Method for constructing silicon / graphene / ferroelectric composite material in-situ on current collector and application thereof

Abstract

The application discloses a method for constructing a silicon-based / graphene / ferroelectric composite material on a current collector in situ and application, and relates to the technical field of lithium ion batteries. The method comprises the following steps: firstly, a ferroelectric / graphene composite material is constructed on a current collector in situ by using a laser induction technology; secondly, a silicon-based / graphene / ferroelectric composite material is constructed on the current collector in situ by using the laser induction technology; and finally, the silicon-based / graphene / ferroelectric composite material is treated by using a high-voltage corona polarization method. The silicon-based / graphene / ferroelectric composite material constructed on the current collector in situ can be applied to a lithium ion battery negative electrode, has a high lithium ion diffusion rate, excellent cycle capacity and cycle stability under a large current density, and has a wide application prospect in the field of secondary batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, and particularly relates to a method for constructing a silicon-based / graphene / ferroelectric composite material in situ on a current collector and application thereof. BACKGROUND

[0002] Lithium ion batteries (LIBs) have been successfully commercialized and widely applied in mobile electronic devices due to their high energy density and long service life. However, the demand for advanced LIBs with higher specific capacity and longer cycle life to drive electric vehicles and high-end electronic devices is growing. The specific capacity of existing electrode materials such as commercialized graphite negative electrode has reached 360 mAh / g, close to its theoretical specific capacity (372 mAh / g), and still cannot meet the demand, which stimulates the research on new electrode materials.

[0003] Silicon-based negative electrode materials are considered as potential candidates for graphite negative electrodes due to their high specific capacity (the theoretical specific capacity of elemental silicon is 4200 mAh / g, and the specific capacity of silicon monoxide is 2680 mAh / g) and low working potential (~0.4 V). The severe volume expansion of silicon-based materials during lithium intercalation is considered as a key limitation, and the resulting pulverization of silicon can lead to significant performance deterioration. By forming silicon-based composites with other active conductive materials (carbonaceous materials such as hard carbon, graphene or carbon nanotubes) or by designing a controllable structure to provide a buffer space (such as a three-dimensional porous structure), the lithium storage behavior of silicon-based materials can be regulated, and the first coulombic efficiency and cycle stability can be improved. However, the cycle performance of lithium ion battery silicon-based negative electrode materials at high rate still needs to be optimized.

[0004] In recent years, various energy generating materials (e.g. piezoelectric, pyroelectric and ferroelectric materials) and their composites have been actively applied in novel energy conversion devices. In particular, artificial interfacial layers based on ferroelectric materials (e.g. polyvinylidene fluoride and barium titanate) have been used to mediate metal deposition in lithium / zinc metal batteries. In addition, ferroelectric materials are also a class of piezoelectric materials that can enable the conversion between mechanical and electrical energy. The piezoelectricity in the present invention is induced by internal stress, i.e. the large volume expansion of silicon-based materials is transferred to the piezoelectric material, which can be polarized. This strategy relies on the ferroelectricity of the coating to induce a uniform and switchable surface polarization that directs the ordered ion migration, which can solve the problem of ion flux inhomogeneity to some extent. In order to realize this concept, strong adhesion between silicon-based materials and ferroelectric materials and carbon matrix is required. The carbon matrix transfers the mechanical stress caused by the large-scale expansion of silicon-based materials to the piezoelectric material, while maintaining the conductive path of lithium ions. However, due to the limited polarization degree of the ferroelectric layer in the vertical direction of the negative electrode, the rapid supply of ions is still insufficient. This is related to the low intensity of the self-built electric field (E) in the battery, which leads to limited polarization domain in the direction of the self-built electric field of the battery, and in addition, the spontaneous polarization direction of the ferroelectric material under pressure is random. Therefore, the fast charging stability is still far from the expected effect.

