Preparation method and application of linear composite lithium metal negative electrode

Abstract

The application discloses a preparation method and application of a linear composite metal lithium negative electrode. The preparation method is characterized by the following steps: partially oxidizing a linear copper surface to improve the interface affinity of lithium and copper, so that molten lithium can be uniformly loaded on the linear copper surface; and loading the molten lithium on a flexible linear copper substrate, so that the mechanical strength, cycle stability and flexibility of lithium wire can be significantly improved. The linear composite metal lithium negative electrode is composed of a surface layer metal lithium and an inner layer linear copper to form a core-sheath structure. The inner layer linear copper has excellent electrical conductivity and mechanical properties, is beneficial to improving the electron transmission efficiency in the long axis direction of the lithium negative electrode, can provide a stable conductive framework for lithium deposition as a lithium carrier, effectively alleviates volume expansion and maintains interface stability, and improves the bending fatigue resistance of the metal lithium wire. When the linear composite metal lithium negative electrode is used in a fiber lithium battery, a fiber lithium-sulfur battery and a fiber lithium-air battery, the electrochemical activity and cycle stability can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery and fiber material, and particularly relates to a preparation method and application of a linear composite metal lithium negative electrode. BACKGROUND

[0002] Fiber battery is an indispensable important component in flexible wearable electronic devices, and has attracted extensive attention and research in recent years. Through literature and patent technology research, it is found that the current fiber battery is mainly a fiber lithium ion battery, i.e., the positive and negative electrodes are respectively lithium cobalt oxide and graphite fiber electrode with a deintercalation lithium mechanism, and the theoretical and actual energy densities are low, which is difficult to meet the long-lasting power supply of flexible wearable electronic devices.

[0003] The lithium metal negative electrode is considered as the first choice of high-energy devices matching wearable electronic devices due to its extremely high theoretical capacity, low electrochemical potential, and good flexibility. So far, there are few studies on linear lithium metal batteries, and most of them use pure metal lithium wire as the negative electrode, which will cause two problems: first, lithium dendrite growth leads to poor battery cycle stability. Second, the yield strength of pure lithium wire is low (<1 MPa), and it is easy to cause bending fatigue fracture under bending, which affects the stability of the battery. SUMMARY

[0004] The present application provides a preparation method and application of a linear composite metal lithium negative electrode, which is used to overcome the defects of poor battery cycle stability and easy bending fatigue fracture under bending in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of a linear composite metal lithium negative electrode, which comprises the following steps:

[0006] S1: heating treatment of linear copper in an oxidizing atmosphere to obtain surface-oxidized linear copper;

[0007] S2: under anhydrous and anaerobic conditions, heating and melting metal lithium into a liquid state, and then immersing the surface-oxidized linear copper into the liquid metal lithium to form a linear composite metal lithium negative electrode by compounding the liquid metal lithium and the linear copper.

[0008] To achieve the above-mentioned purpose, the present application also provides a linear composite metal lithium negative electrode prepared by the above-mentioned preparation method; the linear composite metal lithium negative electrode comprises a core-sheath structure of surface metal lithium and inner linear copper, and the metal lithium is loaded on the surface of the linear copper.

[0009] To achieve the above-mentioned purpose, the present application also provides an application of a linear composite metal lithium negative electrode, which applies the linear composite metal lithium negative electrode prepared by the above-mentioned preparation method or the above-mentioned linear composite metal lithium negative electrode in a lithium metal fiber battery, a lithium-sulfur fiber battery, and a lithium-air fiber battery.

[0010] Compared with the prior art, the present application has the following advantages:

[0011] 1、The preparation method of the linear composite metal lithium negative electrode provided by the present application improves the interfacial affinity of lithium and copper by partially oxidizing the surface of the linear copper, so that the molten lithium can be uniformly loaded on the surface of the linear copper; then loading the molten lithium on the flexible linear copper substrate can significantly improve the mechanical strength, cycle stability and flexibility of the lithium wire.

[0012] 2、The preparation method of the linear composite metal lithium negative electrode provided by the present application is simple and convenient, only including two steps of linear copper oxidation and molten lithium compounding, which is beneficial to large-scale preparation of linear metal lithium negative electrode.

