Metal-doped silicon monoxide composite material and method of preparation

Abstract

The present application relates to the field of battery, especially to a metal-doped silicon monoxide composite material and a preparation method thereof, which comprises silicon monoxide, metal elements, and a graphene layer and a carbon layer coated on the outside of the silicon monoxide. The composite material generates graphene in situ on the surface of silicon monoxide powder, which is more uniform and effective than directly using graphene or graphene oxide physically mixed.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a metal-doped silicon suboxide composite material and its preparation method. Background Technology

[0002] Developing clean and renewable energy sources is crucial for mitigating the environmental pressures of fossil fuel combustion. Lithium-ion batteries (LIBs), as an emerging energy system, are widely used as power systems in computers, communications, and consumer products (3C products) due to their high energy density, excellent stability and cyclicability, low self-discharge rate, and low voltage hysteresis, and have almost monopolized the market for portable device power systems. However, the growing demand for electric vehicles (EVs) highlights the limitations of commercially available LIBs, namely that traditional anodes (such as graphite) cannot provide the energy required to support long ranges. Therefore, developing novel and advanced anode materials is of paramount importance.

[0003] Among currently available anode materials, silicon-based materials possess high specific capacity and advantages in high energy density, natural abundance, and non-toxicity. These characteristics collectively make silicon a promising candidate to replace graphite as the next generation of unique anode material. However, the high capacity of Si (≈4200 mAh g⁻¹) is offset by its significant volume expansion (≈300%) during lithiation. Furthermore, the expansion and contraction of active particles during repeated lithiation / delithiation cycles can easily lead to particle pulverization. Additionally, Si particles may detach from the current collector, losing contact with the electrode. Side reactions between Si and the electrolyte form a solid electrolyte interface (SEI), which is unstable during lithiation / delithiation cycles and continuously consumes electrolyte, leading to SEI thickening and deterioration of Li⁺ ion transport. These problems result in low cycle efficiency and rapid capacity loss for Si anodes. SiOx, with a theoretical capacity of ≈2400 mAh g⁻¹ and smaller volume expansion (≈200%), is more suitable for lithium-ion battery anodes compared to Si. The unique composition and structure of SiOx enable it to offer better cycle performance than Si anodes. However, during initial lithiation, irreversible Li₂O and Li silicates are formed, leading to capacity loss and a decrease in initial coulombic efficiency (ICE). Furthermore, SiOx suffers from inherently low conductivity, electrical isolation effects caused by volume changes during cycling, and numerous side reactions with the electrolyte. To improve the conductivity of SiOx anode materials, current technologies often employ the addition of conductive substances, with graphene being frequently used due to its excellent conductivity. However, direct dispersion of graphene as an additive leads to its re-agglomeration. This re-agglomeration not only hinders lithium-ion diffusion pathways, resulting in heavier polarization and higher irreversible capacity, but also increases the difficulty of coating the electrode composite material on the current collector. This prevents graphene from creating an effective conductive network within the electrode particles, thus limiting improvements in electrochemical performance and severely hindering lithium-ion diffusion pathways, resulting in considerable charge transfer resistance and increasing battery application costs.

[0004] Therefore, mitigating these failure mechanisms is crucial for the commercialization of SiOx in lithium-ion batteries. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention provides a metal-doped silicon suboxide composite material, comprising silicon suboxide, a metal element, and a graphene layer and a carbon layer coating the outside of the silicon suboxide.

[0006] Furthermore, the silicon suboxide is porous silicon suboxide, and there is a void layer between the silicon suboxide and the graphene layer.

[0007] Furthermore, the silicon suboxide contains nano-silicon.

[0008] Furthermore, the metallic element is at least one selected from magnesium, copper, aluminum, zinc, ferrous iron, sodium, potassium, calcium, nickel, manganese, cobalt, or chromium.

[0009] Furthermore, the median diameter of the silicon suboxide is 1-10 μm.

[0010] Furthermore, the coating layer has a thickness of 5-45 nm.

[0011] This application also provides a method for preparing a metal-doped silica-suboxide composite material, wherein silica-suboxide and humic gluconate metal salt are sequentially added to deionized water to form a first dispersion;

[0012] The first dispersion was spray-dried to obtain the second powder;

[0013] The second powder is heat-treated to obtain the silicon suboxide composite material.

[0014] Furthermore, the heat treatment also includes etching.

