Silicon negative electrode material and secondary battery, electric device comprising the same

Abstract

The application relates to the field of secondary batteries, and discloses a silicon negative electrode material, a secondary battery containing the same, and an electric device. The silicon negative electrode material comprises silicon-based particles and a fast ion conductor, the silicon-based particles have a porous structure, and the fast ion conductor is filled in the pores of the porous structure; the silicon-based particles comprise silicon elements and doping elements, and the doping elements comprise at least two of group IV A elements, group VIA elements and lanthanide series elements. By introducing the doping elements into the silicon-based particles, utilizing the different functions of different doping elements, and through high-entropy design, the transmission rate of lithium ions / electrons in the negative electrode sheet can be improved, and the volume expansion of the silicon negative electrode can be relieved; meanwhile, the silicon-based particles also have a porous structure, and the fast ion conductor is filled in the pores, so that the conduction rate of lithium ions in the negative electrode can be further improved, and the volume expansion can be further relieved, so that the rate and cycle performance of the secondary battery are good.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, specifically to a silicon anode material and a secondary battery and electrical device containing the same. Background Technology

[0002] Traditional lithium-ion rechargeable batteries use liquid electrolytes to ensure efficient and stable operation. However, liquid electrolytes are flammable and can easily cause fires or explosions when subjected to mechanical or thermal stress. All-solid-state batteries, which replace the flammable liquid electrolyte in traditional lithium-ion batteries with a non-flammable, non-volatile, and leak-proof solid electrolyte, can fundamentally improve battery safety.

[0003] Currently, solid-state electrolytes mainly include oxides, sulfides, halides, and polymers. Among them, sulfide solid-state electrolytes have the highest room-temperature ionic conductivity and are considered the most promising solid-state battery system. Based on this, researchers have attempted to improve the energy density of all-solid-state batteries by using positive / negative electrode active materials with high specific capacity. For example, high-nickel, lithium-rich materials are used as positive electrode active materials, and silicon anodes are used as negative electrode active materials, enabling all-solid-state batteries to achieve both high energy density and high safety. However, when silicon anodes are applied to sulfide-type all-solid-state batteries, problems such as slow ion / electron transport rates, drastic volume changes, and interfacial contact failure after cycling occur, resulting in poor rate performance and cycle performance. Summary of the Invention

[0004] In view of this, this application provides a silicon anode material to solve the problems of poor rate capability and cycle performance of existing sulfide-type all-solid-state batteries.

[0005] According to an embodiment of this application, in a first aspect, a silicon anode material is provided, the silicon anode material comprising silicon-based particles and a fast ion conductor, the silicon-based particles having a porous structure, and the fast ion conductor filling the channels of the porous structure;

[0006] The silicon-based particles comprise silicon and doping elements, wherein the doping elements comprise at least two of Group IIIA elements, Group VIA elements, and lanthanide elements.

[0007] In some alternative embodiments, the silicon anode material further includes at least one of the following features:

[0008] a. The Group IIIA element includes at least one of B and In;

[0009] b. The VIA group element includes at least one of S and Se;

[0010] c. The lanthanide elements include at least one of La and Ce.

[0011] In some alternative embodiments, the silicon anode material further includes at least one of the following features:

[0012] d. The molar percentage of the Group IIIA element in the silicon anode material is 0.1-0.2;

[0013] e. The molar percentage of the group VIA element in the silicon anode material is 0.1-0.2;

[0014] f. The molar percentage of the lanthanide elements in the silicon anode material is 0.05-0.1.

[0015] In some alternative embodiments, the porosity of the silicon anode material is 1%-15%.

[0016] In some alternative embodiments, the median particle size of the silicon anode material is 0.8 μm-5 μm.

[0017] In some alternative embodiments, the silicon anode material further includes at least one of the following features:

[0018] g. Based on the mass of the silicon anode material, the content of the fast ion conductor is 5%-10%;

[0019] h. The elastic modulus of the fast ion conductor is 2MPa-200MPa;

[0020] i. The fast ion conductor includes at least one of sulfide electrolytes, polymer electrolytes, and oxygen-containing inorganic electrolytes.

