Nanometer silicon material with various morphological structures and preparation method and application thereof

Abstract

The invention relates to a nano silicon material with various morphological structures and a preparation method and application thereof. The nano-silicon material contains crystalline nano-silicon, amorphous nano-silicon and nano-porous silicon, and the three morphological structures of silicon coexist at the same time. The invention also provides a preparation method of the nano silicon material with various morphological structures. The preparation method comprises the following steps: 1) carrying out ball milling on a Li-Zn-Si compound to obtain precursor particles; (2) carrying out lithium removal reaction to obtain a compound of amorphous Si and nano Zn; and 3) annealing the compound of amorphous Si and nano Zn, and carrying out acid pickling, ball milling and drying to obtain the nano silicon material with various morphological structures. The prepared nano silicon material with various morphological structures is high in purity and low in oxygen content, not only has the structural forms of amorphous silicon and crystalline silicon, but also contains rich nano-pore structures, can be used for preparing a lithium battery negative electrode material, and has the advantages of high first efficiency, high capacity, excellent cycle performance and the like.

Description

Technical Field

[0001] The invention relates to a nano silicon material with various morphological structures and a preparation method and application thereof, belonging to the technical field of negative electrode materials for lithium ion secondary batteries. Background Art

[0002] Silicon-based negative electrode materials are considered to be the most promising negative electrode materials to replace graphite (375mAh / g) for high-capacity lithium-ion secondary battery applications due to their extremely high theoretical gram capacity (4200mAh / g) and low lithium insertion potential (0.2V). However, due to the huge volume change caused by silicon during charging and discharging, it will have a serious impact on the safety and cycle life of the battery, which is also an important factor limiting its application.

[0003] At present, in order to solve the expansion problem of silicon-based negative electrode materials, the following solutions are mainly adopted in the prior art: 1) dispersing nano silicon particles in various active and inactive matrix materials, and designing special material coating structures: for example, Chinese patent document CN110752357A adopts Fe-based amorphous alloy to coat silicon particles, and suppresses the volume expansion of silicon particles during charging and discharging through high-strength amorphous alloy, thereby improving the structural stability of negative electrode materials; for example, Chinese patent document CN110571426A adopts nitrogen-doped silicon carbide to coat nano silicon, thereby improving the bonding force and conductivity between the coating layer and the inner core, suppressing the volume expansion of the material, and improving the cycle performance of the negative electrode material during charging and discharging; for example, Chinese patent document CN108511719A proposes a double-shell structured silicon-carbon composite material, which sequentially coats nano metal particles and a carbon coating layer on the surface of the nano silicon inner core, and finally forms a large number of pores in the coated particles to buffer the expansion of the material, thereby obtaining high specific capacity and excellent cycle performance. The Institute of Process Engineering of the Chinese Academy of Sciences has disclosed a crystalline / amorphous silicon-carbon nanowire (CN107768640A), whose structure consists of a crystalline silicon core, an amorphous silicon layer and a carbon outer layer. The mass ratio of crystalline / amorphous silicon to the composite material is between 5% and 95%. The diameter of the silicon nanowire is 10nm to 100nm, and the thickness of the carbon layer is 5nm to 50nm. The Institute of Physical and Chemical Technology of the Chinese Academy of Sciences mixed silicon powder, SiOx and a dispersant for ball milling and calcination to obtain a Si / SiOx / C composite material (CN105789594A), which combines the capacity of Si-based negative electrode materials The advantages of high capacity, stable cycle of SiOx-based negative electrode materials and good conductivity of carbon materials overcome the problems of low initial coulombic efficiency and poor cycle stability of high-capacity negative electrode materials; 2) Constructing nanostructured silicon materials to inhibit expansion: For example, Toyota Automatic Loom Co., Ltd. of Japan applied for a method for manufacturing silicon materials (CN108349740A), which prepared a layered nano-silicon-based material by dealloying CaSi2; similarly, Harbin Institute of Technology obtained layered siloxene by dissolving Ca in CaSi2, and then calcined it at high temperature to remove hydrogen bonds, hydroxyl groups, etc. on the surface of siloxene to obtain an accordion-shaped layered SiO x Materials (CN112194138A); Jinan University provides a method and application of preparing nano-silicon by a liquid phase method (CN115611282A), and obtains 30-100nm nano-silicon; Southwest Jiaotong University announced a method and application of preparing nano-silicon and energy storage testing (CN115571881A), treating silicon dioxide prepared by a liquid phase method with a magnesium thermal reduction method to obtain a nano-silicon with a particle size of about 50nm, and improving the Coulomb first effect; Shandong University announced a method for decomposing a ternary alloy to prepare nano-silicon and germanium materials (CN110284037A), annealing the decomposed amorphous silicon to obtain nanocrystals with a size of 20-50nm.

