Preparation method of single-crystal lithium alloy negative electrode and metal lithium battery

Abstract

The application discloses a preparation method of a single-crystal lithium alloy negative electrode and a metal lithium battery. The single-crystal lithium foil and a lithiumophilic metal foil are stacked and pressed, the ordered single-crystal lithium atoms and the lithiumophilic metal atoms are diffused with each other, the thickness ratio and the pressure of the single-crystal lithium foil and the lithiumophilic metal foil are regulated, the atom diffusion process is controlled, the ordering and alloying of the atom arrangement are realized, the single-crystal alloy lithium foil is prepared, and the single-crystal metal negative electrode is obtained after cutting. The application can significantly improve the electrochemical performance and stability of the battery, and fully exhibits the outstanding effect in improving the battery performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, and particularly relates to a preparation method of a single-crystal lithium alloy negative electrode and a metal lithium battery. BACKGROUND

[0002] In the process of charging and discharging of the lithium metal negative electrode of the metal lithium battery, lithium dendrite growth and large volume change are prone to occur, which not only reduces the cycle stability of the battery, but also may cause safety hazards. Lithium alloy negative electrode materials are concerned due to their good stability and safety. However, the existing preparation methods of the lithium alloy negative electrode have problems such as complex process, high cost, difficulty in controlling alloy composition and structure, etc., which limit their wide application in metal lithium batteries. At the same time, the regulation of lithium atom diffusion kinetics in the negative electrode material is also the key to improve the performance of the metal lithium battery. The current technology still has deficiencies in improving the diffusion kinetics of lithium atoms on the electrode surface and in the bulk phase, and it is difficult to achieve uniform lithium deposition, thereby affecting the cycle stability of the battery. Single-crystal alloy negative electrodes with low diffusion barrier crystal faces exhibit excellent performance, but their preparation methods are relatively complicated and are limited to alloy materials. SUMMARY

[0003] The present application proposes a preparation method of a single-crystal lithium alloy negative electrode and a metal lithium battery to solve the problems of the prior art, such as complicated steps and single pressure form, which can simplify the preparation process, increase the types of single-crystal lithium alloy, significantly improve the electrochemical performance and stability of the battery, and fully demonstrate its outstanding performance in improving the performance of the battery.

[0004] The present application is achieved by the following technical solutions:

[0005] The present application relates to a preparation method of a single-crystal lithium alloy negative electrode, which realizes the mutual diffusion of ordered single-crystal lithium atoms and lithiumophilic metal atoms by stacking and pressing the single-crystal lithium foil and the lithiumophilic metal foil, controls the atomic diffusion process by regulating the thickness ratio and pressure of the single-crystal lithium foil and the lithiumophilic metal foil, realizes the ordering of atomic arrangement and alloying, and prepares a single-crystal alloy lithium foil, which is cut to obtain a single-crystal metal negative electrode.

[0006] The lithiumophilic metal is selected from materials suitable for alloying with lithium metal to form lithium alloy, and is not limited to: indium, magnesium, zinc, aluminum or tin.

[0007] The stacking refers to stacking the single-crystal lithium foil and the lithiumophilic metal foil in an area-overlapping manner to realize uniform atomic diffusion in the process of pressing.

[0008] Preferably, the surface area of the single-crystal lithium metal foil and the lithiumophilic metal foil is the same.

[0009] The thickness ratio of the single-crystal lithium metal foil to the thickness of the lithiumophilic metal foil is 0.1-50.

[0010] The pressure is preferably static pressure perpendicular to the surface of the single-crystal lithium foil and the lithiumophilic metal foil, rolling, or reciprocating pressure.

[0011] The pressure is preferably 20-180℃.

[0012] The pressure is preferably 20-180℃.

[0013] The application relates to the application of the single-crystal lithium alloy foil prepared by the above method, which is cut and used to prepare a negative electrode of a metal lithium battery using an electrolyte or a solid-state electrolyte.

[0014] The positive electrode of the metal lithium battery is preferably, but is not limited to, an oxide positive electrode material, a polyanion positive electrode material, a sulfur positive electrode material, etc.

[0015] The electrolyte is prepared by any one of the following methods:

[0016] ① 1M LiPF6 is dissolved in a mixed solution of EC:DEC=1:1 Vol%,

[0017] ② 10.2M LiPF6, 0.2M LiBF4 and 0.8M LiDFOB are dissolved in a mixed solution of DEC:FEC=2:1 Vol%,

[0018] ③ 1M LiTFSI is dissolved in a mixed solution of DME:DOL=1:1 Vol%.