[0021] In some alternative embodiments, the fast ion conductor is a polymer electrolyte and an oxygen-containing inorganic electrolyte, and the content of the oxygen-containing inorganic electrolyte is 10%-20% based on the mass of the fast ion conductor.

[0022] In some alternative embodiments, the sulfide electrolyte comprises Li 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 At least one of Li3PS4;

[0023] The polymer electrolyte includes at least one of polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN);

[0024] The oxygen-containing inorganic electrolyte includes Li7La3Zr2O12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.3 Al 0.3 Ge 1.7 (PO4)3, Li 0.33 La 0.55 At least one of TiO3.

[0025] According to an embodiment of this application, in a second aspect, a secondary battery is provided, including a positive electrode, a negative electrode, and a solid electrolyte. The negative electrode includes a negative current collector and a negative active layer disposed on at least one side surface of the negative current collector. The negative active layer includes the silicon negative electrode material described in the first aspect of this application.

[0026] In some alternative embodiments, the film resistance of the negative electrode is 0.5mΩ-1mΩ.

[0027] In some alternative embodiments, the negative electrode exhibits an expansion rate of 20%-30% at 100% SOC compared to 0% SOC.

[0028] According to an embodiment of this application, in a third aspect, an electrical device is provided, including the secondary battery described in the second aspect of this application.

[0029] The technical solution of this application has the following advantages:

[0030] The silicon anode material provided in this application includes silicon-based particles and a fast-ion conductor. The silicon-based particles have a porous structure, and the fast-ion conductor fills the channels of the porous structure. The silicon-based particles include silicon and doping elements, wherein the doping elements include at least two of Group IIIA, Group VIA, and lanthanide elements. This application introduces at least two of Group IIIA, Group VIA, and lanthanide elements into the silicon-based particles. By utilizing the different functions of different doping elements, the above design can improve the transport rate of lithium ions / electrons inside the anode sheet and alleviate the volume expansion of the silicon anode. At the same time, the silicon-based particles also have a porous structure, and the channels of the porous structure are filled with fast-ion conductors. This not only further improves the conduction rate of lithium ions in the anode but also further alleviates volume expansion, ensuring good rate capability and cycle performance of the secondary battery.

[0031] Additional aspects and advantages of the embodiments of this application will be described and shown in part in the following description, or illustrated by practice of the embodiments of this application. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of the silicon anode material obtained in this application.

[0034] The reference numerals in the attached figures are explained as follows:

[0035] 1. Silicon-based particles; 2. Fast ion conductor. Detailed Implementation

[0036] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0037] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0038] To address the poor rate capability and cycle performance of existing sulfide-based all-solid-state batteries, according to the first aspect of this application, a silicon anode material is provided, see [link to relevant documentation]. Figure 1 The silicon anode material includes silicon-based particles 1 and fast ion conductors 2. The silicon-based particles 1 have a porous structure, and the fast ion conductors 2 fill the channels of the porous structure.

[0039] The silicon-based particles 1 include silicon and doping elements, wherein the doping elements include at least two of Group IIIA elements, Group VIA elements, and lanthanide elements.

[0040] The silicon anode material provided in this application introduces at least two of Group IIIA, Group VIA, and lanthanide elements into silicon-based particles. By utilizing the different functions of different doping elements, the above design can improve the transport rate of lithium ions / electrons inside the anode sheet and alleviate the volume expansion of the silicon anode. At the same time, the silicon-based particles also have a porous structure, and fast ion conductors are filled in the channels of the porous structure. This can not only further improve the conduction rate of lithium ions in the anode, but also further alleviate the volume expansion, thereby ensuring good rate capability and cycle performance of the secondary battery.

[0041] Specifically, the introduction of Group IIIA elements can act as a framework, especially when Group IIIA elements include at least one of B and In, which can form corresponding silicon alloys with silicon, making the framework structure less prone to collapse. Therefore, it can mainly improve the structural stability of silicon anodes. In addition, the formed silicon alloys also have a slight effect on improving the lithium-ion / electron transport rate in silicon anodes. The introduction of Group VIA elements can improve electronic conductivity by adjusting the band structure of the material, and reduce the brittleness of silicon anodes, delaying particle breakage during volume changes. Furthermore, Group VIA elements including at least one of S and Se can form chemical bonds with silicon, enhancing the interatomic bonding ability and improving the structural stability of silicon anodes during lithium insertion / extraction. The introduction of lanthanides can improve the lithium-ion transport rate, especially when lanthanides include at least one of La and Ce, which can accelerate lithium-ion transport by widening the size of the lithium-ion transport channels.

