A negative electrode material, a preparation method thereof, a flexible negative electrode and a lithium-sulfur battery

Abstract

The present application relates to the technical field of battery, especially to a negative electrode material, a preparation method thereof, a flexible negative electrode and a lithium-sulfur battery. The negative electrode material provided by the present application comprises carbon fibers loaded with Co3O4 nanoparticles and a ZnO layer, and the ZnO layer wraps the carbon fibers loaded with Co3O4 nanoparticles. The flexible self-supporting negative electrode material of the present application has a three-dimensional network structure interlaced with each other; wherein the carbon fibers are used as a three-dimensional conductive framework to provide a stable and large lithium storage space; the Co3O4 on the surface of the carbon fibers which is lithiumophilic and the ZnO which is super-lithiophilic form a lithiumophilic gradient, and jointly act on the deposition of metal lithium to induce uniform lithium deposition and realize the inhibition effect on the growth of negative electrode lithium dendrites. The flexible negative electrode prepared by using the negative electrode material of the present application is used in a lithium-sulfur battery, which effectively improves the capacity and cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a negative electrode material and its preparation method, a flexible negative electrode, and a lithium-sulfur battery. Background Technology

[0002] With the development of efficient and clean energy storage systems, battery energy storage systems need to achieve higher energy density, cycle life, and safety. Lithium-sulfur (Li-S) batteries, which use sulfur as the active material, have high theoretical material specific capacity and theoretical battery specific energy. Lithium-sulfur batteries, in which abundant sulfur is combined as the positive electrode with a high-energy lithium metal anode, are attracting increasing attention.

[0003] A lithium-sulfur battery typically consists of four parts: a sulfur cathode, a separator, an electrolyte, and a lithium metal anode. The battery releases energy through a redox reaction between the lithium (Li) metal anode and the sulfur (S) cathode. Lithium metal is oxidized at the anode to produce lithium ions and electrons, which then travel through the electrolyte and an external circuit to the sulfur cathode, respectively. During discharge, there is a two-step discharge process at the cathode. In the initial state, sulfur is reduced from octasulfide (S8) to liquid long-chain lithium polysulfide (Li2S) at a voltage plateau around 2.3V. n (4≤n≤8), which corresponds to the first voltage plateau in the discharge curve. Subsequently, these soluble lithium polysulfides are further reduced to solid-state Li2S2 / Li2S at a voltage plateau near 2.1V, which corresponds to the second voltage plateau in the discharge curve.

[0004] Currently, there are still some problems in the commercial application of lithium-sulfur batteries: the "shuttle effect" of soluble lithium polysulfides (LiPS) and the slow kinetics of sulfur redox conversion; and the formation of dendritic lithium due to uneven deposition of lithium on the negative electrode side.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this invention is to provide a negative electrode material that can effectively regulate lithium metal deposition, induce uniform lithium deposition, and thereby suppress the growth of lithium dendrites in the negative electrode.

[0007] The second objective of this invention is to provide a method for preparing the negative electrode material as described above.

[0008] The third objective of this invention is to provide a flexible negative electrode with excellent conductivity and mechanical properties, which improves the volume expansion of the electrode before and after charging and discharging and inhibits the growth of lithium dendrites.

[0009] The fourth objective of this invention is to provide a lithium-sulfur battery with high capacity and excellent cycle performance.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0011] The present invention provides a negative electrode material comprising carbon fibers loaded with Co3O4 nanoparticles and a ZnO layer, wherein the ZnO layer encapsulates the carbon fibers loaded with Co3O4 nanoparticles.

[0012] Furthermore, in the negative electrode material, the mass ratio of carbon fiber, Co3O4 and ZnO is 1:(0.1~800):(1~50).

[0013] Furthermore, the thickness of the ZnO layer is 50–300 nm.

[0014] Preferably, the Co3O4 nanoparticles have a particle size of 30–200 nm.

