Silicon negative electrode material for all-solid-state lithium ion battery and preparation method and application thereof

Abstract

The application belongs to the technical field of lithium battery silicon negative electrode materials, and relates to a silicon negative electrode material for a full-solid-state lithium ion battery and a preparation method and application thereof. The silicon negative electrode material for the full-solid-state lithium ion battery comprises a micron silicon material main body, a nanosilicon material coated on the surface of the micron silicon material main body, and a polymer binder bonded between the micron silicon material main body and the nanosilicon material. The silicon negative electrode material with a micro / nano composite structure is constructed, the problems of grain breakage of the micron silicon negative electrode particles in the long cycle process of the full-solid-state battery and the disengagement of the particles from contact with a sulfide solid-state electrolyte are solved, and the long cycle stability of the silicon negative electrode in the full-solid-state sulfide lithium ion battery is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of silicon anode materials for lithium batteries, and relates to a silicon anode material for all-solid-state lithium-ion batteries, its preparation method, and its application. Background Technology

[0002] The development of portable electronic devices, electric vehicles, and new energy sources has placed higher demands on energy storage devices. Replacing organic electrolytes with solid-state electrolytes can fundamentally improve battery safety. Simultaneously, by simplifying the battery structure through internal stringing, it increases the proportion of active materials, thereby improving volume utilization and energy density at the battery pack level. Therefore, all-solid-state batteries, which combine high energy density and high safety, have attracted widespread attention.

[0003] Sulfide electrolyte systems are among the optimal choices due to their high lithium-ion conductivity, extremely low electronic conductivity, and excellent mechanical properties. Suitable electrode active materials play a crucial role in realizing high-energy-density sulfide all-solid-state batteries. Among these, micron-sized silicon anodes are particularly valuable due to their ultra-high theoretical specific capacity (the highest lithium-ion intercalation capacity at room temperature). 15 Si4 theoretical specific capacity 3759 mAh / g; suitable lithium intercalation potential (0.4V, vs. Li). + Micron-sized silicon (MS) is recognized as one of the next-generation advanced anode materials due to its advantages such as avoiding lithium deposition, high safety, huge natural reserves, wide availability, and low cost.

[0004] The use of micron-sized silicon anodes in sulfide solid-state batteries presents several serious problems, as follows: (1) Micron-sized silicon anodes exhibit significant volume expansion and contraction during the lithium insertion / extraction process in sulfide all-solid-state batteries. The micron-sized silicon anode material is in a fully lithium-intercalated state (Li... 15 (1) The volume expansion of the micron-sized silicon anode can reach about 300% of its original volume; the micron-sized Si anode will undergo severe volume expansion and contraction during long-term cycling of the full cell, resulting in large crystal surface cracks in the micron-sized silicon and large interfacial impedance, which leads to a sharp decline in the electrochemical performance of the full cell. (2) During long-term cycling of sulfide solid-state full cells, the micron-sized silicon anode is prone to detachment from the sulfide solid electrolyte, leading to a decline in the electrochemical performance of the full cell. (3) The rate performance of micron-sized Si materials in all-solid-state batteries is poor, and it is difficult to achieve fast charge and discharge in all-solid-state batteries.

[0005] To address the aforementioned problems with micron-sized silicon anodes in sulfide solid-state batteries, this invention is proposed. Summary of the Invention

[0006] This application firstly involves uniformly coating nano-silicon onto the surface of micron-sized silicon particles using high-energy ball milling and a polymer binder, constructing a micro / nano composite silicon anode material with nano-silicon coating on micron-sized silicon. This effectively suppresses crystal plane cracking of the micron-sized silicon anode and addresses the issue of easy detachment of the micron-sized silicon anode from the sulfide solid electrolyte during charging and discharging in sulfide solid-state batteries. Micron-sized Si is abbreviated as mSi, nano-sized Si as Nano-Si, and the composite silicon particles with nano-silicon uniformly coated on the surface of micron-sized silicon particles are abbreviated as mSi@Nano-Si.

[0007] The purpose of this invention is to provide a micro / nano composite silicon anode material suitable for sulfide all-solid-state lithium-ion batteries and its preparation method, so as to meet the current demand for high-energy-density all-solid-state lithium-ion battery production.

[0008] To achieve the above objectives, the technical solution proposed by this invention is as follows:

[0009] The first aspect of the present invention provides a silicon anode material for all-solid-state lithium-ion batteries, the silicon anode material for all-solid-state lithium-ion batteries comprising: a micron-sized silicon material body, a nano-sized silicon material coated on the surface of the micron-sized silicon material body, and a polymer binder bonded between the micron-sized silicon material body and the nano-sized silicon material.

[0010] Preferably, the micron-sized silicon material is composed of 1-micron silicon particles, the nano-sized silicon material is composed of 50-nanometer silicon particles, and the polymer binder is selected from one or more of polyvinylidene fluoride, polyacrylonitrile, or polyacrylic acid.

