Three-dimensional hollow cone array type nano-porous nickel sesquioxide-nickel oxide integrated lithium ion battery negative electrode and preparation method thereof

Abstract

The invention provides a three-dimensional hollow cone array type nano-porous nickel sesquioxide-nickel oxide integrated lithium ion battery negative electrode and a preparation method thereof. The electrode is composed of a nano-porous cone array which grows on the surface of a metal substrate in the vertical direction and has a three-dimensional hollow structure, the metal substrate is mainly made of one of foamed nickel, foamed copper, a copper sheet and a nickel sheet; the cone array is composed of nickel oxide with a hollow nano-porous cone-shaped structure; the nickel oxide is a mixture of nickel sesquioxide and nickel oxide; the nickel oxide is a porous nickel trioxide-nickel oxide shell formed by oxidizing the surface of a three-dimensional nano nickel cone, and finally, nickel elementary substances of a core part are selectively etched to form the three-dimensional hollow cone array type nano porous nickel sesquioxide-nickel oxide lithium ion battery negative electrode. The method provided by the invention integrates the advantages of volume expansion inhibition of the hollow array structure and high theoretical capacity of the nickel oxide, and combines the three-dimensional nano porous structure, so that the lithium storage performance of the negative electrode of the lithium ion battery is improved.

Description

Technical Field

[0001] The present invention belongs to the field of anodes of lithium-ion batteries, and relates to a three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated anode of a lithium-ion battery and a preparation method thereof. Background Art

[0002] In recent years, the world is facing environmental protection and energy crisis problems. Among them, problems such as environmental pollution, climate change, and consumption of non-renewable energy have triggered the demand for new clean energy. Lithium-ion batteries have become one of the key technologies to solve these problems due to their many advantages such as high efficiency, environmental protection, and renewability. As the most advanced chemical battery on the current market, lithium-ion batteries have excellent performances in terms of high energy density, high power output, long life, etc. At the same time, due to the gradual reduction of its cost, more and more application fields begin to accept and use lithium-ion batteries, such as electric vehicles, smart phones, laptops, drones, solar energy storage systems, etc.

[0003] Research has found that: NiO and its composite materials, as a common p-type inorganic semiconductor material, are widely used in fields such as photocatalysis, gas sensing, and supercapacitors. Due to its variable valence and abundant redox sites, the theoretical capacity of NiO is as high as 718 mAh g −1 , almost twice that of commercial graphite. In addition, nickel oxide has stable chemical properties and good designability in terms of morphology, particle size, specific surface area, etc. However, NiO still has characteristics such as low cycle stability, low Coulomb efficiency, large volume expansion, and poor conductivity, which greatly limit the development of high-capacity lithium-ion batteries.

[0004] Rahman M M et al. disclosed a method for preparing NiO-C composite nanoparticles by spray pyrolysis. (Rahman M M, Chou S, Zhong C, et al. Spray pyrolyzed NiO–C nanocomposite as an anode material for the lithium-ion battery with enhanced capacity retention[J]. Solid State Ionics, 2010, 180(40):1646-1651.). An aqueous solution of 0.5 M nickel nitrate hexahydrate (Ni(NO3)2·6 H2O, ≥ 97.0%) was used as a precursor to prepare NiO powder, and NiO-C composite nanoparticles were prepared by mixing the initial solution with citric acid (C6H8O7, ≥ 99.5%) to a concentration of 0.06 M. The theoretical weight ratio of NiO to C was 90:10. Compressed air was used as the carrier gas, and the solution was peristaltically pumped into a three-zone spray pyrolysis furnace at an operating temperature of 600 °C. The resulting powder was separated from the hot gas stream by a collection tank and collected in a sealed sample bottle. The collected NiO-C composite nanoparticles were mixed with carbon black and carboxymethyl cellulose (CMC) binder in a ratio of 80:10:10 in an aqueous solvent to form a homogeneous slurry. The slurry was spread on a copper foil substrate. The coated electrode was dried in a vacuum oven at 110 °C for 24 hours and then pressed into a negative electrode of a lithium-ion battery. The negative electrode of the lithium-ion battery prepared by this method has the following deficiencies that need to be improved urgently: (1) The process conditions of 600 °C used in the spray pyrolysis method are costly, with high energy consumption and serious environmental pollution; (2) The prepared active material is mixed with a solvent and a binder and directly coated on the current collector. Since the binder and the solvent are not conductive, the impedance is increased, the electrode polarization is increased, the electron transfer is hindered, and the electrochemical performance of the battery is reduced; (3) During the lithium ion insertion and extraction process, a huge volume expansion will occur. The active component NiO-C composite nanoparticles are directly coated on the conductive substrate, which cannot inhibit the volume expansion of the active material during the lithium ion insertion and extraction process, and the binding force is limited, so it is easy to fall off; (4) The cycle stability and capacity retention rate of the prepared NiO-C composite nanoparticles are not good.

[0005] The present invention prepares a three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode through a three-step method (electrodeposition-annealing treatment-selective etching). The hollow structure can buffer the volume expansion of NiO during the lithium insertion and extraction process, achieving an improvement in the cycling performance; the three-dimensional array structure has a high specific surface area, which can improve the utilization rate of the NiO active material. The directional spatial configuration can buffer the stress generated during lithium insertion and extraction. At the same time, the nanoporous structure provides a shorter diffusion path, which is beneficial to the transport of lithium ions, improving the transport rate and achieving the purpose of improving the rate performance. The combination of the two can overcome the problem that it is difficult to improve the cycling performance and rate performance simultaneously, and prepare an electrode with both high rate performance and high cycling performance. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode grown on a nickel foam substrate and a preparation method. By improving the structure of the lithium-ion battery anode, a three-dimensional hollow array and a nanoporous structure are combined to improve the specific capacity and cycling performance of the lithium-ion battery and simplify the preparation process, reducing the production cost of the lithium-ion battery anode.

