A high-capacity lithium-ion battery negative electrode material and preparation method thereof and lithium-ion battery

Abstract

The present invention provides a high-capacity lithium-ion battery negative electrode material, a preparation method thereof, and a lithium-ion battery. The method comprises: adding an organic phosphonic acid to an aqueous solution and dissolving it to obtain solution A; then dispersing Si particles into solution A and performing ultrasonic treatment to obtain solution B. Subsequently, an aniline aqueous solution and a phytic acid aqueous solution are added to the above-mentioned solution B, ultrasonic treatment is performed, and then an ammonium persulfate aqueous solution is added and ultrasonicated again to obtain solution C. Solution C is then cooled and allowed to stand; after standing, the product is washed and filtered, and the filtered solid is dried to obtain a dry product. Finally, the dry product is mixed with a surfactant and graphene oxide, stirred evenly, filtered and dried, and sintered at high temperature to obtain a high-capacity lithium-ion battery negative electrode material. This negative electrode material has the characteristics of a comprehensive protective barrier, little effect on silicon content, the ability to provide long-lasting mechanical protection, and the ability to regulate the electrolyte-particle interface to produce a uniform and tough SEI film.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials for lithium-ion batteries, in particular to a high-capacity negative electrode material for lithium-ion batteries and applications thereof. Background Art

[0002] To meet the growing demand for high-performance energy storage systems, the research and development of next-generation lithium batteries focuses on achieving higher charge and discharge rates and longer cycle life. However, graphite, a widely used negative electrode material for lithium-ion batteries, has a low theoretical specific capacity (only 372 mAh g -1 ), which greatly limits the further improvement of battery performance. Silicon (Si) (3579 mAh g -1 ), tin (Sn) (990 mAh g -1 ), phosphorus (P) (2596 mAh g -1 ) and Germanium (Ge) (1600 mAh g -1 ) are considered to be the rising stars of the next generation of lithium battery negative electrode materials. Among them, Si has a very high theoretical capacity (about 4200 mAh g -1 ), delithiation potential (relative to Li + However, silicon anodes face two major challenges in practical application. The first challenge is that silicon expands by up to 400% during lithiation, causing the active material to pulverize, exacerbating side reactions with the electrolyte and significantly shortening the cycle life. In addition, silicon has a low lithium ion diffusion coefficient (10 -14 ~10 -13 cm 2 s -1 )) and inherent insulating properties (electronic conductivity, about 10 -3 S cm -1 )) makes it difficult for it to transfer electrons and lithium ions, greatly hindering its development in the field of fast charging.

[0003] Carbon coating strategies are frequently used to improve the electrochemical performance of Si materials, including mitigating persistent parasitic reactions at the interface, improving ionic / electronic conductivity, and alleviating stress caused by volume changes. However, chemical protection against side reactions caused by solid electrolyte interface (SEI) rupture and electrolyte decomposition remains a challenge. The natural SEI formed on the Si surface by commercial carbonate electrolytes contains a high concentration of organic matter and a small amount of inorganic components, and its distribution is uneven. This fragile SEI cannot adapt to large volume changes, and repeated rupture leads to capacity fading and reduced Coulombic efficiency. Previous work has primarily focused on preventing internal Si particle pulverization by coatings, while ignoring their effects on the external electrolyte and, consequently, the SEI composition. Furthermore, due to the low silicon content in the composite materials, traditional improvement methods struggle to meet the ultra-long cycle life and fast charging requirements of high-energy-density lithium batteries.

[0004] Therefore, there is an urgent need for a lithium-ion battery negative electrode material that has a comprehensive protective barrier, has little effect on silicon content, can provide long-lasting mechanical protection, and can regulate the electrolyte-particle interface to produce a uniform and tough SEI. Summary of the Invention

[0005] In order to prepare a lithium-ion battery anode material with a comprehensive protective barrier, little effect on silicon content, long-lasting mechanical protection, and the ability to regulate the electrolyte-particle interface to produce a uniform and tough SEI, the present invention proposes to synthesize the lithium-ion battery anode through a combined multi-step hydrothermal-high-temperature pyrolysis method to obtain a high-mechanical-strength composite Si anode material (abbreviated as Si@C-CP / G). This solves the problems of low traditional Si content, Si anode crushing, SEI rupture, and side reactions caused by electrolyte decomposition, ultimately achieving high capacity and long cycle performance.

