A method for preparing a sulfide solid-state battery silicon-based negative electrode

Abstract

The application relates to a preparation method of a sulfide solid-state battery silicon-based negative electrode, and belongs to the technical field of solid-state battery electrode preparation. The specific scheme comprises the following steps: step one, an amorphous Li-Zn-P-O precursor plating layer is formed on the surface of a silicon substrate by adopting a double-pulse electroplating method in an electrolyte containing LiH2PO4, Zn(NO3)2 and a complexing agent; step two, the sample obtained in step one is subjected to low-temperature in-situ crystallization under vacuum conditions to form a crystalline Li3PO4-Zn3(PO4)2 double-metal phosphate interface layer; and step three, the Si particles obtained in step two and provided with the double-metal phosphate interface layer are mixed with a porous carbon framework and a sulfide solid-state electrolyte to be formed, so that the sulfide solid-state battery silicon-based negative electrode is prepared. The prepared negative electrode reduces volume expansion in the cycle process, reduces interface impedance, improves cycle capacity retention rate, effectively inhibits a side reaction and is suitable for a high-energy-density solid-state battery system.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery electrode preparation technology, specifically relating to a method for preparing a silicon-based anode for a sulfide solid-state battery based on bimetallic co-plating-in-situ crystallization. Background Technology

[0002] With the rapid development of energy storage and the increasing growth of the new energy vehicle market, the demand for batteries is shifting towards higher performance and greater safety. Traditional lithium-ion batteries mainly use organic liquid electrolytes, which pose risks of flammability and explosion, easily causing safety hazards. To address these issues, the development of solid-state batteries is particularly important, and sulfide solid electrolytes have attracted much attention due to their high ionic conductivity and non-flammability.

[0003] However, sulfide solid-state electrolytes have a narrow electrochemical stability window, suffer from severe interfacial side reactions when matched with lithium metal, and are prone to lithium dendrite growth. Assembled batteries cannot compete with current commercial lithium-ion batteries in terms of positive electrode active material load, cycle life, and charge / discharge rate. Therefore, sulfide all-solid-state battery systems need to find alternative lithium metal anodes. Silicon-based materials, with their excellent theoretical capacity (3580 mAh / g, approximately 10 times that of graphite) and suitable lithium intercalation potential, are considered one of the ideal anode materials for next-generation high-energy-density lithium-ion solid-state batteries. However, silicon-based materials undergo severe volume changes (up to 300% or more) during charge and discharge, leading to particle breakage, pulverization, loss of electrical contact with the current collector, and even detachment. Simultaneously, the drastic volume expansion causes repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, continuously consuming electrolyte and active lithium ions, resulting in capacity decay and reduced cycle life, severely limiting the practical application of silicon-based anodes. Currently used single-component interface modification methods, while partially improving interface stability, struggle to balance high ionic conductivity with good mechanical flexibility. In addition, in traditional electroplating processes, amorphous coatings need to undergo high-temperature (>400℃) crystallization treatment, which can easily lead to damage to the silicon structure and a decrease in interfacial bonding (usually below 30MPa), limiting their practical application.

[0004] Therefore, there is an urgent need to develop a novel silicon-based anode fabrication process that can simultaneously achieve controllable structure, low-temperature crystallization, high bonding strength, and high ion conductivity, enabling the synergistic deposition and complementary performance of two metal ions, and constructing a bimetallic phosphate interface layer with high ion conductivity and high interfacial bonding strength on the silicon surface. Summary of the Invention

[0005] This invention aims to provide a method for preparing a silicon-based anode for a sulfide solid-state battery. The method involves constructing a bimetallic phosphate interface layer with both high ion conductivity and high interfacial bonding strength on the surface of a silicon substrate through bimetallic co-plating and low-temperature in-situ crystallization. Then, silicon-based anodes are prepared by combining Si particles with the bimetallic phosphate interface layer, a porous carbon framework, and a sulfide solid electrolyte. The specific steps are as follows:

[0006] (1) Preparation of bimetallic co-plating amorphous precursor

[0007] An electrolyte was prepared using LiH₂PO₄ as the lithium source, Zn(NO₃)₂ as the zinc source, EDTA-2Na as the complexing agent, and H₃PO₄ as the pH adjuster. The concentrations of LiH₂PO₄, Zn(NO₃)₂, and EDTA-2Na in the electrolyte were 0.10–0.14 mol / L, respectively. The pH of the electrolyte was 3.0–3.2. H₃PO₄ was used as the pH adjuster.