[0007] To achieve the above invention purpose, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode. It is characterized in that the integrated lithium-ion battery anode is composed of a nanoporous cone array with a three-dimensional hollow structure uniformly grown on the surface of a metal substrate; the metal substrate is mainly one of copper sheet, nickel sheet, copper foam, and nickel foam; the nanoporous cone array is composed of nickel oxide with a hollow nanoporous cone-like structure; the nickel oxide is a mixture of nickel oxide and nickel hydroxide; the nickel oxide is formed by the long-term oxidation of the surface of a three-dimensional nano-nickel cone, in-situ forming a porous nickel oxide-nickel hydroxide shell, and constituting a core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel hydroxide-nickel precursor. Finally, the core of the core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel hydroxide-nickel precursor is selectively etched to form a three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide lithium-ion battery anode, and the nickel oxide shell is uniformly distributed on the surface of the metal substrate.

[0009] Preferably, in the technical solution of the above three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, the average height of the cones of the three-dimensional hollow nanoporous cone array is about 500-800 nm.

[0010] Preferably, in the technical solution of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel integrated lithium-ion battery anode, the average width of the conical oxide layer shell of the three-dimensional hollow nanocone array is about 15-30 nm.

[0011] Preferably, in the technical solution of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel integrated lithium-ion battery anode, the pore size of the nanoporous structure on the cone is about 1-10 nm.

[0012] Preferably, in the technical solution of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel integrated lithium-ion battery anode, the size of the hollow core of the cone of the three-dimensional hollow nanoporous cone array is about 50-500 nm.

[0013] The present invention also provides a preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel integrated lithium-ion battery anode, and the steps are as follows:

[0014] (1) Under the condition that the water bath temperature is 30-90 °C, using the metal substrate with the surface oxide layer and grease layer removed as the working electrode and the nickel sheet as the counter electrode, at a current density of 5-60 mA / cm 2 for a constant current deposition of 500-900 s. The electrolyte is composed of nickel chloride hexahydrate, boric acid and ethylenediamine hydrochloride. After the deposition, rinse with deionized water and absolute ethanol alternately until there is no residual liquid on the surface of the sample, and after vacuum drying, a three-dimensional nanocone array type nickel current collector is prepared.

[0015] (2) In an air atmosphere, put the three-dimensional nanocone array type nickel current collector obtained in step (1) into a muffle furnace set at a certain temperature, and heat-treat it at 350-500 °C for 1-5 h to obtain a core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel-nickel precursor.

[0016] (3) Immerse the core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel-nickel precursor prepared in step (2) in a HCl solution with a pH of 1-4 for corrosion for 4-12 h, then take it out, rinse with deionized water and absolute ethanol alternately until there is no residual liquid on the surface of the sample, and after vacuum drying, finally obtain a three-dimensional hollow cone array type nanoporous nickel oxide-nickel integrated lithium-ion battery anode.

[0017] In the above-mentioned preparation method of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel integrated lithium-ion battery anode, the current density and the electrodeposition time in step (1) will affect the morphology, size and density of the three-dimensional nanocone array type nickel current collector.

[0018] In the preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, the conditions such as the temperature and time of heat treatment in step (2) will affect the thickness and composition of the nickel oxide on the shell of the core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel hydroxide-nickel precursor, and the pore size on the cone wall.

[0019] In the preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, the concentration of the HCl solution and the selective etching time in step (3) will affect the thickness of the nickel oxide on the shell of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, the size of the hollow core of the cone, and the nickel content in the core.

[0020] In the preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, a feasible process for removing the oxide layer and grease layer on the surface of the nickel foam substrate is as follows: completely immerse the nickel foam substrate in a dilute hydrochloric acid solution with a preferred concentration of 1-5 wt.%, and let it stand or perform ultrasonic cleaning until the oxide layer and grease layer on the surface of the nickel foam substrate are completely removed. The preferred standing time is 0.5-2 h.

[0021] In the preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, the concentrations of the components in the mixed aqueous solution of nickel chloride hexahydrate and ethylenediamine dihydrochloride borate will affect the quantity and structure of the three-dimensional nanocone array type nickel deposited on the surface of the nickel foam substrate. The preferred concentration of nickel chloride hexahydrate is 0.5-1.5 mol / L, the preferred concentration of boric acid is 0.1-0.8 mol / L, and the preferred concentration of ethylenediamine dihydrochloride is 1.5-2 mol / L.

[0022] In the preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, the temperature of vacuum drying in step (1) does not exceed 100 °C.

[0023] Preferably, in the preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode, the current density is 5-30 mA / cm 2 for electrochemical deposition for 500-900 s, that is, three-dimensional nanocone array type nickel is deposited on the surface of the planar metal substrate; the current density is 31-60 mA / cm 2 for electrochemical deposition for 500-900 s, that is, three-dimensional nanocone array type nickel is deposited on the surface of the nickel foam substrate.

