is the electrolyte material.

[0036] (4) Preparation of buffer layer: A buffer layer is added between the positive electrode and the electrolyte and between the negative electrode and the electrolyte. The preparation method of the buffer layer is as follows: ethanol, ammonia water and ultrapure water are mixed, and stirred at 500 rpm for 3 minutes; ethyl orthosilicate is added dropwise; sealed and stirred at room temperature for 13 hours to obtain a silica sol with a concentration of 27%; a polyethylene film with a thickness of 0.9 mm that has been cleaned by ultrasonic treatment is treated by immersion and pulling in the silica sol, and then taken out and placed at an angle. After natural drying, a polyethylene film coated with nano-silicon dioxide can be obtained. In this embodiment, the thickness of the silica material on the polyethylene diaphragm is 40 nanometers; in this embodiment, the technical means of placing it at an angle to the electrolyte side is adopted, so that the silica material is concentrated on one side (accounting for about 75% of the total amount).

[0037] (5) Assembling the battery: Cut the prepared positive and negative electrodes, sulfide solid electrolyte film and buffer layer into the required size and shape respectively, and then stack them together at a temperature of 25°C (298.15K) and a pressure of 101.325 kPa to form the battery's electrode-buffer layer-electrolyte-buffer layer-electrode structure. Pay attention to placing the side with more concentrated silica material toward the electrolyte.

[0038] Comparative Example 1

[0039] Example 1 was repeated with the same steps, except that the buffer layer was removed when assembling the battery, and finally an electrode-electrolyte-electrode structure was formed.

[0040] Verification Example 1

[0041] Current collectors and packaging materials are installed around the stacked electrode-buffer layer-electrolyte-buffer layer-electrode structure of Example 1 to form a complete solid-state lithium metal battery.

[0042] The solid-state lithium metal battery product has a bending radius of 12.5 mm, a thickness of 2.7 mm, and a bending angle of 90° after testing using a soft-pack lithium-ion battery bending deformation test device. 0.6 Co 0.2 Mn 0.2 O 2 , thickness is 75μm, the negative electrode is metal lithium, the thickness is 150μm, and the electrolyte is Li 6.8 Si 0.8 As 0.2 S 5 I. The thickness is 50 μm, the thickness of the polyethylene film is 0.9 mm, and the thickness of the silicon dioxide layer is 40 nm. In other embodiments, batteries of different sizes and shapes can also be manufactured according to the needs of specific products.

[0043] Verification Example 2

[0044] After Example 1 and Comparative Example 1 were assembled into batteries and left to stand for 1 hour, the energy density of group A batteries was measured using the solid electrolyte integrated test system SEMS1100 to be 250mh / g, and the energy density of group B batteries was 210mh / g.

[0045] It can be seen from the test results that compared with the battery without a buffer layer, the growth of lithium dendrites in the battery of this embodiment is well suppressed. This is because the mutual diffusion between the oxygen atoms provided by silicon dioxide and the sulfur atoms in the electrolyte increases the bonding strength at the grain boundary, which makes the growth of lithium dendrites encounter greater resistance. At the same time, the sulfide solid electrolyte doped with oxygen atoms will react with the metal lithium electrode to generate lithium oxide during the charge and discharge process, thereby forming a stable passivation layer at the interface between the two, thereby achieving the purpose of suppressing the growth of lithium dendrites.

[0046] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A battery interface buffer layer, characterized in that: It comprises a polyethylene film and silicon dioxide layers coated on both sides of the polyethylene film; the thickness of the polyethylene film is 0.4 mm to 1.5 mm, and the total thickness of the silicon dioxide layers coated on both sides is 22 nm to 68 nm.

2. The battery interface buffer layer according to claim 1, characterized in that: The thickness of the polyethylene film is 0.8 mm to 1.2 mm.

3. The battery interface buffer layer according to claim 1, characterized in that: The total thickness of the silicon dioxide layers coated on both sides is 30nm to 50nm.

4. A flexible battery, comprising a positive electrode layer, a negative electrode layer and an electrolyte layer; characterized in that: A battery interface buffer layer according to any one of claims 1 to 3 is arranged between the positive electrode layer and the electrolyte layer, and / or between the negative electrode layer and the electrolyte layer.

5. The flexible battery according to claim 4, characterized in that: The negative electrode layer is made of metallic lithium and has a thickness of 100 μm to 200 μm.

6. The flexible battery according to claim 4, characterized in that: The positive electrode layer is made of nickel cobalt lithium manganese oxide and has a thickness of 50 μm to 100 μm.

7. The flexible battery according to claim 4, characterized in that: The electrolyte layer is a sulfide all-solid electrolyte with a thickness of 1 μm to 100 μm.

8. The flexible battery according to claim 4, characterized in that: In the silicon dioxide coated on both sides of the polyethylene film, the silicon dioxide layer on the side facing the electrolyte layer is thicker than that on the other side.

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