[0006] In order to achieve the above object, the present invention provides a method for preparing a high-capacity lithium-ion battery negative electrode material, comprising the following steps:

[0007] Step 1: adding organic phosphonic acid to an aqueous solution and dissolving it to obtain solution A; then dispersing Si particles into solution A and performing ultrasonic treatment to allow the two to recombine to obtain solution B.

[0008] Step 2: Add the aqueous aniline solution and the aqueous phytic acid solution to the above solution B, then perform ultrasonic treatment, then add the aqueous ammonium persulfate solution and perform ultrasonic treatment again to obtain solution C. Then, cool solution C and allow it to stand to polymerize. After the polymerization is completed, wash and filter the product, and then dry the filtered solid to obtain a dry product.

[0009] Step 3: The dried product prepared above is mixed with a surfactant and graphene oxide, and stirred evenly to obtain a solution D; the solution D is filtered and dried, and then sintered at a high temperature to obtain a high-capacity lithium-ion battery negative electrode material, which is a silicon-carbon composite negative electrode material, named Si@C-CP / G.

[0010] Furthermore, in step 1, the organic phosphonic acid is at least one of ethylenediaminetetramethylenephosphonic acid, aminotrimethylenephosphonic acid, and methylphosphonic acid.

[0011] Furthermore, in step 1, the dissolving includes simultaneous heating and ultrasonic treatment to promote the dissolution of the organic phosphonic acid; preferably, the heating temperature is 80-90° C., the ultrasonic time is preferably 8-12 min, and the ultrasonic power is 100-300 W.

[0012] Furthermore, in step 1, the mass ratio of the organic phosphonic acid to the Si particles is 0.3-0.6:0.8-1.1, preferably 0.35-0.55:0.85-1.05, more preferably 0.4-0.5:0.9-1, and even more preferably 0.5:1.

[0013] Furthermore, in step 2, the ultrasonic power is 100-300W, and the ultrasonic time is 0.5-2h.

[0014] Furthermore, in step 2, the concentrations of the aniline aqueous solution and the phytic acid aqueous solution are both 70 wt %.

[0015] Furthermore, the volume ratio of the aniline aqueous solution in step 2 to the mass ratio of the Si particles in step 1 is 5-8 μL: 0.03-0.08 g, preferably 5.5-7.5 μL: 0.04-0.07 g, further preferably 6-7 μL: 0.05-0.06 g, and further preferably 7 μL: 0.05 g.

[0016] Furthermore, the volume ratio of the phytic acid aqueous solution in step 2 to the Si particles in step 1 is 10-16 μL: 0.03-0.08 g, preferably 12-15 μL: 0.04-0.07 g, further preferably 13-14 μL: 0.05-0.06 g, and further preferably 14 μL: 0.05 g.

[0017] Furthermore, in step 2, the mass ratio of the ammonium persulfate to the Si in step 1 is 0.05-0.35:1, preferably 0.10-0.25:1, and more preferably 0.136:1.

[0018] Furthermore, in step 2, the cooling and standing is to stand the container containing solution C in an ice bath for 3-7 hours, during which the polymerization reaction occurs.

[0019] Furthermore, in step 2, the drying temperature is 50-70°C.

[0020] Furthermore, in step three, the surfactant is at least one of polyvinylpyrrolidone (PVP) and sodium dodecylbenzenesulfonate.

[0021] Furthermore, in step three, the graphene oxide concentration is 1-5 mg / mL.

[0022] Furthermore, in step three, the high-temperature sintering includes two steps: the first step is sintering at 200-400°C, and the second step is sintering at 500-750°C; and the duration of the high-temperature sintering is 0.5-2h in the first step and 2-5h in the second step.

[0023] Furthermore, in step three, the heating rate of the high-temperature sintering may be 1-10°C / min, preferably 2-5°C / min.

[0024] Furthermore, in step 3, the high-temperature sintering is performed in an inert gas, wherein the inert gas is at least one of nitrogen, argon, and helium.

[0025] The present invention also provides a high-capacity lithium-ion battery negative electrode material, including a polymer formed by organic phosphonic acid, phytic acid, and aniline and graphene oxide that wraps internal silicon powder particles layer by layer from the inside to the outside, thereby forming a three-layer wrapped sandwich structure.