[0024] In step (2) of the method for preparing the three-dimensional hollow cone array type nanoporous nickel trioxide-nickel oxide integrated lithium ion battery negative electrode, when the nickel on the surface of the three-dimensional nanocone array type nickel is oxidized, the chemical reaction that occurs is as follows:

[0025] 4Ni+3O2 2Ni2O3

[0026] 2Ni2O3 4NiO+O2

[0027] Preferably, in the preparation method of the above-mentioned three-dimensional hollow cone array type nanoporous nickel trioxide-nickel oxide integrated lithium ion battery negative electrode, the temperature is increased to 350-500 ° C at a heating rate of 4-5 ° C / min in an air atmosphere and kept at this temperature for 1-5 h to obtain a core-shell structured three-dimensional cone array type nanoporous nickel trioxide-nickel oxide-nickel precursor.

[0028] In the method for preparing the three-dimensional hollow cone array nanoporous nickel oxide-nickel oxide integrated lithium ion battery negative electrode, in step (3), the metal nickel element in the core and the nickel oxide in the shell form a primary cell in the HCl solution. + Under the action of the anode, the nickel core is dissolved first as the anode.

[0029] In step (3) of the method for preparing the three-dimensional hollow cone array nanoporous nickel oxide-nickel oxide integrated lithium ion battery negative electrode, when the core nickel is selectively etched by HCl, the chemical reaction that occurs is as follows:

[0030] Ni+2HCl NiCl2+H2

[0031] Preferably, in step (3) of the method for preparing the three-dimensional hollow cone array nanoporous nickel oxide-nickel oxide integrated lithium ion battery negative electrode, the concentration of HCl is 0.1-0.0001 mol / L, and the corrosion time is 4-12 h.

[0032] The three-dimensional hollow cone array type nanoporous nickel trioxide-nickel oxide integrated lithium ion battery negative electrode provided by the present invention has a structure composed of a nanoporous cone array with a three-dimensional hollow structure uniformly grown on the surface of a metal substrate in a vertical direction; the nanocone is composed of an outer shell layer and an internal cavity, wherein the outer shell nickel trioxide-nickel oxide layer serves as a lithium storage active material, and the metal substrate serves as a conductive substrate for the electrode.

[0033] The hollow structure can buffer the volume expansion of nickel oxide hydroxide - nickel oxide during the lithium insertion and extraction process, achieving an improvement in cycling performance. The three - dimensional array structure has a high specific surface area, which can improve the utilization rate of the nickel oxide hydroxide - nickel oxide active material. The oriented spatial configuration can buffer the stress generated during lithium insertion and extraction. At the same time, the nanoporous structure provides a shorter diffusion path, which is beneficial to the transport of lithium ions and improves the transport rate. The active material is loaded onto the three - dimensional nano - cone array - type nickel current collector through heat treatment, which can significantly increase the binding force between the active material and the current collector, avoiding the problems of pulverization and shedding of the active material during the electrochemical reaction process and the use of binders in the traditional coating method. These above - mentioned characteristics can overcome the problem that it is difficult to improve the cycling performance and rate performance simultaneously, which is beneficial to improving the comprehensive electrochemical performance of the negative electrode provided by the present invention.

[0034] Compared with the prior art, the technical solution provided by the present invention has the following technical effects:

[0035] 1. The integrated lithium - ion battery negative electrode of three - dimensional hollow - cone - array - type nanoporous nickel oxide hydroxide - nickel oxide provided by the present invention has a structure composed of nanoporous cone arrays with a three - dimensional hollow structure that grow uniformly on the surface of the nickel foam substrate in the vertical direction; the nano - cones are composed of an outer shell layer and an internal cavity, where the outer nickel oxide hydroxide - nickel oxide layer serves as the lithium - storage active material, and the metal substrate serves as the conductive substrate of the electrode. The hollow structure can buffer the volume expansion of nickel oxide hydroxide - nickel oxide during the lithium insertion and extraction process, achieving an improvement in cycling performance. The three - dimensional array structure has a high specific surface area, which greatly increases the contact area between the active material and the electrolyte, helps to provide more active sites for the insertion of lithium ions, improves the utilization rate of the nickel oxide hydroxide - nickel oxide active material, and thus increases the electrode capacity. The oriented spatial configuration can buffer the stress generated during lithium insertion and extraction. At the same time, the nanoporous structure provides a shorter diffusion path, which is beneficial to the transport of lithium ions and improves the transport rate. The active material is loaded onto the three - dimensional nano - cone array - type nickel current collector through heat treatment, which can significantly increase the binding force between the active material and the current collector, avoiding the problems of pulverization and shedding of the active material during the electrochemical reaction process and the use of binders in the traditional coating method. These above - mentioned characteristics can overcome the problem that it is difficult to improve the cycling performance and rate performance simultaneously, which is beneficial to improving the capacity, cycling stability, and rate performance of the negative electrode provided by the present invention.

[0036] 2. The present invention also provides a method for preparing a negative electrode of a three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery grown on a metal substrate. The method uses a core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel hydroxide as a precursor, selectively etches away the nickel element in the core, and retains the nickel oxide-nickel hydroxide layer on the cone wall shell. Since the active material is in-situ synthesized on the three-dimensional nano-cone array nickel current collector, the prepared three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery negative electrode avoids the coating process of the active material, and has a strong binding force between the active material and the current collector, which can avoid the problem of easy shedding of the active material in the traditional coating method. The negative electrode provided by the present invention will not hinder electron transport, increase electrode polarization and impedance due to the presence of the binder, and has excellent cycle performance and rate performance. At the same time, the specific capacity of this negative electrode also has an advantage over existing materials, with a high reversible capacity and good cycle stability.

