Silicon-based negative electrode material for sulfide all-solid-state battery, preparation method and application thereof

Abstract

The present application relates to the technical field of all-solid-state batteries, and particularly relates to a silicon-based composite negative electrode of an all-solid-state battery, a preparation method and application. The present application mainly solves the problem of kinetic retardation in the cycle process of the existing silicon negative electrode. The composite silicon-based material is mainly based on in-situ mechanical solid-phase conversion reaction of silver metal chalcogenide (or halide) compound and silicon. By adding Ag2S or AgF in the ball milling process, the construction of Ag metal nanodomains can be realized, the ion / electron conductor network is constructed, and the ion / electron transmission kinetics of Si is greatly enhanced.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state battery technology, specifically a silicon-based composite anode for all-solid-state batteries, its preparation method, and its application. Background Technology

[0002] Currently, the flammability issue of liquid lithium-ion batteries remains unresolved, while the energy density of graphite anode batteries has gradually reached its theoretical limit, failing to meet market demand for safer and higher-performance lithium-ion batteries. Sulfide-based all-solid-state batteries hold the promise of simultaneously solving both the flammability and energy density problems. Besides the inherent non-flammability of sulfide solid electrolytes, silicon-based anodes offer the following advantages: a high energy density of up to 3579 mAh g⁻¹ at room temperature. −1 The theoretical specific capacity is more than 10 times that of traditional graphite anodes; the operating voltage is low, but slightly higher than that of traditional graphite anodes, ensuring battery energy density while effectively mitigating lithium desorption; silicon has high elemental abundance, being the second most abundant element in the Earth's crust at 26.4%; and it is non-toxic, posing minimal environmental harm. Therefore, silicon (Si) anodes hold promise as the preferred material for next-generation high-energy-density battery anodes.

[0003] However, silicon itself, as a semiconductor material, has low ionic and electronic conductivity, and is accompanied by large volume expansion. Especially in solid-state battery systems, the transport of lithium ions in the system is further hindered after the solid-solid contact is affected by volume changes, which greatly limits the diffusion rate of lithium ions in the silicon anode, resulting in the inability to achieve full capacity and rapid capacity decay. Summary of the Invention

[0004] This invention primarily addresses the problem of sluggish kinetics during the cycling process of existing silicon anodes. The composite silicon-based material is mainly based on the in-situ mechanical solid-state transformation reaction between silver metal oxo (or halogen) compounds and silicon. By adding Ag₂S or AgF during ball milling, Ag metal nanodomains can be constructed, forming an ion / electron conductor network and greatly enhancing the ion / electron transport kinetics of Si.

[0005] The objective of this invention is achieved through the following technical solution: A method for preparing a sulfide-based silicon-based composite anode material for all-solid-state batteries includes the following steps: Step 1: Mix silicon powder with Ag2S or AgF and perform high-energy ball milling to obtain Si@n-Ag (nano silver); Further, the mass ratio of Si powder, Ag2S or AgF in step one is (80 ~ 95): (5 ~ 20).

[0006] Furthermore, the ball milling speed mentioned in step one is 200~400 r / min. −1 The time is 6 to 10 hours.

[0007] Compared with the prior art, the present invention has the following advantages: (1) One-step synthesis of Ag nanodomains, mechanical solid-state method is more suitable for industrial large-scale production and scale-up.

[0008] (2) The composite Ag nanodomain of the present invention can effectively improve the electrochemical performance of sulfide all-solid-state batteries, such as capacity, charge and discharge rate and cycle life, thereby improving the practicality and commercial value of the battery.

[0009] (3) Compared with the traditional silver modification strategy, the present invention achieves the construction of nanodomains through in-situ reaction, and the connection between Ag and silicon is more compact, which can effectively prevent electrical contact failure during cycling.

[0010] (4) Compared with the traditional silver powder modification strategy, the preparation process of this invention does not require the isolation of air to prevent the oxidation of silver, and the synthesis conditions are less demanding.

[0011] (5) The results of this experiment show that the composite silicon-silver material synthesized by the mechanical solid-state in-situ conversion method can achieve stable cycling in a sulfide all-solid-state battery system with an NCM811 cathode at room temperature and a 2C charge-discharge rate. This invention provides a new protection method for the research and development of silicon-based anodes in sulfide all-solid-state batteries, and is of great significance for the development and application of safe and recyclable battery systems. Attached Figure Description

