Negative active material and preparation method thereof, solid-state battery and electric equipment

Abstract

The invention provides a negative electrode active material and a preparation method thereof, a solid-state battery and electric equipment, the negative electrode active material comprises an inner core and a coating layer, the chemical formula of the inner core comprises MSixPyOz, and M comprises one or more elements in IB group, IIB group and IIIA group. The coating layer coats at least part of the surface of the inner core. According to the negative electrode active material provided by the embodiment of the invention, the solid-state battery can have good normal-temperature cycle performance, high-temperature cycle performance and rate capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative active material manufacturing, in particular to a negative active material, a preparation method thereof, a solid-state battery and an electric device. BACKGROUND

[0002] Solid-state batteries (SSBs) are considered as the next generation of energy storage technology due to their high energy density and safety, and the choice of negative active material can determine the upper limit of its performance. Currently, the theoretical capacity of commercial graphite negative active material is only 372 mAh / g, which is difficult to meet the growing demand for battery energy density. Under this background, silicon material is considered as a potential next-generation negative active material alternative due to its theoretical capacity of up to 4200 mAh / g and relatively low cost. However, during the charging and discharging process of silicon negative active material at room temperature and high temperature, the huge volume expansion (more than 300%) caused by the deintercalation of active ions leads to the problem of low rate performance and cycle performance of solid-state batteries using it, thereby restricting the commercialization process of the above-mentioned batteries. SUMMARY

[0003] The purpose of the present application is to provide a negative active material, a preparation method thereof, a solid-state battery and an electric device, which can make the solid-state battery have good room temperature cycle performance, high temperature cycle performance and rate performance.

[0004] The embodiments of the present application are implemented as follows: In a first aspect, the embodiments of the present application provide a negative active material, which includes a core and a coating layer. The chemical formula of the core includes MSi x P y O z , wherein M includes one or more elements of group IB, group IIB and group IIIA. The coating layer is coated on at least part of the surface of the core, and the coating layer includes a conductive carbon material and a solid-state electrolyte.

[0005] The negative active material provided in the embodiments of the present application belongs to a silicon-based alloy negative active material, and the chemical formula of the core includes MSi x P y O zOn the one hand, the introduction of M elements and P elements can improve the electronic conductivity and ionic conductivity of the silicon-based alloy negative active material, and help to improve the rate performance and room temperature cycle performance of the solid-state battery. On the other hand, the introduction of oxygen elements can reduce the grain size of the silicon-based alloy negative active material. Smaller grain size can help to reduce the volume expansion of the negative active material, and also improve the contact area between the core and the coating layer to facilitate the coating of the coating layer, thereby reducing the side reaction on the surface of the core, and improving the room temperature cycle performance and high temperature cycle performance of the solid-state battery.

[0006] In addition, according to theoretical speculation, the introduction of oxygen elements can also form a mixed structure of near-equiaxed crystals and columnar crystals, and can also produce a cellular dislocation structure and oxygen element segregation. Among them, the near-equiaxed crystal structure can help the silicon-based alloy negative active material to disperse thermal stress, the columnar crystal structure can make the silicon-based alloy negative active material have strong creep resistance and provide an ion high-speed transmission channel for the silicon-based alloy negative active material, and the cellular dislocation structure can improve the yield strength of the silicon-based alloy negative active material. Element segregation can help form an oxygen concentration gradient at the grain boundary of the silicon-based alloy negative active material to further improve the fracture toughness and yield strength, which can help to reduce the volume expansion rate of the silicon-based alloy negative active material at high temperature and improve its ionic conductivity; and can also form a passivation layer on the surface of the core to reduce the side reaction at high temperature.

[0007] In summary, the negative active material provided by the embodiments of the present application can make the solid-state battery have good room temperature cycle performance, high temperature cycle performance and rate performance.

[0008] In a second aspect, the embodiments of the present application provide a preparation method of a negative active material, comprising the following steps: The M-containing metal powder, the silicon powder and the phosphorus powder are subjected to a first mixed grinding treatment in an oxygen-containing atmosphere for 6 hours or more to obtain a core, and the chemical formula of the core comprises MSi x P y O z , wherein M comprises one element or multiple elements in group IB, group IIB and group IIIA; The core and the raw material of the coating layer are mixed and subjected to a coating treatment to form a coating layer on at least part of the surface of the core to obtain a negative active material, wherein the raw material of the coating layer comprises a conductive carbon material and a solid-state electrolyte.

[0009] The preparation method of the negative active material provided by the embodiments of the present application can introduce oxygen elements into the silicon alloy material by subjecting the M-containing metal powder, the silicon powder and the phosphorus powder to a first mixed grinding treatment in an oxygen-containing atmosphere, to obtain a chemical formula comprising MSi x P y O zThe negative active material is prepared by coating the core to form a coating layer on the surface of the core, and the preparation process is simple, the cost is low, and the large-scale commercial production can be realized.

[0010] In a third aspect, the embodiments of the present application provide a solid-state battery comprising the negative active material of any of the embodiments of the first aspect or the negative active material prepared by the preparation method of any of the embodiments of the second aspect.

[0011] In a fourth aspect, the embodiments of the present application provide an electrical equipment comprising the solid-state battery of the third aspect. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0013] Figure 1 A structural schematic diagram of a negative active material provided by the embodiments of the present application is shown in the figure. Figure 2 A process flow diagram of a preparation method of a negative active material provided by the embodiments of the present application is shown in the figure.

[0014] Figure 3 An XRD diagram of the negative active material provided by Embodiment 1 of the present application is shown in the figure.

[0015] Figure 4 An XRD diagram of the negative active material provided by Comparative Example 1 of the present application is shown in the figure.

[0016] Figure 5 A curve diagram of the voltage and specific capacity of the battery provided by Embodiment 1 of the present application is shown in the figure.

[0017] Figure 6 An XRD diagram of the negative active material provided by Embodiment 8 of the present application is shown in the figure.

[0018] Figure 7 A curve diagram of the oxygen mass content of the negative active material provided by Embodiment 1 of the present application and the air grinding time is shown in the figure.

[0019] Figure legend: 10-negative active material; 100-core; 200-coating layer, 210-first coating layer, 220-second coating layer. DETAILED DESCRIPTION

[0020] In order to make the purposes, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not indicated in the embodiments, the conditions are implemented according to conventional conditions or the conditions recommended by manufacturers. If the manufacturers of reagents or instruments are not indicated, the reagents or instruments are conventional products that can be purchased on the market.

[0021] It should be noted that, in the present application, “and / or”, such as “feature 1 and / or feature 2”, refers to “feature 1” alone, “feature 2” alone, or “feature 1” plus “feature 2”.

[0022] In addition, in the description of the present application, “multiple” in “one or more” means two or more; the range of “value a~value b” includes both end values “a” and “b”, and “unit of measurement” in “value a~value b+unit of measurement” represents the “unit of measurement” of both “value a” and “value b”.

[0023] The negative active material, the preparation method thereof, the solid-state battery, and the electric device according to an embodiment of the present application will be described in detail below.

[0024] Negative active material In a first aspect, the embodiments of the present application provide a negative active material, which includes a core and a coating layer. The chemical formula of the core includes MSi x P y O z wherein M includes one or more elements in group IB, group IIB, and group IIIA. The coating layer is coated on at least part of the surface of the core, and the coating layer includes a conductive carbon material and a solid-state electrolyte.

