Preparation method of silicon-based negative electrode all-solid-state battery

Abstract

The invention discloses a preparation method of a silicon-based negative electrode all-solid-state battery, and relates to the technical field of all-solid-state batteries. A silicon-based composite material precursor is prepared by adopting a suspension smelting and rapid quenching technology, the silicon-based composite material precursor is sanded and mixed with a conductive agent to prepare a negative plate, and the all-solid-state battery is assembled in an argon environment. The silicon-based negative electrode all-solid-state battery shows excellent chemical stability and mechanical stability, and has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of all-solid-state batteries, and in particular to a method for preparing a silicon-based negative electrode all-solid-state battery. Background Art

[0002] As energy demand in electric vehicles and grid energy storage continues to escalate, the need for energy storage batteries with improved safety, lower costs, higher energy density, and longer cycle life is becoming increasingly apparent. Safety concerns and range anxiety have always been two major obstacles to the widespread adoption of electric vehicles. However, compared to solid-state batteries, liquid batteries have lower energy density and significant shortcomings in safety, energy density, and service life, and their performance potential is approaching its limit. As an emerging energy storage technology, all-solid-state batteries, with their advantages such as high safety, high energy density, and long service life, are expected to not only gain wider market promotion and application, but will also become a major force in the future energy storage field.

[0003] However, the industrialization of all-solid-state batteries still faces severe challenges, especially the application bottleneck of silicon-based negative electrodes. Silicon is considered an ideal negative electrode material due to its ultra-high theoretical specific capacity (3579 mAh / g), but it undergoes a volume expansion of up to 300% during the charge and discharge process, causing peeling or cracking of the solid-solid interface between the electrode and the solid electrolyte, significantly increasing the interfacial impedance and accelerating capacity decay. In existing technologies, researchers have tried to alleviate the volume effect through nano-silicon particles, carbon coating or polymer buffer layers, but these methods often sacrifice energy density or increase process complexity. In addition, the interface contact of solid-state batteries is highly dependent on external pressure, and existing assembly processes mostly use constant pressure (such as 10-50 MPa), which is difficult to adapt to the dynamic volume changes of silicon-based materials, resulting in contact failure during the cycle. Summary of the Invention

[0004] To address these issues, the present invention provides a method for preparing an all-solid-state battery with a silicon-based anode. This method aims to address the issue of solid-solid interface failure caused by volume expansion of silicon-based materials and improve the cycling stability and energy density of all-solid-state batteries. By combining a silicon-based phase (Si-Sn solid solution) with a functional metal phase (such as rare earth elements Y / Er and low-melting-point metal Bi), the ductility and interfacial wettability of the metal phase are exploited to suppress silicon volume expansion. Furthermore, a gradient pressure control process (pre-load of 50-500 MPa to optimize electrolyte density, and a final pressure of 200-400 MPa to maintain interfacial contact) and a torque fixation technique (5-20 Newton meters) are combined to achieve a stable ion transport path under dynamic volume changes. Experimental results show that this method can achieve a capacity retention of >79% after 500 cycles at a high current density of 1500 mAh / g, an improvement of more than two times that of a pure silicon anode, providing a reliable path for the practical application of high-energy-density all-solid-state batteries. The proposed preparation method is simple and easy to implement.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a method for preparing a silicon-based negative electrode all-solid-state battery, which uses a silicon-based composite material composed of a silicon-based phase and a metal phase as a precursor, prepares the precursor into a negative electrode sheet, and further assembles the all-solid-state battery, specifically comprising the following steps: S1: A silicon-based composite material composed of a silicon-based phase and a metal phase is obtained by suspension melting combined with rapid quenching technology; S2: mixing the silicon-based composite material with a conductive agent, and obtaining a silicon-based composite material-conductive agent powder material by sand milling technology; S3: The silicon-based composite material-conductive agent powder material and the binder are mixed uniformly in proportion (sand milling, ball milling or stirring, etc.) to prepare a slurry, which is then coated on the Cu current collector and dried under vacuum. The electrode sheet is then compacted by holding the pressure at 20 MPa for 60 seconds to form an electrode sheet. The electrode sheet is then punched into discs with a diameter of 10 mm. The mass of the disc is recorded and the disc is placed in a 105°C oven under vacuum for 11 hours. After cooling to room temperature, the disc is transferred to an argon glove box and allowed to stand for 24 hours before battery assembly. S4: All-solid-state battery assembly is carried out in an argon-filled glove box (water content <0.01ppm, oxygen content <0.01ppm). The solid electrolyte powder is weighed and placed in a mold, which is then pre-pressed into a sheet on a tablet press. The sheet is then released and taken out. Electrode sheets, lithium sheets, and indium sheets are placed on both sides of the electrolyte in sequence. The mold is reassembled and placed on a tablet press to be pressed again. The assembly is then sealed, the mold is placed in an external fixture, padded with an insulating PEEK sheet, the nut is tightened, and the glove box is removed. Finally, the nut is tightened again with a torque wrench to complete the battery packaging.

[0006] Furthermore, in step S1, the silicon-based phase is a Si-Sn solid solution phase, collectively referred to as a Si-Sn phase; the content of Sn in the Si-Sn phase does not exceed a molar fraction of 1 to 30% of the total amount of Si-Sn.

[0007] Furthermore, in step S1, the metal phase is (1) any one of Y and Er among rare earth elements; or (2) any one of Bi and other metal elements having a melting point less than 1000 degrees Celsius and a boiling point less than 2200 degrees Celsius; or (3) any one of Ni and Ti among metal elements having a melting point greater than 1000 degrees Celsius and a boiling point less than 5000 degrees Celsius.