[0005] Therefore, if the polarization intensity of the ferroelectric material can be enhanced, a directional uniform and improved built-in electric field can be constructed, which will inevitably improve the fast charging performance of the lithium ion battery. SUMMARY

[0006] The technical problem to be solved by the present invention is to provide a method for in-situ construction of silicon-based / graphene / ferroelectric composite material on the current collector, and to directly apply the silicon-based / graphene / ferroelectric composite material loaded on the current collector as a negative electrode to a lithium ion battery. First, the corona polarization treatment of the ferroelectric layer can produce a directional and uniform built-in electric field, which optimizes the nonlinear spatial distribution of the field gradient and can effectively regulate the ion migration between the electrode and the electrolyte. Second, the ferroelectric layer also has piezoelectric properties. During the lithiation process, the volume expansion of silicon particles causes compressive stress, which partially reverses the deformation of the ferroelectric layer and reduces the local built-in field. Subsequently, the diffusion direction of lithium ions also changes, thereby relieving the excessive internal stress. In addition, this silicon-based / graphene / ferroelectric composite material is prepared in-situ on the current collector, ensuring the losslessness of the self-integrated structure. Moreover, the silicon-based material is in-situ encapsulated into the three-dimensional graphene network, realizing effective physical confinement. At the same time, the three-dimensional hierarchical porous structure promotes ion transport and charge transfer, and relieves mechanical deformation. Therefore, the silicon-based / graphene / ferroelectric composite material constructed in-situ on the current collector has outstanding cycle stability and excellent charge and discharge performance at high rates.

[0007] The technical problems to be solved by the present application are solved by the following technical solutions:

[0008] A first object of the present application is to provide a method for constructing a silicon / graphene / ferroelectric composite material in situ on a current collector, comprising the following steps:

[0009] (1) mixing a ferroelectric material, a polymer or a precursor thereof, and a solvent thoroughly, and then coating the mixture onto the current collector, drying and curing to form a ferroelectric / polymer film on the current collector;

[0010] (2) processing the ferroelectric / polymer film by laser induction technology to construct a ferroelectric / graphene composite material in situ on the current collector;

[0011] (3) mixing a silicon-based material, a polymer or a precursor thereof, and a solvent thoroughly, and then coating the mixture onto the ferroelectric / graphene composite material, drying and curing to form a silicon-based / polymer / ferroelectric / graphene composite on the current collector;

[0012] (4) processing the silicon-based / polymer / ferroelectric / graphene composite by laser induction technology to construct a silicon / graphene / ferroelectric composite material in situ on the current collector;

[0013] (5) processing the silicon / graphene / ferroelectric composite material by high-voltage corona polarization.

[0014] The present application uses laser induction technology to directly prepare a ferroelectric / graphene layer in situ on the current collector, then uses laser induction technology to prepare a silicon / graphene layer in situ on the ferroelectric / graphene layer, and finally processes the silicon / graphene / ferroelectric composite material constructed in situ on the current collector by high-voltage corona polarization to obtain a polarized silicon / graphene / ferroelectric composite material on the current collector.

[0015] A second object of the present application is to provide a silicon / graphene / ferroelectric / current collector composite material prepared by the aforementioned method.

[0016] A third object of the present application is to provide the use of the silicon / graphene / ferroelectric / current collector composite material in lithium ion batteries.

[0017] A fourth object of the present application is to provide a lithium ion battery using the silicon / graphene / ferroelectric / current collector composite material as the negative electrode.

[0018] The present application has the following beneficial effects:

[0019] 1、The application mainly utilizes the high-voltage corona polarization ferroelectric / graphene coating to establish an internal electric field in the ferroelectric layer, optimizes the nonlinear spatial distribution of ion concentration and electric field gradient (especially at high speed), optimizes the transport mechanism of lithium ions in solid-phase particles and liquid-phase electrolyte, provides a new driving force for the migration of lithium ions, promotes the diffusion of lithium ions from the local high-concentration site to the surrounding area to be faster and more uniform, and avoids the damage of lithium dendrite growth to the battery performance; in addition, the ferroelectric / graphene intermediate layer can reduce the crushing effect of silicon particles caused by volume expansion during lithiation; secondly, the ferroelectric material also has piezoelectric properties, and the volume expansion of silicon particles during lithiation causes compressive stress, which partially reverses the deformation of the ferroelectric body, reduces the local internal field (positive piezoelectric effect), and this modulation promotes the dispersion of lithium ions to the alternating site, dynamically adjusts the transport of lithium ions, and thus relieves the excessive internal stress; in addition, the silicon-based / graphene / ferroelectric composite material is prepared in situ on the current collector by laser induction technology, which ensures the losslessness of the self-integrated structure and does not need to add additional inactive binders to cause unnecessary side reactions; in-situ synthesis ensures that the silicon monoxide is encapsulated into the three-dimensional graphene network, which has a complete encapsulation effect and prevents particle shedding; finally, the continuous ion transport channel and conductive network provided by the three-dimensional graphene network increase the contact area of the electrode and the electrolyte, reduce the local current density, delay the formation of lithium dendrites, reduce the spatial steric hindrance of ion transport, and are beneficial to relieving the volume expansion.