[0015] Furthermore, the etching involves immersing the second powder in a hydrofluoric acid solution.

[0016] Furthermore, the composition includes 10wt%-50wt% silica, 5-40wt% humic substances, and 5-75wt% metal gluconate.

[0017] Further, the gluconate is one or more of magnesium gluconate, copper gluconate, zinc gluconate, ferrous gluconate, sodium gluconate, potassium gluconate, calcium gluconate, nickel gluconate, manganese gluconate, cobalt gluconate, and chromium gluconate.

[0018] And / or the humic substance is one or more of humic acid, fulvic acid and humin.

[0019] Furthermore, the heat treatment includes:

[0020] Under an inert gas atmosphere, heat treatment is carried out at 150℃-450℃ for 1-5 hours; then the temperature is further increased to 800-1200℃ for 5-20 hours.

[0021] The beneficial effects of this patent are:

[0022] (1) In-situ generation of graphene on the surface of silica powder is more uniform and effective than direct physical mixing of graphene or graphene oxide.

[0023] (2) A graphene coating and a hard carbon coating are sequentially formed on the surface of silicon suboxide powder. The double-layer structure effectively prevents side reactions between the electrolyte and silicon suboxide material, limits the growth of SEI film and leaves more reversible lithium ions, and improves the overall conductivity and stability of the material.

[0024] (3) The silica-suboxide composite material of this application forms a double-coated egg yolk shell structure, wherein the hollow structure of the egg yolk shell and the porous structure inside the silica-suboxide powder reserve space for the volume expansion of the negative electrode material during cycling, effectively improving the volume expansion problem of the negative electrode material during cycling.

[0025] (4) Introducing metal element doping during the coating process, the high ionic conductivity of metals makes Li + The diffusion rate is accelerated, which effectively improves the initial coulombic efficiency and specific capacity of the material.

[0026] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0027] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of the present invention and do not constitute a limitation on the technical solutions of the present invention.

[0028] Figure 1 This is a schematic diagram of a product according to an embodiment of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] This invention provides a metal-doped silicon suboxide composite material, comprising silicon suboxide, a metal element, and a graphene layer and a carbon layer covering the outside of the silicon suboxide.

[0031] The surface of the silicon suboxide layer is coated with both graphene and hard carbon, forming a double-layer structure that effectively prevents side reactions between the electrolyte and the silicon suboxide material, limits the growth of the SEI film, retains more reversible lithium ions, and improves the overall conductivity and stability of the material. By introducing metal doping, the high ionic conductivity of metals enables Li... + The diffusion rate is accelerated, which effectively improves the initial coulombic efficiency and specific capacity of the material.

[0032] In another embodiment of the present invention, the metal-doped silicon suboxide is porous silicon suboxide, and there is a void layer between the silicon suboxide and the graphene layer.

[0033] like Figure 1 As shown, the metal-doped silicon suboxide composite material of this application forms a double-coated eggshell structure, wherein the eggshell has a hollow structure (i.e. there is a gap between the silicon suboxide and the graphene layer, and they are not in direct contact). This hollow structure and the porous structure inside the silicon suboxide powder reserve space for the volume expansion of the negative electrode material during cycling, effectively improving the volume expansion problem of the negative electrode material during cycling.

[0034] In another embodiment of the present invention, the metal-doped silicon suboxide comprises nano-silicon.

[0035] By introducing nano-silicon, the capacity of silicon suboxide anode material can be improved. Furthermore, nano-silicon can withstand greater volume deformation without breaking, which helps to alleviate the volume expansion of anode material during charging and discharging.

[0036] In another embodiment of the present invention, the metallic element is at least one selected from magnesium, copper, aluminum, zinc, ferrous iron, sodium, potassium, calcium, nickel, manganese, cobalt, or chromium. These elements are common metallic elements in industrial production, are inexpensive, and are readily available.

[0037] In another embodiment of the present invention, the coating layer has a thickness of 5-45 nm.

[0038] When the coating layer is too thin (less than 5 nm), the silicon suboxide expands during lithium intercalation, causing the coating layer to easily crack and failing to achieve the coating effect; when the coating layer is too thick (greater than 45 nm), the lithium ion transport path is too long, affecting the material performance.

[0039] In another embodiment of the present invention, a method for preparing a metal-doped silicon suboxide composite material is provided, comprising:

[0040] Silicone oxide, humic substances, and metal gluconate salt were added sequentially to deionized water to form the first dispersion.