[0026] The present invention also provides a method for preparing a lithium ion battery negative electrode from the above high-capacity lithium ion battery negative electrode material, which comprises the following steps:

[0027] The Si@C-CP / G is mixed with a conductive agent and a binder, mixed in a mixer, and then coated on a copper foil, and dried to obtain a Si@C-CP / G negative electrode.

[0028] The conductive agent can be one or more of artificial graphite, carbon nanotubes, and acetylene black; the mass of the conductive agent and the binder is 8-12 wt% of Si@C-CP / G, preferably 10 wt%.

[0029] When the Si@C-CP / G is mixed with the conductive agent and the binder, a solvent needs to be added; the solvent can be at least one of distilled water and ethanol.

[0030] The present invention also provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode is a Si@C-CP / G negative electrode.

[0031] The present invention has the following beneficial effects:

[0032] 1. The present invention realizes the design of a composite negative electrode sandwich structure, and the mechanical flexibility ensures that the huge volume expansion can be effectively accommodated during the cycle. Organic phosphonic acid, phytic acid and aniline self-polymerize into an elastic coating and effectively wrap the Si surface. The subsequent addition of PVP and graphene oxide further increases the stability of the structure. After high-temperature carbonization, the carbon layer on the Si surface derived from these substances is sufficient to act as a buffer medium to buffer the volume expansion of Si. PVP itself acts as a surfactant, promoting the coating of graphene oxide, but it is easily soluble in water and is removed during filtration and rinsing.

[0033] 2. The aniline of this invention introduces secondary amine groups, which form hydrogen bonds with hydroxyl groups on graphene oxide, firmly anchoring the Si particles to the three-dimensional graphene sheets. The complete encapsulation of the graphene sheets around the Si particles prevents the continuous formation of the SEI, while the nanoporosity of the connected graphene sheets facilitates the diffusion of lithium ions into the sandwich structure. The carbonized carbon coating and graphene sheets formed by the polymer of organic phosphonic acid, phytic acid, and aniline act as a buffer and powerful electron pathway, ensuring rapid charge and discharge of the battery.

[0034] 3. Due to the low total mass of the three-layer coating, the prepared Si@C-CP / G ensures a high internal Si content (80-90%), guaranteeing high capacity and high cycle stability for the entire battery. Carbon derived from organic phosphonic acids (such as ethylenediaminetetramethylenephosphonic acid), phytic acid, and aniline is rich in O, P, and N heteroatoms, which can regulate the electrolyte structure, induce the formation of a more conductive and tough composite SEI, and significantly improve the stability of the composite structure.

[0035] 4. This sandwich structure can also avoid aggregation or accumulation during the charge and discharge process, thereby maintaining the initial active surface and open channels for ion transport.

[0036] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0038] Figure 1The X-ray diffraction (XRD) patterns of the Si@C-CP / G material and other materials obtained in the first preferred embodiment of the present invention are shown in the figure. From top to bottom, the XRD patterns of Si@C-CP / G, silicon powder combined with ethylenediaminetetramethylenephosphonic acid (Si@), and pure silicon powder are shown.

[0039] Figure 2 Schematic diagram of the bonding of the surface hydroxyl groups of silicon powder used in the present invention with ethylenediaminetetramethylenephosphonic acid (a), a schematic diagram of the molecular structure of the bonding of phytic acid with aniline (b), and a schematic diagram of the molecular structure of the product of the bonding and polymerization of phytic acid with aniline (c);

[0040] Figure 3 This is a schematic diagram of the molecular structure of the polymerization product of phytic acid and aniline combined with ethylenediaminetetramethylenephosphonic acid in the present invention;

[0041] Figure 4 1 is a graph showing the battery cycle performance of various embodiments of the present invention and comparative examples;

[0042] Figure 5 This is a scanning electron microscope photograph of the Si@C-CP / G material obtained in Example 1 of the present invention;

[0043] Figure 6 1 is a transmission electron microscope image of the Si@C-CP / G material obtained in Example 1; wherein, (a) is a conventional resolution image, (b) is a high-resolution transmission electron microscope image, (c) and (d) are transmission electron microscope images of the materials prepared by (2) in step 1 and step 3 in Example 1, respectively, and (e) is a transmission electron microscope image of the three-layer structure of the materials prepared by (2) in step 1, step 2 and step 3 in Example 1. DETAILED DESCRIPTION

[0044] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0045] The reagents used in the examples are described as follows:

[0046] Silicon powder: MG-Si-100, average particle size 100 nm, purity 99.9%, specific surface area 60 m 2 / g; The silicon powder production process includes an acid washing and impurity removal step, which causes the silicon powder surface to have hydroxyl groups.