[0013] 3、Compared with pure metal lithium wire, the linear composite metal lithium negative electrode provided by the present application has a thickness of the surface lithium layer that is easy to control, and a lithium wire density that is much lower than that of pure metal lithium wire, which can effectively improve the utilization rate of metal lithium.

[0014] 4、The linear composite metal lithium negative electrode provided by the present application is composed of a surface metal lithium and an inner layer linear copper to form a core-sheath structure, the inner layer linear copper has excellent electrical conductivity and mechanical properties, which is beneficial to improving the electron transport efficiency in the long axis direction of the lithium negative electrode, and can provide a stable conductive framework for lithium deposition as a lithium carrier, effectively relieving the volume expansion and maintaining the interface stability, and improving the bending fatigue resistance of the metal lithium wire. When the linear composite metal lithium negative electrode is used in fiber lithium batteries, fiber lithium-sulfur batteries and fiber lithium-air batteries, the electrochemical activity and cycle stability can be effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0016] Figure 1 A front view of the scanning electron microscope (SEM) of the linear composite metal lithium negative electrode prepared in Example 1 of the present application;

[0017] Figure 2 A cross-sectional view of the scanning electron microscope (SEM) of the linear composite metal lithium negative electrode prepared in Example 1 of the present application;

[0018] Figure 3 An optical photograph of the linear composite metal lithium negative electrode prepared in Example 1 of the present application;

[0019] Figure 4Optical photo of the bending state of the linear composite metal lithium negative electrode prepared in Example 1 of the present application;

[0020] Figure 5 Mechanical bearing test photo of the linear composite metal lithium negative electrode prepared in Example 1 of the present application;

[0021] Figure 6 Charge-discharge curve diagram of the fiber battery assembled by the linear composite metal lithium negative electrode prepared in Example 1 of the present application;

[0022] Figure 7 Photo of the LED light lit in the twisted state of the fiber battery assembled by the linear composite metal lithium negative electrode prepared in Example 1 of the present application.

[0023] The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0025] In addition, the technical solutions in the embodiments of the present application can be combined with each other, but it must be based on that a person of ordinary skill in the art can realize. When the combination of the technical solutions appears contradictory or unachievable, it should be considered that the combination of the technical solutions does not exist, and is not within the protection scope required by the present application.

[0026] Unless otherwise specified, the medicines / reagents used are commercially available.

[0027] The present application proposes a preparation method of a linear composite metal lithium negative electrode, comprising the following steps:

[0028] S1: heating treatment of linear copper under an oxidizing atmosphere to obtain surface-oxidized linear copper;

[0029] S2: under anhydrous and anaerobic conditions, heating and melting metal lithium into a liquid state, and then immersing the surface-oxidized linear copper into the liquid metal lithium to form a linear composite metal lithium negative electrode by compounding the liquid metal lithium and the linear copper.

[0030] Preferably, in step S1, the linear copper is copper wire or copper wire yarn.

[0031] Preferably, in step S1, the copper wire yarn is prepared by twisting a plurality of copper wires of the same diameter or different diameters, and the number of copper wires is 2-500.

[0032] Preferably, the diameter of the linear copper is 30-1000 μm.

[0033] Preferably, in step S1, the oxidizing atmosphere is air or oxygen.

[0034] Preferably, in step S1, the heating treatment is performed at a temperature of 300-600 ℃ for 1-120 min. The suitable heating temperature and heating time help to form a uniform oxide layer on the surface of the linear copper.

[0035] Preferably, in step S2, the temperature for heating and melting into a liquid state is 200-400 ℃. The suitable atmosphere helps to protect the safety of the molten lithium. The suitable lithium melting temperature helps to uniformly composite the liquid lithium with the linear copper.

[0036] The application also provides a linear composite lithium metal negative electrode prepared by the above preparation method; the linear composite lithium metal negative electrode has a core-sheath structure composed of a surface layer of lithium metal and an inner layer of linear copper, and the lithium metal is loaded on the surface of the linear copper.