[0019] The solid-state electrolyte is preferably Li7La3Zr2O 12 The solid-state electrolyte is preferably Li7La3Zr2O 10 The solid-state electrolyte is preferably Li7La3Zr2O 12 The solid-state electrolyte is preferably Li7La3Zr2O 11 The solid-state electrolyte is preferably Li7La3Zr2O

[0020] Technical effects

[0021] The present application directly realizes the preparation of a single-crystal lithium alloy negative electrode by pressurization at a certain temperature. By adjusting the temperature and the pressurization process, the mutual diffusion of single-crystal lithium atoms and lithiumophilic metal atoms is regulated, the ordering of atomic arrangement and alloying are realized, wherein the pressurization process can adopt various pressurization modes and is suitable for different alloying materials, thereby expanding the types of single-crystal lithium alloys. Compared with the prior art, the present application reduces the synthesis steps and the preparation cost, and the prepared single-crystal lithium alloy significantly improves the lithium transport dynamics of lithium ions on the electrode surface and in the bulk phase, thereby promoting uniform lithium deposition. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a flowchart of the preparation of a single-crystal lithium metal foil in Example 1 of the present application;

[0023] Figure 2 is a physical diagram of the single-crystal lithium alloy foil prepared in Example 1 of the present application;

[0024] Figure 3 is an XRD diagram of the single-crystal lithium alloy negative electrode prepared in Example 1 and Comparative Example 1 of the present application;

[0025] Figure 4 is a comparison of the cycle performance test of the single-crystal lithium alloy negative electrode prepared in Example 1 and the lithium alloy negative electrode prepared in Comparative Example 1, respectively, with LPSCl solid-state electrolyte assembled batteries at a 5C rate. DETAILED DESCRIPTION

[0026] Example 1

[0027] As shown in Figure 1 , the present embodiment relates to a single-crystal lithium alloy negative electrode preparation method, comprising:

[0028] S1: preparing a single-crystal lithium foil with a certain thickness A1 and a lithiumophilic indium foil with a certain thickness A2; A1 / A2 = 10;

[0029] S2: overlapping the single-crystal lithium foil and the lithiumophilic metal foil, and applying a pressure of 150 MPa by vertical static pressurization at room temperature (25℃) to prepare a single-crystal lithium alloy foil;

[0030] S3: cutting the single-crystal lithium alloy foil into a single-crystal lithium alloy negative electrode with a diameter of 10 mm;

[0031] The prepared single-crystal lithium alloy negative electrode is assembled with NCM811 as an oxide positive electrode and Li6PS5Cl solid-state electrolyte to form a battery.

[0032] As shown in Figure 2 , the physical diagram of the single-crystal lithium alloy prepared in the present embodiment, as shown in Figure 3 , the XRD diagram on the left shows that the lithium alloy foil prepared in the present embodiment is single-crystal,Figure 4 As shown in the left figure, the assembled battery is tested under 5C condition, and the capacity of the battery does not decay after 100 cycles.

[0033] Example 2

[0034] This embodiment relates to a single-crystal lithium alloy negative electrode preparation method, comprising:

[0035] S1: prepare a single-crystal lithium foil with a certain thickness A1, and prepare a lithiumophilic indium foil with a certain thickness A2; A1 / A2 = 5;

[0036] S2: overlap the single-crystal lithium foil and the lithiumophilic metal foil, and press at room temperature (25°C) by roller pressing to apply a pressure of 100 MPa to prepare a single-crystal lithium alloy foil;

[0037] S3: cut the single-crystal lithium alloy foil into a single-crystal lithium alloy negative electrode with a diameter of 10 mm.

[0038] The prepared single-crystal lithium alloy negative electrode is assembled with LFP as a polyanion positive electrode, 0.2M LiPF6, 0.2M LiBF4, and 0.8M LiDFOB dissolved in DEC:FEC = 2:1 Vol% electrolyte to form a battery.

[0039] The lithium alloy foil prepared in this embodiment is a single-crystal lithium-indium alloy with a thickness of 150 microns. The assembled battery is tested under 1C condition, and the capacity retention rate of the battery is 97% after 100 cycles.

[0040] Example 3

[0041] This embodiment relates to a single-crystal lithium alloy negative electrode preparation method, comprising:

[0042] S1: prepare a single-crystal lithium foil with a certain thickness A1, and prepare a lithiumophilic indium foil with a certain thickness A2; A1 / A2 = 2.