[0041] The first dispersion was spray-dried to obtain the second powder;

[0042] The second powder is heat-treated to obtain the silicon suboxide composite material.

[0043] In this application, silicon suboxide is in an amorphous state, and humic substances have strong solubility in alkaline aqueous solutions. After dispersing silicon suboxide powder in the solution, humic substance molecules tend to be free near the silicon suboxide powder. Then, a metal gluconate salt is added to the solution as a carbon source and a metal source. After being dissolved evenly, the mixture is spray-dried to obtain a powder mixture. After high-temperature calcination, the humic substances and the metal gluconate salt form a graphene coating and a hard carbon coating on the surface of the silicon suboxide powder in sequence under the heat treatment, forming an inner and outer double-coating layer structure. At the same time, since the metal gluconate salt contains metal elements, a double-coating layer silicon suboxide powder with metal element doping is prepared.

[0044] This invention achieves metal doping modification, double-layer carbon coating, and disproportionation modification of silicon suboxide materials in a one-step process, thereby improving the overall stability and conductivity of the material. Graphene and carbon coating layers are uniformly prepared in situ on the surface of silicon suboxide, effectively avoiding graphene agglomeration and uneven coating. The graphene coating layer imparts good conductivity and provides structural support, while the carbon coating layer further enhances structural stability. Simultaneously, the double-layer coating can resist stress changes caused by volume expansion during silicon suboxide charging and discharging, also improving the material's conductivity. Furthermore, the double-layer coating structure reduces the occurrence of side reactions during the first charge and discharge and the repeated formation of the SEI film during cycling, which is beneficial for forming a stable SEI film and improving battery cycle performance. The simultaneous introduction of metal doping suppresses the formation of irreversible phases during the first charge, significantly improving the battery material's initial efficiency and cycle stability, demonstrating promising application prospects.

[0045] In another embodiment of the present invention, the heat treatment further includes etching. During the heat treatment process, silicon suboxide undergoes a disproportionation reaction to generate SiO2. Silicon dioxide tends to deposit more on the particle surface and secondarily inside the particles. Etching removes the silicon dioxide layer located between the graphene layer and the silicon suboxide (i.e., on the silicon suboxide surface), as well as some of the internal silicon dioxide, ultimately yielding a porous silicon suboxide composite anode material with a hollow yolk-shell structure. The hollow yolk-shell structure and the porous structure inside the silicon suboxide powder provide sufficient space for volume expansion of the anode material during cycling, effectively improving the volume expansion problem during cycling.

[0046] Specifically, the etching can be achieved by immersion in hydrofluoric acid. The immersion time is 1-6 hours, preferably 2 hours. This allows for a more thorough removal of the silicon oxide generated by the disproportionation reaction.

[0047] In another embodiment of the present invention, the silicate comprises 10wt%-50wt%, humic acid 5-40wt%, and metal gluconate 5-75wt%. This proportion refers to the mass ratio of silicate (humic acid or metal gluconate) to the total mass of silicate, humic acid, and metal gluconate. In another embodiment of the present invention, the gluconate is one or more of copper gluconate, zinc gluconate, ferrous gluconate, sodium gluconate, potassium gluconate, calcium gluconate, nickel gluconate, manganese gluconate, cobalt gluconate, and chromium gluconate.

[0048] In another embodiment of the present invention, the humic substance is one or more of humic acid, fulvic acid, and humin.

[0049] In another embodiment of the present invention, the heat treatment includes:

[0050] Under an inert gas atmosphere, heat treatment is carried out at 150℃-450℃ for 1-5 hours; then the temperature is further increased to 800-1200℃ for 5-20 hours.

[0051] If heat treatment is not performed in this manner, it will affect the carbonization of humic acid and glucose to form a coating layer, thus limiting the performance of the composite material. Furthermore, it will affect the disproportionation effect, which will affect the porous and hollow structure of subsequent materials, thereby affecting the conductivity of the composite material and its initial efficiency after assembly into a battery.

[0052] To more clearly illustrate the solution of this application, the following embodiments are described. In all embodiments and comparative examples, the solid-liquid ratio (referring to the mass of (silica powder + humic acid + gluconate) / mass of deionized water) is maintained at 15%, and the amount of deionized water can be adjusted accordingly.

[0053] Example 1

[0054] A magnesium-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, magnesium, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 13.2 nm.