[0037] The linear composite lithium metal negative electrode has a one-dimensional fiber structure.

[0038] Preferably, the diameter of the linear composite lithium metal negative electrode is 50-2000 μm; the diameter of the linear copper is 30-500 μm; and the thickness of the lithium metal is 5-500 μm.

[0039] The application also provides an application of the linear composite lithium metal negative electrode, which is prepared by the above preparation method or is applied in a lithium metal fiber battery, a lithium-sulfur fiber battery and a lithium-air fiber battery.

[0040] The linear composite lithium metal negative electrode has the characteristics of easy adjustment of fiber diameter, uniform thickness of the lithium layer on the surface, good mechanical strength and excellent electrical conductivity, and has a wide application prospect in fiber lithium batteries, fiber lithium-sulfur batteries and fiber lithium-air batteries.

[0041] Example 1

[0042] The linear composite lithium metal negative electrode has a one-dimensional fiber structure, and the lithium metal is uniformly loaded on the surface of the copper wire yarn; the diameter of the linear composite lithium metal negative electrode is 100-250 μm; the diameter of the copper wire yarn is 100-180 μm; the copper wire yarn has a spiral structure formed by twisting a plurality of copper wires; and the thickness of the lithium layer is 100-300 μm.

[0043] This invention also proposes a method for preparing the above-mentioned linear composite lithium metal anode, comprising the following steps:

[0044] (1) Five copper wires with a diameter of 50μm are evenly wound around a copper wire with a diameter of 100μm to form a copper wire yarn. The yarn is placed in a muffle furnace and heated to 400℃ in an air atmosphere for 20 minutes. After cooling, gray copper wire is obtained.

[0045] (2) Under the protection of the glove box, take an appropriate amount of lithium sheet and heat it to 300°C on the heater until the lithium melts into liquid. Immerse the gray copper wire into the liquid lithium, and gradually pull it out to cool it, to obtain a silvery white linear composite metal lithium anode.

[0046] like Figure 1 and 2 The images shown are SEM front view and cross-sectional view of the linear composite lithium metal anode prepared in this embodiment. As can be seen from the SEM front view, the diameter of the linear composite lithium metal anode prepared in this embodiment is about 200 μm. As can be seen from the SEM cross-sectional view, copper wires of different diameters are distributed in the core, and the outer layer is covered with lithium metal.

[0047] Figure 3 , Figure 4 The images shown are optical photographs of the linear composite lithium metal anode prepared in this embodiment. It can be seen that the linear composite lithium metal anode has a uniform overall diameter, is easy to bend, and has good flexibility.

[0048] Figure 5 Mechanical load-bearing tests on the linear composite lithium metal anode prepared in this embodiment show that the linear composite lithium anode can easily bear a 100g weight, and its mechanical strength can reach 30MPa, which is far higher than the 1MPa of pure lithium wire.

[0049] The linear composite lithium metal anode prepared in this embodiment can be used as a fiber battery anode. Lithium cobalt oxide or NCM811 cathode slurry is dipped onto the surface of aluminum wire and dried to serve as a fiber cathode. A polymer separator is uniformly wound around the fiber cathode, which serves as the fiber lithium anode. The fiber battery is assembled with the fiber cathode wound with the separator in a drying chamber. The fiber battery is inserted into a heat shrink tubing, with aluminum and copper wires led out from both ends, and electrolyte is injected. The heat shrink tubing is heated and shrunk, and then sealed at both ends to obtain a fiber lithium battery, which is then subjected to charge and discharge tests.

[0050] Figure 6 The charge-discharge curves of the fiber battery assembled with the linear composite lithium metal anode and NCM811 fiber cathode prepared for the example are shown at a 0.1C rate. The charging specific capacity is 215 mAh / g, the discharging specific capacity is 195 mAh / g, and the coulombic efficiency is 90.7%, exhibiting excellent capacity performance.

[0051] Figure 7 The photos of the assembled fiber battery lighting up the LED in a twisted state show that the linear composite metal lithium negative electrode has excellent bending resistance.