[0015] The present invention also provides a method for preparing the negative electrode material as described above, comprising the following steps:

[0016] S1. The spinning solution is subjected to electrospinning, carbonization and oxidation treatment in sequence to obtain carbon fibers loaded with Co3O4 nanoparticles; the spinning solution includes cobalt salt, carbon nanotubes, polymethyl methacrylate and polyacrylonitrile.

[0017] S2. ZnO is deposited on the surface of the carbon fiber loaded with Co3O4 nanoparticles to obtain the negative electrode material.

[0018] Further, in step S1, the mass percentage of the cobalt salt in the spinning solution is 2% to 11%.

[0019] Preferably, the cobalt salt includes at least one of cobalt acetate, cobalt oxalate, and cobalt nitrate.

[0020] Further, in step S1, the carbon nanotubes in the spinning solution have a mass percentage of 0.01% to 2%.

[0021] Preferably, the polymethyl methacrylate in the spinning solution is 2% to 11% by mass.

[0022] Preferably, the polyacrylonitrile in the spinning solution has a mass percentage of 2% to 11%.

[0023] Further, in step S1, the carbonization treatment includes: holding at 120-180°C for 0.5-1.5 hours in an inert atmosphere, then raising the temperature to 200-300°C and holding for 0.5-1.5 hours, then raising the temperature to 600-700°C and holding for 0.5-1.5 hours, and then cooling.

[0024] Further, in step S1, the oxidation treatment includes: holding at 280–350°C for 1–6 hours in an air atmosphere.

[0025] Preferably, in step S2, the deposition method includes vapor deposition.

[0026] The present invention also provides a flexible negative electrode, comprising a spinning fiber layer and a lithium metal layer disposed on the surface of the spinning fiber layer;

[0027] The spun fiber layer includes the negative electrode material as described above or the negative electrode material prepared by the method described above.

[0028] The present invention also provides a lithium-sulfur battery, comprising the flexible negative electrode as described above.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The flexible self-supporting negative electrode material of the present invention has a conductive three-dimensional network structure formed by interlaced fibers, which improves the mechanical properties of the negative electrode material. The robust three-dimensional network structure can effectively reduce the volume expansion of the electrode before and after charging and discharging.

[0031] In the anode material, carbon fiber serves as a three-dimensional conductive framework, providing a stable and large lithium storage space. Then, the surface of the carbon fiber is chemically modified to form a lithium-affinity gradient formed by the interaction of ZnO and Co3O4. The lithium-affinity gradient consists of lithium-affinity Co3O4 and superlithiophilic ZnO, which work together to deposit metallic lithium, induce uniform lithium deposition, and inhibit the growth of lithium dendrites in the anode. This can effectively reduce the local current on the surface of the anode material during the electroplating and stripping process, making the lithium ion distribution more uniform.

[0032] The negative electrode material of this invention is used in the negative electrode of lithium-sulfur batteries, which effectively improves the battery capacity and cycle performance. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 The X-ray diffraction pattern of ZnO-Co3O4@CNF prepared in Example 1 of this invention.

[0035] Figure 2 This is a scanning electron microscope image of ZnO-Co3O4@CNF prepared in Example 1 of the present invention.

[0036] Figure 3 This is a graph showing the cycle capacity of a lithium-sulfur battery prepared using the flexible negative electrode of Example 1 at 1C. Detailed Implementation

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0038] The following provides a detailed description of an anode material, its preparation method, a flexible anode, and a lithium-sulfur battery according to embodiments of the present invention.

[0039] In some embodiments of the present invention, a negative electrode material is provided, comprising carbon fibers loaded with Co3O4 nanoparticles and a ZnO layer, wherein the ZnO layer encapsulates the carbon fibers loaded with Co3O4 nanoparticles.

[0040] The negative electrode material of this invention is a flexible self-supporting negative electrode material, which is named ZnO-Co3O4@CNF.