[0008] On a pretreated silicon conductive substrate, co-deposition was performed using a dual-pulse electroplating system. By adjusting the forward and reverse pulse parameters, Li was achieved. + With Zn 2+ Amorphous Li-Zn-PO precursor coating was formed by synchronous deposition according to a set ratio; the parameters of the dual-pulse electroplating instrument were: forward current density 0.5~0.7 mA / cm². 2 The forward pulse duration is 70-90 ms, and the reverse current density is 0.12~0.18 mA / cm². 2 The reverse pulse duration is 10-20 ms, and the pulse cycle count is 50-70. The coating thickness is 3-4 nm, with a deviation controlled within ±0.3 nm.

[0009] (2) Low-temperature in-situ crystallization

[0010] The obtained amorphous Li-Zn-PO precursor coating was placed in a vacuum furnace and held at 170~190℃ for 2.5-3.5h to complete the transformation from amorphous to crystalline Li3PO4-Zn3(PO4)2.

[0011] During crystallization, Si-OP covalent bonds are formed, increasing the interfacial bonding strength to ≥70 MPa and the electrical conductivity to ≥2×10⁻⁶. -3 S / cm.

[0012] (3) Porous carbon skeleton composite molding

[0013] Si particles with a bimetallic phosphate interface layer, a porous carbon framework, and a sulfide solid electrolyte are mixed in a mass ratio of (65~75):(15~20):(10~15), and N-methylpyrrolidone is added to prepare a slurry.

[0014] The slurry is coated onto a copper current collector, and then vacuum dried and cold-pressed (pressure 12~15 MPa) to form a silicon-based anode for sulfide solid-state batteries.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] (1) Bimetallic synergistic enhancement: Li3PO4 provides a high ion conduction path, and Zn3(PO4)2 imparts flexibility to the interface layer. By sequentially performing Li / Zn bimetallic phosphate co-plating, low-temperature in-situ crystallization and porous carbon framework composite on the silicon surface, a multifunctional interface layer with high ion conduction, high interface bonding strength and good flexibility is constructed, which synergistically suppresses silicon volume expansion and interface side reactions.

[0017] (2) Low-temperature in-situ crystallization: Amorphous to crystalline transformation is achieved at ≤190℃. The crystalline structure has better thermal stability, avoiding damage to the silicon structure at high temperature. At the same time, due to its ordered structure, the occurrence of side reactions is limited, and the interfacial bonding force is significantly improved.

[0018] (3) Structure-function integration: The porous carbon skeleton constructs a conductive buffer network to ensure electron transmission and relieve stress;

[0019] (4) Excellent comprehensive electrochemical performance: The negative electrode prepared by this invention reduces volume expansion during cycling; reduces interfacial impedance; improves cycle capacity retention; effectively suppresses side reactions, and is suitable for high energy density solid-state battery systems. Attached Figure Description

[0020] Figure 1 Example 1: SEM images of the silicon-based anode before and after charge and discharge, where Figure (a) is the SEM image of the silicon-based anode before cycling and Figure (b) is the SEM image of the silicon-based anode after cycling;

[0021] Figure 2 Comparative Example 3: SEM images of silicon-based anode before and after charge and discharge, where Figure (a) is the SEM image of silicon-based anode before cycling and Figure (b) is the SEM image of silicon-based anode after cycling.

[0022] Figure 3 This is an electron diffraction image of silicon particles before crystallization;

[0023] Figure 4 This is an electron diffraction image of silicon particles after low-temperature crystallization in Example 1. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] Example 1:

[0026] A method for preparing a silicon-based anode for a sulfide solid-state battery includes the following steps:

[0027] Step 1: Prepare the electrolyte solution with 0.12 mol / L LiH2PO4, 0.08 mol / L Zn(NO3)2, and 0.02 mol / L EDTA-2Na, pH=3.1; adjust the pulse parameters: forward 0.6 mA / cm. 2 80 ms, reverse 0.15 mA / cm 2 Amorphous Li-Zn-PO precursor coating with a thickness of approximately 3.5 nm was obtained by cycling for 15 ms and 60 times.