[0052] Embodiment 2

[0053] The linear composite metal lithium negative electrode provided in the embodiment has a one-dimensional fiber structure, and metal lithium is uniformly loaded on the surface of the copper wire; the linear composite metal lithium negative electrode has a diameter of 60-800 μm; the copper wire has a diameter of 50-500 μm; and the metal lithium layer has a thickness of 10-300 μm.

[0054] The present application also provides a preparation method of the linear composite metal lithium negative electrode, comprising the following steps:

[0055] (1) the copper wire with a diameter of 200 μm is placed in a muffle furnace and heated to 500 ℃ under air atmosphere for 60 min, and the black copper wire is obtained after cooling;

[0056] (2) under the protection of a glove box, a proper amount of lithium sheet is heated to 300 ℃ on a heater until the lithium is melted into a liquid state, the gray copper wire is immersed in the liquid lithium, and the silver-white linear composite metal lithium negative electrode is obtained by gradually pulling out and cooling.

[0057] Embodiment 3

[0058] The linear composite metal lithium negative electrode provided in the embodiment has a one-dimensional fiber structure, and metal lithium is uniformly loaded on the surface of the copper wire; the linear composite metal lithium negative electrode has a diameter of 60-800 μm; the copper wire has a diameter of 50-500 μm; and the metal lithium layer has a thickness of 10-300 μm.

[0059] The present application also provides a preparation method of the linear composite metal lithium negative electrode, comprising the following steps:

[0060] (1) the copper wire with a diameter of 200 μm is placed in a muffle furnace and heated to 500 ℃ under air atmosphere for 60 min, and the black copper wire is obtained after cooling;

[0061] (2) under the protection of a glove box, a proper amount of lithium sheet is heated to 300 ℃ on a heater until the lithium is melted into a liquid state, the gray copper wire is immersed in the liquid lithium, and the silver-white linear composite metal lithium negative electrode is obtained by gradually pulling out and cooling.

[0062] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural changes made according to the content of the present application specification and drawings, or direct / indirect application in other related technical fields, are included in the patent protection scope of the present application.

Claims

1. A method for producing a wire-shaped composite lithium metal negative electrode, characterized by, The preparation method comprises the following steps: S1: heating treatment of linear copper under an oxidizing atmosphere to obtain surface-oxidized linear copper; S2: under anhydrous and oxygen-free conditions, heating and melting metal lithium into a liquid state, and then immersing the surface-oxidized linear copper into the liquid metal lithium to form a linear composite metal lithium negative electrode by compounding the liquid metal lithium and the linear copper; The linear composite metal lithium negative electrode comprises a core-sheath structure of surface-layer metal lithium and inner-layer linear copper, and the metal lithium is loaded on the surface of the linear copper; the thickness of the metal lithium is 5-500 mm.

2. The production method according to claim 1, wherein In step S1, the linear copper is copper wire or copper wire yarn.

3. The production method according to claim 2, wherein In step S1, the copper wire yarn is prepared by winding and twisting a plurality of copper wires with the same diameter or different diameters, and the number of copper wires is 2-500.

4. The production method according to any one of claims 1 to 3, wherein The diameter of the linear copper is 30-1000 mm.

5. The production method according to claim 1, wherein In step S1, the oxidizing atmosphere is air or oxygen.

6. The production method according to claim 1, wherein In step S1, the temperature of the heating treatment is 300-600 ℃, and the time is 1-120 min.

7. The production method according to claim 1, wherein In step S2, the temperature of the heating and melting into a liquid state is 200-400 ℃.

8. A wire-shaped composite lithium metal anode, characterized by, The linear composite metal lithium negative electrode is prepared by the preparation method in any one of claims 1-7.

9. The wire-shaped composite metal lithium negative electrode according to claim 8, wherein The diameter of the linear composite metal lithium negative electrode is 50-2000 mm, and the diameter of the linear copper is 30-500 mm.

10. Use of a wire-shaped composite metal lithium negative electrode, characterized in that The linear composite metal lithium negative electrode prepared by the preparation method in any one of claims 1-7 or the linear composite metal lithium negative electrode in claim 8 or 9 is applied in a lithium metal fiber battery, a lithium-sulfur fiber battery and a lithium-air fiber battery.

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