[0041] The negative electrode material of the present invention has a conductive three-dimensional network structure formed by interlaced fibers, which provides good mechanical strength and improves the mechanical properties of the negative electrode material. The robust three-dimensional network structure can effectively improve the inherent defect of volume expansion of the electrode before and after charging and discharging.

[0042] The strong concentration gradient of the electrolyte causes uneven lithium deposition on the negative electrode side, forming dendritic lithium. Lithium dendrites grow very rapidly under high current densities. The negative electrode material provided by this invention can effectively control lithium metal deposition, achieving uniform lithium deposition.

[0043] In the anode material, carbon fiber serves as a three-dimensional conductive framework, providing a stable and large lithium storage space. The carbon fiber surface is then chemically modified, with Co3O4 nanoparticles loaded onto it. A ZnO layer is then applied to the surface of the Co3O4-loaded carbon fiber, creating a lithiophilic gradient. This gradient, composed of lithiophilic Co3O4 and superlithiophilic ZnO, works together to promote lithium deposition, inducing uniform lithium deposition and providing more active sites. This inhibits the growth of lithium dendrites in the anode material. Furthermore, it effectively reduces the local current on the anode material surface during electroplating and stripping, resulting in a more uniform lithium ion distribution.

[0044] In some embodiments of the present invention, the mass ratio of carbon fiber, Co3O4 and ZnO in the negative electrode material is 1:(0.1 to 800):(1 to 50). Typical but not limiting examples include, for instance, the mass ratio of carbon fiber to Co3O4 in the negative electrode material can be 1:0.1, 1:5, 1:20, 1:50, 1:100, 1:150, 1:200, 1:300, 1:400, 1:500, 1:600, 1:700 or 1:800, etc.; and the mass ratio of carbon fiber to ZnO can be 1:1, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50, etc.

[0045] In some embodiments of the present invention, the thickness of the ZnO layer is 50 to 300 nm; typically, but not limitingly, for example, the thickness of the ZnO layer can be a range of 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm or any combination thereof; preferably, the thickness of the ZnO layer is 170 to 210 nm.

[0046] In the anode material of the present invention, if the thickness of the ZnO layer is too small or too large, the material’s lithium affinity will decrease and the effect of inhibiting the growth of dendritic lithium will be worse; if the content of Co3O4 is too small or too large, the spinning fiber will have poor toughness.

[0047] In some embodiments of the present invention, the particle size of the Co3O4 nanoparticles is 30 to 200 nm; typically, but not limitingly, for example, the particle size of the Co3O4 nanoparticles is 30 nm, 50 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, 170 nm, 190 nm or 200 nm, etc.

[0048] In some embodiments of the invention, the diameter of the carbon fiber is 1.2 to 1.8 μm; typically, but not limitingly, the diameter of the carbon fiber is 1.2 μm, 1.4 μm, 1.6 μm or 1.8 μm, etc.

[0049] In some embodiments of the present invention, a method for preparing the above-mentioned negative electrode material is also provided, comprising the following steps:

[0050] S1. The spinning solution is subjected to electrospinning, carbonization and oxidation treatment in sequence to obtain carbon fibers loaded with Co3O4 nanoparticles; the spinning solution includes cobalt salt, carbon nanotubes, polymethyl methacrylate and polyacrylonitrile.

[0051] S2. ZnO is deposited on the surface of carbon fibers loaded with Co3O4 nanoparticles to obtain the negative electrode material.

[0052] This invention first electrospins the spinning solution to obtain a nanofiber film, then performs carbonization treatment to obtain a high-toughness nanofiber film loaded with elemental cobalt, then oxidizes the elemental Co to Co3O4 to obtain a carbon fiber film loaded with Co3O4 nanoparticles (Co3O4@CNF), and finally deposits ZnO on the surface to obtain the negative electrode material (ZnO-Co3O4@CNF).

[0053] In some embodiments of the present invention, in step S1, the mass percentage of cobalt salt in the spinning solution is 2% to 11%; typically, but not limitingly, for example, the mass percentage of cobalt salt in the spinning solution is 2%, 4%, 6%, 8%, 10%, or any combination thereof. Preferably, the mass percentage of cobalt salt in the spinning solution is 8% to 11%.