[0008] Furthermore, in step S1, the specific method of combining suspension smelting with rapid quenching technology is as follows: S11: placing a mixture of bulk raw materials Si, Sn and metal M in a graphite crucible and performing vacuum suspension induction melting in an argon atmosphere to obtain a mixed ingot; after the mixed ingot is cooled, the surface graphite is polished off, the ingot is cleaned with kerosene for 30 minutes, and ultrasonicated with ethanol for 1 hour; after drying at room temperature, the ingot is placed in a copper crucible and again subjected to vacuum suspension induction melting three times in an argon atmosphere to achieve compositional uniformity, thereby obtaining a Si-Sn-M composite ingot composed of a silicon-based phase and a metal phase; S12: The Si-Sn-M composite material ingot obtained by the above-mentioned induction melting is mechanically crushed, and blocks of appropriate size are selected and placed in a quartz tube. Suspension melting is carried out in a vacuum rotary quenching furnace under an argon atmosphere. By gradually increasing the heater power, when the material is completely melted and jumps in the form of a flame in the quartz tube, the melt is transmitted through a nozzle carrying an argon flow and spray-casted on a high-speed rotating copper roller. After cooling, the rapidly quenched product is collected to obtain a silicon-based composite material composed of a silicon-based phase and a metal phase.

[0009] Furthermore, in step S11, the vacuum degree during vacuum suspension induction melting is 4×10 -3 Pa; in step S12, the vacuum degree of the vacuum quenching furnace is 6.0×10 -3 ~3.0×10 -3 Pa, the pressure in the furnace is -0.1~-0.02 MPa, the pressure of the argon gas flow in the nozzle that conveys the spray-cast melt is 0.4~3 atmospheres, and the linear speed of the copper roller is 10~150 m / s.

[0010] Furthermore, in step S2, the mass ratio of the silicon-based composite material to the conductive agent is 4:1; the sand milling speed is 300-8000 rpm, the sand milling time is 10-200 minutes, and the grinding medium is any one or more of ethanol, acetone or deionized water; The conductive agent is (1) any one or more of industrial furnace black, channel black, thermal black, high-temperature graphitized carbon black, and acetylene black in carbon black conductive agents; or (2) any one or more of artificial graphite and natural graphite in graphite conductive agents; or (3) any one or more of fiber and nanotube conductive agents; or (4) any one or more of graphene conductive agents; or (5) any one or more of biomass carbon.

[0011] Furthermore, in step S3, the mass ratio of the silicon-based composite material-conductive agent powder material to the binder is 80:20; the binder is sodium alginate, and the binder concentration is 1% to 5%.

[0012] Furthermore, in step S4, the mass of the solid electrolyte powder is 30 mg to 300 mg; preferably, the mass of the solid electrolyte powder is 70 mg to 150 mg.

[0013] Furthermore, in step S4, the pre-pressing pressure is 50 MPa to 500 MPa, and the time is 1 minute to 20 minutes; the final pressure is 200 MPa to 400 MPa, and the time is 1 minute to 10 minutes.