[0020] 2、The silicon-based / graphene / ferroelectric composite material constructed in situ on the current collector of the application can be applied to the negative electrode of a lithium ion battery, has a high lithium ion diffusion rate and excellent cycle capacity and cycle stability at a high current density; and the method provided by the application is simple to operate, has strong expandability, and has a wide application prospect in the field of secondary batteries. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is the scanning electron microscope graph and particle size distribution graph of barium titanate in Example 1.

[0022] Figure 2 It is the X-ray diffraction graph of barium titanate in Example 1.

[0023] Figure 3 It is the Raman spectrum graph of barium titanate in Example 1.

[0024] Figure 4 It is the contact angle test graph of the Si / LIG / UBTO prepared in Example 1 to the lithium ion battery electrolyte.

[0025] Figure 5 It is the contact angle test graph of the Si / LIG / NBTO prepared in Comparative Example 1 to the lithium ion battery electrolyte.

[0026] Figure 6 A comparison chart of lithium ion diffusion coefficients of lithium ion batteries assembled with Si / LIG / UBTO prepared in Example 1, Si / LIG / NBTO prepared in Comparative Example 1 and Si / LIG prepared in Comparative Example 2 as an anode, respectively;

[0027] Figure 7 A comparison chart of cycle performance of lithium ion batteries assembled with Si / LIG / UBTO prepared in Example 1, Si / LIG / NBTO prepared in Comparative Example 1 and Si / LIG prepared in Comparative Example 2 as an anode, respectively. DETAILED DESCRIPTION

[0028] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific embodiments and drawings.

[0029] The present application provides a method for constructing a silicon / graphene / ferroelectric composite material in situ on a current collector, comprising the following steps:

[0030] (1) mixing a ferroelectric material, a polymer or a precursor thereof and a solvent thoroughly, and then coating the mixture onto a current collector, and drying and solidifying to form a ferroelectric / polymer film on the current collector;

[0031] (2) treating the ferroelectric / polymer film by a laser-induced technique to construct a ferroelectric / graphene composite material in situ on the current collector;

[0032] (3) mixing a silicon-based material, a polymer or a precursor thereof and a solvent thoroughly, and then coating the mixture onto the ferroelectric / graphene composite material, and drying and solidifying to form a silicon-based / polymer / ferroelectric / graphene composite on the current collector;

[0033] (4) treating the silicon-based / polymer / ferroelectric / graphene composite by a laser-induced technique to construct a silicon-based / graphene / ferroelectric composite material in situ on the current collector;

[0034] (5) treating the silicon-based / graphene / ferroelectric composite material by a high-voltage corona polarization method.

[0035] Further, the ferroelectric material is selected from one or more of oxide ferroelectrics (such as barium titanate, lead zirconate titanate, lead tungstate, lead titanate, potassium niobate, lithium niobate, etc.), halide ferroelectrics (such as thallium bromide, lead bromide, etc.), chalcogenide ferroelectrics (such as germanium sulfide, gallium sulfide, etc.), hydrogen bond ferroelectrics (such as potassium dihydrogen phosphate, ammonium dihydrogen phosphate, etc.), organic ferroelectrics (such as polyvinylidene fluoride and its copolymer, polyvinyl alcohol, etc.).

[0036] Further, the size of the ferroelectric material is 1 nm to 100 μm.