[0047] All other reagents were of analytical grade unless otherwise specified. Water was ultrapure water.

[0048] Example 1:

[0049] Step 1: Add ethylenediaminetetramethylenephosphonic acid (0.5 g) to 40 mL of water and sonicate for 10 min. Then, heat in an 85 °C water bath until dissolved to obtain solution A. Add Si powder (100 nm, 1 g) to solution A, sonicate and stir for 0.5 h to obtain solution B.

[0050] Step 2: Polyaniline conductive polymer coating.

[0051] (1) Add 140 μL of aniline and 280 μL of phytic acid aqueous solution (70 wt%) to 3 mL of water and disperse by ultrasonication.

[0052] (2) Add the solution of (1) into solution B and disperse it ultrasonically at 300W for 0.5h.

[0053] (3) Dissolve 136 mg of ammonium persulfate in 4 mL of water and add it dropwise to the solution (2) above. Ultrasonicate at 300 W for 2 min to obtain solution C. Place solution C in an ice bath for 5 h to allow polymerization, then filter and dry the filtered solid to obtain a dry product.

[0054] Step 3: Preparation of outer conductive carbon and graphene layers.

[0055] (1) 0.3 g of PVP was added to water and stirred for 20 min to dissolve. The dried product prepared in step 2 was added and ultrasonicated for 0.5 h. 4 mL of graphene oxide (4 mg / mL) was added and ultrasonicated for 0.5 h. The solution was then stirred for 2 h to obtain solution D.

[0056] (2) Solution D was filtered and rinsed, then freeze-dried. The product was heated to 280°C at a rate of 5°C / min for 1 h, and then to 500°C at a rate of 5°C / min for 3 h. Argon was used throughout the sintering process to obtain the negative electrode material, named Si@C-CP / G.

[0057] Example 2:

[0058] All steps are the same as in Example 1, except that the first portion of ethylenediaminetetramethylenephosphonic acid is replaced with methylphosphonic acid.

[0059] Example 3:

[0060] All steps were the same as those in Example 1, except that the amounts of aniline and phytic acid aqueous solutions added in the second part were changed to 110 μL and 220 μL.

[0061] Example 4:

[0062] All steps were the same as those in Example 1, except that the amounts of aniline and phytic acid aqueous solutions added in the second part were changed to 160 μL and 320 μL respectively.

[0063] Comparative Example 1:

[0064] All steps are the same as those in Example 1, except that no organic phosphonic acid is added in step 1.

[0065] Comparative Example 2:

[0066] All steps are the same as those in Example 1, but the operation in subsection (1) of step 3 is not performed, and the dried product prepared in step 2 is directly calcined at a high temperature, i.e., graphene oxide is not coated.

[0067] Comparative Example 3:

[0068] All steps are the same as those in Example 1, but the addition of PVP in step 3 is omitted, and only graphene oxide is added.

[0069] Comparative Example 4:

[0070] All steps were the same as those in Example 1, except that Step 2 was omitted, the solid obtained after filtering and washing Solution B was dried, and the dried product was directly subjected to Step 3. The material obtained in this comparative example lacked the coating of the polyaniline conductive polymer.

[0071] The negative electrode materials obtained in each embodiment and comparative example were prepared into negative electrodes and assembled into batteries:

[0072] (1) The negative electrode material is mixed with a binder (preferably sodium carboxymethyl cellulose) and a conductive agent (preferably carbon nanotubes), and dissolved and dispersed in ethanol and water (preferably 2:5) to obtain a negative electrode slurry.

[0073] (2) The negative electrode slurry was prepared at a concentration of about 4 mg / cm 2 The loading amount was coated on the copper foil current collector and the negative electrode was obtained after drying.