[0014] Furthermore, in step S4, the torque of the torque wrench is 5 Newton meters to 20 Newton meters.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The equipment used in the present invention to prepare silicon-based negative electrode materials is simple to operate, and the synthesis process is efficient and rapid; (2) The all-solid-state battery assembly method described in the present invention is simple to operate and easy to implement; (3) The raw materials used in the present invention are widely available, and the chemical reagents used are safe, environmentally friendly, and pollution-free, meeting the requirements of green chemistry; (4) The solid-state battery assembled with the parameters and electrode sheets used in the present invention exhibits excellent chemical stability and mechanical stability, and has outstanding electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a powder X-ray diffraction spectrum of the Si-Sn-Bi material after sand grinding in Example 1; Figure 2 This is the SEM morphology of the Si-Sn-Bi material after stripping in Example 1; Figure 3 3 is a graph showing the cycle performance of the Si-Sn-Bi negative electrode material in Example 1 at (a) a current density of 1500 mA / g, and (b) the first charge and discharge curve at a current density of 150 mA / g; Figure 4 is a powder X-ray diffraction spectrum of the Si-Sn-Y material after sand grinding in Example 2; Figure 5This is the SEM morphology of the Si-Sn-Y material after stripping in Example 2; Figure 6 1. The cycle performance of the Si-Sn-Y negative electrode material in Example 2 at (a) a current density of 1500 mAh / g, and (b) a first charge-discharge curve at a current density of 150 mAh / g; Figure 7 is the powder X-ray diffraction pattern of the Si-Sn-Ni material after sand grinding in Example 3; Figure 8 This is the SEM morphology of the Si-Sn-Ni material after stripping in Example 3; Figure 9 1. The cycle performance of the Si-Sn-Ni negative electrode material in Example 3 at (a) a current density of 1500 mAh / g, and (b) a first charge-discharge curve at a current density of 150 mAh / g; Figure 10 is a powder X-ray diffraction spectrum of the Si-Sn-Ti material after sand grinding in Example 4; Figure 11 This is the SEM morphology of the Si-Sn-Ti material after stripping in Example 4; Figure 12 1. The cycle performance of the Si-Sn-Ti negative electrode material in Example 4 at (a) a current density of 1500 mAh / g, and (b) a first charge-discharge curve at a current density of 150 mAh / g; Figure 13 (a) Cycling performance at a current density of 1500 mAh / g of the sand-milled Si-Sn-Y negative electrode material with a binder concentration of 1.8% in Example 5, and (b) First charge and discharge curves at a current density of 150 mAh / g; Figure 14 is the powder X-ray diffraction spectrum of the Si-Sn-Er material after sand grinding in Example 6; Figure 15 This is the SEM morphology of the Si-Sn-Er material after stripping in Example 6; Figure 16 1. The cycle performance of the Si-Sn-Er negative electrode material in Example 6 at (a) a current density of 1500 mAh / g, and (b) a first charge-discharge curve at a current density of 150 mAh / g; Figure 17 (a) Cycling performance at a current density of 1500 mAh / g and (b) First charge and discharge curve at a current density of 150 mAh / g of the sand-milled Si-Sn-Ni negative electrode material of Example 7 with a binder concentration of 1.8%; Figure 18 is a powder X-ray diffraction spectrum of the Si-Sn-Bi material after sand grinding in Example 8; Figure 19 This is the SEM morphology of the Si-Sn-Bi material after stripping in Example 8; Figure 20 1. The cycle performance of the Si-Sn-Bi negative electrode material in Example 8 at (a) a current density of 1500 mAh / g, and (b) a first charge-discharge curve at a current density of 150 mAh / g; Figure 21 is a powder X-ray diffraction spectrum of the Si-Sn-Y material sand-milled without adding a conductive agent in Example 9; Figure 22 1. The cycle performance of the Si-Sn-Y negative electrode material in Example 9 at (a) a current density of 1500 mAh / g and (b) the first charge-discharge curve at a current density of 150 mAh / g; Figure 23 10. The figures are (a) the cycle performance of the Si-Sn-Bi negative electrode material at a current density of 1500 mAh / g, and (b) the first charge-discharge curve at a current density of 150 mAh / g; Figure 24 1. The cycle performance of the Si-Sn-Bi negative electrode material in Example 11 at (a) a current density of 1500 mAh / g, and (b) a first charge-discharge curve at a current density of 150 mAh / g; Figure 25 This is the powder X-ray diffraction spectrum of the pure Si material after sand grinding in Comparative Example 1; Figure 26 1. The cycle performance of the pure Si negative electrode material in Comparative Example 1 at (a) a current density of 1500 mAh / g, and (b) the first charge and discharge curve at a current density of 150 mAh / g; Figure 27 1. The cycle performance of the Si-Sn-Bi powder negative electrode material in Comparative Example 2 at a current density of (a) 150 mA / g, and (b) the first charge and discharge curve at a current density of 150 mA / g; Figure 28 This is the powder X-ray diffraction spectrum of the pure Si material obtained by sand-milling the Si-Sn-Bi powder negative electrode material without adding a conductive agent in Comparative Example 3; Figure 29 The following are the cycle performance of the Si-Sn-Bi negative electrode material in Comparative Example 4 at (a) a current density of 1500 mAh / g and (b) the first charge and discharge curve at 150 mAh / g. DETAILED DESCRIPTION

[0017] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] Unless otherwise specified, the instruments, reagents, and materials used in the following examples are all conventional instruments, reagents, and materials available in the prior art and can be obtained through regular commercial channels. The experimental methods and detection methods used in the following examples are all conventional experimental methods and detection methods available in the prior art, unless otherwise specified.

[0019] Example 1 1. Preparation of Si 90 Sn5Bi5 composite materials S1: Si is obtained by suspension melting combined with rapid quenching technology 90 Sn5Bi5 material: (1) Silicon (Si) blocks (purity greater than 99.9wt%), tin (Sn) blocks (purity greater than 99.9wt%), and bismuth (Bi) blocks (purity greater than 99.9wt%) were weighed in a molar ratio of 90:5:5 and placed in a graphite crucible under an argon atmosphere with a vacuum degree of 4×10 -3 Pa, vacuum suspension induction melting was carried out, the gas was inflated to -0.25 MPa, the melting power was 15 kW, and a mixed ingot was obtained; after the mixed ingot was cooled, the surface graphite was polished off, kerosene was cleaned for 30 minutes, and ethanol was ultrasonicated for 1 hour; after drying at room temperature, the ingot was placed in a copper crucible and heated in an argon atmosphere with a vacuum degree of 4×10 -3 Under the condition of Pa, vacuum suspension induction melting was carried out three times to achieve the uniformity of composition and obtain Si-Sn-Bi composite material ingot; (2) The Si-Sn-Bi composite material ingot obtained by induction melting was mechanically crushed, and blocks of appropriate size were selected and placed in a quartz tube. The vertical distance between the nozzle of the quartz tube and the copper roller was adjusted to about 3-5 microns. The vacuum was 4×10 -3 In a vacuum rotary quenching furnace, suspension melting is carried out under an argon atmosphere (chamber pressure is -0.05 MPa). By gradually increasing the heater power, when the material is completely melted and jumps in the form of a flame in the quartz tube, the melt is transmitted through a nozzle carrying an argon flow (spray pressure is 0.15 MPa) and sprayed onto a high-speed rotating (linear speed is 30 m / s) copper roller. After cooling, the rapid quenching product is collected to obtain Si composite of silicon-based phase and metal phase. 90 Sn5Bi5 composite material; S2: Si 90 The Sn5Bi5 composite material was mixed with a conductive agent (4:1) and sand-milled (rotation speed 1500 rpm, time 40 min, grinding medium ethanol). After sand-milling, the sand-milled slurry was collected and passed through a 2000 mesh sieve. After vacuum drying, it was manually ground through a 200 mesh sieve to obtain Si 90 Sn5Bi5 composite material-conductive agent powder material; Figure 1 This is the X-ray diffraction (XRD) pattern of the sample. XRD analysis reveals the presence of Si (JCPDS 27-1402), Sn (JCPDS 86-2265), Bi (JCPDS 44-1246), and C (JCPDS 26-1076) in the composite material. The C peak is attributed to the addition of a conductive agent during the sanding process. The XRD pattern indicates that Si did not form an alloy phase with Sn and Bi during the composite material preparation process. Figure 2 This is the SEM morphology of the sample. The particle size is mainly in the range of 500 nanometers to 1 micron, and a small amount of particles are 1 to 2 microns in size. The introduction of Bi has the effect of refining the grains of the sample, and its surface is flat and evenly distributed.