[0037] Further, the polymer is selected from one or more of polyethylene, polypropylene, polysulfide rubber, polyvinyl chloride, polyetherimide, polyether ether ketone, polyether, polyimide, polyester, polyamide, polyurethane, and the like.

[0038] Further, the mass ratio of the ferroelectric material, the polymer, or the precursor thereof is 1:(0.01-1000).

[0039] Further, the current collector includes, but is not limited to, one or more of single-surface copper foil, double-surface copper foil, carbon-coated copper foil, foamed copper, carbon cloth, carbon paper, nickel foil, and foamed nickel, with a thickness of 100 nm-100 μm.

[0040] Further, the solvent is N-methyl pyrrolidone (NMP). NMP is a commonly used slurry preparation solvent in the process of lithium ion battery electrode preparation, and has the advantages of non-toxicity, low viscosity, small corrosion, good stability, and good wettability to the current collector.

[0041] Further, the temperature for drying and curing is 25-500°C. The curing can be performed at room temperature or under heating conditions.

[0042] Further, the laser is selected from one or more of solid-state laser, gas laser, semiconductor laser, fiber laser, pulsed laser, continuous laser, and excimer laser, with a wavelength of 0.01-100 μm, a power of 0.1-1000 W, a scanning speed of 0.1-1000 mm / s, a scanning interval of 0.001-10 mm, a pulse frequency of 0.01-500 kHz, a focal length of 0.1-200 cm, and a pressure range of 1-2000 kV.

[0043] Further, the silicon-based material includes, but is not limited to, one or more of silicon, silicon-carbon, silicon-oxygen, and silicon-oxygen-carbon.

[0044] Further, the size of the silicon-based material is 1 nm-30 μm.

[0045] Further, the mass ratio of the silicon-based material, the polymer, or the precursor thereof is 1:(0.1-200).

[0046] Further, the polarization voltage of the high-voltage corona polarization is 0.01-1000 kV, the polarization time is 0.001-100 h, the polarization temperature is 5-50°C, and the distance from the tip to the current collector is 0.001-100 cm.

[0047] Further, the mass ratio of the ferroelectric material in the silicon / graphene / ferroelectric composite material is 0.1-50%.

[0048] Further, the silicon-based material has a mass ratio of 1-90% in the silicon-based / graphene / ferroelectric composite material.

[0049] The application provides a silicon-based / graphene / ferroelectric / current collector composite material prepared by the method.

[0050] The application provides application of the silicon-based / graphene / ferroelectric / current collector composite material in a lithium ion battery.

[0051] The application provides a lithium ion battery taking the silicon-based / graphene / ferroelectric / current collector composite material as a negative electrode.

[0052] The technical scheme of the application is described in detail below through specific examples.

[0053] Example 1

[0054] (1) 10 g of barium titanate particles (D50=200 nm) were ultrasonically dispersed in 30 mL of NMP, 35 g of polyamide acid was added, and the mixture was stirred to obtain a uniform slurry, then the slurry was coated on a 15 μm thick single-faceted copper foil with a coating thickness of 50 μm, and then dried and cured in a vacuum oven (heating program: 60℃ / 12h, 80℃ / 2h, 100℃ / 2h, 120℃ / 2h, 140℃ / 2h, 250℃ / 2h), and naturally cooled to room temperature to obtain a barium titanate / polyimide film.

[0055] (2) The barium titanate / polyimide film prepared in step (1) was induced by a carbon dioxide infrared laser with a wavelength of 10.6 μm, the laser scanning power was 6.6 W, the scanning rate was 200 mm / s, the scanning interval was 0.08 mm, the pulse frequency was 20 kHz, the focal length was 3.4 cm, the voltage was 100 kV, and a barium titanate / graphene layer was constructed in situ on the copper foil.

[0056] (3) 20 g of elemental silicon particles (D50=500 nm) were ultrasonically dispersed in 25 mL of NMP, 20 g of polyimide was added, and the mixture was stirred to obtain a uniform slurry, then the slurry was coated on the barium titanate / graphene layer prepared in step (2) with a coating thickness of 60 μm, and then dried and cured in a vacuum oven (heating program: 60℃ / 24h, 100℃ / 1h, 150℃ / 1h, 200℃ / 1h, 250℃ / 1h), and naturally cooled to room temperature to form a silicon / polyimide film on the barium titanate / graphene layer.