[0004] In the methods provided by the above patents, the preparation methods of silicon materials are complicated and involve many steps, all of which require high temperature conditions or special equipment, and it is difficult to control the content of nano-silicon products in large-scale preparation. For example, the preparation of silicon in Chinese patent CN115571881A requires long-term calcination at 800°C, and Chinese patent CN107768640A requires the generation of stable thermal plasma in a thermal plasma generator, etc., so it is not suitable for industrial batch preparation. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a nano-silicon material with various morphological structures and a preparation method and application thereof.

[0006] The technical solution of the present invention is as follows:

[0007] A nano silicon material with multiple morphological structures comprises crystalline nano silicon, amorphous nano silicon and nano porous silicon, and the three morphological structures of silicon coexist simultaneously.

[0008] Preferably according to the present invention, the nano-silicon material is agglomerated silicon particles formed by agglomeration of crystalline nano-silicon, amorphous nano-silicon and nano-porous silicon; the average size of the agglomerated silicon particles is less than 100 nm.

[0009] Preferably according to the present invention, the main body of the nano-silicon material is amorphous nano-silicon, and the crystalline nano-silicon is embedded in the amorphous nano-silicon and wrapped by the amorphous nano-silicon to form an open nanopore structure, and the crystalline nano-silicon and the amorphous nano-silicon are closely connected through silicon atoms, rather than simply physically mixed.

[0010] Preferably according to the present invention, the average particle size of the crystalline nano-silicon is less than 20 nm.

[0011] More preferably, the average particle size distribution of the crystalline nano-silicon is 5 to 10 nm.

[0012] Preferably according to the present invention, the content of crystalline nano-silicon in the crystalline nano-silicon is less than 90%, and the content of amorphous nano-silicon is higher than 10%.

[0013] Preferably, according to the present invention, the nano-silicon material has a rich porous structure inside to form nano-porous silicon; the average pore size distribution of the nano-porous silicon is 5 to 50 nm, and the porosity is greater than 30%.

[0014] Preferably, according to the present invention, Li2ZnSi precursor particles with a particle size of 100 to 1000 mesh are used as raw materials for reaction, and then liquid phase ball milling is combined to prepare nano-silicon materials with various sizes and various morphological structures, which specifically includes the following steps:

[0015] 1) ball-milling the Li-Zn-Si compound to a particle size of 100 to 1000 mesh to obtain precursor particles;

[0016] 2) adding the precursor particles to the organic alcohol to carry out a lithium removal reaction to obtain a composite of amorphous Si and nano Zn;

[0017] 3) The composite of amorphous Si and nano Zn is annealed, and after acid washing, ball milling and vacuum drying, nano silicon materials with various morphological structures are obtained.

[0018] Preferably according to the present invention, in step 1), the Li-Zn-Si compound is a Li2ZnSi ternary alloy compound.

[0019] Preferably according to the present invention, in step 2), the organic alcohol is methanol or ethanol; the mass volume ratio of the precursor particles to the organic alcohol is 1:(10-100), unit: g / mL.

[0020] According to the preferred embodiment of the present invention, in step 3), the annealing is carried out under vacuum conditions, the annealing temperature is 200-800°C, the annealing time is 10-60 minutes, and the vacuum degree is 10 -5 ~10 -1 Pa.

[0021] More preferably, the annealing temperature is 200-500° C., and the annealing time is 15-30 min.

[0022] Preferably according to the present invention, in step 3), the solvent used for pickling is an aqueous solution of an inorganic acid or an organic acid.

