Flexible lithium metal negative electrode framework material as well as preparation method and application thereof

Abstract

The invention discloses a flexible lithium metal negative electrode framework material and a preparation method and application thereof, and belongs to the field of lithium metal battery materials, and the framework material is a nickel oxide modified three-dimensional carbon fiber framework; the nickel oxide particles are uniformly anchored in the three-dimensional carbon fiber frame, and the interior of the three-dimensional carbon fiber frame is communicated and is three-dimensionally porous; according to the preparation method, firstly, hydrochloric acid is used for cleaning and acidifying a carbon fiber skeleton, then a three-electrode method is used for electro-deposition of a metal nickel layer on the surface of the carbon fiber skeleton, finally, carbon fibers covered with the metal nickel layer are subjected to heat treatment to generate nickel oxide nano-particles, and the nickel oxide nano-particles have good flexibility and machining performance. The flexible lithium metal negative electrode loaded with the lithium metal is light in weight, high in energy density and large in specific surface area, and can adapt to severe volume change in the cycle process, so that the coulombic efficiency of the lithium metal negative electrode is improved, and the cycle life of the lithium metal negative electrode is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of lithium metal battery materials, and in particular to a flexible lithium metal negative electrode skeleton material and a preparation method and application thereof. Background Art

[0002] The rapid development of electric vehicles and portable electronics has placed higher demands on the energy density of secondary batteries. Lithium metal anodes have a theoretical specific capacity of up to 3860 mAh / g, 10 times that of graphite, and possess an extremely low electrode potential (-3.04 V vs. standard hydrogen electrode). They are considered the "holy grail" electrode for next-generation high-energy-density batteries. However, during cycling, uneven deposition / dissolution of lithium metal leads to dendrite growth, resulting in a decrease in battery capacity and even safety hazards such as fire and explosion. Three-dimensional current collectors with large specific surface areas can effectively reduce local current density and thus delay the onset of dendrites. Furthermore, current collectors loaded with lithiophilic substances can effectively induce lithium nucleation and growth, thereby promoting uniform lithium deposition. However, during actual cycling, the large volume changes caused by lithium deposition / dissolution lead to electrode interface instability, inducing dendrite formation. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to solve the problems in the prior art of poor energy density, cycle performance and service life of lithium metal batteries caused by stress changes and dendrite growth caused by the deposition and stripping process of the metal lithium negative electrode, the present invention provides a flexible lithium metal negative electrode skeleton material and its preparation method and application.

[0004] The technical solution adopted by the present invention to solve its technical problems is: the present invention provides a flexible lithium metal negative electrode skeleton material, wherein the skeleton material is a three-dimensional carbon fiber framework modified with nickel oxide; the fiber diameter of the framework is 5-20 μm, and the nickel oxide particles are evenly anchored in the three-dimensional carbon fiber framework, and the three-dimensional carbon fiber framework is internally connected and three-dimensionally porous.

[0005] The present invention also provides a method for preparing a flexible lithium metal negative electrode skeleton material, comprising the following steps:

[0006] S1: The three-dimensional carbon fiber frame is ultrasonically cleaned with anhydrous ethanol and deionized water respectively, and then dried. The cleaned and dried three-dimensional carbon fiber frame is then placed in concentrated hydrochloric acid for surface etching;

[0007] S2: placing the etched three-dimensional carbon fiber frame into a nickel electroplating electrolyte to perform electrodeposition of a metal nickel layer;

[0008] S3: The three-dimensional carbon fiber framework deposited with a metal nickel layer is washed multiple times with deionized water and vacuum dried, and finally nickel oxide particles are obtained by heat treatment to obtain a flexible lithium metal negative electrode skeleton material.

[0009] Furthermore, in step S1, the concentration of the concentrated hydrochloric acid is 45 wt.%-75 wt.%, and the etching time is 0.5-3 hours.

[0010] Furthermore, in step S2, the nickel electroplating electrolyte includes but is not limited to nickel sulfate hexahydrate, nickel chloride, citric acid, saccharin, sodium dodecyl sulfate, butynediol and boric acid.

[0011] Furthermore, in step S2, the electrodeposition is a three-electrode method using a constant potential discharge method with a current density of 0.1-0.5 A / cm2, and the deposition time of the metal nickel layer is 10-60 min.