[0057] (4) Using the carbon dioxide infrared laser with a wavelength of 10.6 μm to induce the silicon / polyimide film prepared in step (3), the laser scanning power is 8.0 W, the scanning rate is 100 mm / s, the scanning interval is 0.1 mm, the pulse frequency is 20 kHz, the focal length is 3.4 cm, and the voltage is 100 kV, to form a silicon / graphene layer on the barium titanate / graphene layer, that is, to construct a silicon / graphene / barium titanate composite material in situ on the copper foil. The thickness of the barium titanate / graphene layer is 35 μm, the mass ratio of barium titanate in the composite material is 20%, the thickness of the silicon / graphene layer is 55 μm, and the mass ratio of silicon in the composite material is 55%.

[0058] (5) Using the high-voltage corona polarization method to treat the silicon / graphene / barium titanate composite material prepared in step (4), the polarization voltage is 20 kV, the polarization time is 1 h, the distance from the stainless steel tip to the copper foil is 15 cm, and the polarization temperature is 20°C, to finally construct a barium titanate / graphene intermediate layer and a silicon / graphene active layer (named Si / LIG / UBTO) in situ on the copper foil.

[0059] From Figure 1 It can be seen that the barium titanate is a monodisperse particle, and the size is mainly concentrated in 200 nm.

[0060] From Figure 2 It can be seen that the barium titanate maintains a good crystal structure and can be accurately matched with tetragonal barium titanate (PDF #05-0626).

[0061] From Figure 3 It can be seen that the Raman peaks near 305 and 715 cm -1 are considered to be characteristic peaks of the ferroelectric tetragonal structure.

[0062] From Figure 4 It can be seen that the Si / LIG / UBTO prepared in Example 1 has good wetting performance for the lithium ion battery electrolyte (1M LiPF6+EC / DEC).

[0063] Comparative Example 1

[0064] The preparation method of the present comparative example is the same as that of Example 1, and the difference from Example 1 is that the silicon / graphene / barium titanate composite material (named Si / LIG / NBTO) constructed on the copper foil is not treated by the high-voltage corona polarization method.

[0065] From Figure 5 It can be seen that the Si / LIG / NBTO prepared in Comparative Example 1 also has good wetting performance for the lithium ion battery electrolyte (1M LiPF6+EC / DEC), which indicates that the corona polarization does not affect the wetting performance of the material for the electrolyte.

[0066] Comparative Example 2

[0067] The preparation method of the present comparative example is the same as that of Example 1, with the exception that only steps (1) and (2) are not performed, i.e. the silicon / graphene composite material (named Si / LIG) is directly constructed in situ on the current collector.

[0068] Example 2

[0069] (1) 15 g of thallium bromide (D50 = 500 nm) was ultrasonically dispersed in 40 mL of NMP, 55 g of polyethylene was then added, and the mixture was stirred to obtain a uniform slurry, which was then coated onto a 12 μm thick carbon-coated copper foil with a coating thickness of 30 μm, followed by drying and curing in a vacuum oven (heating program: 80°C / 10 h, 100°C / 1 h, 180°C / 1 h, 250°C / 1 h, 300°C / 2 h), and natural cooling to room temperature, to obtain a thallium bromide / polyethylene film.

[0070] (2) The thallium bromide / polyethylene film prepared in step (1) was induced by a carbon dioxide laser with a wavelength of 1064 nm to construct a thallium bromide / graphene layer in situ on the carbon-coated copper foil, with a laser scanning power of 10.5 W, a scanning rate of 300 mm / s, a scanning interval of 0.12 mm, a pulse frequency of 30 kHz, a focal length of 3.7 cm, and a voltage of 70 kV.