[0020] 2. Si 90 Preparation of Sn5Bi5 composite material negative electrode sheet and test battery and electrode electrochemical performance test: Using copper foil as the current collector, a sand-polished silicon-based composite material and a binder used in conventional lithium-ion battery anode preparation were mixed uniformly at a mass ratio of 80:20. The sodium alginate binder concentration was 2.9 wt%. The mixed slurry was applied to the copper current collector, air-dried, and then vacuum-dried in an oven. The electrode sheet was then compacted at a pressure of 20 MPa for 60 seconds to form an electrode sheet. The sheet was then punched into 10 mm diameter discs. The disc mass was recorded, and the disc was vacuum-dried in a 105°C oven for 11 hours. After cooling to room temperature, it was transferred to an argon glove box and allowed to stand for 24 hours before battery assembly.

[0021] The all-solid-state battery is assembled in an argon-filled glove box (water content <0.01ppm, oxygen content <0.01ppm). First, 150mg of solid electrolyte powder is weighed and placed in a mold. The mold is placed on a tablet press and pre-pressed into a tablet at a pressure of 300 MPa. After 3 minutes, the pressure is released and the tablet is removed. Electrode sheets, lithium sheets, and indium sheets are placed on both sides of the electrolyte. The mold is assembled and placed on a tablet press and pressed at a pressure of 200 MPa for 1 minute. The pressure is released and the tablet is removed. After sealing, the mold is placed in an external fixture, padded with an insulating PEEK sheet, and the nut is tightened. The glove box is removed and the nut is tightened again with a torque wrench to a torque of 10 Newton meters. The specific capacity and cycle performance of the electrode are tested on an electrochemical tester using a constant current test method with a voltage window of -0.6~0.5 volts.

[0022] The composite material obtained in this Example 1 is used as the negative electrode of the all-solid-state battery. The cycle performance at a current density of 1500 mAh / g is shown in Figure 3(a), its first reversible capacity is 1320.00 mAh / g, and after 500 cycles, the capacity is maintained at 1047.24 mAh / g, with a capacity retention rate of 79.34%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 2. Figure 3 (b) Its first charge reversible specific capacity is 2283.89 mAh / g, and its first coulombic efficiency is 66.84%, which are significantly better than the electrochemical performance of Comparative Example 1. The cycling performance test at a current density of 1500 mAh / g was performed after activation five times at a current density of 150 mAh / g.

[0023] Example 2 1. The same method as in Example 1 was used, except that a third phase metal element, yttrium, was introduced. Si 90 Sn5Y5 composite material: Figure 4 This is the X-ray diffraction (XRD) pattern of the sample. XRD detection shows that the composite material contains Si (JCPDS 27-1402), Sn (JCPDS 86-2265), YSi2 (JCPDS 11-0596) and C (JCPDS 26-1076) phases. It can be seen that a new phase YSi2 is generated during the preparation process of the composite material. Figure 5 This is the SEM morphology of the sample. The particle size is about 500 nanometers to 1 micron, and its surface is relatively flat and dense.

[0024] 2. Si 90 Preparation of Sn5Y5 composite material negative electrode sheet and test battery and electrode electrochemical performance test: The negative electrode sheet was prepared and the test battery was assembled in the same manner as in Example 1, and its electrochemical performance was tested. The composite material obtained in Example 2 was used as the negative electrode of the all-solid-state battery. The cycle performance at a current density of 1500 mAh / g is shown in Figure 6 (a), its first reversible capacity is 1374.88 mAh / g, after 500 cycles the capacity is maintained at 1236.43 mAh / g, the capacity retention rate is 89.93%, after 1000 cycles the capacity is maintained at 862.39 mAh / g, the capacity retention rate is 62.73%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 1. Figure 6 (b) Its first charge reversible specific capacity is 2209.43 mAh / g, and its first coulombic efficiency is 77.32%. The cycle performance test at a current density of 1500 mAh / g was first activated 5 times at a current density of 150 mAh / g.

[0025] Example 3 1. The same method as in Example 1 was used, except that the third phase metal element nickel was introduced. Si90 Sn5Ni5 composite material.

[0026] Figure 7 The X-ray diffraction (XRD) pattern of the sample shows that the composite material contains Si (JCPDS 27-1402) and Sn (JCPDS 88-2264) phases, as well as NiSi2 (JCPDS 43-0989) and the conductive agent added during the sanding process. This indicates that a new alloy phase, NiSi2, was formed during the preparation of the composite material. This is essentially the same as in Example 2. Figure 8 This is the SEM morphology of the material. The overall morphology is similar to that of Example 2. The particle size is about 500 nanometers to 1 micron, and the sample surface is flat.