[0037] 3. The present invention has experimentally confirmed that when the charge-discharge current density is 1 mA / cm 2 , after 130 cycles, the capacity retention rate is 98.1%. At the same time, the Coulomb efficiency is stable above 99% after 130 cycles, showing very excellent cycle performance. Even after high-rate charge-discharge cycling (1, 2, 4, 8 mA / cm 2 ), when the current density returns to 1 mA / cm 2 , the capacity retention rate is still as high as 96.1%.

[0038] 4. The preparation process of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery negative electrode provided by the present invention is simpler and has lower cost compared with the existing technology process, and has no special requirements for production equipment and process conditions, and has the characteristics of being easy to realize large-scale production and popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the XRD pattern of the nickel foam used in Example 1.

[0040] Figure 2 is the surface SEM photo of the three-dimensional array type nano-nickel current collector prepared in Example 1.

[0041] Figure 3 is the cross-sectional SEM photo of the three-dimensional array type nano-nickel current collector prepared in Example 1.

[0042] Figure 4 is the SEM photo of the core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel hydroxide precursor prepared in Example 1.

[0043] Figure 5It is the EDS spectrum of the core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel hydroxide precursor prepared in Example 1.

[0044] Figure 6 It is the XRD spectrum of the core-shell structure three-dimensional cone array type nanoporous nickel oxide-nickel hydroxide precursor prepared in Example 1.

[0045] Figure 7 It is the surface SEM photograph of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode prepared in Example 1.

[0046] Figure 8 It is the cross-sectional SEM photograph of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode prepared in Example 1.

[0047] Figure 9 It is the XRD spectrum of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode prepared in Example 1.

[0048] Figure 10 It is the cyclic voltammogram of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode prepared in Example 1.

[0049] Figure 11 It is the galvanostatic charge-discharge curve of the lithium-ion battery prepared in Example 1.

[0050] Figure 12 It is the cycling performance curve of the lithium-ion battery prepared in Example 1.

[0051] Figure 13 It is the rate performance curve of the lithium-ion battery prepared in Example 1.

[0052] Figure 14 It is the AC impedance curve of the lithium-ion battery prepared in Example 1.

[0053] Figure 15 It is the AC impedance curve of the lithium-ion battery prepared in Comparative Example 1.

[0054] Figure 16 It is the SEM photograph of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode prepared in Example 2.

[0055] Figure 17 It is the EDS spectrum of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery anode prepared in Example 2.

[0056] Figure 18It is the cycle performance curve of the anode of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery prepared in Example 2.

[0057] Figure 19 It is the rate performance curve of the anode of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery prepared in Example 2.

[0058] Figure 20 It is the SEM photograph of the anode of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery prepared in Example 3.

[0059] Figure 21 It is the SEM photograph of the three-dimensional nanocone array type nickel current collector prepared in Example 4. Detailed implementation manners

[0060] The following further illustrates the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide lithium-ion battery anode and its preparation method provided by the present invention through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Those skilled in the art still fall within the protection scope of the present invention when making some non-essential improvements and adjustments to the present invention based on the above invention content for specific implementation.

[0061] Example 1

[0062] In this example, a preparation method of the anode of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery is provided, and the steps are as follows:

[0063] (1) Cut the nickel foam with a thickness of 0.5 mm into rectangular pieces with an area of 1 cm×1.5 cm, then immerse it in a 3wt.% hydrochloric acid solution, stand or ultrasonically clean for 1 h to remove the oxide layer and grease layer on the surface of the nickel foam, and then alternately clean it with acetone, absolute ethanol and deionized water for 5 min. After vacuum drying, the nickel foam available for subsequent electrochemical deposition is obtained as the metal substrate.

[0064] (2) Prepare the electrolyte in a beaker. The electrolyte is composed of 1.5 mol / L nickel chloride hexahydrate, 0.8 mol / L boric acid and 2 mol / L ethylenediamine hydrochloride. Then place the beaker in a 60 °C constant temperature water bath. Use the nickel foam prepared in step (1) as the working electrode and a nickel sheet as the counter electrode, and deposit at a current density of 60 mA / cm 2 for 600 s. After the deposition is completed, alternately clean it with deionized water and absolute ethanol for 5 min. After vacuum drying, a three-dimensional nanocone array type nickel current collector is obtained.

[0065] (3) Under air atmosphere, the temperature of the muffle furnace is set to 400 °C, and the three-dimensional nanocone array type nickel current collector obtained in step (2) is placed in the furnace for heat treatment for 5 h. The surface of the nano-nickel cone is oxidized to form a nickel oxide-nickel oxide layer with a certain thickness. The nickel oxide layer is naturally cooled to room temperature to obtain a core-shell structured three-dimensional cone array type nanoporous nickel oxide-nickel oxide precursor with nickel as the core and nickel oxide-nickel oxide as the shell.

[0066] (4) The core-shell structured three-dimensional cone array nanoporous nickel oxide-nickel oxide precursor obtained in step (3) is placed in a HCl solution with a pH of 2, and selectively etched for 4 h at room temperature. After being taken out, it is washed alternately with deionized water and anhydrous ethanol for 5 min, and vacuum dried to obtain a three-dimensional hollow cone array nanoporous nickel oxide-nickel oxide lithium ion battery negative electrode.

[0067] FIG. (1) is an XRD spectrum of the nickel foam described in step (1) of this embodiment. As can be seen from FIG. (1), the nickel foam material treated in step (1) has high purity and can meet the requirements of subsequent operations.