[0025] In this document, “coating layer” refers to a substance layer coated on the core, which can completely or partially coat the core. The use of “coating layer” is only for convenience of description and is not intended to limit the present application. In addition, each coating layer can be completely coated or partially coated. The interface between the coating layer and the core has a clear boundary under an electron microscope image, which can be determined by electron microscope detection methods, such as transmission electron microscopy.

[0026] In this document, the chemical composition of the core and the coating layer can be obtained by the following test method: The chemical formula of the core and the coating layer can be determined by TEM-EDS characterization after FIB sectioning of the material. The specific test method is as follows: Sample pretreatment: uniformly disperse the negative active material particles on the surface of conductive glue, and spray a conductive layer (such as Pt / Ir) to enhance the conductivity.

[0027] FIB slice preparation (Focused Ion Beam, FEI Helios G4): Select an arbitrary position at the edge of the particle, and deposit a protective layer locally with an ion beam.

[0028] FIB rough cutting: 5-30 nA large beam current to excavate the cross section, exposing the internal particles; FIB fine cutting: Stepwise current reduction (1 nA to 50 pA) to thin the sample to an electron-transparent foil of <100 nm, avoiding ion damage.

[0029] TEM sample loading: Transfer the foil to the Cu support net through the in-situ mechanical arm.

[0030] TEM-EDS characterization (Transmission Electron Microscope coupled with Energy Dispersive Spectrometer, such as JEOL ARM-200F): Coating analysis: Perform rapid EDS surface scanning on the material foil, and determine the coating layer and core region based on the surface scanning image (based on surface scanning EDS to obtain element content, the position at the edge of the material foil is the coating layer region, and the other regions of the foil are the core region). Select 3 points in the coating layer region for EDS point scanning, (probe: Centurio SDD, collection time 60 s / point), and the point scanning excitation beam spot must fall within the coating layer region. The average value of the element content of the 3 points is the element content of the coating layer; Core region analysis: Select 3 points in the core region for EDS point scanning, (probe: Centurio SDD, collection time 60 s / point), and the point scanning excitation beam spot must fall within the core region. The average value of the element content of the 3 points is the element content of the core.

[0031] In the negative electrode active material provided in the embodiments of the present application, the chemical formula of the core includes MSi x P y O z On the one hand, the introduction of M elements and P elements can improve the electronic conductivity and ionic conductivity of the silicon-based alloy negative electrode active material, which helps to improve the rate performance and room temperature cycle performance of the solid-state battery. On the other hand, the introduction of oxygen elements can reduce the grain size of the silicon-based alloy negative electrode active material. Smaller grain size can help to reduce the volume expansion of the negative electrode active material, while also increasing the contact area between the core and the coating layer to facilitate the coating of the coating layer. In addition, the oxygen elements and the carbon in the coating layer combine well, which can further improve the coating effect, thereby reducing the occurrence of side reactions on the surface of the core, and thus improving the room temperature cycle performance and high temperature cycle performance of the solid-state battery.

[0032] In addition, according to theoretical speculation, the introduction of oxygen elements can also form a mixed structure of near-equiaxed crystals and columnar crystals, and also produce a cellular dislocation structure and oxygen element segregation. The near-equiaxed crystal structure can help the silicon-based alloy negative active material to disperse thermal stress, the columnar crystal structure can make the silicon-based alloy negative active material have strong creep resistance and provide a high-speed ion transmission channel for the silicon-based alloy negative active material, the cellular dislocation structure can improve the yield strength of the silicon-based alloy negative active material, and the element segregation can help The oxygen concentration gradient is formed at the grain boundary of the silicon-based alloy negative active material to further improve the fracture toughness and yield strength, which can help to reduce the volume expansion rate of the silicon-based alloy negative active material at high temperature and improve the ionic conductivity thereof; and can also form a passivation layer on the surface of the core to reduce the side reaction thereof at high temperature.

[0033] In summary, the negative active material provided by the embodiments of the present application can make the solid-state battery have good normal-temperature cycle performance, high-temperature cycle performance and rate performance.

[0034] In some embodiments, 0.85≤z≤3.32.

[0035] In the above embodiments, z is in the above suitable value range, which can make the negative active material have a higher capacity, and can further improve the normal-temperature cycle performance, high-temperature cycle performance and rate performance of the battery.

[0036] For example, z can be, but is not limited to, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.91, 0.93, 0.94, 0.96, 0.98, 1, 1.02, 1.04, 1.06, 1.08, 1.1, 1.12, 1.14, 1.16, 1.18, 1.2, 1.22, 1.24, 1.26, 1.28, 1.3, 1.32, 1.34, 1.36, 1.38, 1.4, 1.42, 1.44, 1.46, 1.48, 1.5, 1.52, 1.54, 1.56, 1.58, 1.6, 1.62, 1.64, 1.66, 1.68, 1.7, 1.72, 1.74, 1.76, 1.78, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.31, 3.32, or a value range composed of any two of the above numbers.

[0037] In some embodiments, M includes one or more of Zn, Al, Cu and Ga.

[0038] In the above embodiments, M is selected from the above-mentioned metal elements. The above-mentioned metal elements, together with Si, P and O, form the core chemical formula of the negative electrode active material. This can form a disordered silicon-based alloy negative electrode active material without significantly reducing the capacity of the negative electrode active material, thereby giving it high electronic conductivity and ionic conductivity.

[0039] In some implementations, M includes Cu, where 1.48 ≤ z ≤ 2.53.

[0040] In some implementations, M includes Al, 0.98 ≤ z ≤ 1.69.

[0041] In some implementations, M includes Zn, where 1.07 ≤ z ≤ 1.85.

[0042] In some implementations, M includes Ga, where 1.33 ≤ z ≤ 2.75.

[0043] In some implementations, 1 ≤ x ≤ 6.

[0044] In the above embodiments, x is within the above-mentioned suitable range, which enables the negative electrode active material to have a high capacity.

[0045] For example, x can be, but is not limited to, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6, or a range of values ​​consisting of any two of the above.

[0046] In some implementations, 1 ≤ y ≤ 3.

[0047] In the above embodiments, when y is within the above-mentioned value range, the negative electrode active material can have a high capacity, and it can also help to form a zincblende structure to further improve the structural stability and ionic conductivity of the negative electrode active material.

[0048] For example, y can be, but is not limited to, a range of values ​​consisting of 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, or any two of the above values.

[0049] In some embodiments, the coating layer includes a first coating layer and a second coating layer, the first coating layer comprising a conductive carbon material and the second coating layer comprising a solid electrolyte, wherein the first coating layer is located between the core and the second coating layer.

[0050] In the above embodiments, the provision of the first coating layer and the second coating layer can help improve the cycle performance, first efficiency, and rate performance of solid-state batteries.

[0051] In some implementations, the solid electrolyte accounts for 15% to 35% of the mass based on the mass of the negative electrode active material.

[0052] In the above embodiments, when the mass percentage of the solid electrolyte is within the aforementioned suitable range, it helps to improve the ionic conductivity of the negative electrode active material, enabling the solid-state battery to perform well and improve its initial efficiency. Furthermore, when the mass percentage of the solid electrolyte is within the aforementioned suitable range, the amount of solid electrolyte used in the negative electrode film can be reduced, thereby lowering manufacturing costs.