[0023] More preferably, the solvent used for the pickling is aqueous hydrochloric acid solution, aqueous hydrofluoric acid solution or aqueous acetic acid solution, and the concentration is 0.5 mol / L to 3 mol / L.

[0024] Preferably according to the present invention, in step 3), the ball milling method is wet ball milling; the temperature of the vacuum drying is 65-75° C., and the time is 2-4 hours.

[0025] The above-mentioned nano-silicon materials with various morphological structures are used in the preparation of battery negative electrode sheets and batteries.

[0026] Where the present invention is not exhaustive, prior art may be used.

[0027] The beneficial effects of the present invention are:

[0028] 1. The nano-silicon material with various morphological structures prepared by the present invention has high purity and low oxygen content. It not only has the structural morphology of amorphous silicon and crystalline silicon, but also contains rich nanopore structures. By constructing an amorphous Si structure in situ in the nano-Si material and forming a pore structure at the same time, the volume expansion of Si can be alleviated and buffered during the charge and discharge process, thereby increasing the cycle stability. By forming a pore structure in the nano-Si material, the active sites for lithium ion storage can be increased, the contact area between the electrode material and the electrolyte can be increased, the specific capacity can be increased, and the conductivity and lithium ion transmission capacity of the material can be increased. By constructing an amorphous Si structure in situ in the nano-Si material, the dispersion performance of the nano-silicon material can be improved, and secondary agglomeration and the use of additional dispersants can be avoided; at the same time, the secondary grain growth of the nano-Si particles during the sintering process can be prevented, thereby effectively controlling the particle size distribution of the nano-silicon particles.

[0029] 2. Grinding the precursor particles to 100-1000 mesh and then carrying out the subsequent decomposition preparation process is firstly beneficial to the fluidity of the precursor and provides convenience for batch preparation. Secondly, the precursor particles with a certain particle size are beneficial to inhibiting the oxidation reaction of the nano-silicon material during the preparation process and obtaining nano-silicon materials with high capacity and low oxygen content.

[0030] 3. The nano-silicon materials with various morphological structures provided by the present invention can be used to prepare negative electrode materials for lithium batteries. Compared with conventional nano-silicon materials, they have the advantages of high initial efficiency, high capacity and excellent cycle performance.

[0031] 4. The present invention provides a method for preparing nano silicon materials with various morphological structures. The method first decomposes a silicon intermetallic compound of a specific particle size to obtain an amorphous composite, and then regulates the morphology of silicon through the zinc in the amorphous composite during annealing. Specifically, the nano Zn is allowed to migrate inside the agglomerated particles to form a nano porous structure through annealing, and the nano Zn is used to induce the crystallization of amorphous silicon to form nano crystals by using a heterogeneous nucleation mechanism, thereby obtaining nano silicon materials with various morphological structures. In addition, the method of the present invention adopts conventional equipment for synthesis, and does not use flammable, explosive, toxic reagents, etc. in the process. It can realize the batch preparation of nano silicon under mild conditions, and has the advantages of high safety, low production energy consumption, and high synthesis efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structure of nano silicon with various morphological structures of the present invention.

[0033] Figure 2 The high-resolution electron microscope morphology images of nano-silicon with various morphological structures of the present invention are shown.

[0034] Figure 3 The high-resolution transmission electron microscope images of mesocrystalline silicon and amorphous silicon of nano-silicon with various morphological structures of the present invention are shown.

[0035] Figure 4 The XRD diagrams of the nano-silicon materials with various morphological structures of the present invention are shown in FIG.

[0036] Figure 5 This is the XRD diagram of the nano-silicon material prepared in Comparative Example 2 of the present invention.

[0037] Figure 6 The invention discloses the cycle performance of batteries prepared from nano silicon materials with various morphological structures.

[0038] Figure 7 The invention discloses the cycle performance of silicon-carbon negative electrode material batteries prepared from nano silicon materials with various morphological structures. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with the accompanying drawings and specific examples, but should not be construed as limiting the present invention. The experimental methods and reagents without specific conditions in the examples are all based on conventional conditions in the art.