[0011] Preferably, based on the total weight of the silicon anode material for the all-solid-state lithium-ion battery, the mass percentage of the nano-silicon material is 10.56–49 wt.%, the mass percentage of the micron-sized silicon material is 47.5–87.11 wt.%, and the mass percentage of the polymer binder is 2–5 wt.%.

[0012] A second aspect of the present invention provides a method for preparing the silicon anode material for all-solid-state lithium-ion batteries according to any one of the first aspects, the method comprising the following steps:

[0013] Step (1): Place micron-sized silicon, nano-sized silicon, and polymer binder in a ball mill and perform ball milling to form a composite structure of nano-sized silicon coated with micron-sized silicon, and finally obtain a mixed powder;

[0014] Step (2): The mixed powder obtained in step (1) is added to an organic solvent and mixed to obtain a slurry;

[0015] Step (3): Coat the slurry obtained in step (2) onto copper foil to obtain an electrode sheet, then dry the obtained electrode sheet and cut it into a suitable size to obtain a silicon anode material for all-solid-state lithium-ion batteries.

[0016] Preferably, the polymer binder is selected from polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), or polyacrylic acid (PAA).

[0017] Preferably, in step (1), the mass ratio of nano-silicon, micro-silicon, and polymer binder is (10.56-49):(47.5-87.11):(2-5).

[0018] Preferably, in step (1), the rotation speed of the ball mill is 370-510 rpm and the ball milling time is 1-24 h.

[0019] This application utilizes ball milling to increase the interaction between micron-sized and nano-sized silicon and enhances the adhesion of the binder to strengthen the composite of micron-sized and nano-sized silicon materials, ultimately forming a composite structure of nano-sized silicon coated with micron-sized silicon. By constructing the micro / nano composite material, the pulverization and structural breakage of silicon particles during charge and discharge are suppressed, solving the problem of the micron-sized silicon anode losing contact with the sulfide solid electrolyte during long-cycle operation of all-solid-state batteries.

[0020] The third aspect of the present invention provides the application of the silicon anode material for all-solid-state lithium-ion batteries described in the first aspect in sulfide all-solid-state lithium-ion batteries.

[0021] Preferably, the capacity ratio (NP ratio) of the negative electrode to the positive electrode of the battery is (1.1 to 1.68):1.

[0022] Preferably, the operating voltage of the battery is 2-4.3V or 2-4.5V.

[0023] Preferably, the sulfide solid electrolyte used in the sulfide all-solid-state lithium-ion battery is Li. 5.5 PS 4.5 Cl 1.5 .

[0024] Preferably, the positive electrode material used in the battery is a high-voltage positive electrode material, specifically Li. 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coated lithium cobalt oxide (LCO) or ternary high-nickel cathode material Li[Ni 0.8 Co 0.1 Mn 0.1 O2 (NCM811) is used, and during the assembly of solid-state batteries, a certain pressure is applied to maintain good battery contact, thereby improving the areal capacity and cycle performance of all-solid-state lithium-ion batteries.

[0025] The fourth aspect of the present invention provides a method for improving the performance of an all-solid-state lithium-ion battery over a wide voltage operating range, using the silicon anode material for all-solid-state lithium-ion batteries described in the first aspect of the present invention as the anode material of the battery, and using a high-voltage cathode material as the cathode material of the battery, wherein the wide voltage operating range is 2 to 4.3V or 2 to 4.5V.

[0026] Preferably, the performance of the all-solid-state lithium-ion battery includes: areal capacity and cycle performance.

[0027] In this application, cycle performance refers to cycle lifetime and cycle stability. Cycle lifetime refers to the capacity retention rate after multiple cycles, while cycle stability refers to the consistent stability of the areal capacity during each cycle.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention provides a silicon anode material for all-solid-state lithium-ion batteries. The silicon anode material comprises a micron-sized silicon material substrate, nano-sized silicon material coated on the surface of the micron-sized silicon material substrate, and a polymer binder bonding the micron-sized silicon material substrate and the nano-sized silicon material. In other words, the silicon anode material for all-solid-state lithium-ion batteries of this invention has two characteristics: first, nano-sized silicon with a larger specific surface area and greater surface binding energy is incorporated into the micron-sized silicon substrate; second, a binder that interacts with the silicon particles is added between the anode silicon particles.

[0030] This invention first coats a suitable amount of nano-silicon particles onto the surface of a micron-sized silicon anode material, constructing a micro / nano composite silicon anode material with nano-silicon coating on micron-sized silicon. The nano-silicon effectively compensates for the crystal plane cracking and pulverization caused by the large volume expansion and contraction of the micron-sized silicon anode material, and better controls the stress and strain of the silicon anode material in sulfide solid-state batteries. Furthermore, due to the small size of the nano-silicon particles, they have a larger specific surface area and higher binding energy, which can effectively fill the interfacial gap between the sulfide solid electrolyte and the micron-sized silicon anode, alleviating the poor contact between the micron-sized silicon and the sulfide solid electrolyte caused by volume expansion and contraction, improving ion transport between the sulfide solid electrolyte and the silicon anode, thereby enhancing the high-rate and long-cycle performance of the sulfide solid-state battery.