[0053] Furthermore, based on the mass of the negative electrode active material, the mass percentage of the solid electrolyte can be 20% to 25%.

[0054] For example, the mass percentage of the solid electrolyte may be, but is not limited to, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or any combination of two of the above values.

[0055] In some implementations, the mass percentage of conductive carbon material is 8% to 20% based on the mass of the negative electrode active material.

[0056] In the above embodiments, when the mass ratio of conductive carbon material is within the appropriate range, the negative electrode active material can have a high capacity, and the volume expansion of the core can be further buffered to improve the cycle performance of the solid-state battery.

[0057] Furthermore, based on the mass of the negative electrode active material, the mass percentage of the conductive carbon material can also be 10% to 14%.

[0058] For example, the mass percentage of conductive carbon material may be, but is not limited to, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any combination of two of the above values.

[0059] In the embodiments of this application, the mass ratio of conductive carbon material to solid electrolyte can be obtained using the following testing method: The mass percentage of solid electrolytes is quantitatively analyzed using inductively coupled plasma (ICP), specifically the external standard method (standard curve method) in ICP. The external standard method involves preparing standard solutions of different concentrations to establish a standard curve (typically a linear equation: y = kx + by = kx + b) of signal intensity versus concentration, from which the sample concentration can be inferred.

[0060] The mass percentage of conductive carbon is measured using a sulfur-carbon analyzer. Based on the infrared absorption characteristics of gas molecules, the carbon content is analyzed by detecting the infrared absorption intensity of SO2 and CO2 at specific wavelengths. Additionally, the sulfur content in the solid electrolyte can also be measured using a sulfur-carbon analyzer.

[0061] In some embodiments, the conductive carbon material includes one or more of graphene, graphite, carbon nanoparticles, carbon black, carbon nanotubes, and carbon fibers.

[0062] In some embodiments, the solid electrolyte includes a sulfide solid electrolyte.

[0063] In the above embodiments, the sulfide solid electrolyte can further improve the ionic conductivity of the negative electrode active material.

[0064] In some embodiments, the chemical formula of the sulfide solid electrolyte is Li. 7-a PS 6-a Cl a , where 1≤a≤1.5.

[0065] In the above embodiments, the chemical formula of the sulfide solid electrolyte is Li. 7-a PS 6-a Cl a The value of 1≤a≤1.5 can further improve the ionic conductivity of the negative electrode active material, which is beneficial to improving the first-stage efficiency of solid-state batteries.

[0066] In embodiments of this application, the above-mentioned sulfide solid electrolyte can be prepared by the following method, which includes: LiCl, P2S5, and Li2S were weighed according to a certain mass ratio and placed into a ball mill jar, followed by the addition of grinding balls (ball-to-material ratio of 20:1). The ball milling program was as follows: 500 rpm / min, forward rotation for 60 min, stop for 5 min, reverse rotation for 60 min, stop for 5 min, and then repeat this cycle for a total ball milling time of 9 hours. Because the electrolyte material would clump during ball milling, it was loosened every 2 hours, for a total of four loosening processes. The loosening process involved pouring out the grinding balls, crushing the material in the ball mill jar with a grinding pestle, adding the grinding balls back in, and then ball milling again. After ball milling, the material was placed in a sintering furnace, and the sintering program was as follows: heating at 5℃ / min, holding at 500℃ for 5 hours, and cooling at 5℃ / min. Then, it was ground in a mortar and pestle at 500 rpm / min for 60 minutes to obtain a sulfide solid electrolyte.

[0067] Furthermore, the ionic conductivity of the aforementioned sulfide solid electrolyte can be measured by the following method, which includes: 215 mg of sulfide solid electrolyte powder (average particle size 1 μm) was weighed and cold-pressed (4 tons) into a solid electrolyte sheet, and its thickness was measured. Carbon-coated aluminum foil was then laminated to both sides of the solid electrolyte sheet to form a three-layer stack structure of "carbon-coated aluminum foil - solid electrolyte sheet - carbon-coated aluminum foil". A pressure of 2 tons was applied to the entire stack and held for 1 minute. Then, it was placed in an oven at 30°C for 30 minutes, and the electrochemical impedance spectroscopy was measured, and the ionic conductivity was calculated.

[0068] In some implementations, the average particle size of the core is 800 nm to 8000 nm.

[0069] In this paper, the average particle size of the kernel refers to the median diameter (Dv50), where Dv50 is the particle diameter at which the cumulative volume reaches 50% in particle size distribution measurements by laser scattering.

[0070] In the above embodiments, the average particle size of the core is within the above-mentioned suitable range, which can further reduce the volume expansion of the negative electrode active material and improve the coating effect of the coating layer.

[0071] Furthermore, the average particle size of the kernel can be 1000nm~5000nm.

[0072] For example, the average particle size of the kernel can be, but is not limited to, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, 2100nm, 2200nm, 2300nm, 2400nm, 2500nm, 2600nm, 2700nm, 2800nm, 2900nm, or 3000nm. The range of values ​​is 3100nm, 3200nm, 3300nm, 3400nm, 3500nm, 3600nm, 3700nm, 3800nm, 3900nm, 4000nm, 4100nm, 4200nm, 4300nm, 4400nm, 4500nm, 4600nm, 4700nm, 4800nm, 4900nm, 5000nm, 6000nm, 7000nm, 8000nm, or any two of the above values.

[0073] In some embodiments of this application, the thickness of the coating layer is 20nm~150nm.

[0074] In the above-mentioned technical solution, the thickness of the coating layer is within the appropriate range, which can further help reduce the volume expansion of the negative electrode active material.

[0075] In this paper, the thickness of the coating layer refers to the wall thickness from the inner surface to the outer surface of the coating layer.

[0076] For example, the thickness of the coating layer may be, but is not limited to, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, or any combination of two of the above values.

[0077] In the embodiments of this application, transmission electron microscopy (TEM) can be used to test the average core particle size and coating thickness in the negative electrode highly active material. Since the core and coating of a single material particle exhibit different lattices under TEM, the interface between the core and the coating can be observed. Combined with mapping (TEM's built-in software), the core diameter and coating thickness of a single material particle can be measured. A total of 50 to 60 material particles are measured, and the average core diameter (Dv50) and the average coating thickness of all material particles are calculated to obtain the average core diameter and the average coating thickness.

[0078] As an example, a schematic diagram of the structure of the positive electrode active material 10 can be found in [reference needed]. Figure 1 It includes a core 100 and a coating layer 200 covering the core 100. The coating layer includes a first coating 210 and a second coating layer 220. The first coating layer 210 is located between the core 100 and the second coating layer 220, and the first coating layer 210 includes a conductive carbon material. The second coating layer 220 includes a solid electrolyte.

[0079] Method for producing a negative active material For the second party, please refer to [the relevant information]. Figure 2 This application provides a method for preparing a negative electrode active material, comprising the following steps: S100: Metal powder containing M, silicon powder, and phosphorus powder are subjected to a first mixing and grinding treatment in an oxygen-containing atmosphere for at least 6 hours to obtain a core. The chemical formula of the core includes MSi. x P y O z M includes one or more elements from Groups IB, IIB and IIIA; S200: The raw materials of the core and the coating layer are mixed and coated to form a coating layer on at least a portion of the surface of the core, thereby obtaining a negative electrode active material, wherein the raw materials of the coating layer include conductive carbon material and solid electrolyte.