[0012] Furthermore, in step S3, the vacuum drying is carried out at a temperature of 55-140° C. and for a time of 2-5 hours.

[0013] Furthermore, in step S3, the heat treatment is performed in air at a temperature of 300-600°C.

[0014] Furthermore, in step S3, the heating rate of the heat treatment is 5-10°C / min, and the holding time is 1-4 hours.

[0015] The present invention also provides an application of a flexible lithium metal negative electrode skeleton material, wherein the flexible lithium metal negative electrode skeleton material is used to prepare a lithium metal composite negative electrode by a melting method or an electrodeposition method; the melting temperature of the melting method is 180-300°C, and the preparation time is 1-3 minutes.

[0016] Beneficial effects of the present invention:

[0017] (1) The flexible lithium metal negative electrode skeleton material of the present invention can be used as a substrate for loading lithium metal, and can also be used as a current collector for electrodepositing lithium metal to prepare a composite lithium metal negative electrode;

[0018] (2) The flexible lithium metal negative electrode skeleton material of the present invention has good flexibility and mechanical processing properties, which can alleviate the volume expansion of the lithium negative electrode during the cycle and maintain the original size during the cycle;

[0019] (3) The flexible lithium metal negative electrode skeleton material of the present invention can be used at up to 10mA / cm 2 The current density was maintained at 200 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and examples.

[0021] Figure 1This is an SEM image of the flexible three-dimensional carbon fiber skeleton prepared in step S3 of Example 1;

[0022] Figure 2 XRD patterns of the original carbon fiber, nickel-loaded carbon fiber, nickel oxide-loaded carbon fiber, and flexible carbon fiber three-dimensional metal lithium composite negative electrode prepared in Example 1;

[0023] Figure 3 This is an SEM image of the flexible carbon fiber three-dimensional lithium metal composite negative electrode prepared in Example 1;

[0024] Figure 4 This is a comparison chart of the cycle performance of a lithium metal battery using the composite metal lithium negative electrode prepared in Example 1 as the negative electrode and a lithium metal battery using a lithium sheet as the negative electrode;

[0025] Figure 5 This is an SEM image of the flexible carbon fiber three-dimensional metal lithium composite negative electrode prepared in Comparative Example 1;

[0026] Figure 6 This is an SEM image of the flexible carbon fiber three-dimensional metal lithium composite negative electrode prepared in Comparative Example 2;

[0027] Figure 7 This is a structural diagram of the flexible lithium metal negative electrode skeleton material. DETAILED DESCRIPTION

[0028] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0029] In the description of the present invention, it should be understood that the terms "upper", "lower", "horizontal", "top", "inside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] In the description of the present invention, it should be noted that, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, it can mean fixed connection, detachable connection, or integral connection; it can mean mechanical connection or electrical connection; it can mean direct connection or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0031] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0032] Example 1

[0033] A method for preparing a flexible lithium metal negative electrode skeleton material comprises the following steps:

[0034] S1: The three-dimensional carbon fiber frame was ultrasonically cleaned with anhydrous ethanol and deionized water respectively, and then dried. The cleaned and dried three-dimensional carbon fiber frame was then placed in 45% concentrated hydrochloric acid for surface etching for 5 minutes;

[0035] S2: The etched three-dimensional carbon fiber frame was placed in a nickel electroplating electrolyte containing nickel sulfate hexahydrate (150 g / L), nickel chloride (45 g / L), boric acid (40 g / L), citric acid (10 g / L), sodium dodecyl sulfate (1.5 g / L), and butynediol (0.5 g / L) at a current density of 0.25 A / cm 2 , carry out metal nickel layer electrodeposition, the deposition time is 30min;

[0036] S3: The three-dimensional carbon fiber framework with the nickel layer deposited thereon was washed several times with deionized water and vacuum-dried at 80°C for 2 hours. Finally, the framework was heat-treated at a temperature of 500°C at a heating rate of 10°C / min for 2 hours to obtain nickel oxide particles.

[0037] In a glove box, metallic lithium was heated at 200°C to a molten state, and a three-dimensional carbon fiber framework loaded with nickel oxide nanoparticles was immersed in the molten metallic lithium to prepare a flexible metallic lithium composite negative electrode.