[0055] The preparation method of the above-mentioned silica suboxide composite material is as follows: 4g of silica suboxide powder with a D50 (median diameter) of 5µm was added to deionized water and dispersed for 30 minutes; 1g of humic acid was added, and the pH was adjusted to 9 with ammonia water, and dispersed for 30 minutes; finally, 3g of magnesium gluconate powder was added (solid-liquid ratio maintained at 15%), and after stirring evenly, it was spray-dried at 120℃ and 4ml / min to obtain precursor A of the target material. Precursor A was transferred to a tube furnace for heat treatment at 300℃ for 2 hours under Ar atmosphere, and then the temperature was further increased to 1000℃ for 10 hours. After cooling, it was taken out to obtain precursor B of the target material. Precursor B was soaked in HF solution for 1 hour, washed, and dried to obtain a magnesium-doped double-coated eggshell-structured porous silica suboxide composite material.

[0056] Example 2

[0057] A magnesium-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, magnesium, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 13.0 nm.

[0058] The preparation method of the above-mentioned silica suboxide composite material is as follows:

[0059] 8g of silica powder, 1g of humic acid, and 10g of magnesium gluconate powder were used, with the amount of deionized water adjusted accordingly. Everything else was the same as in Example 1.

[0060] Example 3

[0061] A magnesium-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, magnesium, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 8.7 nm.

[0062] The preparation method of the above-mentioned silica suboxide composite material is as follows:

[0063] 8g of silica powder, 1g of humic acid, and 4g of magnesium gluconate powder were used, with the amount of deionized water adjusted accordingly. Everything else was the same as in Example 1.

[0064] Example 4

[0065] A magnesium-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, magnesium, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 8.7 nm.

[0066] The preparation method of the above-mentioned silica suboxide composite material is as follows:

[0067] 4g of silica fume powder, 1g of humic acid, and 5g of magnesium gluconate powder were used, with the amount of deionized water adjusted accordingly. Everything else was the same as in Example 1.

[0068] Example 5

[0069] A magnesium-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, magnesium, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 17.2 nm.

[0070] The preparation method of the above-mentioned silica suboxide composite material is as follows:

[0071] 4g of silica powder, 2g of humic acid, and 3g of magnesium gluconate powder were used, with the amount of deionized water adjusted accordingly. Everything else was the same as in Example 1.

[0072] Example 6

[0073] A magnesium-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, magnesium, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 12.9 nm.

[0074] The preparation method of the above-mentioned silica-suboxide composite material is as follows: under Ar atmosphere, heat treatment at 300°C for 2 hours, then continue to heat to 1000°C for 5 hours, and the rest is the same as in Example 1.

[0075] Example 7

[0076] A magnesium-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, magnesium, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 13.3 nm.

[0077] The preparation method of the above-mentioned silica suboxide composite material is as follows:

[0078] Under an Ar atmosphere, heat treatment was carried out at 300°C for 2 hours, followed by further heating to 800°C and heat treatment for 10 hours. Other procedures were the same as in Example 1.

[0079] Example 8

[0080] A copper-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, copper, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 12.4 nm.

[0081] The preparation method of the above-mentioned silica suboxide composite material is as follows:

[0082] Replace magnesium gluconate with copper gluconate, otherwise remain the same as in Example 1.

[0083] Example 9

[0084] A magnesium-copper dual-doped silicon suboxide composite material is composed of porous silicon suboxide with a median diameter of 5 μm, copper, and graphene and carbon layers covering the periphery thereon, wherein there is a gap between the graphene layer and the porous silicon suboxide, and the coating layer thickness is 12.7 nm.

[0085] The preparation method of the above-mentioned silica suboxide composite material is as follows:

[0086] 8g of silica powder, 2g of humic acid, 3g of magnesium gluconate and 3g of copper gluconate, with the amount of deionized water adjusted accordingly, and the rest is the same as in Example 1.

[0087] Example 10

[0088] Humic acid was replaced with fulvic acid, magnesium gluconate was replaced with sodium gluconate, and the median diameter of silica was selected as 1 μm. Under an Ar atmosphere, the temperature was increased to 150 °C for 5 h, and then the temperature was increased to 800 °C for 20 h. Other steps and reaction parameters were the same as in Example 1.