[0027] 2. Si 90 Preparation of Sn5Ni5 composite material negative electrode sheet and test battery and electrode electrochemical performance test: The negative electrode sheet was prepared and the test battery was assembled in the same manner as in Example 1, and its electrochemical performance was tested. The cycle performance of the composite material obtained in Example 3 as the negative electrode of the all-solid-state battery at a current density of 1500 mAh / g is shown in Figure 9 (a), its first reversible capacity is 1665.91 mAh / g, after 200 cycles the capacity is maintained at 1465.58 mAh / g, the capacity retention rate is 87.97%, after 500 cycles the capacity is maintained at 1166.13 mAh / g, the capacity retention rate is 70%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 1. Figure 9 (b) Its first charge reversible specific capacity is 2301.75 mAh / g, and its first coulombic efficiency is 73.65%. The cycling performance test at a current density of 1500 mAh / g was performed by first activating the battery twice at current densities of 150, 300, 750, and 1050 mAh / g, respectively.

[0028] Example 4 1. The same method as in Example 1 was used, except that the third phase metal element titanium was introduced. Si 90 Sn5Ti5 composite material.

[0029] Figure 10 Figure 2 is the X-ray diffraction (XRD) pattern of the sample. The composite material contains Si (JCPDS 27-1402), Sn (JCPDS 04-0673) phases, TiSi2 (JCPDS 71-0187), and a conductive agent added during the sanding process, indicating that a new phase TiSi2 is generated during the preparation process, which is basically the same as Example 2. Figure 11 This is the SEM morphology of the material. The particle size of the material is small and the surface is relatively flat.

[0030] 2. Si 90 Preparation of Sn5Ti5 composite material negative electrode sheet and test battery and electrode electrochemical performance test: The negative electrode sheet was prepared and the test battery was assembled in the same manner as in Example 1, and its electrochemical performance was tested. The cycle performance of the composite material obtained in Example 4 as the negative electrode of the all-solid-state battery at a current density of 1500 mAh / g is shown in Figure 12 (a), its first reversible capacity is 1638.10 mAh / g, after 200 cycles the capacity is maintained at 1346.15 mAh / g, the capacity retention rate is 82.18%, after 400 cycles the capacity is maintained at 1155.47 mAh / g, the capacity retention rate is 70.54%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 1. Figure 12 (b) Its first charge reversible specific capacity is 2149.84 mAh / g, and its first coulombic efficiency is 73.26%. The cycling performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0031] Example 5 The negative electrode sheet was prepared and the test battery was assembled in the same manner as in Example 1, except that a third phase metal element, yttrium, was introduced, the concentration of the sodium alginate binder was 1.8 wt %, and the amount of electrolyte used in the all-solid-state battery assembly was 70 mg.

[0032] The cycle performance of the composite material obtained in Example 5 as the negative electrode of the all-solid-state battery at a current density of 1500 mAh / g is shown in Figure 13 (a), its first reversible capacity is 1658.64 mAh / g, after 200 cycles the capacity is maintained at 1402.05 mAh / g, the capacity retention rate is 84.53%, after 400 cycles the capacity is maintained at 1155.95 mAh / g, the capacity retention rate is 69.69%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 1. Figure 13 (b) Its first charge reversible specific capacity is 2171.12 mAh / g, and its first coulombic efficiency is 69.71%. The cycle performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0033] Example 6 1. The same preparation method as in Example 1 is used, except that a third phase metal element, erbium, is introduced to prepare Si by Joule heat. 90 Sn5Er5 composite material.

[0034] Figure 14This is the X-ray diffraction (XRD) pattern of the sample. XRD detection shows that the composite material contains Si (JCPDS27-1402) and Sn (JCPDS 86-2264) phases, as well as ErSi2 (JCPDS 72-2003) and a conductive agent added during the sanding process. Figure 15 This is the SEM morphology of the material. There is no obvious difference in the overall morphology. The sample particle size is small and is basically the same as Example 4.

[0035] 2. Si 90 Preparation of Sn5Er5 composite material negative electrode sheet and test battery and electrode electrochemical performance test: The negative electrode sheet and test battery were prepared in the same manner as in Example 1, except that the amount of electrolyte used in the all-solid-state battery assembly was 70 mg. The cycling performance of the composite material obtained in Example 6 as the negative electrode of the all-solid-state battery at a current density of 1500 mAh / g is shown in FIG. Figure 16 (a), its first reversible capacity is 1537.35 mAh / g, after 200 cycles the capacity is maintained at 1303.36 mAh / g, the capacity retention rate is 84.78%, after 300 cycles the capacity is maintained at 1013.07 mAh / g, the capacity retention rate is 65.90%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 1. Figure 16 (b) Its first charge reversible specific capacity is 1898.13 mAh / g, and its first coulombic efficiency is 74.91%. The cycling performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0036] Example 7 An all-solid-state battery was prepared using the same method as in Example 1, except that the third-phase metal element bismuth was replaced with metallic nickel, the concentration of the sodium alginate binder was 1.8 wt %, and the amount of electrolyte used in the all-solid-state battery assembly was 70 mg.

[0037] The cycle performance of the composite material obtained in Example 7 as the negative electrode of the all-solid-state battery at a current density of 1500 mAh / g is shown in Figure 17 (a), its first reversible capacity is 1566.58 mAh / g, and after 150 cycles, the capacity is maintained at 1362.32 mAh / g, with a capacity retention rate of 86.96%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 2. Figure 17 (b) Its first charge reversible specific capacity is 1916.91 mAh / g, and its first coulombic efficiency is 74.83%. The cycle performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0038] Example 8 1. Using the same preparation method as in Example 1, the third phase element bismuth was introduced with an atomic ratio of 2. Si was prepared by this method. 93 Sn5Bi2 composite material.