[0071] (3) 15 g of silicon monoxide particles (D50 = 300 nm) was ultrasonically dispersed in 30 mL of NMP, 50 g of polyethylene was then added, and the mixture was stirred to obtain a uniform slurry, which was then coated onto the thallium bromide / graphene layer prepared in step (2) with a coating thickness of 45 μm, followed by drying and curing in a vacuum oven (heating program: 60°C / 12 h, 140°C / 1 h, 180°C / 1 h, 220°C / 1 h, 250°C / 1 h), and natural cooling to room temperature, to form a silicon monoxide / polyethylene film on the thallium bromide / graphene layer.

[0072] (4) The silicon monoxide / polyethylene film prepared in step (3) was induced by a carbon dioxide laser with a wavelength of 1064 nm to form a silicon monoxide / graphene layer on the thallium bromide / graphene layer, i.e. to construct a silicon monoxide / graphene / thallium bromide composite material in situ on the carbon-coated copper foil, with a laser scanning power of 8.8 W, a scanning rate of 150 mm / s, a scanning interval of 0.12 mm, a pulse frequency of 30 kHz, a focal length of 3.7 cm, and a voltage of 70 kV. The thickness of the thallium bromide / graphene layer was 25 μm, the mass ratio of thallium bromide in the composite material was 25%, and the thickness of the silicon monoxide / graphene layer was 45 μm, the mass ratio of silicon monoxide material in the composite material was 25%.

[0073] (5) The silicon monoxide / graphene / thallium bromide composite material constructed on the carbon-coated copper foil in step (4) is treated by high-voltage corona polarization method, the polarization voltage is 30 kV, the polarization time is 3 h, the distance between the stainless steel tip and the carbon-coated copper foil is 10 cm, and the polarization temperature is 25°C. Finally, a thallium bromide / graphene intermediate layer and a silicon monoxide / graphene active layer are constructed in situ on the carbon-coated copper foil.

[0074] Example 3

[0075] (1) 50 g of germanium sulfide (D50 = 1 μm) is ultrasonically dispersed in 24 mL of NMP, and then 70 g of polyether ether ketone is added and stirred to obtain a uniform slurry. The slurry is then coated onto a 10 μm thick carbon cloth with a coating thickness of 10 μm, and then dried and cured in a vacuum oven (heating program: 60°C / 8 h, 150°C / 2 h, 200°C / 2 h, 250°C / 1 h, 350°C / 2 h), and then naturally cooled to room temperature to obtain a germanium sulfide / polyether ether ketone film.

[0076] (2) The germanium sulfide / polyether ether ketone film prepared in step (1) is induced by visible light laser with a wavelength of 405 nm, the laser scanning power is 14.5 W, the scanning rate is 250 mm / s, the scanning interval is 0.05 mm, the pulse frequency is 55 kHz, the focal length is 4.2 cm, and the voltage is 100 kV. A germanium sulfide / graphene layer is constructed in situ on the carbon cloth.

[0077] (3) 25 g of silicon-oxygen-carbon particles (D50 = 800 nm) is ultrasonically dispersed in 50 mL of NMP, and then 60 g of polyether ether ketone is added and stirred to obtain a uniform slurry. The slurry is then coated onto the germanium sulfide / graphene layer prepared in step (2) with a coating thickness of 75 μm, and then dried and cured in a vacuum oven (heating program: 60°C / 12 h, 140°C / 2 h, 200°C / 1 h, 250°C / 1 h, 320°C / 1 h), and then naturally cooled to room temperature to form a silicon-oxygen-carbon / polyether ether ketone film on the germanium sulfide / graphene layer.

[0078] (4) The silicon-oxygen-carbon / polyether ether ketone film prepared in step (3) is induced by visible light laser with a wavelength of 405 nm, the laser scanning power is 5.4 W, the scanning rate is 200 mm / s, the scanning interval is 0.15 mm, the pulse frequency is 50 kHz, the focal length is 4.2 cm, and the voltage is 40 kV. A silicon-oxygen-carbon / graphene layer is formed on the germanium sulfide / graphene layer, i.e. a silicon-oxygen-carbon / graphene / germanium sulfide composite material is constructed in situ on the carbon cloth. The thickness of the germanium sulfide / graphene layer is 15 μm, the mass percentage of germanium sulfide in the composite material is 20%, the thickness of the silicon-oxygen-carbon / graphene layer is 65 μm, and the mass percentage of silicon-oxygen-carbon material in the composite material is 45%.