[0054] In some embodiments of the present invention, in step S1, the cobalt salt includes at least one of cobalt acetate, cobalt oxalate, and cobalt nitrate.

[0055] In some embodiments of the present invention, in step S1, the mass percentage of carbon nanotubes in the spinning solution is 0.01% to 2%; the mass percentage of cobalt salt in the spinning solution is 0.01%, 0.1%, 0.3%, 0.5%, 0.7%, 1%, 1.4%, 1.6%, 2%, or any combination thereof. Preferably, the mass percentage of carbon nanotubes in the spinning solution is 1% to 2%.

[0056] In some specific embodiments of the present invention, carbon nanotubes include multi-walled carbon nanotubes.

[0057] This invention enhances the electrical conductivity of materials by adding carbon nanotubes.

[0058] In some embodiments of the invention, in step S1, the mass percentage of polymethyl methacrylate (PMMA) in the spinning solution is 2% to 11%; typically, but not limitingly, for example, the mass percentage of PMMA in the spinning solution is 2%, 4%, 6%, 8%, 10%, or any combination thereof. Preferably, the mass percentage of PMMA in the spinning solution is 8% to 11%.

[0059] In some embodiments of the invention, in step S1, the mass percentage of polyacrylonitrile in the spinning solution is 2% to 11%; typically, but not limitingly, for example, the mass percentage of polyacrylonitrile in the spinning solution is 2%, 4%, 6%, 8%, 10%, or any combination thereof. Preferably, the mass percentage of polyacrylonitrile in the spinning solution is 8% to 11%.

[0060] In some embodiments of the present invention, in step S1, the solvent of the spinning solution includes N,N-dimethylformamide.

[0061] In some embodiments of the present invention, the parameters for electrospinning in step S1 are as follows: positive voltage of 1–10 kV and flow rate of 0.1–1.0 mL / h. -1 The needle specification is 20G, the distance between the needle and the collector is 5-20cm, and the collector rotation speed is 100-1000rpm.

[0062] In some embodiments of the present invention, step S1, after electrospinning, further includes drying. Preferably, the drying temperature is 50–70°C.

[0063] In some embodiments of the present invention, step S1, the carbonization treatment includes: holding at 120–180°C for 0.5–1.5 hours in an inert atmosphere, then raising the temperature to 200–300°C and holding for 0.5–1.5 hours, then raising the temperature to 600–700°C and holding for 0.5–1.5 hours, followed by cooling. Preferably, the carbonization treatment includes: holding at 140–150°C for 1 hour in an inert atmosphere, then raising the temperature to 250–300°C and holding for 1 hour, then raising the temperature to 650–700°C and holding for 1 hour, followed by cooling.

[0064] In some embodiments of the present invention, step S1 includes oxidation treatment: holding at 280-350°C for 1-6 hours in an air atmosphere.

[0065] In some embodiments of the present invention, in step S2, the deposition method includes vapor deposition.

[0066] In some embodiments of the present invention, in step S2, the parameters for vapor deposition are as follows: absolute value of relative vacuum degree > 5 × 10 -4KPa, evaporation current increases by 5A every 5-60s starting from 30A, and deposition rate is 0.1-2nm / s. -1 .

[0067] In some embodiments of the present invention, a flexible negative electrode is also provided, comprising a spinning fiber layer and a lithium metal layer disposed on the surface of the spinning fiber layer.

[0068] The spun fiber layer includes the above-mentioned negative electrode material or the negative electrode material prepared by the above-mentioned method.

[0069] The flexible negative electrode made using the negative electrode material of the present invention effectively improves the mechanical properties of the electrode, alleviates the volume expansion of the electrode, and inhibits dendrite growth.