[0068] Figure 2 and Figure 3 is a SEM photo of the three-dimensional nanocone array nickel current collector prepared in step (2) of this embodiment ( Figure 2 is the surface SEM photo, Figure 3 is a cross-sectional SEM photograph). Figure 2 and Figure 3 It can be seen that the three-dimensional nanocone array-type nickel current collector deposited on the surface of nickel foam has good morphology and structure, and the average height of the cone and the average diameter of the cone bottom are approximately 690 nm and 260 nm.

[0069] Figure 4 and Figure 5 They are respectively the SEM photo and EDS spectrum of the core-shell structure three-dimensional cone array nanoporous nickel oxide-nickel oxide precursor prepared in step (3). Figure 4 and Figure 5 It can be seen that through long-term heat treatment, a porous structure appears on the surface of the cone, and nickel oxide has been loaded onto the surface of the three-dimensional nanoporous cone array to obtain a core-shell structured three-dimensional cone array-type nanoporous nickel trioxide-nickel oxide precursor, and the nano-nickel cones still maintain a vertical base-upward structure. Figure 6 is the XRD spectrum of the core-shell structure three-dimensional cone array nanoporous nickel oxide-nickel oxide precursor prepared in step (3), Figure 6 It can be seen that the core-shell structured three-dimensional cone array nanoporous nickel oxide-nickel oxide precursor exists in three phases of Ni, NiO and Ni2O3, indicating that the nanoporous cone shell oxide layer is a mixture of NiO and Ni2O3.

[0070] Figure 7 And Figure 8 are respectively the SEM photos of the anode of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery prepared in step (4) ( Figure 7 is the surface SEM photo, Figure 8 is the cross-sectional SEM photo), compared with Figure 4 , the core-shell structure has changed, with hollow cones appearing, and the walls of the hollow cones are ruptured. It can be thus shown that after the corrosion in step (4) of this embodiment, most of the nickel in the core has been corroded.

[0071] Figure 9 is the XRD pattern of the anode of the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery prepared in step (4).

[0072] Next, lithium-ion batteries are fabricated using the anodes prepared in this embodiment and their performance is tested.

[0073] Using a metal lithium sheet as the counter electrode, the anode prepared in this embodiment as the working electrode, a microporous polypropylene as the separator, and a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) containing 1 M lithium hexafluorophosphate (LiPF6) as the electrolyte. In this electrolyte, the volume ratio of EC, DMC, and DEC is 1:1:1. A lithium-ion battery is assembled in a glove box filled with argon with the water and oxygen contents both lower than 1 ppm.

[0074] Figures 10 - 11 are the cyclic voltammetry curve and the galvanostatic charge-discharge curve of the lithium-ion battery fabricated in this embodiment. As shown by Figure 10 , the downward convex peak position is the reduction peak, corresponding to the lithium intercalation process, the upward convex peak position is the oxidation peak, corresponding to the lithium deintercalation process. The cyclic voltammetry curves of the third and fourth cycles basically overlap, indicating that the electrode has excellent reversible electrochemical performance. As shown by Figure 11 , the initial discharge capacity is 1.72 mA / cm 2 , the initial reversible capacity is 1.18 mA / cm 2 , the Coulombic efficiency is about 68.6%, and the Coulombic efficiencies of the charge and discharge in the second and third cycles are both close to 100%, indicating its excellent cycle stability.

[0075] A galvanostatic charge-discharge tester of model NEWARE BTS-610 is used to test the obtained lithium-ion battery. During the test, the current density is 1 mA / cm 2 , the voltage range is 0.01 - 3.0 V (vs. Li / Li + ), and the test temperature is room temperature. The test results are as shown in Figure 12 shown, as shown by Figure 12It can be seen that the lithium-ion battery assembled with the negative electrode of this embodiment has a specific capacity of 1.06 mA / cm 2 under the condition that the charge-discharge current density is 1 mA / cm 2 in the first charge cycle. After 15 cycles, the capacity rises to 1.23 mA / cm 2 . After 130 cycles, the reversible specific capacity is 1.04 mA / cm 2 , and the capacity retention rate is 98.1%. At the same time, the Coulomb efficiency is stably maintained above 99%.

[0076] The rate performance of the integrated negative electrode of the lithium-ion battery prepared in this embodiment is tested by cycling 130 times in the range of charge-discharge current density of 1-8 mA / cm 2 . The results are shown in Figure 13 . It can be seen from Figure 13 that the lithium-ion battery assembled with the integrated negative electrode of the lithium-ion battery prepared in this embodiment is cycled at the current densities of 1, 2, 4, and 8 mA cm -2 . The first reversible specific capacity is 0.816 mA cm -2 . Although the capacity gradually decreases with the increase of the current density each time, when the current density drops back to 1 mA cm -2 , the reversible capacity immediately climbs to 0.783 mA cm -2 , and the capacity retention rate is as high as 96.1%. Moreover, the Coulomb efficiency is still higher than 99%, showing its excellent rate performance. It can be seen from Figure 12 and 13 that the negative electrode of the lithium-ion battery provided in this embodiment has a high specific capacity and reversible capacity retention rate. It can be seen from Figure 14 that the impedance before cycling is about 200 Ω, and the impedance after cycling is about 70 Ω. The impedance after cycling is much lower than that before cycling because metallic nickel is generated during the charge-discharge process. It shows that the three-dimensional hollow cone array type nanoporous nickel oxide-nickel hydroxide integrated lithium-ion battery negative electrode prepared by the method of the present invention has excellent cycle stability, rate performance and impedance performance.