[0074] (3) The negative electrode is combined with a lithium sheet or a commercially available lithium iron phosphate positive electrode sheet and a separator, an electrolyte is added, and the battery is assembled into a battery case to obtain a battery.

[0075] The batteries obtained in each embodiment and comparative example were subjected to cycle charge and discharge tests to obtain the results shown in Table 1 and Figure 4 data. Figure 4 In the figures, the data of each embodiment or comparative example is the discharge specific capacity.

[0076] Table 1:

[0077]

[0078] The silicon content of the negative electrode material obtained in Example 1 was tested by thermogravimetric analysis, and the silicon content was found to be 86%.

[0079] Figure 1This is an XRD pattern obtained by testing the Si@C-CP / G material obtained in Example 1, the silicon powder (Si@) treated with EDTA (ethylenediaminetetramethylenephosphonic acid) obtained in Step 1 of Example 1, and pure silicon powder. It can be seen that the XRD patterns of the EDTA-treated material and the material prepared in Example 1 do not change significantly, indicating that the Si content in the material is minimally affected.

[0080] Figure 2 Schematic diagram (a) of the silicon powder treated with EDTA (ethylenediaminetetramethylenephosphonic acid) obtained in step 1 of Example 1 of the present invention; (b) a schematic diagram of the molecular structure of the combination of phytic acid and aniline in step 2 of Example 1; and (c) a schematic diagram of the molecular structure of the product of the combination and polymerization of phytic acid and aniline in Example 1. EDTA hydrogen bonds to the hydroxyl groups on the surface of the silicon powder.

[0081] Figure 3 This is a schematic diagram of the molecular structure of the polymerized product of phytic acid and aniline combined with ethylenediaminetetramethylenephosphonic acid in the present invention. The phytic acid and aniline combination polymerizes under the initiation of ammonium persulfate. The resulting product is rich in nitrogen, which can combine with oxygen in PVP and graphene oxide, bringing these materials together to achieve multilayer encapsulation.

[0082] Figure 4 Graphs showing battery cycle performance of various embodiments of the present invention and comparative examples.

[0083] The Si@C-CP / G material obtained in Example 1 was observed using a scanning electron microscope, and the photographs taken are as follows: Figure 5 As shown in the figure, the Si is evenly dispersed and not aggregated. However, since SEM only scans the surface, the inner coating structure cannot be seen, so TEM was used for further observation.

[0084] From Table 1 and Figure 4As can be seen from the test data, Example 1 successfully prepared a lithium-ion battery negative electrode material with high capacity and long cycle performance. This material realizes a composite negative electrode sandwich structure design with multiple advantages. On the one hand, organic phosphonic acid, phytic acid and aniline are self-polymerized and wrapped on the Si surface to form an elastic polymer coating layer. The addition of PVP and graphene oxide and the carbon layer derived after high-temperature carbonization enhance the structural stability and effectively buffer the volume expansion of Si; on the other hand, the secondary amine groups introduced by aniline form hydrogen bonds with the hydroxyl groups of graphene oxide, anchoring the Si particles on the three-dimensional graphene sheets. The encapsulation and nanoporosity of the graphene sheets not only prevent the continuous formation of SEI, but also facilitate the diffusion of lithium ions. The carbon coating and graphene sheets also serve as buffer media and electron channels to achieve rapid charge and discharge. In addition, due to the small amount of added materials, while ensuring that the internal Si content reaches 86%, Si@C-CP / G achieves high capacity and high cycle stability of the full battery, and the derived carbon rich in O, P, and N heteroatoms can regulate the electrolyte structure to form a high-quality composite SEI. At the same time, this sandwich structure prevents aggregation and accumulation during charge and discharge, maintaining the active surface and ion transport channels. Furthermore, the hydroxyl groups naturally present on the surface of the silicon powder facilitate its binding to the organic phosphonic acid, allowing for a tighter bond through hydrogen bonding. However, even using silicon powder without hydroxyl groups, the technical objectives can still be achieved, as the two can be bonded via van der Waals forces. This combined effect results in the best performance of Example 1 across all the examples and comparative examples.