[0040] At the same time, the experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from commercial channels. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0041] The Li2ZnSi ternary alloy compounds involved in the following examples were prepared according to the following method:

[0042] In an argon atmosphere glove box, the single elements Li, Zn, and Si are mixed and sealed in a metal tantalum container at a molar ratio of 2:1:1, and the metal tantalum container is placed in a vacuum environment, and the temperature is increased to 600°C at a heating rate of 190°C / h and kept for 3 hours, and then cooled with the furnace. The metal tantalum container is opened in the argon atmosphere glove box, and the material obtained by the solid phase reaction is ground until there is no metallic luster. Subsequently, the ground material is sealed in a metal tantalum container for a second time, and the metal tantalum is placed in a vacuum environment, and the temperature is increased to 770°C at a heating rate of 210°C / h and kept for 4 hours. The metal tantalum container is opened in an argon atmosphere glove box, and the Li-Zn-Si ternary alloy compound obtained by the solid phase reaction is ground until there is no metallic luster, and a Li2ZnSi ternary alloy compound is obtained.

[0043] Example 1

[0044] A method for preparing nano-silicon materials with various morphological structures comprises the following steps:

[0045] 1) ball-milling a Li2ZnSi ternary alloy compound to a particle size of 500 mesh to obtain precursor particles;

[0046] 2) under argon protection, adding 10 g of precursor particles to 100 mL of ethanol, stirring overnight to carry out a lithium removal reaction, and after the reaction is completed, filtering the material using a suction filtration device to obtain an amorphous composite; the amorphous composite is agglomerated particles containing amorphous silicon and nano-Zn;

[0047] 3) The amorphous composite is placed in a tube furnace, and the vacuum degree of the tube furnace is pumped to 10 -5 Pa, annealing was carried out at a constant temperature of 250°C for 30 minutes, and the furnace was naturally cooled after the constant temperature was completed to obtain an intermediate product; then the intermediate product was slowly added into a stirred hydrochloric acid solution with a concentration of 2 mol / L under the protection of argon, and stirring was continued overnight; filtered using a suction filtration equipment, wet ball milled, and vacuum dried at 70°C for 3 hours to obtain nano-silicon materials with various morphological structures.

[0048] The schematic diagram of the structure of the nano-silicon material prepared in this embodiment is as follows Figure 1 As shown. Figure 1 It can be seen that the main body of the nanosilicon material prepared in this embodiment is amorphous nanosilicon, and the crystalline nanosilicon is embedded in the amorphous nanosilicon and wrapped by the amorphous nanosilicon to form an open nanopore structure, and the crystalline nanosilicon and the amorphous nanosilicon are closely connected through silicon atoms, rather than a simple physical mixture.

[0049] The high-resolution electron microscope morphology of the nano-silicon material prepared in this embodiment is as follows: Figure 2 As shown; high-resolution transmission electron microscopy images of mesocrystalline silicon and amorphous silicon are shown Figure 3 shown.

[0050] Depend on Figure 2 It can be seen that the particle size of the nano-silicon material prepared in this embodiment is about 10-30 nm, there are a large number of nano-pore structures, and the pore size distribution is 5-50 nm.

[0051] Depend on Figure 3 It can be seen that the nano-silicon material prepared in this embodiment has a large number of nano-pore structures and has both crystalline and amorphous forms.

[0052] The nano-silicon material prepared in this embodiment was tested using a nitrogen, oxygen and hydrogen analyzer. The test results showed that the oxygen content of the nano-silicon material prepared in this embodiment was less than 10%.

[0053] The XRD pattern of the nano-silicon material prepared in this embodiment is as follows: Figure 4 shown.

[0054] Depend on Figure 4 It can be seen that the XRD diffraction of the nano-silicon material prepared in this embodiment shows a bun peak near 25° and a broadened peak near 28.5°, which correspond to the (111) crystal plane diffraction of amorphous Si and cubic phase crystalline Si, respectively.