[0043] S2: overlap the single-crystal lithium foil and the lithiumophilic metal foil, and press at room temperature (25°C) by roller pressing to apply a pressure of 200 MPa to prepare a single-crystal lithium alloy foil;

[0044] S3: cut the single-crystal lithium alloy foil into a single-crystal lithium alloy negative electrode with a diameter of 10 mm.

[0045] The prepared single-crystal lithium alloy negative electrode is assembled with a sulfur positive electrode and Li6PS5Cl solid-state electrolyte to form a battery.

[0046] The lithium alloy foil prepared in this embodiment is a single-crystal lithium-indium alloy with a thickness of 50 microns. The assembled battery is tested under 0.3C condition, and the capacity retention rate of the battery is 92% after 100 cycles.

[0047] Example 4

[0048] This embodiment relates to a single-crystal lithium alloy negative electrode preparation method, comprising:

[0049] S1: prepare a single-crystal lithium foil with a certain thickness A1, and prepare a lithiumophilic zinc foil with a certain thickness A2; A1 / A2 = 15;

[0050] S2: overlap the single-crystal lithium foil and the lithiumophilic metal foil, and apply a pressure of 400 MPa at 50°C by vertical standing and pressing to prepare a single-crystal lithium alloy foil;

[0051] S3: cut the single-crystal lithium alloy foil into a single-crystal lithium alloy negative electrode with a diameter of 10 mm.

[0052] Assemble a battery with the prepared single-crystal lithium alloy negative electrode and NCM811 as an oxide positive electrode, Li7La3Zr2O 12 Solid-state electrolyte.

[0053] The lithium alloy foil prepared in this embodiment is a single-crystal lithium zinc alloy with a thickness of 150 microns, and the capacity retention rate of the battery is 99% after 100 cycles at 1C.

[0054] Example 5

[0055] This embodiment relates to a single-crystal lithium alloy negative electrode preparation method, comprising:

[0056] S1: prepare a single-crystal lithium foil with a certain thickness A1, and prepare a lithiumophilic aluminum foil with a certain thickness A2; A1 / A2 = 20;

[0057] S2: overlap the single-crystal lithium foil and the lithiumophilic metal foil, and apply a pressure of 500 MPa at 60°C by rolling and pressing to prepare a single-crystal lithium alloy foil;

[0058] S3: cut the single-crystal lithium alloy foil into a single-crystal lithium alloy negative electrode with a diameter of 10 mm.

[0059] Assemble a battery with the prepared single-crystal lithium alloy negative electrode and NCM811 as an oxide positive electrode, Li6PS5Cl solid-state electrolyte.

[0060] The lithium alloy foil prepared in this embodiment is a single-crystal lithium aluminum alloy with a thickness of 100 microns, and the capacity retention rate of the battery is 99% after 100 cycles at 3C.

[0061] Example 6

[0062] This embodiment relates to a single-crystal lithium alloy negative electrode preparation method, comprising:

[0063] S1: prepare a single-crystal lithium foil with a certain thickness A1, and prepare a lithiumophilic magnesium foil with a certain thickness A2; A1 / A2 = 20;

[0064] S2: overlap the single-crystal lithium foil and the lithiumophilic metal foil, and prepare a single-crystal lithium alloy foil by applying a pressure of 500 MPa at 120°C through vertical static pressing;

[0065] S3: cut the single-crystal lithium alloy foil into a single-crystal alloy negative electrode with a diameter of 10 mm.

[0066] Assemble a battery by using the prepared single-crystal lithium alloy negative electrode and NCM811 as an oxide positive electrode, and Li6PS5Cl solid-state electrolyte.

[0067] The lithium alloy foil prepared in this example is a single-crystal lithium magnesium alloy with a thickness of 180 microns, and the capacity retention rate of the battery is 98% after 100 cycles at 0.5C.

[0068] Example 7

[0069] This example relates to a single-crystal lithium alloy negative electrode preparation method, comprising:

[0070] S1: prepare a single-crystal lithium foil with a certain thickness A1, and prepare a lithiumophilic tin foil with a certain thickness A2; A1 / A2 = 30;

[0071] S2: overlap the single-crystal lithium foil and the lithiumophilic metal foil, and prepare a single-crystal lithium alloy foil by applying a pressure of 450 MPa at 150°C through vertical static pressing;

[0072] S3: cut the single-crystal lithium alloy foil into a single-crystal alloy negative electrode with a diameter of 10 mm.