[0039] Figure 18 This is the X-ray diffraction (XRD) pattern of the sample. XRD detection shows that the composite material contains Si (JCPDS27-1402), Sn (JCPDS 86-2265) and C (JCPDS 26-1076), but no Bi peak is detected. The reason may be that the Bi element is volatile, which has a certain impact on the test results. Figure 19 This is the SEM morphology of the sample. The particle size is 1~2 microns, and the surface is flat and evenly distributed.

[0040] 2. Si 93 Preparation of Sn5Bi2 composite material negative electrode sheet and test battery and electrode electrochemical performance test: The negative electrode sheet was prepared and the test battery was assembled in the same manner as in Example 1, and its electrochemical performance was tested. The cycle performance of the composite material obtained in Example 8 as the negative electrode of the all-solid-state battery at a current density of 1500 mAh / g is shown in Figure 20 (a), its first reversible capacity is 2274.28 mAh / g, and after 150 cycles, the capacity is maintained at 1650.27 mAh / g, with a capacity retention rate of 72.56%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 2. Figure 20 (b) Its first charge reversible specific capacity is 2793.64 mAh / g, and its first coulombic efficiency is 78.99%. The cycle performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0041] Example 9 1. An all-solid-state battery was prepared using the same method as in Example 1, except that the third-phase metal element bismuth was replaced by metal yttrium, and no conductive agent was added during sand grinding.

[0042] Figure 21 This is the X-ray diffraction (XRD) pattern of the sample. XRD detection shows that the composite material contains Si (JCPDS27-1402), Sn (JCPDS 86-2264) phases and YSi2 (JCPDS 11-0596). This is the same as the result of Example 2. The only difference is that no conductive agent was added during sand grinding, and the XRD pattern does not show a C peak.

[0043] 2. Si 90Preparation of Sn5Y5 composite material negative electrode sheet and test battery and electrode electrochemical performance test: The negative electrode sheet and test battery were prepared in the same manner as in Example 1, and their electrochemical performance was tested. The concentration of sodium alginate binder was 1.8%, and the amount of electrolyte used in the assembled all-solid-state battery was 70 mg. The cycling performance of the composite material obtained in Example 9 as the negative electrode of the all-solid-state battery at a current density of 1500 mAh / g is shown in Table 1. Figure 22 (a), its first reversible capacity is 1764.93 mAh / g, after 200 cycles, the capacity is maintained at 1428.19 mAh / g, the capacity retention rate is 80.92%, after 400 cycles, the capacity is maintained at 1187.62 mAh / g, the capacity retention rate is 67.29%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 1. Figure 22 (b) Its first charge reversible specific capacity is 2022.39 mAh / g, and its first coulombic efficiency is 78.10%. The cycle performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0044] Example 10 The negative electrode sheet was prepared and the test battery was assembled in the same manner as in Example 1, and its electrochemical performance was tested, except that the amount of electrolyte used was 100 mg.

[0045] The cycle performance of the composite material obtained in Example 10 as the negative electrode of the all-solid-state battery at a current density of 1500 mA / g is shown in Figure 23 (a), its first reversible capacity is 1195.53 mAh / g, after 150 cycles the capacity is maintained at 1163.34 mAh / g, the capacity retention rate is 97.31%, after 200 cycles the capacity is maintained at 904.01 mAh / g, the capacity retention rate is 75.62%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 1. Figure 23 (b) Its first charge reversible specific capacity is 1509.92 mAh / g, and its first coulombic efficiency is 70.49%. The cycling performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0046] Example 11 The negative electrode sheet was prepared and the test battery was assembled and its electrochemical performance was tested in the same manner as in Example 1, except that the amount of electrolyte used was 120 mg.

[0047] The cycle performance of the composite material obtained in Example 11 as the negative electrode of the all-solid-state battery at a current density of 1500 mA / g is shown in Figure 24(a), its first reversible capacity is 1507.02 mAh / g, and after 150 cycles, the capacity is maintained at 1106.09 mAh / g, with a capacity retention rate of 73.40%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 2. Figure 24 (b) Its first charge reversible specific capacity is 2213.18 mAh / g, and its first coulombic efficiency is 76.15%. The cycle performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0048] Comparative Example 1 The preparation process is basically the same as that of Example 1, except that no metal elements are doped, the binder concentration is 2.9%, and the raw material is pure silicon Si material after sand grinding.

[0049] Figure 25 The XRD pattern of the sand-polished product is shown in Figure 2. It contains Si (JCPDS 27-1402) and C (JCPDS 26-1076) phases. The overall peak intensity of the sample is high, and no other impurities are present. The test battery was prepared using the same method as in Example 1. The cycling performance at a current density of 1500 mAh / g is shown in Figure 2. Figure 26 (a), its first reversible capacity is 1751.33 mAh / g, after 200 cycles the capacity is 586.42 mAh / g, the capacity retention rate is 33.48%, after 400 cycles the reversible capacity is only 300.95 mAh / g, the capacity retention rate is only 17.18%, the capacity decay is very fast. The first charge and discharge curve at a current density of 150 mAh / g is shown in the figure. Figure 26 (b) shows a first-charge reversible capacity of 3012.93 mAh / g and a first-charge coulombic efficiency of 80.05%. This indicates that the pure silicon sample without metal doping exhibits extremely poor cycling stability, exhibits severe volume expansion, and may experience detachment of the active material from the current collector, leading to a loss of electrochemical activity. This further demonstrates that metal doping can effectively mitigate sample volume expansion and significantly improve its electrochemical performance.

[0050] Comparative Example 2 Different from Examples 1 to 11, the negative electrode material used is a powder material after sand grinding. 90 Sn5Bi5 composite material. The all-solid-state battery was assembled using 150 mg of electrolyte at a pressure of 300 MPa. After the electrode, lithium, and indium sheets were placed, a pressure of 200 MPa and a torque of 10 Nm were applied. Activation and cycling were performed at a current density of 150 mA / g.