[0055] Then, the ratio of the crystalline part to the amorphous part in the nano-silicon material prepared in this embodiment is calculated as follows:

[0056] The XRD spectrum of nano-silicon particles is obtained by X-ray diffractometer. XRD analysis of nano-silicon particles is performed at room temperature using a CuKα-1 X-ray source (wavelength λ = 0.15406nm), with a measurement angle of 10° to 90° and a measurement speed of 0.02° / min. The XRD spectrum is deconvoluted using Origin software, and Voigt, Lorentzian and Gaussian functions are applied to the curve fitting of the spectrum to extract single crystalline and amorphous peaks, where the sharp peaks correspond to the crystalline region and the broad peaks correspond to the amorphous region. By the formula The crystallinity of nano-silicon was calculated, where Sc represents the integrated area of ​​the crystalline region and St represents the integrated area of ​​the total region.

[0057] It is calculated that the crystallinity of the nano-silicon material prepared in this embodiment is 62%.

[0058] In order to characterize the porous morphology and pore size of the nano-silicon material prepared in this embodiment, 0.2g of the nano-silicon material prepared in this embodiment was taken for nitrogen adsorption and desorption test, and combined with the BET formula calculation, the measured nano-silicon pore size ranged from 5nm to 100nm, and the average pore size was 30nm; 0.1g of the nano-silicon material prepared in this embodiment was ultrasonically dispersed in anhydrous ethanol solution, the solution was allowed to stand after ultrasonication, the supernatant was dropped onto a copper mesh carbon support film, and the nano-silicon particles were observed to be a porous structure under a high-power transmission electron microscope.

[0059] In order to characterize the porosity of the nano-silicon material prepared in this example, 0.5 g of the nano-silicon material prepared in this example was taken for mercury intrusion testing, and the porosity was measured to be 53%.

[0060] Example 2

[0061] A method for preparing nano-silicon materials with various morphological structures comprises the following steps:

[0062] 1) ball-milling the Li2ZnSi ternary alloy compound to a particle size of 300 meshes to obtain precursor particles;

[0063] 2) under argon protection, 10 g of the precursor particles were added to 150 mL of ethanol, and the mixture was stirred overnight to perform a lithium removal reaction. After the reaction was completed, the material was filtered using a suction filtration device to obtain an amorphous composite; the amorphous composite was agglomerated particles containing amorphous silicon and nano-Zn;

[0064] 3) The amorphous composite is placed in a tube furnace, and the vacuum degree of the tube furnace is pumped to 10 -3 Pa, annealing was carried out at a constant temperature of 350°C for 25 minutes. After the constant temperature was completed, the furnace was naturally cooled to obtain an intermediate product; then the intermediate product was slowly added into a stirred hydrochloric acid solution with a concentration of 2.5 mol / L under argon protection, and stirring was continued overnight; filtered using a suction filtration equipment, wet ball milled, and vacuum dried at 70°C for 3 hours to obtain nano-silicon materials with various morphological structures.

[0065] Example 3

[0066] A method for preparing nano-silicon materials with various morphological structures comprises the following steps:

[0067] 1) ball-milling the Li2ZnSi ternary alloy compound to a particle size of 800 mesh to obtain precursor particles;

[0068] 2) under argon protection, 10 g of the precursor particles were added to 200 mL of methanol, and the mixture was continuously stirred overnight for a lithium removal reaction. After the reaction was completed, the material was filtered using a suction filtration device to obtain an amorphous composite; the amorphous composite was agglomerated particles containing amorphous silicon and nano-Zn;

[0069] 3) The amorphous composite is placed in a tube furnace, and the vacuum degree of the tube furnace is pumped to 10 -1 Pa, annealing was carried out at a constant temperature of 450°C for 15 minutes, and the furnace was naturally cooled after the constant temperature was completed to obtain an intermediate product; then the intermediate product was slowly added to a stirred hydrochloric acid solution with a concentration of 1.5 mol / L under argon protection, and stirring was continued overnight; filtered using a suction filtration equipment, wet ball milled, and vacuum dried at 70°C for 3 hours to obtain nano-silicon materials with various morphological structures.

[0070] Comparative Example 1

[0071] The nano-Si material was prepared according to the method disclosed in Chinese patent document CN110284037A.