[0073] Assemble a battery by using the prepared single-crystal lithium alloy negative electrode and NCM811 as an oxide positive electrode, and Li6PS5Cl solid-state electrolyte.

[0074] The lithium alloy foil prepared in this example is a single-crystal lithium magnesium alloy with a thickness of 120 microns, and the capacity retention rate of the battery is 99% after 100 cycles at 1C.

[0075] Comparative Example 1

[0076] This comparative example relates to a lithium alloy negative electrode preparation method, comprising:

[0077] S1: prepare a polycrystalline lithium foil with a certain thickness A1, and prepare a lithiumophilic indium foil with a certain thickness A2; A1 / A2 = 10;

[0078] S2: overlap the single-crystal lithium foil and the lithiumophilic metal foil, and prepare a single-crystal lithium alloy foil by applying a pressure of 500 MPa at 120°C through vertical static pressing;

[0079] S3: The lithium alloy foil was cut into lithium alloy negative electrodes with a diameter of 10 mm.

[0080] The prepared lithium alloy negative electrode was assembled into a battery with NCM811 as the oxide positive electrode and Li6PS5Cl solid-state electrolyte.

[0081] As shown in the right graph, the lithium alloy foil prepared in this comparative example was polycrystalline, and the thickness was 100 microns. Figure 3 As shown in the right graph, the capacity of the battery began to rapidly decay after 60 cycles at 5C. Figure 4 As shown in the right graph, the capacity of the battery began to rapidly decay after 60 cycles at 5C.

[0082] Comparative Example 2

[0083] This comparative example relates to a method for preparing a lithium alloy negative electrode, comprising:

[0084] S1: Prepare a polycrystalline lithium foil with a thickness A1, and prepare a lithiumophilic indium foil with a thickness A2; A1 / A2 = 10;

[0085] S2: Place the single-crystal lithium foil and the lithiumophilic metal foil on top of each other, and press them together at room temperature (25°C) by rolling, with a pressure of 100 MPa, and roll them back and forth 3 times to prepare a lithium alloy foil.

[0086] S3: Cut the lithium alloy foil into lithium alloy negative electrodes with a diameter of 10 mm.

[0087] The prepared lithium alloy negative electrode was assembled into a battery with LFP as the polyanion positive electrode and 0.2M LiPF6, 0.2M LiBF4, and 0.8M LiDFOB dissolved in DEC:FEC = 2:1 Vol% electrolyte.

[0088] The lithium alloy foil prepared in this comparative example was polycrystalline, with a thickness of 50 microns, and the capacity retention rate of the battery was 90% after 100 cycles at 1C.

[0089] Comparative Example 3

[0090] S1: In an argon-filled glove box, a lithium-magnesium alloy with a thickness of 200 microns and a lithium content of 27 wt.% was placed in a rolling machine.

[0091] S2: The temperature of the rolling machine was set to 100°C.

[0092] S3: The lithium-magnesium alloy in step S1 was rolled forward 3 times, with a deformation of 80%.

[0093] S4: The lithium-magnesium alloy in step S3 was placed in a muffle furnace and aged at 100°C for 1 hour.

[0094] S5: naturally cooled to room temperature to prepare a single-crystal lithium-magnesium alloy.

[0095] The prepared single-crystal lithium alloy negative electrode was assembled into a battery with NCM811 as an oxide positive electrode and Li6PS5Cl solid-state electrolyte.

[0096] The lithium alloy foil prepared in the example is a single-crystal lithium-magnesium alloy, and the capacity retention rate of the battery is 95% after 100 cycles at 0.5C.

[0097] The single-crystal lithium alloy negative electrode prepared in Example 1 and the lithium alloy negative electrode prepared in Comparative Example 1 were subjected to XRD characterization, as shown in Figure 3 The XRD patterns of the metal lithium alloys prepared in Example 1 and Comparative Example 1 show that the lithium alloy foil prepared in Example 1 is a single crystal, and the lithium alloy foil prepared in Comparative Example 1 is a polycrystal.