[0012] Figure 1 XRD patterns of phase characterization of samples with different Ag2S contents after ball milling, prepared in Example 1; Figure 2 XRD patterns of phase characterization of samples with different AgF contents after ball milling, prepared in Example 2; Figure 3 TEM image of the Si@n-Ag sample prepared in Example 1; Figure 4 The first charge-discharge curves of Si@n-Ag sample half-cells with different Ag2S contents were obtained in Example 1. Figure 5 The 2C charge-discharge curves of the Si@n-Ag full cell sample prepared in Example 1 are shown. Figure 6 This is a schematic diagram illustrating the preparation process of the Si@n-Ag sample obtained in Example 1. Detailed Implementation

[0013] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0014] The silver nanodomains prepared by this invention can serve as an ion-electron conductive network between Si particles, and Ag can regulate the lithium deposition process. During lithiation, a Li-Ag interface with high diffusion capability is formed, which promotes the contact lithiation reaction between lithium and active silicon, and achieves high-rate charge and discharge.

[0015] In an embodiment of the present invention, a method for preparing a sulfide-based all-solid-state battery silicon-based composite anode material includes the following steps: Step 1: Mix silicon powder and Ag2S at a mass ratio of 85 ~ 90: 5 ~ 10, with a ball-to-material ratio of 20, and perform high-energy ball milling for 6 hours. Allow the mixture to stand for 0.5 hours after a 2-hour interval to avoid excessive temperature.

[0016] Step 2: Mix the materials obtained in Step 1: conductive carbon: Super P = 8:1:1, add NMP and stir to form a slurry, then coat it onto the copper current collector with a scraper; Step 3: Place the sample from Step 2 in a vacuum drying oven at 100°C. o Dry at C for 12 h, cool to room temperature, and cut into round pieces with a diameter of 10 mm; To make the present invention more fully disclosed, more specific embodiments are described below. Example

[0017] A method for preparing a sulfide-based silicon-based composite anode material for all-solid-state batteries includes the following steps: Accurately weigh 900 mg of silicon powder and 10 mg of Ag₂S into a ball mill jar, weigh 20 g of zirconia grinding beads, stir evenly, place in a ball mill, and mill at a speed of 350 r / min. −1 The material was ball-milled for 6 hours, then allowed to stand for 0.5 hours after a 2-hour interval. The resulting material was mixed with conductive carbon and Super P in an 8:1:1 ratio, and prepared into a slurry with NMP. This slurry was then coated onto a copper current collector and dried in a vacuum oven at 100°C. o Dry at C for 12 hours, then cut into 10 mm diameter round slices for later use.

[0018] The obtained negative electrode was assembled into an all-solid-state battery with a sulfide solid electrolyte and an NCM811 positive electrode, and the electrochemical data were tested.

[0019] Figure 1 The XRD patterns for phase characterization of samples with different Ag₂S contents obtained in Example 1 after ball milling are shown. The appearance of the Ag characteristic peak indicates that the raw material underwent a solid-phase in-situ reaction under mechanical shearing to generate elemental Ag. Example

[0020] A method for preparing a sulfide-based silicon-based composite anode material for all-solid-state batteries includes the following steps: Accurately weigh 900 mg of silicon powder and 10 mg of AgF into a ball mill jar, weigh 20 g of zirconia grinding beads, stir evenly, place in a ball mill, and mill at a speed of 350 r / min. −1 The material was ball-milled for 6 hours, then allowed to stand for 0.5 hours after a 2-hour interval. The resulting material was mixed with conductive carbon and Super P in an 8:1:1 ratio, and prepared into a slurry with NMP. This slurry was then coated onto a copper current collector and dried in a vacuum oven at 100°C. o Dry at C for 12 hours, then cut into 10 mm diameter round slices for later use.

[0021] The obtained negative electrode was assembled into an all-solid-state battery with a sulfide solid electrolyte and an NCM811 positive electrode, and the electrochemical data were tested.

[0022] Figure 2 The XRD patterns for phase characterization of samples with different AgF contents obtained in Example 2 after ball milling are shown. The appearance of the Ag characteristic peak indicates that the raw material underwent a solid-phase in-situ reaction under mechanical shearing to generate elemental Ag.

[0023] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-based composite anode material for a sulfide all-solid-state battery, comprising the following steps: Step 1, mixing silicon powder and Ag2S or AgF, and performing high-energy ball milling to obtain Si@n-Ag (nano silver).

2. The method for preparing the silicon-based composite anode material according to claim 1, characterized in that, The mass ratio of Si powder, Ag2S or AgF mentioned in step one is (80 ~ 95): (5 ~ 20).

3. The method for preparing the silicon-based composite anode material according to claim 1, characterized in that, The ball milling speed mentioned in step one is 200 ~ 400 r / min. −1 .

4. The method for preparing the silicon-based composite anode material according to claim 1, characterized in that, The ball milling time mentioned in step one is 6 to 10 hours.

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