[0031] 2. The micro / nano composite silicon of this invention, when matched with different cathode materials, can maintain the cycle stability of the battery within a suitable voltage range while further promoting the capacity utilization of the silicon anode. The cathode used in the all-solid-state sulfide battery assembled in this invention can be Li... 1.175 Nb 0.645 Ti 0.4Positive electrodes include LiMO2 (where M is such as nickel, cobalt, manganese, etc.), LiMn2O4, lithium iron phosphate (LFP), and ternary materials (lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA)). A suitable negative electrode to positive electrode capacity ratio (NP ratio) is selected to ensure stable lithium insertion and delithiation of the battery. Appropriate pressure is applied to maintain battery contact, reduce battery impedance, and promote battery capacity utilization.

[0032] 3. The silicon anode material of the present invention has the advantages of simple preparation and cheap and readily available raw materials, making it suitable for mass production. It can also be matched with different cathode materials, such as general high-voltage lithium cobalt oxide and high-nickel ternary cathode materials, and has certain commercial prospects. Attached Figure Description

[0033] Figure 1 This is a diagram showing the size distribution of silicon micrometers in Comparative Example 1.

[0034] Figure 2 This is a size distribution diagram of nano-silicon in Comparative Example 2.

[0035] Figure 3 a, 3b, 3c, and 3d are SEM images of the silicon anode materials obtained in Examples 1 to 4, respectively.

[0036] Figure 4 To construct half-cells using silicon anode materials from Examples 1, 1, and 2, respectively, and Li-In,

[0037] Li 5.5 PS 4.5 Cl 1.5 The discharge curve of the first cycle of the half-cell is shown, with the electrolyte being the electrolyte.

[0038] Figure 5 The charge-discharge curves of the battery with Li6PS5Cl as electrolyte, silicon anode material (mSi@Nano-Si1:1) of Example 1, silicon anode material (Nano-Si) of Comparative Example 2, or silicon anode material (mSi) of Comparative Example 1 as anode, and NCM811 as cathode, are shown in the first week charge-discharge curves at an NP ratio of 1.6.

[0039] Figure 6 The first-cycle charge-discharge curve of a battery with Li6PS5Cl as electrolyte, silicon anode material (mSi@Nano-Si1:1) from Example 1 as anode, and high-voltage LCO as cathode, is shown in the figure.

[0040] Figure 7 Li, a chlorine-rich electrolyte 5.5 PS 4.5 Cl 1.5The battery of Example 1, with silicon anode material (mSi@Nano-Si1:1) as the anode and high-voltage LCO as the cathode, shows the charge-discharge diagram of the first cycle with an NP ratio of 1.6.

[0041] Figure 8 The silicon anode materials of Examples 1-4, the silicon anode materials of Comparative Examples 1-2, and Li 1.175 Nb 0.645 Ti 0.4 Cyclic performance of batteries assembled with O3(LNTO) coated lithium cobalt oxide cathodes at 2–4.5V and 25°C.

[0042] Figure 9 The graph shows the rate performance of full cells assembled from mSi and mSi@Nano-Si1:1 materials at different current densities in Application Example 1.

[0043] Figure 10 Focused ion beam microscopy (FIM) images of the electrode surface (10a), magnified electrode surface (10c), and electrode cross-section (10e) of a full cell assembled with mSi material after 100 cycles; and focused ion beam microscopy (FIM) images of the electrode surface (10b), magnified electrode surface (10d), and electrode cross-section (10f) of a full cell assembled with mSi@Nano-Si1:1 material after 100 cycles.

[0044] Figure 11 Electrochemical impedance spectroscopy (EIS) spectra of the mSi, Nano-Si, and mSi@Nano-Si 1:1 assembled full cells from Example 1 after cycling.

[0045] Figure 12 The graph shows the cycle performance of the micro-nano composite silicon-based all-solid-state battery in Application Example 4 at 2–4.5V and 25°C.

[0046] Figure 13 The graph shows the cycle performance of the micro-nano composite silicon-based all-solid-state battery in Application Example 5 at 2–4.5V and 25°C.

[0047] Figure 14 The battery cycle performance of the silicon anode material assembled in Example 1 with an NP ratio (NP ratio is the ratio of anode capacity per unit area to cathode capacity per unit area) of 1.68 is shown.

[0048] Figure 15 The cycle performance of the battery assembled with the silicon anode material prepared in Example 1 with an NP ratio of 1.19 is shown. Detailed Implementation

[0049] The present invention will be described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified. The raw materials required in the following embodiments and comparative examples are all commercially available.