[0080] The method for preparing the negative electrode active material provided in this application introduces oxygen into the silicon alloy material by performing a first mixing and grinding process on metal powder containing M, silicon powder, and phosphorus powder in an oxygen-containing atmosphere, thereby obtaining a material with the chemical formula MSi. x P y O z The core is then coated to form a coating layer on the surface of the core, resulting in a negative electrode active material. This preparation process is simple, low-cost, and suitable for large-scale commercial production.

[0081] In some embodiments, the molar ratio of the metal powder containing M, silicon powder, and phosphorus powder is 1:(2~12):(1~3).

[0082] In the above embodiments, the molar ratio of the metal powder containing M, silicon powder, and phosphorus powder is within the above range, which helps the negative electrode active material to achieve both high capacity and conductivity.

[0083] In some implementations, the mass concentration of oxygen in the oxygen-containing atmosphere is 6% to 20%.

[0084] In the above embodiments, the mass concentration of oxygen in the oxygen-containing atmosphere is within the above-mentioned suitable range, which can enable the prepared negative electrode active material to have a high capacity, and can also further improve the room temperature cycle performance, high temperature cycle performance and rate performance of the battery.

[0085] In some embodiments, the first mixing and grinding process takes 8 to 20 hours and the rotation speed of the first mixing and grinding process is 550 rpm / min to 950 rpm / min.

[0086] In the above embodiments, the time and rotation speed of the first mixing and grinding process are within the above range, which can help to form the chemical formula MSi. x P y O z The kernel.

[0087] For example, the time for the first mixing and grinding process may be, but is not limited to, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 16h, 16.5h, 17h, 17.5h, 18h, 18.5h, 19h, 19.5h, 20h, or a range of any two of the above values.

[0088] For example, the rotational speed of the first mixed grinding process may be, but is not limited to, 550 rpm / min, 600 rpm / min, 650 rpm / min, 700 rpm / min, 750 rpm / min, 800 rpm / min, 850 rpm / min, 900 rpm / min, 950 rpm / min or any combination of two of the above values.

[0089] In some implementations, step S200 includes: S210. The core and conductive carbon material are subjected to a second mixing and grinding process to form a first coating layer on at least a portion of the surface of the core, thereby obtaining a core coated with the first coating layer. S220. The core coated by the first coating layer is mixed with a solution containing solid electrolyte to obtain a mixed slurry. S230. The mixed slurry is sintered to form a second coating layer on at least a portion of the surface of the first coating layer, thereby obtaining a negative electrode active material.

[0090] In the above embodiments, the first coating layer and the second coating layer can be formed on the core surface in sequence through the second grinding process, the mixing process and the sintering process, which is beneficial to improving the conductivity of the negative electrode active material.

[0091] In some embodiments, the mass ratio of the core, conductive carbon material, and solid electrolyte is (45~77):(7~20):(13~24).

[0092] In some embodiments, the mass ratio of conductive carbon material to the core is 1:(3~10).

[0093] In the above embodiments, the mass ratio of conductive carbon material to core is within the appropriate range, which not only helps to improve the capacity and electronic conductivity of the negative electrode active material, but also reduces the volume expansion of the negative electrode active material.

[0094] For example, the mass ratio of conductive carbon material to core can be, but is not limited to, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0095] In some embodiments, the second mixing and grinding process takes 15 to 30 hours and the rotation speed is 350 rpm / min to 650 rpm / min.

[0096] For example, the time for the second mixing and grinding process may be, but is not limited to, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h or a range of values ​​composed of the above two values.

[0097] For example, the rotational speed of the second mixing and grinding process may be, but is not limited to, 350 rpm / min, 400 rpm / min, 450 rpm / min, 500 rpm / min, 550 rpm / min, 600 rpm / min, 650 rpm / min, etc.

[0098] In some embodiments, the mass ratio of the solid electrolyte to the core coated by the first coating layer is (1~5):(5~10).

[0099] In the above embodiments, the mass ratio of the solid electrolyte to the core coated by the first coating layer is within the above-mentioned suitable range, which can help to prepare a negative electrode active material with high ionic conductivity, so that the capacity of the solid battery can be well utilized to improve the first efficiency.

[0100] For example, the mass ratio of the solid electrolyte to the core coated by the first coating layer can be, but is not limited to, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 2:5, 2:6, 2:7, 2:8, 2:9, 2:10, 3:5, 3:6, 3:7, 3:8, 3:9, 3:10, 4:5, 4:6, 4:7, 4:8, 4:9, 4:10, 5:5, 5:6, 5:7, 5:8, 5:9, 5:10, etc.

[0101] In some embodiments, the mixing speed is 1000 rpm / min to 1500 rpm / min, and the mixing time is 0.5 h to 4 h.

[0102] For example, the stirring speed for mixing can be, but is not limited to, 1000 rpm / min, 1050 rpm / min, 1100 rpm / min, 1150 rpm / min, 1200 rpm / min, 1250 rpm / min, 1300 rpm / min, 1350 rpm / min, 1400 rpm / min, 1450 rpm / min, 1500 rpm / min or any combination of two of the above values.

[0103] For example, the mixing time for the mixing process can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, etc.

[0104] In some embodiments, the first solvent of the solution containing the solid electrolyte includes one or more of ethanol, 1,2-ethylenediamine, and 1,2-ethylenedithiol.

[0105] In some embodiments, the sintering temperature is 350℃~650℃ and the sintering time is 2h~5h.

[0106] For example, the sintering temperature may be, but is not limited to, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, or any combination of two of the above values.

[0107] For example, the sintering time can be, but is not limited to, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or any combination of two of the above values.

[0108] In some embodiments, the M-containing metal powder includes one or more of Zn powder, Al powder, Cu powder, and Ga powder.

[0109] In the above embodiments, the metal powder containing M includes the aforementioned metal powder, which forms the core chemical formula of the negative electrode active material with Si, P and O. This allows for the formation of a disordered silicon-based alloy negative electrode active material without significantly reducing the capacity of the negative electrode active material, thereby giving it higher electronic and ionic conductivity.

[0110] In some embodiments, the conductive carbon material includes one or more of graphene, graphite, carbon nanoparticles, carbon black, carbon nanotubes, and carbon fibers.

[0111] In some embodiments, the solid electrolyte includes a sulfide solid electrolyte.

[0112] In the above embodiments, the sulfide solid electrolyte can further improve the ionic conductivity of the negative electrode active material.

[0113] In some embodiments, the average particle size of the sulfide solid electrolyte is 1 μm to 3 μm.

[0114] In the above embodiments, the average particle size of the sulfide solid electrolyte is within the above-mentioned suitable range, which can form a good particle size distribution with the core, which is beneficial to the capacity utilization.

[0115] In the embodiments of this application, the average particle size of the sulfide solid electrolyte can be obtained by the following method: The sulfide solid electrolyte and milling beads (e.g., a ball-to-material ratio of 10:1) were placed together in a ball mill jar, and n-heptane was added as a solvent for ball milling. The ball milling program was as follows: 400 rpm / min, forward rotation for 60 min, stop for 5 min, reverse rotation for 60 min, stop for 5 min, and then this cycle was repeated for a total milling time of 6 h. The material was then drawn into a glass bottle and allowed to stand for 24 h, dried at 200 °C, and then sieved through a sieve of the target mesh size to obtain a refined sulfide solid electrolyte, with an average particle size of 1 μm to 3 μm.