[0038] like Figure 1 As shown, the SEM image of the flexible lithium metal negative electrode skeleton material prepared in step S3 above;

[0039] like Figure 2 As shown in the figure, the XRD patterns of the original carbon fiber, loaded with metallic nickel, loaded with nickel oxide, and the flexible carbon fiber metal lithium composite negative electrode prepared in this embodiment show that after electrodeposition, characteristic peaks of metallic nickel appear at 44.6°, 51.9°, and 76.4°, respectively, corresponding to the (101), (111), and (220) crystal planes of Ni, respectively. After heat treatment, characteristic peaks of nickel oxide appear at 37.5°, 43.6°, and 63.1°, corresponding to the (101), (102), and (110) crystal planes of NiO, respectively.

[0040] Figure 3 This is an SEM image of the flexible lithium metal composite negative electrode prepared in this example;

[0041] Figure 4 The cycle performance comparison chart of the lithium metal battery with the composite metal lithium negative electrode prepared in this embodiment as the negative electrode and the lithium metal battery with the lithium sheet as the negative electrode is shown in the figure. 2 Under high current density, the flexible composite metal lithium negative electrode can stably cycle 200 cycles and the cycle overpotential is stable at 40mA, while the lithium metal battery with lithium sheet as the negative electrode has a very large cycle overpotential (1.2V).

[0042] Example 2

[0043] A method for preparing a flexible lithium metal negative electrode skeleton material comprises the following steps:

[0044] S1: The three-dimensional carbon fiber frame was ultrasonically cleaned with anhydrous ethanol and deionized water respectively, and then dried. The cleaned and dried three-dimensional carbon fiber frame was then placed in 45% concentrated hydrochloric acid for surface etching for 5 minutes;

[0045] S2: The etched three-dimensional carbon fiber frame was placed in a nickel electroplating electrolyte containing nickel sulfate hexahydrate (150 g / L), nickel chloride (45 g / L), boric acid (40 g / L), citric acid (10 g / L), sodium dodecyl sulfate (1.5 g / L), and butynediol (0.5 g / L) at a current density of 0.25 A / cm 2 , carry out metal nickel layer electrodeposition, the deposition time is 30min;

[0046] S3: The three-dimensional carbon fiber framework with the nickel layer deposited thereon was washed several times with deionized water and vacuum-dried at 80°C for 2 hours. Finally, the framework was heat-treated at a heating rate of 10°C / min to a temperature of 450°C for 2 hours to obtain nickel oxide particles.

[0047] In a glove box, metallic lithium was heated at 200°C to a molten state, and a three-dimensional carbon fiber skeleton loaded with nickel oxide nanoparticles was immersed in the molten metallic lithium to prepare a flexible metallic lithium composite negative electrode.

[0048] Example 3

[0049] A method for preparing a flexible lithium metal negative electrode skeleton material comprises the following steps:

[0050] S1: The three-dimensional carbon fiber frame was ultrasonically cleaned with anhydrous ethanol and deionized water respectively, and then dried. The cleaned and dried three-dimensional carbon fiber frame was then placed in 45% concentrated hydrochloric acid for surface etching for 5 minutes;

[0051] S2: The etched three-dimensional carbon fiber frame is placed in a nickel electroplating electrolyte containing nickel sulfate hexahydrate (150 g / L), nickel chloride (45 g / L), boric acid (40 g / L), citric acid (10 g / L), sodium dodecyl sulfate (1.5 g / L) and butynediol (0.5 g / L) at a current density of 0.25 A / cm2 to perform metal nickel layer electrodeposition for 30 min.

[0052] S3: The three-dimensional carbon fiber framework with the nickel layer deposited thereon was washed several times with deionized water and vacuum-dried at 80°C for 2 hours. Finally, the framework was heat-treated at a temperature of 550°C at a heating rate of 10°C / min for 2 hours to obtain nickel oxide particles.

[0053] In a glove box, metallic lithium was heated at 200°C to a molten state, and a three-dimensional carbon fiber skeleton loaded with nickel oxide nanoparticles was immersed in the molten metallic lithium to prepare a flexible metallic lithium composite negative electrode.