[0077] Comparative Example 1

[0078] The operations in this comparative example are the same as steps (1)-(3) of Example 1, without performing the HCl selective etching operation in step (4) of Example 1. The obtained product is used to prepare a lithium battery and its performance is tested. The steps are as follows:

[0079] The following is the same operation as steps (1)-(3) of Example 1 to prepare a core-shell structured three-dimensional nanoporous tin dioxide-copper oxide-cuprous oxide-copper. The prepared core-shell structured three-dimensional cone array type nanoporous nickel oxide-nickel is used to fabricate a lithium battery and perform performance tests according to the following method.

[0080] Using a lithium metal sheet as the counter electrode, the negative electrode prepared in this example as the working electrode, a microporous polypropylene as the separator, and a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) containing 1 M lithium hexafluorophosphate (LiPF6) as the electrolyte. In this electrolyte, the volume ratio of EC, DMC, and DEC is 1:1:1. A lithium-ion battery is assembled in a glove box filled with argon with the water and oxygen content both below 1 ppm.

[0081] The test results are as Figure 15 shown. It can be seen from Figure 15 that the impedance of the lithium-ion battery assembled with the negative electrode prepared in this Comparative Example 1 before cycling is 600 Ω. Compared with Example 1, the lithium battery assembled in this comparative example has poor cycle stability and large impedance.

[0082] It can be seen from Example 1 and Comparative Example 1 that selectively etching part of the nickel with HCl solution improves the structure during the lithium deintercalation-insertion process, provides more lithium deintercalation-insertion sites, and can improve the cycle stability of the lithium battery. It shows that the negative electrode of the lithium-ion battery prepared in Example 1 has more excellent electrochemical performance, not only having a higher specific capacity and a longer cycle life, but also having better cycle stability. This is mainly because the core-shell nanostructure has insufficient stability during repeated charge and discharge processes and cannot effectively buffer the internal mechanical stress caused by volume changes during the de-lithiation / lithiation reaction process, resulting in the exfoliation of active substances and the rapid decline of capacity. At the same time, the hollow structure has more excellent Li + / electron transport ability.

[0083] Example 2

[0084] In this example, a preparation method for the negative electrode of a three-dimensional hollow cone array type nanoporous nickel oxide-nickel integrated lithium-ion battery is provided. The steps are as follows:

[0085] (1) The operation is the same as step (1) of Example 1.

[0086] (2) The operation is the same as step (2) of Example 1.

[0087] (3) Under air atmosphere, the temperature of the muffle furnace is set to 400 °C, and the three-dimensional nanocone array type nickel current collector obtained in step (2) is placed in the furnace for heat treatment for 2 h. The surface of the nano-nickel cone is oxidized to form a nickel oxide-nickel oxide layer with a certain thickness. The nickel oxide layer is naturally cooled to room temperature to obtain a core-shell structured three-dimensional cone array type nanoporous nickel oxide-nickel oxide precursor with nickel as the core and nickel oxide-nickel oxide as the shell.

[0088] (4) The operation is the same as step (4) of Example 1.

[0089] Figure 16 and Figure 17 The SEM photo and EDS spectrum of the core-shell structure three-dimensional cone array nanoporous nickel oxide-nickel oxide precursor prepared in step (3) are Figure 16 It can be seen that the core-shell structure three-dimensional cone array nanoporous nickel oxide-nickel oxide precursor obtained in this embodiment has a sharper cone angle than that in Example 1, and also has a nanoporous structure, but Figure 17 It can be seen that the oxygen content of the precursor is lower.

[0090] The lithium ion battery negative electrode prepared in this example is used to make a lithium ion battery and perform a performance test.

[0091] A lithium ion battery was assembled in a glove box filled with argon gas and containing water and oxygen contents below 1 ppm, using a metallic lithium sheet as a counter electrode, the negative electrode prepared in this embodiment as a working electrode, microporous polypropylene as a separator, and a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) containing 1 M lithium hexafluorophosphate (LiPF6) as an electrolyte, wherein the volume ratio of EC, DMC and DEC was 1: 1: 1.

[0092] The obtained lithium-ion battery was tested using a constant current charge and discharge instrument of model NEWARE BTS-610, and the current density during the test was 0.1 mA / cm 2 , voltage range is 0.01-3.0 V (vs. Li / Li + ), the test temperature is room temperature.

[0093] The test results are shown in the figure. Figure 18 : is the cycle performance diagram of the three-dimensional hollow cone array nanoporous nickel trioxide-nickel oxide integrated lithium ion battery negative electrode prepared in step (4) of this embodiment. Figure 18 It can be seen that the recharge and discharge current density of the lithium-ion battery assembled using the lithium-ion battery negative electrode of this embodiment is 0.1 mA / cm 2 Under the condition of , the first reversible specific capacity is 0.18 mA / cm 2After 300 cycles, the capacity retention rate is about 50%, and the Coulomb efficiency is stabilized at more than 95% after 50 cycles.

[0094] At a charge and discharge current density of 0.1-0.8 mA / cm 2 The rate performance of the integrated negative electrode of the lithium ion battery prepared in this embodiment was tested by cycling 150 times within the range of Figure 19 As shown by Figure 19 It can be seen that after high-rate charge and discharge cycles, it returns to low current density for the first time, and the capacity retention rate is about 70%.

[0095] Example 3

[0096] In this embodiment, a method for preparing a three-dimensional hollow cone array nanoporous nickel trioxide-nickel oxide integrated lithium ion battery negative electrode is provided. The steps are as follows:

[0097] (1) The operation is the same as step (1) of Example 1.

[0098] (2) The operation is the same as step (2) of Example 1.