[0116] As an example, a process flow diagram of the preparation method of the positive electrode active material is exemplarily referred to. Figure 2 .

[0117] Solid-state battery Thirdly, embodiments of this application provide a solid-state battery, including a negative electrode active material as provided in the first aspect of the embodiment or a negative electrode active material prepared by the preparation method provided in the second aspect of the embodiment.

[0118] In this application, the solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte layer. The solid electrolyte layer is located between the positive electrode and the negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material as provided in the first aspect embodiment or a negative electrode active material prepared by the preparation method provided in the second aspect embodiment.

[0119] In some embodiments, the positive electrode active material may be a positive electrode active material known in the art for use in solid-state batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium phosphates, lithium transition metal oxides, and their respective modified compounds.

[0120] Furthermore, the positive electrode active material may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for solid-state batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0121] For example, lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds.

[0122] For example, lithium phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0123] For example, lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), etc. Examples of lithium iron phosphate include LiFePO4 (also known as LFP). Examples of lithium manganese phosphate include LiMnPO4.

[0124] In some embodiments, the positive electrode film layer further includes a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: rubber-based binders, carboxymethyl cellulose, polyolefin-based binders, polyurethane-based binders, polyacrylate-based binders, polyacrylic acid resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0125] In some embodiments, the positive electrode film layer further includes a positive electrode conductive agent. As an example, the positive electrode conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the positive electrode sheet can be prepared by: dry mixing a positive electrode active material, a positive electrode solid electrolyte, a positive electrode binder, a positive electrode conductive agent, and other optional components; then heating and pressurizing the mixed material to knead it into a clump; hot rolling is performed to form a positive electrode film layer; the positive electrode film layer is hot-rolled and bonded to at least one side (one or both sides) of the positive electrode current collector, thereby obtaining a positive electrode sheet. Non-limitingly, a dual planetary mixer can be used for dry mixing. Non-limitingly, a kneading and heating process can be performed using a Banbury mixer. Non-limitingly, the temperature for hot rolling can be 75°C to 85°C, and further, such as 78°C, 80°C, 82°C, etc.

[0127] In some embodiments, the negative electrode film layer further includes a negative electrode binder. As an example, the negative electrode binder may be a non-aqueous binder. Non-limitingly, the non-aqueous binder includes one or more of styrene-butadiene rubber (SBR), polybutene rubber (BR), and nitrile rubber (NBR).

[0128] In some embodiments, the negative electrode film layer further includes a negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of SuperP (SP), acetylene black (AB), vapor-grown carbon fiber (VGCF), and carbon nanotubes (CNT).

[0129] In some embodiments, the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (0.9~1):(0.01~0.03):(0.2~0.1).

[0130] In some embodiments, the positive electrode sheet can be prepared by mixing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and a second solvent, and then degassing to obtain a uniform negative electrode slurry; coating the negative electrode slurry onto the surface of a copper current collector and drying it to obtain the negative electrode sheet.

[0131] In some embodiments, the second solvent may be one or more of butyl butyrate, xylene, and decane.

[0132] Electric device Fourthly, embodiments of this application provide an electrical device including a solid-state battery as provided in the third aspect embodiment.

[0133] For example, solid-state batteries can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric motorcycles, power tools, etc.

[0134] It should be noted that there are no restrictions on the specific type of electrical equipment; adjustments can be made according to actual needs.

[0135] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0136] Example 1 (1) Preparation of sulfide solid electrolyte (the entire process was carried out in a glove box) Weigh 11.925g, 20.84g, and 17.235g of electrolyte raw materials LiCl, P2S5, and Li2S respectively, and place them in a ball mill jar. Add grinding balls (ball-to-material ratio 20:1). The ball milling program is as follows: 500 rpm / min, forward rotation for 60 min, stop for 5 min, reverse rotation for 60 min, stop for 5 min, and then repeat this cycle for a total milling time of 9 hours. Because the electrolyte material may clump during ball milling, loosening is performed every 2 hours, for a total of four loosening operations. The loosening process involves pouring out the grinding balls, crushing the material in the ball mill jar with a grinding pestle, adding the grinding balls back in, and then continuing ball milling. After ball milling, the material is placed in a sintering furnace. The sintering program is as follows: heat up 5℃ / min, hold at 500℃ for 5 hours, and then cool down 5℃ / min. Then, it is ground in a mortar and pestle at 500 rpm / min for 60 minutes to obtain the sulfide solid electrolyte Li. 5.5 PS 4.5 Cl 1.5 .

[0137] (2) Sulfide solid electrolyte Li 5.5 PS 4.5 Cl 1.5 Detailed refinement (conducted entirely within the glove box): Prepared Li 5.5 PS 4.5 Cl 1.5 The material was placed in a ball mill jar along with grinding balls (ball-to-material ratio of 10:1) and heptane solvent for ball milling. The ball milling program was as follows: 400 rpm / min, forward rotation for 60 min, stop for 5 min, reverse rotation for 60 min, stop for 5 min, and then repeat the cycle for a total milling time of 6 h. The material was then transferred to a glass bottle and allowed to stand for 24 h, dried at 200℃, and sieved through a 300-mesh sieve to obtain a sulfide solid electrolyte Li with an average particle size of 1 μm. 5.5 PS 4.5 Cl 1.5 .

[0138] (3) Preparation of negative electrode active materials Copper powder, silicon powder, and red phosphorus were weighed in a molar ratio of 1:2:3 and then placed in a grinding jar (the O-ring seal was removed to allow air to flow in and out during the grinding process, with an oxygen mass concentration of 15%) for the first mixing and grinding treatment. Ball beads were added at a ball-to-powder ratio of 1:50, and the mixture was ball-milled for 15 hours at 650 rpm using a planetary ball mill. The grinding process involved both forward and reverse rotation: 30 minutes of forward rotation followed by a 5-minute rest, then 30 minutes of reverse rotation followed by another 5-minute rest, repeating this process for 15 hours to obtain the core CuSi2P3O. 2.35 ; In the glove box, graphite is combined with the core CuSi2P3O2.35 A second mixing and grinding process was carried out according to a mass ratio of 1:7, wherein the second mixing and grinding process involved ball milling at 500 rpm / min for 16 hours to obtain a core CuSi2P3O with a first coating layer. 2.35 ; In a glove box filled with argon gas, 0.2g of Li... 5.5 PS 4.5 Cl 1.5 Dissolve in 20 mL of anhydrous ethanol solution and stir with a magnetic stirrer (1300 rpm / min) at room temperature until Li 5.5 PS 4.5 Cl 1.5 Completely dissolved in anhydrous ethanol solution, yielding a product containing Li. 5.5 PS 4.5 Cl 1.5 A mixed solution; then 0.8g of a core CuSi2P3O with the first coating layer is added. 2.35 The powder was added to the above mixed solution, and stirring was continued for 4 hours to obtain a mixed slurry. The mixed slurry was then heated in an oven at 80°C until the ethanol solution was completely evaporated to obtain a precursor material. The precursor material was then placed in a sintering furnace for sintering to form a second coating layer on the surface of the first coating layer. After cooling to room temperature, the negative electrode active material was obtained. The sintering procedure was as follows: heating at 5°C / min, holding at 550°C for 3 hours, and cooling at 5°C / min. This negative electrode active material includes a core, a first coating layer, and a second coating layer, with the first coating layer located between the core and the second coating layer, which can be abbreviated as CuSi2P3O. 2.35 @Graphite@Li 5.5 PS 4.5 Cl 1.5 The annealed sample was ground into a fine powder using an agate mortar and pestle, and the particle size was tested to be 8000 nm.