[0072] The transmission electron microscope image of the nano-silicon material in Example 1 and the nano-Si material in Chinese patent document CN110284037A (see Appendix 1 of Patent CN110284037A) Figure 2 ), it can be clearly found that the particle size and dispersibility of the nano-silicon prepared in Example 1 of the present invention are significantly better than those in Comparative Example 1.

[0073] Comparative Example 2

[0074] A method for preparing a nano-silicon material, the steps are the same as those in Example 1, except that in step (2), 5 g of Li2ZnSi precursor particles are added to 100 ml of 1 mol / L hydrochloric acid solution, stirred overnight, to obtain amorphous silicon particles.

[0075] The XRD pattern of the nano-silicon material prepared in this comparative example is as follows Figure 5 shown.

[0076] Comparing the XRD patterns of the nano-silicon material prepared in Example 1 with those of the nano-silicon material prepared in Comparative Example 2, it can be clearly found that in Example 1, nano-Zn migrates inside the agglomerated particles to form a nanoporous structure through annealing, and nano-Zn induces amorphous silicon to crystallize to form nanocrystals by using a heterogeneous nucleation mechanism, and the prepared nano-silicon material has good crystallinity and contains a crystalline structure. However, in Comparative Example 2, zinc element is removed at the same time as lithium element, and the prepared nano-silicon material has no crystallinity and thus no crystalline structure.

[0077] Test Example 1

[0078] The half-cell performance test of nano-silicon materials with various morphological structures is carried out as follows:

[0079] The nano-silicon material, acetylene black and sodium alginate prepared in Example 1 were added to 1.5 ml of deionized water in a mass ratio of 6:2:2, and the mixture was stirred in a porcelain cup for 5 hours to prepare a slurry. The resulting slurry was then evenly coated on a copper foil, vacuum dried overnight, and then cut into 4 pole pieces with a diameter of 14 mm, numbered as electrode pieces 1 to 4. Then, a metal lithium sheet was used as the battery counter electrode, electrode pieces 1 to 4 were used as the battery negative electrode, and the electrolyte was 1.0 M LiPF6 (EC:DMC:DEC=1:1:1 volume ratio, containing 10.0% FEC and 2.0% VC). The batteries were assembled in an Ar atmosphere glove box to obtain batteries 1 to 4. Battery cycle tests were performed on batteries 1 to 4. The current density in the battery cycle test was 0.1C. The test results are as follows: Figure 6 And as shown in Table 1.

[0080] Table 1

[0081]

[0082] Depend on Figure 5 As shown in Table 1, the initial specific capacity of the No. 3 battery prepared using the nano-silicon material of Example 1 of the present invention can reach 2799.4 mAh / g, and the first-cycle coulomb efficiency can reach 82.55%. It has good first-cycle coulomb efficiency and initial specific capacity, and has the potential for commercial application of negative electrodes.

[0083] Test Example 2

[0084] Nano-silicon materials with various morphological structures are used to prepare silicon-carbon negative electrode materials, and the half-cell performance of the silicon-carbon materials is tested. The specific methods are as follows:

[0085] Take 0.5g of asphalt and dissolve it in 5g of toluene solution. After the asphalt is completely dissolved, add 1g of the nano-silicon material prepared in Example 1 to the solution; ultrasonicate the mixed solution for 30min, pour it into a glass container, put it in a vacuum drying oven, and continuously vacuum dry it at 100°C; after drying, obtain solid powder, place the powder in a tube furnace, heat it to 900°C under a flowing argon environment, keep it constant for two hours, and then cool it naturally to obtain a silicon-carbon negative electrode material; add silicon-carbon negative electrode material, acetylene black and sodium alginate in a mass ratio of 7:1.5:1.5 to 1.5ml of deionized water, stir and mix in a porcelain cup for 5h to prepare a slurry. Then evenly apply the obtained slurry on copper foil, vacuum dry it overnight, and then cut it into 5 pole pieces with a diameter of 14mm, numbered as electrode pieces 1 to 5. Then, a lithium metal sheet was used as the battery counter electrode, and electrode sheets 1 to 5 were used as the battery negative electrode. The electrolyte was 1.0M LiPF6 (EC:DMC:DEC = 1:1:1 volume ratio, containing 10.0% FEC and 2.0% VC). The battery was assembled in an Ar atmosphere glove box to obtain batteries 1 to 5. Battery cycle tests were performed on batteries 1 to 5. The current density in the battery cycle test was 0.1C. The test results are as follows: Figure 7 And as shown in Table 2.