[0070] In some embodiments of the present invention, a method for preparing a flexible negative electrode is also provided, comprising the following steps:

[0071] Li metal was deposited onto the spun fiber sheet, with the Li loading controlled at 0.1–8 mAh cm⁻¹. -2 .

[0072] In some embodiments of the present invention, a lithium-sulfur battery is also provided, including the above-described flexible negative electrode.

[0073] The lithium-sulfur battery of the present invention uses the above-mentioned flexible negative electrode, which is beneficial to improving capacity and cycle performance.

[0074] Example 1

[0075] The method for preparing the flexible negative electrode provided in this embodiment includes the following steps:

[0076] S1. Mix 15g N,N-dimethylformamide (75wt%), 1.6g polymethyl methacrylate (8wt%), 1.6g cobalt acetate (8wt%), 1.6g polyacrylonitrile (8wt%), and 0.2g multi-walled carbon nanotubes (1wt%), and heat and stir at 75℃ for 2h to obtain the spinning solution.

[0077] The above spinning solution was added to a syringe, the working voltage was controlled at 10kV, the distance between the receiver and the spinning needle was adjusted to 15cm, the flow rate of the solution was 0.5mL / h, and nanofiber films were obtained after electrospinning for 8h.

[0078] After drying the nanofiber film at 60°C, it was placed in a furnace and kept at 150°C for 1 hour under an argon atmosphere. Then, the temperature was raised to 300°C and kept for 1 hour, and then raised to 700°C and kept for 1 hour. After that, it was allowed to cool naturally to room temperature to obtain the carbonized nanofiber film.

[0079] The carbonized nanofiber film was placed in a tube furnace and heated to 350°C for 2 hours under an argon atmosphere to obtain Co3O4@CNF.

[0080] S2. Using a resistance evaporation coating machine, ZnO powder is placed in the evaporation source, and Co3O4@CNF is fixed. Wait until the vacuum degree reaches 5×10⁻⁶. -4 At a vacuum level above a certain threshold, the evaporation current was started at 30A and preheated for 30 minutes. Then, the current was increased by 5A every 20 seconds until it reached 170A. The evaporation rate was then maintained at 0.2–0.5 nm / s. -1 Once the ZnO layer reaches a thickness of 180 nm, the machine stops the evaporation process to obtain ZnO-Co3O4@CNF.

[0081] S3. Using a preset constant current, Li metal is deposited onto a 10mm diameter ZnO-Co3O4@CNF electrode, with the Li loading controlled at 3mAh cm⁻¹. -2 This yields a flexible negative electrode sheet.

[0082] Example 2

[0083] The method for preparing the flexible negative electrode provided in this embodiment includes the following steps:

[0084] S1. Mix 13g N,N-dimethylformamide (65wt%), 2.2g polymethyl methacrylate (11wt%), 2.2g cobalt acetate (11wt%), 2.2g polyacrylonitrile (11wt%), and 0.4g multi-walled carbon nanotubes (2wt%), and heat and stir at 75℃ for 2h to obtain the spinning solution.

[0085] The above spinning solution was added to a syringe, the working voltage was controlled at 13kV, the distance between the receiver and the spinning needle was adjusted to 15cm, the flow rate of the solution was 1mL / h, and nanofiber films were obtained after electrospinning for 8h.

[0086] After drying the nanofiber film at 60°C, it was placed in a furnace and kept at 150°C for 1 hour under an argon atmosphere. Then, the temperature was raised to 300°C and kept for 1 hour, and then raised to 700°C and kept for 1 hour. After that, it was allowed to cool naturally to room temperature to obtain the carbonized nanofiber film.

[0087] The carbonized nanofiber film was placed in a tube furnace and heated to 300°C for 2 hours under an argon atmosphere to obtain Co3O4@CNF.