[0050] Comparative Example 1 (mSi)

[0051] Comparative Example 1 uses pure micron-sized silicon particle anode material, and its specific operation is as follows:

[0052] (1) Weigh 0.5g of micron-sized silicon particles (source: commercially available 1-micron silicon particles) and 0.01g of PVDF, and stir at 300rpm for 8h to obtain a mixed powder; then mix the mixed powder with an appropriate amount of NMP to obtain a micron-sized silicon particle slurry.

[0053] (2) Pour the slurry obtained in step (1) onto a clean copper foil, and use a 200-micron thick scraper to coat the slurry onto the copper foil to obtain an electrode sheet;

[0054] (3) Place the electrode obtained in step (2) in an oven and dry it at 100°C for 10 hours to obtain coated micron silicon particle electrode. Cut it into round pieces of appropriate size using a cutting machine for later use to obtain silicon anode material for all-solid-state lithium-ion batteries. Figure 1 This is a diagram showing the size distribution of micron-sized silicon particles, and a diagram of the micron-sized silicon particle raw material used in step (1). Figure 1 It can be seen that the Si particles at the micrometer scale are almost uniform and intact.

[0055] The full cell in Comparative Example 1 is: Li 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coated lithium cobalt oxide

[0056] ~Li 5.5 PS 4.5 Cl 1.5 ~ A sulfide-based all-solid-state battery with a micron-sized silicon anode (abbreviation)

[0057] LNTO~LCO / Li 5.5 PS 4.5 Cl 1.5 / mSi. Its assembled battery exhibits electrochemical performance at 25°C during charge-discharge cycles within the 2–4.5V range. Figure 5 middle.

[0058] Comparative Example 2 (Nano-Si)

[0059] Comparative Example 2 uses pure nano-silicon particle anode material, and its specific operation is as follows:

[0060] (1) Weigh 0.5g of nano-silicon particles (source: commercially available 50-nanometer silicon particles) and 0.01g of PVDF, and stir at 300rpm for 8h to obtain a mixed powder; then mix the mixed powder with an appropriate amount of NMP to obtain a nano-silicon particle slurry.

[0061] (2) Pour the slurry obtained in step (1) onto a clean copper foil, and use a 200-nanometer thick scraper to coat the slurry onto the copper foil to obtain an electrode sheet;

[0062] (3) Place the electrode obtained in step (2) in an oven and dry it at 100°C for 10 hours to obtain coated nano-silicon particle electrode. Cut it into round pieces of appropriate size using a cutting machine for later use to obtain silicon anode material for all-solid-state lithium-ion batteries. Figure 2 This is a diagram of the nano-silicon particle raw material used in step (1). Figure 2 It is evident that the nano-silicon particles have a uniform size distribution and are intact.

[0063] The full cell in Comparative Example 2 is: Li 1.175 Nb 0.645 Ti 0.4 O3(LNTO)-coated cobalt acid ~ Li 5.5 PS 4.5 Cl 1.5 ~LNTO (Lithium-ion Toluene-ion) all-solid-state battery with nano-silicon anode ~LCO / Li 5.5 PS 4.5 Cl 1.5 / Nano-Si. Its assembled battery exhibits electrochemical performance at 25°C during charge-discharge cycles within the 2–4.5V range. Figure 5 middle.

[0064] Preparation of silicon anode material samples

[0065] Example 1 (Nano-Si, mSi, and PVDF mass ratio 49:49:2)

[0066] (1) Weigh 0.2g of micron silicon particles (source: commercially available 1-micron silicon particles), 0.2g of nano silicon particles (source: commercially available 50-nanometer silicon particles), and 0.008g of PVDF. The Nano-Si content is 49wt%, the mSi content is 49wt%, and the PVDF content is 2wt%. Stir at 300rpm for 8h until all materials are mixed evenly to obtain a mixed powder. Then mix the mixed powder with an appropriate amount of NMP evenly to obtain a micro-nano composite silicon slurry.

[0067] (2) Pour the slurry obtained in step (1) onto a clean copper foil, and use a 200-micron thick scraper to coat the slurry onto the copper foil to obtain an electrode sheet;

[0068] (3) Place the electrode obtained in step (2) in an oven and dry it at 100°C for 10 hours to obtain the coated micro-nano composite silicon electrode. Cut it into round pieces of appropriate size using a cutting machine for later use to obtain silicon anode material (mSi@Nano-Si1:1) for all-solid-state lithium-ion batteries. Figure 3 a is a SEM image of the silicon anode material in Example 1. Figure 3 a. As can be seen, nano-silicon particles are coated on the surface of the micron-sized silicon particle body.

[0069] Example 2 (Nano-Si, mSi, and PVDF mass ratio: 32.67:65.33:2)

[0070] (1) Weigh 0.4g of micron silicon particles (source: commercially available 1-micron silicon particles), 0.2g of nano silicon particles (source: commercially available 50-nanometer silicon particles), and 0.012g of PVDF. The Nano-Si content is 32.67wt%, the mSi content is 65.33wt%, and the PVDF content is 2wt%. Stir at 510rpm for 1h until all materials are mixed evenly to obtain a mixed powder. Then, mix the mixed powder with an appropriate amount of NMP evenly to obtain a micro-nano composite silicon slurry.