[0139] (4) Preparation of negative electrode sheet (the entire process is carried out in a glove box) CuSi2P3O 2.35 @Graphite@Li 5.5 PS 4.5 Cl 1.5The negative electrode active material and conductive agent carbon nanotubes were ground in a mortar at a mass ratio of 1:0.02 for 1 hour until the particles were completely and uniformly mixed. Then, 0.6 g of styrene-butadiene rubber (SBR) binder was added to obtain the negative electrode slurry, wherein the binder accounted for 3% of the total mass of the mixed slurry. Then, 1.35 g of butyl butyrate was added, and the mixture was stirred and degassed in a degassing machine for 0.5 hours. The negative electrode slurry was then removed. The negative electrode slurry was coated onto copper foil with a scraper and dried at 40°C to obtain the negative electrode sheet. The sheet was cut into pieces with a 10 mm diameter cutter and placed in a clean glass bottle, which was then stored in a glove box for later use.

[0140] (6) Assembly of molded solid-state batteries (half-cells) 80 mg of Li6PS5Cl solid electrolyte powder was weighed and placed into a 10 mm diameter ceramic core of a battery mold. After pressing with 3 tons of pressure for 1 minute, it was pressed into an electrolyte sheet. A pre-cut negative electrode was placed on one side of the electrolyte sheet, and an indium sheet with a diameter of 10 mm and a lithium sheet with a diameter of 9 mm were added sequentially to the other side. Then, after pressing with 4 tons of pressure for 30 minutes, a molded solid-state battery with a structure of negative electrode / solid electrolyte layer / Li-In alloy was obtained.

[0141] Example 2 Except for the use of Zn powder instead of Cu powder in the preparation of the negative electrode active material, the rest of this embodiment is the same as that in Example 1.

[0142] Example 3 Except for the use of Al powder instead of Cu powder in the preparation of the negative electrode active material, the rest of this embodiment is the same as that in Example 1.

[0143] Example 4 Except for the use of Ga powder instead of Cu powder in the preparation of the negative electrode active material, the rest of this embodiment is the same as that in Example 1.

[0144] Example 5 Except for replacing Cu powder with Zn powder in the preparation of the negative electrode active material and adjusting the molar ratio of Zn powder, silicon powder and red phosphorus to 1:1:2, all other contents of this embodiment are the same as those of Example 1.

[0145] Example 6 Except for adjusting the ball milling time in air to 8 hours and the rotation speed to 600 rpm / min during the preparation of the negative electrode active material, this embodiment is the same as Example 1.

[0146] Example 7 Except for adjusting the ball milling time in air to 20 hours and the rotation speed to 850 rpm / min during the preparation of the negative electrode active material, this embodiment is the same as Example 1.

[0147] Example 8 Except for adjusting the ball milling time in air to 10 hours and the rotation speed to 750 rpm / min during the preparation of the negative electrode active material, this embodiment is the same as Example 1.

[0148] Example 9 Except for adjusting the ball milling time in air to 13 hours and the rotation speed to 700 rpm / min during the preparation of the negative electrode active material, this embodiment is the same as Example 1.

[0149] Example 10 Except for adjusting the ball milling time in air to 18 hours and the rotation speed to 650 rpm / min during the preparation of the negative electrode active material, this embodiment is the same as Example 1.

[0150] Example 11 Except for adjusting the ball milling time in air to 6.5 hours and the rotation speed to 700 rpm / min during the preparation of the negative electrode active material, this embodiment is the same as Example 1.

[0151] Example 12 Except for adjusting the ball milling time in air to 26 hours and the rotation speed to 700 rpm / min during the preparation of the negative electrode active material, this embodiment is the same as Example 1.

[0152] Example 13 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 70:8:20, all other contents are the same as in Example 1.

[0153] Example 14 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 70:12:20, everything else is the same as in Example 1.

[0154] Example 15 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 70:15:20, everything else is the same as in Example 1.

[0155] Example 16 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 70:18:20, everything else is the same as in Example 1.

[0156] Example 17 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 70:20:20, everything else is the same as in Example 1.

[0157] Example 18 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 77:7:20, everything else is the same as in Example 1.

[0158] Example 19 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 70:10:15, everything else is the same as in Example 1.

[0159] Example 20 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 70:10:25, all other contents are the same as in Example 1.

[0160] Example 21 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 50:8:20, all other contents are the same as in Example 1.

[0161] Example 22 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 60:9:20, all other contents are the same as in Example 1.

[0162] Example 23 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 65:10:20, everything else is the same as in Example 1.

[0163] Example 24 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 77:10:7, everything else is the same as in Example 1.

[0164] Example 25 In this embodiment, the CuSi2P3O content is adjusted during the preparation of the negative electrode active material. 2.35 Graphite and Li 5.5 PS 4.5 Cl 1.5 Except for the mass ratio of 45:8:24, all other contents are the same as in Example 1.

[0165] Example 26 In this embodiment, Li6PS5Cl is used instead of Li in the preparation of the negative electrode active material. 5.5 PS 4.5 Cl 1.5 Except for the above, all other contents are the same as in Example 1.

[0166] Example 27 In this embodiment, an oxide solid electrolyte Li7La3Zr2O is used in the preparation of the negative electrode active material. 12 Replace Li 5.5 PS 4.5 Cl 1.5 Except for the above, all other contents are the same as in Example 1.

[0167] Example 28 In this embodiment, a halide solid electrolyte Li3YCl6 is used instead of Li in the preparation of the negative electrode active material. 5.5 PS4.5 Cl 1.5 Except for the above, all other contents are the same as in Example 1.

[0168] Comparative Example 1 Except for adjusting the core preparation process during the negative electrode active material preparation process to avoid ball milling in an oxygen-containing atmosphere (i.e., isolating air contact), the contents of this comparative example are the same as those in Example 1.

[0169] Comparative Example 2 This comparative example directly uses CuSi2P3O 2.35 The negative electrode active material is not coated; the remaining contents are the same as in Example 1.

[0170] Comparative Example 3 This comparative example compares CuSi2P3O 2.35 The negative electrode active material only undergoes Li 5.5 PS 4.5 Cl 1.5 Without graphite coating, CuSi2P3O is obtained. 2.35 @Li 5.5 PS 4.5 Cl 1.5 The remaining content is the same as in Example 1.

[0171] Comparative Example 4 This comparative example compares CuSi2P3O 2.35 The negative electrode active material is only coated with graphite, without Li. 5.5 PS 4.5 Cl 1.5 Coating yields CuSi2P3O 2.35 @Graphite, the rest of the content is the same as in Example 1.

[0172] Comparative Example 5 Except for adjusting the ball milling time in air to 5 hours and the rotation speed to 250 rpm / min during the preparation of the negative electrode active material, the comparative example is the same as Example 1.