[0028] Step 2: The obtained Li-Zn-PO precursor coating is in-situ crystallized under vacuum at 180℃ for 3 h to form a crystalline Li3PO4-Zn3(PO4)2 bimetallic phosphate interface layer.

[0029] Step 3: Weigh Si particles with a bimetallic phosphate interface layer, UiO-66 carbon skeleton, and Li6PS5Cl electrolyte in a mass ratio of 70:15:15, and add N-methylpyrrolidone to prepare a slurry. Coat the slurry onto a copper current collector, and then vacuum dry and cold press it at a pressure of 14 MPa to obtain a silicon-based anode sheet.

[0030] Step 4: Assemble the mold battery: Using Li6PS5Cl as the electrolyte, weigh 80mg of electrolyte and prepare it at a pressure of 125MPa. Apply a pressure of 300MPa to the silicon-based negative electrode and use a lithium indium alloy as the counter electrode at a pressure of 50MPa.

[0031] Example 2

[0032] The only difference between this embodiment and Embodiment 1 is that in step three, Si particles with a bimetallic phosphate interface layer, UiO-66 carbon skeleton and Li6PS5Cl electrolyte are weighed in a mass ratio of 65:20:15. The remaining steps are the same as in Embodiment 1 to prepare a silicon-based negative electrode sheet.

[0033] Example 3

[0034] The only difference between this embodiment and Embodiment 1 is that in step three, Si particles with a bimetallic phosphate interface layer, UiO-66 carbon skeleton and Li6PS5Cl electrolyte are weighed in a mass ratio of 75:15:10. The remaining steps are the same as in Embodiment 1 to prepare a silicon-based negative electrode sheet.

[0035] Comparative Example 1

[0036] The only difference between this comparative example and Example 1 is that in step one, the electrolyte is prepared with 0.2 mol / L LiH2PO4, 0.02 mol / L LEDTA-2Na, and pH=3.1. All other steps are the same as in Example 1.

[0037] Comparative Example 2

[0038] The only difference between this comparative example and Example 1 is that in step one, the electrolyte is prepared with 0.2 mol / L Zn(NO3)2, 0.02 mol / L LEDTA-2Na, and pH=3.1. All other steps are the same as in Example 1.

[0039] Comparative Example 3

[0040] A negative electrode sheet was prepared using only untreated silicon particles, and a lithium indium alloy was used as the counter electrode to assemble a mold battery.

[0041] Example 4

[0042] Assemble the full cell: Using Li6PS5Cl as the electrolyte, weigh 80mg of electrolyte and prepare it at a pressure of 125MPa. Use NCM811 as the positive electrode active material and prepare a composite positive electrode with a mass ratio of active material, electrolyte, and conductive carbon VGCF of 70:28:2. Weigh the composite positive electrode with N / P=1.2 and prepare it at a pressure of 200MPa. Use the silicon-based negative electrode sheet prepared in Example 1 as the negative electrode and prepare it at a pressure of 300MPa.

[0043] Example 5

[0044] The only difference between this embodiment and embodiment 4 is that the negative electrode is a silicon-based negative electrode sheet prepared in embodiment 2 used to assemble the full cell.

[0045] Example 6

[0046] The only difference between this embodiment and embodiment 4 is that the negative electrode is a silicon-based negative electrode sheet prepared in embodiment 3 used to assemble the full cell.

[0047] Comparative Example 4

[0048] The only difference between this embodiment and embodiment 4 is that the negative electrode is a silicon-based negative electrode sheet prepared in Comparative Example 1 used to assemble the full cell.

[0049] Comparative Example 5

[0050] The only difference between this embodiment and embodiment 4 is that the negative electrode is a silicon-based negative electrode sheet prepared in Comparative Example 1 used to assemble the full cell.