[0085] In Example 2, the carbon chain of phosphonic acid is shortened, and the phosphorus and oxygen atoms it contains are reduced, resulting in a decrease in heteroatom doping in the outer carbon material, and a decrease in cycle performance. In Example 3, the composite negative electrode prepared by adding less conductive polymer leads to a thinner carbon intermediate protective layer, which alleviates the performance degradation of volume expansion and a decrease in cycle performance. In Example 4, due to the increase in conductive polymer added, the Si main content in the final composite negative electrode prepared is reduced, and the capacity is reduced.

[0086] In Comparative Example 1, due to the lack of inner-layer phosphonic acid modification, the composite anode prepared after high-temperature sintering lacks the inner carbon protection and electron conduction assistance. This results in incomplete silicon utilization during charge and discharge, resulting in a significant decrease in capacity, lower than all other examples. In Comparative Example 2, due to the lack of protection from three-dimensional graphene and PVP-derived carbon, the composite anode cannot withstand the significant volume expansion of the internal silicon, making the structure unfavorable for ion adsorption and rapid transport, and significantly poorer cycling stability. In Comparative Example 3, due to the lack of PVP, the composite anode prepared exhibited significant agglomeration, which impeded ion transport and significantly weakened cycling stability. In Comparative Example 4, the lack of polyaniline prevented hydrogen bonding with the hydroxyl groups on the graphene oxide, making it difficult for the Si particles to be firmly anchored to the three-dimensional graphene sheet. This failure to prevent the continuous formation of the SEI ultimately led to a significant decrease in Coulombic efficiency and cycling stability. The absence of the polyaniline's π-conjugated three-dimensional conductive network disrupts the electron transport pathway, preventing some active silicon from participating in the first-cycle lithium ion reaction. Its elastic structure loses its ability to buffer silicon volume expansion, leading to particle rupture and continued SEI film growth, resulting in irreversible consumption of active lithium. The loss of the nitrogen-doped carbon layer derived from the carbonization of polyaniline weakens the ionic conductivity of the SEI film, causing a surge in interfacial impedance and accelerating capacity decay. Furthermore, the loss of the mesoporous-graphene hierarchical structure constructed by polyaniline leads to a sharp drop in porosity and electrolyte wettability, hindering lithium ion transport and further deteriorating cycling stability.

[0087] Therefore, in summary of the four comparative examples, if any one of the three layers of coating is missing for silicon powder, at least one of its capacity, coulombic efficiency and capacity retention rate will decrease significantly. Therefore, any one layer of coating is indispensable, and the protective effect of the three-layer coating sandwich structure on silicon powder is very obvious.

[0088] The Si@C-CP / G material obtained in Example 1, the material obtained in Example 1 except Step 2 and Step 3 (1) (i.e. the silicon powder obtained in Step 1 is directly dried and calcined in Step 3 (2)), and the material obtained in Example 1 except Step 3 (1) (i.e. not coated with PVP and graphene) were observed using a transmission electron microscope to obtain Figure 6 . Among them, (a) is a conventional resolution image of Si@C-CP / G, and (b) is its high-resolution transmission electron microscope image. (c) and (d) are transmission electron microscope images of the product of step 1 in Example 1 and the material prepared by (2) in step 3 (that is, the silicon powder obtained in step 1 that is only coated with ethylenediaminetetramethylenephosphonic acid is directly dried and calcined in step 3 (2)). (e) Transmission electron microscope image of the two-layer coating structure of the material prepared by steps 1, 2 and (2) in step 3 in Example 1 (that is, not coated with PVP and graphene).

[0089] from Figure 6As shown in (a) and (b), the outermost layer of the Si@C-CP / G material is coated with the thinnest protective layer, graphene oxide. Since TEM contrast of the inner layer is minimal after coating with graphene oxide (see Figure b), TEM analysis was performed on the uncoated product. (c) and (d) are TEM images of silicon powder coated only with EDTA. The inner layer shows silicon powder with lattice fringes, while the outer layer is a carbon layer approximately 5 nm thick, resulting from carbonization of EDTA. (e) shows silicon powder coated with EDTA and polyaniline conductive polymer. From the inside out, the layers are silicon, carbon (EDTA), and carbon (polyaniline conductive polymer), with a clear boundary between the two carbon types. Therefore, it can be seen that Si@C-CP / G has a three-layer structure with silicon powder as the core, and from the inside out, ethylenediaminetetramethylenephosphonic acid, polyaniline conductive polymer, and graphene coating. Because silicon is crystalline, it has distinct lattice fringes, which can be distinguished from carbon.