[0051] The cycle performance of the composite material obtained in this comparative example 2 as the negative electrode of the all-solid-state battery at a current density of 150 mA / g is shown in Figure 27 (a), its first reversible capacity is 2181.99 mAh / g, and after 50 cycles, the capacity is maintained at 134.73 mAh / g, with a capacity retention rate of 6.17%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 2. Figure 27 (b) The initial coulombic efficiency was 74.42%. The negative electrode material obtained in Comparative Example 2 exhibited extremely rapid capacity decay and had lost its electrochemical activity. This may be due to the difficulty in controlling powder uniformity, resulting in uneven current density and severe volume expansion, leading to poor cycling performance.

[0052] Comparative Example 3 Different from Examples 1 to 11, the negative electrode material used is a powder material after sand grinding. 90 Sn5Bi5 composite material. The all-solid-state battery was assembled using 150 mg of electrolyte at a pressure of 100 MPa. After the electrode, lithium, and indium sheets were placed, the pressure was 100 MPa and the torque was 10 Nm. Activation and cycling were performed at a current density of 150 mA / g.

[0053] The cycle performance of the composite material obtained in this comparative example 3 as the negative electrode of the all-solid-state battery at a current density of 150 mA / g is shown in Figure 28 (a), its first reversible capacity is 1762.76 mAh / g, and after 50 cycles, the capacity is maintained at 86.41 mAh / g, with a capacity retention rate of 4.90%. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 2. Figure 28 (b) The initial coulombic efficiency was 74.40%. The negative electrode material obtained in Comparative Example 3 exhibited extremely rapid capacity decay and had lost its electrochemical activity. This may be due to the difficulty in controlling powder uniformity, resulting in uneven current density and severe volume expansion, leading to poor cycling performance.

[0054] Comparative Example 4 The negative electrode sheet was prepared and the all-solid-state battery was assembled using the same method as in Example 1, except that the torque of the torque wrench was 2 Newton meters.

[0055] The cycle performance of the composite material obtained in this comparative example 4 as the negative electrode of the all-solid-state battery at a current density of 1500 mA / g is shown in Figure 29 (a), its first reversible capacity is 425.78 mAh / g, and the capacity is very low at high rates. The first charge and discharge curve at a current density of 150 mAh / g is shown in Figure 2. Figure 29(b), its first reversible capacity is 2321.36 mAh / g, and the first coulombic efficiency is 74.42%. The first reversible capacity at a current density of 750 mAh / g is 1331.63 mAh / g. The first reversible capacity at a current density of 1050 mAh / g is 857.62 mAh / g. The negative electrode material obtained in this comparative example 4 has a very fast capacity decay at high rates and has lost its electrochemical activity. This shows that under lower stack pressures, the battery cannot maintain good interface contact at high rates. At the same time, the volume expansion of silicon itself is large (>300%), so it is more difficult to maintain interface stability under low stack pressures, resulting in poor cycle stability. The cycle performance test at a current density of 1500 mAh / g was first activated twice at 150 / 300 / 750 / 1050 mAh / g respectively.

[0056] In addition to the above embodiments: In some other embodiments of the present invention, the vacuum degree of the vacuum quenching furnace in step S1 is 6.0×10 -3 Pa, the pressure in the furnace is -0.1 MPa, the pressure of the argon gas flow in the nozzle that conveys the spray-cast melt is 0.04 MPa, and the linear speed of the copper roller is 10 m / s.

[0057] In some other embodiments of the present invention, the vacuum degree of the vacuum quenching furnace in step S1 is 3.0×10 -3 Pa, the pressure in the furnace is -0.02 MPa, the pressure of the argon gas flow in the nozzle that conveys the spray-cast melt is 0.3 MPa, and the linear speed of the copper roller is 150 m / s.

[0058] In some other embodiments of the present invention, the conductive agent in step S2 is (1) any one or more of industrial furnace black, channel black, thermal black, high-temperature graphitized carbon black, and acetylene black in the carbon black conductive agent; or (2) any one or more of artificial graphite and natural graphite in the graphite conductive agent; or (3) any one or more of fiber and nanotube conductive agents; or (4) any one or more of graphene conductive agents; or (5) any one or more of biomass carbon.

[0059] In some other embodiments of the present invention, the sand milling speed in step S2 is 300 rpm, the time is 200 minutes, and the grinding medium is acetone.

[0060] In some other embodiments of the present invention, the sand milling speed in step S2 is 8000 rpm, the time is 10 minutes, and the grinding medium is deionized water.

[0061] In some other embodiments of the present invention, the binder concentration in step S3 is 1%, and the mass of the solid electrolyte powder is 30 mg.

[0062] In some other embodiments of the present invention, the binder concentration in step S3 is 5%, and the mass of the solid electrolyte powder is 300 mg.

[0063] In some other embodiments of the present invention, in step S4, the pre-pressing pressure is 50 MPa, the time is 20 minutes; the final pressure is 300 MPa, the time is 10 minutes; and the torque of the torque wrench is 5 Newton meters.

[0064] In some other embodiments of the present invention, in step S4, the pre-pressing pressure is 500 MPa, the time is 1 minute; the final pressure is 400 MPa, the time is 5 minutes; and the torque of the torque wrench is 20 Nm.

[0065] The all-solid-state batteries assembled with the silicon-based composite materials prepared in the above embodiments exhibited excellent chemical stability and mechanical stability, and possessed outstanding electrochemical performance.