[0054] Comparative Example 1

[0055] This comparative example provides a flexible lithium metal negative electrode skeleton material, a preparation method thereof, and an application thereof. Compared with Example 1, the electrodeposition time in step S2 of this comparative example is 15 minutes, and the other steps are the same as in Example 1; Figure 5 This is the SEM image of the flexible carbon fiber three-dimensional metal lithium composite negative electrode prepared in Comparative Example 1. When the electrodeposition time is short, the carbon fiber surface cannot be completely covered with metal nickel particles, and the distribution is relatively sparse, which results in no metal lithium attachment in local areas of the prepared composite metal lithium negative electrode.

[0056] Comparative Example 2

[0057] This comparative example provides a flexible lithium metal negative electrode skeleton material, a preparation method thereof, and an application thereof. Compared with Example 1, the electrodeposition time in step S2 of this comparative example is 60 minutes, and the other steps are the same as in Example 1; Figure 6 This is the SEM image of the flexible carbon fiber three-dimensional metal lithium composite negative electrode prepared in Comparative Example 2. When the electrodeposition time is longer, no area without metal nickel particles attached appears on the carbon fiber surface, but the number of nanoclusters on the carbon fiber surface increases, which causes the prepared composite metal lithium negative electrode to be coated with a large amount of metal lithium and can no longer display the original morphology of the carbon fiber skeleton.

[0058] In this specification, the schematic representations of the terms do not necessarily refer to the same embodiment. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments.

[0059] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A flexible lithium metal negative electrode skeleton material, characterized in that: The skeleton material is a three-dimensional carbon fiber frame modified with nickel oxide; the fiber diameter of the frame is 5-20 μm, the nickel oxide particles are evenly anchored in the three-dimensional carbon fiber frame, and the three-dimensional carbon fiber frame is internally connected and three-dimensionally porous.

2. The method for preparing a flexible lithium metal negative electrode skeleton material according to claim 1, characterized in that: The following steps are involved: S1: The three-dimensional carbon fiber frame is ultrasonically cleaned with anhydrous ethanol and deionized water respectively, and then dried. The cleaned and dried three-dimensional carbon fiber frame is then placed in concentrated hydrochloric acid for surface etching; S2: placing the etched three-dimensional carbon fiber frame into a nickel electroplating electrolyte to perform electrodeposition of a metal nickel layer; S3: The three-dimensional carbon fiber framework deposited with a metal nickel layer is washed multiple times with deionized water and vacuum dried, and finally nickel oxide particles are obtained by heat treatment to obtain a flexible lithium metal negative electrode skeleton material.

3. The method for preparing the flexible lithium metal negative electrode skeleton material according to claim 2, characterized in that: In the step S1, the concentration of the concentrated hydrochloric acid is 45 wt.%-75 wt.%, and the etching time is 0.5-3 hours.

4. The method for preparing a flexible lithium metal negative electrode skeleton material according to claim 2, wherein: In step S2, the nickel electroplating electrolyte includes but is not limited to nickel sulfate hexahydrate, nickel chloride, citric acid, saccharin, sodium dodecyl sulfate, butynediol and boric acid.

5. The method for preparing the flexible lithium metal negative electrode skeleton material according to claim 2, characterized in that: In step S2, the electrodeposition is carried out by a three-electrode method using a constant potential discharge method with a current density of 0.1-0.5 A / cm 2 The deposition time of the metal nickel layer is 10-60 minutes.

6. The method for preparing a flexible lithium metal negative electrode skeleton material according to claim 2, characterized in that: In step S3, the vacuum drying temperature is 55-140° C. and the time is 2-5 hours.

7. The method for preparing a flexible lithium metal negative electrode skeleton material according to claim 2, characterized in that: In step S3, the heat treatment is performed in air at a temperature of 300-600°C.

8. The method for preparing a flexible lithium metal negative electrode skeleton material according to claim 2, characterized in that: In step S3, the heating rate of the heat treatment is 5-10°C / min, and the holding time is 1-4 hours.

9. The use of the flexible lithium metal negative electrode skeleton material according to claim 1, characterized in that: The flexible lithium metal negative electrode skeleton material is used to prepare a lithium metal composite negative electrode through a melting method or an electrodeposition method.

10. The use of the flexible lithium metal negative electrode skeleton material according to claim 9, characterized in that: The melting temperature of the melting method is 180-300° C., and the preparation time is 1-3 minutes.

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