[0042] It is understood that the content of doping elements in silicon-based particles has a significant impact on the improvement of material performance. In some embodiments, the molar percentage of the Group IIIA elements in the silicon anode material is 0.1-0.2, for example, it can be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, or any value within the range of the above. The molar percentage of the Group VIA elements in the silicon anode material is 0.1-0.2, for example, it can be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, or any value within the range of the above. The molar percentage of the lanthanides in the silicon anode material is 0.05-0.1, for example, it can be 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value within the range of the above. This can improve the lithium-ion / electron transport rate in the silicon anode, improve the structural stability of the silicon anode, and mitigate the volume change of the silicon anode.

[0043] It should be noted that the silicon-based particles described in this application are obtained by adding elemental silicon and a dopant element into a high-energy ball mill (the advantage of a high-energy ball mill compared to a traditional ball mill is that it can provide higher energy during the grinding process, promoting the uniform entry of dopant atoms into the bulk structure of the silicon anode) and grinding at a speed of 500-1000 rpm for 20-30 hours to obtain silicon-based particles containing the dopant element. Then, acid etching is used to obtain silicon-based particles with a porous structure. A liquid-phase impregnation method is then used to load fast ion conductors into the channels of the porous silicon-based particles, thereby obtaining the silicon anode material described in this application.

[0044] The silicon anode material provided in this application has a porosity in the range of 1%-15%, which can effectively alleviate the volume expansion of the silicon anode and facilitate the filling of fast ion conductors in the pores of the silicon anode material, thereby improving the lithium-ion transport rate. As an example, the porosity of the silicon anode material can be, for example, 1%, 3%, 5%, 7%, 10%, 13%, 15%, etc., or within any range of the above values.

[0045] In some embodiments, the median particle size of the silicon anode material provided in this application is 0.8 μm-5 μm. This ensures good adhesion of the material to the current collector and improves the cycle stability of the silicon anode. As an example, the median particle size of the silicon anode material can be, for example, 0.8 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, etc., or within any range of the above values. The median particle size in this application is the Dn50 of the material particles, representing the particle size corresponding to a 50% percentage of the silicon anode material.

[0046] It should be noted that the fast ion conductor described in this application has good elasticity, with an elastic modulus between 2 MPa and 200 MPa. This allows for more effective mitigation of silicon anode volume expansion while simultaneously increasing lithium-ion transport rate. As an example, the elastic modulus of the fast ion conductor can be 2 MPa, 10 MPa, 25 MPa, 50 MPa, 75 MPa, 100 MPa, 125 MPa, 150 MPa, 175 MPa, 200 MPa, or any value within the range described above.

[0047] In order to ensure a fast lithium-ion transport rate without affecting the specific capacity of the silicon anode, in some embodiments, the content of the fast ion conductor is 5%-10% based on the mass of the silicon anode material. As an example, the content of the fast ion conductor may be 5%, 6%, 7%, 8%, 9%, 10%, or any of the above values.

[0048] In some embodiments, the fast ion conductor includes at least one of a sulfide electrolyte, a polymer electrolyte, and an oxygen-containing inorganic electrolyte. As an example, the sulfide electrolyte includes Li... 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5The polymer electrolyte comprises at least one of Li3PS4; the polymer electrolyte comprises at least one of polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN); the oxygen-containing inorganic electrolyte comprises Li7La3Zr2O. 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.3 Al 0.3 Ge 1.7 (PO4)3, Li 0.33 La 0.55 At least one of TiO3. The above-mentioned fast ion conductors have excellent ionic conductivity, which is beneficial for improving the lithium ion transport rate.

[0049] In some implementations, the fast ion conductor is a mixture of polymer electrolyte and oxygen-containing inorganic electrolyte, and the content of the oxygen-containing inorganic electrolyte is 10%-20% based on the mass of the fast ion conductor, which can further accelerate the transport of lithium ions.