[0066] In summary, this embodiment uses suspension melting and rapid quenching technology to prepare a silicon-based composite material precursor, which is then sand-milled and mixed with a conductive agent to form a negative electrode sheet. An all-solid-state battery is assembled under an argon environment, and interface stability is achieved through precise pressure and torque control. Experiments show that the negative electrode has good cycle stability and high capacity retention at a high current density of 1500 mA / g, which is a significant improvement compared to the comparative example. This provides a quantifiable and verifiable technical solution for the industrial production of high-energy-density, long-cycle-life all-solid-state batteries.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-based negative electrode all-solid-state battery, characterized in that: The silicon-based composite material composed of a silicon-based phase and a metal phase is used as a precursor to make a negative electrode sheet, and then further assembled into an all-solid-state battery, which specifically includes the following steps: S1: A silicon-based composite material composed of a silicon-based phase and a metal phase is obtained by suspension melting combined with rapid quenching technology; S2: mixing the silicon-based composite material with a conductive agent, and obtaining a silicon-based composite material-conductive agent powder material by sand milling technology; S3: The silicon-based composite material-conductive agent powder material and the binder are mixed uniformly in proportion to prepare a slurry, which is then coated on a Cu current collector and dried under vacuum to prepare a sheet-shaped negative electrode; S4: All-solid-state battery assembly is carried out in an argon-filled glove box. The solid electrolyte powder is weighed and placed in a mold, which is then placed on a tablet press to pre-press into a sheet. The sheet is then released and taken out. Electrode sheets, lithium sheets, and indium sheets are placed on both sides of the electrolyte in sequence. The mold is reassembled and placed on a tablet press to be pressed again. The assembly is then sealed, the mold is placed in an external fixture, padded with an insulating PEEK sheet, the nut is tightened, and the glove box is removed. Finally, the nut is tightened again with a torque wrench to complete the battery packaging.

2. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S1, the silicon-based phase is a Si-Sn solid solution phase, collectively referred to as a Si-Sn phase; the content of Sn in the Si-Sn phase does not exceed a molar fraction of 1 to 30% of the total amount of Si-Sn.

3. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S1, the metal phase is (1) any one of Y and Er among the rare earth elements; or (2) Bi, a metal element having a melting point less than 1000 degrees Celsius and a boiling point less than 2200 degrees Celsius; or (3) any one of Ni and Ti, a metal element having a melting point greater than 1000 degrees Celsius and a boiling point less than 5000 degrees Celsius.

4. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S1, the specific method of combining suspension smelting with rapid quenching technology is as follows: S11: placing a mixture of bulk raw materials Si, Sn and metal M in a graphite crucible and performing vacuum suspension induction melting in an argon atmosphere to obtain a mixed ingot; after the mixed ingot is cooled, the surface graphite is polished off, the ingot is cleaned with kerosene for 30 minutes, and ultrasonicated with ethanol for 1 hour; after drying at room temperature, the ingot is placed in a copper crucible and again subjected to vacuum suspension induction melting three times in an argon atmosphere to achieve compositional uniformity, thereby obtaining a Si-Sn-M composite ingot composed of a silicon-based phase and a metal phase; S12: The Si-Sn-M composite material ingot obtained by the above-mentioned induction melting is mechanically crushed, and blocks of appropriate size are selected and placed in a quartz tube. Suspension melting is carried out in a vacuum rotary quenching furnace under an argon atmosphere. By gradually increasing the heater power, when the material is completely melted and jumps in the form of a flame in the quartz tube, the melt is transmitted through a nozzle carrying an argon flow and spray-casted on a high-speed rotating copper roller. After cooling, the rapidly quenched product is collected to obtain a silicon-based composite material composed of a silicon-based phase and a metal phase.

5. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 4, characterized in that: In step S11, the vacuum degree during vacuum suspension induction melting is 4×10 -3 Pa; in step S12, the vacuum degree of the vacuum quenching furnace is 6.0×10 -3 ~3.0×10 -3 Pa, the pressure in the furnace is -0.1~-0.02 MPa, the pressure of the argon gas flow in the nozzle that conveys the spray-cast melt is 0.4~3 atmospheres, and the linear speed of the copper roller is 10~150 m / s.

6. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S2, the silicon-based composite material and the conductive agent are mixed in a mass ratio of 4:1; the sand milling speed is 300 to 8000 rpm, the sand milling time is 10 to 200 minutes, and the grinding medium is any one or more of ethanol, acetone, or deionized water; The conductive agent is (1) any one or more of industrial furnace black, channel black, thermal black, high-temperature graphitized carbon black, and acetylene black in carbon black conductive agents; or (2) any one or more of artificial graphite and natural graphite in graphite conductive agents; or (3) any one or more of fiber and nanotube conductive agents; or (4) any one or more of graphene conductive agents; or (5) any one or more of biomass carbon.

7. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S3, the mass ratio of the silicon-based composite material-conductive agent powder material to the binder is 80:20; the binder is sodium alginate, and the binder concentration is 1% to 5%.

8. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S4, the mass of the solid electrolyte powder is 30 mg to 300 mg; preferably, the mass of the solid electrolyte powder is 70 mg to 150 mg.

9. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S4, the pre-pressing pressure is 50 MPa to 500 MPa, and the time is 1 minute to 20 minutes; the final pressure is 200 MPa to 400 MPa, and the time is 1 minute to 10 minutes.

10. The method for preparing a silicon-based negative electrode all-solid-state battery according to claim 1, characterized in that: In step S4, the torque of the torque wrench is 5 Nm to 20 Nm.

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