[0088] S2. Using a resistance evaporation coating machine, ZnO powder is placed in the evaporation source, and Co3O4@CNF is fixed. Wait until the vacuum degree reaches 5×10⁻⁶. -4 At a vacuum level above 180A, preheat the evaporation current from 30A for 30 minutes, then increase it by 5A every 20 seconds until the current reaches 180A. Maintain the evaporation rate at 0.2–0.5 nm / s. -1 Once the ZnO layer reaches a thickness of 185 nm, the machine stops the evaporation process to obtain ZnO-Co3O4@CNF.

[0089] S3. Using a preset constant current, Li metal is deposited onto a 10mm diameter ZnO-Co3O4@CNF electrode, with the Li loading controlled at 3mAh cm⁻¹. -2 This yields a flexible negative electrode sheet.

[0090] Example 3

[0091] The method for preparing the flexible negative electrode provided in this embodiment includes the following steps:

[0092] S1. Mix 18g N,N-dimethylformamide (90wt% of the spinning solution), 0.6g polymethyl methacrylate (3wt% of the spinning solution), 0.6g cobalt acetate (3wt% of the spinning solution), 0.6g polyacrylonitrile (3wt% of the spinning solution), and 0.2g multi-walled carbon nanotubes (1wt% of the spinning solution), and heat and stir at 75℃ for 2h to obtain the spinning solution.

[0093] The above spinning solution was added to a syringe, the working voltage was controlled at 20kV, the distance between the receiver and the spinning needle was adjusted to 18cm, the flow rate of the solution was 1.5mL / h, and nanofiber films were obtained after electrospinning for 6h.

[0094] After drying the nanofiber film at 60°C, it was placed in a furnace and kept at 150°C for 1 hour under an argon atmosphere. Then, the temperature was raised to 300°C and kept for 1 hour, and then raised to 700°C and kept for 1 hour. After that, it was allowed to cool naturally to room temperature to obtain the carbonized nanofiber film.

[0095] The carbonized nanofiber film was placed in a tube furnace and heated to 300°C for 2 hours under an argon atmosphere to obtain Co3O4@CNF.

[0096] S2. Using a resistance evaporation coating machine, ZnO powder is placed in the evaporation source, and Co3O4@CNF is fixed. Wait until the vacuum degree reaches 5×10⁻⁶. -4At a vacuum level above 180A, the evaporation current was started at 30A for preheating for 30 minutes, then increased by 5A every 30 seconds until the evaporation current reached 180A. The evaporation rate was maintained at 0.2–0.5 nm / s. -1 Once the ZnO layer reaches a thickness of 190 nm, the machine stops the evaporation process to obtain ZnO-Co3O4@CNF.

[0097] S3. Using a preset constant current, Li metal is deposited onto a 10mm diameter ZnO-Co3O4@CNF electrode, with the Li loading controlled at 3mAh cm⁻¹. -2 This yields a flexible negative electrode sheet.

[0098] Experimental Example 1

[0099] The negative electrode material (ZnO-Co3O4@CNF) prepared in Example 1 was subjected to XRD testing, and the results are as follows: Figure 1 As shown.

[0100] from Figure 1 It can be seen that a hexagonal wurtzite ZnO structure was identified near 36.3°, corresponding to card PDF 36-1451, which is consistent with the (101) crystal plane, and the diffraction peaks corresponding to Co3O4 also match well, proving the successful synthesis of ZnO-Co3O4@CNF. In addition, a bulge in the curve near 26° in the XRD pattern is caused by amorphous carbon.

[0101] The negative electrode material (ZnO-Co3O4@CNF) prepared in Example 1 was tested by scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown.

[0102] from Figure 2 As can be seen, the interwoven fibers form a conductive three-dimensional network structure, providing a good mechanical strength basis for the anode material. The lithiophilic gradient of ZnO-Co3O4@CNF consists of two parts: the lithiophilic Co3O4 on the surface and the superlithiophilic ZnO, which work together to facilitate the deposition of metallic lithium.