[0090] In summary, the present invention synthesizes a lithium-ion battery anode material with a three-layer silicon-coated composite sandwich structure. This material exhibits a comprehensive protective barrier, minimally impacts silicon content, provides durable mechanical protection, and can regulate the formation of a uniform and tough SEI film at the electrolyte-particle interface. The present invention also provides a lithium-ion battery fabricated from this anode material.

[0091] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a high-capacity lithium-ion battery negative electrode material, characterized in that: The following steps are involved: Step 1: adding an organic phosphonic acid to an aqueous solution and dissolving it to obtain solution A; then dispersing Si particles into solution A and subjecting the solution to ultrasonic treatment to allow the two to recombine to obtain solution B; Step 2: adding an aqueous aniline solution and an aqueous phytic acid solution to the above solution B, and then ultrasonically treating the solution. Then, adding an aqueous ammonium persulfate solution and ultrasonicating the solution again to obtain a solution C; then cooling the solution C and allowing it to stand to polymerize; after the polymerization is completed, washing and filtering the product, and then drying the filtered solid to obtain a dry product; Step 3: Mix the dry product prepared above with a surfactant and graphene oxide, stir evenly, filter and dry, and sinter to obtain a high-capacity lithium-ion battery negative electrode material.

2. The method for preparing a high-capacity lithium-ion battery negative electrode material according to claim 1, characterized in that: In step 1, the organic phosphonic acid is at least one of ethylenediaminetetramethylenephosphonic acid, aminotrimethylenephosphonic acid, and methylphosphonic acid.

3. The method for preparing a high-capacity lithium-ion battery negative electrode material according to claim 1, characterized in that: In step 1, the dissolution includes simultaneous heating and ultrasonic treatment, with the heating temperature being 80-90°C, the ultrasonic time being 8-12 minutes, and the ultrasonic power being 100-300W.

4. The method for preparing a high-capacity lithium-ion battery negative electrode material according to claim 1, characterized in that: In step 1, the mass ratio of the organic phosphonic acid to the Si particles is 0.3-0.6:0.8-1.

1.

5. The method for preparing a high-capacity lithium-ion battery negative electrode material according to claim 1, characterized in that: In step 2, the volume ratio of the phytic acid aqueous solution to the mass ratio of the Si particles in step 1 is 10-16 μL:0.03-0.08 g; the volume ratio of the aniline aqueous solution to the mass ratio of the Si particles in step 1 is 5-8 μL:0.03-0.08 g; and the mass ratio of the ammonium persulfate to the Si in step 1 is 0.05-0.35:

1.

6. The method for preparing a high-capacity lithium-ion battery negative electrode material according to claim 1, characterized in that: In step three, the surfactant is at least one of polyvinyl pyrrolidone and sodium dodecylbenzene sulfonate.

7. The method for preparing a high-capacity lithium-ion battery negative electrode material according to claim 1, characterized in that: In step three, the sintering includes two steps: the first step is sintering at 200-400°C, and the second step is sintering at 500-750°C; and the sintering time is 0.5-2 h in the first step and 2-5 h in the second step.

8. A high-capacity lithium-ion battery negative electrode material, characterized in that: It is obtained according to the method for preparing a high-capacity lithium-ion battery negative electrode material according to any one of claims 1 to 7.

9. A lithium ion battery negative electrode, characterized in that A high-capacity lithium-ion battery negative electrode material prepared according to the method of claim 1 or a high-capacity lithium-ion battery negative electrode material according to claim 8 is mixed with a conductive agent and a binder, and then coated on a copper foil, and dried to obtain a lithium-ion battery negative electrode; The conductive agent is at least one of artificial graphite, carbon nanotubes, and acetylene black; the mass of the conductive agent and the binder is 8-12 wt% of the high-capacity lithium-ion battery negative electrode material; When the high-capacity lithium-ion battery negative electrode material is mixed with the conductive agent and the binder, a solvent is added; the solvent is distilled water and ethanol.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that: The negative electrode is a lithium-ion battery negative electrode as claimed in claim 9.

Images