[0071] (2) Pour the slurry obtained in step (1) onto a clean copper foil, and use a 200-micron thick scraper to coat the slurry onto the copper foil to obtain an electrode sheet;

[0072] (3) Place the electrode obtained in step (2) in an oven and dry it at 100°C for 10 hours to obtain the coated micro-nano composite silicon electrode. Cut it into round pieces of appropriate size using a cutting machine for later use to obtain silicon anode material (mSi@Nano-Si1:2) for all-solid-state lithium-ion batteries. Figure 3 b is a SEM image of the silicon anode material in Example 2. Figure 3 b. As can be seen, nano-silicon particles are coated on the surface of the micron-sized silicon particle body.

[0073] Example 3 (Nano-Si, mSi, and PVDF mass ratio: 16.33:81.67:2)

[0074] (1) Weigh 1.0g of micron silicon particles (source: commercially available 1-micron silicon particles), 0.2g of nano silicon particles (source: commercially available 50-nanometer silicon particles), and 0.024g of PVDF. The Nano-Si content is 16.33wt%, the mSi content is 81.67wt%, and the PVDF content is 2wt%. Stir at 370rpm for 24h until all materials are mixed evenly to obtain a mixed powder. Then, mix the mixed powder with an appropriate amount of NMP evenly to obtain a micro-nano composite silicon slurry.

[0075] (2) Pour the slurry obtained in step (1) onto a clean copper foil, and use a 200-micron thick scraper to coat the slurry onto the copper foil to obtain an electrode sheet;

[0076] (3) Place the electrode obtained in step (2) in an oven and dry it at 100°C for 10 hours to obtain the coated micro-nano composite silicon electrode. Cut it into round pieces of appropriate size using a cutting machine for later use to obtain silicon anode material (mSi@Nano-Si1:5) for all-solid-state lithium-ion batteries. Figure 3 c is the SEM image of the silicon anode material in Example 3. Figure 3 c. It can be seen that the nano-silicon particle material is coated on the surface of the micron-sized silicon particle material.

[0077] Example 4 (Nano-Si, mSi, and PVDF mass ratio: 10.89:87.11:2)

[0078] (1) Weigh 1.6g of micron silicon particles (source: commercially available 1-micron silicon particles), 0.2g of nano silicon particles (source: commercially available 50-nanometer silicon particles), and 0.037g of PVDF. The Nano-Si content is 10.89wt%, the mSi content is 87.11wt%, and the PVDF content is 2wt%. Stir at 300rpm for 8h until all materials are mixed evenly to obtain a mixed powder. Then mix the mixed powder with an appropriate amount of NMP evenly to obtain a micro-nano composite silicon slurry.

[0079] (2) Pour the slurry obtained in step (1) onto a clean copper foil, and use a 200-micron thick scraper to coat the slurry onto the copper foil to obtain an electrode sheet;

[0080] (3) Place the electrode obtained in step (2) in an oven and dry it at 100°C for 10 hours to obtain the coated micro-nano composite silicon electrode. Cut it into round pieces of appropriate size using a cutting machine for later use to obtain silicon anode material (mSi@Nano-Si1:8) for all-solid-state lithium-ion batteries. Figure 3 d is the SEM image of the silicon anode material in Example 4. Figure 3 As can be seen, nano-silicon particles are coated on the surface of the micron-sized silicon particle body.

[0081] Example 5 (using PAA and PAN adhesives)

[0082] (1) Weigh 0.2g of micron silicon particles (source: commercially available 1-micron silicon particles), 0.2g of nano silicon particles (source: commercially available 50-nanometer silicon particles), and 0.008g of PAA or PAN. Stir at 300rpm for 8 hours until all materials are mixed evenly to obtain a mixed powder. Then mix the mixed powder with an appropriate amount of water evenly to obtain two micro-nano composite silicon slurries.

[0083] (2) Pour the two slurries obtained in step (1) onto a clean copper foil, and use a 200-micron thick scraper to coat the slurry onto the copper foil to obtain two types of electrodes;

[0084] (3) Place the two types of electrode sheets obtained in step (2) in an oven and dry them at 100°C for 10 hours to obtain two coated micro-nano composite silicon electrode sheets. Cut them into round pieces of appropriate size using a cutting machine for later use, thus obtaining two types of silicon anode materials for all-solid-state lithium-ion batteries.

[0085] Example 6 (Changing the amount of adhesive)

[0086] (1) Weigh 0.2g of micron silicon particles (source: commercially available 1-micron silicon particles) and 0.2g of nano silicon particles (source: commercially available 50-nanometer silicon particles), add 0.008g of PVDF (2wt%) and 0.021g of PVDF (5wt%) respectively, stir at 300rpm for 8h, and mix all materials evenly to obtain a mixed powder. Then mix the mixed powder with an appropriate amount of NMP evenly to obtain two micro-nano composite silicon slurries.