[0173] To better understand the differences between the various embodiments and comparative examples, the following is a summary in tabular form, as detailed in Table 1.

[0174] Table 1. Some preparation conditions of negative electrode active materials

[0175] Note: In Table 1, the mass ratio of a:b:c represents the mass ratio of the core, graphite, and solid electrolyte; " / " indicates that it does not exist, and t1 represents the grinding time.

[0176] II. Testing Section 1. Testing of negative electrode active materials (1)XRD The material to be tested is prepared as a powder sample in a sample pan, flattened with a coverslip, and then placed on the sample stage of an XRD diffractometer for testing. During the test, X-rays irradiate the sample and diffract, and the diffraction signals are received by the detector and converted into data. By analyzing these data, the XRD diffraction pattern of the material to be tested can be obtained.

[0177] The test results of Example 1 are as follows: Figure 3 As shown, the test results of Example 8 are as follows: Figure 6 As shown, by Figure 3 , Figure 6 and Figure 4 Comparison of the XRD patterns with the standard card shows that CuSi2P3O prepared in Examples 1 and 8 was obtained. 2.35 However, CuSi2P3O was not prepared in Comparative Example 5. 2.35 .

[0178] (2) Test of the molar percentage of oxygen in the kernel The oxygen, nitrogen, and hydrogen content in copper, aluminum, zinc, and other metallic materials was determined using the LECO oxygen, nitrogen, and hydrogen analyzer via thermal conductivity. The LECO analyzer primarily measures these three elements, relying on differences in gas thermal conductivity for quantitative analysis. The instrument converts oxygen, nitrogen, and hydrogen into gases through high-temperature combustion or melting of the sample. These gases then enter a thermal conductivity cell; the differences in thermal conductivity between the different gases cause changes in the electrical signal, which are ultimately converted into concentration data, yielding the mass fraction of oxygen in the core, which is then converted into the molar percentage.

[0179] (3) Test of the mass ratio of conductive carbon material and solid electrolyte in negative electrode active material The mass percentage of solid electrolytes is quantitatively analyzed using inductively coupled plasma (ICP), specifically the external standard method (standard curve method) in ICP. The external standard method involves preparing standard solutions of different concentrations to establish a standard curve (typically a linear equation: y = kx + by = kx + b) of signal intensity versus concentration, from which the sample concentration can be inferred.

[0180] The mass percentage of conductive carbon is measured using a sulfur-carbon analyzer. Based on the infrared absorption characteristics of gas molecules, the carbon content is analyzed by detecting the infrared absorption intensity of SO2 and CO2 at specific wavelengths. Additionally, the sulfur content in the solid electrolyte can also be measured using a sulfur-carbon analyzer.

[0181] (4) Tests on the average particle size of the kernel and the thickness of the coating layer Transmission electron microscopy (TEM) was used to test the average core diameter and coating thickness of the anode highly active material. Since the core and coating of a single material particle exhibit different lattices under TEM, the interface between the core and coating can be observed. Combined with mapping (TEM's built-in software), the core diameter and coating thickness of individual material particles were measured. A total of 50-60 material particles were measured, and the average core diameter (Dv50) and average coating thickness of all particles were calculated to obtain the average core diameter and average coating thickness. The tests showed that the core of the anode material in Example 1, CuSi2P3O... 2.35 The particle size is approximately 2000 nm, and it is processed using graphite and the electrolyte Li. 5.5 PS 4.5 Cl 1.5 After the second coating, the thickness of the coating layer is approximately 120 nm.

[0182] (5) Charge transfer resistance test Charge transfer resistance was tested using the electrochemical impedance spectroscopy (EIS). The negative electrode active material was pressed into a tablet or thin film to form a sample. An AC voltage signal was applied, and the impedance response of the sample at different frequencies (frequency 1 MHz to 1 Hz, voltage amplitude 10 mV to 20 mV) was measured. The Nyquist plot was analyzed to extract the bulk resistance (R). The larger the resistance R, the worse the ionic conductivity.

[0183] (6) Volume expansion rate at room temperature The volume expansion rate is tested using scanning electron microscopy (SEM). First, the battery is assembled, and then the thickness of the negative electrode side cross-section when the battery is at rest is measured by SEM. Then, the first charge performance test is performed. After charging, the thickness of the negative electrode side cross-section is measured again by SEM. The formula for the expansion rate is: (thickness of the negative electrode cross-section after charging - thickness of the negative electrode cross-section before charging) / thickness of the negative electrode cross-section after charging.

[0184] 2. Battery performance test (1) First-effect test at room temperature 25℃ The Xinwei Battery Testing System, model CT-4008, was used. The assembled all-solid-state battery underwent charge-discharge testing. The first charge-discharge cycle was performed at a 0.1C rate, and the initial efficiency was calculated as (initial discharge capacity / initial charge capacity) × 100%.

[0185] (2) Rate performance at 25℃ and cycling performance at 25℃ and 45℃ First, the all-solid-state battery was tested for rate performance. It was charged and discharged at 0.1C, 0.2C, 0.5C and 1C, with 2 cycles at each rate. Then it was returned to 0.5C to test its cycle performance at 25℃ and 45℃ at 20.5C. Its capacity retention rate was also tested. The capacity retention rate = discharge capacity at the 50th cycle / discharge capacity at the 9th cycle (when returning to 0.5C to start cycling) × 100%.

[0186] Table 2 Test results of solid-state battery performance

[0187] Referring to Tables 1-2, a comparison of the test results of Example 1 and Comparative Example 1 shows that the introduction of oxygen can help improve the initial efficiency, rate performance, room temperature cycle performance, and high temperature cycle performance of solid-state batteries. Among them, ZnSiP2O... 1.71 The charge transfer resistance is higher than that of CuSi2P3O 2.35 This is because copper has better electrical conductivity than zinc; copper's conductivity is approximately 5.96 × 10⁻⁶. 7 S / m, while the conductivity of zinc is approximately 1.69 × 10⁻⁶. 7 S / m.

[0188] further, Figure 3 and Figure 4 The XRD patterns of Example 1 and Comparative Example 1 are shown below. The XRD patterns reveal a gentle peak around 12°, corresponding to the peak shape of oxygen. Furthermore, the peak intensity decreases significantly and the amorphous state is enhanced after the addition of oxygen, indicating that oxygen is indeed added to the core. Figure 5 It can be seen that the first charge specific capacity, first discharge specific capacity and first efficiency of Example 1 are 1813.07mAh / g, 2001.00mAh / g and 90.61%, respectively.

[0189] A comparison of the test results of Comparative Examples 2-4 and Example 1 shows that Comparative Example 1 has only a core and no coating layer. Although its capacity is high, its initial efficiency, rate performance, room temperature cycle performance, and high temperature cycle performance are far lower than those of Example 1. The coating layer of Comparative Example 2 contains only solid electrolyte, and the coating layer of Comparative Example 3 contains only graphite. Although their capacity is high, their initial efficiency, rate performance, room temperature cycle performance, and high temperature cycle performance are far lower than those of Example 1.