[0089] Example 11

[0090] Humic acid was replaced with humin, magnesium gluconate was replaced with calcium gluconate, the median diameter of silica was selected as 10 μm, and the mixture was heat-treated at 450 °C for 1 h under an Ar atmosphere, then the temperature was increased to 1200 °C and heat-treated for 5 h. Other steps and reaction parameters were the same as in Example 1.

[0091] Comparative Example 1

[0092] No humic acid was added; otherwise, it was the same as in Example 1.

[0093] Comparative Example 2

[0094] Magnesium gluconate was not added; otherwise, it was the same as in Example 1.

[0095] Comparative Example 3

[0096] Humic acid and magnesium gluconate were not added; otherwise, it was the same as in Example 1.

[0097] Comparative Example 4

[0098] Replace magnesium gluconate with glucose, otherwise remain the same as in Example 1.

[0099] Comparative Example 5

[0100] Without adding humic acid, after etching, washing and drying, 0.1g of graphene was added, and the rest was the same as in Example 1.

[0101] The electrochemical performance tests of the materials obtained in the examples and comparative examples are shown in Table 1. Button cell test conditions: constant temperature 25℃, CR2032, initial charge / discharge I = 0.1C, cycle I = 1A·g⁻¹, constant current charge / discharge tests were conducted at room temperature between 0.001 and 2.0V (vs Li / Li⁺) using a battery testing system.

[0102] Table 1. Test results of the examples and comparative examples.

[0103]

[0104]

[0105]

[0106] As shown in the table above, compared with the anode material prepared in the comparative example, the porous silicon suboxide composite anode material prepared by the examples has better initial coulombic efficiency and the best coin cell test results. Compared with the uncoated porous silicon suboxide anode material, the electrochemical performance of the composite anode material is significantly improved, with an initial discharge capacity of 1987.4 mAh / g, an initial charge capacity of 1737.0 mAh / g, an initial coulombic efficiency of 89.6%, a capacity of 1514.7 mAh / g after 200 cycles, and a capacity retention rate of over 87%.

[0107] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes to the form and details of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for preparing a metal-doped silicon suboxide composite material, characterized in that, Silicone oxide, humic substances, and metal gluconate salt were added sequentially to deionized water to form the first dispersion. The first dispersion was spray-dried to obtain the second powder; The second powder is heat-treated to obtain the silicon suboxide composite material; The silicon suboxide composite material includes a double coating layer of graphene and carbon. The humic substance is one or more of humic acid, fulvic acid and humin. The heat treatment includes: heat treatment at 150℃-450℃ for 1-5 hours in an inert gas atmosphere; then further heating to 800-1200℃ for 5-20 hours.

2. The preparation method according to claim 1, characterized in that, The heat treatment process also includes etching.

3. The preparation method according to claim 2, characterized in that, The etching process involves immersing the second powder in a hydrofluoric acid solution.

4. The preparation method according to claim 1, characterized in that, The silica content is 10 wt%-50 wt% of the total silica, humic substances and gluconate metal salt, the humic substances are 5-40 wt% of the total silica, humic substances and gluconate metal salt, and the gluconate metal salt is 5-75 wt% of the total silica, humic substances and gluconate metal salt.

5. The preparation method according to claim 1, characterized in that, The metal gluconate salt is one or more of magnesium gluconate, copper gluconate, zinc gluconate, ferrous gluconate, sodium gluconate, potassium gluconate, calcium gluconate, nickel gluconate, manganese gluconate, cobalt gluconate, and chromium gluconate.

6. A metal-doped silicon suboxide composite material prepared by any one of the preparation methods according to claims 1-5, characterized in that, It includes silicon suboxide, metal elements, and a double coating layer consisting of a graphene layer and a carbon layer covering the outside of the silicon suboxide, wherein the silicon suboxide contains nano-silicon.

7. The metal-doped silicon suboxide composite material according to claim 6, characterized in that, The silicon suboxide is porous silicon suboxide, and there is a void layer between the silicon suboxide and the graphene layer.

8. The metal-doped silicon suboxide composite material according to claim 6, characterized in that, The metallic element is at least one of magnesium, copper, aluminum, zinc, ferrous iron, sodium, potassium, calcium, nickel, manganese, cobalt, or chromium. And / or the median diameter of the silicon suboxide is 1-10 μm.

9. The metal-doped silicon suboxide composite material according to claim 6, characterized in that, The thickness of the double coating layer is 5-45 nm.

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