[0087] (2) Pour the two slurries obtained in step (1) onto clean copper foil, and use a 200-micron thick scraper to coat the slurries onto the copper foil to obtain two types of electrodes;

[0088] (3) Place the two types of electrode sheets obtained in step (2) in an oven and dry them at 100°C for 10 hours to obtain coated micro-nano composite silicon electrode sheets. Cut them into round sheets of appropriate size using a cutting machine for later use, thus obtaining two types of silicon anode materials for all-solid-state lithium-ion batteries.

[0089] Application Example - Battery Application

[0090] Application Example 1 (Exploring the Performance of Different Proportions)

[0091] Half-cells were constructed using silicon anode materials from Examples 1, 1, and 2, respectively, and Li-In. 5.5 PS 4.5 Cl 1.5 As the electrolyte, the discharge curve for the first week is as follows: Figure 4 As shown.

[0092] Figure 4 It can be seen that the discharge surface capacity of the half-cell composed of Comparative Example 2 is 3.51 mAh / cm². 2 The discharge surface capacity of the half-cell composed of Comparative Example 1 is 3.85 mAh / cm³. 2 The discharge surface capacity of the half-cell assembled in Example 1 is 3.80 mAh / cm². 2 .

[0093] In addition, to verify the performance of the silicon anode materials obtained in Examples 1-4, Li was assembled using the silicon anode materials obtained in Examples 1-4 (Nano-Si and mSi ratios of 1:1, 1:2, 1:5, and 1:8, respectively) and the silicon anode materials of Comparative Examples 1-2 (mSi and Nano-Si). 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coated lithium cobalt oxide ~ Li 5.5 PS 4.5 Cl 1.5 A micro / nano composite silicon-based all-solid-state battery was developed, with a fixed negative electrode active material loading of 1 mg and an adjusted positive electrode content to achieve an NP ratio of 1.6. The electrochemical performance of the assembled battery was tested during charge-discharge cycles within the range of 2–4.5 V at 25°C, and the results are as follows: Figure 8 As shown.

[0094] from Figure 8 It can be seen from this:

[0095] (1) Compared to Nano-Si, mSi, mSi@Nano-Si1:2, mSi@Nano-Si1:5, and mSi@Nano-Si1:8, when the ratio of Nano-Si to mSi is 1:1, the cell surface current is 1 mA / cm². 2 Its performance is far superior to other ratios, with a capacity retention rate of 92% after 200 cycles. This is likely due to the addition of nano-silicon particles, whose higher binding energy and high specific surface energy alleviate the volume expansion of the negative electrode, reduce the loss of active lithium, and thus improve the first discharge efficiency, thereby increasing the battery's areal capacity to a certain extent.

[0096] (2) When the ratio of Nano-Si to mSi is 1:1, 1:2, 1:5 or 1:8 respectively, its areal capacity is higher than that of Comparative Example 1. This indicates that the addition of nano-silicon particles to micron-sized silicon particles can alleviate the stress changes caused by volume changes during charging and discharging and promote the free insertion and extraction of active lithium ions. This can promote the utilization of silicon anode capacity and is conducive to the application and promotion of silicon anode all-solid-state batteries.

[0097] comprehensive Figure 4 and Figure 8 It can be seen that although the discharge surface capacity of Comparative Example 1 is better than that of Example 1, the cycle stability of Example 1 is better than that of Comparative Example 1.

[0098] Furthermore, we investigated the rate performance of full cells assembled from mSi and mSi@Nano-Si1:1 materials at different current densities. Li2O3 cells were assembled using mSi and mSi@Nano-Si1:1 materials. 1.175 Nb 0.645 Ti 0.4O3(LNTO) coated lithium cobalt oxide ~ Li 5.5 PS 4.5 Cl 1.5 ~A micro-nano composite silicon-based all-solid-state battery with a fixed negative electrode active material loading of 1mg and an adjusted positive electrode content to achieve an NP ratio of 1.6. Figure 9 The results show that mSi@Nano-Si1:1 has a higher areal capacitance than mSi at different currents (see...). Figure 9 ).

[0099] Furthermore, we characterized the electrode surface and electrode cross-section of the full cells assembled from the above mSi and mSi@Nano-Si1:1 materials after 100 cycles. Figure 10 a, c, and e are respectively the electrode surface image (10a), the magnified electrode surface image (10c), and the focused ion beam microscopy (FIB-SEM) image of the electrode cross-section after cycling (10e). 10a shows that after 100 full-cell cycles, the mSi electrode has developed a large number of cracks; Figure 10 c shows that after 100 cycles of a full cell, the micron-sized Si material has already shown crystal plane cracking. Figure 10 As can be seen from the results, after 100 full-cell cycles, the micron-sized Si material in mSi exhibits de-contact behavior with the sulfide solid electrolyte (SSE). In stark contrast, the mSi@Nano-Si1:1 electrode showed no cracking after 100 full-cell cycles (see [link to full-cell cycle description]). Figure 10 b); Nano-silicon coated with micron-silicon, i.e., mSi@Nano-Si1:1 material itself, does not exhibit crystal plane cracks (see Figure 10 d); Focused ion beam microscopy (FIB-SEM) images of the electrode cross-section show that mSi@Nano-Si1:1 did not exhibit any contact detachment behavior from the SSE. Figure 10 f).