[0190] A comparison of the test results from Examples 1-5 shows that the introduction of element M can improve the electronic and ionic conductivity of the silicon-based alloy anode active material, which helps to improve the rate performance and room-temperature cycling performance of solid-state batteries. Furthermore, since copper has the best conductivity, CuSi₂P₃O₃… 2.35It has relatively high electronic conductivity. The increase in electronic conductivity can reduce the battery's internal resistance, thereby reducing energy loss during charging and discharging, and thus improving the battery's charging and discharging efficiency. At the same time, the increase in conductivity also helps to reduce chemical losses during charging and discharging, enhances battery stability, and extends battery cycle life.

[0191] Table 3 Test results of solid-state battery performance

[0192] As can be seen from the comparison of the test results in Table 3, comparing the test results of Examples 1, Examples 6-12, and Comparative Example 5, the first mixing and grinding time of Example 6 was 8 hours and the rotation speed was 600 rpm / min. Compared with Example 1, due to the short time, the oxygen incorporation was insufficient, and the room temperature cycling performance and high temperature cycling performance were not significantly improved. The first mixing and grinding time of Example 7 was 20 hours and the rotation speed was 850 rpm / min. Compared with Example 1, its ball milling time in air was too long, resulting in a decrease in capacity and a lower rate performance than Example 1. Compared with Example 1, Comparative Example 5 had a shorter ball milling time and a lower rotation speed, which prevented the synthesis of CuSi2P3O. 2.35 This results in a battery with significantly lower capacity, rate performance, room temperature cycle performance, and high temperature cycle performance compared to Example 1. Furthermore, as demonstrated in Examples 7-12, when the molar ratio of oxygen is in the range of 0.85-3.32, the battery can exhibit good cycle performance, initial efficiency, and rate performance.

[0193] Furthermore, from Figure 6 As can be seen, the XRD pattern of Example 8 still shows peaks related to the precursor materials (Cu, Si and amorphous red phosphorus) as well as peaks of binary Cu-P phases (such as Cu3P and CuP2). The formation of Cu-P intermediate compounds is preferred over Si-P or Cu-Si compounds, which can be attributed to the superior thermodynamic stability of Cu-P compounds. Figure 7 CuSi2P3O was shown z During the preparation process, the oxygen mass content varied with grinding time. At a grinding time of 8 hours, the oxygen mass content was approximately 6%. From 8 hours to 20 hours of air grinding, the oxygen mass content increased linearly with the grinding time in air, until it reached approximately 20% oxygen content. After 18 hours, even increasing the air grinding time to 20 hours did not result in a significant change in oxygen content.

[0194] Table 4 Test results of solid-state battery performance

[0195] A comparison of the test results from Examples 1 and 13-18 shows that increasing the proportion of conductive carbon in the negative electrode active material leads to a decrease in charge transfer resistance, indicating that carbon can improve the electronic conductivity of the negative electrode active material. However, if the proportion of conductive carbon in the negative electrode active material is too large, i.e., the coating layer is too thick, lithium-ion transport will be hindered, resulting in a decrease in first-efficiency performance and cycle performance. Simultaneously, increasing the thickness of the conductive carbon coating layer can also reduce the volume expansion rate, because the conductive carbon layer provides structural support to the core, maintaining structural stability during charge / discharge and improving cycle performance.

[0196] Table 5 Test results of solid-state battery performance

[0197] A comparison of the results from Examples 1 and 19-25 shows that increasing the proportion of solid electrolyte in the negative electrode active material improves the ionic conductivity of the material, resulting in improved first-efficiency and rate performance. However, if the proportion of solid electrolyte in the negative electrode active material is too large, the proportion of the active material will decrease, affecting capacity utilization. Simultaneously, the relatively soft solid electrolyte provides a buffering effect for the volume expansion of the core during charging / discharging.

[0198] Table 6 Test results of solid-state battery performance

[0199] A comparison of the test results of Example 1 and Example 26 shows that the molar percentage of chlorine in Example 1 is higher than that in Example 26. Consequently, the ionic conductivity of the negative electrode active material in Example 1 is higher than that in Example 26. Therefore, the battery in Example 1 has higher initial efficiency, room temperature cycle performance, and high temperature cycle performance than that in Example 26.

[0200] A comparison of the test results from Examples 1, 27, and 28 shows that sulfide solid electrolytes are beneficial for improving the ionic conductivity of the negative electrode active material, thereby enabling the battery to have higher initial efficiency, room temperature cycling performance, and high temperature cycling performance.

[0201] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A negative electrode active material, characterized by, The negative active material comprises: A core, a chemical formula of the core comprising MSi x P y O z wherein M comprises one or more elements from Group IB, Group IIB, and Group IIIA. a coating layer coated on at least part of the surface of the inner core, the coating layer comprising an electrically conductive carbon material and a solid-state electrolyte.

2. The negative electrode active material according to claim 1, characterized by 0.85≤z≤3.32； And / or, 1≤x≤6; And / or, 1≤y≤3.

3. The negative electrode active material according to claim 1, characterized by The M comprises one or more of Zn, Al, Cu and Ga; Optionally, the M comprises Cu, 1.48≤z≤2.53; Optionally, the M comprises Al, 0.98≤z≤1.69; Optionally, the M comprises Zn, 1.07≤z≤1.85; Optionally, the M comprises Ga, 1.33≤z≤2.

75.

4. The negative electrode active material according to claim 1, characterized by The coating layer comprises: a first coating layer comprising the electrically conductive carbon material; and a second coating layer comprising the solid-state electrolyte; The first coating layer is located between the inner core and the second coating layer.

5. The negative electrode active material according to claim 4, characterized by The mass percentage of the electrically conductive carbon material is 8% to 20%, optionally 10% to 14%, based on the mass of the negative active material; And / or, the mass percentage of the solid-state electrolyte is 15% to 35%, optionally 20% to 25%, based on the mass of the negative active material.

6. The negative electrode active material according to claim 4 or 5, characterized by The electrically conductive carbon material comprises one or more of graphene, graphite, carbon nanoparticles, carbon black, carbon nanotubes and carbon fibers; And / or, the solid-state electrolyte comprises one or more of sulfide solid-state electrolyte, halide solid-state electrolyte and oxide solid-state electrolyte, optionally sulfide solid-state electrolyte.

7. The negative electrode active material according to claim 6, characterized by The chemical formula of the sulfide solid-state electrolyte is Li 7-a PS 6-a Cl a wherein 1≤a≤1.

5.

8. The negative electrode active material according to claim 1, characterized by The average particle size of the inner core is 800 nm to 8000 nm, optionally 1000 nm to 5000 nm; And / or, the thickness of the coating layer is 20 nm to 150 nm.

9. A method for producing a negative electrode active material, characterized by, The method comprises the following steps: The metal powder containing M, the silicon powder and the phosphorus powder are subjected to a first mixing and grinding treatment in an oxygen-containing atmosphere for 6 hours or more to obtain a core, the chemical formula of which includes MSi x P y O z wherein M includes one or more elements from Group IB, Group IIB and Group IIIA. mixing the inner core with raw materials of the coating layer and performing coating treatment to form a coating layer on at least part of the surface of the inner core, thereby obtaining a negative active material, wherein the raw materials of the coating layer comprise an electrically conductive carbon material and a solid-state electrolyte.

10. The method of claim 9, wherein, The mass ratio of the inner core, the electrically conductive carbon material and the solid-state electrolyte is (45-77):(7-20):(13-24).

11. A solid state battery, characterized by The method comprises the following steps:

12. An electrical device, characterized by The method comprises the following steps: The method comprises the following steps:

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