[0079] (5) The silicon-oxygen-carbon / graphene / germanium sulfide composite material constructed on the carbon cloth in step (4) is treated by high-voltage corona polarization method, the polarization voltage is 50 kV, the polarization time is 12 h, the distance from the stainless steel tip to the carbon cloth is 6 cm, and the polarization temperature is 15°C. Finally, a germanium sulfide / graphene intermediate layer and a silicon-oxygen-carbon / graphene active layer are constructed in situ on the carbon cloth.

[0080] Example 4

[0081] The preparation method of this example is the same as that of Example 1, and the only difference from Example 1 is that the elemental silicon D50 = 800 nm.

[0082] Example 5

[0083] The preparation method of this example is the same as that of Example 2, and the only difference from Example 2 is that the mass of silicon monoxide is 35 g.

[0084] Example 6

[0085] The preparation method of this example is the same as that of Example 3, and the only difference from Example 3 is that the corona polarization voltage is 25 kV.

[0086] Si / LIG / UBTO prepared in Example 1, Si / LIG / NBTO prepared in Comparative Example 1, and Si / LIG prepared in Comparative Example 2 are assembled into CR2032 button lithium ion half-batteries as negative electrodes, and their electrochemical performances are tested, and the results are shown in Figure 6 and Figure 7 .

[0087] Si / LIG / UBTO, Si / LIG / NBTO and Si / LIG are punched into round electrode plates with a diameter of 12 mm, and then the assembly process is completed in an argon-filled glove box (water and oxygen content is less than 0.1 ppm), lithium metal sheet is used as the counter / reference electrode, Celgard2400 microporous membrane is used as the separator, and 1M LiPF6 dissolved in a mixed solution of ethylene carbonate and diethyl carbonate (volume ratio is 1:1) is used as the electrolyte.

[0088] The lithium ion diffusion coefficient and cycle performance are tested at room temperature by using a blue electric CT2001A battery test system (Wuhan Blue Electric Electronics Co., Ltd., China), and the potential window range is from 0.01 to 3V (relative to Li / Li + ). All tests are carried out at 25°C.

[0089] The Li + diffusion coefficient is further analyzed by using the constant current intermittent titration technique (GITT), the pulse duration is 10 min, the interval time is 30 min, and 8 cycles of charge and discharge cycles are carried out at 0.1 A / g before GITT test. When the voltage and pulse duration τ1 / 2 When linearly dependent, the diffusion rate of lithium ions can be calculated according to the second law of Fick diffusion.

[0090] From Figure 6 It can be seen that Si / LIG without ferroelectric layer shows lower Li + diffusion coefficient, in the order of 10-12, which can be attributed to the slow ion transport kinetics inside the battery, especially at the solid electrode material and electrolyte interface, while the large concentration polarization hinders the diffusion of Li + ions. After the construction of the ferroelectric layer between the Si / LIG active layer and the current collector, the Si / CNT / NBTO shows an improved lithium ion diffusion coefficient. This is because the BTO layer at room temperature has ferroelectricity and piezoelectricity, and the mechanical stress generated by the expansion of silicon is transferred to BTO through the carbon matrix. BTO can be polarized, thereby generating a piezoelectric potential. This local piezoelectric potential can improve the electrochemical performance of the Si / LIG / NBTO nanocomposite anode. However, due to the limited built-in battery strength generated by the volume expansion of silicon, and the randomness of the direction of this spontaneous polarization, the rapid supply of ions is still insufficient. The Li + diffusion coefficient of Si / LIG / UBTO prepared by high-voltage corona polarization treatment is significantly enhanced, in the order of 10-10, showing excellent ion transport rate, which is beneficial to the improvement of the cycle performance of lithium ion batteries at large current density. Therefore, the built-in electric field constructed by corona polarization treatment optimizes the spatial distribution of concentration gradient and electric field gradient, showing a rapid and uniform lithium deintercalation behavior.