[0099] (3) Under air atmosphere, the temperature of the muffle furnace is set to 500 °C, and the three-dimensional nanocone array type nickel current collector obtained in step (2) is placed in the furnace for heat treatment for 1 h. The surface of the nano-nickel cone is oxidized to form a nickel oxide-nickel oxide layer with a certain thickness. The nickel oxide layer is naturally cooled to room temperature to obtain a core-shell structured three-dimensional cone array type nanoporous nickel oxide-nickel oxide precursor with nickel as the core and nickel oxide-nickel oxide as the shell.

[0100] (4) The operation is the same as step (4) of Example 1.

[0101] Figure 20 Scanning electron microscopy shows that after heat treatment at 500 °C, the nanoporous structure on the surface is still retained, but many of the three-dimensional cone array structures have disappeared, which is caused by the collapse of the structure due to the increase in temperature. The sample structure under this condition is not uniform, the cone array morphology is severely damaged, and the three-dimensional hollow cone array structure can no longer be maintained.

[0102] Example 4

[0103] In this embodiment, a method for preparing a three-dimensional hollow cone array nanoporous nickel trioxide-nickel oxide integrated lithium ion battery negative electrode is provided. The steps are as follows:

[0104] (1) A 300 μm thick copper sheet was cut into rectangular sheets with an area of ​​1 cm × 5 cm, and then immersed in a 3 wt.% hydrochloric acid solution. The sheet was allowed to stand or ultrasonically cleaned for 1 h to remove the oxide layer and grease layer on the surface of the nickel sheet. The sheet was then cleaned alternately with acetone, anhydrous ethanol, and deionized water for 5 min. After vacuum drying, a copper sheet that could be used for subsequent electrochemical deposition was obtained as a metal substrate.

[0105] (2) The operation is the same as step (2) of Example 1.

[0106] (3) Under air atmosphere, the temperature of the muffle furnace is set to 400 °C, and the three-dimensional nanocone array type nickel current collector obtained in step (2) is placed in the furnace for heat treatment for 5 h. The surface of the nano-nickel cone is oxidized to form a nickel oxide-nickel oxide layer with a certain thickness. The nickel oxide layer is naturally cooled to room temperature to obtain a core-shell structured three-dimensional cone array type nanoporous nickel oxide-nickel oxide precursor with nickel as the core and nickel oxide-nickel oxide as the shell.

[0107] (4) The core-shell structured three-dimensional cone array nanoporous nickel oxide-nickel oxide precursor obtained in step (3) is placed in a HCl solution with a pH of 2, and selectively etched for 6 h at room temperature. After being taken out, it is washed alternately with deionized water and anhydrous ethanol for 5 min, and vacuum dried to obtain a three-dimensional hollow cone array nanoporous nickel oxide-nickel oxide lithium ion battery negative electrode.

[0108] Depend on Figure 21 It can be seen that, compared with Example 1, the nano-nickel cone array deposited on the copper foil has dendrites, which is the result of electrodeposition on a planar conductive substrate.

[0109] Example 5

[0110] In this embodiment, a method for preparing a three-dimensional hollow cone array nanoporous nickel trioxide-nickel oxide integrated lithium ion battery negative electrode is provided. The steps are as follows:

[0111] (1) A 300 μm thick nickel sheet was cut into rectangular sheets with an area of ​​1 cm × 5 cm, and then immersed in a 3 wt.% hydrochloric acid solution and allowed to stand or ultrasonically clean for 1 h to remove the oxide layer and grease layer on the surface of the nickel sheet. The sheet was then cleaned alternately with acetone, anhydrous ethanol, and deionized water for 5 min. After vacuum drying, a nickel sheet that could be used for subsequent electrochemical deposition was obtained as a metal substrate.

[0112] (2)Prepare the electrolyte in a beaker. The electrolyte is composed of nickel chloride hexahydrate at 1.5 mol / L, boric acid at 0.8 mol / L, and ethylenediamine hydrochloride at 2 mol / L. Then place the beaker in a constant temperature water bath at 90 °C. Use the nickel metal sheet obtained in step (1) as the working electrode and a nickel sheet as the counter electrode, and deposit at a current density of 5 mA / cm 2 for 900 s. After the deposition, alternately wash with deionized water and absolute ethanol for 5 min each, and after vacuum drying, a three-dimensional nano-cone array type nickel current collector is obtained.

[0113] (3)The operation is the same as step (3) of Example 1.

[0114] (4)Put the core-shell structured three-dimensional cone array type nano-porous nickel oxide-nickel oxide precursor obtained in step (3) into an HCl solution with a pH of 2. Under room temperature conditions, after selective etching for 6 h, take it out and alternately wash with deionized water and absolute ethanol for 5 min each, and after vacuum drying, a three-dimensional hollow cone array type nano-porous nickel oxide-nickel oxide lithium-ion battery negative electrode is obtained.

[0115] Example 6

[0116] (1)Cut the copper foam with a thickness of 0.5 mm into rectangular pieces with an area of 1 cm × 1.5 cm, then immerse it in a 2wt.% hydrochloric acid solution, and let it stand or ultrasonically clean for 1 h to remove the oxide layer and grease layer on the surface of the copper foam. Then alternately wash with acetone, absolute ethanol, and deionized water for 5 min each, and after vacuum drying, obtain copper foam that can be used for subsequent electrochemical deposition as the metal substrate.

[0117] (2)The operation is the same as step (2) of Example 1.

[0118] (3)The operation is the same as step (3) of Example 1.