[0103] Experimental Example 2

[0104] The preparation method of lithium-sulfur batteries includes the following steps: using components such as separators, gaskets, and spring sheets, and equipping them with S / CNT positive electrode sheets (active material loading 1 mg / cm³). -2The C2032 button cell was assembled with the negative electrode and the negative electrode in an argon-filled glove box. The electrolyte was a mixed solution of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium nitrate (LiNO3), 1,3-dioxolane (DOL), and ethylene glycol dimethyl ether (DME), with a volume ratio of 1,3-dioxolane to ethylene glycol dimethyl ether of 1:1. The concentration of lithium bis(trifluoromethanesulfonyl)imide in the mixed solution was 1.0 mol / L, and the concentration of lithium nitrate was 0.1 mol / L.

[0105] Using the above preparation method, a lithium-sulfur battery was prepared using the flexible negative electrode obtained in Example 1 as the negative electrode sheet. Electrochemical tests were performed on the battery, and the results are as follows: Figure 3 As shown.

[0106] from Figure 3 It can be seen that the battery result is an initial discharge capacity of 1019 mAh g. -1 After 500 cycles, the capacity is 716mAh g. -1 The capacity retention rate is 70.3%. The lithium-sulfur battery made using the negative electrode material of the present invention has high capacity and excellent cycle performance.

[0107] 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; and these 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. A negative electrode material, characterized in that, It includes carbon fibers loaded with Co3O4 nanoparticles and a ZnO layer, wherein the ZnO layer encapsulates the carbon fibers loaded with Co3O4 nanoparticles. The preparation method of the negative electrode material includes the following steps: S1. The spinning solution is subjected to electrospinning, carbonization and oxidation treatment in sequence to obtain carbon fibers loaded with Co3O4 nanoparticles; the spinning solution includes cobalt salt, carbon nanotubes, polymethyl methacrylate and polyacrylonitrile. S2. ZnO is deposited on the surface of the carbon fiber loaded with Co3O4 nanoparticles to obtain the negative electrode material.

2. The negative electrode material according to claim 1, characterized in that, In the negative electrode material, the mass ratio of carbon fiber, Co3O4 and ZnO is 1:(0.1~800):(1~50).

3. The negative electrode material according to claim 1, characterized in that, The thickness of the ZnO layer is 50~300nm.

4. The negative electrode material according to claim 1, characterized in that, The Co3O4 nanoparticles have a particle size of 30~200nm.

5. The negative electrode material according to claim 1, characterized in that, In step S1, the mass percentage of the cobalt salt in the spinning solution is 2% to 11%.

6. The negative electrode material according to claim 1, characterized in that, In step S1, the cobalt salt includes at least one of cobalt acetate, cobalt oxalate, and cobalt nitrate.

7. The negative electrode material according to claim 1, characterized in that, In step S1, the carbon nanotubes in the spinning solution have a mass percentage of 0.01% to 2%.

8. The negative electrode material according to claim 1, characterized in that, In step S1, the mass percentage of polymethyl methacrylate in the spinning solution is 2% to 11%.

9. The negative electrode material according to claim 1, characterized in that, In step S1, the mass percentage of polyacrylonitrile in the spinning solution is 2% to 11%.

10. The negative electrode material according to claim 1, characterized in that, In step S1, the carbonization process includes: holding the temperature at 120~180℃ for 0.5~1.5h under an inert atmosphere, then raising the temperature to 200~300℃ and holding it for 0.5~1.5h, then raising the temperature to 600~700℃ and holding it for 0.5~1.5h, and then cooling.

11. The negative electrode material according to claim 1, characterized in that, In step S1, the oxidation treatment includes: holding at 280~350℃ for 1~6 hours in an air atmosphere.

12. The negative electrode material according to claim 1, characterized in that, In step S2, the deposition method includes vapor deposition.

13. A flexible negative electrode, characterized in that, It includes a spinning fiber layer and a lithium metal layer disposed on the surface of the spinning fiber layer; The spinning fiber layer comprises the negative electrode material according to any one of claims 1 to 12.

14. A lithium-sulfur battery, characterized in that, Includes the flexible negative electrode as described in claim 13.

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