[0091] From Figure 7 It can be seen that the cycle stability of Si / LIG and Si / LIG / NBTO electrodes is poor at a larger current density of 2.0 A / g, and the capacity rapidly decays, while the cycle stability of Si / LIG / UBTO after high-voltage corona polarization treatment is significantly improved, showing excellent capacity retention rate in 100 charge-discharge cycles, and the specific capacity is stably maintained at about 1200 mAh / g, which is significantly better than Si / LIG / NBTO and Si / LIG without polarization treatment. By high-voltage corona polarization treatment, a directional and effective built-in electric field can be generated in the ferroelectric layer, promoting the uniformization and self-acceleration of lithium ion migration and deposition. In addition, the interface coating also acts as a physical barrier, playing a mechanical role in inhibiting the growth of lithium dendrites.

[0092] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for in-situ construction of a silicon-based / graphene / ferroelectric composite material on a current collector, characterized in that: The following steps are involved: (1) thoroughly mixing a ferroelectric material, a polymer or its precursor, and a solvent, and coating the mixture on a current collector, drying and curing the mixture to form a ferroelectric / polymer film on the current collector; (2) Using laser-induced technology to process ferroelectric / polymer films and in situ construct ferroelectric / graphene composite materials on the current collector; (3) fully mixing the silicon-based material, polymer or its precursor, and solvent, and coating the mixture on the ferroelectric / graphene composite material, drying and curing the mixture to form a silicon-based / polymer / ferroelectric / graphene composite on the current collector; (4) Using laser induction technology to process silicon-based / polymer / ferroelectric / graphene composites, in situ constructing silicon-based / graphene / ferroelectric composite materials on the current collector; (5) High voltage corona poling method was used to treat silicon-based / graphene / ferroelectric composite materials.

2. The method according to claim 1, wherein: The ferroelectric material is selected from one or more of oxide ferroelectrics, halide ferroelectrics, chalcogenide ferroelectrics, hydrogen bond ferroelectrics, and organic ferroelectrics.

3. The method according to claim 1, wherein: The mass ratio of the ferroelectric material, polymer or its precursor is 1: (0.01~1000).

4. The method according to claim 1, wherein: The polymer is selected from one or more of polyethylene, polypropylene, polysulfide rubber, polyvinyl chloride, polyetherimide, polyetheretherketone, polyether, polyimide, polyester, polyamide, and polyurethane.

5. The method according to claim 1, wherein: The current collector is selected from one or more of single-sided copper foil, double-sided copper foil, carbon-coated copper foil, foam copper, carbon cloth, carbon paper, nickel foil, and foam nickel.

6. The method according to claim 1, wherein: The silicon-based material is selected from one or more of silicon, silicon-carbon, silicon-oxygen, and silicon-oxygen-carbon.

7. The method according to claim 1, wherein: The mass ratio of the silicon-based material, polymer or its precursor is 1: (0.1~200).

8. The method according to claim 1, wherein: The laser is selected from one or more of solid laser, gas laser, semiconductor laser, and fiber laser, with a laser wavelength of 0.01-100 μm, a laser power of 0.1-1000 W, a scanning rate of 0.1-1000 mm / s, a scanning spacing of 0.001-10 mm, a pulse frequency of 0.01-500 kHz, a focal length of 0.1-200 cm, and a pressure range of 1-2000 kV.

9. The method according to claim 1, wherein: The polarization voltage of the high-voltage corona poling is 0.01-1000 kV, the polarization time is 0.001-100 h, the polarization temperature is 5-50° C., and the distance from the tip to the current collector is 0.001-100 cm.

10. The method according to claim 1, wherein: The mass proportion of the ferroelectric material in the silicon-based / graphene / ferroelectric composite material is 0.1-50%; the mass proportion of the silicon-based material in the silicon-based / graphene / ferroelectric composite material is 1-90%.

11. A silicon-based / graphene / ferroelectric / current collector composite material prepared by the method according to any one of claims 1 to 10.

12. Use of the silicon-based / graphene / ferroelectric / current collector composite material according to claim 11 in lithium-ion batteries.

13. A lithium-ion battery using the silicon-based / graphene / ferroelectric / current collector composite material according to claim 11 as a negative electrode.

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