[0050] According to a second aspect of this application, a secondary battery is provided, comprising a positive electrode, a negative electrode, and a solid electrolyte, wherein the negative electrode comprises a negative current collector and a negative active layer disposed on at least one side surface of the negative current collector, and the negative active layer comprises the silicon negative electrode material described in the first aspect of this application.

[0051] In some embodiments, the film resistance of the negative electrode is 0.5mΩ-1mΩ, thereby ensuring good rate performance of the battery. As an example, the film resistance of the negative electrode can be 0.5mΩ, 0.6mΩ, 0.7mΩ, 0.8mΩ, 0.9mΩ, 1mΩ, or any value within the range described above.

[0052] In some embodiments, the expansion rate of the negative electrode at 100% SOC is 20%-30% compared to 0% SOC, thereby ensuring high cycle performance of the battery. As an example, the expansion rate of the negative electrode can be, for example, 20%, 22%, 24%, 26%, 28%, 30%, or any range thereof. This demonstrates that using the silicon negative electrode material of this application can reduce the expansion rate of the electrode, which is beneficial to improving the cycle performance of the battery.

[0053] It is understood that the solid electrolyte described in this application may be a sulfide-type solid electrolyte, and as an example, it may be Li 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 5.5PS 4.5 Cl 1.5 At least one of Li3PS4.

[0054] According to an embodiment of this application, in a third aspect, an electrical device is provided, including the secondary battery described in the second aspect of this application.

[0055] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0056] Example 1

[0057] This embodiment provides a method for preparing a secondary battery, including the following steps:

[0058] (1) Preparation of silicon anode materials

[0059] Si powder (Dn50 of 3 μm) was ground with elemental B, S, and La powders in a molar ratio of 0.75:0.1:0.1:0.05 in a high-energy ball mill at 500 rpm for 10 h to obtain silicon-based particles doped with B, S, and La elements. The silicon-based particles were then etched with 0.1 M hydrofluoric acid to form silicon-based particles with a porous structure and a porosity of 25%.

[0060] PVDF-HFP was dissolved in DMF solvent (N,N-dimethylformamide), and Li7La3Zr2O was added. 12 A solution of fast ion conductor with a concentration of 0.5 M was prepared by mixing LLZO, PVDF-HFP and LLZO in a mass ratio of 85:15. The porous silicon-based particles were immersed in the fast ion conductor solution, stirred for 12 h, filtered and dried to obtain a silicon anode material with a porosity of 10%.

[0061] (2) Preparation of negative electrode

[0062] The silicon anode material obtained in step (1), the conductive agent carbon nanotubes (CNTs), and the binder polyacrylic acid (PAA) were mixed evenly at a weight ratio of 90:5:5. Distilled water was added, with the mass ratio of distilled water to the total mass of the three substances being 80:20. The mixture was stirred for 1 hour using a planetary stirrer to remove bubbles, resulting in an anode slurry. This anode slurry was then coated onto the surface of a copper foil current collector and dried at 60°C.

[0063] (3) Assembly of all-solid-state batteries

[0064] Li6PS5Cl powder was added to the mold battery, and then a pressure of 30MPa was applied for pre-pressing to obtain a solid electrolyte. Subsequently, the negative electrode sheet prepared in step (2) was placed on one side of the electrolyte, and an indium sheet and a lithium sheet were added on the other side. A pressure of 400MPa was applied to complete the assembly of the all-solid-state battery.

[0065] The preparation methods of Examples 2-17 and Comparative Examples 1-4 are basically the same as those of Example 1. The differences are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] Experimental Example

[0070] 1. Elastic modulus test

[0071] Fast ion conductor slurry was coated onto a PET base film and dried to obtain a fast ion conductor film. The Young's modulus of the fast ion conductor was then tested using an atomic force microscope (AFM).

[0072] 2. Median particle size test

[0073] The particle size distribution of the prepared silicon-based anode powder was tested using a laser particle size analyzer to obtain the median particle size.

[0074] 3. Porosity test

[0075] The adsorption-desorption curves of the prepared silicon-based anode powder were tested using the gas adsorption method (BET method), and the porosity of the material was further calculated.