[0051] Comparative Example 6

[0052] A negative electrode was prepared using only untreated silicon particles. Li6PS5Cl was used as the electrolyte. 80 mg of the electrolyte was weighed and the preparation pressure was 125 MPa. NCM811 was used as the positive electrode active material. A composite positive electrode was prepared with a mass ratio of active material, electrolyte, and conductive carbon VGCF of 70:28:2. 10 mg of the composite positive electrode was weighed and the pressure was 200 MPa. The full cell was then assembled.

[0053] Table 1: Half-cell performance

[0054]

[0055] Table 2: Full Battery Performance

[0056]

[0057] Before the cycle, Example 1 ( Figure 1 ) and Comparative Example 3 ( Figure 2 Compared to Example 1, the silicon-based anode prepared in Example 1 has a more uniform and smoother surface particles, allowing for better contact with the electrolyte. After 100 cycles, the volume change of the particles in Example 1 decreased, the number of cracks was significantly reduced, and the original structure was basically maintained; while the untreated Comparative Example 3 showed significantly larger cracks after cycling, and the number of cracks was also significantly greater than that in Example 1, with drastic volume changes, making it less stable during battery cycling.

[0058] Figure 3 The electron diffraction image of the silicon particles before crystallization shows multiple diffuse diffraction rings, including several broadened rings, indicating that it is amorphous; while Figure 4 The electron diffraction image of silicon particles after low-temperature crystallization shows scattered diffraction spots, but a ring-shaped outline can be vaguely seen, indicating that it is polycrystalline and has many grains.

[0059] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a silicon-based anode for a sulfide solid-state battery, characterized in that, Includes the following steps: Step 1: In an electrolyte containing LiH2PO4, Zn(NO3)2 and a complexing agent, an amorphous Li-Zn-PO precursor coating is co-deposited on the surface of a silicon substrate using a dual-pulse electroplating method. Step 2: The sample obtained in Step 1 is subjected to low-temperature in-situ crystallization under vacuum conditions to form a crystalline Li3PO4-Zn3(PO4)2 bimetallic phosphate interface layer. Step 3: Mix the Si particles with the bimetallic phosphate interface layer obtained in Step 2 with a porous carbon framework and a sulfide solid electrolyte to form a silicon-based anode for a sulfide solid battery.

2. The preparation method according to claim 1, characterized in that: In step one, the concentration of LiH2PO4 in the electrolyte is 0.10~0.14 mol / L, the concentration of Zn(NO3)2 is 0.06~0.10 mol / L, and the pH value of the electrolyte is 3.0~3.

2.

3. The preparation method according to claim 2, characterized in that: The pH adjuster used to adjust the electrolyte is H3PO4.

4. The preparation method according to claim 1, characterized in that: In step one, the complexing agent is EDTA-2Na, and the concentration of EDTA-2Na in the electrolyte is 0.01~0.03 mol / L.

5. The preparation method according to claim 1, characterized in that: In step one, the parameters of the dual-pulse electroplating method are: forward current density 0.5~0.7 mA / cm². 2 The forward pulse duration is 70-90 ms, and the reverse current density is 0.12~0.18 mA / cm². 2 The reverse pulse time is 10-20ms, the number of pulse cycles is 50-70, and the thickness of the obtained precursor coating is 3-4nm with a deviation of ≤0.3nm.

6. The preparation method according to claim 1, characterized in that: In step two, the temperature for low-temperature in-situ crystallization is 170~190℃, and the holding time is 2.5~3.5 h.

7. The preparation method according to claim 1, characterized in that: In step three, the mass ratio of the Si particles with the bimetallic phosphate interface layer, the porous carbon framework, and the sulfide solid electrolyte is (65~75):(15~20):(10~15).

8. The preparation method according to claim 1, characterized in that: In step three, the forming process is cold pressing, with a pressure of 12~15 MPa.

9. The preparation method according to claim 1, characterized in that: In step three, the porous carbon framework is UiO-66 derived porous carbon.

10. A silicon-based anode for a sulfide solid-state battery prepared by the preparation method according to any one of claims 1-9.

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