[0100] Meanwhile, the electrochemical impedance spectroscopy of the above-mentioned mSi, Nano-Si and mSi@Nano-Si 1:1 assembled full cells after cycling was investigated. Figure 11 The results showed that mSi@Nano-Si1:1 had the lowest impedance, followed by Nano-Si, with mSi having the highest. This indicates that mSi@Nano-Si1:1 exhibits excellent interfacial impedance behavior after full cell cycling.

[0101] Application Example 2 (can be matched with different positive electrodes)

[0102] To verify the widely applicable performance of the silicon anode material in Example 1, an assembly was performed.

[0103] The NCM811-Li6PS5Cl micro / nano composite silicon-based all-solid-state battery features a fixed negative electrode active material loading of 1 mg and an adjusted positive electrode content to achieve an NP ratio of 1.6. The assembled battery was tested and operated at 2–4.3 V with an A / cm² voltage of 0.14 mA at 25°C. 2 The first-cycle charge-discharge curve under surface current is as follows Figure 5 As shown in the diagram, mSi@Nano-Si1:1.

[0104] Figure 5 As can be seen, the mSi@Nano-Si1:1 silicon anode material in Example 1 operates at a current of 0.14 mA / cm². 2 The first-week discharge surface capacity in the 2–4.3V voltage range is 1.02 mAh / cm³. 2 The first-week discharge capacity of Comparative Example 1 and Comparative Example 2 were 1.05 mAh / cm³, respectively. 2 and 0.8mAh / cm 2 .

[0105] In addition, assembling Li 1.175 Nb 0.645 Ti 0.4 An O3(LNTO)-coated lithium cobalt oxide-Li6PS5Cl micro / nano composite silicon-based all-solid-state battery was developed, with a fixed negative electrode active material loading of 1 mg and an adjusted positive electrode content to achieve an NP ratio of 1.6. The assembled battery was tested to operate at 2–4.5 V, and at 25°C, the current was 0.2 mA / cm². 2 The first-cycle charge-discharge curves under surface current are shown in the following figures. Figure 6 As shown.

[0106] Figure 6 As can be seen: the mSi@Nano-Si1:1 silicon anode material of Example 1, Li 1.175 Nb 0.645 Ti 0.4 The silicon-based all-solid-state battery composed of O3(LNTO)-coated lithium cobalt oxide and Li6PS5Cl has an initial discharge capacity of 1.93 mAh / cm³ at 2–4.5V. 2 .

[0107] from Figure 5 and Figure 6 It can be seen that the silicon anode material (mSi@Nano-Si1:1) of Example 1 can be matched with cathodes of different voltage ranges and has broad application prospects.

[0108] Application Example 3 (Can be matched with different electrolytes)

[0109] To verify that Example 1 is compatible with different electrolytes, Li was assembled separately. 1.175 Nb 0.645 Ti 0.4O3(LNTO)-coated lithium cobalt oxide-Li6PS5Cl-micro / nano composite silicon-based all-solid-state battery and Li 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coated lithium cobalt oxide ~ Li 5.5 PS 4.5 Cl 1.5 A micro / nano composite silicon-based all-solid-state battery was developed, with a fixed negative electrode active material loading of 1 mg and an adjusted positive electrode content to achieve an NP ratio of 1.6. The assembled battery was tested operating at 2–4.5V, and its first-cycle charge-discharge curve is shown below. Figure 6 and 7 As shown.

[0110] Figure 6 and 7 As can be seen: the mSi@Nano-Si1:1 silicon anode material of Example 1, Li 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coated lithium cobalt oxide cathode material, with Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 The silicon-based all-solid-state battery exhibits an efficiency of 0.2 mA / cm² at 25°C and a voltage range of 2–4.5V. 2 The first-cycle discharge surface capacity under surface current was 1.93 mAh / cm³. 2 and 1.82mAh / cm 2 .from Figure 6 and Figure 7 It can be seen that the silicon anode material (mSi@Nano-Si1:1) in Example 1 can be matched with different electrolytes and all of them have excellent electrochemical performance.

[0111] Application Example 4 (The Influence of Different Binders on Battery Performance)

[0112] To verify the effect of the binder on battery performance, the silicon anode materials prepared in Examples 1 and 5 were used as anodes to assemble Li 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coating LCO~Li 5.5 PS 4.5 Cl 1.5 ~Micro-nano composite silicon-based all-solid-state battery, results as follows Figure 12 As shown.