[0119] (4)Put the core-shell structured three-dimensional cone array type nano-porous nickel oxide-nickel oxide precursor obtained in step (3) into an HCl solution with a pH of 2. Under room temperature conditions, after selective etching for 12 h, take it out and alternately wash with deionized water and absolute ethanol for 5 min each, and after vacuum drying, a three-dimensional hollow cone array type nano-porous nickel oxide-nickel oxide lithium-ion battery negative electrode is obtained.

Claims

1. The negative electrode of a lithium-ion battery with a three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated structure is characterized in that, The integrated lithium-ion battery anode is composed of a nano-porous cone array with a three-dimensional hollow structure that grows uniformly in the vertical direction on the surface of a metal substrate; the metal substrate is mainly one of copper sheets, nickel sheets, copper foam, and nickel foam; the nano-porous cone array is composed of nickel oxide with a hollow nano-porous cone-like structure; the nickel oxide is a mixture of nickel sesquioxide and nickel oxide; the nickel oxide is formed by in-situ oxidation of the surface of the three-dimensional nano-nickel cone to form a porous nickel sesquioxide-nickel oxide shell, and a core-shell structure three-dimensional cone array type nano-porous nickel sesquioxide-nickel oxide-nickel precursor is formed. Finally, the core of the core-shell structure three-dimensional cone array type nano-porous nickel sesquioxide-nickel oxide-nickel precursor is selectively etched to form a three-dimensional hollow cone array type nano-porous nickel sesquioxide-nickel oxide lithium-ion battery anode, and the nickel oxide shell is evenly distributed on the surface of the metal substrate.

2. The negative electrode of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery according to claim 1, characterized in that, The average height of the cones of the three-dimensional hollow nano-porous cone array is about 500 - 800 nm.

3. The three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery negative electrode according to claims 1 to 2, characterized in that, The average width of the oxide layer shell of the cones of the three-dimensional hollow nano-cone array is about 15 - 30 nm.

4. The negative electrode of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery according to claims 1 to 3, characterized in that, The pore size of the nano-porous structure on the cones is about 1 - 10 nm.

5. The negative electrode of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery according to claims 1 to 4, characterized in that, The size of the hollow core of the cones of the three-dimensional hollow nano-porous cone array is about 50 - 500 nm.

6. The preparation method of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery negative electrode according to any one of claims 1 to 5, characterized in that The steps are as follows: (1) Under the condition that the water bath temperature is 30 - 90 °C, with the metal substrate from which the surface oxide layer and grease layer have been removed as the working electrode and a nickel metal sheet as the counter electrode, at a current density of 30 - 60 mA / cm 2 , a constant current deposition is carried out for 500 - 900 s. The electrolyte consists of nickel chloride hexahydrate, boric acid, and ethylenediamine hydrochloride. After the deposition is completed, the sample is alternately rinsed with deionized water and absolute ethanol until there is no residual liquid on the surface of the sample, and then vacuum dried to obtain a three-dimensional nano-cone array type nickel current collector; (2) In an air atmosphere, put the three-dimensional nano-cone array type nickel current collector obtained in step (1) into a muffle furnace set at a certain temperature, and heat-treat it at 350 - 500 °C for 1 - 5 h to obtain a core-shell structure three-dimensional cone array type nano-porous nickel sesquioxide-nickel oxide-nickel precursor; (3) Immerse the core-shell structure three-dimensional cone array type nano-porous nickel sesquioxide-nickel oxide-nickel precursor prepared in step (2) in an HCl solution with a pH of 1 - 4 for 4 - 12 h, then take it out, alternately rinse it with deionized water and absolute ethanol until there is no residual liquid on the surface of the sample, and after vacuum drying, finally obtain a three-dimensional hollow cone array type nano-porous nickel sesquioxide-nickel oxide integrated lithium-ion battery anode.

7. The preparation method of the anode of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery according to claim 6, characterized in that, In step (1), a feasible process for removing the oxide layer and grease layer on the surface of the nickel foam substrate is as follows: completely immerse the nickel foam substrate in a dilute hydrochloric acid solution with a preferably concentration of 1 - 5 wt.%, and let it stand or ultrasonically clean until the oxide layer and grease layer on the surface of the nickel foam substrate are completely removed. The preferred standing time is 0.5 - 2 h.

8. The preparation method of the negative electrode of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery according to claim 6, characterized in that, In step (1), the concentrations of the components in the mixed aqueous solution of nickel chloride hexahydrate, ethylenediamine dihydrochloride borate will affect the quantity and structure of the three-dimensional nano-cone array type nickel deposited on the surface of the nickel foam substrate. The preferred concentration of nickel chloride hexahydrate is 0.5 - 1.5 mol / L, the preferred concentration of boric acid is 0.1 - 0.8 mol / L, and the preferred concentration of ethylenediamine dihydrochloride is 1.5 - 2 mol / L.

9. The preparation method of the anode of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery according to claim 6, characterized in that, In step (1), the current density is 5 - 30 mA / cm 2 for electrochemical deposition for 500 - 900 s, that is, a three-dimensional nano-cone array type nickel is deposited on the surface of a planar metal substrate; the current density is 31 - 60 mA / cm 2 for electrochemical deposition for 500 - 900 s, that is, a three-dimensional nano-cone array type nickel is deposited on the surface of a foam metal substrate.

10. The preparation method of the negative electrode of the three-dimensional hollow cone array type nano-porous nickel oxide-nickel hydroxide integrated lithium ion battery according to claim 6, characterized in that, In step (3), the concentration of HCl is 0.1 - 0.0001 mol / L, and the corrosion time is 4 - 12 h.

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