[0086] Table 2

[0087]

[0088] Depend on Figure 6 As shown in Table 2, the initial specific capacity of battery No. 1 prepared using the nano-silicon material of Example 1 of the present invention can reach 1561.9 mAh / g, and the first-cycle coulomb efficiency can reach 80.21%. It has good first-cycle coulomb efficiency and initial specific capacity, and has the potential for commercial application of negative electrodes.

Claims

1. A nano-silicon material having various morphological structures, characterized in that: The nano silicon material contains crystalline nano silicon, amorphous nano silicon and nano porous silicon, and silicon of three morphological structures coexists at the same time.

2. The nano-silicon material with multiple morphological structures as claimed in claim 1, characterized in that: The nano-silicon material is agglomerated silicon particles formed by agglomeration of crystalline nano-silicon, amorphous nano-silicon and nano-porous silicon; the average size of the agglomerated silicon particles is less than 100 nm.

3. The nano-silicon material with multiple morphological structures as claimed in claim 1, characterized in that: The main body of the nano-silicon material is amorphous nano-silicon, and the crystalline nano-silicon is embedded in the amorphous nano-silicon and wrapped by the amorphous nano-silicon to form an open nano-pore structure; the average particle size of the crystalline nano-silicon is less than 20nm; More preferably, the average particle size distribution of the crystalline nano-silicon is 5 to 10 nm.

4. The nano-silicon material with multiple morphological structures as claimed in claim 1, characterized in that: The crystalline nano-silicon content in the crystalline nano-silicon is less than 90%, and the non-crystalline nano-silicon content is higher than 10%; the nano-silicon material has a rich porous structure inside to form nano-porous silicon; the average pore size distribution of the nano-porous silicon is 5-50nm, and the porosity is greater than 30%.

5. The method for preparing nano-silicon materials with various morphological structures according to claim 1, characterized in that: The steps include: 1) ball-milling the Li-Zn-Si compound to a particle size of 100 to 1000 mesh to obtain precursor particles; 2) subjecting the precursor particles to a lithium removal reaction to obtain a composite of amorphous Si and nano Zn; 3) The composite of amorphous Si and nano Zn is annealed, and after acid washing, ball milling and vacuum drying, nano silicon materials with various morphological structures are obtained.

6. The method for preparing nano-silicon materials having various morphological structures according to claim 6, characterized in that: In step 1), the Li-Zn-Si compound is a Li2ZnSi ternary alloy compound.

7. The method for preparing nano-silicon materials with various morphological structures according to claim 6, characterized in that: In step 2), the delithiation reaction may be carried out using an organic alcohol, including but not limited to methanol or ethanol; the mass volume ratio of the precursor particles to the organic alcohol is 1:(10-100), unit: g / mL.

8. The method for preparing nano-silicon materials with various morphological structures according to claim 6, characterized in that: In step 3), the annealing is carried out under vacuum conditions, the annealing temperature is 200-800°C, the annealing time is 10-60 minutes, and the vacuum degree is 10 -5 ~10 -1 Pa; More preferably, the annealing temperature is 200-500° C., and the annealing time is 15-30 min.

9. The method for preparing nano-silicon materials with various morphological structures according to claim 6, characterized in that: In step 3), the solvent used for pickling is an aqueous solution of an inorganic acid or an organic acid; the ball milling method is wet ball milling; the temperature of the vacuum drying is 65 to 75° C., and the time is 2 to 4 hours; More preferably, the solvent used for pickling is aqueous hydrochloric acid solution, aqueous hydrofluoric acid solution or aqueous acetic acid solution, and the concentration is 0.5 mol / L to 3 mol / L.

10. Use of the nano silicon material with various morphological structures as claimed in claim 1 in the preparation of battery negative electrode sheets and batteries.

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