[0113] from Figure 12 It can be seen that the battery assembled using PVDF as a binder with micro-nano composite silicon exhibits the following cycle performance: at 25℃, within a voltage range of 2–4.5V, at 1mA / cm 2At surface current, it was found that the performance of the battery using PVDF binder was much better than that of the PAA and PAN binders. After 100 cycles, the capacity retention rate was 100%, while that of the PAA-based battery was 29% and that of the PAN-based battery was 36%.

[0114] Application Example 5 (The Effect of Binder Dosage on Battery Performance)

[0115] To verify the effect of binder dosage on battery performance, the two silicon anode materials prepared in Example 6 were used as anodes to assemble Li 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coating LCO~Li 5.5 PS 4.5 Cl 1.5 ~Micro-nano composite silicon-based all-solid-state battery, results as follows Figure 13 As shown.

[0116] from Figure 10 It can be seen that at 25℃, within the voltage range of 2~4.5V, at 1mA / cm 2 At surface current, the battery with a binder content of 2% has the following cycle performance: 100% capacity retention after 100 cycles; the battery with a binder content of 5% has the following cycle performance: 97% capacity retention after 100 cycles. Therefore, the battery with a binder content of 2% performs better than the battery with a binder content of 5%.

[0117] Application Example 6 (The Influence of Different NP Ratios on Battery Performance)

[0118] To verify the effect of the anode-to-cathode capacity ratio (NP ratio) on battery performance, the silicon anode material prepared in Example 1 was used as the anode material in the Li assembly. 1.175 Nb 0.645 Ti 0.4 O3(LNTO) coated lithium cobalt oxide

[0119] ~Li 5.5 PS 4.5 Cl 1.5 ~A micro-nano composite silicon-based all-solid-state battery with a fixed negative electrode loading of 1mg. By adjusting the mass of the positive electrode added, different negative electrode capacities and positive electrode capacity ratios >1 (i.e., N / P>1) can be controlled.

[0120] like Figure 14 and 15 The figures show the performance at N / P ratios of 1.68 and 1.19, respectively. From... Figure 14 It can be seen that at 25℃, 1mA / cm 2 At surface current, with an NP ratio of 1.68, the capacitance retention after 600 turns is 80%. Figure 15It can be seen that at 25℃, 2.25mA / cm 2 At surface current, with an NP ratio of 1.19, the capacity retention rate is 81.2% after 250 cycles. Therefore, the battery exhibits good performance within the NP ratio range of (1.1 to 1.68):1.

Claims

1. A silicon anode material for all-solid-state lithium-ion batteries, characterized in that, The silicon anode material for all-solid-state lithium-ion batteries includes: a micron-sized silicon material body, a nano-sized silicon material coated on the surface of the micron-sized silicon material body, and a polymer binder bonding the micron-sized silicon material body and the nano-sized silicon material; The micron-sized silicon material is composed of 1-micron silicon particles, and the nano-sized silicon material is composed of 50-nanometer silicon particles. The polymer binder is selected from polyvinylidene fluoride, polyacrylonitrile, or polyacrylic acid. Based on the total weight of the silicon anode material for the all-solid-state lithium-ion battery, the mass percentage of the nano-silicon material is 10.56–49 wt%, the mass percentage of the micron-sized silicon material is 47.5–87.11 wt%, and the mass percentage of the polymer binder is 2–5 wt%.

2. A method for preparing the silicon anode material for all-solid-state lithium-ion batteries according to claim 1, characterized in that, The preparation method includes the following steps: Step (1) Micron-sized silicon, nano-sized silicon, and polymer binder are placed in a ball mill and ball milled to form a composite structure of nano-sized silicon coated with micron-sized silicon, and finally a mixed powder is obtained; the polymer binder is selected from polyvinylidene fluoride, polyacrylonitrile, or polyacrylic acid; the mass ratio of nano-sized silicon, micron-sized silicon, and polymer binder is (10.56~49):(47.5~87.11):(2~5); the rotation speed of the ball mill is 370~510 rpm, and the ball milling time is 1~24 h; Step (2) The mixed powder obtained in step (1) is added to an organic solvent and mixed to obtain a slurry; Step (3) Coat the slurry obtained in step (2) onto copper foil to obtain an electrode sheet, then dry the obtained electrode sheet and cut it into a suitable size to obtain silicon anode material for all-solid-state lithium-ion batteries.

3. The silicon anode material for all-solid-state lithium-ion batteries according to claim 1 is used in sulfide all-solid-state lithium-ion batteries.

4. The application according to claim 3, characterized in that, The capacity ratio of the negative electrode to the positive electrode of the battery is (1.1 to 1.68):

1.

5. A method for improving the performance of an all-solid-state lithium-ion battery over a wide voltage operating range, characterized in that, The silicon anode material for all-solid-state lithium-ion batteries as described in claim 1 is used as the anode material of the battery, and a high-voltage cathode material is used as the cathode material of the battery, wherein the wide voltage operating range is 2 to 4.3V or 2 to 4.5V.

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