[0076] 4. Diaphragm resistance test

[0077] The film resistance of the prepared silicon-based negative electrode was tested using the four-probe method.

[0078] 5. Expansion Rate Test

[0079] The length, width, and height of the initial electrode were tested to obtain the initial electrode volume V1 (at 0% SOC). The electrode was then assembled into a battery for electrochemical lithium intercalation. The battery was disassembled in the fully intercalated state, and the length, width, and height of the electrode were tested again to obtain the volume V2 after full intercalation. The expansion rate was calculated as (V2-V1) / V1*100%.

[0080] 6. Battery performance test

[0081] The cycle performance of the all-solid-state battery was measured using a 9th generation Newway machine with a cutoff voltage of 2.5-4.3V. It was first cycled 3 times at 0.1C, and then 500 times at 1C.

[0082] 1C capacity retention rate = 100% * first discharge capacity under 1C / first discharge capacity under 0.1C;

[0083] Capacity retention rate after 500 cycles = Discharge capacity after 100% * 500 cycles under 1C condition / Discharge capacity of the first cycle.

[0084] Please see Tables 1-2 for the test results.

[0085] Table 2

[0086]

[0087] As can be seen from Tables 1 and 2, introducing at least two of the Group IIIA, Group VIA, and lanthanide elements into porous silicon anode materials, and setting fast ion conductors in the pores, can suppress electrode collisions and significantly improve the rate performance and cycle stability of the battery.

[0088] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A silicon anode material, characterized in that, The silicon anode material includes silicon-based particles and a fast ion conductor. The silicon-based particles have a porous structure, and the fast ion conductor fills the channels of the porous structure. The silicon-based particles include silicon and doping elements, wherein the doping elements include Group IIIA elements, Group VIA elements and lanthanide elements; The molar percentage of the Group IIIA element in the silicon-based particles is 0.1-0.

2. The molar percentage of the group VIA element in the silicon-based particles is 0.1-0.

2. The molar percentage of the lanthanides in the silicon-based particles is 0.05-0.

1. Wherein, the group IIIA element is at least one of B and In; The VIA group element is at least one of S and Se; The lanthanide element is at least one of La and Ce; The silicon-based particles are obtained by adding elemental silicon and dopant elements into a high-energy ball mill and grinding them at a speed of 500-1000 rpm for 20-30 hours to obtain silicon-based particles containing dopant elements. Then, they are etched with acid to obtain silicon-based particles with a porous structure.

2. The silicon anode material according to claim 1, characterized in that, The porosity of the silicon anode material is 1%-15%; And / or, the median particle size of the silicon anode material is 0.8 μm-5 μm.

3. The silicon anode material according to claim 1, characterized in that, Includes at least one of the following characteristics: a. Based on the mass of the silicon anode material, the content of the fast ion conductor is 5%-10%; b. The elastic modulus of the fast ion conductor is 2MPa-200MPa; c. The fast ion conductor includes at least one of sulfide electrolytes, polymer electrolytes, and oxygen-containing inorganic electrolytes.

4. The silicon anode material according to claim 3, characterized in that, The fast ion conductor is a polymer electrolyte and an oxygen-containing inorganic electrolyte, and the content of the oxygen-containing inorganic electrolyte is 10%-20% based on the mass of the fast ion conductor.

5. The silicon anode material according to claim 3, characterized in that, The sulfide electrolyte includes Li 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 5.5 PS 4.5 Cl 1.5 At least one of Li3PS4; The polymer electrolyte includes at least one of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, and polyacrylonitrile; The oxygen-containing inorganic electrolyte includes Li7La3Zr2O 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.3 Al 0.3 Ge 1.7 (PO4)3, Li 0.33 La 0.55 At least one of TiO3.

6. A secondary battery, comprising a positive electrode, a negative electrode, and a solid electrolyte, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one side surface of the negative electrode current collector, wherein the negative electrode active layer includes the silicon negative electrode material according to any one of claims 1-5.

7. The secondary battery according to claim 6, characterized in that, The film resistance of the negative electrode is 0.5mΩ-1mΩ; And / or, the expansion rate of the negative electrode at 100% SOC is 20%-30% compared to that at 0% SOC.

8. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 6-7.

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