[0098] The single-crystal lithium alloy negative electrode prepared in Example 1 and the lithium alloy negative electrode prepared in Comparative Example 1 were assembled into batteries with LPSCl solid-state electrolyte and subjected to comparison at a 5C rate. As shown in Figure 2 The battery assembled with the single-crystal lithium alloy negative electrode prepared in Example 1 still did not decay in capacity after 100 cycles, and the battery assembled with the lithium alloy negative electrode prepared in Comparative Example 1 began to rapidly decay in capacity after 60 cycles, which shows that the single-crystal lithium alloy negative electrode exhibits more excellent stability, and the assembled battery also exhibits more excellent electrochemical performance.

[0099] The single-crystal lithium-magnesium alloy negative electrode prepared in Example 6 and the single-crystal lithium-magnesium alloy negative electrode prepared in Comparative Example 3 were assembled into batteries with LPSCl solid-state electrolyte and subjected to comparison at a 0.5C rate, and the capacity retention rate of the single-crystal lithium-magnesium alloy prepared by the method is higher than that of the single-crystal lithium-magnesium alloy prepared by the method provided in Comparative Example 3.

[0100] Compared with the prior art, the method is simple and easy to operate, and is not limited to the type of alloy. The single-crystal lithium alloy prepared by the direct single-pressing method has more outstanding capacity and more excellent cycle stability than the polycrystal lithium alloy and the single-crystal lithium alloy prepared by the prior art.

[0101] The above specific embodiments can be adjusted in different ways by those skilled in the art without departing from the principles and purposes of the present application, the protection scope of the present application is subject to the claims and is not limited by the above specific embodiments, and each implementation scheme within the scope is subject to the constraints of the present application.

Claims

1. A method for producing a single-crystal lithium alloy negative electrode, characterized by, The single crystal lithium foil and the lithiumophilic metal foil are stacked and pressed to realize the ordered diffusion of single crystal lithium atoms and lithiumophilic metal atoms, the thickness ratio of the single crystal lithium foil and the lithiumophilic metal foil and the pressure are controlled to realize the ordering and alloying of the atomic arrangement, and the single crystal alloy lithium foil is prepared, and the single crystal metal negative electrode is obtained after cutting; The thickness ratio of the single crystal lithium foil and the lithiumophilic metal foil is 0.1-50; The pressing is static pressing or rolling pressing perpendicular to the surface of the single crystal lithium foil and the lithiumophilic metal foil. The pressure range is 50-600 MPa.

2. The method for preparing a single-crystal lithium alloy anode according to claim 1, characterized in that, The lithiumophilic metal is indium, magnesium, zinc, aluminum or tin.

3. The method of claim 1, wherein the single-crystalline lithium alloy negative electrode is prepared by the steps of: preparing a single-crystalline lithium alloy negative electrode; and coating the single-crystalline lithium alloy negative electrode with a protective layer. The stacking means that the single crystal lithium foil and the lithiumophilic metal foil are stacked in an area overlapping manner to realize the uniform diffusion of atoms in the pressing process.

4. The method of claim 1, wherein the single-crystalline lithium alloy negative electrode is prepared by the steps of: preparing a single-crystalline lithium alloy negative electrode; and coating the single-crystalline lithium alloy negative electrode with a protective layer. The surface area of the single crystal lithium foil and the lithiumophilic metal foil is the same.

5. The method of claim 1, wherein the single-crystalline lithium alloy negative electrode is prepared by the steps of: preparing a single-crystalline lithium alloy negative electrode; and coating the single-crystalline lithium alloy negative electrode with a protective layer. The pressing temperature is 20-180 DEG C.

6. Use of a single-crystalline alloy lithium foil prepared according to the method of any one of claims 1 to 5, characterized in that After cutting, it is used to prepare the negative electrode of the metal lithium battery.

7. Use according to claim 6, characterized in that, The metal lithium battery uses electrolyte or solid electrolyte, wherein: The electrolyte is prepared by any one of the following methods: 1) 1M LiPF6 is dissolved in a mixed solution of EC:DEC=1:1 Vol%; 2) 10.2M LiPF6, 0.2M LiBF4, 0.8M LiDFOB is dissolved in a mixed solution of DEC: FEC=2:1 Vol%; 3) 1M LiTFSI is dissolved in a mixed solution of DME:DOL=1:1 Vol%. The solid-state electrolyte employs Li7La3Zr2O 12 Solid-state electrolyte, Li6PS5X, solid-state electrolyte, Li 10 GeP2S 12 Solid-state electrolyte, Li7P3S 11 Solid-state electrolyte, Li3InCl6 solid-state electrolyte or Li3YCl6 solid-state electrolyte, X = Cl, Br or I.

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